Properties of Composite Electrodes for All-solid-state Fluoride-ion Secondary Batteries Processed by High-pressure Torsion (Supporting Information)

All-solid-state fluoride-ion batteries (FIBs) using metal/metal fluorides are expected to be the next generation of storage batteries because they exhibit high volumetric energy densities by utilizing multielectron reactions, compared to the current lithium-ion batteries. However, method of fabricating a composite electrode for all-solid-state fluoride-ion batteries has not yet been established. A fabrication method for a composite electrode that disperses the active material and solid electrolyte is required. To approach this problem, in this study, we employed a high-pressure torsion (HPT) method, in which an active material, solid electrolyte, and conductive agent can be mixed with size reduction, as a new process and prepared Cu (active material)/PbSnF₄ (solid electrolyte)/acetylene black (conductive agent) cathode composites. The crystalline sizes of Cu and PbSnF₄ were significantly reduced. The apparent grain boundary resistance was also reduced owing to the more homogeneous distribution in the cathode composites after HPT processing. These structural and morphological changes led to high electrochemical performances, compared to a cathode composite without HPT.