Interfacial reactions of hydride- and halide-containing argyrodite solid electrolytes with Li metal anode in all-solid-state batteries

Abstract

All-solid-state batteries (ASSBs) using solid electrolytes and lithium metal anodes have garnered significant attention as next-generation batteries due to their potential for achieving high energy density and improved safety. Among various solid electrolytes, argyrodite-type sulfide-based electrolytes have emerged as promising candidates. Recent studies have focused on enhancing ionic conductivity at room temperature by substituting free S2− anions with alternative anions. However, argyrodite electrolytes still face challenges related to interfacial incompatibility with lithium metal anodes. In this study, we investigate the interfacial phenomena of hydride- and halide-containing argyrodite solid electrolytes with Li metal anode under low potentials. The results reveal contrasting interfacial stability for the two electrolytes. Li6PS5Cl exhibited significant interfacial instability with lithium metal, as evidenced by dendrite growth during cycling and continuous P-S bond decomposition upon contact. In contrast, Li5PS4(BH4)2 demonstrated stable interfacial behavior, with reversible and uniform lithium ion deposition and dissolution. Despite initial P-S bond decomposition, a stable interfacial phase was formed, ensuring consistent cycling performance. Based on these insights, consistent results were observed in lithium metal all-solid-state batteries fabricated with TiS2. These findings provide valuable insights into the interfacial behavior of argyrodite-type solid electrolytes and the design of anion-substituted solid electrolytes to improve lithium metal compatibility. This study underscores the importance of understanding interfacial phenomena to achieve enhanced electrochemical performance and reliability in next-generation lithium metal batteries.