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

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 Li5.5PS4.5Cl1.5 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 Li5.5PS4.5-xSexCl1.5, 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 Li5.5PS4.5Cl1.5 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 Li6PS5-xSexCl and Li5.5PS4.5-xSexCl1.5, and contribute to the rational design of superionic conductors.