Factors Determining Ionic Mobility in Ion Migration Pathways of Polypropylene (PP) Separator for Lithium Secondary Batteries

Hydride ion conduction in layered perovskites is of great interest for sustainable-energy applications. In this report we study Ba2ScHO3, a recently synthesized oxyhydride with an unusual anion ordering, using a multifaceted density functional theory approach involving both transition state calculations and molecular dynamics simulations. Beyond simply identifying the key ion migration pathways, we perform detailed analysis of transition states and identify key interactions which drive trends in ionic mobility. Our key findings are that ionic mobility is, remarkably, independent of hydride-oxide disorder, the dominant migration pathway changes under pressure, and a reduction in A-site cation size accelerates hydride diffusion. Local structural flexibility along migration pathways is understood in terms of dimensionality and ionic size, and we thus identify crystal engineering principles for rational design of ion conductors. On the basis of our new insights into these materials, we predict that Sr2ScHO3 will show improved conductivity over existing analogues.

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Site preferences and ion dynamics in lithium chalcohalide solid solutions with argyrodite structure: II. Multinuclear solid state NMR of the systems Li6PS5−x Se x Cl and Li6PS5−x Se x Br

Zeitschrift für Physikalische Chemie ◽

10.1515/zpch-2021-3139 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Barbara Koch ◽

Shiao Tong Kong ◽

Özgül Gün ◽

Hans-Jörg Deiseroth ◽

Hellmut Eckert

Keyword(s):

Solid Solutions ◽

Lithium Ion ◽

Ionic Mobility ◽

Magic Angle Spinning ◽

Magic Angle ◽

Ion Migration ◽

Iodide Ions ◽

Nmr Study ◽

Structural Configurations ◽

Migration Pathways

Abstract A comprehensive multinuclear (7Li, 31P, 35Cl, 77Se, 79Br) nuclear magnetic resonance (NMR) study has been conducted to characterize local structural configurations and atomic distributions in the crystallographically disordered solid solutions of composition Li6PS5−x Se x X (0 ≤ x ≤ 1, X = Cl, Br) with the Argyrodite structure. In contrast to the situation with the corresponding iodide homologs, there is no structural ordering between the 4a and 4c sites, with the halide ions occupying both of them with close to statistical probabilities. Nevertheless, throughout the composition range, the 16e Wyckoff sites of the Argyrodite structure are exclusively occupied by the chalcogen atoms, forming PY4 3− (Y = S, Se) tetrahedra, indicating the absence of P-halogen bonds. 31P magic-angle spinning (MAS)-NMR can serve to differentiate between the various possible PS4−n Se n 3− tetrahedral units in a quantitative fashion. Compared to the case of the anion-ordered Li6PS5−x Se x I solid solutions, the preference of P–S over P–Se bonding is significantly stronger, but it is weaker than in the halide free solid solutions Li7PS6−x Se x . Each individual PS4−n Se n 3− tetrahedron is represented by a peak cluster of up to five resonances, representing the five different configurations in which the PY4 3− ions are surrounded by the four closest chalcogenide and halide anions occupying the 4c sites; this distribution is close to statistical and can be used to deduce deviations of sample compositions from ideal stoichiometry. Non-linear 7Li chemical shift trends as a function of x are interpreted to indicate that the Coulombic traps created by sulfur-rich PS4−n Se n 3− ions (n ≤ 2) within the energy landscape of the lithium ions are deeper than those of the other anionic species present (i.e., selenium-richer PY4 3− tetrahedra, isolated chalcogenide or iodide ions), causing the Li+ ions to spend on average more time near them. Temperature dependent static 7Li NMR linewidths indicate higher mobility in the present systems than in the previously studied Li6PS5−x Se x I solid solutions. Unlike the situation in Li6PS5−x Se x I no rate distinction between intra-cage and inter-cage ionic motion is evident. Lithium ionic mobility increases with increasing selenium content. This effect can be attributed to the influences of higher anionic polarizability and a widening of the lithium ion migration pathways caused by lattice expansion. The results offer interesting new insights into the structure/ionic mobility correlations in this new class of compounds.

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Improving Hydride Conductivity in Layered Perovskites via Crystal Engineering

10.26434/chemrxiv.12730553 ◽

2020 ◽

Author(s):

Harry W. T. Morgan ◽

Harry J. Stroud ◽

Neil Allan

Keyword(s):

Crystal Engineering ◽

Density Functional ◽

Rational Design ◽

Ionic Mobility ◽

Theory Approach ◽

Ion Migration ◽

Energy Applications ◽

Migration Pathway ◽

Migration Pathways ◽

Layered Perovskites

Hydride ion conduction in layered perovskites is of great interest for sustainable-energy applications. In this report we study Ba2ScHO3, a recently synthesized oxyhydride with an unusual anion ordering, using a multifaceted density functional theory approach involving both transition state calculations and molecular dynamics simulations. Beyond simply identifying the key ion migration pathways, we perform detailed analysis of transition states and identify key interactions which drive trends in ionic mobility. Our key findings are that ionic mobility is, remarkably, independent of hydride-oxide disorder, the dominant migration pathway changes under pressure, and a reduction in A-site cation size accelerates hydride diffusion. Local structural flexibility along migration pathways is understood in terms of dimensionality and ionic size, and we thus identify crystal engineering principles for rational design of ion conductors. On the basis of our new insights into these materials, we predict that Sr2ScHO3 will show improved conductivity over existing analogues.

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Site preferences and ion dynamics in lithium chalcohalide solid solutions with argyrodite structure: I. A multinuclear solid state NMR study of the system Li6PS5-xSexI and of Li6AsS5I

Zeitschrift für Physikalische Chemie ◽

10.1515/zpch-2021-3135 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Barbara Koch ◽

Shaio Tong Kong ◽

Özgül Gün ◽

Hans-Jörg Deiseroth ◽

Hellmut Eckert

Keyword(s):

Solid Solutions ◽

Ionic Mobility ◽

Magic Angle Spinning ◽

Magic Angle ◽

Temperature Phase ◽

Lithium Ions ◽

Iodide Ions ◽

Nmr Study ◽

Structural Configurations ◽

Migration Pathways

Abstract A comprehensive multinuclear (7Li, 31P, 75As, 77Se, 127I) NMR study has been conducted to characterize local structural configurations and atomic distributions in the crystallographically ordered solid solutions of composition Li6PS5-x Se x I (0 ≤ x ≤ 1) and in Li6AsS5I. Throughout the composition range, structural ordering between the atoms on the Wyckoff sites 4a and 4c is maintained, with the I− ions exclusively occupying the 4a sites. 31P magic-angle spinning nuclear magnetic resonance (MAS NMR) can serve to differentiate between the various possible PS4-n Se n 3− tetrahedral units in a quantitative fashion, indicating a preference of P-S relative to P-Se bonding. Each individual PS4-n Se n 3− tetrahedron is represented by a peak cluster containing up to five resonances, representing the five different configurations in which the PCh4 3− units are surrounded by the four closest chalcogenide anions occupying the 4c sites; the distribution of S2− and Se2− over these sites is close to statistical. Non-linear 7Li chemical shift trends as a function of x are interpreted to indicate that the Coulombic traps created by sulfur-rich PS4-n Se n 3− ions (n ≥ 2) within the energy landscape of the lithium ions are deeper than those of the other anionic species present (i.e. selenium-richer PCh4 3− tetrahedra, isolated chalcogenide or iodide ions), causing the Li+ ions to spend on average more time near them. Temperature dependent static 7Li NMR linewidths measured on Li6PS5I and Li6AsS5I indicate a two-step motional narrowing process characterized by a clear dynamic distinction between a more rapid localized intra-cage process and a slower, long-range inter-cage process. In the solid solutions this differentiation gradually disappears, leading to an overall increase of lithium ionic mobility with increasing selenium content, which can be attributed to the influences of higher anionic polarizability and a widening of the lithium migration pathways caused by lattice expansion. Furthermore, the low-temperature phase transition in Li6PS5I, which tends to immobilize the lithium ions below 170 K, is suppressed in the solid solutions. The results offer interesting new insights into the -structure/ionic mobility correlations in this new class of compounds.

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The inverse perovskite BaLiF3: single-crystal neutron diffraction and analyses of potential ion pathways

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s2052520618014579 ◽

2018 ◽

Vol 74 (6) ◽

pp. 643-650 ◽

Cited By ~ 3

Author(s):

Dennis Wiedemann ◽

Falk Meutzner ◽

Oscar Fabelo ◽

Steffen Ganschow

Keyword(s):

High Temperature ◽

Neutron Diffraction ◽

Scattering Length ◽

Temperature Structure ◽

Luminescent Materials ◽

Lithium Ions ◽

Ion Migration ◽

Mobile Species ◽

Tolerance Factors ◽

Migration Pathways

Doped barium lithium trifluoride has attracted attention as component for scintillators, luminescent materials and electrodes. With lithium and fluoride, it contains two possibly mobile species, which may account for its ionic conductivity. In this study, neutron diffraction on oxide-containing BaLiF3 single-crystals is performed at up to 636.2°C. Unfortunately, ion-migration pathways could not be mapped by modelling anharmonic ion displacement or by inspecting the scattering-length density that was reconstructed via maximum-entropy methods. However, analyses of the topology and bond-valence site energies derived from the high-temperature structure reveal that the anions can migrate roughly along the edges of the LiF6 coordination octahedra with an estimated migration barrier of ∼0.64 eV (if a vacancy permits), whereas the lithium ions are confined to their crystallographic positions. This finding is not only valid for the title compound but for ion migration in all perovskites with Goldschmidt tolerance factors near unity.

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Voltage bias stress effects in metal halide perovskites are strongly dependent on morphology and ion migration pathways

Journal of Materials Chemistry A ◽

10.1039/d0ta10371c ◽

2020 ◽

Vol 8 (47) ◽

pp. 25109-25119

Author(s):

Laura Flannery ◽

Jonathan Ogle ◽

Daniel Powell ◽

Christopher Tassone ◽

Luisa Whittaker-Brooks

Keyword(s):

Solar Cell ◽

Metal Halide ◽

Research Groups ◽

Interfacial Interactions ◽

Ion Migration ◽

Stress Effects ◽

Bias Stress ◽

Voltage Bias ◽

Halide Perovskites ◽

Migration Pathways

We determined how morphology, electronic and interfacial interactions affect perovskite PVs under voltage bias stress. Our findings provide insights into the discrepancies in the solar cell efficiencies observed across many different research groups.

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Design of fast ion conducting cathode materials for grid-scale sodium-ion batteries

Physical Chemistry Chemical Physics ◽

10.1039/c7cp00037e ◽

2017 ◽

Vol 19 (11) ◽

pp. 7506-7523 ◽

Cited By ~ 23

Author(s):

Lee Loong Wong ◽

Haomin Chen ◽

Stefan Adams

Keyword(s):

Exponential Function ◽

Cathode Materials ◽

Sodium Ion ◽

Sodium Ion Batteries ◽

Rate Performance ◽

Ion Migration ◽

Stretched Exponential ◽

Ion Conducting ◽

Fast Ion ◽

Migration Pathways

Using a stretched exponential function the rate performance of sodium-insertion materials is semi-quantitatively determined from characteristics of Na-ion migration pathways.

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K(Na,K)Na2[Cu2(SO4)4]: a new highly porous anhydrous sulfate and evaluation of possible ion migration pathways

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s2052520621010350 ◽

2021 ◽

Vol 77 (6) ◽

Author(s):

Oleg I. Siidra ◽

Dmitry O. Charkin ◽

Vadim M. Kovrugin ◽

Artem S. Borisov

Keyword(s):

Crystal Structure ◽

Potential Candidate ◽

Ion Migration ◽

Coordination Polyhedra ◽

Synthesis And Crystal Structure ◽

Coordination Modes ◽

Split Vertex ◽

Crystallographic Characteristics ◽

Migration Pathways ◽

Highly Porous

Alkali copper sulfates form a rapidly developing family of inorganics. Herein, we report synthesis and crystal structure, and evaluate possible ion migration pathways for a novel Na-K-Cu anhydrous sulfate, K(Na,K)Na2[Cu2(SO4)4]. The CuO7 and SO4 polyhedra share common vertices and edges to form [Cu2(SO4)4]4− wide ribbons, which link to each other via common oxygen atoms forming the host part of the structure. Four guest alkali sites are occupied by solely K+, mixture of K+ and Na+, and solely Na+, which agrees well with the size of the cavities. The crystal structure of K(Na,K)Na2[Cu2(SO4)4] contains two symmetry-independent Cu sites with [4+1+(2)] coordination environments. The overall coordination polyhedra of Cu2+ can be considered as `octahedra with one split vertex'. A similar coordination mode was observed also in some other multinary copper sulfates, mostly of the mineral world. These coordination modes were reviewed and five types of CuO7 polyhedra are identified. CuO7 polyhedra are almost restricted to copper sulfates and phosphates. It was found that a larger amount of the smaller SO4 2− and PO4 3− anions can cluster around a single Cu2+ cation; in addition, for such relatively small anions, both mono (κ1) and bidentate (κ2) coordination modes to the Cu2+ are possible. The correlation between crystallographic characteristics and bond valence energies showed that the new copper sulfate framework, [Cu2(SO4)4]4−, contains one interconnected path suitable for Na+ mobility at tolerable activation energies and that K(Na,K)Na2[Cu2(SO4)4] can be considered as a potential candidate for novel Na-ion conductors.

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