Abstract
Recently, researchers at the University of Waterloo (Canada) and Oak Ridge National Laboratory (USA) reported a new family of lithium thioborate halide electrolytes which have the composition Li7.5B10S18X1.5 (X = Cl, Br, I) and which are very impressive ionic conductors with \U0001d782=10-3 S/cm measured at room temperature [1]. The researchers identified the crystal structure of the three materials with the monoclinic space group C2/c (No. 15) having highly disordered Li and X sites. In this presentation, we report the results of first-principles simulations of these materials, focusing on understanding the mechanisms of Li ion migration and the overall stability of the materials. By optimizing many possible stoichiometric crystalline configurations, we found ordered ground state realizations of the materials for the three halides X = Cl, Br, and I. Molecular dynamics simulations based on the initially ordered structures at various temperatures show significant Li ion hopping within the void channels of the structures at temperatures as low as T = 600 K. Simulations of possible decomposition products suggest that these electrolytes are also chemically stable. Overall, the preliminary simulations are consistent with the experimental findings of Ref. [1], indicating that these materials are very promising solid electrolytes for possible use in solid state Li ion batteries.------------------------------------------[1] K. Kaup, A. Assoud, J. Liu, and L. F. Nazar, Fast Li-ion conductivity in superadamantanoid lithium thioborate halides, Angewandte Chimie, 133, 7051-7056 (2020) doi.org/10.002/anie.202013339.------------------------------------------Acknowledgements -- This work was supported by NSF grant DMR-1940324. Computations were performed on the Wake Forest University DEAC cluster, a centrally managed resource with support provided in part by the university.
Published Version
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