Patent ID: 8354187

Claim:
A secondary battery comprising an electrode group in which a positive electrode plate and a negative electrode plate are wounded with a porous insulation layer interposed therebetween, wherein an end portion of at least one of the electrode plates having one polarity protrudes from the porous insulation layer and abuts a current corrector plate and the current collector plate is arranged in relation to the electrode group so as to entirely cover the end portion of the electrode plate of the electrode group, parts of the end portion of the electrode plate abutting the current collector plate are welded to the current collector plate with a uniform pitch along a winding direction of the electrode group at discrete joint portions on a surface of the current collector plate, the joint portions are discretely provided on the surface of the current collector plate so that a current flowing from the electrode plate to the current collector plate is uniformly distributed, and each of the joint portions is provided according to a location expressed by polar coordinates (r, θ), which is a point at a distance of r from a winding center of the electrode group regarded as an original point in a direction making an angle θ with a radial direction of the current collector plate regarded as an initial line, set on the surface of the current collector plate, wherein the polar coordinates (r, θ) is expressed by the following equation: (r, θ)=(ns, 2 mπ/n), where s is the width of the joint portions, n is 1 or a larger natural number, and m is a natural number satisfying 1≦m≦n.