Negative active material, preparation method thereof, secondary battery and related battery module, battery pack and device

1. A negative active material comprising a core structure and a polymer coating layer coated on at least a part of the outer surface of the core structure, wherein the core structure comprises silicon-based materials;

wherein the negative active material has an infrared spectrum comprising an infrared absorption peak at the wavelength of 1450 cm −1 to 1690 cm −1 , and the infrared absorption peak has a transmittance T that satisfies 85%≤T≤98.5%, as measured according to the description,

wherein the coating layer comprises carbon element and comprises —C═C— linkage, and

wherein the coating layer comprises nitrogen element and comprises —C═N— linkage.

2. The negative active material according to claim 1 , wherein the carbon element in the coating layer is present in an amount of 0.5%˜4.0% based on the total weight of the negative active material.

3. The negative active material according to claim 1 , wherein the nitrogen element is present in an amount of 0.1%˜0.66% based on the total weight of the negative active material.

4. The negative active material according to claim 1 , wherein the negative active material has an X-ray diffraction pattern comprising a diffraction peak at the diffraction angle 2 θ of 19° to 27° and the diffraction peak has a half peak width of 4° to 12°; and/or

the negative active material has a Raman spectrum comprising scattering peaks at the Raman shifts of 1320 cm −1 ˜1410 cm −1 and 1550 cm −1 -1650 cm −1 in which the scattering peak at the Raman shifts of 1320 cm −1 ˜1410 cm −1 has a peak intensity recorded as I D , and the scattering peak at the Raman shifts of 1550 cm −1 ˜1650 cm −1 has a peak intensity recorded as I G , and the I D and the I G stratify 1.60≤I D /I G ≤2.50.

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

(1) the negative active material has a number particle size distribution Dn10 of 0.1 μm˜4 μm;

(2) the negative active material has a number particle size distribution D v 50 of 4 μm˜15 μm;

(3) the negative active material has a number particle size distribution D v 99 of 8 μm˜25 μm;

(4) the negative active material has a compaction density of 1.0 g/cm 3 ˜1.6 g/cm 3 under the test condition of 5 tonnes (equivalent to 49 KN); and

(5) the negative active material has a real density of 2.1 g/cm 3 ˜2.5 g/cm 3 .

6. The negative active material according to claim 1 , wherein the silicon-based material is selected from one or more of elemental silicon, silicon-carbon composites, silicon-oxygen compounds, silicon-nitrogen compounds, and silicon alloys; and the tin-based material is selected from one or more of elemental tin, tin oxide compounds, and tin alloys.

7. A preparation process of a negative active material, comprising:

a) providing silicon-based materials as a core structure;

b) adding a polymer into a solvent and dispersing it homogenously to obtain a solution, wherein the polymer is selected from one or more of polyacrylonitrile and polyacrylamide;

c) adding the core structure to the solution, and mixing it homogeneously to obtain a mixture slurry;

d) spray drying the mixture slurry under an inert non-oxidizing gas atmosphere to obtain a solid powder;

e) subjecting the solid powder to a heat treatment under an inert non-oxidizing gas atmosphere to obtain the negative active material;

wherein the negative active material comprises a core structure and a polymer coating layer coated on at least a part of the outer surface of the core structure, the core structure comprises one or more of silicon-based materials and tin based materials; and the negative active material has an infrared spectrum comprising an infrared absorption peak at the wavelength of 1450 cm −1 to 1690 cm −1 , and the infrared absorption peak has a transmittance T that satisfies 85%≤T≤98.5%,

wherein the coating layer comprises carbon element and comprises —C═C— linkage, and

wherein the coating layer comprises nitrogen element and comprises —C═N— linkage.

8. The preparation process according to claim 7 , wherein

in the step b), the ratio of the polymer mass and the solvent volume of is 0.1 g/L˜15 g/L; and/or

in the step c), the ratio of the core structure mass of and the polymer mass is 10˜180; and/or

in the step d), the spray drying is carried out at a temperature of 80° C.˜300° C.; and/or

in the step e), the heat treatment is carried out at a temperature of 250° C.˜450° C.; the heat treatment is carried out for 2 h˜8 h.

9. A secondary battery comprising the negative active material according to claim 1 .

10. A device comprising the secondary battery according to claim 9 .

11. The negative active material according to claim 1 , wherein the carbon element in the coating layer is present in an amount of 0.74˜1.3% based on the total weight of the negative active material.

12. The negative active material according to claim 1 , wherein the nitrogen element is present in an amount of 0.2%˜0.56% based on the total weight of the negative active material.

13. The negative active material according to claim 1 , wherein the negative active material has an X-ray diffraction pattern comprising a diffraction peak at the diffraction angle 2 θ of 19° to 27° and the diffraction peak has a half peak width of 5° to 10°; and/or

the negative active material has a Raman spectrum comprising scattering peaks at the Raman shifts of 1320 cm −1 ˜1410 cm −1 and 1550 cm −1 ˜1650 cm −1 in which the scattering peak at the Raman shifts of 1320 cm −1 ˜1410 cm −1 has a peak intensity recorded as I D , and the scattering peak at the Raman shifts of 1550 cm −1 ˜1650 cm −1 has a peak intensity recorded as I G , and the I D and the I G stratify 1.80≤I D /I G ≤2.40.

14. The negative active material according to claim 1 , wherein the negative active material satisfies one or more of the following:

(1) the negative active material has a number particle size distribution D n 10 of 0.15 μm˜3 μm;

(2) the negative active material has a number particle size distribution D v 50 of 5 μm˜10 μm;

(3) the negative active material has a number particle size distribution D v 99 of 12 μm˜22 μm;

(4) the negative active material has a compaction density of 1.2 g/cm 3 ˜1.5 g/cm 3 under the test condition of 5 tonnes (equivalent to 49 KN); and

(5) the negative active material has a real density of 2.2 g/cm 3 ˜2.4 g/cm 3 .

15. The negative active material according to claim 1 , wherein the silicon-based material is selected from silicon-oxygen compounds.

16. The preparation process according to claim 7 , wherein

in the step b), the ratio of the polymer mass and the solvent volume of is 0.5 g/L˜10 g/L; and/or

in the step c), the ratio of the core structure mass of and the polymer mass is 16˜100; and/or

in the step d), the spray drying is carried out at a temperature of 110° C.˜250° C.; and/or

in the step e), the heat treatment is carried out at a temperature of 300° C.˜450° C.; and the heat treatment is carried out for 3 h-5 h.