CN108232139B - Graphene composite material and preparation method thereof - Google Patents
Graphene composite material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a graphene composite material and a preparation method thereof, wherein the composite electrode material has a multi-stage core-shell coating structure, wherein nano silicon is used as a core, graphene is used as a first coating layer, carbon is used as a second coating layer, the graphene is coated on the surface of the nano silicon, and the carbon is coated on the surface of the graphene. The graphene has high conductivity, mechanical strength and flexibility, provides a conductive network, an elastic space and a folded structure for the nano silicon, and is beneficial to inhibiting the damage caused by the volume expansion of the silicon; the carbon can keep the stability of the internal structure of the composite electrode material and prevent the aggregation and falling-off phenomenon in the composite electrode material. The composite electrode material has better stability and conductivity when being used in a lithium ion battery. The preparation method has simple reaction, easy control and wide application prospect.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a nano silicon/graphene/carbon composite electrode material and a preparation method and application thereof.
Background
Lithium ion batteries are efficient and practical energy storage devices, which have been widely used in various portable electronic devices, but with the development of space technology, national defense technology and electric vehicles, lithium ion batteries are required to have higher specific capacity and longer cycle life. At present, the negative electrode of the general lithium ion battery is a graphite material, and the theoretical capacity (372 mAh & g) of the graphite material-1) Low, limiting the development of high capacity lithium ion batteries. In order to develop a novel lithium ion battery and/or a lithium ion battery negative electrode material with high capacity, researchers focused on a silicon negative electrode (theoretical capacity 4200mAh g) prepared from a silicon material-111 times as much as the graphite negative electrode). However, the silicon negative electrode has the problems of large volume change, unstable structure, short cycle life, poor conductivity and the like in the charging and discharging processes, and the large-scale commercial application of the silicon negative electrode is limited.
Research shows that the volume change of the silicon negative electrode is very large in the process of lithium intercalation and deintercalation, and can reach as high as 300 percent, and the large volume change causes the phenomena of continuous rupture and formation of a solid-liquid interface film, decomposition of electrolyte, easy pulverization of active substances, deterioration of electric contact among current collectors and the like, thereby causing fast capacity attenuation and poor cycle performance; in addition, the silicon negative electrode is a semiconductor material, and the conductivity of the silicon negative electrode is inferior to that of the graphite negative electrode, which limits the rate performance of the silicon negative electrode, so if the problems of volume change and conductivity of the silicon negative electrode in the lithium intercalation and deintercalation process can be solved, the silicon negative electrode is a material with a great development prospect.
In order to overcome the defects of the silicon cathode material, people begin to carry out nanocrystallization on silicon particles, aim to reduce the volume change degree and research the composite electrode material of graphene and silicon, utilize the good electronic conductivity of the graphene material, and the formed buffer skeleton relieves the internal stress of the material caused by volume expansion in the charge-discharge process, and maintains the structural stability of silicon, so that the cycle performance of the prepared composite electrode material is obviously improved.
Chinese patent CN 105489869a discloses a preparation method of a silicon/graphene composite electrode material, which comprises firstly performing amination treatment on silicon powder, then mixing the silicon powder with graphene oxide, and performing thermal reduction to obtain the silicon/graphene composite electrode material. The composite mode realizes that silicon particles are loaded on the surface of the graphene, only relieves the problem of volume expansion to a certain extent, and greatly limits the service life. In 2015, In Hyuk Son et al, samsung advanced technology research institute In korea, published In nature communication, said that graphene was successfully grown on the surface of silicon nanowires by using a high temperature chemical vapor deposition method, but the high temperature chemical vapor deposition method is high In cost, complicated In operation and difficult In industrial production.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a nano silicon/graphene/carbon composite electrode material, a preparation method and application thereof, wherein the composite electrode material has a multi-stage core-shell coating structure, and is stable in structure and good in conductivity; compared with a pure silicon material, the composite electrode material can greatly improve the electrochemical performance and the stability of the silicon material, and has excellent cycle and rate performance when being used as a lithium ion battery cathode material. The preparation method is simple and easy to operate, and is used for the lithium ion battery.
The purpose of the invention is realized by the following technical scheme:
the composite electrode material has a multi-stage core-shell coating structure, wherein nano silicon serves as a core, graphene serves as a first coating layer, carbon serves as a second coating layer, the surface of the nano silicon is coated with the graphene, and the surface of the graphene is coated with the carbon.
According to the invention, the particle size of the nano-silicon is 5-600 nm, preferably 10-500 nm, such as 10nm, 20nm, 30nm, 50nm, 80nm, 100nm, 200nm, 250nm, 300nm, 400nm or 500 nm.
According to the invention, the thickness of the first coating layer is 0.1 to 15nm, preferably 0.5 to 10nm, for example 0.5nm, 0.8nm, 1nm, 2nm, 3nm, 5nm, 8nm, 9nm or 10 nm.
According to the invention, the thickness of the second coating layer is 1 to 15nm, preferably 2 to 10nm, for example 2nm, 3nm, 5nm, 8nm, 9nm or 10 nm.
According to the invention, the mass ratio of the nano silicon to the graphene to the carbon is (50-90): (1-20): (5-30), preferably (60-85): (1-10): (10-20).
The invention also provides a preparation method of the nano silicon/graphene/carbon composite electrode material, which comprises the following steps:
(1) respectively preparing a graphene oxide colloidal solution A and a nano silicon dispersion liquid B;
(2) mixing the graphene oxide colloidal solution A and the nano-silicon dispersion liquid B prepared in the step (1) with a flocculating agent to prepare a precipitate C, namely, graphene oxide coated nano-silicon particles;
(3) dispersing the precipitate C and a carbon source in the step (2) in a solvent to prepare a precipitate D, namely the carbon source and/or a polymerization product of the carbon source coated graphene oxide coated nano silicon particles;
(4) carrying out high-temperature carbonization on the precipitate D obtained in the step (3) to prepare a nano silicon/graphene/carbon composite electrode material; the composite electrode material has a multi-stage core-shell coating structure, wherein nano silicon serves as a core, graphene serves as a first coating layer, carbon serves as a second coating layer, the surface of the nano silicon is coated with the graphene, and the surface of the graphene is coated with the carbon.
According to the present invention, in step (1), the graphene oxide colloidal solution a is prepared by a preparation method known in the art, for example, a method comprising the following steps: and dispersing graphene oxide in deionized water to prepare a negative graphene oxide colloidal solution A.
According to the invention, the concentration of the graphene oxide in the graphene oxide colloidal solution A is 0.05-5mg/mL, preferably 0.5-2 mg/mL.
According to the invention, the preparation of the graphene oxide colloid solution A is preferably carried out under the ultrasonic condition, the power of the ultrasonic is 50-500W, and the time of the ultrasonic is 0.5-5 h.
According to the present invention, in step (1), the nano-silicon dispersion B is prepared by a preparation method known in the art, for example, by a method comprising the steps of: dispersing the nano silicon in deionized water, and performing ultrasonic dispersion treatment to prepare nano silicon dispersion liquid B.
According to the invention, the concentration of the nano-silicon in the nano-silicon dispersion liquid is 0.05-50mg/mL, preferably 2-10 mg/mL.
According to the invention, the power of the ultrasonic wave is 100-500W, and the time of the ultrasonic wave is 1-12 h.
According to the invention, in the step (2), the mass ratio of the graphene oxide to the nano silicon is 1: 60-3: 5, preferably 1: 60-1: 6; also preferably, the mass ratio is 1: 60-1: 10.
According to the present invention, in the step (2), the mixing of the graphene oxide colloidal solution a, the nano-silicon dispersion liquid B, and the electrolyte and/or the surfactant is not particularly limited, and for example, the graphene oxide colloidal solution a and the nano-silicon dispersion liquid B may be mixed, and then a flocculant may be added to prepare a precipitate C; or directly mixing the graphene oxide colloidal solution A and the nano-silicon dispersion liquid B with a flocculating agent to prepare a precipitate C.
Preferably, the mixing mode is at least one of ultrasonic, ball milling and stirring, and the mixing time is 1-12 h. Illustratively, the power of the ultrasonic wave is 50-500W, preferably 50-100W; the ultrasonic time is 1-12 h, preferably 1-2 h. Illustratively, the ball milling speed is 800-1200 rpm, preferably 900-1000 rpm, and the ball milling time is 3-6 h, preferably 4-5 h. Illustratively, the stirring time is 1-12 h, preferably 4-6 h.
According to the invention, the flocculating agent comprises an electrolyte and a surfactant. Wherein the electrolyte is selected from at least one of sodium chloride, calcium chloride, potassium sulfate, potassium chloride, sodium nitrate, sodium hydroxide, hydrochloric acid, potassium hydroxide, ammonium chloride and sodium oxalate; the surfactant is selected from cationic surfactants, and preferably at least one of Cetyl Trimethyl Ammonium Bromide (CTAB) and phthalic acid diethylene glycol diacrylate (PDDA).
According to the invention, in the step (2), the flocculant is added, and the mixed system can be flocculated after being mixed and further precipitated to prepare the precipitate C.
Preferably, the mass fraction of the flocculant in the mixed solution is 0.5wt% to 5wt%, preferably 1 wt% to 2 wt%.
According to the present invention, in the step (3), the order of dispersing the precipitate C and the carbon source in the solvent is not particularly limited, and for example, the precipitate C and the carbon source may be dispersed in the same solvent, or the carbon source may be dispersed in the solvent and then the precipitate C may be dispersed in the dispersion, or the precipitate C and the carbon source may be dispersed in the solvent and then the two dispersions may be mixed.
Preferably, the dispersing mode is at least one of ultrasonic, ball milling and stirring.
Preferably, the dispersing time is 6-24 h, and further preferably, the dispersing time is 12-24 h.
Preferably, the solvent is selected from at least one of deionized water, nitrogen methyl pyrrolidone, toluene, acetone, ethanol and ethyl acetate.
According to the invention, the carbon source is at least one selected from glucose, sucrose, starch, polyacrylamide, polyvinylpyrrolidone, polyvinyl chloride, acrylic resin, polyvinyl alcohol, polypropylene, polymethyl methacrylate, pyrrole monomer, aniline monomer and thiophene monomer.
According to the invention, in the step (3), the mass ratio of the precipitate C to the carbon source is (60-95): 5-200), preferably (80-95): 5-120), and more preferably (90-95): 10-100).
Preferably, the mass ratio of the precipitate C to the solvent is 1: 500-1: 50.
According to the invention, if the carbon source is selected from pyrrole monomers, the polymerization product of the carbon source is polypyrrole, i.e. a conductive polymer. If the carbon source is selected from aniline monomers, the carbon source polymerization product is polyaniline. If the carbon source is selected from thiophene monomers, the carbon source polymerization product is polythiophene, i.e., a conductive polymer.
According to the invention, if the carbon source is selected from at least one of pyrrole monomers, aniline monomers or thiophene monomers, a catalyst and/or an initiator for polymerization is/are also added, and the graphene oxide-coated nano silicon particles coated by the polymerization product of the corresponding monomer are obtained through polymerization.
According to the invention, the step (3) further comprises a drying step, namely drying the prepared precipitate D to obtain a dried precipitate D.
According to the present invention, the drying method includes freeze drying, heat drying, atmosphere drying, reduced pressure drying, vacuum drying, spray drying and the like. Preferably, the drying is freeze drying.
According to the invention, the drying temperature is-50 to-40 ℃, and the drying time is 12 to 48 hours.
According to the present invention, in the step (4), the high temperature carbonization is preferably performed under an inert gas atmosphere.
Preferably, the inert gas is selected from at least one of nitrogen, argon, helium.
According to the invention, in the step (4), the high-temperature carbonization temperature is 300-1000 ℃, preferably 500-800 ℃, and more preferably 600-800 ℃; the high-temperature carbonization time is 0.5-10 h, preferably 2-8 h, and more preferably 4-6 h.
The invention also provides application of the nano silicon/graphene/carbon composite electrode material, which is used in a lithium ion battery.
Preferably, in lithium ion battery electrodes.
The invention has the beneficial effects that:
the invention provides a nano-silicon/graphene/carbon composite electrode material and a preparation method and application thereof. The first coating layer, namely graphene, has high conductivity, mechanical strength and flexibility, provides a conductive network, an elastic space and a folded structure for the nano silicon, and is favorable for inhibiting the damage caused by the volume expansion of the silicon; the second coating layer, namely carbon, can keep the stability of the internal structure of the composite electrode material and prevent the aggregation and falling-off phenomenon in the composite electrode material. The composite electrode material has better stability and conductivity when being used in a lithium ion battery. The preparation method has simple process, the used equipment is conventional dispersing equipment, the raw materials are graphene oxide and nano silicon, the industrial production is realized, and the cost is low; the reaction is simple and easy to control, and has wide application prospect.
Drawings
Fig. 1 is a flow chart of a preparation process of a nano silicon/graphene/carbon composite electrode material according to a preferred embodiment of the present invention.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, it should be understood that various changes or modifications can be made by those skilled in the art after reading the description of the present invention, and such equivalents also fall within the scope of the invention.
Preparation example 1
Preparation of graphene oxide colloidal solution A
Adding 0.1-10 g of graphene oxide into 2000mL of deionized water, placing the mixture in an ultrasonic cleaning machine under the condition of 100W power for ultrasonic dispersion for 10min, and preparing graphene oxide colloidal solution A with the graphene oxide concentration of 0.05-5 mg/mL.
Specifically, for example, 1g of graphene oxide is added into 2000mL of deionized water, and the mixture is placed in an ultrasonic cleaning machine under the condition of 100W power for ultrasonic dispersion for 10min, so as to prepare a graphene oxide colloidal solution a with the graphene oxide concentration of 0.5 mg/mL.
Preparation example 2
Preparation of Nano-silicon Dispersion B
0.025g to 25g of nano-silicon with the grain diameter of 50nm is dispersed in 500mL of deionized water, and the nano-silicon is ultrasonically dispersed for 1 hour under the condition of 100W power, so that nano-silicon dispersion liquid B with the nano-silicon concentration of 0.05 mg/mL to 50mg/mL is prepared.
Specifically, for example, 1g of nano-silicon with a particle size of 50nm is dispersed in 500mL of deionized water, and ultrasonic dispersion is performed for 1 hour under the condition of 100W power, so as to prepare nano-silicon dispersion liquid B with a nano-silicon concentration of 2 mg/mL.
Example 1
Mixing 200mL of the graphene oxide colloidal solution A with the graphene oxide concentration of 0.5mg/mL prepared in preparation example 1 and 500mL of the nano-silicon dispersion liquid B with the nano-silicon concentration of 2mg/mL prepared in preparation example 2, performing ultrasonic treatment for 10min, stirring for 1h, adding potassium hydroxide, continuing stirring for 2h, flocculating and precipitating the mixed solution, and centrifuging and cleaning to prepare a precipitate C (namely, graphene oxide-coated nano-silicon particles); mixing 0.4g of the precipitate C with 10g of a polyvinyl alcohol aqueous solution with the mass fraction of 2%, performing ball milling for 4 hours to obtain a precipitate D (namely, polyvinyl alcohol-coated graphene oxide-coated nano silicon particles), and performing freeze drying at the temperature of minus 50 ℃; and carbonizing the obtained solid at the high temperature of 800 ℃ for 2 hours under the protection of argon gas to prepare the nano silicon/graphene/carbon composite electrode material.
Example 2
Mixing 200mL of graphene oxide colloidal solution A with the graphene oxide concentration of 0.5mg/mL prepared in preparation example 1 and 500mL of nano-silicon dispersion liquid B with the nano-silicon concentration of 2mg/mL prepared in preparation example 2, performing ultrasonic treatment for 10min, stirring for 1h, adding potassium sulfate, continuing stirring for 2h, flocculating and precipitating the mixed solution, and centrifuging and cleaning to obtain precipitate C (namely graphene oxide-coated nano-silicon particles); adding 0.4g of the washed precipitate C into deionized water, adding 0.1mL of pyrrole monomer and 0.03g of sodium dodecyl benzene sulfonate as surfactants for dispersing the pyrrole monomer, magnetically stirring and dispersing for 12 hours to prepare a uniform solution, then adding ferric trichloride as an oxidant (namely a catalyst for polymerization) under an ice bath condition, after 2 hours of polymerization, washing, filtering, and freeze-drying for 12 hours to obtain a precipitate D (namely a polypyrrole (conductive polymer) -coated graphene oxide-coated nano silicon particle); and carbonizing the obtained solid at the high temperature of 800 ℃ for 2 hours under the protection of argon gas to prepare the nano silicon/graphene/carbon composite electrode material.
Example 3
Mixing 200mL of the graphene oxide colloidal solution A with the graphene oxide concentration of 0.5mg/mL prepared in preparation example 1 and 500mL of the nano-silicon dispersion liquid B with the nano-silicon concentration of 2mg/mL prepared in preparation example 2, performing ultrasonic treatment for 10min, stirring for 1h, adding potassium hydroxide, continuing stirring for 2h, flocculating and precipitating the mixed solution, and centrifuging and cleaning to prepare a precipitate C (namely, graphene oxide-coated nano-silicon particles); adding 0.4g of the washed precipitate C into deionized water, adding 1g of glucose, dispersing for 2 hours by magnetic stirring to prepare a uniform solution, and drying in vacuum at 80 ℃ for 12 hours to obtain a precipitate D (namely, glucose-coated graphene oxide-coated nano silicon particles); and carbonizing the obtained solid at the high temperature of 800 ℃ for 2 hours under the protection of argon gas to prepare the nano silicon/graphene/carbon composite electrode material.
Examples 4 to 13
The preparation process is the same as that of the embodiment 1 or the embodiment 2, and only the mass ratio of the nano silicon to the graphene to the carbon is different; the carbon source is selected differently; the mass ratio of the flocculating agent in the solution is different; the difference in solvent. The specific parameters are shown in Table 1. The parameters of the prepared nano silicon/graphene/carbon composite electrode material are shown in table 2.
Table 1 preparation parameters of nano silicon/graphene/carbon composite electrode materials of examples 1 to 13
Table 2 examples 1-13 production parameters of nano-silicon/graphene/carbon composite electrode materials
| Examples | Mass ratio of nano silicon to graphene to carbon | Particle size of nano silicon | Thickness of the first coating layer | Thickness of the second coating layer |
| 1 | 90:5:5 | 50nm | 20nm | 2nm |
| 2 | 85:1:14 | 50nm | 10nm | 3nm |
| 3 | 85:3:12 | 50nm | 15nm | 4nm |
| 4 | 80:1:19 | 80nm | 10nm | 2nm |
| 5 | 80:3:17 | 80nm | 10nm | 3nm |
| 6 | 80:5:15 | 80nm | 10nm | 3nm |
| 7 | 80:6:14 | 50nm | 8nm | 2nm |
| 8 | 80:7:13 | 50nm | 8nm | 4nm |
| 9 | 75:10:15 | 50nm | 8nm | 4nm |
| 10 | 75:3:15 | 50nm | 10nm | 5nm |
| 11 | 70:5:20 | 100nm | 30nm | 4nm |
| 12 | 70:10:20 | 100nm | 10nm | 5nm |
| 13 | 60:10:20 | 100nm | 40nm | 4nm |
Example 14
Preparing a lithium ion electrode: the composite electrode materials prepared in the examples 1 to 13, acetylene black and polyvinylidene fluoride were weighed in a mass ratio of 80:10:10, respectively, and NMP was used as NMPA solvent, coating the slurry after ball milling on a copper foil to prepare an electrode; adopting a metal lithium sheet as a positive electrode and 1mol/L LiPF6The button lithium ion battery (CR 2025) is assembled by taking the EC-DMC as 1:1 as electrolyte and taking a polypropylene microporous film as a diaphragm (Celgard 2300).
And (3) testing electrical properties: the cycle curve of the lithium ion battery electrode was measured with a battery tester at a current density of 0.1A/g and a voltage of 0.01-3.0V, and the electrical property data of the lithium ion battery electrode prepared from the composite electrode material prepared in examples 1-13 is shown in table 3.
TABLE 3 Performance parameters of composite electrode materials prepared in examples 1-13
| Examples | Second reversible discharge specific capacity/mAh.g-1 | Discharge specific capacity/mAh.g after 50 times of circulation-1 |
| 1 | 1000 | 610 |
| 2 | 1080 | 650 |
| 3 | 1100 | 700 |
| 4 | 1100 | 640 |
| 5 | 960 | 600 |
| 6 | 1000 | 650 |
| 7 | 1200 | 720 |
| 8 | 950 | 560 |
| 9 | 910 | 550 |
| 10 | 850 | 500 |
| 11 | 720 | 420 |
| 12 | 750 | 780 |
| 13 | 500 | 350 |
As can be seen from Table 3, the composite electrode materials prepared in examples 1 to 13 have excellent cycle stability when applied to a lithium ion electrode.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (26)
1. A preparation method of a nano silicon/graphene/carbon composite electrode material is characterized by comprising the following steps:
(1) respectively preparing a graphene oxide colloidal solution A and a nano silicon dispersion liquid B;
(2) mixing the graphene oxide colloidal solution A and the nano-silicon dispersion liquid B prepared in the step (1) with a flocculating agent to prepare a precipitate C, namely, graphene oxide coated nano-silicon particles;
(3) dispersing the precipitate C and a carbon source in the step (2) in a solvent to prepare a precipitate D, namely the carbon source and/or a polymerization product of the carbon source coated graphene oxide coated nano silicon particles;
(4) carrying out high-temperature carbonization on the precipitate D obtained in the step (3) to prepare a nano silicon/graphene/carbon composite electrode material; the composite electrode material has a multi-stage core-shell coating structure, wherein nano silicon is used as a core, graphene is used as a first coating layer, carbon is used as a second coating layer, the surface of the nano silicon is coated with the graphene, and the surface of the graphene is coated with the carbon;
wherein the flocculant comprises an electrolyte and a surfactant;
the electrolyte is selected from at least one of sodium chloride, calcium chloride, potassium sulfate, potassium chloride, sodium nitrate, sodium hydroxide, hydrochloric acid, potassium hydroxide, ammonium chloride and sodium oxalate;
the surfactant is at least one selected from Cetyl Trimethyl Ammonium Bromide (CTAB) and phthalic acid diethylene glycol diacrylate (PDDA).
2. The preparation method according to claim 1, wherein in the step (1), the concentration of the graphene oxide in the graphene oxide colloid solution A is 0.05-5 mg/mL.
3. The preparation method according to claim 1, wherein in the step (1), the preparation of the graphene oxide colloid solution A is carried out under ultrasonic conditions, the power of the ultrasonic is 50-500W, and the time of the ultrasonic is 0.5-5 h.
4. The method according to claim 1, wherein the nano-silicon dispersion liquid B is prepared by a method comprising the steps of, in step (1): dispersing nano silicon in deionized water, and performing ultrasonic dispersion treatment to prepare nano silicon dispersion liquid B;
the concentration of the nano-silicon in the nano-silicon dispersion liquid is 0.05-50 mg/mL.
5. The preparation method according to claim 4, wherein in the step (1), the power of the ultrasonic wave is 100-500W, and the time of the ultrasonic wave is 1-12 h.
6. The preparation method according to claim 1, wherein in the step (2), the mass ratio of the graphene oxide to the nano silicon is 1: 60-3: 5.
7. The preparation method according to claim 1, wherein in the step (2), the mixing manner is at least one of ultrasonic, ball milling and stirring, and the mixing time is 1-12 h.
8. The preparation method according to claim 7, wherein the power of the ultrasound is 50-500W; the ultrasonic time is 1-12 h;
the ball milling speed is 800-1200 rpm, and the ball milling time is 3-6 h;
the stirring time is 1-12 h.
9. The preparation method according to claim 1, wherein the mass fraction of the flocculant in the mixed solution is 0.5wt% to 5 wt%.
10. The method according to claim 1, wherein in the step (3), the precipitate C and the carbon source are dispersed in a solvent, and the method comprises: dispersing the precipitate C and a carbon source in the same solvent; or, firstly dispersing a carbon source in a solvent, and then dispersing the precipitate C in the dispersion liquid; alternatively, the precipitate C and the carbon source are dispersed in the solvent separately, and the two dispersions are mixed.
11. The method according to claim 1, wherein the solvent is at least one selected from the group consisting of deionized water, nitrogen methyl pyrrolidone, toluene, acetone, ethanol, and ethyl acetate.
12. The method according to claim 1, wherein the carbon source is at least one selected from the group consisting of glucose, sucrose, starch, polyacrylamide, polyvinylpyrrolidone, polyvinyl chloride, acrylic resin, polyvinyl alcohol, polypropylene, polymethyl methacrylate, pyrrole monomer, aniline monomer, and thiophene monomer.
13. The method according to claim 1, wherein in the step (3), the mass ratio of the precipitate C to the carbon source is (60-95): 5-200);
the mass ratio of the precipitate C to the solvent is 1: 500-1: 50.
14. The method according to claim 1, wherein the step (3) further comprises a drying step of drying the prepared precipitate D to obtain a dried precipitate D.
15. The method of claim 14, wherein the drying means comprises freeze drying, heat drying, atmosphere drying, reduced pressure drying, vacuum drying, or spray drying.
16. The preparation method of claim 14, wherein the drying temperature is-50 to-40 ℃, and the drying time is 12 to 48 hours.
17. The method according to claim 1, wherein in the step (4), the high-temperature carbonization is performed in at least one of nitrogen, argon, and helium.
18. The method of claim 1, wherein in the step (4), the temperature of the high-temperature carbonization is 300 ℃ to 1000 ℃; the high-temperature carbonization time is 0.5-10 h.
19. The method of claim 18, wherein in the step (4), the temperature of the high-temperature carbonization is 500 ℃ to 800 ℃, and the time of the high-temperature carbonization is 2h to 8 h.
20. The method of claim 19, wherein in the step (4), the temperature of the high-temperature carbonization is 600 ℃ to 800 ℃; the high-temperature carbonization time is 4-6 h.
21. The method according to claim 1, wherein the nano silicon has a particle size of 50 to 100 nm; the thickness of the first coating layer is 0.1-15 nm; the thickness of the second coating layer is 1-15 nm.
22. The method of claim 21, wherein the thickness of the first cladding layer is 0.5-10 nm; the thickness of the second coating layer is 2-10 nm.
23. The method according to claim 1, wherein the mass ratio of the nano silicon to the graphene to the carbon is (50-90): (1-20): (5-30).
24. The method according to claim 23, wherein the mass ratio of the nano silicon to the graphene to the carbon is (60-85): (1-10): (10-20).
25. The application of the nano silicon/graphene/carbon composite electrode material prepared by the method according to any one of claims 1 to 24, wherein the nano silicon/graphene/carbon composite electrode material is used in a lithium ion battery.
26. The use according to claim 25, wherein the nano-silicon/graphene/carbon composite electrode material is used in an electrode of a lithium ion battery.
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