Patent ID: 7758997

Claim:
A secondary battery comprising an electrode unit in which a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween, wherein the electrode unit has a structure characterized in that (a) the positive electrode and/or the negative electrode includes (1) a flexible electrode substrate and (2) active material or material capable of absorbing/discharging active material (hereinafter referred to “pseudo-active material”) impregnated in and/or coated on the electrode substrate, (b) an end portion of the separator wound spirally in a coaxial or elliptical manner is bent toward a center of the electrode unit, (c) the positive electrode has an electrode end portion constituted by the electrode substrate with substantially no active material or pseudo-active material at a positive electrode side end of the positive electrode, wherein at least a part of the electrode end portion is set apart from the bent end portion of the separator, a portion of the electrode end portion is electrically connected to an electrolyte-resistant positive electrode collector plate which is electrically connected to a positive electrode terminal of the battery, and end portions of separators disposed on either side of the negative electrode pack an end portion of the negative electrode, and/or the negative electrode has an electrode end portion constituted by the electrode substrate with substantially no active material or pseudo-active material at a negative electrode side end of the negative electrode, wherein at least a part of the electrode end portion is set apart from the bent end portion of the separator, a portion of the electrode end portion is electrically connected to an electrolyte-resistant negative electrode collector plate which is electrically connected to a negative electrode terminal of the battery, and end portions of separators disposed on either side of the positive electrode pack an end portion of the positive electrode; wherein the separators are arranged so as to prevent the active material or pseudo-active material that sheds from the electrode from contacting the collector plate with the ends of the separators sandwiched by the end portions of the electrodes.