Method for coating graphene through in-situ growth of silica nanoparticles and application of method

Abstract

The invention provides a method for coating graphene through in-situ growth of silica nanoparticles and application of the method, and relates to the technical field of nano material carbon coating modification and graphene growth preparation, the method for coating graphene through in-situ growth of silica nanoparticles comprises the following steps: dissolving a catalyst and melamine in a solvent, and drying to obtain powder A; mixing the powder A with fumed silica nano-powder to obtain powder B; and carrying out chemical vapor deposition reaction on the powder B to grow graphene, so as to obtain the graphene-coated silica nanoparticles. According to the invention, chemical vapor deposition (CVD) is adopted for in-situ growth and coating of graphene on cheap and easily available silica nanoparticles, a catalyst is used for effectively reducing the reaction temperature required by carbon source cracking, and a melamine additive is used for providing gaps among the particles, so that agglomeration, hardening and growth of the silica nanoparticles are avoided.

Description

Technical Field

[0001] The invention relates to the technical fields of carbon coating modification of nano materials and graphene growth preparation, and in particular to a method for in-situ growth of silicon-oxygen nanoparticles and coating of graphene and application thereof. Background Art

[0002] With the booming development of the lithium battery industry, the demand for lithium-ion batteries is gradually moving towards high capacity, high energy and longer cycle life. The graphite negative electrode currently used is close to its theoretical specific capacity of 372mAh / g, which obviously can no longer meet the high energy and high capacity requirements mentioned above. The emergence of silicon negative electrode provides a new solution to this demand. Unlike the intercalation reaction of the layered graphite negative electrode, the silicon negative electrode with a tetrahedral structure undergoes a silicon-lithium alloying process of lithium ions and silicon atoms during charging. Since the silicon negative electrode has a stronger lithium insertion ability than the graphite negative electrode, the theoretical specific capacity of the silicon negative electrode is much higher than that of the graphite negative electrode, reaching 4200mAh / g.

[0003] At present, the commonly used silicon-based negative electrode materials are divided into two categories: silicon-carbon oxide composite materials and silicon-carbon composite materials. However, in the actual application of silicon negative electrodes, it is found that with the cycle of alloying and dealloying during the charge and discharge process, its structure will expand greatly. This volume change will induce the accumulation of stress inside the electrode, leading to the occurrence of problems such as active particle pulverization, electrode structure destruction, and rapid capacity decay. At the same time, the SEI film on the surface of the silicon negative electrode will rupture as the volume of silicon changes, causing the SEI film to rupture and regenerate in the subsequent charge and discharge process, resulting in a large loss of active lithium, thereby reducing the service life. In addition, there are problems such as low initial coulomb efficiency and poor conductivity compared to carbon materials, which limit the practical application of silicon negative electrode materials.

[0004] Carbon coating of the core-shell structure on the silicon-based negative electrode can significantly slow down the occurrence of the above-mentioned problems. The presence of the carbon shell can alleviate the volume expansion and structural fragmentation and pulverization during the cycle, slow down the frequent formation of SEI film caused by structural fragmentation, resulting in large consumption of lithium ions, increase in irreversible capacity and decrease in capacity, improve conductivity and thus enhance rate performance.

[0005] Graphene, carbon atoms are arranged in sp 2 Compared with other materials in the carbon material family, the two-dimensional material of a single layer of carbon atoms bonded in a hybrid manner has the best electrical, thermal and mechanical properties. There are also related studies that use it to coat silicon-based negative electrode materials to improve cycle stability, rate performance and first efficiency. Commonly used methods for carbon coating and graphene coating of silicon negative bases include ball milling, deflagration, spray drying, pyrolysis sintering and CVD chemical vapor deposition.

[0006] SCI document "SiOx Encapsulated in Graphene Bubble Film: An Ultrastable Li-Ion Battery Anode" uses stirring, ultrasonic and ball milling processes to fully mix silicon dioxide nanoparticles and graphene oxide and heat treats them at 800℃ for 3h to obtain graphene-encapsulated silicon-carbon negative electrode materials. The material shows excellent cycle stability and rate performance, but the process of this method is relatively complicated. The physical mixing method adopted inevitably introduces impurities and moisture, and there is also a prominent interface bonding problem between graphene and silicon oxide nanoparticles. Weak interface bonding will lead to larger interface electron scattering, causing the local cross-sectional resistance to increase, resulting in the appearance of hot spots and battery failure; SCI document "Preparation and electrochemical properties of core-shelled silicon-carbon composites as anode materials for lithium-ion Batteries》 adopts the method of mechanical ball milling and heat treatment, mixes nano silicon and artificial graphite by mechanical ball milling, and then heat treats them at 850℃ for 2h in a nitrogen atmosphere to obtain carbon-coated silicon negative electrode material, but this method has problems such as uneven coating and poor interface bonding, and the process is time-consuming, nano silicon is expensive, and is not suitable for large-scale production; China's invention patent "A method for synthesizing carbon-coated silicon dioxide nanomaterials, CN110451514 A" uses benzoic acid and silicon tetrachloride as carbon source and silicon source respectively, and uses detonation method to prepare carbon-coated silicon dioxide nanoparticles.Due to the instantaneous nature of the detonation process, the thickness of the carbon layer coating under this method is not easy to accurately control and the rate is not easy to control. It is also very dangerous and cannot achieve large-scale mass production. The Chinese invention patent "A carbon-coated hollow silica composite material and its preparation method, CN112897536A" uses phenolic resin as a carbon source to coat hollow silica balls, and then carbonizes at 500-900°C for 3-6h to obtain amorphous carbon-coated hollow silica materials. However, the carbon layer coated by this method is amorphous carbon, which has a loose and disordered structure and is prone to peeling off during the charge and discharge cycle, thereby causing the battery performance to deteriorate. In addition, the pyrolysis and carbonization of this process takes a long time and is mainly concentrated in laboratory micro-preparation, which is not suitable for large-scale production. The SCI document "Scalable synthesis of silicon-nanolayer-embedded graphite for high-energy lithium-ion Batteries》Use silane and acetylene as silicon and carbon sources, and use CVD chemical vapor deposition method to first deposit nano-silicon on the surface and inside of porous carbon balls, and then grow a layer of carbon coating on the nano-silicon. The obtained carbon-coated silicon negative electrode has an ultra-high first coulomb efficiency of 92% and an ultra-high capacity retention rate of 96%. However, the silicon source used is silicon tetrachloride, which is expensive, unstable, flammable and explosive, which is also the current constraint of this technology.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] One of the purposes of the present invention is to provide a method for in-situ growth of graphene coated on silicon oxide nanoparticles, so as to solve at least one of the technical problems existing in the prior art. The method for in-situ growth of graphene coated on silicon oxide nanoparticles comprises the following steps: dissolving a catalyst and melamine in a solvent, and obtaining powder A after drying; mixing the powder A with fumed silica nanopowder to obtain powder B; and subjecting the powder B to chemical vapor deposition reaction to grow graphene to obtain graphene-coated silicon oxide nanoparticles. The present invention adopts chemical vapor deposition CVD to in-situ grow and coat graphene on cheap and readily available silicon oxide nanoparticles, and the use of a catalyst effectively reduces the reaction temperature required for carbon source cracking. The use of melamine additive provides gaps between particles, thereby avoiding the occurrence of agglomeration, compaction, and growth of silicon oxide nanoparticles.

[0009] The second object of the present invention is to provide a method for in-situ growth of silicon-oxygen nanoparticles coated with graphene and its application in the preparation of graphene-coated silicon-oxygen nanoparticles.

[0010] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0011] In a first aspect, the present invention provides a method for in-situ growth of silicon-oxygen nanoparticles coated with graphene, the method comprising the following steps:

[0012] The catalyst and melamine are dissolved in a solvent and dried to obtain powder A;

[0013] Mixing the powder A with fumed silica nanopowder to obtain powder B;

[0014] The powder B is subjected to a chemical vapor deposition reaction to grow graphene, thereby obtaining graphene-coated silicon-oxygen nanoparticles.

[0015] Further, the catalyst includes at least one of metal salts containing copper and nickel elements;

[0016] Preferably, the added amount of the catalyst is X% of the mass of the fumed silica nanopowder by the metal elements contained in the catalyst, wherein 0<X≤10.

[0017] Furthermore, the solvent includes at least one of ethanol and deionized water.

[0018] Furthermore, the mass ratio of the powder A to the fumed silica is 1-3:1.

[0019] Furthermore, the particle size of the fumed silica nanopowder is 10-30 nm.

[0020] Further, the chemical vapor deposition reaction includes: growing graphene on the powder B according to a set growth program;

[0021] Preferably, the powder B is loaded into a crucible and then placed in a tube furnace for growth;

[0022] The growth procedure includes: sequentially performing a temperature increase treatment, a temperature-keeping growth treatment and a temperature decrease treatment on the powder B.

[0023] Preferably, the inert gas includes at least one of argon and helium.

[0024] Furthermore, the heat preservation growth includes: introducing a carrier gas and a carbon source gas into the powder B to grow graphene;

[0025] Preferably, the carrier gas is hydrogen, and the carbon source gas includes at least one of methane, ethylene, acetylene, ethanol, and acetone;

[0026] Preferably, the gas flow ratio of the carbon source to the carrier gas is 1:1-5;

[0027] Preferably, the heat preservation growth time is 15-45min;

[0028] Preferably, the temperature of the thermal insulation growth is 750-900°C.

[0029] Furthermore, the cooling treatment includes naturally cooling the product to room temperature after the graphene growth is completed.

[0030] Furthermore, the method for in-situ growth of silicon-oxygen nanoparticles coated with graphene comprises the following steps:

[0031] S1. Weigh a certain amount of catalyst and melamine in proportion, stir and mix in solution and dry to obtain pretreated powder A;

[0032] S2. Weigh a certain amount of the powder A of step S1 and the fumed silica nanopowder according to the ratio and stir and mix to obtain a mixed powder B;

[0033] S3. Powder B is loaded into a crucible and placed in a tube furnace for growth according to the set growth program. After the growth is completed, it is naturally cooled to room temperature and taken out to obtain graphene-coated silicon oxide nanoparticles.

[0034] In a second aspect, the present invention provides an application of the method for in-situ growth of silicon-oxygen nanoparticles coated with graphene in the preparation of graphene-coated silicon-oxygen nanoparticles.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The method for in-situ growth of silicon-oxygen nanoparticles and coating of graphene provided by the present invention promotes the cracking of carbon sources by introducing catalysts, increases the concentration of carbon active substances, reduces the temperature of graphene growth and coating, and avoids the agglomeration, melting and agglomeration, and growth of silicon-oxygen nanoparticles;

[0037] (2) The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene provided by the present invention utilizes the metal atoms in the catalyst and the silicon-oxygen nanoparticles to generate MSI metal-carrier interface interaction at the interface to efficiently promote the migration and diffusion of carbon atoms, thereby obtaining a high-quality graphene coating layer;

[0038] (3) The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene provided by the present invention uses melamine as a carrier for uniformly dispersing and anchoring the catalyst, which is conducive to uniform mixing of the catalyst and the silicon-oxygen nanoparticles, thereby obtaining a uniform graphene coating layer during the catalytic growth process;

[0039] (4) The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene provided by the present invention utilizes the gas released by the decomposition of melamine to provide a micro-atmosphere around the silicon-oxygen nanoparticles, generate micro-region floating, accelerate the mass transfer diffusion and adsorption collision of the activated carbon material in the particles, thereby improving the coating quality and coating uniformity, while avoiding the agglomeration of the silicon-oxygen nanoparticles;

[0040] (5) The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene provided by the present invention can effectively inhibit the sp 3 Generation of amorphous carbon to obtain high quality sp 2 Graphene coating;

[0041] (6) Using cheap and readily available nano-scale fumed silica as raw material, the process is simple and the effect is significant. It can be mass-produced in fluidized beds, rotary kilns and other equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 This is a physical photo of the graphene-coated silicon oxide nanoparticle powder prepared in Example 1 of the present invention;

[0044] Figure 2 This is a scanning electron microscope image of graphene-coated silicon oxide nanoparticles prepared in Example 1 of the present invention;

[0045] Figure 3 The EDX spectrum and element proportions of the graphene-coated silicon-oxygen nanoparticles prepared in Example 1 of the present invention;

[0046] Figure 4 This is the Raman spectrum of the graphene-coated silicon-oxygen nanoparticles prepared in Example 1 of the present invention;

[0047] Figure 5 This is a scanning electron microscope image of graphene-coated silicon oxide nanoparticles prepared in Example 2 of the present invention;

[0048] Figure 6 The EDX spectrum and element proportions of the graphene-coated silicon-oxygen nanoparticles prepared in Example 2 of the present invention;

[0049] Figure 7This is the Raman spectrum of the graphene-coated silicon oxide nanoparticles prepared in Example 2 of the present invention;

[0050] Figure 8 This is a scanning electron microscope image of graphene-coated silicon oxide nanoparticles prepared in Example 3 of the present invention;

[0051] Fig. 9 This is the Raman spectrum of the graphene-coated silicon-oxygen nanoparticles prepared in Example 3 of the present invention;

[0052] Fig.10 This is a scanning electron microscope image of graphene-coated silicon oxide nanoparticles prepared in Example 4 of the present invention;

[0053] Fig.11 This is a scanning electron microscope image of graphene-coated silicon oxide nanoparticles prepared in Example 5 of the present invention;

[0054] Fig.12 This is a scanning electron microscope image of graphene-coated silicon oxide nanoparticles prepared in Example 6 of the present invention;

[0055] Fig.13 This is a scanning electron microscope image of graphene-coated silicon oxide nanoparticles prepared in Example 7 of the present invention;

[0056] Fig.14 This is a scanning electron microscope image of graphene-coated silicon oxide nanoparticles prepared in Example 8 of the present invention;

[0057] Fig.15 This is a scanning electron microscope image of graphene-coated silicon oxide nanoparticles prepared in Example 9 of the present invention;

[0058] Fig.16 This is a scanning electron microscope image of graphene-coated silicon oxide nanoparticles prepared in Example 10 of the present invention;

[0059] Fig.17 This is a scanning electron microscope image of graphene-coated silicon oxide nanoparticles prepared in Example 11 of the present invention;

[0060] Fig.18 This is a scanning electron microscope image of graphene-coated silicon oxide nanoparticles prepared in Example 12 of the present invention;

[0061] Fig.19 This is a scanning electron microscope image of the graphene-coated silicon oxide nanoparticles prepared in Example 14 of the present invention. DETAILED DESCRIPTION

[0062] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear, however, in the case of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-limiting.

[0063] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] A first aspect of the present invention provides a method for in-situ growth of silicon-oxygen nanoparticles coated with graphene, the method comprising the following steps:

[0065] The catalyst and melamine are dissolved in a solvent and dried to obtain powder A;

[0066] Mixing the powder A with fumed silica nanopowder to obtain powder B;

[0067] The powder B is subjected to a chemical vapor deposition reaction to grow graphene, thereby obtaining graphene-coated silicon-oxygen nanoparticles.

[0068] In the present invention, chemical vapor deposition (CVD) is used to in-situ grow and coat graphene on cheap and readily available silicon oxygen nanoparticles. On the one hand, the present invention accelerates the cracking of the carbon source by introducing a catalyst to increase the concentration of the active carbon species, and at the same time constructs an MSI metal-carrier interface interaction on the surface of the silicon oxygen nanoparticles. The interface interaction can accelerate the migration and diffusion of carbon atoms, thereby obtaining a high-quality graphene coating layer. On the other hand, melamine is introduced as an additive. The introduction of melamine can effectively disperse and anchor the catalyst evenly, realize the uniform mixing and distribution of the catalyst and the silicon oxygen nanoparticles, and uniformly catalyze the growth of graphene. At the same time, the gas released by the decomposition of melamine in the growth stage can provide a micro-atmosphere for the reaction, form micro-region floating, provide gaps between particles, facilitate the mass transfer process of the active carbon species in the gas phase, accelerate the contact and collision of the silicon oxygen particles with the active carbon species, thereby achieving rapid and uniform growth and coating. The use of the catalyst effectively reduces the reaction temperature required for the cracking of the carbon source, and the use of the melamine additive provides gaps between the particles, thereby avoiding the occurrence of agglomeration, hardening, and growth of the silicon oxygen nanoparticles.

[0069] Further, the catalyst includes at least one of metal salts containing copper and nickel elements;

[0070] Preferably, the catalyst comprises at least one of cupric chloride, cupric nitrate, nickel chloride, nickel nitrate and hydrates thereof, and on this basis, may further comprise at least one of ferric chloride, ferric nitrate, cobalt chloride, cobalt nitrate and hydrates thereof;

[0071] In the present invention, the catalyst is preferably a copper-containing metal salt and a mixed metal salt containing copper elements, a nickel-containing metal salt and a mixed metal salt containing nickel elements, which can be summarized as: XaY1-a (X = Cu, Ni; Y = other metal elements, such as Fe, Co; where 0 < a ≤ 1).

[0072] Preferably, the added amount of the catalyst is X% of the mass of the fumed silica nanopowder by the metal elements contained in the catalyst, wherein 0<X≤10.

[0073] Furthermore, the solvent includes at least one of ethanol and deionized water.

[0074] In the present invention, the solvent used is a liquid that can dissolve the catalyst metal salt but not dissolve melamine.

[0075] Furthermore, the mass ratio of the powder A to the fumed silica is 1-3:1, for example, 1:1, 2:1, 3:1, etc., and more preferably 1:1.

[0076] Furthermore, the particle size of the fumed silica nanopowder is 10-30 nm, for example, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, etc. The corresponding particle size can be selected according to the actual usage scenario.

[0077] Further, the chemical vapor deposition reaction includes: growing graphene on the powder B according to a set growth program;

[0078] Preferably, the growth procedure comprises: sequentially performing a temperature increase treatment, a temperature-keeping growth treatment and a temperature decrease treatment on the powder B;

[0079] Preferably, the powder B is loaded into a crucible and then placed in a tube furnace for growth.

[0080] In the present invention, the growth procedure includes three stages: heating-keeping growth-cooling.

[0081] Furthermore, the temperature raising treatment includes: introducing an inert gas into the powder B to heat the powder B;

[0082] Preferably, the inert gas includes at least one of argon and helium.

[0083] Furthermore, the heat preservation growth includes: introducing a carrier gas and a carbon source gas into the powder B to grow graphene;

[0084] Preferably, the carrier gas is hydrogen, and the carbon source gas includes at least one of methane, ethylene, acetylene, ethanol, and acetone, more preferably ethylene and acetylene;

[0085] Preferably, the gas flow ratio of the carbon source to the carrier gas is 1:1-5, for example, 1:1, 1:2, 1:3, 1:4, 1:5, etc., more preferably 1:2;

[0086] Preferably, the heat preservation growth time is 15-45 minutes, for example, it can be 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, etc., and more preferably 30 minutes;

[0087] Preferably, the temperature of the thermal insulation growth is 750-900°C, for example, it can be 750°C, 800°C, 850°C, 900°C, etc., and more preferably 850°C.

[0088] Furthermore, the cooling treatment includes naturally cooling the product to room temperature after the graphene growth is completed.

[0089] The second aspect of the present invention provides an application of the method for in-situ growth of silicon-oxygen nanoparticles coated with graphene in the preparation of graphene-coated silicon-oxygen nanoparticles.

[0090] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0091] Example 1

[0092] This embodiment provides a method for in-situ growth of silicon-oxygen nanoparticles coated with graphene, comprising the following steps:

[0093] S1. Weigh 2 g of melamine and 0.0536 g of copper chloride dihydrate in a beaker, add an appropriate amount of ethanol, stir and heat, and after drying, obtain a mixed powder A in which each portion of melamine is loaded with a portion of silicon dioxide and 1% of copper is added;

[0094] S2. Weigh 0.5 g of the mixed powder A and 0.5 g of fumed silica powder and stir and mix evenly to obtain a mixed powder B;

[0095] Wherein, the particle size of the fumed silica nanopowder is 10-30nm;

[0096] S3. Load powder B into a crucible and place it in a tubular furnace. Heat it with an appropriate amount of inert gas argon. When the temperature reaches 850°C, introduce 10sccm of ethylene and 20sccm of hydrogen on the basis of the inert gas. After reacting for 30 minutes, turn off the introduction of ethylene and hydrogen. Cool naturally to room temperature under an inert atmosphere and take out to obtain graphene-coated silicon oxide nanoparticle composite powder.

[0097] Example 2

[0098] This embodiment provides a method for in-situ growth of silicon oxide nanoparticles and coating graphene. The difference from Example 1 is that the weighed amount of copper chloride dihydrate in step S1 is changed to 0.1073 g to obtain a mixed powder A in which each portion of melamine is loaded with one portion of silicon dioxide and an equivalent of 2% of copper element is added. The other steps and parameters are consistent with Example 1.

[0099] Example 3

[0100] This embodiment provides a method for in-situ growth of silicon oxide nanoparticles and coating graphene. The difference from Example 1 is that the weighed amount of copper chloride dihydrate in step S1 is changed to 0.01610 g to obtain a mixed powder A in which each portion of melamine is loaded with one portion of silicon dioxide and an equivalent of 0.3% copper element is added. The other steps and parameters are consistent with Example 1.

[0101] Example 4

[0102] This embodiment provides a method for in-situ growth of silicon oxide nanoparticles and coating graphene. The difference from Example 1 is that the weighed amount of copper chloride dihydrate in step S1 is changed to 0.1609 g to obtain a mixed powder A in which each portion of melamine is loaded with one portion of silicon dioxide and an equivalent of 3% of copper element is added. The other steps and parameters are consistent with Example 1.

[0103] Example 5

[0104] This embodiment provides a method for in-situ growth of silicon oxide nanoparticles and coating graphene. The difference from Example 1 is that the weighed amount of copper chloride dihydrate in step S1 is changed to 0.26826 g to obtain a mixed powder A in which each portion of melamine is loaded with one portion of silicon dioxide and an equivalent of 5% copper element is added. The other steps and parameters are consistent with Example 1.

[0105] Example 6

[0106] This embodiment provides a method for in-situ growth of silicon oxide nanoparticles and coating graphene. The difference from Example 1 is that the weighed amount of copper chloride dihydrate in step S1 is changed to 0.53652 g to obtain a mixed powder A in which each portion of melamine is loaded with one portion of silicon dioxide and an equivalent of 10% copper element is added. The other steps and parameters are consistent with Example 1.

[0107] Example 7

[0108] This embodiment provides a method for in-situ growth of silicon oxide nanoparticles and coating graphene. The difference from Embodiment 1 is that the catalyst in step S1 is replaced with copper nitrate trihydrate, and the weighed amount is correspondingly changed to 0.0760 g to obtain a mixed powder A in which each portion of melamine is loaded with one portion of silicon dioxide and an equivalent of 1% of copper element is added. The other steps and parameters are consistent with Embodiment 1.

[0109] Example 8

[0110] This embodiment provides a method for in-situ growth of silicon oxide nanoparticles and coating graphene. The difference from Example 1 is that the catalyst in step S1 is replaced with nickel chloride hexahydrate, and the weighed amount is correspondingly changed to 0.0810 g to obtain a mixed powder A in which each portion of melamine is loaded with one portion of silicon dioxide and an equivalent of 1% of nickel element is added. The other steps and parameters are consistent with Example 1.

[0111] Example 9

[0112] This embodiment provides a method for in-situ growth of silicon oxide nanoparticles coated with graphene. The difference from embodiment 1 is that the catalyst in step S1 is replaced with a mixture of copper chloride dihydrate and cobalt chloride hexahydrate, the weighed amounts of which are 0.02683 g and 0.0404 g, respectively, to obtain a mixture of 1% Cu2O3 added per melamine. 0.5 Co 0.5 Mixed powder A of copper and cobalt elements, other steps and parameters are consistent with those in Example 1.

[0113] Example 10

[0114] This embodiment provides a method for in-situ growth of silicon oxide nanoparticles coated with graphene. The difference from embodiment 1 is that the catalyst in step S1 is replaced with a mixture of nickel chloride hexahydrate and cobalt chloride hexahydrate, the weights of which are 0.0405 g and 0.0404 g, respectively, to obtain a mixture of one part of melamine loaded with one part of silicon dioxide and 1% Ni added. 0.5 Co 0.5 Mixed powder A of copper and cobalt elements, other steps and parameters are consistent with those in Example 1.

[0115] Embodiment 11

[0116] This embodiment provides a method for in-situ growth of silicon-oxygen nanoparticles coated with graphene, comprising the following steps:

[0117] S1. Weigh 6 g of melamine and 0.0536 g of copper chloride dihydrate in a beaker, add an appropriate amount of ethanol, stir and heat, and after drying, obtain a mixed powder A in which three parts of melamine are loaded with one part of silicon dioxide and 1% of copper is added;

[0118] S2. Weigh 1.5 g of the mixed powder A and 0.5 g of fumed silica powder and stir and mix evenly to obtain a mixed powder B;

[0119] S3. Load powder B into a crucible and place it in a tubular furnace. Heat it with an appropriate amount of inert gas helium. When the temperature reaches 750°C, introduce 10 sccm of methane and 10 sccm of hydrogen on the basis of the inert gas. After reacting for 45 minutes, turn off the introduction of methane and hydrogen. Cool naturally to room temperature under an inert atmosphere and take out to obtain graphene-coated silicon oxide nanoparticle composite powder.

[0120] Example 12

[0121] This embodiment provides a method for in-situ growth of silicon-oxygen nanoparticles coated with graphene, comprising the following steps:

[0122] S1 and S2: consistent with steps S1 and S2 of Example 1;

[0123] S3. Load powder B into a crucible and place it in a tubular furnace. Heat it with an appropriate amount of inert gas helium. When the temperature reaches 900°C, introduce 10sccm of acetylene and 50sccm of hydrogen on the basis of the inert gas. After reacting for 15 minutes, turn off the introduction of acetylene and hydrogen. Cool naturally to room temperature under an inert atmosphere and take out to obtain graphene-coated silicon oxide nanoparticle composite powder.

[0124] Embodiment 13

[0125] This embodiment provides a method for in-situ growth of silicon-oxygen nanoparticles and coating graphene, which is different from Embodiment 1 in that:

[0126] S1. Weigh 8 g of melamine and 0.0536 g of copper chloride dihydrate in a beaker, add an appropriate amount of ethanol, stir and heat, and after drying, obtain a mixed powder A in which one part of silica is added to four parts of melamine and 1% of copper is added;

[0127] S2. Weigh 2 g of the mixed powder A and 0.5 g of fumed silica powder and stir and mix evenly to obtain a mixed powder B;

[0128] Step S3 is consistent with that in Example 1.

[0129] Embodiment 14

[0130] This embodiment provides a method for in-situ growth of silicon oxide nanoparticles coated with graphene. The difference from Embodiment 1 is that the amount of ethylene introduced in step S3 is changed to 50 sccm, and the other steps and parameters are consistent with Embodiment 1.

[0131] Comparative Example 1

[0132] This comparative example provides a method for in-situ growth of graphene coated on the surface of silicon-oxygen nanoparticles, comprising the following steps:

[0133] Except that melamine is not added to load the catalyst, the other steps are the same as those in Example 1, namely:

[0134] S1. Weigh 0.0134 g of copper chloride dihydrate and 0.5 g of fumed silica powder and stir and mix;

[0135] S2. Load the powder in step S1 into a crucible and place it in a tubular furnace. Heat it with an appropriate amount of inert gas. When the temperature reaches 850°C, introduce 10 sccm of ethylene and 20 sccm of hydrogen on the basis of the inert gas. After reacting for 30 minutes, turn off the introduction of ethylene and hydrogen. Cool naturally to room temperature under an inert atmosphere and take it out.

[0136] Comparative Example 2

[0137] This comparative example provides a method for in-situ growth of graphene coated on the surface of silicon-oxygen nanoparticles, comprising the following steps:

[0138] Except that no catalyst is added, the other steps are the same as those in Example 1, namely:

[0139] S1. Weigh 0.5 g of melamine and 0.5 g of fumed silica powder and stir and mix;

[0140] S2. Load the powder in step S1 into a crucible and place it in a tubular furnace. Heat it with an appropriate amount of inert gas. When the temperature reaches 850°C, introduce 10 sccm of ethylene and 20 sccm of hydrogen on the basis of the inert gas. After reacting for 30 minutes, turn off the introduction of ethylene and hydrogen. Cool naturally to room temperature under an inert atmosphere and take it out.

[0141] Comparative Example 3

[0142] This comparative example provides a method for in-situ growth of silicon oxide nanoparticles and coating graphene, which is different from Example 1 in that the catalyst in step S1 is replaced with a mixture of cobalt chloride hexahydrate, weighing 0.08075 g, to obtain a mixed powder A in which each portion of melamine is loaded with one portion of silicon dioxide and added with an equivalent of 1% cobalt element, and the other steps and parameters are consistent with Example 1.

[0143] Test samples: Graphene-coated silicon oxide nanoparticles prepared in Examples 1-14 and Comparative Examples 1-3.

[0144] Test results:

[0145] like Figure 1-4 As shown, the actual picture of the graphene-coated silicon oxide nanoparticle powder material prepared in Example 1 is as follows Figure 1 As shown in the figure, ① is the raw material of fumed silica, ② is the mixed powder before growth, and ③ is the actual picture of graphene-coated silicon oxide nanoparticle powder obtained after growth. It can be seen that the pure white fumed silica powder is still fluffy after being loaded with catalyst and melamine, and there is no obvious agglomeration and uneven color, which means that under this process, the catalyst is evenly anchored and dispersed on melamine and evenly mixed with fumed silica, which is very important for the high-quality and uniform coating of graphene on the surface of silicon oxide particles in the later stage. After growth, what is finally obtained is a black loose powder with uniform color from top to bottom, inside and outside, and evenly dispersed without agglomeration. The scanning electron microscope picture of the product obtained in Example 1 is as follows. Figure 2 As shown, in addition to the uniform color appearance seen in the macroscopic view, the SEM microscopic view further shows that the nanoparticle powder has uniform particle size and complete structure, and the boundaries between the silicon oxide particles are clear, without agglomeration and fusion. Under this process, the surface of the silicon oxide particles can be uniformly coated with graphene in situ, avoiding the occurrence of powder agglomeration and uneven mixing, poor interface bonding, and powder agglomeration that exist in the traditional preparation method. The powder prepared in Example 1 was characterized by EDX energy spectrum, and the results are shown in the figure. Figure 3 As shown in the figure, it can be seen that the powder mainly contains four elements: silicon, oxygen, carbon and copper, without other impurities. The results of the multi-point energy spectrum are also consistent, further indicating that the coating is successful and uniform. The graphene on the surface of the silicon-oxygen nanoparticles prepared in Example 1 was characterized by Raman, and the results are shown in the figure. Figure 4 As shown in the figure, it can be clearly seen that graphene has three sharp and highly symmetrical characteristic peaks: -1 D peak at 1580cm -1 The G peak at 2700 cm -1 2D peak at , where ID / IG = 0.989.

[0146] like Figure 5-7 As shown, the scanning electron microscope image of the product obtained in Example 2 is as follows Figure 5 As shown in the figure, it can be clearly seen that the nanoparticle powder has uniform particle size and complete structure, and the boundaries between silicon-oxygen particles are clear, without agglomeration or fusion. Figure 6As shown, the powder mainly contains four elements: silicon, oxygen, carbon and copper, without other impurities. Compared with the results in Example 1, when the catalyst is increased to 2%, the proportion of carbon in the obtained powder also increases exponentially, which is due to the increase in the amount of deposited coating caused by the increase in carbon active species cracked by the catalyst. The results of the multi-point energy spectrum are also consistent, further illustrating the success and uniformity of the coating. The graphene on the surface of the silicon-oxygen nanoparticles prepared in Example 2 was characterized by Raman, and the results are shown in the figure. Figure 7 As shown in the figure, it is obvious that there are three sharp and highly symmetrical characteristic peaks of graphene: -1 D peak at 1580cm -1 The G peak at 2700 cm -1 2D peak at , where ID / IG = 0.995.

[0147] like Figure 8-9 As shown, the scanning electron microscope image of the product obtained in Example 3 is as follows Figure 8 As shown in FIG. 1 , it can be clearly seen that the nanoparticle powder has uniform particle size and complete structure, and the boundaries between silicon-oxygen particles are clear, without agglomeration or fusion. The graphene on the surface of the silicon-oxygen nanoparticles prepared in Example 3 was characterized by Raman, and the results are shown in FIG. Fig. 9 As shown in the figure, it can be clearly seen that graphene has three sharp and highly symmetrical characteristic peaks: -1 D peak at 1580cm -1 The G peak at 2700 cm -1 2D peak at , where ID / IG = 0.997.

[0148] like Figure 10-12 As shown, the SEM morphology of Examples 4-6 is characterized as follows: Figure 10-12 The obtained nanoparticle powder has uniform particle size and complete structure, with obvious boundaries between silicon-oxygen particles, no agglomeration and no fusion. However, as the amount of catalyst added increases, obvious traces of large-sized copper nanoparticles appear in the powder.

[0149] like Fig.13 As shown, Fig.13 This is a scanning electron microscope image of the product obtained in Example 7. It can be clearly seen that the nanoparticle powder has uniform particle size and complete structure, and the boundaries between the silicon oxide particles are obvious, without agglomeration or fusion.

[0150] like Fig.14 As shown, Fig.14 This is a scanning electron microscope image of the product obtained in Example 8. It can be clearly seen that the nanoparticle powder has uniform particle size and complete structure, and the boundaries between silicon oxygen particles are obvious, without agglomeration and fusion. The nickel catalyst can also achieve good catalytic growth of coated graphene.

[0151] like Fig.15 As shown, Fig.15 This is a scanning electron microscope image of the product obtained in Example 9. Under the action of the bimetallic catalyst, it can be clearly seen that the nanoparticle powder has uniform particle size and complete structure, and the boundaries between the silicon oxide particles are obvious, without agglomeration and fusion.

[0152] like Fig.16 As shown, Fig.16 This is a scanning electron microscope image of the product obtained in Example 10. Under the action of the bimetallic catalyst, it can be clearly seen that the nanoparticle powder has uniform particle size and complete structure, and the boundaries between the silicon oxide particles are obvious, without agglomeration and fusion.

[0153] like Figure 17-18 As shown, the overall size of the product particles obtained in Examples 11-12 is uniform, the structure is complete, the boundaries between the silicon-oxygen particles are obvious, there is no agglomeration, and no fusion, but because the carbon source used in Example 11 is methane, the cracking temperature of methane is higher than that of ethylene, so that the active carbon material that can be cracked at 750°C is slightly less, but the graphene coating can also be successfully grown. Similarly, in Example 12, the carbon source used is changed to acetylene and the temperature is increased to 900°C, and the carbon active material cracked increases significantly, so that a thicker layer of graphene coating can be grown per unit time.

[0154] The product obtained in Example 13 showed uneven color, that is, the powder color on the surface was darker, while the color inside gradually became lighter, resulting in uneven coating and no coating. This was mainly because the addition of too much melamine led to the release of a large amount of gas during high-temperature decomposition, which caused an imbalance in the micro-floating state and excessive nitrogen-containing active gas released by the decomposition of melamine. An appropriate nitrogen-containing atmosphere is beneficial to inhibit the formation of amorphous carbon to generate high-quality graphene, while an excessive amount will lead to etching of the carbon layer, resulting in failure to coat.

[0155] like Fig.19 As shown, Fig.19 This is a scanning electron microscope image of the product obtained in Example 14. Under the microscopic view, the nanoparticle powder has uniform particle size and complete structure, and the boundaries between silicon-oxygen particles are clear, without agglomeration and fusion. However, when the powder is observed macroscopically with the naked eye, it can be found that the powder on the surface of the crucible has slight flocculent agglomerates. This is because at a higher carbon source concentration, the supply exceeds the demand, and a significant concentration gradient of the carbon source appears, resulting in thick amorphous carbon deposition on the surface of the powder.

[0156] The powders obtained in Comparative Examples 1 and 2 show obvious uneven growth. Basically, only the surface powder has a small amount of carbon deposition, while the internal powder is still in the same state as before the reaction. It can be seen that the two additives, catalyst and melamine, are indispensable. The presence of the catalyst can accelerate the cracking of the carbon source, provide the concentration of carbon active species required for uniform growth and coating of graphene on the surface of silicon oxide nanoparticles, and can also interact with silicon oxide particles to construct MSI metal-carrier interface, promote the migration, diffusion and growth of carbon atoms on the surface of silicon oxide particles, thereby improving the growth rate and growth quality; melamine can provide a micro-atmosphere to produce micro-floatation, so as to accelerate the mass transfer and collision of carbon active species between particles, thereby improving the uniformity of growth and coating, and avoiding agglomeration and compaction of particles.

[0157] In comparative example 3, cobalt catalyst was used alone, and the experimental results showed that graphene could not be grown. It can be seen that other metals need to be compounded with copper or nickel to grow graphene.

[0158] In summary, the method for in-situ growth and coating of graphene on the surface of silicon oxide nanoparticles of the present invention increases the concentration of carbon active species and accelerates the migration and diffusion of carbon atoms on the surface of silicon oxide nanoparticles by introducing a catalyst to catalyze the cracking of carbon sources and constructing an MSI metal-carrier interface interaction, thereby achieving the acquisition of a high-quality graphene coating layer; the additive melamine is introduced as a dispersing anchoring agent for the catalyst and a micro-atmosphere is provided to produce micro-region floating, thereby promoting mass transfer and collision of carbon active substances between particles, thereby achieving uniform coating of graphene on the surface of silicon oxide particles. The method has a simple process, obvious effect, and can realize large-scale preparation of graphene-coated silicon oxide nanoparticle composite materials.

[0159] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for in-situ growth of silicon-oxygen nanoparticles and coating graphene, characterized in that: The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene comprises the following steps: The catalyst and melamine are dissolved in a solvent and dried to obtain powder A; Mixing the powder A with fumed silica nanopowder to obtain powder B; The powder B is subjected to a chemical vapor deposition reaction to grow graphene, thereby obtaining graphene-coated silicon-oxygen nanoparticles.

2. The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene according to claim 1, characterized in that: The catalyst includes at least one of metal salts containing copper and nickel elements; Preferably, the added amount of the catalyst is X% of the mass of the fumed silica nanopowder by the metal elements contained in the catalyst, wherein 0<X≤10.

3. The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene according to claim 1, characterized in that: The solvent includes at least one of ethanol and deionized water.

4. The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene according to claim 1, characterized in that: The mass ratio of the powder A to the fumed silica is 1-3:

1.

5. The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene according to claim 1, characterized in that: The particle size of the fumed silica nanopowder is 10-30 nm.

6. The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene according to claim 1, characterized in that: The chemical vapor deposition reaction comprises: growing graphene on the powder B according to a set growth program; Preferably, the growth procedure includes: sequentially subjecting the powder B to a temperature increase treatment, temperature-maintained growth, and a temperature decrease treatment.

7. The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene according to claim 6, characterized in that: The temperature raising treatment comprises: introducing an inert gas into the powder B to heat the powder B; Preferably, the inert gas includes at least one of argon and helium.

8. The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene according to claim 6, characterized in that: The heat preservation growth comprises: introducing a carrier gas and a carbon source gas into the powder B to grow graphene; Preferably, the carrier gas is hydrogen, and the carbon source gas includes at least one of methane, ethylene, acetylene, ethanol, and acetone; Preferably, the gas flow ratio of the carbon source to the carrier gas is 1:1-5; Preferably, the heat preservation growth time is 15-45min; Preferably, the temperature of the thermal insulation growth is 750-900°C.

9. The method for in-situ growth of silicon-oxygen nanoparticles coated with graphene according to claim 6, characterized in that: The cooling treatment includes naturally cooling the product to room temperature after the graphene growth is completed.

10. Use of the method for in-situ growth of silicon-oxygen nanoparticles coated with graphene as claimed in any one of claims 1 to 9 in preparing graphene-coated silicon-oxygen nanoparticles.

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