Electrochemical reactions of surface-fluorinated petroleum coke electrodes in organic solvents

Electrochemical reactions of surface-fluorinated petroleum coke (petroleum coke heat-treated at 2800 °C: PC2800) electrodes have been investigated by cyclic voltammetry and XPS analysis. Three reduction peaks were observed at 2.31 V, 0.70–0.74 V and 0.46–0.59 V versus Li/Li+ in the first reduction curves of cyclic voltammograms. The peak at 2.31 V appeared only for PC2800 fluorinated at 500 °C. Two reduction peaks were also observed at 0.71 V and 0.59 V for surface-oxidized PC2800. The surface oxygen was increased through the electrode preparation process while the amount of surface fluorine was reduced by hydrolysis. The reduction peak at 2.31 V shows the reduction of fluorine bonded to basal plane of graphite, and those at 0.46–0.59 V are due to the reduction of ethylene carbonate (EC) as a solvent. The peak at 0.70–0.74 V would be also attributed to the reduction of EC on the hydrophilic sites of partly oxidized PC2800 surface.