Patent ID: 8072733

Claim:
An electrochemical capacitor comprising a nonaqueous electrolyte and a pair of electrodes, wherein carbon nanotubes are used as an electrode material for at least one electrode from the pair of electrodes, the carbon nanotubes have a specific surface area of from 1000 to 2500 m 2 /g and contain semiconductive carbon nanotubes, the electrode material exhibits a potential-dependant differential capacity due to electrochemical doping, and a differential capacity ratio (C 0.5 /C 0 ) of the electrode material is at least 1.2, where C 0 is a differential capacity per the electrode weight (F/g) at a zero charge potential E 0 , and C 0.5 is the differential capacity per the electrode weight (F/g) at a potential polarized by 0.5 V from the zero charge potential.