Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session F25: Focus Session: Materials for Electrochemical Energy Storage: Beyond Li-ion |
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Sponsoring Units: DMP GERA DCOMP Chair: Paul Kent, Oak Ridge National Laboratory Room: 503 |
Tuesday, March 4, 2014 8:00AM - 8:36AM |
F25.00001: Electrochemistry of dioxygen in lithium-air batteries Invited Speaker: Laurence Hardwick The non-aqueous lithium-oxygen battery is one of a host of emerging opportunities available for enhanced energy storage [1]. Unlike a conventional battery where the reagents are contained within the cell, the lithium-oxygen cell uses dioxygen from the atmosphere to electrochemically form the discharge product lithium peroxide. Degrees of reversible oxidation and formation of lithium peroxide has been demonstrated in a number of non-aqueous electrolyte classes, mostly notably in dimethysulfoxide based electrolytes [2], thus making the lithium-oxygen cell a potential energy storage device. This talk will present our groups recent results of the electrochemistry of dioxygen in non-aqueous electrolytes, of which particular electrolytes could have practical application within a lithium-oxygen cell. Discussion will touch upon how the electrochemistry can be related to electrode substrate and will be presented with in situ spectroscopic studies that identify intermediate and surface species during the oxygen reduction reaction. \\[4pt] [1] P.G. Bruce, S. Freunberger, L.J. Hardwick, J.-M. Tarascon, Nature Mater. (2012) 11 19\\[0pt] [2] Z. Peng, S.A. Freunberger, Y. Chen, P.G. Bruce, Science, (2012) 337 563 [Preview Abstract] |
Tuesday, March 4, 2014 8:36AM - 8:48AM |
F25.00002: First Principles Investigation of Li/Fe-Oxide as a High Energy Material for Hybrid All-in-One Li-ion/Li-O$_{2}$ Batteries Alper Kinaci, Lynn Trahey, Michael M. Thackeray, Scott Kirklin, Christopher Wolverton, Maria K.Y. Chan We recently introduced a vision for high energy all-in-one electrode/electrocatalyst materials that can be used in hybrid Li-ion/Li-O$_{2}$ (Li-air) cells [1]. Recent experiments using Li$_{5}$FeO$_{4}$ demonstrated substantially smaller voltage polarizations and hence higher energy efficiency compared to standard Li-O$_{2}$ cells forming Li$_{2}$O$_{2}$ [2]. The mechanism by which the charge process activates the Li$_{5}$FeO$_{4}$, however, is not well understood. Here, we present first principles density functional theory (DFT) calculations to establish the thermodynamic conditions for the extraction of Li/Li$+$O from Li$_{5}$FeO$_{4}$. A step-by-step, history-dependent, removal process has been followed and the stability of the Li and Li$+$O deficient samples is investigated on the basis of the energies of the extraction reactions. Various stages of Li/Li$+$O removal are identified, and structural changes and electronic structure evolution, as well as computed XRD, XANES, and PDF characterizations are reported. \\[4pt] [1] M. M. Thackeray, M. K. Y. Chan, L. Trahey, S. Kirklin, and C. Wolverton, Journal of Physical Chemistry Letters, 4, 3607 (2013).\\[0pt] [2] L. Trahey, C. S. Johnson, J. T. Vaughey, S.-H. Kang, L. J. Hardwick, S. A. Freunberger, P. G. Bruce, M. M. Thackeray, Electrochemical and Solid-State Letters, 14, A64 (2011). [Preview Abstract] |
Tuesday, March 4, 2014 8:48AM - 9:00AM |
F25.00003: First-principles study on structure stabilities of $\alpha$-S and Na-S battery systems Hiroyoshi Momida, Tamio Oguchi To understand microscopic mechanisms of charge and discharge reactions in Na-S batteries, there has been increasing needs to study fundamental atomic and electronic structures of elemental S as well as that of Na-S phases. The most stable form of S is known to be an orthorhombic $\alpha$-S crystal at ambient temperature and pressure, and $\alpha$-S consists of puckered S$_8$ rings which crystallize in space group $Fddd$. In this study, the crystal structure of $\alpha$-S is examined by using first-principles calculations with and without the van der Waals interaction corrections of Grimme's method, and results clearly show that the van der Waals interactions between the S$_8$ rings have crucial roles on cohesion of $\alpha$-S. We also study structure stabilities of Na$_2$S, NaS, NaS$_2$, and Na$_2$S$_5$ phases with reported crystal structures. Using calculated total energies of the crystal structure models, we estimate discharge voltages assuming discharge reactions from 2Na+$x$S$\rightarrow$Na$_2$S$_x$, and discharge reactions in Na/S battery systems are discussed by comparing with experimental results. [Preview Abstract] |
Tuesday, March 4, 2014 9:00AM - 9:12AM |
F25.00004: Indirect correlation between superionc sodiums in $\beta $-alumina -First principles molecular dynamic study- Kazuo Tsumuraya, Shoichi Yasuda The atoms are ionized in the ion conductors like the atoms in the ionic crystals, yet either cations or anions are mobile under the electric field unlike the ions in the ionic crystals. The elucidation of the conduction mechanism is essential for the development of the secondary batteries which operate at low temperature. Since the Na-Na correlation peak in superionic $\beta $-alumina has been located at a well separated from the peak position arising from the commensurate sites, the analyses of the origin of the correlation peak allows us to give the nature of the conduction mechanism in conductors. The first principles molecular dynamic study shows that split-interstitial sodiums on mid-oxygen produce the correlation. This is an indirect correlation between the superionic sodiums and is consistent with low Haven's ratios in the $\beta $-alumina. [Preview Abstract] |
Tuesday, March 4, 2014 9:12AM - 9:24AM |
F25.00005: Structure of Imidazolium-based Ionic Liquids Marie-Louise Saboungi, Miguel Gonz\'alez, Bachir Aoun, Oleg Borodin, Wesley Henderson, Shinji Kohara, Maiko Kofu, Osamu Yamamuro Room-temperature ionic liquids (RTILs) are receiving increased attention due to their unique properties, including nonvolatility and solvating capability, leading to a wide range of potential uses in catalysis, separation technology, photovoltaics, batteries and fuel cells. We have studied the structures of liquid and solid 1-ethyl, 1-butyl and 1-hexyl-3-methylimidazolium bromide with high-energy x-ray diffraction measurements and atomistic molecular dynamics numerical simulations. Excellent agreement between experiment and simulation is obtained, including the region of the low-Q peak that characterizes the nanoscale heterogeneity in these liquids. Significant changes in this heterogeneity are observed when water is added to the ionic liquid, depending on the length of the ethyl chain. With a longer (octyl) chain length, the degree of heterogeneity is enhanced, possibly reflecting the water nano-domains observed in simulations. [Preview Abstract] |
Tuesday, March 4, 2014 9:24AM - 9:36AM |
F25.00006: First principles simulations of structural phase transformations in the solid electrolyte LiBH$_4$ with chemical substitutions Noam Bernstein, Khang Hoang, Michelle Johannes The proposed hydrogen storage material LiBH$_4$ has been shown to have possible applications as a Li-ion battery solid electrolyte, due to its high Li-ion conductivity over 10$^{-3}$ S/cm$^{-1}$ [1], comparable to polymer gel electrolytes. The high conductivity is only observed above a phase transition temperature that is outside of the useful operating range, but doping the material with various substitutions for the Li or BH$_4$ units can bring the phase transition below room temperature. Both smaller and larger substituting species can stabilize the high T structure, indicating that it is not a simple volume effect. We show that variable-cell-shape molecular-dynamics simulations using density functional theory forces and stresses reproduce the structural phase transition. Using umbrella integration to compute the free energy differences between the two structures, we calculate the phase transition temperature and its dependence on substitutional I, Cl, and Na concentrations, and show that they are in very good agreement with experiment. We calculate the effect of K substitution, and predict that it will be even more effective at stabilizing the high T structure. Decomposing the free energy difference changes into enthalpy and entropy contributions shows that the mechanis [Preview Abstract] |
Tuesday, March 4, 2014 9:36AM - 9:48AM |
F25.00007: Determination of Raman Spectrum of Li$_{28}$La$_{12}$Zr$_{8}$O$_{48}$ as a Function of Dopant Saikat Mukhopadhyay, Travis Thompson, Jeff Sakamoto, Michelle Johannes, Derek Stewart Li$_{28}$La$_{12}$Zr$_{8}$O$_{48}$ is a supervalent conductor with a low conductivity tetragonal phase and a high conductivity cubic phase, making it a strong candidate as a practical Li ion rechargeable battery solid electrolyte. The high conductivity phase can be stabilized via supervalent doping that drives Li$^{+}$ ions out of the lattice, creating vacancies that both relieve the necessity for Li sublattice ordering and provide easier pathways for ionic conduction. The conductivity strongly depends on both doping concentration and site preference. Ta$^{5+}$ has been suggested as an optimal dopant as it likely substitutes for Zr$^{4+}$, thereby leaving the Li sublattice undisturbed. However, it is difficult to accurately establish the actual, as compared to nominal, amount of Ta doped into the lattice which, in turn, determines the vacancy concentration and conductivity. In this talk, we will present the variation of Raman intensities of LLZO as a function of Ta concentration to determine the role of dopant and vacancies in deciding measured Raman intensities via first principles calculations based on Density Functional Theory. A direct comparison of calculated and measured Raman spectrum may provide a definitive measure of vacancy concentration. [Preview Abstract] |
Tuesday, March 4, 2014 9:48AM - 10:00AM |
F25.00008: First principles modeling of interfaces of lithium (thio) phosphate solid electrolytes and lithium metal anodes N.A.W. Holzwarth, N.D. Lepley, A.N.M. Al-Qawasmeh, C.M. Kates Computer modeling studies show that while lithium phosphate electrolytes form stable interfaces with lithium metal anodes, lithium thiophosphate electrolytes are typically structurally and chemically altered by the presence of lithium metal. On the other hand, experiments have shown\footnote{Z. Liu, W. Fu, {\em{et. al.}}, {\bf{\em{J. Am. Chem. Soc.}}} {\bf{135}} 975-978, (2013).} that an electrochemical cell of Li/Li$_3$PS$_4$/Li can be cycled many times. One possible explanation of the apparent experimental stability of the Li/Li$_3$PS$_4$/Li system is that a stabilizing buffer layer is formed at the interface during the first few electrochemical cycles. In order to computationally explore this possibility, we examined the influence of ``thin film'' buffer layers of Li$_2$S on the surface of the electrolyte. Using first principles techniques,\footnote{N. D. Lepley, N. A. W. Holzwarth, Y. A. Du, {\bf{\em{Phys. Rev. B}}} {\bf 88}, 104103 (2013).} stable electrolyte-buffer layer configurations were constructed and the resulting Li$_3$PS$_4$/Li$_2$S and Li$_2$S/Li interfaces were found to be structurally and chemically stable. [Preview Abstract] |
Tuesday, March 4, 2014 10:00AM - 10:12AM |
F25.00009: Mechanisms of dendrite formation in Lithium Ion Batteries Ning Sun, Dilip Gersappe The formation of dendrite on the anode of Lithium-Ion Batteries during charging process can compromise the safety of the battery. By using a Lattice Boltzmann Method we simulated the mechanisms of dendrite formation. We postulated a way to monitor the growth of dendrites by recording the rate of change of the surface area of anode. Our results showed that the onset of dendrite will happen after the Sand's time when the current density is larger than a critical value. We also show that the Sands time is affected by the local curvature, particularly at low current densities. We also find that the roughness of the anode influences dendrite formation only when current density is not very high (around the critical current density). Our results show that it is possible to~suppress the growth of dendrites by~applying pulses during the charging process if the frequency of the pulse is chosen properly. Our model is able to study the discharge process as well, and we find that during the cycling process, high aspect ratio regions formed during charging, might break off from anode during discharging, and the anode surface will get rougher and rougher during the cyclic process, thus possibly increasing the propensity to form dendrites. [Preview Abstract] |
Tuesday, March 4, 2014 10:12AM - 10:24AM |
F25.00010: Lithium Ion Solvation and Diffusion in Bulk Organic Battery Electrolytes from First Principles Molecular Dynamics Mitchell Ong, Vincenzo Lordi, Erik Draeger, John Pask Lithium-ion batteries are commonly used to power many consumer devices. One of the key properties that influence the performance of lithium-ion batteries is the ionic conductivity of the electrolyte. This is dependent on the speed at which Li ions diffuse across the cell and related to the solvation structure of the Li ions. The choice of the electrolyte can greatly impact both solvation and diffusivity of Li ions. In this work, we use first principles molecular dynamics to examine the solvation and diffusion of Li ions in several bulk organic electrolytes. We find that differences in the local environment throughout the liquid can lead to solvation of Li ions by either carbonyl or ether oxygen atoms. In addition, we examine the differences in solvation of associated and dissociated Li(PF$_{6})$ salts, showing that the bulky PF$_{6}$ group blocks complete solvation of Li$^{+}$ by solvent oxygen atoms. Finally, we calculate Li diffusion coefficients in each electrolyte, finding slightly larger diffusivities in a linear carbonate such as ethyl methyl carbonate (EMC) compared to a cyclic carbonate like ethylene carbonate (EC). Results from this work can be used to design new bulk electrolytes that will improve the performance of current Li-ion batteries. [Preview Abstract] |
Tuesday, March 4, 2014 10:24AM - 10:36AM |
F25.00011: First-principles estimates of free energy barriers for Mg desolvation and intercalation at electrolyte/electrode interfaces Liwen Wan, David Prendergast There is a growing interest in developing multivalent ion batteries that could, in principle, double or triple the energy density compared to the monovalent Li-ion batteries. However, the strong electrostatic interaction caused by the extra charge also makes it very challenging to find appropriate intercalation compounds that allow for relatively fast and reversible ion transport. An established working multivalent battery is comprised of Mg(AlCl2BuEt)2 salts in THF solution as the electrolyte, and Mg metal and Mo6S8 Chevrel phase as the anode and cathode, respectively. Currently, we lack a clear understanding of the mechanism for Mg desolvation and intercalation at the interface between the electrolyte and Chevrel phase surfaces, which is critical in designing new advanced battery systems with improved ion diffusion rate. Here, we present a theoretical investigation of the dynamics and kinetics of the Mg desolvation/intercalation process. The surface properties of Mo6S8 are studied for the first time using density functional theory (DFT) and its interaction with the electrolyte is simulated via an ab initio molecular dynamics (AIMD) approach. The free energy barrier for Mg diffusing through the interface is then calculated by performing a set of biased AIMD simulations. [Preview Abstract] |
Tuesday, March 4, 2014 10:36AM - 10:48AM |
F25.00012: Investigation of the Silicon Solid Electrolyte Interface in Lithium Ion Batteries using the Technique of Hard X-Ray Photoelectron Spectroscopy Benjamin Young, David Heskett, Mengyun Nie, Brett Lucht, Joseph Woicik Formation of a stable Solid Electrolyte Interface (SEI) between the anode and electrolyte material of a lithium ion battery (LIB) is essential to battery performance. Silicon anodes represent a theoretical tenfold increase in energy density over more thoroughly investigated carbonaceous anodes, but experience large volume changes during normal cycling which represents a challenge to stable SEI formation. Overcoming this challenge demands more thorough understanding of SEI formation which can be achieved through the technique of Hard X-ray Photoemission Spectroscopy (HAXPES). This work is focused on addition of ethylene carbonate (EC) and fluoroethylene carbonate (FEC) solvents to the base electrolyte LiPF$_{\mathrm{6}}$ material in coin cell LIBs using binder-free silicon nanoparticle anodes. The results of HAXPES experiments carried out at beamline X24-A of the National Synchrotron Light Source at Brookhaven National Laboratory are presented, revealing depth dependent composition information at various points of SEI development. [Preview Abstract] |
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