CN113314703B - Negative electrode material and preparation method and application thereof - Google Patents

Negative electrode material and preparation method and application thereof Download PDF

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CN113314703B
CN113314703B CN202110592875.5A CN202110592875A CN113314703B CN 113314703 B CN113314703 B CN 113314703B CN 202110592875 A CN202110592875 A CN 202110592875A CN 113314703 B CN113314703 B CN 113314703B
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CN113314703A (en
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彭友山
胡涛
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Svolt Energy Technology Co Ltd
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    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
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    • Y02E60/10—Energy storage using batteries

Abstract

The invention provides a negative electrode material and a preparation method and application thereof. The negative electrode material comprises an inner core, a first carbon coating layer coated on the surface of the inner core and a second carbon coating layer positioned on the outermost layer; wherein the inner core is amorphous lithium silicon alloy, and the chemical formula of the amorphous lithium silicon alloy is LixX is more than 1 and less than or equal to 4.4. According to the invention, the double-layer carbon coating is carried out on the surface of the lithium silicon alloy, so that the performance of the lithium silicon alloy core in dry air is hardly attenuated, and the negative electrode material has better environmental stability and cycling stability.

Description

Negative electrode material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, and relates to a negative electrode material, and a preparation method and application thereof.
Background
With the increasing requirements of energy density and other comprehensive properties of power batteries, the theoretical capacity of the natural graphite and artificial graphite cathode materials is 372mAh/g, which can achieve 360mAh/g at present, and the increase of the cathode capacity is difficult, so that the natural graphite and artificial graphite cathode materials are difficult to meet the requirements of high-energy-density batteries. Although nano silicon and silicon monoxide have higher specific capacity, the theoretical specific capacity of the nano silicon negative electrode material is up to 4200mAh/g (Li)4.4Si), but the volume expansion is up to more than 300% during the lithium intercalation process, which not only damages the structure of the electrode and causes problems such as material falling, but also causes cracks in the SEI film formed on the surface of Si particles, resulting in the continuous decomposition of the electrolyte. The expansion of the silicon oxide negative electrode material is smaller than that of a silicon negative electrode, but the initial coulombic efficiency of the silicon oxide negative electrode material is lower and is only about 75 percent.
Lithium silicon alloy LixSi in silicon-based negative electrode material, Si and SiOxIn contrast, LixSi has high reversible specific capacity and high first coulombic efficiency, and has relatively low expansion rate due to pre-intercalation and pre-expansion. Cathode material lithium silicon alloy LixSi can be used as a negative electrode alone and as a pre-lithium additive to compound SiOxGraphite increases its first coulombic efficiency.
CN108565414A discloses a lithium-silicon alloy material with a surface modification layer, a preparation method thereof, an electrode, an electrochemical energy storage device, and a negative electrode lithium supplementing method. The method adopts silicon powder and metallic lithium to directly react to prepare the lithium ion battery. But is flammable due to the high activity of the lithium metal powder. Therefore, the method has high environmental requirements, generally needs to be synthesized in a glove box, and has slow reaction speed. And the obtained lithium-silicon alloy has large granularity and low purity, and has great influence on the expansion and other properties of the material.
Therefore, how to obtain a negative electrode material with high capacity, high first efficiency, low expansion coefficient and the like and excellent comprehensive performance is a technical problem to be solved at present.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a negative electrode material and a preparation method and application thereof. According to the invention, double-layer carbon coating is carried out on the surface of the amorphous lithium silicon alloy, so that the performance attenuation of the lithium silicon alloy core in dry air is smaller, and the negative electrode material has better environmental stability and cycling stability.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides an anode material, which includes an inner core, a first carbon coating layer coated on the surface of the inner core, and a second carbon coating layer located on the outermost layer;
wherein the inner core is amorphous lithium silicon alloy, and the chemical formula of the amorphous lithium silicon alloy is LixSi, 1 < x.ltoreq.4.4, for example 1.71, 3.25, 3.75, or 4.4, etc.
In the present invention, the lithium-silicon alloy is amorphous, and does not have a high capacity and a small expansion.
According to the cathode material provided by the invention, the second carbon cladding layer on the outermost layer forms a compact passivation layer, so that the stability of the lithium-silicon alloy in the core is improved, the performance of the lithium-silicon alloy in dry air is hardly attenuated, and the lithium-silicon alloy serving as the core has high reversible specific capacity and high first coulombic efficiency, so that the finally obtained cathode material is low in expansion and good in environmental stability, and the capacity and the first efficiency of a battery are improved. And the lithium-silicon alloy is externally coated with double layers of carbon, and the two layers of carbon coating are matched with the inner core, so that the surface passivation and protection of the lithium-silicon alloy are facilitated, and the lithium-silicon alloy is more stable in the air.
Preferably, the LixIn Si, x is more than or equal to 1.71 and less than or equal to 3.75, and the amorphous lithium-silicon alloy matrix comprises Li12Si7、Li13Si4、Li15Si4And Li22Si5One or more of (a).
Preferably, the amorphous lithium silicon alloy has a particle size of 100nm to 1 μm, for example, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, or 1 μm.
Preferably, the thickness of the first carbon coating layer is 20-50 nm, such as 20nm, 30nm, 40nm or 50 nm.
Preferably, the thickness of the second carbon coating layer is 30-80 nm, such as 30nm, 50nm, 60nm, 70nm or 800 nm.
In a second aspect, the present invention provides a method for preparing the anode material according to the first aspect, the method comprising the steps of:
(1) depositing a first carbon coating layer on the surface of the nano silicon by a chemical vapor deposition method to obtain a first matrix;
(2) mixing the first matrix with a lithium source, and sintering in vacuum to obtain a second matrix;
(3) carrying out secondary carbon coating on the second matrix in a dry environment to obtain the negative electrode material;
wherein, the molar ratio of the lithium in the lithium source in the step (2) to the silicon in the first matrix is 1-4.4 and does not include 1, such as 1.71, 3.25, 3.75 or 4.4.
The first substrate provided by the invention is characterized in that the surface of the nanometer silicon is coated with a first carbon coating layer, and the surface of the second substrate is specifically amorphous lithium silicon alloy which is coated with a first carbon coating layer.
According to the preparation method provided by the invention, the first carbon coating layer is formed on the surface of the nanometer silicon, then the pre-lithiation operation is carried out, the lithium source is decomposed to obtain lithium metal in a vacuum sintering environment by mixing with the lithium source, the lithium metal enters into the gap of the first carbon coating layer to react with the nanometer silicon to obtain the lithium-silicon alloy, so that a protective layer is favorably formed on the surface of the lithium-silicon alloy to be generated, and the obtained lithium-silicon alloy cathode material has a core with higher reversible specific capacity and higher first coulombic efficiency. And the outermost layer is coated with carbon to form a compact passivation layer, so that the performance of the inner core in dry air is hardly attenuated, and the finally obtained cathode material has good environmental stability, high capacity, first effect and low expansion. Meanwhile, the preparation method provided by the invention has less strict requirements on environment than the preparation method in a glove box, the synthesis reaction speed is high, and the finally obtained material has higher purity.
In the invention, the reason why the lithium source is not adopted to directly react with the nano silicon and then the multi-layer carbon coating is carried out is that a carbon protective layer is formed on the surface of the silicon in advance and the surface of the lithium-silicon alloy to be generated is passivated and protected.
Preferably, the carbon source used in the chemical vapor deposition in step (1) includes any one of methane, ethylene, acetylene or toluene or a combination of at least two of them.
Preferably, the temperature of the chemical vapor deposition in the step (1) is 800-1100 ℃, such as 800 ℃, 900 ℃, 1000 ℃ or 1100 ℃.
Preferably, the chemical vapor deposition time in the step (1) is 1-4 h, such as 1h, 2h, 3h or 4 h.
Preferably, the particle size of the nano silicon in the step (1) is less than or equal to 100nm, such as 100nm, 90nm, 80nm, 70nm, 60nm or 50nm and the like.
Preferably, the molar ratio of lithium in the lithium source in the step (2) to silicon in the first matrix is 1.71-3.75, such as 1.71, 3.25 or 3.75.
Preferably, the lithium source in step (2) comprises LiH.
In the invention, LiH is used as a lithium source, and the dehydrogenation reaction of LiH and silicon in a vacuum environment is more favorable for the rapid reaction and the reaction temperature is reduced.
Preferably, the mixing method in step (2) is ball milling.
Preferably, the rotation speed of the ball mill is 200 to 400rmp, such as 200rmp, 250rmp, 300rmp, 350rmp or 400 rmp.
Preferably, the time of ball milling is 2-5 h, such as 2h, 3h, 4h or 5 h.
Preferably, the temperature of the vacuum sintering in the step (2) is 500-700 ℃, such as 500 ℃, 550 ℃, 600 ℃, 650 ℃ or 700 ℃.
The invention can be sintered at a lower temperature, if the temperature of vacuum sintering is too low, the reaction can not be carried out or only partial reaction can be carried out, and if the temperature of vacuum sintering is too high, the waste of energy can be formed, because the reaction can be completed in a certain temperature range, the too high temperature is not needed.
Preferably, the vacuum sintering time in the step (2) is 2-6 h, such as 2h, 3h, 4h, 5h or 6 h. Preferably, the drying environment in step (3) is: the dew point temperature is-30 to-45 ℃, for example, -30 ℃, 35 ℃, 40 ℃ or-45 ℃.
Preferably, after the vacuum sintering in the step (2), the product after the vacuum sintering is subjected to secondary ball milling.
In the invention, after vacuum sintering, secondary ball milling and high-energy ball milling are carried out, and the high-energy ball milling is favorable for converting the crystalline state of the lithium-silicon alloy material into the amorphous state, thereby improving the specific capacity of the material and reducing the expansion of the material.
Preferably, the rotation speed of the secondary ball milling is 400 to 700rmp, such as 400rmp, 500rmp, 600rmp or 700 rmp.
Preferably, the ball-to-material ratio of the secondary ball milling is (30-60): 1, such as 30:1, 40:1, 50:1 or 60: 1.
Preferably, the secondary carbon coating method of step (3) comprises:
and mixing the second matrix, the secondary carbon-coated coating agent and the solvent to obtain a mixture, filtering, vacuum-drying and carbonizing under a protective atmosphere.
Preferably, the mixing method in the secondary carbon coating process in the step (2) comprises stirring.
Preferably, the rotation speed of the stirring is 300 to 600rmp, such as 300rmp, 400rmp, 500rmp or 600 rmp.
Preferably, the stirring time is 2-6 h, such as 2h, 3h, 4h, 5h or 6 h.
Preferably, the carbonization temperature is 650 to 900 ℃, such as 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃ or 900 ℃.
Preferably, the carbonization time is 2-4 h, such as 2h, 3h or 4 h.
Preferably, the protective atmosphere comprises any one of a nitrogen atmosphere, an argon atmosphere or a helium atmosphere or a combination of at least two thereof.
Preferably, the coating raw material coated with the secondary carbon in the step (3) is polyvinylidene fluoride and/or polytetrafluoroethylene.
In the invention, polyvinylidene fluoride and/or polytetrafluoroethylene are/is selected as the raw material of the secondary carbon coating, and the two coating agents have stable performance and do not react with the lithium-silicon alloy.
Preferably, the coating amount of the secondary carbon coating raw material in the step (3) is 5 to 35%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, or the like, based on 100% by mass of the anode material.
Preferably, the mixture is sequentially filtered and vacuum dried before carbonization.
As a preferred technical scheme, the preparation method of the negative electrode material comprises the following steps:
(1) depositing a first carbon coating layer on the surface of the nano silicon with the particle size less than or equal to 100nm by a chemical vapor deposition method, wherein in the chemical vapor deposition process, the temperature is 800-1100 ℃ and the time is 1-4 h to obtain a first matrix;
(2) ball-milling the first matrix and the lithium source for 2-5 h at 200-400 rmp, vacuum-sintering at 500-700 ℃ for 2-6 h, and carrying out secondary ball-milling on the product after vacuum-sintering at the rotating speed of 400-700 rmp, wherein the ball-to-material ratio is (30-60): 1, so as to obtain a second matrix;
(3) stirring a second matrix, a secondary carbon-coated raw material with a coating amount of 5-35% and a solvent at a dew point temperature of-30 to-45 ℃ for 2-6 h at 300-600 rmp, then sequentially filtering and vacuum drying, and finally carbonizing at 650-900 ℃ for 2-4 h in a protective atmosphere to obtain the negative electrode material;
wherein the molar ratio of lithium in the lithium source in the step (2) to silicon in the first matrix is 1.71-3.75, and the lithium source in the step (2) comprises LiH.
In a third aspect, the present invention also provides a lithium ion battery, which includes the negative electrode material according to the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the invention, the double-layer carbon coating is carried out on the surface of the amorphous lithium-silicon alloy, so that the performance attenuation of the amorphous lithium-silicon alloy core in dry air is less, the negative electrode material has better environmental stability and cycling stability, the charge-discharge reversible capacity of the battery is more than 1680mAh/g, the first coulombic efficiency can reach more than 122%, the capacity retention rate of the battery after 50-week cycling is more than 90%, when the thicknesses of the first carbon coating layer and the second carbon coating layer are within a certain range, the charge-discharge reversible capacity of the battery is more than 2124mAh/g, the first coulombic efficiency can reach more than 135.3%, and the capacity retention rate of the battery after 50-week cycling is more than 92%.
(2) The preparation method provided by the invention has relatively low requirement on environment, the synthesis reaction speed is high, and the finally obtained material has high purity.
Drawings
Fig. 1 is a graph of the cycle performance at 0.1C for the cell provided in example 1.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. 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 embodiment provides a negative electrode material, which comprises a core, a first carbon coating layer coated on the surface of the core and a second carbon coating layer positioned on the outermost layer;
wherein the inner core is amorphous lithium silicon alloy with the particle size of 100nm, and the amorphous lithium silicon alloyHas a chemical formula of Li12Si7The thickness of the first carbon coating layer is 20nm, and the thickness of the second carbon coating layer is 50 nm.
The preparation method of the negative electrode material comprises the following steps:
(1) placing 5g of nano silicon with the particle size of 60nm into a CVD (chemical vapor deposition) furnace, firstly introducing argon for replacement, and then introducing methane for vapor deposition, wherein the deposition temperature is 900 ℃, and the deposition time is 1h, so as to obtain a first matrix;
(2) adding LiH and the first matrix into a mixer according to a molar ratio of 12:7, ball-milling for 4h at 300rmp with a ball-to-material ratio of 30:1, sintering for 5h at 600 ℃ in vacuum, and ball-milling for 48h at a rotating speed of 600rmp with a ball-to-material ratio of 60:1 to obtain a second matrix;
(3) stirring a second matrix, polyvinylidene fluoride with the coating amount of 10 wt% and tetrahydrofuran for 3h at 400rmp under the environment of the dew point temperature of-45 ℃, then sequentially filtering and vacuum drying, and finally carbonizing for 2h at 700 ℃ under the argon atmosphere to obtain the cathode material.
As can be seen from fig. 1, the lithium-silicon alloy negative electrode material coated with double-layer carbon has excellent cycling stability, and the capacity retention rate after charging and discharging for 50 weeks at 0.1C is greater than 90%.
Example 2
The embodiment provides a negative electrode material, which comprises a core, a first carbon coating layer coated on the surface of the core and a second carbon coating layer positioned on the outermost layer;
wherein the inner core is amorphous lithium silicon alloy with the particle size of 120nm, and the chemical formula of the amorphous lithium silicon alloy is Li3.25Si1The thickness of the first carbon coating layer is 40nm, and the thickness of the second carbon coating layer is 60 nm.
The preparation method of the negative electrode material comprises the following steps:
(1) placing 5g of nano silicon with the particle size of 100nm into a CVD (chemical vapor deposition) furnace, firstly introducing argon for replacement, and then introducing acetylene for vapor deposition, wherein the deposition temperature is 1100 ℃ and the deposition time is 4 hours, so as to obtain a first matrix;
(2) adding LiH and the first matrix into a mixer according to a molar ratio of 3.25:1, ball-milling for 5h at 400rmp with a ball-to-material ratio of 30:1, sintering for 2h at 700 ℃ in vacuum, and ball-milling for 60h at a rotating speed of 500rmp with a ball-to-material ratio of 40:1 to obtain a second matrix;
(3) stirring a second matrix, polytetrafluoroethylene with the coating amount of 15 wt% and tetrahydrofuran for 2h at 300rmp under the environment of the dew point temperature of-40 ℃, then sequentially filtering and vacuum drying, and finally carbonizing for 4h at 900 ℃ under the argon atmosphere to obtain the cathode material.
Example 3
The embodiment provides a negative electrode material, which comprises a core, a first carbon coating layer coated on the surface of the core and a second carbon coating layer positioned on the outermost layer;
wherein the inner core is a lithium silicon alloy with the particle size of 100nm, and the chemical formula of the lithium silicon alloy is Li3.75And Si, wherein the thickness of the first carbon coating layer is 30nm, and the thickness of the second carbon coating layer is 80 nm.
The preparation method of the negative electrode material comprises the following steps:
(1) placing 5g of nano silicon with the particle size of 70nm into a CVD (chemical vapor deposition) furnace, firstly introducing argon for replacement, and then introducing ethylene for vapor deposition, wherein the deposition temperature is 950 ℃, and the deposition time is 2 hours, so as to obtain a first matrix;
(2) adding LiH and the first matrix into a mixer according to a molar ratio of 3.75:1, ball-milling for 5h at 600rmp, sintering for 6h at 500 ℃ in vacuum, ball-milling for 48h at a rotating speed of 700rmp after vacuum sintering, wherein the ball-milling ratio is 30:1, and obtaining a second matrix;
(3) stirring a second matrix, polytetrafluoroethylene with the coating amount of 20 wt% and tetrahydrofuran for 2h at 300rmp under the environment of the dew point temperature of-30 ℃, then sequentially filtering and vacuum drying, and finally carbonizing for 3h at 800 ℃ under the argon atmosphere to obtain the cathode material.
Example 4
The difference between this embodiment and embodiment 1 is that the thickness of the first carbon coating layer in this embodiment is 60 nm.
The remaining preparation methods and parameters were in accordance with example 1.
Example 5
The difference between this embodiment and embodiment 1 is that the thickness of the second carbon coating layer in this embodiment is 90 nm.
The remaining preparation methods and parameters were in accordance with example 1.
Example 6
The difference between this example and example 1 is that the vacuum sintering temperature in step (2) of this example is 750 ℃.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 1
The negative electrode material comprises a core and a first carbon coating layer coated on the surface of the core;
wherein the inner core is amorphous lithium silicon alloy with the particle size of 100nm, and the chemical formula of the amorphous lithium silicon alloy is Li12Si7And the thickness of the first carbon coating layer is 20 nm.
This comparative example differs from example 1 in that step (3), i.e., a process without secondary carbon coating, is not performed.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 2
This comparative example provides a commercially available silica negative electrode material having a particle size of 5 μm. The remaining preparation methods and parameters were in accordance with example 1.
Negative electrode materials provided in examples 1 to 6 and comparative examples 1 to 2 were used as negative electrode active materials, negative electrodes were prepared at a mass ratio of negative electrode active material SP: PVDF of 70:15:15, and button cells were prepared, subjected to electrochemical performance test, and charged and discharged at 0.1C, and the results are shown in table 1:
Figure BDA0003090195780000101
Figure BDA0003090195780000111
from the data results of example 1, example 4 and example 5, it is clear that the first effect of the negative electrode material is obviously reduced along with the increase of the coating thickness no matter the thickness of the first carbon coating layer or the second carbon coating layer is increased, but the surface passivation effect is better, and the cycle performance of the material is improved.
From the data results of examples 1 and 6, it can be seen that the capacity, first effect and cycle performance of the obtained lithium-silicon alloy material are not changed much when the vacuum heat treatment temperature is increased to 750 ℃, which indicates that when the pre-lithium reaction temperature is reached, the performance of the material is not greatly affected by increasing the reaction temperature, and the energy consumption is increased.
From the data results of the example 1 and the comparative example 1, it can be seen that after the lithium-silicon alloy core is prepared, the secondary carbon coating is not performed, the passivation protection effect of the material surface is obviously inferior to that of the example 1, and the cycle performance of the material is obviously reduced.
From the data of examples 1 to 6 and comparative example 2, it is understood that the capacity after the pre-lithiation of the silica and the capacity and first effect of the pre-lithiation of the silica are remarkably reduced because lithium silicate is generated by the reaction of oxygen in the silica with lithium and is an inactive material. But at the same time the cycling performance is improved due to the presence of lithium silicate.
The cathode material provided by the invention has the advantages of good environmental stability, higher capacity and first effect.
In summary, in the cathode material provided by the invention, the second carbon coating layer at the outermost layer forms a compact passivation layer, so that the stability of the amorphous lithium-silicon alloy in the core is improved, the performance of the amorphous lithium-silicon alloy in dry air is hardly attenuated, the first carbon coating layer on the surface of the core is firstly coated on the surface of the nano silicon, then lithium metal enters through the gap of the carbon coating layer to form the amorphous lithium-silicon alloy, and the lithium-silicon alloy is used as the core, so that the lithium-silicon alloy has high reversible specific capacity and high first coulombic efficiency, the finally obtained cathode material has low expansion coefficient and good environmental stability, the capacity and the first efficiency of the battery are improved, the charge-discharge reversible capacity of the battery is more than 1680mAh/g, the first coulombic efficiency can reach more than 122%, the capacity retention rate is more than 90% after 50 weeks of circulation, and when the thicknesses of the first carbon coating layer and the second carbon coating layer are within a certain range, the charge-discharge reversible capacity of the battery is more than 2124mAh/g, the first coulombic efficiency can reach more than 135.3 percent, and the capacity retention rate of the battery is more than 92 percent after the battery is circulated for 50 weeks.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.

Claims (24)

1. A preparation method of a negative electrode material is characterized by comprising the following steps:
(1) depositing a first carbon coating layer on the surface of the nanometer silicon by a chemical vapor deposition method to obtain a first matrix;
(2) mixing the first matrix with a lithium source, and sintering in vacuum to obtain a second matrix;
(3) carrying out secondary carbon coating on the second matrix in a dry environment to obtain the negative electrode material;
wherein the molar ratio of lithium in the lithium source in the step (2) to silicon in the first matrix is 1-4.4 and does not include 1; the grain size of the nano silicon in the step (1) is less than or equal to 100 nm; the temperature of the vacuum sintering in the step (2) is 500-700 ℃; the vacuum sintering time in the step (2) is 2-6 h; after the vacuum sintering in the step (2), performing secondary ball milling on a product after the vacuum sintering; the rotation speed of the secondary ball milling is 400-700 rmp; the ball-material ratio of the secondary ball milling is (30-60): 1; the step (3) is that under the dry environment: the dew point temperature is-30 to-45 ℃;
the cathode material comprises a core, a first carbon coating layer coated on the surface of the core and a second carbon coating layer positioned on the outermost layer; the thickness of the second carbon coating layer is 30-80 nm;
wherein the inner core is amorphous lithium silicon alloy, and the chemical formula of the amorphous lithium silicon alloy is LixSi，1＜x≤4.4。
2. The method for producing the anode material according to claim 1, wherein the Li isxIn Si, x is more than or equal to 1.71 and less than or equal to 3.75.
3. The preparation method of the negative electrode material of claim 1, wherein the amorphous lithium-silicon alloy has a particle size of 100nm to 1 μm.
4. The preparation method of the anode material according to claim 1 or 2, wherein the thickness of the first carbon coating layer is 20-50 nm.
5. The method for preparing the anode material according to claim 1, wherein the carbon source used in the chemical vapor deposition in the step (1) comprises any one of methane, ethylene, acetylene or toluene or a combination of at least two of the above.
6. The preparation method of the anode material according to claim 1, wherein the temperature of the chemical vapor deposition in the step (1) is 800-1100 ℃.
7. The preparation method of the anode material according to claim 1, wherein the chemical vapor deposition time in the step (1) is 1-4 h.
8. The method for preparing the negative electrode material of claim 1, wherein the molar ratio of lithium in the lithium source to silicon in the first matrix in step (2) is 1.71 to 3.75.
9. The method for producing an anode material according to claim 1, wherein the lithium source in the step (2) includes LiH.
10. The method for preparing the anode material according to claim 1, wherein the mixing in the step (2) is ball milling.
11. The preparation method of the anode material as claimed in claim 10, wherein the rotation speed of the ball mill is 200 to 400 rmp.
12. The preparation method of the anode material according to claim 10, wherein the ball milling time is 2-5 h.
13. The method for preparing the anode material according to claim 1, wherein the secondary carbon coating method in the step (3) comprises:
and mixing the second matrix, the secondary carbon-coated raw material and the solvent to obtain a mixture, and then carbonizing the mixture in a protective atmosphere.
14. The method for preparing the anode material according to claim 13, wherein the mixing in the secondary carbon coating process in the step (2) comprises stirring.
15. The method for preparing the anode material according to claim 14, wherein the rotation speed of the stirring is 300 to 600 rmp.
16. The preparation method of the anode material according to claim 14, wherein the stirring time is 2-6 hours.
17. The preparation method of the negative electrode material as claimed in claim 13, wherein the carbonization temperature is 650-900 ℃.
18. The preparation method of the negative electrode material as claimed in claim 13, wherein the carbonization time is 2-4 h.
19. The method for preparing the anode material according to claim 13, wherein the protective atmosphere includes any one of a nitrogen atmosphere, an argon atmosphere, or a helium atmosphere, or a combination of at least two of them.
20. The preparation method of the anode material according to claim 1, wherein the coating raw material coated with the secondary carbon in the step (3) is polyvinylidene fluoride and/or polytetrafluoroethylene.
21. The method for producing the anode material according to claim 1, wherein the coating amount of the secondary carbon-coated raw material in the step (3) is 5 to 35% based on 100% by mass of the anode material.
22. The method for preparing the negative electrode material according to claim 13, wherein the mixture is sequentially filtered and vacuum-dried before the carbonization.
23. The method for preparing the anode material according to claim 1, comprising the steps of:
(1) depositing a first carbon coating layer on the surface of the nano silicon with the particle size less than or equal to 100nm by a chemical vapor deposition method, wherein in the chemical vapor deposition process, the temperature is 800-1100 ℃ and the time is 1-4 h to obtain a first matrix;
(2) ball-milling the first matrix and the lithium source for 2-5 h at 200-400 rmp, vacuum-sintering at 500-700 ℃ for 2-6 h, and carrying out secondary ball-milling on the product after vacuum-sintering at the rotating speed of 400-700 rmp, wherein the ball-to-material ratio is (30-60): 1, so as to obtain a second matrix;
(3) stirring a second substrate, a secondary carbon-coated raw material with a coating amount of 5-35% and a solvent at a dew point temperature of-30 to-45 ℃ for 2-6 h at 300-600 rmp, then sequentially filtering and vacuum drying, and finally carbonizing at 650-900 ℃ for 2-4 h in a protective atmosphere to obtain the negative electrode material;
wherein the molar ratio of lithium in the lithium source in the step (2) to silicon in the first matrix is 1.71-3.75, and the lithium source in the step (2) comprises LiH.
24. A lithium ion battery, characterized in that the lithium ion battery comprises the negative electrode material prepared by the method for preparing the negative electrode material according to any one of claims 1 to 23.
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