ductive metals such ascopper, nickel and silver, metal oxides such as tin oxide, titanium oxide and indium oxide, various fillers plated with metal for conductivity, and electroconductive organic fine powders such as powder of polyacetylene, polyprrole and polyaniline.Substances with ionic conduction mechanism to impart electroconductivity to the product include LiCF.sub.3, SO.sub.3, NaCl.sub.4, L