CN114242961B - Graphene/silicon oxide coated nano-silicon composite material and preparation method and application thereof - Google Patents
Graphene/silicon oxide coated nano-silicon composite material and preparation method and application thereof Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 149
- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 145
- 239000005543 nano-size silicon particle Substances 0.000 title claims abstract description 136
- 239000002131 composite material Substances 0.000 title claims abstract description 128
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 124
- 229910052814 silicon oxide Inorganic materials 0.000 title claims abstract description 124
- 238000002360 preparation method Methods 0.000 title claims abstract description 27
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 37
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 37
- 239000010703 silicon Substances 0.000 claims abstract description 37
- 238000000034 method Methods 0.000 claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims description 37
- 239000000725 suspension Substances 0.000 claims description 23
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 21
- 238000002156 mixing Methods 0.000 claims description 17
- 239000007864 aqueous solution Substances 0.000 claims description 14
- 238000001816 cooling Methods 0.000 claims description 11
- 239000002356 single layer Substances 0.000 claims description 11
- 239000003960 organic solvent Substances 0.000 claims description 10
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 9
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 9
- 238000003756 stirring Methods 0.000 claims description 8
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 6
- 229910001416 lithium ion Inorganic materials 0.000 claims description 6
- 239000011259 mixed solution Substances 0.000 claims description 6
- 239000007773 negative electrode material Substances 0.000 claims description 5
- 238000000713 high-energy ball milling Methods 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 239000001307 helium Substances 0.000 claims description 3
- 229910052734 helium Inorganic materials 0.000 claims description 3
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 230000003647 oxidation Effects 0.000 claims description 3
- 238000007254 oxidation reaction Methods 0.000 claims description 3
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 claims description 3
- 238000005245 sintering Methods 0.000 claims description 3
- 230000000630 rising effect Effects 0.000 claims 1
- 239000011247 coating layer Substances 0.000 abstract description 22
- 230000008569 process Effects 0.000 abstract description 7
- 230000000694 effects Effects 0.000 abstract description 6
- 239000003792 electrolyte Substances 0.000 abstract description 6
- 239000011856 silicon-based particle Substances 0.000 abstract description 5
- 239000011248 coating agent Substances 0.000 abstract description 4
- 238000000576 coating method Methods 0.000 abstract description 4
- 238000009776 industrial production Methods 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 239000007784 solid electrolyte Substances 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 12
- 239000000758 substrate Substances 0.000 description 9
- 239000010405 anode material Substances 0.000 description 7
- 238000000227 grinding Methods 0.000 description 6
- 238000007873 sieving Methods 0.000 description 6
- 239000002904 solvent Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 239000012300 argon atmosphere Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000002243 precursor Substances 0.000 description 5
- 239000011261 inert gas Substances 0.000 description 4
- PAZHGORSDKKUPI-UHFFFAOYSA-N lithium metasilicate Chemical compound [Li+].[Li+].[O-][Si]([O-])=O PAZHGORSDKKUPI-UHFFFAOYSA-N 0.000 description 4
- 229910052912 lithium silicate Inorganic materials 0.000 description 4
- 239000002070 nanowire Substances 0.000 description 4
- 238000001237 Raman spectrum Methods 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 238000006138 lithiation reaction Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
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- 239000000843 powder Substances 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
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- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 229910021426 porous silicon Inorganic materials 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000002210 silicon-based material Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 238000003917 TEM image Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
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- 230000001351 cycling effect Effects 0.000 description 1
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- 230000002349 favourable effect Effects 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000001453 impedance spectrum Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000002715 modification method Methods 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- -1 polytetrafluoroethylene Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 229910021487 silica fume Inorganic materials 0.000 description 1
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- 239000011232 storage material Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention discloses a graphene/silicon oxide coated nano silicon composite material, a preparation method and application thereof. By continuing graphene coating on the surface of the oxide coating layer of silicon, the volume expansion effect of nano silicon particles in the charge and discharge process can be effectively relieved, and meanwhile, the direct contact of the silicon particles and electrolyte is avoided to generate an excessively thick solid electrolyte interface film. Therefore, the graphene/silicon oxide coated nano silicon composite material provided by the invention has higher specific capacity, rate capability and cycle stability; the graphene/silicon oxide coated nano silicon composite material has the advantages of simple preparation method, low manufacturing cost and easy industrial production.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a graphene/silicon oxide coated nano silicon composite material, a preparation method and application thereof.
Background
Because the silicon anode material has extremely high theoretical capacity, the capacity of the silicon anode material can reach 4200mAh/g at high temperature, which is far higher than that of the current commercial graphite anode material, and the storage of silicon is extremely abundant, and the silicon anode material is regarded as one of the most potential materials of the next-generation commercial lithium ion battery anode material. However, the silicon anode material is poor in conductivity, has a volume expansion of about 300% during lithiation, and continuously forms a solid electrolyte film (SEI) during charge and discharge cycles, resulting in a series of problems such as continuous decomposition of an electrolyte, rapid decrease in electrode capacity, decrease in coulombic efficiency, and shortening of cycle life.
Accordingly, the prior art is still in need of improvement and development.
Disclosure of Invention
In view of the shortcomings of the prior art, the invention aims to provide a graphene/silicon oxide coated nano silicon composite material, a preparation method and application thereof, and aims to solve the problems of serious volume expansion, poor performance and high preparation cost in the lithiation process when the conventional silicon-based composite material is used as a negative electrode material.
The technical scheme of the invention is as follows:
a graphene/silicon oxide coated nano silicon composite material comprises a nano silicon substrate, a silicon oxide coating layer coated on the surface of the nano silicon substrate and a graphene coating layer coated on the surface of the silicon oxide coating layer.
The graphene/silicon oxide coated nano silicon composite material is characterized in that the raw material of the graphene coating layer is an edge oxidized single-layer graphene aqueous solution.
The preparation method of the graphene/silicon oxide coated nano-silicon composite material comprises the following steps:
providing oxide-coated nano-silicon of silicon;
mixing the nano silicon coated by the silicon oxide with an organic solvent to obtain a suspension;
adding the single-layer graphene aqueous solution with the oxidized edges into the suspension, stirring, heating and drying to obtain the graphene/silicon oxide coated nano-silicon composite material with the oxidized edges;
and performing heat treatment on the graphene/silicon oxide coated nano-silicon composite material with the oxidized edges to obtain the graphene/silicon oxide coated nano-silicon composite material.
The preparation method of the graphene/silicon oxide coated nano silicon composite material specifically comprises the following steps:
mixing micron silicon with an organic solvent to obtain a mixed solution;
and (3) performing high-energy ball milling on the mixed solution to obtain the silicon oxide coated nano silicon.
The preparation method of the graphene/silicon oxide coated nano silicon composite material comprises the step of preparing the graphene/silicon oxide coated nano silicon composite material by using one or more of methanol, ethanol, ethylene glycol and propanol as an organic solvent.
The preparation method of the graphene/silicon oxide coated nano silicon composite material comprises the step of preparing graphene in the edge oxidized single-layer graphene aqueous solution, wherein the mass of graphene in the edge oxidized single-layer graphene aqueous solution is 0.1% -5% of that of the micron silicon.
The preparation method of the graphene/silicon oxide coated nano silicon composite material comprises the steps of performing heat treatment on the graphene/silicon oxide coated nano silicon composite material with oxidized edges to obtain the graphene/silicon oxide coated nano silicon composite material, wherein the preparation method comprises the following steps:
and (3) placing the graphene/silicon oxide coated nano silicon composite material with the oxidized edges into a sintering furnace, and treating for 2-5 hours under the protection of inert gas and at the heat treatment temperature of 600-1100 ℃ to obtain the graphene/silicon oxide coated nano silicon composite material.
The preparation method of the graphene/silicon oxide coated nano silicon composite material comprises the step of preparing the graphene/silicon oxide coated nano silicon composite material, wherein the inert gas is one or more of nitrogen, argon and helium.
The preparation method of the graphene/silicon oxide coated nano silicon composite material comprises the step of performing heat treatment on the graphene/silicon oxide coated nano silicon composite material with oxidized edges at a heating rate of 3 ℃/min, 5 ℃/min or 10 ℃/min; the cooling rate is 5 ℃/min or 7 ℃/min.
The application of the graphene/silicon oxide coated nano silicon composite material is that the graphene/silicon oxide coated nano silicon composite material or the graphene/silicon oxide coated nano silicon composite material prepared by the preparation method of the graphene/silicon oxide coated nano silicon composite material is used as a negative electrode material of a lithium ion battery.
The beneficial effects are that: the invention provides a graphene/silicon oxide coated nano silicon composite material, a preparation method and application thereof. The graphene coating is continuously carried out on the surface of the oxide coating layer of the silicon, so that the volume expansion effect of nano silicon particles in the charge and discharge process can be effectively relieved, and meanwhile, the direct contact of the silicon particles and electrolyte is avoided to generate an excessively thick solid electrolyte interface film; in addition, graphene can effectively improve the electron conductivity of the composite material. Therefore, the graphene/silicon oxide coated nano silicon composite material provided by the invention has higher specific capacity, rate capability and cycle stability; the graphene/silicon oxide coated nano silicon composite material has the advantages of simple preparation method, low manufacturing cost and easy industrial production.
Drawings
FIG. 1 is an X-ray powder diffraction pattern of a graphene/silicon oxide coated nano-silicon composite material obtained in example 1 of the present invention;
FIG. 2 is a Raman spectrum of the graphene/silicon oxide coated nano-silicon composite material obtained in example 1 of the present invention;
FIG. 3 is a scanning electron microscope image of a graphene/silicon oxide coated nano-silicon composite material obtained in example 1 of the present invention;
FIG. 4 is a transmission electron microscope image of the graphene/silicon oxide coated nano-silicon composite material obtained in example 1 of the present invention;
FIG. 5 is a comparative plot of the rate capability test of inventive example 1 and comparative example 1;
FIG. 6 is a graph showing the specific discharge capacity versus cycle number for examples 1, 2, 3 and 1 of the present invention;
FIG. 7 is a graph showing the change of specific discharge capacity with the number of cycles in examples 1, 4 and 5 according to the present invention;
fig. 8 is a graph showing comparison of ac impedance tests of example 1 and comparative example 1 of the present invention.
Detailed Description
The invention provides a graphene/silicon oxide coated nano silicon composite material, a preparation method and application thereof, and aims to make the purposes, technical schemes and effects of the invention clearer and more definite. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
At present, in order to solve the problems of poor conductivity and volume expansion of a silicon material in the prior art, modification methods such as silicon particle nanocrystallization and carbon coating are generally adopted to modify the silicon material, for example, in the patent of the invention with the application number of 201910900037.2, a synthesis method of a porous silicon nanowire and application of the porous silicon nanowire to a lithium ion battery cathode are mentioned, the silicon nanowire is prepared by a sol-gel method, and the silicon nanowire with a porous structure is obtained by utilizing magnesian reduction and acid washing, wherein the porous linear structure relieves the volume expansion of silicon in charge-discharge cycles, but the requirements of society cannot be met. In the invention patent with the application number of 202010877236.9, polytetrafluoroethylene particles and silicon particles are mixed and then ball-milled, and then the ball-milled powder is ignited, so that the carbon-coated silicon composite material is obtained. Therefore, how to prepare the silicon-based composite material with excellent electrochemical performance at low cost is an urgent problem to be solved in developing the silicon anode material.
Based on the above, as shown in fig. 4, the invention provides a graphene/silicon oxide coated nano silicon composite material, which comprises a nano silicon substrate, a silicon oxide coating layer coated on the surface of the nano silicon substrate and a graphene coating layer coated on the surface of the silicon oxide coating layer.
In this embodiment, the silicon oxide coating layer forms lithium silicate after charging, and the lithium silicate has good ionic conductivity and higher modulus, so that the ionic conductivity of the graphene/silicon oxide coated nano silicon composite material can be improved, and the volume expansion effect of silicon is inhibited.
In some embodiments, the graphene in the graphene coating layer is high-crystallinity graphene, and the raw material of the graphene coating layer is an edge-oxidized single-layer graphene aqueous solution; graphene with oxidized edges is adopted, the oxidation degree is low, and a pi plane is not damaged, so that the electron conductivity of the graphene is high, and the electron conductivity of the composite material is effectively improved.
In some embodiments, the oxide coating layer of silicon is obtained by mixing micron silicon with an organic solvent and then performing high-energy ball milling to obtain the nano silicon coated with the oxide of silicon.
In the embodiment, a coating layer is formed on the surface of a nano silicon substrate by sequentially utilizing silicon oxide and graphene to obtain a graphene/silicon oxide coated nano silicon composite material, so that the volume expansion of nano silicon in the lithiation process of the composite material can be effectively limited, and meanwhile, the direct contact between the nano silicon substrate and electrolyte is reduced to continuously generate an SEI film; the silicon oxide coating layer can form lithium silicate after charging, and the lithium silicate has good ionic conductivity and higher modulus, so that the ionic conductivity of the composite material is improved, and meanwhile, the volume expansion effect of silicon is inhibited; in addition, graphene is used as an excellent conductive material, so that the electronic conductivity of the graphene/silicon oxide coated nano silicon composite material can be effectively improved. Therefore, the graphene/silicon oxide coated nano silicon composite material has higher specific capacity, excellent rate capability and cycle stability.
Based on the same inventive concept, the invention also provides a preparation method of the graphene/silicon oxide coated nano silicon composite material, which specifically comprises the following steps:
s10: providing oxide-coated nano-silicon of silicon;
s20: mixing the silicon oxide coated nano silicon with an organic solvent to obtain a suspension;
s30: adding the single-layer graphene aqueous solution with the oxidized edges into the suspension, uniformly stirring, heating and drying to obtain the graphene/silicon oxide coated nano-silicon composite material with the oxidized edges;
s40: and performing heat treatment on the graphene/silicon oxide coated nano-silicon composite material with the oxidized edges, and grinding and sieving after natural cooling to obtain the graphene/silicon oxide coated nano-silicon composite material. At this time, the graphene/silicon oxide coated nano-silicon composite material is in a powder form.
In some embodiments, the method for preparing the silicon oxide coated nano silicon specifically includes:
s11: mixing micron silicon with an organic solvent to obtain a mixed solution;
s12: and (3) performing high-energy ball milling on the mixed solution to obtain the oxide-coated nano silicon of the silicon.
The method for forming the silicon oxide coating layer on the surface of the nano silicon substrate has simple process, can be used for large-scale preparation, and meets the high-efficiency production requirement.
In some embodiments, the organic solvent is one or more of methanol, ethanol, ethylene glycol, propanol.
In some embodiments, the mass of graphene in the edge-oxidized monolayer graphene aqueous solution is 0.1% -5% of the mass of the microsilica. When the addition amount of the graphene is less than 0.1% of the mass of the micron silicon, the electrochemical performance of the prepared graphene/silicon oxide coated nano silicon composite material is not obviously improved due to the fact that the addition amount of the graphene is too small, and the requirement of taking the graphene/silicon oxide coated nano silicon composite material as a negative electrode material cannot be met; when the addition amount of graphene is more than 5% of the mass of the micron silicon, the silicon content is relatively reduced, so that the graphene/silicon oxide coated nano silicon composite material has low capacity and low density, and is not beneficial to the development of commercialization.
In some embodiments, the edge-oxidized graphene/silicon oxide-coated nano-silicon composite is heat treated to obtain the graphene/silicon oxide-coated nano-silicon composite, comprising: and (3) placing the graphene/silicon oxide coated nano silicon composite material with the oxidized edges into a sintering furnace, and treating for 2-5 hours under the protection of inert gas and at the heat treatment temperature of 600-1100 ℃ to obtain the graphene/silicon oxide coated nano silicon composite material. Under the heat treatment temperature and the treatment time, the graphene/silicon oxide coated nano silicon composite material with oxidized edges can be thoroughly converted into the graphene/silicon oxide coated nano silicon composite material, and the capacity and the electrochemical performance of the composite material are improved.
In some embodiments, the inert gas is one or more of nitrogen, argon, helium.
In some embodiments, the temperature rise rate of the heat treatment of the edge-oxidized graphene/silicon oxide-coated nano-silicon composite material may be, but is not limited to, 3 ℃/min or 5 ℃/min or 10 ℃/min; the cooling rate may be, but is not limited to, 5 ℃/min or 7 ℃/min. It should be noted that the heating rate and the cooling rate in the heat treatment process may be the same or different; by controlling the heating rate and the cooling rate during heat treatment, the reaction process can be more stable, and the reaction can be more thoroughly carried out.
In the embodiment, the preparation method of the graphene/silicon oxide coated nano silicon composite material is simple, low in cost and easy for large-scale industrial production; meanwhile, the graphene/silicon oxide coated nano silicon composite material prepared by the simple method realizes that the silicon oxide and the high-crystallinity graphene are sequentially and uniformly coated on the surface of the nano silicon, effectively limits the volume expansion of the nano silicon matrix, reduces direct contact between electrolyte and the nano silicon matrix, and simultaneously remarkably improves the electronic conductivity of the composite material. Therefore, the graphene/silicon oxide coated nano silicon composite material has higher specific discharge capacity, excellent rate capability and charge-discharge cycling stability.
Based on the same inventive concept, the invention also provides an application of the graphene/silicon oxide coated nano silicon composite material, wherein the graphene/silicon oxide coated nano silicon composite material or the graphene/silicon oxide coated nano silicon composite material prepared by the preparation method of the graphene/silicon oxide coated nano silicon composite material is used as a negative electrode material of a lithium ion battery.
The following examples are further illustrative of the invention. It is also to be understood that the following examples are given solely for the purpose of illustration and are not to be construed as limitations upon the scope of the invention, since numerous insubstantial modifications and variations will now occur to those skilled in the art in light of the foregoing disclosure.
Example 1
Mixing the precursors: mixing 8mL of suspension formed by silicon oxide coated nano silicon and ethanol solvent (the concentration of the suspension is 100 mg/mL) with 8mL of edge graphene oxide aqueous solution (the concentration of the suspension is 1 mg/mL), uniformly stirring, and heating and drying to obtain the edge graphene oxide/silicon oxide coated nano silicon composite material;
and (3) heat treatment: and (3) placing the obtained edge graphene oxide/silicon oxide coated nano silicon composite material into a tubular furnace, performing heat treatment for 3 hours at the temperature of 900 ℃ in an argon atmosphere, naturally cooling, grinding and sieving to obtain the powdery graphene/silicon oxide coated nano silicon composite material.
Example 2
Mixing the precursors: mixing 8mL of suspension formed by silicon oxide coated nano silicon and ethanol solvent (the concentration of the suspension is 100 mg/mL) with 4mL of edge graphene oxide aqueous solution (the concentration of the suspension is 1 mg/mL), uniformly stirring, and heating and drying to obtain the edge graphene oxide/silicon oxide coated nano silicon composite material;
and (3) heat treatment: and (3) placing the obtained edge graphene oxide/silicon oxide coated nano silicon composite material into a tubular furnace, performing heat treatment for 3 hours at the temperature of 900 ℃ in an argon atmosphere, naturally cooling, grinding and sieving to obtain the powdery graphene/silicon oxide coated nano silicon composite material.
Example 3
Mixing the precursors: mixing a suspension formed by 8mL of silicon oxide coated nano silicon and an ethanol solvent (the concentration of the suspension is 100 mg/mL) with 12mL of edge graphene oxide aqueous solution (the concentration of the suspension is 1 mg/mL), uniformly stirring, and heating and drying to obtain the edge graphene oxide/silicon oxide coated nano silicon composite material;
and (3) heat treatment: and (3) placing the obtained edge graphene oxide/silicon oxide coated nano silicon composite material into a tubular furnace, performing heat treatment for 3 hours at the temperature of 900 ℃ in an argon atmosphere, naturally cooling, grinding and sieving to obtain the powdery graphene/silicon oxide coated nano silicon composite material.
Example 4
Mixing the precursors: mixing 8mL of suspension formed by silicon oxide coated nano silicon and ethanol solvent (the concentration of the suspension is 100 mg/mL) with 8mL of edge graphene oxide aqueous solution (the concentration of the suspension is 1 mg/mL), uniformly stirring, and heating and drying to obtain the edge graphene oxide/silicon oxide coated nano silicon composite material;
and (3) heat treatment: and (3) placing the obtained edge graphene oxide/silicon oxide coated nano silicon composite material into a tubular furnace, performing heat treatment for 3 hours at the temperature of 800 ℃ in an argon atmosphere, naturally cooling, grinding and sieving to obtain the powdery graphene/silicon oxide coated nano silicon composite material.
Example 5
Mixing the precursors: mixing 8mL of suspension formed by silicon oxide coated nano silicon and ethanol solvent (the concentration of the suspension is 100 mg/mL) with 8mL of edge graphene oxide aqueous solution (the concentration of the suspension is 1 mg/mL), uniformly stirring, and heating and drying to obtain the edge graphene oxide/silicon oxide coated nano silicon composite material;
and (3) heat treatment: and (3) placing the obtained edge graphene oxide/silicon oxide coated nano silicon composite material into a tubular furnace, performing heat treatment for 3 hours at the temperature of 1000 ℃ in an argon atmosphere, naturally cooling, grinding and sieving to obtain the powdery graphene/silicon oxide coated nano silicon composite material.
Comparative example 1
8mL of suspension formed by the oxide coated nano silicon of silicon and ethanol solvent (the concentration of the suspension is 100 mg/mL), and heating and drying are carried out to obtain the oxide coated nano silicon composite material of silicon.
In order to test that the composite material provided by the invention has energy storage characteristics and can be used for a lithium battery cathode material, the energy storage materials obtained in examples and comparative examples are subjected to tests such as X-ray diffraction, raman spectrum, scanning electron microscope, transmission electron microscope, multiplying power performance of the composite material, cycle performance of the composite material, alternating current impedance spectrum of the composite material and the like, and the test results are shown in figures 1 to 8.
As can be seen from the analysis of fig. 1 to 8, fig. 1 is an X-ray diffraction pattern of the powder graphene/silicon oxide coated nano silicon composite material obtained in example 1, and it can be seen from the figure that the diffraction peak of the composite material is consistent with the PDF card of pure silicon, indicating that the main component is silicon.
Fig. 2 is a raman spectrum of the material obtained in example 1 and comparative example 1, and example 1 has more D, G and 2D peaks unique to the graphite structure than comparative example 1, demonstrating the presence of graphene in the graphene/silicon oxide coated nano-silicon composite.
Fig. 3 is a scanning electron micrograph of a single-layer graphene-coated nano-silicon composite material obtained in example 1 (the single-layer graphene-coated nano-silicon composite material is the graphene/silicon oxide-coated nano-silicon composite material of the present invention), so that the particle size of the composite material after heat treatment is relatively uniform, the particle diameter is mainly concentrated between 400 nm and 600nm, and the nano-sized silicon is more favorable for prolonging the cycle life of the composite material.
Fig. 4 is a transmission electron micrograph of the graphene/silicon oxide coated nano-silicon composite material obtained in example 1, and the morphology features of the graphene/silicon oxide coated nano-silicon composite material can be observed to clearly see the lattice fringes of silicon, and the silicon oxide coating layer and the graphene with uniform surface of the silicon oxide coating layer.
FIG. 5 is a graph showing the rate performance test of the materials obtained in comparative example 1 and example 1, wherein the average discharge capacity of the composite material of the present invention is 1650.82mAh/g, 1663.10mAh/g, 1445.99mAh/g, 1167.68mAh/g, 874.45mAh/g and 1684.68mAh/g at current densities of 0.1A/g, 0.2A/g, 0.5A/g, 1A/g, 2A/g and 0.1A/g, respectively.
FIG. 6 is a graph showing the change of specific discharge capacity with cycle number of the composite materials with different graphene contents obtained in comparative example 1, example 2 and example 3, namely a cycle performance test chart, wherein the composite material prepared in example 1 of the present invention still has a specific discharge capacity of 1151.0mAh/g after 140 cycles at a flow density of 0.5A/g, and the initial coulomb efficiency reaches 83.55%; the specific discharge capacities of the composites prepared in comparative example 1, example 2 and example 3 were 527.5mAh/g, 927.9mAh/g and 1058.7mAh/g, respectively, after 140 cycles at a flow density of 0.5A/g.
Fig. 7 is a graph showing the change of specific discharge capacity with cycle number of the composite materials obtained in examples 1, 4 and 5 at different heat treatment temperatures, namely, a cycle performance test chart, and the composite materials prepared in the examples of the present invention have better capacity and stability.
Fig. 8 is an ac impedance test chart of the materials obtained in comparative example 1 and example 1, and in example 1, compared with comparative example 1, the charge transfer resistance is reduced from 294.3 Ω to 202.4 Ω, and the preparation method of the present invention can significantly reduce the charge transfer resistance of the electrode and improve the electron conductivity of the composite material.
In summary, the graphene/silicon oxide coated nano silicon composite material provided by the invention comprises a nano silicon substrate, a silicon oxide coating layer coated on the surface of the nano silicon substrate, and a graphene coating layer coated on the surface of the silicon oxide coating layer. The graphene coating is continuously carried out on the surface of the oxide coating layer of the silicon, so that the volume expansion effect of nano silicon particles in the charge and discharge process can be effectively relieved, and meanwhile, the direct contact of the silicon particles and electrolyte is avoided to generate an excessively thick solid electrolyte interface film; in addition, graphene can effectively improve the electron conductivity of the composite material. Therefore, the graphene/silicon oxide coated nano silicon composite material provided by the invention has higher specific capacity, rate capability and cycle stability; the graphene/silicon oxide coated nano silicon composite material has the advantages of simple preparation method, low manufacturing cost and easy industrial production. Secondly, the capacity of the graphene/silicon oxide coated nano silicon composite material is superior to that of a commercial graphene coated nano silicon material, and the voltage range is between 0.01 and 2V; the average discharge capacity of the composite material is 1650.82mAh/g, 1663.10mAh/g, 1445.99mAh/g, 1167.68mAh/g and 874.45mAh/g respectively under the current density of 0.1A/g, 0.2A/g, 0.5A/g, 1A/g and 2A/g.
It is to be understood that the invention is not limited in its application to the examples described above, but is capable of modification and variation in light of the above teachings by those skilled in the art, and that all such modifications and variations are intended to be included within the scope of the appended claims.
Claims (4)
1. The preparation method of the graphene/silicon oxide coated nano silicon composite material is characterized by comprising the following steps of:
mixing micron silicon with an organic solvent to obtain a mixed solution;
the mixed solution is subjected to high-energy ball milling to prepare the silicon oxide coated nano silicon;
mixing the nano silicon coated by the silicon oxide with an organic solvent to obtain a suspension;
adding an edge oxidized single-layer graphene aqueous solution into the suspension, stirring, heating and drying to obtain an edge oxidized graphene/silicon oxide coated nano silicon composite material;
placing the graphene/silicon oxide coated nano silicon composite material subjected to edge oxidation into a sintering furnace for heat treatment, and treating for 2-5 hours under the conditions of inert atmosphere protection and heat treatment temperature of 600-1100 ℃ to obtain the graphene/silicon oxide coated nano silicon composite material;
the mass of graphene in the edge oxidized single-layer graphene aqueous solution is 0.1% -5% of the mass of the micrometer silicon;
the temperature rising rate of the heat treatment of the graphene/silicon oxide coated nano silicon composite material subjected to edge oxidation is 3 ℃/min, 5 ℃/min or 10 ℃/min; the cooling rate is 5 ℃/min or 7 ℃/min;
the particle size of the graphene/silicon oxide coated nano silicon composite material is 400-600nm.
2. The method for preparing the graphene/silicon oxide coated nano-silicon composite material according to claim 1, wherein the organic solvent is one or more of methanol, ethanol, ethylene glycol and propanol.
3. The method for preparing a graphene/silicon oxide coated nano-silicon composite material according to claim 1, wherein the inert atmosphere is one or more of nitrogen, argon and helium.
4. The application of the graphene/silicon oxide coated nano-silicon composite material, which is characterized in that the graphene/silicon oxide coated nano-silicon composite material prepared by the preparation method of the graphene/silicon oxide coated nano-silicon composite material as claimed in any one of claims 1-3 is used as a negative electrode material of a lithium ion battery.
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