Carbon Based Double-layer Capacitor and Composite Power Source

The electrochemical storage of energy in a special kind of active carbon materials used as capacitor electrodes was considered. Petroleum coke was used to prepared activated carbons with special porosities and structures by NaOH and vapor etching with catalysis of NaHCO3 in turn. Nitrogen adsorption was used to characterize the porous structure of the carbons. Carbon electrodes were fabricated to serve as electrodes of double layer capacitors. The electrochemical performance of the capacitors in 6M KOH was investigated with constant current charge and discharge experiments. A specific capacitance larger than 160F/g was achieved with an electrode composed of 75% active carbon and 20% graphite. Evaluation of capacitor performance by different techniques, e.g. voltammetry, impedance spectroscopy characteristics was also discussed. A hybrid power source consisting of nickel-hydrogen battery and double layer capacitor was demonstrated to power successfully simulated power loads encountered in communication equipment or hybrid electric vehicle (HEV).