Secondary battery

A secondary battery comprising:

• an electrode assembly comprising a first electrode uncoated portion;
• a case receiving the electrode assembly;
• a cap plate coupled to a top portion of the case and sealing the case;
• and
• a current collector comprising a terminal connector positioned between the electrode assembly and the cap plate and an electrode connector bent at an end of the terminal connector and positioned between the electrode assembly and the case,
• wherein the electrode connector comprises a first region connected to the terminal connector and protruding toward the case, a second region positioned under the first region and protruding toward the electrode assembly, a third region positioned under the second region and protruding toward the case, and an auxiliary tab between the first electrode uncoated portion and the second region, the first electrode uncoated portion is bent with the auxiliary tab and welded to the auxiliary tab, the auxiliary tab directly contacts the second region of the electrode connector, and the first region, the second region, the third region, and the auxiliary tab are offset to one side along a stacking direction of the electrode assembly,
• wherein the second region protrudes toward the electrode assembly in a stepwise manner with respect to each of the first region and the third region such that a first step difference is formed between an outer surface of the second region that faces a first side of the case and an outer surface of the first region that faces the first side of the case and a second step difference is formed between the outer surface of the second region and an outer surface of the third region that faces the first side of the case, and a thickness of a portion of the first electrode uncoated portion that is connected to the outer surface of the second region and faces the first side of the case is less than each of the first step difference and the second step difference.