Rechargeable battery having insulation layer

1. A rechargeable battery, comprising:

an electrode assembly including a positive electrode and a negative electrode;

a case receiving the electrode assembly;

a cap plate coupled to the case;

a vent plate under the cap plate, the vent plate including a notch;

a middle plate under the vent plate;

a laminating insulating layer between the vent plate and the middle plate, the laminating insulating layer being laminated to the vent plate or the middle plate, and the laminating insulating layer having a smaller thickness than each of the vent plate and the middle plate; and

a thermally fusing insulating layer on the laminating insulating layer, the thermally fusing insulating layer being between the laminating insulating layer and the vent plate.

2. The rechargeable battery as claimed in claim 1 , wherein the laminating insulating layer is adhered to an upper surface of the middle plate.

3. The rechargeable battery as claimed in claim 1 , wherein the laminating insulating layer is a film.

4. The rechargeable battery as claimed in claim 1 , wherein the laminating insulating layer includes a polypropylene-based resin, and the thermally fusing insulating layer includes a polybutylene-based resin.

5. The rechargeable battery as claimed in claim 1 , wherein the vent plate has a downwardly depressed groove portion, a connection protrusion protruding from a center of the groove portion, and a notch around the connection protrusion.

6. The rechargeable battery as claimed in claim 5 , wherein the vent plate further comprises a downwardly concave step portion at a connection portion between the groove portion and an upper surface of the vent plate.

7. The rechargeable battery as claimed in claim 6 , wherein a thickness of the step portion is smaller than a thickness of an edge of the vent plate.

8. The rechargeable battery as claimed in claim 6 , wherein the groove portion has a bottom and an outer wall protruding upwardly from the bottom, the outer wall having a smaller thickness than the bottom.

9. The rechargeable battery as claimed in claim 6 , wherein the middle plate includes a penetration hole and at least one vent hole, a connection protrusion of the vent plate being inserted into the penetration hole of the middle plate, and the vent hole transmits pressure to from the electrode assembly toward the vent plate.

10. The rechargeable battery as claimed in claim 1 , wherein the laminating insulating layer is adhered to a lower surface of the vent plate.

11. A rechargeable battery, comprising:

an electrode assembly including a positive electrode and a negative electrode;

a case receiving the electrode assembly;

a cap plate coupled to the case;

a vent plate under the cap plate, the vent plate including a notch;

a middle plate under the vent plate;

a laminating insulating layer between the vent plate and the middle plate, the laminating insulating layer being laminated to the vent plate or the middle plate; and

a thermally fusing insulating layer on the laminating insulating layer, the thermally fusing insulating layer being between the laminating insulating layer and the vent plate.

12. A rechargeable battery, comprising:

an electrode assembly including a positive electrode and a negative electrode;

a case receiving the electrode assembly;

a cap plate coupled to the case;

a vent plate under the cap plate, the vent plate including a notch;

a middle plate under the vent plate; and

a laminating insulating layer between the vent plate and the middle plate, the laminating insulating layer being laminated to the vent plate or the middle plate,

wherein the vent plate has a downwardly depressed groove portion, a connection protrusion protruding from a center of the groove portion, a notch around the connection protrusion, and a downwardly concave step portion at a connection portion between the groove portion and an upper surface of the vent plate.