Lithium Transport in Li4.4M0.4M ' S-0.6(4) (M = Al3+, Ga3+, and M ' = Ge4+, Sn4+): Combined Crystallographic, Conductivity, Solid State NMR, and Computational Studies


Leube, Bernhard T, Inglis, Kenneth K, Carrington, Elliot J ORCID: 0000-0001-8855-809X, Sharp, Paul M, Shin, J Felix, Neale, Alex R ORCID: 0000-0001-7675-5432, Manning, Troy D ORCID: 0000-0002-7624-4306, Pitcher, Michael J, Hardwick, Laurence J ORCID: 0000-0001-8796-685X, Dyer, Matthew S ORCID: 0000-0002-4923-3003 et al (show 3 more authors) (2018) Lithium Transport in Li4.4M0.4M ' S-0.6(4) (M = Al3+, Ga3+, and M ' = Ge4+, Sn4+): Combined Crystallographic, Conductivity, Solid State NMR, and Computational Studies. CHEMISTRY OF MATERIALS, 30 (20). pp. 7183-7200.

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Abstract

To understand the structural and compositional factors controlling lithium transport in sulfides, we explored the Li5AlS4-Li4GeS4 phase field for new materials. Both parent compounds are defined structurally by a hexagonal close packed sulfide lattice, where distinct arrangements of tetrahedral metal sites give Li5AlS4 a layered structure and Li4GeS4 a three-dimensional structure related to γ-Li3PO4. The combination of the two distinct structural motifs is expected to lead to new structural chemistry. We identified the new crystalline phase Li4.4Al0.4Ge0.6S4, and investigated the structure and Li+ ion dynamics of the family of structurally related materials Li4.4M0.4M′0.6S4 (M = Al3+, Ga3+ and M′ = Ge4+, Sn4+). We used neutron diffraction to solve the full structures of the Al-homologues, which adopt a layered close-packed structure with a new arrangement of tetrahedral (M/M′) sites and a novel combination of ordered and disordered lithium vacancies. AC impedance spectroscopy revealed lithium conductivities in the range of 3(2) × 10-6 to 4.3(3) × 10-5 S cm-1 at room temperature with activation energies between 0.43(1) and 0.38(1) eV. Electrochemical performance was tested in a plating and stripping experiment against Li metal electrodes and showed good stability of the Li4.4Al0.4Ge0.6S4 phase over 200 h. A combination of variable temperature 7Li solid state nuclear magnetic resonance spectroscopy and ab initio molecular dynamics calculations on selected phases showed that two-dimensional diffusion with a low energy barrier of 0.17 eV is responsible for long-range lithium transport, with diffusion pathways mediated by the disordered vacancies while the ordered vacancies do not contribute to the conductivity. This new structural family of sulfide Li+ ion conductors offers insight into the role of disordered vacancies on Li+ ion conductivity mechanisms in hexagonally close packed sulfides that can inform future materials design.

Item Type: Article
Depositing User: Symplectic Admin
Date Deposited: 16 Nov 2018 10:58
Last Modified: 19 Jan 2023 01:14
DOI: 10.1021/acs.chemmater.8b03175
Open Access URL: http://10.0.3.253/acs.chemmater.8b03175
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3027806
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