Fluorinated Superionic Oxychloride Solid Electrolytes for High-Voltage All-Solid-State Lithium Batteries

As the demand for higher energy density grows rapidly, the development of high-voltage all-solid-state lithium batteries (ASSLBs) becomes essential. However, most existing solid electrolytes (SEs) are still incapable of stable operation at high voltages. Herein, we report a series of fluorinated lithium tantalum oxychlorides (LTOC-F) as amorphous SEs for high-voltage ASSLBs. The optimized LTOC-10%F SE exhibits remarkably improved high-voltage stability and a high ionic conductivity of 2.3 mS cm–1 at 25 °C. The ASSLB using an LCO cathode and LTOC-10%F SE achieves a high capacity of 180 mAh g–1 with a cutoff voltage of 4.5 V and high-capacity retention of 81% after 300 cycles. Furthermore, the underlying mechanisms for enhanced performance are identified as the intrinsically extended electrochemical window of SE and the in-situ-formed LiF-rich cathode-electrolyte interface (CEI). Overall, this work provides a fluorination strategy for high-voltage ASSLBs and also offers insights into the analysis of amorphous SEs and CEIs.