Li1+xTaOxF6-x Oxyfluoride Solid Electrolytes with Amorphization-Driven Enhancement of Ion Conduction Channels for 5 V All-Solid-State Batteries

Abstract

Fluoride solid electrolytes (SEs), despite their extremely low ionic conductivities, offer a promising pathway for enabling 5 V-class chemistries in all-solid-state batteries (ASSBs) owing to their exceptional oxidative stability. Herein, we report a new amorphous oxyfluoride SE, Li1+xTaOxF6-x (x = 0.0-1.0), which exhibits over 3 orders of magnitude higher Li+ conductivity than crystalline LiTaF6, reaching 1.08 x 10(-6) S cm(-1) at 30 degrees C (x = 1.0). Pair distribution function analysis, Raman spectroscopy, and X-ray absorption spectroscopy reveal an extended, corner-sharing chain of Ta(O/F)(6/7) polyhedra framework. Melt-quenching ab initio molecular dynamics simulations further demonstrate that this interconnected structure broadens Li+ diffusion pathways. Leveraging high oxidative stability (>5 V) and improved Li+ conductivity, Li2TaOF5 was implemented as a shielding layer for 5 V-class LiNi0.5Mn1.5O4 cathodes, enabling exceptional cycling performance with 85.8% capacity retention after 1000 cycles at 1.0C and 30 degrees C. Even under high-mass-loading (49.3 mg cm(-2)) or low-temperature (-20 degrees C) conditions, the modified LNMO electrodes with Li2TaOF5 exhibited promising performance, achieving >5.9 mAh cm(-2) with 94% retention. These findings underscore the efficacy of amorphization in advancing fluoride SEs and provide key design insights for advanced halide SEs in high-voltage ASSBs.