CN115215341A - Preparation method of nano silicon - Google Patents
Preparation method of nano silicon Download PDFInfo
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- CN115215341A CN115215341A CN202110419667.5A CN202110419667A CN115215341A CN 115215341 A CN115215341 A CN 115215341A CN 202110419667 A CN202110419667 A CN 202110419667A CN 115215341 A CN115215341 A CN 115215341A
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
- C01B33/021—Preparation
- C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
- C01B33/033—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material by reduction of silicon halides or halosilanes with a metal or a metallic alloy as the only reducing agents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
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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
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- 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 preparation method of nano silicon, which is characterized in that in the presence of a catalyst, a reducing agent is used for reducing silicide at low temperature to prepare the nano silicon with high purity, uniform size and controllability. The method provided by the invention has the advantages of low cost, high yield, simple preparation process and easy amplification for industrial production.
Description
Technical Field
The invention belongs to the field of preparation of nano silicon materials, particularly relates to a preparation method of a size-controllable nano silicon material, and particularly relates to a preparation method of a nano silicon material for a lithium ion battery cathode.
Background
In recent years, as the specific capacity of graphite serving as a mainstream commercial lithium ion battery negative electrode material reaches a limit value (372 mAh/g), and a lithium intercalation potential platform of the graphite is close to the deposition potential of metallic lithium, potential safety hazards are easily caused in the process of quick charging or low-temperature charging, and the application of the graphite in the field of large-capacity batteries in future social development is limited. Silicon has a theoretical specific capacity (4200 mAh/g) 10 times higher than that of graphite, a moderate delithiation potential (<0.5V vs Li + The characteristics of/Li) and abundant reserves (27.6%) are paid close attention by lithium ion battery negative electrode researchers.
However, in practical applications, there are still some problems with silicon materials: firstly, silicon has obvious volume effect in the charging and discharging process, and pulverization and failure of materials are easily caused, so that rapid attenuation of cycle capacity is caused; secondly, the conductivity of the silicon material is poor, which affects the rate performance of the battery. In order to solve the above problems, the most effective method is to perform silicon nanocrystallization, reduce cracks caused by absolute volume expansion by reducing the particle size of silicon, and effectively relieve collapse of an electrode structure, thereby improving cycle stability, and simultaneously, nanocrystallization of silicon can shorten diffusion distance of lithium ions and conduction distance of electrons, improve electrochemical reaction rate, and improve rate performance of the electrode.
At present, there are many methods for silicon nanocrystallization, for example, patent CN101979317A discloses a method for preparing nano silicon powder by grinding micron coarse silicon powder through a ball mill, chemical vapor deposition method used in patent CN 10969883 12A, method for decomposing silane using a plasma generator in patent CN108101061A, magnesiothermic reduction method used in patent CN108832115A, and the like. The traditional mechanical grinding method is simple and low in cost, but in the high-speed sanding process, the local particle collision temperature is high, so that the nano silicon is oxidized, the purity is low, the crystal defects are more, the particle distribution is not uniform, and the like, and the particle size of the product is 80nm at the minimum, so that the product is difficult to be smaller; the Chemical Vapor Deposition (CVD) method adopts silane as a raw material, the prepared particle size is 10-150nm, the oxidation degree is low, but the method has low yield and cannot be used for mass production, and the silane is flammable and explosive, so that the large-scale preparation of the silane has a safety problem; in addition, the particle size and the morphology of the product can be controlled by a magnesiothermic reduction method, but the product has more reaction residues, magnesium oxide, silicon dioxide and the like are difficult to remove, the product purity is not high, and the mass production cannot be realized.
Disclosure of Invention
In order to solve the problems, the invention provides a novel method for preparing nano silicon aiming at the defects of low yield, high cost, larger product particle size, nonuniform particles, low purity of the nano silicon product and the like caused by difficult removal of generated by-products in the conventional method for preparing nano silicon. The method provided by the invention has the advantages of low cost, simple preparation process and easy amplification for industrial production.
In order to achieve the aim, the invention provides a method for preparing nano silicon by low-temperature reduction, which is used for preparing the nano silicon by reacting silicide, a reducing agent and a catalyst according to a certain proportion under a certain condition and then carrying out post-treatment.
In some embodiments, the silicide is a silicon halide selected from SiCl 4 、SiBr 4 、SiI 4 At least one of; the reducing agent is a metal reducing agent and is selected from at least one or more of Li, na, K, mg, al, ca, al, rb, cs, sr, ba and Y, wherein the 'plurality' can be simple physical mixture of a plurality of metals and can also be alloy formed by the plurality of metals; the catalyst is a liquid catalyst, and is selected from one or more of ethers, esters, nitriles, sulfones and ionic liquids, and may be a combination of substances in different classes, or a combination of a plurality of substances in the same class, or a single compound, for example, in some embodiments of the present invention, the liquid catalyst is selected from ethers and esters, in other embodiments, the liquid catalyst is selected from ethers and sulfones, and in other embodiments, the liquid catalyst is a mixture of two ethers or an ether compound.
In the technical scheme provided by the invention, the ether liquid catalyst comprises CH 3 O(CH 2 CH 2 O) n CH 3 ) Diethyl ether, propyl ether, methyl ethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dibutyl ether, anisole, p-xylyl ether, cyclic ether, dibutyl ether, methyl tert-butyl ether, tributyl methyl ethyl ether, n-hexyl ether and isopropyl ether, wherein n is a positive integer; the ester catalyst comprises ethyl formate, ethyl acetate, methyl formate, methyl acetate, isobutyl acetate and butyl acetate; the nitrile catalyst comprises acetonitrile, propionitrile, butyronitrile, succinonitrile and trimethoxy propionitrile; sulfone catalysts include DMSO and sulfolane; the ionic liquid comprises halogenated 1-alkyl-3-methylMethylimidazole, 1-alkyl-3-methylimidazole tetrafluoroborate, 1-alkyl-3-methylimidazole hexafluoroborate, and 1-alkyl-3-methylimidazole bistrifluoromethylimide salt.
In the technical scheme provided by the invention, the reactants of silicide, reducing agent and catalyst are reacted at the temperature of-30-130 ℃, the water content and the oxygen content in the gas atmosphere of the reaction are controlled to be less than 200ppm and less than 200ppm, the reaction is carried out while dispersion is carried out according to a certain feeding mode, and the reaction time is 1-100 h.
The addition modes of the reactants of the silicide, the reducing agent and the catalyst in the invention include but are not limited to adding the three simultaneously according to the proportion or adding the reducing agent firstly according to the proportion and then adding the silicide and the catalyst respectively or uniformly mixing and then slowly adding the silicide and the catalyst, and the slow addition modes include but are not limited to spraying addition and titration addition.
The way in which the reactant silicide, reducing agent and catalyst are dispersed in the present invention includes, but is not limited to, one or more of stirring dispersion, mechanical crushing dispersion or ultrasonic dispersion. In some embodiments of the invention, the silicide, reducing agent, and catalyst are reacted at a temperature of-30 deg.C, and in other embodiments, the silicide, reducing agent, and catalyst may be reacted at-25 deg.C, -20 deg.C, -15 deg.C, -10 deg.C, -5 deg.C, 0 deg.C, 5 deg.C, 10 deg.C, 15 deg.C, 25 deg.C, 30 deg.C, 35 deg.C, 40 deg.C, 50 deg.C, 55 deg.C, 60 deg.C, 70 deg.C, 75 deg.C, 80 deg.C, 90 deg.C, 95 deg.C, 100 deg.C, 110 deg.C, 115 deg.C, 120 deg.C, 125 deg.C, 130 deg.C, etc., i.e., at any one temperature of-30 deg.C-130 deg.C, but the reaction temperature is generally controlled depending on the melting point or boiling point of the silicide and catalyst during the reaction, and the reaction temperature will vary slightly.
In some embodiments of the invention, the water content of the reacting atmosphere is 180ppm, and in other embodiments the water content of the reacting atmosphere may be 180ppm, 190ppm, 195ppm, 198ppm, 186ppm, 188ppm, 182ppm, 170ppm, 172ppm, 174ppm, 178ppm, 160ppm, 165ppm, 150ppm, 155ppm, 140ppm, 145ppm, 130ppm, 120ppm, 110ppm, 100ppm, 90ppm, 80ppm, 70ppm, 50ppm, 40ppm, 30ppm, 20ppm, etc., i.e., the water content of the reacting atmosphere is anywhere from 0ppm to 200 ppm.
In some embodiments of the invention, the oxygen content of the reactive atmosphere is 180ppm, in other embodiments the oxygen content of the reactive atmosphere is 180ppm, 190ppm, 195ppm, 198ppm, 186ppm, 188ppm, 182ppm, 170ppm, 172ppm, 174ppm, 178ppm, 160ppm, 165ppm, 150ppm, 155ppm, 140ppm, 145ppm, 130ppm, 120ppm, 110ppm, 100ppm, 90ppm, 80ppm, 70ppm, 50ppm, 40ppm, 30ppm, 20ppm, etc., i.e., the oxygen content of the reactive atmosphere is anywhere from 0ppm to 200 ppm.
The invention effectively prevents the synthesized nano silicon material from forming an oxide layer and preventing silicide from reacting with water to generate impurities by controlling the content of oxygen and water in the gas atmosphere in the reaction process, thereby improving the purity of the nano silicon, avoiding subsequent complex post-treatment, reducing the whole synthesis process flow, lowering the production cost, and greatly improving the application performance of the synthesized high-purity nano silicon in the application of batteries, particularly lithium batteries.
In some embodiments of the present invention, the reaction time of the reactant silicide, the reducing agent and the catalyst is 1h, while in other embodiments, the reaction time of the reactant silicide, the reducing agent and the catalyst may be 2h, 5h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, 50h, 55h, 60h, 65h, 70h, 75h, 80h, 85h, 90h, 95h, 100h, and the like, i.e., the reaction time is any value from 1h to 100h.
In the technical scheme provided by the invention, the input proportion of the reactants of silicide, reducing agent and catalyst is that the molar ratio of silicide to reducing agent is 1-50; the molar ratio of the catalyst to the reducing agent is 1. In other technical schemes provided by the invention, the adding proportion of the reactants of silicide, reducing agent and catalyst is preferably that the molar ratio of silicide to reducing agent is 1; the molar ratio of the catalyst to the reducing agent is 1.
In some embodiments of the present invention, the molar ratio of the added silicide and the reducing agent is 1. In some embodiments of the present invention, the molar ratio of the catalyst and the reducing agent charged is 1.
In the technical scheme provided by the invention, after reactants of silicide, reducing agent and catalyst which are added according to a certain proportion react under certain conditions, certain post-treatment is required, wherein the post-treatment comprises the following steps:
1) Separating the mixture obtained after the reaction, and removing partial or all of the reactants and the catalyst which are not fully reacted to obtain a solid mixture containing nano silicon;
2) Separating the obtained solid mixture containing the nano-silicon by utilizing the difference of physical and/or chemical properties of each component to obtain nano-silicon particles;
3) And drying the obtained nano silicon particles to obtain finished nano silicon particles.
The separation mode in the step 1) in the post-treatment scheme provided by the invention comprises one or more of drying after suction filtration, drying after filter pressing, distillation, drying after squeezing, spray drying and drying after centrifugation; the separation by utilizing the physical and/or chemical property difference in the post-treatment step 2) is to carry out separation after treatment in a specific solvent by utilizing the physical and/or chemical property difference of each component in the solid mixture, wherein the separation mode comprises dissolution suction filtration, dissolution pressure filtration, dissolution centrifugation and dissolution pressing;
it should be noted that, in the above technical solution of the present invention, step 1) and step 2) are not limited to 1 step, and may be performed in multiple steps. As in step 1), "separating the mixture obtained after the reaction to remove part or all of the insufficiently reacted reactants and catalyst", in some embodiments, the separation may be performed directly 1 or more times to remove the insufficiently reacted liquid reactants and catalyst, leaving a mixture of "solid nanosilicon product and halide salt" or "solid nanosilicon product, halide salt and insufficiently reacted reducing metal"; in other embodiments, a plurality of separation modes (for example, a large-aperture filter membrane is selected to filter and remove the reducing metal, and then distillation is performed to remove the liquid reactant and the catalyst) are respectively used for 1 or more separation operations, so as to remove the insufficiently reacted reducing metal, the liquid reactant and the catalyst, and finally achieve the purpose of obtaining the mixture of the solid nano-silicon product and the halide salt. The "separation by using the difference in physical and/or chemical properties" mentioned in the step 2) means that the separation is performed after the treatment in a specific solvent by using the difference in physical and/or chemical properties of the components in the solid mixture, the separation in the step is not limited to one step, and may be performed in multiple steps, and each step may be repeated 1 or more times until the nano silicon product with high purity is obtained. If the reducing metal remains/remains in the reaction, in this step, in some embodiments, the reducing metal may be removed by reacting in one or more mixed solvents of methanol, ethanol, propanol, anhydrous hydrochloric acid, anhydrous hydrobromic acid, anhydrous hydroiodic acid, anhydrous nitric acid, and anhydrous phosphoric acid, and then the nano-silicon material and the halide salt are separated by using the difference of physical solubility in one or more mixed solvents of pyridine, acetone, ether, benzene, dichloromethane, chloroform, carbon tetrachloride, methanol, ethanol, propanol, ethylene glycol, isopropanol, isoamyl alcohol, and glycerol, so as to obtain the high-purity nano-silicon material, and the above two steps may be repeated 1 or more times per step until the high-purity nano-silicon product is obtained; in other embodiments, if the remaining/residual reduced metal particles are larger, the difference of physical properties can be directly utilized, the solid mixture treated in step 1) is dissolved in one or more mixed solvents of pyridine, acetone, diethyl ether, benzene, dichloromethane, chloroform, carbon tetrachloride, methanol, ethanol, propanol, ethylene glycol, isopropanol, isoamyl alcohol and glycerol, the large-particle reduced metal is filtered out by using a screen with larger pore diameter, then a filter membrane with smaller pore diameter is used for filtering, so that halide salt is left in the filtrate, and the nano-silicon particles are left on the filter membrane, so that the purposes of separation and purification are achieved, and the above two steps can be repeated for 1 or more times per step until a high-purity nano-silicon product is obtained; in other embodiments of the present invention, if no reduced metal remains, the solid mixture treated in step 1) may be directly dissolved in one or more mixed solvents of pyridine, acetone, ether, benzene, dichloromethane, chloroform, carbon tetrachloride, methanol, ethanol, propanol, ethylene glycol, isopropanol, isoamyl alcohol, and glycerol, filtered by a filter membrane with a smaller pore size to leave halide salts in the filtrate, and the nano-silicon particles are left on the filter membrane to achieve the purpose of separation and purification, and the above steps may be repeated 1 or more times until a high-purity nano-silicon product is obtained. Wherein the specific solvent is one or more of methanol, ethanol, propanol, anhydrous hydrochloric acid, anhydrous hydrobromic acid, anhydrous hydroiodic acid, anhydrous nitric acid, anhydrous phosphoric acid, pyridine, acetone, diethyl ether, benzene, dichloromethane, trichloromethane, carbon tetrachloride, ethylene glycol, isopropanol, isoamyl alcohol and glycerol, and the separation mode is one or more of suction filtration, filter pressing, centrifugation and squeezing; the drying in the step 3) refers to drying in inert gas or vacuum atmosphere at 50-200 ℃ for 10-300 min.
The "drying" treatment mentioned in the post-treatment step 3) in the present invention includes, but is not limited to, one or more of standing drying, spray drying, rotary evaporation drying, stirring drying.
In the technical scheme provided by the invention, reactants of silicide, reducing agent and catalyst which are added according to a certain proportion react under certain conditions to obtain the nano-silicon cluster, the cluster is particles of nano-silicon which are agglomerated together due to intermolecular force, the particle size of the cluster is within the range of 0.1-20um, and the particle size of the nano-silicon in the cluster is 15-100 nm.
In the above technical solution of the present invention, the preparation of nano silicon may further include a further heat treatment after the post-treatment step 1) or step 3), wherein the heat treatment is performed in an inert gas atmosphere or a vacuum atmosphere at 260 ℃ to 1300 ℃ for 0.1h to 25h. In some embodiments of the present invention, the solid mixture containing nano-silicon obtained after the post-treatment step 1) is directly further treated, and then the treatment is performed according to the post-treatment steps 2) and 3) to prepare the final product nano-silicon, wherein the treatment manner comprises heat treatment, wherein the heat treatment is performed in an inert gas atmosphere or a vacuum atmosphere at 260-1300 ℃ for 0.1-25 h; in other embodiments of the present invention, the final product nano-silicon is obtained by further processing the finished product nano-silicon obtained after the post-processing step 3), wherein the processing manner comprises heat treatment, wherein the heat treatment is performed in inert gas at 260-1300 ℃ or in vacuum atmosphere for 0.1-25 h; in some other embodiments, the nano-silicon treated according to the post-treatment step is directly used as the final product without further heat treatment.
In some embodiments provided by the present invention, the temperature of the post-treatment is 280 ℃, in other embodiments, the temperature of the post-treatment is 300 ℃, 310 ℃, 320 ℃, 380 ℃, 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃, 1050 ℃, 1180 ℃, 1190 ℃, 1260 ℃, 1370 ℃, 1410 ℃ and the like, i.e., the temperature of the post-treatment is any value within the range of 260 ℃ to 1410 ℃; in the technical scheme provided by the invention, the heat treatment time can be any value within the range of 0.1h-25h, and the crystallinity of the nano silicon after heat treatment has certain difference according to different heat treatment temperatures and times.
The obtained nano silicon particles are further subjected to heat treatment, so that the crystallinity of the nano silicon particles can be further improved, and dangling bonds on the surface of the nano silicon are reduced, so that the stability of the nano silicon to water and oxygen is improved.
The nano silicon prepared by the invention can be applied to the preparation of batteries, in particular to the preparation of negative electrode materials of lithium batteries.
Unless otherwise specified, the term "silicon compound" as used herein refers to a non-metallic silicon-containing compound.
The inert gas in the invention is selected from one or more of carbon dioxide, nitrogen, argon, helium, neon, krypton, xenon and radon.
The invention has the beneficial effects that:
1) The invention provides a method for preparing nano silicon by low-temperature reduction, which utilizes a catalyst to reduce the potential energy of reaction, thereby reducing the temperature and pressure of the reaction, realizing that silicide can be reduced under the environment of low temperature and non-high pressure, preparing nano silicon material with high purity (the purity can reach more than 99 percent) and high yield, and simultaneously generating by-products which can effectively obstruct the connection of silicon along with the continuous reduction of the silicide in the reaction process, thereby generating silicon products which can reach the nano scale;
2) The average particle size distribution width of the nano silicon in the current market is more than 100nm, and the reaction rate is controlled by controlling the amount and the proportion of the catalyst and halide substances enriched on the surface of the reduced metal, so that the size, the uniformity and the like of the nano silicon particles are effectively controlled, the particle size of the nano silicon product prepared by the method can be controlled between 15nm and 100nm, and the particle size distribution width can be controlled between 15nm and 40 nm;
3) The selected reactants are mixed and reacted with solid and liquid reactants, and the liquid reactants fully wrap the solid reactants, so that the reactants can fully react, and the yield is greatly improved;
4) The cost of the nano silicon prepared by the preparation method provided by the invention is very low. Current market D 50 The selling price of the product with the wavelength of 100nm is 50 ten thousand yuan/ton, the selling price of the product with the wavelength of 30nm is 2400 ten thousand yuan/ton, and the unit cost price of the nano silicon prepared by the invention can be controlled in the range of 26 ten thousand yuan/ton or less. The method is mainly caused by the following reasons: a) The raw material silicide is a side product generated by purifying polysiliconThe product is a hazardous waste, and has low cost, such as SiCl 4 The market price of the product is close to 3300 yuan/ton, and the price is low; b) The preparation condition is simple, the high-temperature and high-pressure condition does not exist, the requirement on equipment is low (the requirement can be met by domestic equipment), the energy consumption is low, and the cost can be effectively reduced; c) In the post-treatment process, impurities are removed by utilizing the difference of physical properties, and impurity-removing solvents and the like can be recycled, so that the cost of raw materials for preparing the nano silicon can be further reduced; d) The nano silicon prepared by the method is not oxidized basically, and subsequent operations such as oxide layer removal and the like are not needed, so that the preparation cost of the nano silicon can be further reduced;
5) The method has the advantages of simple process, high reproducibility and easy realization of industrial production;
6) The whole reaction process of the invention is environment-friendly, all solvents can be recycled, no waste liquid is generated, no waste gas is generated in the reaction process, and the only generated solid by-product is reduced metal salts which can be recycled.
Drawings
Fig. 1 is XRD patterns of non-heat-treated nano-silicon and heat-treated nano-silicon in example 1.
FIG. 2 is a scanning electron microscope image of the non-heat-treated nano-silicon (a) and the heat-treated nano-silicon (b) in example 1.
Detailed Description
The following are preferred embodiments of the present invention, and the present invention is not limited to the following preferred embodiments. It should be noted that various changes and modifications based on the inventive concept herein by those skilled in the art are intended to be included within the scope of the invention.
The experimental method and the detection method described in the following examples are conventional methods without specific description, and the reagents and materials are commercially available without specific description, wherein reduced metallic form Li small particles (particle size 2 mm), na small particles (particle size 2 mm), mg chips (size: 10mm × 5mm × 1mm), lithium magnesium alloy large particles (particle size 5 mm), magnesium small particles (particle size 2 mm), K large particles (particle size 5 mm), ca small particles (particle size 2 mm), li powder (particle size 75 μm), and Al small particles (particle size 2 mm).
The preparation and detection method of applying the nano-silicon in the battery described in the following embodiment is as follows:
the nano silicon product is directly used as a negative electrode material to be applied to a lithium battery. Firstly, according to the traditional battery technology of nano-silicon preparation, nano-silicon is dispersed and coated with carbon on the surface to prepare carbon-coated nano-silicon. And (3) coating carbon-coated nano silicon: SP: polyvinylidene fluoride (PVDF) = 6.
After the baking is finished, the mixture is quickly transferred to a glove box, a metal lithium sheet with the diameter of 14mm is used as a counter electrode, a single-sided ceramic diaphragm is used, and 1mol/L LiPF is used 6 V. (EC + DMC) (volume ratio 1) plus 3% VC and 3% fec were used as electrolyte solutions, and button cell assembly was performed on gloves, and the glove box water oxygen content was controlled to 0.1ppm or less.
And carrying out charge-discharge cycle test on the assembled battery under the following test conditions: discharging to 5mV according to 0.5C, 0.1C, 0.05C step, charging to 1.0V by 0.1C constant current, and circulating for 2 weeks. ( The specific capacity of the material is calculated in a mode of charging capacity/composite negative electrode quality; the first cycle efficiency calculation mode of the battery is as follows: specific first cycle charging capacity/specific first cycle discharging capacity of battery )
Example 1
At water content<100ppm, oxygen content<160ppm,10 deg.C, adding SiCl which is a silicon compound 4 The reducing metal Mg scraps and the liquid catalyst glycol dimethyl ether are added into a reaction kettle according to the molar ratio of 3 4 Uniformly mixing the mixture with a liquid catalyst glycol dimethyl ether according to the proportion, slowly spraying and adding the mixture, mechanically crushing and dispersing the mixture for reaction for 96 hours, and filtering the excessive silicon compound SiCl in a suction filtration mode 4 Separated from liquid catalyst glycol dimethyl ether and then dried to leave nano silicon and compound MgCl 2 To a sufficient amount of methanol (methanol in a molar ratio Mg: methanol =1 = 25) to allow the mixture to be added to methanolCompound MgCl 2 Dissolving in the solvent, separating by a filter pressing method, repeating the dissolving and filter pressing operation for three times, putting the obtained nano-silicon into a vacuum oven for vacuumizing, setting the temperature at 70 ℃ for drying for 1.5h, and carrying out heat treatment on the dried nano-silicon at 1000 ℃ for 3h in a vacuum environment to obtain the nano-silicon with the particle size of 25-60nm. Fig. 1 is XRD patterns of the heat-treated and non-heat-treated nano-silicon products of the present example, which shows that there is no distinct characteristic peak in XRD patterns of the non-heat-treated nano-silicon of example 1, indicating that the non-heat-treated nano-silicon is amorphous nano-silicon, while there is distinct characteristic peak in XRD patterns of the heat-treated nano-silicon product of example 1, indicating that the heat treatment improves the crystallinity of the nano-silicon prepared by the present invention, and that it is consistent with the characteristic peak of standard PDF card of silicon and no impurity peak appears, indicating that the nano-silicon product of the present invention has less impurities and higher purity. The finally obtained non-heat-treated nano silicon product and the heat-treated nano silicon product are respectively characterized by a scanning electron microscope, the characterization results are respectively shown in (a) and (b) of fig. 2, and from a micro-topography graph under the scanning electron microscope of fig. 2, the particle size of the non-heat-treated nano silicon is 25-60nm, and the particle size of the heat-treated nano silicon product is 25-60nm.
TABLE 1 ICP characterization of the nanosilica prepared in example 1
Table 1 shows the ICP characterization results of the nano silicon prepared in example 1 without heat treatment and the nano silicon after heat treatment at 1000 ℃, and it can be seen that the purity of silicon is not affected by the heat treatment, and the purity of silicon in the product is as high as 99.60%.
The first-cycle efficiency of the battery measured by the preparation and detection method of applying the non-heat-treated nano-silicon in the embodiment to the battery is 68.8%, and the first-cycle charging specific capacity is 2678mAh/g. The first cycle efficiency of the battery obtained by applying the nano-silicon product obtained by the heat treatment in the embodiment to the preparation and detection method of the battery is 74.8%, and the first cycle specific charge capacity is 3245mAh/g. As can be seen from comparison of the battery data of the non-heat-treated nano silicon and the heat-treated nano silicon in example 1, the non-heat-treated nano silicon has a low first cycle efficiency and a specific first cycle charge capacity of 2678mAh/g, while the heat-treated nano silicon is more stable, so that the first cycle efficiency and the specific first cycle charge capacity of the heat-treated nano silicon applied to the battery are higher. The first cycle efficiency of the battery obtained by testing 30nm-500nm nano-silicon in the current market according to the method is 71% -75%, and the first cycle charging specific capacity is 3000-3300mAh/g. It can be seen that the battery performance of the nano silicon prepared by the invention is relatively excellent.
Example 2
At the water content<100ppm, oxygen content<160ppm,20 deg.C, and mixing SiCl which is a silicon compound 4 And the small particles of the reduced metal Na and the liquid catalyst (50% anisole and 50% ethyl formate) are firstly added into a reaction kettle according to the molar ratio of 2 4 Mixing with liquid catalyst (50% anisole, 50% ethyl formate) at the above ratio, slowly titrating, adding into ultrasonic dispersion reaction for 32h, and directly spray drying to obtain the rest SiCl 4 Separating the nano silicon from a liquid catalyst (50% anisole and 50% ethyl formate), leaving a mixture of nano silicon and a compound NaCl, adding the mixture into enough glycol (the use amount of the glycol is Na: glycol =1 by mol ratio), dissolving the compound NaCl into the solvent, separating by a centrifugal method, repeating the operations of dissolving and centrifuging twice, putting the obtained nano silicon into a blast oven, continuously introducing argon, setting the temperature to 200 ℃, drying for 10min, and carrying out heat treatment on the dried nano silicon at 260 ℃ for 12h in an argon environment to obtain a nano silicon product with the particle size of 30-60 nm.
Table 2 ICP characterization results for nanosilica prepared in example 2
| Element(s) | The mass percentage of each component in the nano silicon |
| Si | 99.50％ |
| Na | 0.10％ |
| Cl | 0.15％ |
| O | 0.25％ |
As can be seen from the table above, the purity of the silicon in the product is as high as 99.50%.
The first-cycle efficiency of the battery measured by the preparation and detection method applied to the battery of the nano-silicon product obtained in the embodiment is 74.3%, and the first-cycle specific charge capacity is 3167mAh/g. The first cycle efficiency of the battery obtained by testing 30nm-500nm nano-silicon in the current market according to the method is 71% -75%, and the first cycle charging specific capacity is 3000-3300mAh/g. It can be seen that the battery performance of the nano silicon prepared by the invention is relatively excellent.
Example 3
At the water content<100ppm, oxygen content<100ppm of SiCl which is a silicon compound at-5 DEG C 4 And adding the small particles of the reduced metal Li and the liquid catalyst diethyl ether into a reaction kettle according to the molar ratio of 1 4 Separating with liquid catalyst diethyl ether and drying to obtain mixture of nano silicon and compound LiCl, subjecting the dried mixture containing nano silicon to heat treatment at 600 deg.C for 2 hr under vacuum environment, adding into pyridine to dissolve compound LiClDissolving into pyridine (the pyridine is used in a molar ratio of Li: pyridine =1 = 9), separating by a centrifugation method, repeating the dissolving and centrifugation operation for four times, putting the obtained nano-silicon into a vacuum oven for vacuumizing, setting the temperature at 130 ℃, and stirring and drying for 4 hours to obtain the nano-silicon product with the particle size range of 30-60 nm.
Table 3 ICP characterization results for nanosilica prepared in example 3
| Element(s) | The mass percentage of each component in the nano silicon |
| Si | 99.62％ |
| Li | 0.03％ |
| Cl | 0.15％ |
| O | 0.20％ |
As can be seen from the above table, the purity of the silicon in the product is as high as 99.62%.
The first-cycle efficiency of the battery is 74.7% and the first-cycle charging specific capacity is 3192mAh/g, which is measured by the preparation and detection method of the obtained nano silicon product applied to the battery. The first-cycle efficiency of the battery obtained by testing 30-500 nm nano-silicon in the current market according to the method is 71-75%, and the first-cycle charging specific capacity is 3000-3300mAh/g. It can be seen that the battery performance of the nano silicon prepared by the invention is relatively excellent.
Example 4
At water content<100ppm, oxygen content<160ppm,0 deg.C, and mixing SiCl which is a silicon compound 4 The large particles of the reduced lithium magnesium metal alloy (molar ratio 5 4 Separated from the liquid catalyst diethylene glycol dimethyl ether and then dried to leave nano silicon and compounds LiCl and MgCl 2 Is added to a sufficient amount of glycerol solvent (glycerol amount in molar ratio lithium magnesium alloy: glycerol =1 2 Dissolving the nano silicon into the solvent, separating by a filter pressing method, repeating the operations of dissolving and filter pressing twice, putting the obtained nano silicon into a vacuum oven for vacuumizing, setting the temperature at 150 ℃, stirring and drying for 2 hours, and carrying out heat treatment on the dried nano silicon at 500 ℃ for 8 hours in a vacuum environment to obtain a nano silicon product with the particle size of 40-60 nm.
Table 4 ICP characterization of the nanosilica prepared in example 4
| Element(s) | The mass percentage of each component in the nano silicon |
| Si | 99.50％ |
| Li | 0.01 |
| Mg | 0.05％ |
| Cl | 0.24％ |
| O | 0.20％ |
As can be seen from the table above, the purity of the silicon in the product is as high as 99.50%.
The first-cycle efficiency of the battery measured by the preparation and detection method of the obtained nano silicon product applied to the battery is 73.6%, and the first-cycle charging specific capacity is 3205mAh/g. The first cycle efficiency of the battery obtained by testing 30nm-500nm nano-silicon in the current market according to the method is 71% -75%, and the first cycle charging specific capacity is 3000-3300mAh/g. It can be seen that the battery performance of the nano silicon prepared by the invention is relatively excellent.
Example 5
At water content<120ppm, oxygen content<150ppm of SiCl, a silicon compound at-10 DEG C 4 And adding the reduced metal Al small particles and a liquid catalyst diethylene glycol dimethyl ether into a reaction kettle according to the molar ratio of 3 4 Separated from liquid catalyst diethylene glycol dimethyl ether and then dried to leave nano silicon and compound AlCl 3 Is added to ethanol in an amount sufficient to cause the compound AlCl to react with the compound AlCl 3 Dissolving in the solvent, separating by suction filtration, repeating the dissolving and suction filtration operation for four times, putting the obtained nano-silicon into a vacuum oven for vacuumizing, setting the temperature at 70 ℃ for spray drying for 2h, and carrying out heat treatment on the dried nano-silicon at 1100 ℃ for 3h in a vacuum environment to obtain a nano-silicon product with the particle size of 30-60 nm.
TABLE 5 ICP characterization of the nanosilica prepared in example 5
| Element(s) | The mass percentage of each component in the nano silicon |
| Si | 99.74％ |
| Al | 0.03％ |
| Cl | 0.05％ |
| O | 0.18％ |
As can be seen from the above table, the purity of the silicon in the product is as high as 99.74%.
The first-cycle efficiency of the battery measured by the obtained nano silicon product applied to the battery preparation and detection method is 74.3%, and the first-cycle charging specific capacity is 3154mAh/g. The first cycle efficiency of the battery obtained by testing 30nm-500nm nano-silicon in the current market according to the method is 71% -75%, and the first cycle charging specific capacity is 3000-3300mAh/g. It can be seen that the battery performance of the nano silicon prepared by the invention is relatively excellent.
Example 6
At water content<100ppm, oxygen content<150ppm,20 deg.C, reacting the compound SiBr of silicon 4 And adding large reducing metal Mg particles and a liquid catalyst DMSO into a reaction kettle according to the molar ratio of 2 4 Separated from the liquid catalyst DMSO and then dried to leave sodiumSilicon carbide and compound MgBr 2 Is added to a sufficient amount of methanolic solvent (methanol in a molar ratio Mg: methanol =1 = 28) to yield the compound MgBr 2 Dissolving in the solvent, separating by squeezing, repeating the dissolving and squeezing operation for three times, putting the obtained nano-silicon into a blast oven, continuously introducing argon gas, setting the temperature at 65 ℃ for spray drying for 0.5h, and carrying out heat treatment on the dried nano-silicon at 600 ℃ for 5h in a vacuum environment to obtain a nano-silicon product with the particle size of 30-50 nm.
Table 6 ICP characterization of nanosilica prepared in example 6
| Element(s) | The mass percentage of each component in the nano silicon |
| Si | 99.55％ |
| Mg | 0.05％ |
| Br | 0.15％ |
| O | 0.25％ |
As can be seen from the above table, the purity of the silicon in the product is as high as 99.55%.
The first-cycle efficiency of the battery is 74.7% and the first-cycle charging specific capacity is 3174mAh/g, which is measured by the preparation and detection method of the obtained nano silicon product applied to the battery. The first cycle efficiency of the battery obtained by testing 30nm-500nm nano-silicon in the current market according to the method is 71% -75%, and the first cycle charging specific capacity is 3000-3300mAh/g. It can be seen that the battery performance of the nano silicon prepared by the invention is relatively excellent.
Example 7
At the water content<100ppm, oxygen content<At 100ppm and 15 deg.C, siBr of silicon compound 4 And adding the reduced metal Ca small particles and the liquid catalyst acetonitrile into a reaction kettle according to the molar ratio of 2 4 Separated from liquid catalyst acetonitrile and dried to leave nano silicon and compound CaBr 2 To a solvent of isoamyl alcohol in an amount sufficient to cause the compound CaBr to be present in a molar ratio Ca: isoamyl alcohol =1 = 12 2 Dissolving into the solvent, separating by a centrifugal method, repeating the dissolving and centrifuging operation for three times, putting the obtained nano-silicon into a vacuum oven for vacuumizing, setting the temperature at 110 ℃, performing rotary evaporation drying for 1.5h, and performing heat treatment on the dried nano-silicon at 460 ℃ for 7h in an argon environment to obtain a nano-silicon product with the particle size of 20-50 nm.
Table 7 ICP characterization results for nanosilica prepared in example 7
| Element(s) | The mass percentage of each component in the nano silicon |
| Si | 99.57％ |
| Mg | 0.05％ |
| Br | 0.15％ |
| O | 0.23％ |
As can be seen from the table above, the purity of the silicon in the product is as high as 99.57%.
The first-cycle efficiency of the battery measured by the obtained nano silicon product applied to the battery preparation and detection method is 74.5%, and the first-cycle charging specific capacity is 3161mAh/g. The first cycle efficiency of the battery obtained by testing 30nm-500nm nano-silicon in the current market according to the method is 71% -75%, and the first cycle charging specific capacity is 3000-3300mAh/g. It can be seen that the battery performance of the nano silicon prepared by the invention is relatively excellent.
Example 8
At the water content<100ppm, oxygen content<190ppm, in an environment of 10 ℃, a compound SiCl of silicon 4 Adding large particles of reduction metal K and liquid catalyst ethylene glycol dimethyl ether into a reaction kettle according to the molar ratio of 100 to 1000, stirring and dispersing for reaction for 50 hours, and then performing pressure filtration on an excessive silicon compound SiCl 4 Separating the nano silicon and liquid catalyst glycol dimethyl ether, drying to obtain a mixture of nano silicon and a compound KCl, adding the mixture into a sufficient amount of acetone solvent (the amount of acetone is in a molar ratio of K: acetone =1: 5), dissolving the compound KCl into the solvent, separating by a pressure filtration method, repeating the operations of dissolving and pressure filtration for two times, putting the obtained nano silicon into a vacuum oven for vacuumizing, setting the temperature to be 80 ℃, and performing rotary evaporation drying for 4 hours to obtain a nano silicon product with the particle size of 30-50 nm.
Table 8 ICP characterization of nanosilica prepared in example 8
As can be seen from the above table, the purity of the silicon in the product is as high as 99.50%.
The first-cycle efficiency of the battery is 74.2% and the first-cycle charging specific capacity is 3185mAh/g, which is measured by the preparation and detection method of the obtained nano silicon product applied to the battery. The first cycle efficiency of the battery obtained by testing 30nm-500nm nano-silicon in the current market according to the method is 71% -75%, and the first cycle charging specific capacity is 3000-3300mAh/g. It can be seen that the battery performance of the nano silicon prepared by the invention is relatively excellent.
Example 9
At the water content<100ppm, oxygen content<160ppm,130 deg.C, adding silicon compound SiI 4 And adding the small particles of the reduction metal Li and the liquid catalyst 1-butyl-3-methylimidazole chloride into a reaction kettle according to the molar ratio of 1 4 Separating the nano silicon and a liquid catalyst 1-butyl-3-methylimidazole chloride, drying the mixture to obtain a mixture of nano silicon and a compound LiI, adding the mixture into sufficient methanol (the methanol is used according to a molar ratio Li: methanol =1 = 5), dissolving the compound LiI into the solvent, separating the mixture by a pressure filtration method, repeating the operation of dissolving and pressure filtration for three times, putting the obtained nano silicon into a vacuum oven for vacuumizing, setting the temperature to be 60 ℃, standing and drying for 3 hours, and carrying out heat treatment on the dried nano silicon at 700 ℃ for 3 hours in a vacuum environment to obtain a nano silicon product with the particle size of 30-70 nm.
Table 9 ICP characterization results prepared in example 9
| Element(s) | The mass percent of each component in the nano siliconContent (wt.) |
| Si | 99.60％ |
| Li | 0.01％ |
| I | 0.18％ |
| O | 0.21％ |
As can be seen from the above table, the purity of the silicon in the product is as high as 99.60%.
The first-cycle efficiency of the battery measured by the method for preparing and detecting the obtained nano silicon product applied to the battery is 74.2%, and the first-cycle charging specific capacity is 3185mAh/g. The first cycle efficiency of the battery obtained by testing 30nm-500nm nano-silicon in the current market according to the method is 71% -75%, and the first cycle charging specific capacity is 3000-3300mAh/g. It can be seen that the battery performance of the nano silicon prepared by the invention is relatively excellent.
Example 10
At the water content<100ppm, oxygen content<160ppm,10 deg.C, and mixing SiCl which is a silicon compound 4 And adding the reduction metal Mg scraps and the liquid catalyst ethylene glycol dimethyl ether into a reaction kettle according to the molar ratio of 35 4 Separated from liquid catalyst glycol dimethyl ether and then dried to leave nano silicon and compound MgCl 2 To a sufficient amount of methanol (in terms of molar ratio Mg: methanol =1 = 25) to allow the compound MgCl 2 Dissolving in the solvent, separating by pressure filtration, repeating the dissolving and pressure filtration for three times, and discharging the obtained nano siliconVacuumizing in a vacuum oven, setting the temperature at 70 ℃, stirring and drying for 1.5h, and performing heat treatment on the dried nano-silicon at 650 ℃ for 3h in a vacuum environment to obtain the nano-silicon with the particle size of 25-55nm.
Table 10 ICP characterization results prepared in example 10
| Element(s) | The mass percentage of each component in the nano silicon |
| Si | 99.60％ |
| Mg | 0.05％ |
| Cl | 0.15％ |
| O | 0.20％ |
As can be seen from the above table, the purity of the silicon in the product is as high as 99.60%.
The first-cycle efficiency of the battery is 74.8% and the first-cycle charging specific capacity is 3245mAh/g, which is measured by the preparation and detection method of the obtained nano silicon product applied to the battery. The first-cycle efficiency of the battery obtained by testing 30-500 nm nano-silicon in the current market according to the method is 71-75%, and the first-cycle charging specific capacity is 3000-3300mAh/g. It can be seen that the battery performance of the nano silicon prepared by the invention is relatively excellent.
Example 11
At the water content<100ppm, oxygenContent (wt.)<160ppm,10 deg.C, and mixing SiCl which is a silicon compound 4 And adding the reduction metal Mg scraps and the liquid catalyst ethylene glycol dimethyl ether into a reaction kettle according to the molar ratio of 5 4 Separated from the liquid catalyst glycol dimethyl ether and then dried, leaving the excess reduced metal magnesium, nano-silicon and the compound MgCl 2 Adding the mixture into sufficient hydrogen chloride methanol solution, removing excessive reduced metal magnesium, and performing solid-liquid separation to obtain nano silicon and a compound MgCl 2 To a sufficient amount of methanol solvent (methanol in a molar ratio Mg: methanol =1 = 25) to allow the compound MgCl 2 Dissolving in the solvent, separating by a filter pressing method, repeating the dissolving and filter pressing operation for three times, putting the obtained nano-silicon into a vacuum oven for vacuumizing, setting the temperature at 70 ℃, stirring and drying for 1.5h, and carrying out heat treatment on the dried nano-silicon at 850 ℃ for 3h in a vacuum environment to obtain the nano-silicon with the particle size of 25-60nm.
Table 11 ICP characterization results prepared in example 11
| Element(s) | The mass percentage of each component in the nano silicon |
| Si | 99.55％ |
| Mg | 0.05％ |
| Cl | 0.15％ |
| O | 0.25％ |
As can be seen from the table above, the purity of the silicon in the product is as high as 99.55%.
The first-cycle efficiency of the battery is 74.2 percent and the first-cycle charging specific capacity is 3217mAh/g, which is measured by the obtained nano silicon product applied to the preparation and detection method of the battery. The first-cycle efficiency of the battery obtained by testing 30-500 nm nano-silicon in the current market according to the method is 71-75%, and the first-cycle charging specific capacity is 3000-3300mAh/g. It can be seen that the battery performance of the nano silicon prepared by the invention is relatively excellent.
Table 12 in examples 1 to 11, important parameters such as raw materials, compounding ratios, reaction conditions, etc. are as follows.
Comparative example
At the water content<100ppm, oxygen content<160ppm, and 120 deg.C, mixing SiCl which is a silicon compound 4 And adding large reducing metal Mg particles into the reaction kettle according to the molar ratio of 3.
The nano silicon prepared by the above examples 1-10 has a particle size of 15-100 nm. The comparative example shows that, when the reaction temperature of the invention is limited, no catalyst liquid is added, the silicide and the reducing metal can not react, and nano silicon particles can not be generated, thus proving that the invention actually utilizes the catalyst to reduce the potential energy of the reaction.
In the description herein, references to the description of the terms "some embodiments," "other embodiments," "an embodiment," "an example," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Moreover, various embodiments or examples and features of various embodiments or examples described in this specification can be combined and combined by one skilled in the art without being mutually inconsistent.
Although embodiments of the present invention and examples have been shown and described above, it is understood that the above embodiments, examples are illustrative and not to be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments, examples by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. The preparation method of the nano silicon is characterized in that the nano silicon is prepared by reacting a silicide, a reducing agent and a catalyst according to a certain proportion under a certain condition and then carrying out post-treatment.
2. The method according to claim 1, wherein the silicide is a silicon halide; the reducing agent is a metal reducing agent; the catalyst is a liquid catalyst.
3. The method of claim 2, wherein the silicon halide is SiCl 4 、SiBr 4 、SiI 4 At least one of; the metal reducing agent is one or more of Li, na, K, mg, al, ca, al, rb, cs, sr, ba and Y; the liquid catalyst is selected from ethers, esters, nitriles, sulfones and ethersOne or more of the sub-liquids.
4. The method according to claim 3, wherein the ether-based liquid catalyst comprises CH 3 O(CH 2 CH 2 O) n CH 3 Diethyl ether, propyl ether, methyl ethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dibutyl ether, anisole, p-xylyl ether, cyclic ether, dibutyl ether, methyl tert-butyl ether, tributyl methyl ethyl ether, n-hexyl ether and isopropyl ether, wherein n is a positive integer; the ester catalyst comprises ethyl formate, ethyl acetate, methyl formate, methyl acetate, isobutyl acetate and butyl acetate; the nitrile catalyst comprises acetonitrile, propionitrile, butyronitrile, succinonitrile and trimethoxy propionitrile; the sulfone catalyst comprises DMSO and sulfolane; the ionic liquid comprises halogenated 1-alkyl-3-methylimidazole, 1-alkyl-3-methylimidazole tetrafluoroborate, 1-alkyl-3-methylimidazole hexafluoroborate and 1-alkyl-3-methylimidazole bistrifluoromethylimide salt.
5. The preparation method of claim 1, wherein the certain conditions are dispersing and reacting for 1h to 100h in a gas atmosphere with a temperature of-30 ℃ to 130 ℃, a water content of less than 200ppm, and an oxygen content of less than 200 ppm;
the silicide, the reducing agent and the catalyst are in a certain proportion that the mol ratio of the silicide to the reducing agent is 1.
6. The preparation method according to claim 1, wherein the silicide, the reducing agent and the catalyst are reacted according to a certain ratio that the molar ratio of the silicide to the reducing agent is 1.
7. The method of claim 1, wherein the post-treatment after the reaction of the silicide, the reducing agent and the catalyst comprises the steps of:
1) Separating the mixture obtained after the reaction, and removing part or all of the reactants and the catalyst which are not fully reacted to obtain a solid mixture containing nano silicon;
2) Separating the obtained solid mixture containing the nano-silicon by utilizing the difference of physical and/or chemical properties of each component to obtain nano-silicon particles;
3) And drying the obtained nano silicon particles to obtain finished nano silicon particles.
8. The method of claim 7, wherein the preparation of the nano-silicon further comprises a further heat treatment after step 1) or step 3), wherein the heat treatment is performed in an inert gas atmosphere or a vacuum atmosphere at 260-1410 ℃ for 0.1-25 h.
9. The method for preparing nano silicon according to claim 7, wherein the separation mode in the post-treatment step 1) comprises one or more of drying after suction filtration, drying after pressure filtration, distillation, drying after pressing, spray drying and drying after centrifugation; the separation by utilizing the physical and/or chemical property difference in the post-treatment step 2) is to carry out separation after treatment in a specific solvent by utilizing the physical and/or chemical property difference of each component in the solid mixture, wherein the separation mode comprises dissolution suction filtration, dissolution pressure filtration, dissolution centrifugation and dissolution pressing; the drying in the post-treatment step 3) is drying for 10min to 300min in an inert gas or vacuum atmosphere at 50 ℃ to 200 ℃.
10. The method of claim 9, wherein the specific solvent is one or more selected from methanol, ethanol, propanol, anhydrous hydrochloric acid, anhydrous hydrobromic acid, anhydrous hydroiodic acid, anhydrous nitric acid, anhydrous phosphoric acid, pyridine, acetone, diethyl ether, benzene, dichloromethane, chloroform, carbon tetrachloride, ethylene glycol, isopropanol, isoamyl alcohol, and glycerol.
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