Secondary battery and method of manufacturing the same

1. A secondary battery, comprising:

an electrode assembly including a first electrode plate, a second electrode plate and a separator;

a case having an opening and housing the electrode assembly and an electrolytic solution; and

a cap assembly including a cap plate, an insulation plate, a terminal plate and an electrode terminal, wherein the cap assembly seals the opening,

wherein the electrode terminal includes a body having a first thickness and a tail, wherein the tail has an upper end,

wherein at least a portion of the tail of the electrode terminal has a second thickness that is less than the first thickness,

wherein the body of the electrode terminal has a bottom end and a top end, wherein the top end extends beyond a lower surface of the cap plate, wherein the thickness at the top end of the body and the thickness at the bottom end of the body are the same as the first thickness, and wherein the bottom end of the body directly contacts the upper end of the tail,

wherein the terminal plate has a terminal through hole extending from a top surface to a bottom surface thereof, wherein the upper end of the tail is located within the terminal through hole,

wherein the terminal through hole has a first diameter which is less than the first thickness and a second diameter which is greater than the first diameter; and

wherein the insulation plate is interposed between the cap plate and the terminal plate and in direct contact with the top surface of the terminal plate.

2. The secondary battery of claim 1 , wherein the electrode terminal is electrically connected to the terminal plate, wherein the tail has a lower end, wherein the upper end of the tail has the second thickness and wherein the lower end of the tail has a third thickness that is greater than the second thickness.

3. The secondary battery of claim 2 , wherein the body of the electrode terminal has a first length, wherein the tail of the electrode terminal has a second length and wherein the second length is less than the first length.

4. The secondary battery of claim 3 , wherein the upper end of the tail of the electrode terminal has a cross-sectional area that is greater than or substantially equal to about 20% of the cross-sectional area of the body of the electrode terminal.

5. The secondary battery of claim 1 , wherein the terminal through hole has the first diameter at the top surface of the terminal plate and the second diameter at the bottom surface of the terminal plate.

6. The secondary battery of claim 1 , wherein the tail of the electrode terminal at least partially fills the portion of the terminal through hole having the second diameter.

7. The secondary battery of claim 1 , wherein the bottom end of the body of the electrode terminal is connected to the tail of the electrode terminal at a junction, a cross-section of the junction defining a rounded edge.

8. The secondary battery of claim 1 , wherein the electrode terminal further includes a head part located at the top end of the body having a fourth thickness that is greater than the first thickness.

9. The secondary battery of claim 8 , wherein the electrode terminal further includes an extension part having a fifth thickness that is greater than the first thickness and less than the fourth thickness and wherein the extension part is interposed between the head part and the top end of the body of the electrode terminal.

10. The secondary battery of claim 7 , wherein the rounded edge of the junction has a first curvature radius that is greater than or substantially equal to about 0.1 mm.

11. The secondary battery of claim 1 , further comprising a gasket interposed between and in direct contact with the body of the electrode terminal and the cap plate.