Hard carbon, method for preparing same, secondary battery comprising same, and electrical apparatus comprising same

1. A hard carbon, wherein a total quantity of adsorbed nitrogen under a relative pressure P/P 0 of nitrogen between 10 −8 and 0.035 is V 1 cm 3 (STP)/g and a total quantity of adsorbed nitrogen under a relative pressure P/P 0 of nitrogen between 0.035 and 1 is V 2 cm 3 (STP)/g in a nitrogen adsorption isotherm determined at a temperature of 77 K for the hard carbon, and the hard carbon satisfies: V 2 /V 1 ≤0.20 and 20≤V 1 ≤150, wherein P represents an actual pressure of nitrogen, and P 0 represents a saturated vapor pressure of nitrogen at a temperature of 77 K.

2. The hard carbon according to claim 1 , wherein 50≤V 1 ≤150.

3. The hard carbon according to claim 2 , wherein 70≤V 1 ≤150.

4. The hard carbon according to claim 1 , wherein 0.05≤V 2 /V 1 ≤0.20.

5. The hard carbon according to claim 4 , wherein 0.08≤V 2 /V 1 ≤0.20.

6. The hard carbon according to claim 1 , wherein 4≤V 2 ≤30.

7. The hard carbon according to claim 6 , wherein 6≤V 2 ≤30.

8. The hard carbon according to claim 1 , wherein, in a Raman spectrum of the hard carbon, I d /I g is in a range from 1.20 to 1.32, wherein I d represents d peak intensity of a Raman shift in a range of 1,300 cm −1 -1,400 cm −1 , and I g represents g peak intensity of the Raman shift in a range of 1,530 cm −1 -1,630 cm −1 .

9. The hard carbon according to claim 1 , wherein, in an X-ray diffraction pattern of the hard carbon, a 2θ value corresponding to peak 002 is between 22° and 24°.

10. The hard carbon according to claim 1 , wherein the hard carbon satisfies at least one of following conditions:

a volumetric particle size Dv50 of the hard carbon is in a range from 2 μm to 15 μm;

a volumetric particle size Dv90 of the hard carbon is in a range from 5 μm to 25 μm;

a specific surface area of the hard carbon is less than or equal to 5 m 2 /g;

a powder compaction density of the hard carbon under a force of 50,000 N is in a range from 0.96 g/cm 3 to 1.05 g/cm 3 ; and

a tap density of the hard carbon is in a range from 0.80 g/cm 3 to 0.95 g/cm 3 .

11. A method for preparing the hard carbon according to claim 1 , comprising:

providing a carbon source;

heat treating the carbon source in an inert atmosphere at a first temperature T 1 for a duration of t 1 to obtain a first intermediate product;

heat treating the first intermediate product in an air atmosphere at a second temperature T 2 for a duration of t 2 to obtain a second intermediate product, 180° C.≤T 1 <T 2 < 400 ° C.; and

carbonizing the second intermediate product in an inert atmosphere at a third temperature T 3 for a duration of t 3 to obtain the hard carbon.

12. The method according to claim 11 , wherein T 1 <T 3 and T 2 <T 3 .

13. The method according to claim 11 , wherein:

T 1 ≤ 300 ° C.; and/or

T 3 is in a range from 1,000° C. to 1,600° C.

14. The method according to claim 11 , wherein:

t 1 is from 4 h to 60 h; and/or

t 2 is from 1 h to 12 h; and/or

t 3 is from 1 h to 12 h.

15. The method according to claim 11 , further comprising at least one of following:

crushing the first intermediate product after heat treating the carbon source and prior to heat treating the first intermediate product;

crushing the second intermediate product after heat treating the first intermediate product and prior to carbonizing the second intermediate product; and

crushing the hard carbon.

16. The method according to claim 11 , wherein the inert atmosphere is one or more selected from a nitrogen atmosphere and an argon atmosphere.

17. The method according to claim 11 , wherein the carbon source includes one or more of a polymer, a resin, and a biomass material.

18. A secondary battery, comprising:

a negative electrode sheet, the negative electrode sheet comprising the hard carbon according to claim 1 .

19. An electrical apparatus, comprising the secondary battery according to claim 18 .