Composite anode material, method for preparing the same, and its application

Abstract

The composite negative electrode material and its preparation method and application belong to the field of battery technology. A composite negative electrode material comprising a core containing a porous carbon material and Si particles, and a coating layer located on at least a part of the surface of the core, the Si particles being distributed on the surface and / or in the pores of the porous carbon material, the composite negative electrode material comprising micropores and mesopores, the ratio of the pore volume of the micropores to the pore volume of the mesopores being 2:98 to 50:50, the oil absorption value of the composite negative electrode material being smaller than that of the composite negative electrode material after the Si particles have been removed, and the difference value when the oil absorption value of the composite negative electrode material after the Si particles have been removed is taken as 100% is ≧10%. In the composite negative electrode material, the porous properties of the porous carbon provide a space for the volume expansion of Si, and the use of porous carbon having a certain strength as a skeleton further ensures the stability of the entire composite negative electrode material, and improves the cycle performance of the composite negative electrode material.

Description

Technical Field

[0001] This application claims the priority of a Chinese patent application filed with the China National Intellectual Property Administration on September 22, 2022, with the application number "2022111553065" and the application title "Composite Anode Material and Its Preparation Method and Application", and incorporates the entire content thereof into this application by reference.

[0002] This application relates to the field of battery technology, and particularly to a composite anode material and its preparation method and application.

Background Art

[0003] Lithium-ion batteries have advantages such as high energy density, long cycle life, low environmental pollution, and no memory effect, so they are widely applied in electric vehicles and consumer electronics products. Conventional anode carbon materials have been widely restricted in use due to their low theoretical specific capacity (372 mAh / g). In order to increase the energy density of lithium-ion batteries, high-capacity anode materials have begun to be explored. Silicon-based anode materials have become an increasingly hot research topic because their theoretical specific capacity is 4200 mAh / g. However, during the process of alloying with lithium, silicon-based anode materials have a large volume expansion. As the cycle progresses, attenuation mechanisms such as powdering, loss due to contact with conductive agents and current collectors, and formation of an unstable solid electrolyte interface (SEI) occur, resulting in poor cycle performance of silicon-based anode materials.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Based on this, there is a need to provide a composite anode material and its preparation method and application that can improve the cycle performance of the battery.

Means for Solving the Problems

[0005] To achieve the above object, this application adopts the following means.

[0006] One aspect of the present application provides a composite negative electrode material including a core containing a porous carbon material and Si (silicon) particles, and a coating layer located at least partially on the surface of the core, wherein the Si (silicon) particles are distributed on the surface and / or in the pores of the porous carbon material. The composite negative electrode material includes micropores and mesopores, and the ratio of the pore volume of the micropores to the pore volume of the mesopores is from 2:98 to 50:50. The oil absorption value of the composite negative electrode material is smaller than the oil absorption value of the composite negative electrode material after removing the Si particles, and the difference value is ≧ 10% when the oil absorption value of the composite negative electrode material after removing the Si particles is taken as 100%.

[0007] In one embodiment, in the FIB-TEM test of the composite negative electrode material, the scanning line concentration of EDS satisfies the relationship of 0.90 ≦ (A1 - C1) / (C1 - B1) ≦ 1.10 and |((A1 - B1) / 2C1)2 - 1| ≦ 0.01 (where A1 is the highest value along the scanning line concentration of Si, B1 is the lowest value along the scanning line concentration of Si, and C1 is the median value along the scanning line concentration of Si).

[0008] In one embodiment, in the FIB-TEM test of the composite negative electrode material, the scanning line concentration of EDS satisfies the relationship of 0.90 ≦ (A2 - C2) / (C2 - B2) ≦ 1.10 and 2 |((A2 - B2) / 2C2)

[0009] In one embodiment, 29 in the Si-NMR spectrum of the composite negative electrode material, there is a Si-C resonance peak between -10 ppm and 20 ppm, and its intensity is D1, there is a Si resonance peak between -90 ppm and -110 ppm, and its intensity is D2, and D2 / D1 ≧ 10.

[0010] In one embodiment, the composite negative electrode material contains amorphous Si-C bonds.

[0011] In one embodiment, the composite anode material exhibits a SiC crystal peak in its X-ray diffraction pattern.

[0012] In one embodiment, the porosity of the composite anode material is 10% to 20%.

[0013] In one embodiment, when the composite anode material is lithium-ionized to 50% of its theoretical lithium-ion capacity, the porosity A1 of the electrode sheet containing the composite anode material becomes A1 ≥ 30%.

[0014] In one embodiment, when the composite anode material is lithium-ionized to 70% of its theoretical lithium-ion capacity, the porosity A2 of the electrode sheet containing the composite anode material becomes 20% ≤ A2 < 30%.

[0015] In one embodiment, when the composite anode material is lithium-ionized to 80% of its theoretical lithium-ion capacity, the porosity A3 of the electrode sheet containing the composite anode material becomes 10% ≤ A3 ≥ 20%.

[0016] In one embodiment, the ratio of the pore volume of the micropores to the pore volume of the mesopores ranges from 5:95 to 23:77.

[0017] In one embodiment, the average pore diameter of the closed pores in the composite negative electrode material after complete insertion of lithium is 0 to 10 nm.

[0018] In one embodiment, the mass percentage of Si in the composite anode material is 10% to 90%, preferably 20% to 80%.

[0019] In one embodiment, the specific surface area of ​​the composite negative electrode material is 0.5 m². 2 / g~50m 2 It is / g.

[0020] In one embodiment, the true density of the composite anode material is 1.80 g / cm³. 3 ~2.90g / cm 3 That is the case.

[0021] In one embodiment, the average particle size D of the composite negative electrode material 50 The particle size is 1 μm to 25 μm, preferably 2 μm to 15 μm, and more preferably 3 μm to 10 μm.

[0022] In one embodiment, the average thickness of the coating layer is 1 nm to 100 nm.

[0023] In one embodiment, the coating layer includes a carbon coating layer.

[0024] In one embodiment, the average pore size of the porous carbon is R1, and the range of R1 is 0.2 nm to 1000 nm, preferably 2 nm to 500 nm.

[0025] In one embodiment, the porous carbon The pore size in 2nm~100nm hole The pore volume of this component accounts for 50% or more of the total pore volume.

[0026] In one embodiment, the ratio of the pore volume of the micropores to the pore volume of the mesopores in the porous carbon is between 95:5 and 50:50.

[0027] In one embodiment, the average distance between pores in porous carbon is H1, and the range of H1 is 1 nm to 500 nm, preferably 1 nm to 100 nm.

[0028] In one embodiment, the average distance between pores in the porous carbon, H1, is equal to the average pore diameter, R1, of the porous carbon.

[0029] In one embodiment, the particle size of the porous carbon is 1 μm to 50 μm, and preferably 2 μm to 20 μm.

[0030] In one embodiment, the Si particles in the composite negative electrode material include amorphous silicon and have a particle size in the range of 1 to 110 nm.

[0031] In one embodiment, the average particle size D of the Si particles in the composite negative electrode material 50 The wavelength is 1 nm to 200 nm, preferably 2 nm to 100 nm, and more preferably 5 nm to 50 nm.

[0032] In one embodiment, the particle size of the Si crystal grains in the composite anode material is 2 nm to 10 nm, and the standard deviation σ ≤ 0.2.

[0033] Another aspect of the present invention provides a method for preparing the composite anode material described above. The above preparation method comprises the following steps. A step of depositing Si particles onto the surface and / or pores of porous carbon by a chemical vapor impregnation process (CVI) to obtain a precursor; and The step of coating the precursor in a protective atmosphere to form a coating layer on the surface of the precursor and obtain a composite negative electrode material; The composite negative electrode material comprises micropores and mesopores, and the ratio of the pore volume of the micropores to the pore volume of the mesopores is between 2:98 and 50:50; The oil absorption value of the composite anode material is smaller than the oil absorption value of the composite anode material after the removal of the Si particles, and the difference is greater than or equal to 10% when the oil absorption value of the composite anode material after the removal of the Si particles is set to 100%.

[0034] In one embodiment, the step of depositing Si particles on the surface and / or pores of the porous carbon using the chemical vapor impregnation process includes the steps of supplying porous carbon, injecting a reaction gas, and thermally decomposing the reaction gas to deposit Si particles on the surface and / or pores of the porous carbon.

[0035] In one embodiment, the reaction gas includes a gaseous Si source, hydrogen gas, and an inert gas.

[0036] In one embodiment, the temperature of the thermal decomposition is 300°C to 500°C;

[0037] In one embodiment, the time for the thermal decomposition is 0.2h to 20h.

[0038] In one embodiment, the flow rate of the reaction gas is 50 L / min to 200 L / min.

[0039] In one embodiment, the reaction gas comprises a gaseous Si source, and the raw material for the gaseous Si source includes at least one of monosilane, disilane, monochlorosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane.

[0040] In one embodiment, the reaction gas comprises an inert gas, the inert gas comprising at least one of nitrogen gas, helium gas, neon gas, and argon gas.

[0041] In one embodiment, the reaction gas comprises an inert gas, and the flow rate of the inert gas is 0.2 L / min to 50 L / min.

[0042] In one embodiment, the flow rate ratio of the gaseous Si source to the inert gas is 1:1 to 20.

[0043] In one embodiment, the method for producing the porous carbon includes the steps of thermally decomposing an organic carbon source and chemically activating an organic carbon source.

[0044] In one embodiment, the coating treatment includes the step of mixing a precursor with a carbon source and controlling the thermal decomposition of the carbon source in a protective atmosphere to form a carbon coating layer on the surface of the precursor.

[0045] In one embodiment, the method for forming the carbon coating layer includes at least one of a gas-phase carbon coating treatment, a solid-phase carbon coating treatment, and a liquid-phase carbon coating treatment.

[0046] In one embodiment, the inert gas includes at least one of nitrogen gas, helium gas, neon gas, argon gas, krypton gas, and xenon gas.

[0047] In one embodiment, the gas flow rate of the protective atmosphere is 20 mL / min to 1000 mL / min.

[0048] In one embodiment, the carbon source includes a gaseous carbon source.

[0049] In one embodiment, the carbon source includes a gas-phase carbon source, and the gas-phase carbon source includes a gas-phase hydrocarbon carbon source.

[0050] In one embodiment, the carbon source includes a gaseous carbon source, which includes at least one of methane, acetylene, ethylene, ethane, propane, propylene, propyne, acetone, and benzene.

[0051] In one embodiment, the carbon source includes a solid-phase carbon source.

[0052] In one embodiment, the carbon source includes a solid-phase carbon source, and the solid-phase carbon source includes a solid-phase organic carbon source.

[0053] In one embodiment, the carbon source includes a solid-phase carbon source, which includes at least one of citric acid, glucose, pitch, phenol resin, and furfural resin.

[0054] In one embodiment, the carbon source includes a liquid-phase carbon source.

[0055] In one embodiment, the carbon source includes a liquid-phase carbon source, and the liquid-phase carbon source includes a liquid-phase organic carbon source.

[0056] In one embodiment, the carbon source includes a liquid-phase carbon source, which includes at least one of n-hexane, toluene, benzene, xylene, methanol, ethanol, propanol, butanol, pentanol, acetone, butanone, 2-pentanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and pentyl acetate.

[0057] In one embodiment, the temperature of the thermal decomposition is 600°C to 1200°C.

[0058] In one embodiment, the heating rate of the thermal decomposition is 0.1°C / min to 50°C / min.

[0059] In one embodiment, the total pressure of the reaction system due to the reaction gas is 100 kPa to 2000 kPa.

[0060] In one embodiment, the total pressure of the reaction system due to the reaction gas is 100 kPa to 2000 kPa, and the partial pressure of the gaseous Si source is 1 kPa to 100 kPa.

[0061] In one embodiment, the total pressure of the reaction system due to the reaction gas is 100 kPa to 2000 kPa, and the partial pressure of the hydrogen gas is 50 kPa to 1000 kPa.

[0062] In one embodiment, the total pressure of the reaction system due to the reaction gas is 100 kPa to 2000 kPa, and the partial pressure of the inert gas is 1 kPa to 1000 kPa.

[0063] Another aspect of the present invention provides a negative electrode sheet comprising the composite negative electrode material described above, or a composite negative electrode material prepared by the preparation method described above.

[0064] Another aspect of the present invention further provides a battery comprising the above-mentioned negative electrode sheet.

[0065] Yet another aspect of this application provides an electrical device comprising the above-mentioned battery. [Effects of the Invention]

[0066] The above-described composite anode material and its preparation method have at least the following advantages compared to the prior art.

[0067] (1) The above composite anode material retains the advantage that Si has a large specific capacity as an anode, while utilizing the porous properties of porous carbon to provide space for the volume expansion of Si, thereby further reducing the volume expansion of the material. By having a coating layer of a certain strength on the core surface, the Si particles exposed on the core surface can also be coated, reducing direct contact between the Si particles and the electrolyte. When the negative electrode material comes into contact with the electrolyte, a thin SEI film is formed, further reducing the consumption of the electrolyte and resulting in a better cycle retention rate. By rationally controlling the volume ratio of micropores to mesopores in the composite anode material, the oil absorption value of the composite anode material after filling with Si particles can be made smaller than the oil absorption value of the composite anode material after removing the Si particles. This indicates that some of the pores in the composite anode material are effectively filled, reducing side reactions between the composite anode material and the electrolyte, mitigating the volume expansion of Si during charge-discharge cycles, and improving the material's cycle performance by maintaining overall material stability and preventing structural collapse during the cycle.

[0068] (2) In composite anode materials manufactured by CVI (Chemical Vapor Infiltration) technology, the Si particles are mainly in an amorphous state, which effectively avoids the problems of crystalline S expanding anisotropically during the lithium insertion process, leading to collapse of the pore structure, rapid specific capacity decay, and poor cycle performance once lithium is embedded. Si particles can be well dispersed in the vacancies and framework of porous carbon, intercalated at the atomic level within the carbon framework, and the coating layer covering the porous carbon framework is complete and strong, improving the compatibility issues between nano-Si and the electrolyte, which is advantageous for the formation of a stable SEI film. [Brief explanation of the drawing]

[0069] [Figure 1] This is a schematic diagram of the structure of a composite negative electrode material according to one embodiment of the present invention, where 1-coating layer, 2-porous carbon material, 3-Si particles, 4-mesopores, and 5-micropores are located. [Figure 2]This is a schematic diagram showing the relationship between the average distance between pores in porous carbon and the average pore diameter of porous carbon according to one embodiment of the present invention. [Figure 3] This is a flowchart of a method for preparing a composite anode material according to another embodiment of the present invention. [Modes for carrying out the invention]

[0070] To further clarify the purpose, technical proposal, and advantages of this application, the application will be described in more detail below, incorporating examples. The specific embodiments described herein are for illustrative purposes only and do not limit the present application.

[0071] All technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs, unless otherwise defined. The terms used in the specification of this application are for the purpose of describing specific embodiments and are not intended to limit the application. As used herein, the terms "and / or" include any and all combinations of one or more related items.

[0072] In this application, technical features described in an open-ended manner include both closed-ended inventions consisting of enumerated features and open-ended inventions containing enumerated features.

[0073] Referring to Figure 1, in one embodiment of the present application, a composite negative electrode material is provided comprising a core containing a porous carbon material 2 and Si particles 3, and a coating layer 1 located on at least a portion of the surface of the core, wherein the Si particles 3 are distributed on the surface and / or within the pores of the porous carbon material 2.

[0074] The composite anode material comprises 5 micropores and 4 mesopores, with a ratio of the pore volume of micropores 5 to the pore volume of mesopores 4 being (2-50):(50-98).

[0075] The oil absorption value of the above composite anode material is smaller than the oil absorption value of the composite anode material after the removal of Si particles, and the difference is greater than or equal to 10% when the oil absorption value of the composite anode material after the removal of Si particles is set to 100%.

[0076] In this embodiment, the negative electrode material comprises a core and a coating layer located on its surface, wherein the Si particles in the core are located on the surface and / or within the pores of the porous carbon material, the porous carbon material supporting the Si particles as a framework, and its porous characteristics further reduce the volume expansion of the material by providing space for the Si to expand during the desorption and insertion processes of lithium. By having a coating layer of a certain strength on the core surface so that the core is mechanically constrained, the volume expansion stress of the core can be relieved, and the Si particles exposed on the core surface can be coated, reducing direct contact between the Si particles and the electrolyte without affecting lithium ion transport, and creating a thin SEI film when the anode material and electrolyte come into contact, which is advantageous for reducing electrolyte consumption and improving cycle retention, as well as improving the capacity of the material, and the structural stability of the entire composite anode material is further improved by the presence of the coating layer. Furthermore, before bonding with Si particles, porous carbon's micropores are primarily fine pores. After the preparation of the composite anode material is complete, most of the micropores are filled with Si particles, so the remaining pores in the porous carbon are closed mesopores distributed mainly within the unfilled particles. By controlling the volume ratio of micropores to mesopores in the negative electrode material, the oil absorption value of the composite negative electrode material after filling with Si particles can be made smaller than the oil absorption value of the composite negative electrode material after removing the Si particles. This indicates that some of the pores in the composite negative electrode material are effectively filled, and side reactions between the composite negative electrode material and the electrolyte can be reduced. Furthermore, it is possible to adjust the packing density of Si particles, improve the specific capacity of the material, and mitigate the volume expansion of Si. In addition, the synergistic effect of the overall structure improves the material's cycle performance, electrochemical performance, etc., in order to maintain the overall stability of the material and prevent its structure from collapsing during the cycle.

[0077] Conventional techniques have sometimes used methods to recombine porous carbon materials with Si to improve the cycle characteristics of Si-based composite anode materials. However, the manufactured Si-based composite anode materials have not been able to achieve a balance in performance such as initial discharge ratio capacity, initial Coulomb efficiency, capacity retention rate after cycling, and expansion rate of electrode sheet thickness after cycling. For example, conventional Si-based composite anode materials have a battery capacity retention rate of about 85% after 50 cycles, but their initial discharge ratio capacity and initial Coulomb efficiency are low, and the expansion rate of electrode sheet thickness after cycling is high, and their structure is prone to collapse during cycling. Therefore, Si-based composite anode materials still need overall performance improvement. In response, the applicant has conducted creative improvements and experiments, verifying that the above problem can be solved by controlling the ratio of the pore volume of micropores to the pore volume of mesopores in the composite anode material.

[0078] This embodiment improves the initial discharge ratio, initial Coulomb efficiency, and capacity retention rate after cycling of the battery, while also reducing the thickness expansion rate of the electrode sheet after cycling, by controlling the ratio of the pore volume of micropores to the pore volume of mesopores in the composite negative electrode material to (2-50):(50-98). Furthermore, if the proportion of pore volume of micropores in the composite anode material is too large, there will not be enough pores to withstand the volume expansion during charging and discharging. Also, in reality, due to diffusion limitations and other factors, 100% of the pores in porous carbon may not be filled with Si. If the proportion of pore volume of mesopores in the composite anode material is too large, there will be too little Si to fill them, resulting in a decrease in specific capacity. On the other hand, because many voids still exist, the overall structural stability of the composite anode material is poor, making it prone to collapse during the cycle. Although the pores on the surface of the porous carbon material are filled with silicon to form micropores, most mesopores are located inside the porous carbon material or remain closed, making efficient filling difficult. Therefore, in the actual filling process, mainly micropores are filled, resulting in a higher proportion of mesopores in the composite anode material after deposition.

[0079] In one specific example, the ratio of the pore volume of micropores to the pore volume of mesopores in a composite negative electrode material may be, for example, 2:98, 5:95, 10:90, 20:80, 24:76, 28:72, 30:70, 38:62, 40:60, 45:55, or 50:50, or any other value within this range, and is not limited thereto. The ratio of the pore volume of micropores to the pore volume of mesopores in the composite anode material is preferably (5-23):(77-95).

[0080] In one specific example, the oil absorption value of the composite anode material is smaller than the oil absorption value of the composite anode material after the Si particles have been removed, and the difference is ≥ 10%.

[0081] It is understood that Si particles distributed on the surface and / or in the pores of a porous carbon material reduce the pores of the porous carbon in the composite anode material, thereby lowering the oil absorption value of the composite anode material. The oil absorption value of the composite anode material is smaller than the oil absorption value of the composite anode material after Si particle removal, and the difference can be, for example, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, or 40% (assuming the oil absorption value of the composite anode material after Si particle removal is 100%). Naturally, the difference between the oil absorption value of the composite anode material and the oil absorption value of the composite anode material after Si particle removal should not reach 100%, nor should it be too high. This is because porous carbon materials need to retain a certain number of voids to mitigate the expansion of Si volume when lithium is inserted. If the difference value is less than 10%, it indicates that the composite anode material has too many pores, resulting in poor strength and structural stability, making the material more prone to structural collapse during cycling and reducing its cycling performance.

[0082] In a specific example, in the FIB-TEM (Focused Ion Beam-Transmission Electron Microscope) test of the composite negative electrode material, the scanning line concentration of EDS (Energy Dispersive Spectroscopy) satisfies the relationship of 0.90 ≦ (A1 - C1) / (C1 - B1) ≦ 1.10 and |((A1 - B1) / 2C1)^2 - 1| ≦ 0.01. Here, A1 is the highest value along the scanning line concentration of Si, B1 is the lowest value along the scanning line concentration of Si, and C1 is the median value along the scanning line concentration of Si. (A1 - C1) / (C1 - B1) can be any value between 0.90 and 1.10. For example, it can be understood that it can be 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.05, 1.07, 1.08 or 1.10, etc. |((A1 - B1) / 2C1) 2 - 1| can be 0.0065, 0.0070, 0.0079, 0.008, 0.0088, 0.0089, 0.009, 0.0093, 0.0098 or 0.01, etc.

[0083] In a specific example, in the FIB-TEM test of the composite negative electrode material, the scanning line concentration of EDS satisfies 0.90 ≦ (A2 - C2) / (C2 - B2) ≦ 1.10, and |((A2 - B2) / 2C2) 2 - 1| ≦ 0.01 satisfies this relationship. Here, A2 is the highest value along the C scanning line concentration, B2 is the lowest value along the C scanning line concentration, and C2 is the median value along the C scanning line concentration. (A2 - C2) / (C2 - B2) can be any value between 0.90 and 1.10. For example, it can be 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, l.02, 1.03, 1.05, 1.08 or 1.10, etc. |((A2 - B2) / 2C2)2 -1| can be 0.0065, 0.0067, 0.0070, 0.0074, 0.0079, 0.008, 0.0088, 0.0089, 0.009, 0.0093, 0.0098, or 0.01, etc.

[0084] The FIB-TEM test measures the distribution of C and Si elements in the cross-section of composite anode material particles. Since the composite anode material contains both Si and C elements, the EDS scan lines consist of at least two lines: one for Si and one for C. When both the Si scan line concentration and the C scan line concentration in EDS satisfy the above relationship, nanosilicon is dispersed in the porous carbon material, and the porous carbon material can efficiently provide expansion space for the surrounding Si particles, thereby ensuring the structural stability of the composite anode material during charging and discharging.

[0085] In one specific example, composite negative electrode material 29 In the Si-NMR spectrum, there is a Si-C resonance peak between -10 ppm and 20 ppm with intensity D1, and a Si resonance peak between -90 ppm and -110 ppm with intensity D2, and D2 / D1 ≥ 10.

[0086] Furthermore, the composite negative electrode material in this embodiment contains trace amounts of SiC. Since SiC is an inactive material, as the SiC content increases, the specific capacity decreases. When D2 / D1 ≥ 10, it explains that there is a certain bonding force between Si and C in the composite anode material, and that an atomic-level bonding force exists between Si and C. At the same time, since only trace amounts of crystalline SiC are present, the composite anode material of this invention can maintain structural stability during the charge-discharge process and exhibits excellent cycle performance. To make it clear, D2 / D1 may be, but is not limited to, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, or 50, etc. A larger D2 / D1 value indicates a lower inert SiC content.

[0087] In one specific example, the composite negative electrode material contains amorphous Si-C bonds, which are formed by bonding between Si atoms and C atoms.

[0088] In this embodiment, the SiC in the composite anode material is basically in an amorphous state.

[0089] In one specific example, the composite anode material contains trace amounts of SiC crystal peaks in its X-ray diffraction pattern.

[0090] Furthermore, a relatively high crystalline SiC content leads to a decrease in the specific capacity of the composite anode material. Therefore, in the composite anode material of this embodiment, most of the SiC is in an amorphous state, with only a small amount of SiC remaining in a crystalline state.

[0091] In one specific example, the porosity of the composite anode material is 10% to 20%. When the porosity is less than 10%, the composite negative electrode material does not have enough pores to withstand the volume expansion during charging and discharging. Due to factors such as diffusion restriction, Si particles precipitate on the surface and / or within the pores of the porous carbon, making it impossible to fill the pores 100%. If the porosity of the composite anode material is higher than 20%, the specific capacity will be low because there is too little filling Si. On the other hand, the presence of a large number of voids in the composite anode material will result in poor overall stability of the anode material, making it prone to collapse during the cycle. The porosity of the composite anode material may be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%. The porosity of the composite anode material may be any other value between 10% and 20%.

[0092] As a specific example, when the composite anode material is lithium-ionized to 50% of its theoretical lithium-ion capacity, the porosity A1 of the electrode sheet containing the composite anode material becomes A1 ≥ 30%. Furthermore, when the composite anode material is lithium-ionized to 70% of its theoretical lithium-ion capacity, the porosity A2 of the electrode sheet containing the composite anode material becomes 20% ≤ A2 < 30%. Furthermore, when the composite anode material is lithium-ionized to 80% of its theoretical lithium-ion capacity, the porosity A3 of the electrode sheet containing the composite anode material becomes 10% ≤ A3 < 20. The term "electrode sheet" refers to an electrode sheet that uses a composite negative electrode material as the active material and consists of one or more types of conductive agents, binders, and solvents commonly used in this art, such as the electrode sheet manufactured in the embodiment of this application. If the electrode sheet does not satisfy the above-mentioned porosity requirements, it indicates that the composite anode material does not have sufficient pore space to mitigate the volume expansion of Si when lithium is lithified. When lithium is inserted in this manner, the expansion of Si brings about large expansion stresses on the surrounding porous carbon, making the structure of the composite anode material unstable and degrading its electrochemical performance. Furthermore, conventional electrode sheets also contain graphite material, and if the porosity is outside the above range, the Si expands in volume and presses against the surrounding graphite sheet structure layer, making the entire electrode sheet unstable.

[0093] In one specific example, the average pore size of the closed pores in the composite anode material after the lithium was completely embedded was 0-10 nm. Furthermore, "completely inserting lithium" means that the composite negative electrode material becomes saturated with lithium ions. If the pore size of closed pores in porous carbon after complete lithium insertion is larger than 10 nm, the large pore size in that region results in insufficient mechanical strength of the composite anode material, making it prone to stress weaknesses. This can lead to structural failure during the charge-discharge process, allowing a large amount of electrolyte to seep in and negatively impacting the electrochemical performance of the composite anode material. Alternatively, the pore diameter of the closed pores in the porous carbon after lithium has been completely embedded may be 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, or 10 nm, or any other value between 0 and 10 nm.

[0094] In one specific example, the mass percentage of Si in the composite anode material is 10% to 90%, preferably 20% to 80%. It can be understood that the mass percentage of Si content in composite anode materials is 10%, 12%, 14%, 16%, 18%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80%, or 90%. The mass percentage of Si in the composite anode material may be any other value between 10% and 90%.

[0095] In one specific example, the specific surface area of ​​the composite anode material is 0.5 m². 2 / g~50m 2 It is / g. The specific surface area of ​​the composite anode material is 0.5 m². 2 / g, 1.0m 2 / g, 5.0m 2 / g, 10m 2 / g, 13m 2 / g, 16m 2 / g, 20m 2 / g, 23m 2 / g, 26m 2 / g, 30m 2 / g, 33m 2 / g, 36m 2 / g, 40m 2 / g, 43m 2 / g, 46m 2 / g or 50mg 2 / g is also acceptable. The specific surface area of ​​the composite anode material is 0.5 m². 2 / g~50m 2 Other values ​​between / g are also acceptable.

[0096] In one specific example, the true density of the composite anode material is 1.80 g / cm³. 3 ~2.90g / cm 3 That is the case. The true density of the composite anode material is 1.80 g / cm³. 3 1.90 g / cm³ 3 2.00 g / cm³ 3 2.10 g / cm³ 3 2.20 g / cm³ 3 2.30 g / cm³ 3 2.40 g / cm³ 3 2.50 g / cm³ 3 2.60 g / cm³ 3 2.70 g / cm³ 3 2.80 g / cm³ 3 Or 2.90 g / cm³ 3 That's fine. The true density of the composite anode material is 1.80 g / cm³. 3 ~2.90g / cm 3 Any other value in between is also acceptable.

[0097] In one specific example, the average particle size D of the composite anode material 50 The particle size is 1 μm to 25 μm, preferably 2 μm to 15 μm, and more preferably 3 μm to 10 μm. Furthermore, if the average particle size of the composite negative electrode material is 1 μm or larger, the decrease in electrode tap density can be minimized to avoid affecting the processability as a negative electrode for lithium-ion batteries. This avoids the problem of low energy density due to excessively low tap density in the electrode sheet, and allows for obtaining an appropriate volumetric capacity. Furthermore, if the average particle size of the composite negative electrode material is 25m or less, the electrode formation slurry can be applied to a uniform thickness in an appropriate manner. Average particle size D of composite anode material 50 The thickness may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 14 μm, 15 μm, 17 μm, 19 μm, 21 μm, 23 μm, or 25 μm. Average particle size D of composite anode material 50 This may be any other value between 1 μm and 25 μm.

[0098] In one specific example, the average thickness of the coating layer is 1 nm to 100 nm. It is understood that the average thickness of the coating layer is 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, or 100 nm. The average thickness of the coating layer may be any other value between 1 nm and 100 nm.

[0099] As a specific example, the coating layer includes a carbon coating layer. The carbon coating layer can mechanically restrain the core as a shale, allowing lithium ions to pass through, but it also hinders the interaction between the electrolyte and the internal active material. This allows the carbon in the carbon coating layer to bond with the amorphous silicon in the porous carbon, forming amorphous Si-C bonds, thus enhancing the interfacial bonding force.

[0100] In one specific example, the average pore size of the porous carbon is R1, and the range of R1 is 0.2 nm to 1000 nm, preferably 2 nm to 500 nm. The pores in porous carbon may be open or closed. The pores inside the porous carbon include closed pores that contribute to the volume increase when lithium is inserted. This allows for further improvement of the stability of the silicon-carbon interface without destroying the structure of the porous carbon or significantly increasing the overall size of the composite anode material. The pores in porous carbon provide space to buffer the volume expansion of Si when lithium is inserted, while the absence of openings connecting to the outside environment makes it difficult for the electrolyte to penetrate, thus avoiding the problem of the SEI layer continuously thickening. The average pore sizes of porous carbon are 0.2 nm, 2 nm, 4 nm, 6 nm, 8 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, or 1000 nm. The average pore size of porous carbon may be any other value between 0.2 nm and 1000 nm.

[0101] One specific example is porous carbon The pore size in 2nm~100nm hole The ratio of pore volume is 50% or more.

[0102] In one specific example, the ratio of the pore volume of micropores to the pore volume of mesopores in porous carbon is (50-95):(5-50).

[0103] Furthermore, if the pores of porous carbon are larger than 100 nm, although Si atoms can penetrate the pores, the Si and C in the porous carbon cannot be uniformly mixed at the nanoscale. In this case, the uneven distribution of Si and C leads to a deterioration of the electrochemical performance. When porous carbon is in good contact with a gaseous silicon source, micropores are effectively filled into the porous carbon material to efficiently allow the gaseous silicon source to penetrate into the interior of the porous carbon material. The pores remaining in the composite anode material are mainly distributed inside the particles and are closed mesopores. When a gaseous silicon source forms a shell on the surface of porous carbon particles, a large number of micropores are not efficiently filled inside the porous carbon, and the pores remaining in the composite anode material are mainly micropores. The ratio of the pore volume of micropores to the pore volume of mesopores in porous carbon may be, for example, 95:5, 90:10, or 80:20, or it may be 70:30, 60:40, 50:50, etc.

[0104] In one specific example, the average distance between pores in porous carbon is H1, and the range of H1 is 1 nm to 500 nm, preferably 1 nm to 100 nm. The average distance between pores in porous carbon refers to the average of the shortest distances between the edges of adjacent pores in porous carbon. The average distance between pores in porous carbon may be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 40 nm, 60 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, or 500 nm, or any other value between 1 nm and 500 nm.

[0105] As a concrete example, Figure 2 shows the relationship between the average spacing H1 between pores in porous carbon and the average pore diameter R1 of porous carbon, where the average spacing H1 ≤ average pore diameter R1, and H1 is the distance from the outer edge of one pore to the outer edge of an adjacent pore. Furthermore, it was explained that when the average distance between pores in porous carbon H1 ≤ the average pore diameter R1 of the porous carbon, the pore distribution in the porous carbon, i.e., the pores in the porous carbon, is relatively well-developed.

[0106] In one specific example, the particle size of the porous carbon is 1 μm to 50 μm, and preferably 2 μm to 20 μm. It is understood that the particle size of porous carbon is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 17 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm. The particle size of the porous carbon may be any other value between 1 μm and 50 μm.

[0107] In a specific example, the Si particles in the composite anode material include amorphous silicon and have a particle size in the range of 1 to 110 nm.

[0108] Furthermore, the silicon in the core of the composite anode material is mainly amorphous. This amorphous silicon acts as the anode, accepting lithium ions that have migrated from the positive electrode and facilitating energy storage. If the Si in the core of the composite anode material is amorphous, it can bond with the C in the coating layer to form amorphous Si-C bonds, thereby increasing the interfacial bonding force. The particle sizes of the Si particles are 1 nm, 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, or 110 nm. The particle size of the Si particles may be any other value between 1 nm and 110 nm.

[0109] In one specific example, the average particle size of the Si particles in the composite anode material is 1 nm to 200 nm, preferably 2 nm to 100 nm, and more preferably 5 nm to 50 nm. Furthermore, if the average particle size of the Si particles is 1 nm or larger, it prevents the Si particles from detaching through the pores in the core. Furthermore, if the average particle size of the Si particles is 200 nm or less, the pores and small Si particles contained in the core can effectively suppress pulverization due to volume expansion of Si during the charge-discharge process, thereby improving the material's cycle performance. The distribution morphology of Si particles in porous carbon is determined by the CVI process and mainly depends on the flow rates, partial pressures, and ratios of the Si source gas, hydrogen gas, and inert gas. The average particle size of Si particles in the composite anode material may be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, or 200 nm. The average particle size of Si particles in the composite anode material may be any other value between 1 nm and 200 nm.

[0110] In one specific example, the particle size of the Si crystal grains in the composite anode material is 2 nm to 10 nm, and the standard deviation σ ≤ 0.2. The particle size of the Si crystal grains in the composite anode material may be 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, or 10 nm. The particle size of the Si crystal grains in the composite anode material may be any other value between 2 nm and 10 nm.

[0111] Conventional Si / C composite anode materials can be synthesized by heating and vaporizing Si-based materials, followed by mixing and precipitation. However, this method involves high-temperature processes exceeding 1600°C, which increases process costs, and also results in a product that is mostly crystalline silicon. The expansion and contraction of crystalline silicon during the charge-discharge process are closely related to the orientation of its crystal grains. Therefore, expansion anisotropy is likely to occur during the cycle process, which is disadvantageous in maintaining structural integrity.

[0112] Conventional Si / C composite anode materials can also be manufactured by calcining hydrogen silsesquioxane (abbreviated as HSQ) and a carbon precursor. The HSQ used in this manufacturing method is expensive, and although this method is limited to the initial precursor of HSQ, it can only synthesize silicon oxides in which the silicon-oxygen ratio cannot be controlled, and SiO x The specific capacity and initial Coulomb efficiency of the material were far lower than those of pure Si material.

[0113] Conventional techniques include preparing porous Si / C composite anode materials by spraying a precursor solution containing a Si-based material source, a carbon source, and a catalyst material, thermally decomposing it, and removing by-products to form pores. While this combines the advantages of a porous structure with Si-based materials, the catalyst used is an alkaline solution, and even if the catalyst is subsequently removed with water, acid, or an alkaline solution, it cannot be completely removed. While it can lead to serious environmental pollution, residual alkaline solutions can cause high pH levels, posing a risk of gas generation during subsequent slurry preparation and cycle charging / discharging.

[0114] The conventional technique also includes mixing activated carbon powder, nano-Si slurry, and coal tar asphalt, then performing coking and low-temperature carbonization treatment, followed by pulverization and classification to prepare Si / C composite anode material. This method does not allow for control over the type or size of pores between the carbon material and nano-Si particles after filling with Si particles, nor does it allow for the formation of Si-C bonds at the interface, resulting in insufficient bond strength between Si and C.

[0115] In response to the above problem, with reference to Figure 3, one embodiment of this application provides a method for preparing a composite anode material, which includes the following steps.

[0116] Step S100 involves depositing Si particles onto the surface and / or pores of porous carbon by a chemical vapor impregnation (CVI) process to obtain a precursor.

[0117] Step S200 involves coating the precursor in a protective atmosphere to form a coating layer on the surface of the precursor, thereby obtaining a composite anode material.

[0118] Here, the composite negative electrode material comprises micropores and mesopores, and the ratio of the pore volume of the micropores to the pore volume of the mesopores is (2-50):(50-98).

[0119] The oil absorption value of the composite anode material described above is smaller than the oil absorption value of the composite anode material after the Si particles have been removed, and the difference is greater than or equal to 10% when the oil absorption value of the composite anode material after the Si particles have been removed is set to 100%. In this embodiment, the Si particles manufactured by CVI technology are primarily in an amorphous state, which effectively avoids the problems of crystalline S expanding anisotropically during the lithium insertion process, leading to structural collapse of the pores, rapid specific capacity decay, and poor cycle performance once lithium is embedded. Furthermore, by embedding Si atoms at the atomic level within the carbon framework and further coating the porous carbon material framework with a coating layer that is complete and strong, the compatibility issues between nano-Si and the electrolyte are improved, which is advantageous for the formation of a stable SEI film. During the lithium insertion process, the amorphous Si in this embodiment expands isotropically, mitigating volume changes and effectively eliminating the problem of amorphous Si particles pulverizing and falling off the electrode. This embodiment controls the ratio of micropore volume to mesopore volume in the composite anode material to (2-50):(50-98), for example, 2:98, 5:95, 10:90, 20:80, 24:76, 28:72, 30:70, 34:66, 38:62, 40:60, 45:55, or 50:50. This is because if the proportion of micropore volume is relatively large, the composite anode material does not have enough pores to withstand the volume expansion during the charge-discharge process. If the proportion of mesopore volume is relatively large, the specific capacity becomes low because there is too little Si to fill the pores. On the other hand, since the composite anode material still has many pores, the overall structural stability is poor and it is prone to collapse during the cycle.

[0120] Step S100 involves depositing Si particles onto the surface and / or pores of porous carbon by a chemical vapor impregnation (CVI) process to obtain a precursor.

[0121] As a specific example, the step of depositing Si particles on the surface and / or pores of porous carbon by a chemical vapor impregnation process includes supplying porous carbon, injecting a reaction gas, and thermally decomposing the reaction gas to deposit Si particles on the surface and / or pores of the porous carbon.

[0122] Alternatively, the chemical vapor infiltration (CVI) process is carried out in a CVI furnace, which comprises a gas preheating zone for preheating the reaction gas and a reactor for preparing the precursor.

[0123] Specifically, the temperature of thermal decomposition is between 300°C and 500°C. The thermal decomposition temperature may be 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 390°C, 400°C, 430°C, 460°C, 490°C, or 500°C. The thermal decomposition temperature may be any other value between 300°C and 500°C.

[0124] Specifically, the thermal decomposition time is between 0.2 hours and 20 hours. The time for thermal decomposition may be 0.2h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, or 20h. The time for thermal decomposition may be any other value between 0.2h and 20h.

[0125] Specifically, the flow rate of the reaction gas is 50 L / min to 200 L / min. The reaction gas flow rate may be 50 L / min, 60 L / min, 70 L / min, 80 L / min, 90 L / min, 100 L / min, 110 L / min, 120 L / min, 130 L / min, 140 L / min, 150 L / min, 160 L / min, 170 L / min, 180 L / min, 190 L / min, or 200 L / min. The flow rate of the reaction gas may be any other value between 50 L / min and 200 L / min.

[0126] As a specific example, a method for preparing porous carbon includes a step of thermally decomposing an organic carbon source and a step of activating the organic carbon source, and the activation treatment may be at least one of a physical activation treatment and / or a chemical activation treatment.

[0127] Chemical activation treatment involves activating carbon materials using an activating pore-forming agent to create pores. The main micropores are generated during the activation process described above, but if the activation is excessive, the pore walls of the micropores collapse, forming mesopores and macropores in the carbon material. As a result, many mesopores are distributed inside the carbon material particles and have a high probability of becoming closed pores.

[0128] As a specific example, the reaction gas includes a gaseous Si source, hydrogen gas, and an inert gas.

[0129] In one specific example, the total pressure of the reaction system due to the reaction gas is between 100 kPa and 2000 kPa. Specifically, the total pressure of the reaction system may be 100kPa, 120kPa, 150kPa, 180kPa, 200kPa, 300kPa, 400kPa, 500kPa, 600kPa, 700kPa, 800kPa, 1000kPa, 1200kPa, 1400kPa, 1600kPa, 1800kPa, or 2000kPa, or any other value between 100kPa and 2000kPa.

[0130] Specifically, the partial pressure of the gaseous Si source is between 1 kPa and 100 kPa. For example, the partial pressure of the gaseous Si source may be 1kPa, 2kPa, 5kPa, 7kPa, 10kPa, 15kPa, 20kPa, 30kPa, 40kPa, 50kPa, 60kPa, 70kPa, 80kPa, 90kPa, or 100kPa, or any other value between 1kPa and 100kPa.

[0131] Specifically, the partial pressure of hydrogen gas is between 50 kPa and 1000 kPa. For example, the partial pressure of hydrogen gas may be 50kPa, 55kPa, 60kPa, 65kPa, 70kPa, 80kPa, 90kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa, 600kPa, 700kPa, 800kPa, 900kPa, or 1000kPa, or any other value between 50kPa and 1000kPa.

[0132] Specifically, the partial pressure of inert gases is between 1 kPa and 1000 kPa. For example, the partial pressure of the inert gas may be 1kPa, 2kPa, 5kPa, 10kPa, 20kPa, 25kPa, 30kPa, 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa, 600kPa, 700kPa, 800kPa, 900kPa, or 1000kPa, or any other value between 1kPa and 1000kPa.

[0133] Specifically, for example, if the total pressure of the reaction system is 100 kPa, the partial pressure of the gaseous Si source can be set to 1 kPa, the partial pressure of the hydrogen gas to 50 kPa, and the partial pressure of the inert gas to 49 kPa. Alternatively, if the total pressure of the reaction system is 500 kPa, the partial pressure of the gaseous Si source can be set to 50 kPa, the partial pressure of the hydrogen gas to 250 kPa, and the partial pressure of the inert gas to 200 kPa. Alternatively, if the total pressure of the reaction system is 1500 kPa, the partial pressure of the gaseous Si source can be set to 100 kPa, the partial pressure of the hydrogen gas to 1000 kPa, and the partial pressure of the inert gas to 400 kPa. Alternatively, if the total pressure of the reaction system is 2000 kPa, the partial pressure of the gaseous Si source can be set to 100 kPa, the partial pressure of the hydrogen gas to 900 kPa, and the partial pressure of the inert gas to 1000 kPa.

[0134] As a specific example, the raw materials for the gaseous Si source include at least one of the following: monosilane, disilane, monochlorosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane. Furthermore, if the raw material for the gaseous Si source is monosilane, disilane, monochlorosilane, or dichlorosilane, it is gaseous at room temperature. If the raw material for the gaseous Si source is trichlorosilane or tetrachlorosilane, it is liquid at room temperature, and during the thermal decomposition process, the liquid Si source vaporizes to become a gaseous Si source.

[0135] As a specific example, the inert gas includes at least one of nitrogen gas, helium gas, neon gas, and argon gas. Specifically, the flow rate of the inert gas is between 0.2 L / min and 50 L / min. The flow rate of the inert gas is, for example, 0.2 L / min, 2 L / min, 5 L / min, 10 L / min, 15 L / min, 20 L / min, 25 L / min, 30 L / min, 35 L / min, 40 L / min, 45 L / min, or 50 L / min. The flow rate of the inert gas may be any other value between 0.2 L / min and 50 L / min.

[0136] Specifically, the flow rate ratio between the gaseous Si source and the inert gas is 1:1 to 20. For example, the flow rate ratio between the gaseous Si source and the inert gas is 1:1, 1:3, 1:6, 1:9, 1:12, 1:15, 1:18, or 1:20. It is understood that the flow rate ratio between the gaseous Si source and the inert gas may be other values ​​from 1:1 to 20. Furthermore, it is believed that the manufactured composite anode material is sufficient to ensure a uniform distribution of Si within the porous carbon if the flow rate ratio of the gaseous Si source to the inert gas is 1:1. Furthermore, if the flow rate ratio of the gaseous Si source to the inert gas is 1:20 or higher, the gaseous Si source can be gently dispersed in the CVI reaction gas, and the deposition rate does not slow down too much.

[0137] Step S200 involves coating the precursor in a protective atmosphere to form a coating layer on the surface of the precursor and obtain a composite anode material.

[0138] Here, the composite negative electrode material comprises micropores and mesopores, and the ratio of the pore volume of the micropores to the pore volume of the mesopores is (2-50):(50-98).

[0139] The oil absorption value of the above composite anode material is smaller than the oil absorption value of the composite anode material after the Si particles have been removed, and the difference is greater than or equal to 10% when the oil absorption value of the composite anode material after the Si particles have been removed is set to 100%.

[0140] In one specific example, the coating process includes the steps of mixing a precursor with a carbon source and controlling the thermal decomposition of the carbon source in a protective atmosphere to form a carbon coating layer on the surface of the precursor.

[0141] Specifically, the temperature of thermal decomposition is between 600°C and 1200°C. The temperatures for thermal decomposition are 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C. The thermal decomposition temperature may be any other value between 600°C and 1200°C.

[0142] Specifically, the heating rate for thermal decomposition is between 0.1°C / min and 50°C / min. The thermal decomposition heating rates are 0.1°C / min, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 15°C / min, 20°C / min, 25°C / min, 30°C / min, 35°C / min, 40°C / min, 45°C / min, or 50°C / min. The thermal decomposition heating rate may be any other value between 0.1°C / min and 50°C / min.

[0143] Specifically, the protective atmosphere includes at least one of nitrogen, argon, helium, neon, krypton, or xenon.

[0144] Specifically, the gas flow rate of the protective atmosphere is 20 mL / min to 1000 mL / min. For example, the gas flow rate of the protective atmosphere may be 20 mL / min, 50 mL / min, 100 mL / min, 150 mL / min, 200 mL / min, 250 mL / min, 300 mL / min, 350 mL / min, 400 mL / min, 450 mL / min, 500 mL / min, 550 mL / min, 600 mL / min, 650 mL / min, 700 mL / min, 750 mL / min, 800 mL / min, 850 mL / min, 900 mL / min, 950 mL / min, or 1000 mL / min. The gas flow rate of the protective atmosphere may be any other value between 20 mL / min and 1000 mL / min.

[0145] Furthermore, the method for forming the carbon coating layer includes at least one of gas-phase carbon coating, solid-phase carbon coating, and liquid-phase carbon coating.

[0146] As a specific example, carbon sources include gaseous carbon sources. Furthermore, the carbon source includes gaseous hydrocarbon carbon sources. Furthermore, the carbon source includes at least one of methane, acetylene, ethylene, ethane, propane, propylene, propyne, acetone, and benzene. During the coating process, a gaseous carbon source is poured in under a protective atmosphere to mix the gaseous carbon source with the solid composite. When a carbon source undergoes thermal decomposition, amorphous carbon deposits on the surface of the precursor, forming a carbon coating. If the carbon source includes a gaseous carbon source, the coating process is carried out in a rotary kiln or a box kiln.

[0147] In another specific example, the carbon source includes a solid-phase carbon source. Furthermore, the carbon source includes a solid-phase organic carbon source. Furthermore, the carbon source includes at least one of the following: citric acid, glucose, pitch, phenolic resin, and furfural resin. If the carbon source includes a solid-phase carbon source, the coating process is carried out in a rotary kiln, box kiln, roller hearth kiln, tunnel kiln, or pusher kiln. When the carbon source includes a solid-phase carbon source, the following mixing methods can be used for the precursor and carbon source: VC mixing, fusion, ball milling, suction filtration, reflux heating, three-dimensional mixing, fluidized bed mixing, etc.

[0148] In another specific example, the carbon source includes a liquid-phase carbon source. Furthermore, the carbon source includes a liquid-phase organic carbon source. Furthermore, the carbon source includes at least one of the following: n-hexane, toluene, benzene, xylene, methanol, ethanol, propanol, butanol, pentanol, acetone, butanone, 2-pentanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and pentyl acetate. When using a liquid-phase carbon source, the flow rate of the liquid-phase carbon source is 1 mL / min to 200 mL / min. The flow rate of the liquid-phase carbon source is, for example, 1 mL / min, 10 mL / min, 20 mL / min, 30 mL / min, 40 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, 100 mL / min, 150 mL / min, or 200 mL / min. The flow rate of the liquid-phase carbon source may be any other value between 1 mL / min and 200 mL / min. If the carbon source includes a liquid-phase carbon source, the coating process is carried out in a rotary kiln, box kiln, roller hearth kiln, tunnel kiln, or pusher kiln. When the carbon source includes a liquid-phase carbon source, the following mixing methods can be used for the precursor and carbon source: VC mixing, fusion, ball milling, suction filtration, reflux heating, three-dimensional mixing, fluidized bed mixing, etc.

[0149] According to yet another embodiment of this application, a negative electrode sheet made of the above-mentioned composite negative electrode material is provided.

[0150] According to yet another embodiment of this application, a battery comprising the above-described negative electrode sheet is provided.

[0151] According to yet another embodiment of this application, an electrical device comprising the above-mentioned battery is provided.

[0152] The parameters in this application can be measured using the following apparatus and method.

[0153] (1) True density test: Using Archimedes' principle of gas substitution (density = mass / volume) and Boyle's law (PV=nRT) under constant conditions with an inert gas with a small molecular diameter, the true volume of the test material was accurately measured and its true density was obtained. The instrument used was the Anton Paar PentaPyc 5200e true density meter.

[0154] (2) Oil absorption test: A fixed mass of powder sample was placed in the mixing chamber, oil (linseed oil or DBP-butyl phthalate) was dropped onto the sample at a constant rate, and the sample was simultaneously stirred with a rotating blade at a constant rotation speed. As the amount of oil absorbed by the sample increases, the mixture changes from a free-flowing state to a semi-plastic agglomerate, and in this process, the viscosity of the mixture gradually increases, and a peak appears. The amount of oil dispensed at 70% of the maximum torque obtained at the endpoint was measured from the torque curve due to changes in viscosity characteristics, and the oil absorption value (mL / 100g) of the sample was calculated. The equipment used was the S-500 oil absorption value tester from ASAHISOUKEN Japan.

[0155] (3) Silicon particle removal method: Weigh approximately 0.5 g of composite negative electrode material sample and place it in a platinum crucible. Add a mixed acid consisting of 35 mL of HNO and 10 mL of HF to stabilize the reaction between the mixed acid and the sample. Then, place the platinum crucible on a 350°C hot plate and heat until the hydrofluoric acid volatilizes and no more white smoke is produced, thereby removing the acid. After the crucible has cooled, another 6 mL of HCl is added, and the mixture is heated until the residue is completely dissolved. The remaining material is the composite anode material after the silicon particles have been removed.

[0156] (4) Measure D50 using a laser particle size analyzer. The volume-based distribution is such that the diameter corresponding to a cumulative frequency of 10% is D 10 Therefore, the diameter corresponding to a cumulative frequency of 50% is D 50 Therefore, the diameter corresponding to a cumulative frequency of 90% is D 90 That is the case.

[0157] (5) The specific surface area is measured using a TriStar3000 specific surface area and pore size analyzer manufactured by Micromeritics, Inc., USA.

[0158] (6) Micropore and mesopore analysis was performed using Micromeritics ASAP2460. At the temperature of liquid nitrogen, the equilibrium adsorption amount of nitrogen gas on an object's surface correlates with its pore size and other characteristics. By applying this to multiple models, the pore size can be calculated according to the rules governing the change in adsorption amount due to relative pressure during the adsorption process. The software-based report calculates the pore size distribution, total pore volume, and pore volume within a certain range using density functional theory (DFT).

[0159] (7) XRD peaks were measured using the X'pertPro X-ray diffractometer manufactured by PANalytical, and then the Si peaks in the XRD were fitted using the Jade6.5 software to obtain the grain size of the Si crystal grains.

[0160] (8) 29 SiMAS NMR Standard Silicon Structural Chemistry Shift 29 SiMASNMR ( 29 The (SiMagicAngleSpinningNuclearMagneticResonanceSpectroscopy) is a Bruker AV300 type nuclear magnetic resonance spectrometer. For quantitative analysis, monopulse testing is used during the test process, rather than cross-polarization. The pulse width is 4.5 ut, θ is 54.7°, the relaxation delay (i.e., the time delay between two samples) is 5 seconds, and the rotation speed is 7 kHz. TMS was used as the chemical shift reference material for measurement.

[0161] (9) The FIB-TEM sample was prepared using the "lift-out method": Using a focused ion-electron dual-beam electron microscope (FEIHeliosG4CX), a layer of Pt was first deposited on the surface sample preparation area (first by electron beam deposition, then by ion beam deposition) to serve as protection. Subsequently, one side of the Pt deposit was etched in one cross-section, followed by the other side being etched in the same way. The sample stage was then rotated 45°, the bottom was cut, and it was returned to its original position. The film was thinned to the required thickness of approximately 0.2 μm, both ends of the film were cut, and the sample was removed using a special pick-up system (a micro-robot arm controlled a glass rod with a tip of 0.2 μm to 0.5 μm to approach the sample. An electrostatic effect was generated between the sample and the tip of the glass rod, causing the sample to be attracted to the tip of the glass rod, and the sample was placed on a collodion-coated copper mesh to obtain a TEM sample). For TEM analysis, we used a Thermo Fisher SpectraS / TEM scanning transmission electron microscope.

[0162] (10) EDS line scan: The electron beam was used to perform line scan analysis on elemental concentrations by selecting a straight line trajectory along the surface of the sample. On a cross-sectional image of a sample, a straight line is arbitrarily drawn from one end of the sample surface to the other. An electron beam is scanned along this line to collect X-rays characteristic of Si and C elements. The changes in their counts are displayed on a fluorescent screen as a graph, with the height of the graph reflecting the changes in scan line density for multiple corresponding elements. Here, the highest value I (Intensities) along the Si scan line density is max A1 is the value, and I (Intensities) is the minimum value along the Si scan line density. min B1 is the value, and I (Intensities) is the median value along the Si scan line density. med The value is C1, and the highest value I (Intensities) is along the scan line density. max The minimum value I (Intensities) is aligned with the scan line density of A2 and C. min The values ​​are B2 and C, and the median I (Intensities) along the scan line density. med The value is defined as C2. The EDS spectrometer used was a Thermo Fisher NORAN System 7, a seventh-generation X-ray spectrometer.

[0163] (11) Measurement of nanoparticle size using SEM (Scanning Electron Microscope): A cross-section of the composite anode material is prepared and an SEM image of the cross-section is saved. I ran the NanoMeasurer software, opened the SEM image of the statistically required cross-section, set the scale, dragged the mouse to display particles on the SEM map, and obtained their particle size. Five 100m x 75m regions were randomly selected, and 20 nano-Si particles were randomly selected from each region. Particle size statistics were then performed to obtain the particle size distribution range. The obtained granularity values ​​were fitted to a normal distribution using the software Origin, and the mean and standard deviation were calculated, resulting in a standard deviation of σ ≤ 0.2.

[0164] (12) Measurement of Si content by gravimetric method: The sample is fired in a box atmosphere furnace under an O2 atmosphere, causing the Si in the sample to react with SiO, the C to burn and be emitted as CO2, and the Si content is weighed.

[0165] The present application will be described in detail below, along with specific examples and comparative examples.

[0166] (Example 1) The material selection was based on the porous carbon D used in this example. 50 The pore size was 7 μm, the average pore diameter was 1.9 nm, and the average distance between pores was 1.6 nm.

[0167] 1000 g of porous carbon was placed in a CVI reactor, and silane at 200°C was injected into the CVI reactor at a rate of 0.5 L / min. Simultaneously, hydrogen gas at 250°C and high-purity nitrogen gas at 250°C were injected at rates of 50 L / min and 4.0 L / min, respectively, to thoroughly mix the gases and obtain a gas mixture. The gas mixture was heated to approximately 400°C, and the turbulent gas mixture remained in the CVI reactor for 8 hours, with a total flow rate of 54.5 L / min. After that, it was allowed to cool to room temperature to obtain the precursor.

[0168] Using methane as the carbon source, the precursor was placed in a rotary kiln for gas-phase coating, methane gas was passed through it, and nitrogen gas was used as a protective atmosphere to carbonize it at 900°C, thereby obtaining a composite anode material having an amorphous carbon coating layer.

[0169] (Example 2) The material selection was based on the porous carbon D used in this example. 50 The pore size was 12 μm, the average pore diameter was 300 nm, and the average distance between pores was 90 nm.

[0170] 1000 g of porous carbon was placed in a CVI reactor, silane at 200°C was injected into the CVI reactor at a rate of 1.0 L / min, and at the same time, hydrogen gas at 250°C and high-purity argon gas at 250°C were injected at rates of 79 L / min and 20 L / min, respectively, to thoroughly mix the gases and obtain a gas mixture. The gas mixture was heated to approximately 400°C, and the turbulent gas mixture was left in the CVI reactor for 10 hours, with a total flow rate of 100 L / min. After that, it was allowed to cool to room temperature to obtain the precursor.

[0171] Using low-temperature liquid-phase asphalt as the carbon source, the precursor and low-temperature liquid-phase asphalt were thoroughly mixed and placed in a rotary kiln for gas-phase coating. Methane gas was passed through, and nitrogen gas was used as a protective atmosphere to carbonize the mixture at 800°C. After that, the mixture was placed in a furnace and heat-treated at 980°C for 24 hours to obtain a composite anode material having an amorphous carbon coating layer.

[0172] (Example 3) The material selection was based on the porous carbon D used in this example. 50 The pore size was 20 μm, the average pore diameter was 120 nm, and the average distance between pores was 70 nm.

[0173] 1000g of porous carbon was placed in a CVI reactor, and silane at 200°C was injected into the CVI reactor at a rate of 0.2 L / min. Simultaneously, hydrogen gas at 250°C and high-purity helium gas at 250°C were injected at rates of 150 L / min and 2.0 L / min, respectively, to thoroughly mix the gases and obtain a gas mixture. The gas mixture was heated to approximately 400°C, and the turbulent gas mixture remained in the CVI reactor for 4 hours, resulting in a total flow rate of 152.2 L / min. After that, it was allowed to cool to room temperature to obtain the precursor.

[0174] Using glucose as a carbon source, the precursor and glucose were thoroughly mixed and placed in a roller hearth kiln. Using argon gas as a protective atmosphere, the mixture was carbonized at 980°C, and then placed in a furnace and heat-treated at 1000°C for 18 hours to obtain a composite anode material.

[0175] (Example 4) This is basically the same as Example 1, the only difference being that the silane rate is 0.4 L / min and the residence time is 6 h.

[0176] (Example 5) The procedure is basically the same as in Example 1, the only difference being that when preparing the precursor, 1000g of porous carbon was placed in a CVI reactor, silane at 900°C was injected into the CVI reactor at a rate of 0.5 L / min, and at the same time, hydrogen gas at 950°C and high-purity nitrogen gas at 950°C were injected at rates of 50 L / min and 4.0 L / min, respectively, to thoroughly mix the gases and obtain a gas mixture. The gas mixture was then heated to approximately 1000°C, and the turbulent gas mixture remained in the CVI reactor for 8 hours, with a total flow rate of 54.5 L / min. After that, it was allowed to cool to room temperature to obtain the precursor.

[0177] (Example 6) The procedure is basically the same as in Example 1, the difference being that silane at 200°C is injected into the CVI reactor at a rate of 1 L / min, and at the same time, hydrogen gas at 250°C and high-purity nitrogen gas at 250°C are injected at rates of 50 L / min and 0.5 L / min, respectively, to thoroughly mix the gases and obtain a gas mixture. The gas mixture is then heated to approximately 400°C, and the turbulent gas mixture is left in the CVI reactor for 8 hours, resulting in a total flow rate of 51.5 L / min for the gas mixture.

[0178] (Comparative Example 1) The procedure was basically the same as in Example 1, the only difference being that when preparing the precursor, the rate at which hydrogen gas was injected into the CVI reactor was 5.0 L / min, the rate at which high-purity nitrogen gas was injected was 4.0 L / min, and the total flow rate of the gas mixture was 9.5 L / min, and the gas mixture passed through the CVI reactor was not in a turbulent state.

[0179] (Comparative Example 2) The procedure is basically the same as in Example 1, the only difference being that when preparing the precursor, 1000g of porous carbon is placed in a CVI reactor, silane at 200°C is injected into the CVI reactor at a rate of 2 L / min, and at the same time, hydrogen gas at 250°C and high-purity nitrogen gas at 250°C are injected at rates of 120 L / min and 100 L / min, respectively, to thoroughly mix the gases and obtain a gas mixture. The gas mixture is then heated to about 400°C, and the turbulent gas mixture is left in the CVI reactor for 30 hours, resulting in a total flow rate of 222 L / min of the gas mixture, after which it is allowed to cool to room temperature.

[0180] (Comparative Example 3) The procedure is basically the same as in Example 1, the difference being that when preparing the precursor, Si with a D50 of 3 μm to 10 μm and anhydrous ethanol were uniformly mixed in a mass ratio of 1:10, a Si slurry with a particle size D50 of 100 nm was obtained by ball milling, the Si slurry and porous carbon were uniformly mixed in a mass ratio of 10:1, and then spray granulation was performed to obtain the precursor.

[0181] (Comparative Example 4) This method is basically the same as Example 1, the only difference being that the precursor is not subjected to carbon coating treatment.

[0182] (Comparative Example 5) This is basically the same as Example 1, the only difference being that the average pore size of the porous carbon is 1200 nm and the average distance between pores is 1000 nm.

[0183] (Comparative Example 6) The procedure is basically the same as in Example 1, the difference being that silane at 200°C is injected into the CVI reactor at a rate of 0.1 L / min, and at the same time, hydrogen gas at 250°C and high-purity nitrogen gas at 250°C are injected at rates of 50 L / min and 4.0 L / min, respectively, to thoroughly mix the gases and obtain a gas mixture. The gas mixture is then heated to approximately 400°C, and the turbulent gas mixture is left in the CVI reactor for 8 hours, resulting in a total flow rate of 54.1 L / min for the gas mixture.

[0184] (Electrochemistry Test) For lithium-ion batteries made of composite negative electrode materials in Examples 1-4 and Comparative Examples 1-8, tests were conducted on the initial discharge ratio capacity, initial Coulomb efficiency, capacity retention rate after 50-week cycles, and electrode sheet thickness expansion rate after 50-week cycles.

[0185] The initial discharge ratio capacity and initial Coulomb efficiency were tested by preparing a negative electrode slurry by mixing composite negative electrode material, conductive carbon black, and PAA glue in a mass ratio of 75:15:10, coating it onto copper foil, and drying it to create a negative electrode sheet. A button-type battery is assembled in a glove box filled with argon, with a lithium metal sheet as the counter electrode. Button-type batteries were subjected to charge-discharge tests at a current density of 0.1C in a charge-discharge range of 0.01V to 1.5V to obtain the initial discharge ratio capacity and initial Coulomb efficiency of the button-type batteries.

[0186] The capacity retention rate after 50-week cycles and the thickness expansion rate of the electrode sheet after 50-week cycles were tested by preparing a negative electrode slurry with a mass ratio of Super-P:KS-6:CMC:SBR = 92:2:2:2:2, coating it onto copper foil, and drying it to create a negative electrode sheet. A button-type battery is assembled in a glove box filled with argon, with a lithium metal sheet as the counter electrode. Button-type batteries were subjected to a 50-week charge-discharge test at a current density of 1C and a charge-discharge interval of 0.01V to 1.5V. The capacity retention rate and electrode sheet thickness expansion rate of the button-type batteries after the 50-week cycle were obtained.

[0187] [Table 1]

[0188] [Table 2]

[0189] The results shown in Tables 1 and 2 indicate that the composite anode material prepared in Example 2 had the best overall performance.

[0190] Comparing Example 1 and Example 5, the composite anode material of Example 1 exhibits relatively high initial discharge ratio capacity, initial Coulomb efficiency, and capacity retention rate after 50 weeks of cycling, and also has a low electrode sheet thickness expansion rate after 50 weeks of cycling. This is because, when the precursor was prepared in Example 1, the temperature of the silane, hydrogen, high-purity nitrogen, and gas mixture was appropriate, suppressing the formation of crystalline Si, which then exhibits expansion anisotropy during the charge-discharge process. Therefore, the composite anode material fabricated in Example 1 has a more stable structure and better electrochemical performance.

[0191] Comparing Example 1 and Example 6, the proportion of micropore volume in the pore volume ratio of micropores to mesopores in the composite anode material fabricated in Example 6 is relatively large. The composite anode material prepared in Example 6 exhibits slightly lower capacity retention rate, initial discharge ratio capacity, and initial Coulomb efficiency after 50 weeks of cycling compared to Example 1. Therefore, it is preferable that the ratio of the pore volume of micropores to the pore volume of mesopores in the composite anode material be (5-23):(77-95).

[0192] The particle size of Si particles in the composite anode materials prepared in Example 1 and Comparative Examples 1-2 was measured using SEM and NanoMeasurer software. In all of the composite anode materials in Example 1, the particle size of the Si particles is less than 100 nm, and the particle size of the 70% particles is between 50 nm and 80 nm. In contrast, the Si particles formed in Comparative Example 1 had a larger particle size, with 70% of the particles having a diameter of 80 nm to 150 nm. In Comparative Example 2, the number of Si particles in the composite anode material was small, and some of the particles had a large particle size. Furthermore, the composite anode materials prepared in Comparative Example 1 and Comparative Example 2 showed a lower capacity retention rate after 50 weeks of cycling compared to Example 1, and the composite anode material prepared in Comparative Example 2 had fewer Si particles and a lower ICE than Example 1. This demonstrates that when precursors are manufactured using CVI technology, the process conditions significantly affect the structure and electrochemical performance of the composite anode material.

[0193] Comparing Example 1 with Comparative Example 3, the composite anode material of Example 1 showed significantly higher capacity retention rates after ICE and 50-week cycles than Comparative Example 3, and significantly lower electrode sheet thickness expansion rates after 50-week cycles than Comparative Example 3. This is because, in the precursor of Example 1, the Si atoms are uniformly embedded in the porous carbon at the atomic level, which corresponds to a porous carbon material that has been modified by bulk phase doping. As a result, the Si atoms can form amorphous Si-C bonds with the C atoms, and the volume expansion during the lithium detachment process is small, and the conductivity of lithium ions is high, thus improving the material's cycle performance.

[0194] Comparing Example 1 with Comparative Example 4, the precursor of Comparative Example 4 was not subjected to carbon coating treatment. However, the capacity retention rate and the thickness expansion rate of the electrode sheet after 50 weeks of cycling of the composite anode material of Example 1 were both better than those of Comparative Example 4. This indicates that the carbon coating layer on the surface of the precursor improves the overall conductivity of the material. The carbon coating layer prevents direct contact between the electrolyte and Si particles, which could otherwise be exposed, thus improving cycle performance.

[0195] Comparing Example 1 with Comparative Example 5, the composite anode material of Comparative Example 5 has a high silicon content and a high initial discharge ratio capacity, but its capacity retention rate after 50 weeks of cycling is low, and its electrode sheet thickness expansion rate after 50 weeks of cycling is high. This is because the average pore size and average distance between pores of the porous carbon used in Comparative Example 5 were large. When Si penetrates into the porous carbon using CVI technology, the Si and C in the porous carbon cannot be uniformly mixed at the nanoscale. This uneven distribution of Si and C leads to a decrease in the electrochemical performance of Comparative Example 5, and because the pores of the porous carbon in Comparative Example 5 do not develop sufficiently, the amount of Si particles deposited on the porous carbon is small.

[0196] The composite anode materials prepared in Example 1 and Comparative Example 6 differ significantly in the ratio of pore volume to mesopore volume. The reason why the pore volume of the mesopores in the composite anode material prepared in Comparative Example 6 is higher than that in Example 1 is that in Comparative Example 6, the inflow rate of silane was low during the deposition process, resulting in insufficient silicon deposited in the pores of porous carbon, which greatly reduced the initial discharge ratio capacity of the material, and thus the pore volume of the mesopores in the final anode material was higher.

[0197] This application explains that by rationally designing the ratio of micropore volume to mesopore volume, the stability of the composite anode material can be effectively improved, its cycle performance can be enhanced, and its initial discharge ratio capacity and initial Coulomb efficiency can be significantly improved.

[0198] Any combination of the technical features of the embodiments described above is possible, and for the sake of brevity, not all possible combinations of the individual technical features in the embodiments described above have been mentioned. However, as long as these combinations of technical features are not contradictory, they should be considered to be within the scope of this specification.

[0199] The embodiments described above are merely examples of some embodiments of this application, and although the descriptions are specific and detailed, they should not be understood as limitations on the scope of the claims. Furthermore, a person skilled in the art may make several modifications and improvements without departing from the concept of this application, and these will fall within the scope of the claims. Therefore, the scope of protection of this application should be in accordance with the claims.

Claims

1. A composite negative electrode material comprising a core containing a porous carbon material and Si particles, and a coating layer located on at least a portion of the surface of the core, The Si particles are distributed on at least one of the surface and pores of the porous carbon material. The composite negative electrode material comprises micropores and mesopores, The ratio of the pore volume of the micropores in the composite anode material to the pore volume of the mesopores in the composite anode material is between 2:98 and 50:

50. The composite anode material is characterized in that the oil absorption value of the composite anode material is smaller than the oil absorption value of the composite anode material after the Si particles have been removed, and the difference value is greater than or equal to 10% when the oil absorption value of the composite anode material after the Si particles have been removed is set to 100%.

2. A composite negative electrode material comprising at least one of the following features (1) to (17): In the FIB-TEM test of the composite negative electrode material, the scanning line concentration of EDS satisfies the relationship: 0.90 ≤ (A １ - C １ ) / (C １ - B １ ) ≤ 1.10, and |((A １ - B １ ) / 2C １ ) ２ - 1| ≤ 0.01, where A １ is the maximum value along the scanning line concentration of Si, B １ is the minimum value along the scanning line concentration of Si, and C １ is the median value along the scanning line concentration of Si. (2) In the FIB-TEM test of the composite anode material, the scan line density of the EDS is 0.90 ≤ (A ２ -C ２ ) / (C ２ -B ２ ) ≤ 1.10, and | ((A ２ -B ２ ) / 2C ２ ) ２ -1 ≤ 0.01 satisfies, however A ２ This is the highest value along the C scan line density, and B ２ This is the lowest value along the C scan line density, and C ２ This is the median value along the C scan line density, (3) The composite negative electrode material ２９ In the Si-NMR spectrum, there is a Si-C resonance peak between -10 ppm and 20 ppm, and its intensity is D １ It has a Si resonance peak between -90 ppm and -110 ppm, and its intensity is D ２ In that case, and D ２ / D １ The condition is that ≥ 10, (4) The composite negative electrode material contains amorphous Si-C bonds, (5) The X-ray diffraction pattern of the composite negative electrode material includes a SiC crystal peak. (6) The porosity of the composite negative electrode material is 10% to 20%. (7) When the composite anode material is lithium-ionized to 50% of its theoretical lithium-ion capacity, the porosity A1 of the electrode sheet containing the composite anode material satisfies A1 ≥ 30%. (8) When the composite anode material is lithiumed to 70% of its theoretical lithium capacity, the porosity A2 of the electrode sheet containing the composite anode material satisfies 20% ≤ A2 < 30%. (9) When the composite anode material is lithiumed to 80% of its theoretical lithium capacity, the porosity A3 of the electrode sheet containing the composite anode material satisfies 10% ≤ A3 < 20%. (10) The ratio of the pore volume of the micropores to the pore volume of the mesopores is between 5:95 and 23:

77. (11) The average pore size of the closed pores in the composite negative electrode material after lithium has been completely inserted is 0 to 10 nm. (12) The mass percentage of Si in the composite anode material is 10% to 90%. (13) The specific surface area of ​​the composite negative electrode material is 0.5 m². ２ / g to 50m ２ It is / g, (14) The true density of the composite anode material is 1.80 g / cm³. ３ ~2.90 g / cm ３ That is, (15) The average particle size of the composite negative electrode material is 1 μm to 25 μm. (16) The average thickness of the coating layer is 1 nm to 100 nm. (17) The composite anode material according to claim 1, characterized in that the coating layer includes a carbon coating layer.

3. A composite negative electrode material comprising at least one of the following features (1) to (9), (1) The average pore size of the porous carbon is R1, and the range of R1 is 0.2 nm to 1000 nm. (2) The pore volume of pores with a diameter of 2 nm to 100 nm in the porous carbon is 50% or more of the total pore volume. (3) The ratio of the pore volume of micropores in the porous carbon to the pore volume of mesopores in the porous carbon is 95:5 to 50:

50. (4) The average distance between the pores of the porous carbon is H1, and the range of the value of H1 is 1 nm to 500 nm. (5) The average distance between pores in the porous carbon H1 ≤ the average pore diameter R1 of the porous carbon. (6) The particle size of the porous carbon is 1 μm to 50 μm. (7) The Si particles in the composite negative electrode material include amorphous silicon and have a particle size in the range of 1 to 110 nm. (8) The average particle size of the Si particles in the composite negative electrode material is 1 nm to 200 nm. (9) The composite anode material according to claim 1 or 2, characterized in that the particle size of the Si crystal grains of the composite anode material is 2 nm to 10 nm and the standard deviation σ ≤ 0.

2.

4. A step of obtaining a precursor by depositing Si particles on less than one of the surface and pores of porous carbon using a chemical vapor impregnation process, and A method for preparing a composite anode material, comprising the steps of coating the precursor with a protective atmosphere to form a coating layer on the surface of the precursor to obtain a composite anode material, The protective atmosphere contains at least one of nitrogen, argon, helium, neon, krypton, and xenon. The composite anode material comprises micropores and mesopores, and the ratio of the pore volume of the micropores to the pore volume of the mesopores in the composite anode material is from 2:98 to 50:

50. A method for preparing a composite anode material, characterized in that the oil absorption value of the composite anode material is smaller than the oil absorption value of the composite anode material after the removal of the Si particles, and the difference value is greater than or equal to 10% when the oil absorption value of the composite anode material after the removal of the Si particles is set to 100%.

5. The step of depositing Si particles on the surface and / or within the pores of porous carbon using the chemical vapor impregnation process includes supplying porous carbon, injecting a reaction gas, and thermally decomposing the reaction gas to deposit Si particles on the surface and / or within the pores of porous carbon, and includes at least one of the following features (1) to (9): (1) The reaction gas includes a gaseous Si source, hydrogen gas, and an inert gas. (2) The temperature of the thermal decomposition is 300°C to 500°C. (3) The time of the thermal decomposition is 0.2 h to 20 h, (4) The flow rate of the reaction gas is 50 L / min to 200 L / min. (5) The reaction gas comprises a gaseous Si source, and the raw material for the gaseous Si source includes at least one of monosilane, disilane, monochlorosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane. (6) The reaction gas comprises an inert gas, and the inert gas includes at least one of nitrogen gas, helium gas, neon gas, and argon gas. (7) The reaction gas comprises an inert gas, and the flow rate of the inert gas is 0.2 L / min to 50 L / min. (8) The reaction gas comprises a gaseous Si source and an inert gas, and the flow rate ratio of the gaseous Si source to the inert gas is 1:1 to 20. (9) The method for preparing a composite anode material according to claim 4, characterized in that the method for preparing the porous carbon includes a step of thermally decomposing an organic carbon source and a step of chemically activating an organic carbon source.

6. The coating treatment includes the steps of mixing the precursor and a carbon source, and in a protective atmosphere, controlling the thermal decomposition of the carbon source to form a carbon coating layer on the surface of the precursor, and is a preparation method comprising at least one of the following features (1) to (13): (1) The method for forming the carbon coating layer includes at least one of gas-phase carbon coating treatment, solid-phase carbon coating treatment and liquid-phase carbon coating treatment. (2) The gas flow rate of the protective atmosphere is 20 mL / min to 1000 mL / min. (3) The carbon source includes a gaseous carbon source. (4) The carbon source includes a gaseous carbon source, and the gaseous carbon source includes a gaseous hydrocarbon carbon source. (5) The carbon source includes a gaseous carbon source, and the gaseous carbon source includes at least one of methane, acetylene, ethylene, ethane, propane, propylene, propyne, acetone, and benzene. (6) The carbon source includes a solid-phase carbon source. (7) The carbon source includes a solid-phase carbon source, and the solid-phase carbon source includes a solid-phase organic carbon source. (8) The carbon source includes a solid-phase carbon source, and the solid-phase carbon source includes at least one of citric acid, glucose, pitch, phenol resin, and furfural resin. (9) The carbon source includes a liquid phase carbon source. (10) The carbon source includes a liquid phase carbon source, and the liquid phase carbon source includes a liquid phase organic carbon source. (11) The carbon source includes a liquid phase carbon source, and the liquid phase carbon source includes at least one of n-hexane, toluene, benzene, xylene, methanol, ethanol, propanol, butanol, pentanol, acetone, butanone, 2-pentanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and pentyl acetate. (12) The temperature of the thermal decomposition is 600°C to 1200°C. (13) The method for preparing a composite anode material according to claim 4, characterized in that the heating rate of the thermal decomposition is 0.1°C / min to 50°C / min.

7. A preparation method comprising at least one of the following features (1) to (4): (1) The total pressure of the reaction system due to the reaction gas is 100 kPa to 2000 kPa. (2) The total pressure of the reaction system due to the reaction gas is 100 kPa to 2000 kPa, and the partial pressure of the gaseous Si source is 1 kPa to 100 kPa. (3) The total pressure of the reaction system due to the reaction gas is 100 kPa to 2000 kPa, and the partial pressure of the hydrogen gas is 50 kPa to 1000 kPa. (4) The method for preparing a composite anode material according to claim 5, characterized in that the total pressure of the reaction system due to the reaction gas is 100 kPa to 2000 kPa, and the partial pressure of the inert gas is 1 kPa to 1000 kPa.

8. A negative electrode sheet characterized by comprising the composite negative electrode material described in claim 1 or 2.

9. A battery characterized by comprising the negative electrode sheet described in claim 8.

10. An electrical device characterized by comprising the battery described in claim 9.

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