CN105006559B - A kind of core shell structure of graphene coated silicon or its oxide and preparation method thereof - Google Patents

Abstract

A core-shell structure of graphene-coated silicon or its oxide and a preparation method thereof, the core-shell structure is a sub/micron particle with silicon or its oxide as the core and graphene as the shell, with a particle size of 0.05- 15μm, the number of graphene layers is 5-30 layers, the weight of graphene accounts for between 1-8wt% of the total weight of the core-shell structure particles, and the specific surface area of the core-shell structure is equal to or smaller than that of the original silicon or its oxide particles specific surface area. The present invention utilizes equipment such as spray granulation, fluidized bed, vibrating screen, jet milling, etc. to complete the secondary structure assembly of silicon or its oxide particles, the growth of graphene shell and the process of independent crushing of the secondary structure, and finally meet the requirements of The above-mentioned core-shell structure product. Since the obtained core-shell composite structure not only has the properties of silicon or its oxides, but also has some properties of graphene, it has broad application prospects in the electrochemical industry. At the same time, the fluidized bed reactor can realize continuous production, and the whole process can be industrialized.

Description

A core-shell structure of graphene-coated silicon or its oxide and its preparation method

technical field

The invention relates to a core-shell structure of graphene-coated silicon or its oxide and a preparation method thereof, belonging to the technical field of new energy materials and preparation thereof.

Background technique

As early as 1991, Sony invented the first generation of commercial lithium-ion batteries, making it possible to popularize electronic devices such as mobile phones. After more than 20 years of development, the types and performance of portable electronic devices have undergone tremendous changes, such as lighter weight, longer standby time, faster charging, flexibility, safety and environmental protection, etc. People have proposed a battery system series of new requirements. Not only that, the rapid development of electric vehicles and hybrid vehicles in recent years has further stimulated people's demand and exploration for power batteries with high energy density and high power density.

According to the components of the battery system - positive electrode material, negative electrode material, separator, electrolyte, current collector and packaging shell, etc., it can be found that the performance of the battery mainly depends on the specific capacity performance of the positive and negative electrode materials. As far as negative electrode materials are concerned, graphite-based carbon materials are generally used as negative electrodes in commercial lithium-ion batteries at present, and the theoretical capacity of graphite is only 372mAh/g, which greatly limits the further development of lithium-ion batteries. As the silicon negative electrode with the highest theoretical specific capacity, its theoretical specific capacity can reach 4200mAh/g, which is an ideal choice for a new generation of high energy density negative electrode materials. However, in the actual application process, the capacity of the silicon negative electrode decays too fast, resulting in poor cycle performance of the battery, which has become one of the problems that must be solved in the commercialization of silicon negative electrodes.

A lot of work has been done to improve the electrochemical cycling stability of silicon or its oxides. On the one hand, researchers hope to improve the capacity fading caused by volume expansion by nanosizing silicon particles and designing specific nanostructures, such as array nanowires (Cui Y, et al. Nature Nanotechnology, 2008, 3:31-35) , nanotubes (Jaephil Cho, et al. Nano Letter, 2009, 9 (11): 3844–3847), nanofibers (Lee YM, Park JK, et al. ACS Appl. Mater. Interfaces, 2013, 5 (22): 12005–12010) and other silicon multilevel structures. According to the experimental results, nanometerization can indeed improve the cycle performance of the battery to a certain extent. However, in practical commercial applications, these novel structures face problems such as complex preparation process, harsh growth conditions, and high cost, so it is not yet possible to achieve large-scale preparation. Not only that, these nano-silicon usually need to add carbon black to enhance the conductivity between particles. In view of such a situation, if the oligolayer graphene can be uniformly coated on the surface of nano- or micro-scale silicon or its oxide particles with various shapes, it will not only be able to improve the volume change caused by the process of intercalating and extracting lithium ions. In order to solve the problem of material pulverization and secondary agglomeration, graphene can also use its own super electron transfer characteristics to enhance the conductivity between particles and between particles and current collectors.

According to the different carbon coating methods on the particle surface, it can be mainly divided into three types: hydrothermal carbonization, high temperature carbonization and chemical vapor deposition. Whether it is hydrothermal carbonization or high-temperature carbonization (Wan Lijun et al., patent publication number: 101931076A), it is to physically mix the raw materials that are prone to dehydration with active particles (silicon or its oxides) in advance, and then heat carbonization at high temperature or hydrothermal Carbonization occurs in the environment and wraps on the surface of active particles. Due to the density difference between the commonly used liquid or solid carbon source and silicon or its oxide, the uniformity of physical mixing is difficult to guarantee, especially in the process of mass production, the product is prone to contain microporous carbon impurities. Some surfactants, as carbon sources, rely on weak chemical forces to coat and carbonize the surface of active particles, but their high cost and requirements for the morphology and surface properties of active particles make their industrialization difficult. greater difficulty. Not only that, but the carbon products obtained by dehydration carbonization usually contain abundant micropores and large specific surface area. In the process of forming SEI film (solid electrolyte interface, solid electrolyte interface film) on the surface of electrode materials, more lithium needs to be consumed to reduce the initial cost. The coulombic efficiency of circle charge and discharge increases the cost of the battery. In contrast, the carbon coating formed by chemical vapor deposition is mainly graphitic carbon, which has good electrical conductivity and basically no micropore formation. The specific surface area of the formed silicon-carbon composite is larger than that of the original silicon or its Oxide particles have a small specific surface area. Considering that the fluidized bed has better heat transfer and mass transfer efficiency, it is important to use it as a reactor to realize the chemical vapor deposition carbon coating process on the surface of nano-scale or micro-scale silicon or its oxides with various shapes. Engineering significance.

Contents of the invention

The object of the present invention is to provide a core-shell structure of graphene-coated silicon or its oxides and a preparation method thereof, so that the formed core-shell structure can reduce its fragmentation due to lithium intercalation and delithiation on the one hand, and improve battery performance. Cycling performance, on the other hand, is conducive to increasing the conductivity between particles, which can reduce the amount of conductive additives and reduce the internal resistance of the battery, so it has broad application prospects in the electrochemical industry and can achieve continuous industrial production.

Technical scheme of the present invention is as follows:

A core-shell structure of graphene-coated silicon or its oxide, characterized in that: the core-shell structure is nano or micro particles with silicon or its oxide as the core and graphene as the shell, with a particle size of 0.05- 15 μm; the number of graphene shell layers is 5-30 layers, the weight of graphene accounts for 1-8wt% of the total weight of the core-shell structure particles, and the specific surface area of the core-shell structure is equal to or smaller than that of the original silicon or its oxide particles specific surface area.

The core-shell structure of the present invention is also characterized in that: the core-shell structure is crystal or amorphous, and its macroscopic appearance is spherical, rod-like, flake-like, irregular polyhedron or two or more of them a mixture of.

A kind of preparation method of the core-shell structure of graphene-coated silicon or its oxide provided by the present invention is characterized in that the method comprises the steps:

5) Dissolve the carbon-containing binder in deionized water at room temperature, continue to stir and slowly raise the temperature to 50-100°C, and keep the constant temperature for 1-6 hours to obtain a viscous liquid;

6) Add silicon or its oxide particles with a particle size of 0.1-10 μm to the viscous liquid prepared in step 1), and stir to obtain a suspension slurry with a solid content of 30-60 wt %;

7) Spray granulating the slurry obtained in step 2) to obtain porous spherical particles with a particle size distribution between 50 and 300 μm, i.e. secondary structure particles;

8) Fill the secondary structure particles obtained in step 3) into a fluidized bed, heat to a reaction temperature of 700-1000° C. in an inert atmosphere, and then feed a carbon source. The total space velocity of the inert gas and the carbon source is 500-1000° C. 900h ^-1 , keep the volume ratio of carbon source and inert gas between 0.5 and 2, conduct chemical vapor deposition, and the reaction time is 20 to 60 minutes to obtain graphene-coated silicon or its oxide with a particle size of 0.05 to 15 μm core-shell structure.

In the method of the present invention, it is characterized in that: the type of carbon-containing binder includes straight chain, pullulan, glucose, polysaccharide or polyhydric alcohol; the quality of carbon-containing binder and silicon or its oxide particles The ratio is between 0.0005 and 0.03.

In the method of the present invention, the spray granulation described in step 3) selects a centrifugal spray granulator, the feed rate is 0.5～2L/h, the inlet temperature is between 280～350°C, and the nozzle speed is 10～20r/h min.

In the method of the present invention, the height of the secondary structure particles packed in the fluidized bed reactor in step 4) is 1 to 3 times the diameter of the fluidized bed; the carbon source is methane, ethane, ethylene, acetylene , propane, propylene, benzene and toluene or a combination of several; the inert gas is nitrogen, argon or a mixture of the two.

The method of the present invention is also characterized in that: the graphene-coated silicon or its oxide core-shell structure obtained in step 4) is sent into a vibrating screen machine for product separation, and for a small number of undisintegrated secondary structure particles, Adopt jet pulverization, add again in the fluidized bed reactor and carry out graphene shell coating.

Compared with the prior art, the present invention has the following advantages and outstanding technical effects: 1. realize the uniform coating of oligolayer graphene (5-30 layers) on the surface of special-shaped, nano or micron silicon or its oxide particles, so On the one hand, the formed core-shell structure can reduce its fragmentation due to lithium intercalation and delithiation, improve battery cycle performance, and on the other hand, it is conducive to increasing the conductivity between particles, which can reduce the amount of conductive additives and reduce the internal resistance of the battery; ② core-shell The specific surface area of the structural particles is equal to or smaller than the specific surface area of the original silicon or its oxide particles, no additional SEI layer will be formed, and the amount of lithium-containing materials in the positive electrode will be reduced, which will help reduce the cost of the battery; 3) the carbon source used in the method Cheap and easy to obtain, the fluidized bed process is convenient for engineering scale-up and mass production.

Description of drawings:

Figure 1 is a scanning electron microscope photo of submicron or micron silicon raw powder.

Fig. 2 is a scanning electron micrograph of micron-sized spherical particles obtained by nano- or micron-sized silicon granulation.

Fig. 3 is a scanning electron micrograph of a nano- or micro-scale silicon-coated oligolayer graphene material.

Fig. 4 is a transmission electron micrograph of a nanometer or micrometer silicon-coated oligolayer graphene material.

detailed description

The present invention provides a graphene-coated core-shell structure of silicon or its oxide, which is a nano or micro particle with silicon or its oxide as the core and graphene as the shell, with a particle size of 0.05-15 μm; graphene The number of layers of the shell is 5-30 layers, the weight of graphene accounts for 1-8 wt% of the total weight of the core-shell structure particles, and the specific surface area of the core-shell structure is equal to or smaller than the specific surface area of the original silicon or its oxide particles ; The core-shell structure is crystal or amorphous, and its macroscopic shape is spherical, rod-like, sheet-like, irregular polyhedron or a mixture of two or more of them.

The preparation method of the core-shell structure of graphene-coated silicon or its oxide of the present invention comprises the steps:

1) Dissolve the carbon-containing binder in deionized water at room temperature, continue to stir and slowly raise the temperature to 50-100°C, and keep the constant temperature for 1-6 hours to obtain a viscous liquid;

2) Add silicon or its oxide particles with a particle size of 0.1-10 μm to the viscous liquid prepared in step 1), and stir to obtain a suspension slurry with a solid content of 30-60 wt %;

3) Spray granulating the slurry obtained in step 2) to obtain porous spherical particles with a particle size distribution between 50-300 μm, i.e. secondary structure particles;

4) Fill the secondary structure particles obtained in step 3) into a fluidized bed, heat to a reaction temperature of 700-1000° C. in an inert atmosphere, and then feed a carbon source. The total space velocity of the inert gas and the carbon source is 500- 900h ^-1 , keep the volume ratio of carbon source and inert gas between 0.5-2, carry out chemical vapor deposition, the reaction time is 20-60min, and obtain graphene-coated silicon or its oxide with a particle size of 0.05-15μm core-shell structure;

Wherein, the macro-morphology of silicon or its oxide particles can be spherical, rod-shaped, flake-shaped, irregular polyhedron and a mixture of the above-mentioned shapes. The types of carbon-containing binder include straight chain, pullulan, glucose, polysaccharide, polyhydric alcohol, etc.; the mass ratio of carbon-containing binder to silicon or its oxide particles is between 0.0005-0.03. In the fluidized bed reactor, the packing height is 1-3 times the diameter of the fluidized bed with silicon or its oxide secondary structure particles; the carbon source is methane, ethane, ethylene, acetylene, propane, propylene, benzene and toluene One or a combination of several of them; the inert gas is nitrogen, argon or a mixture of the two in a certain proportion. During the growth process of the graphene shell, the secondary structure particles in the fluidized state will disintegrate due to collisions, and the core-shell products with a particle size distribution of 0.05-15 μm are obtained. The product is separated by a vibrating sieve machine, and for less Part of the undisintegrated secondary structure particles will be pulverized by airflow, and then added to the fluidized bed for graphene shell coating.

The present invention will be further described below through several specific examples.

Embodiment 1: Preparation of silicon-graphene core-shell structure material in fluidized bed nanometer or micrometer scale

At normal temperature, 0.75 wt% amylopectin was added into water, stirred and heated to 80° C., and kept at constant temperature for 2 hours to obtain a transparent colloid. Add silicon particles with irregular shape and particle size of 0.1-10 μm (as shown in Figure 1) into the starch colloid, wherein the solid content is 50wt% (starch/silicon particles = 0.0075, mass ratio), under constant temperature conditions of 80 ° C Stirring for 2 hours gave a slurry of suspension. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 1L/h, the nozzle temperature is 320°C, and the rotation speed is 15r/min. The obtained product is porous spherical particles with a size of 50-300μm. as shown in picture 2. In the fluidized bed, the above-mentioned spherical particles with a packing height of 2 times the diameter of the fluidized bed are filled, and argon is used as the carrier gas with a flow rate of 45 L/h. Under this atmosphere, the temperature of the reactor is raised from room temperature to the pretreatment temperature of 850°C at a rate of 20°C/min. After constant temperature for 5 minutes, a mixture of propylene and argon is introduced, wherein the volume ratio of propylene:argon is 1:1, the total space velocity of the reaction process is controlled to be 600h ^-1 , and the chemical vapor deposition process is carried out. After 30 min, the carbon source propylene was turned off, and the solid phase product was taken out after cooling to room temperature under an argon atmosphere. The morphology of the graphene-coated silicon particles is similar to that of the original silicon particles through scanning electron microscope observation, and the size distribution is between 0.05-15 μm. As shown in Figure 4, under high-resolution transmission electron microscope photos, a clear graphite layer structure can be seen on the surface of silicon particles. In the Raman spectrum, there are also obvious G peaks, indicating that the carbon on the surface of silicon particles is mainly an oligolayer graphene structure. The results of thermogravimetry show that the amount of carbon deposited on the surface of silicon particles reaches 3.9wt% under this condition. At 77K, the isothermal nitrogen adsorption curve shows that there are no micropores in the product, and the specific surface area is 3.8m ² /g, which is smaller than the original specific surface area of silicon particles (4.2m ² /g).

Embodiment 2: Fluidized bed prepares nano or micron silicon-graphene core-shell structure material

At normal temperature, add 0.5 wt% amylopectin into water, stir and heat up to 75° C., and keep the temperature for 1.5 hours to obtain a transparent colloid. Add silicon particles with an irregular shape and a particle size of 0.1-10 μm into the starch colloid, wherein the solid content is 60 wt% (starch/silicon particles=0.0033, mass ratio), and stir at a constant temperature of 75°C for 2.5 hours to obtain a suspension. Turbid slurry. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 0.8L/h, the nozzle temperature is 300°C, and the rotation speed is 17r/min. The obtained product is porous spherical particles with a size of 50-200μm. . In the fluidized bed, the above-mentioned spherical particles with a packing height of 1 times the diameter of the fluidized bed are filled, argon is used as the carrier gas, and the flow rate is 45 L/h. Under this atmosphere, the temperature of the reactor was raised from room temperature to the pretreatment temperature of 850°C at a heating rate of 20°C/min. After constant temperature for 5 minutes, a mixture of propylene and argon was introduced, wherein the volume ratio of propylene:argon was 1:1, the total space velocity of the reaction process is controlled to be 650h ^-1 , and the chemical vapor deposition process is carried out. After 40 minutes of reaction, the product was blown out, and the catalyst with the same quality as the first time was re-added to carry out continuous reaction. The resulting product is cooled and sieved to obtain irregular particles whose size is mainly distributed between 0.05-15 μm. Under the transmission electron microscope, the surface of the particles has a clear graphite layer coating structure, and the carbon deposition is 4.8wt%. The surface area (4.1m ² /g) is smaller than the original specific surface area (4.2m ² /g) of silicon particles.

Embodiment 3: Fluidized bed prepares nano or micron silicon oxide-graphene core-shell structure material

At normal temperature, add 0.5 wt% amylopectin into water, stir and heat up to 90° C., and obtain a transparent colloid after constant temperature for 3 hours. Add silicon oxide SiO particles with an irregular shape and a particle size of 0.1-10 μm into the starch colloid, wherein the solid content is 60 wt% (starch/silicon particles=0.0033, mass ratio), and stir at a constant temperature of 90°C for 4 hours to obtain a suspension slurry. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 0.6L/h, the nozzle temperature is 340°C, and the rotation speed is 12r/min. The obtained product is porous spherical particles with a size of 80-300μm . In the fluidized bed, the above-mentioned spherical particles with a packing height of 2.5 times the diameter of the fluidized bed are filled, nitrogen is used as the carrier gas, and the flow rate is 60 L/h. Under this atmosphere, the temperature of the reactor is raised from room temperature to the pretreatment temperature of 880° C. at a rate of temperature increase of 40° C./min. After constant temperature for 5 minutes, a mixed gas of propylene and nitrogen is introduced, wherein the volume ratio of propylene: nitrogen is 2: 3. Control the total space velocity of the reaction process to 800h ^-1 , and carry out the chemical vapor deposition process. After 45 min, the carbon source propylene was turned off, and the solid phase product was taken out after cooling to room temperature under a nitrogen atmosphere. Through vibrating sieve, obtain the irregular particle that size mainly distributes between 0.05-15 μm, under the transmission electron microscope, particle surface has clear graphite layer coating structure, and carbon deposit is 5.2wt%, and the specific surface area of product (2.8m ² /g) is smaller than the original specific surface area of silicon particles (3.2m ² /g).

Embodiment 4: Fluidized bed prepares nano or micron silicon oxide-graphene core-shell structure material

At normal temperature, 0.3 wt% amylopectin was added to water, stirred and heated to 100° C., and a transparent colloid was obtained after constant temperature for 6 hours. Add silicon oxide silicon oxide (SiO _x , 0<x<2) particles with irregular morphology and particle size of 0.1-10 μm into the starch colloid, wherein the solid content is 50wt% (starch/silicon particle=0.003, mass ratio), stirred at 100°C for 3 hours at a constant temperature to obtain a suspension slurry. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 1.2L/h, the nozzle temperature is 340°C, and the rotation speed is 13r/min. The obtained product is porous spherical particles with a size of 50-250μm . In the fluidized bed, the packing height is 2 times of the above-mentioned spherical particles of the diameter of the fluidized bed, nitrogen is used as the carrier gas, and the flow rate is 40 L/h. Under this atmosphere, the temperature of the reactor was raised from room temperature to a pretreatment temperature of 750°C at a rate of 25°C/min, and after a constant temperature of 5 minutes, a mixture of ethylene and nitrogen was introduced, wherein the volume ratio of ethylene:nitrogen was 1: 1. Control the total space velocity in the reaction process to be 500h ^-1 , and carry out the chemical vapor deposition process. After 50 min, the carbon source ethylene was turned off, and the solid phase product was taken out after cooling to room temperature under a nitrogen atmosphere. Through vibrating sieve, mainly obtain the irregular particle that size mainly distributes between 0.05-15 μ m, under the transmission electron microscope, particle surface has clear graphite layer coating structure, and carbon deposit is 2.8wt%, and the specific surface area of product (2.4 m ² /g) is smaller than the original specific surface area of silicon particles (3.2m ² /g).

Embodiment 5: Fluidized bed preparation nanometer or micron silicon oxide-graphene core-shell structure material

At normal temperature, 0.1 wt% amylopectin was added into water, stirred and heated to 100° C., and a transparent colloid was obtained after constant temperature for 2 hours. Add silicon oxide silicon oxide (SiO _x , 0<x<2) particles with irregular morphology and particle size of 0.1-10 μm into the starch colloid, wherein the solid content is 50wt% (starch/silicon particle=0.001, mass ratio), stirred at 100°C for 3 hours at a constant temperature to obtain a suspension slurry. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 2.0L/h, the nozzle temperature is 350°C, and the rotation speed is 15r/min. The obtained product is porous spherical particles with a size of 50-220μm . In the fluidized bed, the above-mentioned spherical particles with a packing height of twice the diameter of the fluidized bed are filled, and argon is used as the carrier gas with a flow rate of 50 L/h. Under this atmosphere, the temperature of the reactor is raised from room temperature to the pretreatment temperature of 800°C at a rate of 30°C/min. After constant temperature for 5 minutes, a mixture of ethylene and argon is introduced, wherein the volume ratio of ethylene:argon is 2:3, the total space velocity of the reaction process is controlled to be 650h ^-1 , and the chemical vapor deposition process is carried out. After 35 min, the carbon source ethylene was turned off, and the solid phase product was taken out after cooling to room temperature under an argon atmosphere. Through vibrating sieve, mainly obtain the irregular particle that size mainly distributes between 0.05-15 μm, under the transmission electron microscope, particle surface has clear graphite layer coating structure, and carbon deposit is 1.0wt%, and the specific surface area of product (2.2 m ² /g) is smaller than the original specific surface area of silicon particles (3.2m ² /g).

Embodiment 6: Preparation of nano or micron silicon oxide-graphene core-shell structure material by fluidized bed

At room temperature, 0.05 wt% amylopectin was added to water, stirred and heated to 85° C., and a transparent colloid was obtained after constant temperature for 1 hour. Add silicon oxide silicon oxide (SiO _x , 0<x<2) particles with irregular morphology and particle size of 0.1-10 μm into the starch colloid, wherein the solid content is 50 wt% (starch/silicon particle=0.0005, mass ratio), and stirred for 3 hours at a constant temperature of 85° C. to obtain a suspension slurry. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 0.5L/h, the nozzle temperature is 280°C, and the rotation speed is 20r/min. The obtained product is porous spherical particles with a size of 50-180μm . In the fluidized bed, the above-mentioned spherical particles with a packing height of twice the diameter of the fluidized bed are filled, and argon is used as the carrier gas with a flow rate of 50 L/h. Under this atmosphere, the temperature of the reactor was raised from room temperature to the pretreatment temperature of 900°C at a rate of 20°C/min. After constant temperature for 5 minutes, a mixture of ethylene and argon was introduced, wherein the volume ratio of ethylene:argon was 2:3, the total space velocity of the reaction process is controlled to be 650h ^-1 , and the chemical vapor deposition process is carried out. After 60 min, the carbon source ethylene was turned off, and the solid phase product was taken out after cooling to room temperature under an argon atmosphere. Through vibrating sieve, mainly obtain the irregular particle that size mainly distributes between 0.05-15 μ m, under the transmission electron microscope, particle surface has clear graphite layer coating structure, and carbon deposit is 5.0wt%, and the specific surface area of product (3.2 m ² /g) is smaller than the original specific surface area of silicon particles (4.1m ² /g).

Embodiment 7: Fluidized bed prepares nano or micron silicon oxide-graphene core-shell structure material

At normal temperature, 3 wt % amylose was added into water, stirred and heated to 90° C., and a transparent colloid was obtained after constant temperature for 3 hours. Add silicon oxide (SiO _x , 0<x<2) particles with irregular shape and particle size of 0.1-10 μm into the starch colloid, wherein the solid content is 50wt% (starch/silicon particle=0.03, mass ratio) , and stirred for 2 hours at a constant temperature of 90° C. to obtain a suspension slurry. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 1.8L/h, the nozzle temperature is 330°C, and the rotation speed is 12r/min. The obtained product is porous spherical particles with a size of 70-280μm . In the fluidized bed, the above-mentioned spherical particles with a packing height of 2.5 times the diameter of the fluidized bed are filled, argon is used as the carrier gas, and the flow rate is 60 L/h. Under this atmosphere, the temperature of the reactor is raised from room temperature to the pretreatment temperature of 850°C at a rate of 25°C/min. After constant temperature for 5 minutes, a mixture of ethylene and argon is introduced, wherein the volume ratio of ethylene:argon is 3:2, the total space velocity of the reaction process is controlled to be 600h ^-1 , and the chemical vapor deposition process is carried out. After 35 min, the carbon source ethylene was turned off, and the solid phase product was taken out after cooling to room temperature under an argon atmosphere. Through vibrating sieve, mainly obtain the irregular particle that size mainly distributes between 0.05-15 μ m, under the transmission electron microscope, particle surface has clear graphite layer coating structure, and carbon deposit is 6.2wt%, and the specific surface area of product (2.9 m ² /g) is smaller than the original specific surface area of silicon particles (3.2m ² /g).

Embodiment 8: Preparation of nano or micron silicon oxide-graphene core-shell structure material by fluidized bed

At normal temperature, 1 wt% amylose was added into water, stirred and heated to 100° C., and kept at constant temperature for 2 hours to obtain a transparent colloid. Add silicon oxide (SiO _x , 0<x<2) particles with irregular morphology and particle size of 0.1-10 μm into the starch colloid, wherein the solid content is 60wt% (starch/silicon particle=0.0067, mass ratio) , and stirred at 100° C. for 2 hours to obtain a suspension slurry. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 1.0L/h, the nozzle temperature is 320°C, and the rotation speed is 12r/min. The obtained product is porous spherical particles with a size of 60-240μm . In the fluidized bed, the above-mentioned spherical particles with a packing height of 2.5 times the diameter of the fluidized bed are filled, nitrogen is used as the carrier gas, and the flow rate is 60 L/h. Under this atmosphere, the temperature of the reactor was raised from room temperature to the pretreatment temperature of 800° C. at a heating rate of 25° C./min. After constant temperature for 5 minutes, a mixture of ethylene and nitrogen was introduced, wherein the volume ratio of ethylene: nitrogen was 1: 1. The total space velocity of the reaction process is controlled to be 600h ^-1 , and the chemical vapor deposition process is carried out. After 20 min, the carbon source ethylene was turned off, and the solid phase product was taken out after cooling to room temperature under a nitrogen atmosphere. Through vibrating sieve, mainly obtain the irregular particle that size mainly distributes between 0.05-15 μ m, under the transmission electron microscope, particle surface has clear graphite layer coating structure, and carbon deposit is 5.4wt%, and the specific surface area of product (4.2 m ² /g) is smaller than the original specific surface area of silicon particles (4.8m ² /g).

Embodiment 9: Fluidized bed preparation nanometer or micrometer silicon oxide-graphene core-shell structure material

At normal temperature, 0.3 wt% amylopectin was added into water, stirred and heated to 90° C., and a transparent colloid was obtained after constant temperature for 1 hour. Add silicon oxide (SiO _x , 0<x<2) particles with irregular morphology and particle size of 0.1-10 μm into the starch colloid, wherein the solid content is 60wt% (starch/silicon particles=0.002, mass ratio) , and stirred for 4 hours at a constant temperature of 90° C. to obtain a suspension slurry. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 0.8L/h, the nozzle temperature is 340°C, and the rotation speed is 12r/min. The obtained product is porous spherical particles with a size of 80-300μm . In the fluidized bed, the above-mentioned spherical particles with a packing height of 2.5 times the diameter of the fluidized bed are filled, argon is used as the carrier gas, and the flow rate is 60 L/h. Under this atmosphere, the temperature of the reactor is raised from room temperature to the pretreatment temperature of 950°C at a rate of 30°C/min. After constant temperature for 5 minutes, a mixed gas of methane and argon is introduced, wherein the volume ratio of methane:argon is 2:1, the total space velocity of the reaction process is controlled to be 800h ^-1 , and the chemical vapor deposition process is carried out. After 60 min, the carbon source methane was turned off, and the solid phase product was taken out after cooling to room temperature under an argon atmosphere. Through vibrating sieve, obtain the irregular particle that size mainly distributes between 0.05-15 μm, under the transmission electron microscope, particle surface has clear graphite layer coating structure, and carbon deposit is 2.3wt%, and the specific surface area of product (3.8m ² /g) is smaller than the original specific surface area of silicon particles (4.8m ² /g).

Example 10: Fluidized bed preparation of nano or micro silicon oxide-graphene core-shell structure material

At normal temperature, add 0.5 wt% amylopectin into water, stir and heat up to 90° C., and obtain a transparent colloid after constant temperature for 1 hour. Add silicon oxide (SiO _x , 0<x<2) particles with irregular morphology and particle size of 0.1-10 μm into the starch colloid, wherein the solid content is 60wt% (starch/silicon particle=0.0033, mass ratio) , and stirred for 6 hours at a constant temperature of 90° C. to obtain a suspension slurry. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 0.8L/h, the nozzle temperature is 340°C, and the rotation speed is 12r/min. The obtained product is porous spherical particles with a size of 120-300μm . In the fluidized bed, the above-mentioned spherical particles with a packing height of 2.5 times the diameter of the fluidized bed are filled, argon is used as the carrier gas, and the flow rate is 60 L/h. Under this atmosphere, the temperature of the reactor was raised from room temperature to the pretreatment temperature of 700° C. at a rate of 30° C./min. After constant temperature for 5 minutes, a mixture of toluene (preheated at 200° C.) and argon was introduced, wherein toluene: The volume ratio of argon is 1:1, the total space velocity of the reaction process is controlled to be 800h ^-1 , and the chemical vapor deposition process is carried out. After 25 min, the carbon source toluene was turned off, and the solid phase product was taken out after cooling to room temperature under an argon atmosphere. After vibrating sieve, the irregular particles whose size is mainly distributed between 0.05-15 μm are obtained. Under the transmission electron microscope, the surface of the particles has a clear graphite layer coating structure, the carbon deposit is 8.0wt%, and the specific surface area of the product (4.6m ² /g) is smaller than the original specific surface area of silicon particles (4.8m ² /g).

Example 11: Fluidized bed preparation of nano- or micro-scale silicon oxide-graphene core-shell structure materials

At room temperature, 0.2 wt% amylopectin was added to water, stirred and heated to 90° C., and a transparent colloid was obtained after constant temperature for 1 hour. Add silicon oxide (SiO _x , 0<x<2) particles with irregular shape and particle size of 0.1-10 μm into the starch colloid, wherein the solid content is 50wt% (starch/silicon particles=0.002, mass ratio) , and stirred for 4 hours at a constant temperature of 90° C. to obtain a suspension slurry. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 0.8L/h, the nozzle temperature is 340°C, and the rotation speed is 12r/min. The obtained product is porous spherical particles with a size of 80-280μm . In the fluidized bed, the above-mentioned spherical particles with a packing height of 1.8 times the diameter of the fluidized bed are filled, and argon is used as the carrier gas with a flow rate of 45 L/h. Under this atmosphere, the temperature of the reactor was raised from room temperature to the pretreatment temperature of 850°C at a heating rate of 20°C/min. After constant temperature for 5 minutes, a mixture of propylene and argon was introduced, wherein the volume ratio of propylene:argon was 1:1, the total space velocity of the reaction process is controlled to be 650h ^-1 , and the chemical vapor deposition process is carried out. After 40 minutes of reaction, the product was blown out, and the catalyst with the same quality as the first time was re-added to carry out continuous reaction. The resulting product is cooled and sieved to obtain irregular particles whose size is mainly distributed between 0.05-15 μm. Under the transmission electron microscope, the surface of the particles has a clear graphite layer coating structure, and the carbon deposition is 3.8wt%. The surface area (3.9m ² /g) is smaller than the original specific surface area (4.8m ² /g) of the silicon oxide particles.

Example 12: Fluidized bed preparation of nano- or micro-scale silicon oxide-graphene core-shell structure material

At normal temperature, 1% by mass of glucose was added to water, the temperature was raised to 60°C with stirring, and a transparent liquid was obtained after constant temperature for 1 hour. Silicon oxide (SiO _x , 0<x<2) particles with irregular morphology and particle size of 0.1-10 μm are added to aqueous glucose solution, wherein the solid content is 50 wt% (starch/silicon particles=0.01, mass ratio), Stir for 2 hours at a constant temperature of 60° C. to obtain a suspension slurry. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 0.8L/h, the nozzle temperature is 300°C, and the rotation speed is 15r/min. The obtained product is porous spherical particles with a size of 50-180μm . In the fluidized bed, the above-mentioned spherical particles with a packing height of 2 times the diameter of the fluidized bed are filled, and argon is used as the carrier gas with a flow rate of 45 L/h. Under this atmosphere, the temperature of the reactor is raised from room temperature to the pretreatment temperature of 750°C at a rate of 20°C/min. After constant temperature for 5 minutes, the mixed gas of acetylene and argon is introduced, wherein the volume ratio of acetylene:argon is 1:1, the total space velocity of the reaction process is controlled to be 500h ^-1 , and the chemical vapor deposition process is carried out. After 30 min of reaction, the carbon source acetylene was turned off, and the solid phase product was taken out after cooling to room temperature under an argon atmosphere. Through vibrating sieve, obtain the irregular particle that size mainly distributes between 0.05-15 μm, under the transmission electron microscope, particle surface has clear graphite layer coating structure, and carbon deposit is 5.8wt%, and the specific surface area of product (4.4m ² /g) is smaller than the original specific surface area of silicon oxide particles (4.8m ² /g).

Example 13: Fluidized bed preparation of nano- or micro-scale silicon oxide-graphene core-shell structure materials

At normal temperature, add 0.5 wt% glucose into water, stir and raise the temperature to 50° C., keep the temperature for 1 hour to obtain a transparent liquid. Silicon oxide (SiO _x , 0<x<2) particles with irregular morphology and particle size of 0.1-10 μm are added to aqueous glucose solution, wherein the solid content is 50 wt% (starch/silicon particles=0.005, mass ratio), Stir for 2 hours at a constant temperature of 50° C. to obtain a suspension slurry. Use a centrifugal spray dryer to granulate the above slurry. The feed rate is 0.6L/h, the nozzle temperature is 280°C, and the rotation speed is 12r/min. The obtained product is porous spherical particles with a size of 50-200μm. . In the fluidized bed, the packing height is 2 times of the above-mentioned spherical particles of the diameter of the fluidized bed, nitrogen is used as the carrier gas, and the flow rate is 45L/h. Under this atmosphere, the temperature of the reactor was raised from room temperature to a pretreatment temperature of 800°C at a rate of 20°C/min, and after a constant temperature of 5 minutes, a mixture of propylene and nitrogen was introduced, wherein the volume ratio of propylene:nitrogen was 1: 1. The total space velocity of the reaction process is controlled to be 600h ^-1 , and the chemical vapor deposition process is carried out. After 40 minutes of reaction, the product was blown out, and the catalyst with the same quality as the first time was re-added to carry out continuous reaction. The resulting product is cooled and sieved to obtain irregular particles whose size is mainly distributed between 0.05-15 μm. Under the transmission electron microscope, the surface of the particles has a clear graphite layer coating structure, and the carbon deposition is 4.4wt%. The surface area (4.0m ² /g) is smaller than the original specific surface area (4.8m ² /g) of the silicon oxide particles.

Example 14: Fluidized bed preparation of nano- or micro-scale silicon oxide-graphene core-shell structure materials

At room temperature, polyethylene glycol (PEG2000) with a mass percentage of 1 wt% was added into water, stirred and heated to 50° C., and a transparent liquid was obtained after constant temperature for 1 hour. Irregular morphology and particle size of 0.1-10 μm silicon oxide (silicon oxide (SiO _x , 0<x<2) particles are added to PEG aqueous solution, wherein the solid content is 50wt% (starch/silicon particle=0.01, mass ratio), and stirred for 2 hours at a constant temperature of 50°C to obtain a suspension slurry. Utilize a centrifugal spray dryer to granulate the above slurry, the feed rate is 0.8L/h, the nozzle temperature is 300°C, and the rotation speed Be 12r/min, the product that obtains is porous, and size is the spherical particle of 50-160 μ m.In fluidized bed, packing height is the above-mentioned spherical particle of 2 times of fluidized bed diameter, uses argon as carrier gas, flow rate It is 45L/h.In this atmosphere, the temperature of the reactor is raised from room temperature to the pretreatment temperature of 850°C at a heating rate of 30°C/min. After constant temperature for 5min, a mixture of propylene and argon is introduced, wherein propylene: argon The volume ratio of the gas is 1:1, the total space velocity of the reaction process is controlled to be 500h ^-1 , and the chemical vapor deposition process is carried out. After 45 minutes, the carbon source propylene is closed, and the solid phase product is taken out after cooling to room temperature under an argon atmosphere. After vibrating sieve , to obtain irregular particles whose size is mainly distributed between 0.05-15 μm. Under the transmission electron microscope, the surface of the particles has a clear graphite layer coating structure, the amount of carbon deposition is 5.3wt%, and the specific surface area of the product (4.5m ² /g ) is smaller than the original specific surface area of silicon particles (4.8m ² /g).

Claims (7)

1. the preparation method of the core shell structure of a kind of graphene coated silicon or its oxide, it is characterised in that this method includes as follows Step：

1) carbon binder at normal temperatures, will be contained to be dissolved in deionized water, persistently stir and be to slowly warm up to 50~100 DEG C, holding Constant temperature 1~6 hour, obtains viscous liquid；

2) particle diameter is added in the viscous liquid prepared by step 1) for 0.1~10 μm of silicon or its oxide particle, stirred It is 30~60wt% suspension slurries to obtain solid content；

3) slurry for obtaining step 2) carries out mist projection granulating, obtains porous spherical of the particle diameter distribution between 50~300 μm Grain, i.e. secondary structure particle；

4) secondary structure obtained step 3) is particles filled into fluid bed, is heated to reaction temperature 700 in an inert atmosphere ~1000 DEG C, then pass to carbon source, total air speed of inert gas and carbon source is 500~900h^-1, keep carbon source and inert gas Volume ratio carries out chemical vapor deposition, the reaction time is 20~60min, that is, obtains the silicon of graphene coated between 0.5~2 Or its oxide core shell structure.

2. the preparation method of the core shell structure of a kind of graphene coated silicon as claimed in claim 1 or its oxide, its feature It is：The core shell structure is using the Asia/micron particles of silicon or its oxide as core, graphene for shell, grain size 0.05 ~15 μm；The number of plies of graphene shell is 5~30 layers, and the weight of graphene accounts for 1~8wt% of core-shell structure particles gross weight, and The specific surface area of the core shell structure is equal to or less than original silicon or the specific surface area of its oxide particle.

3. the preparation method of the core shell structure of a kind of graphene coated silicon as claimed in claim 1 or its oxide, its feature It is：The core shell structure is in crystal or amorphous state, its macro morphology be spherical, bar-shaped, sheet, irregular polyhedronses or they In two or more patterns mixture.

4. a kind of preparation method of the core shell structure of graphene coated silicon or its oxide according to claim 1,2 or 3, It is characterized in that：Species containing carbon binder includes direct-connected, amylopectin, glucose, polysaccharide or polyhydroxy-alcohol；Carbon containing bonding The mass ratio of agent and silicon or its oxide particle is between 0.0005~0.03.

5. a kind of preparation method of the core shell structure of graphene coated silicon or its oxide according to claim 1,2 or 3, It is characterized in that：Mist projection granulating described in step 3) selects atomizer comminutor, and charging rate is 0.5~2L/h, entrance Between temperature is 280~350 DEG C, rotating speed of shower nozzle is 10~20r/min.

6. a kind of preparation method of the core shell structure of graphene coated silicon or its oxide according to claim 1,2 or 3, It is characterized in that：Height of secondary structure particle packing described in step 4) in fluidized-bed reactor is the 1 of fluid bed diameter ~3 times；The carbon source is one or more of combinations in methane, ethane, ethene, acetylene, propane, propylene, benzene and toluene；Institute It is nitrogen, argon gas or the mixture of the two to state inert gas.

7. a kind of preparation method of the core shell structure of graphene coated silicon or its oxide according to claim 1,2 or 3, It is characterized in that：The silicon of the graphene coated obtained in step 4) or its oxide core shell structure are sent into vibrating sieving machine and produced Product separate, and the secondary structure particle not disintegrated for small part, using air-flow crushing, rejoin in fluidized-bed reactor Row graphene shell coats.