Patent ID: 8071230

Claim:
A cylindrical secondary battery including: a cap assembly constructed in a structure in which a vent, which intercepts electric current and discharges pressurized gas when an interior pressure of the battery is increased due to abnormal operation of the battery, is in direct contact with upper and lower surfaces of a top cap having a protruding central part, wherein an end of the vent is bent to surround and directly contact an outer circumferential surface of the top cap, and a single continuous groove for preventing the leakage of an electrolyte and preventing the occurrence of defectiveness of the battery during the assembly of the battery is disposed in the top cap at interfaces between the vent and the top cap where the vent and top cap directly contact each other, such that the groove is arranged in parallel with the outer circumferential surface of the top cap, and a weld at the interface between the vent and the top cap, adjacent to the outer circumferential surface of the top cap, and sealing the vent and the top cap to each other.