Lower pressure relief type cylindrical capacitor monomer

The invention discloses a lower pressure relief type cylindrical capacitor monomer, which comprises a battery cell inserted in a shell, the top of the battery cell is connected with a negative electrode cover plate assembly through a negative electrode collector plate, and the bottom of the battery cell is connected with a positive electrode cover plate through a positive electrode collector plate; a boss in the center of the positive electrode collector plate penetrates out of a center hole of the positive electrode cover plate, a liquid injection hole is formed in the boss, and a rubber plug and an aluminum plug are inserted into the liquid injection hole; a pressure relief hole is formed in the positive electrode cover plate, and an anti-explosion valve plate is arranged in the pressure relief hole; a plurality of convex ribs are arranged on the lower side of the positive collector plate, and a plurality of concave cavities are formed in the upper side of the positive collector plate. The pressure relief s