CHARACTERIZATION OF ACTIVATED CARBON-FIBER CLOTHS FOR ELECTRIC DOUBLE-LAYER CAPACITORS BY ADSORPTION METHOD

Two types of phenolic-resin based activated carbon fiber cloths, ACFC (a) and (b), have been characterized for polarizable electrodes of electric double-layer capacitors by the gas adsorption method. Results have been analyzed by means of the Dubinin-Astakhov equation, the t-method, and the micropore analysis method. The BET surface areas (S(BET)) of ACFC (a) and (b) were 1798 and 1061 m2g-1, respectively. In the pore size distribution curve of ACFC, the most popular pore diameter was 0.84 and 0.7 nm for ACFC (a) and (b). Both samples of ACFC had micropores only. With increasing S(BET), the pore diameter became large and the C-constant in the BET equation became small. The electric double-layer formed on the surface of ACFC (a) in an organic electrolyte was stable and that of ACFC (b) was unstable. In accordance with the results, the temperature dependence of capacitance in the capacitors with ACFC (a) was small, while that with ACFC (b) was large. As polarizable electrodes of the capacitors, the ACFC (a) was a more suitable material than the ACFC (b).