Synergistic Oxy-Fluoro-Halide Superionic Conductor Stabilized to Lithium Anode

Halide superionic conductors, distinguished by their remarkable oxidative stability and exceptional mechanical deformability, are emerging as a transformative class of materials poised to revolutionize high-performance, all-solid-state lithium batteries (ASSLBs). However, challenges related to the stability of halide solid-state electrolytes (SSEs) against lithium metal remain unresolved. Designing a halide SSE to address this challenge is crucial for its development. This study proposes an oxy-fluoro-synergistic strategy to synthesize Li_2.8ZrCl_4.8-O_0.8F_0.4 (LZC-OF) with Li₂O&LiF protective layers on its surface. It exhibits an excellent ionic conductivity of 0.72 mS cm^-1 (25 °C) and superior lithium metal stability. The in situ-formed fluoride interfacial layer between LZC-OF and Li results in excellent cycling stability of symmetric Li|LZC-OF|Li cell (600 h @ 0.1 mA cm^-2). Meanwhile, the LZC-OF SSE exhibits satisfactory capacity retention (87.4% after 100 cycles at 0.5C) and excellent high-rate performance (105.3 mAh g^-1 at 1C) in a full cell. This study presents an innovative design approach to enhance the electrochemical stability of halide SSEs and promotes the application of the Li₂ZrCl₆-family in high-performance ASSLBs.