Secondary battery and apparatus including the secondary battery

1. A secondary battery, comprising a negative electrode plate, a positive electrode plate, a separator, and an electrolyte, wherein the electrolyte comprises an organic solvent and an electrolyte salt, the negative electrode plate comprises a negative current collector and negative film layers, wherein the negative film layers comprise a first negative film layer and a second negative film layer, the first negative film layer is disposed on at least one surface of the negative current collector and comprises a first negative active material, and the second negative film layer is disposed on the first negative film layer and comprises a second negative active material;

the first negative active material comprises natural graphite, and the second negative active material comprises artificial graphite;

the first negative active material has a powder orientation index (OI) value COI 1 satisfying 4.7≤COI 1 ≤5.0; and

the second negative active material has a powder orientation index (OI) value COI 2 satisfying 2.8≤COI 2 ≤3.0, and

the first negative active material and the second negative active material further satisfy 1.1≤COI 1 /COI 2 ≤2.5,

wherein

COI 1 is a ratio of peak area of 004 characteristic diffraction peak to peak area of 110 characteristic diffraction peak in an X-ray diffraction pattern of the first negative active material; and

COI 2 is a ratio of peak area of 004 characteristic diffraction peak to peak area of 110 characteristic diffraction peak in an X-ray diffraction pattern of the second negative active material; and

wherein the first negative active material has a particle diameter distribution satisfying 0.8≤(D V 90−D V 10)/D V 50≤1.5, and the second negative active material has a particle diameter distribution satisfying 0.9≤(D V 90−D V 10)/D V 50≤2.

2. The secondary battery according to claim 1 , wherein

the artificial graphite is of a flake shape.

3. The secondary battery according to claim 1 , wherein

a mass percentage of the natural graphite in the first negative active material is ≥60%; and/or

a mass percentage of the artificial graphite in the second negative active material is ≥70%.

4. The secondary battery according to claim 1 , wherein the first negative active material satisfies one or more of the following (1) to (5):

(1) an average particle diameter D V 50 of 9 μm-16 μm;

(2) a degree of graphitization of 95%-99%

(3) a specific surface area (BET) of 1.6 m 2 /g-4.0 m 2 /g;

(4) a tap density of 0.8 g/cm 3 -1.3 g/cm 3 ; and

(5) a powder compacted density of 1.7 g/cm 3 -2.0 g/cm 3 under a force of 30,000 N.

5. The secondary battery according to claim 1 , wherein the second negative active material satisfies one or more of the following (1) to (5):

(1) an average particle diameter D V 50 of 11 μm-19 μm;

(2) a degree of graphitization of 90%-95%;

(3) a specific surface area (BET) of 0.6 m 2 /g-2.2 m 2 /g;

(4) a tap density of 0.7 g/cm 3 -1.4 g/cm 3 ; and

(5) a powder compacted density under a force of 30,000 N is 1.65 g/cm 3 -1.85 g/cm 3 .

6. The secondary battery according to claim 1 , wherein surfaces of particles of the first negative active material and/or particles of the second negative active material are coated with a coating layer.

7. The secondary battery according to claim 1 , wherein a mass ratio of the first negative film layer to the second negative film layer is 1:3-9:5.

8. The secondary battery according to claim 1 , wherein the first negative active material further comprises one or more of artificial graphite, soft carbon, hard carbon, a silicon-based material, and a tin-based material; and/or the second negative active material further comprises one or more of natural graphite, soft carbon, hard carbon, a silicon-based material, and a tin-based material.

9. An apparatus, comprising the secondary battery according to claim 1 .

10. The secondary battery according to claim 1 , wherein 1.3≤COI 1 /COI 2 ≤1.6.

11. The secondary battery according to claim 3 , wherein a mass percentage of the natural graphite in the first negative active material is 80%-100%.

12. The secondary battery according to claim 3 , wherein a mass percentage of the artificial graphite in the second negative active material is 90%-100%.

13. The secondary battery according to claim 1 , wherein the first negative active material satisfies one or more of the following (1) to (6):

(1) an average particle diameter D V 50 of 11 μm-14 μm;

(2) a particle diameter distribution satisfying 0.9≤(D V 90−D V 10)/D V 50≤1.3;

(3) a degree of graphitization of 96%-98%;

(4) a specific surface area (BET) of 2.1 m 2 /g-2.7 m 2 /g;

(5) a tap density of 0.9 g/cm 3 -1.2 g/cm 3 ; and

(6) a powder compacted density of 1.8 g/cm 3 -1.9 g/cm 3 under a force of 30,000 N.

14. The secondary battery according to claim 1 , wherein the second negative active material satisfies one or more of the following (1) to (6):

(1) an average particle diameter D V 50 of 13 μm-17 μm;

(2) a particle diameter distribution satisfying 1.1≤(D V 90−D V 10)/D V 50≤1.6;

(3) a degree of graphitization of 92%-94%;

(4) a specific surface area (BET) of 0.7 m 2 /g-1.3 m 2 /g;

(5) a tap density of 0.8 g/cm 3 -1.2 g/cm 3 ; and

(6) a powder compacted density under a force of 30,000 N is 1.71 g/cm 3 -1.80 g/cm 3 .

15. The secondary battery according to claim 1 , wherein surfaces of particles of the first negative active material and of particles of the second negative active material both are coated with a coating layer.

16. The secondary battery according to claim 1 , wherein a mass ratio of the first negative film layer to the second negative film layer is 1:2-3:2.