Hitachi Vehicle Energy, Ltd.

Takayuki Mitani

Katsunori Suzuki

A cylindrical secondary battery where safety can be secured even when an external pressure accompanying rapid deformation of the battery acts on the battery is provided in a battery having a large capacity. A lithium ion secondary battery has a capacity of 14 Ah, where an upper lid is fixed to a battery can which receives an electrode winding grope therein. The upper lid includes a diaphragmformed with a rupturing valve and an upper lid cap whose peripheral edge portion is fixed to a peripheral edge portion of the diaphragm. The rupturing valve includes a rupturing groovewith a V-shaped section formed on a surface of the diaphragmpositioned on the side of the upper lid cap and a rupturing groovewith a U-shaped section formed on a surface of the diaphragmpositioned on the side of the electrode winding group so as to correspond to the position of the rupturing groove

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Hitachinaka, Japan

Takayuki Mitani