Rectangular nickel-metal hydride secondary cell

A rectangular nickel-metal hydride cell, comprising a rectangular cylindrical metal case having an inner wall, a bottom and an open end portion;

• an electrode group housed in said metal case and constructed such that a nickel positive electrode and a hydrogen absorption alloy negative electrode are alternately superposed one upon the other with a separator interposed between said positive and negative electrodes;
• an alkali electrolyte contained in said metal case;
• a rectangular sealing plate mounted near the open end portion of said metal case;
• and an insulating gasket formed of a synthetic resin and interposed in a compressed state between the inner wall near the open end of said metal case and the peripheral portion of said sealing plate;
• wherein said metal case comprises a folded portion formed by inwardly folding the open end portion of said metal case and an inwardly projecting stepped portion formed along the inner surface of said metal case below the folded portion, said sealing plate is fixed to said metal case at the portion between the folded portion and the stepped portion of said metal case, the folded portion at a corner portion of the open end portion of said metal case has an angle of 80.degree. to 100.degree., and the folded portion at the side positioned between two adjacent corners of the open end portion of said metal case has an angle smaller than that of the corner portion.