Silicon-carbon negative electrode material, preparation method and application thereof

Abstract

The embodiment of the present application relates to a kind of silicon-carbon negative electrode material preparation method, including first precursor raw material is dissolved in deionized water to obtain precursor solution;Soft template agent is dissolved in ethanol or deionized water, then hard template agent is added, to obtain hard soft template agent solution;Then the hard soft template agent solution is added to the precursor solution and mixed, and stationary to obtain mixed solution;The mixed solution is dried to obtain solid powder;The solid powder is calcined under the condition of first inert atmosphere, then after washing, drying, to obtain porous carbon material;Under the condition of second inert atmosphere, porous carbon material and silicon source gas are carried out gas deposition, to obtain porous carbon composite material including porous carbon and nano-silicon particles;Then under the condition of second inert atmosphere, carbon source gas is introduced, and the porous carbon composite material is coated to obtain silicon-carbon negative electrode material with carbon coating layer.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a silicon-carbon anode material, its preparation method, and its application. Background Technology

[0002] In recent years, silicon-carbon anode materials have demonstrated enormous application potential and development prospects due to their advantages such as high energy density, long cycle life, fast charge-discharge, and environmental friendliness. Currently, the mainstream method for preparing silicon-carbon anode materials is chemical vapor deposition (CVD), making the synthesis and selection of porous carbon materials as the matrix particularly important. Porous carbon enhances the performance of silicon-carbon anodes by mitigating volume expansion, improving conductivity, increasing reactive sites, improving electrode structural stability, and promoting electrolyte wetting.

[0003] Traditional methods for preparing porous carbon often involve using chemical etching or gas activation to create pores on the surface and inside of the carbon. However, existing methods have the following problems:

[0004] 1. Difficulty in controlling pore structure: For example, in the activation method, reaction conditions such as temperature, time, and the type and amount of activator all affect the pore structure. However, the interrelationships between these parameters are complex, making it difficult to achieve precise preparation of specific pore sizes. Adjusting the ratio of micropores to mesopores is also challenging. Depending on the different application requirements of silicon-carbon anodes, porous carbon matrix materials need to possess a suitable ratio of micropores to mesopores. However, existing preparation methods have limitations in adjusting the ratio of these two types of pores, which may prevent the material from achieving optimal performance.

[0005] 2. The process is complex, time-consuming, highly polluting, and involves high raw material costs, making it unsuitable for large-scale production. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing silicon-carbon anode materials. Using widely available raw materials, and through adjustments to the composite template agent and optimization of process parameters, a porous carbon material with controllable structure is prepared. This material also possesses a hierarchical structure of micro- and mesoporous components and a specific surface area of ​​1800 m². 2 / g-2200m 2 / g, with an average pore size of 1.75nm-1.95nm and a total pore volume of 0.85cm³. 3 / g-0.95cm 3 With a micropore content of 90%-95%, it can provide more active sites and a larger surface area in the preparation of silicon-carbon anode materials, which is conducive to the adsorption of reactant molecules such as silanes and improves the deposition efficiency. The appropriate pore size range can promote the electrochemical reaction of silicon and improve the reversible specific capacity and cycle stability of silicon-carbon anode materials.

[0007] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a silicon-carbon anode material, comprising:

[0008] S1, firstly, the precursor raw material is dissolved in deionized water to prepare a precursor solution; the soft template agent is dissolved in ethanol or deionized water, and then a hard template agent is added to obtain a hard and soft template agent solution; then the hard and soft template agent solution is added to the precursor solution for mixing, and the mixture is allowed to stand to obtain a mixed solution;

[0009] S2, the mixed solution is dried to obtain a solid powder;

[0010] S3, the solid powder is calcined under a first inert atmosphere, and then washed and dried to obtain a porous carbon material;

[0011] S4, under a second inert atmosphere, porous carbon material is vapor-deposited with silicon source gas to obtain a porous carbon composite material including porous carbon and nano-silicon particles; then, under a second inert atmosphere, carbon source gas is introduced to coat the porous carbon composite material to obtain a silicon-carbon anode material with a carbon coating layer.

[0012] Preferably, the precursor raw material is one or more selected from chitosan, chitosan oligosaccharide, glucose, carboxymethyl cellulose, alginate, hyaluronic acid, polyvinyl alcohol, and soluble starch; the mass fraction of the precursor solution is 2%-10%.

[0013] Preferably, the soft template agent is at least one of the following: polyoxyethylene polyoxypropylene ether triblock copolymer (Pluronic F127), polyethylene oxide-polypropylene oxide-polyoxyethylene triblock copolymer (Pluronic P123), polyethylene glycol-polystyrene (PEO-b-PS), 4-vinylpyridine (PS-b-P4VP), and polyethylene oxide-polymethyl methacrylate (PEO-b-PMMA).

[0014] The hard template agent includes tetraethyl orthosilicate and a salt, wherein the salt is at least one of sodium chloride, potassium chloride, sodium carbonate, and potassium carbonate; the mass ratio of the salt to tetraethyl orthosilicate in the hard template agent is 1:[2-5]; the mass ratio of the soft template agent, the hard template agent, and the precursor raw material is [1-1.2]:[1.5-2]:[4.5-5].

[0015] Preferably, in step S2, the drying method is any one of spray drying, vacuum drying, forced air drying, microwave drying, and infrared drying, the drying temperature is 80℃-180℃, and the drying time is 4h-16h.

[0016] Preferably, in step S3, the first inert atmosphere is nitrogen or argon, the calcination temperature is 600℃-900℃, the heating rate is 2℃ / min-5℃ / min, and the calcination time is 2h-6h.

[0017] The washing method involves impregnating the calcined material with a 1 mol / L to 2 mol / L sodium hydroxide solution, keeping it at 80℃ to 95℃ for 10 to 24 hours, then filtering and washing the turbid liquid until it is neutral, and finally drying it at 80℃ to 100℃ to obtain the porous carbon material.

[0018] Preferably, in step S4, the second inert atmosphere is one or more of nitrogen, argon, and helium;

[0019] The vapor deposition is carried out in a deposition furnace, and the conditions for vapor deposition are as follows: the heating rate is 2℃ / min-5℃ / min, the deposition temperature is 450℃-900℃, the silicon source gas and the inert gas are introduced into the deposition furnace together in a ratio of 1:[1-5], and the temperature is maintained for 2h-6h; the silicon source gas is any one of silane, silane and other silane-containing hydrocarbons.

[0020] Preferably, in step S4, the coating process is carbon coating, which is carried out in a coating furnace;

[0021] The conditions for carbon coating are as follows: the carbon source gas is one or more of alkanes, alkenes, and alkynes; the coating temperature is 500℃-800℃; the coating time is 1-4 hours; and the ratio of the inert gas to the carbon source gas can be 1:[1-3].

[0022] Preferably, the specific surface area of ​​the prepared silicon-carbon anode material with the carbon coating is 1800 m². 2 / g-2200m 2 / g, with an average pore size of 1.75nm-1.95nm and a total pore volume of 0.85cm³. 3 / g-0.95cm 3 / g;

[0023] The NLDFT pore volume of the carbon-coated silicon-carbon anode material is 0.75 cm³. 3 / g-0.90cm 3 / g, of which the micropore volume is 0.68cm³ 3 / g-0.78cm 3 / g, mesoporous pore volume is 0.07cm³ 3 / g-0.12cm 3 / g, with a microporous content of 90%-95%.

[0024] Secondly, embodiments of the present invention also provide a silicon-carbon anode material prepared by the preparation method described in the first aspect above.

[0025] Thirdly, embodiments of the present invention also provide a lithium battery, the lithium battery comprising the silicon-carbon anode material described in the second aspect above.

[0026] The silicon-carbon anode material, its preparation method, and its application provided in this invention have the following advantages:

[0027] 1. Improve the structural controllability of porous carbon materials: By combining various template agents and optimizing the preparation process, the pore size and distribution of porous carbon can be controlled within a certain range, and it has a highly ordered and uniform pore structure, thereby improving the structural controllability and application performance of the material.

[0028] 2. Reduced production costs: Existing technologies often involve high production costs for some high-performance porous carbon materials, limiting their large-scale application. This invention utilizes widely available raw materials and optimized process parameters to reduce raw material and processing costs.

[0029] 3. Expanding the application scope of porous carbon materials: Currently, porous carbon materials have been widely used in energy storage, environmental protection, biomedicine, and other fields. However, with the development of science and technology, the requirements for their performance and functions are becoming increasingly stringent. The porous carbon material prepared in this invention has a specific range of micro-mesopore distribution, high mechanical strength, and excellent conductivity, which can meet the requirements of silicon-carbon anodes for porous carbon matrices and expand its application scope. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a method for preparing a silicon-carbon anode material according to an embodiment of the present invention;

[0031] Figure 2 Scanning electron microscope (SEM) of the porous carbon material prepared in Example 1 of this invention. Figure 1 ;

[0032] Figure 3 Scanning electron microscope (SEM) of the porous carbon material prepared in Example 1 of this invention. Figure 2 ;

[0033] Figure 4 The X-ray diffraction pattern of the porous carbon material prepared in Example 1 of this invention;

[0034] Figure 5 This is a pore size distribution diagram of the porous carbon material prepared in Example 1 of the present invention. Detailed Implementation

[0035] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0036] Figure 1 A process flow for preparing silicon-carbon anode material provided in this embodiment of the invention, such as... Figure 1 As shown, the process for preparing a silicon-carbon anode material according to an embodiment of the present invention includes the following steps:

[0037] Step S1: First, the precursor raw material is dissolved in deionized water to prepare a precursor solution; the soft template agent is dissolved in ethanol or deionized water, and then a hard template agent is added to obtain a hard and soft template agent solution; then the hard and soft template agent solution is added to the precursor solution for mixing, and the mixture is allowed to stand to obtain a mixed solution.

[0038] Specifically, firstly, a precursor solution with a certain mass fraction is prepared by dissolving the precursor raw material in deionized water; secondly, a mixed solution of deionized water or ethanol containing hard and soft template agents is prepared in a certain proportion, that is, the soft template agent is dissolved in ethanol or deionized water, and then the hard template agent is added to obtain a hard and soft template agent solution; finally, the hard and soft template agent solution is added to the precursor solution for thorough mixing, and then allowed to stand at room temperature for a period of time, preferably 1h-6h, to obtain a mixed solution.

[0039] In a preferred embodiment, the precursor raw material is one or more of chitosan, chitosan oligosaccharide, glucose, carboxymethyl cellulose, alginate, hyaluronic acid, polyvinyl alcohol, and soluble starch; the mass fraction of the precursor solution is 2%-10%.

[0040] In a preferred embodiment, the soft template agent is at least one of polyoxyethylene polyoxypropylene ether triblock copolymer (Pluronic F127), polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer (Pluronic P123), polyethylene glycol-polystyrene (PEO-b-PS), 4-vinylpyridine (PS-b-P4VP), and polyoxyethylene-polymethyl methacrylate (PEO-b-PMMA). The hard template agent comprises two parts: tetraethyl orthosilicate (TEOS) and a salt, wherein the salt is at least one of sodium chloride, potassium chloride, sodium carbonate, and potassium carbonate. The mass ratio of salt to tetraethyl orthosilicate in the hard template agent is preferably 1:[2-5].

[0041] In a preferred embodiment, the mass ratio of the soft template agent, hard template agent and precursor raw material is [1-1.2]:[1.5-2]:[4.5-5].

[0042] Step S2: Dry the mixed solution to obtain a solid powder;

[0043] Specifically, the mixed solution obtained in S1 is thoroughly dried to obtain a fixed powder. The drying method can be any one of spray drying, vacuum drying, forced air drying, microwave drying, and infrared drying. The drying temperature is preferably 80℃-180℃, and the drying time is preferably 4h-16h.

[0044] Step S3: The solid powder is calcined under a first inert atmosphere, and then washed and dried to obtain a porous carbon material.

[0045] In a preferred embodiment, the first inert atmosphere is nitrogen or argon, the calcination temperature is 600℃-900℃, the heating rate is 2℃ / min-5℃ / min, and the calcination time is 2h-6h. The washing method involves impregnating the calcined material with a 1mol / L-2mol / L sodium hydroxide solution, holding it at 80℃-95℃ for 10h-24h, then filtering and washing the turbid liquid after holding until neutral, and finally drying it at 80℃-100℃ to obtain the porous carbon material.

[0046] Step S4: Under a second inert atmosphere, porous carbon material is vapor-deposited with silicon source gas to obtain a porous carbon composite material including porous carbon and nano-silicon particles; then, under a second inert atmosphere, carbon source gas is introduced to coat the porous carbon composite material to obtain a silicon-carbon anode material with a carbon coating layer.

[0047] Preferably, the second inert atmosphere is one or more of nitrogen, argon, and helium.

[0048] It is understandable that this step includes two processes: vapor deposition and coating treatment.

[0049] In a specific embodiment, the above-mentioned vapor deposition process can be carried out in a deposition furnace. The conditions for vapor deposition are as follows: the silicon source gas is any one of silane, silane, and other silane-containing hydrocarbons; the heating rate is 2℃ / min-5℃ / min; the deposition temperature is 450℃-900℃; the silicon source gas and the inert gas are introduced into the deposition furnace together in a ratio of 1:[1-5]; and then the temperature is maintained for 2h-6h.

[0050] Furthermore, the above coating treatment is carbon coating, which can be carried out in a coating furnace. The conditions for carbon coating are: the carbon source gas is one or more of alkanes, alkenes, and alkynes; the coating temperature is 500℃-800℃; the coating time is 1-4 hours; and the ratio of inert gas to carbon source gas can be 1:[1-3].

[0051] The silicon-carbon anode material with a carbon coating prepared by the method provided in this embodiment of the invention has a specific surface area of ​​1800 m². 2 / g-2200m 2 / g, with an average pore size of 1.75nm-1.95nm and a total pore volume of 0.85cm³. 3 / g-0.95cm 3 / g; Furthermore, the NLDFT pore volume of the carbon-coated silicon-carbon anode material prepared is 0.75 cm³. 3 / g-0.90cm 3 / g, of which the micropore volume is 0.68cm³ 3 / g-0.78cm 3 / g, mesoporous pore volume is 0.07cm³ 3 / g-0.12cm 3 / g, with a micropore content of 90%-95%. It is understandable that the above total pore volume is indirectly calculated using physical adsorption methods, such as nitrogen adsorption-desorption isotherms; NLDFT pore volume is calculated based on density functional theory models, predicting pore size distribution by simulating the behavior of gas molecules on the material surface.

[0052] This invention provides a method for preparing a silicon-carbon anode material. Using widely available raw materials, and through adjustments to the composite template agent and optimization of process parameters, a porous carbon material with controllable structure is prepared. This material also possesses a hierarchical structure of micro- and mesoporous components and a specific surface area of ​​1800 m². 2 / g-2200m 2 / g, with an average pore size of 1.75nm-1.95nm and a total pore volume of 0.85cm³. 3 / g-0.95cm 3 With a micropore content of 90%-95%, it can provide more active sites and a larger surface area in the preparation of silicon-carbon anode materials, which is conducive to the adsorption of reactant molecules such as silanes and improves the deposition efficiency. The appropriate pore size range can promote the electrochemical reaction of silicon and improve the reversible specific capacity and cycle stability of silicon-carbon anode materials.

[0053] The silicon-carbon anode material prepared by the present invention can be used as an active material for lithium-ion battery anode materials and for preparing lithium-ion battery anode sheets. The anode sheet of this application also includes a negative electrode current collector. This application does not have any particular limitations on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, copper foil, copper alloy foil, nickel foil, stainless steel foil, nickel foam, copper foam, or composite current collectors.

[0054] In this application, the lithium battery anode material may also include a conductive agent. This application does not have any particular restrictions on the conductive agent, as long as it can achieve the purpose of this application.

[0055] The silicon-carbon anode material of this invention can be used in electrochemical devices, such as secondary batteries or ion capacitors. In a specific application, lithium batteries using the silicon-carbon material of this invention as the anode material can include, but are not limited to, lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries. The use of the silicon-carbon anode material of this invention enables electrochemical devices to exhibit excellent cycle performance and safety performance.

[0056] To better understand the technical solution provided by the present invention, the following uses several specific examples to illustrate the specific process of preparing silicon-carbon anode materials using the methods provided in the above embodiments of the present invention, as well as the methods and characteristics of applying them to lithium batteries.

[0057] Example 1

[0058] First, chitosan was dissolved in deionized water to prepare a 6% (w / w) chitosan solution. Then, F127 was dissolved in ethanol at a mass ratio of 1:5 (F127 to chitosan), and TEOS and sodium chloride were added at a mass ratio of 1:5. The mixed solution was then slowly added to the chitosan solution, with the total mass ratio of soft template agent, hard template agent, and precursor raw material being 1:2:5. After thorough mixing, the mixture was allowed to stand at room temperature for 2 hours. The mixed solution was then spray-dried at 180°C for 6 hours. The resulting solid powder was placed in a tube furnace and heated to 900°C at a rate of 2°C / min under nitrogen protection and held for 2 hours to obtain a black powder. This powder was then impregnated with a 1 mol / L sodium hydroxide solution and held at 85°C for 12 hours. The turbid liquid was then filtered and washed until neutral, and then dried at 90°C to obtain a porous carbon material.

[0059] Porous carbon material was placed in a deposition furnace, protected with nitrogen gas, and heated to 600°C at a rate of 2°C / min. Then, a mixture of silane and nitrogen gas was introduced in a 1:5 ratio, and the temperature was maintained for 4 hours to obtain a porous carbon composite material containing porous carbon and nano-silicon particles. Next, under a nitrogen atmosphere, the porous carbon composite material was placed in a coating furnace, and a mixture of nitrogen and methane gas was introduced into the furnace in a 1:1 ratio. The furnace was heated to 550°C and held at this temperature for 2 hours to form a silicon-carbon anode material with a carbon coating layer.

[0060] Figure 2 , Figure 3 and Figure 4 The images are scanning electron microscope (SEM) images and X-ray diffraction (XRD) patterns of the porous carbon material prepared in Example 1 at different magnifications. The SEM images show that the prepared porous carbon exhibits a spherical morphology, and the XRD patterns show typical amorphous characteristic peaks at positions 26° and 44°, with no obvious impurity peaks. Figure 5The figure shows the pore size distribution of the porous carbon material prepared in Example 1. It can be seen from the figure that the prepared porous carbon is mainly composed of micropores, with a maximum pore size of 3-4 nm. The pore size distribution has no tailing and has a good micro-mesoporous structure.

[0061] The silicon-carbon anode material prepared in this embodiment was used to prepare electrode sheets for lithium-ion batteries, and these electrode sheets were used to assemble coin half-cells for testing. The specific process is as follows: First, the above-mentioned anode material, conductive agent Super P, and binder sodium carboxymethyl cellulose were thoroughly mixed in a mass ratio of 8:1:1, deionized water was added, and a uniform slurry was formed in a slurry mixer. This slurry was then coated onto a copper foil current collector. Next, the slurry was dried in a vacuum oven at 80°C for 12 hours. The dried electrode sheets were then cut into circular pieces with a diameter of 14 mm to serve as electrode sheets for the coin half-cells. The electrode sheets were then assembled into coin half-cells in an argon-filled glove box. The electrolyte was 1 mol / L lithium hexafluorophosphate, and the solvents were ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), with a volume ratio of EC, DMC, and DEC of 1:1:1. The counter electrode was a lithium sheet. Finally, the electrochemical performance was evaluated using a Blue Battery testing system. The test conditions were: temperature 25℃, voltage window 0.005-2V.

[0062] The specific surface area test data of the silicon-carbon anode material with carbon coating prepared in this embodiment are shown in Table 1, and the electrochemical test data of the coin half-cell using the anode material of this embodiment are shown in Table 2.

[0063] Comparative Example 1

[0064] First, chitosan was dissolved in deionized water to prepare a 6% chitosan solution. Then, F127 was dissolved in ethanol at a mass ratio of 1:5 to chitosan. The F127 solution was then slowly added to the chitosan solution. After thorough mixing, the mixture was allowed to stand at room temperature for 2 hours. The solution was then spray-dried at 180°C for 6 hours. The resulting solid powder was placed in a tube furnace and heated to 900°C at a rate of 2°C / min under nitrogen protection and held for 2 hours to obtain porous carbon material.

[0065] Porous carbon material was placed in a deposition furnace, protected with nitrogen gas, and heated to 600°C at a rate of 2°C / min. Then, a mixture of silane and nitrogen gas was introduced in a 1:5 ratio, and the temperature was maintained for 4 hours to obtain a porous carbon composite material containing porous carbon and nano-silicon particles. Next, under a nitrogen atmosphere, the porous carbon composite material was placed in a coating furnace, and a mixture of nitrogen and methane gas was introduced into the furnace in a 1:1 ratio. The furnace was heated to 550°C and held at this temperature for 2 hours to form a silicon-carbon anode material with a carbon coating layer.

[0066] The silicon-carbon anode material prepared in this embodiment was used to prepare anode sheets and assemble batteries for testing. The specific process is the same as in Example 1.

[0067] The specific surface area test data of the silicon-carbon anode material with carbon coating prepared in this embodiment are shown in Table 1, and the electrochemical test data of the coin half-cell using the anode material of this embodiment are shown in Table 2.

[0068] Comparative Example 2

[0069] First, chitosan was dissolved in deionized water to prepare a 6% (w / w) chitosan solution. Then, TEOS was added at a TEOS:chitosan mass ratio of 1:3. After thorough mixing, the mixture was allowed to stand at room temperature for 2 hours. The mixed solution was then spray-dried at 180°C for 6 hours. The resulting solid powder was placed in a tube furnace and heated to 900°C at a rate of 2°C / min under nitrogen protection and held for 2 hours. The resulting black powder was impregnated with 1 mol / L sodium hydroxide solution and held at 85°C for 12 hours. The turbid liquid was then filtered and washed until neutral, and then dried at 90°C to obtain porous carbon material.

[0070] Porous carbon was placed in a deposition furnace, protected with nitrogen gas, and heated to 600°C at a rate of 2°C / min. Then, a mixture of silane and nitrogen gas was introduced in a 1:5 ratio, and the temperature was maintained for 4 hours to obtain a porous carbon composite material containing porous carbon and nano-silicon particles. Next, under a nitrogen atmosphere, the porous carbon composite material was placed in a coating furnace, and a mixture of nitrogen and methane gas was introduced into the furnace in a 1:1 ratio. The furnace was heated to 550°C and held at this temperature for 2 hours to form a silicon-carbon anode material with a carbon coating layer.

[0071] The silicon-carbon anode material prepared in this embodiment was used to prepare anode sheets and assemble batteries for testing. The specific process is the same as in Example 1.

[0072] The specific surface area test data of the silicon-carbon anode material with carbon coating prepared in this embodiment are shown in Table 1, and the electrochemical test data of the coin half-cell using the anode material of this embodiment are shown in Table 2.

[0073] Comparative Example 3

[0074] First, chitosan was dissolved in deionized water to prepare a chitosan solution with a mass fraction of 6%. Then, sodium chloride was added at a mass ratio of 1:15 to chitosan. After thorough mixing, the solution was allowed to stand at room temperature for 2 hours. The mixed solution was then spray-dried at 180°C for 6 hours. The resulting solid powder was placed in a tube furnace and heated to 900°C at a rate of 2°C / min under nitrogen protection and held for 2 hours. The resulting black powder was washed with deionized water and then dried at 90°C to obtain porous carbon material.

[0075] Porous carbon material was placed in a deposition furnace, protected with nitrogen gas, and heated to 600°C at a rate of 2°C / min. Then, a mixture of silane and nitrogen gas was introduced in a 1:5 ratio, and the temperature was maintained for 4 hours to obtain a porous carbon composite material containing porous carbon and nano-silicon particles. Next, under a nitrogen atmosphere, the porous carbon composite material was placed in a coating furnace, and a mixture of nitrogen and methane gas was introduced into the furnace in a 1:1 ratio. The furnace was heated to 550°C and held at this temperature for 2 hours to form a silicon-carbon anode material with a carbon coating layer.

[0076] The silicon-carbon anode material prepared in this embodiment was used to prepare anode sheets and assemble batteries for testing. The specific process is the same as in Example 1.

[0077] The specific surface area test data of the silicon-carbon anode material with carbon coating prepared in this embodiment are shown in Table 1, and the electrochemical test data of the coin half-cell using the anode material of this embodiment are shown in Table 2.

[0078] Example 2

[0079] First, chitosan oligosaccharide was dissolved in deionized water to prepare a 5% (w / w) chitosan oligosaccharide solution. Then, P123 was dissolved in ethanol at a mass ratio of 1.1:5. Next, TEOS and potassium chloride were added at a mass ratio of 1:4. The mixed solution was then slowly added to the chitosan oligosaccharide solution, where the total mass ratio of soft template agent, hard template agent, and precursor raw material was 1.1:2:5. After thorough mixing, the mixture was allowed to stand at room temperature for 4 hours. The mixed solution was then placed in a vacuum drying oven and dried at 90°C for 6 hours. The resulting solid mixture was placed in a tube furnace and heated to 700°C at a rate of 4°C / min under nitrogen protection and held for 3 hours. The resulting black powder was impregnated with a 1 mol / L sodium hydroxide solution and held at 85°C for 12 hours. The turbid liquid was then filtered and washed until neutral, and then dried at 90°C to obtain porous carbon material.

[0080] Porous carbon was placed in a deposition furnace, protected with nitrogen gas, and heated to 600°C at a rate of 2°C / min. Then, a mixture of silane and nitrogen gas was introduced at a ratio of 1:5, and the temperature was maintained for 4 hours to obtain a porous carbon composite material containing porous carbon and nano-silicon particles. Next, under a nitrogen atmosphere, the porous carbon composite material was placed in a coating furnace, and a mixture of nitrogen and methane gas was introduced into the furnace at a ratio of 1:3. The furnace was heated to 650°C and maintained at this temperature for 3 hours to form a silicon-carbon anode material with a carbon coating layer.

[0081] The silicon-carbon anode material prepared in this embodiment was used to prepare anode sheets and assemble batteries for testing. The specific process is the same as in Example 1.

[0082] The specific surface area test data of the silicon-carbon anode material with carbon coating prepared in this embodiment are shown in Table 1, and the electrochemical test data of the coin half-cell using the anode material of this embodiment are shown in Table 2.

[0083] Example 3

[0084] First, carboxymethyl cellulose (CMC) was dissolved in deionized water to prepare a 3% (w / w) CMC solution. Then, PEO-b-PS was dissolved in ethanol at a mass ratio of 1.05:5 (PEO-b-PS to CMC). Sodium carbonate and TEOS were added at a mass ratio of 1:5. The mixed solution was then slowly added to the CMC solution, with the total mass ratio of soft template agent, hard template agent, and precursor raw material being 1.05:1.8:5. After thorough mixing, the mixture was allowed to stand at room temperature for 6 hours. The mixed solution was then spray-dried at 170°C for 6 hours. The resulting powder sample was placed in a tube furnace and heated to 800°C at a rate of 2°C / min under nitrogen protection and held for 3 hours. The resulting black powder was impregnated with a 1 mol / L sodium hydroxide solution and held at 85°C for 12 hours. The turbid liquid was then filtered and washed until neutral, and finally dried at 90°C to obtain porous carbon material.

[0085] Porous carbon was placed in a deposition furnace, protected with nitrogen gas, and heated to 450°C at a rate of 2°C / min. Then, a mixture of silane and nitrogen gas was introduced in a 1:5 ratio, and the temperature was maintained for 5.5 hours to obtain a porous carbon composite material containing porous carbon and nano-silicon particles. Next, under a nitrogen atmosphere, the porous carbon composite material was placed in a coating furnace, and a mixture of nitrogen and methane gas was introduced into the furnace in a 1:2 ratio. The furnace was heated to 500°C and held at this temperature for 2 hours to form a silicon-carbon anode material with a carbon coating layer.

[0086] The silicon-carbon anode material prepared in this embodiment was used to prepare anode sheets and assemble batteries for testing. The specific process is the same as in Example 1.

[0087] The specific surface area test data of the silicon-carbon anode material with carbon coating prepared in this embodiment are shown in Table 1, and the electrochemical test data of the coin half-cell using the anode material of this embodiment are shown in Table 2.

[0088] Example 4

[0089] First, soluble starch was dissolved in deionized water to prepare a 10% (w / w) soluble starch solution. Then, F127 was dissolved in ethanol at a mass ratio of 1.1:4.8 to soluble starch. Sodium chloride and TEOS were added at a mass ratio of 1:3. The mixed solution was then slowly added to the soluble starch solution. The total mass ratio of soft template agent, hard template agent, and precursor raw material was 1.1:2:4.8. After thorough mixing, the mixture was allowed to stand at room temperature for 2 hours. The solution was then dried in a forced-air drying oven at 90°C for 10 hours. The resulting solid mixture was placed in a tube furnace and heated to 850°C at a rate of 2°C / min under nitrogen protection and held for 4 hours. The resulting black powder was impregnated with a 1.5 mol / L sodium hydroxide solution and held at 85°C for 12 hours. The turbid liquid was then filtered and washed until neutral, and finally dried at 90°C to obtain porous carbon material.

[0090] Porous carbon was placed in a deposition furnace, protected with nitrogen gas, and heated to 450°C at a rate of 2°C / min. Then, a mixture of silane and nitrogen gas was introduced in a 1:3 ratio, and the temperature was maintained for 3.5 hours to obtain a porous carbon composite material containing porous carbon and nano-silicon particles. Next, under a nitrogen atmosphere, the porous carbon composite material was placed in a coating furnace, and a mixture of nitrogen and methane gas was introduced into the furnace in a 1:2 ratio. The furnace was heated to 520°C and held at this temperature for 3 hours to form a silicon-carbon anode material with a carbon coating layer.

[0091] The silicon-carbon anode material prepared in this embodiment was used to prepare anode sheets and assemble batteries for testing. The specific process is the same as in Example 1.

[0092] The specific surface area test data of the silicon-carbon anode material with carbon coating prepared in this embodiment are shown in Table 1, and the electrochemical test data of the coin half-cell using the anode material of this embodiment are shown in Table 2.

[0093] Example 5

[0094] First, chitosan was dissolved in deionized water to prepare an 8% (w / w) solution. Then, F127 was dissolved in ethanol at a mass ratio of 1.2:5 (w / w). Potassium carbonate and TEOS were added at a mass ratio of 1:2.5 (w / w). The mixed solution was then slowly added to the chitosan solution. The total mass ratio of the soft template agent, hard template agent, and precursor raw material was 1.2:1.8:5. After thorough mixing, the mixture was allowed to stand at room temperature for 6 hours. The mixed solution was then placed in a forced-air drying oven and dried at 80°C for 12 hours. The resulting solid mixture was placed in a tube furnace and heated to 900°C at a rate of 2°C / min under nitrogen protection and held for 2 hours. The resulting black powder was impregnated with a 2 mol / L sodium hydroxide solution and held at 85°C for 10 hours. The turbid liquid was then filtered and washed until neutral, and then dried at 90°C to obtain porous carbon material.

[0095] Porous carbon was placed in a deposition furnace, protected with nitrogen gas, and heated to 600°C at a rate of 2°C / min. Then, a mixture of silane and nitrogen gas was introduced at a ratio of 1:5, and the temperature was maintained for 4 hours to obtain a porous carbon composite material containing porous carbon and nano-silicon particles. Next, under a nitrogen atmosphere, the porous carbon composite material was placed in a coating furnace, and a mixture of nitrogen and methane gas was introduced into the furnace at a ratio of 1:3. The furnace was heated to 650°C and held at this temperature for 2.5 hours to form a silicon-carbon anode material with a carbon coating layer.

[0096] The silicon-carbon anode material prepared in this embodiment was used to prepare anode sheets and assemble batteries for testing. The specific process is the same as in Example 1.

[0097] The specific surface area test data of the silicon-carbon anode material with carbon coating prepared in this embodiment are shown in Table 1, and the electrochemical test data of the coin half-cell using the anode material of this embodiment are shown in Table 2.

[0098] Example 6

[0099] First, chitosan was dissolved in deionized water to prepare a 5% (w / w) chitosan solution. Then, F127 was dissolved in ethanol at a mass ratio of 1:4.75 to chitosan. Potassium chloride and TEOS were added at a mass ratio of 1:4. The mixed solution was then slowly added to the chitosan solution. The total mass ratio of soft template agent, hard template agent, and precursor raw material was 1:2:4.75. After thorough mixing, the mixture was allowed to stand at room temperature for 6 hours. The mixed solution was then placed in a forced-air drying oven and dried at 80°C for 12 hours. The resulting solid mixture was placed in a tube furnace and heated to 900°C at a rate of 2°C / min under nitrogen protection and held for 2 hours. The resulting black powder was impregnated with a 2 mol / L sodium hydroxide solution and held at 80°C for 10 hours. The turbid liquid was then filtered and washed until neutral, and then dried at 90°C to obtain porous carbon material.

[0100] Porous carbon was placed in a deposition furnace, protected with nitrogen gas, and heated to 600°C at a rate of 2°C / min. Then, a mixture of silane and nitrogen gas was introduced at a ratio of 1:5, and the temperature was maintained for 4 hours to obtain a porous carbon composite material containing porous carbon and nano-silicon particles. Next, under a nitrogen atmosphere, the porous carbon composite material was placed in a coating furnace, and a mixture of nitrogen and methane gas was introduced into the furnace at a ratio of 1:3. The furnace was heated to 550°C and held at this temperature for 2 hours to form a silicon-carbon anode material with a carbon coating layer.

[0101] The silicon-carbon anode material prepared in this embodiment was used to prepare anode sheets and assemble batteries for testing. The specific process is the same as in Example 1.

[0102] The specific surface area test data of the silicon-carbon anode material with carbon coating prepared in this embodiment are shown in Table 1, and the electrochemical test data of the coin half-cell using the anode material of this embodiment are shown in Table 2.

[0103] Table 1 shows the comparison test results of porous carbon materials prepared in various embodiments and comparative examples of the present invention.

[0104]

[0105]

[0106] Table 2 shows the electrochemical test data of the coin half-cells prepared in the various embodiments and comparative examples of the present invention.

[0107]

[0108] Referring to Table 1, a comparison of the various embodiments shows that by changing the proportion of multiple template agents and adjusting subsequent processing parameters, a target porous carbon matrix with pore size, pore volume, and micropore ratio within a specific range can be obtained for different precursors. As shown in Example 1 and Comparative Examples 1, 2, and 3, the pore-forming effect of a single template agent is poor. Using only F127 or salt as a template results in a low pore volume, while using only TEOS as a template results in an excessively large pore size and a low micropore ratio, making it difficult to obtain a porous carbon matrix with suitable pore size, pore volume, and micropore ratio. This invention combines multiple template agents, uniformly dispersing hard and soft template agents and precursors in a solution system to ensure uniform and sufficient contact. TEOS provides a stable supporting structure, ensuring that the pore structure does not collapse during heat treatment. The salt template can uniformly and orderly act as a pore-forming agent to form a hierarchically interconnected three-dimensional network carbon structure. The block polymer acts as a soft template, enabling more precise control of the pore structure and morphology of the porous carbon material, and providing a larger specific surface area and more active sites. By combining multiple template agents, the specific surface area and porosity of materials can be increased while maintaining material stability. The pore structure can be precisely controlled by adjusting the mass ratio of template and precursor and subsequent processing parameters.

[0109] As can be seen from the test data in Table 2, different specific surface areas, pore volumes, and pore sizes affect the deposition effect of porous carbon on silicon, thus affecting the overall electrochemical performance. Compared with Comparative Examples 1, 2, and 3, the coin cell prepared in this embodiment of the invention exhibits higher first-cycle coulombic efficiency and cycle stability. This is because a structurally controllable porous carbon material was prepared by adjusting the template agent and process parameters. It also has a hierarchical structure of micro-mesoporous structures. This structure can provide more active sites and a larger surface area, which is beneficial for the adsorption and deposition of reactant molecules such as silanes. Moreover, a suitable pore size range can promote the electrochemical reaction of silicon and improve the reversible specific capacity performance and charge-discharge efficiency of silicon-carbon anode materials. In addition, the higher mechanical strength can provide structural support for silicon deposition and inhibit the agglomeration and volume expansion of silicon particles. The prepared hierarchical porous carbon further improves the conductivity of the material by optimizing the pore structure and increasing the specific surface area.

[0110] The silicon-carbon anode material, its preparation method, and its application provided in this invention have the following advantages:

[0111] 4. Improve the structural controllability of porous carbon materials: By combining various template agents and optimizing the preparation process, the pore size and distribution of porous carbon can be controlled within a certain range, and it has a highly ordered and uniform pore structure, thereby improving the structural controllability and application performance of the material.

[0112] 5. Reduced production costs: Existing technologies often involve high production costs for some high-performance porous carbon materials, limiting their large-scale application. This invention utilizes widely available raw materials and optimized process parameters to reduce raw material and processing costs.

[0113] Expanding the application scope of porous carbon materials: Currently, porous carbon materials have been widely used in energy storage, environmental protection, biomedicine, and other fields. However, with the development of technology, the requirements for their performance and functions are becoming increasingly stringent. The porous carbon material prepared in this invention has a specific range of micro- and mesopore distribution, high mechanical strength, and excellent conductivity, which can meet the requirements of silicon-carbon anodes for porous carbon matrices and expand its application scope.

[0114] In the description herein, the terms "a specific embodiment," "some embodiments," "one embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0115] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-carbon anode material, characterized in that, Preparation methods include: S1, firstly, the precursor raw material is dissolved in deionized water to prepare a precursor solution; the soft template agent is dissolved in ethanol or deionized water, and then a hard template agent is added to obtain a hard and soft template agent solution; then the hard and soft template agent solution is added to the precursor solution for mixing, and the mixture is allowed to stand to obtain a mixed solution; S2, the mixed solution is dried to obtain a solid powder; S3, the solid powder is calcined under a first inert atmosphere, and then washed and dried to obtain a porous carbon material; S4, under a second inert atmosphere, porous carbon material is vapor-deposited with silicon source gas to obtain a porous carbon composite material including porous carbon and nano-silicon particles; then, under a second inert atmosphere, carbon source gas is introduced to coat the porous carbon composite material to obtain a silicon-carbon anode material with a carbon coating layer.

2. The method for preparing silicon-carbon anode material according to claim 1, characterized in that, The precursor raw material is one or more selected from chitosan, chitosan oligosaccharide, glucose, carboxymethyl cellulose, alginic acid, hyaluronic acid, polyvinyl alcohol, and soluble starch; the mass fraction of the precursor solution is 2%-10%.

3. The method for preparing silicon-carbon anode material according to claim 1, characterized in that, The soft template agent is at least one of the following: polyoxyethylene polyoxypropylene ether triblock copolymer, polyethylene oxide-polyoxypropylene-polyoxyethylene triblock copolymer, polyethylene glycol-polystyrene, 4-vinylpyridine, and polyethylene oxide-polymethyl methacrylate; The hard template agent includes tetraethyl orthosilicate and a salt, wherein the salt is at least one of sodium chloride, potassium chloride, sodium carbonate, and potassium carbonate; the mass ratio of the salt to tetraethyl orthosilicate in the hard template agent is 1:[2-5]; the mass ratio of the soft template agent, the hard template agent, and the precursor raw material is [1-1.2]:[1.5-2]:[4.5-5].

4. The method for preparing silicon-carbon anode material according to claim 1, characterized in that, In step S2, the drying method is any one of spray drying, vacuum drying, forced air drying, microwave drying, and infrared drying, the drying temperature is 80℃-180℃, and the drying time is 4h-16h.

5. The method for preparing silicon-carbon anode material according to claim 1, characterized in that, In step S3, the first inert atmosphere is nitrogen or argon, the calcination temperature is 600℃-900℃, the heating rate is 2℃ / min-5℃ / min, and the calcination time is 2h-6h. The washing method involves impregnating the calcined material with a 1 mol / L-2 mol / L sodium hydroxide solution, keeping it at 80℃-95℃ for 10h-24h, then filtering and washing the turbid liquid until it is neutral, and finally drying it at 80℃-100℃ to obtain the porous carbon material.

6. The method for preparing silicon-carbon anode material according to claim 1, characterized in that, In step S4, the second inert atmosphere is one or more of nitrogen, argon, and helium; The vapor deposition is carried out in a deposition furnace, and the conditions for vapor deposition are as follows: the heating rate is 2℃ / min-5℃ / min, the deposition temperature is 450℃-900℃, the silicon source gas and the inert gas are introduced into the deposition furnace together in a ratio of 1:[1-5], and the temperature is maintained for 2h-6h; the silicon source gas is any one of silane, silane and other silane-containing hydrocarbons.

7. The method for preparing silicon-carbon anode material according to claim 1, characterized in that, In step S4, the coating process is carbon coating, which is carried out in a coating furnace; The conditions for carbon coating are as follows: the carbon source gas is one or more of alkanes, alkenes, and alkynes; the coating temperature is 500℃-800℃; the coating time is 1-4 hours; and the ratio of the inert gas to the carbon source gas can be 1:[1-3].

8. The method for preparing silicon-carbon anode material according to claim 1, characterized in that, The specific surface area of ​​the carbon-coated silicon-carbon anode material prepared is 1800 m². 2 / g-2200m 2 / g, with an average pore size of 1.75nm-1.95nm and a total pore volume of 0.85cm³. 3 / g-0.95cm 3 / g; The NLDFT pore volume of the carbon-coated silicon-carbon anode material is 0.75 cm³. 3 / g-0.90cm 3 / g, of which the micropore volume is 0.68cm³ 3 / g-0.78cm 3 / g, mesoporous pore volume is 0.07cm³ 3 / g-0.12cm 3 / g, with a microporous content of 90%-95%.

9. A silicon-carbon anode material prepared by any one of the preparation methods described in claims 1-8.

10. A lithium battery, characterized in that, The lithium battery includes the silicon-carbon anode material as described in claim 9.

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