Cap assembly, secondary battery including the same, and cap assembly manufacturing method

A secondary battery, comprising:

• an electrode assembly comprising a first electrode, a separator, and a second electrode;
• a case having one open side, the case accommodating the electrode assembly through the open side;
• and
• a cap assembly coupled to the open side of the case, wherein the cap assembly comprises:
• a base portion having a through-hole;
• a protrusion joined to the base portion, the protrusion extending downward from a lower end of the through-hole;
• an electrode terminal at least partially inserted into the protrusion, the electrode terminal sealing the through-hole;
• and
• a sealing member between the protrusion and the electrode terminal.

A method for manufacturing a cap assembly, the method comprising:

• forming a through-hole in a base portion;
• joining a protrusion extending downward from a lower end of the through-hole, to the base portion;
• disposing a sealing member on an inner circumferential surface of the protrusion and an upper surface of the base portion;
• and
• sealing the through-hole by inserting an electrode terminal at least partially into the protrusion in which the sealing member is surrounded by the protrusion.