A long cycle life is another important concern for practical application of supercapacitors. The long term cyclic stabilities of
the ACs were monitored by galvanostatic charge-discharge. As is shown inFig. 6, the specific capacitance of CSC-700 was 323.0 F g1 at the very beginning of the charge-discharge, then it gradually decreased to 287.5 F g1 after 350 cycles (capacitance retention ratio of 89.0%). This can be attributed to the existence of irreversible reactions at the beginning of the prolonged cycling (e.g. electro-oxidation, such as carbon oxidation) after which the values tend to stabilize[42]. Then the capacitance values remain practically constant for another 650 cycles.