Silicon-based negative electrode material having artificial SEI film, and preparation method therefor and use thereof

Abstract

The present application provides a silicon-based negative electrode material having an artificial SEI film, and a preparation method therefor and the use thereof. The silicon-based negative electrode material comprises a silicon-based material, and a carbon layer and a conductive artificial SEI composite layer which are arranged on the silicon-based material, wherein the carbon layer is located between the silicon-based material and the conductive artificial SEI composite layer; and the conductive artificial SEI composite layer is obtained by reacting a reactive precursor with a reactive conductive material. In the present application, by means of the design of a three-layer structure and interaction between the layers, the uniform, tight and stable coating of a nanometer conductive material is achieved, the utilization rate of the conductive material is improved, the silicon-based negative electrode material has low expansion, a high capacity, and a good conductivity and cycling stability, and the cycle performance of a lithium-ion battery comprising same is improved. When the silicon-based negative electrode material is used for manufacturing a negative electrode sheet and a battery, an extra nanometer conductive material does not need to be added, thereby simplifying a manufacturing process for the battery and significantly reducing the use cost of the silicon-based negative electrode material.

Description

A silicon-based anode material with an artificial SEI film, its preparation method and application Technical Field

[0001] This application belongs to the field of secondary battery technology, specifically relating to a silicon-based anode material, its preparation method and application, and particularly to a silicon-based anode material with an artificial SEI film, its preparation method and application. Background Technology

[0002] Lithium-ion batteries possess advantages such as high energy density, long cycle life, and low self-discharge rate, and are widely used in energy storage systems, mobile electronic products, electric vehicles, electric bicycles, and aerospace, among other fields. A lithium-ion battery is assembled from a positive electrode, a negative electrode, a separator, and an electrolyte. The choice of positive and negative electrode active materials has a significant impact on the performance of the lithium-ion battery. Currently, commercially available battery negative electrode materials are mainly graphite, but graphite has a relatively low theoretical specific capacity (approximately 372 mAh / g), making further improvements extremely difficult and limiting the development of lithium-ion batteries towards higher energy density. Therefore, developing high-capacity negative electrode materials is key to achieving performance breakthroughs in lithium-ion batteries.

[0003] Silicon-based materials are considered the most promising next-generation anode materials for lithium-ion batteries, with advantages including extremely high theoretical lithium intercalation capacity, suitable operating voltage, and abundant silicon reserves in the Earth's crust. However, silicon-based materials currently face many challenges in their application as anodes. Due to the large volume change (up to 300%) during lithium intercalation and deintercalation, silicon-based anodes exhibit significantly weaker cycle performance compared to graphite anodes. Furthermore, excessive volume expansion can adversely affect other electrochemical properties of the battery. Currently, pure silicon is difficult to use directly as a lithium-ion battery anode; researchers typically prepare silicon materials as silicon suboxide (SiO₂). x ,x<2) or silicon-carbon composite (SiC), such materials are blended with graphite and used as negative electrodes for lithium-ion batteries.

[0004] Compared to pure silicon anodes, the expansion of silicon suboxide and silicon-carbon materials has been suppressed, but their lithium intercalation volume expansion still exceeds 100%, resulting in lower cycle performance compared to traditional graphite anodes. To improve the performance of silicon suboxide / silicon-carbon materials, carbon nanotubes are often added as conductive agents during the anode slurry preparation process. For example, CN116137327A discloses a silicon-containing anode slurry comprising 10-25% conductive slurry, 40-55% silicon-carbon composite material, and 1-5% (by mass) binder aqueous solution with a binder concentration of 30-50%. The conductive slurry includes 0.2-10% conductive agent, 0.1-3% dispersant, and 87-99.7% water. The conductive agent is single- or double-walled carbon nanotubes, or a mixture of single- or double-walled carbon nanotubes and other carbon-based conductive agents. Carbon nanotubes have a fibrous structure and a certain degree of flexibility; as a conductive agent, they can achieve electrical contact between silicon and carbon materials (e.g., graphite) during cycling, reducing the cycle capacity decay of silicon. However, carbon nanotubes are used in large quantities as conductive agents and are difficult to disperse, and their high price significantly increases the process cost of using silicon-based anodes.

[0005] Another method to suppress the expansion of silicon-based anodes and improve cycle performance is to prepare silicon-carbon nanotube composite materials. For example, CN113422015A discloses a silicon-graphite-carbon nanotube anode composite material. The preparation method includes: weighing silicon-graphite material, dissolving and dispersing it in a first solvent to obtain a silicon-graphite pre-dispersion; diluting the silicon-graphite pre-dispersion with a second solvent, and then mixing it with a single-walled carbon nanotube dispersion to obtain a silicon-graphite / single-walled carbon nanotube composite slurry; and spray-drying the silicon-graphite / single-walled carbon nanotube composite slurry to remove the solvent, thereby obtaining a spherical silicon-graphite-carbon nanotube anode composite material. This composite material exhibits good capacity and coulombic efficiency; however, in this composite material, carbon nanotubes are more likely to adhere to the graphite surface, with a small amount adhering to the silicon surface, affecting the performance of the carbon nanotubes. Moreover, the bonding force between the carbon nanotubes and silicon is insufficient, making them prone to detachment during use. Therefore, it cannot effectively suppress the volume expansion of silicon, resulting in poor battery cycle performance. CN111146433A discloses a silicon-based particle for a negative electrode, comprising a silicon-containing matrix and a polymer layer. The polymer layer comprises a polymer and carbon nanotubes, wherein the polymer includes carboxymethyl cellulose, polyacrylic acid, polyvinylpyrrolidone, polyaniline, and polyimide, etc., and the weight ratio of polymer to carbon nanotubes in the polymer layer is 0.5:1-10:1. The preparation method of this silicon-based particle includes: adding carbon nanotubes to a solution containing a polymer to obtain a slurry; adding the silicon-containing matrix to the slurry and dispersing it to obtain a mixed slurry; and removing the solvent from the mixed slurry, crushing and sieving to obtain the silicon-based particle. The polymer layer in this silicon-based particle is prone to detachment during the preparation of the negative electrode slurry and the operation of the battery, thus preventing the carbon nanotubes from being stably distributed on the surface of the silicon-containing matrix, affecting the coating effect, and therefore failing to fundamentally solve the expansion problem of silicon-based materials and the cycle life problem of the battery.

[0006] CN116093273A discloses a silicon-based material for anodes, comprising a silicon-containing matrix and a polymer layer. The polymer layer comprises a polymer and hydroxylated carbon nanotubes, and the polymer includes acrylates, acrylonitrile, and acrylic polyether polyols. Hydroxylated carbon nanotubes and polymer coating can improve the cycle performance of silicon materials and suppress expansion. However, this method places high demands on the silicon substrate; the surface of the silicon substrate must contain hydroxyl functional groups to undergo esterification with the polymer, and the polymer-carbon nanotube coating must interact with the silicon substrate via ester bonds to ensure the stability of the coating layer. This method is not suitable for silicon materials without hydroxyl groups on the surface after carbon coating. Furthermore, although this method can improve the cycle life of silicon anodes, it cannot replace additional carbon nanotubes, increasing production costs.

[0007] CN111769266A discloses a silicon-based anode material comprising a silicon-based material; a carbon layer coating the surface of the silicon-based material; a polymer layer coating the surface of the carbon layer; and carbon nanotubes connected to the surface of the polymer layer via hydrogen bonds and / or covalent bonds. Although this silicon-based anode material can buffer the drastic volume expansion of the silicon anode material during charge and discharge to some extent, the insufficient bonding force between the carbon nanotubes and the polymer layer and the anode material as a whole leads to their easy detachment during slurry preparation, electrode processing, and battery cycling, preventing them from fully utilizing their function. The utilization rate of the carbon nanotubes is low, making it unsuitable to replace the additional addition of carbon nanotubes during slurry preparation.

[0008] Therefore, developing a silicon-containing anode material with low volume expansion, good cycle performance, excellent capacity and conductivity, and low cost is an urgent problem to be solved in this field. Summary of the Invention

[0009] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0010] To address the shortcomings of existing technologies, the purpose of this application is to provide a silicon-based anode material, its preparation method, and its application. Through the design and mutual compounding of silicon-based materials and their coated carbon layers and conductive artificial SEI composite layers, uniform and tight coating of nano-conductive materials is achieved. This enables the silicon-based anode material to have a significantly reduced volume expansion rate, excellent stability, and good cycle performance, while also possessing high capacity and excellent conductivity. The utilization rate of the nano-conductive materials is high, and their performance is well-utilized, greatly reducing the cost of using silicon-based anode materials.

[0011] To achieve the purpose of this application, the following implementation method is adopted:

[0012] In a first aspect, this application provides a silicon-based anode material, the silicon-based anode material comprising a silicon-based material and a carbon layer and a conductive artificial SEI composite layer disposed on the silicon-based material, the carbon layer being located between the silicon-based material and the conductive artificial SEI composite layer; the conductive artificial SEI composite layer is obtained by reacting a reactive precursor with a reactive conductive material.

[0013] The silicon-based anode material provided in this application has a three-layer structure, wherein the inner layer is a silicon-based material, the middle layer is a carbon layer, and the outer layer is a conductive artificial SEI composite layer. The inner silicon-based material serves as a lithium storage layer, exhibiting a significant high capacity advantage; the middle carbon layer enhances the overall conductivity of the silicon-based anode material and reduces the reaction between the electrolyte and the silicon-based material; the outer conductive artificial SEI composite layer is obtained by reacting a reactive precursor with a reactive conductive material, comprising two components: a polymer and a nano-conductive material. The nano-conductive material and the polymer are chemically bonded, thereby effectively suppressing the volume expansion of the silicon material while ensuring electrical contact of the silicon-based material during volume expansion and contraction, significantly improving the cycle performance of the silicon-based anode material.

[0014] The silicon-based anode material provided in this application has a conductive artificial SEI composite layer in which the conductive material is at least partially covered by the product of the reactive precursor reaction; that is, in the conductive artificial SEI composite layer, the conductive material is at least partially covered by the polymer. The polymer and the conductive material undergo a dual composite process of physical morphology and chemical reaction, resulting in a strong bond between the conductive material and the polymer, and the polymer is in situ coated onto the carbon layer surface, thus forming a strong and tight bond between the conductive material and the carbon layer.

[0015] The silicon-based anode material provided in this application has a conductive material in the conductive artificial SEI composite layer that is tightly adhered to the surface of the carbon layer. The conductive material includes dot-shaped nano-conductive materials, fibrous nano-conductive materials, or sheet-like nano-conductive materials, all of which are tightly adhered to the surface of the carbon layer. "Tightly adhered" means that the conductive material is in direct contact with the carbon layer, rather than in a free state without contact with the carbon layer, thereby maximizing the effective coating of the conductive material and significantly reducing the volume expansion rate of the silicon-based material.

[0016] In this application, the conductive artificial SEI composite layer is obtained by reacting a reactive precursor with a reactive conductive material. The conductive material is uniformly distributed on the surface of the silicon-based material (a silicon-based material with a carbon layer) without agglomeration. On one hand, the conductive artificial SEI composite layer grows in situ on the surface of the silicon material (including the surface carbon layer) in a network form, thereby ensuring a tight bond between the nano-conductive material and the silicon-based material (and its surface carbon layer). On the other hand, the conductive artificial SEI composite layer exhibits extremely strong adhesion to the intermediate carbon layer. During the fabrication of the negative electrode sheet and the battery, as well as during the operation of the battery, the conductive artificial SEI composite layer will not fall off and can be stably bonded to the surface of the silicon-based negative electrode material for a long time, thereby exerting the following advantages: (1) The surface-modified conductive materials and polymers bind the silicon-based material, reducing the volume expansion of the negative electrode; (2) The introduction of some filamentous conductive materials ensures the electrical contact between the silicon-based negative electrode material and other active materials (such as graphite materials) and current collectors, significantly improving the cycle performance of the silicon-based negative electrode material; and (3) The conductive artificial SEI composite layer can ensure the electrical contact during the expansion and contraction of the silicon-based material. In the process of fabricating the negative electrode sheet and the battery, no additional nano-conductive materials are needed to achieve good performance, greatly reducing the cost of using the silicon-based negative electrode material, while also improving the cycle performance of the battery.

[0017] This application achieves uniform, tight, and stable coating of nano-conductive materials and polymers through a three-layer structure design of silicon-based materials, a carbon layer, and a conductive artificial SEI composite layer, and the interaction between the layers. The coating layer does not detach, resulting in a significantly reduced volume expansion rate and significantly improved cycle performance of the silicon-based anode material. The silicon-based anode material provided by this application improves the cycle performance of lithium-ion batteries containing it, reduces manufacturing costs, and has broad application prospects.

[0018] The following are preferred embodiments of this application, but are not intended to limit the implementation methods provided in this application. The purpose and beneficial effects of this application can be better achieved through the following preferred embodiments.

[0019] Preferably, the silicon-based anode material has a D 50 The particle size is 0.2-20.0 μm; for example, it can be 0.2 μm, 0.5 μm, 1.0 μm, 2.0 μm, 5.0 μm, 8.0 μm, 10.0 μm, 12.0 μm, 15.0 μm or 18.0 μm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0020] Preferably, the specific surface area of ​​the silicon-based anode material is 0.1-20.0 m². 2 / g, for example, can be 0.2m 2 / g, 0.5m 2 / g, 0.8m 2 / g, 1.0m 2 / g, 2.0m 2 / g, 3.0m 2 / g, 4.0m 2 / g, 5.0m 2 / g, 6.0m 2 / g, 8.0m 2 / g, 10.0m 2 / g, 12.0m 2 / g, 15.0m 2 / g or 18.0m 2 / g, and the specific point values ​​between the above point values, due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0021] Preferably, the resistivity of the silicon-based anode material powder is 0.5-15.0 Ω·cm, for example, it can be 0.8 Ω·cm, 0.9 Ω·cm, 1.0 Ω·cm, 2.0 Ω·cm, 3.0 Ω·cm, 4.0 Ω·cm, 5.0 Ω·cm, 6.0 Ω·cm, 7.0 Ω·cm, 8.0 Ω·cm, 9.0 Ω·cm, 10.0 Ω·cm, 11.0 Ω·cm, 12.0 Ω·cm, 13.0 Ω·cm, 14.0 Ω·cm, or 15.0 Ω·cm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0022] Preferably, the silicon-based material includes any one or a combination of at least two of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy.

[0023] The silicon oxide includes SiO x Where x < 2, for example x can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 or 1.8, and specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range; preferably, the SiO x It is silicon suboxide.

[0024] Preferably, the silicon-based material D 50The particle size is 0.2-20.0 μm, for example, it can be 0.2 μm, 0.5 μm, 1.0 μm, 2.0 μm, 5.0 μm, 8.0 μm, 10.0 μm, 12.0 μm, 15.0 μm or 18.0 μm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0025] Preferably, the specific surface area of ​​the silicon-based material is 0.1-20.0 m². 2 / g, for example, can be 0.2m 2 / g, 0.5m 2 / g, 0.8m 2 / g, 1.0m 2 / g, 2.0m 2 / g, 3.0m 2 / g, 4.0m 2 / g, 5.0m 2 / g, 6.0m 2 / g, 8.0m 2 / g, 10.0m 2 / g, 12.0m 2 / g, 15.0m 2 / g or 18.0m 2 / g, and the specific point values ​​between the above point values, due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0026] Preferably, the thickness of the carbon layer is 1.0-30.0 nm, for example, it can be 2.0 nm, 3.0 nm, 4.0 nm, 5.0 nm, 6.0 nm, 8.0 nm, 10.0 nm, 12.0 nm, 15.0 nm, 18.0 nm, 20.0 nm, 22.0 nm, 25.0 nm or 28.0 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0027] In a preferred embodiment of this application, the carbon layer has a thickness of 1.0-30.0 nm and is located between the silicon-based material and the conductive artificial SEI composite layer. This improves conductivity and, together with the conductive artificial SEI composite layer, synergistically suppresses the volume expansion of the silicon-based material, thereby enhancing its cycle performance. If the carbon layer thickness is too low, it is detrimental to improving conductivity; if the carbon layer thickness is too high, the proportion of carbon material in the silicon-based anode material increases, thus negating the high capacity advantage of the silicon-based material.

[0028] Preferably, based on the mass of the silicon-based material as 100%, the mass of the carbon layer is 0.01%-10.00%, for example, it can be 0.02%, 0.05%, 0.08%, 0.10%, 0.20%, 0.50%, 0.80%, 1.00%, 2.00%, 3.00%, 4.00%, 5.00%, 6.00%, 7.00%, 8.00%, or 9.00%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0029] Preferably, based on the total mass of the silicon-based material and the carbon layer as 100%, the mass of the conductive artificial SEI composite layer is 0.01%-15.00%, for example, it can be 0.02%, 0.10%, 0.80%, 1.50%, 2.00%, 2.50%, 3.00%, 4.00%, 5.00%, 6.00%, 7.00%, 8.00%, 9.00%, 10.00%, 12.00%, or 14.00%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. More preferably, the mass of the conductive artificial SEI composite layer is 0.01%-5.00%, within which a silicon anode material with better overall performance can be obtained.

[0030] Preferably, based on the total mass of the silicon-based material and the carbon layer as 100%, the mass of the precursor is 0.01%-10.00%, for example, it can be 0.02%, 0.10%, 0.80%, 1.50%, 2.00%, 2.50%, 3.00%, 4.00%, 5.00%, 6.00%, 7.00%, 8.00%, or 9.00%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. More preferably, the mass of the precursor is 0.01%-5.00%. Within this range, a silicon anode material with better overall performance can be obtained, and the negative impact of the introduction of polymers can be reduced.

[0031] In a preferred embodiment of this application, with the total mass of silicon-based material and carbon layer as 100%, the mass of the conductive artificial SEI composite layer is 0.01%-15%. It is obtained by reacting a reactive precursor with a reactive conductive material, comprising two components: a polymer and nano-conductive materials. The precursor mass is 0.01%-10%. The polymer and nano-conductive materials are chemically bonded to form a stable polymer-nano-conductive material composite layer, ensuring that the nano-conductive materials are uniformly and tightly coated on the surface of the silicon-based material (and its carbon layer). If the mass of the precursor (polymer) is too low, it will affect the coating stability of the nano-conductive materials, preventing them from continuously and stably suppressing silicon expansion and conducting electrical contacts, thus affecting the cycle stability of the silicon-based anode material. If the mass of the precursor (polymer) is too high, it will not only affect ion transport but also relatively reduce the proportion of silicon-based material in the silicon-based anode material, leading to capacity loss.

[0032] Preferably, the reactive precursor comprises a monomer containing a double bond, and more preferably any one or a combination of at least two of the following: a cyano monomer containing a double bond, an acidic monomer containing a double bond, a carboxylic acid ester monomer containing a double bond, an amide monomer containing a double bond, a hydroxyl monomer containing a double bond, an aromatic vinyl monomer, an aliphatic conjugated diene monomer, a fluorinated olefin monomer, and a vinyl nitrogen heterocyclic monomer.

[0033] Preferably, the cyano monomer containing the double bond is an α,β-unsaturated nitrile monomer, specifically selected from one or a combination of acrylonitrile and methacrylonitrile.

[0034] Preferably, the mass percentage of the cyano monomer containing the double bond in the double-bonded monomer is ≤70%, preferably 0-40%, for example: 0, 1%, 2%, 5%, 8%, 10%, 15%, 20%, 25%, 30% or 35%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0035] Preferably, the acidic monomer containing a double bond is selected from any one or a combination of at least two of carboxylic acid monomers containing double bonds, sulfonic acid monomers containing double bonds, and phosphate monomers containing double bonds.

[0036] Preferably, the carboxylic acid monomer containing a double bond includes monocarboxylic acid, dicarboxylic acid, and their derivatives, specifically selected from any one or a combination of at least two of acrylic acid, methacrylic acid, crotonic acid, 2-ethylacrylic acid, isocrotonic acid, maleic acid, fumaric acid, itaconic acid, and methylmaleic acid.

[0037] The sulfonic acid monomer containing the double bond is not particularly limited, but may be selected from any one or a combination of at least two of vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, ethyl (meth)acrylate-2-sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, and 2-(N-acryloyl)amino-2-methyl-1,3-propane-disulfonic acid.

[0038] The phosphate monomer containing double bonds refers to a monomer having phosphate groups such as -PO3H2 group and -PO(OH)(OR) group (R represents a hydrocarbon group), specifically selected from any one or a combination of at least two of 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate and ethyl-(meth)acryloyloxyethyl phosphate.

[0039] In addition, the salts of the various monomers mentioned above can also be used as acid-containing monomers. Moreover, among the acid-containing monomers mentioned above, monomers containing carboxylic acid groups are preferred, and monocarboxylic acids mentioned above are even more preferred, with methacrylic acid and / or acrylic acid being particularly preferred.

[0040] Preferably, the mass percentage of acidic monomers containing double bonds in the double-bonded monomers is ≤80%, more preferably 0-70%, for example: 0, 1%, 5%, 10%, 20%, 30%, 40%, 45%, 60%, 65%, 70%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0041] The carboxylic acid ester monomer containing the double bond is preferably an alkyl acrylate or an alkyl methacrylate, specifically selected from methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate (n-butyl acrylate), isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate (2-ethylhexyl acrylate), 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, hexyl acrylate, nonyl acrylate, lauryl acrylate, stearyl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isodecanyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, and benzyl methacrylate, or any combination of at least two of these.

[0042] Preferably, the mass percentage of the double-bonded carboxylic acid ester monomer in the double-bonded monomer is ≤50%, preferably 0-30%, for example: 0, 1%, 5%, 10%, 15%, 20%, 25%, 30%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0043] The amide monomer containing a double bond is preferably an acrylamide monomer, specifically selected from any one or a combination of at least two of acrylamide, methacrylamide, N-methoxymethacrylamide, and N-methoxymethylmethacrylamide. Among them, acrylamide and methacrylamide are preferred.

[0044] Preferably, the mass percentage of the amide monomer containing the double bond in the double bond-containing monomer is ≤50%, preferably 0-30%, for example: 0, 1%, 5%, 10%, 15%, 20%, 25%, 30%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0045] The hydroxyl monomer containing the double bond is preferably a hydroxyalkyl acrylate or an N-hydroxyacrylamide monomer, specifically selected from any one or a combination of at least two of the following: hydroxymethyl acrylate, hydroxymethyl methacrylate, β-hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate and hydroxybutyl methacrylate, N-hydroxymethylacrylamide, N-hydroxymethylacrylamide, N-hydroxyethylacrylamide and N-hydroxyethylacrylamide. More preferably, hydroxyethyl methacrylate, β-hydroxyethyl acrylate, N-hydroxymethylacrylamide or N-hydroxyethylacrylamide are selected.

[0046] Preferably, the mass percentage of the hydroxyl monomer containing the double bond in the double bond monomer is ≤50%, preferably 0-30%, for example: 0, 1%, 5%, 10%, 15%, 20%, 25%, 30%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0047] The aromatic ethylene monomer is not particularly limited, but can be selected from any one or a combination of at least two of styrene, α-methylstyrene, vinyltoluene and divinylbenzene.

[0048] Preferably, the mass percentage of aromatic ethylene monomer in the double-bonded monomer is ≤80%, more preferably 0-60%. For example: 0, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list all the specific values ​​included in the range.

[0049] The aliphatic conjugated diene monomers are not particularly limited, and include, but are not limited to, 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, or 2-chloro-1,3-butadiene. These may be used alone or in combination of two or more in any ratio.

[0050] Preferably, the mass percentage of aliphatic conjugated diene monomer in the double-bonded monomer is ≤80%, more preferably 0-20%. For example: 0%, 1%, 5%, 10%, 15%, 20%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0051] The fluorinated olefin monomers are not particularly limited, and can be selected from vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, vinyl chloride trifluoride, vinyl fluoride, or perfluoroalkyl vinyl ethers, etc. These can be used alone, or in combination of two or more in any ratio.

[0052] Preferably, the fluorine-containing monomer content in the double-bonded monomer is ≤80% by mass, and more preferably 0-20%. For example, 0%, 1%, 5%, 10%, 15%, 20%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0053] The vinyl heterocyclic monomer is preferably N-vinylpyrrolidone or vinylpyrrolidone.

[0054] Preferably, the mass percentage of vinyl heterocyclic monomers in the double-bonded monomers is ≤80%, more preferably 0-20%. For example: 0%, 1%, 5%, 10%, 15%, 20%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0055] The polymer in the conductive artificial SEI composite layer is copolymerized from a variety of monomers containing double bonds as described above.

[0056] As some embodiments of this application, the double-bond-containing monomer includes any one or a combination of at least two of the following: cyano monomers containing double bonds, carboxylic acid monomers containing double bonds, sulfonic acid monomers containing double bonds, carboxylic acid ester monomers containing double bonds, amide monomers containing double bonds, and hydroxyl monomers containing double bonds.

[0057] As some embodiments of this application, the double-bond-containing monomer includes any one or a combination of at least two of the following: carboxylic acid monomers containing double bonds, carboxylic acid ester monomers containing double bonds, amide monomers containing double bonds, hydroxyl monomers containing double bonds, and aromatic vinyl monomers.

[0058] As some embodiments of this application, the double-bond-containing monomer includes any one or a combination of at least two of aromatic vinyl monomers, aliphatic conjugated diene monomers, fluorinated olefin monomers, acidic monomers containing double bonds, and N-vinylpyrrolidone monomers.

[0059] In a preferred embodiment of this application, the double-bonded monomer includes a combination of an aromatic vinyl monomer and a second monomer; the second monomer includes any one or a combination of at least two of the following: a double-bonded cyano monomer, a double-bonded amide monomer, a double-bonded carboxylic acid ester monomer, a double-bonded carboxylic acid monomer, and an N-vinylpyrrolidone monomer.

[0060] In a preferred embodiment of this application, the double-bonded monomer includes aromatic vinyl monomers, particularly styrene monomers, thereby forming a polymer containing styrene-based structural units. The benzene ring structure of the polymer side chain can interact π-π with the carbon layer on the surface of the silicon material, exhibiting extremely strong adhesion to the surface carbon layer, further ensuring coating stability and the cycle performance of the silicon-based anode material.

[0061] Preferably, the mass percentage of styrene monomers in the double-bonded monomers is ≤80%, for example, it can be 1%, 5%, 10%, 15%, 20%, 25%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range. Further preferred values ​​are 1%-60%, such as 5%-60%, 10%-60%, 15%-60%, 20%-60%, 30%-60%, 1%-50%, 3%-50%, 5%-50%, 10%-50%, etc.

[0062] Preferably, the cyano monomer containing a double bond includes acrylonitrile and / or methacrylonitrile.

[0063] Preferably, the amide monomer containing a double bond includes acrylamide and / or methacrylamide.

[0064] Preferably, the carboxylic acid ester monomer containing a double bond includes alkyl acrylate and / or alkyl methacrylate, and exemplary includes, but is not limited to, any one or a combination of at least two of methyl acrylate, methyl methacrylate, ethyl acrylate, hydroxyethyl acrylate, ethyl methacrylate, hydroxyethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate and butyl methacrylate.

[0065] Preferably, the carboxylic acid monomer containing a double bond includes acrylic acid and / or methacrylic acid.

[0066] Preferably, the mass percentage of the second monomer in the double-bonded monomer is ≤70%, for example, it can be 0.5%, 1%, 2%, 3%, 4%, 5%, 8%, 10%, 15%, 20%, 25%, 35%, 40%, 45%, 50%, 55%, 60%, 62%, 65%, or 68%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range, but 1%-65% is further preferred.

[0067] It should be noted that, in addition to the monomers listed in detail in this application, other monomers commonly used in the art can also be used in this application. This application only lists one preferred solution and should not be construed as a limitation on the monomers containing double bonds in this application.

[0068] Preferably, based on the total mass of the silicon-based material and the carbon layer as 100%, the mass of the reactive conductive material is 0.01%-10.00%, for example, it can be 0.02%, 0.05%, 0.08%, 0.10%, 0.50%, 0.80%, 1.00%, 2.00%, 3.00%, 4.00%, 5.00%, 6.00%, 7.00%, 8.00%, or 9.00%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0069] Preferably, the reactive conductive material is a nano-conductive material with a surface modified by reactive functional groups.

[0070] Preferably, the reactive functional groups in the reactive conductive material are functional groups containing unsaturated double bonds.

[0071] Preferably, the reactive conductive material comprises any one or a combination of at least two of the following conductive materials modified with reactive functional groups: conductive graphite, carbon black, Ketjen black, conductive carbon black Super P, carbon nanofibers, single-walled carbon nanotubes, multi-walled carbon nanotubes, oligo-walled carbon nanotubes, and graphene.

[0072] Preferably, the particle size of the conductive graphite, carbon black, Ketjen black, and conductive carbon black Super P is independently 10.0-1000.0 nm, for example, it can be 20.0 nm, 50.0 nm, 80.0 nm, 100.0 nm, 200.0 nm, 300.0 nm, 400.0 nm, 500.0 nm, 600.0 nm, 700.0 nm, 800.0 nm, or 900.0 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0073] Preferably, the diameters of the carbon nanotubes, single-walled carbon nanotubes, multi-walled carbon nanotubes, and oligo-walled carbon nanotubes are each independently 1.0-60.0 nm, for example, 2.0 nm, 5.0 nm, 8.0 nm, 10.0 nm, 15.0 nm, 20.0 nm, 25.0 nm, 30.0 nm, 35.0 nm, 40.0 nm, 45.0 nm, 50.0 nm, or 55.0 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0074] Preferably, the lengths of the carbon nanotubes, single-walled carbon nanotubes, multi-walled carbon nanotubes, and oligo-walled carbon nanotubes are each independently 0.1-80.0 μm, for example, 0.5 μm, 1.0 μm, 2.0 μm, 5.0 μm, 8.0 μm, 10.0 μm, 20.0 μm, 30.0 μm, 40.0 μm, 50.0 μm, 60.0 μm, or 70.0 μm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0075] Preferably, the specific surface area of ​​the conductive material is 50-2000 m². 2 / g, for example, can be 80m 2 / g, 100m 2 / g、200m 2 / g、400m 2 / g、500m 2 / g、600m 2 / g、800m 2 / g, 1000m 2 / g、1200m 2 / g, 1500m 2 / g or 1800m 2 / g, and the specific point values ​​between the above point values, due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0076] In a preferred embodiment of this application, the conductive material includes carbon nanotubes. This yields a silicon-based anode material. In the conductive artificial SEI composite layer, the carbon nanotubes are at least partially covered by the polymer. Through a dual composite process of physical morphology and chemical reaction, the polymer and carbon nanotubes form a strong bond, and the polymer is in situ coated onto the surface of the carbon layer, resulting in a strong and tight bond between the carbon nanotubes and the carbon layer. The carbon nanotubes exhibit a filamentary distribution, tightly adhering to the surface of the carbon-coated silicon-based material, effectively binding the silicon-based material and limiting its expansion.

[0077] In a preferred embodiment of this application, the silicon-based anode material includes a silicon-based material and a carbon layer and a conductive artificial SEI composite layer disposed on the silicon-based material, wherein the carbon layer is located between the silicon-based material and the conductive artificial SEI composite layer; the conductive artificial SEI composite layer is a polymer-carbon nanotube composite layer, which is obtained by reacting a reactive precursor (preferably containing a double-bonded monomer) with a reactive conductive material (double-bonded modified carbon nanotubes).

[0078] Secondly, this application provides a method for preparing a silicon-based anode material as described in the first aspect, the method comprising:

[0079] (1) A carbon layer is deposited on a silicon-based material to obtain a carbon-coated silicon-based material; and

[0080] (2) The carbon-coated silicon-based material reacts with a reactive precursor and a reactive conductive material to obtain the silicon-based anode material.

[0081] In the preparation method of the silicon-based anode material provided in this application, a reactive precursor and a reactive conductive material are polymerized in situ on a carbon-coated silicon-based material to form a polymer-nanoconductive material composite layer, resulting in the silicon-based anode material with a three-layer structure. This application combines reactive conductive materials with in-situ reactive coating technology, thereby enabling the nanoconductive material and the polymer network to be bonded together by covalent bonds, and the nanoconductive material is at least partially covered by the polymer, forming a conductive artificial SEI network that tightly coats the surface of the silicon anode.

[0082] Since nano-conductive materials are difficult to disperse in solution, as a preferred embodiment of this application, this application provides an atomic layer deposition (ALD)-like technology, which enables nano-conductive materials and polymers to be uniformly and tightly coated on the surface of carbon-coated silicon-based materials. The coating layer is stable and has strong adhesion, and will not fall off during battery fabrication. This allows the nano-conductive materials to continuously and stably suppress silicon expansion, ensure electrical contact between silicon-based anode materials and other active materials (such as graphite materials) and current collectors, and improve the cycle performance of silicon-based anode materials and batteries.

[0083] Preferably, the method for setting the carbon layer includes chemical vapor deposition (CVD).

[0084] Preferably, the carbon source used in the chemical vapor deposition includes any one or a combination of at least two of acetylene, ethylene, methane, and ethane.

[0085] Preferably, the pressure of the chemical vapor deposition is 1-10 MPa, for example, it can be 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa, 7 MPa, 7.5 MPa, 8 MPa, 8.5 MPa, 9 MPa or 9.5 MPa, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0086] Preferably, the temperature of the chemical vapor deposition is 400-1000℃, for example, it can be 420℃, 450℃, 480℃, 500℃, 520℃, 550℃, 580℃, 600℃, 620℃, 650℃, 680℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 980℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0087] Preferably, the chemical vapor deposition time is 0.5-8 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours or 7.5 hours, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0088] In this application, the preparation method of the reactive conductive material can be carried out by any method known in the art. To facilitate a better understanding of this application, the following preparation method is provided.

[0089] Preferably, the preparation method of the reactive conductive material includes: activating the conductive material in an acidic activating solution to obtain an activated conductive material; and subjecting the activated conductive material to condensation modification to obtain a reactive conductive material.

[0090] In a preferred embodiment of this application, a conductive material (nano-conductive material) is first activated in an acidic activation solution to introduce hydroxyl groups at defects on the surface of the nano-conductive material, thereby obtaining an activated conductive material. The activated conductive material then undergoes a condensation reaction with an unsaturated amine compound under catalytic conditions to obtain the reactive conductive material. Its surface functional groups (unsaturated bonds) can chemically react with the precursor to form chemical bonds, and the nano-conductive material is at least partially covered by a polymer, forming a polymer-conductive material network that tightly coats the surface of the silicon anode. Because the nano-conductive material and the polymer network are covalently bonded, the nano-conductive material can stably coat the surface of the silicon anode without detaching.

[0091] Preferably, the acidic activating solution comprises an aqueous solution of an acidic substance containing a large number of hydroxyl groups.

[0092] Preferably, the acidic substance includes any one or a combination of at least two of nitric acid, hydrochloric acid, and sulfuric acid, and more preferably nitric acid and / or hydrochloric acid.

[0093] Preferably, the concentration of acidic substances in the acidic activation solution is ≥30%, for example, it can be 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, or 70%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range, but ≥40% is further preferred.

[0094] Preferably, the activation treatment is carried out under conditions of ultrasonic vibration and / or stirring (e.g., mechanical stirring).

[0095] Preferably, the activation treatment temperature is 40-80℃, for example, it can be 42℃, 45℃, 48℃, 50℃, 52℃, 55℃, 58℃, 60℃, 62℃, 65℃, 68℃, 70℃, 72℃, 75℃ or 78℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0096] Preferably, the activation treatment time is 1-8 hours, for example, it can be 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours or 7.5 hours, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0097] Preferably, the unsaturated amine compound is not particularly limited, and can be, for example, CH2=CH-(CH2)n-CH2-NH2 (n≥1, for example, 2, 3, 4, 5, 6, etc.). 3-Butene-1-amine can be listed as a specific example.

[0098] Preferably, the mass ratio of the activated conductive material to the unsaturated amine compound is (1-50):1, for example, it can be 2:1, 5:1, 10:1, 12:1, 15:1, 18:1, 20:1, 22:1, 25:1, 28:1, 30:1, 32:1, 35:1, 38:1, 40:1 or 45:1, etc., and more preferably (10-40):1.

[0099] Preferably, the condensation modification is carried out in the presence of a catalyst. The catalyst comprises any one or a combination of at least two of the following: 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride / 1-hydroxybenzotriazole, dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride.

[0100] Preferably, the mass of the catalyst is 0-10% based on 100% of the mass of the unsaturated amine compound, for example, it can be 0.1%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9%, etc.

[0101] Preferably, the activation treatment includes the steps of solid-liquid separation, solid phase collection, washing, and drying to obtain an activated conductive material.

[0102] Preferably, the reaction (condensation reaction) between the activated conductive material and the unsaturated amine compound is carried out in the presence of a solvent.

[0103] Preferably, the solvent includes any one or a combination of at least two of the following: water, aromatic solvents, ether solvents, sulfone solvents, and haloalkane solvents.

[0104] Preferably, the solvent comprises any one or a combination of at least two of water, toluene, tetrahydrofuran, and dimethyl sulfoxide. Water is the preferred solvent.

[0105] Preferably, the reaction (condensation reaction) between the activated conductive material and the unsaturated amine compound is carried out under conditions of ultrasonic vibration and / or stirring (e.g., mechanical stirring).

[0106] Preferably, the reaction temperature (condensation reaction) between the activated conductive material and the unsaturated amine compound is 10-45°C, for example, it can be 12°C, 15°C, 18°C, 20°C, 22°C, 25°C, 28°C, 30°C, 32°C, 35°C, 38°C, 40°C, 42°C or 44°C, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0107] Preferably, the reaction time (condensation reaction) between the activated conductive material and the unsaturated amine compound is 1-8 hours, for example, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours or 7.5 hours, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0108] Preferably, in step (2), based on the mass of the carbon-coated silicon-based material as 100%, the mass of the reactive precursor is 0.01%-5%, for example, it can be 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0109] Preferably, in step (2), based on the mass of the carbon-coated silicon-based material as 100%, the mass of the reactive conductive material is 0.01%-2%, for example, it can be 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5% or 1.8%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0110] Preferably, the reaction in step (2) can be carried out under thermally initiated conditions.

[0111] Preferably, the reaction is carried out in the presence of an initiator, which is a free radical initiator, and more preferably any one or a combination of at least two of persulfate, azo initiators, peroxide, and redox initiators.

[0112] Preferably, the persulfate includes any one or a combination of at least two of ammonium persulfate, sodium persulfate, and potassium persulfate.

[0113] Preferably, the azo initiator includes any one or a combination of at least two of azobisisobutyronitrile, azobisisobutyronitrile, and azobisisobutyramidine hydrochloride.

[0114] Preferably, the peroxide includes any one or a combination of at least two of benzoyl peroxide, lauroyl peroxide, and tert-butyl hydroperoxide.

[0115] Preferably, the redox initiator comprises any one or a combination of at least two of tert-butyl hydroperoxide-sodium metabisulfite, hydroperoxide-ferrous chloride, and cumene hydroperoxide-tetraethyleneimine.

[0116] Preferably, based on the mass of the reactive precursor as 100%, the mass of the initiator for the reaction is ≤2%, for example, it can be 0, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5% or 1.8%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0117] Preferably, the reaction in step (2) is carried out in the presence of a solvent.

[0118] Preferably, the solvent includes water and / or an organic solvent, with water being more preferred.

[0119] Preferably, the reaction in step (2) can be carried out in an atmosphere of air, nitrogen or argon, with nitrogen being more preferred.

[0120] Preferably, the reaction temperature in step (2) is 50-200℃, for example, it can be 52℃, 55℃, 58℃, 60℃, 62℃, 65℃, 68℃, 70℃, 72℃, 75℃, 78℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 180℃ or 190℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0121] Preferably, the reaction time in step (2) is 0.5-24h, for example, it can be 1h, 2h, 3h, 4h, 5h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0122] Preferably, the reaction method in step (2) includes uniform coating by atomic layer deposition (ALD), which includes: reacting carbon-coated silicon-based material, reactive precursor, and reactive conductive material in the presence of a solvent to obtain a dispersion; and drying the dispersion to obtain the silicon-based anode material.

[0123] More preferably, the method for uniform coating by atomic layer deposition includes: placing a carbon-coated silicon-based material, a reactive precursor, a reactive conductive material, and a solvent in a reaction apparatus for reaction, and obtaining a dispersion under high shear stress conditions; and drying the dispersion using a drying apparatus. During the drying process, the dispersion is dispersed into microdroplets by high-speed rotating shear or high-speed airflow impact, and dried under heat flow conditions to obtain the silicon-based anode material.

[0124] Preferably, the reaction apparatus includes a shear dispersion device capable of obtaining a dispersion under high shear force conditions; the shear dispersion device is further preferably any one or a combination of at least two of the following: a sand mill, a ball mill, a high-speed disperser, a double planetary mixer, and a homogenizer.

[0125] Preferably, the solvent includes water and / or an organic solvent.

[0126] Preferably, the reaction is carried out in the presence of a surfactant.

[0127] Preferably, the surfactant comprises any one or a combination of at least two of sodium dodecylbenzenesulfonate, stearic acid, oleic acid, lauric acid, polyethylene glycol, polyvinyl alcohol, 15-crown-5, 18-crown-6 and tetrabutylammonium bromide, and more preferably sodium dodecylbenzenesulfonate.

[0128] Preferably, based on the mass of the carbon-coated silicon-based material as 100%, the mass of the surfactant is 0.01%-5.00%, for example, it can be 0.05%, 0.10%, 0.20%, 0.30%, 0.40%, 0.50%, 0.60%, 0.80%, 1.00%, 1.50%, 2.00%, 2.50%, 3.00%, 3.50%, 4.00%, or 4.50%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0129] As a preferred embodiment of this application, the atomic layer deposition (ALD) uniform coating technology is characterized by: adding carbon-coated silicon-based materials, reactive precursors, reactive conductive materials, and other active substances, along with water and / or organic solvents, to a dispersion device with strong shear force, and uniformly dispersing them with the assistance of surfactants. After dispersion or chemical reaction is complete, the dispersion is instantly dried using a drying device. During the drying process, the dispersion is dispersed into microdroplets by high-speed rotating shear or high-speed airflow impact, and under the action of heat flow, the microdroplets dry in a short time, obtaining the silicon-based anode material uniformly coated with a conductive artificial SEI composite layer.

[0130] Preferably, the shearing and dispersing device is a high-speed disperser with a rotation speed of 400-4000 rpm (revolutions per minute), for example, 500 rpm, 600 rpm, 800 rpm, 1000 rpm, 1200 rpm, 1500 rpm, 1600 rpm, 1800 rpm, 2000 rpm, 2200 rpm, 2500 rpm, 2800 rpm, 3000 rpm, 3200 rpm, 3500 rpm, or 3800 rpm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0131] Preferably, the dispersion time of the high-speed disperser is 1-6 hours, for example, it can be 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours or 5.5 hours, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0132] Preferably, the drying device includes any one or a combination of at least two of the following: a spray dryer, a fluidized bed, an airflow flash dryer, a rotary flash dryer, and a rotary kiln; more preferably, a spray dryer.

[0133] Preferably, the drying method includes: dispersing the dispersion into microdroplets by high-speed rotating shear or high-speed airflow impact, and drying under heat flow conditions to obtain the silicon-based anode material.

[0134] Preferably, the drying temperature is 50-400℃, for example, it can be 80℃, 100℃, 120℃, 150℃, 180℃, 200℃, 220℃, 250℃, 280℃, 300℃, 320℃, 350℃ or 380℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0135] Thirdly, this application provides an apparatus for preparing a silicon-based anode material, the apparatus comprising a first reaction device, a second reaction device, and a drying device connected in sequence; the silicon-based anode material as described in the first aspect is prepared by the apparatus.

[0136] Preferably, the first reaction apparatus includes a chemical vapor deposition apparatus; the silicon-based material is carbon-coated in the chemical vapor deposition apparatus to obtain a carbon-coated silicon-based material.

[0137] Preferably, the second reaction apparatus includes a shearing and dispersing device, and more preferably any one or a combination of at least two of the following: a sand mill, a ball mill, a high-speed disperser, a double planetary mixer, and a homogenizer.

[0138] Preferably, the drying device includes any one or a combination of at least two of the following: spray drying device, fluidized bed, airflow flash dryer, rotary flash dryer, and rotary kiln.

[0139] Fourthly, this application provides a negative electrode material composition comprising a combination of an active material, a binder, and a conductive material, wherein the active material comprises a silicon-based negative electrode material as described in the first aspect.

[0140] To ensure the optimal performance of silicon materials, existing silicon-containing anode sheets (anode material compositions, anode slurries) involve adding a certain amount of nano-conductive materials (such as carbon nanotubes) during fabrication to guarantee electrical contact between silicon, graphite, and the current collector. Without the introduction of carbon nanotubes, the cycle performance of silicon materials would significantly decrease. However, the introduction of carbon nanotubes increases the difficulty of preparing the anode slurry and also raises the manufacturing cost of the battery. The silicon-based anode material provided in this application, used in the preparation of anode material compositions, anode slurries, and anode sheets, eliminates the need for additional carbon nanotubes, enabling silicon-based materials to achieve better performance.

[0141] Preferably, the active material includes the silicon-based anode material and optionally a carbon material, and more preferably a combination of silicon-based anode material and carbon material.

[0142] Preferably, the carbon material includes any one or a combination of at least two of graphite, carbon black, carbon fiber, mesophase carbon microspheres and petroleum coke, with graphite being more preferred.

[0143] Preferably, the graphite is natural graphite and / or artificial graphite.

[0144] Preferably, the mass percentage of silicon-based anode material in the active material is 1-80%, for example, it can be 5%, 10%, 20%, 30%, 40%, 50%, 60% or 70%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0145] Preferably, the mass percentage of active material in the negative electrode material composition is 80-98%, for example, it can be 82%, 85%, 88%, 90%, 92%, 95% or 97%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0146] Preferably, the adhesive comprises any one or a combination of at least two of acrylic polymers, polyacrylonitrile and styrene-based copolymers.

[0147] Preferably, the styrene-based copolymer includes styrene-butadiene rubber (SBR).

[0148] Preferably, the mass percentage of the binder in the negative electrode material composition is 0.1-12%, for example, it can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or 11%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0149] Preferably, the conductive agent comprises any one or a combination of at least two of carbon black, graphite, and carbon fiber.

[0150] Preferably, the mass percentage of the conductive agent in the negative electrode material composition is 0.1-10%, for example, it can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0151] Preferably, the negative electrode material composition further includes a thickener.

[0152] Preferably, the thickener comprises sodium carboxymethyl cellulose (CMC).

[0153] Preferably, the mass percentage of thickener in the negative electrode material composition is ≤5%, for example, it can be 0, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0154] Fifthly, this application provides a negative electrode sheet, the negative electrode sheet comprising a current collector and a coating disposed on the current collector, the material of the coating comprising the negative electrode material composition as described in the fourth aspect.

[0155] Preferably, the method for preparing the negative electrode sheet includes: mixing the negative electrode material composition with a solvent to obtain a negative electrode slurry; and coating the negative electrode slurry onto a current collector and drying it to obtain the negative electrode sheet.

[0156] Preferably, the drying process further includes a rolling step.

[0157] In a sixth aspect, this application provides an electrochemical energy storage device, the electrochemical energy storage device comprising at least one of the silicon-based negative electrode material as described in the first aspect, the negative electrode material composition as described in the fourth aspect, and the negative electrode sheet as described in the fifth aspect.

[0158] Preferably, the electrochemical energy storage device includes any one of lithium-ion batteries, sodium-ion batteries, supercapacitors, and solid-state batteries, with lithium-ion batteries being more preferred.

[0159] Compared with the prior art, this application has the following advantages:

[0160] (1) In the silicon-based anode material provided in this application, the uniform, tight, and stable coating of the nano-conductive material is achieved through the design of a three-layer structure consisting of silicon-based material, a carbon layer, and a conductive artificial SEI composite layer, and the interaction between the layers. The coating layer will not peel off, resulting in a significantly reduced volume expansion rate for the silicon-based anode material, while also possessing high capacity and excellent conductivity, thus improving the cycle performance of lithium-ion batteries containing it. The silicon-based anode material is used in the fabrication of anode sheets and batteries, eliminating the need for the addition of carbon nanotubes, which greatly reduces the cost of using silicon-based anode materials.

[0161] (2) In the preparation method of silicon-based anode material provided in this application, a reactive precursor and a reactive conductive material undergo an in-situ reaction on a silicon-based material coated with a carbon layer to obtain a three-layer silicon-based anode material. This application combines reactive conductive material with in-situ reaction coating technology, so that the nano-conductive material and the polymer network are bonded by covalent bonds, and the nano-conductive material is at least partially covered by the polymer, so that the nano-conductive material can be tightly coated on the surface of the silicon-based anode material. The coating layer is stable and has strong bonding force, and will not fall off during the battery manufacturing process. Thus, the nano-conductive material can continuously and stably play the role of inhibiting silicon expansion and ensuring electrical contact between the silicon-based anode material and other active materials (such as graphite materials) and current collectors, thereby improving the cycle performance of the silicon-based anode material and the battery.

[0162] (3) This application optimizes the precursor and polymer so that the polymer contains a planar benzene ring structure. The benzene ring structure of the polymer side chain can interact with the carbon layer on the surface of the silicon material in a π-π manner, which has a strong adhesion to the surface carbon layer, further improving the coating stability and cycle performance of the silicon-based anode material.

[0163] (4) This application preferably employs atomic layer deposition (ALD)-like uniform coating technology. By uniformly dispersing the reactive precursor, reactive conductive material, and carbon-coated silicon-based material in a solvent under strong shear force with the assistance of surfactant, the problem of difficult dispersion of nano-conductive materials and silicon-based materials is solved. After instantaneous drying, the conductive artificial SEI composite layer containing polymer and nano-conductive materials can be uniformly coated on the surface of silicon-based materials. The ALD-like technology significantly improves the uniformity and integrity of the coating on the surface of silicon-based anodes, thereby enhancing the performance of silicon materials. Attached Figure Description

[0164] Figure 1 is a scanning electron microscope image of the silicon-based anode material provided in Example 1;

[0165] Figure 2 is a scanning electron microscope image of the negative electrode sheet fabricated using the silicon-based negative electrode material provided in Example 1; and

[0166] Figure 3 is a scanning electron microscope image of a negative electrode sheet made using the silicon-based negative electrode material provided in Comparative Example 1. Detailed Implementation

[0167] The embodiments of this application will be further described below through specific implementation methods. Those skilled in the art should understand that the embodiments described are merely illustrative of this application and should not be construed as specific limitations thereof.

[0168] The terms "conductive material" and "nanoconductive material" used in this application have the same meaning and refer to the same thing.

[0169] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not limited to those elements and may also include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0170] "Optionally", "maybe", "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event may occur and the possibility that the event may not occur.

[0171] The indefinite articles “a” and “an” preceding an element or component in this application do not impose any limitation on the quantity (i.e., number of occurrences) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0172] The terms "one embodiment," "some embodiments," "exemplary," "specific example," or "some examples," etc., described in this application refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this document, the illustrative expressions of the above terms are not necessarily directed at the same embodiment or example.

[0173] The terms "active material" and "active substance" as described in this application have equivalent meanings.

[0174] Furthermore, the technical features involved in the various embodiments of this application can be combined with each other as long as they do not conflict with each other.

[0175] In the following specific embodiments of this application, the silicon-based materials, nano-conductive materials, monomers, initiators, solvents, etc. used are all commercially available products. Specifically, the nano-conductive material is a single-walled carbon nanotube with a diameter of 1-3 nm and a length of 3-30 μm; the silicon-carbon composite is SiC with a median particle size of 7-12 μm, purchased from Zhejiang Carbon One New Energy.

[0176] Example 1

[0177] Silicon-based anode materials and their preparation:

[0178] A silicon-based anode material comprises a silicon-carbon composite and a carbon layer and a conductive artificial SEI composite layer sequentially disposed on the silicon-carbon composite. The conductive artificial SEI composite layer is obtained by reacting styrene, acrylic acid, and double-bond modified carbon nanotubes. The preparation method of the silicon-based anode material is as follows:

[0179] (1) Preparation of double bond modified carbon nanotubes: 30g of single-walled carbon nanotubes were added to 200mL of 40% nitric acid solution, ultrasonically vibrated at 45℃ for 2h, filtered, the powder was collected, washed with water until the filtrate was neutral, and dried at 100℃ for 3h to obtain acidified carbon nanotubes; the acidified carbon nanotubes were added to 200mL of water, ultrasonically vibrated for 0.5h to form a dispersion, stirred at 25℃ and 1g of 3-buten-1-amine was slowly added dropwise to the dispersion, 0.08g of 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride was added, and the reaction was continued to be stirred for 4h; the powder was collected by filtration, washed with 100mL of water, and then dried at 60℃ for 3h to obtain double bond modified carbon nanotubes.

[0180] (2) CVD method for coating carbon layer: 200g of silicon-carbon composite was placed in a deposition furnace at 500℃, protected by argon gas, and acetylene gas was introduced at 500℃ at a flow rate of 10L / min and a furnace pressure of 6MPa. After continuous gas supply for 4h, the mixture was cooled to room temperature, thereby forming a carbon layer on the silicon-carbon composite and obtaining an intermediate.

[0181] (3) Preparation of silicon-based anode material: Take 0.6 g of double-bond modified carbon nanotubes obtained in step (1), 100 g of intermediate obtained in step (2), 0.8 g of styrene, 1.2 g of acrylic acid, and 0.5 g of sodium dodecylbenzenesulfonate, and place them in 400 mL of deionized water. Disperse using a high-speed disperser at 3000 rpm for 3 hours. Reduce the speed to 500 rpm, introduce nitrogen gas, heat to 70°C, and continue stirring for 0.5 h. Add 0.02 g of ammonium persulfate to the system and continue stirring at 70°C for 6 h. After cooling to room temperature, atomize the dispersion into microdroplets using a high-speed centrifugal atomizer at 12000 rpm, and then instantaneously dry it with hot air at 200°C. Collect the powder, sieve it, and demagnetize it to obtain the silicon-based anode material.

[0182] Negative electrode sheet and its preparation:

[0183] The silicon-based negative electrode material provided in this embodiment is mixed with artificial graphite at a mass ratio of 1:1 to obtain an active material. The active material, thickener sodium carboxymethyl cellulose (CMC), conductive agent Super P, and binder styrene-butadiene rubber (SBR) are mixed at a mass ratio of 88:2:3:7. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on the negative electrode current collector copper foil, transferred to a vacuum drying oven for drying, and then rolled and punched to obtain small discs, which are the negative electrode sheets.

[0184] Battery manufacturing:

[0185] A coin cell battery is assembled using a lithium metal sheet as the counter electrode, Celgard 2400 as the separator, and an electrolyte injected.

[0186] Example 2

[0187] A silicon-based anode material comprises a silicon-carbon composite and a carbon layer and a conductive artificial SEI composite layer sequentially disposed on the silicon-carbon composite. The conductive artificial SEI composite layer is obtained by reacting styrene, acrylic acid, and double-bond modified carbon nanotubes. The preparation method of the silicon-based anode material differs from that of Example 1 only in that the amount of double-bond modified carbon nanotubes used in step (3) is 0.2g. The types, amounts, preparation steps, and process parameters of other materials are the same as in Example 1, thus obtaining the silicon-based anode material.

[0188] The silicon-based negative electrode material provided in this embodiment is mixed with artificial graphite at a mass ratio of 1:1 to obtain an active material. The negative electrode sheet is prepared and a coin cell is assembled using the same method as in Example 1.

[0189] Example 3

[0190] A silicon-based anode material comprises a silicon-carbon composite and a carbon layer and a conductive artificial SEI composite layer sequentially disposed on the silicon-carbon composite. The conductive artificial SEI composite layer is obtained by reacting styrene, acrylic acid, and double-bond modified carbon nanotubes. The preparation method of the silicon-based anode material differs from that of Example 1 only in that the amount of double-bond modified carbon nanotubes used in step (3) is 1.0 g. The types, amounts, preparation steps, and process parameters of other materials are the same as in Example 1, thus obtaining the silicon-based anode material.

[0191] The silicon-based negative electrode material provided in this embodiment is mixed with artificial graphite at a mass ratio of 1:1 to obtain an active material. The negative electrode sheet is prepared and a coin cell is assembled using the same method as in Example 1.

[0192] Example 4

[0193] A silicon-based anode material comprises a silicon-carbon composite and a carbon layer and a conductive artificial SEI composite layer sequentially disposed on the silicon-carbon composite. The conductive artificial SEI composite layer is obtained by reacting styrene, acrylic acid, and double-bond modified carbon nanotubes. The preparation method of the silicon-based anode material differs from that of Example 1 only in that 0.4g of styrene and 0.6g of acrylic acid are used in step (3), while the types, amounts, preparation steps, and process parameters of other materials are the same as in Example 1, thus obtaining the silicon-based anode material.

[0194] The silicon-based negative electrode material provided in this embodiment is mixed with artificial graphite at a mass ratio of 1:1 to obtain an active material. The negative electrode sheet is prepared and a coin cell is assembled using the same method as in Example 1.

[0195] Example 5

[0196] A silicon-based anode material comprises a silicon-carbon composite and a carbon layer and a conductive artificial SEI composite layer sequentially disposed on the silicon-carbon composite. The conductive artificial SEI composite layer is obtained by reacting styrene, acrylic acid, and double-bond modified carbon nanotubes. The preparation method of the silicon-based anode material differs from that of Example 1 only in that, in step (3), 1.6 g of styrene and 2.4 g of acrylic acid are used. The types, amounts, preparation steps, and process parameters of other materials are the same as in Example 1, thus obtaining the silicon-based anode material.

[0197] The silicon-based negative electrode material provided in this embodiment is mixed with artificial graphite at a mass ratio of 1:1 to obtain an active material. The negative electrode sheet is prepared and a coin cell is assembled using the same method as in Example 1.

[0198] Example 6

[0199] A silicon-based anode material comprises a silicon-carbon composite and a carbon layer and a conductive artificial SEI composite layer sequentially disposed on the silicon-carbon composite. The conductive artificial SEI composite layer is obtained by reacting styrene, acrylic acid, and double-bond modified carbon nanotubes. The preparation method of the silicon-based anode material differs from that of Example 1 only in that 0.2g of styrene and 1.8g of acrylic acid are used in step (3), while the types, amounts, preparation steps, and process parameters of other materials are the same as in Example 1, thus obtaining the silicon-based anode material.

[0200] The silicon-based negative electrode material provided in this embodiment is mixed with artificial graphite at a mass ratio of 1:1 to obtain an active material. The negative electrode sheet is prepared and a coin cell is assembled using the same method as in Example 1.

[0201] Example 7

[0202] A silicon-based anode material, differing from Example 1 in that it does not employ an ALD-like coating technology, is prepared using the same method as in Example 1 to obtain double-bond modified carbon nanotubes and an intermediate (i.e., a silicon-carbon composite with a surface carbon layer). 0.6 g of double-bond modified carbon nanotubes, 0.8 g of styrene, 1.2 g of acrylic acid, 0.5 g of sodium dodecylbenzenesulfonate, and 100 g of the intermediate are placed in 400 mL of deionized water. The mixture is stirred at 500 rpm, nitrogen gas is introduced, and the mixture is heated to 70°C and stirred for 0.5 h. 0.02 g of ammonium persulfate is added to the system, and the reaction is continued at 70°C for 6 h. The mixture is cooled to room temperature and dried in a forced-air drying oven at 120°C for 24 h to remove residual moisture. The material is then crushed, sieved, and demagnetized to obtain the silicon-based anode material.

[0203] The silicon-based negative electrode material provided in this embodiment is mixed with artificial graphite at a mass ratio of 1:1 to obtain an active material. The negative electrode sheet is prepared and a coin cell is assembled using the same method as in Example 1.

[0204] Comparative Example 1

[0205] Silicon-based anode materials and their preparation:

[0206] A silicon-based anode material includes a silicon-carbon composite and a carbon layer disposed on the silicon-carbon composite. The preparation method includes: placing 200g of silicon-carbon composite in a deposition furnace at 500°C, and forming a carbon layer on the silicon-carbon composite using the same method as in step (2) of Example 1, to obtain the silicon-based anode material.

[0207] Negative electrode sheet and its preparation:

[0208] The silicon-based anode material provided in this comparative example is mixed with artificial graphite at a mass ratio of 1:1 to obtain the active material. The active material, single-walled carbon nanotubes, thickener CMC, conductive agent Super P and binder SBR are mixed at a mass ratio of 87:1:2:3:7. Deionized water is added as a solvent, and the mixture is stirred under vacuum until the system is homogeneous to obtain the anode slurry. The anode slurry is uniformly coated on the copper foil of the anode current collector, transferred to a vacuum drying oven for drying, and then rolled and punched to obtain small discs, which are the anode sheets.

[0209] Battery manufacturing:

[0210] A coin cell was assembled using a lithium metal sheet as the counter electrode, following the same method as in Example 1.

[0211] Comparative Example 2

[0212] A silicon-based anode material includes a silicon-carbon composite and a carbon layer disposed on the silicon-carbon composite. The preparation method includes: placing 200g of silicon-carbon composite in a deposition furnace at 500°C, and forming a carbon layer on the silicon-carbon composite using the same method as in step (2) of Example 1, to obtain the silicon-based anode material.

[0213] The silicon-based anode material provided in this comparative example was mixed with artificial graphite at a mass ratio of 1:1 to obtain an active material. The anode sheet was then prepared and a coin cell was assembled using the same method as in Example 1.

[0214] Comparative Example 3

[0215] A silicon-based anode material comprises a silicon-carbon composite, a carbon layer and a conductive artificial SEI composite layer sequentially disposed on the silicon-carbon composite, wherein the conductive artificial SEI composite layer is prepared by styrene, acrylic acid, and carbon nanotubes. The preparation method of the silicon-based anode material is as follows:

[0216] (1) CVD method for coating carbon layer: 200g of silicon-carbon composite was placed in a deposition furnace at 500℃, protected by argon gas, and acetylene gas was introduced at 500℃ at a flow rate of 10L / min and a furnace pressure of 6MPa. After continuous gas supply for 4h, the mixture was cooled to room temperature, thereby forming a carbon layer on the silicon-carbon composite and obtaining an intermediate.

[0217] (2) Preparation of silicon-based anode material: Take 0.6g of carbon nanotubes, 100g of the intermediate obtained in step (1), 0.8g of styrene, 1.2g of acrylic acid, and 0.5g of sodium dodecylbenzenesulfonate, and place them in 400mL of deionized water. Disperse using a high-speed disperser at 3000 rpm for 3 hours. Reduce the speed to 500 rpm, introduce nitrogen gas, heat to 70℃, and continue stirring for 0.5h. Add 0.02g of ammonium persulfate to the system and continue stirring at 70℃ for 6h. After cooling to room temperature, atomize the dispersion into microdroplets using a high-speed centrifugal atomizer at 12000 rpm, and then instantly dry it with hot air at 200℃. Collect the powder, sieve it, and demagnetize it to obtain the silicon-based anode material.

[0218] The silicon-based anode material provided in this comparative example was mixed with artificial graphite at a mass ratio of 1:1 to obtain an active material. The anode sheet was then prepared and a coin cell was assembled using the same method as in Example 1.

[0219] Comparative Example 4

[0220] A silicon-based anode material comprises a silicon-carbon composite and a carbon layer and a conductive artificial SEI composite layer sequentially disposed on the silicon-carbon composite. The conductive artificial SEI composite layer is prepared by a styrene-acrylic acid copolymer and double-bond modified carbon nanotubes. The preparation method of the silicon-based anode material is as follows:

[0221] (1) Preparation of styrene-acrylic acid copolymer:

[0222] 4 g of styrene and 6 g of acrylic acid were placed in 1500 mL of deionized water, nitrogen gas was introduced, and the mixture was stirred at room temperature for 0.5 h. The mixture was then heated to 70 °C and stirred for another 0.5 h. 0.1 g of ammonium persulfate was added to the system, and the reaction was continued at 70 °C with stirring for 6 h. The mixture was then evacuated for 0.5 h, restored to normal pressure, and cooled to room temperature to obtain an aqueous solution of the styrene-acrylic acid copolymer. The solid content was tested to be 7.5%.

[0223] (2) Preparation of silicon-based anode materials:

[0224] Double-bond modified carbon nanotubes and intermediates were obtained using the same method as in Example 1. 0.6 g of double-bond modified carbon nanotubes, 100 g of the intermediate, 0.5 g of sodium dodecylbenzenesulfonate, and 26.7 g of the prepared styrene-acrylic acid copolymer aqueous solution (containing 2 g of polymer) were placed in 400 mL of deionized water and dispersed using a high-speed disperser at 3000 rpm for 3 hours. The dispersion speed was then reduced to 500 rpm and stirred at 70°C for 6 hours. After cooling to room temperature, the dispersion was atomized into microdroplets using a high-speed centrifugal atomizer at 12000 rpm. The microdroplets were then instantaneously dried with hot air at 200°C, and the collected powder was sieved, demagnetized, and the silicon-based anode material was obtained.

[0225] The silicon-based anode material provided in this comparative example was mixed with artificial graphite at a mass ratio of 1:1 to obtain an active material. The anode sheet was then prepared and a coin cell was assembled using the same method as in Example 1.

[0226] Comparative Example 5

[0227] A silicon-based anode material comprises a silicon-carbon composite and a carbon layer and a conductive artificial SEI composite layer sequentially disposed on the silicon-carbon composite. The conductive artificial SEI composite layer is prepared by using styrene, acrylic acid, and double-bond modified carbon nanotubes. The preparation method of the silicon-based anode material is as follows:

[0228] Double-bond modified carbon nanotubes and an intermediate (i.e., a silicon-carbon composite with a surface carbon layer) were obtained using the same method as in Example 1. Then, 0.6 g of the double-bond modified carbon nanotubes, 0.8 g of styrene, 1.2 g of acrylic acid, and 0.5 g of sodium dodecylbenzenesulfonate were placed in 400 mL of deionized water. The mixture was dispersed using a high-speed disperser at 3000 rpm for 3 hours. The speed was reduced to 500 rpm, nitrogen gas was introduced, and the mixture was heated to 70°C and stirred for another 0.5 hours. 0.02 g of ammonium persulfate was added to the system, and the reaction was continued at 70°C for 6 hours. Then, 100 g of the intermediate was added to the system, and the mixture was stirred for 1 hour. The mixture was cooled to room temperature, and the dispersion was atomized into microdroplets using a high-speed centrifugal atomizer at 12000 rpm. The microdroplets were then instantaneously dried with hot air at 200°C, the collected powder was sieved, demagnetized, and the silicon-based anode material was obtained.

[0229] The silicon-based anode material provided in this comparative example was mixed with artificial graphite at a mass ratio of 1:1 to obtain an active material. The anode sheet was then prepared and a coin cell was assembled using the same method as in Example 1.

[0230] Comparative Example 6

[0231] A silicon-based anode material differs from Example 1 in that it does not include a carbon layer. Instead, the silicon-based anode material comprises a silicon-carbon composite and a conductive artificial SEI composite layer disposed thereon. The conductive artificial SEI composite layer is prepared using styrene, acrylic acid, and double-bond modified carbon nanotubes. The preparation method of the silicon-based anode material differs from Example 1 only in that step (2) is omitted, and the intermediate used in step (3) is replaced with an equal mass of silicon-carbon composite. The types, amounts, preparation steps, and process parameters of other materials are the same as in Example 1, resulting in the silicon-based anode material.

[0232] The silicon-based anode material provided in this comparative example was mixed with artificial graphite at a mass ratio of 1:1 to obtain an active material. The anode sheet was then prepared and a coin cell was assembled using the same method as in Example 1.

[0233] Performance testing:

[0234] (1) Basic performance testing of silicon-based anode materials

[0235] The surface morphology of the silicon-based anode material was tested using scanning tunneling electron microscopy. The morphology of the silicon-based anode material provided in Example 1 is shown in Figure 1. Filamentous carbon nanotubes are completely integrated on the silicon surface, and the carbon nanotubes are tightly attached to the surface of the carbon-coated silicon-based anode material in a network form.

[0236] The median particle size (D) of silicon-based anode materials was measured using a Malvern laser particle size analyzer. 50 (Particle size), the test results are detailed in Table 1.

[0237] The powder resistance of silicon-based anode materials was tested using a powder resistance tester. The test results are detailed in Table 1.

[0238] (2) Morphology test of negative electrode sheet

[0239] The surface morphology of the negative electrode sheet was tested using scanning tunneling electron microscopy. The scanning electron microscope image of the negative electrode sheet made of the silicon-based negative electrode material provided in Example 1 is shown in Figure 2. The filamentous carbon nanotubes are completely integrated on the silicon surface. The carbon nanotubes are tightly and stably coated on the surface of the silicon-based negative electrode material in a network form. There are no carbon nanotubes distributed on the graphite surface, so that the carbon nanotubes can effectively play the role of suppressing the volume expansion of silicon and ensuring the electrical contact of the silicon-based material during the volume expansion and contraction process.

[0240] Figure 3 shows a scanning electron microscope image of the anode sheet made of the silicon-based anode material provided in Comparative Example 1. The filamentous carbon nanotubes are evenly distributed on the surface of graphite and silicon, which not only affects the performance of carbon nanotubes, but also leads to a greater amount of carbon nanotubes used, resulting in waste and increased costs.

[0241] (2) Battery performance testing

[0242] Initial charge / discharge cycle: 0.1C-0.02C / 0.1C, voltage range 0.005V-1.5V, to obtain the battery's first-week lithium stripping capacity. 2-30 cycle charge / discharge cycle: 0.2C-0.02C / 0.2C, voltage range 0.005V-1.5V, to perform a 30-cycle test on the battery. Calculate the capacity retention rate after the cycle test; disassemble the coin cell, measure the thickness of the negative electrode plate under full charge, and calculate the negative electrode's full-charge expansion rate.

[0243] 30-week cycle capacity retention = 30-week cycle delithiation capacity / 1-week delithiation capacity × 100%; 10-week electrode expansion = (electrode thickness after 10 cycles - initial electrode thickness) / initial electrode thickness × 100%.

[0244] The test results are shown in Table 1:

[0245] Table 1

[0246] As shown in Table 1, the silicon-based anode material provided in this application comprises a three-layer structure consisting of a silicon-based material, a carbon layer, and a conductive artificial SEI composite layer. By combining reactive conductive materials (reactive functional group modified carbon nanotubes) with in-situ polymerization coating technology, the carbon nanotubes can be uniformly and tightly coated on the surface of the silicon anode, preventing them from detaching during the fabrication of the anode sheet and battery. Furthermore, this effectively suppresses the volume expansion of the silicon-based material and improves the battery's cycle performance. Simultaneously, the introduction of the polymer and nano-conductive material composite layer does not significantly increase the powder resistivity of the silicon anode material, thus avoiding any adverse effects on the material.

[0247] As shown in Comparative Example 1, based on silicon-carbon material with surface carbon coating, the battery retains 91.1% capacity after 30 cycles when 1% carbon nanotubes are added to the negative electrode material composition. Examples 1-6 show that when the silicon-based negative electrode material is used to prepare the negative electrode sheet, the battery retains 91.2%-94.5% capacity after 30 cycles without any additional carbon nanotubes. This indicates that the introduction of the conductive artificial SEI composite layer in this application achieves a better effect than adding carbon nanotubes, more effectively suppressing volume expansion and resulting in superior battery cycle performance. The mechanism lies in the fact that in Comparative Example 1, where carbon nanotubes are added, most of the carbon nanotubes are distributed on the surface of graphite, with only a small portion adhering to the silicon surface. Because carbon nanotubes only function on the silicon surface, the distribution of carbon nanotubes in Comparative Example 1 results in significant waste. In the silicon-based negative electrode materials of Examples 1-6 of this application, all carbon nanotubes are concentrated on the surface of the silicon-based material, maximizing the role of the carbon nanotubes. Compared to Comparative Example 1, the total amount of carbon nanotubes used in Examples 1-5 was reduced by more than 50%, which greatly reduced the battery manufacturing cost and achieved more significant effects in suppressing expansion and improving cycle performance.

[0248] As can be seen from Examples 1, 2, and 3, as the carbon nanotube content of the conductive artificial SEI composite layer increases, the battery's 30-cycle capacity retention rate also improves. After reaching a certain level, further increasing the carbon nanotube content does not result in significant performance changes.

[0249] As can be seen from Examples 1 and 4 and 5, too much or too little polymer in the conductive artificial SEI composite layer will affect the performance of the material. Too little polymer is not conducive to the stability of the coating layer, while too much coating will hinder ion transport and affect the capacity of the silicon material.

[0250] As can be seen from Examples 1 and 6, the styrene-based structural units in the polymer play a key role. Reducing the proportion of styrene will affect the stability of the coating layer and the cycling performance and volume expansion of the silicon material. The mechanism is that the interaction between the benzene rings of the polymer side chain and the carbon layer increases the bonding force between the coating layer and the intermediate carbon layer.

[0251] As can be seen from Examples 1 and 7, the ALD-like uniform coating technology of this application is a more preferred solution. Products made without this technology exhibit relatively larger expansion and decreased cycle performance. This is because the uniformity of the surface conductive artificial SEI composite layer coating decreases in products prepared without this technology.

[0252] A comparison of Example 1, Comparative Example 1, and Comparative Example 2 shows that carbon nanotubes are crucial for the performance of silicon-based anode materials. Whether carbon nanotubes are added externally during battery fabrication or integrated onto the silicon material surface in the form of a conductive artificial SEI composite layer, the cycle performance of silicon-carbon anodes can be significantly improved. Compared to the external addition of carbon nanotubes in Comparative Example 1, the silicon-based anode material with a conductive artificial SEI composite layer designed in this application achieves superior suppression of expansion and improved cycle performance while reducing the amount of carbon nanotubes used and saving costs.

[0253] The comparisons of Examples 1, 3, 4, and 5 show that modification of the double-bond functional groups on the carbon nanotube surface and in-situ polymerization are both essential. The double bonds introduced by surface modification of carbon nanotubes endow them with reactivity, enabling them to chemically bond with polymers. If carbon nanotubes are not functionalized, their stability on the silicon anode surface is poor, and they are prone to detachment, failing to achieve the expected improvement in cycle life for silicon materials. If carbon nanotubes and polymers are directly mixed and then coated onto the silicon-based material surface without in-situ polymerization, the coating layer stability is also poor, resulting in poor cycle performance of the silicon-based anode material. If polymers are grown on the surface of carbon nanotubes without forming chemical bonds, or if in-situ polymerization is not used and the polymer is directly coated onto the silicon-carbon surface, the coating layer stability is poor, easily detaches, and fails to achieve the desired effect.

[0254] As can be seen from Example 1 and Comparative Example 6, the presence of the intermediate carbon layer plays a crucial role in the silicon-based anode material provided in this application; without the carbon layer, the cycle performance of the silicon anode decreases significantly, and the electrode expansion increases.

[0255] The above results demonstrate that the silicon-based anode material with a surface-modified conductive artificial SEI composite layer designed in this application can suppress the full-charge expansion of silicon materials and reduce the pulverization of the anode sheet after multiple cycles. The cycle performance of batteries using this silicon-based anode material will be significantly improved. Compared to ordinary anode materials, the silicon-based anode material with a conductive artificial SEI composite layer provided in this application has lower volume expansion and higher cycle capacity retention. Simultaneously, it can integrate carbon nanotubes onto the surface of the silicon anode, eliminating the need for additional carbon nanotubes and greatly reducing the amount of carbon nanotubes used. The preparation method is simple, energy-efficient, low-cost, and environmentally friendly, facilitating large-scale production.

[0256] The applicant declares that this application illustrates the silicon-based anode material, its preparation method, and its application through the above embodiments. However, this application is not limited to the above process steps, meaning that this application does not necessarily rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to this application, equivalent substitutions of the raw materials used, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this application.

Claims

1. A silicon-based anode material, wherein, The silicon-based anode material includes a silicon-based material and a carbon layer and a conductive artificial SEI composite layer disposed on the silicon-based material, wherein the carbon layer is located between the silicon-based material and the conductive artificial SEI composite layer; the conductive artificial SEI composite layer is obtained by reacting a reactive precursor with a reactive conductive material.

2. The silicon-based anode material according to claim 1, wherein, The silicon-based anode material satisfies at least one of the following conditions: (1) The conductive material in the conductive artificial SEI composite layer is at least partially covered by the products of the reactive precursor reaction; and (2) The conductive material in the conductive artificial SEI composite layer is tightly attached to the surface of the carbon layer.

3. The silicon-based anode material according to claim 1 or 2, wherein, The silicon-based anode material satisfies at least one of the following conditions: (1) The D of the silicon-based anode material 50 The particle size is 0.2-20.0 μm; (2) The specific surface area of ​​the silicon-based anode material is 0.1-20.0 m². 2 / g; and (3) The resistivity of the silicon-based anode material is 0.5-15.0 Ω·cm.

4. The silicon-based anode material according to any one of claims 1-3, wherein, The silicon-based material includes any one or a combination of at least two of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy; Preferably, the silicon-based material D 50 The particle size is 0.2-20.0 μm; as well as Preferably, the specific surface area of ​​the silicon-based material is 0.1-20.0 m². 2 / g.

5. The silicon-based anode material according to any one of claims 1-4, wherein, The thickness of the carbon layer is 1.0-30.0 nm; Preferably, the carbon layer comprises 0.01%-10.00% of the silicon-based material by mass, which is 100% of the total mass. Preferably, the mass of the conductive artificial SEI composite layer is 0.01%-15.00% based on the total mass of the silicon-based material and the carbon layer as 100%. Preferably, the mass of the reactive precursor is 0.01%-10.00% based on the total mass of the silicon-based material and the carbon layer being 100%. Preferably, the reactive precursor comprises a monomer containing a double bond, and the monomer containing a double bond is further preferably any one or a combination of at least two of the following: a cyano monomer containing a double bond, an acidic monomer containing a double bond, a carboxylic acid ester monomer containing a double bond, an amide monomer containing a double bond, a hydroxyl monomer containing a double bond, an aromatic vinyl monomer, an aliphatic conjugated diene monomer, a fluorinated olefin monomer, and a vinyl nitrogen heterocyclic monomer. Preferably, the mass percentage of aromatic vinyl monomers in the double-bonded monomers is ≤80%, more preferably 30%-60%; Preferably, the reactive conductive material comprises 0.01%-10.00% of the total mass of the silicon-based material and the carbon layer, which is 100% of the total mass. Preferably, the reactive conductive material comprises any one or a combination of at least two of the following conductive materials modified with reactive functional groups: conductive graphite, carbon black, Ketjen black, conductive carbon black Super P, carbon nanofibers, single-walled carbon nanotubes, multi-walled carbon nanotubes, oligo-walled carbon nanotubes, and graphene. Preferably, the particle size of the conductive graphite, carbon black, Ketjen black and conductive carbon black Super P is independently 10.0-1000.0 nm; Preferably, the diameters of the carbon nanotubes, single-walled carbon nanotubes, multi-walled carbon nanotubes, and oligo-walled carbon nanotubes are each independently 1.0-60.0 nm. Preferably, the lengths of the carbon nanotubes, single-walled carbon nanotubes, multi-walled carbon nanotubes, and oligo-walled carbon nanotubes are each independently 0.1-80.0 μm; as well as Preferably, the specific surface area of ​​the conductive material is 50-2000 m². 2 / g.

6. A method for preparing a silicon-based anode material as described in any one of claims 1-5, wherein, The preparation method includes: (1) A carbon layer is deposited on a silicon-based material to obtain a carbon-coated silicon-based material; and (2) The carbon-coated silicon-based material reacts with a reactive precursor and a reactive conductive material to obtain the silicon-based anode material.

7. The preparation method according to claim 6, wherein, The method for setting the carbon layer includes chemical vapor deposition; Preferably, the method for preparing the reactive conductive material includes: activating the conductive material in an acidic activating solution to obtain an activated conductive material; and subjecting the activated conductive material to condensation modification to obtain a reactive conductive material.

8. The preparation method according to claim 6 or 7, wherein, The reaction described in step (2) is carried out under thermally initiated conditions; Preferably, the reaction is carried out in the presence of an initiator; Preferably, the initiator comprises ≤2% of the mass of the reactive precursor, which is 100% of the total mass. Preferably, the initiator is a free radical initiator, and more preferably any one or a combination of at least two of persulfate, azo initiators, peroxide, and redox initiators; Preferably, the reaction temperature in step (2) is 50-200℃. Preferably, the reaction time in step (2) is 0.5-24 hours; Preferably, the reaction method in step (2) includes uniform coating by atomic layer deposition, wherein the uniform coating method includes: reacting carbon-coated silicon-based material, reactive precursor, and reactive conductive material in the presence of a solvent to obtain a dispersion; and drying the dispersion to obtain the silicon-based anode material. Preferably, the solvent includes water and / or an organic solvent; Preferably, the reaction is carried out in the presence of a surfactant; Preferably, the surfactant comprises any one or a combination of at least two of sodium dodecylbenzenesulfonate, stearic acid, oleic acid, lauric acid, polyethylene glycol, polyvinyl alcohol, 15-crown-5, 18-crown-6 and tetrabutylammonium bromide; Preferably, based on the mass of the carbon-coated silicon-based material being 100%, the mass of the surfactant is 0.01%-5.00%; Preferably, the drying method includes: dispersing the dispersion into microdroplets by high-speed rotating shear or high-speed airflow impact, and drying under heat flow conditions to obtain the silicon-based anode material; and Preferably, the drying temperature is 50-400°C.

9. An apparatus for preparing a silicon-based anode material, wherein, The preparation apparatus includes a first reaction device, a second reaction device, and a drying device connected in sequence; the silicon-based anode material as described in any one of claims 1-5 is prepared by the preparation apparatus. Preferably, the first reaction apparatus includes a chemical vapor deposition apparatus; Preferably, the second reaction apparatus includes a shear dispersion device, and more preferably any one or a combination of at least two of a sand mill, ball mill, high-speed disperser, double planetary mixer, and homogenizer; and Preferably, the drying device includes any one or a combination of at least two of the following: spray drying device, fluidized bed, airflow flash dryer, rotary flash dryer, and rotary kiln.

10. A negative electrode material composition, wherein, The negative electrode material composition comprises a combination of an active material, a binder, and a conductive material, wherein the active material comprises a silicon-based negative electrode material as described in any one of claims 1-5.

11. A negative electrode plate, wherein, The negative electrode sheet includes a current collector and a coating disposed on the current collector, wherein the material of the coating includes the negative electrode material composition as described in claim 10.

12. An electrochemical energy storage device, wherein, The electrochemical energy storage device includes at least one of the silicon-based negative electrode material as described in any one of claims 1-5, the negative electrode material composition as described in claim 10, and the negative electrode sheet as described in claim 11; Preferably, the electrochemical energy storage device includes any one of lithium-ion batteries, sodium-ion batteries, supercapacitors, and solid-state batteries.

Images