FLUORINATION OF FULLERENE C-60 AND ELECTROCHEMICAL PROPERTIES OF C60FX

Fluorinated fullerene polycrystalline powders C60Fx have been obtained by direct fluorination of C-60 at 100 degrees C. Electrochemical behaviors of C-60 and C60Fx were investigated by the cyclic voltammetry and galvanostatic discharges on Li/1M LiClO4-PC/C-60 and C60Fx cells. The electronic structure changes of C-60 upon fluorination were also investigated by XANES and UPS. Three stepwise reversible reduction peaks (2.50, 2.15 and 1.85 V), and an irreversible reduction peak (2.8-3.2 V) corresponding to C-F reduction were observed on the cyclic voltammograms. The fluorination of C-60 renders the open circuit voltage (OCV) higher by 1 V (OCV = 4 V vs. Li reference electrode), and the reversible reduction potentials nobler by 0.15 V. These electrode behaviors reflect the changes in the C-60 electronic structure through fluorination.