EXPLOSION-PROOF SEAL PLATE FOR ENCLOSED TYPE CELL AND PRODUCTION METHOD THEREOF

摘要

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/cm<2> 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/cm<2> 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 A>/=B. 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).