Electrochemical Introduction/Extraction of Fluoride Ions into/from Graphene-like Graphite for Positive Electrode Materials of Fluoride-Ion Shuttle Batteries

A cathode material, graphene-like graphite, was developed for all-solid-state-type fluoride-ion shuttle batteries (FSBs). Fluoride ions were electrochemically introduced/extracted into/from it, and covalent C–F bonds were formed upon electrochemical oxidation. The introduction of fluoride ions into it occurred at a lower voltage than that into graphite. While the layered structure of graphite was completely destroyed during charging, that of graphene-like graphite was still maintained to some extent. The discharge voltage was higher than 1 V versus Pb/PbF2, which was higher than that of most of the previously reported cathode materials. The first discharge capacity (161 mAh g–1) was larger than that of graphite (140 mAh g–1), and the Coulombic efficiency and cyclability were much higher. This work demonstrates that graphene-like graphite prepared by thermal reduction of graphene oxide at 300 °C, GLG300, is a promising material for positive electrodes of FSBs.