Porous silicon carbon negative electrode material and preparation method and application thereof

Abstract

The invention discloses a porous silicon carbon negative electrode material and a preparation method and application thereof, and belongs to the technical field of energy storage materials. Phenolic resin-based porous carbon microspheres are obtained through emulsion polymerization, high-temperature carbonization and gas corrosion, the porous carbon microspheres are used as a matrix, nano silicon particles are deposited in pores of the porous carbon by using a chemical vapor deposition technology, a carbon layer is coated on the outer layer again, and finally the porous silicon-carbon negative electrode material is obtained. According to the porous silicon-carbon negative electrode material, the porous structure of the porous carbon microspheres and the external carbon layer are combined to limit the expansion space of the nano silicon particles and reduce the influence of silicon expansion on the electrode structure, a three-dimensional conductive network constructed by the internal and external carbon materials makes up the defect of poor conductivity of silicon, the rate capability and cycling stability of the battery are improved, and the service life of the battery is prolonged. And the porous silicon carbon negative electrode material is simple in preparation process flow and low in theoretical cost, and has great commercial potential.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage materials, and particularly relates to a porous silicon-carbon anode material, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries dominate the electrochemical energy storage market indisputably due to their advantages of high energy density, long cycle life, no memory effect, low self-discharge, and being green and pollution-free. Currently, they are widely used in the fields of aerospace, electric vehicles, digital 3C, and military equipment. However, the specific capacity per gram of traditional commercial graphite anodes has reached nearly the theoretical limit (372 mAh·g -1 ), which greatly restricts the further development of high specific energy secondary batteries.

[0003] Silicon is regarded as the most promising next-generation anode material for lithium-ion batteries due to its ultra-high theoretical specific capacity (3590 mAh·g -1 , Li 15 Si4), relatively low lithiation / delithiation potential (0.4 V vs Li / Li + ), abundant natural reserves (26.4 wt.%), and environmental friendliness. However, silicon undergoes a huge volume expansion (>300%) during the process of lithium insertion and extraction, which leads to a series of problems such as particle pulverization, separation of active substances from the current collector, and damage to the electrode structure during cycling, affecting the cycling performance and rate performance of the electrode. Introducing carbon materials to composite with silicon is considered an effective way to reduce the influence of silicon anode expansion. By reasonable pore structure design, a certain space is provided to accommodate and limit the expansion of silicon, reducing its impact on the electrode structure. At the same time, carbon materials also compensate for the disadvantage of poor conductivity of silicon. Therefore, designing a porous silicon-carbon anode material with high capacity, long cycle life, low cost, and capable of mass production is of great significance for promoting the development of high specific energy secondary batteries.

[0004] The prior art patent application CN114188533A discloses a cathode material, a preparation method thereof, and an application thereof. First, graphite is subjected to gas corrosion and pore-forming treatment, then nitrogen elements are doped by chemical vapor deposition technology, and then it is mixed with a silicon source and a liquid-phase coating agent, and a silicon-carbon material with low expansion, high capacity, and high rate performance is obtained through heat treatment. However, the liquid-phase coating method is not suitable for mass production. When the production volume is increased, phenomena such as sagging and agglomeration will occur, resulting in uneven performance and poor consistency, and low industrialization potential.

[0005] The prior art patent application CN118553900A discloses a porous silicon-carbon anode material, its preparation method, an anode sheet, and a battery. First, graphite, carbon nanotubes, conductive carbon black, and a polymer material are mixed, and then successively subjected to stirring, granulation, and high-temperature sintering to obtain a porous carbon skeleton coated with a first coating layer. Nano-silicon particles are deposited in the pores, and a second coating layer is coated by chemical vapor deposition or solid-phase coating method to obtain a porous silicon-carbon material. However, the solid-phase mixing method has poor uniformity. The uneven distribution of the polymer material in the granular materials leads to uneven pore distribution, and the pores obtained by the decomposition of the polymer material are relatively large, resulting in a small restrictive effect on the volume expansion of the nano-silicon particles deposited in the pores, affecting the rate performance and cycling performance of the battery. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention provides a porous silicon-carbon anode material, its preparation method, and application. In the present invention, a phenolic resin compound is first carbonized, and then successively subjected to CO2 gas corrosion, nano-silicon particle deposition, and carbon material coating to obtain a porous silicon-carbon anode material. The porous silicon-carbon anode material obtained by the method of the present invention effectively restricts the expansion of silicon particles, reduces the influence of silicon particle expansion on the electrode structure, and makes up for the disadvantage of poor intrinsic conductivity of silicon, significantly improving the cycling performance and rate performance of the silicon-based anode material.

[0007] To achieve the purpose, the present invention adopts the following technical solutions:

[0008] The present invention protects a preparation method of a porous silicon-carbon anode material, including the following steps:

[0009] S1. Dissolve phenolic substances and aldehyde substances in water or water containing alcohol, add a catalyst to cause the condensation reaction between phenolic hydroxyl groups and aldehyde groups, and then obtain carbon microspheres through centrifugation, drying, and carbonization.

[0010] S2. Place the carbon microspheres in a CVD tube furnace, introduce CO2 gas, activate at a high temperature, and create pores on the carbon microspheres to obtain porous carbon microspheres. In this process, by adjusting the temperature and gas flow rate of gas activation, the pore size of the porous carbon microspheres is adjusted to obtain porous carbon microspheres with a hierarchical porous structure. The pore structure not only has the function of inhibiting the expansion of silicon nanoparticles but also provides a fast channel for the transport of electrolyte ions, shortening the diffusion distance and improving the cycling stability of the lithium-ion battery under high-current conditions.

[0011] S3. Replace the gas source, introduce silane into the CVD tube furnace, and deposit nano-silicon particles in the pores of the porous carbon microspheres to obtain a silicon-carbon material.

[0012] S4. Replace the gas source, introduce a carbon source into the CVD tube furnace, and coat the silicon-carbon material to obtain a porous silicon-carbon anode material.

[0013] Preferably, in step S1, the mass ratio of the phenolic substance to the aldehyde substance is 1:1.2 to 2.5.

[0014] Preferably, in step S1, the phenolic substance is selected from phenol, cresol, xylenol or resorcinol; the aldehyde substance is selected from formaldehyde, furfural or acetaldehyde.

[0015] Preferably, in step S1, the catalyst is ammonia water, and the mass ratio of the total amount of the phenolic substance and the aldehyde substance to ammonia water is 10 - 15:100.

[0016] Preferably, in step S1, the inert gas used in the carbonization process is N2 or Ar.

[0017] Preferably, in step S1, the carbonization temperature is 600°C to 700°C, the carbonization time is 1 h to 3 h, and the gas flow rate is 50 mL·min -1 ~80 mL·min -1 .

[0018] Preferably, in step S2, the activation temperature is 700°C to 900°C, the activation time is 1 h to 2.5 h, and the CO2 flow rate is 50 mL·min -1 ~130 mL·min -1 .

[0019] Preferably, in step S3, the deposition temperature is 500°C to 700°C, the deposition time is 1.5 h to 3 h, and the silane flow rate is 50 mL·min -1 ~80 mL·min -1 .

[0020] Preferably, in step S4, the carbon source is selected from methane, ethane, ethylene, acetylene, propylene or propyne.

[0021] Preferably, in step S4, the coating temperature is 450°C to 650°C, the coating time is 1 h to 1.5 h, and the carbon source gas flow rate is 60 mL·min -1 ~100 mL·min -1 .

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention discloses a preparation method of a porous silicon-carbon anode material. The present invention uses a phenolic resin compound as a raw material, obtains carbon microspheres through carbonization, then corrodes the phenolic resin-based carbon microspheres with a gas to obtain porous carbon microspheres, and then uses the porous carbon microspheres as a matrix to deposit nano-silicon particles in the pores of the matrix through chemical vapor deposition, and coats a carbon layer again on the outermost layer. By adjusting the temperature and gas flow rate during the gas activation process, the pore size is adjusted to obtain porous carbon microspheres with a hierarchical porous structure. The "confining effect" of the pores of the porous carbon microspheres and the combined action of the outer carbon layer limit the expansion space of the silicon nanoparticles, effectively inhibiting the expansion of the silicon nanoparticles. The three-dimensional conductive network constructed by the matrix porous carbon microspheres and the outer carbon layer makes up for the disadvantage of the low intrinsic conductivity of the silicon nanoparticles.

[0024] The silicon-carbon anode material includes porous carbon microspheres with a hierarchical porous structure distribution. Nano-silicon particles are deposited in the pores of the porous carbon microspheres, and a carbon layer is wrapped on the outermost layer. The design of this three-dimensional porous spherical structure and the double coating layer not only improves the conductivity of the porous silicon-carbon anode material, but also reduces the influence brought by silicon expansion, stabilizes the electrode structure, has a high capacity, and improves the rate performance and cycle stability of the lithium-ion battery after preparing the lithium-ion battery with it.

[0025] 2. During the preparation process of the present invention, activation, deposition and coating are all carried out in the same equipment. Only the gas source needs to be replaced, and the theoretical cost is greatly reduced. The preparation method is simple and suitable for large-scale industrial preparation, and has great commercial potential.

[0026] 3. Applying the porous silicon-carbon anode material of the present invention in a lithium-ion battery combines the high specific capacity of the silicon material and the excellent conductivity and cycle performance of the carbon material. The initial Coulomb efficiency and capacity are relatively high, and the cycle stability is better. It is a very promising anode material for lithium-ion batteries. Specifically, under the test conditions of the initial current of 200 mA g -1 the initial Coulomb efficiency is 91.40%, and the initial week discharge capacity is 1599.41 mAh g -1 , and then under the condition of a current of 1000 mA g -1 after 100 cycles, the capacity is 753.66 mAh g -1 , and the capacity retention rate is 92.96%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a scanning electron microscope image of the porous silicon-carbon anode material prepared in Example 1.

[0028] Figure 2 It is a cycle performance graph of the porous silicon-carbon anode material prepared in Example 1.

[0029] Figure 3The first charge-discharge graph of the porous silicon-carbon anode material prepared in Example 1.

[0030] Figure 4 The BET data graph of the silicon-carbon material prepared in Example 1, where (a) is the pore volume distribution graph and (b) is the pore area distribution graph. Detailed implementation manners

[0031] The following is a detailed description of the specific implementation manners of the present invention. However, it should be understood that the protection scope of the present invention is not limited by the specific implementation manners. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0032] Considering that although various types and structures of porous silicon-carbon anode materials have been obtained in the prior art, they cannot simultaneously meet the requirements of high capacity, long cycle life, low cost, and mass production. They can only stay in the laboratory stage and cannot replace graphite for mass application. The present invention provides a porous silicon-carbon anode material and a preparation method thereof. The present invention first prepares a phenolic resin compound using cheap phenolic substances and aldehyde substances, and then successively performs carbonization, activation, deposition, and coating treatments to obtain a porous silicon-carbon anode material with high capacity and long cycle life. During the preparation process, carbonization, activation, deposition, and coating are all carried out in a tube furnace. By only adjusting the temperature of the tube furnace and the types of gases, the preparation of the porous silicon-carbon anode material can be achieved, which has the advantages of low cost and mass production, and overcomes the technical defects of the prior art porous silicon-carbon anode materials and their preparation methods.

[0033] The present invention provides a preparation method of a porous silicon-carbon anode material, and the specific steps are as follows:

[0034] Step 1: Dissolve phenolic substances and aldehyde substances in water or a water solvent containing alcohol, add ammonia water, stir at 55 °C for 12 h, and after centrifugation by a centrifuge, transfer to a vacuum oven and dry at 80 °C for 6 h to obtain a phenolic resin compound.

[0035] Step 2: Perform high-temperature carbonization and gas corrosion to create pores on the phenolic resin compound to obtain porous carbon microspheres with a particle size of 5 μm to 20 μm in a spherical shape.

[0036] Step 3: Replace the gas source, and use silane for the deposition of nano-silicon particles to obtain a silicon-carbon material with nano-silicon particles deposited in the pores of the porous carbon microspheres.

[0037] Step 4: Replace the gas source, and use a carbon source for carbon layer coating to obtain the final porous silicon-carbon anode material.

[0038] The present invention also provides a lithium-ion half-cell, which is composed of a working electrode, a counter electrode, an electrolyte and a separator. Among them, the working electrode is made of the porous silicon-carbon anode material of the present invention, the counter electrode is selected from a lithium metal sheet, the separator is selected from a 2325 separator, and the electrolyte is selected from a solution of ethylene carbonate (EC), diethyl carbonate (DEC) and fluoroethylene carbonate (FEC) containing 1 mol / L lithium hexafluorophosphate (LiPF6), and the volume ratio of EC, DEC and FEC is 4.5:4.5:1.

[0039] The technical solution of the present invention will be further described in detail by the following examples, which are specifically as follows:

[0040] Example 1

[0041] A preparation method of a porous silicon-carbon anode material includes the following steps:

[0042] S1. Resorcinol and formaldehyde are mixed in water according to a mass ratio of 1:1.2, where the solid content is 30% (the solid content is the total mass of resorcinol and formaldehyde), the water content is 70%, and then ammonia water with a mass of 10% of the solid content is added as an alkaline catalyst, and stirred at 55 °C for 12 h to obtain a phenolic resin compound; after the phenolic resin compound is centrifuged and vacuum dried, it is placed in a CVD tube furnace at 650 °C, and N2 is introduced, and the gas flow rate is 50 mL·min -1 , and heat-treated for 2 h to obtain carbon microspheres.

[0043] S2. Replace the gas source with CO2, and the flow rate is 80 mL·min -1 , and the carbon microspheres are gas-etched at 800 °C for 1.5 h to obtain porous carbon microspheres.

[0044] S3. Replace the gas source with silane, and the flow rate is 60 mL·min -1 , and the porous carbon microspheres are deposited at 700 °C for 2 h to obtain a silicon-carbon material with nano-silicon particles deposited inside the pores.

[0045] S4. Replace the gas source with ethylene, and the silicon-carbon material is carbon-coated at 500 °C for 1 h, and the carbon coating flow rate is 80 mL·min -1 , to obtain a porous silicon-carbon anode material.

[0046] The porous silicon-carbon anode material prepared in Example 1 is mixed with a conductive agent and a binder in a mass ratio of 8:1:1, and ball-milled in a planetary ball mill to obtain a uniformly dispersed negative electrode slurry; the negative electrode slurry is uniformly coated on a copper foil current collector, and vacuum dried to obtain a working electrode. The working electrode is transferred to a vacuum glove box filled with argon, and a CR2032 type button half-cell is assembled for testing. Specifically, the first-cycle current is 200 mAg -1Under the test conditions, the initial Coulombic efficiency is 91.40%, and the discharge capacity in the first week is 1599.41 mAh g -1 , and then under the condition of a current of 1000 mA g -1 , after 100 cycles, the capacity is 753.56 mAh g -1 , and the capacity retention rate is 92.96%.

[0047] Example 2

[0048] A preparation method of a porous silicon-carbon anode material includes the following steps:

[0049] S1. Mix resorcinol and formaldehyde in water according to a mass ratio of 1:2, where the solid content is 30% (the solid content is the total mass of resorcinol and formaldehyde), the water content is 70%, and then add ammonia water with a mass of 10% of the solid content as an alkaline catalyst, and stir at 55°C for 12 h to obtain a phenolic resin compound; after centrifuging and vacuum drying the phenolic resin compound, place it in a CVD tube furnace at 600°C, introduce N2, and the gas flow rate is 50 mL·min -1 , and perform heat treatment for 3 h to obtain carbon microspheres.

[0050] S2. Replace the gas source with CO2, and the flow rate is 60 mL·min -1 , and perform gas corrosion on the carbon microspheres at 800°C for 1.5 h to obtain porous carbon microspheres.

[0051] S3. Replace the gas source with silane, and the flow rate is 60 mL·min -1 , and perform a 2-h deposition treatment on the porous carbon microspheres at 700°C to obtain a silicon-carbon material with nanosilicon particles deposited inside the pores.

[0052] S4. Replace the gas source with ethylene, and perform a 1-h carbon coating treatment on the silicon-carbon material at 550°C, and the carbon coating flow rate is 80 mL·min -1 , to obtain a porous silicon-carbon anode material.

[0053] Mix the porous silicon-carbon anode material prepared in Example 2 with a conductive agent and a binder in a mass ratio of 8:1:1, and ball mill in a planetary ball mill to obtain a uniformly dispersed anode slurry; uniformly coat the anode slurry on a copper foil current collector, and obtain a working electrode after vacuum drying. Transfer the working electrode to a vacuum glove box filled with argon, and assemble a CR2032-type button half-cell for testing. Specifically, at the first-cycle current of 200 mAg -1 Under the test conditions, the initial Coulombic efficiency is 87.34%, and the discharge capacity in the first week is 1763.56 mAh g -1 , and then under the condition of a current of 1000 mA g -1After 100 cycles under the conditions, the capacity is 834.83 mAh g -1 , and the capacity retention rate is 89.68%.

[0054] Example 3

[0055] A preparation method of a porous silicon-carbon anode material, comprising the following steps:

[0056] S1. Resorcinol and formaldehyde are mixed in water according to a mass ratio of 1:1.5, wherein the solid content is 30% (the solid content is the total mass of resorcinol and formaldehyde), the water content is 70%, and 10% of the solid content of ammonia water is added as an alkaline catalyst, and stirred at 55 °C for 12 h to obtain a phenolic resin compound; the phenolic resin compound is centrifuged and vacuum dried and then placed in a CVD tube furnace at 600 °C, and N2 is introduced, and the gas flow rate is 50 mL·min -1 , and heat-treated for 3 h to obtain carbon microspheres.

[0057] S2. Replace the gas source with CO2, and the flow rate is 100 mL·min -1 , and the carbon microspheres are gas-etched at 900 °C for 1.5 h to obtain porous carbon microspheres.

[0058] S3. Replace the gas source with silane, and the flow rate is 80 mL·min -1 , and the porous carbon microspheres are subjected to a 2-h deposition treatment at 550 °C to obtain a silicon-carbon material with nanosilicon particles deposited inside the pores.

[0059] S4. Replace the gas source with ethylene, and the silicon-carbon material is carbon-coated at 450 °C for 1.5 h, and the carbon-coating flow rate is 70 mL·min -1 , to obtain a porous silicon-carbon anode material.

[0060] The porous silicon-carbon anode material prepared in Example 3 is mixed with a conductive agent and a binder in a mass ratio of 8:1:1, and ball-milled in a planetary ball mill to obtain a uniformly dispersed anode slurry; the anode slurry is uniformly coated on a copper foil current collector and vacuum dried to obtain a working electrode. The working electrode is transferred to a vacuum glove box filled with argon, and a CR2032 type button half-cell is assembled for testing. Specifically: at the first-cycle current of 200 mAg -1 Under the test conditions, the first Coulombic efficiency is 86.98%, and the first-week discharge capacity is 1679.58 mAh g -1 , and then at a current of 1000 mA g -1 After 100 cycles under the conditions, the capacity is 734.82 mAh g -1 , and the capacity retention rate is 87.31%.

[0061] Example 4

[0062] A preparation method of a porous silicon-carbon anode material, comprising the following steps:

[0063] S1. Mix resorcinol and formaldehyde in water at a mass ratio of 1:2.5, where the solid content is 30% (the solid content is the total mass of resorcinol and formaldehyde), the water content is 70%, and then add ammonia water with a mass of 10% of the solid content as an alkaline catalyst, and stir at 55 °C for 12 h to obtain a phenolic resin compound; after centrifuging and vacuum drying the phenolic resin compound, place it in a CVD tube furnace at 700 °C, introduce N2, and the gas flow rate is 50 mL·min -1 , and perform heat treatment for 1 h to obtain carbon microspheres.

[0064] S2. Replace the gas source with CO2, and the flow rate is 50 mL·min -1 , and perform gas corrosion on the carbon microspheres at 700 °C for 2 h to obtain porous carbon microspheres.

[0065] S3. Replace the gas source with silane, and the flow rate is 80 mL·min -1 , and perform deposition treatment on the porous carbon microspheres at 600 °C for 2 h to obtain a silicon-carbon material with nanosilicon particles deposited inside the pores.

[0066] S4. Replace the gas source with acetylene, and perform carbon coating treatment on the silicon-carbon material at 650 °C for 1 h, and the carbon coating flow rate is 70 mL·min -1 , to obtain a porous silicon-carbon anode material.

[0067] Mix the porous silicon-carbon anode material prepared in Example 4 with a conductive agent and a binder at a mass ratio of 8:1:1, and ball mill in a planetary ball mill to obtain a uniformly dispersed negative electrode slurry; uniformly coat the negative electrode slurry on a copper foil current collector, and obtain a working electrode after vacuum drying. Transfer the working electrode to a vacuum glove box filled with argon, and assemble a CR2032 type button half-cell for testing. Specifically, it shows that: at the first cycle current of 200 mAg -1 Under the test conditions, the initial Coulombic efficiency is 90.21%, and the initial week discharge capacity is 1843.26 mAh g -1 , and then after cycling 100 times under the condition of a current of 1000 mA g -1 , the capacity is 956.81 mAh g -1 , and the capacity retention rate is 89.34%.

[0068] Example 5

[0069] A preparation method of a porous silicon-carbon anode material, comprising the following steps:

[0070] S1. Mix phenol and formaldehyde in water at a mass ratio of 1:1.5, with a solid content of 30% (the total mass of phenol and formaldehyde), a water content of 70%. Then add ammonia water with a mass of 10% of the solid content as an alkaline catalyst, and stir at 55 °C for 12 h to obtain a phenolic resin compound; centrifuge and vacuum dry the phenolic resin compound, then place it in a CVD tube furnace at 700 °C, introduce N2, and the gas flow rate is 50 mL·min -1 , and perform heat treatment for 3 h to obtain carbon microspheres.

[0071] S2. Replace the gas source with CO2, and the flow rate is 50 mL·min -1 , and perform gas corrosion on the carbon microspheres at 900 °C for 2 h to obtain porous carbon microspheres.

[0072] S3. Replace the gas source with silane, and the flow rate is 60 mL·min -1 , and perform deposition treatment on the porous carbon microspheres at 550 °C for 2 h to obtain a silicon-carbon material with nano-silicon particles deposited inside the pores.

[0073] S4. Replace the gas source with acetylene, and perform carbon coating treatment on the silicon-carbon material at 500 °C for 1.5 h, and the carbon coating flow rate is 60 mL·min -1 , to obtain a porous silicon-carbon negative electrode material.

[0074] Mix the porous silicon-carbon negative electrode material prepared in Example 5 with a conductive agent and a binder at a mass ratio of 8:1:1, and ball mill in a planetary ball mill to obtain a uniformly dispersed negative electrode slurry; uniformly coat the negative electrode slurry on a copper foil current collector, and vacuum dry to obtain a working electrode. Transfer the working electrode to a vacuum glove box filled with argon, and assemble a CR2032 type coin half-cell for testing. Specifically: under the test condition of a first-cycle current of 200 mAg -1 , the first Coulombic efficiency is 87.49%, and the first-week discharge capacity is 1781.26 mAh g -1 , and then cycle 100 times under the condition of a current of 1000 mA g -1 , the capacity is 895.37 mAh g -1 , and the capacity retention rate is 85.87%.

[0075] Example 6

[0076] A preparation method of a porous silicon-carbon negative electrode material, comprising the following steps:

[0077] S1. Mix xylenol and formaldehyde in water at a mass ratio of 1:1.5, with a solid content of 30% (the solid content is the total mass of xylenol and formaldehyde), a water content of 70%. Then add ammonia water with a mass of 10% of the solid content as an alkaline catalyst, and stir at 55 °C for 12 h to obtain a phenolic resin compound; after centrifuging and vacuum drying the phenolic resin compound, place it in a CVD tube furnace at 600 °C, introduce N2, and the gas flow rate is 50 mL·min -1 , and perform heat treatment for 3 h to obtain carbon microspheres.

[0078] S2. Replace the gas source with CO2, and the flow rate is 120 mL·min -1 , and perform gas corrosion on the carbon microspheres at 900 °C for 1 h to obtain porous carbon microspheres.

[0079] S3. Replace the gas source with silane, and the flow rate is 80 mL·min -1 , and perform deposition treatment on the porous carbon microspheres at 500 °C for 3 h to obtain a silicon-carbon material with nano-silicon particles deposited inside the pores.

[0080] S4. Replace the gas source with ethylene, and perform carbon coating treatment on the silicon-carbon material at 450 °C for 1.5 h, and the carbon coating flow rate is 80 mL·min -1 , to obtain a porous silicon-carbon anode material.

[0081] Mix the porous silicon-carbon anode material prepared in Example 6 with a conductive agent and a binder at a mass ratio of 8:1:1, and ball mill in a planetary ball mill to obtain a uniformly dispersed anode slurry; uniformly coat the anode slurry on a copper foil current collector, and obtain a working electrode after vacuum drying. Transfer the working electrode to a vacuum glove box filled with argon, and assemble a CR2032 type coin half-cell for testing. Specifically, at the first-cycle current of 200 mAg -1 Under the test conditions, the initial Coulombic efficiency is 89.32%, and the first-week discharge capacity is 1635.49 mAh g -1 , and then under the condition of a current of 1000 mA g -1 After cycling 100 times, the capacity is 791.36 mAh g -1 , and the capacity retention rate is 87.69%.

[0082] Example 7

[0083] A preparation method of a porous silicon-carbon anode material, comprising the following steps:

[0084] S1. Mix resorcinol and furfural in water at a mass ratio of 1:1.5, with a solid content of 30% (the solid content is the total mass of resorcinol and furfural), a water content of 70%. Then add ammonia water with a mass of 10% of the solid content as an alkaline catalyst, and stir at 55 °C for 12 h to obtain a phenolic resin compound. After centrifuging and vacuum drying the phenolic resin compound, place it in a CVD tube furnace at 600 °C, introduce N2, and the gas flow rate is 70 mL·min -1 , and perform heat treatment for 3 h to obtain carbon microspheres.

[0085] S2. Replace the gas source with CO2, and the flow rate is 130 mL·min -1 , and perform gas corrosion on the carbon microspheres at 900 °C for 1 h to obtain porous carbon microspheres.

[0086] S3. Replace the gas source with silane, and the flow rate is 60 mL·min -1 , and perform deposition treatment on the porous carbon microspheres at 650 °C for 2 h to obtain a silicon-carbon material with nano-silicon particles deposited inside the pores.

[0087] S4. Replace the gas source with ethylene, and perform carbon coating on the silicon-carbon material at 500 °C for 1.5 h, and the carbon coating flow rate is 100 mL·min -1 , to obtain a porous silicon-carbon negative electrode material.

[0088] Mix the porous silicon-carbon negative electrode material prepared in Example 7, a conductive agent, and a binder in a mass ratio of 8:1:1, and ball mill in a planetary ball mill to obtain a uniformly dispersed negative electrode slurry; uniformly coat the negative electrode slurry on a copper foil current collector, and obtain a working electrode after vacuum drying. Transfer the working electrode to a vacuum glove box filled with argon, and assemble a CR2032 type coin half-cell for testing. Specifically, under the test conditions of a first-cycle current of 200 mAg -1 , the initial Coulombic efficiency is 88.36%, and the first-week discharge capacity is 1735.24 mAh g -1 , and then cycle 100 times under the condition of a current of 1000 mA g -1 , the capacity is 883.42 mAh g -1 , and the capacity retention rate is 86.42%.

[0089] Example 8

[0090] A preparation method of a porous silicon-carbon negative electrode material, comprising the following steps:

[0091] S1. Cresol and furfural are mixed in water at a mass ratio of 1:1.5, with a solid content of 30% (the solid content is the total mass of cresol and furfural), a water content of 70%. Then, ammonia water with a mass of 10% of the solid content is added as an alkaline catalyst, and the mixture is stirred at 55 °C for 12 h to obtain a phenolic resin compound. The phenolic resin compound is centrifuged and vacuum dried, and then placed in a CVD tube furnace at 700 °C. N2 is introduced, and the gas flow rate is 80 mL·min -1 , and heat-treated for 3 h to obtain carbon microspheres.

[0092] S2. Replace the gas source with CO2, and the flow rate is 60 mL·min -1 , and the carbon microspheres are gas-etched at 800 °C for 2.5 h to obtain porous carbon microspheres.

[0093] S3. Replace the gas source with silane, and the flow rate is 50 mL·min -1 , and the porous carbon microspheres are deposited at 550 °C for 1.5 h to obtain a silicon-carbon material with nano-silicon particles deposited inside the pores.

[0094] S4. Replace the gas source with ethylene, and the silicon-carbon material is carbon-coated at 500 °C for 1.5 h, and the carbon-coating flow rate is 80 mL·min -1 , to obtain a porous silicon-carbon anode material.

[0095] The porous silicon-carbon anode material prepared in Example 8 is mixed with a conductive agent and a binder at a mass ratio of 8:1:1, and ball-milled in a planetary ball mill to obtain a uniformly dispersed anode slurry; the anode slurry is uniformly coated on a copper foil current collector and vacuum dried to obtain a working electrode. The working electrode is transferred to a vacuum glove box filled with argon, and a CR2032 type coin half-cell is assembled for testing. Specifically, at the first-cycle current of 200 mAg -1 under the test conditions, the first Coulombic efficiency is 90.38%, and the first-week discharge capacity is 1538.62 mAh g -1 , and then, after cycling 100 times under the condition of a current of 1000 mAg -1 , the capacity is 702.45 mAh g -1 , and the capacity retention rate is 88.31%.

[0096] The pore size analysis of the silicon-carbon material (after depositing nano-silicon particles) in Example 1 of the present invention is carried out, and the BET data is shown in Table 1 and Figure 4 as shown, indicating that the silicon-carbon material has a hierarchical porous structure.

[0097] Table 1 Pore distribution analysis table of silicon-carbon material

[0098]

[0099] The applicant declares that the above description is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a porous silicon-carbon anode material, characterized in that, The steps include the following: Carbonize the phenolic resin compound to obtain carbon microspheres; Activate the carbon microspheres with CO2 gas to create pores on the carbon microspheres and obtain porous carbon microspheres; Replace the gas source and introduce silane for deposition to deposit nano-silicon particles in the pores of the porous carbon microspheres to obtain a silicon-carbon material; Replace the gas source and introduce a carbon source to coat the silicon-carbon material to obtain a porous silicon-carbon anode material.

2. The preparation method of a porous silicon-carbon anode material according to claim 1, characterized in that, The conditions for carbonization are: carbonize at 600°C to 700°C for 1h to 3h.

3. The preparation method of a porous silicon-carbon anode material according to claim 1, characterized in that, The activation conditions are as follows: activation is carried out at 700 °C to 900 °C for 1 h to 2.5 h, and the CO2 gas flow rate is 50 mL·min -1 ~130 mL·min -1 .

4. The preparation method of a porous silicon-carbon anode material according to claim 1, characterized in that, The deposition conditions are as follows: deposition is carried out at 500 °C to 700 °C for 1.5 h to 3 h, and the flow rate of silane gas is 50 mL·min -1 ~80 mL·min -1 .

5. The preparation method of a porous silicon-carbon anode material according to claim 1, characterized in that, The coating conditions are as follows: coating is carried out at 450 °C to 650 °C for 1 h to 1.5 h, and the flow rate of the carbon source gas is 60 mL·min -1～ -100 mL·min -1 .

6. The preparation method of a porous silicon-carbon anode material according to claim 1, characterized in that, The carbon source is selected from methane, ethane, ethylene, acetylene, propylene or propyne.

7. The preparation method of a porous silicon-carbon anode material according to claim 1, characterized in that, The phenolic resin compound is prepared according to the following steps: using phenolic substances and aldehyde substances as raw materials, in the liquid phase, under catalytic action, causing the phenolic hydroxyl group and the aldehyde group to undergo a polycondensation reaction, separating the solvent, and obtaining the phenolic resin compound.

8. The preparation method of a porous silicon-carbon anode material according to claim 7, characterized in that, The phenolic substances are selected from phenol, cresol, xylenol or resorcinol; the aldehyde substances are selected from formaldehyde, furfural or acetaldehyde.

9. A porous silicon-carbon anode material prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The porous silicon-carbon anode material uses phenolic resin-based porous carbon microspheres as the matrix, deposits nano-silicon particles in the pores of the porous carbon microspheres, and then coats a carbon layer outside the nano-silicon particle layer.

10. Use of the porous silicon-carbon anode material according to claim 9 in the preparation of a negative electrode sheet for a lithium-ion battery.

Images