CN117038907A - Silicon-carbon negative electrode and surface coating modification method and application thereof - Google Patents

Silicon-carbon negative electrode and surface coating modification method and application thereof Download PDF

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CN117038907A
CN117038907A CN202311072309.7A CN202311072309A CN117038907A CN 117038907 A CN117038907 A CN 117038907A CN 202311072309 A CN202311072309 A CN 202311072309A CN 117038907 A CN117038907 A CN 117038907A
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silicon
carbon
negative electrode
carbon negative
surface coating
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岳之浩
徐国军
金晨鑫
周浪
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Jiangxi Siying New Energy Technology Co ltd
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Jiangxi Siying New Energy Technology Co ltd
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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
    • 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
    • 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
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • 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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  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention provides a silicon-carbon negative electrode, a surface coating modification method and application thereof, and relates to the technical field of new energy battery negative electrode materials. The method comprises the following steps: stirring and mixing graphite particles with a first cellulose solution, performing regeneration treatment, and performing vacuum heat treatment to obtain modified graphite particles; stirring and mixing the modified graphite particles with a second cellulose solution, sequentially carrying out regeneration treatment and vacuum heat treatment, and then carrying out gaseous silicon deposition to obtain a silicon-graphite compound; stirring and mixing the silicon-graphite composite and a third cellulose solution, and sequentially carrying out regeneration treatment and vacuum heat treatment, and then carrying out gaseous carbon deposition; and S5, repeating the step S4 until the thickness of the carbon layer on the surface of the silicon-graphite composite reaches the preset thickness of the carbon layer, and obtaining the silicon-carbon anode material. The silicon-carbon negative electrode prepared by the method can relieve the lithium storage expansion effect of a silicon material and improve the problem of poor cycle life of the silicon-carbon negative electrode.

Description

Silicon-carbon negative electrode and surface coating modification method and application thereof
Technical Field
The invention relates to the technical field of new energy battery anode materials, in particular to a silicon-carbon anode, a surface coating modification method and application thereof.
Background
The lithium ion battery has the advantages of high energy storage density, high open circuit voltage, low self-discharge rate and the like, and has been widely used in recent years. At present, the commercial lithium battery mainly adopts graphite carbon as a negative electrode material, but the theoretical capacity of graphite is only 372mAh/g and the multiplying power performance is poor, the theoretical specific capacity of silicon is up to 4200mAh/g, which is higher than the specific capacity of the graphite negative electrode material by one order of magnitude, the lithium intercalation/deintercalation potential is moderate, the reactivity with electrolyte is low, the reserve in crust is abundant, the price is low, and the lithium battery is an ideal choice of a new generation lithium ion battery negative electrode battery.
However, during the alloying reaction of silicon and lithium, the silicon material may undergo a volume expansion (lithium storage expansion) of up to 300% or more, which easily results in rapid pulverization and falling off of the active material during the cycling process, and the electrode active material is in reduced electrical contact with the current collector, so that the cycle life of the battery is rapidly reduced. Meanwhile, due to the volume expansion effect of the silicon material, a firm surface solid electrolyte membrane (Solid Electrolyte Interface, SEI) cannot be generated in the electrolyte by the silicon material, the electrode structure is damaged, a new SEI film can be continuously formed on the newly exposed silicon surface, the charge and discharge efficiency is reduced, and the capacity fading is further accelerated.
At present, a small amount (not more than 5%) of nano silicon particles and graphite particles are often compounded to prepare a silicon-carbon composite material for use, so that the lithium storage expansion effect of the silicon material can be relieved to a certain extent, however, the problem of poor cycle life still exists, and therefore, a scheme is needed to be provided for improving the problem.
Disclosure of Invention
The invention aims to provide a silicon-carbon negative electrode, a surface coating modification method and application thereof, and the prepared silicon-carbon negative electrode can relieve the lithium storage expansion effect of a silicon material and improve the problem of poor cycle life of the silicon-carbon negative electrode.
In a first aspect, the invention provides a silicon-carbon negative electrode surface coating modification method, which comprises the following steps:
s1, stirring and mixing graphite particles with a first cellulose solution, performing regeneration treatment, and performing vacuum heat treatment to obtain modified graphite particles;
s2, stirring and mixing the modified graphite particles with a second cellulose solution, and sequentially carrying out regeneration treatment and vacuum heat treatment, and then carrying out gaseous silicon deposition;
s3, repeating the step S2 until the thickness of the silicon layer on the surface of the modified graphite particle reaches the preset thickness of the silicon layer, and preparing a silicon-graphite compound;
s4, stirring and mixing the silicon-graphite composite and a third cellulose solution, and sequentially carrying out regeneration treatment and vacuum heat treatment, and then carrying out gaseous carbon deposition;
and S5, repeating the step S4 until the thickness of the carbon layer on the surface of the silicon-graphite composite reaches the preset thickness of the carbon layer, and obtaining the silicon-carbon anode material.
The silicon-carbon negative electrode surface coating modification method provided by the invention has the beneficial effects that: the prepared silicon-carbon negative electrode can relieve the lithium storage expansion effect of a silicon material and improve the problem of poor cycle life of the silicon-carbon negative electrode.
Optionally, the solvents of the first cellulose dissolution solution, the second cellulose dissolution solution and the third cellulose dissolution solution are all alkaline urea solutions.
Optionally, the regeneration solution used in performing the regeneration treatment is an acidic solution having a pH of less than 5.
Optionally, in the process of executing the vacuum heat treatment, the temperature is controlled to be 300-400 ℃ for 4-5 hours.
Optionally, the preset thickness of the silicon layer is 100-500nm.
Optionally, the carbon layer is preset to have a thickness of 5-20nm.
Optionally, during the deposition of gaseous silicon, the deposition is performed in a vacuum environment at 600-1000 ℃ using a gaseous silicon source; the gaseous silicon source is silane.
Optionally, during the gaseous carbon deposition, the gaseous carbon source is used for deposition in a vacuum environment at 600-1000 ℃; the gaseous carbon source is acetylene and/or methane.
In a second aspect, the invention provides a silicon carbon anode prepared by any of the alternative methods described above.
In a third aspect, the invention provides the use of a silicon-carbon negative electrode prepared by any of the above-described alternative methods in a lithium ion battery.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. Unless otherwise defined, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. As used herein, the word "comprising" and the like means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof without precluding other elements or items.
The embodiment of the invention provides a silicon-carbon negative electrode surface coating modification method, which comprises the following steps:
s1, stirring and mixing graphite particles with a first cellulose solution, performing regeneration treatment, and performing vacuum heat treatment to obtain modified graphite particles;
s2, stirring and mixing the modified graphite particles with a second cellulose solution, and sequentially carrying out regeneration treatment and vacuum heat treatment, and then carrying out gaseous silicon deposition;
s3, repeating the step S2 until the thickness of the silicon layer on the surface of the modified graphite particle reaches the preset thickness of the silicon layer, and preparing a silicon-graphite compound;
s4, stirring and mixing the silicon-graphite composite and a third cellulose solution, and sequentially carrying out regeneration treatment and vacuum heat treatment, and then carrying out gaseous carbon deposition;
and S5, repeating the step S4 until the thickness of the carbon layer on the surface of the silicon-graphite composite reaches the preset thickness of the carbon layer, and obtaining the silicon-carbon anode material.
In some embodiments, the solvents in the first cellulose solution, the second cellulose solution, and the third cellulose solution are all alkaline urea solutions, and the solute cellulose in the first cellulose solution, the second cellulose solution, and the third cellulose solution is at least one of microcrystalline cellulose, filter paper, and absorbent cotton fiber independently of each other.
In practice, the alkaline urea solution may be a mixed solution of lithium hydroxide and urea or a mixed solution of sodium hydroxide and urea, and after the cellulose enters the alkaline urea solution, alkali hydrate, urea hydrate and free water molecules surround and penetrate the cellulose, and the cellulose is dynamically assembled with cellulose molecules at a low temperature to form hydrogen bonds so as to break the intramolecular and intermolecular hydrogen bonds of the cellulose, so that cellulose chains are dissolved.
In some embodiments, when the alkaline urea solution is a mixed solution of sodium hydroxide and urea, the concentration of sodium hydroxide in the alkaline urea solution is 7% and the concentration of urea in the alkaline urea solution is 12%. In this way, when preparing cellulose solution, cellulose is put into a mixed solution of sodium hydroxide and urea and stirred to form a fiber suspension, and then the fiber suspension is filtered after eliminating cellulose gel by adopting a freeze-thawing cycle mode, so that a clarified cellulose solution is prepared.
In some embodiments, the first, second, and third cellulose solutions have a cellulose content of 3-6%. Specifically, the cellulose content in the first cellulose solution, the second cellulose solution and the third cellulose solution decreases in sequence.
In some embodiments, in the regeneration treatment process, the used regeneration treatment solution is an acidic solution, and the acidic solution is added into the cellulose dissolution solution, so that the alkaline environment in the cellulose dissolution solution can be destroyed, and the dissolved cellulose is precipitated and attached to the solid matters such as graphite particles, and further the coating of the cellulose on the solid matters such as graphite particles is realized.
Specifically, the acidic solution used during the regeneration treatment has a pH of less than 5. More specifically, during the regeneration treatment, the acidic solution is at least one of hydrochloric acid, sulfuric acid, phosphoric acid and acetic acid.
In some embodiments, the vacuum and heating apparatus used during the vacuum heat treatment is a rotary vacuum tube furnace. Specifically, in the vacuum heat treatment process, the heating temperature is controlled to be 300-400 ℃, and the vacuum degree is controlled to be 100-200pa.
In some embodiments, the graphite particles selected for use in performing step S1 have a particle size of between 5 and 15 μm.
In some embodiments, when step S1 is performed, graphite particles are put into a first cellulose solution, dispersed for 1-2 hours in an environment of 40-50 ℃ under stirring at a rotation speed of 300-350rpm, then hydrochloric acid solution is dropwise added into the mixed solution until the pH of the mixed solution is 6.7, the mixed solution is filtered and washed with deionized water and then dried, and the dried product is transferred into a rotary vacuum tube furnace to be subjected to heat treatment in a vacuum environment of 300-400 ℃ for 4-5 hours, so as to obtain modified graphite particles.
In some embodiments, when step S1 is performed, the mass ratio of graphite particles to cellulose dissolved in the first cellulose solution is 1: (0.3-0.7).
In some embodiments, when step S2 is performed, the modified graphite particles are put into the second cellulose solution, and after being stirred and dispersed for 1-2 hours at a rotation speed of 300-350rpm in an environment of 40-50 ℃, the hydrochloric acid solution is dropwise added into the mixed solution until the pH of the mixed solution is 6.7, the mixed solution is filtered and washed by deionized water and then dried, the dried product is transferred into a rotary vacuum tube furnace to be heat treated for 4-5 hours in a vacuum environment of 300-400 ℃, and then the temperature is raised to 600-1000 ℃, and then a gaseous silicon source is introduced into the rotary vacuum tube furnace, so that the gaseous silicon enters into the carbonized cellulose layer on the surfaces of the modified graphite particles, and the surfaces of the graphite particles are coated with a uniform silicon layer. In particular, the gaseous silicon source may be silane.
In some embodiments, when step S2 is performed, the mass ratio of the modified graphite particles to the cellulose dissolved in the second cellulose solution is 1: (0.2-0.5).
In some embodiments, in step S3, the preset thickness of the silicon layer is 100-500nm, in order to improve the dispersion uniformity of the silicon layer on the surface of the modified graphite particles, step S2 may be repeated, and the modified graphite particles are deposited layer by layer, so that the thickness of the silicon layer can be effectively controlled, and when the silicon layer is deposited, the second cellulose solution is used to attach cellulose to the modified graphite particles, which is favorable for improving the adhesion strength of the silicon layer on the surface of the graphite particles, and the carbonized cellulose can provide a plurality of sites for the deposition of gaseous silicon, and the silicon layer is uniformly expanded in the use process of the silicon carbon negative electrode, so as to avoid falling off. Specifically, the preset thickness of the silicon layer in step S3 may be adjusted according to the particle size of the modified graphite particles.
In some embodiments, when step S4 is performed, the silicon-graphite composite is put into the third cellulose solution, and after being stirred and dispersed for 1-2 hours at a rotation speed of 300-350rpm in an environment of 40-50 ℃, the hydrochloric acid solution is dropwise added into the mixed solution until the pH of the mixed solution is 6.7, the mixed solution is filtered and washed by deionized water, and then dried, the dried product is transferred into a rotary vacuum tube furnace, and after being heat treated for 4-5 hours in a vacuum environment of 300-400 ℃, the temperature is raised to 600-1000 ℃, a gaseous carbon source is introduced into the rotary vacuum tube furnace, so that the gaseous carbon enters into the carbonized cellulose layer on the surface of the silicon-graphite composite, and the surface of the silicon-graphite composite is coated with a uniform carbon layer. In particular, the gaseous silicon source may be acetylene and/or methane.
In some embodiments, when step S4 is performed, the mass ratio of the silicon-graphite composite to the cellulose dissolved in the third cellulose solution is 1: (0.1-0.4).
In some embodiments, the carbon layer in step S5 is preset to a thickness of 5-20nm.
The embodiment of the invention also provides the silicon-carbon anode material prepared in any embodiment and application of the silicon-carbon anode material in lithium ion electrons.
Example 1
The embodiment 1 of the invention provides a silicon-carbon negative electrode surface coating modification method, which comprises the following steps:
s1, putting graphite particles with the average particle size of 10 mu m into a first cellulose dissolving solution, stirring and dispersing for 2 hours at the rotating speed of 300rpm in the environment of 45 ℃, dropwise adding a hydrochloric acid solution into the mixed solution until the pH value of the mixed solution is 6.7, filtering, washing the precipitate by using deionized water, drying, transferring the dried product into a rotary vacuum tube furnace, and performing heat treatment for 4 hours in the vacuum environment of 350 ℃ to obtain modified graphite particles; the solvent in the first cellulose dissolving solution is a mixed solution of sodium hydroxide and urea, the concentration of the sodium hydroxide in the alkaline urea solution is 7%, the concentration of the urea in the alkaline urea solution is 12%, and the mass ratio of graphite particles to cellulose dissolved in the first cellulose dissolving solution is 1:0.5;
s2, putting modified graphite particles into a second cellulose solution, stirring and dispersing for 2 hours at a rotating speed of 300rpm in an environment of 45 ℃, dropwise adding a hydrochloric acid solution into the mixed solution until the pH value of the mixed solution is 6.7, filtering, washing the precipitate by using deionized water, drying, transferring the dried product into a rotary vacuum tube furnace, performing heat treatment in a vacuum environment of 350 ℃ for 4 hours, heating to 1000 ℃, and introducing silane into the rotary vacuum tube furnace to enable the silane to enter into a carbonized cellulose layer on the surfaces of the modified graphite particles, so that the surfaces of the graphite particles are coated with a uniform silicon layer; the solvent in the second cellulose dissolving solution is a mixed solution of sodium hydroxide and urea, the concentration of the sodium hydroxide in the alkaline urea solution is 7%, the concentration of the urea in the alkaline urea solution is 12%, and the mass ratio of graphite particles to cellulose dissolved in the second cellulose dissolving solution is 1:0.4;
s3, repeating the step S2 until the thickness of the silicon layer on the surface of the modified graphite particles reaches 500nm, and obtaining the silicon-graphite composite;
s4, putting the silicon-graphite composite into a third cellulose solution, stirring and dispersing for 2 hours at a rotating speed of 300rpm in a 45 ℃ environment, dropwise adding a hydrochloric acid solution into the mixed solution until the pH value of the mixed solution is 6.7, filtering, washing the precipitate by using deionized water, drying, transferring the dried product into a rotary vacuum tube furnace, performing heat treatment in a vacuum environment of 350 ℃ for 4 hours, heating to 1000 ℃, and introducing acetylene into the rotary vacuum tube furnace to enable the acetylene to enter into a carbonized cellulose layer on the surface of the silicon-graphite composite, so that the surface of the silicon-graphite composite is coated with a uniform carbon layer; the solvent in the third cellulose dissolving solution is a mixed solution of sodium hydroxide and urea, the concentration of the sodium hydroxide in the alkaline urea solution is 7%, the concentration of the urea in the alkaline urea solution is 12%, and the mass ratio of graphite particles to cellulose dissolved in the third cellulose dissolving solution is 1:0.3;
and S5, repeating the step S4 until the thickness of the carbon layer on the surface of the modified graphite particles reaches 20nm, and obtaining the silicon-carbon anode material.
Example 2
The difference between the silicon-carbon negative electrode surface coating modification method provided in the embodiment 2 and the embodiment 1 is that in the step S2 of the embodiment 2, silane is introduced into a rotary vacuum tube furnace after the temperature is raised to 600 ℃; in the step S4, acetylene is introduced into the rotary vacuum tube furnace after the temperature is raised to 600 ℃.
Example 3
The difference between the method for coating and modifying the surface of the silicon-carbon negative electrode provided in the embodiment 3 and the embodiment 1 is that in the step S2 of the embodiment 2, silane is introduced into a rotary vacuum tube furnace after the temperature is raised to 800 ℃; in the step S4, acetylene is introduced into the rotary vacuum tube furnace after the temperature is raised to 700 ℃.
Comparative example
Comparative example 1
The comparative example 1 provides a silicon-carbon negative electrode surface coating modification method, which comprises the following steps:
and (3) putting graphite particles with the average particle size of 10 mu m into a rotary vacuum tube furnace, heating to 1000 ℃, introducing silane, so that the surfaces of the graphite particles are coated with a silicon layer with the thickness of 500nm, and introducing acetylene at a certain temperature, so that the surfaces of the silicon layers are coated with a carbon layer with the thickness of 20nm, thereby preparing the silicon-carbon anode material.
Performance detection
The silicon-carbon negative electrode materials in examples 1-3 and comparative example 1 were respectively mixed with conductive carbon black and sodium carboxymethyl cellulose as a binder in a mass ratio of 8:1:1, coating the slurry on copper foil by a scraper, drying the slurry in a vacuum drying oven for 12 hours, cutting the copper foil loaded with electrode materials into button cell electrode slices of 12mm by using a sheet punching machine, using a metal lithium slice as a counter electrode, assembling the button cell, and then standing the button cell for 12 hours to test the first discharge capacity and the capacity retention rate of 0.2C and 2C for 500 times, as shown in the following table 1.
TABLE 1 Primary discharge capacities of the silicon carbon negative electrode materials prepared in examples 1 to 3 and comparative example 1 and capacity retention ratios of 500 cycles of 0.2C and 2C
It can be seen from the combination of examples 1 to 3 and comparative example 1 and the combination of table 1 that the silicon-carbon negative electrode prepared by the method provided by the invention has good first discharge capacity and good capacity retention after multiple cycles of 0.2C and 2C, so that the method provided by the invention can alleviate the expansion of lithium storage of silicon materials and improve the problem of poor cycle life of the silicon-carbon negative electrode.
While embodiments of the present invention have been described in detail hereinabove, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. It is to be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the following claims. Moreover, the invention described herein is capable of other embodiments and of being practiced or of being carried out in various ways.

Claims (10)

1. The surface coating modification method of the silicon-carbon negative electrode is characterized by comprising the following steps of:
s1, stirring and mixing graphite particles with a first cellulose solution, performing regeneration treatment, and performing vacuum heat treatment to obtain modified graphite particles;
s2, stirring and mixing the modified graphite particles with a second cellulose solution, and sequentially carrying out regeneration treatment and vacuum heat treatment, and then carrying out gaseous silicon deposition;
s3, repeating the step S2 until the thickness of the silicon layer on the surface of the modified graphite particle reaches the preset thickness of the silicon layer, and preparing a silicon-graphite compound;
s4, stirring and mixing the silicon-graphite composite and a third cellulose solution, and sequentially carrying out regeneration treatment and vacuum heat treatment, and then carrying out gaseous carbon deposition;
and S5, repeating the step S4 until the thickness of the carbon layer on the surface of the silicon-graphite composite reaches the preset thickness of the carbon layer, and obtaining the silicon-carbon anode material.
2. The method for modifying a surface of a silicon-carbon negative electrode according to claim 1, wherein the solvents of the first cellulose solution, the second cellulose solution, and the third cellulose solution are all alkaline urea solutions.
3. The method according to claim 2, wherein the regeneration solution used in the regeneration treatment is an acidic solution having a pH of less than 5.
4. The method for modifying the surface coating of a silicon-carbon negative electrode according to claim 1, wherein the vacuum heat treatment is performed at a temperature of 300-400 ℃ for 4-5 hours.
5. The method for modifying a surface coating of a silicon-carbon negative electrode according to claim 1, wherein the preset thickness of the silicon layer is 100-500nm.
6. The method for modifying a silicon-carbon negative electrode surface coating according to claim 1, wherein the carbon layer has a preset thickness of 5-20nm.
7. The method for modifying the surface coating of a silicon-carbon negative electrode according to claim 1, wherein the gaseous silicon source is used for deposition in a vacuum environment of 600-1000 ℃ during the gaseous silicon deposition; the gaseous silicon source is silane.
8. The method for modifying the surface coating of a silicon-carbon negative electrode according to claim 1, wherein the gaseous carbon source is used for deposition in a vacuum environment of 600-1000 ℃ during the gaseous carbon deposition; the gaseous carbon source is acetylene and/or methane.
9. A silicon-carbon negative electrode prepared by the silicon-carbon negative electrode surface coating modification method as claimed in any one of claims 1 to 8.
10. Use of a silicon-carbon negative electrode prepared by the surface coating modification method of a silicon-carbon negative electrode according to any one of claims 1 to 8 in a lithium ion battery.
CN202311072309.7A 2023-08-24 2023-08-24 Silicon-carbon negative electrode and surface coating modification method and application thereof Pending CN117038907A (en)

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