阅读说明：本技术 一种基于持续电接触网络的自发碎化硅电极及其制备方法 (Self-breaking silicon electrode based on continuous electric contact network and preparation method thereof ) 是由 吴子平 张志勇 罗琴 胡英燕 尹艳红 于 2021-08-15 设计创作，主要内容包括：本发明涉及一种基于持续电接触网络的自发碎化硅电极及其制备方法,通过碳纳米管网络固定硅颗粒,在碳层的包覆下锚定该网络结构与硅颗粒,得到具有柔性的且结构稳定的复合薄膜作硅负极。通过高能的碳纳米管凝胶体在乙醇中的强力聚合作用,形成的网络结构固定住分散在乙醇溶液中的硅颗粒。网络间留有的间隙可以作为硅颗粒循环膨胀的预留空间,同时可被电解液填充；碳层的包覆在加强网络结构的同时,外延了网络的电接触位点。硅颗粒循环膨胀碎化之后,该网络结构可以接住纳米硅颗粒,提供持续的电接触,进而提高碎化硅颗粒的活性,实现硅负极的高性能应用。本发明制备工艺适用于亚微米及微米硅颗粒作为负极,也可用于30-100 nm粒径的硅颗粒作为负极,简单实用,成本低廉,易实现规模化商业生产。(The invention relates to a self-breaking silicon electrode based on a continuous electric contact network and a preparation method thereof. The network structure formed by the strong polymerization of the high energy carbon nanotube gel in ethanol immobilizes the silicon particles dispersed in the ethanol solution. Gaps left among the networks can be used as reserved spaces for silicon particle cyclic expansion and can be filled with electrolyte; the carbon layer wraps the reinforcing network structure and extends the electrical contact sites of the network. After the silicon particles are circularly expanded and crushed, the network structure can catch the nano silicon particles to provide continuous electric contact, so that the activity of the crushed silicon particles is improved, and the high-performance application of the silicon cathode is realized. The preparation process is suitable for submicron and micron silicon particles as the negative electrode, can also be used for silicon particles with the particle size of 30-100 nm as the negative electrode, is simple and practical, has low cost, and is easy to realize large-scale commercial production.)

1. A self-fragmenting silicon electrode based on a continuous electrical contact network, comprising: the preparation method sequentially comprises the following steps:

step one, preparing a composite film of carbon nano tube coated silicon particles: pouring 30 nm-10 μm diameter powder silicon particles into a certain amount of ethanol to obtain silicon particles with concentration of 1-20 mg ml^-1The silicon/ethanol solution is subjected to ultrasonic dispersion for later use; preparing carbon nanotube aerogel continuum by floating catalytic cracking method, collecting the continuum and simultaneously matching with a sprayer for 0.1-10 ml min^-1Spraying an ethanol solution containing silicon particles on the aerogel continuum at a speed, wherein the continuum with extremely high surface energy is quickly shrunk under the action of ethanol, and is connected to the silicon particles dispersed in the ethanol; repeating the operation to obtain a composite film with the thickness of 5-60 mu m, and removing the film for later use after drying;

step two, soaking treatment: preparing polyvinylpyrrolidone and ethanol into a solution according to the mass fraction of 0.1-5% in a beaker, and uniformly dispersing for later use; soaking the composite film in the first step in a solution at room temperature and normal pressure for 2-60 min, and wrapping the soaked silicon particles and the network structure with polyvinylpyrrolidone to form an organic coating layer; taking out the film, laying the film flat, drying the film and then removing the film for later use;

step three, heat treatment of the composite film: according to the carbonization temperature of the polyvinylpyrrolidone organic coating layer, the membrane soaked in the step two is placed in a high-temperature furnace cavity under the protective atmosphere at 500-^oC, preserving heat for 0.5-5 h, cooling and taking out after the coating is completely carbonized to obtain a film with silicon particles doubly coated by a carbon nanotube film and a carbon layer, converting the carbonized coating into a conductive carbon layer, and anchoring the network structure and the silicon particles while further extending the electric contact of the filmA locus; cutting the film into a suitable shape results in a self-fragmenting silicon electrode based on a continuous electrical contact network.

2. The self-fragmenting silicon electrode based on a continuous electrical contact network as claimed in claim 1, wherein: the unit area loading capacity of the silicon on the composite film obtained in the step one is 0.2-10 mg cm^-2。

3. The self-fragmenting silicon electrode based on a continuous electrical contact network as claimed in claim 1, wherein: in the step one, the sprayer is one of a commercial spray bottle, an electrostatic powder sprayer or an electrostatic powder gun and the like.

4. The self-fragmenting silicon electrode based on a continuous electrical contact network as claimed in claim 1, wherein: and the device used for dispersing in the second step is one of a microwave ultrasonic device, a vibration ultrasonic device or a stirrer and the like.

5. The self-fragmenting silicon electrode based on a continuous electrical contact network as claimed in claim 1, wherein: the equipment used in the high temperature furnace chamber in the third step is one of a horizontal low temperature furnace, a horizontal high temperature furnace, a vertical low temperature furnace or a vertical high temperature furnace and the like.

6. A preparation method of a spontaneous fragmentation silicon electrode based on a continuous electric contact network is characterized by comprising the following steps: the method sequentially comprises the following steps:

step one, preparing a composite film of carbon nano tube coated silicon particles: pouring 30 nm-10 μm diameter powder silicon particles into a certain amount of ethanol to obtain silicon particles with concentration of 1-20 mg ml^-1The silicon/ethanol solution is subjected to ultrasonic dispersion for later use; preparing carbon nanotube aerogel continuum by floating catalytic cracking method, collecting the continuum and simultaneously matching with a sprayer for 0.1-10 ml min^-1The ethanol solution containing the silicon particles is sprayed on the aerogel continuum at a speed, the continuum with extremely high surface energy is quickly shrunk under the action of ethanol, and the aerogel continuum is connected to a gridSilicon particles dispersed in ethanol; repeating the operation to obtain a composite film with the thickness of 5-60 mu m, and removing the film for later use after drying;

step two, soaking treatment: preparing polyvinylpyrrolidone and ethanol into a solution according to the mass fraction of 0.1-5% in a beaker, and uniformly dispersing for later use; soaking the composite film in the first step in a solution at room temperature and normal pressure for 2-60 min, and wrapping the soaked silicon particles and the network structure with polyvinylpyrrolidone to form an organic coating layer; taking out the film, laying the film flat, drying the film and then removing the film for later use;

step three, heat treatment of the composite film: according to the carbonization temperature of the polyvinylpyrrolidone organic coating layer, the membrane soaked in the step two is placed in a high-temperature furnace cavity under the protective atmosphere at 500-^oC, preserving heat for 0.5-5 h, cooling and taking out after the coating is completely carbonized to obtain a carbon nanotube film and carbon layer double-coated silicon particle film, converting the carbonized coating into a conductive carbon layer, and anchoring the network structure and the silicon particles while further extending the electric contact sites of the film; cutting the film into a suitable shape results in a self-fragmenting silicon electrode based on a continuous electrical contact network.

7. The method of claim 6, wherein the method comprises the steps of: the unit area loading capacity of the silicon on the composite film obtained in the step one is 0.2-10 mg cm^-2。

8. The method of claim 6, wherein the method comprises the steps of: in the step one, the sprayer is one of a commercial spray bottle, an electrostatic powder sprayer or an electrostatic powder gun and the like.

9. The method of claim 6, wherein the method comprises the steps of: and the device used for dispersing in the second step is one of a microwave ultrasonic device, a vibration ultrasonic device or a stirrer and the like.

10. The method of claim 6, wherein the method comprises the steps of: the equipment used in the high temperature furnace chamber in the third step is one of a horizontal low temperature furnace, a horizontal high temperature furnace, a vertical low temperature furnace or a vertical high temperature furnace and the like.

Technical Field

The invention relates to a spontaneous fragmentation silicon electrode based on a continuous electric contact network and a preparation method thereof. In particular to a technology which fixes silicon particles through an anchored carbon nano tube network and releases the expansion stress of the silicon particles by utilizing the gaps among the networks so as to stabilize the structure, provide continuous electric contact and realize the application of high performance of a silicon electrode.

Background

With the rapid popularization of high-capacity and high-power electricity utilization terminals, the energy density of commercial lithium ion batteries cannot meet the requirements of human beings. In the future, it is necessary to develop a positive electrode material and a negative electrode material with higher energy density to fill up the huge gap of the current demand of portable electronic products or electric vehicles for high specific energy storage devices.

Among many novel high energy density anode and cathode materials, the practical application of silicon is in the forefront. The silicon cathode which is preliminarily commercialized is one of silicon-carbon cathodes, and is characterized in that the mass content of silicon in an active substance is less than 15%, so that the silicon cathode has ultrahigh specific capacity (3579 mAh g)^-1) The advantages are difficult to be really exerted. The high-silicon-content negative electrode has specific capacity comparable to lithium metal and low lithiation potential (0.01-0.1V), and also has the advantages of abundant reserves and no biotoxicity, and is known as a negative electrode revolution engine in the next decade. However, silicon forms Li during complete lithiation₁₅Si₄The alloy is accompanied by 280% volume expansion in the process, which brings a series of problems of particle breakage, active substance separation from a current collector, repeated consumption of electrolyte, weak current contact and the like, so that the performance of the battery is rapidly reduced, and the cycle life is greatly reduced.

To address these problems, researchers have proposed a series of strategies. Liu et al published a Size-dependent fraction of silicon nanoparticles reduction degradation on ACS Nano 2012, Vol.6, pp.2 to 1531Theoretical simulation and experiments in the paper prove that the critical relationship between the nano-crystallization degree of the silicon particles and the particle crushing is realized, and when the diameter of the particles is less than 150 nm, the silicon particles can be cyclically expanded without crushing; du et al published a Surface binding of polypyrole on porous silicon nanoparticles for Li-ion batteries and with high structure stability on pages 6145 to 6150 at volume 26, vol.26, Advanced Materials 2014, and proposed a strategy for coating porous silicon with polypyrrole organic, the coating structure and the porous structure relieving most of the expansion stress of silicon particles; wang et al in Energy&An article of Binder-free high silicon content flexible anode for Li-ion batteries is published in Environmental Science (energy and Environmental Science) 2020, volume 13, pages 848 to 858, and a strategy for constructing a three-dimensional structure by carbon nanotubes is proposed, so that the advantage of the carbon nanotube network as a conductive agent is reflected; 1000 Wh L was published by Chen et al in National Science Review 2021⁻¹A paper of lithium-ion batteries enabled by cross silicon resin-crushed silicon nanoparticles proposes a strategy of combining graphene prepared by a hydrothermal method with carbon-coated silicon microparticles, and utilizes the combined action of the carbon layer and the graphene to disperse the huge expansion stress of the silicon microparticles, so that the cheap silicon microparticles have the performance comparable to that of the silicon nanoparticles when being used as a negative electrode.

However, the polypyrrole organic coating layer reduces the conductivity of the silicon negative electrode while coating the nano silicon particles to relieve the volume cycle expansion stress of the nano silicon particles. Although carbon nanotube networks, graphene, etc. can improve the activity of nano-silicon particles as a conductive agent, these strategies are not suitable for submicron and micron silicon particles, and their extreme volume cycle expansion stress can destroy the integrity of the coating layer and destroy the existing conductive system. This will further exacerbate the dependence of high performance silicon cathodes on silicon nanostructures (particle nanocrystallization, porous silicon, etc.). The nanostructure design of the silicon negative electrode is to process the silicon raw material again, so that a large number of new surfaces can be manufactured while the cost of the negative electrode is increased, Solid Electrolyte Interphase (SEI) can be formed on the surfaces in contact with the electrolyte in the lithiation process, the irreversible loss of a lithium source is increased, and the first coulombic efficiency of the silicon negative electrode is reduced. Furthermore, during the preparation of the electrode, the gaps existing between the nano-silicon particles make the tap density thereof lower than that of the micro-silicon particles. In contrast, submicron and micron silicon particles are simple to prepare and have more economic benefits. However, during the circulation process, the submicron and micron silicon particles are inevitably crushed, and the resulting structural damage can make the crushed silicon particles lose electric contact, so that the circulation performance of the silicon negative electrode is gradually reduced. Therefore, the structure which can release huge expansion stress of submicron and micron silicon particles and provide continuous electric contact for the crushed silicon particles is designed by combining the high-conductivity conductive agent, so that the activity of the crushed silicon particles is improved, and the structure has important significance for improving the performance of silicon negative and commercial application.

Disclosure of Invention

The invention aims to solve the problems and provides a self-fragmentation silicon electrode based on a continuous electric contact network, wherein silicon particles are fixed through a developed network structure of carbon nano tubes, the network structure and the silicon particles are coated by polyvinylpyrrolidone to form an organic coating layer, the organic coating layer is converted into a conductive carbon layer after high-temperature carbonization, and the network and the silicon particles are anchored at the same time to obtain a flexible and stable-structure composite film as the electrode. The anchored network structure can utilize the gaps between the network itself to relieve the expansion stress of the silicon particles, and simultaneously net up the fragmented silicon particles to provide a continuous electrical contact.

Another object of the present invention is to provide a method for preparing a self-fragmenting silicon electrode based on a continuous electrical contact network

The purpose of the invention is realized by the following technical scheme.

A spontaneous fragmentation silicon electrode based on a continuous electric contact network and a preparation method thereof sequentially comprise the following steps:

step one, preparing the composite film of the carbon nano tube coated silicon particles. Pouring 30 nm-10 μm diameter powder silicon particles into a certain amount of ethanol to obtain silicon particles with concentration of 1-20 mg ml^-1The silicon/ethanol solution is subjected to ultrasonic dispersion for later use. Preparing carbon nanotube aerogel continuum by floating catalytic cracking method, collecting the continuum and simultaneously matching with a sprayer for 0.1-10 ml min^-1The ethanol solution containing the silicon particles is sprayed on the aerogel continuum, the continuum with extremely high surface energy is quickly shrunk under the action of ethanol, and the silicon particles dispersed in the ethanol are connected with each other by a carbon nanotube network, and the network serves as a conductive material and simultaneously becomes a reserved space for the expansion of the silicon particles. Repeating the operation to obtain a composite film with the thickness of 5-60 μm (the unit area loading of silicon is 0.2-10 mg cm)^-2) And removing the film for later use after drying.

And step two, soaking treatment. Preparing polyvinylpyrrolidone and ethanol into solution according to the mass fraction of 0.1-5% (polyvinylpyrrolidone) in a beaker, and uniformly dispersing for later use. And (3) soaking the composite film obtained in the first step in a solution at room temperature and normal pressure for 2-60 min, and then wrapping the soaked silicon particles and the network structure with polyvinylpyrrolidone to form an organic coating layer. Taking out the film, laying the film flat, drying the film and then removing the film for later use.

And step three, performing heat treatment on the composite film. According to the carbonization temperature of the polyvinylpyrrolidone organic coating layer, the membrane soaked in the step two is placed in a high-temperature furnace cavity under the protective atmosphere at 500-^oC, preserving heat for 0.5-5 h, cooling and taking out after the coating is completely carbonized to obtain a carbon nanotube film and carbon layer double-coated silicon particle film, converting the carbonized coating into a conductive carbon layer, and anchoring the network structure and the silicon particles while further extending the electric contact points of the film. Cutting the film into a suitable shape results in a self-fragmenting silicon electrode based on a continuous electrical contact network. The conductivity of the composite film as an electrode is 2237.5-3549.3S m through a four-probe conductivity test^-1The electric conductivity of the pole piece after 100 cycles of charge-discharge cycle is 1569.2-2986.3S m^-1150.6-315.2S m of silicon electrode pole piece prepared by far-beyond-traditional mode before circulation^-1。

The performance of the film as an electrode. The film is used as a positive electrode to assemble a half cell: under chargingGlove box full of protective atmosphere (H)₂O≤0.1 ppm；O₂Not more than 0.1 ppm), using a sheet punching machine to obtain an electrode with a required shape on the film prepared in the step three, using the electrode as a positive electrode of a half-cell, using a lithium foil as a negative electrode of the half-cell, and using ethylene carbonate and diethyl carbonate in a mass ratio of 1:1 is LiPF₆And the solvent is a polyethylene or polypropylene film as a diaphragm, and the half cell is assembled. The film is used as a negative electrode to assemble a full cell: in a glove box (H) filled with a protective atmosphere₂O≤0.1 ppm；O₂Not more than 0.1 ppm), a pole piece prepared from commercial positive pole materials (including but not limited to lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium iron phosphate and the like) is taken as a full-cell positive pole, a film is taken as a negative pole, and the mass ratio of ethylene carbonate to diethyl carbonate is 1:1 is LiPF₆Solvent, one of polyethylene or polypropylene film is used as diaphragm, and the full cell is assembled. Testing the performance of the half-cell prepared by the film in an electrochemical test cabinet, detecting the charge-discharge platform and coulomb efficiency of the half-cell through first charge-discharge circulation, wherein the constant-current charge-discharge voltage of the silicon electrode is 2-0.01V, the discharge platform of the half-cell is stabilized at 0.01-0.1V, the charge platform is stabilized at 0.4-0.5V, the coulomb efficiency of the first charge-discharge exceeds 70%, and the coulomb efficiency is higher than 3200 mAh g^-1The specific capacity of (A). The electrochemical impedance test frequency range of the half-cell after one cycle is from 100 kHz to 0.01 Hz, the starting point value of the semicircle is only 1-3.2 Ω which is less than 5-10 Ω of the traditional silicon electrode, and the reduction of the starting point value reflects the increase of the electric contact points of the anchoring carbon nanotube network structure and excellent conductivity; the semi-circle diameter is only 8-21 Ω, which is far smaller than 110 Ω -200 Ω of the traditional silicon electrode, and the great reduction of the semi-circle radius is benefited by the filling of the electrolyte between the anchoring networks, so that the silicon particles are fully infiltrated with the electrolyte, and the interface impedance is reduced. At 0.3A g^-1The current density of (1) is 100 cycles, and 1000-2600 mAh g is also shown^-1The specific capacity of (A). The cycle performance of the lithium cobaltate full battery is detected, the test voltage is 2.75-4.2V, and the battery shows 145-155 mAh g after 50 circles^-1The specific capacity of (A).

In the step one, the sprayer is one of a commercial spray bottle, an electrostatic powder sprayer or an electrostatic powder gun and the like.

And the device used for dispersing in the second step is one of a microwave ultrasonic device, a vibration ultrasonic device or a stirrer and the like.

The equipment used in the high temperature furnace chamber in the third step is one of a horizontal low temperature furnace, a horizontal high temperature furnace, a vertical low temperature furnace or a vertical high temperature furnace and the like.

The invention has the following beneficial effects:

compared with numerous methods, the spontaneous fragmentation silicon electrode based on the continuous electric contact network and the preparation method thereof provided by the invention have obvious beneficial effects. Firstly, the space occupied by the carbon nanotube network among the silicon particles can be a reserved space for the silicon particles to circularly expand, so that the damage stress in the pole piece structure is greatly released, and the structural integrity is maintained; secondly, the space occupied by the carbon nanotube network among the silicon particles can be filled with electrolyte, so that the silicon particles and the electrolyte can be fully infiltrated, the interface resistance of the silicon particles is reduced, and the performance of the battery is improved; thirdly, the organic coating layer is converted into a carbon layer after heat treatment, so that not only is the network structure anchored and silicon particles coated, but also contact sites of the carbon nanotube conductive network are extended, the cyclic expansion stress of the silicon particles is reduced, and meanwhile, the stability of the network structure is enhanced, and the activity of the silicon particle fragments is improved; fourthly, the preparation process is suitable for submicron and micron silicon particles as a negative electrode, and can also be applied to silicon particles with the diameter of 30-100 nm as a negative electrode, and the pole piece can be prepared in a large scale. The invention can realize the macro preparation of the high-performance silicon cathode by utilizing the low-cost submicron or micron silicon and combining with the mature carbon nano tube floating catalytic cracking preparation process. The reserved space and the continuous electric contact provided by the structure effectively stabilize the pole piece structure, improve the activity of the silicon chip particles, realize the high performance of the silicon cathode and are expected to produce greater economic benefits.

Detailed Description

The following examples illustrate the invention in detail: the present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a process are given, but the scope of the present invention is not limited to the following embodiments.

Example 1

Step one, preparing the composite film of the carbon nano tube coated silicon particles. Pouring weighed 50 nm diameter silicon particles into a certain amount of ethanol solution to prepare the silicon particle content of 10 mg ml^-1The silicon/ethanol solution is put into a spray bottle for standby after being treated with full-power ultrasonic treatment for 5 min in a 650W ultrasonic crusher. Preparing a carbon nano tube aerogel continuum by a floating cracking method, and matching with a spraying device for 1 ml min while collecting the continuum in a round roller^-1The ethanol solution containing the silicon particles is uniformly sprayed on the aerogel continuum at the speed, the continuum with extremely high surface energy is quickly shrunk under the action of ethanol, and the aerogel continuum is connected to the silicon particles dispersed in the ethanol. Repeating the above operation for 1.5 h to obtain a substrate with a thickness of 12 μm and an area of 900 cm²Naturally drying the film for 12 h, and then uncovering the film to obtain the silicon particle surface loading of 1 mg cm^-2The composite film of (1).

And step two, soaking treatment. The polyvinylpyrrolidone and the ethanol are prepared into solution according to the mass fraction of 1 percent (polyvinylpyrrolidone) in a beaker, and the solution is subjected to full-power ultrasound for 10 min in a 650W ultrasonic crusher for standby. And (3) soaking the composite film of the carbon nano tube coated silicon particles in the solution for 30 min at room temperature and normal pressure, taking out, spreading on a glass plate, naturally drying for 1h, and then taking off for later use.

And step three, performing heat treatment on the composite film. According to the carbonization temperature of the polyvinylpyrrolidone organic coating layer, the heat treatment function of a horizontal high-temperature furnace is utilized, and the soaked film is placed into a cavity of the horizontal high-temperature furnace in the nitrogen protection atmosphere to reach the temperature of 5 DEG C^oC min^-1At a temperature rising rate of from room temperature to 800^oAnd C, preserving the heat for 2h, naturally cooling and then taking out to obtain the film with the carbon nanotube network and the carbon layer double-coated silicon particles.

And step four, the film has the performance of an electrode. The film is used as a positive electrode to assemble a half cell: in a glove box (H) filled with high-purity argon gas₂O≤0.1 ppm；O₂Less than or equal to 0.1 ppm), a sheet punching machine is used for obtaining a circular electrode on the film prepared in the step three, and the circular electrode is used as a positive electrode of a half cell and a lithium foilThe wafer is used as the negative electrode of a half-cell, and LiPF is a mixed solution of 1.0M ethylene carbonate and diethyl carbonate in a mass ratio of 1:1₆And the solvent is a polyethylene film or a polypropylene film which is taken as a diaphragm to assemble the half cell. The film is used as a negative electrode to assemble a full cell: in a glove box (H) filled with high-purity argon gas₂O≤0.1 ppm；O₂Not more than 0.1 ppm), a pole piece prepared from commercial lithium cobaltate is taken as a full cell anode, a film pre-embedded with lithium in a half cell is taken as a full cell cathode, and a mixed solution of 1.0M ethylene carbonate and diethyl carbonate with the mass ratio of 1:1 is taken as LiPF₆Solvent, polyethylene and polypropylene film as diaphragm, to form the whole battery. The performance of the half-cell is tested on an electrochemical test cabinet, the constant current charging and discharging voltage is 2-0.01V, and 3621.3 mAh g is released from a silicon electrode in the first circulation^-1The specific capacity of the electrode also shows 99.9 percent of capacity retention rate in the subsequent two circles; the electrochemical impedance test frequency range is from 100 kHz to 0.01 Hz, the semicircle starting point is 1.5 Ω, and the diameter is 8.6 Ω. The stability of the silicon electrode can be reflected by the long-cycle performance of the half cell, and is 0.3A g^-1The current density of (a) was cycled for 100 cycles, and the electrode also exhibited 2631.2 mAh g^-1The specific capacity of (A). The full cell is prepared by taking commercial lithium cobaltate material as the anode, the constant current charging and discharging voltage of the full cell is 4.2-2.75V, and 146.3 mAh g is generated after 1C circulation for 50 circles^-1The specific capacity of (A).

Example 2

Step one, preparing the composite film of the carbon nano tube coated silicon particles. Pouring weighed silicon particles with the diameter of 0.5 mu m into a certain amount of ethanol solution to prepare the silicon particle content of 5 mg ml^-1The silicon/ethanol solution is put into a spray bottle for standby after being treated with full-power ultrasonic treatment for 5 min in a 650W ultrasonic crusher. Preparing a carbon nano tube aerogel continuum by a floating cracking method, and matching a spraying device for 2 ml min while collecting the continuum in a collecting round roller^-1The ethanol solution containing the silicon particles is uniformly sprayed on the aerogel continuum at the speed, the continuum with extremely high surface energy is quickly shrunk under the action of ethanol, and the aerogel continuum is connected to the silicon particles dispersed in the ethanol. Repeating the above operation for 1.5 h to obtain a substrate with a thickness of 12 μm and an area900 cm²Naturally drying the film for 12 h, and then uncovering the film to obtain the silicon particle surface loading of 1 mg cm^-2The composite film of (1).

And step two, soaking treatment. The polyvinylpyrrolidone and the ethanol are prepared into solution according to the mass fraction of 1 percent (polyvinylpyrrolidone) in a beaker, and the solution is subjected to full-power ultrasound for 10 min in a 650W ultrasonic crusher for standby. And (3) soaking the composite film of the carbon nano tube coated silicon particles in the solution for 30 min at room temperature and normal pressure, taking out, spreading on a glass plate, naturally drying for 1h, and then taking off for later use.

And step three, performing heat treatment on the composite film. According to the carbonization temperature of the polyvinylpyrrolidone organic coating layer, the heat treatment function of a horizontal high-temperature furnace is utilized, and the soaked film is placed in a furnace chamber of the horizontal high-temperature furnace under the nitrogen protection atmosphere to reach the temperature of 5 DEG C^oC min^-1At a temperature rising rate of from room temperature to 800^oAnd C, preserving the heat for 2h, naturally cooling and then taking out to obtain the film with the carbon nanotube network and the carbon layer double-coated silicon particles.

And step four, the film has the performance of an electrode. The film is used as a positive electrode to assemble a half cell: in a glove box (H) filled with high-purity argon gas₂O≤0.1 ppm；O₂Not more than 0.1 ppm), a sheet punching machine is used for obtaining a circular electrode on the film prepared in the step three to be used as a positive electrode of a half-cell, a lithium foil disc is used as a negative electrode of the half-cell, and 1.0M of mixed solution of ethylene carbonate and diethyl carbonate with the mass ratio of 1:1 is LiPF₆And the solvent is a polyethylene film or a polypropylene film which is taken as a diaphragm to assemble the half cell. The film is used as a negative electrode to assemble a full cell: in a glove box (H) filled with high-purity argon gas₂O≤0.1 ppm；O₂Not more than 0.1 ppm), a pole piece prepared from commercial lithium cobaltate is taken as a full cell anode, a film pre-embedded with lithium in a half cell is taken as a full cell cathode, and a mixed solution of 1.0M ethylene carbonate and diethyl carbonate with the mass ratio of 1:1 is taken as LiPF₆Solvent, polyethylene and polypropylene film as diaphragm, to form the whole battery. The performance of the half-cell is tested on an electrochemical test cabinet, the constant current charging and discharging voltage is 2-0.01V, and 3589 mAh g is released from a silicon electrode in the first circulation^-1Specific capacity of, two subsequentIn circles, the electrode also exhibited a capacity retention of 99.9%, indicating that the anchoring network was in full continuous electrical contact with the silicon particles; the electrochemical impedance test frequency range is from 100 kHz to 0.01 Hz, the semicircle starting point is 1.8 Ω, and the diameter is 9 Ω. The rate capability and the long cycle performance of the half cell can reflect the stability of the silicon electrode, and the current densities of the long cycles with different rates are respectively 0.3A g^-1、1 A g^-1、3 A g^-1The electrode also showed 2345.3 mAh g^-1、1938.1 mAh g^-1、910.9 mAh g^-1A specific capacity of (a), wherein is 1A g^-1After circulating for 500 circles under the current density of the current, 703.4 mAh g is remained on the pole piece^-1The specific capacity and the excellent electrochemical cycle performance of the anchoring network structure show the stability of the anchoring network structure. In order to verify the practicability of the silicon electrode with the structure, a full battery is prepared by taking a commercial lithium cobaltate material as a positive electrode, the constant-current charge-discharge voltage of the full battery is 4.2-2.75V, and 147.5 mAh g is obtained after 1C circulation for 50 circles^-1The specific capacity of (A).

Example 3

Step one, preparing the composite film of the carbon nano tube coated silicon particles. Pouring weighed silicon particles with the diameter of 1 mu m into a certain amount of ethanol solution to prepare the silicon particle content of 5 mg ml^-1The silicon/ethanol solution is put into a spray bottle for standby after being treated with full power ultrasonic for 5 min in a 1000W ultrasonic crusher. Preparing a carbon nano tube aerogel continuum by a floating cracking method, and matching a spraying device for 0.5 ml min while collecting the continuum in a round roller^-1The ethanol solution containing the silicon particles is uniformly sprayed on the aerogel continuum at the speed, the continuum with extremely high surface energy is quickly shrunk under the action of ethanol, and the aerogel continuum is connected to the silicon particles dispersed in the ethanol. Repeating the above operation for 2h to obtain a film with a thickness of 15 μm and an area of 900 cm²The film is naturally dried for 12 hours, and then the film is uncovered, so that the silicon particle surface loading capacity is 0.7 mg cm^-2The composite film of (1).

And step two, soaking treatment. The polyvinylpyrrolidone and the ethanol are prepared into solution according to the mass fraction of 2 percent (polyvinylpyrrolidone) in a beaker, and the solution is subjected to full-power ultrasound for 10 min in a 1000W ultrasonic crusher for standby. And (3) soaking the composite film of the carbon nano tube coated silicon particles in the solution for 15 min at room temperature and normal pressure, taking out, spreading on a glass plate, naturally drying for 1h, and then taking off for later use.

And step three, performing heat treatment on the composite film. According to the carbonization temperature of the polyvinylpyrrolidone organic coating layer, the heat treatment function of a horizontal high-temperature furnace is utilized, and the soaked film is placed into a cavity of the horizontal high-temperature furnace in the nitrogen protection atmosphere to reach the temperature of 5 DEG C^oC min^-1At a temperature rising rate of from room temperature to 700 deg.C^oAnd C, preserving the heat for 2h, naturally cooling and then taking out to obtain the integrated film of the carbon nanotube network and the carbon layer double-coated silicon particles.

And step four, the film has the performance of an electrode. The film is used as a positive electrode to assemble a half cell: in a glove box (H) filled with high-purity argon gas₂O≤0.1 ppm；O₂Not more than 0.1 ppm), a sheet punching machine is used for obtaining a circular electrode on the film prepared in the step three to be used as a positive electrode of a half-cell, a lithium foil disc is used as a negative electrode of the half-cell, and 1.0M of mixed solution of ethylene carbonate and diethyl carbonate with the mass ratio of 1:1 is LiPF₆And the solvent is a polyethylene film or a polypropylene film which is taken as a diaphragm to assemble the half cell. The film is used as a negative electrode to assemble a full cell: in a glove box (H) filled with high-purity argon gas₂O≤0.1 ppm；O₂Not more than 0.1 ppm), a pole piece prepared from commercial lithium cobaltate is taken as a full cell anode, a film pre-embedded with lithium in a half cell is taken as a full cell cathode, and a mixed solution of 1.0M ethylene carbonate and diethyl carbonate with the mass ratio of 1:1 is taken as LiPF₆Solvent, polyethylene and polypropylene film as diaphragm, to form the whole battery. The performance of the half-cell is tested on an electrochemical test cabinet, the constant current charging and discharging voltage is 2-0.01V, and 3275.3 mAh g is released from a silicon electrode in the first circulation^-1The specific capacity of the electrode also shows 99.9 percent of capacity retention rate in the subsequent two circles; the electrochemical impedance test frequency range is from 100 kHz to 0.01 Hz, the semicircle starting point is 2.3 Ω, and the diameter is 12 Ω. Half cell is at 0.3A g^-1After circulating for 50 circles under the current density, 2406 mAh g is remained on the pole piece^-1The specific capacity of (A). The full cell prepared by using commercial lithium cobaltate material as the anode circulates for 50 circles at 1CThen 145.3 mAh g^-1The performance of (c).

Example 4

Step one, preparing the composite film of the carbon nano tube coated silicon particles. Pouring weighed silicon particles with the diameter of 5 mu m into a certain amount of ethanol solution to prepare the silicon particle content of 15 mg ml^-1The silicon/ethanol solution is put into a spray bottle for standby after being treated with full-power ultrasonic treatment for 5 min in a 650W ultrasonic crusher. Preparing a carbon nano tube aerogel continuum by a floating cracking method, and matching with a spraying device for 1 ml min while collecting the continuum in a round roller^-1The ethanol solution containing the silicon particles is uniformly sprayed on the aerogel continuum at the speed, the continuum with extremely high surface energy is quickly shrunk under the action of ethanol, and the aerogel continuum is connected to the silicon particles dispersed in the ethanol. Repeating the above operation for 2h to obtain a film with a thickness of 16 μm and an area of 900 cm²Naturally drying the film for 12 h, and then uncovering the film to obtain the silicon particle surface loading of 3 mg cm^-2The composite film of (1).

And step two, soaking treatment. The polyvinylpyrrolidone and the ethanol are prepared into solution according to the mass fraction of 0.5 percent (polyvinylpyrrolidone) in a beaker, and the solution is subjected to full-power ultrasound for 10 min in a 650W ultrasonic crusher for standby. And (3) soaking the composite film of the carbon nano tube coated silicon particles in the solution for 60 min at room temperature and normal pressure, taking out, spreading on a glass plate, naturally drying for 1h, and then taking off for later use.

And step three, performing heat treatment on the composite film. According to the carbonization temperature of the polyvinylpyrrolidone organic coating layer, the heat treatment function of a horizontal high-temperature furnace is utilized, and the soaked film is placed into a cavity of the horizontal high-temperature furnace in the nitrogen protection atmosphere to reach the temperature of 5 DEG C^oC min^-1At a temperature rising rate of 1000 from room temperature^oAnd C, preserving the heat for 1h, naturally cooling and then taking out to obtain the integrated film of the carbon nanotube film and the carbon layer double-coated silicon particles.

And step four, the film has the performance of an electrode. The film is used as a positive electrode to assemble a half cell: in a glove box (H) filled with high-purity argon gas₂O≤0.1 ppm；O₂Less than or equal to 0.1 ppm), a sheet punching machine is used for obtaining a circular electrode on the film prepared in the step three and the circular electrode is used as the positive electrode of a half cellA lithium foil disc is used as a negative electrode of the half-cell, and a mixed solution of 1.0M ethylene carbonate and diethyl carbonate with the mass ratio of 1:1 is LiPF₆And the solvent is a polyethylene film or a polypropylene film which is taken as a diaphragm to assemble the half cell. The film is used as a positive electrode to assemble a full cell: in a glove box (H) filled with high-purity argon gas₂O≤0.1 ppm；O₂Not more than 0.1 ppm), a pole piece prepared from commercial lithium cobaltate is taken as a full cell anode, a film pre-embedded with lithium in a half cell is taken as a full cell cathode, and a mixed solution of 1.0M ethylene carbonate and diethyl carbonate with the mass ratio of 1:1 is taken as LiPF₆Solvent, polyethylene and polypropylene film as diaphragm, to form the whole battery. The performance of the half-cell is tested on an electrochemical test cabinet, the constant current charging and discharging voltage is 2-0.01V, and 3215.6 mAh g is released from a silicon electrode in the first circulation^-1The specific capacity of the electrode also shows 99.9 percent of capacity retention rate in the subsequent two circles; the electrochemical impedance test frequency range is from 100 kHz to 0.01 Hz, the semicircle starting point is 2.9 Ω, and the diameter is 13.9 Ω. Half cell is at 0.3A g^-1After circulating for 50 circles under the current density, 1235.1 mAh g is remained on the pole piece^-1The specific capacity of (A). The full cell prepared by using commercial lithium cobaltate material as the anode has 145.9 mAh g after 1C cycle of 50 circles^-1The performance of (c).

Example 5

Step one, preparing the composite film of the carbon nano tube coated silicon particles. Pouring weighed silicon particles with the diameter of 10 mu m into a certain amount of ethanol solution to prepare the silicon particle content of 10 mg ml^-1The silicon/ethanol solution is put into a spray bottle for standby after being treated with full-power ultrasonic treatment for 5 min in a 650W ultrasonic crusher. Preparing a carbon nano tube aerogel continuum by a floating cracking method, and matching with a spraying device for 1 ml min while collecting the continuum in a round roller^-1The ethanol solution containing the silicon particles is uniformly sprayed on the aerogel continuum at the speed, the continuum with extremely high surface energy is quickly shrunk under the action of ethanol, and the aerogel continuum is connected to the silicon particles dispersed in the ethanol. Repeating the above operation for 3 h to obtain a film with a thickness of 25 μm and an area of 900 cm²Naturally drying the film for 12 h, and then uncovering the film to obtain the silicon particle surface loading of 2 mg cm^-2The composite film of (1).

And step two, soaking treatment. The polyvinylpyrrolidone and the ethanol are prepared into solution according to the mass fraction of 0.5 percent (polyvinylpyrrolidone) in a beaker, and the solution is subjected to full-power ultrasound for 10 min in a 650W ultrasonic crusher for standby. And (3) soaking the composite film of the carbon nano tube coated silicon particles in the solution for 60 min at room temperature and normal pressure, taking out, spreading on a glass plate, naturally drying for 1h, and then taking off for later use.

And step three, performing heat treatment on the composite film. According to the carbonization temperature of the polyvinylpyrrolidone organic coating layer, the heat treatment function of a horizontal high-temperature furnace is utilized, and the soaked film is placed into a cavity of the horizontal high-temperature furnace in the nitrogen protection atmosphere to reach the temperature of 5 DEG C^oC min^-1At a temperature rising rate of 1000 from room temperature^oAnd C, preserving the heat for 1h, naturally cooling and then taking out to obtain the integrated film of the carbon nanotube film and the carbon layer double-coated silicon particles.

And step four, the film has the performance of an electrode. The film is used as a positive electrode to assemble a half cell: in a glove box (H) filled with high-purity argon gas₂O≤0.1 ppm；O₂Not more than 0.1 ppm), a sheet punching machine is used for obtaining a circular electrode on the film prepared in the step three to be used as a positive electrode of a half-cell, a lithium foil disc is used as a negative electrode of the half-cell, and 1.0M of mixed solution of ethylene carbonate and diethyl carbonate with the mass ratio of 1:1 is LiPF₆And the solvent is a polyethylene film or a polypropylene film which is taken as a diaphragm to assemble the half cell. The film is used as a positive electrode to assemble a full cell: in a glove box (H) filled with high-purity argon gas₂O≤0.1 ppm；O₂Not more than 0.1 ppm), a pole piece prepared from commercial lithium cobaltate is taken as a full cell anode, a film pre-embedded with lithium in a half cell is taken as a full cell cathode, and a mixed solution of 1.0M ethylene carbonate and diethyl carbonate with the mass ratio of 1:1 is taken as LiPF₆Solvent, polyethylene and polypropylene film as diaphragm, to form the whole battery. The performance of the half-cell is tested on an electrochemical test cabinet, the constant current charging and discharging voltage is 2-0.01V, and 3204.3 mAh g is released from a silicon electrode in the first circulation^-1The specific capacity of the electrode also shows 99.9 percent of capacity retention rate in the subsequent two circles; electrochemical impedance test frequencyRanging from 100 kHz to 0.01 Hz, a semicircle starting point of 2.8 Ω, and a diameter of 15 Ω. Half cell is at 0.3A g^-1After circulating for 50 circles under the current density of the current, 1189.6 mAh g is remained on the pole piece^-1The specific capacity of (A). The full cell prepared by using commercial lithium cobaltate material as the anode has 146.3 mAh g after 1C cycle of 50 circles^-1The performance of (c).