Room-Temperature Operation of Thin-Film All-Solid-State Fluoride Shuttle Batteries Using CeF ₃ Anodes and Ag Cathodes

All-solid-state-fluoride-shuttle batteries (AFSBs) offer higher theoretical energy density than lithium-ion batteries but generally require elevated temperatures (>80 °C). Here, we demonstrate reversible room-temperature operation of an AFSB full cell with a CeF3 anode, LaF3 solid electrolyte, and Ag cathode. Thin-film CeF3 (50–200 nm) and Ag (30–120 nm) electrodes almost deliver theoretical capacities at 25 °C, and a coin cell powers a light-emitting diode. Operando synchrotron X-ray diffraction simultaneously tracking both electrodes reveals reversible phase transitions of the CeF3 anode between tysonite-type CeF3 and fcc γ-Ce and multistep reactions of the Ag cathode involving Ag, AgF, and Ag2F.