CN111416124A - Self-standing Sn-SnS/CNTs @ C flexible film and preparation and application thereof - Google Patents

Abstract

The invention discloses a self-supporting Sn-SnS/CNTs @ C flexible film, and a preparation method and application thereof. The synthesized flexible Sn-SnS/CNTs @ C film is a conductive network, electrons can be freely transmitted through the high-conductivity carbon fibers and the CNT, and the problem of poor conductivity caused by agglomeration of Sn-SnS nano particles is greatly relieved. Furthermore, carbon fibers outside the Sn-SnS/CNTs can effectively prevent particles from falling off, and the electrochemical cycle life of the film is prolonged.

Description

A self-supporting Sn-SnS/CNTs@C flexible film and its preparation and application

technical field

The invention belongs to the technical field of sodium ion batteries, and in particular relates to a self-supporting Sn-SnS/CNTs@C flexible film and its preparation and application.

Background technique

Lithium-ion batteries have the advantages of high energy density, high average output voltage, low self-discharge, and excellent cycle stability, and are widely used in mobile phones, notebook computers, and power vehicles. At present, the theoretical capacity of commercial graphite-based anode materials is only 372mAh/g, which can no longer meet the demand for high-capacity batteries in the future. Moreover, the shortage of lithium resources also restricts the long-term development of lithium-ion batteries. With abundant sodium reserves and low cost, sodium-ion batteries have gradually become a research hotspot in the energy field in recent years. Relative to Li ions, the radius of Na ions is about 1.4 times that of Li ions, which makes the reversible oxidation/reduction reactions of typical intercalation-based Li ion electrode materials difficult.

At present, people have carried out in-depth research on new electrode materials for sodium-ion batteries. Anode material for sodium ion batteries, utilizing the alloying/dealloying process of sodium ion storage for energy storage. Theoretical predictions suggest that Ge, Sn, Pb, etc. can undergo alloying/dealloying reactions with sodium and thus can be used as anode materials for sodium-ion batteries. Among these materials, Sn is of great interest to researchers due to its high theoretical capacity (847 mA hg ^-1 ). Sn can be based on chemical transformations and reversible Na alloying reactions. On the other hand, the bulk change from Sn to Na ₁₅ Sn ₄ alloy has a volume expansion ratio calculated to be 424%. This leads to particle fracture and growth of an unstable solid-electrolyte interphase (SEI film), which in turn, leads to rapid capacity loss in Sn-based Na-ion anodes. Therefore, the selection of a suitable battery electrode material is of great significance for the development of a new type of sodium-ion battery with green environmental protection, stable structure, suitable electrochemical platform and large specific capacity.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a self-supporting Sn-SnS/CNTs@C flexible film and its preparation and application in view of the deficiencies in the above-mentioned prior art, which relieves the large volume change of Sn during the charging and discharging process. , the defects of poor conductivity and poor electrode stability.

The present invention adopts following technical scheme:

A preparation method of a self-supporting Sn-SnS/CNTs@C flexible film, comprising the following steps:

S1. High-energy ball milling of Sn particles and S powder to obtain Sn-SnS composite powder A; then, Sn-SnS composite powder A is mixed with CNTs and ball-milled to obtain Sn-SnS/CNTs composite powder B;

S2. Using DMF as a solvent, the carbon precursor polyacrylonitrile is blended with the pyrolysis polymer polymethyl methacrylate solution to obtain a spinning dope C; then, the Sn-SnS/CNTs composite powder B prepared in step S1 is mixed Add to spinning dope C and stir to obtain spinning solution D; then electrospinning to obtain spinning film E;

S3. The spinning film E was dried under vacuum to remove residual DMF, and then a free-standing Sn-SnS/CNTs@C flexible film was obtained by heat treatment and annealing treatment.

Specifically, in step S1, the weight ratio of Sn particles to S powder is 1:0.5, in the high-energy ball milling treatment, the weight ratio between steel balls and particles is 15:1, and the ball milling time is 6-10h.

Specifically, in step S1, the weight ratio of Sn-SnS composite powder A to CNTs is (3-9): (2-1), and the ball milling time is 2-3h.

Specifically, in step S2, the mass ratio of the carbon precursor polyacrylonitrile to the pyrolysis polymer polymethyl methacrylate is (7-9): (3-1).

Specifically, in step S2, the mass fraction of the Sn-SnS/CNTs composite powder B in the spinning dope C is 20%-30%, and the spinning solution D is obtained by stirring at 70-90° C. for 2-3 hours.

Specifically, in step S2, the electrospinning is as follows: the speed is 1-3mL/h, the voltage is 20kV, the distance between the needle and the rotating collector is 10-20cm, the temperature in the electrospinning chamber is 25±5°C, and the humidity is 50 ±5%.

Specifically, in step S3, the removal of residual DMF is as follows: drying at a temperature of 60-80° C. for 1-2 hours.

Specifically, in step S3, the heat treatment is specifically: heat treatment at 250-300°C for 2 hours; annealing treatment is specifically: in a high-purity nitrogen atmosphere, the temperature is 600-800°C, and the time is 2-3 hours.

Another technical solution of the present invention is to provide a self-supporting Sn-SnS/CNTs@C flexible film prepared by the method.

Another technical solution of the present invention is a button battery, wherein the self-supporting Sn-SnS/CNTs@C flexible film prepared by the method is used as the negative electrode material of the sodium ion battery, and the metal sodium is used as the counter electrode ; The electrolyte is the solution of NaPF6 ethyl carbonate and dimethyl carbonate mixed according to the volume ratio of 1:1; the diaphragm is celgard2400 film; Gaskets, spring sheets, positive case, assembled into a button cell in a glove box filled with an inert atmosphere.

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

The invention provides a preparation method of a self-supporting Sn-SnS/CNTs@C flexible film. The Sn-SnS/CNTs@C flexible film is prepared by high-energy ball milling technology and electrospinning technology, and the synthesis process is simple and easy to operate. . Moreover, the carbonized spinning product can be directly used as a self-supporting substrate for battery anode materials, avoiding the influence of binders in traditional battery assembly.

Further, SnS can act as a buffer matrix to ease the agglomeration of nanoparticles. The flexibility and ultra-high conductivity of carbon nanotubes can greatly alleviate the problem of poor internal conductivity caused by Sn-SnS agglomeration.

Further, the carbonized conductive carbon fibers can further limit the crushing of the material, and at the same time can increase the conductivity of the entire electrode.

Further, the conductive carbon fiber network can form a film by itself, and at the same time, it can enhance the transport of electrons on the film.

A free-standing Sn-SnS/CNTs@C flexible thin film.

A button battery can avoid the coating process of the battery and greatly shorten the manufacturing process of the battery. In addition, the influence of the binder on the conductivity of the electrode is avoided, and the active material of the electrode plays a maximum role, so that the electrochemical performance of the entire electrode is in an optimal state.

To sum up, the material of the present invention is easy to obtain and synthesize the process is simple, easy to operate, and can be used in large-scale production. The as-synthesized flexible Sn-SnS/CNTs@C thin films form a self-conducting network with fast electron transport. The carbon fibers outside the Sn-SnS/CNTs can effectively prevent the particles from falling off and enhance the cycle life of the films.

The technical solutions of the present invention will be further described in detail below through the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is the SEM image of the present invention, wherein (a) is the XRD pattern of the prepared flexible film; (b) is Roman; (c) is the SEM image of Sn-SnS/CNTs; (d) is the Sn-SnS in Fig. c Particle size distribution of /CNTs particles; (e) is the SEM image of the 50 μm Sn-SnS/CNTs@C carbon fiber network; (f) is the SEM image of the 2 μm Sn-SnS/CNTs@C carbon fiber network; (g) is the 500 nm Sn -SEM image of SnS/CNTs@C carbon fiber network; Figure h is the particle size distribution of fiber tube diameter in Figure e;

Figure 2 shows the TEM images of Sn-SnS/CNTs at different magnifications, in which (a) is the TEM image of 1 μm Sn-SnS/CNTs, (b) is the TEM image of 100 nm Sn-SnS/CNTs, and (c) is TEM images of 10 nm Sn-SnS/CNTs, (d) Mapping image of Sn-SnS/CNTs; (e) TEM images of 1 μm Sn-SnS/CNTs@C carbon fiber network at different magnifications; (f) 500 nm TEM images of Sn-SnS/CNTs@C carbon fiber network at different magnifications; (g) is Roll; (h) is Fold; (i) is the flexible display image of the film; (j) is the free-standing display image of the film;

Figure 3 is a comparison diagram, in which (a) is the electrochemical performance diagram of the thin film electrode cycled for 1000 cycles at a high current density of 1 A g ^-1 . (b, c) are the SEM images of the thin film electrode after 100 cycles and 500 cycles, respectively.

Detailed ways

A preparation method of a self-supporting Sn-SnS/CNTs@C flexible film of the present invention comprises the following steps:

S1. Preparation of Sn-SnS/CNTs composites:

First, the Sn particles and S powder were subjected to high-energy ball milling at a weight ratio of 1:0.5 (the weight ratio between the steel balls and the particles was 15:1), and the Sn-SnS composite powder A was obtained after ball milling for 6 to 10 hours; then, the A and CNTs are mixed and ball-milled at a weight ratio of 3:2 to 9:1 for 2 to 3 hours to obtain Sn-SnS/CNTs composite powder B;

S2. Preparation of self-supporting Sn-SnS/CNTs flexible films:

Using DMF as a solvent, the carbon precursor polyacrylonitrile (PAN) was blended with the pyrolyzed polymer polymethyl methacrylate (PMMA) solution to obtain a spinning dope C (the mass ratio of PAN/PMMA was 7:3-9 : 1); then, add the above-prepared B to the spinning solution C (mass fraction: 20%-30%), and stir at 70-90° C. for 2-3 hours to obtain the spinning solution D; then The spinning solution D was electrospun at a speed of 1 to 3 mL/h, a voltage of 20 kV and a distance between the needle and the rotating collector of 10 to 20 cm. The temperature and humidity in the electrospinning chamber were controlled at 25 ± 5°C and 50±5% to obtain spinning film E;

S3. Preparation of free-standing Sn-SnS/CNTs@C flexible films:

The spinning film E was dried under vacuum at 60-80°C for 1-2 hours to completely remove the residual DMF, and the film E was heat-treated at 250-300°C for 2 hours to pre-oxidize PAN and then dried in high-purity nitrogen (99.99%). ) at 600-800 °C for 2-3 hours to obtain the final free-standing Sn-SnS/CNTs@C flexible film.

A self-supporting Sn-SnS/CNTs@C flexible film of the present invention is prepared based on the high-energy ball milling technology and electrospinning technology, and the self-supporting Sn-SnS/CNTs@C flexible film is used as a sodium ion battery The negative electrode material is assembled into a button battery.

The specific method of assembling the button battery is as follows: the self-supporting Sn-SnS/CNTs@C flexible film is directly used as a self-supporting substrate, and a cutting machine is used to cut the negative electrode sheet for the experimental battery with a diameter of 10 mm.

Sodium metal is used as the counter electrode; the electrolyte is a solution of NaPF6 ethyl carbonate and dimethyl carbonate mixed in a volume ratio of 1:1; the diaphragm is celgard2400 film; the order of assembling the battery is the negative shell, the sodium sheet , diaphragm, negative electrode sheet, gasket, spring sheet, positive electrode shell, assembled into a button battery in a glove box filled with an inert atmosphere.

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all embodiments. The components of the embodiments of the invention generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations. Thus, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

Step 1, Preparation of Sn-SnS/CNTs composites:

First, the Sn particles and S powder were subjected to high-energy ball milling at a weight ratio of 1:0.5 (the weight ratio between steel balls and particles was 15:1), and the Sn-SnS composite powder A was obtained after ball milling for 6 hours; CNTs were mixed and ball-milled at a weight ratio of 3:2 for 2 hours to obtain Sn-SnS/CNTs composite powder B;

Step 2, preparation of free-standing Sn-SnS/CNTs flexible thin films:

Using DMF as a solvent, the carbon precursor polyacrylonitrile (PAN) was blended with the pyrolyzed polymer polymethyl methacrylate (PMMA) solution to obtain spinning dope C (the mass ratio of PAN/PMMA was 7:3); Then, B prepared above was added to mixed solution C (mass fraction: 20%), and stirred at 70 °C for 2 hours to obtain spinning solution D; then spinning solution D was added at a rate of 1 mL/h, The electrospinning process was performed at a voltage of 20 kV and the distance between the needle and the rotating collector was 10. The temperature and humidity in the electrospinning chamber were controlled at 25±5°C and 50±5%, respectively, to obtain the spinning film E;

Step 3, preparation of free-standing Sn-SnS/CNTs@C flexible thin films:

Finally, the spun film E was dried under vacuum at 60 °C for 1 h to completely remove the residual DMF, and the film E was heat-treated at 250 °C for 2 h to pre-oxidize PAN under high-purity nitrogen (99.99%) at 600 °C After annealing for 2 h, the final free-standing Sn-SnS/CNTs@C flexible film was obtained.

A self-supporting Sn-SnS/CNTs@C flexible film is prepared based on the high-energy ball milling technology and electrospinning technology, and the self-supporting Sn-SnS/CNTs@C flexible film is used as a negative electrode of a sodium ion battery material, assembled as a button battery.

The specific method of assembling the button battery is as follows: the self-supporting Sn-SnS/CNTs@C flexible film is directly used as a self-supporting substrate, and a cutting machine is used to cut the negative electrode sheet for the experimental battery with a diameter of 10 mm.

Sodium metal is used as the counter electrode; the electrolyte is a solution of NaPF6 ethyl carbonate and dimethyl carbonate mixed in a volume ratio of 1:1; the diaphragm is celgard2400 film; the order of assembling the battery is the negative shell, the sodium sheet , diaphragm, negative electrode sheet, gasket, spring sheet, positive electrode shell, assembled into a button battery in a glove box filled with an inert atmosphere.

Example 2

Step 1, Preparation of Sn-SnS/CNTs composites:

First, the Sn particles and S powder were subjected to high-energy ball milling at a weight ratio of 1:0.5 (the weight ratio between the steel balls and the particles was 15:1), and the Sn-SnS composite powder A was obtained after ball milling for 7 hours; CNTs were mixed and ball-milled at a weight ratio of 7:3 for 2 hours to obtain Sn-SnS/CNTs composite powder B;

Step 2, preparation of free-standing Sn-SnS/CNTs flexible thin films:

Using DMF as a solvent, the carbon precursor polyacrylonitrile (PAN) was blended with the pyrolyzed polymer polymethyl methacrylate (PMMA) solution to obtain spinning dope C (the mass ratio of PAN/PMMA was 7:3); Then, B prepared above was added to mixed solution C (mass fraction: 25%), and stirred at 80°C for 2 hours to obtain spinning solution D; then spinning solution D was added at a rate of 1 mL/h, The electrospinning process was performed at a voltage of 20kV and the distance between the needle and the rotating collector was 15cm, and the temperature and humidity in the electrospinning chamber were controlled at 25±5°C and 50±5%, respectively, to obtain the spinning film E;

Step 3, preparation of free-standing Sn-SnS/CNTs@C flexible thin films:

Finally, the spun film E was dried under vacuum at 60 °C for 1 h to completely remove residual DMF, and the film E was heat treated at 280 °C for 2 h to pre-oxidize PAN under high-purity nitrogen (99.99%) at 700 °C After annealing for 2 h, the final free-standing Sn-SnS/CNTs@C flexible film was obtained.

A self-supporting Sn-SnS/CNTs@C flexible film is prepared based on the high-energy ball milling technology and electrospinning technology, and the self-supporting Sn-SnS/CNTs@C flexible film is used as a negative electrode of a sodium ion battery material, assembled as a button battery.

The specific method of assembling the button battery is as follows: the self-supporting Sn-SnS/CNTs@C flexible film is directly used as a self-supporting substrate, and a cutting machine is used to cut the negative electrode sheet for the experimental battery with a diameter of 10 mm.

Sodium metal is used as the counter electrode; the electrolyte is a solution of NaPF6 ethyl carbonate and dimethyl carbonate mixed in a volume ratio of 1:1; the diaphragm is celgard2400 film; the order of assembling the battery is the negative shell, the sodium sheet , diaphragm, negative electrode sheet, gasket, spring sheet, positive electrode shell, assembled into a button battery in a glove box filled with an inert atmosphere.

Example 3

Step 1, Preparation of Sn-SnS/CNTs composites:

First, the Sn particles and S powder were subjected to high-energy ball milling at a weight ratio of 1:0.5 (the weight ratio between steel balls and particles was 15:1), and the Sn-SnS composite powder A was obtained after ball milling for 8 hours; The CNTs were mixed and ball-milled at a weight ratio of 4:1 for 3 hours to obtain Sn-SnS/CNTs composite powder B;

Step 2, preparation of free-standing Sn-SnS/CNTs flexible thin films:

Using DMF as a solvent, the carbon precursor polyacrylonitrile (PAN) was blended with the pyrolyzed polymer polymethyl methacrylate (PMMA) solution to obtain spinning dope C (the mass ratio of PAN/PMMA was 7:3); Then, B prepared above was added to mixed solution C (mass fraction: 25%), and stirred at 70° C. for 3 hours to obtain spinning solution D; then spinning solution D was added at a rate of 1.5 mL/h , the electrospinning process was carried out at a voltage of 20 kV and the distance between the needle and the rotating collector was 18 cm, and the temperature and humidity in the electrospinning chamber were controlled at 25±5°C and 50±5%, respectively, and the spinning film E was obtained;

Step 3, preparation of free-standing Sn-SnS/CNTs@C flexible thin films:

Finally, the spun film E was dried under vacuum at 60 °C for 1.5 h to completely remove the residual DMF, and the film E was heat treated at 280 °C for 2 h to pre-oxidize PAN at 800 °C under high-purity nitrogen (99.99%). After annealing for 2 h, the final free-standing Sn-SnS/CNTs@C flexible film was obtained.

A self-supporting Sn-SnS/CNTs@C flexible film is prepared based on the high-energy ball milling technology and electrospinning technology, and the self-supporting Sn-SnS/CNTs@C flexible film is used as a negative electrode of a sodium ion battery material, assembled as a button battery.

The specific method of assembling the button battery is as follows: the self-supporting Sn-SnS/CNTs@C flexible film is directly used as a self-supporting substrate, and a cutting machine is used to cut the negative electrode sheet for the experimental battery with a diameter of 10 mm.

Sodium metal is used as the counter electrode; the electrolyte is a solution of NaPF6 ethyl carbonate and dimethyl carbonate mixed in a volume ratio of 1:1; the diaphragm is celgard2400 film; the order of assembling the battery is the negative shell, the sodium sheet , diaphragm, negative electrode sheet, gasket, spring sheet, positive electrode shell, assembled into a button battery in a glove box filled with an inert atmosphere.

Example 4

Step 1, Preparation of Sn-SnS/CNTs composites:

First, the Sn particles and S powder were subjected to high-energy ball milling at a weight ratio of 1:0.5 (the weight ratio between steel balls and particles was 15:1), and the Sn-SnS composite powder A was obtained after ball milling for 8 hours; The CNTs were mixed and ball-milled at a weight ratio of 4:1 for 3 hours to obtain Sn-SnS/CNTs composite powder B;

Step 2, preparation of free-standing Sn-SnS/CNTs flexible thin films:

Using DMF as a solvent, the carbon precursor polyacrylonitrile (PAN) was blended with the pyrolyzed polymer polymethyl methacrylate (PMMA) solution to obtain spinning dope C (the mass ratio of PAN/PMMA was 4:1); Then, B prepared above was added to mixed solution C (mass fraction: 25%), and stirred at 80°C for 3 hours to obtain spinning solution D; then spinning solution D was added at a rate of 1.5 mL/h , the electrospinning process was carried out at a voltage of 20kV and the distance between the needle and the rotating collector was 15cm, and the temperature and humidity in the electrospinning chamber were controlled at 25±5°C and 50±5%, respectively, to obtain the spinning film E;

Step 3, preparation of free-standing Sn-SnS/CNTs@C flexible thin films:

Finally, the spun film E was dried under vacuum at 60 °C for 2 h to completely remove the residual DMF, and the film E was heat-treated at 280 °C for 2 h to pre-oxidize PAN under high-purity nitrogen (99.99%) at 800 °C After annealing for 2 h, the final free-standing Sn-SnS/CNTs@C flexible film was obtained.

A self-supporting Sn-SnS/CNTs@C flexible film is prepared based on the high-energy ball milling technology and electrospinning technology, and the self-supporting Sn-SnS/CNTs@C flexible film is used as a negative electrode of a sodium ion battery material, assembled as a button battery.

The specific method of assembling the button battery is as follows: the self-supporting Sn-SnS/CNTs@C flexible film is directly used as a self-supporting substrate, and a cutting machine is used to cut the negative electrode sheet for the experimental battery with a diameter of 10 mm.

Sodium metal is used as the counter electrode; the electrolyte is a solution of NaPF6 ethyl carbonate and dimethyl carbonate mixed in a volume ratio of 1:1; the diaphragm is celgard2400 film; the order of assembling the battery is the negative shell, the sodium sheet , diaphragm, negative electrode sheet, gasket, spring sheet, positive electrode shell, assembled into a button battery in a glove box filled with an inert atmosphere.

Example 5

Step 1, Preparation of Sn-SnS/CNTs composites:

First, the Sn particles and S powder were subjected to high-energy ball milling at a weight ratio of 1:0.5 (the weight ratio between steel balls and particles was 15:1), and the Sn-SnS composite powder A was obtained after ball milling for 8 hours; The CNTs were mixed and ball-milled at a weight ratio of 9:1 for 2 hours to obtain Sn-SnS/CNTs composite powder B;

Step 2, preparation of free-standing Sn-SnS/CNTs flexible thin films:

Using DMF as a solvent, the carbon precursor polyacrylonitrile (PAN) was blended with the pyrolyzed polymer polymethyl methacrylate (PMMA) solution to obtain spinning dope C (the mass ratio of PAN/PMMA was 9:1); Then, B prepared above was added to mixed solution C (mass fraction: 20%) and stirred at 70°C for 2 hours to obtain spinning solution D; then spinning solution D was added at a rate of 3 mL/h, The electrospinning process was performed at a voltage of 20kV and the distance between the needle and the rotating collector was 20cm, and the temperature and humidity in the electrospinning chamber were controlled at 25±5°C and 50±5%, respectively, to obtain the spinning film E;

Step 3, preparation of free-standing Sn-SnS/CNTs@C flexible thin films:

Finally, the spun film E was dried under vacuum at 70 °C for 2 h to completely remove the residual DMF, and the film E was heat-treated at 250 °C for 2 h to pre-oxidize PAN under high-purity nitrogen (99.99%) at 750 °C After annealing for 2-3 hours, the final free-standing Sn-SnS/CNTs@C flexible film was obtained.

A self-supporting Sn-SnS/CNTs@C flexible film is prepared based on the high-energy ball milling technology and electrospinning technology, and the self-supporting Sn-SnS/CNTs@C flexible film is used as a negative electrode of a sodium ion battery material, assembled as a button battery.

The specific method of assembling the button battery is as follows: the self-supporting Sn-SnS/CNTs@C flexible film is directly used as a self-supporting substrate, and a cutting machine is used to cut the negative electrode sheet for the experimental battery with a diameter of 10 mm.

Sodium metal is used as the counter electrode; the electrolyte is a solution of NaPF6 ethyl carbonate and dimethyl carbonate mixed in a volume ratio of 1:1; the diaphragm is celgard2400 film; the order of assembling the battery is the negative shell, the sodium sheet , diaphragm, negative electrode sheet, gasket, spring sheet, positive electrode shell, assembled into a button battery in a glove box filled with an inert atmosphere.

Example 6

Step 1, Preparation of Sn-SnS/CNTs composites:

First, the Sn particles and S powder were subjected to high-energy ball milling at a weight ratio of 1:0.5 (the weight ratio between steel balls and particles was 15:1), and the Sn-SnS composite powder A was obtained after ball milling for 8 hours; CNTs were mixed and ball-milled at a weight ratio of 9:1 for 3 hours to obtain Sn-SnS/CNTs composite powder B;

Step 2, preparation of free-standing Sn-SnS/CNTs flexible thin films:

Using DMF as a solvent, the carbon precursor polyacrylonitrile (PAN) was blended with the pyrolyzed polymer polymethyl methacrylate (PMMA) solution to obtain spinning dope C (the mass ratio of PAN/PMMA was 7:3); Then, B prepared above was added to mixed solution C (mass fraction: 25%), and stirred at 90°C for 2 hours to obtain spinning solution D; then spinning solution D was added at a rate of 2.5 mL/h , the electrospinning process was carried out at a voltage of 20kV and the distance between the needle and the rotating collector was 20cm, and the temperature and humidity in the electrospinning chamber were controlled at 25±5°C and 50±5%, respectively, to obtain the spinning film E;

Step 3, preparation of free-standing Sn-SnS/CNTs@C flexible thin films:

Finally, the spun film E was dried under vacuum at 80 °C for 2 h to completely remove the residual DMF, and the film E was heat treated at 300 °C for 2 h to pre-oxidize PAN at 800 °C under high-purity nitrogen (99.99%). After annealing for 2 h, the final free-standing Sn-SnS/CNTs@C flexible film was obtained.

A self-supporting Sn-SnS/CNTs@C flexible film is prepared based on the high-energy ball milling technology and electrospinning technology, and the self-supporting Sn-SnS/CNTs@C flexible film is used as a negative electrode of a sodium ion battery material, assembled as a button battery.

The specific method of assembling the button battery is as follows: the self-supporting Sn-SnS/CNTs@C flexible film is directly used as a self-supporting substrate, and a cutting machine is used to cut the negative electrode sheet for the experimental battery with a diameter of 10 mm.

Sodium metal is used as the counter electrode; the electrolyte is a solution of NaPF6 ethyl carbonate and dimethyl carbonate mixed in a volume ratio of 1:1; the diaphragm is celgard2400 film; the order of assembling the battery is the negative shell, the sodium sheet , diaphragm, negative electrode sheet, gasket, spring sheet, positive electrode shell, assembled into a button battery in a glove box filled with an inert atmosphere.

Example 7

Step 1, Preparation of Sn-SnS/CNTs composites:

First, the Sn particles and S powder were subjected to high-energy ball milling at a weight ratio of 1:0.5 (the weight ratio between steel balls and particles was 15:1), and the Sn-SnS composite powder A was obtained after ball milling for 10 hours; CNTs were mixed and ball-milled at a weight ratio of 9:1 for 3 hours to obtain Sn-SnS/CNTs composite powder B;

Step 2, preparation of free-standing Sn-SnS/CNTs flexible thin films:

Using DMF as a solvent, the carbon precursor polyacrylonitrile (PAN) was blended with the pyrolyzed polymer polymethyl methacrylate (PMMA) solution to obtain spinning dope C (the mass ratio of PAN/PMMA was 9:1); Then, B prepared above was added to mixed solution C (mass fraction: 30%), and stirred at 90°C for 3 hours to obtain spinning solution D; then spinning solution D was added at a rate of 3 mL/h, The electrospinning process was performed at a voltage of 20kV and the distance between the needle and the rotating collector was 20cm, and the temperature and humidity in the electrospinning chamber were controlled at 25±5°C and 50±5%, respectively, to obtain the spinning film E;

Step 3, preparation of free-standing Sn-SnS/CNTs@C flexible thin films:

Finally, the spun film E was dried under vacuum at 80 °C for 2 h to completely remove the residual DMF, and the film E was heat treated at 300 °C for 2 h to pre-oxidize PAN at 800 °C under high-purity nitrogen (99.99%). After annealing for 3 hours, the final free-standing Sn-SnS/CNTs@C flexible film was obtained.

A self-supporting Sn-SnS/CNTs@C flexible film is prepared based on the high-energy ball milling technology and electrospinning technology, and the self-supporting Sn-SnS/CNTs@C flexible film is used as a negative electrode of a sodium ion battery material, assembled as a button battery.

The specific method of assembling the button battery is as follows: the self-supporting Sn-SnS/CNTs@C flexible film is directly used as a self-supporting substrate, and a cutting machine is used to cut the negative electrode sheet for the experimental battery with a diameter of 10 mm.

Sodium metal is used as the counter electrode; the electrolyte is a solution of NaPF6 ethyl carbonate and dimethyl carbonate mixed in a volume ratio of 1:1; the diaphragm is celgard2400 film; the order of assembling the battery is the negative shell, the sodium sheet , diaphragm, negative electrode sheet, gasket, spring sheet, positive electrode shell, assembled into a button battery in a glove box filled with an inert atmosphere.

Please refer to Figure 1, (a) is the XRD pattern of the prepared flexible film; (b) is Roman; (c) is the SEM image of Sn-SnS/CNTs; (d) is the particle size of Sn-SnS/CNTs particles in Figure c diameter distribution; (e) is the SEM image of the 50 μm Sn-SnS/CNTs@C carbon fiber network; (f) is the SEM image of the 2 μm Sn-SnS/CNTs@C carbon fiber network; (g) is the 500 nm Sn-SnS/CNTs@C carbon fiber network SEM image of carbon fiber network in C; Figure h is the particle size distribution of the fiber tube diameter in Figure e.

Please refer to Fig. 2, (a) is the TEM image of 1 μm Sn-SnS/CNTs, (b) is the TEM image of 100 nm Sn-SnS/CNTs, (c) is the TEM image of 10 nm Sn-SnS/CNTs, (d) Mapping images of Sn-SnS/CNTs; (e) TEM images of 1 μm Sn-SnS/CNTs@C carbon fiber network with different magnifications; (f) 500 nm Sn-SnS/CNTs@C carbon fiber network with different magnifications TEM image of ; (g) is Roll; (h) is Fold; (i) is the flexible display image of the film; (j) is the free-standing display image of the film.

Please refer to Figure 3, (a) is a graph of the electrochemical performance of the thin film electrode cycled for 1000 cycles at a high current density of 1A g ^-1 . (b, c) are the SEM images of the thin film electrode after 100 cycles and 500 cycles, respectively.

To sum up, the structure of the present invention uses carbon fibers to confine Sn-SnS/CNTs to improve the cycling stability of the electrode. To address the low electrical conductivity inside the large agglomerates due to interparticle adhesion, we used carbon nanotubes (CNTs) with excellent flexibility and electrical conductivity interwoven with Sn-SnS agglomerates. Moreover, carbon fiber design has multiple benefits:

1) Carbon fiber can effectively adapt to the expansion of Sn-SnS during the oxygenation/deoxidation process, enhance the integrity and stability of the electrode, and thus achieve excellent cycle performance;

2) The carbon fiber as the conductive matrix provides a large accessible area for the electrolyte, which further interconnects the electrolyte to form an effective 3D conductive network, resulting in excellent electronic conductivity;

3) To avoid Sn-SnS nanoparticles being detached from CNTs due to volume change during cycling, and to further maximize the contact area between the agglomerates and conductive carbon, carbon fibers have volume expansion space to encapsulate Sn-SnS/CNTs agglomerates (Sn-SnS/CNTs@C). Benefiting from the above-mentioned unique features, Sn-SnS/CNTs@C has extended cycle life and excellent sodium storage performance.

The above content is only to illustrate the technical idea of the present invention, and cannot limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention all fall within the scope of the claims of the present invention. within the scope of protection.

Claims (10)

1. A preparation method of a self-supporting Sn-SnS/CNTs @ C flexible film is characterized by comprising the following steps:

s1, carrying out high-energy ball milling on the Sn particles and the S powder to obtain Sn-SnS composite powder A; then, mixing the Sn-SnS composite powder A with CNTs, and then carrying out ball milling to obtain Sn-SnS/CNTs composite powder B;

s2, blending carbon precursor polyacrylonitrile and a pyrolytic polymer polymethyl methacrylate solution by using DMF as a solvent to obtain a spinning solution C; then, adding the Sn-SnS/CNTs composite powder B prepared in the step S1 into the spinning solution C, and stirring to obtain a spinning solution D; then carrying out electrostatic spinning to obtain a spinning film E;

s3, drying the spinning film E under the vacuum condition to remove residual DMF, and carrying out heat treatment and annealing treatment to obtain the free-standing Sn-SnS/CNTs @ C flexible film.

2. The method of claim 1, wherein in the step S1, the weight ratio of Sn particles to S powder is 1:0.5, the weight ratio of steel balls to particles in the high-energy ball milling treatment is 15:1, and the ball milling time is 6-10 h.

3. The method of claim 1, wherein in step S1, the weight ratio of Sn-SnS composite powder A to CNTs is (3-9): (2-1) the ball milling time is 2-3 h.

4. The method according to claim 1, wherein in step S2, the mass ratio of the carbon precursor polyacrylonitrile to the pyrolyzed polymer polymethyl methacrylate is (7-9): (3-1).

5. The method according to claim 1, wherein in step S2, the mass fraction of Sn-SnS/CNTs composite powder B in the spinning solution C is 20% -30%, and the spinning solution D is obtained by stirring at 70-90 ℃ for 2-3 h.

6. The method of claim 1, wherein the electrospinning in step S2 is performed at a speed of 1-3 m L/h, a voltage of 20kV, a distance between the needle and the rotating collector of 10-20 cm, a temperature in the electrospinning chamber of 25 + -5 deg.C, and a humidity of 50 + -5%.

7. The method of claim 1, wherein the step S3, the removing of the residual DMF comprises: drying for 1-2 hours at the temperature of 60-80 ℃.

8. The method according to claim 1, wherein in step S3, the heat treatment is specifically: heat treatment is carried out for 2 hours at the temperature of 250-300 ℃; the annealing treatment specifically comprises the following steps: and (3) in a high-purity nitrogen atmosphere, the temperature is 600-800 ℃, and the time is 2-3 hours.

9. A free-standing Sn-SnS/CNTs @ C flexible film prepared by the process of any one of claims 1 to 8.

10. Button cell, characterized in that the free-standing Sn-SnS/CNTs @ C flexible film prepared by the process of any one of claims 1 to 8 or claim 9 is used as negative electrode material for sodium ion battery, with metallic sodium as counter electrode; mixing ethyl carbonate and dimethyl carbonate solution of NaPF6 as electrolyte in the volume ratio of 1 to 1; the diaphragm is a celgard2400 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.

Images