Patent ID: 7153606

Claim:
A secondary battery comprising an electrode group, an electrolyte, a battery case for accommodating therein said electrode group and said electrolyte, and a current collector plate positioned at the bottom of said battery case, wherein said electrode group is formed by winding a positive electrode and a negative electrode with the interposition of a separator, said positive electrode comprises a belt-shaped positive electrode core and a positive electrode material mixture carried on said positive electrode core, said negative electrode comprises a belt-shaped negative electrode core and a negative electrode material mixture carried on said negative electrode core, at least one of said positive electrode and said negative electrode has an end portion parallel to the lengthwise direction thereof exposing said core, said end portion positioned at an end face of said electrode group is directly connected to said current collector plate, said battery case comprises a cylindrical part with an inwardly extending bottom, said cylindrical part with the bottom has a through hole in the bottom, said current collector plate is provided with a protrusion to be fitted in said through hole, and said protrusion is welded to the edge around said through hole.