CYLINDRICAL LITHIUM ION SECONDARY BATTERY

摘要

A cylindrical lithium ion secondary battery, including a cylindrical can; an electrode assembly in the cylindrical can with an electrolyte solution; and a cap assembly sealing the cylindrical can, the cap assembly including a positive temperature coefficient (PTC) device connected to the electrode assembly, a cap-up connected to the PTC device, solder between the PTC device and the cap-up, and an exterior space without the solder on external circumferences of the PTC device and the cap-up.