CN113636561A - Carbon-coated hollow silicon material and preparation method and application thereof - Google Patents

Carbon-coated hollow silicon material and preparation method and application thereof Download PDF

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CN113636561A
CN113636561A CN202110991364.0A CN202110991364A CN113636561A CN 113636561 A CN113636561 A CN 113636561A CN 202110991364 A CN202110991364 A CN 202110991364A CN 113636561 A CN113636561 A CN 113636561A
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hollow
silicon
hollow silicon
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carbon
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严大洲
温国胜
杨涛
李艳平
韩治成
刘诚
孙强
万烨
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China ENFI Engineering Corp
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    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C01B33/023—Preparation by reduction of silica or free silica-containing material
    • C01B33/025—Preparation by reduction of silica or free silica-containing material with carbon or a solid carbonaceous material, i.e. carbo-thermal process
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • 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
    • C01B33/023—Preparation by reduction of silica or free silica-containing material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • H01M4/366—Composites as layered products
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention provides a carbon-coated hollow silicon material and a preparation method and application thereof. The preparation method comprises the following steps: carrying out first heating on a first dispersion liquid containing sodium borohydride and silica microspheres to obtain hollow silica; in the first heating process, the pH value of the system is controlled to be more than 8, the temperature is controlled to be 45-55 ℃, and the time is controlled to be 5-7 hours; mixing hollow silicon dioxide and a reducing agent for reduction reaction to obtain a hollow silicon material; carrying out spray granulation on a second dispersion liquid containing the hollow silicon material, the organic matter and the formaldehyde aqueous solution to obtain an intermediate product; and calcining the intermediate product in inert gas or nitrogen to obtain the carbon-coated hollow silicon material. The preparation method disclosed by the invention is low in cost, good in environmental protection property, good in safety, simpler in process condition and easier to regulate and control the morphology and the dispersity of the material, so that when the obtained material is used as a silicon cathode, the battery has higher conductivity and better cycling stability.

Description

Carbon-coated hollow silicon material and preparation method and application thereof
Technical Field
The invention relates to the technical field of silicon-based negative electrode materials, in particular to a carbon-coated hollow silicon material and a preparation method and application thereof.
Background
Various problems due to volume expansion pose significant challenges to the development and application of silicon-based anodes. To develop a silicon negative electrode with high cycle stability, a great deal of research and study is carried out. Among them, the nano hollow structure is a very effective method. The hollow silica is generally prepared by using a template, for example, chinese patent application No. 201711085365 discloses a preparation method of hollow silicon nanospheres and application thereof. The invention provides a preparation method of a hollow structure material, which takes benzene hexadecyl trimethyl ammonium bromide, octane and ethyl orthosilicate as raw materials to prepare hollow silicon dioxide through a template. The method mainly comprises the following steps: firstly, carrying out solvothermal reaction on a mixed solution of hexadecyl trimethyl ammonium bromide, octane and ethyl orthosilicate to obtain an intermediate reactant; sintering the intermediate reactant to obtain hollow silica spheres; mixing the hollow silica spheres with magnesium powder, grinding, calcining, and cooling to room temperature to obtain the silicon powder. However, the traditional template method faces a series of problems which cannot be avoided in the process of preparing the hollow structure, the treatment cost of the hard template in the template removing process is high, strong acid and alkali reagents, even highly toxic chemical reagents are used, and the process has the problems of environmental protection and safety. The soft template method has the problems of rigorous precise control conditions and difficult regulation and control of the shape and the dispersity of the hollow structure.
In addition, the problem of poor conductivity of silicon is another important reason for limiting the application of silicon, and in order to solve the problem of poor conductivity of silicon-based materials, the current method is to utilize the physical properties of other materials to improve the electrochemical performance of silicon negative electrode materials. The ideal scheme is that silicon is compounded with a carbon material with a stable structure and excellent conductivity, the high capacity of the silicon material is fully exerted, the conductivity of the negative electrode material is improved, and further improvement of the conductivity and the processing performance of the carbon material is an effective way for improving the electrochemical performance of the silicon-carbon composite material. For example, application No. 201911025032 discloses a method of preparing a silicon carbon negative electrode material for a lithium battery, a negative electrode material, and a lithium battery. The invention discloses a method for preparing a silicon-carbon composite material by high-energy ball milling and heat treatment. The preparation method mainly comprises the following steps: mixing nano silicon and graphite according to a mass ratio, and carrying out ball milling; secondly, mixing asphalt and tetrahydrofuran according to a certain mass ratio to form an asphalt mixed solution, and adding the asphalt mixed solution into a ball milling tank for ball milling to form a first mixture; thirdly, adding a certain amount of carboxymethyl cellulose (CMC), mixing and ball-milling for 3-5 hours to obtain a second mixture; placing the mixture in an oven for drying for 8-12 hours to enable all the organic solvent in the second mixture to volatilize, and then crushing and sieving the mixture; fifthly, placing the sieved substance in a box-type carbonization furnace, introducing nitrogen, preserving heat at 900-1000 ℃, and naturally cooling to obtain the silicon-carbon negative electrode material.
In summary, when the silicon-based material is used as a battery cathode material in the prior art, the battery has poor conductivity and poor cycle stability, or the preparation process has the problems of high treatment cost, poor environmental protection, poor safety, harsh process conditions and difficulty in regulating and controlling the morphology and the dispersibility of the material.
Disclosure of Invention
The invention mainly aims to provide a hollow silicon material and a preparation method and application thereof, and aims to solve the problems that in the prior art, when the silicon-based material is used as a battery cathode material, the battery conductivity is poor, the cycle stability is poor, or the preparation process has high treatment cost, poor environmental protection property, poor safety, harsh process conditions and difficult regulation and control of material morphology and dispersity.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a method of preparing a carbon-coated hollow silicon material. The preparation method comprises the following steps: step A1, carrying out first heating on a first dispersion liquid containing sodium borohydride and silica microspheres to obtain hollow silica; in the first heating process, the pH value of the system is controlled to be more than 8, the first heating temperature is 45-55 ℃, and the time is 5-7 hours; step A2, mixing hollow silicon dioxide and a reducing agent for reduction reaction to obtain a hollow silicon material; step A3, performing spray granulation on a second dispersion liquid containing a hollow silicon material, an organic matter and a formaldehyde aqueous solution to obtain an intermediate product; and A4, calcining the intermediate product in inert gas or nitrogen to obtain the carbon-coated hollow silicon material.
Further, the mass ratio of the sodium borohydride to the silicon dioxide microspheres is (2-8) to (0.8-3.2).
Further, the first dispersion also comprises a surfactant; preferably, the surfactant is a cationic surfactant; more preferably the cationic surfactant is selected from one or more of polyvinylpyrrolidone, cetyltrimethylammonium bromide or dioctadecyldimethyl sodium chloride; preferably, the mass ratio of the surfactant to the silica microspheres is (5-20): 0.8-3.2.
Further, the preparation method also comprises the process of preparing the silicon dioxide microspheres: carrying out second heating on a third dispersion liquid containing the first ethanol aqueous solution, the catalyst and a silicon source, and then filtering and washing to obtain silicon dioxide microspheres; preferably, the heating temperature of the second heating is 30-40 ℃ and the time is 1-4 h; preferably, the silicon source is tetraethoxysilane; preferably, the catalyst is selected from one or more of ammonia water, hydrofluoric acid and hydrochloric acid; preferably, the volume ratio of the first ethanol aqueous solution to the silicon source to the catalyst is (90-180): 6-12): 2-8; the volume ratio of ethanol to water in the first aqueous ethanol solution is preferably (8:1) to (1:1), more preferably (4:1) to (1: 1); the particle size of the preferred silicon dioxide microspheres is 200-300 nm.
Further, in the reduction reaction process, the reaction temperature is 650-800 ℃, and the time is 3-6 h; preferably, the reducing agent is selected from one or more of magnesium, aluminum and carbon, and more preferably, the mass ratio of the reducing agent to the hollow silica is (2-4): (0.8 to 3.2).
Further, the mass ratio of the hollow silicon material to the organic matter to the formaldehyde aqueous solution is (0.8-3.2) to (1.17-9.36): (8-32).
Further, the organic matter is nitrogen-containing organic matter; preferably, the nitrogen-containing organic is melamine.
Further, the spray pressure of the spray granulation is 0.1MPa to 0.6MPa, the spray temperature of the spray granulation is preferably 100 ℃ to 200 ℃, and the feed rate of the spray granulation is preferably 10mL/min to 60 mL/min.
Further, in the calcining process, the treatment temperature is 600-800 ℃ and the time is 2-6 h.
In order to achieve the above object, according to an aspect of the present invention, there is provided a negative electrode material, which is a carbon-coated hollow silicon material prepared by the above preparation method.
According to another aspect of the present invention, a lithium ion battery is provided, which includes a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode includes a negative electrode material, and the negative electrode material is the negative electrode material described above.
Based on the preparation method, the invention effectively solves the problems that the silicon-based material is poor in battery conductivity and poor in cycle stability, or the preparation process has high treatment cost, poor environmental protection property, poor safety, harsh process conditions and difficult regulation and control of material morphology and dispersibility when used as a battery cathode material in the prior art. When the prepared material is used as a silicon cathode, the prepared material has high conductivity and high cycle stability.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 shows a flow diagram for preparing carbon-coated hollow silicon material in one embodiment of the present invention;
FIG. 2 shows a TEM image of a hollow silicon material in an embodiment of the invention;
fig. 3 shows an SEM image of an intermediate product obtained after spray granulation in one embodiment of the present invention.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
As described in the background art of the present application, in the prior art, a silicon-based material has poor conductivity or poor cycle stability, or has problems of high processing cost, poor environmental protection, poor safety, harsh process conditions, difficult regulation of material morphology and dispersibility, and the like in the preparation process. In order to solve the problems, the application provides a hollow silicon material, and a preparation method and application thereof.
In an exemplary embodiment of the present application, a method for preparing a carbon-coated hollow silicon material is provided, as shown in fig. 1, the method comprising: step A1, carrying out first heating on a first dispersion liquid containing sodium borohydride and silica microspheres to obtain hollow silica; in the first heating process, the pH value of the system is controlled to be more than 8, the first heating temperature is 45-55 ℃, and the time is 5-7 hours; step A2, mixing hollow silicon dioxide and a reducing agent for reduction reaction to obtain a hollow silicon material; step A3, performing spray granulation on a second dispersion liquid containing a hollow silicon material, an organic matter and a formaldehyde aqueous solution to obtain an intermediate product; and A4, calcining the intermediate product in inert gas or nitrogen to obtain the hollow silicon material coated by the carbon layer.
Firstly, the first dispersion liquid containing sodium borohydride and silicon dioxide microspheres is subjected to first heating for 5-7 hours under the conditions that the pH value is more than 8 and the temperature is 45-55 ℃. In the heating process, the surface layer of the silicon dioxide microspheres is continuously dissolved under the alkaline condition to generate micromolecular silicate, and hydrolysis is carried out along with sodium borohydrideBO in system of2 -Increased concentration, BO2 -Further reacts with the small molecular silicate to generate silicon dioxide so as to deposit on the surface of the silicon dioxide microsphere to form a new silicon dioxide shell layer. Meanwhile, Ostwald ripening occurs in the system, which leads to the spontaneous phagocytosis of small grains by large grains, and further promotes the dissolution of silicon dioxide microsphere cores, and finally forms hollow structures. And within 5-7 h, the silicate deposition and the Ostwald curing reach a balance, and the outer diameter of the hollow silica cannot be increased continuously in the curing and hollowing process, so that the nano-scale hollow silica is formed. On one hand, the hollow silicon dioxide is prepared by using the method, the silicon dioxide microspheres are used as templates, the small crystal grains are phagocytosed by the large crystal grains, the hollow structure is formed, the templates are not required to be removed by strong acid and strong alkali, and the operation safety and the environmental protection performance of the preparation method are improved; on the other hand, the silicon dioxide belongs to a hard template, has stronger rigidity, can effectively improve the sphericity of the formed hollow silicon dioxide, can still promote the material to keep the better structural performance in the subsequent reduction reaction process, the spray granulation process and the calcination process, and then has better cycling stability when being used as a cathode material.
Secondly, the hollow silicon material obtained by reduction, the organic matter and the aqueous solution of formaldehyde are sprayed and granulated, so that the organic matter is uniformly coated on the outer side of the hollow silicon material to form an intermediate product, and the obtained intermediate product particles have better dispersibility and cannot be adhered to each other, thereby promoting the characteristics of high sphericity and high morphology regularity of the hollow silicon material to be better maintained in the subsequent calcination process.
Then, the intermediate product is calcined in inert gas or nitrogen to obtain the hollow silicon material coated by the carbon layer. The carbon has higher conductivity, and can effectively improve the conductivity of the coated composite material, thereby improving the electrochemical performance of the composite material. In addition, in the calcining process, H and O in the nitrogen-containing organic matter are volatilized, and finally a carbon layer doped with nitrogen is formed on the surface of the hollow silicon material. The nitrogen doping enables the carbon layer to have more active sites, can enhance the interaction between lithium and carbon structures, improves the dynamic capability of lithium ion diffusion and transfer, and further improves the electrochemical performance of the coating material.
In a word, the invention effectively solves the problems that the silicon-based material in the prior art has poor conductivity, or the preparation process has high treatment cost, poor environmental protection, poor safety, harsh process conditions and difficult regulation and control of material morphology and dispersibility based on the preparation method. The preparation method disclosed by the invention is low in cost, good in environmental protection property, good in safety, simpler in process condition and easier to regulate and control the morphology and the dispersity of the material, so that when the obtained material is used as a silicon cathode, the battery has higher conductivity and better cycling stability.
In the first heating process, when the heating temperature is higher than the above range, the ostwald ripening reaction hardly occurs, and solid silica composed of large crystal grains is finally obtained instead of hollow silica. In addition, when the heating temperature is higher than the above temperature, the corrosion speed of sodium borohydride is too high, so that silica is corroded into pores, and the molding rate of the hollow silicon is reduced. When the heating time is longer than the above range, the ostwald ripening reaction continues, the shell layer is excessively large to extrude the hollow structure, and it is difficult to control the hollow structure of the final silicon material. When the temperature and time are lower than the above ranges, the ostwald ripening reaction is too low to form a hollow structure. When the heating temperature is lower than the above temperature, the corrosion rate of sodium borohydride is too slow, and hollow silica cannot be formed.
In order to further improve the structural performance of the material and further improve the cycling stability of the battery, the mass ratio of the sodium borohydride to the silica microspheres is preferably (2-8) to (0.8-3.2).
In some embodiments, it is preferred that the first dispersion further comprises a surfactant; preferably the surfactant is a cationic surfactant; more preferably the cationic surfactant is selected from one or more of polyvinylpyrrolidone, cetyltrimethylammonium bromide or dioctadecyldimethylsodium chloride. By adding the surfactant, the prepared hollow silica can have high dispersity in the second dispersion liquid even if the hollow silica is nano-scale particles, and the increase of particle size and the increase of shape irregularity caused by agglomeration are avoided. More preferably, the mass ratio of the surfactant to the silica microspheres is (5-20): 0.8-3.2.
The silica sol of this application can adopt the known commercialized silica microballon among the prior art, especially nanometer silica microballon, for making silica microballon size, content and system pH valve more controllable, this application still provides the process of preparation silica microballon, and this process of preparing silica microballon includes: and carrying out second heating on the third dispersion liquid containing the first ethanol water solution, the silicon source and the catalyst, and then carrying out filtering and washing to obtain the silicon dioxide microspheres, wherein the second heating is preferably carried out at the heating temperature of 30-40 ℃ for 1-4 h. The silicon source is preferably selected from ethyl orthosilicate, the catalyst is preferably selected from one or more of ammonia water, hydrofluoric acid and hydrochloric acid, and the dispersity of the silicon source in the third dispersion liquid can be improved, the reaction speed can be improved and the silicon dioxide particles with proper particle size can be obtained through the preferable raw materials and reaction conditions. The volume ratio of the first ethanol aqueous solution, the silicon source and the catalyst is preferably (90-180): (6-12): 2-8), the volume ratio of ethanol to water in the first ethanol aqueous solution is preferably (8:1) - (1:1), and more preferably (4:1) - (1:1), within the above numerical range, the dispersion degree of the silicon source can be further improved, and the silica particles with the target particle size can be obtained by controlling the alkalinity of the third dispersion liquid. The particle size of the preferred silicon dioxide microspheres is 200-300 nm, the particle size of the silicon dioxide microspheres prepared by the method is nano, and the particle size of the hollow silicon dioxide microspheres can be controlled to be nano.
In some embodiments, the temperature of the reduction reaction is 650-800 ℃ and the time is 3-6 h; preferably, the reducing agent is selected from one or more of magnesium, aluminum and carbon, and the mass ratio of the reducing agent to the hollow silica is (2-4): (0.8 to 3.2). Through optimization of the reducing agent and the heating condition, the hollow silicon material can be quickly prepared through the thermal reduction reaction, and meanwhile, the hollow silicon material is not deformed and agglomerated, so that the finally prepared hollow silicon material has high sphericity and dispersity. The particle size of the hollow silicon material obtained after reduction is 200-300 nm, preferably, the thickness of a silicon shell layer in the hollow silicon material is 5-10 nm, and the shape of the hollow silicon material is similar to a sphere.
Compared with a solid silicon material, the hollow silicon material prepared by the preparation method has the advantages that the volume change of the material can be effectively buffered in the process of releasing and inserting lithium in the space inside the silicon, the effective diffusion distance of lithium ions can be shortened by the shell structure, and the effective capacity of the material is improved. In addition, the hollow silicon material prepared by the method has the advantages of high sphericity, good dispersion and small particle size.
Preferably, the mass ratio of the hollow silicon material to the organic matter to the formaldehyde aqueous solution is (0.8-3.2): (1.17-9.36): (8-32). More preferably, the organic substance is a nitrogen-containing organic substance, and preferably the nitrogen-containing organic substance is melamine.
In a preferred embodiment, melamine, an aqueous formaldehyde solution and hollow silicon are mixed and polycondensed before being spray granulated. In the polycondensation process, the hollow silicon is used as a nucleation center, so that macromolecules obtained by polycondensation are uniformly gathered on the surface of the hollow silicon. In the polycondensation process, the treatment temperature is 60-85 ℃, preferably 70-85 ℃, and the treatment time is 20-60 min. Within the temperature and time range, the polymerization degree can be controlled, so that the polymerization reaction of the nitrogen-containing organic monomer and the polymer monomer can not completely carry out the nitrogen-containing organic matter forming a macromolecular chain, but less nitrogen-containing organic matter forming a micromolecular chain among the monomers. Compared with the welding spot organic matter of the macromolecular chain, the nitrogen-containing organic matter of the micromolecular chain can be more tightly and compactly crosslinked on the surface of the hollow silicon-containing material, so that the binding force and the uniformity of the coating are further improved. In order to fully combine the nitrogen-containing organic substance and the hollow silicon and fully disperse the hollow silicon in the dispersion liquid, the first ultrasonic dispersion is preferably performed in the polycondensation process, and the power of the first ultrasonic dispersion is preferably 80-120 w.
In some embodiments, the spray pressure of the spray granulation is preferably 0.1MPa to 0.6MPa, the spray temperature of the spray granulation is preferably 100 ℃ to 200 ℃, and the feed rate of the spray granulation is preferably 10mL/min to 60 mL/min. Under the process conditions, intermediate product particles with better coating compactness and dispersity can be obtained. The calcination temperature is preferably 600-800 ℃, and the calcination time is preferably 2-6 h. By limiting the conditions, the carbon layer tightly combined with the hollow silicon material can be efficiently formed, and simultaneously, the hollow silicon material is prevented from agglomerating and deforming, so that the hollow silicon material coated by the carbon layer has uniform appearance and high dispersity. The temperature is too low to complete spray granulation, and the granules are all liquid. Too high a temperature may cause the carbon source to soften and stick to the wall. The speed is too low, the production significance is avoided, and the atomization cannot be realized at too high speed.
In another exemplary embodiment of the present application, a negative electrode material is provided, where the negative electrode material is a hollow silicon material prepared by any one of the above preparation methods or a carbon-coated hollow silicon material prepared by any one of the above preparation methods. The negative electrode material can well reduce the volume expansion in the lithium releasing and embedding process, is uniform in shape like a ball, and has higher compaction density when being prepared into a battery negative electrode, so that the cycling stability of the battery is improved. In addition, the coating of the carbon layer promotes better conductivity of the battery.
A lithium ion battery comprises a positive electrode, a negative electrode and electrolyte, wherein the negative electrode comprises a negative electrode material, and the negative electrode material is any one of the negative electrode materials. For the reasons mentioned above, the conductivity and the cycling stability of the battery are better.
The following examples and comparative examples are provided to further illustrate the advantageous effects of the present application.
Example 1
(1) Weighing 140mL of ethanol and 20mL of deionized water to prepare a mixed solution, adding 10mL of tetraethyl orthosilicate (TEOS) into the mixed solution, heating to 30 ℃ after dissolving, then slowly adding 3mL of ammonia water into the mixed solution under the stirring condition (speed: 500rpm), reacting for 1h, washing the mixed solution with deionized water and ethanol for multiple times to be neutral after the reaction is finished, and performing centrifugal separation and collection to obtain SiO2。
(2) Weighing 15g of PVP, dissolving in 60mL of deionized water to prepare solution AWeighing 2g of NaBH4Dissolving the mixture in 40mL of deionized water to prepare a solution B, and performing step (1) to obtain 2.676g of SiO2Putting the solution B into the solution A, after ultrasonic full dispersion, slowly adding the solution B into the solution A under the stirring condition of 53 ℃, adding ammonia water to control the pH of a system to be 8-9, reacting for 5 hours, after the reaction is finished, washing the solution B with deionized water and ethanol for 3 times, and then performing centrifugal separation and collection to obtain hollow SiO2. The mass ratio of the sodium borohydride to the silica microspheres is 2:2.676, and the mass ratio of the surfactant to the silica microspheres is 15: 2.676.
(3) 2.676g of hollow SiO obtained in step (2)2After being mixed with 3g of magnesium powder in a glove box, the mixture is transferred into a tube furnace and reacts for 6 hours at 650 ℃ under the argon atmosphere, and hollow silicon is obtained.
(4) Dispersing 1.25g of the hollow silicon obtained in the step (3) into 200mL of a deionized mixed solution containing 50 vol.% of ethanol, stirring (speed: 500rpm) for 30min, then maintaining ultrasonic agitation (power: 100w) at a temperature of 25 ℃ for 1h, then adding 4.68g of melamine thereto, continuing heating to 80 ℃ and ultrasonic agitation (power: 100w) for 20min, then adding 16mL of formaldehyde thereto, reacting at 80 ℃ for 20min, and cooling to room temperature to obtain a mixed solution. Hollow SiO2The mass ratio of the organic matter to the organic matter was 1.25: 4.68.
(5) And (4) carrying out spray granulation on the mixed solution obtained in the step (4) under the condition of stirring, wherein the spray pressure is 0.1MPa, the temperature is 100 ℃, the feeding speed is 60mL/min, and a product is obtained after the reaction is finished.
(6) And (5) putting the product obtained in the step (5) into a tube furnace, heating to 700 ℃, preserving heat for 4 hours, and collecting the carbon-coated silicon cathode material after the reaction is finished.
Example 2
(1) Weighing 100mL of ethanol and 20mL of deionized water to prepare a mixed solution, adding 12mL of TEOS into the mixed solution, heating to 40 ℃ after dissolving, then slowly adding 3mL of ammonia water into the mixed solution under a stirring condition (speed: 500rpm), reacting for 1h, washing the mixed solution with deionized water and ethanol for multiple times to be neutral after reaction is finished, and performing centrifugal separation and collection to obtain SiO2。
(2) Weighing 20g of PVP, dissolving in 60mL of deionized water to prepare solution A, weighing1.6g of NaBH was taken4Dissolving the mixture in 40mL of deionized water to prepare a solution B, and performing step (1) to obtain 3.2112g of SiO2Putting the solution B into the solution A, after ultrasonic full dispersion, slowly adding the solution B into the solution A under the stirring condition at 55 ℃, adding ammonia water to control the pH of a system to be 8-9, reacting for 6 hours, after the reaction is finished, washing the solution B with deionized water and ethanol for 3 times, and then performing centrifugal separation and collection to obtain hollow SiO2。
(3) 3.2112g of hollow SiO obtained in step (2)2Mixing the mixture with 4g of magnesium powder in a glove box, transferring the mixture into a tube furnace, and reacting for 3 hours at 800 ℃ under the argon atmosphere to obtain the hollow silicon.
(4) Dispersing 1.5g of the hollow silicon obtained in the step (3) into 200mL of a deionized mixed solution containing 20 vol.% of ethanol, stirring (speed: 500rpm) for 30min, then maintaining 25 ℃ for ultrasonic stirring (power: 100w) for 1h, then adding 1.17g of melamine thereto, continuing to heat to 80 ℃ for ultrasonic stirring (power: 100w) for 20min, then adding 8mL of formaldehyde thereto, reacting at 80 ℃ for 20min, and cooling to room temperature to obtain a mixed solution.
(5) And (4) carrying out spray granulation on the mixed solution obtained in the step (4) under the condition of stirring, wherein the spray pressure is 0.2MPa, the temperature is 150 ℃, the feeding speed is 40mL/min, and collecting a product after the reaction is finished.
(6) And (5) putting the product obtained in the step (5) into a tube furnace, heating to 600 ℃, preserving heat for 6 hours, and collecting the carbon-coated silicon cathode material after the reaction is finished.
Example 3
(1) Weighing 80mL of ethanol and 10mL of deionized water to prepare a mixed solution, adding 6mL of TEOS into the mixed solution, heating to 31 ℃ after dissolving, then slowly adding 2mL of ammonia water into the mixed solution under a stirring condition (speed: 500rpm), reacting for 1h, washing the mixed solution with deionized water and ethanol for multiple times to be neutral after reaction is finished, and performing centrifugal separation and collection to obtain SiO2。
(2) Weighing 20g of PVP, dissolving in 60mL of deionized water to prepare a solution A, and weighing 6g of NaBH4Dissolving the mixture in 40mL of deionized water to prepare a solution B, and performing step (1) to obtain 1.6056g of SiO2Putting the solution B into the solution A, fully dispersing the solution B by ultrasonic waves, and stirring the solution B at the temperature of 51 DEG CSlowly adding the mixture into the solution A, adding ammonia water to control the pH of a system to be 8-9, reacting for 6 hours, after the reaction is finished, washing deionized water and ethanol for 3 times, and then performing centrifugal separation and collection to obtain hollow SiO2。
(3) 1.6056g of hollow SiO obtained in step (2)2After being mixed with 2g of magnesium powder in a glove box, the mixture is transferred into a tube furnace and reacts for 4 hours at 700 ℃ under the argon atmosphere, and hollow silicon is obtained.
(4) Dispersing 0.75g of the hollow silicon obtained in the step (3) into 200mL of deionized mixed solution containing 60 vol.% ethanol, stirring (speed: 500rpm) for 30min, then maintaining 25 ℃ temperature ultrasonic (power: 100w) for 1h, then adding 9.36g of melamine, continuing to heat to 85 ℃ and ultrasonic stirring (power: 100w) for 20min, then adding 32mL of formaldehyde, reacting at 85 ℃ for 20min, and cooling to room temperature to obtain a mixed solution.
(5) And (4) carrying out spray granulation on the mixed solution obtained in the step (4) under the condition of stirring, wherein the spray pressure is 0.3MPa, the temperature is 150 ℃, the feeding speed is 40mL/min, and collecting a product after the reaction is finished.
(6) And (5) putting the product obtained in the step (5) into a tube furnace, heating to 650 ℃, preserving the temperature for 5 hours, and collecting the carbon-coated silicon negative electrode material after the reaction is finished.
Example 4
(1) Weighing 80mL of ethanol and 80mL of deionized water to prepare a mixed solution, adding 10mL of TEOS into the mixed solution, heating to 35 ℃ after dissolving, then slowly adding 5mL of ammonia water into the mixed solution under the stirring condition (speed: 500rpm), reacting for 1h, washing the mixed solution with deionized water and ethanol for multiple times to be neutral after the reaction is finished, and performing centrifugal separation and collection to obtain SiO2。
(2) Weighing 10g of PVP, dissolving in 60mL of deionized water to prepare a solution A, and weighing 3g of NaBH4Dissolving the mixture in 40mL of deionized water to prepare a solution B, and performing step (1) to obtain 2.676g of SiO2Putting the solution B into the solution A, after ultrasonic full dispersion, slowly adding the solution B into the solution A under the stirring condition at 47 ℃, adding ammonia water to control the pH of the system to be 8-9, reacting for 4 hours, after the reaction is finished, washing the deionized water and ethanol for 3 times, and then performing centrifugal separation and collection to obtain hollow SiO2。
(3) 2.676g of hollow SiO obtained in step (2)2After being mixed with 3g of magnesium powder in a glove box, the mixture is transferred into a tube furnace and reacts for 5 hours at 750 ℃ under the argon atmosphere, and hollow silicon is obtained.
(4) Dispersing 1.5g of the hollow silicon obtained in the step (3) into 200mL of a deionized mixed solution containing 30 vol.% ethanol, stirring (speed: 500rpm) for 30min, then maintaining 25 ℃ ultrasonic sound (power: 100w) for 1h, then adding 2.34g of melamine thereto, continuing heating to 60 ℃ and ultrasonic sound stirring (power: 100w) for 20min, then adding 12mL of formaldehyde thereto, reacting at 60 ℃ for 20min, and cooling to room temperature to obtain a mixed solution.
(5) And (4) carrying out spray granulation on the mixed solution obtained in the step (4) under the condition of stirring, wherein the spray pressure is 0.6MPa, the temperature is 120 ℃, the feeding speed is 10mL/min, and collecting a product after the reaction is finished.
(6) And (5) putting the product obtained in the step (5) into a tube furnace, heating to 700 ℃, preserving heat for 4 hours, and collecting the carbon-coated silicon negative electrode material after the reaction is finished.
Example 5
(1) Weighing 120mL of ethanol and 60mL of deionized water to prepare a mixed solution, adding 8mL of TEO into the mixed solution, heating to 33 ℃ after dissolving, then slowly adding 8mL of ammonia water into the mixed solution under the stirring condition (speed: 500rpm), reacting for 1h, washing the mixed solution with deionized water and ethanol for multiple times to be neutral after the reaction is finished, and performing centrifugal separation and collection to obtain SiO2。
(2) Weighing 5g of PVP, dissolving in 60mL of deionized water to prepare a solution A, and weighing 8g of NaBH4Dissolving the mixture in 40mL of deionized water to prepare a solution B, and performing step (1) to obtain 2.1408g of SiO2Putting the solution B into the solution A, after ultrasonic full dispersion, slowly adding the solution B into the solution A under the stirring condition of 45 ℃, adding ammonia water to control the pH of a system to be 8-9, reacting for 3 hours, after the reaction is finished, washing the solution B with deionized water and ethanol for 3 times, and then performing centrifugal separation and collection to obtain hollow SiO2。
(3) 2.1408g of hollow SiO obtained in step (2)2Mixing the mixture with 2g of magnesium powder in a glove box, transferring the mixture into a tube furnace, and reacting for 3 hours at 700 ℃ under the argon atmosphere to obtain hollow silicon。
(4) Dispersing 1g of the hollow silicon obtained in the step (3) into 200mL of deionized mixed solution containing 50 vol.% of ethanol, stirring (speed: 500rpm) for 30min, then maintaining 25 ℃ for ultrasonic stirring (power: 100w) for 1h, then adding 7.02g of melamine, continuing to heat to 70 ℃ for ultrasonic stirring (power: 100w) for 20min, then adding 24mL of formaldehyde, reacting at 70 ℃ for 20min, and cooling to room temperature to obtain a mixed solution.
(5) And (4) carrying out spray granulation on the mixed solution obtained in the step (4) under the condition of stirring, wherein the spray pressure is 0.1MPa, the temperature is 180 ℃, the feeding speed is 20mL/min, and collecting a product after the reaction is finished.
(6) And (5) putting the product obtained in the step (5) into a tube furnace, heating to 700 ℃, preserving heat for 2 hours, and collecting the carbon-coated silicon negative electrode material after the reaction is finished.
Comparative example 1
The patent application with the application number of CN02112180.X discloses a preparation method and application of a Si/C/graphite composite negative electrode material. The invention provides a preparation method of a composite cathode material, which takes nano silicon powder, asphalt and graphite powder as raw materials to prepare a Si/C/graphite composite cathode material.
Topography characterization
Fig. 2 is a TEM image of a hollow silicon material according to an embodiment of the present invention, and fig. 3 is an SEM image of an intermediate product obtained after spray granulation according to an embodiment of the present invention.
Performance testing
Button cell assembly
The prepared material, a conductive agent (Super P) and a high polymer binder (polyvinylidene fluoride) are prepared into an electrode plate of the button cell according to the ratio of 8:1:1, the electrode plate is assembled into the button cell, and a 8-channel cell tester BTS-5V is used for testing.
TABLE 1
First Capacity (Mass energy Density) mAh.g-1 100 times of cycle performance mAh & g-1
Example 1 1400 870
Example 2 2580 560
Example 3 1490 1080
Example 4 1760 620
Example 5 1120 710
Comparative example 1 990 Less than 100
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (11)

1. A preparation method of a carbon-coated hollow silicon material is characterized by comprising the following steps:
step A1, carrying out first heating on a first dispersion liquid containing sodium borohydride and silica microspheres to obtain hollow silica; in the first heating process, the pH value of the system is controlled to be more than 8, the first heating temperature is 45-55 ℃, and the time is 5-7 hours;
step A2, mixing the hollow silicon dioxide and a reducing agent for reduction reaction to obtain the hollow silicon material;
step A3, performing spray granulation on a second dispersion liquid containing the hollow silicon material, an organic matter and a formaldehyde aqueous solution to obtain an intermediate product;
step A4, calcining the intermediate product in inert gas or nitrogen to obtain the carbon-coated hollow silicon material.
2. The preparation method of claim 1, wherein the mass ratio of the sodium borohydride to the silica microspheres is (2-8) to (0.8-3.2).
3. The production method according to claim 1 or 2, wherein the first dispersion further comprises a surfactant;
preferably, the surfactant is a cationic surfactant; more preferably the cationic surfactant is selected from one or more of polyvinylpyrrolidone, cetyltrimethylammonium bromide or dioctadecyldimethylsodium chloride;
preferably, the mass ratio of the surfactant to the silicon dioxide microspheres is (5-20): 0.8-3.2.
4. The production method according to any one of claims 1 to 3, characterized in that the production method further comprises a process of producing the silica microspheres:
carrying out second heating on a third dispersion liquid containing a first ethanol water solution, a catalyst and a silicon source, and then carrying out filtering washing to obtain the silicon dioxide microspheres;
preferably, the heating temperature of the second heating is 30-40 ℃ and the time is 1-4 h;
preferably, the silicon source is tetraethoxysilane; preferably, the catalyst is selected from one or more of ammonia water, hydrofluoric acid and hydrochloric acid;
preferably, the volume ratio of the first ethanol aqueous solution to the silicon source to the catalyst is (90-180): 6-12):
(2～8)；
the volume ratio of ethanol to water in the first aqueous ethanol solution is preferably (8:1) to (1:1), more preferably (4:1) to (1: 1);
preferably, the particle size of the silicon dioxide microspheres is 200-300 nm.
5. The preparation method according to any one of claims 1 to 4, wherein in the reduction reaction process, the reaction temperature is 650-800 ℃ and the time is 3-6 h;
preferably, the reducing agent is selected from one or more of magnesium, aluminum or carbon, and more preferably, the mass ratio of the reducing agent to the hollow silica is (2-4): (0.8 to 3.2).
6. The method according to any one of claims 1 to 5, wherein the mass ratio of the hollow silicon material, the organic matter and the formaldehyde aqueous solution is (0.8-3.2): (1.17-9.36): (8-32).
7. The production method according to any one of claims 1 to 6, wherein the organic matter is a nitrogen-containing organic matter; preferably, the nitrogen-containing organic substance is melamine.
8. The production method according to any one of claims 1 to 4, wherein the spray pressure of the spray granulation is 0.1 to 0.6 MPa; preferably, the spraying temperature of the spray granulation is 100-200 ℃; preferably, the feeding rate of the spray granulation is 10-60 mL/min.
9. The method according to any one of claims 1 to 4, wherein the calcination is carried out at a treatment temperature of 600 to 800 ℃ for 2 to 6 hours.
10. A negative electrode material, characterized in that the negative electrode material is a carbon-coated hollow silicon material prepared by the preparation method of any one of claims 1 to 9.
11. A lithium ion battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode comprises a negative electrode material, and wherein the negative electrode material is the negative electrode material of claim 10.
CN202110991364.0A 2021-08-26 2021-08-26 Carbon-coated hollow silicon material and preparation method and application thereof Pending CN113636561A (en)

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Publication number Priority date Publication date Assignee Title
CN106374088A (en) * 2016-10-14 2017-02-01 浙江天能能源科技股份有限公司 Method for preparing silicon/carbon composite material with magnesiothermic reduction process
CN106575747A (en) * 2014-06-20 2017-04-19 加利福尼亚大学董事会 Porous silicon nanostructured electrode and method
CN108615860A (en) * 2018-03-15 2018-10-02 山东理工大学 Nitrogen-doped graphene/silicon 3 D lithium-ion negative pole composite material and preparation method
CN111564614A (en) * 2020-05-11 2020-08-21 厦门高容纳米新材料科技有限公司 Silicon-carbon composite negative electrode material, negative electrode plate, preparation method of negative electrode plate and lithium ion battery

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106575747A (en) * 2014-06-20 2017-04-19 加利福尼亚大学董事会 Porous silicon nanostructured electrode and method
CN106374088A (en) * 2016-10-14 2017-02-01 浙江天能能源科技股份有限公司 Method for preparing silicon/carbon composite material with magnesiothermic reduction process
CN108615860A (en) * 2018-03-15 2018-10-02 山东理工大学 Nitrogen-doped graphene/silicon 3 D lithium-ion negative pole composite material and preparation method
CN111564614A (en) * 2020-05-11 2020-08-21 厦门高容纳米新材料科技有限公司 Silicon-carbon composite negative electrode material, negative electrode plate, preparation method of negative electrode plate and lithium ion battery

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