Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session J38: Focus Session: Materials for Electrochemical Energy Storage II |
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Sponsoring Units: GERA Chair: Shengbai Zhang, Rensselaer Polytechnic Institute Room: 347 |
Tuesday, March 19, 2013 2:30PM - 2:42PM |
J38.00001: Structural phase transition and Li-ion diffusion in Li$_7$La$_3$Zr$_2$O$_{12}$ Khang Hoang, Noam Bernstein, Michelle Johannes Garnet-type Li$_7$La$_3$Zr$_2$O$_{12}$ (LLZO) is a promising candidate for solid electrolytes in Li-ion battery applications because of its high ionic conductivity and electrochemical and chemical stability. The material has a low-conductivity tetragonal phase and a high-conductivity cubic phase. It has been reported that the cubic phase can be stabilized at ambient conditions, usually with the incorporation of a certain amount of supervalent impurities. In this talk, we present results from density-functional theory and variable cell shape molecular dynamics simulations, and discuss the origin of structural phase transition, effects of extrinsic impurities, and diffusion of Li ions in LLZO. By identifying relevant mechanisms and critical concentrations of the impurities (Li vacancies) for achieving the high-conductivity phase, this work shows how controlled synthesis could be used to improve the material's electrolytic performance. [Preview Abstract] |
Tuesday, March 19, 2013 2:42PM - 2:54PM |
J38.00002: ABSTRACT WITHDRAWN |
Tuesday, March 19, 2013 2:54PM - 3:06PM |
J38.00003: Redox potential of liquid water: A first-principles theory Michael Lucking, Yiyang Sun, Damien West, Shengbai Zhang A first-principles molecular dynamic method is proposed to calculate the absolute redox potentials of liquid water. The key of the method is the evaluation of the difference between the vacuum level and the average electrostatic potential inside liquid water, which employs an average over both time and space. By avoiding the explicit use of the Kohn-Sham level, such as the position of the valence band maximum, as the reference energy for the excited electrons, we are able to calculate water redox potentials accurately. The results using the PBE functional are in good agreement with experiment. We attribute the success of the method to the accurate charge density given by density functional calculation under the local or semi-local approximations. This establishes the validity to apply these effective and efficient approximations to study both the energetics and dynamics of the redox processes at more complex systems such as solid/solution interfaces. [Preview Abstract] |
Tuesday, March 19, 2013 3:06PM - 3:18PM |
J38.00004: Models of novel battery architectures Paul Haney, Dmitry Ruzmetov, Alec Talin We use a 1-dimensional model of electronic and ionic transport, coupled with experimental data, to extract the interfacial electrochemical parameters for LiCoO2-LIPON-Si thin film batteries.~ TEM imaging of batteries has shown that charge/discharge cycles can lead to breakdown of the interfaces, which reduces the effective area through which further Li ion transfer can occur.~ This is modeled phenomenologically by changing the effective cross sectional area, in order to correlate this structural change with the change in charge/discharge I-V curves.~ Finally, by adopting the model to radial coordinates, the geometrical effect of nanowire architectures for batteries is investigated. [Preview Abstract] |
Tuesday, March 19, 2013 3:18PM - 3:30PM |
J38.00005: Paraquinone-Hydroquinone Couple for Flow Battery Saraf Nawar, Brian Huskinson, Michael Aziz At present, there is an ongoing search for the storage of energy from intermittent renewable sources like wind and solar. Flow batteries have gained attention due to their potential viability in inexpensive storage of large amounts of energy. Because of its high reversibility, low toxicity, and low component costs, the paraquinone/hydroquinone redox couple could be a viable candidate for use in a grid-scale storage device. In this report, we will present half-cell data for the 1,4-parabenzoquinone/1,4-hydroquinone redox couple and related couples in sulfuric acid. We will present results from a flow battery with maximum current density of up to 200 mA/cm2 using a mixture of 1,4-parabenzoquinone and 1,4-hydroquinone as the cathode material and hydrogen as the anode material. We report the effects of reactant concentration, reactant flow rate to the electrode, and temperature on the performance of the fuel cell. [Preview Abstract] |
Tuesday, March 19, 2013 3:30PM - 3:42PM |
J38.00006: Exploring the electronic structure and dynamics of lithium compounds through first-principles interpretation of X-ray absorption spectra David Prendergast, Tod Pascal, Xin Li, Jinghua Guo, Yi Luo In situ X-ray spectroscopy will reveal fundamental details of elecltrochemistry in working cells, provided that the data is interpretable. To this end, we are developing first-principles methods to simulate core-level absorption spectra of molecules, condensed phases, and interfaces with explicit inclusion of dynamics. We validate this approach by application to various lithium compounds that may be present in the solid electrolyte interphase (SEI) and to lithiation of graphite in the anode. Our calculations reveal that instantaneous broken symmetry about the x-ray excited atom may be evident in the resulting spectroscopy and highlights both dynamical and static disorder in these materials. Furthermore, we observe complex anisotropic interactions upon charge transfer between lithium and graphite that contradict a simplistic view of intercalation in terms of complete electron transfer and the rigid band approximation. [Preview Abstract] |
Tuesday, March 19, 2013 3:42PM - 3:54PM |
J38.00007: Characterization of silicate based cathodes for Li Ion Batteries Ajay Kumar, Gholam-Abbas Nazri, Maryam Nazri, Vaman Nail, Prem Vaishnava, Ratna Naik The silicate compounds Li$_{\mathrm{2}}$MSiO$_{\mathrm{4}}$, where M$=$ Mn, Fe, Co and Ni have gained interest as electrode materials for Lithium ion batteries due to their high theoretical capacity (\textgreater 330mAh/g), high thermal stability due to strong Si-O covalent bonds, environmental friendliness, and low cost. However, these materials intrinsically have low electrical conductivity. To improve conductivity of these classes of electrode materials, we synthesized Li$_{\mathrm{2}}$MnSiO$_{\mathrm{4}}$ and Li$_{\mathrm{2}}$FeSiO$_{\mathrm{4}}$ by solid state reaction in an argon atmosphere. The lithium transition metal silicates were compounded with graphene nano-sheets and the composites were used as positive electrode in a coin cell configuration. . The materials structure-composition, morphology, conductivity and electrochemical performance were characterized by XRD, XPS, SEM, TEM and electrochemical techniques.The detail structure-composition analysis and electrochemical performance of the silicate electrodes will be reported. [Preview Abstract] |
Tuesday, March 19, 2013 3:54PM - 4:06PM |
J38.00008: Solid state electrochemical studies on single crystals with hexafluoro metal centers Qifan Yuan, Yao Zhang, Sarah True, Victoria Soghomonian Electrochemical energy storage is of importance for current and future storage schemes. Our electrochemical studies on hydrothermally synthesized single crystals of metal hexafluoride, [NH$_{\mathrm{4}}$]$_{\mathrm{3}}$[V$_{\mathrm{x}}$M'$_{\mathrm{1-x}}$F$_{\mathrm{6}}$], probe the redox chemistry of the V center as a function of substitution, temperature, and contact configuration. The various compositions are probed by XRD and IR spectroscopy. The measured 2 and 4 point resistivity is around 10$^{\mathrm{7}} \quad \Omega^{\mathrm{\thinspace }}$cm. Cyclic voltammograms were obtained by both 2 and 3 point geometries, and current peaks corresponding to the electrochemical reaction recorded. To understand the observed voltammograms of the various configurations measured, the potential distribution in the crystal is calculated numerically, and equipotential lines extracted. Preliminary analysis indicates the extent of the space charge for 2 versus 3 contact measurements, and the influence of the space charge region on the electrochemical reaction when performed at micron scales. For a fixed sweep rate, the amplitude of the current peak diminishes as the temperature is increased, suggesting a dissipation of the space charge. [Preview Abstract] |
Tuesday, March 19, 2013 4:06PM - 4:18PM |
J38.00009: Enhanced Lithiation of Graphitized SiC: In Situ X-ray Scattering Study at Electrolyte / Graphene / SiC(0001) Interface Sudeshna Chattopadhyay (Bandyopadhyay), Albert Lipson, Hunter Karmel, Jonathan Emery, Vinayak Dravid, Mark Hersam, Michael Bedzyk, Paul Fenter, Timothy Fister, Michael Thackeray Silicon carbide is an inert material and not traditionally viewed as a promising electrode material. However, we observed a large enhancement to the electrochemical lithiation capacity for SiC anodes that were electrically activated by the combination of surface graphitization and substrate doping. In-situ X-ray scattering studies for lithiation at the electrolyte/EG/SiC interface show that the interfacial structure of the proposed anode system is stable in the electrolyte and graphene layers remain unaltered. While a decrease in the SiC Bragg peak intensity during lithiation indicates changes to the bulk crystallinity, the emergence of a diffuse scattering feature suggests that lithiation is associated with the development of substrate defects. Characterization via multiple depth resolved spectroscopies shows that Li penetrates the activated SiC upon lithiation. These results illustrate that the electrochemical capacity of a traditionally inert material can be increased substantially by effecting the surface and bulk conductivity [1].\\[4pt] [1] Chattopadhyay, Lipson et al., Chem. Mater. 24, 3038 (2012); Lipson, Chattopadhyay et al., J. Phys. Chem. C 116, 20949 (2012). [Preview Abstract] |
Tuesday, March 19, 2013 4:18PM - 4:30PM |
J38.00010: Dynamic dimer formation between superionic fluorines in PbF$_{2}$ Nobutaka Nakamura, Kazuo Tsumuraya Recently Tsumuraya $et\ al$.(J. Phys. Soc. Jpn. 81,055603(2012).) have elucidated the formation of the dynamic dimers in the superionic conductor $\alpha $-CuI with the first principles molecular dynamics (MD) method. They, for the first time in research, confirmed the dimer formation through the analyses the origin of the correlation peaks of the partial pair distribution functions and the partial angle distribution functions. The present study elucidates the dynamic structure of the superionc fluorines in PbF$_{2}$ crystal with the MD method through identifying the origins of the correlation peaks. The fluorines form the dynamic 32$f$-8$c$ and 4$b$-8$c$ dimers. [Preview Abstract] |
Tuesday, March 19, 2013 4:30PM - 4:42PM |
J38.00011: First-principles study of lithium ion diffusion in crystalline $\beta $-Li$_3$PS$_4$ for solid state electrolytes Myung-Soo Lim, Seung-Hoon Jhi The safety and stability are major issues to resolve in developing high-capacity lithium secondary batteries, particularly for application to electric vehicles. Solid-state lithium-ion electrolytes have been studied as a substitute of liquid electrolytes in order to enhance the stability and increase the energy density. However, low ion-mobility and poor material integrity are limiting the use of the solid electrolytes. We study the lithium-ion diffusion in crystalline $\beta $-Li$_{3}$PS$_{4}$ using first-principles methods and the nudged elastic band method. Considering diffusion paths through both interstitials and vacancy exchanges, we calculate the migration energies of lithium ions. Our results suggest that lithium ion diffusion is likely to occur through the zigzag-shaped paths along the $b$-direction that comprises of two lithium ion sites with fractional occupancy factors. We discuss the implication of our calculations for understanding the lithium ion diffusion in solid electrolytes. [Preview Abstract] |
Tuesday, March 19, 2013 4:42PM - 4:54PM |
J38.00012: Structural and Electrochemical Impacts of Oxygen Doped and Surfactant Coated Activated Carbon Electrodes in Li-ion Batteries John Collins, Gerald Gourdin, Deyang Qu, Michelle Foster Passive charge and discharge dynamics are necessary for advancing Li-ion batteries. Surfactant adsorption on activated carbon has been shown to promote advancements in the discharge capacity, time and cycle-ability of electrochemical systems---specifically by enhancing diffusion pathways for ion insertion/de-insertion and suppressing pore blockage from precipitates known to form during charge/discharge states. Enhancement of surfactant chemisorption on activated carbon is achieved through oxygen doping of the carbon surface. In addition, doping alters the degree of Faradaic processes occurring in solution, resulting in prolonged reduction at the carbon surface\textbf{.} The work presented describes how surface oxygen groups on a granulated activated carbon have been manipulated using nitric acid in a controlled, stepwise fashion. A nonionic surfactant was applied to oxidized and non-oxidized samples at various concentrations. The composition and structure of the activated carbon surface was characterized using DRIFTS, Raman Spectroscopy, SEM and Porosimetry. The charge/discharge Li insertion capacities along with correlating surface microstructure changes were analyzed for all treated electrodes at progressive oxidation stages. [Preview Abstract] |
Tuesday, March 19, 2013 4:54PM - 5:06PM |
J38.00013: Simulation of dendrite formation in lithium-ion batteries Ning Sun, Dilip Gersappe The design of the next generation of energy storage technologies requires both a fundamental understanding of the physical and chemical reactions taking place in a complex electrochemical environment and the factors that limit the performance of these systems. We have developed a Lattice-Boltzmann model to simulate 2-D dendrite formation during charging and discharging processes on the anode of lithium-ion batteries. Our results show that the formation of dendrites is strongly influenced by the morphology of the anode, and operating conditions, in particular the charging current density. Our simulation is able to recover the structures that form on Li anodes, including mossy and dendritic structures as a function of parameters such as the curvature of the interface and the applied current density. We also show that we can observe a linear relationship between the log current density (J) and the log dendrite formation onset time (ts) in the low current density region, which also agrees with experiment data quite well. We study additional effects such as the role of the separator and the Solid Electrolyte Interphase (SEI) layer on the formation of dendrites. [Preview Abstract] |
Tuesday, March 19, 2013 5:06PM - 5:18PM |
J38.00014: Surface Structure and Stability in Li$_3$PS$_4$ and Li$_3$PO$_4$ Electrolytes from First Principles Nicholas Lepley, N.A.W. Holzwarth Crystalline solid electrolyte materials continue to show considerable promise for lithium ion battery applications. Recent experiments on these materials\footnote{Chengdu Liang, ORNL, (private communication).} suggest that in some cases surface effects may play a significant role with regard to both stability and ionic conductivity. In this study, we extend our previous modeling work\footnote{N. A. W. Holzwarth, N. D. Lepley, Y. A. Du, {\em{J. Power Sources}} {\bf{196}}, 6870 (2011).} to an examination of idealized surfaces of several phases of Li$_3$PX$_4$ (X=O,S). Our preliminary results suggest that energy contributions from the surface affect the relative phase stability in Li$_3$PS$_4$, although this is not observed in the phosphate analogue. Our presentation will focus on surface energies and structures, as well as examining the calculated stability of the interface between the electrolyte and lithium metal. [Preview Abstract] |
Tuesday, March 19, 2013 5:18PM - 5:30PM |
J38.00015: Synthesis and Performance of LiFe$_{\mathrm{1-x}}$Mn$_{\mathrm{x}}$PO$_{4}$ in Lithium-ion Battery Khadije Bazzi, Maryam Nazri, Prem Vaishnava, Vaman Naik, Gholam-Abbas Nazri, Ratna Naik Olivine-type lithium transition metal phosphates (i.e. LiFePO$_{4})$ have been intensively investigated as promising electrode materials for rechargeable lithium-ion batteries. There have been attempts to improve energy density and voltage quality of phosphate based electrode. In this study, we have partially substituted Fe$^{\mathrm{II}}$/Fe$^{\mathrm{III}}$ redox center with Mn$^{\mathrm{II}}$/Mn$^{\mathrm{III}}$ in LiFePO$_{4}$ that provides over 600 mV higher voltage. We prepared various compositions of LiFe$_{\mathrm{1-x}}$Mn$_{\mathrm{x}}$PO$_{4}$ (x$=$0, 0.2, 0.4, 0.6, 0.8 and 1) between the two end members (LiFePO$_{\mathrm{4}}$ - LiMnPO$_{4})$. Due to intrinsic low electronic conductivity of lithium transition metal phosphates, we coat these materials with a uniform conductive carbon through a unique sol-gel process developed in our laboratory. In addition, we made a composite of the carbon coated phosphate with carbon nano-tubes to develop a highly conductive matrix electrode. We report the materials structure, morphology, electrical conductivity and electrochemical performances of LiFe$_{\mathrm{1-x}}$Mn$_{\mathrm{x}}$PO$_{4}$ using XRD, Raman spectroscopy, SEM, TEM, XPS, electrical conductivity and galvanostatic charge/discharge measurements. [Preview Abstract] |
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