Preparation method of silicon-carbon negative electrode material for lithium ion battery

Abstract

The application provides a preparation method of a silicon-carbon negative electrode material of a lithium ion battery, and comprises the following steps: mixing nano-silicon, a modifier and water according to a preset mixing ratio, and then performing high-pressure pulse homogenization treatment to form a uniform nano-silicon suspension; adding phenolic resin into the nano-silicon suspension and performing dispersion or dissolution to form a nano-silicon-phenolic resin suspension; adding isocyanate additives into the nano-silicon-phenolic resin suspension and performing dispersion or dissolution to form a nano-silicon-phenolic resin-isocyanate precursor slurry; performing atomization drying and solidification treatment on the nano-silicon-phenolic resin-isocyanate precursor slurry to form a nano-silicon-phenolic resin composite powder; and performing high-temperature pyrolysis on the nano-silicon-phenolic resin composite powder to obtain the silicon-carbon negative electrode material. By using the application, the problems of complex process and high cost in the existing preparation method of the lithium ion battery negative electrode material can be solved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a method for preparing silicon-carbon anode materials for lithium-ion batteries. Background Technology

[0002] Against the backdrop of global energy transition, the rapid development of renewable energy sources such as photovoltaics and wind power, as well as the electric vehicle and grid energy storage industries, has led to a surge in demand for high-energy-density energy storage devices and materials. Among these, lithium-ion batteries, with their advantages of no memory effect, high operating voltage, high theoretical specific capacity, and long cycle life, have stood out from various energy storage forms and become one of the research hotspots in the current new energy academic and industrial communities. As the demand for high-energy-density energy storage devices continues to increase in the new energy industry, especially for electric vehicles and grid energy storage, the development of high-specific-capacity lithium-ion battery materials has become one of the key tasks affecting the sustainable development of the new energy industry.

[0003] Graphite is the most widely used anode material in existing commercial lithium-ion battery products. After years of development, its specific capacity has increased from 170 mAh g / g. -1 Increased to 360mAh g -1 It is close to the theoretical specific capacity (372mAh g). -1 The current limits of lithium storage are no longer sufficient to meet the demands of high specific energy applications, making the development of anode materials with greater lithium storage capacity imperative. Silicon, a group of elements in the same family as carbon, is abundant and plentiful in the Earth's crust, providing a foundation for large-scale production and application. The theoretical specific capacity of silicon materials at room temperature can reach 3579 mAh g⁻¹. -1 It is recognized as the next-generation lithium-ion battery anode material.

[0004] The surge in demand from the industry has fueled the development of silicon-based anode materials. However, the large-scale application of silicon-based anode materials still faces numerous bottlenecks. Volume changes, interface issues, and charge transport are challenges that must be overcome to develop high-performance anode materials. Next-generation lithium-ion battery anode materials must achieve high capacity while also possessing excellent mechanical and charge transport properties. To achieve these goals, researchers have conducted extensive studies on silicon-based anode material preparation technologies, focusing on exploring methods such as nanotechnology, composite technology, and material structure modification to address issues like volume expansion and low conductivity. Among these, silicon-carbon composites, combining the high capacity of silicon with the high conductivity and low expansion rate of carbon, are expected to replace graphite as a lithium-ion battery anode material in the near future. Whether in academic research or industrial applications, the preparation of silicon-carbon anode materials mainly involves processes such as granulation, grinding, and pyrolysis. The key carbon sources include various types such as sucrose, starch, glucose, pitch, and phenolic resin. In particular, phenolic resin can form bonds with silicon, enhancing the bonding force between silicon and carbon and improving the structural stability of the material. Furthermore, the porous amorphous carbon matrix obtained by pyrolysis not only plays a good role in buffering volume expansion and improving conductivity, but also has a certain lithium storage capacity, which can significantly improve the specific capacity of the material. In addition, its good compatibility with electrolytes makes silicon-carbon anode materials have a high reversible specific capacity.

[0005] The following three patented preparation methods all use phenolic resin. Phenolic resin has mature synthesis process, low cost, large interlayer spacing of hard carbon material produced by pyrolysis, fast lithium ion diffusion speed, and better compatibility with electrolyte than graphite. It has good mechanical and electrochemical properties and is therefore widely used as a key carbon source in the preparation process of silicon-carbon anode materials.

[0006] 1) A method for preparing a silicon-based anode material for lithium-ion batteries modified with phenolic resin (CN109817962A) discloses a method for obtaining silicon-carbon anode material by pyrolysis after modifying silicon nanoparticles with phenolic resin: silicon nanoparticles are added to an aqueous solution of phenolic resin and mixed evenly, then an ethanol solution of 2,5-dimercapto-1,3,4-thiadiazole is added, and a surfactant is added under stirring conditions, followed by the dropwise addition of an initiator. After stirring for 24-72 hours, the solvent is evaporated, and the resulting solid product is heated to 20-120℃ in an oxygen-free environment for preliminary crosslinking. Finally, it is pyrolyzed at 700-1000℃ in an inert gas atmosphere to obtain a porous carbon-coated silicon nanocomposite material, i.e., a silicon-based anode material for lithium-ion batteries modified with phenolic resin.

[0007] 2) A method for preparing a negative electrode composite material for lithium-ion batteries (CN109817966A) discloses a method for preparing a negative electrode composite material: first, graphite and silicon suboxide are mixed and ball-milled to obtain mixed powder a, then mixed powder a is added to carboxymethyl chitosan solution, dried and then added to phenolic resin solution for mixing and stirring, and finally calcined to obtain the battery negative electrode composite material.

[0008] 3) A modified carbon-coated silica-suboxide composite material, its preparation method and its application (CN108899488A) discloses a preparation method comprising: dissolving phenolic resin in ethanol to obtain material A; adding graphene oxide to material A and mixing evenly, adding silica-suboxide powder, heating and stirring until evaporated to dryness, and then vacuum drying to obtain material B; and carbonizing material B to obtain the modified carbon-coated silica-suboxide composite material.

[0009] Phenolic resins are a general term for resins formed by the condensation of phenol and aldehyde, with phenol and formaldehyde resins being the most important. Based on the difference in the catalyst used in the condensation process, they can be further divided into thermosetting phenolic resins and thermoplastic phenolic resins. Thermosetting phenolic resins can be cured by heating, making them an excellent raw material for preparing silicon-carbon anode materials. However, they are only soluble in organic solvents, which negatively impacts the cost, safety, and environmental friendliness of the process. Thermoplastic phenolic resins, on the other hand, have a soluble and fusible linear structure and dissolve very well in aqueous solvents, better meeting the requirements of low cost, environmental friendliness, and safety in the preparation of silicon-carbon anode materials. However, thermoplastic phenolic resins cannot be cured under normal conditions; after mixing with raw materials such as silicon, solvent removal requires processes such as evaporation, significantly extending the process time and increasing energy consumption. Furthermore, the precursors, after pyrolysis and carbonization, are bulk materials that need to be crushed and granulated to obtain the finished silicon-carbon anode material, increasing not only the process length and complexity but also the probability of introducing impurities.

[0010] To address the aforementioned issues, there is an urgent need to provide a method for preparing silicon-carbon anode materials for lithium-ion batteries. Summary of the Invention

[0011] In view of the above problems, the purpose of this invention is to provide a method for preparing silicon-carbon anode materials for lithium-ion batteries, so as to solve the problems of complex processes and high costs in existing methods for preparing lithium-ion battery anode materials.

[0012] The method for preparing silicon-carbon anode material for lithium-ion batteries provided by this invention includes:

[0013] After mixing nano-silicon with modifier and solvent water according to the preset mixing ratio, high-pressure pulse homogenization treatment is performed to form a uniform nano-silicon suspension.

[0014] Phenolic resin is added to the nano-silicon suspension and dispersed or dissolved to form a nano-silicon-phenolic resin suspension.

[0015] An isocyanate additive is added to the nano-silicon-phenolic resin suspension and dispersed or dissolved to form a nano-silicon-phenolic resin-isocyanate precursor slurry.

[0016] The nano-silicon-phenolic resin-isocyanate precursor slurry is subjected to atomization drying and curing treatment to form nano-silicon-phenolic resin composite powder.

[0017] The nano-silicon-phenolic resin composite powder was subjected to high-temperature pyrolysis to obtain silicon-carbon anode material.

[0018] Furthermore, a preferred embodiment is that the mass ratio of the nano-silicon to the solvent water is 1 / 30 to 1 / 20.

[0019] Furthermore, a preferred approach is to use a pressure of not less than 60 MPa during high-pressure pulse homogenization.

[0020] Furthermore, in a preferred embodiment, the phenolic resin is a phenolic resin solution or phenolic resin powder, wherein the viscosity of the phenolic resin solution is ≤600 cP.

[0021] Furthermore, a preferred embodiment is that, during the process of adding phenolic resin to the nano-silicon suspension, the mass ratio of the phenolic resin to the solvent water is 1 / 10 to 1 / 2.5.

[0022] Furthermore, a preferred embodiment is that the isocyanate auxiliary is any one of monoisocyanate, diisocyanate, or polyisocyanate.

[0023] Furthermore, a preferred embodiment is that, during the process of adding the isocyanate auxiliary agent to the nano-silica-phenolic resin suspension, the mass ratio of the isocyanate auxiliary agent to the phenolic resin is 1 / 500 to 1 / 50.

[0024] Furthermore, a preferred approach is that during the atomization drying and curing process of the nano-silicon-phenolic resin-isocyanate precursor slurry,

[0025] The nano-silicon-phenolic resin-isocyanate precursor slurry was atomized and dried using a spray dryer, wherein the inlet temperature of the spray dryer was 150-250℃ and the pressure was 0.15-0.25MPa.

[0026] Furthermore, a preferred approach is to perform high-temperature pyrolysis on the nano-silicon-phenolic resin composite powder.

[0027] The nano-silicon-phenolic resin composite powder was subjected to high-temperature pyrolysis treatment in an argon atmosphere furnace, wherein the inlet temperature of the nano-silicon-phenolic resin composite powder was 150-250℃ and the pressure was 0.15-0.25MPa.

[0028] Furthermore, a preferred embodiment is that the pyrolysis temperature of the nano-silicon-phenolic resin composite powder is 750-950℃.

[0029] As can be seen from the above technical solution, the method for preparing silicon-carbon anode material for lithium-ion batteries provided by this invention has the following advantages compared to the prior art:

[0030] 1) The silicon-carbon anode material preparation method of the present invention is fast and efficient: by utilizing the cross-linking effect of isocyanate-NCO and phenolic resin functional groups, the precursor granulation process can be simultaneously solidified and molded, which has a high degree of continuity and is suitable for large-scale industrial production. It can not only save the long bulk phase evaporation in the traditional process, but also avoid the finished product crushing process, thereby greatly shortening the process flow and preparation cycle.

[0031] 2) The silicon-carbon anode material preparation method of the present invention is safe, energy-saving and environmentally friendly: the shortening of the process flow and preparation cycle can reduce process energy consumption, and the isocyanate crosslinking allows the entire process to use water-soluble phenolic resin, avoiding the use of toxic and flammable organic solvents, thereby improving process safety and environmental protection, while reducing material costs.

[0032] 3) The silicon-carbon anode material prepared by the method of the present invention has strong quality control: the silicon-carbon anode material is granulated and formed in one step, avoiding secondary crushing process, thereby avoiding the introduction of impurities such as metals that seriously affect the material performance.

[0033] 4) The silicon-carbon anode material prepared by the present invention has excellent performance: the silicon-hard carbon composite structure obtained by using phenolic resin as carbon source has good electronic and ion transport performance and high compatibility with electrolyte. The micro-pore structure of carbon matrix can effectively buffer the volume expansion of silicon-based material. At the same time, the spray drying process can easily adjust key physical properties such as product particle size and specific surface area, and improve the electrochemical performance of the product by adding any additives. Therefore, the silicon-carbon anode material product has high specific capacity and high initial coulombic efficiency.

[0034] To achieve the foregoing and related objectives, one or more aspects of the invention include the features that will be described in detail below. The following description and accompanying drawings illustrate certain exemplary aspects of the invention. However, these aspects indicate only a few of the various ways in which the principles of the invention can be used. Furthermore, the invention is intended to encompass all such aspects and their equivalents. Attached Figure Description

[0035] Other objects and results of the invention will become more apparent and readily understood with reference to the following description taken in conjunction with the accompanying drawings. In the drawings:

[0036] Figure 1 This is a schematic diagram of the process for preparing silicon-carbon anode material for lithium-ion batteries according to an embodiment of the present invention.

[0037] Figure 2 This is a schematic diagram of the microstructure of the silicon-carbon anode material prepared according to Examples 1-4 of the present invention;

[0038] Figure 3 This is a schematic diagram of the microstructure of the silicon-carbon anode material prepared according to Example 5 of the present invention;

[0039] Figure 4 This is a schematic diagram of the microstructure of the silicon-carbon anode material prepared for comparison.

[0040] In all the accompanying drawings, the same reference numerals indicate similar or corresponding features or functions. Detailed Implementation

[0041] In the following description, numerous specific details are set forth for illustrative purposes and to provide a thorough understanding of one or more embodiments. However, it will be apparent that these embodiments may also be implemented without these specific details. In other instances, well-known structures and devices are shown in block diagram form for ease of description of one or more embodiments.

[0042] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] In view of the problems of complex processes and high costs in the existing methods for preparing lithium-ion battery negative electrode materials, the present invention provides a method for preparing silicon-carbon negative electrode materials for lithium-ion batteries.

[0044] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0045] To illustrate the method for preparing silicon-carbon anode material for lithium-ion batteries provided by this invention Figure 1A process flow diagram for preparing silicon-carbon anode materials for lithium-ion batteries according to an embodiment of the present invention is shown.

[0046] like Figure 1 As shown, the method for preparing silicon-carbon anode material for lithium-ion batteries provided by the present invention includes:

[0047] S110: After mixing nano-silicon with modifier and solvent water according to the preset mixing ratio, high-pressure pulse homogenization treatment is performed to form a uniform nano-silicon suspension.

[0048] S120: Add phenolic resin to the nano-silicon suspension and disperse or dissolve it to form a nano-silicon-phenolic resin suspension;

[0049] S130: Add isocyanate additive to the nano-silicon-phenolic resin suspension and disperse or dissolve it to form a nano-silicon-phenolic resin-isocyanate precursor slurry;

[0050] S140: The nano-silicon-phenolic resin-isocyanate precursor slurry is atomized, dried and cured to form nano-silicon-phenolic resin composite powder.

[0051] S150: The nano-silicon-phenolic resin composite powder is subjected to high-temperature pyrolysis to obtain silicon-carbon anode material.

[0052] The method for preparing silicon-carbon anode materials for lithium-ion batteries of the present invention can realize the preparation of silicon-carbon composite powder by direct granulation of silicon and phenolic resin raw materials, which is of great significance for the efficient preparation and large-scale production of high-performance silicon-carbon anode materials.

[0053] The preparation method of the present invention uses nano-silicon and phenolic resin as raw materials, and achieves direct granulation and molding of precursors under the action of specific additives (isocyanate-NCO) to efficiently prepare silicon-carbon anode materials. The preparation method includes three stages: precursor slurry preparation, granulation and molding, and pyrolysis carbonization.

[0054] In step S110, nano-silicon and other additives or modifiers are added to water, with the mass ratio of nano-silicon to water between 1 / 30 and 1 / 20. A transient high-voltage pulse is used to fully disperse the silicon particles in the water under the coupling effects of high shear, cavitation, and collision, forming a uniform nano-silicon suspension. The pressure used during the high-voltage pulse homogenization process is no less than 60 MPa.

[0055] The modifier can be asphalt powder, carbon nanofibers, or a mixture of carbon nanofibers and graphite, etc. Furthermore, the homogenization process in the precursor slurry preparation of this invention can also be achieved using ultrasonic pulverization or high-intensity mechanical shearing.

[0056] In step S120, a phenolic resin solution or powder is added to the nano-silicon suspension at a mass ratio of 1 / 10 to 1 / 2.5 with the solvent water. The phenolic resin is dispersed or dissolved by mechanical stirring to form a nano-silicon-phenolic resin suspension.

[0057] The phenolic resin is either a phenolic resin solution or phenolic resin powder, preferably a phenolic resin solution with a viscosity ≤600 cP. In embodiments of the present invention for preparing silicon-carbon anode materials, a safe and environmentally friendly water-soluble phenolic resin is used as the main composite carbon source, including but not limited to water-soluble phenolic resin powder and aqueous phenolic resin solutions.

[0058] In step S130, isocyanate additive is added to the nano-silica-phenolic resin suspension, and mechanical stirring is used to disperse or dissolve the isocyanate to form a uniform precursor slurry.

[0059] The isocyanate additive can be a monoisocyanate, represented by hexyl isocyanate; a diisocyanate, represented by toluene diisocyanate; or a polyisocyanate, represented by triphenylmethane triisocyanate. The mass ratio of the isocyanate additive to the phenolic resin is 1 / 500 to 1 / 50.

[0060] In the embodiments of the present invention for preparing silicon-carbon anode materials, the isocyanate (-NCO) groups react with hydroxyl, carboxyl, amino and other groups on the molecular chain of aqueous resin to form a cross-linked structure, thereby achieving in-situ rapid curing and molding of phenolic resin.

[0061] In step S140, during the atomization drying and curing process of the nano-silicon-phenolic resin-isocyanate precursor slurry,

[0062] The nano-silicon-phenolic resin-isocyanate precursor slurry was atomized and dried using a spray dryer, wherein the inlet temperature of the spray dryer was 150-250℃ and the pressure was 0.15-0.25MPa.

[0063] The embodiments of the present invention for preparing silicon-carbon anode materials use isocyanate as an additive and a spray pyrolysis drying process to achieve one-step composite, curing and molding of silicon and carbon sources, thereby realizing the continuous and efficient preparation of silicon-carbon anode materials. This overcomes the shortcomings of traditional composite processes, such as reliance on organic solvents, long processing time, need for secondary crushing and treatment and introduction of impurities.

[0064] In step S150, during the high-temperature pyrolysis of the nano-silicon-phenolic resin composite powder, an argon atmosphere furnace is used to perform high-temperature pyrolysis treatment on the nano-silicon-phenolic resin composite powder. The inlet temperature of the nano-silicon-phenolic resin composite powder is 150-250℃, and the pressure is 0.15-0.25MPa. The pyrolysis temperature of the nano-silicon-phenolic resin composite powder is 750-950℃.

[0065] Based on the above-described method for preparing silicon-carbon anode materials for lithium-ion batteries, the present invention will be further described according to the embodiments in the table below. The following is a list of the components, processes, and testing performance of each embodiment and comparative example of the present invention.

[0066] In this embodiment of the invention, silicon-carbon anode material is prepared using nano-silicon with an average particle size of 100 nm and 70 wt% phenolic resin aqueous solution as raw materials.

[0067] Example 1:

[0068] Weigh 10g of nano-silicon and 1.3g of asphalt powder, add them to 300mL of water, and use mechanical stirring for 2-5 minutes to initially disperse them into a suspension. Then pump the suspension into a homogenizing hopper and homogenize it under a high-pressure pulse of 80MPa to obtain a uniform nano-silicon suspension.

[0069] Add 120g of 70wt% phenolic resin aqueous solution to the nano-silicon suspension, stir and mix evenly, then add 1.68g of hexyl isocyanate and stir to completely dissolve or disperse evenly to form a precursor slurry.

[0070] Set the spray dryer inlet temperature to 200℃ and the pressure to 0.2MPa. After the temperature stabilizes, spray at a rate of 40mL / min. -1 The flow rate pumps the precursor slurry in, and the precursor droplets are dried and solidified to form nano-silicon-phenolic resin composite powder.

[0071] The nano-silicon-phenolic resin composite powder was transferred to an argon atmosphere furnace for high-temperature pyrolysis at 800℃, and finally the silicon-carbon anode material was obtained.

[0072] The morphology, particle size, and specific surface area of ​​the silicon-carbon anode material were tested using scanning electron microscopy, laser diffraction, and gas adsorption BET method, respectively. The electrochemical performance of the material was then tested by assembling coin cells with the material as the active material. The results are shown in Table 1.

[0073] Example 2:

[0074] Weigh 15g of nano-silicon, add it to 300mL of water, and use mechanical stirring for 2-5 minutes to initially disperse it into a suspension. Then pump it into a homogenizing hopper and homogenize it under a high-pressure pulse of 60MPa to obtain a uniform nano-silicon suspension.

[0075] Add 90g of 70wt% phenolic resin aqueous solution to the nano-silicon suspension, stir and mix evenly, then add 0.63g of toluene diisocyanate and stir to completely dissolve or disperse evenly to form a precursor slurry.

[0076] Set the spray dryer inlet temperature to 250℃ and the pressure to 0.25MPa. After the temperature stabilizes, spray at a rate of 50mL / min. -1 The flow rate pumps the precursor slurry in, and the precursor droplets are dried and solidified to form nano-silicon-phenolic resin composite powder.

[0077] The nano-silicon-phenolic resin composite powder was transferred to an argon atmosphere furnace for high-temperature pyrolysis at a temperature of 900℃, ultimately yielding the finished silicon-carbon anode material.

[0078] The morphology, particle size, and specific surface area of ​​the silicon-carbon anode material were tested using scanning electron microscopy, laser diffraction, and gas adsorption BET method, respectively. The electrochemical performance of the material was then tested by assembling coin cells with the material as the active material. The results are shown in Table 1.

[0079] Example 3:

[0080] Weigh 20g of nano-silicon, add it to 500mL of water, and use mechanical stirring for 2-5 minutes to initially disperse it into a suspension. Then pump it into a homogenizing hopper and homogenize it under a high-pressure pulse of 80MPa to obtain a uniform nano-silicon suspension.

[0081] Add 100g of 70wt% phenolic resin aqueous solution to the nano-silicon suspension, stir and mix evenly, then add 0.14g of triphenylmethane triisocyanate and stir to completely dissolve or disperse evenly to form a precursor slurry.

[0082] Set the spray dryer inlet temperature to 150℃ and the pressure to 0.15MPa. After the temperature stabilizes, spray at a rate of 70mL / min. -1 The flow rate pumps the precursor slurry in, and the precursor droplets are dried and solidified to form nano-silicon-phenolic resin composite powder.

[0083] The nano-silicon-phenolic resin composite powder was transferred to an argon atmosphere furnace for high-temperature pyrolysis at a temperature of 950℃, ultimately yielding the finished silicon-carbon anode material.

[0084] The morphology, particle size, and specific surface area of ​​the silicon-carbon anode material were tested using scanning electron microscopy, laser diffraction, and gas adsorption BET method, respectively. The electrochemical performance of the material was then tested by assembling coin cells with the material as the active material. The results are shown in Table 1.

[0085] Example 4:

[0086] Weigh 25g of nano-silicon and 1.25g of carbon nanofibers, add them to 500mL of water, and use mechanical stirring for 2-5 minutes to initially disperse them into a suspension. Then pump the suspension into a homogenizing hopper and homogenize it under a high-pressure pulse of 70MPa to obtain a uniform nano-silicon suspension.

[0087] Add 200g of 70wt% phenolic resin aqueous solution to the nano-silicon suspension, stir and mix evenly, then add 0.7g of lysine diisocyanate and stir to completely dissolve or disperse evenly to form a precursor slurry.

[0088] Set the spray dryer inlet temperature to 200℃ and the pressure to 0.2MPa. After the temperature stabilizes, spray at a rate of 70mL / min. -1 The flow rate pumps the precursor slurry in, and the precursor droplets are dried and solidified to form nano-silicon-phenolic resin composite powder.

[0089] The nano-silicon-phenolic resin composite powder was transferred to an argon atmosphere furnace for high-temperature pyrolysis at 750℃, ultimately yielding the finished silicon-carbon anode material.

[0090] The morphology, particle size, and specific surface area of ​​the silicon-carbon anode material were tested using scanning electron microscopy, laser diffraction, and gas adsorption BET method, respectively. The electrochemical performance of the material was then tested by assembling coin cells with the material as the active material. The results are shown in Table 1.

[0091] Example 5:

[0092] Weigh 10g of nano-silicon, 0.5g of carbon nanofiber and 38g of graphite, add them to 300mL of water, and use mechanical stirring for 2-5min to initially disperse them into a suspension. Then pump the suspension into a homogenizing hopper and homogenize it under a high-pressure pulse of 80MPa to obtain a uniform nano-silicon suspension.

[0093] Add 30g of 70wt% phenolic resin aqueous solution to the nano-silicon suspension, stir and mix evenly, then add 0.084g of hexamethylene diisocyanate and stir to completely dissolve or disperse evenly to form a precursor slurry.

[0094] Set the spray dryer inlet temperature to 200℃ and the pressure to 0.2MPa. After the temperature stabilizes, spray at a rate of 30mL / min. -1 The flow rate pumps the precursor slurry in, and the precursor droplets are dried and solidified to form nano-silicon-phenolic resin composite powder.

[0095] The nano-silicon-phenolic resin composite powder was transferred to an argon atmosphere furnace for high-temperature pyrolysis at a temperature of 900℃, ultimately yielding the finished silicon-carbon anode material.

[0096] The morphology, particle size, and specific surface area of ​​the silicon-carbon anode material were tested using scanning electron microscopy, laser diffraction, and gas adsorption BET method, respectively. The electrochemical performance of the material was then tested by assembling coin cells with the material as the active material. The results are shown in Table 1.

[0097] Comparative example:

[0098] Weigh 10g of nano-silicon, add it to 300mL of water, and use mechanical stirring for 2-5 minutes to initially disperse it into a suspension. Then pump it into a homogenizing hopper and homogenize it under a high-pressure pulse of 80MPa to obtain a uniform nano-silicon suspension.

[0099] Add 120g of 70wt% phenolic resin aqueous solution to the nano-silicon suspension, stir and mix evenly, then add 1.68g of hexyl isocyanate and stir to completely dissolve or disperse evenly to form a precursor slurry.

[0100] The precursor slurry was transferred to a 100°C oil bath and treated for 6-8 hours under continuous stirring to allow the solvent to fully evaporate, forming a nano-silicon-phenolic resin composite material.

[0101] The nano-silicon-phenolic resin composite material was transferred to an argon atmosphere furnace for high-temperature pyrolysis at 800℃. The pyrolysis products were then crushed using a ball milling process to finally obtain the finished silicon-carbon anode material.

[0102] The morphology, particle size, and specific surface area of ​​the silicon-carbon anode material were tested using scanning electron microscopy, laser diffraction, and gas adsorption BET method, respectively. The electrochemical performance of the material was then tested by assembling coin cells with the material as the active material. The results are shown in Table 1.

[0103] Table 1. Particle size, specific surface area, and electrochemical performance of silicon-carbon anode materials

[0104]

[0105] Based on the above embodiments 1-5 and comparative examples, Figure 2 The microstructures of the silicon-carbon anode materials prepared according to Examples 1-4 of the present invention are shown. Figure 3 The microstructure of the silicon-carbon anode material prepared according to Example 5 of the present invention is shown. Figure 4 The microstructure of silicon-carbon anode materials prepared in a comparative manner is illustrated. The comparison shows that the silicon-carbon anode material prepared using this invention has a porous structure, which can significantly improve charge transport performance and buffer volume expansion.

[0106] As can be seen from the above embodiments, the method for preparing silicon-carbon anode materials for lithium-ion batteries provided by the present invention directly granulates and forms a solid-liquid mixture precursor, eliminating the product crushing process, shortening the process flow, and reducing impurity contamination; by adding additives, phenolic resin can be rapidly cured, thus spray drying can be used to replace the direct evaporation process to treat the precursor, shortening the solvent removal time; due to the large droplet evaporation area in the spray drying process, under the dual action of heating and convection, the energy consumption for solvent removal is greatly reduced compared to the traditional direct evaporation process.

[0107] The method for preparing silicon-carbon anode materials for lithium-ion batteries according to the present invention has been described above by way of example with reference to the accompanying drawings. However, those skilled in the art should understand that various modifications can be made to the method for preparing silicon-carbon anode materials for lithium-ion batteries according to the present invention without departing from the scope of the invention. Therefore, the scope of protection of the present invention should be determined by the contents of the appended claims.

Claims

1. A method for preparing a silicon-carbon anode material for lithium-ion batteries, characterized in that, include: After mixing nano-silicon with modifier and solvent water according to the preset mixing ratio, high-pressure pulse homogenization treatment is performed to form a uniform nano-silicon suspension. Phenolic resin is added to the nano-silicon suspension and dispersed or dissolved to form a nano-silicon-phenolic resin suspension, wherein the mass ratio of the phenolic resin to the solvent water is 1 / 10 to 1 / 2.

5. An isocyanate additive is added to the nano-silicon-phenolic resin suspension and dispersed or dissolved to form a nano-silicon-phenolic resin-isocyanate precursor slurry, wherein the mass ratio of the isocyanate additive to the phenolic resin is 1 / 500 to 1 / 50. The nano-silicon-phenolic resin-isocyanate precursor slurry is subjected to atomization drying and curing treatment to form nano-silicon-phenolic resin composite powder. The nano-silicon-phenolic resin-isocyanate precursor slurry is subjected to atomization drying treatment using a spray dryer. The inlet temperature of the spray dryer is 150-250 °C and the pressure is 0.15-0.25 MPa. The nano-silicon-phenolic resin composite powder was subjected to high-temperature pyrolysis to obtain silicon-carbon anode material.

2. The method for preparing the silicon-carbon anode material for lithium-ion batteries as described in claim 1, characterized in that, The mass ratio of the nano-silicon to the solvent water is 1 / 30 to 1 / 20.

3. The method for preparing the silicon-carbon anode material for lithium-ion batteries as described in claim 1, characterized in that, The pressure used in the high-pressure pulse homogenization process is not less than 60 MPa.

4. The method for preparing the silicon-carbon anode material for lithium-ion batteries as described in claim 1, characterized in that, The phenolic resin is a phenolic resin solution or phenolic resin powder, wherein the viscosity of the phenolic resin solution is ≤600 cP.

5. The method for preparing the silicon-carbon anode material for lithium-ion batteries as described in claim 1, characterized in that, The isocyanate auxiliaries are any one of monoisocyanates, diisocyanates, or polyisocyanates.

6. The method for preparing the silicon-carbon anode material for lithium-ion batteries as described in claim 1, characterized in that, During the high-temperature pyrolysis of the nano-silicon-phenolic resin composite powder... The nano-silicon-phenolic resin composite powder was subjected to high-temperature pyrolysis treatment in an argon atmosphere furnace, wherein the inlet temperature of the nano-silicon-phenolic resin composite powder was 150-250 °C and the pressure was 0.15-0.25 MPa.

7. The method for preparing the silicon-carbon anode material for lithium-ion batteries as described in claim 6, characterized in that, The pyrolysis temperature of the nano-silicon-phenolic resin composite powder is 750-950 °C.

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