Secondary battery

1. A secondary battery comprising:

an electrode assembly including a first electrode and a second electrode and a separator interposed between the first electrode and the second electrode;

a can that contains the electrode assembly and that has a closed end and an open end;

a cap assembly connected to the open end of the can, the cap assembly including a lower projected part facing the electrode assembly; and

an insulation case between the electrode assembly and the cap assembly, wherein the insulation case includes a first recess that receives at least a portion of the lower projected part of the cap assembly.

2. The secondary battery of claim 1 , wherein the insulation case comprises a plate portion forming a base and a side wall that extends upwardly at the edge of the plate portion away from the electrode assembly, and wherein the first recess is formed on the upper face of the plate portion.

3. The secondary battery of claim 2 , wherein the cap assembly comprises a cap plate connected to the upper part of the can and provided with a terminal hole, an electrode terminal installed through the terminal hole and having a gasket located on its outer face that insulates the electrode terminal from the cap plate, a terminal plate installed below the cap plate and connected to a lower end of the electrode terminal and an insulation plate installed between the cap plate and the terminal plate, and wherein the lower projected part of the cap plate received in the first recess is a lower end of the electrode terminal and a first portion of the terminal plate.

4. The secondary battery of claim 3 , wherein the inside of the first recess is stepped to have an upper step and a lower step and wherein the upper step of the first recess receives the first portion of the terminal plate and the lower step of the first recess receives the lower end of the electrode terminal.

5. The secondary battery of claim 3 , wherein:

a lower face of the cap plate includes a first seat recess that seats a first portion of the insulation plate, and

a lower face of the insulation plate includes a second seat recess that seats a second portion of the terminal plate and wherein the second seat recess aligns with the first seat recess.

6. The secondary battery of claim 5 , wherein:

a space is provided between the second portion of the terminal plate seated in the second seat recess and the upper face of the plate portion of the insulation case,

a first electrode tab extends from the first electrode of the electrode assembly, wherein the insulation case includes a slot,

the first electrode tab passes through the slot in the plate portion of the insulation case and extends into the space provided between the insulation case and the second portion of the terminal plate and

the first electrode tab is welded to a lower face of the terminal plate.

7. The secondary battery of claim 6 , wherein the upper face of the insulation case includes a second recess that provides the space between the second portion of the terminal plate and the upper face of the plate portion of insulation case into which the first electrode tab extends.

8. The secondary battery of claim 5 , wherein:

a space is provided between the lower face of the cap plate and the upper face of the plate portion of the insulation case,

a second electrode tab extends from the second electrode of the electrode assembly,

the insulation case includes a side recess, wherein the second electrode tab passes through the side recess of the insulation case and extends into the space provided between the lower face of the cap plate and the upper face of the plate portion of the insulation case, and

the second electrode tab is welded to the lower face of the cap plate.

9. The secondary battery of claim 2 , wherein the upper face of the side wall of the insulation case contacts the lower face of the cap plate.