Se-doped Li6PS5Cl and Li5.5PS4.5Cl1.5 with improved ionic conductivity and interfacial compatibility: a high-throughput DFT study

Abstract

Developing solid-state electrolytes (SSEs) with high Li⁺ ionic conductivity at room temperature and good interfacial compatibility with electrode materials has proven to be challenging. We employed density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations to explore the effects of Se dopant on the performance of Li₆PS₅Cl and Li_5.5PS_4.5Cl_1.5 as SSEs. At room temperature, the Li⁺ ionic conductivity of Li₆PS₅Cl was determined to be 2.592 mS cm⁻¹, and a 7-fold increase in Li⁺ ionic conductivity was achieved for the Li₆PSSe₄Cl structure. As for Li_5.5PS_4.5−xSe_xCl_1.5, the Li⁺ ionic conductivity increased from 8.916 mS cm⁻¹ to 19.286 mS cm⁻¹. The changes in the static lattice structure and its lattice dynamics provide wider diffusion pathways and more polarizable lattices, which can positively affect the Li⁺ ionic conductivity of Se-doped SSEs. Meanwhile, the Se-doped Li₆PS₅Cl and Li_5.5PS_4.5Cl_1.5 materials had better stability with LiCoO₂ than sulfide-type SSEs such as Li₁₀GeP₂S₁₂ and Li₃PS₄. These results provide fundamental insights into the Li⁺ ionic conductivity and interfacial compatibility of Li₆PS_5−xSe_xCl and Li_5.5PS_4.5−xSe_xCl_1.5, and contribute to the rational design of superionic conductors.