Patent ID: 8512895

Claim:
A secondary battery, comprising: an electrode assembly and an electrolyte solution in a case; a current collection unit in the case and electrically connected to the electrode assembly; a cap plate coupled to an open side of the case for sealing the case; an electrode terminal penetrating the cap plate through a terminal hole to be exposed to an exterior of the case, the electrode terminal being electrically connected to the current collection unit; and an insulation unit separating the cap plate from the electrode terminal and the current collection unit, the insulation unit being configured to block penetration of the electrolyte solution therethrough toward the cap plate, wherein the insulation unit includes: an upper gasket partially inserted from outside the cap plate into the terminal hole; a seal gasket that has a first stepped surface structure, an upper portion of the first stepped surface structure being inserted from inside the cap plate into the terminal hole and a lower portion of the first stepped surface structure being adjacent to an insulation member of the insulation unit, the seal gasket including: a terminal hole insert unit of the first stepped surface structure inserted into the terminal hole, a cap support unit of the first stepped surface structure connected to the terminal hole insert unit and inserted into a through hole of the insulation member, the cap support unit having an upper surface contacting the cap plate and a side surface contacting the insulation member, the side surface of the cap support unit being adjacent to the upper surface, and a support base of the first stepped surface structure connected to the cap support unit, the support base having a side surface contacting the insulation member and a lower surface contacting the current collection unit, the side surface of the support base being adjacent to the lower surface and being spaced apart from the side surface of the cap support unit to have a step difference between the cap support unit and the support base at opposite surfaces of the seal gasket, and the insulation member of the insulation unit including a second stepped surface structure and being interposed between the cap plate and the current collection unit, the second stepped surface structure being adjacent to the lower portion of the first stepped structure of the seal gasket, a portion of the seal gasket being between the insulation member and the cap plate, and the opposite surfaces of the seal gasket contacting the insulation member and the cap plate.