The invention relates to an explosion-proof cap of a micro-resistance cylindrical
lithium ion battery. The explosion-proof cap comprises an upper cap, a
gasket, an explosion-proof membrane with a wall body, an
orifice plate and a sealing ring. A plurality of air holes are arranged on the upper cap. The wall body of the explosion-proof membrane is bent and wraps the
gasket and the upper cap in the cavity of the explosion-proof membrane. After the explosion-proof membrane wraps the
gasket and the upper cap, the explosion-proof membrane is embedded in the sealing ring coated with glue. The
orifice plate is embedded at the bottom surface of the sealing ring. The
orifice plate is welded with the explosion-proof membrane through
laser spot welding. A circular
welding platform which protrudes downward is arranged on the bottom surface of the explosion-proof membrane. A prestressed pressure relief ring is formed between the circular
welding platform and the bottom surface of the explosion-proof membrane. In combination with the
cutting of the prestressed pressure relief ring along a sharp spiny flanged edge in the gasket, the
flanging of the cap edge of the upper cap and the tight
welding between a convex welding spot on the cap edge and the bent wall body of the explosion-proof membrane, the invention realizes that the explosion-proof membrane can be exploded open when being turned over and the overall
internal resistance of the cap is reduced, and has the advantages that the structure is simple, compact and stable, the deformation and the misplacement are not apt to occur, the
internal resistance of the cap is low, the battery performance is high, the explosion-proof membrane can be normally exploded open to relieve pressure after the explosion-proof membrane is turned over, the explosion-proof performance is stable and the service life is long.