Synergistic Coupling of Li_6.4La₃Zr_1.4Ta_0.6O₁₂ and Fluoroethylene Carbonate Boosts Electrochemical Performances of Poly(Ethylene Oxide)-Based All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) with poly(ethylene oxide) (PEO)-based composites solid-state electrolytes have received much attention owing to their higher energy density and better safety compared with conventional liquid electrolytes. However, ASSLBs with PEO-based solid-state electrolytes generally suffer from severe capacity degradation and interface transfer obstacles during the charge/discharge process. In this work, fluoroethylene carbonate (FEC) is employed as a reducing additive to in-situ form LiF-rich and stable solid-state electrolyte interface (SEI). Benefiting from the integrated advantages of Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) and FEC binary additives, the number of lithium-ion transference increases to 0.48, which facilitates the stable cycling of Li||Li symmetrical batteries over 900 h at 0.1 mA cm⁻². The synergistic interplay of LLZTO and FEC constructs a stable LiF-rich SEI film, effectively addressing the interfacial problems caused by lithium dendrites and promoting the transport of Li ions. Therefore, the high ionic conductivity and self-healing anode-electrolyte interface are achieved. This study provides a facile and economical strategy to solve the problem of the lithium-electrolyte interface. It is of great scientific significance for the development of dendrite-free solid-state lithium metal batteries.