Patent ID: 8449999

Claim:
A battery cell constructed in a structure in which an electrode assembly is mounted in a battery case made of a laminate sheet including a metal layer and at least one resin layer, the battery case being thermally welded along the edge of a receiving part thereof to form a sealing part, the electrode assembly extending longer in the longitudinal direction than the lateral direction, the electrode assembly having first and second electrode leads, and the first electrode lead having a lower flexibility than the second electrode lead, wherein a weak part is formed at a portion of the sealing part corresponding to the first electrode lead, the weak part being physically deformable, such that internal gas is discharged outside through the weak part, when predetermined pressure is applied to the weak part, and the weak part is not formed at the second electrode lead, and wherein the weak part is formed in a slit structure in which slits are arranged in the lateral direction of the electrode assembly.