Large capacitance electric double layer capacitor using activated carbon/carbon composite

An electric double-layer capacitor with large capacitance, 1000 F at 5.5 V, has been developed. It uses activated carbon/carbon (AC/C) composite as the polarizable electrodes and sulfuric acid as the electrolyte. The AC/C composite was synthesized through a simple process, namely, a cured mixture of activated carbon and phenol-formaldehyde resin was carbonized. The AC/C composite has a large surface area, 1300 mg, and low resistivity, 0.01 Ω-cm. Two kinds of pores exist in the AC/C composite: macropores with submicrometer diameters, and micropores with below 4-nm diameter. The micropores are impregnated with the sulfuric acid aqueous solution through the macropores open to the outer surface. The electric double-layer capacitance per unit volume for the AC/C composite in sulfuric acid is greater than that for activated carbon powder as a raw material. The capacitor is expected to be used as an energy storage device and a supplementary power source