Double-sealed cap assembyly, and cylinderical secondary battery comprising the same

PURPOSE: A cap assembly is provided to prevent the leakage of electrolyte caused by the impact applied to a battery due to double sealing, thereby improving the safety of a battery. CONSTITUTION: A cap assembly(400a) comprises: a top cap(410a) which has a gas exhaust hole(412a) and forms protruded terminals; a safety vent in which a protrusion part is included in the center thereof and two or more notches are formed; a CID(440a) equipped with the gas exhaust hole and a central part welded with the protrusion part of the safety vent; and a gasket(500a) which includes an inclined part or a stepped part and seals the outer circumference of devices.