Preparation method of mesoporous carbon material with high mesopore rate and application in silicon-carbon negative electrode

Abstract

The application provides a preparation method of a mesoporous carbon material with high mesoporosity and application of the mesoporous carbon material in a silicon-carbon negative electrode. The application uses styrene, (methyl) acrylic acid (ester) compounds and vinyl silane compounds as comonomers to prepare an organic silicon modified styrene-acrylic emulsion, then uniformly mixes biomass powder, the organic silicon modified styrene-acrylic emulsion, a surfactant and a sodium hydroxide solution, dries, heats under an inert atmosphere for carbonization, cools, washes and dries to obtain a pre-preparation mesoporous activated carbon, then immerses the pre-preparation mesoporous activated carbon in an epoxy silane coupling agent solution, takes out after the immersion is completed, dries, heats under an inert atmosphere, cools, washes and dries to obtain the mesoporous carbon material with high mesoporosity; and mixes the mesoporous carbon material and graphite and silicon powder to prepare a silicon-carbon composite negative electrode material. The obtained silicon-carbon composite negative electrode material is particularly suitable for being used as a sodium ion battery negative electrode active material.

Description

Technical Field

[0001] This invention belongs to the field of mesoporous carbon materials technology, specifically relating to a method for preparing a high-mesoporous carbon material and its application in silicon-carbon anodes. Background Technology

[0002] Mesoporous activated carbon refers to a class of porous materials with pore sizes ranging from 2 to 50 nm. It possesses extremely high specific surface area, a regular and ordered pore structure, a narrow pore size distribution, and continuously adjustable pore size, enabling it to play a role in adsorption, separation, and especially catalytic reactions. Additionally, it can be used to prepare silicon-carbon anodes. my country has abundant biomass resources, and waste biomass has a high carbon content and is rich in lignocellulose, providing a good material foundation. Utilizing waste biomass for activated carbon production has enormous potential value and good feasibility.

[0003] Silicon-carbon anode materials possess high lithium storage capacity and good conductivity, making them a promising candidate to replace graphite as the anode material in high-energy-density lithium-ion batteries. Currently, the main preparation methods for silicon-carbon composite materials are coating and intercalation. Coating typically employs vapor deposition, but this process is demanding and suffers from uneven carbon coating, limiting the material's applications. Intercalation methods have relatively lower requirements for the preparation process, but offer limited improvement in electrochemical performance, particularly due to the use of template agents, which often results in insufficiently rich mesoporous structures in the final material.

[0004] CN105489891A discloses a method for preparing a high-capacity silicon-based anode material for lithium-ion batteries. The silicon-based composite anode material for lithium-ion batteries prepared by this invention is made by combining mesoporous carbon and nano-silicon prepared by a specific process as raw materials, so that the carbon and silicon are uniformly distributed and more tightly bonded. Therefore, when this composite material is used in lithium-ion batteries, it has high conductivity and good cycle stability, and the lithium-ion batteries have high specific capacity and long service life.

[0005] CN102867944A discloses a novel mesoporous carbon / silicon composite anode material and its preparation method. This mesoporous carbon / silicon composite anode material possesses a mesoporous structure. The carbon and silicon are composited at the molecular level, effectively utilizing the ultra-high theoretical capacity of silicon while avoiding the significant volume changes of silicon atoms during repeated charge-discharge cycles. This improves the capacity of the electrode material itself and plays a crucial role in enhancing cycle performance.

[0006] CN114105154A discloses a method for preparing a negative electrode material based on nitrogen-doped graphene / modified silicon suboxide, including: preparing SiO xThe invention comprises three steps: preparing a core-shell material, preparing modified graphene fibers, and preparing a negative electrode material based on nitrogen-doped graphene / modified silicon suboxide. The method for preparing a nitrogen-doped graphene / modified silicon suboxide negative electrode material produces a mesoporous carbon-coated modified silicon suboxide composite material. The nanoporous spheres exhibit good conductivity, resulting in numerous surface pores that facilitate the subsequent insertion of nitrogen-doped graphene and CNTs. This process stabilizes the nitrogen-doped graphene and CNTs, aids in constructing a three-dimensional conductive framework, improves overall conductivity, and facilitates the insertion or extraction of lithium ions into the modified silicon suboxide through the three-dimensional conductive framework, thereby increasing the electrode capacity. The invention also provides a nitrogen-doped graphene / modified silicon suboxide negative electrode material and its applications.

[0007] CN115394972A discloses a sandwich-structured mesoporous carbon-silicon anode material. It is produced by spray-drying a mixed solution of dispersed graphite, silicon nanoparticles, a dispersant, and a binder to obtain a graphite-silicon composite material. Then, the graphite-silicon composite material, a catalyst, a carbon precursor, and a template agent are dispersed in a water-organic solvent to obtain a graphite@silicon@mesoporous polymer material. Finally, the template agent is removed by high-temperature calcination to obtain a mesoporous carbon-silicon composite anode with a three-layer sandwich structure: an inner layer of graphite, a middle layer of silicon, and an outer layer of mesoporous carbon. This material exhibits excellent electrochemical performance.

[0008] However, existing technologies for preparing mesoporous activated carbon from biomass materials suffer from problems such as dense voids, easily broken frameworks, small average pore size, large micropore area, uneven mesopore size, or uneven or unstable nitrogen doping, which limit its suitability as a negative electrode material for secondary batteries. Furthermore, most research on the aforementioned silicon-carbon composite negative electrode materials focuses on lithium-ion batteries, with limited research on sodium-ion batteries.

[0009] The applicant's previous patent CN202311754660.4 disclosed a mesoporous activated carbon and its preparation method, comprising the following raw materials: biomass carbon material, organosilicon-modified styrene-acrylic emulsion, surfactant, and sodium hydroxide solution. The organosilicon-modified styrene-acrylic emulsion is obtained through emulsion polymerization, with monomers including styrene, (meth)acrylate compounds, (meth)acrylate compounds, and vinylsilane compounds. Specifically, the organosilicon-modified styrene-acrylic emulsion is first prepared using styrene, (meth)acrylate compounds, and vinylsilane compounds as comonomers. Then, biomass powder and the organosilicon-modified styrene-acrylic emulsion are blended, and after carbonization and activation, a mesoporous carbon with a well-developed mesoporous structure is obtained, suitable for use as an adsorbent. This material shows promise for use as a silicon-carbon anode. Based on this, the inventors have further researched and proposed a method for preparing a silicon-carbon anode material suitable for secondary batteries, particularly as an active material for sodium-ion batteries, exhibiting excellent electrochemical performance. Summary of the Invention

[0010] To address the technical problems of insufficient performance of existing mesoporous carbon-silicon composite anode materials and poor compatibility between mesoporous carbon materials and sodium-ion battery anode materials, this invention provides a method for preparing high-mesoporous carbon using biomass materials. First, an organosilicon-modified styrene-acrylic emulsion is prepared using styrene, (meth)acrylate compounds, and vinyl silane compounds as comonomers. Then, biomass powder and the organosilicon-modified styrene-acrylic emulsion are blended, and after carbonization and activation, a mesoporous carbon material with a well-developed mesoporous structure and large mesoporous area is obtained. This material is then impregnated in an epoxy silane coupling agent solution to prepare a mesoporous carbon material suitable for silicon-carbon anodes. The mesoporous carbon material is then mixed with graphite and silicon powder to prepare a silicon-carbon composite anode material, which is used as a sodium-ion battery anode and exhibits excellent electrochemical performance.

[0011] This invention provides a method for preparing a mesoporous carbon material with high mesopority, comprising the following steps:

[0012] (1) 100 parts by weight of biomass powder, 70-80 parts by weight of organosilicon-modified styrene-acrylic emulsion, 3-5 parts by weight of surfactant, and 200-400 parts by weight of sodium hydroxide solution are mixed evenly, dried, heated under an inert atmosphere for carbonization, cooled, washed, and dried to obtain pre-prepared mesoporous activated carbon; the organosilicon-modified styrene-acrylic emulsion is obtained by emulsion polymerization, and the raw materials of the organosilicon-modified styrene-acrylic emulsion include styrene, (meth)acrylate, (meth)acrylic acid, vinyl silane compounds, water, and emulsifier; the solid content of the organosilicon-modified styrene-acrylic emulsion is 30-35%, and the vinyl silane compounds include monofunctional vinyl silanes and difunctional vinyl silanes;

[0013] (2) The pre-prepared mesoporous activated carbon obtained in step (1) is immersed in an epoxy silane coupling agent solution. After immersion, it is taken out, dried, heated under an inert atmosphere, cooled, washed, and dried to obtain a mesoporous carbon material with high mesopority.

[0014] The high mesoporosity refers to a mesoporosity of 89-92%, such as 89.3-91.8%; and an average pore size of 7-8 nm, such as 7.05-7.50 nm.

[0015] Further, in step (1), the (meth)acrylic acid is selected from at least one of acrylic acid and methacrylic acid; the (meth)acrylate is selected from at least one of methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, and propyl methacrylate; the monofunctional vinylsilane compound is selected from at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, methylvinyldiethoxysilane, and methylvinyldimethoxysilane; and the difunctional vinylsilane is tetramethyldivinyldisilazane.

[0016] Furthermore, in the preparation of organosilicon-modified styrene-acrylic emulsion, the mass ratio of monomer styrene, (meth)acrylate compounds, (meth)acrylic compounds, and vinylsilane compounds is 15-20:20-25:2-5:12-16.

[0017] Furthermore, the vinylsilane compounds are monofunctional vinylsilanes and difunctional vinylsilanes in a mass ratio of 2.7-3.5:1. The inventors have discovered that using monofunctional and difunctional vinylsilanes in the above ratio as monomers can reduce the formation of macropores or small mesopores in mesoporous carbon materials. The resulting organosilicon-modified styrene-acrylic polymer is more suitable as a raw material for secondary battery anode materials. Compared to the previous adsorbent materials, adding a certain amount of difunctional monomers to generate a certain cross-linking structure is more conducive to obtaining a mesoporous structure suitable for sodium ion insertion / extraction. In addition, the added difunctional monomers contain nitrogen, which will form a certain nitrogen doping in the mesoporous carbon, which is also beneficial to the electrochemical performance of the silicon-carbon composite anode material. Moreover, the nitrogen doping in the form of styrene-acrylic emulsion copolymer monomers results in more robust nitrogen fixation.

[0018] Furthermore, in step (1), the carbonization temperature is 800-900℃ and the carbonization time is 1-2h. In step (2), the heating temperature is 200-300℃ and the heating time is 2-4h.

[0019] Graphite and silicon have many interactions, making it difficult to form a stable composite structure. This invention uses a process of carbonization and silane coupling agent impregnation followed by heat treatment, which not only yields porous carbon with abundant mesoporous structure, but also enhances the structural stability of the mesoporous carbon-graphite-silicon ternary composite material, laying a good foundation for obtaining high-performance and stable battery anode materials.

[0020] The biomass powder has a particle size of 50-60 mesh, and the biomass is selected from one or a combination of two of wood, coconut shell, bamboo, and walnut shell; the surfactant is selected from at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium hexadecylbenzenesulfonate; the sodium hydroxide solution has a mass fraction of 40-50 wt%; the emulsifier is selected from one or a combination of two of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and polyethylene glycol octylphenyl ether, and the amount of emulsifier used is 7-10 wt% of the total mass of monomers, and the amount of water is controlled so that the solid content of the organosilicon-modified styrene-acrylic emulsion is 30-35 wt%.

[0021] Further, in step (2), the epoxy silane coupling agent is selected from at least one of 3-glycidyl etheroxypropyltrimethoxysilane (KH-560), 3-(2,3-epoxypropoxy)propyltriethoxysilane (KH-561), and 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane (KH-563), the solvent of the epoxy silane coupling agent solution is ethanol, and the concentration of the epoxy silane coupling agent is 5-8 wt%; the impregnation is carried out at 30-40°C for 1-2 hours.

[0022] The organosilicon-modified styrene-acrylic emulsion was prepared according to the previous patent CN202311754660.4, specifically, it was obtained through a preparation method including the following steps:

[0023] S1. Add the comonomer, water, and emulsifier to the mixing vessel and stir at room temperature to prepare the pre-emulsion;

[0024] S2. Take 1 / 3 to 1 / 2 of the pre-emulsion from step S1, and 1 / 3 to 1 / 2 of the initiator and buffer, add them to the reactor, heat and keep the temperature constant to react and form a prepolymer emulsion;

[0025] S3. Add the remaining pre-emulsion and remaining initiator to the prepolymer emulsion from step S2, react at a constant temperature, cool down after the reaction is complete, adjust the pH, filter, and obtain organosilicon-modified styrene-acrylic emulsion.

[0026] Furthermore, the initiator is selected from at least one of potassium persulfate, ammonium persulfate, and sodium persulfate, and the amount of initiator used is 1-3 wt% of the total mass of the monomers; the buffer is selected from sodium bicarbonate, and the amount of buffer used is 0.5-1 wt% of the total mass of the monomers.

[0027] Furthermore, the constant temperature reaction temperature in steps S2 and S3 is 70-80℃, the reaction time is 1-3h, and the pH is adjusted to 8-9 in step S3.

[0028] The inventors unexpectedly discovered that the mesoporous carbon prepared by this invention, combined with graphite and nano-silicon, forms a composite material that is very suitable as an anode active material for sodium-ion batteries. This is likely because the mesoporous carbon of this invention provides a rich mesoporous structure, which is conducive to the insertion and extraction of sodium ions. During battery cycling, the uniformly distributed mesoporous structure provides a fast sodium ion transport channel. Moreover, the presence of mesopores can mitigate the volume expansion and contraction during charging and discharging. The larger specific surface area increases the reactivity of the material, resulting in excellent rate performance. Furthermore, the silicon-carbon composite anode prepared by this invention also has the advantage of high initial coulombic efficiency.

[0029] The second objective of this invention is to provide a silicon-carbon composite anode material comprising the following raw materials in parts by weight: 100 parts by weight of graphite, 30-40 parts by weight of mesoporous carbon prepared by the above method, and 20-28 parts by weight of silicon powder.

[0030] The silicon-carbon composite anode material is obtained by a preparation method including the following steps: dispersing graphite, mesoporous carbon, and silicon powder in an aqueous solution containing a dispersant, spray drying to obtain a composite material precursor, and calcining in a non-oxidizing atmosphere to obtain the silicon-carbon composite anode material.

[0031] Furthermore, the dispersant is selected from at least one of polyvinyl alcohol, polyvinylpyrrolidone, carboxymethyl cellulose, and long-chain alkyl quaternary ammonium salt, wherein the long-chain alkyl quaternary ammonium salt is selected from at least one of hexadecyltrimethylammonium chloride and hexadecyltrimethylammonium bromide.

[0032] Furthermore, the amount of dispersant used is 3-5 wt% of the total mass of graphite, mesoporous carbon, and silicon powder, and the amount of aqueous solution containing the dispersant is 4-6 times the total mass of graphite, mesoporous carbon, and silicon powder. The spray drying outlet temperature is 180-240℃. The non-oxidizing atmosphere is nitrogen and / or argon, the calcination temperature is 600-800℃, and the calcination time is 3-5 hours.

[0033] The third objective of this invention is to provide a sodium-ion battery anode, comprising the aforementioned silicon-carbon composite anode material, conductive additives, and binders.

[0034] Furthermore, the mass ratio of carbon composite negative electrode material, conductive additive, and binder is 80-90:5-10:5-10, for example, 8:1:1. The conductive additive is selected from at least one of Super P and acetylene black; the binder is selected from at least one of PVDF and polytetrafluoroethylene.

[0035] Compared with the prior art, the advantages of the present invention are:

[0036] I. In the preparation of mesoporous carbon according to the present invention, an organosilicon-modified styrene-acrylic emulsion is added. The organosilicon-modified styrene-acrylic particles can buffer the activation reaction rate and degree of strong alkali on carbon, concentrate the generation of mesoporous structures with appropriate pore size, reduce the proportion of micropores on activated carbon, and increase the proportion of mesopores.

[0037] II. This invention employs a process involving the addition of a specific organosilicon-modified styrene-acrylic emulsion for carbonization, followed by treatment with a silane coupling agent and subsequent heating. This process not only yields porous carbon with abundant mesoporous structures but also enhances the structural stability of the mesoporous carbon-graphite-silicon ternary composite material, laying a solid foundation for obtaining high-performance and stable battery anode materials. Preferably, controlling the composition of the styrene-acrylic emulsion raw material can reduce the formation of macropores or smaller mesopores in the mesoporous carbon material.

[0038] Thirdly, after the surface of the mesoporous carbon of the present invention is modified with a silane coupling agent, it serves as an intermediate linker, which strengthens the interaction between silicon and graphite, making the structure stable. After spray drying, it can be uniformly mixed, and then calcined to obtain a high-quality silicon-carbon composite material.

[0039] Fourthly, the present invention adds a bifunctional monomer containing nitrogen element in the preparation of styrene-acrylic emulsion, which will form a certain nitrogen doping in mesoporous carbon, which is beneficial to the electrochemical performance of silicon-carbon composite anode material. Moreover, the nitrogen is doped in the form of styrene-acrylic emulsion copolymer monomer, and the nitrogen is more firmly fixed. Attached Figure Description

[0040] Figure 1 This is a particle size distribution diagram of the high mesoporous carbon material obtained in Example 1.

[0041] Figure 2 This is a particle size distribution diagram of the high mesoporous carbon material obtained in Example 2. Detailed Implementation

[0042] The present invention will be further described below with reference to specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, all "parts" mentioned in the embodiments of the present invention are parts by weight. All reagents used are commercially available in the art.

[0043] Preparation Example 1

[0044] S1. Add 100 parts by weight of comonomer, water, and 8 parts by weight of emulsifier to a mixing vessel and stir at room temperature (25°C) to prepare a pre-emulsion; the comonomer is a compound of styrene, butyl acrylate, acrylic acid, and vinyl silane in a mass ratio of 20:20:4:12, wherein the vinyl silane is a compound of vinyltrimethoxysilane and tetramethyldivinyldisilazane in a mass ratio of 2.7:1; the emulsifier is a mixed emulsifier of polyethylene glycol octylphenyl ether and sodium dodecyl sulfate in a mass ratio of 4:1, and the amount of water used is such that the final solid content of the organosilicon-modified styrene-acrylic emulsion is 30wt%;

[0045] S2. Take 1 / 2 of the pre-emulsion prepared in step S1, 1 part by mass of ammonium persulfate, and 1 part by mass of sodium bicarbonate and add them to the reactor. Heat the reactor to 75°C and keep it at that temperature for 2 hours to form a prepolymer emulsion.

[0046] S3. Add the remaining 1 / 2 pre-emulsion and 1 part by mass of ammonium persulfate to the prepolymer emulsion in step S2, continue to keep warm for 3 hours, cool down after the reaction is completed, adjust the pH to 8, filter, and obtain organosilicon modified styrene-acrylic emulsion 1 with a solid content of 30%.

[0047] Preparation Example 2

[0048] The other conditions are the same as in Preparation Example 1, except that in step S1, the mass ratio of the comonomers styrene, butyl acrylate, acrylic acid, and vinyl silane is changed to 15:25:5:16, and the vinyl silane is a mixture of vinyltrimethoxysilane and tetramethyldivinyldisilazane in a mass ratio of 3.5:1. The solid content of the organosilicon-modified styrene-acrylic emulsion 2 obtained in Preparation Example 2 is 35% by controlling the amount of water used.

[0049] Preparation Example 3

[0050] The other conditions are the same as in Preparation Example 1, except that in step S1, the vinylsilane is a mixture of vinyltrimethoxysilane and tetramethyldivinyldisilazane in a mass ratio of 2:1.

[0051] Preparation Example 4

[0052] The other conditions are the same as in Preparation Example 1, except that in step S1, the vinylsilane is a mixture of vinyltrimethoxysilane and tetramethyldivinyldisilazane in a mass ratio of 4:1.

[0053] Comparative Preparation Example 1

[0054] The other conditions are the same as in Preparation Example 1, except that in step S1, all vinylsilanes are vinyltrimethoxysilanes.

[0055] Comparative Preparation Example 2

[0056] The other conditions are the same as in Preparation Example 1, except that in step S1, all vinylsilanes are tetramethyldivinyldisilazane.

[0057] Example 1

[0058] (1) 100 parts by weight of 60-mesh coconut shell powder, 80 parts by weight of organosilicon-modified styrene-acrylic emulsion prepared in Example 1, 5 parts by weight of sodium dodecyl sulfate, and 300 parts by weight of 50wt% sodium hydroxide solution were mixed evenly and dried at 80°C to constant weight. Under nitrogen atmosphere, the temperature was increased to 800°C at a heating rate of 5°C / min and carbonized at 800°C for 2 hours. After carbonization, the carbon was cooled, washed, and dried to obtain pre-prepared mesoporous activated carbon.

[0059] (2) Take the pre-prepared mesoporous activated carbon obtained in step (1), immerse it in an ethanol solution with a concentration of 5wt% KH-560 at 40℃ for 2 hours, take it out, dry it, heat treat it at 200℃ for 4 hours under a nitrogen atmosphere, cool it, wash it, and dry it to obtain the mesoporous carbon material.

[0060] The particle size distribution and specific surface area of ​​the mesoporous carbon materials obtained from the tests, such as Figure 1 As shown, the mesoporous carbon obtained by this invention has high mesoporosity and significantly reduced microporosity (pore size less than 2 nm), with mesopores having a pore size between 5-20 nm accounting for over 80%. The pore size and uniformity are suitable for preparing silicon-carbon anode preforms. The resulting silicon-carbon anode preform exhibits high and uniform silicon loading in the carbon anode. Furthermore, because the mesoporous carbon is also doped with nitrogen, it provides more electrochemical active sites for sodium ion transport and diffusion, improving sodium storage performance and thus increasing the cycle life of sodium-ion batteries.

[0061] Example 2

[0062] The other conditions are the same as in Example 1, except that 80 parts by mass of the organosilicon-modified styrene-acrylic emulsion 1 prepared in Example 1 is replaced with 70 parts by mass of the organosilicon-modified styrene-acrylic emulsion 2 prepared in Example 2.

[0063] Examples 3-4

[0064] The other conditions are the same as in Example 1, except that the organosilicon-modified styrene-acrylic emulsion prepared in Example 1 is replaced with the organosilicon-modified styrene-acrylic emulsion prepared in Examples 3-4.

[0065] Example 5

[0066] The other conditions are the same as in Example 1, except that the 5 wt% KH-560 ethanol solution is replaced with an 8 wt% KH-561 ethanol solution.

[0067] Comparative Example 1

[0068] The other conditions are the same as in Example 1, except that step (2) is omitted, that is, the impregnation of epoxy silane coupling agent and subsequent steps are omitted.

[0069] Comparative Examples 2-3

[0070] The other conditions were the same as in Example 1, except that the organosilicon-modified styrene-acrylic emulsion prepared in Example 1 was replaced with the organosilicon-modified styrene-acrylic emulsion prepared in Comparative Preparation Example 1 and Comparative Preparation Example 2.

[0071] Test equipment: Specific surface area analyzer, model: TRISTAR IIPLUS 3030; Test standard: GB / T 19587-2017 Determination of specific surface area of ​​solid materials by gas adsorption BET method. The data of mesoporous carbon obtained from the above examples and comparative examples are shown in Table 1 below. Figure 1 This is a particle size distribution diagram of the mesoporous carbon material used as the negative electrode of a battery obtained in Example 1. Figure 2 The image shows the particle size distribution of the mesoporous carbon material used as the negative electrode of a battery obtained in Example 2. It can be seen that the mesoporous carbons prepared in Examples 1 and 2 have a high mesoporous ratio and a moderate average pore size.

[0072] Table 1

[0073]

[0074]

[0075] Application Example 1

[0076] 100 parts by mass of graphite, 30 parts by mass of mesoporous carbon prepared in Example 1, and 20 parts by mass of silicon powder were mixed evenly and dispersed in 600 parts by mass of an aqueous solution containing 5 parts by mass of dispersant (polyvinyl alcohol and hexadecyltrimethylammonium bromide in a mass ratio of 4:1). The mixture was then spray-dried at an outlet temperature of 240°C to obtain a precursor powder. This powder was calcined at 800°C for 5 hours under a nitrogen atmosphere to obtain a silicon-carbon composite material. The silicon-carbon composite material, Super P, and PVDF were mixed in a mass ratio of 8:1:1 to obtain a slurry. This slurry was coated onto copper foil to form a negative electrode. Sodium metal was used as the counter electrode, Celgard 2400 was used as the separator, and a 1M NaPF6 diethylene glycol dimethyl ether solution was used as the electrolyte. A CR2025 coin cell was assembled in an argon glove box. The cell was discharged at 1C at a constant current to 0.005V and charged at 1C at a constant current to 1.7V. The electrochemical performance test results are shown in Table 2 below.

[0077] Application Example 2-5

[0078] The other conditions are the same as in Application Example 1, except that the mesoporous carbon was prepared in Examples 2-5 respectively.

[0079] Application Example 6

[0080] The other conditions are the same as in Application Example 1, except that the raw materials are 100 parts by mass of graphite, 40 parts by mass of mesoporous carbon prepared in Example 1, and 28 parts by mass of silicon powder.

[0081] Comparative Application Examples 1-3

[0082] The other conditions are the same as in Application Example 1, except that the mesoporous carbon was prepared in Comparative Examples 1-3.

[0083] Table 2

[0084]

[0085]

[0086] It can be seen that the mesoporous carbon prepared by the method of the present invention has a high mesoporous ratio, and the abundant mesoporous structure is beneficial to improving the electrochemical performance of silicon-carbon anodes. A comparison between Example 1 and Comparative Example 1 shows that the mesoporous carbon in Comparative Example 1 has a similar mesoporous ratio and mesopore size to that in Example 1, but the electrochemical performance of the resulting silicon-carbon composite material is not good, indicating that the impregnation of the epoxy silane coupling agent is equally important in the preparation of the mesoporous carbon. A comparison between Example 1 and Comparative Examples 3 and 4 shows that appropriate mesoporous ratio and mesopore size have a significant impact on the anode material. Comparative Example 3 has a high mesoporous ratio, but the mesopore size is too large, and optimal electrochemical performance cannot be obtained.

Claims

1. A method for preparing a mesoporous carbon material with high mesopority, characterized in that, Includes the following steps: (1) 100 parts by weight of biomass powder, 70-80 parts by weight of organosilicon-modified styrene-acrylic emulsion, 3-5 parts by weight of surfactant, and 200-400 parts by weight of sodium hydroxide solution are mixed evenly, dried, heated under an inert atmosphere for carbonization, cooled, washed, and dried to obtain pre-prepared mesoporous activated carbon; the organosilicon-modified styrene-acrylic emulsion is obtained by emulsion polymerization, and the raw materials of the organosilicon-modified styrene-acrylic emulsion include styrene, (meth)acrylate, (meth)acrylic acid, vinyl silane compounds, water, and emulsifier; the solid content of the organosilicon-modified styrene-acrylic emulsion is 30-35%, and the vinyl silane compounds... The compound is a mixture of monofunctional vinyl silane and difunctional vinyl silane in a mass ratio of 2.7-3.5:1; the monofunctional vinyl silane is selected from at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, methylvinyldiethoxysilane, and methylvinyldimethoxysilane; the difunctional vinyl silane is tetramethyldivinyldisilazane; the mass ratio of styrene monomer, (meth)acrylate compound, (meth)acrylate compound, and vinyl silane compound is 15-20:20-25:2-5:12-16. (2) The pre-prepared mesoporous activated carbon obtained in step (1) is immersed in an epoxy silane coupling agent solution. After immersion, it is taken out, dried, heated under an inert atmosphere, cooled, washed, and dried to obtain a mesoporous carbon material with high mesopority.

2. The preparation method according to claim 1, characterized in that, In step (1), the (meth)acrylic acid is selected from at least one of acrylic acid and methacrylic acid; the (meth)acrylate is selected from at least one of methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, and propyl methacrylate.

3. The preparation method according to claim 1, characterized in that, In step (1), the carbonization temperature is 800-900℃ and the carbonization time is 1-2h; in step (2), the heating temperature is 200-300℃ and the heating time is 2-4h.

4. The preparation method according to claim 1, characterized in that, In step (1), the biomass powder has a particle size of 50-60 mesh, and the biomass is selected from one or a combination of two of wood, coconut shell, bamboo, and walnut shell; the surfactant is selected from at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium hexadecylbenzenesulfonate; the sodium hydroxide solution has a mass fraction of 40-50 wt%; the emulsifier is selected from one or a combination of two of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and polyethylene glycol octylphenyl ether, and the amount of emulsifier used is 7-10 wt% of the total mass of monomers, and the amount of water is controlled so that the solid content of the organosilicon modified styrene-acrylic emulsion is 30-35 wt%.

5. The preparation method according to claim 1, characterized in that, In step (2), the epoxy silane coupling agent is selected from at least one of 3-glycidyl etheroxypropyltrimethoxysilane (KH-560), 3-(2,3-epoxypropoxy)propyltriethoxysilane (KH-561), and 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane (KH-563), the solvent of the epoxy silane coupling agent solution is ethanol, and the concentration of the epoxy silane coupling agent is 5-8 wt%; the impregnation is carried out at 30-40°C for 1-2 hours.

6. The preparation method according to claim 1, characterized in that, The organosilicon-modified styrene-acrylic emulsion is obtained by a preparation method including the following steps: S1. Add the comonomer, water, and emulsifier to the mixing vessel and stir at room temperature to prepare the pre-emulsion; S2. Take 1 / 3 to 1 / 2 of the pre-emulsion from step S1, and 1 / 3 to 1 / 2 of the initiator and buffer, add them to the reactor, heat and keep the temperature constant to react and form a prepolymer emulsion; S3. Add the remaining pre-emulsion and remaining initiator to the prepolymer emulsion from step S2, react at a constant temperature, cool down after the reaction is complete, adjust the pH, filter, and obtain organosilicon-modified styrene-acrylic emulsion.

7. The preparation method according to claim 6, characterized in that, The initiator is selected from at least one of potassium persulfate, ammonium persulfate, and sodium persulfate, and the amount of initiator used is 1-3 wt% of the total mass of the monomers. The buffer is selected from sodium bicarbonate, and the amount of buffer used is 0.5-1 wt% of the total mass of the monomers.

8. The preparation method according to claim 6, characterized in that, The constant temperature reaction temperature in steps S2 and S3 is 70-80℃, and the reaction time is 1-3h. In step S3, the pH is adjusted to 8-9.

9. A silicon-carbon composite anode material, which is prepared from raw materials comprising the following parts by weight: 100 parts by weight of graphite, 30-40 parts by weight of mesoporous carbon material prepared by any one of claims 1-8, and 20-28 parts by weight of silicon powder.

10. The method for preparing the silicon-carbon composite anode material according to claim 9, characterized in that, The process includes the following steps: dispersing graphite, mesoporous carbon, and silicon powder in an aqueous solution containing a dispersant, spray drying to obtain a composite material precursor, and calcining it in a non-oxidizing atmosphere to obtain a silicon-carbon composite anode material.

11. The preparation method according to claim 10, characterized in that, The dispersant is selected from at least one of polyvinyl alcohol, polyvinylpyrrolidone, carboxymethyl cellulose, and long-chain alkyl quaternary ammonium salts, wherein the long-chain alkyl quaternary ammonium salt is selected from at least one of hexadecyltrimethylammonium chloride and hexadecyltrimethylammonium bromide; the amount of dispersant is 3-5 wt% of the total mass of graphite, mesoporous carbon, and silica powder, and the amount of aqueous solution containing the dispersant is 4-6 times the total mass of graphite, mesoporous carbon, and silica powder; the spray drying outlet temperature is 180-240℃; the non-oxidizing atmosphere is nitrogen and / or argon, the calcination temperature is 600-800℃, and the calcination time is 3-5 h.

12. A sodium-ion battery negative electrode, comprising the silicon-carbon composite negative electrode material as described in claim 9, a conductive additive, and a binder.

13. The sodium-ion battery negative electrode according to claim 12, characterized in that, The mass ratio of carbon composite anode material, conductive additive, and binder is 80-90:5-10:5-10.

14. The sodium-ion battery negative electrode according to claim 12, characterized in that, The conductive additive is selected from at least one of SuperP and acetylene black; the binder is selected from at least one of PVDF and polytetrafluoroethylene.

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