CN115215342A - In-situ symbiotic nano silicide and preparation method thereof - Google Patents
In-situ symbiotic nano silicide and preparation method thereof Download PDFInfo
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Abstract
The invention discloses an in-situ intergrowth nano silicide and a preparation method thereof, and the method utilizes a reducing agent to reduce silicon halide and other halides together in the presence of a catalyst, realizes the in-situ intergrowth at an atomic level, and prepares the in-situ intergrowth nano silicide which has high conductivity, high yield, uniform doping, uniform size and controllability. The in-situ intergrowth nano silicide provided by the invention has excellent performances such as higher conductivity and the like, and the preparation method has the advantages of low cost, low energy consumption, simple preparation process and easiness in amplification and industrial production.
Description
Technical Field
The invention belongs to the field of preparation of nano-silicon materials, particularly relates to an in-situ intergrowth nano-silicide material with controllable size and a preparation method thereof, and particularly relates to an in-situ intergrowth nano-silicide material for a lithium ion battery cathode and a preparation method thereof.
Background
In recent years, graphite as a mainstream commercial lithium ion battery negative electrode material has a specific capacity reaching a limit value (372 mAh/g), and a lithium-insertion potential platform of the graphite is close to the deposition potential of metallic lithium, so that potential safety hazards are easily caused in the process of quick charging or low-temperature charging, and the development of graphite in future society to the great extent is limitedApplication in the field of capacity batteries. Silicon has a theoretical specific capacity (4200 mAh/g) 10 times higher than that of graphite, a moderate delithiation potential (<0.5V vs Li + Li) and abundant reserves (27.6%), etc. are of great concern to 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 is easy to cause pulverization and failure of materials, so that the rapid attenuation of the 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 problems, the most effective method is to carry out silicon nanocrystallization, reduce cracks caused by absolute volume expansion by reducing the particle size of silicon, and effectively relieve collapse of an electrode structure, so that the circulation stability is improved.
Although silicon nanomaterials have many advantages, pure silicon nanomaterials have some disadvantages in terms of electrical conductivity, etc. Therefore, in order to improve the conductivity of nano silicon, some groups of subjects begin to try to dope silicon nanoparticles, and at present, there are two main ways of doping, namely directly coating the synthesized nano silicon surface and in-situ doping the nano silicon from the atomic level to improve the conductivity. The doped nano silicon particles synthesized in the former way only improve the conductivity of the surface of the nano particles, and do not obviously improve the conductivity of the interior of the particles. For example, patent CN 112110448A provides a nitrogen-doped carbon and nano-silicon composite negative electrode material, which is formed by compounding nitrogen-doped carbon with existing nano-silicon particles, patent CN 108400293A discloses a nitrogen-doped carbon-coated silicon nano-material, and both patents essentially compound/coat a layer of nitrogen-doped carbon material on the surface of silicon nano-particles, but both patents can only improve the conductivity of the surface of the nano-silicon particles, but cannot improve the conductivity inside the nano-silicon particles; in the second method, some doped elements are not uniform or the preparation cost of the doping process is high, and some doped elements or preparation methods can only realize surface doping of the silicon nanomaterial and cannot realize internal or integral uniform doping. For example, in patent CN 111799460A, by mixing nano silicon with a boron source and then performing high-temperature treatment, boron forms substitutional doping on silicon, and the doping of boron can improve the intrinsic conductivity and electrochemical activity of the silicon material, but this method cannot ensure that boron can be uniformly doped in nano silicon, which is still limited by the size of the nano silicon prepared by itself, and this method requires high-temperature heat treatment, which consumes much energy; the doped elements in the nano silicon material prepared by the patent CN 105399099A are four non-metal elements of C, N, B and P, the doping mode is to introduce gas containing non-metal doped elements into the reaction atmosphere, and the doped elements mainly exist on the surface of the nano silicon material.
Disclosure of Invention
In order to solve the problems, the invention provides an in-situ intergrowth nano silicide material and a preparation method thereof, and the method utilizes a reducing agent to reduce silicon halide and other halides together in the presence of a catalyst, so as to realize the in-situ intergrowth at an atomic level and prepare the in-situ intergrowth nano silicide which has high conductivity, high yield, uniform doping, uniform size and controllability. The method provided by the invention has the advantages of low cost, low energy consumption, simple preparation process and easy amplification for industrial production.
In order to achieve the aim, the invention provides an in-situ symbiotic nano silicide, wherein the chemical formula of the in-situ symbiotic nano silicide is Si a Y b And a is more than b is more than 0, wherein Y is at least one of titanium, zirconium, carbon, germanium and tin.
In the technical scheme provided by the invention, Y element and Si element in the in-situ intergrowth nano silicide are simultaneously reduced and intergrowth at the atomic scale, and the Y element is uniformly distributed around the Si element.
In the technical scheme provided by the invention, the in-situ intergrowth nano silicide also contains trace impurities including metal elements M, halogen X and oxygen, wherein the total content of the impurities is not higher than 0.6%.
In the technical scheme provided by the invention, the in-situ intergrowth nano silicide comprises the following elements in percentage by mass: si is more than or equal to 70 percent, Y is more than 0 and less than or equal to 30 percent, M is more than or equal to 0 and less than or equal to 0.1 percent, X is more than or equal to 0 and less than or equal to 0.2 percent, and O is more than or equal to 0 and less than or equal to 0.3 percent.
The invention also provides a preparation method of the in-situ symbiotic nano silicide material, which is prepared from silicon halide SiX 4 Other halides YX c And the reducing agent reacts in the presence of a catalyst and is prepared by post-treatment.
In the technical scheme provided by the invention, the input proportions of reactants of silicon halide, other halides, reducing agent and catalyst are as follows: the molar ratio of the silicon halide to other halides is 3. In some other embodiments provided by the present invention, the input ratio of the silicon halide, the reactant silicon halide, the reducing agent and the catalyst is preferably: the molar ratio of the silicon halide to other halides is 10-100, the molar ratio of the silicon halide to the reducing agent is 1.
In some embodiments of the present invention, the molar ratio of the silicon halide and the other halide to be fed is 3. In some embodiments of the present invention, the molar ratio of the silicon halide and the reducing agent fed is 1. In some embodiments of the present invention, the molar ratio of the catalyst and the reducing agent fed is 1.
In the technical scheme provided by the invention, the halogen X in the silicon halide and other halides is selected from at least one of Cl, br and I; wherein the silicon halide may be selected from SiCl 4 、SiBr 4 、SiI 4 At least one of; other halides YX c One or more of titanium halide, zirconium halide, halocarbon, germanium halide and tin halide, wherein the titanium halide is TiCl 4 、TiBr 4 、TiI 4 At least one of zirconium halide is ZrCl 4 、ZrBr 4 、ZrI 4 At least one of (a); the halocarbon being CCl 4 、CBr 4 、CI 4 At least one of, germanium halide is GeCl 4 、GeBr 4 、GeI 4 At least one of tin halide is SnCl 4 、SnBr 4 、SnI 4 At least one of (1).
In the technical scheme provided by the invention, the reducing agent is a metal reducing agent M selected from at least one or more of Li, na, K, mg, ca, al, rb, cs, sr and Ba, wherein the 'plurality' can be simple physical mixture of a plurality of metals or alloy formed by a plurality of metals.
In the technical scheme provided by the invention, 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 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 ether compounds or a certain 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 (n is a positive integer), 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; 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-methylimidazole, 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 silicon halide, other halides, 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, other halides, the reducing agent and the catalyst in the invention include, but are not limited to, adding the four materials simultaneously according to the proportion or adding the reducing agent firstly according to the proportion and then adding the silicide and the catalyst slowly respectively or after mixing uniformly, and the slow addition modes include, but are not limited to, spraying addition and titration addition.
The manner in which the reactant silicon halide, other halide, 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 silicon halide, the other halide, the reducing agent and the catalyst are reacted at a temperature of-30 ℃, in other embodiments, the silicide, the other halide, the reducing agent and the catalyst may be reacted at a temperature of-25 ℃, -20 ℃, -15 ℃, -10 ℃, -5 ℃,0 ℃, 5 ℃, 10 ℃,15 ℃, 20 ℃,25 ℃,30 ℃, 35 ℃, 40 ℃, 50 ℃, 55 ℃, 60 ℃, 70 ℃, 75 ℃, 80 ℃, 90 ℃, 95 ℃, 100 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃ and the like, i.e., at any temperature of-30 ℃ to 130 ℃, but the reaction temperature is generally controlled depending on the melting or boiling point of the silicide and the catalyst during the reaction, different silicides and catalysts are selected, and the reaction temperature may be slightly different.
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 reacting atmosphere is 180ppm, and in other embodiments the oxygen content of the reacting 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 reacting atmosphere is anywhere from 0ppm to 200 ppm.
The method effectively prevents the synthesized in-situ intergrowth silicide material from forming an oxide layer and the silicide from reacting with water to generate impurities by controlling the content of oxygen and water in the gas atmosphere in the reaction process, simultaneously avoids subsequent complex post-treatment, reduces the whole synthesis process flow, reduces the production cost, and greatly improves the application performance of the synthesized in-situ intergrowth silicide which does not contain the oxide layer in the application of batteries, particularly lithium batteries.
In some embodiments of the present invention, the reaction time of the reactants, the silicon halide, the other halide, the reducing agent and the catalyst is 1h, while in other embodiments, the reaction time of the silicide, the other halide, 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, etc., i.e., the reaction time is any value from 1h to 100h.
In the technical scheme provided by the invention, after reactants of silicon halide, other halides, 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, removing partial or all of the reactants and the catalyst which are not fully reacted, and obtaining the Si-containing in-situ symbiotic nano silicide a Y b The solid mixture of (1);
(2) The obtained Si containing in-situ intergrowth nano silicide a Y b The solid mixture is separated and dried by utilizing the difference of the physical and/or chemical properties of all the components to obtain the finished product of the in-situ intergrowth nano silicide Si a Y b 。
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 in the post-treatment step 2) is performed after the components are treated in a specific solvent by utilizing the difference of the physical and/or chemical properties of the components in the solid mixture, wherein the specific solvent is selected from one or more of methanol, ethanol, propanol, anhydrous hydrochloric acid, anhydrous hydrobromic acid, anhydrous hydroiodic acid, anhydrous nitric acid, anhydrous pyridine phosphate, acetone, diethyl ether, benzene, dichloromethane, trichloromethane, carbon tetrachloride, ethylene glycol, isopropanol and isoamyl alcohol, the separation mode comprises dissolution suction filtration, dissolution pressure filtration, dissolution centrifugation, dissolution pressure filtration and drying in an inert gas or vacuum atmosphere at 50-200 ℃ for 10-300 min.
It should be noted that, in the above-mentioned 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 reactants and catalyst, and a mixture of "solid in-situ formed nano silicide product and halide salt" or "solid in-situ formed nano silicide product, halide salt and insufficiently reacted reducing metal and other reactants" is left; 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 performed for 1 or more times to remove the liquid reactant, the catalyst, the reducing metal and other reactants which are not fully reacted, so as to finally achieve the purpose of obtaining the mixture of the solid in-situ symbiotic nano silicide product and the halide salt. The "separation by utilizing the difference in physical and/or chemical properties of the components" mentioned in the step 2) means that the separation is performed after the treatment in a specific solvent by utilizing 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 in-situ intergrown nano silicide product with high purity is obtained. If there is a remaining/remaining solid reactant such as reducing metal in the reaction, in some embodiments of the present invention, the solid reactant may be removed after 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 in-situ intergrown nano-silicide 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 in-situ intergrown nano-silicide, and the above two steps may be repeated 1 or more times per step until a high-purity in-situ intergrown nano-silicide product is obtained; in other embodiments, if the remaining/remaining solid reactant particles are large, the difference of physical properties can be directly utilized, the solid mixture treated in the 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, a screen with a large pore diameter is used for filtering out the reduced metal of the large particles, a filter membrane with a small pore diameter is used for filtering so as to leave the halide salt in the filtrate, and the in-situ co-generated nano silicide particles are left on the filter membrane, so that the purposes of separation and purification are achieved, and the two steps can be repeated for 1 or more times per step until the in-situ co-generated nano silicide product with high purity is obtained; in other embodiments of the present invention, if no solid reactant such as a reducing metal remains/remains, the solid mixture treated in step 1) may be directly 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, and filtered by a filter membrane with a small pore size to leave a halide salt in the filtrate, and the in-situ co-generated nano silicide 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 in-situ co-generated nano silicide 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 refers to drying for 10min to 300min in inert gas or vacuum atmosphere at 50 ℃ to 200 ℃.
The "drying" treatment mentioned in the post-treatment step 2) in the present invention includes, but is not limited to, one or more of standing drying, spray drying, rotary evaporation drying, stirring drying.
According to the technical scheme provided by the invention, reactants of silicon halide, other halides, a reducing agent and a catalyst which are added according to a certain proportion react under a certain condition to obtain the in-situ intergrowth nano silicide cluster, the cluster is particles of in-situ intergrowth nano silicide 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 in-situ intergrowth nano silicide in the cluster is 15-100 nm.
In the above technical solution of the present invention, the preparation of the in-situ intergrown nano silicide may further include a further heat treatment after the post-treatment step 1) or step 2), wherein the heat treatment is performed in an inert gas or vacuum atmosphere at 260 ℃ to 1300 ℃ for 0.1h to 25h. In some embodiments of the present invention, the in-situ intergrowth-containing nano silicide Si obtained after the post-treatment step 1) can be directly treated a Y b The solid mixture is further processed, and then the operation is carried out according to the post-processing step 2) after the processing to prepare the final product in-situ intergrowth nano silicide, wherein the processing mode comprises heat treatment, and the heat treatment is carried out for 0.1 to 25 hours in the inert gas or vacuum atmosphere at the temperature of between 260 and 1300 ℃; in other embodiments of the present invention, the finished product in-situ intergrowth nano silicide obtained after the treatment in the post-treatment step 2) is further treated to obtain a final product in-situ intergrowth nano silicide, wherein the treatment manner comprises a heat treatment, wherein the heat treatment is carried out for 0.1h to 25h in an inert gas atmosphere or a vacuum atmosphere at 260 ℃ to 1300 ℃; in still other embodiments, the in-situ intergrown nano-silicide treated according to the post-treatment step is directly used as the final product without further heat treatment.
In some embodiments of the present invention, the heat treatment temperature is 280 ℃, in other embodiments, the heat treatment temperature is 300 ℃, 310 ℃, 320 ℃, 380 ℃, 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃, 1050 ℃, 1180 ℃, 1190 ℃, 1250 ℃, 1300 ℃, etc., i.e., the heat treatment temperature is any value in the range of 260 ℃ to 1300 ℃; in the technical scheme provided by the invention, the time of the heat treatment can be any value within the range of 0.1h-25h, and the crystallinity of the in-situ intergrowth nano silicide after the heat treatment has certain difference according to different temperatures and times of the heat treatment. According to the invention, the obtained in-situ intergrowth nano silicide particles are further subjected to heat treatment, so that the crystallinity of the in-situ intergrowth nano silicide particles can be further improved, and dangling bonds on the surfaces of the in-situ intergrowth nano silicide particles are reduced, thereby improving the stability of the in-situ intergrowth nano silicide to water and oxygen.
The in-situ symbiotic nano silicide prepared by the method can be applied to the preparation of batteries, in particular to the preparation of negative electrode materials of lithium batteries.
The inert gas in the invention is selected from one or more of carbon dioxide, nitrogen, argon, helium, neon, krypton, xenon and radon.
At least one of the above-mentioned substances in the present invention may be one of the above-mentioned substances, or may be a mixture of two or more of the above-mentioned substances.
The invention has the beneficial effects that:
1) The invention provides an in-situ intergrowth nano silicide, which is characterized in that silicon halide and other halides are simultaneously reduced in the presence of a reducing agent, so that silicon and titanium, zirconium, carbon, germanium and tin with good conductivity are intergrowth, the conductivity of pure nano silicon is improved by orders of magnitude, and the conductivity of the finally synthesized in-situ intergrowth nano silicide can reach 10 of that of pure nano silicon 6 -10 9 And (4) multiplying.
2) The invention provides a method for preparing in-situ symbiotic nano silicide 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 silicon halide and other halides can be reduced under the environment of low temperature and non-high pressure, preparing the simple substance of the in-situ symbiotic nano silicide, wherein the simple substance has high conductivity, high purity (the purity can reach more than 99 percent) and high yield, and all elements in the simple substance are uniformly doped;
3) At present, no nano silicide with the grain diameter of 15-100 nm exists in the market, but the reaction rate is controlled by controlling the quantity and the proportion of substances of catalyst and halide enriched on the surface of reduced metal, so that the size, the grain uniformity and the like of the in-situ symbiotic nano silicide are effectively controlled, the grain diameter of the in-situ symbiotic nano silicide product prepared by the invention can be controlled between 15-100 nm, and the grain diameter distribution width can be controlled between 15-40 nm; compared with commercial nano silicon with equal grain diameter, the in-situ intergrowth nano silicide has higher first-week efficiency, and shows that the in-situ intergrowth elements can improve the electrochemical performance of the nano silicon.
4) The selected reactants are solid reduction metal, silicon halide and other halides which are dissolved in the liquid catalyst, and the silicon halide and other halides which are dissolved in the liquid catalyst fully wrap the solid reactants in the solid-liquid mixed reaction, so that the reactants can fully react, and the yield is greatly improved;
5) The preparation method provided by the invention has low cost for preparing the in-situ intergrowth nano silicide. Current market D 50 The selling price of the nano-silicon product with the size of 100nm is 50 ten thousand yuan/ton, the selling price of the product with the size of 30nm is 2400 ten thousand yuan/ton, the market selling price of the in-situ intergrowth nano silicide with the same size and higher conductivity is inevitably higher, and the unit cost price of the in-situ intergrowth nano silicide prepared by the invention can be controlled to be below 30 ten thousand yuan/ton. The main reasons are as follows: a) The raw material silicide is a byproduct generated by purifying polysilicon, is hazardous waste, and has very low price, such as SiCl 4 The market price of the fertilizer is close to 3300 yuan/ton, the price is low, other halides are also cheaper and less used; b) The preparation condition is simple, the high-temperature and high-pressure condition does not exist, the requirement on equipment is low (can be met by domestic equipment), the energy consumption is low, and the cost can be effectively reduced; c) Impurities are removed by utilizing the difference of physical properties in the post-treatment process, and impurity-removing solvents and the like can be recycled, so that the cost of raw materials for preparing the in-situ symbiotic nano silicide can be further reduced; d) The in-situ symbiotic nano silicide 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 can be further reduced;
6) The method has the advantages of simple process, high reproducibility and easy realization of industrial production;
7) 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 salt which can be recycled.
Drawings
FIG. 1 is a scanning electron microscope image of in-situ intergrown nano-silicide obtained in example 1;
FIG. 2 is a SEM-EDS profile of the in-situ grown nano-silicide obtained in example 1, wherein (a) is a scanning electron micrograph of a selected sample area, (b) is a distribution diagram of Si in the selected sample area, and (c) is a distribution diagram of Sn in the selected sample area, wherein black is a background plate.
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 will occur to those skilled in the art and are intended to be included within the scope of the present 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 metal form Li small particles (particle size 2 mm), na small particles (particle size 2 mm), mg chips (size: 10mm × 5mm × 1mm), mg spheres (diameter 5 mm), 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), al small particles (particle size 2 mm), li powder (particle size 75 μm), rb small particles (particle size 2 mm), cs small particles (particle size 2 mm), sr small particles (particle size 2 mm), ba small particles (particle size 2 mm).
The preparation and detection method of the in-situ symbiotic nano silicide applied to the battery, which is described in the following embodiment, comprises the following steps:
the in-situ intergrowth nano silicide product is directly used as a negative electrode material to be applied to a lithium battery. In-situ symbiotic nano silicide: 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 phi 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 charged capacity/mass of the negative active material; 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 the water content<100ppm, oxygen content<180ppm, at 15 deg.C, mixing SiCl 4 、SnCl 4 And the small reducing metal Mg particles and the liquid catalyst ethylene glycol dimethyl ether are added into a reaction kettle according to the molar ratio of 15 to 14 4 、SnCl 4 After being uniformly mixed with liquid catalyst glycol dimethyl ether, slowly titrating, adding into a mechanical crushing dispersion reaction for 86 hours, separating redundant liquid halide and catalyst in a filter pressing mode, and then drying to leave in-situ symbiotic tin-containing nano silicide (stannic silicide) and MgCl 2 To a sufficient amount of methanol (in terms of molar ratio Mg: methanol =1 = 30) to allow the compound MgCl 2 Dissolving in the solvent, separating by suction filtration, repeating the dissolving and suction filtration operation for three times, putting the obtained in-situ symbiotic tin-containing in-situ symbiotic nano silicide (stannic silicide) into a vacuum oven for vacuumizing, setting the temperature at 80 ℃, stirring and drying for 1.5h, and then carrying out heat treatment at 950 ℃ for 3h in a vacuum environment to obtain the in-situ symbiotic tin-containing nano silicide (stannic silicide) with the particle size of 25-50 nm. The in-situ symbiotic tin-containing in-situ symbiotic nano-grade obtained in the example 1The silicide (tin silicide) was characterized by ICP, SEM and EDS (energy spectroscopy), and the ICP characterization results are shown in table 1, the SEM characterization results are shown in fig. 1, and the EDS characterization results are shown in fig. 2. As can be seen from Table 1, the product of example 1 had a silicon atom content of 95.20% by mole, a tin atom content of 82.61% by mass, a tin atom content of 4.79% by mole, and a tin atom content of 17.29% by mass. The purity of the in-situ symbiotic nano silicide containing tin is 99.90 percent, the total mass percentage of impurities is only 0.10 percent, the purity is higher, and the particle size of the product obtained from the example 1 in figure 1 is approximately distributed between 25 nm and 50 nm. The electrochemical performance test of the in-situ co-formed tin-containing nano silicide (tin silicide) and pure nano silicon in the embodiment 1 is carried out by using a semiconductor characteristic analysis system and two probes, and the tested conductivities can be respectively as follows: the electron conductivity of pure nano silicon is 1.1 multiplied by 10 -7 S/cm, and the electron conductivity of the in-situ co-produced tin-containing nano silicide (tin silicide) is 1.3S/cm, which shows that the intrinsic conductivity of the in-situ co-produced nano silicide is greatly improved due to in-situ co-produced tin. Fig. 2 is a characterization diagram obtained by performing SEM-EDS surface analysis characterization on the in-situ intergrown silicon nano sample obtained in this example, wherein (a) is a scanning electron microscope diagram of a selected sample region of the in-situ intergrown nano silicon containing tin obtained in this example, (b) is a distribution diagram of silicon element in the sample region shown in (a), and (c) is a distribution diagram of tin element in the sample region shown in (a), wherein black is a background plate, from which it can be seen that tin element is uniformly distributed in silicon, which indicates that tin element is reduction intergrown with silicon at the atomic scale, and in addition, it can also be seen that the amount of tin is significantly less than the amount of silicon, and therefore, belongs to a small amount of doping, and matches with the test result in ICP.
Table 1 ICP characterization results for in situ intergrown silicide prepared in example 1
The first cycle efficiency of the battery measured by applying the prepared in-situ symbiotic tin-containing in-situ symbiotic nano silicide to the battery according to the preparation and detection method is 77.3%, and the first cycle charging specific capacity is 3106mAh/g.
Example 2
At the water content<100ppm, oxygen content<160ppm, at 25 deg.C, adding SiCl 4 、TiCl 4 Adding the reduced metal Na small particles and a liquid catalyst anisole into a reaction kettle according to the molar ratio of 2.02. ICP characterization is carried out on the in-situ intergrowth nano silicon (titanium silicide) containing titanium obtained in the example 2, and ICP characterization results are shown in the table 2, and as can be seen from the table 2, the mol percentage content of silicon atoms in the product of the example 2 is 99.00%, the mass percentage content of the silicon atoms is 98.38%, the mol percentage content of titanium atoms is 0.89%, and the mass percentage content of the titanium atoms is 1.51%. The purity of the titanium-containing in-situ symbiotic nano silicide is 99.89 percent, the total mass percentage of impurities is only 0.11 percent, and the purity is higher. The electrochemical performance test of the in-situ co-generated titanium-containing nano silicide (titanium silicide) in the embodiment 2 is carried out by using a semiconductor characteristic analysis system and two probes, and the conductivity of the in-situ co-generated titanium-containing nano silicide is 2.3S/cm, which shows that the intrinsic conductivity of the in-situ co-generated nano silicide is greatly improved due to the in-situ co-generation of titanium in the in-situ co-generated nano silicide.
Table 2 ICP characterization results for in situ intergrown silicide prepared in example 2
| Element(s) | The mole percentage of each element | The mass percentage of each element |
| Si | 99.00％ | 98.38％ |
| Ti | 0.89％ | 1.51％ |
| Na | 0.05％ | 0.04％ |
| Cl | 0.05％ | 0.06％ |
| O | 0.01％ | 0.01％ |
The first-cycle efficiency of the battery is measured to be 78.1% and the first-cycle charging specific capacity is 3196mAh/g by applying the prepared in-situ co-generated titanium-containing in-situ co-generated nano silicide product to the battery according to the preparation and detection method.
Example 3
At water content<100ppm, oxygen content<100ppm of SiCl which is a silicon compound at-3 DEG C 4 、CI 4 The small particles of the reduction metal Li and the liquid catalyst ethylene glycol dibutyl ether are added into a reaction kettle according to the molar ratio of 1.02 4 、CI 4 Uniformly mixing the solution and liquid catalyst ethylene glycol dibutyl ether, slowly spraying the solution, adding the solution into the solution, stirring the solution for dispersion reaction for 48 hours, separating redundant liquid halide from the catalyst in a distillation drying mode, and drying the separated liquid halide and the catalyst to leave in-situ co-generated carbon-containing in-situ co-generated nano silicide and trace unreacted CI 4 Mixture of the compounds LiCl and LiI, which was added to sufficient methanol to remove traces of insufficiently reacted CI 4 Then filtering to obtain a mixture of in-situ carbon-containing in-situ symbiotic nano silicide and compounds LiCl and LiI, adding the mixture into sufficient pyridine, dissolving the compounds LiCl and LiI into ethanol (the ethanol dosage is Li: ethanol = 1. ICP characterization is carried out on the in-situ co-produced carbon-containing nano silicide (carbon silicide) obtained in the example 3, and ICP characterization results are shown in the table 3, wherein the ICP characterization results are shown in the table 3, and the product in the example 3 comprises 98.50% of silicon atoms in percentage by mol, 99.30% of carbon atoms in percentage by mol, and 0.56% of carbon atoms in percentage by mol; the purity of the carbon-containing in-situ symbiotic nano silicide is 99.86 percent, the total mass percentage of impurities is only 0.14 percent, and the purity is higher. Example 3 electrochemical performance test of in-situ co-formed carbon-containing nano silicide (carbon silicide) and pure in-situ co-formed nano silicide with conductivity of 5.2 × 10S/cm using a semiconductor characteristic analysis system with two probesThe bright in-situ symbiotic nano silicide has carbon in situ, so that the intrinsic conductivity of the in-situ symbiotic nano silicide is greatly improved.
Table 3 ICP characterization results for in situ intergrown silicide prepared in example 3
| Element(s) | The mole percentage of each element | The mass percentage of each element |
| Si | 98.50％ | 99.30％ |
| C | 1.30％ | 0.56％ |
| Li | 0.05％ | 0.01％ |
| Cl | 0.05％ | 0.07％ |
| O | 0.10％ | 0.06％ |
The first-cycle efficiency of the battery is 77.5 percent and the first-cycle charging specific capacity is 3142mAh/g according to the preparation and detection method of the prepared in-situ symbiotic tin-containing in-situ symbiotic nano silicide product applied to the battery.
Example 4
At the water content<120ppm, oxygen content<150ppm of SiCl which is a silicon compound at-5 DEG C 4 、ZrCl 4 After the reduction metal Mg particles and the liquid catalyst (50% ethylene glycol dimethyl ether, 50% dimethyl sulfoxide (DMSO) are added into the reaction kettle according to the molar ratio of 3 4 In-situ intergrowth zirconium-containing in-situ intergrowth nano silicide and compound MgCl 2 To a mixture of (a) and adding the mixture to a sufficient amount of methanol (amount of methanol in molar ratio Mg: methanol =1 = 25) to allow the compound MgCl to be present 2 Dissolved in the solvent, and a trace of insufficiently reacted ZrCl 4 Dissolving the in-situ symbiotic zirconium-containing nano silicide in the solvent after reaction with methanol, separating by a filter pressing method, repeating the operation of dissolving and filter pressing for four times, putting the obtained in-situ symbiotic zirconium-containing in-situ symbiotic nano silicide into a vacuum oven for vacuumizing, setting the temperature at 70 ℃, standing and drying for 3h, and carrying out heat treatment on the dried in-situ symbiotic zirconium-containing in-situ nano silicide at 1100 ℃ for 3h under a vacuum environment to obtain the in-situ symbiotic zirconium nano silicide product with the particle size of 30-60 nm. ICP characterization was performed on the in-situ intergrowth zirconium-containing in-situ intergrowth nano silicide (zirconium silicide) obtained in example 4, and ICP characterization results are shown in table 4, which can be obtained from table 4, where in the product of example 4, the molar percentage content of silicon atoms is 97.20%, the mass percentage content is 92.12%, the molar percentage content of zirconium atoms is 2.50%, and the mass percentage content is 7.70%. The purity of the zirconium-containing in-situ intergrowth nano silicide is 99.82 percent, the total mass percentage content of impurities is only 0.18 percent, and the purity is higher. In the embodiment 4, the electrochemical performance test of the in-situ co-formed zirconium-containing in-situ co-formed nano silicide (zirconium silicide) is carried out by using a semiconductor characteristic analysis system and adopting two probes, and the conductivity of the in-situ co-formed nano silicide is 1.4 multiplied by 10S/cm, which shows that the in-situ co-formed nano silicide is formed by in-situ co-formationZirconium, thereby greatly improving the intrinsic conductivity of the in-situ symbiotic nano silicide.
Table 4 ICP characterization results for in situ intergrown silicides prepared in example 4
| Element(s) | Mole percentage of each element | The mass percentage of each element |
| Si | 97.20％ | 92.12％ |
| Zr | 2.50％ | 7.70％ |
| Li | 0.05％ | 0.01％ |
| Cl | 0.05％ | 0.06％ |
| O | 0.20％ | 0.11％ |
The first-cycle efficiency of the battery is 77.6 percent and the first-cycle charging specific capacity is 3173mAh/g according to the preparation and detection method of the prepared in-situ symbiotic zirconium-containing in-situ symbiotic nano silicide product applied to the battery.
Example 5
At water content<100ppm, oxygen content<160ppm,15 deg.C, adding SiCl which is a silicon compound 4 、GeCl 4 Adding large particles of reduced metal K and a liquid catalyst (50% ethylene glycol dimethyl ether and 50% ethylene glycol diethyl ether) into a reaction kettle according to the molar ratio of 100.1, stirring and dispersing for reaction for 60 hours, then separating redundant liquid halide and the catalyst in a pressure filtration mode, drying to leave a mixture of in-situ symbiotic nano silicide of in-situ symbiotic germanium and compound KCl, adding the mixture into a sufficient acetone solvent (the acetone content is K: acetone =1 8) to dissolve the compound KCl into the solvent, separating by a pressure filtration method, repeating four times of dissolving and pressure filtration operation, putting the obtained in-situ symbiotic germanium-containing in-situ nano silicide into a vacuum oven for vacuumizing, standing and drying for 4 hours at the temperature of 80 ℃, and then carrying out heat treatment on the dried in-situ symbiotic germanium-containing in-situ nano silicide for 3 hours at the temperature of 1000 ℃ in a vacuum environment to obtain an in-situ symbiotic germanium-containing in-situ nano silicide product with the particle size of 35-70 nm. ICP characterization is carried out on the in-situ intergrowth germanium-containing nano silicide (germanium silicide) obtained in the example 5, and ICP characterization results are put into a table 5, wherein the ICP characterization results can be obtained from the table 5, and the product obtained in the example 5 comprises 99.70% of silicon atoms in percentage by mol, 99.67% of germanium atoms in percentage by mol, and 0.10% of germanium atoms in percentage by mol, and 0.27% of germanium atoms in percentage by mass. The purity of the in-situ symbiotic nano silicide containing germanium is 99.94 percent, the total mass percentage of impurities is only 0.04 percent, and the purity is higher. In the embodiment 5, the electrochemical performance test of the in-situ intergrowth germanium-containing nano silicide (germanium silicide) is carried out by using a semiconductor characteristic analysis system and two probes, and the conductivity of the in-situ intergrowth nano silicide is 0.41S/cm, which shows that the in-situ intergrowth nano silicide has germanium in situ, so that the intrinsic conductivity of the in-situ intergrowth nano silicide is greatly improved.
Table 5 ICP characterization results for in situ intergrown silicide prepared in example 5
| Element(s) | The mole percentage of each element | The mass percentage of each element |
| Si | 99.8％ | 99.67％ |
| Ge | 0.1％ | 0.27％ |
| K | 0.01％ | 0.01％ |
| Cl | 0.01％ | 0.01％ |
| O | 0.08％ | 0.04％ |
The first-cycle efficiency of the battery is 77.7 percent and the first-cycle charging specific capacity is 3189mAh/g according to the preparation and detection method of the prepared in-situ symbiotic zirconium-containing in-situ symbiotic nano silicide product applied to the battery.
Comparative example
At the water content<100ppm，Oxygen content<180ppm,15 deg.C, adding SiCl 4 The small reducing metal Mg particles and the liquid catalyst ethylene glycol dimethyl ether are firstly added into a reaction kettle according to the molar ratio of 15 4 Uniformly mixing with a liquid catalyst ethylene glycol dimethyl ether, slowly titrating, adding into a mechanical crushing and dispersing reactor for 86 hours, separating redundant liquid halide and the catalyst in a filter pressing mode, and drying to leave nano-silicon and MgCl 2 To a sufficient amount of methanol (in terms of molar ratio Mg: methanol =1 = 30) to allow the compound MgCl 2 Dissolving in the solvent, separating by suction filtration, repeating the dissolving and suction filtration operation for three times, putting the obtained nano-silicon into a vacuum oven for vacuumizing, setting the temperature at 80 ℃, stirring and drying for 1.5h, and then carrying out heat treatment at 950 ℃ for 3h in a vacuum environment to obtain the nano-silicon with the particle size of 25-50 nm.
The electrochemical performance test of the pure nano silicon prepared in the comparative example is carried out by using a semiconductor characteristic analysis system and adopting two probes, and the tested conductivity is as follows: the electron conductivity of pure nano-silicon is 1.1 × 10 -7 S/cm. The first-cycle efficiency of the battery obtained by applying the nano silicon product obtained in the comparative example to the battery is 74.6% according to the preparation and detection method, and the first-cycle charging specific capacity is 3243mAh/g.
Table 6 important parameters such as raw materials, compounding ratios, reaction conditions, etc. in examples 1 to 5 and comparative examples are shown below.
Table 7 various performance test parameters of in-situ intergrown nano-silicide synthesized in examples 1 to 5 and nano-silicon synthesized in comparative example
It can be seen from the above table that the doped elements of titanium, germanium, carbon, tin, zirconium, etc. have different degrees of conductivity and first cycle charge specific capacity lower than that of silicon, but the first cycle charge specific capacity of nano-silicon is not reduced after the elements are doped in silicon nano-particles in an in-situ intergrowth mode, but the conductivity of the finally prepared in-situ intergrowth nano-silicide is improved due to the doping of the elements, so that the internal resistance of a battery pole piece is reduced, and the first cycle efficiency of the battery is improved.
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 (11)
1. The in-situ intergrowth nano silicide is characterized in that the chemical formula of the in-situ intergrowth nano silicide is Si a Y b And a is more than b is more than 0, wherein Y is at least one of titanium, zirconium, carbon, germanium and tin.
2. The in-situ intergrowth nano silicide according to claim 1, wherein Y element and Si element are simultaneously reduced and intergrown at atomic scale, and the Y element is uniformly distributed around the Si element; the in-situ symbiotic nano silicide also contains trace impurities including metal elements M, halogen X and oxygen, wherein the total content of the impurities is not higher than 0.6%.
3. The in-situ intergrowth nano silicide according to claim 1, wherein the in-situ intergrowth nano silicide comprises the following elements in percentage by mass: si is more than or equal to 70 percent, Y is more than 0 and less than or equal to 30 percent, M is more than or equal to 0 and less than or equal to 0.1 percent, X is more than or equal to 0 and less than or equal to 0.2 percent, and O is more than or equal to 0 and less than or equal to 0.3 percent.
4. The method for preparing in-situ intergrown nano silicide as claimed in claims 1 to 3, wherein the in-situ intergrown nano silicide is prepared from silicon halide SiX 4 Other halides YX c And the reducing agent reacts in the presence of a catalyst and is prepared by post-treatment.
5. The method for preparing in-situ intergrowth nano silicide according to claim 4, wherein the molar ratio of the using amount of each component in the reaction system is as follows: 1 of silicon halide and reducing agent, 1 of silicon halide and other halides is (3);
the catalytic reaction is carried out for 1-100 h in a dispersed manner in a gas atmosphere with the temperature of-30-120 ℃, the water content of less than 200ppm and the oxygen content of less than 200 ppm.
6. The method for preparing in-situ intergrown nano silicide according to claim 4, wherein the halogen X in the silicon halide and other halides is selected from at least one of Cl, br and I; said other halides YX c Is one or more of titanium halide, zirconium halide, carbon halide, germanium halide and tin halide; the reducing agent is a metal reducing agent M; the catalyst is a liquid catalyst.
7. The method for preparing in-situ intergrowth nano silicide according to claim 6, wherein the metal reducing agent M is at least one of Li, na, K, mg, ca, al, rb, cs, sr and Ba; the liquid catalyst is selected from one or more of ethers, esters, nitriles, sulfones and ionic liquid.
8. The method for preparing in-situ intergrowth nano silicide according to claim 7, wherein 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; 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.
9. The method for preparing in-situ symbiotic nano silicide according to claim 4, wherein the post-treatment after the reaction of the silicide, other halides and reducing agent in the presence of a catalyst comprises the following steps:
1) Separating the mixture obtained after the reaction, removing partial or all of the reactants and the catalyst which are not fully reacted, and obtaining the Si-containing in-situ symbiotic nano silicide a Y b The solid mixture of (a);
2) The obtained Si containing in-situ intergrowth nano silicide a Y b The solid mixture is separated and dried by utilizing the difference of physical and/or chemical properties of each component to obtain the finished product of the in-situ symbiotic nano silicide Si a Y b 。
10. The preparation method according to claim 9, wherein the preparation of the finished in-situ intergrown nano silicide may further comprise a further heat treatment after step 1) or step 2), wherein the heat treatment is performed in an inert gas or vacuum atmosphere at 260-1300 ℃ for 0.1-25 h.
11. The method for preparing the in-situ symbiotic nano silicide according to claim 9, wherein the separation mode in step 1) comprises drying after suction filtration, drying after filter pressing, distillation, drying after squeezing, spray drying, and drying after centrifugation; the separation using the difference in physical and/or chemical properties of the components in step 2) is performed after the components are treated using the difference in physical and/or chemical properties of the components in the mixture in a specific solvent, wherein the specific solvent is selected from one or more of methanol, ethanol, propanol, anhydrous hydrochloric acid, anhydrous hydrobromic acid, anhydrous hydroiodic acid, anhydrous nitric acid, anhydrous pyridine phosphate, acetone, diethyl ether, benzene, dichloromethane, trichloromethane, carbon tetrachloride, ethylene glycol, isopropanol and isoamyl alcohol; the separation mode in the step 2) comprises dissolving and filtering, dissolving and filter pressing, dissolving and centrifuging and dissolving and squeezing, wherein the drying is carried out for 10-300 min in inert gas or vacuum atmosphere at 50-200 ℃.
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| CN106495161A (en) * | 2016-10-24 | 2017-03-15 | 中南大学 | A kind of method that nano-silicon is prepared based on metal intervention metallothermic reduction |
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