Patent ID: 8753760
Filing Date: 2014-06-17
Classification: H01M,Y02E,Y02P

Abstract:
1. A secondary battery comprising a gas release valve located at a battery container housing a power generating element, wherein: the gas release valve includes a valve disk caused to expand outward by internal pressure in the battery container; wherein a plurality of grooves is formed at the valve disk in order that a plurality of valve element pieces becomes fractured along the grooves when the valve disk expands due to the internal pressure; a scatter-deterring portion is formed at the valve disk in order to prevent the fractured valve element pieces along the grooves from scattering away from the valve disk; and retarding areas that slow propagation of fracturing along the grooves while the valve disk is being deformed following a start of fracturing at the grooves are formed, wherein the plurality of grooves includes a perimeter groove formed along a perimeter of the gas release valve and an inside groove formed in an inner area surrounded by the perimeter groove; the perimeter groove includes a plurality of perimeter groove elements set discontinuously in a circular form; the inside groove includes a plurality of inside groove elements radially extending from a central area of the gas release valve toward the perimeter, the inside groove elements dividing an inner area of the valve disk into the plurality of valve element pieces; at least one pair of perimeter groove elements between first discontinuous areas is set along at least one perimeter side of the valve element pieces; ends of the inside groove elements on a perimeter side each reach a second discontinuous area formed between the perimeter groove elements; the scatter-deterring portion is constituted with the first discontinuous area set between the pair of perimeter groove elements along the perimeter side of the valve element; the retarding area is constituted with the second discontinuous area assuming a position between a perimeter-side end of the inside groove element defining the valve element pieces and the perimeter groove element; and the perimeter groove elements and the inside groove elements are grooves formed at a surface of the valve disk, with the perimeter groove elements assuming a groove depth smaller than a groove depth of the inside groove elements.