Negative electrode and lithium secondary battery containing it

Abstract

This application relates to a negative electrode comprising a negative electrode active material layer containing a silicon-based active material, wherein, with respect to the total thickness T which is the distance between the opposing first and second surfaces of the negative electrode active material layer, the cohesion strength is measured at positions 25%, 50%, and 75% of the total thickness from the first surface, the average of the measured cohesion strengths is 1 MPa to 20 MPa, the deviation of the measured cohesion strengths is 140% or less, and the vertical resistance is 0.005 Ω to 0.3 Ω.

Claims

1. A negative electrode comprising a negative electrode active material layer containing a silicon-based active material, Based on the total thickness, which is the distance between the first and second opposing surfaces of the negative electrode active material layer, When the cohesion strength was measured at positions 25%, 50%, and 75% of the total thickness from the first surface, The average of the measured cohesive strengths is 1 MPa to 20 MPa, and the deviation of the measured cohesive strengths is 140% or less. The negative electrode has a vertical resistance of 0.005Ω to 0.3Ω.

2. The negative electrode according to claim 1, wherein the deviation of the measured cohesive strength is 50% or less.

3. The aforementioned silicon-based active material is SiO ｘ (0 < x < 2), silicon carbon composite and SiO ｘ The negative electrode according to claim 1, comprising at least one of (x=0).

4. The negative electrode according to claim 1, wherein the negative electrode active material layer further comprises a graphite-based active material.

5. The negative electrode according to claim 1, wherein the negative electrode active material layer further comprises a binder and a conductive material.

6. The negative electrode according to claim 5, wherein the conductive material comprises one or more selected from point conductive materials and linear conductive materials.

7. The negative electrode according to claim 5, wherein the conductive material comprises at least one of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (TWCNTs).

8. The negative electrode according to claim 5, wherein the conductive material comprises single-walled carbon nanotubes (SWCNTs).

9. The negative electrode according to claim 7, wherein the total amount of at least one of the single-walled carbon nanotubes (SWCNTs) and the few-walled carbon nanotubes (TWCNTs) is 0.001 parts by weight or more and 0.3 parts by weight or less, based on 100 parts by weight of the negative electrode active material layer.

10. The negative electrode according to claim 5, wherein the binder comprises a polymer copolymer having an elastic modulus of 500 MPa or more, and a rubber-based binder.

11. A lithium secondary battery comprising a negative electrode, a positive electrode, and a separator membrane according to any one of claims 1 to 10.

12. A battery module comprising the lithium secondary battery described in claim 11 as a unit cell.

13. A battery pack comprising the lithium secondary battery described in claim 11.

14. A battery pack comprising the battery module described in claim 12.

15. An electric vehicle comprising the battery pack described in claim 13.

16. An electric vehicle comprising the battery pack described in claim 14.

17. A method for manufacturing a negative electrode including a negative electrode active material layer containing a silicon-based active material, A method for manufacturing a negative electrode, comprising adjusting the weight ratio of the total composition contained in the negative electrode active material layer, and the type and content of any or more of the active material / binder / conductive material contained in the negative electrode active material layer, thereby adjusting the cohesive strength and vertical resistance values ​​at different depths of the negative electrode active material layer.

18. Based on the total thickness, which is the distance between the first and second opposing surfaces of the negative electrode active material layer, When the cohesion strength was measured at positions 25%, 50%, and 75% of the total thickness from the first surface, The average of the measured cohesive strengths is 1 MPa to 20 MPa, and the deviation of the measured cohesive strengths is 140% or less. A method for manufacturing a negative electrode according to claim 17, wherein the vertical resistance is 0.005 Ω to 0.3 Ω.

19. The aforementioned silicon-based active material is SiO ｘ (0 < x < 2), silicon carbon composite and SiO ｘ A method for manufacturing a negative electrode according to claim 17, comprising at least one of (x=0).

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