| 摘要 |
A secondary cell comprises a gastight can 1 having a cylinder 11 and a lid 12 fixed to an opening portion of the cylinder, and a secondary cell element accommodated in the can 1. The lid 12 is fixedly provided with a gas vent closure 4 in the form of a disk and having a diaphragm 42 openable upon the internal pressure of the can 1 exceeding a predetermined value. The gas vent closure 4 has an outer peripheral portion welded to an opening edge defining a through bore 14 formed in the lid 12. The lid 12 is formed in a front surface thereof with a circumferential groove 5 surrounding the welded portion of the gas vent closure 4, and a diminished portion 51 is provided between the groove 5 and the welded portion for reducing the sectional area of a heat flow path for the heat of welding to pass therethrough. The lid 12 thus constructed makes it possible to weld the vent closure 4 to the lid 12 free of defects such as pinholes or cracks.
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