Rechargeable Graphite Fluoride Electrodes Realized by Fluoride Anion Insertion and Deinsertion

This study found for the first time that F– anions can be electrochemically inserted or deinserted into or from carbon-based materials, respectively, using a combination of graphite fluoride (GF) and a Li-based organic electrolyte with a suitably high potential (>5.0 V vs Li+/Li). The GF materials used in this study produced amorphous carbon and LiF after the first discharge, with a discharge capacity of 600 mAh g–1 that was almost in line with the theoretical value (about 630 mAh g–1). As determined by subsequent electrochemical measurements, a reversible charge or discharge capacity of ∼200 mAh g–1 in addition to a Coulombic efficiency of ∼86% and a capacity retention of ∼85% after 30 cycles were observed within a potential range of 1.5–5.3 V. Various analyses clearly demonstrate that the electrochemical properties resulted from the reversible insertion and deinsertion of F– anions into and from amorphous carbon formed in the GF cathode, respectively, which was triggered by the formation of LiF, the source of the F– anions.