Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session F38: Energy Storage: Ionic Conductors, Electrolyte, Electrolyte Interfaces |
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Sponsoring Units: GERA Chair: Michelle Johannes, NRL Room: 385 |
Tuesday, March 14, 2017 11:15AM - 11:27AM |
F38.00001: Cluster-inspired Superionic Conductors Hong Fang, Puru Jena Superionic conductors with desirable properties hold the key to the development of next generation of rechargeable metal-ion batteries. In this study, we report a new family of superionic conductors composed by clusters based on the antiperovskite fast-ion conductors. The new lightweight conductor shows larger electrochemical stability window and favorable thermal and mechanical properties, while maintain a high~Li$^{\mathrm{+}}$-ionconductivity~at room temperature and a low activation energy. We reveal the conduction mechanism of the material by identifying the relation between the orientational symmetry of the cluster rotors and the potential surface felt by the lithium ion. We also find that the mixed phase of the new conductors show further enhanced conductivity. [Preview Abstract] |
Tuesday, March 14, 2017 11:27AM - 11:39AM |
F38.00002: Rb$_{\mathrm{2}}$Ti$_{\mathrm{2}}$O$_{\mathrm{5}}$ a new superionic conductor remi federicci, brigitte leridon, stephane hole, benoit baptiste, florin popa, luc brohan Rb$_{\mathrm{2}}$Ti$_{\mathrm{2}}$O$_{\mathrm{5}}$ is a layered material that crystallizes in the space group C2/m and whose titanium atoms present the exceptional 5-coordinence. We will demonstrate remarkable highly non linear transport properties in this compound together with colossal relative dielectric constant values (10$^{\mathrm{8}})$ and huge polarizations (0.1 C.cm$^{\mathrm{-2}})$ between 200K and 330K. We will show that the mechanism at play in this material can not be conventional ferroelectricity caused by a structural phase transition. We will show instead that the electrical transport properties of Rb$_{\mathrm{2}}$Ti$_{\mathrm{2}}$O$_{\mathrm{5}}$ can be explained by electromigration of some ionic species within the material creating charge accumulation at the edges of the material. This solid electrolyte is therefore an interesting candidate for supercapacitors. [Preview Abstract] |
Tuesday, March 14, 2017 11:39AM - 11:51AM |
F38.00003: Polaronic and ionic conduction in NaMnO$_2$: influence of native point defects Zhen Zhu, Hartwin Peelaers, Chris G. Van de Walle Layered NaMnO$_2$ has promising applications as a cathode material for sodium ion batteries. We will discuss strategies to improve the electrical performance of NaMnO$_2$, including how to optimize the conditions of synthesis and how impurity doping affects the performance. Using hybrid density functional theory, we explored the structural, electronic, and defect properties of bulk NaMnO$_2$. It is antiferromagnetic in the ground state with a band gap of 3.75 eV. Small hole and electron polarons can form in the bulk either through self-trapping or adjacent to point defects. We find that both Na and Mn vacancies are shallow acceptors with the induced holes trapped as small polarons, while O vacancies are deep defect centers. Cation antisites, especially ${\rm Mn_{Na}}$, are found to have low formation energies. As a result, we expect that ${\rm Mn_{Na}}$ exists in as-grown NaMnO$_2$ in moderate concentrations, rather than forming only at a later stage of the charging process, at which point it causes undesirable structural phase transitions. Both electronic conduction, via polaron hopping, and ionic conduction, through ${\rm V_{Na}}$ migration, are significantly affected by the presence of point defects. This work was supported by DOE. [Preview Abstract] |
Tuesday, March 14, 2017 11:51AM - 12:03PM |
F38.00004: Composite Polymer-Garnet Solid State Electrolytes Andres Villa, Muhammed R. Oduncu, Gregory D. Scofield, Ernesto E. Marinero, Scott Forbey Solid-state electrolytes provide a potential solution to the safety and reliability issues of Li-ion batteries. We have synthesized cubic-phase Li7-xLa3Zr2-xBixO12 compounds utilizing inexpensive, scalable Sol-gel synthesis and obtained ionic conductivities ~ 1.2 x 10-4 S/cm at RT in not-fully densified pellets. In this work we report on the fabrication of composite polymer-garnet ceramic particle electrolytes to produce flexible membranes that can be integrated with standard battery electrodes without the need for a separator. As a first step we incorporated the ceramic particles into polyethylene oxide polymers (PEO) to form flexible membranes. Early results are encouraging yielding ionic conductivity values ≈1.0 x 10-5 S/cm at RT. To increment the conductivity in the membranes, we are optimizing amongst other: the ceramic particle size distribution and weight load, the polymer molecular weight and chemical composition and the solvated Li-salt composition and content. Unhindered ion transport across interfaces between the composites and the battery electrode materials is paramount for battery performance. To this end, we are investigating the effect of interface morphology, its atomic composition and exploring novel electrode structures that facilitate ionic transport. [Preview Abstract] |
Tuesday, March 14, 2017 12:03PM - 12:15PM |
F38.00005: Transition metal impurities in the solid electrolyte LLZO (Li$_{7}$La$_{3}$Zr$_{2}$O$_{12})$: Transport rates and their impact on Li-ion mobility Sheng Yang, Donald Siegel LLZO has many properties of an ideal solid electrolyte in lithium-ion batteries since it could enable the use of high voltage electrodes and hence enhance the energy density of lithium ion batteries. With supervalent cation doping such as Al$^{3+}$, Ga$^{3+}$ on the Li-site, the room temperature ionic conductivity of the cubic LLZO can accomplish high ionic conductivity up to 1mS/cm. However, some experiments suggest that mutual diffusion layers were formed between LLZO and cathode where transition metal (TM) diffused into LLZO, which could possibly lead to large interfacial resistance. In this study, we quantified the performance of LLZO after doping with cobalt, manganese, iron and nickel. In particular, we used molecular dynamics simulations with empirical Morse-type potentials to investigate the TM transport rates and their impact on Li-ion mobility. Our work indicates that TM impurities diffuse slower than Li-ion and they will result in a decrease in the Li-ion mobility by blocking Li-ion pathways. Our work shines light on the origin of interfacial resistance between LLZO and different cathodes. [Preview Abstract] |
Tuesday, March 14, 2017 12:15PM - 12:27PM |
F38.00006: Bismuth Aliovalent Substitution in LiLaZrO Garnets Derek K Schwanz, Ernesto E. Marinero We report on the synthesis of cubic-phase solid-state electrolytes based on Li7La3Zr2O12 (LLZO). Ionic conductivities up to 1.2 x 10-4 S/cm are readily achieved. Moreover, these results are accomplished at unprecedented low synthesis temperatures. Bismuth aliovalent substitution into LLZO utilizing the Pechini method processing is successfully employed to synthesize Li7-xLa3Zr2-xBixO12 compounds. Cubic phase Li6La3ZrBiO12 powders are generated in the temperature range from 650 ⁰C to 900 ⁰C in air. In contrast, in the absence of Bi and under identical synthesis conditions, the cubic garnet phase is not formed below 700 ⁰C, in addition, at 900 ⁰C the un-doped compounds are observed to transform to the tetragonal phase. The critical role of Bi in lowering the formation temperature of the garnet cubic phase and the improvements in ionic conductivity are elucidated in this work through microstructural and impedance measurements, correlating stoichiometry variations to both improved intergranular degree of sintering and ionic conductivity. We ascribe the effect of Bi doping in achieving these remarkable improvements to significant enhancements in grain growth and densification. In addition Bi optimizes the Li+ occupancy resulting in increased ionic conductivity. [Preview Abstract] |
Tuesday, March 14, 2017 12:27PM - 12:39PM |
F38.00007: Understanding ionic conductivity trends in polyborane solid electrolytes from ab initio molecular dynamics Joel Varley, Kyoung Kweon, Prateek Mehta, Patrick Shea, Tae Wook Heo, Vitalie Stavila, Terrence Udovic, Brandon Wood Polyborane salts based on B$_{\mathrm{12}}$H$_{\mathrm{12}}^{\mathrm{2-}}$, B$_{\mathrm{10}}$H$_{\mathrm{10}}^{\mathrm{2-}}$, and their carboborane counterparts CB$_{\mathrm{11}}$H$_{\mathrm{12}}^{\mathrm{-}}$ and CB$_{\mathrm{9}}$H$_{\mathrm{10}}^{\mathrm{-}}$ demonstrate extraordinary Li and Na superionic conductivity that make them attractive as electrolytes in all-solid-state batteries. Their rich chemical and structural diversity creates a versatile design space that could be used to optimize materials with even higher conductivity at lower temperatures; however, many mechanistic details remain enigmatic, including reasons why certain modifications lead to improved performance. Here, we use extensive ab initio molecular dynamics simulations to broadly explore the dependence of ionic conductivity on cation/anion pair combinations for Li and Na polyborane salts. Further simulations based on Li$_{\mathrm{2}}$B$_{\mathrm{12}}$H$_{\mathrm{12}}$ as a model system are used to probe the additional influence of local perturbations, including modifications to chemistry, stoichiometry, and composition. Carbon doping, anion alloying, and cation off-stoichiometry are found to be favorable because they introduce intrinsic disorder, which facilitates local deviations from the expected cation population. Anion reorientations are also discovered to be critical for conduction, with benefits associated with lattice expansion traceable to the facilitation of anion rotation at larger volumes. [Preview Abstract] |
Tuesday, March 14, 2017 12:39PM - 12:51PM |
F38.00008: Computational study of Li$_2$OHCl as a possible solid state battery material Jason Howard, N. A. W. Holzwarth Preparations of Li$_2$OHCl have recently been experimentally studied$^{2,3}$ as solid state Li ion electrolytes. A disordered cubic phase is known$^4$ to be stable at temperatures $T>35^o$ C. Following previous ideas,$^3$ first principles supercells are constructed with up to 320 atoms to model the cubic phase. First principles molecular dynamics simulations of the cubic phase show Li ion diffusion occuring on the $t = 10^{-12}$ s time scale, at temperatures as low as $T=400$ K. The structure of the lower temperature phase ($T<35^o$ C) is not known in detail$^4$. A reasonable model of this structure is developed by using the tetragonal ideal structure found by first principles simulations and a model Hamiltonian to account for alternative orientations of the OH groups.\\ $^2$ Hood {\em{et al.}} {\bf{JACS 138}}, 1768-1771 (2016). $^3$ Li {\em{et al.}} {\bf{Angew. Chem. Int. Ed. 55}}, 9965-9968 (2016). $^4$ Schwering {\em{et al.}} {\bf{CHEMPHYCHEM 4}}, 343-348 (2003). [Preview Abstract] |
Tuesday, March 14, 2017 12:51PM - 1:03PM |
F38.00009: Diffusion of lithium ions in amorphous and crystalline PEO$_{3}$:LiCF$_{3}$SO$_{3}$ polymer electrolytes: ab initio calculations and simulations Sha Xue, Yingdi Liu, Yaping Li, Dale Teeters, Daniel Crunkleton, Sanwu Wang The PEO$_{3}$:LiCF$_{3}$SO$_{3}$polymer electrolyte has attracted significant research due to its high conductivity and enhanced stability in lithium polymer batteries. Most experimental studies have shown that amorphous PEO lithium salt electrolytes have higher conductivity than the crystalline ones. Other studies, however, have shown that crystalline phase can conduct ions. In this work, we use ab initio molecular dynamics simulations to obtain the amorphous structure of PEO$_{3}$:LiCF$_{3}$SO$_{3}$. The diffusion pathways and activation energies of lithium ions in both crystalline and amorphous PEO$_{3}$:LiCF$_{3}$SO$_{3}$are determined with first-principles density functional theory. In crystalline PEO$_{3}$:LiCF$_{3}$SO$_{3}$, the activation energy for the low-barrier diffusion pathway is approximately 1.0 eV. In the amorphous phase, the value is 0.6 eV. This result would support the experimental observation that amorphous PEO$_{3}$:LiCF$_{3}$SO$_{3}$has higher ionic conductivity than the crystalline phase. [Preview Abstract] |
Tuesday, March 14, 2017 1:03PM - 1:15PM |
F38.00010: Li$_{14}$(PON$_3$)$_2$O: Computational study of a possible new electrolyte for Li ion batteries Ahmad Al-Qawasmeh, N. A. W. Holzwarth Recently, Li$_{14}$(PON$_{3}$)$_2$O, containing Li$_6$PON$_{3}$ and Li$_2$O groups within a trigonal crystal structure (space group $P\bar{3}$ (\#147)) has been synthesized by Baumann and Schnick.\footnote{Baumann and Schnick, {\bf{Eur. J. Inorg. Chem. 2015}}, 617-621 (2015)} We report the results of a first principles computational study of this material in comparison with other crystalline electrolytes having LiPON composition and iosolated tetrahedral oxonitridophosphate ions such as Li$_3$PO$_4$ and Li$_7$PN$_4$. The structure of Li$_{14}$(PON$_{3}$)$_2$O is characterized by a relatively large Li ion density (0.07 Li/\AA$^3$) which is between that of Li$_3$PO$_4$ (0.04 Li/\AA$^3$) and Li$_2$O (0.09 Li/\AA$^3$). Using a nudged elastic band approach, we find Li ion migration barriers in Li$_{14}$(PON$_{3}$)$_2$O to be comparable or lower than those of Li$_3$PO$_4$ and Li$_7$PN$_4$. The most efficient migration appears to occur via a vacancy mechanism with net motion within planes perpendicular to the c-axis in the vicinity of the O sites. Models of interfaces of Li$_{14}$(PON$_{3}$)$_2$O with Li metal were also studied. [Preview Abstract] |
Tuesday, March 14, 2017 1:15PM - 1:27PM |
F38.00011: Computational study of ideal electrolyte/anode interfaces for Na$_3$SbS$_4$/Na Larry E. Rush Jr., N. A. W. Holzwarth As part of an effort to develop energy storage technology based on all-solid-state Na-ion batteries, recent papers in the literature\footnote{Wang {\em{et al.}}, {\bf{Angew. Chem. Int. Ed. 55}}, 8551–8555 (2016), Zhang {\em{et al.}}, {\bf{Adv. Sci. 2016}}, 1600089 (2016)} demonstrate the electrochemical stability of the solid electrolyte Na$_3$SbS$_4$ interfaced with a metallic Na anode. The integrity of this electrolyte/anode interface, which is essential to the success of these battery components, is attributed to the formation of a stable solid electrolyte interphase (SSEI). We report the results of a computational study of this system, using first principles methods to model ideal interfaces of Na$_3$SbS$_4$ with Na metal. The ideal interfaces were constructed from (110), (100), and (001) surfaces of tetragonal crystals of Na$_3$SbS$_4$ and Na metal in various configurations. The results show several likely components of the SSEI including a few broken Sb$-$S bonds and Na$_2$S groups stabilized at the outer layer of the interface. [Preview Abstract] |
Tuesday, March 14, 2017 1:27PM - 1:39PM |
F38.00012: Effect of Aprotic Solvents on the Dynamics of a Room Temperature Ionic Liquid Naresh Osti, Katherine Van Aken, Matthew Thompson, Felix Tiet, De-en Jiang, Peter Cummings, Yury Gogotsi, Eugene Mamontov Room temperature ionic liquids (RTILs) have attracted much attention as electrolytes in energy storage devices because of their peculiar physical and chemical characteristics. However, their remarkably high viscosity, which results in low conductivity and diffusivity, may adversely affect the charging and discharging rates. Despite changing molecular configurations, use of aprotic solvent allows to enhance the transport properties of ionic liquids by disrupting the cation-anion interactions. We explore the impact of dipole moment of aprotic solvents on the cation-anion interaction and transport in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [BMIM$+$][Tf2N-], RTIL using molecular dynamics (MD) simulations and quasi-elastic neutrons scattering (QENS) measurements. We observed an increase in cation diffusivity with the increasing dipole moment of the solvent. This effect is due to a decrease in the solvation free energy induced by the increasing solvent polarity. A clear nano-phase separation into ionic liquid-rich and ionic liquid-poor phases as observed by QENS will be also discussed. [Preview Abstract] |
Tuesday, March 14, 2017 1:39PM - 1:51PM |
F38.00013: DFT-MD study of highly concentrated Li-salt electrolytes for Lithium-ion batteries Keitaro Sodeyama, Yoshitaka Tateyama Li-salt concentration has been recently proposed as an important control parameter of reduction stability of electrolytes and high ion conductivity in Lithium-ion batteries. For example, highly concentrated (HC) Li-FSA salt in acetonitrile (AN) shows strong electrochemical stability against the reductive decomposition, though in low concentration (LC) solution AN is easily reduced and decomposed. In this study, we investigated the mechanism of the improvement of the reduction stability and Li-ion diffusion mechanism depending on the salt concentration by using DFT-MD simulations. We also calculated the diffusion coefficients of the Li-ions, anions, and solvents in the LC and HC electrolytes to elucidate how Li-ion diffusion was affected by concentration. For the reduction stability, we found that TFSA anion sacrificially accepts reductive electron and decomposed in the HC systems, because specific chained network structure is formed and the electron affinity of the anion shifts lower. For the diffusion mechanism, we analyzed the motions of individual Li ions in HC system, and found Li-ion hopping between the oxygen atoms of the anions. We concluded that change of the diffusion mechanism can be an origin of the high Li-ion conductivity in the HC electrolytes. [Preview Abstract] |
Tuesday, March 14, 2017 1:51PM - 2:03PM |
F38.00014: Atomistic Structure and Dynamics of the Solvation Shell Formed by Organic Carbonates around Lithium Ions via Infrared Spectroscopies Daniel Kuroda, Kristen Fufler Lithium-ion batteries have become ubiquitous to the portable energy storage industry, but efficiency issues still remain. Currently, most technological and scientific efforts are focused on the electrodes with little attention on the electrolyte. For example, simple fundamental questions about the lithium ion solvation shell composition in commercially used electrolytes have not been answered. Using a combination of linear and non-linear IR spectroscopies and theoretical calculations, we have carried out a thorough investigation of the solvation structure and dynamics of the lithium ion in various linear and cyclic carbonates at common battery electrolyte concentrations. Our studies show that carbonates coordinate the lithium ion tetrahedrally. They also reveal that linear and cyclic carbonates have contrasting dynamics in which cyclic carbonates present the most ordered structure. Finally, our experiments demonstrate that simple structural modifications in the linear carbonates impact significantly the microscopic interactions of the system. The stark differences in the solvation structure and dynamics among different carbonates reveal previously unknown details about the molecular level picture of these systems. [Preview Abstract] |
Tuesday, March 14, 2017 2:03PM - 2:15PM |
F38.00015: First-Principles Molecular Dynamics Study on the Electric-double layer Capacitance of Water-MXene interfaces Yasunobu ANDO, Minoru Otani MXenes are a new, large family of layered materials synthesized from MAX phases by simple chemical treatments. Due to their enormous variations, MXenes have attracted great attention as promising candidates as anode materials for next-generation secondary batteries. Unfortunately, the specific capacitance of MXenes supercapacitors is lower than that of active-carbon ones. Theoretical investigation of the electric-double layer (EDL) at electrode interfaces is necessary to improve their capacitance. First-principles molecular dynamics (FPMD) simulation based on the density functional theory (DFT) is performed to estimate the EDL capacitance from a potential profile V($z)$ and a charge distribution q(z) induced by the ions at water-Ti$_{\mathrm{2}}$CT$_{\mathrm{x}}$ (T$=$O, F) interfaces. Potential profiles V(z) of both Ti$_{\mathrm{2}}$CO$_{\mathrm{2}}$ and Ti$_{\mathrm{2}}$CF$_{\mathrm{2}}$ decrease about 1.0 eV steeply in a region of only 3 {\AA} from a Ti layer, which is the same profile at the platinum interfaces. On the other hand, induced charge distribution q(z) depends on the species of surface termination. Induced electrons are introduced at Ti layers in the case of O surface termination. However, Ti$_{\mathrm{2}}$CF$_{\mathrm{2}}$ is not capable to store electrons at Ti layers because it is mono-valence anions. It indicates that effective surface-position of MXenes depends on the surface terminations. Our results are revealed that small induced charge leads the low EDL capacitance at MXene interfaces. This is because interface polarization due to strong interaction between water and Ti$_{\mathrm{2}}$CT$_{\mathrm{x}}$ induces net charge. The surface net charge hinders the introduction of ion-induced charges. [Preview Abstract] |
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