Dynamics of Hydroxyl Anions Promotes Lithium Ion Conduction in Antiperovskite Li 2 OHCl
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Author(s)
Wang, Fei
Evans, Hayden A
Kim, Kwangnam
Yin, Liang
Li, Yiliang
Tsai, Ping-Chun
Liu, Jue
Lapidus, Saul H
Brown, Craig M
Siegel, Donald J
Date Issued
2020
Journal
Chemistry of Materials
Publisher
American Chemical Society (ACS)
Citation
Wang, Fei, Evans, Hayden A, Kim, Kwangnam, Yin, Liang, Li, Yiliang et al. 2020. "Dynamics of Hydroxyl Anions Promotes Lithium Ion Conduction in Antiperovskite Li 2 OHCl." Chemistry of Materials, 32 (19).
Version
Author's final manuscript
Abstract
Li2OHCl is an exemplar of the antiperovskite family of ionic conductors, for which high ionic conductivities have been reported, but in which the atomic-level mechanism of ion migration is unclear. The stable phase is both crystallographically defective and disordered, having ∼1/3 of the Li sites vacant, while the presence of the OH- anion introduces the possibility of rotational disorder that may be coupled to cation migration. Here, complementary experimental and computational methods are applied to understand the relationship between the crystal chemistry and ionic conductivity in Li2OHCl, which undergoes an orthorhombic to cubic phase transition near 311 K (≈38 °C) and coincides with the more than a factor of 10 change in ionic conductivity (from 1.2 × 10-5mS/cm at 37 °C to 1.4 × 10-3 mS/cm at 39 °C). X-ray and neutron experiments conducted over the temperature range 20-200 °C, including diffraction, quasi-elastic neutron scattering (QENS), the maximum entropy method (MEM) analysis, and ab initio molecular dynamics (AIMD) simulations, together show conclusively that the high lithium ion conductivity of cubic Li2OHCl is correlated to "paddlewheel"rotation of the dynamic OH- anion. The present results suggest that in antiperovskites and derivative structures a high cation vacancy concentration combined with the presence of disordered molecular anions can lead to high cation mobility.
MIT Department
Massachusetts Institute of Technology. Department of Materials Science and Engineering
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DOI of Published Version
https://doi.org/10.1021/ACS.CHEMMATER.0C02602
