CN115881918A - Silicon-carbon negative electrode material with core-shell structure, preparation method and lithium ion battery - Google Patents
Silicon-carbon negative electrode material with core-shell structure, preparation method and lithium ion battery Download PDFInfo
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- 239000011258 core-shell material Substances 0.000 title claims abstract description 70
- 239000007773 negative electrode material Substances 0.000 title claims abstract description 54
- 238000002360 preparation method Methods 0.000 title claims abstract description 31
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 17
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 17
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 41
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 31
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 31
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical group [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 20
- 229910052799 carbon Inorganic materials 0.000 claims description 14
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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 silicon-carbon anode material with a core-shell structure, a preparation method thereof and a lithium ion battery, wherein the preparation method comprises the following steps: s1, obtaining a graphite material coated by a silicon nanowire through chemical vapor deposition of graphite and an organic silicon precursor under a high-temperature condition; and S2, introducing hydrocarbon gas under the condition of protective atmosphere and preserving heat to obtain the silicon-carbon negative electrode material with the core-shell structure. The silicon-carbon cathode material prepared by the invention not only can effectively relieve the volume expansion of the silicon-based cathode material, but also can effectively prevent the silicon nanowire from directly contacting with the electrolyte, thereby greatly improving the cycle performance of the lithium ion battery.
Description
Technical Field
The invention relates to the field of battery manufacturing, in particular to a silicon-carbon negative electrode material with a core-shell structure, a preparation method and a lithium ion battery.
Background
With the rapid development of economy, electrochemical energy storage taking a lithium ion battery as a main expression form is greatly concerned and favored in various portable electronic products due to the characteristics of environmental friendliness, long cycle life, small self-discharge, high energy density, high voltage and the like, and is widely applied to various portable electronic products. However, the low specific capacity (372 mAh/g) of the commercial graphite negative electrode material is difficult to meet the use requirement of a new energy automobile power battery and the like on high energy density.
The silicon material is most expected to be the first choice material of the next generation of negative electrode material due to the higher specific capacity (4200 mAh/g) and rich crust reserve, however, silicon is used as a semiconductor material, the conductivity to lithium ions and electrons is poor, and the volume expansion of particles in the charging and discharging process is up to 300% due to the alloying reaction of silicon and lithium, which easily causes the damage of an electrode structure and the severe attenuation of battery capacity, the problems seriously limit the large-scale use of silicon as the negative electrode material, the nanocrystallization of the silicon material is an effective way, and the batch and efficient preparation of nano silicon becomes an important technical basis for realizing industrialization and is also the current faced difficult problem.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a silicon-carbon negative electrode material with a core-shell structure, a preparation method and a lithium ion battery.
In order to achieve the purpose, the invention adopts the following technical scheme:
the first aspect of the invention provides a preparation method of a silicon-carbon anode material with a core-shell structure, which comprises the following steps:
s1, under a vacuum condition, obtaining a graphite material coated by a silicon nanowire through chemical vapor deposition of graphite and an organic silicon precursor under a high-temperature condition;
and S2, introducing hydrocarbon gas under the condition of protective atmosphere, and preserving heat to obtain the silicon-carbon negative electrode material with the core-shell structure.
Preferably, in step S1:
the organic silicon precursor is selected from SiCl 4 、HSiCl 3 、H 2 SiCl 2 、H 3 SiCl、CH 3 SiCl 3 、(CH 3 ) 2 SiHCl 2 、HSiBr 3 、H 2 SiBr 2 、H 3 SiBr、SiBr 4 、HSiI 3 、H 2 SiI 2 、H 3 SiI、SiI 4 、CH 5 One or more of SiI; and/or
The particle size of the graphite is 5-10 mu m.
Preferably, in step S1:
under the vacuum condition, the pressure is more than or equal to 10 -5 Pa; and/or
Under the condition of high temperature, the heating rate is 1-10 ℃/min, and the high temperature is 700-1000 ℃; and/or
The heat preservation time is 0.6 to 6 hours under the high temperature condition.
Preferably, in the step S1, the diameter of the silicon nanowire on the graphite material coated with the silicon nanowire is 10 to 200nm.
Preferably, in step S2:
the protective atmosphere is argon, nitrogen, hydrogen and CO 2 One or more of the above; and/or
The hydrocarbon gas is one or more of methane, ethylene, acetylene, propylene, benzene and toluene; and/or
The feeding speed of the hydrocarbon gas is 0.5-1L/h; and/or
In the heat preservation process, the heat preservation temperature is 700-1000 ℃, and the heat preservation time is 1-3 h.
The second aspect of the present invention provides a core-shell structured silicon carbon negative electrode material prepared by the preparation method of the core-shell structured silicon carbon negative electrode material according to the first aspect of the present invention, which comprises the following components by mass: graphite: 5-99%, silicon nanowire: 1-90% and vapor deposition carbon 0.1-20%.
Preferably, the silicon nanowire is coated on the surface of the graphite core to form a silicon-carbon composite core, and the vapor deposition carbon is attached to the surface of the silicon-carbon composite core to form a vapor deposition carbon layer.
Preferably, the thickness of the vapor deposition carbon layer is 5-50 nm; and/or
The granularity of the silicon-carbon negative electrode material with the core-shell structure is 10-15 mu m, and the specific surface area is 1-3 m 2 /g。
Preferably, the first efficiency of the silicon-carbon anode material with the core-shell structure is greater than 86%.
The third aspect of the present invention provides a lithium ion battery, wherein the negative electrode of the lithium ion battery adopts the core-shell structured silicon-carbon negative electrode material prepared by the preparation method of the core-shell structured silicon-carbon negative electrode material according to the first aspect of the present invention.
The invention has the beneficial effects that:
1. according to the silicon-carbon negative electrode material with the core-shell structure and the preparation method thereof, the silicon-carbon negative electrode material with the core-shell structure is prepared by taking organic silicon as a precursor through a chemical vapor deposition process, and the silicon-carbon negative electrode material not only can effectively relieve the volume expansion of a silicon-based negative electrode material, but also can effectively prevent a silicon nanowire from being in direct contact with an electrolyte, so that the cycle performance of a lithium ion battery is greatly improved;
2. the invention adopts the chemical vapor deposition process to obtain the vapor deposition carbon, which can improve the conductivity of the silicon-carbon cathode material, thereby effectively reducing the impedance and the polarization degree and realizing the purpose of improving the electrochemical performance of the lithium battery;
3. the silicon-carbon anode material with the core-shell structure prepared by the invention has the advantages of simple and convenient process, environmental friendliness, no pollution and easy realization of large-scale production.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic structural diagram of a silicon-carbon anode material with a core-shell structure according to the present invention;
fig. 2 is a powder diffraction XRD spectrogram of the core-shell structured silicon-carbon anode material prepared in example 1 of the present invention;
fig. 3 is an electrochemical performance diagram of the core-shell structured silicon-carbon negative electrode material prepared in example 7 of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way.
Aiming at the problems of low initial efficiency, poor cycling stability, high preparation cost and the like of a silicon-carbon negative electrode material in the prior art, the silicon-carbon negative electrode material with a core-shell structure is prepared by taking organic silicon as a precursor and adopting a chemical vapor deposition process, has the advantages of low initial irreversible specific capacity, excellent cycling performance, low preparation cost and the like, and shows high initial efficiency and stable long cycling performance when applied to a lithium ion negative electrode.
The invention provides a preparation method of a silicon-carbon anode material with a core-shell structure, which specifically comprises the following steps:
s1, under a vacuum condition, obtaining a graphite material coated by a silicon nanowire through chemical vapor deposition of graphite and an organic silicon precursor under a high-temperature condition;
specifically, if the organosilicon precursor is a gas, placing graphite in a chemical vapor deposition furnace, and introducing the organosilicon precursor under a vacuum condition; if the organic silicon precursor is solid or liquid, mixing graphite and the organic silicon precursor, placing the mixture in a chemical vapor deposition furnace, and vacuumizing the chemical vapor deposition furnace; and then heating to raise the temperature for chemical vapor deposition, keeping for a period of time under a high-temperature condition, and decomposing the organic silicon precursor into silicon nanowires to coat the surfaces of the graphite in the process to form the graphite material coated by the silicon nanowires.
Wherein the particle size of the graphite is 5-10 μm; the organosilicon precursor is selected from SiCl 4 、HSiCl 3 、H 2 SiCl 2 、H 3 SiCl、CH 3 SiCl 3 、(CH 3 ) 2 SiHCl 2 、HSiBr 3 、H 2 SiBr 2 、H 3 SiBr、SiBr 4 、HSiI 3 、H 2 SiI 2 、H 3 SiI、SiI 4 、CH 5 One or more of SiI.
In the Chemical Vapor Deposition (CVD) process, the pressure under the vacuum condition is more than or equal to 10 -5 Pa; in the high-temperature treatment process, the heating rate is 1-10 ℃/min, the high-temperature is 700-1000 ℃, and the heat preservation time is 0.6-6 h.
The diameter of the silicon nanowire on the prepared graphite material coated by the silicon nanowire is 10-200 nm.
And S2, introducing hydrocarbon gas under the condition of protective atmosphere, and preserving heat to obtain the silicon-carbon negative electrode material with the core-shell structure.
Specifically, after the treatment in the step S1, the introduction of the organic silicon precursor is stopped, the introduction of the hydrocarbon gas is performed under a protective atmosphere condition, and the temperature is maintained for a period of time, in the process, the hydrocarbon gas is pyrolyzed, and vapor deposition carbon is generated on the surface of the graphite material coated with the silicon nanowires, so that the silicon-carbon negative electrode material with the core-shell structure is obtained.
Wherein the protective atmosphere is argon, nitrogen, hydrogen, CO 2 One or more of the above; the hydrocarbon gas is one or more of methane, ethylene, acetylene, propylene, benzene and toluene; the feeding speed of hydrocarbon gas is 0.5-1L/h; the flow rate ratio of the hydrocarbon gas to the gas used in the protective atmosphere is 1 to 5:1 to 10. In the heat preservation process, the heat preservation temperature is 700-1000 ℃, and the heat preservation time is 1-3 h.
The core-shell structure silicon-carbon negative electrode material prepared by the preparation method of the core-shell structure silicon-carbon negative electrode material comprises the following components in percentage by mass: graphite: 5-99%, silicon nanowire: 1-90% and vapor deposition carbon 0.1-20%. As shown in fig. 1, the silicon nanowire 2 is coated on the surface of the graphite core 1 to form a silicon-carbon composite core, and the vapor deposition carbon is attached to the surface of the silicon-carbon composite core to form a vapor deposition carbon layer 3.
With reference to fig. 1, the thickness of the vapor deposition carbon layer of the silicon-carbon negative electrode material with the core-shell structure is 5-50 nm; the granularity of the silicon-carbon negative electrode material with the core-shell structure is 10-15 mu m, and the specific surface area is 1-3 m 2 /g。
Electrochemical performance tests are carried out on the silicon-carbon negative electrode material with the core-shell structure, the first effect of 0.1C (1C = 600mA/g) is greater than 86%, and the charge capacity is greater than 495mAh/g.
The invention also provides a lithium ion battery, and the cathode of the lithium ion battery adopts the silicon-carbon cathode material with the core-shell structure.
The core-shell structured silicon-carbon negative electrode material and the preparation method thereof according to the present invention will be further described with reference to specific examples.
Example 1
The preparation method of the core-shell structured silicon-carbon negative electrode material of the embodiment is as follows:
10g of graphite is put into a chemical vapor deposition furnace and is vacuumized to 10 DEG -5 Pa, raising the temperature to 900 ℃ at the speed of 5 ℃/min, and introducing SiCl 4 Keeping the temperature for 2 hours; at this time, siCl4 was changed to acetylene (hydrocarbon gas) and argon gas (protective gas) at a flow rate ratio of 1.
Fig. 2 is a powder diffraction XRD spectrum diagram of the core-shell structured silicon carbon negative electrode material, wherein XRD diffraction peaks show the presence of graphite and crystalline silicon phases.
The silicon-carbon cathode material with the core-shell structure is used for manufacturing a cathode, lithium metal is used as an anode, and the electrolyte is 1.0M LiPF 6 DEC: DEC =1Electrochemical tests were performed, with a charge capacity of 545.3mAh/g at 0.1C (1C = 600mA/g) and a first effect of 86.4%.
Example 2
The preparation method of the core-shell structured silicon-carbon negative electrode material of the embodiment is as follows:
10g of graphite is put into a chemical vapor deposition furnace and is vacuumized to 10 DEG -5 Pa, heating to 850 deg.C at a speed of 10 deg.C/min, and introducing SiCl 3 H, keeping the temperature for 2 hours; at this time, siCl is introduced 3 H is replaced by ethylene (hydrocarbon gas) and argon (protective gas), the flow rate ratio is 2.
The silicon-carbon anode material with a core-shell structure is used for manufacturing an anode, lithium metal is used as a cathode, and the electrolyte is 1.0M LiPF 6 DEC: DEC =1 = 11 vol% with 5.0% fec, separator Celgard 2400, electrochemical tests were performed with a charge capacity of 545.3mAh/g and a first effect of 86.4% at 0.1C (1c = 600ma/g).
Example 3
The preparation method of the core-shell structured silicon-carbon negative electrode material of the embodiment is as follows:
10g of graphite is put into a chemical vapor deposition furnace and is vacuumized to 10 DEG -5 Pa, heating to 800 deg.C at a speed of 10 deg.C/min, and introducing SiCl 2 H 2 Keeping the temperature for 3 hours; at this time, siCl is added 2 H 2 And (3) changing the reaction temperature to ethylene (hydrocarbon gas) and argon (protective gas), wherein the flow rate is 1.
The silicon-carbon cathode material with the core-shell structure is used for manufacturing a cathode, lithium metal is used as an anode, and the electrolyte is 1.0M LiPF 6 DEC: DEC =1 = th 5.0% fec with diaphragm cellgard 2400, electrochemical tests were performed with a charge capacity of 574.2mAh/g at 0.1C (1c =600ma/g) and a first effect of 86.6%.
Example 4
The preparation method of the core-shell structured silicon-carbon negative electrode material of the embodiment is as follows:
10g of graphite and 4g of SiBr 4 The solution is mixed and placed in a chemical vapor deposition furnace and is vacuumized to 10 DEG -5 Pa, heating to 900 ℃ at the speed of 10 ℃/min, and preserving heat for 3 hours; at this time, ethylene (hydrocarbon gas) and argon (protective gas) are introduced, the flow rate ratio is 1.
The silicon-carbon cathode material with the core-shell structure is used for manufacturing a cathode, lithium metal is used as an anode, and the electrolyte is 1.0M LiPF 6 DEC: DEC =1 = 11 vol% with 5.0% fec, separator Celgard 2400, electrochemical tests were performed with a charge capacity of 521.7mAh/g and a first effect of 86.1% at 0.1C (1c = 600ma/g).
Example 5
The preparation method of the core-shell structured silicon-carbon negative electrode material of the embodiment is as follows:
10g of graphite and 4g of SiBr 4 The solution is mixed and placed in a chemical vapor deposition furnace and is vacuumized to 10 DEG -5 Pa, heating to 800 ℃ at the speed of 10 ℃/min, and keeping the temperature for 2 hours; at this time, acetylene (hydrocarbon gas) and argon (protective gas) are introduced, the flow rate ratio is 1.
The silicon-carbon cathode material with the core-shell structure is used for manufacturing a cathode, lithium metal is used as an anode, and the electrolyte is 1.0M LiPF 6 DEC: DEC =1 = th 5.0% fec with diaphragm cellgard 2400, for electrochemical testing, charge capacity 502.5mAh/g at 0.1C (1c =600ma/g), first effect 86.2%.
Example 6
The preparation method of the core-shell structured silicon-carbon negative electrode material of the embodiment is as follows:
10g of graphite and 6g of SiI 4 Mixing, placing in a chemical vapor deposition furnace, and vacuumizing to 10% -5 Pa, raising the temperature to 900 ℃ at the speed of 5 ℃/min, and preserving the heat for 2 hours; at the moment, acetylene (hydrocarbon gas) and argon (protective gas) are introduced, the flow rate is 1The physical properties and electrochemical characteristics are shown in Table 1.
The silicon-carbon cathode material with the core-shell structure is used for manufacturing a cathode, lithium metal is used as an anode, and the electrolyte is 1.0M LiPF 6 DEC: DEC =1 = 11 vol% with 5.0% fec, separator Celgard 2400, electrochemical tests were performed with a charge capacity of 513.6mAh/g and a first effect of 87.1% at 0.1C (1c = 600ma/g). As shown by the charging and discharging performance of the graph in FIG. 3, the silicon-carbon anode material with the core-shell structure circulates for 300 cycles at 0.25 ℃, and the capacity retention rate is more than 90%.
Example 7
The preparation method of the core-shell structured silicon-carbon negative electrode material of the embodiment is as follows:
10g of graphite and 5g of SiI 4 Mixing, placing in a chemical vapor deposition furnace, and vacuumizing to 10% -5 Pa, heating to 900 ℃ at the speed of 10 ℃/min, and keeping the temperature for 1 hour; at this time, ethylene (hydrocarbon gas) and argon (shielding gas) were introduced at a flow rate ratio of 5:1, and preserving the heat at 900 ℃ for 2 hours to prepare the silicon-carbon anode material with the core-shell structure, wherein the physical properties and the electrochemical properties of the silicon-carbon anode material are shown in Table 1.
The silicon-carbon cathode material with the core-shell structure is used for manufacturing a cathode, lithium metal is used as an anode, and the electrolyte is 1.0M LiPF 6 DEC: DEC =1 = 1vol% with 5.0% fec, separator Celgard 2400, electrochemical tests were performed with a charge capacity of 499.8mAh/g at 0.1C (1c = 600ma/g) and a first effect of 87.5%.
Example 8
The preparation method of the core-shell structured silicon-carbon negative electrode material of the embodiment is as follows:
10g of graphite and 5g of SiI 4 Mixing, placing in a chemical vapor deposition furnace, and vacuumizing to 10% -5 Pa, heating to 950 ℃ at the speed of 10 ℃/min, and keeping the temperature for 1 hour; at this time, methane (hydrocarbon gas) and hydrogen (protective gas) were introduced at a flow rate ratio of 5:1, and preserving the heat at 950 ℃ for 2 hours to prepare the silicon-carbon anode material with the core-shell structure, wherein the physical properties and the electrochemical properties of the silicon-carbon anode material are shown in Table 1.
The silicon-carbon cathode material with the core-shell structure is used for manufacturing a cathode, lithium metal is used as an anode, and the electrolyte is 1.0M LiPF 6 DEC: DEC =1 = th 5.0% fec with separator Celgard 2400, for electrochemical testing, charge capacity 501.7mAh/g at 0.1C (1c =600ma/g), first effect 86.7%.
TABLE 1 physical and electrochemical properties of silicon-carbon anode materials with core-shell structure
| Specific surface area (m) 2 /g) | Particle size D50 (μm) | First effect (%) | |
| Example 1 | 2.1 | 11.2 | 86.5 |
| Example 2 | 2.6 | 11.3 | 86.4 |
| Example 3 | 2.5 | 10.9 | 86.6 |
| Example 4 | 2.6 | 11.8 | 86.1 |
| Example 5 | 2.7 | 12.1 | 86.2 |
| Example 6 | 2.8 | 11.7 | 87.1 |
| Example 7 | 2.3 | 11.8 | 87.5 |
| Example 8 | 2.7 | 12 | 86.7 |
Comparative example
Mixing 10g of graphite and 1g of nano silicon ball mill to prepare a silicon-carbon negative electrode material;
the silicon-carbon cathode material with the core-shell structure is used for manufacturing a cathode, lithium metal is used as an anode, and the electrolyte is 1.0M LiPF 6 DEC: DEC =1 = 11 vol% with 5.0% fec, separator Celgard 2400, electrochemical tests were performed with a charge capacity of 556.7mAh/g at 0.1C (1c = 600ma/g) and a first effect of 76.3%.
Shown in the combination table 1, the specific surface area of the silicon-carbon anode material with the core-shell structure is 3m 2 The grain diameter D50 is below 10-12 mu m, and the first effect is more than 86 percent.
Compared with a comparative example, the silicon-carbon negative electrode material with the core-shell structure is prepared by taking the organic silicon as the precursor through a chemical vapor deposition process, and not only can the volume expansion of the silicon-based negative electrode material be effectively relieved, but also the direct contact between the silicon nanowires and the electrolyte can be effectively prevented, so that the cycle performance of the lithium ion battery is greatly improved.
Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A preparation method of a silicon-carbon anode material with a core-shell structure is characterized by comprising the following steps:
s1, under a vacuum condition, obtaining a graphite material coated by a silicon nanowire through chemical vapor deposition of graphite and an organic silicon precursor under a high-temperature condition;
and S2, introducing hydrocarbon gas under the condition of protective atmosphere and preserving heat to obtain the silicon-carbon negative electrode material with the core-shell structure.
2. The preparation method of the core-shell structured silicon-carbon negative electrode material according to claim 1, wherein in the step S1:
the organic silicon precursor is selected from SiCl 4 、HSiCl 3 、H 2 SiCl 2 、H 3 SiCl、CH 3 SiCl 3 、(CH 3 ) 2 SiHCl 2 、HSiBr 3 、H 2 SiBr 2 、H 3 SiBr、SiBr 4 、HSiI 3 、H 2 SiI 2 、H 3 SiI、SiI 4 、CH 5 One or more of SiI; and/or
The particle size of the graphite is 5-10 mu m.
3. The preparation method of the core-shell structured silicon-carbon negative electrode material according to claim 1, wherein in the step S1:
under the vacuum condition, the pressure is more than or equal to 10 -5 Pa; and/or
Under the condition of high temperature, the heating rate is 1-10 ℃/min, and the high temperature is 700-1000 ℃; and/or
The heat preservation time is 0.6 to 6 hours under the high temperature condition.
4. The preparation method of the core-shell structured silicon-carbon negative electrode material according to claim 1, wherein in the step S1, the diameter of the silicon nanowire on the graphite material coated with the silicon nanowire is 10 to 200nm.
5. The preparation method of the core-shell structured silicon-carbon negative electrode material according to claim 1, wherein in the step S2:
the protective atmosphere is argon, nitrogen, hydrogen and CO 2 One or more of the above; and/or
The hydrocarbon gas is one or more of methane, ethylene, acetylene, propylene, benzene and toluene; and/or
The feeding speed of the hydrocarbon gas is 0.5-1L/h; and/or
In the heat preservation process, the heat preservation temperature is 700-1000 ℃, and the heat preservation time is 1-3 h.
6. The core-shell structure silicon-carbon negative electrode material prepared by the preparation method of the core-shell structure silicon-carbon negative electrode material according to any one of claims 1 to 5 is characterized by comprising the following components in percentage by mass: graphite: 5-99%, silicon nanowire: 1-90% and vapor deposition carbon 0.1-20%.
7. The silicon-carbon anode material with the core-shell structure according to claim 6, wherein the silicon nanowires are coated on the surface of the graphite core to form a silicon-carbon composite core, and the vapor deposition carbon is attached to the surface of the silicon-carbon composite core to form a vapor deposition carbon layer.
8. The silicon-carbon negative electrode material with the core-shell structure as claimed in claim 7, wherein the thickness of the vapor deposition carbon layer is 5-50 nm; and/or
The granularity of the silicon-carbon negative electrode material with the core-shell structure is 10-15 mu m, and the specific surface area is 1-3 m 2 /g。
9. The core-shell structured silicon-carbon negative electrode material according to claim 6, wherein the first efficiency of the core-shell structured silicon-carbon negative electrode material is greater than 86%.
10. A lithium ion battery is characterized in that the negative electrode of the lithium ion battery is the core-shell structure silicon-carbon negative electrode material prepared by the preparation method of the core-shell structure silicon-carbon negative electrode material according to any one of claims 1 to 5.
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