Carbon nanotube reinforced CVD carbon coated SiO x Anode material and its preparation and application

Abstract

The present invention provides a carbon nanotube reinforced CVD carbon-coated SiO x composite anode material and its preparation method and application, belonging to the technical field of preparation of electrochemical energy storage materials. The method includes: placing SiO x powder in a tube furnace, and using chemical vapor deposition to deposit a carbon coating on the surface of SiO x particles, and then dispersing SiO x @C and CNTs slurries in deionized water, and using spray drying to coat CNTs on the surface of SiO x @C to form a three-dimensional conductive network, obtaining SiO x @C@CNTs composite material. The CVD-derived carbon coating enhances the structural stability and improves the cycling performance of SiO x . The 3D-structured CNT conductive network improves the rate performance of the composite material and provides rich pathways for the transport of lithium ions. The prepared material has excellent rate performance and cycling performance as the anode material of a lithium-ion battery, and the preparation method is simple and large-scale production can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing anode materials for lithium-ion batteries, and specifically relates to a carbon nanotube CNTs reinforced CVD carbon-coated SiO x composite anode material, and also relates to its preparation method and application as an anode material for lithium-ion batteries. Background Art

[0002] For next-generation energy storage devices and systems with high energy density, as well as the growing demand for cost-effective and convenient strategies to provide sustainable power for modern lifestyles, higher requirements are placed on the energy density of lithium-ion batteries (LIBs). Currently, improving the energy density by developing high-capacity anode materials with appropriate working potentials is the most feasible solution. Recently, SiO x (0 < x < 2) has received increasing attention due to its high theoretical capacity, abundant resources, good environmental affinity, and suitable lithium intercalation potential. Compared with pure silicon, SiO x has lower production costs and smaller volume changes. In particular, lithium silicates (such as Li4SiO4 and Li2Si2O5, etc.) and Li2O formed in-situ during the initial lithiation process can alleviate the volume change of SiO x and act as stable solid electrolytes. This is beneficial to maintaining its structural stability and achieving better cycling performance, but at the same time, it will consume a large amount of active lithium, resulting in a lower initial Coulombic efficiency (ICE) of the SiO x anode material. In addition, the volume change of the SiO x anode still exists, which leads to the crushing / separation of SiO x particles and the cracking of the SEI film.

[0003] To solve the inherent defects of SiO x , various improvement strategies have been proposed. Two of the most effective measures include: one is to reduce SiO x to the nanoscale, thereby shortening the electron / lithium-ion transport path to ensure good contact between the electrode and the electrolyte. However, this method has a complex process and high preparation costs. Another method is to composite SiO x particles with carbon materials, which provides enhanced conductivity and partially buffers the volume expansion. In this case, some core-shell structured SiO x @C anodes exhibit impressive durability. Under this principle, we adopted a method combining CVD and spray drying to design a carbon nanotube CNTs reinforced CVD carbon-coated SiO x (SiO x@C@CNTs) composite anode material. Among them, the CVD-derived carbon coating enhances the structural stability of the composite material and significantly improves the cycle performance of SiO x anode. The 3D carbon nanotube conductive network endows the SiO x @C@CNTs composite material with excellent electrical conductivity, provides a rich path for the transport of lithium ions, and effectively improves the rate performance of the composite material. Summary of the Invention

[0004] The object of the present invention is to propose a CNTs (carbon nanotubes)-reinforced CVD (chemical vapor deposition) pyrolytic carbon SiO x anode composite material for the problems of poor cycle performance and electrical conductivity caused by volume change of SiO x material. The carbon coating on the surface of SiO x improves its electrical conductivity and has strong mechanical properties, which can effectively relieve the volume change of SiO x and ensure the structural stability of SiO x . CNTs can provide more transmission channels for lithium ions and electrons, improving the rate performance and cycle life of the SiO x anode.

[0005] The second object of the present invention is to provide a method for preparing CNTs-reinforced CVD carbon-coated SiO x anode material with simple process, low cost and easy large-scale production.

[0006] The third object of the present invention is to provide an application of CNTs-reinforced CVD carbon-coated SiO x anode material. As the anode material of lithium-ion battery, this anode material not only greatly improves the energy density of lithium-ion battery, but also extends its service life.

[0007] To achieve the above object, the specific technical solutions of the present invention are as follows:

[0008] A method for preparing a carbon nanotube-reinforced CVD carbon-coated SiO x anode material, the anode material is composed of CNTs-reinforced CVD-derived carbon-coated SiO x particles, and the preparation method includes the following steps:

[0009] Step 1: Deposit a carbon coating on the surface of SiO x particles by CVD method to obtain SiO x @C composite material. The specific process is as follows: Place SiO xThe powder is dispersed in a porcelain boat, placed in a tube furnace, heated to 800 - 1000 °C in an inert atmosphere or a nitrogen atmosphere, and then a carrier gas and a carbon source gas are introduced for carbon deposition. After the carbon deposition is completed, the carbon source gas is stopped from being introduced, and it is naturally cooled to room temperature in an inert atmosphere or a nitrogen atmosphere to obtain carbon-coated SiO x SiO x @C composite material;

[0010] Step 2: The SiO x @C composite material and the CNTs slurry are dispersed in deionized water. First, it is ultrasonically treated for 30 min, and then stirred for 12 h to obtain a mixed solution of SiO x @C and CNTs;

[0011] Step 3: The mixed solution prepared in Step 2 is spray-dried with a peristaltic pump rotation speed of 10 - 20 r / min and a blower frequency of 10 - 30 Hz; then the composite material obtained by spray drying is placed in a tube furnace and heated to 800 °C at a heating rate of 5 °C / min for heat treatment for 2 h to obtain CNTs-reinforced CVD carbon-coated SiO x SiO x @C@CNTs composite material.

[0012] As a preferred method, the SiO x material with a particle size of 1 - 10 μm is used in Step 1.

[0013] As a preferred method, the inert atmosphere in Step 1 is argon or helium, and the flow rate of the inert atmosphere or nitrogen atmosphere is 100 sccm.

[0014] As a preferred method, the heating rate of CVD carbon deposition in Step 1 is 30 °C / min, the holding time at the carbon deposition temperature is 30 - 180 min, and after the carbon deposition is completed, it is naturally cooled to room temperature.

[0015] As a preferred method, the carbon source gas in Step 1 is one or a mixture of methane, propylene, and acetylene, with a flow rate of 20 sccm, and the carrier gases are hydrogen and argon with flow rates of 10 sccm and 100 sccm respectively.

[0016] As a preferred method, the solid content of the CNTs slurry in Step 2 is 6.5%, the solid content of the mixed solution of SiO x @C and CNTs is between 5 - 10%, and the mass ratio of the SiO x @C composite material to the CNTs slurry is 1:(2 - 6).

[0017] As a preferred method, the inlet temperature in the spray drying process in step 3 is 150 - 200 °C, and the outlet temperature is 80 - 100 °C.

[0018] To achieve the above-mentioned invention purpose, the present invention also provides a CNTs-enhanced CVD carbon-coated SiO x (SiO x @C@CNTs) composite material.

[0019] To achieve the above-mentioned invention purpose, the present invention also provides an application of a CNTs-enhanced CVD carbon-coated SiO x negative electrode material in the preparation of a lithium-ion secondary battery, wherein the SiO x @C@CNTs composite material is used as the negative electrode material of the lithium-ion battery.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. The present invention provides a preparation method of a CNTs-enhanced CVD carbon-coated SiO x negative electrode material. First, a carbon coating is deposited on the surface of SiO x particles by the CVD method. The carbon coating derived from CVD effectively improves the structural stability of the SiO x material and greatly improves its cycling performance. Then, the spray drying method is used to coat a CNTs conductive network on the surface of the SiO x @C composite material. The CNTs conductive network with high flexibility and interconnected structure provides good electrical contact, greatly improves the transport of electrons and ions, and significantly improves the electrochemical performance of the SiO x material.

[0022] 2. The SiO x @C@CNTs composite negative electrode material prepared by the present invention not only has the advantages of high specific capacity and long cycle life, but also the CVD and spray drying processes adopted are simple and controllable, and large-scale production can be realized, which can meet the requirements of power batteries. Description of the Drawings

[0023] Figure 1 SEM image of the SiO x material of Comparative Example 1 of the present invention;

[0024] Figure 2 SEM image of the SiO x @C composite material obtained after CVD deposition of a carbon coating in step 1 of Comparative Example 2 of the present invention;

[0025] Figure 3 SEM image of the SiO xSEM image of the @C@CNTs composite anode material;

[0026] Figure 4 SiO prepared for Comparative Example 1 x and SiO prepared for Example 2 of the present invention x Raman spectra of the @C@CNTs composite anode material;

[0027] Figure 5 SiO prepared for Example 2 of the present invention x Cycling performance graph of the @C@CNTs composite material at a current density of 1 A / g;

[0028] Figure 6 SiO prepared for Example 2 of the present invention x Rate performance graph of the @C@CNTs composite material at different current densities. Detailed implementation manners

[0029] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0030] Comparative Example 1

[0031] As Figure 1 shown is the SEM image of the SiO x material without any treatment; it can be seen from Figure 1 that the SiO x material is some irregular blocks with a smooth surface and some small particles scattered sporadically. The particle size of the SiO x particles is between 1 - 10 μm.

[0032] The electrode sheets used in this comparative example were prepared using SiO xThe material is used as the active material, the conductive agent is Ketjen black, and the binder is SONE. They are mixed and dissolved in deionized water at a mass ratio of 8:1:1, and magnetically stirred for more than 8 h to prepare a uniformly dispersed battery slurry for use. The battery slurry is uniformly coated on the surface of the copper foil, vacuum dried at 80 °C for 12 h, and then pressed and weighed for use. A button-type half-cell (CR2032) is assembled in a glove box filled with argon, and the electrochemical performance of the counter electrode is tested. Lithium sheets are used as the counter electrodes for all the button-type half-cell assemblies, and the water and oxygen contents in the production environment are: the water concentration is lower than 0.01 ppm, and the oxygen concentration is lower than 0.01 ppm. The electrolyte used is a mixed solution obtained by dissolving 1.2 M LiPF6 in a mixed solution of EC:DEC:FEC with a volume ratio of 3:6:1 and 2% VC as an additive. The battery cycle performance is tested on a BlueTEC device.

[0033] Comparative Example 2

[0034] This Comparative Example 2 provides a CVD carbon-coated SiO x preparation method of the negative electrode material. The preparation method specifically includes the following steps:

[0035] Step 1: Deposit a carbon coating on the surface of SiO x particles by CVD method to form SiO x @C composite material. The specific process is as follows: Disperse the SiO x powder in a porcelain boat, place it in a tubular furnace, heat it to 900 °C under an inert atmosphere. After the temperature rises to the specified temperature, then introduce the carrier gas and the carbon source gas for carbon deposition for 120 min. After the carbon deposition is completed, stop introducing the carbon source gas, and naturally cool it to room temperature under an inert atmosphere to obtain the SiO x @C composite material.

[0036] As Figure 2 shown is the SEM image of the SiO x @C composite negative electrode material after CVD deposition of the carbon coating; From Figure 2 it can be seen that compared with Comparative Example 1, the microscopic morphology of the SiO x @C composite material obtained after CVD deposition of the carbon coating has not changed significantly, and it is still an irregular block, but the surface becomes rougher. It shows that the CVD carbon deposition does not damage the morphology and structure of the SiO x material.

[0037] The electrode plate used in this Comparative Example 2 is prepared by using the SiO xThe @C composite material is used as the active material, the conductive agent is Ketjen black, and the binder is SONE. They are mixed and dissolved in deionized water at a mass ratio of 8:1:1, and magnetically stirred for more than 8 hours to prepare a uniformly dispersed battery slurry for use. The battery slurry is evenly coated on the surface of the copper foil, vacuum dried at 80 °C for 12 hours, and then pressed and weighed for use. A button-type half-cell (CR2032) is assembled in a glove box filled with argon, and the electrochemical performance of the counter electrode is tested. All button-type half-cells are assembled using lithium sheets as the counter electrode, and the water and oxygen content in the production environment are: the water concentration is less than 0.01 ppm, and the oxygen concentration is less than 0.01 ppm. The electrolyte used is a mixed solution obtained by dissolving 1.2 M LiPF6 in a mixed solution of EC:DEC:FEC with a volume ratio of 3:6:1 and 2% VC as an additive. The battery cycle performance is tested on a Blue-Energy device.

[0038] Example 1

[0039] Example 1 provides a preparation method of carbon nanotube-reinforced CVD carbon-coated SiO x negative electrode material. The preparation method specifically includes the following steps:

[0040] Step 1: Deposit a carbon coating on the surface of SiO x particles by CVD method to form SiO x @C composite material. The specific process is as follows: Disperse the SiO x powder in a porcelain boat, place it in a tubular furnace, heat it to 800 °C under an argon atmosphere, and the gas flow rate is 100 sccm. After the temperature rises to the specified temperature, then introduce the carrier gas and the carbon source gas for carbon deposition. The carrier gas is hydrogen and argon, and the flow rates are 10 sccm and 100 sccm respectively. The carbon source gas is methane, and the flow rate is 20 sccm. The heating rate of CVD carbon deposition is 30 °C / min, and the holding time at the carbon deposition temperature is 30 min. After the carbon deposition is completed, stop introducing the carbon source gas, and naturally cool it to room temperature under an argon atmosphere to obtain carbon-coated SiO x SiO x @C composite material;

[0041] Step 2: Disperse the SiO x @C composite material prepared in Step 1 and the CNTs slurry in deionized water at a mass ratio of 1:2. First, ultrasonically treat for 30 min, and then stir for 12 h to obtain a mixed solution of SiO x @C and CNTs. The solid content of the CNTs slurry is 6.5%, and the solid content of the mixed solution of SiO x @C and CNTs is between 5-10%;

[0042] Step 3: Spray-dry the mixed solution prepared in Step 2 with a peristaltic pump speed of 10 r / min and a blower frequency of 10 Hz. The inlet temperature during the spray-drying process is 150 °C, and the outlet temperature is 80 °C. Then, place the composite material obtained by spray-drying in a tube furnace and heat it to 800 °C at a heating rate of 5 °C / min for heat treatment for 2 h to obtain CNTs-reinforced CVD carbon-coated SiO x SiO x @C@CNTs composite material.

[0043] The negative electrode plate used in this Example 1 was prepared by using the SiO x @C@CNTs composite material prepared by the method described in Example 1 as the active material, the conductive agent was Ketjen black, and the binder was SONE. They were mixed and dissolved in deionized water at a mass ratio of 8:1:1, and magnetically stirred for more than 8 h to prepare a uniformly dispersed battery slurry for use. The battery slurry was uniformly coated on the surface of the copper foil, vacuum-dried at 80 °C for 12 h, and then pressed into tablets and weighed for use. A button-type half-cell (CR2032) was assembled in a glove box filled with argon, and the electrochemical performance of the counter electrode was tested. All the button-type half-cells were assembled using lithium sheets as the counter electrode, and the water and oxygen contents in the production environment were: the water concentration was less than 0.01 ppm, and the oxygen concentration was less than 0.01 ppm. The electrolyte used was a mixed solution obtained by dissolving 1.2 M LiPF6 in a mixed solution of EC:DEC:FEC with a volume ratio of 3:6:1 and 2% VC as an additive. The battery cycle performance was tested on a Wuhan Blue Electric device.

[0044] Example 2

[0045] This Example 2 provides a preparation method of a carbon nanotube-reinforced CVD carbon-coated SiO x negative electrode material. The preparation method specifically includes the following steps:

[0046] Step 1: Deposit a carbon coating on the surface of SiO x particles by CVD method to form SiO x @C composite material. The specific process is as follows: Disperse the SiO x powder in a porcelain boat, place it in a tube furnace, heat it to 900 °C under an argon atmosphere, and the flow rate of the atmosphere is 100 sccm. After the temperature rises to the said temperature, then introduce a carrier gas and a carbon source gas for carbon deposition. The carrier gas is hydrogen and argon, and the flow rates are 10 sccm and 100 sccm respectively. The carbon source gas is methane, and the flow rate is 20 sccm. The CVD carbon deposition heating rate is 30 °C / min, and the holding time at the carbon deposition temperature is 100 min. After the carbon deposition is completed, stop introducing the carbon source gas and naturally cool it to room temperature under an argon atmosphere to obtain carbon-coated SiO x SiOx @C composite material;

[0047] Step 2: Disperse the SiO x @C composite material and CNTs slurry in deionized water at a mass ratio of 1:4. First, ultrasonically treat for 30 min, and then stir for 12 h to obtain a mixed solution of SiO x @C and CNTs. The solid content of the CNTs slurry is 6.5%, and the solid content of the mixed solution of SiO x @C and CNTs is between 5 - 10%;

[0048] Step 3: Spray-dry the mixed solution prepared in Step 2. The peristaltic pump speed is 15 r / min, and the fan frequency is 20 Hz. The inlet temperature during the spray-drying process is 180 °C, and the outlet temperature is 90 °C. Then, place the composite material obtained by spray-drying in a tubular furnace and heat-treat it at a heating rate of 5 °C / min to 800 °C for 2 h to obtain SiO reinforced with CNTs and coated with CVD carbon x of SiO x @C@CNTs composite material.

[0049] As Figure 3 shown is the SEM image of the SiO x @C@CNTs composite anode material obtained by the preparation method described in Example 2; It can be seen from Figure 3 that the CVD-derived carbon coating completely covers the surface of the SiO x particles. However, since the SiO x particles are some irregular blocks, the thickness of the derived carbon coating is uneven and the surface is relatively rough. After coating a CNT conductive network on the surface by spray-drying, it can be seen that the CNTs are relatively evenly distributed on the surface of the SiO x @C particles. The CNTs not only improve the lithium-ion diffusion rate and electronic conductivity but also improve the structural stability of the SiO x @C@CNTs composite material.

[0050] The negative electrode plate used in this Example 2 is prepared by using the SiO prepared by the method described in Example 2 xThe CNTs composite material is used as the active material, the conductive agent is Ketjen black, and the binder is SONE. They are mixed and dissolved in deionized water according to the mass ratio of 8:1:1, and magnetically stirred for more than 8 hours to prepare a uniformly dispersed battery slurry for use. The battery slurry is evenly coated on the surface of the copper foil, vacuum dried at 80 °C for 12 hours, and then pressed and weighed for use. A button-type half-cell (CR2032) is assembled in a glove box filled with argon, and the electrochemical performance of the counter electrode is tested. All button-type half-cells are assembled using lithium metal as the counter electrode, and the water and oxygen content in the production environment are: the water concentration is less than 0.01 ppm, and the oxygen concentration is less than 0.01 ppm. The electrolyte used is a mixed solution obtained by dissolving 1.2 M LiPF6 in a mixed solution of EC:DEC:FEC with a volume ratio of 3:6:1 and 2% VC as an additive. The battery cycle performance is tested on a Wuhan Blue Electric device.

[0051] Example 3

[0052] This Example 3 provides a method for preparing a carbon nanotube reinforced CVD carbon-coated SiO x negative electrode material, and the preparation method specifically includes the following steps:

[0053] Step 1: Deposit a carbon coating on the surface of SiO x particles by CVD method to form a SiO x @C composite material. The specific process is as follows: Disperse the SiO x powder in a porcelain boat, place it in a tube furnace, heat it to 1000 °C in an argon atmosphere, and the flow rate of the atmosphere is 100 sccm. After the temperature rises to the specified temperature, then introduce the carrier gas and the carbon source gas for carbon deposition. The carrier gas is hydrogen and argon, and the flow rates are 10 sccm and 100 sccm respectively. The carbon source gas is methane gas, and the flow rate is 20 sccm. The heating rate of CVD carbon deposition is 30 °C / min, and the holding time at the carbon deposition temperature is 180 min. After the carbon deposition is completed, stop introducing the carbon source gas, and naturally cool it to room temperature in an argon atmosphere to obtain the carbon-coated SiO x SiO x @C composite material;

[0054] Step 2: Disperse the SiO x @C composite material and the CNTs slurry in deionized water according to the mass ratio of 1:6, first ultrasonically treat for 30 min, and then stir for 12 h to obtain a mixed solution of SiO x @C and CNTs. The solid content of the CNTs slurry is 6.5%, and the solid content of the mixed solution of SiO x @C and CNTs is between 5-10%;

[0055] Step 3: Spray-dry the mixed solution prepared in Step 2 with a peristaltic pump speed of 20 r / min and a blower frequency of 30 Hz. The inlet temperature during the spray-drying process is 200 °C, and the outlet temperature is 100 °C. Then, place the composite material obtained by spray-drying in a tube furnace and heat-treat it at 800 °C for 2 h with a heating rate of 5 °C / min to obtain CNTs-reinforced CVD carbon-coated SiO x SiO x @C@CNTs composite material.

[0056] The negative electrode plate used in this Example 3 was prepared by using the SiO x @C@CNTs composite material prepared by the method described in Example 3 as the active material, the conductive agent was Ketjenblack, and the binder was SONE. They were mixed and dissolved in deionized water at a mass ratio of 8:1:1 and magnetically stirred for more than 8 h to prepare a uniformly dispersed battery slurry for use. The battery slurry was uniformly coated on the surface of the copper foil, vacuum-dried at 80 °C for 12 h, and then pressed and weighed for use. A button-type half-cell (CR2032) was assembled in a glove box filled with argon to test the electrochemical performance of the counter electrode. All button-type half-cells were assembled using lithium metal as the counter electrode, and the water and oxygen contents in the production environment were: water concentration < 0.01 ppm, oxygen concentration < 0.01 ppm. The electrolyte used was a mixed solution obtained by dissolving 1.2 M LiPF6 in a mixed solution of EC:DEC:FEC with a volume ratio of 3:6:1 and 2% VC as an additive. The battery cycle performance was tested on a Wuhan Blue Electric device.

[0057] Performance analysis

[0058] Figure 4 The Raman spectra of the SiO x and SiO x @C@CNTs composite materials prepared in Comparative Example 1 and Example 2 of the present invention are shown. For the SiO x sample, the peaks at 289, 504, and 924 cm -1 are related to the vibrations of polysilicon. After depositing a carbon coating and coating a CNT conductive network on the surface by CVD and spray-drying, the intensity of the characteristic peak of Si in the SiO x @C@CNTs sample is significantly weakened. In addition, two characteristic peaks appear at 1348 and 1596 cm -1 , which are attributed to the defective graphite (D peak) and crystalline graphite (G peak) of the carbon material, respectively. The D peak is caused by the structural defects and partial disordered structure of the sp2 domain, and the G peak is caused by the in-plane stretching vibration of sp2 hybridization of carbon atoms. In addition, a 2D peak appears at 2698 cm -1 , which is generated by the second-order zone boundary phonon scattering in the carbon nanotubes.

[0059] Figure 5 shows the long - cycle performance of the SiO x @C@CNTs composite anode material at a current density of 1 A / g. First, it was activated for 5 cycles at a current density of 0.2 A / g, and then cycled 1500 times at a current density of 1 A / g. The reversible capacity was 570 mAh / g, the capacity retention rate reached 100% (relative to the sixth cycle), and the Coulomb efficiency after 1500 cycles was close to 100%.

[0060] Figure 6 shows the SiO prepared in Example 2 x @C@CNTs electrode rate curves at different current densities. It is not difficult to see that the SiO x @C@CNTs electrode had reversible capacities of 1277.4, 1094.0, 864.8, 645.1, 484.0, and 325.8 mAh / g at current densities of 0.1, 0.2, 0.5, 1, 2, and 4 A / g, respectively. When the current density was restored to 0.5 A / g, the specific capacity recovered to 989.5 mAh / g. This indicates that even during charge - discharge at a high current density, the SiO x @C@CNTs electrode structure could maintain good integrity, thus ensuring that the SiO x @C@CNTs composite anode material had excellent rate performance. The main reason is that the CNTs network can provide sufficient pathways and void space for carrier transport to relieve volume expansion, and the CVD - derived carbon coating can also achieve further physical protection to improve the stability of SiO x during the cycling process. Therefore, the SiO x @C@CNTs composite material constrained by the double - carbon coating finally obtained excellent specific capacity and cycle durability, thus achieving higher capacity and enhanced rate ability.

[0061] In summary, the present invention prepared a CNTs - enhanced CVD carbon - coated SiO x anode material by combining CVD and spray - drying methods, achieving uniform coating of the carbon coating on the surface of SiO x , avoiding side reactions between the electrolyte and the surface of the SiO x material caused by uneven coating, and improving the cycle stability. Therefore, the preparation method of the present invention has simple and controllable process, low cost, and is easy to scale up production. The SiO x @C@CNTs composite material prepared by this method has small volume expansion, excellent and stable cycle performance and rate performance, effectively improving the electrochemical performance of the SiO x anode material.

[0062] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A preparation method of a carbon nanotube reinforced CVD carbon-coated SiO x negative electrode material, characterized in that, The anode material consists of CNTs-reinforced CVD-derived carbon-coated SiO x particles, and the preparation method includes the following steps: Step 1: Deposit a carbon coating on the surface of SiO x particles by CVD method to obtain SiO x @C composite material. The specific process is as follows: Disperse SiO x powder in a porcelain boat, place it in a tube furnace, heat it to 800 - 1000 °C in an inert atmosphere or nitrogen atmosphere, then introduce carrier gas and carbon source gas for carbon deposition. After the carbon deposition is completed, stop introducing the carbon source gas and cool it naturally to room temperature in an inert atmosphere or nitrogen atmosphere to obtain SiO x coated with carbon x SiO@C composite material; Step 2: Disperse the SiO x @C composite material and CNTs slurry in deionized water, first perform ultrasonic treatment for 30 min, and then stir for 12 h to obtain a mixed solution of SiO x @C and CNTs; the solid content of the CNTs slurry in Step 2 is 6.5%, and the solid content of the mixed solution of SiO x @C and CNTs is between 5 - 10%, and the mass ratio of the SiO x @C composite material to the CNTs slurry is 1:(2 - 6); Step 3: Spray-dry the mixed solution prepared in Step 2 with a peristaltic pump speed of 10 - 20 r / min and a fan frequency of 10 - 30 Hz; then place the composite material obtained by spray drying into a tube furnace and heat it to 800 °C at a heating rate of 5 °C / min for 2 h to obtain the CNTs-reinforced CVD carbon-coated SiO x SiO x @C@CNTs composite material.

2. A preparation method of a carbon nanotube reinforced CVD carbon-coated SiO x negative electrode material, characterized in that: In step 1, SiO with a particle size of 1 - 10 μm is used. x Material.

3. The preparation method of a carbon nanotube reinforced CVD carbon-coated SiO x negative electrode material, characterized in that: The inert atmosphere in step 1 is argon or helium, and the flow rate of the inert atmosphere or nitrogen atmosphere is 100 sccm.

4. A method for preparing a negative electrode material of carbon nanotube reinforced CVD carbon-coated SiO x , characterized in that: In step 1, the heating rate of CVD carbon deposition is 30 °C / min, the holding time at the carbon deposition temperature is 30 - 180 min. After carbon deposition is completed, it is naturally cooled to room temperature.

5. A preparation method of a carbon nanotube reinforced CVD carbon coated SiO x negative electrode material, characterized in that: The carbon source gas in step 1 is one or a mixture of methane, propylene, and acetylene, and the flow rate is 20 sccm. The carrier gases are hydrogen and argon, and the flow rates are 10 sccm and 100 sccm respectively.

6. The preparation method of a carbon nanotube reinforced CVD carbon-coated SiO x negative electrode material, characterized in that: In step 3, the inlet temperature of the spray drying process is 150 - 200 °C, and the outlet temperature is 80 - 100 °C.

7. The CNTs enhanced CVD carbon-coated SiO obtained by the preparation method according to any one of claims 1 to 6 x negative electrode material.

8. Use of the CNTs-enhanced CVD carbon-coated SiO x negative electrode material in the preparation of a lithium-ion battery, characterized in that: The SiO x @C@CNTs composite material is used as the anode material for lithium-ion batteries.

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