Coherent x-ray diffractive imaging (CXDI), a lensless form of microscopy capable of discerning electron density and strain with 20 nm resolution, is used to map the strain evolution of a single cathode particle in a functional battery as it is cycled in-situ. The evolution of compressive/tensile strain reveals a number of interesting phenomena. For instance, a strain front nucleates and propagates inward/outward during discharge/charge. Strain can be quantitatively correlated to the Lithium amount in the initial cycles, eventually becoming uncorrelated upon longterm cycling. More recently we report three-dimensional imaging of dislocation dynamics in individual battery cathode nanoparticles under operando conditions using CXDI. Dislocations are static at room temperature and mobile during charge transport. During the structural phase transformation, the lithium-rich phase nucleates near the dislocation and spreads inhomogeneously. The dislocation field is a local probe of elastic properties, and we find that a region of the cathode material exhibits a negative Poisson&’s ratio at high voltage. Operando dislocation imaging thus opens a powerful avenue for facilitating improvement and rational design of nanostructured materials. We demonstrate that CXDI is a powerful diagnostic tool to reveal correlation between strain and electrochemistry at the single particle level and offers valuable information for electrode/battery modeling and future battery design.

LiNi_0.4Mn_0.4Co_0.2O₂ cathodes for Li-ion batteries exhibit significant advantages over the commonly-used commercial material LiCoO₂ in terms of higher capacity, increased thermal stability, and reduced cost. However, the substitution of Co by Mn and Ni results in a decrease in the electronic conductivity, leading to poor performance at high cycling rates, and increased reactivity with the electrolyte which results in a limited lifetime. To mitigate these effects we have employed the use of single-walled carbon nanotubes in place of the typical polymer binder to increase rate-capability,[1] and an ultrathin Al₂O₃ coating prepared using atomic layer deposition to improve structural stability.[2] This approach enables remarkable high rate, highly stable performance at high voltages, representing an exciting development in Li-ion battery research.
An understanding of how the Al₂O₃ coating affords this structural stability is critical for further advances in the field. To this end, we have employed a multimodal approach to investigate the effect of the Al₂O₃ coating. Electrochemical impedance spectroscopy (EIS), operando synchrotron-based X-ray diffraction (XRD), and operando X-ray absorption near edge fine structure spectroscopy (XANES) have been utilized to characterize the structure and chemical evolution of the LiNi_0.4Mn_0.4Co_0.2O₂ cathode during cycling. Data were collected on both coated and uncoated electrodes using each technique during electrochemical cycling to high voltages. Using this combination of techniques, we are able to determine the effect of the ALD Al₂O₃ coating at both high and low voltages. The results of this study will be presented, providing insight into the structural and electrochemical effects of ALD coating on these layered NMC cathodes. This knowledge will help to direct future developments to further improve the performance of this class of material for Li-ion batteries and beyond, and highlights the power of a multimodal operando characterization approach applicable to the investigation of many different energy storage systems.
1. C. Ban, et al., Adv. Energy Mater., 1 (2011) 58-62.
2. L. A. Riley, et al., J. Power Sources, 196 (2011) 3317-3324.

Crystalline polyanionic (CP) materials (e.g., phosphates, borates, silicates) are being actively researched for possible use as lithium ion battery cathodes because of their high theoretical capacity and their expected cycling and safety performance. While lithium iron phosphate is a CP cathode material that has been commercially successful, other CP cathode materials (such as lithium manganese silicate, lithium cobalt borate) with theoretically higher potentials or specific capacities experimentally have demonstrated poor electrochemical performance. Their poor electrochemical performance typically has been caused by very low electrical conductivity (~10^-12 S/cm) and/or irreversible phase transformations.
Mixed polyanion (MP) glasses are a relatively unexplored class of cathode materials that have compositions and theoretical capacities similar to their crystalline counterparts. Their mixed polyanion content (ex., partial substitution of vanadate for phosphate in a phosphate glass) can provide a dramatically increased electrical conductivity through an electron hopping mechanism. Also, glass cathodes would not be expected to undergo irreversible crystalline phase transformations during the compositional changes associated with intercalation reactions.
Research has focused on metal phosphate glasses with substitution of vanadate polyanions. Traditional glass processing methods (graphite mold casting and splat quenching) have been used to produce the glasses. Slurry casting onto depassivated aluminum foil has been used to produce cathodes. MP glass cathodes have been demonstrated to undergo two different high capacity reversible electrochemical reactions: intercalation and conversion. Full theoretical capacity and good cycling performance of the intercalation reaction has been demonstrated in iron pyrophosphate/vanadate glass. A glass-state conversion reaction has been observed in Ag, Co, Cu, Fe, and Ni-bearing glasses with capacities of 250-500 mAh/g and reaction voltages up to 2.9V. The conversion reaction mechanism has been confirmed and characterized by XANES and EDXS. The electrochemical performance of MP glass cathodes has been studied using the galvanostatic intermittent titration technique, cyclic voltammetry, and cycling tests.

Despite widespread commercial success, Li-ion battery technologies require significant improvements to keep pace with increasing energy demands. The scientific community has dedicated considerable time and resources to develop superior Li-ion battery materials. Nevertheless, today&’s Li-ion battery performance is limited in terms of: (i) capacity, (ii) rate capabilities, and (iii) cycle life.
Particle/polymer electrospinning is a robust platform which is utilized here to prepare high performance nanofiber electrodes for Li-ion batteries. The approach taken in the present study builds upon the recent work of Pintauro and co-workers^[1-3] who used particle/polymer electrospinning to fabricate hydrogen/air fuel cell electrodes. Potential advantages of electrospun anodes and cathodes over conventional slurry cast materials for Li-ion batteries include: (i) a large electrode/electrolyte interfacial area for enhanced electrochemical oxidation/reduction kinetics, (ii) a controllable interfiber void volume to ensure good electrolyte infiltration into the electrode, and (iii) micron/sub-micron fibers with high nanoparticle content and short Li⁺ transport pathways in the radial fiber direction.
A primary focus of this work is to create electrodes with high areal and volumetric capacities. These metrics are often underemphasized in the battery literature, but they are of critical importance for practical battery applications. An electrode may perform well with a low areal capacity but become less useful at higher loadings (i.e., increased thickness) due to Li⁺ transport limitations. Likewise, volumetric capacity is an important parameter for applications where battery space allocation is limited (e.g., electric vehicles). New electrode architectures should be prepared with high areal and volumetric capacities at fast charging rates for consumer device applications^[4].
In this presentation, experimental results will be presented on the fabrication and use of: (i) nanofiber Li-ion battery anodes containing either titania or carbon as the active material and (ii) LiCoO₂-based Li-ion battery nanofiber cathodes. The effects of electrode thickness and fiber volume fraction on performance will be highlighted. Data on full cells containing electrospun anodes and cathodes will also be presented.
References
1. W. Zhang and P. N. Pintauro, ChemSusChem, 4, 1753 (2011).
2. M. Brodt, R. Wycisk and P. N. Pintauro, Journal of The Electrochemical Society, 160, F744 (2013).
3. M. Brodt, T. Han, N. Dale, E. Niangar, R. Wycisk and P. Pintauro, Journal of The Electrochemical Society, 162, F84 (2015).
4. E. C. Self, R. Wycisk and P. N. Pintauro, Journal of Power Sources, 282, 187 (2015).

Current commercial Li-ion batteries employ positive electrode materials (e.g. LiCoO₂, LiFePO₄) that allow Li cations to be topotactically inserted and removed from a stable host crystal structure through single electron transfer reactions. A goal toward achieving significantly higher capacity Li batteries is to replace this insertion reaction material with an electrode characterized by the formation and decomposition of new phases and the transfer of multiple electrons per redox active species. Common examples include O₂, S and transition metal fluoride electrodes. Success with these electrodes in Li cells has proven elusive, as they generally exhibit very high voltage hysteresis and rapid irreversible capacity loss, particularly when operated using rates, active mass ratios and electrode thicknesses of commercial significance.
We present an alternative high capacity electrode concept based on a liquid molten salt active material comprising the nitrate anion, NO₃^-. Molten nitrates have been previously used in Li primary thermal batteries based on the cell reaction, 2Li + LiNO₃ agrave; Li₂O + LiNO₂, which has heretofore proven to be both chemically and electrochemically highly irreversible. We will describe the use of nanoparticle heterogeneous catalysts which enable rechargeable cells employing molten nitrate electrodes that exhibit very low voltage hysteresis (<5%) along with excellent capacity retention and cycle life. Additionally, we report the formation of large (>5 micron diameter) Li₂O particles exhibiting equilibrium octahedral morphology. The mechanism of formation and decomposition of unprecedented of large deposits of the electronically insulating Li₂O phase, allowing very high practical capacity and electrode utilization, will be described. We note that the active material in this system additionally serves as the electrolyte, or catholyte in cells additionally employing a solid electrolyte, and that this multifunctionality enables cells with relatively high active to inactive mass ratios.
This presentation will additionally provide a discussion of issues relating to design and scale-up of this and other Li molten salt conversion reaction battery systems toward the goal of providing >400 Wh/kg at the pack level.

The prospects for developing alternative anodes to improve overall energy and power of lithium based batteries are promising and close to the integration in new cell chemistries than the alternative cathodes. We will present a new class of alternative anodes for structural-conformal batteries, and review the current status and future prospects of alternative anodes. Results of using a highly dense Silicon based anode composite with high capacity (>1500 mAh/g for electrode and >3500 mAh/g for silicon componenet) in a new and flexible electrode in structural battery will be reported.
Lithium batteries are currently dominating the field of electrochemical energy storage systems, providing high energy and high power capabilities. Current R&D focus is on further improvement of electrodes capacity for a new class of batteries for electric-based transportation. The challenges of using high capacity metallic lithium foil as an anode are still remaining despite many years of research efforts, due to the intrinsic problems associated with the electrodeposition of reactive light metals such as lithium. In addition, the required excess lithium (3-5 times) to satisfy the battery long cycle life, and the safety concern associated with the large format cells containing metallic lithium anode have force the battery community to search for other alternatives. Some of the alternative anodes may exceed the energy density of metallic lithium when the excess lithium is considered. The initial success of intercalation anodes (i.e. carbonaceous materials) that is still serving in many practical lithium cells is an excellent example of a compromise between capacities and practicality. We are also encountering a new stage of lithium battery development that provides opportunities, but also brings confusions in the field. As an example, the high gravimetric energy dense mixed oxide cathodes are being challenged with the low density lower voltage polyanions, low voltage conversion cathodes, and the complex air cathodes. The lithium battery technology is also being challenged with higher valence elements (i.e. Mg, Al, Si), ignoring the high activation overpotential to disengage these elements from their lattices due to strong columbic force, and also challenges with those batteries that must be constructed in their charged state (i.e. Li-S). Theoretical and practical energy densities of battery chemistry based on dense metal oxide cathode and high energy density Silicon based anode will be compared with other commercial and proposed battery chemistries.

The development of novel electrodes with high capacity, good cyclability and low cost for lithium batteries is of pivotal importance in applications to portable electronics, electric vehicles and power backups. The combination of high capacity, low cost, ease of fabrication and low discharged voltage of the layered metal sulfide (LMS) family (e.g. MoS₂, WS₂ and SnS₂) makes this family an attractive candidate for an anode in lithium ion batteries. Recent investigations have demonstrated that these materials with thin layers close to a monolayer achieved much better electrochemical performance compared to the pristine bulk materials. However, most LMS-based electrodes suffer from limited cyclability and poor rate capability caused by the intrinsically poor electrical conductivity of the LMS as well as the generation of polysulfides Li₂S_x (2 < x < 8) during the Li charging process. There have been attempts to resolve these issues by the construction of carbon-LMS composites or the expansion of the interlayer distance of metal sulfides using polymers. Nevertheless, the electrochemical performance of LMS is not satisfactory yet. Most of the synthesized or mixed LMS with carbon support (e.g. graphene, carbon nanotubes and mesoporous carbons) has undesirable electronic pathways because of their partial carbon coating and non-exfoliating state of LMS. Although the incorporation of polymer such as polyethylene oxide is an effective way to exfoliate LMS sheets, additional carbon is required to increase the electrical conductivity of LMS. Consequently, a fully carbon wrapped and exfoliated LMS with a core-shell structure has been investigated to improve electrical conductivity and prevent the dissolution of polysulfides.
We report a simple and scalable process to synthesize the core-shell nanostructure of MoS₂@N-doped carbon nanosheets (MoS₂@C), where polydopamine is coated on the MoS₂ surface and then carbonized. Transmission electron microscopy and Raman spectroscopy reveals that the as-synthesized MoS₂@C possesses a nanoscopic and ultrathin layer of MoS₂ sheets with a thin and conformal coating of carbon layers (sim;3 nm). The MoS₂@C demonstrates a superior electrochemical performance as an anode material for lithium ion batteries compared to exfoliated MoS₂ and bulk MoS₂. This unique core-shell structure is capable of excellent delivery of Li⁺ ion in charging-discharging process: a specific capacity as high as 1239 mA h g^minus;1, a high rate of charging-discharging capability even at a high current rate of 10 A g^minus;1 while retaining 597 mA h g^minus;1, and a good cycle stability over 200 cycles at a high current rate of 2 A g^minus;1.

Designing a solid electrolyte interphase (SEI) with high ionic conductivity and low electronic conductivity is believed to be important for high performance and durable Li ion batteries. Li ionic conduction in SEI affects the rate performance, while the electron leakage through SEI causes electrolyte decomposition and, thus, causes capacity loss. To help design an artificial SEI, it is necessary to know the defect chemistry and transport in the multi-component SEI present on electrodes.
In this study, we developed a multi-scale model based on density functional theory and space charge model to investigate the defect distribution in a multi-component SEI consisting of LiF and Li₂CO₃. We consider the effects of LiF/Li₂CO₃ interface on the defect redistribution in the bulk of LiF and Li₂CO₃ that are both in equilibrium with the electrode. On negative electrodes, the dominant defect type in LiF is Schottky pair while the major ionic carrier in Li₂CO₃ is Li ion interstitial whose charge is balanced by electrons. Based on these bulk defects, we calculated the defect redistribution near the LiF/Li₂CO₃ interface by considering the defect migrations and reactions across the interface. Because the low concentration of ionic carriers in the bulk LiF, we approximated LiF as an ionic insulator in the mixture. We found that, in the ionic space charge region of Li₂CO₃ near the LiF/Li₂CO₃ interface, Li ion interstitial is accumulated but the electron is depleted. This demonstrates a possibility that, by engineering a mixture of LiF and Li₂CO₃ in an artificial SEI, the ionic conduction can be enhanced and the electron leakage through the SEI can be reduced, thus enhancing the durability and performance of electrodes.

Although ion-exchange reactions have traditionally been carried out in liquid solvents or in molten salts, we demonstrate that the use of non-molten salts is a very effective alternative method of preparing metastable energy storage materials at intermediate temperatures (150 - 350 C) that would otherwise be difficult to access. We have utilized non-molten salt ion exchange techniques to prepare new Li-ion and Na-ion battery cathode materials, as well as to prepare new solid state Li-ion conductors. Furthermore, it is found that these techniques are very well suited for in situ diffraction experiments. The full Rietveld refinement of in situ powder X-ray and neutron diffraction collected during ion exchange reactions has been carried out, and provides insights into the unexpected mechanisms of some ion exchange reactions used to prepare novel Li-ion conductors.

Energy storage has an important role in the next generation devices like portable electronics and electric vehicles for transportation. Lithium ion batteries play a significant role in the energy storage. However, the need for high energy density battery is growing enormously. Hence, there is still room for improvement urging the quest for finding new materials to store energy. Battery research has utilized vast majority of compounds exhibiting redox behavior as possible electrode material. Arsenic is one of the elements that were least explored. Although the formation of lithium solid ionic conductor such as Li₃As was demonstrated by Nazri et al [1] in 1994, the compound was shown to have electrochemical activity very recently using a FeAs alloy [2] as an anode material for lithium secondary batteries.
Based on these limited studies, the Li₃As compound was chosen as a possible electrode material for lithium ion batteries for our analysis. A novel approach for synthesizing Li₃As from Li metal and As metallic powders will be demonstrated. Solid electrolyte and solid state batteries offer improved safety by avoiding electrolyte depletion and Li dendrite growth. On the other hand, solid state batteries offer higher mechanical and thermal stability compared to than those of liquid based batteries. In this regard, Li₃As was tested in a solid state battery setup using metallic Lithium as counter and reference electrode and Lithium thiophosphate (LPS) as electrolyte. LPS was synthesized by the method reported in literature [3] and used in this study without further modifications. The composite electrode for testing the electrochemical activity consists of Li₃As, LPS for ionic conduction and Super P carbon for electronic conduction. The room temperature operation of the battery displayed a flat potential plateau at 2.2V during charging and a sloping potential plateau at 1.0V during discharge. This represents the electrode materials undergoes intercalation reaction and the continuously sloppy nature of the potential versus time plot demonstrates a single phase reaction. The details of various characterizations and the electrochemical behavior of the Arsenic compound under different solid state configurations will be discussed in detail at the meeting.
References:
[1] G.A. Nazri, C. Julien and H.S. Mavi, Solid State Ionics 70/71 (1994) 137-143.
[2] J. Chen, H. Zhao, N. Chen, X. Wang, J. Wang, R. Zhang and C. Jin, J. Power Sources 200 (2012) 98- 101.
[3] Z. Liu, W. Fu, E. A. Payzant, X. Yu, Z. Wu, N. J. Dudney, J. Kiggans, K. Hong, A. J. Rondinone and C. Liang, J. Am. Chem. Soc. 135 (2013) 975-978.

Lithium trimethyl alkyl and aryl borates (LTMB) has been prepared and investigated as a novel cathode film forming additive to improve the performance of LiNi_0.5Mn_1.5O₄ cathodes cycled to high potential (4.8 V). Addition of LTMB to 1.2 M LiPF₆ in EC/EMC (3/7) improves the capacity retention of graphite/LiNi_0.5Mn_1.5O₄ cells cycled at 55 ^oC. The added LTMB is sacrificially oxidized on the surface of the cathode during the first charging cycle. The LTMBs can be used as a functional group delivery agent via reaction of trimethyl borate with of the appropriate lithium alkoxide. Over 40 different LTMBs have been prepared and investigated. Ex-situ surface analysis of the LiNi_0.5Mn_1.5O₄ by Attenuated Total Reflectance Infrared Spectroscopy (ATR-IR), Transmission Electron Microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) reveals inhibition of electrolyte oxidation on the cathode surface and the presence of a borate based passivating layer. The novel cathode electrolyte interface (CEI) leads to the performance improvements.

Among several cathode materials such as spinel and Li-rich layered oxides, lithium transition metal orthophosphates with the formula LiMPO₄ (M = Fe, Mn, Co, Ni) have received particular attention due to their excellent electrochemical properties, good thermal stability and low cost [1]. LiCoPO₄ (LCP) offers a high redox potential (~4.8 V) and reduced cobalt weight fraction per formula unit compared to the commercial LiCoO₂ [2]. Additionally to the well-known olivine-type (LCP - Pnma) and the metastable (LCP - Pna2₁) LCP polymorphs [3], a third modification of LCP showing a Na₂CrO₄-type structure (LCP - Cmcm) was reported by Amador et al. [4]. The synthesis of LCP - Cmcm was done using a high-pressure/high-temperature (HP,HT) (6-15 GPa/1173 K) route, starting from LCP - Pnma previously prepared by solid state reaction. However, there is a lack of information around complete crystallographic data, morphology, and magnetic properties. The polyol pathway allows a simple and efficient method to synthetize LCP - Cmcm using tetraethylene glycol as solvent at 200 °C and under ambient pressure. The material was characterized using X-ray powder diffraction. Full Rietveld refinement data suggest an orthorhombic structure (space group Cmcm, No. 63) with the lattice parameters a = 5.4434(1) Å, b = 8.1693(2) Å, c = 6.2128(1) Å, and V = 276.28(1) ų, which are in good agreement with the reported values for the pure (HP,HT) polymorph. The low R-values, chi;² of 1.12 and the absence of any additional Bragg peaks further indicate no impurities or presence of secondary phases. Scanning electron microscopy shows a unique hierarchical self-assembled bow-tie like microstructure consisting of primary nanolayers units. The procedure does not require the use of any surfactant or template. Ex situ XRD studies of the sample annealed under air and cooled down to room temperature, suggesting a transition from the LCP-Cmcm type to the LCP-Pnma at temperatures above 550 °C. The results of the magnetic susceptibility as a function of temperature indicate a paramagnetic Curie-Weiss behavior at high temperatures and show a long-range antiferromagnetic order below T_N = 11 K. This low-temperature study, aiming at crystallites or agglomerates much smaller than those obtained in conventional solid-state syntheses, may yield metastable phases difficult to achieve at higher temperatures. Therefore, this synthesis techniques are well suited to address the experimental study of novel crystalline structures from a fundamental point of view.
References
[1] A.K. Padhi, K. S. Nanjundaswamy, J. B. Goodenough, J. Electrochem Soc., 1997, 144, 1188.
[2] S. Brutti, S. Panero, J. Am. Chem. Soc., 2013, 1140, 67.
[3] C. Jaehne, C. Neef, C. Koo, H. Meyer, R. Klingeler, J. Mater. Chem., A, 2013, 1, 2856.
[4] U. Amador, J. Gallardo, G. Heymann, H. Huppertz, E. Morean, M. Arroyo, Solid State Sci., 2009, 11, 343.

For high energy densities for all solid-state batteries, high capacity and low potential anode materials like lithium metal are preferred. Due to the highly reducing potential of lithium metal, the electrochemical stability of the interface between lithium metal and solid ion conductor plays a crucial role for the performance and function of all solid-state batteries.
Thus, the contact of lithium metal and a solid ion conductor can lead to three different types of interfaces [1]: Considering thermodynamic stability of the lithium metal and the solid electrolyte, a sharp two-dimensional interface is formed. In contrast, three-dimensional interphases are formed when both materials are thermodynamically unstable in contact with each other. Both differ in their physical and chemical properties and in their growth characteristics. When the reaction products are electronically conducting, a mixed-conducting interphase [2] (MCI) is formed. In addition, the electronic and ionic conductivity of the interphase induces a steady growth of the MCI. In the third case, the lithium metal and the solid ion conductor react and form a non-growing interphase, as the products are electronically insulating and are therefore limiting the film growth.
Here, we shortly introduce an in situ XPS technique to study interphase formation between lithium metal and lithium solid ion conductors, using a standard lab-scale photoelectron spectrometer. Additionally, we report on the interphase formation between lithium metal and some lithium ion conductors, including widely used and promising materials like LPS (Li₇P₃S₁₁) [3]. Interphase formation is investigated and compared using an in situ XPS technique [1] and impedance spectroscopy. In accordance with this results it is discussed whether a MCI or an SEI is formed. Additionally, the potential effects for all types of interfaces (or interphases) on the performance of an all solid state battery are described.
[1] Wenzel, S.; Leichtweiss, T.; Krueger, D.; Sann, J.; Janek, J. submitted to Solid State Ionics.
[2] Hartmann, P.; Leichtweiss, T.; Busche, M. R.; Schneider, M.; Reich, M.; Sann, J.; Adelhelm, P.; Janek, J. J. Phys. Chem. C 2013, 117, 21064.
[3] Wenzel, S.; Weber, D.; Leichtweiss, T.; Sann, J.; Janek, J. in preparation.

Lithium-alloying elements such as Si, Ge, and Sn are promising, high-capacity candidate materials as rechargeable Li-ion battery negative electrodes, but the large volume changes upon lithiation can result in early degradation. Nanowire geometries can help alleviate stress development and improve rate performance, but material restructuring during cycling remains problematic. To understand dynamic battery material behavior, in-situ observation while immersed in standard aprotic liquid electrolyte is necessary. Here, we directly observed the lithiation and delithiation processes in Ge nanowires using a transmission electron microscope (TEM) liquid cell that closely replicates a standard battery environment. This TEM liquid cell contains up to 10 electrodes and a thin, ~100 nm liquid layer hermetically sealed between two electron-transparent membranes. For this study, Ge nanowires were placed on the electrodes, and the cell was filled with 1:1 ethylene carbonate:dimethyl carbonate (EC:DMC) with 1M lithium hexafluorophosphate. By applying controlled sub-pA level currents, the Ge wires were lithiated and delithiated over multiple cycles. We observed nanowire swelling and amorphization during lithiation, the development of pores upon delithiation, and the growth of the pores with further cycling. The nanowires lithiated radially in this fully-immersed geometry. We compare our results to previous Ge nanowire lithiation in an “open” TEM cell that used a solid electrolyte. The TEM liquid cell provides revealing detail of the lithiation process in Ge nanowires, and our approach can be readily adapted to other nanowire battery materials.

Li-ion battery technology is considered as the most efficient solution for the electrochemical energy storage. While standard liquid electrolyte - based configurations provide best performances, solid state electrolytes are developed as a safer alternative. In fact, solid-state electrolytes are being considered the keystone element for the development of safer and high energy (high voltage) all-solid-state lithium-ion batteries. While poly(ethylene oxide) (PEO) solid-state polymer electrolytes are known to support a Li⁺ flux, satisfying conductivities are reached only above the melting point of the PEO crystallites (> 65°C) rendering PEO unpractical. In this contribution we will discuss how by means of block copolymer engineering mechanically clamped liquid-PEO electrolyte that combines the high ionic conductivity of a low molar mass PEO with the dimensional integrity of a solid material can be designed. Attractive ionic conductivities of about 0.01 mS/cm are attained at room temperature without compromising mechanical properties. The electrolyte shows a wide electrochemical stability window and help in building a stable interface with lithium metal. Competitive performances are attained when integrating the developed materials into operational/functional prototype batteries highlighting the provided potential. Newt, we will discuss a three step synthesis procedure of self-doped solid block copolymer electrolyte, combining a single-ion poly(lithium methacrylate-co-oligoethylene glycol methacrylate) ion conducting block (P(MALi-co-OEGMA)) and a structuring polystyrene block (PS). The macromolecular design allows the formation of a self-standing film with excellent mechanical properties provided by the PS anchoring nanodomains while attaining attractive ionic conductivities of up to 0.02 mS/cm at room temperature. Moreover, the single-ion configuration based on polyanionic backbone affords high transference numbers, close to unity, and alleviates the power limitation encountered in salt-doped solid polymer electrolyte (SPE). The electrolyte exhibits a wide electrochemical stability window up to 4.5 V vs. Li⁺/Li and promotes the formation of stable interfaces at the electrodes.

Lithium-ion batteries are expected as next generation energy storage devices due to its high capacity and eco-friendliness. However, their energy density and capacity are still insufficient for high-power applications such as electric vehicles. To overcome these problems, many kind of materials are studied as anode material substituting graphite.
A silicon atom reacts with 4.4 Li ions by alloying mechanism, so silicon has large theoretical capacity (4200 mAh/g) and low and flat reaction potential. In spite of these advantages, silicon still has a long way to go to put to practical use because of its large volume expansion and low conductivity.
Germanium also alloys with lithium showing high capacity up to 1600 mAh/g. It&’s smaller than silicon but germanium has high lithium-ion diffusivity (400 times faster than in Si) and electrical conductivity. (10⁴ times higher than Si) However, mechanical stresses induced by the volume changes during cycling result in pulverization and exfoliation from current collector also.
In many studies, nano-structured carbon composite materials are frequently applied to the lithium ion batteries as an anode material to solve these problems. In this context, magnesiothermic reduction is one of the most popular methods to make silicon electrode material because it can easily make mesoporous silicon particles from silica.
In this study, we reacted Mg₂Si with GeO₂ to fabricate porous Si@Ge core-shell particles. This redox reaction is derived from reaction between Mg₂Si and SiO₂ during magnesiothermic reduction. Porous Si@Ge core-shell particles show high capacity and good cyclability.

The lack of stable, high-capacity, low-cost cathodes limits the energy density in current-generation lithium-ion batteries. Orthorhombic Li₂NiO₂, Li₂CuO₂, and solid solutions have been studied as potential cathode materials for lithium-ion batteries due to their high theoretical capacity and relatively low cost. While neither endmember shows good cycling stability, the intermediate composition, Li₂Cu_0.5Ni_0.5O₂, yields high reversible capacities. In this contribution, we present a new synthesis of Li₂Cu_0.5Ni_0.5O₂ and detailed characterization using X-ray and neutron diffraction, X-ray absorption spectroscopy (XAS), and Raman spectroscopy. The cycle life of Li₂Cu_0.5Ni_0.5O₂ is shown to depend critically on the voltage window. In situ XAS and gas evolution measurements are used to follow the chemical and structural changes that occur as a function of cell voltage. Remaining challenges that need to be addressed for practical applications in lithium batteries will also be discussed.
Acknowledgements
This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy. The authors acknowledge the support of Stanford Synchrotron Radiation Lightsource, a Directorate of SLAC National Accelerator Laboratory and an Office of Science User Facility operated for the U.S. Department of Energy Office of Science by Stanford University. X-ray diffraction was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. Neutron diffraction at ORNL&’s Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.

The lithiation of silicon nanostructures is subject to intense experimental and computational research efforts. This interest is due to the fact that silicon might replace graphite as the anode material in high performance Li-ion batteries (LIBs), provided that the resulting battery lifetime can be enhanced. It is well known that immense volume changes take place during the (de)lithiation of Si anodes, more than 300%. It is also known that structural changes play a crucial role in the unacceptably fast deterioration of the reversible LIB capacity. To address this issue, a deeper insight into the Li-Si interplay is needed, together with a better understanding of how the (de)lithiation processes affect the ionic and electron conductance.
The here presented simulations investigate structural changes taking place in Si nanoclusters and nanopillars while they undergo (de)lithiation. The calculations are performed either at the density-functional theory (DFT) accuracy level or based on semi-empirical force-fields methods. Preliminary results have revealed a strong correlation between the average separation of Li atoms and their site preference on the host Si cluster. At a low coverage the Li atoms tend to reside on the Si surface. As the Li coverage increases a shift occurs and Li starts to penetrate into subsurface layers. This transition appears as a critical coverage is reached, which corresponds to the situation where the distance between Li atoms becomes comparable to the first-neighbors distance in bulk Li. To explain this transition, we notice that only by penetrating into the Si surface the Li atoms are able to avert the energetically unfavorable situation where the distance between Li atoms is so short that strong repulsion arises. However, this process requires significant rearrangements of the Si bond network that are associated with an energy cost. As a consequence Si and Li will remain segregated for as long as the Li atoms can be contained in an uncompressed configuration in the surface layers. The concept of Si bond-breaking allows to explain the sharp lithiation front that is experimentally observed during the first loading cycle of Si nanoclusters [1]. Similarly, a sharp lithiation front is also seen in bulk a-Si [2] and is consistent with the critical coverage theory proposed here. Additional work includes investigating how the occurring Li-Si or LiSi-Si interfaces affect the ionic and electronic conductance.
1 M. T. McDowell et al., Nano Letters, 13, 758, (2013)
2 J. W. Wang et al., Nano Letters, 13, 709, (2013)

Silicon is a promising anode material for lithium-ion batteries for its excellent specific capacity (3579 mAh/g). However, the large capacity of Si is accompanied by a large volume expansion (~400%) which irreversibly destroys the Si crystallinity, resulting in loss of mechanical/electrical contact and capacity fading. A better understanding of the structural aspects of lithiation in Si can provide fresh insights to mitigate the large volume change and loss of crystallinity and is the goal of our work.
We focus on a model system consisting of a single crystal silicon electrode in a half cell configuration, with lithium metal as counter/reference electrode. Recent studies have shown that there exists a well-defined phase boundary between lithiated Si (Li_xSi) and crystalline Si during the lithiation of single crystal Si. In order to characterize the Li_xSi layer, we use a specially designed X-ray transparent cell to perform in-situ synchrotron X-ray reflectivity (XRR) on the single crystal Si wafer electrode in real time during electrochemical cycling. The surface-sensitive XRR technique can follow the movement of this phase boundary through the Si, as well as the growth of solid electrolyte interface (SEI) layer. In-situ XRR was obtained at a 25 mu;A/cm2 rates in 1 M LiPF₆ in 1:1 EC:DMC electrolyte. From fits to the data, we find that the surface Li_xSi layer becomes thicker and somewhat rougher with increasing time (charge). We quantify the Li_xSi layer thickness, roughness and density and relate these to the charge passed. From this, we develop a mechanistic model of the initial lithiation process in crystalline Si.

Lithium/sulfur (Li/S) batteries have attracted intense attention, because it has a great potential to provide high energy density storage for next generation power storage systems. Li/S batteries have a theoretical energy density of 2600 Wh kg^-1, which is almost three times the energy density of current lithium-ion batteries. Sulfur cathode can deliver a high specific capacity of 1672 mAh g^-1, which is more than five times that of currently widely used LiCoO₂. Meanwhile, sulfur is abundant, low cost and environmentally benign. However, the insulating intrinsic of sulfur, the dissolution of polysulfides, shuttling of polysulfide between the negative and positive electrodes and huge volume expansion are still the main challenges that hinder the Li/S systems practical application.
To address these issues, much effort on designing and constructing novel microstructured/nanostructured S cathode has been devoted to modifying the cathode materials. Significant advances have been achieved using carbon, oxides,or conducting polymers, as the hosts of S cathode.
Herein, new nanostructured S cathodes were reported to address the problems of Li-S battery. We introduce the electroactive polymer, poly (N-vinylcarbazole) (PVK) and graphene oxide, into the Li/S systems as a conductive matrix and reservoir of S. By a facile two-step dissolution-precipitation treatment, novel core-shell S quantum dots/PVK nanocomposites (SQD/PVK) are synthesized, which a large number of sulfur quantum dots (~5 nm) with plenty of internal void spaces are encapsulated in the PVK shell . The S-core consisting of uniformly dispersed sulfur quantum dots, and large void spaces, which can form effective transportation pathway of both electrons and ions among these sulfur quantum dots, act as a buffer zone to accommodate the volume expansion during cycling and facilitate the electrolyte wetting. Meanwhile, the conducting PVK shell coated on the surface of S-core can restrain the polysulfide dissolution and suppress shuttle effect. Galvanostatic testing shows that this SQD/PVK nanocomposite could maintain a specific capacity 443.9 mAh g^-1 at 0.75 C after 500 cycles.
Following, graphene oxide was introduced to the S /PVK system to further improve the electrochemical performance of sulfur. The as-prepared micron-sized PVK/S@RGO composites containing 71 wt.% sulfur exhibit excellent cycling and rate properties with a high discharge capacity of 517.6 mAh g^-1 at 0.75 C after 400 cycles .
ACKNOWLEDGEMENTS
This work was supported by the Startup Foundation of China Academy of Engineering Physics, Institute of Chemical Materials (KJCX201301 and KJCX201306), National Natural Science Foundation of China (No. 21401177 and 51403193 ), the “1000 plan” from the Chinese Government, and the R&D Foundation of China Academy of Engineering Physics (2014B0302036).

Carbon based materials functionalized with metal nanoparticles (NPs) are promising candidates to replace existing electrode materials in energy storage devices [1]. In this report, we present a detailed transmission electron microcopy (TEM) analysis of a nanoporous carbon material functionalized with cobalt-oxide/cobalt (CoO/Co) core-shell nanoparticles (NPs) whose performance was also evaluated for lithium (Li)-ion battery electrodes. The nanoporous carbon is functionalized with CoO/Co core-shell NPs using an impregnation technique followed by its annealing at 500 °C in an inert environment. The prepared samples were then characterized with various TEM techniques to investigate their morphology, crystal structure and composition. Specifically, morphology and crystal structure were characterized by using the bright-field TEM (BF-TEM) technique. Our results revealed that the nanoporous carbon had pores of about a nanometer size. Moreover, it showed that the CoO/Co NPs have core-shell morphology in which CoO oxide possesses rock-salt crystal structure while the Co metal has face-centered cubic structure. Scanning TEM, in conjunction with electron energy-loss spectroscopy, revealed the elemental distribution of Co and O elements in NPs as well as it allowed determining the oxidation state of Co which turned out to be partly +2 and +3. Electron tomography in BF-TEM mode on the samples showed the distribution of CoO/Co NPs throughout the nanoporous carbon material. Li-ion battery testing for several hundred cycles demonstrated that these materials perform superbly for such applications. Finally, the TEM analysis battery-tested samples was performed as well to compare and contrast the results with as prepared samples. The observed higher performance of these materials is attributed to their superior quality functionalization with core-shell NPs.
[1]. D. S. Dhawale, G. P. Mane, S. Joseph, S. N. Talapaneni, C. Anand, A. Mano, S. S. Aldeyab, K. S. Lakhi, and A. Vinu, Cobalt oxide functionalized nanoporous carbon electrodes and their excellent supercapacitive performance, RSC Adv., 2015, 5, 13930.

Electrochemical performances of lithium rechargeable batteries are closely associated with the adhesion properties between electrode/current collector interfaces. Recently, there are some reports to unveil the relation between adhesion property and electrochemical performance. [1, 2] However, they mainly focused on new binder materials, not current collectors.
In this work, an electrochemically roughened copper foil is evaluated as a current collector for silicon (Si) electrodes. Cycle life of the Si electrode, with specific capacity of about 3500mAh/g, has been greatly improved by applying highly roughened copper current collector. And it exhibits a quite good adhesive properties, as confirmed from peeling tests when compared with conventional flat Cu current collector. 2032 coin half-cells are used to evaluate the electrochemical performances of the electrodes.
References
[1] Choi, J.; Ryou, M.-H.; Son, B.; Song, J.; Park, J.-K.; Cho, K. Y.; Lee, Y. M., Improved High Temperature Performance of Lithium-Ion Batteries through Use of a Thermally Stable Co-Polyimide-Based Cathode Binder. J. Power Soures 2014, 252, 138-143.
[2] Choi, J.; Kim, K.; Jeong, J; Cho, K. Y.; Ryou, M.-H.; Lee, Y. M., Highly Adhesive and Soluble Co-polyimide Binder: Improving the Long-Term Cycle Life of Silicon Anodes in Lithium-Ion Batteries, ACS Appl. Mater. Interfaces, Accepted
Acknowledgements
This research was financially supported by the Ministry of Education (MOE) and National Research Foundation of Korea (NRF) through the Human Resource Training Project for Regional Innovation (No. 2014066977)

The cell performance and cycle life of a lithium-ion battery (LIB) depend on several factors including the quality (extent of defects) of the electrodes that are used to fabricate the cell. During LIB electrode manufacturing by a slot-die coater, it is difficult to avoid certain defects such as agglomeration, contaminates, and blisters. Currently, these defects are not well detected during electrode coating because the optical CCD cameras do not offer 100% inspection of the electrode structure, which contain these defects. Therefore, cells with high value added can be constructed and subjected to formation cycling with defective electrode resulting in an increase in the cell rejection rate. The associated electrode scrap rates and increase in finished cell reject rate contribute to increasing the cost of LIBs to an unacceptable level. This presentation will showcase our investigations into understanding the impact of various electrode defects on the LIB cell performance. First, we will show our efforts to implement infrared thermography as a non-destructive quality control (QC) tool for detecting flaws and defects during LIB manufacturing by a slot-die coater. IR thermograms from dry electrodes (LiNi_0.5Mn_0.3Co_0.2O₂ or TODA NMC 532) were evaluated to detect the nature of flaws. The post-experiment analysis revealed a temperature increase or decrease across the defective region. A temperature increase across the defect region corresponds to a blister or agglomerate where heat cannot be released as quickly, and a temperature decrease corresponds to pinholes and divots where heat is released from the coating surface more quickly. Secondly, in order to quantify and correlate the effect of electrode coating defects such as divots, blisters, pinholes, agglomerates, and metal-particle contaminants on cell rate performance and cycle life, such defects were intentionally introduced while producing electrodes. Acquired IR thermograms of the defective regions were subsequently evaluated. Lithium-ion full cells containing those defective electrodes were cycled in order to investigate the electrochemical performance (rate capability and capacity fade). Our results show that cathode agglomerates did not have an effect on full cell discharge capacity, but aggravated cycle efficiency. Excessive metal particle contaminants (in this case, Co powder) have an extremely negative effect on performance, especially at higher C rates. Detailed understanding of the effect of electrode defects on LIB performance will be presented, and suggestions will be made for initial pass/fail criteria of LIB electrodes.
Acknowledgement:
This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy for the Vehicle Technologies Office's Applied Battery Research Program (Program Managers: Peter Faguy and David Howell).

One of the challenges in the development of batteries consists in the investigation of new electrode materials and comprehension of the electrochemical mechanism. Herein, we report on the first operando measurements of electron magnetism on a battery during cycling. We have succeeded in designing a non-magnetic cell and have investigated the conversion mechanism of FeSb₂, a high energy density anode material [1].
Operando electron magnetic measurements on LIB allow us revisiting the electrochemical mechanism of the high energy density anodic material FeSb₂. The plateau reached by the magnetic moment during in situ monitoring implies the reversible alloying of Sb only, while the stepwise increase of magnetic moment at room temperature is caused by the increase of Fe particle size on the first order.
Since most of the electrode materials are based on 3d transition metals with high electron magnetic moment, we believe in-situ electron magnetic measurements will bring valuable information on conversion or alloying mechanism to forecast more efficient electrodes.
[1] Operando Electron Magnetic Measurements in Li-ion Batteries, G. Gershinsky, E. Bar, L. Monconduit, D. Zitoun Energy and Environmental Science 2014, 7, 2012

Li₇La₃Zr₂O₁₂ (LLZO) is the prototypical example of the lithium-stuffed garnet-type solid lithium-electrolytes. At high temperature LLZO adopts a cubic structure and has a high ionic conductivity of 2 × 10^-4 S cm^-1. At low temperature, in contrast, LLZO is tetragonally distorted, which is associated by lithium ordering and a decrease in ionic conductivity to 1.6 × 10^-6 S cm^-1[1]. In both phases, the lithium ions occupy networks of tetrahedral and octahedral sites with identical topologies. It is therefore interesting that the tetragonal distortion is associated with a significant decrease in ionic conductivity, despite the close similarity in lithium-site networks.
We have used atomistic molecular dynamics with a first-principles-derived interatomic potential to study lithium transport in cubic- and tetragonal-LLZO. Analysing the spatial and temporal relationships between the motion of separate lithium ions reveals qualitatively different behaviour in the two phases, which explains the large observed difference in ionic conductivities. By considering chains of connected lithium movements, we find that lithium transport in t-LLZO is dominated by the concerted cyclic movement of groups of lithium ions with strongly favoured ion-populations. This cyclic motion is explained by the tetragonal lattice distortion, which makes the tetrahedral lattice sites non-equivalent. This mechanism is associated with strong negative correlations between individual ionic motions, which explains the extremely low ionic conductivity of the tetragonal phase. In contrast, chains of lithium movements in c-LLZO have logarithmically distributed ion-populations, allowing effective collective motion and charge displacement.

We have developed a lithium focused ion beam (FIB) instrument with probe sizes of a few tens of nanometers at energies from 500 eV to 6 keV and beam currents of a few picoamperes [1]. The lithium FIB can be used as a general purpose ion microscope and has already demonstrated high quality imaging using both secondary electrons and backscattered ions. The lithium FIB also has a unique ability to locally implant lithium into any material with nanoscale precision, making it a potentially powerful tool for battery materials research.
We will present the design and operation of the lithium FIB and a survey of the measurement possibilities, including measurements of local structural changes and high spatial resolution mapping of lithium ion transport pathways in prospective electrode materials. As an example of the imaging capabilities of the lithium FIB, we will show low energy surface sensitive imaging of new copolymerized sulfur-based nanocomposite cathodes. We will also show preliminary results of localized lithium implantation into thin amorphous and crystalline silicon membranes and micrometer-sized volumes of tin. Correlative analyses of the implanted areas with a combination of analytical scanning and transmission electron microscopy techniques reveals information about lithium diffusion in these materials and the structural, compositional, and phase changes that can occur on small length scales.
[1] K. A. Twedt et al., Ultramicroscopy142 (2014) 24-31

Microelectromechanical systems (MEMS) devices for sensors, microfluidics, wireless
communications, and optics require miniaturized or microbatteries with areal energy densities
exceeding 100 J/cm2, which is higher than that provided by current planar Lithium-ion (Li+)
batteries (< 5 J/cm2). Microbattery designs (e.g. three dimensional or 3D batteries) address this
challenge by using high surface area, non-planar electrode structures that increase areal energy
density, while also maintaining the short ion-transport distances necessary for high power
densities. A key obstacle to the development of such microbatteries is the synthesis of an
ionically conducting electrolyte, which must also be conformal, pinhole-free, and electronically
insulating. Unlike liquid electrolytes, conformal, solid-state electrolytes that uniformly “shrinkwrap”
non-planar electrode structures can minimize the volume devoted to the electrochemically
inactive electrolyte; increasing energy density to levels suitable for powering autonomous
devices. Liquid electrolytes further suffer from surface tension and de-wetting effects leading to
undesirable current shunting pathways in a battery. Finally, solid-state electrolytes with
thicknesses on the nanoscale can provide significantly shorter ionic transport times compared to
their micron-scale or liquid-state counterparts.
This work will demonstrate that initiated chemical vapor deposition (iCVD) can be used
to synthesize nanoscale polymer films of cyclic siloxane polymers with thicknesses in the 10 -
40 nm range. Such ultrathin films can be converted into ionic conductors through a solutionbased
Li+ doping process, referred to as lithiation. Ionic conductivity of the films was determined
by Electrochemical Impedance Spectroscopy (EIS) to be ~ 10-6 S/cm at room temperature. The
films were also demonstrated to be conformal over high aspect ratio nanowires with excellent
mechanical and chemical stability. Inductively Coupled Plasma Mass Spectroscopy (ICP-MS)
experiments revealed a Li+ content of 1 wt. % in these films and computational experiments were
used to demonstrate how Li+ interacts with the oxygen atom of the siloxane rings. Specifically,
we carried out standard Density Functional Theory (DFT) calculations on siloxane rings both
with and without coordinating Li+. The results of these calculations suggest that ion transport in
these materials may involve a collective mechanism in which the hopping of Li+ is assisted by
attractive and repulsive contributions of different siloxane rings. The studies detailed here
provide a basis for understanding the ion transport mechanisms that can be used to engineer
novel polymer electrolyte films whose conformality is critical for the emerging field of 3D
batteries. Finally, the solvent-free iCVD approach used to engineer these solid-state ionic
conductors is scalable and easily integrated with roll-to-roll processing.

Rechargeable lithium ion batteries, because of their high energy density, have conquered most of today&’s portable electronics and they stand as serious contenders for EV&’s and grid applications. Therefore, for this to happen, materials with higher energy densities while being sustainable, scalable, reliable and low cost must be developed. The challenges for chemists are enormous and this calls for new materials, new processes and new concepts. These different aspects will be addressed through this presentation.
Firstly, the strategy towards the design of novel high voltage polyanionic compounds involving either Li or Na-based fluorosulfates, sulfates and oxysulfates such as Li2CuO(SO4)2 will be described [1]. Turning to new concepts, we will show how discovery, via a chemical game approach[3,4]., of a reversible Li-driven anionic redox process among Li-rich layered oxides represents a transformational approach for creating advanced electrode materials for Li-based energy storage batteries[5]. Lasty, concerning sustainability our new findings regarding Na-ion chemistry which enlists novel materials design (4) and their implementation in full Na-ion cells will be shared as well.
1) G. Rousse, J.M. Tarascon, Chemistry of Materials, 26(1), 394, 2014.
2) M. Sathiya, G. Rousse, K. Ramesha, C.P. Laisa...and J.M. Tarascon J-M, Nature Materials, 12, 827, 2013.
3) M. Sathiya, A.M. Abakumov, D. Foix, G. Roussehellip; and J.M. Tarascon, Nature Materials 14, 230-238 (2015)
4) P.Rozier, S. Mariyappan A. Paulraj, D. Foix, T. Desaunay, PL Taberna, P. Simon, J-M. Tarascon, Electrochemistry Communications Vol 53, (2015)

For developing durable high-energy cathodes in lithium-ion batteries, adding a second or even third cation to form solid solution is becoming an effective strategy of stabilizing the structure and/or tailoring electrochemical properties. One notable example is the NMC, i.e. Li-Ni-Mn-Co-O system, which has been the subject to intense investigation. Nevertheless, the study of this system is still far from being complete due to the complexity of the phase space in this quaternary system. In addition to those known single phases (layered or spinel) there are a large number of composite phases and even new phases at the phase boundaries. Among the NMC phases, layered Ni-rich oxides are particularly interesting for the high capacity and low cost, but suffer from poor cycling stability. Herein, we report on developing new high-capacity Ni-rich cathodes with enhanced cyclability via tuning the stoichiometry and structure of the materials. Systemic investigation is made to the phase evolution of Ni-rich LiNi_1-x-yMn_xCo_yO₂ (x+y le; 0.2) under different annealing temperatures by ex-situ and in-situ synchrotron X-ray diffraction (XRD) measurements, coupled with quantitative structural analysis (through refinements). Structural characterization indicates an intriguing phase transition of LiNi_1-x-yMn_xCo_yO₂ from a spinel structure in a Fd3m symmetry at low annealing temperatures to a layered α-NaFeO₂-type structure with a R-3m space group at high temperatures; while determining all of the phases in such a complicated Ni-Mn-Co composition space has been challenging due to their strong dependence on the Mn and Co stoichiometry (i.e. x and y values). The in-situ XRD studies gain us access to the phase diagram in the confined Ni-rich region of the Ni-Mn-Co space (x+y le; 0.2), thereby enabling the design of synthetic protocols for preparing high-capacity LiNi_1-x-yMn_xCo_yO₂ cathodes with stabilized structure and reasonable cycling stability. This work sheds light on the fundamental relationship between crystal structure and electrochemical performance of Ni-rich cathodes for high-energy lithium-ion batteries. The work is supported by DOE-EERE under the Advanced Battery Materials Research (BMR) program, under Contract No. DE-SC0012704.

Transition metal fluorides are an appealing alternative to conventional intercalation compounds for use as cathodes in next-generation lithium batteries due to their extremely high capacity (3-4 x greater than current state-of-the-art). Cu based fluorides are particularly attractive due to the intrinsic high redox potential and extraordinarily high specific energy density. However, issues related to reversibility, energy efficiency and kinetics prevent their practical application. Here we report on the development of new ternary metal fluorides (M1_yM2_1-yF_x: M1, M2 = Fe, Cu), which may overcome some of theissues. By substituting Cu into the Fe lattice, forming the solid-solution Cu_yFe_1-yF₂, reversible Cu and Fe redox reactions were achieved with surprisingly small hysteresis (<150mV). This finding indicates that cation substitution may provide a new avenue for tailoring key electrochemical properties of conversion electrodes.
Some of the recent results on synthesis, structural and electrochemical characterization of the ternary metal fluorides will be presented. The Li storage/release mechanisms in Cu_yFe_1-yF₂, with comparison to that of the binary metal counterparts (i.e. FeF₂, CuF₂) [2-4],will also be discussed.This work is supported as part of the NorthEastern Center for Chemical Energy Storage, an EFRC Center funded by the U.S. DOE-BES, under Award Number DESC0001294, and also by DOE-EERE under the Advanced Battery Materials Research program, under Contract No. DE-SC0012704.[1] F. Wang, S-W. Kim, D-H. Seo, K. Kang, L. Wang, D. Su, J. J. Vajo, J. Wang, and J. Graetz. "Ternary metal fluorides as high-energy cathodes with low cycling hysteresis." Nat.Commun. 6, 6668 (2015); [2] F. Wang, et al., “Conversion Reaction Mechanisms in Lithium Ion Batteries: Study of the Binary Metal Fluoride Electrodes”, J. Am. Chem. Soc., 133, 18828 (2011); [3] F. Wang, et al., “Tracking Li Transport and Electrochemical Reaction in Nanoparticles”, Nat. Commun., 3, 1201(2012); [4]X. Hua, et al., “Comprehensive Study of the CuF₂ Conversion Reaction Mechanism in a Lithium Ion Battery”, J. Phys. Chem. C 118, 15169 (2014).

Structural changes take place in high-voltage lithium- and manganese-rich nickel-manganese-cobalt oxide (Li_1.2Mn_0.55Ni_0.15Co_0.1O₂) (LMR-NMC) cathodes because of the activation of the Li₂MnO₃ phase during first cycle. The changes are responsible for irreversible capacity loss during the first charging cycle and for voltage fade in succeeding cycles. Our study investigated the atomic rearrangements that occur in the structure of an LMR-NMC oxide cathode during the first charge-discharge cycle of a lithium-ion battery. The activation mechanism leading to structural transformation in the LMR-NMC structure is discussed in this presentation. By utilizing the multiple materials diagnostic techniques, such as neutron diffraction, temperature-dependent magnetic susceptibility, and atom probe tomography, this study unravels the key mechanistic features for Li₂MnO₃ activation during first charge cycle. Rietveld refinements of the neutron diffraction patterns collected at various states of charge provided cation/anion site occupancy factors and indicated the migration of lithium and transition metal ions from octahedral sites to available foreign sites. Magnetic susceptibility revealed that cation ordering (i.e., the presence of LiMn₆-like units) disappeared after the battery was charged to 4.8 V and that the ordering was retained (but suppressed) after it was discharged to 3.0 V. Atom probe tomography aided in quantifying the Li concentration as a function of state of charge and in mapping Li, Ni, Mn, Co, and O at subnanometer-scale spatial resolution.
Acknowledgement:
This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy for the Vehicle Technologies Office (VTO) Applied Battery Research Program (Program Managers: Peter Faguy and David Howell). Research conducted at ORNL&’s Spallation Neutron Source was sponsored by the DOE Scientific User Facilities Division, Office of Basic Energy Sciences. The tom probe tomography experiment was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. Part of this research (magnetic measurements) was supported by the DOE Basic Energy Sciences (BES), Materials Sciences and Engineering Division. LMR-NMC material was obtained from Argonne National Laboratory, in collaboration with Andrew Jansen and Bryant Polzin. We thank Dr. E Andrew Payzant and Dr. Ashfia Huq for useful discussion and help in neutron diffraction analysis.

Over the past few years, we have performed a survey of Li₂MO₃ materials with a wide variety of M compositions including mixtures of such elements as Ru, Ir, Sn, Fe, Te, Sb, Ti, and Mn. The purpose of this survey was to discover model systems that each represent idealized behavior for Li-rich oxides of high interest as next generation cathodes for Li-ion batteries. Herein, we will report on three key systems which we have studied in the past year, each of which add important aspects to our understanding of the role of oxygen during redox in Li-rich layered oxides: Li-Ir-Sn-O, Li-Fe-Sb-O, and Li-Fe-Te-O.
The Ir based samples constitute an important model system as they allow for the visualization of O-O peroxo-like dimers for the very first time with TEM, confirmed with neutron diffraction. This is a very important step to better grasp the source of the extra capacity seen in these materials. This work leads to the conclusion that the transition towards an S-curve seen in the electrochemical cycling is set into motion by the transformation of the oxygen sublattice caused by the reversible migration of the cations.
The Li-Fe-Te-O materials show no cationic redox whatsoever, instead nearly all capacity arises due to oxygen release during first charge. This system is therefore ideal to study the role of oxygen once released from the cathode and shows behavior detrimental to cell performance as reactions between the oxygen and the electrolyte take place.
Finally, Li-Fe-Sb-O is of interest as oxygen release and oxygen redox occurs at two distinct potentials and so it helps transition towards the complexity seen in Li-rich NMC materials where both processes are seen at the same potential. The impact of these studies upon the design of next-generation cathodes will be discussed in detail.

The cathode material xLi₂MnO₃#8729;(1-x)LiMO₂, where M is typically Ni, Co, Mn or a combination of these transition metals, has gained much attention due to its demonstrated high capacity (>200 mAh g^-1) [1] compared to other common cathode materials such as LiCoO₂ (sim;160 mAh g^-1), LiFePO₄ (sim;160 mAh g^-1) and LiMn₂O₄ (sim;130 mAh g^-1) [2]. However, this material has drawbacks such as the largely studied structural change, voltage fade and hysteresis. Although the material is commonly thought to attain its high capacity through, at least in part, the loss of oxygen from the Li₂MnO₃ component, the amount and effects of the oxygen vacancies are unknown and difficult to understand experimentally. Thus, this study takes a computational approach and studies the coupling effects of oxygen vacancies and lithium vacancies on stress and the diffusion of lithium within Li_2-xMnO_3-δ.
Density functional theory is used to determine the location of and stress induced by oxygen vacancies. Additionally, the location of and the stress induced by the lithium vacancies during the delithiation process, with oxygen vacancies present, was studied. The vacancies appear to be energetically favorable when formed near other vacancies and both vacancies appear to induce compressive stress into the Li₂MnO₃ structure. Additionally, when multiple vacancies, of both lithium and oxygen, are generated in the system the stress induced by the vacancies does not follow a linear combination rule with respect to the number of vacancies, suggesting that the vacancies interact or are coupled.
Due to this coupling, the diffusion of lithium was hindered by oxygen vacancies as well, as shown in both ab-initio molecular dynamics calculations and kinetic Monte Carlo simulations. The kinetic Monte Carlo method was used to determine how many oxygen vacancies can be present until the lithium diffusion is dramatically hindered.
1. Thackeray, M.M., et al., Li2MnO3-stabilized LiMO2 (M = Mn, Ni, Co) electrodes for lithium-ion batteries. Journal of Materials Chemistry, 2007. 17(30): p. 3112-3125.
2. Lithium-Ion Batteries: Advanced Materials and Technologies. Green Chemistry and Chemical Engineering, ed. S. Lee. 2012, Boca Raton, Florida: CRC Press. 406.

Herein, we report the effects of Fe and F substitutions on the electrochemical and structural changes of LiMn_1.45Ni_0.45Fe_0.1O₄ (LMNO-Fe) and LiMn_1.45Ni_0.45Fe_0.1O_3.9F_0.1 (LMNO-Fe-F) cathode materials using in-operando X-ray absorption spectroscopy (XAS). With the help of the specially designed electrochemical cell, LMNO-Fe and LMNO-Fe-F were cycled between 2.0 V - 5.0 V and XAS data were recorded at the Mn, Ni and Fe K-edges of these materials in the transmission mode for various states of charge and discharge.
In case of LMNO-Fe, the average valence states of Mn, Ni and Fe are expected to be 4+, 2+ and 3+, respectively. However, XAS analysis revealed a small amount of Ni³⁺ along with Ni²⁺ and consequently a small amount of Mn³⁺ along with Mn⁴⁺ in the pristine material. Between 3.5 V - 5.0 V, the electrochemical activity of the material is attributed to Ni²⁺/Ni⁴⁺ and Fe³⁺/Fe⁴⁺ redox reactions. However, a small amount of Mn³⁺ present in the pristine material also participates in electrochemical processes via a Mn³⁺/Mn⁴⁺ redox reaction. The excess Li inserted into the material by deep discharge of the cell down to 2.0 V delivers an additional capacity corresponding to the reduction of Mn⁴⁺ to Mn³⁺, while Ni remains electrochemically inactive. An increased proportion of Mn³⁺ in the material increases the distortion of MnO₆ octahedra by the Jahn-Teller effect, giving rise to the formation of domains of a Li₂M₂O₄-type tetragonal phase. Upon subsequent charging, these domains tend to revert back to the original cubic phase, however, with some hysteresis. The observed decline in the electrochemical performance of the material when cycled between 2.0 V - 5.0 V can be attributed to repetitive structural changes associated with the cubic to tetragonal phase transition.
In case of LMNO-Fe-F, the presence of F stabilizes Mn⁴⁺. Thus, the major charge compensation mechanism between 3.5 V - 5.0 V involves Ni²⁺/Ni⁴⁺ and Fe³⁺/Fe⁴⁺ redox reactions. Upon deeply discharging the cell down to 2.0 V, no notable capacity corresponding to the reduction of Mn⁴⁺ to Mn³⁺ was observed. Quite consistently, no major structural distortions corresponding to the Jahn-Teller effect were observed. Unlike LMNO-Fe, seemingly inferior electrochemical performance of LMNO-Fe-F in the beginning becomes better and stable upon cycling. The reasons for this contrasting behavior of LMNO-Fe and LMNO-Fe-F will be discussed in the context of the F-substitution.

Spinel cathode materials have attracted much attention for applications of lithium ion batteries in electrical vehicles (EVs) and hybrid electrical vehicles (HEVs). The most interesting spinel cathodes are LiMn2O4 and LiNi0.5Mn1.5O4 due to their environmental friendliness, inexpensiveness and good electrochemical performance.
However, the main issue hindering these materials from practical applications is the capacity degradation during electrochemical cycling, particularly at high temperature. Recently, our group as well as many others reported that the capacity degradation in spinel and other cathode materials is closely associated with its structure transformation during cycling, in particular the surface structure, which is clearly observed by advanced electron microscopy techniques. It was further suggested that the structure transformation is associated with oxygen loss, however the exact underlying mechanism is not fully understood due to such phenomena occurs only on the several nanometers of the surface area. In this work we investigated relationships between the structure (local and average) and electrochemical performance of spinel LiMn2O4 and LiNi0.5Mn1.5O4 in detail by controlling the degree of oxygen content in these materials. With increasing amount of oxygen loss, both of these materials showed an increased degree of migration of transition metal (TM) ions to form a Mn3O4-like and a rocksalt-like structures, as observed by STEM (local structure) and XRD (average structure). The reversible capacity of these materials showed a decrease with increasing amount of oxygen loss and associated degree of structure transformation, which is due to the lowered lithium kinetics caused by occupation of TM ions on the lithium migration pathways. The most interesting observation is that the capacity retention of oxygen nonstoichiometric LiMn2O4 is very different from that of oxygen nonstoichiometric LiNi0.5Mn1.5O4. The later showed an excellent capacity retention even at elevated temperature (55 oC) whereas the former exhibited fast capacity degradation. The capacity degradation in these materials at high temperature is mainly attributed to the dissolution of Mn. However for oxygen nonstoichiometric LiNi0.5Mn1.5O4, the presence of migrated Ni at the lithium site mitigates the dissolution of Mn and consequently improve the capacity retention at high temperature. Our work not only sheds light on understanding of the relationships between structure transformation, oxygen loss and electrochemical performance of spinel cathode materials but also suggest that to improve the electrochemical performance at high temperature, it is essential to stabilize the TM ions on the surface via doping or coating.

It is vital to reduce the cost of lithium-ion batteries (LIBs) and the environmental impact associated to their mass production for electric vehicles (EVs) application. The current LIBs cost for all EVs is between $325-$500/kWh and is 2-4x of the target cost set by EV Everywhere ($125/kWh). Majority of the battery cost comes from materials and associated processing. This presentation will discuss manufacturing LIB electrodes through aqueous processing, which induces significant cost reduction and is more environmental benign. The talk will include 4 sections:
Analysis of cost reduction from aqueous processing
how to enables aqueous processing for LiNi_0.5Mn_0.3Co_0.2O₂ (NMC532) cathodes for desired performance
Scale-up in NMC532 fabrication
Excellent results from large format pouch cells with both NMC532 and graphite electrodes fabricated via aqueous processing
Acknowledgement:
This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy for the Vehicle Technologies Office's (VTO) Applied Battery Research Program (Program Managers: Peter Faguy and David Howell).

Li-ion battery technology has advanced significantly in the last two decades. However, future energy storage demands will require safer, cheaper and higher performance electrochemical energy storage. While the primary strategy for improving performance has focused on electrode materials, the development of new electrolytes has been overlooked as a potential means to revolutionize electrochemical energy storage. This work explores a new class of ceramic electrolyte based on a ceramic oxide with the garnet structure. The garnet, with the nominal formulation Li₇La₃Zr₂O₁₂ (LLZO), exhibits the unprecedented combination of high ionic conductivity (~1mS/cm at 298 K) and chemical stability against metallic Lithium. This presentation will discuss fundamental and applied aspects involving the development of garnet-based LLZO electrolyte. The purpose of the fundamental activities is to correlate the atomic structure with transport data to hypothesize strategies for further increasing the ionic conductivity. The applied aspects will include DC cycling data to assess the compatibility between metallic Lithium anodes and LLZO.

Li metal is the anode with the highest possible capacity for Li batteries, but it cannot be used for practical applications due to the high reactivity and dendritic growth. While the integration of the Li₇La₃Zr₂O₁₂ (LLZO) solid electrolyte holds great promise for addressing these problems, its interaction with Li metal is poorly understood, which prevents the rational interface optimization. Presently, there are no conclusive studies on this subject, because the examination of the LLZO/Li interface is challenging. For most interfacial characterization techniques, the possible evaporation/overspray of Li metal during sample preparation cannot ensure that the interface remains intact for observation. In the present study, this difficulty was overcome by using in-situ transmission electron microscopy (TEM); instead of preparing an interfacial specimen from Li-coated bulk LLZO, the LLZO-Li contact was made in-situ within the TEM, thereby preventing the creation of artifacts associated with sample preparation. In this way, the interactions between LLZO and Li metal was unambiguously revealed. The interface was observed to exhibit distinct structure and chemistry from the bulk LLZO. Combined with theoretical calculations, such characteristics were found to correlate excellently with the measured interfacial ionic conductivity. This discovery unraveled the elusive microscopic origin of the LLZO/Li interfacial behavior, which is an important step in realizing durable cycling of the high-capacity Li metal anodes.

Many new types of high energy Li batteries may require a solid Li-ion conducting electrolyte. The major requirements for the solid Li-ion electrolyte are; high Li-ion conductivity, low electronic conductivity and good chemical/electrochemical stability. However, in many applications adequate mechanical properties are also relevant. For example, an electrolyte with a high shear modulus is required to prevent dendrite penetration when using a Li anode. At present information on the mechanical properties of a promising solid Li-ion conductor; Li₇La₃Zr₂O₁₂ (LLZO) is lacking. It is therefore the purpose of this talk to present some of the first information on the room temperature and elevated temperature mechanical behavior of LLZO. These include: hardness, elastic modulus, fracture strength, fracture toughness and thermal expansion. The results will compared to existing data for other solid Li-ion conductors and theoretical predictions. In addition, methods to improve the mechanical behavior of LLZO while retaining high ionic conductivity will be discussed.

Li-ion battery technology has advanced significantly in the last two decades. However, future energy storage demands will require safer, cheaper and higher performance electrochemical energy storage. While the primary strategy for improving performance has focused on liquid electrolyte Li-ion battery chemistries, this work supports the development of solid-state batteries employing Li metal anodes. One approach to stabilize Li anodes entails the replacement of a liquid with a solid electrolyte. Recently, the ceramic electrolyte, Li₇La₂Zr₃O₁₂ (LLZO) cubic garnet, has shown promise owing to its unique combination of properties such as high Li-ion conductivity (1 mS/cm at room temperature) and electrochemical stability between 0-6 V vs. Li/Li⁺. While understanding and characterizing these properties has been intensely studied, little is known about the maximum sustainable current density in LLZO. The purpose of this work is to present one of the first studies to evaluate the stability of the Li-LLZO interface as a function of current density. Specific attention is given to LLZO phase purity, density, and surface preparation. The LLZO was densified using a rapid densification process achieving > 97% relative density, with < 10% grain boundary resistance; effectively consisting of an ensemble of single LLZO crystals. DC cycling, comprehensive electrochemical impedance spectroscopy, x-ray photoelectron spectroscopy, and atomic force microscopy were used in a concerted effort to determine the reactions that govern the maximum sustainable current density of the Li-LLZO interface.

Composites of ceramic and polymer lithium electrolytes provide a means to tailor both the mechanical properties and ion transport properties of the electrolyte to enable batteries with a high energy lithium anode. Fabrication and characterization of the PEO-based composites with high ceramic loading will be presented. These will be compared with layered structures designed to extract the interface resistance for ion transport across a ceramic-polymer junction.
Acknowledgement: Research has been supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy through the Advanced Battery Materials Research (BMR) Program.

Replacing the flammable liquid electrolytes and enabling safe cycling of high energy lithium anodes, solid electrolytes and solid state batteries have been pursued as one of the approaches for the next generation of energy-dense, safe batteries. However, the use of solid electrolytes in a battery system is challenged by grand problems of charge transfer and mass transport in solids and through the solid-solid interfaces. This talk presents the discoveries of synergistic effects for ion transport in solid state batteries from three aspects: (1) at the interface of lithium metal anode and solid electrolyte; (2) within the matrix of a mixed oxide and sulfide solid electrolytes; and (3) at the interface of cathode and solid electrolytes. Three specific examples will be discussed in details to elaborate the ion transport phenomena in solid state batteries.

LiFePO₄ has not generally used for all-solid-state lithium ion battery, because it is difficult to fabricate the high performance battery with theoretical capacity and low resistance due to low electronic conductivity and low-rate lithium ion diffusion coefficient of LiFePO₄. N. Ohta et al. reported that LiFePO₄ with Nd-riched amorphous layer having high electronic conductivity performed 110 mAhg^-1 corresponding to 65% of the theoretical capacity of LiFePO₄ [1]. In this study, we developed the LiFePO₄ electrode having theoretical capacity and studied the interfacial reaction mechanism at the interface of electrode/electrolyte.
Fine particles of carbon coated LiFePO₄ and sulfide solid electrolyte and carbon were mixed to prepare positive electrodes. A triple-layer pellets consisting of the positive electrode, sulfide solid electrolyte and mixture of Li₄Ti₅O₁₂, sulfide solid electrolyte and carbon as a negative electrode was pressed under 400 MPa. The charge/discharge cycles were performed between 0 and 2.5 V at 60°C. The initial charge of the battery showed a capacity of 147 mAhg^-1 around 1.8 V corresponding to theoretical redox potential of LiFePO₄, while there were two plateaux in the next discharge. First plateau had a capacity of 20 mAhg^-1 at 1.8V and second plateau had a capacity of 104 mAhg^-1 around 1.0 V, which is not theoretical redox potential of LiFePO₄. We analyzed this phenomenon in detail with several analytical equipment. As a result of XRD measurement of positive electrode recovered after initial charge and initial cycle, the phase transition of LiFePO₄ occurred during initial discharge. It indicates that lithium ions were extracted from LiFePO₄ at two plateaux in the discharge. From the TEM-EDX analysis, it was observed that there were two-regions, surrounding LiFePO₄ and near solid state electrolyte at the active materials/sulfide solid electrolyte interface. One region near solid state electrolyte consisted of almost Fe and S, whereas Fe concentration at another region surrounding LiFePO₄ was lower than LiFePO₄ particle. It is indicated that two SEI phases consisting of iron sulfide and Fe-poor phosphate could be formed. The initial charge capacity was always larger than discharge, and a discharge capacity at the plateau of 1.0 V decreased when the upper limit of charge potential was decreased to 2.2 V. It is assumed that iron ions of LiFePO₄ diffused into sulfide solid electrolyte and reacted electrochemically with sulfur ions during initial charge. In the discharge process, lithium ions were firstly inserted into iron sulfide at 1.0 V [2], and then lithium ions were inserted into LiFePO₄ at 1.0 V instead of 1.8 V. We predict that a potential of Li insertion into LiFePO₄ is determined by the redox potential of iron sulfide surrounding LiFePO₄ because LiFePO₄ does not contact directly with sulfide solid electrolyte.
[1] A. Sakuda et al., Chem. Lett., 41, 260-261 (2012)
[2] J. Choi et al., J. Power Sources, 163, 158-165 (2006)

Poly(sulfur-random-(1,3-diisopropenylbenzene) (poly(S-r-DIB)) copolymers synthesized recently via inverse vulcanization represent an emerging class of novel electrochemically active polymers, which are capable of realizing enhanced capacity retention as cathodes for Li-S batteries [1]. These sulfur polymer cathodes exhibit an initial discharge capacity of 1225 mAh/g and high reversible discharge capacity and cycle stability (1005 mAh/g at 100 cycles) and lifetimes of over 500 cycles [2]. DIB in this case serves as a multifunctional cross-linking agent responsible for the generation of lithiated organosulfur products Li₄(S_x)₄-DIB (xasymp;8), which effectively prevent the irreversible deposition of insoluble lower Li polysulfides generated during cycling, and improve the long term battery performance. To explore the origins of the enhanced capacity retention, we have employed a suite of high-spatial resolution analytical electron microscopy techniques combined with multivariate statistical analysis, tomography and electrical conductivity measurements to analyze multiscale 3D structural architectures as well as porosity, compositional distributions and bonding in composite cathodes produced when poly(S-r-DIB) copolymers with DIB contents varying from 0 % to 50 % by mass are blended with conductive carbon black particles [3]. Furthermore, we use valence electron energy-loss spectroscopy in scanning transmission mode to probe phase compositions and mechanical properties of the poly(S-r-DIB) cathodes. Our study suggests that the incorporation of the DIB into the sulfur copoloymers drastically enhances the molecular level compatibility and interfacial contacts between the poly(S-r-DIB) active material and onion-like carbons forming random electrically conductive percolation networks within the composite. As a result, this creates a unique hierarchical cathode morphology that is electrochemically and mechanically more robust, thus leading to both increased specific capacity and enhanced cycle life over traditional Li-S batteries.
[1] W.J. Chung, et al., Nature Chem.5 (2013), 518-524. [2]. A.G. Simmonds, et al., J. ACS Macro Lett. 3 (2014), 229-232. [3] V.P. Oleshko et al., MRS Comm. (2015) in press.

Lithium superionic conductors promise the potential to replace organic liquid electrolytes and thereby improve safety of the next-generation batteries. Among the electrolytes proposed, the sulphide system is a candidate for practical batteries because of their high ionic conductivity. For example, the Li₁₀GeP₂S₁₂ (LGPS) phase exhibits high bulk conductivity of over 10^-2 S cm^-1 at room temperature and is promising for applications requiring batteries with high powers and energy densities. On the other hand, material variations are key issues for the practical use of these solid electrolytes, which provide suitable combinations of the electrodes and the electrolyte. To improve the materials variety, the cation substitution systems with the LGPS type structure were examined, and their phase diagram, structure and ionic conduction were studied. In these substitution systems, the conductivities and stabilities varied as a function of the changing cations. The relationship between ionic conduction, structure, and lithium concentration is discussed based on the structural and electrochemical information for substitution systems. All solid-state batteries using these electrolytes were examined and the effects of conductivities and electrochemical stabilities for the electrolytes on the battery characteristics will be discussed.

Modern battery technology is limited by the use of organic liquid electrolytes, which are known to have considerable safety and stability issues. Fast solid-state inorganic conductors offer a path toward safer batteries with high energy density, but apart from a few material classes, the inorganic solid-state space remains mostly unexplored. Computational approaches using density functional theory (DFT) have been proven to be successful for the screening and discovery of electrode materials, but have not been used for screening solid electrolytes. Unlike electronic conductivity, which can be estimated from the electronic structure, the physiochemical factors that regulate ionic conductivity are poorly understood. We present relationships between the ionic conductivity and several potential structural descriptors, such as the size and dimensionality of ion-conducting pathways, void fraction, Li-concentration, sensitivity to volume, etc. We use these relationships, obtained from automated ab-initio molecular dynamics simulations (AIMD), to develop strategies for rapid screening and deploy them on a dataset of 1500 distinct crystal structures.
Our results indicate that there exists a sharp threshold channel size, below which there is no motion of Li-ions. We have also found that almost all materials that show conductivity have a three dimensional channel of the threshold size. Conductivity has also been found to be sensitive in some cases to slight changes in volume. A 10% reduction in volume leads to a decrease in conductivity in a large fraction of materials and a similar volume increase causes numerous non-conducting materials to become conducting. We also show that it is possible to change the conductivity by altering the concentration of Li ions present in the material. Using these results, we have developed a pre-screening methodology that dramatically reduces the set of candidate materials. By accepting only three-dimensional conductors, and using conservative thresholds on the band gap and the channel size, we can reduce the size of dataset by 50% before performing a simulation. Short AIMD simulations constitute the next level of screening, and though the obtained conductivity is not converged, it is sufficient to differentiate between conductors and non-conductors. We test the non-conducting materials by varying volume and Li-concentration, and eliminate those that are immobile. The resulting dataset is then used for more detailed investigations of transport mechanisms. We show that this approach can successfully rediscover known ionic conductors. We expect that these results are a vital first step towards accelerating the discovery of new solid-state electrolyte materials.

Surface (and interfacial) chemistry can be found in myriad environments of scientific significance including biological membranes, ocean and atmospheric chemistry, and electrochemistry. In fact, molecular behavior on the surface and at the interface can be drastically different than their bulk counterpart. Scanning electrochemical microscopy (SECM) is a powerful tool to probe various surface and interfaces in wide ranging applications and determining charge transfer kinetics, imaging electrochemical reactions and topography, as well as fabricating microstructures. The most significant advantage offered by SECM is its capability of probing chemical information of interfacial electron and ion transfer processes at the solid/liquid and air/liquid interfaces which is the focus of the present study. A constant potential is applied to the electrode (and the substrate in electrolyte) to drive an electrochemical reaction of one redox species (known as the mediator) in a bulk solution and to probe the surface of certain thickness of graphene-based hybrids with conducting polymers and carbon nanotube multilayers. The 2D and 3D micrograph, cyclic voltammograms (CV), and SECM approach curves (current versus tip-substrate distance) were chosen to characterize the single bilayer of graphene/conducting polymer and graphene/carbon nanotube as supercapacitor cathodes to probe the ion adsorption and map highly reactive (‘hot spots&’) surface sites. The SECM setup has a resolution and repeatability of ~40 nm and can locate and relocate areas of interest precisely after a coarse image. SECM approach curves as well as two dimensional scans elucidated the existence of regions of different conductivity (semiconducting/insulating vs. conducting) and the imaging data is analyzed in terms of defects density within the probes regions. We acknowledge WKURF and NSF KY EPSCoR for the financial support.

Rechargeable multivalent ion batteries have been vigorously studied as alternatives of current lithium ion battery technologies due to their high theoretical volumetric capacities. However, realizing multivalent ion storage with as fast kinetics as that of lithium is challenging. The multivalency of the insertion ions causes strong electrostatic interactions between multivalent insertion ions and atoms in the host framework. For this reason, the current state-of-the-art, Chevrel phases and dicalcogenides, only achieved the multivalent ion storage due to the moderate polarity of sulfur or selenide in the host. Therefore, expanding the range of materials that have potentials for multivalent ions intercalation with fast kinetics is an important subject.
Hydrated titanium phosphate, Ti(HPO₄)₂#8729;H₂O, is a two-dimensional structure made up of PO₃(OH) tetrahedra and TiO₆ octahedra. The structure incorporates interlayer water molecules that involve hydrogen bonding with acidic protons on the phosphate groups. These protons can be exchanged with metal cations such as Li⁺, Na⁺, and Ca²⁺. In addition, the interlayer space can be tuned by organic molecules intercalation such as alkyl diamines. Ti(HPO₄)₂#8729;H₂O, thus, is an attractive candidate material for multivalent ion storage due to its interlayer water and the amenable interlayer properties with ion exchange and intercalation. In this work, Ti(HPO₄)₂#8729;xH₂O (x = 0 to 1) was synthesized by dissolving titanium metal in phosphoric acid followed by hydrothermal treatment. While dehydrated form, Ti(HPO₄)₂ did not intercalate ions, hydrated Ti(HPO₄)₂#8729;H₂O intercalated a various monovalent and divalent ions in aqueous solution. This result reveals an important role of the interlayer water which can shield the electrostatic interactions between insertion ions and phosphate groups in the host. Experimental details and our findings will be presented.

Water-based activated-carbon (AC) double-layer capacitors (DLC) are promising low-cost devices for providing high power densities, since water is a low-cost and non-toxic material. Aqueous electrolytes do not require specific manufacturing conditions, and have relatively high conductivity. However, the energy density of aqueous-electrolyte DLCs is relatively low because of the limited cell voltage. Specific energy can be further enhanced by using asymmetric configurations, called hybrid double-layer capacitors (HDLCs). For these, one carbon electrode is replaced by electrode materials that store charge via rapid and reversible pseudo electron-exchange reactions on or near the electrode surface in addition to the electrical-double-layer capacitance. The exact mechanism is not well known; however, it is commonly explained in the literature, as adsorption of cations on and near the surface of the particles of the electrode. Thus, the term “pseudocapacitance” is used to describe their charge-storage mechanism. The HDLC designs also circumvent the main limitation of aqueous electrolytes by extending their operating-voltage window beyond the thermodynamic water limit of 1.2V to operating voltages higher than 1.5V. Thus, HDLCs offer five times, or more, higher energy density than do DLCs. We will report on the effect of anions and cations on the parameters of such HDLCs, including capacitance, energy and power density, and durability. These vary (depending on the type of the electrode and the ions) over the range of 30-500F/g, 1-20 Wh/kg of active mass and 0.1 to 5kW/kg of active mass. These HDLCs were cycled for many thousands of stable cycles over the voltage range of 0.1 to 1 and 0.1 to1.5V.

The development of innovative processes leading to reduced electrode production cost and environmental pollution is needed to enable lithium ion batteries for automotive and other large-scale applications. Water-soluble binders could enable greener and cheaper Li-ion battery manufacturing by eliminating the standard fluorine-based formulations and associated to that, reduced use of volatile organic compounds. The main issue however is that water-based dispersion are difficult to stabilize requiring additional processing complexity and additives.
Herein, we will show that mechanochemical conversion of a regular PEDOT:PSS water solution produces a supramolecular hydrogel that meets most of the requirements as binder for lithium battery electrodes. The conversion is realized by ball milling in the presence of metallic Iron. Released Fe-ions are complexed by sulfonate groups of the PSS chain resulting in a stable coordination network. Slow corrosion of Fe combined with continuous milling produces a homogeneous polymer-metal framework that incorporates all the originally contained water (of up to 98% by mass). The supramolecular hydrogel has suitable rheology (viscosity of 2000 to 4000 mPas) to be applied as a lithium battery binder. When including also the electrode constituents (anode and cathode materials, conductive carbon and additives) the mechanochemical processing induces in situ gelation as well as fine mixing of the components. The corresponding battery slurries are stable, show no phase segregation (over several months) and produce highly uniform thin (25 mu;m) to very thick (500 mu;m) films in a single coat, with no material migration even upon slow drying.
Cyclic voltammetry confirmed that the PEDOT:PSS gel formulations have good anodic stability (up to 4.5 V vs. Li/Li⁺). The cathodic stability is also demonstrated with first cycle irreversible processes attributed to the redox on the PEDOT chain. Physicochemical characterization confirmed that the electrical conductivity is preserved upon metal-induced gelation enabling higher power in the fabricated electrodes. Active materials such as Si, Sn, graphite, Al (negatives) but also LiCoO₂, LiMn₂O₄, LiFePO₄ and carbon-sulfur composites (positives) have been successfully tested in half and full cells. The electrochemical analysis demonstrated that improved power performances with similar to enhanced cycling stability was obtained using PEDOT:PSS gel binders when compared to standard aqueous binder formulation (including pristine PEDOT:PSS solution).
Overall, the mechanochemically synthesized PEDOT:PSS metal-ligand supramolecular hydrogels, when applied as binder for lithium-ion batteries, show net advantages given the simple aqueous processing, excellent dispersion stability, preserved electrical conductivity, enhanced structural integrity and adhesion of the prepared electrodes as well as improved power and cycling stability performances[1].
[1] A. Vlad et al., (2015) submitted.

All solid-state batteries (ASSB) are promising concepts for energy storage, as they exhibit inherent safety and long cycle life. For high energy densities, high capacity and low potential anode materials like lithium metal are preferred. Due to the highly reducing potential of lithium metal, the electrochemical stability of the interface between lithium metal and solid ion conductor plays a crucial role for the performance and function of all ASSB.
The contact of lithium metal and the solid ion conductor can lead to three different types of interfaces [1]: For the first case, both form a simple sharp two-dimensional interface, as the solid ion conductor does not react with the lithium metal. In the second and third case both materials react and form three-dimensional interphases, which differ in their physical and chemical properties. The second case is described as mixed-conducting interphase [2] (MCI) as the reaction products are electronically conductive, which may lead to self-discharge. In addition, the electronic and ionic conductivity of the interphase induces a steady growth of the MCI. In the third case, the lithium metal and the solid ion conductor react and form a non-growing interphase, as the products are electronically insulating and are limiting the film growth.
The investigation of interfaces and interphases in electrochemical cells is mainly conducted by cyclic voltammetry and less often by impedance techniques. Due to the inaccessibility of the buried interfaces microscopic and surface-sensitive techniques like photoelectron spectroscopy (XPS) are therefore often of limited use.
Here, we report an in situ technique to investigate the formation of interphases and interfaces by XPS [1]. The key concept is to use the internal ion gun in a standard lab-scale photoelectron spectrometer to deposit thin metal films (e.g. lithium) on the sample surface. The reaction between metal and solid electrolyte is then studied directly after deposition by XPS.
The experimental approach will be described and prospects and pitfalls will be discussed. The setup provides the opportunity to deposit virtually any metal. Potential applications of the method include the enhancement of the electronic conductivity in situ, studies of contact properties of materials (including reactions) and analysis of emission depth distribution functions.
As an example for the strength of the method, the formation of an interphase on a Li₂S-P₂S₅ compound (Li₇P₃S₁₁) in contact with lithium metal [3] will be shown and it will be discussed whether an MCI or an SEI is formed.
[1] Wenzel, S.; Leichtweiss, T.; Krueger, D.; Sann, J.; Janek, J. submitted to Solid State Ionics.
[2] Hartmann, P.; Leichtweiss, T.; Busche, M. R.; Schneider, M.; Reich, M.; Sann, J.; Adelhelm, P.; Janek, J. J. Phys. Chem. C 2013, 117, 21064.
[3] Wenzel, S.; Weber, D.; Leichtweiss, T.; Sann, J.; Janek, J. in preparation.

Solid solutions of Li₂MnO₃ and LiMO₂ (M = Mn, Ni, Co) are under development for high-voltage, high-energy-density cathodes for next-generation lithium-ion batteries. The LiMO₂ endmember is a standard NMC intercalation cathode, but the Li₂MnO₃ endmember cycles poorly and the mechanism of its electrochemical activity is controversial. In this study, Raman spectroscopy and mapping are used to follow the chemical and structural changes that occur in Li₂MnO₃ during electrochemical cycling. Both conventional composite cathodes cast from a slurry and thin film cathodes are studied as a function of voltage and cycle number. Thin films have similar electrochemical properties as electrodes prepared from slurries, but enable spectroscopy of uniform samples without carbon additives. First-principles density functional theory is used to calculate the phonon spectra and identify the Raman active modes. Based on the calculations of phonon spectra for pristine Li₂MnO₃ and structures with Li vacancies, we discuss the origin of Raman active peaks observed during the electrochemical cycling. The spectral changes correlate well with the electrochemical behavior and support a mechanism whereby capacity is lost upon extended cycling due to the formation of new manganese oxide phases. A principle component analysis is used to isolate and identify the new phases which form during charge.
Acknowledgements
This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy. H.D. and V.R.C. were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, and the Office of Science Early Career Research Program (V.R.C.). This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Si has been regarded as one of the most promising anode materials in Li-ion battery because it have natural abundance, environmental friendliness and extremely high theoretical capacity (4200mAh/g in Li_4.4Si). But, it is very difficult to use Si in industrial application due to tremendous volume change (about 400%) during the lithiation/delithiation process and formation/destruction of solid electrolyte interface (SEI) film on the Si surface. Because of these critical disadvantages, the capacity retention after just 5 cycles is below 200mAh/g. To solve these problems, various structure including nanowire, nanotube, hollow sphere and carbon coated composite have been reported. However, the capacity stability problem is still remained. Meanwhile, MoS₂ has been received a lot of attention because it&’s layered structural stability similar to graphite and low cost. Herein, we report Si@MoS₂ yolk-shell structure with higher capacity and stability for anode in Li-ion battery. The yolk-shell structure was synthesized using thin polydopamine layer on the SiO₂ template and MoS₂ was formed by hydrothermal method. Various York-shell structures were formed by controlling the thickness of space size and polydopamine, and MoS₂ thickness. Structure and performance of Si@MoS₂ yolk-shell electrode was evaluated. Si@MoS₂ yolk-shell showed more than 1300mAh/g with good stability.

Lithium metal anodes for secondary batteries have been a major goal of the battery community for many years owing to a large capacity of 3,680 mAh/g and the lowest theoretical anode potential. However stability, cyclability, efficiency, and safety issues have prevented their commercialization.¹ Li metal anodes with long cycle life and improved stability would enable a range of next-generation battery technologies including Li-Sulfur and Li-air.²
This work demonstrates that ultrathin Atomic Layer Deposition (ALD) treatments (less than 30 ALD cycles of Al₂O₃) directly on lithium metal anodes dramatically suppress dendrite formation and excessive SEI formation.³ The reduced dendritic character of the plated lithium leads to significant improvements in cell performance, doubling cell life under both extended cycling (1,259 cycles) and galvanostatic deep discharge (75% of electrode thickness) at a current density of 1mA/cm² in Li/Li symmetric coin cells before failure occurs. An optimum coating thickness of 20 ALD deposition cycles was revealed above and below which coatings are less effective at preventing these failure modes, demonstrating the importance of highly reproducible and scalable deposition processes. The precise control of ALD affords the ability to tune and engineer interfaces at the atomic scale, a previously unattainable means of modifying Li metal anodes.
Due to the highly reactive nature of Li metal, a glovebox-integrated ALD tool was used to allow electrode preparation/cleaning, ALD treatment, and cell assembly all without air exposure. The electrodes were characterized with x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) before and after failure in order to study the mechanism behind improved performance. XPS reveals that the Al-content on the electrode/SEI surface decreases during cycling, but the improved morphology and dendrite resistance continues to failure, indicating that the initial charge-discharge cycles are of great importance to cell life. SEM analysis shows stark differences in morphology both during early cycles and after failure. EIS was used to decouple the effects of different interfaces in the cell, and the improved performance is attributed to a more homogeneous of ion flux across the SEI/electrode interface as a result of the ALD treatment. These results demonstrate both an applied synthesis approach to prevent dendrite formation in Li metal, while also providing valuable fundamental insight into the nature of the interfacial contributions to Li metal failure.
References
¹ D. Aurbach, E. Zinigrad, Y. Cohen, and H. Teller, Solid State Ion. 148, 405 (2002).
² K.G. Gallagher, S. Goebel, T. Greszler, M. Mathias, W. Oelerich, D. Eroglu, and V. Srinivasan, Energy Environ. Sci. 7, 1555 (2014).
³ E. Kazyak, K. N. Wood, N. P. Dasgupta, Submitted (2015).

Silicon having high specific capacity of 4200 mAh/g is a potential candidate for anode material in Li ion battery. However, it can not be used practically due to its huge volume change during lithiation and delithiation. To protect Si anode, carbon based materials have been used experimentally as an artificial solid electrolyte interface (SEI) on the top of it. In order to maintain the high performance, efficient Li kinetics is required in an artificial SEI. Here, theoretically we investigated Li kinetics in bulk FCC fullerene by scanning the potential energy surface. Li diffuses along the path through tetrahedral and octahedral voids alternatively with an energy barrier of 0.62 eV at octahedral void. This energy barrier reduces further under the application of hydrostatic pressure upto 17.7% volume strain leading to two orders of magnitude gain in diffusivity compared to unstrained case [1]. This lowering of barrier can be attributed to the charge transfer triggered by strong interaction between fullerene and Li. Further enhancement of pressure leads to inter-fullerene bond formation that makes Li diffusion barrier high.
1. D. Das, S-S. Han, K-R. Lee, and A. K. Singh, Pressure induced manifold enhancement of Li-kinetics in FCC fullerene, Phys. Chem. Chem. Phys. 16, 21688 (2014)

In “Beyond Li-Ion Battery” concepts, e.g., Li/air, Li/sulfur, and Li-flow batteries, Li-metal anodes are used to replace graphite anodes. Li-metal has an extremely high theoretical specific capacity (3860 mA h g^-1), low density (0.59 g cm³) and the lowest negative electrochemical potential (3.04 V vs. the standard hydrogen electrode), nevertheless safety issues related to the high reactivity of Li-metal with liquid electrolytes have stymied commercialization of rechargeable high energy batteries with lithium metal anodes.
Li₇La₃Zr₂O₁₂ (LLZO) garnet and variants,¹ with high Li-ion conductivities and chemical/electrochemical stability, in particular its stability against Li-metal, are exceptionally well suited to be used as protecting layer to enable Li-metal based battery concepts.
Despite the promising prerequisites of LLZO, the fabrication of LLZO providing simultaneously high ionic conductivity, and low interfacial resistances (versus electrode interfaces), remains challenging.
However, we prepared cubic Li₇Al_0.2-xGa_xLa₃Zr₂O₁₂ garnets,² with x = {0, 0.05, hellip;, 0.1} by solid state sintering methods and obtained LLZO samples with ionic conductivities and interface area specific resistances (ASR) of about 10^-3 S cm^-1 and 20 Omega; cm², respectively. The samples were characterized by means of X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), Raman spectroscopy, neutron powder diffraction (NPD), and impedance spectroscopy, using blocking (Ti/Pt), and ohmic electrodes (Li).
[1] Murugan, R.; Thangadurai, V. Weppner, W. Fast Lithium Ion Conduction in Garnet-type Li₇La₃Zr₂O₁₂: Angew. Chem. Int. Ed. 2007, 46, 7778.
[2] Rettenwander, D.; Langer, J.; Schmidt, W.; Arrer, C.; Harris, K.; Terskikh, V.; Goward, G.; Wilkening, M.; Amthauer, G. Site Occupation of Ga and Al in Stabilized Cubic Li_7-3(x+y)Ga_xAl_yLa₃Zr₂O₁₂ Garnets As Deduced from ²⁷Al and ⁷¹Ga MAS NMR at Ultrahigh Magnetic Fields:Chem. Mater.2015, 27, 3135.

Today lithium-ion batteries still have insufficient energy density or life-time for use in electric vehicles and suffer serious safety problems. Due to the rich chemistry of Lithium, great progresses have been made in this kind of technology by developing advanced materials and innovative strategies to further overcome such issues. Significant improvements in the electrode kinetics, control of the damaging strain and reaction pathways were also reached by switching to nanostructures, which are differently possible by means of the continuous progresses of nanotechnology.
Zinc oxide, ZnO, is potentially a promising anode system, alternative to Li metal, because of a very high theoretical capacity (978 mA h g^-1), low cost, chemical stability and reduced environmental impact. However, it suffer large volume changes upon delithiation, which results in a capacity fading and reduced cycle life.
Here we show that strong improvements of the ZnO electrochemical performances can be obtained by developing properly optimized nanoarchitectures. Variously nano-arrays were directly deposited on stainless steel current collectors via an easy and low-cost wet chemistry. In detail, nanorods (1D structures), nanosheets (2D) and a hierarchical brush-like systems (3D) were prepared through hydrothermal synthesis and characterised in terms of physico-chemical and electrochemical points of view, so to address the role of both array morphology and microstructure on the anode functional perfomances.
The nanostructured ZnO anodes show better properties with respect to the bulk material. In particular, the nanosheets are much more performing that the other nanoarchitectures, due to: i) the presence of small nanoparticles, with average diameter of about 10 nm, maximizing the array specific surface area and favoring the formation of the LiZn alloy; ii) the presence of a mesoporous texture, allowing larger space for accommodating the volume changes upon delithiation.
The additional application on such nanoparticles of a graphite coating preserves the morphology during cycling, and enables further improvement in terms of capacity retention and high rate (dis)charge capability.

Hollow spheres with complex shell structures have stimulated tremendous interest because the multi-level architecture could enable the materials a wealth of optimized properties in vaious applications including catalysis, drug delivery, gas sensors, energy storage systems and many others.Despite these exciting progresses, there are still great challenges in the synthesis of complex hollow spheres. First, most of the current methods are only suitable for synthesizing complex hollow sphere of individual specific material, which undoubtedly hinder the practical applications of the complex hollow structures. On the other hand, the existed strategies could only be feasible for the synthesis simple binary metal oxide hollow spheres. Therefore, a universal strategy which could be general for both binary and multi-component metal oxide hollow spheres with controlled shell structures is highly dirable, but remains an urgent task.
Transition metal oxide (TMO), especially those mixed valence oxides invloving different metal elements have found great potentials as electrode materials for energy storage devices. Although this class of materials exhibit very high theoretical capacity/capacitance, unfortunately, the inevitablely poor cycling performance derived from the large volume expansion and mechanic strain stress becomes the major obstacle. As one of the promising solutions, to construct TMO hollow spheres with multi-shelled structures have recently received tremendous attention because of the uniquely structural features which could benefit the optimization of the cycling capability. However, it remains a great challenge to build mixed metal oxide hollow spheres with controlled shell structures, which is exceptionally desirable.
In this work, we demonstrate a universal strategy called “Penitration-Solidification-Annealing” , which could be utilized for various binary and multi-component TMO hollow spheres with controlled shell structures, followed by studying their structure dependent lithium storage performance. Complex hollow spheres of various TMOs, including binary NiO, Mn2O3, Co3O4, Fe2O3 and mixed metal oxides CoMn2O4, ZnMn2O4, ZnCo2O4, NiCo2O4 etc. are successfully synthesized through the unified system. Moreover, the well controlled shell structures of binary Co₃O₄ and ternary ZnCo2O4 are performed to demonstrated the possibility of engineering the complexity of the shell structures. Importantly, it is found that the complex hollow spheres exhibit largely enhanced lithium storage properties which are highly dependent with the shell structures. Specifically, the carbon coated CoMn₂O₄ triple-shelled hollow spheres exhibit a specific capacity of 726.7 mA h g-1 and a nearly 100 % capacity retention after 200 cycles. Such a universal strategy could make a significant contribution on not only the synthetic methodology of the hollow structure, but also the application of the transition metal oxides as negative electrodes in lithium ion batteries.

Good adhesion property of the electrode composite should be well maintained to deliver the designed energy and power throughout the long period. However, the only peel test has been widely utilized to compare relative adhesion strengths for a long time. On the other hand, we have just proposed a new tool, the Surface and Interfacial Cutting and Analysis System (SAICAS), to measure shear stress as well as adhesion strength of the electrode composite [1-3]. But, due to limited studies, we should investigate this tool with various electrode systems and analyse their relationship in more deep.
In this study, we applied the SAICAS tool to measure the adhesion properties of lithium-ion battery (LIB) cathodes containing active materials, a polymeric binder, and an electric conductor. First, some cathodes having the same loading level and different thickness and density are prepared by roll-pressing machine. Thereafter, the adhesion properties of corresponding cathodes are evaluated at the interface between electrode composite and current collector and various depths. From those data, we depict apparent adhesion strength as a function of depth, and then figure out a bare adhesion strength free from the measuring thickness.
Acknowledgements
This research was financially supported by the Ministry of Education(MOE) and National Research Foundation of Korea(NRF) through the Human Resource Training Project for Regional Innovation (No. 2014066977)
References
[1] Son, B.; Ryou, M.-H.; Choi, J.; Lee, T.; Yu, H. K.; Kim, J. H.; Lee, Y. M., Measurement and Analysis of Adhesion Property of Lithium-Ion Battery Electrodes with SAICAS. ACS Appl. Mater. Interfaces 2013, 6, 526-531.
[2] Choi, J.; Ryou, M.-H.; Son, B.; Song, J.; Park, J.-K.; Cho, K. Y.; Lee, Y. M., Improved High Temperature Performance of Lithium-Ion Batteries through Use of a Thermally Stable Co-Polyimide-Based Cathode Binder. J. Power Soures 2014, 252, 138-143.
[3] Choi, J.; Kim, K.; Jeong, J; Cho, K. Y.; Ryou, M.-H.; Lee, Y. M., Highly Adhesive and Soluble Co-polyimide Binder: Improving the Long-Term Cycle Life of Silicon Anodes in Lithium-Ion Batteries, ACS Appl. Mater. Interfaces, Accepted

Making a high thickness or loading electrode in lithium ion batteries is one of the important technologies for achieving high energy density, which results from decrease of other inactive materials. However, the electric conductivity goes down as electrode active materials are getting far from the current collector. In order to maintain the electrochemical reactivity of even thick electrodes, additional or high conductive electric conductive agents should be introduced or the electrode morphology should be controlled evenly.
In this work, two types of conductive agents, nano-sized particles (Super-P) and fiber-like conductive agents (VGCF, vapor-grown carbon fibers), are comparatively investigated with thick cathodes(LiCoO₂, LiNi_0.6Co_0.2Mn_0.2O₂, and LiFePO₄). In particular, since VGCF has not only good electric conductivity but also long length 20um, it can provide long-range electric conduction pathway from the current collector to electrode active materials. [1,2] Thus, we prepared 9 different cathodes having different thicknesses (50, 70, and 90 um) and different conductive agent blends (Only Super-P, Super-P/VGCF, and only VGCF). And then, their electrochemical performances were evaluated with 2032 coin half-cells. Moreover, SEM and 4-point probe analysis were conducted to find the morphological changes and electric conductivity, respectively.
References
[1] M. Endo, Carbon 39 (2001) 1287-1297
[2] catalog, VGCF^#9415;-H, Showa Denko Carbon Sales, Inc.
Acknowledgements
This research was financially supported by the Ministry of Education(MOE) and National Research Foundation of Korea(NRF) through the Human Resource Training Project for Regional Innovation (No. 2014066977)

Candidates of novel solid electrolytes are essential for developing all solid-state batteries, in the concern of drawback of battery with liquid electrolyte, such as flammable, cost and cruise-ability for mobile electronic device. Na-rich antiperovskite system was a recent developed solid electrolyte with enhanced sodium ionic conductivity through structural manipulation. In this work, the sodium ionic transportation pathways of the parent phase Na₃OBr, as well as a modified layer structure of Na₄OI₂ were studied by temperature dependent neutron diffraction combined with maximum entropy method (MEM). The activation energy is related to the different thermal expansion of Na₃OBr and Na₄OI₂ crystal lattice. The nuclei density distribution maps at 500 K indicated that sodium ions are hopping in the oxygen octahedron and Br^- ions were not evolved in the system of Na₃OBr cubic antiperovskite; in the Na₄OI₂ tetragonal antiperovskite, Na1 in the (001) plan had a higher jumping energy than Na2 along the c axis. The transportation of Na2 along the c axis needs the assistance of I^- ions, forming a 3D network of sodium transportation.

The rechargeable lithium-oxygen battery has attracted attention due to its large theoretical energy density compared to modern lithium-ion batteries. This large energy density is attributed to the reaction of lithium with molecular oxygen to form lithium peroxide, which grows on the surface of the cathode. While this is a promising chemistry, there are many practical challenges that remain to be solved, such as the decomposition of organic electrolyte in the presence of superoxide anions and large overpotentials on charge. Additionally, the mechanism of lithium peroxide growth and its resulting morphologies is not fully understood.
Here we propose a system which inherently avoids many of the issues associated with organic electrolyte decomposition, while also forming lithium peroxide with a unique morphology. By using a molten salt (Li/K nitrate) in place of a conventional solvent/salt electrolyte, solvent decomposition is obviated. In addition, the elevated temperature of the molten salt as well as the large concentration of lithium ions encourage faster diffusion and kinetics.
In literature, the three commonly observed morphologies of electrochemically grown lithium peroxide are thin films, platelets, and “toroids” which are small stacks of platelets. While we do observe the platelet style growth of lithium peroxide, we also see much larger structures which appear to be stacks of hexagonal layers (see attached figure). We believe these stacks to be a new morphology of lithium peroxide growth. To substantiate this claim, we note that the Wulff construction for lithium peroxide is a short hexagonal prism, while also confirming the reaction product using XRD. This new morphology could be attributed to the fact that our cell operates with elevated temperature and large concentration of lithium and superoxide ions, making it easier to achieve an equilibrium (Wulff) structure.
We have shown a lithium-oxygen battery chemistry that produces a new morphology of lithium peroxide, and begun to develop a mechanism for why it forms. In addition, we have explored the effect of various cell parameters such as discharge rate on the morphology of the resulting lithium peroxide.

The question whether olivine LiFePO₄ undergoes two-phase or non-equilibrium single-phase reaction during electrochemical processes has taken center stage in the understanding of the faster reaction kinetics observed in this material. Here we report the lithiation/delithiation mechanism of Mg substituted LiFePO₄ using high resolution XRD, TEM and electrochemical measurements. Ex-situ partially (de)lithiated olivine-LiMg_0.2Fe_0.8PO₄ show the existence of stable equilibrium intermediate phases as characterized by the presence of more than two phases and broadness of diffraction peaks. EELS profiles across individual nanoparticles further confirm uniform lithiation with a constant Fe-L₃ energy measured across each nanoparticle. In addition, we observe a continuous shift in the diffraction peak position even in the “two-phase” region in the ex-situ electrochemical (de)lithiated electrodes.
This research is supported as part of the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under Award Number DE-SC0001294.

The current status of LIBs is not enough to meet commercial demands for new applications, in particular, with respect to energy density. To improve the energy density of LIBs, first of all, the new anode material needs to be considered to acquire higher capacity. Up to now, graphite and hard carbons are commercially used as a negative electrode material for LIBs, but higher-capacity alternatives are being consistently thought due to their limited capacity as an anode material of next generation LIBs for large-scale power applications. Recently, various Si, and Sn based compound including transition metal oxide, multiphase alloy, and intermetallic compounds have been extensively studied as alternatives to the existing carbon based anode materials. Among alternative anode materials, transition metal phosphides offer great promise for lithium ion batteries due to high reversible capacity at relatively low potential.[1] However, these materials electrochemically reacted with lithium induce large irreversible volume changes by the formation of Li_xM, Li_xP, and M^o. Volume expansion of these materials during cycling leads to degradation of the capacity fading. In order to solve this problem, numerous material concepts have been suggested and some of them prove to be effective in improving the cycle performance. One of the effective ways to enhance the cycle performance is the use of active/inactive composite material [2] and nano-crystallization of active materials. [3]
In this work, we developed a new MoP/MP (transition metal phosphide) composite alloy to improve the structural stability and electrochemical properties with introducing the MoP in the pristine MP. MoP acts as buffer layer to suppress the volume expansion in MoP/MP composite. We investigated the differences in physical and electrochemical properties between MoP and MoP/MP composite, examined using powder X-ray diffraction, SEM, and TEM, and galvanostatic charge-discharge test. We also investigated the volume expansion of MP and MoP/MP composite during cycling, considering the influence of introducing MoP layers in MoP/MP composte.
References
1. D. C. S. Souza, V. Pralong, A. J. Jacobson, L. F. Nazar, Science 2002, 296, 2012.
2. G. Park, C. Lee, J. Lee, J. Choi, Y. Lee, S. Lee, J. Alloys compd. 2014, 585,534.
3. P. G. Bruce, B. Scrosati, J.-M. Tarascon, Angew. Chem. Int. Ed. 2008, 47, 2930.

Solid electrolytes that are chemically stable and have a high ionic conductivity would dramatically enhance the safety and operating lifespan of rechargeable lithium batteries. Here, we apply a multi-technique approach to the Li-ion conducting system (1-z)Li₄SiO₄ -(z)Li₃PO₄ with the aim of developing a solid electrolyte with enhanced ionic conductivity. Previously unidentified superstructure and immiscibility features in high purity samples are characterized by X-ray and neutron diffraction across a range of compositions (z = 0.0 to 1.0). Ionic conductivities from AC impedance measurements and large-scale molecular dynamics (MD) simulations are in good agreement, showing very low values in the parent phases (Li₄SiO₄ and Li₃PO₄), but orders of magnitude higher conductivities (10^-3 S/cm at 573 K) in the mixed compositions. The MD simulations reveal new mechanistic insights in the mixed Si/P compositions in which Li ion conduction occurs through 3D pathways and a cooperative-type interstitial mechanism; such correlated motion is a key factor in promoting high ionic conductivity. Disorder on the polyanion sublattice is shown to reduce the temperature at which partial melting occurs leading to superionic lithium conduction. Solid state 7 Li and 31 P NMR experiments reveal enhanced local Li-ion dynamics and atomic disorder in the solid solutions, which are correlated to the ionic diffusivity. These insights will be useful for developing strategies to optimize the conductivity in this system and to identify next-generation solid electrolytes.
'Structural and mechanistic insights into fast lithium-ion conduction in Li₄SiO₄-Li₃PO₄ solid electrolytes', Y. Deng, C. Eames, J-N. Chotard, F. Lalère, V. Seznec, S. Emge, O. Pecher, C. P. Grey, C. Masquelier, M. S. Islam, JACS, in press, 2015.

Lithium solid electrolytes can potentially address two key limitations of the organic electrolytes used in today&’s lithium-ion batteries, namely, their flammability and limited electrochemical stability. Several of the key properties of solid state electrolytes, including their ionic conductivity and stability against electrode materials under oxidizing and reducing potentials, can be computed with ab-initio methods. This has led us to speculate on the existence of several LGPS-derivatives, many of which have now been synthesized now.
By combining high-throughput ab initio techniques for ionic conductivity with structure analysis tools we have been able to discover a fundamental relation between anion packing and ionic transport in fast Li-ion conducting materials and which allows one to preselect structures for high Li-ion conductivity. We find that an underlying body-centered cubic (bcc)-like anion framework, which allows direct Li hops between adjacent tetrahedral sites, is most desirable for achieving high ionic conductivity, and that indeed this anion arrangement is present in several known fast Li-conducting materials and other fast-ion conductors. These findings provide important insight towards the understanding of ionic transport in Li-ion conductors and serve as novel design principles for future discovery and design of improved electrolytes for Li-ion batteries.
Finally, I will discuss the anodic and cathodic stability of various classes of conductors and demonstrate that the high stable electrochemical voltage window claimed in many recent publications is unlikely to be correct.

The lithium-stuffed lithium garnets, of which Li₇La₃Zr₂O₁₂ (LLZO) is the prototypical example, are a family of promising high-conductivity solid-state lithium-ion electrolytes [1]. Optimising the ionic conductivity of these materials through targeted doping strategies depends on understanding the effect of dopants on the microscopic transport mechanisms of lithium, and in turn on macroscopic lithium transport coefficients; diffusion coefficients and ionic conductivities.
Within a site-hopping model, and for the reference "random-walk" case, simple relationships exist between lithium jump frequencies, tracer diffusion coefficients, and ionic conductivities. Correlations in ionic motion, however, can be significant in solid electrolytes. In the particular case of LLZO, a number of theoretical studies have reported evidence for correlated diffusion behaviour [2-6]. Yet these correlations are often assumed to be negligible in calculations of diffusion coefficients (e.g. from single-ion jump frequencies) or ionic conductivities (from directly calculated diffusion coefficients, by applying the Nernst-Einstein relation). The quantitative effects of correlated motion are contained in the self- and collective-correlation factors, f and f_I, and in the Haven ratio, H_R = f / f_I [7].
I will describe two simulation approaches to calculating self- and collective-correlation factors in stoichiometric and doped cubic LLZO. We have firstly used lattice-gas kinetic Monte Carlo simulations to directly calculate "geometric" correlation factors for an idealised c-LLZO lattice as a function of lithium stoichiometry and nearest-neighbour interaction strength. Complementing this, we have also performed long-time molecular dynamics simulations using first-principles-derived interatomic potentials. These simulations allow direct calculation of the lithium self-diffusion coefficient and ionic conductivity, and hence the Haven ratio, as a function of dopant concentration. We also analyse the correlation behaviour of lithium ion motion from these trajectories to give a quantitative microscopic description of self- and collective-correlation factors.
[1] Thangadurai et al. J. Phys. Chem. Lett.6, 292 (2015).
[2] Klenk and Lai, Phys. Chem. Chem. Phys.17, 8758 (2015).
[3] Adams and Rao, J. Mater. Chem.22, 1426 (2012).
[4] Wang et al. Chem. Mater.26, 5613 (2014).
[5] Meier et al. J. Phys. Chem. C118, 6668 (2014).
[6] Jalem et al. Chem. Mater.25, 425 (2013).
[7] Murch and Belova, Diffusion Fundamentals2, 1 (2005).

Next generation batteries will require a broad range of energy densities to meet the challenges of portable electronic storage from electric vehicles to microelectromechanical systems (MEMS). Solid state electrolytes are researched heavily because they have the potential to improve capacity loss, cycle lifetime, operation temperature and safety [1]. Lithium lanthanum titanate (LLTO), with the perovskite structure (ABO₃), has gained interest due to its high bulk conductivity (10^-3 S cm^-1) at room temperature [2]. LLTO has many advantages including negligible electronic conductivity, high voltage stability (> 8 V), atmospheric stability, and temperature stability [3]. Furthermore, LLTO is transferable to thin film structures for fabricating micro-batteries such as on-chip batteries [4]. However, LLTO has a relatively low grain boundary conductivity (<10^-5 S cm^-1), lowering the overall material conductivity [3]. In this work, we investigate the role of titanium (Ti) stoichiometry in LLTO ionic conductivity both in crystalline bulk and amorphous thin film.
LLTO polycrystalline powder was prepared via solid state synthesis and pressed into pellets composed of a mixture of tetragonal and cubic phases. Pellets of varying titanium stoichiometry were fabricated and we explored the resulting grain boundary conductivity. Additionally, amorphous thin films of various titanium stoichiometry were deposited by pulsed laser deposition allowed characterization of ionic conductivity without grain boundaries. By controlling the laser fluence and background pressure, we were able to grow dense films with controlled thickness and stoichiometry. The electrolyte performance is investigated for various stoichiometries to elucidate the relationship between titanium stoichiometry and LLTO ionic conductivity in both bulk and thin film forms.
[1] A. Hayashi et al. “ Superionic glass-ceramic electrolytes for room-temperature rechargeable sodium batteries,” Nature Communications. 3 (2012) 856-860.
[2] O. Bohnke. “The fast lithium-ion conducting oxides Li_3xLa_{2/3 minus; x}TiO₃ from fundamentals to application,” Solid State Ionics. 179 (2008) 9-15.
[3] C. Cao et al. “Recent advances in inorganic solid electrolytes for lithium batteries,” Frontiers in Energy Research. 2 (2014) 1-10.
[4] A. Furusawa et al. “Ionic conductivity of amorphous lithium lanthanum titanate thin film,” Solid State Ionics. 176 (2005) 553-558.

The development of solid electrolytes that facilitate fast Li-ion diffusion is critical for enabling new energy storage technologies including Li-S and Li-O₂ batteries. We present a combined experimental and computational investigation into the ionic conductivity of Li₆Y(BO₃)₃, a new class of solid electrolyte possessing a pseudo-layered structure with very low energy barriers for migration between the numerous Li sites. Using temperature-dependent impedance spectroscopy, we find an ionic conductivity in the pristine phase of 1e-3 S/cm at 350°C. Density functional theory calculations reveal low energy diffusion pathways for lithium vacancies within the ac plane, and for lithium interstitials along distinct c-aligned 1D channels. Comparison of the calculated vacancy and interstitial hopping barriers with solid state NMR spin-relaxation data indicates lithium conduction in the pristine material is dominated by 1D Li-interstitial transport. We find no evidence for reactivity with moisture in the atmosphere or metallic lithium, so this exceptional stability, alongside ionic conductivity at modest temperatures, make Li₆Y(BO₃)₃ an promising new candidate as a solid electrolyte.

The systematic research of size effects on transport has led to the field of nanoionics, which might gain similar significance for energy research as the field of nanoelectronics has gained for information technology. While previous treatments concentrated on transport,¹ the present contribution concentrates on nanoionic aspects of storage² thermodynamics and storage kinetics. In the introductory part novel results on composite electrolytes will be mentioned, but the main part focusses on electrodes. The talk will address exciting phenomena such as capillary effects in nanoparticle electrode systems, synergistic storage in nanocomposite systems and conversion reaction involving nanodots.^3,4 In short, the contribution aims at explaining interfacial storage anomalies but also at demonstrating the use of nanoionics for high performance batteries.
References
[1] J. Maier, Nat. Mater. 4, 805-815 (2005).
[2] J. Maier, Angew. Chem. Int. Ed. 52, 4998-5026 (2013).
[3] L. J. Fu, C. C. Chen, D. Samuelis, and J. Maier, Phys. Rev. Lett. 112, 208301 (2014); L. J. Fu, K. Tang, H.-C. Oh, K. Manickam, T. Bräuniger, C. V. Chandran, A. Menzel, M. Hirscher, D. Samuelis, and J. Maier Nano Lett., 15, 4170-4175 (2015).
[4] C. Zhu, X. K. Mu, P. A. van Aken, Y. Yu, and J. Maier, Angew. Chem. Int. Ed. 53, 2152-2156 (2014)

Li_1.2Zr_1.9A_0.1(PO₄)₃ (A = Ca, Sr) is a solid Li-ion electrolyte that can potentially enable high energy density electrochemical storage. Substitution of Zr by Ca or Sr in LiZr₂(PO₄)₃ stabilizes the rhombohedral NASICON structure with conductivity up to ~ 10^-4 S cm^-1. ¹ Importantly, the lack of easily-reducible elements such as Ti as found in commercial Li-ion solid electrolyte (LTP, Li_1.3Ti_1.7Al_0.3(PO₄)₃) suggests stability of Li_1.2Zr_1.9A_0.1(PO₄)₃ versus Li metal which may enable Li metal anode based high energy density storage. Furthermore, it may be highly compatible with phosphate type electrodes such as the phospho-olivine structured Li-ion cathodes.
This paper will present our recent results on the synthesis of Li_1.2Zr_1.9A_0.1(PO₄)₃, characterization of its structure, preparation of dense samples and measurement of properties including Li-ion and electronic conductivity, mechanical properties and stability with Li. Furthermore, the effect of Ca versus Sr substitution on the properties and phase stability of Li_1.2Zr_1.9A_0.1(PO₄)₃ will be presented.
References
1. H. Zie, J.B. Goodenough, Y. Li, J. Power Sources 2011, 196, 7760.

Doped Li₇La₃Zr₂O₁₂ garnets, oxide-based solids with high Li⁺ conductivity, show great potential as leading electrolyte material candidates for all-solid-state lithium ion batteries. The ionic conductivity is attributed to the disordered distribution of Li⁺ and Li vacancy in the cubic phase. Using in-situ neutron diffraction, we show that the cubic-phase-stabilizing aliovalent dopants have decisive impacts on the Li⁺ and Li vacancy distribution in the garnets during synthesis while they obey the same rule of constraining the vacancies at the neighboring sites; the valance and concentration of dopants determine the Li vacancy density in the “active” octahedral sites. A simple active vacancy density model predicts a tendency toward high ionic conductivity from low dopant content with high valance. The relationship of ionic conductivity and aliovalent dopants provides direct guidance to optimize doping for the purpose of improving garnet electrolytic performance.

In the search for solid-state electrolytes suitable for battery applications, the Li and Na salts of the extremely stable hydro-closo-borate anions, [B₁₂H₁₂]^2- and [B₁₀H₁₀]^2-, have recently emerged as potentially promising materials. Indeed, superionic conductivity was observed for Na₂B₁₂H₁₂ and Na₂B₁₀H₁₀ above their respective order-disorder transition temperatures of 529 K ^[1] and 370 K ^[2]. These compounds exhibited sudden jumps to high-conductivity values of ~0.1 S cm^-1 (at 540 K) for the former and ~0.01 S cm^-1 (at 380 K) for the latter. This sudden surge in conductivity was closely linked to the entropy-driven phase transformations from ordered low-temperature structures to highly mobile, disordered high-temperature structures, with a vacancy-rich cation sublattice and a concomitant onset of high reorientational mobility (>10¹⁰-10¹¹ reorientational jumps/s) for the large, quasi-spherical anions ^{[2, 3]}. Since the transition temperature affects the applicability of these materials as electrolytes in next-generation solid-state batteries, it is vital to study and fine-tune this property. Partial cationic substitutions of Na⁺ into Li₂B₁₂H₁₂ in different concentrations have seen a reduction in its phase transition temperature of 615 K towards lower values ^[4]. With this positive note, further investigations on such structures containing the large polyhedral units were embarked upon by various chemical and morphological modifications for both the Li⁺ and Na⁺ analogs. The results from x-ray diffraction, neutron powder diffraction, differential scanning calorimetry, neutron vibrational spectroscopy, quasielastic neutron scattering, and ionic conductivity experiments will be described, pertaining to the structural and dynamical behaviors of the light-weight alkali closo-boranes.
References:
[1] T. J. Udovic, M. Matsuo, A. Unemoto, N. Verdal, V. Stavila, A. V. Skripov, J. J. Rush, H. Takamura, and S. Orimo, “Sodium superionic conduction in Na₂B₁₂H₁₂” Chem. Commun.50 (2014) 3750-3752.
[2] T. J. Udovic, M. Matsuo, W. S. Tang, H. Wu, V. Stavila, A. V. Soloninin, R. V. Skoryunov, O. A. Babanova, A. V. Skripov, J. J. Rush, A. Unemoto, H. Takamura, and S. Orimo, “Exceptional Superionic Conductivity in Disordered Sodium Decahydro-closo-decaborate”, Adv. Mat.26 (2014) 7622-7626.
[3] N. Verdal, T. J. Udovic, V. Stavila, W. S. Tang, J. J. Rush, and A. V. Skripov, “Anion Reorientations in the Superionic Conducting Phase of Na₂B₁₂H₁₂”, J. Phys. Chem, C118 (2014) 17483-17489.
[4] W. S. Tang, T. J. Udovic, and V. Stavila, “Altering the Structural Properties of A₂B₁₂H₁₂ Compounds via Cation and Anion Modifications”, J. Alloys and Comp. (2015) In Press, DOI:10.1016/j.jallcom.2015.01.061.

Recent history has shown that electromobility is capable of offering a dynamic driving experience without local emissions, raising the interest of OEMs, and customers. Today electrification of the drive train, ranging from hybrid vehicles to plug-in hybrids and finally to pure electric vehicles is the commonly accepted next step in this direction. BMW is strongly committed to this path, which is expressed by the launch of its sub-brand BMW i dedicated to electric vehicles. Nonetheless, the challenges for mass market penetration are far from being solved. Cost-to-range ratio is the main factor for the slower than expected increase of the share of electric vehicles in the worlds&’ automotive market. Driving ranges of at least 300 miles might then be required to achieve large customer acceptance and guarantee the success of future electric vehicles.
Although an increase in volumetric and gravimetric energy densities is still possible by improvements of cell, modules, and battery packs design as well as through optimized sub-components, the development of novel materials seems at this point mandatory. The necessity to develop new materials that allow for the simultaneous achievement of higher energy density, maintaining at the same time similar, or improved, rate capability, lifetime, cost, and safety represents a tremendous challenge.
Solid state electrolytes are promising candidates for the development of rechargeable lithium batteries with enhanced life and safety relative to current lithium-ion battery technologies. Considerable research has focused on a few classes of crystalline structures including perovskites garnet, LISICON and Thio-LISICON structures, which have been shown to provide high conductivities approaching that of liquid electrolytes. However, there is a lack of fundamental understanding in key parameters that universally govern the conductivities among different classes of conductors. In this presentation, particular emphasis will be given to summarize key physical parameters that have a large influence on the ion conductivities of solids independent of structural families and to underline the challenges, which need to be overcome for solid electrolytes for automotive lithium batteries.

Silicon has attracted much attention because its theoretical capacity is 4200mAhg^minus;1. Nevertheless, the main disadvantage of high-capacity anode materials is their very large volume expansion and contraction (~320% ) during Li insertion/de-insertion. Several degradation mechanisms are involved in the charge-discharge process including: 1) SEI thickness and resistance increase, 2) solvent and salt reduction 3) large increase in battery impedance and reduced power, 4) breaking or disintegration of the particles, 5) loss of SiNW and SiNPs contact to the current collector and 6) cracks in the electrode. In this work, in addition to the synthesis and characterization of novel three-dimensional high-capacity SiNWs and SiNPs-based anodes, we focused on studying their degradation mechanisms. We have been able to produce remarkably high loadings of 3-15 mAh/cm², very low irreversible capacity (of the order of only 10% for the 3-4 mAh/cm² samples), current efficiency greater than 99.5% and a fast charge-discharge rate (up to 2.7C (20mA/cm2) which is not common for silicon anodes). These properties meet the requirements of lithium batteries for portable and electric-vehicle applications. These SiNWs-based binder free anodes and the SiNPs anodes have been cycled for 200 - 300 cycles, exhibiting a stable cycle life. Loss of capacity, at 0.1 mA/cm², is about 20-30% only indicating that at least 70-80% of the SiNWs and the SiNPs are still connected to the substrate. The thickness of a freshly formed SEI on lithium or on other substrates is a few nm (Peled 1979). It was found that all measured parameters for the 3D SiNWs anode: R_sei, ρ_sei and SEI thickness grow with cycle number. For example: the SEI thickness after one and eleven cycles is 22 and 72 nm respectively. The structure and composition changes of the SiNWs, the SiNPs and of the SEI will be reported.

Silicon-based electrodes are very attractive negative electrodes for lithium-ion batteries (LiB) compared to graphite due to their very high specific capacities (3572mAh g^-1 vs 372mAh g^-1 for graphite). Silicon-electrodes have, however, a high cycling irreversibility due to 300% volume expansion of the silicon particles upon lithiation, leading to cracks and decrepitation during cycling, creating new surfaces of silicon bound to react with the electrolyte. These processes lead to disconnection of silicon particles from the percolating network. Solving the subsequent large capacity fade observed during cycling of silicon electrodes is a complex issue [1].
The behavior of silicon electrode cycled vs lithium metal is now well known and methods to optimize its performance have been extensively described in the literature [2-3]. In this configuration, the lithium supply is not limited, therefore failure mechanisms can be completely different from those obtained in Li-ion batteries. In this work, silicon electrode is cycled vs a lithium nickel manganese cobalt oxide (NMC) that initially contains the cyclable lithium. As of today, the failure mechanism of silicon-based in full batteries has not been understood. Classical and advanced techniques (NMR, XPS, TEM-EELS) are used to investigate and characterize silicon/electrolyte interphase, as well as their evolution upon aging/cycling of the full cell.
The capacity of full batteries decreases rapidly, due to the loss of cyclable lithium, progressively trapped in the SEI. From the very early stages of the electrochemical cycling, the SEI does not appear as a homogenous layer that would cover all the silicon particles involved in the electrochemical reaction but rather as very heterogeneous thick patches of LiF and carbonates. The accumulation of SEI in cycling is well visible in the STEM-EELS elemental mapping. After the 100^th lithiation, silicon particles can be seen trapped inside a thick LiF matrix covered by a thin carbonate layer. Moreover, post-mortem analyses show that no lithium remain in both active materials after 100 cycles, which seem not to be degraded by the cycling.
References
1. Mazouzi, D.et al. J. Power Sources, 220, 180-184 (2012)
2. Obrovac, M. N., Krause, L. J. J. Electrochem. Soc., 154, A103 (2007)
3. Mazouzi, D., Lestriez, B., Roue#769;, L., & Guyomard, D. Electrochem. Solid-State Lett., 12(11) (2009)

Silicon (Si) has attracted tremendous attention as a high-capacity anode material for next generation Li-ion batteries (LIB); unfortunately, it suffers from poor cyclic stability due to excessive volume expansion and reduced electrical conductivity after repeated cycles. Nanocarbon materials have been used to enhance the cyclic stability of LIB anodes, but they have an inherently low specific capacity. To address these issues, in this presentation, we present a novel ternary nanocomposite of Si, metal oxide (MOx), and reduced graphene oxide (rGO) for LIB anodes, in which Si-MOx hybridized phase offers high capacity characteristic and the nanoscale-embedded rGO confers structural stability for extended periods of time. First, Si-Mn/rGO ternary nanocomposites were readily synthesized by mechanical complexation and subsequent thermal reduction of mixtures of Si nanoparticles, MnO2 nanorods, and rGO nanosheets. Resulting ternary nanocomposite anodes displayed a specific capacity of 600 mAh/g with ~ 90 % capacity retention after 50 cycles at a current density of 100 mA/g. The enhanced performances can be attributed to facilitated Li ion reactions with the MnSi alloy phase and the formation of a structurally-reinforced electroconductive matrix of rGO nanosheets.
Next, we propose that Si can be complexed with electrically conductive Ti2O3 to significantly enhance the reversible capacity and cyclic stability of Si-based anodes. We prepared a ternary nanocomposite of Si/Ti2O3/reduced graphene oxide (rGO) using mechanical blending and subsequent thermal reduction of the Si, TiO2 nanoparticles, and rGO nanosheets. As a result, the obtained ternary nanocomposite exhibited a specific capacity of 985 mAh/g and a coulombic efficiency of 98.4% after 100 cycles at a current density of 100 mA/g. Furthermore, these ternary nanocomposite anodes exhibited outstanding rate capability characteristics, even with an increased current density of 10 A/g. This excellent electrochemical performance can be ascribed to the improved electron and ion transport provided by the Ti2O3 phase within the Si domains and the structurally reinforced conductive framework comprised of the rGO nanosheets. The ternary nanocomposite design paradigm presented in this presentation can be exploited to develop high capacity and long-life anode materials for versatile LIB applications.

Operando X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) studies of Ge anodes are carried out to understand the effect of cycling rate on Ge phase transformation during charge/discharge process and to relate that effect to capacity. It is discovered that the formation of crystalline Li₁₅Ge₄ (c-Li₁₅Ge₄) during lithiation is suppressed beyond a certain cycling rate. A very stable and reversible high capacity of ~ 1800 mAhg^-1 can be attained up to 100 cycles at a slow C-rate of C/21 when there is complete conversion of Ge anode into c-Li₁₅Ge₄. When the C-rate is increased to ~ C/10, the lithiation reaction is more heterogeneous and a relatively high capacity of ~ 1000 mAhg^-1 is achieved with poorer electrochemical reversibility. An increase in C-rate to C/5 and higher reduces the capacity (~ 500 mAhg^-1) due to an impeded transformation from amorphous Li_xGe to c-Li₁₅Ge₄, and yet improves the electrochemical reversibility. A proposed mechanism is presented to explain the C-rate dependent phase transformations and the relationship of these to capacity fading. The operando XRD and XAS results present new insights to the relationship between structural changes in Ge and battery capacity, which are important in guiding better design of high-capacity anodes.

The lithiation process of crystalline silicon anodes in Li-ion batteries has been investigated extensively in both theoretical and experimental studies. Upon high lithiation, the material can expand up to 400% and the anode fractures. This greatly reduces the number of recharging cycles of the battery before it fails. Experiments show that crystalline Si anodes become amorphous after the first lithiation cycle, but much less is known about the nature of lithium insertion in amorphous Si (a-Si) anodes. Understanding the atomistic view of the changes a-Si anodes undergo with the lithium absorption process is important and requires realistic simulations with large numbers of atoms and long time scales. These simulations can be carried out using model interatomic potentials that can capture the dependence of structure on chemical composition. Using ab-initio density functional theory (DFT) data for training, we developed an environment-dependent artificial neural network (ANN) potential for Li-Si alloys. We carried out geometry optimizations for the equilibrium structures and calculated total energies of amorphous Si and Li-Si (a-Li-Si) using the developed potential. Furthermore, we investigated the lithium addition into a-Si anodes. We calculated the formation energies of Li-Si alloys and analyzed the structural changes in a-Si and a-Li-Si alloys upon Li insertion using total energy calculations and molecular dynamics simulations. The results show that our ANN potential is capable of reproducing total energies and structural changes of a-Li-Si alloys with different Li concentrations.

Effects of diferent binders including polyvinylidene difluoride (PVDF) and water-soluble poly(acrylic acid) (PAA), sodium carboxymethyl cellulose (CMC) and a mixture of PAA-CMC on cycling performance and the SEI formation at silicon electrodes have been investigated using electrochemical cycling, IR-ATR and XPS and SEM. Capacity retention of electrodes with PAA and PAA-CMC are slightly better than CMC and remarkably greater than PVDF. Surprisingly, the electrodes after cycling with PVDF shows less cracks than the ones with PAA, CMC and c-PA-CMC. In addition, the carboxylic, -COOH, and -OH from PAA and CMC are electrochemically reduced during first cycle to form an “artifical SEI” and suppress the decomposition of electrolyte solvents on Si particles. However, the PAA and CMC accelerate the decomposition of LiPF₆ during the “wetting” process before cycling, especially at temperature above 25⁰C. This suggests that time and temperature during “wetting” should be controlled cautiously to minimize the negative effects of water-soluble binders.

Aluminum oxide is one of the most studied materials in atomic layer deposition (ALD), with applications as wide-ranging as gate oxides, encapsulants, and catalyst supports. Synthesized most commonly from the precursors trimethylaluminum (TMA) and water, it is, when grown at below 600 °C, universally amorphous on all substrates so far reported.
We report here on the first recorded growth of crystalline Alshy;shy;₂O₃, obtained by thermal ALD at 200 °C at a growth rate of 1.2 Å/cycle. The 5 nm thick films were deposited, from precursors TMA and water, on various substrates, including ZnO, Ga₂O₃, and Si nanowires (NW), with diameters ranging from 5 nm to >100 nm. Using various transmission electron microscopy (TEM) techniques, including high-resolution TEM imaging, energy-filtered TEM (EFTEM), and scanning TEM coupled with high-resolution electron energy-loss spectroscopy (EELS), we study the transition from fully crystalline films on small NW diameters to fully amorphous on larger diameter NWs. NWs thinner than 5-10 nm have fully crystalline Al₂O₃ coatings, whereas no crystallinity could be found on any NWs thicker than 75 nm. NWs of intermediate size show partial crystallinity, with nanocrystalline Al₂O₃ suspended within the nominally 5 nm thick amorphous Al₂O₃ matrix. This trend is the same on all three NW compositions, indicating that this is a size effect dependent upon both the ALD film thickness and the NW diameter. Thicker films yielded no observable crystallinity, as was also the case with 5 nm films on both larger NWs and single-crystal Si substrates. The substrate-agnostic nature of the crystallinity reinforces the size-dependent nature of the effect.
EFTEM images confirm that the crystalline layers are indeed Al₂O₃, and no discernable amount of NW material has diffused into them. To elucidate the nature of the crystalline phase present, we acquired high-resolution EEL spectra from various points on various NWs. Several phases of Al₂O₃, including the amorphous phase, exhibit distinct near-edge EEL spectra. We show that the thinner NWs have variously α, γ, and theta; Al₂O₃ spectral characteristics, while the thicker NWs have amorphous Al₂O₃ spectral characteristics.

In this work, different promising electrolyte salts, solvents and additives have been evaluated for nano-silicon (nano-Si) negative-electrode materials. For a wide range of solvents and salts used to formulate electrolytes, we found that fluoroethylene carbonate (FEC) is important for good Si-electrode performance. The combination of FEC with dimethyl carbonate (DMC) gives the best electrochemical performance. We provide arguments to support our perspective that the superior solubility of the salts and FEC decomposition products in DMC leads to a more protective solid-electrolyte interphase (SEI). Consistent with this view, some SEI-forming precursors such as VC, LiBOB, LiODFB, if added in relatively large quantities (>2wt%), have deleterious effects on Si electrode performance due to competitive reactions with FEC decomposition, which, in the absence of such precursors, can form a more robust SEI on Si.

Intense research activity on alternative energy is stimulated by increasing global demand of electric energy. Electrochemical energy storage/conversion systems represent some of the most efficient and environmentally benign technologies and the need for next generation stable, high-performance electrode materials and architectures is the driving force. The interaction between graphene-based and other nanomaterials allows developing novel architectures and tunable physical properties (higher specific surface area, mechanical strength, and facile electron and ion transport via higher electron mobility and conductivity). This work presents the development of composites of graphene and encapsulated mesoporous silicon (po-Si) as practically viable, high-performance anodes for rechargeable secondary Li-Ion batteries (LIB). We synthesize controlled B-doped po-Si nanospheres by facile electroless etching followed by carbon coating for stable solid-electrolyte interphase layer and wrapping with reduced graphene oxide nanoplatelets. We characterized their structure using a range of analytical techniques revealing surface morphology and C-Si interfaces. The electrochemical properties are measured in half- and full-cell formats in terms of cyclic voltammetry, charge-discharge (or recharge) cyclability, current carrying capacity and reliability, ac impedance spectroscopy and determining energy and power density, especially the ratio of energy density/(weight x cost). The knowledge gained can tap into next-generation scalable high energy density LIB for space applications as well as sodium and co-intercalated multivalent ion batteries.

Carbon-based negative electrodes have played a significant role for the widespread use of lithium-ion batteries (LIBs) owing to their long-term stability and cheap prices. Due to their limited capacity, however, alternatives have been highly sought.
One of the promising candidates for negative electrode is the metal oxides that store lithium through the conversion reaction. In the conversion-type lithiation, the theoretical lithium storage capacity is determined by the metal valence; two Li⁺ ions/electrons for CoO and four for MoO₂. Thus, the specific capacity is much larger than those for the carbon-based negative electrodes or other addition-type electrodes. Lithiation behavior in metal oxides depends on the transition metal ions that work as the redox center for conversion reaction. There exists a correlation between the atomic number of transition metals and the working potential for conversion reaction. This correlation is the result of the difference in energy levels of 3d and 4s orbitals, which are affected by the number of protons in the nucleus. It is known that lithiation in the early transition metal oxides (titanium oxides and vanadium oxides) is limited to the addition-type reaction. This feature can be rationalized by the following two reasons. First, the reduction potential of early transition metal ions is lower than those for the later transition metals, such that the conversion-type lithiation is not thermodynamically favored. Second, the stronger metal-oxygen bond strength for the early transition metal oxides as compared to those for the later transition metal oxides impedes the bond cleavage reaction, such that the conversion reaction is kinetically hindered.
At ambient temperature, almost of vanadium oxides (for example, V₂O₅) is not lithiated by the conversion reaction due to the above-mentioned factors. However, it is allowed at elevated temperature because the kinetic barrier is overcome. We found in this work that lithium metavanadate (LiVO₃) is lithiated by the conversion reaction even at room temperature near 0.0 V (vs. Li/Li⁺). To unravel this unexpected feature, a comparative study was performed for vanadium pentoxide (V₂O₅) and LiVO₃. Note that that latter is lithiated by the conversion reaction at room temperature but the former is not. The electrode potential (thermodynamic values) and kinetic barrier for the conversion reaction were compared for the two vanadium oxides on the basis of the quasi-open-circuit voltage (QOCV) and polarization that were obtained by using the galvanostatic intermittent titration technique (GITT). To examine the crystallographic difference affecting the kinetics of conversion reaction, the defect formation energy and ion exchange activation energy of the lithiated vanadium oxides (Li_2.5VO₃ and Li₃V₂O₅) were calculated by using the ab-initio quantum simulation.

Cubic Li₇La₃Zr₂O₁₂ (LLZO) garnet (Ia-3d) and its variants¹ show high Li-ion conductivity, (σ_bulk asymp; 10^-3-10^-4 S cm^-1 at room temperature (RT)) and superior chemical and electrochemical stabilities. In particular, the stability against Li-metal makes LLZO exceptionally well suited to be used as protecting layer in Li-metal based battery concepts. Unfortunately, the tetragonal polymorph of LLZO is more stable at RT than the cubic phase. Therefore, supervalent dopants are needed to stabilize the cubic phase at RT. In this study we were able to stabilize cubic LLZO via substitution of Zr⁴⁺ by Mo⁶⁺. With a Mo⁶⁺ content of 0.25 pfu the cubic LLZO phase is overall stabilized in the synthesis. The solubility limit of Mo⁶⁺ is about 0.3 pfu. Based on neutron powder diffraction and Raman spectroscopy Mo⁶⁺ is located at the 16a site of LLZO. Since Mo⁶⁺ has a smaller ionic radius compared to Zr⁴⁺ the lattice parameter, a₀, decreases as a function of the Mo⁶⁺ content (12.970 to 12.955 Å). The highest σ_bulk is about ~10^-3 S cm^-1 but varies significantly for nominally identical samples, i.e. within samples identically prepared/stored. The voltage stability window of Mo⁶⁺ doped LLZO was checked by using cyclic-voltammetry measurements indicating that the material is stable up to 6 V. In addition, Mo-doped LLZO was used as a model system to investigate the elementary steps of Li-ion diffusion within the cubic garnet lattice by using various ⁷Li NMR techniques. For instance, NMR relaxometry points to a less pronounced distribution of Li jump in the Li-ion sublattice than it was observed for the Al-stabilized LLZO. Since Al occupies the 24d and 96h sites this feature can most probably be related to the Li-ion sublattice that remains intact by using Mo⁶⁺ for stabilization of the cubic phase.
[1] Murugan, R.; Thangadurai, V. Weppner, W. Fast Lithium Ion Conduction in Garnet-type Li₇La₃Zr₂O₁₂: Angew. Chem. Int. Ed. 2007, 46, 7778.

Since the electrochemical activity of LiMPO₄ (M = Fe, Mn) was reported, olivine-type cathode materials have triggered the battery field due to their structural stability and excellent electrochemical properties [1]. Although LiFePO₄ has been intensively studied and is now commercially used, the manganese, cobalt or nickel based olivines are attracting considerable attention within the scientific community. Due to its high operating voltage of 4.8 V, LiCoPO₄ offers the potential to increase the energy and power density and thus, might bring a significant performance improvement [2]. Several procedures for the synthesis of nanosized LiCoPO₄ are reported, including hydrothermal [3], sol-gel [4] and mainly solid state synthesis [5]. However, these methods generally require long reaction times and post heat treatments at high temperatures to get phase pure LiCoPO₄.
Using a variety of water/polyol 1:1 binary solvent mixtures, including ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), tetraethylene glycol (TTEG), and polyethylene glycol (PEG), high-performance and highly crystalline LiCoPO₄ nanoparticles have been synthesized by a novel, simple and rapid microwave-assisted solvothermal route within short reaction times, at temperatures as low as 250 °C, and without any post-annealing. Scanning electron microscope studies reveal a strong influence of the co-solvent on the particle size and morphology with variations between square, rhombic and hexagonal platelets. The particles exhibit a length range of 500-800 nm and a thickness of 100-300 nm in the case of EG, DEG, TEG, and TTEG, and a particle size of about 9 mu;m × 7 mu;m × 3 mu;m for PEG. Brunauer-Emmett-Teller (BET) measurements show specific surface areas from 2 to 7 msup2;/g. According to selected area electron diffraction (SAED) experiments, the smallest crystal dimension is in the direction of the lithium diffusion paths (b axis), which is particularly beneficial to achieve high-power capability in lithium-ion cells. The favorable crystal orientation results in leading-edge initial discharge capacities (up to 141 mAh/g at 0.1 C), excellent rate capabilities and cycling stabilities. In conclusion, the fast reaction kinetics, facilitated by microwave irradiation, as well as the appropriate choice of reaction parameters allow controlling the particle size and morphology of LiCoPO₄ with enhanced electrochemical performance. Furthermore, the synthesis design and facile process might be applied for the preparation of other electrode materials.
[1] A.K. Padhi, K.S. Nanjundaswamy, J.B. Goodenough, J. Electrochem Soc.1997, 144, 1188.
[2] B. Brutti, S. Panero, J. Am. Chem. Soc.2013, 1140, 67.
[3] X. Huang, J. Ma, P. Wu, Y. Hu, J. Dai, Z. Zhu, H. Chen, H. Wang, Mater. Lett.2005, 59, 578.
[4] E.J. Kim, H.Y. Hu, J.S. Lim, J.W. Kang, J.H. Gim, V. Mathew, J. Kim, J. Solid State Electrochem.2012, 16, 149.
[5] K. Amine, H. Yasuda, M. Yamaguchi, Electrochem. Solid State Lett.2000, 3, 178.

Transition-metal oxides, such as LiCoO₂ and LiMn₂O₄, are currently the most widely used cathode materials for lithium-ion batteries because of their high specific capacity and low cost. However, large inhomogeneous volume changes can induce severe mechanical stresses in these electrode particles under high charging/discharging rates, thus causing failure and capacity fading. In this work, we consider the concept of utilizing a graded material to improve the performance of the electrode particles on a mechanical basis.
Varying the material composition of the particle in a specified way can impose residual stresses that reduce the resultant stress levels. Here, we model a spherical LiMn_2-xNi_xO₄ cathode particle, which has a specified Ni concentration distribution along the radius. The coupled elasticity-diffusion problem of the particle is solved by using a two dimensional finite element code. The fracture behavior of the particle is analyzed with linear elastic fracture mechanics. We will present the effect of residual stresses on the resultant diffusion induced stresses and fracture behavior of the particle. This analysis shows that the mechanical reliability of the particle under high charging rates can be improved by using chemical changes to induce residual compressive stresses.

Carbon is an attractive material for use in electrochemical energy storage devices because its low density ensures the high gravimetric energy density desired for this class of applications. However, carbon has been shown to suffer from degradation during cell cycling leading to poor cycling performance. The problem is particularly acute for Li-O2 batteries, whose operation processes involve reactive intermediates species of O₂. Here we present a strategy to meet the challenge presented by the carbon electrode. Inverse opal carbon of mesoporous sizes was synthesized and coated with an FeOx layer by atomic layer deposition (ALD) for protection and then also decorated with Pd nanoparticles by ALD as an oxygen reduction catalyst. The FeOx layer was characterized by Brunauer-Emmet-Teller pore size measurement, transmission electron mircrographs, and raman spectroscopy, and found to be amorphous and uniformly 1.4 nm thick over the carbon skeleton. By physically separating carbon from Li₂O_2shy;, reaction intermediates, and the electrolyte, the cycling performance of the protected carbon cathode was shown to improve from 16 cycles without to 68 cycles with FeOx. Proof of reversible Li₂O₂ formation and decomposition was provided by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and differential electrochemical mass spectrometry (DEMS) revealing the stability of the carbon against the Li-O₂ battery environment. These results show that the problem of cathode stability can be mitigated in Li-O₂ battery chemistry provided the correct cathode architecture is used to maximize performance.

The inhomogneous Li electrodeposition of lithium metal electrode has been a major impediment to the realization of rechargeable lithium metal batteries. Although single ion conducting ionomers can induce more homogeneous Li electrodeposition by preventing Li⁺ depletion at Li surface, currently available materials do not allow room-temperature operation due to their low room temperautre conductivities. In the paper, we report that a highly conductive ionomer/liquid electrolyte hybrid layer tighly laminated on Li metal electrode can realize stable Li electrodeposition at high current densities up to 10 mA cm^-2 and permit room-temperature operation of corresponding Li metal batteries with low polarizations. The hybrid layer is fabricated by laminating few micron-thick Nafion layer on Li metal electrode followed by soaking 1M LiPF₆ EC/DEC (1/1) electrolyte. The Li/Li symmetric cell with the hybrid layer stably operates at a high current density of 10 mA cm^-2 for more than 2000 h, which corresponds to more than five-fold enhancement compared with bare Li metal electrode. Also, the prototype Li/LiCoO₂ battery with the hybrid layer offers cycling stability more than 350 cycles. These results demonstrate that the hydrid strategy successfuly combines the advantages of bi-ionic liquid electrolyte (fast Li⁺ transport) and single ionic ionomer (prevention of Li⁺ depletion).

Recently, high energy density lithium ion batteries (LIBs) play an important role in the field of portable and electronic devices and electrical vehicles. Although conventional layered LiCoO₂ cathode material has good electrical properties, the capacity of current LiCoO₂ is around 160 mAhg^-1 with lithium utilization in the structure less than 50%. Moreover, their cost and safety requirement are still problems for the adoption of lithium ion technology for these large-battery application. In this reasons, during the past two decades, several cathode materials have been emerged as an alternative layered structure compounds, such as olivine phosphates (LiMPO₄; M = Fe, Co, Ni, and Mn) and spinel oxides (LiM₂O₄; M = Mn, Ni and Co), however these still have a relatively low capacity. To overcome this problem, Over-lithiated Layered Oxide materials have been considered one of the promising cathode materials for the next generation of cathode materials. Among them, 0.5Li₂MnO₃middot;0.5LiNi_0.5Mn_0.5O₂ which is known as high capability (250 mAhg^-1) has excellent electrochemical performance and stability at higher cut-off voltage beyond 4.8 V. However, its severe capacity fading during high current rates is generally related to the unstable structure and the side reaction with electrolytes cause problems while cathode carries out beyond 4.8 in a range of high voltage. Herein, we reported Li₂ZrO₃ -coated Li_1.2Ni_0.2Mn_0.8O₂ for the High Performance Cathode Material in Lithium Ion Batteries. The concept is either to decrease the interface resistance by crystallization of the surface layer, or to cover the particles with Li2ZrO3 that would suppress the particles against side reactions with the electrolyte. In addition, it can circumvent the loss of transition-metal ions of oxygen, without changing the electronic and ionic conductivities. In this study, X-ray diffraction, Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy, Electrochemical Impedance Spectroscopy and various Charge-discharge measurements were also performed to further investigate the effect of surface-coating layer.

Silicon(Si) is one of the promising anode candidates owing to its high theoretical capacity of 3500 mAh g^-1 [1], which is approximately 10 times higher than the capacity of conventional graphites. However, Si anodes have not been widely introduced into commercial lithium-ion batteries (LIBs), because they experience large volume expansion (~400%) during the Li⁺ insertion and extraction. In order to mitigate this expansion during the cycles, the choice of binder for holding all of the material in the Si anode is very important. Although polyvinylidene fluoride (PVdF) has been widely utilized as a polymeric binder for commercialized LIBs over decades, lots of previous works have proved that PVdF could not provide the Si anodes with sufficient mechanical property to maintain their original electrode structure. In order to overcome the limitation of PVdF, many researchers have proposed new polymeric binder materials such as polyacrylic acid (PAA) [2], alginate [3] and polyimide (PI).[4]
In this study, we newly introduce highly adhesive and thermally stable co-polyimide (P84), which is soluble in organic solvents, to Si anodes for high energy density LIBs. The Si anodes with the P84 binder shows not only a little higher initial discharge capacity (2392 mAh g^-1) but also fairly improved Coulombic efficiency (71.2%) compared with the Si anode using conventional PVdF binder (2148 mAh g^-1 and 61.2%, respectively). The Si anode with P84 also shows stable long-term cycle performance of 1313 mAh g^-1 after 300 cycles at 1.2 A g^-1 and 25 °C. Moreover, from the electrode adhesion properties with surface and interfacial cutting analysis system (SAICAS) and peel tests, the P84 could maintain the original electrode structure very well even after cycling.
Acknowledgements
This research was financially supported by the Ministry of Education(MOE) and National Research Foundation of Korea(NRF) through the Human Resource Training Project for Regional Innovation (No. 2014066977)
References
[1] Obrovac, M.; Christensen, L., Structural Changes in Silicon Anodes during Lithium Insertion/Extraction. Electrochem. Solid-State Lett. 2004, 7, A93-A96.
[2] Magasinski, A.; Zdyrko, B.; Kovalenko, I.; Hertzberg, B.; Burtovyy, R.; Huebner, C. F.; Fuller, T. F.; Luzinov, I.; Yushin, G., Toward Efficient Binders for Li-Ion Battery Si-Based Anodes: Polyacrylic acid. ACS Appl. Mater. Interfaces 2010, 2, 3004-3010.
[3] Ryou, M. H.; Kim, J.; Lee, I.; Kim, S.; Jeong, Y. K.; Hong, S.; Ryu, J. H.; Kim, T. S.; Park, J. K.; Lee, H., Mussel#8208;Inspired Adhesive Binders for High#8208;Performance Silicon Nanoparticle Anodes in Lithium#8208;Ion Batteries. Adv. Mater. 2013, 25, 1571-1576.
[4] Choi, J.; Ryou, M.-H.; Son, B.; Song, J.; Park, J.-K.; Cho, K. Y.; Lee, Y. M., Improved High-Temperature Performance of Lithium-Ion Batteries through Use of a Thermally Stable Co-Polyimide-Based Cathode Binder. J. Power Sources 2014, 252, 138-143.

In order to enhance the commercial feasibility of silicon-based lithium ion battery, the structural degradation issue caused by the significant volume changes (>300%) during the insertion/extraction of lithium ions needs to be resolved. Herein, an extraordinary anode material, mesoporous Si wafer was developed from the wasted-Si wafer after the chemical etching process. A matrix of silicon and carbon is synthesized via in-spaced carbonization with high-energy ball milling process. The well-dispersed nanoparticle demonstrates a significant improvement of electrochemical performance in comparison with the commercial nano-Si. The matrix delivers a high capacity retention above 900mAhg^-1 after the first 10 cycles and a Coulombic efficiency higher than 99%. Overall, the crystallinity of silicon is decreased, and a lesser extent, to a rise of the lattice strain with the high-energy milling process. The synthesis method can be easily scaled up for mass production. This wok introduces a new method using recycled-Si wafer to achieve the goal of manufacturing Si-based lithium ion battery.

The most widely used anode materials for commercial Li-ion batteries (LIBs), graphite, is hard to expand its application to large scale energy storage because of low theoretical capacity (372 mAhg^-1). To meet the increasing demand for higher capacity and better rate capabilities, it is necessary to find alternative anode materials. Transition metal oxides (TMOs), which are interact with Li based on conversion reaction mechanisms, can deliver specific capacities around 1000 mAhg^minus;1, nearly, three times that of graphite. As a typical TMO, Fe₂O₃, owing to its high theoretical specific capacity (1007 mAhg^minus;1), abundant resources, nontoxicity, high corrosion resistance and low cost, has long been considered as a promising candidate for the new generation of anode materials. However, the practical application of Fe₂O₃ is hindered by pulverization and poor electrical conductivity, which cause fast capacity fading and bad rate performance during electrochemical cycling. One of the suggested strategy is constructing 3D-framework. Recently, many reports with 3D-frameworks have showed great rate capabilities and long-term cyclic performance due to its large reaction area and good structural integration. Meanwhile, large volume change during the operation causes significant challenges in selecting the binder and electrolyte, which hold the active material together in the electrode and form SEI layer. Therefore, it is also important task to choose binder and electrolyte for enhanced electrochemical properties in TMOs.
In this study, we fabricated 3D hierarchical Fe₂O₃ nanosheets/carbon composite structures for highly stable LIBs. Fe₂O₃ hierarchical structure was obtained by reflux method using FeCl₃#8729;6H₂O, ethylene glycol, urea, and tetrabutyl amonnium bromide as precursors, and annealing 500°C in air. The structure of particles was characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. As-synthesized powder was self-assembly structure of porous nanosheet with thickness about 10nm. We subsequently evaluated the electrochemical properties of these Fe₂O₃ hierarchical structure as anode materials for rechargeable LIBs. Before cyclic test, we tested binders and electrolytes effects on hierarchical Fe₂Oshy;₃ structures to obtain optimum electrochemical conditions. As-prepared samples were demonstrated superior rate performance and good cyclic capacity retention especially at high charging-discharging rate over 1000mAg^minus;1. The hierarchical Fe₂O₃ samples showed as high as 990mAhg^minus;1, near theoretical capacity, over 170 cycles at current density 1000mAg^minus;1 and stable capacity recovery at 1000mAg^minus;1 after 20Ag^minus;1 charging-discharging rate. Additional carbon coating process was applied on obtained Fe₂O₃ powder to enhance structural stability and electron conductivity by hydrothermal method using glucose as a precursor. After carbon coating, the sample showed excellent cycleability compared to other reports about Fe₂O₃ powders.

High voltage cathode materials show promise for improving the specific energy of the state-of-the-art lithium ion battery. One notable cathode material that displays a discharge voltage of ~4.8V, and has the potential to improve the specific energy to ~802Wh/kg, is the olivine-structured LiCoPO₄. A significant issue, however, that has plagued LiCoPO₄-based systems is the irreversible electrolyte decomposition that occurs at the electrolyte/electrode interface at higher voltages. Electrolyte additives have long been used to improve the passivation layer on the anode, but little is known about the importance of electrolyte additives on the cathode surface. The following study demonstrates a design of experiment (DOE) approach for optimizing the electrolyte additive concentration. The optimized electrolyte improves the cycle life and specific capacity of the cell, while reducing the interfacial impedance. The resulting full-cell containing the optimized electrolyte demonstrates a specific energy that is greatly improved over a full-cell containing the standard electrolyte.

The next generation of energy storage devices relies on a broad and adaptable range of volumetric and gravimetric energies to compete with the challenges in stationary, mobile and particularly portable electronics electricity supply. Here, all solid state batteries based on Li-garnet-based structures are interesting model systems as these allow for complete solid state microbattery prototypes based on thin film structures for powering of portable electronics on chip in the future. Additionally, by the use of microfabrication tools it is possible to fabricate advanced and optimized microbattery designs able to overcome the most important issues found on microbattery operation, namely their mechanical stability towards silicon-based substrates. I.e. volume expansion and strain adaptation during lithiation/delithiation. From a materials perspective, cubic garnet Li₇La₃Zr₂O₁₂-structure electrolyte has been found to be one of the fastest conducting solid state electrolytes ^[1,2]. Although stable in its tetragonal phase at room temperature, one can stabilize its more conductive cubic phase by adding different dopants in either the A site or C site. In this work, we newly report on Al- and Ta-doped Li₇La₃Zr₂O₁₂ thin films grown by Pulsed Laser Deposition. Their crystallization and ionic transport characteristics are discussed towards thin film phase stabilization. Special attention is placed on the Li loss compensation both during target processing ^[3] and thin film growth ^[4] vs. phase stability. Secondly, we report on suitable Li₄Ti₅O₁₂-spinells for the electrode sides on our microbattery being a potential anode deposited by pulsed laser deposition. We report on half cells for the model Li₄Ti₅O₁₂/Li₇La₃Zr₂O₁₂ anode/electrolyte bilayers microbattery systems. Finally, novel types of thin film microbatteries tunable and adaptable to electro-chemo-mechanical variations ^[5] during operation will be presented, which allow to compensate mechanical stresses to avoid cracking upon operation on silicon substrates. Here, two different model designs are described: (i.) the fabrication of microbattery dot arrays and (ii.) novel “Tortilla wrapped Li⁺ microbattery structures” with engineered strain fields to control the electro-chemo-mechanic variations during operation.
References
^[1] Knauth, Solid State Ionics 180(14-16), 911.
^[2] Thangadurai et al., Chemical Society Reviews 43(13), 4714.
^[3] Buschmann, Janek et al., Phys. Chem. Chem. Phys. 13, 19378.
^[4] Park et al. Thin Solid Films 576, 55.
^[5] Shi, Rupp et al., Nat. Mater. DOI. 10.1038/nmat4278, 2015.

Thin-film batteries show increasing interest in e.g. medicine and biotechnologies where miniaturized batteries are required or toxic liquid electrolytes should be avoided. Another focus lies on their use as model systems for larger applications. In any case, materials processing and battery operation requires reliable enthalpy data on phase transformations in a large temperature range.
In this work, enthalpy data are determined using the recently developed measurement technique Thin-Film Calorimetry (TFC), which is based on piezoelectric resonators vibrating in thickness shear mode. They are applicable up to 1000 °C. To the best of our knowledge, no other TFC system for this operation temperature range exists. The temperature dependence of the resonance frequency is used as a carrier signal. Deviations from the undisturbed course of the temperature dependent resonance frequency can be assigned to phase transformations of the investigated film consuming or generating a certain amount of heat. The sensitivity is about 0.7 mJ. Further, improvements such as the application of free-standing resonators and modeling of the heat conductivity are realized. Required data including the thermal diffusivity are determined by Laser Flash Analysis in the range of room temperature (RT) up to 700 °C.
The TFC can be operated in two modes:
(I.) Applying constant temperature ramps comparable to e.g. Dynamic Scanning Calorimetry.
(II.) Isothermal mode. Here, thermal changes in a thin-film battery can be monitored in-situ during dis-/charging or reaction enthalpies under equilibrium conditions.
Application examples related to lithium ion battery materials are shown. Thin films of the family Li-Ni-Mn-Co-Al-Oxide (NMC/NMCA) are investigated and compared when annealed in ambient air or 0.5 %H₂/Ar up to 900 °C. They show three phase transformations. In air, all samples crystallize in the range of 250-325 °C. In 0.5 %H₂/Ar, the transformations occur at higher temperatures. Especially in air, stoichiometric NMC shows its crystallization at lower temperatures compared to Ni-rich compositions. Additional doping with Al enhances the thermal stability which is valid for all phase transformations at higher temperatures.
Further, molybdenum disulfide (MoS₂) nanostructures with different morphologies are synthesized and tested with respect to phase transformations. The nanostructured samples are compared with thin-film samples to evaluate the influence of the morphologies on the electrochemical performance.

Abstract
Understanding interfacial phenomena occurring across active, nanostructured electrochemical membrane electrode assemblies demands in situ characterization techniques with increased spatial resolution. Recent advancements in atomic force microscopy (AFM) instrumentation and sub-systems in realizing real time imaging at high temperatures and ambient pressures, and the use of these in situ, multi-stimuli probes in collecting local information related to physical and fundamental processes are reviewed and discussed. Here we first demonstrate direct probing of local surface potential gradients related to the ionic conductivity of yttria-stabilized zirconia (YSZ) within symmetric fuel cells under intermediate operating temperatures (500 °C - 600 °C) via variable temperature scanning surface potential microscopy (VT-SSPM). The conductivity values obtained at different temperatures yield direct, locally-derived estimates of the activation energy. Subsequent comparisons to macroscopic electrochemical impedance results and bulk literature values support the validity of the approach. Utilizing the advantage of high spatial resolution of this approach, we further investigated the local physical properties near the interfaces of STO/YSZ heterostructured multilayers under intermediate operating temperature (500 °C). Potential variations occurring near the interface indicated oxygen vacancy diffusion between the STO and YSZ layers. Application of Poisson&’s equation and dopant concentration analysis determined the density of oxygen vacancies diffused from the interface. These results provide a possible explanation to the colossal conductivity recently observed in epitaxial YSZ/STO heterostructures¹.
Reference
(1) Garcia-Barriocanal, J.; Rivera-Calzada, a; Varela, M.; Sefrioui, Z.; Iborra, E.; Leon, C.; Pennycook, S. J.; Santamaria, J. Science2008, 321 (5889), 676-680.

Thin-film solid state electrolytes are a key technology not only for the development of all solid state microbatteries but also for fundamental studies on the diffusion process in solid electrolyte materials. Pulsed laser deposition is an ideal method for depositing thin-film solid state electrolytes as it allows for: higher control of the stoichiometry by directly transferring the stoichiometry from the target to the thin film; a wide range of temperatures, process gases, and deposition rates to be utilized; and epitaxial growth through the use of various substrates.¹ Li_3+xGe_xP_1-xO₄ in its crystalline phase is isostructural with Lithium Superionic Conductors (LISICON) and displays high lithium conductivities around 10^-5S/cm at room temperature.² We demonstrate the deposition of Li_3+xGe_xP_1-xO₄ thin films for the first time through pulsed laser deposition. These films are ideal candidates for studying the diffusion process in LISICON systems and for use in microbatteries as it shows conductivities comparable to the commonly used LiPON solid state electrolyte.³ This study provides insights into the mechanism of Li-ion conduction in solid state electrolytes and the design of thin-film electrolytes.
1. Chrisey D.B. and Hubler G.K., eds, 1994, Pulsed Laser Deposition of Thin Films, Wiley, New York.
2. Rodger A.R., Kuwano J., West A.R., Solid State Ionics 15 (1985) 185-198.
3. Yu X. et al., Journal of the Electrochemical Society 144 (1997) 524-532.

Nanostructured silicon has been widely studied for use in lithium ion batteries because silicon has a high lithium storage capacity and nanostructures can survive the over 300% volume expansion of silicon experiences during lithiation. Stable cycling at high capacities has been shown, using a variety of nanostructured silicon geometries. However, these capacities can be misleading as they are often normalized by the mass of silicon or the mass of the silicon and one or two other components. For practical application of silicon in lithium ion batteries, the capacity normalized by the total mass of the electrode must be increased. This can be achieved by decreasing the mass of the electrolyte and the current collector while increasing the volume of the electrode occupied by silicon. Many electrodes that have been demonstrated are grown on or adhered to metal foils that are at least several micrometers thick and often weigh more than the silicon in the electrode. Furthermore, the electrodes must be porous to allow for the expansion of the silicon. If the silicon expands by 300%, at least two thirds of the cell must be empty which means it becomes filled with electrolyte or solid electrolyte interphase (SEI) during assembly and cycling. Finally, most stable electrodes have a low volumetric silicon loading or only a few percent of the volume of the electrode is occupied by silicon. We have observed the capacity fade rate during cycling to be strongly dependent on the silicon loading and attribute the low silicon loading in reported electrodes to this phenomenon.
We have developed a nanoporous monolith scaffolding for silicon as a potential platform to address these issues. It is made by growing vertically aligned carbon nanotubes (VACNTs) and further coating them with graphitic carbon layers, effectively adding walls to the carbon nanotubes (CNTs) and locking the VACNTs together forming a highly interconnected nanoporous monolith. The rigidity of the monolith allows it to be immersed in liquid and dried without deformation. Consequently, we have removed it from the growth substrate by a wet etching process, and evaporated copper films as thin as 125 nm onto the backside to serve as ultra-light current collectors. Additionally, a sacrificial etching process has been used to allow the application of a thin encapsulating shell to the exterior of the monolith, which prevents electrolyte (and SEI) from occupying the interior of the electrode decreasing the total amount of electrolyte needed in the cell. Finally, the monolith structure has allowed us to study the mechanisms responsible for the failure of electrodes high loadings and achieve stable cycling with electrodes that are approximately 20% silicon by volume.

Energy provision and storage are well recognised issues for wireless sensors envisaged in the Internet of Things scenario. Solid state electrolytes enhance battery lifetimes with 5,000+ cycles typically achieved in 2D, thin-film geometries which would be ideal for wireless sensors. However, slow lithium diffusion and poor electronic conductivity limit the electrode thickness to micrometers and thus large surface areas are required resulting in a battery dominated by the substrate and other inactive cell components. Energy sources with increased performance per unit substrate area are therefore required. Long life sensors necessitate a hybrid energy harvester/storage device to meet the energy demands.
Commercial thin film Li-ion batteries are the most energy dense option but have limited storage capacity and power delivery capability. Multiphysics simulations (COMSOL) of the active materials in 3D, 1D and core-shell architectures have shown the advantages of this approach for next generation energy storage devices. The simulations described in this research will show that nanoscale and core-shell nanowires of relatively low conductivity cathode oxide materials can operate within the appropriate potential range (cut-off voltage 2.5 V) at 3 times the C-rate while still accessing 90% of the cathode oxide material in comparison with micron scale thin film materials.
Cell footprint or volume is a significant issue for microbatteries. The most energy dense alternatives to Li metal anodes are Si, Ge or Sn which can store between 4.8 and 3.5 times more energy per µm of thickness than Li metal, the most common anode in Li microbatteries. However, these high-energy materials suffer mechanical instability (for micron scale materials) due to volume expansion and contraction on cycling. Nanowires, core-shell nanowires and high electronic conductivity supports such as copper nanotubes^[1] alleviate the effect of volume expansion enhancing mechanical stability at the nanoscale while also increasing the surface area and improving the electronic characteristics for increased rate capabilities. This research will present results from the investigation of high energy dense materials in nanostructured architectures^[2,3]. It will also show the effects of ultrathin interfacial metallic films on these high energy dense anode materials.
References:
1. M. Hasan, T. Chowdhury and J. F. Rohan, Journal of The Electrochemical Society, 2010, 157, A682-A688
2. J.F. Rohan, M. Hasan, S. Patil, D. Casey and T. Clancy, Chapter 6, in ICT-Energy concepts towards Zero-Power Information and Communication Technology, 2014.
3. T. Clancy, M. Hasan and J. F. Rohan, ECS Transactions, 2014, 61, 21-28.

High gravimetric and in particular volumetric capacity electrodes are of great significance for secondary batteries, and “nanostructured” systems have often been reported as a possible pathway to realize these attributes. However, most nanostructured electrodes actually have rather low gravimetric and/or volumetric capacities on a full electrode basis (often their performance is reported on an active materials basis only). Here we discuss several strategies for high full electrode basis capacity 3D nanostructured electrodes. In one, a structurally robust, scaffold-free, Fe₃O₄/C nanocomposite was fabricated which consists of ~5 nm diameter Fe₃O₄ nanoparticles embedded within a carbon matrix. The high capacity of the Fe₃O₄ nanoparticles enables the nanocomposites anode to exhibit a full electrode volumetric discharge capacity of about 1064 mAh cm^-3 which significantly exceeds the ~300 mAh cm^-3 capacity of a typical commercial carbon anode (theoretical capacity 837 mAh cm^-3). On a full electrode basis, the capacity is greater than 710 mAh g^-1 (about twice of theoretical capacity of graphite anode). As a proof-of-concept for real-world applications, a 100 µm thick Fe₃O₄/C composite anode was fabricated which exhibited similar performance metrics as the model system. Importantly, the scaffold-free nanocomposite design is quite general, and may serve as a guide for many emerging nanostructured anode and cathode systems. For example, via a related method, a V₂O₅@graphene@V₂O₅ cathode and a graphene@Si@graphene anode were fabricated; in both systems, the capacities significantly exceeded conventional systems. The cycle life of the V₂O₅ system was particularly good. Even over 2000 cycles, the capacity is ~203 mAh g^#8210;1 and the Coulombic efficiency is around 99.7%.

Cathode materials for commercial Li-ion batteries are lagging behind their anode counterparts in term of energy density. From the perspective of enhancing cathode performances, organic redox materials enable easy manipulation on compound structure and functionality, and thus tuning of the resulting electrode properties. They also possess the contextual advantage of being more environment-friendly than currently used inorganic materials. The carbonyl reversible redox process has been intensely studied over the past years, with the quinone - hydroquinone based molecular structures being the most representative example. Theoretically, those compounds can reversibly exchange two electrons per quinone unit, resulting in high specific capacities. In this talk, we will discuss about the simple synthesis via a two-step chemical approach of poly(2,5-dihydroxyaniline) (PDHA), a cross-hybrid molecular architecture of redox quinone and electron conductive polyaniline. This polymer is obtained through oxidative polymerization of 2,5-dimethoxyaniline followed by chemical demethylation that is found to be more efficient than the previously reported methods[1]. This novel organic cathode material has a theoretical capacity of 443 mAh g^-1. PDHA is insoluble yet swells adequately in organic electrolytes to enable efficient ion transport. The electrical conductivity of PDHA is as high as 0.1 S/cm, ranking this material amongst the most conductive positive electrodes for Li-ion batteries. The active material is processed into a slurry with conductive carbon and PVDF binder, which is subsequently spread on carbon-coated aluminium foil. Synthesis as well as electrode processing optimization routes will also be discussed[2]. The cyclic voltammetry response hints at a two electron reversible redox process attributed to the quinone groups. A specific capacity of 290 mAh g^-1 is achieved via galvanostatic charge-discharge measurements with a potential window of 1.8 - 3.2 V (vs. Li/Li⁺) at a C/10 rate in a half-cell configuration. PDHA holds thus great potential as an active component for Li-ion batteries, with room for further improvements in terms of energy density and capacity retention.
[1] A. Vlad et al. J. Mater. Chem. A 3, 11189 (2015).
[2] L. Sieuw et al. in preparation.

Solid-state electrolytes will have their greatest impact in electrical energy storage (EES) once non-line-of-sight protocols and processes are established that incorporate them conformally and with nanometric control into next-generation 3D EES devices—especially those that are scaled beyond microbattery sizes. Because the interface between the cathode and anode is maximized in a 3D EES configuration and the anode/cathode separation distance is minimized, power limitations that would otherwise be imposed by modest ionic conductivity in a bulk (thick) solid-state electrolyte are mitigated when using ultrathin solid-state electrolytes [1,2]. We have demonstrated the ability to oxidatively electropolymerize poly(phenyleneoxide) within sponge/foam scaffolds [3,4], but when the initial architecture is metallic, alternate chemistry is required. We have selected a common siloxyl monomer (1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, V3D3) that can be polymerized in non-line-of-sight fashion by either reductive polymerization (EP) or by initiated chemical vapor deposition (iCVD [5]); iCVD-derived poly(V3D3) was recently shown to be a promising solid-state electrolyte when deposited on planar indium-tin oxide [6]. Both EP and iCVD yield conformal, nanoscale, passivating polymer coatings at complex, 100 mu;m-thick 3D architectures, with EP-derived poly(V3D3) exhibiting a more gel-like nature, consistent with residual vinyl groups in the film [7]. We have focused on the siloxane-type polymer coatings for two energy-storage designs: (i) Al electrolytic capacitors in which the polymer serves as a charge-storing dielectric, and (ii) an all-solid-state 3D Li-ion battery in which the polymer is transformed into an ion-conducting electrolyte by impregnation with Li⁺ salt. The resulting polymers and associated interfaces are characterized by spectroscopy and microscopy to determine chemical structure and morphology, while key energy-storage parameters are assessed using AC and DC methods.
1. J.W. Long, B. Dunn, D.R. Rolison, H.S. White, Chem. Rev. 10, 4463 (2004).
2. C.P. Rhodes, J.W. Long, M.S. Doescher, J.J. Fontanella, D.R. Rolison, J. Phys. Chem. B108, 13079 (2004).
3. C.P. Rhodes, J.W. Long, K.A. Pettigrew, R.M. Stroud, D.R. Rolison, Nanoscale3, 1731 (2011).
4. J.C. Lytle, J.W. Long, C.N. Chervin, M.B. Sassin, D.R. Rolison, SPIE: Micro- and Nanotechnology Sensors, Systems, and Applications III8031, #80311N (2011).
5. W.E. Tenhaeff and K.K. Gleason, Adv. Func. Mater. 18, 979 (2010).
6. N. Chen, B. Reeja-Jayan, J. Lau, P. Moni, A. Liu, B. Dunn, and K.K. Gleason, Mater. Horizons2, 309 (2015).
7. M.B. Sassin, J.W. Long, J.M. Wallace, D.R. Rolison, Mater. Horizons2, (2015) in the press.

The use of metallic lithium anodes will enable higher energy density and higher specific capacity lithium-based batteries. For example, the specific capacity gain in lithium-air batteries is coupled to the use of a metallic lithium anode. However, the successful use of lithium anodes relies critically on enabling dendrite-free electrochemical deposition of lithium during the charge cycle. Li-ion conducting ceramics (LICC) can mechanically suppress dendritic growth but are too fragile and also have lower Li-ion conductivity than is preferred for battery applications. In this talk, we will present a versatile and scalable procedure for fabricating flexible Li-ion conducting composite membranes composed of a single layer of LICC particles firmly embedded in a polymer matrix with their top and bottom surfaces exposed to allow for ionic transport. The procedure for making one-particle thick membranes is uniquely simple and amenable for large-scale manufacturing. The membranes are thin (< 100 mu;m) and possess high Li-ion conductance at thicknesses where LICC disks are mechanically unstable. These membranes suppress Li-dendrite growth even when the shear modulus of the polymer matrix is lower than that of lithium. We anticipate that these membranes will enable the use of metallic lithium anodes in conventional and solid-state Li-ion batteries as well as in future Li-S and Li-O₂ batteries.

Metallic lithium is the most promising negative electrode for high-energy rechargeable batteries due to its extremely high specific capacity and its extremely low redox potential. However, the low cycle efficiency and lithium dendrite formation during the charge/discharge processes consistently hinder its practical application. In this report, we present a stabilized Li electrode on which a Li⁺ ion conductive inorganic/organic composite protective layer (CPL) is coated. With the introduction of the CPL, the Li dendrite growth and electrolyte decomposition are effectively suppressed; consequently, stable Li plating/stripping at high current densities up to 10 mA cm^-2 is possible. Nanoindentation tests demonstrate that the shear modulus of the CPL at narrow indentations is 1.8 times higher than that of the Li metal, which provides a theoretical understanding for its efficacy. Moreover, the LiCoO₂/Li cell incorporating CPL exhibits excellent cycling stability up to 400 cycles at 1 mA cm^-2 (1 C-rate), which demonstrates practical applicability in Li ion batteries through replacing the graphite anode with a CPL-coated Li metal anode.

The unending demand for portable, flexible and wearable electronic devices that have an aesthetic appeal and unique functionality stimulates the development of advanced power sources that have excellent electrochemical performance, flexibility and more importantly, shape versatility. The challenges in the fabrication of next-generation wearable power sources mainly arise from their limited form factors, which prevent their facile integration into differently shaped electronic devices and from the lack of reliable electrochemical materials that exhibit optimized attributes and suitable processability. Here we report a cable-type structure for lithium-ion batteries with exceptional mechanical flexibility. The batteries comprise several anode strands coiled into a hollow-spiral core, which is surrounded by a heat-resistive separator wetted with liquid electrolyte and a tubular outer cathode, and finally enclosed in a heat-shrinkable packaging tube. A prototype showed stable discharge characteristics regardless of bending strain and successfully powered an LED screen and MP3 player under severe twisting and bending. The proposed battery design will free product designers from conventional constraints and might facilitate breakthroughs in flexible and wearable electronics.

Electrical energy storage for transportation applications has gone beyond the limit of conventional lithium ion batteries. A series of SeSx-carbon (x = 0-7) composite materials has been prepared and evaluated as the positive electrodes in secondary lithium cells with ether-based electrolyte. In situ synchrotron high-energy X-ray diffraction was utilized to investigate the crystalline phase transition during cell cycling. Complementary, in situ Se K-edge X-ray absorption near edge structure analysis was used to track the evolution of the Se valence state for both crystalline and noncrystalline Phases, including amorphous and electrolyte-dissolved phases in the (de)lithiation process. In addition, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy demonstrated the reversibility of the Li/Se system in ether-based electrolyte and the presence of side products in the carbonate-based electrolytes. For Li/SeS2 and Li/SeS7 cells, Li2Se and Li2S are the discharged products with the presence of Se only as the crystalline phase in the end of charge.

Lithium-sulfur (Li-S) batteries have attracted significant interests because of their high energy density and promising potential to revolutionize the future electric energy storage systems. With the significant progresses made in the development of S-cathodes in recent years, the stability of Li-anode has become one of the more urgent challenges in order to reach the long-term stability of Li-S batteries.
Lithium metal is the preferred anode material for Li-S batteries because of its ultrahigh specific capacity. However, lithium polysulfides formed in cathode side during discharge process may migrate to anode side and react with Li metal (so called shuttle problem) and lead to limited cycle life and poor Coulombic efficiency of Li-S batteries. A passivation layer is easily formed on the metallic Li anode surface due to the presence of polysulfides and electrolyte additives, which is supposed to corrode Li anode and result in failure of the Li-S battery. Various strategies used to minimize the corrosion of Li anode and to reduce its impedance increase have been developed, including electrolyte additives, polymer electrolytes and interlayers. Recently, concentrated electrolytes were demonstrated to offer lower solubility of polysulfides and lead to longer cycling stability in Li-S batteries. The decrease of solubility of lithium polysulfides in concentrated electrolytes is due to the lack of available solvent molecules to partially solvate Li⁺ cations and the effect of coordinating anions through interacting with Li⁺ cations in different solvation strength. In this work, the failure mechanism and the stability of anode/electrolyte interface in Li-S batteries with highly concentrated electrolytes have been studied and the results will be reported at the meeting. In particularly, we compared various salts in concentrated electrolytes for Li-S batteries. It is found that the morphology and composition of SEI layer on Li metal anode formed in concentrated electrolyte are significantly different from that in the conventional electrolyte. NMR spectroscopy was used to investigate the solution structure of concentrated electrolytes with various lithium salts, which suggested different solvation structure and diffusion coefficient. The impedance evolution at the anode/electrolyte in concentrated electrolytes is also investigated in this work.
Acknowledgements
This work was supported by the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the Basic Energy Sciences, Office of Science of the U.S. DOE. The spectroscopic measurements were performed in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE&’s Office of Biological and Environmental Research and located at PNNL.

The development of advanced multivalent batteries that have a higher energy density than current state-of-the-art Li-ion battery (LIB) is predicated on the identification of new chemistries, including a compatible combination of cathode, anode and non-aqueous electrolyte. We used pulsed laser deposition to identify and control the factors that influence electrochemical activity for Mg insertion/de-insertion in Mn-based spinels (i.e., MgMn₂O₄). Epitaxial stabilization is used to grow thin films in the distinct tetragonal and cubic phases, where the latter is only thermodynamically stable at high temperature (> 950 °C) or high pressure (> 15.6 GPa). This comparison reveals that the two phases exhibit distinct electrochemical activity in the non-aqueous electrolyte, Mg(TFSI)₂ in propylene carbonate. Specifically, while the cubic phase exhibits reversible Mg²⁺ insertion and extraction with associated changes in film structure and Mn-oxidation states, the tetragonal phase has negligible charge/discharge activity. These results demonstrate the potential for multivalent cation intercalation in a spinel host material using non-aqueous/non-Grignard electrolytes, and provide a new strategy for material design for next-generation battery materials

MoS₂, a layered transition-metal dichalcogenide, has drawn interest as a new anode material for lithium-ion batteries. After years of development the improvement of the electrochemical properties of MoS₂ through structural modifications has probably reached its limits. Further improvements of the Li⁺ storage properties of MoS₂ would have to be based on the maximization of various Li⁺storage mechanismsin MoS₂. With this understanding we have developed a novel ternary composite of MoS₂ nanosheets, graphene, and a small amount (1 wt%) of silver nanoclusters (NCs)(MoS₂/G/Ag). Thereversible storage of Li⁺in MoS₂/graphene composite was significantly enhanced by the presence of this small amount of AgNCs. For example, the addition of Ag NCs to MoS₂/graphene composite could increase the Li⁺ storage capacity by 60%.The MoS₂/G/Ag composite also exhibited impressive rate performance.

MXenes are a new family of two-dimensional, 2D, transition metal carbides and carbonitrides produced by selective etching atomically thin metal layers from ternary layered ceramic material. They have a nominal composition of M_n+1X_n where M stands for early transition metal, X is carbon/nitrogen, and n = 1, 2, or 3. So far, nine different MXenes were reported MXenes were reported, viz., Ti₃C₂, Ti₂C, Nb₂C, V₂C, (Ti_0.5,Nb_0.5)₂C, (V_0.5,Cr_0.5)₃C₂, Ti₃CN, Ta₄C₃, and Nb₄C₃. In addition, many more are predicted to be stable. The surfaces of the as synthesized material are terminated with a mixture of surface groups including O, OH, and F. Unlike other MXenes, Titanium carbonitride is predicted to be metallic even after termination. Other MXenes with surface terminations are predicted to be semiconductors, with relatively small band gaps. Herein we report on a new Ti₃CN/nano-S composite with a high sulfur content of ~75 wt.%, and high mass loading. Analysis for their performance as cathodes in Li-S batteries in addition to the composite material characterization will be presented.

The stability of the solid electrolyte interphase (SEI) is critically important in rechargeable Li-ion batteries. In particular, the volume changes that occur in the active electrode materials during lithiation and delithiation can create significant mechanical deformations in SEI layers. It is difficult to probe the mechanical response of the SEI directly in complex electrode microstructures that consist of powdered active components and other constituents. However, thin films provide an opportunity to investigate fundamental processes more directly. This approach has been used to investigate SEI formation on silicon and carbon electrodes. To accomplish this, we employed in situ stress, AFM, conventional in situ electrochemistry, and ex situ surface characterization. These experiments allowed us to investigate SEI behavior in different electrolytes and with different cycling conditions. Significant differences between Si and graphitic carbon were observed in SEI growth and passivation mechanism. Both the electrolyte composition and the formation conditions had significant effects on the SEI structure and properties. The results from these experiments and corresponding models also suggest that stresses can be engineered during SEI formation, to enhance the electrochemical and mechanical integrity of these critical passivation layers.

Real-time stress evolution in aluminum thin-film electrodes during electrochemical lithiation and delithiation is measured using the substrate-curvature method. The LiAl phase that forms during lithiation is under a state of constant compressive yield stress of ca. 1 GPa. Further lithiation towards Li₃Al₂ causes the compressive stress to increase linearly with lithium concentration to ca. 1.5 GPa. Delithiation results in straining in the opposite direction leading to a peak tensile stress of ca. 0.75 GPa. Biaxial modulus of LiAl alloy is measured by electrochemically perturbing the LiAl electrode by a small amount of strain while simultaneously measuring the change in stress. Using the above measured values of stress and a simple thermodynamic argument based on the Larché-Cahn chemical potential of a solid solution under stress, the ratio of electric-potential change to stress change is estimated to be ca. 67 mV/GPa.

The formation of metallic lithium (Li) dendrites has major safety implications on current and future Li-based rechargeable batteries. Despite decades of research, the mechanisms and the conditions of dendritic growth are still not well understood, as suitable test systems and characterization methods are challenging to develop. Theoretical efforts are underway and experimental studies have already established general conditions for Li plating [1,2]. However, these studies typically require specific materials and electrode geometries to enable optical access for in-situ analysis, and do not yet mimic the conditions in commercial batteries.
Dendrites that cause failure of today's commercial Li-ion batteries grow within the pores of a polymeric separator. In addition to the electrochemical cycling (e.g., cycling rate) and environmental conditions (e.g., cell temperature), the microstructure of the separator influences dendrite growth via electro-mechanical interfacial coupling. The transport parameters of electrolyte filled separators depend on the overall cell pressure and local pore closure [3,4], and require multi-length scale analysis. Therefore, advanced characterization techniques to locate, visualize, and quantify dendrites within commercial separators with sub-micrometer resolution, as well as the separator microstructure itself, are needed to advance the understanding of dendrite formation and growth.
Here, we show focused ion-beam scanning electron microscopic (FIB-SEM) and x-ray tomographic analysis as complementary ex-situ characterization techniques on different length scales. We demonstrate three-dimensional visualization and quantification of dendrites in commercial separators, following cycling in both model Li⁰|separator|Li⁰ and commercial cells. In a next step, we link the occurrence and three-dimensional morphology of dendrites and their spatial location within the separator to electrochemical testing conditions and to commercial separator microstructure, which we image and quantify using FIB-SEM tomography. We provide our 3D data-sets open source to the battery community to enable researchers working on simulations to employ realistic separator microstructure and thereby promote model development and validation.
[1] J. Steiger, et al., "Comparison of the Growth of Lithium Filaments and Dendrites Under Different Conditions", Electrochem. Comm.50, 11-14 (2015).
[2] C. T. Love, et al., "Observation of Lithium Dendrites at Ambient Temperature and Below", ECS Electrochem. Lett.4, A24-A27 (2015).
[3] G. Y. Gor, et al., "A Model for the Behavior of Battery Separators in Compression at Different Strain/Charge Rates", J. Electrochem. Soc.161, F3065-F3071 (2014).
[4] J. Cannarella and C. B. Arnold, "The Effects of Defects on Localized Plating in Lithium-Ion Batteries" J. Electrochem. Soc.162, A1365-A1373 (2015).

Li-ion batteries are now indispensably used as energy storage devices for portable electronics, electric vehicles, and are starting to enter the market of the renewable energies. The rechargeable capacity and the battery life depends critically on the structural stability of the electrodes themselves, the electrolyte degradation rate, and the electrode-electrolyte interaction layer-the so called solid electrolyte interphase (SEI) layer. Over the last few years tremendous progress has been made towards direct in-situ TEM observation of structural and chemical evolution of electrodes used for lithium ion batteries. However, capturing of molecular information across the solid-liquid interface has never been possible. Here we report the development of an in-situ liquid SIMS and its usage for the first time to directly observe the molecular structural evolution on the electrode and within the liquid electrolyte for lithium ion battery under dynamic operating condition. We observed that, upon charging of the battery, PF₆^- anions were repelled from the anode side, Li⁺ ions were reduced at the anode, and a liquid layer with a significantly low concentration of Li⁺ and PF₆^- was formed around the anode. Formation of the lean electrolyte layer around the electrode will lead to reduced ionic conductivity and therefore contributing to the overpotential of the battery. The present work opens the door for in-situ SIMS studies of both dynamic structural and chemical evolution of the electrodes and the SEI layer formation in batteries using real battery relevant electrolytes.

In all traditional closed batteries, the density and elastic modulus of each electrode changes as a function of its state of charge (SOC), regardless of the reaction mechanism (intercalation, dissolution/reprecipitation, phase change, etc.). This, in turn, changes how sound waves behave as they travel through the cell. Additionally, the progressive formation/degradation of critical surface layers, mechanical degradation of electrodes, consumption of electrolyte, etc. that occur as a battery is cycled also affect the behavior of acoustic waves passing through the cell. Thus, the distributions of density and modulus as well as the rates of change of these distributions (and the resulting effect on the acoustic echoing behavior) in the cell can act as a fingerprint for its state of health (SOH).
Here, we present a simple electrochemical-acoustic model and experiment as the basis for a potentially universal in operando method for determining the mechanical evolution, SOC and SOH of any closed battery. This technique, which we call Electrochemical Acoustic Time of Flight (EAToF) analysis, was tested on several commercially-available Li-ion batteries, including NCA 18650s and LCO pouch cells. We also investigate the cycling of experimental cells based on silicon anodes and sulfur cathodes. Our results demonstrate strong correlations between SOC and the density distribution within a cell, as determined by the acoustic measurements, and suggest that this is an effective analysis technique regardless of battery chemistry and form factor. Beyond SOC, changes in density are indicative of underlying physical processes occurring in the electrodes during cycling, and changes in the echo profiles and acoustic signal amplitudes as a function of cycle number appear to be key indicators of critical phenomena occurring within the battery, including changes in critical surface layers/interfaces. In both the commercial Li-ion cells and experimental cell, we correlate changes in the acoustic behavior to known changes in phase/structure reported in the literature. Such correlations suggest that EAToF can be used to determine SOH. Our experiments demonstrate that this simple, high-speed technique is effective across nearly all battery technologies because it exploits a common thread to all cells: critical manufacturing control of layers and the shifting of mass within the cell during cycling. While different batteries will have different acoustic fingerprints during operation, the same theory should be broadly applicable.

A composite cathode coating made of a high energy density layered oxide (Li_1.2Ni_0.15Mn_0.55Co_0.1O₂, theoretical capacity ~377 mAh-g^-1), polyvinylidene fluoride binder, and electron-conduction additives, was bonded to an elastic substrate. An electrochemical cell, built by pairing the cathode with a capacity-matched graphite anode, was electrochemically cycled and the real-time stress evolution in the cathode coating was measured using a substrate-curvature technique. Features in the stress evolution profile showed correlations with phase changes in the oxide, thus yielding data complementary to in situ XRD studies on this material. The stress evolution showed a complex variation with lithium concentration suggesting that the volume changes associated with phase transformations in the oxide are not monotonically varying functions of lithium concentration. The peak tensile stress in the cathode during oxide delithiation was approximately 1.5 MPa and the peak compressive stress during oxide lithiation was about 6 MPa. Stress evolution in the anode coating was also measured separately using the same technique. The measured stresses are used to estimate the internal pressures that develop in a cylindrical lithium-ion cell with jelly-roll electrodes.

Ni-rich complex oxide LiNi_0.8 Co_0.15 Al_0.05 O₂ (NCA) has emerged as the most potential cathode material in Li-ion batteries due to its high discharge capacity (~ 200 mA h g^-1). With ageing, however, capacity fade, impedance increment, and eventual thermal runaway occur in NCA, limiting its potential. Most of these phenomena are associated with the phase change at the surface that alters the oxygen network of the layered NCA. The present study directly correlates the capacity-limiting behavior of NCA aged via constant voltage with the local phase and chemical change at the surface and subsurface region of the material. The STEM/ EELS results are also compared with the x-ray absorption spectroscopy (XAS) data. Funding provided by NECCESS, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0012583.

Lithium-ion battery (LIB) is one of the most promising energy-storage systems for electric vehicles and renewable energy storage. For the developing of high-performance LIB, the non-destructive evaluation technique for practical cells is important. The neutron diffraction technique is considered to be the most effective because of peculiar features of neutrons, e.g. sensitive to light atoms (lithium and oxygen) and high penetration depth. In this study, we applied neutron diffraction to analyze degradation mechanisms of 18650-type LIB.
18650-type LIB with nominal capacity of 1800 mAh were fabricated using LiNi_1/3Co_1/3Mn_1/3O₂ and graphite as cathode and anode materials. 1M LiPF₆ dissolved in ethylene carbonate (EC) / ethyl methyl carbonate (EMC) (3:7 by volume) solution was used as electrolyte. Cells were cycled 200 times at 50 °C, 400 times at 25 °C, 400 times at 0 °C (Charge: 4.2 V, CCCV, 0.5 C, Discharge: 2.7 V, CC, 1 C) and stored at 50 °C for 1000 h at 4.2 V. The in situ neutron diffraction experiments were performed on the special environment neutron powder diffractometer, SPICA [1] in MLF/J-PARC. Neutron diffraction data were collected either at charged and discharged state or during charge/discharge process. The crystal structures of the both electrodes were refined by the Rietveld method using Z-Rietveld [2] program.
The capacity loss estimated by electrochemical investigation was 15 % regardless of degradation conditions. The structural refinement of the both electrodes in the degraded cell indicated the amount of Li-ion was reduced 14 % and 13 % from the cathode and the anode respectively. This reduction was consistent with the capacity loss of the cell obtained by electrochemical analysis. In addition, the both electrodes themselves were less deteriorated because the Li-ion reduction of both electrodes was almost same. These results suggested that capacity loss was caused by the loss of Li-ions due to side reactions like SEI growth or Li dendrites formation. In the presentation, the more detail will be reported.
Acknowledgement:
This work was supported by the Research and Development Initiative for Science Innovation of New Generation Batteries (RISING) project of the New Energy and Industrial Technology Development Organization (NEDO). Neutron diffraction experiment was carried out under the S-type project with Proposal No. 2014S10.
Reference:
[1] M. Yonemura, K. Mori, T. Kamiyama, T. Fukunaga, S. Torii, M. Nagao, Y. Ishikawa, Y. Onodera, D. S. Adipranoto, H. Arai, Y. Uchimoto and Z. Ogumi,J. Phys.: Conf. Ser. 502 (2014) 012053.
[2] R. Oishi, M. Yonemura, Y. Nishimaki, S. Torii, A. Hoshikawa, T. Ishigaki, T. Morishima, K. Mori and T. Kamiyama, Nucl. Instrum. Methods Phys. Res., Sect. A 600, 94 (2009)

The epsilon polymorph of vanadyl phosphate ε-VOPO₄ is a promising cathode material for high-capacity Li ion batteries, owing to its demonstrated ability to reversibly incorporate more than one lithium per redox center, with a total theoretical capacity of 331 mAh/g. As in the case of the olivines, the problem of the inherently low electronic conductivity of ε-VOPO₄ is overcome by the use of nano-sized particles within the cathode. At these dimensions the electrochemical reaction can be largely affected by the interfacial chemistry at the nanoparticle surface. An investigation of these surface reactions is critical for obtaining a complete understanding of the mechanism by which lithium intercalates and how it relates to the electrochemical performance.
We performed x-ray photoelectron spectroscopy using both soft and hard x-rays (XPS/HAXPES) to chemically distinguish and depth-resolve the interfacial phase transitions as a function of electrochemical discharge. Core level analysis supports a straightforward two-phase reaction as the first lithium is intercalated. In contrast, the insertion of the second lithium is more complicated with evidence of a significant radial lithium gradient, due to a possible disruption of the kinetics. From inspection of the valence band region, we were able to monitor the reversible evolution of ε-VOPO₄ to Li₂VOPO₄ at the surface of our nanoparticles. These assignments were supported by hybrid density functional theory of the three phases. The origin of the radial gradient is likely associated with the presence of stable intermediate phases during the second reaction and warrants further attention. This work was supported as part of the NorthEast Center for Chemical Energy Storage (NECCES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0012583.

β"-Al₂O₃ has been the dominated choice for the electrolyte materials of sodium batteries because of its high ionic conductivity, excellent stability with the electrode materials, satisfactory mechanical strength, and low material cost. To achieve adequate electrical and mechanical performance, sintering of β"-Al₂O₃ is typically carried out at temperatures above 1600^oC with deliberate efforts on controlling the phase, composition, and microstructure. Here, we reported a simple method to fabricate β"-Al₂O₃/YSZ electrolyte at relatively lower temperatures. With the starting material of boehmite, single phase of β"-Al₂O₃ can be achieved at as low as 1200^oC. It was found that TiO₂ was extremely effective as a sintering aid for the densification of β"-Al₂O₃ and similar behavior was observed with MnO₂ for YSZ. With the addition of 2 mol% TiO₂ and 5 mol% MnO₂, the β"-Al₂O₃/YSZ composite was able to be densified at as low as 1400^oC with a fine microstructure and good electrical/mechanical performance. This study demonstrated a new approach of synthesis and sintering of β"-Al₂O₃/YSZ composite, which represented a simple and low-cost method for fabrication of high-performance β"-Al₂O₃/YSZ electrolyte.

Manganese dioxide (MnO₂) is a promising material for the supercapacitor electrodes to achieve high-density electrochemical energy storage because of its high theoretical capacitance (1370 F/g), low cost, natural abundance and environmental friendliness. However, its low conductivity causes a low loading amount in electrodes. Therefore, the accomplishment of high-capacity electrode is still challenging. In the present study, we report an electrode design to overcome this limitation by preparing hierarchy-structured carbon nanofiber (CNF) electrodes whose surfaces were modified by needle-like crystalline MnO₂ nanowires. These hierarchy-structured electrodes can accomplish high energy density and high power density due to the large loading of MnO₂ on CNF with high surface area and efficient charge collection supported by conductive CNFs, respectively.
Toward practical design of high-energy-density capacitors, herein, capacitance properties were evaluated by using three kinds of capacitances (i.e., per unit weight, unit volume, and unit area of total electrode). Then we investigated the relationship between the electrode properties such as capacitance and resistance and the electrode structures including the diameter of CNFs, the loading amount of MnO₂, and the whole volume of electrodes. In addition, we fabricated hybrid supercapacitor with the hierarchy-structured electrode as a cathode and active carbon as an anode material. This supercapacitor showed high energy density (8.9 Wh/kg) and power density (4.9 kW/kg) and good cycle performance of ~80% capacitance retention over 2000 cycles. Our systematic evaluation of capacitance properties of the hierarchy-structured electrode provides a guideline to design high-energy-density supercapacitor electrodes.

Organic ionic plastic crystals (OIPCs) have been focused as new solid electrolytes because they have some unique properties such as film-forming ability, non-volatility, and relatively high ionic conductivity at room temperature [1]. N-Ethyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([C₂mpyr][TFSA]) showed a melting point (T_m) at 890C with a OIPC behavior, and the ionic conductivity value was approximately 10^-8 S cm^-1 at 250C [2]. Recently, we reported that N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl)amide ([C₂mpyr] [FSA]) showed a high T_m at 2050C with a OIPC behavior in a wide temperature range, and the ionic conductivity value was 1.23 × 10^-6 S cm^-1 at 250C [3]. FSA anion is considered as an effective anion for improving the properties of OIPCs. Furthermore, it has been reported that the ionic conductivity was improved by adding lithium salts to the OIPCs.
In this study, three kinds of pyrrolidinium-based OIPCs with FSA anion were prepared. These pyrrolidinium-based OIPCs have different side chain lengths. In order to investigate the effect of lithium salts, the physico-chemical properties of these OIPCs were evaluated by thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), scanning electron microscope (SEM), impedance technique, and linear sweep voltammetry (LSV). The solid-solid phase transitions were observed for all the OIPCs in the range of -400C and -200C, and their T_ms were over 1000C with a small entropy change of melting. The obtained entropy values were consistent with Timmermans criterion (< 20 J K^-1 mol^-1) for PCs. The OIPC with a longer side chain length, N,N-diethylpyrrolidinium bis(fluorosulfonyl)amide ([C₂epyr][FSA]), exhibited the lowest T_m. The ionic conductivity value of [C₂epyr][FSA] was 8.44 × 10^-6 S cm^-1 at room temperature, which was about 10 times higher than that of the analogous, [C₂mpyr][FSA]. This result suggested that a longer side chain of cation was effective to improve the ionic conductivity of OIPCs. The ionic conductivity of neat OIPCs was improved by doping a certain amount of lithium salt. [C₂epyr][FSA] doped 5 mol% lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) exhibited the ionic conductivity value of 7.77 × 10^-5 S cm^-1 at room temperature.
References
[1] J. M. Pringle, P. C. Howlett, D. R. MacFarlane, and M. Forsyth, J. Mater. Chem., 2010, 20, 2056.
[2] D. R. MacFarlane, J. Huang, and M. Forsyth, Nature., 1999, 402, 792.
[3] M. Yoshizawa-Fujita, E. Kishi, M. Suematsu, T. Takekawa, and M. Rikukawa, Chem.Lett., 2014, 43, 1909.

The demand for batteries with higher energy density continues to grow for applications ranging from consumer electronice to vehicles (hybrid, plug-in hybrid electric and electric vehicles). This can be acheived by using materials with higher specific capacity, e.g. silicon-based anodes, or by using cathode materials that operate at higher voltages. There are some examples of materials such as LiNi_0.5Mn_1.5O₄, LNMO, and LiCoPO₄, LCP, that have discharge plateaus of 4.6V and 4.8V, respectively.
The state of the art, SOA, electrolyte consisting of lithium hexafluorophosphate dissolved in linear and cyclic carbonates with trace amounts of additives. This mixture successfully passivates graphite forming a solid electrolyte interface, SEI, but is not oxidatively stable above ~4.2V. One strategy for new electrolyte formulations is using additives that have a lower oxidative stability than the SOA and decompose on the cathode surface forming a protective layer to prevent the bulk electrolyte from decomposing. Another strategy is using different solvents that have higher oxidative stability than the current SOA electrolyte. With either route, it is still critical to form a stable SEI on the anode surface as both electrodes need to maintain their integrity throughout the battery&’s life.
This research focuses on LNMO//Graphite full cells with SOA-based electrolytes with various additives. The electrolyte stability, electrode/electrolyte interactions and cycling behavior will be discussed.

Graphene&’s attractive properties have inspired concentrated exploration and development in the field of energy storage and catalysis. Specifically, the construction of three-dimensional (3D) graphene architectures offers new possibilities for developing flexible and porous carbon scaffolds, which not only inherit some of the core properties of individual graphene sheets, but also improve additional functions that are of significant importance for variety of energy applications. However, its practical application depends on substantial cost reduction by using novel synthetic methods and further improvement of the properties of graphene structure.
In this work, we report a novel, low-cost and scalable, template-assisted synthesis for preparation of three-dimensional graphene network. Unlike in most other efforts in this area, pyrolysis is used instead of CVD to incorporate carbon atoms. In our approach, 3D network is synthesized in controlled environment by thermal decomposition of the organic materials in the presence of nickel foam, which plays a role of the catalyst and 3D template. Nitrogen-doped 3D graphene structures can be produced by using nitrogen-containing organic materials as the source of carbon and the amount of nitrogen can be controlled by adjusting growth parameters and choosing the right organic materials such as different nitrogen-containing organic acids. Preliminary results are promising and show the formation of 3D few-layered graphene structures. Detailed characterization, including Raman spectroscopy, electron microscopy and surface analysis, will be presented. In addition, the performance of this material in several energy applications, such as Li-ion batteries, supercapacitors or catalysis will be evaluated and reported.

SnO₂ operates by adopting the alloy/de-alloy reaction mechanism and it has attracted intensive research interest as a promising alternative anode material for LIBs due to its high theoretical specific capacity of 782 mAh g^-1, which is more than twice the theoretical capacity of currently used graphite (372 mAh g^-1). Interestingly, tin-based lithium storage compounds need reasonably low potentials for Li⁺ insertion and they have high storage capacities. However, the practical use of SnO₂ based anodes is challenged by their capacity fading due to the large volume change during repeated charge-discharge cycling process. Such volume variation causes cracking and result in electrical disconnection from the current collector, and eventually limit the cycling capability of electrodes.
In this work an attempt have been made to synthesize a high capacity, good cycle performance, and good rate capacity tin-based anode materials for LIB applications. Accordingly, nanostructured SnO₂ anode materials were synthesized and then SnO₂/C nanocomposites have been prepared to improve the cyclability of the anode materials. The morphology, structural and electrochemical properties of the as-synthesized anode materials were characterized by means of SEM, X-ray diffraction (XRD), and galvanostatic charge/discharge battery tester.

Li₂MnO₃-LMO₂ is an attractive cathode material for lithium-ion batteries due to its low cost and relatively high reversible capacity, greater than 200 mAh/g. The Li₂MnO₃ component is of particular interest because it contributes to the stability and high capacity; it is the focus of this investigation. Li₂MnO₃ was synthesized and characterized by XRD, Raman spectroscopy and impedance measurements at varying states of charge to fully investigate the layered-to-spinel phase transition as well as surface reactions occurring during electrochemical cycling. Acid treatment and ALD oxide coatings were employed to independently control the creation of oxygen and lithium vacancies. During activation, oxygen and lithium are removed from the structure, leading to compositional stresses that impact battery performance. In situ stress measurements were used to support atomistic modelling and ex situ characterization to understand the effects of stress on kinetics and phase transformations. Our overall goal is the development of improved Li₂MnO₃-LMO₂ for automotive energy batteries applications.

Commercial liquid organic electrolytes in Li-ion batteries are the main obstacle for adapting them into high energy density Li-ion batteries. Above 60°C, organic electrolytes are decomposed and concerns safe usage of batteries. They also form Solid-Electrolyte Interphase (SEI) which inhibits Li-ion transport between electrodes. Garnet type solid electrolytes for Li-ion batteries are attracted much more interest nowadays since their non-explosive and non-flammable properties, high ionic conductivity among other solid electrolytes, low electronic conductivity and wide electrochemical stability window. Li₇La₃Zr₂O₁₂, as one of the widely studied garnet type solid electrolyte, is considered to replace liquid electrolytes in Li-ion battery applications. Li₇La₃Zr₂O₁₂ has 2 polymorphs that are tetragonal (low temperature stable form) and cubic (high temperature stable form). Garnet type fast ion conductor is cubic form of Li₇La₃Zr₂O₁₂. Several approaches such as increasing synthesis temperature and dopant addition have been used to stabilize cubic Li₇La₃Zr₂O₁₂ at room temperature.
In this study, garnet type Li_6.10Al_0.30La₃Zr₂O₁₂ solid electrolytes were synthesized by solid state reaction method. The starting powders of Li₂CO₃ (Merck), La₂O₃ (Sigma-Aldrich) and ZrO₂ (Inframat Corp.) were first dried at 200°C, 900°C and 900°C respectively. However, Al₂O₃ powder (Ceralox APA 0.5) was used as received. Precursors were mixed in 2-propanol using zirconia balls and calcined at 900°C and 980°C for 12 hours. Before each calcination, powders were again mixed in 2-propanol overnight. Calcined powders were then isostatically pressed into pellets at 290 MPa and sintered at 1150°C for 24 hours within its powder bed to minimize unexpected lithium losses under air. Heating and cooling rate was constant and 2°C/min for all heat treatments. After each experiment, pellets first were grinded using 2-propanol and their crystal structures were determined by X- Ray Diffraction (XRD-Rigaku MiniFlex 600). Microstructure and elemental analysis of each pellet were demonstrated by Scanning Electron Microscope (SEM-Zeiss SUPRA 50VP) attached with an Energy Dispersive Spectrometer (EDS-Oxford Instruments). Pellets were polished using appropriate polishing media (alcohol based 0.25 micron diamond solution) before microstructural analysis. Due to surface ion-exchange when contacting, water was avoided in every treatment of pellets.
According to XRD results, only cubic Li₇La₃Zr₂O₁₂ crystalline phase formation was identified. Backscattered electron images of polished samples showed homogeneously distributed pores in microstructure. Elemental analysis showed nearly stoichiometric La:Zr:O ratio. Secondary electron images from fracture surface imply particle size was in a wide distribution from 3mu;m to 100mu;m. Smaller grains were deposited especially on bigger grains. Both intergranular and transgranular type fracture was observed. The electronic conductivity of samples will also be measured.

An in situ study of stress evolution and deformation behavior of germanium as a lithium-ion battery electrode material is presented. Thin films (100 nm) of germanium are cycled in a half-cell configuration with lithium metal foil as counter/reference electrode, with 1M lithium hexafluorophosphate in ethylene carbonate, diethylene carbonate, dimethyl carbonate solution (1:1:1, wt. %) as electrolyte. Real-time stress evolution in the germanium thin-film electrodes during electrochemical lithiation and delithiation is measured by monitoring the substrate curvature using the multi-beam optical sensing method. Germanium thin film undergoes extensive inelastic deformation during electrochemical lithiation and delithiation similar to silicon. The peak compressive stress during lithiation in germanium was 0.6±0.05 GPa.

Desired properties of solid electrolytes are high lithium conductivity and transference number, high shear modulus to prevent dendrite growth, chemical compatibility with electrodes, and ease of fabrication into thin films. We use the sol-gel method to synthesize silica-based hybrid organic-inorganic materials for this application. The silica network provides chemical stability and mechanical rigidity. We use polyethene glycol (PEG), covalently grafted onto silica network, as the organic filler that provides the environment for ion conduction. The effects of PEG molecular weight, organic-to-inorganic matter ratio, lithium concentration, and different grafting chemistries, on the degree of crystallinity, nano-mechanical properties, and ionic conductivity will be discussed. We use Brillouin light scattering, IR, DSC, dielectric impedance spectroscopy and X-ray diffraction to characterize these materials. Brillouin light scattering reveals the complex mechanical moduli and the degree of connectivity in the network at the molecular level. The combination of experimental techniques allows us to find the optimal processing parameters and to identify the underlying structural and chemical origins of particular electrolyte performances. We find that both the ionic conductivity and the mechanical modulus strongly depend on the molecular weight of PEG, as well as polymer molecular weight and lithium concentration. Our results indicate that the hybrid organic-inorganic electrolytes are generally highly conductive compared to purely inorganic ones. With only one side of polymer chain attached to the silica network and the other side free to move, the conductivity is further increased compared to hybrid materials with both side attached to silica. At room temperature conductivities as high as 10^-5 S/cm are reached. Importantly, by varying molecular weight of the ion conducting polymer chain length, the mechanical properties of the samples can be decoupled from their ionic conductivity and controlled independently.

Interfacial defect transport plays an essential role in determining ionic conductivity of materials. For instance, yttrium stabilized zirconia and strontium titanate (YSZ/STO) interface exhibit enhanced ionic conductivity. Oxide superlattices have a large interface to volume ratio and could serve as a central platform to reveal how complex structural and electronic interactions at interfaces influence defect transport. In this work, we performed first-principles calculations of oxygen vacancy diffusion in three model perovskite superlattices, PbTiO₃/SrTiO₃, PbTiO₃/BaTiO₃ and BaTiO₃/SrTiO₃. Combining the effect of oxygen octahedral rotation and superlattice structure, different oxygen vacancy diffusion paths were identified; the vacancy migration energy barrier of each path were calculated. It is found the migration energies of oxygen vacancy at the interface could be significantly different from that of the bulk. Furthermore, the vacancy diffusion is highly anisotropic in these superlattices. We compared the energy barriers between different superlattices and explored how layer thickness alters the migration barriers. The insights from this study may help us to comprehensively understand the role of interface in tuning the oxygen vacancy diffusion in oxide superlattices and to achieve desired defect transport properties.

Widespread implementation of high-performance electric vehicles (EVs) requires high energy density, low-cost and long cycle life rechargeable batteries. Despite significant strides made to-date, the current high energy density active materials, e.g. lithium- and manganese-rich NMC cathodes, suffer from degradation mechanisms that prevent their implementation in cells for commercially viable EVs. Degradation phenomena accompanied by capacity and power fade are strictly related to excessive SEI growth, electrolyte oxidation processes, Mn (cathode) dissolution, materials structure degradation, and phase transitions. Capacity and voltage fade in Layered-Layered cathode active materials are intimately connected to phase transitions from Layered-Layered Oxide to spinel particularly when exposed to high voltages (>4.6 V). In this paper we show that atomic layer deposition (ALD) is effective in conformally coating the surface NMC active materials and to create a nanometer scale SEI layer which inhibits the initiation and propagation of layered-oxide-to-spinel phase transitions. XRD, TEM, and SAED techniques have been used by our team to identify and demonstrate the significant reduction in phase transition in coated active materials. XALT Energy has integrated these coated materials in pouch cells of 95x64 mm size (2.5 Ah) and has demonstrated the effects of the coatings in full scale cells cycled under various temperatures and protocols; these cells are projected to achieve above 1,000 cycles at C/3-C/3 rate and energy density in excess of 500 Wh/L in large format (255x255 mm) production cells hence demonstrating the validity and scalability of this approach for use in the manufacture of economical EV cells.

We demonstrate a novel method to construct a lithium ion transport network in cathode materials by replacing PVDF with lithiated poly(bis(4-carbonyl benzene sulfonyl)imide-co-bis(4-amino benzene sulfonyl)imide) as the binder. The single ion conducting polymer was synthesized via polycondensation of bis(4-carbonyl benzene sulfonyl)imide and bis(4-amino benzene sulfonyl)imide followed by lithium ion exchange. By blending the ionomers with LiFePO₄and acetylene carbon, the ionic network was well constructed, resulting in a maximum use of active cathode material inside the cathode. The membrane of the polymer electrolyte exhibits an ionic conductivity of 0.14 mS cm^-1 at room temperature, a high ion transference number of 0.92 and a wide electrochemical window of 4.5 V (vs. Li⁺/Li). A lithium ion battery assembled with the single ion conducting polymer electrolyte delivers excellent performance at room temperature with various C-rates.

Reliable, high performance commercial battery technology is invested in the lithium ion battery (LIB) model, which consists of Li intercalation compounds (active materials) in the form particulate matter. In order to effectively incorporate these materials into a working module, the active material must be bound into a matrix that supports it mechanically and facilitates efficient transport of both Li+ ions to the electrolyte phase and electrons to the external circuit. Therefore, typical LIBs consist of electrodes with several different materials, including binding polymers, carbon powders, and metallic collector plates, all of which dramatically decrease the specific capacity of the overall device. The electrode architecture could be greatly improved by introducing a dually conductive (electrons and ions) polymer-based composite to act as the single, all-encompassing matrix material. This presentation will explore the composite of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(ethylene oxide) (PEO), and shows that its electronic and ionic conductivities can be tuned easily by adjusting the component ratio and optimized for LIB application. We have performed physical characterization (SEM, AFM, XPS) to map the conductive pathways formed and show that the homogeneous nature of the blend allows for efficient electrical and electrolyte interfacial contacts on the scale of the micro/nano-scale active materials. By incorporating active materials, we demonstrate this material acts a complete charge transport highway throughout the electrode and that charge/discharge cyclability is on par with current approaches for both anodes and cathodes with improved specific capacity and decreased resistance. Further, we show preliminary data to suggest that the flexible polymer nature also can potentially accommodate silicon anodes, which can theoretically improve the LIB capacity by an order of magnitude.

All-solid-state lithium batteries are attracting significant interest for their potential to go beyond state-of-the-art Li-ion technology. Solid-state batteries could offer higher energy density, because the solid electrolyte eliminates electrolyte leakage enabling novel configurations such as bipolar stacking leading to less dead space. To enhance the energy density of solid-state batteries, both a high capacity/low working voltage anode must be coupled with a high capacity/high working voltage cathode. A Li metal anode is the ultimate goal, because it offers a high theoretical capacity (3861 mAh/g, 2061 mAh/cc) and low working voltage. At the same time, solid electrolytes are expected to suppress Li dendrite growth. However, the research on cathode electrode is still mainly focused on traditional intercalation type materials, such as LiCoO₂. The limited theoretical capacity of the intercalation cathode materials consequently restrict the further enhance of energy density of solid state batteries.
Recently, we proposed a novel all solid-state metal-metal battery, which employs metallic electrodes for both cathode and anode [1]. In this cell, metallic cathodes and anodes were coupled with corresponding solid electrolytes of the same ionic species. Thus, the simultaneous oxidation of one ionic species was coupled to the reduction of a dissimilar ion species during charging and discharging. Prototypical cells demonstrate unprecedented performance exhibiting voltage plateaus of approximately 2 Volts. In order to shed light on this novel battery system, the reaction mechanism was characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. From the analysis, we will propose the charge transfer, ion diffusion, etc. mechanism between catholytes and anolyte. This study will provide a promising route to design new cathode materials for solid state batteries.
Reference:
Fuminori Mizuno, et al “Proof-of-concept of all-solid-state metal-metal battery” (submitted).

Many novel materials used in clean energy applications such as LiFePO₄, hematite, and perovskites are known to exhibit polaronic behavior. Being transition metal oxides, the strongly correlated interaction of the d shell electrons opens a gap and localizes conduction electrons into polaronic states, leading to the hopping conduction observed in these materials. To model electronic conductivities from a theoretical point of view, it is therefore necessary to calculate activation energies of these polarons. Studies typically assume a nearest-neighbor (NN) pathway and calculate this barrier with nudged elastic band (NEB) methods. Additionally, it is assumed that hopping is adiabatic. In this study we attempt to justify these assumptions by means of ab-initio molecular dynamics (AIMD) calculations using LiFePO₄ as our model system. Our results show that dynamic barriers obtained from MD are comparable to static (NEB) barriers, and that there is a significant amount of non-NN hopping. Using a basic two-site hopping model, we then show that only the NN pathway is within the adiabatic regime, validating both assumptions in the case of LiFePO₄. We argue that it is necessary to verify these conditions when modeling materials with similar polaronic properties.

The anisotropy is studied in β-Li₃PS₄ fast Li⁺ conductor, one of the low-symmetric crystalline electrolyte candidates of the all-solid-state lithium ion batteries for large-scale energy storage applications. The anisotropy shows in its physical properties including the charge carrier transport, thermal expansion, stress-strain response and so forth, which are crucial for the compatibility in the solid-state system and the battery performance. Here the anisotropy in β-Li₃PS₄ is evidenced by the thermal expansion in the temperature range of 15-300 K. The neutron and X-ray diffractions confirm the crystal structure of well-synthesized β-Li₃PS₄ and determine the thermal stability. The stable orthorhombic lattice exhibits anisotropic thermal expansions along the principal axes, which are non-linear functions of the temperature. The crystallographic b-axis is revealed as a fast expansion direction around the temperatures of battery operation while a-axis has a nearly zero coefficient of thermal expansion. The anisotropic behavior is structurally originated from the array of LiS_x channels with incomplete Li occupancy and the flexible connections of LiS₄ and PS₄ tetrahedra in the framework, which indicates the correlation to the directional ionic transport in the low-symmetric β-Li₃PS₄.

Abstract: Improvement of lithium-ion battery electrodes with high charge and discharge capacities is in high need especially for electronic devices and electric vehicles (Gong et al., 2013). For that reason, development of ion transport in the crystal structure is needed (Li et al., 2013). The general idea is synthesizing nanometer scale particles. Reducing the particle size helps the ion diffusion in the structure (He et al., 2014). Titanate nanotubes are promising materials because of their special morphology and high specific surface area. The nanotubes are formed by rolling-up of titanate nanosheets (Kasuga et al., 1998). These titanates provide high rate capability and low volume expansion upon lithiation (Ren et al., 2010). More importantly their tubular structure helps the transport of ions through the crystal. In this study, we synthesized micron-long titanate nanotubes and treated them with surfactants to modify their interlayer distances. For the structural characterization XRD, SEM, BET and TEM techniques were used. In addition, the effect of interlayer distance on energy capacity and rate capability was investigated. XRD patterns of the samples indicate that titanate peak at 2theta; = 9.8#730; shifted to lower angles after surfactant treatment which means that interlayer distance was increased. Moreover, BET and TEM results also support this argument. Potential-capacity profiles of titanates before and after the surfactant treatment show that capacity was significantly increased from 750 mAh/g to 1310 mAh/g. More importantly, surfactant treated titanates showed exceptional rate capabilities especially at wider interlayer distances due to higher mobility of ions in the structure. It was found that interlayer distance plays an important role in rate capability.
Acknowledgement. This study is supported by The Scientific and Technological Research Council of Turkey (TUBITAK): Project No. 113M575.
References:
Gong , Y. J., Yang, S. B., Liu, Z., Ma, L. L., Vajtai, R., Ajayan, P. M. (2013), Graphene-Network-Backboned Architectures for High-Performance Lith-ium Storage, Adv. Mater., 25, 3979.
Li, L., Raji, A.-R. O., Tour, J. M. (2013), Graphene-Wrapped MnO2-Graphene Nanoribbons as Anode Materials for High-Performance Lithium Ion Batteries, Adv.Mater., 25, 6298.
He, M., Kravchyk, K., Walter, M., Kovalenko, M. V. (2014), Monodisperse Antimony Nanocrystals for High-Rate Li-ion and Na-ion Battery Anodes: Nano versus Bulk, Nano Lett., 14, 1255.
Kasuga, T., Hiramatsu, M., Hoson, A., Sekino, T., Niihara, K. (1998), Formation of Titanium Oxide Nanotube, Langmuir, 14, 3160.
Ren, Y., Hardwick, L. J., Bruce, P. G. (2010), Lithi-um Intercalation into Mesoporous Anatase with an Orderd 3D

Conversion type materials have recently been considered as a plausible alternative to conventional electrode materials, owing to their strong gravimetric and volumetric energy densities. The ternary alloy TiSnSb was recently proposed as being a suitable negative electrode material in Li-ion batteries owing to its excellent electrochemical performance [1-4].
Using complementary in situoperando X-ray diffraction (XRD) and in situoperando¹¹⁹Sn Mössbauer spectroscopy, it was determined that during the first discharge, TiSnSb undergoes a conversion process leading to the simultaneous formation of Li-Sb and Li-Sn intermetallic compounds and, as a result, the corresponding electrochemical equation was proposed for Li insertion:
TiSnSb + 6.5Li --> Ti + Li₃Sb + 0.5Li₇Sn₂
However, some ambiguities remain: A shifted, group of resonances appear in the ⁷Li NMR spectra at approx. 20 ppm, in addition to a contribution from Li₃Sb at 3.5 ppm and a resonance at 8.5 ppm (assigned to Li₇Sn₂), and could correspond to intermediate phases.
In addition, changes in the local environments of Sn and Li nuclei have been detected upon OCV relaxation after the lithiation process, using ¹¹⁹Sn Mössbauer and ⁷Li NMR spectroscopies, respectively. These results suggest an intrinsic instability of the phases formed at the end of the lithiation process. Ex situ⁷Li NMR indicates that this evolution is stopped or at least slowed down when the active material is in contact with the electrolyte. Both "in situ" and "ex situ" type experiments have been completed using the two techniques in order to understand the influence of small changes in composition on Mössbauer signal and ⁷Li NMR shifts. Following this approach, the ternary alloy NbSnSb was investigated and directly compared to TiSnSb to determine the influence of the inactive metal on the ⁷Li NMR shift. The obtained results highlight the sensitivity of ⁷Li NMR to the chemical or electronic environment around the Li₃Sb phase or clusters and not only to the direct local environment (Li₃Sb). This result shows the crucial importance of interfaces between the phases formed along the redox processes in the case of conversion materials.
A systematic study using both Mössbauer spectroscopy and NMR the phases formed during discharge and subsequent relaxation will be presented and discussed.
References
[1]: Sougrati, M. T.; Fullenwarth, J.; Debenedetti, A.;Fraisse, B.; Jumas, J. C.; Monconduit, L. J. Mater. Chem.2011, 21, 10069.
[2]: Marino, C.; Sougrati, M. T.; Gerke, B.; Pöttgen, R.; Huo, H.; Ménétrier, M.; Grey, C. P.; Monconduit, L. Chem. Mater.2012, 24, 4735.
[3]: Marino, C. ; Darwiche, A. ; Dupré, N. ; Wilhelm, H. A. ; Lestriez, B. ; Martinez, H. ; Dedryvère, R. ; Zhang, W. ; Ghamouss, F. ; Lemordant, D. ; Monconduit, L. J. Phys. Chem. C2013, 117, 19302.
[4] : Wilhelm, H. A. ; Marino, C. ; Darwiche, A. ; Monconduit, L. ; Lestriez, B. Electrochem. Commun. 2012, 24, 89.

Rechargeable metal-air batteries have emerged as a possible alternative to lithium ion batteries due to their potential to provide high energy density [1]. Understanding the oxygen reduction and evolution reaction kinetics is, however, key to achieving these high volumetric energy densities. Nonaqueous Na-O₂ batteries are receiving growing attention for their demonstration of highly reversible formation of NaO₂ as the discharge product, with energy efficiencies during the first cycle greater than 90% [2]. This performance is in stark contrast with more heavily investigated Li-O₂ batteries, for which analogous efficiencies of <70% are routinely achieved for carbon-based cathodes [3]. While Na-O₂ batteries represent a possible alternative route to the development of rechargeable nonaqueous metal-air batteries, the decomposition mechanisms of the discharge products and the charging mechanism are poorly understood.
One technique capable of providing great insight into electrochemical behavior is electrochemical impedance spectroscopy (EIS), which is widely used in the field of Li-ion batteries. Its application to metal-air batteries is, however, limited to a small number of investigations performed by a few research groups, and its potential in metal-air battery technology has yet to be fully exploited. In this work, a model of the discharge and charge reaction mechanisms is proposed, which allows the development of new approaches to better understand these mechanisms and their relation to material and morphological properties through EIS, X-ray diffraction and scanning electron microscopy analysis and appropriate interpretation. This fundamental knowledge is critical in understanding Na-O₂ batteries and will facilitate the development of new, inexpensive catalysts, in turn allowing the engineering of novel electrode materials with appropriate porous structure and pore size. Further insight into the charge/discharge mechanisms, especially those pertinent to the reversibility of the electrochemical reactions, will be gleaned through the study of the growth process of NaO₂.
REFERENCES
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Polymeric materials can offer a variety of functions such as good electronic and ionic conductivity, mechanical flexibility, stretchability and self-healing capability. These properties are of great interest for electronic and energy-related applications. In next-generation high-energy lithium-ion batteries, their electrode active materials (e.g., silicon, sulfur) suffer from mechanical and electronic degradation, which limits the battery capacity and cycling life time. In this presentation, we will show how to use novel functional polymers to solve some of the most critical issues related to silicon anodes. Specifically, a dynamic hydrogen-bonding based self-healing polymer is developed to effectively coat and bond onto silicon particle surface, which can maintain good electronic conductivity and mechanical integrity in electrodes over repeatedly charging/discharging. Therefore, silicon electrodes can be cycled with significantly improved stability. Typically, using low-cost large Si particles, we achieved stable cycling of over 500 cycles at moderate mass loading. Even with a high areal capacity of > 3mAh/cm², the electrodes can still be cycled stably over 120 cycles. Such performance is comparable or even better than that of the state-of-art Si nanostructure designs. Our polymer approach provides great promise to renovate electrode structure and improve battery performance by tuning their structures and compositions.

Among the various fullerides, the compound Li₄C₆₀ was reported to show a very interesting ionic conductivity around 10^-2 S/cm at room temperature, with relatively low activation energy [1]. This high mobility was supposed to be due to 2D polymeric structure of this compound, in which C₆₀ units are interconnected by alternate single and double bonds ([2+2] cycloaddition) to form a planar network [2]. The large voids created among the C₆₀ units in this polymer allow the Li ions diffusion to extend not only among the 2D polymerized layers, but also through them following a three-dimensional path, as suggested also by DFT calculations (see Figure 1) [1]. However, recently, it has been suggested that, despite the presence of a certain level of ionic conductivity, electronic transport is dominant both below and near room temperature [3].
Here we report a careful structure and transport analysis of pure Li₄C₆₀ and its composites with poly(ethyleneoxide) (PEO), which is one of the most important matrices of choice for electrolytes for lithium batteries [4]. By combining ⁷Li MAS-NMR, electrochemical impedance spectroscopy and OCV measurements of Li-based cells, we show that a fraction of the Li atoms enter the polymer strands and take part to ionic transport. The remaining fraction stays in the fulleride, where the transport is electronic in nature. A percolation threshold between ionic and mixed conductivity is found in the range 30-40 wt% of Li₄C₆₀.
References
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3. B. Sundquist et al., New J. Phys. 17, 023010 (2015)
4. E. Quartarone, P. Mustarelli, Chem. Soc. Rev. 40, 2525 (2015)

Lithium ion battery safety is critically important for a variety of applications such as electric vehicles, aerospace, medical devices, and consumer electronics. Due to the flammability of liquid electrolytes, solid electrolytes provide an ultimate way to improve battery safety and reliability. In these systems, volume changes in electrode materials during Li insertion and removal can lead to mechanical failure at the electrolyte interface. This work considers these issues in batteries with polyethylene oxide (PEO) polymer electrolytes, using adhesion tests and several other methods. A multi-beam optical stress sensor (MOSS) was used to obtain in situ measurements of stress evolution and electrolyte deformation during electrochemical cycling. Analysis of these measurements was performed with finite element analysis (FEA). The results of this work demonstrate that the strain rate dependent response of these electrolytes is an important issue.

All-solid-state batteries using solid electrolyte materials provide intrinsic safety and high energy density. Problems at the interfaces between the electrode and electrolyte materials, such as high interfacial resistance and interfacial degradation, are limiting the development of all-solid-state batteries. Computational modeling based on first principles methods can provide valuable insights into the fundamental mechanisms regarding both thermodynamics and kinetics at the solid interfaces. In this talk, I will present our recent computational study about the solid-solid interfaces in all-solid-state Li-ion batteries. Our first-principles modeling study reveals the compatibility issues of the electrolyte and electrode which lead to the failure of sulfide and oxide solid electrolyte materials. We will also discuss how to resolves these interfacial problems on the basis of the insights from first-principles computation.

Lithium ion batteries (LIBs) have features of a high voltage, high energy density and long life time. The most commonly used anode material of LIBs is graphite, whose energy storage capacity is 370 mAh/g, and there is no room for increase in its capacity. On the other hand, the other group-IV materials, Si, Sn and Ge, form alloys with lithium and are expected to be candidates for high capacity anodes¹⁾. Si exhibits the highest energy capacity among these materials, but Si anode have some drawbacks, such as their large volume change during the electrochemical charge/discharge cycles, which causes short life time, and low diffusivity of lithium ions in Si crystal, which makes a high rate charge/discharge difficult. Silicon nanowires (Si-NWs) are promising materials for anodes of lithium ion batteries²⁾, because they can solve the above-mentioned drawbacks. The mechanical stress can be decreased via relaxation owing to the spacing between individual NWs, and the problem of large volume change can be solved. The low diffusivity of lithium ions can also be overcome by a large increase in the surface area.
In a previous paper³⁾, we have already reported that a robust Si anodes equipped with the nanowires combined with the supportive micropillars combination can be fabricated using patterned Si substrate.
We fabricated Si-NWs by the metal assisted chemical etching (Mac etching), in which noble metal is used as a catalyst in the reaction of Si with a HF and H₂O₂ mixed solution. Using this technique, a high density and a high aspect ratio of Si-NWs can be realized in a large scale by a simple process. The nanowire structure fabricated by this method is determined by the noble metal morphology. We have developed a new process to fabricate an Au nano-mesh for the catalytic template in the Mac-etching, which consists of only deposition of an Au thin film followed by annealing. We have found that the pore diameter and density of the Au thin films on Si substrate can be controlled by selecting the Au film thickness, annealing temperature and annealing time. This means that the diameter and density of the Si-NWs are also controllable. This method is much simpler than the other techniques for controlling diameter and density of Si-NWs, such as the porous alumina template method⁵⁾.
We also observed the structural change induced by the insertion/extraction of lithium ions during the electrochemical charge/discharge process and confirmed that the structural change is small in comparison with that in bulk Si.
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Recent studies on Li ion battery projected SnO₂ as a promising anode material due to its high capacity and abundance in nature. But the unavoidable pulverization leading to the mechanical degradation upon lithiation/de-lithiation cycles demands for support materials, preferably carbon nanomaterials eg. graphene, carbon nanotubes (CNTs) etc. in order to get increased electrical conductivity along with higher cycle life. The lower surface area of CNTs and self-aggregation issue of graphene restricts higher capacity and rate capability of the material, respectively. For favorable Li transfer mechanism with higher available surface area and practical strategy for the volume change of SnO₂, herein we employ graphene wrapped CNTs,a hybrid of carbon nanotubes and graphene sheets, as the support. In comparison to wet chemical methods for nanoparticles synthesis, here we employ, nature-friendly, solar energy mediated reduction method to decorate SnO₂ over the support material using comparatively less chemicals. Diverse characterizations confirm the formation of about 3 nm SnO₂ nanoparticles, dispersed homogeneously over graphene wrapped CNTs. Temperature controlled wrinkles on the surface of graphene wrapped CNTs provides better channels for Li⁺ for individual entity as well as in the bunch by providing more interspace in between, giving porous structure in contrast to comparatively smooth CNTs.This well-connected 1-D buffer structure with high conductivity, porosity and surface area, provides better Li ion transfer channels and less charge transfer resistance giving high performance and thereby presenting SnO₂/graphene wrapped CNTs to be a potential Lithium-anodic material.
Ref:[1]Y. Idota, T. Kubota, A. Matsufuji, Y. Maekawa, T. Miyasaka, Science, 276 (1997) 1395-1397; [2]S.S. JyothirmayeeAravind, V. Eswaraiah, S. Ramaprabhu, Journal of Materials Chemistry, 21 (2011) 15179-15182; [3]G. Du, C. Zhong, P. Zhang, Z. Guo, Z. Chen, H. Liu, Electrochimica Acta, 55 (2010) 2582-2586; [4] L. Ding, S. He, S. Miao, M.R. Jorgensen, S. Leubner, C. Yan, S.G. Hickey, A. Eychmüller, J. Xu, O.G. Schmidt, Sci. Rep., 4 (2014) 4647-1-4647-8.

Understanding and controlling the surface reactivity at the electrode/electrolyte interface (EEI) is one of the key challenges for the development of high capacity and efficient lithium-ion batteries. The heterogeneous, partially catalytic reaction of the electrode with the electrolyte leads to the formation of surface films on the electrode which can cause cell degradation and performance loss. While the EEI layer nature is quite well known on negative electrodes such as graphite and lithium metal,^1,2 there is still a grey area around the characteristics of the EEI layer on positive electrode materials. Especially, the interface of high voltage and high capacity positive electrodes, whose potentials approach the limit of electrolyte stability against oxidation,³ is quite unexplored. One of the challenges in understanding the reactions at the surface of the electrode is the complicated composition of the positive electrodes, containing not only the active material but also conductive agents (carbon) and polymeric binders, that can modify the nature of the EEI film on the electrode. To circumvent these ambiguities, there is a need for studying model electrodes such as thin films, which allow for investigating solely the reactivity of the electrolyte at the active material surface, and offer the possibility to determine the effect of surface termination on the EEI layer properties. Here, combining in situ and ex situ characterization (X-ray Photoelectron Spectroscopy (XPS), X-ray Absorption Spectroscopy (XAS), Raman, Fourier Transform Infrared Spectroscopy (FTIR)) of model electrodes, we will show how the species formed at the electrode/electrolyte interface are affected by the charging potential and the structure and nature of the transition metal in the material. Studies of the electrolyte reactivity at the interface of positive electrode oxide (LiCoO₂, LiNi_1/3Mn_1/3Co_1/3O₂ (NMC), Li₂MnO₃ or Li₂RuO₃) thin films prepared by Pulsed Laser Deposition (PLD), or binder-free carbon-free electrodes will be presented.
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3. Xu, K. et al., Chem. Rev., 114, 11503-11618 (2014).

The La₂NiO₄ ternary phase with a layered perovskite structure is known as highly active for the oxygen reduction reaction (OOR) and the oxygen evolution (OER) in Metal-Air Batteries. Doped lanthanum nickelates have also been considered as a potential cathode material for intermediate temperature solid oxide fuel cell applications. In recent works it is reported that the performance of nickelate type cathode can be improved by SrO doping. However, there is no detailed literature information on phase equilibria of the La₂O₃-SrO-NiO ternary oxide system. In order to build chemically stable battery and fuel cells, not only the thermodynamic stability of the electrolyte and electrodes themselves, but also the reactivity between component materials should be well established. The work aimed to investigate ternary phase equilibria in the La₂O₃-SrO-NiO oxide system in order to investigate thermodynamic stability of SrO doped La₂NiO₄ ternary compound.
The experimental work has been designed based on the calculated phase diagrams (CALPHAD calculations). In the La-Sr-Ni-O system, extended solid solutions (La,Sr)2NiO₄ was found and the homogeneity range was experimentally determined. Also chemical potential diagrams of the system simulating fabricating and operation conditions were calculated.

Silicon, with a high specific capacity ~ 3,579 mAh/g, has attracted tremendous attentions as anode materials in lithium ion battery. The volume expansion during lithiation, unstable SEI and the low electrical conductivity prevents silicon from being commercialized. The scientific community has shown great progress at addressing these issues, although many of the proposed nanostructures are realized using techniques that are difficult to scale. Moreover, most of the silicon-based anodes discussed in the literature use a weight loading that is not compatible with commercial applications. We propose to use a one-step spray pyrolysis method starting from a water-based dispersion of silicon nanoparticles and NiCl₂ to produce NiO-Si yolk-shell particles. After coating and annealing in the presence of polyvinylpyrrolidone, the nickel oxide shell is reduced into a porous nickel cage enclosing the silicon particles. The polymer decomposition leads to the formation of an amorphous carbon layer surrounding the nickel cage. This structure (a) has good electrical conductivity, (b) prevents the direct contact between silicon nanoparticle and the electrolyte and (c) maintains a buffer volume that accommodates for the silicon expansion during lithiation [1]. The resulting anode shows high specific discharge capacity (>1240 mAh/g, silicon basis) for 110 cycles at 0.5 C discharge rate with excellent performance even at high weight loading conditions (~2 mAh/cm²). In addition, the good electrical conductivity of the coating allows removing the copper substrate to achieve a free-standing active layer, leading to additional weight and volume savings at the device scale.
[1] Zhong, L., Kwok, T., Mangolini, L. (2015). Spray pyrolysis of yolk-shell particles and their use for anodes in lithium-ion batteries. Electrochemistry Communications, 53, 1-5

With the rapid development of porous materials, a lot of novel porous materials with different structures have emerged, among which metal-organic frameworks (MOFs) have experienced explosive development during the past decade. Because of their extremely large surface area, high porosity, low density, controllable structure, tunable pore size, and tailorable functionality, MOFs have been investigated for a wide range of potential applications, including gas separation and storage, energy storage, catalysis, and drug delivery. In particular, applications in energy storage and conversion systems hold great promise, including fuel cells, lithium-ion batteries (LIBs), and supercapacitors.
However, the rational design of highly porous MOFs kinetically stable under humid conditions is critical to many practical applications of this class of materials. As an extension of our previous work,¹ we have synthesized nickel-based, water-stable, pillared DMOFs of similar topologies Ni(L)(DABCO)_0.5, where L is the functionalized BDC (1,4-benzenedicarboxylic acid) and DABCO is 1,4-diazabicyclo[2.2.2]-octane. The stability of these materials is confirmed by comparing the X-ray diffraction patterns and BET surface areas before and after exposure to 90% relative humidity. When used as an electrode for a supercapacitor, these mixed-ligands pillared MOFs exhibited large specific capacity, high rate capability, and excellent cycling stability. This work provides a general approach to the development of water stable MOFs by ligand functionalization and opens a new avenue to the application of water stable MOFs in electrical energy storage.
Reference
1. Jasuja, H.; Jiao, Y.; Burtch, N. C.; Huang, Y. G.; Walton, K. S., Synthesis of cobalt-, nickel-, copper-, and zinc-based, water-stable, pillared metal-organic frameworks. Langmuir 2014, 30 (47), 14300-7.

The garnet-type Li₇La₃Zr₂O₁₂ (LLZrO) is presently regarded as one of the most promising solid electrolyte materials because it possesses a good combination of high Li ionic conductivity (relative to other candidate inorganic materials) and excellent electrochemical stability vs. Li metal. To further improve the Li ion transport property of LLZrO, various doping strategies have since been made which, depending on the guest cation and synthesis condition, could either result to a non-blocked or blocked pathway for the Li ions. In order to understand better the effects of these two doping conditions, we used materials simulations and investigated the structural and Li ion transport properties of LLZrO with respect to Ta (pathway-non-blocking, at Zr site) and Ga (pathway-blocking, at Li site) addition. For Ta-doped LLZrO, we predicted: i) a linearly decreasing occupancy in the 48g/96h octahedral site with increasing Ta content and ii) a conductivity maximum in the range 0 le; x le; 1 for Li_7-xLa₃Zr_2-xTa_xO₁₂. For the Ga-doped case, we found out that Ga³⁺: i) has no preference for occupancy between the two Li sites (24d and 48g/96h), ii) does not cause any enlargement of the Li pathway, and iii) leads to a decreasing trend in bulk Li⁺ ion conductivity for 0 le; x le; 0.10 and a relatively flat trend for 0.10 < x le; 0.30 (for the Li_7-3xGa_xLa₃Zr₂O₁₂ cubic phase).

Li-ion battery is reaching a limit in its energy density. In particular the capacity of graphite is too low (372 mAh.g^-1) to meet the increasing energy demand. Silicon (Si) anode appears as a possible solution as carbon replacement in LIB thanks to its high theoretical specific capacity (3579 mAh.g^-1). However, rapid pulverization of the particles and SEI instability cause capacity fading in few cycles.
Silicon nanostructuration together with association of carbon to Si greatly enhance the performances in terms of both cyclability and capacity. Using a-Si as core material, instead of c-Si, is a less considered option but appears promising to enhance cyclability. Indeed, a-Si is not subject to the drastic crystalline state alteration upon its first lithiation. In order to cumulate all the benefits cited above, active material should be a composite of an a-Si core covered with a carbon shell.
A major drawback of such structures is related to their synthesis processes not meeting the quantity requirement for industrial development. Having this point in mind, the Laser Pyrolysis (LP) process was adapted for the one step synthesis of C-coated nanoparticles. This versatile process was used with success to synthetize many types of nanoparticles. Interestingly, the amount of final product is directly correlated to the flow of gas precursor, thus leading to easily scalable process. However the synthesis of a complex material such as nanoparticles composed of a-Si core covered with a carbon shell implies the development of specific reactor.
We demonstrate here the successful use of a two stage reactor. This reactor, composed of two reaction zones, allow the synthesis of Si@C nanoparticle in a one-step process, without manipulation of nanopowders. We develop the synthesis of a-Si and a-Si@C core shell nanoparticles, with the exact same silicon core, and we bring in evidence the protective effect of the carbon shell. The two active materials were characterized and studied as anode materials versus metallic lithium in cyclic voltammetry and galvanostatic experiment. We highlighted the beneficial effects related to the use of a-Si over c-Si and the beneficial of a carbon covered active material over a bare one. Results show that a-Si without any carbon coverage presents very poor cycling capacity, due to the presence of a thick and electronically insulant silicon oxide shell. At the opposite, a-Si protected with a carbon shell presents outstanding electrochemical properties: In coin cell configuration, it can be cycled for more than 500 cycles, with a specific capacity superior to 1000 mAh.g^-1 and with an exceptional coulombic efficiency of 99,91% at the end of the 500^th cycle. This very high stability can be explained by the low oxidation of silicon through the carbon shell that act as an efficient barrier to oxygen diffusion. In good agreement with the stability of the device, post mortem SEM analysis shows an important residual porosity in the electrode.

Rechargeable Li-ion batteries are the most prevalent type of battery found in portable electronics due to their high energy density and operating voltage. However, the capacity of cathode materials requires significant improvement before Li-ion batteries can become practical power sources in other technologies, such as electrical vehicles. LiMn₂O₄ (LMO) has received considerable attention in recent years because it is inexpensive, environmentally friendly and has a high charge capacity. However, LMO suffers from capacity fading during cycling, which is associated with a number of electrochemical and mechanical degradation processes and their interactions. Detailed knowledge and a fundamental understanding of the mechanical and electrochemical properties of the cathode material is required to effectively improve the performance of Li-ion batteries.
We investigated in-situ strain generation in LMO composite cathodes under an applied voltage in a custom battery cell. Free-standing electrodes were cycled between 3.5 and 4.5 V at different scan rates during cyclic voltammetry, and digital image correlation (DIC) was applied to measure in-situ strain generation during lithiation/delithiation¹. As expected, LMO cathodes expanded during the cathodic scan (ca. 0.7 % strain) when lithium was inserted into the electrode and contracted during the anodic scan when lithium was removed². Sharp peaks in the strain derivative during lithiation/delithiation were observed, which are correlated with phase transformations that occur in the LMO structure during potential scaning^3,4. Additionally, dissolution of the spinel electrode may also contribute to the mechanical deformation of the electrode⁵.
[1] Jones, E. M. C., Silberstein, M. N., White, S. R. & Sottos, N. R., Exp. Mech. 54, 971-985 (2014).
[2] Julien C.M.,Mauger A., Zaghib K. & Groult H., Inorganics 2, 1-23 (2014).
[3] Thackeray, M. M. & Cho, J., J. Electrochem. Soc. 146, 3577 (1999).
[4] Thackeray, M. M. et al., Sol. St. Lett. 1, 7 (1998).
[5] Oh, S. M., Jang, D. H. & Shin, Y. J., J. Electrochem. Soc. 143, 2204 (2004).

We introduce one-step process that consisted of thermal disproportionation and impurity doping to enhance the reversible capacity and electrical conductivity of silicon monoxide (SiO)-based negative electrode materials for Li-ion batteries. Transmission electron microscope (TEM) results reveal that thermally treated SiO at 900 °C (H-SiO) is consisted of uniformly dispersed nano-crystalline Si (nc-Si) in amorphous silicon oxide (SiO_x) matrix. The electrochemical performances of H-SiO exhibit improved specific capacity compare to those of pristine SiO as a negative electrode due mainly to the increased reversible capacity from nc-Si and reduced volume expansion by thermally disproportionated SiO_x matrix. Further electrochemical improvements can be obtained by boron-doping on SiO (HB-SiO) using solution dopant during heat treatment. HB-SiO electrode without carbon coating exhibits significantly enhanced specific capacity superior to those of H-SiO with 947 mAh g^-1 at 0.5 C rate, having excellent capacity retention of 93.3% over 100 cycles. The electrochemical impedance spectroscopy (EIS) measurement reveals that the internal resistance of HB-SiO electrode is significantly reduced by boron doping.

Lightweight complex hydrides are extensively studied as hydrogen storage systems. Sodium alanate is one of the most studied due to appropriate thermodynamic properties and high gravimetric and volumetric hydrogen content (7.5 wt % H₂ and 94 g H₂/L) [1]. As recently emerged, its use could be extended at the field of electrical storage systems. Studies on MgH₂ and TiH₂ have already proved that metal hydrides can react in lithium cells through a conversion mechanism (Hydride Conversion Reaction, HCR) [2].
Besides the studies on the binary hydride systems, it has recently been reported the use of alanates as conversion anode materials in lithium cells [3] [4]. The electrochemical reactivity and the conversion mechanism of NaAlH₄ in lithium cells have been proved. The redox mechanism seems to proceed via a multistep process with initial development of LiNa₂AlH₆, and then the decomposition of hexa-alanate phase into sodium, aluminum and lithium hydride. Capacity values close to theoretical (1985mAh/g) have been achieved during first discharge. Unfortunately, the process is characterized by a low efficiency and only a low percentage of discharge capacity was recovered on charge.
A feasible cause of its irreversible capacity could be ascribed to structural rearrangements that take place during the conversion reaction [5] [6]. This causes a severe volume expansion resulting in damages to electrode mechanical integrity, with loss of electric contact, renewal of the surface and electrolyte decomposition.
In order to improve the performance of these materials in electrochemical cells stabilizing the chemical reactivity, limiting large volumetric changes and preventing grain growth and sintering [7], several nanocomposites confining sodium alanate in different nanoporous carbon host matrixes have been developed. Both melt and wet impregnation methods have been chosen. The successful of infiltration have been evaluated by morphological and thermal analysis. The effects of carbon matrix on sodium alanates have been studied by Infrared Spectroscopy. Electrochemical performances have been studied by potentiodynamic cycling with galvanostatic acceleration (PCGA) and galvanostatic measurement (CG).
References
[1] T. K. Nielsen, M. Polanski, D. Zasada, P. Javadian, F. Besenbacher, J. Bystrzycki, J. Skibsted, and T. R. Jensen, ACS Nano, 2011, 5, 4056-4064.
[2] Y. Oumellal, A. Rougier, G. A. Nazri, J.-M. Tarascon, and L. Aymard, Nat. Mater., Nov. 2008, 11, 916-921.
[3] J. A. Teprovich, J. Zhang, H. Coloacute;n-Mercado, F. Cuevas, B. Peters, S. Greenway, R. Zidan, and M. Latroche, J. Phys. Chem. C, 2015.
[4] L. Silvestri, S. Forgia, L. Farina, D. Meggiolaro, S. Panero, A. La Barbera, S. Brutti, P. Reale, ChemElectroChem, DOI: 10.1002/celc.201402440.
[5] Zhang, W.-J., Journal of Power Sources, 2011 196 (1), 13-24.
[6] G.A.Nazri, G.Pistoia, Lithium Batteries, Springer 2003.
[7] A. F. Gross, C. C. Ahn, S. L. V. Atta, P. Liu, and J. J. Vajo, Nanotechnology, 2009, 20, 204005.

Among the large variety of carbon materials, ordered nanoporous carbon with uniform mesopores is particularly interesting for application as a conductive framework for lithium-sulfur battery electrodes. Their synthesis is based on the utilization of mesoporous matrices (nanocasting) [1]. For example, elemental sulfur can be incorporated in the pores of mesoporous CMK-3 carbon, offering new opportunities for lithium-sulfur cells [2]. Elemental sulfur, as a non-toxic and abundant cathode material, bears the advantage of a high theoretical capacity of 1675 mAh/g [3]. Sulfur-carbon electrodes require a high dispersity of sulfur, good contact between sulfur and carbon, and a high porosity of the entire composite for effective permeation of the electrolyte and short diffusion paths for Li ions.
Our approach is based on ordered, bimodal mesoporous carbon materials with two distinct pore systems. Such materials are accessible by advanced nanocasting procedures, using silica as a structural matrix [4]. So-called CMK-5-type carbon [5] consists of hollow, linear tubes, arranged in parallel orientation. As a result, two distinct modes of nanopores exist, intra-tubular and inter-tubular pores. Selective modification of either of the two pore systems provides new opportunities; for example, one pore mode may be filled with sulfur while the other remains empty, thus providing transport channels to be filled with electrolyte. The surface of the 'empty' pores can also be chemically modified by attachment of organic functions, which may be useful to prevent leaching of solute polysulfides. Thus, two large interfaces are generated in the carbon, namely (i) to the intra-tubular guest species (sulfur) and (ii) to the free space between the carbon tubes. The latter can be infiltrated by an electrolyte in a rechargeable cell and allows short diffusion paths for Li ions. Since Li ion diffusion is often the limiting factor in the charge/discharge kinetics [1], our materials are promising candidates for future lithium-sulfur battery design.
[1] T. Wagner, S. Haffer, C. Weinberger, D. Klaus, M. Tiemann, Chem. Soc. Rev. 42 (2013) 4036-4053.
[2] X. Ji, K. T. Lee, L. F. Nazar, Nature Mater. 8 (2009) 500-506.
[3] J. Shim, K. A. Striebel, E. J. Cairns, J. Electrochem. Soc. 149 (2002) A1321-A1325.
[4] S.H. Joo, S.J. Choi, I. Oh, J. Kwak, Z. Liu, O. Terasaki, R. Ryoo, Nature 412 (2001) 169-172.

The global energy challenge has motivated great effort to the development of rechargeable batteries that are not only of high energy and high power, but also chemo-mechanically reliable. Lithium ion batterie (LIB) is currently the best performing electrochemical energy storage technique. However, LIBs with high-capacity electrodes (such as Si) suffer from rapid irreversible capacity decay and poor cyclability due to lithium insertion/extraction induced huge volume changes and subsequent fracture. Here we report our recent progress in chemomechanical modeling and in-situ transmission electron microscopy of the degradation mechanisms of a set of high-capacity electrode materials, including Si and Ge. We will then demonstrate how nanoporosity and surface coatings can mitigate the chemomechanical degradation and enable capacity retention and long cycle life. Our mechanistic understanding provides guidance to the rational design of durable high-performance electrodes for LIBs.

Various anode materials have been proposed and developed to increase the capacity of Li-ion batteries, and thereby expand its use in transportation, industrial machines, portable electronics, and stationary storage. Phosphorus theoretically has one of the highest capacities of any element, at 2596 mAh/g and 2266 mAh/ml, and interest in this material has increased in recent years [1]. Many groups around the world have put forth efforts to create well performing phosphorus anodes. However, publications thus far have been limited to 100 cycles of stable galvanostatic charge-discharge at most, and there is a lack of studies into the degradation of phosphorus anodes.
Alloying electrode degradation generally occurs through two mechanisms, volume change and solid electrolyte interphase (SEI) growth. Drastic volume change can push particles apart and/or cause fractures, resulting in a loss of electrical contact. SEI growth can itself cause a buildup of ionic resistance or indirectly increase electrical resistance if the SEI can grow between particles. While these mechanism can be largely generalized for all materials, the extent to which mechanisms such as volume change and fracturing affect an electrode is specific to each material [2, 3]. Similarly, the composition of the SEI can be material specific as well [4]. In this study, the degradation of phosphorus anodes was investigated through multiple analysis methods in order to better understand the material-property-performance relationships for phosphorus anodes. Electrochemical Impedance Spectrometry (EIS) was used to directly measure performance characteristics in Li-ion cells, while Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) depth profiling, and Raman Spectroscopy were used to observe the chemical and structural degradation of the electrodes ex-situ.
[1] N. Nitta, F. Wu, J.T. Lee, G. Yushin, Materials Today, 18 (2015) 252-264.
[2] Y. Liu, N.S. Hudak, D.L. Huber, S.J. Limmer, J.P. Sullivan, J.Y. Huang, Nano Letters, 11 (2011) 4188-4194.
[3] W. Liang, H. Yang, F. Fan, Y. Liu, X.H. Liu, J.Y. Huang, T. Zhu, S. Zhang, ACS Nano, 7 (2013) 3427-3433.
[4] B. Philippe, R. Dedryvère, M. Gorgoi, H. Rensmo, D. Gonbeau, K. Edström, Chemistry of Materials, 25 (2013) 394-404.

A macroscopic high-performance non-aqueous supercapacitor device was fabricated for the first time with soft landed (SL) mass- and charge- selected molybdenum polyoxometalate (POM) anions ([PMo₁₂O₄₀]^3- - a stable anionic metal oxide cluster with 24-electron redox activity), and compared with electrodes prepared using ambient electrospray deposition (ESD) of Na₃[PMo₁₂O₄₀] and (NH₄)₃[PMo₁₂O₄₀] solutions. Ion soft-landing enables the controlled deposition of mass-selected ions with specific charge states, kinetic energies, and composition. The main advantage of the ion soft-landing approach to surface modification is its capability to deliver focused, mass-selected ion beams directly to surfaces, thereby avoiding the complications resulting from contaminants, counterions, and solvent molecules that are inherent with solution-based techniques.
Galvanostatic charge-discharge (GCD) measurements conducted at 8 A/g showed that the total specific capacitance and energy density of the supercapacitor electrodes modified with soft landed PMo₁₂O₄₀^3- ions (SL electrodes) are ~27% and 101% higher than that of the Na₃[PMo₁₂O₄₀] and (NH₄)₃[PMo₁₂O₄₀] electrodes prepared by ESD, respectively. Approximately 60 % higher retention of capacity was also observed after 1000 GCD cycles with the SL electrodes compared to the ESD electrodes. Furthermore, SL electrodes exhibited a maximum Faradaic capacitance with only 1.5 x 10¹³ POM anions asymp; 50 ng, whereas ESD electrodes required twice this amount of POM. Any further addition of POMs lead to a decrease in the total specific capacitance which showcases the remarkable contribution derived from nanograms quantities of SL POM anions. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM) were employed to provide insight into the enhanced performance of the SL electrodes. XPS analysis revealed higher crystallinity of [PMo₁₂O₄₀] clusters in ESD electrodes than SL electrodes, but no significant change in the oxidation state of Mo in both electrodes. The presence of aggregates on the electrode surface and agglomerated [PMo₁₂O₄₀] clusters was evident in the SEM and STEM analysis of the ESD electrodes. In contrast, SL electrodes showed a uniform distribution of ~0.9 nm sized PMo₁₂O₄₀^3- clusters without aggregates. The GCD measurements along with the characterization results demonstrate that the uniform distribution of redox active species without strongly coordinating yet inactive counter ions at the electrode plays a significant role in imparting improved performance and stability in the surface pseudocapacitance. This study establishes the fact that the formation of crystalline aggregates is largely responsible for the reduced performance of POM-based supercapacitors fabricated from solution versus deposited as discrete ions using soft landing.

In recent years, increasing works on solid state ionics have demonstrated the drastic impact of the solid state electrolyte interfaces on the ionic transport properties, leading to emergence of nanoionics as a new field. Numerous works have proved that intelligently designed interfacial structures indeed improve the ionic conductivity of the composite materials as well as the output power of the solid state batteries. In most studies in the field of nanoionics, the energy and charge concentration profiles in the vicinity of the interface have been explained by space charge layer (SCL) formation in the same analogy with Schottky junction of semiconductor heterogeneous interfaces. However, the direct experimental evidences for the SCL formation has been quite limited, and therefore, the critical interfacial characteristics such as SCL thickness, built-in potential, ionic concentration profiles are yet to be elaborated.
Here we report the direct evidences of SCL formation and accumulation of mobile ions at the solid state electrolyte / metal electrode interface formed by epitaxial thin film technique. Detailed investigations of electrochemical impedance spectroscopy (EIS) with particular focus on its capacitance behavior at the pristine interface provided the evidence of SCL formation as well as revealed the polarity of the space charges. Furthermore, hard X-ray photoelectron spectroscopy (HAXPES) enabled to detect the accumulated ionic species underneath the electrode.
To allow us to study the ionic concentration-dependent interfacial characteristics, the sample structures we employed were epitaxial BaZr_{1- x}Y_xO₃H_x (BZY, x = 0.1 - 0.5) proton conducting oxide thin films grown on conductive La:SrTiO₃ (100) substrates on which Pt electrodes were subsequently formed. The measured capacitance values at the Pt/BZY interfaces were as high as order of 1 - 10 mu;F/cm², indicating the solid state electric double layer (EDL) formation. The bias-dependent capacitance revealed that the interfacial capacitance increased with negative bias applied on the electrode, which indicate that the SCL thickness varies from ~ 1 nm (at + 0.4 V bias) to ~ 5 nm (at -1.0 V bias). This capacitance behavior can be interpreted that the SCL consisted of positive charges, namely protons were accumulated under platinum electrode for ~ 1 - 5 nm depth. Proton accumulation was further revealed by HAXPES using a synchrotron radiation X-ray source at SPring-8 in Japan. The HAXPES spectra showed the presence of O-H peak in BZY beneath the thin platinum electrode. This set of studies, for the first time to our knowledge, provides the direct evidences to show (a) the formation of SCL, (b) the polarity of the space charges, (c) SCL thickness, and (d) the accumulated ionic species in the vicinity of the solid electrolyte interfaces. These analysis can be utilized to for solid state batteries to better understand their electrode/electrolyte interfaces.

Electrode materials for Li-ion battery are vigorously studied due to increasing demand in energy sources. Among them, silicon (Si) has been recognized as one of the most attractive candidates for anode materials because of its high theoretical capacity (4200 mAh/g). However, the more than 300% volume change during Lithium ion insertion/extraction processes results in poor cycle life. Meanwhile, graphene has been utilized to enhance the electrochemical performance in varied application. In this work, nano-sized Si powders were encapsulated by graphene to improve the electric and ionic conductivity. The Si nanopowders were first decorated by silane agent to introduce positive charges on the surface. Then negatively charged graphene oxide (GO) were added to form the Si/GO nanocomposite. The Si/Graphene (Si/G) nanocomposite was finally obtained by in-situ reduction. The microstructure of Si/G nanocomposite was investigated by X-Ray diffraction (XRD). The morphology was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).Chemical characterization was also obtained by Fourier Transformation Infrared Spectroscopy (FTIR), Zeta potential and X-ray photoelectron spectroscopy (XPS). Electrochemical performance of the Si/G nanocomposite was tested in coin cell batteries. The preliminary data indicated a very high initial discharge capacity of 100 nm Si/G at 1/10 C current rate and improved cycle performance.

Lithium phosphorus oxynitride (LiPON) is one of the promising electrolyte materials for thin-film batteries due to its superior electrochemical stability, moderate ionic conductivity and low electronic conductivity. In addition, LiPON has a wide optical bandgap (>3 eV) which makes it transparent for UV-Vis light and suitable for using it in electrochromic thin film devices.
The typical value of ionic conductivity of LiPON is in the range of 0.2 to 3.3×10^-6 S/cm[1]. Here we report the deposition of amorphous LiPON thin films by RF sputtering from a commercial Li₃PO₄ target in nitrogen atmosphere with the ionic conductivities at room temperature as high as 4.9×10^-6 S/cm with an activation energy of 0.55 eV.The average growth rate is 14 nm per minute.The electronic conductivity is found to be 2.2×10^-12 S/cm. The film composition is determined to be Li_3.13PO_1.69N_1.39 by inductively coupled plasma-optical emission spectrometry (ICP-OES) and Rutherford backscattering spectrometry (RBS), which demonstrates that the LiPON film possesses a relatively high nitrogen content and a low oxygen content. The local structure is probed by XPS and Raman spectrometry. The incorporation of nitrogen into the matrix is confirmed by both methods and the nitrogen is present in two different chemical environments, i.e. P-N

The optical properties of LiPON are studied by variable-angle spectroscopic ellipsometry (SE) and transmission measurements. The LiPON film is found to have a bandgap of about 3 eV and is highly transparent for UV-Vis light. The optical constants determined include the refractive index n, the extinction coefficient k and the absorption coefficient α in the energy range of 0.58~5.5 eV. The Urbach tail is also observed in LiPON thin films when the photon energy is lower than the bandgap. To study its suitability for electrochromic devices, WO₃/LiPON half-cells are prepared and the electrochromic properties are studied and discussed.
[1] J.F. Ribeiro, R. Sousa, J.P. Carmo, L.M. Gonccedil;alves, M.F. Silva, M.M. Silva, J.H. Correia, Thin Solid Films 522 (2012) 85-89.

Recently, molybdenum oxide (MoO₂) has been found to be a chemically stable and relatively inexpensive material for the application as the anode in a lithium ion battery [1-5]. The use of MoO₂ in battery applications has been hindered due to a long, complicated, and multi-step synthesis process. We present a simple one-pot hydrothermal technique to synthesize MoO₂ nanoparticles directly onto a copper (Cu) substrate.
This is a first report of the synthesis of MoO₂ directly onto a Cu substrate, and could lead to the ability to both fabricate other materials in a similar manner as well as depositing MoO₂ onto other substrates. This technique can reduce anode production time by eliminating the coating process, and also decrease the total amount of chemicals used when compared to a typical powder synthesis and coating processes. The MoO₂ coated Cu electrode was characterized using FTIR, Raman Spectroscopy, XRD and SEM techniques to confirm the composition, crystallinity and structure of the synthesized material. Electrochemical investigation of the MoO2 coated Cu electrode was performed to understand the charge -discharge profile, electrochemical stability and possible battery applications of the synthesized material.
References:
[1] McCrory, Ram, Kumar. “Facile and Scalable Solution-Phase Synthesis of MoO2 Nanoparticles for use as the Anode of a Lithium-Ion Battery.” (Publication Pending)
[2] McCrory, Ram, Kumar. “Review: Novel Nanocomposite Anodes for Secondary Lithium-Ion Batteries.” (Publication Pending)
[3] X. Chen, Z. Zhang, X. Li, C. Shi, and X. Li, “Selective synthesis of metastable MoO2 nanocrystallites through a solution-phase approach,” Chem. Phys. Lett., vol. 418, no. 1-3, pp. 105-108, Jan. 2006.
[4] Q. Tang, Z. Shan, L. Wang, and X. Qin, “MoO2-graphene nanocomposite as anode material for lithium-ion batteries,” Electrochimica Acta, vol. 79, pp. 148-153, Sep. 2012.
[5] A. Bhaskar, M. Deepa, T. N. Rao, and U. V. Varadaraju, “Enhanced nanoscale conduction capability of a MoO2/Graphene composite for high performance anodes in lithium ion batteries,” J. Power Sources, vol. 216, pp. 169-178, Oct. 2012.

Lithium-rich anti-perovskite (LiRAP) was reported to be a novel class of superionic conductor with 3D fast-ionic channels for Li⁺ migrating, and could be used as solid electrolyte for lithium ion battery (LiIB). Solid electrolyte should fulfill some requirements such as high Li⁺ conductivity, wide electrochemical window and stability with cathode and anode. However, many superionic conductors are found to be unstable at lower voltage range, which means they could not work directly together with lithium metal anode. In this work, we studied the stability of Li₃OBr, one member of LiRAP materials, as solid electrolyte for LiIB. Firstly, to determine the electrochemical window, cyclic voltammetry was adopted on a half battery of {stainless steel #9553;Li₃OBr#9553;lithium metal} with scanning rate as 1 mV/s at 100 ^oC. No obvious redox peaks expect for lithium dissolution/deposition were observed from -0.5 V to 4.8 V, indicating Li₃OBr is stable in this voltage range. Secondly, to test the stability with lithium metal, DC and AC measurements were applied on symmetrical battery {Li#9553;Li₃OBr#9553;Li}. DC current of 0.5 mV was applied on the battery for one hour and then reversed direction, and the results show that the voltage did not increase for 30 hours. AC electrochemical impedance spectra were recorded at 25 ^oC for 120 hours and then at 50 ^oC for 44 hours. Fitting results show that the conductivity of the battery remains the same after the system get balanced at given temperature, which means no reaction in the Li₃OBr-Li interface. In conclusion, Li₃OBr could work in a wide electrochemical rang up to 4.8 V, and it could work directly together with lithium metal. It reveals that LiRAP is a promising solid electrolyte, and could also be used for lithium protection. These results are helpful for the research and development of solid state lithium ion battery.

One of the most critical issues associated with high specific capacity anode materials such as Si is chemical and mechanical stability of solid electrolyte interphase (SEI) layer. Although there have been lot of studies on chemistry of SEI layer; very little information is available on its mechanical properties. In this work we present a new approach that is based on patterned Si islands, with measurements that include galvanostatic cycling, electrochemical impedance spectroscopy (EIS), in situ optical microcopy, and in situ stress measurements. By calibrating the lateral expansion and contraction of these islands, it is possible to systematically investigate the impact that large volume changes have on the SEI stability after formation cycling. These patterned island samples serve as a model system to study the behavior of SEI and these learnings were further correlated to SEI stability on composite electrode architectures. SEI stability data will be presented on Si nanoparticle based composite electrodes with different active material loading; different binders and different electrolyte additives. This kind of study will serve as a tool in optimizing the electrode composition, choosing right binder and electrolyte additive to tailor a stable interphase layer that can improve performance of Li-ion batteries.

Carbon nanotube (CNT) has been considered as a potential carbon nanomaterial exhibiting excellent physical and chemical properties to serve both as active current collector and free standing electrodes for next generation Li-ion battery (LIB). However, their low packing density hinders their application in large-scale energy storage systems. Here, we rationally design a free standing multi-layered micro-channeled 3D CNT anode architecture by a simple binder-conducting additive aid hot press method to enhance the areal loading and tap density of CNT. The 3D CNTs shows excellent volumetric capacity of 465 mAh/cm3 at 0.5C rate, superior to other reported carbon based nanostructured anodes and comparable apparent density of 1.85mg/cm3. The excellent properties resulted from this novel approach are attributed to the synergetic effect of the high structural integrity of CNTs and their intrinsic properties. This strategy may substantially provide a powerful platform for the advanced LIB technology.

Lithium-air battery (LAB) with high energy density and high power performance is a promising way to meet the demand of large-scale energy storage for grid integration of renewable energy sources and sustainable full-range electromobility. While organic Lithium-air batteries feature the highest energy density and therefore have been the subject of intense studies, high polarization during charge and discharge in these cells continue to limit the available power performance and energy efficiency of this type of LABs. This has drawn renewed attention to aqueous LABs where catholytes with high solubility for discharge products are employed enhancing the cycle efficiency, power density and practical energy density.
Realising a stable high performance aqueous LAB essentially depends on a fast ion lithium conducting membrane. This membrane protects the lithium anode from reacting chemically with the catholyte. For that propose, NASICON-type Li_1+xAl_xGe_2-x(PO₄)₃ glass is prepared using solid state reaction followed by heat treatment to ensure crystallization. Rietveld refinement confirms the formation of rhombohedral LAGP (space group R-3c) with GeO₂ (P3₁21) as a secondary phase. Room temperature total conductivity of the ceramic pellet reaches 4×10^-4 Scm^-1 with an activation energy of 0.35 eV. As a measure of chemical stability of the LAGP ceramic, powder was immersed in distilled water and the changes in pH were monitored. The observed decrease in pH with immersion time due to a partial decomposition of LAGP to GeO₂. The pH stabilizes at a value of 4 after 2 hours of immersion, suggesting that unprotected LAGP is more suitable for acidic catholytes.
Fast Li⁺ ion conducting, light-weight, flexible hybrid inorganic-organic membranes have the fundamental advantage that they are more easily scalable and more easily moulded into desired shapes than ceramic solid electrolytes. Here we demonstrate hybrid inorganic-organic membranes consisting of NASICON-type (LAGP) as the fast ion conducting ceramic filler and various polymer components and test them in LAGP cells. High conductivity membrane 1 used PEO:PVDF:LiBF₄ and high stability (but lower conductivity) membrane 2 used plasticized Polyvinyl-butyral:LiBF₄:PVDF as the polymer component. According to XRD patterns of membrane 2 before and after immersion in acidified LiCl (10M; pHasymp;2) for 22 days, there is no sign of decomposition in the membrane 2. A cell comprising of membrane 2 as anode-protecting membrane and acidified LiCl (10M; pHasymp;2) worked for 138 cycles (each cycle limited to 1 hour), while cells for membrane 1 can only be used with neutral catholytes (When using the acidified LiCl catholyte cells using membrane 1 failed typically after about 10 cycles each limited to 40 minutes) . The greatly enhanced stability of membrane 2 resulted in significantly improved battery performance and cycle life.

Silicon is widely regarded as one of the most promising anode materials for next-generation lithium-ion batteries, making Li-Si an important energy storage system. During Li insertion into Si, stress of gigapascal level is introduced accompanied by a volume expansion up to 280%, alters properties of materials, and leads to mechanical failure of Si anodes.
Li15Si4 (alpha-Li15Si4, space group: I-43d), the only crystalline phase that forms during lithiation of the Si anode in lithium-ion batteries, was found to undergo a structural transition to a new phase (beta-Li15Si4) at approximately 7 GPa. Moreover, this new phase could be quenched to ambient pressure. Ab initio evolutionary metadynamics calculations suggest beta-Li15Si4 has an orthorhombic structure with an Fdd2 space group. In the new beta-Li15Si4 phase the atomic packing is more efficient owing to the higher Si-Li coordination number and shorter Si-Li, Li-Li bonds. Therefore it has substantially larger elastic moduli compared with alpha-Li15Si4, and has good electrical conductivity. As a result, beta-Li15Si4 has superior resistance to deformation and fracture under stress. The theoretical volume expansion of Si would decrease 25% if it transformed to beta-Li15Si4, instead of alpha-Li15Si4, during lithiation. In addition, the fact that beta-Li15Si4 can be recovered back to ambient pressure, provides opportunities to further investigate its properties and potential applications.

The stability of cubic Al_xLi_(7-3x)La₃Zr₂O₁₂ (LLZO) is affected by current density. In beta alumina solid electrolyte, microstructural failure was caused by Na dendrite penetration, and was shown to be a function of the fracture toughness, K_IC. The relationship between dendrite penetration and K_IC indicates failure is related to creation of microstructural damage. In this paper we developed a non-invasive, in-situ cell monitoring apparatus to help to correlate stability with Li-ion current density in LLZO. A pulse-echo transducer was integrated into into all solid-state Li-LLZO-Li cells. The capability enables the characterization of microscopic inhomogeneities through the careful measurement of the elastic moduli. The elastic moduli and fracture toughness of have been previously reported for dense (>99%) specimens, but monitoring of the relative change in moduli during cycling has not been explored. Further, stress intensity near a sufficiently large flaw may affect degradation at and above a certain current density in a material that is otherwise impenetrable to dendrite growth. Therefore, the complete elimination of porosity and cracks are desirable for the monitoring of fundamental failure mode studying. In this study, an acoustic monitoring method is presented to monitor LLZO specimens during cycling. LLZO membranes were prepared with high phase purity, >98 % relative density and uniformly stabilized in the high conductivity cubic polymorph. The authors acknowledge the support of DOE EERE Award # DE-0991-01663

The nanosizing of materials for energy storage applications is a promising route to improve their specific properties due to both the increased surface/interface area, which is important for rapid charge transfer, and the short length scales within the material that are essential for fast charge and mass transport phenomena.
The present work reports on the synthesis of MgH₂ nanoparticles, by a bottom-up approach, confined in a porous carbon for application as anode material for Li-ion batteries ^[1].
The use of magnesium hydride as anode material for Li-ion batteries has been demonstrated according to a conversion mechanism, where the hydride MgH₂ reacts with lithium ions to form at the end of the discharge the metal Mg and lithium hydride LiH:
MgH₂ + 2 Li⁺ + 2 e^- harr; M⁰ + 2LiH ^[2,3]
The use of MgH₂ nanoparticles leads to faster lithium/hydrogen diffusion and to a better electronic conductivity within the composite electrode, thereby a lower cell polarization and an improvement of the electrochemical performance. Our bottom-up synthesis route allows the formation of Mg-based nanoparticles with sizes ranging from 5 to 10 nm via in situ hydrogenation of an organometallic precursor ^[4].
The effect of both Mg loading (15, 25, 50 and 70 wt.%) and textural properties of different carbon hosts (surface area and pores size distribution) on the nanoparticle size distribution has been investigated. The average particle size and distribution increase with Mg loading.
The electrochemical performance of the material containing 50 wt% of Mg has been tested as negative electrode material in Li-ion batteries. Our results show that nanoconfined MgH₂ has better discharge/charge capacities and greatly improved cycle life as compared to ball milled macrocrystalline MgH₂.
[1] Y. Oumellal, C. Zlotea, S. Bastide, C. Cachet-Vivier, E. Léonel,a S. Sengmany, E. Leroy, L. Aymard, J-P. Bonnet and M. Latroche. Nanoscale (2014),6, 14459
[2] Y. Oumellal et al., Nature Materials, 7 (2008) 916
[3] Y. Oumellal, A. Rougier, J-M. Tarascon and L. Aymard. J. Power Sources, 192 (2009) 698.
[4] C. Zlotea, C. Chevalier-César, E. Léonel, E. Leroy, F. Cuevas, P. Dibandjo, C. Vix-Guterl, T. Martens et M. Latroche, 151 (2011) 117.

The Li-O₂ battery offers one of the highest gravimetric energy densities for all electrochemical energy storage technologies. The development of this technology, however, has been hindered by poor cycling performance. One important reason is the degradation of the carbon cathode, aside from electrolyte decomposition. Here we propose an approach that addresses the stability issue of the carbon cathode. Our strategy is based on the understanding that an inert substrate, a proper catalyst and robust adhesion between catalyst and substrate are essential for a stable cathode. As a proof of concept, we fabricated Pd nanoparticle loaded on functionalized TiSi₂ nanonets by atomic layered deposition (ALD). In comparison to carbon containing systems, the non-active but conductive TiSi₂ substrate served as a unique platform to study the intrinsic behavior of the catalyst by decoupling the oxygen reduction reaction (ORR) catalytic activity from cathode substrate. The well-known ORR activity of Pd was investigated and confirmed. Oxygen evolution reaction (OER) catalytic activity was observed on Pd as well. However, with Pd deposition by ALD alone, gradual cell failure induced by Pd nanoparticle aggregation was observed. By introducing a functional metal oxide layer onto TiSi₂ substrate using ALD for Pd immobilization, we obtained significantly improved cycling performance. Importantly, reversible formation and decomposition of Li₂O₂ was confirmed by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and differential electrochemical mass spectrometry (DEMS). Our results support that through rational design of the cathode composition and structure, stability of the cathode of Li-O₂ battery can be readily improved. This rational design opens up new doors toward practical Li-O₂ batteries by providing a practically functional cathode support.

LiFePO₄ is a promising cathode for Li-ion batteries due to the outstanding cycling stability and safety compared to other oxide cathodes. Pioneer studies have focused on the improvement of low electronic conductivity (sim;10^minus;9 Scm^minus;1) and slow Li⁺ diffusion (sim;1.8×10^minus;14 cm²s^minus;1) which cause poor rate capability at quick charge.¹ In battery production, the energy density is a challenge that limits the battery designs. Even though nano materials improve battery kinetics and conductivity, they reduces the manufacturing compatibility because of its low density. In this study, 2D morphology is aimed to be synthesized at nano scale thickness to overcome this challenge on battery design. Nucleation control mechanisms were studied via US assisted subsequential precipitation to obtain fast rechargeable nano plates LiFePO₄. Due to the high aspect ratio of synthesized nano plates, high tap density electrodes are obtained for adequate processability to get high energy and power dense batteries which are strongly compatible with solid state battery electrode thicknesses.
In early study, aqueous based vivianite (VVT, Fe₃(PO₄)₂#903;8H₂O) synthesis route has not been considered suitable due to the bad reproducibility, micron size particles and its oxidation sensitivity.² In this study, US reduces Fe²⁺ ions, induction time, and metastable zone width of growth region so that crystallization process yields high and controllable nucleation rate. VVT formation and sub-sequential sono-crystallization are driven by US stimulation which enhances slow reactive crystallization rate within a very small space and time in atmospheric conditions. This new technique provides high reproducibility with control on size distribution and morphology of particles as well as reaction kinetics.
For conductivity and preservation of the synthesized nano plate (40-80 nm) morphology, carbon encapsulation is conducted under reducing atmosphere on VVT precursors before the calcination step which is crucial for well crystallinity. Following the meta-morphologic phase transformation, calcination yields 50-100 nm thick polycrystalline LiFePO₄/C nano plates which survived at 700 ^oC. XRD and SAED patterns support that VVT nano plates are synthesized with strong preferred orientation at (010) as single crystalline while newly formed sub-grains are weakly oriented at [010] in each LiFePO₄/C nano plates. Beside slightly localized preferred orientation, polycrystalline structure positively contributes to Li⁺ diffusion mechanism by creating higher ionic conduction paths through grain boundaries.³
The highest discharge capacity is 125.1 mAhg^-1 at 0.1C cycling rate. In the fast charge at 1C, discharge capacities are found as 103.8 and 80.3 mAhg^-1 at slow (0.1C) and fast (1C) discharges, respectively. In this study, facile and cost efficient aqua based synthesis is developed to synthesize energy and power dense LiFePO₄ which provides fast rechargeability compared to other high temperature solvothermal synthesis.^4,5

To meet the growing demand for Li-ion batteries, inexpensive cathode materials from abundant natural resources are required. In this sense, it is desirable to move away from cobalt based to iron based cathode materials. Recently, it was shown that the electrochemical performance of tavorite LiFeSO₄F can be significantly enhanced by coating the material with the electronically conducting polymer PEDOT.¹ It was suggested that the advantageous electronic pathways provided by the polymer, in combination with the fast Li-ion transport within the bulk LiFeSO₄F,² improved the battery performance.
In this contribution, we dig deeper into determining the limiting factors for LiFeSO₄F. We aim to bring deeper insight into the function of PEDOT coated LiFeSO₄F in batteries via thorough electrochemical testing, combined with advanced materials analysis.³ Cyclic voltammetry showed that the electrode material itself was not limiting the battery performance when loaded as powder into a Swageloktrade; cell. The amount of PEDOT coated on LiFeSO₄F was varied; and galvanostatic cycling revealed that the more PEDOT present, the higher the practical capacity of the battery.
The promising results from powder material in Swageloktrade; cells encouraged us to make casted electrodes, more relevant for practical applications. Surprisingly, the cycling performance was extremely bad for these electrodes. However, capacity loss could be regained by cycling the electrode at a very slow rate (C/100). Additionally, XRD showed that the active material was still intact and FT-IR revealed that PEDOT was still present in the sample. On the other hand, electrochemical impedance spectroscopy demonstrated that the charge transfer resistance increased with several orders of magnitudes, also in line with the large overpotential in the galvanostatic cycling. These problems in electrochemical properties could be improved by calendaring the electrodes to lower porosities. The charge transfer resistance was thus lowered dramatically, and for electrodes having a porosity of le; 30% a stable galvanostatic cycling was obtained.
These results indicate that:
i) The more PEDOT coated on LiFeSO₄F, the more particles are electronically connected.
ii) The rate performance of the battery is no longer limited by the powder itself.
iii) For casted LiFeSO₄F/PEDOT electrodes, controlling the porosity of the coating is essential for the battery performance.
References
(1) Sobkowiak, A.; Roberts, M. R.; Younesi, R.; Ericsson, T.; Häggström, L.; Tai, C.-W.; Andersson, A. M.; Edström, K.; Gustafsson, T.; Björefors, F. Chem. Mater.2013, 25, 3020-3029.
(2) Recham, N.; Chotard, J.-N.; Dupont, L.; Delacourt, C.; Walker, W.; Armand, M.; Tarascon, J.-M. Nat. Mater.2010, 9, 68-74.
(3) Blidberg, A.; Sobkowiak, A.; Tengstedt, C; Gustafsson, T.; Björefors, F. In preparation.

Chemical energy storage using batteries will become increasingly important in the future for environmentally friendly societies. Lithium iron phosphate, LiFePO₄, is an important class of cathode material for large-scale lithium-ion batteries, because of its highly safe nature and the Earth's natural abundance of Fe. Regardless of the biphasic reaction between the insulating end members, in Li_xFePO4, x ~ 0 and x ~ 1, optimization of nano-structured architecture has substantially improved the power density of positive LiFePO₄ electrode. Recent research has revealed that the charge transport that occurs in the interphase region across the bi-phasic boundary is the primary stage of solid-state electrochemical reactions, in which the Li concentrations and the valence state of Fe deviate significantly from the equilibrium end-members. Complex interactions among Li ions and charges at the Fe sites have made understand stability and transport properties of the intermediate domains difficult. Here, we discovered long-range ordering at metastable intermediate eutectic composition of Li_2/3FePO₄ and determined its superstructure, which reflected predominant polaron crystallization at the Fe sites followed by Li+ redistribution to optimize the Li-Fe interactions.

Li-O₂ batteries provide high-capacity energy storage, but for aprotic Li-O₂ batteries, it is reported that the charge-discharge efficiency is ultimately limited by the crystal growth of insoluble Li₂O₂ on the porous cathode. Catalysts have been reported to improve the nucleation and morphology of Li₂O₂, which helps achieve high energy densities. We provide a new insight into the catalytic mechanism of the oxygen reduction reaction (ORR) in aprotic Li-O₂ batteries—the oxygen sites on the surface play a more important role than the exposed metal sites—via a study based on the density functional theory (DFT) examining α-MnO₂ surfaces. Lithium ions from electrolytes are found to interact with the surface oxygen sites and form surface lithium sites, facilitating further growth of Li₂O₂. A larger number of initial growth points with uniform distribution makes Li₂O₂ well dispersed, forming small particles that benefit both the ORR and oxygen evolution reactions (OER). This design concept for oxygen sites has been successfully validated by the real experiments with α-MnO₂ nanowires.

Sustainable paper-based energy storage devices consisting of electrochemically active materials and nanocellulose fibres have attracted considerable interest because of their inexpensiveness, flexibility, light-weight and good electrochemical properties [1,2]. Recent work has demonstrated that conductive cellulose paper composites comprising nanocellulose and carbon nanotubes can provide high conductivities with excellent mechanical properties and that these composites may be employed as high-performance, paper-like, battery/supercapacitors electrodes [3-4]. The present presentation will focus on the results of our recent research on the possibility of fabricating flexible freestanding paper-like Si anodes for lithium-ion batteries [4-6]. It will be shown that such conductive cellulose paper-based flexible Si anodes exhibit high areal capacities and high electrode-normalized gravimetric capacities and that this approach holds great promise for the fabrication of electrodes for next-generation sustainable lithium-ion battery based electrical energy storage.
References
[1] L. Nyholm, G. Nyström, A. Mihranyan, M. Stroslash;mme, Adv. Mater., 2011, 23, 3751.
[2] Z.H. Wang, P. Tammela, P. Zhang, M. Stroslash;mme, L. Nyholm, J. Mater. Chem. A 2014, 2, 7711.
[3] Z.H. Wang, P. Tammela, M. Stroslash;mme, L. Nyholm, Nanoscale 2015, 7, 3418.
[4] Z.H. Wang, C. Xu, P. Tammela, J.X. Huo, K. Edström, M. Stroslash;mme, T. Gustafsson, L. Nyholm, J. Mater. Chem. A 2015, doi: 10.1039/C5TA02136G.
[5] C. Xu, F. Lindgren, B. Philippe, M. Gorgoi, F. Björefors, K. Edström, T. Gustafsson,. Chem. Mater., 2015, 27, 2591.
[6] B. Philippe, R. Dedryvère, M. Gorgoi, H. Rensmo, D. Gonbeau, K. Edström, J. Am. Chem. Soc., 2013, 135, 9829.

Two dimensional (2D) silicon nanosheets is a promising anode material for next generation lithium-ion batteries due to its high theoretical storage capacity. Calcium silicide (CaSi₂) is typical layered material with Si corrugated (111) layers that are linked by calcium ions. However, the commercial application of CaSi₂ as anode material is hindered by its poor performance due to the huge volume change during cycling. Alternatively, encapsulation of silicon nanosheets with reduced graphene oxide (RGO) results in better electrochemical performances. In the present study, we adopt a novel strategy to generate encapsulated silicon nanosheets in RGO sheets. The typical synthesis involved three steps: In the first step, layered silicon material was synthesized by a topotactical reaction using CaSi₂. In the second step, surface functionalization of layered silicon material was done using 4-aminostyrene to get Si-NH₂ nanosheets. In the final step, encapsulation of silicon nanosheets with RGO was done by diazzonium coupling reactions followed by the calcination at 500^oC for 8 hrs. The resulting composite structures were characterized using characterization tools like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), field emission transmittance electron microscopy (FE-TEM), Thermogravimetric analysis (TGA), Raman spectroscopy to corroborate the successful formation of silicon-graphene nano sheet composites. Finally, galvanostatic charge discharge studies were done for above composites by fabricating a Lithium ion battery. The initial capacity for CaSi₂ and RGO/Si nano sheets composite was 1088 mAh/g and 2720 mAh/g respectively.

We demonstrate an application of the electrospray to synthesize oxide nanoparticles for energy storage. A twin electrospray technique is employed in which two sprays of droplets of uniform size but opposite polarity are aimed at each other and used to obtain a charge-neutral aerosol of monodisperse liquid droplets containing graphene and metal nitrates. Each liquid droplet serves as a micro-reactor, allowing for precise control over particle composition, size, and composite structure. This aerosol flows through a tubular furnace to yield, ultimately, metal oxide nanoparticles entangled with graphene sheets through a process of pyrolysis and oxidation. The resulting composite material is of interest as nanocatalysts for lithium-air batteries and as high-capacity nanostructured anode for lithium-ion batteries. We will report on the electrocatalytic behavior of the material and eventually its battery performance.

We report the surprisingly low solid-electrolyte/electrode interface resistance of 8.6 Omega;cm² observed in thin-film lithium batteries. [1] This value is an order of magnitude smaller than that presented in the previous reports on all-solid-state lithium batteries, and the value is also smaller than that found in a liquid electrolyte based batteries.
The observation of the low interface resistance indicates that the negative space-charge layer effects at Li₃PO_4-xN_x/LiCoO₂ interfaces are negligible.
Consequently, the results imply that there is no physical limitation to go beyond liquid-electrolyte-based lithium-ion batteries,namely, it is possible to fabricate fast charging/discharging all-solid state batteries.
[1] Masakazu Haruta, Susumu Shiraki, Tohru Suzuki, Akichika Kumatani, Takeo Ohsawa, Yoshitaka Takagi, Ryota Shimizu, and Taro Hitosugi, Nano Lett. 15, 1498-1502 (2015).

Exchanging the active specie, Li⁺ in Li-ion batteries by multivalent, abundant and cheap cations, such as Mg²⁺, are projected to boost the energy density and lower the cost per kilo-watt-hour significantly, making the Mg-ion battery technology a promising candidate for one of the battery technologies of the future.^1,2
The increase in energy density is i.a. a result of the divalent Mg²⁺ carrying twice as much charge as the monovalent Li⁺.^1,2 However, the higher charge also poses a problem as it significantly increases the charge density of the ion, which results in stronger interactions with the host lattice of the electrodes and hampers facile ion transport. Therefore, development of novel electrode materials for effective Mg-ion storage is a vital step for the realization of this battery technology.³
In this study, we have synthesized a series of vanadium-based oxides and phosphates with varying chemical composition and varying nanotopologies, e.g. nanosheets and nanotubes. The mechanism for Mg-intercalation and deintercalation is studied through operando synchrotron powder X-ray diffraction measured during battery operation. These results show e.g. that Mg-intercalation in multivalled V₂O₅-nanotubes solely occurs within the space between the individual vanadium oxide layers building the walls of the nanotubes while the underlying V₂O₅ frameworks constructing the walls are not affected by the intercalation. This provides new insights into the size requirements of the channels/layers in the host frameworks that will allow for efficient Mg-ion storage.
Reference:
1. R. van Noorden, Nature 2014, 507, 26
2. Pellion Technologies, “Moving Beyond Lithium with Low-Cost, High-Energy, Rechargeable Magnesium Batteries”, Pellion White Paper, September 2011
3. P. Saha, M. K. Datta, O. I. Velikokhatnyi, A. Manivannan, D. Alman, P. N. Kumta, Progress in Materials Science 2014, 66, 1.

Rechargeable metal-air (oxygen) batteries are receiving a great deal of interest as possible alternatives to lithium ion batteries, due in particular to their potential to provide higher gravimetric energies. ¹ While much attention has been focused on aprotic Li-O₂ batteries, substantial challenges must be addressed before widespread commercial implementation is possible. Recently, a metal-air battery in which lithium is replaced by sodium has received increasing attention.² Although Na-O₂ batteries present lower gravimetric energies than Li-O₂ batteries on a cell basis (1605 or 1108 Wh/kg¹ based on Na₂O₂ or NaO₂ discharge products, respectively, vs. 3505 Wh/kg_Li2O2²), much lower charge overpotentials than those in typical Li-O₂ batteries have been reported during discharge and charge (~100 mV vs. ~1000 mV), based on reversible sodium superoxide (NaO₂) formation. In addition, Na-O₂ batteries can exhibit energy efficiencies higher than 90 %.
Here we report the electrochemical performance of graphene aerogel as an electrode for the Na-O₂ system. The graphene gels are formed from interlinking of the graphene sheets by concentrating an electrochemically exfoliated graphene suspension, and transforming it into an aerogel by freeze-drying. The resultant graphene aerogels have very low density, high porosity and surface area, with pore sizes ranging from several nanometers to several tens of micrometers, and remarkable electrical conductivity. In addition, aerogel formation is a very simple process that allows large-scale production at a low cost. Phase-pure NaO₂ (pyrite structure, Fmm) was found as the sole discharge product, as confirmed by X-ray diffraction and Raman spectroscopy. The high surface area of the graphene aerogel provides abundant sites for discharge product formation and is seen to be extensively covered by cubes post-discharge, a morphology characteristic of NaO₂. The graphene electrode therefore exhibits a very high capacity (22000 mAh g^minus;1, 4.84 mAh cm^minus;2) and high cycle life (more than 200 cycles), identifying graphene aerogels as the top-performing electrode to-date.
REFERENCES
1. D. G. Kwabi, N. Ortiz-Vitoriano, S. A. Freunberger, Y. Chen, N. Imanishi, P. G. Bruce, Y. Shao-Horn, MRS Bull.39, 443 (2014).
2. P. Hartmann, C. L. Bender, M. Vra#269;ar, A. K. Dürr, A. Garsuch, J. Janek, P. Adelhelm, Nat. Mater.12, 228 (2013).

Li-air battery is a great deal of attention in recent years. The energy density of the Li-ion battery that is practically used is 200-250 Wh/g. On the other hand, theoretical energy density of Li-air battery has 11,000 Wh/g by weight of lithium metal alone or about 5,200 Wh/g when the oxygen weight is included. However, there still remain some challenges that must be overcome for commercialization. Especially the main issue is overvoltage due to Li₂O₂ generated by the cathode reaction of Li⁺ and O₂. In our previous study, effect to the overvoltage by structure of the carbon surface and deposition form is elucidated[W. Yamamoto, Md. K. Alam and H. Takaba:ECS Transaction, 2014, Vol.61, (13), pp.63-69]. However, it didn&’t consider the effect of the electrode. In this study, we analyzed deposition and decomposition mechanism of Li₂O₂ and reveal the relationship between deposited of Li₂O₂ with carbon and electrolyte using first principles molecular dynamics method. We analyzed deposition and decomposition process of Li₂O₂ when the charge of the system were changed. As a result, production of Li₂O₂ particle is observed when the charge of the system Li₂O₂ approaches to neutral. The charge of the system Li₂O₂ approaches to more positive, we could observe decomposition of Li₂O₂. Furthermore, we analyzed the solvation energy of Li₂O₂ to ether-based electrode triglyme(G3) that is not decomposed during charge and discharge. The deposition energy of Li₂O₂ with consideration of solvation free energy are determined. Free energy diagram for the reactions at the oxygen electrode is elucidated. More detailed simulation result will be presented at the conference.

Catalyzing the oxygen reduction reaction is critical to enabling several emerging energy storage and conversion technologies such as metal-oxygen batteries and fuel cells. Non-aqueous Li-O₂ batteries in particular are estimated to deliver gravimetric energies two to three times that of conventional Li-ion batteries at comparable gravimetric power. Solvation of Li⁺ and superoxide ions (O₂^-) can greatly influence the kinetics and capacity of non-aqueous Li-oxygen battery upon discharge. Here, using a combination of first principles calculations and electrochemical measurements, we show how redox potentials of O₂/O₂^- and Li⁺/Li increase and decrease with the strength of O₂^- and Li⁺ solvation respectively. We also show how increasing computed solvation energies of O₂^- and Li⁺ increase with the solubility and coupling strength of Li⁺-O₂^-. Implications of this work for understanding the morphologies and chemistries of Li-O₂ discharge products will also be addressed, using spectroscopic and electrochemical quartz crystal microbalance techniques. These results reveal the importance of the interplay between ion-solvent and ion-ion interactions for rationalizing and controlling the energetics of intermediate species produced during the non-aqueous oxygen reduction reaction.

The development of rechargeable Mg batteries, driven by the desire to overcome the limiting specific energy density and high cost of Li ion batteries, is currently frustrated by the lack of stable, functional electrolytes compatible with high voltage cathodes. Successful electrolytes have relied on Lewis acid - base reactions to form Mg cation-solvent complexes that include the traditional Grignard based and more recently reported inorganic MgCl₂ based complex electrolytes containing either BR₄^- or AlR_xCl_4-x^- species. However, the stability of organometallic and chloroaluminate electrolytes against traditional current collectors and proposed oxide intercalation cathodes are of significant concern. Novel Mg battery electrolytes based on the weakly coordinating N(SO₂CF₃)₂^- (TFSI) anion have recently received interest due to their wide electrochemical window and general chemical compatibility while maintaining the ability to deposit and strip Mg, a feature previously unknown for “conventional” Mg salt solutions. However, Mg deposition in these systems is typically characterized by low coulombic efficiency (< 50%) and Mg surface passivation in the absence of chloride additives.
In this presentation we describe Mg deposition and stripping from a chloride-free MgTFSI₂-glyme electrolyte at nearly 90% coulombic efficiency, demonstrating that such “conventional” electrolytes have the ability to support reversible Mg deposition at application-relevant rates (> 1 mA/cm²). This finding demonstrates that the use of weakly coordinating salts in glymes need not prevent Mg²⁺ transport across the anode/electrolyte interface. The MgTFSI₂ system further teaches us that non-reducing, non-chloride electrolytes are highly sensitive to impurities, which regulate the interfacial processes controlling deposition irreversibility. We will discuss the influence of specific impurities, identified through spectroscopic techniques including and GC-MS, on the activity of MgTFSI₂-glyme electrolytes and demonstrate the importance of impurity removal for attaining good performance. We will further discuss the origins of poor coulombic efficiency (< 90%) and the passivation of Mg in MgTFSI₂-glyme electrolytes. Characterization of cycled electrolytes by ESI-MS and cycled electrode interfaces by XPS implicates TFSI decomposition during Mg deposition and stripping as the most likely source of these problems. This finding corroborates previous computational work performed by our collaborators, which predicts an electrochemical-chemical TFSI decomposition mechanism involving S-C bond cleavage and liberation of a CF₃ group.
This work is supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science. Sandia is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. DOE&’s NNSA under contract DE-AC04-94AL85000.

By combining a multivalent cation with the high capacity of a gas-breathing positive electrode, the energy density of a non-aqueous Mg/O₂ battery is projected to surpass that of other ‘beyond-Li-ion&’ chemistries. Nevertheless, research into Mg/O₂ systems has been limited. A rechargeable, non-aqueous Mg/O₂ cell that operates at room temperature will be discussed and used to clarify fundamental electrochemical characteristics, including the nature of the product phase(s) and the reaction mechanism for discharge. The discharge product differs from alkali-metal-based chemistries in that it is a mixed phase, primarily comprising crystalline MgO, with a substantial minority of MgO₂. The open-circuit cell voltage is 2.0 V, lower than the theoretically expected ~2.9 V. Both the low voltage and the two-phase discharge product are consistent with a multi-step discharge reaction in which a superoxide (O₂^-) intermediate forms at ~2 V vs. Mg/Mg²⁺. Chemical reactions subsequently yield MgO₂ and MgO, but do not contribute to the cell&’s electrical energy output. During charging, MgO₂ is preferentially decomposed. Bypassing the multi-step discharge mechanism in favor of direct electrochemical formation of MgO_x would allow for a higher discharge potential and, consequently, higher energy density.

The discovery of new materials and microstructures for sodium ion battery (aka NIB, NaB or SIB) electrodes is of scientific interest. Here we provide the first report on several compositions of ternary Sn-Ge-Sb thin film alloys for application as NIB anodes, employing Sn50Ge50, Sb50Ge50 and pure Sn, Ge, Sb as baselines. Sn33Ge33Sb33, Sn50Ge25Sb25, Sn60Ge20Sb20 and Sn50Ge50 all demonstrate promising electrochemical behavior, with Sn50Ge25Sb25 being the best overall. This alloy has an initial reversible specific capacity of 833 mAhg^-1 (at 85 mAg^-1), and 662 mAhg^-1 after 50 charge - discharge cycles. Sn50Ge25Sb25 also shows super rate capability, displaying a stable capacity of 381 mAhg^-1 at a current density of 8500 mAg^-1 (~ 10C). A survey of published literature indicates that 833 mAhg^-1 is among the highest reversible capacities reported for a Sn-based NIB anode, while 381 mAhg^-1 represents the most optimum fast charge value. We employ transmission electron microscopy (TEM) analysis to assay the cycling microstructure of the binary and ternary electrodes, showing that Sn50Ge25Sb25 is a composite of Sn and Sn-alloyed Ge nanocrystallites that are densely dispersed within an amorphous matrix. Comparing the microstructures of alloys where in the capacity significantly exceeds the rule of mixtures prediction to those where it does not, leads us to hypothesize that this new phenomena originates from the Ge(Sn) that is able to sodiate beyond the 1:1 Na:Ge ratio reported for the pure element.

O3 layered sodium transition metal oxides (i.e., NaMO₂, M = Ti, V, Cr, Mn, Fe, Co or Ni) are a promising class of cathode materials for Na-ion battery applications. These materials, however, all suffer from severe capacity decay when more than 0.5 Na is extracted from the hosts. Understanding the causes of this capacity decay is the key to fully unlock the potential of these materials for battery applications.
In this work, we elaborate the capacity fading mechanism for one of the compounds in this class, i.e., NaCrO₂. The desodiation process of NaCrO₂ were first characterized by in situ XRD. We chose a slow cycling rate (C/50) for the measurement to construct the phase diagram of Na_xCrO₂ that is close to thermodynamic equilibrium. This phase diagram guided us to pinpoint the compositions that required a more detailed structural study. Ex situ synchrotron XRD and electron diffraction were then performed on samples that were charged to selected stages of charge. While synchrotron XRD allows us to collect bulk structural information on these samples, electron diffraction offers a unique opportunity to probe the structures of individual particles or selected domains. The electron diffraction study was aided by electron energy loss spectroscopy which provides valuable insights into the oxidation state and local geometry of Cr. We demonstrate that Na_xCrO₂ (0 < x < 1) remains in the layered structural framework without Cr migration up to a composition of Na_0.4CrO₂. A further removal of Na beyond this composition triggers a layered to rock-salt transformation converting the P'3-Na_0.4CrO₂ to a rock-salt CrOshy;₂ phase, which is responsible for the capacity fade of NaCrO₂.. This structural transformation proceeds via the formation of an intermediate O3-CrO₂ phase that contains Cr in both Na and Cr slabs and shares a very similar lattice as the rock-salt CrO₂. It is intriguing to note that intercalation of alkaline ions (i.e., Na⁺ and Li⁺) into the rock-salt CrO₂ is actually possible, albeit in a limited amount (~0.2 per formula).
When these results were analyzed under the context of electrochemistry data, it is clear that preventing the layered to rock-salt transformation is of uttermost importance to improve the cyclibility of NaCrO₂. Possible strategies for circumventing this detrimental phase transition will be proposed. We believe insights obtained in this work can be potentially applied to other O3 type of Na and Li transition metal oxides, and can serve as strong basis for future materials design of NaCrO₂ based cathodes.

The demand for large-scale batteries for electric energy storage systems has increased significantly over the years. Sodium-ion batteries (NIBs) are promising substitutes for lithium-ion batteries (LIBs) in grid-scale energy storage applications, which is initially driven by cost considerations. Although several studies have been conducted on various structured cathode materials such as layered, olivine, and alluadite, these materials suffer from low reversibility and poor rate performance during the electrochemical cycling.¹ In particular, layered P2minus;Na_xTMO₂ suffers from phase transformation during electrochemical cycling. Moreover, the instability of the carbonate electrolyte at high voltage contributes to the formation of the solid electrolyte interphase, lowering the coulombic efficiency. Lee, Xu, et al. improved Na_xNi_1/3Mn_2/3O₂ (02 albeit limiting the capacity of the material. Therefore, other alternatives are needed to maintain the capacity of Na_xNi_1/3Mn_2/3O₂ (0Herein, we report the aluminum oxide (Al₂O₃) atomic layer deposition (ALD) as a potential coating to improve the electrochemical performance of Na_xNi_1/3Mn_2/3O₂ (0xNi_1/3Mn_2/3O₂ (02 The effect of Al₂O₃ was investigated through a series of electrochemical studies. The optimal Al₂O₃ on the electrode is characterized using Focused Ion Beam and Transmission Electron Microscopy.
References:
(1) Kim, D.; Kang, S. H.; Slater, M.; Rood, S.; Vaughey, J. T.; Karan, N.; Balasubramanian, M.; Johnson, C. S. Enabling Sodium Batteries Using Lithium-Substituted Sodium Layered Transition Metal Oxide Cathodes. Adv. Energy Mater.2011, 1, 333-336.
(2) Lee, D. H.; Xu, J.; Meng, Y. S. An Advanced Cathode for Na-Ion Batteries with High Rate and Excellent Structural Stability. Phys. Chem. Chem. Phys.2013, 15, 3304-3312.

Over the last 25 years lithium-ion batteries have been a key component in the miniaturisation and mobilisation of electronics. The worldwide need for effective charge storage is increasing as transport and levelling of loads due to renewable power generation, and both the supply of lithium and the limited geographical spread of exploitable lithium sources are concerns. Interest in sodium cells as an alternative has ramped up rapidly in recent years, with ~1800 papers published in 2014 compared with ~100 in 2007.
Metal nitrides have been examined fairly extensively as charge storage electrodes. In aqueous supercapacitors their high electronic conductivity results in high charge/discharge rate capability while surface oxidation provides redox capacity. In lithium batteries they typically act as conversion electrodes, with formation of the metal plus lithium nitride during reduction and reformation of the metal nitride on oxidation. Nickel nitride has good capacity and cycle life in the low potential region and hence is a useful negative electrode material.¹ Higher capacities and better cycling stability are found in manganese and copper nitride.^2,3 Tin nitride maintains this good stability but achieves a doubling of the capacity.⁴ These results will be presented in the context of other improvements in these cells in the recent literature.
1. X. Li, M. M. Hasan, A. L. Hector and J. R. Owen, J. Mater. Chem. A, 2013, 1, 6441.
2. X. Li, A. L. Hector and J. R. Owen, J. Phys. Chem. C, 2014, 118, 29568.
3. S. I. U. Shah, A. L. Hector, X. Li and J. R. Owen, J. Mater. Chem. A, 2015, 3, 3612.
4. X. Li, A. L. Hector, J. R. Owen and S. I. U. Shah, submitted for publication.

The earth-abundance and low cost of sodium led to intensive exploration of sodium transition metal oxides as cathode materials for Na-ion batteries (NIB). Despite the cost motivation a considerable fraction of this activity focused on cathode materials analogous to those in Li-ion batteries containing costly transition metals such as Co, which appears problematic for various reasons including also differences in reaction mechanisms of the Na analogues, and different structural requirements for Na⁺ mobility. Hence, research on cathode materials for Na-ion batteries will have to concentrate on relatively abundant transition metals (essentially Fe, Ti, Mn, Cr, V). Within this framework the preferably insertion type cathode materials should not only exhibit high capacity and high voltage, but also exhibit fast ionic and electronic conductivity to ensure a high power performance. It should be noted that while NIBs will almost inevitably have lower energy densities than Li⁺ ion batteries (LIBs), the heavier and more polarisable Na⁺ ions have the potential to migrate considerably faster than Li⁺ ions within solids, so that NIBs have a strong potential to outshine LIBs in terms of power performance.
In this work we explore a wide range of oxides and oxyfluoride structures containing the above-mentioned relatively abundant transition metals as potential NIB cathode materials with respect to their power performance potential. In the initial screening stage ion migration barriers were estimated from energy landscapes for the mobile Na⁺ ions calculated using our bond-valence based transferable softBV potentials. For short-listed candidates ionic conductivity have been explored more in detail by molecular dynamics simulations, while structural stability, voltage and electronic conductivity are analysed based on a combination of DFT calculations with empirical approaches.
For selected compounds we also explored the sometimes drastic effects of structural defects on the Na+ ion mobility. As an example we will discuss how stoichiometry deviations and anti-site defects control the power performance of Na_2+2xFe_2-x(SO₄)₃. In this low cost high-voltage cathode material the cross-linking of the otherwise 1D Na⁺ migration channels across iron vacancies prevents easy blockage of the migration pathways and thereby enables a high power performance.
An often overlooked factor when judging the power capability of electrode materials is the charge transfer resistance at the electrode:electrolyte interface. Here we demonstrate how the variation of our bond-valence based predicted Na⁺ site energies (as ionic work function analogues) across MD-simulated interface structures helps to identify favourable electrode:electrolyte combinations.
Finally, a room temperature all-solid state Na⁺ ion battery. is realised based on the computational design guidelines and its performance is characterised experimentally.