CN116525798A - Nanoscale silicon-based composite anode material and preparation method thereof - Google Patents
Nanoscale silicon-based composite anode material and preparation method thereof Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 45
- 239000002131 composite material Substances 0.000 title claims abstract description 38
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 32
- 239000010703 silicon Substances 0.000 title claims abstract description 31
- 239000010405 anode material Substances 0.000 title claims abstract description 20
- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- 239000000243 solution Substances 0.000 claims abstract description 68
- 239000002245 particle Substances 0.000 claims abstract description 64
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 60
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 55
- 239000011258 core-shell material Substances 0.000 claims abstract description 51
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 50
- 229910052751 metal Inorganic materials 0.000 claims abstract description 45
- 239000008367 deionised water Substances 0.000 claims abstract description 44
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 44
- 239000000203 mixture Substances 0.000 claims abstract description 42
- 238000003756 stirring Methods 0.000 claims abstract description 42
- 239000012046 mixed solvent Substances 0.000 claims abstract description 35
- 239000006087 Silane Coupling Agent Substances 0.000 claims abstract description 33
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 29
- 238000000034 method Methods 0.000 claims abstract description 28
- 238000002156 mixing Methods 0.000 claims abstract description 25
- 239000000126 substance Substances 0.000 claims abstract description 24
- 239000002184 metal Substances 0.000 claims abstract description 22
- 239000005543 nano-size silicon particle Substances 0.000 claims abstract description 17
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- 239000007787 solid Substances 0.000 claims description 13
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- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 8
- 239000002041 carbon nanotube Substances 0.000 claims description 8
- 229910021389 graphene Inorganic materials 0.000 claims description 8
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 8
- 238000001694 spray drying Methods 0.000 claims description 8
- 238000001291 vacuum drying Methods 0.000 claims description 8
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- 230000008020 evaporation Effects 0.000 claims description 7
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- 238000004108 freeze drying Methods 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 4
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 4
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- 238000001132 ultrasonic dispersion Methods 0.000 claims description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- -1 polytetrafluoroethylene Polymers 0.000 claims description 3
- 238000000527 sonication Methods 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 5
- 239000003575 carbonaceous material Substances 0.000 description 21
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 14
- 229910001416 lithium ion Inorganic materials 0.000 description 14
- 238000009210 therapy by ultrasound Methods 0.000 description 12
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- 238000012360 testing method Methods 0.000 description 8
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 6
- 229910052744 lithium Inorganic materials 0.000 description 6
- 230000002441 reversible effect Effects 0.000 description 6
- 238000003860 storage Methods 0.000 description 6
- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 5
- 239000011812 mixed powder Substances 0.000 description 5
- 239000002210 silicon-based material Substances 0.000 description 5
- 235000010413 sodium alginate Nutrition 0.000 description 5
- 229940005550 sodium alginate Drugs 0.000 description 5
- 239000000661 sodium alginate Substances 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
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- 239000011856 silicon-based particle Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
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- 238000009831 deintercalation Methods 0.000 description 2
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- 208000032953 Device battery issue Diseases 0.000 description 1
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
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- 150000003839 salts Chemical class 0.000 description 1
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- 230000007704 transition Effects 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/626—Metals
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
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- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention discloses a preparation method of a nanoscale silicon-based composite anode material, which comprises the following steps: mixing nano silicon powder and a metal simple substance to obtain a mixture A; mixing an organic adhesive with an absolute ethyl alcohol solution to obtain a mixed solvent B; mixing the mixture A with the mixed solvent B to obtain a mixed solution; ball-milling and dispersing the mixed solution, stirring and evaporating in a water bath to obtain Si@ metal nano particles C; putting Si@ metal nano particles C into absolute ethyl alcohol for dispersion; adding deionized water and a silane coupling agent into the solution, stirring and standing at room temperature, and carrying out suction filtration and washing to obtain a particle product; adding the particle product into deionized water to obtain Si@ metal@coupling agent solution D; and (3) dropwise adding the carbon source solution into the solution D, stirring and ultrasonically drying to obtain the Si@ metal@carbon composite material with the core-shell structure. The silicon-based composite anode material prepared by the method solves the problems of material expansion, unstable SEI film, low coulombic efficiency, poor electronic conductivity and the like.
Description
Technical Field
The invention relates to the technical field of lithium ion battery anode materials, in particular to a nanoscale silicon-based composite anode material and a preparation method thereof.
Background
In the 21 st century, lithium ion batteries have gained weight in the global market. The anode and cathode materials are key factors for the stable operation of the lithium ion battery, wherein the ideal anode has the following characteristics: low working potential and high theoretical specific capacity, higher coulombic efficiency, high ionic and electronic conductivity, excellent structural stability, small volume change of electrode materials in the lithiation/delithiation process, good chemical stability, no reaction with lithium salt, no dissolution in electrolyte, low cost, safety and environmental friendliness.
Si is inferior to oxygen element in storage in crust, is nontoxic, pollution-free and convenient for large-scale production, and theoretically has lithium storage capacity of 3579mAhg at room temperature -1 The volume capacity is 8322mAhcm -3 The characteristics are known as the anode material with the most potential of the lithium battery. However, the volume expansion of Si after complete lithiation can cause cracking and stripping of the electrode material, resulting in failure of electrical contact between the silicon substrate and the conductive network and an increase in the degree of structural irreversibility. In addition, poor electron conductivity and ion diffusion coefficient can cause serious polarization phenomenon of the electrode during circulation, so that irreversible deintercalation of lithium ions is aggravated, and battery failure is accelerated. The SEI film is unstable during cycling, and the SEI layer may have an increased thickness or be broken, thereby causing a decrease in diffusion efficiency of lithium ions. Two main strategies for improving the electrochemical performance of a silicon-based anode material are provided, one is to prepare a novel silicon nano structure, and the main strategies are to improve the breaking bearing capacity of the anode, enhance the ion transmission efficiency and ensure the stability of an SEI film; secondly, constructing a composite materialThe material is used for controlling the volume expansion of a base material and improving the stability of the SEI film.
Although some documents report methods for improving the electrochemical properties of silicon-based materials, the volume expansion of the silicon-based materials prepared by the methods is still quite obvious and the stability of the material properties is still to be improved.
Disclosure of Invention
The invention aims to provide a nanoscale silicon-based composite anode material and a preparation method thereof, which are used for solving at least one of the problems in the prior art.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
according to an aspect of the present invention, there is provided a method for preparing a nanoscale silicon-based composite anode material, the method comprising:
step S1: mixing nano silicon powder and a metal simple substance in proportion to obtain a mixture A;
step S2: mixing an organic adhesive and an absolute ethyl alcohol solution in proportion to obtain a mixed solvent B;
step S3: uniformly mixing the mixture A and the mixed solvent B to ensure that the mixed solvent B completely coats the mixture A to obtain a mixed solution;
step S4: ball-milling and dispersing the mixed solution, then performing stirring water bath evaporation until only solid particles exist, and obtaining Si@ metal nano particles C with a core-shell structure;
step S5: putting a preset amount of Si@ metal nano particles C into absolute ethyl alcohol to be uniformly dispersed;
step S6: adding deionized water and a silane coupling agent into the solution obtained in the step S5, stirring at room temperature, standing, and then carrying out suction filtration and washing to obtain a particle product;
step S7: adding the particle product obtained in the step S6 into deionized water to obtain a core-shell structure Si@ metal@coupling agent solution D connected with a silane coupling agent;
step S8: and (3) dripping the pre-prepared carbon source solution into the solution D in the step (S7), stirring and ultrasonically drying to obtain the core-shell structure Si@ metal@carbon composite material to be prepared.
According to one embodiment, in the step S1, the size of the nano silicon powder is 30-100nm, the metal simple substance is selected from one or more of Ag, au, V, ti, and the mass ratio of the nano silicon powder to the metal simple substance is 1:1-1:5.
According to one embodiment, in step S2, the organic adhesive is one or more selected from polyacrylonitrile, polyvinyl alcohol, polyamide and polytetrafluoroethylene, and the volume ratio of the organic adhesive to the absolute ethyl alcohol is 1:3-1:7.
According to one embodiment, in step S3, the mixture A and the mixed solvent B are mixed and then subjected to ultrasonic treatment for 20-60min, and the ultrasonic temperature is controlled to be not higher than 60 ℃.
According to one embodiment, in step S4, the ball milling dispersion time is 20-80min, the stirring speed is 300-600 rpm, and the water bath evaporation temperature is 80-100 ℃.
According to one embodiment, in step S5, the volume ratio of absolute ethanol to Si@ metal nanoparticles C is 2:1-20:1, and the ultrasonic dispersion is performed for 30-120min.
According to one embodiment, in step S6, deionized water and silane coupling agent are used in amounts such that the absolute ethyl alcohol: deionized water: the volume ratio of the silane coupling agent is 5:5:1-20:20:1, stirring is carried out for 4-8 hours, standing is carried out for 2-6 hours, the deionized water and the silane coupling agent are added dropwise and are rapidly stirred, and the stirring speed is 300-700 rpm.
According to one embodiment, in step S7, the particulate product is added to deionized water and then dispersed ultrasonically, the volume ratio of the particulate product to deionized water being 1:100-1:20.
According to one embodiment, in step S8, the carbon source is selected from one or more of carbon nanotubes, graphene and graphite, and is configured into a carbon source solution, the solvent is absolute ethanol or deionized water, the concentration is 1g/L-3g/L, the molar ratio of the core-shell structure Si@ metal@coupling agent particles to the carbon source in the solution D is controlled to be 1:20-1:8, the stirring time is 2-6h, the ultrasonic time is 30-120min, and the drying treatment is spray drying, freeze drying or vacuum drying.
According to another aspect of the present invention, there is provided a nanoscale silicon-based composite anode material prepared according to the method described above.
Due to the adoption of the technical scheme, the first-stage flue and the system matched with the molten salt chlorination furnace have at least one of the following beneficial effects compared with the prior art:
(1) The ionic/electronic migration channel is provided, the capacity of the composite electrode under high-rate current density is favorably exerted, meanwhile, the direct contact between silicon particles and electrolyte is avoided, the integrity of an SEI film is favorably maintained, and the coulomb efficiency and the circulation capacity of the composite material are remarkably improved;
(2) The outer wrapping of the metal particles and the carbon composite core-shell structure and the two-dimensional or three-dimensional material can effectively inhibit the transitional expansion of the silicon material in the circulation process, and good contact between the electrode material and the electric current collector is maintained;
(3) The metal shell layer on the surface of the silicon nano-particles enhances the electronic conductivity between the silicon particles and the carbon material, and meanwhile, the carbon material is coated to effectively prevent the aggregation of the Si@ metal nano-particles, so that a sufficient space is provided for the expansion support of the matrix in the lithiation process;
(4) The carbon material constructed three-dimensional conductive network with hardness and softness is beneficial to overcoming the dynamic constraint in the discharge process, improving the lithium ion intercalation depth and reducing the concentration difference of lithium ions on the particle surface, so that the composite electrode shows the optimal reversible capacity and good dynamic reaction;
(5) The inner core is connected to one end of the silane coupling agent, the carbon material is connected to the other end of the silane coupling agent, and chemical bond action is generated between the silane coupling agent and the silicon inner core and between the carbon material and the silicon inner core, so that the connection strength between the carbon material on the outer layer and the silicon inner core is enhanced, the carbon material can be firmly wrapped on the surface of the metal particles without falling off during the expansion and contraction of silicon, meanwhile, the supporting effect can be achieved, and the stability of the SEI film is improved.
Drawings
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate the invention and together with the description serve to explain, without limitation, the invention. In the drawings:
FIG. 1 is a schematic diagram of a Si@ metal/carbon composite material having a core-shell structure according to the present invention;
fig. 2 is a flowchart of a method of preparing a nanoscale silicon-based composite anode material according to an embodiment of the present invention.
Detailed Description
Specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.
Furthermore, references herein to "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.
Fig. 1 shows a schematic diagram of a Si@ metal/carbon composite material having a core-shell structure according to the present invention, and the improved concept of the present invention will be described with reference to the drawing. As shown in the figure, the nano silicon 1 is used as the inner core, the outer layer of the nano silicon 1 is coated with a layer of nano metal simple substance 2 with high conductivity, such as Ag, au, V, ti, and the like, and the metal simple substance layer 2 can effectively inhibit the transition expansion of the silicon material in the cyclic process of the composite material and can also enhance the electronic conductivity between the silicon particles 1 and the carbon material 4. The metal simple substance layer 2 is also coated with a carbon material 4 capable of forming a two-dimensional or three-dimensional conductive network, and the carbon material 4 can be a carbon material with good conductivity, such as a carbon nanotube, graphene, graphite and the like. The metal simple substance layer 2 and the carbon material 4 provide a rapid migration channel for ions/electrons, are beneficial to the capacity exertion of the composite electrode under high-rate current density, simultaneously avoid the direct contact of silicon particles and electrolyte, are beneficial to maintaining the integrity of an SEI film, and remarkably improve the coulomb efficiency and the circulation capacity of the composite material. And moreover, the carbon material 4 is wound on the outer layer in a two-dimensional or three-dimensional structure, so that the transitional expansion of the silicon material in the circulation process can be effectively inhibited, the good contact between the electrode material and the electric current collector is kept, the rigid-flexible three-dimensional conductive network constructed by the carbon material 4 is beneficial to overcoming the dynamic constraint in the discharge process, the lithium ion intercalation depth is improved, the concentration difference of lithium ions on the particle surface is reduced, and the composite electrode shows the optimal reversible capacity and good dynamic reaction. Meanwhile, the carbon material 4 is coated to effectively prevent the aggregation of Si@ metal nano particles, so that a sufficient space is provided for the expansion and support of the matrix in the lithiation process. In addition, the invention also adopts the silane coupling agent 3 as a connecting structure for connecting the carbon material 4 and the nano silicon 1, and utilizes the chemical bond effect of the silane coupling agent, the silicon inner core and the carbon material, thereby enhancing the connection strength between the outer carbon material and the silicon inner core, ensuring that the carbon material can still be firmly wrapped on the surface of the metal particles without falling off during the expansion and contraction of the silicon, and improving the stability of the SEI film.
Fig. 2 is a flowchart of a method of preparing a nanoscale silicon-based composite anode material according to an embodiment of the present invention. The preparation method of the nanoscale silicon-based composite anode material is described in detail below with reference to the figure.
The preparation method of the nanoscale silicon-based composite anode material generally comprises the following steps:
step S1: mixing nano silicon powder and a metal simple substance in proportion to obtain a mixture A;
step S2: mixing an organic adhesive and an absolute ethyl alcohol solution in proportion to obtain a mixed solvent B;
step S3: uniformly mixing the mixture A and the mixed solvent B to ensure that the mixed solvent B completely coats the mixture A to obtain a mixed solution;
step S4: ball-milling and dispersing the mixed solution, then performing stirring water bath evaporation until only solid particles exist, and obtaining Si@ metal nano particles C with a core-shell structure;
step S5: putting a preset amount of Si@ metal nano particles C into absolute ethyl alcohol to be uniformly dispersed;
step S6: adding deionized water and a silane coupling agent into the solution obtained in the step S5, stirring at room temperature, standing, and then carrying out suction filtration and washing to obtain a particle product;
step S7: adding the particle product obtained in the step S6 into deionized water to obtain a core-shell structure Si@ metal@coupling agent solution D connected with a silane coupling agent;
step S8: and (3) dripping the pre-prepared carbon source solution into the solution D in the step (S7), stirring and ultrasonically drying to obtain the core-shell structure Si@ metal@carbon composite material to be prepared.
The specific operation of each step will be described in detail.
In the step S1, the size of the nano silicon powder is preferably 30-100nm, and the metal simple substance is selected from one or more of metal simple substances with high conductivity, such as Ag, au powder, V powder and Ti powder, and the mass ratio of the nano silicon powder to the metal simple substance is 1:1-1:5. The particle size of the metal simple substance is smaller than that of the silicon simple substance, and the metal simple substance and the silicon simple substance are placed into a beaker to be mixed, so that the mixture A is obtained.
In step S2, the organic adhesive is selected from one or more of Polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyamide (PI), polytetrafluoroethylene (PTFE). The volume ratio of the organic adhesive to the absolute ethyl alcohol is 1:3-1:7. Mixing the two in proportion to obtain the mixed solvent B. The mixed solvent B is a dispersion medium of the mixture A, so that two particles in the mixture A are uniformly adhered together, and a Si@ metal nanoparticle C core-shell structure is formed.
In step S3, the mixture A and the mixed solvent B are mixed and then are subjected to ultrasonic treatment for 20-60min, and the ultrasonic temperature is controlled to be not higher than 60 ℃. The volume ratio of the mixture A to the mixed solvent B is not particularly required, but the mixed solvent B is required to be satisfied, the mixture A can be completely coated by the mixed solvent B, solid particles are uniformly mixed in the solvent by ultrasonic treatment for 20-60min, the ultrasonic temperature is controlled to be not higher than 60 ℃, and the solvent is prevented from volatilizing too quickly.
In the step S4, the mixed solution obtained in the step S3 is subjected to ball milling and dispersing for 20-80min, then stirred water bath evaporation is carried out, the stirring speed is 300-600 r/min, the water bath evaporation temperature is 80-100 ℃, and the mixture is evaporated until only solid particles exist, so as to obtain Si@ metal nano particles C with a core-shell structure. The Si@ metal nanoparticle C with the core-shell structure can be Si@Ag, si@Au, si@V and Si@Ti.
In step S5, a predetermined amount of Si@ metal nanoparticles C are put into absolute ethanol to be uniformly dispersed. The volume ratio of the absolute ethyl alcohol to the Si@ metal nano particles C is 2:1-20:1, and the ultrasonic dispersion is carried out for 30-120min until the dispersion is uniform.
In step S6, deionized water and a silane coupling agent are added to the solution obtained in step S5, and the amounts of deionized water and the silane coupling agent satisfy the absolute ethyl alcohol: deionized water: the silane coupling agent is stirred for 4-8 hours at room temperature in a volume ratio of 5:5:1-20:20:1, is kept stand for 2-6 hours, and is filtered and washed by suction to obtain a granular product. The deionized water and the silane coupling agent are added dropwise and are rapidly stirred, and the stirring speed is 300-700 rpm, so that the silane coupling agent is uniformly dispersed and prevented from being coagulated. The silane coupling agent is selected from one or more of KH-550, KH-560, KH-570, KH-792, KH-580, etc.
In the step S7, adding the particle product obtained in the step S6 into deionized water, and performing ultrasonic dispersion to obtain a core-shell structure Si@ metal@coupling agent solution D connected with a silane coupling agent, wherein the volume ratio of the particle product to the deionized water is 1:100-1:20.
In the step S8, the pre-prepared carbon source solution is dripped into the solution D in the step S7, stirred for 2-6h, and dried after ultrasonic treatment for 30-120min, so as to obtain the core-shell structure Si@ metal@carbon composite material to be prepared. The carbon source is one or more of carbon nano tube, graphene and graphite, and the carbon source solution is a solution formed by the carbon source and deionized water or ethanol, and the concentration of the carbon source solution is 1g/L-3g/L. The dosage of the carbon source solution and the solution D needs to meet the requirement that the molar ratio of the core-shell structure Si@ metal@coupling agent particles to the carbon source in the solution D is controlled to be 1:20-1:8. The drying treatment can be spray drying, freeze drying or vacuum drying, wherein the spray drying temperature is controlled to be 100-160 ℃, the freeze drying time is controlled to be 12-48h according to the liquid conveying rotating speed, the vacuum drying temperature is controlled to be 80-100 ℃, and the time is controlled to be 1-4 h. The carbon source solution is slowly dripped into the solution D, the dripping speed is 1ml/min-5ml/min, and the situation that the carbon layer is coated after a large amount of core-shell particles are aggregated and cannot be fully dispersed due to the excessively high speed is avoided. In the step, the dosage ratio of the solution D to the carbon source solution is strictly controlled, too little carbon material is unfavorable for constructing a stable structure, and too much carbon material can cause rapid capacity attenuation and increase of lithium ion deintercalation resistance. The prepared Si@ metal@carbon composite material with the core-shell structure can be Si@ metal@CNT, si@ metal@rGO, si@ metal@C and the like.
The invention also provides a nano silicon-based composite anode material which is prepared according to the method.
The following is a specific example of a method for preparing a nanoscale silicon-based composite anode material according to the present invention. Unless otherwise indicated, the raw materials, equipment, consumables and the like used in the following examples are all available by conventional commercial means.
For those parts of the numerical range, any value in the numerical range defined by the present invention can be selected by one skilled in the art according to actual needs, and is not limited to the numerical values set forth in the specific examples.
Example 1
The nano silicon powder (particle size of 50 nm) and the metal simple substance Ag (particle size of 10 nm) are put into a beaker according to a mass ratio of 1:2 to be mixed, and then the mixture A is obtained.
And mixing the organic adhesive Polyacrylonitrile (PAN) with the absolute ethyl alcohol solution in a volume ratio of 1:5 to obtain the mixed solvent B.
The mixture A and the mixed solvent B are mixed, the volume ratio of the mixture A and the mixed solvent B is not required to be special, but the mixed solvent B is required to completely cover the mixture A, the solid particles are uniformly mixed in the solvent by ultrasonic for 30min, the ultrasonic temperature is controlled to be not higher than 60 ℃ to avoid the solvent from volatilizing too fast, and then the mixed solution is put into a planetary ball mill for ball milling and dispersing treatment for 40min.
And (3) evaporating the mixture in a water bath with stirring at the temperature of 100 ℃ at the stirring speed of 450 revolutions per minute until only solid particles exist in a container, namely the Si@Ag nano particles with a core-shell structure.
And (3) adding a certain amount of the core-shell structure Si@Ag particles obtained in the previous step into absolute ethyl alcohol, wherein the volume ratio of the ethyl alcohol to the particles is 10:1, performing ultrasonic treatment for 50min, adding a certain amount of deionized water and a silane coupling agent KH-550, and rapidly stirring at a stirring rate of about 400 revolutions per minute. Ethanol: deionized water: the volume ratio of the coupling agent is 10:10:1, and the solution is stirred for 5 hours at room temperature and is kept stand for 2 hours.
After the absolute ethyl alcohol and deionized water are subjected to suction filtration and washing, the product is ultrasonically dispersed in a certain volume of deionized water, and the particles are: the volume ratio of deionized water is 1:50, and the core-shell structure Si@Ag@KH-550 solution D connected with the silane coupling agent is obtained. A solution of carbon nanotubes CNT (50 nm) at a concentration of 3g/L was slowly added dropwise to a volume of solution D at a drop rate of 1ml/min. And (3) controlling the molar ratio of the core-shell structure Si@ metal@coupling agent particles to the carbon nano tube CNT in the solution D to be 1:8, continuously stirring for 3 hours, performing ultrasonic treatment for 40 minutes, and performing spray drying at 120 ℃ until the core-shell structure Si@Ag@CNT is completely dried to obtain the core-shell structure Si@Ag@CNT with completely removed water.
The core-shell structure particles prepared by the method are weighed according to the molar ratio of 3:2:2: acetylene black: and (3) a sodium alginate solution, namely placing Si@Ag@CNT particles and acetylene black into a mortar, fully and uniformly mixing for 20min, then dropwise adding the sodium alginate solution into the mixed powder, and continuously manually grinding for 30min to form uniform slurry. Coating a uniform slurry on the copper foil with a coater, wherein the surface density is about 0.8mgcm -2 Vacuum drying overnight at 80 ℃. After cooling for 2 hours, the electrode sheet was cut into a desired shape as required. And assembling the electrode plates into a battery for electrochemical performance testing.
The test results show that when the current density is from 0.1Ag -1 、0.2Ag -1 、0.5Ag -1 、1Ag -1 、2Ag -1 To 5Ag -1 When the composite material Si@Ag@CNT is used, the reversible discharge capacity of the composite material Si@Ag@CNT is 4123.6mAhg in sequence -1 、3834.8mAhg -1 、3426.7mAhg -1 、3017.7mAhg -1 、2780.8mAhg -1 And 2406.1mAhg -1 . When the current density returns to 0.1Ag again -1 When Si@Ag@CNT electrode material is still as high as 3814.8mAhg -1 The lithium storage capacity of the lithium ion battery, the capacity retention rate of the specific charge capacity is as high as 95.3%, and the silicon section expansion rate is 30.2%.
Example 2
The nano silicon powder (particle size of 80 nm) and metal simple substance Au (particle size of 10 nm) are put into a beaker according to a mass ratio of 1:2 to be mixed, and then the mixture A is obtained.
And mixing the organic adhesive polyvinyl alcohol (PVA) and the absolute ethyl alcohol solution in a volume ratio of 1:6 to obtain the mixed solvent B.
And then mixing the mixture A and the mixed solvent B, wherein the volume ratio of the mixture A and the mixed solvent B does not have special requirements, but the mixed solvent B is required to completely cover the mixture A, the solid particles are uniformly mixed in the solvent by ultrasonic for 40min, the ultrasonic temperature is controlled to be not higher than 60 ℃ so as to avoid the solvent from volatilizing too fast, and then the mixed solution is put into a planetary ball mill for ball milling and dispersing treatment for 30min.
And (3) evaporating the mixture in a water bath with stirring at 100 ℃ at the stirring speed of 500 revolutions per minute until only solid particles exist in a container, namely the Si@Au nano particles with a core-shell structure.
And (3) adding a certain amount of the core-shell structure Si@Au particles obtained in the previous step into absolute ethyl alcohol, wherein the volume ratio of the ethyl alcohol to the particles is 15:1, performing ultrasonic treatment for 30min, adding a certain amount of deionized water and a silane coupling agent KH-560, and rapidly stirring at a stirring rate controlled at 300 revolutions per minute. Ethanol: deionized water: the volume ratio of the coupling agent is 20:20:1, and the solution is stirred for 4 hours at room temperature and is kept stand for 2 hours.
After the absolute ethyl alcohol and deionized water are subjected to suction filtration and washing, the product is ultrasonically dispersed in a certain volume of deionized water, and the particles are: the volume ratio of the deionized liquid is 1:60, and the core-shell structure Si@Au@KH-560 solution D connected with the silane coupling agent is obtained. A volume of graphene oxide rGO (50 nm) solution (with a concentration of 2 g/L) is slowly added into the solution D in a dropwise manner, and the dropping speed is 2ml/min. And (3) controlling the molar ratio of the core-shell structure Si@ metal@coupling agent particles to the graphene oxide rGO in the solution D to be 1:10, continuously stirring for 5 hours, performing ultrasonic treatment for 30 minutes, and performing spray drying at 120 ℃ until the core-shell structure Si@Au@rGO is completely dried to obtain the core-shell structure Si@Au@rGO with completely removed water.
Weighing the prepared core-shell structure particles Si@Au@rGO according to the molar ratio of 3:1:1: carbon black: the preparation method comprises the steps of firstly placing Si@Au@rGO particles and acetylene black into a mortar, fully and uniformly mixing for 30min, then dripping sodium alginate solution into the mixed powder, and continuously manually grinding for 30min to form uniform slurry. Coating a uniform slurry on the copper foil with a coater, wherein the surface density is about 1mgcm -2 Vacuum drying overnight at 90 ℃. After cooling for 3 hours, the electrode plate is cut into required shape according to the requirementShape. . And assembling the electrode plates into a battery for electrochemical performance testing.
The test results show that when the current density is from 0.1Ag -1 、0.2Ag -1 、0.5Ag -1 、1Ag -1 、2Ag -1 To 5Ag -1 When the composite material Si@Au@rGO has the reversible discharge capacity of 4012.4mAhg in sequence -1 、3612.4mAhg -1 、3212.7mAhg -1 、2819.6mAhg -1 、2547.9mAhg -1 And 2207.2mAhg -1 . When the current density returns to 0.1Ag again -1 When the Si@Au@rGO electrode material is used, the Si@Au@rGO electrode material still has a temperature of up to 3672.8mAhg -1 The lithium storage capacity of the lithium ion battery, the capacity retention rate of the specific charge capacity is as high as 92.6%, and the silicon section expansion rate is 39.6%.
Example 3
Nanometer silicon powder (particle size 80 nm) and metal simple substance V (particle size 50 nm) are mixed according to the mass ratio of 1: and 1, putting the mixture into a beaker for mixing, and obtaining a mixture A.
And mixing the organic adhesive Polyamide (PVA) and the absolute ethyl alcohol solution in a volume ratio of 1:7 to obtain a mixed solvent B.
The mixture A and the mixed solvent B are mixed, the volume ratio of the mixture A and the mixed solvent B is not required to be special, but the mixed solvent B is required to completely cover the mixture A, the solid particles are uniformly mixed in the solvent by ultrasonic for 20min, the ultrasonic temperature is controlled to be not higher than 60 ℃ to avoid the solvent from volatilizing too fast, and then the mixed solution is put into a planetary ball mill to be subjected to ball milling dispersion treatment for 50min.
And (3) evaporating the mixture in a stirring water bath at the temperature of 100 ℃ at the stirring speed of 350 revolutions per minute until only solid particles exist in a container, namely the Si@V nano particles with a core-shell structure.
And (3) adding a certain amount of the core-shell structure Si@V particles obtained in the previous step into absolute ethyl alcohol, wherein the volume ratio of the ethyl alcohol to the particles is 20:1, performing ultrasonic treatment for 30min, adding a certain amount of deionized water and a silane coupling agent KH-570, and rapidly stirring at a stirring speed of 550 r/min. Ethanol: deionized water: the volume ratio of the coupling agent is 15:15:1, and the solution is stirred for 6 hours at room temperature and is kept stand for 2 hours.
After the absolute ethyl alcohol and deionized water are subjected to suction filtration and washing, the product is ultrasonically dispersed in a certain volume of deionized water, and the particles are: the volume ratio of the deionized liquid is 1:70, and the core-shell structure Si@V@KH-570 solution D connected with the silane coupling agent is obtained. A volume of a carbon nanotube CNT (50 nm) solution (1 g/L concentration) was slowly added dropwise to solution D at a drop rate of 4ml/min. And (3) controlling the molar ratio of the core-shell structure Si@ metal@coupling agent particles to the carbon nano tube CNT in the solution D to be 1:12, continuously stirring for 4 hours, performing ultrasonic treatment for 40 minutes, and performing spray drying at 120 ℃ until the core-shell structure Si@V@CNT is completely dried to obtain the core-shell structure Si@V@CNT with completely removed water.
Weighing the prepared core-shell structure particles Si@V@CNT according to a molar ratio of 4:1:1: carbon black: the preparation method comprises the steps of firstly placing Si@V@CNT particles and acetylene black into a mortar, fully and uniformly mixing the particles and the acetylene black for 40min, then dripping sodium alginate solution into the mixed powder, and continuously manually grinding the mixed powder for 30min to form uniform slurry. Coating a uniform slurry on the copper foil with a coater, wherein the surface density is about 0.6mgcm -2 Vacuum drying overnight at 90 ℃. After cooling for 3 hours, the electrode sheet was cut into a desired shape as required. And assembling the electrode plates into a battery for electrochemical performance testing.
The test results show that when the current density is from 0.1Ag -1 、0.2Ag -1 、0.5Ag -1 、1Ag -1 、2Ag -1 To 5Ag -1 When the composite material Si@V@CNT is subjected to reversible discharge capacity of 3901.4mAhg -1 、3721.9mAhg -1 、3409.2mAhg -1 、3001.6mAhg -1 、2631.2mAhg -1 And 2317.5mAhg -1 . When the current density returns to 0.1Ag again -1 At the same time, si@V@CNT electrode material still has a temperature of up to 3580.9mAhg -1 The lithium storage capacity of the lithium ion battery, the capacity retention rate of the specific charge capacity is as high as 93.6%, and the silicon section expansion rate is 33.7%.
Example 4
Nanometer silicon powder (particle size 100 nm) and metal simple substance Ti (particle size 50 nm) are mixed according to a mass ratio of 1: and 1, putting the mixture into a beaker for mixing, and obtaining a mixture A.
And mixing the organic adhesive Polyacrylonitrile (PAN) with the absolute ethyl alcohol solution in a volume ratio of 1:5 to obtain the mixed solvent B.
And then mixing the mixture A and the mixed solvent B, wherein the volume ratio of the mixture A and the mixed solvent B does not have special requirements, but the mixed solvent B is required to completely cover the mixture A, the solid particles are uniformly mixed in the solvent by ultrasonic for 30min, the ultrasonic temperature is controlled to be not higher than 60 ℃ so as to avoid the solvent from volatilizing too fast, and then the mixed solution is put into a planetary ball mill for ball milling and dispersing treatment for 40min.
And (3) evaporating the mixture in a water bath with stirring at the temperature of 100 ℃ at the stirring speed of 400 revolutions per minute until only solid particles exist in a container, namely the Si@Ti nanoparticles with a core-shell structure.
And (3) adding a certain amount of the core-shell structure Si@Ti particles obtained in the previous step into absolute ethyl alcohol, wherein the volume ratio of the ethyl alcohol to the particles is 20:1, carrying out ultrasonic treatment for 30min, rapidly adding a certain amount of deionized water and a silane coupling agent KH-550, and rapidly stirring, wherein the stirring speed is controlled to be 700 revolutions per minute. Ethanol: deionized water: the volume ratio of the coupling agent is 10:10:1, the solution was stirred at room temperature for 6 hours and allowed to stand for 2 hours.
After the absolute ethyl alcohol and deionized water are subjected to suction filtration and washing, the product is ultrasonically dispersed in a certain volume of deionized water, and the particles are: the volume ratio of the deionized liquid is 1:60, and the core-shell structure Si@Ti@KH-550 solution D connected with the silane coupling agent is obtained. A volume of graphene oxide rGO (50 nm) solution (1 g/L concentration) was slowly added dropwise to solution D at a drop rate of 5ml/min. And (3) controlling the molar ratio of the core-shell structure Si@ metal@coupling agent particles to the graphene oxide rGO in the solution D to be 1:8, continuously stirring for 6 hours, performing ultrasonic treatment for 30 minutes, and performing spray drying at 160 ℃ until the core-shell structure Si@Ti@rGO is completely dried to obtain the core-shell structure Si@Ti@rGO with completely removed water.
Weighing the prepared core-shell structure particles Si@Ti@rGO according to the molar ratio of 3:1:1: acetylene black: and firstly, placing the Si@Ti@rGO particles and the acetylene black in a mortar, fully and uniformly mixing for 40min, then, dropwise adding a sodium alginate solution into the mixed powder, and continuously manually grinding for 20min to form uniform slurry. Coating a uniform slurry on the copper foil with a coater, wherein the surface density is about 0.8mgcm -2 Vacuum drying overnight at 80 ℃. After cooling for 2 hours, the electrode sheet was cut into a desired shape as required. And assembling the electrode plates into a battery for electrochemical performance testing.
The test results show that when the current density is from 0.1Ag -1 、0.2Ag -1 、0.5Ag -1 、1Ag -1 、2Ag -1 To 5Ag -1 When the composite material Si@V@CNT is subjected to reversible discharge capacity of 3801.3mAhg -1 、3503.2mAhg -1 、3207.0mAhg -1 、2982.3mAhg -1 、2424.2mAhg -1 And 2109.5mAhg -1 . When the current density returns to 0.1Ag again -1 At the same time, si@V@CNT electrode material still has a temperature of up to 3402.7mAhg -1 The lithium storage capacity of the lithium ion battery, the capacity retention rate of the specific charge capacity is as high as 94.2%, and the silicon section expansion rate is 39.7%.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the scope of the technical concept of the present invention, and all the simple modifications belong to the protection scope of the present invention.
In addition, the specific features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various possible combinations are not described further.
Moreover, any combination of the various embodiments of the invention can be made without departing from the spirit of the invention, which should also be considered as disclosed herein.
Claims (10)
1. The preparation method of the nanoscale silicon-based composite anode material is characterized by comprising the following steps of:
step S1: mixing nano silicon powder and a metal simple substance in proportion to obtain a mixture A;
step S2: mixing an organic adhesive and an absolute ethyl alcohol solution in proportion to obtain a mixed solvent B;
step S3: uniformly mixing the mixture A and the mixed solvent B to ensure that the mixed solvent B completely coats the mixture A to obtain a mixed solution;
step S4: ball-milling and dispersing the mixed solution, then performing stirring water bath evaporation until only solid particles exist, and obtaining Si@ metal nano particles C with a core-shell structure;
step S5: putting a preset amount of Si@ metal nano particles C into absolute ethyl alcohol to be uniformly dispersed;
step S6: adding deionized water and a silane coupling agent into the solution obtained in the step S5, stirring at room temperature, standing, and then carrying out suction filtration and washing to obtain a particle product;
step S7: adding the particle product obtained in the step S6 into deionized water to obtain a core-shell structure Si@ metal@coupling agent solution D connected with a silane coupling agent;
step S8: and (3) dripping the pre-prepared carbon source solution into the solution D in the step (S7), stirring and ultrasonically drying to obtain the core-shell structure Si@ metal@carbon composite material to be prepared.
2. A method according to claim 1, wherein in step S1, the nano silicon powder has a size of 30-100nm, the metal element is selected from one or more of Ag, au, V, ti, and a mass ratio of the nano silicon powder to the metal element is 1:1-1:5.
3. The method according to claim 1, wherein in step S2, the organic adhesive is one or more selected from polyacrylonitrile, polyvinyl alcohol, polyamide and polytetrafluoroethylene, and the volume ratio of the organic adhesive to the absolute ethanol is 1:3-1:7.
4. The method according to claim 1, wherein in step S3, the mixture a and the mixed solvent B are mixed and then sonicated for 20 to 60 minutes, and the temperature of the sonication is controlled to not exceed 60 ℃.
5. The method according to claim 1, wherein in step S4, the ball milling dispersion time is 20 to 80min, the stirring speed is 300 to 600 rpm, and the water bath evaporation temperature is 80 to 100 ℃.
6. The method according to claim 1, wherein in step S5, the volume ratio of absolute ethanol to Si@ metal nanoparticles C is 2:1-20:1, and the ultrasonic dispersion is performed for 30-120min.
7. The method according to claim 1, wherein in step S6, deionized water and silane coupling agent are used in amounts such that the absolute ethyl alcohol: deionized water: the volume ratio of the silane coupling agent is 5:5:1-20:20:1, stirring is carried out for 4-8 hours, standing is carried out for 2-6 hours, the deionized water and the silane coupling agent are added dropwise and are rapidly stirred, and the stirring speed is 300-700 rpm.
8. The method of claim 1, wherein in step S7, the particulate product is added to deionized water and then dispersed ultrasonically, the volume ratio of the particulate product to deionized water being 1:100-1:20.
9. The method according to claim 1, wherein in step S8, the carbon source is one or more selected from the group consisting of carbon nanotubes, graphene and graphite, and is configured as a carbon source solution, the solvent is absolute ethanol or deionized water, the concentration is 1g/L to 3g/L, the molar ratio of the core-shell structure Si@ metal @ coupling agent particles to the carbon source in the solution D is controlled to be 1:20 to 1:8, the stirring time is 2 to 6 hours, the ultrasonic time is 30 to 120 minutes, and the drying treatment is spray drying, freeze drying or vacuum drying.
10. A nanoscale silicon-based composite anode material, characterized in that it is prepared by the method according to any one of claims 1 to 9.
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