Symposium Organizers
Yury Gogotsi Drexel University
John R. Miller JME, Inc.
Katsuhiko Naoi Tokyo University of Agriculture & Technology
Yang Shao-Horn Massachusetts Institute of Technology
Bruno Scrosati University of Rome
U1: Battery Materials
Session Chairs
Yang Shao-Horn
Stanley Whittingham
Monday PM, November 30, 2009
Room 200 (Hynes)
9:30 AM - **U1.1
Designing Advanced Anode and Cathode Materials for Lithium-Ion Batteries.
Michael Thackeray 1 , Christopher Johnson 1 , Sun-Ho Kang 1 , Harold Kung 2 , Vilas Pol 1 , Lynn Trahey 1 2 , John Vaughey 1
1 Electrochemical Energy Storage Department, Argonne National Laboratory, Argonne, Illinois, United States, 2 Department of Chemical and Biochemical Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractState-of-the-art lithium-ion batteries do not yet meet the stringent energy and safety requirements for heavy-duty batteries being targeted for ‘plug-in’ hybrid electric vehicles (PHEVs) and all-electric vehicles (EVs). The energy limitation results predominantly from the inability of the anode and cathode materials to react with a sufficient amount of lithium during charge and discharge at acceptable potentials, whereas the safety limitation results largely from the instability and highly reactive nature of the fully charged electrodes and side reactions with the electrolyte that can ensue therefrom. In this presentation, various approaches to design high capacity and safe electrode materials will be discussed. Focus will be placed, in particular, on recent advances that have made in enhancing the electrochemical properties of lithium-mixed-metal-oxide cathodes, and intermetallic- and TiO2 anodes by improved compositional and materials design.
10:00 AM - U1.2
A 3D Ordered Carbon Nanotube Architecture as Active Cathode Material for Li-Ion Batteries.
Joerg Schneider 1 , Jayaprakash Khanderi 1
1 Department of Chemistry, TU Darmstadt, Darmstadt Germany
Show AbstractInorganic oxides are currently intensively studied as cathode materials in Li-ion batteries. However, there inherently bad electrical conductivity is a serious drawback into the future development and optimization of these materials for applications. Currently, composite materials like carbon./.LiFePO4 conductive mixtures are used to enhance the electrical conductivity for the cathode side in battery applications. We will present our studies towards the development of a unique 3D carbon nanotube (CNT) grid which offers a highly ordered arrangement of CNTs over several mm2 and allows the deposition of electroactive oxides like LiFePO4 as well as other oxides in an ordered fashion on the outside of the tubes thus giving rise rise to a well ordered CNT grid cathode architecture. This new cathode grid structure has the potential to be integrated into a battery device structure. First studies will be presented into this.
10:15 AM - U1.3
Understanding the Improvement in the Electrochemical Properties of Surface Modified 5 V Spinel Cathodes.
Arumugam Manthiram 1 , Jun Liu 1
1 Materials Science and Engineering, University of Texas at Austin, Austin, Texas, United States
Show AbstractWith an aim to increase the energy and power densities, there is growing interest in 5 V spinel cathodes, particularly for automotive applications, as the three-dimensional lithium ion diffusion in the spinel lattice offers high intrinsic rate capability. Among the various 5 V spinel cathodes investigated, LiMn1.5Ni0.5O4 has drawn much attention due to its high capacity arising from the operation of Ni2+/3+ and Ni3+/4+ redox couples. However, LiMn1.5Ni0.5O4 is often accompanied by the formation of LixNi1-xO impurity phase and is hampered by capacity fade due to the corrosion reaction between the cathode surface and the electrolyte at the high operating voltage of ~ 5 V. Partial substitution of Mn and Ni in LiMn1.5Ni0.5O4 by other cations has been found to eliminate the impurity phase. However, only a few groups have focused on improving the cyclability by suppressing the corrosion reaction via surface modification. We present here a systematic investigation of various cation substituted LiMn1.5Ni0.5O4 and their surface modification with Al2O3, ZnO, Bi2O3, and AlPO4 by an electrostatic self-assembly method. The bare and surface modified samples are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high resolution transmission electron microscopy (TEM), charge-discharge measurements in lithium cells, electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). The surface modified samples exhibit better cycling performance, better rate capability, and better rate capability retention during cycling compared to the bare sample. EIS and XPS studies show that the inferior electrochemical performances of the bare spinel cathode are closely related to the formation of thick solid-electrolyte interfacial (SEI) layer at the high operating voltages of ~ 5 V. Surface modifications with nano-size Al2O3, ZnO, Bi2O3, and AlPO4 suppress the formation of thick SEI layers on the spinel oxide and thereby improve the electrochemical performances significantly. Moreover, the differences in the surface compositions formed during the annealing or electrochemical cycling processes also influence the electrochemical properties.
10:30 AM - U1.4
Understanding Phase Transformations and Conversion Reactions in Li2CuxNi1-xO2.and Li2CuO2
Karen Swider-Lyons 1 , Wojtek Dmowski 2 , Corey Love 1 , Michelle Johannes 1
1 , Naval Research Laboratory, Washington, District of Columbia, United States, 2 , University of Tennessee, Knoxville, Tennessee, United States
Show AbstractWe are pursuing high capacity cathodes for lithium-ion batteries. One high capacity material is Li2CuxNi1-xO2, which has a high theoretical charge capacity (e.g., 320 mAh/g) due to the opportunity to intercalate more than one electron per metal atom [1,2,3]. The material has an orthorhombic Immm structure, which is unfortunately not stable upon lithium insertion. It undergoes a phase transformation upon discharge, plus much of the capacity is below 2.5 V, and appears to be due to an irreversible conversion reaction: M(Cu,Ni)O + 2Li -> Li2O + M(Cu,Ni). We probe the structural details of the phases that form during a charge-discharge cycle using pair density function (PDF) analysis, which can resolve the short range atomic structure of disordered materials. The resulting structures are modeled with density functional theory, to provide a better understanding of the phase diagram of Li2CuxNi1-xO2. Li2CuO2 is studied as a model system.[1] C.T. Love, M.D. Johannes, A.M. Stux, and K.E. Swider-Lyons, ECS Transactions, 16 (29) 27-35 (2009).[2] N. Imanishi, K. Shizuka, T. Ikenishi, T. Matsumura, A. Hirano and Y. Takeda,Solid State Ion., 177, 1341 (2006).[3] K. Kang, C. H. Chen, B. J. Hwang and G. Ceder, Chem. Mat., 16, 2685 (2004).
10:45 AM - U1:Battery
BREAK
11:15 AM - **U1.5
Electrical Energy Storage for Transportation and Renewable Energy.
Yet-Ming Chiang 1 , W. Craig Carter 1 , Bryan Ho 1 , Mihai Duduta 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractDue to recent advances in Li-ion battery technology, the mass adoption of hybrid electric vehicles (HEVs) now seems assured, and the introduction of plug-in hybrids (PHEVs) is well underway. All-electric or “battery electric vehicles” (BEVs) can ultimately have the largest impact on oil use and greenhouse gas emission, but current development is restricted to vehicles of relatively small size and/or limited driving range. The reasons for this become apparent upon considering the specific energy (Wh/kg), energy density (Wh/L), and cost ($/Wh) of current technology. Similarly, the growth of most forms of renewable energy will be constrained by the need to store energy efficiently and economically over relatively long durations (hours). Thus, the breakthroughs now needed lie more in the area of higher energy than higher power. Along with efforts to develop higher energy density storage materials, methods to improve the mass and volume efficiency of electric energy storage devices can have great impact. To illustrate, taking the active materials alone, existing lithium ion battery couples have the energy density to permit a 200 mile range for a 3000 lb electric car using ~150 kg of active materials. However, due to the inefficient design of present batteries, this mass is roughly tripled at the device level.In this talk, various use scenarios in transportation and electric grid storage that illustrate the important metrics, as well as the shortcomings of present technology, will first be presented. New device concepts that have the potential to increase stored energy density by factors of two or more, using existing and emerging storage materials, will be discussed. Results from prototype devices and the materials challenges within will be described.
11:45 AM - U1.6
Advanced Lithium-Ion Batteries for High-Temperature Energy Storage.
Sebastian Osswald 1 , Yan Zhu 1 , Qichao Hu 1 , Steven Wesel 1 , Robert Daniel 1 , Luis Ortiz 1 , Donald Sadoway 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe high temperature service of lithium-ion batteries is currently limited by the thermal stability of the electrodes in contact with carbonate electrolyte. Most carbonate-based electrolytes are considered volatile organic compounds (VOCs), thus their reactivity with cell components and volatility rise with temperature. There exist numerous applications that employ batteries at high temperature, but are forced to use primary systems. Recent advances in polymer synthesis lead to the development of novel materials that exhibit solid-like behavior while providing the ionic conductivity of liquid electrolytes. Graft copolymer electrolytes (GCEs) of poly[(oxyethylene)methacrylate]-g-poly(dimethyl siloxane) (POEM-g-PDMS) synthesized by free radical polymerization show high thermal stability over a wide temperature range (25-300 °C). Solid-state batteries comprised of a metallic lithium anode, a 0.1 µm thick LiFePO4 cathode, and a 0.2 µm thick layer of lithium triflate-doped POEM-g-PDMS were tested at different temperatures. Our results demonstrate the opportunity for the GCEs to enable rechargeable high temperature energy storage systems.
12:00 PM - U1.7
Co-synthesis of LiMn2O4 and Carbon Electrodes for High Power Batteries.
Robert Buechel 1 , Timothy J. Patey 2 , See How Ng 2 , Frank Krumeich 1 , Petr Novak 2 , Sotiris E. Pratsinis 1
1 D-MAVT, ETH Zurich, Zurich Switzerland, 2 Electrochemistry Laboratory, PSI, Zurich Switzerland
Show AbstractA flame spray and a diffusion flame are combined to continuously produce LiMn2O4 nanoparticles [1] and carbon black in a rapid, one-step and industrially scalable process [2]. The powder carbon content was varied by adjusting the diffusion flame conditions. The powders are characterized by X-ray diffraction (XRD), thermo gravimetric analysis (TGA) and transmission electron microscopy (TEM), cyclic voltammetry (CV)and galvanostatic cycling for a range of current densities. These LiMn2O4/carbon nanocomposites retain over 80% of their initial galvanostatic discharge capacity for current densities ranging from 5 to 50C-rates and showed significantly better performance compared to pure LiMn2O4 nanoparticles mixed conventionally with commercial carbon blacks. The improved performance of the LiMn2O4/carbon nanocomposites was attributed to the carbon particle contact and/or film coating of the freshly-made LiMn2O4 nanoparticles. This additional well-distributed carbon provides an electrically conductive network that induces a more homogeneous charge transfer throughout the electrode. [1]F.O. Ernst, H.K. Kammler, A. Roessler, S.E. Pratsinis, W.J. Stark, J. Ufheil, P. Novak, Mater. Chem. Phys. 101 (2007) 372-378.[2]T.J. Patey, R. Buchel, S.H. Ng, F. Krumeich, S.E. Pratsinis, P. Novak, 189 (2009) 149-154.
12:15 PM - U1.8
What’s the Optimum Composition of LiNiyMnyCo1-2yO2?
Zheng Li 1 , Natasha Chernova 1 , Megan Roppolo 1 , Shailesh Upreti 1 , Michael Whittingham 1
1 Institute for materials research, Binghamton University, Binghamton, New York, United States
Show AbstractAn unresolved question for the layered oxides is: what is the optimum value of y in the formula LiNiyMnyCo1-2yO2? This work attempts to answer this question with a study of the specific capacity and rate capability of a series of layered compounds (y=0.5, further called 550; y=0.45, 992; y=0.4, 442; y=0.33, 333). Factors such as transition metal oxidation sequence, Li/Ni exchange rate, electronic conductivity and particle size that influence the capacity and rate capability were investigated. A higher nickel content in LiNiyMnyCo1-2yO2 leads to higher capacity when charging the cells to 4.3V. When focusing on 333, we find out that the Co3+/Co4+ redox reaction begin to get involved when more than 50% of the lithium ions were extracted. This leads to slightly smaller capacity than LiNiyMnyCo1-2yO2 with reduced cobalt. Using the same synthesis condition (mixed hydroxide method, 800 °C annealing followed by quenching the sample), the Li/Ni exchange rate decreases and particle size increases with increasing cobalt content. All these factors lead to rather complicated comparison results. On one hand, higher nickel content and smaller particle size result in better rate performance. On the other hand, less cobalt content means possibly lower lithium ion mobility and electronic conductivity. We found the best rate performance at moderate current density falls in the 992 or 442. In order to further improve the rate capability of LiNiyMnyCo1-2yO2 with reduced cobalt at high current density, we also investigate influence of the morphology on rate performance through different synthesis procedures. Besides traditional co-precipitation method, spray dry or hard-template method is used to synthesize the large particles with mesoporous structure, which improves the contact between electrolyte and active material. This work is supported by the US Department of Energy Office of Freedom Car and Fuel Partnership through the BATT program at LBNL.
12:30 PM - **U1.9
Binary Nickel Compounds as Negative Electrode Materials for Lithium Batteries: Syntheses and Performance.
Frederic Gillot 1 , Anne-Claire Louer 1 , M. Rosa Palacin 1
1 Solid State Chemistry, Institut de Ciencia de Materials de Barcelona, Bellaterra, Catalonia, Spain
Show AbstractCompounds allowing the so termed “conversion reaction” have been intensively studied in recent years as possible electrode materials to be implemented in lithium ion batteries. These are binary phases of general formula MaXb, (X=O, S, N, P, H, F…), that react with lithium to yield metallic nanoparticles embedded in a matrix of LiyX. Many transition metal compounds that do not have any vacant sites in the structure had been disregarded as intercalation electrode materials but turned out to yield extremely high capacities associated to these conversion processes that entail full reduction of the transition metal. Tough the initial reports dealt with oxides which are still and by far the most investigated class of compounds, conversion reactions have been shown to exist for other materials such as sulphides, nitrides, phosphides, fluorides and also hydrides. The potential of the reaction increases with the ionicity of the M-X bond and, with the exception of fluorides, is usually between 0.5 and 1 V vs. lithium metal. We will describe the synthesis of nickel oxide and nickel nitride through different routes involving mostly thermal decomposition of precipitated precursors (hydroxides and amides respectively). While hydroxides are easily obtained in aqueous alkaline medium, amides have been precipitated in liquid ammonia from a nickel salt and an alkaline amide using a specially designed experimental setup. Alternatively, nickel nitride was also prepared by ammonolysis of diverse precursors at different temperatures with comparative purposes. The effect of the synthesis conditions and further thermal treatments for the decomposition of precursors on the phase composition and microstructure of the obtained samples will be discussed. Tough the reaction mechanism in the case of nickel nitride is still under study, preliminary electrochemical characterisation indicates that conversion reaction effectively takes place in all cases. Nonetheless, the reversibility of the process is severely dependent on the synthesis and processing conditions. Precipitation in the presence of carbon additive does have a beneficial impact in terms of cyclability, especially in the case of nickel oxide, certainly due to a more intimate mixture that results in enhanced electronic conductivity.
U2: <i>In-situ</i> Studies of Electrode Materials and Processes
Session Chairs
Monday PM, November 30, 2009
Room 200 (Hynes)
2:30 PM - **U2.1
In-situ Study on Morphological Evolution of Alloying Anodes of Li-Ion Batteries by Transmission X-ray Microscopy.
Nae-Lih Wu 1
1 Chemical Engineering, National Taiwan University , Taipei Taiwan
Show AbstractLi-alloying anode materials suffer from cyclic volumetric expansion and contraction during the charging and discharging processes. Therefore, information regarding the morphological properties of working alloy anode particles during the cyclic processes will be valuable to the research in establishing viable Li-ion battery technology based on these materials. We demonstrate in this presentation the use of transmission X-ray microscopy to in-situ monitoring morphological variations of individual working Sn and SnO anode particles dispersed on graphite during the course of cyclic lithiation/delithiation. Micrographs of Sn particles subjected to different charge/discharge depth will be presented, along with real-time moving pictures of Sn particles during the courses of lithiation and delithiation. These results are also supplemented with in-situ XRD data.
3:00 PM - U2.2
In-situ TEM Observations of LiNiO2-based Batteries During Thermal Decomposition.
Lijun Wu 1 , Yongning Zhou 1 , Xiaojian Wang 1 , Xiao-Qing Yang 1 , Yimei Zhu 1
1 , Brookhaven National Laboratory, Upton, New York, United States
Show AbstractLayer structured oxides with transition metals such as Ni, Co, and Mn have been considered as good cathode materials to replace LiCoO2 for lithium batteries due to their lower cost and higher capacity. The thermal instability in charged, especially over charged states at elevated temperatures, however, is still a major concern on this class of materials. Recent studies on Co, Al, Mn doped LiNiO2-based materials using time-resolved X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) with or without the presence of electrolyte show a series of phase transformations during heating [1]. However, due to the averaging nature of X-ray techniques, detailed information about how the structure changes initiated and propagated through new phase nucleation and growth in the microscopic level is quite limited. Therefore further studies using a local probe with high spatial resolution are needed. Here, we present our in-situ transmission electron microscopy (TEM) studies on the structural changes of over charged LiNi0.8Co0.15Al0.05O2 and LiNi0.33Co0.33Mn0.33O2 cathode materials during heating.High resolution transmission electron microscopy (HRTEM) and electron diffraction were carried out using JEM-3000F equipped with an ultra high resolution objective-lens pole-piece and a Gatan double-tilt heating stage capable with temperature ranging from room temperature to 1000 °C. The LiNi0.8Co0.15Al0.05O2 particles harvested from overcharged cell were first examined at room temperature. Electron diffraction and HRTEM show that the main phase is a layered structure with rhombohedral symmetry. Interestingly, rock-salt structure and spinel structure, which only observed at elevated temperatures using X-ray techniques, were presented at the edges and thin areas of the particles, respectively. This implies that after charging, the particles start losing some oxygen atoms near the particle surface, resulting in the structural changes. By heating the sample, we observed that the phase with the spinel structure nucleates and grows more and more into the thick area of the particles, while the rock-salt phase propagates from the surface to the interior of the particles. After heating the sample to 400 °C, the structure of the whole sample completely transformed to the rock-salt structure. For over charged LiNi0.33Co0.33Mn0.33O2 sample, spinel structure was also observed on the surfaces of the particles at room temperature. The work was supported by the U.S. Department of Energy, Office of Basic Energy Science, and the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, under the program of Vehicle Technology Program, under Contract Number DEAC02-98CH10886.[1] K.W. Nam, W.S. Yoon, X.Q. Yang, J. Power Sources 189 (2009) 515.
3:15 PM - U2.3
Study of Li-ion Intercalation in MOx by X-Ray Absorption Spectroscopy (XAS) and Inelastic X-Ray Scattering (IXS) Techniques.
Swati Pol 1 , Mahalingam Balasubramanian 1 , Kenneth Nagle 2 , Gerald Seidler 2 , Christopher Johnson 3
1 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States, 2 Physics Department, University of Washington, Seattle, Washington, United States, 3 Chemical Sciences and Engineering, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractRechargeable Li-ion batteries are the key components of today’s portable electronic technology owing to their high energy and power density. A comprehensive understanding of the local atomic structure and charge transfer mechanism on lithium ion (de)intercalation is of great impact to develop new battery materials with superior properties. The advent of third-generation synchrotron sources coupled with dedicated and specialized instruments for specific-type of x-ray scattering studies has opened a new window to systematically investigate the structure-property relationship of advanced materials under operating conditions. By means of x-ray absorption spectroscopy (XAS) and inelastic x-ray scattering (IXS) methods, we attempt to explore the charge compensation mechanism behind redox chemistry of various metal oxides in operating batteries. The techniques of XAS, namely X-ray absorption near edge structure (XANES) and X-ray absorption fine structure (XAFS), have been used to probe local structural details around specific metal atoms and are used to discern the oxidation states of the metal. The core-shell electronic properties of light elements at the lithium/metal-oxide electrode of a lithium-ion battery were studied using the lower energy resolution inelastic x-ray scattering (LERIX) spectrometer [Ref. 1], which is capable of making simultaneous IXS measurements at nineteen values of momentum transfer. This hard x-ray technique provides soft x-ray absorption-like information but with bulk-sensitivity. In addition, non-dipole transitions that are inaccessible by soft x-ray spectroscopic methods can be investigated at high momentum transfer. Acknowledgments:PNC/XOR facilities at the Advanced Photon Source, and research at these facilities, are supported by the US Department of Energy - Basic Energy Sciences, a major facilities access grant from NSERC, the University of Washington, Simon Fraser University and the Advanced Photon Source. Use of the Advanced Photon Source is also supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract DE-AC02-06CH11357. References:1. T.T. Fister, G.T. Seidler, L. Wharton, A.R. Battle, T.B. Ellis, J.O. Cross, A.T. Macrander, W.T. Elam, T.A. Tyson, Q. Qian, "Multielement spectrometer for efficient measurement of the momentum transfer dependence of inelastic x-ray scattering," Rev. Sci. Instrum. 77 (6), 063901-1-063901-7 (2006).
3:30 PM - U2.4
Nuclear Magnetic Resonance Investigation of Structure and Dynamics in Single-ion Conducting PEG600 Ionomers.
David Roach 1 , Karl Mueller 1 , Ralph Colby 2
1 Chemistry, Pennsylvania State University, University Park, Pennsylvania, United States, 2 Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractWe are studying a new class of low glass transition temperature ionomers that comprise polyethers with sulfonated anions and either Li+, Na+ or Cs+ counterions. We aim to thoroughly understand ion conduction mechanisms in this class of materials, with the ultimate goal of being able to design ionomer membranes for facile ion transport. A mixture of neutral dimethyl isophthalate and dimethyl 5-sulfo isophthalate sodium salt were used with M = 600 PEG to produce a range of ion contents. Understanding the structure and conduction mechanisms of these single-ion conducting ionomers requires an array of analytical techniques, and in studies reported here nuclear magnetic resonance (NMR) spectroscopy has been utilized for elucidating the structure and dynamics of various components within the ionomer series. Both lithium and sodium series of PEG600 ionomer with varying cation content (0%, 6%, 11%, 17% and 100%) have been investigated using several NMR methods. 7Li and 23Na magic angle spinning (MAS) assessed that the cationic species are in an aggregated state. Variable temperature (294 to 373 K) 23Na MAS detected a downfield shift and a broadening of the 23Na resonance indicating larger aggregations of cations, consistent with small angle x-ray scattering data. 13C MAS with 1H decoupling identified the major carbon chemical environments and the overall mobility of the polymer backbone within the samples. Variable temperature (233 K to 353 K) 1H-13C cross-polarization MAS (CPMAS) mapped out the motions of the polymer backbone as a function of temperature. 7Li and 23Na pulsed field gradient (PFG) NMR have also been utilized to investigate the self diffusion of the cations within these ionomer systems. Together, these data present an improved picture of the structure and dynamics in these systems.
3:45 PM - U2: In-situ
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U3: Nanomaterials for Battery Electrodes
Session Chairs
Yet-Ming Chiang
Keith Stevenson
Monday PM, November 30, 2009
Room 200 (Hynes)
4:15 PM - **U3.1
The Opportunity for Nano-materials for Lithium-Ion Batteries.
M. Stanley Whittingham 1
1 Materials, SUNY, Binghamton, New York, United States
Show AbstractTransformative changes in chemical energy storage (lithium-ion batteries) demand higher energy densities combined with lower costs. Advances in materials for both the anode and cathode are focusing on the opportunities that nano-sized and nano-structured materials have to offer. Nano-sized materials allow for much higher rates and greater long-term reversibility of the reaction. However, this can come with increased side-reactions and with lower tap density (lower volumetric capacity). Nano-structured composites can incorporate the positive attributes, whilst minimizing side-reactions and increasing the density. A number of examples from our laboratory will be used to exemplify the opportunities in the field of nanomaterials.
4:45 PM - U3.2
Nanostructured Metals and Metal Oxides for Anodes of Li-Ion Batteries.
Ming Au 1 , Thad Adams 1 , Scott McWhorter 1 , Yiping Zhao 2 , John Gibbs 2
1 , Savannah River National Lab, Aiken, South Carolina, United States, 2 , University of Georgia, Athens, Georgia, United States
Show AbstractCurrently, carbon base anodes are being used for Li-ion rechargeable batteries through Li ion intercalation process. The theoretic capacity is limited at 372 mAh/g. The volume expansion and breakdown of solid electrochemical interface (SEI) of carbon anodes during overcharging is one of the reasons of thermal runaway and fire ignition. Searching for new anode materials that possesses higher energy storage capacity and inherent fire safety is not only scientist’s passion, but the mandate of industries and customers, particularly for plug-in hybrid vehicles and portable power sources.It is found that metal oxides and metals can host Li ions through conversion process that changes lattice structure of metal oxides or forms metal alloys. The theoretic capacity of metal oxides and metals is in the range of 500 ~ 4000 mAh/g. The metal oxides do not react with polymer electrolyte and generate exceed heat. The aligned nanostructure, such as nanorods, creates large inter-rods space that is capable to store the charges and accommodates the volume expansion caused by conversion. It is expected the aligned nanorods of metal oxides will offer high energy density and power density and inherent safety. Growing free standing nanostructured anode materials on current collectors directly without additives and binders represent a new trend of anode fabrication with simplified process and low cost. In other hand, the nanoparticles of metal oxides can be assembled as the hollow spheres that offers unique feature for anodes of Li-ion rechargeable batteries. We will present our experimental results and discuss the aspects related to practical applications in the conference.
5:00 PM - U3.3
Free-standing Semiconductor Carbon Nanotube Electrodes for Lithium Ion Batteries.
Roberta DiLeo 1 , Matthew Ganter 1 , Arnold Stux 1 , Brian Landi 1 , Ryne Raffaelle 1
1 NanoPower Research Labs, Rochester Institute of Technology, Rochester, New York, United States
Show AbstractThe advancements in mobile technology have created a considerable demand for high energy density batteries for many applications including for plug-in hybrid electric vehicles, cell phones, and satellite technologies. The higher volumetric and specific energy densities of lithium ion batteries make them a compelling solution for this demand. However, even the current state-of-the art lithium ion batteries can still be improved through the use of alternative electrode materials. Lithium alloys with semiconductors such as silicon, germanium, and tin are known to have high lithium ion capacities in the range of 500 – 4000 mAh/g; but these semiconductor alloys demonstrate limitations in charge rates and cyclability due to crystal lattice expansion and contraction. The innovative pairing of nanoparticles and nanoscale coatings with CNT electrodes can significantly improve the battery energy density by eliminating the heavy inactive copper substrate. In addition, this structure can provide efficient electron transport through the CNTs and allow for a potential improvement in the crystal structure changes of the nanoparticles. In the present work, a systematic study of semiconductor deposition techniques correlating material properties, such as crystal structure and particle size, with electrochemical performance was completed. A variety of deposition techniques has been used including sputtering, thermal evaporation, and electrochemical reduction to evaluate the ability to control material properties of silicon, germanium, and tin as they are incorporated into CNT papers. Using a conventional half cell setup, the lithium ion capacity of these composites was measured with a LiPF6 and mixed carbonates electrolyte opposite a pure lithium metal anode. Values of over 800 mAh/g for the initial testing of Ge-SWNT electrodes were demonstrated. Studies investigating concentration, morphology, annealing treatments, and the oxide/reduced state of the semiconductors have been performed using Raman spectroscopy, scanning electron microscopy, and x-ray diffraction to understand more clearly how these material properties influence lithium ion capacity. Raman spectroscopy has shown an upward shift and a narrowing of characteristic peaks from as-deposited to oxidized germanium thin films suggesting the degree of crystallinity can be observed through this technique. Differences in crystallinity through deposition and processing have been monitored to demonstrate the influence of amorphous and crystalline materials on the capacity and voltage profile. In addition, studies on lithium ion capacity as a function of c-rate, ranging from C/10 to 1C, indicate the power capabilities of these semiconductor-nanotube electrodes. Also the influence of electrolyte on capacity and the formation of the SEI are investigated through the use of various mixed carbonates.
5:15 PM - U3.4
Design of Resilient Nano-Silicon Anodes.
Alexandre Magasinski 1 , Bogdan Zdyrko 2 , Benjamin Hertzberg 1 , Frank Jones 1 , Thomas Fuller 3 , Igor Luzinov 2 , Gleb Yushin 1
1 School of Materials Science and Engineering , Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Department of Material Science, Clemson University, Greenville, South Carolina, United States, 3 School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractSi anodes offer high Li storage capacity, but demonstrate low capacity retention with battery cycling due to large volume changes in Si during Li insertion and extraction. Conventional binders, developed decades ago for graphitic anodes, are not resilient enough to elastically accommodate large changes in spacing between the particles. They quickly become ineffective in holding the particles together and maintaining electrical conductivity within the anode. A few studies on the optimization of anode binders or development of Si-polymer composites have demonstrated enhancement in the cycle life and performance of Si-based anodes, but further improvements in the elastic properties of the polymers and the Si-binder adhesion are required to satisfy the industrial demands. The desired characteristics of novel Si binders include good and stable adhesion to the Si electrode particles and Cu current collectors, chemical and electrochemical stability in conventional electrolytes. The binder should allow a uniform dispersion of Si particles and be able to withstand the large dimensional changes in the anode over a large number of cycles. In this study we systematically investigated the effects of the binder chemistry, its elastic properties, functional groups, swelling behavior, as well as anode density and Si, C and binder content on the electrochemical performance of the produced anodes. Morphology of the anodes before and after cycling has been analyzed using SEM. The interface between active particles and a binder has been studied using TEM. XPS, FTIR, AFM and tensile-tests were utilized to detect changes in the binder properties. Peel tests have been performed to monitor anode adhesion to Cu current collectors. Specific anode capacity in excess of 1400 mAh/g and stable performance has been achieved for selected nanoSi-nanoC-binder formulations.
5:30 PM - **U3.5
What Are the Adjusting Screws for Tuning Materials for Electrical Storage?
Joachim Maier 1
1 , Max Planck Institute for Solid State Research, Stuttgart Germany
Show AbstractThe contribution discusses the strategies enabling the realization of functional materials for electrochemical devices. Besides synthesizing new compounds and structures, modification of given compounds is of major significance. The classical way of homogeneously doping solids is complemented by a strategy of equal importance, characterized by the purposeful introduc-tion of interfaces (“heterogeneous doping”). The potential of the latter is particularly obvious and even more pronounced in the context of nanostructuring (“nanoionics”). Using the exam-ple of Li-based batteries, the applicability of size effects is systematically investigated and the efficiency of this strategy explored.
U4: Poster Session I
Session Chairs
Yury Gogotsi
Katsuhiko Naoi
Tuesday AM, December 01, 2009
Exhibit Hall D (Hynes)
9:00 PM - U4.1
LiFePO4 Nanorod Arrays for High Performance Lithium Battery.
Xiangyang Kong 1
1 School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai China
Show Abstract We employed the oriented nanorod arrays of LiFePO4 for high capacity and high charge/discharge rate. The nanorod arrays of LiFePO4 have been prepared without any impurities by using hydrothermal process under the magnetic field up to 2T. The LiFePO4 nanorod arrays perform the well alignment along the b-axis, which is of benefit for the fast transport for lithium ions. The batteries with the aligned nanorods cathode exhibit higher electrochemical reactivity than the routinely prepared samples, and the discharge capacity was about 165mAh/g measured at a current density of 17 mA/g.
9:00 PM - U4.10
Templating of Porous Metal Nanostructures with Non-ionic Surfactants on 2-D and 3-D Substrates.
Martin Bakker 1 2 , Elizabeth Junkin 1 , Franchessa Maddox 1 , Allison Hu 1 2 , Christopher Redden 2 1
1 Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama, United States, 2 Center for Materials for Information Technology, The University of Alabama, Tuscaloosa, Alabama, United States
Show AbstractSupercapacitors and advanced batteries capable of rapid charge and discharge need conductive three dimensional porous electrodes. The high conductivities of porous metal electrodes are attractive, and are used as current collectors in Ni-Cadmium and Ni-metal hydride batteries. However, the surface areas of such electrodes are still well short of those achievable in carbon. We have been assessing the use of non-ionic surfactants of the Triton X series as soft templates for the electrodeposition of nickel, cobalt and copper on both planar electrodes and on nickel foam. High surface area nickel nano-wire networks are observed on planar substrates. On nickel foam a thin film of ca. 10 nm pores is observed. On planar electrodes cobalt forms two nanowire network structures. Copper also forms nanostructures on both substrates. Differences in the nanostructure are also observed for different ion concentrations.
9:00 PM - U4.11
Using Soft X-ray Absorption Spectroscopy to Study the Phase Transition of LiFePO4 during Lithium De-intercalation.
Xiaojian Wang 1 3 , Cherno Jaye 2 , Bin Zhang 3 , Yongning Zhou 1 , Kyung-Wan Nam 1 , Hong Li 3 , Xuejie Huang 3 , Daniel Fischer 2 , Xiao-Qing Yang 1
1 , Brookhaven Nat. Lab., Upton, New York, United States, 3 , Institute of Physics,Chinese Academy of Sciences, Beijing China, 2 , National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show AbstractSince the pioneering work of Goodenough’s group [1], olivine-structured LiFePO4 has been studied intensively as cathode material for lithium ion batteries due to its excellent safety characteristic and high thermal and chemical stabilities. In-situ XRD shows the lithiation/delithiation of LiFePO4 is a two-phase transition between LiFePO4 and FePO4. However, the details of how the new phase is nucleated and propagated are still being debated. One description uses the shrinking-core model [1]: during charge, the FePO4/LiFePO4 interface migrates from the surface to the core simultaneously in each particle, accompanied with the increase of lithium-deficient phase of and the decrease of Li-rich phase. It is reversible process for discharge. On the other hand, using electron microscopy, Chen et al., [2] and Laffont et al.[3], reported their observation of the formation of FePO4 and LiFePO4 domains in platelet-like primary particles (platelet-type model). By X-ray diffraction and high resolution transmission electron microscopy, Delmas et al., observed the co-existence of fully intercalated and fully deintercalated individual particles at a certain charged state, and proposed a domino-cascade model [4]. Recent X-ray Photoelectron Spectroscopy (XPS) results [5] also revealed a continuous evolution of the Fe3+/Fe2+ ratio at the surface of the particles upon charge, corresponding to the average content of electrochemical reaction. Although XPS serves as an excellent tool for obtaining chemical information of surfaces, it has a limitation of providing information only at the surface (analysis depth of about 5 nm). Therefore for studies involving bulk properties, XPS may not provide a full picture. In this study, we use synchrotron-based near edge x-ray absorption fine structure (NEXAFS) at the metal L-edges to simultaneously probe the surface and bulk electronic structure of LixFePO4 during Li ion deintercalation. The work was supported by the U.S. Department of Energy, Office of Basic Energy Science, and the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, under the program of Vehicle Technology Program, under Contract Number DEAC02-98CH10886.[1] Padhi, A. K.; Nanjundaswamy, K. S.; Goodenough, J. B. J. Electrochem. Soc. 144 (1997) 1188.[2] Chen, G.; Song, X.; Richardson, T. J. Electrochem. Solid-State Lett., 9 (2006) A295.[3] Laffont, L.; Delacourt, C. et al., Nat. Mater., 18 (2006) 5520.[4] Delmas, C.; Maccario, M. Et al., Nat. Mater. 7 (2008) 665.[5] Dedryvere, R. ; Maccario, M. et al., Chem. Mater., 20 (2008) 7164.[6] Yoon, W. S.; Balasubramanian, M. et al., J. Electrochem. Soc. 151-2 (2004) A246.
9:00 PM - U4.12
Single-Wall Carbon Nanotubes as Conductive Carbon Additives in Li-Ion Batteries.
Arnold Stux 1 , Matthew Ganter 1 , Robyn Schwartz 1 , Anthony Castigilia 1 , Brian Landi 1 , Ryne Raffaelle 1
1 , RIT - NanoPower Research Labs, Rochester, New York, United States
Show Abstract There are ongoing efforts to incorporate high-aspect-ratio conductive carbon additives into Li-ion batteries in order to improve the physical percolation network for enhanced electronic transport and matrix integrity over conventional carbon additives. Enhanced electronic transport can lead to an increase in capacity, high-rate performance, and cycle life which are important metrics for Li-ion batteries. In the present work, Li-ion coin cells with mesocarbon microbead (MCMB) anodes as the active material have been studied utilizing high purity single wall carbon nanotubes (SWCNTs) as a replacement for the standard conductive carbon. SWCNTs are proposed to interact with MCMB particles such that improved electronic transport and mechanical stability of the coating is achieved during cycling. Preliminary electrochemical performance has been systematically evaluated as a function of SWCNT content within the MCMB anode between 0.1 and 1.0% w/w SWCNT loading. The anode properties were probed by electrochemical impedance spectroscopy (EIS), differential scanning calorimetry (DSC), 4-point probe conductivity, and scanning electron microscopy (SEM) to study the effects of SWCNT loading. Specific capacities exceeding 300 mAh/g for MCMB anodes have been measured with SWCNT additives at an order of magnitude less mass than conventional carbon black additives. The electrochemical performance of the SWCNT-enhanced anodes was also measured as a function of charge/discharge rates to monitor the effect on rate capability. Overall, the incorporation of SWCNTs into the Li-ion anode is shown to enhance the structure-performance relationship by improving electron transport.
9:00 PM - U4.13
Chemical and Structural Stability of the Chemically Delithiated Li0.95[Fe2+0.70Fe3+0.10Cu0.15Li0.05)]PO4 Single Crystal.
Shailesh Upreti 1 , Natalya Chernova 1 , M. Whittingham 1 , Olga Yakubovich 2 , J. Cabana 3 , Clare Grey 3 , Janice Musfeldt 4
1 Chemistry and Materials, State University of New York at Binghamton, Binghamton, New York, United States, 2 Geology, Moscow State University, Moscow, Russian Federation, Russian Federation, 3 Chemistry, SUNY Stony Brook, Stony Brook, New York, United States, 4 Chemistry, University of Tennessee, Knoxville, Tennessee, United States
Show AbstractThe adoption of electric vehicles and renewable energy, based on solar or wind, demands chemical energy storage, probably based on low-cost batteries. LiFePO4 provides a green battery technology that in principle should be low cost. However, this class of material still has a number of technological limitations such as cost and volumetric energy density. In addition, its reaction mechanism is still not fully understood. A greater electronic conductivity would be a great asset, as would additional lithium capacity. The role of substitution on any of the atom sites is not at all well understood, with recent studies suggesting that isovalent substitution such as Mg on the Fe site or V on the P site enhances the capacity and increases the tap-density by forming a denser nanostructure. In nature, lithium-deficient olivine phosphates are stabilized by isovalent substitutions of ions, such as Mg2+ or Ca2+, on the Fe sites of the structure. This inspires us to produce a series of doped olivine phosphates and study their structure, electrochemical behavior and diffusion kinetics. In this work, the chemistry of dark brown single crystals of composition Li0.95[(Fe2+)0.70 (Fe3+)0.10Cu0.15Li0.05)]PO4 grown under hydrothermal condition at 400C and autogenous pressure, is reported. A remarkably high level of Cu-substitution is achieved compared to earlier reports. A systematic single crystal x-ray examination revealed Pnma space group with unit cell dimensions a = 10.226(2) Å, b = 6.012(1) Å, c = 4.682(1) Å and V = 287.8(1) Å3. In order to ascertain the presence of Li ions at the transition metal sites, a detailed solid-state Li NMR study was performed. Optical properties have been examined confirming that the electronic excitations are p-p and p-d in nature. Temperature dependent magnetic studies further validate the oxidation states expected from the reported composition and show an antiferromagnetic behavior below 49.5 K with magnetic moments aligned along [010]. This compound delivers a discharge capacity over 100 mAhg-1 when cycled between 2 and 4.5 V at a current density of 0.1 mAcm-2; this capacity is sustained at higher current rates. A 3.4 V plateau is observed at the charge curve, indicating that Li removal occurs mostly as a two-phase reaction. Chemical delithiation, executed on single crystal in a bromine acetonitrile solution, allowed a comparative X-ray structural characterization on delithiated samples. Furthermore, in situ and ex situ chemical delithiation studies, using time resolved synchrotron diffraction tools with a goal of screening Li diffusion pathway, are in progress. This work is supported by the US Department of Energy, Office of FreedomCAR and Vehicle Technologies through the BATT program.
9:00 PM - U4.14
3D Nano- and Micro- Templated Composite Electrodes for Use in Electrochemical Capacitors.
Michael Brumbach 1 , Mark Roberts 1 , Bruce Burckel 1 , Ronen Polsky 1 , Bonnie McKenzie 1 , David Wheeler 1 , Susan Brozik 1 , Bruce Bunker 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractThis work has focused on advanced electrode design through material deployment in templated electrodes for use in pseudo- and electrochemical- capacitors. The intent is to understand material and nanofunctional design of electrodes for high power delivery. Templates evaluated include nanoscale polymeric structure, sacrificial or inert oxides, as well as ordered 3-dimensional porous carbon films. Pseudocapacitive properties were evaluated by creating metal oxide electrodes with nanoscale architectures to: 1) maximize interfacial contact area with electrolyte, 2) increase solution access to electroactive material, and 3) decrease diffusion distances for charge compensating cations. Electrochemical and electroless deposition of electroactive metal oxides and conducting polymers was employed to develop complex, composite electrodes for enhanced charge/discharge behavior. Several challenges are imposed by the coupling of electroactive metal oxides and conducting polymers for charge storage including the need for a suitable electrolyte which effectively utilizes both electrode components. Cyclic voltammetry and impedance spectroscopy were used to evaluate electrode compositions and the efficacy of certain nanoscale architectures for increasing capacitance. Mechanisms for charge storage were investigated using materials characterization including XRD, SEM, and XPS.Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
9:00 PM - U4.15
Lipon Coated LiCoO2 Particles by RF-magnetron Sputtering.
Yoongu Kim 1 , Gabriel Veith 1 , Nancy Dudney 1
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractA solid polymer electrolyte suffers from oxidation problems in batteries employing a high voltage cathode over 4.0 V. A recent study indicates that a partial coating of Li3PO4 electrolyte layer on LiCoO2 powders acts as an oxidation barrier in lithium batteries with a solid polymer electrolyte [1]. Use of this Li3PO4-coated LiCoO2 cathode enables reversible cycling up to 4.6 V. Glassy lithium phosphorus oxynitride (Lipon) film electrolytes have both higher ionic conductivity (~1×10^-6 S/cm) and higher voltage windows (~5.5 V) than a Li3PO4 film electrolyte [2,3]. Previously, catalyst coatings on powder materials have been done by RF-magnetron sputtering method [4]. Here, we report a similar coating technique for Lipon electrolyte on micron size LiCoO2 powders. We will describe optimum vapor deposition conditions and effects of the Lipon electrolyte coatings on performances of rechargeable polymer lithium batteries.References[1] Yo Kobayashi, Shiro Seki, Atsushi Yamanaka, Hajime Miyashiro, Yuichi Mita and Toru Iwahori, J. Power Sources 146 (2005) 719-722.[2] J. B. Bates, N. J. Dudney, G. R. Gruzalski, R. A. Zuhr, A. Choudhury and C. F. Luck, J. Power Sources 43-44 (1933) 103-110.[3] Xiaohua Yu, J. B. Bates, G. E. Jellison, Jr. and F. X. Hart, J. Electrochem. Soc. 114 (1997) 524-532. [4] Gabriel M. Veith, Andrew R. Lupini, Stephen J. Pennycook, Gary W. Ownby and Nancy J. Dudney, J. Catal. 231 (2005) 151-158.AcknowledgementThis work was supported by DARPA Defense Sciences Office and by the Division of Materials Sciences and Engineering, U.S. Department of Energy.
9:00 PM - U4.16
Observation of Overpotential Dependent Phase Transformation Sequences in Nanoscale Olivines and a Model for their Prediction.
Ming Tang 1 , Yu-Hua Kao 2 , Nonglak Meethong 2 , James Belak 1 , W. Craig Carter 2 , Yet-Ming Chiang 2
1 Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Dept. of Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractRecent extensive experimental study has revealed a rich variety of unusual phase transition behaviors in nanosized lithium metal olivine cathodes during electrochemical cycling. In particular,amorphous phase formation was observed to be increasingly significant as particle sizes shrinks, a phenomenon not seen in larger particles. In a companion theoretical study, we developed a diffuse-interface model to rationalize experimental observations and to further predict the electrochemically-driven phase transition behavior of nanoscale olivines. Due to the preference of disordered structure by the particle surface energy, our model predicts the existence of a critical particle size below which amorphization is favored. The critical size increases considerably with the misfit strain between LiFePO4 and FePO4 olivine phases. Furthermore, the electrical overpotential applied on cathodes is identified as an important parameter that controls the transition behavior. Three regimes with distinct transition pathways were found at different overpotential levels. At low overpotentials, cathode particles undergoe the conventional crystalline transition between LiFePO4 and FePO4 olivines. Spontaneous amorphization is the main transition pathway at intermediate overpotential values. However, the crystalline transition becomes dominant again at higher overpotentials due to 1) the recrystallization of amorphous phase and 2) the kinetic limitation of amorphization. The model predictions have been verified by recent in-situ X-ray diffraction experiments.
9:00 PM - U4.18
Layer-by-Layer Assembled TiO2 – Multiwall Carbon Nanotube Nanostructures for Lithium-Ion Battery Electrodes.
Betar Gallant 1 , Seung Woo Lee 2 , Jung Ah Lee 2 , Paula Hammond 2 , Yang Shao-Horn 1
1 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States, 2 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractWhile a large number of metals and metal oxides can react with lithium by intercalation or displacement reactions, large chemical strains associated with lithium uptake and surface film growth upon electrolyte decomposition often result in considerable capacity loss during cycling. Nanomaterials can better accommodate volumetric strains resulting from lithium insertion, and therefore offer one opportunity for improving electrode lifetime. In addition, the high surface area to volume ratio enables faster charging and discharging, and can therefore address a critical limitation of typical bulk materials. However, in conventional composite electrodes, significant amounts of conductive additive and insulating binder are needed to ensure that active nanoparticles remain electrically connected, and this can reduce the electrochemically active surface area. It is therefore of interest to develop nanostructures that are additive-free and in a 3D network with facile electronic and ionic conduction. Such electrodes can not only allow fundamental understanding of size effects on lithium reaction mechanisms but also potentially lead to enhanced power capability of lithium batteries.In this study, we create thin-film nanostructures that combine the high theoretical capacities of metal oxides with good electrical conductivity and high surface area of multiwall carbon nanotubes (MWNTs). In particular, we employ anatase TiO2 nanoparticles, a promising negative electrode material with reported capacities of 170 mAh/g and higher, a redox potential (1.8 V vs. Li) outside the voltage window for surface film formation (below 1 V vs. Li), low cost, and widespread availability. We prepare TiO2-MWNT thin films using the layer-by-layer (LbL) technique, which utilizes electrostatic interactions between positively charged anatase TiO2 nanoparticles and negatively charged functionalized MWNTs. MWNT-TiO2 film growth and quality are investigated in terms of electrical conductivity and film roughness as a function of electrode thickness. Cyclic voltammogram and galvanostatic testing data of MWNT-TiO2 electrodes in lithium cells will be presented and the effect of electrode thickness and microstructure on lithium reaction kinetics will be discussed.
9:00 PM - U4.2
Improved Lithium Ion Intercalation Property of Sol-gel Derived Amorphous LiFePO4-V2O5 Films.
Yanyi Liu 1 , Dawei Liu 1 , Qifeng Zhang 1 , Anqiang Pan 1 , Guozhong Cao 1
1 Materials Science and Engineering, University of Washington, Seattle, Washington, United States
Show AbstractThis paper for the first time reports sol-gel derived amorphous LiFePO4-V2O5 films exhibiting much enhanced electrochemical properties and cyclic stabilities. V2O5 and LiFePO4 sols were synthesized first and then combined to form a stable LiFePO4-V2O5 sol with a molar ratio of LiFePO4: V2O5 =2:1. LiFePO4-V2O5 films were obtained by spreading the sol on FTO substrates followed by ambient drying overnight and nitrogen atmosphere annealing at 500oC for 3 hours. For comparison purpose, pure LiFePO4 and V2O5 thin films were also prepared. Uniform crack-free LiFePO4, V2O5 and LiFePO4 - V2O5 films were readily obtained. While V2O5 films are made of orthorhombic vanadium pentoxide phase, both LiFePO4 and LiFePO4-V2O5 films are amorphous after annealing at 500oC for 3 hours as determined by means of X-Ray Diffractometry. Scanning Electron Microscopy images revealed that the LiFePO4-V2O5 films consisted of two types of homogeneously dispersed and closely packed distinct particles. The electrochemical characterization revealed that the LiFePO4-V2O5 films exhibited the Li-ion intercalation capacity of 252mAh/g at a current density of 100mA/g and 168mAh/g at 200mA/g, which were among the highest up-to-date data according in authors’ knowledge. The LiFePO4-V2O5 films also demonstrated an extraordinary cyclic stability of Li-ion intercalation and deintercalaion even at high current densities. Both Li-ion intercalation capacity and cyclic stability of the LiFePO4-V2O5 films exceeded that of LiFePO4 or V2O5 films fabricated under the same condition. Such enhanced Li-ion intercalation capacity and cyclic stability could be attributed, at least in part, to the amorphous structure of LiFePO4-V2O5 films, which has a relatively lower density than its crystalline counterpart with more void space allowing easy mass transport and change of volume associated with Li-ion intercalation. Amorphous, as a thermodynamic metastable phase, also has a broader potential range for Li-ion intercalation as its constituent ions possess different local environment compared to its crystalline form. The mixture and coexistence of V2O5 and LiFePO4 during film casting and subsequent thermal annealing prevented the crystallization of both V2O5 and LiFePO4 due to complexity and interferences.
9:00 PM - U4.21
Analysis of Active Materials Debonding from Polymeric Binders caused by Insertion Reaction in Lithium-ion Batteries.
Nanshu Lu 1 2 , Joost Vlassak 1 , Zhigang Suo 1
1 SEAS, Harvard University, Cambridge, Massachusetts, United States, 2 Beckman Institute, University of Illinois at Urbana-Champaign, Urbana-Champaign, Illinois, United States
Show AbstractIn a lithium-ion battery, both electrodes are atomic frameworks that host mobile lithium ions. When the battery is being charged or discharged, lithium ions diffuse from one electrode to the other. Such an insertion reaction deforms the active materials, and may cause the active particles to debond from the polymeric binders, resulting in loss of electrical conductivity of the electrode. Using fracture mechanics, we show that the volume fraction of the active materials and the stiffness of the polymeric binder have significant effects on the driving force of partical-binder debonding. Critical conditions are determined to avert debonding.
9:00 PM - U4.22
Silicon-Carbon Nanocomposite Anodes for Li-ion Batteries.
Benjamin Hertzberg 1 , Patrick Dixon 1 , Alexandre Magasinski 1 , Gleb Yushin 1
1 School of Materials Science and Engineering , Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractThe specific capacity of Si exceeds that of graphite, the conventional anode in Li-ion batteries, by an order of magnitude. However, achieving stable performance of Si anodes is a challenge. Recent experiments suggest that individual Si nanoparticles and thin films below a critical size do not fracture and exhibit high reversible capacity for Li. The often observed rapid degradation of Si-based anodes is related not to the intrinsic property of Si but to the loss of electrical contact within the anodes caused by the large volume changes that takes place during Li insertion and extraction. In this project we have produced high capacity nanocomposite Si-C particles that do not exhibit volume changes during Li insertion and extraction. According to our approach Si thin films are deposited on the internal pore walls of porous carbon and expand within the available pore volume during electrochemical alloying with Li. The predicted cost of the nanocomposite is comparable or lower than that of the graphite. Morphology of the anodes particles has been analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Charge-discharge, cyclic voltammetry and electrochemical impedance spectroscopy studies have been performed in 2016 coin cell and pouch cell configurations. Charge-discharge experiments have been performed in the 0.01-2 V range vs. Li/L+. Specific anode capacity in excess of 700 mAh/g and stable performance of up to 40 cycles has been achieved.
9:00 PM - U4.23
Improvement of Battery Performance by Controlling Electrode/Electrolyte Interface Structure of All Solid-State Lithium Secondary Batteries.
Kyosuke Kishida 1 , Haruyuki Inui 1 , Yasutoshi Iriyama 2 , Zempachi Ogumi 3
1 Department of Materials Science and Engineering, Kyoto University, Kyoto Japan, 2 Department of Materials Science & Chemical Engineering, Shizuoka University, Hamamatsu Japan, 3 Department of Energy and Hydrocarbon Chemistry, Kyoto University, Kyoto Japan
Show AbstractSolid state lithium-ion conductors have received a considerable amount of attentions as solid electrolytes for all solid-state lithium rechargeable batteries, which have great advantages in terms of safety, thermal stability and resistance to shocks and vibrations. In the case of the all solid-state batteries, structure of interface between the electrode and solid electrolyte must have great influences on the battery performance such as resistivity and mechanical stability of the interface. However, the relationship between the interface and electrochemical properties has not been studied in detail. Recently, we have studied influences of microstructures of the electrolyte/cathode interfaces on electrochemical properties using model assemblies with a perovskite-based lithium lanthanum titanate (LLT: La2/3-xLi3xTiO3) solid electrolyte and a HT-LiCoO2 cathode with a layered rock-salt type structure). Our previous results suggest that the resistivity and mechanical stability of the interface can be controlled mainly by two factors, namely nano-scale defect regions such as amorphous LLT at the interface and geometrical configuration of Li layers in LiCoO2 crystal against the interface plane. In the present study, we prepared various model samples each composed of LiCoO2 cathode thin film deposited on polycrystalline LLT solid electrolyte with different type of surface finishes or single crystalline LLT with different surface orientations. Microstructures of the various LLT/LiCoO2 interfaces and their influences on the electrochemical properties of the model cells were investigated in order to elucidate the influence of the two structural factors on the battery performance.LiCoO2 thin-film cathode with a thickness about 100nm is epitaxially grown with the orientation relationships: {110}LLT//{11-20}LiCoO2 and <001>LLT// <4-401>LiCoO2. LiCoO2 domains with their layered structure aligned perpendicular to the interface are dominantly formed when the interface is parallel to (110) of a single crystalline LLT, whereas those with the layered structure inclined about 20° against the interface are dominantly grown when the interface is parallel to (112) of a single crystalline LLT. CV tests of these two assemblies reveal that the former sample exhibits much better battery performance in terms of the interfacial resistivity and the cycle stability, which stems from the advantageous geometrical configuration of the layered structure of LiCoO2 and the fine-scale domain size. In addition, improvement of battery performance is confirmed by the experiments using assemblies prepared on ion-irradiated or shot-peened surfaces of polycrystalline LLT, both of which have a layer of thin amorphous LLT at the interface. These results confirm that the apparent interface resistivity can be lowered partly by controlling the surface plane of LLT and also by the introduction of amorphous LLT layer through surface modification processes for LLT surface.
9:00 PM - U4.25
Tunable Mechanical and Electronic Properties of Nanoporous Foams.
Tony van Buuren 1 , Juergen Biener 1 , Ted Baumann 1 , Sergei Kucheyev 1 , Jon Lee 1 , Morris Wang 1 , Alex Hamza 1 , Ln Shao 2 3 , Raghavan Nadar Viswanath 2 , Dominik Kramer 2 , Joerg Weissmueller 2 3 , Arne Wittstock 4 , Marcus Baeumer 4
1 , LLNL, Livermore , California, United States, 2 , Institute of Nanotechnology Forschungszentrum, Karlsruhe Germany, 3 Technische Physik,, Universität des Saarlandes, Saarbrücken Germany, 4 Institut für Angewandte und Physikalische Chemie, Universität Bremen, Bremen Germany
Show AbstractUnderstanding the correlations between electronic structure, surface chemistry, and surface energy is of fundamental importance to the development of new nanoporous materials for energy storage applications. Nanoporous solids are unique in a way that their macroscopic properties can be determined by surface properties. For example, charge-transfer induced changes of the surface stress have been shown to trigger macroscopic and reversible strain effects in nanoporous carbon and nanoporous Au. We will report on our first attempts to measure changes in the electronic structure of nanoporous materials by in situ x-ray adsorption and emission spectroscopies, and correlate these results with macroscopically measurable properties such as capacity and strain.
9:00 PM - U4.26
Synthesis of SnO/carbon Nanotube Nanocomposites for an Anode of Lithium-ion Battery.
Ken Sakaushi 1 , Yuya Oaki 1 , Eiji Hosono 2 , Haoshen Zhao 2 , Hiroaki Imai 1
1 Faculty of Science and Technology, Keio University, Yokohama Japan, 2 Energy Technology Research Institute , National Institute of Advanced Industrial Science and Technology, Tsukuba Japan
Show AbstractAt the present, tin is one of the most interested elements for the anode of lithium-ion battery. Especially, tin oxides are greatly focused of all other tin based materials since they have large theoretical maximum reversible capacity: tin monoxide SnO has 875 mAh/g and tin dioxide SnO2 has 790 mAh/g. However, it is difficult to commercialize SnO or SnO2 anode because of their poor cycle properties caused by a large volume expansion (ca. 300%). Nanosizing, morphological control and integrating with other materials are clues of enhancing electrochemical properties of the elements that making alloy with lithium. There are a lot of reports about nanostructured SnO2 composites, such as composites with carbon nanotubes (CNTs) or carbon hollow spheres. They show good electrochemical properties. Particularly, they succeeded to develop cycle performance. From this point of view, fabrication of nanostrucutred SnO composites with carbon materials may also be able to improve electrochemical performances of SnO. However, a few reports about nanostructured SnO composites are studied since SnO is difficult to fabricate in nanostructured materials. Therefore, it is necessary to find fabrication routes to synthesize nanostructured SnO composite materials. Our group has studied synthesis of SnO in the aqueous solution by controlling the value of pH and amount of starting materials. Our focus for this study is fabrication of SnO/CNT composite. Therefore, we studied crystal growth of nanostructured SnO by homogeneous nucleation on substrates. In consequence, SnO nanosheets were successfully obtained on CNTs that are ca.100 nm in diameter and ca.5 μm in length. Thermal decomposition of urea was utilized to control supersaturated condition with gradual increase in pH. SnO nanosheets that were grown in c axis oriented was ca.5 nm in thickness and ca.200 nm in size. The specific surface area of SnO/CNT composite was 42.5 m2/g. This SnO/CNT composite material is expected as excellent anode material for lithium-ion battery because long CNTs that have good electronic conductivity would act as smooth electronic paths.
9:00 PM - U4.27
Electrical Transport Properties of Graphite Nanosheets Doped Polyvinylidene Fluoride Composites.
Yuchao Li 1 , Sie Chin Tjong 1 , Robert Kowk Yiu Li 1
1 Physics and Material Science, City University of Hong Kong, Hong Kong China
Show AbstractGraphite nanosheets (GN) were introduced into piezoelectric polyvinylidene fluoride (PVDF) via solution mixing technique. The nanocomposites were then subjected to compression molding for electrical measurements. Solution mixing enabled homogeneous dispersion of GN within PVDF matrix. The electric transport behavior of such nanocomposites was studied by means of impedance spectroscopy in a wide frequency range from 102 to 107. The results showed that the dielectric constant and conductivity of the composites are frequency dependent and well obeyed with the scale law (σ ∝ ωu and ε ∝ ω-v ) in the vicinity of percolation threshold (Φc = 2.4 wt%). A large dielectric constant of 173 with a low loss tangent of 0.65 was found for PVDF/GN 2.5 wt% composites at 1 KHz. Such enhancement in dielectric constant could be interpreted in terms of the formation of mini-capacitors associated with the dispersion of graphite nanoplatelets in insulating PVDF matrix.
9:00 PM - U4.28
Pore Width Dependence of Hydrated Ca2+ Structure in Hydrophobic Nanopore.
Natsuko Kojima 1 , Tomonori Ohba 1 , Hirofumi Kanoh 1 , Katsumi Kaneko 1
1 Graduate School of Science, Chiba University, Chiba Japan
Show Abstract The structure of molecules or ions in solid nanospace is often different from their bulk structure1 2. Especially, the structure of aqueous solution in nanopore is not understood regardless of the importance in the wide area of science and technology. We have studied the structure of Ca2+ aqueous solution in slit-carbon space with canonical ensemble Monte Carlo simulation. The pore width of the hydrophobic nanopore was changed from 0.6 to 1.8 nm and the concentration of solution was 1.0 mol dm-3. The parameters of ions were determined by lattice enthalpy of CaCl2 crystals and the TIP5P potential model 3 for water was used. The interaction energy of molecules and ions with graphite pore was calculated with Steele potential 4.
Water molecules form the layered structure of which thickness depends on the pore width. Ca2+ ions are distributed near the central region of the pore. The radial distribution function analysis showed that the Ca2+ ion had a planer hydration structure in the 0.6 nm slit-pore, being completely different from the hydrated structure of the Ca2+ ion in the wider pores and the bulk Ca2+ ions.
1 Kaneko, K. Adsorption 1997, 3, 197.
2 Ohba, T.; Kaneko, K. Mol. Phys., 2007, 105, 139.
3 Mahoney, M. W.; Jorgensen, W. L. J.Chem.Phys. 2000, 112, 8910.
4 Steele, W. A. Surf. Sci. 1973, 36, 317.
9:00 PM - U4.3
Tin (Sn) Whiskers and Nanowires as Negative Electrodes for Li-ion Batteries.
Juchuan Li 1 , Fuqian Yang 1 , Yang-Tse Cheng 1
1 Chemical & Materials Engineering, University of Kentucky, Lexington, Kentucky, United States
Show AbstractSn is a candidate material for the negative electrodes of lithium-ion batteries due to its high theoretical energy capacity. However, bulk Sn electrodes can fracture as a result of lithium insertion and de-insertion, causing mechanical degradation. Recently, it has been shown that whiskers and nanowires can substantially enhance battery cycle life and durability than their bulk counterparts. These observations and theoretical predictions [1] paved the way for developing new materials and structures for high capacity lithium-ion batteries. In this paper, we report three stress-induced growth methods for creating Sn whiskers and nanowires for lithium-ion battery applications. High compressive stresses are generated using substrate bending, indentation [2], and co-deposition [3]. The characteristics of Sn whiskers, including size, density, crystal structure, and growth rate for each method are investigated and compared. The electrochemical behavior of the whiskers and nanowires as lithium ion battery electrodes will also be reported, including cycle life and energy capacity of the electrodes. [1] Y.-T. Cheng and M. W. Verbrugge. The influence of surface mechanics on diffusion induced stresses within spherical nanoparticles. J. Appl. Phys. 104 (8), 083521 (2008).[2] F. Yang and Y. Li. Indentation-induced tin whiskers on electroplated tin coatings. J. Appl. Phys. 104 (11), 113512 (2008).[3] Y.-T. Cheng, A. M. Weiner, C. A. Wong, M. P. Balogh, and M. J. Lukitsch. Stress-induced growth of bismuth nanowires. Appl. Phys. Lett. 81 (17), 3248-3250 (2002).
9:00 PM - U4.31
Synchrotron Based X-ray Studies on the Thermal Decomposition Mechanism of Charged Cathode Materials for Li-ion Batteries.
Kyung-Wan Nam 1 , Xiao-Jian Wang 1 , Yong-Ning Zhou 1 , Won-Sub Yoon 2 , Otto Haas 1 , Xiao-Qing Yang 1
1 Chemistry department, Brookhaven National Laboratory, Upton, New York, United States, 2 School of Advanced Materials Eng, Kookmin University, Seoul Korea (the Republic of)
Show AbstractThe research and development of hybrid electric vehicle (HEV) and plug-in hybrid electric vehicle (PHEV) are intensified due to the energy crisis and environmental concerns. Having the highest energy density among all rechargeable batteries, lithium-ion battery is considered as the best candidate of rechargeable batteries for transportation applications. In order to meet the challenging requirements of powering HEV and PHEV, the safety characteristics of lithium battery need to be thoroughly studied and significantly improved. The thermal stability of the cathode materials is one of the key issues of the safety characteristics, which is related to the occurrence of exothermic reactions in charged batteries at elevated temperatures that can result in thermal runaway and catastrophic failure of the battery. The thermal runaway has been attributed to the reactions between the charged electrodes and the electrolyte. Therefore, in-depth understanding of the structural changes of the charged cathode material during thermal decomposition, with or without the presence of electrolytes and their relationship to the thermal stability of the cathode material is very important. We have developed techniques using the combination of a high intensity synchrotron X-ray beam and fast detectors (image plate or position sensitive detectors) to do time resolved X-ray diffraction (TR-XRD) during the thermal decomposition of charged cathode materials. Recently, we have developed synchrotron based hard X-ray absorption (XAS) techniques to study the oxidation state and local structural changes of each element during the thermal decomposition of charged cathode materials. In addition, the in situ soft XAS techniques we have developed allow us to distinguish the structural differences between the surface and bulk of electrodes using both partial electron yield (PEY) and fluorescence yield (FY) detectors simultaneously during heating of charged cathode materials. In this presentation, we will report our studies on the structural changes of layered nickel based cathode materials (e.g., Li1-xNiO2, Li1-xNi0.8Co0.15Al0.05O2 and Li1-xNi1/3Co1/3Mn1/3O2) during thermal decompositions. The combined results from these synchrotron based X-ray techniques will provide valuable information for synthesizing thermally stable cathode materials and improving the thermal properties of the materials being used currently.TR-XRD spectra were recorded as a set of circles on a Mar 345-image plate detector in the transmission mode at beamline X7B at National Synchrotron Light Source (NSLS). Soft and hard XAS spectra were measured at beamline U7A and X19A&X18B at NSLS, respectively. ACKNOWLEDGMENTThe work done at Brookhaven National Lab. was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. DOE under Contract No. DE-AC02-98CH10886.
9:00 PM - U4.33
High-Throughput Computational Search for New Li-ion Battery Cathode Materials.
Anubhav Jain 1 , Geoffroy Hautier 1 , Charles Moore 1 , Christopher Fischer 1 , Kristin Persson 2 , Robert Doe 1 , Byoungwoo Kang 1 , Xiaohua Ma 1 , Jae Chul Kim 1 , Hailong Chen 1 , Denis Kramer 1 , Timothy Mueller 1 , Shirley Meng 3 , Gerbrand Ceder 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 , Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 , University of Florida, Gainesville, Florida, United States
Show AbstractAb initio computational methods have been critical in understanding properties of existing battery materials and predicting trends useful in the design of next-generation compounds[1]. High-throughput ab initio computations, performed over tens of thousands of compounds, can use these developments to potentially screen new Li-ion battery cathode materials on an unprecedented scale. To date, our group has performed via density functional theory over 50,000 total energy computations and 7,000 voltage predictions. These calculations have covered the space of materials in the Inorganic Crystal Structure Database[2], as well as variations on these materials generated using data-mined crystal structure prediction methods[3].The infrastructure needed to generate, manage, store, and analyze such large computational data sets composes a major portion of our project and is briefly described. Our calculations have recovered the properties of known battery materials, validating our approach towards the search for new cathode materials with high capacity, high rate capability, and high stability. Synthesis efforts are now underway on novel compounds suggested by our computational screening procedure. In addition to its application for materials discovery, high-throughput computational data can serve as a knowledge base which can be data mined for cathode design principles. We show in particular how existing theories describing the tuning of redox couple voltage via the inductive effect can be combined with our large data set to create voltage prediction models which hold across several structure types, redox couples, and polyanion chemistries. Such models lead to ‘cathode design maps’ which show the interesting redox couples for a given polyanion chemistry, based on necessary voltage and energy density constraints.1.Ceder, G., et al., Identification of cathode materials for lithium batteries guided by first-principles calculations. Nature, 1998. 392(6677): p. 694-696.2.Bergerhoff, G., et al., The Inorganic Crystal-Structure Data-Base. Journal of chemical information and computer sciences, 1983. 23(2): p. 66-69.3.Fischer, C.C., et al., Predicting crystal structure by merging data mining with quantum mechanics. Nature Materials, 2006. 5(8): p. 641-646.
9:00 PM - U4.34
Multifunctional Zeolite-like Materials for Energy Applications.
Victoria Soghomonian 1
1 Physics, Virginia Tech, Blacksburg, Virginia, United States
Show AbstractElectrically conducting zeolite-like frameworks are largely unstudied as electronic materials, but may offer new avenues in energy applications, ranging from electrical energy storage to catalysis. Zeolitic materials are characterized by the presence of nanoscale channels and cavities delineated by their crystalline framework. As a function of the structure, the specific surface area in zeolitic materials is high. Thus, for instance a novel avenue for realizing higher energy density capacitive electrical storage capabilities can be addressed by a materials system that combines the structural properties of well known but electrically insulating microporous zeolites, with an electronically active framework, as our work indicates. We present a 3-D oxo-vanadium arsenate electrically conducting zeolite-like material, isolated by hydrothermal methods. The vanadium arsenate framework crystallizes in a cubic space group, and we discuss the crystal structure, the thermal stability and the microporous properties of the framework. We then present the experimentally measured electronic and ionic conductivities on single crystals, the temperature dependences of the conductivities, and discuss possible electronic and ionic conduction mechanisms at play in the material, in the empty framework and in the ion-exchanged framework. Measurements suggest that the ionic conductivity occurs through channeling of ions through a sublattice, mediated by phonon-assisted hopping, whereas the electronic conductivity indicates non-metallic behavior. In a zeolite-like material, the pore density is high, due to the regular crystalline arrangement and the small pore size, allowing the packing of large number of ions into the framework. If the framework is electrically conducting, an electrical double-layer may form between a charge in a pore and the framework, resulting in electrical double layer capacitive electrical energy storage. The distance between the charge and the microporous and electrically conducting framework is atomic in scale and this property combines with the high pore density to yield very high capacitances. Thus higher energy per unit volume is realized. Our preliminary calculations and measurements for the vanadium arsenate suggest up to an 8-fold increase in energy density over existing mesoporous carbon implementations.
9:00 PM - U4.35
Electrocatalytic Activity of Oxygen Reduction Reactions on Platinum and Glassy Carbon for Li-Air Batteries.
Yi-Chun Lu 1 4 , Hubert Gasteiger 4 , Robert McGuire 3 4 , Ethan Crumlin 2 4 , Yang Shao-Horn 1 2 4
1 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Electrochemical Energy Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractLi-air batteries replace the traditional intercalation electrode with a catalytic porous electrode (air electrode), which can absorb and reduce O2 from the air. During discharge, Li+ ions can react with dissolved oxygen to form insoluble reaction products such as lithium (per)oxide within the pores of the air electrode. Upon charging, lithium (per)oxide can decompose to oxygen and lithium. Li-air batteries have much greater energy density compared to traditional lithium ion batteries based on lithium intercalation compounds. However, current Li-air batteries have low reversibility, low power capability, and short cycle life, which is limited primarily by the reaction kinetics and transport resistances in the air electrode. Kinetics of O2 reduction and evolution in the air electrode is poorly understood. In this study, we examine the electrocatalytic activity of the oxygen reduction reaction (ORR) on platinum and glassy carbon model electrodes in lithium-conducting nonaqueous electrolyte using rotating disk electrode (RDE) measurements.Well-defined model surfaces of polycrystalline platinum and glassy carbon (5 mm OD x 4 mm thick, mirror polished) were studied via RDE to identify the various transport/reaction processes occurring on the catalytic surfaces and uncover the true catalytic activity of the materials toward the interested reactions. Cyclic voltammogram for polycrystalline platinum and glassy carbon electrode were studied in 1M LiClO4 in PC:DME (1:2, by volume) under argon or in the presence of oxygen, with sweep rate equals to 5 or 20 mV/s and at various rotation rates. Initial RDE results have shown that (i) the catalytic activity of ORR for the 1st cycle is higher than the subsequent cycles due to the accumulation of lithium (per)oxide on the surfaces. The catalytic activity will then reach steady state soon after the first two cycles, (ii) the lithium (per)oxide-poisoned surfaces can be regenerated by holding the potential at ~ 4.4 V(vs. Li) for a few minutes to get back to the same activity as the clean surface in the first cycle, (iii) the ORR behavior is highly correlated with the accumulation rate (controlled by scan rate) of lithium (per)oxide during oxygen reduction reaction and (iv) the glassy carbon surfaces seem to have higher catalytic activity toward oxygen reduction than the polycrystalline platinum surfaces in the Li-air battery system. Mechanisms of the reaction kinetics on these model surfaces will be discussed.
9:00 PM - U4.36
Electronic Properties of Polypropylene Capacitor Dielectrics from First Principles.
M. Stournara 1 , R. Ramprasad 1
1 , Institution of Materials Science, UConn, Storrs, Connecticut, United States
Show AbstractPolypropylene, being one of the fastest growing engineering plastics, has wide industrial and everyday life applications due to attractive properties such as low density, high melting point, high tensile strength, and a high resistance to chemical attack. A major application area where (biaxially oriented) polypropylene has already found a niche is in high density energy storage capacitor dielectric systems. Still, demands for ever higher electrical energy density continues. Since the energy density scales with the square of the electric field in the dielectric, significant improvements of energy density for a given dielectric can only be achieved by increasing the electrical breakdown strength, and consequently through a fundamental understanding of the factors controlling the breakdown strength and high field electrical conduction. These considerations provide the motivation for the present ab initio density functional theory (DFT) study of the electronic properties of defect-free and defective isotactic polypropylene (iPP).Our DFT calculations have focused on single chains of iPP as well as bulk iPP in the α form (α-iPP). These bulk calculations constitute the first-ever DFT calculations of this system. Our results for the physical structure (in terms of C-C and C-H bond lengths, C-C-C and C-C-H bond angles, and lattice parameters of α-iPP) are in excellent agreement with experiments. We have computed the band structure of α-iPP, and using the self-consistent local electronic potential, we have also determined the electron affinity of this system to be 0.31 eV; this is in contrast to the small but negative electron affinity values of polyethylene. Furthermore, we have also studied various types of chemical imperfections in α-iPP, and have assessed the impact of these defects on its electronic structure. Specifically, hydroxyl, carbonyl and double bond defects were considered. In each of these cases, a doubly occupied state and an unoccupied state were created in the band gap of α-iPP (constituting hole and electron traps, respectively). We find that the carbonyl defects cause the most significant impact to the band structure, resulting in the deepest electron and hole traps. Finally, we have also studied the interface between metal electrodes and iPP, and have determined the interface barrier heights as a function of the atomic-level structure of the interface.
9:00 PM - U4.37
A Comparison of the Li-M-P-O2 (M=Fe, Mn) Phase Diagrams from First Principles Calculations.
Shyue Ping Ong 1 , Byoungwoo Kang 1 , Anubhav Jain 1 , Gerbrand Ceder 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractWe present a comparison of the phase diagrams of the quaternary Li-M-P-O2 (M = Fe, Mn) systems developed from first principles calculations. These phase diagrams are of interest to material scientists developing synthesis routes for the well-established positive electrode material, LiFePO4, as well as the potentially promising LiMnPO4. Using the methodology outlined in our earlier work, the phase diagrams were constructed as a function of oxidation conditions, with the oxygen chemical potential, μO2, capturing both temperature and oxygen partial pressure dependence. The Li-Fe-P-O2 phase diagram shows LiFePO4 to be stable over a wide range of oxidation environments. The predicted phase relations and reduction conditions compare well to experimental findings on stoichiometric and Li-off-stoichiometric LiFePO4. Kang et al. subsequently showed that the phase diagram can be applied to identify off-stoichiometric synthesis routes which led to LiFePO4 with very high rate capabilities. In comparison, the Li-Mn-P-O2 phase diagram shows LiMnPO4 to be stable over an even wider range of oxidation environments. Consistent with experimental evidence, LiMnPO4 is first formed at more oxidizing conditions than LiFePO4. LiMnPO4 is also reduced at more reducing conditions that LiFePO4, again consistent with the experimental observations of Ellis et al. We will also highlight salient differences between the two phase diagrams under various oxidation environments.
9:00 PM - U4.38
Heavy Doping of Li+-ion into NiO Epitaxial Thin Films via Unequilibrium Room-temperature Processing for New Functionalization.
Naoki Shiraishi 1 , Yushi Katou 1 , Yuki Sugimoto 1 , Hideki Arai 1 , Nobuo Tsuchimine 2 , Susumu Kobayashi 2 , Masahiko Mitsuhashi 3 , Mamoru Yoshimoto 1
1 Department of Innovative and Engineered Materials, Yoshimoto laboratory, Tokyo Institute of Technology, YOKOHAMA-SHI, KANAGAWA, Japan, 2 , TOSHIMA manufacturing company, HIGASHIMATSUYAMA-SHI, SAITAMA, Japan, 3 , Kanagawa Industrial Technology Center, EBINA-SHI, KANAGAWA, Japan
Show AbstractNiO is a typical material for new p-type oxide semiconductors. Conductivity of NiO can be raised with Li+ doping. In case of Li-heavy doping, we can obtain LixNiO2(0.5< x <1.0). Recently the importance of LiNiO2 has been increased as an electrode material for rechargeable lithium cells.In this work, we tried to fabricate a novel NiO material with Li+-heavily doped by applying the pulsed laser-induced room temperature (R.T.) film process. Previously, we have succeeded in the epitaxial growth of various oxide thin films at R.T. such as Sn-doped In2O3 transparent electrodes [1]. Although the many studies have been made on the deposition of NiO epitaxial thin film at low temperatures [2], there are few reports on fabrication and the conductive characteristic for Li-heavily doped NiO epitaxial films. The film deposition at R.T., which is the unequilibrium vapor phase process, is expected to result in different crystal structure and characteristics from the films grown at high-temperatures.A composition-adjusted thin film of LixNi1-xO(0.10< x <0.40) was deposited on a sapphire (α-Al2O3)(0001) or MgO(100) substrates by pulsed laser deposition (PLD) technique in 10-6 Torr of oxygen at R.T. and the high temperatures of 350 and 515°C. Crystalline properties of thin films deposited at R.T. or high temperatures were examined using reflection high energy electron diffraction (RHEED) and X-ray diffraction. For the Li-heavily doped NiO films(x>0.30) grown at R.T., a clear streak RHEED pattern showing epitaxial growth was observed. But the Li-heavily doped NiO films grown at high temperatures, exhibited the ring RHEED pattern, which indicates the policrystal growth of films. Electric conductivity of various Li-doped NiO thin films deposited at R.T. or high temperatures on sapphire (0001) substrates were measured by two-probe method. The interesting results were obtained that conductivity of the film was increased remarkably with an increase of Li-doping for R.T. deposition, but was not changed so much regardless of Li-doping for high-temperature depositions. [1] J.Tashiro et al., Thin Solid Films 415(2002)pp272[2] A.Matsuda et al, Appl. Phy. Lett. 90.182107(2007)
9:00 PM - U4.39
Olivine Electrode Engineering Impact on the Electrochemical Performance of Lithium Ion Batteries.
Wenquan Lu 1 , Andrew Jansen 1 , Dennis Dees 1
1 , Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractIntroductionIn order to improve the power capability of lithium iron phosphate, several approaches, such as carbon coating, doping, and/or particle size reduction, have been successfully utilized to mitigate the poor electronic conductivity and slow lithium ion diffusion. However, electrode engineering is also very critical, but easily overlooked, to fully optimize its electrochemical performance in lithium ion batteries. Electrode engineering becomes increasingly important when the active material is less electronically conducting and has a very small particle size, such as LiFePO4. In this work, a carbon coated LiFePO4 with sub-micron particle size is investigated for high power applications, such as a hybrid electric vehicle (HEV) and a plug-in HEV (PHEV). This study will focus on how the engineering process affects the cell impedance and its electrochemical performance.Results and DiscussionActive lithium iron phosphate (LiFePO4) (including 6 wt.% carbon coating) was mixed with 4 wt.% SFG-6 graphite, 4 wt.% acetylene black, and 8 wt.% PVDF binder. The cast electrode laminate was calendered into different thickness, corresponding to various porosities. The electronic conductivity of the electrode was checked using a four point probe method, which indicated that the electronic resistance increased with increasing electrode porosity. In general, the electronic resistance of the cast electrode can be attributed to the carbon/olivine, carbon/carbon, and electrode composite/current collector contact resistances. In order to elucidate the contribution of the electronic resistance to the overall impedance, electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM) were carried out. It is obvious from SEM images that the low porosity olivine electrode has better contact. The EIS results indicate that the high particle/particle electronic contact resistance seems to be a major contributor to the overall impedance of the sub-micron carbon coated olivine electrode with less calendering. Direct Current (DC) studies on Lithium/LiFePO4 half cells, fabricated using the electrodes with various porosities, were also conducted. The cells were subjected to the hybrid pulse power characterization (HPPC) test for electrochemical performance evaluation. Lower area specific impedances were obtained for the electrodes with correspondingly lower porosity (i.e. more extensive calendering). The studies indicate that the sub-micron carbon coating olivine, when optimized, is a very promising cathode material for HEV/PHEV applications once the electrode is properly prepared.
9:00 PM - U4.4
High Conducting NASICON-like Phases in InPO4-Li3PO4 and InPO4-Na3PO4 Quasibinary Systems.
Anna Potapova 1 , Irina Smirnova 1 , Alexander Mosunov 2 , Andrey Novoselov 1 , Sergey Stefanovich 2 , Galina Zimina 1
1 Department of Chemistry and Chemical Engineering for Rare and Dispersed Elements, Lomonosov Moscow State Academy of Fine Chemical Technology, Moscow Russian Federation, 2 Department of Chemistry, Lomonosov Moscow State University, Moscow Russian Federation
Show AbstractAdvances in development of reliable, compact and inexpensive sources of electric current such as Li-ion batteries is an acute problem for further technology progress. NASICON-like phases, e.g. complex phosphates in ScPO4-Li3PO4 quasibinary system, were proposed as promising solid-state electrolytes, but obtained data on ionic conductivity were far from expected. In addition, these compounds have complex polymorphism that makes it difficult to obtain NASICON-like ceramics of high phase homogeneity. Looking for the ceramics of better conducting performance and trying to use less expensive metal then scandium, we have investigated quasibinary systems InPO4-Li3PO4 and InPO4-Na3PO4 at 950 °C. Samples were prepared through every 2-10 mol% and investigated by XRD method to determine phase-formation in the systems. Measurements of ionic conductivity were carried out with impedance spectroscopy method plotting hodographs. Na3In2(PO4)3 and Li3In2(PO4)3 have ionic conductivity of about 10-2 S/cm at 300 °C. This value is comparable to that of well-known NASICON-like compounds such as Li3Fe2(PO4)3. To improve ionic conductivity, samples were heterovalent Zr-substituted according to scheme In3+→Zr4++v, where v–is a vacancy in cationic sublattice, with solid solutions formation up to 10 mol% Zr. Vacancy formation increases mobility of Na/Li ions and leads to improved ionic conductivity. In these samples ionic conductivity was measured to be of about 10-1 S/cm at 300 °C. Further substitution up to 20 mol% Zr results in formation of a secondary phase without any effect on conductivity. We will present the obtained results, demonstrate established regularity of composition-structure-properties and discuss techniques of obtaining high conducting superionic NASICON-like phases in complex phosphate systems.
9:00 PM - U4.40
High Performance Supercapacitor based on Polyaniline Nanowires /Carbon Cloth Flexible Electrode.
Ying-Ying Horng 1 2 , Yi-Chen Lu 1 2 , Yu-Kuei Hsu 3 , Chia-Chun Chen 1 3 , Li-Chyong Chen 2 , Kuei-Hsien Chen 3 2 1
1 Department of Chemistry, National Taiwan Normal University, Taipei Taiwan, 2 , Center for National Taiwan Normal University, Teipei Taiwan, 3 , Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei Taiwan
Show AbstractExcellent electrochemical performance was achieved from polyaniline nanowires (PANI-NWs) electrode directly grown onto a porous carbon cloth (CC) via electrochemical technique. The three-dimensional architecture of these nanowires not only showed remarkable increase in the electrochemical performance, but also exhibited high gravimetric capacitance of 1079 Fg-1 at a specific energy of 100.9 Whkg-1 and a specific power of 12.1 kWkg-1. Especially, an exceptionally high area-normalized capacitance of 1.8 Fcm-2 was achieved. The diffusion length of protons within the PANI-NWs was estimated to be about 60 nm by electrochemical impedance analysis, which indicates that the electrochemical performance of the electrode is not limited by the thickness of PANI-NWs. These results clearly present a cost-effective and simple method of fabrication of the NWs with enormous potential in energy storage device applications.
9:00 PM - U4.41
Preparation of Orientation-controlled LiCoO2 Epitaxial Thin Films.
Hideki Oki 1 , Taro Hitosugi 2 3 , Tetsukazu Tsuruhama 4 , Tetsuya Hasegawa 3 4
1 Battery Research Div., Toyota Motor Corporation, Susono Japan, 2 WPI, Tohoku University, Sendai Japan, 3 , Kanagawa Academy of Science and Technology, Kawasaki Japan, 4 Department of Chemistry, The University of Tokyo, Tokyo Japan
Show Abstract Layered-rhombohedral LiCoO2, a typical electrode material for Li-ion batteries, has been intensively studied in polycrystalline form due to the easiness of preparation and link to applications. The mechanism of Li-ion and electron conductivity in intra-grain LiCoO2 has not been elucidated, since polycrystalline samples include many grain boundaries that hide the properties of intra-grain properties. Therefore, investigation of the mechanism of Li-ion and electron conductivity requires high quality epitaxial thin films or large single crystals. In this study, we prepared orientation-controlled LiCoO2 epitaxial thin films, and cyclic voltammogram was measured. We succeeded in the preparation of LiCoO2 epitaxial thin films on Al2O3(0001) and metal (Au and Pt) substrates using pulsed laser deposition. Annealing precursor films deposited at substrate temperature (Tsub) of room temperature, resulted in the formation of LiCoO2 films with flat surface. In contrast, the surface of the film deposited at Tsub = 500oC showed island structures with secondary phase such as Co3O4. From X-ray diffraction analysis, we confirmed that LiCoO2(0001) plane is parallel to the substrate Al2O3(0001) surface, indicating that the direction of Li-ion conductivity and the CoO2 layer is in a plane parallel to the substrate. The pole figure measurement of the LiCoO2 confirmed epitaxial relation of [10-10]Al2O3 // [1000]LiCoO2. On Pt and Au(100) and (111) substrates, the CoO2 layer is parallel to the substrates, while on (110), the layer is perpendicular. Although XRD measurement indicates single phase, Raman spectroscopy and transmission electron microscopy reveal that the films include a trace of Co3O4 . Cyclic voltammogram (CV) measurements were performed on LiCoO2(110) on Pt(110) and LiCoO2(001) on Pt(111) // 1M LiClO4 in EC/DEC // Li metal cell. The latter showed no electrochemical activity, while the former appeared reversible peaks at 3.93 V(D1), 4.08 V(D2) and 4.17 V(D3) on discharge, and at 3.90 V(C1), 4.05 V(C2) and 4.16 V(C3) on charge. The main D1-C1 peaks correspond to de-intercalation/intercalation reaction of Li ion. Other small peaks are attributed to phase transitions. This electrochemical behavior is similar to powder samples, showing that our thin films are capable for the further analysis of the physical and chemical properties of Li-ion conductivity.
9:00 PM - U4.42
Electrochemical Lithium Intercalation into Cation-Substituted LiMnPO4 Electrode.
Jong-Won Lee 1 , Jin-Hwan Park 1 , Meen-Seon Paik 1 , Seok-Gwang Doo 1
1 Energy Laboratory, Samsung Advanced Institute of Technology, Yongin, Gyeonggi-do, Korea (the Republic of)
Show AbstractA lithium manganese phosphate (LiMnPO4) with an orthorhombic olivine structure shows a redox potential of 4.1 V vs. Li/Li+, resulting in a higher energy density when compared with LiFePO4 operating at 3.4 V vs. Li/Li+. These properties combined with good thermal stability and low materials cost make LiMnPO4 attractive as an alternative electrode to LiFePO4 and other transition metal oxides. With few exceptions, however, much lower reversible capacities have been typically obtained for LiMnPO4. Several hypotheses have been proposed in the literature to explain such poor electrochemical performances, including Jahn-Teller instability caused by Mn3+ ions, low ionic/electronic conductivities and large mechanical strains developed at the boundary of Li-rich and -poor phases. The present work examines the structural and electrochemical properties of LiMnPO4 in which various divalent and/or supervalent cations were substituted for part of Mn atoms. The materials were synthesized by a solid-state reaction route in the presence of high-surface area carbons and then were subject to extensive characterizations to evaluate their structures and electrochemical behaviors. The experimental results indicate that the materials are tolerant, to some extent, to cation substitution, and the reversible capacity and polarization resistances strongly depend on the ionic size, oxidation state and concentration of the substituent atoms introduced into the LiMnPO4 structure.
9:00 PM - U4.43
Electrochemical Li-Ion Storage in Oriented Anatase TiO2 Nanotubes Arrays.
Jae-Hun Kim 1 , Kai Zhu 1 , Qing Wang 1 , Ahmad Pesaran 1 , Arthur Frank 1
1 , National Renewable Energy Laboratory, Golden, Colorado, United States
Show AbstractOriented nanostructures arrays (e.g., nanotubes) have shown promise for advanced Li-ion batteries [1,2]. Such batteries are of interest due to their improved energy density, rate capability, and cycling stability. Oriented nanotube (NT) arrays with their linear arrangement of pores are expected to facilitate fast electronic/ionic conduction and to accommodate significant volume changes of the electrode materials during charge/discharge cycling. Among the various electrode materials, TiO2 has attracted [3-5] attention because of their high rate capability and enhanced safety, which are essential properties of rechargeable Li-ion batteries and supercapacitors for hybrid electric vehicle (HEV) applications. In this presentation, we discuss the electrochemical characteristics of anatase TiO2 NT arrays as negative electrode materials for Li-ion batteries. The NT arrays, which are aligned normal to a substrate, were fabricated by electrochemical anodization of Ti foil. Galvanostatic charge/discharge measurements show that reversible Li+ storage capacities of the NT electrodes at low current rates were higher than the theoretical value for bulk materials. Analyses of cyclic voltammograms indicate that there is significant pseudocapacitive Li+ storage associated with the NT surface in addition to the Li+ storage within the bulk material. The NT film morphology (e.g., pore diameter, wall thickness, NT length) and pore alignment are found to affect significantly the Li insertion-extraction kinetics (e.g., electrons/ions conduction and interfacial charge transfer) and the performance of the electrodes in Li-ion batteries. These results and others are discussed. [1] C. K. Chan et al., Nat. Nanotechnol. 3, 31 (2008). [2] L. Taberna et al., Nat. Mater. 5, 567 (2006). [3] L. Kavan et al., Chem. Mater. 16, 477 (2004). [4] Y. S. Hu et al., Adv. Mater. 18, 1421 (2006). [5] A. R. Armstrong et al., Adv. Mater. 17, 862 (2006).
9:00 PM - U4.45
Highly Improved Fe3O4 Electrodes for Lithium-ion Battery.
Chunmei Ban 1 , Zhuangchun Wu 1 , Jeffrey Blackburn 1 , Dane Gillaspie 1 , Anne Dillon 1
1 , National Renewable Energy Laboratory, Golden, Colorado, United States
Show AbstractNew electrodes with large reversible capacities and high rate capabilities are aimed to accelerate the development of all-electrical vehicles for commercial uses. The classical intercalation electrodes has benefited from nano-technologies to achieve stable performance, however the intrinsic capacities due to inability of insertion more than one Li+ ion per 3d metal barely satisfy the demand of high capacities. As potential negative electrodes, transition metal oxides having conversion reactions during discharging/charging exhibit large, reversible capacities. But such electrodes using conversion chemistry suffer not only from low ionic and electronic conductivity that other electrodes also forbear with, but also from the volume change and the formation of agglomerated cluster due to conversion reactions. Thus Nano-architectured electrodes by employing nano Fe3O4-CNTs (carbon nanotubes) composite materials are presented here to prevent the sever fade observed when using commercial Fe3O4 materials as an anode in Li-ion cells. High capacities (nearly theoretical capacity of 926 mAhg-1) have been achieved and maintained for hundreds of cycles even at C rate. By using above 95% hydrothermally made nano-Fe3O4 materials in the electrodes, high energy densities of the cells have been obtained. The very low amount of CNTs using in the composite nanomaterials, produced by a laser vaporization method, doesn’t lessen the advantages of magnetite as a low-cost, environmentally friendly anode material for Li-ion batteries. The synthesis of nano Fe3O4-CNTs materials, the surface and structural analysis of the electrodes will be discussed in this presentation,
9:00 PM - U4.46
Phase Stability Study of Li1-xMnPO4 (0 ≤ x ≤ 1) Cathode for Li Rechargeable Battery.
Sung-Wook Kim 1 , Jongsoon Kim 1 , Hyeokjo Gwon 1 , Kisuk Kang 1
1 Department of Materials Science and Engineering, KAIST, Daejeon Korea (the Republic of)
Show Abstract Olivine-type LiMPO4 (M = Fe, Mn, Co, Ni) compound is one of the promising cathode materials for Li rechargeable battery due to its high stability originated from strong PO43- bonding. While LiFePO4 is a leading candidate among the olivine-type electrode materials, its intrinsically low energy density has been problematic. LiMnPO4 can theoretically deliver high energy density than its Fe counter part due to the high redox potential of Mn2+/Mn3+ vs. Li/Li+ (4.1 V). However, the utilization of its theoretical energy density has not been easily demonstrated even in mild operating conditions. Many factors have been considered to contribute to the difficulty in utilization such as low electronic/ionic conductivity, small polaronic conduction of Jahn-Teller active Mn3+, sluggish phase boundary movement, high surface energy barrier for Li diffusion, and the metastable nature of the delithiated phase. However, clear understanding of these factors has not yet been established, and intensive research efforts on the LiMnPO4 system are still in progress. Phase stability of Li1-xMnPO4 (0 ≤ x ≤ 1) is investigated in this study for different Li compositions and temperatures by electron microscopy and high temperature XRD. The Li1-xMnPO4 is prepared by chemical delithiation of LiMnPO4 using NO2BF4 in acetonitrile. The clear two-phase reaction between LiMnPO4 and MnPO4 is confirmed by XRD during the delithiation. Electron microscopy study indicates the instability of the delithiated phase. The morphology of LiMnPO4 is found to be severely destructed upon delithiation. The map of stable phases is determined at temperature ranges between room temperature and 410 °C. While pure LiMnPO4 phase is stable at high temperature, partial phase transformation of MnPO4 into Mn2P2O7 is observed in delithiated phases above 210 °C with following oxygen evolution reaction.2MnPO4 → Mn2P2O7 + 1/2O2Since it is widely known that PO43- bonding in the olivine-type compound is strong, it is noticeable that O2 gas evolution can readily occur through decomposition at a temperature as low as 210 °C. The irreversible phase transformation of the delithiated phase, if it occurs, will deteriorate the electrochemical performance of a LiMnPO4 electrode. In comparison, PO43- bonding is reported to be stable up to 500 °C in various Li composition of Li1-xFePO4. The instability of the delithiated phase and the phase transformation into Mn2P2O7 may imply that safety concerns can be raised regarding the LiMnPO4 cathode, unlike its Fe counterpart.
9:00 PM - U4.47
The Effect of Al2O3-Coating Coverage on the Electrochemical Properties in LiCoO2 Thin Films.
Yuhong Oh 1 , Donggi Ahn 1 , Seunghoon Nam 1 , Byungwoo Park 1
1 Department of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractThe electrochemical properties of nanoscale Al
2O
3-coated LiCoO
2 thin films were examined as a function of the coating coverage. Al
2O
3-coated LiCoO
2 films showed enhanced cycle-life performance with increasing degree of coating coverage, which was attributed to the suppression of Co dissolution from LiCoO
2. Moreover, an Al
2O
3-coating layer with partial coverage clearly improved the electrochemical properties, even at 60°C or with a water-contaminated electrolyte. Even though metal-oxide coating on LiCoO
2 has been actively investigated, the mechanisms of nanoscale coating have yet to be clearly identified. Through the surface analysis, it is suggested that the Al
2O
3-coating layer had transformed to an AlF
3●3H
2O layer during cycling, which inhibited the generation of HF by scavenging H
2O molecules present in the electrolyte. [1] B. Kim, C. Kim, D. Ahn, T. Moon, J. Ahn, Y. Park, and B. Park,
Electrochem. Solid-State Lett. 10, A32 (2007). [2] Y. J. Kim, H. Kim, B. Kim, D. Ahn, J.-G. Lee, T.-J. Kim, D. Son, J. Cho, Y.-W. Kim, and B. Park,
Chem. Mater. 15, 1505 (2003). Corresponding Author: Byungwoo Park:
[email protected]9:00 PM - U4.48
The Effect of Synthesis Temperature and Stoichiometry on the Electrochemical Properties of Li[Li1/3-2x/3NixMn2/3-x/3]O2.
Christopher Fell 1 , Shirley Meng 1
1 Materials Science and Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractThe layered lithium-excess oxide compounds Li[Li1/3-2x/3NixMn2/3-x/3]O2. are of interest as a new generation of cathode materials for high energy density lithium-ion batteries. This series of compounds were first reported by Lu and Dahn, and Ohzuku et al. in 2001.1,2 Three Ni2+ ions substitute for two Li+ ions and one Mn4+ ion in the layered compound Li2MnO3 (Li[Li1/3Mn2/3]O2). Additional Li ions are present in the transition metal layers and results in additional superstructure peaks. Following lithium deintercalation and the associated oxidation of Ni2+ to Ni4+, lithium may continue to be extracted from this material despite the fact that all the manganese and nickel ions are in their fully charged (+4) oxidation state. Our research has found that formation of a pure layered material depends on the synthesis conditions. The key processing conditions include stoichiometry, sintering temperature and cooling rate. The electrochemical properties of the synthesized materials depend highly on these parameters. Optimized materials exhibit high capacity at reasonable rates.To improve the rate capabilities of this material it is important to understand the atomistic delithiation mechanisms. We will compare the high voltage phase stability and rearrangement of cation ions through a combination of X-ray diffraction and electron microscopy of the Li-excess electrode materials with varying synthesis conditions. References:1. Lu, Z. H.; MacNeil, D. D.; Dahn, J. R., Electrochem. Solid St. Lett. A200 (2001).2. T. Ohzuku and Y. Makimura, Chemistry Letters, 744 (2001).
9:00 PM - U4.49
Using Calorimetric Data in Conjunction with Modeling to Make Inherently Safer Li-Ion Batteries.
Peter Ralbovsky 1 , Elena Moukhina 2
1 , Netzsch Instruments, Burlington, Massachusetts, United States, 2 BU Analyzing & Testing, NETZSCH-Gerätebau GmbH, Selb Germany
Show AbstractAccelerating Rate Calorimetry (ARC®) and Differential Scanning Calorimetry (DSC) are commonly used to study the materials used in manufacturing Li-ion cells. Materials are looked at alone and in combination with each other to measure thermal stability and to determine the chemical compatibility of the components with each other. Adiabatic calorimeters have been used to study components but also full operating cells as well. Instruments have been designed to allow the cycling of batteries inside the calorimeter so that exotherms can be monitored. Some instrument manufacturers have even created large scale adiabatic calorimeters to measure large battery and battery packs. This approach is fundamentally flawed. A better approach is to measure kinetics at the small scale (i.e., 18650 size or less) and then use modeling to determine the effects of “bulk” heating of the battery or the thermal effects of shorts within the battery itself.Various calorimetric techniques are used to develop the data for screening components and for proper model development. Adiabatic calorimetry, DSC, Simultaneous Thermal Analysis (STA) coupled with an analytical finish, and isothermal calorimetry are all useful in developing the thermodynamic and kinetic information required for model development. Good thermal property data on the materials is also important.
9:00 PM - U4.5
Comparison of Morphology, Particle Size and Pretreatment Effects on Cycling Performance of Si-based Anodes for Li-ion Batteries.
Sigita Urbonaite 1 , Ida Baglien 1 , David Ensling 1 , Kristina Edstrom 1
1 Department of Materials Chemistry, Structural Chemistry, Uppsala Sweden
Show AbstractCurrently carbon materials are most commonly used as anodes in commercial batteries with an upper capacity limit of 372 mAh/g. The search for new anode materials leading to increased energy density in the battery is one extensive research field. The safety issues with the potential for lithium intercalation in graphite being close to that of metallic lithium leads to inevitable search for more efficient new anode materials. Theoretically, the most promising anode material is silicon which can alloy with 4 lithium ions per silicon. Among the advantages associated to Si-based anodes are properties such as: high capacity – 4200 mAh/g, which is more than ten times higher than that of graphite, abundance, low cost, environmental friendliness, etc.Si-based electrodes were made using three different silicon sources: Si mesh 325 with particle size of 44 micrometers, nano-Si, with particle size of 50 nm and carbon coated nano-Si. Anodes, containing ~80% of silicon and ~12% of carbon black were prepared with CMC binder using water or water/ethanol mixture as a solvent. Each type of silicon required special adjustments of anode preparation procedure, such as specs milling for Si mesh 325, and ethanol treatment or carbon coating of nano-Silicon to achieve best adhesion to the copper current collector.Anode films prepared at different conditions and from different precursors were casted on the current collector trying to avoid cracking of the casted film. It was found that nano-Si based electrode films, more homogeneous and with better adherence, are formed using silicon sonicated in ethanol and using water\ethanol mixture as a solvent, which seems to help avoiding agglomeration of nano-Si and cracking of the pristine coatings.Electrodes, prepared under the above described conditions from different precursors, were cycled and their performance will in this presentation be compared and related to the morphology and pretreatments applied. Ethanol treated nano-Si based anodes exhibited 2-3 times higher capacity over 25 cycles compared with other high silicon content anodes published [1, 2], with a loss of 8% of capacity during the measurement, and the total irreversible capacity being less than 82 mAh/g. The coulombic efficiency is almost perfect at 96%.Responsibility for the increase of nano-Si based electrode capacity falls to the ethanol ultrasonic bath pretreatment and the use of ethanol/water mixture as a solvent. Attempt to understand the role of the ethanol treatment effect on the nano-Si surface was made. The differences of nano-Si surface species before and after ethanol treatment were analyzed by XPS. It seems that some C-O species add to the surface, covering the Si 2p signal; it is probably some kind of functionalisation of the Si (Si-O) surface that takes place.1. X. Yang, Z. Wen, X. Xu, B. Lin, S. Huang; Journal of Power Sources, 2007(164), 880-884.2. X. He, W. Pu, J. Ren, L. Wang, C. Jiang, C. Wan; Ionics, 2007(13), 51-54.
9:00 PM - U4.50
Control of Point Defects in Olivine-Type LiFePO4 Nanocrystals for High-Power Li Batteries.
Sung-Yoon Chung 1
1 Materials Sci. & Eng., Inha University, Incheon Korea (the Republic of)
Show AbstractIn a number of Li intercalation compounds in which an ordered array of Li is usually maintained, the control of point defects including cation disordering is of major significance for application to electrodes in rechargeable cells. Furthermore, as the chemically different environment induced by point defects leads to breaking of the ordered arrangement of atoms in crystals with a complex structure, mass and charge transport behaviors are also considerably affected by the presence of the defects.A variety of investigations on Li vacancies and cation intermixing have been reported for layered oxides. In contrast, few experimental details revealing the atomic-scale point defects in olivine-type lithium metal phosphates, LiMPO4 (where M = Fe, Mn, Ni, Co), available in the literature (S.-Y. Chung et al., Phys. Rev. Lett., 100, 125502 (2008); Angew. Chem. Int. Ed., 48, 543 (2009)), while these phosphates have attracted a great deal of attention as alternative cathode materials in Li-ion cells over the past decade (S.-Y. Chung et al., Nature Mater., 1, 123 (2002)). Proper control and direct identification of their distribution in the lattice on the basis of crystal chemistry will be crucial steps toward enhancement of effective Li mobility during the intercalation reaction in olivine phosphates. In this presentation, the observations of a variety of lattice defects in ordered olivine LiFePO4 crystals after rapid phase transformation during crystallization (S.-Y. Chung et al., Nature Phys., 5, 68 (2009)) will be presented, showing notable distribution behaviors of the defects. For this direct observation, in siu and ex situ high-resolution transmission electron microscopy is utilized. This analysis suggests that the lattice defects in LiFePO4 can be adjusted for improved Li ion transport.
9:00 PM - U4.51
Process Kinetics During RF Sputtering of LiCoO2 Thin Films for Micro Battery Applications.
Nimisha Cs 1 , Venkatesh Gopal 2 , Thulasi Raman Kh 1 , Munichandraiah Nookala 2 , Mohan Rao Gowravaram 1
1 Instrumentation, IISc, Bangalore, Karanataka, India, 2 Inorgonic and Physical chemistry, Indian Institute of Science, Bangalore India
Show AbstractSputtering from multi-elemental targets often results in non-stoichiometric films when the target is not conditioned for a stable composition. In this study we present the target conditioning analysis of LiCoO2 sputter cathodes in terms of the real time monitoring and analysis of neutral and ionic species of elements present in the Rf plasma using Optical Emission Spectroscopy (OES). During these studies it was also seen that the target-substrate distance plays a major role in achieving the required composition in the deposited films. The X-ray photoelectron spectroscopy (XPS) core level spectrum of Li+,Co3+ and O2- of films sputtered from a conditioned target is presented. Electrochemical data in relation to these process parameters supports the optimum substrate to target distance predicted by OES. The optimized conditions for the deposition of good quality LiCoO2 films with a capacity of 64 microAmpHr/cm2/µm are given. These conditions are different from the data available in the existing literature, where it was demonstrated that good quality films could be deposited at larger target-substrate distance. Our study shows that due to thermalization distance of different elements, a target-substrate distance of 5 cm is ideal and this was supported by OES data.
9:00 PM - U4.53
Averting Cracks Caused by Insertion Reaction in Lithium-ion Batteries.
Yuhang Hu 1 , Xuanhe Zhao 1 , Zhigang Suo 1
1 Mechanical engineering, Harvard University, Cambridge, Massachusetts, United States
Show AbstractIn a lithium-ion battery, both electrodes are atomic frameworks that host mobile lithium ions. When the battery is being charged or discharged, lithium ions diffuse from one electrode to the other. Such an insertion reaction deforms the electrodes, and may cause the electrodes to crack. This paper uses fracture mechanics to determine the critical conditions to avert cracking. The method is applied to cracks induced by the mismatch between phases in crystalline particles of LiFePO4.
9:00 PM - U4.54
High-Performance Li-ion Battery Cathodes Using Prelithiated Ferroselite Nanoflowers.
Liqiang Mai 1 2 , Shuang Yang 1 , Yuan Gao 1 , Lin Xu 1 , Bin Hu 1
1 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, Hubei, China, 2 Department of Chemistry and Chemical Biology, Harvard University, Boston, Massachusetts, United States
Show AbstractRecently, considerable attention has been devoted to complex nanostructures with different morphology, orientation, and dimensionality due to their size- and shape-dependent photocatalytical, optical, electrical, photoelectric properties. Ferroselite (FeSe2) has been investigated as a VIII-VI semiconductor with a direct 1.0 eV band gap and as a model system to explore chemical processes and applications in electronics, optics, optoelectronics, spintronics and batteries. Until now, there are few reports on synthesis of FeSe2 nanoflowers, and Li+ ion insertion and extraction behavior and electrochemical properties for this novel nanomaterial are very poorly understood, which limits their wide application in energy field. In the present work, ferroselite (FeSe2) nanoflowers have been prepared by a mild hydrothermal method at 170°C with Na2SeSO3 and FeC2O4 as the raw materials, and prelithiated through a secondary hydrothermal reaction with Li salt solution. The products were characterized by XRD, FE-SEM, EDS, CV and model battery testing. The results show that the as-prepared FeSe2 nanoflowers composed of uniform nanoplates about 20 nm in thickness and 100 nm in diameter, exhibit high discharge capacity of ca. 431 mAh/g. Notably, the capacity retention rate of FeSe2 nanoflower electrodes is greatly improved from 45% before lithiation to 63% after lithiation through secondary hydrothermal lithiation modification and this improvement of cycling property is confirmed by CV investigation, probably resulting from increase of structure stability and weakening of electrostatic interaction between FeSex layers and Li+ ions in interlayer during the discharge when Li ions occupy the interstitial site of FeSe2 lattice. It is shown that the prelithiated FeSe2 nanoflowers exhibit good cycling capability and it is suitable for use as high-property electrode material in rechargeable lithium-ion batteries.AcknowledgementsThis work was supported by the National Nature Science Foundation of China (50702039), the Research Fund for the Doctoral Program of Higher Education (20070497012), Scientific Research Foundation for Returned Scholars, Ministry of Education of China (2008-890) and Innovation Special Foundation of Excellent Returned Scholars of Wuhan (2008-84). The authors are pleased to thank the strong support and helpful discussion of Prof W Chen and Prof JG Guan of Wuhan University of Technology.
9:00 PM - U4.7
Generation of Manganese Oxide Nanoparticle-Dispersed Porous Carbon Nanofiber Anodes for High-Performance Rechargeable Lithium-Ion Batteries.
Liwen Ji 1 , Zhan Lin 1 , Quan Shi 1 , Andrew Medford 1 , Xiangwu Zhang 1
1 Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science , North Carolina State University, Raleigh, 27695-8301, North Carolina, United States
Show Abstract In this study, MnOx nanoparticles dispersed to porous carbon nanofibers (C/MnOx) are prepared by thermally-treating electrospun polyacrylonitrile (PAN) nanofibers containing 50 wt% Mn(CH3COO)2 (Mn(OAc)2) salt at elevated temperatures (stabilization in air environment , followed by carbonization in argon atmosphere). C/MnOx nanofibers prepared from this scalable process are mechanically stable. Moreover, the fibers deliver promising electrochemical performance, including high reversible capacity, enhanced cyclability, and excellent rate capability when used as anodes for rechargeable LIBs. Scanning electron microscopy (SEM) images indicate that the electrospun precursor exhibits a very long and straight fibrous morphology with relatively uniform diameter of about 200 nm. After stabilization in air environment, the fibers become slightly more undulated and exhibit significantly larger diameters. When thermally treated in inert gas, the morphology of the carbonized nanofibers became highly uneven and undulate, and more irregular morphology, porous structure and largely decreased average diameter are also clearly shown. These structural changes may be caused by a large weight loss accompanied with gas evolution. Galvanostatic charge-discharge experiments were carried out to evaluate the electrochemical performance of cells using C/MnOx composite nanofibers as the working electrode and lithium ribbon as the counter electrode with a voltage window of 0.01-2.8 V and a constant specific current of 50 mA g-1. The preliminary results indicated that the C/MnOx anode shows remarkably improved lithium-storage capacities, high reversible lithium-storage capacity and also good capacity retention. We are currently carrying out the further experiment to evaluate the rate capability of these C/MnOx nanofibers.
9:00 PM - U4.8
Development of Microstructured and Nanostructured 3-D Porous Electrodes via Monolithic Silica Templates.
Martin Bakker 2 1 , Franchessa Maddox 2 , Elizabeth Junkin 2 1 , Amy Grano 2 , Jan-Henrik Smatts 3 , Mika Linden 3
2 Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama, United States, 1 Center for Materials for Information Technology, The University of Alabama, Tuscaloosa, Alabama, United States, 3 Department of Physical Chemistry, Åbo Akademi University, Turku Finland
Show AbstractSupercapacitors and advanced batteries capable of rapid charge and discharge need conductive three dimensional porous electrodes. The high conductivities of porous metal electrodes are attractive. However, the surface areas of such electrodes have been well short of those achievable in carbon. Silica monoliths have extremely high surface areas as well as hierarchal porosity. These properties make silica monoliths attractive as templates for formation of porous metal electrodes. Two methods of utilizing monolithic silica templates have been investigated. Electrodeposition potentially allows control of the crystallinity of the resulting metal. Further, by control of the electrodeposition conditions is should be possible to grow metal into only the mesopores or the macropores within the silica monolith. An alternative approach that has proven successful is infiltration of metal nitrate solution into the silica monoliths followed by drying and calcination to precipitate and then decompose the metal nitrate into metal oxide. In the case of silver nitrate this results in formation of silver replicas of the monolith silica structure. For other metals such as nickel, the nickel oxide formed can be reduced to nickel metal under mild hydrogenation conditions.
9:00 PM - U4.9
Electrodeposition of Mesoporous Silica on 3-D Scaffolds as Templates for 3-D Porous Metal Electrodes.
Martin Bakker 1 2 , Nikolaus Cordes 1 , Caleb Hill 1 2 , Katrina Staggemeier 2
1 Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama, United States, 2 Center for Materials for Information Technology, The University of Alabama, Tuscaloosa, Alabama, United States
Show AbstractSupercapacitors and advanced batteries capable of rapid charge and discharge need conductive three dimensional porous electrodes. The high conductivities of porous metal electrodes are attractive. However, the surface areas of such electrodes are still well short of those achievable in carbon. One approach to formation of high surface area porous metal electrodes is to electrodeposit metal into nanostructured templates on 3-D scaffolds such a nickel foam. By careful control of composition and voltage thin films of mesoporous silica can be deposited onto 3-D scaffolds such as nickel foam. Removal of the templating surfactant produces a very high surface area mesoporous coating. Metal can be plated into the mesoporous silica, which after removal leaves a high surface area 3-D porous electrode.
9:00 PM - U8.44
Sn/SnOx Core-Shell Nanoparticles as Anodes for Lithium Batteries.
Xiao-Liang Wang 1 , Weiqiang Han 1
1 Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, United States
Show Abstract Tin is an attractive anode material for lithium batteries, principally due to its high theoretical capacity of 994 mAh/g, far more than that of state-of-art graphite (372 mAh/g). Sony’s recent commercialization of a tin-based anode further triggered research in this material. Besides its high capacity, tin possesses other favorable characteristics: (1) Slightly higher operating potential than graphite; (2) no solvent co-intercalation; and, (3) a high lithium-diffusion coefficient at room temperature. However, its cycling stability is poor, i.e., inferior capacity retention and reversibility. It is also difficult for tin to be fully lithiated and achieve the theoretical capacity. For example, Ui et al. demonstrated that the initial capacity of ca. 750 mAh/g of an electroplated tin anode decreased precipitously to ca. 200 mAh/g just in the second cycle. One cause is its huge volume change upon cycling; another is the slow rate of Li+ extraction. Among the routes to resolving these problems is employing small-grained tin, especially nano tin. This approach could suppress the absolute volume change, and shorten the diffusion distance for Li+. While many studies have demonstrated the merits of nano tin, most dealt with single size-ranges. To understand better the effect of nano size, it is essential to study the cell performance of tin over a wide range of sizes. We synthesized different sized tin particles, from ca. 20 nm to ca. 700 nm. Interestingly, these nanoparticles are Sn/SnOx core-shell nanostructures; typically, the thickness of the SnOx shells is about several nanometers, as revealed by TEM and EDS. We discuss the effect of size of this type of core-shell nanostructure on cell performance. This work is supported by the U. S. DOE under contract DE-AC02-98CH10886 and E-LDRD Fund of Brookhaven National Laboratory. We thank Drs. Feng Wang, Jason Graetz, Xiao-Qing Yang, and Yimei Zhu (BNL) for their technical help and valuable discussions.
Symposium Organizers
Yury Gogotsi Drexel University
John R. Miller JME, Inc.
Katsuhiko Naoi Tokyo University of Agriculture & Technology
Yang Shao-Horn Massachusetts Institute of Technology
Bruno Scrosati University of Rome
U5: Modeling and Simulation of Battery Materials
Session Chairs
Tuesday AM, December 01, 2009
Room 200 (Hynes)
9:30 AM - **U5.1
Ionic Liquids as Electrolytes for Electrical Energy Storage: Insights from Molecular Dynamics Simulations.
Grant Smith 1 , Oleg Borodin 1 , Jenel Vatamanu 1
1 Materials Science and Engineering, University of Utah, Salt Lake City, Utah, United States
Show AbstractRoom temperature ionic liquids (ILs) are receiving increasing attention as electrolytes in lithium battery and supercapacitor applications for a variety of reasons, including a wide electrochemical stability window, low volatility, ability to dissolve lithium salts, ability to form high-capacitive double layers, and not least, the tremendous number of conceivable cation/anion combinations. In both battery and supercapacitor applications, the properties of the interface between the electrolyte and the electrode are of paramount importance in understanding the performance of the electrical energy storage devices and how to improve both power and energy density of the device. We have employed atomistic molecular dynamics simulations utilizing a new electroactive interface methodology that allows us to control the potential of the electrode during the simulation in order to study the structure and dynamics of IL-based electrolytes at the interface with model electrodes for both battery and supercapacitor applications. I will present insights we have gained into these important interfaces from our simulation studies.
10:00 AM - U5.2
Mathematical Models for Optimizing Electrode Shape, Size and Charging Conditions for Durable Li Ion Battery.
Rutooj Deshpande 1 , Yang-Tse Cheng 1 , Mark Verbrugge 2
1 Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Lexington, Kentucky, United States, 2 Materials and Processes Laboratory, General Motors R&D Center, Warren, Michigan, United States
Show AbstractAbstract:Diffusion induced stresses (DISs) in Li ion battery electrodes can cause cracking of the electrodes which limits battery cycle life. We are developing several mathematical models [1, 2, 3, 4] relating DISs with lithium concentration in the electrode material, electrode geometry, and charging condition. In this paper, we show that at nano scale, surface stress and surface tension play an important role in mitigating cracking caused DISs. We model these stresses and strain energy for different operating conditions, such as galvanostatic and potentiostatic charging and discharging. We also consider several electrode geometries, including nanowires, nanotubes, and nano-particles. We show that these models can be used to help develop strategies to increase battery life by optimizing electrode geometry and size, as well as charging conditions.[1] Y.-T. Cheng and M. W. Verbrugge, The influence of surface mechanics on diffusion induced stresses within spherical nanoparticles, J. Appl. Phys. 104, 083521 (2008).[2] M. W. Verbrugge and Y.-T. Cheng, Stress Distribution within Spherical Particles Undergoing Electrochemical Insertion and Extraction, The Electrochemical Society (ECS) Transactions 16, 127 (2008).[3] Y.-T. Cheng and M. W. Verbrugge, Evolution of stress within a spherical insertion electrode particle under potentiostatic and galvanostatic operation, J. Power Sources 190, 453 (2009).[4] M. W. Verbrugge and Y.-T. Cheng, Stress and strain-energy distributions within diffusion-controlled insertion-electrode particles subjected to periodic potential excitations, J. Electrochem. Soc. (to be published).
10:15 AM - U5.3
Elucidation of Layered Cathode Material from First-principles Computational Studies and its Structural and Electrochemical Behavior.
Jose Saavedra-Arias 1 , Reji Thomas 1 , Loraine Torres 1 , Yasuyuki Ishikawa 2 , Ram Katiyar 1
1 Department of Physics, University of Puerto Rico, San Juan, Puerto Rico, United States, 2 Department of Chemistry, University of Puerto Rico, San Juan, Puerto Rico, United States
Show AbstractNowadays, the implementation of combined experimental/computational studies is probably the best way to understand the physical and chemical properties of materials and to discover new materials for different technological applications. Hence, the study of new cathode materials by first-principles calculations and their experimental characterization can be the most efficient way to find the proper substitute for LiCoO2. In the present study, we first employed ab initio calculations to screen layered cathode materials, and then synthesize and study electrochemical properties of the best candidate. Our first-principles calculations were performed in the local density approximation (LDA) to density-functional theory (DFT) as implemented in the Vienna Ab Initio Simulation Package (VASP). In order to reduce the number of the plane waves required for simulating the interactions between ions and electrons, ultra-soft Vanderbilt pseudo-potentials have been used. All structures were fully relaxed with respect to external and internal parameters. The substitution of the transition metal atoms was performed by equivalent position replacement for minimizing the energy of the system. By the alloy metal method (D. de Fontaine, Solid State Physics; H. Ehrenreich, D. Turnbull, Eds, p. 33, 1994), we analyzed the interactions between the transition metals by examining the energy of the solid solution. The computed energies of the transition metals in Li-layered structure may be obtained by the expression, ΔEmix=E(LiNi(1-x-y)CoxMnyO2)-(1-x-y)E(LiNiO2)-xE(LiCoO2)-yE(LiMnO2).Based on the phase stability, the composition LiNi0.66Co0.17Mn0.17O2 revealed the formation energy below zero, suggesting that the compound may be synthesized readily. At full delithiation, the ΔEmix is positive, suggesting repulsion between the transition metals. We carried out phase-stability calculations of the structures up to 50% delithiation, and found that this composition shows the highest stability. These results indicate that the compound LiNi0.66Co0.17Mn0.17O2 is a potential candidate material for cathode application in Li-ion rechargeable batteries. Therefore, this compound was prepared by sol-gel process. Calcinations conditions (time, ambient and temperature) were optimized for the single-phase formation of the layered structure. The structural properties were investigated using X-ray diffraction (XRD) and Raman Spectroscopy. Electrochemical testing was done on the coin cells (cathode/LiPF6 electrolyte/Li-foil anode) with Cyclic Voltametry, and the galvanostatic charge-discharge methods. These results, along with Li+ diffusion and cycleability, will be presented.
10:30 AM - U5.4
Computational Design of a Hybrid Organic-Inorganic Li-Ion Conductor.
Jinhua Zhou 1 , John Kieffer 1
1 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractThe role of electrolytes in batteries and fuel cells is to effectively separate the reactants, selectively mediate the transport of specific ions that establish the electrochemical process responsible for power generation, and provide sufficient structural rigidity to ensure the mechanical stability of the device. As these are in effect opposing qualities, promising designs of electrolyte materials are often based on a composite approach. Accordingly, we pursue hybrid materials in which a rigid inorganic and a flexible organic component are linked at the molecular level. To efficiently identify the basic design concepts for such materials, we rely on simulations guiding the experimental developments. We carry out large-scale molecular dynamics (MD) simulations based on a reactive force field that we developed, to first generate realistic structural models of the porous networks by reproducing the self-assembly processes of the hybrid building blocks. Using the models so created, we then study the mechanisms underlying ionic transport and establish the relationship between conductivity, materials chemistry, and pore structure. We present the case study of lithium ion transport in a structure constructed from polyhedral oligomeric silsesquioxane (POSS) cubes functionalized with alkane chains of various lengths. In one case the lithium is donated by a siloxy group connected to the POSS cube and in the other case by a carboxyl group connected to the free tail of the alkane chain. Li+ conductivity is significantly higher in the latter case, but not as expected because of the higher range of motion provided by flexibility of the alkane chain. The insights gained from this study suggest a specific synthesis route for electrolyte materials.
10:45 AM - U5:Modeling
BREAK
U6: Novel Approaches to Advanced Batteries
Session Chairs
Tuesday PM, December 01, 2009
Room 200 (Hynes)
11:15 AM - **U6.1
Fabricating Genetically Engineered High Power Lithium Ion Batteries Using Multiple Virus Genes.
Angela Belcher 1 5 , Yun Jung Lee 1 , Hyunjung Yi 1 , Woo-Jae Kim 2 , Kisuk Kang 3 4 , Dong Soo Yun 1 , Michael Strano 2 , Gerbrand Ceder 1
1 Materials Science and Engineering , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 5 Biological Engineering , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Chemical Engineering , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of), 4 Institute for Eco-Engergy, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractDevelopment of materials that deliver more energy at high rates is important for high power applications including portable electronic devices and hybrid electric vehicles. For lithium ion batteries, reducing materials dimensions can boost Li+ ion and electron transfer in nanostructured electrodes. By manipulating two-genes, viruses were equipped with peptide groups with affinity for single-walled carbon nanotubes (SWNTs) on one end and peptides capable of nucleating amorphous iron phosphate (a-FePO4) fused to the viral major coat protein. The virus clone with the greatest affinity towards SWNTs enabled power performance of a-FePO4 comparable to that of crystalline lithium iron phosphate (c-LiFePO4) and showed excellent capacity retention upon cycling at 1C. This environmentally benign low temperature biological scaffold could facilitate fabrication of electrodes from materials previously excluded because of extremely low electronic conductivity.
11:45 AM - U6.2
Kinetics of the Lithium (Per)Oxide Decomposition in Lithium-Air Batteries.
Yi-Chun Lu 2 3 , Hubert Gasteiger 2 3 , Ethan Crumlin 2 3 , Robert McGuire 4 3 , Yang Shao-Horn 1 2 3
2 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Electrochemical Energy Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 1 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractIn lithium-air batteries, the traditional positive intercalation electrode is replaced by a porous air electrode, which catalyzes the formation of lithium (per)oxide (discharge reaction) and its decomposition into oxygen and lithium ions (charging reaction). Battery tests with these air electrodes were shown to exceed the energy density of conventional positive intercalation electrodes, promising the development of sufficiently light-weight lithium-air batteries for plug-in electric vehicles. However, the overpotential for the charging reaction, i.e., the oxygen evolution reaction (OER), is very large and significantly reduces the efficiency of the battery. Therefore, improved OER catalysts are required for lithium-air batteries, but little is currently known about the kinetics of this reaction.Unfortunately, determination of the reaction kinetics of the OER in actual lithium-air batteries is compromised by undefined mass transport losses, caused by plugging of electrode pores with solid lithium (per)oxide and by undefined contact between the catalytically active surfaces and the lithium ion conducting electrolyte. Therefore, we developed a novel rotating disk electrode (RDE) approach which allows to determine the OER kinetics on model electrode surfaces in the absence of undefined mass transport resistances. Applying this method, we will present a detailed study of the lithium (per)oxide decomposition reaction in a lithium ion conducting organic electrolyte (PC:DME (1:2, by volume) and 1M LiClO4) on glassy carbon and noble metal disk electrodes as well as on oxide electrodes prepared by thin-film deposition methods. Mechanisms of the reaction kinetics on these model surfaces will be discussed.
12:00 PM - U6.3
Design of Free-standing Electrodes for 3D Architectured Li-ion Micro-batteries.
Emilie Perre 1 2 , Manikoth Shaijumon 1 , Pierre-Louis Taberna 1 , Torbjorn Gustafsson 2 , Kristina Edstrom 2 , Patrice Simon 1
1 CIRIMAT, Université Paul Sabatier, Toulouse cedex 9 France, 2 Materials Chemistry, Uppsala Universitet, Uppsala Sweden
Show AbstractDue to increasing demand of faster, better, smaller energy storage systems research onto Li-ion batteries is facing new challenges. New batteries not only based on new materials but also on new designs are now considered in order to fulfil the upcoming energy and power requirements. In this context, the conception of 3-dimensional nano-architectured micro-batteries is being explored. Such battery designs have been considered in order to maintain the advantages of thin films, especially fast kinetics, while greatly increase the content of active material, thus the capacity available, onto a small foot-print area(1). Different designs have already been presented and show improved performances compared to 2D batteries(2,3,4,5). We propose a 3D-battery design based on templated-growth of free-standing arrays of metallic current collector and subsequent deposition of active material and separator onto the 3D nano-structure. While electrodeposition appears as a tool of choice for the preparation of free-standing forest-like metallic current collectors, different synthesis techniques can be considered for the preparation of the subsequent coatings of active material and separator. Keeping in mind that the quality of the interfaces between the different battery components is of crucial importance, we are exploring different in-situ synthesis techniques being not only electrodeposition but also ALD or sol-gel methods. The advantages of the different techniques for the synthesis of 3D micro-batteries will be discussed. Experimental difficulties and electrochemical performances obtained for the 3D-structured cells will be presented and compared to those for 2D cells. Further, the synthesis of a thin, conformal and pinhole-free separator coating will be presented and its effect on the cell stability will be addressed.References (1)J. W. Long, B. Dunn, D. R. Rolison, H. S. White, Chem. Rev. 104 (2004) 4463. (2)D. Golodnitsky, V. Yufit, M. Nathan, I. Shechtman, T. Ripenbein, E. Strauss, S. Menkin, E. Peled, J. Power Sources 153 (2006) 281. (3)H. S. Min, B. Y. Park, L. Taherabadi, C. L. Wang, Y. Yeh, R. Zaouk, M. J. Madou, B. Dunn, J. Power Sources 178 (2008) 795. (4)P. L. Taberna, S. Mitra, P. Poizot, P. Simon, J. M. Tarascon, Nature Materials 5 (2006) 567. (5)S.-K. Cheah, E. Perre, M. Rooth, M. Fondell, A. Harsta, M. Boman, L. Nyholm, P. Simon, T. Gustafsson and K. Edström, Accepted by Nano Letters.
12:15 PM - U6.4
LiCoO2 with a Novel Concaved Cuboctahedron Morphology Formed from Lithiation of Cobalt Oxide.
Hailong Chen 1 , Lijun Wu 2 , Lihua Zhang 2 , Yimei Zhu 2 , Clare Grey 1
1 Department of Chemistry, Stony Brook University, Stony Brook, New York, United States, 2 Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractMost of the Li-intercalation compounds that have been studied as cathode or anode materials for lithium ion batteries (LIBs) have anisotropic 1-D or 2-D Li diffusion channels/layers. LiCoO2 [1], the first cathode material to be used in commercial LIBs, has 2-D Li diffusion channels parallel to the ab planes of the lattice. LiFePO4, a cathode material with good rate performance [2-4], has 1-D diffusion channels along the b direction, as demonstrated by both theoretical calculation [5] and neutron diffraction experimental observation [6]. Only a few electrode materials, such as LiMn2O4 [7] and other spinel materials with a cubic symmetry, have 3-D Li diffusion channels. The anisotropic 1-D or 2-D diffusion of Li in the lattice results in the inactivity of some surfaces of the electrode material particles towards Li-intercalation reactions. Thus, the electrochemical properties, especially the rate performance of these materials, are strongly morphologically dependant. In our previous work [8], we have demonstrated that by controlling the morphology and by forming a 3-D assembled nanostructure, the rate performance of LiCoO2 can be greatly improved. Here we demonstrate that by choosing an appropriate precursor crystal and reaction conditions, the layered positive electrode material, LiCoO2, which exhibits rhombohedral symmetry, can grow to form a quadruple-twinned crystal with overall cubic symmetry. The twinned crystals show an unusual, concaved-cuboctahedron morphology, with uniform particle sizes of 0.5-2 μm. On the basis of a range of synthetic and analytical experiments, including solid state NMR and X-ray powder diffraction analysis and HRTEM, we propose that these twinned crystals are formed via the selective dissolution and an ion-exchange reaction, accompanied by oxidation, of a cubic parent crystal of CoO; this is accompanied by the growth of four LiCoO2 twin crystals. This “crystal engineering” converts a highly anisotropic, layered material into a pseudo-3-dimensional, isotropic material. Extended study on synthesis of other materials by using this method, such as LiFeO2, which shows a different type of twinned morphology, implies the possibility of generalizing this approach to other intercalation compounds. Thus, this work opens up new opportunities to control the morphology of electrode materials for LIBs and this crystal engineering method is a promising approach to help improve the rate performance of LIBs in the future.1. Mizushima, K., et al. Mater. Res. Bull. 1980, 15 (6), 7832. Padhi, A. K.et al.J. Electrochem. Soc. 1997, 144 (4), 11883. Chung, S. Y.et al. Nat. Mater. 2002, 1 (2), 1234. Kang, B.and Ceder, G., Nature 2009, 458 (7235), 190.5. Islam, M. S.,et al. Chem. of Mater. 2005, 17 (20), 5085.6. Nishimura, S., et al. Nat. Mater. 2008, 7 (9), 7077. Thackeray, M. M. et al. Mater. Res. Bull. 1983, 18 (4), 461.8. Chen, H. L. and Grey, C. P., Adv. Mater. 2008, 20 (11), 2206.
U7: Hybrid Devices
Session Chairs
Tuesday PM, December 01, 2009
Room 200 (Hynes)
2:30 PM - U7.1
Nanohybrid Capacitor: A New Hybrid System, Triply Enhanced Energy Density of EDLCs by use of UC-derived nc-Li4Ti5O12/CNF.
Katsuhiko Naoi 1
1 , Institute of Science and Technology, Tokyo University of Agriculture & Technology, Tokyo Japan
Show AbstractThere is presently a major effort to increase the energy density of EDLCs up to a target value in the vicinity of 20 Wh kg-1. One important alternative approach to meet this goal that is under serious investigation is to develop “Li-ion capacitors”. This approach can overcome the energy density limitation of the conventional EDLC because it employs a hybrid system of a battery-like (faradic) electrode and an EDLC-like (non-faradic) electrode, producing higher working voltage and capacitance. However, the Li-ion capacitors based on a carbonaceous Li intercalation negative electrode have some possible disadvantages, such as long-term stability and safety. Here we suggest a novel hybrid system that certainly achieves a high energy density (triple of conventional EDLCs), high stability and high safety at the same time.This is the new lithium-ion based hybrid capacitor using the lithium titanate Li4Ti5O12 negative intercalation electrode that can operate at unusually high current densities. The high-rate Li4Ti5O12 negative electrode has a unique nano-structure consisting of unusually small single nano-crystalline Li4Ti5O12 nucleated and grafted onto carbon nano-fiber anchors (nc-LTO/CNF). The novel super-high-rate nano-crystalline Li4Ti5O12 nested and grafted onto carbon nano-fibers were prepared by a unique technique (UC method) of a mechano-chemical sol-gel reaction under ultracentrifugal force field (65,000 N), followed by an instantaneous heat-treatment under vacuum for very short duration (3 min). These processes are quite simple and require only a few minutes. Actually, the power characteristic of the prepared composite (nc-Li4Ti5O12/CNF) made a new bench mark which exceeds greatly the maximum 300C-rate value that has ever been attained anywhere in the world.In the present lecture, the author presents the representative data for the super-high-rate nano-crystalline Li4Ti5O12 nested and grafted onto carbon nanofibers for practical supercapacitors.
3:00 PM - U7.3
New Hybrid Capacitor based on Nanostructured Composite Electrodes.
Hakkwan Kim 1 , Dong Hyeok Choi 1 , Hyun Chul Jung 1 , Yong Soo Oh 1
1 Central R&D Institute, eMD Lab, Samsung Electro-Mechanics Co., LTD, Suwon (Gyunggi-Do) Korea (the Republic of)
Show AbstractAsymmetric hybrid capacitor has drawn much attention in recent years, because it can increase the overall cell potential, resulting in higher energy and power densities than conventional electrical double-layered capacitors (EDLC). In this research, we developed an asymmetric hybrid capacitor using MnFe2O4/Carbide Derived Carbon (CDC) nanocomposite as positive electrode and carbon based materials such as activated carbon (AC), graphene, multi-walled carbon nanotube (MWCNT) or CDC as negative electrode combined with organic Li ion electrolyte including partial or complete unsolvated ions. This novel asymmetric hybrid capacitor system shows that we can obtain high energy density without losing innate high power density due to the pseudocapacitance of MnFe2O4 and electrostatic capacitance of micropore CDC. The electrochemical mechanism has been resolved by in-situ X-ray diffraction (XRD), DTA and energy filtering transmission electron microscope (EFTEM). Pore size distribution, surface area, morphology and elements mapping are also investigated using BET and FE-SEM. This system also demonstrates superior cycling stability as compared with the conventional transition metal oxide supercapacitors due to the relatively small variation in lattice spacing under the charge-discharge cycling.
3:15 PM - U7.4
Flexible Supercapacitors Based on Transition Metal Oxide Nanowire/Carbon Nanotube Heterogeneous Films.
PoChiang Chen 2 1 , Haitian Chen 2 , Guozhen Shen 2 , Saowalak Sukcharoenchoke 2 , Chongwu Zhou 2
2 Ming-Hsieh Department of Electrical Eng., University of Southern California, Los Angeles, California, United States, 1 Material Science and Eng., USC, Los Angeles, California, United States
Show AbstractDue to the increased consumption of energy in recent years, numerous research efforts have been made to develop different kinds of energy conversion and storage devices. Supercapacitors, having higher energy density than conventional capacitors and higher power density than batteries, are widely investigated and become one of the most attractive power solutions for an increasing number of applications. Supercapacitors are usually made from three different materials including electronically conducting polymers, carbon related materials, and metal oxides. Among these materials, nanostructured metal-oxide materials, with the advantages of high surface-to-volume ratio and short diffusion path length to ions, can be one of the best candidates applied in energy storage and conversion devices.In this concern, a supercapacitor with the features of optical transparency and mechanical flexibility has been fabricated using transition metal oxide nanowire / carbon nanotube heterogeneous film, and studies found that the power density can reach 7.5 kW/kg after galvanostatic measurements. In addition, to study the stability of flexible and transparent supercapacitor, the device was examined for a large number of cycles and showed a good retention of capacity (~ 88%). This approach could work as the platform for future transparent and flexible nanoelectronics.To increase the cell voltage and power density, a flexible asymmetric supercapacitor has been fabricated by using indium oxide nanowire / carbon nanotube film as an anode and manganese oxide nanowire / carbon nanotube film as cathodes. The cell operation window is 2 V with the specific capacitance of 126 F/g in 1 M Na2SO4 electrolyte and the power density can be improved up to 12 kW/kg. These values are comparable with those of standard electrochemical double layer capacitors working in organic electrolytes.
3:30 PM - U7: Hybrids
BREAK
U8: Pseudocapacitors
Session Chairs
Tuesday PM, December 01, 2009
Room 200 (Hynes)
4:00 PM - **U8.1
Pseudocapacitor Materials Based on Mesoporous Transition Metal Oxides.
Torsten Brezesinski 2 3 , John Wang 1 , Sarah Tolbert 3 , Bruce Dunn 1
2 Department of Physical Chemistry, Justus-Liebig-University Giessen, Giessen Germany, 3 Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California, United States, 1 Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California, United States
Show AbstractCapacitive energy storage is distinguished from other types of electrochemical energy storage by short charging times and the ability to deliver significantly more power than batteries. A key limitation to this technology is its low energy density and for this reason there is considerable interest in exploring pseudocapacitive charge storage mechanisms which offer the tantalizing possibility of bridging the performance gap between batteries and double layer capacitors. In this paper we review our recent studies on nanostructured transition metal oxides which exhibit increased levels of pseudocapacitance and enhanced energy storage properties.We investigated the pseudocapacitive responses for two different forms of nanocrystalline TiO2 films; nanoparticle films with particle sizes less than 10 nm and mesostructured films with pore diameters in the range of 15 – 25 nm. We used a detailed cyclic voltammetric analysis to establish quantitatively the dependence of pseudocapacitance on nanocrystalline TiO2 particle size. At particle sizes below 10 nm, capacitive contributions become increasingly important, leading to greater amounts of total stored charge (gravimetrically normalized) and faster charge/discharge kinetics. We have now extended these studies to consider the pseudocapacitor properties of mesoporous transition metal oxides prepared by using structure-directing agents. The advantage of the interconnected mesoporous network is that it enables greater electrolyte access to the oxide framework than occurs with dense films. In the case of TiO2, we find that films prepared by co-assembly of TiO2 nanoparticles with block co-polymers maintain the high capacitive charge storage properties of the isolated nanoparticles. Moreover, such mesoporous crystalline films offer much greater lithium-ion storage capacity and faster kinetics than non-templated films. Mesoporous films of iso-oriented α-MoO3 exhibit even higher levels of capacitance because of an additional contribution associated with lithium ions being inserted into the Van der Waals gap of the α-MoO3. The pseudocapacitive behavior exhibited by these mesoporous materials leads to enhanced levels of charge storage and offers the prospect of designing electrochemical capacitors that can achieve both high energy and high power densities.
4:30 PM - U8.2
Electrodeposition of Manganese Dioxide for Electrochemical Supercapacitors.
Igor Zhitomirsky 1
1 Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada
Show AbstractNew methods have been developed for the electrosynthesis and electrophoretic deposition of nanostructured manganese dioxide films for application in electrochemical supercapacitors. Nanostructured manganese dioxide films were obtained cathodically using polymer-mediated electrosynthesis from solutions of Mn2+ salts, containing polymers. Thin films were obtained potentiostatically, galvanostatically or in pulsed deposition regime. The deposition yield was studied using quartz crystal microbalance. It was shown that polymer-mediated electrosynthesis resulted in the formation of Mn3O4 phase, which was converted into manganese dioxide by electrochemical oxidation. The size of manganese oxide nanoparticles was varied in the range of 2-10 nm, by variation in the concentration of cationic or chelating polymers. Another approach was based on the cathodic reduction of KMnO4 or NaMnO4 salts. The increase in KMnO4 and NaMnO4 concentration from 20 mM to 100 mM resulted in reducing deposition rate. Porous and crack free films were obtained from 20 mM KMnO4 or 20 mM NaMnO4 solutions. The increase in salt concentration resulted in the formation of dense films which exhibited cracking. It was shown that crack prevention in porous films is based on crack tip blunting mechanism. Film porosity can be increased in a pulse deposition mode. Capacitive behavior of the films was studied in the Na2SO4 and K2SO4 electrolytes using cyclic voltammetry, chronopotentiometry and impedance spectroscopy. The films showed ideal capacitive behavior in a voltage window of 1 V. The specific capacitance of the films was in the range of 200-400 F g-1. The specific capacitance decreased with increasing film thickness and increasing scan rate in the range of 2-100 mV s-1. The films showed good cycling stability.New methods were developed for the fabrication of nanoparticles of manganese dioxide for electrophoretic deposition. Additives have been developed for charging and electrostatic stabilization of manganese dioxide nanoparticles and carbon nanotubes. Composite films containing manganese dioxide and carbon nanotubes were deposited on current collectors and investigated for application in electrochemical supercapacitors. The composite films containing fibrous manganese dioxide nanoparticles showed higher specific capacitance compared to the films containing spherical nanoparticles. Electrophoretically deposited films showed specific capacitance in the range of 250-650 F g-1. The films deposited cathodically showed higher specific capacitance compared to anodically deposited films. The specific capacitance decreased with increasing scan rate in the range of 2-100 mV s-1 and with increasing film thickness in the range of 1-20 microns. The electrochemical behavior of the films deposited by electrophoretic and electrolytic deposition and deposition mechanisms are discussed.
4:45 PM - U8.3
Advanced Nanocomposite Material Based on Manganese Oxide Nanowires and Carbon Nanotubes for Capacitive Energy Storage.
Tarik Bordjiba 1 , Daniel Belanger 1
1 chemistry, Université du Québec à Montréal, Montreal, Quebec, Canada
Show AbstractThe development of advanced composite materials based on metal oxide-carbon nanotubes is a new route for achieving highly efficient electrode for electrochemical power sources such as fuel cells, lithium batteries and electrochemical capacitors. For electrochemical capacitors, active electrode materials include carbon, conducting polymers and transition metal oxides. Manganese oxide is a promising electrode material for electrochemical capacitors due to its low cost, natural abundance, environmental safety and its high theoretical capacitance. If one Mn atom in MnO2 is assumed to store one electron, then the specific capacitance of MnO2 should be around 1370 F/g. But, practically, this oxide show a specific capacitance of only one-fifth or one-sixth of the above value. Such low practical specific capacitance is due to the intrinsically poor electronic conductivity and dense morphology of the oxide [1]. Currently, there are mainly two efficient ways to reach high specific capacitance with manganese oxide. The first one is by developing nanostructred manganese oxide, which allows reaching a specific capacitance in the range of 700 F/g [2]. The second one is by the incorporation of carbon nanotubes in the MnO2 matrix which allows to reach specific capacitance ranging from 325 to 580 F/g [3-5]. We report, for the first time, the synthesis of a new composite electrode based on manganese oxide nanowires and carbon nanotubes (CNTs) by electrophoretic deposition of CNTs on a stainless steel (SS) substrate followed by direct spontaneous reduction of MnO4- ions to MnO2 to form the multi scaled SS-CNT-MnO2 electrode. The resulting material was characterized by scanning electron microscopy, energy dispersive X-ray analysis, cylic voltammetry and galvanostatic charge-discharge in a 0.65 M K2SO4 aqueous solution. The binderless SS-CNT-MnO2 nanocomposite electrode shows a very high specific capacitance of 869 F/g of CNT-MnO2 and good stability during long galvanostatic charge-discharge cycling. To the best of our knowledge, this is one of the highest capacitance for manganese oxide electrode ever reported. In addition to its applicability in electrochemical capacitors, this methodology could be extended to develop other high performance nanocomposite material electrodes based on carbon nanotubes and metal oxide for the future generation of electrochemical power sources. This strategy can find application not only in electrochemical power sources devices but also for catalysis, sensors and microelectronics.Reference: 1- M. Toupin, T. Brousse, D. Bélanger, Chem. Mater. 2004, 16, 3184.2- S. C. Pang, M. A. Anderson, T. W. Chapman, J. Electrochem. Soc. 2000, 147, 444.3- T. Bordjiba, D. Bélanger, J. Electrochem. Soc. 156 (5), A378 4- C. Y. Lee, H. M. Tsai, H.J. Chuang, S. Y. Li, P. Lin, T. Y. Tseng, J. Electrochem. Soc. 2005, 152, A716. 5- S. B. Ma, K. W Nam, W. S. Yoon, X. Q. Yang, K.Y. Ahn, K.H. Oh, K.B. Kim, J. Power Sources 2008, 178, 483.
5:00 PM - U8.4
High-Capacitance Ultracapacitor Electrodes Based on Novel Conducting Polymers.
Mark Roberts 1 , David Wheeler 1 , Bonnie Mckenzie 1 , Bruce Bunker 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractUltracapacitors are electrical energy storage devices that combine the high power, rapid switching, and exceptional cycle life of a classical capacitor with the high-energy density of a battery. Power sources based on ultracapacitors are emerging as the preferred option for applications requiring short power pulses, particularly when combined with conventional batteries. In order to maximize capacitance, switching speed, and power, materials for ultracapacitors need to incorporate conductive and redox-active materials into high surface area structures that are engineered to provide intimate contact between the redox sites and the electrolyte. Conducting polymers are well suited to address these challenges owing to the myriad of synthetic and processing methods available which provide a variety of nanostructures and electrical behaviors.In this presentation, we will present novel conducting polymer electrode materials for electrical energy storage devices. Two classes of materials were investigated: conducting polymers with a triarylamine backbone and thiophene-phenazine containing polymers. The monomers were synthesized using Stille coupling chemistry and used to fabricate porous electrode structures via electrochemical polymerization on conductive substrates. The electrodes were characterized structurally with scanning electron microscopy and electrochemically with cyclic voltammetry, charge-discharge and electrical impedance spectroscopy. Electrodes structures fabricated with triarylamine-based conducting polymers exhibited a remarkably high specific capacitance approaching 1000 F/g in 100 mM tetrabutylammonium tetrafluoroborate in acetonitrile with power and energy densities greater than 6 kW/kg and 25 W-hr/kg, respectively. The electrical performance of the electrodes in electrochemical half-cells, reported for highly porous and nanotube electrodes, is used to provide insight into the electrochemical storage mechanism of polymer-based systems.*Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
5:15 PM - **U8.5
Pseudocapacitance Effects based on Carbon/Hydrogen and Carbon/Iodide Interactions.
Elzbieta Frackowiak 1 , Grzegorz Lota 1 , Krzysztof Fic 1
1 Institute of Chemistry and Technical Electrochemistry, Poznan University of Technology, Poznan Poland
Show AbstractA considerable improvement of capacitance can be obtained by pseudo-capacitive effects connected with quick faradaic reactions. Among many possibilities hydrogen electrosorbed reversibly in the nanoporous carbons is of great interest. Carbon/hydrogen interactions with a weak chemical character (110 kJ/mol) are responsible for capacitance enhancement of negative electrode operating in aqueous medium. Correlation of hydrogen capacity with microtexture, surface functionality of carbon (heteroatoms) and electrical parameters of charging/discharging process will be presented. Combination of carbon electrode with another positive electrode gives a significant extension of voltage, in turn, higher energy of supercapacitor. As a second pseudocapacitive example, striking electrochemical behaviour of carbon/iodide interface will be shown and used for supercapacitor application. This efficient charge storage is based on specific sorption of iodide ions as well as stable reversible redox reactions connected with various possible oxidation states of iodine from –1 to +5. An intriguing effect of iodide ions has been observed for positive electrode operating in a narrow range of potential and giving extremely high capacitance values exceeding 1840 F/g. Potassium iodide (1 mol/L) plays a bi-functional role, i.e. electrolytic solution with a good ionic conductivity as well as a source of pseudo-capacitive effects. However, the role of carbon texture in efficient charging of this system cannot be neglected. As opposed to typical pseudocapacitive effects, which are often characterized by some diffusion limitations and observed only at moderate regimes, our innovative two-electrode system can be loaded until 50 A/g supplying still 125 F/g. Amazing capacitance of carbon/iodide interface has also been confirmed during long-term cycling (over 10 000 cycles).
5:45 PM - U8:Pseudocaps
MEDAL AWARD PRESENTATION: The Opportunities and Challenges for First Principles Materials Design and Applications to Li battery Materials.
Gerbrand Ceder 1
1 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractThe idea of first principles methods is to determine the properties of materials by solving the basic equations of quantum mechanics and statistical mechanics. With such an approach one can in principle predict the behavior of novel materials without the need to synthesize them, and create a virtual design laboratory. By showing several examples of new electrode materials that have been computationally designed, synthesized and tested, I will show the impact of first principles methods in the field of Li battery electrode materials.A significant advantage of computational property prediction is its scalability which we are currently implementing into the Materials Genome project at MIT. Using a high throughput computational environment, coupled to database of all known inorganic materials, we are computing basic information on all known materials and a large number of novel “designed” materials. To predict the crystal structure of hypothetical new materials we have implemented a data mining algorithm that can with high accuracy guess the structure of any new material. With this ability we have obtained several new candidate Li electrode materials. Finally, I will discuss some the challenges that need to be overcome to further enable the impact of first principles methods.BIOGRAPHY Gerbrand Ceder is the R.P. Simmons Professor of Materials Science and Engineering at the Massachusetts Institute of Technology. He received an engineering degree in Metallurgy and Applied Materials Science from the University of Leuven, Belgium, in 1988, and a Ph.D. in Materials Science from the University of California at Berkeley in 1991 at which time he joined the MIT faculty. Dr. Ceder’s research interests lie in computational modeling of material properties and the design of novel materials. Currently, much of the focus of his work is on materials for energy generation and storage, including battery materials, hydrogen storage, thermoelectrics, electrodes for fuel cells and photovoltaics. He has published over 220 scientific papers in the fields of alloy theory, oxide phase stability, high-temperature superconductors, and Li-battery materials, and holds 5 current or pending U.S. patents. His most recent scientific achievement has been the development of materials for ultra fast battery charging. He has received the Battery Research Award from the Electrochemical Society, the Career Award from the National Science Foundation, and the Robert Lansing Hardy Award from The Metals, Minerals and Materials Society for “exceptional promise for a successful career.” He has also received three awards from the graduate students at MIT for best teaching. He is the founder of Computational Modeling Consultants.
Symposium Organizers
Yury Gogotsi Drexel University
John R. Miller JME, Inc.
Katsuhiko Naoi Tokyo University of Agriculture & Technology
Yang Shao-Horn Massachusetts Institute of Technology
Bruno Scrosati University of Rome
U9: New Electrode Structures and Architectures for Capacitive Energy Storage
Session Chairs
Wednesday AM, December 02, 2009
Room 200 (Hynes)
9:30 AM - **U9.1
Multifunctional Carbon Nanoarchitectures as Designer Platforms for Electrochemical Power Sources.
Jeffrey Long 1 , Megan Sassin 1 , Azzam Mansour 2 , Christopher Chervin 3 , Jean Wallace 3 , Jennifer Dysart 1 , Katherine Pettigrew 3 , Debra Rolison 1
1 Code 6170, Surface Chemistry Branch, Naval Research Laboratory, Washington, District of Columbia, United States, 2 Systems and Materials for Power and Protection Branch, Naval Surface Warfare Center - Carderock Division, West Bethesda, Maryland, United States, 3 , Nova Research, Inc., Alexandria, Virginia, United States
Show AbstractWe use carbon aerogels and nanofoams as ultraporous, conductive 3-D scaffoldings onto which we incorporate nanoscopic, electroactive functionalities such as metal oxides, metal nanoparticles, and ultrathin polymers. The resulting multifunctional nanoarchitectures are designed to serve as high-performance electrode structures in applications ranging from high-rate Li-ion batteries and electrochemical capacitors to metal-air batteries and fuel cells [1]. For electrochemical capacitor applications, we have developed self-limiting electroless deposition protocols to apply nanoscopic coatings of either manganese or iron oxides onto the exterior and interior surfaces of carbon nanofoams such that the through-connected pore network of the native nanofoam is retained. The nanoscopic morphology of the metal oxide results in charge-storage capacities higher than typically observed for the oxide used in conventional composite electrode structures, while the nanoarchitecture design itself facilitates rapid charge-discharge of the oxide coating. The MnOx-carbon and FeOx-carbon nanofoam structures function as complementary electrodes (positive and negative, respectively) in asymmetric aqueous electrochemical capacitors that exhibit operating voltages approaching 2 V, and deliver an optimal combination of power and energy densities within a 1–100 s charge-discharge timeframe. In related work, multifunctional nanoarchitectures are designed as air-cathodes for metal-air batteries, in which the nanoscopic oxide coating (in particular manganese oxide) enhances the electrocatalytic turnover for molecular oxygen reduction. En route to practical high-performance energy-storage and conversion devices, these multifunctional nanoarchitectures are also convenient platforms with which to investigate fundamental electrochemical processes at nanoscale interfaces using a variety of spectroscopic techniques.[1] D.R. Rolison, J.W. Long, J.C. Lytle, A.E. Fischer, C.P. Rhodes, T.M. McEvoy, M.E. Bourg, and A.M. Lubers, Chem. Soc. Rev. 38, 226-252 (2009).
10:00 AM - U9.2
Three Dimensional Carbon Architectures as Electrodes for Capacitors.
Francisco del Monte 1 , Maria C. Gutierrez 1 , Daniel Carriazo 1 , Maria L. Ferrer 1 , Fernando Pico 1 , Jose Maria Rojo 1
1 , ICMM-CSIC, Madrid Spain
Show AbstractThe main aim of this work was the design of a synthetic procedure for preparation of monolithic carbon aerogels CA) of utility as three-dimensional electrodes in electrical doble layer capacitors (EDLC). 3D monolithic architectures are lately gaining increased interest in energy storage since they can directly assembled into the supercapacitor cell which allows the miniaturization of the device. The synthetic approach that we have used for preparation of the carbon aerogels (CA) is based on the use of pluronic type surfactants as templates. The use of pluronic type surfactants had been widely described for preparation of mesoporous carbons (as thin films or fine powder) but there is one single report (Chem. Commun. 2008, 2641) on their use for preparation of 3D monolithic CA with well ordered mesopores of ca. 3 nm and macropores of ca. 3 micrometers which, unfortunately, were not useful for EDLC (micropores are required). Thus, in this work, we have further explored the use of PPO-PEO-PPO block copolymers (in this case, having short PPO and PEO segments) for the preparation of hierarchically micro- (rather than meso) and macroporous CA. The achievement of this particular structure has provided remarkable properties to the CA, such high electric conductivity (~2.5 S/cm). structure (micro and macroporous) of the CA obtained in this work, has allowed their (Chem. Commun. 2008, there was only a very recent work (PPO-PEO-PPO type) for the preparation of highly porous (ca. 65%) and ultraweightlighted (specific gravity 5×10-2) macroporous monolithic carbon aerogels built of sintered microporous carbon colloids. The three-dimensional continuous macroporous network allowed the achievement of a remarkably This hierarchical structure was also highly suitable for EDL, with the macroporous network structure providing an efficient transport of electrolyte throughout the monolith and the microporosity being crucial for the formation of extended double layer at the electrode/electrolyte interface. This feature was indeed reflected in the achievement of remarkable capacitances of up to 225 F/g (normalized by mass of CA monolith) and ~31 microF/cm2 (normalized by BET surface area of CA monolith).[1] MC Gutierrez et al. "PPO15-PEO22-PPO15 Block Copolymer Assisted Synthesis of Monolithic Macro and Microporous Carbon Aerogels Exhibiting High Conductivity and Remarkable Capacitance." J. Mater. Chem. 2009, 19, 1236-1240
10:15 AM - U9.3
Enhanced Electric Double Layer Capacitance of Poly Sodium 4-Styrensulfonate/Graphene Oxide Electrodes with High Cyclic Performance.
Hae Kyung Jeong 1 , Mei Hua Jin 1 , Eun Ju Ra 1 , Kang Pyo So 1 , Sivaram Arepalli 1 , Young Hee Lee 1
1 Physics and Energy Science, Sungkyunkwan University, Suwon Korea (the Republic of)
Show AbstractWe have synthesized poly sodium 4-styrensulfonate intercalated graphite oxide and characterized its chemical and physical properties. We found that the interlayer distance of a PSS-treated graphite oxide increased by about 1 Å compared to that of the precursor graphite oxide. This increase in interlayer spacing was attributed to the intercalation of a monolayer of planar PSS into the graphite oxide interlayers facilitated by a π-π interaction between the aromatic rings of the graphite oxide and PSS. The PSS-intercalated graphite oxide had a higher structural stability than the pristine graphite oxide during thermal treatment because of the high melting point of PSS, resulting in high specific capacitance (189.4 F/g), energy density (26.16 Wh/kg), and momentum density (90.68 W/kg) with high cyclic performance. We will discuss more detail in the talk.
10:30 AM - **U9.4
Electrochemical Capacitors Utilizing Single-Walled Carbon Nanotubes.
Kenji Tamamitsu 1 , Shunzo Suematsu 1 , Daisuke Horii 1 , Hiroaki Hatori 2
1 Functional Material Laboratory, Nippon Chemi-Con.Corporation, Takahagi Japan, 2 Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Japan
Show Abstract An electric double layer capacitor (EDLC) utilizing a unique single-walled carbon nanotube called as Super Growth(SG)-SWCNT prepared by a highly efficient CVD process will be presented. We have been investigating the SG-SWCNT as a unique capacitor material mainly because of its high specific surface area (ca. 1,100 m2/g), aligned structure and ultrahigh purity (99.98%), as well as higher growth efficiency (ca. 3,000 times higher) as a practical industrial consideration [1]. We have been successfully developing an electrode that consists only of SG-SWCNT and a current collector with a simple preparation method. Probably due to the absence of complicated additives (e.g., conductive agents, binders, and/or agents for adhesion of the carbon sheets with the current collectors) and the high purity of the SG-SWCNT, much better life performances of the EDLCs based on the SG-SWCNT as both anode and cathode (SG-SG-EDLC) compared with conventional activated carbon EDLCs (AC-AC-EDLC) were found under several DC floating conditions (e.g., 3.5V at 40C and 3.0V at 85C)[2, 3]. In energy and power performances for the SG-SG-EDLC, the power density ( >10 kW/L on the basis of device excluding the case volume) was superior to that for the AC-AC-EDLC though the energy density was comparable to each other when applied voltages of both EDLCs were equal to be 3.0 V. Considering the life performance of the SG-SG-EDLC and the AC-AC-EDLC, however, the SG-SG-EDLC would exhibit higher energy density because of its higher applied voltage with similar life performance (i.e. less voltage derating for the SG-SG-EDLC). For more practical trial, we also prepared a multi-stacked SG-SG-EDLC to estimate the capacitor performance based on the device including the case mass. The capacitor displayed gravimetric energy and power densities of 16Wh/kg and 10kW/kg, respectively. Some approaches for further improvement in the energy and power densities as well as life performances are ongoing and some of the results would be shown in the presentation. [1] K. Hata et al., Science, 306, 1362-1364 (2004). [2] S. Suematsu et al., Abstract of the 8th International Advanced Automotive Batteries, FL, USA (2008).[3] K. Tamamitsu et al., Abstract of the 18th International Seminar on Double Layer Capacitors & Hybrid Energy Storage Devices, FL, USA (2008). AcknowledgementThis work is partially supported by the New Energy and Industrial Technology Development Organization (NEDO) of "Carbon Nanotube Capacitor Project", Japan.
11:00 AM - U9:Supercaps
BREAK
U10: New Carbon-Based Materials for Electrochemical Capacitors
Session Chairs
Wednesday PM, December 02, 2009
Room 200 (Hynes)
11:30 AM - **U10.1
Nanoporous Carbons for Electrochemical Double Layer Capacitors: Electrochemical Study of the Ion Size Versus the Carbon Pore Size Effect.
Patrice Simon 1 , Pierre-Louis Taberna 1 , John Chmiola 3 2 , Yury Gogotsi 2
1 CIRIMAT UMR CNRS 5085, Université Paul Sabatier, Toulouse France, 3 Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractElectrochemical Capacitors (EC), also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors, EDLC) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. In this talk, we will present the latest results on the electrochemical characterization of nanoporous Carbide-Derived Carbons (CDCs) for EDLC applications. CDCs with controlled pore size ranging from 0.6 up to 1 nm were prepared by the chlorination of TiC powder. A 3-electrode cell set-up has been used to study the adsorption of NEt4+,BF4- (TEABF4) and Ethyl-methylImidazolium Trifluoromethanesulfonyl-Imide (EMI+,TFSI-) dissolved in acetonitrile and Propylene Carbonate (PC).Using large-electrode cells, we showed that the gravimetric capacitance of the carbons was maximum when the ion size was close to the carbon pore size. Then, a kinetic study in 2M EMI,TFSI in AN or PC electrolytes was conducted with the Cavity Micro-electrode (CME) cell at various scan rates (from few mV/s up to few V/s). Results show that for the smaller carbon pore size (0.68 nm), the ion adsorption kinetics was controlled by the diffusion of the ions inside the pores. For carbon pore size in the same range as the anion size, an extra capacitance was measured on the Cyclic Voltammetry plots. This reversible extra-capacitance is suspected to be issued from an increase of the electrostatic interactions between the ions and the carbon pore walls in this confined environment. These new results confirm that matching the pore size of carbon to the ion size of electrolyte is of vital importance for optimizing specific capacitance, when using either solvated or solvent-free ionic liquid electrolytes.
12:00 PM - U10.2
Layer-by-Layer Assembled Multiwall Carbon Nanotube Electrodes for Energy Storage Devices.
Seung Woo Lee 1 , Naoaki Yabuuchi 2 , Betar Gallant 2 , Shuo Chen 2 , Byeong-Su Kim 1 , Junhyung Kim 2 , Paula Hammond 1 , Yang Shao-Horn 2 3
1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States, 2 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States, 3 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractDevelopment of novel energy storage devices using nanoscience and technology has been acknowledged as one of the most important technical issues in the recent energy crisis. Since the efficiency of energy storage devices primarily depends on the materials and structures utilized, both synthesizing unique nanomaterials and designing ideal nanostructures are essential to this research. Potential advantages of nanostructured electrodes for batteries and supercapacitors include higher electrode/electrolyte contact area and faster charge/discharge rates, ultimately leading to higher energy and power density of devices. Layer-by-layer (LBL) assembly is a versatile thin-film fabrication technique which consists of the repeated, sequential immersion of a substrate into aqueous solutions of complementary functionalized materials. We recently demonstrated all multiwall carbon nanotube (MWNT) thin electrodes using LBL assembly with functionalized MWNTs1. The LBL assembled MWNT electrodes are unique in that they yield distinct advantages such as 1) water-based or “green” electrode processing at ambient conditions, 2) elimination of polymeric/insulating binding agents, surfactants and electronic carbon supports, and 3) precise control of electrode thickness. In addition, the LBL method can be adapted to virtually any 2D, 3D, or flexible substrate to increase electrode surface area for increased energy and power. LBL assembled functionalized MWNT electrodes exhibit a high energy density (200 Wh/kg) delivered at a high power of 100 kW/kg in lithium nonaqueous cells. The high energy densities of LBL-MWNT electrodes can be attributed to the Faradaic reactions between lithium ions and surface functional groups on MWNT electrodes rendering high pseudocapacitance.(1) Lee, S. W.; Kim, B.-S.; Chen, S.; Shao-Horn, Y.; Hammond, P. T. Journal of the American Chemical Society 2009, 131, 671-9.
12:15 PM - U10.3
Enhanced Performance Electrochemical Capacitors from Graphene Nanosheets Having Diverse Physical and Chemical Characteristics.
Sanjib Biswas 1 , Lawrence Drzal 1
1 Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan, United States
Show AbstractGraphene is considered to be the basic building block for many potential applications because of its exceptional electrical, thermal and mechanical properties. Acid intercalation followed by thermal exfoliation of natural graphite, developed by Drzal research group in Michigan State University, has been shown to be an easy approach to produce graphene nanosheets with an average thickness from 3 to 5 nm and lateral dimensions ranging from sub micron to more than 50 um. Retention of aromaticity and the absence of significant oxygen functionalities on the graphene basal plane are evident from the thermal stability (only 6 %wt loss) of these nanosheets in the temperature range from 120 to 300oC, where a considerable weight loss is expected for highly oxidized graphene basal plane from the generation of decomposed gaseous products like CO and CO2. XPS elemental analysis further confirms the high degree of aromaticity with a C/O atomic ratio close to 21.2. For graphene based EDLC application, attaining high capacitance, while maintaining low electronic resistance, can be realized through enhanced particle surface area, porosity and wettability of the active electrode material. With increasing ratio of edge to basal plane area, on going from large to small sized nanosheets, the relative proportion of oxygen functional groups bound to the active edge sites of these nanosheets increases. While the presence of these oxygen functionalities enhances the wettability of the electrode, the decreasing particle size significantly contributes towards a larger electronic resistivity of the electrode from increasing inter particle contact resistances. In order to retain high electronic conductivity of the electrode, large and small sized nanosheets have been combined into a 100% binder-free aligned multilayer composite structure to optimize the electrode performance for high capacitance and superior frequency responses in aqueous 6M KOH electrolyte. In this aligned configuration the highly electrically conductive large sized nanosheets not only contributes towards the double layer capacitance but also acts as a series of current collectors within the bulk electrode structure for facile electronic conduction from the inside to the outside current collector. This aligned configuration exhibits a symmetrical CV response with nearly straight rectangular sides even at a scanning rate 500 mv/sec. A nearly vertical low frequency line and a ‘knee’ frequency close to 150 Hz point to the suitability of this electrode for high power applications. The average specific capacitance of the aligned composite at 10 A/gm discharge current density is close to 80 F/gm. 1.Fukushima H. “Graphite Nanoreinforcements in Polymer Nanocomposites” PhD Dissertation, Michigan State University, East Lansing, MI, 20032.Biswas. S, Drzal. L.T, Nano Lett., 2009, 9 (1), pp 167–172
12:30 PM - **U10.4
Tunable Nanoporous Carbons for Supercapacitor Electrodes.
Ranjan Dash 1 2 , John Chmiola 2 , Lawrence Weinstein 1 , Patrice Simon 3 , Yury Gogotsi 2
1 , Y-Carbon, Inc., King of Prussia, Pennsylvania, United States, 2 Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania, United States, 3 CIRIMAT, UMR-CNRS 5085, Université de Toulouse, Toulouse France
Show AbstractY-Carbon’s tunable nanoporous carbon based on its proprietary Carbide Derived Carbon technology, offers carbon electrodes whose pore size can be tuned to specific electrolyte for use in a supercapacitor. Such material has shown high capacitance and low resitance, and can be advantageous in high-energy, high-power applications. Experimental evidence will be shown that the pore size to ion size ratio determines the efficiency of electrochemical energy storage systems. In addition to pore size control, Y-Carbon’s simple and scalable technology allows control of structure and offers high accessible surface area and a wide range of structures that can be potentially be useful in various electrochemical storage devices, including supercapacitors and batteries. Physical, structural and electrochemical properties of highly pure carbide-derived carbons will be presented. References [1] P. Simon, Y. Gogotsi, Nature Materials, 7 (2008) 845.[2] R. Dash, J. Chmiola, G. Yushin, Y. Gogotsi, G. Laudisio, J. Singer, J.E. Fischer, S. Kucheyev, Carbon, 44 (2006) 2489[3] J. Chmiola, C. Largeot, P.-L. Taberna, P. Simon, Y. Gogotsi, Angewandte Chemie Int. Edition, 47 (2008) 3392[4] C. Largeot, C. Portet, J. Chmiola, P.L. Taberna, Y. Gogotsi, P. Simon, J. Am. Chem. Soc., 130 (2008) 2730[5] J. Chmiola, G. Yushin, Y. Gogotsi, C. Portet, P. Simon, and P. L. Taberna, Science, 313 (2006) 1760
U11: Electrolyte Confinement in Porous Electrodes
Session Chairs
Wednesday PM, December 02, 2009
Room 200 (Hynes)
2:30 PM - **U11.1
Graphitic Nanopore-Field Induced Ordering Effect for Molecules and Ions.
Katsumi Kaneko 1 , Akemi Tanaka 1 , Natsuko Kojima 1 , Taku Iiyama 2 , Tomonori Ohba 1 , Sumio Ozeki 2 , Hirofumi Kanoh 1 , Patrice Simon 3
1 Chemistry, Graduate School of Science, Chiba University, Chiba Japan, 2 Chemistry, Faculty of Science, Shinshu University, Matsumoto Japan, 3 CIRMAT Laboratory, University of Paul Sabatier of Toulouse, Touluse France
Show AbstractGraphitic nanoporous materials such as activated carbon fiber (ACF), carbide-derived carbon (CDC), single wall carbon nanotube (SWCNT), and single wall carbon nanohorn (SWCNH) show a considerably high electronic conductivity compared with zeolites, ordered mesoporous silicas, and metal organic frameworks. Also the graphitic wall has the high atomic density, providing the strong interaction potential for molecules and ions per unit weight, although the carbon wall is almost penetrable for X-ray. This paper presents special functions of the carbon nanopore spaces that the strong interaction potential field gives rise to a unique high density structure for molecules and ions including the organic electrolytes. For example, alcohol molecules and SO2 are oriented to the carbon pore-walls. The structure of water in the carbon pores at 303 K is close to that at 140 K . The hydration number around an inorganic ion such as a Rb ion is smaller than that of the bulk ion by 30 %. The addition of TEABF4 induces the higher population of PC molecules at the carbon walls.
3:00 PM - U11.2
Effect of Salt Depletion on Charging Dynamics in Nanoporous Electrodes.
David Robinson 1 , Benjamin Jacobs 1 , Chung-An Max Wu 1
1 Energy Nanomaterials, Sandia National Laboratories, Livermore, California, United States
Show AbstractDouble-layer supercapacitors built from nanoporous electrodes can have such a high ratio of electrode surface area to pore volume that charging the capacitor can deplete the salt from the liquid volume. Experimentally, this effect is often masked by external solution resistance or by transport of salt into the pore from an external reservoir. However, in some practical cases, the phenomenon can have an important effect on charging time and linearity. It can be mitigated through attention to those masking effects and to the symmetry of ion mobilities. We have observed salt depletion effects using dealloyed gold, which has well-defined 10 nm pores and a chemically well understood surface, and by minimizing the salt reservoir. Good correspondence is observed with a modified de Levie model that accounts for reduced conductivity due to salt depletion.This work was performed under the Laboratory-Directed Research and Development Program at Sandia National Laboratories, a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
3:15 PM - **U11.3
Theoretical and Computational Modeling of Carbon-Based Supercapacitors.
Vincent Meunier 1 , Bobby Sumpter 1 , Jingsong Huang 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractTheoretical methods have evolved to a point where the properties of materials can be successfully predicted based solely on their atomic structure. As such, they provide a unique tool, able to help identifying the origins of the properties of a given structure and uncovering principles that can be used to tailor structure for target applications.
In this talk, I will present an overview of the theoretical and computational work we have recently performed on capacitive electrical energy storage [1-2]. I will present a heuristic model that avoids the shortcomings of the electrical double-layer capacitor (EDLC) model by considering explicitly pore curvature into account. The density functional theory based model explains experimental observations for a range of pore sizes: from the micropore regime (< 2 nm), mesopore regime (2–50 nm), and macropore regime (> 50 nm); and diverse carbon materials and electrolytes. The model allows the properties of a supercapacitor to be correlated with pore size, specific surface area, Debye length, electrolyte concentration, dielectric constant, and solute ion size, and lead to a optimization pathway of carbon supercapacitors properties through experiments.References:[1] Theoretical Model for Nanoporous Carbon Supercapacitors, J. Huang, B.G. Sumpter, and Vincent Meunier, Angewandte Chemie 47, 520 (2008).[2] Universal Model for Nanoporous Carbon Supercapacitors Applicatble to Diverse Pore Regimes, Carbons, and Electrolyte, J. Huang, B. Sumpter, and V. Meunier, Chemistry: A European Journal (CEJ), 14, 6014 (2008).This work was supported in part by the Laboratory Directed Research and Development Program of ORNL, managed by UT-Battelle, LLC, and by the Center for Nanophase Materials Sciences (CNMS), sponsored by the Division of Scientific User Facilities, U. S. Department of Energy under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory.
3:45 PM - U11:Confinement
BREAK
U12: Nanostructured Materials for Batteries and Capacitors
Session Chairs
Michael Thackeray
Gleb Yushin
Wednesday PM, December 02, 2009
Room 200 (Hynes)
4:15 PM - **U12.1
Ionothermal Preparation of Li-based Electrode Materials: A Myriad of Opportunities.
Jean-Marie Tarascon 1 , Nadir Recham 1 , Jean-Noel Chotard 1 , Michel Armand 1 , Loic Dupont 1
1 Laboratory of Chemistry of Solids, Université de Picardie Jules Verne, Amiens France
Show AbstractOne of the major challenges of the next decades is undoubtedly the development of new technologies for energy storage in order to better handle our planet’s energy resources. Much hope has been put into the Li-ion battery technology. Yet, its success will depend on the chemist’s ability to create electrode materials more performing in terms of power, energy density, safety and cost, while following the concept of sustainability. Nature has not been of much help since the most interesting materials (LiFePO4 for example) are the most insulating, thereby having been left aside for many years. To thwart such difficulties chemists have acted either on the surface of the material (coating technique) or on its size and morphology using low temperature hydrothermal/solvothermal aqueous processes. To simplify this hydrothermal process and free ourselves from working under pressure, we recently implemented the ionothermal synthesis approach to the field of inorganic compounds. We showed, thanks to ionic liquids which do not have vapour tension, the possibility of preparing electrode materials of controlled size and morphology while working at temperatures < 250°C and under atmospheric pressure. Besides, we demonstrated than ionic liquids can act both as reacting medium and structuring agent during the synthesis process. This step forward due to the richness of ionic liquids chemistry, which number of combinations is practically boundless, opens many new opportunities in the synthesis/design of inorganic compounds; opportunities that we have explored to prepare and stabilize known new Li-based electrode materials whose attractive electrochemical properties will be reported.
4:45 PM - U12.2
Composite Tin-Carbon Electrospun Nanofibers for Use as Lithium-Ion Battery Anodes.
Christopher Bonino 1 , Liwen Ji 2 , Xiangwu Zhang 2 , Saad Khan 1
1 Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractComposite tin-carbon nanofibers are a promising material for rechargeable lithium-ion battery anodes. The high storage capacity of tin complements the long cycle life of carbon. In addition, the nanofiber structure has a high surface-to-volume ratio, which improves the accessibility for lithium intercalation as compared to traditional graphite-based anodes. In this study, we prepare polymer nanofibers containing tin salts by electrospinning. Subsequent thermal treatment not only carbonizes the nanofiber, but converts the tin salts to metallic tin, thereby providing tin-carbon composite nanofibers all in a one-step protocol. The performance of the fiber mats as anodes is evaluated in Li-ion half cells. The effects of the properties of the precursor polymer solution on the morphology of the electrospun fibers are studied. The conversion of different tin salts is also investigated.
5:00 PM - U12.3
High-Dielectric Constant (K) Al2O3 / TiO2 Atomic Scale Multilayers For Supercapacitors for Energy Storage.
Wei Li 1 , Bernd Kabius 2 , Ramesh N Premnath 1 , Orlando Auciello 1 3
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Electron Microscopy Center, Argonne National Lab., Argonne, Illinois, United States, 3 Center for Nanoscale Materials, Argonne National Lab., Argonne, Illinois, United States
Show AbstractDielectric materials exhibiting high dielectric constants have recently gained considerable attention for their potential applications in microelectronics such as capacitors and memory devices. Recently, a new kind of Pb/Bi-free dielectric material, CaCu3Ti4O12 (CCTO), was reported to possess high dielectric constant over a broad temperature range, which shows a step-like decrease with decreasing temperature accompanying the appearance of a Debye-like relaxation loss peak. Al2O3 and TiO2 have been investigated as high-K materials to replace SiO2 as gate and for high-capacitance oxide-based capacitors for electronics. The dielectric constants of Al2O3 and TiO2 are approximately 7 and 60-70, respectively. Our previous studies indicate that amorphous TixAl1-xOy films (Ti:Al=75:25 at %, a trading-off between high-K and offset barrier height) demonstrate a dielectric constant of ~ 30. Other work has shown that the dielectric constant of mixtures of Al2O3 and TiO2 varies between 7 and 60-70 depending on the mixture ratio. Here, we report here that high dielectric constants (> 800) can be achieved in Al2O3/TiO2 multilayers with sub-layer thickness ≤ 1 nm, fro frequencies ≤ 104 Hz. A step-like cecrease in dielectric constant to ~ 50 occurs between 10 4 – 10 5Hz. The high dielectric constant can be attributed to M-W relaxations, which occurs not due to the orientation of dipole but to the electrical heterogeneity of the multilayers. The Ellingham diagram indicates that the Al oxidation is more favored than Ti-oxide since the Al Gibbs free energy for oxidation is more negative than for Ti. Therefore, O atoms will have a diffusion tendency from TiO2 to Al2O3 sublayers,that can result in reduction of oxygen content in the TiO2 sublayers, leading to TiOx stoichiometry, thus electrical conductivity. As a consequence, the conductivities of TiO2 and Al2O3 sublayers become so different that surface charges would accumulate at the interfaces when electric current pass through. The surface charges relax with a.c. field and cause MW relaxation (the equations expressing the dispersion are completely identical to Debye relaxation although the origins are quite different). A discussion will be presented on the use of the ALD process to produce large area capacitors via conformal coating of large area ridge arrays fabricated on Si surfaces. These capacitors can yield ≥ 10 µF capacitance. We are exploring these capacitors for applications such as energy storage embedded capacitors in a Si microchip implantable in the human retina, as part of an artificial retina to restore sight to people blinded by genetically-induced degeneration of photoreceptors, and for super-capacitors integrated with ferroelectric-based high-efficiency photovoltaic devices for energy generation/storage systems.
5:15 PM - U12.4
Silicon Nanowire/Carbon Composite Electrodes for Lithium-ion Battery Anodes.
Candace Chan 1 , Seung Sae Hong 2 , Yi Cui 3
1 Chemistry, Stanford University, Stanford, California, United States, 2 Applied Physics, Stanford University, Stanford, California, United States, 3 Materials Science and Engineering, Stanford University, San Antonio, Texas, United States
Show AbstractSilicon nanowires (SiNWs) have the potential to perform as anodes for lithium-ion batteries with a much higher energy density than graphite. Previously (1), we have shown that reversible capacities >3,000 mAh/g can be obtained by using an electrode geometry consisting of SiNWs grown on metallic current collector substrates using the CVD-based vapor-liquid-solid (VLS) method. These electrodes consisted of SiNWs directly attached and vertically oriented off of the current collector.SiNWs can be synthesized in large quantities using the supercritical-fluid-solid (SFLS) method (2). Slurries were prepared composed of silicon nanowires synthesized using the SFLS method mixed with amorphous carbon or carbon anotubes and binder and coated onto Cu foil. Recent results regarding the cycling behavior of the SiNWs using different experimental conditions will be presented. The performance of these composite electrodes will also be compared with our previous work using the VLS SiNWs to determine how the electrode architecture affects the electrochemical performance.In collaboration with Reken Patel and Brian A. Korgel, Dept. of Chemical Engineering, The University of Texas at AustinReference List1. Chan, C. K.; Peng, H.; Liu, G.; McIlwrath, K.; Zhang, X. F.; Cui, Y. High performance lithium battery anodes using silicon nanowires. Nature Nanotech. 2008, 3, 31-35.2. Hanrath, T.; Korgel, B. A. Supercritical fluid-liquid-solid (SFLS) synthesis of Si and Ge nanowires seeded by colloidal metal nanocrystals. Adv. Mater. 2003, 15, 437-440.
5:30 PM - U12.5
Nanostructured Mesoporous TiO2 Electrodes for Energy Storage.
Keith Stevenson 1 , Jing Wu 1 , Alan May 1
1 , University of Texas at Austin, Austin, Texas, United States
Show AbstractNanostructured, mesoporous materials have shown significant promise for application in batteries. These materials and assembled interfaces are difficult to characterize by ensemble-averaging, bulk experimental methods since they do not exhibit long-range order, contain unique nano-morphological features and possess localized chemical compositions and defect chemistry. This presentation will highlight the development of several high resolution ellisometric porosimetry and electrochemical methods for studying the properties and reactivity of nanostructured, mesoporous TiO2 electrodes. Information obtained from these tools provides fundamental understanding of electron and charge transfer processes for materials utilized in energy conversion and storage technologies.
5:45 PM - U12.6
Nanoparticles Assemblies for Extreme Power Devices.
Maxim Tchoul 1 3 , Scott Fillery 1 3 , Hilmar Koerner 1 2 , Lawrence Drummy 1 4 , Peter Mirau 1 , Michael Durstock 1 , Richard Vaia 1
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Dayton, Ohio, United States, 3 , National Research Council, Washington, District of Columbia, United States, 2 , UTC Inc., Dayton, Ohio, United States, 4 , UES Inc., Dayton, Ohio, United States
Show AbstractFuture applications, such as all-electrical aircraft, require new energy storage technologies with combinations of high energy density (> 20 J/cc), efficiency (dielectric loss < 1E-4) and discharge rate (< 1 µs). These must incorporate innovative materials that combine increased dielectric strength (> 1000 V/µm) and dielectric constant (> 3) with gradual failure modes and higher temperature durability. Polymeric nanocomposites offer potential material option by combining high dielectric constant of inorganic fillers with high dielectric strength of polymers. Traditional nanocomposites produced by blending of components, however, do not provide sufficient control over morphology, and therefore at high inorganic loadings exhibit a drastic reduction in dielectric strength. Assemblies of core-shell nanoparticles, as a single-component system, offer a possibility for optimization of structure and properties through the modification of the interface. Herein, we report the synthesis and dielectric properties of the assembly of hybrid nanoparticles consisted of titanium dioxide core surrounded by covalently attached polystyrene corona via phosphate coupling and “click” chemistry. The use of mixture of low and high molecular weight polymer in different ratios enabled tuning of nanoparticle density, arrangement, and particle-particle spacing, as well as thermoplastic characteristics of the assembly. Direct solution casting of these hybrid particles without addition of free polymer yielded the solid films of high inorganic content (30-60%) and sufficient robustness. The films exhibited dielectric constants up to 6.5 and flat frequency response up to 100 kHz.
U13: Poster Session II
Session Chairs
John Miller
Yang Shao-Horn
Thursday AM, December 03, 2009
Exhibit Hall D (Hynes)
9:00 PM - U13.1
Nanoporous SnO2 as Anode Material for Li-ion Batteries.
Rolf Ochs 1 , Dorothee Szabo 1 , Sylvio Indris 2 , Sebastian Becker 2
1 Institute for Materials Research III (IMF III), Forschungszentrum Karlsruhe, Eggenstein-Leopoldshafen, Baden-Wuerttemberg, Germany, 2 Institute for Nanotechnology (INT), Forschungszentrum Karlsruhe, Eggenstein-Leopoldshafen, Baden-Wuerttemberg, Germany
Show AbstractNanomaterials based on tin dioxide (SnO2) possess very promising potential as anode material in Li-ion batteries because they exhibit in principle much higher specific capacities (790 mAh/g) than currently used carbon anodes (372 mAh/g). Bulk SnO2 anode material however shows very poor long-term cycle stability due to internal stress caused by the large volume change (>200%) during the alloying process from Li and Sn to Li4.4Sn resulting in cracks and loss of active material. Nanoporous materials could resolve this issue because they feature local free space to compensate this volume change. Bare tin dioxide (SnO2) nanoparticles and SnO2/carbon core/shell nanoparticles have been synthesized utilizing the Karlsruhe Microwave Plasma Process (KMPP), a versatile gas phase process. For the utilization as negative electrode material for Li-ion batteries the nanoparticles have been deposited as a film on Ni-Substrates on the one hand by in-situ depositing and on the other hand by a standard powder processing method for comparison. Scanning electron microscopy (SEM) characterization of the in-situ deposited films reveal a highly porous, club-like morphology. Nevertheless, these films exhibit a high mechanical stability. Transmission electron microscopy (TEM) of the particles shows a relatively uniform particle or core size of about 5 nm. The crystal structure of the particles is identified by electron diffraction to be the tetragonal cassiterite structure. Electrochemical performance measurements show specific charge and discharge capacities for the first cycle in the region of their theoretical values. With increasing cycle number the specific capacities actually decrease. This is attributed to the large volume change during the charging/discharging process and resulting in an island formation in the layer. Compared to the powder samples the capacity loss of the in-situ deposited layers is significantly reduced. This may be actually attributed to the nanoporous morphology of these layers. Optimizing the carbon shell thickness should further enhance the cycle stability as this carbon shell acts as a scaffold between the SnO2 particles. These results indicate that this is a promising approach for high capacity anodes in Li-ion batteries.
9:00 PM - U13.10
Chemically Reduced Graphene Sheets Separated by Layer-by-Layer Assembled Carbon Nanotubes for Electrochemical Capacitor Applications.
Hye Ryung Byon 1 , Seung Woo Lee 2 , Paula Hammond 2 , Yang Shao-Horn 1
1 Department of Materials Science and Engineering, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractWe present high specific capacitance of chemically reduced graphene (CRG) sheets separated by layer-by-layer (LbL) assembled multi-walled carbon nanotubes (MWNTs) in acidic aqueous solution. Amine-functionalized MWNT (MWNT-NH2) and graphene oxide (GO) were alternately adsorbed onto ITO-coated glasses via the LbL assembly method, which were then subject to a 24-h hydrazine treatment at 120 oC in order to convert GO to CRG. The MWNT/CRG films showed ~10 times greater electronic conductivity in comparison with original MWNT/GO LbL films upon removal of a large number of surface oxygen groups on GO sheets. The specific capacitance of MWNT/CRG films from cyclic voltammetry measurements in 0.5 M H2SO4 was measured to be ~150 F/gMWNT/CRG, from which the capacitance of CRG layers in the films was estimated to ~230 F/gCRG by excluding the MWNT capacitance contribution. The high specific capacitance of CRG films can be attributed to 1) the availability of electrochemically active surface area of CRG sheets separated by the MWNTs in the LbL films, and 2) pseudo-capacitive charge storage associated with redox of nitrogen-containing and oxygen-containing surface functional groups on the CRG surface.
9:00 PM - U13.12
New Binder Materials for Si Electrode.
Gao Liu 1 , Shidi Xun 1 , Xiangyun Song 1 , Honghe Zheng 1 , Vince Battaglia 1
1 Environmental Energy Technologies Division, Lawrence Berkeley National Lab, Berkeley, California, United States
Show AbstractHigh-capacity electrodes for lithium-ion batteries have to be developed in order to meet the 40-mile plug-in hybrid electric vehicle energy density needs. Si, with a high volumetric and gravimetric density (2446 mAh/mL and 4200 mAh/g at Li4.4Si), may be a viable candidate. Full capacity cycling of Si results in significant capacity fade due to a large volume change during Li insertion and removal. Decreasing the particle size to nanometer scale can be an effective means of accommodating the volume change; however, the repeated volume change during cycling can also lead to repositioning of the particles in the electrode matrix and result in particle dislocation from the conductive matrix. This dislocation of particles causes the rapid fade of the electrode capacity during cycling, even though the Si particles are not fractured. In our opinion, any new approach to enable Si material should be compatible with the current Li-ion chemistry and manufacturing processes. To this end, a new class of binder material was designed and synthesized. These new binders provide improved binding force to the Si surface to help maintain good electronic connectivity throughout the electrode. The electrodes made with these binders have significantly improved the cycling capability of Si.
9:00 PM - U13.13
Nanowire Composites for Electrochemical Energy Storage.
Zheng Chen 1 , Yunfeng Lu 1
1 , UCLA, Los Angeles, California, United States
Show AbstractIn order to design a better electrochemical capacitor with both high energy and power density, a common strategy is to construct a hybrid capacitor that integrates both the electric double-layer capacitance and pseudocapacitance within a single electrode. For example, Sato et al. loaded ruthenium oxide onto activated carbon, resulting in a capacity of 308 F g-1 at 7.1 wt % ruthenium loading and a low scanning rate of 2 mV s-1. Dong et al. reported the composite of MnO2 and the templated carbon with a capacitance of 156 F g-1 at 20 wt-% MnO2 loading and a scanning rate of 50mV s-1, which is about two times of that of the constituent carbon. Kim et al. dispersed ruthenium oxide nanoparticles on carboxylated CNTs and obtained a total capacitance of 304 F g-1 at a RuO2 loading amount of 50 wt-%. Similarly, composites prepared by electrodepositing MnO2 on vertically aligned CNT arrays exhibit a capacitance up to 199 F g-1 (or 305 F cm-3) with long cycle life; however, the complex fabrication process may limit their actual use. In spite of extensive research and effort, making supercapacitors with high energy and power density still remains challenging. Herein, we report the synthesis of novel supercapacitor materials based on the composites of low-cost, interpenetrating CNTs and V2O5 nanowires. This unique architecture provides several major advantages: 1) the small dimension of the CNTs and the nanowires provide high surface areas, leading to a high EDLC and better utilization of the V2O5 active sites (higher specific pseudocapacitance); 2) the interpenetrating nanotube/nanowire structure creates hierarchical porous channels, enabling effective electrolyte transport and active-site accessibility; (3) the nanowires are intimately intertwined with highly conductive CNTs, facilitating a faster electron transport and efficient current collection. Experimentally, these novel composites were readily synthesized using a one-pot hydrothermal approach. Note that V2O5/CNT composites were prepared by depositing a thin layer of V2O5 (6 nm thick) on a CNT film, exhibiting a high Li-ion capacitance up to 910F g-1 at a scan rate of 10mV s-1. However, such composite thin films with extremely low V2O5 loadings may not be suitable for practical applications. This work provides a simple but effective synthesis route and structure design towards better supercapacitors.
9:00 PM - U13.15
Electrical Conductivity Enhanced by Proton Irradiation in Hydrogen-bonded KH2PO4.
Jin Jung Kweon 1 , In Hwan Oh 1 , Kyu Won Lee 1 , Cheol Eui Lee 1
1 , Department of Physics, Institute for Nano Science, Korea University, Seoul Korea (the Republic of)
Show AbstractHydrogen-bonded proton conductors, which can be used in fuel cells in the intermediate temperature range (100 ~ 300 °C), are recently attracting great interest due to their potential as electrolytes in fuel cells. KH2PO4 (KDP) may be used as a model system of the proton conducting materials. We have investigated the effects of proton irradiation, with different irradiation energies and doses, on the anisotropic electrical conductivity of KDP. The room-temperature electrical conductivity exhibited a more than an order of magnitude enhancement along the a-axis in proton-irradiated KDP. From the temperature-dependent measurements of the a-axis and c-axis electrical conductivities, the proton irradiation is found to have given rise to changes in the activation energy presumably of the proton intersite hopping. Our work demonstrates the potential of the proton irradiation as a means of controlling the electrical conductivity of the proton conductors for the use of efficient proton fuel cells.
9:00 PM - U13.16
Materials Selection Criteria for Mechanically Durable Insertion Electrodes for Lithium Ion Batteries.
Yang-Tse Cheng 1 , Mark Verbrugge 2
1 Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky, United States, 2 Materials and Processes Lab, General Motors Research and Development Center, Warren, Michigan, United States
Show AbstractLithium ion battery electrodes may experience large volume changes caused by 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. In this paper, we present a set of analytic solutions for the evolution of stresses within a spherically-shaped electrode element under several representative charging-discharging conditions, including the ones developed earlier [1-4]. Based on the analytic solutions, we develop a set of criteria for the initiation of cracks in spherical insertion electrodes. These criteria may help guide the development of new materials for lithium ion batteries with enhanced mechanical durability. [1] Y.-T. Cheng and M. W. Verbrugge, The influence of surface mechanics on diffusion induced stresses within spherical nanoparticles, J. Appl. Phys. 104, 083521 (2008).[2] M. W. Verbrugge and Y.-T. Cheng, Stress Distribution within Spherical Particles Undergoing Electrochemical Insertion and Extraction, The Electrochemical Society (ECS) Transactions 16, 127 (2008).[3] Y.-T. Cheng and M. W. Verbrugge, Evolution of stress within a spherical insertion electrode particle under potentiostatic and galvanostatic operation, J. Power Sources 190, 453 (2009).[4] M. W. Verbrugge and Y.-T. Cheng, Stress and strain-energy distributions within diffusion-controlled insertion-electrode particles subjected to periodic potential excitations, J. Electrochem. Soc. (to be published).
9:00 PM - U13.17
Core-Shell NiSi/Si Nanowires for Li-ion Battery Anodes.
Gil-Sung Kim 1 , Kibum Kang 1 , Geunhee Lee 1 , Hyun-Seung Lee 1 , Cheol-Joo Kim 1 , Donghun Lee 1 , Dong An Kim 1 , Yong-Mook Kang 3 , Moon-Ho Jo 1 2
1 Department of Materials Science and Engineering, POSTECH, Pohang, Gyungbuk, Korea (the Republic of), 3 Division of Advanced Materials Engineering, Kongju National University, Cheonan, Chungnam, Korea (the Republic of), 2 Division of Advanced Materials Science, POSTECH, Pohang, Gyungbuk, Korea (the Republic of)
Show AbstractThere has recently been growing interests in the development of alloy-type anodes with the higher energy capacity and longer cycle life for Li-ion batteries. Si is an attractive alternative to the existing carboneous anodes due to the highest theoretical charge capacity (4200 mAh/g) and a low discharge potential (below 0.5 V). Single-crystalline Si nanowires (NWs) can provide further advantages over bulk Si or Si powders, mainly due to their affordable accommodation of large volume-changes upon Li-Si alloying/dealloying and efficient charge collection capability, otherwise they are seen as a major source for the cell performance degradation as in the case of bulk Si or Si powders. In this study, we employ core-shell metallic NiSi/amorphous Si (m-NiSi/a-Si) NWs on the stainless steel substrates, where the electrochemically inactive, conducting m-NiSi core acts as a stable mechanical support and an efficient current collector during the alloying and de-alloying reactions. We have fabricated a coin-type half cell by incorporating m-NiSi/a-Si NWs, and find the enhanced rate capability and superior cycling performance, compared to monolithic Si NWs. In particular, we have investigated the electrochemical reaction of Li+ with a-Si NW shells, and discuss the roles of the m-NiSi core on the cycling performance, in terms of the structural deformations and the reaction kinetics.
9:00 PM - U13.19
Cubic Mesoporous TiO2 for Next Generation Electrochemical Capacitors: Templated Sol-Gel vs. Nanocrystal Based Films.
Torsten Brezesinski 1 2 , John Wang 3 , Bruce Dunn 3 , Sarah Tolbert 2
1 Physical Chemistry, Justus Liebig University Giessen, Giessen Germany, 2 Chemistry & Biochemistry, University of California at Los Angeles, Los Angeles, California, United States, 3 Materials Science & Engineering, University of California at Los Angeles, Los Angeles, California, United States
Show AbstractCapacitive energy storage has been somewhat overlooked as an energy storage technology. It is based on electrochemical capacitors (ECs), which include double layer capacitors and pseudocapacitors. These energy storage devices are related to batteries, but have different storage mechanisms. Capacitive storage offers a number of desirable properties, such as charging within seconds and the ability to deliver up to 10 x more power than batteries. The limiting feature that prevents more widespread usage of ECs has been the relatively low energy density of the materials employed. Here, we present methods to overcome the limitations of ECs through the use of nanoporous transition metal oxides.A significant feature occurs as materials approach nanometer-scale dimensions. The charge storage from faradaic processes occurring at the surface becomes increasingly important.[1] However, capacitive energy storage in bulk materials is hindered by slow molecular transport of solvent and ions through the network. To address this problem, we turn to nanoporous films. In recent years, it has been shown that such materials can be readily formed by co-assembly of inorganic oligomers with amphiphiles. However, despite the fact that a broad range of ordered porous materials can be made, the majority of the templated materials do not allow the inorganic walls to be crystallized while retaining nanoscale order.Here, we report the fabrication as well as pseudocapacitive characteristics of block copolymer templated anatase TiO2 thin films synthesized using either sol-gel reagents or preformed nanocrystals as precursors. Both materials are 100 % crystalline and have large surface areas; yet, the structure of the porosity is not identical. Following our previously reported approach, we are able to use the voltammetric sweep rate dependence to determine quantitatively the capacitive contribution to the current response.[1] Considerable enhancement of the electrochemical properties results when the films are both made from nanocrystals and mesoporous. Such materials show high levels of capacitive charge storage and high insertion capacities. By contrast, when nanoscale porosity is created in a material with dense walls rather than porous walls derived from the aggregation of nanocrystals, insertion capacities comparable to templated nanocrystal based films can be achieved, but the capacitance is much lower. The results presented here underscore the importance of pseudocapacitive behavior that develops in mesoporous oxide films. Also, they suggest that both a mesoporous morphology and the use of nanocrystals as the basic building blocks are very promising for the rational development of metal oxide capacitors. Through this combination, it may become possible to attain greater power densities while maintaining energy density in next generation electrochemical capacitors.[1] Brezesinski, T.; Wang, J.; Polleux, J.; Dunn, B.; Tolbert, S. H. J. Am. Chem. Soc. 2009, 131, 1802.
9:00 PM - U13.20
Binding Site of Li+ Ions in 1D Nanostructured β-MnO2 Probed by 7Li MAS-NMR Spectroscopy.
In Young Kim 1 , Hyung-Wook Ha 1 , Tae Woo Kim 1 , Seong-Ju Hwang 1
1 Dpartment of Chemistry and Nano Sciences, Center for Intelligent Nano-Bio Materials (CINBM), Ewha Womans University, Seoul Korea (the Republic of)
Show AbstractWe have found that the formation of 1D nanostructures increases remarkably the charge capacity of β-MnO2 phase for lithium secondary batteries. To elucidate the origin of the capacity increases after the nanostructure formation, we have carried out systematic 7Li magic angle spinning-nuclear magnetic resonance (7Li MAS-NMR) analyses for lithiated β-MnO2 nanorod and its bulk microcrystalline homologue. The β-MnO2 1D nanorods were synthesized by the hydrothermal treatment of diverse manganese oxide precursors. The electrochemical measurements clearly demonstrated that the electrode performance of the β-MnO2 nanorod is much superior to that of bulk β-MnO2, confirming the positive effect of nanostructure formation. According to 7Li MAS-NMR analysis, the lithiated β-MnO2 shows a strong peak near 0 ppm, underscoring that the Li+ ions are mainly adsorbed on the surface of lithiated β-MnO2 nanorod. Based on the present MAS-NMR results, we could conclude that the increase of the surface area upon the nanostructure formation is mainly responsible for the obtained excellent electrode performance of the β-MnO2 nanorod.
9:00 PM - U13.21
Highly Reversible Li Storage in Si Nanowires with the Maximum Capacity.
Kibum Kang 1 , Dong-Wook Han 4 , Hyun-Seung Lee 1 , Gil-Sung Kim 1 , Donghun Lee 1 , Geunhee Lee 1 , Yong-Mook Kang 3 , Moon-Ho Jo 1 2
1 Materials Science & Enginnering, POSTECH, Pohang, Gyungbuk, Korea (the Republic of), 4 Department of Materials Science & Engineering, Korea Advanced Institute of Science & Technology, Daejon Korea (the Republic of), 3 Division of Advanced Materials Engineering, Kongju National University, Cheonan, Chungnam, Korea (the Republic of), 2 Division of Advanced Materials Science, POSTECH, Pohang, Gyungbuk, Korea (the Republic of)
Show AbstractThe electrochemical LixSi intermetallics form various crystalline compounds with x up to 4.4, correspondingly symptomatic of the largest known gravimetric charge capacity of 4,200 mAhg-1 in the bulk limit, thus can represent an interesting anodic system for the high capacity Li-ion battery. Here, we show direct evidence of reversible phase transitions during the Li-Si alloying/dealloying in Si nanowire (NW) hosts at the full electrochemical cycle by the electron diffraction and energy loss spectroscopic observations at the individual NW level. Concomitantly, we report highly reversible Li charge/discharge capacity whose corresponding composition is Li4.4Si upon the full electrochemical lithiation in a coin-type Si NWs half-cell. Specifically, we have found that an amorphous Si shell/crystalline Si core NWs initially transformed into crystalline and amorphous Li13±Si4 NWs, followed by crystalline and amorphous Li22Si5 NWs. Upon the delithiation, the Li22Si5 NWs progressively transformed into Li12±Si7 NWs in the radial direction, followed by a recovery to crystalline and amorphous Si NWs.
9:00 PM - U13.22
The Change of Elastic Properties in Graphite Anode During Li Intercalation.
Yue Qi 1 , Haibo Guo 3 , Louis Hector 1 , Adam Timmons 2
1 Materials and Processes Lab, GM R&D Center, Warren, Michigan, United States, 3 Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina, United States, 2 Chemical and Environmental Science Lab, GM R&D Center, Warren, Michigan, United States
Show AbstractStresses induced by lithium diffusion can lead to fracture of electrode materials resulting in capacity and voltage decreases in Li ion rechargeable batteries. The diffusion-induced stress field is often derived from an analytical formulation in which coupling between the mechanical and diffusion problems is based upon an analogous thermal stress problem. Here, we demonstrate that this analogy is invalid for anode materials where diffusion induced staging and phase transition occur. The elastic properties of Li intercalation graphite compounds (Li-GIC) at various stages were predicted from first principles density functional calculations. The results show that Li intercalation significantly increases the elastic moduli perpendicular to the graphite basal planes, and slightly decreases the elastic moduli along the basal planes. Changes in elastic moduli can be accounted for by the changes in bonding nature due to Li intercalation. Inter-plane bonding is strengthened by the additional ionic bonds formed between positively charged Li ions and negatively charged carbon atoms; while the extra charge on C atoms occupies the anti-π bonding thereby weakening the intra-plane bonds. The predicted elastic constants were input to a core-shell model with a moving phase boundary. A two phase coexisting state is predicted wherein the Li-rich region is under compression and Li-deficient region is under tension. This study suggests that the assumption of constant material properties, used in many current battery models is inappropriate.
9:00 PM - U13.23
Synthesis and Electrochemical Characterization of 0.5Li2MnO3-0.5Li[Mn0.375Ni0.375Co0.025]O2 Cathode Materials for Li Rechargeable Batteries.
Sivaprakash Sundaresan 1 , S. Majumder 1
1 Materials Science Center, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India
Show AbstractFor lithium rechargeable battery, composite cathodes with high discharge capacity, rate capability, cycleability and stability are one of the most attractive material candidates. In the present work, using self combustion route, we have successfully synthesised 0.5Li2MnO3 (inactive)-0.5Li[Mn0.375Ni0.375Co0.025]O2 (active) composite layered cathode for lithium rechargeable batteries. The synthesized cathodes were characterized in terms of their phase formation behaviour, microstructure evolution and electrochemical properties. X-ray Rietveld refinement analyses confirm the hexagonal layered structure of these cathode materials. In the cut-off voltage between 4.6 to 2.0 V, using a discharge current ~ 10 mA/g, the charge and discharge capacity of the synthesized cathode material was measured to be 340 and 180 mAh/g respectively. By analyzing the charge and discharge profiles in conjunction with Nyquist plots we have investigated the lithium intercalation behaviour of these composite cathode materials. Through these analyses, it has been postulated that during charging these cathode beyond 4.5 V, lithium is extracted simultaneously both from active as well as inactive components while during discharge part of the lithium is intercalated back which leads to the observed irreversible loss in capacity. In the subsequent charge-discharge cycles, the irreversible loss in capacity was found to be reduced and these cells yield excellent cycleability.
9:00 PM - U13.24
TiO2 Nanotubes with the Controlled Morphology as High Performance Anode Materials in Rechargeable Lithium Ion Battery.
YoungJin Yoon 1 , Changdeuck Bae 2 , Hyunjun Yoo 1 , Jooho Moon 2 , Joosun Kim 3 , Won-Sub Yoon 1 , Hyunjung Shin 1
1 School of Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of), 2 Department of Materials Science and Engineering, Yonsei University, Seoul Korea (the Republic of), 3 Center for Energy Materials Research, Korea Institute of Science and Technology, Seoul Korea (the Republic of)
Show AbstractOne-dimensional nanostructures such as nanowires, nanorods, and nanotubes (NTs) are actively being investigated as efficient charge collectors for energy storage and conversion applications. TiO2 NTs has been confirmed as a safe anode material in lithium ion batteries due to its intrinsic higher chemical stability. They also show higher lithium insertion potential in comparison with the commercialized carbon anode materials. Nanotubular structures of TiO2 allow for better accommodation of the large volume changes without the initiation of fracture that can occur often in bulk or micron-sized TiO2. Each of TiO2 NTs is electrically connected to the metallic current collector so that all the NTs contribute to the capacity as direct 1-D electronic pathways allowing for efficient charge transport. We have studied the electrochemical characteristics of TiO2 NTs as anodes for lithium ion batteries that have large surface area, high aspect ratio as well as high areal density. TiO2 nanotubular anodes have been fabricated by template-directed atomic layer deposition (ALD) process onto porous alumina membranes. With the ALD process, in principal, all of the physical dimensions including diameter, length, and wall thickness of TiO2 NTs are readily adjustable. In particular, the electrochemical characteristics of TiO2 NTs with different crystallinity and structural dimensions were investigated in this work. As a result, the optimum structures of NTs are determined as follows: With the same morphological feature, rate capacity of TiO2 NTs with thinner wall was much higher than that of thicker wall of TiO2 NTs. The thinner TiO2 NTs (i.e., 5nm-thick) show especially high specific capacity (typically 312mAhg-1 with C/10) and ultrafast discharge rate (typically 50mAhg-1 with 370C). Higher specific capacity (typically 200mAhg-1 with C/10) is obtained from the crystalline TiO2 NTs compared to the amorphous ones (typically 138mAhg-1 with C/10). This is probably due to disordered structures and lower electronic carrier mobility in amorphous TiO2 NTs. The modest capacity fading was also observed in accordance with faster C-rates. It is noted that the cell retained full capacity of 200mAhg-1 when more than 300 cycling at C/3, indicating the chemical/mechanical robustness of our NT electrodes. We have also controlled the morphology of TiO2 NTs to improve further their electrochemical performances. Upon the demonstration of the capability with pristine, smooth NTs, a few approaches might be possible to improve the design of the NTs’ morphology. We have fabricated the branched TiO2 NTs obtained by a mild alkali treatment. It shows extremely fast cycling time with high specific capacity (typically 100mAhg-1 with 300C). The proposed nanoarchitectures should make our nanotubular TiO2 NTs ideal in lithium ion battery applications with significantly high capacity as well as ultrafast lithium ion intercalation.
9:00 PM - U13.25
Layer-by-Layer Assembled Thin Films for Battery Electrolytes.
Lang Sui 1 , Arthur Feldman 1 , Nicholas Kotov 1 2 , John Kieffer 1
1 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractBattery electrolytic thin films were fabricated using exponentially grown layer-by-layer (eLBL) assembly method. In eLBL, poly(ethylene oxide) (PEO), poly(acrylic acid) (PAA) and fumed silica (f-SiO2) were combined through weakly opposite charge attractions between polymers or through hydrogen bonding. This way, relatively thick films of 40-60 microns were made using few deposition steps. Unlike traditional LBL, eLBL films have high levels of interpenetration where each layer is not easily distinguishable. [(PEO/PAA)x/SiO2]y films were fabricated with a total of 30 PEO/PAA bilayers. The amount of SiO2 is varied by changing the PEO/PAA thickness between each SiO2 deposition. The amount of deposited SiO2 was measured using thermogravimetric analysis. NaCl salt was dissolved into PEO solution and incorporated into the film during deposition. Fluorescence spectroscopy of tagged PEO and PAA showed that homogeneously blended films were created during exponential growth. The in-plane and out-of-plane elastic moduli were measured using Brillouin light scattering and found to be of comparable magnitude, indicating the elimination of interfaces between layers. Ionic conductivities of the films were measured using impedance spectroscopy. Impedance spectroscopy showed an improvement in ion conductivity for eLBL as compared to cast films. Furthermore, the addition of f-SiO2 layers also resulted in an increase of conductivity.
9:00 PM - U13.26
Carbide-derived Carbon for Thin Film Supercapacitors.
Min Heon 1 , Yury Gogotsi 1 , Jeffrey Hettinger 2 , Magali Brunet 3 , David Pech 3 , Pierre-Louis Taberna 4 , Patrice Simon 4
1 Department of Materials Science and Engineering and A.J. Drexel Nanotechnology Institute, Drexel University, Philadelphia, Pennsylvania, United States, 2 Department of Physics and Astronomy, Rowan University, Glassboro, New Jersey, United States, 3 LAAS-CNRS, Université de Toulouse, Toulouse France, 4 CIRIMAT UMR CNRS, Université Paul Sabatier, Toulouse France
Show AbstractThin film batteries and supercapacitors are potentially capable of providing power to a new generation of advanced power-thirsty electronic devices, portable electronics, sensors, etc. They may also be integrated with solar batteries, storing electrical energy and providing high power density. However, compared to Lithium-ion batteries, very little work has been done to integrate supercapacitors on a silicon chip or produce thin film supercapacitors in general. Carbide-derived carbon has been shown to perform very well in supercapacitor electrodes. In this research, we will demonstrate continuous thin films of carbide-derived carbon formed on various substrates, which were produced by selective etching and vacuum decomposition of Silicon Carbide (SiC) and Titanium Carbide (TiC) films. The synthesis process of CDC thin film has been investigated in details using different carbides on several substrates. Selective etching by chlorine has been optimized for thin-film CDC synthesis on a variety of substrates through analysis of the film growth using Raman spectroscopy and electron microscopy. The electrochemical properties of the thin film supercapacitors using carbide-derived carbon will be discussed as well.
9:00 PM - U13.27
Electrochemical Behavior of Amorphous Tin–Cobalt Anode.
Ruigang Zhang 1 , Shailesh Upreti 1 , M. Stanley Whittingham 1
1 , Binghamton University, Binghamton, New York, United States
Show AbstractLithium-ion batteries are ideal power sources for portable electronic devices. However, safer and less costly electrodes are the need of next generation rechargeable batteries, particularly for the applications where high pulse charging and discharge is required, example includes; hybrid electric vehicles and all-electric vehicles. Amorphous tin based anodes have attracted much interest due to their higher volumetric capacity than graphite and excellent capacity retention. Here we compare the electrochemical behavior of amorphous and crystalline tin based material. At all cycling depths of discharge, 10% to 100%, the amorphous anode showed no loss of capacity in direct contrast to crystalline Sn foil. Lithium removal was found to show excellent rate capabilities, but lithium insertion was found to be rate limited. An ex-situ X-ray analysis revealed that annealing triggers the crystallization and grain size increase in Sn based material. A detailed in-situ, ex-situ X-ray diffraction, EIS and CV analysis, will be presented with an aim to throw more light on the chemistry and limitations of this class of material. 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.
9:00 PM - U13.28
Effect of Annealing on the Dielectric Properties of BaTiO3 - High-k Polymer Nanocomposites.
Sai Shiva Reddy 1 , Youngjin Choi 1 , William Milne 1 , Gehan A. Amaratunga 1
1 Engineering, University of Cambridge, Cambridge United Kingdom
Show AbstractHigh-k materials find usage in a variety of electronic applications such as high-frequency, high energy density capacitors, transducers, piezo-sensors, etc. Barium Titanate (BaTiO3 ) nanoparticles are known to possess a very high dielectric constant, typically in the range of 1- 10000, that largely depends on the particle size and the post annealing temperature. In this paper, we attempt to improve the dielectric properties of BaTiO3 nanoparticles by post annealing and blending with polymers. Hydrothermally synthesized BaTiO3 nanoparticles are first annealed and then suspended in a high-k polymer matrix (cyanoethylated cellulose, k of 21 at 1Khz). We report the effect of annealing BaTiO3 nanoparticles, at various temperatures in the range of 50-1100°C, on the dielectric properties of the nanocomposites. The performances as a function of the fraction of BaTiO3 filler in the polymer matrix are also investigated.
9:00 PM - U13.29
Electrochemical Supercapacitors Confined in Nanopores of Anodic Aluminum Oxide on Silicon Substrate.
Juchao Yan 1
1 , Eastern New Mexico University, Portales, New Mexico, United States
Show AbstractElectrochemical supercapacitors include electrical double-layer capacitors and/or electrochemical redox capacitors. On demand, electrochemical supercapacitors can supply charge more quickly than batteries, making them ideal for smart cards, displays, implantable medical devices, and hybrid cars. During the past nearly thirty years, electrochemical supercapacitors have evolved through several generations of designs.1 However, their rational designs on a nanoscale for higher power performance (e.g., higher energy-density) than most batteries are still needed.Nanoporous anodic aluminum oxide (AAO) is a self-ordered, hexagonal array of straight cylindrical pores with tunable diameters (between 5 nm and 300 nm) and depths (up to hundreds of μm). Since 1995,2 AAO has been the most popular template for synthesizing one-dimensional metals, semiconductors, inorganic composites, conducting polymers, etc. Surprisingly, there have been very few reports on the fabrication of electrochemical supercapacitors using AAO as a template. Using layer-by-layer assembly in cylindrical nanopores of AAO, Jiang et al.3 reported the first nano-supercapacitor array, consisting of an electro-polymerized polypyrrole (PPy), a porous TiO2 separator, and a chemo-polymerized PPy. This supercapacitor array forms an excellent concept, but suffers from low capacitance and very limited cycleability (probably due to the difficult control of the electropolymerization process).At Eastern New Mexico University, we have developed a cost-effective, enabling technology to fabricate freestanding AAO membranes with ordered, interconnected pore features. If such interconnected nanopores were used for electropolymerization, one could experimentally control the depth of the electropolymerized layer on the basis of the sharp change in the electropolymerization parameters. Here, we wish to report a three-step, bottom-up fabrication process to form composite supercapacitors in interconnected nanopores of AAO. We will use pyrrole, thiophene, and aniline respectively as the monomers for the in-pore electro- and chemo-polymerization of the conducting polymers, and to electrodeposit porous TiO2, MnO2, and RuO2 respectively on the electropolymerized layer as the separators. High-resolution scanning electron microscopy and transmission electron microscopy will be used to characterize the composites supercapacitors. The electrochemical performance of these composite supercapacitors will be investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. References:1.Pushparaj, V.L.; Shaijumor, M.M.; Kumar, A.; Murugesan, S.; Ci, L.; Vajtai, R.; Linhardt, R.J.; Nalamasu, O.; Ajayan, P.M. Proc. Natl. Acad. Sci., USA 2007, 104, 13574.2.Masuda, H.; Fukuda, K. Science 1995, 268, 1466.3.Liu, L.; Zhao, Y.M.; Zhou, Q.; Xu, H.; Zhao, C.J.; Jiang, Z. Y. J. Solid State Electrochem. 2006, 11, 32.
9:00 PM - U13.3
Control of Particle Size and Thin Film Surface Morphology using Femtosecond Pulsed Laser Deposition: For Growth of Li-ion Battery Electrode and its Applications.
Makoto Murakami 1 , Bing Liu 1 , Zhendong Hu 1 , Yong Che 1
1 , IMRA America, Inc, Ann Arbor, Michigan, United States
Show AbstractFor battery applications of electrode materials, controlling their particle size and surface morphology is one of the most important approaches to maximize their battery performances. In this presentation, we introduce a novel method to control the particle size and the surface morphology, and a method of pulsed laser deposition (PLD) using a femtosecond pulsed laser with burst-mode, which is a multi-pulse mode of selected number of pulses with very short time separation (20 ns) in between the pulses (Burst-PLD). This method enables controllability for thin-film morphologies, ranging from nanoparticle aggregates to epitaxial thin films with completely droplet-free and atomically smooth surfaces [1]. Using the Burst-PLD, we are potentially design the electrode materials to overcome the problems such as overvoltage which is dominated by solid-state diffusion of lithium in positive electrode.As for demonstrations, we have grown several cathode (LiMn2O4 and LiCoO2) and anode (LixTiO2, LixSnO2) and their composite thin films for lithium ion battery electrode materials using the Burst-PLD. A fiber based femtosecond laser (FCPA μJewel™ D-1000 laser developed by IMRA America, Inc.) is used for generating burst-mode laser pulses. The number of burst-mode pulses is selectively controlled from 1 to 20, and the repetition rate of the burst is also tunable in the range of 0.1 – 5 MHz. Ceramic targets placed in vacuum chamber are ablated with different number of pulses. When more number of pulses is used for the ablation (typically more than 10 pulses), smoother thin films free of droplets and clusters are obtained. While by decreasing the number of bust-pulses and/or increasing pulse energy for the ablations, rougher films of nanoparticle aggregates are obtained with increasing particle size. LiMn2O4 and LiCoO2 composite thin films are also grown by switching each targets, and the ratio of the composition are controlled by changing the ratio of ablation time of both targets. Epitaxial LiMn2O4 and LiCoO2 thin films are successfully grown on Al2O3 (0001) single crystal substrate. In case of conventional PLD using excimer laser and such, solid solution thin films are successfully obtained; however, when femtosecond pulsed laser is used, we obtained composite of epitaxial LiMn2O4 and LiCoO2 thin films rather than solid solution. We attribute the reason why solid solution thin films cannot be obtained in case using femtosecond PLD is that the particles are created very early stage of the ablation and they fly onto the substrate, and the materials do not have enough energy to react each other on the substrate in the typical growth temperature.[1] M. Murakami et al. Appl. Phys. Express, 2 042501 (2009)
9:00 PM - U13.30
Si Nanopartricle Composites as High-density Energy Storage Material for Li-ion Batteries.
Jung-Kyoo Lee 2 , Kurt Smith 1 , Cary Hayner 1 , Harold Kung 1
2 Chemical Engineering, Dong-A University, Saha-gu, Susan, Korea (the Republic of), 1 Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractSi is known to have a very high energy storage density when used as in a negative electrode for a Li ion battery. However, when used as a simple physical mixture with conducting carbon powder or graphite, nanosize Si particles exhibit very poor cycling stability. The initial high storage density (over 3000 mAh/g) disappears rapidly within a few charge/discharge cycles. Since composites of Si nanoparticles are easy to prepare, they offer a huge advantage on cost of manufacturing compared with highly sophisticated engineered structure. Thus, it is of great interest to find ways to stabilize the Si nanoparticles.We postulate that the cycling stability of Si nanoparticle composite can be enhanced if the particles can be dispersed homogeneously in the composite. Using this guideline, we prepared and tested two types of Si-carbon composites in which the carbonaceous component was derived either from a resorcinol-formaldehyde gel or from graphene sheets. The results show that when the Si nanoparticles are successfully dispersed in the composite, the cycling stability is much enhanced, and capacity loss of less than 0.5% per cycle can be obtained even for deep charge/discharge cycles. For samples prepared using the RF gel, the effect of surface treatment of the Si particles by introducing phenolic groups by hydrosilylation was examined. Introducing the phenolic groups onto Si enabled direct attachment of the Si particles onto the RF gel, which might facilitate contact of the particles with the gel. This surface modification could be followed by FTIR, and isolation of Si particles from each other was confirmed by TEM. Different methods were investigated to prepare samples with graphene sheets. These include using exfoliated graphene oxide sheets with or without pre-reduction and Si nanoparticles with or without surface treatment. The cycling stability depends strongly on the method of preparation. In general, methods that result in better dispersed Si samples show higher stability. Interestingly, even for an electrode thickness less than 1 mm, the initial storage capacity was found to increase with decreasing thickness, suggesting the importance of transport process to access to all Si nanoparticles and possible ways of improvement.
9:00 PM - U13.31
The Hydrothemal Synthesis and Characterization of Carbon-Free LiFePO4 and Li(Tix,Coy)Fe1-x-yPO4 Powders for Li-Ion Batteries.
Gangqin Shao 1 2 , Xuhui Mao 1 , Luis Ortiz 1 , Donald Sadoway 1
1 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States, 2 State Key Laboratory of Advanced Technology for Materials Synthesis & Processing, Wuhan University of Technology, Wuhan China
Show AbstractEven though in most situation, LiFePO4 and the related cathode powders have excess carbon or carbon coating for their applications, the carbon-free powders are needed to have a reduced primary particle size in order to shorten Li+ diffusion lengths and ohmic drop, as well as a narrow size distribution, in order to ensure a homogeneous current distribution, and achieve a high power efficiency and a long cycle life. The evaluation of ionic and electronic conductivity can be easier processed from carbon-free powders. Besides, the iron-ion in the olivine structur of LiFePO4 can be partially or wholly substituted by other metal-ion such as the transition metal of cobalt for the application in higher discharge potentials. In this study, LiFePO4 and Li(Tix,Coy)Fe1-x-yPO4 powders were hydrothemally synthesized from carbon-free raw materials in aqueous medium. The thermogravimetry analysis (TGA) was conducted to investigate the energy and weight changes. Phase structure was determined from X-ray diffraction (XRD) by using the Rietveld method. The microstructure and the corresponding chemical composition were examined by a scanning electron microscopy (SEM) combined an energy dispersive spectroscopy (EDS). The electrochemical lithium deinsertion/insertion characterization were also performed.
9:00 PM - U13.32
Kinetics of Li Ion Diffusion in LiFePO4.
Gopi Krishna Phani Dathar 1 , Graeme Henkelman 1
1 Chemistry & Biochemistry, University of Texas at Austin, Austin, Texas, United States
Show AbstractLithium olivine phosphates are one of the most studied cathode materials in Li ion batteries due to their low cost, non-toxic nature, high specific charge capacity and reversibility of lithium insertion. In this work we investigate how Li ions diffuse in the bulk and on the surface of these materials. Diffusion mechanisms that we can anticipate are determined with the nudged elastic band method. The adaptive kinetic Monte Carlo method is also used to directly model the dynamics of Li diffusion over long time scales. This method does not require that the final state of each diffusion event be specified so that we are able to discover complex reaction mechanisms directly from density functional theory.
9:00 PM - U13.33
Dielectric Characteristics of Nano-scale, Multilayered Polymer Films Fabricated by Plasma Enhanced Chemical Vapor Deposition.
Scott Fillery 1 , Jesse Enlow 1 , Rachel Jakubiak 1 , Timothy Bunning 1 , Michael Durstock 1
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States
Show AbstractPolymer films, such as biaxially oriented polypropylene, are widely used as the active dielectric in current capacitor designs due to their low dielectric loss and high reliability. However, higher energy density capacitors are likely to necessitate dielectric materials with improved permittivity or dielectric strength. The current nanocomposite approaches to this challenge have been dominated by random morphologies that exhibit drastic reductions in breakdown strength at higher filler loadings. One promising approach is the creation of a polymer nanocomposite with an extreme density of internal interfaces (500-1000 m2/g) which could effectively trap locally injected carriers, inhibiting the breakdown event. In this contribution, we report on the fabrication and characterization of a multilayer structure, using plasma enhanced chemical vapor deposition, a solvent free process for depositing films with excellent spatial uniformity and thickness control. Polymer stacks of between 10 and 40 alternating layers of benzene and octafluorocyclobutane, with layer thicknesses between 10 and 100nm, were deposited on conductive substrates. Permittivity, dielectric loss and dielectric strength were probed as a function of the relative individual layer thickness.
9:00 PM - U13.35
Electrochemical Evaluation of Melt-Cast LiMPO4.
Dean MacNeil 1 , M. Gauthier 2 , C. Michot 2 , G. Liang 2
1 Department of Chemistry, Université de Montréal, Montréal, Quebec, Canada, 2 , Phostech Lithium Inc., Montréal, Quebec, Canada
Show Abstract LiFePO4 has received a large amount of attention as a positive electrode material for lithium-ion batteries (1,2). It represents a low cost, thermally stable and environmentally friendly substitute for cobalt-based lithium metal oxides currently used as cathodes in the batteries of portable computers and cellular phones. In addition, the realization of high power batteries that have large capacity at high rates of charge and discharge are possible using small particle sized, carbon coated LiFePO4 (3).Thus far, most commercial LiFePO4 material has been synthesized using solid-state chemistry methods, while a large amount of work has been devoted to developing hydrothermally prepared LiFePO4 due to the smaller particle size obtained through this method. These two methods have drawbacks in that they both require long reaction times and costly precursors.We have recently introduced a new method of LiFePO4 synthesis that has the capability to provide large amounts of samples from a variety of precursors within a short reaction time (4,5). This melt-casting procedure uses typical metallurgical synthesis methods and can easily provide samples in kilogram quantities. The process involves the formation and cooling of a liquid phase from which we obtain ingots of pure crystalline LiMPO4. Subsequent grinding procedures and carbon coating treatments are critical to prepare LiMPO4 material with tunable electrochemical performance. This presentation will detail the synthesis and characterization of LiMPO4 obtained from various precursors in the molten state as well as the preparation of carbon coated LiMPO4 products and their electrochemical performance. The importance of obtaining material with nano-scale dimensions will be stressed.References1. A.K. Padhi, K.S. Nanjundaswamy, and J.B. Goodenough (1997). "Phospho-Olivines as Positive Electrode Materials for Rechargeable Lithium Batteries". J. Electrochem. Soc. 144: 1188-1194.2. B. Ellis, W. H. Kan, W. R. M. Makahnouk, and L. F. Nazar J. Mater. Chem., 17, 3248 (2007).3. N. Ravet, S. Besner, M. Simoneau, A. Vallee, M.Armand, and J. Magnan, U.S. Pat., 6,962,666 (2005).4. L. Gauthier, M. Gauthier, D. Lavoie, C. Michot, N. Ravet World Patent 2005/0624045. K. Zaghib, G. Liang, F. Labrecque, A. Mauget, C. Julien, M. Gauthier, Abstract #582, The Electrochemical Society and The Electrochemical Society of Japan Meeting Abstracts, 214th ECS Meeting, Honolulu, HI, Oct., 2008.
9:00 PM - U13.36
Theoretical Improvement in Lithium Ion Battery Energy Density with a Free-Standing Carbon Nanotube Anode.
Brian Landi 3 1 , Cory Cress 2 , Ryne Raffaelle 1
3 Chemical Engineering, Rochester Institute of Technology, Rochester, New York, United States, 1 NanoPower Research Labs, Rochester Institute of Technology, Rochester, New York, United States, 2 , Naval Research Labs, Washington , District of Columbia, United States
Show AbstractThere is an ever growing demand for electrical energy storage to support mobile electronics, hybrid-electric/full electric vehicles, and utility scale grid management. Lithium ion technology has recently emerged as the premier rechargeable battery chemistry due to the increased energy density over other technologies. Although the cathode is generally the limiting electrode in today’s devices, an attractive strategy being investigated to increase the battery energy density is to augment the anode capacity sufficiently to increase the number of active layers contained within an individual battery. This could be achieved with a multi-functional free-standing anode that has both high lithium ion specific capacity and sufficient electronic transport. Since no binder or inactive metal foil collector is used in such a design, the entire mass of the electrode can factor into the usable electrode capacity. The most promising developments to date using free-standing electrodes have been with carbon nanotube (CNT) papers which have capacities ranging from 600-1000 mAh/g depending upon morphology and electrolyte characteristics. In addition, the CNTs can be used to support high capacity anode materials like silicon and germanium with recent measurements exceeding 1000 mAh/g for free-standing silicon-CNT electrodes. At present, however, there currently lacks a quantitative framework to predict the intended impact and relative improvement using free-standing electrodes in a full battery design. The replacement of conventional anode designs which use graphite composites coated on copper foil with a free-standing CNT anode can result in a 200-300% increase in usable anode capacity depending on composite thickness. In the present work, a numerical model has been developed to calculate the relative improvement in battery energy density for any free-standing anode paired with conventional LiCoO2, LiFePO4, and LiNiCoAlO2 cathode chemistries. The results show a nonlinear dependence on battery improvement with anode capacity, density, and the nominal battery voltage. Overall, performance metrics with optimized cathode conditions and free-standing silicon-SWCNT anodes show energy densities in excess of 300 Wh/kg and 650 Wh/L to be theoretically achievable at the battery level. The expected enhancement in lithium ion battery performance through the use of free-standing anodes represents a dramatic increase in energy density, and potential directions to overcome present-day technical challenges will be highlighted.
9:00 PM - U13.39
Silicon/Carbon Composite Anode Materials for Lithium-ion Batteries.
Wenchao Zhou 1 , Shailesh Upreti 1 , M. Stanley Whittingham 1
1 Institute for Materials Research, SUNY-Binghamton, Binghamton, New York, United States
Show AbstractSilicon has attracted much attention as a possible anode candidate to replace the graphitic carbon materials because of its high capacity. Nevertheless, there are a few issues that prevent its use as a durable active anode in battery commercialization. Notably, the huge volumetric expansion that leads to the quick capacity fade, the irreversible lithium loss in the first cycle due to Si-Li alloying and the electrolytic surface reactions, which are issues that require substantial attention before its viable commercialization. Recently there have been reports on nano-sized Silicon/Carbon (Si/C) composites prepared by high energy mechanical milling that exhibit interesting electrochemical performance. We synthesized nano-sized material using an intrinsically low-cost method where Si is reduced from its oxide by Al during ball milling. Si was subsequently coated with conductive carbon by means of pyrolytic decomposition of Polyacrylonitrile (PAN) at 800C in an inert atmosphere. Electrochemical tests show that this nano Si offers a reversible capacity over 600 mAh/g for more than 30 cycles. The electrochemistry of the material was also collected in carbonate electrolyte with LiBOB additive. It is found that the additive helps to form stable surface film which reduces the electrolyte reaction. The Si/C composite was characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. 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.
9:00 PM - U13.4
Structural Studies of Chemically Delithiated Mixed Olivine Phosphates.
Joel Miller 1 , Natalya Chernova 1 , Shailesh Upreti 1 , Stanley Whittingham 1
1 Material Science, SUNY Binghamton, Binghamton, New York, United States
Show AbstractLithium iron phosphate’s value as a cathode material in lithium ion batteries is well known. However, the ionic diffusion in LiFePO4 and related olivine phosphates is still poorly understood due to essentially two-phase nature of their delithiation and lithiation. For example, during most of a galvanostatic cycle of LiFePO4, a lithium dilute (vacancy rich) phase and a lithium rich (vacancy dilute) phase are present. Therefore, a lithium diffusion coefficient determined for LixFePO4 at a value of x < 0.90 and > 0.05 via impedance spectroscopy (IS) or galvanostatic intermittent titration technique (GITT) will reflect diffusion at the phase boundary between these two phases in this miscibility gap region. In this study we suggest the possibility of overcoming this problem by synthesizing olivines with controlled ratios of metals on the M1 site, similar to those observed in mineral olivines. In nature, there are single-phase olivine-type phosphates for which lithium concentration is within the aforementioned miscibility gap of lithium iron phosphate. Nature accomplishes this by incorporating other cations (Mg2+, Ca2+, etc.) on the M1 site to stabilize the structure. One example of such a mineral is simferite, Li0.5Mg0.5Fe0.3Mn0.2)PO4. According to single crystal x-ray diffraction data of mineral simferite, the Mg2+ substitution creates randomly distributed lithium vacancies (Doklady Akademii Nauk SSSR, 307, 1119, 1989). Furthermore, Mn+2 substitution might lead to single phase lithium cycling. Such substituted compounds with randomly distributed lithium vacancies can be used to determine the lithium diffusion coefficient as a function of lithium vacancies. We have had success substituting Mg2+ and Mn2+ on to the M1 site via hydrothermal reaction followed by chemical oxidation with NO2BF4 or Br2. Li0.5Mg0.5Mn0.3Fe0.2PO4 and related Lix[Mg,Mn,Fe]PO4 were prepared in this manner. Products were evaluated by powder x-ray diffraction, DC-Plasma emission spectrometry, transmission electron microscopy, scanning electron microscopy, and temperature dependent magnetic studies. X-ray diffraction showed that single phase powders were synthesized with lattice parameters consistent with Vegard’s law predictions. DCP and magnetic properties confirm the metal contents and oxidation states. Micron particle size limits the electrochemical performance of the compounds, so that only about half of the available lithium can be extracted electrochemically. The nature of delithiation reaction (one-phase vs. two-phase) will be discussed. GITT and impedance spectroscopy studies will be used to estimate the effect of lithium vacancies on the diffusion. 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.
9:00 PM - U13.41
Impedance Spectroscopy of SEI on Porous SnO2/CNTs Composite Anodes for Lithium Ion Batteries.
Abirami Dhanabalan 1 , Xifei Li 1 , Yan Yu 2 , Kevin Bechtold 1 , Chunlei Wang 1
1 Mechanical & Materials Engineering Department, Florida International University, Miami, Florida, United States, 2 , Max-Planck-Institute for Solid State Research, Heisenbergstrasse, Stuttgart, Germany
Show AbstractTin oxide based amorphous composites have been studied extensively because of the high theoretical specific capacity compared to the commercialized carbon anode. During charge and discharge, solid electrolyte interface (SEI) film is formed at the interface between the electrolyte and the anode due to the reaction between the anode and the electrolyte. It is a thin lithium ion conductive film which protects the anode from co-intercalation of solvents and consequent exfoliation. The SEI film formed on the anode has important influence on the irreversible capacity, cycle performance and stability of Li+ insertion into anode. The significant volume change of the SnO2 could lead to some cracks on the surface of the anode, which results in the contact between acting anode material and electrolyte again, and new SEI film is possible to be formed on the cracks. The progressive structural changes of SEI film on the SnO2 strongly affects its electrochemical performance.In this work, impedance studies were carried out on SnO2/CNT anode which was prepared by means of electrostatic spray deposition (ESD). Tin acetate was dissolved in the glycol and ethanol based solvent as precursor solution in which CNT was homogeneously dispersed using sonication method. The as-obtained precursor solution was pumped through the stainless steel nozzle. The deposition temperature was kept at 200°C, 250°C and 300°C, respectively. The concentration of CNT was also varied. Coin cells were assembled using a SnO2/CNT working electrode, a Li metal counter electrode, a separator and an electrolyte solution of 1M LiPF6 in ethylene carbonate/dimethyl carbonate (EC/DMC). The electrochemical impedance spectroscopy (EIS) test was performed by Versatile Multichannel Potentiostat (VMP3), in order to understand the formation and the change of SEI film on SnO2/CNT anode with subsequent cycling. The equivalent circuit was proposed to fit the EIS plots. The experimental results will be discussed in detail at the conference.
9:00 PM - U13.42
Effect of Fe Substation on the Phase Formation and Charge Storage Characteristic of LiMn1/3Ni1/3Co1/3O2.
Naba Karan 1 , Rahul Singhal 1 , Jose Lopez 1 , Reji Thomas 1 , Ram Katiyar 1
1 Physics, University of Puerto Rico, San Juan, Puerto Rico, United States
Show AbstractRecently, layered LiMn0.5Ni0.5O2 has drawn attention as an alternate cathode material for secondary lithium-ion batteries due to its lower cost, better stability at high voltages and improved thermal safety characteristics compared with LiCoO2.1 However; LiMn0.5Ni0.5O2 suffers from poor rate capability. Partial substitution of nickel and manganese in LiMn0.5Ni0.5O2 by cobalt has reduced the Li/Ni intermixing, and has produced improvements in the rate capability and thermal stability properties.2-3 One such compound, LiMn1/3Ni1/3Co1/3O2 (NMC), has been investigated extensively, and is a leading candidate for the positive electrode active material in lithium-ion batteries for transportation applications. However, this particular composition also has substantial amount of “undesirable” cobalt. In order to reduce the cobalt content in NMC, it would be interesting to study the effect of iron substitution for cobalt in NMC as iron could potentially contribute actively to the electrochemistry. In the present work, LiMn1/3Ni1/3FexCo1/3-xO2 bulk cathodes (x = 0.0 – 1/3) were synthesized using a cost effective chemical solution technique. The structural properties and oxidation state of Mn, Fe, Co and Ni were investigated using X-ray diffraction (XRD), Raman Spectroscopy and X-ray photoelectron spectroscopy (XPS). The morphology was studied using scanning electron microscopy (SEM). The electrochemical measurements (cyclic voltametry, charge-discharge tests) of the synthesized cathodes were performed in a two-electrode coin-cell configuration (CR2032), using liquid electrolyte [1M LiPF6 in (1EC:1DMC v/v)] and Li-metal as anode. The major peaks in the XRD patterns of the synthesized LiMn1/3Ni1/3FexCo1/3-xO2 cathode materials could be indexed to R-3m symmetry. Minor peaks from an additional phase also appear in the data, especially for the higher iron content oxides. These features are visible as shoulders to the main R-3m peaks on the higher angle side. The crystal structure of this impurity phase has not been conclusively determined at this time; the various possibilities include rocksalt or ordered rocksalt-type structures.The first charge and discharge capacity for x=0 were 178 and 154 mAh/g , respectively correspond to a coulombic efficiency of 86%. Both charge and discharge capacity decreased with increasing x, for x=1/6 the charge and discharge capacity were 170 and 108 mAh/g, respectively. The effect of Fe substitution on the phase formation and electrochemical behavior of LiMn1/3Ni1/3FexCo1/3-xO2 along with the effect of annealing conditions upon electrochemical properties will be presented and discussed in conjunction with structure of the as prepared and electrochemically cycled electrode materials using ex-situ Raman spectroscopy and XRD.
9:00 PM - U13.43
Synthesis of Electrochemically Active LiMnPO4 via a Novel Precipitation Method.
Jie Xiao 1 , Wu Xu 1 , Daiwon Choi 1 , Ji-Guang Zhang 1
1 , Pacific Northwest National Laboratory, Richland, Washington, United States
Show AbstractLiMnPO4 was synthesized from MnPO4●H2O precursor precipitated via a spontaneous reaction. These MnPO4●H2O nano-plates reacted easily with lithium source forming LiMnPO4 pure phase with excellent electrochemical properties providing a low cost manufacturing process. The morphology of the MnPO4●H2O precursor varied in different solvents used in washing process and affectted the electrochemical behavior of the LiMnPO4 accordingly. Different lithium salts were used in the precursors and TGA was applied to understand their reaction mechanisms. Their corresponding LiMnPO4 products were then compared in terms of structure, morphology, electrochemical performances and magnetic properties. The weight percent of carbon in the LiMnPO4/C composite was adjusted between 10 % and 20 % to optimize the electrode compostion while still maintaining high performances. This work is supported by US Department of Energy, Office of Vehicle Technologies through the BATT program and Laboratory Directed Research and Development Program at the Pacific Northwest National Laboratory (PNNL).
9:00 PM - U13.45
New Electrode Architecture For Enhancing Energy Density In Rechargeable Batteries.
Can Erdonmez 1 , Wei Lai 1 , Chang-Jun Bae 1 , Yet-Ming Chiang 1
1 , MIT, Cambridge, Massachusetts, United States
Show AbstractCurrent lithium-ion batteries are based on thin, large area (“2D”), laminated, composite electrodes with highly optimized compositions, microstructures and geometries that minimize and trade off various kinetic limitations to cell operation. While yielding impressive rate capabilities, this approach also severely limits volumetric and gravimetric utilization of active materials, due both to the significant volume of inactive additives present in the electrodes, and to cell components whose amounts scale with electrode area (e.g. collectors, separators) or volume (e.g. external packaging).Here, we pursue an alternative electrode architecture, demonstrating thick, three-dimensionally porous, high-density intercalation cathodes that are largely free of the electrochemically-inert additives which are conventionally employed. We show that such structures can have sufficient electronic conductivity and are surprisingly tolerant of the substantial, cyclic stresses that accompany electrochemical cycling of intercalation compounds. For LiCoO2-based cathodes of this configuration, discharge capacity vs. C-rate has been systematically characterized as a function of porosity and thickness for several distinct microstructures. At low discharge rates (~C/50), full capacity utilization is obtained in cathodes with thicknesses up to 800 microns and densities up to 87% by volume, providing ~8 times the capacity per area of conventional cathodes. At C/3 to C/2 continuous discharge rates, 80% of the theoretical capacity can be obtained in cathodes of 74% density and 400 micron thickness. These and other experimental methods used in conjunction with existing theoretical models allow us to identify the most relevant rate-limiting processes. Microstructure modifications to measurably enhance rate capability are demonstrated. Small prototype cells show that specific energy and energy density can be more than doubled compared to conventional technology.
9:00 PM - U13.46
Metal Oxide Nanofiber Structures for Energy Storage.
Lukas Rubacek 1 , Jiri Duchoslav 1 , Jan Macak 1
1 Research and development, Elmarco, Ltd., Liberec Czechia
Show AbstractThe presentation deals with the use of nanofiber materials in lithium-ion batteries. These nanofiber materials are produced by electrospinnig that has recently attracted a lot of attention as a progressive method for production of a range of materials. In the present case, the NanospiderTM technology has been used for the hunderds of nanometers. The as-produced material has a specific surface area of about 35m2/g. We have investigated charging-discharging properties by means of cyclic voltammetry. The achieved results have demonstrated very promising features that suggest the suitability of electrospun nanofibers for advandced high-rate batteries.
9:00 PM - U13.47
Three Dimensional Microsupercapacitors: As-Pyrolyzed and Porous Carbon Structures.
Majid Beidaghi 1 , Wei Chen 1 , Chunlei Wang 1
1 Mechanical and Materials Engineering, Florida International University, Miami , Florida, United States
Show AbstractDue to their efficacy as high power density energy storage devices, electric double layer capacitors (EDLCs) have been the subject of much research and consideration in recent years. In this study, the Carbon-Microelectromechanical system (C-MEMS) technique is used to fabricate microsupercapacitors with high aspect ratio three dimensional (3D) carbon electrodes at a small footprint. C-MEMS technique is a simple process for fabricating carbon electrodes, in which patterned photoresist can be pyrolyzed and converted to carbon under high temperature in inert atmosphere. In our microsupercapacitor design, we employed an improved electrode design by placing carbon posts as electrodes on interdigited carbon strips as current collectors on a single SiO2 coated Si substrate. Two different carbon structures, one with solid pyrolyzed carbon and the other with porous carbon, were fabricated and their performance were compared. Also, the effect of pyrolysis temperature profile and amount of porosity on the capacity of the micorsupercapacitors were investigated. Electrochemical performance of the microsupercapacitor was tested by AC impedance and cyclic voltammetry (CV) methods. Detailed result will be presented at the conference.
9:00 PM - U13.48
Structure and Electrochemical Performance of Reduced Spinel Li4Ti5O12.
Natalya Chernova 1 , Jian Hong 1 , Stanley Whittingham 1
1 MSE, SUNY at Binghamton, Vestal, New York, United States
Show AbstractLi4Ti5O12 is a well-known zero-stress anode material for lithium batteries, which combines virtually unlimited cycle life with safe operation; the latter is due to high working potential (1.55 V vs. Li/Li+). Nano-Li4Ti5O12 anode combined with LiFePO4 cathode provides high power capability making this system a viable candidate to replace electrochemical super-capacitors and for use in electrical vehicles. However, low tap density of nano-powders and low electronic conductivity of Li4Ti5O12 requiring addition of conductive carbons limit the volumetric energy density of the material. Here we explore the possibility to enhance the electronic conductivity of Li4Ti5O12 by partial reduction. Li4Ti5O12-δ spinels were synthesized by high-energy ball milling followed by heat treatment in reductive He/H2. In some samples carbon black (3~5 wt %) was added at the ball-milling stage to control the particle size; the annealing temperature and time were varied. In the resulting dark-blue products, some Ti4+ is reduced to Ti3+, introducing oxygen vacancies as suggested by the Rietveld refinement of the x-ray diffraction data and a weight gain upon TGA in oxygen. The magnetic tests indicate the presence of 1-2% paramagnetic Ti3+. An increase of the magnetic susceptibility at high temperatures suggests that strongly antiferromagnetically coupled Ti3+ clusters might also be present. The electronic conductivity of the reduced spinels is improved by many orders of magnitude as compared to Li4Ti5O12, but is still low, 10-8-10-7 S/cm, which is consistent with small amount of isolated Ti3+ ions. The powders synthesized in the presence of carbon show excellent electrochemical performance and power capability exceeding those of nano-Li4Ti5O12. The particle size of these powders is several hundred nanometers and the tap density is 2.1 g/cm3. The exact amount of Ti3+ and the nature of charge-compensating defects are currently under investigation. 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.
9:00 PM - U13.49
Doping Effects on LiFePO4 Cathode Materials for Lithium-Ion Batteries.
Hui Fang 1 , Travis Neeley 1 , Thomas Murphy 1 , Erica Cerda 1 , Gan Liang 1 , Mark Croft 2
1 Department of Physics, Sam Houston State University, Huntsville, Texas, United States, 2 Department of Physics, Rutgers University, Piscataway, New Jersey, United States
Show AbstractLiFePO4 cathode materials doped with various elements, Al, Cr, Ti, Nb, Zr, and W, at both Li and Fe sites for lithium-ion batteries are synthesized by two different methods, solid-state reaction and template method. X-ray diffraction, X-ray absorption, cyclic voltammetry, and constant current charge/discharge measurements are employed to characterize the structural, electronic, and electrochemical properties of the samples. The effects brought by doping on both Li and Fe sites will be discussed and presented.
9:00 PM - U13.5
Conversion Reactions Electrodes of Transition-Metal Oxides Using Nanoporous Conductive Scaffolds.
John Vajo 1 , Adam Gross 1 , Elena Sherman 1 , Ping Liu 1
1 , HRL Laboratories, Malibu, California, United States
Show AbstractLithium ion storage based on intercalation reactions in transition-metal oxides is generally limited to one, or at most two, electron reductions. However, compete multi-electron reductions to Li2O + transition metals, designated as conversion reactions, are possible provided that the reactants and products have the proper nanoscale structure[1]. These reactions can have capacities exceeding ~1000 mAh/g and, therefore, are of interest for advanced lithium batteries. We have studied conversion reactions of Mn, Fe, and Co oxides incorporated into the pore volume of electrically conductive nanoporous carbon aerogels. The aerogels confine the oxide domains to the nanoscale and further provide good electrical contact, electrical conductivity, and electrolyte access. Carbon aerogels were synthesized using resorcinol–formaldehyde condensation followed by pyrolysis. Typically, we used aerogels with a total pore volume of ~1.3 cm3/g and a peak in the pore size distribution at 25 nm, although, pores sizes from 5 nm to 30 nm are possible by adjusting the synthesis conditions. After synthesis, oxides were incorporated using metal nitrate hydrates as precursors. The hydrates were melted at 50 – 100 °C and infiltrated into the aerogels filling the pore volume. Heating was then used to first decompose the hydrates and, subsequently, the nitrate anions within the pores of the aerogel to yield the corresponding nanoscale metal oxides: MnO2, Fe2O3, and Co3O4. Oxide mass loadings from 25% to ~50% were achieved. Electrochemical cycling behavior was studied using Swagelok cells against Li metal counter electrodes. When corrected for the capacity contribution from the carbon aerogel (~200 mAh/g), lithium capacities of the oxides approached 1000 mAh/g. These capacities indicate complete reduction to Li2O + Mn, Fe, and Co. In this presentation, we will describe the preparation, characterization, and cycling behavior of these nanoconfined oxide electrodes.[1] P. G. Bruce, B. Scrosati, J.-M. Tarason, Nanomaterials for Rechargeable Lithium Batteries, Angew. Chem. Int. Ed. 2008, 47, 2930 – 2946 and references therein.
9:00 PM - U13.50
Carbon Nanotubes grown on Cu Substrates using a Ni Catalyst for Battery Anode Applications.
Gowtam Atthipalli 1 , Prashant Kumta 1 2 3 , Wei Wang 4 , Alexander Star 5 , Brett Allen 5 , Yifan Tang 5 , Jennifer Gray 1
1 Materials Science and Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 3 Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 4 Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States, 5 Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractCarbon nanotubes with their unique 1-D character and their large aspect ratio are ideal candidates for anodes on suitable conducting substrates for battery applications. We studied the growth of carbon nanotubes on copper substrates using a nickel thin film as a catalyst. The catalyst was sputtered in a chamber having a base pressure in the ultra-high-vacuum regime. By adjusting the sputtering parameters including sputtering time, power, and pressure, the effects of the morphology and the structure of nickel catalyst on the growth of carbon nanotubes have also been investigated. Multiple hydrocarbon sources were used as carbon feedstock and the corresponding catalyst precursors, during the chemical vapor deposition (CVD) of the carbon nanotubes to determine the ideal conditions for carbon nanotube growth on copper. Correlations between the thickness of the thin film nickel catalyst and the carbon nanotube diameter and alignment are also presented in the study. A hypothesis for critical catalyst thickness range below which no carbon nanotube growth is observed is also postulated. The structure and morphology of the carbon nanotubes and the thin film nickel catalyst were studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Results will also be presented on experiments designed to yield aligned carbon nanotubes on copper substrates.
9:00 PM - U13.52
Silicon Based High Capacity Anode for Li-Ion Battery Applications.
Jiguang Zhang 1 , Jie Xiao 1 , Donghai Wang 1 , Jun Liu 1 , Daiwon Choi 1 , Chongmin Wang 1 , Zhenguo Yang 1 , Wu Xu 1 , Graff Gordon 1
1 , Pacific Northwest National Laboratory, Richland, Washington, United States
Show AbstractSi-based lithium alloys are well known for their potential to attain high specific energies. Silicon has a theoretical specific capacity of nearly 4,200 mAh/g (Li
21Si
5), which is 10 times larger than that of graphite (LiC
6, 372 mAh/g). However, the high capacity of silicon is associated with huge volume changes (up to 300 percent) when alloyed with lithium, which can cause severe cracking and pulverization of the electrode and lead to significant capacity loss. We have investigated the electrochemical properties of Si-based anode by several approaches. First, electrochemical properties of carbon coated nano-porous Si powder were investigated. The Si powder with nanosized pores is the ideal starting materials for high capacity anode because the nano pores in these particles can tolerate large volume expansion during the change and discharge process. The main barrier for battery application of these porous silicon samples is their poor electrical conductivity. To solve this problem, the micron size nano-porous Si particles were coated with ~6% weight of carbon by CVD process. The morphology change of the original Si and carbon coated Si before and after electrochemical cycling has been investigated. In a separate effort, self-assembling approach has been used to prepare Si-graphene superstructures. Unlike mechanical mixing, self-assembling process produces a new class of nanocomposites in which the conductive and mechanically robust graphene sheets are uniformly distributed in the ordered domains of silicon powders, representing a new concept in the design and synthesis of nanocomposite materials. Such materials can be further assembled into free standing papers for direct macroscopic use of self-assembled nanomaterials in energy storage devices. The graphene sheets can also be dispersed into three dimensional, ordered nanoporous networks, forming conductive, high surface area nanoporous materials. The third approach to prepare high capacity Si based anode is the gas induced 3D-growth (or Solid-Liquid-Solid growth) of silicon nanowires. Si-based anodes prepared by these three approaches have demonstrated an initial capacity of exceeding 1,000 mAh/g, but their long term stability strongly depends on the preparation conditions, binder, and cycling conditions. Electrochemical performances of Si-based anode prepared by these approaches will be compared in this report. This work is supported by DOE Office of Vehicle Technologies (OVT) through Batteries for Advanced Transportation Technologies (BATT) Program and PNNL Laboratory Directed Research and Development (LDRD) Project.* Corresponding author. Tel.: 509-372-6515; fax: 509-375-3864. E-mail address:
[email protected]9:00 PM - U13.53
Synthesis and Characterization of LiFePO4 Nanoparticles as Cathode Material for Lithium Ion Batteries.
Hui Zhou 1 , Natasha Chernova 1 , Shailesh Upreti 1 , Stanley Whittingham 1
1 Materials Science Program, State University of New York at Binghamton, Binghamton, New York, United States
Show AbstractLithium transition metal phosphate olivines such as LiFePO4 have been recognized as promising electrodes for lithium-ion batteries due to their outstanding electrochemical and thermal stability. Several synthesis techniques have been explored so far with the goal of improved electrochemical behavior and lower cost. Our laboratory pioneered the hydrothermal method which leads to a uniform particle size and good electrochemical performance. However, alternative solvents might lead to smaller particle sizes and lower costs, by using a continuous process. In the present work, LiFePO4 nanoparticles were synthesized through the polyol process under N2 atmosphere, where pressurized vessels are not needed. The polyol medium itself acts not only as a solvent in the process, but also as reducing agent and as a strong stabilizer, limiting particle growth. A N2 protective atmosphere is helpful in getting a pure LiFePO4 phase. With increasing reaction time, the purity and electrochemical property becomes better. X-ray and TGA analysis revealed the presence of a few amorphous organic impurities in the sample; a post-heat treatment eliminated these impurities. This treatment improved the electrochemical capacity and rate capability. A reversible specific capacity of 130 mAh/g was achieved at 0.4 mA/cm2, significantly less than hydrothermal samples. Efforts to optimize the synthesis and post-treatment conditions are under progress. Particle morphology, composition, magnetic properties and detailed electrochemical performance will 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.
9:00 PM - U13.54
Facile Approach to Prepare Porous Ni Foam Supported–porous NiO Anode for Lithium Ion Batteries.
Xifei Li 1 , Abirami Dhanabalan 1 , Kevin Bechtold 1 , Chiwon Kang 1 , Chunlei Wang 1
1 , Florida International University, Miami, Florida, United States
Show AbstractThe graphite with the theoretical capacity of 372 mAhg-1 is commercialized as the first generation anode for lithium ion batteries. However, its limited capacity cannot match with the recent request of lithium ion batteries with the high energy density and the high power density. So the second generation anode materials are coming with the high theoretical capacity. In 2000, Tarascon et.al were the first to propose the transition–metal oxides (MxOy, M=Ni, Co, Cu etc.) as anode materials for lithium ion batteries. NiO shows the high capacity up to 718 mAhg-1. Furthermore, its density, 6.81 g/cm3, is much higher than that of graphite, 2.268 g/cm3. The volumetric energy density of NiO anode is about 5.8 times as large as graphite. However, during charge/discharge process, the formed nanosized Ni and NiO particles are easy to aggregate. NiO also has the inherent bad electric conductivity. Both of these cause the poor cycle performance of NiO anode.In this research, we report a simple yet efficient method to create NiO films on the porous nickel foam substrate. By controlling the preparation process nickel foam was partly oxidized to prepare the special structure of porous nickel foam substrate supported porous NiO films. This material design has been demonstrated with good adhesion and good electric contact between the NiO film and the Ni substrate. The special porous structure can effectively reduce the aggregation of nanoscale particles during cycle. As–prepared porous Ni foam supported–porous NiO film can be used as anode materials for lithium ion batteries, and no conductive agent and binder are needed, therefore, the anode resistances are efficiently reduced and the energy density of lithium ion batteries can be tremendously increased.In an argon-filled glove box the thin films were assembled as the electrochemical cells using lithium sheet as the counter electrode. Cyclic voltammetry and electrochemical impedance spectroscopy were performed on Versatile Multichannel Potentiostat (VMP3) at a scan rate of 0.2 mV s-1 over a potential range of 0.02 and 3.0 V (vs. Li/Li+). All cells were galvanostatically cycled between 0.02 and 3.0 V (vs. Li/Li+) at room temperature by NEWARE BTS-610 battery tester. The experimental results will be discussed in detail.
9:00 PM - U13.55
Macroporous Composite Anodes for Lithium Ion Batteries.
Wu Xu 1 , Nathan Canfield 1 , Jie Xiao 1 , Deyu Wang 1 , Zimin Nie 1 , Ji-Guang Zhang 1
1 Energy and Efficiency Division, Pacific Northwest National Laboratory, Richland, Washington, United States
Show AbstractLithium ion batteries to power plug-in hybrid electrical vehicles (PHEV) need to have higher energy density, longer cycle life and calendar life, higher safety and lower cost than the state-of-the-art lithium ion batteries. The currently commercially available lithium ion batteries mainly use carbonaceous materials especially graphite as anode material which has a theoretic specific capacity of 372 mAh/g and good cell performance. Alternative anode materials that are being investigated include silicon, tin, aluminum, alloys, metal oxides, and others. Although silicon, tin, aluminum, and tin oxide as anode materials have much higher theoretical specific capacities (4,200 mAh/g, 993 mAh/g, 993 mAh/g, and 782 mAh/g, respectively) than graphite, they have not been practically used because of the poor cycle life and fast capacity fade resulted from the electrode cracking and pulverization due to the high volume change associated with lithium alloying and de-alloying during charge and discharge. Extensive efforts have been made on these alternative anode materials by reducing electrode cracking and pulverization during charge and discharge. It has been reported that porous 3D substrates are helpful to accommodate the volume changes of these high capacity anode materials during the charge/discharge cycles. Conventional approach to prepare anode active materials inside the porous substrate is to use electrochemical deposition, which is difficult to make thick and uniform deposition coatings and generates a lot of wastes harmful to environment and more efforts and costs are needed on waste treatment. Here we report a new approach to prepare macroporous composite anodes, which is versatile and suitable to produce large quantity of porous composite anode sheets for battery applications. The macroporous composite anodes developed in this method have shown improved discharge capacity and cycle life than those from conventional tape-casting method.AcknowledgementThis work is sponsored by PNNL Laboratory Directed Research and Development (LDRD) Project and DOE Office of Vehicle Technologies (OVT) through Batteries for Advanced Transportation Technologies (BATT) Program.
9:00 PM - U13.56
Development of Novel Li2MPO4F (M = Mn, Co) Cathode for Li Ion Battery Applications.
Deyu Wang 1 , Jie Xiao 1 , Wu Xu 1 , Ji-Guang Zhang 1
1 Energy and Efficiency Division, Pacific Northwest National Laboratory, Richland, Washington, United States
Show AbstractLiFePO4 has been widely used in batteries for portable tools and will also be used in plug in electrical vehicles because of its high stability, low cost, and high power rate. However, its practical specific energy is limited by both low voltage (~3.4V) and moderate capacity (~150 mAh/g). To further improve the capacity of olivine phosphate based cathode materials, Li2MPO4F (M = Mn, Co) is investigated in this work. In addition to the stability and safety of phosphate based cathodes, Li2MPO4F (M = Mn, Co) exhibit higher voltage than LiFePO4 and has a theoretical capacity of ~290 mAh/g, which is 70% higher than current olivine phosphate based cathode materials. Although Li2FePO4F has been reported before, its theoretical capacity is only 145 mAh/g due to the absence of Fe (IV) and only one lithium can be extracted from Li2FePO4F. Various synthesis approaches for Li2CoPO4F and Li2MnPO4F have been investigated. Their structure, morphology, and electrochemical properties will be reported in this work. AcknowledgementThis work is sponsored by DOE Office of Vehicle Technologies (OVT) through Batteries for Advanced Transportation Technologies (BATT) Program and PNNL Laboratory Directed Research and Development (LDRD) Project.
9:00 PM - U13.57
Investigation of Battery Materials Using Scanning Probe Microscopy.
Nina Balke 1 , Yoongu Kim 1 , Nancy Dudney 1 , Sergei Kalinin 1
1 CNMS, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractThe 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. In one approach, a Scanning Probe Microscopy tip is used to detect local surface strains developing in the operational battery with a thin (10-100 nm) top electrode. The use of the top-electrode system allows measurements to be taken reversibly, while spatial localization of the process on the top interface suggests this method has the potential for high spatial resolution. In parallel, the tip-electrode studies has been used to study local tip-induced processes and we demonstrate the mapping of local Li mobility within the material.
9:00 PM - U13.58
Directing the Growth of Nanoscale Hybrid Architectures for Electrical Energy Storage.
Erik Spoerke 1 , Erica Martin 1 , Mark Roberts 1 , Michael Brumbach 1 , David Wheeler 1 , Bruce Bunker 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractThe growing demand for electrical energy storage currently surpasses existing technologies, driving the need to develop new materials and technologies. One area of expanding exploration in the electrochemical community is focused on the development and integration of nanoscale electroactive oxide materials and functional organics for incorporation into technologies such as lithium ion batteries or ultracapacitors. We describe here a materials synthesis strategy that utilizes both organic and inorganic templates to synthesize and assemble mesoporous electroactive nanocomposites with promising electrochemical behaviors. By integrating both organic templates, such as functional amphiphilic molecules or electroactive polymers, and inorganic templates, such as zinc oxide, we can produce nanostructure electroactive oxides, such as ruthenium oxide or molybdenum oxide, with texture and porosity on multiple length scales. This process furthermore directs the in situ growth of these nanostructured materials on electrodes, dramatically simplifying electrode preparation and improving electrical and ionic transport across the active material. Electrochemical characterization reveals these templated, functional metal oxides to be promising candidates for incorporation into next generation electrical energy storage applications. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000.
9:00 PM - U13.59
Metal Oxide-Graphene Hybrid Materials for Li-Ion Battery.
Donghai Wang 1 , Daiwon Choi 1 , Juan Li 1 , Zhenguo Yang 1 , Zimin Nie 1 , Rong Kou 1 , Chongmin Wang 1 , Laxmikant Saraf 1 , Jiguang Zhang 1 , Ilhan Aksay 2 , Jun Liu 1
1 , Pacific Northwest National Laboratory, Richland, Washington, United States, 2 , Princeton University , Princeton, New Jersey, United States
Show AbstractElectrochemical energy storage has been receiving great attention for potential applications in electric vehicles and renewable energy systems from intermittent wind and solar sources. Currently, Li-ion batteries are being considered as one of the leading energy storage techniques for the applications. However, many potential electrode materials (e.g., oxide materials) in Li-ion battery are limited by slow Li-ion diffusion, poor electron transport in electrodes, and poor cycling stability due to phase transformation and volume change during charge/discharge process. A promising approach to improve electrode performance is to develop multifunctional nanocomposites that combine high redox activity, good mechanical properties, and good electron and ion conductivity of different functional materials with controlled architectures. In this presentation, we discuss synthesis and characterization of metal oxide-graphene hybrid materials and their application in Li-ion battery. The hybrid materials were directly synthesized by assembling in-situ grown metal oxide nanocrystals with graphene sheets and characterized using XPS, Raman, XRD, TEM, and SEM techniques. Li-ion insertion properties of the graphene-TiO2 (rutile or antase) hybrids were investigated showing superior Li-ion insertion capacity with good retention at high charge/discharge rate. In particular, the hybrid material is able to reversibly accommodate Li up to 85 mAh/g at 1–3 V versus Li+/Li at charge/discharge rate of 30C, which is much higher than 43 mAh/g capacity of nanocrystalline TiO2. Other nanocrystalline metal oxide-graphene hybrid materials have also been studied in terms of capacities and stability as anode materials. The self-assembled metal oxide-graphene hybrid materials are expected to be used for studying synergetic properties and improving performance of materials and devices in electrochemical energy storage and conversion.Ref: Wang, D. et al. Self-Assembled TiO2-Graphene Hybrid Nanostructures for Enhanced Li-Ion Insertion. ACS Nano 3, 907-914, (2009).
9:00 PM - U13.7
High Rate, Nanocomposite Zinc – doped LiFePO4 Cathode for Lithium Ion Batteries.
Arun Kumar 1 , Reji Thomas 1 , Maharaj Tomara 1 , Ram Katiyar 1
1 Physics, University of Puerto Rico,, San Juan, Puerto Rico, United States
Show AbstractThe cost effectiveness, environmental benevolently, and thermal stability have made Lithium iron phosphate (LiFePO4) as one of the most attractive cathode materials for rechargeable Li-ion batteries. LiFePO4 exhibiting theoretical capacity of ~170 mAh/g and a flat charge/discharge profile at ~ 3.4 V Li1+/Li. However, slow diffusivity of Li+ in LiFePO4 (DLi ~ 10-14 – 10-16 cm2/s) compared to the widely used layered LiCoO2 ((DLi ~ 10-12 – 10-13 cm2/s) allowed only 60% of the capacity to be tapped in the early work. To overcome the poor ionic as well as electronic conductivities of LiFePO4, carbon coating has been described to improve the Li-ion kinetics. The control on the particle size in the nano-regime along with a narrow particle size distribution of the synthesized LiFePO4 cathode materials is found beneficial to increase capacity. Even though, researchers solved the problem of obtaining higher capacity near to the theoretical capacity, but its remarkable capacity loss at larger current density is still a problem. To improve the rate-capability we have studied the effect of the Zinc oxide doping of LiFePO4 on the electrochemical properties. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical properties were investigated systematically. The XRD pattern demonstrated that an olivine phase of ZnO-doped LiFePO4 and the structure was indexed to the orthorhombic Pnma space group. The SEM image revealed that the particles were agglomerated and the particle sizes were almost homogeneously distributed. Olivine compound LiFe1-xZnxPO4/C (x=0.03 and 0.06), results indicate that Zn2+ does not affect the olivine structure of the cathode but considerably improve its initial capacity and rate capability. The cyclic voltammetry (CV) and galvanostatic charge and discharge test showed the 3% ZnO- doped LiFePO4 with x=0.03 has higher electrochemical reactivity for lithium insertion and extraction than 6% ZnO- doped LiFePO4. LiFe0.97Zn0.03PO4/C showed initial specific discharge capacity of 159.32 and 109.67 mAh/g with C/10 and 12C rate, respectively. This enhancement might be due to increase in the electronic conductivity by Zn2+ substitution and carbon coating.
9:00 PM - U13.8
Electron Energy-loss Spectroscopy (EELS) Mapping of Lithium Compounds in the Solid-electrolyte Interphase (SEI) on Graphite Anode Materials for Li-ion Battery.
Feng Wang 1 , Lijun Wu 1 , Vyacheslav Volkov 1 , Yimei Zhu 1 , Xiaoqing Yang 1 , Toshihiro Aoki 2 , Jason Graetz 1
1 , Brookhaven National Lab, Upton, New York, United States, 2 , JEOL USA, Peabody, Massachusetts, United States
Show AbstractThe formation of a thin and stable solid-electrolyte interphase (SEI) film on the electrodes of lithium-ion batteries is a critical factor determining the battery performance. A comprehensive understanding of how the SEI forms and the composition of the SEI layer is one of the great challenges in lithium battery research, after the three decades of effort [1]. Besides Peled’s “mosaic” model, several other different models have been proposed based on various spectroscopic analyses. It is desirable to resolve and visualize the distribution of various lithium compounds in the nanometer-thick SEI film. Unfortunately, not much work on this has been reported so far. Taking the advantage of high spatial resolution of EELS in the TEM [2], we are making progress in mapping main components in the SEI layer for several graphite anode materials for lithium-ion cells.In this study the elemental concentration distribution was extracted from the energy-filtered images. The different lithium compounds were further differentiated by the Li-K near-edge fine structure, electron diffraction and high-resolution TEM imaging. High-vacuum transfer and cryo-holders were used to minimize the air exposure and to reduce the radiation damage. Filtered images and EELS spectra were recorded on JEOL 3000F attached with a GIF spectrometer. Other data were collected on a double aberration-corrected JEOL 2200 MCO equipped with an in-column W filter. Our results for synthetic graphite (from Alfa-Aesar and TIMCAl) and highly oriented pyrolytic graphite (HOPG) cycled in a standard EC/DMC/LiPF6 electrolyte will be presented. In addition, the issue of radiation damage, the main factor limiting the spatial resolution will also be discussed [3].The work was supported by the U.S. Department of Energy, Office of Basic Energy Science, and the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, under the program of Vehicle Technology Program, under Contract Number DEAC02-98CH10886.Reference:[1] P. B. Balbuena, Y. Wang (Ed.), Lithium batteries: solid electrolyte interphase. Imperial College Press (2004).[2] R.F. Egerton, Electron energy-loss spectroscopy in the TEM, Rep. Prog. Phys. 72 (2009) 016502.[3] R.F. Egerton, F. Wang, and P.A. Crozier, Micros. and Microan. 12 (2006) 65.
9:00 PM - U13.9
High Conductivity in Carbon Nanotube Array/Ionomer Composite with Aligned Ion Transport Paths.
Yang Liu 1 , Sheng Liu 1 , Junhong Lin 1 , Hulya Cebeci 2 , Roberto de Villoria 2 , Brian Wardle 2 , Qiming Zhang 1 3
1 Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractIn supercapciators and Li-Ion batteries, the design of the composite electrode morphology is important since the ion transport speed in it determines the charging/discharging period. As electrodes in our suprcapacitor, the Ionomeric polymer/conductive network composite dominate the charge/discharge speed and the charging capacitance. In this study, CNT forest is applied as conductive network due to its extraordinary electronic and mechanical properties and high stability. Free standing CNT forest enables the possibility of further densifying the forest into high volume fraction, up to about 20%, to enhance its properties. The CVD grown 1% volume fraction multiwall carbon nanotubes generally have 3-5 walls, about 10nm diameter. Higher volume fractions of carbon nanotubes are achieved by mechanical densification. Composite is made by wetting the carbon nanotube array with Nafion solution and evaporating excess solvent with a modified solution-cast procedure to avoid the forming of islands and voids. The electronic conductivity of 1%, 10% and 20% carbon nanotube array/Nafion composite is measured as 0.4 S*cm-1, 2.8 S*cm-1 and 3.5 S*cm-1, respectively. Moreover, compared to the ionic conductivities of neat Nafion membrane 6x10-4 S*cm-1 and conductive nanoparticle/Nafion composite 1.1x10-5 S*cm-1, the ionic conductivity of carbon nanotube array/Nafion composite ~10-4 S*cm-1 holds enormous promise for faster ionic and electronic transports than conductive nanoparticle/Nafion composite. A further impedance analysis of the device structure and the prototype device fabrication are also investigated in the work. With this improvement in charging/discharging speed, there is a huge potential of enhancing the supercapacitor performance in HEV, LEV and etc.