Vol.29 No.2(2) [2007]

Properties of electric field activated carbon derived from needle coke

Satoshi MITANI, Sang-Ick LEE, Koji SAITO, Yozo KORAI and Isao MOCHIDA


Electric double layer capacitor(EDLC) is expected to be various emerge storage applications. High performance activated carbon for EDLC needs high surface area with optimized pore diameter. KOH activation is one of the effective methods for preparation of activated coke for EDLC, However, KOH activation is argued to carry many problems from views of cost and safety. More moderate activation is wanted against graphitizable carbon to be activated. The electrodes of particular carbons showed higher capacitance when it charged at higher voltage(2.5~3.7V), it was reported as electric field activation. In this study, activation of carbon higher charging voltage was examined to prepare higher performance electrode. Although the surface area of the coke K2CO3 activated at 900oC was as small as 20 m2/g, the activated coke achieved capacitances per weight and volume of 27 F/g and 29 F/ml, respectively, in the two-electrode system, by charging at 3.7 V. The graphitic and pore structures of the coke before and after the electric field activation were analyzed by XRD and 129Xe-NMR. The model of structural changes by electric field activated coke.