Preparation of high-performance activated carbons for electric double layer capacitors by KOH activation of mesophase pitches

Two kinds of mesophase pitches with different softening points were prepared at different soaking times and directly activated with KOH to study the effects of the softening point on the textural characteristics of the resulting activated carbons and their behavior as electrodes in capacitors. Results show that the softening points of the two mesophase pitches are 280 and 330 (C, and the specific surface areas of the activated carbons are 1 337 and 1 300 m2·g−1, respectively. The specific capacitance of the higher softening point mesophase pitch-derived carbon is higher (255.6 F·g−1) than that of the lower softening point mesophase pitch-derived carbon (190.8 F·g−1) at the same current density. Cyclic voltammograms show that the lower softening point mesophase pitch-derived carbon exhibits better rectangular-shaped I-V curves. The softening points of the mesophase pitches prepared from even the same precursor can significantly affect the electrochemical performance of the resulting activated carbons.