Preparation of graphite oxide and its electrochemical performance for electric double layer capacitor

The carbon materials, having different degree of the graphitization, were oxidation-treated with a sodium chlorate and 70 wt.% of nitric acid to achieve an electrochemically active material with a larger capacitance. Among non-graphitizable pitch, needle coke and natural graphite, the structure of needle coke was easily changed to the graphite oxide after oxidation treatment, and the inter-layer distance of the oxidized needle coke was expanded to 6.8 nm. This oxidized needle coke has exhibited largest specific capacitance per weight and volume of 29.5 F/g and 24.5 F/ml, respectively, at the two-electrode system in the potential range of 0–2.5 V. The electrochemical performance of the oxidized needle coke was discussed with the phenomenon of the electric field activation, and was compared with the results of KOH-activated needle coke as previously reported.