Patent ID: 8568916

Claim:
A lithium ion secondary battery comprising a case; a positive electrode film; a negative electrode film; a separator sandwiched between the positive electrode film and the negative electrode film, the films and the separator being arranged in multiple layers to form a group of electrodes enclosed in the case, the group of electrodes in the case being impregnated with a non-hydrous electrolyte solution, a positive collector disc plate connected to a positive electrode side of the group of the electrodes, and a negative collector disc plate connected to a negative electrode side of the group of the electrodes, wherein each of the electrode films has a non-coated portion extended along one side thereof, a part of the non-coated portion or the entire non-coated portion being exposed from a side of the separator, and wherein at least one of the collector disc plates is welded to the side of the exposed non-coated portion of the group of the electrodes at a welded portion, the periphery of each of the collector disc plates having a projected annular rim, which is bent towards the group of electrodes, wherein the annular rim of each of the disc plates covers an outer periphery of the group of the electrodes, and wherein an edge of the exposed non-coated portion is bent and included in the annular rim, and a thickness of the annular rim is larger than a width of the welded portion; wherein each of the positive collector disc plate and the negative collector disc plate has radial projections on one face, the one face being on an opposite side of the collector disc plate from the other face opposing the group of electrodes, the radial projections extending from the center thereof towards the periphery thereof, and each of the projections is formed in a parallel groove extending along the projection.