Modified silicon carbide negative active material, preparation method thereof, negative active material and lithium ion battery

Abstract

The application provides a modified silicon carbide negative active material, a preparation method of the modified silicon carbide negative active material, a negative active material and a lithium ion battery. x C y M z , 0<=x<=3, 0<=y<=5, 0<=z<=0.5y, M is any one or a combination of at least two of a group IIIA element, a group VA element or a group VIA element; and the preparation raw material of the modified silicon carbide negative active material comprises an organic compound containing the element M and a silicon-based compound containing a polymerizable group. The application uses the organic compound containing the element M and the silicon-based compound containing the polymerizable group as the raw material, on the one hand, the carbon content can be increased, the free carbon band structure can be increased, and the electrical conductivity can be improved; on the other hand, the introduction of the element M can change the electronic structure of the silicon carbide and the carbon band structure, reduce the energy gap, and be helpful to the rapid transmission of electrons; and the skeleton structure of the material is stable, and the volume expansion in the lithium ion intercalation and deintercalation process can be effectively inhibited.

Description

Technical Field

[0001] This invention belongs to the fields of chemical engineering and materials science, specifically relating to a modified silicon carbide anode active material and its preparation method, anode material, and lithium-ion battery. Background Technology

[0002] Lithium-ion batteries, as crucial energy storage devices widely used in mobile communications, electric vehicles, and energy storage systems, are constantly undergoing technological improvements and innovations to enhance performance and meet ever-increasing energy demands. The anode material of lithium-ion batteries plays a vital role in determining battery performance and cycle life. Traditional anode materials typically use graphite; however, with the increasing prevalence of electric vehicles and the development of renewable energy, the requirements for battery energy density, charge / discharge rates, and cycle life are constantly rising, gradually revealing the limitations of traditional graphite anodes.

[0003] Silicon carbide has attracted much attention as a novel anode material due to its high specific capacity and excellent chemical stability, demonstrating great potential. It can store more lithium ions, increasing battery energy density, while also exhibiting faster electron transport speeds and better electrochemical performance, potentially meeting the demands of high-performance batteries. However, silicon carbide anode materials still face a series of challenges, such as high resistivity, cycle stability, and continuous optimization of electrochemical performance.

[0004] Therefore, how to further improve the performance of silicon carbide anode materials is one of the key research directions at present. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a modified silicon carbide anode active material, its preparation method, the anode material itself, and a lithium-ion battery. This invention uses organic compounds containing element M and silicon-based compounds containing polymerizable groups as raw materials. On the one hand, it can increase the carbon content of the material, increase the free carbon band structure in silicon carbide, provide a high-speed channel for electron transport, and improve conductivity. On the other hand, the introduction of element M can change the electronic structure of silicon carbide and the carbon band structure, reduce the band gap, facilitate rapid electron transport, and enhance its conductivity and lithium-ion diffusion rate. Furthermore, the material's framework structure is stable, effectively suppressing volume expansion during lithium-ion insertion and extraction, maintaining the material's stability. Therefore, this anode active material exhibits excellent performance in lithium battery applications and is expected to have a profound impact in multiple fields.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a modified silicon carbide anode active material, wherein the chemical formula of the modified silicon carbide anode active material is Si. x C y Mz , 0≤x≤3, 0≤y≤5, 0≤z≤0.5y, M is any one or at least two of the elements of group IIIA, group VA or group VIA;

[0008] The raw materials for preparing the modified silicon carbide anode active material include organic compounds containing the element M and silicon-based compounds containing polymerizable groups.

[0009] This invention uses organic compounds containing element M and silicon-based compounds containing polymerizable groups as raw materials. On the one hand, it can increase the carbon content of the material, increase the free carbon ribbon structure in silicon carbide, provide a high-speed channel for electron transport, and improve conductivity. On the other hand, the introduction of element M can change the electronic structure of silicon carbide and carbon ribbon structure, reduce the band gap, facilitate rapid electron transport, and enhance its conductivity and lithium-ion diffusion rate. Furthermore, the material's framework structure is stable, effectively suppressing volume expansion during lithium-ion insertion and extraction, and maintaining the material's stability. Therefore, this negative electrode active material exhibits excellent performance in lithium battery applications and is expected to have a profound impact in multiple fields.

[0010] In this invention, 0 ≤ x ≤ 3, for example, it can be 1, 1.5, 2, 2.5 or 3, etc.

[0011] In this invention, 0≤y≤5, for example, it can be 3, 3.5, 4, 4.5 or 5, etc.

[0012] In this invention, 0 ≤ z ≤ 0.5y, for example, it can be 0.3, 0.4, 0.5, 0.8 or 0.85, etc.

[0013] In this invention, if the value of z is too small, that is, if the doping amount of element M is too small, the conductivity will be too small and the impedance will be large. The maximum range of z depends on the value of y.

[0014] As a preferred embodiment of the present invention, M includes any one or a combination of at least two of nitrogen, boron, or sulfur, preferably sulfur and / or nitrogen.

[0015] In this invention, sulfur is preferably introduced as the M element into silicon carbide, which helps to improve the transport of ions / electrons.

[0016] As a preferred embodiment of the present invention, the polymerizable groups include unsaturated vinyl groups and / or Si-H groups.

[0017] In this invention, the silicon-based compound contains unsaturated ethylene and / or Si-H groups, which facilitates the hydrosilylation reaction between the silicon-based compound and an organic compound containing element M, thereby introducing element M in situ into silicon carbide.

[0018] In a second aspect, the present invention provides a method for preparing the modified silicon carbide anode active material as described in the first aspect, the preparation method comprising the following steps:

[0019] (1) Mix an organic compound containing element M, a silicon-based compound containing polymerizable groups, and a solvent to carry out a polymerization reaction to obtain a modified polymer precursor.

[0020] (2) The modified polymer precursor is subjected to heat treatment to obtain the modified silicon carbide anode active material.

[0021] As a preferred technical solution of the present invention, the organic compound containing element M in step (1) is an organic active small molecule containing element M.

[0022] Preferably, the organic active small molecule containing element M includes any one or a combination of at least two of the following: vinylpyridine, 5,5-divinyl-2,2-bipyridine, tetramethyltetravinylcyclotetrasiloxane, trimethylborene, dimethylborene, lithium dimethylborohydride, vinyl-terminated dimethylpolysiloxane, divinylthiophene, trivinyltrimethylcyclotrisilazane, vinylthiol, triallylamine, or 1,3,5-triallyl-1,3,5-triazine-2,4,6-trione.

[0023] Preferably, the silicon-based compound containing polymerizable groups in step (1) includes any one or a combination of at least two of allyl hydrogenated polycarbosilane, vinyl polysilane, vinyl polysiloxane, or polydimethyldivinylsiloxane.

[0024] Preferably, the solvent in step (1) includes any one or a combination of at least two of toluene, xylene, benzene, hexane, heptane, tetrahydrofuran, dimethyl ether, chloroform, or dichloromethane.

[0025] Preferably, the mass ratio of the organic compound containing element M and the silicon-based compound containing polymerizable groups in step (1) is (0.5-1):(1-2), wherein the range of selection for the organic compound containing element M, “0.5-1”, can be, for example, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc., and the range of selection for the silicon-based compound containing polymerizable groups, “1-2”, can be, for example, 1, 1.2, 1.4, 1.6, 1.8 or 2, etc.

[0026] As a preferred technical solution of the present invention, the mixing method in step (1) includes:

[0027] A silicon-based compound containing polymerizable groups is dispersed in a solvent, and then an organic compound containing element M is added.

[0028] Preferably, the mixing process in step (1) is accompanied by stirring.

[0029] Preferably, the polymerization reaction in step (1) is carried out in an inert atmosphere.

[0030] It should be noted that the present invention does not limit the gas in the inert atmosphere; for example, it may be argon.

[0031] Preferably, the polymerization reaction temperature in step (1) is 100-150°C, for example, 100°C, 130°C or 150°C.

[0032] In this invention, if the polymerization temperature is too low, the polymerization reaction cannot be induced; if the polymerization temperature is too high, the organic molecules will decompose and the solvent will evaporate, both of which will affect the polymerization reaction.

[0033] As a preferred technical solution of the present invention, the heat treatment process in step (2) includes primary heating, secondary heating and tertiary heating.

[0034] Preferably, the temperature of the first-stage heating is 200-400℃, for example, 200℃, 250℃, 300℃, 350℃ or 400℃, and the time is 1-3h, for example, 1h, 2h or 3h.

[0035] Preferably, the temperature of the secondary heating is 800-1000℃, for example, 800℃, 850℃, 900℃, 950℃ or 1000℃, and the time is 1-3h, for example, 1h, 2h or 3h.

[0036] Preferably, the temperature of the three-stage heating is 1200-1500℃, for example, it can be 120℃, 1300℃, 1400℃ or 1500℃, etc., and the time is 2-4h, for example, it can be 2h, 3h or 4h.

[0037] In this invention, if the temperature of the three-stage heating is too low, crystallization products cannot be formed and the electrical conductivity is low; if the temperature of the three-stage heating is too high, some of the effective components will volatilize, resulting in a decrease in material performance.

[0038] Preferably, the heat treatment in step (2) is carried out in a vacuum atmosphere or an inert atmosphere.

[0039] Preferably, the gas in the inert atmosphere includes any one or a combination of at least two of nitrogen, argon, ammonia, or carbon dioxide.

[0040] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0041] (1) A silicon-based compound containing polymerizable groups is stirred and mixed with a solvent, and then an organic active small molecule containing element M is added under stirring conditions. The polymerization reaction is carried out at 100-150℃ for 12-72h. After the reaction is completed, a modified polymer precursor is obtained.

[0042] The mass ratio of organic active small molecules containing element M to silicon-based compounds containing polymerizable groups is (0.5-1):(1-2).

[0043] (2) The modified polymer precursor is dried at 100-150°C to obtain a solid product. The solid product is then ball-milled for 1-3 hours. The obtained powder product is then placed in an inert atmosphere or a vacuum atmosphere and subjected to first-stage heating, second-stage heating and third-stage heating. After the heating is completed, the product is cooled to room temperature and then ball-milled for 1-3 hours to obtain the modified silicon carbide anode active material.

[0044] The first stage of heating is at a temperature of 200-400℃ for 1-3 hours, the second stage is at a temperature of 800-1000℃ for 1-3 hours, and the third stage is at a temperature of 1200-1500℃ for 2-4 hours.

[0045] Thirdly, the present invention provides a negative electrode material, the negative electrode material comprising the modified silicon carbide negative electrode material, conductive agent, and binder as described in the first aspect;

[0046] Based on the mass of the negative electrode material, the content of the conductive agent is 10-30%, for example, it can be 10%, 15%, 20%, 25% or 30%, etc., and the content of the binder is 5-15%, for example, it can be 5%, 10% or 15%, etc.

[0047] In this invention, by precisely controlling the ratio of conductive agent and binder, the conductivity, structural stability and cycle performance of silicon carbide anode active material can be further improved, thereby enabling lithium batteries to have higher charge and discharge efficiency, longer lifespan and higher energy density.

[0048] It should be noted that the present invention does not limit the type of conductive agent; for example, it may be graphene, graphite, acetylene black, carbon nanotubes, conductive polymers, or activated carbon fibers. The present invention also does not limit the type of binder; for example, it may be polyacryl alcohol, polypropylene, or polyurethane.

[0049] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the modified silicon carbide anode material as described in the first aspect, or comprising the anode material as described in the third aspect.

[0050] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] This invention uses organic compounds containing element M and silicon-based compounds containing polymerizable groups as raw materials. On the one hand, it can increase the carbon content of the material, increase the free carbon band structure in silicon carbide, provide a high-speed channel for electron transport, and improve conductivity. On the other hand, the introduction of element M can change the electronic structure of silicon carbide and carbon band structure, reduce the band gap, facilitate the rapid transport of electrons, and enhance its conductivity and lithium-ion diffusion rate. Furthermore, the material has a stable framework structure, which can effectively suppress the volume expansion during the lithium-ion insertion and extraction process and maintain the stability of the material.

[0053] (2) The modified silicon carbide anode active material provided by the present invention exhibits excellent performance in lithium battery applications and is expected to have a profound impact on electric vehicles, energy storage systems and portable electronic devices. Attached Figure Description

[0054] Figure 1 This is a SEM image of the modified silicon carbide anode active material prepared in Example 1 of the present invention.

[0055] Figure 2 This is a SEM image of the modified silicon carbide anode active material prepared in Example 8 of the present invention. Detailed Implementation

[0056] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0057] It should be noted that the room temperature below refers to 25℃.

[0058] Example 1

[0059] This embodiment provides a modified silicon carbide anode active material, wherein the chemical formula of the modified silicon carbide anode active material is Si. x C y M z , x=1.6, y=4.08, z=0.44, M is N;

[0060] The raw materials for preparing the modified silicon carbide anode active material include organic active small molecules containing the M element and silicon-based compounds containing polymerizable groups.

[0061] The organic active small molecule containing element M is 2,6-divinylpyridine, and the silicon-based compound containing polymerizable groups is vinyl polysilane.

[0062] This embodiment also provides a method for preparing the above-mentioned modified silicon carbide anode active material, the preparation method comprising the following steps:

[0063] (1) 5g of vinyl polysilane and excess toluene were loaded into the reactor under the protection of an inert atmosphere of argon. 5g of 2,6-divinylpyridine was added under continuous stirring and the polymerization reaction was carried out at 140℃ for 48h. After the reaction was completed, the mixture was cooled to room temperature to obtain the modified polymer precursor.

[0064] The mass ratio of 2,6-divinylpyridine to vinyl polysilane is 1:1;

[0065] (2) The modified polymer precursor was rotary evaporated at 100°C for 1 hour to obtain a solid product. The solid product was then placed in a ball mill jar and ball milled for 2 hours. The obtained powder product was then placed in an argon atmosphere and subjected to first-stage heating, second-stage heating and third-stage heating. After the heating was completed, the product was naturally cooled to room temperature and ball milled for 2 hours to obtain the modified silicon carbide anode active material.

[0066] The first stage of heating is at a temperature of 300℃ for 2 hours, the second stage is at a temperature of 900℃ for 2 hours, and the third stage is at a temperature of 1400℃ for 3 hours.

[0067] This embodiment also provides a negative electrode material, which includes the modified silicon carbide negative electrode material, conductive agent and binder as described above;

[0068] The conductive agent is graphene, and the content of the conductive agent is 20%. The binder is polyacryl alcohol, and the content of the binder is 10%.

[0069] Example 2

[0070] This embodiment provides a modified silicon carbide anode active material, wherein the chemical formula of the modified silicon carbide anode active material is Si. x C y M z , x=2.08, y=3.31, z=0.7, M is N;

[0071] The raw materials for preparing the modified silicon carbide anode active material include organic active small molecules containing the M element and silicon-based compounds containing polymerizable groups.

[0072] The organic active small molecule containing element M is 5,5-divinyl-2,2-bipyridine, and the silicon-based compound containing polymerizable groups is allyl hydrogenated polycarbosilane.

[0073] This embodiment also provides a method for preparing the above-mentioned modified silicon carbide anode active material, the preparation method comprising the following steps:

[0074] (1) 5g of allyl hydrogenated polycarbosilane and excess toluene were loaded into a reactor under the protection of an inert atmosphere of argon. 5g of 5,5-divinyl-2,2-bipyridine was added under continuous stirring and the polymerization reaction was carried out at 140℃ for 48h. After the reaction was completed, the mixture was cooled to room temperature to obtain the modified polymer precursor.

[0075] The mass ratio of 5,5-divinyl-2,2-bipyridine to allyl hydrogenated polycarbosilane is 1:1.

[0076] (2) The modified polymer precursor was rotary evaporated at 100°C for 1 hour to obtain a solid product. The solid product was then placed in a ball mill jar and ball milled for 2 hours. The obtained powder product was then placed in an argon atmosphere and subjected to first-stage heating, second-stage heating and third-stage heating. After the heating was completed, the product was naturally cooled to room temperature and ball milled for 2 hours to obtain the modified silicon carbide anode active material.

[0077] The first stage of heating is at a temperature of 300℃ for 2 hours, the second stage is at a temperature of 900℃ for 2 hours, and the third stage is at a temperature of 1500℃ for 3 hours.

[0078] This embodiment also provides a negative electrode material, which includes the modified silicon carbide negative electrode material, conductive agent and binder as described above;

[0079] The conductive agent is graphene, and the content of the conductive agent is 15%. The binder is polyacryl alcohol, and the content of the binder is 10%.

[0080] Example 3

[0081] This embodiment provides a modified silicon carbide anode active material, wherein the chemical formula of the modified silicon carbide anode active material is Si. x C y M z x = 2.2, y = 3.35, z = 0.49, M includes N and O;

[0082] The raw materials for preparing the modified silicon carbide anode active material include organic active small molecules containing the M element and silicon-based compounds containing polymerizable groups.

[0083] The organic active small molecule containing element M is 1,3,5-triallyl-1,3,5-triazine-2,4,6-trione, and the silicon-based compound containing polymerizable groups is vinyl polysilane.

[0084] This embodiment also provides a method for preparing the above-mentioned modified silicon carbide anode active material, the preparation method comprising the following steps:

[0085] (1) 5g of vinyl polysilane and excess toluene were loaded into the reactor under the protection of an inert atmosphere of argon. 5g of 1,3,5-triallyl-1,3,5-triazine-2,4,6-trione was added under continuous stirring. The polymerization reaction was carried out at 140℃ for 72h. After the reaction was completed, the mixture was cooled to room temperature to obtain the modified polymer precursor.

[0086] The mass ratio of 1,3,5-triallyl-1,3,5-triazine-2,4,6-trione to vinyl polysilane is 1:1.

[0087] (2) The modified polymer precursor was rotary evaporated at 100°C for 1 hour to obtain a solid product. The solid product was then placed in a ball mill jar and ball milled for 2 hours. The obtained powder product was then placed in an argon atmosphere and subjected to first-stage heating, second-stage heating and third-stage heating. After the heating was completed, the product was naturally cooled to room temperature and ball milled for 2 hours to obtain the modified silicon carbide anode active material.

[0088] The first stage of heating is at a temperature of 300℃ for 2 hours, the second stage is at a temperature of 900℃ for 2 hours, and the third stage is at a temperature of 1400℃ for 3 hours.

[0089] This embodiment also provides a negative electrode material, which includes the modified silicon carbide negative electrode material, conductive agent and binder as described above;

[0090] The conductive agent is graphene, and the content of the conductive agent is 25%. The binder is polyacryl alcohol, and the content of the binder is 10%.

[0091] Example 4

[0092] This embodiment provides a modified silicon carbide anode active material, wherein the chemical formula of the modified silicon carbide anode active material is Si. x C y M z , x=1.6, y=4.04, z=0.85, M is S;

[0093] The raw materials for preparing the modified silicon carbide anode active material include organic active small molecules containing the M element and silicon-based compounds containing polymerizable groups.

[0094] The organic active small molecule containing element M is divinylthiophene, and the silicon-based compound containing polymerizable groups is allyl hydrogenated polycarbosilane.

[0095] This embodiment also provides a method for preparing the above-mentioned modified silicon carbide anode active material, the preparation method comprising the following steps:

[0096] (1) 5g of allyl hydrogenated polycarbosilane and excess toluene were loaded into the reactor under the protection of an inert atmosphere of argon. 5g of divinylthiophene was added under continuous stirring. The polymerization reaction was carried out at 130°C for 48h. After the reaction was completed, the mixture was cooled to room temperature to obtain the modified polymer precursor.

[0097] The mass ratio of divinylthiophene to allyl hydrogenated polycarbosilane is 1:1.

[0098] (2) The modified polymer precursor was rotary evaporated at 100°C for 1 hour to obtain a solid product. The solid product was then placed in a ball mill jar and ball milled for 2 hours. The obtained powder product was then placed in an argon atmosphere and subjected to first-stage heating, second-stage heating and third-stage heating. After the heating was completed, the product was naturally cooled to room temperature and ball milled for 2 hours to obtain the modified silicon carbide anode active material.

[0099] The first stage of heating is at a temperature of 300℃ for 2 hours, the second stage is at a temperature of 900℃ for 2 hours, and the third stage is at a temperature of 1400℃ for 3 hours.

[0100] This embodiment also provides a negative electrode material, which includes the modified silicon carbide negative electrode material, conductive agent and binder as described above;

[0101] The conductive agent is graphene, and the content of the conductive agent is 10%. The binder is polyacryl alcohol, and the content of the binder is 15%.

[0102] Example 5

[0103] This embodiment provides a modified silicon carbide anode active material, wherein the chemical formula of the modified silicon carbide anode active material is Si. x C y M z , x=1.4, y=4.72, z=0.61, M is S;

[0104] The raw materials for preparing the modified silicon carbide anode active material include organic active small molecules containing the M element and silicon-based compounds containing polymerizable groups.

[0105] The organic active small molecule containing element M is divinylthiophene, and the silicon-based compound containing polymerizable groups is vinyl polysilane.

[0106] This embodiment also provides a method for preparing the above-mentioned modified silicon carbide anode active material, the preparation method comprising the following steps:

[0107] (1) 5g of vinyl polysilane and excess toluene were loaded into the reactor under the protection of an inert atmosphere of argon. 5g of divinylthiophene was added under continuous stirring. The polymerization reaction was carried out at 130°C for 48h. After the reaction was completed, the mixture was cooled to room temperature to obtain the modified polymer precursor.

[0108] The mass ratio of divinylthiophene to vinyl polysilane is 1:1.

[0109] (2) The modified polymer precursor was rotary evaporated at 120°C for 1 hour to obtain a solid product. The solid product was then placed in a ball mill jar and ball milled for 1 hour. The obtained powder product was then placed in an argon atmosphere and subjected to first-stage heating, second-stage heating and third-stage heating. After the heating was completed, the product was naturally cooled to room temperature and ball milled for 1 hour to obtain the modified silicon carbide anode active material.

[0110] The first stage of heating is at a temperature of 200℃ for 3 hours, the second stage is at a temperature of 800℃ for 3 hours, and the third stage is at a temperature of 1400℃ for 4 hours.

[0111] This embodiment also provides a negative electrode material, which includes the modified silicon carbide negative electrode material, conductive agent and binder as described above;

[0112] The conductive agent is graphene, and the content of the conductive agent is 30%. The binder is polyacryl alcohol, and the content of the binder is 5%.

[0113] Example 6

[0114] The difference between this embodiment and Embodiment 1 is that the polymerization temperature in step (1) is 80°C.

[0115] The remaining preparation methods and parameters are consistent with those in Example 1.

[0116] Example 7

[0117] The difference between this embodiment and Embodiment 1 is that the polymerization temperature in step (1) is 180°C.

[0118] The remaining preparation methods and parameters are consistent with those in Example 1.

[0119] Example 8

[0120] The difference between this embodiment and embodiment 1 is that the temperature of the three-stage heating in step (2) is 900℃.

[0121] The remaining preparation methods and parameters are consistent with those in Example 1.

[0122] Figure 1 and Figure 2SEM images of the modified silicon carbide anode active materials prepared in Examples 1 and 8 are shown respectively. As can be seen from the figures, with the increase of the pyrolysis temperature, the phase of the modified silicon carbide anode active material gradually changes from an amorphous state to a crystalline state.

[0123] Example 9

[0124] The difference between this embodiment and embodiment 1 is that the temperature of the three-stage heating in step (1) is 1600℃.

[0125] The remaining preparation methods and parameters are consistent with those in Example 1.

[0126] Comparative Example 1

[0127] The difference between this comparative example and Example 1 is that in step (1), 2,6-divinylpyridine is replaced with an equal mass of divinylbiphenyl, so that the value of z is 0.

[0128] The remaining preparation methods and parameters are consistent with those in Example 1.

[0129] Performance testing

[0130] The product yields of the polymerization reactions in the preparation methods provided in the above embodiments and comparative examples were tested, and the conductivity of the obtained negative electrode materials was tested.

[0131] The test results are shown in Table 1.

[0132] Table 1

[0133]

[0134]

[0135] analyze:

[0136] As can be seen from the table above, the battery prepared based on the negative electrode material provided by the present invention has excellent electrochemical performance.

[0137] As can be seen from Examples 1 and 6-7, if the polymerization temperature is too low, the polymerization reaction cannot be initiated; if the polymerization temperature is too high, the organic molecules decompose, the solvent evaporates, and the polymerization reaction cannot continue.

[0138] As can be seen from Examples 1 and 8-9, if the temperature of the three-stage heating is too low, the product will remain amorphous and have low electrical conductivity; if the temperature of the three-stage heating is too high, it will continue to crystallize, the effective components will volatilize, and the weight ratio will decrease.

[0139] As can be seen from Example 1 and Comparative Examples 1-2, if 2,6-divinylpyridine is replaced with divinylbiphenyl, M cannot be introduced, and the conductivity decreases.

[0140] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A modified silicon carbide anode active material, characterized in that, The chemical formula of the modified silicon carbide anode active material is Si. x C y M z , 0 < x ≤ 3, 0 < y ≤ 5, 0 < z ≤ 0.5y, M is sulfur; The raw materials for preparing the modified silicon carbide anode active material include organic compounds containing the element M and silicon-based compounds containing polymerizable groups.

2. The modified silicon carbide anode active material according to claim 1, characterized in that, The polymerizable groups include unsaturated vinyl groups and / or Si-H groups.

3. A method for preparing the modified silicon carbide anode active material as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) Mix an organic compound containing element M, a silicon-based compound containing polymerizable groups, and a solvent to carry out a polymerization reaction to obtain a modified polymer precursor; (2) The modified polymer precursor is subjected to heat treatment to obtain the modified silicon carbide anode active material.

4. The preparation method according to claim 3, characterized in that, The organic compound containing element M in step (1) is an organic active small molecule containing element M.

5. The preparation method according to claim 4, characterized in that, The organic active small molecules containing the M element include divinylthiophene and / or vinyl thiols.

6. The preparation method according to claim 3, characterized in that, The silicon-based compound containing polymerizable groups in step (1) includes any one or a combination of at least two of allyl hydrogenated polycarbosilane, vinyl polysilane, vinyl polysiloxane or polydimethyldivinylsiloxane.

7. The preparation method according to claim 3, characterized in that, The solvent in step (1) includes any one or a combination of at least two of toluene, xylene, benzene, hexane, heptane, tetrahydrofuran, dimethyl ether, chloroform, or dichloromethane.

8. The preparation method according to claim 3, characterized in that, The mass ratio of the organic compound containing element M and the silicon-based compound containing polymerizable groups in step (1) is (0.5-1):(1-2).

9. The preparation method according to claim 3, characterized in that, The mixing method described in step (1) includes: A silicon-based compound containing polymerizable groups is dispersed in a solvent, and then an organic compound containing element M is added.

10. The preparation method according to claim 3, characterized in that, The mixing process described in step (1) is accompanied by stirring.

11. The preparation method according to claim 3, characterized in that, The polymerization reaction in step (1) is carried out in an inert atmosphere.

12. The preparation method according to claim 3, characterized in that, The polymerization reaction in step (1) is carried out at a temperature of 100-150℃.

13. The preparation method according to claim 3, characterized in that, The heat treatment process described in step (2) includes primary heating, secondary heating and tertiary heating.

14. The preparation method according to claim 13, characterized in that, The temperature of the first-stage heating is 200-400℃, and the time is 1-3 hours.

15. The preparation method according to claim 13, characterized in that, The secondary heating temperature is 800-1000℃, and the time is 1-3 hours.

16. The preparation method according to claim 13, characterized in that, The three-stage heating process involves heating at a temperature of 1200-1500℃ for 2-4 hours.

17. The preparation method according to claim 3, characterized in that, The heat treatment in step (2) is carried out in a vacuum atmosphere or an inert atmosphere.

18. The preparation method according to claim 17, characterized in that, The gas in the inert atmosphere includes any one or a combination of at least two of nitrogen, argon, ammonia, or carbon dioxide.

19. The preparation method according to claim 3, characterized in that, The preparation method includes the following steps: (1) A silicon-based compound containing polymerizable groups is stirred and mixed with a solvent, and then an organic active small molecule containing element M is added under stirring conditions. The polymerization reaction is carried out at 100-150℃ for 12-72h. After the reaction is completed, a modified polymer precursor is obtained. The mass ratio of the organic active small molecule containing element M to the silicon-based compound containing polymerizable groups is (0.5-1):(1-2). (2) The modified polymer precursor is dried at 100-150°C to obtain a solid product. The solid product is then ball-milled for 1-3 hours. The obtained powder product is then placed in an inert atmosphere or a vacuum atmosphere and subjected to first-stage heating, second-stage heating and third-stage heating. After the heating is completed, the product is cooled to room temperature and then ball-milled for 1-3 hours to obtain the modified silicon carbide anode active material. The first stage of heating is at a temperature of 200-400℃ for 1-3 hours, the second stage is at a temperature of 800-1000℃ for 1-3 hours, and the third stage is at a temperature of 1200-1500℃ for 2-4 hours.

20. A negative electrode material, characterized in that, The negative electrode material includes the modified silicon carbide negative electrode material as described in claim 1 or 2, a conductive agent, and a binder; Based on the mass of the negative electrode material, the content of the conductive agent is 10-30%, and the content of the binder is 5-15%.

21. A lithium-ion battery, characterized in that, The lithium-ion battery includes the modified silicon carbide anode material as described in claim 1 or 2, or includes the anode material as described in claim 20.

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