Patent ID: 8586223

Claim:
A cylindrical secondary battery, comprising: a hollow center pin having a closed circular cross section and being disposed in a core of an electrode assembly formed in a jelly-roll type, wherein the sum of both lengths from an external surface of the core to an outer diameter of the center pin corresponds to 5 to 11% of an inner diameter of the center pin, wherein when the core has a diameter of approximately 4.2 mm, and the center pin has a thickness of 0.1 mm to prevent explosion and combustion of the battery by facilitating the escape of exhaust gas and heat generated within the battery, the center pin has an inner diameter in the range of 3.6 to 3.8 mm, and the sum of the radial lengths from the external surface of the core to the outer diameter of the center pin is in the range of 0.2 to 0.4 mm.