Yukari Kibi

Fabrication of high-power electric double-layer capacitors

Abstract The electrochemical behavior of activated carbon/carbon (AC/C) composite electrodes was investigated for high-power electric doublelayer capacitors (EDLCs). It was found that high-rate charge/discharge characteristics are affected by the resistance of the electrolyte phase in the pores of the electrode. The charge/discharge characteristics were improved by optimizing the pore-size distribution of the electrodes. The size and total volume of the macro-pores in the electrodes were controlled by mixing and burning out polymer spheres. A high-power EDLC (15V, 470 F), which can discharge as much as 500 A, was fabricated by using improved AC/C composite electrodes.

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 Omega -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. >