Secondary battery and manufacturing method thereof

A secondary battery comprising:

• a case for accommodating an electrode assembly in an internal accommodating space;
• a cap plate;
• a first terminal inserted into the cap plate in a first direction, defining a first hollow, and bent at an inner surface of the cap plate to be coupled to the cap plate;
• and
• a collector plate in the case, electrically connected to a first electrode of the electrode assembly, and coupled to an interior of the first terminal defining the first hollow,
• wherein the first terminal comprises a terminal portion forming an upper surface thereof, a coupling portion formed under the terminal portion and defining the first hollow therein, and a deformed portion defining a second hollow having a larger diameter than that of the first hollow,
• wherein the collector plate comprises a protrusion,
• wherein the protrusion defines a third hollow,
• wherein a lower surface of the terminal portion is exposed inside the first hollow of the coupling portion,
• wherein an upper surface of the protrusion is welded to the lower surface of the terminal portion exposed through the first hollow of the coupling portion, and
• wherein a side surface of the protrusion directly contacts a side surface of the coupling portion.