Negative electrode for lithium secondary battery, and lithium secondary battery containing the same

Abstract

To provide a negative electrode for a lithium secondary battery having improved operational stability, reliability, and output characteristics, and a lithium secondary battery containing the same. [Solution] The negative electrode for a lithium secondary battery according to an embodiment of the present disclosure includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer disposed on the first negative electrode active material layer. The degree of diffusion (D) of the entire negative electrode active material layer, as determined by X-ray microscopy (XRM) analysis, is 4.6% to 5.8%.

Claims

1. It includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer disposed on the first negative electrode active material layer. The degree of diffusion (D) of the entire negative electrode active material layer, as determined by X-ray microscopy (XRM) analysis, is 4.6% to 5.8%, for a lithium secondary battery negative electrode.

2. The degree of diffusion (D) is defined by the following formula 1, wherein the negative electrode for a lithium secondary battery according to claim 1. [Math 1] (In the above formula 1, P is the porosity of the negative electrode active material layer, L ｔ L is the thickness of the negative electrode active material layer. ｐ This is the average distance that lithium ions travel when they permeate the negative electrode active material layer in the thickness direction.

3. The degree of diffusion of the first negative electrode active material layer (D １ The degree of diffusion of the second negative electrode active material layer relative to (D ２ The negative electrode for a lithium secondary battery according to claim 1, wherein the ratio of ) is 1.50 or more.

4. D １ It is 2.0% or more, D ２ The negative electrode for a lithium secondary battery according to claim 3, wherein the content is 4.0% or more.

5. The negative electrode for a lithium secondary battery according to claim 1, wherein the porosity of the first negative electrode active material layer is smaller than the porosity of the second negative electrode active material layer.

6. The negative electrode for a lithium secondary battery according to claim 5, wherein the ratio of the porosity of the second negative electrode active material layer to the porosity of the first negative electrode active material layer is 1.35 to 1.

45.

7. The negative electrode for a lithium secondary battery according to claim 6, wherein the porosity of the first negative electrode active material layer is 15% to 20%, and the porosity of the second negative electrode active material layer is 24% to 30%.

8. The negative electrode for a lithium secondary battery according to claim 1, wherein the ratio of the load amount of the second negative electrode active material layer to the load amount of the first negative electrode active material layer is 0.4 to 1.

0.

9. The anode for a lithium secondary battery according to claim 1, wherein the first anode active material layer comprises a first anode active material, the second anode active material layer comprises a second anode active material, the first anode active material comprises a first artificial graphite in single-particle form, and the second anode active material comprises a second artificial graphite in a form in which a plurality of sub-particles are assembled.

10. The first negative electrode active material further comprises a first silicon-based active material, and the second negative electrode active material further comprises a second silicon-based active material. The negative electrode for a lithium secondary battery according to claim 9, wherein the first and second silicon-based active materials are selected from the group consisting of Si, SiOx (0 < x ≤ 2), metal-doped SiOx (0 < x ≤ 2), and silicon-carbon composites.

11. The negative electrode for a lithium secondary battery according to claim 10, wherein the content of the first artificial graphite is 85% to 95% by weight and the content of the first silicon-based active material is 1% to 10% by weight, based on the total weight of the first negative electrode active material.

12. The negative electrode for a lithium secondary battery according to claim 10, wherein the content of the second artificial graphite is 80% to 95% by weight and the content of the second silicon-based active material is 5% to 20% by weight, based on the total weight of the second negative electrode active material.

13. The negative electrode for a lithium secondary battery according to claim 10, wherein the weight ratio of the first silicon-based active material to the first artificial graphite is 0.05 to 0.

15.

14. The negative electrode for a lithium secondary battery according to claim 10, wherein the weight ratio of the second silicon-based active material to the second artificial graphite is 0.06 to 0.

2.

15. The negative electrode for a lithium secondary battery according to claim 1, A lithium secondary battery comprising a positive electrode facing the negative electrode.

Images