Patent ID: 6423440
Filing Date: 2002-07-23
Classification: H01M,Y02E

Abstract:
A closed battery comprising: an electrode element consisting of a positive electrode, a negative electrode, and a separator; an electrolyte; a battery container accommodating said electrode element together with said electrolyte; and a closing member fitted in the inner periphery of an open end portion of said battery container to close the open end portion of the battery container, wherein said closing member consists of a metal substrate, a valve element which has a tongue-shaped format and which is provided in said metal substrate so as to serve as a releasing chip such that when the internal pressure of the battery is elevated, the valve element is bent from a bending fulcrum so as to provide the metal substrate with an opening portion for releasing the internal pressure, by bursting a metal foil which is adhered to the inner surface of the metal substrate, wherein said valve element is provided with a slit between the circumference thereof and the metal substrate, wherein said slit, comprising the opening portion of the metal substrate and the metal foil which seals the opening portion, has a width equal to 10 to 40% of the inside diameter of the valve element.