Recent Progress and Perspectives of Li-Argyrodite Sulfide Electrolytes: From Fundamental Mechanisms to Practical All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) are widely regarded as a promising next-generation energy-storage technology because they offer the potential to simultaneously improve the safety and energy density of conventional lithium battery systems. Among various solid electrolytes, Li-argyrodite sulfide electrolytes (Li6PS5X, X = Cl, Br, I) have attracted considerable attention owing to their high room-temperature ionic conductivity, good mechanical deformability, and favorable cost-effectiveness. However, for the practical deployment of Li-argyrodite sulfide electrolytes in ASSLBs, several critical challenges still need to be addressed, including limited synthesis strategies, insufficient air stability, and poor interfacial compatibility with both cathodes and anodes. This review summarizes recent advances in Li-argyrodite sulfide electrolytes from fundamental understanding to practical applications. The crystal structure characteristics and Li+ conduction mechanisms are first discussed to elucidate the origins of fast ion transport, followed by an overview of major synthesis strategies. Strategies for improving ionic conductivity, air stability, and electrode interfacial compatibility through compositional engineering and interfacial regulation are also highlighted. Finally, the prospects of Li-argyrodite sulfide electrolytes for practical all-solid-state batteries are discussed, together with the remaining challenges and future research directions.