Classification and Analysis of Halide Mixtures in Li10P3S12M (M = Cl, Br, I) Solid Electrolytes for Superionic Conductors

The lithium thiophosphate group of solid electrolytes (SEs) is considered one of the best lithium-ion conductors that could be compatible with liquid electrolytes. However, the interface stability of lithium thiophosphate SEs against the lithium anode and oxide cathode could be a challenge due to severe degradation over charge–discharge cycles. In this study, we aim to analyze and introduce the addition of halides into lithium thiophosphate SEs with a molar ratio of 3Li3PS4 to 1LiM (M = Cl, Br, I) in order not only to improve ion conductivity but also to increase the interface stability of the SEs. Li10P3S12Br (LPSBr) and Li10P3S12I (LPSI) results in high ionic conductivity at 1.7 and 2.9 mS cm–1, respectively, at room temperature. Although LPSBr has lower ion conductivity, it shows better electrochemical stability compared to LPSI. By combining the advantages of both LiI and LiBr to form Li10P3S12Br1–xIx, we have observed improvements not only in high ionic conductivity but also in the interface stability of SEs, which is important for extending the lifetime cycle of all-solid-state lithium batteries (ASSLBs).