Silicon-carbon negative electrode material based on vertical graphene and preparation method and application thereof

Abstract

The application belongs to the technical field of electrode materials, and particularly relates to a silicon-carbon negative electrode material based on vertical graphene and a preparation method and application thereof. The method comprises the following steps: preparing mixed slurry containing nanosilicon-based material and micrometer graphite material; performing spray drying treatment to obtain silicon-carbon composite particles; performing sintering treatment on the silicon-carbon composite particles under a protective atmosphere, and performing screening to obtain micrometer porous silicon-carbon particles; and performing chemical vapor deposition treatment on the porous silicon-carbon particles under the condition of containing carbon source gas and etching atmosphere, to obtain the silicon-carbon negative electrode material based on vertical graphene. Vertical graphene nanosheets are grown in the internal pores and outer surface of the porous silicon-carbon particles, to form a developed and robust conductive network with high mechanical strength and structural stability, and to relieve the volume expansion of the silicon-based material in the lithium intercalation process. Meanwhile, the problem of low bulk density of the silicon-based material is solved in the secondary granulation process, the volume expansion effect of the silicon-based material is inhibited, and the rate charge-discharge performance is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrode materials, and particularly relates to a silicon-carbon negative electrode material based on vertical graphene and a preparation method and application thereof. BACKGROUND

[0002] The development of electric vehicles (EVs) has made a significant contribution to the global economy, but their market share still lags behind that of internal combustion engine vehicles. Consumer concerns about "range anxiety" have a significant impact on their purchasing decisions and hinder the widespread adoption of electric vehicles. The main way to alleviate range anxiety is to increase the energy density of the battery or reduce the charging time. However, the traditional graphite anode has a low theoretical capacity (372 mAh / g) and a low lithium insertion potential (~0.1 V), which is a major bottleneck in improving the energy density and rate performance of power batteries.

[0003] Silicon has an exceptionally high theoretical specific capacity (4200 mAh / g) and a suitable lithiation potential (0.2-0.4 V vs. Li / Li + ), providing significant potential for improving the fast charging capability and energy density of current lithium-ion batteries. However, during lithiation, silicon undergoes a volume expansion of about 400%, leading to challenges such as repeated formation of solid electrolyte interphase (SEI), electrode pulverization, and collapse of the conductive network. In addition, the inherent low electrical conductivity of silicon hinders fast electron transport during fast charging, which has a negative impact on charging performance. To alleviate these problems, a common method is to fabricate micron-scale silicon-carbon negative electrodes by combining nanoscale silicon particles smaller than the critical size (~150 nm) with carbon materials.

[0004] However, the current silicon-carbon negative electrode material still has the following problems: first, the volume expansion of silicon particles during lithium intercalation leads to electrode pulverization and collapse of the conductive network; second, excessive concentration polarization caused by poor conductive network leads to uneven expansion of silicon particles, which in turn destroys the electrode structure, reduces high-rate charge-discharge performance, and shortens cycle life; third, unevenly stable SEI increases side reactions, reducing initial efficiency and cycle life. SUMMARY

[0005] The purpose of the present application is to provide a silicon-carbon negative electrode material based on vertical graphene and a preparation method and application thereof, which aims to solve the problem of silicon particle volume expansion, electrode, conductive network, and SEI film stability in existing silicon-carbon negative electrode materials to some extent.

[0006] To achieve the above application purposes, the technical solutions adopted by the present application are as follows:

[0007] In a first aspect, the present application provides a preparation method of a silicon-carbon negative electrode material based on vertical graphene, comprising the following steps:

[0008] a mixed slurry containing a nanosilicon-based material and a micrometer graphite material is prepared;

[0009] the mixed slurry is subjected to a spray drying process to obtain silicon-carbon composite particles;

[0010] the silicon-carbon composite particles are subjected to a sintering process in a protective atmosphere, and are sieved to obtain micrometer porous silicon-carbon particles;

[0011] the porous silicon-carbon particles are subjected to a chemical vapor deposition process in a carbon source gas and etching atmosphere, so that vertical graphene nanosheets grow in the internal pores and external surface of the porous silicon-carbon particles, to obtain a vertical graphene-based silicon-carbon negative electrode material.

[0012] In a second aspect, the present application provides a vertical graphene-based silicon-carbon negative electrode material, comprising porous silicon-carbon particles and vertical graphene nanosheets grown in the internal pores and external surface of the porous silicon-carbon particles.

[0013] In a third aspect, the present application provides a negative electrode sheet, comprising a current collector and a negative electrode active layer formed on the surface of the current collector, wherein the negative electrode active layer contains the vertical graphene-based silicon-carbon negative electrode material prepared by the above method, or the vertical graphene-based silicon-carbon negative electrode material described above.

[0014] In a fourth aspect, the present application provides a secondary battery containing the negative electrode sheet described above.

[0015] The preparation method of the vertical graphene-based silicon-carbon negative electrode material provided in the first aspect of the present application is as follows: after a mixed slurry containing a nano-silicon-based material and a micro graphite material is prepared, the mixed slurry is granulated by using a spray drying method. The spray drying is a simple, fast, low-cost and scalable technology. In the spray drying process, the nano-silicon-based material and the micro graphite material coexist as a whole in time and space. The silicon-based material and the graphite material with different particle sizes are granulated to form silicon-carbon composite particles with a micro size, and the silicon-carbon composite particles are endowed with new properties that cannot be provided by a single component. The silicon-carbon composite particles are subjected to a sintering treatment in a protective atmosphere, the structure of the silicon-carbon composite particles is stabilized, impurity components and active sites in the composite particles are removed, and the micro porous silicon-carbon particles are obtained through screening. The porous silicon-carbon particles are subjected to a chemical vapor deposition treatment in a carbon source gas and etching atmosphere, vertical graphene nanosheets grow in the internal pores and on the outer surface of the porous silicon-carbon particles, and the vertical graphene-based silicon-carbon negative electrode material is obtained. Through the combination of spray drying and chemical vapor deposition, the vertical graphene nanosheets grow in the internal pores and on the outer surface of the micro porous silicon-carbon particles through secondary granulation. The flexible vertical graphene nanosheets form a high-strength conductive network with directional channels, which can better alleviate the volume expansion of the silicon-based material during lithium intercalation. At the same time, the problem of low bulk density of the silicon-based material is significantly solved in the secondary granulation process, and the high-performance porous silicon-carbon particles are jointly produced, which suppresses the volume expansion effect of the silicon-based material and improves the rate charge-discharge performance.

[0016] The vertical graphene-based silicon-carbon negative electrode material provided in the present application includes porous silicon-carbon particles and vertical graphene nanosheets grown in the internal pores and on the outer surface of the porous silicon-carbon particles. The flexible vertical graphene nanosheets form a high-strength conductive network with directional channels, which allows the electrode to operate at a high area load without pulverization and can better alleviate the volume expansion of the silicon-based material during lithium intercalation. Therefore, the negative electrode material has high mechanical strength, structural stability and a developed and robust conductive structure. When the silicon-carbon negative electrode material is applied to a secondary battery, a uniform and stable SEI layer can be formed on the surface of the silicon-carbon negative electrode during the operation of the battery, thereby improving the high-quality specific capacity, structural stability at a high load and good cycle performance of the battery, and other electrochemical properties.

[0017] The negative electrode active layer of the negative electrode sheet provided in the present application contains the vertical graphene-based silicon-carbon negative electrode material described above, which has high mechanical strength, structural stability and a developed and robust conductive structure, and thus can improve the structure and cycle stability of the negative electrode sheet, improve the carrier transport efficiency, and improve the energy density and rate performance of the electrode sheet.

[0018] The secondary battery comprises the negative electrode sheet, and has high structural stability and cycle stability, high carrier transport efficiency, high energy density and high rate performance, and can improve the cycle life, energy density and rate performance and other electrochemical properties of the secondary battery. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0020] Figure 1 is a flowchart of a preparation method of a silicon-carbon negative electrode material based on vertical graphene provided by an embodiment of the present application;

[0021] Figure 2 is a scanning electron microscope image of a silicon-carbon negative electrode material s-Gr / n-Si / VGs provided by embodiment 1 of the present application based on vertical graphene;

[0022] Figure 3 is a transmission electron microscope image of a silicon-carbon negative electrode material s-Gr / n-Si / VGs provided by embodiment 1 of the present application based on vertical graphene;

[0023] Figure 4 is an XRD image of a silicon-carbon negative electrode material s-Gr / n-Si / VGs provided by embodiment 1 of the present application based on vertical graphene;

[0024] Figure 5 is a Raman spectrum image of a silicon-carbon negative electrode material s-Gr / n-Si / VGs provided by embodiment 1 of the present application based on vertical graphene;

[0025] Figure 6 is a CV curve image of a button cell prepared by a silicon-carbon negative electrode material s-Gr / n-Si / VGs provided by embodiment 1 of the present application based on vertical graphene;

[0026] Figure 7 is a GCD curve image of a button cell prepared by a silicon-carbon negative electrode material s-Gr / n-Si / VGs provided by embodiment 1 of the present application based on vertical graphene;

[0027] Figure 8 is a mechanism diagram of SEI on the surface of a silicon-carbon negative electrode material s-Gr / n-Si / VGs after a button cell prepared by the silicon-carbon negative electrode material s-Gr / n-Si / VGs provided by embodiment 1 of the present application based on vertical graphene is subjected to charge and discharge tests;

[0028] Figure 9 is the cryo-EM test of the silicon-carbon negative electrode material s-Gr / n-Si / VGs after the charge-discharge test of the button cell prepared based on the vertical graphene-based silicon-carbon negative electrode material s-Gr / n-Si / VGs provided in Embodiment 1 of the present application. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and beneficial effects to be solved in the present application clearer, the present application will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0030] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0031] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one" or similar expressions mean any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b or c", or "at least one of a, b and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b and c can be single or multiple.

[0032] It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence, and the execution order of the processes should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0033] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0034] The weight of the related components mentioned in the embodiments of the present application can not only refer to the specific content of each component, but also represent the weight ratio relationship between each component, therefore, as long as the content of the related components in the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the embodiments of the present application. Specifically, the mass mentioned in the embodiments of the present application can be μg, mg, g, kg and other mass units commonly known in the chemical field.

[0035] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0036] The term "SEI" is an abbreviation for "Solid Electrolyte Interface membrane." The SEI membrane is a passivation layer formed on the surface of the electrode material during the first charge and discharge cycle of a lithium-ion battery, resulting from the reaction between the electrode material and the electrolyte at the solid-liquid interface. Located between the battery's electrodes and electrolyte, it exhibits the properties of a solid electrolyte.

[0037] Silicon possesses an exceptionally high theoretical specific capacity (4200 mAh / g) and a suitable lithiation potential (0.2–0.4 V vs Li / Li+), offering significant potential for improving the fast-charging capability and energy density of current lithium-ion batteries. However, during lithiation, silicon undergoes approximately 400% volume expansion, leading to challenges such as repetitive solid electrolyte interphase (SEI) formation, electrode fragmentation, and the collapse of the conductive network. Furthermore, silicon's inherently low conductivity hinders rapid electron transport during fast charging, negatively impacting charging performance. To mitigate these issues, a common approach is to fabricate micron-scale silicon-carbon anodes using nanoscale silicon particles smaller than the critical size (~150 nm) in conjunction with carbon materials. This strategy not only addresses the challenges of silicon volume expansion and poor conductivity but also overcomes the adverse effects of the low density of nanomaterials. Currently, silicon-carbon anode materials still have the following problems: First, the volume expansion of silicon particles during lithium intercalation leads to electrode pulverization and the collapse of the conductive network; Second, the excessive concentration polarization caused by poor conductive network leads to uneven expansion of silicon particles, which in turn damages the electrode structure, reduces high-rate charge-discharge performance, and shortens cycle life; Third, the non-uniform and unstable SEI increases side reactions, reducing initial efficiency and cycle life.

[0038] The optimal micron-scale silicon-carbon composite electrode should meet the following criteria: ① High mechanical strength and structural stability. The considerable volume changes that silicon undergoes during repeated charge-discharge cycles generate significant stress. High mechanical strength and a robust electrode structure are crucial to preventing damage to the electrode structure and the collapse of the conductive network, thereby improving cycle life. ② A well-developed and robust conductive network. Micron-sized particles require rapid ion / electron transport to reduce polarization. Excessive concentration polarization leads to uneven particle expansion, which in turn damages the electrode structure, reduces high-rate charge-discharge performance, and shortens cycle life. ③ A uniform and stable SEI layer. During lithiation and delithiation, the significant volume changes of silicon result in repeated exposure to the electrolyte, leading to the formation of the SEI—one of the main causes of capacity decay in silicon anodes. The formation of a uniform and stable SEI can reduce side reactions, improve initial efficiency and cycle life, establish robust ion transport channels, and improve fast-charging performance. To enable large-scale commercial applications of micron-scale silicon-carbon anodes, these criteria must be met while minimizing production costs.

[0039] In some embodiments, graphene oxide (GO) is coated onto silicon nanoparticles using spray drying to assemble ultrafine particles, followed by atomic layer deposition (ALD) of alumina to reduce the surface silicon content and construct an artificial SEI. The resulting Si@rGO@C-SD-AlO exhibits a capacity of 900 mAh / g at a current density of 1 A / g after 1000 cycles and 806 mAh / g at 5 A / g. However, graphene oxide is significantly more expensive than graphite-based carbon materials, and the ALD process is costly and unsuitable for large-scale production. In some embodiments, resorcinol-formaldehyde resin and commercial silica sol are used as templates and silicon precursors, respectively, for spray drying, followed by magnesium thermal reduction (MRR) to produce porous silicon. A thin carbon layer is then coated by chemical vapor deposition (CVD) to reduce cycling stress and improve conductivity. The prepared M-pSi@C exhibits a high capacity of 1002 mAh / g after 500 cycles at 2 A / g, with a capacity retention of 95%. However, the MRR process is only suitable for small-scale preparation and raises safety concerns for large-scale production. In some embodiments, silicon nanoparticles, graphite nanosheets, carbon nanotubes, and resin carbon are uniformly mixed, followed by spitting and CVD to reduce the surface silicon content. The resulting high mechanical strength Si / C-HIP exhibits a capacity of 650 mAh / g after 1000 cycles, with a capacity retention of 83.8%. However, the high cost of carbon nanotubes and the excessive carbon source result in high raw material costs and a discontinuous conductive network.

[0040] Therefore, utilizing spray drying technology for the production of silicon-carbon anodes requires a low-cost, highly safe, and scalable process chain. Furthermore, it must meet the three design criteria mentioned earlier, which remains a significant challenge. Developing innovative solutions to address these key issues is crucial for improving the performance and manufacturability of silicon-carbon anodes.

[0041] To address the shortcomings of current silicon-carbon anode materials, the first aspect of this application provides a method for preparing a silicon-carbon anode material based on vertical graphene, as shown in the attached figure. Figure 1 As shown, it includes the following steps:

[0042] S10. Prepare a mixed slurry containing nano-silicon-based materials and micro-graphite materials;

[0043] S20. The mixed slurry is spray-dried to obtain silicon-carbon composite particles;

[0044] S30. The silicon-carbon composite particles are sintered under a protective atmosphere and then sieved to obtain micron-sized porous silicon-carbon particles.

[0045] S40. Under conditions containing carbon source gas and etching atmosphere, porous silicon-carbon particles are subjected to chemical vapor deposition treatment to grow vertical graphene nanosheets in the internal pores and outer surface of the porous silicon-carbon particles, thereby obtaining silicon-carbon anode material based on vertical graphene.

[0046] The method for preparing silicon-carbon anode materials based on vertical graphene provided in the first aspect of this application involves preparing a mixed slurry containing nano-silicon-based materials and micron-sized graphite materials, followed by granulation using spray drying. Spray drying is a simple, rapid, low-cost, and scalable technology. During the spray drying process, the nano-silicon-based materials and micron-sized graphite materials coexist as a whole in time and space, granulating silicon-based materials and graphite materials of different particle sizes into micron-sized silicon-carbon composite particles, endowing the silicon-carbon composite particles with new properties that cannot be provided by a single component. The silicon-carbon composite particles are sintered under a protective atmosphere to stabilize the structure of the silicon-carbon composite particles, remove impurities and active sites from the composite particles, and sieve to obtain micron-sized porous silicon-carbon particles. Under conditions containing carbon source gas and an etching atmosphere, the porous silicon-carbon particles are subjected to chemical vapor deposition treatment, causing vertical graphene nanosheets to grow in the internal pores and on the outer surface of the porous silicon-carbon particles, thus obtaining silicon-carbon anode materials based on vertical graphene. This application utilizes a combination of spray drying and chemical vapor deposition (CVD) to achieve secondary granulation, enabling the growth of vertical graphene nanosheets within the pores and on the outer surface of micron-sized porous silicon-carbon particles. In the silicon-carbon anode material based on vertical graphene, the flexible vertical graphene nanosheets form a high-strength conductive network with oriented channels, allowing operation under high areal loads without electrode pulverization and effectively mitigating the volume expansion of silicon-based materials during lithium intercalation. Simultaneously, the secondary granulation process significantly addresses the low packing density issue of silicon-based materials, collectively producing high-performance porous silicon-carbon particles that suppress the volume expansion effect of silicon-based materials and improve rate charge / discharge performance. The silicon-carbon anode material prepared by this method possesses high mechanical strength, structural stability, and a well-developed and robust conductive network. This facilitates the formation of a uniform and stable SEI layer on the surface of the silicon-carbon anode material during battery operation, contributing to improved specific capacity, structural stability under high loads, and good cycle performance when used as a secondary battery anode material.

[0047] In step S10 above:

[0048] In some possible implementations, the solid content of the mixed slurry is 20% to 40%; for example, the solid content of the mixed slurry can be any typical but non-limiting point value or a range between any two points, such as 20%, 25%, 30%, 35%, or 40%. In this case, the solid content of the mixed slurry is more conducive to subsequent spray granulation, ensuring that the particles dry quickly after spraying and do not clog the nozzle.

[0049] In some possible implementations, the mass ratio of nano-silicon-based material to micron-graphite material in the mixed slurry is (5–20):(80–95). This ratio is beneficial for improving the dispersion stability of the mixed slurry, facilitating subsequent spray drying, and ensuring the silicon content in the silicon-carbon anode material, thus guaranteeing a balance between the capacity and structural stability of the silicon-carbon anode material. In this case, the mass ratio of nano-silicon-based material to micron-graphite material in the mixed slurry can be a typical but not limiting arbitrary point value or a range between any two points, such as 5:95, 10:90, 15:85, or 20:80.

[0050] In some possible implementations, the average particle size of the nano-silicon-based material is 30 nm to 500 nm. In this case, the silicon-based material used is a 30 nm to 500 nm nanoscale particle, and the smaller the particle size, the smaller the corresponding volume expansion effect. For example, the average particle size of the nano-silicon-based material can be any typical but non-limiting point value or a range between any two points, such as 30 nm, 50 nm, 100 nm, 150 nm, 200 nm, 300 nm, 400 nm, 500 nm, etc.

[0051] In some possible implementations, the nano-silicon-based material includes at least one of elemental silicon, silicon oxide, and silicon carbide; these silicon-based materials all have high capacity.

[0052] In some embodiments, the nano-silicon-based material uses elemental silicon with an average particle size of 30 nm to 50 nm.

[0053] In some possible implementations, the average particle size of the micron-sized graphite material is 6 μm to 15 μm. In this case, the graphite material consists of micron-sized particles of 6 μm to 15 μm, which is relatively small and facilitates the formation of a stable composite particle structure with the nano-silicon-based material. This improves the structural stability and conductivity of the silicon-carbon composite particles and helps suppress the volume expansion of the silicon-based material. For example, the average particle size of the micron-sized graphite material can be any typical but non-limiting point value or a range between any two points, such as 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, or 15 μm.

[0054] In step S20 above:

[0055] In some possible implementations, the feed rate for spray drying is 100 mL / h to 500 mL / h, the spray gas pressure is 1 bar to 3 bar, the nozzle diameter is 100 μm to 200 μm, and the drying temperature is 150℃ to 200℃. Under these conditions, the feed rate and spray gas pressure are conducive to ensuring good atomization, the nozzle diameter is beneficial for controlling the particle size of the sprayed slurry, and the drying temperature avoids the adverse effects of high temperatures on material properties. By adjusting the feed rate, spray gas pressure, nozzle diameter, and drying temperature, the spray drying effect can be flexibly controlled.

[0056] For example, the feed rate of the spray drying process can be any typical but non-limiting point value or a range between any two points, such as 100 mL / h, 200 mL / h, 300 mL / h, 400 mL / h, 500 mL / h; the spray gas pressure can be any typical but non-limiting point value or a range between any two points, such as 1 bar, 2 bar, 3 bar; the nozzle diameter can be any typical but non-limiting point value or a range between any two points, such as 100 μm, 120 μm, 150 μm, 180 μm, 200 μm; and the drying temperature can be any typical but non-limiting point value or a range between any two points, such as 150℃, 160℃, 170℃, 180℃, 190℃, 200℃.

[0057] In step S30 above:

[0058] In some possible implementations, the protective atmosphere includes at least one of argon, nitrogen, and helium; the silicon-carbon composite particles are sintered under the protective atmosphere to avoid high-temperature oxidation of the silicon-carbon composite particles.

[0059] In some possible implementations, the sintering temperature does not exceed 600℃, and the sintering time is 1h to 3h. Sintering at relatively low temperatures can quickly stabilize the silicon-carbon composite particle structure, ensuring good bonding between silicon and graphite, while simultaneously removing impurities and some active sites, preventing excessive oxidation. For example, the sintering temperature can be any typical but non-limiting value, such as 100℃, 200℃, 300℃, 400℃, 500℃, or 600℃, or a range between any two values; the sintering time can be any typical but non-limiting value, such as 1h, 2h, or 3h, or a range between any two values.

[0060] In some possible implementations, the cooling rate after sintering is 1℃ / min to 5℃ / min. In this case, using a relatively low cooling rate helps to prevent internal stress caused by rapid cooling and improves the structural stability of the porous silicon-carbon particles. For example, the cooling rate after sintering can be a typical but non-limiting arbitrary point value or a range between any two points, such as 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, or 5℃ / min.

[0061] In some possible implementations, the average particle size of the porous silicon-carbon particles is 10 μm to 50 μm. In this case, the particle size of the porous silicon-carbon particles can better meet the application requirements of secondary batteries, which is beneficial to improving the electrochemical performance of the electrode sheet, such as compaction density, areal capacity, and energy density. For example, the average particle size of the porous silicon-carbon particles can be any typical but non-limiting point value or a range between any two points, such as 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm.

[0062] In some possible implementations, the porosity of the porous silicon-carbon particles ranges from 15% to 40%. In this case, the porosity of the porous silicon-carbon particles is beneficial for the subsequent vertical growth of graphene nanosheets while ensuring the structural stability of the porous silicon-carbon particles. For example, the porosity of the porous silicon-carbon particles can be any typical but non-limiting point value or a range between any two point values, such as 15%, 20%, 25%, 30%, 35%, or 40%.

[0063] In step S40 above:

[0064] In some possible implementations, the flow rate of the inert atmosphere during the chemical vapor deposition process is 30 mL / min to 80 mL / min. In some possible implementations, the inert atmosphere includes at least one of argon, nitrogen, and helium. In this case, the inert atmosphere is used to remove oxidizing gas components from the reaction system, improving reaction purity, while simultaneously controlling the content of carbon source gas and etching atmosphere to improve the efficiency of vertical growth of graphene nanosheets. Exemplarily, the flow rate of the inert atmosphere during the chemical vapor deposition process can be any typical but non-limiting point value or a range between any two points, such as 30 mL / min, 40 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, or 80 mL / min.

[0065] In some possible implementations, the carbon source gas includes at least one of methane, ethanol, and acetylene; these carbon source gases can induce the growth of vertical graphene nanosheets.

[0066] In some possible implementations, the flow rate of the carbon source gas is 10 mL / min to 20 mL / min; at this flow rate, the carbon source gas can better induce the growth of vertical graphene nanosheets. For example, the flow rate of the carbon source gas can be a typical but non-limiting arbitrary point value or a range between any two points, such as 10 mL / min, 13 mL / min, 15 mL / min, 18 mL / min, or 20 mL / min.

[0067] In some possible implementations, the etching atmosphere includes at least one etching gas selected from hydrogen, ammonia, oxygen, and hydrogen fluoride, and at least one carrier gas selected from argon, nitrogen, and helium. The etching gas can regulate the number of carbon atoms deposited, thereby achieving a vertically oriented growth structure of graphene nanosheets. Flexible vertical graphene nanosheets form a high-strength conductive network with oriented channels within the silicon-carbon composite particles, creating a highly mechanically strong, structurally stable, and robust conductive network. This improves the conductivity of the silicon-carbon anode and suppresses the volume expansion effect of silicon-based anode materials.

[0068] In some possible implementations, the volume percentage of the etching gas in the etching atmosphere is 70% to 90%. In this case, the content of the etching gas sufficiently ensures that graphene nanosheets grow vertically within the internal pores and outer surface of the porous silicon-carbon particles, thereby enhancing the vertical growth of graphene. Exemplarily, the volume percentage of the etching gas in the etching atmosphere can be any typical but non-limiting point value or a range between any two points, such as 70%, 75%, 80%, 85%, or 90%.

[0069] In some possible implementations, the flow rate of the etching atmosphere is 100 mL / min to 200 mL / min; in this case, the vertical growth of graphene can be better enhanced, achieving a vertically oriented structure in the internal pores and outer surface of the porous silicon-carbon particles. Exemplarily, the flow rate of the etching atmosphere can be any typical but non-limiting point value or a range between any two points, such as 100 mL / min, 120 mL / min, 150 mL / min, 180 mL / min, or 200 mL / min.

[0070] In some embodiments, during the chemical vapor deposition process, the flow rate of the inert atmosphere is 30 mL / min to 80 mL / min; the flow rate of the carbon source gas is 10 mL / min to 20 mL / min; and the flow rate of the etching atmosphere is 100 mL / min to 200 mL / min. The inert atmosphere includes at least one of argon, nitrogen, and helium; the carbon source gas includes at least one of methane, ethanol, and acetylene; the etching atmosphere includes at least one etching gas selected from hydrogen, ammonia, oxygen, and hydrogen fluoride, and at least one carrier gas selected from argon, nitrogen, and helium; and the volume percentage of the etching gas in the etching atmosphere is 70% to 90%.

[0071] In some possible implementations, the heating rate of chemical vapor deposition (CVD) is 5℃ / min to 10℃ / min, the holding temperature is 1000℃ to 1200℃, and the holding time is 8h to 30h. Under these temperature conditions, the carbon source gas can be decomposed smoothly, initiating the growth of vertical graphene; the growth of vertical graphene is enhanced under the action of the etching atmosphere, while avoiding the formation of by-products and improving product purity.

[0072] In some possible implementations, the chemical vapor deposition process includes: heating to 1000℃ to 1100℃ at a heating rate of 5℃ / min to 10℃ / min under an inert atmosphere with a flow rate of 30mL / min to 80mL / min, then introducing a carbon source gas and an etching atmosphere, and holding at 1100℃ to 1200℃ for 8h to 30h to grow vertical graphene nanosheets, thereby growing vertical graphene nanosheets in the internal pores and on the outer surface of porous silicon carbon particles.

[0073] For example, chemical vapor deposition (CVD) is performed under inert atmosphere flow rates of 30 mL / min, 40 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, etc., with heating rates of 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, 10 °C / min, etc., to reach 1000 °C, 1050 °C, 1100 °C, etc., respectively. Then, carbon source gas and etching atmosphere are introduced, and the temperature is maintained at 1100 °C, 1150 °C, 1200 °C, etc. for 8 h, 10 h, 15 h, 20 h, 25 h, 30 h, etc., to grow vertical graphene nanosheets, thereby growing vertical graphene nanosheets in the internal pores and outer surface of porous silicon carbon particles.

[0074] In some possible implementations, the silicon-based material in the vertical graphene-based silicon-carbon anode material has a silicon-based material mass percentage of 5% to 20%. In this case, the capacity of the vertical graphene-based silicon-carbon anode material is sufficiently ensured, guaranteeing a balance between battery capacity and structural stability. For example, the silicon-based material mass percentage in the vertical graphene-based silicon-carbon anode material can be any typical but non-limiting point value or a range between any two points, such as 5%, 8%, 10%, 15%, 18%, or 20%.

[0075] In some possible implementations, the mass percentage of vertical graphene nanosheets in the vertical graphene-based silicon-carbon anode material is 5% to 15%. In this case, it sufficiently ensures the formation of a highly mechanically strong, structurally stable, and robust conductive network within the silicon-carbon composite particles, thereby improving the conductivity of the silicon-carbon anode and suppressing the volume expansion effect of the silicon-based anode material. For example, the mass percentage of vertical graphene nanosheets in the vertical graphene-based silicon-carbon anode material can be any typical but non-limiting point value or a range between any two points, such as 5%, 8%, 10%, 12%, or 15%.

[0076] In some possible implementations, the graphite content in the silicon-carbon anode material based on vertical graphene is 65%–90% by mass. In this case, the graphite content can effectively mitigate the volume expansion efficiency of the silicon-based material and maintain the structural stability of the silicon-based anode material. For example, in the silicon-carbon anode material based on vertical graphene, the graphite content can be any typical but non-limiting point value or a range between any two points, such as 65%, 70%, 75%, 80%, 85%, or 90%.

[0077] In some embodiments, in the silicon-carbon anode material based on vertical graphene, the mass percentage of silicon-based material is 5% to 20%; the mass percentage of vertical graphene nanosheets is 5% to 15%; and the mass percentage of graphite material is 65% to 90%.

[0078] Secondly, embodiments of this application provide a silicon-carbon anode material based on vertical graphene, comprising porous silicon-carbon particles and vertical graphene nanosheets grown in the internal pores and on the outer surface of the porous silicon-carbon particles.

[0079] This application presents a silicon-carbon anode material based on vertical graphene, comprising porous silicon-carbon particles and vertical graphene nanosheets grown on the internal pores and outer surface of the porous silicon-carbon particles. The flexible vertical graphene nanosheets form a high-strength conductive network with oriented channels, allowing operation under high areal loads without electrode pulverization, and effectively mitigating the volume expansion of silicon-based materials during lithium intercalation. This ensures the anode material possesses high mechanical strength, structural stability, and a robust conductive structure. When applied to secondary batteries, the silicon-carbon anode material forms a uniform and stable SEI layer on the silicon-carbon anode surface during battery operation, thereby improving the battery's high specific capacity, structural stability under high loads, and excellent cycle performance, among other electrochemical characteristics.

[0080] The silicon-carbon anode material based on vertical graphene in this application embodiment can be prepared by the preparation method of the silicon-carbon anode material based on vertical graphene described in the above embodiment.

[0081] In some possible implementations, the average particle size of silicon-carbon anode materials based on vertical graphene ranges from 10 μm to 50 μm. This better meets the application requirements of secondary batteries and is beneficial for improving the electrochemical performance of the electrode sheet, such as compaction density, areal capacity, and energy density.

[0082] In some possible implementations, the silicon-carbon anode material based on vertical graphene contains 5%–20% silicon-based material by mass; 5%–15% vertical graphene nanosheets by mass; and 65%–90% graphite material by mass. This simultaneously ensures the high specific capacity, high structural stability, cycle stability, and high conductivity of the silicon-carbon anode material based on vertical graphene.

[0083] Thirdly, embodiments of this application provide a negative electrode sheet, including a current collector and a negative electrode active layer formed on the surface of the current collector. The negative electrode active layer contains a silicon-carbon negative electrode material based on vertical graphene prepared by the above method, or the aforementioned silicon-carbon negative electrode material based on vertical graphene.

[0084] The negative electrode active layer of the negative electrode sheet in this application embodiment contains the above-mentioned silicon-carbon negative electrode material based on vertical graphene. The silicon-carbon negative electrode material has electrochemical characteristics such as high mechanical strength, structural stability and well-developed and robust conductive structure, which can improve the structural and cycle stability of the negative electrode sheet, improve the carrier transport efficiency, and improve the energy density and rate capability of the electrode sheet.

[0085] In some possible implementations, the mass percentage of the silicon-carbon anode material based on vertical graphene in the negative electrode active layer is 85% to 90%. Under this condition, the energy density of the anode sheet can be sufficiently ensured. For example, the mass percentage of the silicon-carbon anode material based on vertical graphene in the negative electrode active layer can be any typical but non-limiting point value or a range between any two points, such as 85%, 86%, 87%, 88%, 89%, or 90%.

[0086] In some possible implementations, the current collector of the negative electrode includes, but is not limited to, any one of copper foil or aluminum foil.

[0087] In some possible implementations, the negative electrode active layer also contains a binder, which includes any one or a combination of at least two of ethylene-vinyl acetate copolymer, polyethylene, unsaturated polyester, silicone rubber, polyurethane rubber or ethylene propylene rubber, preferably ethylene-vinyl acetate copolymer.

[0088] In some possible implementations, the negative electrode active layer also contains a conductive agent, which includes any one or a combination of at least two of carbon black, conductive graphite, carbon fiber, carbon nanotubes or graphene, preferably carbon fiber.

[0089] In some possible implementations, the mass ratio of the silicon-carbon anode material based on vertical graphene, the binder, and the conductive agent in the anode active layer is (85–90):(5–15):(1–5).

[0090] In some possible implementations, the steps for making the negative electrode sheet include: mixing the negative electrode active material with conductive agents such as conductive carbon black, binders such as carboxymethyl cellulose and styrene-butadiene rubber, and solvents such as water in a mass ratio of (85-90):(1-5):(5-15):100 to form a negative electrode slurry, then degassing under vacuum, discharging the material, coating it on a coating machine, and obtaining the negative electrode sheet after rolling, slitting, and die-cutting.

[0091] Fourthly, embodiments of this application provide a secondary battery, which includes the aforementioned negative electrode sheet.

[0092] The secondary battery in this application embodiment includes the above-mentioned negative electrode sheet. The negative electrode sheet has a high structure and cycle stability, high carrier transport efficiency, high energy density and rate performance, and can improve the electrochemical performance of the secondary battery, such as cycle life, energy density and rate performance.

[0093] This application does not specifically limit the positive electrode, electrolyte, separator, etc. in the secondary battery of the embodiments, and can be applied to any battery system.

[0094] In some possible implementations, the positive electrode includes a current collector and a positive electrode active layer formed on the surface of the current collector.

[0095] In some possible implementations, the preparation of the positive electrode sheet includes the following steps: mixing the positive electrode material, conductive agent and binder to form an electrode slurry, coating the electrode slurry onto the current collector, and then preparing the positive electrode sheet through steps such as drying, rolling and die cutting.

[0096] In some possible implementations, the mass percentage of the positive electrode material in the positive electrode active layer of the positive electrode sheet is 90% to 95%.

[0097] In some possible implementations, the current collector of the positive electrode includes, but is not limited to, any one of copper foil or aluminum foil.

[0098] In some possible implementations, the binder content in the positive electrode active material layer is 2wt% to 5wt%.

[0099] In some possible implementations, the binder includes one or more of the following: polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives.

[0100] In some possible implementations, the conductive agent content in the positive electrode active material layer is 1 wt% to 5 wt%.

[0101] In some possible implementations, the conductive agent includes graphite, carbon black, acetylene black, graphene, carbon fiber, and C. 60 And one or more of carbon nanotubes.

[0102] In some possible implementations, the membrane is capable of blocking electrons while allowing ions to pass through. Exemplary membranes include, but are not limited to, at least one material selected from polypropylene fibers, polyacrylonitrile fibers, polyvinyl formal fibers, poly(ethylene glycol terephthalate), polyethylene terephthalate, polyamide fibers, and poly(p-phenylene terephthalamide).

[0103] In some possible implementations, the electrolyte comprises at least one soluble metal salt. In some specific embodiments, the metal salt includes LiClO4, LiBF4, LiPF6, LiAsF6, LiCF3SO3, LiTDI, Li[(CF3SO2)2N], Li[(FSO2)2N], Li[(C m F 2m+1 SO2)(C n F 2n+1 At least one of SO2(N)[m, n], where m and n are natural numbers. These electrolytic salts can ensure high ionic conductivity of the electrolyte and do not undergo harmful side reactions with electrode materials, electrolyte, diaphragm, etc., and have good chemical stability.

[0104] In some possible implementations, the secondary battery includes at least one of a battery cell, a battery module, and a battery pack.

[0105] In some possible implementations, the battery cell types include lithium-ion batteries, as well as novel batteries such as lithium-air batteries and lithium metal batteries.

[0106] In some possible implementations, the battery cells of this application embodiment can be assembled into a battery module. The number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Furthermore, the battery module may also include a housing with a receiving space, in which multiple battery cells are received.

[0107] In one possible implementation, battery cells and / or battery modules can also be assembled into a battery pack, and the number of battery cells or battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0108] To enable those skilled in the art to clearly understand the above-described implementation details and operations of this application, and to demonstrate the significant advancements in the performance of the silicon-carbon anode material based on vertical graphene, its preparation method, and its application in the embodiments of this application, the following examples illustrate the above technical solutions.

[0109] Example 1

[0110] A silicon-carbon anode material based on vertical graphene, the preparation of which includes the following steps:

[0111] 1. Prepare the mixed slurry: Weigh 12.5g of s-Gr (micron graphite material with an average particle size of 10μm) and 2.5g of n-Si (nano silicon with an average particle size of 50nm) and place them in a beaker. Mix them thoroughly to obtain the mixed slurry.

[0112] 2. Spray drying: The slurry concentration is controlled at 25%, the feed rate is generally 270 mL / h, and the spray gas pressure is between 1.5 bar to ensure good atomization. A nozzle diameter of 130 μm and a drying temperature of 160℃ are used to spray dry the mixed slurry to obtain silicon-carbon composite particles.

[0113] 3. Sintering: The sintering temperature is controlled at 500℃ and the sintering time is 2h. The sintering process is carried out in an argon protective atmosphere. In the post-treatment stage, the cooling rate is controlled at 5℃ / min to sinter the silicon-carbon composite particles. S-Gr / n-Si particles with a diameter between 10 and 50 micrometers are screened out to obtain micron-sized porous silicon-carbon particles with a porosity of about 20%.

[0114] 4. CVD Process: s-Gr / n-Si particles are placed in a crucible at the center of the furnace. The furnace tubes are thoroughly purged with Ar at a flow rate of 200 mL / min to eliminate any residual air. Under ambient pressure, the temperature is gradually increased at a stable rate of 8 °C / min with a continuous argon flow rate of 50 mL / min. When the temperature reaches 1050 °C, acetylene is introduced at a flow rate of 10 mL / min, followed by an H2 / Ar mixture at a flow rate of 150 mL / min. Finally, the temperature is maintained at 1100 °C for 12 hours to allow vertical graphene nanosheets to grow on the internal pores and outer surface of the porous silicon-carbon particles, resulting in a silicon-carbon anode material based on vertical graphene, labeled s-Gr / n-Si / VGs. The content of silicon-based material is 10%, the content of graphene nanosheets is 10%, and the content of graphite is 80%.

[0115] A negative electrode is prepared by means of the following steps: coating a slurry composed of s-Gr / n-Si / VGs active material, carbon black, SBR, and CMC in a mass ratio of 8:1:0.5:0.5 onto copper foil, and then drying it under vacuum at 80°C for 12 hours. The electrode weight ranges from 0.8 to 1.5 mg / cm³. 2 s-Gr / n-Si / VGs electrodes were prepared.

[0116] A secondary battery is prepared by the following steps:

[0117] The prepared s-Gr / n-Si / VGs electrode was cut into small pieces with a diameter of 10 mm and used as the working electrode in the CR2032 coin cell. The cell was assembled in an argon-filled glove box, with moisture and oxygen concentrations maintained below 0.01 ppm. Lithium foil was used as the counter electrode; a Celgard 2500 membrane was used as the separator; the electrolyte was prepared by dissolving 1 M LiPF6 in a mixture of ethylene carbonate (EC), dimethyl carbonate (DEC), and diethyl carbonate (DMC) in a volume ratio of 1:1:1, with 5% fluoroethylene carbonate (FEC) added. The coin cell was then assembled.

[0118] Example 2

[0119] A silicon-carbon anode material based on vertical graphene, the preparation of which includes the following steps:

[0120] 1. Prepare the mixed slurry: Weigh 15g of s-Gr (micron graphite material with an average particle size of 6μm) and 3g of n-Si (nano silicon with an average particle size of 50nm) and place them in a beaker. Mix them thoroughly to obtain the mixed slurry.

[0121] 2. Spray drying: Control the slurry concentration at 32%, the feed rate at approximately 420 mL / h, and the spray gas pressure at approximately 1.7 bar to ensure good atomization. A nozzle diameter of 180 μm is commonly used, and the drying temperature is generally 175℃. Spray drying of the mixed slurry yields silicon-carbon composite particles.

[0122] 3. Sintering: The sintering temperature is controlled at 550℃ and the sintering time is 2h. The sintering process is carried out in an argon protective atmosphere. In the post-treatment stage, the cooling rate is controlled at 5℃ / min to sinter the silicon-carbon composite particles. S-Gr / n-Si particles with a diameter between 10 and 50 micrometers are screened out to obtain micron-sized porous silicon-carbon particles with a porosity of about 20%.

[0123] 4. CVD Process: s-Gr / n-Si particles are placed in a crucible at the center of the furnace. The furnace tubes are thoroughly purged with Ar at a flow rate of 200 mL / min to eliminate any residual air. Under ambient pressure, the temperature is gradually increased at a stable rate of 8 °C / min with a continuous argon flow rate of 50 mL / min. When the temperature reaches 1050 °C, acetylene is introduced at a flow rate of 10 mL / min, followed by an H2 / Ar mixture at a flow rate of 150 mL / min. The temperature is then maintained at 1100 °C for 15 hours to allow vertical graphene nanosheets to grow on the internal pores and outer surface of the porous silicon-carbon particles, resulting in a silicon-carbon anode material based on vertical graphene, labeled s-Gr / n-Si / VGs. The content of silicon-based material is 10%, the content of graphene nanosheets is 10%, and the content of graphite is 80%.

[0124] A negative electrode is prepared by means of the following steps: coating a slurry composed of s-Gr / n-Si / VGs active material, carbon black, SBR, and CMC in a mass ratio of 8:1:0.5:0.5 onto copper foil, and then drying it under vacuum at 80°C for 12 hours. The electrode weight ranges from 0.8 to 1.5 mg / cm³. 2 s-Gr / n-Si / VGs electrodes were prepared.

[0125] A secondary battery is prepared by the following steps:

[0126] The prepared s-Gr / n-Si / VGs electrode was cut into small pieces with a diameter of 12 mm and used as the working electrode in the CR2032 coin cell. The cell was assembled in an argon-filled glove box, with moisture and oxygen concentrations maintained below 0.01 ppm. Lithium foil was used as the counter electrode; a Celgard 2500 membrane was used as the separator; the electrolyte was prepared by dissolving 1 M LiPF6 in a mixture of ethylene carbonate (EC), dimethyl carbonate (DEC), and diethyl carbonate (DMC) in a volume ratio of 1:1:1, with 5% fluoroethylene carbonate (FEC) added. The coin cell was then assembled.

[0127] Example 3

[0128] A silicon-carbon anode material based on vertical graphene, the preparation of which includes the following steps:

[0129] 1. Prepare the mixed slurry: Weigh 8g of s-Gr (micron graphite material with an average particle size of 8μm) and 1.6g of n-Si (nano silicon with an average particle size of 50nm) and place them in a beaker. Mix them thoroughly to obtain the mixed slurry.

[0130] 2. Spray drying: Control the slurry concentration at 35%, the feed rate at 320 mL / h, and the spray gas pressure at 2.8 bar to ensure good atomization. A nozzle diameter of 100 μm is commonly used, and the drying temperature is generally 180℃. Spray drying of the mixed slurry yields silicon-carbon composite particles.

[0131] 3. Sintering: The sintering temperature is controlled at 520℃, and the sintering time is 2 hours. The sintering process is carried out in an argon protective atmosphere. In the post-treatment stage, the cooling rate is controlled at 5℃ / min to sinter the silicon-carbon composite particles; s-Gr / n-Si particles with a diameter between 10 and 50 micrometers are screened out, thus obtaining micron-sized porous silicon-carbon particles with a porosity of approximately 20%.

[0132] 4. CVD Process: s-Gr / n-Si particles are placed in a crucible at the center of the furnace. The furnace tubes are thoroughly purged with Ar at a flow rate of 200 mL / min to eliminate any residual air. Under ambient pressure, the temperature is gradually increased at a stable rate of 8 °C / min with a continuous argon flow rate of 50 mL / min. When the temperature reaches 1050 °C, acetylene is introduced at a flow rate of 10 mL / min, followed by an H2 / Ar mixture at a flow rate of 150 mL / min. The temperature is then maintained at 1100 °C for 15 hours to allow vertical graphene nanosheets to grow on the internal pores and outer surface of the porous silicon-carbon particles, resulting in a silicon-carbon anode material based on vertical graphene, labeled s-Gr / n-Si / VGs. The content of silicon-based material is 10%, the content of graphene nanosheets is 20%, and the content of graphite is 70%.

[0133] A negative electrode is prepared by means of the following steps: coating a slurry composed of s-Gr / n-Si / VGs active material, carbon black, SBR, and CMC in a mass ratio of 8:1:0.5:0.5 onto copper foil, and then drying it under vacuum at 80°C for 12 hours. The electrode weight ranges from 0.8 to 1.5 mg / cm³. 2 s-Gr / n-Si / VGs electrodes were prepared.

[0134] A secondary battery is prepared by the following steps:

[0135] The prepared s-Gr / n-Si / VGs electrode was cut into small pieces with a diameter of 10 mm and used as the working electrode in the CR2032 coin cell. The cell was assembled in an argon-filled glove box, with moisture and oxygen concentrations maintained below 0.01 ppm. Lithium foil was used as the counter electrode; a Celgard 2500 membrane was used as the separator; the electrolyte was prepared by dissolving 1 M LiPF6 in a mixture of ethylene carbonate (EC), dimethyl carbonate (DEC), and diethyl carbonate (DMC) in a volume ratio of 1:1:1, with 5% fluoroethylene carbonate (FEC) added. The coin cell was then assembled.

[0136] Example 4

[0137] A silicon-carbon anode material based on vertical graphene, the preparation of which includes the following steps:

[0138] 1. Prepare the mixed slurry: Weigh 14.25g of s-Gr (micron graphite material with an average particle size of 10μm) and 0.75g of silicon carbide (with an average particle size of 50nm) into a beaker, mix them thoroughly to obtain the mixed slurry.

[0139] 2. Spray drying: The slurry concentration is controlled at 25%, the feed rate is generally 270 mL / h, and the spray gas pressure is between 1.5 bar to ensure good atomization. A nozzle diameter of 130 μm and a drying temperature of 160℃ are used to spray dry the mixed slurry to obtain silicon-carbon composite particles.

[0140] 3. Sintering: The sintering temperature is controlled at 500℃ and the sintering time is 2h. The sintering process is carried out in an argon protective atmosphere. In the post-treatment stage, the cooling rate is controlled at 5℃ / min to sinter the silicon-carbon composite particles. s-Gr / SiC particles with a diameter between 10 and 50 micrometers are screened out to obtain micron-sized porous silicon-carbon particles with a porosity of about 20%.

[0141] 4. CVD Process: s-Gr / SiC particles are placed in a crucible at the center of the furnace. The furnace tubes are thoroughly purged with Ar at a flow rate of 200 mL / min to eliminate any residual air. Under ambient pressure, the temperature is gradually increased at a stable rate of 8 °C / min with a continuous argon flow rate of 50 mL / min. When the temperature reaches 1050 °C, acetylene is introduced at a flow rate of 10 mL / min, followed by an H2 / Ar mixture at a flow rate of 150 mL / min. Finally, the temperature is maintained at 1100 °C for 12 hours to allow vertical graphene nanosheets to grow on the internal pores and outer surface of the porous silicon-carbon particles, resulting in a silicon-carbon anode material based on vertical graphene, labeled s-Gr / SiC / VGs. The content of silicon-based material is 7%, the content of graphene nanosheets is 13%, and the content of graphite is 80%.

[0142] A negative electrode is prepared by the following steps: coating a slurry composed of s-Gr / SiC / VGs active material, carbon black, SBR, and CMC in a mass ratio of 8:1:0.5:0.5 onto copper foil, and then drying it under vacuum at 80°C for 12 hours. The electrode weight ranges from 0.8 to 1.5 mg / cm³. 2 s-Gr / SiC / VGs electrode was prepared.

[0143] A secondary battery is prepared by the following steps:

[0144] The prepared s-Gr / SiC / VGs electrode was cut into 10mm diameter pieces and used as the working electrode in the CR2032 coin cell. The cell was assembled in an argon-filled glove box, with moisture and oxygen concentrations maintained below 0.01ppm. Lithium foil was used as the counter electrode; a Celgard 2500 membrane was used as the separator; the electrolyte consisted of 1M LiPF6 dissolved in a 1:1:1 volume ratio mixture of ethylene carbonate (EC), dimethyl carbonate (DEC), and diethyl carbonate (DMC), with 5% fluoroethylene carbonate (FEC) added. The coin cell was then assembled.

[0145] Example 5

[0146] A silicon-carbon anode material based on vertical graphene, the preparation of which includes the following steps:

[0147] 1. Prepare the mixed slurry: Weigh 12g of s-Gr (micron graphite material with an average particle size of 10μm) and 3g of SiO (with an average particle size of 50nm) into a beaker, mix them thoroughly to obtain the mixed slurry.

[0148] 2. Spray drying: The slurry concentration is controlled at 25%, the feed rate is generally 270 mL / h, and the spray gas pressure is between 1.5 bar to ensure good atomization. A nozzle diameter of 130 μm and a drying temperature of 160℃ are used to spray dry the mixed slurry to obtain silicon-carbon composite particles.

[0149] 3. Sintering: The sintering temperature is controlled at 500℃ and the sintering time is 2h. The sintering process is carried out in an argon protective atmosphere. In the post-treatment stage, the cooling rate is controlled at 5℃ / min to sinter the silicon-carbon composite particles. S-Gr / SiO particles with a diameter between 10 and 50 micrometers are screened out to obtain micron-sized porous silicon-carbon particles with a porosity of about 20%.

[0150] 4. CVD Process: s-Gr / SiO particles are placed in a crucible at the center of the furnace. The furnace tubes are thoroughly purged with Ar at a flow rate of 200 mL / min to eliminate any residual air. Under ambient pressure, the temperature is gradually increased at a stable rate of 8 °C / min with a continuous argon flow rate of 50 mL / min. When the temperature reaches 1050 °C, acetylene is introduced at a flow rate of 10 mL / min, followed by an H2 / Ar mixture at a flow rate of 150 mL / min. Finally, the temperature is maintained at 1100 °C for 12 hours to allow vertical graphene nanosheets to grow on the internal pores and outer surface of the porous silicon-carbon particles, resulting in a silicon-carbon anode material based on vertical graphene, labeled s-Gr / SiO / VGs. The content of silicon-based material is 12%, the content of graphene nanosheets is 10%, and the content of graphite is 78%.

[0151] A negative electrode is prepared by the following steps: coating a slurry composed of s-Gr / SiO / VGs active material, carbon black, SBR, and CMC in a mass ratio of 8:1:0.5:0.5 onto copper foil, and then drying it under vacuum at 80°C for 12 hours. The electrode weight ranges from 0.8 to 1.5 mg / cm³. 2 An s-Gr / SiO / VGs electrode was prepared.

[0152] A secondary battery is prepared by the following steps:

[0153] The prepared s-Gr / SiO / VGs electrode was cut into 10mm diameter pieces and used as the working electrode in the CR2032 coin cell. The cell was assembled in an argon-filled glove box, with moisture and oxygen concentrations maintained below 0.01ppm. Lithium foil was used as the counter electrode; a Celgard 2500 membrane was used as the separator; the electrolyte consisted of 1M LiPF6 dissolved in a 1:1:1 volume ratio mixture of ethylene carbonate (EC), dimethyl carbonate (DEC), and diethyl carbonate (DMC), with 5% fluoroethylene carbonate (FEC) added. The coin cell was then assembled.

[0154] Comparative Example 1

[0155] A silicon-carbon anode is provided, which has the same preparation process as in Example 1, except that: carbon source gas and etching gas are not introduced in step 4, and vertical graphene nanosheets are not grown in the internal pores and outer surface of the porous silicon-carbon particles.

[0156] Comparative Example 2

[0157] A silicon-carbon anode is provided, which has the same preparation process as that of Example 1, except that step 2 uses a wet milling method to prepare silicon-carbon composite particles, while the other processes are the same as those in Example 1.

[0158] Comparative Example 3

[0159] A silicon-carbon anode is provided, which has the same preparation process as in Example 1, except that: in step 4, no etching gas is introduced, and the carbon material is deposited on the surface of porous silicon-carbon particles in the form of amorphous carbon and a small amount of graphene, without forming a high-strength conductive network with directional channels.

[0160] Furthermore, to verify the progressiveness of the embodiments of this application, the following performance tests were performed on the above embodiments and comparative examples:

[0161] 1. The morphology of the silicon-carbon anode materials based on vertical graphene prepared in the examples was observed. The scanning electron microscope (SEM) image of the silicon-carbon anode material s-Gr / n-Si / VGs based on vertical graphene prepared in Example 1 is attached. Figure 2 As shown, the cross-sectional SEM image clearly reveals the integrated structure of nano-silicon particles, graphite sheets, graphene layers, and porous structures. A transmission electron microscope (TEM) image of the silicon-carbon anode material s-Gr / n-Si / VGs based on vertical graphene prepared in Example 1 is attached. Figure 3 As shown in the TEM image, flocculent graphene layers are visible on the surface of the material, and the graphene nanosheets are evenly distributed and grow vertically.

[0162] 2. X-ray diffraction tests were performed on the silicon-carbon anode material s-Gr / n-Si / VGs based on vertical graphene prepared in Example 1, as shown in the attached figure. Figure 4 As shown in the XRD pattern, the graphene coating enhances the carbon peaks, while some signals from silicon are masked.

[0163] 3. Raman spectroscopy was performed on the silicon-carbon anode material s-Gr / n-Si / VGs based on vertical graphene prepared in Example 1, as shown in the attached figure. Figure 5 As shown in the Raman spectrum, the characteristic peaks of graphene, the 2D peak, the G peak, and the D peak, appeared when graphene was grown by CVD.

[0164] 4. Cyclic voltammetry tests were performed on the coin cells prepared using the vertical graphene-based silicon-carbon anode material s-Gr / n-Si / VGs obtained in Example 1, as shown in the attached figure. Figure 6 As shown in the CV curve, the first CV curve shows the formation of an SEI film; the second to fourth CV curves are highly overlapping, indicating that the material has good stability.

[0165] 5. A constant current charge-discharge test was performed on the coin cell prepared using the silicon-carbon anode material s-Gr / n-Si / VGs based on vertical graphene obtained in Example 1, as shown in the attached figure. Figure 7 As shown in the GCD curve, the stability at different rates is very good and the capacity is high, indicating good rate performance.

[0166] 6. As attached Figure 8The figure shows a schematic diagram of the SEI mechanism on the surface of silicon-carbon anode material s-Gr / n-Si / VGs particles after charge-discharge testing of a coin cell prepared by the silicon-carbon anode material s-Gr / n-Si / VGs based on vertical graphene obtained in Example 1. It can be seen that a stable SEI film is formed after the reactive graphene coating.

[0167] 7. After performing charge-discharge tests on the coin cells prepared using the vertical graphene-based silicon-carbon anode material s-Gr / n-Si / VGs obtained in Example 1, cryo-electron microscopy was performed, as shown in the attached figure. Figure 9 As shown, the graphene layer can be observed first; then the SEI layer covering the surface of the graphene layer is observed, which is analyzed by high-resolution data to be a continuous and dense LiF layer.

[0168] 8. Using the Neware battery testing system at 30°C, the specific capacity, cycle stability, and other electrochemical performance of the above examples and comparative examples were evaluated within a voltage range of 0.01-2.0V (vs. Li / Li+) and current density. The test results are shown in Table 1 below:

[0169] Table 1

[0170]

[0171] The test results above show that the embodiments of this application combine nano-silicon with graphite anodes through spray granulation, and grow vertical graphene nanosheets in the internal pores and outer surface of porous silicon-carbon particles, forming a highly mechanically strong, structurally stable, and robust conductive network. This better alleviates the volume expansion of silicon-based materials during lithium intercalation, enabling the silicon-carbon anode material based on vertical graphene to simultaneously possess high capacity and cycle stability. Furthermore, the secondary granulation process solves the problem of low packing density in silicon-based materials, suppresses the volume expansion effect of silicon-based materials, and improves rate charge / discharge performance.

[0172] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a vertical graphene-based silicon-carbon negative electrode material, characterized in that, The method comprises the following steps: preparing a mixed slurry containing a nano-silicon-based material and a micro-graphite material; subjecting the mixed slurry to a spray drying process to obtain silicon-carbon composite particles; subjecting the silicon-carbon composite particles to a sintering process in a protective atmosphere to obtain micro-sized porous silicon-carbon particles through sieving; subjecting the porous silicon-carbon particles to a chemical vapor deposition process in a carbon source gas and etching atmosphere to grow vertical graphene nanosheets on the internal pores and external surface of the porous silicon-carbon particles, thereby obtaining a vertical graphene-based silicon-carbon negative electrode material.

2. The method for preparing a vertical graphene-based silicon-carbon negative electrode material according to claim 1, characterized in that, The solid content of the mixed slurry is 20% to 40%; and / or, the mass ratio of the nano-silicon-based material to the micro-graphite material in the mixed slurry is (5 to 20):(80 to 95); and / or, the average particle size of the nano-silicon-based material is 30 nm to 500 nm; and / or, the nano-silicon-based material comprises at least one of elemental silicon, silicon oxide, and silicon carbide; and / or, the average particle size of the micro-graphite material is 6 μm to 15 μm.

3. The production method of the vertical graphene-based silicon-carbon negative electrode material according to claim 1 or 2, characterized by, The feed rate of the spray drying process is 100 mL / h to 500 mL / h, the spray gas pressure is 1 bar to 3 bar, the nozzle diameter is 100 μm to 200 μm, and the drying temperature is 150 ℃ to 200 ℃; and / or, the protective atmosphere comprises at least one of argon, nitrogen, and helium; and / or, the sintering temperature is not higher than 600 ℃, and the sintering time is 1 h to 3 h; and / or, the cooling rate after the sintering process is 1 ℃ / min to 5 ℃ / min; and / or, the average particle size of the porous silicon-carbon particles is 10 μm to 50 μm; and / or, the porosity of the porous silicon-carbon particles is 15% to 40%.

4. The method of claim 3, wherein the vertical graphene-based silicon-carbon negative electrode material is prepared by the steps of: preparing a vertical graphene-based silicon-carbon negative electrode material by mixing a vertical graphene-based silicon-carbon negative electrode material precursor with a solvent; and drying the vertical graphene-based silicon-carbon negative electrode material precursor. The carbon source gas comprises at least one of methane, ethanol, and acetylene; and / or, the etching atmosphere comprises at least one etching gas selected from the group consisting of hydrogen, ammonia, oxygen, and hydrogen fluoride, and at least one carrier gas selected from the group consisting of argon, nitrogen, and helium; and / or, the flow rate of the inert atmosphere during the chemical vapor deposition process is 30 mL / min to 80 mL / min; and / or, the flow rate of the carbon source gas is 10 mL / min to 20 mL / min; and / or, the flow rate of the etching atmosphere is 100 mL / min to 200 mL / min; and / or, the temperature rising rate of the chemical vapor deposition process is 5 ℃ / min to 10 ℃ / min, the holding temperature is 1000 ℃ to 1200 ℃, and the holding time is 8 h to 30 h.

5. The method for preparing a vertical graphene-based silicon-carbon negative electrode material according to claim 4, characterized in that, The step of the chemical vapor deposition treatment comprises: after heating to 1000-1100°C at a temperature increasing rate of 5-10°C / min under the condition that the flow rate of the inert atmosphere is 30-80 mL / min, the carbon source gas and the etching atmosphere are introduced, and the growth of the vertical graphene nanosheet is carried out under the condition that the temperature is 1100-1200°C and the holding time is 8-30 h, so as to grow the vertical graphene nanosheet in the internal pores and the outer surface of the porous silicon-carbon particle. And / or, the inert atmosphere comprises at least one of argon, nitrogen and helium. And / or, in the etching atmosphere, the volume percentage of the etching gas is 70-90%.

6. The method for preparing silicon-carbon anode material based on vertical graphene as described in any one of claims 1-2 and 4-5, characterized in that, In the vertical graphene-based silicon-carbon negative electrode material, the mass percentage of the silicon-based material is 5-20%. And / or, in the vertical graphene-based silicon-carbon negative electrode material, the mass percentage of the vertical graphene nanosheet is 5-15%. And / or, in the vertical graphene-based silicon-carbon negative electrode material, the mass percentage of the graphite material is 65-90%.

7. A vertical graphene-based silicon-carbon anode material prepared according to the method of any one of claims 1 to 6, characterized in that, The vertical graphene-based silicon-carbon negative electrode material comprises a porous silicon-carbon particle and a vertical graphene nanosheet grown in the internal pores and the outer surface of the porous silicon-carbon particle.

8. A negative electrode sheet characterized by comprising: The vertical graphene-based silicon-carbon negative electrode material comprises a current collector and a negative electrode active layer formed on the surface of the current collector, and the negative electrode active layer comprises the vertical graphene-based silicon-carbon negative electrode material prepared by the method according to any one of claims 1-6 or the vertical graphene-based silicon-carbon negative electrode material according to claim 7.

9. The negative electrode sheet according to claim 8, wherein In the negative electrode active layer, the mass percentage of the vertical graphene-based silicon-carbon negative electrode material is 85-90%.

10. A secondary battery characterized by comprising: The secondary battery comprises the negative electrode sheet according to claim 9.

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