| 摘要 |
Provided is a lithium ion secondary battery to discharge the gas of a battery by breaking a first crack line and a second crack line at a certain pressure, thereby improving the safety of a battery. The lithium ion secondary battery(100) has a relatively thinner safety vent(148), wherein at least one crack line(149) is formed at the safety vent. Preferably the crack line is a form of a plurality of continuous curved parts and is almost linear. Preferably the crack line is arranged radially with the center part of the safety vent. Preferably the safety vent has a flat first surface and an opposite flat second surface, and the crack line is formed at any one surface of two surfaces or at both surfaces. |
