Sulfide solid electrolytes (SEs) are considered to be some of the most promising SEs for commercialization due to their high ionic conductivity, good mechanical ductility, and good interfacial contact with electrodes. The Ohmic resistance of solid-state batteries assembled with sulfide SEs is significantly reduced, but the problem of high interfacial impedance due to poor interfacial chemical/electrochemical stability between sulfide SEs and the electrodes is serious. Therefore, the formation and evolution of the electrode/sulfide SE interface during battery assembly and cycling have a crucial impact on the performance of the battery, which is one of the key issues to be solved in battery commercialization. Herein, a variety of compatible interface protective layers, including PEO and β-Li 3 PS 4 /S, are obtained between sulfide SEs and ether-based room-temperature liquid lithium anodes for long-term stable cycling of >1000 h. Such a technical method for stabilizing the solid-liquid interface between a sulfide SE and an organic liquid lithium anode successfully solves the key problem of interfacial side reactions, making this battery configuration safe and stable for long-cycle operation.