Negative electrode active material, process for preparing the same, and secondary battery, battery module, battery pack and apparatus related to the same

1. A negative electrode active material, comprising a core material and a polymer-modified coating layer on at least part of a surface of the core material;

wherein

the core material comprises one or more of a silicon-based negative electrode material and a tin-based negative electrode material;

the polymer-modified coating layer comprises sulfur element and carbon element;

the sulfur element has a mass percentage of from 0.2% to 4% in the negative electrode active material;

the carbon element has a mass percentage of from 0.5% to 4% in the negative electrode active material;

the polymer-modified coating layer comprises —S—C— bond; and

the polymer-modified coating layer further comprises —S—S— bond.

2. The negative electrode active material according to claim 1 , wherein the sulfur element has a mass percentage of from 0.7% to 2% in the negative electrode active material.

3. The negative electrode active material according to claim 1 , wherein the carbon element has a mass percentage of from 0.9% to 3% in the negative electrode active material.

4. The negative electrode active material according to claim 1 ,

wherein the negative electrode active material has a volume average particle size D v 50 of from 2μm to 12 μ; and/or

wherein the negative electrode active material has a volume particle size distribution width (D v 90 −D v 10 )/D v 50 of from 0.5 to 2.5; and/or

wherein the negative electrode active material has a specific surface area BET of from 0.5 m 2 /g.

5. The negative electrode active material according to claim 1 , wherein the negative electrode active material has a compacted density of from 1.0 g/cm 3 to 2.0 g/cm 3 , measured under a pressure of 5 tons (equivalent to 49 KN) ; and/or wherein the negative electrode active material has a tap density of from 0.5 g/cm 3 to 1.5 g/cm 3 .

6. The negative electrode active material according to claim 1 , wherein the silicon-based negative electrode material is one or more selected from the group consisting of elemental silicon, a silicon-carbon composite, a silicon-oxygen compound, a silicon-nitrogen compound, and a silicon alloy; and

the tin-based negative electrode material is one or more selected from the group consisting of elemental tin, a tin-oxygen compound, and a tin alloy.

7. A process for preparing a negative electrode active material, comprising the following steps:

(1) dissolving a polymer precursor in a solvent, and stirring until uniform dispersion, to obtain a solution of the polymer precursor;

(2) adding a core material into the solution of the polymer precursor, and stirring, to obtain a mixed slurry, wherein the core material is one or more selected from the group consisting of a silicon-based negative electrode material and a tin-based negative electrode material;

(3) drying the mixed slurry in an inert non-oxidizing gas atmosphere, to obtain a solid powder; and

(4) mixing the solid powder with a sulfur powder to obtain a mixture, and subjecting the mixture to heat-treatment under an inert non-oxidizing gas atmosphere, to obtain the negative electrode active material;

wherein the negative electrode active material comprises the core material and a polymer-modified coating layer on at least part of a surface of the core material, the polymer-modified coating layer comprises sulfur element and carbon element, the sulfur element has a mass percentage of from 0.2% to 4% in the negative electrode active material, the carbon element has a mass percentage of from 0.5% to 4% in the negative electrode active material, the polymer-modified coating layer comprises —S—C— bond, and the polymer-modified coating layer further comprises —S—S— bond.

8. The process according to claim 7 , wherein in step (1), a ratio of a mass of the polymer precursor to a volume of the solvent is from 0.1 g/L to 20 g/L.

9. The process according to claim 7 , wherein in step (2), a mass ratio of the core material to the polymer precursor is from 7 to 200.

10. The process according to claim 7 , wherein in step (4), a mass ratio of the sulfur powder to the polymer precursor is from 1 to 5.

11. The process according to claim 7 , wherein the heat treatment is carried out at from 250° C. to 450° C.

12. The process according to claim 11 , wherein the heat treatment is carried out for from 2 h to 8 h.

13. A secondary battery, comprising the negative electrode active material according to claim 1 .

14. An apparatus, comprising at least one of the secondary battery according to claim 13 .

15. The process according to claim 7 , wherein the polymer precursor comprises one or more of polystyrene, polyvinyl chloride, polyethylene, polyacrylonitrile, polyaniline, polyacetylene, and polyvinylidene chloride.