Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session D24: Focus Session: Materials for Electrochemical Energy Storage: Battery Materials |
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Sponsoring Units: DMP GERA DCOMP Chair: Javier Bareno, Argonne National Laboratory Room: 504 |
Monday, March 3, 2014 2:30PM - 2:42PM |
D24.00001: Graphene modified LiMPO$_{4}$ (M$=$Fe, Mn) as a cathode material for lithium ion batteries Kulwinder Dhindsa, Balaji Prasad Mandal, Khadije Bazzi, Ming-Wei Lin, Maryam Nazri, Gholam Abbas Nazri, Vaman M. Naik, Vijay K. Garg, A.C. Oliveira, Prem Vaishnava, Ratna Naik, Zhixian Zhou We have synthesized LiFePO$_{4}$/graphene nano-composites using sol-gel method by adding water dispersed graphene oxide to the LiFePO$_{4}$ precursors during the synthesis. The graphene oxide was subsequently reduced by annealing the composite at 600$^{\circ}$C for 5h in forming gas (90{\%} Ar and 10{\%} H$_{2})$ which was confirmed by Raman spectroscopy and X-ray Photoelectron spectroscopy. Addition of graphene significantly improved the electronic conductivity of LiFePO$_{4}$. Scanning Electron microscopy and Transmission electron microscopy images show LiFePO$_{4}$ particles being covered uniformly by graphene sheets throughout the material forming a three dimensional conducting network. Cyclic voltammetry results show that composite is a typical two-phase system. Li ion diffusion coefficient calculations show two orders of magnitude enhancement. At low currents, (C/3), the capacity of LiFePO$_{4}$/graphene composite cathode reaches 160 mAh/g, which is very close to the theoretical limit. More significantly, the graphene modified LiFePO$_{4}$ shows a dramatically improved rate capability up to 27C, and excellent charge-discharge cycle stability over 500 stable cycles. In addition to~LiFePO$_{4}$, LiMnPO$_{4}$/graphene composite has also been synthesized and the results will be discussed. [Preview Abstract] |
Monday, March 3, 2014 2:42PM - 2:54PM |
D24.00002: Effect of excess Li on electrochemical properties of LiFePO$_{4}$ cathode material for Li ion batteries K. Bazzi, M. Nazri, P. Vaishnava, V.M. Naik, G.A. Nazri, R. Naik Application of lithium iron phosphate as a cathode material in lithium cell is limited by its poor electronic and ionic conductivity. Here, we report the synthesis of C-LiFePO$_{4}$ and C- Li$_{1.05}$FePO$_{4}$ cathode materials via sol gel method using oleic acid as a surfactant/source of carbon to improve the electronic conductivity. Our aim is to investigate the role of excess Li on the electrochemical performance of C-LiFePO$_{4}$. The phase purity was confirmed by x-ray diffraction. When excess lithium is used, the agglomeration is reduced and spherical particles are formed. Our results show that C-Li$_{1.05}$FePO$_{4}$ has lower charge transfer resistance, higher Li-ion diffusion coefficient, and superior electrochemical performance in terms of the specific capacity, rate capability and cycling stability. The correlation between the electrochemical characteristics and the particle size and morphology will be presented. [Preview Abstract] |
Monday, March 3, 2014 2:54PM - 3:06PM |
D24.00003: Phase transformation and electronic structure characterization of Li$_{x}$FePO$_{4}$ by ab-initio calculations and soft x-ray spectroscopy Yung Jui Wang, B. Barbiellini, Xiaosong Liu, Ruimin Qiao, B. Moritz, T. P. Devereaux, Hsin Lin, Zahid Hussain, Wanli Yang, A. Bansil Olivine-structured Li$_{x}$FePO$_{4}$ with appropriate surface treatment is a battery cathode material with promising capacity, cost and safety specifications. Fe-L and O-K edge soft x-ray absorption and emission spectra directly probe the unoccupied and occupied electronic states in the vicinity the Fermi energy. We present a first principles calculation and a comparison with the spectra to investigate the electronic states of Li$_{x}$FePO$_{4}$. Upon fully (de)lithiation, the redistributed unoccupied Fe-3d and O-2p states indicate the fingerprints of the two-phase transformation. The redox couple is pinned such that a single electron injection into the valence states is well separated from the top of O-2p valence states due to Coulomb repulsion. We further explore the surface properties and discuss their implications on the performance and optimization of Li$_{x}$FePO$_{4}$. Work supported by the US DOE. [Preview Abstract] |
Monday, March 3, 2014 3:06PM - 3:18PM |
D24.00004: Insolubility of intercalants in strongly correlated oxides and phosphates Eric Isaacs, Chris Marianetti Olivine lithium iron phosphate (Li$_x$FePO$_4$), a cathode material for Li-ion batteries, phase separates into the fully lithiated and fully delithiated phases according to experiment. Previous electronic structure calculations showed that while this phase separation is not predicted by DFT, it is captured by DFT+U due to the improved treatment of electronic correlations [F. Zhou et al., Phys. Rev. B 69, 201101 (2004).]. In order to understand the role of electronic correlations in phase separation, here we investigate the phase stability of Li$_x$FePO$_4$ and other strongly correlated oxide and phosphate intercalation compounds within DFT+U and DFT+DMFT. We present the relationship between computed formation energies and the on-site Coulomb repulsion and double-counting correction across different systems. In addition, we perform p-d model calculations in order to understand the mechanism at a minimal level. [Preview Abstract] |
Monday, March 3, 2014 3:18PM - 3:30PM |
D24.00005: Synthesis and Electrochemical Characterization of Li$_{2}$FeSiO$_{4}$/Carbon Nanofiber Composite Cathode Material for Li Ion Batteries Ajay Kumar, Gholam Abbas Nazri, Ratna Naik, Vaman M Naik Lithium transition metal silicates (Li$_{2}$MSiO$_{4})$, where, M$=$Ni, Mn, Fe, and Co with a theoretical capacity of $\sim$ 330 mAh/g have attracted great interest as possible replacements for cathode material in rechargeable batteries. However, this class of materials exhibit very low electronic conductivity and low lithium diffusivity. In order to enhance the electronic conductivity and reduce the diffusion length for lithium ion, we have synthesized Li$_{2}$FeSiO$_{4}$/carbon nanofiber (15 {\%} wt) composites by sol-gel method. The composite materials were characterized by x-ray diffraction and scanning electron microscopy. The XRD data confirmed the formation of Li$_{2}$FeSiO$_{4}$ crystallites with size $\sim$ 25 nm for composites annealed at 600 $^{\circ}$C under argon atmosphere. The composite material was used as positive electrode in a coin cell configuration and the cells were characterized by AC impedance spectroscopy, cyclic voltammetry, and galvanostatic charge/discharge cycling. The cells showed a discharge capacity of $\sim$ 230 mAh/g in the initial cycles, which suggests that more than one Li ion is extracted from the electrode. The effect of annealing at higher temperature on the electrochemical performance of Li$_{2}$FeSiO$_{4}$/carbon nanofiber composites will be presented. [Preview Abstract] |
Monday, March 3, 2014 3:30PM - 3:42PM |
D24.00006: Polycrystalline TiO2(B) Nanosheet Films Deposited via Langmuir-Blodgett Method Laura Biedermann, Paul Kotula, Thomas Beechem, Anthony Dylla, Keith Stevenson, Calvin Chan As an energy storage material, TiO$_2$ offers higher Li$^+$ capacities and smaller volume changes with lithiation than graphite electrodes. In particular, the bronze phase, TiO$_2$(B) has a higher lithiation capacity (1.0~Li$^+$/Ti) and faster lithiation kinetics due to its larger lattice parameters than other TiO$_2$ polymorphs. Direct observation of lithiation will require TiO$_2$(B) monolayers, such as those prepared via Langmuir-Blodgett deposition of the nanosheets (NS). Optical microscopy of the TiO$_2$(B)-NS Langmuir monolayer at the air/water interface shows that these nanosheets assemble into large ($>$1~mm) islands. These elastic TiO2(B)-NS monolayers are deposited on diverse substrates for further characterization. Electron diffraction in both transmission electron microscopy (TEM) and low-energy electron microscopy (LEEM) of these films confirm that their polycrystalline structure is predominately composed of TiO$_2$(B) nanocrystals, $\sim$10s nm across. Discrimination of monolayer and bilayer TiO$_2$(B) is evident in LEEM. Thermal stability of these nanosheets is investigated via in-situ TEM and ex-situ Raman spectroscopy. This monolayer TiO$_2$(B) deposition will allow future observations of lithiation and phase changes. [Preview Abstract] |
Monday, March 3, 2014 3:42PM - 3:54PM |
D24.00007: {\em{Ab initio}} study of layered chromium disulfide (CrS$_2$) toward a new anode material for Li-ion batteries Seoung-Hun Kang, Young-Kyun Kwon There has been considerable interest in use of transition-metal disulfides, such as MS$_2$ (M$=$Mo, W), as new anode materials in Li-batteries to improve their battery performance. Since CrS$_2$, if synthesized, would be much lighter than MoS$_2$ or WS$_2$, it would exhibit higher Li capacity. To verify this expectation, we investigate the adsorption and diffusion properties of Li on layered Cr$_2$ and its Li capacity using DFT implemented with van der Waals correction. We thoroughly search for variuos Li adsorption sites, on which the binding energies are higher than Li clustering energy ($\sim1.6$~eV). Based on the these calculations, we identify the diffusion paths and barriers of Li atoms within the layered CrS$_2$ as well as on a free-standing single-layer of CrS$_2$. We find that Li atoms exhibit almost free intra-layer diffusion resulting in an improved mobility of Li at room temperature, while inter-layer diffusion is difficult to occur. We also estimate the Li-capacity of the CrS$_2$ by evaluating the energy gain as well as the average binding energy while intercalating more Li atoms. We find that CrS$_2$ can have larger Li-capacity than graphite, which is being widely used for anode material, implying that CrS$_2$ may be a good candidate for Li-battery electrode. [Preview Abstract] |
Monday, March 3, 2014 3:54PM - 4:06PM |
D24.00008: Dopant based stabilization of LiCoO$_{2}$ Juan A. Santana, Jeongnim Kim, Fernando A. Reboredo, Paul R. Kent LiCoO$_{2}$ is still one of the commonly used cathode materials for Li-ion batteries. Yet, the usable specific capacity is limited to approximately 150 mAh/g, only above half of its theoretical capacity (280 mAh/g). The limitation arises predominantly from the decomposition (or mechanical failure) of the LiCoO$_{2}$ cathode into Co$_{3}$O$_{4}$ when more than 50{\%} of Li is deintercalated. The stability of the cathode and its electrochemical performance can be improved by coating the cathode surface with inner metal oxides. This approach has been widely used for different cathode materials, but the origin of the stabilization effect is poorly understood. Various models have been proposed to rationalize the stabilization, e.g., $i)$ the inner metal oxides act as a physical barrier preventing cathode-electrolyte reactions, and \textit{ii}) the layered structure of the cathode material is stabilized by the migration of metal ions from the coating oxides. To elucidate the origin of the higher stability, we have performed first-principles DFT calculations of LiCoO$_{2}$ when doped with inner metal ions. Our calculations explore the effect of the dopants on the formation of point defects and the thermal decomposition of the cathode electrode. [Preview Abstract] |
Monday, March 3, 2014 4:06PM - 4:18PM |
D24.00009: ABSTRACT WITHDRAWN |
Monday, March 3, 2014 4:18PM - 4:30PM |
D24.00010: First-principles study of the electronic properties and discharge profile of AgNa(VO$_{2}$F$_{2}$)$_{2}$ Masatoshi Onoue, Giancarlo Trimarchi, Arthur J. Freeman Implantable cardiac defibrillators (ICDs) require batteries with high capacities and high discharge rates to ensure the optimal operation of the device over several years. Ag$_{2}$V$_{4}$O$_{11}$ has been a cathode material of choice for the ICDs owing to its high capacity and fast rate of electronic discharge. To reduce ICD size and improve ICD performance, a new cathode material would need to display a higher volumetric capacity and redox potential. Recently, the new cathode compound AgNa(VO$_{2}$F$_{2}$)$_{2}$ (SSVOF) was synthesized and displayed favorable voltage for sodium-ion batteries. However, the discharge reaction has been unclear. In this presentation, we study the discharge reaction of SSVOF through DFT calculations. All calculations are performed within the PAW method using the GGA and GGA$+U$ functionals. Among several possible reactions, we focus on the reaction Ag$X$ + $A \rightarrow AX$ + Ag, where $X$ is Na(VO$_{2}$F$_{2}$)$_{2}$ and $A$ is Li or Na. In this reaction, the discharge occurs by replacing Ag with $A$. The calculated discharge potential for Li is 3.3 V in GGA and 2.9 V in GGA$+U$ and that for Na is 3.1 V in GGA and 2.8 V in GGA$+U$. These values are consistent with the experimental ones. [Preview Abstract] |
Monday, March 3, 2014 4:30PM - 4:42PM |
D24.00011: Structural Stability and Electronic Properties of Na$_2$C$_6$O$_6$ for a Rechargeable Sodium-ion Battery Tomoki Yamashita, Akihiro Fujii, Hiroyoshi Momida, Tamio Oguchi Sodium-ion batteries have been explored as a promising alternative to lithium-ion batteries owing to a significant advantage of a natural abundance of sodium. Recently, it has been reported that disodium rhodizonate, Na$_2$C$_6$O$_6$, exhibit good electrochemical properties and cycle performance as a minor-metal free organic cathode for sodium-ion batteries. However, its crystal structures during discharge/charge cycle still remain unclear. In this work, we theoretically propose feasible crystal structures of Na$_{2+x}$C$_6$O$_6$ using first principles calculations. A structural phase transition has been found: Na$_4$C$_6$O$_6$ has a different C$_6$O$_6$ packing arrangement from Na$_2$C$_6$O$_6$. Electronic structures of Na$_{2+x}$C$_6$O$_6$ during discharge/charge cycle are also discussed. Our predictions could be the key to understanding the discharge/charge process of Na$_2$C$_6$O$_6$. [Preview Abstract] |
Monday, March 3, 2014 4:42PM - 4:54PM |
D24.00012: Strongly localized electronic screening of Mg intercalants in the Chevrel phases Mo$_6$S$_8$ Florian Th\"{o}le, David Prendergast The problem of multivalent ion insertion into cathode materials is still poorly understood. Using the Chevrel phases (CPs) as a model material, we study the effect of Mg ion insertion using density functional theory (DFT). By inspection of the electron charge density difference associated with the insertion of Mg into a supercell of the material, which is metallic below the full intercalation limit, we arrive at the conclusion that the response to Mg insertion is best described in terms of a local screening cloud, effectively shielding the Mg charge with a length scale on the order of one unit cell. The density differences are localized mostly on the nearest neighbor sulfur anions with only minor differences on the nearest Mo cations. This behaviour is surprising, because in an ideal metal one might expect that insertion of an isolated ionic dopant might lead to localized screening with the Thomas-Fermi length scale $r_{TF}=0.29$~{\AA}, while in an insulator or semiconductor comprising transition metal cations, traditional redox chemistry might be expected. To provide a link to experiments, we simulate X-ray absorption spectra for the Mg K-edge. In full agreement with our model, the resulting spectra show an edge position which lies between metallic Mg and ionic MgO. [Preview Abstract] |
Monday, March 3, 2014 4:54PM - 5:06PM |
D24.00013: The Lithium-Induced Conversion Reaction of CoO Thin Film Battery Materials as Studied by ARXPS Ryan Thorpe, Sylvie Rangan, Mahsa Sina, Frederic Cosandey, Robert Bartynski Conversion reaction compounds such as CoO exhibit high charge density as electrodes in Li-ion batteries. Upon exposure to lithium, Co ions are reduced from a 2+ oxidation state to Co$^{0}$ in a reaction that drastically changes the electronic structure and morphology of the electrode. In order to characterize the atomistics of this conversion reaction without contamination from electrolytes or ambient gases, we have grown CoO thin films in (100), (111), and polycrystalline orientations, and exposed these surfaces to atomic Li in ultra-high vacuum. The diffusion of Li and the phase evolution of the substrate were then characterized with STM and angle-resolved XPS. Differences in the reactivities of each crystalline face have been observed. Additionally, a parasitic reaction between Li-rich reaction products and residual H$_{2}$O was observed to produce Li$_{2}$O$_{2}$, which inhibited further Li diffusion at room temperature. This could explain the capacity losses observed in CoO electrodes by previous studies. [Preview Abstract] |
Monday, March 3, 2014 5:06PM - 5:18PM |
D24.00014: Different behavior of lithium interaction with SiO2 and Al2O3 Yufeng Zhao, Chunmei Ban, Branden B. Kappes, Qiang Xu, Chaiwat Engtrakul, Cristian V. Ciobanu, Anne C. Dillon Lithiation of SiO2 and lithium intercalation in Al2O3 is studied both theoretically and experimentally. Lithium interacts with these two types of oxides in distinctly different behaviors. Reversible insertion/extraction of lithium in SiO2 up to a Li density of 2/3 Li per Si are demonstrated experimentally. Density-functional-theory (DFT) calculation shows that neither free interstitial Li atoms (no reduction) nor formation of a local Li2O cluster plus a Si-Si bond (full reduction) is energetically favorable. However, two Li atoms can effectively break a Si-O bond and be stabilized between the Si and O atoms. Such a defect, representing a state of partial reduction of SiO2, is energetically favorable. DFT simulation shows that intercalation of SiO2 at high Li density through partial reduction results in crystalline compounds LixSiO2 (x \textless 2/3) with tunable band-gaps in the range of 2-3.4 eV. In sharp contrast, Al2O3 is very stable against lithiation through any form of reduction. However, good conductivity of Li ions is shown in porous Al2O3. [Preview Abstract] |
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