Abstract: In activated carbon obtained by subjecting a carbonaceous material to an activation treatment, the overall content of alkali metals is set at 100 ppm or less, or the overall content of heavy metals is set at 20 ppm or less and the overall content of alkali metals is set at 200 ppm or less. In cases where such activated carbon is used as a raw material in electronic devices, the formation of dendrites by the reductive deposition of alkali metals or heavy metals tends not to occur, so that problems such as short-circuiting or the like tend not to arise, and a good rate of self-discharge retention is shown.

Abstract: Activated carbon useful as polarizable electrode material for an electric double-layer capacitor can be obtained by mixing a carbonaceous material and an alkali metal hydroxide while maintaining a solid state, granulating the obtained mixture while maintaining its solid state, dehydrating the obtained granulated substance while maintaining its solid state, and subjecting the granulated dehydration product obtained in the dehydration step to an activation treatment. The preferred pressure of the granulation treatment in the granulation step is 0.01 to 300 Torr, and the preferred temperature of the granulation treatment is 90 to 140° C. The preferred pressure of the dehydration treatment in the dehydration step is 0.01 to 10 Torr, and the preferred temperature of the dehydration treatment is 200 to 400° C.

Abstract: To produce activated carbon for an electrode of an electric double-layer capacitor, the following steps are carried out sequentially: a step of subjecting a massive mesophase pitch to a pulverizing treatment to provide a pulverized powder; a step of subjecting the pulverized powder to an infusibilizing treatment under conditions of a temperature in a range of 300° C. (inclusive) to 450° C. (inclusive) in the atmospheric air current, a step of subjecting the pulverized powder to a carbonizing treatment under conditions of a temperature in a range of 600° C. (inclusive) to 900° C. (inclusive) in an inert gas current to provide a carbonized powder, a step of subjecting the carbonized powder to an alkali activating treatment under conditions of a temperature in a range of 500° C. (inclusive) to 1,000° C. (inclusive) in an inert gas atmosphere, followed by the post treatments, thereby producing alkali-activated carbon, and a step of subjecting the alkali-activated carbon to a pulverizing treatment.

Abstract: To produce activated carbon for an electrode of an electric double-layer capacitor, the following steps are carried out sequentially: a step of subjecting a massive mesophase pitch to a pulverizing treatment to provide a pulverized powder; a step of subjecting the pulverized powder to an infusibilizing treatment under conditions of a temperature in a range of 300° C. (inclusive) to 450° C. (inclusive) in the atmospheric air current, a step of subjecting the pulverized powder to a carbonizing treatment under conditions of a temperature in a range of 600° C. (inclusive) to 900° C. (inclusive) in an inert gas current to provide a carbonized powder, a step of subjecting the carbonized powder to an alkali activating treatment under conditions of a temperature in a range of 500° C. (inclusive) to 1,000° C. (inclusive) in an inert gas atmosphere, followed by the post treatments, thereby producing alkali-activated carbon, and a step of subjecting the alkali-activated carbon to a pulverizing treatment.

Abstract: In activated carbon obtained by subjecting a carbonaceous material to an activation treatment, the overall content of alkali metals is set at 100 ppm or less, or the overall content of heavy metals is set at 20 ppm or less and the overall content of alkali metals is set at 200 ppm or less. In cases where such activated carbon is used as a raw material in electronic devices, the formation of dendrites by the reductive deposition of alkali metals or heavy metals tends not to occur, so that problems such as short-circuiting or the like tend not to arise, and a good rate of self-discharge retention is shown.

Abstract: Activated carbon useful as polarizable electrode material for an electric double-layer capacitor can be obtained by mixing a carbonaceous material and an alkali metal hydroxide while maintaining a solid state, granulating the obtained mixture while maintaining its solid state, dehydrating the obtained granulated substance while maintaining its solid state, and subjecting the granulated dehydration product obtained in the dehydration step to an activation treatment. The preferred pressure of the granulation treatment in the granulation step is 0.01 to 300 Torr, and the preferred temperature of the granulation treatment is 90 to 140° C. The preferred pressure of the dehydration treatment in the dehydration step is 0.01 to 10 Torr, and the preferred temperature of the dehydration treatment is 200 to 400° C.

Abstract: A process for producing a mesophase pitch based active carbon fiber, comprising the steps of carbonizing a mesophase pitch based infusibilized fiber at 600 to 900° C., activating the thus obtained carbon fiber with alkali, and immersing the thus obtained mesophase pitch based active carbon fiber in an electrolyte and subjecting the immersed mesophase pitch based active carbon fiber to such a charge and discharge treatment that a voltage gradually increased until exceeding 2.5 V is applied at a constant current density to the mesophase pitch based active carbon fiber so that an electric double layer is formed at an interface of the mesophase pitch based active carbon fiber and the electrolyte to thereby effect a charging and thereafter a discharging is effected at a constant current density. There are further provided an active carbon fiber produced by the above process and an electric double layer capacitor including an electrode comprising this active carbon fiber.

Abstract: Mesophase pitch-based activated carbon fibers which are obtained by milling infusibilized mesophase pitch fibers, as they are or after carbonizing at a temperature of 350 to 1,000.degree. C., to an average particle diameter of 5 to 50 .mu.m and then activating in the presence of an alkali metal compound. The activated carbon fibers have a pore distribution suitable for forming a electric double layer and is excellent as the material for an electrode of an electric double layer capacitor. The electric double layer capacitor having the electrode using the activated carbon fiber exhibits high discharge capacity.