CYLINDRICAL SECONDARY BATTERY INCLUDING GASKET HAVING RECESS FORMED THEREIN

Disclosed is a cylindrical secondary battery configured such that a first gasket and a second gasket are applied in the state in which the shape of each of a first gasket and a second gasket is modified in order to secure hermetic sealability and insulation. The cylindrical secondary battery includes a cylindrical can configured to receive an electrode assembly including a positive electrode, a negative electrode, and a separator, a cap assembly located at the upper part of the cylindrical can, a first gasket configured to hermetically seal the cylindrical can in the state of being added so as to cover outer circumferential edges of a top cap and a venting member of the cap assembly, a current interrupt device (CID) located at the lower part of the cap assembly, and a second gasket located at the outer circumferential edge of the current interrupt device, wherein an upper end portion of the first gasket has a structure configured to cover the upper surface of the outer circumferential edge of the top cap, and a recessed portion is formed in at least a part of the inner surface of the upper end portion of the first gasket, the recessed portion being configured to prevent the first gasket from being brought into tight contact with the upper surface of the outer circumferential edge of the top cap.