Rechargeable battery

A rechargeable battery for improving stability by quickly transmitting generated gas to a vent plate when an internal short circuit occurs, the rechargeable battery including: an electrode assembly including a first electrode, a second electrode, and a separator between the first and second electrodes; a case containing the electrode assembly; and a cap plate sealing an opening of the case and including an electrode terminal connected to the electrode assembly, the cap plate further including a round unit arranged at an inner side of the case.