CN116093275A - Carbon nanotube reinforced CVD carbon coated SiO x Negative electrode material, preparation and application - Google Patents

Carbon nanotube reinforced CVD carbon coated SiO x Negative electrode material, preparation and application Download PDF

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CN116093275A
CN116093275A CN202211457005.8A CN202211457005A CN116093275A CN 116093275 A CN116093275 A CN 116093275A CN 202211457005 A CN202211457005 A CN 202211457005A CN 116093275 A CN116093275 A CN 116093275A
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周海平
杨彬
周行
吴孟强
张庶
徐自强
冯婷婷
方梓煊
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University of Electronic Science and Technology of China
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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Abstract

The invention provides a carbon nano tube reinforced CVD carbon coated SiO x A composite anode material and a preparation method and application thereof belong to the technical field of electrochemical energy storage material preparation. The method comprises the following steps: siO is made of x Placing the powder in a tube furnace, and using chemical vapor deposition method to deposit SiO x Depositing a carbon coating on the surface of the particles, and then coating SiO x Dispersing the slurry of @ C and CNTs in deionized water, and coating CNTs on SiO by adopting a spray drying method x The @ C surface is formed into a three-dimensional conductive network to obtain SiO x Composite material of @ C @ CNTs. The CVD derived carbon coating enhances structural stability and improves SiO x Is a cyclic performance of (c). CNTs conductive network with 3D structureThe multiplying power performance of the composite material is improved, and a rich way is provided for the transportation of lithium ions. The prepared material has excellent multiplying power performance and cycle performance as a lithium ion battery anode material, and the preparation method is simple and can realize mass production.

Description

Carbon nanotube reinforced CVD carbon coated SiO x Negative electrode material, preparation and application
Technical Field
The invention relates to the technical field of preparation of lithium ion battery anode materials, in particular to a carbon nanotube CNTs reinforced CVD carbon coated SiO x The composite anode material also relates to a preparation method thereof and application of the composite anode material as an anode material of a lithium ion battery.
Background
There is an increasing demand for next generation energy storage devices and systems with high energy density, as well as cost-effective and convenient strategies to provide sustainable electricity for modern lifestyles, placing greater demands on the energy density of Lithium Ion Batteries (LIBs). Currently, increasing energy density by developing high capacity anode materials with appropriate operating potentials is the most viable approach. Recently, siO x (0<x<2) There is increasing interest in the advantages of high theoretical capacity, abundant resources, good environmental affinity, and suitable lithium intercalation potential. SiO compared with pure Si x With lower production costs and smaller volume variations. In particular, lithium silicate (e.g., li 4 SiO 4 And Li (lithium) 2 Si 2 O 5 Etc.) and Li 2 O can relieve SiO x And acts as a stable solid state electrolyte. This is advantageous in maintaining its structural stability and achieving better cycle performance, but at the same time also consumes a large amount of active lithium, resulting in SiO x The first coulombic efficiency (ICE) of the negative electrode material is low. Furthermore, siO x The volume change of the anode still exists, which results in SiO x Crushing/separating of particles and cracking of SEI film.
To solve SiO x Various improvement strategies have been proposed. Two of the most effective measures include: one is to make SiO x Down to the nanometer scale, thereby shortening the electron/lithium ion transport path to ensure good contact of the electrode and electrolyte. However, this method is complicated in process and expensive in preparation. Another method is to use SiO x The particles are composited with the carbon material, which provides enhanced electrical conductivity and partially buffers the volume expansion. In this case, some of the SiO of the core-shell structure x The @ C negative electrode exhibited impressive durability. Under the principle, we have designed a carbon nanotube CNTs-reinforced CVD carbon-coated SiO by combining CVD with spray drying x (SiO x @ C @ CNTs) composite anode material. Wherein, the CVD derived carbon coating enhances the structural stability of the composite material and remarkably improves SiO x Cycle performance of the negative electrode. While the 3D structure carbon nanotube conductive network endows SiO with x The composite material of @ C@CNTs has excellent conductivity, provides a rich path for transporting lithium ions, and effectively improves the rate capability of the composite material.
Disclosure of Invention
The invention aims at SiO x The material has poor circulation performance and conductivity caused by volume change, and is one kind of CVD pyrolytic carbon SiO with CNTs enhancement x A negative electrode composite material. In SiO x The carbon coating on the surface improves the conductivity and has stronger mechanical property to effectively relieve SiO x Is to ensure SiO x Stability of the structure. CNTs can provide more transmission channels for lithium ions and electrons, thereby improving SiO x The rate performance and cycle life of the negative electrode.
The second object of the present invention is to provide a method for preparing CNTs-enhanced CVD carbon-coated SiO which is simple in process, low in cost and easy for mass production x A method of forming the negative electrode material.
A third object of the present invention is to provide a CNTs-reinforced CVD carbon-coated SiO x Application of negative electrode materialThe negative electrode material is used as a negative electrode material of a lithium ion battery, so that the energy density of the lithium ion battery is greatly improved, and the service life of the lithium ion battery is prolonged.
In order to achieve the above purpose, the specific technical scheme of the invention is as follows:
carbon nanotube reinforced CVD carbon-coated SiO x Preparation method of anode material, anode material is prepared by carbon-coated SiO derived from CNTs enhanced CVD x The preparation method comprises the following steps:
step 1: in SiO x Depositing a carbon coating on the surface of the particles by adopting a CVD method to obtain SiO x The @ C composite material comprises the following specific processes: siO is made of x Dispersing the powder in a porcelain boat, placing in a tube furnace, heating to 800-1000 ℃ under an inert atmosphere or nitrogen atmosphere, then introducing carrier gas and carbon source gas for carbon deposition, stopping introducing the carbon source gas after carbon deposition is completed, and naturally cooling to room temperature under the inert atmosphere or nitrogen atmosphere to obtain carbon-coated SiO x SiO of (2) x A @ C composite;
step 2: siO obtained in the step 1 is treated x Dispersing the @ C composite material and CNTs slurry in deionized water, performing ultrasonic treatment for 30min, and stirring for 12h to obtain SiO x Mixed solution of @ C and CNTs;
step 3: spray drying the mixed solution prepared in the step 2, wherein the rotating speed of a peristaltic pump is 10-20r/min, and the frequency of a fan is 10-30Hz; then placing the composite material obtained by spray drying in a tube furnace, heating to 800 ℃ at a heating rate of 5 ℃/min, and performing heat treatment for 2 hours to obtain the CNTs reinforced CVD carbon coated SiO x SiO of (2) x Composite material of @ C @ CNTs.
Preferably, siO with a particle size of 1-10 μm is used in the step 1 x A material.
Preferably, the inert atmosphere in the step 1 is argon or helium, and the flow rate of the inert atmosphere or nitrogen atmosphere is 100sccm.
Preferably, the heating rate of the CVD carbon deposition in the step 1 is 30 ℃/min, the heat preservation time is 30-180min at the carbon deposition temperature, and the CVD carbon deposition is naturally cooled to the room temperature after the carbon deposition is completed.
Preferably, the carbon source gas in the step 1 is one or more mixed gases selected from methane, propylene and acetylene, the flow rate is 20sccm, the carrier gas is hydrogen and argon, and the flow rates are 10sccm and 100sccm, respectively.
Preferably, the CNTs slurry in the step 2 has a solid content of 6.5%, siO x The solid content of the mixed solution of the @ C and the CNTs is between 5 and 10 percent, siO x The mass ratio of the @ C composite material to the CNTs slurry is 1 (2-6).
Preferably, the spray drying process in step 3 has an inlet temperature of 150-200deg.C and an outlet temperature of 80-100deg.C.
In order to achieve the aim of the invention, the invention also provides a CNTs reinforced CVD carbon coated SiO obtained by the preparation method x (SiO x @ C @ CNTs) composite.
To achieve the above object, the present invention also provides a CNTs-reinforced CVD carbon-coated SiO x Application of anode material in preparation of lithium ion secondary battery, siO x The @ C@CNTs composite material is used as a lithium ion battery anode material.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention provides a CNTs reinforced CVD carbon-coated SiO x The preparation method of the anode material comprises the steps of firstly adopting a CVD method to prepare SiO x A carbon coating is deposited on the surface of the particles, and the CVD derived carbon coating effectively improves SiO x The structural stability of the material greatly improves the cycle performance of the material. Then, spray drying method is adopted to produce the SiO x The CNTs conductive network with high flexibility and interconnection structure is coated on the surface of the @ C composite material, so that good electrical contact is provided, the transmission of electrons and ions is greatly improved, and the SiO is remarkably improved x Electrochemical properties of the material.
2. SiO prepared by the invention x The @ C@CNTs composite anode material not only has the advantages of high specific capacity and long cycle life, but also adopts simple and controllable CVD and spray drying processes, can realize mass production, and can meet the requirements of power batteries。
Drawings
FIG. 1 is a SiO of comparative example 1 in accordance with the present invention x SEM images of the material;
FIG. 2 is a SiO obtained after depositing a carbon coating by CVD in step 1 of comparative example 2 of the present invention x SEM image of @ C composite;
FIG. 3 is a SiO obtained in example 2 of the present invention x SEM image of the @ C @ CNTs composite anode material;
FIG. 4 is a diagram showing SiO obtained in comparative example 1 x And SiO obtained in example 2 of the present invention x Raman spectrum diagram of composite anode material of @ C@CNTs;
FIG. 5 is a SiO obtained in example 2 of the present invention x A cycle performance diagram of the @ C @ CNTs composite at a current density of 1A/g;
FIG. 6 shows SiO obtained in example 2 of the present invention x Multiplying power performance graphs of the @ C@CNTs composite material under different current densities.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
Comparative example 1
As shown in FIG. 1, siO is not treated at all x SEM images of the material; as can be seen from FIG. 1, siO x The material is irregular blocks, the surface is smooth and small particles are scattered, siO x The particle size is 1-10 μm.
The electrode sheet used in this comparative example was prepared using SiO without any treatment x The material is used as an active material, the conductive agent is ketjen black, the binder is SONE, and the mass ratio is 8:1:1 are mixed and dissolved in deionized water, and the mixture is magnetically stirred for more than 8 hours to prepare the uniformly dispersed battery slurry for standby. Battery sizing agentUniformly coating on the surface of copper foil, vacuum drying at 80 ℃ for 12 hours, tabletting and weighing for later use. Button half cells (CR 2032) were assembled in a glove box filled with argon and the electrochemical performance of the electrodes was tested. The button half-cell assembly totally adopts lithium sheets as counter electrodes, and the water and oxygen contents in the manufacturing environment are respectively as follows: the water concentration is lower than 0.01ppm and the oxygen concentration is lower than 0.01ppm. The electrolyte component adopted is 1.2M LiPF 6 And (3) dissolving the mixed solution in a mixed solution of which the volume ratio is 3:6:1 and of which the volume ratio is EC:DEC:FEC and the volume ratio is 2% of VC as additives to obtain the mixed solution. Battery cycling performance was tested on a blue device.
Comparative example 2
Comparative example 2 provides a CVD carbon coated SiO x The preparation method of the anode material specifically comprises the following steps:
step 1: in SiO x Depositing a carbon coating on the surface of the particles by adopting a CVD method to form SiO x The @ C composite material comprises the following specific processes: siO is made of x Dispersing powder in a porcelain boat, placing in a tube furnace, heating to 900 ℃ under inert atmosphere, introducing carrier gas and carbon source gas to perform carbon deposition for 120min after the temperature is increased to the temperature, stopping introducing the carbon source gas after carbon deposition is completed, and naturally cooling to room temperature under inert atmosphere to obtain SiO x @ C composite.
As shown in FIG. 2, siO after CVD deposition of the carbon coating x SEM image of @ C composite anode material; as can be seen from FIG. 2, siO obtained after CVD deposition of the carbon coating is compared with comparative example 1 x The microscopic morphology of the @ C composite material did not change significantly, was still an irregular mass, but the surface became rougher. Indicating that CVD carbon deposition does not destroy SiO x Morphology and structure of the material.
Preparation of electrode sheet for comparative example 2 SiO prepared by the method described in comparative example 2 was prepared x The @ C composite material is used as an active material, the conductive agent is ketjen black, the binder is SONE, and the mass ratio is 8:1:1 are mixed and dissolved in deionized water, and the mixture is magnetically stirred for more than 8 hours to prepare the uniformly dispersed battery slurry for standby. Uniformly coating the battery slurry on the surface of a copper foil, vacuum drying at 80 ℃ for 12 hours, tabletting and weighing for later use. Button half cells (CR 2032) were assembled in a glove box filled with argon and the electrochemical performance of the electrodes was tested. The button half-cell assembly totally adopts lithium sheets as counter electrodes, and the water and oxygen contents in the manufacturing environment are respectively as follows: the water concentration is lower than 0.01ppm and the oxygen concentration is lower than 0.01ppm. The electrolyte component adopted is 1.2M LiPF 6 And (3) dissolving the mixed solution in a mixed solution of which the volume ratio is 3:6:1 and of which the volume ratio is EC:DEC:FEC and the volume ratio is 2% of VC as additives to obtain the mixed solution. Battery cycling performance was tested on a blue device.
Example 1
This example 1 provides a carbon nanotube-reinforced CVD carbon-coated SiO x The preparation method of the anode material specifically comprises the following steps:
step 1: in SiO x Depositing a carbon coating on the surface of the particles by adopting a CVD method to form SiO x The @ C composite material comprises the following specific processes: siO is made of x Dispersing the powder in a porcelain boat, placing in a tube furnace, heating to 800 ℃ under an argon atmosphere, wherein the flow rate of the atmosphere is 100sccm, and after the temperature is raised to the temperature, introducing carrier gas and carbon source gas for carbon deposition, wherein the carrier gas is hydrogen and argon, and the flow rates are 10sccm and 100sccm respectively. The carbon source gas is methane, the flow is 20sccm, the heating rate of CVD carbon deposition is 30 ℃/min, the heat preservation time is 30min at the carbon deposition temperature, the carbon source gas is stopped being introduced after the carbon deposition is completed, and the carbon source gas is naturally cooled to the room temperature in the argon atmosphere, thus obtaining the carbon-coated SiO x SiO of (2) x A @ C composite;
step 2: siO obtained in the step 1 is treated x Dispersing the @ C composite material and CNTs slurry in deionized water according to the mass ratio of 1:2, performing ultrasonic treatment for 30min, and stirring for 12h to obtain SiO x Mixed solution of @ C and CNTs, solid content of CNTs slurry is 6.5%, siO x The solid content of the mixed solution of the @ C and the CNTs is 5-10%;
step 3: and (3) spray drying the mixed solution prepared in the step (2), wherein the rotating speed of a peristaltic pump is 10r/min, and the frequency of a fan is 10Hz. The spray drying process had an inlet temperature of 150℃and an outlet temperature of 80 ℃. Then placing the composite material obtained by spray drying in a tube furnace, heating at 5 ℃/minHeating to 800 ℃ at a certain speed for 2h to obtain CNTs reinforced CVD carbon-coated SiO x SiO of (2) x Composite material of @ C @ CNTs.
Preparation of the negative electrode sheet used in this example 1 SiO prepared by the method described in example 1 x The composite material of @ C@CNTs is used as an active material, the conductive agent is ketjen black, the binder is SONE, and the mass ratio is 8:1:1 are mixed and dissolved in deionized water, and the mixture is magnetically stirred for more than 8 hours to prepare the uniformly dispersed battery slurry for standby. And (3) uniformly coating the battery slurry on the surface of the copper foil, drying the battery slurry in vacuum at 80 ℃ for 12 hours, and tabletting and weighing the battery slurry for later use. Button half cells (CR 2032) were assembled in a glove box filled with argon and the electrochemical performance of the electrodes was tested. The button half-cell assembly totally adopts lithium sheets as counter electrodes, and the water and oxygen contents in the manufacturing environment are respectively as follows: the water concentration is lower than 0.01ppm and the oxygen concentration is lower than 0.01ppm. The electrolyte component adopted is 1.2M LiPF 6 And (3) dissolving the mixed solution in a mixed solution of which the volume ratio is 3:6:1 and of which the volume ratio is EC:DEC:FEC and the volume ratio is 2% of VC as additives to obtain the mixed solution. Battery cycling performance was tested on a marchand blue electrical device.
Example 2
This example 2 provides a carbon nanotube-reinforced CVD carbon-coated SiO x The preparation method of the anode material specifically comprises the following steps:
step 1: in SiO x Depositing a carbon coating on the surface of the particles by adopting a CVD method to form SiO x The @ C composite material comprises the following specific processes: siO is made of x Dispersing the powder in a porcelain boat, placing in a tube furnace, heating to 900 ℃ under an argon atmosphere, wherein the flow rate of the atmosphere is 100sccm, and after the temperature is raised to the temperature, introducing carrier gas and carbon source gas for carbon deposition, wherein the carrier gas is hydrogen and argon, and the flow rates are 10sccm and 100sccm respectively. The carbon source gas is methane, the flow is 20sccm, the heating rate of CVD carbon deposition is 30 ℃/min, the heat preservation time is 100min at the carbon deposition temperature, the carbon source gas is stopped being introduced after the carbon deposition is completed, and the carbon coated SiO is obtained by naturally cooling the carbon source gas to the room temperature in the argon atmosphere x SiO of (2) x A @ C composite;
step 2: siO obtained in the step 1 is treated x Dispersing the @ C composite material and CNTs slurry in deionized water according to the mass ratio of 1:4, performing ultrasonic treatment for 30min, and stirring for 12h to obtain SiO x Mixed solution of @ C and CNTs, solid content of CNTs slurry is 6.5%, siO x The solid content of the mixed solution of the @ C and the CNTs is 5-10%;
step 3: and (3) spray drying the mixed solution prepared in the step (2), wherein the rotating speed of a peristaltic pump is 15r/min, and the frequency of a fan is 20Hz. The spray drying process had an inlet temperature of 180℃and an outlet temperature of 90 ℃. Then placing the composite material obtained by spray drying in a tube furnace, heating to 800 ℃ at a heating rate of 5 ℃/min, and performing heat treatment for 2 hours to obtain the CNTs reinforced CVD carbon coated SiO x SiO of (2) x Composite material of @ C @ CNTs.
As shown in FIG. 3, siO was obtained by the production method described in example 2 x SEM image of the @ C @ CNTs composite anode material; as can be seen from FIG. 3, the CVD-derived carbon coating completely covered the SiO x Particle surface, but due to SiO x The particles are irregular masses, resulting in uneven thickness of the derivatized carbon coating and a rough surface. After a layer of CNTs conductive network is coated on the surface through spray drying, the CNTs can be seen to be on SiO x The surface distribution of the @ C particles is uniform, and CNTs not only improve the diffusion rate of lithium ions and the electric conductivity, but also improve SiO x Structural stability of @ C @ CNTs composites.
Preparation of the negative electrode sheet used in this example 2 SiO prepared by the method described in example 2 x The composite material of @ C@CNTs is used as an active material, the conductive agent is ketjen black, the binder is SONE, and the mass ratio is 8:1:1 are mixed and dissolved in deionized water, and the mixture is magnetically stirred for more than 8 hours to prepare the uniformly dispersed battery slurry for standby. And (3) uniformly coating the battery slurry on the surface of the copper foil, drying the battery slurry in vacuum at 80 ℃ for 12 hours, and tabletting and weighing the battery slurry for later use. Button half cells (CR 2032) were assembled in a glove box filled with argon and the electrochemical performance of the electrodes was tested. The button half-cell assembly totally adopts lithium sheets as counter electrodes, and the water and oxygen contents in the manufacturing environment are respectively as follows: the water concentration is lower than 0.01ppm and the oxygen concentration is lower than 0.01ppm. The electrolyte component adopted is 1.2M LiPF 6 And (3) dissolving the mixed solution in a mixed solution of which the volume ratio is 3:6:1 and of which the volume ratio is EC:DEC:FEC and the volume ratio is 2% of VC as additives to obtain the mixed solution. Battery cycling performance was tested on a marchand blue electrical device.
Example 3
Embodiment 3 provides a carbon nanotube-reinforced CVD carbon-coated SiO x The preparation method of the anode material specifically comprises the following steps:
step 1: in SiO x Depositing a carbon coating on the surface of the particles by adopting a CVD method to form SiO x The @ C composite material comprises the following specific processes: siO is made of x Dispersing the powder in a porcelain boat, placing in a tube furnace, heating to 1000 ℃ in an argon atmosphere, wherein the flow rate of the atmosphere is 100sccm, and after the temperature is raised to the temperature, introducing carrier gas and carbon source gas for carbon deposition, wherein the carrier gas is hydrogen and argon, and the flow rates are 10sccm and 100sccm respectively. The carbon source gas is methane gas, the flow is 20sccm, the heating rate of CVD carbon deposition is 30 ℃/min, the heat preservation time is 180min at the carbon deposition temperature, the carbon source gas is stopped being introduced after the carbon deposition is completed, and the carbon source gas is naturally cooled to the room temperature in the argon atmosphere, thus obtaining the carbon-coated SiO x SiO of (2) x A @ C composite;
step 2: siO obtained in the step 1 is treated x Dispersing the @ C composite material and CNTs slurry in deionized water according to the mass ratio of 1:6, performing ultrasonic treatment for 30min, and stirring for 12h to obtain SiO x Mixed solution of @ C and CNTs, solid content of CNTs slurry is 6.5%, siO x The solid content of the mixed solution of the @ C and the CNTs is 5-10%;
step 3: and (3) spray drying the mixed solution prepared in the step (2), wherein the rotating speed of a peristaltic pump is 20r/min, and the frequency of a fan is 30Hz. The spray drying process had an inlet temperature of 200℃and an outlet temperature of 100 ℃. Then placing the composite material obtained by spray drying in a tube furnace, heating to 800 ℃ at a heating rate of 5 ℃/min, and performing heat treatment for 2 hours to obtain the CNTs reinforced CVD carbon coated SiO x SiO of (2) x Composite material of @ C @ CNTs.
Preparation of negative electrode sheet for use in example 3 SiO prepared by the method described in example 3 x Composite material of @ C @ CNTs as living materialThe conductive material is ketjen black, the adhesive is SONE, and the mass ratio is 8:1:1 are mixed and dissolved in deionized water, and the mixture is magnetically stirred for more than 8 hours to prepare the uniformly dispersed battery slurry for standby. And (3) uniformly coating the battery slurry on the surface of the copper foil, drying the battery slurry in vacuum at 80 ℃ for 12 hours, and tabletting and weighing the battery slurry for later use. Button half cells (CR 2032) were assembled in a glove box filled with argon and the electrochemical performance of the electrodes was tested. The button half-cell assembly totally adopts lithium sheets as counter electrodes, and the water and oxygen contents in the manufacturing environment are respectively as follows: the water concentration is lower than 0.01ppm and the oxygen concentration is lower than 0.01ppm. The electrolyte component adopted is 1.2M LiPF 6 And (3) dissolving the mixed solution in a mixed solution of which the volume ratio is 3:6:1 and of which the volume ratio is EC:DEC:FEC and the volume ratio is 2% of VC as additives to obtain the mixed solution. Battery cycling performance was tested on a marchand blue electrical device.
Performance analysis
FIG. 4 shows the SiO obtained in comparative example 1 and example 2 according to the invention x 、SiO x Raman spectrum of @ c @ cnts composites. For SiO x Samples 289, 504 and 924cm -1 The peak at which is related to the vibration of the polysilicon. Depositing a carbon coating on the surface and coating a CNTs conductive network by CVD and spray drying, siO x The characteristic peak intensity of Si in the sample of @ C@CNTs is obviously weakened. In addition, at 1348 and 1596cm -1 Two characteristic peaks appear at the site, defective graphite (D peak) and crystalline graphite (G peak) respectively assigned to the carbon material. The D peak is caused by structural defects and partially disordered structures of the sp2 domain, and the G peak is caused by in-plane stretching vibration of sp2 hybridization of a carbon atom. In addition, at 2698cm -1 There is a 2D peak, which is generated by the scattering of phonons at the boundary of the second order region in the carbon nanotubes.
FIG. 5 shows the SiO obtained in example 2 x Long cycle performance of @ c @ cnts composite anode material at a current density of 1A/g. The reversible capacity is 570mAh/g after activation for 5 circles at a current density of 0.2A/g and then circulation for 1500 circles at a current density of 1A/g, the capacity retention rate reaches 100% (relative to the sixth circle), and the coulombic efficiency after 1500 circulation is close to 100%.
FIG. 6 shows example 2SiO obtained by the preparation x Multiplying power curves of the @ C@CNTs electrodes at different current densities. As can be seen, siO x The reversible capacities of the @ C @ CNTs electrodes were 1277.4, 1094.0, 864.8, 645.1, 484.0 and 325.8mAh/g at current densities of 0.1,0.2,0.5,1, 2 and 4A/g, respectively. After the current density was restored to 0.5A/g, the specific capacity was restored to 989.5mAh/g. Indicating that even when charging and discharging are performed at a high current density, siO x The electrode structure of the @ C@CNTs can also keep good integrity, thereby ensuring SiO x The @ C@CNTs composite anode material has excellent rate capability. The main reason is that CNTs networks can provide adequate pathways and void space for carrier transport to mitigate volume expansion, and CVD derived carbon coatings can also achieve further physical protection to enhance SiO during cycling x Is stable. Thus, two carbon coating constrained SiO x The @ C @ CNTs composite material eventually achieves excellent specific capacity and cycle durability, thereby achieving higher capacity and enhanced rate capability.
In summary, the invention prepares a CNTs reinforced CVD carbon coated SiO by combining CVD and spray drying x Negative electrode material, siO is realized x Uniform coating of surface carbon coating, avoiding electrolyte and SiO caused by uneven coating x The side reaction on the surface of the material improves the circulation stability. Therefore, the preparation method has simple and controllable process, low cost and easy mass production, and the SiO prepared by the method x The composite material of @ C@CNTs has small volume expansion, excellent and stable cycle performance and rate capability, and effectively improves SiO x Electrochemical properties of the negative electrode material.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims of this invention, which are within the skill of those skilled in the art, can be made without departing from the spirit and scope of the invention disclosed herein.

Claims (9)

1. Carbon nanotube reinforced CVD carbon-coated SiO x The preparation method of the anode material is characterized in that the anode material is derived from CNTs reinforced CVD and is coated with SiO x The preparation method comprises the following steps:
step 1: in SiO x Depositing a carbon coating on the surface of the particles by adopting a CVD method to obtain SiO x The @ C composite material comprises the following specific processes: siO is made of x Dispersing the powder in a porcelain boat, placing in a tube furnace, heating to 800-1000 ℃ under an inert atmosphere or nitrogen atmosphere, then introducing carrier gas and carbon source gas for carbon deposition, stopping introducing the carbon source gas after carbon deposition is completed, and naturally cooling to room temperature under the inert atmosphere or nitrogen atmosphere to obtain carbon-coated SiO x SiO of (2) x A @ C composite;
step 2: siO obtained in the step 1 is treated x Dispersing the @ C composite material and CNTs slurry in deionized water, performing ultrasonic treatment for 30min, and stirring for 12h to obtain SiO x Mixed solution of @ C and CNTs;
step 3: spray drying the mixed solution prepared in the step 2, wherein the rotating speed of a peristaltic pump is 10-20r/min, and the frequency of a fan is 10-30Hz; then placing the composite material obtained by spray drying in a tube furnace, heating to 800 ℃ at a heating rate of 5 ℃/min, and performing heat treatment for 2 hours to obtain the CNTs reinforced CVD carbon coated SiO x SiO of (2) x Composite material of @ C @ CNTs.
2. A carbon nanotube reinforced CVD carbon coated SiO according to claim 1 x The preparation method of the anode material is characterized by comprising the following steps: the step 1 adopts SiO with the grain diameter of 1-10 mu m x A material.
3. A carbon nanotube reinforced CVD carbon coated SiO according to claim 1 x The preparation method of the anode material is characterized by comprising the following steps: the inert atmosphere in the step 1 is argon or helium, and the flow of the inert atmosphere or the nitrogen atmosphere is 100sccm.
4. Root of Chinese characterA carbon nanotube reinforced CVD carbon coated SiO according to claim 1 x The preparation method of the anode material is characterized by comprising the following steps: and (2) heating up the CVD carbon deposition in the step (1) at a speed of 30 ℃/min, preserving the temperature for 30-180min at the carbon deposition temperature, and naturally cooling to room temperature after the carbon deposition is completed.
5. A carbon nanotube reinforced CVD carbon coated SiO according to claim 1 x The preparation method of the anode material is characterized by comprising the following steps: the carbon source gas in the step 1 is one or more mixed gases of methane, propylene and acetylene, the flow rate is 20sccm, the carrier gas is hydrogen and argon, and the flow rates are 10sccm and 100sccm respectively.
6. A carbon nanotube reinforced CVD carbon coated SiO according to claim 1 x The preparation method of the anode material is characterized in that the solid content of the CNTs slurry in the step 2 is 6.5 percent, and SiO x The solid content of the mixed solution of the @ C and the CNTs is between 5 and 10 percent, siO x The mass ratio of the @ C composite material to the CNTs slurry is 1 (2-6).
7. A carbon nanotube reinforced CVD carbon coated SiO according to claim 1 x The preparation method of the anode material is characterized by comprising the following steps: the inlet temperature of the spray drying process in the step 3 is 150-200 ℃, and the outlet temperature is 80-100 ℃.
8. CNTs reinforced CVD carbon coated SiO obtained by the method according to any one of claims 1 to 7 x A negative electrode material.
9. The CNTs-reinforced CVD carbon-coated SiO of claim 8 x The application of the anode material in preparing the lithium ion battery is characterized in that: the SiO is x The @ C@CNTs composite material is used as a lithium ion battery anode material.
CN202211457005.8A 2022-11-21 2022-11-21 Carbon nanotube reinforced CVD carbon coated SiO x Negative electrode material, preparation and application Pending CN116093275A (en)

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