CN112678806A

CN112678806A - Carbon @ SiOx/C @ carbon nanotube composite material and preparation method thereof

Info

Publication number: CN112678806A
Application number: CN202011557828.9A
Authority: CN
Inventors: 周亮; 张媛媛; 沙玉静; 麦立强
Original assignee: Wuhan University of Technology WUT
Current assignee: Wuhan University of Technology WUT
Priority date: 2020-12-25
Filing date: 2020-12-25
Publication date: 2021-04-20
Anticipated expiration: 2040-12-25
Also published as: CN112678806B

Abstract

The invention provides carbon @ SiO_xThe preparation method of the/C @ carbon nanotube composite material comprises the following specific steps: s1, dispersing a silicon source and the carbon nano tube in a mixed solvent, adding ammonia water, and centrifugally drying to obtain the productAn organic silicon @ carbon nanotube composite; s2, placing the organic silicon @ carbon nanotube composite material in a tubular furnace, carrying out primary carbonization in a protective atmosphere, then introducing organic gas for secondary carbonization, and finally cooling to room temperature to obtain carbon @ SiO_xthe/C @ carbon nanotube composite material. The invention utilizes a sol-gel method to grow organic silicon on a carbon nano tube in situ, and the carbon @ SiO is prepared after two times of high-temperature carbonization_xthe/C @ carbon nanotube composite material comprises an inner carbon nanotube, an outer carbon shell and small-particle SiO (silicon dioxide) sandwiched between the carbon shell and the carbon nanotube_xthe/C layer has the synergistic effect of the three-layer structure, so that the volume expansion of the composite material is reduced, and the electronic conductivity is improved.

Description

Carbon @ SiOx/C @ carbon nanotube composite material and preparation method thereof

Technical Field

The invention relates to the technical field of electrochemical energy storage, in particular to carbon @ SiO_xa/C @ carbon nanotube composite material and a preparation method thereof.

Background

New devices typified by portable electronic devices and electric vehicles have placed a great demand on high energy density lithium ion battery technology capable of rapid charging. However, most of the lithium ion batteries at present use a graphite material as a negative electrode, and the theoretical specific capacity of the graphite negative electrode is only 372mAh g^-1The development of lithium ion batteries is severely limited. In contrast, the theoretical specific capacity of the silicon Si negative electrode is up to 4200mAh g^-1And the potential of the deintercalated lithium is comparable to that of graphite, the Si-based negative electrode is one of the best materials to replace the graphite negative electrode in the development process of a battery with high energy and high power density. However, the silicon-based negative electrode material is easy to cause pulverization and shedding of the material structure due to large expansion/contraction in the circulation process, and the industrial development of the silicon-based negative electrode material is seriously hindered.

Silicon-oxygen cathode material SiO_x(0<x<2) The lithium silicate and the lithium oxide substances generated after the material is firstly embedded with lithium can play a certain buffering role on volume expansion, have relatively stable cycle performance and attract the wide attention of researchers; however, the problems of volume expansion and low electronic conductance still exist, and how to reduce the volume expansion and improve the electronic conductance is a problem which needs to be solved at present.

Disclosure of Invention

In view of the above, the present invention is directed to a carbon @ SiO_xa/C @ carbon nanotube composite material and a preparation method thereof for improving SiO_xMaterial for replacing graphite cathodeThe conductivity in lithium ion battery is enlarged, and SiO is enlarged_xThe industrialization advantage of the material.

In order to achieve the purpose, the technical scheme of the invention is realized as follows: carbon @ SiO_xThe preparation method of the/C @ carbon nanotube composite material comprises the following specific steps:

s1, dispersing a silicon source and carbon nanotube particles in a mixed solvent, adding ammonia water, and centrifugally drying to obtain the organic silicon @ carbon nanotube composite material;

s2, placing the organic silicon @ carbon nanotube composite material in a tubular furnace, carrying out primary carbonization in a protective atmosphere, then introducing organic gas for secondary carbonization, and finally cooling to room temperature to obtain carbon @ SiO_xthe/C @ carbon nanotube composite material.

Optionally, the silicon source comprises one or more of vinyltrimethoxysilane, vinyltriethoxysilane, ethynyltriethoxysilane, ethynyltrimethoxysilane, triaminopropyltrimethoxysilane, and triaminopropyltriethoxysilane;

the carbon nanotube particles comprise one or more of single-walled carbon nanotube dispersion liquid, multi-walled carbon nanotube dispersion liquid, single-walled carbon nanotube powder and multi-walled carbon nanotube powder;

the mixed solvent comprises at least one of deionized water, ethanol, ethylene glycol, n-butanol and isopropanol.

Optionally, in S1, the volume/mass ratio of the silicon source to the carbon nanotube particles is 0.001 to 100.

Optionally, the concentration of the aqueous ammonia is (0.01-25) wt.%.

Alternatively, the ammonia water is added at a rate of (0.01 to 20) seconds per drop.

Optionally, in S2, the performing of the primary carbonization under the protective atmosphere specifically includes: under the protective atmosphere, the reaction temperature is controlled to be 100-1500 ℃, the reaction time is 3-12 h, and primary carbonization is carried out.

Optionally, in S2, the introducing organic gas is performed to perform secondary carbonization, specifically: introducing ethylene gas, acetylene gas, benzene steam or toluene steam, controlling the reaction temperature to be 500-1200 ℃ and the reaction time to be 10min-10h, and carrying out secondary carbonization.

Compared with the prior art, the carbon @ SiO provided by the invention_xThe preparation method of the/C @ carbon nanotube composite material has the following advantages:

the method comprises the steps of growing organic silicon on a carbon nano tube in situ by using a sol-gel method to form a shell layer or a beaded shell layer conformal with the carbon nano tube; after twice high-temperature carbonization, the prepared carbon @ SiO_xthe/C @ carbon nanotube composite material comprises an inner carbon nanotube, an outer carbon shell and small-particle SiO (silicon dioxide) sandwiched between the carbon shell and the carbon nanotube_xthe/C layer and the three-layer structure have synergistic effect, so that the volume expansion of the composite material is reduced, and the electronic conductivity is improved, so that carbon @ SiO is used_xWhen the/C @ carbon nanotube composite material is applied to a lithium ion battery cathode material, excellent electrochemical performance is shown, and a new technology is provided for the development of a high-performance cathode material. In addition, the preparation method has the advantages of simple operation process, safe reaction, low equipment cost and high experimental repeatability, and is beneficial to industrial large-scale production and popularization.

The invention also aims to provide carbon @ SiO_xThe composite material of/C @ carbon nanotube for SiO_xThe material has expansion and conductivity problems when used in lithium ion batteries as a replacement for graphite negative electrodes.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

carbon @ SiO_xthe/C @ carbon nano tube composite material adopts the carbon @ SiO_xPreparation method of/C @ carbon nanotube composite material, and carbon @ SiO_xthe/C @ carbon nanotube composite material comprises a carbon nanotube and a shell layer loaded on the surface of the carbon nanotube, wherein the shell layer is in a bead string shape or is matched with the shape of the carbon nanotube.

Optionally, the shell layer comprises particulate SiO in contact with the carbon nanotubes_xa/C layer and a coating layer coated on the SiO_xA carbon shell on the surface of the C layer.

Optionally, the shell layer has a thickness of (1-300) nm.

The carbon @ SiO_xthe/C @ carbon nanotube composite material and the carbon @ SiO_xCompared with the prior art, the preparation method of the/C @ carbon nanotube composite material has the same advantages, and the detailed description is omitted.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief description will be given below to the drawings required for the description of the embodiments or the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.

FIG. 1 is a schematic representation of carbon @ SiO in accordance with an embodiment of the present invention_xA schematic diagram of a synthetic principle of the/C @ carbon nanotube composite material;

FIG. 2 shows carbon @ SiO solid obtained in example 1_xSEM image of/C @ carbon nanotube composite material;

FIG. 3 is a SiO solid obtained in comparative example of example 1_xSEM image of/C composite material;

FIG. 4 shows carbon @ SiO solid obtained in example 1_xthe/C @ carbon nanotube composite material is 0.1A g^-1A lower charge-discharge curve;

FIG. 5 shows the carbon @ SiOx/C @ carbon nanotube composite obtained in example 1 and SiO in comparative example_xThe material/C is 0.5A g^-1Comparative plot of lower cycle performance;

FIG. 6 shows carbon @ SiO solid obtained in example 1_x(iii) the/C @ carbon nanotube composite and the comparative example SiO_xA comparison graph of rate performance of the/C material;

FIG. 7 shows carbon @ SiO solid obtained in example 1_x(iii) the/C @ carbon nanotube composite and the comparative example SiO_xImpedance test comparison graph of the/C material;

FIG. 8 shows carbon @ SiO solid obtained in example 2_xSEM image of/C @ carbon nanotube composite material;

FIG. 9 shows carbon @ SiO solid obtained in example 3_xSEM image of/C @ carbon nanotube composite material;

FIG. 10 is a schematic representation of carbon @ SiO in accordance with an embodiment of the present invention_xPreparation method of/C @ carbon nanotube composite materialIs a schematic flow diagram.

Description of reference numerals:

1-carbon nanotube, 2-organosilicon, 3-SiO_xLayer C, 4-carbon shell.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.

Carbon nanotubes exhibit unique characteristics due to their one-dimensional carbon tube structure, and the loading materials on carbon nanotubes have been widely used in the preparation of various electrode materials. The silicon-oxygen cathode material has relatively good cycle performance due to relatively low expansion compared with nano silicon-carbon, and is a hotspot of industrial research. However, SiO has not been obtained yet_xthe/C homogeneous mixed material is compounded with a carbon nanotube material and developed to be used as a lithium ion battery cathode material.

To solve the above problem, in conjunction with fig. 1 and 10, an embodiment of the present invention provides a carbon @ SiO_xThe preparation method of the/C @ carbon nanotube composite material comprises the following specific steps:

According to the embodiment of the invention, the selected silicon source is hydrolyzed into silanol in ammonia water, the silanol is adsorbed on the carbon nano tube 1 with negative electricity on the surface through the action of hydrogen bonds, and the silanol causes organosilicon to grow on the carbon nano tube 1 through polycondensation reaction to form organosilicon @ carbon nanoRice-tube composites; then, the organic silicon is carbonized to form SiO through high-temperature carbonization and carbon coating_xAtomically homogeneous mixture with C to give carbon @ SiO_xthe/C @ carbon nanotube composite material. The preparation method provided by the embodiment of the invention is simple and safe in reaction, does not need the dangerous and complicated operation step of reducing silicon dioxide by using a metal reducing agent, and the prepared carbon @ SiO_xthe/C @ carbon nanotube composite material comprises an inner carbon nanotube 1, an outer carbon shell 4 and small-particle SiO (silicon dioxide) sandwiched between the carbon shell 4 and the carbon nanotube 1_xthe/C layer 3, the integration of the three carbon structures can greatly improve the electronic conductivity of the composite material, so that carbon @ SiO_xWhen the/C @ carbon nanotube composite material is applied to the cathode material of the lithium ion battery, the excellent electrochemical performance is shown, a new technology is provided for the development of the high-performance cathode material, and the SiO is expanded_xThe industrialization advantage of the material.

Specifically, in step S1, the silicon source includes one or more of vinyltrimethoxysilane, vinyltriethoxysilane, ethynyltriethoxysilane, ethynyltrimethoxysilane, triaminopropyltrimethoxysilane, and triaminopropyltriethoxysilane; the carbon nanotube particles include one or more of a single-walled carbon nanotube dispersion, a multi-walled carbon nanotube dispersion, a single-walled carbon nanotube powder, and a multi-walled carbon nanotube powder. The carbon nano tube is of a one-dimensional structure, so that the transmission path of lithium ions is favorably shortened, and the carbon nano tube is convenient to combine with organic silicon by adopting a dispersion liquid or powder structure. Wherein the volume/mass ratio (mL/mg) of the silicon source to the carbon nanotube particles is 0.001-100.

The mixed solvent comprises at least one of deionized water, ethanol, ethylene glycol, n-butanol and isopropanol. Wherein, when two solvents are adopted, the volume ratio of any two solvents is (1-99) to (99-1).

Compared with the prior art, the preparation method provided by the embodiment of the invention has the advantages that the raw materials are cheap, for example, dangerous and expensive silicon sources such as silane gas are not needed, and the production cost is effectively reduced.

Further, since the silicone 2 grows on the carbon nanotube 1 by the polycondensation reaction between the silanols, the carbon nanotube can be obtainedThe thickness of the organic silicon is adjusted by changing the adding amount of the silicon source; after the organic silicon 1 is carbonized, SiO can be formed_xWith an atomically homogeneous mixture of C, the surface roughness of which is related to the rate of polycondensation between silanols, i.e. carbonized SiO_xThe roughness of the/C layer 3 can be adjusted by changing the concentration of the aqueous ammonia and the dropping speed. In the present embodiment, preferably, the concentration of ammonia water is (0.01-25) wt.%; the rate of addition of ammonia was (0.01-20) sec/drop.

In step S2, carbonizing in a protective atmosphere, specifically: under the protective atmosphere, the reaction temperature is controlled to be 100-1500 ℃, the reaction time is 3-12 h, and primary carbonization is carried out. After primary carbonization, the organosilicon forms SiO_xAtomically homogeneous mixture of SiO with C_xA layer of/C.

In step S2, an organic gas is introduced to perform secondary carbonization, specifically: introducing ethylene gas, acetylene gas, benzene steam or toluene steam, controlling the reaction temperature to be 500-1200 ℃ and the reaction time to be 10min-10h, and carrying out secondary carbonization. Through secondary carbonization, the method is convenient to be carried out on SiO_xThe surface of the/C layer forms a carbon shell which can inhibit the expansion of silicon and maintain the stability of the material structure.

The embodiment of the invention provides carbon @ SiO_xThe preparation method of the/C @ carbon nanotube composite material comprises the steps of growing organic silicon 2 on a carbon nanotube 1 in situ by a sol-gel method, and carbonizing the organic silicon for two times at high temperature to prepare carbon @ SiO_xthe/C @ carbon nanotube composite material comprises an inner carbon nanotube 1, an outer carbon shell 4 and small-particle SiO (silicon dioxide) sandwiched between the carbon shell 4 and the carbon nanotube 1_xthe/C layer 3 has the synergistic effect of the three-layer structure, so that the volume expansion of the composite material is reduced, and the electronic conductivity is improved.

With reference to fig. 1 and 2, the embodiment of the invention further provides carbon @ SiO_xa/C @ carbon nanotube composite material, the carbon @ SiO_xthe/C @ carbon nanotube composite material adopts the weight of carbon @ SiO_xThe preparation method of the/C @ carbon nanotube composite material. The carbon @ SiO_xthe/C @ carbon nanotube composite material comprises a carbon nanotube 1 and a shell layer loaded on the surface of the carbon nanotube 1, wherein the shell layer is in a bead string shape or a shape similar to that of the carbon nanotubeAnd (4) adapting. Wherein the shell layer comprises granular SiO contacting with the carbon nanotube 1_xLayer 3 of/C and wrapping in SiO_xA carbon shell 4 on the surface of the C layer 3.

Thus, SiO_xThe electronic conductivity of the composite material can be improved by three carbon structures, so that the composite material has good electrochemical performance. Further, the shell layer has a thickness of (1-300) nm.

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are examples of experimental procedures not specified under specific conditions, generally according to the conditions recommended by the manufacturer. Unless otherwise indicated, percentages and parts are by mass.

Example 1

This example provides a carbon @ SiO_xThe preparation method of the/C @ carbon nanotube composite material comprises the following specific steps:

1) adding 1mL of vinyltrimethoxysilane and 1.5mL of single-walled carbon nanotube aqueous solution (3mg/mL) into 150mL of distilled water, namely the volume/mass ratio of the silicon source to the carbon nanotube is 0.22, then dropwise adding 25 wt.% of ammonia aqueous solution at the speed of 0.01 second/drop, stirring for 12 hours, centrifuging, washing and drying to obtain the organic silicon @ carbon nanotube composite material.

2) Carrying out primary carbonization on the dried organic silicon @ carbon nanotube composite material in a tubular furnace under the protection of argon, wherein the carbonization time is 4 hours, the carbonization temperature is 800 ℃, then introducing acetylene gas/argon mixed gas for 30 minutes for secondary carbonization, the carbonization time is 30 minutes, the carbonization temperature is 800 ℃, and cooling to room temperature to obtain carbon @ SiO_xthe/C @ carbon nanotube composite material.

FIG. 2 is a representation of carbon @ SiO as obtained in example 1_xSEM image of/C @ carbon nanotube composite material, wherein a) is a scale image of 1 mu m, b) is a scale image of 100nm, and as can be seen from FIG. 2, the whole composite material still maintains a one-dimensional continuous linear structure of the carbon nanotubes, namely SiO_xthe/C material grows on the carbon tube in a bead shape, and the maximum spherical diameter is about 100 nm.

Example 1 comparative example:

1) adding 1.0mL of vinyl trimethoxy silane into 200mL of distilled water, quickly adding 25.0 wt.% of ammonia water solution, stirring for 12 hours, centrifuging, washing and drying to obtain the organic silicon sphere material.

2) Carbonizing the dried organic silicon ball material in a tubular furnace for one time under the protection of argon at the carbonization temperature of 800 ℃ for 4 hours to obtain SiO after cooling to room temperature_xa/C composite material.

FIG. 3 is a SiO solid obtained in comparative example of example 1_xSEM image of/C composite material, as can be seen from FIG. 3, SiO shown in comparative example_xthe/C composite material is in a monodisperse spherical shape, and the particle size is about 300 nm.

Example 1 carbon @ SiO_x(iii) the/C @ carbon nanotube composite and the SiO obtained in the comparative example_xThe application of the/C composite material as the negative electrode material of the lithium ion battery is as follows:

the preparation process of the electrode slice respectively adopts carbon @ SiO_x/C @ carbon nanotube composite material and SiO_xthe/C composite material is used as an active material, acetylene black is used as a conductive agent, and sodium alginate is used as a binder. Fully mixing the three materials according to the mass ratio of 7:2:1, dispersing the mixture in deionized water, and uniformly stirring to obtain the electrode slurry. And coating the surface of the copper foil, and drying at 70 ℃ to obtain the negative electrode plate. Wherein the electrolyte is 1mol/L LiPF₆The material is prepared into a CR2016 button cell by adopting a/EC (lithium ion battery electrolyte) + DMC (dimethyl carbonate) (volume ratio of 1:1) and 5% FEC (fluoroethylene carbonate) membrane, wherein the membrane is a glass fiber GF/A membrane, and the CR2016 button cell is used for testing the half-cell buckling performance of the material.

FIG. 4 shows carbon @ SiO solid obtained in example 1_xthe/C @ carbon nanotube composite material is 0.1A g^-1The following charge-discharge curves, as can be seen from FIG. 4, carbon @ SiO_xthe/C @ carbon nanotube composite material is 0.1A g^-1The specific capacity of the next first circulation discharge is 1553mAh g^-1。

FIG. 5 shows carbon @ SiO solid obtained in example 1_x(iii) the/C @ carbon nanotube composite and the comparative example SiO_xThe material/C is 0.5A g^-1The cycle performance of carbon @ SiO, as can be seen from FIG. 5_x/C @ carbon nanotube composite materialAt 0.5A g^-1After 500 cycles of lower circulation, the capacity is 573.9mAh g^-1Attenuation to 479.45mAh g^-1The capacity retention rate is 83.5%; and SiO of comparative example_xAfter 500 cycles of the/C composite material circulation, the capacity is 642.9mAh g^-1Attenuation to 406.13mAh g^-1And the capacity retention rate is only 63.2 percent, so that the carbon @ SiO prepared by the invention can be seen_xthe/C @ carbon nanotube composite material shows excellent cycle performance when being used as a lithium ion battery cathode material.

FIG. 6 shows carbon @ SiO solid obtained in example 1_x(iii) the/C @ carbon nanotube composite and the comparative example SiO_xComparison graph of rate performance of/C material, as can be seen from FIG. 6, charging and discharging under large current, carbon @ SiO_xSiO (silicon dioxide) with rapid charge/discharge advantage ratio of/C @ carbon nanotube composite material_xthe/C composite material is more obvious, namely the carbon @ SiO prepared by the invention_xthe/C @ carbon nanotube composite material shows excellent rate capability when being used as a lithium ion battery cathode material, and indicates carbon @ SiO to a certain extent_xthe/C @ carbon nanotube composite material has better quick-charging capability.

FIG. 7 shows carbon @ SiO solid obtained in example 1_x(iii) the/C @ carbon nanotube composite and the comparative example SiO_xComparative graph of impedance test for the/C material, as can be seen in FIG. 7, carbon @ SiO_xThe charge transfer resistance of the/C @ carbon nanotube composite material is smaller and is consistent with the excellent quick charging capability of the battery under high current.

The above properties show that the carbon @ SiO prepared by the invention_xthe/C @ carbon nanotube composite material has excellent electrochemical performance and is a good lithium ion battery cathode material.

Example 2

This example differs from example 1 in that:

in the step 1), 0.3mL of vinyltrimethoxysilane and 2.0mL of a single-walled carbon nanotube aqueous solution (3mg/mL) are added into 200mL of distilled water, namely the volume/mass ratio of the silicon source to the carbon nanotube is 0.05, and 0.3 wt.% of ammonia water is dropwise added at the speed of 5 seconds per drop;

in the step 2), the primary carbonization time is 5 hours, and the carbonization temperature is 800 ℃;

other parameters were the same as in example 1.

FIG. 8 is carbon @ SiO solid prepared in example 2_xSEM image of/C @ carbon nanotube composite material, wherein a) is a 100nm scale image, b) is a 50nm scale image, and as can be seen from FIG. 8, carbon @ SiO prepared in example 2_xThe shape of the/C @ carbon nanotube composite material keeps a one-dimensional continuous linear structure of the carbon nanotube, a shell layer and the carbon nanotube grow on the carbon nanotube conformally, the overall diameter is about 35nm, and the surface is smooth, which shows that the thickness and the surface roughness of the shell layer of the composite material can be adjusted by changing the adding amount of a silicon source and controlling the concentration and the dropping speed of ammonia water.

Example 3

This example differs from example 1 in that:

in the step 1), 0.2mL of vinyltrimethoxysilane and 1.5mL of a single-walled carbon nanotube aqueous solution (3mg/mL) are added into 150mL of distilled water, namely the volume/mass ratio of the silicon source to the carbon nanotube is 0.04, and 0.3 wt.% of ammonia water is dropwise added at the speed of 1 second/drop;

in the step 2), the carbonization time of the primary carbonization is 5 hours, the carbonization temperature is 900 ℃, the carbonization time of the secondary carbonization is 20 minutes, and the carbonization temperature is 900 ℃;

other parameters were the same as in example 1.

FIG. 9 is carbon @ SiO solid prepared in example 3_xSEM image of/C @ carbon nanotube composite material, wherein a) is a 100nm scale image, b) is a 50nm scale image, and as can be seen from FIG. 9, carbon @ SiO prepared in example 3_xThe shape of the/C @ carbon nanotube composite material keeps a one-dimensional continuous linear structure of the carbon nanotube, and the shell grows on the carbon tube in a bead string shape and has a rough surface, which indicates that the thickness and the surface roughness of the shell of the composite material can be adjusted by changing the adding amount of a silicon source and controlling the concentration and the dropping speed of ammonia water.

Example 4

This example differs from example 1 in that:

in the step 1), 0.2mL of vinyltrimethoxysilane and 1.5mL of multiwall carbon nanotube aqueous solution (3mg/mL) are added into a mixed solution of 150mL of distilled water and 50mL of ethanol, namely the volume/mass ratio of a silicon source to the carbon nanotubes is 0.04, and 3 wt.% of ammonia water is dropwise added at the speed of 1 second/drop;

in the step 2), the carbonization time of the primary carbonization is 5 hours, the carbonization temperature is 800 ℃, the carbonization time of the secondary carbonization is 5 minutes, and the carbonization temperature is 800 ℃;

other parameters were the same as in example 1.

Example 5

This example differs from example 1 in that:

in the step 1), 0.6mL of triaminopropyltrimethoxysilane and 2mL of multiwall carbon nanotube aqueous solution (2mg/mL) are added into a mixed solution of 150mL of distilled water and 50mL of ethanol, namely the volume/mass ratio of a silicon source to carbon nanotubes is 0.15, and 2 wt.% of ammonia water solution is dropwise added at the speed of 5 seconds per drop;

in the step 2), the carbonization time of the primary carbonization is 3 hours, the carbonization temperature is 1000 ℃, the carbonization time of the secondary carbonization is 60 minutes, and the carbonization temperature is 1000 ℃;

other parameters were the same as in example 1.

Example 6

This example differs from example 1 in that:

in step 1), 0.4mL of triaminopropyltrimethoxysilane and 5mg of multiwalled carbon nanotubes were added to a water-ethanol mixed solution (water: the volume ratio of ethanol is 1:1) namely, the volume/mass ratio of the silicon source to the carbon nanotube is 0.08, and 2.5 wt.% of ammonia water solution is dripped at the speed of 2 seconds/drip;

in the step 2), the carbonization time of the primary carbonization is 3 hours, the carbonization temperature is 1000 ℃, the carbonization time of the secondary carbonization is 10 minutes, and the carbonization temperature is 1000 ℃;

other parameters were the same as in example 1.

Example 7

This example differs from example 1 in that:

in step 1), 0.8mL of vinyltrimethoxysilane and 5mg of single-walled carbon nanotubes were added to a water-ethanol mixed solution (water: the volume ratio of ethanol is 4: 1) namely, the volume/mass ratio of the silicon source to the carbon nanotube is 0.16, and 25 wt.% of ammonia water solution is dripped at the speed of 2 seconds per drip;

in the step 2), the carbonization time of the primary carbonization is 6 hours, the carbonization temperature is 900 ℃, the carbonization time of the secondary carbonization is 15 minutes, and the carbonization temperature is 900 ℃;

other parameters were the same as in example 1.

Example 8

This example differs from example 1 in that:

in the step 1), 0.4mL of vinyltriethoxysilane and 0.4mL of multiwall carbon nanotube aqueous solution (10mg/mL) are added into 100mL of distilled water, namely the volume/mass ratio of the silicon source to the carbon nanotube is 0.1, and 2 wt.% of ammonia water is dropwise added at the speed of 20 seconds per drop;

in the step 2), the carbonization time of the primary carbonization is 6 hours, the carbonization temperature is 900 ℃, the carbonization time of the secondary carbonization is 10 minutes, and the carbonization temperature is 900 ℃;

other parameters were the same as in example 1.

Example 9

This example differs from example 1 in that:

in the step 1), 0.1mL of vinyltriethoxysilane and 0.5mL of single-walled carbon nanotube aqueous solution (4mg/mL) are added into 100mL of distilled water, namely the volume/mass ratio of the silicon source to the carbon nanotube is 0.05, and 3 wt.% of ammonia aqueous solution is dropwise added at the speed of 15 seconds/drop;

in the step 2), the carbonization time of the primary carbonization is 4 hours, the carbonization temperature is 800 ℃, the carbonization time of the secondary carbonization is 10 minutes, and the carbonization temperature is 800 ℃;

other parameters were the same as in example 1.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims

1. Carbon @ SiO_x/C @ carbon nanotube composite materialThe preparation method of the material is characterized by comprising the following specific steps:

2. The method of claim 1, wherein the silicon source comprises one or more of vinyltrimethoxysilane, vinyltriethoxysilane, ethynyltriethoxysilane, ethynyltrimethoxysilane, triaminopropyltrimethoxysilane, and triaminopropyltriethoxysilane;

3. The method according to claim 1 or 2, wherein a volume/mass ratio of the silicon source to the carbon nanotube particles in S1 is 0.001 to 100.

4. The method according to claim 1, wherein the concentration of the aqueous ammonia is (0.01-25) wt.%.

5. The production method according to claim 1, wherein the ammonia water is added at a rate of (0.01 to 20) sec/drop.

6. The method according to claim 1, wherein in S2, the primary carbonization is performed under a protective atmosphere, specifically:

under the protective atmosphere, the reaction temperature is controlled to be 100-1500 ℃, the reaction time is 3-12 h, and primary carbonization is carried out.

7. The preparation method according to claim 1, wherein in S2, the organic gas is introduced for secondary carbonization, specifically:

introducing ethylene gas, acetylene gas, benzene steam or toluene steam, controlling the reaction temperature to be 500-1200 ℃ and the reaction time to be 10min-10h, and carrying out secondary carbonization.

8. Carbon @ SiO_xA/C @ carbon nanotube composite material, characterized in that the carbon @ SiO of any one of claims 1 to 7 is used_xPreparation method of/C @ carbon nanotube composite material, and carbon @ SiO_xthe/C @ carbon nanotube composite material comprises a carbon nanotube (1) and a shell layer loaded on the surface of the carbon nanotube (1), wherein the shell layer is in a bead string shape or is matched with the shape of the carbon nanotube (1).

9. Carbon @ SiO as in claim 8_xthe/C @ carbon nanotube composite material is characterized in that the shell layer comprises granular SiO in contact with the carbon nanotube (1)_xa/C layer (3) and a coating layer coated on the SiO_xA carbon shell (4) on the surface of the C layer (3).

10. Carbon @ SiO according to claim 8 or 9_xthe/C @ carbon nanotube composite material is characterized in that the thickness of the shell layer is (1-300) nm.