Reversible Fluoride-Ion (De)Intercalation of CuLaO₂ Cathodes with Crystalline/Amorphous Phase Transition Involving Multi-Electron Reaction

All-solid-state fluoride-ion batteries (FIBs) are considered as a promising alternative to lithium-ion batteries (LIBs) for next-generation energy storage devices. Intercalation-type cathode materials for FIBs have been developed in the past. However, they are limited by low theoretical capacities, which fail to meet the high energy density and high rate capability demand. This study reports the first application of the intercalation-type cathode material CuLaO2 in all-solid-state FIBs. This cathode maintains a high capacity of 184 mAh g–1 over 50 cycles. Compared to the metal/metal fluoride (M/MFx) and the intercalation-type cathode materials reported so far, CuLaO2 exhibits an outstanding rate capability with a capacity of 102 mAh g–1 even at a high current density of 200 mA g–1. Electrochemical measurements, coupled with X-ray absorption spectroscopy and X-ray diffraction prove that the charge/discharge processes of CuLaO2 proceed via intercalation reaction with the reversible phase transition between crystalline/amorphous phases, and the charge compensation is responsible for multielectron redox of Cu+/Cu3+. We believe that this study can bring insight into all-solid-state FIBs.