Abstract: The carbon electrode materials for electrochemical capacitors were prepared from petroleum coke precursor carbonized at different temperatures followed by KOH activation. The precursors and activated products were characterized by XRD, TEM and N₂ adsorption techniques. The capacitive behavior of activated petroleum coke was also examined. Results show that crystallite structure and pore structure of activated petroleum cokes can be controlled by adjusting the precarbonization temperature, and so non-crystalline high surface area activated carbons and crystalline low surface area novel activated carbons which consist of large amount of graphite-like crystallite are obtained. The energy storage for the low surface area activated carbon depends on the intercalation of electrolyte ions into graphite-like crystallite layers during the charge process. The surface specific capacitance of the low surface area activated carbon is over ten times of that for high surface activated carbon, and the low surface area activated carbon has a higher volumetric specific capacitance.

Key words: electrochemical capacitors, graphite-like crystallite, electrochemical activation, specific capacitance