Unveiling the Growth Mechanism of the Interphase between Lithium Metal and Li2S‐P2S5‐B2S3 Solid‐State Electrolytes

Chalcogenides with high ionic conductivity and appropriate mechanical properties are promising solid-state electrolytes (SSEs) to substitute current liquid electrolytes in lithium-ion batteries. Yet, their practical applications in all-solid-state batteries are still retarded by both the low critical current density and the inferior interfacial stability toward electrodes. In this work, a series of superior SSEs, that is, Li2S-P2S5-B2S3 electrolytes, are developed via a ball-milling and then melt-quenching strategy. These SSEs exhibit a high critical current density of 1.65 mA cm−2 and a long cycling life of over 300 h. In addition, the evolution mechanism of the interphase between SSEs and metallic lithium is revealed via operando electrochemical impedance spectroscopy, depth-profiling XPS, and in situ Raman spectroscopy. The structural and chemical heterogeneities are found to be the main origins of the continual interphase evolution. The resulting “multi-layer mosaic like” interphase facilitates the suppression of Li dendrite growth, and hence, prolongs the lifetime of lithium-ion all-solid-state batteries. In addition, the preparation technique of SSEs developed in the present work is feasible for scale-up production.