Cylindrical lithium ion secondary battery and fabrication method thereof

摘要

A lithium ion secondary battery is so designed as to facilitate the insertion of the top insulator plate and to secure the fixation of the electrode group. This structure can reduce the probability of the electrode group moving around in the battery case to be damaged when the battery is dropped or shocked, thereby maintaining high safety standards even when a high pressure is applied from outside the battery. In a lithium ion secondary battery provided with a safety valve and composed of an electrode group which consists of a band-shaped positive electrode plate and a band-shaped negative electrode plate wound together with a separator disposed therebetween and which is housed in a cylindrical metal battery case with a bottom, together with a top insulator plate, the top insulator plate is designed to be elastic and is provided in its center with a through hole into which a center core member is press-fitted.