Symposium Organizers
Timothy Armstrong Oak Ridge National Laboratory
Christian Masquelier University of Picardie-CNRS
Yoshihiko Sadaoka Ehime University
Enrico Traversa University of Rome Tor Vergata
AA1: High Temperature Protonic Conductors: Materials and Applications
Session Chairs
Enrico Traversa
Eric Wachsman
Monday PM, November 27, 2006
Republic B (Sheraton)
9:15 AM - **AA1.1
Selected Topics in High Temperature Proton Conductor.
Wilhelm Meulenberg 1 , José Serra 1
1 Institute for Materials and Processes in Energy Systems 1, Forschungszentrum Juelich GmbH, Juelich, North-Rhine Westphalia, Germany
Show AbstractHigh temperature proton conducting membranes can find application in different key energy processes such as hydrocarbon reforming and water-gas-shift, allowing obtaining in turn a hydrogen stream and a humid CO2 stream that can readily be liquefied. Moreover, protonic conductors such as doped BaCeO3 and BaZrxCe1-xO3 can be employed as solid oxide fuel cell (SOFC) electrolyte operating at intermediate temperatures as low as 500C. In contrast with oxygen-anion conducting SOFC, the great advantage of protonic SOFCs is the full fuel-utilization operation without affecting the cell performance, when employing pure hydrogen as fuel. For these purposes, thin electrolyte layers should be obtained preferably over porous substrates with good electronic conductivity. In this contribution different fabrication methods will be outlined, considering the different technologies and the alternatives to prepare thin membranes or electrolytes without passing through very high temperature (1600C) treatments, which typically lead to metals evaporation problems, support densification or degradation and expensive manufacture. Furthermore, manufacture methods, electrochemical performance and operation modus of protonic SOFC will be review and thoroughly compared with state-of-the-art SOFC (YSZ- or CGO-based electrolytes).
9:45 AM - **AA1.2
Non-Perovskite-Structured High-Temperature Proton and Mixed Proton-Electron Conductors.
Reidar Haugsrud 1 , Truls Norby 1
1 Chemistry, Centre for Materials Science and Nanotechnology, University of Oslo, Oslo Norway
Show Abstract10:15 AM - AA1.3
Proton Transfer Mechanism in LaPO4.
Rong Yu 1 , Lutgard De Jonghe 1 2
1 , Lawrence Berkeley National Lab, Berkeley, California, United States, 2 , University of California, Berkeley, California, United States
Show Abstract10:30 AM - AA1.4
Proton Diffusion in Hydrated Acceptor-Doped Barium Zirconate.
Dirk Wilmer 1 , Klaus-Dieter Kreuer 2 , Tilo Seydel 3
1 Institute of Physical Chemistry, Münster University, Münster Germany, 2 , Max-Planck-Institute for Solid State Research, Stuttgart Germany, 3 , Institut Laue-Langevin, Grenoble France
Show AbstractAcceptor-doped perovskites incorporate water by dissociative absorption. Owing to the mobility of oxygen vacancies and protonic defects, these materials are ionic conductors. If such a material is fully hydrated, the transference number of the protonic defects is close to unity.For use in electrochemical devices such as solid oxide fuel cells (where reducing the operating temperature is a key objective), high proton conductivity has to be accompanied by reasonable thermodynamics phase stability. In this respect, acceptor-doped BaZrO3 exhibits promising properties [1].Despite its significantly higher ionic radius when compared to Zr4+, Y3+ turns out to be optimal as an acceptor-dopant for BaZrO3. For temperatures below 700 °C, the observed proton conductivities clearly exceed the oxide ion conductivites of the best oxide ion conductors.We performed incoherent quasielastic neutron scattering measurements on Y-doped and hydrated BaZrO3 in order to study the proton diffusion in this material. Key questions to be addressed are i) how does the proton conduction mechanism look like and ii) does the dopant play the role of a trap for the proton [2], or are the protonic defects more or less delocalized.Our spectra obtained at the backscattering spectrometer IN16 (ILL Grenoble) exhibited quasielastic broadening at all temperatures (473 K to 673 K) studied. Model-free fitting using two Lorentzians results in good agreement with the data. As expected, a simple description of proton diffusion in terms of the Chudley-Elliott model (random walk on a Bravais lattice) does not yield satisfactory results. The observed scattering with two Lorentzians exhibiting a characteristic dependence of linewidths and weights on scattering vector Q suggest the use of the two-state model [2,4] which describes the protons alternating between a state of relatively free diffusion and situations where they are trapped in the vicinity of a lattice defect, viz., the dopant heterovalent metal ion. Simultanous fitting of the two-state model to all spectra taken at a single temperature yields good agreement with the experimental data. The parameters, however, especially the trapping and escape rates, do not show the expected temperature dependence, whereas the mean jump distance obtained from the fit (3.3 to 4 Å) compares favorably with typical proton intersite distances. Given that the two-state model cannot give full account of all our experimental findings, we shall present an extended model description in our contribution.[1] W. Münch, K.-D. Kreuer, G. Seifert, J. Maier, Solid State Ionics 137-137 (2000) 183.[2] Ch. Karmonik, R. Hempelmann, Th. Matzke, T. Springer, Z. Naturforsch. 50a (1995) 539.[3] K.-D. Kreuer, St. Adams, W. Münch, A. Fuchs, U. Klock, J. Maier, Solid State Ionics 145 (2001) 295.[4] D. Richter, T. Springer, Phys. Rev. B 18 (1978) 126.
10:45 AM - AA1.5
Synthesis and Characterization of Perovskite-Type Oxide Ceramic Based on BaCexY1-xO3 and BaZrxY1-xO3 for Solid Oxide Fuel Cell (SOFCs).
Alessandra D'Epifanio 1 , Emiliana Fabbri 1 , Enrico Traversa 1 , Silvia Licoccia 1
1 , university of Rome Tor Vergata, Rome Italy
Show Abstract11:00 AM - AA1: HTPCs
BREAK
11:30 AM - **AA1.6
Study on the Perovskite-type Oxide Cathodes in Proton-conducting SOFC.
Hidenori Yahiro 1
1 Department of Materials Science and Biotechnology, Ehime University, Matsuyama Japan
Show AbstractMetal ion-doped perovskite-type oxides such as SrCe0.95Yb0.05O3 and BaCe0.8Y0.2O3 showed high protonic conductivities and are of interest for applying to solid oxide fuel cell (SOFC). In the present study, the polarizations of the perovskite-type oxide cathodes were investigated in the H2-O2 fuel cell employing high proton-conducting electrolytes mentioned above. Among the perovskite-type oxides tested, La0.7Sr0.3FeO3 showed the lowest cathodic overpotential in the temperature range 773-973 K. The overpotential of La0.7Sr0.3FeO3 cathode was smaller than that of the sputtered platinum at 973 K. In addition, it was demonstrated that the cathodic overpotential of La0.7Sr0.3FeO3 was comparable to the anodic overpotential of the sputtered platinum, in contrast to the general consensus that the cathodic overpotential was much higher than the anodic one in H2-O2 SOFC using oxygen ion-conducting electrolytes. The dependences of partial pressures of both oxygen and water vapor on the cathodic overpotential of La0.7Sr0.3FeO3 suggested that the rate-determining step is either the reaction of surface oxygen atom with proton to yield water or the desorption of water produced on cathode. In order to reduce the electrolyte resistance, thin films of SrCe0.95Yb0.05O3 and BaCe0.8Y0.2O3 were prepared on the substrate made of the perovskite-type oxides. The spin-coating technique employed in the present study resulted in the preparation of the dense SrCe0.95Yb0.05O3 and BaCe0.8Y0.2O3 thin films on La0.7Sr0.3FeO3 oxide substrate. The electrical peoperties were studied for the resulting electrolyte/electrode devices.
12:00 PM - AA1.7
Pulsed Laser Deposition of Proton-conducting Yttrium-doped Barium Zirconate Films.
Joon Shim 1 , Turgut Gür 2 , Fritz Prinz 1 2
1 Mechanical Engineering, Stanford University, Stanford, California, United States, 2 Material Science Engineering, Stanford University, Stanford, California, United States
Show Abstract12:15 PM - **AA1.8
Cell Performance Stability of HMFC using Ba(Ce1-xZrx)0.8Y0.2O3 Perovskite Type Proton Conductor as Electrolyte.
Masahiko Iijima 1 , Naoki Ito 1 , Shinichi Matsumoto 1 , Satoshi Iguchi 1
1 , Toyota Motor Corporation, Susono, Shizuoka Japan
Show AbstractThe use of an on-board reformer with an FC system is a very attractive option for FC vehicles because of its long cruising range and no need for new hydrogen infrastructure. PEMFC is not suitable with a reformer because the PEMFC and reformer have different operating temperatures. We have developed a new type of FC which shows high performance at intermediate temperatures. The essence of this new FC is an ultra-thin proton conductor electrolyte supported by a metal hydrogen membrane. We named it Hydrogen Membrane Fuel Cell and believe that it is suitable not only for vehicle applications but also for stationary applications.The HMFC using BaCe0.8Y0.2O3 as the electrolyte and pure Palladium as the substrate exhibits a high cell performance of 2.0 A/cm2 @0.5V, 600C and 1.5 A/cm2 @0.5V, 400C. BaCeO3 proton conducting ceramics have high proton conductivity, in contrast to its low chemical and mechanical stability.Using BaCeO3 as the HMFC electrolyte, there is the concern that cell performance stability may drop because the cathode side electrolyte is dissolved by hydrothermal reaction caused by H2O vapor generated at the cathode.The electrolyte can be changed from BaCeO3 to BaZrO3, which has higher chemical and mechanical stability. However, BaZrO3 exhibits lower proton conductivity than BaCeO3. In this study, we investigated the possibility of Ba(Ce1-xZrx)0.8YO3 (x=0-1) electrolytes, in which the B site of BaCe0.8Y0.2O3 perovskite ceramics is exchanged from Ce to Zr to produce a high resistance against hydrothermal dissolution and high proton conductivity. Each electrolyte thin film on Pd substrate was treated in 100% H2O at 400C for 200Hrs to evaluate the resistance against hydrothermal dissolution. After 200Hrs of H2O treatment, Ba(OH)2 was generated on the surface of BaCe0.8Y0.2O3 (BCY). On the other hand, after 1100Hrs of treatment, the generation of Ba(OH)2 on the surface of Ba(Ce0.5Zr0.5)0.8YO3 (BCZY) and BaZr0.8Y0.2O3 (BZY) was not confirmed. Consequently, the resistance against the hydrothermal dissolution was increased as a result of the displacement of the B site of BCY from Ce to Zr The cell performance of the HMFC using BCZY as electrolyte was the same level as the cell using BCY. In addition, the durability of the cell using BCZY as electrolyte was higher than the cell using BCY. After measuring the cell performance stability, an interface between the electrolyte and cathode was observed by TEM-EDX to confirm the absence of products by hydrothermal dissolution. The condensation of Ba was observed at the interface between the electrolyte and cathode of the BCY cell. It was inferred that the phenomenon occurred by the generation of Ba(OH)2. On the other hand, the condensation of Ba was not observed at the interface between the electrolyte and cathode of the BCZY cell. Consequently, the reason for improvement in the durability of the BCZY cell was inferred to be the prevention of hydrothermal dissolution of the electroly
12:45 PM - AA1.9
Solid Oxide Fuel Cells based on Proton Conducting Electrolytes.
U. (Balu) Balachandran 1 , Tae Lee 1 , Beihai Ma 1 , Stephen Dorris 1
1 Energy Systems/Ceramics Section, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractAA2: Mixed Ionic (Protonic and Oxygen) Electronic Conductors
Session Chairs
Tim Armstrong
Enrico Traversa
Monday PM, November 27, 2006
Republic B (Sheraton)
2:30 PM - **AA2.1
Mixed-Conducting Membranes for Hydrogen Production and Separation.
U. (Balu) Balachandran 1 , Beihai Ma 1 , Tae Lee 1 , Sun-Ju Song 1 , Ling Chen 1 , Stephen Dorris 1
1 Energy Systems/Ceramics Section, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractMixed-conducting oxides, possessing both ionic and electronic charge carriers, have found wide application in recent years in solid-state electrochemical devices that operate at high temperatures, e.g., solid-oxide fuel cells, batteries, and sensors. These materials also hold promise as dense ceramic membranes that separate gases such as oxygen and hydrogen from mixed-gas streams. We are developing Sr-Fe-Co oxide (SFC) as a membrane that selectively transports oxygen during partial oxidation of methane to syngas (mixture of CO and H2) because of SFC's high combined electronic and ionic conductivities. We have evaluated extruded tubes of SFC for conversion of methane to syngas in a reactor that was operated at ≈850°C. Methane conversion efficiencies were >90%, and some of the reactor tubes were operated for >1000 h. We are also developing dense proton-conducting oxides to separate pure hydrogen from product streams that are generated during methane reforming and coal gasification. Hydrogen selectivity in these membranes is nearly 100%, because they are free of interconnected porosity. Although most studies of hydrogen separation membranes have focused on proton-conducting oxides by themselves, we have developed cermet (i.e., ceramic-metal composite) membranes in which metal powder is mixed with these oxides in order to increase their hydrogen permeability. The hydrogen flux through these membranes has been measured in the temperature range of 500-900°C. In this talk, the development of oxygen and hydrogen transport membranes for hydrogen production and separation will be presented.Work supported by U.S. Department of Energy, Office of Fossil Energy, National Energy Technology Laboratory’s Hydrogen and Gasification Technologies Program, under Contract W-31-109-Eng-38.
3:00 PM - **AA2.2
Hydrogen Production with Mixed Protonic-Electronic Conducting Perovskite Membranes.
Eric Wachsman 1 , Heesung Yoon 1
1 UF-DOE High Temperature Electrochemistry Center, University of Florida, Gainesville, Florida, United States
Show Abstract3:30 PM - AA2: MIECs
BREAK
4:30 PM - AA2.3
Measuring of Partial Ionic Conductivity of Donor Doped SrTiO3.
Wenhua Huang 1 , Srikanth Gopalan 1 , Uday Pal 1
1 Manufacturing Engineering, Boston University, Boston, Massachusetts, United States
Show AbstractA-site donor doped strontium titanate (SrTiO3) is a n-type material suggested for use as an anode in solid oxide fuel cells (SOFC) due to its high electrical conductivity in reducing atmosphere. Its defect structure and electrical properties have been studied extensively. However, its partial ionic conductivity has not been accurately measured. The available ionic conductivity data is obtained by curve fitting the total conductivity data to a defect structure model based on some simplified assumptions. In this paper, the partial ionic conductivity of donor doped strontium titanate has been directly measured by blocking the electronic current and the data is reported as a function of oxygen partial pressure over a temperature range of 700 oC to 850 oC.
4:45 PM - AA2.4
Oxygen Permeation and Hydrogen Generation Using MIEC Membranes.
Hengdong Cui 1 , Srikanth Gopalan 1 , Annamalai Karthikeyan 1 , Uday Pal 1
1 Manufacturing Engineering, Boston University, Brookline, Massachusetts, United States
Show AbstractPorous mixed ionic and electronic conducting (MIEC) oxides that conduct both ions (H+, O2-, etc) and electrons (or holes) are used as electrode materials in battery and fuel cell technology. Dense MIEC membranes are also recently receiving increasing attention due to their potential application as gas separation membranes to separate oxygen from air. We have been studying a new process that utilizes oxygen ion and electron conducting MIECs for generating and separating hydrogen from steam. This research aims at exploring new routes for high-purity hydrogen production for use in fuel cells and hydrogen-based IC engines. The MIEC membrane separation process involves steam dissociation on the steam-rich side of the membrane (feed side). The oxygen ions formed as a result of steam dissociation are transported across the membrane in a coupled transport process with electrons being transported in the opposite direction. Upon reaching the methane side of the membrane (permeate side) the oxygen ion reacts with the methane to form products of combustion such as carbon monoxide, carbon dioxide and water vapor and releasing two electrons. This process results in hydrogen production at the feed side. The oxygen partial pressure gradient is the driving force for this process. Membrane requirements for such process are (i) high ambipolar conductivity characterized by high chemical diffusion rates of oxygen, (ii) stability under the prevailing conditions of low oxygen partial pressure and high water content and (iii) high surface reaction rates.A new dual-phase composite mixed ionic and electronic conducting (MIEC) membrane system comprising of rare-earth doped ceria with high oxygen ion conductivity and donor-doped strontium titanate with high electronic conductivity has been developed. In this work, the oxygen chemical diffusion coefficient and the oxygen surface exchange coefficient of the dual-phase materials, two parameters which control the eventual rate of oxygen transport across the membrane have been measured as a function of oxygen partial pressure, using the electrical conductivity relaxation technique. We also present results of permeation experiments under oxygen partial pressure gradients representative of the methane assisted steam electrolysis process. Electrical conductivity relaxation and permeation experiments have been used as experimental tools to study the effect of electrocatalysts on oxygen transport through such membranes.
5:00 PM - AA2.5
Mixed Conductivity and Oxygen Permeability of(BaxSr1-x)0.98Fe1-yMyO3-δ (x=0.1-0.3, y=0.1-0.4 and M=Ga, Al).
Chun yong Kang 1 , Hajime Kusaba 2 , Yasutake Teraoka 2
1 Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Hukuoka, Japan, 2 Department of Molecular and Material Sciences, Faculty of Engineering Sciences, Kyushu University, Kasuga, Hukuoka, Japan
Show Abstract1. INTRODUCTIONOxygen-permeable mixed ionic-electronic conductors (MIECs) can be applied in catalytic membrane reactors. La-Sr-Co-Fe-O perovskites (LSCFs), which is the first-generation materials for the oxygen permeation membrane, show high oxygen permeability, but the lack of reduction tolerance makes it difficult to apply LSCFs for membrane reactors. Although materials having both oxygen permeability and reduction tolerance have been reported such as SrFeCo0.5Ox, (La,Sr)(Ga,Fe)O3-δ and (Ca,Sr)(Ti,Fe)O3-δ, the development of more excellent materials is necessary to meet requirements in practical application. Recently, we have revealed that Ba-Sr-Fe-O perovskites (BSFs) show both relatively high oxygen permeability and reduction tolerance. In this study, the effect of partial substitution of Ga and Al for Fe in BSFs have been investigated with respect to electrical property, oxygen permeability and reduction tolerance. 2. EXPERIMENTAL Target materials in this study were (BaxSr1-x)0.98Fe1-yMyO3-δ (x=0.1-0.3, y=0.1-0.4), where M is Ga (BSFG) or Al (BSFA). Mixed aqueous solution of nitrates of Ba, Sr, Fe, Ga(Al) and malic acid was evaporated to dryness, and the residue was calcined at 350 oC for 2 h and then at 850 °C for 5 h. Sample powder was compressed into a disk by the successive pressing of uniaxial and isostatic methods, and the disk was sintered at 1200-1250 oC in air. Both surfaces of sintered disks were polished to reach 1.0 mm thicknesses. Crystal structure analysis was performed by XRD analysis. Electrical property was measured by the 4-point method and electrochemical cell technique. The oxygen permeability was measured with the air/He gradient of oxygen partial pressure between 900 and 600 oC with an interval of 50 oC. Concentration of oxygen permeated from the air to He sides was measured by TCD.3. RESULTS AND DISCUSSIONXRD investigation revealed that the solubility limits of Ga and Al were ca. 30 mol% and 20mol%, respectively, irrespective of the A-site composition (x=0.1-0.3). The cubic perovskite-type structure of BSFG and BSFA was maintained even after the reduction in 5%H2/95%N2 at 900 oC. All the materials synthesized were p-type semiconductor, and the total conductivity tended to decrease with increasing the Ga and Al contents. Ionic transference numbers (ti) of BSFs were between 0.37 and 0.41. The substitution with Al had little effect on ti, but that with Ga resulted in the increase in ti; for example, 0.51 (y=0.2) and 0.55(y=0.3). The oxygen permeability was little affected by the substitution with Ga and Al, and the permeation rate of BSFG and BSFA were ca.1.0-1.04(cm3 (STP) /cm2 min) at 900 oC. The present results have revealed that BSFG and BSFA are MIEC materials with excellent reduction tolerance.
5:15 PM - AA2.6
ITM Ceramic Membrane Technology to Produce Synthesis Gas.
Christopher Miller 1 , Michael Carolan 1 , Christopher Chen 1 , Eric Minford 1 , James Steppan 2 , William Waldron 1
1 , Air Products and Chemicals, Inc., Allentown, Pennsylvania, United States, 2 , Ceramatec, Inc., Salt Lake City, Utah, United States
Show AbstractThe ITM Syngas Team, led by Air Products and including Chevron, Ceramatec, and other partners, in collaboration with the U.S. Department of Energy, is developing Ion Transport Membrane (ITM) technology for the production of synthesis gas, a mixture of hydrogen and carbon monoxide. The ITM Syngas process is a breakthrough technology that combines air separation and high-temperature synthesis gas generation processes into a single ceramic membrane reactor, with significant savings in the capital cost of synthesis gas production. Because synthesis gas is a feedstock for a range of different processes, ITM Syngas represents a technology platform that has numerous applications, such as hydrogen, clean fuels and chemicals. ITM ceramic membranes are fabricated from non-porous, mixed-metal oxides and operate with exceptionally high oxygen flux and selectivity when exposed to an oxygen chemical potential gradient at high temperatures. Oxygen from low-pressure air permeates, as oxygen ions, through the ceramic membrane and is consumed through chemical reactions, thus creating the chemical driving force for the transport of oxygen ions across the membrane at high rates. This oxygen then reacts with high-pressure natural gas in a partial oxidation process to produce synthesis gas. Significant advances have been made in developing and scaling up the ITM Syngas technology. This paper describes the development of commercial-size ceramic membranes and the ITM Syngas reactor system. Recent laboratory and pilot unit test results will also be discussed.
5:30 PM - AA2.7
Characterization of (La0.9Sr0.1)0.95Cr0.85Mg0.1Ni0.05O3 Perovskite Ceramics for a Perovskite Related Membrane Reactor.
Rachel Rosten 1 , Mattew Swanson 1 , Nina Orlovskaya 1
1 Materials Science and Engineering, Michigan Technological University, Houghton, Michigan, United States
Show AbstractAA3: Poster Session: Fuel Cells
Session Chairs
Tim Armstrong
Christian Masquelier
Yoshihiko Sadaoka
Enrico Traversa
Tuesday AM, November 28, 2006
Exhibition Hall D (Hynes)
9:00 PM - AA3.1
Sintering and Properties of Nano-porous Doped Ceria Synthesized via Direct Condensation Method.
Vincenzo Esposito 1 , Silvia Licoccia 1 , Enrico Traversa 1
1 , Università di Roma Tor Vergata, Rome Italy
Show Abstract9:00 PM - AA3.10
Double Perovskite Cathodes for Intermediate Temperature Solid Oxide Fuel Cells.
Wenquan Gong 1 , Guntae Kim 1 , Susan Wang 1 , Manoj Yadav 1 , Allan Jacobson 1
1 Chemistry, University of Houston, Houston, Texas, United States
Show AbstractThe oxygen-deficient double perovskite PrBaCo2O5+x (PBCO) was synthesized and evaluated as a promising cathode material for intermediate temperature solid oxide fuel cells (SOFCs) based on a gadolinium doped ceria (CGO) electrolyte. The electrical conductivity relaxation (ECR) and oxygen-isotope exchange and depth profiling (IEDP) measurements revealed that PBCO had high electronic conductivity and rapid oxygen ion diffusion and surface exchange kinetics. PBCO also showed good compatibility with CGO electrolyte material. Moreover, AC impedance measurements of the symmetrical cells of PBCO/CGO composite cathodes on a CGO electrolyte indicated excellent area specific resistance (ASR) performance. The electrochemical performance of PBCO/CGO composite cathodes in CGO electrolyte- supported and nickel/CGO composite anode- supported single cells were subsequently studied at 500~700 C with humidified (3% H2O) hydrogen as fuel and air as oxidant.
9:00 PM - AA3.11
A Study of SOFC Cathode Materials Under Low Oxygen Partial Pressures.
Jeffrey White 1 , Scott Misture 1
1 , Alfred University, Alfred, New York, United States
Show AbstractThe SOFC cathode materials LaxSr1-xCoO3-δ (x = 0.2, 0.3, and 0.4) and La0.3Sr0.7FeO3-δ were studied at temperatures up to 1173K with oxygen partial pressures from 1 atm to 3 x 10-4 atm, as well as under 4% H2. In-situ high temperature X-ray diffraction was used to monitor the phase evolution as a function of time over multiple heating/cooling cycles. All four compositions phase separated on heating to form LSMe, SrLaMeO4 and MeO, (where Me = Fe or Co), but not necessarily during the first heating cycle. Diffraction data indicate that the reverse reaction caused by step changes to higher PO2 cause exceedingly rapid re-solution of SrLaMeO4 and MeO to form X-ray phase pure LSC and LSF. A new phenomenon was observed that is characterized by a slow drift in unit cell volume over the course of at least 24 hours after stepwise changes in the oxygen partial pressure. The implications of the phase stability and reaction rates on applications in the fuel cell environment will be discussed for LSC, LSF, and the newer cathode materials such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ.
9:00 PM - AA3.12
High-Performance and Stable Intermediate Temperature Cathodes for Anode Supported Planar Solid Oxide Fuel Cells.
Peter Zink 1 , Kyung Yoon 1 , Wenhua Huang 1 , Guosheng Ye 1 , Srikanth Gopalan 1 , Uday Pal 1 , Donald Seccombe 2
1 Manufacturing Engineering, Boston University, Boston, Massachusetts, United States, 2 , BTU International, North Billerica, Massachusetts, United States
Show AbstractSintering characteristics of scandia-stabilized zirconia (ScSZ) and ytrria-stabilized zirconia (YSZ) were investigated with and without sintering aids at temperatures between 1250 and 1335°C for application as an electrolyte material in solid oxide fuel cells. In this temperature range, with sintering aids, both materials densified to over 96% theoretical density. Four probe DC conductivity tests were performed in air at 50 degree intervals between 700 and 900°C. The conductivity tests demonstrated the conductivity of ScSZ to be approximately 2.5 times that of YSZ. A one-step co-firing process was employed to manufacture complete SOFCs. SOFCs made with the ScSZ or YSZ electrolyte and Ni-stabilized zirconia cermet anode and lanthanum manganite-based cathode materials showed virtually no difference in electrical performance at intermediate temperatures (600-800C). Analytical investigation indicated that the limits on cell performance were not due to the electrolyte, but more likely due to polarization resistance in the cathode. To lower the polarization resistance of the cathode, A-site-deficient-acceptor-doped lanthanum ferrite and lanthanum cobaltite cathode materials with various dopants were synthesized for further investigation. Ongoing experiments include reactivity studies, as well as partial conductivity, dilatometry, and impedance spectroscopy measurements. Based on these measurements, optimum cathode compositions are being selected for fabricating and electrochemically evaluating complete Ni-stabilized zirconia-anode-supported SOFCs with stabilized zirconia electrolyte at intermediate temperatures.
9:00 PM - AA3.13
Nafion® Composite Membrane Modified by Phosphoric Acid-Functionalized 3-APTES.
Jung-Soo Kang 1 , Young-Taek Kim 1 , Jinhwa Piao 2 , Hee-Woo Rhee 1
1 Chemical and Biomolecular Engineering, Sogang University, Seoul Korea (the Republic of), 2 chemical engineering, Harbin Institute of Technology, Harbin China
Show Abstract9:00 PM - AA3.14
Hybrid Inorganic-organic Polymer Composites for Polymer-electrolyte Membrane Fuel Cells.
Andrea Ambrosini 1 , Cy Fujimoto 1 , Zachariah Harris 1
1 Chemical and Biological Systems, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show Abstract9:00 PM - AA3.15
Carbon Nanotubes Doped Active Direct Methanol Fuel Cell Cable.
Jaewu Choi 1 , Yuan Xu 1 , Jayasri Narayanamoorthy 1
1 , wayne state university, Detroit, Michigan, United States
Show Abstract9:00 PM - AA3.2
Rare Earth Stabilized Zirconia – Energetics and Phase Stability.
Petra Simoncic 1 , Alexandra Navrotsky 1
1 Thermochemistry Facility, UC Davis, Davis, California, United States
Show Abstract9:00 PM - AA3.3
A Comparative Study Of Electrical And Electrochemical Transport In Nanoscale Oxide-Ion Conductors.
Annamalai Karthikeyan 1 , Shriram Ramanathan 1
1 Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show AbstractSpace charge layers and their effects on electrical properties at nanoscales have been well studied in semiconductors and other dielectric materials. An analogous study of ionic conductors at nanoscale is largely unexplored. The field of nanoionics has a high potential for miniaturization of electrochemical devices and fundamental understanding of ionic migration properties. Of the various types of ionic conductors, oxide ion conductors and mixed oxide and electronic conductors are key components in energy conversion devices such as solid oxide fuel cells. Study of transport properties of these materials at nano-scale will provide useful information on the effect of space charge layers at the substrate-film interface and interactions between oxygen vacancies in thin film oxide sytems. Systematic electrical conductivity studies of nanoscale oxide conductors such as lanthanum-doped zirconia, gadolinium-doped ceria, lanthanum-doped ceria, and doped perovskites are being carried out as function of film thickness in the range of few nm to 200nm. The measurements have been performed as a function of temperature typically ranging from 700°C to about 950°C and also as a function of oxygen partial pressure. Theoretical calculations are being performed on space charge potentials as a function of doping level, temperatures and defect association energies by numerically solving Poisson’s equation. Dielectric and conductivity measurements at high temperatures using parallel plate geometry are also being carried out to study transport properties across the film interfaces. These calculated values and experimental observation are being analyzed using dielectric and conductivity relaxation profiles as a function of frequency. This poster will report the experimental observation of various oxide conductors at nano-scales and their analysis based on conductivity relaxation profiles and space charge potential calculations. Our initial results indicate that space charge effects play a significant role when the sample thickness is less than 200nm.
9:00 PM - AA3.4
Characterization of Sc2O3–CeO2-ZrO2 Powders as a Promising Electrolyte Ceramics for Lower Temperature Solid Oxide Fuel Cells.
Alexandra Zevalkink 1 , Allen Hunter 1 , Nina Orlovskaya 1
1 Materials Science and Engineering, Michigan Technological University, Houghton, Michigan, United States
Show Abstract9:00 PM - AA3.5
Nano-composite Porous Pt/YSZ Thin Films for Micro-SOFC Electrodes.
Woo Sik Kim 1 , WooChul Jung 1 , Avner Rothschild 1 , Joshua Hertz 1 , Harry Tuller 1
1 Material Science and Technology, MIT, Cambridge, Massachusetts, United States
Show AbstractNano-porous electrodes are attractive for applications in solid state ionic devices such as fuel cells and chemical sensors. The conventional methods for fabricating such electrodes are typically based on wet processes such as electroplating and sol-gel techniques. In this work we report on novel methods to fabricate nano-composite porous thin film electrodes using physical vapor deposition (PVD) techniques. This approach is particularly attractive for micro-SOFCs since it enables fabricating the entire SOFC stack (anode/electrolyte/cathode) in the sputtering machine without breaking vacuum.The challenge in sputtered electrodes lies in making them porous in order to enhance their electrochemical performance by increasing the TPB length and gas permeability through the electrode. We developed a unique method for sputtering nano-composite porous Pt/YSZ thin film electrodes. We examined the electrode microstructure as function of deposition conditions and observed the electrochemical performance of porous electrodes compared with dense electrodes. The relationship between the porosity and electrochemical properties as well as nano-structure of the porous electrodes will be discussed in the presentation.
9:00 PM - AA3.6
Design of Anodes for IT SOFC: Effect of Complex Oxide Promoters and Pd on Activity and Stability in Methane Steam Reforming of Ni/YSZ (ScSZ) Cermets.
Vladislav Sadykov 1 , Natalia Mezentseva 1 , Rimma Bunina 1 , Galina Alikina 1 , Anton Lukashevich 1 , Vladimir Rogov 1 , Ella Moroz 1 , Vladimir Zaikovskii 1 , Oleg Bobrenok 2 , Alevtina Smirnova 3 , John Irvine 5 , Oleksandr Vasylyev 4
1 , Boreskov Institute of Catalysis SB RAS, Novosibirsk Russian Federation, 2 , Institute of Thermophysics SB RAS, Novosibirsk Russian Federation, 3 Global Fuel Cells Center, University of Connecticut, Storrs, Connecticut, United States, 5 School of Chemistry, University of St Andrews, Fife United Kingdom, 4 , Institute for Problems of Materials Science, Kiev Ukraine
Show Abstract9:00 PM - AA3.7
Gd0.2Ce0.8O2-based Composite Ceramics for Lower Temperatures SOFC Cathodes.
Nina Orlovskaya 1 , Rachel Rosten 1 , Mattew Swanson 1 , Peter Moran 1 , Natee Tangtrakam 1 , Jakob Kuebler 2
1 Materials Science and Engineering, Michigan Technological University, Houghton, Michigan, United States, 2 High Performance Ceramics, EMPA, Duebendorf Switzerland
Show Abstract9:00 PM - AA3.8
Electrochemical Properties of Nanocrystalline Y2-XPrxRu2O7 Pyrochlore for Electrodic Application in IT-SOFCS.
Chiara Abate 1 2 , Enrico Traversa 1 , Eric Wachsman 2
1 , University of Rome Tor Vergata, Rome Italy, 2 , University of Florida, Gainesville, Florida, United States
Show AbstractRu pyrochlore oxides have been evaluated as possible candidates for SOFCs’ cathodic applications because they showed excellent electro catalytic behaviour for oxygen reduction and good electrical conductivity. In this work, nanocrystalline powders of Praseodymium doped Yttrium Ruthenium Oxide Y2-xPrxRu2O7 were prepared by a co-precipitation method. Pr was chosen as the A-site dopant in order to increase the electrical conductivity of Y2Ru2O7. Phase and morphology were studied by XRD and FE-SEM, which showed single pyrochlore phase and particle size of about 100 nm.The electrical conductivity of Y2-xPrxRu2O7 was measured as function of praseodymium content, oxygen partial pressure and temperature by d.c. 4-probe method and a.c. 2-probe method. The temperature dependence of the electrical conductivity has been investigated for a range of 5-25% of dopant elements, in 473-1073K temperature range. The values of conductivity increased with increasing dopant concentration and holes are the main charge carries.The isothermal electrical conductivity of Y2-xPrxRu2O7 has been investigated at 800°C at different oxygen partial pressure in order to understand the Praseodymium function into the pyrochlore structure. The experimental results are presented and discussed.
9:00 PM - AA3.9
Structural Characterization and Chemical Stability of Nanoscale La0.5Sr0.5CoO3-δ Cathodes on YSZ.
Levin Dieterle 1 , Dagmar Gerthsen 1 , Christoph Peters 2 , André Weber 2 , Uwe Guntow 3
1 Laboratorium für Elektronenenmikroskopie, Universität Karlsruhe, Karlsruhe Germany, 2 Institut für Werkstoffe der Elektrotechnik, Universität Karlsruhe, Karlsruhe Germany, 3 , Fraunhofer-Institut für Silicatforschung, Würzburg Germany
Show AbstractThere is a considerable interest in low-to-medium temperature (500-800 °C) solid oxide fuel cells (SOFCs), because cells operating at reduced working temperatures exhibit less problems with thermal activated degradation. In this temperature range a new design of the cathode/electrolyte interface is necessary to compensate the lower diffusivity of oxygen ions and the reduced catalytic activity. One concept for the improvement of the cathode performance is the use of a nanocrystalline cathode material with mixed (ionic and electronic) conductivity like La0.5Sr0.5CoO3-δ.Nanocrystalline La0.5Sr0.5CoO3-δ layers were deposited on 3.5 mol% Yttria stabilized Zirconia (YSZ) electrolytes by a sol-gel process, a fabrication technique that is cheap and suitable for industrial mass production compared to other techniques like pulsed laser deposition (PLD). The sol was deposited by spin-coating and treated by a rapid thermal annealing (RTA) process to obtain a perovskite type thin film. A final annealing process was performed at temperatures of 700 °C and 1000 °C for 8 h to evaluate the stability of the thin film at elevated temperatures.Microstructural surface characterization of the deposited layers was carried out by scanning electron microscopy (SEM). It could be shown that the grain size distribution can be controlled by the annealing temperatures. However, the chemical inhomogeneity, which increases with increasing annealing temperature, could be visualized by SEM micrographs and verified by energy dispersive X-Ray spectroscopy (EDS). Several secondary phases like CoO and SrZrO3 could be identified by means of transmission electron microscopy (TEM) using electron diffraction, electron energy-loss spectroscopy (EELS) and TEM-EDS in the cathode layer. The distribution of the chemical elements could be directly imaged by electron spectroscopic imaging (ESI) in cross-section TEM samples. The analysis shows that a reaction between Sr and Zr takes place at cathode/electrolyte interface which leads to the formation of a SrZrO3 reaction layer. The thickness of this layer increases with increasing annealing temperatures.In addition to the different secondary phases electron-beam induced superstructures could be observed in the lanthan-strontium-cobaltate. They exhibit a doubling or tripling of the lattice constant depending on the local Sr stoichiometry. The ordered domains are rotated against each other by 90° and their size depends on the local electron radiation dose.The presence of secondary phases and the resulting chemical inhomogeneity of the lanthan-strontium-cobaltate shows that the thin film is not stable on a YSZ electrolyte at elevated temperatures. To suppress the reaction between LSC and the YSZ electrolyte a diffusion barrier layer was applied between cathode and electrolyte. First investigations of a Gd-doped CeO2 (GCO) barrier layer are promising and show that the formation of secondary phases can be strongly suppressed.
Symposium Organizers
Timothy Armstrong Oak Ridge National Laboratory
Christian Masquelier University of Picardie-CNRS
Yoshihiko Sadaoka Ehime University
Enrico Traversa University of Rome Tor Vergata
AA4: Modelling/Fundamental Studies
Session Chairs
Stuart Adler
Christian Masquelier
Tuesday AM, November 28, 2006
Republic B (Sheraton)
9:30 AM - **AA4.1
From Perovskites to Apatites: Atomic-Scale Studies of Complex Oxide Materials for Fuel Cells.
M.Saiful Islam 1
1 Chemistry, University of Bath, Bath United Kingdom
Show Abstract10:00 AM - AA4.2
The Effect of Point Defects on the Physical properties of Acceptor-Doped Ceria.
Keith Duncan 1 , Eric Wachsman 1
1 Materials Science and Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractPoint defects can have a significant effect on the physical properties of ceramics. This is particularly true for ceramics used in thermal barrier coatings, electrochromic devices, sensors, gas separation membranes and solid oxide fuel cells. Consequently, the development of ceramics for these applications requires an understanding of the effects that point defects have on their material properties. Moreover, it is important to be able to predict the defect population as a function of operating conditions, e.g., oxygen partial pressure, PO2. An analytical approach is developed herein to explore the relationship between point defect populations and material properties in ceramics. For clarity, model development is constrained to crystalline oxides with the fluorite structure, but is applicable to other crystalline ceramics.The introduction of point defects into a crystal lattice results in expansion or contraction [1, 2]. This is called chemical expansion, αchem. Measurement of the lattice constant, a, reveals that, for fluorite-structured oxides, a is linearly dependent on the dopant concentration, ca, and the vacancy concentration, cv, thusa = a0 + βcv + β'caorαchem = (a - a0 - β'ca)/ a0 = βcv/a0 (1)where a0 is the lattice constant in the absence of defects; and the constant β and β' are the increase in lattice parameter due to defect formation from external equilibria and doping, respectively.The bond energy, U, between atoms in a crystal, may be approximated byU = A/rn – B/rm (2)where r is the interatomic distance, A and B are empirically determined constants for the repulsive and attractive components of the ionic bond energy in a perfect (defect free) crystal, respectively, n is the Born exponent and m arises from Coulombic forces. By setting the first derivative of Eq. (2) to zero and evaluating it at r = req, the equilibrium interatomic distance (for the fluorite structure, req = 1.732a/4, ), the elastic modulus, E, may be estimated from the 2nd derivative of U, with the resultE = E0(1 + βcv/a0)-n-3 (3)where E0 is the elastic modulus of a perfect crystal. Eq. (3) provides the functional dependence of the elastic modulus on point defect concentration, predicting that the elastic modulus decreases as the oxygen lattice vacancy concentration increases. Good fits to experimental data were obtained for both chemical expansion and elastic modulus, using β ≈ 1.73 × 10-3 nm [2, 5], ca ≈ 1.25 nm-3 and n = 9.
10:15 AM - AA4.3
Ionic Conductivity and Red-ox Properties of Ceria Solid Solutions from First-principles Calculations.
David Andersson 1 , Sergei Simak 2 , Natalia Skorodumova 3 , Igor Abrikosov 2 , Börje Johansson 1 3
1 Department of Materials Science & Engineering, Royal Institute of Technology, Stockholm Sweden, 2 Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping Sweden, 3 Department of Physics, Uppsala University, Uppsala Sweden
Show Abstract10:30 AM - AA4.4
Interfacial Structure and Point Defects in Ceria/Zirconia Superlattices.
Michael Dyer 1 , Anter El-Azab 1 2 , Fei Gao 3
1 Mechanical Engineering, Florida State University, Tallahassee, Florida, United States, 2 School of Computational Science, Florida State University, Tallahassee, Florida, United States, 3 Fundamental Science Directorate, Pacific Northwest National Laboratory, Richland, Washington, United States
Show AbstractCeria and zirconia have the ability to conduct oxygen ions rapidly, which makes them excellent candidates for use as electrolytes in devices such as oxygen sensors and solid oxide fuel cells. Ionic conductivity in these materials is limited by the oxygen vacancy diffusivity and concentration, which can be increased by doping. Recently, it has been found that the in-plane conductivity of ceria/zirconia superlattices with nanoscale layer thickness exceeds those of the individual materials. Although the exact mechanisms responsible for this conductivity increase are yet to be pinned down, they can be generally attributed to the role of interfaces, epitaxial strain and interfacial dislocations, which impact the point defect energetics in these materials. We report the results of a molecular dynamics simulation study aiming to understand the interfacial structure in ceria/zirconia superlattices and the impact of the interfaces on the energies of oxygen vacancy formation and Gd ion substitution in ceria and zirconia layers of the superlattice structure. It is found that the semi-coherent interface is characterized by misfit dislocations, paired at approximately 3-4 nm, with stacking-fault-like region in between, which agrees with the TEM observations. It is also found that the vacancy formation energy and the Gd substitution energy vary as a function of distance from the interface in the individual layers, and that these energies depend on the layer thickness. In addition, the simulations showed that the defect energy variations across the thickness of the ceria and zirconia layers are consistent with the XPS data for composition profile in the superlattice structure. Finally, in the semi-coherent superlattice structure, the formation energy of oxygen vacancies and the Gd substitution energy are found to depend on the position of these defects relative to the interfacial dislocation core. In particular, the oxygen vacancy formation energy is found to be negative close to the dislocation core, indicating that vacancy concentration will increase in such regions allowing for high conduction parallel to the interface.
10:45 AM - AA4.5
Chemical Stresses and Diffusion in Nonstochiometric Oxide Thin Films.
Sunil Mandowara 1 , Brian Sheldon 1 , Sidharth Bhatia 1 , Tai Hee Eun 1 , Janet Rankin 1
1 , Brown University, Providence, Rhode Island, United States
Show Abstract11:00 AM - AA4: Model
BREAK
11:30 AM - **AA4.6
Ab Initio Study of Dopant-Oxygen-Vacancy Coupling in Oxygen Conducting Perovskites.
Dane Morgan 1
1 , Univ. of Wisconsin - Madison, Madison, Wisconsin, United States
Show AbstractHigh oxygen conductivity ceramics are important for a wide range of applications, including solid oxide fuel cell electrolytes and catalysts, solid-state oxygen sensors, solid-state oxygen separation systems, and ceramic membrane conversion systems. There are a number of fast ion-conducting perovskites, and their wide range of possible dopants make them a very promising structural family for developing optimized materials. Of particular interest are perovskites with stoichiometry A2B2O5 (e.g., Ba2In2O5), where there is a high concentration of vacancies (1/6 of the oxygen sites) available to mediate transport. The vacancies are so prevalent in these systems that they interact strongly, creating significant short- and long-range-order effects (e.g., the vacancy ordered Brownmillerite phase). The chemical ordering strongly influences the oxygen transport and can be tuned through different dopants. However, detailed understanding of the coupling between the dopants and chemical ordering is still lacking. We will discuss ab initio studies of dopant-oxygen-vacancy coupling in doped Ba2In2O5 materials. We construct an ab initio based thermodynamic model with the cluster expansion method, which makes it possible to model the finite temperature behavior of the oxygen-vacancy ordering (e.g., order-disorder transition temperatures, oxygen site preferences, and short-range-order). Finally, we will discuss how these thermodynamic effects can couple to oxygen conductivity.
12:00 PM - AA4.7
Simulations of Anisotropic Oxygen Ion Conductivity in Layered Perovskite Type Materials.
Antony Cleave 1 , Mark Levy 1 , John Kilner 1 , Stephen Skinner 1 , Robin Grimes 1
1 Materials Department, Imperial College, London United Kingdom
Show AbstractThe current impetus for the development of alternative forms of power generation has led to the rapid development of devices such as solid oxide fuel cells (SOFC’s). Despite significant progress, many problems still exit. The high temperatures at which the cells must operate to achieve sufficiently high electrical conductivities pose serious problems due to mechanical problems such as thermal fatigue and limits on the choice of materials for the cell components. Consequently, there is an emphasis towards the development of materials with high conductivities at lower temperatures. To this end, much current work is given to perovskite related, mixed conducting materials for next generation cathodes. Of this class of material, one of the most studied is La2NiO4+δ. This material consists of alternating layers of perovskite-like LaNiO3 and rocksalt-like LaO. The excess oxygen is usually considered to be accommodated as an interplanar interstitial species that has led to interest in a possible oxygen interstitial conductivity mechanism. Given the layer structure, the anisotropy has been closely studied. Here, the aim of this work is to use atomistic simulation to predict the lowest energy path for oxygen migration through this system assuming both interstitial and vacancy mechanisms, parallel and perpendicular to the layer planes.As a first step, the sites for single oxygen interstitial ions were identified; both O2- and O- ions were considered. Subsequently defect cluster formation was considered. Results will be discussed in the light of available experimental data.
12:15 PM - AA4.8
The Unusual Role of Electronic Entropy in the Defect Equilibrium and Phase Diagram of LixFePO4.
Fei Zhou 1 , Thomas Maxisch 1 , Gerbrand Ceder 1
1 , MIT, Cambridge, Massachusetts, United States
Show Abstract12:30 PM - AA4.9
First Principles Study on the Coupling of Sodium Ordering and Co3+ / Co4+ Charge Ordering in P2-NaxCoO2.
Yoyo Hinuma 1 , Ying Meng 1 , Gerbrand Ceder 1
1 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe unusual electronic properties of NaxCoO2 are attracting considerable interest in recent years. At high sodium content, the system displays unusually strong thermoelectric effect and a low metallic resistance1. In addition, for low sodium content, the hydrated material shows superconducting behavior2.
NaxCoO2 is a mixed valence system with a fraction x Co4+ and (1- x) Co3+ ions. Mixed Co3+ / Co4+ systems tends to display rich physics as they are often close to spin transitions and metal insulator transitions, as has already been demonstrated in LixCoO23, 4. It is highly possible that there is ordering both in the Na/V sublattice and Co3+ / Co4+ sublattice, and that these ordering are coupled.
In this study, we analyze the coupling between the Na-vacancy and Co-charge ordering. Density Functional Theory (DFT) in the Generalized Gradient Approximation with Hubbard U correction (GGA+U) is combined with the coupled cluster expansion technique to study ordering in the 0.5 ≤ x ≤ 1 range. We have discovered a number of new ground states, and investigated in-plane ordering and stacking strategies in the lowest energy configurations. We will also discuss the key interactions that determine the ground states of the system, and which may be important for understanding the high thermopower of these mixed valence oxides.
References:
1I. Terasaki, Y. Sasago, and K. Uchinokura, Physical Review B 56, 12685 (1997).
2K. Takada, H. Sakurai, E. Takayama-Muromachi, et al., Nature 422, 53 (2003).
3C. A. Marianetti, G. Kotliar, and G. Ceder, Nature Materials 3, 627 (2004).
4M. Ménétrier, I. Saadoune, S. Levasseur, et al., Journal of Materials Chemistry 9, 1135 (1999).
12:45 PM - AA4.10
Modeling of The Area Specific Resistance and Interpretation of Impedance Spectra of Composite Cathodes.
Martin Sogaard 1 , Mogens Mogensen 1
1 , Risø National Laboratory, Roskilde Denmark
Show AbstractAA5/QQ2: Joint Session: Solid State Chemistry of Ionic Conductors
Session Chairs
Allan Jacobson
Silvia Licoccia
Tuesday PM, November 28, 2006
Grand Ballroom (Sheraton)
2:30 PM - **AA5.1/QQ2.1
Mesoporous Transition Metal Oxides for Energy Storage.
Feng Jiao 1 , Shaju Kuthanapillil 1 , Peter Bruce 1
1 Chemisty, University of St Andrews, St Andrews United Kingdom
Show AbstractMesoporous materials based on main group elements are well established; this is not the case for transition metal oxides, in part because their synthesis has proved more intractable. Yet mesoporous transition metal oxides can exhibit many unique and important properties leading to a diverse range of applications. The synthesis and characterisation of several ordered mesoporous transition metal oxides with highly crystalline walls, α-Fe2O3, γ-Fe2O3, Fe3O4 (inverse spinel), Mn3O4 (spinel), low temperature-LiCoO2, will be described as will the significance of such materials in enabling a step change in the performance of energy storage devices, vital to address the problem of global warming.The synthesis of mesoporous transition metal compounds is often limited to transition metals in oxidation states that are stable in solution. We have synthesised several of the above ordered mesoporous materials, e.g. Fe3O4 and Mn3O4, by reducing/oxidising other ordered mesoporous transition metal oxides, e.g. Fe2O3 and Mn2O3, while preserving the ordered mesostructures throughout, thus enabling access to new mesoporous transition metal compounds. LT - LiCoO2 was synthesised by reacting mesoporous Co3O4 with LiOH in the solid-state, converting the former to the low temperature polymorph of LiCoO2, with preservation of the ordered mesostructure and with a high level of crystallinity in the walls.The magnetic properties of crystalline mesoporous materials are distinct from those of the corresponding bulk phases and from nanoparticulate forms of the same material in which the nanoparticle diameter is comparable to the thickness of the walls. Data on the magnetic behaviour will be presented.LT-LiCoO2 is an intercalation host from which lithium may be removed and re-inserted. As a mesoporous material, when used as an electrode in key energy storage devices such as rechargeable lithium batteries, the electrolyte can flood the pores providing a high surface area in intimate contact with the electrode. Furthermore, the thin walls (typically 7 nm) provides short diffusion distances for Li+ and e– on intercalation/deintercalation. Both features lead to rapid intercalation processes and much greater reversibility than is the case for corresponding nanoparticulate LT-LiCoO2. The ordered mesostructure is preserved on repeated intercalation/deintercalation. Data on the superior properties of the mesoporous material as an energy storage electrode will be presented.
3:00 PM - AA5.2/QQ2.2
Nonstoichiometry of Vanadium (IV) Oxide.
Dilan Seneviratne 1 , Harry Tuller 1
1 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show Abstract3:15 PM - AA5.3/QQ2.3
New Insights Into The Formation Of Organically Templated Vanadium Oxides.
Arunachalam Ramanan 1 2 , M Stanley Whittingham 2
1 Chemistry, Indian Institute of Technology, Delhi, New Delhi , Delhi, India, 2 Chemistry and Materials Research Center, Binghamton University, Binghamton, New York, United States
Show Abstract3:30 PM - AA5.4/QQ2.4
Bio-controlled Synthesis of Nanostructured Vanadium Oxides.
Olivier Durupthy 1 , Axel Marchal 1 , Nathalie Steunou 1 , Thibaud Coradin 1 , Gervaise Mosser 1 , Jacques Livage 1
1 Université Paris 6, Chimie de la Matière Condensée de Paris, Paris France
Show Abstract3:45 PM - AA5.5/QQ2.5
Exploring Ionic Conductivity Mechanisms in Interfaces and Nanoparticles Using Magic-angle Spinning Nuclear Magnetic Resonance (MAS NMR).
Stephen Boyd 1 , Clare Grey 1
1 Chemistry, Stony Brook University, Stony Brook, New York, United States
Show AbstractSeveral systems, including solid oxide fuel cells (SOFC) and gas sensors, rely on fast, reliable ionic conductivity within particles and at interfaces. Consequently, much research has centered on finding new materials that can support fast ionic movement at a reasonable temperature and at understanding conduction mechanisms. Here, two systems were studied in an attempt to investigate interfacial and surface phenomena. First, a heterostructurual material consisting of thin, alternating layers of BaF2 and CaF2 deposited by molecular beam epitaxy (MBE) was investigated by using 19F MAS NMR. New resonances were observed, in addition to those due to BaF2 and CaF2, and the relaxation times of all these peaks were investigated as a function of temperature. Second, nanoparticles of BaF2, treated with the a super-Lewis acid, SbF5, were studied by NMR as a function of loading level. SbF5 treatment resulted in the creation of local environments with very short spin-lattice relaxation (T1) times, indicating enhanced ionic mobility. More detailed NMR experiments are currently in progress to correlate ionic mobility with local structure.We thank Prof. J. Maier for providing the heterostructure sample and for helpful discussions.
4:00 PM - AA5/QQ2: Joint
BREAK
4:30 PM - **AA5.6/QQ2.6
Ionic and Mixed Conductors for Energy: Preparation and Properties.
Philippe Knauth 1
1 MADIREL, University of Provence, Marseille France
Show Abstract5:00 PM - AA5.7/QQ2.7
Electrochemical Synthesis of Inorganic Films Containing Ordered Nanoporous Structures Using Interfacial Surfactant Templating.
Ellen Steinmiller 1 , Ryan Spray 1 , Matthew Yarger 1 , Nikhlendra Singh 1 , Kyoung-Shin Choi 1
1 Department of Chemistry, Purdue University, West Lafayette, Indiana, United States
Show Abstract Porous electrodes have been the center of interest in the development of devices for use in energy production, catalysis, and sensing application. By providing an enhanced surface area per unit volume, porous structures can significantly improve the kinetics and mass transfer at the interfaces of electrodes, thus enhancing the efficiency of various chemical and electrochemical reactions. Creating electrodes with ordered nanoporous structures is of special interest because it not only increases surface areas enormously but also makes it possible to study the effect of specific nanostructural details (i.e. pore sizes and pore connections) on chemical and physical properties of the electrodes. In this presentation, we introduce an electrochemical strategy for producing inorganic nanoporous films by utilizing self-assembly of amphiphilic molecules at solid-liquid interfaces for electrodeposition. The spontaneous aggregation of amphiphiles at solid-liquid interfaces is a well-established phenomenon. Surface micelles form at concentrations well below the critical micelle concentration (cmc) because the surface forces increase the interfacial concentration of amphiphiles. The novelty of our approach lies in exploiting these phenomena for inorganic synthesis by combining it with electrodeposition. This can be achieved by using a working electrode for both the organic assemblies and inorganic deposition. By selecting surfactants with appropriate hydrophilic groups, the metal ions that need to be deposited can be strongly bound on the surface of surfactant micelles as counter ions, thereby forming stable organic-inorganic interfacial aggregates. When an electrical bias is applied to initiate the deposition process, the organization of these metal ions in the interfacial assemblies directly becomes the skeleton of the inorganic deposits, resulting in ordered inorganic nanostructures. In this presentation, we will explain the principles of our electrochemical interfacial surfactant templating method in detail and discuss synthesis and characterization of several oxide and hydroxide films (e.g. zinc oxide, tin oxide) containing various nanoporous structures.
5:15 PM - AA5.8/QQ2.8
Anisotropy in Layered Polymer-Clay Nanocomposite Electrolytes.
Jodie Lutkenhaus 1 , Paula Hammond 1
1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show Abstract5:30 PM - AA5.9/QQ2.9
The Effect of Na Content on the Electrical Properties of Polycrystalline Na0.7Ga4.7Ti0.3O8 (x~0.7).
Jake Amoroso 1 2 3 , Doreen Edwards 1 2 3
1 , Alfred University, Alfred, New York, United States, 2 , New York State College of Cermaics, Alfred , New York, United States, 3 , Kazuo Inamori School of Engineering, Alfred , New York, United States
Show AbstractNew Presenting AuthorTues 11/28AA5.9/QQ2.94:30 - 4:45 pmThe Effect of Na Content on the Electrical Properties of Polycrystalline. Doreen D. Edwards
5:45 PM - AA5.10/QQ2.10
New Developments in Fluoride and Oxyfluoride Structural Chemistry.
Philip Lightfoot 1 , Nicholas Stephens 1 , Anil Jayasundera 1 , David Aldous 1
1 , University of St Andrews, St Andrews United Kingdom
Show AbstractThe development of the solid state chemistry of fluorides and oxyfluorides has lagged significantly behind that of the corresponding oxides. This is partly due to the more difficult and hazardous synthetic conditions generally required. Recently, milder methods of synthesising novel fluoride-based materials have come to the fore, both using relatively high-temperature solid state methods, and also through the increased use of solvothermal methods. We have recently been exploring the scope for preparing novel fluoride-based materials using organically-templated hydrothermal reactions. Our interests in functional materials lie in the areas of optical activity, ferroelectricity, magnetism and luminescence. In each case, the exploitation of fluoride rather than oxide-based systems may have advantages. Our recent exploratory work in this field has produced more than fifty novel compounds and structure types This talk will focus on the structural chemistry and preliminary physical property measurements of these systems, including reduced vanadium oxyfluorides, rare-earth fluorides and d0 metal oxyfluorides.
AA6: Poster Session: Batteries
Session Chairs
Tim Armstrong
Christian Masquelier
Yoshihiko Sadaoka
Enrico Traversa
Wednesday AM, November 29, 2006
Exhibition Hall D (Hynes)
9:00 PM - AA6.1
Ion Mobility in PMMA Doped with Small Amounts of a Lithium Salt.
Peter Kohn 1 , Klaus Schroeter 1 , Thomas Thurn-Albrecht 1
1 Physics Department, Martin Luther University Halle, Halle Germany
Show AbstractPolymer electrolytes are ionically conducting materials consisting of ions dissolved in a polymer matrix. As for other conducting materials the conductivity of these systems is determined by the product of the mobility and the number density of the free charge carriers. Apart from the mechanical properties the decisive quantity for application of these materials is the conductivity and its dependence on various variables, like temperature, salt concentration etc. For a basic understanding of this behaviour at least one of the quantities mentioned above, mobility or density of ions, is needed in addition to the conductivity. Normally NMR techniques are used to determine the mobilities of ions in polymer electrolytes (via determination of diffusion coefficients and use of the Einstein relation). We here discuss two electrical measurements in a parallel plate capacitor geometry as alternative methods to determine the density and the mobility of the ions, respectively. The basic idea for the first experiment is that if the density of free ions is small and a high, constant voltage is applied across the capacitor all the ions will accumulate near the electrodes in the Helmholtz double layers. Integration of the measured current during this charging of a double layer capacitor yields the total ionic charge in the system and the number of free ions can be calculated.In the second experiment like in the first one the ions of opposite charge are forced to separate and accumulate at the different electrodes by applying a constant voltage. Subsequently the voltage is reversed and the ions migrate from one electrode to the other. The current measured during this process gives the transit time which is directly related to the mobility of the charge carriers.For an exemplary application we used these methods to study ion mobility in amorphous polymethylmethacrylate (PMMA) doped with lithiumtrifluorosulfonate (LiCF3SO3) above the glass transition temperature of PMMA. The measurements were complemented by dielectric spectroscopy in the frequency domain. While the experiments described above allow a determination of the density and the mobility of the ions, the frequency dependent dielectric measurements give the temperature and salt-concentration dependence of the ohmic conductivity of the electrolyte.
9:00 PM - AA6.10
Magnetic Studies of Layered Cathode Materials for Lithium Ion Batteries.
Natasha Chernova 1 , Miaomiao Ma 1 , Jie Xiao 1 , M. Stanley Whittingham 1
1 Institute for Materials Research, State University of New York at Binghamton, Binghamton, New York, United States
Show AbstractTemperature dependences of DC and AC magnetic susceptibilities and magnetization curves of Lix(NiyMnyCo1-2y)O2 and Lix(NiyMnyCo1-2y)2-xO2 were studied to understand transition metal (TM) ion distribution through the magnetic interactions between the TM ions. In LiNi1/3Mn1/3Co1/3O2 and LiNi0.4Mn0.4Co0.2O2 spin-glass transitions were found, which implies random distribution of the TMs in the layers. The absence of magnetization hysteresis indicates good layered structure with small amount of Ni2+ in the Li layer. In LiNi0.45Mn0.45Co0.1O2 cluster-glass transition is observed provided by magnetic clusters formation around Ni2+ ions in the Li layer. In LiNi0.5Mn0.5O2 series of magnetic transitions is observed and explained assuming imperfect flower order of the TMs. This model is consistent with NMR data and Monte-Carlo simulations by C. Grey’s and G. Ceder’s groups. Upon chemical removal of only 0.06Li from LiNi0.5Mn0.5O2 the large hysteresis of magnetization observed in the pristine compound due to magnetic moment of clusters around Ni2+ on Li sites drastically decreases. The same effect is observed upon electrochemical removal of Li. This indicates that Ni2+ ions on Li sites are affected from the very beginning of Li removal. Possible mechanisms may include preferential oxidation of interslab Ni2+ or their migration to tetrahedral sites. Upon discharge the magnetic properties are not retained, therefore the TM distribution should be different than at the corresponding charge stage. The latter two facts were observed using the neutron diffraction by C. Grey’s group. In Lix(Ni0.45Mn0.45Co0.1)1-xO2 the largest hysteresis loop was observed at x=0.9; with increasing Li content the hysteresis diminished indicating decrease of the Ni/Li disorder. At lower Li contents the hysteresis loop diminishes and changes shape; additional magnetic transition observed from the temperature dependence of susceptibility is likely due to the appearance of a second phase. At x=0.5 this second phase becomes dominant; its nature will be discussed. This work is supported by the US Department of Energy, Office of FreedomCAR and Vehicle Technologies through the BATT program and by NSF, DMR 0313963.
9:00 PM - AA6.11
Influence of Lithium Content on Performance of Layered Li1+x(Ni0.45Mn0.45Co0.1)1-xO2 in Lithium Ion Batteries.
Jie Xiao 1 , Natasha Chernova 1 , M. Stanley Whittingham 1
1 Chemistry, State University of New York at Binghamton, Binghamton, New York, United States
Show Abstract9:00 PM - AA6.12
Effect of ZnO Coating on LiMn1.5Ni0.5O4 Cathode Materials or Application to Li Ion Rechargeable Batteries.
Rahul Singhal 1 , Juan Burgos 2 , Maharaj Tomar 1 , Ram Katiyar 2
1 Physics, University of Puerto Rico, Mayaguez, Puerto Rico, United States, 2 Physics, University of Puerto Rico, San-Juan, Puerto Rico, United States
Show Abstract9:00 PM - AA6.13
A New Lithium Iron Phosphate LiFe2P3O10 Synthesized by Wet Chemistry.
Atmane Ait-Salah 1 , Chintalapalle Ramana 2 , Francois Gendron 3 , Jean Francois Morhange 4 , Alain Mauger 5 , Christian Julien 6
1 INSP, Universite P & M Curie, Paris France, 2 Nanoscience and Surface Chemistry Laboratory, Michigan University, Ann Arbor, Michigan, United States, 3 INSP, Universite P & M Curie, Paris France, 4 INSP, Universite P & M Curie, Paris France, 5 MIPPU, CNRS, Paris France, 6 Institut des NanoSciences de Paris, Universite P & M Curie, Paris France
Show Abstract9:00 PM - AA6.14
Aligned LiFePO4 Nanorods: Formation, Modification and Electrochemistry.
Lin Xu 1 , Liqiang Mai 1 2 , Tao Hu 1 , Wanli Guo 1
1 Institute of Materials Science and Engineering, Wuhan University of Technology, Wuhan, Hubei, China, 2 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show Abstract9:00 PM - AA6.15
Local Structure and Magnetic Properties of LixFePO4 (0≤x≤1) Glasses.
Pavel Jozwiak 1 , Jerzy Garbarczyk 2 , Francois Gendron 3 , Alain Mauger 4 , Christian Julien 5
1 Faculty of Physics, Warsaw University of Technology, Warsaw Poland, 2 Faculty of Physics, Warsaw University of Technology, Warsaw Poland, 3 INSP, University of Paris 6, Paris France, 4 MIPPU, CNRS, Paris France, 5 Institut des NanoSciences de Paris, Universite P & M Curie, Paris France
Show Abstract9:00 PM - AA6.16
Synthesis and Characterization of Li4Ti5O12 Thin Films by Rapid Thermal Annealing.
Chen Hu 1 , Wen Zhang 1 , Hanxing Liu 1
1 materials sicence, Wuhan university of technology, WuHan, HuBei , China
Show Abstract9:00 PM - AA6.18
Ionic Conductivity of NASICON-like Compounds in InPO4-Li3PO4 System.
Galina Zimina 1 , Irina Smirnova 1 , Anna Potapova 1 , Andrey Novoselov 1 , Felix Spiridonov 2 , Sergey Stefanovich 2
1 Department of Chemistry and Chemical Engineering for Rare and Dispersed Elements, Lomonosov Moscow State Academy of Fine Chemical Technology, Moscow Russian Federation, 2 Department of Chemistry, Lomonosov Moscow State University, Moscow Russian Federation
Show Abstract9:00 PM - AA6.19
The Influence of Heteroatomic Nitrogen on Lithium Intercalation in Oligophenylenes.
Walter Doherty 1 , Rainer Friedlein 1 , Thierry Renouard 2 3 , Claude Mathis 2 , William Salaneck 1
1 Surface Physics and Chemistry, Linköping University, Linköping Sweden, 2 , Institut Charles Sadron, Strasbourg France, 3 Equipe Chimie et Ingénierie des Procédés (CIP), Université de Rennes 1, Rennes France
Show Abstract9:00 PM - AA6.2
Development of Solid Electrolyte Membranes for Use in Lithium Water Batteries.
Clifford Cook 1 , Robert Doe 1 , Michael Wagner 1
1 Chemistry, George Washington University, Washington, District of Columbia, United States
Show AbstractLithium metal in combination with water is a highly attractive power source because of the high specific energy for this system. Because of the vigorous nature of the reaction between lithium and water, many obstacles must be overcome in order to harness the energy that this system is capable of producing. Parasitic reactions must be controlled so as not to passivate the lithium or consume it totally. In addition, production of hydrogen gas that may accompany the parasitic reactions presents a serious challenge. As a result it is difficult to maintain high voltage and control the current density in these systems.In order to overcome these obstacles we are developing composite membranes of various lithium-ion conducting solid electrolytes and polymers. Lithium-ion conducting solid electrolytes are known to achieve ionic conductivities as large as 10-3 S/cm2. Utilizing these materials in conjunction with polymers and other materials, we are striving to create durable, hydrophobic membranes that will allow us to limit the parasitic reactions, maintain low cell impedance and thus achieve Li/water batteries for long-term use in practical applications. Results of the experiments will be presented herein.
9:00 PM - AA6.3
Charge-Discharge Reaction of Cu2Sb as Anode Material for Lithium Ion Battery.
Masanobu Nakayama 1 , Makiko Noji 1 , Tomoaki Kashiwagi 1 , Shinsuke Matsuno 1 , Masataka Wakihara 1 , Yo Kobayashi 2 , Hajime Miyashiro 2
1 , Tokyo Institute of Technology, Tokyo Japan, 2 , Central Research Institute of Electric Power Industry, Tokyo Japan
Show Abstract9:00 PM - AA6.4
LixCn as Anode Material for Lithium Ion Batteries.
Wang Shun 1 , Xie Haiming 1
1 chemistry, Northeast Normal university, Changchun, Jilin, China
Show Abstract9:00 PM - AA6.5
Nanocrystalline Diamond Anodes for Rechargeable Lithium Ion Batteries.
Joel De Jesus 1 , Sri Katar 2 , Fabrice Piazza 1 , Ram Katiyar 1 , Carlos Cabrera 2 , Brad Weiner 2 , Gerardo Morell 1
1 Physics, University of Puerto Rico, San Juan, Puerto Rico, United States, 2 Chemistry, University of Puerto Rico, San Juan, Puerto Rico, United States
Show Abstract9:00 PM - AA6.6
Acicular Silver Vanadium Oxide Nanofibers Prepared by Hydrothermal Synthesis.
Kenneth Takeuchi 1 , Amy Marschilok 2 , Randolph Leising 2 , Esther Takeuchi 2
1 Department of Chemistry, University at Buffalo (SUNY), Buffalo, New York, United States, 2 Research and Development, Greatbatch, Inc., Clarence, New York, United States
Show AbstractSilver vanadium oxide (SVO, Ag2V4O11) has demonstrated commercial success as a solid-state cathode material in power sources for implantable biomedical devices. This report describes the synthesis of SVO via a hydrothermal method. This novel synthetic approach allows low temperature production of acicular SVO nanofibers with a high surface area. This material was investigated as a cathode material in primary lithium batteries for high rate pulse applications.
9:00 PM - AA6.7
The Effect of Rare-earth Doping LiMn2O4 on Its Use as a Cathode in Li-ion Batteries
Maharaj Tomar 1 , Osbert Oviedo 1 , Ricardo Melgarejo 1 , Rahul Singhal 1 , Ram Katiyar 2
1 Physics, University of Puerto Rico, Mayaguez, Puerto Rico, United States, 2 Physics, University of Puerto Rico, San-Juan, Puerto Rico, United States
Show Abstract9:00 PM - AA6.8
Analysis of Composition and Valence States in Positive Electrode Materials (Fe-substituted Li2MnO3) for Lithium Ion Batteries by Analytical Transmission Electron Microscopy.
Jun Kikkawa 1 , Tomoki Akita 1 , Mitsuharu Tabuchi 1 , Masahiro Shikano 1 , Kuniaki Tatsumi 1 , Masanori Kohyama 1
1 , National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, Osaka, Japan
Show Abstract9:00 PM - AA6.9
Li Batteries with Porous SOL-GEL Cathodes.
Antonela Dima 1 , Maurizio Casalino 1 , Francesco Della Corte 1 , Ivo Rendina 1
1 IMM, CNR , Napoli Italy
Show Abstract
Symposium Organizers
Timothy Armstrong Oak Ridge National Laboratory
Christian Masquelier University of Picardie-CNRS
Yoshihiko Sadaoka Ehime University
Enrico Traversa University of Rome Tor Vergata
AA7/BB8: Joint Session: Solid State Ionics for Mobile Energy
Session Chairs
Rosa Palacin
Stanley Whittingham
Wednesday AM, November 29, 2006
Republic B (Sheraton)
9:30 AM - **AA7.1/BB8.1
Enabling Aspects of Metal Halide Nanocompositesfor Reversible Energy Storage.
Glenn Amatucci 1 , Fadwa Badway 1 , Nathalie Pereira 1 , Wei Tong 1 , Irene Plitz 1 , Jafar Al-Sharab 1 , Frederick Cosandey 1 , Adam Skrzypczak 1 , John Gural 1
1 Energy Storage Research Group, Department of Materials Science and Engineering, Rutgers, the State University of New Jersey, North Brunswick, New Jersey, United States
Show Abstract10:00 AM - AA7.2/BB8.2
A Study on the LiMn2O4 Cathodes with Mesh-like Structures for Li Secondary Batteries.
Min Park 1 , Dong-Hoon Chung 1 , Bong-Kwan Shin 1 , Seung-Ki Joo 1
1 School pf Material Science and Engineering, Seoul National University, Seoul Korea (the Republic of)
Show Abstract10:15 AM - AA7.3/BB8.3
Nanosized Amorphous Materials as Anodes for Lithium Batteries.
Quan Fan 1 , M. Stanley Whittingham 1
1 Department of Chemistry, State University of New York at Binghamton, Binghamton, New York, United States
Show Abstract10:30 AM - AA7.4/BB8.4
Macroporous Silicon Inverse Opals as Electrodes for Lithium-Ion Secondary Batteries.
Alexei Esmanski 1 , Geoffrey Ozin 1
1 Chemistry, University of Toronto, Toronto, Ontario, Canada
Show AbstractColloidal crystal templating methods are among the “hottest” areas in materials science today. Three-dimensional macroporous ordered structures (“opals” and “inverse opals”) can be produced by these methods on a large scale. Although a principal area of research for materials with opal and inverse opal morphologies is that of photonic crystals, a few investigations have examined the possibility of using these structures as gas sensors, catalysts and battery electrodes.Specifically, there are several potential advantages of lithium-ion battery electrodes, based on inverse opal structures. High electrode-electrolyte interfacial surface area and easier access to the bulk of electrode, as well as reduced lithium diffusion length allow for the use of batteries at higher discharge rates [1]. Highly open hierarchical structures also provide better mechanical stability to volume swings during battery cycling.The theoretical capacity of silicon for lithium insertion at room temperature is 3579mAh/g (Li15Si4 phase) [2]. For comparison, the theoretical capacity of graphite, the material of choice in modern state-of-the-art lithium-ion batteries, is only 372mAh/g. This makes silicon one of the most promising anode materials despite its relatively low electronic conductivity and lithium diffusion rates.In this study, opal films (10–40 μm thick) of monodisperse silica nanospheres were fabricated by the evaporation induced self-assembly method [3]. These templates were uniformly infiltrated with amorphous silicon via chemical vapor deposition, with subsequent removal of the silica template [4]. The structural/electrochemical property relationships of silicon inverse colloidal crystal films have been investigated and compared to traditional negative electrode materials, so as to outline the main benefits of the inverse opal hierarchical structure. Electrochemical cycling of silicon inverse opal films demonstrated their good cycling ability, high lithium insertion capacity approaching the theoretical value and excellent coulombic efficiency. Electron microscopy studies confirmed that the open hierarchical structure is maintained during lithium insertion-deinsertion and revealed interesting morphological changes occurring in the system during cycling.References:1. J. S. Sakamoto, B. Dunn, J. Mater. Chem., 2002, 12, 28592. M. N.Obrovac, L. Christensen, El-Chem. Solid-State Lett., 2004, 7, A933. P. Jiang, J. F. Bertone, K. S. Hwang, V. L. Colvin, Chem. Mater., 1999, 11, 21324. A. Blanco, E. Chomski, S. Grabtchak, M. Ibisate, S. John, S. W. Leonard, C. Lopez, F. Messeguer, H. Miguez, J. P. Mondia, G. A, Ozin, O. Toader, H. M. van Driel, Nature, 2000, 405, 437
10:45 AM - AA7.5/BB8.5
Preparation and Characterization of ALD TiN Thin Films on Lithium Titanate Spinel (Li4Ti5O12) for Lithium Ion Battery Applications.
Mark Snyder 1 , Boris Ravdel 4 , Joseph DiCarlo 4 , M. Wheeler 1 , Carl Tripp 2 3 , William DeSisto 1 3
1 Chemical & Biological Engineering, University of Maine, Orono, Maine, United States, 4 , Lithion Corp., Pawcatuck, Connecticut, United States, 2 Chemistry, University of Maine, Orono, Maine, United States, 3 Laboratory for Surface Science & Technology (LASST), University of Maine, Orono, Maine, United States
Show AbstractLithium titanate spinel (Li4Ti5O12) has received an increasing level of attention over the last five years as a nanopowder lithium-ion battery anode. Nanopowder electrodes may provide a higher energy density than currently available. Applying a thin film that is both conducting and chemically inert to harmful reactions with the solvent/electrolyte may enhance battery cycle life. We are investigating thin TiN films on Li4Ti5O12 prepared by atomic layer deposition (ALD) and have characterized their properties, including their influence, on Li-ion battery performance. ALD consists of sequential deposition of self-terminating, surface layer half-reactions (an “A step” and “B step”) and has the potential to uniformly coat irregular surfaces like nanoparticles. To gain a basic understanding of the mechanism of thin film formation on a powder surface, modification of a silica powder surface with TiCl4 (step A) and NH3 (step B) to form a TiN thin film has been performed and characterized in situ with FTIR. Six layers were deposited at 400 C. IR spectra of a TiClx-terminated surface after step A, and an NH-terminated surface after step B were obtained. Insight was gained on causes of incomplete surface film coverage. ALD thin films have been deposited on Li4Ti5O12 as well. Thin films of 200 to 1000 layers were deposited at temperatures from 400 to 600 C. A 200-layer film deposited at 500 C had an estimated thickness of 6 nm on a particle of about 50 nm in length. Nitrogen analysis and transmission electron microscopy were used to verify the presence of nitrogen and formation of a thin film, respectively, on Li4Ti5O12. Modifying the powder with an ALD thin film coating produced a powder that maintained charge longer with shorter transient periods during cyclic voltammetry. It also held a more consistent charge capacity over varying discharge rates in coin cell testing than unmodified Li4Ti5O12. Furthermore, the surface of the spinel nanopowder has been studied under vacuum and at varying temperatures with diffuse reflectance infrared Fourier transform spectroscopy revealing surface hydroxyls, carbonates and water. Several probe molecules have been used to determine the presence of acid/base sites and explore potential methods of bonding with thin film precursors. Pyridine bonded with the surface at Lewis acid sites. No evidence of Brönsted acid sites were observed. Hexamethyldisilazane formed Ti-O-Si bonds. Both of these reactions proceeded at room temperature and 400 C.
11:00 AM - AA7/BB8: Joint
BREAK
11:30 AM - **AA7.6/BB8.6
Nanostructured Catalysts for Portable Fuel Cells Applications.
Vincenzo Antonucci 1 , Vincenzo Baglio 1 , Alessandra Di Blasi 1 , Alessandro Stassi 1 , Claudia D'Urso 1 , Antonino Arico' 1
1 Energy and Transport, CNR-ITAE, Messina Italy
Show AbstractStationary and automotive fuel cells (FC) devices are expected to play an important role for the sustainable energy generation in the next years. Significant interest is also addressed to small portable fuel cells that possibly will find market application before large-size FC systems. The potential market for portable fuel cell systems deals with remote and micro-distributed electrical energy generation including mobile phones, lap-top computers, energy supply for weather stations, medical devices, auxiliary power units (APU) etc. The main advantages of such systems rely on the high energy density of liquid fuels such as methanol and ethanol, long-life-time, easy recycle and low emission of pollutants in the environment. The CNR-ITAE Istitute is involved in European and National projects with the aim to develop nanostructured catalyst for portable direct methanol and ethanol fuel cells. The target for DMFC/DEFC devices for portable application is to work at relatively low temperatures and atmospheric pressure with high efficiency and performance. The effective operation at this low temperature is particularly challenging and requires innovation in different aspects of materials and system development. In particular to address the poor reaction kinetics at the anode, high surface area catalysts composed of nanosised noble metal particles need to be developed and investigated for operation at low temperatures starting from sub-ambient to 60 °C. Although, one of the main drawback of DMFC systems i.e. the methanol cross-over through the membrane is strongly depressed by the decrease of the operating temperature, this constraint affects the cathode performance even at low temperature by causing a mixed potential and poisoning of the cathode surface. Accordingly, it is strongly necessary to develop methanol /ethanol tolerant cathode catalysts with suitable activity at low temperature. Also in this case, a proper catalytic activity for achieving portable fuel cells performance targets is assured by noble metal catalyst properly modified with transition metals capable of reducing the adsorption of alcohols on the cathode surface. The activity presented in this communication deals with both anode and cathode catalysts synthesised by a low–temperature colloidal route characterised by high concentration of metallic phase on carbon black and particle size smaller than 3 nm. The structure and morphology of the catalysts has been investigated and these properties have been correlated with the electrochemical activity and tolerance to methanol poisoning.
12:00 PM - AA7.7/BB8.7
Synthesis of Bimetallic and Trimetallic Alloy Nanoparticles as Catalysts in Fuel Cells.
Peter Njoki 1 , Jin Luo 1 , Bilal Khan 1 , Suprav Mishra 1 , Ravishanker Sujakumar 1 , Chuan-Jian Zhong 1
1 Chemistry, State Univ. of New York at Binghamton, Binghamton, New York, United States
Show Abstract12:15 PM - AA7.8/BB8.8
Passive Air Breathing Fuel Cells For Portable Applications: What are the Limits to Cathode Performance?
Ryan O'Hayre 1 2 , Tibor Fabian 2 , Shawn Litster 2 , Fritz Prinz 2 , Juan Santiago 2
1 Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado, United States, 2 Mechanical Engineering, Stanford University, Stanford, California, United States
Show Abstract12:30 PM - AA7.9/BB8.9
Direct-Write Microfabrication of Single-Chamber Solid Oxide Fuel Cells with Interdigitated Electrodes.
Melanie Kuhn 1 , Teko Napporn 2 , Michel Meunier 2 , Daniel Therriault 1 , Srikar Vengallatore 3
1 Department of Mechanical Engineering, Ecole Polytechnique de Montreal, Montreal, Quebec, Canada, 2 Department of Engineering Physics, Ecole Polytechnique de Montreal, Montreal, Quebec, Canada, 3 Department of Mechanical Engineering, McGill University, Montreal, Quebec, Canada
Show AbstractMiniaturized single-chamber solid-oxide fuel cells (SC-SOFC) are a promising class of devices for portable power generation required in the operation of distributed networks of microelectromechanical systems (MEMS) in harsh environments. The single-face configuration, which consists of interdigitated (comb-like) array of electrodes on an yttria-stabilized zirconia (YSZ) electrolyte substrate, is of particular interest because of the ease of high-temperature microfluidic packaging and integration with MEMS. The primary design consideration for this configuration is the minimization of electrode widths and inter-electrode spacings to dimensions on the order of a few micrometers. This is necessary to minimize polarization resistance and increase fuel cell efficiency. Achieving these geometries using standard microfabrication methods is difficult because of the thickness, porosity, and complex chemistries of the electrodes. Here, we report the development of an innovative and rapid method for manufacturing SC-SOFCs with interdigitated electrodes using robot-controlled direct-writing. The main steps consist of: (i) formation of inks (or suspensions) using anode (NiO-YSZ) and cathode (lanthanum strontium manganite) powders, (ii) pressure-driven extrusion of inks through a micronozzle using a robot-controlled platform, and (iii) sequential sintering to form the fuel cell. The first-generation SC-SOFC device, with electrode widths of 130 μm and inter-electrode spacing of 300 μm, has been manufactured using direct-write microfabrication. The electrodes have been extensively characterized using electron microscopy and x-ray diffraction to assess porosity and to confirm phase identity. The primary process parameters in this approach are the particle size and size distribution, rheological properties of the suspension, extrusion pressure, nozzle size, stage velocity, and sintering conditions. As the first step in the development of detailed process-structure-performance correlations for the fuel cells, we have studied the effects of extrusion pressure (in the range 30-40 bar) and stage velocity (in the range 0.2-2.0 mm/s) on the geometry and size of electrodes, for fixed suspension viscosity and nozzle diameter. An optimal combination of speed and pressure has been identified and catalogued in the form of process maps. Similarly, the particle size distribution of the anode and cathode powders is found to have a significant effect on the microstructure, especially porosity, of the sintered electrodes. The implications of these results for the design of the next generation of SC-SOFC, with reduced electrode dimensions and improved electrochemical performance, will be discussed.
12:45 PM - AA7.10/BB8.10
Materials and Design Study for Micromachined Solid Oxide Fuel Cells Membranes.
Samuel Rey-Mermet 1 , Paul Muralt 1
1 STI-IMX-LC, Ecole Polytechnique Fédérale de Lausanne, Lausanne Switzerland
Show AbstractIn this work we studied materials design and processes for the realization of a micro SOFC entirely based on silicon MEMS technology. As electrolyte materials, ceria doped gadolinia Ce0.8Gd0.2O2-x (CGO) and zirconia stabilized with yttria Zr 0.92Y0.08O2-x (YSZ) were investigated in the form of 0.2 to 2 μm thick films deposited by reactive magnetron sputtering. X-rays diffraction patterns and scanning electron microscopy show that both types of films exhibit a crystalline columnar structure. Predominant texture are are (111) for CGO and (101) for YSZ. The ionic conductivities measured by DC and AC techniques matched well with the literature values. For the CGO thin films, the conductivity of the film perpendicular to the substrate was slightly smaller (1.8 S/m at 700°C in air) than the conductivity in the plane of the film (2 S/m at 700°C in air) proving that there was no short through the grain boundaries. The activation energies for ionic conduction were measured as 0.51-0.58 eV for CGO films and are thus slightly smaller than the bulk ceramics values. The ionic conductivity of the YSZ thin film in reducing conditions at 500°C amounts to 35 S/m in reducing atmosphere at 900°C, with an activation energy of 0.21 eV. Stress analysis made by curvature measurements show that a thermal treatment of the CGO films reduces the compressive stress after deposition. This heat treatment reorganizes or removes the oxygen vacancies in the film leading to a change of the strain. Free standing 200 nm thick CGO membranes of 500 μm diameter were realized. These membranes are too fragile for application in real conditions. A supporting nickel grid was developed giving mechanical stability up to at least 550°C. The electrochemically deposited nickel grid is applied on the anode side and serves as a current collector at the same time. With this design, it is possible to fabricate 1 μm thin free standing membranes with a diameter of 5 mm. The grid is composed of hexagonal cells with a diagonal of 100 μm and a line width of 10 μm. The anode is made of porous Ni-CGO co-sputtered by reactive magnetron sputtering using a nickel and a CGO target. The anode has a total conductivity of 5000 S/cm in argon atmosphere. The cathode of cobalt doped lanthanum perovskite La0.32Sr0.68CoO3 (LSC) is also deposited by reactive magnetron sputtering. A dense and thin LSC film covers the entire cell surface and has a conductivity of 80 S/cm at 600°C in air. A platinum current collector mesh is also deposited on the LSC to increase the electronic conductivity of the cathode. In this work we realized large, mechanically stable fuel cell membranes and developed materials by sputtering with sufficient properties for applications.
AA8: Fuel Cells: PEM-FCs
Session Chairs
Vincenzo Antonucci
Hidenori Yahiro
Wednesday PM, November 29, 2006
Republic B (Sheraton)
2:30 PM - **AA8.1
Hybrid Proton Conducting Polymeric Electrolytes for Intermediate Temperature PEMFCs.
Silvia Licoccia 1
1 Chemical Science and Technology, University of Rome Tor Vergata, Rome Italy
Show AbstractTo successfully perform in Polymer Electrolyte Membrane Fuel Cells (PEMFCs), the electrolytes must meet several requirements, most important among them high proton conductivity, high hydrolytic stability, high oxidative resistance, good mechanical properties and, possibly, low cost. New generation electrolytes should maintain such performances above 100 °C to increase CO tolerance, enhance fuel oxidation kinetics, ease thermal balance. Furthermore, for automotive application, operating a FC vehicle at ambient temperature above 20 °C requires either a large radiator, a solution certainly not ideal for most car manufactures, or an increase the operation T above 100 °C.Significant research efforts are devoted to the achievement of the above mentioned goals and two main topics have been identified: understanding the mechanisms of functioning of Nafion, the most widely accept standard for PEMFCs, and sulfonation and/or modification of different polymers.In our laboratory attention has been focused on the development of composite Nafion-based membranes to obtain systems capable to perform at T > 100 °C and on possible modifications that can be introduced in sulfonated arylene main chain polymers, in particular polyetheretherchetone (PEEK) and polyphenylsulfone (PPSU). Both these latter polymers show rather large conductivity when sulfonated, but their mechanical, morphological and solubility properties progressively deteriorate with the degree of sulfonation (DS) because acid groups directly linked to the aromatic hydrophobic backbones cannot assemble in phase separated domains as well as perfluorinated systems with more hydrophobic flexible side chains.Different strategies are under investigation to increase the operation temperature of Nafion and to implement the properties of SPEEK with high DS: i)preparation of Class I hybrids, where components are bound by weak interactions, using as fillers ceramic oxides, inorganic proton conductors or functionalized organically modified silanes (ormosils).ii)preparation of organic/inorganic Class II hybrid systems where -Si-O-Si-units link two polymeric chains, and the inorganic part would offer thermal and mechanical stability and the organic component flexibility and processability. The combination of the two features could contribute to sharpen the border between the hydrophobic and hydrophilic regions, thus modulating the requirements of high conductivity and low permeability.iii)preparation of polymer blends to combine the positive features of different polymeric materials. Membranes deriving from these different approaches were successfully prepared by casting. Their structure, fuel permeability, and electrochemical performances were investigated by means of several techniques including 1-H and 29-Si NMR, ATR/FTIR, FE-SEM and EIS and tested in a prototype fuel cell.
3:00 PM - AA8.2
New High Temperature Polymer Electrolyte Membranes and their Fuel Cell Performance.
Nora Gourdoupi 1 , Maria Daletou 2 3 , Maria Geormezi 2 3 , Joannis Kallitsis 2 3 , Stelios Neophytides 3
1 Advent Technologies S.A., Patras Science Park, Patras Greece, 2 Department of Chemistry, University of Patras, Patras Greece, 3 , Institute of Chemical Engineering and High Temperature Chemical Processes, Patras Greece
Show AbstractPolymer electrolyte membrane fuel cells are the most promising renewable power generators for zero-emissions vehicles and portable applications. PEMFCs that operate at high temperatures (>120 oC) show certain advantages which relate to increased tolerance of the anode to carbon monoxide (>0.1 CO at 150 oC), enhancement of reaction rate, electrochemical performance relatively independent of humidity, simplification of the system. Membrane electrode assembly (MEA) is the heart of a PEM fuel cell and consists of a proton exchange membrane, catalyst layers and gas diffusion layers. Concerning the membrane, the properties that should be met in order to be used as an electrolyte are the following: good mechanical properties, high thermal, chemical and oxidative stability, high doping ability with strong acids, high proton conductivity, low electronic conductivity, low gas permeability and low cost.Polybenzimidazole (PBI) doped with H3PO4 is the state of the art high temperature polymer electrolyte. Although it exhibits high thermal stability, high ionic conductivity and high fuel cell performance, its low oxidative stability is a critical disadvantage for its long term performance. Our approach to the development of new polymer membranes include the synthesis of new aromatic polyethers containing polar units in the main chain and the preparation of PBI based and PBI-free blends. Aromatic polyethers are chosen due to their good mechanical properties and high thermal stability while the insertion of polar pyridine is done with the view of having sites that can interact with phosphoric acid resulting thus in highly conductive materials. Characterization of the prepared polymers with conventional techniques showed that they fulfill all the prerequisites in order to be used as high temperature electrolytes.In addition, membrane electrode assemblies were prepared with the new materials and were further tested in 2x2 and 5x5 cm2 single cells. The conductivity of the polymer membranes as well as the different MEAs performance were tested by means of AC impedance. It is shown that upon current application, water is dragged through the membrane while the conductivity of the H3PO4 doped membranes strongly depends on the partial pressure of steam and on the applied potential. Conductivities in the range of 10 -2 S/cm were obtained while the single cell performance is comparable and in some cases better to that reported for the PBI-membranes.
3:15 PM - AA8.3
New Polybenzimidazole-based Membranes for Fuel Cells.
Eliana Quartarone 1 , Arianna Carollo 1 , Federico Belotti 1 , Piercarlo Mustarelli 1 , Aldo Magistris 1 , Corrado Tomasi 3 , Luigi Garlaschelli 2 , Pierpaolo Righetti 2
1 Dept. of Physical Chemistry, University of Pavia, Pavia Italy, 3 , IENI-CNR, Pavia Italy, 2 Dept. of Organic Chemistry, University of Pavia, Pavia Italy
Show Abstract3:30 PM - AA8.4
Fuel Crossover and Fuel Cell Performance of Layer-by-Layer Assembled Proton Exchange Membranes.
J. Ashcraft 1 , Avni Argun 1 , Paula Hammond 1
1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractRecent research has shown layer-by-layer (LBL) assembly to be a robust technique for the fabrication of proton exchange membranes with tunable properties. In this work, multilayer systems of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) assembled at different numbers of bilayer pairs and several pH values are characterized with respect to z-plane ionic conductivity and gas permeation. By altering the pH of assembly conditions, the relative amounts of each polymer deposited in the film are controlled, which impacts many bulk properties of the film. A 30 bilayer film assembled at pH=2.5 is shown to effectively block the permeation of nitrogen through a LBL membrane. Hydrogen crossover can be minimized by tuning the pH of film assembly and film thickness. Also, we report a maximum ionic conductivity of 3.8 x 10-4 S/cm for a PEO/PAA film at 100% RH. These films will then be tested as the proton exchange membrane in commercial fuel cell hardware to determine the optimal film assembly conditions for fuel cell operation. The PEO/PAA films, along with multilayer films of Nafion® and linear poly(ethylene imine) (LPEI) will be investigated as thin coatings on commercial Nafion® membranes. Barrier layers of PEO/PAA and Nafion/LPEI have the potential to reduce fuel crossover and membrane degradation while minimally impacting the overall fuel cell performance.
3:45 PM - AA8.5
Proton Conducting Hybrid Phosphosilicate Membranes for Medium Temperature H2/O2 Fuel Cells.
Martin Mika 1 , Marketa Masinova 1 , Martin Paidar 1 , Karel Bouzek 1 , Bretislav Klapste 2 , Jiri Vondrak 2
1 Department of Glass and Ceramics, Institute of Chemical Technology Prague, Prague Czech Republic, 2 Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, Rez near Prague Czech Republic
Show AbstractA limited supply and high costs of crude oil force the main car producers to focus more on the development of alternative engines and fuels for their future vehicles. One of the promising solutions can be a car powered by affordable hydrogen fuel cells. In these fuel cells a suitable membrane represents a critical component. For transportation applications a membrane must exhibit sufficiently high proton conductivity and tolerate a wide range of operating conditions including low humidity and intermediate temperatures up to 130°C. Currently, the low operating temperatures of available proton conducting polymer membranes and their humidity requirements add high complexity to the fuel cell system that impacts its cost and durability. Therefore, our recent research has been focused on the development of improved membranes with better performance at lower cost.Our membranes are based on hybrid inorganic-organic phosphosilicate polymers. The backbone of the membrane is the polydimethylsiloxane polymer with phosphorus heteroatoms. Generally, polysiloxanes (silicones) possess high temperature stability and chemical durability as the result of their -Si-O-Si- bonds having high bonding energy and stabilizing the organic groups bonded to Si atoms. The synthesis of our membranes is based on the reactions of dimethyldichlorosilane and tetraethoxysilane in liquid or molten orthophosphoric acid. The developed preparation procedure ensures a high concentration of hydroxyl groups in the polymer that facilitate fast proton migration at low humidity. The prepared polymers were thoroughly characterized with analytical tools, including optical and electron microscopy (SEM-EDS), differential thermal analysis-thermal gravimetric analysis, infrared and Raman spectroscopy, and nuclear magnetic resonance. The temperature dependence of the proton conductivity was measured using electrochemical impedance spectroscopy. The recorded impedance data were fitted with an equivalent circuit and from its parameters the proton conductivity was calculated. In a dry atmosphere the conductivity was about 0.02 S/cm at 130°C. We tested our membranes in a commercial H2/O2 fuel cell operating in the temperature range from 22 to 130°C using dry H2 and O2 gases. We employed standard electrodes made of carbon paper with Pt/C catalyst. The surface area of the electrodes was 5 cm2. The performance of the fuel cell significantly improved as the temperature increased; the maximum of power density increased and moved to higher current densities and the absolute value of the slope of the voltage/current characteristic decreased. In our paper we report and discuss the observed effects of composition and preparation conditions on the measured properties of our membranes and on their performance in the H2/O2 fuel cell at elevated temperatures using dry reactant streams.
4:00 PM - AA8: PEMFCs
BREAK
4:30 PM - AA8.6
Spatial and Temporal Mapping of Water Content across Nafion Membranes under Wetting and Drying Conditions.
Ziheng Zhang 1 , Bruce Balcom 1 , Andrew Marble 1 2
1 MRI Centre, Department of Physics, University of New Brunswick, Fredericton, New Brunswick, Canada, 2 Department of Electrical and Computer Engineering, University of New Brunswick, Fredericton, New Brunswick, Canada
Show Abstract4:45 PM - AA8.7
State of Water in Nafion 117 Proton Exchange Membranes Studied by Dielectric Relaxation Spectroscopy.
Georgios Polizos 1 , Zijie Lu 1 , Digby Macdonald 1 , Evangelos Manias 1
1 Materials Science & Engineering, Penn State University, University Park, Pennsylvania, United States
Show Abstract5:15 PM - AA8.9
Ten Fold Catalytic Activity Enhancement in Pt/C by Doping Single Wall Carbon Nanotubes for DAFC.
Jayasri Narayanamoorthy 1 , Yuan Xu 1 , Jaewu Choi 1
1 Electrical and Computer Engineering, Wayne State University, Detroit, Michigan, United States
Show Abstract5:30 PM - AA8.10
Mediated Biocatalytic Cathode Operating on Gas-Phase Oxygen for Fuel Cells.
Nicholas Hudak 1 , Scott Calabrese Barton 2
1 Chemical Engineering, Columbia University, New York, New York, United States, 2 Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan, United States
Show AbstractA mediated biocatalytic cathode comprising an osmium-based redox polymer and the oxygen-reducing enzyme laccase [1] can operate on gas-phase oxygen as part of a membrane-electrode assembly in a hydrogen fuel cell. When the cathode initially contains a small amount of buffer solution and is supplied with a humidified oxygen stream, the fuel cell produces 1 mA/cm2 at 0.8 V and 25°C for 5 hours or longer. Such bio-cathodes are typically tested by providing convective flow of oxygen-saturated buffer solution through the electrode. This flow increases current density but requires stirring or pumping, creating a parasitic power loss.[2] The use of gas-phase oxygen instead of oxygen-saturated solution at the cathode is a step towards an air-breathing biocatalytic electrode, which would operate passively by using ambient air. As in conventional fuel cells, water management is crucial in such an air-breathing biocatalytic cathode. Water loss by diffusion to the anode or evaporation to the oxygen stream must be balanced with water production by the fuel cell to maintain the optimum level of hydration. The enzyme and mediator are dependent on water for catalytic activity and electron transport, respectively. When the cathode is initially saturated with buffer solution and supplied with a dry oxygen stream, current density is low because the electrode is flooded. At a constant potential of 0.8 volts, the cell steadily increases to 1.2 mA/cm2 over two hours as water evaporates and oxygen diffusion into the electrode increases. After this maximum is reached, continued drying out of the cathode adversely affects the enzyme and mediator and results in a steady decrease in current density over the following 8 hours. Use of a humidified oxygen stream significantly slows down this rate of decrease. The performance of the cell over time will be studied as a function of humidification conditions, cell temperature, and cathode catalyst composition. Cell polarization and impedance spectroscopy will be used to characterize hydration, electron transport, and oxygen transport in the cathode. In addition, hydrophobic phases will be incorporated into the carbon support to facilitate gas transport into and throughout the cathode. References: [1] S. C. Barton, H.-H. Kim, G. Binyamin, Y. Zhang, and A. Heller, Journal of Physical Chemistry B 2001, 105, 11917-11921. [2] N. S. Hudak, and S. C. Barton, Journal of the Electrochemical Society 2005, 152, (5), A876-A881.
5:45 PM - AA8.11
Investigation of the Structural Evolution and Ionic Characterization of Monolithic Phosphosilicate Gels by Concurrent Brillouin and Raman Scattering.
Arthur Feldman 1 , Liping Huang 1 , John Kieffer 1
1 Materials Science & Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractPhosphosilicate glasses are a promising material for the design of medium temperature, low humidity proton exchange membranes in fuel cells due to their relatively good conductivity and environmental robustness. However, these materials have not yet achieved the high conductivities seen in polymeric exchange membranes such as Nafion. In order to better elucidate the proton transport mechanisms in these gels we have employed a combination of light scattering techniques coupled with impedance spectroscopy. The structural development of the gels is monitored using concurrent Brillouin and Raman scattering. The latter is used to track the development of the structural units themselves and the former to gauge the connectivity between these structural units. The conductivity of the final product, as determined from impedance spectroscopy, can then be correlated to multi-scale structural information provided by the light scattering. We present the results for a series of phosphosilicate compositions and examine the relationship between the molar ratios of the phosphate and silica precursors and their application performance, both in terms of mechanical rigidity and proton conductivity.
AA9: Poster Session: Solid State Ionics
Session Chairs
Tim Armstrong
Christian Masquelier
Yoshihiko Sadaoka
Enrico Traversa
Thursday AM, November 30, 2006
Exhibition Hall D (Hynes)
9:00 PM - AA9.1
Gas Sensing Properties of Nanostructured BiCoO3 Prepared by Solution-polymerization Method using Polyvinyl Alcohol and Sucrose.
Carlos Michel 1 , Martinez Alma 1 , Gloria Santillan 1 , Arturo Chavez 1
1 Department of Physics, Universidad de Guadalajara, Guadalajara, Jalisco, Mexico
Show AbstractCeramic oxides with the perovskite structure (ABO3) such as: La1-xSrxCoO3, LaFeO3 and SrFexCo1-xO3 have been successfully tested as gas sensor materials, the application of these sensors includes the detection of methanol vapor, hydrocarbons in exhaust gas outlets in combustion engines, detection of oxygen at various partial pressures, etc. Many other possible combinations of rare earth elements, alkali metals and transition metals in the perovskite structure may expand the range of electrical and gas sensing properties of these oxides; these combinations may result from the aliovalent doping with alkali metals and/or by the partial replacement of the B site by another transition metal.For cobalt-perovskites, aliovalent doping produces a mixed-valence state in cobalt: Co2+ and Co3+, which improves the catalytical and transport properties. In this work, polycrystalline samples of BiCoO3 were prepared by three different synthesis methods: solid state reaction method, solution method and solution-polymerization method using polyvinyl alcohol and sucrose. In the ceramic method, Bi(NO3)35H2O and Co(OH)2, were used as reagents; by solution method Bi(NO3)35H2O and Co(NO3)26H2O were dissolved in water containing citric acid in a low concentration. The solution polymerization (SP) route involved the preparation of a mixture of polyvinyl alcohol and sucrose in a 1:1 ratio, then this solution was mixed with an aqueous solution containing stoichiometric amounts of Bi(NO3)35H2O and Co(NO3)26H2O. The precursor materials obtained at low temperature, from each route, were calcined at 600oC for 4 hours, the powders were analyzed by X-ray powder diffraction indicating that BiCoO3 was the main phase. All the powders were observed by SEM, however, a nanostructured powder was formed only by SP method, this material was also observed by TEM in bright field mode. The average particle size of the latter was approximately 30 nm, and selected area electron diffraction was used to confirm its crystallinity. DC electrical conductivity measurements were performed in air, O2 and CO2, from room temperature to 700oC, on thick films prepared by the screen printing technique. BiCoO3 shows a p-type semiconductor behaviour, and high O2 and CO2 sensitivities at approximately 420oC. On the other hand, whereas nanostructured perovskites with composition Sm1-xAxCoO3 (A = Sr, Ba) respond with an increment (or decrement) of few ohms to a change in gas type, nanostructured BiCoO3 thick-films yield a higher change in electrical resistance of three orders of magnitude; also shorter recovery times and faster response to gases, compared to samarium cobaltites, were registered.
9:00 PM - AA9.11
High Contrast Electrochromism and Surface Characterization of Ionic Self-Assembled Multilayer Nanocomposites.
Vaibhav Jain 1 , Randy Heflin 2 , Reza Montazami 2
1 Macromolecular Science and Engineering, Virginia Tech, Blacksburg, Virginia, United States, 2 Physics, Virginia Tech, Blacksburg, Virginia, United States
Show Abstract9:00 PM - AA9.12
Novel Green Organic Electrochromic Anode for High Contrast Smart Window.
Xiangxing Kong 1 , Chunye Xu 1 , Minoru Taya 1
1 Department of Mechanical Engineering, University of Washington, Seattle, Washington, United States
Show Abstract9:00 PM - AA9.13
Effect Of Water On the IR Properties of Mg2+ Intercalated Electrochromic Nb2O5 Thin Films.
Gargi Agarwal 1 , G. Reddy 1
1 Physics, Indian Institute of Technology Delhi, New Delhi India
Show Abstract9:00 PM - AA9.14
Influence of Stoichiometry of V2O5 Thin Films on the Electrochemical Properties.
M. Sahana 1 , C. Sudakar 1 , R. Baird 2 , G. Auner 2 , G. Lawes 1 , K. Padmanabhan 1 , Vaman Naik 3 , R. Naik 1
1 Department of Physics and Astronomy, Wayne State University, Detroit, Michigan, United States, 2 Department Electrical and Computer Engineering, Wayne State University, Detroit, Michigan, United States, 3 Department of Natural Sciences, U Michigan-Dearborn, Dearborn, Michigan, United States
Show Abstract9:00 PM - AA9.15
Light-Emitting Devices from Solid-State Ionic Complexes.
Jason Slinker 1 , Leonard Soltzberg 2 , Ji-Seon Kim 3 , Hector Abruna 4 , George Malliaras 1
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 Chemistry, Simmons College, Boston, Massachusetts, United States, 3 Cavendish Laboratory, University of Cambridge, Cambridge United Kingdom, 4 Chemistry and Chemical Biology, Cornell University, Ithaca, New York, United States
Show AbstractA recent concept in the field of organic solid-state electroluminescent devices involves the use of ionic transition metal complexes (iTMCs). These devices differ significantly from conventional organic light-emitting diodes (OLEDs) due to the presence of mobile ions in the organic film. In an iTMC device, ions redistribute under the influence of an applied bias and assist in the elementary injection of electrons and holes, which recombine in the iTMC layer to produce light. Contrary to conventional OLEDs that require low work function cathodes, iTMC devices show efficient operation even with air-stable cathodes due to ionic double-layer formation at the metal electrodes. This ionic nature enables fabrication by means of soft-contact lamination, as well as the development of fault-tolerant architectures for large-area illumination panels.In the emerging field of iTMC electroluminescent devices, our recent findings suggest that ionic dissociation and transport have a dramatic impact on the fundamentals of operation. We show that enhancement of ion conductivity can improve device performance, yielding decreased turn-on time and improved elementary charge injection. Our recent progress in understanding the failure modes of these devices reveals the identity of degradation products by mass spectrometry and Raman spectroscopy. Finally, we demonstrate iTMC lighting panels capable of operation directly from domestic AC power at 120 volts and 60 hertz.
9:00 PM - AA9.3
Merits of Bi3TiNbO9 for Humidity Sensors.
Ricardo Avila 1 , A. Castro 2 , D. Serafini 3 , H. Ulloa 1 , R. Jiménez 2 , A. Cabrera 4
1 Depto. de Materiales Nucleares , Comisión Chilena de Energía Nuclear, Santiago Chile, 2 , Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid Spain, 3 Departamento de Física, Universidad de Santiago de Chile, Santiago Chile, 4 Facultad de Física, Pontificia Universidad Católica de Chile, Santiago Chile
Show Abstract9:00 PM - AA9.4
Structural Characterization and Ionic Conductivity of Metastable Gd2(Ti0.65Zr0.35)2O7 Powders Prepared by Mechanical Milling.
Antonio Fuentes 1 , Karla Moreno 1 , Ulises Amador 3 , Jacobo Santamaria 2 , Carlos Leon 2
1 Unidad Saltillo, Cinvestav, Ramos Arizpe, Coahuila, Mexico, 3 Departamento de Quimica, Facultad de Farmacia, Universidad San Pablo CEU, Boadilla del Monte, Madrid, Spain, 2 Departamento de Fisica Aplicada III, Facultad de Fisica, Universidad Complutense, Madrid, Madrid, Spain
Show Abstract9:00 PM - AA9.5
Room-temperature Synthesis and Electrical Properties of La, Nd and Gd Apatite-type Silicates.
Antonio Fuentes 1 , Luis Martinez-Gonzalez 1 , Karla Moreno 1 , Evelyn Rodriguez-Reyna 1 , Ulises Amador 2
1 Unidad Saltillo, Cinvestav, Ramos Arizpe, Coahuila, Mexico, 2 Departamento de Quimica, Facultad de Farmacia, Universidad San Pablo CEU, Boadilla del Monte, Madrid, Spain
Show Abstract9:00 PM - AA9.6
PDF Investigation of the LAMOX Fast Oxygen Ion Conductor.
Lorenzo Malavasi 1 , Cristina Tealdi 1 , Simon Billinge 2 , Hyunjeong Kim 2 , Thomas Proeffen 3 , Giorgio Flor 1 , Gaetano Chiodelli 4
1 Dipartimento di Chimica Fisica "M. Rolla", University of Pavia, Pavia Italy, 2 , University of Michigan, East Lansing, Michigan, United States, 3 , LANSCE, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 4 CNR-IENI Department, University of Pavia, Pavia Italy
Show Abstract9:00 PM - AA9.7
Preparation and Oxygen Permeability of Acceptor Doped BiFeO3 Mixed Conducting Ceramics.
Kyle Brinkman 1 , Takashi Iijima 1 , Hitoshi Takamura 2
1 HDMRG/RIIF, AIST, Tsukuba Japan, 2 Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai Japan
Show AbstractBismuth Ferrite (BiFeO3) has typically been of keen interest as in the field of multiferroics which combine two or more properties of ferromagnetism, ferroelectricity and ferroelasticity. The principal problem in the processing and applications of these materials in useful devices has been the large leakage current attributed to the multivalent Fe ion and the possible existence of oxygen vacancies. In this study, we turn the “disadvantages” of these materials to the ferroelectrics community into “advantages” for the solid state ionics community by producing a simple, low thermal expansion(α~10 K-1) perovskite with mixed conductivity. Acceptor doping was performed using Ca+2 (ionic radius 0.99 A) and Sr+2 (ionic radius 1.12 A) in order to facilitate A site substitution (ionic radius Bi+3 ionic radius 1.2 A) which should enhance oxygen vacancy concentration. The impact on structure and oxygen permeability of the resulting ceramics was examined. Bismuth ferrite ceramics were observed to have p-type conductivity at elevated temperatures over the PO2 range of Air to He (0.21 bar to 10-6bar). Oxygen permeation measurements of ceramics >1mm for bulk property determination exhibited flux’s on the order of 0.014 μmol/cm2s at 800oC over the same PO2 range corresponding to bulk ionic conductivity of ~0.01 S/cm for doped samples. Although the ionic conductivity of BiFeO3 based materials is small compared to Ceria based mixed conductors such as CGO-CoFe composites1 (~0.1 S/cm), and Bi2O3 based composites2 (~0.5 S/cm) the oxygen flux of ceramics is comparable at intermediate temperatures near 800oC suggesting good surface catalysis properties of this material system. 1 H. Takamura, M. Kawai, K. Okumura, A. Kamegawa, M. Okada, Mat. Res. Soc. Symp. Proc. Vol 756 EE8.11.1 (2003).2 E. Capoen, M. Steil, G. Nowogrocki, M. Malys, C. Pirovano, A. Lofberg, E. Bordes-Richard, J. Boivin, G. Mairesse, R. Vannier, Solid State Ionics 177 483 (2006).
9:00 PM - AA9.8
Electrochromic Nickel Hydroxide Thin Films Chemically Deposited.
Monica Araceli Vidales-Hurtado 1 , Arturo Mendoza 1
1 Unidad Queretaro, Cinvestav, Queretaro, Queretaro, Mexico
Show AbstractElectrochromic nickel hydroxide thin films were deposited on ITO-coated glass substrates by the chemical bath deposition method. Two formulations using nickel nitrate were employed to obtain the films. The first one is through coordination compounds by using an ammonia complex producing the well crystallized phase β(II)-Ni(OH)2 The second formulation is based on the decomposition of urea at temperatures above of 90 °C, which promotes the deposition of the turbostratic phase α(II)- Ni(OH)2. After thermal annealing in air at temperatures of 250-300 °C, the β(II) films retain their polycrystalline structure, while the α(II) films are amorphous. The electrochromic behavior of the films was tested by cyclic voltammetry in a three electrodes configuration cell. Depending on nickel concentration in the solution, the colored state of β(II) films corresponds, either the β(III) or γ(III) phase of NiOOH. By their side, for α(II) films the colored phase have not been clearly identified. The structural transformations between colored and blanched states are studied by x-ray diffraction, Raman spectroscopy and infrared reflectance. Also, the optical contrast was evaluated from reflectance and transmittance spectra. The dependence of the electrochromic behavior (coulometric capacity, response time, cycle life) on composition in solution and annealing temperature is discussed.
9:00 PM - AA9.9
High Performance of the Hybrid Organic-Inorganic Polyelectrolyte in Electrochromic (EC) Devices.
Flavio de Souza 1 2 , Edson Leite 1 , Michel Aegerter 1 2
1 Materials Science and Engineering, UFSCar, Jaú, São Paulo, Brazil, 2 Schichttechnologie, Leibniz – Institut fuer Neue Materialien gGmbH – INM, Saarbruecken, Saarland, Germany
Show Abstract
Symposium Organizers
Timothy Armstrong Oak Ridge National Laboratory
Christian Masquelier University of Picardie-CNRS
Yoshihiko Sadaoka Ehime University
Enrico Traversa University of Rome Tor Vergata
AA10: Solid Oxide Fuel Cells (SOFCs)
Session Chairs
William Meulenberg
Enrico Traversa
Thursday AM, November 30, 2006
Republic B (Sheraton)
9:30 AM - **AA10.1
New Strategies on SOFC.
Juan Carlos Ruiz-Morales 1 , Juan Pena-Martinez 1 , David Marrero-Lopez 1 , Domingo Perez-Coll 1 , Pedro Nunez 1
1 Inorganic Chemistry, University of La Laguna, La Laguna Spain
Show Abstract10:00 AM - AA10.2
One-Step Co-Firing Technique for Manufacturing High Performance Solid Oxide Fuel Cells (SOFC)
Kyung Joong Yoon 1 , Wenhua Huang 1 , Peter Zink 1 , Guosheng Ye 1 , Srikanth Gopalan 1 , Uday Pal 1 , Donald Seccombe, Jr. 2
1 Manufacturing Engineering, Boston University, Brookline, Massachusetts, United States, 2 , BTU International, North Billerica, Massachusetts, United States
Show AbstractAnode-supported planar solid oxide fuel cells (SOFC) were fabricated by a single step co-firing process. The cells were composed of a Ni + yittria-stabilized zirconia (YSZ) or scandia-stabilized zirconia (ScSZ) anode, a YSZ or ScSZ electrolyte, a Ca-doped LaMnO3 (LCM) + YSZ or ScSZ cathode active layer, and a LCM cathode current collector layer. The fabrication processes involved tape casting of the anode, screen printing of the electrolyte and the cathode, and one step co-firing of the green-state cells at 1300°C for 2 hours. Through the optimization of materials and process parameters, the maximum power densities of 0.2 ~ 1.0W/cm2 were obtained with humidified hydrogen as fuel and air as oxidant in the temperature range between 700 ~ 900°C. The long-term stability tests showed that these cells could provide a stable cell performance for over 14 days at 800°C without any degradation. Various polarization effects were studied by impedance spectroscopy and by curve-fitting the voltage versus current density traces at various temperatures into an appropriate model. Based on these measurements and curve-fitting results, the relationships between cell performance and various polarization losses, and their dependence on temperature and microstructure were rationalized.
10:15 AM - AA10.3
Interaction Between Grain Size and Electrical Conductivity in YSZ Thin Films.
Christoph Peters 1 , André Weber 1 , Ellen Ivers-Tiffée 1 , Heike Störmer 2 , Dagmar Gerthsen 2 , Matthias Bockmeyer 3 , Reinhard Krüger 3
1 Institute of Materials for Electrical Engineering (IWE), University of Karlsruhe (TH), Karlsruhe Germany, 2 Laboratory for Electron Microscopy (LEM), University of Karlsruhe (TH), Karlsruhe Germany, 3 , Fraunhofer Institute for Silicate Research (ISC), Würzburg Germany
Show AbstractFor the realization of micro solid oxide fuel cells at temperatures below 600 °C an increase of the electrolyte performance is an essential issue. Nanocrystalline thin film electrolytes hold potentially enhanced ionic conductivity because of two reasons. Firstly, the high density of interfaces in the nanoscale is regarded to lower the grain boundary resistivity by space charge effects. Secondly, ionic transport along the grain boundaries is enhanced by a large number of displaced atoms and a high mobility [1]. Conductivity data of 8 mol% yttria doped zirconia (8YSZ) obtained by Kosacki et al. strongly supports this hypothesis [2]. In this work dense, crack-free 8YSZ thin films were prepared on sapphire substrates via sol-gel method. In a metal organic deposition (MOD) process the sapphire substrates were multiple dip-coated with an 8YSZ sol. Subsequent tempering with various rapid thermal annealing steps and annealing between 500 °C and 1400 °C for 24 h resulted in the formation of dense, crack-free 8YSZ films with varying mean grain size [3].Microstructural investigations of the bulk and the grain boundaries of the 8YSZ thin film layers were performed employing scanning (SEM) and transmission electron microscopy (TEM). For TEM investigations thin lamellas of the interface region 8YSZ thin film - substrate were prepared using focused ion beam (FIB).The electrical conductivity of the thin films was studied by means of electrical impedance spectroscopy as a function of microstructure (10 nm < mean grain size < 1000 nm) and temperature (200 °C < T < 400 °C) in air. To facilitate a homogeneous electric field distribution during the impedance measurements, platinum electrodes (4 mm long, 100 µm apart) were sputtered onto the 8YSZ thin films. The electrodes were contacted by microprobes. In contrast to previous investigations [2] the analyses of the impedance spectra showed a decrease of the electrical conductivity with decreasing mean grain size. Grain size effects enhancing the electrical conductivity at the nanoscale could not be observed.[1] H.L. Tuller: Ionic conduction in nanocrystalline materials, Solid State Ionics 131 (2000), 143-157[2] I. Kosacki et al.: Electrical conductivity of nanocrystalline ceria and zirconia thin films, Solid State Ionics 136-137 (2000), 1225-1233[3] C. Peters et al.: Processing of Dense Nanocrystalline Zirconia Thin Films by Sol-Gel Method, in Current and Future Trends of Functional Oxide Films, edited by D. Kumar, V. Craciun, M. Alexe, K.K. Singh (Mater. Res. Soc. Symp. Proc. 928E, Warrendale, PA, 2006), GG16-01
10:30 AM - AA10.4
Effect of Microstructure on the Grain Ionic Conductivity of Ceria based Electrolytes.
Shobit Omar 1 , Hassan El-Shall 1 , Eric Wachsman 1 , Juan Nino 1
1 Materials Science and Engineering, University of Florida, Gainesville, Florida, United States
Show Abstract10:45 AM - AA10.5
Scandia –Stabilized Zirconia: Dopant/Admixtures Segregation on Surface/Grain Boundaries and Transport Properties.
Vladislav Sadykov 1 , Natalia Mezentseva 1 , Vitalii Muzykantov 1 , Vyacheslav Ivanov 1 , Vladimir Zaikovskii 1 , Oleksandr Vasylyev 2 , Viktor Vereschak 2 , Alevtina Smirnova 3 , Nigel Sammes 3 , John Kilner 4 , Igor Kosacki 5 , John Irvine 6 , Nikolai Uvarov 7 , Vladimir Zyryanov 7
1 , Boreskov Institute of Catalysis SB RAS, Novosibirsk Russian Federation, 2 , Institute for Problems of Materials Science, Kiev Ukraine, 3 Global Fuel Cells Center, University of Connecticut, Storrs, Connecticut, United States, 4 Department of Materials, Imperial College, London United Kingdom, 5 Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 6 School of Chemistry , University of St Andrews, Fife United Kingdom, 7 , Institute of Solid State Chemistry SB RAS, Novosibirsk Russian Federation
Show Abstract11:00 AM - AA10: SOFCs
BREAK
11:30 AM - AA10.6
Space Charge Induced Electrical Conductivity Enhancements in Nanoscale Yttria-doped Zirconia Thin Films.
Annamalai Karthikeyan 1 , Shriram Ramanathan 1
1 Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show Abstract11:45 AM - AA10.7
Investigation of Novel Nanostructured Electrolyte for IT-SOFC Applications.
William McPhee 1 , Zhang Xiaoyu 2 1 , Nigel Sammes 2 1
1 Connecticut Fuel Cell Center, University of Connecticut, Storrs, Connecticut, United States, 2 Department of Mechanical Engineering, University of Connecticut, Storrs, Connecticut, United States
Show AbstractSolid Oxide Fuel Cells (SOFC) are operated at 1000○C to achieve the required ionic conductivity for the electrolyte, typically yttrium stabilized zirconia. The relationship between ionic conductivity and temperature is directly proportional. However, the development of an ionic conductive electrolyte for operation at 500-800○C is necessary to reduce the overall system cost. These systems are referred to as Intermediate Temperature - Solid Oxide Fuel Cells (IT-SOFC). One route that has been investigated is the use of new ionic electrolytes, including lanthanum gallate and doped ceria. These electrolytes still have a number of technology hurdles associated with them. However, ionic conductivity is a diffusion driven phenomenon and is therefore heavily influenced by microstructure. It follows that radically altering the microstructure of existing ionic conductors will affect the ionic conductivity. A new approach to improve existing high temperature (1000○C) ionic conductors is the altering the microstructure from polycrystalline to a nanoscale and/or nanocrystalline. Review articles on ionic conductivity in nanocrystalline materials by Tuller (1), and by Heitjans and Indris (2) show that ionic conductivity is increased in nanocrystalline material, although the exact mechanism to explain this effect is still to be determined. The results presented are from characterization performed on yttrium stabilized zirconia electrolytes with nanoscale and/or nanocrystalline microstructures. The green density and sintered density was determined for a range of processing conditions. The aim was to find the lowest sintering conditions that allowed for the formation of a fully dense electrolyte. This data was then used in conjunction with impedance spectrometry to draw conclusions about optimum processing conditions. Impedance samples were also examined using electron microscopy. The electrolyte was then trialed in a single cell fuel cell to obtain IV and power density curves. This has allowed tentative conclusion to be drawn about the behaviour of nanoscale and nanocrystalline electrolytes for IT-SOFC applications1.Tuller, H.L., Solid State Ionics. 131(1-2), 143. (2000)2.Heitjans, P. and S. Indris, Journal of Physics Condensed Matter. 15(30). (2003)
12:00 PM - AA10.8
Preparation and Characterization of Nano-Crystallite Electrolytes for SOFCs.
Zhigang Xu 2 , Jeremiah Abiade 2 , Jag Sankar 1
2 Center for Advanced Materials and Smart Structures, North Carolina A&T State University, Greensboro, North Carolina, United States, 1 Mechanical Engineering, North Carolina A&T State University, Greensboro, North Carolina, United States
Show Abstract12:15 PM - AA10.9
Grain Boundary Effects on Charge Transport and Stability in Nanocrystalline CeO2 Thin Films.
Scott Litzelman 1 , Harry Tuller 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show Abstract12:30 PM - AA10.10
Efficient Oxide Ion Conduction in sub-100 nm-thick Membranes of Amorphous Hafnium Silicate.
Yoshitaka Aoki 1 , Toyoki Kunitake 1
1 Topochemical Design Lab., Institute of physics and chemistry, RIKEN, Wako Japan
Show AbstractOxide ion conductor is a material that preferentially transports oxide ions by the applied potential without permeation of gas molecules and migration of electrons, and is now being used and developed as membrane electrolytes in solid-oxide-fuel-cells (SOFC), oxygen-pump devices and other applications. In particular, SOFC’s are expected to be the most promising candidate among the next-generation fuel cells, and a fierce development race is in progress. To be technologically viable, area-specific-resistance (ASR) of the electrolyte membrane must be less than 0.15 Ω cm2 at operating temperatures, where ASR = ρ-1 d and ρ is electrical conductivity of material and d the thickness of membrane. Existing fast oxide ion conductors are essentially limited to a small group of crystalline ceramic oxides. It is essential to lower their operating temperatures still more, in order to facilitate broader applications of SOFC. Here we report our discovery that amorphous nano-films of a solid solution of silica and hafnium oxide act as oxide ion conductor and that the ASR value of less than 0.15 Ω cm2 is attained below 400°C with 60-70 nm film thickness. These amorphous thin films are fabricated by the layer-by-layer adsorption from solution, void-free, and thermally stable at least below 450°C. They exhibit electromotive force close to the theoretical one at temperatures as low as 200°C. The ceramic SOFC is believed to possess many technical advantages over the currently-available polymer electrolyte fuel cells (PEFC), since the operation temperature of the latter is usually restricted to 100°C or below due to its high humidity requirement. More flexible temperature management with robust ceramic membranes will greatly improve the usefulness of fuel cells, in terms of mobile use, the ease of cell design and richer fuel resources, to name a few. The present finding may drastically affect the direction of the current fuel cell research.
12:45 PM - AA10.11
Microstructural Design Of Solid Oxide Fuel Cells.
Kei Yamamoto 1 , Edwin Garcia 1
1 Materials Science and Engineering, Purdue University, West Lafayette, Indiana, United States
Show AbstractAA11: Electrodes for Solid Oxide Fuel Cells (SOFCs)
Session Chairs
Shriram Ramanathan
Yoshihiko Sadaoka
Thursday PM, November 30, 2006
Republic B (Sheraton)
2:30 PM - **AA11.1
Nonlinear Impedance Analysis of SOFC Electrodes.
Stuart Adler 1
1 Chemical Engineering, University of Washington, Seattle, Washington, United States
Show Abstract3:00 PM - AA11.2
Cu-based Anodes for SOFC by in-situ Infiltration.
Kyoung Han 1 , Yoonji Jung 2 1 , Chang Kim 1 , Haiwon Lee 2
1 Materials Science and Engineering, KIST, Seoul Korea (the Republic of), 2 Chemistry, Hanyang University, Seoul Korea (the Republic of)
Show Abstract Although Cu-based cermets are promising alternative anodes for the Ni-YSZ cermet anodes in SOFC, not much research have been carried out due to processing limitations. The Cu-based cermets have been prepared by Infiltration of copper nitrate solution to YSZ(8 mol% Y2O3 stablized zirconia) porous ceramics. The infiltration process has inherent demerits such as higher concentration near surfaces, limited loading at a time, inhomogeneous coating, etc. In Cu-based anodes Cu works as only an electron carrier, so it needs oxidation catalysts such as ceria. Ceria is also applied by infiltration. Thus, it is needed to develop a process for Cu-based cermets by sintering as for Ni-YSZ cermets. Here, we demonstrated an easy fabrication method of Cu-based cermets by in-situ infiltration of Cu2O to porous YSZ body. The grain growth was controlled by surface modification of CuO/YSZ composite powder and/or GDC(Ce0.9Gd0.1O3)powder with MgO. Homogeneous Cu-YSZ-GDC cermet anodes were achieved with good electrical conductivity of >400 S/cm at 800C with rigid YSZ skeletons. Processing parameters and cermet properties will be discussed in the aspects of microstructures and electrical conductivities.
3:15 PM - AA11.3
Microstructure Characterization of Porous Lanthanum Strontium Manganite (LSM) Electrodes.
Aijie Chen 1 , Kerry Siebein 1 , Jerry Bourne 1 , Kevin Jones 1 , Eric Wachsman 1
1 , Univ. of Florida, Gainesville, Florida, United States
Show AbstractThursday, 11/30Title and Author Change2:15 PM AA11.3Microstructure Characterization of Porous Lanthanum Strontium Manganite (LSM) Electrodes. Aijie Chen, Kerry Siebein, Jerry Bourne, Kevin Jones and Eric Wachsman; Univ. of Florida, Gainesville, Florida.
3:30 PM - AA11.4
Electrochemical Characterization of La2-xPrxNiO4+x for Application as Cathodes in Intermediate Temperature SOFCs.
Allan Jacobson 1 , Guntae Kim 1
1 Chemistry, University of Houston, Houston, Texas, United States
Show AbstractA challenge for commercialization of SOFC technology is to reduce the operating temperature to 500-700 C. Lower temperatures require improvements in materials particularly for interconnects and cathodes. The perovskite related oxide, Ln2NiO4+x, (LNO) is currently of interest as a potential SOFC cathode due to the high diffusivity of the oxygen ion interstitials and good electrocatalytic properties at intermediate temperature. In this paper, we report electrochemical performance of symmetrical cells (LNO/CGO/LNO) where CGO is 10% gadolinium doped ceria using AC impedance spectroscopy. The polarization resistance due to ionic transfer at the electrode/electrolyte interface and diffusion/adsorption in the bulk electrode was studied as a function of temperature and oxygen partial pressure. The results obtained are in good agreement with the values of the diffusion coefficient, Do, and of the surface exchange coefficients, kex, previously measured by Electrical Conductivity Relaxation (ECR) assuming the ALS model. The results are compared with previous data for the LNO series and for other perovskite materials.
3:45 PM - AA11.5
Low Temperature Synthesis and Electrochemical Properties of M0.8Sr0.2Co1-xFexO3 (M = Ba, La, Pr) Nanoparticles: Effect of Grain Size on Lattice Symmetry.
Edoardo Magnone 1 2 , Masaru Miyayama 2 , Enrico Traversa 1
1 Department of Chemical Science and Technology, University of Rome Tor Vergata, Rome Italy, 2 Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Tokyo Japan
Show AbstractElectrochemical properties of fine-particle systems have assumed great importance in recent years because of their scientific and technological utility. Reducing interfacial polarization resistance by reduction of crystallite size of the powder is one of the most effective way of enhancing the performance of low-temperature Solid Oxide Fuel Cells (SOFCs). Therefore, expanding the length of Three-Phase Boundary (TPB) in a cathode is crucial for intermediate temperature operating of SOFC. It is well established that the most physical and chemical properties of a solid matter change when the particle size is decreased to the nanometer regime.This study was performed to investigate the crystal size reduction effect of M0.8Sr0.2Co1-xFexO3 (M = Ba, La, Pr)nanoparticles, as a suitable model for SOFC study, and possible correlation between size powder, crystallographic structure and electrochemistry properties. Different sets of perovskite-type mixed oxides were successfully prepared by the amorphous citrate method. A particle size dependent modification in crystal structure of M0.8Sr0.2Co1-xFexO3 (M = Ba, La, Pr) nano-powders was observed. We saw a clear correlation between crystal size, oxygen content, crystallographic structure and electrochemical performance. The aim of the present paper is to contribute to a better understanding of the size-induced changes in the crystal symmetry for the nano-structured cathode materials.AcknowledgmentsThis work was partly supported by the Italian Ministry of Foreign Affairs (MAE) under the frame of the Italy-Japan joint lab on “Nanostructured Materials for Environment and Energy”.
4:00 PM - AA11: ElecSOFCs
BREAK
AA12: Gas Sensors
Session Chairs
Tim Armstrong
Masaru Miyayama
Thursday PM, November 30, 2006
Republic B (Sheraton)
4:30 PM - AA12.1
NASICON based CO2 Gas Sensor with Mixtures of Lithium carbonate and Trivalent Metal Oxide as an Auxiliary Electrode.
Yoshihiko Sadaoka 1
1 Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Matsuyama Japan
Show AbstractTo develop a potentiometric CO2 gas sensor with Pt.Li2CO3/NASICON/Pt structure, the addition of some metal oxides as a Li2CO3 stabilizer was considered. When sole LiCO3 was used as an auxiliary electrode material, gradual decreases in the EMF level were observed and an apparent electron number for the electrochemical equilibrium reactions was deviated from the theoretical value, 2.0. By using the mixture of Li2CO3 with metal oxides, long-term stability was improved. To clarify the adding effects, a thorough examination of thermal stress was performed on the materials of the auxiliary electrode and NASICON. For Li2CO3 mixed with NASICON, the heat-treatment induced the insertion of Li2O and the crystal structure of the NASICON deformed at the temperature above 400oC. For the mixture of Li2CO3 with the oxides, the decomposition temperature of Li2CO3 phase is raised of about 100oC even in CO2-free air. The matrix effects of the oxides in stabilizing the Li2CO3 phase and the preferred wettability of metal oxide were effective to depress the diffusion of Li2O in the auxiliary electrode applied to NASICON.
4:45 PM - AA12.2
Impedance Analysis of Electrochemical NOx Sensor Using a Au/Yttria-Stabilized Zirconia (YSZ)/Au cell.
Leta Woo 1 , L. Martin 1 , Robert Glass 1 , Raymond Gorte 2
1 Energy and Environment Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractAn electrochemical cell employing a YSZ electrolyte and two Au electrodes was utilized as a model system for investigating the mechanisms responsible for impedancemetric NOx (NO and NO2) sensing. The cell consists of two dense Au electrodes on top of a porous/dense YSZ bilayer structure (with the additional porous layer present only under the Au electrodes). Both electrodes were co-located on the same side of the cell, resulting in an in-plane geometry for the current path. The porous YSZ appears to extend the triple phase boundary and allows for enhanced NOx sensing performance, although the exact role of the porous layer is not completely understood. Impedance data were obtained over the frequency range of 0.1 Hz to 1 MHz, and over a range of oxygen (2 to 18.9%) and NOx (10 to 100ppm) concentrations, and temperatures (600 to 700°C). Data were fit with an equivalent circuit, and the values of the circuit elements were obtained for different concentrations and temperatures. Changes in a single low-frequency arc were found to correlate with concentration changes, and to be temperature dependent. In the absence of NOx, the effect of O2 on the low-frequency resistance could be described by a power law, and the temperature dependence described by a single apparent activation energy at all O2 concentrations. When both O2 and NOx were present, however, the power law exponent varied as a function of both temperature and concentration, and the apparent activation energy also showed dual dependence. Adsorption mechanisms are discussed as possibilities for the rate-limiting steps.Work performed under the auspices of the U.S. DOE at the University of California/Lawrence Livermore National Laboratory under contract W-7405-ENG-48.
5:00 PM - AA12.3
Potentiometric Detection of VOCs using Non-Nernstian SmFeO3/Pt/YSZ/Pt Sensors.
Laure Chevallier 1 , Elisabetta Di Bartolomeo 1 , Enrico Traversa 1 , Masami Mori 2 , Yoshihiko Sadaoka 2
1 Department of Chemical Science and Technology, University of Rome Tor Vergata, Rome Italy, 2 Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Matsuyama, Ehime, Japan
Show AbstractNon-Nernstian electrochemical sensors based on commercial tape-cast YSZ layers were prepared using a perovskite-type SmFeO3 powder as sensing electrode. Two different sensor structures were investigated. In the first structure, two Pt electrodes were deposited on both sides of the YSZ layer in a “sandwich” way and one of the electrode was then covered with the SmFeO3 powder. In the second structure, two parallel finger-shaped Pt electrodes were first deposited on the same side of the YSZ layer and then the SmFeO3 was deposited on one of the Pt electrode. In both cases, the two metallic electrodes (Pt) were sputtered using a JEOL Fine Coater, while the SmFeO3 powder, which was prepared by the thermal decomposition of heteronuclear complexes, was deposited by electrophoretic deposition (EPD).The influence of the thickness of the Pt electrodes on the sensor response was also studied in both types of sensors, using different Pt sputtering times in the range between 10 and 60 min.Sensing experiments were carried out in a conventional gas-flow apparatus equipped with a controlled heating facility. The sensors were alternatively exposed to air or different concentrations of volatile organic compounds (VOCs) (Methyl ethyl ketone, acetic acid, and ethanol) at 400°C. In all the cases, the two electrodes of the sensors were wholly exposed to the same atmosphere. The electromotive force (EMF) was measured with a digital multimeter.For all the “sandwich” sensors, high EMF responses under exposure to the VOCs were observed even at low concentrations such as 1 ppm of gas, and the best sensitivity was obtained under exposure to acetic acid. Increasing the thickness of the Pt electrodes led to more stable and faster responses but the EMF amplitudes decreased.By comparing both sensors structures, the “sandwich” one seemed to respond better to the VOCs, showing larger and faster EMF responses than the “monoside” structure.
5:15 PM - AA12.4
Impedancemetric Technique for NOx Sensing Using a YSZ-Based Electrochemical Cell.
Louis Martin 1 , Leta Woo 2 , Robert Glass 3
1 Mechanical Engineering, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 3 Energy and Environment, Lawrence Livermore National Laboratory, Livermore, California, United States
Show Abstract5:30 PM - AA12.5
Preparation of SrFeO3-X Thin Films by the Spin-Coating Method and its Gas Sensing Properties.
Abdul Majid 1 , Jim Tunney 1 , Michael Post 1
1 ICPET, NRC of Canada, Ottawa, Ontario, Canada
Show AbstractNanostructured coatings have recently attracted increasing interest because of the possibilities of synthesizing materials with unique physical-chemical properties. Highly sophisticated surface related properties, such as optical, magnetic, electronic, catalytic, mechanical, chemical and tribological properties can be obtained by advanced nanostructured coatings, making them attractive for various industrial applications. In this report we describe our efforts at developing a methodology for the fabrication of SrFeO3-X based thin films using a modified Pechini method. Thin films of SrFeO3-X were fabricated using a spin coating and a drop coating method developed in-house on Al2O3 and Si/SiO2substrates. The films annealed at 600 oC for one hour show a perovskite phase. The grain size increases with increasing annealing temperature. The influence of various variables such as metal to chelant ratio, drying control reagents, calcination conditions, substrate type and mode of film formation were studied using XRD, optical microscopy, SEM and AFM. The sensors based on SrFeO3-X thin films on alumina were fabricated, and the sensing properties were determined using propane and propene as the probing gases. A good sensitivity and selectivity was found for both gases.
Symposium Organizers
Timothy Armstrong Oak Ridge National Laboratory
Christian Masquelier University of Picardie-CNRS
Yoshihiko Sadaoka Ehime University
Enrico Traversa University of Rome Tor Vergata
AA13: Batteries
Session Chairs
Phillipe Knauth
Christian Masquelier
Friday AM, December 01, 2006
Republic B (Sheraton)
9:15 AM - **AA13.1
Microstructural Characterisation from Powder Diffraction Data: Application to Nickel Hydroxide Battery Materials and Correlation with Electrochemical Properties.
Montse Casas-Cabanas 1 2 , Juan Rodriguez-Carvajal 2 , M. Rosa Palacin 1
1 Solid State Chemistry, Institut de Ciencia de Materials de Barcelona, Bellaterra, Catalonia, Spain, 2 , Laboratoire Léon Brillouin, CEA-CNRS, Saclay France
Show Abstract9:45 AM - **AA13.2
Intermediate Phases in LixFePO4.
Atsuo Yamada 1 , Shin-ichi Nishimura 1 , Hiroshi Koizumi 1 , Ryoji Kanno 1 , Shiro Seki 2 , Yo Kobayashi 2 , Hajime Miyashiro 2 , Joanna Dodd 3 , Rachid Yazami 3 4 , Brent Fultz 3
1 , Tokyo Institute of Technology, Tokyo Japan, 2 , Central Research Institute of the Electric Power Industry, Tokyo Japan, 3 , California Institute of Technology, Pasadena, California, United States, 4 , CNRS, St. Martin d’Heres France
Show Abstract10:15 AM - AA13.3
Correlation Between Ionic Conductivity and Segmental Motions in Solid Polymer Electrolytes.
Naba Karan 1 , Baskaran Natesan 1 , Ram Katiyar 1
1 Department of Physics, University of Puerto Rico, San Juan, Puerto Rico, United States
Show Abstract10:30 AM - AA13.4
The Safety Characteristics of the Li4Ti5O12/LiMn2O4 Li-Ion Battery System.
Ilias Belharouak 1 , Khalil Amine 1
1 Chemical Engineering Division, Argonne National Laboratory, Argonne, Illinois, United States
Show Abstract10:45 AM - AA13.5
Influence of Microstructures of the Cathode/Electrolyte Interface on the Electrochemical Properties of All Solid-State Li-ion Batteries.
Kyosuke Kishida 1 , Naoyuki Wada 1 , Yuji Yamaguchi 1 , Katsushi Tanaka 1 , Yasutoshi Iriyama 2 , Zempachi Ogumi 2 , Haruyuki Inui 1
1 Department of Materials Science and Engineering, Kyoto University, Kyoto Japan, 2 Department of Energy and Hydrocarbon Chemistry, Kyoto University, Kyoto Japan
Show AbstractThe perovskite-type oxide (La,Li)TiO3 (LLT) has attracted a great deal of interest as a solid-state electrolyte for all solid-state lithium-ion rechargeable batteries since it possesses very high Li-ion conductivity and high-temperature stability. In the case of the all solid-state rechargeable batteries, interface structures between the electrode and electrolyte are considered to have great influences on the battery performance such as resistivity and stability of interface upon charging and discharging. However, the relationship between the microstructures of the solid-state-electrolyte/electrode interface and electrochemical properties has not been studied in detail. In the present study, we have investigated the evolutions of the microstructures and electrochemical properties of two different types of LLT/LiCoO2 cathode interfaces upon charging and discharging operations.Two different types of the surfaces of the polycrystalline LLT, namely cleaved and polished surfaces, were prepared. LiCoO2 cathode was then deposited on each surface by pulsed laser deposition. These two samples are hereafter assigned as cleaved and polished samples. Electrochemical properties were analyzed by cyclic voltammetry (CV), AC impedance spectroscopy and charge-discharge test. Microstructures were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) using cross sectional samples. The LiCoO2 thin-film cathode with a thickness about 100nm is epitaxially grown on the {110}LLT cleavage plane with the orientation relationships: {110}LLT//{11-20}LiCoO2 and <001>LLT// <4-401>LiCoO2 for the cleaved samples. Cyclic voltammograms of the cleaved sample shows that the anodic and cathodic peak respectively shift to higher and lower potential with the number of cycles, which suggests that the interface resistance increase upon charge-discharge cycles for the cleaved sample. Some part of the LiCoO2 thin-film separates off from the interface after 3 CV cycles, which must be responsible for the increase of the LLT/LiCoO2 interface resistance and low cyclic stability of the cleaved sample. In contrast, the peak potential for the anodic and cathodic reactions observed in the CV test as well as the interface structures for the polished sample do not change much during cycles of potential sweeps, indicating that the polished samples have much higher stability upon insertion and extraction of lithium ion. HRTEM observation reveals that amorphous regions exist in places at the interface, which is in marked contrast to the rather clean interface in the cleaved sample. The existence of the amorphous regions are thus considered to play an important role for stabilizing the interface upon charge / discharge operations.
11:00 AM - AA13: Batteries
BREAK
11:30 AM - **AA13.6
Nanosheet-assembly Process and its Application to Lithium Battery Electrodes.
Masaru Miyayama 1 , Shinya Suzuki 1
1 RCAST, University of Tokyo, Tokyo Japan
Show AbstractSome layer-structured oxides delaminate into nanosheets with several nanometers in thickness and submicro- to micrometers in lateral dimensions, when large-size ions like tetrabutylammonium ions are inserted to enlarge the interlayer space. The nanosheets reassemble when some cationic species are provided for the interlayer space. This nanosheet-assembly process was applied for the fabrication of electrodes for high-rate lithium-ion batteries. Redox currents by lithium inter/deintercalations were confirmed in one-layer titanate nanosheet, and a redox capacity larger than that of bulk sample was suggested. Reassembled titanate / carbon-fiber composites showed small overpotential in redox reaction, and a high-rate charge/discharge property reaching 160 mAh/g even at 3 A/g was observed. The electrodes prepared by reassembly of mixed MnO2 and Ti1-δO2 nanosheets showed redox responses of both nanosheets and also a new response with redox potentials different from component materials. The nanosheets and their reassembled bodies were found to be the candidates for electrode materials of lithium-ion batteries with high capacity and energy density. These results demonstrate the nanosheet-process to be a promising wet-process for nanostructure-designed functional materials.
12:00 PM - AA13.7
Characterization of the Carbon-coating of LiFePO4.
Michel Massot 1 , Karim Zaghib 2 , Alain Mauger 3 , Francois Gendron 4 , Christian Julien 5
1 IMPMC, Universite P & M Curie, Paris France, 2 , IREQ, Varennes, Quebec, Canada, 3 MIPPU, CNRS, Paris France, 4 INSP, Universite P & M Curie, Paris France, 5 Institut des NanoSciences de Paris, Universite P & M Curie, Paris France
Show AbstractNowadays, LiFePO4 is currently the subject of many investigations because this material realizes the highest capacity (160 mAh/g) at moderate current densities. It is an positive electrode candidate for rechargeable lithium-ion batteries used in hybrid-electric vehicle (HEV). However, the poor electronic conductivity of LiFePO4 results in significant losses of capacity during high-rate discharge. To overcome this weakness, efforts have been made including the use of carbon additives, supervalence cation doping, nano-sized grains, and carbon coating. A careful control of the synthesis procedure is needed to optimized the carbon thin film deposited at the particle surface. Raman scattering (RS) spectroscopy is known as a powerful tool to characterize carbon coating as a huge number of works have been devoted in the past to investigate the different form of carbon from graphite to diamond [1]. This work is devoted to the characterization of the structure and morphology of the carbon deposited onto the LiFePO4 particles. A series of C-LiFePO4 powders synthesized by different techniques have been studied for evaluation of the carbon deposit. FTIR measurements show that carbon does not penetrate into the LiFePO4 grains. The carbon coating investigated by Raman is an amorphous graphite deposit hydrogenated with a very small H/C ratio, with the same RS characteristics as a-C carbon films obtained by pyrolysis method at temperature 830 °C [2]. Analysis of the D- and G-band made by Gaussian fitting documents the carbon coating such as its structure, thickness, adherence, hardness, electrical conduction, hydrogenation, etc. For some coatings, the small sp3/sp2 ratio indicates the best carbon film observed so far [3].Finally the electrochemical performance of Li/LiPF6-EC-DEC/C-LiFePO4 cells operating at high temperature (60 °C) is shown and discussed in details.[1] D.S Knight, W.B. White, J. Mater. Res. 4, 385 (1989).[2] R. Kostecki et al., Solid Thin Films 396, 36 (2001).[3] A. Ait Salah, K. Zaghib, A. Mauger, F. Gendron, C.M. Julien, Phys. Status Sol.(a) 203, R1 (2006).
12:15 PM - AA13.8
The Hydrothermal Synthesis of Lithium Iron Phosphate.
Jiajun Chen 1 , M. Stanley Whittingham 1
1 Chemistry Department, Binghamton University, Binghamton, New York, United States
Show AbstractIron phosphates and related materials are potential cathode candidates for rechargeable lithium ion batteries. Of the iron phosphates, the olivine phase lithium iron phosphate has attracted the most attention because of its high thermal and chemical stability. We first reported the hydrothermal preparation of LiFePO4 in 2001 (Electrochem. Commun. 3, 505) but lithium/iron disorder in the structure caused a relatively low electrochemical reactivity. We have now determined the optimum conditions to provide excellent electrochemical behavior. Well-crystalline LiFePO4 particles were successfully prepared in the temperature range between 120 and 220°C, and complete ion ordering was obtained above 175°C where the unit cell dimensions were identical to high temperature material. The use of a soluble reductant, such as sugar or ascorbic acid, was found to minimize the oxidation of the iron to ferric. The electronic conductivity was enhanced by the deposition of carbon from the sugar, or by the addition of carbon nanotubes to the hydrothermal reactor when over 90% of the lithium could be de-intercalated electrochemically. We have extended the hydrothermal synthesis method to the Mn, Co and Ni analogs as well as to the mixed phosphates, such as LiMnyFe1-yPO4. This work is being supported by the US Department of Energy, Office of FreedomCAR and Vehicle Technologies, through the BATT program at LBNL.
12:30 PM - AA13.9
High Rate LiFePO4/Carbon Composites Utilizing Graphitization Catalysts.
James Wilcox 1 2 , Marca Doeff 1
1 Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Material Science and Engineering, University of California Berkeley, Berkeley, California, United States
Show AbstractDue to the high electronic resistivitiy of LiFePO4 (~10-9 S/cm at room temperature) the manipulation of the physical properties of the carbon component of LiFePO4/C composites is vital in achieving a high rate electrode. It has been found that the addition of readily decomposed carbon-containing additives, such as pyromellitic acid [1], in conjunction with graphitization catalysts during synthesis yields composites with a decreased D/G (disordered/graphene) carbon ratio and improved rate capabilities. Furthermore, the overall carbon content is maintained below 2 wt%, thereby avoiding any adverse effects on the tap density [2]. Pressed pellet conductivity measurements of LiFePO4/C composites reveal good correlation with the electrochemical performance of lithium cells and is further evidence of the significance of the graphitic nature of the carbon component [3] in producing a high rate material. The effects of various catalysts including iron nitrate as well as ferrocene and its derivatives on the capacity and rate performance of sol-gel produced LiFePO4 powders will be discussed along with the effects of catalyst loading and pyromellitic acid content. Further exploration of the thermal decomposition of ferrocene in contact with pyromelltic acid under conditions similar to those used in the synthesis of LiFePO4 has revealed the production of several forms of nanostructured Fe/C composites, including multiwalled carbon nanotubes, depending on the component ratio. The co-synthesis of LiFePO4 powder containing carbon nanotubes represents an opportunity to significantly reduce the amount of carbon black that needs to be added to composite electrodes, yielding increased practical energy and power densities. Furthermore, co-synthetic techniques may avoid processing difficulties associated with nanotube mixing in the composite electrode along with many of the related cost and health issues. [1] Y. Hu, M. M. Doeff, R. Kostecki, and R. Fiñones, J. Electrochem. Soc. 151 (2004) A1279. [2] Z. Chen and J. R. Dahn, J. Electrochem. Soc. 149 (2002) A1184. [3] R. Kostecki, B. Schnyder, D. Alliata, X. Song, K. Kinoshita, and R. Kötz, Thin Solid Films 396 (2001) 36.
12:45 PM - AA13.10
Impact of Surface Chemistry on the Electrochemical Performance of LiCoO2.
Nathalie Pereira 1 , Jafar Al-Sharab 1 , Fadwa Badway 1 , Irene Plitz 1 , Cheryl Matthias 2 , Kia Bell 2 , Frederic Cosandey 1 , Pinakin Shah 2 , Nathan Isaacs 2 , Glenn Amatucci 1
1 Department of Materials Science and Engineering, Energy Storage Research Group, Rutgers, The State University of New Jersey, North Brunswick , New Jersey, United States, 2 , Mine Safety Appliances Company, Sparks , Maryland, United States
Show Abstract