Preparation And Electrochemical Performances Of Activated Carbon Electrodes From Petroleum Cokes For Supercapacitors

Supercapacitor is a new kind of electrochemical energy storage devices with high power density, which can be used in many fields such as memory back-up devices and electric vehicles. The practical electrode materials for supercapacitor are usually porous carbon materials such as activated carbon (AC) because of its high surface area and low cost. However, since the energy density of supercapacitor is only several Whkg, much lower than that of rechargeable batteries, the capacitance of supercapacitor has to be increased. In this work, the activated carbon materials were prepared by the catalytic activation method from petroleum cokes pre-oxidized in air. The relationship between the pore characteristics of carbons impregnated by different catalysts and the capacitance behaviors were investigated. The main results are as follows:1,There are great influences of original cokes on the pre-oxidation and activation. The petroleum coke possessing small mosaics, small crystals and low volatile component was favorable for the preparation of activated carbon with large specific surface owing to its higher reaction activity. 2,By pre-oxidation in air before the activation, the primary pores were generated which is beneficial for the impregnation of catalyst and activation. The specific surface of activated carbon can achieve 299．7m/g which increased 4 times than that of the samples without pre-oxidation. And the specific capacitance can achieve 80F/g which increased 2 times. During the pre-oxidation process, many factors especially the temperature have great effects on the degree of oxidation.3,In the same activation condition, the activated carbons prepared by impregnating different catalysts have different structures and electrochemical performances. The reactivity of catalysts with carbons in terms of special surface area and specific capacitance of activated carbon is as following: ZrOCl〉Zr(ac)〉ZrO(NO)〉Fecl.4,By impregnating chlorine zirconia, the activation was remarkably accelerated. Compared to the activated carbons without using catalyst, the activated carbons with catalyst exhibit the specific capacitance of 105．1F/g, which increased by 30%. With the increase of catalyst addition from 0．5% to 10%, both the specific surface areas and capacitances show the tendency of increase at first and then decrease, and at the amount of 2% in mass, the specific surface and capacitance can achieve the maximum of 407m/g and 105．1F/g respectively. The catalyst powders in the activated carbons have not found any influence on the specific capacitance in the current charge-discharge cycling. 5,There are great influences of activation condition on the catalytic activation. As the temperature increase and time elongation, the specific surface and capacitance of active carbons also increase. And the effect of increasing temperature is more available than the activation time.