A silicon-carbon porous negative electrode material and its preparation method and application

Abstract

The present disclosure provides a method for preparing a silicon-carbon porous negative electrode material, including: mixing a first dispersion containing ZIF-67 powder and a first organic solvent, a Zn source and nano-silicon to obtain a first material; centrifuging the first material to obtain a first precipitate, washing the first precipitate with a first washing liquid and performing a first drying process to obtain a Zn-containing silicon-carbon material precursor; grinding the Zn-containing silicon-carbon material precursor with melamine powder to obtain a mixture, subjecting the mixture to high temperature treatment and cooling to obtain an annealed product; adding the annealed product to an acid solution for pickling to obtain a precipitate, and washing the precipitate with a washing liquid and performing a vacuum drying process. The material prepared by the present disclosure has good electronic conductivity and can improve the energy density and cycle performance of a power battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and specifically relates to a CNT-Si / C-HCM silicon-carbon porous composite material and a preparation method thereof. Background Art

[0002] The new energy vehicle industry and market are growing rapidly. The energy density of power batteries directly affects the cruising range of new energy vehicles. Improving energy density has always been one of the development directions of power batteries. The theoretical gram capacity of traditional graphite negative electrodes for power batteries is 372mAh / g. At present, the traditional graphite negative electrode has been developed close to the upper limit of gram capacity, while the upper limit of the theoretical gram capacity of silicon materials is more than 10 times that of traditional graphite negative electrodes, which can reach 4200mAh / g. Therefore, the gram capacity advantage of silicon materials is obvious. In addition, silicon materials are environmentally friendly, have abundant reserves, and are low in cost. However, silicon negative electrode materials also have problems such as low cycle life, large volume expansion, and poor conductivity. After a lot of research, it has been found that silicon-carbon lithium-ion battery negative electrode materials can improve the above problems of silicon negative electrode materials to a certain extent.

[0003] Existing silicon-carbon composite negative electrode materials still have problems such as poor conductivity, complicated process steps, and irregular morphology of synthesized particles. Summary of the invention

[0004] The purpose of the present disclosure is to provide a silicon-carbon porous composite material with excellent electrical conductivity, high energy density and good cycle performance when applied to power batteries.

[0005] In order to achieve the above object, the first aspect of the present disclosure provides a method for preparing a silicon-carbon porous negative electrode material, comprising:

[0006] S1, mixing a first dispersion containing ZIF-67 powder and a first organic solvent, a Zn source and nano-silicon to obtain a first material; centrifuging the first material to obtain a first precipitate, washing the first precipitate with a first washing liquid and performing a first drying treatment to obtain a Zn-containing silicon-carbon material precursor;

[0007] S2, mixing the Zn-containing silicon-carbon material precursor with melamine powder and grinding them to obtain a mixture, and subjecting the mixture to high-temperature treatment and cooling to obtain an annealed product;

[0008] S3, adding the annealed product into an acid solution for pickling.

[0009] Optionally, in step S1, in the first dispersed solution, the content of the ZIF-67 powder is 2-10 mg / mL, preferably 3.122-6.690 mg / mL, and more preferably 4.460 mg / mL; in the first material, the mass ratio of the Zn source, nano-silicon and the ZIF-67 powder is 1:2-10:5-15, preferably 1:5-6:8-10, and more preferably 1:5:10.

[0010] Optionally, in step S2, the mass ratio of the Zn-containing silicon-carbon material precursor to the melamine powder is 1:5-7, preferably 1:5.

[0011] Optionally, the Zn source is a Zn salt, preferably Zn(NO 3 ) 2 6H 2 O、ZnCl 2 and ZnSO 3 One of the above, preferably Zn(NO 3 ) 2 6H 2 O; the first organic solvent is selected from alcohols having 1 to 4 carbon atoms, preferably ethanol and / or methanol, and more preferably ethanol; the first washing liquid is selected from at least one of ethanol, deionized water and methanol, and preferably a mixed solution of ethanol and deionized water; the acid solution is selected from at least one of sulfuric acid, hydrochloric acid and nitric acid, and preferably sulfuric acid; H + The content is 1-4 mol / mL, preferably 2-3 mol / mL.

[0012] Optionally, step S1 includes: adding the Zn source and the nano-silicon to the first dispersion and stirring to obtain the first material; the stirring is magnetic stirring, the speed is 600-800rpm, and the time is 20-80min; the centrifugal conditions include: the speed is 8000-10000rpm, and the time is 8-20min; the conditions of the first drying treatment include: the temperature is 60-90℃, the time is 10-20h, and the pressure is -0.2~-0.1MPa; in step S2, the high temperature treatment is pre-treatment and post-treatment in an oxygen-free gas atmosphere, wherein the pre-treatment conditions include: gradient heating to 200-300℃ for 30-90min, the heating rate is 2-8℃ / min, and the oxygen-free gas is H 2 and Ar mixed gas, the flow rate of the oxygen-free gas is 250-350sccm; the post-treatment conditions include: gradient heating to 700-1000℃ for 120-240min, the heating rate is 2-8℃ / min, the oxygen-free gas is H 2and Ar mixed gas, the flow rate of the oxygen-free gas is 80-120sccm; in step S3, the pickling is magnetic stirring cleaning, the rotation speed of the magnetic stirring cleaning is 8000-10000rpm, and the time is 30-60min.

[0013] Optionally, the preparation method of the ZIF-67 powder comprises:

[0014] S11, adding a Co source to a second dispersed solution containing polyvinyl pyrrolidone and a second organic solvent, and mixing to obtain a second material; adding the second material to a third dispersed solution containing dimethyl imidazole and a third organic solvent, and stirring to obtain a precursor solution;

[0015] S12, sealing the precursor solution and allowing it to stand to obtain a standing solution; centrifuging the standing solution to obtain a second precipitate, washing the second precipitate and performing a second drying process.

[0016] Optionally, in the second dispersed solution, the content of polyvinyl pyrrolidone is 1-3 mg / mL, preferably 1.5-2 mg / mL, and more preferably 2 mg / mL; relative to each mL of the second dispersed solution, the amount of Co source added is 0.1-2 mol, preferably 0.25-0.75 mol, and more preferably 0.5 mol; in the third dispersed solution, the content of dimethylimidazole is 2-10 mg / mL, preferably 3.122-6.690 mg / mL, and more preferably 4.460 mg / mL; Co 2+ The molar ratio of the mixture with dimethylimidazole is 1:5-7, preferably 1:5.5-6.5, and more preferably 1:6.

[0017] Optionally, the Co source is selected from Co(NO 3 ) 2 6H 2 O、CoCl 2 and CoSO 4 One of the following, preferably Co(NO 3 ) 2 6H 2 O; the second organic solvent is selected from alcohols having 1-4 carbon atoms, preferably ethanol and / or methanol, and more preferably methanol; the third organic solvent is selected from alcohols having 1-4 carbon atoms, preferably ethanol and / or methanol, and more preferably methanol.

[0018] Optionally, in step S11, the stirring treatment is magnetic stirring, the rotation speed is 600-800rpm, and the time is 20-80min; in step S12, the standing time is 30-60min; the centrifugal conditions include: the rotation speed is 8000-10000rpm, and the time is 8-20min; the second drying treatment conditions include: the temperature is 60-90℃, the time is 10-20h, and the pressure is -0.2~-0.1MPa.

[0019] The second aspect of the present disclosure provides a silicon-carbon porous negative electrode material, comprising Zn-containing silicon-carbon composite material grains and a carbon nanotube surface layer coated on the surface of the grains, the grains having a core-shell structure, the core of the grains being nano-silicon, and the shell of the grains comprising ZIF-67 material.

[0020] Optionally, the particle size of the silicon-carbon porous negative electrode material is 0.8-2 μm, the particle size of the crystal grains is 0.8-2 μm, and the thickness of the carbon nanotube surface layer is 100-300 nm.

[0021] Optionally, the pore size of the silicon-carbon porous negative electrode material is 10-200 nm, preferably 10-50 nm; the specific surface area of ​​the silicon-carbon porous negative electrode material is 400-1000 m 2 / g, preferably 800-1000m 2 / g.

[0022] A third aspect of the present disclosure provides a lithium-ion battery, comprising a positive electrode and a negative electrode, wherein the negative electrode comprises a negative electrode plate and a negative electrode material coated on the negative electrode plate, wherein the negative electrode material is the silicon-carbon porous negative electrode material of the present disclosure.

[0023] Through the above technical scheme, the present disclosure synthesizes Zn-MOF (ZIF-67) @ Si by a hydrothermal method, dries and fully grinds with melamine, and forms a porous silicon-carbon composite material (CNT-Si / C-HCM) doped with Zn and coated with carbon nanotubes after high-temperature treatment and annealing. The present disclosure uses melamine as a silicon-carbon negative electrode material for the first time, providing a carbon source and a nitrogen source for CNT growth. The silicon-carbon porous negative electrode material is synthesized by controlling the ratio of elements in the precursor and the time and temperature of the hydrothermal. The annealing process of the present disclosure ensures that the grain structure is intact and does not collapse, and obtains CNT-Si / C-HCM; a large number of CNTs are autocatalytically grown on the surface, so that the material has good electronic conductivity; the porous silicon-carbon composite material provides space for the expansion of silicon, thereby improving the energy density and cycle performance of the power battery.

[0024] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0026] Figure 1 is a schematic flow chart of the preparation method disclosed herein;

[0027] Figure 2 This is an electron microscope image of the CNT-Si / C-HCM silicon-carbon porous composite material prepared in Example 1 of the present disclosure, wherein a is a low-magnification scanning electron microscope image, and b and c are high-magnification scanning electron microscope images. DETAILED DESCRIPTION

[0028] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0029] The MOF in the present disclosure refers to a metal-organic framework material (Metal-Organic Frameworks), specifically a crystalline porous material with a periodic network structure formed by self-assembly of transition metal ions and organic ligands.

[0030] The CNT in the present disclosure is Carbon nanotubes. The HCM in the present disclosure is Hollow-porous Carbon Materials.

[0031] A first aspect of the present disclosure provides a method for preparing a silicon-carbon porous negative electrode material, comprising:

[0032] S1, mixing a first dispersion containing ZIF-67 powder and a first organic solvent, a Zn source and nano-silicon to obtain a first material; centrifuging the first material to obtain a first precipitate, washing the first precipitate with a first washing liquid and performing a first drying treatment to obtain a Zn-containing silicon-carbon material precursor;

[0033] S2, mixing the Zn-containing silicon-carbon material precursor with melamine powder and grinding them to obtain a mixture, and subjecting the mixture to high-temperature treatment and cooling to obtain an annealed product;

[0034] S3, adding the annealed product into an acid solution for pickling.

[0035] The present invention synthesizes a silicon-carbon porous negative electrode material by a hydrothermal method, dries it and fully grinds it with melamine, and forms a porous silicon-carbon composite material (CNT-Si / C-HCM) doped with Zn and coated with carbon nanotubes after high-temperature treatment and annealing. The present invention uses melamine as a silicon-carbon negative electrode material for the first time, providing a carbon source and a nitrogen source for CNT growth. The annealing process of the present invention ensures that the grain structure is complete and does not collapse, thereby obtaining CNT-Si / C-HCM; in the present application, metal ions are reduced by a reducing gas to a metal element with catalytic activity, and the carbon source generates carbon nanotubes under the catalysis of the metal element with catalytic activity, so that the material has good electronic conductivity; the porous silicon-carbon composite material of the present invention is a porous hollow carbon skeleton material, and the internal space can effectively alleviate the expansion during the cycle, providing space for the expansion of silicon, thereby improving the energy density and cycle performance of the power battery.

[0036] According to the present disclosure, in step S1, in the first dispersed solution, the content of the ZIF-67 powder can be 2-10 mg / mL, preferably 3.122-6.690 mg / mL, and more preferably 4.460 mg / mL; in the first material, the mass ratio of the Zn source, nano-silicon and the ZIF-67 powder can be 1:2-10:5-15, preferably 1:5-6:8-10, and more preferably 1:5:10.

[0037] According to the present disclosure, in step S2, the mass ratio of the Zn-containing silicon-carbon material precursor to the melamine powder may be 1:5-7, preferably 1:5.

[0038] According to the present disclosure, the Zn source may be a Zn salt, preferably Zn(NO 3 ) 2 6H 2 O、ZnCl 2 and ZnSO 3 One of the above, preferably Zn(NO 3 ) 2 6H 2 O; the first organic solvent can be selected from alcohols with 1 to 4 carbon atoms, preferably ethanol and / or methanol, and more preferably ethanol; the first washing liquid can be selected from at least one of ethanol, deionized water and methanol, and preferably a mixed solution of ethanol and deionized water; the acid solution can be selected from at least one of sulfuric acid, hydrochloric acid and nitric acid, and preferably sulfuric acid; H in the acid solution + The content of can be 1-4 mol / mL, preferably 2-3 mol / mL.

[0039] According to the present disclosure, step S1 may include: adding the Zn source and the nano-silicon to the first dispersion and stirring to obtain the first material; the stirring may be magnetic stirring, the speed may be 600-80rpm, and the time may be 20-80min; the centrifugal conditions may include: the speed is 8000-10000rpm, and the time is 8-20min; the conditions for the first drying treatment may include: the temperature is 60-90°C, the time is 10-20h, and the pressure is -0.2 to -0.1MPa; in step S2, the high temperature treatment may be pre-treatment and post-treatment in an atmosphere of oxygen-free gas, wherein the conditions for the pre-treatment may include: gradient heating to 200-300°C for 30-90min, the heating rate is 2-8°C / min, and the oxygen-free gas is H 2 and Ar mixed gas, the flow rate of the oxygen-free gas is 250-350sccm; the post-treatment conditions may include: gradient heating to 700-1000°C for 120-240min, the heating rate is 2-8°C / min, the oxygen-free gas is H 2 and Ar mixed gas, the flow rate of the oxygen-free gas is 80-120sccm; in step S3, the acid cleaning can be magnetic stirring cleaning, the rotation speed of the magnetic stirring cleaning can be 8000-10000rpm, and the time is 30-60min.

[0040] The ZIF-67 material in the present disclosure is a Zn-MOF material. In a specific embodiment of the present disclosure, the preparation method of the ZIF-67 powder includes:

[0041] S11, adding a Co source to a second dispersed solution containing polyvinyl pyrrolidone and a second organic solvent, and mixing to obtain a second material; adding the second material to a third dispersed solution containing dimethyl imidazole and a third organic solvent, and stirring to obtain a precursor solution;

[0042] S12, sealing the precursor solution and allowing it to stand to obtain a standing solution; centrifuging the standing solution to obtain a second precipitate, washing the second precipitate and performing a second vacuum drying process.

[0043] According to the present disclosure, in the second dispersed solution, the content of polyvinyl pyrrolidone can be 1-3 mg / mL, preferably 1.5-2 mg / mL, and more preferably 2 mg / mL; relative to each mL of the second dispersed solution, the amount of Co source added can be 0.1-2 mol, preferably 0.25-0.75 mol, and more preferably 0.5 mol; in the third dispersed solution, the content of dimethylimidazole can be 2-10 mg / mL, preferably 3.122-6.690 mg / mL, and more preferably 4.460 mg / mL; Co2+ The molar ratio of the mixture with dimethylimidazole can be 1:5-7, preferably 1:5.5-6.5, and more preferably 1:6.

[0044] According to the present disclosure, the Co source can be selected from Co(NO 3 ) 2 6H 2 O、CoCl 2 and CoSO 4 One of the following, preferably Co(NO 3 ) 2 6H 2 O; the second organic solvent can be selected from alcohols having 1-4 carbon atoms, preferably ethanol and / or methanol, and more preferably methanol; the third organic solvent can be selected from alcohols having 1-4 carbon atoms, preferably ethanol and / or methanol, and more preferably methanol.

[0045] According to the present disclosure, in step S11, the stirring treatment can be magnetic stirring, the rotation speed can be 600-800rpm, and the time can be 20-80min; in step S12, the standing time can be 30-60min; the centrifugal conditions may include: the rotation speed is 8000-10000rpm, and the time is 8-20min; the conditions of the second vacuum drying treatment may include: the temperature is 60-90℃, the time is 10-20h, and the pressure is -0.2~-0.1MPa.

[0046] The second aspect of the present disclosure provides a silicon-carbon porous negative electrode material, comprising Zn-containing silicon-carbon composite material grains and a carbon nanotube surface layer coated on the surface of the grains, the grains having a core-shell structure, the core of the grains being nano-silicon, and the shell of the grains comprising ZIF-67 material.

[0047] According to the present disclosure, the particle size of the silicon-carbon porous negative electrode material may be 0.8-2 μm, the particle size of the crystal grains may be 0.8-2 μm, and the thickness of the carbon nanotube surface layer may be 100-300 nm.

[0048] According to the present disclosure, the pore size of the silicon-carbon porous negative electrode material can be 10-200nm, preferably 10-50nm; the specific surface area of ​​the silicon-carbon porous negative electrode material can be 400-1000m 2 / g, preferably 800-1000m 2 / g.

[0049] The third aspect of the present disclosure provides a lithium-ion battery, including a positive electrode and a negative electrode, wherein the negative electrode includes a negative electrode plate and a negative electrode material coated on the negative electrode plate, wherein the negative electrode material is a silicon-carbon porous negative electrode material disclosed in the present disclosure. The silicon-carbon porous composite material of CNT-Si / C-HCM disclosed in the present disclosure can be used as a negative electrode material for solid, semi-solid and liquid lithium-ion batteries. The silicon-carbon porous composite material of the present application has a porous hollow carbon skeleton, which effectively alleviates the problem of silicon volume expansion during the cycle, can effectively improve the energy density of lithium-ion batteries, and improve the cycle performance of lithium-ion batteries.

[0050] The present disclosure is further described in detail by way of examples. The raw materials used in the examples can all be obtained through commercial sources.

[0051] Example 1

[0052] The CNT-Si / C-HCM silicon-carbon porous composite material in this embodiment is prepared by the following method:

[0053] (1) Prepare the precursor solution: disperse 240-840 mg PVP in 10-30 mL methanol solution, sonicate for 1 h, then add 2.336 g Co(NO 3 ) 2 6H 2 O, magnetically stirred at room temperature for 1 hour to obtain solution A; 3.936 g of dimethylimidazole was dispersed in 30 mL of methanol solution, and magnetically stirred at room temperature for 1 hour to obtain solution B. Then solution A was quickly poured into solution B, and magnetically stirred at room temperature for 20 minutes to prepare the precursor solution;

[0054] (2) Preparation of MOF (ZIF-67): The precursor solution prepared above was sealed with a sealing film and allowed to react at room temperature for 24 hours, then centrifuged at 10,000 r / min for 10 minutes, and then washed with ethanol and deionized water to obtain the ZIF-67 product, and dried under vacuum at 75°C for 12 hours;

[0055] (3) Preparation of Zn-MOF (ZIF-67) @ Si: 200 mg of ZIF-67 powder was dispersed in ethanol, stirred for 30 min, and 582 mg of Zn (NO 3 ) 2 6H 2 O and 300 mg of nano-silicon were added, and the mixture was stirred for 40 min, and then centrifuged at 10000 r / min for 10 min, and then washed with ethanol and deionized water to obtain the Zn-MOF (ZIF-67) @ Si product, which was then dried at 75 °C in vacuum for 12 h.

[0056] (4) Annealing: 200 mg of Zn-MOF (ZIF-67)@Si and 1 g of melamine powder were mechanically mixed and fully ground. The final products were placed in a tube furnace and heated under H 2 / Ar atmosphere, the flow rate was 300 sccm in the early stage (room temperature to 250°C) and 80 sccm in the later stage (250-800°C), the temperature was increased to 250°C at 2°C / min and kept at that temperature for 1 hour, kept at 800°C for 2 hours, and then cooled to room temperature;

[0057] (5) Pickling: Add the above annealed products into 1 mol / L H 2 SO 4 The mixture was stirred at medium magnetic force for 1 hour, then centrifuged at 10000 r / min for 10 minutes, washed by centrifugation with deionized water for 3 times, and vacuum dried at 75°C for 12 hours to obtain Ni / Co-CNT / NHPC electrode material.

[0058] The material prepared in this example was scanned by electron microscope, and the scanning results are shown in Figure 2 ,pass Figure 2 It can be seen that the material particles prepared in this embodiment are uniform and regular in shape.

[0059] The preferred embodiments of the present disclosure are described in detail above; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0060] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0061] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for preparing a silicon-carbon porous negative electrode material, It is characterized in that include: S1, mixing a first dispersion liquid containing ZIF-67 powder and a first organic solvent, a Zn source and nano-silicon to obtain a first material; Centrifuging the first material to obtain a first precipitate, washing the first precipitate with a first washing liquid and then performing a first drying treatment to obtain a Zn-containing silicon-carbon material precursor; S2, mixing the Zn-containing silicon-carbon material precursor with melamine powder and grinding them to obtain a mixture, and subjecting the mixture to high-temperature treatment and cooling to obtain an annealed product; The high temperature treatment is a pre-treatment and a post-treatment in an oxygen-free gas atmosphere, wherein the conditions of the pre-treatment include: a gradient temperature rise to 200-300°C for 30-90 min, a heating rate of 2-8°C / min, and the oxygen-free gas is H 2 and Ar mixed gas, the flow rate of the oxygen-free gas is 250-350sccm; the post-treatment conditions include: gradient heating to 700-1000℃ for 120-240min, the heating rate is 2-8℃ / min, the oxygen-free gas is H 2 A mixed gas of argon and Ar, wherein the flow rate of the oxygen-free gas is 80-120 sccm; S3, adding the annealed product into an acid solution for pickling.

2. The preparation method according to claim 1, in, In step S1, in the first dispersion, the content of the ZIF-67 powder is 2-10 mg / mL; In the first material, the mass ratio of the Zn source, nano-silicon and the ZIF-67 powder is 1:2-10:5-15.

3. The preparation method according to claim 2, in, In step S1, in the first dispersion, the content of the ZIF-67 powder is 3.122-6.690 mg / mL; In the first material, the mass ratio of the Zn source, nano-silicon and the ZIF-67 powder is 1:5-6:8-10.

4. The preparation method according to claim 3, in, In step S1, in the first dispersion, the content of the ZIF-67 powder is 4.460 mg / mL; In the first material, the mass ratio of the Zn source, nano-silicon and the ZIF-67 powder is 1:5:

10.

5. The preparation method according to claim 1, in, In step S2, the mass ratio of the Zn-containing silicon-carbon material precursor to the melamine powder is 1:5-7.

6. The preparation method according to claim 5, in, In step S2, the mass ratio of the Zn-containing silicon-carbon material precursor to the melamine powder is 1:

5.

7. The preparation method according to claim 1, in, The Zn source is a Zn salt; The first organic solvent is selected from alcohols having 1 to 4 carbon atoms; The first washing liquid is selected from at least one of ethanol, deionized water and methanol; The acid solution is selected from at least one of sulfuric acid, hydrochloric acid and nitric acid; H + The content is 1-4 mol / mL.

8. The preparation method according to claim 7, in, The Zn source is Zn(NO 3 ) 2 6H 2 O、ZnCl 2 and ZnSO 3 One of; The first organic solvent is ethanol and / or methanol; The first washing liquid is a mixed solution of ethanol and deionized water; The acid solution is sulfuric acid; The acid solution contains H + The content is 2-3 mol / mL.

9. The preparation method according to claim 8, in, The Zn source is Zn(NO 3 ) 2 6H 2 O; The first organic solvent is ethanol.

10. The preparation method according to claim 1, in, Step S1 comprises: adding the Zn source and the nano-silicon to the first dispersion and stirring to obtain the first material; the stirring is magnetic stirring, the speed is 600-800rpm, and the time is 20-80min; the centrifugal conditions include: the speed is 8000-10000rpm, and the time is 8-20min; the first drying conditions include: the temperature is 60-90°C, the time is 10-20h, and the pressure is -0.2~-0.1MPa; In step S3, the pickling is magnetic stirring cleaning, the rotation speed of the magnetic stirring cleaning is 8000-10000 rpm, and the time is 30-60 min.

11. The preparation method according to claim 1, in, The preparation method of the ZIF-67 powder comprises: S11, adding a Co source to a second dispersed solution containing polyvinyl pyrrolidone and a second organic solvent, and mixing to obtain a second material; adding the second material to a third dispersed solution containing dimethyl imidazole and a third organic solvent, and stirring to obtain a precursor solution; S12, sealing the precursor solution and allowing it to stand to obtain a standing solution; centrifuging the standing solution to obtain a second precipitate, washing the second precipitate and performing a second drying process.

12. The preparation method according to claim 11, in, In the second dispersed solution, the content of polyvinyl pyrrolidone is 1-3 mg / mL; relative to 1L of the second dispersed solution, the amount of the Co source added is 0.1-2 mol; In the third dispersed solution, the content of dimethylimidazole is 2-10 mg / mL; Co 2+ The molar ratio of mixing with dimethylimidazole is 1:5~7.

13. The preparation method according to claim 12, in, In the second dispersed solution, the content of polyvinyl pyrrolidone is 1.5-2 mg / mL; relative to 1L of the second dispersed solution, the amount of the Co source added is 0.25-0.75 mol; In the third dispersed solution, the content of dimethylimidazole is 3.122-6.690 mg / mL; Co 2+ The molar ratio of mixing with dimethylimidazole is 1:5.5-6.

5.

14. The preparation method according to claim 13, in, In the second dispersed solution, the content of polyvinyl pyrrolidone is 2 mg / mL; relative to 1L of the second dispersed solution, the amount of the Co source added is 0.5 mol; In the third dispersed solution, the content of dimethylimidazole is 4.460 mg / mL; Co 2+ The molar ratio of mixing with dimethylimidazole is 1:

6.

15. The preparation method according to claim 11, in, The Co source is selected from Co(NO 3 ) 2 6H 2 O、CoCl 2 and CoSO 4 One of; The second organic solvent is selected from alcohols having 1 to 4 carbon atoms; The third organic solvent is selected from alcohols having 1 to 4 carbon atoms.

16. The preparation method according to claim 15, in, The Co source is Co(NO 3 ) 2 ·6H 2 O; The second organic solvent is ethanol and / or methanol; The third organic solvent is ethanol and / or methanol.

17. The preparation method according to claim 15, in, The second organic solvent is methanol; The third organic solvent is methanol.

18. The preparation method according to claim 11, in, In step S11, the stirring treatment is magnetic stirring, the rotation speed is 600-800 rpm, and the time is 20-80 min; In step S12, the standing time is 30-60 min; the centrifugal conditions include: a rotation speed of 8000-10000 rpm and a time of 8-20 min; the second drying conditions include: a temperature of 60-90°C, a time of 10-20 h, and a pressure of -0.2~-0.1 MPa.

19. A silicon-carbon porous negative electrode material prepared according to the method according to any one of claims 1 to 18, It is characterized in that It comprises Zn-containing silicon-carbon composite material crystal grains and a carbon nanotube surface layer coated on the surface of the crystal grains. The crystal grains have a core-shell structure, the core of the crystal grains is nano-silicon, and the shell of the crystal grains contains ZIF-67 material.

20. The material according to claim 19, in, The particle size of the silicon-carbon porous negative electrode material is 0.8-2 μm, the particle size of the crystal grains is 0.8-2 μm, and the thickness of the carbon nanotube surface layer is 100-300 nm.

21. The material according to claim 19, in, The pore size of the silicon-carbon porous negative electrode material is 10-200 nm; The specific surface area of ​​the silicon-carbon porous negative electrode material is 400-1000m 2 / g.

22. The material according to claim 21, in, The pore size of the silicon-carbon porous negative electrode material is 10-50 nm; The specific surface area of ​​the silicon-carbon porous negative electrode material is 800-1000m 2 / g.

23. A lithium ion battery, It is characterized in that It comprises a positive electrode and a negative electrode, wherein the negative electrode comprises a negative electrode plate and a negative electrode material coated on the negative electrode plate, wherein the negative electrode material is the silicon-carbon porous negative electrode material according to any one of claims 19 to 22.

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