Trimethylsilyl Compounds for the Interfacial Stabilization of Thiophosphate-Based Solid Electrolytes in All-Solid-State Batteries

Argyrodite-type Li6PS5Cl (LPSCl) has attracted much attention as a solid electrolyte for all-solid-state batteries (ASSBs) because of its high ionic conductivity and good mechanical flexibility. LPSCl, however, has challenges of translating research into practical applications, such as irreversible electrochemical degradation at the interface between LPSCl and cathode materials. Even for Li-ion batteries (LIBs), liquid electrolytes have the same issue as electrolyte decomposition due to interfacial instability. Nonetheless, current LIBs are successfully commercialized because functional electrolyte additives give rise to the formation of stable cathode-electrolyte interphase (CEI) and solid-electrolyte interphase (SEI) layers, leading to supplementing the interfacial stability between electrolyte and electrode. Herein, inspired by the role of electrolyte additives for LIBs, trimethylsilyl compounds are introduced as solid electrolyte additives for improving the interfacial stability between sulfide-based solid electrolytes and cathode materials. 2-(Trimethylsilyl)ethanethiol (TMS-SH), a solid electrolyte additive, is oxidatively decomposed during charge, forming a stable CEI layer. As a result, the CEI layer derived from TMS-SH suppresses the interfacial degradation between LPSCl and LiCoO2, thereby leading to the excellent electrochemical performance of Li | LPSCl | LiCoO2, such as superior cycle life over 2000 cycles (85.0% of capacity retention after 2000 cycles). Trimethylsilyl compounds, such as 2-(trimethylsilyl)ethanethiol (TMS-SH), are introduced as solid electrolyte additives for improving the interfacial stability between sulfide-based solid electrolytes and cathode materials. The CEI layer derived from TMS-SH suppresses the interfacial degradation between LPSCl and LiCoO2, thereby leading to the excellent electrochemical performance of Li | LPSCl | LiCoO2, such as superior cycle life over 2000 cycles (85.0 % of capacity retention after 2000 cycles).image

Automated summary

Argyrodite-type Li6PS5Cl (LPSCl) has attracted attention as a solid electrolyte for all-solid-state batteries due to its high ionic conductivity and mechanical flexibility. However, the interface between LPSCl and cathode materials faces challenges such as electrochemical degradation. In this study, trimethylsilyl compounds were introduced as solid electrolyte additives to improve the interfacial stability between sulfide-based solid electrolytes and cathode materials, resulting in excellent electrochemical performance and enhanced cycle life.