阅读说明：本技术 一种具有中空结构的还原氧化石墨烯包裹CNTs/SnO2复合薄膜及其制备方法和应用 (Reduced graphene oxide coated CNTs/SnO with hollow structure2Composite film and preparation method and application thereof ) 是由 杨艳玲 孙瑜 郭文宁 薛帆 刘佳隽 和茹梅 锁国权 侯小江 冯雷 张荔 叶晓慧 于 2021-09-10 设计创作，主要内容包括：本发明公开了一种具有中空结构的还原氧化石墨烯包裹CNTs/SnO-(2)复合薄膜及其制备方法和应用,属于钠离子电池技术领域,空隙结构能有效缩短了电子/Na～(+)扩散路径,加速SIB的反应动力学,并为Na～(+)提供了丰富的活性位点。此外,rGO还可以有效地缓解SnO-(2)的体积膨胀,并作为一种纽带为整个rGO@CNTs/SnO-(2)@void复合薄膜提供电子传输的通道。得益于这种独特的结构优势,rGO@CNTs/SnO-(2)@void复合薄膜作为钠离子电池的负极材料展现出了优异的电化学性能,即使在1A g～(-1)的高电流密度下,其循环寿命仍能达1000圈,表现出了超高的循环稳定性。(The invention discloses reduced graphene oxide coated CNTs/SnO with a hollow structure 2 A composite film and a preparation method and application thereof, belongs to the technical field of sodium ion batteries, and comprises a gapThe structure can effectively shorten electrons/Na + Diffusion path, acceleration of SIB reaction kinetics, and Na + Provides abundant active sites. In addition, rGO can also effectively mitigate SnO 2 And as a ligament is the whole rGO @ CNTs/SnO 2 The @ void composite film provides a channel for electron transport. Thanks to this unique structural advantage, rGO @ CNTs/SnO 2 The @ void composite film as the anode material of the sodium-ion battery shows excellent electrochemical performance even at 1A g ‑1 The cycle life of the high-current-density capacitor can still reach 1000 circles, and ultrahigh cycle stability is shown.)

1. Reduced graphene oxide coated CNTs/SnO with hollow structure₂The preparation method of the composite film is characterized by comprising the following steps:

step 1) preparation of polystyrene microspheres:

synthesizing polystyrene microspheres (PS) by a microemulsion polymerization method;

step 2) CNTs/SnO₂Preparation of @ PS composite film:

SnCl₄·5H₂Mixing O, polystyrene microspheres, hexadecyl trimethyl ammonium bromide, CNTs and deionized water, and after reaction, sequentially cleaning and drying to obtain CNTs/SnO₂@ PS composite film;

step 3) rGO @ CNTs/SnO₂Preparation of @ void composite film:

mixing CNTs/SnO₂Mixing the @ PS composite film, ascorbic acid and graphene oxide, and drying and calcining the mixture in sequence after reaction to obtain reduced graphene oxide coated CNTs/SnO with a hollow structure₂The composite film of (1).

2. Reduced graphene oxide-coated CNTs/SnO with hollow structure according to claim 1₂The preparation method of the composite film is characterized in that the SnCl₄·5H₂The feeding ratio of O, polystyrene microspheres, cetyl trimethyl ammonium bromide, CNTs and deionized water is (0.2-1.0) g: (0.5-1.5) g: (0.1-0.5) g: (0.01-0.1) g: (30-150) ml.

3. Reduced graphene oxide-coated CNTs/SnO with hollow structure according to claim 1₂The preparation method of the composite film is characterized in that the composite film is prepared from CNTs/SnO₂The material feeding ratio among the @ PS composite film, the ascorbic acid and the graphene oxide is (0.5-3.0) g: (0.2-0.5) g: (5-15) ml;

the concentration of the graphene oxide is 1-5 mg/ml.

4. Reduced graphene oxide-coated CNTs/SnO with hollow structure according to claim 1₂The preparation method of the composite film is characterized in that the reaction conditions in the step 2) are as follows:

firstly, SnCl is added₄·5H₂Mixing O, polystyrene microspheres, hexadecyl trimethyl ammonium bromide, CNTs and deionized water, and reacting for 1.0-5 h to obtain a solution B;

secondly, reacting the solution B at 150-220 ℃ for 8-15 hours to obtain a product C;

and finally, alternately washing the product C for 3-5 times by using deionized water and ethanol to obtain CNTs/SnO₂@ PS composite film.

5. Reduced graphene oxide-coated CNTs/SnO with hollow structure according to claim 1₂The preparation method of the composite film is characterized in that the reaction conditions in the step 3) are as follows:

first, CNTs/SnO₂Stirring and reacting the @ PS composite film, ascorbic acid and graphene oxide for 2-5 h to obtain a mixed solution E;

secondly, drying the mixed solution E at 80-120 ℃ for 1-5 h to obtain gel F;

and finally, calcining the gel F at 150-250 ℃ for 1-5 hours to obtain rGO @ CNTs/SnO₂@ void composite film.

6. Reduced graphene oxide-coated CNTs/SnO with hollow structure according to claim 1₂The preparation method of the composite film is characterized in that CNTs are single-walled carbon nanotubes;

the graphene oxide is a single layer of graphene oxide.

7. Reduced graphene oxide coated CNTs/SnO obtained based on preparation method of any one of claims 1-6₂The composite film is characterized in that the reduced graphene oxide wraps CNTs/SnO₂The composite film is of a hollow structure, and the size of a gap in the hollow structure is 100-250 nm.

8. Reduced graphene oxide-coated CNTs/SnO according to claim 7₂The application of the composite film in the button cell is characterized in that the structure of the button cell is as follows:

the metal sodium is used as a counter electrode;

the electrolyte is NaPF₆Ethyl carbonate and dimethyl carbonate;

the diaphragm is a celgard 2400 film;

reduced graphene oxide coated CNTs/SnO₂The composite film is used as a negative electrode material of the sodium-ion battery and assembled into a button cell.

Technical Field

The invention belongs to the technical field of sodium ion batteries, and relates to reduced graphene oxide coated CNTs/SnO with a hollow structure₂A composite film and a preparation method and application thereof.

Background

In recent decades, environmental pollution and energy crisis have attracted more and more attention worldwide due to rapid development of industrialization and increasing energy demand. In order to solve these problems, development and popularization of green renewable energy are urgently needed. Therefore, high performance energy storage devices have become a focus of research in recent years. Rechargeable ionic batteries are considered to be one of the most potential energy storage devices due to their significant advantages of high energy density, reasonable operating voltage, and good cyclability.

Since Sony commercialization of Lithium Ion Batteries (LIBs) for the first time in 1991, LIBs have become the dominant energy storage batteryEquipment and is being applied to the aspects of people's life. However, the problem of lithium resource shortage in the crust will severely limit the rapid development of LIB in the future. Sodium is considered to be one of the more suitable energy storage batteries that can replace LIB because of its similar physicochemical properties as lithium. Notably, Na⁺Diameter to size ratio of Li⁺Larger (Li)⁺Is composed ofNa⁺Is composed of) Na of this larger size⁺This results in SIB with lower electrochemical performance and more severe volume expansion problems, which slows down the pace of SIB marketization.

The tin (Sn) base material has very high theoretical specific capacity (Na)₁₅Sn₄Exhibit 847mA h g^-1High theoretical specific capacity), low cost, environmental friendliness and appropriate low charge-discharge potential, and is considered as a potential negative electrode material of the SIB. However, from Sn to Na₁₅Sn₄The reaction process of (a) is accompanied by a volume expansion phenomenon of about 520%, which seriously shortens the cycle life of the SIB and degrades the electrochemical performance of the SIB. In addition, due to the characteristic that nano-scale Sn-based particles are easy to agglomerate, the internal conductivity of the Sn-based material is poor. Therefore, how to effectively alleviate the volume expansion phenomenon of the Sn-based material during SIB charging and discharging still faces a serious challenge to increase the internal conductivity of the material.

Disclosure of Invention

The invention aims to overcome the defect that the Sn-based material has volume expansion in the SIB charging and discharging process in the prior art, and provides reduced graphene oxide coated CNTs/SnO with a hollow structure₂A composite film and a preparation method and application thereof.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

reduction with hollow structureCNTs/SnO coated by graphene oxide₂The preparation method of the composite film comprises the following steps:

step 1) preparation of polystyrene microspheres:

synthesizing polystyrene microspheres (PS) by a microemulsion polymerization method;

step 2) CNTs/SnO₂Preparation of @ PS composite film:

SnCl₄·5H₂Mixing O, polystyrene microspheres, hexadecyl trimethyl ammonium bromide, CNTs and deionized water, and after reaction, sequentially cleaning and drying to obtain CNTs/SnO₂@ PS composite film;

step 3) rGO @ CNTs/SnO₂Preparation of @ void composite film:

mixing CNTs/SnO₂Mixing the @ PS composite film, ascorbic acid and graphene oxide, and drying and calcining the mixture in sequence after reaction to obtain reduced graphene oxide coated CNTs/SnO with a hollow structure₂The composite film of (1).

Preferably, SnCl₄·5H₂The feeding ratio of O, polystyrene microspheres, cetyl trimethyl ammonium bromide, CNTs and deionized water is (0.2-1.0) g: (0.5-1.5) g: (0.1-0.5) g: (0.01-0.1) g: (30-150) ml.

Preferably, CNTs/SnO₂The material feeding ratio among the @ PS composite film, the ascorbic acid and the graphene oxide is (0.5-3.0) g: (0.2-0.5) g: (5-15) ml;

the concentration of the graphene oxide is 1-5 mg/ml.

Preferably, the reaction conditions in step 2) are:

firstly, SnCl is added₄·5H₂Mixing O, polystyrene microspheres, hexadecyl trimethyl ammonium bromide, CNTs and deionized water, and reacting for 1.0-5 h to obtain a solution B;

secondly, reacting the solution B at 150-220 ℃ for 8-15 hours to obtain a product C;

and finally, alternately washing the product C for 3-5 times by using deionized water and ethanol to obtain CNTs/SnO₂@ PS composite film.

Preferably, the reaction conditions in step 3) are:

first, CNTs/SnO₂Stirring and reacting the @ PS composite film, ascorbic acid and graphene oxide for 2-5 h to obtain a mixed solution E;

secondly, drying the mixed solution E at 80-120 ℃ for 1-5 h to obtain gel F;

and finally, calcining the gel F at 150-250 ℃ for 1-5 hours to obtain rGO @ CNTs/SnO₂@ void composite film.

Preferably, the CNTs are single-walled carbon nanotubes;

the graphene oxide is a single layer of graphene oxide.

Reduced graphene oxide coated CNTs/SnO obtained based on preparation method₂The composite film is prepared by reducing graphene oxide to coat CNTs/SnO₂The composite film is of a hollow structure, and the size of a gap in the hollow structure is 100-250 nm.

The reduced graphene oxide coated CNTs/SnO₂The composite film is applied to the button cell, and the structure of the button cell is as follows:

the metal sodium is used as a counter electrode;

the electrolyte is NaPF₆Ethyl carbonate and dimethyl carbonate;

the diaphragm is a celgard 2400 film;

[email protected]/SnO₂the @ void composite film is used as a negative electrode material of the sodium ion battery and assembled into the button cell.

Compared with the prior art, the invention has the following beneficial effects:

the invention discloses reduced graphene oxide coated CNTs/SnO with a hollow structure₂The composite film has a gap structure capable of effectively shortening electron/Na⁺Diffusion path, acceleration of SIB reaction kinetics, and Na⁺Provides abundant active sites. In addition, rGO can also effectively mitigate SnO₂And as a ligament is the whole rGO @ CNTs/SnO₂The @ void composite film provides a channel for electron transport. Thanks to this unique structural advantage, rGO @ CNTs/SnO₂@ void composite filmExhibits excellent electrochemical performance for the anode material of sodium ion battery, even at 1A g^-1The cycle life of the high-current-density capacitor can still reach 1000 circles, and ultrahigh cycle stability is shown.

The invention also discloses reduced graphene oxide coated CNTs/SnO with a hollow structure₂The preparation method of the composite film takes the polystyrene microspheres as the template, provides sufficient gaps for the structure after high-temperature calcination, and is favorable for relieving the volume expansion problem of the material. In order to improve rGO @ CNTs/SnO₂The conductivity of the @ void composite film, highly conductive CNTs are used as electron transport channels. CNTs and rGO have stronger conductivity, and electrons are facilitated to be carried out at rGO @ CNTs/SnO₂The @ void composite film has rapid transport, and increases the conductivity inside the material. Synthetic rGO @ CNTs/SnO₂The @ void composite film can effectively disperse SnO₂Particles, moderated SnO₂The volume expansion of the particles during charging and discharging is a problem.

Further, a hydrothermal method and a tubular furnace calcination process are adopted to prepare the reduced graphene oxide coated CNTs/SnO with a hollow structure₂The composite film has simple synthesis process and easy operation.

Drawings

FIG. 1 shows reduced graphene oxide coated CNTs/SnO₂The preparation process of the composite film of (1);

FIG. 2 is a schematic diagram of reduced graphene oxide-coated CNTs/SnO according to example IV₂Microscopic SEM images of the composite film of (a);

FIG. 3 is a diagram of reduced graphene oxide-coated CNTs/SnO according to example IV₂A partially enlarged SEM image of the composite film of (a);

FIG. 4 is a diagram of reduced graphene oxide-coated CNTs/SnO according to example IV₂High power SEM image of the composite film;

FIG. 5 is a graph of the elemental content and elemental distribution of Line 1 of FIG. 4;

FIG. 6 is a diagram of reduced graphene oxide-coated CNTs/SnO according to example IV₂The composite film is used as a high-stability long-cycle graph of an SIB negative electrode material.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings:

example one

Reduced graphene oxide coated CNTs/SnO₂The preparation of the composite film, as shown in fig. 1, comprises the following steps:

step 1, preparation of PS microspheres:

the diameter of the Polystyrene (PS) microspheres synthesized by the Michelin Biochemical technology Limited, Shanghai, is 300 nanometers.

Step 2, CNTs/SnO₂Preparation of @ PS composite film:

first, 0.2g of SnCl₄·5H₂O, 0.5g of PS microspheres, 0.1g of cetyltrimethylammonium bromide (CTAB) and 0.01g of CNTs were added to 30mL of an aqueous solution and subjected to sonication for about 0.5 hour to give solution A, and then solution A was stirred for 0.5 hour to give solution B. And putting the solution B into a polytetrafluoroethylene reactor, and reacting the solution B for 8 hours at 150 ℃ to obtain a reaction product C. Finally, the reaction product C is centrifuged and washed for 3 times with deionized water and ethanol alternately to obtain a product D which is CNTs/SnO₂@ PS composite film.

Step 3, self-supporting rGO @ CNTs/SnO₂Preparation of @ void composite film:

0.5g of product D and 0.2g of ascorbic acid are dispersed to a concentration of 1mg mL in 5mL^-1And magnetically stirring for 2 hours to obtain a mixed solution E. Then, the mixed solution E was placed in an oven at 80 ℃ for 1 hour to obtain a gel F, rGO @ CNTs/SnO₂@ PS gel. Finally, the gel F was sliced and calcined in a muffle furnace at 150 ℃ for 1 hour to form free-standing rGO @ CNTs/SnO₂@ void composite film, namely reduced graphene oxide coated CNTs/SnO with hollow structure₂The composite film of (1).

Free-standing rGO @ CNTs/SnO₂The @ void composite film is based on the high-stability rGO coated CNTs/SnO₂A preparation method and an application method of the @ void composite film. The rGO @ CNTs/SnO₂The @ void composite film is used as the cathode material of the sodium ion battery and assembled into a buttonA battery is provided.

The specific method for assembling the button cell is as follows: rGO @ CNTs/SnO₂The @ void composite film has integrity and can be directly used as a self-supporting electrode and is cut into a negative plate for an experimental battery with the diameter of 10mm by a cutting machine.

Taking metal sodium as a counter electrode; the electrolyte is NaPF₆Mixing the ethyl carbonate and the dimethyl carbonate solution according to the volume ratio of 1: 1; the diaphragm is a celgard 2400 film; the order of assembling the battery is that a negative electrode shell, a sodium sheet, a diaphragm, a negative electrode sheet, a gasket, a spring piece and a positive electrode shell are assembled into a button battery in a glove box filled with inert atmosphere.

Example two

Step 1, preparation of PS microspheres:

the diameter of Polystyrene (PS) microspheres synthesized by the microemulsion polymerization method provided by Shanghai Michelin Biochemical technology Ltd is 400 nm.

Step 2, CNTs/SnO₂Preparation of @ PS composite film:

first, 0.3g of SnCl₄·5H₂O, 0.5g of PS microspheres, 0.3g of CTAB and 0.03g of CNTs are added into 50mL of aqueous solution and subjected to ultrasonic treatment for about 1 hour to obtain a solution A, and then the solution A is stirred for 1 hour to obtain a solution B. And putting the solution B into a polytetrafluoroethylene reactor, and reacting the solution B for 10 hours at 180 ℃ to obtain a reaction product C. Finally, the reaction product C is centrifuged and washed with deionized water and ethanol alternately for 4 times to obtain a product D of CNTs/SnO₂@ PS composite film.

Step 3, self-supporting rGO @ CNTs/SnO₂Preparation of @ void composite film:

0.6g of product D and 0.3g of ascorbic acid are dispersed to a concentration of 2mg mL in 8mL^-1And magnetically stirring for 4 hours to obtain a mixed solution E. Then, the mixed solution E was placed in an oven at 100 ℃ for 3 hours to obtain a gel F, rGO @ CNTs/SnO₂@ PS gel. Finally, the gel F was sliced and calcined in a muffle furnace at 180 ℃ for 2 hours to form free-standing rGO @ CNTs/SnO₂@ void composite film, namely reduced graphene oxide coated CNTs/SnO with hollow structure₂The composite film of (1).

Free-standing rGO @ CNTs/SnO₂The @ void composite film is based on the high-stability rGO coated CNTs/SnO₂A preparation method and an application method of the @ void composite film. The rGO @ CNTs/SnO₂The @ void composite film is used as a negative electrode material of the sodium ion battery and assembled into the button cell.

The specific method for assembling the button cell is as follows: rGO @ CNTs/SnO₂The @ void composite film has integrity and can be directly used as a self-supporting electrode and is cut into a negative plate for an experimental battery with the diameter of 10mm by a cutting machine.

Taking metal sodium as a counter electrode; the electrolyte is NaPF₆Mixing the ethyl carbonate and the dimethyl carbonate solution according to the volume ratio of 1: 1; the diaphragm is a celgard 2400 film; the order of assembling the battery is that a negative electrode shell, a sodium sheet, a diaphragm, a negative electrode sheet, a gasket, a spring piece and a positive electrode shell are assembled into a button battery in a glove box filled with inert atmosphere.

EXAMPLE III

Step 1, preparation of PS microspheres:

the diameter of Polystyrene (PS) microspheres synthesized by mini-emulsion polymerization, supplied by the Shanghai Michelin Biochemical technology Ltd, is about 350 nm.

Step 2, CNTs/SnO₂Preparation of @ PS composite film:

first, 0.35g of SnCl₄·5H₂O, 0.9g of PS microspheres, 0.35g of CTAB and 0.06g of CNTs are added into 90mL of aqueous solution and subjected to ultrasonic treatment for about 2 hours to obtain a solution A, and then the solution A is stirred for 1 hour to obtain a solution B. Putting the solution B into a polytetrafluoroethylene reactor, and reacting for 12 hours at 200 ℃ to obtain a reaction product C. Finally, the reaction product C is centrifuged and washed alternately with deionized water and ethanol for 5 times to obtain a product D of CNTs/SnO₂@ PS composite film.

Step 3, self-supporting rGO @ CNTs/SnO₂Preparation of @ void composite film:

1.3g of product D and 0.25g of ascorbic acid are dispersed in 10mL of a concentration of 3mg mL^-1And magnetically stirring for 4h to obtainThe solution E was mixed. The mixed solution E was then placed in an oven at 100 ℃ for 4 hours to obtain a gel F, rGO @ CNTs/SnO₂@ PS gel. Finally, the gel F was sliced and calcined in a muffle furnace at 200 ℃ for 3 hours to form free-standing rGO @ CNTs/SnO₂@ void composite film, namely reduced graphene oxide coated CNTs/SnO with hollow structure₂The composite film of (1).

Free-standing rGO @ CNTs/SnO₂The @ void composite film is based on the high-stability rGO coated CNTs/SnO₂A preparation method and an application method of the @ void composite film. The rGO @ CNTs/SnO₂The @ void composite film is used as a negative electrode material of the sodium ion battery and assembled into the button cell.

The specific method for assembling the button cell is as follows: rGO @ CNTs/SnO₂The @ void composite film has integrity and can be directly used as a self-supporting electrode and is cut into a negative plate for an experimental battery with the diameter of 10mm by a cutting machine.

Taking metal sodium as a counter electrode; the electrolyte is NaPF₆Mixing the ethyl carbonate and the dimethyl carbonate solution according to the volume ratio of 1: 1; the diaphragm is a celgard 2400 film; the order of assembling the battery is that a negative electrode shell, a sodium sheet, a diaphragm, a negative electrode sheet, a gasket, a spring piece and a positive electrode shell are assembled into a button battery in a glove box filled with inert atmosphere.

Example four

Step 1, preparation of PS microspheres:

the diameter of Polystyrene (PS) microspheres synthesized by the microemulsion polymerization method, which is provided by Shanghai Michelin Biochemical technology Ltd, is about 450 nm.

Step 2, CNTs/SnO₂Preparation of @ PS composite film:

first, 0.5g of SnCl₄·5H₂O, 1.0g of PS microspheres, 0.35g of CTAB and 0.05g of CNTs are added into 80mL of aqueous solution and subjected to ultrasonic treatment for about 1 hour to obtain a solution A, and then the solution A is stirred for 1 hour to obtain a solution B. Putting the solution B into a polytetrafluoroethylene reactor, and reacting for 12 hours at 180 ℃ to obtain a reaction product C. Finally, the reaction product C was centrifuged and mixed with deionized water and ethanolReplacing and cleaning for 5 times to obtain product D which is CNTs/SnO₂@ PS composite film.

Step 3, self-supporting rGO @ CNTs/SnO₂Preparation of @ void composite film:

1.35g of product D and 0.3g of ascorbic acid dispersed in 10mL of 3mg mL^-1And magnetically stirring for 5 hours to obtain a mixed solution E. Then, putting the mixed solution E into an oven at 90 ℃ for 1-5 hours to obtain gel F, namely rGO @ CNTs/SnO₂@ PS gel. Finally, the gel F was sliced and calcined in a muffle furnace at 200 ℃ for 3 hours to form free-standing rGO @ CNTs/SnO₂@ void composite film, namely reduced graphene oxide coated CNTs/SnO with hollow structure₂The composite film of (1).

[email protected]/SnO₂SEM images of the @ void composite film are shown in FIGS. 2, 3 and 4. The rGO @ CNTs/SnO can be seen in SEM images of different scales₂The @ void composite film has a significant presence of voids, which facilitates rapid penetration of an electrolyte solution, thereby accelerating the progress of the reaction kinetics of the electrode. FIG. 5 is an EDX test performed on Line 1 of FIG. 4, which clearly identifies rGO @ CNTs/SnO₂The ratio of each component in the @ void composite film is determined. Thanks to the above unique structural design, rGO @ CNTs/SnO₂The @ void composite film as the SIB negative electrode material exhibited excellent electrochemical properties, as shown in FIG. 6. Even at 1A g^-1The high-current density of the copper-based alloy can be cycled for 1000 times, can still maintain higher specific capacity, and simultaneously shows excellent cycling stability and long cycling life.

Free-standing rGO @ CNTs/SnO₂The @ void composite film is based on the high-stability rGO coated CNTs/SnO₂A preparation method and an application method of the @ void composite film. The rGO @ CNTs/SnO₂The @ void composite film is used as a negative electrode material of the sodium ion battery and assembled into the button cell.

The specific method for assembling the button cell is as follows: rGO @ CNTs/SnO₂The @ void composite film has integrity and can be directly used as a self-supporting electrode and is cut into a negative plate for an experimental battery with the diameter of 10mm by a cutting machine.

Taking metal sodium as a counter electrode; the electrolyte is NaPF₆Mixing the ethyl carbonate and the dimethyl carbonate solution according to the volume ratio of 1: 1; the diaphragm is a celgard 2400 film; the order of assembling the battery is that a negative electrode shell, a sodium sheet, a diaphragm, a negative electrode sheet, a gasket, a spring piece and a positive electrode shell are assembled into a button battery in a glove box filled with inert atmosphere.

EXAMPLE five

Step 1, preparation of PS microspheres:

the diameter of Polystyrene (PS) microspheres synthesized by the microemulsion polymerization method provided by Shanghai Michelin Biochemical technology Ltd is 500 nm.

Step 2, CNTs/SnO₂Preparation of @ PS composite film:

first, 0.6g of SnCl₄·5H₂O, 1.2g of PS microspheres, 0.4g of CTAB and 0.06g of CNTs are added into 100mL of aqueous solution and subjected to ultrasonic treatment for about 3 hours to obtain a solution A, and then the solution A is stirred for 2 hours to obtain a solution B. The solution B was placed in a Teflon reactor and reacted at 210 ℃ for 13 hours to produce a reaction product C. Finally, the reaction product C is centrifuged and washed alternately with deionized water and ethanol for 5 times to obtain a product D of CNTs/SnO₂@ PS composite film.

Step 3, self-supporting rGO @ CNTs/SnO₂Preparation of @ void composite film:

1.8g of product D and 0.4g of ascorbic acid dispersed in 10mL of 4mg mL^-1And magnetically stirring for 5 hours to obtain a mixed solution E. Then, the mixed solution E was placed in an oven at 100 ℃ for 2 hours to obtain a gel F, rGO @ CNTs/SnO₂@ PS gel. Finally, the gel F was sliced and calcined in a muffle furnace at 200 ℃ for 2 hours to form free-standing rGO @ CNTs/SnO₂@ void composite film, namely reduced graphene oxide coated CNTs/SnO with hollow structure₂The composite film of (1).

Free-standing rGO @ CNTs/SnO₂The @ void composite film is based on the high-stability rGO coated CNTs/SnO₂A preparation method and an application method of the @ void composite film. The rGO @ CNTs/SnO₂@void the composite film is used as the negative electrode material of the sodium ion battery and assembled into a button cell.

The specific method for assembling the button cell is as follows: rGO @ CNTs/SnO₂The @ void composite film has integrity and can be directly used as a self-supporting electrode and is cut into a negative plate for an experimental battery with the diameter of 10mm by a cutting machine.

Taking metal sodium as a counter electrode; the electrolyte is NaPF₆Mixing the ethyl carbonate and the dimethyl carbonate solution according to the volume ratio of 1: 1; the diaphragm is a celgard 2400 film; the order of assembling the battery is that a negative electrode shell, a sodium sheet, a diaphragm, a negative electrode sheet, a gasket, a spring piece and a positive electrode shell are assembled into a button battery in a glove box filled with inert atmosphere.

EXAMPLE six

Step 1, preparation of PS microspheres:

the diameter of Polystyrene (PS) microspheres synthesized by the microemulsion polymerization method provided by Shanghai Michelin Biochemical technology Ltd is 500 nm.

Step 2, CNTs/SnO₂Preparation of @ PS composite film:

first, 0.8g of SnCl₄·5H₂O, 1.3g of PS microspheres, 0.45g of CTAB and 0.08g of CNTs are added into 100mL of aqueous solution and subjected to ultrasonic treatment for about 2 hours to obtain a solution A, and then the solution A is stirred for 1 hour to obtain a solution B. Putting the solution B into a polytetrafluoroethylene reactor, and reacting for 12 hours at 200 ℃ to obtain a reaction product C. Finally, the reaction product C is centrifuged and washed with deionized water and ethanol alternately for 4 times to obtain a product D of CNTs/SnO₂@ PS composite film.

Step 3, self-supporting rGO @ CNTs/SnO₂Preparation of @ void composite film:

2.8g of product D and 0.45g of ascorbic acid dispersed to a concentration of 4mg mL in 13mL^-1And magnetically stirring for 5 hours to obtain a mixed solution E. The mixed solution E was then placed in an oven at 110 ℃ for 3 hours to obtain a gel F, rGO @ CNTs/SnO₂@ PS gel. Finally, the gel F was sliced and calcined in a muffle furnace at 240 ℃ for 3 hours to form free-standing rGO @ CNTs/SnO₂@ void composite film,namely reduced graphene oxide coated CNTs/SnO with hollow structure₂The composite film of (1).

Free-standing rGO @ CNTs/SnO₂The @ void composite film is based on the high-stability rGO coated CNTs/SnO₂A preparation method and an application method of the @ void composite film. The rGO @ CNTs/SnO₂The @ void composite film is used as a negative electrode material of the sodium ion battery and assembled into the button cell.

The specific method for assembling the button cell is as follows: rGO @ CNTs/SnO₂The @ void composite film has integrity and can be directly used as a self-supporting electrode and is cut into a negative plate for an experimental battery with the diameter of 10mm by a cutting machine.

Taking metal sodium as a counter electrode; the electrolyte is NaPF₆Mixing the ethyl carbonate and the dimethyl carbonate solution according to the volume ratio of 1: 1; the diaphragm is a celgard 2400 film; the order of assembling the battery is that a negative electrode shell, a sodium sheet, a diaphragm, a negative electrode sheet, a gasket, a spring piece and a positive electrode shell are assembled into a button battery in a glove box filled with inert atmosphere.

EXAMPLE seven

Step 1, preparation of PS microspheres:

the diameter of Polystyrene (PS) microspheres synthesized by the microemulsion polymerization method provided by Shanghai Michelin Biochemical technology Ltd is 500 nm.

Step 2, CNTs/SnO₂Preparation of @ PS composite film:

first, 0.9g of SnCl₄·5H₂O, 1.35g of PS microspheres, 0.45g of CTAB and 0.08g of CNTs are added into 140mL of aqueous solution and subjected to ultrasonic treatment for about 2.5 hours to obtain a solution A, and then the solution A is stirred for 1.5 hours to obtain a solution B. The solution B was placed in a Teflon reactor and reacted at 210 ℃ for 13 hours to produce a reaction product C. Finally, the reaction product C is centrifuged and washed alternately with deionized water and ethanol for 5 times to obtain a product D of CNTs/SnO₂@ PS composite film.

Step 3, self-supporting rGO @ CNTs/SnO₂Preparation of @ void composite film:

0.25g of product D and 0.35g of ascorbic acid are dispersed in14mL of 3mg mL^-1And magnetically stirring for 5 hours to obtain a mixed solution E. The mixed solution E was then placed in an oven at 100 ℃ for 4 hours to obtain a gel F, rGO @ CNTs/SnO₂@ PS gel. Finally, the gel F was sliced and calcined in a muffle furnace at 240 ℃ for 3 hours to form free-standing rGO @ CNTs/SnO₂@ void composite film, namely reduced graphene oxide coated CNTs/SnO with hollow structure₂The composite film of (1).

Free-standing rGO @ CNTs/SnO₂The @ void composite film is based on the high-stability rGO coated CNTs/SnO₂A preparation method and an application method of the @ void composite film. The rGO @ CNTs/SnO₂The @ void composite film is used as a negative electrode material of the sodium ion battery and assembled into the button cell.

The specific method for assembling the button cell is as follows: rGO @ CNTs/SnO₂The @ void composite film has integrity and can be directly used as a self-supporting electrode and is cut into a negative plate for an experimental battery with the diameter of 10mm by a cutting machine.

Taking metal sodium as a counter electrode; the electrolyte is NaPF₆Mixing the ethyl carbonate and the dimethyl carbonate solution according to the volume ratio of 1: 1; the diaphragm is a celgard 2400 film; the order of assembling the battery is that a negative electrode shell, a sodium sheet, a diaphragm, a negative electrode sheet, a gasket, a spring piece and a positive electrode shell are assembled into a button battery in a glove box filled with inert atmosphere.

Example eight

Step 1, preparation of PS microspheres:

the diameter of Polystyrene (PS) microspheres synthesized by the microemulsion polymerization method provided by Shanghai Michelin Biochemical technology Ltd is 500 nm.

Step 2, CNTs/SnO₂Preparation of @ PS composite film:

first, 1.0g of SnCl₄·5H₂O, 1.5g of PS microspheres, 0.5g of cetyltrimethylammonium bromide (CTAB) and 0.1g of CNTs were added to 150mL of an aqueous solution and subjected to ultrasonication for about 3 hours to obtain a solution A, and then the solution A was stirred for 2 hours to obtain a solution B. Putting the solution B into a polytetrafluoroethylene reactor,the reaction product C was reacted at 220 ℃ for 15 hours. Finally, the reaction product C is centrifuged and washed alternately with deionized water and ethanol for 5 times to obtain a product D of CNTs/SnO₂@ PS composite film.

Step 3, self-supporting rGO @ CNTs/SnO₂Preparation of @ void composite film:

3.0g of product D and 0.5g of ascorbic acid are dispersed in 15mL of a concentration of 5mg mL^-1And magnetically stirring for 5 hours to obtain a mixed solution E. Then, the mixed solution E was placed in an oven at 120 ℃ for 5 hours to obtain a gel F, rGO @ CNTs/SnO₂@ PS gel. Finally, the gel F was sliced and calcined in a muffle furnace at 250 ℃ for 5 hours to form free-standing rGO @ CNTs/SnO₂@ void composite film, namely reduced graphene oxide coated CNTs/SnO with hollow structure₂The composite film of (1).

Free-standing rGO @ CNTs/SnO₂The @ void composite film is based on the high-stability rGO coated CNTs/SnO₂A preparation method and an application method of the @ void composite film. The rGO @ CNTs/SnO₂The @ void composite film is used as a negative electrode material of the sodium ion battery and assembled into the button cell.

The specific method for assembling the button cell is as follows: rGO @ CNTs/SnO₂The @ void composite film has integrity and can be directly used as a self-supporting electrode and is cut into a negative plate for an experimental battery with the diameter of 10mm by a cutting machine.

Taking metal sodium as a counter electrode; the electrolyte is NaPF₆Mixing the ethyl carbonate and the dimethyl carbonate solution according to the volume ratio of 1: 1; the diaphragm is a celgard 2400 film; the order of assembling the battery is that a negative electrode shell, a sodium sheet, a diaphragm, a negative electrode sheet, a gasket, a spring piece and a positive electrode shell are assembled into a button battery in a glove box filled with inert atmosphere.

Taking example four as an example, rGO @ CNTs/SnO₂The microstructure results of the @ void composite film are shown in fig. 2, 3 and 4, and it can be seen that there are significant voids in the structure, providing sufficient reaction space for the structure. In addition, the coated rGO of the CNTs outer layer can greatly alleviate the problem of volume expansion of the structure, and at the same time, can also be used as a barrier to gas diffusionAs ligaments connecting the entire composite film. Thanks to a unique structural design, rGO @ CNTs/SnO₂The @ void composite film as the negative electrode material of the sodium-ion battery shows excellent electrochemical stability even at 1A g^-1The cycle life can still reach 1000 circles under the high current density.

It should be noted that the Carbon Nanotubes (CNTs) used in the present invention are all multi-walled carbon nanotubes, and the Graphene Oxide (GO) used in the present invention is all single-layer graphene oxide.

In conclusion, the reduced graphene oxide coated CNTs/SnO with the hollow structure provided by the invention₂The preparation method of the composite film adopts a hydrothermal method and a tubular furnace calcination process, and the synthesis process is simple and easy to operate. Synthetic rGO @ CNTs/SnO₂The @ void composite film can effectively disperse SnO₂Particles, moderated SnO₂The volume expansion of the particles during charging and discharging is a problem. In addition, CNTs and rGO have stronger conductivity, which is beneficial to electrons in rGO @ CNTs/SnO₂The @ void composite film has rapid transport, and increases the conductivity inside the material. The void structure can effectively shorten electron/Na⁺Diffusion path, acceleration of SIB reaction kinetics, and Na⁺Provides abundant active sites. rGO can also be effective in relieving SnO₂And as a ligament is the whole rGO @ CNTs/SnO₂The @ void composite film provides a channel for electron transport.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.