Secondary battery

1. A secondary 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 accommodating the electrode assembly;

a cap assembly comprising:

a cap plate having a first through-hole and coupled to the case; and

a short-circuiting member electrically coupled to one of the first and second electrodes; and

a displacement plate in the first through-hole and spaced from a bottom surface of the short-circuiting member at a first position, and configured to be separated from the first through-hole and to contact the bottom surface of the short-circuiting member at a second position.

2. The secondary battery of claim 1 , wherein the displacement plate is welded to the cap plate.

3. The secondary battery of claim 2 , wherein one or more welding portions of the displacement plate are configured to be ruptured when the displacement plate moves from the first position to the second position.

4. The secondary battery of claim 1 , wherein the cap plate further comprises a protrusion protruding toward an interior of the first through-hole.

5. The secondary battery of claim 4 , wherein the protrusion is configured to be broken by movement of the displacement plate.

6. The secondary battery of claim 1 , wherein the displacement plate is electrically coupled to the cap plate by a connecting member, and is configured to remain electrically coupled to the cap plate when the displacement plate moves.

7. The secondary battery of claim 6 , wherein the connecting member comprises:

a lead wire having exposed ends and configured to be fixed to the displacement plate; and

an insulating member partially surrounding the lead wire.

8. The secondary battery of claim 1 , wherein the short-circuiting member has a second through-hole at a location corresponding to the displacement plate.

9. The secondary battery of claim 8 , wherein the second through-hole has an area that is smaller than that of the displacement plate.

10. The secondary battery of claim 8 , further comprising a guide member at least partially located in the second through-hole and comprising a first side coupled to a top surface of the displacement plate and a second side coupled to an upper insulating member on the short-circuiting member.

11. The secondary battery of claim 10 , wherein the guide member comprises a spring.

12. The secondary battery of claim 1 , further comprising:

a first collector plate electrically coupled to the first electrode; and

a second collector plate electrically coupled to the second electrode,

wherein the displacement plate is electrically coupled to one of the first collector plate or the second collector plate by a connecting member.

13. The secondary battery of claim 12 , wherein the first collector plate comprises a first extending portion coupled to the first electrode, and a first connecting portion extending from the first extending portion and coupled to a first electrode terminal of the first electrode.

14. The secondary battery of claim 13 , wherein the first connecting portion comprises a fuse region.

15. The secondary battery of claim 12 , wherein the second collector plate comprises a second extending portion coupled to the second electrode, and a second connecting portion extending from the second extending portion and coupled to a second electrode terminal of the second electrode.