Symposium Organizers
Yuyan Shao, Pacific Northwest National Laboratory
David Mitlin, Clarkson University
Jin Suntivich, Cornell University
Lynn Trahey, Argonne National Laboratory
Symposium Support
Army Research Office
ES13.2: Battery Anodes and Interfaces
Session Chairs
Tuesday AM, April 18, 2017
PCC North, 200 Level, Room 227 AB
11:30 AM - *ES13.2.01
Observation of Ionic Transport and Electrochemistry at Nanoscale
Reza Shahbazian-Yassar 1
1 , University of Illinois at Chicago, Chicago, Illinois, United States
Show AbstractThe modern battery devices face many challenges in terms of safety, energy density, cyclability, and weight. Extensive efforts have been made to address these shortcoming by designing new electrode materials and architechures but the progress has been quite slow due to lack of fundamental knowledge on how these materials behave at nanoscale under the electrochemical cycling. This has motived many research groups to develop operado or in situ techniques in order to investigate the nanoscale chemistry of battery materials. It is found that new materials in rechargeable batteries undergo complex electrochemically-driven phase transformations upon driving Li or Na ions into their structure. We have observed interesting phenomenon in crystalline materials where lithium or sodium ions prefer to move in crystallographic directions that have lowest energy barrier similar to the way that dislocation move in deformable materials. Defects such as twin boundaries can alter the transport path of alkaline ions and further assist the fast charging/discharging rate of batteries. We also have found that external cations can also interact with the incoming lithium ions and affect the battery performance.
12:00 PM - ES13.2.02
Activation with Li Enables Facile Sodium Storage in Germanium
David Mitlin 1
1 , Clarkson University, Edmonton, Alberta, Canada
Show AbstractGermanium is a promising sodium ion battery (NIB, NAB, SIB) anode material that is held back by its extremely sluggish kinetics and poor cyclability. We are the first to demonstrate that activation by a single lithiation - delithiation cycle leads to a dramatic improvement in the practically achievable capacity, in rate capability, and in cycling stability of Ge nanowires (GeNWs) and Ge thin films (GeTFs). TEM and TOF-SIMS analysis shows that without activation, the initially single crystal GeNWs are effectively Na inactive, while the 100 nm amorphous GeTF sodiates only partially and inhomogeneously. Activation with Li induces amorphization in GeNWs reducing the barrier for nucleation of the NaxGe phase(s), and accelerates solid-state diffusion that aids the performance of both GeNWs and GeTFs. Low rate (0.1C) Li activation also introduces a dense distribution of nanopores that lead to further improvements in the rate capability, which is ascribed to the lowered solid-state diffusion distances caused by the effective thinning of the Ge walls and by an additional Na diffusion path via the pore surfaces. The resultant kinetics are promising: Tested at 0.15C (1C = 369 mA/g, i.e. Na:Ge 1:1) for 50 cycles the GeNWs and GeTF maintain a reversible (desodiation) capacity of 346 mAh/g and 418 mAh/g, respectively. They also demonstrate a capacity of 355 and 360 mAh/g at 1C and 284 and 310 mAh/g at 4C. Even at a very high rate of 10C the GeTF delivers 169 mAh/g. Preliminary results demonstrate that Li activation is also effective in promoting cycling stability of Sb blanket films.
12:15 PM - ES13.2.03
Dendrite-Free Sodium Metal Interface in Highly Concentrated Na+-Conductive Inorganic Electrolyte
Juhye Song 1 , Goojin Jeong 2 , Young-Jun Kim 3 , Hansu Kim 1
1 , Hanyang University, Seoul Korea (the Republic of), 2 , Korea Electronics Technology Institute, Seongnam Korea (the Republic of), 3 , Sungkyunkwan University, Suwon Korea (the Republic of)
Show AbstractSodium metal is a very attractive anode material with the advantages of high theoretical capacity and low-operating voltage. However, chemical reactivity with the electrolyte, low Coulombic efficiency and dendritic growth of sodium metal during cycling still remain challenges for practical application. In this presentation, we report the morphological changes of sodium metal interphase in highly-concentrated NaAlCl4-2SO2 inorganic electrolyte and electrochemical performance as an anode for Na based rechargeable battery. We found that NaAlCl4-2SO2 inorganic electrolyte enables stable solid electrolyte interface formation, creating highly dense passivation film mainly composed of NaCl on the sodium metal as well as dendrite-free polygonal sodium electrodeposition. These remarkable outcomes lead to far superior electrochemical characteristics to that in conventional organic electrolyte. The dendrite-free polygonal sodium deposits with stable interface in NaAlCl4-2SO2 inorganic electrolyte are very encouraging findings in the development of room-temperature sodium metal-based rechargeable batteries. The morphological changes of sodium metal and outstanding electrochemical performance will be discussed in more detail in the presentation.
12:30 PM - ES13.2.04
New Insights on SEI Formation and Its Effects on Long-Term Cycling Life of Na/C Batteries
Clement Bommier 1 , Xiulei Ji 1 , Alex Greaney 2
1 , Oregon State University, Corvallis, Oregon, United States, 2 , University of California, Riverside, Riverside, California, United States
Show Abstract
When evaluating new battery materials, there is a premium placed on longevity. An ideal candidate material must demonstrate a stable cycling over the long term. While materials that meet such standards are great, there are many that don’t. Yet little effort has been devoted towards investigating the root of this problem. Thus, the following research attempts to fill this knowledge gap by elucidating the mechanisms leading performance drops. The conclusions provided lead to novels insight on the role of electrolyte kinetics as well as the nature of SEI formation in Na/C half-cells.
Through an investigation of long-term cycling using self-standing carbon anode with an Na-metal counter electrode, we are able to show that side-reactions between the Na-metal and the electrolyte causes a severe degradation of the electrolyte. This in turn induces kinetic problems, which leads to severe drop in capacity over long-term cycling, and subsequent cell failure. Surprisingly, this drop in performance can be reversed through the replacement of the Na-metal counter-electrode and the electrolyte. However, such findings stand in sharp contrasts to a priori convictions that SEI and SEI alone is the reason for capacity fading.
However if SEI was the sole reason, why did the faded carbon anode recover the entirety of its capacity once the extrinsic cell components were replaced? Is it possible that the SEI is soluble and therefore can be removed? or could it be that the SEI is being mistaken for a degraded electrolyte? and if that is to be the case, is the degraded state of the electrolyte due to the presence of the Na metal? There are no clear answers to the following questions, but the following research brings up new insights, along with discussion worth having when considering the current state of material research for electrochemical energy storage.
12:45 PM - ES13.2.05
Anode Surface Evolution in Aqueous Sodium-Ion Batteries
Xiaowen Zhan 1 , Mona Shirpour 1
1 Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky, United States
Show AbstractAqueous sodium-ion batteries may solve the cost and safety issues associated with the energy storage systems for the fluctuating supply of electricity based on solar and wind power. Compared to their lithium counterparts, aqueous sodium-ion batteries offer multiple advantages including more earth abundant sodium, cheaper electrode materials and electrolyte solutions as well as less costly manufacturing conditions. However, poor overall performance and low electrode utilization (much of the electrode material ends up being electrochemically inactive) are the main barriers implementing them in (micro)grid systems.
Here we characterize the surface reactions on NASICON-type phosphate anode material and rationalize their close associations with capacity fading upon slow cycling of aqueous sodium-ion batteries. The surface reactions result in the formation of an electrically insulating surface layer causing the failure of electrochemical performance and the precipitation of surface particles that blocks the pores thereby leading to poor electrode utilization. These findings provide insight into new possibilities of improving the electrochemical performance of aqueous sodium-ion batteries by the design of protective layers through surface modifications that prevent the formation of insulating surface layers and insoluble precipitates.
ES13.3: Electrocatalysis
Session Chairs
David Mitlin
Jin Suntivich
Tuesday PM, April 18, 2017
PCC North, 200 Level, Room 227 AB
2:30 PM - *ES13.3.01
The Oxygen Evolution Reaction on Nano-Scaled Perovskites
Thomas Schmidt 1 2
1 Electrochemistry Laboratory, Paul Scherrer Institute, Villigen Switzerland, 2 Laboratory of Physical Chemistry, ETH Zurich, Zurich Switzerland
Show AbstractOxygen electrodes are playing a key role in electrochemical energy conversion devices such as fuel cells and water electrolyzers. In both acidic and alkaline environment, both the oxygen reduction and oxygen evolution reaction (ORR and OER), respectively, are limiting the overall energy/voltage efficiency due to its sluggish kinetics. [1, 2]
Whereas in acidic environment, mainly precious metals are used to catalyze the ORR (e.g., Pt or its alloys) or the OER (e.g., IrO2), the variety of possible catalysts in alkaline electrolyte is significantly increased and also many metal oxide based systems can be employed. Generally the oxygen reduction or evolution mechanisms are only partly understood independent of the electrolyte environment and material used. In order to help to understand the underlying mechanisms for the two reactions and to support the experimental results, very often computational methods are used, mainly using density functional theory (DFT) calculations. Similar approaches are also used for gaining insights into catalyst stabilities under operational conditions. In order to elucidate reaction mechanisms, it is critical to make use of advanced operando spectroscopic and scattering tools, e.g., operando XAS or SAXS.
In this talk, some of your recent findings on non-noble metal catalysts, mainly from the perovskite family will be presented.
References
[1] A. Rabis, P. Rodriguez, T.J. Schmidt, ACS Catal., 2012, 2 (5), 864–890
[2] E. Fabbri, A. Habereder, K. Waltar, R. Kötz, T.J. Schmidt, Cat. Sci. Tech., 2014, 4, 3800-3821
3:00 PM - ES13.3.02
Electrocatalysis on Epitaxially Grown, Single-Crystal Transition-Metal Oxides
Ding-Yuan Kuo 1 , Jason Kawasaki 1 3 , Geoffroy Hautier 2 , Darrell Schlom 1 , Jin Suntivich 1
1 , Cornell University, Ithaca, New York, United States, 3 , University of Wisconsin-Madison, Madison, Wisconsin, United States, 2 , Université catholique de Louvain, Louvain-la-Neuve Belgium
Show AbstractWe present insights on the electrochemical adsorptions on single-crystal transition-metal oxides. Electrochemical generation of oxygen via the oxygen evolution reaction (OER) is an efficient-limiting step for many air-breathing electrochemical energy storage devices. IrO2 ranks among the most active known OER catalysts, believed to be due to the ability to stabilize the intermediates (O*) by surface adsorption. We use single-crystal IrO2 to characterize this electrochemical adsorption experimentally. Over the past decade, advances in deposition technologies and substrate availabilities have enabled the growth of transition-metal oxides with high structural perfection. We utilize these advances, specifically Molecular-Beam Epitaxy (MBE), to prepare single-crystal IrO2(110) on TiO2(110) single crystal. The well-defined nature of IrO2 allow us to identify the adsorption features and reveal the role of electrolyte chemistry, which we will compare to first-principle calculations. We use these studies to reveal insights into how to tune the surface physicochemical properties of transition-metal oxides and discuss the implications on electrocatalysis.
3:15 PM - ES13.3.03
Adsorbates Energy during Oxygen Evolution Reaction—A Theory-Experiment Comparison
Jan Kloppenburg 1 , Ding-Yuan Kuo 2 , Jason Kawasaki 2 , Jocienne Nelson 2 , Kyle Shen 2 , Darrell Schlom 2 , Jin Suntivich 2 , Geoffroy Hautier 1
1 IMCN, UCLouvain, Louvain-la-Neuve Belgium, 2 , Cornell University, Ithaca, New York, United States
Show AbstractThe transition from fossil fuel based energy to renewable sources requires efficient energy conversion and storage solutions. Hydrogen and oxygen production from water is an attractive approach among the storages. The oxygen evolution reaction (OER) is sluggish and must be facilitated by a catalyst that is designed to catalyze the OER at low overpotential to maximize the energy conversion efficiency. Recently, the scientific interest has grown for oxide-based catalysts. The powerful yet-simple thermodynamic rate-limiting approach to optimize catalysts for OER using ab initio computed adsorption energies has shown predictive power on metals but still shows limits on oxides. A fundamental step back is required using model systems and comparing ab initio computed adsorption energies using density functional theory (DFT) to high quality single-crystal model catalysts. We present results of such a theory-experiment comparison using cyclic voltammetry (CV) experiments using single-crystals of IrO2 and RuO2 grown by molecular beam-epitaxy (MBE). We discuss the accuracy, strength and limits of DFT computations in modeling adsorption energies. We especially focus on effects from water such as water coverage and pH-shifts.
4:00 PM - *ES13.3.04
Electrocatalytic Challenges in High pH Environment
Sanjeev Mukerjee 1 , Nagappan Ramaswamy 1 , Shraboni Ghoshal 1 , Qingying Jia 1
1 Northeastern University Center for Renewable Energy Technology, Northeastern University, Boston, Massachusetts, United States
Show AbstractEnabling reversibility to seemingly facile electrode processes such as HOR/HER are a challenge when subject to high pH. These clearly form technical barriers towards their application in hydrogen based energy storage devices such as in Hydrogen-Bromine batteries. While hydrogen oxidation under acidic conditions involves rapid kinetics, the same process under alkaline electrolyte conditions is known to be a very sluggish process with orders of magnitude lower kinetic activity and the concomitant need for a higher loading of precious metal catalysts. The real advantage of alkaline electrolytes is their ability to enable the use of non-precious fuel cell electrocatalysts as opposed to the corrosive acidic conditions where highly precious metals are unavoidable. The sluggish kinetics of hydrogen oxidation at high pH conditions seriously undermines this major advantage of alkaline electrolyte thereby necessitating the use of precious metal catalysts. In this presentation, we undertake a fundamental mechanistic approach to unravel the causes of sluggishness of hydrogen oxidation reaction in alkaline electrolyte. We also delineate reaction mechanistic and catalysis parameters that are to design the next-generation of non-precious electrocatalysts for hydrogen oxidation, and other related processes. This is achieved by unifying the principles of electrochemistry, surface science and coordination chemistry to comprehensively expound the scientific theory behind the modus-operandi of alkaline electrocatalysis.
This presentation is not only of interest to the fuel cell research community, but to the larger audience interested in the fields of catalysis, surface science, nanotechnology, and materials science for the following reasons:
For the first time, we unravel a non-Sabatier type catalysis principle involving a complex interplay between specifically- and quasi-specifically adsorbed reaction intermediates in the reaction layer. This is opposed to the conventional catalysis models that largely emphasize the importance of adsorption energies of the reaction intermediates on reaction pathways
We initiate a new trend that focuses on elucidating electrochemical reaction mechanisms as opposed to plethora of studies that focus on reaction kinetics and pathways. While reaction kinetics and pathways are easily accessible in catalysis studies, we have employed a combination of electrochemical and spectroscopic studies along with a series of thought experiments to unravel very profound catalytic reaction mechanisms that are largely unknown so far.
The findings from our work related to electrochemical charge transfer are expected to be applicable to other complex catalytic processes as well.
4:30 PM - ES13.3.05
Bifunctional CoP and Co-Ni-P Nanowire Electrocatalysts for Efficient and Ultrastable Electrochemical Water Splitting
Wei Li 1 , Lifeng Liu 1
1 , International Iberian Nanotechnology Laboratory, Braga Portugal
Show AbstractExploitation of abundant yet intermittent renewable energy sources requires efficient and robust energy conversion and storage technologies. Electrochemical water splitting has emerged as a promising technique to convert electricity harvested from renewable sources into high-purity hydrogen fuel for energy storage. Precious metal Pt and noble metal oxides (e.g., RuO2, IrO2) are the state-of-the-art electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. However, the exorbitant price and scarcity of noble metals restrict their widespread use in water electrolysis. It still remains a formidable challenge to develop ultrastable, efficient and low-cost bifunctional earth-abundant electrocatalysts that are active for both HER and OER and able to sustain overall water splitting for long time at high current densities for scalable hydrogen fuel production.
Herein, we present the fabrication of a monolithic bifunctional electrode (Co@CoP) covered with dense CoP nanowires through a facile and scalable one-step thermal phosphorization treatment of metallic Co foam with red phosphorous. The self-supported Co@CoP electrode shows high electrocatalytic activities and favorable kinetics for both the HER (delivering -10 and -100 mA cm-2 at overpotentials of 124 and 244 mV, respectively and a Tafel slope of 105 mV dec-1) and OER (affording 10 and 100 mA cm-2 at overpotentials of 248 and 300 mV, respectively and a Tafel slope of 80 mV dec-1) in the alkaline solution. Besides, ternary Co-Ni-P nanowires were also synthesized on metallic Ni foam to form a monolithic integrated electrode (Ni@Co-Ni-P) by combining the hydrothermal and similar phosphorization reaction. The self-supported Ni@Co-Ni-P electrode also demonstrates remarkable electrocatalytic activities for HER in acidic and basic media as well as OER in the alkaline solution. Given their well-defined bifunctionality, two Co@CoP electrodes or Ni@Co-Ni-P electrodes were assembled to construct their respective alkaline electrolyzers for overall water splitting. The Co@CoP electrolyzer delivers 20 and 100 mA cm-2 under small cell voltages of 1.67 and 1.78 V, respectively and shows excellent stability, capable of working for 1000 h without obvious degradation. The Ni@Co-Ni-P electrolyzer exhibits extraordinary long-term stability, able to operate for 3175 h under 1.96 V delivering a current density of 100 mA cm-2 without deterioration, leading to exceptionally high H2 production rate of 311 mmol h-1 g-1 catalyst cm-2. The outstanding stability of these electrolyzers for overall water splitting results from the structural integrity of Co@CoP and Ni@Co-Ni-P electrodes as well as formation of interfaces consisting of metal phosphide nanowires/oxyhydroxide nanosheets core/shell nanostructure. Therefore, the monolithic Co@CoP and Ni@Co-Ni-P electrodes hold substantial promise for use as efficient and ultrastable electrodes in alkaline electrolyzers.
4:45 PM - ES13.3.06
Unified View of Cation Segregation, Precipitation and Surface Reconstruction in (La,Sr)FeO3-δ
Michael Machala 1 , Sangchul Lee 1 , David Mueller 1 , Zixuan Guan 1 , Hendrik Bluhm 2 , William C. Chueh 1
1 , Stanford University, Stanford, California, United States, 2 Advance Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractDuring synthesis and under catalytic reaction conditions, chemical heterogeneities develop at the surface of perovskite oxides (ABO3) and profoundly affect electrocatalytic activity and stability. By studying the solid-gas interface at elevated temperature in Ca, Sr, and Ba-substituted LaFeO3-δ using ambient-pressure X-ray photoelectron spectroscopy (APXPS) and high-resolution transmission electron microscopy (HR-TEM), we deconvoluted cation segregation, the precipitation of secondary phases, and reconstruction at the perovskite surface.
We observed that segregation, precipitation, as well as surface termination depended strongly on bulk A-to-B-site nonstoichiometry. Specifically, HR-TEM of atomically flat, dense thin films of (La,Sr)FeO3-δ (LSF) revealed that surface termination depends on bulk A-to-B-site ratios. In-situ APXPS confirmed this trend and revealed that Ca-subsitution does not produce a spectroscopically distinct secondary species though Ca does segregate; this behavior contrasts Sr- and Ba-substitution, which is consistent with intuition based on ionic radii.
These observations were connected to the area-specific resistance (ASR) of the oxygen incorporation reaction. At 650 °C and in 23% O2, the ASR of all variations of LSF were below 2 Ω cm2, where both A-site excess and stoichiometric LSF electrodes exhibited an ASR lower than the A-site deficient electrodes. Further, the stoichiometric LSF electrode exhibited the lowest degradation rate, below +0.001 Ω cm2 h-1.
5:00 PM - ES13.3.07
Ultrasensitive Probing of the Local Electronic Structure of Nitrogen Doped Carbon and Its Applications to 2D Electronics, Catalysis and Bio-Physics
Charles Titus 1 , Sang Jun Lee 1
1 Physics, Stanford University, Stanford, California, United States
Show AbstractChemical doping of carbon is an effective way to tailor their electronic and chemical properties such as band level alignment, charge carrier mobilities, and catalytic activity. Nitrogen doped carbon-based materials have received a lot of attention due to its premise in 2D electronics (e.g. as contact layer with tunable electronic properties), fuel cell applications (e.g. ORR) or metal-air batteries.
It has been shown that different bond types such as graphitic, pyrrolic, and pyridinic can exist in N-doped carbon, and they play a crucial role in determining the electronic properties both locally and for the whole matrix (doping effect). Core-level X-ray spectroscopy has been proven to be a powerful analytic method for characterizing different bond types in doped carbon. X-ray emission spectroscopy has the ability to map out the local electronic structure around elements in a site- and symmetry-specific way, and direct comparison to DFT based theory is possible. However, XES has been inaccessible in the soft x-ray regime since the current technology lacks the sensitivity to measure the weak signal from low concentration dopants.
Superconducting transition edge sensor (TES) technology presents a unique opportunity to build novel detectors with greatly increased sensitivity in the soft x-ray regime while maintaining excellent energy resolution. We have commissioned a new generation soft x-ray superconducting TES spectrometer with a scientific motivation to probe the local electronic structure of ultra-low concentration sites in biology, chemistry, and materials, currently inaccessible in the soft x-ray regime due to the limited sensitivity of existing technology.
We will show the applicability of TES based spectrometers to provide detailed insight into the local electronic structure of nitrogen in graphene, carbon catalysts, carbon for chemical storage as well as nano-diamond. The applicability of this unprecedented photon in / photon out sensitivity in the soft x-ray regime to future in-operando studies of chemical transformations and the (potential) active role of nitrogen sites will also be discussed.
5:15 PM - ES13.3.08
Core/Shell Interface and Surface Nanophase Structure-Controlled Functionality of Metallic Catalysts by Resonant High-Energy X-Ray Diffraction
Valeri Petkov 1
1 , Central Michigan University, Mt Pleasant, Michigan, United States
Show AbstractEvidence is mounting that, in addition to controlling the size, shape and chemical composition, the catalytic functionality of metallic nanoparticles can be improved significantly by utilizing internal interfaces and ‘skin-like’ surface nanophases. However, though proven advantageous, the approach is still pursued largely by trial-and-error. That is because the interfaces and ‘skin-like’ nanophases are only a few atomic layers thick and so difficult to characterize structurally. Without precise structure knowledge, the interface and ‘skin-like’ nanophase-controlled catalytic functionality is difficult to take control of. Using the core/shell interface inside Ru-Pt NPs and the ‘skin-like’ nanophase enveloping Au-Pd NPs as examples, we will demonstrate that the missing knowledge can be obtained by resonant high-energy x-ray diffraction coupled to element-specific atomic pair distribution analysis. Also, we will demonstrate how the knowledge obtained helps assess the functionality of Ru-Pt and Au-Pd NPs as catalysts for electrooxidation of methanol, activation of oxygen in fuel cells, decomposition of alcohols for hydrogen storage purposes, and others.
5:30 PM - ES13.3.09
Gold Micromeshes as Highly Active Electrocatalysts for Methanol Oxidation Reaction
Jingying Sun 1 , Feng Wang 2 , Yuan Liu 1 , Chuanfei Guo 2 3 , Yizhou Ni 1 , Haiqing Zhou 2 , Shuo Chen 1
1 Physics, University of Houston, Houston, Texas, United States, 2 Texas Center for Superconductivity at The University of Houston, University of Houston, Houston, Texas, United States, 3 , South University of Science and Technology of China, Shenzhen, Guangdong, China
Show AbstractHigh density of surface defects is the key element for efficient nanoscale gold (Au) electrocatalysts for oxidation of small organic molecules. Here we present tunable pore size Au micromeshes (from ~1 μm to ~2 μm) with a high density of steps, kinks, twin boundaries and stacking faults made by template method. The Au micromeshes are prepared by coating Au on the top of poly(methyl methacrylate) (PMMA) porous film templates formed via a phase separation method. Electrocatalytic measurements on methanol oxidation reaction show that peak current density of our Au in alkaline electrolyte (0.5 M KOH) can reach 0.264 mA cm-2, which is three times higher than well–studied nanoporous Au (0.081 mA cm-2). The current density can maintain over 90% after 500 cycling tests. Through transmission electron microscopy (TEM) studies, the superior catalytic activity and stability can be attributed to high linear density of surface defects, exposure of active facets, and superficial tensile strain on the out-most layers.
5:45 PM - ES13.3.10
Rational Design of Solid Electrode Interface for Highly Reversible Lithium-Metal Battery
Snehashis Choudhury 1 , Lynden Archer 1
1 , Cornell University, Ithaca, New York, United States
Show AbstractRecent safety issues related to overcharging or fast-charging lithium-ion battery in addition to its limitations in terms of capacity and energy density have compelled researchers to look beyond lithium ion batteries. In this regard, metal batteries that involves use of a reactive metal like lithium or sodium, has gained great attention, because of their promise of improving the anode-specific capacity by 10-fold compared to Li-ion batteries. The greatest advantage of replacing the graphite host with a lithium metal as anode lies in the use of a lithium-free cathode-high capacity cathode like Oxygen or Sulfur, that can improve the gravimetric energy density of a battery from ~0.2kWh/kg to ~12kWh/kg (comparable to that of gasoline). However, in these metal batteries, the issue of dendrite-induced short circuit and loss of active material by parasitic reaction limit their practical use. Several strategies have been proposed to prevent the dendrite-induced short circuits by modifying the ion transport properties and using high modulus separators, though a more elegant method of not only inhibiting dendrites but also suppressing the parasitic reactions between the electrode and electrolyte, is creating a stable solid electrolyte interface (SEI).
In this study, we use density functional theory to calculate the surface diffusion barrier of ions with various SEI components, including commonly observed compounds like Li2CO3, LiOH, LiF; and also other metal halides. Interestingly, it is observed that bromide salts, have very low diffusion barrier (comparable to that of pristine Magnesium), thus it is hypothesized that the presence of bromide salts in the SEI layer can also promote smooth electrodeposition similar to Mg metal. In order to evaluate this hypothesis, we use electrolyte media based on a high donor number amide solvent (DMAc), which is known to promote solution mediated peroxide formation and high discharge capacity in Li-O2 batteries, but is chemically unstable in the presence of a lithium metal anode. With simplistic in-situ modification of lithium surface with bromide salts and fixed anions, we show that the anodic stability of lithium metal batteries is significantly enhanced. The formation of an artificial SEI layer on Li is confirmed using XPS and electrochemical impedance spectroscopy measurements. In-fact, without the modification, the lithium metal is seen to spontaneously decompose when in contact with the reactive electrolyte as seen from different experiments like scanning electron microscopy, linear scan voltammetry as well as galvanostatic charge-discharge tests. Finally, as an application in a lithium metal battery, we design Li-O2 cells using the modified Lithium metal anode and the high donor number electrolyte. Interestingly, the bromide salts provide additional benefit of a redox-mediation for the oxygen-evolution reaction (OER), which leads to the increase of round-trip efficiency of the Li-O2 battery.
Symposium Organizers
Yuyan Shao, Pacific Northwest National Laboratory
David Mitlin, Clarkson University
Jin Suntivich, Cornell University
Lynn Trahey, Argonne National Laboratory
Symposium Support
Army Research Office
ES13.4: Solid-State and Concentrated Electrolytes
Session Chairs
David Mitlin
Jin Suntivich
Wednesday AM, April 19, 2017
PCC North, 200 Level, Room 227 AB
9:15 AM - *ES13.4.01
Evolution of the Lithium Metal/Solid Electrolyte Interface
Nancy Dudney 1 , Miaofang Chi 1 , Jeff Sakamoto 2
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 , University of Michigan, Ann Arbor, Michigan, United States
Show AbstractEven with solid electrolytes that are proving to be practically stable with metallic lithium, interesting changes occur on both sides of the interface upon contact and electrochemical cycling. Several examples will be presented. In the case of a thin film battery with a Lipon electrolyte, the lithium anode gradually redistributes in patterns that depend on both the cathode and the duty cycle. Here the change is visible by eye and recorded using a stylus profilometer. To see changes in the solid electrolyte requires an atomic scale view afforded by in situ TEM analysis as the lithium first contacts the electrolyte surface. With the cubic LLZO garnet solid electrolyte, a very thin reaction layer forms and passivates the interface towards lithium.
Acknowledgement: This research was sponsored by the U.S. Department of Energy (DOE), Office of Basic Energy Sciences (BES), Materials Sciences and Engineering Division; and by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy for the Vehicle Technologies, Advanced Battery Materials Research program.
9:45 AM - ES13.4.02
Engineering Interfaces and Performances for All Solid State Li-Battery Architectures and Novel Types of CO2 Sensing Devices Based on Li-Garnet Electrolytes
Jennifer Rupp 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe next generation of energy storage and sensing devices may largely benefit from fast Li+ ceramic electrolyte conductors to allow for safe and efficient batteries and real-time monitoring anthropogenic CO2. Recently, Li-solid state conductors based on Li-garnet structures received attention due to their fast transfer properties and safe operation over a wide temperature range. Through this presentation basic theory and history of Li-garnets will first be introduced and critically reflected towards new device opportunities. Central to our research is the fundamental investigation of the electro-chemo-mechanic characteristics and design of electrode-Li garnet interfaces to new battery architectures and sensors. Here, we firstly present new Li-garnet battery architectures for which we discuss lithium titanate and antimony electrodes in their making, electrochemistry and assembly to full battery architectures1-4. Secondly, new insights on processing of Li-garnet thin films are presented based on first developed field maps for pulsed laser deposition processing. Here, the thermodynamic stability range of maximum Li-conduction, phase and nanostructure is discussed using high resolution TEM studies, near order Raman investigations on the Li-bands and electrochemical transport measurements. Finally, we present for the very first time a new type of a CO2 sensor based on Li-zirconate garnet structure electrolytes and show the full material development up to the successful engineering and control of the sensing performance. The insights provide novel aspects of material structure designs for both the Li-garnet structures (bulk to films) and their interfaces to electrodes, which we either functionalize to store energy or to track chemical species such as anthropogenic CO2 for next generation batteries and environmental sensors.
1) Interface-Engineered All-Solid-State Li-Ion Batteries Based on Garnet-Type Fast Li+ Conductors
J van den Broek, S Afyon, JLM Rupp
Advanced Energy Materials 6 (19), 2016
2) A shortcut to garnet-type fast Li-ion conductors for all-solid state batteries
S Afyon, F Krumeich, JLM Rupp
Journal of Materials Chemistry A 3 (36), 18636-18648, 2015
3) On the chemical stability of post-lithiated garnet Al-stabilized Li 7 La 3 Zr 2 O 12 solid state electrolyte thin films
M Rawlence, I Garbayo, S Buecheler, JLM Rupp
Nanoscale 8 (31), 14746-14753, 2016
4) Investigating the all-solid-state batteries based on lithium garnets and a high potential cathode-LiMn1. 5Ni0. 5O4.
C Hänsel, S Afyon, JLM Rupp
Nanoscale, in press 2016
10:00 AM - ES13.4.03
Atomic Layer Deposition of Conformal Solid State Batteries
Alexander Pearse 1 , Keith Gregorczyk 1 , Thomas Schmitt 1 , Chanyuan Liu 1 , Alec Talin 2 , Farid El Gabaly 2 , Gary Rubloff 1
1 , University of Maryland, College Park, College Park, Maryland, United States, 2 , Sandia National Laboratories, Livermore, California, United States
Show AbstractThin film solid state batteries, generally made using physical vapor deposition (PVD) techniques, are the only currently commercially available inorganic solid state batteries and have multiple attractive properties including high electrode/electrolyte interface quality and exceptional cycling stability, but have not seen significant implementation because their overall capacity is very low (on the order of 0.1 mAh/cm2). This is due to the fact that PVD is nonconformal and PVD-based SSBs are limited to planar substrates, placing an upper limit on the cathode thickness of a few microns before they are limited by solid state Li diffusion or residual film stress. Realizing practical energy or power densities in thin film SSBs will involve the development of entirely new fabrication processes in order to allow the integration of thin film SSBs with 3D substrates, such as micromachined silicon or conductive fabrics.
We show the development and successful synthesis of a solid state battery made entirely using atomic layer deposition, a highly conformal thin film deposition technique. We describe an additive process for testing novel ALD-grown materials by first coupling them with established PVD materials before combining them into the first all-ALD SSB. For the solid electrolyte, we have developed a novel 2-precursor plasma-free ALD process for Li2PO2N, a material in the LiPON family, and show how the pinhole-free, conformal nature of ALD allows the successful fabrication of SSBs with <50 nm thick electrolytes, leading to electrolyte resistances of <40 Ω.cm2. ALD-grown tin-based conversion materials are used for the anode. Using quasi in-situ x-ray photoelectron spectroscopy, we also carefully examine the electrode/electrolyte interface chemistry in the highly reactive ALD growth environment, and show how our previously described plasma-enhanced ALD process for LiPON (A. Kozen, A. Pearse, C. Lin, M. Noked and G. Rubloff, Chem. Mater., 2015, 27.) damages the surface of several common cathode materials in contrast with the gentler thermal process for Li2PO2N. Finally, we integrate the all-ALD battery with 3D silicon substrates in order to demonstrate an area enhancement factor and increased performance.
10:15 AM - ES13.4.04
Na2S Based Glassy Electrolytes for Solid State Sodium Ion Batteries—A Modeling-Based Study
Aniruddha Dive 1 , Clarence King 1 , Scott Beckman 1 , Soumik Banerjee 1
1 , Washington State University, Pullman, Washington, United States
Show AbstractLithium-ion batteries dominate the consumer market in automobiles and electronic devices for cost-effective energy storage. However, due to the limited availability of lithium and safety concerns stemming from the flammability of liquid electrolytes, it is essential to explore technologies beyond conventional lithium-ion batteries for electric power grid applications. Solid-state sodium-ion batteries are promising candidates with relatively high energy densities and improved safety. They are typically nontoxic and environmentally-friendly, compared to their liquid counterparts. However, obtaining an electrolyte with suitably high ionic conductivity at room temperature is challenging.
In this study, we consider sodium sulfide (Na2S) based glasses as electrolytes for solid-state sodium-ion batteries. The specific glass composition we consider is sodium sulfide–silicon sulfide [xNa2S – (1-x) SiS2]. We employed classical molecular dynamics (MD) to model representative glass structures that were formed using a typical melt and quench technique. The atomic potentials were parameterized using a Buckingham model. We were able to replicate the experimentally determined densities and glass structures. The ionic conductivity of these glasses were calculated at a range of temperatures and agreed with experimental measurements. The calculated ionic conductivity at room temperature was in the range of 10-5 S/cm. The corresponding activation energy was obtained by fitting the ionic conductivity data that follows a near-Arrhenius pattern and compared well with experimental data. A kinetic Monte Carlo (kMC) approach was used, based on input structures from MD, to evaluate the behavior of these glasses at spatial and temporal scales that are several orders of magnitude greater than that accessible to MD simulations.
Electrochemistry and ion transport at electrode–electrolyte interfaces play a key role in determining the performance of sodium-ion batteries. We performed MD simulations of the interface between pure sodium metal, which is a representative anode, and the glassy electrolyte. Structural properties of the sodium anode–glass interface were estimated by calculating the density distribution and pair distribution functions. The ion hopping mechanisms and corresponding self-diffusion of sodium ions at the interface was evaluated both in the presence and absence of external electric field. The kMC model employed these parameters as inputs and calculated the area specific resistance (ASR) values for the interface. Ultimately, the ASR and the ionic conductivity obtained from the MD and kMC simulations can be used to assist in designing high-performance all-solid-state sodium-ion batteries for power grid applications.
10:30 AM - ES13.4.05
Design of Stable Non-Oxide Sodium Superionic Conductor
Amitava Choudhury 1 , Hooman Yaghoobnejad Asl 1
1 , Missouri University of Science and Technology, Rolla, Missouri, United States
Show AbstractA sodium ion conducting solid with high conductivity at room temperature and low activation energy can be a game changer in all-solid-state sodium-ion battery performance. A sodium superionic conductor can alleviate the life-time limiting problem of organic electrolytes in multiple ways. Firstly, organic electrolytes are rarely stable within the lower and upper voltage cut off. Secondly, high flammability of organic solvents, and the corrosiveness arising out of HF produced from dissolved NaPF6 used to enhance the solvent’s ionic conductivity, pose major safety concerns for the batteries. Third, several high voltage cathodes are now available but unfortunately the common organic electrolytes are not compatible in that high voltage regime, a high sodium ion conducting solid state electrolyte can pave the way to improve the power density of sodium ion battery systems.
Recently chalcogenide hosts are being touted as good candidates for Na-ion conduction. For example, cubic Na4PS4 (sI = 0.2×10−3 S cm−1, Ea = 0.28 eV) [Hayashi et al. Nature Commun.2012, 3, article #:856] and recently discovered Na10SnP2S12 (si = 0.4 x 10–3 S/cm, Ea = 0.36 eV) [Richards et al. Nature Commun. 2016, 7, Article #:11009] and Na4PSe4 (si = 0.11 x 10–3 S/cm, Ea = 0.28 eV) [Bo et al. Chem. Mater. 2016, 28, 252-258] are very impressive and reaching the conductivity of liquid electrolyte.
Despite having such outstanding ionic conductivities these chalcogenide materials suffer from extreme sensitivity towards air and moisture. A momentary exposure in air often lowers the conductivity by manifold due to surface oxidation.
In the present work we have focused our attention towards achieving stability in chalcogenide lattice through cross-linking of these tetrahedral anions through covalent bonding by introducing a +1 ion such as copper or +2 ion such as zinc. The proposed quaternary compounds will have three-dimensionally (3D) connected network and alkali ions will reside in channels or pores. In our approach we replace part of the alkali ions by Cu and Zn through metathesis reactions with ternary alkali ion-main group metal-chalcogen (A – X – Q, A = Na, X = P, Si, Sn, Ga, Ge etc).
Employing this strategy we have synthesized a series of compounds with composition Na3ZnGaQ4 (Q = S, Se) with open-framework structure made up of super tetrahedral [{Ga2ZnQ4}n]6– unit. These compounds are stable in air and moisture and ionic conductivity measurements on the selenide analogue reveal that it is super-ionic conductor with an activation energy (si = 0.11 x 10–3 S/cm, Ea = 0.3 eV) comparable to most sought after current compounds. Another quaternary compound, Na15Cu3Ga6S18 has unprecedented seven crystallographically distinct Na sites and several of them display high displacement parameters indicating facile sodium ion movement. In this presentation structural features and ionic conductivities of these newly synthesized materials will be discussed.
11:15 AM - *ES13.4.06
Forming Interphase in Aqueous Media
Kang Xu 1
1 Electrochemistry Branch, U.S. Army Research Laboratory, Adelphi, Maryland, United States
Show AbstractSolid-Electrolyte-Interphases (SEI) play a key role in enabling Li-ion intercalation chemistries in non-aqueous electrolytes, where solvents reduction mainly contribute the chemical building blocks 1, 2. Due to the inability of water to produce any useful chemical building blocks for electrode surface passivation, SEI has never been seen in aqueous media, until Suo et al discovered for the first time that such aqueous SEI is possible via manipulation of the Li-ion solvation structure 3.
While effective, solvation structure approach requires high salt concentrations that bring negative aspects such as high viscosity, high cost etc. In this work we explore alternative approaches to forming such protective SEI.
11:45 AM - *ES13.4.07
Ultraconcentrated "Solutions" for Alkali Metal and Multivalent Energy Storage Electrolytes—Common Features and Ionicities
C. Austen Angell 1 , M. Hasani 1 , Zuofeng Zhao 1
1 School of Molecular Sciences, Arizona State University, Tempe, Arizona, United States
Show Abstract"Solvate" ionic liquids and so-called "deep eutectic" electrolytes are further examples of the "solvent-in-salt" electrolytes that have recently been getting a lot of attention (particularly the "water-in-salt sub class). All share common features of facile metal electrodeposition despite low fluidities. All of them feature incomplete solvation shells for the depositing cations. Molecule:cation ratios can range from 2 to 0.2 depending on constituents. We discuss their different backgrounds, chemistries and also their ionicities. Cases of surprising "superionicity" are identified, and merit further study.
12:15 PM - ES13.4.08
Asymmetric Microsupercapacitors with Vertically Scaled 3D Porous Current Collectors
Husam Alshareef 1 , Qiu Jiang 1 , Narendra Kurra 1
1 , King Abdullah University of Science and Technology (KAUST), Thuwal Saudi Arabia
Show AbstractVertical scaling effects (thickness scaling effects) to explore the third dimension of energy storage devices by transforming two-dimensional current collectors into three-dimensional (3D) architecture, while optimizing the mass loading, is a promising strategy to achieve optimal areal energy and power densities in microsupercapacitors. In this study, a direct-write, laser-based strategy is proposed for fabricating ultra-thick (3D) co-planar asymmetric microsupercapacitors with varying heights and mass loadings. The devices employ Faradaic nickel cobalt sulfide as a positive electrode material, and electrochemical double-layer carbon nanofiber as a negative electrode, both of which were directly grown on Ni foam interdigital electrodes by hydrothermal and chemical vapor deposition methods, respectively. The Ni foam collector thickness was systematically varied, and so was the mass loading for each Ni foam collector thickness. The porous nature of Ni foam allows us to simultaneously increase collector height, while independently optimizing mass loading. Using this approach, we have demonstrated 3D asymmetric microsupercapacitors with high areal energy density (200 μWh/cm2) and excellent cycling stability (capacity retention of 89% after 10000 cycles). The high areal energy density may meet the demand of on-chip storage for the next generation of integrated microsystems.
1. Qiu Jiang, Narendra Kurra, Chuan Xia and H.N. Alshareef, Advanced Energy Materials DOI: 10.1002/aenm.201601257.
2. Narendra Kurra, Bilal Ahmed, Yury Gogotsi, and H.N. Alshareef, Advanced Energy Materials DOI: 10.1002/aenm.201601372.
3. Qiu Jiang, Narendra Kurra, and H.N. Alshareef, Advanced Functional Materials 2015, 25: 4976–4984.
4. Narendra Kurra, Xia Chuan, and H.N. Alshareef, Chemical Communications 2015, 51, 10494-10497.
5. Narendra Kurra, Qiu Jiang, and H.N. Alshareef, Nano Energy Volume 16, 2015, Pages 1–9.
6. N. Kurra, N.A. Alhebshi, H.N. Alshareef, Advanced Energy Materials 4 (2014), 1401303.
12:30 PM - ES13.4.09
In Operando SEM of Plating in All-Solid-State Lithium-Ion Battery with Carbon Anodes
Alexander Yulaev 1 2 3 , Vladimir Oleshko 4 , Alec Talin 5 , Marina Leite 2 6 , Andrei Kolmakov 1
1 CNST, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 2 MSE, University of Maryland, College Park, Maryland, United States, 3 Maryland NanoCenter, University of Maryland, College Park, Maryland, United States, 4 Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 5 , Sandia National Laboratories, Livermore, California, United States, 6 IREAP, University of Maryland, College Park, Maryland, United States
Show AbstractThe rapid progress in all-solid-state lithium-ion battery (SSLIB) research opened up new avenues to miniaturize energy storing electrochemical cells used in medical devices and micro-electronics. Today SSLIBs outperform their liquid electrolyte counterparts in significantly improved cycle life and reduced safety risks due to non-flammability and suppression of dendrites growth in solid electrolytes. The absence of volatile components also makes SSLIBs ideal for in operando studies using electron microscopy to better understand how active phases evolve during charge and discharge processes. Here we probe the lithium plating on the surface of a model ultra-thin anode of SSLIB during its charging using in operando electron microscopy. Our Li-ion battery consists of an ultra-thin carbon anode, LiPON as an electrolyte, and LiCoO2 as a cathode. Varying the charging rate and ambient oxidizing conditions at the anode, we find that the surface morphology of the plated lithium is altered between quasi-1D and 3D microstructures. We also observed that the nucleation and growth of the Li deposit can be affected by an electron beam during plating reaction. In addition, it was revealed that even under UHV conditions, the oxygen containing residues can significantly degrade the plated lithium, resulting in appreciable capacity loss upon battery cycling. We envision that our approach will shed light on details of SSLIB performance under different operating conditions and will help define a risk-free parameter space.
12:45 PM - ES13.4.10
On the Interface and Role of Interlayers between High Voltage Cathode LMNO and Solid State Electrolyte LLZO
Alejandro Filippin 1 , Michael Rawlence 1 , Aneliia Waeckerlin 1 , Yaroslav Romanyuk 1 , Stephan Buecheler 1
1 , Empa, Dübendorf, Zürich, Switzerland
Show AbstractConventional Li-based liquid electrolytes such as LiPF6 are electrochemically stable up to 4.3 V vs Li+/Li electrode, after which the electrolyte decomposes generating by-products that in turn degrade the cathode material. High voltage cathodes like the spinel LiMn1.5Ni0.5O4 (LMNO) require electrolytes which are electrochemically stable up to at least 4.7 V vs Li+/Li. The gallium-doped garnet Li7La3Zr2O12 (LLZO) is amongst the solid-state-electrolytes with highest Li-ion conductivities if crystallized in the cubic phase reaching values above 1 mS/cm, which is high enough for thin films. Although the electrochemical stability window of LLZO is still unclear, the maximum potential it can withstand without undergoing electrochemical reactions is beyond 4 V vs Li+/Li, making it a suitable candidate to be coupled with high potential cathodes. However, LMNO and LLZO require temperatures of 700 °C for their proper crystallization, and the effects of high temperature on the LMNO/LLZO interface and their crystallization have not been reported in literature so far.
We have investigated the high temperature reactivity of thin film multilayers of LMNO and LLZO deposited by magnetron sputtering on conductive substrates, following the evolution of the distinct phases using in-situ grazing incidence X-ray diffraction in the temperature range 30 °C-700 °C. The morphology of the thin films before and after annealing was investigated by secondary electron microscopy, while X-ray photoelectron spectroscopy sputter-depth profiles where carried out to study the diffusion of atomic species across the solid-state interface after annealing in oxygen at 700 °C. We have observed that LLZO in direct contact with LMNO remains amorphous even at temperatures as high as 600 °C whereas the formation of a lanthanum manganate phase was detected at 700 °C. The influence on the diffusion/reaction of species at high temperatures of an oxide electrolyte interlayer, particularly LiNbO3, between LMNO and LLZO will be presented.
ES13.5: Li-S/Li-O2 Batteries
Session Chairs
Wednesday PM, April 19, 2017
PCC North, 200 Level, Room 227 AB
2:30 PM - *ES13.5.01
Anion-Redox Solid Nanolithia Cathode for Li-Ion Battery
Jun Lu 1 , Yifei Yuan 2
1 Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 , University of Illinois at Chicago, Chicago, Illinois, United States
Show AbstractThe development of lithium-air batteries is plagued by a high potential gap (>1.2 V) between charge and discharge and poor cyclability, due to the drastic phase change of O2 (gas) and Ox- (condensed phase) at the cathode during battery operations. Here we report a cathode consisting of nanoscale amorphous lithia (nano-lithia) confined in a cobalt oxide, enabling charge/discharge between solid Li2O/Li2O2/LiO2 without any gas evolution. The cathode has a theoretical capacity of 1341 Ah/kg, a mass density exceeding 2.2 g/cm3 and a practical discharge capacity of 587 Ah/kg at 2.55 V. It also displays stable cycling performance (only 1.8% loss after 130 cycles in lithium-matched full-cell tests against Li4Ti5O12 anode), as well as a round-trip overpotential of only 0.24 V. Interestingly, the cathode is automatically protected from O2 gas release and overcharging through the shuttling of self-generated radical species soluble in the carbonate electrolyte.
3:00 PM - ES13.5.02
Real Time Study of a Working Li-Oxygen Battery Using In Situ TEM in Organic-Based Liquid Electrolyte
Kun He 1 , Yifei Yuan 1 2 , Xuanxuan Bi 2 3 , Jun Lu 2 , Reza Shahbazian-Yassar 1 , Wentao Yao 4 , Boao Song 1
1 , University of Illinois at Chicago, Chicago, Illinois, United States, 2 Chemical Science and Engineering Division, Argonne National Laboratory, Lemont, Illinois, United States, 3 , Ohio State University, Columbus, Ohio, United States, 4 , Michigan Technological University, Houghton, Michigan, United States
Show AbstractRecently, rechargeable lithium-oxygen battery is gradually becoming a promising candidate to replace lithium ion battery as the next-generation battery system due to its high energy density (>3500 W h/kg)1, which is 2-4 times larger than that of current lithium-ion batteries. However, lithium-oxygen battery suffers from several issues such as poor cyclability, limited rate capability and high overpotential (0.4-1.5 V)2. What’s worse, the mechanisms of lithium-oxygen battery system are poorly understood to date due to thermodynamic nature of a working battery, which is hard to be tracked directly. Consequently, lots of questions are not well answered, such as the formation of complicated discharge products (LiOH, Li2O, Li2O2 LiO2),3 the detailed nucleation growth and dissolution processes of lithium oxides during charge and discharge, and the origins for large overpotential. In addition, although many catalysts based on noble metals and transitional metal oxides are reported to show good catalytic property, the specific roles of the catalysts in improving the kinetics of (dis)charge processes are not clear. Here, using in situ transmission electron microscopy (TEM) combined with electron energy loss spectroscopy (EELS), the (dis)charge processes are studied in real time. We detect the shift of O K-edge prepeak in lithium oxides products during cycling. In addition, the energy gap between O K-edge prepeak and the core loss peak is used to differentiate Li2O2, LiO2 and Li2O.4 The formation and decomposition of the discharge products are also dynamically recorded based on which the discharge process (oxygen evolution reaction) is found to be limited by electronic conductivity rather than lithium diffusion rate. In summary, by using in situ TEM, the (dis)charge processes in a working lithium-oxygen battery are studied at nanoscale in real time, and the mechanisms associated with the detailed cycling products and the battery kinetics are well understood.
1. Lu, J.; Li, L.; Park, J.-B.; Sun, Y.-K.; Wu, F.; Amine, K. Aprotic and aqueous Li–O2 batteries. Chemical reviews 2014, 114, 5611-5640.
2. Yang, J.; Zhai, D.; Wang, H.-H.; Lau, K. C.; Schlueter, J. A.; Du, P.; Myers, D. J.; Sun, Y.-K.; Curtiss, L. A.; Amine, K. Evidence for lithium superoxide-like species in the discharge product of a Li–O 2 battery. Physical Chemistry Chemical Physics 2013, 15, 3764-3771.
3. Lu, J.; Lee, Y. J.; Luo, X.; Lau, K. C.; Asadi, M.; Wang, H.-H.; Brombosz, S.; Wen, J.; Zhai, D.; Chen, Z. A lithium–oxygen battery based on lithium superoxide. Nature 2016.
4. Wang, Z.; Santhanagopalan, D.; Zhang, W.; Wang, F.; Xin, H. L.; He, K.; Li, J.; Dudney, N. J.; Meng, Y. S. In situ STEM/EELS Observation of Nanoscale Interfacial Phenomena in All-Solid-State Batteries. Nano letters 2016.
3:15 PM - ES13.5.03
Enhanced Cycling Stability of Lithium-Oxygen Batteries through In Situ Formed Electrode Interface Layers
Bin Liu 1 , Wu Xu 1 , Pengfei Yan 1 , Jianming Zheng 1 , Mark Engelhard 1 , Chongmin Wang 1 , Ji-Guang Zhang 1
1 , Pacific Northwest National Lab, Richland, Washington, United States
Show AbstractRechargeable Li-O2 battery is no doubt a fascinating energy storage system that has been extensively pursued in recent years because of its extremely high theoretical specific energy, especially for its application in emerging electric vehicles. However, there exist several well-known issues regarding the instabilities of widely used carbon-based air-electrode and Li metal anode towards reactive reduced oxygen species, which need to be further addressed before the practical application of Li-O2 batteries. Herein we demonstrate a simple strategy to greatly enhance the cycling stability of Li-O2 batteries with carbon nanotube (CNT) air-electrodes by employing a one-step in-situ electrochemical process to simultaneously generate thin interface films on the CNT air-electrode surface and the Li metal anode surface. The reasons behind the performance improvement have been well investigated and the results will be discussed at the meeting.
4:30 PM - *ES13.5.04
Lithium Sulfur Batteries—Fundamental Understanding and Materials Design
Yi Cui 1
1 Department of Materials Science and Engineering, Stanford University, Stanford, California, United States
Show AbstractLithium-sulfur (Li-S) batteries have high theoretical specific energy (2500Wh/kg) and energy density (2800Wh/L) for portable and stationary energy storage although both lithium metal anodes and sulfur cathodes present many materials challenges for the operation of Li-S batteries. Here I will present the recent understanding of Li-S battery chemistry and a number of innovative materials design concepts to address these challenges. Some highlights include: 1) Understanding LixS speciation and their interaction with solid support, which guides the materials selection 2) Advanced nanomaterials designs addressing the polysulfide dissolution problems 3) Utilizing separators to control polysulfide species and enhance battery safety.
5:00 PM - *ES13.5.05
Protected Lithium Anodes for Enhanced Cycle Life of Lithium – Sulfur Batteries
Kevin Zavadil 1
1 , Sandia National Labs, Albuquerque, New Mexico, United States
Show AbstractThe application of metallic lithium as the anode is the most direct way of increasing the energy density (both volumetric and specific) of lithium or lithium ion based batteries through the elimination of the host (e.g., graphite, silicon) volume and mass penalty. The challenge in using lithium metal in liquid electrolytes is its poor electrocrystallization properties due to its inherent reactivity with the solvent and salts and the subsequent formation of a non-optimum solid electrolyte interphase (SEI). Creating an optimum SEI, one for which parasitic loss of both electrolyte and lithium and dendritic lithium growth is eliminated, is a long standing challenge but essential for high cycle life lithium - sulfur (Li-S) batteries. Where forming an optimum SEI can be thought of as creating a protected lithium anode, pack level modelling demonstrates that achieving high energy density requires a greatly reduced electrolyte volume fraction (50% versus 90%) relative to that commonly used for materials development and mechanistic studies making this challenge one of preserving the electrolyte.
In this presentation, several strategies for anode protection in Li-S cells and their efficacy for reducing parasitic loss will be described and compared. These strategies include mechanically compliant membranes and scaffolds that block solvent access to the anode or direct the evolution of an SEI to a stable and compliant state. Additionally, methods that utilize electrolyte design to produce self-healing films are explored. In select cases, we demonstrate a Coulombic efficiency of > 99%; a significant improvement on the standard electrolyte composed of lithium bis(trifluoromethylsulfonyl)imide, 1,3-dioxolane, 1,2-dimethoxyethane with lithium nitrate as an additive. The properties, composition and structure of these protective films have been characterized and in select cases operando methods are used to probe their evolution. Protection efficacy is evaluated at high relative areal capacity (60% of 10 mAh/cm2), high current density (2 mA/cm2), and low electrolyte volume ratio (3 ml electrolyte per gram of sulfur) using half-cells (lithium and electrolyte only) and full-cells (sulfur cathode).
The author acknowledges the contribution of the Joint Center for Energy Storage Research Li-S team in this presentation.
This work was 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 multiprogram 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.
5:30 PM - ES13.5.06
Chemical Routes for the Formation of Solid Electrolyte Interphase Layers on Sulfur Cathodes in Li-S/Na-S Batteries
Luning Wang 1 , Samantha DeCarlo 1 , Kang Xu 2 , Chunsheng Wang 1 , Bryan Eichhorn 1
1 , University of Maryland, College Park, College Park, Maryland, United States, 2 Electrochemistry Branch, Power and Energy Division Sensor and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, Maryland, United States
Show AbstractWhile they have shown tremendous influence on electrochemical performance of Li-S
batteries, solid electrolyte interphase (SEI) layers on sulfur cathodes still largely
remain ambiguous in terms of their chemical nature and forming mechanisms. Combining
direct detections of SEI layer components on different types of sulfur cathodes and
chemical reactions between sulfides and carbonate electrolyte, this work identifies
the chemical routes for the formations of two types of SEI layers. A kinetic reaction
route between monosulfide and ethylene carbonate (EC) generates a special SEI layer
that helps to protect active materials from corrosion reactions and enables a
superiorly stable Li-S battery. On the other hand, a thermodynamic reaction route
explains well on the capacity degradation of sulfur batteries with carbonate
electrolytes. In chemical reactions, we observe the transformation from kinetic
products to thermodynamic products and the critical role of Li+ cations in stabilizing
the kinetic products. Different chemical compositions of SEI are detected in a Li-S
and Na-S battery. This work intends to illustrate fundamental issues in terms of SEI
formations in Li-S/Na-S batteries, which demonstrate determining effects in the
retaining or degradation of battery capacity.
Symposium Organizers
Yuyan Shao, Pacific Northwest National Laboratory
David Mitlin, Clarkson University
Jin Suntivich, Cornell University
Lynn Trahey, Argonne National Laboratory
Symposium Support
Army Research Office
ES13.6: Li-Ion Batteries—Cathode
Session Chairs
Thursday AM, April 20, 2017
PCC North, 200 Level, Room 227 AB
9:15 AM - *ES13.6.01
Structural Stability of Layered Oxide Cathode Materials for High Energy Density Lithium Ion Batteries
Yingchun Lyu 1 2 , Enyuan Hu 3 , Jienan Zhang 1 , Yi Wang 1 , Xiqian Yu 1 , Lin Gu 1 , Hong Li 1 , Xiao-Qing Yang 3 , Xuejie Huang 1
1 , Institute of Physics, Chinese Academy of Sciences, Beijing China, 2 Materials Genome Institute, Shanghai University, Shanghai China, 3 Department of Chemistry, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractThe layered oxide materials with the α-NaFeO2 type composition (LiTMO2, TM=transition metal ions) are most attractive cathode materials for lithium-ion batteries, owing to larger capacities (200 mAh/g) than spinels or polyanionic compounds. In particular, LiTMO2 with the substitution of the transition metals by Li, forming the Li-rich or Li-excess materials (Li1+xTM1-xO2), can deliver reversible capacities exceeding 270 mAh/g. However, these materials need to charge to high voltage, which is normally above 4.5V and beyond the electrochemical window of conventional non-aqueous electrolyte, to obtain full capacity. The structural stability of particle surface and its interaction with electrolyte at high charging voltage play an important role in determining the overall electrochemical performances of these cathode materials. In addition, the crystal structural stability of these materials upon deep extent of lithium extraction and insertion remains a problem. In this presentation, the lithium storage mechanisms of several layered oxide cathode materials (Li1+xTM1-xO2, TM=transition metal ions), with various combination of 3d and 4d transition metal ions, are discussed in details to provide in depth understanding of the key factors governing both the bulk and surface structural stability of these materials for high-energy density applications. These discussions are expected to provide valuable insights for designing layered oxide cathode materials with significantly improved structural stability for safe and long life lithium ion batteries.
The work at Institute of Physics, CAS, is supported by National Scientific Foundation of China through grant No. 51325206. The work at Brookhaven National Laboratory was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies under Contract No. DE-SC0012704.
Reference
[1] X. Yu, Y. C. Lyu, L. Gu, H. M. Wu, S. M. Bak, Y. N. Zhou, K. Amine, S. N. Ehrlich, H. Li, K. W. Nam, X. -Q. Yang, Adv. Energy Mater. (2014), 4, 1300950.
[2] Y. Lyu, N. Zhao, E. Hu, R. Xiao, X. Yu, L. Gu, X.Q. Yang, H. Li, Chem. Mater. (2015), 27, 5238.
[3] Y. Xu, E. Hu, F. Yang, J. Corbett, Z. Sun, Y. Lyu, X. Yu, Y. Liu, X.-Q. Yang, H. Li, Nano Energy (2016), 28, 164.
[4] E. Hu, Y. Lyu, H. Xin, J. Liu, L.L. Han, S.M. Bak, J. Bai, X. Yu, H. Li, X.-Q. Yang, Nano Letters (2016), DOI: 10.1021/acs.nanolett.6b01609.
9:45 AM - *ES13.6.02
Deterioration of Interfaces/Interphases in Lithium Ion Battery Cathodes and Their Solutions
Jaephil Cho 1 , Sanghan Lee 1
1 , Ulsan National Institute of Science and Technology, Ulsan Korea (the Republic of)
Show AbstractAs applications of Lithium Ion Batteries (LIBs) are diversified from mobile devices to electric vehicles (EVs), and energy storage systems (ESSs), electrochemical characteristics of batteries such as high energy density, power density, and even thermal stability has been becoming more and more important today. Since the energy density of the batteries relies heavily on the cathode material used, major research efforts have been made to develop alternative cathode materials with a higher degree of lithium utilization and specific energy density. In particular, layered, Ni-rich, lithium transition-metal oxides can deliver higher capacity at lower cost than the conventional LiCoO2. However, Ni-rich compounds suffer from surface deterioration and structure degradation during electrochemical cycling, resulting in several problems associated with their cycle life, thermal stability, and safety. Herein, we introduce variable interfaces and interphases in a cathode electrode and a single particle electrode material, respectively. The performance enhancement of Ni-rich cathode materials through interface/interphase engineering will be discussed.
10:15 AM - ES13.6.03
Surface Nano-Coating as a Novel Approach to Improve the Structural Stability of Layered Oxide Cathodes in Li-Ion Batteries
Soroosh Sharifi-Asl 1 , Fernando Soto 2 , Yifei Yuan 3 , Tara Foroozan 1 , Jun Lu 3 , Perla Balbuena 2 , Reza Shahbazian-Yassar 1
1 Mechanical and Industrial Engineering, UIC, Chicago, Illinois, United States, 2 Department of Chemical Engineering, Texas A&M University, College Station, Texas, United States, 3 , Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractIntegration of Li-ion batteries to large-scale systems such as electrical transportation has drawn much attention to the safety aspect. Also, according to 2015 NASA Technology Roadmap, developing high energy density batteries that can withstand high-voltage and high-temperature conditions with no thermal runaway is an important objective. Lithium cobalt oxide (LiCoO2) is one of the most heavily used cathodes for lithium-ion batteries. Because of the safety concerns its usage in high power, and high energy density batteries are abandoned. At elevated temperatures or high cut-off voltages, LiCoO2 decomposes and desorbs oxygen. The evolved oxygen reacts exothermically with the flammable electrolyte. This reaction jeopardizes the safety of the cell due to the magnitude of this highly exothermic reaction.
In this study, we utilized surface coating method to enhance the structural stability of LiCoO2 by providing a physical barrier for oxygen evolution. We conducted electrochemical cycling, in-situ heating TEM and also ab-initio molecular dynamics (AIMD) simulations to characterize the role of surface coating on the stability of LiCoO2. SEM and Raman's characterizations were also performed to confirm the presence of an ultrathin coating on the LiCoO2 particles. Coin cells have been fabricated from coated LiCoO2 and pristine LiCoO2 to probe the electrochemical performance. We conducted the cycling with a cut-off voltage of 4.8 V (0.5 C) to explore the effectiveness of the coating on preventing oxygen release and battery failure in an abusive condition. Interestingly, coated sample could exhibit more than 75% capacity retention after 40 cycles while pristine sample failed after 20 cycles with the same condition. In-situ heating TEM was conducted on charged samples (one cycle to 4.4 V), and electron energy loss spectroscopy (EELS) was done at different temperatures to compare thermal stability of samples. Results show much higher stability in the coated sample up to 400 °C. TEM movies captured at 350 °C shows how coating can preserve the crystal structure of the sample while areas without coating are decomposing and the crystal structure is totally disrupted. AIMD simulations were performed to understand the underlying mechanism. Results show that the under-coordinated oxygens are dissociating from the LiCoO2 structure bond with the atoms in the surface being stopped from evolving as O2 molecule. Further complementary experiments are planned to better characterize the role of the coating on the stability of LiCoO2. Overall, this novel approach which can be employed in synthesis process of Li-ion batteries can eventually lead to safer and more stable Li-ion battery systems.
11:00 AM - *ES13.6.04
Advanced Diagnosis Tools for Probing Interfaces and Surfaces in Electrochemical Systems
Y. Shirley Meng 1
1 , University of California, San Diego, La Jolla, California, United States
Show AbstractSeveral high voltage cathode materials such as Li-excess layered oxide Li(LixNiCoMn)O2 and spinel LiNi0.5Mn1.5O4 are considered to be promising candidates for high-energy electrode material for Li-ion batteries, particularly for electric vehicle applications. Nevertheless, many of these high voltage cathodes suffer from poor cycle life and capacity degradation, especially at elevated temperatures. In this work new findings on surface and interface stability affecting the electrochemical longevity of the high voltage cathode material are investigated using a combination of in situ and ex situ imaging and spectroscopic tools, including: transmission X-ray microscopy, synchrotron X-ray absorption spectroscopy, and double-aberration-corrected scanning transmission electron microscopy. These tools unveil that cation migration and subsequent surface structural changes at the atomic levels are majorly responsible for the degradation. Combining the DFT + U calculations with our experimental observations, a correlation between these interface structural instability and the capacity degradation can be established. On the other hand, with the development of solid-state electrolytes, the solid/solid electrode/electrolyte interfaces present some major challenges in diagnosis methods. We will discuss some of the new diagnosis method development for anode materials as well, the extreme beam sensitivity of the lithiated anode materials such as silicon presents greater challenges for quantitative diagnosis of interphase at anodes.
11:30 AM - *ES13.6.05
Meso and Micron Scale Chemical and Morphological Heterogeneities in High Energy Density Lithium-Ion Electrodes
Jagjit Nanda 1 , Rose Ruther 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractMajority of electrode materials used for advanced lithium based batteries have well defined chemical composition, microstructure and morphologies. The chemistry as well as the microstructure can undergo reversible or irreversible changes under continuous electrochemical charge-discharge cycles. These could have measurable impact on the battery performance such as discharge capacity, power and life. The talk will highlight application of various multi-scale techniques directed towards probing the bulk and interfacial structure of lithium-ion battery electrodes under operando and ex-situ conditions. Specifically, I will present our recent work related to applying x-ray transmission microscopy (TXM) combined with near edge absorption spectroscopy (XANES) for studying the evolution of chemical oxidation state of the transition metal (TM) cations accompanied by changes in the particle morphologies in a number of high capacity lithium battery chemistries such as multi-lithium cathodes (Li2Cu0.5Ni0.5O2) and lithium-manganese rich NMC (LMR-NMC) cathodes.1-2 Moving onto micron-scale inhomogeneties, I shall discuss our current effort towards using micro-Raman and neutron imaging to spatially map the phase transformations and contrast in battery materials.1.
1. H. Dixit, J. Nanda et al, ACS Nano, 8 (12) 12710 (2014); R. Ruther, J. Nanda et al. Chem. Mater. 227, 6746 (2015).
2. F. Yang, Y. Liu, J. Nanda et al. Nano Letts. 14, 4334, (2014).
3. R. Ruther, J. Nanda et al J. Phys. Chem. C 119, 18022 (2015).
4. J. Nanda, H. Bilheux, et al, J. Phys. Chem. C, 116, 8401 (2012); H. Zhou, J. Nanda et al, ACS Energy Letters (2016).
12:00 PM - *ES13.6.06
Insight into Microstructural Evolution in Lithium-Based Batteries by Electron Microscopy
Dean Miller 1 , Jianguo Wen 1 , Lifen Wang 1 , Huaping Sheng 1
1 , Argonne National Laboratory, Lemont, Illinois, United States
Show AbstractThe evolution of microstructure, and in particular the development of new phases and interfaces, can have a profound effect on the performance of lithium-based batteries. As an example for Li-ion batteries, grain-to-grain separation and cracking can lead to loss of capacity in Ni- and Mn-rich cathode materials when grains become electrically isolated and no longer fully contribute to performance. For cathode materials themselves, the specific crystal structure and chemistry can play an important role in capacity and long-term stability. For lithium-oxygen batteries, nanoparticle catalysts, reaction products, and coatings to passivate defects all influence charge overpotential and the charge/discharge profile. Electron microscopy can provide new insight into each of these performance issues. For example, correlated electrochemistry and electron microscopy has shown how particle fragmentation is a significant issue that contributes to loss of capacity by decreasing grain-to-grain connectivity in Ni-Mn-based cathode oxides. Aberration-corrected HREM showed that a “composite” strategy for cathode oxides provides a thermodynamically favorable structure that yields better performance than the end member constituents, while low-dose, low-voltage electron microscopy and diffraction revealed how surface and catalyst control can influence the reaction pathway and microstructure of the reaction product in lithium-oxygen batteries. This presentation will detail our approaches to these issues and the insights gained from them.
12:30 PM - ES13.6.07
Depth and Width of Interfaces—Assessment Soft X-Ray Electronic Structure of Battery Electrodes Operando with Hard X-Rays
Artur Braun 1 , Elton Cairns 2
1 , EMPA, Duebendorf Switzerland, 2 EETD, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractElectrochemistry is traditionally considered as a matter of surface science because the electrochemical reactions are believed to take place at the interface of electrode and electrolyte, or at the interface of electrode with fluids such as liquids and gases. In the case of intercalation batteries, however, the chemical reactions emerge as front lines which propagate from the electrode surface into the interior of the electrode bulk. This manifests, for example, in the observation of diffusion controlled processes in the electrode. The concept of interface and interphase are therefore just approximations of a more complex reality.
I will present the first experimental assessment of the electronic structure of the bulk of a lithium ion battery cathode with soft x-rays, although this is seemingly impossible given their limited penetration depth of 1 micrometer only in the soft x-ray energy reason. This experiment was performed using a spectroscopic trick which has been done for the first time on a full lithium ion battery in operation by use of a synchrotron radiation source. We found particularly that the oxidation state of the Mn in the LiMn2O4-based positive electrode is not only changing its oxidation state, but that the Mn3+ ion passes during the dis-/charing process a high spin and also a low spin configuration. This scenario has not yet been considered previously in published literature. Due to the Pauli exclusion principle and Hund's rules, the orbital overlap of the Mn3d levels with the O2p levels is affected depending on state of charge of the battery, and thus the electronic transport properties are altered accordingly - depending on the lithium concentration in the corresponding region in the spinel particle and location of the particle in the electrode. It is therefore evident that the interface and interphase concepts deserve even more attention than hitherto acknowledged.
A. Braun, D. Nordlund, S.-W. Song, T.-W. Huang, D. Sokaras, X. Liu, W. Yang, T.C. Weng, Z. Liu, Hard X-rays in – Soft X-rays out: An operando piggyback view deep into a charging lithium ion battery with X-ray Raman spectroscopy, J. Electron Spec. Rel. Phenom. 2015, 200, 257–263.
A. Braun, H. Wang, T. Funk, S. Seifert, E.J. Cairns, Depth profile analysis of a cycled lithium ion LiMn2O4 battery electrode via the valence state of Mn with soft x-ray emission spectroscopy, Journal of Power Sources 2010, 195(22), 7644-7648.
A. Braun, S. Shrout, A. C. Fowlks, B. A. Osaisai, S. Seifert, E. Granlund, E. J. Cairns. Electrochemical in-situ reaction cell for X-ray scattering, diffraction and spectroscopy. Journal of Synchrotron Radiation (2003), 10, 320-325.
A. Braun, H. Wang, U. Bergmann, M.C. Tucker, Weiwei Gu, S.P. Cramer, and E.J. Cairns. Origin of chemical shift of manganese in lithium battery electrode materials - A comparison of hard and soft X-ray techniques. Journal of Power Sources 112 (1) 231-235 (2003).
12:45 PM - ES13.6.08
The Dissociation of Dimethyl Carbonate (DMC) on Layered Oxide LiCoO2(110)—A First–Principles Study
Jun Li 1 , Liyuan Huai 1 , Zhenlian Chen 1
1 , NIMTE, Ningbo China
Show AbstractIn recent years, rechargeable Lithium-ion battery (LIB) is widely recognized as one of the competing energy storage technologies due to its high energy and power densities at reasonable costs. Thin-film layered metal oxides LiCoO2 has been extensively considered as the prevailing cathode material for LIBs due to its comparatively higher energy density and electrochemical cycle. The interface between electrode and electrolyte inside LIB has been reported to play a very important role for lithium ion transfer and the cell performance, whereas increased voltages may cause side reactions occurring at the electrode-electrolyte interface (EEI) and therefore result in surface deterioration of the electrode, loss of electrolyte and the degradation of cell performance.
In the present study, periodic density functional theory (DFT) calculations were carried out to elucidate the dissociation mechanisms of dimethyl carbonate (DMC) on LiCoO2(110) surface. Three possible pathways for DMC dissociation were found and the results show that the dehydrogenation reaction of DMC (CH3OCOOCH3 → CH3OCOOCH2 + H) is the most favorable pathway with the energy barrier of 0.41 eV and reaction energy of -1.12 eV. Then we investigated the following dissociation of CH3OCOOCH2 and the formation of possible products. The above results can help to understand the fundamental mechanism of side reactions between the electrode-electrolyte interface and to develop more stable and efficient Li-ion batteries.
ES13.7: Li-Ion Batteries—Anodes
Session Chairs
Thursday PM, April 20, 2017
PCC North, 200 Level, Room 227 AB
2:30 PM - *ES13.7.01
Advanced Electron Microscopy Probing of Functioning Mechanisms of Nanoscale Surface Coating Layer for Mitigating Capacity Fading of Lithium Ion Battery
Chongmin Wang 1 , Pengfei Yan 1
1 , Pacific Northwest National Lab, Richland, Washington, United States
Show AbstractCapacity fading is always a big challenge for lithium ion batteries. The fading can be contributed by a range of factors, such as degradation in cathode, anode, electrolyte, and the interface between them or a combination and coupling of all these factors. Recent studies have shown that applying nanometer-thick coating layers on either anode or cathode can enhance cyclability and capacity retention. However, it is far from clear how the coating layer function from the point of view of both surface chemistry and electrochemi-mechanical effect. In this presentation, we use ex-situ and in-situ TEM to evaluate the functioning mechanism of coating effect on the lithiation kinetics of Si anode and lithium transition metal oxide cathode.
Evaluating from the point of view of both surface chemistry and electrochemi-mechanical effect, we found that the coating layer can play dual roles of both beneficial and detrimental. For Si, owing to the constraint effect of the coating layer, large compressive stress may be generated both at the reaction front and in the lithiated shell, which not only retards lithiation, but also causes fluctuant lithiation/delithiation, leading to self-discharge of the battery. On the other hand, the coating layer acts as a mechanical confinement that buffers the volume change of the anode during cycling, rendering the Si nanoparticle electrochemi-mechanically more durable. Our findings suggest the significance of the coupled electrochemi-mechanical effects of surface coatings in the design of high-performance Si-based anodes for lithium ion batteries. For the case of cathode, it appears that the surface chemical reaction will be the dominate factor. The atomic to nanoscale observation of the effect of the coating layer provides insight for optimized tailoring of artificial SEI layer toward enhanced battery performance.
3:00 PM - ES13.7.02
Li Ion Intercalation and Conversion Reactions in WO3 Thin Film Electrodes Studied by In Situ TEM
Yingge Du 1 , Yang He 2 , Scott Mao 2 , Chongmin Wang 1
1 , Pacific Northwest National Lab, Richland, Washington, United States, 2 , University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractTransition metal oxides with interconnected, ordered vacant lattice sites (e.g., WO3 and MoO3) enable facile, synchronous electron/ion intercalation reactions, and have been extensively investigated for energy conversion and storage applications. A topotactic phase transition (TPT), in which the final crystal lattice is closely related to that of the original material, may occur through the displacement and exchange of atoms as a result of intercalation. Even though the change in crystal structure is small, a TPT can significantly alter the electronic structure, lattice charge, and physical properties of a material. Thus, the ability to directly drive and characterize TPTs in situ can provide basis for the rational design, synthesis, and utilization of such materials. In addition, WO3 can be a conversion-type electrodes which is capable of providing up to 6 electrons per W. Understanding the atomistic conversion mechanism is fundamentally important in searching for new conversion-type electrode materials and the application of these materials. Unfortunately, the conversion mechanism has not been explicitly established mostly because it can be entangled with intercalation process.
In this presentation, we report our in-situ STEM, EELS, and Nano beam diffraction (NBD) studies, which reveal atomic level structural and chemical evolution across a conversion reaction front in WO3 thin films upon electrochemical Li ions insertion. A TPT induced by ion intercalation right prior to conversion is explicitly revealed. Nanoscale diffraction and ab initio molecular dynamic simulations found that going beyond intercalation, the inserted ion-oxygen bonding formation destabilized the transition-metal framework which gradually shrunk, distorted and finally collapsed to amorphous W and lithium oxide composite structure. In addition, we also illustrate the effect of ordered defects unique to epitaxial WO3 films on the ion transport processes. This study provides a full atomistic picture on the intercalation and subsequent conversion reactions, which is of essential importance for both secondary ion batteries and electrochromic devices.
3:15 PM - ES13.7.03
Artificial Solid Electrolyte Interphase-Protected LixSi Nanoparticles—An Efficient and Stable Prelithiation Reagent for Lithium-Ion Batteries
Jie Zhao 1 , Zhenda Lu 1 , Haotian Wang 1 , Wei Liu 1 , Hyun-Wook Lee 1 , Kai Yan 1 , Denys Zhao 1 , Dingchang Lin 1 , Nian Liu 1 , Yi Cui 1
1 , Stanford University, Stanford, California, United States
Show AbstractArtificial Solid Electrolyte Interphase-Protected LixSi Nanoparticles: An Efficient and Stable Prelithiation Reagent for Lithium-Ion Batteries
Jie Zhao,1 Zhenda Lu,1 Haotian Wang,2 Wei Liu,1 Hyun-Wook Lee,1 Kai Yan,1 Denys Zhuo,1 Dingchang Lin,1 Nian Liu,3 and Yi Cui1,4,*
1Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
2Department of Applied Physics, Stanford University, Stanford, California 94305, United States
3Department of Chemistry, Stanford University, Stanford, California 94305, United States
4Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
Prelithiation is an important strategy to compensate for lithium loss in lithium-ion batteries, particularly during the formation of solid electrolyte interphase (SEI) from reduced electrolytes in the first charging cycle. We recently demonstrated that thermal-alloying synthesized LixSi nanoparticles (NPs) can serve as a high-capacity prelithiation reagent although its chemical stability in the battery processing environment remained to be improved.1 Here we successfully developed a surface modification method to enhance the stability of LixSi NPs by exploiting the reduction of 1-fluorodecane on the LixSi surface to form a continuous and dense coating, through a similar reaction process to SEI formation.2 The coating, consisting of LiF and Li alkyl carbonate with long hydrophobic carbon chains, serves as an effective passivation layer under ambient environment. Remarkably, artificial-SEI protected LixSi NPs show a high prelithiation capacity of 2100 mAh/g with negligible capacity decay in dry air after 5 days and maintain a high capacity of 1600 mAh/g in humid air (~10% relative humidity (RH)). Silicon, tin and graphite were successfully prelithiated with these NPs to eliminate the irreversible first cycle capacity loss. The use of prelithiation reagents offers a new approach to realize next generation high-energy-density lithium-ion batteries.
1. Zhao J, et al. Dry-air-stable lithium silicide-lithium oxide core-shell nanoparticles as high-capacity prelithiation reagents. Nat Commun 5:5088 (2014).
2. Zhao J, et al. Artificial solid electrolyte interphase-protected LixSi nanoparticles: An efficient and stable prelithiation reagent for lithium-ion batteries. J Am Chem Soc 137(26):8372–8375 (2015). JACS Spotlight
3:30 PM - ES13.7.04
In Situ Electrochemical Atomic Force Microscopy of the Solid Electrolyte Interphase Formed on HOPG in Superconcentrated Electrolyte
Ngoc Duc Trinh 1 2 3 , Christopher Dip 1 , Yvon Rodrigue Dougassa 1 3 , David Lepage 1 3 , Antonella Badia 1 2 , Dominic Rochefort 1 3
1 , Universite de Montreal, Montreal, Quebec, Canada, 2 , Regroupement Québécois pour les matériaux de pointe, Montreal, Quebec, Canada, 3 , Centre Québécois sur les matériaux fonctionnels, Montreal, Quebec, Canada
Show AbstractUnderstanding the mechanism of formation of the solid-electrolyte interphase (SEI) layer on the graphite anode in superconcentrated electrolytes is primordial for lithium-ion batteries (LIBs). Electrochemical atomic force microscopy (EC-AFM) is one of the most powerful tools to characterize the topography of the SEI and was used in this work to investigate in-situ layer formation during the charge/discharge process. SEI formation on highly oriented pyrolytic graphite (HOPG) in superconcentrated acetonitrile electrolyte was studied at two different concentrations (3.0 M and 4.2 M) of lithium bis(trifluoromethanesulfonyl)imide (LiTFSi). The results show that the growth and morphology of the SEI layer is a function of the salt concentration. The 4.2 M LiTFSi/acetonitrile electrolyte demonstrated better Li+ (de-)lithiation stability on HOPG. X-ray photoelectron spectroscopy was used to identify and quantify the chemical composition of the passivation layer. Finally, the electrochemical performances of the electrolytes in coin cell batteries will be discussed.
4:15 PM - *ES13.7.05
Designing Silicon Based High Energy Cells through Active Materials Surface Modification and Process Optimization
Jun Wang 1 , Xianxing Shi 2 , Paul Gionet 1 , Ronnie Wilkins 1 , Paul Graham 1 , Derrick Maxwell 1 , Huimin Wang 2 , Derek Johnson 1
1 , A123 Systems, LLC, Waltham, Massachusetts, United States, 2 , A123 Systems Asia Co., Ltd., Hangzhou China
Show AbstractSilicon is a promising active material for high energy density Li-ion batteries due primarily to its extremely high specific capacity over incumbent carbon based anodes. However, fast capacity fade and cell gassing have been frequently observed in cells fabricated with silicon in the anode during long term cycling or storage testing; for which the root causes are fundamentally tied to large volume expansion of alloy type active materials as well as unstable SEI formation. Among the potential solutions to such challenges, surface modification of the Si-containing active material together with a compatible electrode formulation offer great potential to extend cycle life and reduce cell gas generation.
In this study, silicon-containing high capacity alloy active materials were processed to obtain composite anode powders. Prior to slurry mixing and electrode coating, a number of techniques were applied to modify the surface of the composite. Standard single layer pouch electrochemical test vehicles were constructed to evaluate the impact of such surface treatments to cell cycle life. The process and inactive materials that significantly impact cycle life in a positive way will be presented. By combining optimal electrode formulations as well as balancing cell design and precise control of testing parameters with Si-containing anodes, we identified a thorough and systematic approach for demonstrating cell level energy densities that will enable a significant increase in EV driving range compared to current cell technologies. The details and results of this study will be presented.
4:45 PM - ES13.7.06
Elucidating Li4Ti5O12 (111) Surface Evolution upon Electrochemical Cycling
Jokin Rikarte 1 , Begona Acebedo 1 , Arantxa Vilalta-Clemente 2 , Juan Rubio Zuazo 3 , Miguel A. Munoz-Marquez 1
1 , CIC-energiGUNE, Vitoria-Gasteiz Spain, 2 Department of Materials, University of Oxford, Oxford United Kingdom, 3 , SpLine Spanish CRG Beamline at the ESRF, Grenoble France
Show AbstractDespite being the dominant technology in the portable electronics technology, Li-ion batteries are also spreading in different areas such as Electric Vehicle (EV) and Grid Storage applications. New materials have been demonstrated to be good alternatives to the most conventional electrode materials, namely LiCoO2 and graphite. Among the various possibilities Li4Ti5O12 (LTO) stands out for negative electrodes in stationary applications owing to its stability and safety. Although in the beginning it was described as Solid Electrolyte Interphase (SEI) free material1, many works demonstrated during the last years the presence of activity on LTO surface upon cycling2–4. Among others, formation of rough α-Li2TiO3 phase on top of the LTO (111) surface during the first cycle was suggested on the grounds of experimental transmission electron microscopy (TEM) data, electron energy loss spectroscopy (EELS) and atomic force microscopy (AFM) investigations5 and theoretical ab-initio calculations. However, the limited extent of DFT calculations being performed under thermodynamic equilibrium at zero-bias and the local character of TEM, EELS and AFM triggered our interest to further investigate the surface evolution of LTO (111) upon electrochemical cycling by means of long-range surface sensitive techniques. In this study, a highly oriented LTO (111) layer was grown on top of a rutile TiO2 (111) single crystal following a solid state synthesis route. The obtained thin-film was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), AFM and X-ray photoelectron spectroscopy (XPS). The evolution of the LTO surface upon electrochemical cycling was studied by means of long-range surface sensitive techniques, namely High Resolution Electron Backscattered Diffraction (HREBSD) and Synchrotron Thin Film XRD. In contrast with previous studies, no presence of α-Li2TiO3 was detected in the cycled samples. However, an increase on the surface strain was measured by HREBSD, which could be related to the increment in the roughness reported by other studies, and could have a critical effect in long cycling performance of this electrode material. Understanding the effects of this surface roughness will have a positive effect on the stability of the LTO which is always considered a good candidate for long cycle life applications.
1 D. Peramunage and K. M. Abraham, J. Electrochem. Soc., 1998, 145, 2609–2615.
2 Y.-B. He, M. Liu, Z.-D. Huang, B. Zhang, Y. Yu, B. Li, F. Kang and J.-K. Kim, J. Power Sources, 2013, 239, 269–276.
3 T. Nordh, R. Younesi, D. Brandell and K. Edström, J. Power Sources, 2015, 294, 173–179.
4 J.-B. Gieu, C. Courrèges, L. El Ouatani, C. Tessier and H. Martinez, J. Power Sources, 2016, 318, 291–301.
5 M. Kitta, T. Akita, Y. Maeda and M. Kohyama, Langmuir, 2012, 28, 12384–12392.
5:00 PM - ES13.7.07
First-Principles Study of the Reduction Mechanisms of Ethylene Carbonate on the Amorphous Lithiated Surfaces of Silicon Anodes in Lithium-Ion Battery
Chin-Lung Kuo 1 , Han-Hsin Chiang 1
1 , National Taiwan University, Taipei Taiwan
Show AbstractIn this study, we employed first-principles density functional theory calculations and ab initio molecular dynamic simulations to investigate the reduction mechanisms of ethylene carbonate (EC) molecule on the amorphous lithiated surfaces of Si anodes in Li-ion batteries. We first generated the amorphous surface models of Si anodes within four different levels of lithiation (Li40Si88, Li64Si64, Li84Si44, and Li100Si28) via the MD “melt-and-quench” approach and then examined the possible reduction pathways of EC molecules on these amorphous lithiated Si surfaces using ab initio molecular dynamic simulations.
Our results showed that EC molecules can be reduced on the LixSi surfaces via three distinct two-electron processes, which appear to be highly dependent on the surface composition of the Si-based anodes. As the Li concentration on the anode surface was low, EC reduction was predominately initiated by the adsorption of a EC molecule onto the anode surface via the formation of Si-C bond followed by a two-electron transfer process leading to ring-opening as represented using the following formula: EC + 2e- → OCOC2H4O2- . In this case, the interaction between the surface Si atom and an EC molecule was found to be the main driving force leadting to this surface reduction reaction. However, on the highly lithiated Si surfaces, the reduction of EC was found to majorly proceed via another two-electron transfer process, in which EC adsorption was driven by the electrostatic interaction between the C=O bond of an EC molecule and the Li ions on the anode surfaces. Moreover, our results showed that the reduction rate of EC decomposition tends to increase with the Li content on the anode surfaces, and the increment of EC reduction can be attributed to the enhanced electron transfer from the anode surfaces to the EC molecules as revealed in our work function calculations. Our calculations further showed that EC molecules can even go through a four-electron transfer process on these highly lithiated Si anode surfaces, leading to the formation of CO2- and O(C2H4)OCO2- products. On the other hand, our simulations also revealed that EC reduction can occur via electron tunneling on the highly lithiated Si surfaces. In this case, EC reduction was found to proceed via a sequential one-electron transfer processes: EC + e- → EC- , EC- + e- → CO32- + C2H4. Our calculations showed that this non-adsorption EC reduction reaction was actually more energetically favorable than the reaction paths initiated by surface adsorption. However, it turns out to be an infrequent reaction event on the lithiated Si surfaces due to its relatively higher energy barriers to induce EC reduction. Furthermore, our calculations showed that the reaction rate of EC reduction on the amorphous lithiated Si anode surfaces can be manipulated by some surface doping or chemical modification. These interesting new findings will also be addressed in this presentation.
5:15 PM - ES13.7.08
Multi-Graft Copolymer Polymer Binder for Silicon Anode
Pengfei Cao 1 , Michael Naguib 1 , Eric Stacy 3 , Bingrui Li 1 , Tao Hong 2 , Jagjit Nanda 1 , Alexei Sokolov 1 2 , Tomonori Saito 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 Department of Physics, University of Tennessee, Knoxville, Tennessee, United States, 2 Department of Chemistry, University of Tennessee, Knoxville, Tennessee, United States
Show AbstractDeveloping sustainable energy storage technologies has been attracting significant attentions due to the ever-growing energy needs and depleting fossil fuels. Increasing the energy density of the lithium-ion battery (LIB) is highly required due to their expanding applications from portable electronics to large-scale emerging applications, such as an electric vehicle that requires longer driving distance upon a single charging. Theoretically, using silicon instead of the traditional graphite on anode can raise the capacity up to 10 times higher, while the significant volume change during lithiation and delithiation seriously limits the long cycle life of the silicon anode.
In this project, a multiphase graft copolymer of lithium polyacrylate was synthesized and tested as a polymer binder for silicon-based anode in lithium-ion battery. A macro RAFT-CTA was synthesized by amidation reaction of carboxylic acid terminated RAFT-CTA with primary amine on chitosan in aqueous solution, and the following RAFT polymerization of acrylic acid allows the synthesis of well-defined comb-like copolymers, i.e., chitosan-graft-PAA. Further titration of the chitosan-graft-PAA with lithium hydroxide gives the comb-like copolymer with chitosan as a backbone with lithium polyacrylate as the side chains. Multi-grafting lithium acrylate with different grafting densities and side chain lengths were also synthesized. The electrochemical performance of chitosan-graft-PAA and chitosan-graft-LiPAA was assessed in comparison to other conventional polymer binders, such as PVDF, PAA, and LiPAA. The galvanostatic test result demonstrated that the comb-like copolymer exhibit the better cycling performance compared with the linear analogue.
5:30 PM - ES13.7.09
Suppression of Lithium Dendrites using Graphene Oxide
Tara Foroozan 1 , Soroosh Sharifi-Asl 1 , Zhennan Huang 1 , Reza Shahbazian-Yassar 1
1 , University of Illinois at Chicago, Chicago, Illinois, United States
Show AbstractLithium (Li) metal is the ideal anode material in batteries due to its large theoretical capacity (3860 mAh/g) and low redox potential (−3.04V vs standard hydrogen potential, H2/H+). Nevertheless, considering the hostless nature of Li metal, surface dendrite formation during repeated charge−discharge limits the cycle life and Li metal practical usage. Therefore, inhibiting the uncontrolled growth of Li dendrites during the Li plating process is critically essential to improve the cycle life of Li-metal batteries. Inhomogeneous surface charge distribution and also mechanical stress on the Li metal surface causes uneven Li ion deposition, which is considered as the origin of Li dendrite formation. Different approaches have been considered to solve this problem. Improving the stability of SEI layer by using additives, use of solid electrolytes and coating of Li metal with hard films are among the works done in this aspect.
In this study, we have employed multilayer graphene oxide (MGO) sheets to control the Li deposition on metal surface. MGO is an ideal electronic insulator material with high mechanical strength which can prevent shorting of the system. Defective structure of graphene oxide and high interlayer spacing of GO (~0.7 nm) allows for facile Li ion diffusion through the coating. Also the inherent negative charge of MGO layers can provide a more uniform charge distribution and also a better adhesion between separator and the metal surface. A more uniform surface charge and less metal surface tension, forces further the deposition of lithium to adjacent regions of the metal surface instead of the initial growth tips, preventing the dendritic Li deposition. The FIB SEM cross sectional images show the more uniform deposition of Li metal on the MGO coated sample. The battery performance also shows an order of magnitude improvement in the cycleability of our sample compared to bare Li-Cu half-cell. Our results confirm the effectiveness of our approach for better performance and longer life time of battery systems.
5:45 PM - ES13.7.10
Conditioning of Na+ Conductivity in a Glass Electrolyte by Dipole - Dipole Interactions, "Role of Electric Dipoles in a Na+ Glass Electrolyte"
Andrew Murchison 1 , M. Helena Braga 1 , John Goodenough 1
1 , University of Texas Austin, Austin, Texas, United States
Show AbstractGlass, unlike a crystalline solid, contains atoms and molecules that do not occupy fixed positions. A glass that contains molecules that attract one another can age with time. We report such a glass that contains A2O and (OA)- electric dipoles (A = Li or Na). At a temperature T < 1.2Tg ≈ 110°C (Tg is glass transition temperature) the electric dipoles coalesce with time into clusters within which, unlike in ice, some dipoles condense into ferroelectric, negatively charged molecules locally charge-compensated by weakly attracted A+ ions. In an applied electric field, the dipoles are oriented and, over time depending on the T < 110°C, are aligned parallel to the field axis to yield a solid A+ electrolyte with an ionic conductivity si > 10-2 S cm-1 and a huge dielectric constant that makes it suitable for many applications, including safe rechargeable batteries of high energy density and long cycle life.
ES13.8: Poster Session
Session Chairs
David Mitlin
Yuyan Shao
Jin Suntivich
Lynn Trahey
Friday AM, April 21, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - ES13.8.01
Amorphous Molybdenum Disulfide as a Hydrogen Evolution Reaction Catalyst for Photoelectrochemical Water Splitting
Tian Lan 1 , Ahmad Fallatah 1 , Sonal Padalkar 1
1 , Iowa State University, Ames, Iowa, United States
Show AbstractCopper (I) oxide (Cu2O) is a very favorable p-type semiconductor, which finds potential applications in areas like solar water splitting. Here we report the fabrication of Cu2O photocathode for solar water splitting. Additional zinc oxide (ZnO) and aluminum doped zinc oxide (AZO) passivating layers were electrodeposited on Cu2O photocathode. Also an amorphous layer of molybdenum disulfide (MoS2) was electrodeposited, which works as a hydrogen evolution reaction (HER) catalyst. The fabricated photocathode will be characterized by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The photoelectrochemical measurements of Cu2O photocathode will be used as a control sample. Other PEC measurements of Cu2O-ZnO, Cu2O-AZO and Cu2O-AZO-MoS2 will be compared with the control sample.
9:00 PM - ES13.8.02
Computational Insights to Charge Transfer Reactions at Electrode/SEI/Electrolyte Interface
Yunsong Li 1 , Yue Qi 1
1 , Michigan State University, East Lansing, Michigan, United States
Show AbstractThe performance of Li-ion batteries (LIB) are highly dependent on the electrochemical reactions occurring at the Solid Electrolyte Interface (SEI). However, its nanometric scale thickness combined with its complex structure makes the SEI remains “the most important but the least understood in LIB”. Simulations can provide critical insights to the electrochemical reactions at the electrode/SEI/electrolyte interface.
To overcome the simulation size limitation of Density Function Theory (DFT), and the lack of electrochemistry description of ReaxFF, Density Functional Tight Binding (DFTB) was used to model the charge transfer reaction at a Li/Li2CO3/liquid electrolyte interface.
Since the accuracy of DFTB is highly dependent on parameters, we first developed a new set of DFTB parameters for Li-X (X=Li, H, C, O) interactions by fitting and calibrating with various DFT calculations. The simulation clearly showed during lithiation, it is energetically favorable to remove Li atoms at the Li/Li2CO3 interface than from the bulk of Li.
The lithiation process was simulated as three steps: Li+ desolvation at the SEI/Electrolyte interface, Li+ diffusion through the Li2CO3 layer, and annihilation of e- and Li+ at the Li surface. During this reaction, electron is always located on the Li-metal slab corresponding to the applied electron density or voltage. The energy profile of this reaction was simulated under different voltage. The impact of intrinsic point defects (as Li+ interstitials) in Li2CO3 on the charge transfer reaction barrier was also investigated.
9:00 PM - ES13.8.03
Electrochemical Impedance Spectroscopy Investigation of Solid-Electrolyte Interphase Formation in Lithium-Ion Battery Anodes
Yige Li 1 , Kazi Ahmed 1 , Bo Dong 1 , Chueh Liu 1 , Changling Li 1 , Yiran Yan 1 , Zafer Mutlu 1 , Cengiz Ozkan 1 , Mihri Ozkan 1
1 , University of California, Riverside, Riverside, California, United States
Show AbstractThe formation of a stable solid-electrolyte interphase (SEI) layer during the initial cycles of a lithium-ion cell is critical to the cell’s lifetime, performance, and safety. A stable SEI isolates the electrode surface from the electrolyte, which would otherwise undergo irreversible and parasitic side-reactions under the existing difference in potential between the two phases. We employ electrochemical impedance spectroscopy (EIS) as a primary technique to investigate the formation of this interphase on lithium-ion anode in half-cell configuration. EIS allows us to observe the impedance and associated time constant of the SEI layer in-situ in isolation from other electrochemical phenomena within the cell.
9:00 PM - ES13.8.04
Tungsten Disulfide as a Photocatalyst for Efficient Solar Water Splitting
Tian Lan 1 , Sonal Padalkar 1
1 , Iowa State University, Ames, Iowa, United States
Show AbstractHere we report the fabrication of a copper (I) oxide – tungsten disulfide (Cu2O-WS2) photoelectrode for efficient solar water splitting. Hierarchical structures of Cu2O were fabricated by varying conditions for anodization of a Cu foil. Initially, CuO or Cu(OH)2 was formed on the Cu foil during anodization. This anodized Cu foil was then thermally treated at 400 °C in nitrogen atmosphere for 1 h to obtain Cu2O nanostructures. The photocatalyst WS2 was electrodeposited on the Cu2O nanostructures. For this deposition, an electrolytic bath of sodium tungstate and thioacetamide was used. The deposition was carried out in a three-electrode electro-chemical analyzer, to fabricate Cu2O – WS2 photoelectrode for solar water splitting. Photoelectrochemical measurements of Cu2O-WS2 was performed. The samples were also characterized by X-ray diffraction, UV-Visible spectroscopy, Gas chromatography and scanning electron microscopy.
9:00 PM - ES13.8.05
Metal-Organic Frameworks Derived Metal Embedded Carbons Materials as Catalysts for Efficient Electrocatalysis
Yan Liang 1 , Jing Wei 1 , Huanting Wang 1
1 , Monash University, Melbourne, Victoria, Australia
Show AbstractMetal-organic-frameworks (MOFs) assembled by metal ions clusters with electron donating organic ligands, have attracted increasing attention due to their extremely high surface area, well defined morphology and uniform porosity. These intrinsic properties make them to be perfect precursors to construct nanostructure of carbon, and carbon-metal composite with high specific surface areas. For example, porous carbon/metal composite can be synthesized by directly annealing Prussian Blue (PB), a subclass of MOFs, which used as carbon support for dispersing Pt nanoparticles for methanol oxidation. The high contents of N and Fe in PB are beneficial for forming carbon materials with N doping and a high degree of graphitization. N doping into the carbon lattice can increase the number of interactions between the metal nanoparticles and the carbon surface, as a strong coordination exists between metals and N atoms. Therefore, highly dispersed metal nanoparticles would be readily obtained.
Hollow metal-organic structures with fascinating properties, such as well-defined morphology, uniform size, large surface area, low density, and high loading capacity, have been studied for a wide range of potential applications including nanoreactors, catalysis, biomedicine, sensors, and environmental remediation. However, previous synthesis methods for construction of shells of hollow materials by linking metal ions or metal oxide clusters with organic ligands often result in hollow spheres with micro-sizes, relatively wide size distribution and ill-defined shapes. We present a one-step method for in-situ transformation of metal-organic framework (MOF) crystals into metal-polydopamine (PDA) hollow polyhedral particles through polymerization of dopamine, dissolution of MOF and coordination between metal ion and PDA, simultaneously. MOFs (ZIF-67 and ZIF-8) are not only used as templates, but also provide metal (Co and Zn) ions for coordination with PDA. This method avoids an additional step in removing templates during the synthesis of hollow structures, and is a simple way to construct hollow metal-polymer structures with well-retained shapes of templates and controllable sizes. Furthermore, Co-PDA hollow polyhedral particles were carbonized to produce hollow carbon particles with high surface area and rich active catalytic sites, exhibiting excellent oxygen reduction electrocatalysis activity at the same catalyst loading as commercial Pt/C catalyst.
To date, how to improve the physical and chemical properties of MOF derived porous carbons and related nanostructure, and apply these nanostructure materials to desired area are still our major aims.
9:00 PM - ES13.8.06
Co and N Co-Doped Carbon Nanotubes for Efficient Oxygen Reduction Reaction Electrocatalyst
Yinggang Zhu 1 , Chaoqun Shang 1 , Zhouguang Lu 1
1 Department of Materials Science and Engineering, South University of Science and Technology of China, Shenzhen, Guangdong, China
Show AbstractA kind of cobalt and nitrogen co-doped carbon nanotubes electrocatalysts, Co-N-CNTs, have been prepared with sustainable organic-rich chitosan waste serving as nitrogen source by the solution method. The cobalt was extracted into the electrocatalysts to improve the electrocatalytical properties.1 The linear sweep voltammograms (LSV) measurement exhibits excellent eletrocatalytic activity because of the synthetic effect of co-doped cobalt and nitrogen elements. To monitor the hydrogen peroxide yield, rotating ring-disk electrode measurements were carried out and the result indicates a nearly four-electron pathway for Co-N-CNTs electrocatalysts. This kind of electrocatalyst also shows superior long-term durability and better methanol tolerance than that of commercial Pt/C, which makes it a potential ORR electrocatalyst in proton exchange membrane fuel cells.
Acknowledgments
This work was financially supported by the Shenzhen Peacock Plan (KQCX20140522150815065), the Natural Science Foundation of Shenzhen (JCYJ20150331101823677) and the Science and Technology Innovation Foundation for the Undergraduates of SUSTC (2015x19 and 2015x12).
Reference
1. Wu, Z. Y.; Chen, P.; Wu, Q. S.; Yang, L. F.; Pan, Z.; Wang, Q. Nano Energy 2014, 8, 118-125.
9:00 PM - ES13.8.07
Controllable Synthesis of Inorganic Electrocatalysts for Energy Conversion Related Reactions
Yong Zhao 1
1 , Henan University, Kaifeng China
Show AbstractEfficient and non-precious metal electrocatalysts are highly important for increasing conversion efficiency and decreasing the cost of energy-related devices, such as fuel cells, water splitting and artificial photosynthesis.[1-7] In this work, we show the effective methods to synthesize the non-precious metal electrocatalysts for oxygen evolution reactions, oxygen reduction reactions and hydrogen evolution reactions, which are the essential and fundamental reactions in the above-mentioned devices. The influence of the absorption energetic between catalyst and intermediates, active site densities, and electrochemical active surface area on the activity of catalysts is illustrated. It hopefully provides the guidance for design of high-performance electrocatalysts for energy conversion devices.
References
[1] Y. Zhao, K. Watanabe, K. Hashimoto, J. Am. Chem. Soc. 2012, 134, 19528-19531.
[2] Y. Zhao, K. Kamiya, K. Hashimoto, S. Nakanishi, Angew. Chem. Int. Ed. 2013, 52, 13638-13641.
[3] Y. Zhao, R. Nakamura, K. Kamiya, S. Nakanishi, K. Hashimoto, Nat. Commun. 2013, 4:2390.
[4] Z. Y. Lu, W. Zhu, X. Y. Yu, H. C. Zhang, Y. J. Li, X. M. Sun, X. W. Wang, H. Wang, J. M. Wang, J. Luo, X. D. Lei, L. Jiang, Adv. Mater. 2014, 26, 2683-2687.
[5] Y. Zhao, K. Kamiya, K. Hashimoto, S. Nakanishi, J. Am. Chem. Soc. 2015, 137, 110-113.
[6] Y. Zhao, K. Kamiya, K. Hashimoto, S. Nakanishi, J. Phys. Chem. C 2015, 119, 2583-2588.
[7] Y. Zhao, K. Kamiya, K. Hashimoto, S. Nakanishi, J Mater Chem A 2016, 4, 3858-3864.
[8] J. L. He, B. B. Hu, Y. Zhao, Adv. Funct. Mater. 2016, 26, 5998-6004
9:00 PM - ES13.8.08
The Effect of Electrochemical Modification of the Glass Carbon Surface in Conditions of Chemisorption of Fluorine-Containing Nanogroups on Its Electrophysical Properties
Yulia Stryuchkova 1 , Sergey Karabanov 1 , Dmitry Suvorov 1 , Evgeny Slivkin 1 , Gennady Gololobov 1 , Dmitry Tarabrin 1
1 , Ryazan State Radioengineering University, Ryazan Russian Federation
Show AbstractCreation of glass carbon electrodes with high power active surface by its electrochemical modification by nanodimensional groups of chemisorption character results in increase of their catalytic activity and opens larger possibilities of their use as anodes in various areas of electronics.
The paper studies the influence of electrochemical surface modification of glass carbon in conditions of chemisorption of fluorine-containing nanogroups on its electrophysical properties. The research has been carried out by the methods of scanning tunnel micro- and spectroscopy.
High chemical resistance of glass carbon electrodes in combination with high catalytic activity of their surface allows to use them in various media, allowing to take into account high rate of electrode reactions.
The conducted research results show that the modifying effects on glass carbon by electrochemical oxidation in 40% ammonium bifluoride solution have an influence on electrophysical properties of surface atoms. Herewith modification in proportion of donor and acceptor properties of surface atoms, decrease of effective resistance to tunnel electron transfer and increase of the general tunnel activity degree occurs. The surface modification results in its anode activity increase.
9:00 PM - ES13.8.09
Designing Bifunctional Catalyst for Oxygen Reduction/Evolution Reactions with Long Life Time and High Efficiency
Niranjanmurthi Lingappan 1 2 , Bing Li 1 2 , Young Hee Lee 1 2
1 , Sungkyunkwan University, Suwon Korea (the Republic of), 2 Institute for Basic Science, Center for Integrated Nanostructure Physics, Suwon Korea (the Republic of)
Show AbstractDeveloping an efficient and durable multi-functional catalyst to replace Pt catalyst is prerequisite for practical applications to portable electronics, cars, and chemical industries. Although various types of nanocarbon/metal oxides heterostructures have been suggested, achieving high efficiency and more importantly long-term durability is still challenging. Here, we report a self-assembly strategy to design bifuntional electrocatalyst comprised of interconnected nickel-cobaltite nanocrystals on nitrogen-doped graphene (i-NiCo2O4/N-Gr). The dispersed metal precursors and N-doped Gr in block-copolymer solution was hydrothermalized, followed by thermal annealing to form interconnected NiCo2O4 nanocrystals anchored on N-Gr. This structure provides bifunctional oxygen reduction/evolution catalytic functions. Metal oxide nanocrystals offer high active sites, while open space between nanocrystals allows for oxygen molecules to access to active catalysts on Gr surfaces. Well-dispersed Gr plays as a platform for anchoring interconnected nanocrystals and improve conductivity to retain high saturation current and onset potential similar to Pt/C. Life times as long as 200 hours for oxygen reduction and 300 hours for oxygen evolution were retained with negligible degradation. Our approach paves the way toward rational design of various types of Gr-metal oxides hybrids for numerous practical applications.
9:00 PM - ES13.8.10
α-Hematite -Molybdenum Disulfide Nanocomposite Films for Photoelectrochemical Applications
Hussein Alrobei 1 , Ashok Kumar 1 , Manoj Ram 1
1 Mechanical Engineering, University of South Florida, TAMPA, Florida, United States
Show AbstractThe alpha (α)- hematite (Fe2O3) nanomaterials has been attractive due its band gap, chemical robustness and availability in the nature, and excellent photoelectrochemical (PEC) properties to split water into oxygen and hydrogen [1]. However, the α-Fe2O3 suffers from low conductivity, slow surface kinetic, low carrier diffusion, and greater electron-hole combination. The electronic properties such as carrier mobility and diffusion of α- Fe2O3 can be improved through doping, synthesis of composite material or formation of structured films. Recently, 2D- molybdenum disulfide (MoS2) has shown interesting photocatalytic activity due to its bonding, chemical composition, doping and nanoparticles grown on graphene film [2],
We have synthesized nanocomposite α-Fe2O3-MoS2 using sol-gel technique. The nanocomposite α-Fe2O3-MoS2 nanomaterials were characterized using SEM, X-ray diffraction, UV-vis, FTIR and Raman techniques. The electrochemical techniques were used to understand the photocurrent, electrode/electrolyte interface of α-Fe2O3-MoS2 nanocomposite films. The nanocomposite α-Fe2O3-MoS2 films shows rhombohedra structure and lower band gap than α-Fe2O3 films. The nanocomposite α-Fe2O3-MoS2 films reveals improved production of hydrogen compared to α-Fe2O3 and aluminum doped α-Fe2O3 nanostructured films. The band structure has been used to understand the mechanism of photoelectrochemical water splitting in nanocomposite α-Fe2O3-MoS2 films.
References:
[1] D.A. Wheeler, G. Wang, Y. Ling, Y. Li, J.Z. Zhang, Nanostructured hematite: synthesis, characterization, charge carrier dynamics, and photoelectrochemical properties, Energy & Environmental Science, 5 (2012) 6682-6702.
[2] Y. Li, H. Wang, L. Xie, Y. Liang, G. Hong, H. Dai, MoS2 nanoparticles grown on graphene: an advanced catalyst for the hydrogen evolution reaction, Journal of the American Chemical Society, 133 (2011) 7296-7299.
9:00 PM - ES13.8.11
Silicon Nanoparticles-Conducting Hydrogel Composite Wrapped with Reduced Graphene Oxide as Anodes for Lithium-Ion Batteries
Changling Li 1 , Chueh Liu 1 , Zafer Mutlu 1 , Jeffrey Bell 1 , Rachel Ye 1 , Kazi Ahmed 1 , Mihri Ozkan 1 , Cengiz Ozkan 1
1 Materials Science Engineering, University of California, Riverside, Riverside, California, United States
Show AbstractHerein, silicon nanoparticles (SiNPs) coated with conducting hydrogel is wrapped with reduced graphene oxide sheets (rGO) via a facile and scalable solution-based sol-gel process. The in-situ polymerized polypyrrole (PPy) hydrogel forms an interconnected three-dimensional (3D) fiber matrix. Amine and hydroxyl groups from the hydrogel assist the encapsulation of the SiNPs through hydrogen bonding. The hierarchically porous PPy fiber network coupled with rGO sheets offer efficient electron and ion transport paths. The PPy/SiNPs/rGO electrodes can produce highly reversible capacities for long-term cycling. Hydrogel polymerization renders the Si anodes without resistive binders and carbon black. Of greater importance, this procedure requires low energy consumption, environmentally benign process, and economical doctor-blading to the industrial scale production of anode material.
9:00 PM - ES13.8.12
Using COMSOL to Study Electrochemical Dynamics at Electrode-Electrolyte Interface of a Lithium-Ion Electrode
Bo Dong 1 , Kazi Ahmed 1 , Yige Li 1 , Cengiz Ozkan 2 , Mihri Ozkan 1
1 Electrical and Computer Engineering, University of California, Riverside, Riverside, California, United States, 2 Mechanical Engineering, University of California, Riverside, Riverside, California, United States
Show AbstractLithium-ion battery models are ubiquitously significant across areas within research, development, and application. The models assist in characterizing distinct electrochemical phenomena within a cell and especially at interfaces, and in understanding ties between theoretical parameters and experimental observations. COMSOL is a powerful tool that allows the use of first principles to develop robust lithium-ion cell models that meet the above needs. In this poster, we make a demonstration of using COMSOL in battery modeling to understand interface dynamics. We build on established theories such as Fick’s law of diffusion, Butler-Volmer equation for electrochemical kinetics at interfaces, Ohm’s law, and conservation of charge law to design a lithium-ion battery model that will simulate experimental results.
9:00 PM - ES13.8.13
Efficient Nanostructured Brass for Water-Splitting Applications
Dina Eissa 1 , Nageh Allam 2
1 Physics and Chemistry, American University in Cairo, Cairo Egypt, 2 Physics, American University in Cairo, Cairo Egypt
Show Abstract
Unlike gasoline and coal, hydrogen is a non-toxic, green fuel. One of the ways to produce hydrogen is via water splitting. In this regard, a material that efficiently captures energy from the sun and splits water is needed. Brass is a promising material for such an application due to its stability and absorption in the visible region of the light spectrum. Both, zinc and copper oxides are used in many applications due to their favorable band gaps. They have been investigated independently and many progresses have been made. However, little research has been done on brass due to its challenging optimization. Herein, we combine the advantages of both zinc and copper oxides in one composite electrode. In this work, using controlled anodization at room temperature, we were able to produce nanoparticles and nanorods of Cu-Zn oxides which were characterized by multiple techniques such as XRD,XPS and raman. The fabricated nanostructures have been used to split water photoelectrochemically under AM 1.5 illumination. The affect of annealing time on the structure and the efficiency of the material has been investigated. The study shows very promising results towards visible light water splitting. Incident photon to current efficiency (IPCE) and current transients were conducted to understand the charge transfer and stability of such composite material. Mott-Schottky analysis was also used to calculate the density of charge carriers and the flat band potential.
9:00 PM - ES13.8.14
CeO2 Doped FeNx/C Catalyst with Enhanced Durability toward Oxygen Reduction Reaction
Jianguo Liu 1 , Zhigang Zou 1 , Congping Wu 1
1 , Nanjing University, Nanjing China
Show AbstractWe reported the solid phase polymerization of phenylenediamine with template toward the self-supported FeNx/C catalyst [1]. The morphology of poly-p-phenylenediamine(PpPD) changed from bulk to thin shell with the addition of ZnO nanoparticles, thus the Brunauer–Emmett–Teller surface area of PpPD-Fe-ZnO increased by 9 times. And rotating disc electrode tests in the O2-saturated 0.1 M HClO4 solution showed that the oxygen reduction activity of PpPD-Fe-ZnO was radically enhanced, to 21.9 A g-1 at 0.80 V (versus reversible hydrogen electrode).
However, the durability of PpPD-Fe-ZnO in 0.1 M HClO4 solution was not as good as its activity. As we known, CeO2 as free-radical scavengers could enhance the durability of Nafion membrane and catalyst [2]. Thus, CeO2 doped PpPD-Fe-ZnO catalyst was prepared. To evaluate the stability of catalyst, the accelerated durability test with cyclic voltammograms ranging from 0.6 V to 1.0 V at 100 mVs-1 in O2-saturated 0.1 M HClO4 were carried out. As shown in the following graph, slight change in half-wave potential (~25 mV) was observed after 1000 cycles, which indicated that the durability of CeO2 doped PpPD-Fe-ZnO was enhanced.
[1] X. Su, J. Liu, Y. Yao, Y. You, X. Zhang, C. Zhao, H. Wan, Y. Zhou, Z. Zou, Solid phase polymerization of phenylenediamine toward a self-supported FeNx/C catalyst with high oxygen reduction activity, Chemical Communications, 51 (2015) 16707-16709.
[2] Z. Wang, H. Tang, H. Zhang, M. Lei, R. Chen, P. Xiao, M. Pan, Synthesis of Nafion/CeO 2 hybrid for chemically durable proton exchange membrane of fuel cell, Journal of Membrane Science, 421 (2012) 201-210.
9:00 PM - ES13.8.15
Using In Situ Neutron Reflectometry to Study Solid-Electrolyte Interphase Formation in aSi and Sn Anode Materials
Jim Browning 1 , Joshua Kim 1 , Gabriel Veith 1 , Mathieu Doucet 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractInterfacial reactions between liquid electrolytes and electrode surfaces in energy storage devices are responsible for their long term behavior and may mediate certain safety concerns regarding unwanted oxidation/reduction of the electrolyte. These reactions occur when an aprotic electrolyte is reduced, or oxidized, on the surface of an electrode at a given potential forming the so called solid electrolyte interphase (SEI). These redox reactions form a passivating layer on the electrode surface that has been shown to be a mixture of inorganic and organic/polymeric species. A properly formed SEI prevents additional redox reactions from occurring and enables long term cycling. A poor SEI layer leads to safety issues, such as fires and gassing, as well as lifetime and power limitations due to consumption of electrolyte and the resistance of the SEI to both ionic and electronic transport. Understanding these reactions in situ is difficult since they occur at the liquid-solid interface of optically absorbing materials that hinder the use of traditional spectroscopic techniques. Furthermore, since some interfaces involve liquids it is necessary to use an analytical technique that can “see” through structural materials required to contain the liquid. Neutron reflectometry (NR) is a neutron scattering technique highly sensitive to morphological and compositional changes occurring across surfaces and interfaces, including buried interfaces and those occurring at the boundary between a liquid and a solid. Neutrons, by virtue of their nature, are deeply penetrating and therefore ideally suited as a probe to study materials in complicated environments, such as electrochemical cells. NR can be used to study thin film morphology and composition over broad lengths scales. We will present results of the application of NR to the study of SEI formation on the high-capacity anode materials of aSi and Sn as a function of charge, electrolyte and electrolyte additives.
9:00 PM - ES13.8.16
Controlled Crystallization of Cesium Lead Halide Perovskite Films on Modified TiO2 Surfaces for Photovoltaic Applications
Kara Saunders 1 , Brieanne Fessler 1 , Neal Armstrong 1
1 Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, United States
Show AbstractWe demonstrate how modification of TiO2 surfaces impact the morphology, and interfacial energetics of crystalline CsPbBrI2 perovskite films. Perovskite materials are gaining momentum as active layers for optoelectronic devices due to their cheap, solution-processable fabrication platform with power conversion efficiencies that rival crystalline silicon. Although the most studied perovskite for PV applications is methylammonium lead iodide, this material suffers greatly from instabilities, likely resulting from the volatile cation. Recent research is moving toward replacing methylammonium with a cesium cation, which affords increased stability while maintaining a favorable band gap of ca. 2.0 eV. However, there remains questions as to whether this material has compatible energetics with the electron selective layer, TiO2 and whether film growth can be controlled. We hypothesize that the nucleation free energy and the energetic offsets at the TiO2/perovskite interface significantly impacts photo-generated charge collection efficacy and that we are able to tune both properties using carboxylic acid self-assembled monolayers (SAMs) and adsorbed lead to modify the TiO2 surface. By atomic force microscopy, we observe no significant changes to the morphology of modified vs. unmodified TiO2, likely due to a negligible change in surface free energy. However, UPS data indicates the SAM induces an interfacial vacuum level shift, implying a change in the interface dipole thus affecting the work function of the TiO2. Furthermore, we introduce surface modification with lead ions that increase the crystallinity as seen by x-ray diffraction of the perovskite precursor lead iodide. Such results demonstrate a novel method to retain perovskite morphology and orientation while tuning the energetics for power-harvesting ability in perovskite devices.
9:00 PM - ES13.8.17
In Situ Characterization of ZnO Formation during Electrodeposition of Zn
Dian Yu 1 , Christine Orme 2 , Yixuan Yu 2 , Alexandra Golobic 2 , Suneel Kodambaka 1
1 , University of California Los Angeles, Los Angeles, California, United States, 2 , Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractOne of the challenges of developing rechargeable Zn-air batteries is the formation of unstable growth morphologies -- dendrites during charging cycles. The regained interest in understanding the formation of Zn dendrites has led to extensive studies on zinc electrodeposition in many geometries and chemical systems. Among various studies, the formation of ZnO was often proposed as a secondary effect observed during Zn electrodeposition due to pH shifts at the driven interface. For example, Hecker effect [1], reported as a morphological transition during Zn electrodeposition in thin layer geometry, was triggered by the formation of interfacial ZnO [2]. In the studies of oscillatory growth behavior during Zn electrodeposition, the alternating formation and breakdown of interfacial ZnO was suggested to pause and restart the Zn electrodeposition [3]. However, characterization of Zn and ZnO is challenging because they have similar hexagonal crystallographic structures and Zn easily converts to ZnO upon exposure to air. To gain a deeper understanding of the interplay between Zn and ZnO during the recharging cycle, we used three in situ techniques to monitor morphological evolution, structure, and growth rates.
In this work we used in situ electrochemical atomic force microscopy to image the growth of Zn and ZnO as a function of solution pH and to show that sharp thin ZnO platelets nucleate on blocky, faceted Zn crystals upon increasing the pH from 3 to 4. In situ wide angle X-ray scattering experiments was used to prove that Zn and ZnO co-electrodeposition occurred when the pH increased above 4. In situ electrochemical quartz crystal microbalance was used to distinguish chemical and electrochemical growth. These results revealed that ZnO was deposited due to the supersaturation of Zn(OH)2, induced by higher local concentration of OH- near the cathode surface. Together these in situ measurements provide direct information on the nucleation and growth of Zn and ZnO under conditions where multiple competitive processes occur. We find that even intermittent ZnO coatings can alter subsequent nucleation and growth of Zn suggesting a change in interfacial chemistry that persists even after ZnO dissolves.
This work was supported by National Science Foundation Grant 1310639 and Lawrence Livermore National Laboratory Directed Research and Development Program, 12-LW-030. Portions of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52- 07NA27344.
References
[1] Hecker, N. et al. Fractal Aspects of Materials. Materials Research Society, University Park, PA (1985).
[2] Kuhn, A. & Argoul, F. Spatiotemporal morphological transitions in thin-layer electrodeposition: The Hecker effect. Physical Review E 49, 4298 (1994).
[3] Wang, M. & Ming, N.b. Concentration field oscillation in front of a dendrite tip in electrochemical deposition. Physical Review A 45, 2493 (1992).
9:00 PM - ES13.8.18
Characterization of Lithium Batteries Electrodes Using Glow Discharge Optical Emission Spectrometry
Matthieu Chausseau 1 , Philippe Hunault 1 , Kayvon Savadkouei 1 , Patrick Chapon 2 , Sofia Gaiaschi 2
1 , HORIBA Scientific, Edison, New Jersey, United States, 2 , HORIBA Scientific, Palaiseau France
Show AbstractGlow Discharge Optical Emission Spectrometry (GD-OES) provides direct measurement of the chemical composition of materials as a function of depth, with nanometer resolution and the capability to measure both thin and thick layers.
It consists in a pulsed radiofrequency glow discharge plasma source that is sputtering a large area of the material of interest and real time detection by a high resolution optical spectrometer of the sputtered species excited by the same plasma. All elements from H to U can be measured using this technique.
The use of an advanced pulsed RF source allows the measurements of both conductive and non-conductive samples, addressing a wide range of applications for materials science.
Thanks to recent development, GD-OES can be applied to the characterization of Lithium batteries and can bring answers for the study of anode or cathode after charge and discharge cycles and also for the study of degraded electrodes and identification of its cause. One of the main interest of GD-OES is its ability to provide information from the surface but also from inside the layers as reactions on electrodes occurring inside the layer is non negligible.
The recent development making possible the analysis of Lithium batteries will be introduced and results obtained on Lithium batteries electrodes will be shown. The complementarity of GD-OES with other techniques such as SEM will also be presented.
9:00 PM - ES13.8.19
Study of Cuprate Thin Film Heterostructures Combining La2CuO4+δ and LaCuO3-δ for Fuel Cell Applications
Nicholas Prill 1 , Rodrigo Marmol 1 , Milad Audi 1 , Franklin Burquest 1 , Brittany Nelson-Cheeseman 1
1 , University of St. Thomas, Saint Paul, Minnesota, United States
Show AbstractCuprate materials have shown promise as fuel cell cathode materials for their electronic and ionic transport abilities. Both the layered perovskite, La2CuO4+δ, and its three-dimensional perovskite counterpart, LaCuO3-δ, demonstrate the simultaneous electronic and ionic conduction necessary for fuel cell cathode materials. The layered perovskite intercalates excess oxygen between the LaO/LaO double layers, allowing for two-dimensional oxygen interstitial diffusion through the material. Meanwhile, the 3D perovskite readily creates oxygen vacancies, allowing for three-dimensional oxygen vacancy diffusion through the material. In this work, we investigate thin film heterostructures created from these two disparate materials in order to understand how the local oxygen diffusion phenomena (interstitial vs. vacancy, 2D vs. 3D) affect the local structure and electrical transport of cuprates. The growth of these heterostructures is possible through the atomic monolayer control of Molecular Beam Epitaxy (MBE) with in-situ monitoring during growth via Reflection High Energy Electron Diffraction (RHEED). The crystal structure of the disparate phases is characterized by x-ray diffraction. X-ray reflectivity is used to characterize the film density, surface smoothness, and interface region between the two materials. A custom electrical transport system is used to characterize the sheet resistance of the films as a function of temperature to understand how the presence of the interface region affects the electrical transport. We directly compare these heterostructures with the single-phase films of La2CuO4+δ and LaCuO3-δ in order to understand how this heterostructuring may modify the structure and electrical properties of these materials.
9:00 PM - ES13.8.20
Selective Electrochemical Reactions on Superhydrophobic Plastron-Supporting Electrodes
Hamed Mehrabi 1 , Robert Coridan 1
1 , University of Arkansas, Fayetteville, Arkansas, United States
Show AbstractAn electrochemical route for the conversion of gas-phase reactions would be advantageous over conventional chemical reactors. Electrochemical processes are generally more efficient, selective, and cost-effective, though it is difficult to design heterogeneous electrodes specific to gas-phase reactants. Gas-phase electrolytic reactors require high pressure and the application of impractically large bias potentials to drive electrocatalysis. Liquid-phase electrochemical cells dramatically improve conductivity, but low gas solubility and competing electrolytic processes make catalysis of gas-phase reactants difficult in liquid cells. Here, we describe an electrode design that is inspired by natural hydrophobic surfaces that overcome the same problem. To avoid water entering their respiratory system, some water dwelling insects use an array of hydrophobic hairs that traps air between the body and the surrounding water which is known as a plastron layer. The partial pressure gradient of gases inside the plastron due to respiration results in a net flux of depleted gases into the plastron and maintaining a constant partial pressure of oxygen even under water. In this sense, a plastrons acts as a physical gill. Plastron-supporting electrodes take advantage of the physics of surface tension to increase the effective concentration of the desired reactants while maintaining an efficient electrochemical process. The aim of this research is to prepare a favorable, plastron-supporting hydrophobic surface over electrocatalytic layers to inhibit electrochemical reactions with the electrolyte, such as hydrogen evolution and water oxidation, while being able to perform other redox reactions. We describe analytical and electrochemical experiments for controlling liquid-phase (hydrogen evolution, water oxidation) and volatile-molecule gas phase (methanol oxidation) reactions on lithographically-patterned, plastron supporting electrodes. The results indicate a clear difference between electrodes that can support a plastron and ones that cannot, suggesting that this design can be useful in developing hybrid gas-liquid phase electrochemical reactors.
9:00 PM - ES13.8.21
Nanoscale Surface Evolution in Li-Rich Mn-Rich Layered Oxide Cathodes
Chengcheng Fang 1
1 , University of California, San Diego, La Jolla, California, United States
Show AbstractAs the capacity-determining component of lithium ion batteries, cathode materials have been extensively studied to gain higher energy density and longer cycle life. Among all cathodes, lithium-rich layered oxide compounds, xLi2MnO3 (1 − x)LiMO2 (M = Ni, Mn, and Co), have been considered as a promising next-generation cathode candidate, as they can deliver reversible discharge capacity over 280 mAh g-1 with an average voltage of 4 V vs. Li/Li+ when cycled between 2 – 4.8 V. Surface properties influence electrochemical behaviors significantly. In the present work, scanning transmission electron microscopy and electron energy loss spectroscopy (STEM/EELS), X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectroscopy (XAS) have been utilized to systematically study the detailed surface oxygen and transition metal (TM) ions evolution at different state of charge during the first cycle of the Li-rich Mn-rich layered oxide Li7/6Ni1/6Mn1/2Co1/6O2. XPS analysis reveals surface Ni and Co ions are slightly reduced during plateau region due to oxygen oxidation; low coordinated oxygen is found start from 4.0 V, along with the extraction of Li ions upon charging; in plateau region, both low coordinated oxygen and peroxo-like species (O2n-) present. STEM-EELS results after the first cycle indicate the reduction of Mn ions and oxygen local environment change within 2 nm on the surface.
9:00 PM - ES13.8.22
Microscopic Origin of High Open Circuit Voltage in Solid State Dye Solar Cells with Polymer Electrolyte
Tea-Yon Kim 1 , Yong Soo Kang 1
1 , Hanyang Univ, Seoul Korea (the Republic of)
Show AbstractHerein, the energy level alignment and electron recombination kinetics in solid state dye-sensitized solar cells (DSCs) employing a solid polymer electrolyte (SPE) have been quantitatively characterized. In order to determine the microscopic origin of the enhanced characteristics in polymer electrolytes, we carried out an extensive study of the photovoltaic properties with respect to the electrolyte type and composition, including a liquid electrolyte (LE) and various salt types and concentrations. We observed a smaller downward shift in the conduction band energy of the TiO2 layer upon contact with the SPE as well as a retarded electron recombination rate. These led to an increase in the Voc for DSCs with an SPE, which is mostly attributable to the coordinative interactions of the ethylene oxide (EO) units in poly(ethylene oxide) (PEO) and poly(ethylene glycol) dimethyl ether (PEGDME) with metallic Li+ ions and Ti atoms. Such coordinative interactions induce 1) the capture of Li+ cations in the bulk of the polymer electrolyte, thereby reducing their effective concentration and 2) the facile formation of a PEO passivation layer on top of the TiO2 layer. Therefore, it was concluded that the high Voc in solid state DSCs employing a polymer electrolyte is attributable to the coordinative properties of the EO units in PEO and PEGDME in the SPE.
9:00 PM - ES13.8.23
Lithiation Mechanism and Lithium Storage Capacity of Reduced Graphene Oxide Nanoribbons—A First-Principles Study
Chin-Lung Kuo 1
1 , National Taiwan University, Taipei Taiwan
Show AbstractWe employed first-principles calculations to investigate the lithiation mechanisms of functionalized graphene nanoribbons (GNRs) and to examine the effect of various functional groups on the electrochemical performance of graphene-based nanomaterials. In this work, we have extensively explored the Li storage behaviors of various types of functional groups located on the basal plane and those terminating the edge sites within different levels of lithiation and functionalization on GNRs. For functional groups terminating the edge sites, only ketone and its related derivatives (pyrone/quinone) can effectively enhance Li adsorption on GNRs, and the most favorable sites for Li adsorption turn out to be these edged-oxidized groups rather than the hollow sites on the basal plane. In addition, as the ketone-terminated GNRs were fully lithiated, the Li/O atomic ratio was found to be ~1.0 and that for the ketone-ether pair (pyrone) was ~0.5, indicating that these edge-oxidized groups can effectively enhance the Li capacity of GNRs as compared with that of graphite (Li1/6C). As regards the in-plane functional groups, the epoxy and hydroxyl groups were shown to have multiple Li uptakes on the basal plane and appeared to serve as the nucleation centers for Li clustering, thereby resulting in the great enhancement of the Li capacity of GNRs. Our calculations showed that the achievable Li/O atomic ratio was 4 for the epoxy group (Li4O pyramid cluster) and 3 for the hydroxyl group (Li3(OH) cluster), respectively, which suggest that these in-plane functional groups can be more effective in enhancing the Li storage capacity than those terminating the edge sites of graphene-based nanomaterials.
9:00 PM - ES13.8.24
Surface and Interface Engineering of Lithium Metal Anodes for Next Generation Secondary Batteries
Taner Zerrin 1 , Jeffrey Bell 1 , Rachel Ye 1 , Zafer Mutlu 1 , Cengiz Ozkan 1 , Mihri Ozkan 1
1 , University of California Riverside, Riverside, California, United States
Show AbstractSolving the menacing energy and environmental issues require rechargeable batteries with high energy densities. A lot of research has been carried out on finding new anode materials to improve the lithium storage capability of Li-ion batteries. Also, lithium-sulfur batteries have attracted attention recently for their extremely high capacity. So as to meet the growing demand for rechargeable batteries with higher power and energy densities, advancements in electrochemical performance of Li metal anode is extremely urgent. However, two main problems still remain to be solved. One is a low cycling efficiency due to the activity of Li and its reaction with electrolyte. The other one is the formation of dendritic lithium between the anode and electrolyte which may lead to the safety problems. Herein, we present an approach to form protective amorphous carbon films on the surface of metallic Li using sputtering technique which is very suitable for industrial production. The effects of sputtering gas pressure and film thickness on the electrochemical properties of Li/C anodes are studied in detail. The surface morphologies of the coatings are observed using scanning electron microscopy and the bonding structure of coatings is characterized by X-ray photoelectron spectroscopy. The coatings on Li surface can prevent the contact between the metallic Li and electrolyte efficiently, thus suppressing the formation of dendritic lithium. By controlling the sputtering pressure and thickness of the coatings, Li/C electrodes can be optimized for an enhanced electrochemical performance.
9:00 PM - ES13.8.25
Pushing the Cycling Stability Limit of Polypyrrole for Supercapacitors
Tianyu Liu 1 , Yu Song 2 1 , Yat Li 1 , Xiaoxia Liu 2
1 , University of California, Santa Cruz, Santa Cruz, California, United States, 2 Chemistry, Northeastern University, Shenyang China
Show AbstractPolypyrrole (PPy) is a promising pseudocapacitive material for supercapacitor electrodes. However, its poor cycling stability is the major hurdle for its practical applications. Previous studies have demonstrated that two major factors lead to such instability, namely the structural pulverization and the counter-ion drain effect. In this presentation I will introduce a two-prong strategy to effectively stabilize PPy film by growing it on a functionalized partial-exfoliated graphite (FEG) substrate as well as doping it with β-naphthalene sulfonate anions (NS-). Our PPy electrode achieved a remarkable capacitance retention rate of 97.5% for 10000 cycles, much higher than other conventional PPy films (fast degradation after 1000 cycles). Moreover, an asymmetric pseudocapacitor using the stabilized PPy film as anode also retained 97% of capacitance after 10000 cycles, which is an exceptional value reported for PPy based supercapacitors. The outstanding stability of PPy electrode can be attributed to two reasons: 1) the flexible nature of FEG substrate accommodates large volumetric deformation and alleviate structural alternation and 2) the presence of immobile NS- dopants suppresses the counter-ion drain effect during charge-discharge cycles.
9:00 PM - ES13.8.26
Nanopores Reveal Interface and Mesoscale Ion Transport Properties of LiClO4-PMMA Gel
Timothy Plett 1 , Wenjia Cai 1 , Mya Le 1 , Reginald Penner 1 , Zuzanna Siwy 1
1 , University of California, Irvine, Irvine, California, United States
Show AbstractEnergy storage technologies are required to balance trade-offs in energy density, power density, size, cyclability, cost, etc. to fit different demands in market and industry applications. A move from liquid to solid-state electrolytes offers some advantages, especially in terms of stability and cyclability, demonstrated in an ACS Nano paper by Le Thai et al. They fabricated a system of ultra-long, δ-phase MnO2 mesowires which demonstrated stable capacitance over 100k cycles in a LiClO4-PMMA gel electrolyte. While the bulk properties of the LiClO4-PMMA are well-studied in the bulk, nanopores introduce interesting and novel effects which can be considered for ion transport in mesowire systems. We present here experiments with LiClO4-PMMA gel in polymer nanopore systems which reveal interesting interface and transport properties of LiClO4-PMMA at the mesoscale. Firstly, we demonstrate bulk ion transport behavior in sub-micron conditions, as well as confirm information about ionic and electronic transference in LiClO4-PMMA. Secondly, we report the rectifying behavior of LiClO4-PMMA gel in conical nanopores and confirm that it is a property of its ion transport, also demonstrating, to our knowledge, the first fully solid-state ionic rectifier. Thirdly, we identify unusual interface properties of LiClO4-PMMA gel when it is in contact with a compatible liquid electrolyte (i.e. LiClO4-Propylene Carbonate) both at macro- and nanoscale, namely a statistically absent (n = 15) energy barrier existing between the gel and liquid electrolytes. We consider many of these observations to be a result of intrinsic properties in the gel and its composition, but the nanopore environment serves to more clearly identify these effects.
9:00 PM - ES13.8.28
Template-Free Synthesis of N, P and S Ternary-Doped 3D Aerogel of Graphene-Based Carbon as Excellent Electrocatalyst for the Oxygen Reduction Reaction
Md. Selim Arif Sher Shah 2 , Jooyoung Lee 1 , Byungkwon Lim 1 , Pil Jin Yoo 2 3 , Kyungwha Chung 2
2 School of Chemical Engineering, Sungkyunkwan University, Suwon Korea (the Republic of), 1 School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon Korea (the Republic of), 3 SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon Korea (the Republic of)
Show AbstractThe oxygen reduction reaction (ORR) at cathode is the most important electrochemical process occurs in practical realization of green energy conversion systems like, fuel cells and rechargeable metal-air batteries. The state-of-the-art electrocatalyst for ORR is Pt, which suffers from high cost, scarcity and stability against fuel cross-over and CO tolerance. Heteroatom, especially nitrogen, doped carbon-based materials, which are inexpensive, durable and methanol-tolerant, are highly attractive electrocatalysts to replace Pt-based catalysts. These catalysts, however, show low activity and poor stability due to low electrical conductivity of carbon. In the present contribution, we developed a simple, template-free and cost-effective approach to synthesize three dimensional (3D) aerogel of N, P and S ternary-doped graphene-based carbon.Ternary doping increased the overall concentration of dopants. Mporeover, the optimal electrocatalyst showed interconnected mesopores with high pore volume and specific surface area of 0.84 cc g-1 and 1107 m2 g-1, respectively. Owing to these properties, the electrocatalyst displayed excellent electrocatalytic activity for the ORR via a four-electron pathway with onset potential at 0.97 V (vs. RHE, reversible hydrogen electrode) which was more positive than the commercial electrocatalyst Pt/C having onset potential of 0.95 V. As a result, it exhibited a current density of -0.76 mA cm-2 against that of -0.33 mA cm-2 displayed by the Pt/C catalyst at 0.9 V. Moreover, the catalyst demonstrated excellent current retention than the Pt/C electrocatalyst at 0.9 V. We anticipate that the present work will open up new arenas for the easy, scalable and template-free synthesis of multi-heteroatom doped graphene-based carbon materials which will find applications as electrocatalysts in renewable energy sources.
9:00 PM - ES13.8.29
Alkali Metal Fullerides—Applications in Electrochemical Energy Storage
Kurumi Austin 1 , Tony Jefferson Gnanaprakasa 1 , Palash Gangopadhyay 2 , Krishna Muralidharan 1
1 Department of Materials Science and Engineering, The University of Arizona, Tucson, Arizona, United States, 2 College of Optical Sciences, The University of Arizona, Tucson, Arizona, United States
Show AbstractAlkali metal fullerides have been demonstrated to exhibit superionic conductivity. This property has triggered interest in the use of alkali metal fullerides as electrode/solid-state electrolytes for electrochemical energy storage. Alkali metal ions occupy octahedral or tetrahedral sites within the fulleride fcc structure and provide an electron to the fulleride lattice. The presence of the alkali metal ions within the lattice allows for easy activation of these carbon-based nanomaterials by creating continuous channels for facile ionic conduction. In this context, the ionic conductivity of lithium ions through lithium fulleride structures was investigated with the goal of using this system as a solid state electrolyte for lithium ion batteries. The underlying structural characteristics that underlie the ionic conductivity properties were also examined. Raman spectroscopy revealed a shift in the Ag mode from 1465.53 cm-1 to 1459.3 cm-1, which is attributed to the inclusion of lithium ion and to the resulting alteration of the structure of the fullerene crystal lattice. Formation of lithium fulleride also shifts the [111] diffraction peak of C60 to significantly lower 2θ, indicating an increase in the d-spacing. The development of these alkali metal fulleride materials may provide a safer, and more efficient alternative to current solid-state electrolyte technologies, while further progressing the fundamental science behind using C60 based nanomaterials for supercapacitors, lithium ion batteries, and photonic applications.
9:00 PM - ES13.8.30
All-Solid-State Batteries Based on Nanocrystalline LiBH4
Marlena Uitz 1 , Stefan Breuer 1 , Corina Taeubert 2 , Volker Hennige 2 , Martin Wilkening 1
1 , Graz University of Technology, CD-Laboratory for Lithium Batteries, Graz Austria, 2 , AVL List GmbH, Graz Austria
Show AbstractLi (ion) batteries with solid electrolytes such as oxidic or sulfidic ceramics are regarded as intrinsically safe; they are expected to offer a long cycle life with stable capacity retention. Compared to systems with liquid electrolytes such systems may, however, suffer from low discharge rates due to large inner resistances especially at the macroscopic interfaces. Moreover, mechanical instability and yet unknown methods of large-scale production may delay their availability. Over the last couple of years we have witnessed an impressive progress in developing highly conducting solids [1]. The materials presented so far are single ion conductors with room-temperature conductivities in some cases, particularly if sulfides are considered, reaching values known for conventional liquid, but flammable electrolytes, see, e.g., [2].
Here, we investigated the suitability of LiBH4-based solid electrolytes [3] that were mechanically treated in high-energy ball mills to obtain fine powders that can be cold-pressed to fabricate the Li|LiBH4|Li4Ti5O12 cells. At room temperature LiBH4 crystallizes with orthorhombic structure, at elevated T, however, it transforrms into the highly conducting hexagonal, layer-structured polymorph [4,5]. The latter form can be stabilized through incorporation of large iodine anions leading to nanocrystalline LiBH4:LiI composites. We carried out cyclic voltammetry, galvanostatic cycling at different discharge rates, impedance measurements as well as polarization experiments to understand electrochemical stability, possible self-discharge processes and long-term cycling behavior. First results show that the battery withstands temperatures as high as 390 K operating at reversible discharge capacities in the order of 110 mAh/g being an encouraging value if the theoretical capacity of the cathode material Li4Ti5O12 (ca. 170 mAh/g) is considered. Beside LTO we tested the compatibility of other active materials such as graphite and rutile nanorods.
[1] J. C. Bachmann et al. Chem. Rev. 116 (2016) 140.
[2] N. Kamaya et al. Nature Mater. 10 (2011) 682; V. Epp, O. Gün, H.-J. Deiseroth, M. Wilkening, J. Phys. Chem. Lett., 4 (2013) 2118; Y. Seino et al. Energy Environ. Sci. 7 (2014) 627.
[3] Sveinbjörnsson, D., et al., Journal of the Electrochemical Society, (2014). 161(9): p. A1432-A1439.
[4] H. Maekawa et al. J. Am. Chem. Soc. 131 (2009) 894.
[5] V. Epp and M. Wilkening, Phys. Rev. B 82 (2010) 020301; V. Epp, M. Wilkening, ChemPhysChem 14 (2013) 3706.
9:00 PM - ES13.8.31
Lower Symmetry Bimetallic (Co & Fe) Corrole N4 as an Efficient Electrocatalyst for Oxygen Reduction Reaction
Satyanarayana Samireddi 2 3 , Indrajit Shown 2 , Ken-Tsung Wong 4 , Li-Chyong Chen 1 , Kuei-Hsien Chen 2
2 Institute of Atomic and Molecular Science, Academia Sinica, Taipei Taiwan, 3 Chemistry, National Tsing Hua University, Taipei Taiwan, 4 Chemistry, National Taiwan University, Taipei Taiwan, 1 Center For Condensed Matter Science, National Taiwan University, Taipei Taiwan
Show AbstractThe limited natural abundance, high cost and carbon monoxide deactivation of Pt and other noble metals possess a major barrier in its applications for hydrogen fuel cells and therefore; development of alternative electrocatalytic materials based on non-precious metal-N4 is a key challenge in the current growing demand for the clean-energy fuel cell research. In this regard, in our group, a new cobalt-corrole molecule functionalized with ferrocene has been successfully synthesized with structural confirmation from UV-Vis, NMR and HR-Mass spectroscopic studies. The lower symmetric nature was confirmed by obtaining single crystal X-ray diffraction data and explained with structural orientation of the atoms and attached moieties. Furthermore, this molecule mixed with activated carbon was pyrolyzed at different temperatures and among the resulting electrocatalysts, particularly at 500 °C was shown to be performed as promising ORR active behavior. The unique Co-corrole integrated with mono substituted peripheral Fe complex in its pyrolyzed form provides a bimetallic (Co and Fe) active center and facilitates the ORR via a 4-electron pathway. The optimized catalyst exhibits higher electron transfer number 3.92 for ORR in acidic medium with better stability, which is superior to the previously reported pyrolyzed Co-corroles. The enhancement of the ORR activity of this well characterized bimetallic N4 macrocyclic complex provides a new prospect for the next-generation of non-precious metal-N4 electrocatalysts for fuel cell application. In this presentation, I will talk more in detail of the electrochemical experimental process of the catalyst and its characterization using different analytical techniques.
9:00 PM - ES13.8.32
Improved Ionic Conductivity in NASICON-Type Sr2+ Doped LiZr2(PO4)3
Sunil Kumar 1 , Palani Balaya 2
1 , Indian Institute of Technology Indore, Indore India, 2 , National University of Singapore, Singapore Singapore
Show AbstractLithium ion conducting Li1+2xZr2-xSrx(PO4)3 with x = 0 - 0.2 were synthesized via a sol-gel method using citric acid. The effects of Sr2+ substitution on the structure, microstructure, and conductivity of LiZr2(PO4)3 ceramics were studied. Rietveld refinement of powder XRD patterns showed that 5% of Sr2+ substitution for Zr4+ in LiZr2(PO4)3 stabilizes the rhombohedral (space group R-3c) phase at room temperature. Sr2+ doped LiZr2(PO4)3 samples exhibited significantly improved ionic conductivity with Li1.2Zr1.9Sr0.1(PO4)3 showing highest conductivity of 0.34 x 10-4 ohm-1cm-1 at room temperature. Activation energy was found to decrease from 0.56 eV for LiZr2(PO4)3 to 0.40 eV for Li1.4Zr1.8Sr0.2(PO4)3. Li+ transference number determined by DC polarization for Li1.2Zr1.9Sr0.1(PO4)3 was close to 1 confirming the ionic nature of conductivity.
9:00 PM - ES13.8.33
Molecular Ni-Complex Containing Tetrahedral Nickel Selenide Core as Highly Efficient Electrocatalyst for Oxygen Evolution Reaction in Alkaline Medium
Manashi Nath 1 , Jahangir Masud 1 , Panayotis Kyritsis 2
1 , Missouri University of Science and Technology, Rolla, Missouri, United States, 2 Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens, Greece
Show AbstractRecently transition metal selenides have shown high efficiency towards water oxidation in alkaline medium outperforming some of the conventional precious metal-based and transition metal oxides. In spite of their high activity, there is still a doubt about the nature of the actual catalytically active species. In this presentation we will address this issue and will offer proof about the highly efficient intrinsic catalytic activity of nickel selenides by studying the electrochemical activity of a pure, crystalline, seleno-based molecular complex containing a NiSe4 core. Accordingly, we will present the highly efficient catalytic activity of Ni-selenide-based coordination complex, [Ni{(SePiPr2)2N}2], for oxygen evolution and hydrogen evolution reactions (OER and HER, respectively) in alkaline solution. This molecular complex has similar coordination around the Ni atom as is found in several Ni-selenides. But on the contrary, since these are pure crystalline molecular complexes, there is limited or no propensity to form surface metal oxides. Apart from proving the intrinsic catalytic activity of the selenides, another motivation behind using such seleno-based transition metal complexes is that they frequently exhibit coordination expansion due to ligation of solvent or other molecules, and such a phenomenon will be very useful for the catalytic pathway, which typically is initiated by hydroxide coordination to the transition metal site. Using this complex as catalyst at the respective electrode, very low overpotentials of 200 mV and 310 mV were required to achieve 10 mA/cm2 for OER and HER, respectively. The overpotential for OER is one of the lowest that has been reported up to now, making this one of the best OER electrocatalysts. In addition, this molecular complex exhibits an exceptionally high gravimetric current density (111.02 Ag-1) and a much higher TOF value (0.26 s-1) at a overpotential of 300 mV. Such high mass activity highlights the practical usefulness of this catalyst by reducing the amount of active material required, without compromising performance. A full water electrolysis could be achieved by coating this bifunctional catalyst at both the cathode and the anode with this catalyst, achieving a current density of 10 mA/cm2 at 1.75 V. The enhanced OER catalytic activity is attributed to the increased covalency of the metal–chalcogen bond, which decreases the Ni(II) to Ni(III) oxidation potential compared to that of nickel oxides, thereby enhancing catalyst performance. We will present the detailed studies including electrochemical characterization, structural and compositional details of this catalyst and focus on the stability of the catalyst composition under conditions of OER and HER. An important insight that we have acquired through this study is that the surface of the selenide electrocatalysts can be described as a hydroxylated surface as opposed to an oxide-coated surface.
9:00 PM - ES13.8.34
Novel Battery Architecture for Next Generation Lithium Ion Battery Materials Based on Sulfur and Silicon Utilizing Smart Lithium Placement
Rachel Ye 1 , Jeffrey Bell 1 , Kazi Ahmed 1 , Leon Peng 1 , Andrew Scott 1 , Daisy Patino 1 , Mihri Ozkan 1 , Cengiz Ozkan 1
1 , University of California, Riverside, Riverside, California, United States
Show AbstractWith an increase in demand for longer lasting batteries, researchers have turned towards sulfur-based batteries owing to its high energy density, low cost, and abundance of material. Current lithium-ion batteries rely on the cathode as the lithium source for the system. This poses a problem for sulfur-based batteries since the only lithiated sulfur material is lithium sulfide, which is extremely hazardous and difficult to use. As a result, most research examines cells consisting of a sulfur cathode countered by lithium foil. This cannot be scaled to industry due to the numerous issues of having a pure lithium as a counter electrode. Here we present a novel battery architecture synthesized through smart electrode placement that addresses the aforementioned issues. The novel battery architecture utilizes smart electrode placement with a lithium source to bypass problems that currently inhibit advancement of sulfur and silicon-based full-cells. This promising novel battery architecture shows stable formation of the solid electrolyte interface along with several cycles at a high energy density.
Symposium Organizers
Yuyan Shao, Pacific Northwest National Laboratory
David Mitlin, Clarkson University
Jin Suntivich, Cornell University
Lynn Trahey, Argonne National Laboratory
Symposium Support
Army Research Office
ES13.9: Interfaces/Interphases—Characterization/Simulation
Session Chairs
Friday AM, April 21, 2017
PCC North, 200 Level, Room 227 AB
9:15 AM - *ES13.9.01
In Situ and Operando Investigations of Electrochemical Interfaces Using Ambient Pressure XPS
Ethan Crumlin 1 2
1 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Joint Center for Energy Storage Research, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractInterfaces play an important role in nearly all aspects of life, and are essential for electrochemistry. Electrochemical systems ranging from high temperature solid oxide fuel cells (SOFC) to batteries to capacitors have a wide range of important interfaces between solids, liquids, and gases which play a pivotal role in how energy is stored, transferred, and/or converted. The ability to study these interfaces has proven to be difficult and is only further exacerbated by the limited number of techniques capable of operating under in situ/operando environments. To overcome these challenges, we use in situ/operando ambient pressure X-ray Photoelectron Spectroscopy (APXPS). APXPS is a photon-in/electron-out process that can provide both atomic concentration and chemical specific information at pressures greater then 20 Torr. Using synchrotron X-rays at Lawrence Berkeley Nation Laboratory, the Advanced Light Source has several beamlines dedicated to APXPS endstations that are outfitted with various in situ/operando features such as heating to temperatures > 500 °C, pressures greater then 20 Torr to support solid/liquid experiments and electrical leads to support applying electrical potentials supports the ability to collect XPS data of actual electrochemical devices while its operating in near ambient pressures. This talk will introduce this technique and provide several solid/gas and solid/liquid interface electrochemistry examples using operando APXPS including solid-state Li-air batteries, magnesium metal anode surface chemistry, and the ability to probe the electrochemical double layer (EDL). Gaining new insight to guide the design and control of future electrochemical interfaces.
9:45 AM - ES13.9.02
Structures at the Solid–Ionic Liquid Interface—A Complementary X-Ray Reflectivity and Molecular Dynamics Approach
Andreas Magerl 1 , Michael Klimczak 1 , Zlatko Brkljaca 1 , Ana-Suncana Smith 1 , David Smith 1
1 , University of Erlangen-Nurnberg, Erlangen Germany
Show AbstractWhile known for more than a century, ionic liquids – commonly defined as salts with a melting point around or below room temperature – have only become a staple in science during the last quindecinnial. It is their unique properties including a large electrochemical window and negligible vapor pressure, that makes these substances particularly interesting for the development of novel applications including, among others, catalysis, lubrication and, most notably, electrochemistry. While downsizing technology in an attempt to build smaller, yet more powerful devices, interface effects start to become more and more dominant in these systems and a sound understanding of occurring structural phenomena is a prerequisite for engineering applications.
In a complementary approach, combining experimental X-ray reflectivity data and atomistic simulation we study the behaviour of an archetypical family of protic ionic liquids, dialkylimidiazolium–bis(trifluormethylsulfonyl)imide ([CnMIm][NTf2]), at the sapphire (001)–liquid interface. X-ray reflectivity (XRR) allows us to reveal an interface-normal layering profile of the buried solid–ionic liquid interface. We report a strong excess of cations at the interface, followed by alternating anion/cation layers, slowly decaying towards the bulk over a region of about 40 Å. Moreover, the experimental data can be employed to parametrize and verify force fields used in our molecular dynamics simulations (MD). Reaching a good agreement between XRR and MD puts us in a position to extract reliable information on an atomic level that is otherwise inaccessible by the experiment alone. We find that both cations and anions in the vicinity of the substrate tend to assume a very specific orientation/conformation, enabling them to efficiently form hydrogen bonding with the substrate. The anions remaining close to the interface take a well-defined lateral order, intercalating the network of cations.
Acknowledgement
Work supported by the DFG Research Unit 1878 funCOS - Functional Molecular Structures on Complex Oxide Surfaces
10:00 AM - ES13.9.03
Ultrasensitive Probing of Local Electronic Structure in the Soft X-Ray Regime
Dennis Nordlund 1
1 , SLAC National Accelerator Laboratory, Menlo Park, California, United States
Show AbstractWe are interested in the applicability and potential transformative impact of ultra-sensitive soft x-ray spectroscopy to map out the local electronic structure of reactants, intermediates, and products in chemical reactions. There is a need to go beyond current limitations in detection technology that can measure below 10% of a monolayer and see reactants/intermediates/products below 10mM in solution, which is close to current detection limitations.
We have recently commissioned a transition edge sensor (TES) based spectrometer at Stanford Synchrotron Radiation Laboratory (SSRL) that has the ability to explore new paradigms in soft x-ray spectroscopy, achieving sensitivity of sub-mMol concentrations in aqueous/organic solvents, sub-percent sensitivity for monolayer films immersed in a solvent, solid matrix, or high-pressure gas, and sensitivity to concentrations <1019/cm3 for defects and dopants in condensed phase samples.
We will demonstrate the ability of our TES based setup to probe carbon and nitrogen (e.g. CO2 and N2) dissolved in aqueous solutions, nitrogen detection below 1% of a monolayer, as well as preliminary results from gas-phase catalytic reduction. The prospects for soft x-ray spectroscopy to follow chemical reactions at complimentary timescales under realistic conditions will be discussed.
10:15 AM - ES13.9.04
Ultrafast Current-Voltage Measurements in Scanning Probe Microscopy
Suhas Somnath 1 , Stephen Jesse 1 , Sergei Kalinin 1 , Rama Vasudevan 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractThe acquisition of local current-voltage (I-V) measurements using scanning probe microscopes (SPMs) is one of the earliest and most popular spectroscopies used for electrochemical characterization of materials. These techniques have allowed an enormous number of electronic phenomena to be measured and correlated to individual features of the sample, such as grain boundaries, domain walls, phase boundaries, and in the case of STM, individual atoms and molecules. In general, the waveform used by I-V techniques use a sequence of DC pulses whose amplitude is modulated by a bipolar triangular envelope (~ 1 – 5 Hz). At each DC pulse, the current is measured either through the tip or the sample using a lock-in amplifier. Currently, the integration time of the lock-in-amplifier (> 1 msec) limits the speed at which the IV curve is measured at each location. Thus, I-V measurements over a spatial grid of points using the state-of-art techniques are acquired over few hours. Such long durations typically result in significant spatial drift in the measurements and also result in undesirable compromises in the measurement area, density of the spatial grid, voltage and spatial resolutions.
Here, we show that it is possible (under certain conditions) to acquire I-V curves at two orders of magnitude faster rates, by capturing the current response from a sinusoidal excitation at ~200-600Hz. The technique is demonstrated by I-V measurements acquired during scanning of ultrathin films of LaMnO3 in ultrahigh vacuum, yielding more than 100,000 I-V curves in less than 10 minutes. We use adaptive signal filtering to identify and reject noise components. k-means clustering of the data allows identification and subtraction of low current regions, dramatically reducing the influence of the capacitive current contribution to the measured signal. This technique facilitates increased the spatial and temporal resolution of current I-V measurement protocols in some cases, and has substantial implications for both atomic force microscopy and scanning tunneling spectroscopy.
10:30 AM - ES13.9.05
Enabling Local Electrochemistry with Fast, High-Resolution Scanning Probe Microscopy
Nathan Kirchhofer 1 , Irene Revenko 1 , Roger Proksch 1
1 , Asylum Research, Goleta, California, United States
Show AbstractDue to its exceptional sensitivity, scanning probe microscopy (SPM) enables detailed interrogation of surfaces and interfaces. However, when correlating spatial information to additional scanning probe surface measurements (such as force, electrical potential or conductivity, impedance, thermal mapping, viscoelastic parameters, redox activity, and more), spatial resolution is often limited. Here, we present the development and demonstrate the utility of an Electrochemical (EC) Cell comprised of a sample mount, probe, potentiostat, and electrodes that is employed on a high-resolution, fast scanning Cypher ES atomic force microscope (AFM) in different measurement modes. This EC-Cell enables detailed characterization of localized, electrochemically-controlled morphologies without sacrifices to spatial resolution. These EC-AFM measurements bear on the continued development of various metrologies such as electrochemical scanning tunneling microscopy (EC-STM), scanning electrochemical microscopy (SECM), electrochemical strain microscopy (ESM), and more, and relevant results are presented.
11:15 AM - *ES13.9.06
Understanding the Nature of Chemical and Electrochemical Stability of Electrolytes at Mg Anode Surfaces
David Prendergast 1 , Artem Baskin 1
1 , Lawrence Berkeley National Lab, Berkeley, California, United States
Show AbstractThe fundamental bottlenecks to advancement of new battery technologies, such as multivalent ion, are intimately connected to the nature of the electrochemical interfaces involved. Knowing molecular and atomic scale details of these interfaces is vital to reveal the mechanisms of any unwanted chemistry or electorchemistry that can reduce Coulombic efficiency. Furthermore, in the context of multivalent anions, such as magnesium, the small ionic radius and high charge generally enhance coordination - either by anions or solvent - which can lead to unexpected and detrimental chemistry. We explore such effects using first-principles density functional theory calculations in the context of Mg ions, complex anions, in aprotic solvents, in the vicinity of the Mg anode. Our results highlight the surprising chemical role of impurities at the interface in addition to intrinsic reductive instability of coordination complexes near the anode surface.
11:45 AM - *ES13.9.07
Modeling Spatial Heterogeneity and Potential Effects at Battery Reactive Anode/SEI Interfaces
Kevin Leung 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractSolid-solid interfaces are ubiquitous in lithium ion batteries (LIB). Even liquid organic carbonate electrolyte-based LIB form "solid electrolyte interphase" (SEI) films on the anode surface. The SEI passivates the anode; structural defects that permit electron transfer through the SEI are detrimental to battery operations and lifetimes. It is challenging to conduct atomic lengthscale resolution imaging of the buried solid-solid interfaces between the active anode material and the innermost inorganic SEI components. A similar challenge exists in studies of anode-solid electrolyte interfaces. Atomic lengthscale modeling work can yield insights and help frame the relevant science questions that need to be addressed in this area. In this presentation, we focus on spatial heterogeneities at anode/SEI interfaces, and apply electronic structure calculations to elucidate the atomic structure and properties of defects (such as grain boundaries and cracks) in stable SEI inorganic components found on reactive anode surfaces. The possible existence of electron conduction pathways through such defects is examined. The effects of potentials are also examined by adjusting the applied voltage of model interfaces under ultrahigh vacuum conditions. We demonstrate that "local potential" arising from surface inhomogeneities can affect the passivation function of thin films on electrode surfaces. The computation method used will be applicable to interfaces in all-solid-state batteries.
Sandia National Laboratories is a multimission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Deparment of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. This work was supported by Nanostructures for Electrical Energy Storage (NEES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DESC0001160.
12:15 PM - ES13.9.08
Validating Structure of the Solid/Liquid Interface with First Principles Molecular Dynamics and X-Ray Reflectivity
Kendra Letchworth-Weaver 1 , Alex Gaiduk 2 , Giulia Galli 2 , Maria Chan 1 , Paul Fenter 3
1 Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois, United States, 2 Institute for Molecular Engineering, University of Chicago, Chicago, Illinois, United States, 3 Chemical Sciences and Engineering, Argonne National Laboratory, Lemont, Illinois, United States
Show AbstractThe interface between a metal oxide electrode and liquid water plays a crucial role in energy conversion processes such as photo-electrochemical water splitting and CO2 reduction to create fuel from sunlight, yet fundamental insights regarding the atomic-scale structure of such surfaces and a contacting liquid under operating conditions often remain elusive. X-ray reflectivity can probe the electron density at the interface with sub-Angstrom resolution, but extracting the atomic structure from the data requires model-dependent empirical fitting and lighter atoms (such as protons) may be difficult to detect. First principles calculations predict electronic properties relevant to catalysis, such as electron energy alignment between the electrode surface and a reacting molecule, but may not predict realistic surface structure without additional validation. Combining complementary information from both in situ X-ray reflectivity and density-functional theory calculations offers a more complete description of the structure and properties of the solid/liquid interface.
Extending the approach of (1) to include dynamical information, we join a first principles molecular dynamics (MD) simulation of the structure of the solid/liquid interface to a simulation of the bulk crystalline substrate, allowing direct computation of structure factors without empirical fitting. We compute structure factors from first principles MD of the water/Al2O3 (001) interface (2) and compare directly with experimental reflectivity measurements (3). From this comparison, we verify that the displacement of surface atoms due to thermal motion predicted by AIMD agrees with experimental measurements. We also gain insight unavailable from either experiment or theory alone regarding chemical composition and bonding at the interface, demonstrating that our technique for direct first-principles computation of X-ray reflectivity signals advances the fundamental science required for discovery of novel energy materials.
1. M. Plaza et al, JACS 138, 4 (2016).
2. P. Huang, T. A. Pham, G. Galli, E. Schwegler, J. Phys. Chem. C 118, 8 (2014).
3. J. G. Catalano, Geochimica et Cosmochimica Acta 75, 10 (2011).
Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
12:30 PM - ES13.9.09
Towards Realistic Continuum Models of Electrified Interfaces
Artem Baskin 1 2 , David Prendergast 1 2
1 The Molecular Foundry, Lawrence Berkeley National Lab, Berkeley, California, United States, 2 Joint Center for Energy Storage Research, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractSince the efficiency of electrochemical conversion is dictated by the energetics of elementary charge transfer reactions it is vital to gain an atomistic description of electrode/electrolyte interfaces. To this end, we require a computational methodology powerful enough to describe the electric double layer (EDL) at different external bias conditions, i.e., both for zero and non-zero Faradaic current. Such simulations require thermodynamic equilibrium between electronic and ionic/molecular degrees of freedom characterized by drastically different time scales. Purely ab initio molecular dynamics (AIMD) approaches, necessarily limited in system size by computational cost, suffer from thermodynamic instability in terms of ionic/molecular equilibrium, since even an elementary fluctuation of an ion in the EDL may cause a drastic change in the associated electrode potential, on the order of ±1.0 V. However, even advanced up-to-date continuum models are limited by descriptions of the classical EDL regime which exclude the important effects of specific ion adsorption. Here, we develop a generalized free-energy functional-based continuum theory and use it to explore the structure of the EDL at various electrochemical conditions. The model captures the effects of specific adsorption of ions and solvent polarization, and can be applied on the same footing to cases with non-zero Faradaic current, beyond the classical double layer regime. These advances permit: the prediction of peculiar character in the ion density profiles at electrode potentials near redox levels; exploration of the electrochemical stability of the interface; and differentiation between the mechanisms of electron and ion transport and their associated time scales. The developed methodology enables us to self-consistently determine the fundamental limits for a microscopic description of biased interfaces, in terms of characteristic sizes and time scales of relevant processes. As such, it can be used to inform the construction of thermodynamically consistent (and stable) atomistic and ab initio molecular dynamics simulations.
12:45 PM - ES13.9.10
Uncovering the Interfacial Properties of Hybrid Perovskite Films on Metal Oxides via Conductive Probe AFM
James Stanfill 1 , R. Shallcross 1 , Kara Saunders 1 , Neal Armstrong 1
1 Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, United States
Show AbstractThis presentation focuses on the use of conductive probe AFM (cAFM) to characterize heterogeneity in dark electrical properties, on sub-micron length scales, for device-relevant, well-ordered metal halide perovskite thin films (MABr-doped FAPbI3) on metal oxide contacts such as TiO2 and ITO. Perovskite active layers in photovoltaic platforms have recently demonstrated energy conversion efficiencies above 20%, but there are challenges in scaling these printable technologies to module level without significant loss in efficiency and concerns for device stability. Recent evidence of significant grain-to-grain current-voltage heterogeneity within the perovskite film may be one manifestation of the efficiency and stability challenges. We believe that such heterogeneity arises from not controlling the physical and chemical properties of the underlying metal oxide surface from which the pervoskite film growth begins. We demonstrate two different ways of ascertaining the role of the oxide surface on the electrical heterogeneity of the perovskite thin film. In the first approach we focus on surface pretreatments of TiO2 thin films that have been prepared on ITO substrates by chemical vapor deposition. Differences in plasma pre-treatment steps, designed to remove traces of carbonaceous material from the near surface region of the oxide, play a significant role in the degree of electrical heterogeneity of the perovskite film likely do to: a) introduction of significant disorder at the pervoskite/oxide interface lending sites for charge trapping, b) poor electrical coupling between the oxide and the active layer materials. In the second approach we focus on comparisons of cAFM electrical activity for FAPbI3 active layers grown on molecularly-modified oxides where there is a clear influence of the modifier on crystal growth. Both approaches confirm the critical role played by the oxide substrate in controlling electrical activity of these perovskite active layers which ultimately affects device efficiency and stability.
ES13.10: High Temperature Electrochemistry
Session Chairs
Friday PM, April 21, 2017
PCC North, 200 Level, Room 227 AB
2:30 PM - ES13.10.01
Improving Oxygen Electrocatalysis in Perovskite Thin Films by Epitaxial Strain
Dongkyu Lee 1 , Ryan Jacobs 2 , Youngseok Jee 3 , S. S. Ambrose Seo 4 , Changhee Sohn 1 , Kevin Huang 3 , Dane Morgan 2 , Ho Nyung Lee 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 , University of Wisconsin Madison, Madison, Wisconsin, United States, 3 , University of South Carolina, Columbia, South Carolina, United States, 4 , University of Kentucky, Lexington, Kentucky, United States
Show AbstractThe slow kinetics of oxygen electrocatalysis is a bottleneck in developing oxide-based energy conversion and storage devices. Recently, it was reported that introducing the lattice strain in an epitaxial film induced by lattice mismatch with a substrate enhances the oxygen reduction reaction (ORR) at elevated temperatures. However, there are limited choices of available solid-state electrolytes to induce strain in high temperature electrochemical applications, in which yttria-stabilized zirconia (YSZ) uniquely satisfies both the growth (i.e. lattice mismatch) and electro-chemical requirements (i.e. ionic conductor and electronic insulator). Here, we explore the dramatically enhanced ORR kinetics in epitaxial La0.6Sr0.4CoO3-δ (LSCO) thin films grown on (001) YSZ substrates. The strain was varied by changing the film thickness to control the degree of epitaxial strain. We found that the surface exchange coefficient (kq) of a 10 nm-thick LSCO thin film with only ~1 % in-plane tensile strain could be dramatically enhanced by up to two orders of magnitude as compared to fully relaxed thicker films (~50, 80, and 100 nm in thickness). We also confirmed by density functional theory (DFT) calculations that this enhancement is strongly associated with the upshift of the O 2p band center toward the Fermi level. In addition, the changed electronic structure resulted in a decrease in the kinetic barriers for oxygen surface exchange kinetics by tensile strain. This result suggests that the change of the electronic structure induced by strain can contribute to the significantly enhanced surface exchange kinetics of LSCO. Thus, our work illustrates that a simple thickness control can drastically impact on the performance of the solid-state electrochemical oxide thin films.
This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Materials Science and Engineering Division (synthesis and physical property characterization) and by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy (electrochemical characterization).
2:45 PM - ES13.10.02
In Situ Probing of Interfacial Phenomena in Solid Oxide Electrochemical Cells
Jiaxin Zhu 1 , Jung-Woo Lee 2 , Hyungwoo Lee 2 , Roger De Souza 3 , David Mebane 4 , Chang-Beom Eom 2 , Stephen Nonnenmann 1
1 , University of Massachusetts Amherst, Amherst, Massachusetts, United States, 2 , University of Wisconsin-Madison, Madison, Wisconsin, United States, 3 , RWTH Aachen University, Aachen Germany, 4 , West Virginia University, Morgantown, West Virginia, United States
Show AbstractSolid oxide electrochemical cells (SOC) represents an attractive, sustainable pathway towards clean energy generation, storage, and production. Interfaces in SOC display an extraordinary array of exotic collective and correlated physical phenomena that mediate the electrochemical exchange reactions underpinning operation and performance. Clarifying interfacial phenomena remains vital to optimizing SOCs properties and functionality. Electrochemical redox reactions and subsequent ion transport in SOCs require elevated temperatures (T > 500 °C) and gaseous fuel. We accounted for such dynamic environments to enable in situ scanning probe measurements under standard operating conditions with nanoscale resolution. Here we 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), with a resolution ~50 nm. We also investigated the surface potential across a four-layer yttria-stabilized zirconia / strontium titanate (YSZ/STO) heteroepitaxial film at 500 °C. As vacancies represent an n-type dopant in STO, subsequent application of a classic semiconductor electronic band structure model to the work function profile enables mapping of the oxygen vacancy distribution within STO with a resolution < 100 nm. Our analysis shows activated processes occur at high temperatures that yield large (microns) depletion regions within NSTO substrates near the NSTO/STO/YSZ interfaces. Comparisons to the SSPM measurements at room temperature indicate an ionic charge transport process across the multilayers dominates at high temperature while electronic conduction dominates at room temperature. Finally we applied in situ HT-SSPM to characterize CO2/CO co-electrolysis on doped ceria SOC, where surface potential gradients extending from the Au current collector-gadolinium doped ceria MIEC interface are fitted using electrocatalytic phase field modeling. The fit between experimentally collected surface potential and electrocatalytic models establishes a semi-quantitative framework for critical electrochemical reactions parameters along the electrode-electrolyte interface. The results presented herein demonstrate the promise of in situ scanning surface potential microscopy (SSPM) to investigate complex oxide interfacial multilayer systems that exhibit vacancy-mediated exchange reactions and transport under extreme environmental perturbation, on a highly localized scale.
3:00 PM - ES13.10.03
Colloidal Nanocrystal Films as Model Materials for Intermediate Temperature Proton Conductivity in Porous Metal Oxides
Gary Ong 2 1 , Evan Runnerstrom 2 , Delia Milliron 1
2 Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States, 1 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States
Show AbstractThe high density of solid-liquid interfaces and/or confinement of the liquid within small pore volumes can fundamentally alter ion transport processes in porous inorganic materials. One exciting extension over the past few years is the observation of unexpected but significant proton conductivity in porous nanocrystalline ceramics at intermediate temperatures despite them being poor bulk proton conductors. Beyond scientific curiosity, these materials are also of engineering interest due to their potential for enabling fuel cell operation in the “gap” temperature that currently exists between 200°C and 500°C where traditional proton conductors like Nafion or ternary proton conducting oxides cannot operate. By utilizing colloidally synthesized cerium oxide and titanium dioxide as model systems, we systematically studied how effects such as nanocrystal size, porosity and composition influenced proton conduction. Temperature-dependent impedance measurements of porous nanocrystal thin films under dry and wet atmospheres show that both CeO2 and TiO2 display significant proton conductivity at intermediate temperatures between 100°C and 350°C. Furthermore, use of oxygen as a carrier gas drastically reduced the proton conductivity by up to 60 times, suggesting a dominant influence of oxygen activity on proton conduction. These findings cumulate to a schema of dissociative water adsorption at surface oxygen vacancies being responsible for the generation of mobile protons. Furthermore, manipulation of the defect equilibria of nanocrystalline metal oxides such as through the use of aliovalent dopants to alter oxygen vacancy concentrations can be used to tune both the temperature range of intermediate temperature conduction and the magnitude of proton conductivity. These findings of interface mediated proton conduction further motivate the study of interface mediated lithium conduction in the presence or absence of solvent vapor.
3:15 PM - ES13.10.04
Interfaces in Doped LaGaO3 and Their Impact on Solid Oxide Fuel Cell Performance
Aoife Lucid 1 , Graeme Watson 1
1 , Trinity College Dublin, Dublin Ireland
Show AbstractLaGaO3 doped with Sr2+ on the A-site and Mg2+ on the B-site (LSGM) has been suggested as an alternative electrolyte material for a range of devices which can operate in the intermediate temperature range of 600-800°C.1 These include solid oxide fuel cells (SOFCs)2, solid oxide electrolysis cells (SOECs)3 and solid oxide reversible cells (SORCs).4 While bulk conductivity has been extensively studied for LSGM the interfaces present, due to multi-crystallinity, and their effect on oxide ion conductivity in LSGM have been largely ignored despite their importance in the oxide ion conduction of materials such as fluorite.
Here we present the derivation of a highly accurate dipole polarizable ion model (DIPPIM)5 force field for doped-LaGaO3 where the dopants are Sr2+ on the A-site and Mg2+ on the B-site. In the DIPPIM polarization effects resulting from induced dipoles on ions in the system are taken into account, which is of great importance due to the polarizable nature of the O2- ions in doped-LaGaO3. The force field is fitted to force, stress and dipole data obtained from DFT calculations, allowing non-equilibrium details on the potential energy surface to be accounted for, which is not possible when fitting to experimental data. Consequently the DIPPIM force field is highly accurate.
The DIPPIM force field has been used to perform a molecular dynamics study of the effects of interfaces (surfaces and grain boundaries) on oxygen diffusion in LSGM along with diffusion in bulk LSGM at range of dopant concentrations and temperatures.
[1] Morales et al, J. Eur. Ceram. Soc., 36, 1-6 (2016)
[2] Ishihara et al, J. Electrochem. Soc., 145, 3177-3183 (1998)
[3] Ishihara et al, Energy Enviorn. Sci., 3, 664-672 (2010)
[4] Hosoi et al, J. Phys. Chem. C, 120, 16110-16117 (2016)
[5] Castiglione et al, J. Phys: Condens. Matter, 11, 9009-9024 (1999)
3:30 PM - ES13.10.05
Evolution in Crystal Structure and Electronic Structure of Functional Oxides Probed In Situ during Electrochemically Driven Phase Transition
Qiyang Lu 1 2 , Sean Bishop 1 2 , Yan Chen 1 3 , Dongkyu Lee 4 , Hendrik Bluhm 5 , Harry Tuller 2 , Ho Nyung Lee 4 , Bilge Yildiz 1 3 2
1 Laboratory for Electrochemical Interfaces, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 5 Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractPhase transition induced by the change of oxygen stoichiometry has become a focal point in the study of functional oxides. The interest is sparked not only by the crystal structure change during the phase transition, but more importantly, the drastic change in physical and chemical properties, including electrical conductivity, magnetism as well as oxygen diffusivity and surface reactivity. Therefore, oxide systems with this phenomenon are promising for a number of important technologies ranging from non-volatile memristive devices to thermo-chemical oxygen separation and oxygen electro-catalysis. Nevertheless, triggering the phase transition by changing oxygen content is not an easy task, which usually requires high-temperature annealing in oxygen atmosphere for a long period, thus not practical for applications. Recently, we have shown that applying electrochemical potential is a practical way of inducing the phase transition without changing the oxygen partial pressure (pO2) in the gas atmosphere. We used epitaxial SrCoOx and VOx thin films as model systems, both grown on oxide ion conducting (Y,Zr)O2 substrates. In situ X-ray spectroscopy and scattering characterizations were performed to monitor the change in crystal and electronic structure under well-controlled temperature, pO2 and applied bias. For SrCoOx, we found that an electrical bias of merely 30 mV was enough to trigger the phase transition from Brownmillerite (BM) phase SrCoO2.5 to Perovskite (P) phase SrCoO3-δ. While for VOx, we succeeded in switching between VO2 and V2O5 by applying electrochemical bias, which is also accompanied by a metal to semiconductor transition. We thoroughly studied the change in electronic structure of these two systems as a function of applied potential, by using in situ ambient pressure X-ray photoelectron/absorption spectroscopy (AP-XPS/XAS). Furthermore, due to the large changes in near-edge X-ray absorption intensity, we developed a novel experimental method of probing the kinetics of phase transition via monitoring the time-dependence of X-ray absorption coefficient. The studies we carried out on SrCoOx and VOx novel demonstrations of the power and necessity of in situ characterization in probing the crystal and electronic structure of functional oxides under electrochemical polarization. More importantly, we believe that these results lay the fundamental principles for using electrochemically driven phase transition in re-dox based memristive devices as well as in oxide (electro-)catalysts.
3:45 PM - ES13.10.06
Sodium-Based Batteries—Engineering Interfaces for Optimized Performance
Erik Spoerke 1 , Leo Small 1 , Sai Bhavaraju 2 , Alexis Eccleston 2 , Joshua Lamb 1 , Paul Clem 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , Ceramatec, Inc., Salt Lake City, Utah, United States
Show AbstractSafe, low-cost, grid-scale electrical energy storage remains a national priority, essential for revitalization of the national grid infrastructure, including large-scale integration and widespread utilization of intermittent renewable energy, such as solar and wind power. Sodium-based batteries show tremendous promise for grid-scale storage, offering high performance, long cycle life, and inherent, engineered improvements in battery safety. Realizing the potential of these systems, however, requires optimizing the chemical, electronic, and ionic behavior across the numerous interfaces in these systems. Here, I will discuss recent work developing intermediate temperature (below 200oC) sodium iodine and sodium-nickel chloride battery chemistries, enabled by the solid state sodium ion conductor NaSICON. Understanding and manipulating phase chemistry and interfacial interactions at the ion-conductor interfaces as well in the catholyte and at the cathode current collector we can improve battery performance through reduced cell resistance, increased cycle life, and enhanced battery safety. For example, through careful selection of molten salt catholytes, we show that we can maintain high cycle life in an all-inorganic system fundamentally safer than, for example, lithium ion batteries that are inherently intolerant to severe environmental conditions. Simultaneously, integrating this catholyte with a new hybrid, porous current collector we show important reductions in performance-limiting cell resistance. I will highlight our understanding of these systems to date and discuss our fundamental materials chemistry work improving these promising battery technologies.
Sandia National Laboratories is a multi-mission laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the US Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
4:00 PM - ES13.10.07
The Impact of Interfaces on Oxide Ion Diffusion in Doped Ceria
Aoife Lucid 1 , Graeme Watson 1
1 , Trinity College Dublin, Dublin Ireland
Show AbstractThe doping of ceria (CeO2) is known to enhance the oxide ion conductivity of ceria, which is important for a number of applications such as fuel cells, oxygen sensors and catalysis. Samarium (Sm) and Gadolinium (Gd) doped ceria are known to display high oxide ion conductivity in the intermediate temperature range (600-800°C) which is desirable for applications.1
In most applications of doped ceria multi-crystalline materials are used, which contain extended defects such as surfaces and grain boundaries. It has been suggested that the interfaces in these materials can result in reduced oxide ion conductivity; however, the majority of studies consider only the average effect of the interface and not the possible effects of different specifically defined interfaces. Despite their importance, there is little information about the effects of specific interfaces which is amenable to molecular dynamics simulations. Here we employ an interatomic potential derived for a range of trivalent dopants in ceria from ab initio data, a dipole polarizable ionic model (DIPPIM).2,3 The DIPPIM allows for polarization effects resulting from induced dipoles, which is important in systems containing O2- due to the highly polarizable nature of the ion.
We discuss the effect of the (111), (221) and (210) surfaces and their corresponding specific tilt grain boundaries (Σ3, Σ9 and Σ5) on the performance of SDC and GDC as oxide ion conductors. Segregation of the oxygen vacancies to the boundary is observed along with enhanced diffusion of the oxide ions parallel to the grain boundary, while it is restricted perpendicular to the boundary.
[1] Zha et al, J. Power Sources, 115, 44-48 (2003) – SDC and GDC
[2] Castiglione et al, J. Phys: Condens. Matter, 11, 9009-9024 (1999)
[3] Burbano et al, Phys. Chem. Chem. Phys., 16, 8320-8331 (2014)