Performance of Electric Double Layer Capacitors using Active Carbons Prepared from Petroleum Coke by KOH and Vapor Re-Etching

The electrochemical storage of energy in a special kind of active carbon materials used as capacitor electrodes is considered. Petroleum coke was used for preparation of carbons with different porosities by KOH and vapor etching with catalysis of FeCI3 in turn. Carbon electrodes were fabricated and used as electrodes of double layer capacitors. Nitrogen adsorption was used to characterize the porous structure of the carbons. The electrochemical performance of the capacitors in 6 mol/L KOH was investigated with constant current charge and discharge experiments. A specific capacitance larger than 160 F/g was achieved with an electrode composed of 75% active carbon with a specific surface area of 1180 m2/g and 20% graphite as conductive agent. Evaluation of capacitor performance was conducted by different techniques, e.g. voltammetry and impedance spectroscopy. Characteristics of the capacitor were also discussed. A hybrid power source consisting of nickel- hydrogen and double layer capacitor was demonstrated by powering successfully a simulated power load encountered in communication equipment.