Silicon-based hard carbon composite material, preparation method and application thereof

Abstract

This invention relates to the field of lithium-ion battery anode material technology, specifically to a silicon-based hard carbon composite material, its preparation method, and its application. The silicon-based hard carbon composite material includes a core and a shell covering the core. The core includes silicon oxide, graphene oxide, and hard carbon, and the shell includes amorphous carbon. The interlayer spacing of the silicon-based hard carbon composite material is 0.375~0.395 nm. This application combines a core containing graphene oxide and hard carbon with silicon oxide materials and controls the interlayer spacing within the above range, thereby reducing the full-charge expansion of the anode sheet while improving the battery's cycle performance, high-temperature storage performance, and rate performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery anode material technology, specifically to a silicon-based hard carbon composite material, its preparation method, and its application. Background Technology

[0002] Hard carbon materials, as amorphous carbon, are characterized by high isotropy, zero expansion, and excellent low-temperature performance. However, their low specific capacity, low initial efficiency, and poor high-temperature performance limit their application to HEVs (hybrid electric vehicles) and 48V (mild hybrid systems). Silicon-carbon materials, on the other hand, have high specific capacity, but their high full-charge expansion and high electronic impedance result in poor low-temperature performance. While physically mixing hard carbon and silicon-carbon materials can compensate for each other's shortcomings, the compatibility between the two materials (hard carbon and silicon-based) leads to poor dispersion uniformity, causing significant local expansion. Furthermore, the weak bonding between the two materials through physical mixing severely degrades rate performance. Additionally, the increased surface defects further reduce initial efficiency and high-temperature storage performance. For example, patent application number CN202211216754.1 discloses a hard carbon-silicon carbon composite material, its preparation method and application. The core includes Si / SiOx and amorphous carbon components, and the outer shell is hard carbon doped with metallic silver. Although the specific capacity of the obtained material is improved, the silver doped hard carbon in the outer shell is in contact with the electrical contact and has strong activity, which reduces its initial efficiency and high-temperature performance. Moreover, the amorphous carbon in the core has little effect on the expansion of Si / SiOx, and the full-charge expansion is still large. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of existing hard carbon and silicon carbon composite materials, which still have large expansion when fully charged, insufficient bonding force, and many surface defects, resulting in poor rate performance, high-temperature storage performance and low initial efficiency of the battery. The present invention provides a silicon-based hard carbon composite material, its preparation method and application.

[0004] To this end, in a first aspect, this application provides a silicon-based hard carbon composite material, the silicon-based hard carbon composite material comprising a core and a shell covering the core, the core comprising silicon oxide material, graphene oxide and hard carbon, and the shell comprising amorphous carbon; the interlayer spacing of the silicon-based hard carbon composite material is 0.375~0.395 nm.

[0005] In some embodiments, the tap density of the silicon-based hard carbon composite material is 0.8~0.9 g / cm³. 3 .

[0006] In some embodiments, the powder resistivity of the silicon-based hard carbon composite material is 0.202-0.276 Ω·cm.

[0007] In some embodiments, the interlayer spacing of the silicon-based hard carbon composite material is 0.38~0.39 nm.

[0008] Secondly, this application also provides a method for preparing a silicon-based hard carbon composite material, comprising the following steps: Step S1: Phenolic monomers, aldehyde monomers, silicon oxide materials, graphene oxide, and melamine are mixed in the presence of water, heated and reacted, and then dried to obtain silicon oxide hard carbon precursor materials. Step S2: The silicon-oxygen hard carbon precursor material is pressed, activated to create pores, and carbonized for the first time. Then, it undergoes a second carbonization treatment in the presence of carbon-containing gas to obtain a silicon-based hard carbon composite material.

[0009] In some embodiments, the mass ratio of the phenolic monomer, silicon oxide material, graphene oxide, and melamine is 200:1-5:0.5-2:1-5; And / or, the molar ratio of the phenolic monomer to the aldehyde monomer is 1:1~3; And / or, the phenolic monomers include one or more of 3-ethylamino-4-methylphenol, p-acetaminophenol, 2-amino-5-nitrophenol, p-aminophenol, and 4-aminophenol; And / or, the aldehyde monomers include one or more of formaldehyde, acetaldehyde, propionaldehyde, and benzaldehyde; And / or, the heating reaction is carried out at a temperature of 50-100°C, a pressure of 1-15 MPa, and a reaction time of 1-6 h.

[0010] In some embodiments, the pressure of the pressure block is 5-15T.

[0011] In some embodiments, the activation of pore formation is carried out at 200-300°C in the presence of an activating gas for 1-6 hours.

[0012] In some embodiments, the activating gas is selected from one or more of carbon dioxide, ammonia, or oxygen.

[0013] In some embodiments, the temperature of the first carbonization treatment is 1000~1500℃, preferably 1100~1400℃; the time is 1~6h, preferably 2~4h.

[0014] In some embodiments, the carbon-containing gas is selected from one or more of acetylene, methane, ethylene, and ethane; And / or, the temperature of the second carbonization treatment is 700~900℃; the time is 1~6h.

[0015] In some embodiments, the second carbonization process is chemical vapor deposition.

[0016] Thirdly, this application also provides a negative electrode sheet, including a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, wherein the negative active material layer includes a silicon-based hard carbon composite material as described in any of the first aspects or a silicon-based hard carbon composite material prepared according to the preparation method of the silicon-based hard carbon composite material as described in any of the second aspects.

[0017] Fourthly, this application also provides a secondary battery, including the negative electrode sheet described in the third aspect.

[0018] The technical solution of this invention has the following advantages: 1. The silicon-based hard carbon composite material provided in this application includes a core and a shell covering the core. The core includes silicon oxide, graphene oxide, and hard carbon, and the shell includes amorphous carbon. The interlayer spacing of the silicon-based hard carbon composite material is 0.375~0.395nm. This application combines a core containing graphene oxide and hard carbon with silicon oxide on the basis of silicon oxide material and controls the interlayer spacing within the above range, so that the negative electrode sheet can improve the cycle performance, high-temperature storage performance, and rate performance of the battery while reducing the full-charge expansion.

[0019] Among them, doping hard carbon with silicon-oxygen materials significantly improves the specific capacity of the material, and doping with graphene oxide significantly improves the electronic conductivity of the hard carbon precursor and the expansion of bound silicon-oxygen. The amorphous carbon coating improves the first efficiency of the material. When applied to lithium-ion batteries, the material has the advantages of high energy density, small expansion, and high first efficiency, and can improve the high-temperature storage and rate performance of the battery.

[0020] 2. The silicon-based hard carbon composite material provided in this application has a tap density of 0.8~0.9 g / cm³. 3 ; and / or, the powder resistivity of the silicon-based hard carbon composite material is 0.202-0.276 Ω·cm, and / or, the interlayer spacing of the silicon-based hard carbon composite material is 0.38~0.39 nm.

[0021] By controlling the interlayer spacing within the above-mentioned preferred range, the lithium ion insertion / extraction rate during charging and discharging can be further improved to enhance rate performance, while also reducing negative electrode expansion and improving cycle performance.

[0022] The tap density of the silicon-based hard carbon composite material is 0.8~0.9 g / cm³. 3 By controlling the tap density within the above range, the processing performance of the material, such as the bonding process, can be improved, and the compaction density of the electrode sheet can be increased.

[0023] The powder resistivity of the silicon-based hard carbon composite material is 0.202-0.276 Ω·cm. By controlling the powder resistivity within the above range, the ion diffusion and electron diffusion of the material can be improved, thereby improving the rate performance.

[0024] 3. The preparation method of the silicon-based hard carbon composite material provided in this application includes the following steps: S1: Phenolic monomers, aldehyde monomers, silicon oxide materials, graphene oxide, and melamine are mixed in the presence of water, heated and reacted, and then dried to obtain a silicon oxide hard carbon precursor material; S2: The silicon oxide hard carbon precursor material is pressed into blocks, activated to create pores, and subjected to a first carbonization followed by a second carbonization treatment in the presence of a carbon-containing gas to obtain the silicon-based hard carbon composite material. The preparation method of this invention is simple and convenient, and suitable for industrial production.

[0025] Among them, silicon-based hard carbon composite material is obtained by pressing and activating silicon-oxygen hard carbon precursor material and then performing first and second carbonization treatments. This results in a more uniform carbon coating layer on the core surface and a more uniform porous structure in the core, which further improves the cycle performance and rate performance of the battery.

[0026] In step S1, during the heating reaction of phenolic monomers and aldehyde monomers to form the hard carbon precursor phenolic resin, silicon oxide materials and graphene oxide can be uniformly doped into the hard carbon precursor, which can better reduce the expansion of silicon oxide materials.

[0027] In step S2, activation and pore-forming are performed before the first carbonization. This activation activates the surface of the silicon-oxygen hard carbon precursor material, forming nano- and micro-sized pores. After the first carbonization, an intermediate product (i.e., a porous core) is obtained. The formation of the porous core can better reduce the expansion of the silicon-oxygen material. Compaction increases the material's density. The subsequent activation, pore-forming, and carbonization processes after compaction ensure more complete activation and carbonization reactions. Finally, a second carbonization process (e.g., chemical vapor deposition) is performed in the presence of a carbon-containing gas (e.g., acetylene) to deposit amorphous carbon on the outermost layer of the intermediate product, achieving a suitable specific surface area, thereby improving the initial efficiency and high-temperature storage performance.

[0028] 4. The method for preparing silicon-based hard carbon composite material provided in this application, by controlling the temperature of the first carbonization treatment to 1000~1500℃, especially 1100~1400℃, can improve the anisotropy of the material, reduce the defects of the material and improve the structural stability of the material, and can also reduce the impurity content of the material, improve the first efficiency of the material and its cycle performance and storage performance. Attached Figure Description

[0029] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is a SEM image of the high-capacity silicon-based hard carbon composite material obtained in Example 1 of this invention. Detailed Implementation

[0031] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0032] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0033] Example 1 This embodiment provides a method for preparing a silicon-based hard carbon composite material, including the following steps: Step S1: Mix 200g of 3-ethylamino-4-methylphenol (1.32mol) and 79.2g of formaldehyde (2.64mol) solution evenly to obtain a mixture. Then add 3g of silicon oxide material (SiO), 100g of graphene oxide aqueous solution with a mass percentage of 1wt%, and 3g of melamine and mix evenly. Transfer the mixture to a high-pressure reactor and react at 80℃ and 3MPa for 3h. Filter and vacuum dry at 80℃ for 24h to obtain silicon oxide hard carbon precursor material.

[0034] Step S2: The silicon-oxygen hard carbon precursor material is briquetted under a pressure of 10T, then activated with carbon dioxide gas (flow rate 100ml / min), heated to 150℃ for 3h, then crushed and dispersed to obtain a semi-finished product. The product is then heated to 1200℃ and carbonized in a nitrogen atmosphere for 3h (first carbonization treatment). The obtained material is then transferred to a tube furnace, where argon inert gas is first introduced to purge the air from the tube, followed by acetylene gas at a flow rate of 100ml / min, and the temperature is raised to 800℃ for 3h (second carbonization treatment). The material is then cooled to room temperature to obtain a high-capacity silicon-based hard carbon composite material.

[0035] Example 2 This embodiment provides a method for preparing a silicon-based hard carbon composite material, including the following steps: Step S1: 200g of acetaminophen (1.32mol) and 79.2g of formaldehyde (2.64mol) are mixed evenly to obtain a mixture. Then, 1g of silicon oxide material (SiO), 100g of graphene oxide aqueous solution with a mass percentage of 0.5wt%, and 1g of melamine are added and mixed evenly. The mixture is then transferred to a high-pressure reactor and reacted at 50℃ and 5MPa for 6h. After filtration, the mixture is vacuum dried at 80℃ for 24h to obtain the silicon oxide hard carbon precursor material. Step S2: The silicon-oxygen hard carbon precursor material is briquetted under a pressure of 5T, then activated with ammonia gas (flow rate 100ml / min), heated to 100℃, and activated for 1h. After that, it is crushed and dispersed to obtain a semi-finished product. Then, it is heated to 1000℃ and carbonized in a nitrogen atmosphere for 6h. After that, the obtained material is transferred to a tube furnace. First, argon inert gas is introduced to purge the air in the tube, then acetylene gas is introduced at a flow rate of 50ml / min, and the temperature is raised to 700℃ for 6h. After that, it is cooled to room temperature to obtain a high-capacity silicon-based hard carbon composite material.

[0036] Example 3 This embodiment provides a method for preparing a silicon-based hard carbon composite material, including the following steps: Step S1: Mix 200g (1.29mol) of 2-amino-5-nitrophenol and 77.4g (2.58mol) of formaldehyde solution evenly to obtain a mixture. Then add 5g of silicon oxide material (SiO), 100ml of graphene oxide solution with a mass percentage of 2wt%, and 5g of melamine and mix evenly. Transfer the mixture to a high-pressure reactor and react at 100℃ and 1MPa for 6h. Filter and vacuum dry at 80℃ for 24h to obtain silicon oxide hard carbon precursor material. Step S2: The silicon-oxygen hard carbon precursor material is briquetted under a pressure of 15T, then oxygen activation gas (flow rate 100ml / min) is introduced and heated to 300℃ for 1 hour to achieve pore formation. After that, it is crushed and dispersed to obtain a semi-finished product. Then, the temperature is raised to 1500℃ and carbonized in a nitrogen atmosphere for 1 hour. After that, the obtained material is transferred to a tube furnace. First, argon inert gas is introduced to purge the air in the tube, then acetylene gas is introduced at a flow rate of 200ml / min and the temperature is raised to 900℃ for 1 hour. After that, it is cooled to room temperature to obtain a high-capacity silicon-based hard carbon composite material.

[0037] Example 4 The only difference from Example 1 is that the temperature of the first carbonization treatment in step S2 is adjusted to 1500°C.

[0038] Example 5 The only difference from Example 1 is that the temperature of the first carbonization treatment in step S2 is adjusted to 1000°C.

[0039] Comparative Example 1 This comparative example provides a method for preparing a silicon-based hard carbon composite material, which is basically the same as that in Example 1, except that 232g of phenolic resin is used instead of 3-ethylamino-4-methylphenol and formaldehyde used in Example 1.

[0040] Comparative Example 2 This comparative example provides a method for preparing a silicon-based hard carbon composite material, comprising the following steps: Unlike Example 1, step S2 does not involve briquetting or introducing activation gas. The detailed preparation process is as follows: the silicon-oxygen hard carbon precursor material obtained in step S1 of Example 1 is heated to 1200°C and carbonized for 3 hours; then the obtained material is transferred to a tube furnace, argon inert gas is first introduced to purge the air in the tube, then acetylene gas is introduced, the temperature is raised to 800°C and carbonized for 3 hours, and then cooled to room temperature to obtain the silicon-based hard carbon composite material.

[0041] Comparative Example 3 This comparative example provides a method for preparing a silicon-based hard carbon composite material, which is basically the same as that in Example 1, except that the addition of graphene oxide is omitted in step S1.

[0042] Experimental Example 1 The high-capacity silicon-based hard carbon composite material prepared in Example 1 was subjected to SEM testing, and the results are as follows: Figure 1 As shown in the figure, the composite material prepared in Example 1 has a granular structure. The white material on the surface is silicon-based, and the size distribution is uniform with a particle size of 3-8 μm. Experiment Example 2 (1) The particle size, tap density, specific surface area, silicon content, specific capacity and initial efficiency of the silicon-based hard carbon composite materials prepared in each embodiment and comparative example were tested. The test methods refer to GBT-24533-2019 "Graphite Anode Materials for Lithium-ion Batteries".

[0043] The interlayer spacing and powder resistance of the silicon-based hard carbon composite materials prepared in each embodiment and comparative example were tested, with the interlayer spacing of the silicon-based hard carbon composite materials being tested by XRD.

[0044] The powder resistance test method is as follows: Silicon-based hard carbon composite material is pressed into a block structure at a pressure of 5T using a tablet press, and its powder resistance is tested using a four-probe tester.

[0045] (2) The silicon-based hard carbon composite materials obtained in each embodiment and comparative example are assembled into button cells and their electrical performance is tested. The specific method is as follows: add binder, conductive agent and solvent to the negative electrode material, stir and slurry, coat it on copper foil, and dry and press it to obtain the desired product. The binder used was LA132 binder (polyacrylic acid binder), the conductive agent was SP (conductive carbon black), and the negative electrode material was the silicon-based hard carbon composite material prepared in each example and comparative example. The solvent was double-distilled water, and the ratio was: negative electrode material: SP: LA132: double-distilled water = 94g: 2g: 4g: 220mL, and a negative electrode sheet was prepared. The electrolyte was LiPF6 / EC+DEC (EC to DEC volume ratio 1:1, LiPF6 concentration 1.1mol / L), the counter electrode was lithium metal sheet, and the separator was PMMA (9µm PMMA base layer + 2µm alumina upper coating + 2µm alumina lower coating, purchased from Shanghai Enjie Co., Ltd.). The simulated battery was assembled in an argon-filled glove box. Electrochemical performance was tested on a Wuhan Landian CT2001A battery tester, as follows: 1. Initial efficiency, initial discharge capacity, and cycle performance At room temperature, the battery is charged to 2.0V at 0.2C and then discharged to 0V at 0.2C to obtain the first discharge capacity (Q1) and the first charge capacity (Q2) of the battery. This process is repeated for 300 cycles to obtain the discharge capacity (Q300) of the 300th cycle.

[0046] Battery initial efficiency = Q1 / Q2 × 100%, cycle performance = (Q300 - Q1) / Q1 * 100%.

[0047] 2. Ratio performance The ambient temperature is 25℃. First, let it stand for 2 hours, then discharge at 0.1C to 0 V, and record the discharge capacity at the reference rate (0.1C) as C0. Let it stand for 60 minutes, then charge at 2C to 2 V, maintain the voltage at 0.05C, let it stand for 30 minutes, then discharge at 2C to 0 V, and record the discharge capacity at the high rate (2C) as C1. Then the 2C discharge capacity retention rate = (C1 / C0) × 100%.

[0048] 3. Full charge expansion Before assembling the battery, the thickness of the negative electrode sheet after rolling is measured as D1. Then, the button cell is charged to 0.005V at 0.1C. After that, the battery is dissected to obtain the negative electrode sheet, and the thickness of the negative electrode sheet is measured as D2. Then, the full charge expansion = (D2-D1) / D1*100%.

[0049] The test results are shown in Tables 1 and 2 below.

[0050] Table 1

[0051] Table 2

[0052] As can be seen from Tables 1 and 2, Examples 1-5 are significantly better than Comparative Examples 1-3 in terms of initial efficiency, rate performance, cycle performance, and full-charge expansion. The reason for this is that in this invention, silicon oxide is uniformly doped into the hard carbon core through the phenolic reaction, which reduces expansion and improves cycle performance. At the same time, the material surface is modified by the activation gas to increase the interlayer spacing, specific surface area, and reduce surface defects, thereby improving rate performance, reducing expansion, and improving cycle performance. Experimental Example 3 The silicon-based hard carbon composite materials obtained in each embodiment and comparative example were assembled into pouch cells and their electrical performance was tested. The specific method was as follows: the silicon-based hard carbon composite material was used as the negative electrode active material. A binder, conductive agent, and solvent were added to the negative electrode active material, and the mixture was stirred to form a slurry. This slurry was then coated onto copper foil, dried, and rolled to obtain the negative electrode sheet. The binder used was LA132 binder (polyacrylic acid binder), the conductive agent was SP (conductive carbon black), the negative electrode material was the silicon-based hard carbon composite material prepared in each embodiment and comparative example, and the solvent was double-distilled water. The ratio was: negative electrode material: SP: LA132: double-distilled water = 94g: 2g: 4g: 220mL.

[0053] With ternary materials (Li(Ni) 1 / 3 Co 1 / 3 Mn 1 / 3 O2) is the positive electrode active material. During positive electrode preparation, a binder, conductive agent, and solvent are added to the positive electrode active material and stirred until uniformly mixed to form a positive electrode slurry. The positive electrode slurry is coated onto aluminum foil, dried, rolled, and cut to obtain the positive electrode sheet. The binder is PVDF, the conductive agent is SP, and the solvent is N-methylpyrrolidone. The weight ratio of the positive electrode active material, conductive agent, binder, and solvent is 93:3:4:140, resulting in the positive electrode sheet.

[0054] Using the above-mentioned negative and positive electrodes, with LiPF6 / EC+DEC (EC to DEC volume ratio 1:1, LiPF6 concentration 1.3mol / L) as electrolyte and Celegard 2400 as separator, a 2Ah soft-pack battery was prepared.

[0055] High-temperature storage performance test: At 25℃, the battery is charged to 4.2V at a rate of 0.33C, and its capacity is measured as X1. After being placed at 60℃ for 7 days, the battery is discharged at a rate of 0.33C, and its discharge capacity is measured as X2. The charge retention is calculated as X2 / X1*100%. Then, at 25℃, the battery is fully charged to 4.2V at a rate of 0.33C, and its capacity is measured as X3. The recovery capacity is calculated as X3 / X1*100%. Cycling performance: At 25℃, the battery is charged to 4.2V at 1C, and then discharged to 2.5V at 1C to obtain the initial discharge capacity Q1. This cycle is repeated for 500 cycles to obtain the discharge capacity Q2 after the 300th cycle. Cycling performance = (Q2 - Q1) / Q1 * 100%.

[0056] Rate performance: Charge the soft-pack battery to 4.2V at a rate of 2C and calculate the capacity, denoted as A1. Then charge it at a constant current of 50mA for 60 minutes and calculate the capacity, denoted as A2. Then calculate the constant current ratio of the battery according to the following formula: Constant current ratio = A1 / (A1 + A2) * 100%.

[0057] The results are detailed in Table 3.

[0058] Table 3

[0059] As can be seen from Table 3, the high-temperature storage performance and rate performance of the batteries made of silicon-based hard carbon composite materials in each embodiment are better than those of the comparative examples. The reason is that the silicon-oxygen hard carbon precursor material is surface activated by an activator to form nano-micro pores, which reduces the expansion of silicon-oxygen material. Amorphous carbon is deposited on its outermost layer to reduce the specific surface area, thereby improving the high-temperature storage performance and constant current ratio.

[0060] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A silicon-based hard carbon composite material, characterized in that, The silicon-based hard carbon composite material includes a core and an outer shell covering the core. The core includes silicon oxide, graphene oxide, and hard carbon, and the outer shell includes amorphous carbon. The interlayer spacing of the silicon-based hard carbon composite material is 0.375~0.395 nm.

2. The silicon-based hard carbon composite material according to claim 1, characterized in that, The tap density of the silicon-based hard carbon composite material is 0.8~0.9 g / cm³. 3 ; And / or, the powder resistivity of the silicon-based hard carbon composite material is 0.202-0.276 Ω·cm; And / or, the interlayer spacing of the silicon-based hard carbon composite material is 0.38~0.39 nm.

3. A method for preparing a silicon-based hard carbon composite material, characterized in that, Includes the following steps: Step S1: Phenolic monomers, aldehyde monomers, silicon oxide materials, graphene oxide, and melamine are mixed in the presence of water, heated and reacted, and then dried to obtain silicon oxide hard carbon precursor materials. Step S2: The silicon-oxygen hard carbon precursor material is pressed, activated to create pores, and carbonized for the first time. Then, it undergoes a second carbonization treatment in the presence of carbon-containing gas to obtain a silicon-based hard carbon composite material.

4. The method for preparing the silicon-based hard carbon composite material according to claim 3, characterized in that, The mass ratio of the phenolic monomer, silicon oxide material, graphene oxide, and melamine is 200:1-5:0.5-2:1-5; And / or, the molar ratio of the phenolic monomer to the aldehyde monomer is 1:1~3; And / or, the phenolic monomers include one or more of 3-ethylamino-4-methylphenol, p-acetaminophenol, 2-amino-5-nitrophenol, p-aminophenol, and 4-aminophenol; And / or, the aldehyde monomers include one or more of formaldehyde, acetaldehyde, propionaldehyde, and benzaldehyde; And / or, the heating reaction is carried out at a temperature of 50-100°C, a pressure of 1-15 MPa, and a reaction time of 1-6 h.

5. The method for preparing the silicon-based hard carbon composite material according to claim 3 or 4, characterized in that, The pressure of the pressure block is 5-15T.

6. The method for preparing the silicon-based hard carbon composite material according to claim 3 or 4, characterized in that, The activation pore-forming process involves activation at 100-300℃ in the presence of an activation gas for 1-6 hours. Optionally, the activating gas is selected from one or more of carbon dioxide, ammonia, or oxygen.

7. The method for preparing the silicon-based hard carbon composite material according to claim 3 or 4, characterized in that, The temperature of the first carbonization treatment is 1000~1500℃, preferably 1100~1400℃; And / or, the duration of the first carbonization treatment is 1 to 6 hours; preferably 2 to 4 hours.

8. The method for preparing the silicon-based hard carbon composite material according to claim 3 or 4, characterized in that, The carbon-containing gas is selected from one or more of acetylene, methane, ethylene, and ethane; And / or, the temperature of the second carbonization treatment is 700~900℃; the time is 1~6h; And / or, the second carbonization treatment is performed by chemical vapor deposition.

9. A negative electrode sheet, characterized in that, It includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes the silicon-based hard carbon composite material according to any one of claims 1 or 2 or the silicon-based hard carbon composite material prepared according to the preparation method of the silicon-based hard carbon composite material according to any one of claims 3-8.

10. A secondary battery, characterized in that, Includes the negative electrode sheet as described in claim 9.

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