Antiperovskite Ionic Conductor Layer for Stabilizing the Interface of NASICON Solid Electrolyte Against Li Metal in All-Solid-State Batteries

The instability of the interface between solid-state electrolytes (SSEs) and Li metal anodes is a critical factor restricting the application of NASICON-type ionic conductors in all-solid-state lithium batteries (ASSLBs). Here, the lithium-rich antiperovskite (LiRAP) Li2OHBr ionic conductor is introduced as a protective layer for the NASICON-type solid electrolyte Li1.5Al0.5Ge1.5(PO4)(3) (LAGP) by a simple way of rapid solidification of molten Li2OHBr, to prevent the adverse reaction caused by direct contact between LAGP and Li metal. The Li/Li symmetric cells with Li2OHBr protective layer exhibit long-term cycle stability compared with the bare LAGP, and the mechanisms are analyzed by XPS measurements for the interface between SSEs and Li metal. Also, the LiFePO4/Li ASSLBs have been assembled to further demonstrate this advantage. This work shows that LiRAP Li2OHBr can improve the cycling stability of ASSLBs from the perspective of Li metal anode protection.