A pitch powder for use in the manufacture of negative electrode materials for secondary batteries

Abstract

This invention relates to a pitch powder for manufacturing a negative electrode material for secondary batteries. The pitch powder has advantageous properties, namely, that the composite powder produced using the pitch powder has a low BET specific surface area and, once used as a negative electrode of a battery, can achieve a long cycle life.

Claims

1. A pitch powder for manufacturing a negative electrode material for a secondary battery, the pitch powder having: (a) a maximum weight loss temperature Tmax characterized by a local maximum value in the DTG derivative pyrolysis gravimetric analysis at a rate of at least 445°C; (b) a temperature Tf at which significant weight loss terminates in the TGA pyrolysis gravimetric analysis at a rate of at least 490°C; (c) a toluene-insoluble fraction TI expressed as a weight percentage (wt%), wherein the TI is at least 25 wt% and at most 45 wt%; (d) a quinoline-insoluble fraction QI, wherein the difference TI-QI expressed as a weight percentage (%) is at least 25 wt% and at most 45 wt%; (e) residual carbon at 900°C at a rate of at least 60 wt%; and (f) hydrogen content H and carbon content C, both expressed as the number of molecules, wherein the ratio H / C is at least 0.65 and at most 0.

75.

2. For the asphalt powder in Request 1, the pyrolysis weight curve of its DTG derivative does not have a local maximum at temperatures below 440°C.

3. The bitumen powder as requested in item 1, wherein Tmax is at least 450°C.

4. The bitumen powder of any one of the requests 1 to 3, wherein Tf is at least equal to 495°C.

5. The bitumen powder of any one of claims 1 to 3, wherein the residual carbon at 900°C is at least 65 wt%.

6. The bitumen powder of any one of claims 1 to 3, wherein the ratio H / C is at least equal to 0.65 and at most equal to 0.

70.

7. The bitumen powder of any one of claims 1 to 3 contains petroleum bitumen.

8. The bitumen powder of any one of claims 1 to 3 has a softening point of at least 180°C.

9. A method for producing a silicon-based composite material used as a negative electrode material for a secondary battery, the method comprising the steps of: a) providing a silicon source and pitch powder as claimed in any one of claims 1 to 8; b) mixing the silicon source and the pitch powder in a liquid to form a dispersion; c) drying the dispersion to obtain an intermediate powder; and d) heating the intermediate powder in an oxygen-free atmosphere at a temperature between 800°C and 1100°C to obtain the silicon-based composite material.

10. The method of claim 9, wherein the silicon source in step a) is a slurry containing silicon-based particles having a volume-based size distribution with a d90 of less than 200 nm.

11. The method of claim 9, wherein the liquid in step b) is an alcohol or a mixture of alcohols.

12. The method of any one of claims 9 to 11, wherein in step b), the weight ratio of the asphalt powder to the silicon in the dispersion is 0.5 to 3.0, both of which refer to the dry content.

13. The method of any one of claims 9 to 11, wherein a shear force is applied to the intermediate powder between step c) and step d).

14. A silicon-based composite material for use as a negative electrode material in a secondary battery, which can be obtained by any one of claims 9 to 13.

15. The silicon-based complex of claim 14, having a BET specific surface area of ​​less than 5.0 m² / g.

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