Cylindrical secondary battery with cap assembly configured for deformation during gas discharge

Abstract

A cylindrical secondary battery is disclosed comprising: a cylindrical can having one opened end to form an opening; an electrode assembly accommodated in the cylindrical can; and a cap assembly including a vent plate which is disposed on the outermost side in the direction away from the opening and which has at least one notch, a cap down which is spaced apart from the vent plate in the direction of the opening and which is electrically connected to the electrode assembly, a support plate between the vent plate and the cap down so as to be coupled to the vent plate, and an insulating member inserted between the support plate and the cap down to insulate the support plate and the cap down from each other. When the gas inside the can is discharged toward the opening, the vent plate is ruptured to be separated from the cap assembly.