A positive electrode made of lithium contained metal oxide and a negative electrode made of a carbon material as active material are separated by a separator impregnated with organic electrolyte solution or a solid electrolyte layer. In particular, the carbon material is added with the metal oxide which can electrochemically be reduced by charge to generate a metal. The metal oxide consists mainly of a mixture of the carbon material and at least one metal oxide selected from a group of TiO.sub.2, Cr.sub.2 O.sub.3, MnO.sub.2, Fe.sub.3 O.sub.4, CoO, Co.sub.2 O.sub.3, Co.sub.3 O.sub.4, NiO, Ni.sub.2 O.sub.3, Ag.sub.2 O, PbO, Sb.sub.2 O.sub.3, Bi.sub.2 O.sub.3, SeO.sub.2, and TeO.sub.2.