Lithium secondary battery

1. A lithium secondary battery comprising:

an electrode assembly;

a can to receive the electrode assembly;

a cap assembly including:

a safety vent to close an opening of the can, the safety vent having a central region that protrudes inward and is deformable outward by an internal pressure of the battery, the safety vent comprising a top surface, a bottom surface and a thin side surface,

a current isolation member having an upper side, and

a cap up connected to the upper side of the current isolation member;

a gasket disposed between the cap assembly and the can to maintain an airtight seal, the gasket having horizontal and vertical surfaces; and

a first supporting sealing member formed between the safety vent and the gasket, wherein the first supporting sealing member forms a seal between the safety vent and the gasket and a first surface of the first supporting sealing member contacts only the bottom surface of the safety vent and a second surface of the first supporting sealing member contacts a horizontal surface of the gasket.

2. The lithium secondary battery according to claim 1 , wherein the supporting sealing member is formed of at least one of a rubber, a silicone, and a polymer material.

3. The lithium secondary battery according to claim 1 , wherein the supporting sealing member has an annular shape with a round hole in the center thereof.

4. The lithium secondary battery according to claim 1 , further comprising a second supporting sealing member formed between the gasket and the can.

5. The lithium secondary battery according to claim 1 , wherein the first supporting sealing member is formed of an adhesive layer.

6. The lithium secondary battery according to claim 5 , wherein the first supporting sealing member comprises a double sided tape having the adhesive layer formed on both sides thereof.

7. The lithium secondary battery according to claim 6 , wherein the double sided tape is silicone.

8. The lithium secondary battery according to claim 5 , wherein the adhesive layer is formed by inserting an amorphous fluid adhesive between the safety vent and the gasket and solidifying the amorphous fluid adhesive.

9. The lithium secondary battery according to claim 1 , wherein the gasket is formed of at least one of a polyethylene, a polypropylene, and a polyimide.

10. The lithium secondary battery according to claim 1 , wherein the cap assembly includes a single piece current isolation member and cap up.

11. The lithium secondary battery according to claim 1 , wherein the current isolation member includes a conductive layer of at least one of copper and a copper alloy.

12. The lithium secondary battery according to claim 11 , wherein the conductive layer is formed by a plating process.

13. The lithium secondary battery according to claim 1 , wherein a secondary protective element is attached to the safety vent at an upper side thereof.

14. The lithium secondary battery according to claim 13 , wherein the secondary protective element is a positive temperature coefficient (PTC) element formed of a layer of resin and carbon powder.

15. A rechargeable battery, comprising:

a receptacle having an opened end and containing electrolyte;

a cap to close the opened end;

a gasket interposed between the receptacle and the cap, the gasket having horizontal and vertical surfaces; and

a sealer interposed between the gasket and the cap, wherein the sealer forms a seal between the gasket and the cap to hinder leakage of at least one of a gas and the electrolyte,

wherein the cap includes a safety vent having a top surface, a bottom surface and a side surface, and the sealer is disposed between the safety vent and the gasket and contacts only the bottom surface of the safety vent and contacts a horizontal surface of the gasket.

16. The rechargeable battery of claim 15 , further comprising another sealer interposed between the gasket and the receptacle.

17. The rechargeable battery of claim 15 , wherein the sealer is tape having an adhesive on both sides thereof.

18. The rechargeable battery of claim 17 , wherein the tape is formed of silicone.

19. The rechargeable battery of claim 15 , wherein the sealer is an adhesive that is applied and dried.

20. The rechargeable battery of claim 15 , wherein the sealer is annular.

21. A rechargeable battery, comprising:

a can;

a safety vent to couple with the can, the safety vent having a top surface, a bottom surface and a side surface;

a gasket interposed between the can and the safety vent, the gasket having horizontal and vertical surfaces; and

a sealing member interposed between the safety vent and the gasket,

wherein the sealing member forms a seal and strengthens the attachment between the safety vent and the gasket and contacts only the bottom surface of the safety vent and contacts a horizontal surface of the gasket.