To obtain an optically isotropic pitch-based activated carbon fiber capable of providing excellent characteristics as an electrode material for electric double layer capacitor, and to obtain an electric double layer capacitor using the activated carbon fiber.
This activated carbon fiber is obtained by grinding an optically isotropic pitch-based infusibilized fiber or an optically isotropic pitch-based carbon fiber obtained by carbonization at temperature 350°C to 1,000°C after infusibilization into a ground material having 5 μm to 50 μm average particle diameter and activating the ground material with an alkali. This electric double layer capacitor using the activated carbon fiber as an electrode material has pores (A) of 0.4-1.5 nm pore radius (MP method) and pores (B) of 3.5-6 nm pore radius (mercury porosimeter method) and the ratio [(Bv)/(Av)] of the pore volume (Bv) of the pores (B) to the pore volume (Av) of the pores (A) of 0.01-0.25. The electric double layer capacitor using the optically isotropic pitch-based activated carbon fiber as an electrode material shows a high service capacity.
YAMAMOTO TETSUO
KAWABUCHI YUJI
HOSOTSUBO TOMIMORI
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