The present invention relates to an explosion-proof seal plate for a sealed
cell and a production method thereof and aims at providing an explosion-proof seal plate and production method thereof, wherein problems of a risk of explosion of a
cell due to an excessive pressure inside the
cell caused by abnormal generation of a gas through a
chemical reaction accompanying over charge or erroneous use of the cell or damaging of
electronic equipment using the cell as the power source are solved, ignition and other accidents can be prevented with a high accuracy by reliably
cutting off an
electric current when the cell
internal pressure increases, and the increase in the resistance due to
permeation of an
electrolyte can be limited. In order to accomplish this aim, the present invention provides a thin portion 7a having a
breaking strength of 18-24 kg / cm2 in the central portion of an upper
metallic foil 7 made of aluminum and a thin portion 8a having a
breaking strength of 10-13 kg / cm2 in the central portion of a lower
metallic foil 8 made of aluminum, wherein the
diameter A of the thin portion 7a of the upper
metallic foil and the
diameter B of the thin portion 8a of the lower metallic foil 8 satisfy the relation AB. The two metallic foils are welded at the central portions with an insulating
gasket interposed, and encased in a metallic case 4 made of aluminum having 4 vent holes, on top of which a temperature dependent
resistor 5 and a metallic cap 6 having 4 vent holes are then placed. A seal plate is obtained by sealing the periphery of the metallic case 4, with which it is possible to prevent accidents such as ignition and explosion of a cell by reliably allowing internal gas to exhaust in the event of generation of a large volume of gas under an abnormal condition of a sealed cell.