Symposium KK: Materials for Advanced Lithium Batteries

2010 MRS Fall Meeting Logo

November 29 - December 3, 2010

Chairs  

Gholam-Abbas Nazri
GM Research and Development Center
MC 480-102
30500 Mound Rd.
Warren, MI 48090
586-986-0737

       

 

Jean-Marie Tarascon
Universite Picardie Jules Verne
33 rue St. Leu
Amiens Cedex, 80039 France
33-3-2282-7604

 

Dominique Guyomard
Institut des Materiaux Jean Rouxel Nantes
P. B. 32229
2 Rue de la Houssiniere
Nantes Cedex 3, 44322 France
33 -2-4037-3912

 

       

 

Atsuo Yamada
Dept. of Chemical System Engineering
The University of Tokyo
Bldg. 5-607
7-3-1 Hongo
Bunkyo-ku, Tokyo, 113-8656 Japan
81-3-5841-7295



 

Proceedings to be published in both print and electronic formats
(see MRS Online Proceedings Library at www.mrs.org/opl)
as volume 1313
of the Materials Research Society
Symposium Proceedings Series.
 




* Invited paper

 

SESSION KK1: Lithium Battery Cathode Materials
Chairs: Gholam-Abbas Nazri and Jean-Marie Tarascon
Monday Morning, November 29, 2010
Constitution A (Sheraton)


8:00 AM *KK1.1
Porous Electrodes and Catalysts for Li-S and Li-Air Batteries.Linda F. Nazar, David Ji, SiHyoung Oh and Scott Evers; Chemistry, Univ. Waterloo, Waterloo, Ontario, Canada.

In this presentation, the key materials phenomena critical to the development of non-aqueous rechargeable Li-air and Li-S energy storage batteries will be discussed, and we will show how to exploit this knowledge to develop novel battery platforms and chemistries. These “integration-chemistry” systems are related, and have the potential for gravimetric energy densities that exceed that of conventional lithium-ion batteries: by a factor of up to 7-9 in the case of Li-O2 and by 3-5 in the case of Li-S. Given this exciting promise, they are the subject of outstanding interest worldwide as next-generation replacements for large scale energy storage. However, performance criteria that include volumetric capacity, charge/discharge efficiency, rate capability, and longevity are also important, presenting hurdles that must be addressed. This can be carried out in part with the development of hierarchical cathode structures, and the interfacing of these with new electrolytes and improved negative electrodes. The presentation will focus on these topics, and our efforts to create tunable nano and mesoporous architectures based on carbon and/or metal oxides that will act as new porous air (or sulfur) electrodes. With respect to Li-air, a key limitation s is that it requires a bifunctional catalyst to enable both oxygen reduction and peroxide oxidation. We will present our results on exploring high surface area transition metal oxide catalysts where surface defects offer increased levels of catalytic activity and stability. We demonstrate that the catalytic properties of highly electronically conductive, ordered mesoporous and nanocrystalline metal oxides for the Li-O2 cell are superior to those of the bulk material and to the most active and stable catalysts previously reported, in terms of activity and cycling stability.


8:30 AM KK1.2
Understanding the Rechargeable Lithium-air Battery. Stefan A. Freunberger, Zhangquan Peng, Laurence J. Hardwick, Yuhui Chen and Peter G. Bruce; School of Chemistry, Univeristy of St Andrews, St Andrews, Fife, United Kingdom.

The rechargeable lithium-air battery is generating much excitement because of its potential to store significantly more energy than current rechargeable batteries; something that is critical in order to address global warming. Theoretically a 5-10 fold increase in specific capacity has been suggested as the upper limit for the O2 electrode compared with present cathodes. However, the lithium-air battery is far from a technology at the present time and many hurdles must be overcome before we can even evaluate its potential as a future battery technology. Unlike a conventional battery where the reagents are contained within the cell, the lithium-air battery uses oxygen from the atmosphere. On discharge dioxygen entering from the air is reduced at the electrode surface by electrons from the external circuit, the resulting species combining with lithium ions in the pores to form Li2O2. Charging reverses the process. A deep understanding of the fundamental processes occurring in the cell is essential if we are to make progress. To this end we have carried out studies of the reactions occurring at the cathode with a particular focus on electrolyte stability and side reactions. Results of these studies will be discussed.


8:45 AM KK1.3
Electrocatalysis of Oxygen Reduction and Oxygen Evolution Reactions for Li-Air Batteries. Yi-Chun Lu1, Jonathon R. Harding2, Hubert A. Gasteiger3 and Yang Shao-horn1,4; 1Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts; 2Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts; 3Chemistry, Technische Universität München, Garching, Germany; 4Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.

In lithium-air batteries, the traditional positive intercalation electrode of Li-ion batteries is replaced by a porous air electrode, which catalyzes the formation of lithium (per)oxide (oxygen reduction reaction, ORR) and its decomposition into oxygen and lithium ions (oxygen evolution reaction OER). Li-air batteries can provide much greater energy density (3x) compared to traditional lithium ion batteries based on lithium intercalation compounds. However, current Li-air batteries have low round-trip efficiency, low power capability, and short cycle life, which is limited primarily by the reaction kinetics in the air electrode. We examine the ORR activity on series of model electrodes as well as carbon support high-surface area catalysts in lithium-containing aprotic electrolyte using rotating disk electrode (RDE) and Li-O2 cell measurements. As low solubility of lithium peroxide/oxide in organic solvents prevents RDE measurements of OER activity, we first screen OER activity of different high-surface area catalysts in Li-O2 cells. Since the determination of the OER kinetics in actual lithium-air batteries is compromised by undefined reaction products and mass transport losses associated with plugging of electrode pores with solid lithium (per)oxide, we developed novel Li/Li2O, Li/Li2O2 cells to further examine the OER kinetics on various catalysts with well-defined reaction product and cell capacity. Current results show that Au is the most active for ORR while Pt is the most active for Li-O2 cell charging and catalyzing the decomposition of Li2O2 among all surfaces examined. Proposed mechanisms of the ORR and OER kinetics on different catalysts will be discussed. Such studies allow the understanding of physical parameter(s) that govern the catalytic activity, and provide insights into the design of highly active bifunctional catalysts needed for Li-air batteries.


9:00 AM KK1.4
Development of Post Lithium Ion Battery Based on the Hybrid Electrolytes.Haoshen Zhou, Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan.

Lithium ion battery (LIB), which has the highest energy density among all currently available rechargeable batteries, has recently been considered for use in hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and pure electric vehicles (PEV). Although the power density of LIB has been remarkably improved by the developed Nano- and Micro- structured electrode actice materials to satisfy the industrial needs of HEVs, PHEVs, and PEVs, there is still a main challenge for HEV, PHEV and PEV, which is to increase the energy density of LIBs. Recently, a new type of lithium-air battery and lithium-copper battery employing hybrid electrolytes, with a large energy densities, have attracted significant attention. These batteries are expected to succeed lithium ion batteries as next-generation power sources. In this talk, I will introduce the some new type batteries based on the concept of hybrid electrolytes.


9:15 AM KK1.5
Investigation on Rechargebility of Lithium/Air Batteries.Ming Au1, Thad Adams1, Elise Fox1, Hector Colon-Marcado1, James Zheng2 and Guoqing Zhang2; 1Savannah River National Lab, Aiken, South Carolina; 2Florida State University, Tallahassee, Florida.

The carbon based Li-ion batteries used currently fall short in meeting the requirements of utilization for renewable energy, electrification of transportation, smart grid and portable devices with regard to energy density, power density and cost. Metal/air batteries use oxygen directly from the atmosphere to produce electricity. The cathode active material, oxygen, does not have to be stored in the batteries, which allows for higher total energy capacity in a smaller designed package. Very high energy density can be achieved due to essentially unlimited cathode capacity. Our model predicts that the overall theoretical energy density of polymer electrolyte Li/air battery could be as high as 2790 Wh/kg and 2800 Wh/L, which is comparable to gasoline-air combustion engines [1]. In past decades, various metal/air batteries have been investigated; however, three major challenges still prevent Li/air batteries from practical application. The oxygen reduction and evolution both take place on the cathode and the effective and long-lasting bifunctional cathodes have not been developed yet. In order to reduce the products of the discharge, such as Li2O2 and Li2O, effective catalysts have to be discovered. Lastly, Li2O2 or Li2O are not soluble in the non-aqueous electrolyte currently used by researchers. They will clog the pores of the cathodes and eventually seize the cell. Focusing on these issues, we have conducted our initial investigation on cathode architecture, catalyst, electrolyte and the performance of the Li/air cells developed in out lab. We will discuss our results and share our vision for the future of this technology.


10:00 AM KK1.6
New Structures and New Properties of LiFePO4-based Cathodes.Christian Masquelier1, Stephane Hamelet1, Montse Casas Cabanas1, Loic Dupont1, Carine Davoisne1, Clare Grey2 and Rosa Palacin3; 1LRCS, Université de Picardie Jules Verne, Amiens, France; 2University of Cambridge, Cambridge, United Kingdom; 3ICMAB, Barcelona, Spain.

Aqueous routes used for the synthesis of nanoscale particles of LiFePO4 may lead, under specific conditions, to a full solid solution behavior upon Li+ extraction at ambient temperature, hence favoring an easier monitoring of the state of charge/discharge of the electrode [1]. We demonstrated through neutron diffraction that this behavior is strongly connected with the presence of significant amounts of structural defects within the crystallites (Li / Fe exchange, vacancies) [2]. We demonstrated as well that it was possible to monitor and adjust the amount of structural defects through careful annealing in air between 140°C and 500°C, up to a composition close to LiFe0.67PO4 [3]. An important feature is that these findings suggest unusually high mobility of Fe within the triphylite framework. The resulting powders show complete new electrochemical features at various redox steps between 3.5 V and 2.8 V vs Li, associated with partial redistribution of Fe and Li within the octahedral sites. New crystal super-structures with long range ordering of Fe, vacancies and/or Li, determined through high resolution Synchrotron X-Ray diffraction, neutron diffraction and Solid state NMR will be presented [4] [1] F. Mestre-Aizpurua, S. Hamelet, C. Masquelier & R. Palacin ; J. Power Sources, 195(19), 6897-6901 (2010) [2] P. Gibot, M. Casas-Cabanas, L. Laffont, S. Levasseur, P. Carlach, S. Hamelet, J-M. Tarascon and C. Masquelier, Nature Materials, 7, 741-747 (2008) [3] S. Hamelet, P. Gibot, M. Casas Cabanas, D. Bonnin, C. Grey, J. Cabana, J. B. Leriche, J. Rodriguez Carvajal, M. Courty, S. Levasseur, P. Carlach, M. Van Thournout, J. M. Tarascon & C. Masquelier ; J. Mater. Chem., 19, 3979-3991 (2009) [4] S. Hamelet, M. Casas Cabanas, L. Dupont, C. Davoisne, C. Grey, J.M. Tarascon & C. Masquelier, submitted, June 2010


10:15 AM KK1.7
Unusual Kinetics and Nanosize Effects on the First Order Phase Transformation in LiFePO4. Rahul Malik and Gerbrand Ceder; Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.

LiFePO4 has been shown to display very high rate performance. This is remarkable given that LiFePO4 stores Li through a first order phase transformation between FePO4 and LiFePO4. Despite this two-phase reaction, which requires nucleation of the second phase and motion of a phase boundary through the material, this compound is probably the fastest intercalation compound known. Surprisingly, good performance is only achieved with nano-scale particles, despite the fact that diffusion scaling theory would indicate that micron size material should also be well performing. Investigating in detail the kinetics of various kinetic steps in the lithiation and delithiation of LiFePO4 with first principles methods and Monte Carlo simulations, we have arrived at a new picture for the mechanisms that control the kinetics of LiFePO4. We find strong nanoeffects on the Li diffusion constant, indicating that the excellent performance of nanomaterials is not solely due to the reduced transport paths. We will show how this understanding of Li diffusion can be integrated into a new theory for the first order phase transformation in LiFePO4 , which we believe will have significant implications for finding other high rate materials that require a two-phase reaction for Li storage.


10:30 AM KK1.8
Electrochemical Characterization of LiFePO4 with Single Particle Measurement.Kiyoshi Kanamura, Applied Chemistry, Tokyo Metropolitan University, Hachioji, Japan.

Materials for rechargeable lithium ion batteries have been widely investigated in order to improve capacity density and rate capability. Usually, a composite type electrode has been used to evaluate their electrochemical performances. However, the use of composite electrode leads to more complicated explanation for material performance. In order to prevent such misunderstanding, a single particle measurement is one of useful tools to make clear physical and electrochemical properties of powder active materials. In the case of a single particle measurement, a micro current collector is used to establish electrical connection to active material particle. The discharge and charge currents are in order of nA, so that we can neglect IR drop and diffusion of Li+ ions in electrolyte. This means that obtained data reflect diffusion of Li+ ion in solid state and charge transfer behavior at interface between active material and electrolyte. These are important characteristics of active material. By using this technique, we carefully investigated some of cathode materials, such as LiCoO2, LiFePO4, and Li4Ti5O12. The capacity of cathode material is determined by a number of sites in solid phase (crystal structure), when powder is ideal. In practical, secondary particles are used as cathode material. When all of primary particles in secondary particle are utilized, the observed capacity should be consistent with theoretical one. However, entire particles in secondary particle cannot be utilized when secondary particle has adequate electric and ionic conductivities. In order to clarify utilization of particle, a single particle measurement is very useful. In this study, this technique has been applied to an electrochemical evaluation of LiFePO4 particle. A hydrothermally prepared LiFePO4 with or without carbon coating was investigated to evaluate an effect of electronic conductivity of secondary particle on its rate capability as cathode material by using a single particle measurement. Our measurement clearly showed that carbon coating is necessary to utilize entire secondary particle. Without carbon coating, the capacity of LiFePO4 dramatically decreased. With carbon coating, LiFePO4 secondary particle with 10 μm exhibited 80 mA h g-1 at 720 C rate (5 seconds discharge and charge duration). Intrinsically, LiFePO4 primary particle has very high rate capability. Therefore, a network for electron conduction inside secondary particle is a key issue to obtain high performance cathode. In this sense, the carbon coating is very useful. From a single particle measurement, the charge transfer resistance and diffusion coefficient of Li+ in solid phase can be estimated to draw Tafel plot from polarization value at the same utilization and different current density.


10:45 AM KK1.9
Solubility Limits and Anti-site Disorder in Nano-sized LiFePO4.M. Wagemaker1, D. P. Singh1, W. J. Borghols1, U. Lafont1, F. M. Mulder1, S. P. Badi2, W. H. Kan2, B. L. Ellis2 and L. F. Nazar2; 1Applied Science, Delft University of Technology, Delft, Netherlands; 2Chemistry, University of Waterloo, Waterloo, Ontario, Canada.

Recent research has shown that equilibrium solubility limits in insertion compounds for Li-ion batteries change with decreasing particle size, in LiFePO4 leading to a reduction of the miscibility gap. Here we investigated the solubility limits as a function of overall composition and size using Neutron and X-ray diffraction in anti-site-free material. The results give direct insight in the origin of the changing solubility limits. In addition we investigated nano size LiFePO4 prepared by the polyol method as a function of overall composition using Neutron and X-ray diffraction. These results give insight in the distribution of anti-site defects and their role during (dis)charge.


11:00 AM KK1.10
Reversible Lithium Intercalation in (Li,H)FePO4(OH) Tavorite-type Materials.Laurence Croguennec1, Nicolas Marx1,2, Dany Carlier1, Lydie Bourgeois3, Alain Wattiaux1, Frederic Le Cras2 and Claude Delmas1; 1ICMCB-CNRS and IPB-ENSCBP, Pessac, France; 2CEA DRT/LITEN/DTN/LCE, Grenoble, France; 3Université de Bordeaux, ISM, Talence, France.

Since the very interesting properties, especially in terms of thermal stability, discovered for LiFePO4 as positive electrode in lithium-ion batteries, a lot of researches were driven to propose new polyanionic materials as alternative electrodes for lithium-ion batteries. Very recently a few groups focus their interest on Tavorite-type materials AMPO4X (A = Li or H; M = Fe, V or Ti and X = OH or F). Their structure is characterized by chains of MO6 octahedra, interconnected through PO4 tetrahedra, such as the resulting framework encloses tunnels of two different sizes. Through the results obtained for the phases (Li,H)FePO4(OH), we will discuss the structure and electrochemical behaviour of tavorite-type phases. Pure tavorite LiFePO4(OH) was synthesized through an hydrothermal route, whereas the new phase HFePO4OH was obtained from that latter through an Li+/H+ exchange. Localization of lithium and hydrogen in these two phases was achieved thanks to neutron diffraction: the hydrogen atoms are linked to the oxygen atoms shared by two adjacent FeO6 octahedra, whereas the lithium ions occupy a single LiO5 site in a corner of the tunnels. The nature of the -OH and -OH2 groups in LiFePO4OH and FePO4.H2O (or HFePO4OH) respectively was confirmed by vibrational spectroscopies, whereas theoretical (GGA+U) calculations performed for LiFePO4X materials (X = OH, F) revealed for instance that a unique lithium position is expected in LiFePO4(OH), as experimentally observed. For the first time, lithium intercalation was shown to occur in LiFePO4(OH) through the reduction of Fe3+ to Fe2+ at an average voltage of ~2.6 V (vs. Li+ / Li), and at ~2.8 V in FePO4.H2O. Good cyclability was obtained for the two systems. A comparison of these results with those obtained for instance for LiFePO4F will be given.


11:15 AM KK1.11
Studies of the Cathode Material Li2MP2O7.Hui Zhou, Shailesh Upreti, Natasha Chernova and M. Stanley Whittingham; Materials Science, Binghamton University, Binghamton, New York.

Although olivine structured phosphate compounds, like LiFePO4, have been greatly explored and are seeing use in a number of applications, they fall short of the desired capacity, > 200Ah/kg desired for PHEV and EV use. Such capacities can only be attained in phosphate materials when the redox reaction exceeds one electron per transition metal. Recently, a new member of Li2MP2O7 family, Li2MnP2O7, was reported, which has a 3D framework built up of MnO5 trigonal bipyramids sharing edge with MnO6 octahedra, which interconnect through P2O7 groups. The lithium ions are located in the tunnels that could allow the access to two lithium atoms per transition metal cation changing Mn oxidation state from 2+ to 4+. In our preliminary work, transition metals - Mn, Fe, and V have been used and samples synthesized by a variety of methods. We have shown that lithium can be reversibly intercalated into the phase Li2FeyMn1-yP2O7 for 0 ≤ y ≤ 1. The pure iron phase has been formed for the first time, and its structure determined. The Fe containing phase has much better performance than the Mn phase. Vanadium substitution improves the capacity. The completely vanadium containing material, “Li2VP2O7”, has a reversible capacity in excess of 200 mAh/g; the precise nature of this composite material will be described. The composition, magnetic properties, detailed electrochemical performance and structural information during the insertion and extraction of lithium ions will also be discussed. This work is supported by the US Department of Energy, Office of FreedomCAR and Fuel Partnership through the BATT program at Lawrence Berkeley National Laboratory.


11:30 AM KK1.12
Investigation of Dopant and Li-vacancy Distributions in Al-doped LiFePO4 at Atomic-scale by Advanced Electron Microscopy.Miaofang Chi1, She-Huang Wu2 and Shirley Meng3; 1Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; 2Department of Materials Engineering, Tatung University, Taipei, Taiwan; 3Department of NanoEngineering, UC San Diego, San Diego, California.

Olivine LiFePO4 is considered one of the most promising materials to substitute present LiCoO2 as cathode for secondary Lithium ion batteries, owning to its many appealing features including a reasonably high capacity (170mAhg-1), a relatively low cost, and its considerably high intrinsic safety. However, its limited charge transport prevents its large-scale applications. Recently, it was reported that doping with aliovalent cations, including Al3+, Mg2+, Nb5+ atoms etc., could improve its electrochemical performance significantly. 1-2 The most fundamental questions related to such doping method, however, currently are under intensive debate. For example, whether doping of aliovalent cations is possible in LiFePO4; which atomic site(s) (Li or Fe) the dopants could be located, and how much of the dopants can enter the crystalline lattice. To elucidate these questions, we directly observe the distribution of doping atoms in the crystalline lattice of Al-doped LiFePO4 by using high-resolution Z-contrast imaging and Electron Energy Loss Spectroscopy (EELS) with a sub-Å spatial resolution. The experiments were performed on an aberration corrected FEI-Titan 80/300 Scanning Transmission Electron Microscope (STEM). Li and Fe atomic columns are clearly distinguished in Z-contrast STEM images. The atomic positions of Al dopants thus were determined by combining Z-contrast imaging and theoretical image simulations. The detailed quantitative distribution of Al in LiFePO4 was further proved by high resolution EELS. Moreover, we have compared the differences of electronic structures and elemental distributions of the Al-doped sample to the undoped LiFePO4. The effect of Al doping on the property-controlling parameters, such as Li vacancies and Fe2+/Fe3+ multivalence ratio, will also be discussed in the presentation. The mechanism regarding how aliovalent dopants improving the performance of LiFePO4 will be concluded by combining the structural and compositional results with the corresponding electrochemical performances. [1] S. P. Herle, B. Ellis, N. Coombos and L. F. Nazar, Nat. Mater., 3, 147 (2004). [2] R. Amin, C. Lin, and J. Maier, Phys. Chem. Chem. Phys., 10, 3519 (2008). [3] D. Morgan, A. Van der Ven and G. Ceder, Electrochem. Solid-state Lett., 7 (2), A30. (2004). [4] C. A. J. Fisher, V. M. Hart Prieto, M. S. Islam, Chem. Mater. 20, 5907 (2008). [5] Research at the ORNL SHaRE User Facility supported by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.


11:45 AM KK1.13
Sodium Iron Fluorophosphate Energy Storage Materials: Synthesis and Characterization of Nanoscale Heterostructures.Yueying Fan1, Todd Gardner2 and Victor Abdelsayed1; 1URS/RES, National Energy Technology Lab, Morgantown, West Virginia; 2National Energy Technology Lab, Morgantown, West Virginia.

The development of low cost, high energy density energy storage cathode materials with increased charge/discharge cycle life is critical for grid scale energy storage solutions. The charge/discharge kinetics of intercalation materials are drastically improved through size reduction to the nanoscale. Sodium iron fluorophosphate nanoscale heterostructures have been synthesized using microwave and thermolysis methods for use as energy storage cathode materials. The addition of fluorine changes the intercalation dimensionality of the material structure which improves the energy storage capacity, intercalation kinetics and the life cycle of the cathode. Layered NaFePO4F and Na2FePO4F and channel-structured Na3Fe2(PO4)2F3 nanoscale heterostructures are synthesized and characterized by XRD, SEM, surface area, TEM and impedance spectroscopy.


 

SESSION KK2: Lithium Battery Polyanion Cathode Materials
Chairs: Dominique Guyomard and Atsuo Yamada
Monday Afternoon, November 29, 2010
Constitution A (Sheraton)


1:30 PM KK2.1
Novel Pyrophosphate Lithium Battery Electrode.Atsuo Yamada1, Shin-ichi Nishimura1, Megumi Nakamura2 and Ryuichi Natsui2; 1The University of Tokyo, Tokyo, Japan; 2Tokyo Institute of Technology, Yokohama, Japan.

The olivine LiFePO4 compound (170 mAh/g, 3.4 V vs. Li) has been recognized as the most promising positive electrode for large capacity lithium-ion battery systems for applications such as plug-in hybrid electric vehicles. Recent studies have identified fluorinated iron phosphate compounds, Li2FePO4F (110 mAh/g, 3.4 V vs. Li) and LiFeSO4F (130 mAh/g, 3.6 V vs. Li), as alternative competitive candidates. However, synthesis of these fluorinated compounds requires complex routes such as in- or ex-situ ion-exchange processes including ionothermal techniques with expensive ionic liquids. Here we report a conventional solid-state synthesis and structural determination of a new pyrophosphate compound, Li2FeP2O7, and its reversible electrode operation at 3.5 V vs. Li with one-electron theoretical value of 110 mAh/g, without any technical efforts such as nanosizing or carbon coating.


1:45 PM KK2.2
Scalable Synthesis of Alkali Metal Fluorosulfate and Fluorophosphate Tavorites, and Modelling to Understand Ion Mobility.Linda F. Nazar1, Rajesh Tripathi1, T. Ramesh1, M. Saiful Islam2 and Grahame Gardiner2; 1Chemistry, Univ. Waterloo, Waterloo, Ontario, Canada; 2Chemistry, University of Bath, Bath, United Kingdom.

In this presentation, we demonstrate a scalable, cost-effective synthesis route to single phase alkali LiMSO4F that is broadly applicable to a range of related materials, including LiFeSO4F. Excellent electrochemical properties are exhibited. At a C/10 rate, a reversible capacity of 0.86 Li (130 mAh/g) was sustained on cycling at an average potential of 3.6 V, with no capacity fading on cycling (not shown). Two-thirds of the theoretical capacity (100 mAh/g) is accessible at a rate of C/2. Increasing the cycling rate from C/10 to C/2 increases the polarization only slightly, indicating that the kinetics are rapid in this material owing to its excellent structural characteristics. The electrochemical properties are similar to those reported for material prepared from much more costly IL‘s. We show the properties can be further improved by tailoring the media to tune particle size. Because of the ease of the synthesis to form a variety of metastable alkali metal polyanion frameworks with new architectures in a simple and low-cost manner, this will significantly broaden our ability to explore these as cathode materials. We furthermore show that ion mobility in this, and the closely related NaFeSO4F tavorite framework is strongly governed by subtle factors that relate to the depth of the “thermodynamic well” of the mobile ion, and lattice strain on ion extraction.


2:00 PM KK2.3
Scaling up the Synthesis of Li2FeSiO4 for LIB Cathodes. Serdar Tan, Anti Liivat, Torbjörn Gustafsson and Josh Thomas; Materials Chemistry, Uppsala University, Uppsala, Sweden.

The production of high quality advance electrode materials for large-scale energy storage applications is a major challenge. We report here a “green”, low-cost cathode material with high energy- and power-density. Li2FeSiO4 (LFS) with a theoretical capacity of 166mAh/g (for the one-electron Fe2+-Fe3+ redox-couple reaction) offers a cheap cathode material alternative. Various synthetic methods have been examined to prepare phase-pure Li2MSiO4. We report here three techniques for the production of electrochemically active LFS: precipitation, solution and hydrothermal. The simplicity of the process and the relative abundance of the raw materials used have been our prime focus throughout. Solvothermal techniques have been used successfully for the synthesis of both phosphate- and silicate-based cathode materials. LFS has here been synthesized in a hydrothermal process using Na2SiO3, LiOH and FeCl2 as start materials. Good reversible electrochemical activity was demonstrated, with some over-potential during cycling. The precipitation technique has been used widely to obtain nano-size powders of many oxide systems. In our study, Na2SiO3 (“water glass”) has been used as Si source because of its high solubility in water-based systems. The amount of LiOH is found to be critical in achieving optimal silicate purity. The effect of atmospheric conditions on material purity has also been documented. Commercial grade silica (Aerosil 200) has been used in the solution technique. LiOH is used to dissolve the silica; an Fe source is then added. Straightforward mixing of the start chemicals followed by mild heat treatment yields active Li2FeSiO4 material. Its purity and electrochemical activity depend mainly on the heat-treatment procedure. Acknowledgements: This work has been support by The Global Climate and Energy Project (GCEP) of Stanford.


2:15 PM KK2.4
Structural and Electrochemical Investigations of Li2FeSiO4 Polymorphs.Robert Dominko1,3, Chutchamon Sirisopanaporn1,2,3, Robert Armstrong5,3, Darko Hanzel4, Miran Gaberscek1,3, Peter Bruce5,3 and Christian Masquelier2,3; 1Laboratory for Materials Electrochemistry, National Institute of Chemistry, Ljubljana, Slovenia; 2LRCS, Université Picardie Jules Verne, Amiens, France; 3ALISTORE-ERI, Amiens, France; 4Institute Jozef Stefan, Ljubljana, Slovenia; 5EaStCHEM, School of Chemistry, University of St Andrews, St. Andrews, United Kingdom.

Lithium transition metal silicates, with a general formula Li2MSiO4 (M = Fe, Mn, Co), are considered as attractive positive electrode material due to the theoretical possibility to exchange two mol of lithium per formula unit. Their crystal structure consists of slightly distorted close packed oxygen slabs between which cations occupy only tetrahedral sites. Depending on the synthesis parameters, Li2MSiO4 compounds crystallize within different crystallographic polymorphs [1-5]. The abundance of raw materials (particularly true for Fe and Si) and the reversibility of the FeII/FeIII redox couple are attractive attributes for Li2FeSiO4 to be chosen as a cathode material for large scale battery applications. In our recent publications we have showed that several phase pure Li2FeSiO4 polymorphs, whose crystal structures are derived from the low and high temperature forms of Li3PO4, can be obtained via different synthesis routes. Polymorphs of Li2FeSiO4 crystallizing in Pmn21 space group (LFS@400), in P21/n (LFS@700) and Pmnb (LFS@900) were successfully isolated and used for electrochemical characterization. Electrode composites were prepared by ball milling using 20 wt.% of carbon black. Lowering the particle size into nanometric particles and embedding them into a conductive matrix is a required process step to overcome the low intrinsic conductivity of Li2FeSiO4. The difference in the structure between Li2FeSiO4 polymorphs is based on the interconnection of lithium and iron tetrahedra and on their respective orientations. Those small differences in the structures affect the electrochemical potential in the first cycles. The measurable differences are mostly pronounced during the first oxidation process. Latter all three polymorphs are transformed into the more thermodynamic favorable phase obtained during the cycling, but the transformation does not occur within the same mechanism. This will be discussed based on the electrochemical experiments and from data obtained by in-situ Mössbauer spectroscopy. [1] Boulineau, A.; Sirisopanaporn, C.; Dominko R.; Armstrong, A. R.; Bruce, P. G.; Masquelier, C., Dalton Transactions, in Press, 2010. [2] Sirisopanaporn, C.; Boulineau, A.; Armstrong, A. R.; Bruce, P. G.; Hanzel, D.; Budic, B.; Dominko R.; Masquelier, C., 2010, Inorganic Chemistry, accepted. [3] Lyness, C.; Delobel, B.; Armstrong, A. R.; Bruce, P. G. Chem. Comm. 2007, (46), 4890-4892. [4] Nishimura, S. I.; Hayase, S.; Kanno, R.; Yashima, M.; Nakayama, N.; Yamada, A., Structure of Li2FeSiO4. J. Amer. Chem. Soc. 2008, 130 (40), 13212-13213. [5] Mali, G., Meden, A., Dominko, R., Chem. Comm., 2010, 43, 3306.


2:30 PM KK2.5
New Progress in the Development of Electrode Materials with High Capacity for Li-ion Battery.Yong Yang, State Key Lab for Physical Chemistry of Solid Surface, Xiamen University, Xiamen, Fujian Province, China.

In recent years, many efforts have been put into the developments of battery in power-type for (hybrid)-electric vehicles. For example, LiFePO4 has been widely investigated as a new generation of cathode materials for Li-ion batteries. The safe, cheap and environmental-friendly characteristics of the materials make them an excellent candidate. However, the one of disadvantages of LiFePO4 is their low capacity and lower energy density ( ~ 600 Wh/kg ), its energy density is not satisfied to develop large-size batteries for pure electric vehicles. In order to search some new systems in high energy density, new cathode materials with high capacity and high potential should be developed. In this presentation, some new results about novel cathode materials investigated in this lab such as silicates, Li-rich layered Li-Ni-Mn-Co-O2 and novel organic electrode materials will be presented and compared. Although these new materials show some promising results in energy density, they all have some intrinsic deficiency such as structural stability and reversibility in reaction process. In addition, some new results about structural characteristics of the silicates such as Li2Mn0.5Fe0.5SiO4 investigated by XAS and In-situ XRD with synchrotron sources and Solid NMR techniques will be presented. It seems that if we hope to explore some new Li-batteries systems with high energy density, new electrode/electrolytes materials, different reaction routes/mechanisms and new ideas should be explored in the future.


2:45 PM KK2.6
Thermal and Electrochemical Performance of High Energy Density Carbon Fiber Paper - LiFePO4 Positive Electrodes. Surendra Martha1, Jagjit Nanda1, Jim Kiggans1, Andrew Kercher1, Hsin Wang1, Wallace Porter1, Egwu Kalu2, Sreekanth Pannala3 and Nancy Dudney1; 1Materials Science and Technology, Oak Ridge National Lab, Oak Ridge, Tennessee; 2FAMSU-FSU College of Engineering, FAMU-FSU, Tallahasse, Florida; 3Computational Engineering and Energy Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee.

Good electronic, ionic and thermal conductivity are prerequisites for positive electrode materials for Lithium battery application. In a recent communication1 we reported composite electrodes of carbon fiber paper-LiFePO4 electrodes showing excellent capacity, rate and cycling performance. In this approach nanosized uniform LiFePO4 particles were uniformly coated on the electronically conductive carbon fiber network and bonded by highly conducting mesophase carbon pitch. The electrode fabrication approach in principle eliminates the use of organic binders and the metal foil current collector thereby increasing the energy density (per unit area) of the electrode. In addition to these, the carbon fiber composite electrodes offer significant thermal properties in terms of thermal diffusivity and transport compared to conventional binder based slurry method. We shall present thermal conductivity, heat capacity and differential scanning calorimetry results of fiber-LiFePO4 cathodes (and of the individual constituents) compared with the conventional LiFePO4-PVDF-carbon electrodes. Results showed that LiFePO4-pitch matrix showed two-fold higher thermal conductivity compared to the usual LiFePO4-binder composite when normalized to the same porosity. The experimental result is used in a simulation effort that verifies the role of the electrode's electronic, ionic and thermal conductivities to the cell performance and also addresses the optimal electrode architecture. 1. A. Kercher, Jim Kiggans, and Nancy J. Dudney, J. Electrochem. Soc. 2010 (in press) Acknowledgement This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy.


3:30 PM KK2.7
Multi-components Olivine Cathode: Combined Study of First Principles Calculations and Experiments.Kisuk Kang, Materials Science & Engineering, KAIST, Daejeon, Korea, Republic of.

The electrochemical properties and phase stabilities of the multi-component olivine compound LiMn1/3Fe1/3Co1/3PO4 are studied experimentally and with first principles calculation. The formation of the solid solution between LiMnPO4, LiFePO4, and LiCoPO4 at this composition is confirmed by XRD patterns and the calculated first principles energy. The experimental and first principles results indicate that there are three distinct regions in the electrochemical profile at QOCPs of ca. 3.5 V, 4.1 V, and 4.7 V, which are attributed to Fe3+/Fe2+, Mn3+/Mn2+, and Co3+/Co2+redox couples, respectively. However, exceptionally large polarization is observed only for the region near 4.1 V of Mn3+/Mn2+ redox couples, implying the intrinsic charge transfer problem of Mn. An ex-situ XRD study reveals that the reversible one-phase reaction of Li extraction/insertion mechanism prevails, unexpectedly, for all lithium compositions of LixMn1/3Fe1/3Co1/3PO4 (0 ≤ x ≤ 1) at room temperature. The well-ordered, non-nanocrystalline (less than 1% Li - M disorder and a few hundred nanometer size particle) olivine electrode is demonstrated to be operated solely in a onephase behavior . The in-depth study of the multi-component effect on the structural and electrochemical properties of olivine cathodes is conducted using state-of-the-art first-principles calculations. The distribution of multiple transition metals in olivine structure alters local crystal structure and electronic structure, affecting its kinetic and thermodynamic properties. We find that local structure change, such as the reduced Jahn-Teller effect of Mn, significantly enhances both Li mobility and electron (polaron) conductivity when the redox Mn element neighbors Fe or Co . The unexpected one-phase Li insertion/extraction reaction of the multi-component olivine cathode is explained with respect to the multiple interactions of M/Li or M/Vacancy (M=transition metals). The redox potential of each transition metal also could shift as a result of charge redistribution and the relative energy change from the multiple M/Li interactions.


3:45 PM KK2.8
New Tools for a Rationale Optimization of Thick LiFePO4 Composite Rlectrodes.Bernard Lestriez1, Claire Fongy2, Willy Porcher2, Kalid Seid1, Jean-Claude Badot3, Olivier Dubrunfaut4, Severine Jouanneau2, Stephane Levasseur5 and Dominique Guyomard1; 1Institut des Matériaux Jean Rouxel, Université de Nantes, CNRS, Nantes, France; 2Laboratoire des Composants pour l'Energie, CEA, Grenoble, France; 3Laboratoire de Chimie de la Matière Condensée de Paris, ENSCP, CNRS, Paris, France; 4Laboratoire de Génie Electrique de Paris, SUPELEC, UPMC, CNRS, Paris, France; 5Cobalt & Speciality Materials, UMICORE, Olen, Belgium.

The improvement of battery performance requires the rationale optimization of the composite electrode. The development of “new tools”, i.e. experimental techniques as well as methodologies, is needed to understand the so-called composition-architecture-properties and performance relationships. Otherwise, the composite electrode formulation and processing have to be optimized by “try and see” experiments. In our last works we showed that rheology is a must for the tailoring of the aqueous processing of the C-LiFePO4 active material. It allows the selection of the proper thickener and dispersant additives and of their optimal content. By adding to these additives an efficient binder, we were able to prepare thick films with a surface capacity reaching up to 3.6 mAh per cm square which is crucial to get high energy batteries. Apart from mechanical strength, the problem with thick composite electrodes is their high impedance. To optimize the rate performance of these thick electrodes we developed a new efficient and easy-handling methodology. Several key parameters can be extracted from the C-LiFePO4 discharge curves to determine the optimal electrode engineering and to interpret the origins of the electrode limitations. We identified a simple model to discriminate the ionic and the electronic contributions to rate limitations. This model demonstrates that low packing results in electronic limitation while the ionic contribution dominates for dense electrodes. The improvement of the electronic conductivity of the composite electrode is thus crucial toward high rate performance. However, the dc electronic conductivity has been the only measured quantity to date. It is a macroscopic averaged value which corresponds mainly to the electronic percolation. It gives poor information on the electrical transport properties of granular materials, such as composite electrodes, constituted of clusters of particles (eventually) and particles separated by resistive and capacitive barriers, which limit the charge transport in the material. Thus the dc conductivity does not relate directly to the real electronic wiring of the active material particles and hardly correlates with the electrochemical performance of the composite electrode. Recently, we used the broadband dielectric spectroscopy (BDS), from low (a few Hz) to microwave (a few GHz) frequencies. We demonstrated that this technique is very sensitive to the different scales of the electrode architecture involved in the electronic transport, from interatomic distances to macroscopic sizes, as well as to the morphology at these scales. As an example, BDS allows determining independently the conductivity of both the C-coating and of the clusters of the C-LiFePO4 grains. Financial funding from CEA, ADEME, CNRS, Université de Nantes, UMICORE, and the ANR program n° ANR-09-STOCK-E-02-01 is acknowledged.


4:00 PM KK2.9
Characterization Of Air Exposed LiFePO4 Nano-powders for Li-ion Batteries.Nicolas Dupré1, Marine Cuisinier1, Jean-Frederic Martin1,2, Atsuo Yamada3, Ryoji Kanno2 and Dominique Guyomard1; 1CNRS-IMN, Nantes, France; 2Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Tokyo, Japan; 3Department of Chemical Systems Engineering, The University of Tokyo, Tokyo, Japan.

The olivine-type compositions LiMPO4 (M = Fe, Mn, Co) are among the most attractive materials for the positive electrode of Li-ion batteries, and now stand as a good choice for power tools and hybrid vehicles. The purpose of the present work is to shed light on the surface reaction mechanism of LiFePO4 in air, on the characterization of the resulting surface side phase(s) and on their consequence on battery performance. Prolonged atmosphere contact at room temperature leads to the formation of FeIII-rich side phases and cell volume shrinkage [1]. Based on cycling experiments as well as XRD data, this phenomenon has been attributed to both the formation of lithium vacancies leading to a Li1-xFePO4 solid solution existing for low values of x and an unknown disordered phase [3]. Aging of the material for a longer time at 120°C worsens the damages, hence increasing the amount of FeIII-containing phase, to be characterized. Neither Mössbauer nor magnetic susceptibility measurements show any evidence of the presence of iron oxide, but suggest that FeIII is present in an amorphous phosphate environment The FeIII-based phase can be obtained via hydroxylation and/or oxidation of olivine [4]. Indeed, in the aim of crystallizing this amorphous phase, tavorite LiFePO4(OH) has been identified by XRD after aging the LiFePO4 material under water vapor pressure at 120°C. In accordance to this result, the side phase formed at the surface is electrochemically active and can accept lithium around 2.6V, as tavorite. While the presence of the surface disordered phase deteriorates the performance of LiFePO4, annealing of the aged material leads to the disappearing of the 2.6V process and partial recovery of the capacity, suggesting the reversibility of the aging process upon heat treatment [5]. The Li battery behavior of the pristine and altered materials has been studied. The effect of the electrolyte degradation and the deposit of species on the positive electrode surface have been followed by XPS, In-situ Impedance Spectroscopy and NMR (7Li, 19F, 31P) upon cycling. References 1. J.-F. Martin, A. Yamada, G. Kobayashi,, S. Nishimura, R. Kanno, D. Guyomard and N. Dupré, Electrochem. Solid-State Lett,. 11, A12 (2008). 3. A. Yamada, S. C. Chung and K. Hinokuma, J. Electrochem. Soc., 148 (3), A224-229 (2001). 4. A. M. Fransolet, in Granitic Pegmatites : The state of the art - International Symposium 06th (Porto, 2007). 5. M. Cuisinier, J-F. Martin, N. Dupré, A. Yamada, R. Kanno, Electrochem. Comm. 12, 238 (2010).


4:15 PM KK2.10
Hydrothermally Synthesized Nano-Scale LiMnPO4.Michael Stark1,5, Qian Liu1,2, Andrey Chuvilin1, Yun Yoshida3, Norio Sato4, Toshiya Saito4, Ute Kaiser1 and Nicola K. Huesing1,5; 1Inorganic Chemistry, Ulm University, Ulm, Germany; 2Materials Science Electron Microscopy, Ulm University, Ulm, Germany; 3Battery Research Division, Toyota Motor Corp, Shizuoka, Japan; 4Materials&Research R&D, Toyota Motor Europe, Zaventem, Belgium; 5Materials Chemistry, Paris Lodron University of Salzburg, Salzburg, Austria.

Since the pioneering work from Padhi et al.[1] in 1997, lithium transition metal phosphate compounds have driven so much attention that they are considered to be promising cathode materials for the next generation rechargeable lithium ion batteries. In the olivine structure of LiMPO4, the existence of PO43- tetrahedral polyanions stabilizes the three-dimensional framework, which guarantees thermal and electrochemical stability of the electrodes. In addition, LiMPO4 is safe and more environmentally benign than lithium transition metal oxides such as LiCoO2, LiNiO2, etc. Although iron is much cheaper, LiMnPO4 is particularly attractive due to its higher redox potential versus Li/Li+ (4.1V). The only drawback of LiMnPO4 is its poor ionic and electronic conductivity.[1] This drawback can be overcome by reducing the lithium diffusion length, thus by decreasing the particle size[2] in the active material and/or coating the material with something exhibiting a higher electronic conductivity such as carbon.[3] Therefore, as a promising candidate, nano-scale LiMnPO4 has been synthesized and applied in lithium ion batteries, owing to its unique properties such as high specific surface area and the potential to reduce the lithium diffusion length. In this work, nanocrystalline LiMnPO4 was successfully synthesized by a wet-chemical hydrothermal method under basic conditions at 150 °C. Different organic surfactants were employed as additives in the hydrothermal synthesis. The effects of the surfactants and reaction parameters on the resulting LiMnPO4 nanocrystals have been investigated. The obtained materials were characterized by XRD, (HR)-TEM, FT-IR-ATR, N2-sorption, Raman spectroscopy, ICP-OES and STA. The electrochemical performance was measured by the use of a galvanostatic charge/ discharge method. The results demonstrate that the organic additives have profound effects on controlling the nucleation and growth of LiMnPO4, resulting in nanocrystalline LiMnPO4 with special morphology, extraordinary high specific surface area and exceptionally good electrochemical performance. [1] A. K. Padhi, K. S. Nanjundaswamy, J. B. Goodenough, J. Electrochem. Soc. 1997, 144, 1188 [2] N.H. Kwon, T. Drezen, I. Exnar, I. Teerlinck, M. Isono, M. Graetzel, Electrochem. Solid-State Lett., 2006, 9, A277 [3] Z. H. Chen, J. R. Dahn, J. Electrochem. Soc., 2002, 149, A1184


4:30 PM KK2.11
Novel Urchin-like Mesocrystals of LiFePO4 Coated with Nitrogen-doped Carbon for Li-ion Batteries.Jelena Popovic, Markus Antonietti and Maria-Magdalena Titirici; Max Planck Institute of Colloids and Interfaces, Potsdam, Germany.

Mesocrystals as described by Cölfen et al. [1] are 3D ordered nanoparticle superstructures with new chemical and physical properties rising from their unique hierarchical mesostructure. These specific morphologies composed of nanoscaled hierarchically assembled units can be considered as possible future high rate capability electrodes for Li-ion batteries due to porous internal framework that provides high accessibility for the electrolyte. Since its discovery by Padhi et. al. [2], olivine LiFePO4 has been highlighted as one of the most promising cathode material for large size Li-ion batteries due to its high stability, high power and low cost. However, the main drawback of LiFePO4 as electrode material lies in its low intrisinc and electronic conductivity. In this context, extensive research has been done to address present problem including reduction of the particle size, coating with conductive agents and most recently synthesis of porous LiFePO4 monoliths [3]. Here we present a simple solvothermal template-free route for the preparation of novel and exciting mesocrystals of LiFePO4 coated in-situ with a tunable amount of Nitrogen-doped carbon (5-15 wt %). Nitrogen-doping in carbon materials is known to dramatically increase the conductivity due to its electron excess [4]. X-ray diffraction followed by Rietveld refinement of the as-prepared powders showed the existence of a single crystalline phase indicated as olivine LiFePO4 (space group: Pnma). Scanning electron microscopy of LFP/Nitrogen-doped carbon composite showed uniform and dispersed urchin-like mesocrystals ca. 20 μm in diameter. Mesocrystals were formed by the arrangement of primary plate units in a manner very similar to one of the earth magnet. High-resolution transmission electron microscopy further revealed high crystallinity of primary plates with clear lattice fringes (d~2.5A) corresponding to (020) planes of orthorhombic LiFePO4 with additional amorphous carbon layer (~2 nm) on the surface of the crystal. Preliminary conductivity measurements confirm that indeed the materials coated with Nitrogen-doped carbon exhibit a substantial increase in their electronic conductivity and promising electrochemical performance. [1] Cölfen H, Antonietti M, Mesocrystals: Inorganic Superstructures Made by Highly Parallel Crystallization and Controlled Alignment, Angew. Chem., Int. Ed. 2005; 44(35):5576-5591; [2] Padhi, AK., Nanjundaswamy KS, Goodenough JB, Phospho-olivines as Positive-Electrode for Rechargeable Lithium Batteries. J. Electrochem. Soc. 1997; 144(4):1188-1194; [3] Doherty CM, Caruso RA, Smarsly BM, Adelhelm P, Drummond CJ, Hierarchically Porous Monolithic LiFePO4/Carbon Composite Electrode Materials for High Power Lithium Ion Batteries, Chem. Mater. 2010; 21(21):5300-5306; [4] Paraknowitch JP, Zhang J, Su DS, Thomas A, Antonietti M, Ionic Liquids as Precursors for Nitrogen-Doped Graphitic Carbon, Adv. Mater. 2010; 22(1):87


4:45 PM KK2.12
New Advances in Battery Materials and Concepts for Electric-based Transportation.Gholam-Abbas Nazri, Electrochemical Energy Research Lab, GM Global R&D Center, Warren, Michigan.

The current global energy consumption needs to be directed urgently toward renewable. While energy generation from renewable is vital, the energy storage systems and conservation strategy are the critical parts of any energy scenarios. The lithium-based electrochemical energy storage systems are more preferred as compared to other alternatives energy storage systems, and there are tremendous opportunities to design new lithium-based chemistries to satisfy the contradictory requirements of the electric-based transportation. Despite significant incremental improvement in cell packaging, storage capacity remains substantially lower than that required for large vehicle market penetration. New battery technology based on new cell chemistries and new concepts are urgently needed. New battery technologies beyond current lithium-ion cell chemistries are under intense global research and development. Among the new proposed chemistries, the Silicon-based chemistry for electrodes and electrolyte is the technology that meets the requirements of low cost, high energy density, and high power capability. Present and future prospect of new energy storage systems based on silicon chemistry will be discussed. In addition, the novel electrode and cell architecture that accommodates high energy density electrode materials will be presented. Practicality of newer battery chemistries for large format cells and hybrid power sources will be reported.


 

SESSION KK3: Lithium Battery Oxide Cathode Materials I
Chairs: Laurence Croguennec and Gholam-Abbas Nazri
Tuesday Morning, November 30, 2010
Constitution A (Sheraton)


8:00 AM *KK3.1
Microwave-assisted Solvothermal Synthesis of Nanostructured Materials for Lithium-ion Batteries.Arumugam Manthiram, T. Muraliganth, A. Vadivel Murugan and Katharine L. Harrison; Materials Science and Engineering Program, University of Texas at Austin, Austin, Texas.

Lithium-ion batteries have revolutionized the portable electronics market, and they are being intensively pursued for vehicle applications and efficient storage and utilization of renewable energies like solar and wind. Cost, safety, cycle life, and energy and power densities are the critical parameters for these applications. With this perspective, there is immense interest to develop new cathode and anode materials and to develop novel synthesis and processing approaches. We present here a novel microwave-assisted solvothermal (MW-ST) and hydrothermal (MW-HT) approaches to obtain high-performance, nanostructured phosphate and silicate cathodes as well as iron oxide nanowire and graphene nanosheet anodes. These microwave-assisted processes offer highly crystalline materials with unique nanomorphologies within a short reaction time at much lower temperatures compared to the conventional synthesis approaches. For example, single crystalline olivine LiMPO4 (M = Mn, Fe, Co, Ni, and VO) and their solid solutions with a nanorod morphology could be obtained within 5 minutes at < 300 oC in a polyol medium without requiring any reducing gas atmosphere. The dimensions of the naorods could be varied by controlling the concentrations of the reactants in the reaction medium. More importantly, the MW-ST process produces LiMPO4 nanorods with the easy lithium diffusion direction (b axis) perpendicular to the length of the nanorod, offering unique advantages to enhance the rate capability. Similarly, graphene nanosheets could be produced by a reduction of graphite oxide with polyol within 15 minutes at < 300 oC without requiring the conventional toxic reducing agent, hydrazine. Carbon-decorated, single-crystalline Fe3O4 nanowires could be produced by a two-step MW-HT process. The iron oxide nanowires produced exhibit capacity values > 800 mAh/g with stable cycle life. Carbon-coated Li2MSiO4 (M = Fe and Mn) silicates that offer theoretical capacities two times higher than that of olivines could be obtained by a MW-ST process followed by firing at 650 oC in an inert atmosphere. While Li2FeSiO4 exhibits discharge capacities of 148 mAh/g at room temperature and 203 mAh/g at 55 oC with good rate capability and stable cycle life, Li2MnSiO4 shows higher discharge capacities of 210 mAh/g at room temperature and 250 mAh/g at 55 oC, but with poor rate performance and cycle life.


8:30 AM KK3.2
Structural Characterization of Layered Li2MnO3-stabalized Li1+xM1-xO2 (M = Mn, Co, Ni) Cathodes.Karalee Jarvis1, Zengqiang Deng1, Lawrence Allard2, Arumugam Manthiram1 and Paulo Ferreira1; 1University of Texas at Austin, Austin, Texas; 2Materials Science & Technology Div, Oak Ridge Nation Laboratory, Oak Ridge, Tennessee.

One of the most promising cathode materials for next generation lithium-ion batteries is Li2MnO3-stabalized Li1+xM1-xO2 (M = Mn, Co, Ni) as they exhibit much higher capacity than the currently used cathode materials. However, the structure of these materials has been the subject of much debate. Using electron diffraction, HRTEM, and/or aberration-corrected STEM, some groups have reported homogenous solid solutions, while others have reported ordered or disordered domains of Li2MnO3 integrated within the LiMO2 structure. In this context, the present work examines the structure of pure Li2MnO3 and Li[Li0.2Mn0.6Ni0.2]O2 using a novel STEM electron diffraction technique, as well as aberration- corrected STEM. We find that on a local scale (up to 1.5 nm) both materials have primarily a monoclinic structure with some changes in crystal orientation, as well as trigonal ordering. In addition, in some cases, we observe the presence of a spinel phase within the particles of Li[Li0.2Mn0.6Ni0.2]O2. Details of these observations will be discussed. This work was supported by a DOE Energy Frontier Research Center Award (DE-SC-001091). The research at the Oak Ridge National Laboratory's High Temperature Materials Laboratory was sponsored by the U. S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program.


8:45 AM KK3.3
Crystal and Microstructure Characterization of LiNi1/2Mn3/2O4 as a High Voltage Positive Electrode for Li batteries.Jordi Cabana1, Montserrat Casas-Cabanas2, Dongli Zeng4, Clare P. Grey3,4 and Muharrem Kunduraci1; 1Lawrence Berkeley National Laboratory, Berkeley, California; 2Laboratoire CRISMAT, ENSICAEN, Caen, France; 3Department of Chemistry, University of Cambridge, Cambridge, United Kingdom; 4Department of Chemistry, Stony Brook University, Stony Brook, New York.

Li-ion batteries stand out as a central player in the path toward a greener society, but exponential increases in their electrical energy density are still necessary. Li[Ni1/2Mn3/2]O4 has emerged as a promising high power, high energy electrode material, due, in part, to the high potential (~4.7 V vs. Li+/Li0) at which lithium is removed from the structure. Its crystal structure has been reported to be dependent on the existence of Ni and Mn ordering in the octahedral sites of the spinel structure; the transition metals can either exhibit a 3/1 ordering in the 4a and 12d sites of a P4332 space group or be randomly distributed in the 16d sites of a Fd3m-type unit cell. Different groups have proved that such ordering is dependent on the temperature of synthesis of the compound, which has an impact on the creation of a slight oxygen non-stoichiometry and formation of Mn3+. More importantly, it was also shown that the structural characteristics of different Li[Ni1/2Mn3/2]O4 samples had an impact on their electrochemical performance, the disordered samples having much better rate capabilities. Another factor that can impact both cycle life and rate capabilities is the formation of tailored nanostructures. Since such nanostructures will be sensitive to the temperature and precursors used in the synthesis, it is expected to correlate with the ordering within the crystal structure. In the course of this study, different samples of Li[Ni1/2Mn3/2]O4 were prepared at different temperatures by both a solid state reaction using mixed hydroxide precursors, with and without activation by mechanical milling, by a modified Pechini method, and from precursors made solvothermally. The changes in microstructure (i.e. particle size, morphology and agglomeration) were followed using electron microscopy, whereas the impact of the synthesis route on the composition, crystal structure and Ni/Mn ordering was monitored by neutron diffraction and 6Li MAS NMR. In addition, changes in the oxidation state of Ni and Mn were followed by XANES. The dependence of the different parameters on the precursors and synthetic method used and on the preparation temperature will be described. Finally, attempts to establish a correlation between microstructure, crystal structure and electrochemical performance as a positive electrode in Li batteries will be discussed.


9:00 AM KK3.4
Polyol-made Nanoplatelets as Starting Materials for Li+ Batterie Cathodes.Tahar Azib1, Souad Ammar1, Karim Zaghib3 and Alain Mauger2; 1ITODYS UMR-CNRS 7086, Paris 7 university, Paris, France; 2UMR-CNRS UMR 7590, Paris 6 University, Paris, France; 3Institut de Recherche, Hydro-Quebec, Varennes, Quebec, Canada.

The demand for high energy density rechargeable batteries for portable electronic devices, electrical vehicles and dispersed-type energy storage systems has promoted the development of lithium ion batteries. Since the performance and cost of these batteries are often decided by the properties of the cathode material, many kinds of material have been investigated. One of the most important among them is the olivine-like LiFePO4 that is environmentally benign, and has advantages in terms of safety and stability [1]. We present here the synthesis, the characterization and the electrochemical activity of pure and highly-crystalline LiFePO4 ultra-fine nanoplatelets. The particles were produced using the well known polyol process, which is an alternative sol-gel chemical route. Acting on the synthesis parameters, namely the solvent nature and the precursor concentration, we suceeded to decrease the thickeness of the particles down to 20 nm, without opposing their crystallinity. Transmission electron microscopy has shown that all the produced platelets are single crystals whom the basal direction is perpendicular to the lithium channel in the olivine-like lattice (b axe). Magnetic measurements have shown that the particles are free from any magnetic foreign phase contamination, such as an iron phosphate or an iron oxide. The high purity and the optimized morphology of the polyol-made LiFePO4 particles make them very promising for Li+ batteries application. To confirm that, all the produced particles were coated by graphite in different mass ratio and tested in a home-made electrochemical cell. The measured electrochemical properties on the resulting composites are very interesting and evidence clearly the important role of the microstructure of the starting LiFePO4 nanoparticles. [1] Padhi, A. K.; Nanjundaswamy, K. S.; Goodenough, J. B. J. Electrochem. Soc. 1997, 144, 1188.


9:15 AM KK3.5
Nano-architectured Manganese Oxide Electrodes for Lithuim-ion Batteries.Sanja Tepavcevic1, Tijana Rajh1 and Christopher Johnson2; 1CNM, Argonne National Laboratory, Lemont, Illinois; 2Chemical Sciences and Engineering Division, Argone National Laboratory, Lemont, Illinois.

The intense interest in manganese oxides for battery applications is driven by their low cost and low toxicity, very rich chemistry and fact that they can be synthesized in dozens of crystalline and disordered forms, each with distinctive physical and electrochemical properties. Here we present electrochemically synthesized nano-architectured manganese oxide electrodes composed of interconnected nanowires. They were synthesized in manganous acetate solution at room temperature without any template or catalyst.1 Effect of annealing temperature on the electrode morphology and crystallization was investigated by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). X-ray diffraction (XRD) was used to identify crystalline structure of the deposited manganese oxide. Electrochemical performance of nano-architectured electrodes was compared with conventional, bulk Mn2O3. Reversible capacity of nanostructured Mn2O3 anode reached theoretical value of 1100 mAhg-1, four times higher then the conventional, bulk Mn2O3 electrodes and three times higher then traditional graphite materials for lithium storage. With this simple electrochemical deposition technique one can optimize manganese oxide electrode for particular electrochemical performance characteristics (stability, capacity, voltage, etc.). The reaction mechanism has been proposed as the formation/decomposition of Li2O facilitated by metallic manganese.2 Owing to the nanostructured nature of these electrodes reactions are highly reversible and the specific capacity remains nearly constant after 100 cycles. Large irreversible capacity occurring only in the first cycle may be caused by the structural or textural modifications, the decomposition reactions of electrolyte, and the formation of the SEI film. References: 1. M.S. Wu at all, J. Phys. Chem. B, 2005, 109, 23279 2. P. Poizot at all, Nature, 2000, 407, 496


9:45 AM KK3.6
Electromechanical Probing of Li-Activity on the Nanometer Scale in Cathode Materials.Nina Balke1, Stephen Jesse1, Anna N. Morozovska2, Eugene Eliseev2, Ding-Wen Chung3, Yoongu Kim1, Leslie A. Adamczyk1, Edwin Garcia3, Nancy J. Dudney1 and Sergei V. Kalinin1; 1Oak Ridge National Laboratory, Oak Ridge, Tennessee; 2National Academy of Science of Ukraine, Kiev, Ukraine; 3Purdue University, West Lafayette, Indiana.

The electrochemical energy storage systems based on Li-based insertion and reconstitution chemistries are a vital aspect of energy technologies. A distinctive feature of these systems is a significant change of molar volume, which can be as large as tens of percent, during electrochemical processes. This expansion is highly anisotropic; e. g., in LiCoO2 it is the most pronounced in the c-axis direction and smallest in the direction of the CoO2 layers. Here, the strong strain-bias coupling in electrochemical materials is used to develop the capability for mapping electrochemical reactions on the nanometer scale, and hence get insight into the mesoscale mechanisms of battery operation. The Scanning Probe Microscopy tip concentrates a periodic electric field in a nanoscale volume of material, resulting in Li-ion redistribution. The associated changes in molar volume result in local surface expansion and contraction that is transferred to the Scanning Probe Microscopy probe and detected by microscope electronics. The simple estimates suggest that the extremely high (~3-10 pm) sensitivity of dynamic Atomic Force Microscopy potentially allows detecting Li concentration change of 10% in ~300 nm3 volumes, exceeding the state of the art by 6-9 orders of magnitude. Finally, with dc fields applied to the Scanning Prope Microscopy tip, the Li concentration underneath the tip can be changed and hysteretic strain loops related to electrochemical charge-discharge processes can be measured. Theoretical calculations are shown to support the experimental data and to give insight into the signal generating mechanism. This material is based upon work supported as part of the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number ERKCC61. Part of this research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. Department of Energy. N.B. acknowledges the Alexander von Humboldt foundation for financial support. R.E.G. and D.W.C. thank the support provided by NSF grant CMMI 0856491.


10:00 AM KK3.7
Investigation of the Chemical and Morphological Origin of the Mechanisms of Failure in Electrode Materials for Advanced Lithium Batteries.Carmen M. Lopez1, Margret Wohlfahrt-Mehrens1, Dennis W. Dees2 and Jonh T. Vaughey2; 1Accumulators Material Research, Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg Helmholtzstr. 8, Ulm, Germany; 2Electrochemical Energy Storage, Chemical Science and Engineering Division, Argonne National Laboratory, Argonne, Illinois.

Due to their high energy and power densities, lithium batteries are considered the energy storage system of choice for applications ranging from portable electronics and biomedical applications, to hybrid-electric and plug-in hybrid vehicles. Despite their widespread used and promising properties, their further application in transportation technologies has been prevented by cost, safety concerns, poor performance at low temperature, and limited cell life. A key aspect in developing safer batteries with lower cost and better performance is to understand the physical, chemical and morphological properties of the active electrode materials that are at the core of the electrochemical behavior of these systems. In this work we use a combination of electroanalytical techniques, and morphological and spectroscopic characterization to shed light into the different mechanisms of failure in advanced lithium batteries. In particular, we demonstrate how electroanalytical cell response can be analyzed by utilizing morphological information obtained from electron microscopy techniques to yield a better understanding of the physical phenomena that trigger the electrochemical response and affect battery performance.


10:15 AM KK3.8
Crystal Structure Analysis of Li-ion Conducting Perovskites with Both Tilting of BX6 Octahedra and Layered Ordering of A-cations by Transmission Electron Microscopy.Kyosuke Kishida1, Kengo Goto1, Haruyuki Inui1 and Zempachi Ogumi2; 1Department of Materials Science and Engineering, Kyoto University, Kyoto, Japan; 2Kyoto University, Kyoto, Japan.

Solid lithium-ion conductors have received a considerable amount of attentions as solid electrolytes for all solid-state lithium rechargeable batteries, since they have great advantages over currently-used lithium-ion conducting liquid electrolytes in terms of safety, thermal stability and resistance to shocks and vibrations. Li-substituted La2/3TiO3 (La2/3-xLi3xTiO3 (LLT)) is the most promising electrolyte in all-solid-state lithium batteries because of its very high ionic conductivity of 1.1 x 10-3 S/cm at room temperature (x ~ 0.1) and temperature stability. Since the ionic conductivity of LLT strongly depends on its chemical composition, and thereby its crystal structure, extensive structure determinations have been conducted. These reveal that La3+ ordering is layered, such that La3+-rich and La3+-poor A-cation layers stack alternatively along one of the pseudo-cubic axes. In addition, tilting of TiO6 octahedra occurs. However, the crystal structures of the LLT phases remain controversial. We thus believe it is timely to establish a systematic method for determining the space groups of perovskites containing both tilted BX6 octahedra and layered ordering of A-cations. In the present study, we examine on the basis of the group-subgroup relations the space groups of ABX3 perovskites when tilting of BX6 octahedra and layered ordering of A-cations are simultaneously introduced. We describe how to distinguish all possible space groups for these perovskites by electron diffraction in transmission electron microscopy on the basis of systematic absences. This approach is used to analyze lithium lanthanum titanate pseudomorphic structural pair. For Li-rich LLT (x = 0.1), the space group is determined to be P4/nbm (#125, origin choice 2) purely by SAED analysis. For Li-poor LLT (x = 0.03), the space group is determined to be Cm2m (#38, standard notation: Amm2) by SAED analysis together with additional CBED analysis. This result differs from previously reported space group of Cmmm(#65) for LLT with similar chemical compositions. The reason for the discrepancy is believed to be due to the fact that previous studies discarded Cm2m simply because it has a lower symmetry than Cmmm, both of which exhibit the same systematic absences of diffraction peaks/spots. These results clealry indicates the great advantages of the electron diffraction technique in TEM for precise analysis of the space group of Li-ion conducting perovskites.


10:30 AM KK3.9
In situ X-ray Absorption Spectrosopy Study of Nanostructured, Mg-doped, Nickel Manganese Spinels for use in Li-ion Batteries.Richard Apps1, Gavin Mountjoy1 and Ugo Lafont2; 1School of Physical Sciences, University of Kent, Canterbury,, Kent, United Kingdom; 2Technical University of Delft, Delft, Netherlands.

LiMn2O4 is a cheaper and more environmentally friendly cathode material compared to the currently commercially used materials such as LiCoO2 and LiNiO2. The reason it isn’t used commercially is that it suffers from degradation during cycling. Introducing a second transition metal into the structure, i.e. LiMe0.5Mn1.5O4, where Me= Fe, Ni etc., improves the cycling performance and in the case Me= Ni the spinel has a well defined high voltage profile. It has also been found that doping spinels with Mg increases the conductivity of the structure while not playing a direct role in the redox reaction during Li insertion. Previous studies on similar spinel structures have shown that the synthesis route taken can effect the structural and electrochemical properties. To study the effect of synthesis route, nanostructured LiMg0.05Ni0.45Mn1.5O4 has been prepared via four different methods. To better understand both the structural and electrochemical changes occurring in the active battery in-situ x-ray absorption measurements where made to collect XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) spectra. The XANES and EXAFS spectra have been analysed to enable a study of the valence state of Ni and Mn in these battery materials during discharging and charging cycles. The observations are discussed in relation to different synthesis routes for the materials.


10:45 AM KK3.10
Mo- and V- substituted Spinel Ferrites as Enhanced Positive Electrode Materials for Lithium-ion Batteries.Benjamin P. Hahn1, Jeffrey W. Long1, Katherine A. Pettigrew3, Michael S. Osofsky2 and Debra R. Rolison1; 1Surface Chemistry Branch (Code 6170), Naval Research Laboratory, Washington, District of Columbia; 2Materials and Sensors Branch (Code 6360), Naval Research Laboratory, Washington, District of Columbia; 3Nova Research, Inc., Alexandria, Virginia.

Iron (III) oxides are potential low-cost positive-electrode materials for Li-ion batteries, but their poor charge-storage capacities and the relatively low potential of the Fe2+/3+ redox couple hinder their performance for such applications. Recent publications address this issue by decreasing the particle size and/or creating metal-organic hybrids that enhance the surface reactivity,[1,2] but it is also possible to improve both the thermodynamics and capacities for Li+ intercalation by creating cation vacancies within the lattice that can reversibly store Li+.[3] Starting with the defect spinel γ-Fe2O3, we dramatically increase the number cation vacancies per unit cell by exchanging a fraction of the Fe3+ content for more highly oxidized cations (e.g., Mo6+, V5+). Preliminary charge-discharge experiments using these binary oxides demonstrate lithium-ion capacities ≥ 100 mAhg-1 over a potential window of 4.1-2.0 V vs. Li/Li+, a factor of 4-5 improvement with respect to the parent γ-Fe2O3 structure. By comparing the structural and electrochemical properties of our Mo- and V- substituted ferrites to a γ-Fe2O3 control, we establish the influence that cation-vacancies have upon the Li+ charge-storage mechanism and offer a general strategy to create new iron oxide based compounds for electrochemical energy storage. [1]. J. Manuel, J.-K. Kim, J.-H. Ahn, G. Cheruvally, G. S. Chauhan, J.-W. Choi, and K.-W. Kim, J. Power Sources, 184, 527 (2008). [2]. M. Quintin, O. Devos, M. H. Delville, and G. Campet, Electrochim. Acta, 51, 6426 (2006). [3]. M. Pernet, P. Strobel, B. Bonnet, P. Bordet, and Y. Chabre, Solid State Ionics, 66, 259 (1993).


11:00 AM KK3.11
Layered Oxides with High Energy, High Power and High Thermal Stability.Zheng Li1, Natasha Chernova1, Shailesh Upreti1, Chunmei Ban2, Anne Dillon2, Cole Petersburg3, Faisal Alamgir3 and Michael Whittingham1; 1Materials Science, Binghamton University, Binghamton, New York; 2Materials and Chemical Science Center, National Renewable Energy Lab, Golden, Colorado; 3Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia.

Based on our comparative study of mixed transition metal oxides LiNiyMnyCo1-2yO2 the y = 0.4 composition has the best electrochemical performance with a theoretical capacity around 200 mAh/g when charged up to 4.4 V. Charging to higher voltage leads to increased capacity fading. The irreversible capacity appears to be an intrinsic property of these materials. In this work we discuss the ways to improve the electrochemical capacity, stability and rate capability of layered oxides. We prepared two series of compounds: LiNi0.4+zMn0.4-zCo0.2-yAlyO2 and 0.5Li2MnO3-0.5LiNi0.4Mn0.4Co0.2-yAlyO2. The aluminum improves the thermal stability in both series, and the added Li2MnO3 the capacity. The latter materials show capacity above 200 mAh/g when charged to 4.6 V and good cycle life. For all the compounds powder x-ray diffraction, synchrotron x-ray absorption, magnetic susceptibility, electrical resistivity, and electrochemical data were collected. The long-range and local structure as well as physical properties were characterized and related to the electrochemical performance. The rate capability of the compounds was found to be optimized by the use of specially designed carbon nanotube/layered oxides composites. These composites show maintenance of full capacity at rates beyond 10C. The work at Binghamton University and NREL are supported by the US Department of Energy, Office of FreedomCAR and Fuel Partnership through the BATT program at Lawrence Berkeley National Laboratory, at Georgia Institute of Technology - by Creating Energy Options program.


11:15 AM KK3.12
Polyoxometalate Molecular Cluster Batteries: In-situ XAFS and Nano-hybridazation.Hirofumi Yoshikawa1, Shun Hamanaka1, Heng Wang1, Toshihiko Yokoyama2 and Kunio Awaga1; 1Nagoya Univ., Nagoya, Japan; 2Institute of Molecular Science, Okazaki, Japan.

Recently, much attention has been focused on the creation of new energy systems, such as high-performance rechargeable batteries. To achieve both rapid charging/discharging and high power density, we have proposed the use of polynuclear metal complex clusters, which undergo multi-step redox reactions, as a cathode active material for lithium batteries. So far we have fabricated a rechargeable molecular cluster battery, in which Mn12 cluster, Mn12O12(CH3COO)16(H2O)4, was utilized as a cathode active material. A discharging capacity (ca. 200 Ah/kg) in the first cycle was larger than those of usual Li ion batteries (148 Ah/kg), while discharging capacities after second cycle significantly decreased due to a decomposition of Mn12. In order to modify a cycle performance, we attempted to use polyoxometalate clusters (POMs), which are more stable than Mn12. Here we fabricated phosphomolybdate ([PMo12O40]3-, PMo12) MCBs and measured their charging/discharging curves and cycle performances. The 1st cycle discharging capacity showed ca. 260 Ah/kg, which was higher than that of Mn12 MCB. Even after the 10th cycle, it maintained ca. 200 Ah/kg. To investigate solid-state electrochemistry of PMo12, in-situ Mo K-edge X-ray absorption fine structure (XAFS) analysis were performed on the PMo12 MCBs in charging/discharging processes. In-situ XAFS spectra revealed repeatable valence changes of the Mo ions in PMo12 in charging/discharging processes. In the discharging process, PMo12 underwent twenty four-electron reduction, which indicated that all of Mo6+ ions in PMo12 changed into Mo4+. The theoretical capacity estimated from the Mo valence change corresponded to the actual capacity of ca. 260 Ah/kg. These results suggest that molecular clusters such as POMs are promising for next generation cathode active materials. We also report the preparation of PMo12-single walled carbon nanotubes (SWNTs) hybrid materials and their applications for cathode materials.


11:30 AM KK3.13
Vanadium Oxide-based Mesoporous Films as Positive Electrode Materials in Li-ion Batteries.Natacha Krins, Sebastien Caes, Jose Carlos Arrebola, Rudi Cloots and Benedicte Vertruyen; Chemistry, University of Liège, Liège, Belgium.

Mesoporous films are a promising architecture for positive electrodes in Li-ion battery applications [1, 2], in view of the expected next generation of 3D-microbatteries with interdigitated electrodes [3]. In this work, vanadium-based oxide materials known for their ability to host lithium, such as NbVO5, V2O5 and LiV3O8, are investigated and designed as mesoporous thin films. Templating of vanadium-based oxides through traditional soft-chemistry approaches is hindered by the thermal instability of the hybrid vanadium-oxide network [4]. To address these problems, successful soft-templating of these compounds was achieved through Evaporation Induced Micelles Packing. Dip-coating was carried out from a precursor solution with thermally stable polystyrene-b-polyethyleneoxide as structuring agents. A finely tuned thermal treatment is another requirement to obtain template-free amorphous vanadium oxide-based mesoporous films. TEM, electron tomography and AFM analyses reveal homogeneous wormlike mesoporous networks whose pore and inorganic wall sizes can be tuned between 15 and 100 nm by changing the hydrophobic/hydrophilic surfactant chain lengths. Ellipsometric porosimetry shows that 100 nm thick films with a 15 nm pore size displays 25% electrolyte accessible porosity. Thicker films up to 1.3 µm are prepared by a multidipping process. The superiority of such nanoarchitectures compared to non porous materials in terms of electrochemical properties such as capacity and cycling behavior is revealed using the NbVO5 candidate: the structural distortion accompanying the modification of the vanadium coordination during the first electrochemical cycle is significantly better accommodated by the mesostructured material. [1] Ren, Y.; Armstrong, a. R.; Jiao, F.; Bruce, P. G. J. Am. Chem. Soc. 2010, 132, 996-1004. [2] Sayle, T. X.; Maphanga, R. R.; Ngoepe, P. E.; Sayle, D. C. J. Am. Chem. Soc. 2009, 131, 6161-6173. [3] Rolison, D. R.; Long, J.W.; Lytle, L. C.; Rhodes, C. P.; Mcevoy, T. M.; Bourg, E.; Lubers, A. M. Chem. Soc Rev. 2009, 38, 226-252. [4] Crepaldi, E. L.; Grosso, D.; Soler-illia, G. J.; Albouy, P.; Amenitsch, H.; Curie, M. Thin Films. 2002, 3316-3325.


11:45 AM KK3.14
High Lithium Ionic Conductivity in Garnet-type Oxide: Li7-XLa3(Zr2-X, NbX)O12 (X = 0 ~ 2).Shingo Ohta, Tetsuro Kobayashi and Takahiko Asaoka; TOYOTA Central R&D Labs., Inc., Aichi, Japan.

All-solid-state lithium ion batteries containing solid electrolytes are considered to be more stable than lithium ion batteries using liquid organic electrolytes. In order to improve the performance of all-solid-state lithium ion secondary batteries, new solid electrolytes are strongly required, which have the following properties; 1) high lithium ionic conductivity, 2) chemical stability and 3) wide potential window. The garnet-type oxide Li7La3Zr2O12(1) is expected to be one of promising candidates for a solid electrolyte because it has advantages such as high chemical stability and a wide potential window. However the lithium ion conductivity of Li7La3Zr2O12 is ~ 0.2 mS/cm at 25 degree C., it is about two orders of magnitude lower than that of a common liquid organic electrolyte. In this study, we successfully improved the lithium ion conductivity of Li7La3Zr2O12 due to the substitutional Nb-doping with optimized the composition. Li7-XLa3(Zr2-X, NbX)O12 (X = 0 ~ 2) bulk ceramic samples were fabricated by conventional solid-state reactions. XRD measurement revealed that Li7-XLa3(Zr2-X, NbX)O12 were indexed as cubic garnet like structure. The lithium ion conductivity of Li7-XLa3(Zr2-X, NbX)O12 which was measured by a two-probe a.c. impedance method, was constant for a week independently of exposure time in air at room temperature. This is considered that Li7-XLa3(Zr2-X, NbX)O12 is stable at room temperature in air. Potential window was examined by cyclic voltammetry (CV). Au electrode and lithium metal were attached onto both faces of the sintered sample as working and counter electrodes, respectively. The cyclic voltammogram showed only lithium deposition and dissolution peaks at around 0 V vs. Li+/Li and no other reactions up to 9V vs. Li+/Li. This result indicates that Li7-XLa3(Zr2-X, NbX)O12 has wide potential window. The lithium ion conductivity of Li7-XLa3(Zr2-X, NbX)O12 increased with Nb-content and reached the maximum ~ 0.8 mScm-1 (25 C) at around X = 0.25, which is comparable to those of other fast lithium ion conducting oxides such as NASICON type oxides. From the above study, we constructed all solid state lithium ion battery using Li7-XLa3(Zr2-X, NbX)O12 (solid electrolytes), lithium (anode) and LiCoO2 (cathode), and good charge and discharge behaviors of this battery were seen. Therefore we conclude that Li7-XLa3(Zr2-X, NbX)O12 is expected to one of promising candidates for a solid electrolyte for all-solid-state lithium ion batteries.


 

SESSION KK4: Lithium Battery Oxide Cathode Materials II
Chairs: Dominique Guyomard and Yang Shao-Horn
Tuesday Afternoon, November 30, 2010
Constitution A (Sheraton)


1:30 PM KK4.1
Transmission Electron Microscopy Structural Studies of 0.5Li2MnO3+0.5LiNi0.44Co0.25Mn0.31O2 Layered-layered Composited Cathode.Christopher E. Carlton1, Sun-Ho Kang2, Michael M. Thackeray2 and Yang Shao-Horn1; 1Department of Mechanical Engineering, MIT, Cambridge, Massachusetts; 2Argonne National Laboratory, Argonne, Illinois.

While Li ion batteries have already been highly successful in many commercial applications, energy density, power density and durability must all be increased before their implementation in practical plug-in hybrid electric vehicles. To this end, attempts have been made to structurally stabilize the layered LixMO2 phase with a second Li intercalation phase on the nanometer scale. The goal is to increase the specific capacity and rate capabilities while structurally stabilizing LixMO2, allowing x to be reduced below 0.5. To this end, 0.5Li2MnO3+0.5LiNi0.44Co0.25Mn0.31O2 layered-layered composite cathodes were synthesized and a TEM structural analysis was performed on the pristine and cycled cathodes. A structural analysis was conducted using diffraction contrast imaging, phase contrast imaging, and selected area electron diffraction techniques. Particularly interesting results were obtained by electron diffraction, where novel long range cation ordering was observed. Cation ordering and structure changes upon cycling will be discussed in detail.


1:45 PM KK4.2
High-energy Scalable Lithium-ion Battery by Using Electrospun Nanofiber as Cathodic Materials.Jin Wang1, Minoru Taya1,2 and Yanyi Liu2; 1Mechanical Engineering, University of Washington, Seattle, Washington; 2Materials Science and Engineering, University of Washington, Seattle, Washington.

Lithium-ion batteries have been widely investigated and applied for powerful energy storage devices due to their high specific capacities and rechargeable abilities. Recently, nanostructured electrode materials become extensively explored due to its benefits in terms of simple process, high aspect ratio, high specific capacity and energy density as well as materials sustainability. In the present work, we have successfully fabricated nanostructured LiCoO2 fibers using electrospinning technique from a viscous solution of lithium acetate/cobalt acetate/PVP (polyvinyl alcohol). XRD (X-ray diffraction) and SEM (scanning electron microscopy) were performed to investigate the phase transitions and microstructures of the electrospinning fibers respectively. Furthermore CV (cyclic voltammetry) and charge-discharge experiments were applied to characterize the electrochemical properties of LiCoO2 nanofibers. It is noteworthy that the nanostructured cathode offers a higher charge-discharge capacity compared with conventional powder or film cathodes. Finally, LiCoO2 nanofiber cathode was assembly with other component into a thin-film device, the mechanical strength and extreme condition test were performed, demonstrating the mechanical robust as well as property stabilities.


2:00 PM KK4.3
Influence of Controlled Pore Topology in Sintered Li-ion Battery Cathodes on Electrochemical Performance.Chang-Jun Bae1, Can K. Erdonmez1, John W. Halloran2 and Yet-Ming Chiang1; 1Material Science Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts; 2Material Science Engineering, University of Michigan, Ann Arbor, Michigan.

Recently, Lai et al. [1] demonstrated an alternative sintered electrode architecture to conventional powder-based electrodes that improves the energy density over existing lithium ion batteries. By eliminating electrochemically-inert additives, and achieving lower pore tortuosity, this new architecture permits higher density, greater thickness electrodes that increase the volumetric and gravimetric utilization of active material at the cell level. As electrode thickness increases and pore fraction decreases, transport in the pore phase becomes limiting. In order to maximize rate capability at any given electrode thickness and density, tailoring the pore topology is a useful approach. In this work, we have used a co-extrusion approach to introduce periodic, 1-dimensional, optimally spaced porosity into powder preforms that then undergo binder pyrolysis and sintering. LiCoO2 powder was used as a model cathode material, and was formulated for co-extrusion in the green state with carbon as a fugitive pore former. Systematic investigation of pore size, pore spacing, and sintered matrix density while holding overall electrode density approximately constant allowed the optimal pore configuration in sintered electrodes to be identified for a given cell design, with high capacity retention being observed at galvanostatic rates up to 2C.


2:15 PM KK4.4
Fabrication of Graphene-polythiophene and Graphene - polyethylenedioxythiophene Nanocomposites as Novel Electrode for Lithium Battery.Manoj K. Ram2,1, Humberto Gomez1,2,5, Jeremiah Browne4, Farah Alvi1,2,3 and Ashok Kumar1,2; 1Department of Mechanical Engineering, University of South Florida, Tampa, Florida; 2Nanotechnology Research & Education Center, University of South Florida, Tampa, Florida; 3Department of Electrical Engineering, University of South Florida, Tampa, Florida; 4Department of Mechanical Engineering, University of Florida, Gainesville, Florida; 5Departamento de Ingenieria Mecanica, Universidad del Norte, Barranquilla, Colombia.

The new, low-cost, long cycle life, high reversible capacity, and environmentally friendly energy storage systems are the needs of modern society, and emerging ecological concerns of modern times. The chemically modified and environmentally friendly graphene material has shown to exhibit enormous active edges and oxygen functional groups with superior electrochemical and mechanical properties as comparable to most of the carbon based materials. Moreover, graphene offers superior chemical stability, large surface-to-volume ratio, and a broad electrochemical window, which could find possible applications in electrode material for lithium ion batteries. Recently, we fabricated supercapacitor from graphene-polyaniline, and continued studying the graphene-conducting polymeric nanomaterials with a focus on understanding the use in rechargeable battery applications. We present here the synthesis, characterization and application of graphene-polythiophene (PTH) and graphene-polyethylenedioxythiophene (PEDOT) nanocomposites as electrode materials for lithium-ion batteries. The graphene-PEDOT and graphene-PTH nanocomposites electrode active materials were synthesized by weight fraction monomer to graphene (1 to 3) ratio by weight using emulsion chemical polymerization technique, and characterized using Raman, X-ray, UV-Vis, FTIR, impedance, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), electrical conductivity and electrochemical techniques, respectively. The anode was prepared using graphene-PEDOT as well as graphene-PHT, conductivity-promoting ingredient and a binder by dispersing the resultant mixture in a suitable solvent, using stainless steel as current collector. The cathode electrode was made from lithium manganese oxide cathode electrode with conducting material and polyvinylidene fluoride binder. The battery was studied in lithium perchlorate and lithium hexafluorophosphate electrolytes with porous PTFE film as a separator. The open circuit voltage, life cycle, charges capacity etc. of graphene-PEDOT or graphene-PTH nanocomposite based battery was studied. The electrode showed the capacity ≈600 mAh/g (for up to 50 cycles). The tailoring of the composition of anode electrode material has shown a reversible capacity of ≥800 mAh/g for over 100 cycles with little decrease till 300 cycles. Further, in order to identify the cause of the capacity fade of the whole-battery, half-cell studies were carried out on both fresh and cycled batteries. SEM images have demonstrated that graphene based composite deposits less material on the surface of electrode. The testing of charge capacity as a function of time is under progress in our laboratories. Clearly, graphene based composites are capable of maintaining the structure of an active electrode. The charge capacity and open circuit voltage potential obtained using graphene-polythiophenes offer the possibilities to use the novel materials for lithium battery application.


2:30 PM KK4.5
High Rate Micron-sized Ordered LiNi0.5Mn1.5O4.Xiaohua Ma, Byoungwoo Kang and Gerbrand Ceder; Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.

Developing positive electrode materials with high energy density is one of the key challenges for lithium ion batteries. High energy density can be obtained either by high voltage or high capacity. Several compounds have been investigated for their high voltage. LiNi0.5Mn1.5O4 is one of these, which can work with a conventional carbonate based electrolyte though some side reaction occurs. Previous work in the literature has distinguished between two types of LiNi0.5Mn1.5O4 depending on the ordering of Ni/Mn in the octahedral sites. Most investigators have shown disordered LiNi0.5Mn1.5O4 to have better rate capability and cyclability than ordered LiNi0.5Mn1.5O4, though the difference in performance between the two phases varies. The explanations, however, are still not clarified. On the other hand, nano-particle LiNi0.5Mn1.5O4 has given mixed results. While Shaju and Bruce showed high rate capability and cyclability with 50 nm LiNi0.5Mn1.5O4, some other groups did not achieve comparable rate performance on nanomaterials with a similar size. This indicates that particle size may not be the critical factor affecting the electrochemical performance. In our work, ordered LiNi0.5Mn1.5O4 was synthesized through a solid-state reaction. Even though the material has a particle size of 3-5 μm, it shows better rate capability than previously published work on LiNi0.5Mn1.5O4 with 50 nm particle size . The fact that micron-sized particles show higher rate capability than nanomaterials strongly indicates that ion or electron transport in the particle is not the rate-limiting process at least for 40C. With 65 wt% carbon mixed in the electrode, the capacity is as high as ~78 mAh/g at a 167C discharge rate. This high discharge rate performance is consistent with first-principles calculations of the activation barrier for lithium motion, which predict the lithium diffusivity in this material to be around 10-9 ~ 10-8cm2/s. We also systematically investigated the effect of several cell components and electrode construction on the measured rate performance and conclude that care has to be taken to remove all other rate limitations from the cell to measure the rate performance of an electrode material.


3:15 PM KK4.6
Electronic, Structural and Electrochemical Properties of LiNixCuyMn2-x-yO4 High-voltage Spinel Materials. Bo Xu1, Ming-Che Yang2 and Shirley Meng1,2; 1NanoEngineering, U.C. San Diego, La Jolla, California; 2Materials Science & Engineering, University of Florida, Gainesville, Florida.

First principles computation is carried out for investigating the electronic, structural and electrochemical properties of LiM1/2Mn3/2O4 (M= Cr, Fe, Co, Ni and Cu). The computation results suggest that LiM1/2Mn3/2O4 spinel materials family can have quite different activation barriers for Li diffusion depending on the doping elements, and doping with Co or Cu can potentially lower Li diffusion barrier compared with Ni doping. Our experimental research has focused on LiNixCuyMn2-x-yO4 (0<x<0.5, 0<y<0.5) and we found that the amount of Cu will affect the lattice parameters, the cation disorder in the spinel lattice, the particle morphology, as well as the electrochemical properties. Crystal structures, electronic structures and electrochemical properties of spinel oxides LiNixCuyMn2-x-yO4 are studied by X-ray diffraction, scanning electron microscopy(SEM) , X-ray absorption spectroscopy (XAS) and electrochemical measurements including potentiostatic intermittent titration technique (PITT). With electrochemical measurements and in situ XAS experiment of LiNixCuyMn2-x-yO4, the proposed explanation of voltage profile by the first principles computation was proven. The first plateau at 4.0V originates from the oxidation of Mn3+to Mn4+, the second plateau at 4.2V originates from the oxidation of Cu2+ to Cu3+ and the third plateau at 4.95V originates from extra electrons provided by oxygen ions. Although the reversible discharge capacity decreases with increasing Cu amount, optimized composition such as LiCu0.25Ni0.25Mn1.5O4 exhibits high capacities at high rates.


3:30 PM KK4.7
Using AlPO4 Coatings to Mitigate Metal-ion Displacement and Oxygen Vacancy Formation in Li2CuO2.Karen Swider-Lyons1, Wojtek Dmowski2, Albert Epshteyn1 and Corey T. Love1; 1Naval Research Laboratory, Washington, District of Columbia; 2University of Tennessee, Knoxville, Tennessee.

Li2CuO2 and Li2CuxNi1-xO2 have the theoretical the capability to exchange up to 2 Li+ per unit cell as cathodes of Li-ion batteries [1]. Their high capacity is not realized due to transformations within the materials during cycling. We have used pair density function (PDF) analysis of high-energy X-ray diffraction patterns to resolve the short-range structure of the materials that were cycled to different potentials. The results indicate that in Li2CuO2 materials, capacity is irreversibly lost due to the formation of oxygen vacancies and the migration of Cu2+ to the Li+ planes [2]. We now use AlPO4 coatings to determine whether controlling the battery|electrolyte interface can mitigate vacancy formation and ion migration. Nanoscale AlPO4 coatings are applied to the Li2CuO2 via solution deposition methods. New PDF and cycling results will be presented to show how control and modification of the Li2CuO2 surface affects the bulk stability. [1] K. Kang, C. H. Chen, B. J. Hwang and G. Ceder, Chem. Mat., 16, 2685 (2004). [2] K. Swider-Lyons, W. Dmowski, C. T. Love, M. D. Johannes, in symposium on “Materials Challenges Facing Electrical Energy Storage,” Fall 2009 MRS meeting.


3:45 PM KK4.8
Graphene Nanosheets/Metal Oxide Composites for High-performance Li Ion Batteries.Hui-Ming Cheng, Zhongshuai Wu, Guangmin Zhou Zhou, Ying Shi, Na Li, Lei Wen and Feng Li; Shenyang National Lab for Materials Science, Institute of Metal Research, CAS, Shenyang, China.

Graphene is a new carbon-based material with one or several atomic layers, and it possesses unique properties and expected to have many promising applications. Among these applications, the electrochemical energy storage of graphene and its composites may be most practical. Chemical exfoliation is widely considered to be an efficient method for large scale synthesis of graphene nanosheets (GNSs). In order to take the full advantages of the electrochemical performance of GNSs and high capacity electrode materials, such as metal oxides, we synthesized GNSs with different sizes and layers by controlled chemical exfoliation and develop GNS/various metal oxide composites, and it is found that these GNS/metal oxide composites have high lithium charging/discharging capacity, good cyclic ability, and high rate capability. These results indicate that GNS/metal oxide composites are very promising for applications in high-performance lithium ion batteries.



4:00 PM KK4.9
Performance of Thiophene-based Electrolyte Additive in Lithium Ion Batteries.Ali Abouimrane1, Susan A. Odom2, Huiming Wu1, Wei Weng1, Zhengcheng Zhang1, Jeffrey S. Moore2 and Khalil Amine1; 1Electrochemical Technology Department, Argonne National Laboratory, Argonne, Illinois; 2The Beckman Institute and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois.

Lithium batteries currently dominate the battery market in the area of cellular phones, cam-recorders, computers, and other electronic equipments. However, attempts to apply these battery technologies to electric and hybrid vehicles have met with limited success. Problematic areas include safety, calendar life and cost and many efforts were concentrated in the development of new electrode materials that are able to face these challenges. However, less attention has been paid to the electrolyte which has a major impact on the thermal stability of galvanic cells and accounts for poor cycle life to a certain extent. In this work, we focused on the use of monomer electrolyte additive that can be polymerized during the battery cycling. Because the polymer formed in this case is conductive, it does not impact the electron transport and significant improvements are observed in cell cycling performance both at room and high temperature. In addition, the cell efficiency increases significantly during cycling. The contribution of a new electrolyte additive based 3-hexyl thiophene on the battery performance will be discussed and a mechanism of the battery cycling improvement will be proposed with the aid of various characterizations technique (cyclic voltammetry, impedance spectroscopy and DSC). We found that this electrolyte additive enhances the capacity retention of the half cell batteries using the high capacity cathode material (LiNi0.15Co0.1Mn0.55O2) and the 5V (LiNi1.5Mn0.5O4) material at room and high temperature by protecting the cathode surface from electrolyte reactivity. The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.


4:15 PM KK4.10
Transferred to KK4.3

4:30 PM KK4.11
Transferred to KK4.8

 

SESSION KK5: Lithium Battery Anode Materials
Chairs: Dominique Guyomard and Yang Shao-Horn
Wednesday Morning, December 1, 2010
Constitution A (Sheraton)


8:00 AM *KK5.1
Titanium Based Anode System for Long Life and Safe Lithium Battery for PHEV Applications.Khalil Amine, Huiming Wu, Ilias Belharouak, Damien Dambournet and Ali Abouimrane; Argonne National Laboratory, Argonne, Illinois.

Lithium-ion batteries are being considered to power a new generation of clean vehicles. Battery life span, cost, and safety are still major barriers. The instability of the solid-electrolyte interface (SEI) at the graphitic electrode significantly impacts both cycle life and the safety of lithium ion batteries. These key barriers can be overcome through the development of alternative anodes that can operate within the electrochemical stability zone of conventional electrolytes. This region is generally known to be above the potential (~1 V) of SEI formation and below the potential (~4.3 V) of electrolyte oxidation. The voltage profiles of tetravalent titanium-based materials such as Li4Ti5O14 fall within this region and has shown to provide thousand of cycles when combined with LiMn2O4 spinel cathode. The long cycle of this system can meet easily the 5000 cycles required for Plug in Hybrid electric vehicle. However, the voltage profile of the system is very low (2.5V) and therefore offers very low energy density that limit the electric drive range. In this study, we report combining a nano-LTO having micron-size (~0.5-2 μm) secondary particles composed of nanometer-size (<10 nm) primary particles with ZrO2 coated LiNi0.5Mn1.5O4 as high energy and high power system that offers long cycle life and improve abuse tolerance for plug in hybrid electric vehicle. This system can cycle for more than 4500 cycle with very limited capacity loss and show excellent safety characteristics. The cycle life of this system can be further improved by passivating the high voltage cathode using electrolyte additives. To increase further the energy density of this system, we investigated new titanate with the general chemical formula MLi2Ti6O14 with M = 2Na, Ba, Sr, since their average voltage is lower than the one displayed by LTO. The paper will also present a comparative study between Na2Li2Ti6O14, SrLi2Ti6O14, and BaLi2Ti6O14 compounds. The focus will be on establishing the relationship between their structures and electrochemical properties.


8:30 AM KK5.2
High-capacity and High-rate Metal Oxide Anodes for Li-ion Batteries.Anne C. Dillon1, Chunmei Ban1, Leah A. Riley2, Andrew S. Cavanagh3, Steven M. George3, Yoon Seok Jung1, Zhuangchun Wu1, Dane T. Gillaspie1, Yanfa Yan1 and Se-Hee Lee2; 1Center for Materials and Chemical Sciences, National Renewable Energy Laboratory, Golden, Colorado; 2Department of Mechanical Engineering, University of Colorado, Boulder, Colorado; 3Chemistry and Biochemistry, University of Colorado, Boulder, Colorado.

Significant advances in both energy density and rate capability for Li-ion batteries will be necessary for implementation in next generation electric vehicles. By employing metal oxide nanostructures, it is possible to achieve Li-ion anodes that have significantly higher capacity than the state-of-the-art graphite technology. However, because of the large volume expansion it is difficult to achieve stable cycling, especially at high rate. We have demonstrated that thin film MoO3 nanoparticle electrodes (~2 µm thick) have a stable reversible capacity of ~630 mAh/g[1]. when tested at C/2. By fabricating more conventional electrodes (~35 µm thick) with a conductive additive and binder, an improved reversible capacity of ~1000 mAh/g is achieved but unfortunately, the rate-capability is decreased[2]. In order to achieve high-rate capability for thicker electrodes we applied a thin atomic layer deposition coating of Al2O3 to enable the high volume expansion and prevent mechanical degradation[3]. More recently we have focused our work on iron oxide nanostructures, as iron is an inexpensive, abundant and non-toxic material. Furthermore, we have synthesized binder-free, high-rate capability electrodes. The electrodes contain Fe3O4 nanorods as the active lithium storage material and carbon single-wall nanotubes (SWNTs) as the conductive additive. The highest reversible capacity is obtained using 5 wt.% SWNTs, reaching ~1000 mAh/g (~2000 mAh/cm3) at C rate when coupled with a lithium metal electrode, and this high capacity is sustained over 100 cycles. Furthermore, the electrodes exhibit high-rate capability and stable capacities of 800 mAh/g at 5C and 600 mAh/g at 10C. Scanning electron microscopy (SEM) indicates that this high-rate capability is achieved because Fe3O4 nanorods are uniformly suspended in a conductive matrix of SWNTs. Raman spectroscopy is employed to understand how the SWNTs function as a highly flexible conductive additive, and new mechanistic understanding will be presented. We expect that this method can be used to achieve other binder-free anodes as well as cathodes with similar high-rate capability[4]. [1] Lee, S.-H.; Kim, Y.-H.; Deshpande, R.; Parilla, P. A.; Whitney, E.; Gillaspie, D. T.; Jones, K. M.; Mahan, A. H.; Zhang, S. B.; Dillon, A. C. Advanced Materials 2008, 20, 3627-3632. [2] Riley, L. A.; Lee, S.-H.; Gedvilias, L.; Dillon, A. C. Journal of Power Sources 2010, 195, 588-592. [3] Riley, L. A.; Cavanagh, A. S.; George, S. M.; Jung, Y.-S.; Yan, Y.; Lee, S.-H.; Dillon, A. C. ChemPhysChem 2010, available on line. [4] Ban, C.; Wu, Z.; Gillaspie, D. T.; Chen, L.; Yan, Y.; Blackburn, J. L.; Dillon, A. C. Advanced Energy Materials 2010, available on line.


8:45 AM KK5.3
Electrochemical Reaction of Li(LixTiO1-x)2O4 with Lithium in a Wide Voltage Range: Synchrotron X-ray and Electron Microscopy Studies.Feng Wang, Jian Hong, Chao Ma, Lijun Wu, Dong Su, Yimei Zhu and Jason Graetz; Brookhaven National Laboratory, Upton, New York.

There is much interest in “zero-strain” materials, such as Li(LixTi1-x)2O4 (x=0.33; LTO) for their immediate application as high cycle life electrodes in Li-ion batteries. Higher capacity may also be achieved by a deep discharge, where more than one lithium is cycled. We studied the structural evolution and the change of the electronic structure accompanying the charge/discharge of LTO electrode materials in a wide voltage range (50 mV - 4.5 V)using in-situ synchrotron X-ray scattering (XRD), combined with ex-situ x-ray photoelectron spectroscopy (XPS), x-ray absorption spectroscopy (XAS), and electron absorption spectroscopy (EELS). Two different phase transitions were observed in the high-angle scattering results; the first was a small volume contraction in the shallow lithiation (above 0.6 V) due to the Li(LixTi1-x)2O4 => Li2(LixTi1-x)2O4 transition, and the second was a bigger expansion in the deep lithiation (down to 50 mV) due to the Li2 (LixTi1-x)2O4 => Li3(LixTi1-x)2O4 transition. The lithium insertion sites and amount of charge compensation were determined from the core-shell absorption and emission spectra of Li, O and Ti, in a combination with ab-initio calculations. In addition, spatially-resolved EELS was used to measure the size effect and the non-uniform lithiation at the nanometer scale over a single nanoparticle. According to our studies, the slow decay of the LTO capacity when cycling over a wide voltage range is due to the large volume expansion, and the formation of the solid-electrolyte interphase (SEI); the latter being measured by XPS and transmission electron microscopy (TEM). This work was supported by the U.S. DOE under contract DE-AC02-98CH10886 with funding from Laboratory Directed Research and Development at Brookhaven. JG and FW were also partially supported by the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Basic Energy Sciences under Award Number DE-SC0001294.


9:00 AM KK5.4
High-surface-area TiO2 Brookite: From The Synthesis To Structural Changes Upon Lithiation.Damien Dambournet1, Ilias Belharouak1, Karena W Chapman2, Peter J Chupas2 and Khalil Amine1; 1Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois; 2X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois.

Lithium-ion batteries are now facing the challenge of meeting the energy and power requirements for plug-in hybrid vehicles and electric vehicles. Concerning negative electrode, titanium oxide is an interesting alternative anode to graphite due to its operating voltage (~1.5V) that lies within the electrolyte stability zone. This may enable extended cycle life as well as enhanced safety. Although extensive works have been carried out on the TiO2 anatase and rutile forms, only few articles are related to the use of brookite as anode in lithium ion batteries. This is due to the difficulty to prepare such a phase. This work will present a new and simple method to prepare the metastable TiO2 Brookite consisting of an aqueous precipitation of a titanium oxalate phase followed by its thermal decomposition to form TiO2 brookite. The prepared TiO2 brookite exhibits unusual morphology consisting of nano-domains of TiO2 embedded in large micron-size mesoporous particles. In a first part, the talk will describe the mechanism by which the titanium oxalate precursor was prepared. Thereafter, the lithium insertion mechanism that occurs during the first discharge will be discussed in the light of Pair Distribution Function (PDF) analysis results. The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on be half of the Government.


9:15 AM KK5.5
CuO Based Anode Materials for High-rate Lithium Ion Batteries.Ryan M. Lawrence1, Joe Gnanaraj2 and Jianyu Liang1; 1Department of Mechanical Engineering, Worcester Polytechnic Institute, Worcester, Massachusetts; 2Yardney Technical Products, Inc., Pawcatuck, Connecticut.

Nanostructured transition metal oxide materials are often cited for their excellent cyclability and high-rate capabilities as electrodes in lithium ion batteries. In this report, we synthesize CuO thin films on a copper substrate by means of a simple solution immersion and heat treatment. The morphology of such films is plate-like, making for greatly increased electrode surface area. CuO films are characterized by scanning electron microscope (SEM) and x-ray diffraction (XRD). The effect of solution time on the morphology and electrochemical performance is discussed. In electrochemical tests, half-cells made from CuO thin film anodes display excellent high-rate performance and reversible capacity. The low cost, ease of synthesis, and electrochemical performance make CuO thin films an attractive anode material for lithium ion battery systems.


10:00 AM KK5.6
Template-free Synthesis of Fe3O4 Nanoparticles and Their Performance as Anode Materials in Lithium-ion Batteries.Zichao Yang, Jingguo Shen, Surya S. Moganty and Lynden A. Archer; Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York.

The growing demand for small, light-weight, and inexpensive power sources for portable electronics and automotive uses is driving interest in lithium-ion battery (LIB) technologies that exceed performance of today’s batteries. Metal oxides are attractive as anode materials for LIBs due to their high lithium intercalation capacity and generally high natural abundances. Magnetite, Fe3O4, is a particularly promising candidate because of its high theoretical capacity of 924 mAh/g (cf. 372 mAh/g for currently used graphite), low cost, and low environmental footprint. A major challenge that limits development of superior anode materials based on this material is the pulverization problem, namely, the breakdown of electrical contact between particles of the active material produced by the large, cyclic volume changes which accompany repeated lithium insertion/extraction. Herein, we report results from a systematic study of hollow Fe3O4 nanoparticles synthesized via a template-free solvothermal method. Temporal XRD and TEM characterization indicate that the growth follows an inside-out Ostwald ripening mechanism, that spontaneously produces hollow nanostructures irrespective of the particle chemistry. Electrochemical cyclic voltammetry studies show that both hollow and filled Fe3O4 nanostructures reversibly intercalate lithium at ~0.9 and 1.2 V vs. Li/Li+. When integrated in the LIB anode, we find a systematic improvement in performance as the internal void space is increased. We also study the effects of creating a carbon-Fe3O4 nanocomposite by compositing Fe3O4 with polyacrylonitrile (PAN) followed by calcination to convert PAN to carbon. This procedure was found to consistently improve the electrochemical performance of the particles. The origin of this improvement is investigated using post-mortem TEM and nanoindentation studies, as well as in-situ characterization of the lithium ion diffusion by impedance spectroscopy.


10:15 AM KK5.7
In-situ Raman Spectroscopy Studies of SnO2/CNTs Composite Thin Film Li-Ion Batteries Anodes.Abirami Dhanabalan1, Wei Chen1, Xifei Li1, Yan Yu2 and Chunlei Wang1; 1Department of Mechanical and Materials Engineering, Florida International University, Miami, Florida; 2Max-Planck Institute for Solid State Research, Heisenbergstrasse 1, Stuttgart 70569, Germany.

SnO2 as a anode material for Li-ion batteries has been extensively investigated since 1997 owing to its high theoretical specific capacities during the reactions with Li.[1] However, the practical use of these materials is hampered because it suffer from severe volume change (~ 300%) during Li insertion and extraction that often cause electrode disintegration and rapid capacity fading.[2] The repeated huge expansion/contraction causes great stress in Sn lattice, which results in the cracking, crumbling and pulverization of Sn particles and the consequent loss of electrical contact between anode and current collector.[1, 2] Also, the nano Sn particles formed during cycling aggregate causing poor capacity retention. CNTs can act as a barrier to prevent the aggregation, and improve the conductivity of SnO2, which is crucial for the charge transfer kinetics and buffer the volume change, resulting in higher battery performance.[3, 4] However, the mechanism of SnO2/CNTs composite is not yet fully understood, which affect the further improvement of the electrochemical performance and structural optimization. Raman spectroscopy is a powerful tool to observe the phase and structural transitions of metal oxide. [5] In this work, we prepare SnO2/CNTs anodes by using electrostatic spray deposition (ESD) technique and in situ Raman is used to observe the phase change of the composites during the alloying and de-alloying process. We hope the studies can increase the understanding of the reaction mechanism of Li insertion/extraction in SnO2 matrix and further improve the performance of the composites. References [1] I.A. Courtney and J.R. Dahn: Key Factors Controlling the Reversibility of the Reaction of Lithium with SnO2 and Sn2BPO2 Glass. J. Electrochem. Soc. 1997, 144, 2943. [2] M. Winter and J. O. Besenhard: Electrochemical lithiation of tin and tin-based intermetallics and composites. Electrochim. Acta 1999, 45, 31. [3] Y. Fu, R. Ma, Y. Shu, Z. Cao and X. Ma: Preparation and characterization of SnO2/carbon nanotube composite for lithium ion battery applications. Mater. Lett. 2009, 63, 1946. [4] A. Dhanabalan, Y.Yu, X. Li, W.Chen, K. Bechtold, L. Gu and C.Wang: Porous SnO2/CNTs Composite Anodes: Influence of Composition and Deposition Temperature on the Electrochemical Performance. J. Mater. Res. 2010 (accepted) [5] C. Gejke, E. Zanghellini, L. Börjesson, L. Fransson and K. Edström: Structural investigation of the Li1 ion insertion/extraction mechanism in Sn-based composite oxide glasses. J. Phys. Chem.Solids. 2001, 62, 1213.


10:30 AM KK5.8
In situ SEM Investigation of SnO2 Electrodes for Li-ion Batteries.Di Chen, Sylvio Indris, Michael Schulz, Oliver Kraft and Reiner Moenig; Karlsruhe Institute of Technology, Karlsruhe, Germany.

Electrode materials critically determine the energy and power density as well as the reliability of Li-ion batteries. In particular conversion electrode materials are of interest due to their very high theoretical capacities. Often, detailed reaction pathways and microscopic mechanisms in such systems are difficult to investigate and therefore cannot fully be clarified. In order to better investigate the microscopic behavior of such electrode materials, we have developed a method for the real-time observation of a working electrode inside a scanning electron microscope (SEM). Using a home-built transfer system to prevent from contact with atmosphere and a piezoelectric manipulator, a battery cell was assembled and operated inside the vacuum of an SEM. Here we present our observations from Li insertion and extraction into/from SnO2. SnO2 is an anode material with a very high theoretical reversible capacity of ~800 mAh/g. In the in situ experiments, SnO2 powder and pure Li were used as electrodes and microscopic details of the electrochemical reaction between Li and SnO2 were observed. During Li insertion, the growth of a surface layer on the electrode particles could be monitored and upon further Li insertion, the growth of extrusions was observed. In the experiments, large volume expansions occurred and cracks inside the SnO2 particles were frequently found. Our results demonstrate that mechanical as well as morphological processes can strongly affect the reversibility of the electrochemical reactions in SnO2 and indicate that such processes may be also important for the performance and degradation of real batteries.


10:45 AM KK5.9
A Structural and Electrochemical Study of Li2Ti6O13.Juan Carlos Perez-Flores, Alois Kuhn and Flaviano Garcia-Alvarado; Department of Chemistry, Universidad San Pablo CEU, Boadilla del Monte, Madrid, Spain.

Several titanium oxides have been investigated in the last years as possible anodes for lithium rechargeable batteries [1, 2] and more recently, once the role of morphology and particle size was unveiled, even the binary oxide TiO2 has been proposed as an improved negative electrode material [3]. In this communication we present a study of Li2Ti6O13 which has been obtained from Na2Ti6O13 using ion exchange reaction with molten lithium salts at low temperature. Full exchange has been achieved as indicated by flame atomic emission spectroscopy and EDS results. Besides, different aspects of Li2Ti6O13 like morphology, structure and electrochemical behaviour have been studied and compared to those of Na2Ti6O13 [4,5] In the case of Na2Ti6O13, the specific capacity of first discharge down to 1 V is ca. 125 mAh/g at C/72 rate which is equivalent to the insertion of 2.4 Li/formula. On the other hand, cells made using Li2Ti6O13 as the positive electrode yields up to 250 mAh/g that corresponds to the insertion of approximately 4.8 Li/formula. This first discharge capacity is fairly kept at different current rates up to C/6. For higher current rates capacity decays rapidly. After the first charge the observed capacity loss is large: 30% and 40 % for the Na and Li titanates respectively indicating that processing of the electrode needs to be optimised. However, Li2Ti6O13 under equilibrium conditions shows a reversible capacity of 210 mAh/g. On the other hand, the difference observed in the shape of the two electrochemical curves suggests that during lithium ion exchange, lithium ions may occupy positions different from those of sodium. A structural study by means of neutron diffraction is now under progress to elucidate some details of both exchange and insertion mechanisms. Having in mind that the reported capacity of other related materials, in particular those based on the redox couple Ti(IV)/Ti(III), are ca. 160 mAh/g, the results obtained for Li2Ti6O13 are also promising and deserve further studies to optimize electrochemical performances.. References [1] M. deDompablo, E. Moran, A. Varez, F. GarciaAlvarado, Materials Research Bulletin 32 (1997) 993-1001. [2] K. M. Colbow, J. R. Dahn, R. R. Haering, Journal of Power Sources 26 (1989) 397-402. [3] A. R. Armstrong, G. Armstrong, J. Canales, P. G. Bruce, Angewandte Chemie International Edition 43 (2004) 2286-2288. [4] R. Dominko, E. Baudrin, P. Umek, D. Arcon, M. Gaberscek, J. Jamnik, Electrochemistry Communications 8 (2006) 673-677. [5] R. Dominko, L. Dupont, M. Gaberscek, J. Jamnik, E. Baudrin, Journal of Power Sources 174 (2007) 1172-1176.


11:00 AM KK5.10
Structural stability of C-Co3O4 upon Extended Li Insertion Deinsertion Reaction.Jayaprakash Navaneedhakrishnan, Surya Sekhar Moganty and Lynden Archer; Cornell University, Ithaca, New York.

Today’s world of modernization and miniaturization lays greater emphasis on more power from smaller and lighter battery packs. Among the competing systems, rechargeable lithium batteries show the highest energy density, due to the high reducing power of lithium that leads to large cell voltage. The limitations in the overall performance of Li-ion batteries depend on the intrinsic performances of the materials (anode, cathode and electrolyte) and the technology aspects (material processing, electrode fabrication and battery conception), taking into consideration of the environment of each material in the complete cell. Tremendous amount of work has been done worldwide in these two directions over the last twenty years. The active anode material of a secondary Li-ion battery is a host material into / from which lithium can be reversibly inserted / extracted over a composition range. Currently, carbonaceous materials are widely used as anodes in Li-ion batteries because of their low cost, even discharge characteristics and low operating voltage. Generally, the commercialized carbonaceous anodes though have found widespread applications, problems like the high irreversible capacity, swelling behavior or failure of the electrode through intercalation of propylene carbonate (PC) based electrolyte and the formation of surface electrolyte interface (SEI) layer, remain as severe unsolved problems till date. Disruption of this SEI layer in conventional Li-ion batteries is a primary source of capacity and power fade. Recent advances in the synthesis of tin (Sn), silicon (Si), nickel (Ni), cobalt (Co), and their corresponding oxides as replacements for carbon-based anodes have resulted in batteries with higher specific capacity and enhanced cycle life. Based on this ground, we have made an attempt to exploit carbon coated Co3O4 as anode for high power lithium battery applications. Herein, hydrothermal method has been used to synthesize monodisperesed spherical Co3O4 particles and subsequent carbon coating using glucose as the carbon source. Experimental: Monodispersed, spherical Co3O4 particles was synthesized by the ammonia assisted hydrothermal method at 180 °C and the carbon coating to the synthesized Co3O4 particles was done using glucose as the carbon source at the same temperature. Electrochemical properties of the pristine and C-Co3O4 materials were evaluated. Results and discussion The C-Co3O4 has delivered a charge capacity (Li deinsertion) of 610 mAh/g at the end of 120 cycles whereas the pristine Co3O4 demonstrated a drastic capacity fade upon extended lithium battery cycling. The cycled cells were subjected to post mortem studies after 120 charge discharge cycles and found that the C-Co3O4 retained the initial spherical shape whereas the pristine Co3O4 underwent severe volume expansion and particle breaking. Various possible reasons for the enhanced electrochemical behavior C-Co3O4 are discussed in detail.


11:15 AM KK5.11
Analysis of the Mechanism of Conversion and the Microstructural Changes upon Cycling of High Capacity NiO Electrodes.Jordi Cabana1, Florian Meirer2, Yijin Liu2, M. Rosa Palacin3, Rosa Robert4,5, Clare P. Grey4,5, Apurva Mehta2, Joy C. Andrews2 and Piero Pianetta2; 1Lawrence Berkeley National Laboratory, Berkeley, California; 2Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California; 3Institut de Ciència de Materials de Barcelona (ICMAB CSIC ), Barcelona, Spain; 4Department of Chemistry, Stony Brook University, Stony Brook, California; 5Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.

Despite the imminent commercial introduction of Li-ion batteries in electric drive vehicles and their proposed use as enablers of renewable energy technologies, an intensive quest for new electrode materials that bring about improvements in energy density, cycle life, cost and safety is still underway. Among the phases proposed to date as an eventual replacement for the negative electrode, transition metal oxides (MxOy, where M=Mn-Cu) emerge as attractive candidates because they can store as much as twice the amount of charge per unit of mass than carbon electrodes. Unlike the latter, which react with lithium through an intercalation mechanism, transition metal oxides react through a conversion reaction that leads to the formation of metallic nanoparticles embedded in a matrix of Li2O. This reaction is highly reversible, mostly thanks to the nanometric character of the metal particles. Nonetheless, several factors currently handicap the applicability of electrode materials entailing conversion reactions. First, the massive particle reorganization induced through these complex reactions can easily lead to pulverization and loss of electrical contact, thereby dramatically shortening the cycle life of the electrode. Second, coulombic inefficiencies between discharge and charge in the first cycles make the design of a device difficult. Lastly, an even more important obstacle to application is the staggering voltage hysteresis observed between discharge and charge, which severely diminishes the round-trip efficiency of the electrode. The origins of these inefficiencies lie on the particularities of the conversion reaction, both at the particle and the electrode level. In order to better understand the barriers toward application of conversion electrodes, NiO was taken as a case example. A combination of Li nuclear magnetic resonance (NMR) and X-ray absorption spectroscopy (XAS) was used to offer insight into the mechanism of conversion, evaluate the existence of intermediate compounds and assess the electronic structure of the different phases involved. In order to gather information on the kinetics of the reaction and how temperature affects the voltage hysteresis, experiments at temperatures from 30 to 150C were performed. Finally, the effects of the strong structural reorganization on the microstructure and the evolution of phase conversion fronts were followed for a 30 um thick electrode composed of NiO, carbon and PVDF, using a novel experimental setup that combines the benefits of 2D and 3D imaging of transmission X-ray microscopy (TXM) with the chemical resolution of XAS, at sub-100 nm resolution. The results of this multifaceted approach will be discussed.


11:30 AM KK5.12
Thin Films of Li-conducting Garnet Phases.Henrik Buschmann, Jochen Reinacher and Juergen Janek; Institute of Physical Chemistry, Justus-Liebig-University, Giessen, Germany.

Li-ion conducting phases with the garnet structure are considered as superior lithium solid electrolytes [1,2]. But despite considerable efforts the available experimental information on this relatively new class of materials is still rather narrow, and it appears not to be straightforward to obtain homogeneous phases with high lithium ion conductivity. In this contribution we report on the reproducible preparation of bulk samples of garnets with nominal compositions Li7La3Zr2O12 and Li6BaLa2Ta2O12, their temperature dependent ionic conductivity (both AC impedance and dc conductivity) and the interface resistance (from AC impedance) of lithium metal electrodes. All materials are characterized by XRD, Li-NMR and TEM. The original results in [1] and [2] are confirmed and extended. By pulsed laser deposition we were successful to deposit thin films of Li-ion conducting garnets on different substrates and to determine their electrical transport properties. Whereas the deposition of the phase Li6BaLa2Ta2O12 leads to homogeneous films with virtually the same conductivity as the bulk material, the Li7La3Zr2O12 phase does yet not result in films of the same quality. The potential of Li-garnet phases as functional materials (electrolytes or protecting films) in different types of lithium-based cells is discussed. [1] R. Murugan, V. Thangadurai, W. Weppner, Angew. Chemie - Inter. Ed. 46 (2007) 7778-7781 [2] R. Murugan, V. Thangadurai, W. Weppner, Ionics 13 (2007) 195-203


 

SESSION KK6: Lithium Battery Silicon and Carbon Anode Materials
Chairs: Linda Nazar and Atsuo Yamada
Wednesday Afternoon, December 1, 2010
Constitution A (Sheraton)


1:30 PM *KK6.1
Silicon/Carbon Nanofiber Composites for Li-ion Battery Anodes; Manufacturing Technology.David J. Burton1, Andrew C. Palmer1, Patrick D. Lake1, Maryam Nazri1, Max L. Lake1, Jane Y. Howe2 and Gholam-Abbas Nazri3; 1Applied Sciences, Inc., Cedarville, Ohio; 2Oak Ridge National Laboratory, Oak Ridge, Tennessee; 3General Motors R&D, Warren, Michigan.

Commercially available lithium ion batteries currently use graphite materials for the anode, owing to advantages of a practical capacity of approximately 250 mAh/g, high cycle efficiency, and low cost. Higher capacity anodes can be manufactured from materials that form alloys with lithium. A leading candidate material is silicon, which has a theoretical capacity of 4,200 mAh/g. A large body of research extending for over 20 years has sought to capture the benefits of silicon in improved charge capacity for Li-ion technology, but until recently has failed to yield a practical anode material, as a result of the volume expansion of up to 300% which silicon undergoes when lithiated. The volume expansion generates sufficiently high values of stress at the interface between the silicon and the electronic structure to which it is attached that the interface ultimately fails upon charge/discharge cycling, resulting in loss of electrical conductivity. Repetitive cycling of a silicon-based anode typically may show an excellent initial charge capacity, followed by capacity fade as more of the silicon fractures out of the electrical network. Nano-silicon/carbon nanofiber composites have shown promise for anodes having the high energy capacity of Si combined with the long cycle life of carbon; however, such materials still suffer from fade in energy capacity with cycling. A promising advance is a production process for incorporating amorphous, nanometer-thick silicon with a highly conductive graphitic nanofiber, leading to a stable anode capable of 1000 mAh/g over extended cycling. The manufacturing technology is well-suited to high volume production of low-cost Si/CNF for Li-ion battery anodes.


2:00 PM KK6.2
Silicon/Carbon Nanofiber Composites for Li-ion Battery Anodes: Optimization of Electrochemical Performances.Maryam Nazri2, Gholam-Abbas Nazri1, David Burton2 and Max Lake2; 1Electrochemical Energy Research Lab, GM Global R&D Center, Warren, Michigan; 2Applied Sciences Inc, Ceadarville, Ohio.

Silicon based anode is the frontier alternative anode in term of capacity to replace the current carbonaceous anode. In this study, we report the electrochemical lithiation-delithiation of a Si-carbon nanofiber composite anode. The optimization of the electrochemical performance in term of capacity retention during multiple charge-discharge cycling will be discussed. The improvement of the capacity retention by the effect of compositional gradient at the Si-carbon interface during cycling will be discussed. A significant reduction in first cycle irreversibility is achieved by optimization of Si-electrolyte interface. Specific capacity and rate capability of the Si-carbon composite anode in half cell and full cell will be reported. The structural and compositional modification of the Si during cycling and nature of the Si-electrolyte have been investigated by Raman spectroscopy. Detailed microanalysis will be discussed.


2:15 PM KK6.3
Silicon/Carbon Nanofiber Composites for Li-ion Battery Anodes: Microstructural Characterization.Jane Y. Howe1, Harry Meyer1, David Burton2, Maryam Nazri2, G. Abbas Nazri3, Anrew Palmer2 and Patrick Lake2; 1Oak Ridge National Laboratory, Oak Ridge, Tennessee; 2Applied Sciences Inc., Cedarville, Ohio; 3General Motors R&D, Warren, Michigan.

Silicon is an attractive anode material for Li-ion batteries mainly because it has the highest known theoretical charge capacity at 4,200 mAh/g. To take advantage of both silicon’s high capacity and carbon’s high conductivity, efforts have been made to use silicon/carbon composite particles for use as anode material. A structurally more superior design is to develop silicon-coated hollow carbon nanofibers (CNF) as the anode material for Li-ion batteries. A stable, high-performance Li-ion battery anode has been developed by depositing silicon-based materials onto low-cost CNF. The performance of the anodic application of this Si/CNF composite is dictated by its microstructure, from the atomic-level and up. Using electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, we found that the Si/CNF composites have amorphous silicon coatings on both internal and external surfaces of the hollow CNFs (the as-produced CNF nanofibers are hollow with an outer diameter of 80-180 nm and an inner diameter of 20-65 nm). Depending on deposition conditions, silicon may form a complete coverage about 12 nm thick, or it may form sub-20nm nodules that partially cover the surfaces. The Si/CNF composite described in this paper has many unique features that lead to the high cycling performance. First, having silicon coatings on both inner and outer surface of a hollow carbon nanofiber maximizes the efficiency of the Si/CNF composite during cycling. Nano-size channels provide fast mass transport of Li ions whereas the graphite core offers high electric conductivity. The Si/CNF structure contributes to weight reduction. Such structure may also be effective in slowing down the growth of the SEI layer. The manufacturing process provides a controllable size and distribution of silicon. Finally, the integrity of the anodic material is preserved largely due to the mechanical strength of the CNF.


2:30 PM KK6.4
Elastic Softening and Failure Mechanisms of Amorphous and Crystalline Li-Si Phases with Increasing Li Concentration: A First-principles Study.Vivek Shenoy, Brown University, Providence, Rhode Island.

Knowledge of the elastic properties of Li-Si alloys as a function of Li concentration is crucial in the development of reliable deformation and fracture mechanics models for Si anodes in Li-ion batteries. We have studied these properties [1] using first principles calculations for both amorphous and crystalline phases observed during lithiation of Si anodes. In the case of crystalline alloys, we present the anisotropic elastic tensors as well as the homogenized Young’s, shear, and bulk moduli and the Poisson’s ratios. We find that while these moduli decrease in an approximately linear manner with increasing Li concentration leading to significant elastic softening (by about one order of magnitude) in both crystalline and amorphous systems, the Poisson's ratios remain in the range of 0.05-0.20 and 0.20-0.30 in the case of crystalline and amorphous systems, respectively. Further, for a given Li concentration, we find that the amorphous structures are elastically somewhat softer than their crystalline counterparts, the difference being more significant (about 30-40 %) in Li-poor phases. Our results underscore the importance of including the concentration dependence of elastic constants in the analysis of stress and deformation fields during lithiation and de-lithiation of Si anodes. [1] V. B. Shenoy, P. Johari and Y. Qi Elastic Softening of Amorphous and Crystalline Li-Si Phases with Increasing Li Concentration: A first-principles study JOURNAL OF POWER SOURCES 195: 6825-6830 OCT 2010


2:45 PM KK6.5
Aerosol Technology and Si Nano-composite Electrode Assembly for Li-ion Batteries.David Munao, Jan v. Erven, Mario Valvo, Esteban Garcia Tamayo and Erik Kelder; ChemE, TUDelft, Delft, Zuid Holland, Netherlands.

Li-ion batteries are among the most useful devices for electrochemical energy storage, because of their high energy density (more than 150 Wh kg-1) and very high efficiency (up to 95% overall). Increasing further the energy density would lead to new types of applications for these batteries, such as sustainable mobility based on electric/hybrid vehicles. Silicon-based negative electrodes are considered the best alternative to the commercially used graphite or carbon anodes (i.e. 372 mAhg-1) due to the fact that their theoretical capacity (i.e. 4200 mAhg-1) is roughly ten times higher. However, severe capacity fading still represents a limiting factor for the commercialization of Si-based anodes. The capacity fading is caused by the volume change of the host Si structure upon alloying/de-alloying with lithium. This results in fractures and loss of electrical wiring between the various parts of an electrode. In this work three approaches to increase the mechanical stability of the films are considered: reducing the size of the host particles, nano-structuring the electrode film and using different binders to form a nano-composite structure. In this way practical shortcomings of silicon are considerably reduced. Silicon nano-particles are produced via Laser assisted Chemical Vapor Pyrolysis (LaCVP). In LaCVP process gases are heated by absorbing the energy of a laser beam. In this work a d-mode CO2 laser, with a wavelength of 10.6 micron, is used in combination with SiH4 as gaseous reactant in a N2 atmosphere. SiH4 is thermally decomposed within the reaction zone into Si and H2. Nozzle design has been carefully studied in relation to the laser cross section area. A uniform energy distribution inside the reaction zone, achieved by focusing the laser beam with a cylindrical lens on top of a rectangular nozzle, leads to particles, which are monodispersed in size and composition. Thin films composite electrodes are fabricated using Electro Hydrodynamic Atomization, also called ElectroSpray (ES). Particles produced via LaCVP are suspended into a polymer solution in order to form so-called precursor ink. The ink is loaded into a glass syringe and electrosprayed onto a stainless steel heated substrate. The temperature of the substrate is set according to the boiling point of the solvent used to prepare the ink. A good control over the morphology is achieved by setting a stable cone-jet mode in the ES, which leads to a thin layer that is highly porous and homogenous in thickness over the entire sprayed surface. Novel electrodes show superior electrochemical performances, in terms of specific capacity, when compared to the commercial ones based on graphite. Moreover, the overall mechanical stability of the electrode structure has been substantially improved and the capacity fading issue has been drastically minimized.


3:30 PM KK6.6
Stress Evolution in Model C-Si Composite Electrodes for Li Ion Batteries.Amartya Mukhopadhyay1, Anton Tokranov1, Xingcheng Xiao2, Will Ellis1, Kevin Sena1, Fei Guo1, Robert Hurt1 and Brian Sheldon1; 1Engineering, Brown University, Providence, Rhode Island; 2General Motors R and D center, Warren, Michigan.

A major factor limiting the cycle life and capacity retention of Li-ion batteries is mechanical failure via cracking/disintegration of the active electrode materials due to stresses that are generated during Li-ion intercalation and de-intercalation. The concomitant loss in electronic contact with the current collectors is a challenging problem to study in electrodes with complex porous microstructures, where it is difficult to study interrelated chemical and stress induced changes in a controlled fashion. Thus to investigate the fundamental mechanisms, our work focuses on model thin film systems, where it is much easier to analyze the interrelated changes in voltage, composition, and stress that occur as Li is added and removed from these materials. The work presented here is primarily based on simple carbon - silicon bilayers (on top of a metal current collector). A primary focus of this study is to identify ways in which differences in the carbon structure affect the lithiation/delithiation response of the two phase structure, based on the in situ stress response, cyclic voltammetry, and characterization of changes in the material structure after one or more cycles. An electrochemical cell with a multibeam optical stress sensor (MOSS) was used for the in situ quantitative determination of the stress developed during charging and discharging cycles. Several different types of carbon films were used for the current study. Materials deposited by chemical vapor deposition, with semi-ordered graphene layers that are loosely parallel to the substrate, showed typical graphitic features in cyclic voltammetry. Another class of carbon films was produced with chromonic liquid crystal precursors that made it possible to create graphene layers with different orientations. Several experiments were also conducted with HOPG substrates. Using physical vapor deposition methods, amorphous Si layers were formed on top of these carbon materials. Subsequent heat treatments of these bilayers made it possible to vary the interfacial bonding between C and Si (i.e., with some SiC formation at the interface at sufficiently high temperatures). It is believed that the present investigation will lead to better understanding of the stress induced mechanical disintegration/failure of the anode materials, and explore the possibilities of developing novel high performance anode materials based on composite structures of C-Si.


3:45 PM KK6.7
Nanoscale Si-based Anode Materials for Li-ion Batteries: An In-situ X-ray Diffraction Study.Sumohan Misra1, Seung Sae Hong2, Yi Cui3 and Michael F. Toney1; 1Stanford Synchrotron Radiation Lightsource (SSRL), SLAC National Accelerator Laboratory, Menlo Park, California; 2Department of Applied Physics, Stanford University, Stanford, California; 3Department of Materials Science and Engineering, Stanford University, Stanford, California.

Silicon is a promising candidate for an anode material in Li-ion batteries. Its theoretical capacity, 4200 mAh/g, is the largest among available materials for Li-ion batteries and is more than ten times that of existing commercial battery anode - graphite (372 mAhr/g). In addition, Si has a low discharge potential and is non-toxic. However, the large capacity of Si is accompanied by large volume expansion (ca. 400%) due to Li-ion insertion into Si. This large volume change results in loss of mechanical/electrical contact after a few cycles. In order to solve this problem, we have developed Si nanowire (SiNW) assemblies as a Li-ion anode material [1]. Due to their nanoscale diameter, SiNWs maintain good electrical contact along the length of the NWs. This allows facile volume expansion while preventing cracking of the material. To better understand these anode materials, we have studied the structural changes that the nanoscale Si-based anodes undergo during Li intercalation/deintercalation by means of in-situ synchrotron X-ray diffraction. To study these processes, we developed a sealed ″coffee-bag″ type cell with X-ray transparent Kapton windows which allowed us to monitor the phase changes in-situ during electrochemical cycling. We have probed both Si-nanoparticles and SiNWs as anodes subjected to galvanostatic charge, discharge and relaxation (current, I = 0) cycles to understand the growth of the Li-Si phases. As the Si-cells are cycled the intensity for the Si (111) and (220) diffraction diminishes and new diffraction peaks appear. These additional peaks cannot be indexed to any materials in the cell and were not observed for anode-less cells. Hence these peaks correspond to Li-Si phases (possibly metastable) that form during electrochemical cycling. We will discuss the origin of these new peaks and their behavior during charge, discharge and relaxation cycles. [1] Chan, C. K., et al., Nat. Nanotechnol.2008, 3, 31.


4:00 PM KK6.8
On the Understanding of the Failure Mechanism of Si Based Negative Electrode.Yassine Oumellal, Nicolas Dupre, Joel Gaubicher, Philippe Moreau, Bernard Lestriez and Dominique Guyomard; IMN, Nantes, France.

Silicon based materials are much more attractive anode materials for lithium-ion batteries than graphite due to a very high gravimetric energy density (3572 mAh/g vs. 372 mAh/g for carbon) and volumetric capacity (8322 mAh/cm3). However, understanding the large capacity fade observed during cycling of a powder silicon electrode is a complex issue and no effective method exists. Two distinct causes likely may explain this fading: (i) disintegration of the composite electrode architecture and further loss of electrical contacts either with the current collector or between the Si phase and the conductive matrix; (ii) continuous liquid electrolyte degradation at the surface of the Si phase. Here, we tried to understand the origin of the capacity loss using ex-situ 7Li NMR on charged and discharged batteries, electrical impedance spectroscopy measurement (EIS) and fine electrochemical analysis. The electrode formulation and battery testing conditions are similar to those reported by Mazouzi et al [Electrochem. Solid-State Lett, 12 A215 (2009)]. The post-mortem 7Li MAS NMR analysis of the charged batteries showed only diamagnetic lithium assigned to lithium trapped at the surface of the Si particles as a degradation product of the liquid electrolyte, confirming that the major part of lithium lost during the charge of batteries is not trapped in LixSi alloys. EIS and three electrodes based electrochemical analysis show that impedance increase accounts for the capacity fading. This impedance alteration only occurs on discharge and is strongly limited when electrolyte additives are used. We thus demonstrate that the main cause of capacity fade of Si-based anodes is the liquid electrolyte degradation which results in the formation of an insulating layer on the active mass, which further inhibits lithium insertion.


4:15 PM KK6.9
Al-Si-graphite Composite Material for Anode in Li-ion Batteries.Wenchao Zhou1, Shailesh Upreti2 and M. Stanley Whittingham1,2; 1Materials Science and Engineering, SUNY-Binghamton, Binghamton, New York; 2Institute for Materials Research, SUNY-Binghamton, Binghamton, New York.

In the past decades there has been extensive research on metal-based (Si, Sn, Al, etc.) materials for anode in Li-ion batteries. The huge volume change during lithium insertion/removal is a big problem that deteriorates the cycling performance. Compared with Si and Sn, Al exhibits much smaller volume expansion when fully lithiated. We have previously investigated the electrochemistry of pure aluminum powder and Al-Graphite composite materials as anode in lithium batteries. Al-Graphite composite shows improved capacity retention upon pure Al powder but it’s still far from satisfactory. Recently we’ve found that a small amount of Si greatly improves the cycling performance of the Al-based composite. The Al-Si-Graphite (ASG) composite synthesized by simple ball-milling delivers high capacity of more than 600 mAh/g and there is little capacity loss in the first 10 cycles. Also, the voltage delay during lithium insertion is reduced. It is found that the Si component in the composite not only contributes to the total capacity but also enhances the particle-electrolyte interface thus improving the cycling performance. Ex-situ X-ray diffraction shows that Si becomes amorphous in the first cycle. LiAl is detected when the electrode is lithiated and it cycles back to crystalline Al when delithiated. Future work on the structure change of the electrode material may reveal some hints for the capacity decay in long cycles. This work is supported by the US Department of Energy, Office of FreedomCAR and Fuel Partnership through the BATT program at Lawrence Berkeley National Laboratory.


4:30 PM KK6.10
Gas Phase Synthesis of High-purity Silcon Nanoparticles on Pilot Plant Scale.Tim P. Huelser1, Mathias Spree1, Hartmut Wiggers1,2,3 and Christof Schulz1,2,3; 1Nano Energy & Nano Particle Synthesis, Institute of Energy & Environmental Technology, Duisburg, NRW, Germany; 2Institute for Combustion and Gasdynamics, University of Duisburg-Essen, Duisburg, NRW, Germany; 3CeNIDE, Center for NanoIntegration Duisburg-Essen, Duisburg, NRW, Germany.

Si nanoparticles are a promising candidate for anode material in lithium-ion batteries because silicon can alloy with lithium and delivers a markedly higher theoretical capacity compared to graphite, which is actually the most widely used anode material. Typically, this application requires highly-specific silicon particles with a high- purity and a narrow size distribution as they can be obtained from gas-phase synthesis processes. Therefore, this synthesis route is favored for the production of pure and doped nanoparticles and nanocomposites. Highly specific nanomaterials are often available in minute quantities only, that are not suited for the investigation of subsequent processing steps. Therefore, many nanomaterials have not yet found their way into practical applications. In this work we report on the gas-phase synthesis of highly specific silicon nanoparticles in a hot-wall reactor under defined conditions on the pilot-plant scale. The silicon nanoparticles are synthesized in the reactor by thermal dissociation of the gas-phase precursor silane (SiH4) using convective heating to a temperature of 1000°C. The process pressure can be varied from 15 to 100 kPa. The particles are collected on a filter membrane and subsequently detached from the membrane by a back pressure impulse. Finally, the nano-sized material is packed under inert gas in sealed bags. Depending on the precursor concentration, production rates up to 1 kg/h can be applied. The resulting nanoparticulate powder is characterized using (HR)-TEM, BET, SEM and XRD. TEM analysis reveal agglomerated particles with distinct sinter necks as expected for hot-wall synthesis with the respective residence time at high temperature. To investigate the influence of the process pressure on the particle size, the pressure is kept stable for the duration of synthesis and the resulting powder material is extracted. Experiments have been performed in the pressure range from 15 kPa to 100 kPa. BET investigations on the material reveal a decreasing particle size with decreasing process pressure and show that the particle size can be adjusted in the range from 55 to 120 nm by varying the process pressure. From SEM investigations a standard deviation of σ = 1.26 was calculated for the particles within the agglomerates. XRD investigations of the Si nano powder prove a crystallite structure like the respective bulk material. Crystal sizes of 12 nm in the case of particles with a mean diameter of 55 nm are detected. HR-TEM investigations confirm the crystalline structure throughout the particles, an oxygen content of ~5 at.%, but do not indicate the presence of a SiO2 shell. The synthesized particles exhibit a very homogenous crystallite structure and a pure surface, furthermore, the size and the morphology of the particles can be adjusted. Therefore these materials might enable for next steps in the field of lithium ion battery technology that require larger amounts of customized particles.


4:45 PM KK6.11
In-situ Stress Diagnosis and Size Effects during the Lithiation of Patterned Amorphous Si Thin Films.Sumit K. Soni1,2, Brian W. Sheldon1, Xingcheng Xiao2 and Anton Tokranov1; 1Division of Engineering, Brown University, Providence, Rhode Island; 2General Motors Global Research & Development Center, Warren, Michigan.

Incorporating Si in negative electrodes could significantly improve the capacity of the carbon-based electrodes that are widely used in Li-ion batteries. Although Si has a large specific capacity, it generally suffers from poor cycling stability because of mechanical degradation. The large volume expansion that occurs during lithiation is a key problem here. To investigate strategies for developing architectures that can better tolerate this expansion, we designed an electrochemical cell that enables us to investigate the stress evolution with different states of charge during lithium insertion and removal. These in situ stress measurements show that during lithiation cycles simple Si films expand and develop compressive stresses which on further lithium insertion forces Si to flow. During delithiation, these films then contract and eventually exhibit tensile stress. To mitigate mechanical degradation due to these stresses, we investigated the effects of varying key length scales. In additional to altering the film thickness, we also studied arrays of patterned Si islands that were fabricated using through mask magnetron sputtering. This patterning allowed us to systematically study additional length scale effects by varying both the size and spacing between these islands. These specimens were then subjected to lithiation at different charging rates (C rates), while employing the in situ multi beam optical stress sensor. After exposing these films to several cycles, the materials were also characterized with electron microscopy, atomic force microscopy, and nanoindentation. These experiments have led to an improved understanding of the size scale dependence of material flow during lithiation cycling.


 

SESSION KK7: Lithium Battery Carbon and Alloy Anode Materials
Chairs: Jane Howe and Gholam-Abbas Nazri
Thursday Morning, December 2, 2010
Constitution A (Sheraton)


8:00 AM KK7.1
Preparation of Spherical Carbon Particles and their Characterization as Lithium Battery Anodes.Vilas G. Pol and Michael M. Thackeray; Electrochemical Energy Storage Department, Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois.

Spherical carbon particles have been prepared by the decomposition of polyethylene (plastic waste) using an autogenic process at 700°C and 68 atmospheres pressure, and evaluated as a possible anode material for lithium-ion cells. Raman spectra indicated that the as-prepared spheres were characteristic of a hard carbon, being composed of turbostratically disordered carbon as well as more ordered graphitic sheets. The SEM images of cycled electrodes indicated that the spheres were unstable to electrochemical cycling and disintegrated during this process. Nevertheless, these electrodes provided a steady reversible capacity of approximately 240 mAh/g for hundreds of cycles, when charged and discharged at a C/1 rate between 1.5 and 0.005 V. To increase the graphitic order in the carbon spheres, the particles were heated to 2400°C in an inert atmosphere. Raman spectra confirmed the success of this experiment. Of particular significance was that the spheres remained intact not only to thermal treatment at 2400°C but also to electrochemical cycling, the latter image showing the presence of what is believed to be residual binder material (PVDF) or carbon black current collector on the surface of the spheres. The retention of both turbostratically disordered- and ordered graphitic components during electrochemical cycling was apparent in the Raman spectra of the uncycled and cycled products. Heating the spheres reduced the first cycle irreversible capacity loss of Li/C half cells containing as-prepared carbon electrodes (700°C treatment) from 60 to 20%; in this case, the spherically-stable carbon electrode yielded a steady 252 mAh/g on cycling. Physical properties of the carbon spheres, such as particle size distribution, surface area, tap density and true density will be provided. Funding for this work by the U. S. Department of Energy, Office of Basic Energy Sciences, Energy Frontier Research Center - Tailored Interfaces is gratefully acknowledged. Superior Graphite is thanked for performing the high-temperature treatment of the carbon spheres.


8:15 AM KK7.2
In-situ Observation of Strains during Lithiation of a Graphite Electrode.Yue Qi1 and Stephen J. Harris2; 1Chemical Sciences and Materials Systems Lab, General Motors Corp., Warren, Michigan; 2Electrochemical Energy Research Lab, General Motors R&D, Warren, Michigan.

The mechanics and microstructure of electrodes are critical in determining the performance and durability of lithium-ion batteries, especially the new large format cells and packs developed for transportation applications. During battery operation, Li diffuses into and out of electrode particles, causing microstructural changes and deformation-induced degradation. A variety of models have been proposed to interpret these mechanical and microstructural changes, but they have no direct experimental support. We report the first direct in-situ measurements of microstructural strain in a composite electrode during lithium insertion, using a side-by-side cell geometry. The color variation of graphite with Li concentration creates lithium spatial maps. Digital image correlation analysis provides corresponding deformation and strain fields, displaying both dilation and contraction. Through a combination of experimental measurement and theoretical analysis, the unexpected contraction during lithiation is explained by the stiffening of graphite upon lithiation. The result confirms the change in modulus that we predicted based on first principle calculations. Quantification of local strains shows that increased graphite crystallite volume during lithiation is accommodated primarily by a decrease in the composite (or particle) porosity. The change in porosity can substantially impact battery power; however, this effect has generally been ignored in cell performance models for lithium-ion batteries.


8:30 AM KK7.3
In situ Measurements of Stress Evolution and Stress-Potential Coupling in Silicon Thin Films during Electrochemical Cycling.Pradeep R. Guduru1, Vijay A. Sethuraman1, Michael Chon1, Allan Bower1 and Venkat Srinivasan2; 1Brown University, Providence, Rhode Island; 2Lawrence Berkeley National Laboratory, Berkeley, California.

Silicon anodes are considered to be one of the promising choices for next generation high-energy-density lithium-ion batteries due their high charge capacity. Since silicon undergoes large volume expansion upon lithiation, which is responsible for cracking and capacity fading, real-time measurement of stress evolution and mechanical energy dissipation are very important. In this study, we report in situ measurements of stress evolution in silicon thin-film electrodes during electrochemical lithiation and delithiation by using the Multi-beam Optical Sensor (MOS) technique. Upon lithiation, due to substrate constraint, the silicon electrode initially undergoes elastic deformation, resulting in rapid rise of compressive stress. The electrode begins to deform plastically at a compressive stress of ca. -1.75 GPa; subsequent lithiation results in continued plastic strain, dissipating mechanical energy. Upon delithiation, the electrode first undergoes elastic straining in the opposite direction, leading to a tensile stress of ca. 1 GPa; subsequently, it deforms plastically during the rest of delithiation. The plastic flow stress evolves continuously with lithium concentration. Thus, mechanical energy is dissipated in plastic deformation during both lithiation and delithiation, and it can be calculated from the stress measurements. We show that it is comparable to the polarization losses in the cell; hence, mechanical deformation and stress considerations are important in evaluating the electrochemical performance of and energy loss in silicon anodes. Next, we present a thermodynamic analysis which suggests that stress and electrical potential are coupled in silicon anodes and the magnitude of the coupling is substantial (~ 60 mV/GPa). An in situ experimental study has been carried out to measure the coupling at different values of state of charge (SOC); the results of which are in good agreement with the theoretical prediction.


8:45 AM KK7.4
Mechanically Compliant Silicon Nanostructures for Rechargeable Lithium Ion Batteries.Hanqing Jiang1, Cunjiang Yu1 and Bingqing Wei2; 1Arizona State University, Tempe, Arizona; 2University of Delaware, Newark, Delaware.

The development of high-energy storage devices has been one of the research areas of top most importance in recent years and the rechargeable batteries are anticipated to be the primary sources of power for modern-day requirements. There is a great interest in developing next generation lithium (Li) ion batteries with higher energy capacity and longer cycle life for applications in portable electronic devices, satellites, and electric vehicles. Silicon (Si) is an attractive anode material being closely scrutinized for use in Li-ion batteries because of its highest-known theoretical charge capacity of 4,200 mAh/g. However, the development of Si-anode Li-ion batteries has lagged behind because of their large volumetric change (400%) upon insertion and extraction of Li (each Si atom can accommodate 4.4 Li atoms leading to the formation of Li22Si5 alloy), which results in pulverization and early capacity fading. How to release the stress due to the large volumetric change becomes the most challenging problem in the development of Si-anode Li-ion batteries. In order to circumvent this remaining hurdle, we develop a method to utilize mechanical compliant Si nanostructures as anodes in Li-ion batteries to release the stress induced by Li ion diffusion during charge-discharge cycles, thereby realizing theoretically maximum energy density while avoiding fracture. We have realized almost unchanged capacity over 500 charge/discharge cycles using this method.


9:00 AM KK7.5
In-situ TEM Studies of Silicon Nanowires for Li-ion Batteries.Khim Karki1, Paris Alexander1, Tom Picraux2, Chunsheng Wang3, YuHuang Wang4 and John Cumings1; 1Materials Science & Engineering, University of Maryland College Park, College Park, Maryland; 2Los Alamos National Laboratory, Los Alamos, New Mexico; 3Chemical & Biomolecular Engineering, University of Maryland, College Park, Maryland; 4Department of Chemistry & Biochemistry, University of Maryland, College Park, Maryland.

Silicon nanowires have been shown to offer promising anode materials for lithium ion batteries owing to their exceptional theoretical energy density (4200 mAhg-1), 10 times greater than existing graphite (372 mAhg-1) and relatively low working potential (~ 0.5V vs. Li/Li+). However, a large volume change (up to 400%) of silicon during lithiation and delithiation can result in the cracking and pulverization of the electrodes, leading to poor capacity retention and mechanical degradation of the cell. Nanowires have been shown to mitigate some of these effects, although the technology is still not ready for industrial application, due to limitations in the basic scientific underpinnings. In this study, we use in-situ TEM with piezo-actuated nanomanipulation holder capable of sub-angstrom accurate positioning system and simultaneous ability to apply voltages to the specimen. This experimental setup allows us to characterize the structural, electrical, and mechanical properties including the breaking stress of individual wires, which we will report for pristine, lithiated, and delithiated nanowires. This work is supported by the US Department of Energy, Office of Basic Energy Sciences as part of an Energy Frontier Research Center.


9:15 AM KK7.6
Porous Anodic Alumina (PAA) Templated Fabrication of Ni-Sn Nanowire Arrays for Li-ion Batteries.Miao Tian, Wei Wang and Ronggui Yang; Mechanical Engineering, University of Colorado at Boulder, Boulder, Colorado.

Nanowire arrays have recently attracted great attention for their potential applications as electrode materials for lithium-ion batteries. In this work, we developed a versatile method that can be used to fabricate Ni-Sn nanowire arrays, both on traditional copper-foil current collectors and on Si substrates, by electrochemically depositing Ni-Sn alloys with the assistance of porous anodic alumina (PAA) templates. When tested in a coin-type cell without any binder material, the Ni-Sn nanowire anodes can deliver a much higher specific capacity than anodes using Ni-Sn thin films deposited under the same conditions. Micro-structural characterization has been performed to confirm the structural stability of the nanowire electrodes after the cycling tests. Ni-Sn nanowire arrays with different dimensions and compositions were systematically studied as anode materials to optimize the electrochemical performance. Furthermore, the effects of coatings such as atomic layer deposited (ALD) alumina on the formation of the solid electrolyte interphase (SEI) were also investigated to improve capacity retention. This work broadens the research on nanostructured anodes of lithium ion batteries to include intermetallic nanowires and might pave the way for on-chip and three-dimensional nanostructured lithium ion batteries.


9:30 AM KK7.7
Understanding the Reaction Mechanism of SnCo-Carbon Anode.Shailesh Upreti1, Ruigang Zhang1, Natasha A. Chernova1, Wang Feng2, Lin-Shu Du3, Faisal Alamgir4, Cole Petersburg4, Elaine Lin4, Jason Graetz2, Clare P. Grey3 and M. S. Whittingham1; 1Int for Materails Research, Binghamton University, Binghamton, New York; 2Condensed Matter Physics and Material Science Department, Brookhaven National Laboratory, Upton, New York; 3Department of Chemistry, SUNY Stony Brook, Stony Brook, New York; 4Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia.

A combination of conversion and intercalation reactions in Li-ion battery materials offers a great potential for increasing their gravimetric and volumetric capacity. Differentiating and elucidating these fundamental mechanisms is required to build a roadmap for developing such crossover materials. In this work, nanostructured SnCo embedded in carbon matrix is considered as a model system, where both intercalation reaction forming LixSnCo and conversion reaction with LixSn+Co products could occur. We investigate how the nano-SnCo alloy reacts with lithium in the electrochemical cell by 7Li MAS NMR, STEM, x-ray absorption (XAS), small-angle x-ray scattering (SAXS), and magnetic studies. In-situ characterization is conducted whenever possible (XAS, SAXS). Particle size variations observed in SAXS are small unlike the large changes typical of pure Sn. Co displacement upon Li insertion is confirmed by STEM data and magnetic properties; the latter revealing formation of superparamagnetic Co particles. The existence of LixSnCo phase is being investigated. The magnetic studies indicate that initial stages of lithiation reaction do not lead to a magnetization increase, pointing toward the intercalation mechanism. This conclusion is supported by in-situ XAS. However, the corresponding Li NMR spectra reveal only small shifts, indicating diamagnetic Li environment, which is unexpected in the presence of paramagnetic Co. Further studies are being conducted to clarify this complex system. This research is supported as part of the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Basic Energy Sciences under Award Number DE-SC0001294, Office of Science, and at Georgia Institute of Technology - by the Creating Energy Options program.


10:00 AM KK7.8
Magnetic Signature of Conversion in Lithium-ion Anode Batteries. Simeon Boyanov1, Villevieille Claire1, Manfred Womes1, Laure Monconduit1 and David Zitoun1,2; 1Bar Ilan Institute of Nanotechnology and Advanced Materials, Bar Ilan University, Ramat Gan, Israel; 2Institut Charles Gerhardt Montpellier, Universite Montpellier 2, Montpellier, France.

We have recently proposed an approach using both Mossbauer spectroscopy and magnetic measurements to follow the conversion of anode materials upon lithiation/delithiation processes. Combining Mössbauer spectroscopy and magnetic measurements is an interesting approach to the analysis of electrode materials if different magnetic phases are involved (antiferromagnetic, ferromagnetic, paramagnetic). The two techniques are complementary in so far as measurements of the magnetic susceptibilities allow detecting even small amounts of a ferromagnetic phase like metallic iron, provided all other phases present are dia- or paramagnetic or give only a weak susceptibility from antiferromagnetism. Their detection is possible even in cases where Mössbauer spectroscopy fails to reveal them unambiguously due to overlap with absorption lines of other phases. On the other hand, the presence of paramagnetic compound, even when X-ray amorphous, is easily demonstrated by Mössbauer spectroscopy. These methods are very general and have been applied to the study of numerous systems involving a ferromagnetic transition metal (Fe, Co or Ni) and a Mössbauer active element (Fe, Sn, Sb). Among the alloys investigated (FeP, [1] FeP2, FeP4,[2] CoSn2, Ni3Sn4,[3] FeSn2, FeSb2, NiSb2 [4]), the case of FeP was particularly interesting. This complementary analysis by Mössbauer spectroscopy and magnetisation measurements was a powerful tool i) to quantitatively identify 3 nm iron nanoparticles at the end of discharge and ii) to unambiguously identify the LixFeP intermediate phase reversibly formed upon cycling, and the restructured FeP at the end of charge. All these phases are X-ray amorphous. [1] S. Boyanov, M. Womes, L. Monconduit, D. Zitoun Chem. Mater. 2009, 21 (15), 3684 [2] S. Boyanov, D. Zitoun, M. Menetrier, J.C. Jumas, M. Womes, L. Monconduit J. Phys. Chem. C 2009, 113 (51), 21441 [3] S. Naille, R. Dedryvère, D. Zitoun, P.E. Lippens J. Power Sources, 2009, 189, 806. [4] C. Villevieille, C.M. Ionica-Bousquet, B. Fraisse, D. Zitoun, M. Womes, J.C. Jumas, L. Monconduit Solid State Ion. 2010, http://dx.doi.org/10.1016/j.ssi.2010.04.029


10:15 AM KK7.9
Electrodeposition as a Tool to Investigate the Battery Cycling Behavior of Copper Antimonide.Amy Prieto, James M. Mosby and Derek C. Johnson; Chemistry, Colorado State University, Fort Collins, Colorado.

New anode materials for lithium-ion batteries have been sought after for over a decade. The most promising materials boast much higher capacities and slightly higher operating potentials than graphite. The major drawback to these materials is a large irreversible capacity loss that occurs during cycling. The majority of the capacity loss is due to significant volume changes that occur during the lithiation and de-lithiation processes. One class of alternative anode materials that have comparatively low volume changes are intermetallic compounds where the parent and lithiated crystal structures are closely related. A specific example is Cu2Sb in which the Sb atoms stay in a face center cubic array throughout the lithiation to Li3Sb. We have developed a procedure to directly electrodeposit Cu2Sb from aqueous solutions1, thereby allowing the anode material to be deposited onto transmission electron microscopy grids.2 This unique synthesis approach enables high resolution mapping of the material during the lithiation and delithiation processes. This is a critical step toward understanding the sources of capacity loss to this promising anode material. We will present cycling data coupled with TEM images, selected area electron diffraction, and compositional mapping of Cu2Sb. (1) J. Mosby, A. L. Prieto, “Direct Electrodeposition of Cu2Sb for Lithium-ion Battery Anodes,” J. Am. Chem. Soc.2008, 130, 10656-10661. (2) J. Mosby, D. C. Johnson, A. L. Prieto, “Evidence of Induced Underpotential Deposition of Crystalline Copper Antimonide via Instantaneous Nucleation,” J. Electrochem. Soc. 2010, 157, E99-E105.


10:30 AM KK7.10
Ultrahigh Power Density Bulk Battery Electrodes.Paul Braun, Hui Gang Zhang and Xindi Yu; Materials Science and Engineering, Univ. of Illinois at Urbana-Champaign, Urbana, Illinois.

Here we show that a three-dimensional (3D) bicontinuous nanoarchitecture formed via templating of a self-assembled colloidal crystal results in a Li-ion battery cathode which enables charging and discharging with minimal capacity loss at rates up to 400C and 1,000C, respectively. The final structure consists of an electrolytically active material sandwiched between rapid ion and electron transport pathways. The final structure also has energy densities comparable to current commercial systems. This bulk electrode structuring approach is demonstrated for both Li-ion and NiMH chemistries. A Li-ion battery constructed from a bicontinuous lithiated MnO2 cathode and a conventional graphite anode could be charged to 90% capacity in 2 minutes. The 3D bicontinuous electrode approach presented here is quite general, and is applicable to many battery chemistries.


10:45 AM KK7.11
High Specific Capacity and Excellent Stability of Interface-controlled MWCNT Based Anodes in Lithium Ion Battery.Indranil Lahiri1, Sung-Woo Oh2, Yang-Kook Sun2 and Wonbong Choi1; 1Mechanical and Materials Engineering, Florida International University, Miami, Florida; 2Department of Energy Engineering, Hanyang University, Seoul, Korea, Republic of.

Rechargeable batteries are integral part of present society. Among different varieties of rechargeable batteries, Li-ion batteries have become most popular for their obvious advantages. These batteries are much lighter (causing higher energy density), offer higher operating voltage, do not have any memory effect, operate over a wider temperature range and have a lower self-discharge rate. Despite their established market, researchers have shown great deal of interest in developing new, improved electrode materials for lithium ion batteries leading to higher specific capacity, longer cycle life and extra safety. Among other promising materials like Si and Sn-oxide, carbon nanotubes (CNT) are also being considered as possible alternative to the presently used graphite anodes due to their huge surface area and expected higher capacity. However, initial research efforts were not encouraging. In the present study, we have shown that an anode prepared from interface-controlled multiwall carbon nanotubes (MWCNT), directly grown on copper current collectors, may be the best suitable anode for a Li-ion battery. The newly developed anode structure has shown very high specific capacity (almost three times as that of graphite), excellent rate capability, nil capacity degradation in long-cycle operation and introduced a higher level of safety by avoiding organic binders. Enhanced properties of the anode were well supported by the structural characterization and can be related to very high Li-ion intercalation on the walls of CNTs, as observed in HRTEM. In contrast to the recently reported Si-nanowire anodes, these anodes show zero capacity degradation even at 1C rate and offer a simple industrially scalable synthesis process. This newly developed CNT-based anode structure is expected to revolutionize Li-ion battery applications.


11:00 AM KK7.12
Utilization of Exfoliation to Activate/Protect Electrode Materials for Lithium Ion Batteries.John P. Lemmon, Jie Xiao, Philip K. Koech, Yuliang Cao and Jun Liu; Pacific Northwest National Laboratory, Richland, Washington.

Conventional Li-ion batteries utilize graphite as the anode materials. The low theoretical capacity of graphite (372 mAh/g) makes it important to find alternative negative electrodes. The investigation of MoS2 as an anode material for Li-ion batteries has been reported and the particle size and morphology was shown to have significant influence on the electrochemical properties of the disordered MoS2. In this work nanocomposites of molybdenum disulfide (MoS2) and poly(ethylene oxide) (PEO) were prepared by the exfoliation/absorption method that involved the hydrolysis of lithiated MoS2 in an aqueous solution of PEO. The absorption and subsequent interaction of PEO on the colloidal MoS2 formed a nanocomposite which restacked into layered secondary particles. X-ray diffraction and high resolution TEM indicated that highly disordered nanocomposites were produced when the Lix(PEO)yMoS2 stoichiometry was limited to y < 1. A significant improvement in capacity and cycling stability was observed for the disordered nanocomposites. After further incorporation of graphene during the exfoliation process extremely stable cylcling performance is achieved in the MoS2/PEO/graphene nanocomposite. The reaction mechanism for the composite will be discussed in detail. Moreover, the possibility to combine this exfoliation approach with Li-S battery to protect the soluble lithium polysulfide intermediates by the in-situ formed metal Mo during first deep discharge will also be investigated.


11:15 AM KK7.13
Study of High Energy Density Graphene Nanoribbons for Advanced Li-ion Batteries.Tarun K. Bhardwaj1, Aleks Antic2, Veronica Barone2 and Bradley Fahlman1; 1Chemistry, Central Michigan University, Mt Pleasant, Michigan; 2Physics, Central Michigan University, Mt Pleasant, Michigan.

Our recent computational studies showed that graphene nanoribbons (GNRs) have very high lithium uptake capacity due to the presence of reactive edges. Therefore, in order to study their electrochemical behavior, GNRs were synthesized by the chemical oxidation of multi-walled carbon nanotubes. Synthesized GNRs were characterized by different techniques such as TGA, Raman spectroscopy, SEM, and TEM. These GNRs were tested as a potential high energy density anode material for advanced Li-ion batteries. Both oxidized and reduced GNRs were electrochemically intercalated and de-intercalated with lithium. The first charge capacity of oxidized GNRs was observed to be 1300 mAh/g. The coulombic efficiency for the first cycle was about 50%, and around 90% for the following cycles. After the first cycle, these GNRs showed very little capacity loss for the following cycles. The specific capacity of GNRs for the following cycles was stabilized around 800 mAh/g.


11:30 AM KK7.14
Aligned Graphene-based Electrode for Lithium Ion Battery with High Rate Capability.Xingcheng Xiao1, Ping Liu2, John W. Wang2, Mark W. Verbrugge1 and Michael P. Balogh1; 1General Motors Global R&D Center, Warren, Michigan; 2HRL Labs, Malibu, California.

Despite much progress, the power density of current lithium ion batteries, or the coulombic capacity at high rates of charge and discharge, are too low for many automotive applications, such as charge-sustaining hybrid electric vehicles. One practical approach to achieve the high rate capability is to optimize the nanostructure of the existing electrodes to facilitate electron transport and ion diffusion. In this report, we present new results based on a simple (patent pending) process to grow multilayered graphene sheets vertically aligned on the current collector. The overall result facilitates both electron and lithium ion transport and increases the active material rate capability. Because electrons can directly transport from the current collector to the graphene basal planes, the architecture eliminates the need for carbon black as the conductive additive used in the conventional electrodes. Our results show that a vertically aligned graphene structure can serve as an electrode in lithium ion batteries with extremely fast kinetics. The optimized electrode structure and the reduced diffusion distance, rather than an enhanced diffusion coefficient due to the graphene structure, is responsible for the improved kinetics. While more work remains, we envision the use of this highly stable structure as an integral addition to high capacity anode materials for lithium ion batteries of high power and energy density.


11:45 AM KK7.15
Transferred to KK7.10

 

SESSION KK8: Lithium Battery Characterization, Modeling of Battery Materials
Chairs: Jane Howe and Gholam-Abbas Nazri
Thursday Afternoon, December 2, 2010
Constitution A (Sheraton)


1:30 PM *KK8.1
Recent Advances in the Understanding of the Reactivity of Si-based Composite Electrodes for Li-ion Batteries.Dominique Larcher1,3, J. S. Bridel1,3, T. Azais2, M. Morcrette1,3 and J. M. Tarascon1,3; 1Laboratoire de Reactivite et Chimie des Solides CNRS UMR, Universite de Picardie - Jules Verne, Amiens, France; 2Laboritoire de Chimie de la Matiere Condensee de Paris, Universite Pierre et Marie Curie-Paris, College de France, Paris, France; 3ALISTORE-European Research Institute, Federation de Recherche CNRS, Amiens, France.

Despite the high hopes placed in the Li-ion battery technology and its adaptability to the demands, further improvements are still required in view of implementation in several systems such as EV’s, autonomy being a top priority. In contrast to the positive electrode which capacity is still hindered by the extent of the 3d metals redox processes, negative electrode can benefit from the high capacities of the alloying reactions, among which Si can deliver about 10 times the capacity of graphite. However, such a huge amount of incorporated lithium (Li15Si4) logically implies large volume changes of the reacting particles, up to 300% accordingly to the raise in atom count. By-passing their impairing effects on the electrode texture, percolating organisation and subsequent electrochemical reversibility are remaining issues. A recent major breakthrough was the very positive binder effect to maintain the full capacity for tens of cycles [1]. Among them, polymers (CMC, polyacrylate …) hanging carboxyl groups were found to be the most suitable. Previous reports [2,3] highlight that the key parameters for a proper functioning of the Si/C/binder electrode are i) its porosity, ii) the chain conformation, and iii) the nature of the chemical Si-binder bound with the whole being controlled by the electrode processing and the chemical characteristics of the binder (chains length, cation, degree/nature of the substitution) while the binder elasticity was not found to play a major role. In spite of the aforementioned findings, several aspects of the interactions between the various components of the composite are nevertheless still subject to controversies calling for further and more cross-linked investigations. To throw further insight on this issue, we report here, Si-NMR, in-situ SEM observations, complex impedance spectroscopy measurements together with alternative electrode processing approaches. We could then confirm that the nature of the Si-binder link can be tuned from covalent to hydrogen-type interaction by playing with the pH of the initial carbon/CMC mother aqueous suspension. Besides, a two-step electrode volume evolution upon the electrochemical uptake (x) of Li was found with x=2 being the intercept. For x<2 we note the full ability of the porosity to buffer the Si swelling. Beyond, the reversibility is ensured by the self-healing properties of the hydrogen-type Si-CMC bonding, explaining then the lack of reversibility of fully reacted electrodes having Si covalently bound to the binder. Such adaptability also provides a stable polymeric environment to the Si particles as shown by complex impedance spectroscopy. By playing with the electrode drying process, we could master the electrode porosity from few to 99 %, and found that 50- 0% is a good compromise to preserve enough electrode buffer capability while preserving an adequate electronic conductivity. The systematic long-term fading observed after 100-120 cycles was identified as due to the limited reversibility of the Li electrode. [1] J.Li, R.B.Lewis, J.R.Dahn, Electrochem. Solid-State Lett., 10(2), A17 (2007) [2] B.Lestriez, S.Bahri, I.Sandu, L.Roue, D.Guyomard, Electrochem. Commun., 9, 2801 (2007) [3] J.-S.Bridel, T.Azaïs, M.Morcrette, J.-M.Tarascon, D.Larcher. Chem. Mater., 22, 1229 (2010)


2:00 PM KK8.2
Atomic-scale Structure of Fine Graphite Powders by High-energy XRD and 3D Computer Simulations.Valeri Petkov1, Adam Timmons2, John Camaradese3 and Yang Ren4; 1Physics, CMU, Mt.Pleasant, Michigan; 2Electrochemical Energy Research Lab, GM Global Research and Development, Warren, Michigan; 3Department of Natural Sciences, Lawrence Technological University, Southfield, Michigan; 4Advanced Photon Source, Argonne National laboratory, Chicago, Illinois.

Graphite powders with grain sizes ranging from a few microns down to several tens of nanometers have been produced by ball-milling. The powders have been tested in electrochemical cells as negative electrodes in Li batteries and found to have a considerably improved Li storage capacity as compared to non-milled graphite. The Li capacity, however, have been found to vary non-linearly with the ball-milling time. Initially it increases steeply with the milling time reaching a maximum value of 900 mAh/g for samples milled for about 150 mins. The capacity then starts diminishing and reaches a value of 600 mAh/g for milling times of 1200 mins. To understand how exactly the atomic-scale structure of graphite and, hence, its ability to accommodate Li is affected by ball-milling the graphite powders have been studied by a non-traditional technique involving high-energy synchrotron X-ray diffraction (XRD) coupled to atomic pair distribution function (PDF) data analysis and large-scale, reverse Monte Carlo-type simulations. The reason is that the XRD patterns of fine graphite powders are very diffuse in nature and may not be analyzed in the traditional crystallographic way. The experimental and modeling results show that all ball-milled samples preserve the structure of bulk graphite that may be viewed as a stack of hexagonal layers of carbon atoms. The stacks show local structural defects and are of much smaller lateral and vertical dimensions in the ball-milled samples likely facilitating enhanced Li intercalation. Prolonged ball milling, however, increasingly makes the initially flat carbon layers more and more curved thus impeding the intercalation of Li into the material. Possibilities for applying this experimental approach for ex and in situ studies of Li intercalated fine graphite powders will be discussed as well.


2:15 PM KK8.3
Application of Magnetic Studies Toward Understanding of Conversion Reactions.Natasha A. Chernova1, Ruigang Zhang1, M. Stanley Whittingham1, Nathalie Pereira2 and Glenn G. Amatucci2; 1Institute for Materials Research, SUNY Binghamton, Binghamton, New York; 2Department of Materials Science and Engineering, Rutgers The State University of New Jersey, North Brunswick, New Jersey.

Fundamental studies of reaction mechanisms in Li-ion batteries are driven by a demand for high energy density and safe electrodes capable of fast lithiation/delithiation reactions. While intercalation systems are currently limited to one Li per red-ox center, conversion systems do not have this limitation. Conversion electrodes are usually nanostructured, which facilitates phase transformations, but makes their characterization quite challenging. In this work we explore how the magnetic properties can be used in mechanistic studies of conversion reactions. We consider three model systems: nanocomposites of SnCo, FeF2, and FeF3 embedded in a carbon matrix, which form Co and Fe nanoparticles, respectively, upon Li insertion. Bulk Co and Fe are ferromagnetic at room temperature, while small (< 6-8 nm) nanoparticles become superparamagnetic, meaning that the magnetic moment of the whole particle can flip under the influence of thermal energy. The amount of displaced Co and Fe is determined from the saturation magnetization and the particle size is estimated from the blocking temperature below which the magnetic moments cannot flip. The initial experimental data for the materials extracted from the Li cells shows saturation magnetization increase with lithiation for all the systems. This is consistent with the displacement of metal particles. For the SnCo system, superparamagnetic Co particles are formed, meaning that the particle size does not exceed several nm. Superparamagnetism in FeF3 and FeF2 systems is not clearly pronounced, which is unusual for 2-3 nm particles observed in TEM. One of the possible reasons is magnetic interaction between the particles. The obtained magnetic data will be discussed and related to the structural data available from other characterization methods (x-ray diffraction and absorption, Li MAS NMR, TEM) to give insights into the reaction mechanism. Further development of this method toward in-situ magnetic measurements will also be discussed. This research is supported as part of the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under Award Number DE-SC0001294.


2:30 PM KK8.4
XAS and AEM Investigation of Layered Mn-based Oxides for Li-ion Batteries.Javier Bareño and Daniel P. Abraham; Electrochemical Energy Storage, Argonne National Laboratory, Argonne, Illinois.

Rechargeable Li-ion cells present the highest energy density of any battery technology and are expected in next generation hybrid electric vehicles (HEVs), plug-in HEVs, and electric vehicles (EVs). Lithium manganese oxides are of significant interest as cathode materials in these cells because they are cheap, plentiful, non-toxic, and environmentally benign. Li-Mn layered oxides − Li1+y(Mn1-xMx)1-yO2 with M a transition metal such as Ni, Co, Cr, Fe, Ga, Nb or a combination of transition metals − are promising positive electrode candidates because they have the potential for higher energy densities, better stability at high voltages, and longer calendar life than currently used materials. We have embarked on a multi-institution effort to synthesize, characterize, and model the Li1+y(Mn1-xMx)1-yO2 structures. After synthesis and initial examination of oxide crystal structure and electrochemical performance, we conduct both ex situ and in situ X-ray absorption spectroscopy (XAS) measurements that provide information on oxidation states, coordination number around the transition metal (TM) elements and changes in these parameters during electrochemical cycling. The XAS study is complemented by Analytical Electron Microscopy (AEM), which includes high-resolution electron microscopy (HREM), and high-angle annular dark-field imaging (HAADF) to examine the crystal structure and electron energy loss spectroscopy (EELS) to examine composition variations at near-atomic spatial resolutions. In this talk, we will discuss detailed crystallographic data pertaining cation arrangements in Li2MnO3, Li1.2Ni0.2Mn0.6O2, and Li1.2Co0.4Mn0.4O2 samples. XAS data showed a dearth of TM atoms around Mn absorbers, in both Li1.2Ni0.2Mn0.6O2, and Li1.2Co0.4Mn0.4O2 samples, which suggests that Li atoms preferentially surround (i.e., order around) Mn forming LiMn6-like areas. The relative stacking of these areas across neighboring TM-planes results in Li2MnO3-like monoclinic local structures percolating through the layered rock salt framework. These locally monoclinic structures are also observed in Z-contrast (HAADF-STEM) images and electron diffraction patterns. Z-contrast micrographs of Li1.2Ni0.2Mn0.6O2, and Li1.2Co0.4Mn0.4O2 samples displayed rectangular and parallelogram patterns consistent with a Li-TM-TM-Li arrangement (i.e., lithium ordering) in the transition metal planes similar to those observed in Li2MnO3. The transition metal planes follow several stacking sequences, bounded by stacking faults along the c-axis. This quasi-random plane stacking sequence induces streaks in electron diffraction patterns and prevents the assignment of a single crystal structure through the sample. We observed no evidence of long-range ordering or phase segregation in the oxide over lengthscales larger than 2-3 nm.


2:45 PM KK8.5
In Situ Raman Spectroscopy of Semiconductors for Li-ion Battery Applications.Andrew Gewirth and Brandon Long; Chemistry, University of Illinois, Urbana, Illinois.

In situ Raman Spectroscopy of low energy phonon modes in single crystal Si substrates provides a measure of crystallinity in the Si sample. In the electrochemical environment, spectra obtained at potentials very positive of 0 V vs. Li+/Li exhibit this phonon mode at 520 cm-1. As the potential is moved close to 0 V, Li intercalation into the Si occurs. On a Si(100) single crystal, this intercalation is associated with the irreversible loss of intensity in the 520 cm-1 band at ca. 600 mV vs. Li+/Li . However, the potential at which this intensity loss occurs on Si(111) is found to be below 250 mV suggesting that Li insertion is considerably more difficult on this face. We also report on the effect of dopants on the Li insertion behavior of these electrodes. The consequences of this anisotropy for electrode design will be discussed.


3:00 PM KK8.6
Model for Lithium-Ion Batteries at Low Temperatures.Shriram Santhanagopalan, Kandler Smith, Kyu-Jin Lee and Gi-Heon Kim; National Renewable Energy Laboratory, Golden, Colorado.

Extending the operating range for lithium ion batteries is an important problem faced by industry. The performance of lithium-ion batteries decreases dramatically when the operating range drops below -10oC. Such limitations arise primarily from the electrolyte solution, which not only determines the ionic mobility between electrodes but also strongly affects the nature of the Solid-Electrolyte Interface (SEI) formed on the anode. Aiming at enhancing low-temperature cell performance, attempts have been made to reduce the viscosity of the electrolyte by adding ternary and quaternary carbonates, and/or solvents with low melting point such as esters. In addition to optimizing the composition of the solvents, other components such as the lithium salts, and electrode materials have been proposed for low temperature applications. Several experimental studies [1-5] have focused on elucidating the dominant mechanism that limits the low-temperature performance. Fan [2] proposed that the lithium diffusion in the SEI layer on the positive surface as the most important rate-limiting factor in the cell discharge capability. Zhang et al. [3-4] found that the slow kinetics of the Faradic reactions on the electrode/electrolyte interfaces was the major limitation. They also proposed to improve the conductivity of the SEI film by increasing the propylene carbonate content. Smart et al. [5] found that the electrochemical kinetics of cathode showed a strong dependence on the ethylene carbonate (EC) content in the electrolytes at different temperatures. In this work, we present a model that captures the reduction in the ionic conductivity and diffusivity of the electrolyte, entropic effects and other changes to material properties such as solid state diffusion and polarization across the electrode electrolyte interface. The effect of sharp changes in these properties on the distribution of ions along the interface will be discussed. The key parameters that contribute to the resistance build-up and cell heating at low temperatures will be identified. Electrochemical characterization experiments performed on coin cell level will be used to validate our model and further enhance our understanding of the performance limitations at low temperatures. References: 1. Jansen, A.J., Dees, D.W., Abraham, D.P., Amine K., Henriksen G.L., J. Power Sources, 174 373, (2007). 2. Fan J., J. Power Sources 117, 170, (2003). 3. Zhang S.S., Xu K., Allen J.L. and Jow T.R., J. Power Sources 110, 216, (2002). 4. Zhang S.S., Xu K. and Jow T.R., J. Power Sources 115, 137, (2003). 5. Smart M.C., Whitacre J.F., Ratnakumar B.V. and Amine K., J. Power Sources, 168, 501, (2007).


3:30 PM KK8.7
Atomic Layer Deposition Coatings Improve Electrode Architectures for Lithium-ion Batteries.Yoon Seok Jung1, Andrew S. Cavanagh2, Zhuangchun Wu1, Isaac Scott2, Chunmei Ban1, Se-Hee Lee2, Steven M. George2, Gi-Heon Kim1, Ahmad Pesaran1 and Anne C. Dillon1; 1National Renewable Energy Laboratory, Golden, Colorado; 2University of Colorado at Boulder, Boulder, Colorado.

<dd>Interfacial stability between the electrode and electrolyte governs durability and safety of lithium-ion batteries. Undesirable surface-related reactions include electrolyte decomposition, metal dissolution, and oxygen evolution that can increase the cell impedance leading to capacity fade during repeated charge-discharge cycles especially under severe conditions. As the cell temperature increases exothermic interfacial reactions between the electrode and electrolyte occurs and may cause thermal runaway, a significant safety concern.< dd> (A) AlOH* + Al(CH3)3 → AlO-Al(CH3)2* + CH4 (B) AlCH3* + H2O → Al-OH* + CH4 ALD on fabricated electrodes was demonstrated to significantly improve the performance for LiCoO2,[1] natural graphite (NG),[2] and nanosized MoO3.[3] Because ALD employs self-limiting vapour phase reactions it is possible to put thin conformal coatings directly on the tortuous porous structures of conventional composite electrodes. <dd>As mentioned previously, we have explored the effects of Al2O3 ALD on various electrode materials. Here we will focus on changes in the kinetic properties as a function of the electrode architecture. The ALD process on fully fabricated electrodes provides a very thin protective coating and significantly improved cycling performance. However, if the insulating and conformal Al2O3 coating, only 20 atomic layers (~23 Å) is applied directly to LiCoO2 powders, rather than the full electrode, the discharge capacity is only 4 mA h g-1 at 1 C-rate, suggesting much slower kinetics. In contrast 20 cycles of ALD on electrodes results in 71 mA h g-1 for the discharge capacity at 1 C-rate. In the case of NG the durability is dramatically improved by direct ALD on as-formed electrodes at 50 oC. In sharp contrast ALD on powders resulted in poorer cycle life than bare NG powders. Recently, C. Ban et al. demonstrated that single-walled nanotubes (SWNT) can be employed as highly conductive wires for binder-free electrodes.[4] We have now employed ALD coatings directly on the binder-free electrode to maximize the kinetic properties and also demonstrate surface protection. These results and new developments to nano-engineer ALD coatings on binder-free electrodes will be discussed in detail.REFERENCES [1] Y. S. Jung et al., J. Electrochem. Soc.157, A75 (2010). [2] Y. S. Jung et al., Adv. Mater.22, 2172 (2010). [3] L. A. Riley et al., Chem. Phys. Chem. (available on line). [4] C. Ban et al. Adv. Mater. (available on line).


3:45 PM KK8.8
All Solid-state Lithium-ion Battery for High-temperature Service.Qichao Hu, Sebastian Osswald, Robert Daniel, Yan Zhu, Steven Wesel, Luis Ortiz and Donald Sadoway; DMSE, MIT, Cambridge, Massachusetts.

The high-temperature performance of lithium-ion batteries is currently limited by the thermal stability of the electrolyte and the electrode/electrolyte interface. Carbonate-based liquid electrolytes are considered volatile organic compounds (VOCs), and so their reactivity with cell components and volatility increase with temperature to such an extent that safe high-temperature operation of lithium-ion batteries is precluded. Graft copolymer electrolytes (GCEs) of poly[(oxyethylene)methacrylate]-g-poly(dimethyl-siloxane) (POEM-g-PDMS) exhibit the mechanical stability of a solid while possessing the ionic conductivity approaching that of liquid electrolytes [1]. The GCE synthesized in the present study proved to be thermally stable over a wide temperature range (25 - 300°C) and was able to serve not only as electrolyte but also as binder for the electrodes. All solid-state batteries comprised of a metallic lithium anode, a LiFePO4 cathode, and a solid polymer electrolyte (20 µm thick) composed of lithium triflate-doped POEM-g-PDMS were safely operated at temperatures up 150°C without significant capacity fade. In a number of applications that employ batteries at elevated temperatures, people are forced to use primary batteries as power supplies. Our results demonstrate that by incorporating GCEs into the cell structure it may be possible to develop rechargeable high-temperature energy storage systems. Acknowledgments The authors are thankful to Chevron, USA for providing financial support. References 1. P.E. Trapa, et al., J. Electrochem. Soc. 152 (1), A1-A5 (2005)


4:00 PM KK8.9
Novel Computational Approaches to Li Diffusion and Transport for High Capacity Battery Materials.Stefano Leoni1,2 and Salah Eddine Boulfelfel3,2; 1Physical Chemistry, Technical University Dresden, Dresden, Germany; 2Physical/Theoretical Chemistry, Max-Planck Institute for Chemical Physics of Solids, Dresden, Germany; 3Department of Geosciences, Stony Brook University, Stony Brook, New York.

The intrinsic channel structure and low volume work makes olivines versatile for Li uptake and release. The relatively low bulk conductivity can be enhanced by particle size reduction and composite formation, but also by heterovalent cation substitution. Point defects have a decisive impact on physical properties and on ionic conducting properties. The understanding of Li cation diffusion/transport mechanisms inside olivines under different chemical substitution conditions are crucial aspects which we address using a dedicated method based on advanced molecular dynamics simulations. Activations energies calculated from DFT conclude 1D diffusion within channels as also indicated by neutron diffraction direct imaging techniques. Other diffusions paths are hindered by high activation energies for cation hopping. Nonetheless, while the energetics of point defects and single lithium cation displacements have been addressed in detail, no finite temperature simulations have been considered up to now. However, the way Li cations are moving inside the materials are central for property control. Explicitly including temperature gives indeed access to surprising aspects of olivine materials. Besides main conduction paths along the channels we also discover other, less frequent but relevant paths. We point out that capacity and diffusion/conduction issues must be understood in a much more detail-rich framework, under realistic simulation conditions within finite temperature simulations. Along this line we unravel a diverse set of diffusion pathways, without the need to artificially speed-up Li difusion by large temperatures. With atomistic level of detail we are able to shed light on the role of antisite defects in boosting Li mobility. Like in nanoionics, defects are affecting Debye lengths under creation of extended nanointerfaces within the bulk material, along which Li can travel faster. We extend the simulation setup to realistic charge/discharge scenarios towards a fully ab initio battery material simulation platform.


4:15 PM KK8.10
Electrochemical Shock of Lithium Battery Materials During Cycling - Modeling and Experiments.William H. Woodford, Yet-Ming Chiang and W. Craig Carter; Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.

``Electrochemical shock” - fracture of electrode particles due to diffusion-induced stresses - has been implicated as a possible mechanism for capacity fade and impedance growth in lithium-ion batteries. Models with realistic fracture criteria are needed to understand the role of fracture in electrode degradation and to design mechanically robust electrodes and operating conditions. We have derived a fracture mechanics failure criterion for individual electrode particles. Our fracture mechanics model predicts a critical C-rate above which active particles fracture; the critical C-rate decreases with increasing particle size. Fracture dynamics are sensitive to the pre-existing flaw size: short initial flaws grow unstably - and are potentially more damaging - than larger initial flaws, which grow stably. Numerical results are provided for galvanostatic charging of LixMn2O4, a model system. Our model predictions are compared with literature reports of particle level fracture due to electrochemical shock. Finally, we present new experimental acoustic emission and electrochemical results that validate our theoretical predictions.


4:30 PM KK8.11
Lithium Ion Intercalation Induced Stress and Fracture of Active Electrode Material.Sergiy Kalnaus1, Kevin J. Rhodes2,1 and Claus Daniel1,2; 1Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; 2Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee.

The working principle of Li ion battery is based on repeated transport of lithium ions through electrolyte and insertion/extraction from the electrode host structure (intercalation compound). It has been well documented that cycles of charge and discharge lead to capacity fade in battery over its lifetime. Such capacity fade suggested to be partially attributed to mechanical cracking of the active material particles induced by repeated lithium intercalation/deintercalation. While the fracture of particles has been observed and documented, investigation of processes leading to crack formation and development of models capable of predicting initiation of cracking is still under way. Determination of stress state of a particle during charge/discharge will lead to understanding of the origin of fracture and will provide solution in order to improve the battery service life. In the present investigation the fracture of Si particles due to internal stresses formed during the intercalation of lithium ions was described by means of thermal analogy model and brittle fracture damage parameter. The stresses were computed following the diffusion equation and equations of elasticity with appropriate volumetric expansion term. The damage parameter takes into account triaxiality of the stress state and change in elasticity upon tension and compression, and represents the probability of fracture under given stress state, - an approach suitable for brittle materials. The results were compared with the acoustic emissions data from the experiments on electrochemical cycling of Li ion half-cells with silicon electrodes. A good correlation between experiment and prediction was observed. The computational predictions suggest the existence of critical size of the particle below which the intercalation of lithium ions will not result in fracture. Acoustic emission experiments involving particles with sizes close to such critical dimension confirm the above suggestion. This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725 was sponsored by the Vehicle Technologies Program for the Office of Energy Efficiency and Renewable Energy. Parts of this research were performed at the High Temperature Materials Laboratory, which is a user facility sponsored by the same office.


4:45 PM KK8.12
Thermodynamics and Kinetics of Phase Transformation in Intercalation Battery Electrodes - Phenomenological Modeling.Wei Lai1 and Francesco Ciucci2; 1Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan; 2Heidelberg Graduate School of Mathematical and Computational Methods for the Sciences, University of Heidelberg, Heidelberg, Germany.

Thermodynamics and kinetics of phase transformation in intercalation battery electrodes are investigated by phenomenological models which include a mean-field lattice-gas thermodynamic model and a generalized Poisson-Nernst-Planck equation set based on linear irreversible thermodynamics. The application of modeling to a porous intercalation electrode leads to a hierarchical equivalent circuit with elements of explicit physical meanings. The equivalent circuit corresponding to the intercalation particle of planar, cylindrical and spherical symmetry is reduced to a diffusion equation with concentration dependent diffusivity. The numerical analysis of the diffusion equation suggests the front propagation behavior during phase transformation. The present treatment is also compared with the conventional moving boundary and phase field approaches.


 

SESSION KK9: Poster Session: Lithium Battery Materials
Chairs: Dominique Guyomard, Gholam-Abbas Nazri, Jean-Marie Tarascon and Atsuo Yamada
Thursday Evening, December 2, 2010
8:00 PM
Exhibition Hall D (Hynes)


KK9.1
Development of a Secondary Self-formed Lithium Iodide Battery. William M. Yourey, Lawrence Weinstein, Anna Halajko and Glenn G. Amatucci; Rutgers University, North Brunswick, New Jersey.

As MEMS devices continue to develop and decrease in dimensions, the need for micro power sources with the appropriate energy density and dimensions continues to grow. Different pathways have been proposed as a solution to this problem, such as thin film batteries, novel 3-D architectures, and aqueous battery approaches. Our group recently developed electrochemically self formed microbatteries to address such challenges. This approach, when successfully applied, allows an unparalleled ability to form cells in appropriate dimensions to fit specific MEMS applications. In addition, such an approach greatly simplifies cell fabrication by containing fewer components along with allowing construction in a large array of dimensions. Traditionally, LiI has been used in primary cells for biomedical applications, such as pacemaker batteries, which are known to have long life spans, >10 years, competitive volumetric energy density, and little self discharge. These important characteristics of LiI batteries make LiI an ideal candidate for a micro secondary battery and to our knowledge; this is the first study using LiI in a secondary battery. The self formed batteries discussed here begin with a homogenous lithium iodide polymer composite which electrolytically forms the cell’s anode and cathode in-situ. An important factor in a self formed secondary battery is the development of a stable sold electrolyte interphase (SEI). Two methods for forming a stable SEI have been performed by our group. By either engineering the starting composite, or altering current collector material, we are able to form stable SEI layers that allow for the elimination of shorts and improved cycling. A new interdigitated cell design will be introduced that demonstrates the flexibility of this self assembled system along with enabling the in-situ visual and spectroscopic inspection of a cell as a function of cell formation and cycling.


KK9.2
Abstract Withdrawn


KK9.3
Thermoresponsive Microcapsules for Autonomic Lithium-ion Battery Shutdown. Marta Baginska1, Benjamin J. Blaiszik2,4, Ryan J. Merriman1, Susan A. Odom3,4, Wei Wang5, Zhengcheng Zhang5, Khalil Amine5, Jeffrey S. Moore3,4, Nancy R. Sottos2,4 and Scott R. White1,4; 1Department of Aerospace Engineering, University of Illinois Urbana-Champaign, Champaign, Illinois; 2Department of Materials Science, University of Illinois Urbana-Champaign, Champaign, Illinois; 3Department of Chemistry, University of Illinois Urbana-Champaign, Champaign, Illinois; 4Beckman Institute for Advanced Science and Technology, Champaign, Illinois; 5Argonne National Laboratory, Argonne, Illinois.

Lithium-ion batteries are used in a variety of applications ranging from consumer electronics such as cellular phones and computers to hybrid vehicles. However, safety remains an important issue when lithium ion batteries undergo external heating, over-charging, high current charging, or physical damage. Lithium-ion batteries must be safe and damage tolerant for full market penetration. Functionalization of battery electrodes with thermoresponsive microcapsules is proposed as a fail-safe mechanism for autonomic shutdown of unsafely operating lithium-ion batteries. The proposed concept can be achieved by either of two approaches. In one approach, battery electrodes are functionalized with monomer-filled microcapsules that can be triggered to rupture within a desired temperature range and deliver a thermally polymerizable core to the electrode surface. This release and polymerization may prevent ionic conductivity by forming an ionically insulating polymer film, thus, shutting down the battery cell. In the second approach, the electrode is coated with capsules that undergo a phase transformation (melt) at a predetermined temperature, coating the electrodes with a non-conductive barrier. Capsules containing thermally polymerizable monomers or phase transformation materials must satisfy a rigorous set of requirements for autonomic shutdown including (1) long term stability in the electrochemical environments typical for lithium-ion batteries, (2) survival of battery processing conditions, and (3) thermal triggering of capsules in the target temperature range. Initial work on the selection and microencapsulation of thermally polymerizable monomers, design of thermally triggered microcapsules and encapsulation of phase transformation materials for thermal shutdown is described.


KK9.4
Influence of Catalysts on Electro-oxidation Activity of Lithium Oxide and Peroxide for Lithium-air Batteries. Jonathon R. Harding1, Yi-Chun Lu2, Yasuhiro Tsukada3, Hubert A. Gasteiger4 and Yang Shao-Horn2,3; 1Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts; 2Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts; 3Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts; 4Department Chemie, Technische Universität München, Garching, Germany.

Lithium-air batteries can potentially provide ~3 times the energy density of current lithium-ion batteries. However, the round-trip efficiency of lithium-air batteries is very low, which is limited primarily by the oxygen evolution reaction (OER). Our recent work has shown that Pt/C is very active in promoting OER kinetics relative to Au/C and C, giving rise to one of the lowest reported charging voltages of Li-O2 cells to date. As these catalysts may influence the composition of discharge products (relative fractions of Li2O2 and Li2O), we here examine the activity of Pt/C, Au/C and C toward electro-oxidation of Li2O2 and Li2O. We have found that C can catalyze Li2O2 reasonably well but is inactive towards Li2O at voltages below 4.5 VLi. We compare the activity of Pt/C and Au/C to C towards these two reactions. Such a study allows us to discuss the physical origin of high Pt/C OER activity.


KK9.5
Detecting Li-ion Currents on the Nanoscale. Nina Balke1, Stephen Jesse1, Yoongu Kim2, Leslie A. Adamczyk2, Nancy J. Dudney2 and Sergei V. Kalinin1; 1Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, Tennessee; 2Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.

The development of the capability for probing ion transport on the nanometer scale is a key challenge for development of energy storage and generation systems including Li-ion batteries, and can potentially unravel complex interplay between structure, functionality, and performance in these systems. However, the existing electrochemical methods invariably utilize slow and large scale ion electrodes, limiting these studies to ~10 micron scale, well above the characteristic size of grains and sub-granular defects. Consequently, the nanoscale mechanisms underpinning Li-ion battery functionality remain unexplored, precluding developing strategies for improvement of energy and power densities and life times of these devices. Here we demonstrate the Scanning Probe Microscopy approach for mapping ionic current in Li-ion batteries. The high frequency periodic bias is applied between the cathode and anode of Li-ion battery, and the Scanning Probe Microscopy tip acts as a probe of local periodic strains generated due to Li-ion redistribution and associated changes in molar volume of material. A slower voltage sweep is used to induce Li ion redistribution on the length scale of the probe, providing optimal conditions for high-resolution imaging. Using the band excitation method, the quantitative cross-talk free imaging is demonstrated. The lithium diffusivity is mapped on a level of a single grain-boundary like defect in Si-anode material. The evolution of Li activity during fade-out process is observed and correlated with macroscopic measurements. Finally, the bias-dependence of response is used to explore the critical bias required for the onset of electrochemical transformation, potentially allowing to deconvolute reaction and diffusion processes. This material is based upon work supported as part of the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number ERKCC61 (Y.K., S.J., L.A., N.D., S.V.K.). N.B. acknowledges the Alexander von Humboldt foundation for financial support.


KK9.6
Hollow Nanostructures for Lithium Ion Battery Application. Bonil Koo1, Elena V. Shevchenko1, Tijana Rajh1,2 and Christopher S. Johnson2; 1Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois; 2Chemical Sciences and Engineering, Argonne National Laboratory, Argonne, Illinois.

We explored the hollow geometry of nanoparticles for the lithium ion battery application. Cobalt oxide (CoxOy) and iron oxide (FexOy) were chosen as models of anode material for lithium ion battery. Nano-sized electrode materials provide large surface area, short diffusion length, and high tolerance against volume expansion during lithium displacement reaction. In addition to that, the hollow particles have polycrystalline nature of the shell, which also enhances lithium ion reaction. We synthesized the hollow nanoparticles by nanoscale Kirkendall effect[1,2] and controlled the oxidation state, leading different metal core sizes. We will report systematic study on the effect of shell thickness of hollow nanocrystals on the battery efficiency. We optimized the concentration of organic ligands at the surface of nanocrystals by multiple washing and plasma cleaning in order to achieve connectivity and uniformity of nanoparticle films that serve as anodes. The battery electrodes were prepared by simply dropcasting the particle solution onto a substrate (e.g. Ti foil) without commonly used binder and carbon. The nanocrystal battery electrodes were assembled into coin cells with lithium as the counter electrode for half cell measurement. The measured capacity was ~400 mAh/g (normalized by total weight of 5nm/2nm Co core/CoxOy shell nanoparticles) after ten cycles, which was approximately three times higher than commercial cobalt oxide power sample.[3] Moreover, the capability between discharge and charge was stabilized after the first cycle. Also, we present detailed characterizations of hollow structures using transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). 1. Puntes, V. F.; Krishnan, K. M.; Alivisatos, A. P. Science 2001, 291, 2115. 2. Yin, y.; Rioux, R. M.; Erdonmez, C. K.; Hughes, S.; Somorjai, G. A.; Alivisatos, A. P. Science 2004, 304, 711. 3. Nam, K. T.; Kim, D.-W.; Yoo, P. J.; Chiang, C.-Y.; Meethong, N.; Hammond, P. T.; Chiang, Y.-M.; Belcher, A. M. Science 2006, 312, 885.


KK9.7
Abstract Withdrawn


KK9.8
Plasma-enhanced Metalorganic Chemical Vapor Deposition of Lipon Thin films. Lamartine Meda, Chemistry, Xavier University of LA, New Orleans, Louisiana.

Lithium phosphorus oxynitride (Lipon) thin films have been deposited by a plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD) method. When Lipon thin films were deposited on 1600 Å thick Au coated alumina substrate in a N2-H2 plasma at 150 watts and at 180 C using triethyl phosphate [(CH2CH3)3PO4] and lithium tert-butoxide [(LiOC(CH3)3] precursors, growth rates were between 100 and 415 Å/min, and thicknesses ranged from 1 to 2.5 mm. X-ray powder diffraction showed that the films were amorphous, and X-ray photoelectron spectroscopy revealed approximately 4.8 at.% carbon in the films. The ionic conductivity of Lipon was measured using AC impedance spectroscopy and approximately 1.02 mS/cm was obtained, which is consistent with the ionic conductivity of Lipon deposited by radio frequency magnetron sputtering of L3PO4 targets. An all-solid-state thin-film lithium battery such as Li/Lipon/LiCoO2/Au/substrate was successfully fabricated with Lipon deposited by PE-MOCVD, for which a capacity of ca. 20 mAh/cm2mm was measured. Carbon impurities had minimal effect on the ionic conductivity.


KK9.9
Abstract Withdrawn


KK9.10
Li Storage in Nano-graphene Platelets and Their Composites. Sree Cheekati1, Yun Xing2, Yan Zhuang2 and Hong Huang1; 1Mechanical and Materials Engineering, Wright State University, Dayton, Ohio; 2Electrical Engineering, Wright State University, Dayton, Ohio.

Improved lithium storage capacity, cycle life, and rate capability were reported in graphene-based nanomaterials for Li-ion batteries. Since mass-production of monolayer graphene is still challenging, one route to harness graphene’s outstanding properties for immediate applications can be based on Nano Graphene Platelets (NGPs). NGPs include monolayer as well as multi-layered graphene sheets, whose x and y dimensions are less than hundreds of nanometers and z dimension less than ten nms. NGPs can be achieved via exfoliation from graphite at low cost. We recently experimentally investigated lithium storage characteristics in different kinds of NGPs and their composites, which showed high lithium storage capacities. The pristine NGPs (less than 0.1 at % of oxygen)were fabricated via wet intercalation followed by thermal shock and high temperature reduction in H2, provided by Angstron Materials. The two pristine NGP specimens , i.e. NGP001 and NGP010 with average thicknesses of 1nm and 3nm, respectively, were investigated. Oxide NGP (NGP-O, containing over 1 at % of oxygen) was synthesized by traditional Hummers’ approach with no hydrazine reduction. The NGP-nano oxide composites were synthesized via either solid and liquid mixing approaches. The NGP electrode was used as the working electrode, LiPF6 -EC-EMC as the electrolyte, and Li foil as counter and reference electrode. Lithium storage characteristics were monitored on battery testing station at either galvanostatic or intermittent mode. AFM imaging indicated that the as-prepared pristine NGP specimens were the mixtures of monolayer and multilayer graphene nanosheets. Two different potential regions (5-200mV and 1.5-2.5V) were observed in the discharge/charge (d/c) profile with the pristine NGP as the working electrodes. The first discharge capacity of NGP 001 was 890 mAh/g and the first charge/ discharge columbic efficiency was 62%. NGP100 showed less charge/discharge capacities realtive to NGP001. In the d/c profile with the NGP-O electrode no potential plateau was observed. Large portion of the discharge capacity was generated at potential below 0.5V. In contrast, the charge potential increased rapidly to 1V and then gradually to the cut-off voltage 3.0V, which contributed to the major charge capacity. A high discharge and charge capacities of 1086mAh/g and 780mAh/g were achieved on NGP-O during the first cycle. The capacities stabilized around 750mAh/g in the following d/c cycles with no significant loss. The NGP specimen in compositing with nano Fe2O3, Co3O4, and Mn3O4 were also investigated. The reversible capacities were in the range of 500 and 800mAh/g. Composites prepared via the liquid approach exhibited higher capacities and better cycleabilities.


KK9.11
Understanding the Mechanism of TiSi2 Nanonet Lithiation Process. Sa Zhou and Dunwei Wang; Chemistry, Boston College, Chestnut Hill, Massachusetts.

In lithium ion batteries silicides powders have been widely used as an inert, conducting matrix. Nanostructured silicides are far less studied, particularly as active components to participate in the lithiation and and delithiation processes. Fox example, bulk TiSi2 was demonstrated to have negligible reaction with lithium, low dimensional nanostructured TiSi2 exhibit different behaviors. TiSi2, a webbed nanowire structure developed by us, can be lithiated at 90 ~ 0 mV. In this presentation, we employ impedance spectroscopy (EIS) to study the ac response at different charge/discharge states. TEM and EDS analyses show only Si component in the silicide react with lithium. Distinct features are revealed by the EIS measurement to distinguish this novel material. The results indicate the formation of TiSix/Si interface once Si is lithiated. Charge transfer across this interface experiences low impedance, facilitating the charge/discharge processes and affording superb performance. We show that Si and Ti play different roles in this process. To the best of our knowledge, we are the first time to use nanostructured TiSi2 as an active component in lithium ion battery. This is also the first time a detailed understanding of the lithiation mechanism of anisotropic silicide nanostructures. Given the intensity of interest in using nanostructures to innovate electrochemical energy storage, we are confident this study will contribute significantly to the community.


KK9.12
Abstract Withdrawn


KK9.13
Characterization of LiFePO4 Synthesized via a Solid State Method Starting with Precipitated Amorphous FePO4. Karen Galoustov1, Dean MacNeil1 and Dominic Ryan2; 1Chemistry, Université de Montreal, Montreal, Quebec, Canada; 2Physics, McGill University, Montreal, Quebec, Canada.

Lithium ion batteries play an important role in various portable electronic devices. Many different cathode materials have been shown to provide good electrochemical performance. Among them, lithium iron phosphate (LiFePO4) has additional advantages such as thermal stability, nontoxicity and environmental friendliness. In this work, synthesis of amorphous iron phosphate (a-FePO4) through a precipitation route [1], along with a solid state reaction involving lithium hydroxide and ascorbic acid in order to obtain LiFePO4 was evaluated and characterized. SEM analysis on a-FePO4 demonstrates homogeneous spherical particles ranging from 100 to 200 nm in diameter. The mixture of lithium hydroxide, a-FePO4 and ascorbic acid was analyzed using Mössbauer spectroscopy before the thermal treatment and the data suggests the presence of only Fe3+ species. When the mixture was heated to 350 °C under a N2 atmosphere, the Mössbauer analysis demonstrated a significant presence of Fe2+ in addition to a weak presence of Fe3+ species. The X-ray diffraction pattern of the sample that was heated to 350 °C suggests a poorly crystallized product. From the obtained data, it seems that an amorphous Fe2+ species was synthesized. Additional characterization using FTIR Photoacoustic spectroscopy along with electrochemical analysis on the synthesized products will be presented. [1] S. Scaccia, M. Carewska, P. Wisniewski Prosini P.P., Materials Research Bulletin 38 (2003) 1155


KK9.14
On the Electrochemical Properties of α-Li3FeF6 Prepared by Precipitation from Aqueous Solution.Anna Basa2, Elena Gonzalo1, Alois Kuhn1 and Flaviano Garcia-Alvarado1; 1Department of Chemistry, Universidad San Pablo CEU, Boadilla del Monte, Madrid, Spain; 2Faculty of Chemistry, University of Bialystok, Bialystok, Poland.

We have recently reported on the electrochemical lithium insertion properties of new potential positive electrode materials in the Li-Fe-F system: the α- and β polymorph of cryolite-like Li3FeF6 [1,2] . Performances of both forms regarding capacity and capacity loss upon cycling seem to be quite similar, provided that they are processed by mechanical milling with carbon to enhance electronic conductivity of the composite and to reduce particle size of the fluoride. However, α- Li3FeF6 was presented as an advantageous material, in as much as it can be prepared by precipitation from aqueous solution. The procedure is easy scalable, although an additional milling process with carbon is necessary after the precipitation step. Recently, we have known about a modified method by precipitation with ethanol [3]. However, in that work no further details were given whether the conditions used produced crystals suitable for lithium insertion without being reduced in size by long milling process. We have carried out a systematic study of the influence of the precipitating media on the particle size and its distribution in the as prepared α-Li3FeF6. Water soluble alcohols with different polarities have been used to modify the mixed solvent media. In particular, 50:50 mixtures of water and alcohol have been used with the main result being the preparation of crystals with particle sizes of approximately 200 nm by using 2-propanol. Although these crystals are not much smaller than those obtained from pure water as the solvent (250-400 nm), the particle size distribution is very narrow. Besides, different ratios of water and organic component have been also used for the precipitation of the fluoride. In this case, we have observed that high content of the organic component in the mixture produces a broader particle size distribution, but a large number of crystals with sizes below 100 nm can be found. In any case, we have not obtained yet an improvement in the electrochemical performance of the as prepared material. Mechanical milling with carbon seems to be still needed to enhance lithium insertion. We are presently investigating other organic components for the mixed solvent media aiming to obtain particle sizes below 50 nm. References. [1] E. Gonzalo, A. Kuhn, F. Garcia-Alvarado, Journal of Power Sources 195 (2010) 4990-4996. [2] E. Gonzalo, A. Kuhn, F. García-Alvarado, Journal of the Electrochemical Society In press (2010). [3] I. D. Gocheva, Y. Kamimura, T. Doi, S. Okada, J. Yamaki, T. Nishida, Engineering Sciences Reports, Kyushu University 31 (2009) 7-11.


KK9.15
Advanced Nanocomposite of Carbon-sulfur Cathodes for Lithium Batteries. Guang He, Xiulei Ji and Linda Nazar; Chemistry, University of Waterloo, Waterloo, Ontario, Canada.

Lithium sulfur battery is considered as a promising candidate for next generation of electronic vehicles because of its extremely high energy capacity (2500 Wh/kg)[1] and low cost of element sulfur. However, although it has been investigated for decades, there are still some obstacles affecting its practical application, such as the cycling stability, especially at high discharge rate. In this work, we reported on a novel nanocomposite of carbon-sulfur cathodes which significantly promotes the cyclability of the lithium batteries. Ordered mesoporous carbon 46* was prepared following the previously literature[2] with a little modification. This carbon has bimodal pore sizes (2.2 nm and 5.6 nm), high specific surface area (2300 cm2/g) and large pore volume (2.0 cm3/g). The 46*/S nanocomposite and corresponding cathodes were accomplished by melt-diffusion and slurry-cast strategies[3], respectively. The electrochemistry performance was evaluated using coin cell fabrication at room temperature. The initial discharge capacity of the battery is 995 mAh/g at 1C (1.68 A/g of the current density) rate. After 100 cycles, the battery retains a capacity of 550 mAh/g, which is 55.3% of the initial capacity. Even at a higher rate 2C (3.34 A/g of the current density), the initial capacity is as high as 939 mAh/g and is kept to 400 mAh/g after 100 cycles. The excellent performance of the sulfur cathodes might be attributed to the existence of small pores (2.2 nm in diameter) in the bimodal mesoporous carbon which helps to suppress the diffusion of polysulfides species to the anodes. References [1] Peramunage, D.; Licht, S. Science, 1993, 261, 1029. [2] Liu, R.L.; Shi, Y.F.; Zhao, D.Y. et al. J. Am. Chem. Soc., 2006, 128, 11652. [3] Ji, X.L.; Lee, K.T.; Nazar, L. Nature Materials, 2009, 8, 500. [4] Mikhaylik, Y. V.; Akridge, J.R. J. Electrochem. Soc., 2004, 151, A1969.


KK9.16
Abstract Withdrawn


KK9.17
Silicon/Carbon Nanofiber Composites for Li-ion Battery Anodes. Maryam Nazri1, David J. Burton1, Jane Y. Howe2, Harry M. Meyer III2, Patrick D. Lake1, Andrew Palmer1, Gholam-Abbas Nazri3 and Max L. Lake1; 1Applied Sciences, Inc., Cedarville, Ohio; 2Oak Ridge National Laboratory, Oak Ridge, Tennessee; 3General Motors Research, Warren, Michigan.

Silicon is an attractive anode material for Li-ion batteries because it has the highest known theoretical charge capacity at 4,200 mAh/g. To take advantage of both silicon’s high capacity and carbon’s high conductivity, efforts have been made to use silicon/carbon composite particles for use as anode material. A structurally more superior design is to develop silicon-coated hollow carbon nanofibers (CNF) as the anode material for Li-ion batteries. A stable, high-performance Li-ion battery anode has been developed by incorporating nano-scale silicon-based materials on and within low-cost CNF. The as-produced CNF are hollow with an outer diameter of 80-180 nm, and an inner diameter of 20-65 nm. Using electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, it was found that the Si/CNF composites have amorphous silicon coatings on both internal and external surfaces of the hollow CNF. Capacities in excess of 1000 mAh/g for 20 cycles and 500 mAh/g for 50 cycles (half-cell configuration) and near 1000 mAh/g (full cell configuration) have been achieved. The retention efficiency of these anodes has been measured in excess of 99.5% efficiency.


KK9.18
Nano-size Effect on the Insertion Process into Rutile-type Structure Materials: RuO2 and VO2. David Munoz-Rojas1,2, Montserrat Casas-Cabanas1 and Emmanuel Baudrin1; 1LRCS, Amiens, France; 2University of Cambridge, Cambridge, United Kingdom.

The recent introduction of nanostructuring and electrode nanoengineering in the field of Li Batteries has shown that materials that had traditionally been discarded as possible electrodes due to i) their low conductivity or ii) having unfavourable structures, can indeed present very interesting reactivities when used at the nanoscale. [1,2] Such is the case of oxides having the rutile type structure, such as TiO2, MnO2, VO2 and RuO2, which as bulk present very low reactivity vs Li. Contrarily, when scaled down to the nanoscale, the same oxides show a significant improvement in terms of capacity and cyclability. [3-5] Here we present a study of the electrochemical activity towards lithium of VO2 and RuO2 samples having different crystallite size and compare them to their bulk counterparts.[6-8] The samples have been synthesized using a hydrothermal reaction followed by successive annealing. In the case of VO2, we have tested for the first time the reactivity of the hydrous precursor, namely VO2.xH2O, which reaches capacities of over 200 mA.h/g. The capacity obtained depends on the oxide morphology, which in turn is a function of the temperature used during the hydrothermal synthesis of the precursor. After annealing of this precursor at 300 and 340 C, nanometric rutile type VO2 was obtained and it showed a huge increase in capacitance against Li as compared with a commercial bulk VO2.[6] In the case of RuO2, our results show that capacity increases when lowering particle size, while cyclability is on the other hand compromised due to parasitic reactions, which are enhanced by the higher surface area of the smaller samples. In addition, a careful pattern matching of XRD patterns taken in situ during Li intercalation and deintercalation showed that the same three phases are always involved during reaction, yielding a triphasic mechanism. The undavoidale presence of the intermediate phase LixRuO2 is due to the large lattice mismatch between the two end members. Also, particle size has a big impact in the miscibility gap of the different phases and thus, the solid solution domain tends to increase with decrease in particle size. [7, 8] References [1] Poizot, P.; Laruelle, S.; Grugeon, S.; Dupont, L.; Tarascon, J-M., Nature 407 (2000) 496-499. [2] Armand, M.; Gauthier, M.; Magnan, J-F.; Ravet, N. WO 02/27823 Patent, 2002. [3] Tarascon, J-M.; Armand, M., Nature 414 (2001) 359-367. [4] Binotto, G.; Larcher, D.; Prakash, A.S.; Herrera-Urbina, R.; Hegde, M.S.; Tarascon, J-M., Chem.Mater 19 (2007) 3032-3040. [5] Baudrin, E.; Cassaignon, S.; Koelsch, M.; Jolivet, J-P.; Dupont, L.;. Tarascon, J-M., Electrochem. Commun. 9 (2007) 337-342. [6] Muñoz-Rojas, D.; Baudrin, E., Solid State Ionics 178 (2007) 1268-1273. [7] Muñoz-Rojas, D.; Casas-Cabanas, M.; Baudrin, E., Solid State Ionics 180 (2009) 308-313. [8] Muñoz-Rojas, D.; Casas-Cabanas, M.; Baudrin, E., Solid State Ionics 181 (2010) 536-544.


KK9.19
Low Temperature Structural and Vibrational Studies of Mixed Carbonate Based Electrolyte s for Lithium Batteries. Nicholas Pieczonka and Gholam-Abbas Nazri; Electrochemical Energy Research Lab, GM Global R&D Center, Warren, Michigan.

A major challenge for the wide spread adoption of electric vehicles is their performance at below zero temperatures. The performance of lithium ion batteries in particular at low temperatures strongly depends on the behavior of the electrolytic solution used. Common electrolytes components such as mixed carbonate solvents containing lithium salt transition to a solid phase below -10 C. To achieve the necessary requirements of the electrolyte, various blends of solvents are used to achieve tolerable performance at low temperatures. In practice electrolytic solution contain anywhere from 2 or more different carbonated based solvents with LiPF6 as the salt. These multi-component mixtures present complex interactions that may affect the behavior of the individual components at low temperatures. To better understand the structures and phases present at low temperatures, in situ XRD and Raman spectroscopy are used to investigate the low temperature behavior of a set of carbonate solvent based electrolytic solutions.


KK9.20
High Rate Performance of Lithium Manganese Nitride and Oxynitride as Negative Electrodes in Lithium Batteries. Jordi Cabana1,2,4, Costana M. Ionica-Bousquet4,5, Clare P. Grey2,3 and M. Rosa Palacin4; 1Lawrence Berkeley National Laboratory, Berkeley, California; 2Department of Chemistry, Stony Brook University, Stony Brook, New York; 3Department of Chemistry, University of Cambridge, Cambridge, United Kingdom; 4Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Barcelona, Spain; 5AIME-ICG, Université Montpellier II, Montpellier, France.

Almost 20 years after the commercialization of Li-ion batteries, graphite (theoretical capacity: 372 mAh/g) remains the most widespread negative electrode material. Efforts are currently underway to find alternatives that show either higher energy density, such as silicon (3572 mAh/g), or higher power density, such as Li4Ti5O12 (175 mAh/g). The latter also offers the benefit of enhanced safety derived from its activity at potentials (ca. 1.5 V vs. Li+/Li0) that remove the danger of lithium plating at high current densities. Lithium transition metal nitrides and oxynitrides have been reported to show interesting performance, making them candidates for the negative electrode. Among them, antifluorite-type Li7MnN4 and Li7.9MnN3.2O1.6 show specific gravimetric capacities in excess of 300 mAh/g with excellent retention, most likely due to the small volume changes undergone during lithium extraction/insertion. Interestingly, significant lithium mobility through their framework was proven to exist even at room temperature and be enhanced as lithium is removed from the structure, presumably due to the formation of Li vacancies. In view of these observations and the excellent cycling behavior at moderate rates (0.1C), we decided to investigate the response of Li7MnN4 and Li7.9MnN3.2O1.6 at higher rates, and compare them to a benchmark high rate compound such as Li4Ti5O12. Capacities of 180 and 230 mAh/g were obtained after 50 cycles at 1C rate for the oxynitride and the nitride, respectively, values that compare well with Li4Ti5O12. Quite surprisingly, the rate at which the first charge is performed has an effect on the subsequent cycling; enhanced properties are found if the cycling is preceded by one charge at 0.1C instead of the target rate. If a first “conditioning” charge is carried out at C/10, great performance is observed for Li7.9MnN3.2O1.6 and Li7MnN4 at remarkably high rates (5C), with capacities of 120-135 mAh/g after 100 cycles. These results compare favorably with those obtained for Li4Ti5O12. The origins of this intriguing phenomenon were studied by 6Li MAS-NMR.


KK9.21
Polymer-based Cathode Material for Energy Delivery and Storage. (Undergraduate Research) David Pan1, Shuhuai Xiang2, Randall Babaoye1, and Jennifer Lu1;School of Engineering, University of California, Merced, Merced, California; School of Natural Sciences, University of California, Merced, Merced, California.

There is a growing demand for light-weight, high power, reliable electricity delivery and storage media for portable devices, medical implants and electric tractions. The conventional lithium battery cathode contains layered or spinel metal oxide which degrades rapidly over time from cycled ion intercalation. We are developing a new cathode material system where redox centers are in the form of ions, distributed in a conductive polymer network for improved charge/discharge rate, enhanced reliability, and superior stability.

The ratio of polymer to metal redox center is analyzed by TGA and XPS. Morphology characterization of electrode is imaged by SEM and TEM. Cyclic voltammetry characterization for electrochemical performance of polymer electrode with different metal condition and load will be presented. A comparative study of ion composition on specific capacity and charge/discharge rate will be presented. The effect of the polymer matrix properties with regards to electrical conductivity, thermal conductivity, and mechanical integrity on performance will be discussed. The optimized matrix for maximum performance will be introduced.

 


KK9.22

Encapsulation of Conductive Particles for Restoration of Electrical Interfaces. Sen Kang1,2, Benjamin J. Blaiszik1,2, Susan A. Odom2,3, Scott R. White2,4, Jeffrey S. Moore2,3 and Nancy R. Sottos1,2; 1Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois; 2Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois; 3Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois; 4Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois.

Restoration of electrical conductivity has potential to increase the reliability and safety of high performance batteries. In Li-ion batteries, silicon (Si) anodes undergo enormous volume expansion and contraction upon lithium insertion and extraction. Continued cycling results in cracking or pulverization of the Si, and ultimately destruction of the conductive network. New anode designs currently focus on accommodating the volume change through changes in the material architecture, e.g. via incorporation of Si nanoparticles and nanowires. Here, we consider an alternate approach to increase cycle lifetimes and reliability through restoration of anode conductivity. Recent investigations have demonstrated the ability to restore electrical conductivity of thin metal films through the use of microencapsulated components that form a conductive network when released [1,2]. Successful translation of this microencapsulated approach to the extreme environment of a Li-ion battery anode presents significant challenges. In this study, we report on the encapsulation of several types of conductive particles and the integration of these capsules into commercially available anode materials. Microcapsules are prepared by the encapsulation of solvent via the formation of a cross-linked polymer shell by in situ emulsion polymerization, and soluble microspheres are prepared by a solvent evaporation method. A variety of liquid cores, polymer shells, conductive particles, and polymer binders are investigated. We identify promising encapsulated systems based on the ability to survive anode fabrication and coin cell assembly. Preliminary tests are also performed to investigate conductivity restoration outside of the battery environment. 1. Odom, S. A.; Caruso, M. M.; Finke, A. D.; Prokup, A. M.; Ritchey, J. A.; Leonard, J. H.; White, S. R.; Sottos, N. R.; Moore, J. S. Adv. Funct. Mater. 2010, 20, 1721-1727. 2. Caruso, M. M.; Schelkopf, S. R.; Jackson, A. C.; Landry, A. M. Braun, P. V.; Moore, J. S. J. Mater. Chem. 2009, 19, 6093-6096.


KK9.23
Abstract Withdrawn


KK9.24
Discharge-power and Reliability Characteristics of Organic Radical Battery Composed of Nitroxyl Radical Cathode and Carbon Anode. Shigeyuki Iwasa, Motoharu Yasui, Takanori Nishi, Kentaro Nakahara, Masahiro Suguro and Kaichiro Nakano; Green Innovation Research Laboratories, NEC Corporation, Tsukuba, Ibaraki, Japan.

The organic radical battery (ORB) is a new class of rechargeable battery that utilizes charge storable plastics. The battery charges and discharges by the redox of stable radical plastics such as nitroxyl radical polymers. We had proposed the concept of the ORB in 2001[1,2], and then have reported the fundamental performance of the battery with nitroxyl radical polymer/carbon composite cathode. These studies showed that the ORB with poly (2,2,6,6-tetramethylpiperidinoxyl-4-yl methacrylate) (PTMA)/carbon composite cathode can discharge with a high current [3]. However, the high current discharge capability was degraded with a high PTMA content (approximately >70%) in the cathode. To find a way to prevent the degradation, we improved the dispersion state of carbon, which is used as a conducting additive, in the composite cathode and obtained a large contact surface between the PTMA and the carbon. The ORB with a composite electrode with uniformly dispersed carbon showed extremely high current discharge capability (>100 mA per one square centimeter of an electrode area at one second discharging). The ORB with the improved PTMA/carbon composite electrode showed six times higher power per electrode area than an ORB with the composite electrode. In this battery carbon was dispersed around PTMA powders that were several tens of microns in diameter. The ORB showed 10 kW/L of the power density and 70 Wh/L of the energy density (estimated without Al-laminate package volume). We also evaluated the pulse-discharge stability of the ORB with PTMA/carbon composite cathode. The pulse-discharge stability was measured after repeating the discharging at 100 mA for 1 second and charging every 1 minute. The discharge capacity and the cell resistance were unchanged through repeating the discharge and charge 10000 times. Acknowledgments This work was partially supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. References [1] K. Nakahara, S. Iwasa, M. Satoh, J. Iriyama, Y. Morioka, M. Suguro, and E. Hasegawa, The 42nd Battery Symposium in Japan, 1A21, 124-125 (2001). [2] K. Nakahara, S. Iwasa, M. Satoh, Y. Morioka, J. Iriyama, M. Suguro, and E. Hasegawa, Chem. Phys. Lett., 359, 351-354 (2002). [3] K. Nakahara, J. Iriyama, S. Iwasa, M. Suguro, M. Satoh and E. J. Cairns, J. Power Sources, 165, 870-873 (2007).


KK9.25
Freeze Dried α-Fe2O3 Nanoparticles as Conversion Anode for Li-ion Batteries. Amaia Iturrondobeitia1, Veronica Palomares1, Aintzane Goni1, Izaskun Gil de Muro1, Iratxe de Meatza2, Oscar Miguel2, Miguel Bengoechea2 and Teofilo Rojo1,3; 1Dpto. de Química Inorgánica, Universidad del País Vasco UPV/EHU, Bilbao, Spain; 2Energy Department, CIDETEC-IK4, San Sebastián, Spain; 3CIC Energigune, Miñano, Alava, Spain.

Transition metal binary oxides stand out among the potential candidates for anode components in the new generation Li-ion batteries. These compounds react reversibly with Li via a conversion reaction in which the formed metallic nanoparticles get dispersed in Li2O. α-Fe2O3 is extensively studied in this field, by the great number of possible nanostructures (nanorods, nanospheres, nanotubes…). Nanostructuring this phase has accounted for significant enhancement in electrochemical properties versus a Li anode. In this work, freeze-drying method was used to prepare a nanosized α-Fe2O3 sample. The as prepared material was characterized by powder X-ray diffraction, Transmission Electron Microscopy (TEM), cyclic voltammetry and galvanostatic cycling. X-ray diffractogram was indexed as single-phase α-Fe2O3 (JCPDS 89-0599). TEM micrographs showed that material comprised 20-25 nm size globular particles that formed bigger aggregates, of about 800 nm size. Microdiffraction measurements performed on the TEM microscope confirmed that nanoparticles were made of α-Fe2O3 phase. Electrochemical tests were made vs. Li/Li+ electrode on Swagelok cells. Cyclic voltammetry tests showed electrochemical activity at 0.8 and 1.7 V when reducing and oxidizing, respectively. Galvanostatic cycling at C/20 rate exhibited an initial specific capacity of 1732 mAh/g that stabilized on the second cycle at 1300 mAh/g. Coulombic efficiency evolved from 71% in the first discharge/charge cycle to 94% in the subsequent ones. Thus, freeze-drying method has proven to be a valid method for the synthesis of α-Fe2O3 nanoparticles with application as conversion anodes in Li-ion batteries.


KK9.26
NMR Study of the Interaction of LiMn2O4 with an Aqueous Electrolyte. Dino Tonti, Isabel Sobrados, Jose Manuel Amarilla and Jesus Sanz; Inst. Ciencia de Materiales Madrid (ICMM CSIC), Madrid, Spain.

A strategy to improve the electrode kinetics in lithium batteries is to make use smaller particles of active material so that diffusion lengths are shortened and surface area is increased. This approach has the advantage of improving the performance of already known materials, however the extended electrode/electrolyte interface increases the organic electrolyte decomposition, passivating the electrode and slowering its kinetics. To avoid this, we have previously shown that using macro-mesoporous LiMn2O4 in an aqueous electrolyte it is possible to obtain high rate capability and excellent stability [1]. In this study, we further characterize the LiMn2O4-aqueous electrolyte interface by NMR, and prove that even in this case due to the ionic exchange, new surface species form. NMR is able to provide valuable information on the lithium environment in the whole electrode-electrolyte system, allowing the identification of processes in the electrode bulk, at the interface or in the electrolyte bulk. In order to separately detect Li in the solid and in solution, we used commercial micrometric 7LiMn2O4particles and solutions of 6LiOH in water. When a small quantity of electrolyte is added to the LiMn2O4 powder, its static Li signal presents two components: one sharp, centered at a few tens ppm positive chemical shift from the reference, and the other broad, at about 100 ppm of negative chemical shift. We interpret this effect as the result of the interaction of the paramagnetic LiMn2O4 with the magnetic field of the spectrometer, and attribute the broad and the sharp component respectively to lithium in proximity of the solid or in the bulk of the electrolyte. Remarkably the electrolyte only shows one unperturbed sharp component when added to a diamagnetic lithium conductor such as Li4Ti5O12. In a Magic Angle Spinning (MAS) NMR experiment after washing and drying the LiMn2O4 powder, a new Li component appeared at slightly negative shift, with a large number of spinning sidebands. As also recently shown by Dupré et al. [2] this signal originates outside the material, since lithium in the usual crystalline tetrahedral position gives a signal at about 500 ppm. However, a strong magnetic coupling with the material is proven by the spinning sidebands. This species can be attributed to lithium located at the surface after ionic exchange with surface protons. It indicates that in the static experiment more complex magnetic interactions affect the electrode electrolyte system. < p> 1. Tonti, M. Torralvo, E. Enciso, I. Sobrados, Sanz, Chem. Mater., 20, 4783 (2008). 2. N. Dupre, J.-F. Martin, D. Guyomard, A. Yamada, and R. Kanno, J. Mater. Chem., 18, 4266 (2008).


KK9.27
Synthesis and Characterization of the Composite La0.50Li0.50TiO3/PANI for Application in Lithium Batteries. Silvia L. Fernandes1, Gisele Gasparotto1, Maria A. Zaghete1, Alejandra H. Gonzalez2 and Jose A. Varela1; 1Department of Biochemistry and Biotechnology, UNESP, Araraquara, SP, Brazil; 2Department of Chemistry, UNESP, Bauru, SP, Brazil.

Li ion-conducting materials have been widely studied in the last few years because of their potential applications as solid electrolytes in high energy batteries and other electrochemical devices [1]. The perovskite-type lithium lanthanum titanate, La2/3-xLi3xTiO3, is well known to be a high lithium ionic conductor having bulk conductivity of 10-3 Scm-1 at room temperature for x = 0.10 [2]. Despite this high conductivity, the use of ceramic materials as electrodes has been limited by their brittle nature, which spurred the research for the formation the hybrid materials by mixing between the ceramics and flexible materials as the organic conductors [3]. The polyaniline has been the polymeric conductor most studied in recent years. So, this research presents the synthesis of lithium lanthanum titanate (La0.50Li0.50TiO3) powder by polymeric precursor method. Also, it is discussed the synthesis of La0,50Li0,50TiO3/polyaniline composite in order to obtain electrochemical properties compatible for application in rechargeable lithium batteries. The crystallization of phases and the structural characterization were evaluated by XRD. Powder morphology was analyzed by SEM-FEG. Electrochemically, powder and composite were characterized by chronopotentiometry technique. To define with accuracy the temperature that begins the crystallization process, La0.50Li0.50TiO3 powders were heated between 350°C and 800°C for 3h. XRD patterns indicated the evolution of the crystallization process with increase in calcination temperature, indicating a correlation between the process of phase crystallization and organic fraction elimination. The images obtained by SEM-FEG have shown the size of the particles as well as the interaction between powders and polyaniline. The electrochemistry study was performed by means a Swagelok cell configuration using a La0.50Li0.50TiO3 pellet as cathode, a mixture of lithium perchlorate, ethylene carbonate and dimethyl carbonate as a liquid electrolyte, and lithium as anode material. Another cell was prepared using a composite pellet as cathode. Charge-discharge curves revealed that deintercalation and intercalation processes of lithium ions are not fully reversible in the La0.50Li0.50TiO3 structure. On the other hand, the La0.50Li0.50TiO3/PANI composite demonstrated total reversibility of this process, even when are used higher conditions of current. It is evident, therefore, the best effort of the electrochemical cell when used the La0.50Li0.50TiO3/PANI composite as material for the cathode. References [1]A. Várez, M. L. Sanjuán, M. A. Laguna, J. I. Peña, J. Sánz, de La Fuente, G. F.Journal of Materials Chemistry, v.11, p.125-130, 2001. [2] Y. Inaguma, C. Liquan, M. Itoh, T. Nakamura, T. Uchida, H. Ikuta and M. Wakihara. Solid State Communications, 86 (1993) 689 [3] H. Kawaoka, M. Hibino, H. Z. Hou, I. Honma, Journal of Power Sources, v.125, p. 85-89, 2004.


KK9.28
Coating Positive Electrode Materials on Recycled Carbon Fibers for Lithium Battery Application. Surendra Martha, Jagjit Nanda, Jim Kiggans, Wallace Porter, Hsin Wang, Fred Baker and Nancy Dudney; Materials Science and Technology, Oak Ridge National Lab, Oak Ridge, Tennessee.

In this work, we demonstrate a new framework for building Li-ion battery cathodes by using conductive LiFePO4 coated on PAN based recycled loose carbon fibers. Unlike the carbon nanofibers or nanotube based approach, we coat nanometer sized positive electrode active materials on micron thick carbon fibers. This electrode fabrication approach eliminates the use of organic binders and Al-foil current collector thereby increasing the energy density. Details regarding the coating procedure, characterization and approach for maximizing the energy density through multiple coating processes shall be discussed. The electrochemical stability (rate capabilities, cycleability) of the electrodes has been studied in two and three electrode coin and pouch cells. We also present the thermal properties such as heat capacity, conductivity and stability of these cathodes in EC-DMC/LiPF6 electrolyte solution. We shall compare the electrochemical and thermal properties of these cathodes in relation to lithium rich high voltage and high capacity Li1+xNi0.5Mn0.3Co0.2O cathodes fabricated using the conventional binder based slurry procedure that could be operated as high as 4.6 V in Li-ion cells. Acknowledgement This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy.


KK9.29
NMR Studies on Ionic Liquids for Advanced Li-ion Batteries. Sufia Khatun1, Steve Greenbaum1, Phill Stallworth1, Paul Sideris1 and Maria Navarra2; 1Physics Department, Hunter College, New York, New York; 2Chemistry, Sapienza University of Rome, Rome, Italy.

In route to achieving safer, more reliable lithium batteries with higher specific energy, the use of liquid electrolytes must be addressed. Research on Ionic liquids (ILs) is growing exponentially as they have several desirable properties for an electrolyte, such as high thermal stability, low vapor pressure, and high conductivity [1]. To provide the electroactive species for the cell reactions, a proper lithium salt is dissolved in the IL. This creates a variety of ion-ion interaction phenomena, which need to be characterized and understood. For instance, it is found in some cases that IL/lithium salt mixtures have increased viscosity and reduced ionic conductivity with respect to the pure IL. Current research reported here is for Py24TFSI (N-n-butyl-N-ethylpyrrolidinium N,N-bis(trifluoromethanesulfonyl)imide), as this ionic liquid displays improved cathodic stability over conventional electrolytes, without a reduction in its ionic conductivity [2]. Py24TFSI is currently being explored as main component in polymer electrolyte membranes for safe and reliable battery applications [3]. In order to characterize ion transport in these systems, we have used the NMR pulsed field gradient technique to obtain self-diffusion coefficients and spin-lattice relaxation times of both gel-type and liquid electrolytes based on Py24TFSI. References: 1. M. Armand, F. Endres, D.F. MacFarlane, H. Ohno, B. Scrosati, Nature Materials, 8 (2009) 621 2. A. Fernicola, F. Croce, B. Scrosati, T. Watanabe, H. Ohno, J. Power Sources, 174 (2007) 342 3. S. Sirisopanaporn, A. Fernicola, B. Scrosati, J. Power Sources, 186 (2009) 490


KK9.30
Development of a Ceramic Based Internal PTCR Device for Battery Safety Applications. Teyeb Ould-Ely1, Krisztian Niesz1, Joshua Stone2, Ng S. Migo2, Ryo Tamaki2, Hisashi Tsukamoto2 and Daniel E. Morse1; 1ICB-UCSB, Santa Barbara, California; 2Quallion LLC, Sylmar/Los Angeles, California.

With the current expanding market for lithium ion batteries, safety issues are increasingly coming under the spotlight. Hazards are posed by the use of combustible organic electrolytes and the threats of thermal runaway resulting from internal short circuits or external environmental or operational factors. A major challenge for Li-ion battery chemistry (in addition to storing more energy while maintaining stable electrode-electrolyte interfaces) is the ability to detect and interdict thermal runaway as soon as an incipient short circuit occurs. A number of safety approaches have been developed (such as gas release valves, fuses and external thermistors). Although these approaches have improved safety, because thermal runaway is an internal phenomenon, these external protective measures are not very efficient. We are investigating the possibility of incorporating an internal PTCR (positive thermal coeffcient of resistivity) device within Li-ion batteries. Our approach is based on the strong PTCR of a fine-grained, lanthanum-doped BaTiO3 ceramic obtained from 6 nm BaTiO3 nanocrystals produced by a room temperature, bioinspired scalable process. We will present the challenges and advantages encountered in integrating an internal PTCR layer into Li-ion batteries. We also will highlight the low-temperature catalytic synthesis and scale-up of BaTiO3 nanocrystals used as precursor, and the conditions of sintering used to produce the desired ceramic.


KK9.31
Solid State NMR Studies of Electrochemically Discharged CFx. Sohan R. De Silva1, Rafael Vazquez1, Guo Rui2, Hong Gan2, Joe Lehnes2, Barry C. Muffoletto2, Phillip E. Stallworth1 and Steve Greenbaum1; 1Physics, Hunter College of The City University of New York, Manhattan, New York; 2Greatbatch, Incorporated, Clarence, New York.

The lithium/carbon monoflouride (Li/CFx) battery was one of the first lithium/solid cathode systems used commercially1 (typically x = 1 for commercial grade batteries) having the highest theoretical energy2 among solid cathode systems. Three types of CFx (F - Fiber based, C - Pertrolum coke based, G - Graphite based) have demonstrated different electrochemical performances. In practice, upon electrical discharge, lithium oxidizes while producing elemental carbon and LiF which precipitates on the remaining CFx structure3. Although the fundamental process is known, the small scale structure of CFx during discharge and the mechanism of defluorination is not completely understood. 21 different sample (7 of each type: F, C and G) batteries were discharged at seven different discharging levels at Greatbatch laboratories. Extracted samples were investigated by 13C and 19F MAS (Magic Angle Spinning) NMR to identify the atomic/molecular structural level factors among the different types of CFx. Differences of covalent F and LiF were noted in each step of discharge. NMR results reveal distinct differences with the F based CFx samples over C and G types. 1. D. Linden and T. B Reddy, Handbook of Batteries, 3rd ed., Chap. 14, McGraw-Hills, New York (2001). 2. Ganesan Nagasubramanian, Bryan Sanchez, A new chemical approach to improving discharge capacity of Li/(CFx)n cells, Journal of Power Sources 1645 630-634 (2007). 3. N. D. Leifer, V. S. Johnson, R. Ben-Ari, H. Gan, J. M. Lehnes, R. Guo, W. Lu, B. C. Muffoletto, T. Reddy, P. E. Stallworth and S. G. Greenbaum, Solid-state NMR studies of chemically lithiated CFx, Journal of the Electrochemical Society 157 (2010)


KK9.32
Enhanced Electrochemical Stability of the Electrolytes for High-voltage Lithium Battery by Hydrophobic Clay as Electrolyte Additive. Ting-Ju Yeh, Jin-Ming Chen, Shih-Chieh Liao and Yen-Po Chang; Materials and Chemical Engineering, Industrial Technology Research Institute, Hsinchu, Taiwan.

The organic clay, CPC-MMT, was prepared by the ionic exchange reaction of montmorillonite (MMT) with cetylpyridinium chloride (CPC), and was used as electrolyte additive of Li/MCMB cells. The addition of CPC-MMT not only improved the compatibility of the electrolytes towards lithium anodes but also enhanced the formation of solid electrolyte interphase film to protect lithium anodes from corrosion. According to the study results, linear sweep voltammograms (LSV) of CPC-MMT based electrolyte shows an onset oxidation voltage of 5.9 V, which is higher than the neat electrolyte significantly. Electrochemical impedance spectroscopy disclosed that the addition of CPC-MMT enhanced Li-ion diffusion and depressed interfacial resistance slightly. Moreover, charge-discharge cycling test of CPC-MMT based electrolyte indicated better capacity retention.


KK9.33
First Principles Study on Local Structure of LiNiO2, LiNi1-xCoxO2 and LiNi1-yMnyO2. Hung-Ru Chen, Colin Freeman, John Harding and Anthony R. West; Department of Engineering Materials, University of Sheffield, Sheffield, United Kingdom.

LiNiO2 is considered as a potential material for rechargeable lithium ion batteries. Despite the enormous amount of effort directed towards this compound, the ground state properties and local structure of LiNiO2 remain unclear. Low spin Ni3+(t2g6eg1), a strong Jahn-Teller ion, is the commonly accepted picture. Unlike NaNiO2 and LiMnO2, however, no monoclinic distortion has been observed in LiNiO2. Nevertheless, different Ni-O bond lengths have been observed which implies the existence of local Jahn-Teller distortion[1]. Previous work suggests that the hole states induced by the substitution of lithium ions in nickel oxide systems go to the oxygen ions[2]. In that case the nickel ions should be divalent. However, ab initio calculations on LiNiO2 suggest the formation of Ni3+ ions [3]. In order to improve electrochemical properties, cobalt and manganese doped LiNiO2 has been intensively studied. However, most of the previous studies have only focused on the performance of the material as a cathode and no detailed investigation has been made on the influence of cobalt and manganese. We have studied LiNiO2 by first principle density functional theory calculations. Our results show that in order to lower the energy of orbital degeneracy of Ni3+, both charge disproportionation and Jahn-Teller distortion occur in LiNiO2 at the same time. Therefore the valence state of nickel in LiNiO2 is a mixture of 2+, 3+ and 4+ with a possible ordering. Also from a systematic study on different concentration of cobalt and manganese doped LiNiO2, the effects of cobalt and manganese dopants on crystal structure and electronic structure are discussed.


KK9.34
Effect of Crystalline Structure of Silicon on Its Anode Characteristics for Lithium-ion Secondary Battery. Shota Tsukagoshi1, Hideyuki Takahashi1, Yoshinori Sato1, Ryuichi Kasahara2, Hiro Takahashi2, Jiro Iriyama3, Tetsuya Kajita3, Tatsuji Numata3, Koji Utsugi3, Akira Kishimoto4 and Kazuyuki Tohji1; 1Graduated school of Environmental studies, Tohoku University, Sendai, Japan; 2NEC Tokin Co.,Ltd, Sagamihara, Japan; 3NEC Co.,Ltd, Sagamihara, Japan; 4Nittetsu Co.,Ltd, Tokyo, Japan.

Lithium-ion secondary battery (LIB) is widely used in electric manufacturing fields, because of its high performances such as high energy density. Their energy densities have increased by approximately 10% every year. However, to utilizing the LIB as the energy source and/or reservoir of electric vehicle (EV), drastically improvement of LIB performances should be required. It is theoretically expected that the use of silicon anode material, alternated to carbon anode materials, lead the greatly improvement of LIB properties, such as charge-discharge efficiency and discharge capacity. However, it is also well known that silicon anode material was destructed and deactivated by the repeat of volume changes during charge-discharge process. Thus, it can be considered that restriction of silicon material’s destruction process read the enhancement of life time of LIB using the silicon anode. These destructions were considered to originate from the destruction of silicon crystal phase. Therefore, in this study, the relationship between the properties, such as size and also phase, of silicon crystal and performances of the silicon anode materials was investigated. The effect of protective layer was also studied. Crystalline Si powder was treated by high energy ball milling as the function of treatment time, treatment ball size, revolution rate. Treated powder was analyzed by XRD, HR-TEM, SEM-EDX, BET, and electric properties measurement process. From the results of XRD measurements, only the peaks of silicon crystal (PDF#27-1402) were observed from every sample. Crystalline diameter calculated from FWMH (full width at half maximum) of main peak and Scherrer low was 15.1 nm(1h), 9.3 nm(3h) and 8.0nm(10h), respectively. Thus, crystalline diameter from XRD profiles became smaller with increasing treatment time. On the other hand, particle size calculated from the results of BET surface area measurement (12.8m2/g) was estimated to 203 nm, while that from particle size distribution measurement was 287 nm. These particle sizes from BET and size distribution measurement was almost the same in each condition, thus it was independent to the variation of treatment time. Therefore, it is supposed that treated silicon particles had the aggregate or agglomerate form, because of increased surface energy during the mechanochemical treatment. Raman spectroscopy measurement demonstrated that amorphous part was existed in treated silicon. Charge-discharge measurements of treated powder clearly indicated that high charge capacity had maintained, which was 1.5 times higher than that of un-treated silicon. Moreover, charge-discharge efficiency of treated silicon anode was about 97%, which was about twice as high as that of un-treated one. Thus, it can be said that decreasing the crystalline structure of silicon materials lead increasing the efficiency of the anode performance of LIB.


KK9.35
A Novel Vapor Phase Route to Cobalt Oxide Nanomaterials as Lithium Battery Negative Electrodes. Davide Barreca1, Manuel Cruz-Yusta2, Alberto Gasparotto3, Chiara Maccato3, Julian Morales2, Andrea Pozza3, Cinzia Sada4, Luis Sanchez2 and Eugenio Tondello3; 1Department of Chemistry - Padova University, CNR-ISTM and INSTM, Padova, Italy; 2Departamento de Química Inorgánica e Ingeniería Química, Universidad de Córdoba, Córdoba, Spain; 3Department of Chemistry, Padova University and INSTM, Padova, Italy; 4Department of Physics and CNISM, Padova University, Padova, Italy.

Among 3d transition metal oxide nanosystems, cobalt oxides (CoO and Co3O4) have received a considerable attention as anode materials for Li-ion batteries with attractive electrochemical performances. In spite of this widespread interest, a major drawback for their technological utilization is the modest capacity retention, which is still far from meeting the actual technological requests. On this basis, an open challenge is the development of alternative synthetic routes to cobalt oxide nanomaterials, enabling the simultaneous control of their phase composition and morphology and the exploitation of their applicative potential. This contribution presents an innovative procedure for the preparation of cobalt oxide nanoelectrodes supported on Ti substrates, whose key advantage is the absence of ancillary materials (e.g. binders, conductors) commonly used in electrode preparation. The target systems were grown by Chemical Vapor deposition (CVD) from a novel precursor, Co(hfa)2.TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate, TMEDA = N,N,N’,N’-tetramethylethylenediamine), and characterized by Glancing Incidence X-ray Diffraction (GIXRD), Secondary Ion Mass Spectrometry (SIMS), Field Emission-Scanning Electron Microscopy (FE-SEM), and Atomic Force Microscopy (AFM). A suitable selection of the growth temperature and reaction atmosphere enabled to control both the phase composition (CoO vs. Co3O4) and the morphology of the resulting nanosystems, key issues to obtain improved functional performances as Li-cell anodes. The electrochemical reaction with Li+ ions was studied in the potential window 3.0-0.0 V, revealing a fast lithium storage process. High coulombic efficiencies and capacity retention upon cycling were observed for electrodes characterized by lower-sized particles and a higher surface roughness, enabling a shorter Li+ path length. Remarkably, the capacity recovery was the highest ever obtained up to date for nano-electrodes assembled without the use of ancillary materials. The present results candidate the proposed synthetic strategy as a valuable mean for the tailored synthesis of oxide nanoelectrodes endowed with improved functional performances.


KK9.36
Synthesis and Assembly of Colloidal Carbon Spheres and Ge Nanocrystal Modification. Christopher A. Barrett1, Robert D. Gunning1,2, Edric Gill1, Catriona O'Sullivan1, Hugh Geaney1, Ajay Singh1,2, Emma Mullane1, Dervla Kelly1 and Kevin M. Ryan1,2; 1Chemical and Environmental Sciences and Materials and Surface Science Institute, University of Limerick, Limerick, Ireland; 2SFI-Strategic Research Cluster in Solar Energy Research, University of Limerick, Limerick, Ireland.

Nanostructured-carbon composite anode arrays are sought to attribute higher interfacial contact area with electrolyte and generate superior electrical contact between nanocrystal and current collector. Here we show that colloidal carbon spheres of excellent monodispersity can be achieved by the thermolysis of a low-volatile solvent in supercritical carbon dioxide. The method utilizes the spontaneous formation of reverse micelles in a supercritical fluid subsequent to template-free carbonization. Growth control is achieved through pressure modulation and affords close packed carbon spheres of tailored diameters ranging from 300-1500 nm. Ge-C composites are subsequently formed by inducing the growth of 10-30 nm sized germanium nanocrystals from the spheres in a hierarchical bottom-up approach. Extensive characterisation of the spheres and nanocrystals was conducted with transmission and scanning electron microscopy coupled with the analytical techniques of X-ray diffraction Raman, energy-dispersive X-ray, and X-ray photoelectron spectroscopy.


KK9.37
Self-assembled Si Nanoparticle / Polymer Composites as Anode Materials for High Performance Li-ion Battery. Il Young Choi2,1 and Moon Jeong Park1,2; 1Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, Korea, Republic of; 2Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, Korea, Republic of.

Current rechargeable batteries deliver energy between 100 and 200 Wh/kg. For an anode material in Li-ion battery, graphite has been employed due to its good charge/discharge cycle properties and reasonable theoretical energy capacity of 372mAh/g. However, to meet increasing demand for high-energy-density batteries the investigation of new anode materials is essential. For example, the development of safe, rechargeable batteries with a specific energy of 550 Wh/kg will enable the operation of electric cars. Silicon is an attractive candidate for new anode materials due to its high specific energy capacity (~4200mAh/g). Theoretical designs of batteries that could deliver as much as 2500 Wh/kg, however, it has been known that repeated expansion and contraction of Si during charge/discharge cycles results in cracking and capacity loss. In present study, we have created new anode materials with an aid of ion conducting polymers, coated on silicon nanoparticle (Si-NP) surfaces. Self-assembled composite anodes were created by casting solutions of polyethylene oxide coated Si-NPs / graphite / Li ions mixtures. By varying relative compositions of each component, we were able to control the spacings between functionalized Si-NPs with optimized electronic and ionic conductivity. The presence of ion conducting polymers significantly suppresses volume expansion of Si-NP upon insertion of lithium and helps in controlling over the transports of ions and electrons to the active centers in the anodes. The efficacy of the self-assembled anodes was examined by galvanostatic electrochemical test, which shows a reversible capacity of ca. 1700mAh/g. The morphological changes of self-assembled composite anodes during charge/discharge cycles were investigated by combining high resolution power diffraction and high resolution transmission electron microscopy equipped with energy dispersive x-ray spectroscopy.


KK9.38
Abstract Withdrawn


KK9.39
Li-Ion Battery Material Studies by Thermal Analysis. Peter J. Ralbovsky, Robert Campbell and Ilir Beta; Netzsch Instruments, Burlington, Massachusetts.

Li-ion technology is the growth leader for portable power storage from cell phone to vehicle (HEV & PHEV) use. Performance and safety requirements drives the material research. Thermal analysis can be useful in determining key attributes of single materials or combination of the materials. These analysis techniques often times need to be modified so that samples can be prepared and tested in an environment free from air and water. Recently we have been working on developing instruments and methods to tailored specifically to these applications. Basic thermal properties of battery materials such as heat capacity and thermal conductivity are needed to understand how heat energy will be dissipated in the battery cell. Layers of solid materials in a liquid phase, which is normally consists in cells, can be technically challenging. We have developed a new method which allows these multiple layer samples to be prepared and tested in a controlled environment. Calorimetry is useful to look at material properties, such as melting points, but is also important to screen for unwanted chemical reactions. Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) coupled together or separately can be used effectively to look at thermal stability of individual materials. In particular TGA coupled with evolved gas analysis can be a key tool for looking at cathode stability. Measuring the thermal stability of multiple materials, for instance such as the cathode with the electrolyte, normally requires larger sample sizes to get more repeatable results. Scanning and adiabatic calorimeters have been used successfully to do this type of work. The addition of Evolved Gas Analysis (EGA) can also play an important role to determine the formation of trace compounds, such as HF, which can reduce cell life and performance. A summary of results will be provided using the different techniques and methods described.


KK9.40
Li Motion Mechanisms in (Li,Na)3xLa2/3-xTiO3 (x = 0.067 and 0.167) Series Followed by ND, NMR and Impedance Spectroscopy. Alejandro Varez1, Alberto Rivera2, Wilmer Bucheli3, Ricardo Jimenez3, Dino Tonti3 and Jesus Sanz3; 1Materials Science and Engineering, Universidad Carlos III de Madrid, Leganes, Spain; 2Fisica Aplicada III, Universidad Complutense de Madrid, Madrid, Spain; 3Instituto Ciencia de Materiales-CSIC, Madrid, Spain.

The dependence of Li mobility on structure and composition of the Li0.5-xNaxLa0.5TiO3 (0 ≤ x < 0.5) and Li0.2-xNaxLa0.6TiO3 (0 ≤ x < 0.2) perovskite series, has been investigated by means of Neutron Diffraction (ND), Nuclear Magnetic Resonance (NMR) and Impedance Spectroscopy (IS). In the first series, samples display rhombohedral unit cells (√2 ap, √2 ap, 2√3 ap; S.G. R-3c), but in the second series unit cells are orthorhombic (2 ap, 2 ap, 2 ap; S.G. Cmmm). These two solid solutions correspond to the end members of the Li ion conductors La2/3-xLi3xTiO3, in which Li has been replaced by Na in order to study percolation mechanisms. The replacement of Li by Na does not modify structural features of perovskites. Both solid solutions display tilted perovkiste networks with different tilting scheme and different La vacancy distribution. In the case of the Li0.5-xNaxLa0.5TiO3, La vacancies and Na are randomly distributed on the A-site (disordered phase), while in the case of Li0.2-xNaxLa0.6TiO3, cation vacancy are preferentially located in alternating layers along the c-axis (ordered phase). Li ions are shifted from A sites and fourfold coordinated at unit cell faces of the single cubic perovskite(1). By heating, symmetry of different samples changes as a consequence of tilting elimination: in Li-rich samples, cubic phases are formed while in Li-poor samples, tetragonal phases are detected. Along the transitions, no changes were detected in the La-vacancy distribution in two analyzed series. Na ions occupy vacant A-sites, and for a particular value of lithium (x=0.2 Li0.5-xNaxLa0.5TiO3 and x=0.07 Li0.2-xNaxLa0.6TiO3)conductivity drops several orders of magnitude(2,3). These facts are discussed in terms of three and two-dimensional percolation models for Li-cation diffusion. In disordered and ordered series, Li conducting samples displays a non-Arrhenius conductivity behavior, decreasing activation energy during heating between 77-500 K, from 0.4 to 0.25 eV in disordered samples and from 0.37 to 0.14 eV in ordered samples. Li motion mechanisms has been analyzed by NMR spectroscopy. The structural sites occupancy has been deduced from the analysis of ND and 7Li and 23Na MAS-NMR spectra, the local Li mobility has been deduced from NMR spin-lattice data, and long-range motions from electric, NMR line-width and diffusion coefficients(4). Changes detected on activation energy values have been related to the elimination of octahedral tiltings. The temperature dependence of B factors has been correlated to elimination of square window distortions. Finally, Li sites occupancy and more probable diffusion paths have been investigated at increasint temperature with Fourier Map difference techniques in two analyzed series. References [1]J.A. Alonso et al., Angew. Chem. Int. Ed. 39 (2000) 619. [2]Y. Inaguma et al, Solid State Ionics, 86-88 (1996) 257. [3]A. Rivera et al., Chem. Mater. 14 (2002) 5148. [4]R. Jimenez et al, Solid State Ionics, 180 (2009) 1362-1371.


KK9.41
Energetics and Stability of Fe1-yMnyPO4. Gene M. Nolis, Joel K. Miller, Natasha A. Chernova, Shailesh Upreti and M. Stanley Whittingham; Materials Science and Engineering, SUNY Binghamton University, Nichols, New York.

Commercialized electrode materials must demonstrate the ability to maintain their chemical structure over the course of hundreds of charge/discharge cycles and range of climate conditions. Although the olivine phosphates o-LixFe1-yMnyPO4 are used in rechargeable battery systems, the thermodynamics and stability data for their delithiated forms is scarce and contradictory. o-FePO4 is stable in air up to 620°C, while o-MnPO4 is reported to decompose above 210°C with oxygen release. The stability of intermediate compositions is not known. In addition to the olivine phase, FePO4 exists in trigonal (t-FePO4), monoclinic and orthorhombic Pbca phases; upon heating, the monoclinic and both orthorhombic phases transform to t-FePO4. Theoretical calculations confirm that the t-FePO4 is more stable than o-FePO4. However, calorimetry data obtained by the Navrotsky group suggests that o-FePO4 is more thermodynamically stable at 25°C, by approximately 1%. The low percentage difference alludes the importance of having pure phase oxides, because even small amounts of impurities or structural defects could render the results inaccurate. In this work we have synthesized o-LiFe1-yMnyPO4 by hydrothermal and solid state methods and performed chemical delithiation using NO2BF4 or Br2 in acetonitrile to obtain o-Fe1-yMnyPO4. The products are characterized by powder x-ray diffraction (PXRD), thermogravimetric analysis, and magnetic susceptibility. Their thermal stability is being studied by various-temperature PXRD and differential scanning calorimetry. This research is supported as part of the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under Award Number DE-SC0001294.


KK9.42
Phase-field Modelling of Lithium Intercalation in LixCoO2. Shunsuke Yamakawa1, Toshiyuki Koyama2, Taichi Abe3, Hisatsugu Yamasaki4, Hiroshi Suzuki4 and Shi-Aki Hyodo1; 1Toyota Central R&D Labs., Inc., Nagakute, Aichi, Japan; 2Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya Institute of Technology, Nagoya, Aichi, Japan; 3Particle Simulation and Thermodynamics Group, Computational Materials Science Center, National Institute for Materials Science, Tsukuba, Ibaraki, Japan; 4Toyota Motor Corporation, Susono, Shizuoka, Japan.

Transition metal oxides are widely used as the active material for the positive electrode of Li-ion rechargeable batteries. Because the amount of electrical power generated by the batteries is constrained by the transport of Li, the Li intercalation in the metal oxide is a fundamental phenomenon that determines the performance of the batteries. The intercalation/deintercalation process is significantly affected by the phase transition, crystal anisotropy, and grain boundaries. Therefore, in order to improve the batteries, we believe that a thorough understanding of the intercalation/deintercalation process on the nanometer length scale is essential. To provide an insight into the relationship between the factors that influence the intercalation/deintercalation process and the dynamics of Li intercalation in LixCoO2, we constructed a phase-field model describing the diffusion of Li and the phase changes in LixCoO2; this model was based on the formulation of thermodynamic energy functions. Specifically, the thermodynamic parameters in the Gibbs energy functions of the individual phases in the LixCoO2 system were assessed, and a two-sublattice model was adopted for the Li-vacancy ordered phase. The Butler-Volmer equation was incorporated into this model to describe the charge-transfer reaction occurring across the LixCoO2-electrolyte interface. In order to determine the accuracy of the phase-field model, we used it to estimate the thermodynamic factor of Li, which is defined as the ratio of the chemical diffusion coefficient to the self-diffusion coefficient. The simulation results represented the change in the thermodynamic factor, which includes the effect of order/disorder phase transition, effectively. This result implies that the phase-field model provides a reasonable time evolution of the Li concentration profile influenced by phase transition. We also used the phase-field model to study the dynamics of Li intercalation in polycrystalline LiCoO2 thin films. The simulation results demonstrated that the influence of the grain boundary on the charge/discharge property was affected by other microstructural characteristics such as the crystallographic texture and crystallite size.


KK9.43
Electrochemistry, Structure and Stability of the Sodium Olivine Na/FePO4 System. Joel Gaubicher, Philippe Moreau, Marine Cuisinier, Dominique Guyomard and Florent Boucher; Institut des Materiaux Jean Rouxel, Nantes, France.

Numerous publications exist concerning LiFePO4, especially with regard to its remarkable electrochemical storage properties. Aside from research in the field of phosphate based water treatments for high pressure steam generators, NaFePO4, the chemical equivalent with sodium, has not been as extensively explored. The typical NaFePO4 maricite phase seems to be the thermodynamically favored phase since it is obtained at high temperature or in hydrothermal conditions. The maricite phase, however, presents one-dimensional, edge-sharing FeO6 octahedrons and no cationic channels, contrary to the olivine LiFePO4. An olivine-based NaFePO4 phase would therefore be particularly interesting in order to study its electrochemical properties, especially in the context of the renewed interest for sodium batteries. Sodium intercalated samples were synthesized electrochemically using a positive electrode made with a mixture of 70% FePO4 (olivine) and 30% carbon black (Ketjen). FePO4 was obtained from LiFePO4, by chemical oxidation in acetonitrile using NO2BF4. The complete sodiation of the FePO4 olivine is obtained and is reversible. Theoretical calculations also allowed to determine the theoretical potential of a hypothetical plateau between FePO4 and NaFePO4 versus Na/Na+. The obtained value, 2.92 V, is in good accordance with the average potential of the plateaus experimentally observed at 2.85 V. We note that with respect to a Li/Li+ reference electrode (3.15 V), this value is substantially lower than that expected from the Li/FePO4 system (3.45V). Unlike the Li/FePO4 system, a discontinuity in the potential-composition curve occurs in the vicinity of x = 0.65 both on discharge and on charge. As inferred from electrochemical, Mossbauer and XRD studies, this discontinuity corresponds to two biphasic processes involving FePO4, Na0.7FePO4 and NaFePO4. Resolution of the NaFePO4 olivine structure, along with that of the intermediate Na0.7FePO4 phase, obtained during the charge of a sodium battery will be described. Both ab initio calculations, as well as thermal analyses relative to these phase stability will be reported.


KK9.44
Vanadium Substitution at Different Sites of LiFePO4. Fredrick Omenya, Shailesh Upreti, Natasha A. Chernova and Stanley M. Whittingham; Chemistry, Binghamton University, Binghamton, New York.

Lithium iron phosphate suffers from low electronic conductivity and low lithium ion diffusion. To overcome these challenges carbon coating, reducing the particle sizes to nano scale, and cation substitution have been used. The last results in improved rate capability when small amounts of various elements are incorporated; example include 5% of magnesium or vanadium in LiFePO4. However, in the case of vanadium, there is no conclusive evidence as to which site(s) the vanadium occupies in the LiFePO4 structure. To answer these questions we explore different synthesis methods: polyol, solid state and hydrothermal to substitute vanadium at iron, phosphorus, and lithium sites of LiFePO4 considering charge compensation either by Li or transition metal deficiency. This can give an insight on the most favorable substitution site, the optimal substitution that can be tolerated, the charge compensation mechanism and the effect of such substitutions on electrochemical performance. All the compounds were characterized by powder x-ray diffraction, x-ray absorption, Fourier transform infrared spectroscopy, thermogravimetric analysis, magnetic susceptibility, morphological, and electrochemical tests. Different synthesis methods show different optimal vanadium substitution with polyol giving the highest, up to 10%, of vanadium incorporated into the olivine structure without emergence of a second phase. Substitution at the phosphorus site results in the smallest lattice parameters as determined by the Rietveld refinement. Magnetic studies indicate that Fe or V may occupy Li sites in some of the compounds not intentionally substituted on the Li site. Fe-site substitution gives the best electrochemical result, with improved rate capabilities. This work is supported by the US Department of Energy, Office of FreedomCAR and Fuel Partnership through the BATT program at Lawrence Berkeley National Laboratory.


KK9.45
Amino Acid-assisted Hydrothermal Synthesis towards LiMnPO4. Qian Liu1, Michael Stark1 and Nicola K. Huesing1,2; 1Inorganic Chemistry, Ulm University, Ulm, Germany; 2Materials Chemistry, Paris Lodron University of Salzburg, Salzburg, Austria.

In the past decades, extremely flourishing worldwide markets of portable electronic devices, for instance cell phones, laptops, digital cameras, music/video-players, power tools and even electric vehicles (EVs), have stimulated the rapid development of electrical energy storage technologies. To meet the increasing demand for more efficient and clean energy, scientists and engineers are now devoting themselves to the investigation of lithium rechargeable batteries. This relatively new electrochemical system is outstanding due to the light weight and high energy densities, at the same time it is “memory effect” free and environmentally benign[1]. However, there are some problems that still need to be addressed. The present lithium ion batteries have several limitations: they are too expensive to be widely used; and their power densities need to be increased. Although lithium ion batteries have high energy densities, “the slow lithium diffusion in the active materials produces a large polarization at high charging-discharging rates” [2], thus results in a lower power density. Nanomaterials having a special morphology, high specific surface areas and thus, shorter lithium diffusion paths are under investigation at the moment. In the present work, nanocrystalline flake-like LiMnPO4 was successfully synthesized by a wet-chemical hydrothermal method under basic condition at a relatively low temperature which was 150 °C. Phosphate-based surfactants and amino acids were used as additives. Six typical amino acids, namely glycine, alanine, valine, aspartic acid, glutamic acid and tyrosine, were employed in the hydrothermal synthesis. The effects of different kinds of amino acids and different amino acid concentrations on the resulting LiMnPO4 nanocrystals will be discussed. The obtained materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform-infrared-attenuated total reflection (FT-IR-ATR) spectroscopy, nitrogen sorption and thermogravimetric-differential thermal analysis (TG-DTA). The data demonstrate that both additives have profound effects on controlling the nucleation and growth of LiMnPO4, resulting in nano-layered crystals with a specific surface area as high as 100 m2/g. [1] K. Padhi, K. S. Nanjundaswamy, J. B. Goodenough, J. Electrochem. Soc. 1997, 144, 1188 [2] C. Cai, Y. Wang, Materials 2009, 2, 1205-1238.


KK9.46
Growth and in-situ Studies of Single Crystal LiFePO4. Qiyin Lin1, Hong Zheng1, Yang Ren2, Mahaling Balasubramanian2 and John Mitchell1; 1Materials Science Division, Argonne National Lab, Argonne, Illinois; 2Advanced Photon Source, Argonne National Lab, Argonne, Illinois.

LiFePO4 (LFPO) is extensively investigated as a promising candidate of the positive cathode for the next generation of lithium ion batteries designed for transportation. However, most the studies have been carried out on poly-crystalline LFPO-based materials. Some controversies still exist regarding electrical transport properties, LFPO-FPO phase transitions, lithium ion diffusion behaviors for LFPO cathode materials, such as electrical conductivity, electronic bandgap, and dimensionality of Li+ conduction. Our approach to resolving these outstanding issues has been to explore well-characterized and controlled LFPO single crystals using synchrotron radiation probes. Here we report progress on growth of the single crystals LFPO by optical floating zone and a melt casting techniques. LFPO crystals have been characterized by various x-ray techniques including Synchrotron XRPD, XRSD, XRR and topography, and TGA/DSC. We also present some preliminary studies using as-grown LFPO single crystal as an electrode, with the objective of in-situ study the following issues: bulk Fe2+/Fe3+ redox reactions and Li+ intercalation/extraction phase transition, and surface properties such as electrode surface chemistry, structural/morphological evolution, and electrochemical properties, as a function of crystallographic orientation upon cycling.


KK9.47
Carbon Nanotube-confined MnO2 Composites as Electrode Materials for Lithium-ion Batteries. Wei Chen, Abirami Dhanabalan, Chunhui Chen and Chunlei Wang; Mechanical & Materials Engineering, Florida International University, Miami, Florida.

Manganese dioxide has been widely studied as electrode materials for rechargeable lithium-ion batteries (LIB) because of their high theoretical capacity, environmental friendliness, natural abundance and low cost. However, poor electrical conductivity of MnO2 limits it from use in high-performance LIB. In addition, another issue is its rapid capacity decay with cycling due to the large volume expansion during the lithium insertion/extraction process. Extensive efforts are devoted to overcome these problems by fabricating various structures or using electronically conductive additives. In this work, we are using carbon nanotube (CNT) confined MnO2 composite as electrode materials of lithium batteries. Profiting from the geometrical confinement of nanotube, the particle size of MnO2 nanoparticles remain stable, which is beneficial for the improvement of battery performance. As a result, the capacity of CNT-confined MnO2 composites increase about 30% and keep more stable compared to the samples with MnO2 outside CNTs. In addition, Electrochemical impedance spectroscopy is measured to analysize the lithium insertion/extraction behaviors in the MnO2 nanocrystalline. The studies will help us to understand the charge transfer kinetics and further optimize the electrochemical energy storage systems.


KK9.48
Influence of Nanoparticle Morphology in Combination with Various Conductive Carbon Coatings on Electrochemical Performance of LiMnPO4. Nicholas Pieczonka and Gholam-Abbas Nazri; Electrochemical Energy Research Lab, GM Global R&D Center, Warren, Michigan.

Lithium metal phosphates (phospho-olivines, LiMPO) have generated a great deal of interest as potential advanced Li-ion battery cathode materials due to their relative low cost, thermal stability and good electrochemical performance. To achieve the potential of this class of cathodes, a major disadvantage must be overcome, low intrinsic electronic and ionic conductivity. In particular, lithium manganese phosphate (LiMnPO4) which demonstrates an attractive redox potential of 4.1V (vs . Li/Li+) has a major drawback of extremely poor electronic conductivity (10-10 S/cm-1) and ionic conductivity. It has been demonstrated that use of nano-structured particles with preferred growth direction and the use of conductive carbon coatings can partially overcome these limitations. Looking to further improve on the performance of LiMnPO4 as a positive battery material we have explored the influence of synthesis parameters and the application of various carbon coating strategies on the performance of LiMnPO4 as an advance electrode material. Pure phase nano-structured LiMnPO4 was synthesized using a modified polyol process. The generated nano-particles size and morphology was strongly influenced by the conditions of the syntheses, which included temperature, amount of water present, and the concentration of precursors. Various carbon coating approaches were also employed and their relative effectiveness is also presented. The nano-structured LiMnPO4 and carbon coated LiMnPO4 ( C- LiMnPO4) were characterized with X-ray powder diffraction, Raman spectroscopy, TEM, and SEM in an attempt to establish a correlation between the electrochemical performance and the particle size, morphology and extent and type of carbon coating.


KK9.49
Electroactive Materials and Systems Development of Rechargeable Lithium-Carbon Batteries (LCB).Cheng Huang1, Xiaochuan Lu1, Royce Mathews1, Daiwon Choi1, John Lemmon1, Jun Liu1, Gordon Graff1, Ken Johnson1, Mike Rinker1 and John M. Miller2; 1Energy & Environment Directorate, Engineering Materials Group, Battelle, Pacific Northwest National Laboratory, Richland, Washington; 2Maxwell Technologies, Inc., San Diego, California.

Electrochemical energy storage properties of capacitors are inferior to batteries, but their specific power and efficiency are far greater, and cycle life is far longer. Using a hybrid approach may be the key for advanced electric energy storage applications. Individual Li ion cells and /or capacitors are connected together in series or parallel configurations to form modules, strings, and ultimately systems, combining the figures of merits of carbon ultracapacitors in multi kilo-farad ranges with the high energy densities of Li ion batteries. However, slight differences in individual cells can grow over time, leading to premature failure of the system. Expensive external circuitry sometimes is applied for capacitor/battery hybrid energy modules in an attempt to minimize this problem. The development of lithium-carbon batteries (LCB) could provide one of hybrid energy storage solutions for intrinsic cell balancing, without the use of external circuitry at the cell level, which gives lithium batteries a makeover by crossing them with ultracapacitors. We will talk about electroactive materials design and systems development for lithium-carbon batteries, including our innovative electrode materials design and manufacturing, membrane/electrolyte formulations, and cell/stack design, as well as lithium ion asymmetric supercapacitor in series and ultrabattery in parallel analysis for fast charging and long cycle life. While cost, safety and cycle life are still a concern for lithium batteries, lithium-carbon batteries share a mutual goal of dramatically improving the safety, durability, performance and price of advanced lithium ion batteries for electricity storage.


KK9.50
Coupled Electrochemical and Hydrodynamic Modelling for Flow Battery Design. Victor E. Brunini, W. Craig Carter and Yet-Ming Chiang; Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.

Redox flow battery performance was modelled by solving a system of PDEs that couple fluid flow, mass transport and electrochemical reactions. The model was applied to a variety of cell geometries with varying cell architectures and we show that performance can be improved by cell design. In particular we examine the use of current collectors designed to induce convective mixing in a laminar fluid flow and demonstrate that higher rates may be achieved when compared to standard cell geometries. This effect is explained by the increased transport of reactants to the current collectors.


KK9.51
Abstract Withdrawn


KK9.52
Highly Active Bifunctional Electrocatalysts for Li-air Batteries. Yi-Chun Lu1, Zhichuan Xu2,3, Hubert A. Gasteiger2,4, Shuo Chen2, Kimberly Hamad-Schifferli2,3 and Yang Shao-Horn1,2; 1Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts; 2Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts; 3Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts; 4Chemistry, Technische Universität München, Garching, Germany.

Lithium-air batteries have promise to reach over 3-fold greater energy density than lithium-ion batteries in the fully-packed cell level. During discharge of a lithium-air battery, oxygen is reduced by lithium ions to form lithium (per)oxides via: (1) 2Li+ + 2e- + O2 → (Li2O2)solid having Erev = 2.96 VLi and/or (2) 4Li+ + 4e- + O2 → 2(Li2O)solid having Erev = 2.91 VLi. Critical challenges that limit the practical use of this technology include the sluggish oxygen reduction reaction (ORR) (during discharge) and oxygen evolution reaction (OER) kinetics (during charging) in Li+- containing aprotic electrolytes. Therefore, it is vital to develop effective electrocatalysts to catalyze both ORR and OER, namely a bifunctional electrocatalyst. Our recent work has shown that Au exhibits high ORR activity and Pt exhibits high OER activity in 1 M LiClO4 PC:DME(1:2 v/v). In this study, we combine Au and Pt onto the surfaces of individual nanoparticles and examine the ORR and OER activity of such particles supported on carbon in Li-O2 cells. PtAu nanoparticles were synthesized by reducing HAuCl4 and H2PtCl6 in oleylamine and then loaded onto Vulcan carbon (XC-72) to yield 40 wt% PtAu/C. We show that PtAu/C exhibits bifunctional catalytic activity, where it is hypothesized that surface Au and Pt atoms are primarily responsible for ORR and OER kinetics in Li-O2 cells, respectively. To our knowledge, PtAu/C reported here demonstrates the lowest charging voltage and highest round-trip efficiency of Li-O2 cells reported to date. Ongoing work examines and compares the activity of other Pt alloy NPs with PtAu in Li-O2 cells, which details will be presented.


KK9.53
Abstract Withdrawn


KK9.54
Electrochemical and Structural Evaluation of the Effect of CNTs (Carbon Nanotubes) on Layered Oxide Cathodes. Chunmei Ban1, Zheng Li2, Zhuangchun Wu1, Yanfa Yan1, Yoon Seok Jung1, Melanie J. Kirkham3, Andrew Payzant3, Dane T. Gillaspie1, M. Stanley Whittingham2 and Anne C. Dillon1; 1Material Science Center, National Renewable Energy Laboratory, Golden, Colorado; 2Institute for Material Research, State University of New York at Binghamton, Binghamton, New York; 3High Temperature Materials Laboratory, Oak Ridge National Laboratory, Oak Ridge, Tennessee.

In order to reduce the cobalt content without loss of performance, layered oxide cathodes (LiNiyMnyCo1-2yO2) have been extensively studied. Although higher capacity can be obtained with higher Ni content, cobalt-less compound leads to structural and performance deterioration. Carbon surface coatings have been demonstrated to help durability because of increased conductivity and stabilized surface. Here we employ single-wall carbon nanotubes (SWNTs, 5-10%) in the electrode fabrication to ameliorate electrochemical performance of the LiNi0.4Mn0.4Co0.2O2 cathode material, which has been successfully applied to high-volume expansion anode materials (Adv. Mater. 22 (20) E145 2010). The composite electrodes show no degradation for one hundred cycles between 3.0 V and 4.2 V at various rates (0.1 C to 5 C); however, the intrinsic electrode without SWNTs rapidly loses most of its capacity even at low cycling rates. Furthermore, the composite electrode containing 10 wt.% of SWNTs exhibits a highly durable capacity of 120 mAh/g at 5 C rate for one hundred cycles. We found that not just the superior conductivity of SWNTs, but also the SWNT induced surface modification of the cathode material plays a role in the improved performance. Electrochemical, structural, and spectroscopic characterization have been used to probe the surface modification of the oxide particles, elucidating the effect of utilizing SWNTs on the electrochemical performance of layered oxide cathodes.


KK9.55
The Reversible Capacity of Cross-over Materials: Silver Vanadium Phosphorous Oxide, Ag2VO2PO4.Ruigang Zhang, Shailesh Upreti, Natasha A Chernova and M. Stanley Whittingham; Binghamton University, Binghamton, New York.

Several electrode materials display a mix of intercalation and conversion reactions, where for example lithium first intercalates with structure retention and then on further reaction the structure converts to a new structurally different phase. Silver and copper vanadium oxides are a special example of such reactions, wherein lithium is first intercalated into the structure with extrusion of the silver or copper; further lithiation results in reduction of the vanadium ions. Here we describe the reversible lithiation of the model compound Ag2VO2PO4, first reported by Takeuchi et al, with the goal of understanding the reaction mechanisms occurring. Electrochemical cycling of this phase shows 200 mAh/g capacity when discharged to 2.0 V and a reversible 180 mAh/g capacity when charged to 4.5 V. Ex-situ XRD at different stages of charge indicates the SVOP crystal structure fading and recovering during the discharge and charge process. Magnetic susceptibility and x-ray absorption explain the red-ox process of V and Ag ion at charge and discharge. The reversible mechanism is further studied by SEM, which indicates the morphology change during lithium ion insertion and removal. This research is supported as part of the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under Award Number DE-SC0001294.


KK9.56
Ionic Mobility in Nasicon-type LiMIV2(PO4)3 Materials Followed by 7Li NMR Spectroscopy. Jesus Sanz5, Isabel Sobrados2, Alois Kuhn3, Flaviano Garcia4 and Kamel Arbi1; 1Departamento de Energia, Instituto Ciencia de Materiales, CSIC, Cantoblanco, 28049 Madrid, Spain; 2Departamento de Energia, Instituto Ciencia de Materiales, CSIC, Cantoblanco, 28049 Madrid, Spain; 3Departamento de Quimica, Universidad San Pablo-CEU, Boadilla del Monte, 28668 Madrid, Spain; 4Departamento de Quimica, Universidad San Pablo-CEU, Boadilla del Monte, 28668 Madrid, Spain; 5Departamento de Energia, Instituto Ciencia de Materiales, CSIC, Cantoblanco, 28049 Madrid, Spain.

Among phosphates, NASICON type materials have been proposed as electrode and/or electrolyte for secondary lithium batteries(1). Lithium mobility in LiMIV2(PO4)3 compounds, with M= Ge, Ti, Sn, Zr and Hf, has been investigated by 7Li Nuclear Magnetic Resonance (NMR) spectroscopy in the temperature range 100-500 K. From the analysis of 7Li NMR quadrupole interactions (CQ and η parameters), the Li sites occupancy and exchange processes between structural sites have been analyzed(2). Below 250 K, Li ions are preferentially located at M1 sites in rhombohedral phases, but occupy M12 sites in triclinic ones. The superionic state can be achieved by large order-disorder transformations in rhombohedral phases, or by sharper first order transitions in triclinic ones. At increasing temperatures, Li mobility has been deduced from spin-spin T2-1 and spin-lattice T1-1 relaxation rates. In this analysis, the presence of two relaxation mechanisms has been associated with departures of conductivity from the Arrhenius behavior. In high-temperature phases, residence times at M1 and M12 sites become similar and correlation effects on Li motions decrease significantly . Results described in the LiTi2(PO4)3 sample have been compared with those obtained in the rhombohedral LiTi2-xZrx(PO4)3 and Li1+xTi2-xAlx(PO4)3 series, displaying lower and higher conductivities than the LiTi2(PO4)3 phase(3-5). In the case of the best ion conductor, Li1.2Ti1.2Al0.2(PO4)3, NMR results are compared with those obtained by Neutron diffraction (ND) and Impedance spectroscopy (IS). Diffusion coefficients determined by NMR pulse field gradient technique are similar to those estimated by impedance spectroscopy and NMR relaxation data. References (1).C. Delmas, A. Nadiri, J.L. Soubeyroux, Solid State Ionics 28-30 (1988) 419. (2).K. Arbi, M.A. Paris, J. Sanz, J. Phys. Chem. B, 110 (2006) 6454. (3).K. Arbi, M. Tabellout, M.G. Lazarraga, J.M. Rojo, J. Sanz, Phys. Rev. B, 72 (2005) 94302. (4).K. Arbi, M. Tabellout, J. Sanz, Solid State Ionics, 180, (2010) 1613. (5).M.A. Subramanian, R. Subramanian and A. Clearfield, Solid State Ionics 18&19 (1986) 562.


KK9.57
Progress Towards Using LiCoPO4 as Li-ion Battery Cathode. Jan L. Allen, Jeff Wolfenstine and T. Richard Jow; Electrochemistry Branch, U.S. Army Research Laboratory, Adelphi, Maryland.

LiCoPO4 is a promising cathode material owing to its high discharge voltage of around 4.8 V and its theoretical capacity of about 170 mAh/g.1. However, so far, it has been shown to suffer from a severe loss of discharge capacity upon multiple charge-discharge cycles. For example, Tadanga et al2. observed a 10th cycle discharge capacity of ~52% of the initial capacity, Bramnik et al.3 reported ~59% and Wolfenstine et al.4 reported ~53% capacity retention. This has been attributed to irreversible structural changes or amorphization of the charged, low-lithium content material and electrolyte degradation. This work will report improved capacity retention using substitutionally modified LiCoPO4 in conjunction with electrolyte additives that improve oxidative stability at high voltage. The results reported will include x-ray diffraction including Rietveld refinement, spectroscopic analysis and electrochemical measurements of cycle life and rate capability. The method of synthesis of the cathode materials will be discussed. 1.K. Amine, H. Yasuda, M. Yamachi, Electrochem. Solid State Lett.3 (2000) 178. 2.K. Tadanaga, F. Mizuno, A. Hayashi, T. Minami, M. Tatsumisago, Electrochemistry 71 (2003) 1192. 3. N.N. Bramnik,K.G.Bramnik, T. Buhrmester,C. Baehtz, H. Ehrenberg, H. Fuess, J Solid State Electrochem 8 (2004)558. 4. J. Wolfenstine, U. Lee, B. Poese, J.L. Allen, Journal of Power Sources 144 (2005) 226-230.


KK9.58
Olivine LiFexMn1-xPO4 (x = 0, 0.05, 0.1, 0.15, and 0.2) as the Cathode Material for Lithium Ion Batteries. Jian Hong1, Feng Wang2 and Jason Graetz1; 1Energy Science and Technology Department, Brookhaven National Lab, Upton, New York; 2Center for Functional Nanomaterials, Brookhaven National Lab, Upton, New York.

LiMnPO4 is a promising candidate to replace LiCoO2 as the cathode material in Li-ion batteries because of high redox potential (~4.0 vs. (Li+/Li)) and theoretical capacity (170 mAh/g). However, it has received little attention in the research community because of severe problems with poor cycling kinetics. It was recently shown that the introduction of iron into crystalline LiMnPO4 forms a solid solution of LiFexMn1-xPO4 and increases the kinetics. These results have generated much interest in determining the Fe to Mn ratio in LiFexMn1-xPO4 that yields optimal electrochemical performance. In this effort, several LiFexMn1-xPO4 compounds (with x=0, 0.05, 0.1 0.15, and 0.2) were synthesized and electrochemically characterized to determine the optimal composition. X-ray diffraction (XRD) and energy dispersive spectroscopy were used to examine the crystal structure and elemental distribution and revealed a decreasing unit cell volume with increasing iron concentration. Scanning, tunneling and transmission electron microscopy (SEM, STEM and TEM) were used to characterize the micro morphology of the materials and showed that all of the samples have a mesoporous structure. In-situ synchrotron XRD studies performed during cycling revealed a reversible structural change when the lithium was inserted and extracted from the material. We demonstrate that the electrochemical performance of LiFexMn1-xPO4 increases continuously with increasing iron content, reaching optimal performance at an iron concentration of 20% (e.g., LiFe0.2Mn0.8PO4) with a capacity of 130 mAh/g. The improved electrochemical activity of LiFexMn1-xPO4 may also relate to the mesoporous morphology and decreasing unit cell volume.


KK9.59
Abstract Withdrawn


KK9.60
Characterizing the Electrochemical and Mechanical Properties of Glass and Polymer Electrolytes and Predicting the Effective Conductivity of Their Composite Structures by Random Resistor Networks. Wyatt Tenhaeff1, Erik G. Herbert2, George M. Pharr1,2, Sergiy Kalnaus1, Sarah Newman3, Adrian S. Sabau1, Claus Daniel1, Xiang Yu4, Kunlun Hong4 and Nancy J. Dudney1; 1Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; 2Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee; 3Department of Mathematical Sciences, University of Memphis, Memphis, Tennessee; 4Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.

Solid state batteries will be safer than conventional Li ion technology, which utilizes flammable organic liquid electrolytes. Modeling has shown that solid electrolytes with sufficient mechanical properties can inhibit lithium anode roughening and dendrite formation. Dry polymer, glass, and ceramic electrolytes have been studied extensively as solid electrolytes, but they are too resistive for most applications. An approach to overcome the poor conductivity and mechanical properties of polymer electrolytes consists of adding inert inorganic fillers to the polymer matrix. Addition of these nonconductive particles enhances the effective conductivity of the composite electrolyte. It has been speculated that a highly conductive amorphous polymer shell is created around the particle. In this study, nanocomposites were fabricated where both phases were ionically conductive. Bilayer structures of inorganic and polymer electrolyte layers were studied to determine the effect of the interface on conductivity and mechanical properties. The inorganic layer was lithium phosphorous oxynitride (Lipon). Two copolymer electrolytes were characterized: poly[styrene-co-poly(ethylene oxide) methacrylate] and poly[methyl methacrylate-co-poly(ethylene glycol) methacrylate]. To characterize Li+ conductivities, thin films of Lipon with compositions near Li3.3PO3.8N0.24 were sputter deposited. Polymer electrolytes thin films were then fabricated on top of the Lipon film via spin coating. Electrochemical impedance spectroscopy revealed that the interfacial resistance was dominant in the bilayer structure. Nanoindentation was used to characterize the elastic modulus and hardness of LiPON films ranging in thickness from 100 nm to 10 μm. The modulus of LiPON was found to be approximately 77 GPa and independent of the substrate, film thickness, and annealing. Using Sneddon’s stiffness equation and assuming the modulus is 77 GPa, the hardness was found to be approximately 3.9 GPa for all but the annealed film. The hardness of the annealed film was approximately 5% higher, at 4.1 GPa. A random resistor network method was used to model the conductivity of traditional composite structures where nanoscale particulates are mixed into a polymer electrolyte matrix. The model system consisted of three phases, all of which were conductive: polymer matrix (σ1), conductive particulate reinforcement (σ2), and amorphous conductive layer surrounding particles (σ3). The model targeted the simulation of a system consisting of a poly(ethylene oxide) (PEO)10LiClO4 matrix with spherical Lipon particles as filler. The simulation results revealed an initial increase in effective conductivity as a function of Lipon volume fraction, followed by rapid drop in conductivity of the composite electrolyte. The results of simulations were compared to predictions based on existing theories. Research sponsored by: the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory; the Oak Ridge National Laboratory’s SHaRE User Facility for electron microscopy, sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences; and the Oak Ridge National Laboratory Weinberg Fellowship (WT), managed by UT-Battelle, LLC, for the U. S. Department of Energy.


 

SESSION KK10: Lithium Battery Electrolyte Materials
Chairs: Dominique Guyomard and Steve Harris
Friday Morning, December 3, 2010
Constitution A (Sheraton)


8:00 AM *KK10.1
Semi-solid Lithium Ion Flow Cells.Yet-Ming Chiang, W. Craig Carter, Mihai Duduta, Bryan Y. Ho, Vanessa Wood, Pimpa Limthongkul and Victor Brunini; Massachusetts Institute of Technology, Cambridge, Massachusetts.

We demonstrate a new electrical storage concept, the semi-solid flow cell (SSFC), that aims to combine the best attributes of rechargeable batteries and flow batteries. In this approach, energy-dense Li-ion cathode or anode particles suspended in liquid electrolytes are used as flowable rechargeable “fuels” that are delivered to a flow battery stack that separates the respective active materials particles and allows extraction of electrochemical energy. Using nanoscale carbon dispersions, we produced a flowable yet continuously percolating suspension that permits suspended active material particle to be “wired” to the respective current collectors of the flow cell. We show that the energy densities achievable are an order of magnitude or more higher than conventional aqueous flow batteries. In contrast to rechargeable batteries, the device’s power and stored energy are decoupled: the stack can be sized for necessary power, while the total energy can be independently scaled. The potential of this new approach to address electrical storage needs for transportation and the grid will be discussed.


8:30 AM KK10.2
Disperse Lithium Electrolytes with Nano- and Mesostructured Silica Fillers.Kerstin Sann1, Nastaran Ariai1, Jan Roggenbuck2, Henrik Buschmann1, Juergen Janek1 and Michael Froeba2; 1Institute of Physical Chemistry, Justus-Liebig-University, Giessen, Germany; 2Institute of Inorganic and Applied Chemistry, University of Hamburg, Hamburg, Germany.

To improve the performance and safety of lithium ion batteries new or enhanced electrolytes are a major research issue. The well established liquid electrolytes consist of organic solvents, predominantly organic carbonates with lithium salts like lithium-hexafluorophosphate (LiPF6) dissolved therein. In the present contribution we investigate the effect of inert solid materials like mesoporous or nonporous silica particles added to the electrolyte as “nanofillers”. These inorganic fillers reduce the volume fraction of the inflammable phase. Once the electrolyte/filler interface provides efficient transport paths for the lithium ions, one might even expect improved transport properties. We present results of systematic conductivity experiments with dispersions of different silica-based materials, like mesostructured SBA-15, MCM-41 and KIT-6 and nonporous silica particles in standard electrolytes. The inorganic materials have been used as-received as also in surface functionalized form with organic surface groups obtained via a grafting procedure. As electrolyte for the dispersions a standard battery electrolyte EC/DEC 3:7 with 1 mol/L lithium-hexafluorophosphate (LiPF6) was used. DMC containing 1 mol/L LiPF6 and LiTFSI in EC/DEC 3:7 were also investigated. In none of these systems as reproducible conductivity increase could be observed, and thus, liquid electrolytes with high ionic conductivity may most probably not be improved with respect to their electrochemical properties by inorganic fillers. First results on comparable dispersions on the basis of ionic liquids will also be presented.


8:45 AM KK10.3
Polymer-ionic Liquid Hybrid Electrolytes for Lithium Batteries.Aaron Fisher1 and Peter Kofinas2; 1Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland; 2Fischell Bioengineering, University of Maryland, College Park, Maryland.

Flexible thin film batteries have many attractive properties that would lead to enhanced performance for the next generation of lithium ion batteries. Polymeric systems have as of yet been able to gain widespread usage because of performance limitations that can be overcome with the proper use of additives. New room temperature ionic liquid (RTIL) chemistries based upon second period of elements are being explored to maintain the elevated conductivity of RTILs while utilizing the wide electrochemical stability (high cathodic stability) displayed by these scaffolds. The synthesized RTILs have been blended with a lithium salt in lithium conducting polymer matrices to produce solid electrolytes. Such shape-conforming materials could be easily wound up into coils or processed as coatings or sheets, thus providing large area devices with integrated electronics. These materials would be inherently safer replacing the current combustible liquid electrolyte systems with a non-flammable polymer system. For the electrochemical characterization of the polymer electrolytes potentiodynamic, potentionstatic and galvanostatic measurements as well as impedance spectroscopy have all been analyzed. At slightly elevated temperatures the synthesized electrolytes have demonstrated conductivity >10-3 S/cm and cathodic stability in excess of 5 V vs. lithium. Given the widely accepted performance benchmarks needed for a commercial electrolyte this latter value is of great scientific interest, which will allow commercial access to higher power cathodes that have been currently unusable due to limitations in carbonate based electrolytes.


9:00 AM KK10.4
Electrochemical Cycling of Lithium-ion Cells in Propylene-carbonate Based Electrolytes.Gang Cheng and Daniel P. Abraham; Argonne National Lab, Argonne, Illinois.

Recent advances in high energy and high power positive and negative electrode materials have refocused attention on electrolytes as the technological bottleneck limiting the operation and performance of lithium-battery systems. Lithium battery electrolytes typically consist of alkyl carbonate solvents and lithium-bearing salts. The solvents are typically a mixture of cyclic alkyl carbonates, such as ethylene carbonate (EC), and linear alkyl carbonates, such as ethyl methyl carbonate (EMC). The highly polar cyclic carbonates enable the dissolution of salts to sufficient concentrations, but are rather viscous. The linear carbonates, on the other hand, are weakly polar but their low viscosity promotes rapid ion transport. The electrolyte salt of choice for most lithium-ion cells is lithium hexafluorophosphate (LiPF6) because of its high solubility and excellent conductivity in alkyl carbonate solvents, and ability to form stable electrode passivation layers. Research on alternative electrolyte solvents, salts, and functional electrolyte additives is being conducted at Argonne as part of the U.S. DOE’s efforts to overcome the performance, life, safety and cost limitations that currently hinder the widespread commercialization of lithium-ion batteries for transportation applications. Propylene carbonate (PC) is often considered as an alternative to EC because it costs less, has excellent ionic conductivity, and, (unlike EC) is liquid at ambient temperatures. However, typical PC-based electrolytes are known to decompose on graphite negative electrodes and cause exfoliation of graphene layers, which hinders the lithium intercalation/deintercalation required for cycling of lithium-ion cells. In our presentation we show that lithium-ion cells containing pure PC solvents can be cycled when the salt concentration exceeds 2.8M LiPF6. Our data obtained using a combination of experimental (cycling, impedance, electrode surface analysis, etc.) and modeling techniques suggest that a pseudo-polymeric Lix(PC)y complex forms at higher LiPF6 concentrations, which facilitates Li+ desolvation and prevents PC- cointercalation into graphite. Details of our experimental and modeling data, and their relevance to electrolyte development will be discussed in the presentation.


9:15 AM KK10.5
Designing Ionomers for Facile Ion Transport.Ralph H. Colby, Wenjuan Liu and James Runt; Materials Science and Engineering, Penn State University, University Park, Pennsylvania.

We synthesize single-ion conducting ionomers with low glass transition temperatures to prepare ion conducting membranes for actuators and lithium battery separators. We use dielectric spectroscopy to determine the number density of conducting ions and their mobility from electrode polarization (using the 1953 Macdonald model [1]) and the number density of ion pairs from measured dielectric constant (using the 1936 Onsager model [2]). This experimental work concludes that the number density of conducting ions is tiny [3], and we discuss ways to boost that using more polar polymers with weak-binding anions attached to the chain. We use ab initio quantum chemical calculations at 0 K in vacuum to characterize ion interactions and ion solvation by various functional groups on ion-containing polymers. Simple ideas for estimating the ion interactions and solvation at practical temperatures and dielectric constants are presented that indicate the rank ordering observed at 0 K in vacuum should be preserved. Hence, such ab initio calculations are useful for screening the plethora of combinations of polymer-ion, counterion and polar functional groups, to decide which are worthy of synthesis for new ionomers. The results provide estimates of parameters for a simple four-state model for counterions in ion-containing polymers: free ions, isolated ion pairs, triple ions and quadrupoles. We show some examples of how ab initio calculations can be used to understand experimental observations of dielectric constant, glass transition temperature and conductivity of polymerized ionic liquids with either lithium or ionic liquid counterions. [1] J. R. Macdonald, Phys. Rev. 92, 4 (1953). [2] L. Onsager, J. Amer. Chem. Soc. 58, 1486 (1936). [3] D. Fragiadakis, S. Dou, R. H. Colby and J. Runt, J. Chem. Phys. 130, 064907 (2009).


9:30 AM KK10.6
Computational Studies of the Reduction and Adsorption Mechanisms of Ethylene Carbonate on the Surface of Carbon Anodes of Lithium-ion Batteries.Qing Peng, Zhiyao Duan and Guofeng Wang; Mechanical Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana.

Solid electrolyte interface (SEI) plays a critical role in affecting the performance, including capacity, cycle life, and safety, of Li-ion batteries. Ethylene Carbonate (EC) based multi-component electrolytes are widely used in current Li-ion batteries and it is generally recognized that the decomposition of EC contributes to the SEI's formation. Using first principles density functional theory calculations, we studied the atomistic structure of the decomposed EC, the new compound of EC-Li, and adsorption of EC-Li on graphite surface. The first step of the EC’s decomposition is to destroy its ring structure by breaking one of its C-O bonds. Further, we found that such open ring structure of EC can be stabilized by bonding with a lithium atom, with a binding energy of 1.35 eV, and forming an intermediate compound EC-Li. Once the graphite is presented, EC-Li can be adsorbed onto the basal plane of the graphite with adsorption energy of 0.24 eV. More importantly, our study revealed that EC-Li can also be bonded with graphite on the layers sides of graphite surface with a binding energy of 1.81 eV. Hence, we propose a molecule-level mechanism of SEI's formation in the EC based electrolytes based on our calculations. That is that EC is decomposed by bonding with Li atom, and further bind to carbon anode to form the first layer of the SEI.


9:45 AM KK10.7
Characterizing the Mechanical Behavior of LiPON Films by Nanoindentation.Erik G. Herbert1, Wyatt E. Tenhaeff2, Nancy J. Dudney2 and George M. Pharr1,3; 1Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee; 2Oak Ridge National Laboratory, Oak Ridge, Tennessee; 3Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.

Nanoindentation has been used to characterize the elastic modulus and hardness of LiPON films ranging in thickness from 100 nm to 10 μm. Five amorphous films were deposited on glass and sapphire substrates and one film was annealed at 200 °C for 20 minutes. Experimental factors such as the frame stiffness, time dependence, and pileup are discussed thoroughly because they are found to significantly affect the reliability of the elastic modulus and hardness determined by traditional nanoindentation techniques. The modulus of LiPON is found to be approximately 77 GPa and independent of the substrate, film thickness, and annealing. Using Sneddon’s stiffness equation and assuming the modulus is 77 GPa, the hardness is found to be approximately 3.9 GPa for all but the annealed film. The hardness of the annealed film is approximately 5% higher, at 4.1 GPa. AFM images of the residual impressions from two of the five films confirm the presence of pileup behavior and the unexpected increase in hardness of the annealed film. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory and the Oak Ridge National Laboratory Weinberg Fellowship (WET). ORNL is managed by UT-Battelle, LLC, for the U. S. Department of Energy.


10:15 AM KK10.8
Soft Electrolytes Based on Spiroammonium Imide Salts for Lithium Batteries.Yaser Abu-Lebdeh, Pamela Whitfield and Isobel Davidson; National Research Council of Canada, Ottawa, Ontario, Canada.

Spiroammonium imide salts exhibit plastic crystalline phases over a wide temperature range. The addition of carefully optimized amounts of the lithium salt LiTFSI allows the formation of soft materials with high ionic conductivity applicable as solid electrolytes for lithium batteries [1]. We successfully synthesized, in high purity, three salts with a systematic variation in the size of the two aliphatic rings by reacting a ringed amine with the corresponding aliphatic dibromide in a strong basic aqueous solution. We found that all the SP-TFSI salts were solids with melting points above 100 °C. Two of the salts showed a plastic crystalline phase that in the case of the SP-56 salt extended well below room temperature as evidenced by the DSC scans. XRD powder diffraction patterns of the salts at variable temperatures showed, despite their complexity, the distinctive phase changes at temperatures that correlate well with the thermal events observed in the DSC scans. Further studies showed that the SP-56 salt can be mixed with 5 mol% LiTFSI with no effect on the integrity of the plastic crystalline phase, i.e. a solid solution is formed. The electrochemical stability of the solid solution was studied and a 5 V electrochemical stability window is observed but it onset at a potential more positive than that of the Li/Li+ redox couple, a very common behavior in these types of organic salts. In order to allow for its use in a lithium battery, ethylene carbonate was added and Li/LiFePO4 batteries were assembled. The batteries showed capacities over 100 mAh/g at C/12 well retained over 100 cycles. A full description of the thermal, electrochemical and crystallographic behavior of all the synthesized salts will be presented besides their performance in lithium batteries. [1] Y. Abu-Lebdeh, E. Austin and I. Davidson, Chem. Lett., 38 (8), 782 (2009).


10:30 AM KK10.9
Ab initio Study of Room Temperature Ionic Liquids Interactions with Li Metal Surfaces as a Model for Ionic-liquids Based Li Batteries Electrodes.Hubert Valencia, Masanori Kohyama, Shingo Tanaka and Hajime Matsumoto; Research Institute for Ubiquitous Energy Devices, Advanced Industrial Science and Technology (AIST), Osaka, Japan.

Room temperature ionic liquids (RTIL), consisting of charged cationic and anionic molecules, have remarkable properties such as high conductivity, low viscosity, low melting point and nonflammability [1], making them a candidate of choice for safer and more efficient Li-ion battery electrolytes [2]. Despite existing studies of Li transport within the RTIL electrolyte itself, only little is known about its interaction with the electrode Li surface. For this purpose, we investigate the adsorption of a typical RTIL EMIM-BF4 (1-ethyl-3-methyl imidazolium tetrafluoroborate) molecular pair [3] or crystal layer [4] onto Li surfaces by means of periodic density functional theory (DFT) calculations. Using several DFT analysis, we showed that a RTIL adsorption onto Li surfaces leads to significant changes in the Li surface, such as Li atoms being attracted toward the anion, charge density depletion occurring underneath the Li surface, and a significant electron transfer being observed between the Li surface and the RTIL. Now, aiming at more experimental-oriented systems, we study the adsorption of EMIM-[(fluoroalkyls)-sulfonamides] RTILs molecules which, while retaining the general same behavior than the model EMIM-BF4, introduce a new conformational issue. The examination of this different molecules anion such as [(FSO2)2N]- (FSA), [(CF3SO2)2N]- (TFSA), [(CF3SO2)(FSO2)N]- (FTA), and [C2F4(SO2)2N]- (CTFSA) thus gives an insight of this new complexity, yet leading to a first theoretical approach of the inner design of RTIL electrolytes. The present study was supported by NEDO (New Energy and Industrial Technology Development Organization) as Li-EAD project. [1] F. Endres, S.Z. El Abedin, Phys. Chem. Chem. Phys.8, 2101 (2006), [2] H. Sakaebe, H. Matsumoto, K. Tatsumi, Electrochem. Acta53, 1048 (2007), [3] H. Valencia, M. Kohyama, S. Tanaka, H. Matsumoto, Phys. Rev. B78, 205402 (2008), [4] H. Valencia, M. Kohyama, S. Tanaka, H. Matsumoto, J. Chem. Phys.131, 244705 (2009).


10:45 AM KK10.10
Effects of the Mechanical Properties and Thickness of SEI (Solid-electrolyte Interface) on the Coupled Mechanical-chemical Degradation of Lithium ion Battery Electrodes.Rutooj D. Deshpande1, Yang T. Cheng1 and Mark W. Verbrugge2; 1Chemical and materials engineering, University of Kentucky, Lexington, Kentucky; 2Chemical Sciences and Materials Systems Laboratory, General Motors Global R&D Center, Troy, Michigan.

Coupled mechanical-chemical degradation of electrodes upon charging and discharging has been recognized as a major problem in lithium ion batteries. The instability of commonly employed electrolytes results in SEI formation. Although SEI formation contributes to irreversible capacity loss, the SEI layer is necessary, as it serves to passivate the electrode-electrolyte interface relative to further solvent decomposition. Due to volume changes and the associated stresses within the SEI layer and at the interface between the SEI layer and the underlying active electrode materials, the SEI layer may fracture, causing the growth of SEI on the newly exposed electrode surfaces and commensurate loss of active lithium (and Coulombic capacity) from the cell; i.e., irreversible capacity loss. Recently, several groups have attempted to make artificial SEI layers on the electrode particles that have shown improved performance and durability. In this study, through mathematical modeling, we provide an understanding of the effects of the mechanical properties and thickness of the SEI on the stress evolution inside an electrode particle and within the protective SEI layer. We calculate stresses inside the SEI and at the interface between the electrode and the SEI. Our model can be used to help design improved SEI’s with desired mechanical properties and thickness so as to minimize irreversible losses caused by coupled mechanical-chemical degradation processes.


11:00 AM KK10.11
Electrochemical and Mechanical Characterization of Composite Nanostructures of Solid Glass and Polymer Electrolytes.Wyatt Tenhaeff1, Erik G. Herbert1,3, George M. Pharr1,3, Xiang Yu2, Kunlun Hong2, Sergiy Kalnaus1, Claus Daniel1, Adrian S. Sabau1, Kelly A. Perry1, Karren L. More1 and Nancy J. Dudney1; 1Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; 2Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; 3Department of Materials Science and Technology, University of Tennessee, Knoxville, Tennessee.

Solid state batteries will be safer than conventional Li ion technology, which utilizes flammable organic liquid electrolytes. Dry polymer, glass, and ceramic electrolytes have been studied extensively as solid electrolytes, but they are still too resistive. Moreover, the mechanical properties and conductivities of polymer electrolytes are typically inversely related. Mechanical properties are sacrificed to achieve higher conductivities. Many research groups have shown that the mechanical properties of polymer electrolytes can be enhanced while maintaining or improving the conductivity by creating composite materials with inert inorganic nanoparticles. The interface between the polymer and nanoparticle, as well as the suppression of crystallization, is believed to be responsible for the enhanced conductivities. In this study, bilayer composite structures of inorganic and polymer electrolyte layers were studied to determine the effect of the interface on conductivity and mechanical properties. The inorganic layer was lithium phosphorous oxynitride (Lipon). Two copolymer electrolytes were characterized: poly[styrene-co-poly(ethylene oxide) methacrylate] containing 50% styrene (PS-EO) and poly[methyl methacrylate-co-poly(ethylene glycol) methacrylate] containing 30% MMA (PMMA-EO). To characterize Li+ conductivities, thin films of Lipon (nominal thickness of 1 μm) with compositions near Li3.3PO3.8N0.24 were deposited on Au electrodes via RF-magnetron sputtering. Polymer electrolytes thin films were fabricated on top of the Lipon film via spin coating. The film thicknesses of PS-EO and PMMA-EO were 1940 and 1490 nm, respectively. Au electrodes were sputter deposited on top of the polymer, thus sandwiching the bilayer between two electrodes. Electrochemical impedance spectroscopy revealed that the interfacial resistance was dominant in the bilayer structure. At 25 °C, the resistance of the interface between PS-EO and Lipon was 2.8 times greater than the sum of the two layers. For PMMA-EO and Lipon, the interfacial resistance was 3.2 times greater. The elastic moduli of Lipon thin films were measured using nanoindentation. Lipon films with thicknesses of 1 μm and 10 μm were deposited on glass substrates. The elastic modulus was determined to be 77 GPa, and using Sneddon’s stiffness equation, the hardness was calculated to be 3.9 GPa. Mechanical testing of the polymer electrolyte layer and bilayer composite structure is underway. Research sponsored by: the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory; the Oak Ridge National Laboratory’s SHaRE User Facility for electron microscopy, sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences; and the Oak Ridge National Laboratory Weinberg Fellowship (WT), managed by UT-Battelle, LLC, for the U. S. Department of Energy.


11:15 AM KK10.12
Ionic Liquid Tethered Nanoparticle Hybrid Electrolytes for Li Batteries.Surya Sekhar Moganty, N. Jayaprakash, Jennifer L. Nugent, Jingguo Shen and Lynden A. Archer; Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York.

Secondary batteries containing Li metal as anode provide one of the highest known energy densities. They are therefore desirable candidates for electric and hybrid electric vehicles. However, current liquid electrolytes cannot be employed with lithium metal anode because they allow dangerous lithium dendrite growth during the charge discharge cycles. Solid polymer electrolytes, on the other hand, are known to be effective in reducing dendrite growth and hence, spurred lot of interest in the development of polymer and composite polymer electrolytes for use in lithium batteries. The well-known solid ionic conductor, poly ethylene oxide (PEO), is crystalline and exhibits poor ionic conductivities at room temperature. Several alternatives are currently being investigated to improve the ionic conductivity and mechanical properties of PEO. Alternatively, Ionic liquids (IL’s) are emerging as novel electrolytes for energy storage devices due to their attractive properties such as, ultralow vapor pressure, high thermal stability, high ionic conductivity and wide redox stability. But, IL’s suffer from the low lithium transference numbers and also problems pertaining to dendrite growth. Tethering IL’s to nano particles may mitigate the above problems. Recently, we have created organic-inorganic nano composite materials by covalently tethering PEO oligomers to a variety of nano particles [1-3]. Liu et al. [4] synthesized luminescent ZnO nanocrystals stabilized by ammonium based IL. The IL modified ZnO nano crystals showed tunable photoluminescence properties. Herein, we report IL tethered nano particle hybrid materials (NILs) synthesis and characterization as electrolytes for Li batteries. NILs exhibit reasonably high ionic conductivities, when doped with lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) salt, and manifest yield stress fluid type mechanical properties with wide redox stability window. [1] A. B. Bourlinos, R. Herrera, N. Chalkias, D. D. Jiang, Q. Zhang, L. A. Archer, E. P. Giannelis, Advanced Materials, 17, 234, 2005. [2] P. Agrawal, H. Qi, L. A. Archer, Nano Letters, 10, 111, 2010. [3] J. L. Nugent, S. S. Moganty, L. A. Archer, Advanced Materials, 2010 (In Press). [4] D. P. Liu, G. D. Li, Y. Su, J. S. Chen, Angew. Chem. Int. Ed, 45, 7370, 2006.


11:30 AM KK10.13
Nanoscale Hybrid Electrolytes for Lithium Metal Batteries.Jennifer L. Nugent, Surya S. Moganty and Lynden A. Archer; Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York.

Polymer and composite polymer electrolytes have been studied for many years for their potential to couple sufficient ionic conductivity, and therefore discharge rate, with the mechanical strength necessary for suppression of metallic lithium growth and thus safe operation of a lithium metal battery. The most widely studied polymer electrolyte, polyethylene oxide, is crystalline and has low conductivity at room temperature. The use of free nanoparticles, molecular plasticizers, and large anion salts has led to varying levels of improvement in electrochemical and mechanical properties. More recently, hybrid ceramic-polymer electrolyte frameworks have also been demonstrated. We report on a new class of nanoscale hybrid electrolytes that show promise for use in lithium metal batteries. Nanoparticle organic hybrid materials (NOHMs) were created by grafting polyethylene glycol oligomers (the corona) to silica nanocores. NOHMs were purified by precipitation in ethanol to remove free organic material, then doped to 1 M LiTFSI in the organic phase. Unlike traditional composite polymer electrolyes, NOHMs based electrolytes are homogenous with evenly distributed, non-agglomerated nanoparticle cores. Properties of the hybrid electrolytes may be tuned by changing the core size or chemistry, length of the corona chains, or by adding dilutant. Suspension of the NOHMs in free polyethylene glycol dimethyl ether (PEGDME) with 1 M LiTFSI results in a family of materials with properties ranging from liquid-like to solid-like. At a critical NOHMs fraction, the blend is jammed and the electrolytes display soft-glassy rheology. This jamming phenomenon results in a 6 order of magnitude increase in storage modulus with only a fractional decrease in ionic conductivity. Electrochemical tests show that these electrolytes have typical lithium transference numbers and very wide stability windows. We aim to study the effect of jamming, and changes in mechanical properties such as modulus and yield stress, on initiation and propagation of dendrite growth from lithium electrodes. In addition, as dendritic lithium growth initiates from uneven mass transport pathways of Li+ to the electrode interface, the length scale of homogeneity in the transporting organic phase may have morphological effects on dendrite growth. The effect of length scale may be investigated by varying spacing between cores as well as core size. The unique rheological properties of these nanoscale hybrid electrolytes provide a mechanism for achieving mechanical strength without sacrificing ionic conductivity, as well as serving as a convenient, tunable platform with which to study dendrite growth.


 

SESSION KK11: Lithium Battery Modeling, Electrolyte, SEI Materials
Chairs: Jagjit Nanda and Gholam-Abbas Nazri
Friday Afternoon, December 3, 2010
Constitution A (Sheraton)


1:30 PM *KK11.1
New Insight Into Electrochemical Differences in Cycling Behaviors of a Lithium-ion Battery Cell Between the Ethylene Carbonate- and Propylene Carbonate-based Electrolytes.Ken Tasaki1, Alexander Goldberg2, Jian-Jie Liang2 and Martin Winter3; 1Mitsubishi Chemical USA, Redondo Beach, California; 2Accelrys, San Diego, California; 3University of Muenster, Muenster, Germany.

It has long been known that a lithium-ion battery cell having graphite as the anode in the EC-based electrolyte can be cycled, while charging a similar cell in the PC-based electrolyte only gives rise to exfoliation of graphite. Despite numerous reports on the electrochemical differences between the two electrolytes, this observation is still not well understood. Since the EC-based electrolyte generally forms an SEI film on the graphite surface, better understanding of the electrochemical differences between the two electrolyte systems may be helpful in controlling the SEI film formation. We believe that the co-intercalation model, developed originally by Besenhard and co-workers, later used to explain the difference between the two solvent-based electrolytes by Ogumi’s group, plays a central role in this subject. Here, we attempt to shed light on a series of experimental observations using a combination of density functional theory (DFT) calculations and molecular dynamics (MD) simulations. The systems examined by DFT calculations included the solvated lithium ion, Li(S)i=1-4, and the ternary graphite-intercalated-compounds (GIC), Li(S)i=1-3Cn, where S can be either EC or PC for the both systems. Our DFT calculations suggest that Li(EC)i is more likely to be reduced than Li(PC)i as the number i increases. Sharp differences in the structures of Li(S)i were found in that while Li(S)4 was rectangular, Li(S)3 was more or less flat. This structural difference underlines a significance of desolvation in lithium intercalation into graphite. We will also discuss Li(S)i=1-3Cn where S is EC or PC in order to examine the difference in the energetics and the structures between the two. We found significant structural deformations on Li(PC)3Cn. Three methyl groups gave rise to large repulsive interactions against the inter-layers, creating extreme stresses on the PC molecules inside graphite. In addition, we examine the salt concentration effect on the lithium intercalation into graphite through MD simulations. Our results seem consistent with the recent observations by Jeong et al. and Yamada et al.


2:00 PM *KK11.2
Fundamental Mechanisms of SEI Operation.Stephen Harris and Peng Lu; General Motors Research, Warren, Michigan.

The chemical and physical properties of the SEI layer are critical to battery operation and life, and considerable information is available on the chemical identities of species making up the SEI. There is less information about the mechanisms for its formation and on the rates of its degradation and failure in different environments. However, there is almost no information about the chemical and physical reactions that take place at and within the SEI during the charging/discharging process and the kinetics of those reactions. These reactions control the function of the SEI, both in terms of allowing Li to enter and leave the electrode and in terms of how well it survives during operation. In the talk we will describe experimental efforts using a new and unique instrument, a Focused Ion Beam-Time of Flight Secondary Ionization Mass Spectrometer (FIB-TOF-SIMS) to determine location and distribution of Li within the SEI layer and to use this information to describe the kinetics and the mechanism by which lithium ions are transported through the SEI. We will also describe how SEI properties vary with the voltage at which it was formed. Our aim is to provide an understanding, in microscopic detail, of how the SEI interacts with the electrolyte and how these interactions relate to cell operation, degradation and failure.


2:30 PM KK11.3
Structure Property Relationship of Imidazole Based Ionic Liquids on Surface and in Confined Interfaces by Theoretical and Experimental Investigation.Mousumi Mani Biswas1, Tahir Cagin1,2 and Mustafa Akbulut2; 1Materials Sc. and Eng. Program, Texas A&M University, College Station, Texas; 2Chemical Engineering, Texas A&M University, College Station, Texas.

Ionic liquids (IL), consisting of only anions and cations, have interesting properties such as low melting point, low volatility, wide electrochemical range, very good solvency and coordination property, non-flammability, etc. and thus they have potential application in electrochemistry, fuel cell, batteries, chemical synthesis, catalysis, etc. In these applications, ILs come in contact with interface of other materials like solids, polymers, etc. Therefore, understanding the structure property relationship and ionic mobility at the solid/liquid interface and in confinement is important for successful performance of ILs in these applications. In the current work we present the structure and thermodynamic properties of imidazolium based IL - [BMIM][BF4] (1-butyl-3-methyl imidazolium- tetrafluoro borate). In the first stage, using QM calculation based on density functional theory (DFT) in Gaussian code we calculate the charge distribution, optimum bond length and angles, and optimum anion-cation orientation. We see that preferred position of anion is in the vicinity of imidazole ring, since this is the most positive zone in the cation. It was observed that the butyl chain becomes neutral, but the fluorine on the anion becomes the negative side and the imidazole ring becomes the most positive site. Then using large scale molecular dynamic simulation in LAMMPS code we study the structure and dynamics of [BMIM][BF4] system on graphite and mica surface and interface (in the free surface, on the bulk and in confinement). We will discuss the effect of IL properties such as degree of delocalization and hydrophobicities, and relative magnitudes of intermolecular interactions involved on the properties relevant to Lithium batteries such ionic mobility, conductivity, electrolyte viscosity, surface wettability as a function of IL film thickness. These findings will be complemented by the experimental work. Our preliminary study shows that the forces across ILs are repulsive at all measured distances, decaying exponentially with distance. Effective Debye screening lengths are found to be around 1−4 nm, and strongly dependent on the size and molecular structure of the anion/cation. We will discuss in detail the structure dynamics and conductivity of nano-scale thick IL films obtained by Atomic Force Microscopy (AFM) studies and Surface Force Apparatus (SFA) studies, which is coupled with in situ conductivity measurements.


2:45 PM KK11.4
Effective Conductivity and Percolation Threshold of Polymer Composite Electrolyte by Random Resistor Networks.Sergiy Kalnaus1, Adrian S. Sabau1, Sarah Newman3, Wyatt E. Tenhaeff1, Nancy J. Dudney1 and Claus Daniel1,2; 1Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; 2Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee; 3Department of Mathematical Sciences, University of Memphis, Memphis, Tennessee.

Development of polymer electrolytes has been driven by the high promise of their application in secondary lithium or lithium-ion batteries. However the use of such polymer-lithium salt systems is limited due to poor mechanical properties as well as low ambient and sub-ambient temperature ionic conductivity. The approach developed for overcoming the above problems consists of addition of inorganic non-conductive fillers (Al2O3 or TiO2) to the polymer matrix. It has been observed that while the particle reinforcement phase is non-conductive itself, addition of such particulate matter enhances the effective conductivity of the composite electrolyte. The phenomenon has been explained by creation of highly conductive amorphous polymer shell around the grain. The computations based on percolation theory are expected to model the effective conductivity behavior of composite electrolyte. Traditionally, the site percolation and bond percolation problems have been considered for mixtures of conductive and non-conductive phases (two-phase systems). In this case, the composite material is represented as a network of resistors with conductivities randomly assigned to either zero or to the value corresponding to the conductive phase. Such an approach gives a good approximation of percolation threshold in two-phase systems. In addition, Effective Medium Theory (EMT) analytical approaches have been developed to model the behavior of composite systems. In the current investigation we apply the random resistor network method to the system, which consists of three phases, all of which are conductive: polymer matrix (σ1), conductive particulate reinforcement (σ2), and amorphous conductive layer surrounding particles (σ3). The model targets the simulation of system consisting of the poly(ethylene oxide) (PEO)10LiClO4 matrix with lithium phosphorous oxynitride (Lipon) Li3.3PO3.8N0.24 filler in form of spherical particles. Such a system promises increase in conductivity as well as enhancement of mechanical properties of electrolyte. The results of simulations reveal the initial increase in effective conductivity as a function of volume fraction of Lipon followed by rapid drop of conductivity of composite electrolyte. Thus two percolation thresholds can be identified. The effect of different statistical distributions of particle sizes on the location of percolation thresholds was investigated. The results of simulations are compared to the predictions based on existing EM-type theories. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, the Oak Ridge National Laboratory’s SHaRE User Facility for electron microscopy, sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, and the Oak Ridge National Laboratory Weinberg Fellowship (WT), managed by UT-Battelle, LLC, for the U. S. Department of Energy.


3:00 PM KK11.5
Single-step Aqueous Electropolymerization of Separators for Li-ion Rechargeable Batteries.Daniel J. Bates, Matthew Rawls, Timothy S. Arthur and Amy L. Prieto; Chemistry, Colorado State University, Fort Collins, Colorado.

One key to increasing the power output of lithium ion batteries is to increase the surface area of the cathode and anode.<1> A high surface area can be achieved through the synthesis of nanoparticles or a 3-dimensional nanostructured electrode. Whether the cathode/anode are nanoparticles or a nanowire array, a significant challenge is thin, conformal coating of the active electrode material with a separator. Our approach is to use Cu2Sb, an anode material, as the electrode for the electropolymerization of a solid electrolyte directly onto a high surface area structure.<2> The film is polymerized out of aqueous media via free radical electrodeposition, making the process environmentally friendly and easily scalable. Electrodeposition affords thin and conformal polymer films because the electrode becomes insulated as the polymerization occurs, leading to self limiting behavior; that is, polymerization occurs more rapidly over bare electrode regions which results in a complete, uniform modification of the conducting surface.<3> Furthermore, the potential and deposition time can be varied to alter the film thickness in a predictable manner. The aqueous media can be doped with a lithium salt and the monomers are chosen such that lithium ions are incorporated into the polymer matrix during polymerization. The in-situ Li-ion doping negates the common doping step involving organic plasticizers. This technique is a fast, cheap, single-step method of producing Li-ion conducting solid polymer electrolytes. Reference: 1) Kim, M. G.; Cho, J. Adv. Funct. Mater. 2009, 19, 1497-1514. 2) Mosby, J. M.; Prieto, A. L. JACS. 2008, 130, 10656-10661. 3) Rhodes, C. P.; Long, J. W.; Rolison, D. R. Electrochemical and Solid State Letters. 2005, 8, A579-A584.


3:30 PM KK11.6
Integration of Material Properties into Li-ion Battery Failure Modeling.Yue Qi1, Rutooj Deshpande2 and Yang-Tse Cheng2; 1Chemical Sciences and Materials Systems Lab, General Motors R&D, Warren, Michigan; 21Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky.

Integration of material properties into Li-ion battery failure modeling Yue Qi Most lithium ion battery electrodes experience volume changes associated with Li concentration changes within the host particles during charging and discharging. Electrode failure, in the form of fracture or decrepitation, can occur as a result of repeated volume changes. However, besides the volume change many electrode materials change their elastic properties, fracture energies, bonding natures upon lithiation. However, previous electrode mechanics model have always assumed constant materials properties. Recently, based on first principle calculations, we found graphite is stiffened and silicon is softened with increasing Li concentration, and the change can be as much as three fold. In both cases, the average Young’s modulus changes linearly with Li concentration, while the Poisson ratio remained constant. A mathematical model of diffusion induced stress and fracture tendency in battery electrodes has been developed. The model shows that the dependence of Young’s modulus on Li concentration has a significant effect on peak stress and stress evolution in the electrodes. Our results underscore the importance of integrating the material properties into Li-ion battery failure modeling.


3:45 PM KK11.7
Tracing Reversible and Irreversible Li Insertion in SiCO Ceramics with Modeling and Ab-Initio Simulations.Peter Kroll, Chemistrty & Biochemistry, UT Arlington, Arlington, Texas.

We present combined modeling and simulation studies of Li insertion in amorphous SiCO ceramics. Atomistic models of amorphous SiCO with and without so-called “free” carbon have been crafted using a network modeling approach and subsequently relaxed and optimized within density functional theory. In a first series, Li atoms are randomly inserted to test for sites with high binding energy. We find that Li prefers always bonding to O. The enthalpy of insertion, however, depends strongly on electronic states available in the SiCO host matrix. While Li inserted into insulating SiO2 is an energetically unfavorable process, the enthalpy of insertion in SiCO glass is decreased. Some glassy SiCO models exhibit favorable sites for Li insertion, which share a common motif in their local atomic environment. The presence of “free” carbon in SiCO then promotes Li insertion, because carbon-related structural imperfections give rise for low-lying unfilled electronic states. Consequently, strong and irreversible bonding of Li into SiCO is provided, if bonding of Li-cations in Li-O bonds outweighs the promotion energy for the electron to occupy unfilled electronic states. In a second series of models, we successively filled all strongly bonding sites first. Into such a lithiated model, we then added Li at sites weakly bonding or non-bonding. Some loosely bonded Li atoms are found interacting with O atoms, some are close to carbon segregations. Noteworthy is a third class of weakly bonded Li sites, which are found in structural voids. Ab-initio molecular dynamic simulations indicate a high mobility of all weakly bonded Li atoms.


4:00 PM KK11.8
A First-principles Study of the Oxygen Reduction Reaction by Lithium on Various Catalytic Surfaces.Ye Xu1 and William A. Shelton2; 1Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee; 2Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.

The reduction of O2 by lithium (Li-ORR) is the central electrochemical process that occurs at a Li-air cathode. Li-air batteries can potentially far exceed the specific energy of state-of-the-art lithium-ion batteries and thus greatly enhance the performance of BEVs. However, prototype Li-air cells using carbon cathodes suffer significant overpotentials in discharging and charging as well as rapid loss of capacity with cycling.(1,2) Improving the cycling efficiency of the Li-air cathode is critical to making rechargeable Li-air batteries a reality. Recently, a handful of studies have reported that the inclusion of various substances, including metals and oxides,(2-6) in the carbon matrix can improve the cathode efficiency to a limited extent. Unfortunately, experiment has so far yielded little understanding for the action of the catalysts beyond what overall kinetics can reveal. The initial Li-ORR products may modify the state of the cathode and fundamentally affect the efficiency of both the discharge and charge processes of a Li-air cathode. We have therefore performed density functional theory calculations coupled with electrochemical modeling(7,8) to investigate the mechanistic details of Li-ORR on a series of metal, carbon, and oxide surfaces.(9) We find that the adsorption energetics of Li-oxygen surface intermediates, the reduction product selectivity, and the intrinsic activity for the reaction are distinctly different on these surfaces. The material dependence of Li-ORR will be discussed. This research is sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy. References 1. K. M. Abraham and Z. Jiang, J. Electrochem. Soc., 143, 1 (1996). 2. A. Débart, J. Bao, G. Armstrong and P. G. Bruce, J. Power Sources, 174, 1177 (2007). 3. A. Débart, A. J. Paterson, J. Bao and P. G. Bruce, Angew. Chem. Int. Edit., 47, 4521 (2008). 4. B. Kumar, J. Kumar, R. Leese, J. P. Fellner, S. J. Rodrigues and K. M. Abraham, J. Electrochem. Soc., 157, A50 (2010). 5. Y.-C. Lu, H. A. Gasteiger, M. C. Parent, V. Chiloyan and Y. Shao-Horn, Electrochem. Solid. St., 13, A69 (2010). 6. Y.-C. Lu, et al., J. Am. Chem. Soc. (2010), doi:10.1021/ja1036572. 7. J. K. Nørskov, J. Rossmeisl, A. Logadottir, L. Lindqvist, J. R. Kitchin, T. Bligaard and H. Jonsson, J. Phys. Chem. B, 108, 17886 (2004). 8. J. S. Hummelshøj, J. Blomqvist, S. Datta, T. Vegge, J. Rossmeisl, K. Thygesena, A. C. Luntz, K. W. Jacobsen and J. K. Nørskov, J. Chem. Phys., 132, 071101 (2010). 9. Y. Xu and W. A. Shelton, J. Chem. Phys. in press.


4:15 PM KK11.9
Pseudocapacitor Models for Phase Transforming Li-ion Battery Electrodes.Todd R. Ferguson1, Ben Derrett2,3 and Martin Z. Bazant1,2; 1Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts; 2Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts; 3Mathematics, University of Cambridge, Cambridge, United Kingdom.

Phase separating materials are of great interest to the battery community. Materials such as lithium iron phosphate offer great performance and low material costs. But to improve upon this performance and understand rate limiting steps inside the cell, it is necessary to model the internal transport and kinetic processes. Modeling phase separating materials has traditionally been done using computation-intensive phase-field models involving the Cahn-Hilliard and Allen-Cahn equations. While particle-scale dynamics play an important role in battery performance, these processes represent a fraction of the total dynamics in the electrode. In this work, we investigate pseudocapacitor models that capture the same dynamics described by phase-field models, while being less computationally intensive. These models are rooted in non-equilibrium thermodynamics and capture the same overall dynamics described by phase-field models. Furthermore, these models do not require solving the Cahn-Hilliard equation inside each particle. These methods offer many advantages. Their low computation time enables other overlying processes, such as electrolyte transport and particle-particle interactions, to be modeled as well. By modeling transport and kinetic processes at both the particle and electrode scales, it is possible to identify different regimes of operation, including solid diffusion limited, reaction limited, and electrolyte diffusion limited regimes. Once these regimes have been identified, it may be possible to improve performance by lessening or even removing these limitations. The work presented will demonstrate methods of modeling graphite intercalation using Porous Electrode Theory as well as methods of modeling phase separating materials using non-linear circuit models. These models will be able to capture intercalation dynamics as well as electrode-scale particle-particle interactions, and demonstrate the effect these processes have on the cell during constant current and constant potential discharging.


4:30 PM KK11.10
Models of Porous Electrode Behavior by Using Systems of Equivalent Circuits in Percolative Networks.Victor E. Brunini, W. Craig Carter and Yet-Ming Chiang; Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.

A percolation model was applied to porous electrodes composed of a mixture of conductive carbon black, active intercalation compound material, and insulating electrolyte. This model produces varying degrees of percolation clusters in a finite geomtery as a function of the conductive additive volume fraction. The percentage of active material in the system incorporated in this network is characterized as is the system-level impedance by using a microstructural network of equivalent circuits model. We present results that correspond to the size scales and volume fractions of the microstructural components of each component phase.


4:45 PM KK11.11
First-principles Theoretical Approach for the Design and Characterization of Rechargeable Li-Air Batteries.Roel S. Sanchez-Carrera and Kozinsky Boris; Research and Technology Center, Robert Bosch LLC, Cambridge, Massachusetts.

Despite the wide popularity in the mobile consumer electronics sector, the high cost and relatively low-energy density of conventional Li-ion batteries have limited their introduction in today's most challenging energy-related applications, such as electric vehicles and cost-effective solutions for grid energy storage. To overcome such limitations, researchers around the world have started to investigate the use of alternative chemistries; one of the most exciting uses lithium metal as the anode material and air as the cathode-active material. These, so-called, Li-air batteries may offer the possibility of storing several times the energy of conventional lithium-ion batteries of the same weight, on the basis of active materials weight only. Realizing this enormous potential, however, presents formidable challenges due the lack of fundamental understanding of the electrochemical reactions and products involved in the operation of lithium-air battery systems. Aiming to aid in the development of such a disruptive technology, we have computed within the framework of density functional perturbation theory, the Raman intensities of the possible intermediate and final reaction products related to the lithium-air battery operation and compare directly against the experimental spectra. Additionally, the NMR chemical shifts and quadrupole couplings of the possible reaction product structures (and several other complex morphologies) have been also computed using the GIPAW linear response formalism as implemented in the Quantum-Espresso code. The results of our calculations can be used to identify the reaction products by correlating the computed spectra with experimental measurements. We also suggest the most appropriate spectroscopic techniques to distinguish the likely candidate reaction-product species. Finally, we address the question of electronic conductivity in the lithium-air system by systematically looking at the electronic and vibrational structure of different reaction product morphologies and defective structures.

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