Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session Y4: Materials for Electrochemical Energy Storage II |
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Sponsoring Units: GERA DMP FIAP Room: Mayor Cockrell Room 004 |
Friday, March 6, 2015 8:00AM - 8:36AM |
Y4.00001: First-principles molecular dynamics simulations of electrochemical reaction s using the ESM method Invited Speaker: Minoru Otani It is important to elucidate a microscopic detail of an electrochemical reaction that takes place at the electrode and electrolyte interface to improve the performance of electrochemical energy storage/harvesting devices, such as secondary batteries, capacitors, fuel cells, and photovoltaic cells. Major difficulties for understanding the reaction are how to incorporate and control the bias potential applied to the interface. To solve these difficulties, we have been developing some intuitive methods to simulate the interfacial electrochemical reaction using first-principles molecular dynamics simulations [1-3]. In this talk I will present our methods and show the bias dependent free-energy profile of the desolvation process of a Li-ion battery and other recent results.\\[4pt] [1] M. Otani and O. Sugino, Phys. Rev. B 73, 115407 (2006).\\[0pt] [2] N. Bonnet, T. Morishita, O. Sugino, and M. Otani, Phys. Rev. Lett. 109, 266101 (2012)\\[0pt] [3] I. Hamada, O. Sugino, N. Bonnet, and M. Otani, Phys. Rev. B 88, 155427 (2013). [Preview Abstract] |
Friday, March 6, 2015 8:36AM - 8:48AM |
Y4.00002: Ab-Initio Molecular Dynamics Study of the Concentration Dependent Diffusivity of Lithium Ions in Acetonitrile Electrolyte using the van der Waals Density Functional Keith Ray, Zhenxing Wang, Isaak Daniels, David Olmsted, Brian Laird, Mark Asta Pseudocapacitors are devices that store electrical energy faradaically, but feature fast reactions/intercalations enabling high power applications. Power density may be improved by utilizing electrolytes with fast Li ion diffusion. In this study we utilize ab-initio molecular dynamics to elucidate the solvation structure as well as the vibrational and diffusion dynamics of Li ions in the acetonitrile electrolyte. Acetonitrile is a promising electrolyte for energy storage applications due to its lower viscosity and higher ionic conductivity when compared to other battery electrolytes such as ethylene carbonate and propylene carbonate. Interestingly, the trends in the Li ion concentration dependent diffusivity are calculated to be qualitatively different depending on whether the PBE or vdW-DF density functional is used. [Preview Abstract] |
Friday, March 6, 2015 8:48AM - 9:00AM |
Y4.00003: A joint \emph{first principles} and ATR-IR study of the vibrational properties of interfacial water at Si(100):H-H$_2$O solid-liquid interfaces Lei Yang, Stefanie Tecklenburg, Andreas Erbe, Stefan Wippermann, Francois Gygi, Giulia Galli Understanding the structural and bonding properties of solid-liquid interfaces is crucial for a wide range of (photo-)electrochemical applications, such as e. g. solar water splitting and electrolysis. However, there are no experimental techniques presently available allowing one to directly probe the microscopic structure of solid-liquid interfaces. We present a joint investigation of the vibrational properties of interfaces between liquid water and prototypical semiconductor substrates, i.e. hydrogenated silicon surfaces. We carried out attenuated total internal reflection (ATR-IR) spectroscopy measurements and \emph{ab initio} molecular dynamics simulations. The latter allowed us to interpret the experiments and to unravel specific bonding configurations and interactions of water molecules with the solid surfaces. Our study highlights the key role of coupled theory-experimental investigations on well controlled and characterized interfaces, in order to develop robust strategies to interpret experiments and validate theory. [Preview Abstract] |
Friday, March 6, 2015 9:00AM - 9:12AM |
Y4.00004: High ionic conductivity NASICON based materials for Na-ion batteries: a density functional approach K. M. Bui, V. A. Dinh, S. Okada, T. Ohno Sodium ion batteries are now believed to~be the best candidate for large-scale~applications. Simultaneously, it is required to develop solid-state~batteries using solid electrolytes for advancing the safety and reliability~of batteries. The most promising solid-state battery is composed of the~3-D NASICON electrode~Na$_{\mathrm{3}}$V$_{\mathrm{2}}$(PO$_{\mathrm{4}})_{\mathrm{3}}$~(NVP) and electrolyte~Na$_{\mathrm{3}}$Zr$_{\mathrm{2}}$Si$_{\mathrm{2}}$PO$_{\mathrm{12\thinspace }}$(NZSP). In this~work, we aim to theoretically investigate the structures and the diffusion pathway of Na in these~materials. Using density functional theory (DFT) method, we investigated the structures and diffusion mechanism of Na ions in the materials. They are~insulators with large band. The polaron formation is found to occur only in NVP. Na ions can diffuse along three preferable~diffusion pathways; those are, two intra-layer and one~inter-layer pathway that takes place between Na layers via the empty Na~site. In accordance with experiments reported before, the materials~have high ionic conductivity with the activation barrier of about 760meV and~370meV for NVP and NZSP, respectively.~ \newline [Preview Abstract] |
Friday, March 6, 2015 9:12AM - 9:24AM |
Y4.00005: Quasielastic neutron backscattering studies of Li-ion dynamics in Li$_{2}$SO$_{4}$ substituted lithium modified phosphate glasses Tom Heitmann, Gavin Hester, Madhu Tyagi, Munesh Rathore, Anshuman Dalvi, Saibal Mitra A solid with high Li ionic conductivity and a simultaneously low electronic conductivity is an attractive candidate for use as an electrolyte in an all solid-state Li ion battery. Solid state electrolytes would not only improve the reliability, safety, and the ability of the battery to be operated in harsher conditions, but also allow to be scaled for heavy duty industrial applications. We have studied a series of glassy electrolyte candidate materials using neutron scattering as a probe. Neutron backscattering spectroscopy is a useful probe of Li ion dynamics because their diffusion dynamics occur on the same timescales to which backscattering is sensitive and because neutrons are sensitive to nuclei and not electrons. Thus, the observed Li dynamics are naturally separated from any electronic motions. Our materials of interest are lithium modified phosphate glasses with a range of Li$_{2}$SO$_{4}$ substitution amounts: xLi$_{2}$SO$_{4}\cdot $(1-x)[0.5Li$_{2}$O$\cdot $0.5P$_{2}$O$_{5}$], x$=$0.0 to 0.6. We demonstrate an enhancement of the Li ion diffusion as a function of Li$_{2}$SO$_{4}$ content via quasielastic neutron scattering performed on the High Flux Backscattering Spectrometer at the NIST Center for Neutron Scattering. [Preview Abstract] |
Friday, March 6, 2015 9:24AM - 9:36AM |
Y4.00006: X-ray Scattering Studies of Ionic Liquid Structure and Dynamics at Charged Graphene Interface Ahmet Uysal, Sang Soo Lee, Hua Zhou, Paul Fenter, Pengfei Zhang, Sheng Dai Room temperature ionic liquids (RTILs) are promising electrolytes for energy storage systems, especially for supercapacitors. However, our knowledge of these highly dense ionic plasmas at electrified interfaces is still at its infancy due to the lack of \textit{in situ} experimental data about their potential-dependent electric double layer (EDL) structures and dynamics. In particular, the behavior of mixed electrolytes (RTIL/RTIL and Solvent/RTIL), which are significantly important for practical applications, have been little studied with structural probes. We use \textit{in situ}, real-time X-ray reflectivity to elucidate the role of different anion-cation combinations and solvents on the interfacial ionic liquid structure and dynamics at epitaxial graphene electrode during cyclic voltammetry and potential steps. Our results give direct information about the EDL structure and response, which helps us to connect the macroscopic system properties to the nanoscale structure. [Preview Abstract] |
Friday, March 6, 2015 9:36AM - 9:48AM |
Y4.00007: The Electronic Structures and Diffusion Kinetics of Li, Na, and Mg Intercalated TiO$_{2}$ Anatase and TiO$_{2}$ (B) Handan Yildirim, Jeffrey P. Greeley Large-scale electrochemical storage that would allow wider use of renewable electricity not only requires new and advanced electrode materials for Li ion batteries, but also beyond-Li technologies such as Na and Mg ion batteries. This grand challenge puts forward the necessity for designing efficient electrode materials providing suitable energetics and rapid diffusion kinetics. In this contribution, we evaluate TiO$_{2}$ anatase and TiO$_{2}$ (B) as attractive candidates for anodes in Li, Na, and Mg batteries due to their low cost, non-toxicity, cycling stability, reasonable capacity, and high operating potential. While the TiO$_{2}$ anatase is discussed as promising material for Li storage, structurally, TiO$_{2\, }$(B) with large interlayer spacing can be considered as a good electro-active material for Na intercalation. We will report the results of the first principles calculations using generalized gradient approximation (GGA) for Li, Na, and Mg intercalation at low concentration. The differences in the electronic and atomic structures obtained using GGA, Hubbard ``$+$U'' correction (GGA$+$U), and Heyd, Scuseria, and Ernzerhof (HSE) hybrid functional will be reported, and the importance of the ``$+$U'' correction for modeling the electronic structure of the intercalated TiO$_{2\, }$will be discussed. The detailed information on the differences in the diffusion mechanisms and barriers will also be reported for each ion in both structures. [Preview Abstract] |
Friday, March 6, 2015 9:48AM - 10:00AM |
Y4.00008: Joint Density-Functional Theory for Atomically Detailed Structure of the Electrode/Electrolyte Interface Kendra Letchworth-Weaver, Christine Umbright, Ravishankar Sundararaman, T.A. Arias Understanding the complex and inherently multi-scale interface between a charged electrode surface and a fluid electrolyte would inform design of more efficient and less costly electrochemical energy storage and conversion devices. Joint density-functional theory (JDFT) bridges the relevant length-scales by joining a fully {\it ab initio} description of the electrode with a highly efficient, yet atomically detailed classical DFT description of the liquid electrolyte structure. First, we introduce a universal functional to couple any quantum-mechanical solute system with a classical DFT for any liquid. This universal coupling functional captures aqueous and non-aqeuous solvation free energies of small molecules with a mean absolute error of only 1-2 kcal/mol. We also present classical density-functionals for ionic species which reproduce the key features of ion-water correlation functions when combined in a mixture with existing functionals for water. Leveraging the above theoretical innovations and our framework to treat charged systems in periodic boundary conditions, we then predict the voltage-dependent structure and energetics of solvated ions at the interface between a graphene electrode and an aqueous electrolyte. [Preview Abstract] |
Friday, March 6, 2015 10:00AM - 10:12AM |
Y4.00009: Ab Initio Electrochemical Capacitance Studies of Supercapacitor Materials in Aqueous and Non-Aqueous Electrolytes Christine Umbright, Kendra Letchworth-Weaver, T.A. Arias Novel electrical energy storage devices are becoming increasingly necessary as technological advances demand higher energy capacity and more efficient methods of charging. \textit{Ab initio} Joint Density-Functional Theory (JDFT) allows for the simultaneous study of electrodes, electrolytes, and their interactions in a uniform, comprehensive way. In this work, JDFT is utilized to study the energy storage capabilities of supercapacitor materials, such as graphene. The unique electronic structure of graphene results in a heightened influence of fluid capacitance on the total capacitance of the electrode. Confinement effects on capacitance are also investigated, as JDFT allows for prediction of ion structuring within the fluid. This research hopes to further the understanding of electrochemical systems for use in future energy storage solutions. [Preview Abstract] |
Friday, March 6, 2015 10:12AM - 10:24AM |
Y4.00010: Thermodynamics of alloyed nanoparticles for hydrogen evolution reaction including configurational and adsorbate effects Lin-Lin Wang, Teck L. Tan, Duane D. Johnson Changes in the chemical configuration of alloyed nanoparticle (NP) catalysts induced by adsorbates under working conditions are crucial to understand and design NP functionality. We extend the cluster expansion method to predict the configurational thermodynamics of alloyed NPs on equal footing with adsorbate thermodynamics based on density functional theory data. Exemplified with alloyed PdPt NPs having H-coverage up to a full layer, we describe both the configurational and adsorbate thermodynamics behavior simultaneously across the entire range of NP composition and H-coverage to obtain the H-adsorption isotherms and simulated cyclic voltammetry for hydrogen evolution reaction. [Preview Abstract] |
Friday, March 6, 2015 10:24AM - 10:36AM |
Y4.00011: Self-consistent continuum solvation (SCCS): Towards the accurate modeling of electrochemical systems in plane-wave DFT Stephen Weitzner, Ismaila Dabo Implicit solvent models have been widely used to study quantum systems in solutions. Nevertheless, these models differ greatly in their phenomenological details and in the complexity of their parameterization. While conventional implicit models rely on atomic positions and tabulated atomic radii to construct the solvation shell that surrounds the quantum solute, recent models aim to reduce the number of parameters by building solvation shells directly from computed electronic densities. The self-consistent continuum solvation (SCCS) model, which belongs to the latter class, has been shown to reproduce the solvation energies of a wide range of molecular species in good agreement with experiment, using only two fitted parameters [J. Chem. Phys. 136, 064102 (2012)]. Here, we report on the SCCS model's performance in describing the electrical properties of quantum electrodes embedded in continuum electrolytes. We show that one additional parameter is needed to capture experimental shifts in the neutral electrode potential as a function of surface composition and structure, and to correctly calibrate computed results to a common electrochemical reference. Utilizing this approach, we establish a novel framework for studying interfacial electrochemical phenomena. [Preview Abstract] |
Friday, March 6, 2015 10:36AM - 10:48AM |
Y4.00012: Fast motif-network scheme for extensive exploration of complex crystal structures in silicate cathodes Kai-Ming Ho, Xin Zhao, Shunqing Wu, Xiaobao Lv, Manh Cuong Nguyen, Cai-Zhuang Wang, Zijing Lin, Zi-Zhong Zhu A motif-network search scheme is proposed to study the crystal structures of the dilithium/disodium transition metal orthosilicates A$_{2}$MSiO$_{4}$. Using this fast and efficient method, the structures of all six combinations with A $=$ Li or Na and M $=$ Mn, Fe or Co were extensively explored in this work. In addition to finding all previously reported experimental structures, we discover many other different crystal structures which are highly degenerate in energy. These tetrahedral-network-based structures can be classified into 1D, 2D and 3D types. A clear trend of the structural preference in different systems is revealed and possible indicators that affect the structure stabilities are introduced. For the case of Na systems which have been much less investigated in the literature relative to the Li systems, we predicted their ground state structures and found evidence for the existence of new structural motifs. [Preview Abstract] |
Friday, March 6, 2015 10:48AM - 11:00AM |
Y4.00013: Comparison of electrochemical activity in nanoporous and bulk $\beta $-MnO$_{2}$ Phuti Ngoepe, Thi Sayle, Dean Sayle Simulated amorphisation recrystallisation method has been successfully used to nucleate and crystallise bulk [1] and nanoporous $\beta $-MnO$_{2}$ [2]. In the current study molecular dynamics simulation reveals that the reason nanoporous $\beta $-MnO$_{2}$ is electrochemically active, in contrast to the parent bulk material, is because strain imposed upon nanoporous $\beta $-MnO$_{2}$ during lithium intercalation does not influence the structure or dimensions of the 1D tunnels in which the lithium ions intercalate and reside. Conversely, the parent bulk material suffers structural collapse of the 1D tunnels under strain.\\[4pt] [1] T.X.T. Sayle, C.R.A. Catlow, R.R. Maphanga, P.E. Ngoepe and D.C. Sayle, \textit{J. Crystal Growth}, \textbf{294},118-129, 2006.\\[0pt] [2] T.X.T. Sayle, R.R. Maphanga, P.E. Ngoepe and D.C. Sayle, \textit{J. American Chem. Soc.}, \textbf{131}, 6161-6173, 2009. [Preview Abstract] |
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