A negative electrode material for circular batteries and its preparation method

Abstract

This application relates to the field of battery materials, and more particularly to a negative electrode material specifically for spherical batteries and its preparation method. The negative electrode material for spherical batteries, by weight, comprises: 10-25 parts silicon-based composite, 40-60 parts spherical graphite, 10-20 parts modifier, 5-10 parts modified particles, 0.5-1.2 parts corrosion inhibitor, 2-5 parts binder, 1-3 parts gelatinizer, 1-2 parts conductive additive, and 20-30 parts solvent. The spherical batteries prepared using the negative electrode material obtained in this application not only possess excellent battery capacity and discharge time, but also exhibit good stability, cycle life, safety, and storage stability, meeting the battery requirements of current high-power small electronic products and demonstrating excellent market and application prospects.

Description

Technical Field

[0001] This application relates to the field of battery materials, and in particular to a negative electrode material for circular batteries and its preparation method. Background Technology

[0002] With the increasing prevalence 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 crucial role, as it directly affects performance indicators such as energy density, cycle life, safety, and cost. For applications specifically designed for miniaturization and high energy density (such as smartwatches, medical implants, and other wearable technologies), spherical batteries are widely used due to their compact structure and ease of integration.

[0003] Traditional lithium-ion battery anodes primarily use graphite materials, with a theoretical specific capacity of 372 mAh / g. However, with the market's pursuit of higher energy density, researchers have begun exploring alternative materials with higher theoretical specific capacities, such as silicon (Si)-based materials. Silicon, as an anode material, boasts a theoretical specific capacity of nearly 4200 mAh / g, far exceeding that of traditional graphite, and is abundant on Earth and environmentally friendly.

[0004] Furthermore, to adapt to the design of spherical batteries for specific applications, anode materials also need to meet special physical requirements, such as good flexibility for winding processes and uniform coating thickness to ensure consistent electrochemical reactions. However, most current research on novel anode materials focuses on planar batteries, with relatively few anode materials optimized for spherical batteries, especially lacking effective solutions to address the aforementioned volume effects and initial coulombic efficiency. Therefore, developing anode materials specifically tailored for spherical batteries has become crucial for improving the overall performance of these batteries.

[0005] Therefore, in order to effectively solve the above problems, this application provides a special negative electrode material for circular batteries and its preparation method. The circular batteries prepared from the special negative electrode material for circular batteries prepared by this application not only have excellent battery capacity and discharge time, but also have good stability, battery cycle performance, safety and storage stability. They can meet the battery needs of existing high-power small electronic products and have excellent market and application prospects. Summary of the Invention

[0006] To address the aforementioned problems, the first aspect of this application provides a negative electrode material specifically for circular batteries, comprising, by weight, the following raw materials: 10-25 parts silicon-based composite, 40-60 parts spherical graphite, 10-20 parts modifier, 5-10 parts modified particles, 0.5-1.2 parts corrosion inhibitor, 2-5 parts binder, 1-3 parts gelatinizer, 1-2 parts conductive additive, and 20-30 parts solvent.

[0007] As a preferred embodiment, the silicon-based composite is a combination of nano-silica and porous silicon.

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

[0009] As a preferred embodiment, the average particle size of the nano-silica is 25–35 nm.

[0010] As a preferred embodiment, the average pore size of the porous silicon is 20–24 nm.

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

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

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

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

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

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

[0017] As a preferred embodiment, the preparation method of the modifier includes the following steps: S1: Petroleum asphalt is added to a container and heated to 110-130°C and stirred evenly. Then, hexane is added for extraction to remove impurities. Afterward, high-viscosity residue precipitate is removed by centrifugation, and a second hexane extraction is performed to remove impurities, obtaining the purified product; S2: The purified product is mixed with polyvinyl acetate and phenolic epoxy resin and stirred evenly. Then, the temperature is raised to 140-160°C and the reaction is maintained for 10-12 hours. After the reaction is completed, the product is added to deionized water; S3: Triethanolamine is added to adjust the pH of the system to 7-7.5 until it no longer changes. Then, the product is vacuum dried at 90-110°C for 4-5 hours, and the product is obtained.

[0018] As a preferred embodiment, the hexane extraction for impurity removal involves a mass ratio of petroleum asphalt to hexane of (3-4):(1.5-1.8).

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

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

[0021] The modifier added in this application can effectively improve the electrical performance of the anode material and ensure its cycle life and stability. The added modifier acts as a flexible carrier for the mixing of spherical graphite and silicon-based composites during the preparation and mixing of the anode material. This carrier, under the premise of coating and mixing, can significantly improve the adhesion between the spherical graphite system and the silicon-based composite, thus becoming a carrier of strong intermolecular forces after the addition of modified particles and conductive additives. This reduces molecular chain migration within the anode material, reduces the probability of cracks and silver streaks, and thus ensures that the anode material has excellent electrical performance, stability, and cycle life.

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

[0023] As a preferred embodiment, the preparation method of the modified carbon nanotubes includes the following steps: S1: Multi-walled carbon nanotubes and titanium dioxide are mixed and stirred and added to DMF solution. After adding glutaric anhydride, the temperature is raised to 60-65℃ and kept at this temperature for 2-3 hours to obtain pretreated particles; S2: The pretreated particles are added to deionized water, and ammonia is added to adjust the pH to 8.5-9.5. Then triethanolamine and tetraethyl orthosilicate are added, and the temperature is raised to 65-70℃ and kept at this temperature for 2-2.5 hours. The product is filtered, washed, and dried to obtain the preproduct; S3: The preproduct is mixed with zinc nitrate and 2-methylimidazole and added to deionized water. The temperature is raised to 60-70℃ and kept at this temperature for 4-6 hours. After completion, the product is filtered, washed, and dried to obtain the final product.

[0024] As a preferred embodiment, 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 embodiment, 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 embodiment, the preproduct has a mass ratio of zinc nitrate to 2-methylimidazole of (2-2.5):(0.8-1):(0.3-0.5).

[0027] As a preferred embodiment, the titanium dioxide has an average particle size of 5–10 nm.

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

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

[0030] As a preferred embodiment, the epoxy block polyether has a weight-average molecular weight of 8000–10000 Da.

[0031] As a preferred embodiment, the adhesive is a polyvinylidene fluoride adhesive.

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

[0033] As a preferred embodiment, the gelatinizing agent is sodium carboxymethyl cellulose.

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

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

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

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

[0038] The second aspect of this application provides a method for preparing the above-mentioned circular battery-specific negative electrode material, specifically including the following steps: S1: adding silicon-based composite, spherical graphite, modifier and modified particles to a high-speed mixer, and stirring at 350-500 rpm for 3-4 hours to ensure complete mixing; S2: adding solvent, binder, gelling agent, corrosion inhibitor and conductive additive in sequence and continuing to stir at 350-500 rpm for 16-20 hours until a uniform and particle-free slurry is obtained;

[0039] S3: Apply the slurry onto the copper foil current collector using a doctor blade coater, controlling the coating thickness to be 80–120 μm, then vacuum dry at 80–90 °C for 6–10 h to obtain the pre-product; S4: Calender the pre-product using a calender, controlling the density to be 1.5–3 g / cm³. 3 That is, you get it.

[0040] The beneficial effects of this application are:

[0041] 1. The negative electrode material for circular batteries provided in this application not only has excellent battery capacity and discharge time, but also has good stability, battery cycle performance, safety and storage stability, which can meet the battery needs of existing high-power small electronic products and has excellent market and application prospects.

[0042] 2. The circular battery-specific negative electrode material provided in this application includes a modifier that acts as a flexible carrier for mixing spherical graphite and silicon-based composites during the preparation and mixing of the negative electrode material. Under the premise of coating and mixing, this carrier can significantly improve the adhesion between the spherical graphite system and the silicon-based composites, thus becoming a carrier for strong intermolecular forces after the addition of modified particles and conductive additives. This reduces the migration of molecular chains inside the negative electrode material, reduces the probability of cracks and silver streaks, and thus ensures that the negative electrode material has excellent electrical performance, stability and cycle performance.

[0043] 3. The circular battery-specific negative electrode material provided in this application has modified particles that can form a composite particle structure with amorphous silicon as the outer shell. This structure can form a good ion movement pathway inside, and the transport speed and stability of the pathway can be greatly improved through enrichment. This can significantly enhance the diffusion and migration speed of lithium ions, thereby effectively enhancing the overall electrical performance. Moreover, the formed composite structure can use the modifier as a good carrier to achieve site stability, thereby reducing segregation and migration in long-term use, and exhibiting excellent stability and cycle performance. Detailed Implementation

[0044] The following will further illustrate and demonstrate the technical solutions described above in this application through specific implementation schemes. Furthermore, the following embodiments are merely practical examples used to illustrate and explain the content 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 this application should be covered within the scope of protection of this application.

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

[0046] Example 1

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

[0048] The silicon-based composite is a combination of nano-silica and porous silicon in a mass ratio of 1.2:4.5.

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

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

[0051] The preparation method of the modifier includes the following steps: S1: 3.6 parts of petroleum asphalt are added to a container, heated to 115℃ and stirred evenly. Then, 1.6 parts of n-hexane are added for extraction to remove impurities. After that, high-viscosity residue precipitate is removed by centrifugation and a second n-hexane extraction is performed to remove impurities (the mass ratio is the same as the first n-hexane extraction). The impurity-removed product is obtained. S2: 4.6 parts of the impurity-removed product are mixed with 0.95 parts of polyvinyl acetate and 0.48 parts of phenolic epoxy resin and stirred evenly. Then, the temperature is raised to 150℃ and the reaction is maintained for 12 hours. After the reaction is completed, the product is added to 250 parts of deionized water. S3: Triethanolamine is added to adjust the pH of the system to 7.5 until it no longer changes. Then, the product is vacuum dried at 95℃ for 4.5 hours. The product is then obtained.

[0052] The petroleum asphalt was purchased from Hebei Hankai Energy Technology Development Co., Ltd., with a softening point of 110℃.

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

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

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

[0056] The modified particles are modified carbon nanotubes. The preparation method of modified carbon nanotubes includes 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. After adding 0.85 parts of glutaric anhydride, the temperature is raised to 65℃ and kept at that temperature 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. Then, 0.06 parts of triethanolamine and 0.42 parts of tetraethyl orthosilicate are added. The temperature is raised to 70℃ and kept at that temperature for 2 hours. The product is filtered, washed, and dried to obtain the preproduct; S3: 2.2 parts of the preproduct, 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℃ and kept at that temperature for 5 hours. After completion, the product is filtered, washed, and dried to obtain the final product.

[0057] The 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, with a mass ratio of 2.7:1.3.

[0060] The epoxy block polyether was purchased from BASF Germany as product L87, with a weight-average molecular weight of 8200 Da.

[0061] The adhesive is polyvinylidene fluoride adhesive, purchased from Shanghai Sanaifu New Material Technology Co., Ltd., China, product model FR905.

[0062] The gelatinizing agent is sodium carboxymethyl cellulose.

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

[0064] The solvent is a combination of NMP and DMF in a mass ratio of 5:1.

[0065] The second aspect of this embodiment provides a method for preparing the above-mentioned circular battery-specific negative electrode material, specifically including the following steps: S1: Add silicon-based composite, spherical graphite, modifier, and modified particles to a high-speed mixer and stir at 400 rpm for 4 hours to ensure complete mixing; S2: Add solvent, binder, gelling agent, corrosion inhibitor, and conductive additive sequentially and continue stirring at 400 rpm for 18 hours until a uniform and particle-free slurry is obtained; S3: Coat the slurry onto a copper foil current collector using a doctor blade coater, controlling the coating thickness to 100 μm, and then vacuum dry at 85°C for 9 hours to obtain a pre-product; S4: Calender the pre-product using a calender to control the density at 2 g / cm³. 3 That is, you get it.

[0066] Example 2

[0067] The specific implementation method of this embodiment is basically the same as that of Embodiment 1, except that: the negative electrode material for circular batteries, by mass, consists of: 19.6 parts silicon-based composite, 46.8 parts spherical graphite, 15.5 parts modifier, 6.1 parts modified particles, 0.8 parts corrosion inhibitor, 3.2 parts binder, 2.2 parts gelatinizer, 1.3 parts conductive additive, and 28.5 parts solvent.

[0068] Example 3

[0069] The specific implementation method of this embodiment is basically the same as that of Embodiment 1, except that: the negative electrode material for circular batteries, by mass, consists of: 15.5 parts silicon-based composite, 54.6 parts spherical graphite, 11.5 parts modifier, 8.6 parts modified particles, 0.8 parts corrosion inhibitor, 3.2 parts binder, 2.2 parts gelatinizer, 1.1 parts conductive additive, and 30.2 parts solvent.

[0070] Comparative Example 1

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

[0072] Comparative Example 2

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

[0074] Comparative Example 3

[0075] The specific implementation method 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, with a mass ratio of 3:0.2.

[0076] Comparative Example 4

[0077] The specific implementation method of this comparative example is basically the same as that of Example 1, except that the preparation method of the modifier includes the following steps: S1: 3.6 parts of petroleum asphalt are added to a container, heated to 115°C and stirred evenly. Then, 1.6 parts of n-hexane are added for extraction to remove impurities. After that, high-viscosity residue precipitate is removed by centrifugation and a second n-hexane extraction is performed to remove impurities (the mass ratio is the same as the first n-hexane extraction). The impurity-removed product is obtained. S2: 8.8 parts of the impurity-removed product are mixed with 0.55 parts of polyvinyl acetate and 0.12 parts of phenolic epoxy resin and stirred evenly. Then, the temperature is raised to 150°C and the reaction is kept at that temperature for 12 hours. After the reaction is completed, the product is added to 250 parts of deionized water. S3: Triethanolamine is added to adjust the pH of the system to 7.5 until it no longer changes. Then, the product is vacuum dried at 95°C for 4.5 hours. The product is obtained after the reaction is completed.

[0078] Comparative Example 5

[0079] The specific implementation method of this comparative example is basically the same as that of Example 1, except that the preparation method of the modifier includes the following steps: S1: 3.6 parts of petroleum asphalt are added to a container, heated to 115°C and stirred evenly. Then, 1.6 parts of n-hexane are added for extraction to remove impurities. After that, high-viscosity residue precipitate is removed by centrifugation and a second n-hexane extraction is performed to remove impurities (the mass ratio is the same as the first n-hexane extraction). The impurity-removed product is obtained; S2: 3.5 parts of the impurity-removed product are mixed with 1.62 parts of polyvinyl acetate and 1.1 parts of phenolic epoxy resin and stirred evenly. Then, the temperature is raised to 150°C and kept at that temperature for 12 hours. After the reaction is completed, the product is added to 340 parts of deionized water; S3: Triethanolamine is added to adjust the pH of the system to 7.5 until it no longer changes. Then, the product is vacuum dried at 95°C for 4.5 hours. The product is then obtained.

[0080] Comparative Example 6

[0081] The specific implementation method of this comparative example is basically the same as that of Example 1, except that the preparation method of modified carbon nanotubes includes 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. After adding 0.45 parts of glutaric anhydride, the temperature is raised to 65°C and kept at that temperature 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. Then, 0.06 parts of triethanolamine and 0.42 parts of tetraethyl orthosilicate are added. The temperature is raised to 70°C and kept at that temperature for 2 hours. After filtering, washing and drying the product, the preproduct is obtained; S3: 2.2 parts of the preproduct, 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 kept at that temperature for 5 hours. After completion, the product is filtered, washed and dried to obtain the final product.

[0082] Comparative Example 7

[0083] The specific implementation method of this comparative example is basically the same as that of Example 1, except that the preparation method of modified carbon nanotubes includes 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. After adding 0.85 parts of glutaric anhydride, the temperature is raised to 65°C and kept at that temperature 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. Then, 0.02 parts of triethanolamine and 0.22 parts of tetraethyl orthosilicate are added. The temperature is raised to 70°C and kept at that temperature for 2 hours. After filtering, washing and drying the product, the preproduct is obtained; S3: 3.9 parts of the preproduct, 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 kept at that temperature for 5 hours. After completion, the product is filtered, washed and dried to obtain the final product.

[0084] Performance Evaluation

[0085] 1. Electrical performance testing: The negative electrode materials prepared in the examples and comparative examples were used as negative electrodes, LiPF6 / EC+EMC+DMC (1:1:1) was used as electrolyte, lithium metal sheets were used as positive electrodes, and Celgard 2400 separators were used. The batteries were assembled in an argon-filled glove box. The electrochemical performance was tested on a Wuhan Landian CT2001A battery tester. The charge and discharge voltage range was 0.005V to 3.0V, and the charge and discharge rate was 1C. The initial efficiency and initial discharge capacity were tested respectively, and the test values ​​were the average of 10 tests and recorded in Table 1.

[0086] 2. Cyclic performance test: Based on performance test 1, the current density was set to 500mA / g, and the battery cycle performance was tested using a battery testing system. 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] From the embodiments and comparative examples of this application, as well as the data results in Table 1, it can be seen that embodiments 1-3 of this application have significant advantages over comparative examples 1-7 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 additives specified in this application. In contrast, comparative examples 1-7, because they did not adopt the technical solution specified in this application, showed significant disadvantages in the above performance tests. This further proves the necessity of the technical solution specified in this application for the technical effect of this application and for solving the technical problem.

Claims

1. A negative electrode material specifically for circular batteries, characterized in that: The raw materials, by weight, are: 10-25 parts silicon-based composite, 40-60 parts spherical graphite, 10-20 parts modifier, 5-10 parts modified particles, 0.5-1.2 parts corrosion inhibitor, 2-5 parts binder, 1-3 parts gelatinizer, 1-2 parts conductive additive, and 20-30 parts solvent. The silicon-based composite is a combination of nano-silica and porous silicon; the mass ratio of nano-silica to porous silicon is (1~1.5):(4~5). The average particle size of the nano-silica is 25-35 nm; the average pore size of the porous silicon is 20-24 nm. The preparation method of the modifier includes the following steps: S1: Petroleum asphalt is added to a container and heated to 110~130℃ and stirred evenly. Then, hexane is added for extraction to remove impurities. After that, high-viscosity residue precipitate is removed by centrifugation and a second hexane extraction is performed to remove impurities, thus obtaining the purified product; S2: The purified product is mixed with polyvinyl acetate and phenolic epoxy resin and stirred evenly. Then, the temperature is raised to 140~160℃ and the reaction is maintained for 10~12h. After the reaction is completed, the product is added to deionized water; S3: Triethanolamine is added to adjust the pH of the system to 7~7.5 until it no longer changes. Then, the product is vacuum dried at 90~110℃ for 4~5h. After the reaction is completed, the product is obtained. The process involves hexane extraction to remove impurities, with the mass ratio of petroleum asphalt to hexane being (3~4):(1.5~1.8). The mass ratio of polyvinyl acetate to phenolic epoxy resin in the purified product is (4~5):(0.8~1.2):(0.4~0.6).

2. The negative electrode material for circular batteries according to claim 1, characterized in that: The silicon-based composite has a mass ratio of spherical graphite to modifier of (15~20):(45~55):(11~16).

3. The negative electrode material for circular batteries 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 negative electrode material for circular batteries according to claim 3, characterized in that: The average particle size of the spherical graphite is 2~3.5μm.

5. The negative electrode material for circular batteries according to claim 4, characterized in that: The modified particles are modified carbon nanotubes; The preparation method of the modified carbon nanotubes includes the following steps: S1: Multi-walled carbon nanotubes and titanium dioxide are mixed and stirred and added to DMF solution. After adding glutaric anhydride, the temperature is raised to 60~65℃ and kept at the temperature for 2~3h to obtain pretreated particles. S2: Add the pretreated particles to deionized water, add ammonia to adjust the pH to 8.5~9.5, then add triethanolamine and tetraethyl orthosilicate, heat to 65~70℃ and keep warm for 2~2.5h, filter, wash and dry the product to obtain the preproduct; S3: Mix the preproduct with zinc nitrate and 2-methylimidazole and add to deionized water, heat to 60~70℃ and keep warm for 4~6h, after which filter, wash and dry the product to obtain the final product.

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

7. The negative electrode material for circular batteries according to claim 6, characterized in that: The preproduct has a zinc nitrate to 2-methylimidazole mass ratio of (2~2.5):(0.8~1):(0.3~0.5); the titanium dioxide has an average particle size of 5~10 nm.

8. The negative electrode material for circular batteries 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 bisphenol A diglycidyl ether phosphate to epoxy block polyether is (2.5~3):(1.2~1.4); the weight average molecular weight of the epoxy block polyether is 8000~10000 Da.

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

10. A method for preparing a circular battery-specific negative electrode material according to any one of claims 1 to 9, characterized in that: Specifically, the following steps are included: 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 sequentially and continue stirring at 350-500 rpm for 16-20 hours until a uniform and particle-free slurry is obtained; S3: Apply the slurry to a copper foil current collector using a doctor blade coater, controlling the coating thickness to 80-120 μm, and then vacuum dry at 80-90℃ for 6-10 hours to obtain the pre-product; S4: Calender the preproduct using a calender to control the density at 1.5~3 g / cm³. 3 That is, you get it.

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