Plasma-fluorination of petroleum coke and those heat-treated at 1860, 2300 and 2800°C (abbreviated to PC, PC1860, PC2300 and PC2800) was conducted for 15, 30 and 60min using CF4 gas at 90°C. Fluorine contents obtained by elemental analysis were negligible except PC fluorinated for 60min (0.7at.%). Fluorine concentration on the surface decreased with increasing heat-treatment temperature of petroleum coke, i.e. from PC to PC2800 when plasma-fluorination was made for 30 and 60min. Transmission electron microscopic observation revealed that the closed edges of PC2800 were destroyed and opened by plasma-treatment. Plasma-fluorination increased surface disorder of heat-treated petroleum cokes, however, slightly reduced surface areas. These surface structure changes increased first coulombic efficiencies of PC2300 and PC2800 by 6–8 and 8–10% at both 60 and 150mAg−1, respectively.