Rechargeable battery with short circuit member

1. A rechargeable battery comprising:

an electrode assembly comprising a first electrode, a second electrode, and a separator between the first electrode and the second electrode;

a case containing the electrode assembly; and

a cap assembly coupled to the case, the cap assembly comprising a cap plate, a deformable short circuit member, and a short circuit tab, the deformable short circuit member being attached to the cap plate, the short circuit tab being located outside of the case and on the cap plate and being electrically coupled to the first electrode,

wherein the thickness of the short circuit member is greater at its central region than at its peripheral region.

2. The rechargeable battery of claim 1 , wherein the deformable short circuit member is configured to deform in response to an increase in pressure inside the case to electrically couple the first electrode and the second electrode to each other.

3. The rechargeable battery of claim 1 , wherein the deformable short circuit member comprises a protruded portion at its central region that is thicker than at least one other portion of the short circuit member.

4. The rechargeable battery of claim 1 , wherein the thickness of the deformable short circuit member gradually increases from its peripheral region toward its central region.

5. The rechargeable battery of claim 1 , wherein the deformable short circuit member is configured to deform in response to an increase in pressure inside the case to contact the short circuit tab.

6. The rechargeable battery of claim 5 , wherein the deformable short circuit member is configured for its thicker portion to contact the short circuit tab when deformed.

7. The rechargeable battery of claim 1 , wherein the cap assembly further comprises an insulation member between the short circuit tab and the cap plate for electrically insulating the short circuit tab from the cap plate.

8. The rechargeable battery of claim 1 , wherein the cap assembly further comprises a first terminal electrically coupled to the first electrode and mounted on the cap plate, and a gasket electrically insulating the first terminal from the cap plate, wherein the short circuit tab has an opening through which the first terminal protrudes from interior to exterior of the case.

9. The rechargeable battery of claim 8 , wherein the short circuit tab is fixed to the cap plate by a nut coupled to the first terminal.

10. The rechargeable battery of claim 1 , wherein the second electrode is electrically coupled to the cap plate.

11. The rechargeable battery of claim 10 , wherein the cap assembly further comprises a second terminal electrically coupling the second electrode to the cap plate.

12. The rechargeable battery of claim 11 , wherein the cap assembly further comprises a connection plate electrically coupling the second terminal to the cap plate.

13. The rechargeable battery of claim 1 , wherein the deformable short circuit member is curved to protrude toward inside of the case.

14. The rechargeable battery of claim 1 , wherein the cap assembly has a vent opening, and further comprises a vent plate mounted on the cap plate to cover the vent opening.

15. The rechargeable battery of claim 14 , wherein the vent plate has a notch configured to be opened in response to a further increase in pressure inside the case.