Special negative electrode material for circular battery and preparation method thereof

Abstract

The invention relates to the field of battery materials, in particular to a special negative electrode material for a circular battery and a preparation method thereof. The special negative electrode material for the circular battery comprises the following raw materials in parts by mass: 10-25 parts of a silicon-based compound, 40-60 parts of spherical graphite, 10-20 parts of a modifier, 5-10 parts of modified particles, 0.5-1.2 parts of a corrosion inhibitor, 2-5 parts of a binder, 1-3 parts of a gelatinizing agent, 1-2 parts of a conductive additive and 20-30 parts of a solvent. The circular battery prepared from the special negative electrode material for the circular battery prepared by the invention not only has excellent battery capacity and discharge time, but also has good stability, battery cyclicity, safety, storage stability and the like, and can meet the battery requirements of existing high-power small electronic products; and the method has very excellent market and application prospects.

Description

Technical Field

[0001] The present application relates to the field of battery materials, and in particular to a negative electrode material specifically for circular batteries and a preparation method thereof. Background Art

[0002] With the popularity of portable electronic devices, electric vehicles and energy storage systems, the demand for high-performance lithium batteries is growing. In the construction of lithium batteries, the negative electrode material plays a vital role because it is directly related to the performance indicators of the battery, such as energy density, cycle life, safety and cost. For application scenarios specifically designed for miniaturization and high energy density requirements (such as smart watches, medical implants and other wearable technology products), round batteries are widely used due to their compact structure and easy integration.

[0003] Traditional lithium-ion battery negative electrodes mainly use graphite materials, which have a theoretical specific capacity of 372mAh / g. However, as the market pursues higher energy density, researchers have begun to explore alternative materials with higher theoretical specific capacity, such as silicon (Si)-based materials. Silicon as a negative electrode material has a theoretical specific capacity of nearly 4200mAh / g, which is much higher than traditional graphite, and it is abundant in reserves on the earth and environmentally friendly.

[0004] In addition, in order to adapt to the circular battery design in specific application scenarios, the negative electrode material also needs to meet special physical form requirements, such as good flexibility to facilitate the winding process, and uniform coating thickness to ensure the consistency of the electrochemical reaction. However, most of the research on new negative electrode materials on the market is currently focused on planar batteries, and there are relatively few negative electrode materials optimized for circular batteries, especially in solving the above-mentioned volume effect and first coulomb efficiency. There is a lack of effective solutions. Therefore, the development of negative electrode materials customized for circular batteries has become the key to improving the overall performance of such batteries.

[0005] Therefore, in order to effectively solve the above problems, the present application provides a circular battery-specific negative electrode material and a preparation method thereof. The circular battery prepared using the circular battery-specific negative electrode material prepared in the present application not only has excellent battery capacity and discharge time, but also has good stability, battery cyclability, safety and storage stability and other properties, which can meet the battery needs of existing high-power small electronic products and has very excellent market and application prospects. Summary of the invention

[0006] In order to solve the above problems, the first aspect of the present application provides a negative electrode material for circular batteries. The raw materials are, by mass: 10 to 25 parts of silicon-based composites, 40 to 60 parts of spherical graphite, 10 to 20 parts of modifiers, 5 to 10 parts of modified particles, 0.5 to 1.2 parts of corrosion inhibitors, 2 to 5 parts of binders, 1 to 3 parts of gelatinizers, 1 to 2 parts of conductive additives, and 20 to 30 parts of solvents.

[0007] As a preferred solution, the silicon-based composite is a composition of nano-silicon dioxide and porous silicon.

[0008] As a preferred solution, the mass ratio of the nano-silicon dioxide to the porous silicon is (1-1.5):(4-5).

[0009] As a preferred solution, the average particle size of the nano-silicon dioxide is 25 to 35 nm.

[0010] As a preferred solution, the average pore diameter of the porous silicon is 20-24 nm.

[0011] As a preferred solution, the mass ratio of the silicon-based composite, spherical graphite and modifier is (15-20): (45-55): (11-16).

[0012] As a preferred solution, the mass ratio of the silicon-based composite, spherical graphite and modifier is (15-18): (48-53): (12-14).

[0013] As a preferred solution, the mass ratio of the spherical graphite to the modified particles is (45-55):(6-9).

[0014] As a preferred solution, the mass ratio of the spherical graphite to the modified particles is (48-53):(7-8).

[0015] As a preferred solution, the average particle size of the spherical graphite is 2 to 3.5 μm.

[0016] As a preferred solution, the average particle size of the spherical graphite is 2.2-2.6 μm.

[0017] As a preferred scheme, the preparation method of the modifier comprises the following steps: S1: adding petroleum asphalt into a container, heating it to 110-130°C, stirring it evenly, then adding n-hexane to extract and remove impurities, then centrifuging to remove high-viscosity residue precipitation, performing secondary n-hexane extraction and impurity removal, and obtaining an impurity-removed product; S2: mixing the impurity-removed product with polyvinyl acetate and phenolic epoxy resin and stirring them evenly, then heating it to 140-160°C, keeping the temperature for reaction for 10-12h, and adding the product into deionized water after completion; S3: adding triethanolamine to adjust the pH of the system to 7-7.5 until it no longer changes, and then vacuum drying the product at 90-110°C for 4-5h, and obtaining the product after completion.

[0018] As a preferred solution, in the n-hexane extraction and impurity removal, the mass ratio of petroleum asphalt to n-hexane is (3-4): (1.5-1.8).

[0019] As a preferred solution, the mass ratio of the impurity-removed product, polyvinyl acetate and phenolic epoxy resin is (4-5): (0.8-1.2): (0.4-0.6).

[0020] As a preferred solution, the softening point of the modifier is 125-135°C.

[0021] The modifier prepared and added in this application can effectively improve the electrical properties of the negative electrode material and ensure its circulation and stability. The added modifier can be used as a mixed flexible carrier of spherical graphite and silicon-based composites in the preparation and mixing of the negative electrode material. The carrier can greatly improve the adhesion of the spherical graphite system and the silicon-based composite under the premise of coating and mixing, so that after the modified particles and the conductive additive are added, it becomes a carrier of strong intermolecular forces, thereby reducing the molecular chain migration phenomenon inside the negative electrode material, reducing the probability of cracks and silver streaks, and thus ensuring that the negative electrode material has excellent electrical properties, stability and cycle performance.

[0022] As a preferred solution, the modified particles are modified carbon nanotubes.

[0023] As a preferred scheme, the preparation method of the modified carbon nanotubes includes the following steps: S1: mixing and stirring multi-walled carbon nanotubes and titanium dioxide and adding them to a DMF solution, adding glutaric anhydride, heating to 60-65°C and keeping warm for 2-3 hours to obtain pretreated particles; S2: adding the pretreated particles to deionized water, adding ammonia water to adjust the pH to 8.5-9.5, then adding triethanolamine and ethyl orthosilicate, heating to 65-70°C and keeping warm for 2-2.5 hours, filtering the product, washing and drying to obtain a pre-product; S3: mixing the pre-product, zinc nitrate and 2-methylimidazole and adding them to deionized water, heating to 60-70°C, keeping warm for 4-6 hours, and filtering, washing and drying the product after completion.

[0024] As a preferred solution, the mass ratio of the multi-walled carbon nanotubes, titanium dioxide and glutaric anhydride is (3-3.2): (0.3-0.5): (0.8-1).

[0025] As a preferred solution, the mass ratio of the pretreated particles, triethanolamine and tetraethyl orthosilicate is (2-2.5): (0.05-0.1): (0.4-0.5).

[0026] As a preferred solution, the mass ratio of the pre-product, zinc nitrate and 2-methylimidazole is (2-2.5): (0.8-1): (0.3-0.5).

[0027] As a preferred solution, the average particle size of the titanium dioxide is 5 to 10 nm.

[0028] As a preferred solution, the corrosion inhibitor is a composition of bisphenol A diglycidyl ether phosphate and epoxy block polyether.

[0029] As a preferred solution, the mass ratio of bisphenol A diglycidyl ether phosphate and epoxy block polyether is (2.5-3): (1.2-1.4).

[0030] As a preferred solution, the weight average molecular weight of the epoxy block polyether is 8000 to 10000 Da.

[0031] As a preferred solution, the binder is a polyvinylidene fluoride binder.

[0032] As a preferred solution, the gelatinizer is at least one of sodium carboxymethyl cellulose, polyvinyl alcohol, alginate and guar gum.

[0033] As a preferred solution, the gelatinizer is sodium carboxymethyl cellulose.

[0034] As a preferred solution, the conductive additive is at least one of acetylene black, carbon black, carbon fiber, silver powder, copper powder and graphene.

[0035] As a preferred solution, the conductive additive is acetylene black.

[0036] As a preferred solution, the solvent is a combination of NMP and DMF.

[0037] As a preferred solution, the mass ratio of NMP to DMF is (5-6): (1-1.1).

[0038] The second aspect of the present application provides a method for preparing the above-mentioned circular battery-specific negative electrode material, which specifically comprises the following steps: S1: adding the silicon-based composite, spherical graphite, modifier and modified particles to a high-speed mixer, stirring at a speed of 350-500 rpm for 3-4 hours to ensure complete mixing; S2: adding the solvent, binder, gelatinizer, corrosion inhibitor and conductive additive in sequence, and continuing to stir at a speed of 350-500 rpm for 16-20 hours until a uniform slurry without a grainy feeling is obtained;

[0039] S3: The slurry is coated on the copper foil current collector using a doctor blade coater to control the coating thickness to 80-120 μm, and then vacuum dried at 80-90° C. for 6-10 hours to obtain a pre-product; S4: The pre-product is calendered by a calender to control the density to 1.5-3 g / cm 3 , you will get it.

[0040] The beneficial effects of this application are:

[0041] 1. The circular battery-specific negative electrode material provided in the present application not only has excellent battery capacity and discharge time, but also has good stability, battery cyclability, safety and storage stability, etc., which can meet the battery requirements of existing high-power small electronic products and has excellent market and application prospects.

[0042] 2. A negative electrode material for circular batteries provided in the present application, the added modifier can serve as a mixed flexible carrier of spherical graphite and silicon-based composites in the preparation and mixing of the negative electrode material. The carrier can greatly improve the adhesion of the spherical graphite system and the silicon-based composite under the premise of coating and mixing, thereby becoming a carrier of strong intermolecular forces after the addition of modified particles and conductive additives, thereby reducing the molecular chain migration phenomenon inside the negative electrode material, reducing the probability of cracks and silver streaks, and ensuring that the negative electrode material has excellent electrical properties, stability and cycle performance.

[0043] 3. A circular battery-specific negative electrode material provided in the present application, wherein the modified particles added thereto can form a composite particle structure with amorphous silicon as the outer shell, and the structure can form a good ion movement path inside, and greatly improve the transport speed and stability of the path through enrichment, thereby greatly enhancing the diffusion and migration speed of lithium ions, thereby effectively enhancing the overall electrical properties, and the formed composite structure can achieve site stabilization through the modifier as a good carrier, thereby reducing segregation, migration and other phenomena during long-term use, and has excellent stability and cyclability. DETAILED DESCRIPTION

[0044] The following will further explain and demonstrate the technical solutions in the above invention content of this application in the form of specific implementation schemes. The following embodiments are only practical examples used to illustrate and explain the contents of the technical solutions in the specification, and should not limit the scope of the claims to be protected by this application. All technical products based on the technical solutions described in the invention content of this application should be included in the scope to be protected by this application.

[0045] In the following examples, unless otherwise specified, the raw materials are all commercially available products, or can be prepared by methods well known to those skilled in the art.

[0046] Example 1

[0047] Example 1 The first aspect provides a negative electrode material for circular batteries. The raw materials are, by mass: 16.2 parts of silicon-based composite, 51.4 parts of spherical graphite, 12.8 parts of modifier, 7.4 parts of modified particles, 0.8 parts of corrosion inhibitor, 3.5 parts of binder, 2.1 parts of gelatinizer, 1.2 parts of conductive additive, and 24.5 parts of solvent.

[0048] The silicon-based composite is a composition of nano-silicon dioxide and porous silicon, and the mass ratio of the two is 1.2:4.5.

[0049] The average particle size of nano-silicon dioxide is 33nm. The average pore size of porous silicon is 21nm.

[0050] The average particle size of spherical graphite is 2.5 μm. It was purchased from Shijiazhuang Huabang Mineral Products Co., Ltd., China.

[0051] The preparation method of the modifier comprises the following steps: S1: adding 3.6 parts of petroleum asphalt into a container, heating to 115°C, stirring evenly, then adding 1.6 parts of n-hexane to extract and remove impurities, then centrifuging to remove high-viscosity residue precipitate, performing secondary n-hexane extraction and impurity removal (the mass ratio is consistent with the primary n-hexane extraction and impurity removal), and obtaining an impurity-removed product; S2: mixing 4.6 parts of the impurity-removed product with 0.95 parts of polyvinyl acetate and 0.48 parts of phenolic epoxy resin and stirring evenly, then heating to 150°C, keeping the temperature for reaction for 12 hours, and adding the product to 250 parts of deionized water after completion; S3: adding triethanolamine to adjust the pH of the system to 7.5 until it no longer changes, and then vacuum drying the product at 95°C for 4.5 hours, and obtaining the product after completion.

[0052] Petroleum asphalt was purchased from Hebei Hankai Energy Technology Development Co., Ltd. with a softening point of 110°C.

[0053] Polyvinyl acetate was purchased from Shengwanjia New Materials (Shandong) Co., Ltd. as SWJ-99 product.

[0054] The phenolic epoxy resin was purchased from Wuxi Jiunai Anticorrosion Materials Co., Ltd. as a product of model F44.

[0055] The softening point of the modifier is 128°C.

[0056] The modified particles are modified carbon nanotubes; the preparation method of the modified carbon nanotubes comprises the following steps: S1: 3.1 parts of multi-walled carbon nanotubes and 0.4 parts of titanium dioxide are mixed and stirred and added to 120 parts of DMF solution, 0.85 parts of glutaric anhydride are added, the temperature is raised to 65°C and kept warm for 3 hours to obtain pretreated particles; S2: 4.3 parts of pretreated particles are added to 100 parts of deionized water, ammonia water is added to adjust the pH to 9, and then 0.06 parts of triethanolamine and 0.42 parts of ethyl orthosilicate are added, the temperature is raised to 70°C and kept warm for 2 hours, and the product is filtered, washed and dried to obtain a pre-product; S3: 2.2 parts of the pre-product, 0.85 parts of zinc nitrate and 0.32 parts of 2-methylimidazole are mixed and added to 120 parts of deionized water, the temperature is raised to 70°C, and the temperature is kept warm for 5 hours. After completion, the product is filtered, washed and dried to obtain.

[0057] Multi-walled carbon nanotubes were purchased from Shanghai Gaibang Industrial Co., Ltd., China.

[0058] The average particle size of titanium dioxide is 5 nm.

[0059] The corrosion inhibitor is a composition of bisphenol A diglycidyl ether phosphate and epoxy block polyether, and the mass ratio of the two is 2.7:1.3.

[0060] The epoxy block polyether was purchased from BASF of Germany, and the epoxy block polyether polymer model L87 product had a weight average molecular weight of 8200 Da.

[0061] The adhesive is polyvinylidene fluoride adhesive, purchased from Shanghai San Ai Fu New Material Technology Co., Ltd., China, and sold as model FR905.

[0062] The gelatinizer is sodium carboxymethyl cellulose.

[0063] The conductive additive was acetylene black, which was purchased from Tianjin Xinglongtai Chemical Products Technology Co., Ltd., China.

[0064] The solvent is a composition of NMP and DMF, and the mass ratio of the two is 5:1.

[0065] The second aspect of the present embodiment provides a method for preparing the above-mentioned circular battery-specific negative electrode material, which specifically includes the following steps: S1: adding the silicon-based composite, spherical graphite, modifier and modified particles to a high-speed mixer, stirring at 400 rpm for 4 hours to ensure complete mixing; S2: adding the solvent, binder, gelatinizer, corrosion inhibitor and conductive additive in sequence, and continuing to stir at 400 rpm for 18 hours until a uniform and particle-free slurry is obtained; S3: coating the slurry on a copper foil current collector using a blade coater, controlling the coating thickness to 100 μm, and then vacuum drying at 85°C for 9 hours to obtain a pre-product; S4: calendering the pre-product through a calender to control the density to 2 g / cm 3 , you will get it.

[0066] Example 2

[0067] The specific implementation of this embodiment is basically the same as that of Example 1, with the only difference being that: the raw materials for the negative electrode material for round batteries, in parts by mass, are: 19.6 parts of silicon-based composite, 46.8 parts of spherical graphite, 15.5 parts of modifier, 6.1 parts of modified particles, 0.8 parts of corrosion inhibitor, 3.2 parts of binder, 2.2 parts of gelatinizer, 1.3 parts of conductive additive, and 28.5 parts of solvent.

[0068] Example 3

[0069] The specific implementation of this embodiment is basically the same as that of Example 1, with the only difference being that: the raw materials for the negative electrode material for round batteries, in parts by mass, are: 15.5 parts of silicon-based composite, 54.6 parts of spherical graphite, 11.5 parts of modifier, 8.6 parts of modified particles, 0.8 parts of corrosion inhibitor, 3.2 parts of binder, 2.2 parts of gelatinizer, 1.1 parts of conductive additive, and 30.2 parts of solvent.

[0070] Comparative Example 1

[0071] The specific implementation of this comparative example is basically the same as that of Example 1, except that: the raw materials for the special negative electrode material for round batteries, in parts by mass, are: 8.2 parts of silicon-based composite, 68.5 parts of spherical graphite, 10.8 parts of modifier, 4.4 parts of modified particles, 0.8 parts of corrosion inhibitor, 3.5 parts of binder, 2.1 parts of gelatinizer, 1.2 parts of conductive additive, and 32.8 parts of solvent.

[0072] Comparative Example 2

[0073] The specific implementation of this comparative example is basically the same as that of Example 1, except that: the raw materials for the special negative electrode material for round batteries, in parts by mass, are: 28.8 parts of silicon-based composite, 39.2 parts of spherical graphite, 15.8 parts of modifier, 3.2 parts of modified particles, 0.8 parts of corrosion inhibitor, 3.3 parts of binder, 2.6 parts of gelatinizer, 1.4 parts of conductive additive, and 30.1 parts of solvent.

[0074] Comparative Example 3

[0075] The specific implementation of this comparative example is basically the same as that of Example 1, except that the corrosion inhibitor is a composition of bisphenol A diglycidyl ether phosphate and epoxy block polyether, and the mass ratio of the two is 3:0.2.

[0076] Comparative Example 4

[0077] The specific implementation of this comparative example is basically the same as that of Example 1, except that: the preparation method of the modifier comprises the following steps: S1: adding 3.6 parts of petroleum asphalt into a container, heating it to 115°C and stirring it evenly, then adding 1.6 parts of n-hexane for extraction and impurity removal, and then centrifuging to remove the high-viscosity residue precipitate for secondary n-hexane extraction and impurity removal (the mass ratio is consistent with the primary n-hexane extraction and impurity removal) to obtain an impurity-removed product; S2: mixing 8.8 parts of the impurity-removed product with 0.55 parts of polyvinyl acetate and 0.12 parts of phenolic epoxy resin and stirring them evenly, then heating it to 150°C, keeping the temperature for reaction for 12 hours, and adding the product to 250 parts of deionized water after completion; S3: adding triethanolamine to adjust the pH of the system to 7.5 until it no longer changes, and then vacuum drying the product at 95°C for 4.5 hours, and obtaining the product after completion.

[0078] Comparative Example 5

[0079] The specific implementation of this comparative example is basically the same as that of Example 1, except that: the preparation method of the modifier comprises the following steps: S1: adding 3.6 parts of petroleum asphalt into a container, heating to 115°C and stirring evenly, then adding 1.6 parts of n-hexane for extraction and impurity removal, and then centrifuging to remove high-viscosity residue precipitation for secondary n-hexane extraction and impurity removal (the mass ratio is consistent with the primary n-hexane extraction and impurity removal) to obtain an impurity-removed product; S2: mixing 3.5 parts of the impurity-removed product with 1.62 parts of polyvinyl acetate and 1.1 parts of phenolic epoxy resin and stirring evenly, then heating to 150°C, keeping the temperature for reaction for 12 hours, and adding the product into 340 parts of deionized water after completion; S3: adding triethanolamine to adjust the pH of the system to 7.5 until it no longer changes, and then vacuum drying the product at 95°C for 4.5 hours, and obtaining the product after completion.

[0080] Comparative Example 6

[0081] The specific implementation of this comparative example is basically the same as that of Example 1, except that: the preparation method of modified carbon nanotubes comprises the following steps: S1: 5.5 parts of multi-walled carbon nanotubes and 0.1 parts of titanium dioxide are mixed and stirred and added to 120 parts of DMF solution, 0.45 parts of glutaric anhydride are added, the temperature is raised to 65°C and kept warm for 3 hours to obtain pretreated particles; S2: 4.3 parts of pretreated particles are added to 100 parts of deionized water, ammonia water is added to adjust the pH to 9, and then 0.06 parts of triethanolamine and 0.42 parts of ethyl orthosilicate are added, the temperature is raised to 70°C and kept warm for 2 hours, and the product is filtered, washed and dried to obtain a pre-product; S3: 2.2 parts of the pre-product, 0.85 parts of zinc nitrate and 0.32 parts of 2-methylimidazole are mixed and added to 120 parts of deionized water, the temperature is raised to 70°C, and the temperature is kept warm for 5 hours. After completion, the product is filtered, washed and dried to obtain.

[0082] Comparative Example 7

[0083] The specific implementation of this comparative example is basically the same as that of Example 1, except that: the preparation method of modified carbon nanotubes comprises the following steps: S1: 3.1 parts of multi-walled carbon nanotubes and 0.4 parts of titanium dioxide are mixed and stirred and added to 120 parts of DMF solution, 0.85 parts of glutaric anhydride are added, the temperature is raised to 65°C and kept warm for 3 hours to obtain pretreated particles; S2: 8.5 parts of pretreated particles are added to 160 parts of deionized water, ammonia water is added to adjust the pH to 9, and then 0.02 parts of triethanolamine and 0.22 parts of tetraethyl orthosilicate are added, the temperature is raised to 70°C and kept warm for 2 hours, and the product is filtered, washed and dried to obtain a pre-product; S3: 3.9 parts of the pre-product, 0.45 parts of zinc nitrate and 0.16 parts of 2-methylimidazole are mixed and added to 120 parts of deionized water, the temperature is raised to 70°C, and the temperature is kept warm for 5 hours. After completion, the product is filtered, washed and dried to obtain.

[0084] Performance Evaluation

[0085] 1. Electrical performance test: The negative electrode material prepared in the embodiment and the comparative example was used as the negative electrode, LiPF6 / EC+EMC+DMC (1:1:1) was used as the electrolyte, the metal lithium sheet was used as the positive electrode, the diaphragm was Celgard2400 diaphragm, the battery was assembled in an argon-filled glove box, and the electrochemical performance was carried out on a Wuhan Blue Electric CT2001A battery tester. The charge and discharge voltage range was 0.005V~3.0V, and the charge and discharge rate was 1C; the first efficiency and the first discharge capacity were tested respectively, and the test values ​​were taken as the average of 10 tests and recorded in Table 1.

[0086] 2. Cycle performance test: Based on performance test 1, the current density was set to 500 mA / g, and the battery test system was used to test the cycle performance of the battery. The battery capacity rate and coulombic efficiency were calculated and recorded after 100 cycles. The test values ​​were taken as the average of 10 tests and recorded in Table 1.

[0087] Table 1 Performance test results

[0088]

[0089]

[0090] It can be seen from the examples and comparative examples of the present application and the data results in Table 1 that examples 1 to 3 of the present application have obvious advantages over comparative examples 1 to 7 in terms of electrical performance, electrical performance stability, cycle performance and durability. This is mainly due to the combined effect of the modifiers, modified particles and other co-factors specified in the present application. Comparative examples 1 to 7 did not adopt the technical solution specified in the present application, resulting in obvious disadvantages in the above performance tests. This further proves the necessity of the technical solution specified in the present application for the technical effect of the present application and solving technical problems.

Claims

1. A negative electrode material for circular batteries, characterized in that: The raw materials are as follows: 10-25 parts of silicon-based composite, 40-60 parts of spherical graphite, 10-20 parts of modifier, 5-10 parts of modified particles, 0.5-1.2 parts of corrosion inhibitor, 2-5 parts of binder, 1-3 parts of gelatinizer, 1-2 parts of conductive additive, and 20-30 parts of solvent. The silicon-based composite is a composition of nano-silicon dioxide and porous silicon; the mass ratio of the nano-silicon dioxide to the porous silicon is (1-1.5): (4-5); The average particle size of the nano-silicon dioxide is 25-35 nm; the average pore size of the porous silicon is 20-24 nm; The preparation method of the modifier comprises the following steps: S1: adding petroleum asphalt into a container, heating it to 110-130° C., stirring it evenly, then adding n-hexane to extract and remove impurities, then centrifugation is used to remove high-viscosity residue precipitation, and then secondary n-hexane extraction and impurity removal is performed to obtain an impurity-removed product; S2: mixing the impurity-removed product with polyvinyl acetate and phenolic epoxy resin and stirring them evenly, then heating it to 140-160° C., keeping the temperature for reaction for 10-12 hours, and adding the product into deionized water after completion; S3: adding triethanolamine to adjust the pH of the system to 7-7.5 until it no longer changes, and then vacuum drying the product at 90-110° C. for 4-5 hours, and obtaining the product after completion; The n-hexane extraction and impurity removal, the mass ratio of petroleum asphalt and n-hexane is (3-4): (1.5-1.8); The mass ratio of the impurity-removed product, polyvinyl acetate and phenolic epoxy resin is (4-5): (0.8-1.2): (0.4-0.6).

2. The circular battery-specific negative electrode material according to claim 1, characterized in that: The mass ratio of the silicon-based composite, spherical graphite and modifier is (15-20): (45-55): (11-16).

3. The circular battery-specific negative electrode material according to claim 2, characterized in that: The mass ratio of the spherical graphite to the modified particles is (45-55): (6-9).

4. The circular battery-specific negative electrode material according to claim 3, characterized in that: The average particle size of the spherical graphite is 2-3.5 μm.

5. The circular battery-specific negative electrode material according to claim 4, characterized in that: The modified particles are modified carbon nanotubes; The preparation method of the modified carbon nanotubes comprises the following steps: S1: adding multi-walled carbon nanotubes and titanium dioxide to a DMF solution by stirring, adding glutaric anhydride, heating to 60-65° C. and keeping the temperature for 2-3 hours to obtain pretreated particles; S2: Add the pretreated particles into deionized water, add ammonia water to adjust the pH to 8.5-9.5, then add triethanolamine and ethyl orthosilicate, heat to 65-70°C and keep warm for 2-2.5 hours, filter the product, wash and dry it to obtain the pre-product; S3: Mix the pre-product, zinc nitrate and 2-methylimidazole and add them into deionized water, heat to 60-70°C, keep warm for 4-6 hours, filter the product, wash and dry it to obtain the pre-product.

6. The circular battery-specific negative electrode material according to claim 5, characterized in that: The mass ratio of the multi-walled carbon nanotubes, titanium dioxide and glutaric anhydride is (3-3.2): (0.3-0.5): (0.8-1); the mass ratio of the pretreated particles, triethanolamine and tetraethyl orthosilicate is (2-2.5): (0.05-0.1): (0.4-0.5).

7. The circular battery-specific negative electrode material according to claim 6, characterized in that: The mass ratio of the pre-product, zinc nitrate and 2-methylimidazole is (2-2.5): (0.8-1): (0.3-0.5); the average particle size of the titanium dioxide is 5-10 nm.

8. The circular battery-specific negative electrode material according to claim 7, characterized in that: The corrosion inhibitor is a composition of bisphenol A diglycidyl ether phosphate and epoxy block polyether; the mass ratio of the bisphenol A diglycidyl ether phosphate and the epoxy block polyether is (2.5-3): (1.2-1.4); the weight average molecular weight of the epoxy block polyether is 8000-10000Da.

9. The circular battery-specific negative electrode material according to claim 8, characterized in that: The conductive additive is acetylene black; the solvent is a composition of NMP and DMF; the mass ratio of NMP to DMF is (5-6): (1-1.1).

10. A method for preparing a negative electrode material for a circular battery according to any one of claims 1 to 9, characterized in that: The specific steps include: S1: Add the silicon-based composite, spherical graphite, modifier and modified particles to a high-speed mixer, and stir at 350-500 rpm for 3-4 hours to ensure complete mixing; S2: Add the solvent, binder, gelatinizer, corrosion inhibitor and conductive additive in sequence, and continue stirring at 350-500 rpm for 16-20 hours until a uniform and particle-free slurry is obtained; S3: Use a doctor blade coater to coat the slurry on the copper foil current collector, control the coating thickness to 80-120 μm, and then vacuum dry at 80-90° C. for 6-10 hours to obtain a pre-product; S4: The pre-product is calendered through a calender to control the density between 1.5 and 3 g / cm 3 , you will get it.

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