Patent ID: 8227111
Filing Date: 2012-07-24
Classification: H01M,Y02E,Y10T

Abstract:
1. A secondary battery comprising, an electrode assembly including a winding having a positive electrode plate and a negative electrodes plate stacked together with a separator interposed between the positive and negative electrode plate; a can having an opening portion to receive the electrode assembly; a cap assembly including a cap plate to close the opening portion of the can, the cap plate having an electrolyte injection hole arranged therein; a first extension groove having a greater diameter than that of the electrolyte injection hole, the first extension groove having a circular side wall and a bottom wall extending from the circular side wall, said first extension groove being arranged in an entering portion of the electrolyte injection hole and having a plurality of hollow portions arranged on the surface of the first extension groove, wherein each of said plurality of hollow portions is positioned such that a flat portion of the surface of the first extension groove is located between two neighboring hollow portions and said plurality of hollow portions having a trapezoidal sectional shape, said trapezoidal sectional shape having two parallel sides of different lengths to have an upper side larger than a bottom side; and a plug for sealing the electrolyte injection hole, the plug being provided with a head portion attached to the side wall and bottom wall of the first extension groove and a body portion coupled to the electrolyte injection hole.