Preparation and electrochemical characterization of an activated carbon material with high surface area for supercapacitor

A coal-tar pitch was selected as precursor and a chemical activation method was used to prepare an activated carbon material with large surface area,and the activated carbon electrodes with high specific capacitance were fabricated for supercapacitor. Impact of activating temperature on the specific capacitance of activated carbon electrode was studied; the relationship among the pore structure; surface area and specific capacitance of activated carbon electrode was discussed; and the electrochemical characterization was also conducted with cyclic voltammetry and AC impedance methods. The results show that,in the range of 500 ℃ to 700 ℃,the specific capacitance of activated carbon electrodes obviously increases with the increasing activated temperature. When the activated temperature is above 700 ℃,the specific capacitance of activated carbon changes little with further increase of the activating temperature. The activated carbon prepared at 700 ℃ has obvious porous structure,and its pore volume and surface area are 1.038 cm3/g and 1959 m2/g,respectively. The electrode fabricated with the activated carbon prepared at 700 ℃ exhibits a high specific capacitance of 211 F/g at a charge-discharge current of 10 mA/cm2,an ESR (equivalent series resistance) of about 0.9 Ω/cm2,and a residual capacitance more than 90% after 500 cycles. A pure capacitance behavior can be found at the frequency below the knee in its AC impedance spectroscopy,and the cyclic voltammetry curve of activated carbon electrode shows good reversibility.