US Patent 7153606 Secondary battery

A secondary battery including an electrode group formed by winding a positive electrode and a negative electrode with the interposition of a separator, the positive electrode includes a belt-shaped positive electrode core and a positive electrode material mixture carried on the positive electrode core, the negative electrode includes a belt-shaped negative electrode core and a negative electrode material mixture carried on the negative electrode core, at least one of the positive electrode and the negative electrode has an end portion parallel to the lengthwise direction thereof exposing the core, the end portion positioned at an end face of the electrode group is directly connected to a current collector plate, and at least part of the current collector plate is exposed outside at the bottom of a battery case.