Secondary battery

A secondary battery, comprising:

• an electrode assembly including a first electrode plate and a second electrode plate that are spirally wound together with respect to a winding axis, with a separator between the first electrode plate and the second electrode plate, the first electrode plate including a first coating portion on which a first active material is applied and a first non-coating portion on which the first active material is not present, the first non-coating portion being at a first end of the electrode assembly in a direction parallel to the winding axis, and the second electrode plate including second coating portion on which a second active material is applied and a second non-coating portion on which the second active material is not present, the second non-coating portion being at a second end of the electrode assembly in a direction parallel to the winding axis, wherein the separator does not overlap the first non-coating portion of the second non-coating portion;
• a single first current collector joined to the first non-coating portion at the first end of the electrode assembly and a single second current collector joined to the second non-coating portion at the second end of the electrode assembly;
• a case that accommodates the electrode assembly;
• and
• a cap assembly that seals the case,
• wherein the first current collector includes a first overlapping portion that overlaps and joins the first non-coating portion and a first connection unit that is bent from the first overlapping portion in a direction toward the second non-coating portion, the first overlapping portion having a length in a direction perpendicular to the winding axis and a width in the direction parallel to the winding axis, and the first non-coating portion having a length in the direction perpendicular to the winding axis and a width in the direction parallel to the winding axis, the length of the first overlapping portion being 30% to 70% of the length of the first non-coating portion and the width of the first overlapping portion being 50% to 70% of the width of the first non-coating portion, and
• the second current collector includes a second overlapping portion that overlaps and joins the second non-coating portion and a second connection unit that is bent from the second overlapping portion in a direction toward the first non-coating portion, the second overlapping portion having a length in the direction perpendicular to the winding axis and a width in the direction parallel to the winding axis and the second non-coating portion having a length in a direction perpendicular to the winding axis and a width in the direction parallel to the winding axis, the length of the second overlapping portion being 30% to 70% of the length of the second non-coating portion and the width of the second overlapping portion being 50% to 70% of the width of the second non-coating portion.