Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session A24: Focus Session: Materials for Electrochemical Energy Storage: Characterization and Computation Methods |
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Sponsoring Units: DMP GERA DCOMP Chair: Brandon Wood, Lawrence Livermore National Laboratory Room: 504 |
Monday, March 3, 2014 8:00AM - 8:36AM |
A24.00001: Electron microscopy characterization of Li-based cathode materials for battery applications Invited Speaker: Patrick Phillips While recent advances in energy storage have revolutionized the consumer electronics market, we still lack an understanding of the aging effects that currently limit the batteries' lifetime and energy storage capacity. Aberration-corrected scanning transmission electron microscopy (STEM) is becoming one of the most promising characterization tools to study the effects of repeated charging/discharging cycles on electrode aging in Li-ion battery materials, due to the wide-range of techniques available on advanced STEM instruments, including the direct imaging of both heavy and light elements, energy-dispersive X-ray and electron energy loss (EEL) spectroscopies and a variety of in-situ methods. This talk will focus on the structural and chemical characterization of Li-ion battery electrode materials, both in a pristine and lithiated/delithiated state. We will examine the nucleation of structural transitions with STEM experiments utilizing various imaging modes, including annular dark field and bright field imaging, and in-situ electro-chemical experiments using the open-cell design. These results will be combined with EELS measurements and first principle density functional theory calculations to elucidate the role of the observed transitions on the material's structural stability.\\[4pt] In collaboration with Robert Klie, University of Illinois at Chicago; Hakim Iddir, Roy Benedek, and Daniel Abraham, Chemical Sciences and Engineering Division, Argonne National Laboratory. [Preview Abstract] |
Monday, March 3, 2014 8:36AM - 8:48AM |
A24.00002: Finite temperature effects on the X-ray absorption spectra of energy related materials Tod Pascal, David Prendergast We elucidate the role of room-temperature-induced instantaneous structural distortions in the Li K-edge X-ray absorption spectra (XAS) of crystalline LiF, Li$_{2}$SO$_{4}$, Li$_{2}$O, Li$_{3}$N and Li$_{2}$CO$_{3}$ using high resolution X-ray Raman spectroscopy (XRS) measurements and first-principles density functional theory calculations within the eXcited electron and Core Hole (XCH) approach. Based on thermodynamic sampling via \textit{ab-initio} molecular dynamics (MD) simulations, we find calculated XAS in much better agreement with experiment than those computed using the rigid crystal structure alone. We show that local instantaneous distortion of the atomic lattice perturbs the symmetry of the Li 1$s$ core-excited-state electronic structure, broadening spectral line-shapes and, in some cases, producing additional spectral features. This work was conducted within the Batteries for Advanced Transportation Technologies (BATT) Program, supported by the U.S. Department of Energy Vehicle Technologies Program under Contract No. DE-AC02-05CH11231. [Preview Abstract] |
Monday, March 3, 2014 8:48AM - 9:00AM |
A24.00003: Soft X-ray Spectroscopy for Understanding the Cycling Mechanism of Novel Lithium-ion Batteries Ruimin Qiao, Robert Kostecki, Ivan Lucas, Kristin Persson, Wei Chen, Hong Li, Rui Wang, Wanli Yang Energy and environment are two major concerns of the modern world. Transition to the sustainable clean energy globally in the future, however, depends on the development of next generation electrical energy storage systems. Among the energy storage techniques considered at present, rechargeable lithium-ion batteries, which are ubiquitous in today's portable electronic devices and now enable the electric vehicles, remain promising to facilitate the use of renewable energy on a large scale. For such application, transformational changes in battery technologies are critically needed, which require a fundamental understanding of the complex, interrelated physical and chemical processes between electrode materials and electrolytes Soft x-ray absorption spectroscopy(sXAS) is a powerful tool to probe the chemical species and the electronic states with elemental sensitivity. This presentation will discuss examples on using sXAS to study battery materials for both fundamental understanding and practical developments. We will showcase how sXAS fingerprints the battery operation by detecting the evolving electron states. Recent results on SEIs and Li-rich cathode materials will be discussed. Our results offer important information for improving Li batteries. [Preview Abstract] |
Monday, March 3, 2014 9:00AM - 9:12AM |
A24.00004: First-principles investigation of the structural changes in Li-rich cathode composites Hemant Dixit, Wu Zhou, Jagjit Nanda, Juan-Carlos Idrobo, Valentino Cooper Lithium ion batteries have high energy densities and are widely used in consumer electronics. However, it is essential to improve their power rate and cycle life for long-term usage. Cathode materials containing Li-excess layered oxide compounds, $x$Li$_2$MnO$_3$(1-$x$)LiMO$_2$, (where M=Mn, Co, Ni and $x$= 0.2-0.7) have two times higher capacities than the conventional cathode material but during cycling a decrease in energy density and a concomitant development of a low voltage plateau are often observed. Furthermore, recent experimental studies have observed the formation and clustering of the anti-site defects near the surface. Thus a detailed understanding of the structural changes at the atomic scale of these Li-rich composites is essential to establish the correlation between the structural and electrochemical property. We present first-principles density functional theory study of the structural and electronic properties in Li-rich cathode composites. These cathode composites are modelled as solid solutions of the LiMnO$_2$ (R$\bar{3}$m) and Li$_2$MnO$_3$ (C$_2$m) phases. We discuss the stability of the proposed model, the diffusion energy barriers of Li$^+$ ions calculated using nudged-elastic band method and the formation energies of the antisite defects. [Preview Abstract] |
Monday, March 3, 2014 9:12AM - 9:24AM |
A24.00005: Atomistic simulation studies of nanostructured Li2MnO3 Phuti Ngoepe, Thi Sayle, Dean Sayle The structures of the lithium-rich layered materials are basically derived from the layered rock-salt a- NaFeO2 type structure with space group R-3m. Nano-sized crystalline cathode material, Li2MnO3, was prepared by single step hydrothermal reaction [1]. The prepared materials delivered a high electrochemical reversible capacity charged/discharged between 2.0-4.3V, which indicates their promising future potential. In the current study simulated amorphisation recrystallisation method [2] is used to nucleate and crystallise ternary a nanoparticle of Li2MnO3, which is an end member compound of composites. The generated structure is characterized and the Li layer is found to accommodate some Mn ions. The latter is explained in terms of heats of formation deduced from DFT calculations. Microstructural features and transport properties are presented and a possible origin of the electrochemical activity is discussed. [1] G. R. Liu, S.C. Zhang, X. X. Lu, X. Wei, Proceedings Int. Conf. Nanomaterials: Applications and Properties, Vol. \textbf{2, }No 2, 02PCN25(3pp) (2013). [2] P.E.Ngoepe, R.R. Maphanga and D.C. Sayle, (2013), ``Towards the Nanoscale'', Chapter 9 in Computational Approaches to Energy Materials, pp 261-290, edited by C.R.A. Catlow, A. Sokol and A. Welsch, John Wiley and Sons Ltd. [Preview Abstract] |
Monday, March 3, 2014 9:24AM - 9:36AM |
A24.00006: In Situ Tomographic Profiling of Ag$_{2}$VP$_{2}$O$_{8}$ Li-Ion Batteries using Energy Dispersive X-ray Diffraction Kevin Kirshenbaum, David Bock, Amy Marschilok, Zhong Zhong, Kenneth Takeuchi, Esther Takeuchi Bimetallic cathodes for use in Li-ion batteries have been studied in recent years as they may provide multiple electron reduction, yielding both high capacity and high current on discharge. In this study, we investigate the progress of the reaction of Ag$_{2}$VP$_{2}$O$_{8}$ on discharge in a lithium anode cell using in-situ energy dispersive x-ray diffraction at beamline X17B1 at NSLS I. By measuring diffraction patterns in 20 $\mu$m segments through the cathode as a function of depth of discharge we are able to produce tomographic images of discharged cells. After analyzing the resulting spectra, we were able to observe the presence and relative intensity of Ag metal formed in the cathode upon discharge shedding light on the mechanisms limiting performance. [Preview Abstract] |
Monday, March 3, 2014 9:36AM - 9:48AM |
A24.00007: Hybrid functional studies of defects in layered transition metal oxides Khang Hoang, Michelle Johannes Layered oxides LiMO$_{2}$ (M is a transition metal) have been studied extensively for Li-ion battery cathodes. It is known that defects have strong impact on the electrochemical performance. A detailed understanding of native point defects in LiMO$_{2}$ is however still lacking, thus hindering rational design of more complex materials for battery applications. In fact, first-principles defect calculations in LiMO$_{2}$ are quite challenging because standard density functional theory (DFT) calculations using the generalized gradient approximation (GGA) of the exchange-correlation functional fail to reproduce the correct physics. The GGA+U extension can produce reasonable results, but the transferability of U across the compounds is limited. In this talk, we present our DFT studies of defects in LiMO$_{2}$ (M=Co, Ni) using the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid functional. The dominant point defects will be identified and compared with experiment; and their impact on the structural stability and the charge (electronic and ionic) and mass transport will be addressed. We will also discuss possible shortcomings of the HSE functional in the study of these electron-correlated materials. [Preview Abstract] |
Monday, March 3, 2014 9:48AM - 10:24AM |
A24.00008: Li-ion energy storage of two-dimensional ``MXene'' transition metal carbides Invited Speaker: Paul Kent A new class of two-dimensional early transition metal carbides and carbonitrides, the so-called MXenes, has been synthesized by extracting the ``A'' element from MAX phases. Experiments have demonstrated that MXenes (Ti$_2$C, V$_2$C, Nb$_2$C, Ti$_3$C$_2$...) are promising anode materials for lithium ion batteries, delivering high storage capacity and good rate performance. However, the mechanism of Li-ion storage on MXene surfaces is not clear, with counterintuitive differences in predicted vs measured capacities, and large differences between exfoliated and delaminated samples. I will discuss how a strong collaboration between theory and a range of experimental characterization methods, including x-ray adsorption spectroscopy and inelastic neutron scattering, is able to provide a including for the highest measured Li capacities.\\[4pt] In collaboration with Yu Xie, Alexander Kolesnikov, Oak Ridge National Laboratory; Xiquan Yu, Kyung-Wan Nam, Xiao-Qing Yang, Brookhaven National Laboratory; Michael Naguib, Vadym Mochalin, Michel Barsoum, and Yury Gogotsi, Department of Materials Science and Engineering, and A.J. Drexel Nanotechnology Insititute, Drexel University. [Preview Abstract] |
Monday, March 3, 2014 10:24AM - 10:36AM |
A24.00009: Post-test analysis of lithium-ion battery materials at Argonne National Laboratory Javier Bareno, Nancy Dietz-Rago, Ira Bloom Electrochemical performance is often limited by surface and interfacial reactions at the electrodes. However, routine handling of samples can alter the very surfaces that are the object of study. Our approach combines standardized testing of batteries with sample harvesting under inert atmosphere conditions. Cells of different formats are disassembled inside an Argon glove box with controlled water and oxygen concentrations below 2 ppm. Cell components are characterized \textit{in situ}, guaranteeing that observed changes in physicochemical state are due to electrochemical operation, rather than sample manipulation. We employ a complementary set of spectroscopic, microscopic, electrochemical and metallographic characterization to obtain a complete picture of cell degradation mechanisms. The resulting information about observed degradation mechanisms is provided to materials developers, both academic and industrial, to suggest new strategies and speed up the Research {\&} Development cycle of Li-ion and related technologies. This talk will describe Argonne's post-test analysis laboratory, with an emphasis on capabilities and opportunities for collaboration. Cell disassembly, sample harvesting procedures and recent results will be discussed. [Preview Abstract] |
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