Secondary battery and battery pack having the same

1. A secondary battery comprising:

a case having an opening;

an electrode assembly housed in the case, the electrode assembly comprising first and second electrode plates and a separator coupled together;

at least one current collector coupled to an uncoated portion of the electrode assembly and forming an electrode terminal, the at least one current collector comprising a first region spaced from the electrode assembly, a second region extending from the first region in a first direction and directly contacting one of the first and second electrode plates, and a third region extending from the first region in a second direction different from the first direction and spaced from the electrode assembly, wherein the case has a coupling groove recessed toward the at least one current collector; and

a cap plate sealing the opening of the case.

2. The secondary battery of claim 1 , wherein the at least one current collector comprises a plurality of current collectors, and wherein the case has a plurality of coupling grooves, each of the coupling grooves being recessed toward a respective one of the plurality of current collectors.

3. The secondary battery of claim 1 , wherein the coupling groove of the case is generally aligned with a positive electrode current collector of the at least one current collector.

4. The secondary battery of claim 3 , wherein the case contacts the positive electrode current collector via the coupling groove.

5. The secondary battery of claim 3 , wherein the case is coupled to the positive electrode current collector by a weld.

6. The secondary battery of claim 1 , wherein the coupling groove of the case is generally aligned with a negative electrode current collector of the at least one current collector.

7. The secondary battery of claim 6 , wherein an insulation member is between the coupling groove of the case and an electrode terminal of the negative electrode current collector.

8. The secondary battery of claim 6 , wherein a through-hole is formed in the coupling groove of the case through which the electrode terminal of the negative electrode current collector passes.

9. The secondary battery of claim 8 , wherein the electrode terminal of the negative electrode current collector is engaged with a nut that is outside of the case.

10. The secondary battery of claim 9 , further comprising an insulation member between the case and the nut.

11. The secondary battery of claim 1 , wherein the case further includes at least one inwardly recessed auxiliary groove.

12. The secondary battery of claim 1 , wherein the cap plate further includes a safety vent on a surface generally opposite to the opening, wherein the safety vent is thinner than a remainder of the case.

13. A battery pack comprising:

a plurality of secondary batteries each comprising a battery case having an opening, an electrode assembly housed in the case and forming an electrode terminal, the electrode assembly comprising first and second electrode plates and a separator coupled together, a pair of current collectors coupled to an uncoated portion of the electrode assembly, the at least one current collector comprising a first region spaced from the electrode assembly, a second region extending from the first region in a first direction and directly contacting one of the first and second electrode plates, and a third region extending from the first region in a second direction different from the first direction and spaced from the electrode assembly, and a cap plate sealing the opening of the battery case, wherein the case has a coupling groove that is inwardly recessed toward at least one of the pair of current collectors; and

a pack case having a coupling protrusion generally corresponding to the coupling groove of each of the secondary batteries to be coupled to a respective one of the secondary batteries.

14. The battery pack of claim 13 , wherein the coupling protrusion is electrically coupled to at least one of the pair of current collectors through the coupling groove of each of the secondary batteries.

15. The battery pack of claim 13 , wherein each of the secondary batteries further includes at least one auxiliary groove in the battery case, and the pack case further includes an auxiliary protrusion generally corresponding to the auxiliary groove.

16. The battery pack of claim 13 , wherein the pair of current collectors of each of the secondary batteries comprises a positive electrode current collector and a negative electrode current collector, and wherein the battery case is coupled to the positive electrode current collector by a weld.

17. The battery pack of claim 16 , wherein the negative electrode current collector has an electrode terminal exposed outside of the case through an insulation member, and wherein a nut is engaged with the electrode terminal.