Secondary battery having sealing portion of novel structure

1. A plate-shaped secondary battery constructed in a structure in which an electrode assembly of a cathode/separator/anode structure is mounted in a battery case, and the battery case is sealed by thermal welding, wherein

the battery case is provided at a sealing portion around an electrode assembly receiving part thereof with an exhaust guide sealing portion configured in a structure in which a width of the exhaust guide sealing portion decreases from an inside of the sealing portion toward an outside of the sealing portion such that a sealing force of the exhaust guide sealing portion is first released, when high-pressure gas is generated in a battery cell, and therefore, the high-pressure gas is exhausted outside, the exhaust guide sealing portion being thermally welded with a sealing force less than that of a sealing portion located at a remaining region ('a remaining sealing portion'),

the battery case is further provided at a middle of the exhaust guide sealing portion with a bridge sealing portion extending in parallel to the electrode assembly for interconnecting opposite sides of the remaining sealing portion with a predetermined width, the bridge sealing portion being thermally welded with a sealing force greater than that of the exhaust guide sealing portion;

the exhaust guide sealing portion has a lower-end (inside) width equivalent to 5 to 30% of a major-axis length of the battery case; and

the bridge sealing portion has a width equivalent to 10 to 60% of that of the remaining sealing portion.

2. The secondary battery according to claim 1 , wherein the exhaust guide sealing portion has a relatively small upper-end (outside) width equivalent to 10 to 50% of a relatively large lower-end (inside) width thereof.

3. The secondary battery according to claim 1 , wherein the exhaust guide sealing portion is formed in a horizontal plane shape of at least one selected from a group consisting of a semicircle, a triangle, and a trapezoid.

4. The secondary battery according to claim 3 , wherein the exhaust guide sealing portion is formed in the trapezoidal shape.

5. The secondary battery according to claim 1 , wherein the battery case is further provided at an interface between the exhaust guide sealing portion and the remaining sealing portion with an interface sealing portion thermally welded with a sealing force greater than that of the remaining sealing portion.

6. The secondary battery according to claim 5 , wherein the interface sealing portion has a width equivalent to 2 to 20% of that of the remaining sealing portion.

7. The secondary battery according to claim 1 , wherein the exhaust guide sealing portion is formed at a middle of one side or each side sealing portion located on a minor axis of the battery case on the basis of a middle of the battery case.

8. The secondary battery according to claim 1 , wherein the battery case is formed of a laminate sheet including a resin layer and a metal layer.

9. The secondary battery according to claim 8 , wherein the sheet is an aluminum laminate sheet.

10. The secondary battery according to claim 1 , wherein the electrode assembly is constructed in a folding, stacking, or stacking/folding type structure.

11. The secondary battery according to claim 1 , wherein the battery is a lithium ion polymer battery.

12. A middle- or large-sized battery module comprising the secondary battery according to claim 1 , as a unit cell.

13. A method of manufacturing the secondary battery according to claim 1 , the method comprising:

mounting the electrode assembly in the receiving part of the battery case; and

thermally welding the sealing portion at the outer circumference of the battery case on a heating jig formed in an engraved shape corresponding to the exhaust guide sealing portion, the bridge sealing portion, and/or the interface sealing portion and having a depth inversely proportional to sealing forces of the sealing portions.