Negative electrode active material, method for preparing same, secondary battery and apparatus including the secondary battery

1. A method for preparing a negative electrode active material comprising a core and a coating layer covering a surface of the core, comprising the following steps:

a) providing a coke raw material, wherein the coke raw material has a volume average particle size D v 50 of from 6 μm to 12 μm, and the coke raw material has a volatile content C 1 satisfying 1% ≤C 1 ≤12%;

b) shaping and grading the coke raw material to obtain a precursor, wherein the precursor has a particle size uniformity U 1 satisfying 0.2≤U 1 ≤0.5;

c) granulating the precursor, during which a binder is added in an amount of C 2 , wherein C 1 , C 2 and U 1 satisfy 21% ≤(C 1 +C 2 )/U 1 ×100%≤50%;

d) graphitizing the granulated product at a temperature of from 2800° C. to 3200° C. to obtain an artificial graphite, wherein the artificial graphite has a particle size uniformity U 2 satisfying 0.22≤U 2 ≤0.48; and

e) coating the artificial graphite with an organic carbon source, performing heat treatment to form an amorphous carbon coating layer on at least a part of the surface of the artificial graphite, to obtain the negative electrode active material, wherein the organic carbon source added during forming the coating layer has an amount C 3 , and wherein C 3 , C 1 , C 2 and U 2 satisfy 20% ≤(C 1 +C 2 +C 3 )/U 2 ×100%≤55%, and 1.5% ≤C 3 ×carbon residue rate ≤2.5%,

wherein the core comprises artificial graphite, the coating layer comprises amorphous carbon, and the negative electrode active material has a particle size uniformity of from 0.25 to 0.45.

2. The method according to claim 1 , wherein the coke raw material comprises one or more of petroleum-based non-needle coke and petroleum-based needle coke.

3. The method according to claim 1 , wherein the coke raw material comprises petroleum green coke.

4. The method according to claim 1 , wherein the particle size uniformity of the negative electrode active material is from 0.3 to 0.4.

5. The method according to claim 1 , wherein the negative electrode active material has a particle size specific surface area of from 0.3 m 2 /g to 0.65 m 2 /g.

6. The method according to claim 1 , wherein the negative electrode active material satisfies 0.8≤(D v 90−D v 10)/D v 50≤1.6.

7. The method according to claim 1 , wherein the negative electrode active material comprises secondary particles, and wherein the secondary particles have a number proportion of ≥30% in the negative electrode active material.

8. The method according to claim 1 , wherein the negative electrode active material further satisfies one or more of the following conditions from (1) to (4):

(1) the negative electrode active material has a volume particle size distribution D v 10 satisfying 5 μm≤D v 10≤10 μm; the negative electrode active material has a volume average particle size D v 50 satisfying 8 μm≤D v 50≤16 μm;

(2) the negative electrode active material has a graphitization degree of from 91.0% to 96.0%;

(3) the negative electrode active material has a gram capacity of from 345 mAh/g to 360 mAh/g; and

(4) the negative electrode active material has a tap density of from 0.8 g/cm 3 to 1.2 g/cm 3 .

9. The method according to claim 1 , wherein the particle size uniformity of the negative electrode active material is from 0.31 to 0.38.

10. The method according to claim 1 , wherein the negative electrode active material has a particle size specific surface area of from 0.4 m 2 /g to 0.55 m 2 /g.

11. The method according to claim 1 , wherein the negative electrode active material satisfies 0.9≤(D v 90−D v 10)/D v 50≤1.4.

12. The method according to claim 1 , wherein the negative electrode active material comprises secondary particles, and wherein the secondary particles have a number proportion of ≥50% in the negative electrode active material.

13. The method according to claim 1 , wherein the negative electrode active material further satisfies one or more of the following conditions from (1) to (4):

(1) the negative electrode active material has a volume particle size distribution D v 10 satisfying 6.0 μm≤D v 10≤8.0 μm; the negative electrode active material has a volume average particle size D v 50 satisfying 10 μm≤D v 50≤14 μm;

(2) the negative electrode active material has a graphitization degree of from 92.0% to 94.5%;

(3) the negative electrode active material has a gram capacity of from 348 mAh/g to 355 mAh/g; and

(4) the negative electrode active material has a tap density of from 0.95 g/cm 3 to 1.05 g/cm 3 .

14. The method according to claim 1 , wherein the coke raw material has a volatile content C 1 satisfying 5%≤C 1 ≤9%.

15. The method according to claim 1 , wherein C 1 , C 2 and U 1 satisfy 31%≤(C 1 +C 2 )/U 1 ×100%≤35%.