A selenium and sulfur co-doped pitch-based hard carbon material, a preparation method and application thereof

Abstract

The application discloses a selenium-sulfur co-doped pitch-based hard carbon material and a preparation method and application thereof. The selenium-sulfur co-doped pitch-based hard carbon material is prepared from raw materials, and the raw materials comprise pitch, a selenium source and a sulfur source. The selenium-sulfur co-doped pitch-based hard carbon negative electrode material has a high lithium storage capacity; and the preparation method realizes co-doping of selenium and sulfur in the carbonization process, and inhibits the tendency of pitch graphitization in the high-temperature carbonization process. The preparation method is simple, economical and environmentally friendly, and the selenium-sulfur co-doped pitch-based hard carbon material is used as a lithium ion battery negative electrode material, so that the lithium ion battery has good electrochemical performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of battery negative electrode materials, in particular to a selenium and sulfur co-doped pitch-based hard carbon material and a preparation method and application thereof. BACKGROUND

[0002] Although the lithium ion battery with graphite as the negative electrode has excellent performance, the improvement of its energy density is approaching the theoretical limit. The charging efficiency of the graphite negative electrode is low, and lithium dendrites are easily formed during fast charging or cycling.

[0003] Hard carbon as a lithium ion battery negative electrode material has a series of significant advantages: (1) the lithium storage reversible specific capacity of hard carbon is relatively high, generally 500 mAh / g to 700 mAh / g, or even above 1000 mAh / g, which is much higher than the theoretical capacity of graphite material 372 mAh / g; (2) the hard carbon material can provide higher charging and discharging rate due to its high specific surface area, which is suitable for application scenarios requiring fast charging and discharging; (3) the raw material source of hard carbon is wide, and the cost is relatively low, which is conducive to large-scale production and application. Pitch is mainly divided into petroleum pitch and coal pitch due to different sources and production processes, and has a high proportion of carbon atoms, rich in small-size aromatic molecular compounds, which are composed of aromatic nuclei and side chains, and can easily form nearly parallel stacked carbon layers during the heating process, which is an ideal carbon material precursor for preparing carbon negative electrodes. However, pitch is prone to graphitization during heat treatment, and the prepared carbon material exhibits the bottleneck problem of low lithium storage specific capacity. SUMMARY

[0004] The technical problem solved by the present application is to overcome the existing lithium ion battery with graphite as the negative electrode material, which is approaching the theoretical limit in the improvement of energy density, and lithium dendrites are easily formed during fast charging or cycling, resulting in low charging efficiency, and the ideal carbon material precursor pitch is prone to graphitization during heat treatment, and the prepared carbon material exhibits the defect of low lithium storage specific capacity, thereby providing a selenium and sulfur co-doped pitch-based hard carbon material and a preparation method and application thereof. The selenium and sulfur co-doped pitch-based hard carbon negative electrode material of the present application has a high lithium storage capacity and good electrochemical performance, and can be used to prepare the negative electrode material of the lithium ion battery. The preparation method of the selenium and sulfur co-doped pitch-based hard carbon material also has the characteristics of simplicity, economy and environmental protection.

[0005] The present application adopts the following technical scheme to achieve the above-mentioned purpose:

[0006] The present application provides a selenium and sulfur co-doped pitch-based hard carbon material, which is prepared from the following raw materials, the raw materials comprising: pitch, selenium source and sulfur source.

[0007] In the present application, the pitch can be a conventional pitch in the art, and is preferably one or both of petroleum pitch and coal pitch, for example, petroleum pitch (purchased from China Petroleum).

[0008] In the present application, the selenium source can be one or more of selenium powder, selenium dioxide and sodium selenite, preferably selenium powder (purchased from Mitsubishi, purity 99.9%) or selenium dioxide (purchased from Macklin, purity 99%), for example selenium powder.

[0009] In the present application, the sulfur source can be one or more of thiourea (purchased from Aldrin) and sulfur powder (purchased from Macklin, purity 99%), for example thiourea.

[0010] In the present application, the mass ratio of the pitch, the selenium source and the sulfur source can be 10-20:1:2, for example 10:1:2.

[0011] In the present application, the particle size of the selenium-sulfur co-doped pitch-based hard carbon material can be 4-6 μm, for example 5 μm.

[0012] The present application provides a preparation method of a selenium-sulfur co-doped pitch-based hard carbon material, which comprises the following steps: (1) mixing pitch with a selenium source and a sulfur source, and processing to obtain a solid powder; (2) carbonizing the solid powder to obtain a selenium-sulfur co-doped pitch-based hard carbon material.

[0013] In step (1), the pitch, the selenium source and the sulfur source are as previously described.

[0014] In step (1), the pitch is prepared by a pre-oxidation step in advance.

[0015] Preferably, the pre-oxidation step oxidizes the pitch in air at about 300°C for about 3h.

[0016] In step (1), the processing includes grinding and sieving steps in sequence.

[0017] The grinding time can be a conventional grinding time in the art, for example about 1h.

[0018] The sieving can be performed in a conventional sieving device in the art, which is preferably an air flow sieve.

[0019] The particle size of the air flow sieve is preferably about 200 mesh.

[0020] In step (2), the carbonization is performed under a protective gas.

[0021] The protective gas can be a conventional protective gas in the art, which is preferably nitrogen.

[0022] In step (2), the carbonization temperature is preferably programmed.

[0023] Preferably, the temperature program is from 25℃ to 1150℃.

[0024] Preferably, the temperature program rate is about 5℃ / min.

[0025] Preferably, the carbonization is at 1150℃ for about 2h.

[0026] In step (2), before the solid powder is carbonized, the solid powder can be placed in any holding vessel, preferably a ceramic boat.

[0027] In a preferred embodiment of the present application, the holding vessel containing the solid powder is placed in any reaction container, preferably a tube furnace.

[0028] The present application provides a negative electrode material comprising the selenium-sulfur co-doped pitch-based hard carbon material as described above.

[0029] The present application provides a method for preparing a negative electrode material, comprising the following steps: (i) mixing and grinding the selenium-sulfur co-doped pitch-based hard carbon material as described above with a conductive agent and a binder to obtain a mixture powder; (ii) adding a solvent to the mixture powder to obtain a slurry; (iii) coating the slurry on a metal foil and drying to obtain a selenium-sulfur co-doped pitch-based hard carbon negative electrode material.

[0030] In step (i), the conductive agent can be a conventional conductive agent in the art, preferably acetylene black, Super P, or Ketjen black, for example, acetylene black.

[0031] In step (i), the binder can be a conventional binder in the art, preferably polyvinylidene fluoride (PVDF), styrene butadiene rubber emulsion (SBR), or carboxymethyl cellulose (CMC), for example, polyvinylidene fluoride (PVDF).

[0032] In step (i), the mass ratio of the selenium-sulfur co-doped pitch-based hard carbon material, the conductive agent, and the binder is preferably 90:5:5.

[0033] In step (ii), the solvent can be a conventional solvent in the art, preferably N-methyl-2-pyrrolidone.

[0034] Preferably, the mass ratio of the solvent to the mixture powder is 1:1 to 1:1.1, for example, 1:1.05.

[0035] In step (ii), the slurry is preferably a viscous slurry.

[0036] Preferably, the viscosity of the viscous slurry is 3000-4500 centipoise.

[0037] In step (iii), the metal foil can be a metal foil conventional in the art, for example, a copper foil.

[0038] In step (iii), the temperature for drying is preferably about 100°C.

[0039] In step (iii), the time for drying is preferably about 12h.

[0040] The drying can be performed in a drying machine conventional in the art, which is preferably an air-blowing drying machine. The present application removes the solvent in the slurry by an air-blowing drying machine, thereby forming a negative electrode material containing a selenium-sulfur co-doped pitch-based hard carbon material on the surface of the copper foil.

[0041] In step (iii), the slurry is coated on the metal foil using a doctoring tool to uniformly coat the slurry on the metal foil.

[0042] The doctoring tool can be a doctoring tool conventional in the art, for example, a doctor blade.

[0043] The doctoring size of the doctoring tool can be a doctoring size conventional in the art, for example, 100μm.

[0044] The diameter D50 of the selenium-sulfur co-doped pitch-based hard carbon negative electrode material is preferably 4-6μm, for example, 5μm.

[0045] The present application also provides a lithium ion battery comprising the selenium-sulfur co-doped pitch-based hard carbon material as described above, which is used as a negative electrode material.

[0046] In the present application, the operations and conditions for the preparation method of the lithium ion battery can be conventional operations and conditions in the art.

[0047] In the present application, the lithium ion battery further comprises a separator, a positive electrode material and an electrolyte.

[0048] The separator is preferably a polypropylene microporous membrane or a polyethylene microporous membrane, for example, a polypropylene microporous membrane.

[0049] The positive electrode material can be a positive electrode material conventional in the art, which is preferably lithium.

[0050] The electrolyte is preferably a lithium hexafluorophosphate (LiPF6) solution.

[0051] In a preferred embodiment of the present application, the lithium hexafluorophosphate (LiPF6) solution is obtained by mixing lithium hexafluorophosphate and a solvent, which is preferably a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), methyl ethyl carbonate (EMC) and vinylene carbonate (VC).

[0052] The volume ratio of the ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) is preferably 1:1:1.

[0053] The content of the vinylene carbonate (VC) is preferably 5% of the total volume of the ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0054] In a preferable embodiment of the present application, the concentration of the lithium hexafluorophosphate (LiPF6) solution is preferably 0.6-1 mol / L, for example, 1 mol / L.

[0055] In the present application, the selenium-sulfur co-doped pitch-based hard carbon material is preferably punched to obtain the electrode sheet.

[0056] The diameter of the electrode sheet is preferably 18 mm.

[0057] The shape of the electrode sheet can be a conventional shape in the art, and is preferably an irregular block, for example, a circle.

[0058] In the present application, the voltage window interval of the lithium ion battery is preferably 0-2 V.

[0059] On the basis of the common knowledge in the art, the above-mentioned preferable conditions can be combined arbitrarily, thereby obtaining preferable examples of the present application.

[0060] The reagents and raw materials used in the present application are commercially available.

[0061] In addition, unless otherwise indicated, the term "about" modifying the value of a quantity of an amount, a reaction condition, and the like, as used herein, refers to a range of values that fall within 5% of the recited value, for example:

[0062] About 300°C means 285°C-315°C. About 3h means 2.85-3.15h. About 1h means 0.95-1.05h. About 2h means 1.9-2.1h. About 5°C / min means 4.75-5.25°C / min.

[0063] The positive progress effect of the present application is that:

[0064] (1) The selenium-sulfur co-doped pitch-based hard carbon material provided by the present application has a high lithium storage capacity, for example, 343-380 mAh / g.

[0065] (2) The preparation method of the above-mentioned selenium-sulfur co-doped pitch-based hard carbon material provided by the present application realizes the co-doping of selenium and sulfur in the carbonization process, and inhibits the tendency of pitch graphitization in the high-temperature carbonization process. The preparation method has the characteristics of simplicity, economy and environmental protection.

[0066] (3) The selenium-sulfur co-doped pitch-based hard carbon material is used as a negative material of a lithium ion battery. The lithium ion battery has good electrochemical performance due to the good electrochemical performance of the selenium-sulfur co-doped pitch-based hard carbon material. BRIEF DESCRIPTION OF DRAWINGS

[0067] Figure 1 XRD patterns of pitch-based hard carbon materials prepared for Example 1, Comparative Example 1 and Comparative Example 2;

[0068] Figure 2 First circle charge-discharge curve of the battery prepared for Example 1, Comparative Example 1 and Comparative Example 2;

[0069] Figure 3 First circle charge-discharge curve of the battery prepared for Example 2;

[0070] Figure 4 First circle charge-discharge curve of the battery prepared for Example 3;

[0071] Figure 5 First circle charge-discharge curve of the battery prepared for Comparative Example 3 and Comparative Example 4;

[0072] Figure 6 EDS element analysis chart in the SEM test for Comparative Example 4;

[0073] Figure 7 First circle charge-discharge curve of the battery prepared for Comparative Example 5;

[0074] Figure 8 First circle charge-discharge curve of the battery prepared for Comparative Example 6. DETAILED DESCRIPTION

[0075] The present application is further illustrated by the following examples without limiting the present application to the examples. The experimental methods in the following examples without specific conditions are selected according to the conventional methods and conditions, or according to the commercial instruction.

[0076] Example 1

[0077] 1. Preparation of selenium-sulfur co-doped pitch-based hard carbon material:

[0078] The pre-oxidized petroleum pitch (wherein the pre-oxidation step is by oxidizing the petroleum pitch in air at 300℃ for 3h), selenium powder (purchased from Mitsubishi, purity of 99.9%) and thiourea (purchased from Aldrich) are mixed, and then ground for 1h and sieved, the sieving is performed in an air flow sieve with a particle size of 200 mesh, to obtain a solid powder. The mass ratio of the petroleum pitch, selenium powder and thiourea is 10:1:2. Then the obtained solid powder is placed in a porcelain boat, and carbonized in a tube furnace under the protection of nitrogen atmosphere, the temperature is raised from room temperature 25℃ to 1150℃ at a rate of 5℃ / min and kept at this temperature for 2h, to obtain the selenium and sulfur co-doped pitch-based hard carbon material.

[0079] 2. Preparation of lithium ion battery: The selenium and sulfur co-doped pitch-based hard carbon material prepared in step 1, acetylene black and binder PVDF are put into a mortar in a mass ratio of 90:5:5, and ground to obtain a mixture powder, then N-methyl-2-pyrrolidone is added until the mixture powder is a black viscous slurry, wherein the N-methyl-2-pyrrolidone (purchased from Maybridge Chemical Co., Ltd., purity≥99.8%) and the mixture powder have a mass ratio of 1:1.05. The obtained slurry is uniformly coated on a copper foil using a 100μm doctor blade, and then the copper foil is vacuum dried at 100℃ for 12h to obtain a selenium and sulfur co-doped pitch-based hard carbon negative electrode material with a particle size D50 of 5μm, which is then punched into a circular electrode sheet with a diameter of 18mm, and the electrode sheet is used as the negative electrode of the lithium ion battery; the obtained electrode sheet is used as the negative electrode, lithium metal is used as the positive electrode, a polypropylene microporous membrane is used as the separator, and a 1mol / L LiPF6 solution is used as the electrolyte, wherein the LiPF6 solution is composed of solute LiPF6 and solvent, and the solvent is composed of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and vinylene carbonate (VC), wherein the volume ratio of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) is 1:1:1, and the content of vinylene carbonate (VC) is 5% of the total volume of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC), and the voltage interval is set to 0-2V, to obtain the lithium ion battery.

[0080] Example 2

[0081] Except that the thiourea is replaced by sulfur powder (purchased from Macklin, purity of 99%); other conditions are the same as in Example 1.

[0082] Example 3

[0083] Except that the selenium powder is replaced by selenium dioxide (purchased from Macklin, purity of 99%); other conditions are the same as in Example 1.

[0084] Comparative Example 1

[0085] 1. Preparation of pure pitch-based hard carbon material:

[0086] A pure pitch-based hard carbon material was prepared using the same procedure as in Example 1, except that the only raw material used was the pre-oxidized petroleum pitch used in Example 1.

[0087] Comparative Example 2

[0088] 1. Preparation of selenium-doped pitch-based hard carbon material:

[0089] A selenium-doped pitch-based hard carbon material was prepared using the same procedure as in Example 1, except that the only raw materials used were the pre-oxidized petroleum pitch used in Example 1 and selenium powder, and the mass ratio of petroleum pitch to selenium powder was 10:1.

[0090] 2. Preparation of lithium ion battery: A lithium ion battery was prepared by the same procedure as in Example 1, except that the particle size D50 of the prepared selenium-doped pitch-based hard carbon anode material was 5.5 μm.

[0091] Comparative Example 3

[0092] 1. Preparation of nitrogen-doped pitch-based hard carbon material:

[0093] A nitrogen-doped pitch-based hard carbon material was prepared using the same procedure as in Example 1, except that the only raw materials used were the pre-oxidized petroleum pitch used in Example 1 and melamine, and the mass ratio of petroleum pitch to melamine was 5:1.

[0094] 2. Preparation of lithium ion battery: A lithium ion battery was prepared by the same procedure as in Example 1, except that the particle size D50 of the prepared nitrogen-doped pitch-based hard carbon anode material was 5.4 μm.

[0095] Comparative Example 4

[0096] 1. Preparation of nitrogen-sulfur co-doped pitch-based hard carbon material:

[0097] A nitrogen-sulfur co-doped pitch-based hard carbon material was prepared using the same procedure as in Example 1, except that the raw materials were the pre-oxidized petroleum pitch used in Example 1, and melamine and thiourea, and the mass ratio of petroleum pitch to melamine to thiourea was 5:1:1.

[0098] 2. Preparation of lithium ion battery: A lithium ion battery was prepared by the same procedure as in Example 1, except that the particle size D50 of the prepared nitrogen-sulfur co-doped pitch-based hard carbon anode material was 5.6 μm.

[0099] Comparative Example 5

[0100] 1. Preparation of boron-doped pitch-based hard carbon material:

[0101] The same procedure as in Example 1 was used, except that the raw materials were pre-oxidized petroleum pitch used in Example 1 and boric acid, and the mass ratio of petroleum pitch to boric acid was 5:1, to prepare the boron-doped pitch-based hard carbon material.

[0102] 2. Preparation of lithium ion battery: The lithium ion battery was prepared by the same procedure as in Example 1, except that the particle size D50 of the prepared boron-doped pitch-based hard carbon negative electrode material was 6 μm.

[0103] Comparative Example 6

[0104] In addition to petroleum pitch, the mass ratio of selenium powder to thiourea was 20:1:2; other components, compositions, and operations were exactly the same as in Example 1.

[0105] Effect Example 1

[0106] The pitch-based hard carbon materials in each of the above Example 1 and Comparative Examples 1-2 were subjected to XRD spectrum testing, and the results are shown in Figure 1 , and Figure 1 are XRD patterns of the pitch-based hard carbon materials prepared in Example 1 and Comparative Examples 1-2. The name and model of the instrument used for testing are: D8 ADVANCE (Bruker, Germany).

[0107] The XRD spectrum of the pitch-based hard carbon material has two broad diffraction peaks at 25° and 43°, which are typical diffraction peaks of hard carbon at the (002) and (100) crystal planes. It can be found that the (002) peak of the pitch-based hard carbon material co-doped with selenium and sulfur becomes wider, indicating that the degree of graphitization of the hard carbon material after doping is lower, and more defects are introduced to provide more lithium storage sites. And the (002) peak has a certain shift to the left, indicating that the interlayer spacing of the pitch-based hard carbon material after doping has also been improved to a certain extent.

[0108] Effect Example 2

[0109] The EDS element analysis in the SEM test of Comparative Example 4 was performed using a JSX-1000S instrument. As shown in Figure 6 , the presence of N and S elements was detected in Comparative Example 4, indicating that nitrogen and sulfur elements were successfully introduced.

[0110] Effect Example 3

[0111] The lithium ion batteries of the above Examples 1-3 and Comparative Examples 2-6 were respectively subjected to electrochemical performance testing, and the results are shown in Figures 2-5 , and Figures 7-8The results are shown in Table 1 below, and all the galvanostatic charge-discharge (GCD) tests of the batteries were performed using a CT-4008T test system with a voltage window of 0-2.0 V.

[0112] Table 1

[0113]

[0114] It can be seen that the lithium storage capacity of Comparative Example 1 of the undoped pitch-based hard carbon material is 280 mAh / g, the lithium storage capacity of Comparative Example 2 of the selenium-doped pitch-based carbon material is 340 mAh / g, the lithium storage capacity of Comparative Example 3 of the nitrogen-doped pitch-based hard carbon material is 254 mAh / g, the lithium storage capacity of Comparative Example 4 of the nitrogen-sulfur co-doped pitch-based hard carbon material is 312 mAh / g, the lithium storage capacity of Comparative Example 5 of the boron-doped pitch-based hard carbon material is 332 mAh / g, and the lithium storage capacity of Comparative Example 6 of the pitch-based hard carbon material co-doped with selenium and sulfur having a mass ratio different from that of the present application is 330 mAh / g. It can be seen that the lithium storage capacity of the pitch-based carbon materials of Examples 1-3 of the present application is significantly improved, and the lithium storage capacity is 343-380 mAh / g, and in particular, the lithium storage capacity of Example 1 is as high as 380 mAh / g.

Claims

1. A selenium and sulfur co-doped pitch-based hard carbon material, characterized in that, The selenium-sulfur co-doped pitch-based hard carbon material is prepared from raw materials including pitch, selenium source and sulfur source; the mass ratio of the pitch, the selenium source and the sulfur source is 10:1:2; the selenium source is one or more of selenium powder, selenium dioxide and sodium selenite; the sulfur source is one or more of thiocyanate and sulfur powder; the pitch is one or both of petroleum pitch and coal pitch; and the particle size of the selenium-sulfur co-doped pitch-based hard carbon material is 4-6 μm.

2. The selenium and sulfur co-doped pitch-based hard carbon material of claim 1, wherein, The particle size of the selenium-sulfur co-doped pitch-based hard carbon material is 5 μm.

3. A method of producing a selenium and sulfur co-doped pitch-based hard carbon material as claimed in claim 1 or 2, characterized in that, The method comprises the following steps: (1) mixing pitch with a selenium source and a sulfur source and processing to obtain a solid powder; and (2) carbonizing the solid powder to obtain a selenium-sulfur co-doped pitch-based hard carbon material.

4. The method for preparing a selenium-sulfur co-doped pitch-based hard carbon material according to claim 3, characterized in that: The method satisfies one or more of the following conditions: (1) in step (1), the pitch is prepared by a pre-oxidation step in advance; (2) in step (1), the processing comprises, in sequence, a grinding treatment and a screening treatment step; (3) in step (2), the carbonization is performed under a protective gas; (4) in step (2), the carbonization comprises programmed temperature rising; (5) before the carbonization of the solid powder in step (2), the solid powder is placed in a holding device; The holding device containing the solid powder is placed in a reaction container.

5. The method for preparing a selenium-sulfur co-doped pitch-based hard carbon material according to claim 4, characterized in that: In condition (1), the pre-oxidation step is oxidation under air at 300 ℃ for 3 h.

6. The method for preparing a selenium-sulfur co-doped pitch-based hard carbon material according to claim 4, characterized in that: In condition (2), the grinding treatment is performed for 1 h.

7. The method for preparing a selenium-sulfur co-doped pitch-based hard carbon material according to claim 4, characterized in that: In condition (2), the screening treatment is performed by an air flow screen.

8. The method for preparing a selenium-sulfur co-doped pitch-based hard carbon material according to claim 7, characterized in that: The particle size of the air flow screen is 200 mesh.

9. The method for preparing a selenium-sulfur co-doped pitch-based hard carbon material according to claim 4, characterized in that: In condition (3), the protective gas is nitrogen.

10. The method for preparing a selenium-sulfur co-doped pitch-based hard carbon material according to claim 4, characterized in that: In condition (4), the programmed temperature rising is from 25 ℃ to 1150 ℃.

11. The method for preparing a selenium-sulfur co-doped pitch-based hard carbon material according to claim 4, characterized in that: In condition (4), the programmed temperature rising is held at 1150 ℃ for 2 h.

12. The method for preparing a selenium-sulfur co-doped pitch-based hard carbon material according to claim 4, characterized in that: In condition (4), the programmed temperature rising has a temperature rising rate of 5 ℃ / min.

13. The method for preparing a selenium-sulfur co-doped pitch-based hard carbon material according to claim 4, characterized in that: In condition (5), before the carbonization of the solid powder, the solid powder is placed in a porcelain boat.

14. The method for preparing a selenium-sulfur co-doped pitch-based hard carbon material according to claim 4, characterized in that: In condition (5), the holding device containing the solid powder is placed in a tube furnace.

15. A negative electrode material, characterized by, The method comprises the following steps:

16. A method for producing a negative electrode material, characterized by, (i) mixing the selenium-sulfur co-doped pitch-based hard carbon material of claim 1 or 2 with a conductive agent and a binder and grinding to obtain a mixture powder; (ii) adding a solvent to the mixture powder to obtain a slurry; and (iii) coating the slurry on a metal foil and drying to obtain a selenium-sulfur co-doped pitch-based hard carbon negative electrode material. The method satisfies one or more of the following conditions:

17. The method of claim 16, wherein the method further comprises the step of: (1) the mass ratio of the selenium-sulfur co-doped pitch-based hard carbon material, the conductive agent and the binder is 90:5:5; (2) the conductive agent is acetylene black, SuperP or Ketjen black; (3) the binder is polyvinylidene fluoride, butadiene-styrene rubber emulsion or carboxymethyl cellulose; (3) the solvent is N-methyl-2-pyrrolidone; (4) the mass ratio of the solvent to the mixture powder is 1:1 to 1:1.1; (5) the slurry is a viscous slurry; The viscosity of the viscous slurry is 3000-4500 centipoise. ​ (6) the metal foil is a copper foil; (7) in step (iii), the temperature of the drying is 100°C; (8) in step (iii), the time of the drying is 12h; (9) in step (iii), the drying is performed in a drying machine; (10) in step (iii), the slurry is coated on the metal foil using a scraping tool; wherein the scraping tool is a doctor blade; wherein the scraping size of the scraping tool is 100μm; (11) the selenium and sulfur co-doped pitch-based hard carbon negative electrode material has a diameter D50 of 4-6μm.

18. The method of claim 17, wherein the method further comprises: In condition (4), the mass ratio of the solvent to the mixture powder is 1:1.

05.

19. The method of claim 17, wherein the method further comprises a step of mixing the carbon material and the metal compound. In condition (9), the drying machine is a blast drying machine.

20. The method of claim 17, wherein the method further comprises: In condition (11), the selenium and sulfur co-doped pitch-based hard carbon negative electrode material has a diameter D50 of 5μm.

21. A lithium-ion battery, characterized by, It comprises the selenium and sulfur co-doped pitch-based hard carbon material according to claim 1 or 2, a separator, a positive electrode material and an electrolyte.

22. The lithium-ion battery of claim 21, wherein, It satisfies one or more of the following conditions: (1) the separator is a polypropylene microporous membrane or a polyethylene microporous membrane; (2) the positive electrode material is lithium; (3) the electrolyte is a lithium hexafluorophosphate solution; wherein the lithium hexafluorophosphate solution is obtained by mixing lithium hexafluorophosphate and a solvent; (4) the selenium and sulfur co-doped pitch-based hard carbon material is punched to obtain an electrode sheet; (5) the voltage window interval of the lithium ion battery is 0-2V.

23. The lithium-ion battery of claim 22, wherein, In condition (3), the solvent is a mixture of ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate and vinylene carbonate.

24. The lithium-ion battery of claim 23, wherein, The volume ratio of the ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate is 1:1:

1.

25. The lithium-ion battery of claim 23, wherein, The content of the vinylene carbonate accounts for 5% of the total volume of the ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate.

26. The lithium-ion battery of claim 22, wherein, In condition (3), the concentration of the lithium hexafluorophosphate solution is 0.6-1mol / L.

27. The lithium-ion battery of claim 22, wherein, In condition (4), the diameter of the electrode sheet is 18mm.

28. The lithium-ion battery of claim 22, wherein, The shape of the electrode sheet is circular.

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