Secondary battery

1. A secondary battery, comprising:

a cap plate provided with a first electrode terminal;

an electrode assembly comprising a main body and a first electrode tab provided to the main body, the first electrode tab comprising a first connecting portion;

a first connecting piece connected between the first connecting portion and the first electrode terminal; and

a first welding protecting piece provided on the first connecting portion, the first connecting portion being positioned between the first welding protecting piece and the first connecting piece, and the first welding protecting piece, the first connecting portion and the first connecting piece being securely connected.

2. The secondary battery according to claim 1 , wherein

the first electrode tab further comprises a first bending portion, and the first bending portion is bent downwardly and connected between the main body of the electrode assembly and the first connecting portion.

3. The secondary battery according to claim 2 , wherein

the first welding protecting piece, the first connecting portion and the first connecting piece are at least partially overlapped in a height direction.

4. The secondary battery according to claim 2 , wherein

the first welding protecting piece, the first connecting portion and the first connecting piece are welded together and form weld zones facing the main body of the electrode assembly;

the secondary battery further comprises a first insulating adhesive adhered on the weld zones facing the main body of the electrode assembly.

5. The secondary battery according to claim 4 , wherein

the first connecting portion is positioned below the first connecting piece in a height direction, and the first welding protecting piece is positioned below the first connecting portion in the height direction;

at least a part of the first insulating adhesive is adhered on a surface of the first welding protecting piece away from the first connecting portion.

6. The secondary battery according to claim 5 , wherein

the first insulating adhesive comprises a first portion and a second portion connected with the first portion, the first portion is adhered on the surface of the first welding protecting piece away from the first connecting portion, the second portion is positioned at a side of the first welding protecting piece in a width direction, and the second portion is adhered with a part of the first connecting portion exceeding the first welding protecting piece in the width direction.

7. The secondary battery according to claim 6 , wherein

in the height direction, a step is formed between the first portion and the second portion, and the first portion is closer to the main body than the second portion.

8. The secondary battery according to claim 4 , wherein

the first connecting portion is positioned above the first connecting piece in a height direction, and the first welding protecting piece is positioned above the first connecting portion in the height direction;

at least a part of the first insulating adhesive is adhered on a surface of the first connecting piece away from the first connecting portion.

9. The secondary battery according to claim 2 , wherein the secondary battery further comprises a second insulating adhesive adhered on an outside portion of the first bending portion.

10. The secondary battery according to claim 2 , wherein

an angle between the first connecting portion and the first bending portion ranges from 85 degrees to 95 degrees; or

an angle between the first connecting portion and the first bending portion ranges from 0 degrees to 45 degrees.

11. The secondary battery according to claim 1 , wherein

the secondary battery further comprises a case and an insulating frame, the case receives the electrode assembly and is assembled with the cap plate, and the insulating frame is received in the case and isolates the cap plate from the electrode assembly;

two ends of the insulating frame in a width direction are provided with side edges extending downwardly, and two ends of the insulating frame in a length direction are provided with side edges extending downwardly, all the side edges isolate the first electrode tab from the case.

12. The secondary battery according to claim 1 , wherein

the cap plate is provided with a second electrode terminal, the electrode assembly further comprises a second electrode tab provided to the main body, and the second electrode tab comprises a second connecting portion;

the secondary battery further comprises a second connecting piece and a second welding protecting piece, the second connecting piece is connected between the second electrode terminal and the second connecting portion, and the second welding protecting piece is provided on the second connecting portion;

the second connecting portion is positioned between the second connecting piece and the second welding protecting piece, and the second connecting piece, the second connecting portion and the second welding protecting piece are securely connected.

13. The secondary battery according to claim 12 , wherein

the second electrode tab further comprises a second bending portion, and the second bending portion is bent downwardly and connected between the main body of the electrode assembly and the second connecting portion.

14. The secondary battery according to claim 12 , wherein

the second welding protecting piece, the second connecting portion and the second connecting piece are welded together and form weld zones facing the main body of the electrode assembly;

the secondary battery further comprises a second insulating adhesive adhered on the weld zones facing the main body of the electrode assembly.