Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session E20: Energy Storage: Mn-based CathodesFocus
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Sponsoring Units: GERA Chair: Y. Shirley Meng, University of California San Diego Room: LACC 308B |
Tuesday, March 6, 2018 8:00AM - 8:36AM |
E20.00001: In Situ Characterization of Battery Materials using X-ray Absorption Spectroscopy Invited Speaker: Carlo Segre X-ray absorption spectroscopy using synchrotron radiation has become an essential tool for operando studies of batteries where nanoparticles and amorphous materials preclude the use diffraction to study structural changes. The ability to take full data sets in only a few minutes is well-matched to typical time scales of battery charge and discharge cycles for in situ and operando experiments. I will briefly discuss the fundamentals of x-ray absorption spectroscopy and present our recent results on a novel, high cycling performance, Sn4P3/graphite composite anode material for lithium ion batteries using the MRCAT beamlines at the Advanced Photon Source. |
Tuesday, March 6, 2018 8:36AM - 8:48AM |
E20.00002: In Situ Scanning Probe Microscopy of MnO2 Cathodes for Li-Ion Batteries Mina Baghgar Bostan Abad, Tetyana Ignatova, Mackenzie Turvey, Philip Collins Designing the next generation of high performance energy storage devices requires a deeper understanding of structural degradation. To this end, a wide variety of scanning probe microscopy techniques can help characterize charge transport and aging mechanisms in Li-ion batteries and supercapacitors. We use in-situ probe microscopy and Kelvin probe force microscopy (KPFM) to investigate the mechanical and potentiostatic changes in MnO2 cathodes as they undergo charge cycling. Topography monitors mechanical expansion during charging, and the dependence of expansion on scan rate reveals the separate roles of Mn3+/4+ pseudocapacitance and faster surface double-layer capacitance. KPFM observes the evolution of surface potentials with lateral resolution as low as 40 nm, at which scale inhomogeneous lithiation is observed as a highly nonuniform, fractal growth or shrinkage of Mn3+ and Mn4+ phases. Via surface potential, KPFM reveals “dead” zones that do not participate in charging, the “hot” zones that charge or discharge most readily, and the evolution of each type as an electrode is repeatedly cycled. |
Tuesday, March 6, 2018 8:48AM - 9:00AM |
E20.00003: Density functional theory modeling of MnO2 polymorphs as multivalent cathode materials Taylor Juran, Joshua Young, Manuel Smeu Multivalent ion batteries (MVIBs) provide an energy dense alternative to Li-ion batteries (LIBs). While MVIBs are not competitive for use in portable devices, they are a desirable alternative to LIBs for large-scale applications such as grid storage. MnO2 polymorphs are a popular choice for MVIB cathodes; they offer a high voltage and capacity, as well as structural versatility. Many of the polymorphs are abundant and consequently inexpensive. While several MVIB studies with MnO2 polymorphs as the cathode material exist, only Mg and Zn were chosen as the primary intercalation agents. Here, we computationally investigate several MnO2 polymorphs as cathode materials, and the resulting properties upon their intercalation with ions from several multivalent metal anodes (Mg, Ca, Zn, Al), as well as Li for comparison. We use the SCAN functional, to calculate the average voltages for each MnO2 polymorph upon intercalation with the ions listed above. We also investigate volume change and energy barriers associated with diffusion of those ions in the cathode materials. |
Tuesday, March 6, 2018 9:00AM - 9:12AM |
E20.00004: Hydrogen-assisted manganese migration in NaMnO2 Zhen Zhu, Hartwin Peelaers, Chris Van de Walle We investigate the structure and energetics of point defects in layered NaMnO2. Our study is aimed at elucidating potential degradation mechanisms when the material is used as a positive electrode in Na-ion rechargeable batteries. Hydrogen has been implicated in this process. Using hybrid density functional theory, we find that hydrogen interstitials and Na vacancies have low formation energies and moderate migration barriers, and the proton/Na+ exchange process can proceed with fast kinetics. Degradation occurs when Mn moves to an antisite position, where it migrates with a low barrier of 0.18 eV. In the absence of hydrogen, formation of MnNa antisites is suppressed due to the high energy of the VMn it leaves behind, and due to the large interlayer-migration barrier for Mn. But when hydrogen is present, VMn is stabilized by forming VMn-3H complexes; in addition, the interlayer-migration barrier for Mn is substantially reduced from 1.48 eV to as low as 0.20 eV in the presence of hydrogen interstitials. Therefore, with the assistance of hydrogen, the formation of MnNa antisites becomes thermodynamically favorable and kinetically allowed, which eventually leads to loss of Mn2+. |
Tuesday, March 6, 2018 9:12AM - 9:24AM |
E20.00005: Discharge Mechanism of the γ-MnO2 Electrode in Shallow-Cycled Zn/MnO2 Batteries: An Ab Initio Study Birendra Ale Magar, Timothy Lambert, Jonathon Duay, Babu Chalamala, Igor Vasiliev Alkaline Zn/MnO2 batteries hold great promise for electrical energy storage due to their high energy density, non-toxicity, and low cost. At a low depth of discharge, the reduction reaction in the Zn/MnO2 battery cathode is governed by hydrogen trapping in the solid phase of γ-MnO2. We applied ab initio computational methods based on density functional theory to study the mechanism of hydrogen insertion into the pyrolusite and ramsdellite tunnels of γ-MnO2. Our calculations were carried out using the Quantum ESPRESSO electronic structure code combined with Vanderbilt ultrasoft pseudopotentials. We found that the trapped hydrogen initially occupied the 2x1 ramsdellite tunnels of γ-MnO2. Our study showed that the insertion of hydrogen into the 1x1 pyrolusite tunnels induced significant structural distortions leading to the breakdown of the crystal structure of γ-MnO2. These results could explain the presence of groutite and the absence of manganite among the reaction products of partially reduced γ-MnO2. |
Tuesday, March 6, 2018 9:24AM - 9:36AM |
E20.00006: Modeling Diffusion-Induced Stress In Li-Mn-O Nanocomposite Cathode Materials Raesibe Sylvia Ledwaba, Phuti Ngoepe, Dean Sayle We employ molecular dynamics methods to simulate spontaneously growth [1], visualize and characterize the evolution of mechanical degradation in layered-spinel Li-Mn-O composite electrode materials, applicable in next-generation application in high energy density lithium ion batteries [2]. When compressive stress was imposed on the nanoporous and bulk materials, the composite nanoporous revealed structural resilience enable by flexing of the pore. This allows it to mitigate the effect of stress by expanding or contracting into the void/channel space of the material, whilst diffusion paths within the bulk were vastly blocked by tetrahedral manganese (Mn2+) due to structural collapse induced by diffusion. The stress-strain curves depicted yield stress of 11.35 GPa for bulk whilst nanoporous materials experienced lower stress of 4.32 GPa when subjected to equivalent strain. |
Tuesday, March 6, 2018 9:36AM - 9:48AM |
E20.00007: Magnetic Compton scattering study of LixMn2O4 battery material at the Verwey transition Hasnain Hafiz, Kosuke Suzuki, Bernardo Barbiellini, Yuki Orikasa, Vincent Callewaert, Staszek Kaprzyk, Masayoshi Itou, Kentaro Yamamoto, Ryota Yamada, Yoshiharu Uchimoto, Yoshiharu Sakurai, Hiroshi Sakurai, Arun Bansil We discuss magnetic Compton scattering spectra and parallel calculations for interpreting these spectra from the Spinel LixMn2O4 (LMO). Due to its high redox voltage (~ 4.5 V) and lower cost compared to lithiated Co and Ni oxides, LMO is one of the leading candidates for next generation Li-ion battery cathodes. LMO has a mixed-valence Mn3+/Mn4+ state with a strong magnetic Jahn-Teller (J-T) effect. The high temperature phase is cubic with a random distribution of Mn3+/ Mn4+ ions. However, because of J-T distortion, LMO undergoes a structural transition from cubic to orthorhombic around 280K with charge and orbital ordering of Mn3+/ Mn4+ ions. This structural transition known as the Verwey transition plays an important role in the functioning of the LMO cathode. Our x-ray magnetic Compton spectra allow a faithful reconstruction of the redox orbitals at the Verwey transition, and our analysis gives insight into the interplay between effects of J-T distortion, charge and spin ordering, and the mechanism of LMO cathode degradation at the Verwey transition. |
Tuesday, March 6, 2018 9:48AM - 10:00AM |
E20.00008: Computational Predictions of NMC Cathode Materials Gregory Houchins, Venkat Viswanathan One of the most commercially successful Li-ion battery cathodes, LiMO2 (M=Ni,Mn,Co mixtures) has continued to be of interest to many as more of the possibly infinite combinations are tested. Yet there are still very few known phases. In this work, we attempt to explore the full ternary phase diagram through high throughput computation. A set of training data is generated from first principles using Density Functional Theory. The data is then used to train a reduced order model that is then solve in high resolution with Monte Carlo Simulations and ultimately generates a convex hull of stable maxtures. From this we can theoretically predict a collection of properties that will identify a set of promising new materials for experimental testing. |
Tuesday, March 6, 2018 10:00AM - 10:12AM |
E20.00009: Probing Oxygen Activity in Li-Rich Cathodes with Core-Level Spectroscopy Liang Li, Eungje Lee, John Freeland, John Vinson, Eric Shirley, Michael Thackeray, Maria Chan It is commonly recognized that utilization of oxygen redox is an intriguing route for obtaining higher capacity in Li-ion batteries (LIBs). Despite numerous experimental and theoretical studies attempting to unravel the electronic origin of oxygen redox behavior, whether the oxidation of oxygen occurs via the formation peroxo-like species or depletion of electrons from the non-bonding states is still, however, an open question, and it is unclear how the electron-depleted oxygen states manifest themselves under spectroscopic observations. In this study, using the Li-rich Li5FeO4 as a model system, we performed ab-initio Molecular Dynamics (AIMD) simulations to investigate the structural response of oxygen matrix to delithiation. The oxygen K-edge X-ray absorption near-edge spectra (XANES) were modeled using Bethe-Salpethe Equation (BSE) approach and compared with experiments, from which the oxygen redox mechanism is uncovered. |
Tuesday, March 6, 2018 10:12AM - 10:24AM |
E20.00010: Advanced spectroscopic characterization of olivine Lithium battery materials using x-ray Compton scattering Bernardo Barbiellini, Hasnain Hafiz, Kosuke Suzuki, Yuki Orikasa, Vincent Callewaert, Staszek Kaprzyk, Masayoshi Itou, Kentaro Yamamoto, Ryota Yamada, Yoshiharu Uchimoto, Yoshiharu Sakurai, Hiroshi Sakurai, Arun Bansil In order to develop advanced spectroscopic tools for characterizing battery materials, we consider x-ray Compton scattering spectra along with parallel first-principles computations from lithium iron phosphate (LFP) as an exemplar lithium-ion battery cathode material [1]. Visualization of the redox orbitals in momentum and real spaces reveals relationships between wave function localization, bonding properties, voltage and energy density of the battery. Insight is obtained, in particular, into how voltage shift is connected with the modification of the bond between the transition metal and oxygen atoms in the cathode material. We also discuss effects of substituting Fe atoms in LFP with other transition metals such as Mn, Co and Ni as a pathway toward improving the limited energy density of LFP. |
Tuesday, March 6, 2018 10:24AM - 10:36AM |
E20.00011: Prediction of Optimal Crystal Water Concentration for Maximized Performance in Transition-Metal Oxide Electrodes Nathan Frey, Bryan Byles, Hemant Kumar, Dequan Er, Ekaterina Pomerantseva, Vivek Shenoy Crystal water has been shown to stabilize next-generation energy storage electrodes with structural tunnels to accommodate cation intercalation, but the stabilization mechanism is poorly understood. In this study, we present a simple physical model to explain the energetics of interactions between electrochemically cycled ions, structural water, and the electrode crystal lattice. Our model is applied to understand the effects of crystal water on sodium ion intercalation in a tunnel manganese oxide structure, and we predict that precisely controlling the crystal water concentration can optimize the ion intercalation voltage and capacity, and promote stable cycling. The analysis yields a critical structural water concentration by accounting for the interplay between elastic and electrostatic contributions to the free energy. Our predictions are validated with electrochemical measurements and first-principles calculations. The theoretical framework used here can be extended to predict critical concentrations of stabilizing molecules to optimize performance in next-generation battery materials. |
Tuesday, March 6, 2018 10:36AM - 10:48AM |
E20.00012: Transition Metal Segregation and Phase Transformations on the Surfaces of Layered Li(Ni1-x-yMnxCoy)O2 (NMC) Cathode Materials for Li-ion Batteries Juan Garcia, Marton Voeroes, Guoying Chen, Hakim Iddir Layered Li(Ni1-x-yMnxCoy)O2 (NMC) oxides are promising cathode materials capable of addressing some of the challenges associated with next-generation energy storage devices. In particular, improved energy densities, longer cycle-life, and improved safety characteristics with respect to current technologies are needed. However, transformations taking place in the positive electrodes of battery cells decrease electrochemical performance. For instance, the segregation of transition metals from the bulk to the surface of cathode particles plays a critical role in the formation of surface reconstruction layers (SRLs). Such layers are thought to decrease the performance of batteries by, for example, impeding the diffusion of lithium during charge and discharge. A preferential segregation of Ni and Co to specific facets of as-prepared, pristine NMC materials has been found previously. This presentation will discuss recent results of a computational analysis of segregation and phase transformation processes using Density Functional Theory (DFT). A discussion on the thermodynamics that govern such processes will be given. |
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