Hybrid Liquid–Solid Composite Electrolytes for Sulfide‐Based Solid‐State Batteries: Advantages and Limitation

Abstract All‐solid‐state batteries (SSBs) represent one of the most promising avenues for surpassing the energy density limitations of conventional lithium‐ion batteries. However, the unstable interfacial contact between the solid‐state electrolyte and the electrode poses a critical challenge for practical applications. To tackle this issue, a hybrid system incorporating both liquid electrolytes (LEs) and sulfide solid‐state electrolytes may serve as a viable alternative. In this hybrid system, the LE facilitates the in situ formation of a solid electrolyte interphase layer, thereby enhancing the physical interface contact. Consequently, the electrochemical lifetime of the hybrid all‐SSBs is significantly improved, as evidenced by the stable lithium plating behavior observed through analytical techniques such as in situ X‐ray imaging. Nonetheless, the hybrid system exhibits clear limitations, and several issues that need to be addressed for its practical implementation are identified. In conclusion, potential solutions that could be employed to overcome these challenges are proposed.