Pouch type secondary battery having safety vent

1. A pouch type secondary battery comprising:

an electrode assembly electrically coupleable to at least one electrode lead; and

a pouch type case in which the electrode assembly is accommodated, the pouch type case comprising an upper case and a lower case, the lower case including a sealing part having four sides defining a rectangular perimeter enclosing the electrode assembly, the at least one electrode lead protruding from a first side of the four sides,

wherein the sealing part comprises:

an inner sealing part forming a closed curve surrounding the electrode assembly to protect the electrode assembly against the outside; and

an outer sealing part spaced away from the inner sealing part and defining a gas flow path between the inner and outer sealing parts to surround a peripheral portion of the inner sealing part, the outer sealing part having a safety vent in communication with the gas flow path, the safety vent being disposed on a second side of the four sides, the second side being adjacent the first side, wherein the sealing part further comprises an intermediate sealing part surrounding the inner sealing part and disposed along the gas flow path in a state where the intermediate sealing part is spaced apart from both of the inner and outer sealing parts.

2. The pouch type secondary battery of claim 1 , wherein a sealing surface of the outer sealing part has a width greater than that of a sealing surface of the inner sealing part.

3. The pouch type secondary battery of claim 1 , wherein the sealing surface of the outer sealing part has a width greater than that of a sealing surface of the intermediate sealing part, and the sealing surface of the intermediate sealing part has a width greater than that of the sealing surface of the inner sealing part.

4. The pouch type secondary battery of claim 1 , wherein the intermediate sealing part forms a closed curve.

5. The pouch type secondary battery of claim 1 , wherein the safety vent is constituted by a plurality of vents that are grouped.

6. The pouch type secondary battery of claim 1 , wherein the first side and the second side share a corner.

7. The pouch type secondary battery of claim 1 , wherein the first side and the second side are perpendicular.

8. The pouch type secondary battery of claim 1 , wherein the safety vent is disposed on only one side.

9. The pouch type secondary battery of claim 1 , wherein the safety vent is configured to always be in an open position.