Cap assembly for secondary battery, secondary battery and battery module

1. A cap assembly for a secondary battery, comprising a cap plate, a first electrode terminal, a sealing member, a fixing member and a connecting member, wherein:

the cap plate has an electrode lead-out hole;

the first electrode terminal comprises a first terminal board and a second terminal board connected with the first terminal board, wherein the first terminal board is located at a side of the second terminal board away from the cap plate, the second terminal board completely covers the electrode lead-out hole, and the material of the first terminal board and the material of the second terminal board have different base metals;

the sealing member surrounds the electrode lead-out hole and is disposed between the cap plate and the first electrode terminal to seal the electrode lead-out hole;

wherein the cap plate is made of a metal material, the connecting member is made of a metal material, the fixing member is a hard plastic member, the fixing member is directly fixed to the connecting member, the connecting member is in direct contact with the cap plate so that the connecting member is fixed to the cap plate, the fixing member is directly fixed to the cap plate by the connecting member, and an outer peripheral surface of the first electrode terminal is at least partially surrounded by the fixing member to fix the first electrode terminal to the fixing member, and wherein the first electrode terminal is completely located outside a shell of the secondary battery.

2. The cap assembly of claim 1 , wherein the sealing member is in close contact with the cap plate and the second terminal board.

3. The cap assembly of claim 1 , wherein the first terminal board and the second terminal board form a composite board strip.

4. The cap assembly of claim 1 , wherein the second terminal board further comprises an extension portion extending into the electrode lead-out hole.

5. The cap assembly of claim 1 , wherein the first terminal board and the second terminal board are joined together by a cold rolling method, a hot rolling method, an explosion compound method, or an explosion rolling method.

6. The cap assembly of claim 1 , wherein one of the first electrode terminal and the fixing member has a convex portion, and the other has a concave portion that accommodates the convex portion, and the convex portion is fitted with the concave portion.

7. The cap assembly of claim 6 , wherein the convex portion is provided on the outer peripheral surface of the first electrode terminal, the concave portion is provided on an inner wall surface of the fixing member corresponding to the convex portion, and a surface of the first electrode terminal away from the cap plate protrudes from a surface of the fixing member away from the cap plate.

8. The cap assembly of claim 7 , wherein the convex portion is provided on an outer peripheral surface of the first terminal board.

9. The cap assembly of claim 1 , wherein a portion of the fixing member is located between the cap plate and the first electrode terminal.

10. The cap assembly of claim 1 , wherein the connecting member comprises a nail body and a limiting portion which are connected with each other, and wherein an outer peripheral surface of the limiting portion protrudes from an outer peripheral surface of the nail body, an end of the nail body away from the limiting portion is fixed on the cap plate, and the limiting portion is engaged with the fixing member.

11. The cap assembly of claim 1 , wherein the connecting member comprises a first connecting plate, and wherein a portion of the first connecting plate is embedded into the fixing member and engaged with the fixing member, and another portion of the first connecting plate is welded with the cap plate.

12. The cap assembly of claim 1 , wherein the connecting member comprises an undercut and an undercut hole, wherein the undercut hole is provided on a surface of the cap plate facing the fixing member, and an aperture of the undercut hole is increased along a direction from the first terminal board to the cap plate, the undercut is connected with the fixing member and is adapted with the undercut hole in form, and the undercut is fitted with the undercut hole.

13. The cap assembly of claim 1 , further comprising a second electrode terminal, a deformable sheet and a conductive sheet, wherein the second electrode terminal is electrically connected with the cap plate, the first electrode terminal is insulated from the cap plate, the deformable sheet is attached to the cap plate, the conductive sheet is electrically connected with the first electrode terminal, wherein when a pressure within the secondary battery exceeds a predetermined pressure value, the deformable sheet deforms and is electrically connected with the conductive sheet.

14. The cap assembly of claim 13 , wherein the conductive sheet and the first electrode terminal are located on a same side of the cap plate, a surface of the conductive sheet away from the cap plate protrudes from a surface of the first electrode terminal away from the cap plate.

15. The cap assembly of claim 13 , wherein the material of the first terminal board and the material of the conductive sheet have a same base metal.

16. A secondary battery, comprising:

a shell having an opening;

an electrode assembly accommodated in the shell; and

the cap assembly of claim 1 , wherein the cap assembly covers the opening of the shell to enclose the electrode assembly in the shell.

17. A battery module, comprising:

a busbar; and

the secondary battery of claim 16 , wherein the busbar is welded to the first terminal board.

18. The battery module of claim 17 , wherein the material of the busbar and the material of the first terminal board have a same base metal.