Silicon-carbon material, method for preparing the same, negative electrode, and battery

Abstract

The application discloses a silicon-carbon material, a preparation method thereof, a negative electrode and a battery. The silicon-carbon material comprises silicon-carbon particles and a coating layer covering the silicon-carbon particles. The silicon-carbon particles comprise porous carbon and nano-silicon. At least part of the nano-silicon is located in the pores of the porous carbon. The material of the coating layer comprises amorphous material. The silicon-carbon material satisfies 3≤A / B≤6 and 0.88Ω·cm≤B≤2Ω·cm. A represents the powder resistivity of the silicon-carbon material under a pressure of 5 MPa, and B represents the powder resistivity of the silicon-carbon material under a pressure of 30 MPa. The silicon-carbon material has high conductivity.

Description

Technical Field

[0001] This application relates to the field of new energy technology, and in particular to a silicon-carbon material and its preparation method, a negative electrode and a battery. Background Technology

[0002] With the rapid growth in energy demand and increasing environmental awareness, the development of high-efficiency, long-life energy storage devices has become particularly important. In the battery field, the choice of anode material directly affects battery performance. In recent years, silicon-carbon materials, as anode materials, have shown broad application prospects due to their advantages such as high capacity, low cost, and environmental friendliness.

[0003] However, existing silicon-carbon materials have poor electrical conductivity and need further improvement. Summary of the Invention

[0004] In view of this, this application provides a silicon-carbon material, a method for preparing the same, a negative electrode, and a battery.

[0005] This application provides a silicon-carbon material, comprising silicon-carbon particles and a coating layer covering the silicon-carbon particles. The silicon-carbon particles include porous carbon and nano-silicon, with at least a portion of the nano-silicon located within the pores of the porous carbon. The coating layer is made of an amorphous material.

[0006] The silicon-carbon material satisfies: 3≤A / B≤6, and 0.88Ω·cm≤B≤2Ω·cm; A represents the powder resistivity of the silicon-carbon material at 5MPa pressure, and B represents the powder resistivity of the silicon-carbon material at 30MPa pressure.

[0007] Optionally, in some embodiments, the amorphous material includes one or more of amorphous metal oxides and amorphous carbon, wherein the amorphous metal oxide includes one or more of amorphous titanium dioxide and amorphous aluminum oxide.

[0008] Optionally, in some embodiments, the Dv50 particle size of the porous carbon is 4~10 μm;

[0009] The specific surface area of ​​the porous carbon is 1600~3000 m². 2 / g;

[0010] The porous carbon has a pore volume of 0.85~1.5 cm³. 3 / g;

[0011] The volume percentage of micropores in the porous carbon is 90%~100%;

[0012] The average thickness of the coating layer is 2~30 nm;

[0013] The specific surface area of ​​the silicon-carbon material is 1~8 m². 2 / g;

[0014] The silicon-carbon material contains 40% to 75% silicon by mass.

[0015] Accordingly, this application also provides a method for preparing silicon-carbon materials, comprising the following steps:

[0016] S1, porous carbon is placed in a reaction chamber, and silicon-containing gas is used as the silicon source to deposit silicon nanoparticles into the pores of the porous carbon through chemical vapor deposition, thereby obtaining silicon-carbon particles. The silicon-containing gas is introduced from the bottom of the reaction chamber to suspend the porous carbon in the reaction chamber, and the suspension height of the porous carbon is 1.6 to 2.2 times the stacking height of the porous carbon in the static state.

[0017] S2, Amorphous material is coated on the surface of the silicon-carbon particles to obtain silicon-carbon material.

[0018] Optionally, in some embodiments, the temperature of the chemical vapor deposition in step S1 is 400~1000℃ and the time is 0.5~50 h;

[0019] The flow rate of the silicon-containing gas is 35~80 slm;

[0020] The silicon-containing gas includes a silicon source gas and a carrier gas, wherein the silicon source gas includes one or more of silane, disilane, monochlorotrihydrosilane, dichlorodihydrosilane, and trichloromonohydrosilane.

[0021] Optionally, in some embodiments, the silicon deposition step S1 includes a first stage, a second stage, and a third stage performed sequentially, wherein the volume concentration of silicon source gas in the silicon-containing gas in the second stage is greater than the volume concentration of silicon source gas in the silicon-containing gas in the first stage and the volume concentration of silicon source gas in the silicon-containing gas in the third stage.

[0022] In the second stage, the volume concentration of silicon source gas in the silicon-containing gas is greater than 12% and less than or equal to 40%; in the first stage, the volume concentration of silicon source gas in the silicon-containing gas is 3% to 12%; and in the third stage, the volume concentration of silicon source gas in the silicon-containing gas is 3% to 12%.

[0023] Optionally, in some embodiments, the step of coating the surface of the silicon-carbon particles with an amorphous material in step S2 includes: replacing the silicon-containing gas in step S1 with a carbon-containing gas, and performing carbon deposition by chemical vapor deposition to obtain the coating layer;

[0024] The flow rate of the carbon-containing gas is 1~20 slm;

[0025] The carbon deposition temperature is 400~900℃, and the time is 20~300 min;

[0026] The carbon-containing gas includes a carbon source gas and a carrier gas, wherein the carbon source gas includes C1-C3 hydrocarbons and C5-C4 hydrocarbons. 10 One or more of hydrocarbon vapors and aromatic compound vapors having 6 to 60 ring atoms, wherein the C1 to C3 hydrocarbons include one or more of methane, ethane, propane, ethylene, propylene, 1,3-butadiene, acetylene, and propyne, and the C5 to C6 hydrocarbons are... 10 The hydrocarbon vapors include one or more of hexane vapor and cyclohexane vapor, and the aromatic compound vapors having a ring atom number of 6 to 60 include one or more of benzene vapor and toluene vapor;

[0027] The volume concentration of the carbon source gas in the carbon-containing gas is 5-100%.

[0028] Optionally, in some embodiments, the step of coating the surface of the silicon-carbon particles with amorphous material in step S2 includes: replacing the silicon-containing gas in step S1 with gas I including water vapor, introducing gas II including metal salt precursor vapor into the reaction chamber, and performing heat treatment to obtain the coating layer.

[0029] The gas I containing water vapor and / or the gas II containing metal salt precursor vapor also contain a carrier gas;

[0030] The flow rate of gas I, which includes water vapor, is 20-50 slm;

[0031] The flow rate of gas II, which includes metal salt precursor vapor, is 15~45 slm.

[0032] The heat treatment temperature is 80~220℃, and the time is 50~180 min;

[0033] The metal salt precursor in the metal salt precursor vapor includes metal halides; the metal halide includes TiCl4.

[0034] Accordingly, this application also provides a negative electrode comprising the silicon-carbon material.

[0035] Accordingly, this application also provides a battery including the negative electrode.

[0036] The silicon-carbon material described in this application has good electrical conductivity. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a flowchart of a method for preparing silicon-carbon material provided in an embodiment of this application. Detailed Implementation

[0039] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0040] In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operating state, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish a numerical order.

[0041] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0042] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0043] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, whichever applies. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0044] Silicon-carbon materials, as anode materials, have broad application prospects in the field of lithium-ion battery anode materials due to their advantages such as high capacity, low cost, and environmental friendliness. However, silicon-carbon materials still face some challenges in practical applications, such as: 1. Insufficient conductivity: Silicon itself has poor conductivity, and its performance is not ideal during high-current charge and discharge. Although carbon materials have good conductivity, how to achieve uniform dispersion and effective contact during silicon-carbon composite processes remains a challenge; 2. Volume expansion: Silicon undergoes severe volume changes (approximately 300%) during charge and discharge, resulting in rapid capacity decay. The introduction of carbon materials can alleviate this problem, but how to optimize its structure and content to achieve the best volume expansion suppression effect requires further research; 3. Poor interfacial contact: Poor interfacial contact between silicon and carbon can lead to obstructed electron transport paths, affecting overall performance. How to improve interfacial contact and increase electron transport efficiency is key to improving the performance of silicon-carbon materials.

[0045] The technical solution of this application is as follows:

[0046] In a first aspect, embodiments of this application provide a silicon-carbon material, comprising silicon-carbon particles and a coating layer covering the silicon-carbon particles, wherein the silicon-carbon particles comprise porous carbon and nano-silicon, and at least a portion of the nano-silicon is located in the pores of the porous carbon.

[0047] The silicon-carbon material satisfies: 3≤A / B≤6, and 0.88Ω·cm≤B≤2Ω·cm; where A represents the powder resistivity of the silicon-carbon material at 5 MPa pressure, and B represents the powder resistivity of the silicon-carbon material at 30 MPa pressure.

[0048] It should be noted that in this application, the powder resistivity of silicon-carbon material under pressure of 5 MPa / 30 MPa was obtained by testing the silicon-carbon material using an FT-301B powder resistivity tester. The test was conducted using the four-probe method, with a test pressure of 5 MPa / 30 MPa and a holding time of 20 s.

[0049] In some embodiments, the coating layer is made of an amorphous material; in other words, the coating layer is an amorphous layer. The amorphous material includes, but is not limited to, one or more of amorphous metal oxides and amorphous carbon. The amorphous metal oxides include, but are not limited to, one or more of amorphous TiO2 (amorphous titanium dioxide) and amorphous Al2O3 (amorphous aluminum oxide).

[0050] The powder resistivity of the silicon-carbon material described in this application satisfies the above-mentioned relationship. Therefore, on the one hand, the distribution of nano-silicon in the porous carbon pores of the silicon-carbon material is more uniform, and the porous carbon and nano-silicon have better interfacial contact performance, which can effectively improve the conductivity of the silicon-carbon material. This performance improvement, combined with the small size of the nano-silicon particles and the rigid framework and buffer space of the porous carbon, allows the silicon-carbon material to exhibit minimal volume expansion even after hundreds of battery cycles, effectively improving the battery's capacity retention and lifespan. On the other hand, the coating layer in the silicon-carbon material can more uniformly coat the surface of the silicon-carbon particles, which helps reduce the specific surface area of ​​the silicon-carbon material, thereby improving the battery's initial efficiency. Simultaneously, the amorphous coating layer provides a favorable pathway for electron transport, which is beneficial for improving the rate performance of the silicon-carbon material. Therefore, when the silicon-carbon material of this application is applied to a battery, it can reduce the volume effect during battery cycling, improve the battery's cycle performance, and also enhance the battery's conductivity.

[0051] In some embodiments, the Dv50 particle size of the porous carbon is 4~10μm, for example, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, and any value or range between any two of the above values.

[0052] It should be noted that, in this application, the Dv50 particle size of the porous carbon was obtained by testing the porous carbon with reference to GB / T 19077-2016 and using a Mastersizer 3000+ laser particle size analyzer.

[0053] In some embodiments, the specific surface area of ​​the porous carbon is 1600~3000 m². 2 / g, for example, 1600 m 2 / g、1800 m 2 / g、2000 m 2 / g、2200 m 2 / g、2300 m 2 / g、2500 m 2 / g、2600 m 2 / g、2800 m 2 / g、3000 m 2 / g and the numerical value or range between any two values, etc.

[0054] In some embodiments, the porous carbon has a pore volume of 0.85~1.5 cm³. 3 / g, for example, 0.85 cm 3 / g, 0.9cm 3 / g, 1 cm 3 / g, 1.1 cm 3 / g, 1.2 cm 3 / g, 1.3 cm 3 / g, 1.4 cm 3 / g, 1.5 cm 3 / g and the numerical value or range between any two values, etc.

[0055] In some embodiments, the volume percentage of micropores in the porous carbon is 90% to 100%, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, and any value or range between any two of these values.

[0056] It should be noted that in this application, the volume percentage of micropores in the porous carbon, the pore volume of the porous carbon, and the specific surface area of ​​the porous carbon are measured using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, Inc., in accordance with GB / T 19587-2017.

[0057] In some embodiments, the pore size of the micropores in the porous carbon is 0.7~2 nm, for example, 0.7 nm, 0.8 nm, 1 nm, 1.2 nm, 1.3 nm, 1.5 nm, 1.6 nm, 1.8 nm, 2 nm, and any value or range between any two of the above values.

[0058] In some embodiments, the porous carbon includes, but is not limited to, one or more of resin-based porous carbon, biomass-based porous carbon, petroleum coke-based porous carbon, and pitch-based porous carbon.

[0059] In some embodiments, the average thickness of the coating layer is 2 to 30 nm, for example, 2 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, and any value or range between any two of the stated values.

[0060] It should be noted that, in this application, the average thickness of the coating layer was obtained by testing the silicon-carbon material using a JEOL JEMF200 field emission transmission electron microscope (TEM) and by processing and analyzing the obtained images using data processing software (DigitalMicrograph).

[0061] In some embodiments, the specific surface area of ​​the silicon-carbon material is 1~8 m². 2 / g, for example, 1 m 2 / g、2 m 2 / g、3m 2 / g、4 m 2 / g、5 m 2 / g、6 m 2 / g、7 m 2 / g、8 m 2 / g and the numerical value or range between any two values, etc.

[0062] It should be noted that, in this application, the specific surface area of ​​the silicon-carbon material was measured using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, Inc., in accordance with GB / T 19587-2017.

[0063] In some embodiments, the silicon-carbon material contains 40% to 75% silicon by mass, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, and any value or range between any two of these values.

[0064] It should be noted that, in this application, the mass percentage of silicon element is obtained by testing the mass content of silicon element in the silicon-carbon material in accordance with GB / T 38823-2020.

[0065] Understandably, in some embodiments, some nano-silicon may be located on the outer surface of the porous carbon. It should be noted that the outer surface of the porous carbon refers to the exposed surface of the porous carbon excluding the pore walls.

[0066] Secondly, please refer to Figure 1 This application also provides a method for preparing silicon-carbon materials, comprising the following steps:

[0067] Step S1: Porous carbon is placed in a reaction chamber, and silicon is deposited by chemical vapor deposition using silicon-containing gas as the silicon source to deposit nano-silicon into the pores of the porous carbon, thereby obtaining silicon-carbon particles. The silicon-containing gas is introduced from the bottom of the reaction chamber to suspend the porous carbon in the reaction chamber, and the suspension height of the porous carbon is 1.6 to 2.2 times the stacking height of the porous carbon in the static state.

[0068] Step S2: Deposit an amorphous material on the surface of the silicon-carbon particles to form a coating layer, thereby obtaining the silicon-carbon material.

[0069] It should be noted that, in this application, "suspension height" refers to the vertical distance from the distribution plate (the substrate supporting the porous carbon) at the bottom of the reaction chamber to the upper interface (the highest point of the porous carbon) of the stable suspended region of the porous carbon after the porous carbon has been stably suspended in the reaction chamber. It can be understood that the suspension height can also be called the fluidization height.

[0070] It should be noted that, in this application, "stack height" refers to the vertical distance from the highest point of the upper surface of the stacked area of ​​porous carbon in a static state before the silicon-containing gas is introduced from the bottom of the reaction chamber to the distribution plate (the substrate carrying the porous carbon) at the bottom of the reaction chamber.

[0071] It is understood that in the preparation method, placing porous carbon in the reaction chamber means placing porous carbon powder containing multiple porous carbon particles in the reaction chamber.

[0072] In the silicon-carbon material preparation method described in this application, during silicon deposition, after silicon-containing gas is introduced from the bottom of the reaction chamber, the porous carbon is suspended and moves within the reaction chamber. The suspension height of the porous carbon is 1.6 to 2.2 times its stacked height in the static state. This allows the porous carbon to be in a better and more stable fluidized state, which is beneficial for the prepared silicon-carbon material to meet the requirements of 3 ≤ A / B ≤ 6 and 0.88 Ω·cm ≤ B ≤ 2 Ω·cm. If the suspension height is too low, the silicon-containing gas and porous carbon cannot be in uniform and sufficient contact, and the residence time of the silicon-containing gas is short, which may lead to uneven deposition of nano-silicon and reduced utilization of silicon-containing gas, resulting in a lower specific capacity of the prepared silicon-carbon material. If the suspension height is too high, it may cause the porous carbon to run off, reducing the yield and wasting raw materials.

[0073] In some embodiments, the silicon deposition step S1 includes a first stage, a second stage, and a third stage performed sequentially. In the second stage, the volume concentration of the silicon source gas in the silicon-containing gas is greater than the volume concentration of the silicon source gas in the silicon-containing gas in the first stage and the volume concentration of the silicon source gas in the silicon-containing gas in the third stage.

[0074] In some embodiments, the silicon-containing gas includes, but is not limited to, a silicon source gas and a carrier gas. Further, the silicon source gas includes, but is not limited to, one or more of silane, silane, monochlorosilane, dichlorosilane, and trichlorosilane.

[0075] In some embodiments, the volume concentration of silicon source gas in the silicon-containing gas during the first stage is 3% to 12%, for example, 3%, 5%, 8%, 10%, 12%, and any value or range between these two values. Within this range, it is more conducive to the micropores of porous carbon fully adsorbing the silicon source gas into the pores.

[0076] In some embodiments, the volume concentration of the silicon source gas in the silicon-containing gas during the second stage is greater than 12% and less than or equal to 40%, for example, 13%, 15%, 20%, 25%, 30%, 35%, 40%, and any value or range between these two values. Within this range, it is more conducive to the rapid decomposition of the silicon source gas into nano-silicon after adsorption into the pores.

[0077] In some embodiments, the volume concentration of the silicon source gas in the silicon-containing gas during the third stage is 2% to 12%, for example, 2%, 3%, 5%, 8%, 10%, 12%, and any value or range between these two values. Within this range, it is more conducive to the sufficient deposition of nano-silicon in the pores of porous carbon, and it is more conducive to avoiding excessive deposition of nano-silicon.

[0078] In some embodiments, during the first stage, the suspension height of the porous carbon is 1.6 to 1.9 times the stacking height of the porous carbon in its static state, for example, 1.6 times, 1.65 times, 1.7 times, 1.75 times, 1.8 times, 1.85 times, 1.9 times, and any value or range between any two of these values. Within this range, it is more conducive to the micropores of the porous carbon fully adsorbing the silicon source gas into the pores.

[0079] In some embodiments, during the second stage, the suspension height of the porous carbon is 1.6 to 1.9 times the stacking height of the porous carbon in its static state, for example, 1.6 times, 1.65 times, 1.7 times, 1.75 times, 1.8 times, 1.85 times, 1.9 times, and any value or range between any two of these values. Within this range, it is more conducive to the rapid decomposition of silicon source gas into nano-silicon after adsorption into the pores.

[0080] In some embodiments, during the third stage, the suspension height of the porous carbon is 1.9 to 2.2 times the stacking height of the porous carbon in its static state, for example, 1.9 times, 2.0 times, 2.1 times, 2.2 times, and any value or range between these two values. Within this range, it is more conducive to the sufficient deposition of nano-silicon in the pores of the porous carbon, and it is more conducive to avoiding over-deposition of nano-silicon.

[0081] The method for preparing silicon-carbon materials described in this application utilizes the high microporosity of porous carbon and a specific suspension height of the porous carbon. In the initial stage (first stage), a silicon-containing gas with a relatively low silicon source gas volume concentration is used for silicon deposition, which facilitates the full adsorption of the silicon source gas into the micropores of the porous carbon. In the intermediate stage (second stage), a silicon-containing gas with a higher silicon source gas volume concentration than in the initial stage is used for silicon deposition, which facilitates the rapid decomposition of the adsorbed silicon source gas into nano-silicon. Since the pores of the porous carbon are basically filled with nano-silicon in the intermediate stage, the final stage (third stage) uses a silicon-containing gas with a lower silicon source gas volume concentration than in the intermediate stage for silicon deposition. This ensures sufficient deposition of nano-silicon in the pores of the porous carbon while avoiding over-deposition. Thus, using different silicon source gas concentrations in different deposition stages is more conducive to ensuring that the prepared silicon-carbon material satisfies 3≤A / B≤6 and 0.88Ω·cm≤B≤2Ω·cm.

[0082] In some embodiments, the ratio of the flow rate of the silicon-containing gas to the total weight of the porous carbon ranges from (7 to 16) slm:1g, for example, 7 slm:1g, 8 slm:1g, 9 slm:1g, 10 slm:1g, 11 slm:1g, 12 slm:1g, 13 slm:1g, 14 slm:1g, 15 slm:1g, 16 slm:1g, and any ratio or range between any two of these ratios. Within this range, it is more advantageous to make the suspension height of the porous carbon in the first and second stages 1.6 to 1.9 times the stacking height of the porous carbon in the static state, and to make the suspension height of the porous carbon in the third stage 1.9 to 2.2 times the stacking height of the porous carbon in the static state, thus making the deposition of nano-silicon more uniform.

[0083] In some embodiments, the flow rate of the silicon-containing gas is 35-80 slm, for example, 35 slm, 40 slm, 45 slm, 50 slm, 55 slm, 60 slm, 65 slm, 70 slm, 75 slm, 80 slm, and any value or range between these two values. Within this range, it is more advantageous to ensure that the suspension height of the porous carbon after the silicon-containing gas is introduced from the bottom of the reaction chamber is within a better height range, which is more conducive to more uniform silicon deposition.

[0084] In some embodiments, the reaction chamber is a fluidized bed reaction chamber.

[0085] The porous carbon, the nano-silicon, and the coating layer are described above and will not be repeated here.

[0086] It is understood that the silicon source gas used in the first stage, the second stage, and the third stage may be the same or different. It is also understood that the carrier gas used in the first stage, the second stage, and the third stage may be the same or different.

[0087] In some embodiments, the temperature of the chemical vapor deposition is 400~1000℃, for example, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, and any value or range between any two of these values. The time of the chemical vapor deposition is 0.5~50 h, for example, 0.5 h, 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 50 h, and any value or range between any two of these values. It is understood that the temperature and time of the first stage of chemical vapor deposition, the second stage of chemical vapor deposition, and the third stage of chemical vapor deposition can be the same or different, respectively.

[0088] In some embodiments, the duration of the first stage is 0.0625 to 6.25 h, for example, 0.0625 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.25 h, and any value or range between any two of the stated values.

[0089] In some embodiments, the duration of the second stage is 0.375 to 37.5 h, for example, 0.375 h, 1 h, 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 37.5 h, and any value or range between any two of the stated values.

[0090] In some embodiments, the time of the third stage is 0.0625 to 6.25 h, for example, 0.0625 h, 1 h, 1.5, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.25 h, and any value or range between any two of the above values.

[0091] In some embodiments, step S2, which involves coating the surface of the silicon-carbon particles with an amorphous material, includes replacing the silicon-containing gas in step S1 with a carbon-containing gas and performing carbon deposition by chemical vapor deposition to obtain the coating layer.

[0092] In some embodiments, the flow rate of the carbon-containing gas is 1 to 20 slm, for example, 1 slm, 5 slm, 10 slm, 15 slm, 20 slm, and any value or range between any two of the above values.

[0093] In some embodiments, the carbon deposition temperature is 400–900°C, for example, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, and any value or range between these two values; the carbon deposition time is 20–300 min, for example, 20 min, 50 min, 100 min, 150 min, 200 min, 250 min, 300 min. Within the temperature and time range, it is advantageous to prepare a coating layer with better performance.

[0094] In some embodiments, the carbon-containing gas includes a carbon source gas and a carrier gas.

[0095] In some embodiments, the volume concentration of the carbon source gas in the carbon-containing gas is 5% to 100%, for example, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, and any value or range between any two of these values. It can be understood that a volume concentration of 100% for the carbon source gas indicates that the carbon-containing gas does not include the carrier gas.

[0096] In some embodiments, the carbon source gas in the carbon-containing gas includes, but is not limited to, C1-C3 hydrocarbons and C5-C4 hydrocarbons. 10 One or more of hydrocarbon vapors and aromatic compound vapors with 6 to 60 ring atoms. The C1 to C3 hydrocarbons include, but are not limited to, one or more of methane, ethane, propane, ethylene, propylene, 1,3-butadiene, acetylene, and propyne. The C5 to C6 hydrocarbons... 10 The hydrocarbon vapors include, but are not limited to, one or more of hexane vapor and cyclohexane vapor, and the aromatic compound vapors having a ring atom number of 6 to 60 include, but are not limited to, one or more of benzene vapor and toluene vapor.

[0097] In some other embodiments, step S2, which involves coating the surface of the silicon-carbon particles with an amorphous material, includes: replacing the silicon-containing gas in step S1 with gas I, which includes water vapor; introducing gas II, which includes metal salt precursor vapor, into the reaction chamber; and performing heat treatment to obtain the coating layer.

[0098] In some embodiments, the gas I comprising water vapor and / or the gas II comprising metal salt precursor vapor further comprises a carrier gas.

[0099] In some embodiments, the metal salt precursor in the metal salt precursor vapor includes, but is not limited to, metal halides, and the metal halides include, but are not limited to, TiCl4.

[0100] In some embodiments, the flow rate of gas II, which includes metal salt precursor vapor, is 15 to 45 slm, for example, 15 slm, 20 slm, 25 slm, 30 slm, 35 slm, 40 slm, 45 slm, and any value or range between any two of these values.

[0101] In some embodiments, the flow rate of the gas I, which includes water vapor, is 20 to 50 slm, for example, 20 slm, 30 slm, 40 slm, 50 slm, and any value or range between any two of these values.

[0102] In some embodiments, the temperature of the heat treatment is 80~220℃, for example, 80℃, 100℃, 150℃, 180℃, 200℃, 220℃, and any value or range between any two of the above values; the time of the heat treatment is 50~180min, for example, 50 min, 80 min, 100 min, 130 min, 150 min, 180 min, and any value or range between any two of the above values.

[0103] In some embodiments, step S2, before coating the surface of the silicon-carbon particles with an amorphous material, further includes: introducing a passivation gas comprising a carbon source gas and a carrier gas to passivate the silicon-carbon particles.

[0104] In some embodiments, the carbon source gas in the passivation gas includes, but is not limited to, C1-C3 hydrocarbons and C5-C4 hydrocarbons. 10 One or more of hydrocarbon vapors and aromatic compound vapors with 6 to 60 ring atoms. The C1 to C3 hydrocarbons include, but are not limited to, one or more of methane, ethane, propane, ethylene, propylene, 1,3-butadiene, acetylene, and propyne. The C5 to C6 hydrocarbons... 10 The hydrocarbon vapors include, but are not limited to, one or more of hexane vapor and cyclohexane vapor, and the aromatic compound vapors having a ring atom number of 6 to 60 include, but are not limited to, one or more of benzene vapor and toluene vapor.

[0105] It is understood that the carbon source gas in the passivation gas may be the same as or different from the carbon source gas in the carbon-containing gas.

[0106] In some embodiments, the passivation gas flow rate is 20~70 slm, for example, 20 slm, 30 slm, 40 slm, 50 slm, 60 slm, 70 slm, and any value or range between any two of the stated values.

[0107] In some embodiments, the volume concentration of the carbon source gas in the passivation gas is greater than 0 and less than or equal to 30%, for example, 0.1%, 5%, 10%, 15%, 20%, 25%, 30%, and any value or range between any two of the above values.

[0108] In some embodiments, the passivation temperature for silicon-carbon particles is 380~1000℃, for example, 380℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, and any value or range between any two of these values; the passivation time for silicon-carbon particles is 0.5~10 h, for example, 0.5 h, 1 h, 3 h, 5 h, 8 h, 10 h, and any value or range between any two of these values.

[0109] It should be noted that each carrier gas described in this application appears independently, including but not limited to one or more of argon, nitrogen, or helium.

[0110] The method for preparing silicon-carbon materials described in this application effectively improves the conductivity of silicon-carbon materials by optimizing the suspension height of porous carbon during chemical vapor deposition, matching appropriate silicon deposition amounts and processes, effectively suppressing volume expansion of silicon-carbon materials, and effectively improving the interfacial contact between porous carbon and nano-silicon, thereby effectively enhancing the overall performance of the prepared silicon-carbon materials. Furthermore, the method for preparing silicon-carbon materials described in this application is simple, low-cost, and easy to scale up for production.

[0111] Thirdly, embodiments of this application also provide a negative electrode material, including the silicon-carbon material described above.

[0112] In some embodiments, the negative electrode material further includes a binder and conductive additives.

[0113] The conductive additive is a known conductive additive used in negative electrode materials, such as one or more of conductive carbon black (SP), carbon nanotubes (CNTs) and graphene, including but not limited to.

[0114] The binder is a known binder for negative electrode materials, and may include, but is not limited to, one or more of lithium polyacrylate (PAA-Li), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), hydroxypropyl methylcellulose (HPMC), and polyacrylate (PAA).

[0115] The negative electrode material includes the silicon-carbon material, which has a good ability to suppress volume expansion and good conductivity.

[0116] Fourthly, embodiments of this application also provide a negative electrode, including a negative electrode current collector and an active material layer bonded to at least one surface of the negative electrode current collector, wherein the active material layer includes the silicon-carbon material described above.

[0117] Fifthly, embodiments of this application also provide a battery, including a positive electrode, a separator, an electrolyte, and the negative electrode described above.

[0118] In some embodiments, the battery may be a lithium-ion battery or a sodium-ion battery.

[0119] The negative electrode of the battery described in this application includes the silicon-carbon material mentioned above, and has high specific capacity, initial coulombic efficiency, rate performance and cycle performance.

[0120] The present application will be specifically described below through specific embodiments. These embodiments are only some embodiments of the present application and are not intended to limit the present application. The materials or reagents used in the embodiments and comparative examples of this application are commercially available.

[0121] Silicon-carbon material Example 1

[0122] The method for preparing silicon-carbon material in this embodiment includes:

[0123] Step S1: Provide 5000g of porous carbon, wherein the porous carbon is phenolic resin-based porous carbon. Place the porous carbon in a fluidized bed reaction chamber. After introducing a silicon-containing gas including silane and nitrogen from the bottom of the reaction chamber, perform chemical vapor deposition in the first, second, and third stages sequentially to obtain silicon-carbon particles. The silicon-carbon particles include porous carbon and nano-silicon, wherein the nano-silicon is located in the pores of the porous carbon.

[0124] In the first stage, the volume concentration of silane in the silicon-containing gas is 10%, the flow rate of the silicon-containing gas is 70 slm, and the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.79 times the stacking height of the porous carbon in the static state. Silicon deposition is carried out at 490°C for 1 h.

[0125] In the second stage, the volume concentration of silane in the silicon-containing gas is 14%, the flow rate of the silicon-containing gas is 70 slm, and the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.79 times the stacking height of the porous carbon in the static state. Silicon deposition is carried out at 490°C for 6 h.

[0126] In the third stage, the volume concentration of silane in the silicon-containing gas is 7.7%, the flow rate of the silicon-containing gas is 65 slm, and the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 2.12 times the stacking height of the porous carbon in the static state. Silicon deposition is carried out at 490°C for 2.3 h.

[0127] Step S2: Stop the introduction of silicon-containing gas, and introduce nitrogen into the reaction chamber to replace the residual silicon-containing gas. After sufficient nitrogen replacement, introduce a passivation gas including acetylene and nitrogen at a flow rate of 35 slm and a carbon source gas volume concentration of 14%. Passivate the silicon-carbon particles at 580°C for 3.5 h. Then stop the introduction of passivation gas and introduce a carbon-containing gas including acetylene and nitrogen at a flow rate of 30 slm and a carbon source gas volume concentration of 20%. Deposit at 600°C for 120 min to form a coating layer with an average thickness of 15 nm on the surface of the silicon-carbon particles, thus obtaining silicon-carbon material.

[0128] The porous carbon in this embodiment has a Dv50 particle size of 7 μm and a specific surface area of ​​2000 m². 2 / g, the pore volume of porous carbon is 1.2 cm³. 3 / g, the volume percentage of micropores in porous carbon is 95%.

[0129] This embodiment prepares a silicon-carbon material comprising silicon-carbon particles and a coating layer covering the silicon-carbon particles. The specific surface area of ​​the silicon-carbon material is 1~8 m². 2 / g.

[0130] Silicon-carbon material Example 2

[0131] This embodiment is basically the same as Embodiment 1 of silicon-carbon material, except that in this embodiment, the flow rate of silicon-containing gas in the first, second, and third stages is 60 slm. Correspondingly, in the first stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.73 times the stacking height of the porous carbon in the static state; in the second stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.73 times the stacking height of the porous carbon in the static state; and in the third stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 2.11 times the stacking height of the porous carbon in the static state.

[0132] Silicon-carbon material Example 3

[0133] This embodiment is basically the same as Embodiment 1 of silicon-carbon material, except that in this embodiment, the flow rate of silicon-containing gas in the first, second, and third stages is 35 slm. Correspondingly, in the first stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.63 times the stacking height of the porous carbon in the static state; in the second stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.63 times the stacking height of the porous carbon in the static state; and in the third stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.93 times the stacking height of the porous carbon in the static state.

[0134] Silicon-carbon material Example 4

[0135] This embodiment is basically the same as Embodiment 1 of silicon-carbon material, except that in this embodiment, the flow rate of silicon-containing gas in the first, second, and third stages is 80 slm. Correspondingly, in the first stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.85 times the stacking height of the porous carbon in the static state; in the second stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.85 times the stacking height of the porous carbon in the static state; and in the third stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 2.12 times the stacking height of the porous carbon in the static state.

[0136] Silicon-carbon material Example 5

[0137] This embodiment is basically the same as Embodiment 1 of silicon-carbon material, except that the preparation method of the coating layer in this embodiment is as follows: stop the passivation gas supply, feed 250g of TiCl4 into the upper steam generator, add 30slm of upper carrier gas and 35slm of lower carrier gas, and introduce TiCl4 vapor through the upper carrier gas and water vapor through the lower carrier gas. The reaction is carried out at 180°C for 120min and stabilized at 400°C for 60min to form a coating layer with an average thickness of 15 nm on the surface of the silicon-carbon particles, thereby obtaining the silicon-carbon material.

[0138] Silicon-carbon materials comparative example 1

[0139] This comparative example is basically the same as Example 1 of silicon-carbon material, except that in this comparative example, the flow rate of silicon-containing gas in the first, second, and third stages is 15 slm. Correspondingly, in the first stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.52 times the stacking height of the porous carbon in the static state; in the second stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.52 times the stacking height of the porous carbon in the static state; and in the third stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.75 times the stacking height of the porous carbon in the static state.

[0140] Silicon-carbon materials comparative example 2

[0141] This comparative example is basically the same as Example 1 of silicon-carbon material, except that in this comparative example, the flow rate of silicon-containing gas in the first, second, and third stages is 30 slm. Correspondingly, in the first stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.61 times the stacking height of the porous carbon in the static state; in the second stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.61 times the stacking height of the porous carbon in the static state; and in the third stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.87 times the stacking height of the porous carbon in the static state.

[0142] Silicon-carbon materials comparative example 3

[0143] This comparative example is basically the same as Example 1 of silicon-carbon material, except that in this comparative example, the flow rate of silicon-containing gas in the first, second, and third stages is 100 slm. Correspondingly, in the first stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.97 times the stacking height of the porous carbon in the static state; in the second stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 1.97 times the stacking height of the porous carbon in the static state; and in the third stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 2.26 times the stacking height of the porous carbon in the static state.

[0144] Silicon-carbon materials comparative example 4

[0145] This comparative example is basically the same as Example 1 of silicon-carbon material, except that in this comparative example, the flow rate of silicon-containing gas in the first, second, and third stages is 120 slm. Correspondingly, in the first stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 2.09 times the stacking height of the porous carbon in the static state; in the second stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 2.09 times the stacking height of the porous carbon in the static state; and in the third stage, the suspension height of the porous carbon after the silicon-containing gas is introduced into the reaction chamber is 2.40 times the stacking height of the porous carbon in the static state.

[0146] The silicon-carbon materials of Examples 1-5 and Comparative Examples 1-4 were subjected to powder resistivity tests at 5 MPa and 30 MPa, respectively. The test results are shown in Table 1.

[0147] Powder resistivity testing: The testing instrument is Suzhou Jinglü ST2742B. The sample to be tested is first dried at 105℃ for 2 hours to remove any possible moisture. The equipment is preheated for 30 minutes. The feeder is placed on the lifting platform, the sample mass is entered, and automatic measurement is started. The instrument will execute the preset pressure step curve and simultaneously display the resistivity and conductivity test results and the current test conditions in real time.

[0148] Table 1 - Resistivity test results of silicon-carbon powder:

[0149]

[0150] As shown in Table 1, when the flow rate of silicon-containing gas is 50~70 slm, the resistivity of silicon-carbon material powder satisfies 0.88Ω·cm≤B≤2Ω·cm, and 3≤A / B≤6. This indicates that, under the synergistic effect of the flow rate and the volume concentration of silicon source gas in the silicon-containing gas, the preparation method described in this application allows nano-silicon to be deposited more uniformly in the pores of porous carbon, and is beneficial to make the protection of the subsequently deposited amorphous carbon layer on the surface of silicon-carbon particles more uniform.

[0151] Lithium-ion battery Example 1

[0152] Step 01: Mix the silicon carbide material, SP, CNT, and LA136DL from Example 1 at a mass ratio of 85:9.8:0.2:5 to obtain a mixture;

[0153] Step 02: Add NMP (solvent, N-methylpyrrolidone) to the mixture and stir until homogeneous to obtain electrode slurry. Coat the electrode slurry onto copper foil. Then transfer the copper foil to a vacuum oven and dry at 80°C for 2 hours. Then use a cutting machine to cut the copper foil into round pieces with a diameter of 12 mm to obtain electrode sheets.

[0154] Step 03: Provide an electrode shell, electrolyte, separator, and counter electrode. The electrode shell is made of 2016 steel. The electrolyte includes lithium hexafluorophosphate (electrolyte) and solvents ethylene carbonate / dimethyl carbonate (EC / DEC, volume ratio 1:1). The concentration of the electrolyte is 0.8M. The separator is a glass fiber battery separator. The counter electrode is lithium metal. Assemble the electrode shell, electrolyte, separator, counter electrode, and electrode sheet into a coin cell.

[0155] Examples of lithium-ion batteries 2-5

[0156] The lithium-ion battery examples 2-5 are basically the same as those of lithium-ion battery example 1, except that the silicon-carbon material of the silicon-carbon material example 2-5 is replaced with the silicon-carbon material of the silicon-carbon material example 1.

[0157] Comparative examples of lithium-ion batteries 1-4

[0158] The lithium-ion battery comparative examples 1 to 4 are basically the same as those of lithium-ion battery example 1, except that the silicon-carbon material of the lithium-ion battery comparative examples 1 to 4 is replaced by silicon-carbon material of the silicon-carbon material of the silicon-carbon material of the silicon-carbon material of the lithium-ion battery comparative examples 1 to 4.

[0159] The discharge capacity, initial coulombic efficiency, rate performance, and cycle performance of the lithium-ion batteries in Examples 1-5 and Comparative Examples 1-4 were tested respectively. The test results are shown in Table 2.

[0160] The test method for discharge capacity and initial coulombic efficiency is as follows: under constant temperature of 25±2℃, the battery is placed in the cabinet for 6 hours; left to stand for 5 minutes; discharged at a constant current of 0.1C to 1mV; left to stand for 5 minutes; discharged at a constant current of 0.01C to 1mV; left to stand for 5 minutes; charged at a constant current of 0.05C to 1.5V; the discharge capacity and initial coulombic efficiency are obtained; initial coulombic efficiency = initial charge capacity / initial discharge capacity × 100%.

[0161] The cycle performance test method is as follows: at a constant temperature of 25±2℃, the above batteries are subjected to constant current charge and discharge tests using a Blue Electric charge and discharge tester. The discharge cutoff voltage is 2.75V and the charging cutoff voltage is 4.2V. The charge and discharge tests are all carried out at a current density of 1C. After 100 cycles, the capacity retention rate after 100 cycles is recorded. The capacity retention rate = discharge capacity of the 100th cycle / discharge capacity of the 1st cycle × 100%.

[0162] The rate performance test method is as follows: 1. Stand at a constant temperature of 25±2℃ for 6 hours; 2. Discharge at 0.2C to 5mV; 3. Stand for 30 minutes; 4. Charge at 0.2C using CC-CV to 2V, and maintain constant voltage to 0.05C; 5. Stand for 30 minutes; 6. Cycle 2-5 steps for 3 weeks; 7. Discharge at different rates of 0.05C / 0.1C / 0.33C / 1C / 1.2C to 5mV; 8. Stand for 30 minutes; 9. Charge at the corresponding rates of 0.05C / 0.1C / 0.33C / 1C / 1.2C to 2V; 10. Stand for 30 minutes; 11. End.

[0163] Table 2 - Test results of lithium-ion battery discharge capacity, initial coulombic efficiency, rate performance, and cycle performance:

[0164]

[0165] As shown in Table 2, compared to the lithium-ion batteries in Comparative Examples 1-4, the lithium-ion batteries in Examples 1-5 simultaneously exhibit higher discharge capacity, initial coulombic efficiency, rate performance, and cycle performance. Therefore, the silicon-carbon material prepared using the method described in this application as an electrode material can effectively improve the battery's discharge capacity, initial coulombic efficiency, rate performance, and cycle performance. The reason may be that the silicon-carbon material described in this application satisfies the following conditions: 3 ≤ A / B ≤ 6, and 0.88 Ω·cm ≤ B ≤ 2 Ω·cm. On the one hand, the distribution of nano-silicon in the silicon-carbon material within the pores of the porous carbon is more uniform, and the porous carbon and nano-silicon have good interfacial contact performance, which can effectively improve the conductivity of the silicon-carbon material. Thus, the performance improvement, combined with the small size characteristics of the nano-silicon particles and the rigid framework and buffer space of the porous carbon, allows the silicon-carbon material to still exhibit small volume expansion after hundreds of battery cycles, effectively improving the battery's capacity retention and lifespan. On the other hand, the coating layer in the silicon-carbon material can more uniformly coat the surface of the silicon-carbon particles, which helps to reduce the specific surface area of ​​the silicon-carbon material, thereby improving the battery's initial efficiency. At the same time, the amorphous coating layer can provide a favorable pathway for electron transport, which is beneficial to improving the rate performance of the silicon-carbon material. Therefore, when the silicon-carbon material of this application is applied to a battery, it can reduce the volume effect during battery cycling, improve the battery's cycle performance, and also improve the battery's conductivity.

[0166] The technical solutions provided by the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A silicon-carbon material, characterized in that, The device includes silicon-carbon particles and a coating layer covering the silicon-carbon particles. The silicon-carbon particles comprise porous carbon and nano-silicon, with at least a portion of the nano-silicon located within the pores of the porous carbon. The coating layer is made of an amorphous material, which includes one or more of amorphous metal oxides and amorphous carbon. The silicon-carbon material satisfies: 3≤A / B≤6, and 0.88Ω·cm≤B≤2Ω·cm; A represents the powder resistivity of the silicon-carbon material at 5 MPa pressure, and B represents the powder resistivity of the silicon-carbon material at 30 MPa pressure.

2. The silicon-carbon material as described in claim 1, characterized in that, The amorphous metal oxide includes one or more of amorphous titanium dioxide and amorphous aluminum oxide.

3. The silicon-carbon material as described in claim 1, characterized in that, It also includes at least one of the following features (1) to (7): (1) The Dv50 particle size of the porous carbon is 4~10μm; (2) The specific surface area of ​​the porous carbon is 1600~3000 m². 2 / g; (3) The porous carbon has a pore volume of 0.85~1.5 cm³. 3 / g; (4) The volume percentage of micropores in the porous carbon is 90%~100%; (5) The average thickness of the coating layer is 2~30 nm; (6) The specific surface area of ​​the silicon-carbon material is 1~8 m². 2 / g; (7) The mass percentage of silicon in the silicon-carbon material is 40% to 75%.

4. A method for preparing a silicon-carbon material as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1, porous carbon is placed in a reaction chamber, and silicon-containing gas is used as the silicon source to deposit silicon nanoparticles into the pores of the porous carbon through chemical vapor deposition, thereby obtaining silicon-carbon particles. The silicon-containing gas is introduced from the bottom of the reaction chamber to suspend the porous carbon in the reaction chamber, and the suspension height of the porous carbon is 1.6 to 2.2 times the stacking height of the porous carbon in the static state. S2, Amorphous material is coated on the surface of the silicon-carbon particles to obtain silicon-carbon material.

5. The preparation method according to claim 4, characterized in that, The temperature for chemical vapor deposition in step S1 is 400~1000℃, and the time is 0.5~50 h; The flow rate of the silicon-containing gas is 35~80 slm; The silicon-containing gas includes a silicon source gas and a carrier gas, wherein the silicon source gas includes one or more of silane, disilane, monochlorotrihydrosilane, dichlorodihydrosilane, and trichloromonohydrosilane.

6. The preparation method according to claim 4 or 5, characterized in that, The silicon deposition step S1 includes a first stage, a second stage and a third stage performed sequentially, wherein the volume concentration of silicon source gas in the silicon-containing gas in the second stage is greater than the volume concentration of silicon source gas in the silicon-containing gas in the first stage and the volume concentration of silicon source gas in the silicon-containing gas in the third stage. In the second stage, the volume concentration of silicon source gas in the silicon-containing gas is greater than 12% and less than or equal to 40%; in the first stage, the volume concentration of silicon source gas in the silicon-containing gas is 3% to 12%; and in the third stage, the volume concentration of silicon source gas in the silicon-containing gas is 3% to 12%.

7. The preparation method according to claim 4, characterized in that, Step S2, which involves coating the surface of the silicon-carbon particles with an amorphous material, includes replacing the silicon-containing gas in step S1 with a carbon-containing gas and performing carbon deposition by chemical vapor deposition to obtain the coating layer. The flow rate of the carbon-containing gas is 1~20 slm; The carbon deposition temperature is 400~900℃, and the time is 20~300 min; The carbon-containing gas includes a carbon source gas and a carrier gas, wherein the carbon source gas includes C1-C3 hydrocarbons and C5-C4 hydrocarbons. 10 One or more of hydrocarbon vapors and aromatic compound vapors having 6 to 60 ring atoms, wherein the C1 to C3 hydrocarbons include one or more of methane, ethane, propane, ethylene, propylene, 1,3-butadiene, acetylene, and propyne, and the C5 to C6 hydrocarbons are... 10 The hydrocarbon vapors include one or more of hexane vapor and cyclohexane vapor, and the aromatic compound vapors having a ring atom number of 6 to 60 include one or more of benzene vapor and toluene vapor; The volume concentration of the carbon source gas in the carbon-containing gas is 5-100%.

8. The preparation method according to claim 4, characterized in that, The step of coating the surface of the silicon-carbon particles with amorphous material in step S2 includes: replacing the silicon-containing gas in step S1 with gas I including water vapor, introducing gas II including metal salt precursor vapor into the reaction chamber, and performing heat treatment to obtain the coating layer. The gas I containing water vapor and / or the gas II containing metal salt precursor vapor also contain a carrier gas; The flow rate of gas I, which includes water vapor, is 20-50 slm; The flow rate of gas II, which includes metal salt precursor vapor, is 15~45 slm. The heat treatment temperature is 80~220℃, and the time is 50~180 min; The metal salt precursor in the metal salt precursor vapor includes metal halides; the metal halide includes TiCl4.

9. A negative electrode, characterized in that, It includes silicon-carbon materials as described in any one of claims 1 to 3, or silicon-carbon materials prepared by the preparation method described in any one of claims 4 to 8.

10. A battery, characterized in that, Includes the negative electrode as described in claim 9.

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