Metal collector foil for electric double layer capacitor, method of producing the metal collector foil, and electric double layer capacitor using the metal collector foil

Abstract

A metal collector foil for an electric double layer capacitor has etched upper and lower surface layers and an unetched central layer disposed between the etched upper and lower surface layers. The etched upper and lower surface layers have a total thickness sufficient to provide the metal collector foil with a capacitance per unit area that corresponds to a capacitance value obtained when the etched metal collector foil is subjected to an anodic formation process with application of a withstanding voltage of 65.6 volts, the capacitance value being not less than 1.7 &mgr;F/cm . The unetched central layer has a thickness sufficient to provide the metal collector foil with a tensile strength not less than 9,000 N/cm . A method of producing the metal collector foil and an electric double layer capacitor incorporating therein the metal collector foil are also disclosed.