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.