CN112635721A - Silicon-carbon composite material and preparation method and application thereof - Google Patents

Silicon-carbon composite material and preparation method and application thereof Download PDF

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CN112635721A
CN112635721A CN201910953719.XA CN201910953719A CN112635721A CN 112635721 A CN112635721 A CN 112635721A CN 201910953719 A CN201910953719 A CN 201910953719A CN 112635721 A CN112635721 A CN 112635721A
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CN112635721B (en
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李祥龙
张兴豪
智林杰
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National Center for Nanosccience and Technology China
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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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • 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
    • 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
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    • Y02E60/10—Energy storage using batteries

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Abstract

The invention relates to a silicon-carbon composite material and a preparation method and application thereof. The silicon-carbon composite material comprises: two-dimensional silicon materials and two-dimensional carbon materials covalently bonded through heteroatoms. In the silicon-carbon composite material, the two-dimensional carbon material is covalently bonded on the two-dimensional silicon material in a face-to-face contact manner through the heteroatom, so that reliable and efficient contact is formed between silicon and carbon, transmission of electrons and lithium ions is greatly facilitated, direct contact between silicon and electrolyte is effectively prevented, and a solid electrolyte interface layer on the surface of the silicon is greatly stabilized, so that the stability of contact between the silicon and the carbon in the volume change process is ensured, and the silicon-carbon composite material is favorably used as a negative active material to be applied to a lithium ion battery.

Description

Silicon-carbon composite material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of battery cathode materials, and particularly relates to a silicon-carbon composite material and a preparation method and application thereof.
Background
Silicon is a negative active material with great development prospect due to its extremely high theoretical specific charge capacity, and can replace graphite negative active material for secondary batteries. However, the silicon material is accompanied by a great volume change during charge and discharge, and the generated mechanical stress causes pulverization and structural collapse of the active material and detachment between the active materials and between the active material and the current collector, thereby causing rapid capacity fading and a sharp decrease in battery cycle performance.
Meanwhile, the silicon interface is difficult to form a stable Solid Electrolyte Interface (SEI) film due to the volume expansion of silicon, resulting in the consumption of active materials and the reduction of charge and discharge efficiency, accelerating the deterioration of cycle performance. The nano-structured silicon and carbon hybrid composite material can solve the problems of unstable structure, surface interface and performance of silicon caused by volume expansion in the charging and discharging processes to a certain extent.
CN102437318B discloses a preparation method of a silicon-carbon composite material, the prepared silicon-carbon composite material and a silicon-carbon composite material containing the silicon-carbon composite material. The preparation method comprises the steps of directly mixing a phenol monomer, an aldehyde monomer and silicon monoxide, carrying out polymerization reaction under certain conditions to obtain a mixture of silicon monoxide coated by phenolic resin, and carrying out heat treatment and corrosion processes to obtain the silicon-carbon composite material with the core-shell structure. Through simple coating structure design, can effectively improve silicon carbon composite's electric conductivity, stabilize electrolyte contact interface, but the huge volume change in the charge-discharge process can directly lead to the destruction of outer carbon coating, and then makes the cladding strategy inefficacy, and the rapid decay of capacity and battery cycle performance sharply reduce.
At present, in the Silicon-Carbon composite material with great potential, a cavity must be reserved between Silicon and Carbon components to accommodate the volume expansion of Silicon, so as to effectively avoid the damage of the Carbon components and the Contact interface between the Carbon components and the electrolyte, such as a representative egg yolk shell structure, a representative tube center line structure and the like (Contact-Engineered and volume-induced Silicon/Carbon Nanohybrids as Lithium-Ion-Battery antibodies, Advanced Materials 2013,25, 3560). However, in such a composite structure, silicon and carbon belong to a point-to-point contact mode, which is not favorable for the transmission of electrons and lithium ions, and seriously restricts the improvement of the lithium storage performance.
Therefore, a simple-process and large-scale method is found, and the problem to be solved at present is to find a silicon-carbon composite structure material which has a structure, stable interface and excellent electron/lithium ion transmission characteristics.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a silicon-carbon composite material and a preparation method and application thereof. The silicon-carbon composite material prevents direct contact between silicon and electrolyte, and greatly stabilizes a solid electrolyte interface layer on the surface of the silicon, so that the contact stability between the silicon and carbon in the volume change process is ensured.
In order to achieve the purpose, the invention adopts the following technical scheme:
one of the objects of the present invention is to provide a silicon carbon composite material, comprising: two-dimensional silicon materials and two-dimensional carbon materials covalently bonded through heteroatoms.
In the silicon-carbon composite material, the two-dimensional carbon material unit is covalently bonded on the two-dimensional silicon material unit through the heteroatom in a face-to-face contact mode, so that reliable and efficient contact is formed between silicon and carbon, transmission of electrons and lithium ions is greatly facilitated, direct contact between silicon and electrolyte is effectively prevented, and a silicon surface solid-phase electrolyte interface layer is greatly stabilized, so that the contact stability of silicon and carbon in the volume change process is ensured, and the silicon-carbon composite material is favorably used as a negative active material for a lithium ion battery.
The structural schematic diagram of the silicon-carbon composite material is shown in fig. 1, wherein 1 represents a two-dimensional covalently bonded silicon-carbon composite material, the right side of 1 is an enlarged structural diagram of a silicon-carbon composite material unit, wherein 11 represents a two-dimensional silicon material, 12 represents a two-dimensional carbon material, and 112 represents a heteroatom for bonding and/or bridging the two-dimensional silicon material and the two-dimensional carbon material.
Preferably, the hetero atom includes any one of an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom and a boron atom or a combination of at least two thereof.
The hetero atoms are easy to form stable combination with the carbon material and the silicon material, so that a stable bonding effect is formed between silicon and carbon, reliable and efficient contact is formed between silicon and carbon, transmission of electrons and lithium ions is greatly facilitated, direct contact between silicon and electrolyte is effectively prevented, a solid electrolyte interface layer on the surface of the silicon is greatly stabilized, and accordingly stable contact between the silicon and the carbon in the volume change process is ensured.
Preferably, the two-dimensional silicon material is covalently bonded to the two-dimensional carbon material through a heteroatom in a face-to-face contact.
Preferably, the thickness of the two-dimensional carbon material is 2 to 50nm, such as 5nm, 8nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, or 45 nm.
Preferably, the size of the two-dimensional silicon material is 3-1000 nm, such as 5nm, 8nm, 10nm, 20nm, 30nm, 50nm, 80nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm or 900 nm.
Preferably, the content of the two-dimensional silicon material in the silicon-carbon composite material is 50 wt% to 99 wt%, preferably 80 wt% to 96 wt%, such as 52 wt%, 55 wt%, 58 wt%, 60 wt%, 62 wt%, 65 wt%, 68 wt%, 70 wt%, 75 wt%, 78 wt%, 80 wt%, 82 wt%, 85 wt%, 90 wt%, 95 wt%, 98 wt%, or the like.
Preferably, the content of the two-dimensional carbon material in the silicon-carbon composite material is 1 to 50 wt%, such as 2 wt%, 5 wt%, 8 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, or 45 wt%.
Preferably, the content of the heteroatom in the silicon-carbon composite material is 2-10 wt%, such as 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt% or 9 wt%.
The silicon-carbon composite material has excessive heteroatom content (more than 10 wt%), and an excessive dense bonding layer is formed between silicon and carbon, so that the rapid transmission of lithium ions is hindered, and the electrochemical lithium storage performance is not favorably exerted; when the content of the hetero atom is too small (less than 2 wt%), it is difficult to form a stable bonding effect between silicon and carbon, and direct contact between silicon and an electrolyte cannot be effectively prevented, so that the cycle performance is sharply reduced.
A second object of the present invention is a method for preparing a silicon-carbon composite material according to the first object, comprising the steps of:
and (3) taking hydrogen as a carrier gas, and carrying out chemical vapor deposition on the two-dimensional silicon material to obtain a carbon source.
The carrier gas in the chemical vapor deposition process is hydrogen, in the high-temperature process, the hydrogen reduces the intrinsic silicon dioxide layer on the surface of the two-dimensional silicon nanosheet to generate active silicon or a silicon-oxygen dangling bond which is combined with active carbon atoms generated by hydrocarbon pyrolysis to form a heteroatom-bonded two-dimensional silicon/carbon hybrid material, the carrier gas in the chemical vapor deposition process can only be hydrogen, other gases cannot achieve the technical effect of the chemical vapor deposition process, and the product cannot be prepared.
Preferably, the flow rate of the carrier gas is 5-2000 sccm, such as 10sccm, 20sccm, 50sccm, 100sccm, 200sccm, 400sccm, 500sccm, 600sccm, 800sccm, 1000sccm, 1200sccm, 1400sccm, 1500sccm, 1600sccm, 1800sccm, or 1900 sccm.
Preferably, the chemical vapor deposition is carried out under a non-oxidizing atmosphere, preferably any one or a combination of at least two of hydrogen, nitrogen, argon, helium and carbon dioxide.
Preferably, the temperature of the silicon material of the two-dimensional structure unit in the chemical vapor deposition process is 500-1200 ℃, preferably 750-1050 ℃, such as 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃, 1050 ℃, 1100 ℃ or 1150 ℃.
The temperature is too high, and the two-dimensional silicon nanosheet is molten to cause structural damage; at too low a temperature, the hydrocarbons are difficult to crack to produce activated carbon species.
Preferably, the time of the chemical vapor deposition is 5s to 60min, preferably 10s to 20min, such as 8s, 10s, 15s, 20s, 30s, 40s, 50s, 1min, 2min, 5min, 8min, 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min, or the like.
The deposition time is too long (more than 60min), and an excessively thick carbon coating layer is generated on the surface of the two-dimensional silicon nanosheet, so that the rapid transmission of lithium ions is inhibited, and the electrochemical lithium storage performance is not favorably exerted; too short a time (less than 5s) makes it difficult to form an effective carbon coating layer, which is disadvantageous in forming a stable surface solid phase electrolyte interface layer.
Preferably, the carbon source is a hydrocarbon.
Preferably, the carbon source is added in an amount of 5 to 2000sccm, such as 10sccm, 20sccm, 50sccm, 100sccm, 200sccm, 500sccm, 800sccm, 1000sccm, 1200sccm, 1500sccm, or 1800 sccm.
Preferably, the hydrocarbon compound includes any one of aliphatic compounds, alicyclic compounds, aromatic compounds, heterocyclic compounds or a combination of at least two thereof, preferably any one of methane, propane, ethylene, acetylene, methanol, ethanol, ethylene glycol, propanol, isopropanol, acetone, acetonitrile, toluene, xylene, cyclohexane, thiophene and pyridine or a combination of at least two thereof.
Preferably, the two-dimensional silicon material is prepared by a metallothermic reduction method or a chemical stripping method.
As a preferred technical scheme, the preparation method of the silicon-carbon composite material comprises the following steps:
heating the silicon material with the two-dimensional structure unit in a non-oxidizing atmosphere to a reaction temperature of 750-1050 ℃, and depositing a carbon material on the silicon material with the two-dimensional structure unit by a chemical vapor deposition method for 5 s-60 min by taking a hydrocarbon as a carbon source and hydrogen as a carrier gas to form the silicon-carbon composite material.
It is a further object of the present invention to provide a use of the silicon-carbon composite according to one of the objects for an electrochemical energy storage device and/or an energy storage system, preferably for any one or a combination of at least two of a lithium ion, sodium ion battery, potassium ion battery and supercapacitor.
The fourth object of the present invention is to provide a negative electrode material comprising the silicon-carbon composite material according to one of the objects.
Compared with the prior art, the invention has the following beneficial effects:
(1) the method directly starts from a silicon material with a two-dimensional structure unit, improves chemical vapor deposition by adopting hydrogen as carrier gas, and further obtains the two-dimensional covalently bonded silicon-carbon composite cathode material.
(2) The two-dimensional covalent bonding silicon-carbon composite material prepared by the invention has stable structure and interface, is very suitable for being used as a lithium ion battery cathode active material, and is mainly characterized in that the composite material integrates the characteristics (high-capacity and relatively stable structure and interface) of a two-dimensional silicon material, the characteristics (high-efficiency transmission medium of electrons and ions) of a two-dimensional carbon material and the advantages (being beneficial to establishing a high-efficiency and reliable silicon-carbon mixed transmission channel and fundamentally inhibiting SEI generation, thereby ensuring the stability of the reliable and efficient electron/lithium ion transmission channel in the circulation process), shows extremely excellent specific charge-discharge capacity and circulation stability, has the specific capacity as high as 2765mAh/g even under the charge-discharge current density as high as 0.5C, and has the capacity retention rate as high as 97 percent after 500 times of circulation, the capacity retention rate at 800 weeks is up to 94 percent, and the capacity retention rate at 950 weeks is up to 91 percent.
Drawings
Fig. 1 is a schematic structural diagram of a silicon-carbon composite material according to the present invention, wherein 1 represents a silicon-carbon composite material, the right side of 1 is an enlarged structural diagram of a silicon-carbon composite material unit, 11 represents a two-dimensional silicon material, 12 represents a two-dimensional carbon material, and 112 represents a heteroatom;
fig. 2 is a schematic structural diagram of a silicon-carbon composite material obtained in comparative example 1 of the present invention, where 2 represents the silicon-carbon composite material, the right side of 2 is an enlarged structural diagram of a silicon-carbon composite material unit, 21 represents a two-dimensional silicon material, and 22 represents a two-dimensional carbon material.
Detailed Description
For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The preparation method of the silicon-carbon composite material comprises the following steps:
placing a two-dimensional silicon material with the thickness of 0.5nm and prepared by a metallothermic reduction method in a high-temperature tubular furnace, heating to 750 ℃ under the atmosphere of argon, closing the argon, introducing 200sccm hydrogen and 200sccm acetylene, reacting for 10min, and reducing to room temperature under the atmosphere of argon to obtain the silicon-carbon composite material, wherein the weight percentage of silicon is 95 wt%, the heteroatom covalently bonded between the two-dimensional silicon material and the two-dimensional silicon material is oxygen atom, and the content of the heteroatom is 4 wt%.
Example 2
The preparation method of the silicon-carbon composite material comprises the following steps:
placing a two-dimensional silicon material with the thickness of 0.7nm and prepared by a chemical stripping method in a high-temperature tubular furnace, heating to 800 ℃ under the atmosphere of nitrogen, closing the nitrogen, introducing thiophene into a reaction system by taking hydrogen (15sccm) as carrier gas, reacting for 60min, and reducing to room temperature under the atmosphere of nitrogen to obtain the silicon-carbon composite material, wherein the weight percentage of silicon is 92 wt%, and heteroatoms covalently bonded between the two-dimensional silicon material and the two-dimensional silicon material are oxygen atoms and the content of the heteroatoms is 5 wt%.
Example 3
The preparation method of the silicon-carbon composite material comprises the following steps:
placing a two-dimensional silicon material with the thickness of 1nm of silicon oxide prepared by a chemical stripping method in a high-temperature tube furnace, heating to 500 ℃ under the atmosphere of helium, closing the helium, introducing pyridine into a reaction system by taking hydrogen (50sccm) as carrier gas, reacting for 40min, and reducing to room temperature under the atmosphere of argon to obtain the two-dimensional covalent bonding silicon-carbon composite material, wherein the weight percentage of silicon is 61 wt%, and heteroatoms in covalent bonding between the two-dimensional carbon material and the two-dimensional silicon material are oxygen atoms and the content of the heteroatoms is 8 wt%.
Example 4
The preparation method of the silicon-carbon composite material comprises the following steps:
placing a two-dimensional silicon material with the thickness of 0.5nm and prepared by a metallothermic reduction method in a high-temperature tubular furnace, heating to 1200 ℃ under the atmosphere of argon, closing the argon, introducing 250sccm hydrogen and 500sccm methane, reacting for 5s, and reducing to room temperature under the atmosphere of argon to obtain the silicon-carbon composite material, wherein the weight percentage of silicon is 85 wt%, the heteroatom covalently bonded between the two-dimensional silicon material and the two-dimensional silicon material is oxygen atom, and the content of the heteroatom is 4 wt%.
Example 5
The difference from example 1 is that the temperature of the elevated temperature was 1050 ℃ and the content of the hetero atom was 3% by weight.
Example 6
The difference from example 1 is that the temperature of the elevated temperature was 400 ℃ and the content of the hetero atom was 6 wt%.
Example 7
The difference from example 1 is that the temperature of the elevated temperature was 1300 ℃ and the content of the hetero atom was 2% by weight.
Comparative example 1
The difference from embodiment 1 is that 200sccm hydrogen gas is replaced by 200sccm argon gas, that is, argon gas is used as a carrier gas, and the structural diagram of the obtained silicon-carbon composite material is shown in fig. 2, where 2 represents a silicon-carbon composite material, the right side of 2 is an enlarged structural diagram of a silicon-carbon composite material unit, 21 represents a two-dimensional silicon material, and 22 represents a two-dimensional carbon material, and it can be seen from the diagram that the obtained silicon-carbon composite material does not contain heteroatoms.
And (3) performance testing:
taking the obtained silicon-carbon composite material as a negative active material, uniformly mixing the negative active material, a conductive agent (acetylene black) and a binder (sodium alginate) to prepare slurry, coating the slurry on a copper foil current collector, carrying out vacuum drying at 70 ℃ for 2 hours, and rolling to prepare a negative pole piece; the negative pole piece is taken as a test electrode, the metal lithium is taken as a counter electrode, and the mixed solution of ethylene carbonate and diethyl carbonate dissolved with lithium hexafluorophosphate is taken as electrolyte (1mol/L LiPF)6DEC, the volume ratio of EC and DEC is 1:1), Celgard 2400 polypropylene membrane is taken as a diaphragm, and a button type lithium ion battery is assembled in a glove box with the oxygen content and the water content both less than 0.1 ppm.
(1) Specific capacity of initial discharge: testing the first discharge specific capacity of the obtained battery at room temperature, wherein the charge-discharge voltage interval is 0.02-1V and the current density is 0.5C;
(2) and (3) testing the cycle performance: the obtained battery is tested for the cycle performance at the current density of 0.5C under the conditions that the charging and discharging voltage interval is 0.02-1V at room temperature.
TABLE 1
Figure BDA0002226586900000091
As can be seen from table 1, in the silicon-carbon composite material prepared by the present invention, the two-dimensional carbon material is covalently bonded to the two-dimensional silicon material through the heteroatom in a surface-to-surface contact manner, and compared to the comparative sample (comparative example 1), the silicon-carbon composite material not only forms reliable and efficient contact between silicon and carbon, greatly facilitates the transmission of electrons and lithium ions, but also efficiently prevents direct contact between silicon and electrolyte, and greatly stabilizes the solid electrolyte interface layer on the silicon surface, thereby ensuring the stability of contact between silicon and carbon during the volume change process, and being beneficial to being applied to a lithium ion battery as a negative active material.
As can be seen from table 1, the cycle performance of example 6 of the present invention is inferior to that of example 1, because the temperature of the temperature rise in example 6 is 400 ℃, the temperature is too low, and the hydrocarbons are difficult to crack to generate activated carbon species, so the cycle performance is poor; compared with the embodiment 1, the embodiment 7 of the invention has poor cycle performance, because the temperature of the temperature rise in the embodiment 7 is 1300 ℃, and the temperature is too high, the two-dimensional silicon nanosheet melts to cause structural damage, and thus the cycle performance is poor.
The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims (10)

1. A silicon carbon composite, comprising: two-dimensional silicon materials and two-dimensional carbon materials covalently bonded through heteroatoms.
2. The silicon-carbon composite of claim 1, wherein the heteroatoms comprise any one or a combination of at least two of oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, and boron atoms;
preferably, the two-dimensional silicon material is covalently bonded to the two-dimensional carbon material through a heteroatom in a face-to-face contact manner;
preferably, the thickness of the two-dimensional carbon material is 2-50 nm;
preferably, the size of the two-dimensional silicon material is 3-1000 nm.
3. Silicon-carbon composite material according to claim 1 or 2, wherein the content of the two-dimensional silicon material in the silicon-carbon composite material is 50-99 wt%, preferably 80-96 wt%;
preferably, the content of the two-dimensional carbon material in the silicon-carbon composite material is 1-50 wt%;
preferably, the content of the heteroatom in the silicon-carbon composite material is 2-10 wt%.
4. A method for the preparation of a silicon-carbon composite material according to any one of claims 1 to 3, characterized in that it comprises the following steps:
and (3) taking hydrogen as a carrier gas, and carrying out chemical vapor deposition on the two-dimensional silicon material to obtain a carbon source.
5. The method according to claim 4, wherein the carrier gas has a flow rate of 5 to 2000 sccm;
preferably, the chemical vapor deposition is carried out under a non-oxidizing atmosphere, preferably any one or a combination of at least two of hydrogen, nitrogen, argon, helium and carbon dioxide.
6. The preparation method according to claim 4 or 5, wherein the temperature of the silicon material of the two-dimensional structural unit in the chemical vapor deposition process is 500-1200 ℃, preferably 750-1050 ℃;
preferably, the time of the chemical vapor deposition is 5s to 60min, preferably 10s to 20 min.
7. The production method according to any one of claims 4 to 6, wherein the carbon source is a hydrocarbon;
preferably, the adding amount of the carbon source is 5-2000 sccm;
preferably, the hydrocarbon compound comprises any one of aliphatic compounds, alicyclic compounds, aromatic compounds and heterocyclic compounds or a combination of at least two of the compounds, preferably any one of methane, propane, ethylene, acetylene, methanol, ethanol, ethylene glycol, propanol, isopropanol, acetone, acetonitrile, toluene, xylene, cyclohexane, thiophene and pyridine or a combination of at least two of the compounds;
preferably, the two-dimensional silicon material is prepared by a metallothermic reduction method or a chemical stripping method.
8. The method according to any one of claims 4 to 7, wherein the method comprises the steps of:
heating the silicon material with the two-dimensional structure unit in a non-oxidizing atmosphere to a reaction temperature of 750-1050 ℃, and depositing a carbon material on the silicon material with the two-dimensional structure unit by a chemical vapor deposition method for 5 s-60 min by taking a hydrocarbon as a carbon source and hydrogen as a carrier gas to form the silicon-carbon composite material.
9. Use of a silicon-carbon composite material according to any one of claims 1 to 3 in an electrochemical energy storage device and/or energy storage system, preferably in any one or a combination of at least two of lithium ion, sodium ion, potassium ion and supercapacitor.
10. A negative electrode material, characterized in that it comprises a silicon-carbon composite material according to any one of claims 1 to 3.
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