Secondary battery

1. A secondary battery comprising:

an electrode assembly; and

a thermal contractible protection layer disposed on an outer surface of the electrode assembly and contracted by heat, wherein the thermal contractible protection layer is provided as a biaxial oriented film.

2. The secondary battery of claim 1 , wherein the thermal contractible protection layer is provided to surround a circumference of the electrode assembly.

3. The secondary battery of claim 2 , wherein the thermal contractible protection layer is provided to surround to an entire circumference of the electrode assembly.

4. The secondary battery of claim 2 , wherein the thermal contractible protection layer is provided to surround a portion of the circumference of the electrode assembly.

5. The secondary battery of claim 4 , wherein the thermal contractible protection layer is wound in a width direction of the electrode assembly to surround a portion of the circumference of the electrode assembly.

6. The secondary battery of claim 5 , wherein a plurality of thermal contractible protection layers are wound in the width direction of the electrode assembly.

7. The secondary battery of claim 4 , wherein the thermal contractible protection layer is wound in a longitudinal direction of the electrode assembly to surround a portion of the circumference of the electrode assembly.

8. The secondary battery of claim 7 , wherein a plurality of thermal contractible protection layers are wound in the longitudinal direction of the electrode assembly.

9. The secondary battery of claim 1 , wherein the thermal contractible protection layer is provided as a thermal contractible protection tape.

10. A secondary battery comprising:

an electrode assembly;

a thermal contractible protection layer disposed on an outer surface of the electrode assembly and contracted by heat; and

a case in which the electrode assembly comprising the thermal contractible protection layer is accommodated,

wherein the case comprises an outer thermal contractible protection layer that is contracted by heat.

11. The secondary battery of claim 10 , wherein the outer thermal contractible protection layer is made of an insulative material.

12. The secondary battery of claim 10 , wherein the outer thermal contractible protection layer is provided as a biaxial oriented film.

13. The secondary battery of claim 10 , wherein the outer thermal contractible protection layer is made of one of nylon, polypropylene, polyester, polyamide, polyethylene, polyethylene phthalate, and polystyrene.

14. The secondary battery of claim 1 , wherein the thermal contractible protection layer is made of a material having no thermosetting property.

15. The secondary battery of claim 10 , wherein the case has a structure in which a metal layer, an outer adhesion layer, and the outer thermal contractible protection layer are sequentially stacked.

16. The secondary battery of claim 10 , wherein the outer thermal contractible protection layer is attached to the outermost side of the case.

17. The secondary battery of claim 10 , wherein the outer thermal contractible protection layer is provided in the case and disposed on the outermost side of the case.

18. The secondary battery of claim 10 , wherein the outer thermal contractible protection layer is disposed on the innermost side of the case.

19. The secondary battery of claim 10 , wherein the outer thermal contractible protection layer is made of a material having no thermosetting property.

20. The secondary battery of claim 15 , wherein a sealing layer and an inner adhesion layer are further stacked on an inner surface of the case.