Preparation of mesophase-pitch-based activated carbons for electric double layer capacitors with high energy density

The activated carbons (ACs) prepared from mesophase pitch with KOH etching are used to fabricate electrodes for electric double layer capacitors. The ACs with pre-carbonization are also prepared. Nitrogen adsorption at 77 K is used to characterize the surface area and porous structure of the ACs, which show a bimodal pore distribution. By adjusting the residence time at 800 °C, the intersection of the ACs’ microcrystallites is changed and the peak value varies between 1.7 nm and 2.1 nm. Pre-carbonization promotes the growth of graphitic microcrystallites and hinders the crystallites from intersecting, and thus the surface area decreases and the size of the pore is more difficult to adjust. The performance of the ACs in the organic solvent (1 M of Et4NBF4 in propylene carbonate) is investigated with voltage sweep cyclic voltammetry and constant-current charge–discharge cycling. The sample with the surface area of 2258 m2/g possesses a specific capacitance as high as 145 F/g. When power density is increased to 12 kW/kg, its capacitance does not decrease, and energy density keeps at 31 Wh/kg.