Preparation of mesoporous carbon microsphere/activated carbon composite for electric double-layer capacitors

Mesoporous carbon microspheres (MCMs) with specific surface area and diameter of 1850 m2·g−1 and 1μm, respectively, were synthesized using the solvothermal method. When 20 wt% of these were added to a high surface area-activated carbon (HSAC: 3 200 m2·g−1) its interfacial resistance and ion diffusion resistance decreased significantly. The specific capacitance of the composite electrode is 230 F·g−1 in 6 mol·L−1 KOH electrolyte, whereas those of pure HSAC and MCMs are only 190 and 148 F·g−1, respectively, at a high current density of 12 A·g−1. The improvement in electrochemical performance of the HSAC electrode at high current densities is attributed to the small particle diameter, mesoporous structure and high specific surface area of the added MCMs.