CN112909246B - A kind of bismuth telluride/carbon nanowire composite material and its preparation method and application - Google Patents

Abstract

The present application belongs to the technical field of battery energy storage. The present application provides a bismuth telluride/carbon nanowire composite material and a preparation method and application thereof. The bismuth telluride/carbon nanowire composite material is formed by coating bismuth telluride particles with carbon nanowires, and has a self-supporting structure. Since the bismuth telluride particles are encapsulated in carbon nanofibers with a porous structure, not only the specific capacity and rate performance of the material can be improved, but also the volume expansion of the bismuth telluride material during charge and discharge can be effectively suppressed, which improves its use as a negative electrode for potassium ion batteries. Cycle stability of the material; good flexibility and self-supporting structure, which can ensure the close contact between the active material and the current collector, improve the electrochemical performance, and maximize the advantages as a potassium ion electrode material. The bismuth telluride/carbon nanowire composite material of the present application has high capacity, good rate performance and long cycle stability, and has broad application prospects as an anode material for potassium ion secondary batteries.

Description

A kind of bismuth telluride/carbon nanowire composite material and its preparation method and application

technical field

The application belongs to the technical field of battery energy storage, and in particular relates to a bismuth telluride/carbon nanowire composite material and a preparation method and application thereof.

Background technique

Due to its high energy density, low self-discharge efficiency, and long environmental life, lithium-ion batteries have occupied a large share of the energy storage device market in a relatively short period of time, and are widely used in various fields of people's lives. However, due to the scarcity and uneven distribution of lithium resources in the earth's crust, the high cost of lithium-ion batteries limits its application in the field of energy storage. Compared with lithium-ion batteries, potassium-ion batteries (PIBs) have lower redox potentials, very high potassium reserves in the earth's crust, and low prices. Therefore, potassium-ion batteries are favored by researchers and are considered to be the most promising lithium-ion batteries. Ion battery is one of the alternative energy storage devices. However, potassium ions are bulky and have slow diffusion kinetics, so it is particularly important to develop a potassium ion electrode material with high ionic conductivity and high ionic diffusion coefficient.

Bismuth-based chalcogenides, especially bismuth sulfide and bismuth selenide, have been widely studied due to their high theoretical potassium storage capacity and low operating voltage. However, such compounds still have the problem of low electrical conductivity and large volume changes during the charge and discharge process, resulting in the gradual pulverization of electrode materials and rapid capacity decay, hindering their commercial application.

SUMMARY OF THE INVENTION

In view of this, the present application provides a bismuth telluride/carbon nanowire composite material and a preparation method and application thereof, which have high capacity, good rate performance and long cycle stability.

The specific technical scheme of this application is as follows:

The application provides a bismuth telluride/carbon nanowire composite material, which is formed by coating bismuth telluride particles with carbon nanowires;

The bismuth telluride/carbon nanowire composite material has a self-supporting structure.

In this application, the guest ion site of the bismuth telluride compound is located between two consecutive cation or anion layers parallel to the monoclinic crystal plane, and the interlayer of its lattice provides a channel for the migration and absorption of guest ions, enhancing the The ability to accommodate the insertion and extraction of potassium ions; the bismuth telluride compound has higher electrical conductivity, which makes the utilization rate of active materials higher, which can be reduced to metal Bi more efficiently, and further alloying and dealloying with potassium ions. The alloying reaction produces K ₃ Bi, and this alloying reaction process is highly reversible, so it has high capacity and good rate performance as a potassium-ion battery anode material.

Since the bismuth telluride particles are encapsulated in carbon nanofibers with a porous structure, they not only improve the specific capacity and rate performance of the material, but also effectively suppress the volume expansion of the bismuth telluride material during charge and discharge, improving its use as a potassium-ion battery anode. The cycle stability of the material; good flexibility and self-supporting structure, which can ensure the close contact between the active material and the current collector, improve the electrochemical performance, and maximize the advantages as a potassium ion electrode material. The bismuth telluride/carbon nanowire composite material of the present application has high capacity, good rate performance and long cycle stability, and has broad application prospects as a negative electrode material for potassium ion secondary batteries.

Preferably, the diameter of the carbon nanowires is 1.5-3 μm, and the diameter of the bismuth telluride particles is 70-130 nm.

The application also provides a preparation method of the bismuth telluride/carbon nanowire composite material, comprising the following steps:

S1: Dissolve the high molecular polymer in a solvent and stir, add bismuth salt and TEOS and stir to obtain a spinning solution;

S2: performing electrospinning and drying on the spinning solution, and immersing it in the solution for drying to obtain a spinning sample;

S3: adding tellurium powder to the spinning sample, and performing heat treatment to obtain the bismuth telluride/carbon nanowire composite material.

In this application, high molecular polymer is used as carbon source, bismuth salt and tellurium powder are used as raw materials, and carbon nanowires with porous structure are formed by electrospinning method to encapsulate bismuth telluride particles uniformly and densely, and the specific surface area can be obtained. Tall and flexible self-supporting bismuth telluride/carbon nanowire composites. Among them, using a strong acid solution to etch the coated bismuth telluride nanofibers can make the surface of the material loose and porous, which is more conducive to the infiltration of the electrolyte and the entry and extraction of potassium ions during the potassiumization reaction. The preparation method of the present application has simple steps, abundant raw material sources, and controllable appearance of the obtained product, and is suitable for large-scale production.

It should be noted that the mass concentration of the solution is 10 wt %, which is used to etch the silica in the spinning solution to generate a fine and uniform pore size structure. The heat treatment is carried out under inert atmosphere conditions.

Preferably, the bismuth source is selected from one or more of bismuth iodide, bismuth chloride, bismuth subnitrite and bismuth nitrate pentahydrate;

The high molecular polymer is selected from one or more of polyacrylonitrile, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylpyrrolidone, polyvinylidene fluoride and polyacrylic acid.

Preferably, the molecular weight of the polyvinylpyrrolidone is 10,000, the molecular weight of the polyvinylpyrrolidone is 58,000, and the molecular weight of the polyvinylpyrrolidone is 1,300,000.

Preferably, the solvent is selected from N,N-dimethylformamide, deionized water, absolute ethanol or acetone;

The solution is selected from nitric acid or hydrofluoric acid.

Preferably, the dosage ratio of the high molecular polymer to the solvent is (0.05-0.1) g: 1 mL;

The molar ratio of the bismuth source to the high molecular polymer is 2 mmol/g to 3 mmol/g.

Preferably, the dosage ratio of the TEOS to the high molecular polymer is 1 mL/g to 5 mL/g;

The mass ratio of the tellurium source to the spinning sample was 3:2.

Preferably, the operating conditions of the electrospinning are: voltage 15-18KV, needle diameter 0.5-1.5mm, spinning distance 12-15cm, temperature 20-30°C, humidity 40%-60%, jet speed 2-5mm /h.

Preferably, the drying temperature is 60°C and the drying time is 24h;

The temperature of the heat treatment is 600-700°C, the heating rate is 2-5°C/min, and the time is 2-4h.

In summary, the present application provides a bismuth telluride/carbon nanowire composite material and a preparation method and application thereof. The bismuth telluride/carbon nanowire composite material is formed by coating bismuth telluride particles with carbon nanowires, and has a self-supporting structure. Since the bismuth telluride particles are encapsulated in carbon nanofibers with a porous structure, they not only improve the specific capacity and rate performance of the material, but also effectively suppress the volume expansion of the bismuth telluride material during charge and discharge, improving its use as a potassium-ion battery anode. The cycle stability of the material; good flexibility and self-supporting structure, which can ensure the close contact between the active material and the current collector, improve the electrochemical performance, and maximize the advantages as a potassium ion electrode material. The bismuth telluride/carbon nanowire composite material of the present application has high capacity, good rate performance and long cycle stability, and has broad application prospects as a negative electrode material for potassium ion secondary batteries.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present application, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

Fig. 1 is the field emission scanning electron microscope image of the product obtained in Example 1 of the application;

Fig. 2 is the transmission electron microscope photograph of the product obtained in Example 1 of the application;

Fig. 3 is the X-ray diffraction pattern of the product obtained in Example 1 of the application;

FIG. 4 is a real shot of the self-supporting performance of the product obtained in Example 1 of the application;

Fig. 5 is the cycle performance diagram of the product obtained in Example 1 of the application;

6 is a field emission scanning electron microscope image of the product obtained in Example 2 of the application;

Fig. 7 is the field emission scanning electron microscope image of the product obtained by the comparative example of the application;

Fig. 8 is the cycle performance diagram of the product obtained by the comparative example of the present application.

Detailed ways

In order to make the purpose, features and advantages of the present application more obvious and understandable, the technical solutions in the embodiments of the present application are clearly and completely described. Obviously, the embodiments described below are only a part of the embodiments of the present application, and Not all examples. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

Example 1

(1) Dissolve 0.5 g of polyacrylonitrile (PAN) in 10 mL of N,N-dimethylformamide, and continue magnetic stirring for 24 hours to obtain a homogeneous yellow solution. Dissolve 0.5 mmol of bismuth chloride in the yellow solution in batches, add 1 mL of TEOS, and magnetically stir at room temperature for 12 hours to obtain a spinning solution;

(2) Take 5mL of spinning solution with a syringe, select a steel needle with a diameter of 0.5 mm, set the jet speed to 2mm/h, the positive voltage of 18KV, the negative pressure of 1KV, the receiving end is received by a roller, and tin foil is used as the Receive the carrier, start electrospinning, until the spinning solution is completely sprayed, put it in a blast drying oven at 60 °C for drying for 24 hours, then remove it, put it in a hydrofluoric acid with a concentration of 10Wt% for etching, and use it after removal. Deionized water was filtered for 4 times, cleaned and dried to obtain spinning samples;

(3) Take out the spinning sample and add tellurium powder into the tube furnace, wherein the mass ratio of the spinning sample to the tellurium powder is 2:3, heat treatment at 600 °C for 2 hours under an argon atmosphere, and the heating rate is 5 °C /min to obtain a bismuth telluride/carbon nanowire composite material.

Fig. 1 is a field emission scanning electron microscope image of the product prepared in Example 1 of the application, and Fig. 2 is a transmission electron microscope photo of the product prepared in Example 1 of the application. It can be seen that the prepared bismuth telluride/carbon nanowire composite In the material, the bismuth telluride particles are uniformly and densely distributed in the porous carbon nanowire, the width of the carbon nanowire is 1.8-2.5 microns, and the size of the bismuth telluride particles is 80-150 nm.

Fig. 3 is the X-ray diffraction pattern of the product obtained in Example 1 of the application, it can be seen that the obtained product has good crystalline properties, and the X-ray diffraction peaks can all be indicators of bismuth telluride compounds, indicating that the telluride in the obtained product is The high content of bismuth particles can fully exert the ability to enhance the insertion and extraction of potassium ions, as well as improve the electrical conductivity and active material utilization, showing high capacity and good rate performance.

4 is a real shot of the self-supporting performance of the product obtained in Example 1 of the application. It can be seen that the obtained product is a self-supporting structure, which is flexible and can be bent, which can ensure the close contact between the active material and the current collector, and does not The battery can be assembled directly without a current collector.

Figure 5 is the cycle performance diagram of the product prepared in Example 1 of the application. When the current density is 200mA/g, the capacity retention rate after 100 cycles is 95.2%, and the discharge specific capacity is 300mAh/g, indicating that the bismuth telluride particles Encapsulated in carbon nanofibers with a porous structure not only improves the specific capacity and rate performance of the material, but also effectively suppresses the volume expansion of the bismuth telluride material during charge and discharge, and improves its cycle stability as a potassium-ion battery anode material. .

Example 2

(1) Dissolve 0.5 g of polyacrylonitrile (PAN) in 10 mL of N,N-dimethylformamide, and continue magnetic stirring for 24 hours to obtain a clear yellow solution. Dissolve 0.5 mmol of bismuth chloride in the yellow solution in batches, add 3 mL of TEOS, and magnetically stir at room temperature for 12 hours to obtain a spinning solution;

(2) Take 5mL of spinning solution with a syringe, select a steel needle with a diameter of 0.1 mm, set the jet speed to 1.5mm/h, the positive voltage of 15KV, and the negative pressure of 1KV. As a receiving carrier, electrospinning was started until all the spinning solution was sprayed, put it in a blast drying oven at 60 °C for drying for 24 hours, and then removed it, put it into nitric acid with a concentration of 10Wt% for etching, and then took out the Deionized water was filtered for 4 times, cleaned and dried to obtain spinning samples;

(3) Take out the spinning sample and add tellurium powder into the tube furnace, wherein the mass ratio of the spinning sample to the tellurium powder is 2:3, heat treatment at 650°C for 2 hours under an argon atmosphere, and the heating rate is 5°C /min to obtain a bismuth telluride/carbon nanowire composite material.

6 is a field emission scanning electron microscope image of the product obtained in Example 2 of the application, and the figure shows that the surface of the carbon nanowires has obvious etching effect, and the bismuth telluride particles are uniformly and densely coated therein. The width is 2.5 to 3 microns, and the particle size of bismuth telluride is 80 to 120 nm.

Comparative ratio

(1) Dissolve 0.5 g of polyvinylpyrrolidone (molecular weight 130000) in 10 mL of N,N-dimethylformamide, and continue magnetic stirring for 24 hours to obtain a uniform and transparent solution. Dissolve 0.5 mmol of bismuth nitrate pentahydrate in the transparent solution in batches, and magnetically stir at room temperature for 12 hours to obtain a spinning solution;

(2) Take 5mL of spinning solution with a syringe, select a steel needle with a diameter of 0.1 mm, set the jet speed to 2.5mm/h, the positive voltage of 18KV, the negative pressure of 1KV, the receiving end is received by a roller, and the tin foil is used for receiving. As a receiving carrier, start electrospinning until all the spinning solution is sprayed, put it in a blast drying oven at 60°C for 24 hours, and take it out to obtain a spinning sample;

(3) Add the spinning sample to the tellurium powder and put it into a tube furnace, wherein the mass ratio of the spinning sample to the tellurium powder is 2:3, heat treatment at 700°C for 2 hours under a nitrogen atmosphere, and the heating rate is 5°C/min , to obtain bismuth telluride/carbon nanowire composites.

Fig. 7 is the field emission scanning electron microscope image of the product obtained by the comparative example of the present application. The figure shows that the surface of the carbon nanowire is relatively smooth and has no etching effect. Micron, bismuth telluride particle size is 70 ~ 130nm.

Figure 8 is the cycle performance diagram of the product prepared by the comparative example of the application. When the current density is 200 mA/g, the capacity retention rate after 100 cycles is 57.9%, and the discharge specific capacity is 175 mAh/g, which shows that although the bismuth telluride particles It is encapsulated in carbon nanofibers, but because its surface is not etched, there are fewer through holes on the surface of the material, the electrolyte is difficult to infiltrate, and the efficiency of potassium ion entry and extraction is low, resulting in poor electrochemical cycle stability and capacity decay. quick.

As mentioned above, the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand: The technical solutions described in the embodiments are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions in the embodiments of the present application.

Claims (7)

1. The application of the bismuth telluride/carbon nanowire composite material in the potassium ion electrode material is characterized in that the bismuth telluride/carbon nanowire composite material is formed by coating bismuth telluride particles with carbon nanowires;

the bismuth telluride/carbon nanowire composite material has a self-supporting structure;

the preparation method of the bismuth telluride/carbon nanowire composite material is characterized by comprising the following steps:

s1: dissolving a high molecular polymer in a solvent, stirring, adding bismuth salt and TEOS, and stirring to obtain a spinning solution;

s2: carrying out electrostatic spinning and drying on the spinning solution, and soaking the spinning solution in the solution for drying to obtain a spinning sample;

s3: adding tellurium powder into the spinning sample, and carrying out heat treatment to obtain the bismuth telluride/carbon nanowire composite material;

the solvent is selected from N, N-dimethylformamide or acetone;

in step S2, the step of immersing in the solution for drying specifically includes: etching in 10 Wt% hydrofluoric acid, taking out, vacuum filtering with deionized water for 4 times, cleaning, and oven drying.

2. The use of claim 1, wherein the diameter of the carbon nanowire is 1.5-3 μm, and the diameter of the bismuth telluride particle is 70-130 nm.

3. The use according to claim 1, wherein the bismuth salt is selected from one or more of bismuth iodide, bismuth chloride, bismuth subnitrate and bismuth nitrate pentahydrate;

the high molecular polymer is selected from one or more of polyacrylonitrile, polyvinylpyrrolidone, polyvinylidene fluoride and polyacrylic acid.

4. The use according to claim 3, wherein the ratio of the amount of the high molecular polymer to the amount of the solvent is (0.05 to 0.1) g: 1 mL;

the molar ratio of the bismuth salt to the high molecular polymer is 2-3 m mol/g.

5. The use according to claim 3, wherein the amount ratio of TEOS to the high molecular polymer is 1mL/g to 5 mL/g;

the mass ratio of the tellurium powder to the spinning sample is 3: 2.

6. use according to claim 3, characterized in that the operating conditions of the electrospinning are: the voltage is 15-18 KV, the diameter of a needle is 0.5-1.5 mm, the spinning distance is 12-15 cm, the temperature is 20-30 ℃, the humidity is 40% -60%, and the injection speed is 2-5 mm/h.

7. Use according to claim 3, wherein the drying is carried out at a temperature of 60 ℃ for a period of 24 h;

the temperature of the heat treatment is 600-700 ℃, the heating rate is 2-5 ℃/min, and the time is 2-4 h.

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