CN114068904B - A carbon-coated tin-based chalcogenide composite material and its preparation method and application - Google Patents

Abstract

The invention discloses a carbon-coated tin-based chalcogenide composite material and its preparation method and application. It is mainly realized through the following steps: first, the stannate is hydrolyzed into a nano-spherical tin dioxide precursor; Layered polydopamine; finally, it is heat-treated with selenium powder or sulfur powder to obtain a carbon-coated tin-based chalcogenide (SnSe or SnS) composite material. The material has a typical core-shell structure, and nitrogen-selenium or nitrogen-sulfur co-doped carbon can not only relieve the volume expansion of tin-based chalcogenides, but also provide more active sites. When the target product is used as an anode material for sodium-ion batteries, it exhibits excellent rate performance and cycle stability, especially the ultra-high first-cycle Coulombic efficiency.

Description

A carbon-coated tin-based chalcogenide composite material and its preparation method and application

technical field

The invention relates to the technical field of anode materials for sodium-ion batteries, in particular to a carbon-coated tin-based chalcogenide composite material and a preparation method and application thereof.

Background technique

With the increasing development of human society, traditional fossil energy is facing exhaustion, energy shortage and environmental pollution are becoming more and more serious. As a result, mankind's demand for clean and efficient energy is becoming more and more urgent, and the development of clean and renewable energy has become a hot issue in today's society. To make effective use of clean renewable energy, it needs to be converted into electricity and stored. Lithium-ion batteries, which are widely used at present, will be constrained by the depletion of lithium resources in the future. Sodium-ion batteries are more and more favored by researchers because of their abundant and cheaper sodium reserves. However, electrode materials originally used for lithium-ion batteries cannot be directly used for sodium-ion batteries because the radius of sodium ions is larger than that of lithium ions. Therefore, exploring electrode materials suitable for sodium-ion batteries is the primary task of current researchers.

Sn-based anode materials have attracted extensive attention due to their abundant raw materials, low price and high theoretical specific capacity. Among them, chalcogenides (stannous sulfide, stannous selenide) are a representative class of negative electrode materials. They all have a two-dimensional layered structure. During the sodium storage process, Na ⁺ will first be embedded in the interlayer to form sodium tin sulfur (selenium) compounds, and then undergo conversion reactions and alloying reactions into Na ₂ S (Na ₂ Se) and Na _x Sn. The combination of multi-step sodium storage reactions makes tin-based chalcogenides possess high theoretical specific capacity, however, their low electrical conductivity and large volume expansion during sodium storage are still two key issues to be solved.

In this regard, researchers often adopt two methods of material nano-design (such as quantum dots, nanowires, nanosheets, etc.) and composites with carbon materials with good conductivity (such as graphene, carbon nanotubes, etc.) Compounds are modified. Although the modification work has made great progress, the synthesis process of most of the work is complicated and time-consuming. In addition, the weak interfacial coupling between tin-based chalcogenides and carbon materials makes it easy for the active species to fall off from the carbon materials, eventually leading to a rapid capacity fading.

Contents of the invention

The purpose of the present invention is to provide a carbon-coated tin-based chalcogenide compound for the current complex and time-consuming preparation process of tin-based chalcogenides, as well as the problems of serious volume expansion and poor conductivity when they are used as negative electrode materials for sodium-ion batteries. Materials and their preparation methods and applications. The raw material and the generated solution in the preparation process of the material are easy to handle and have no pollution, the preparation cost is low, the operation process is simple, and the repeatability is high. At the same time, the unique double heteroatom-doped carbon layer has more defects and active sites than the pure carbon layer, the conductivity is improved, and the adsorption capacity for sodium ions is also greatly improved. When the electrode material is used as an anode material for sodium-ion batteries, it has high rate performance, high cycle stability and ultra-high first cycle coulombic efficiency.

The invention prepares uniform tin dioxide nanoparticles by a simple method and uses them as a precursor, coats polydopamine with a certain thickness on its surface, and then carries out heat treatment with selenium powder or sulfur powder under the protection of an inert gas. The obtained carbon-coated tin-based chalcogenide composites have a typical core-shell structure.

A method for preparing a carbon-coated tin-based chalcogenide composite material, comprising the following steps:

(1) dissolving stannate in deionized water to prepare a certain concentration of stannate solution, and continuously stirring;

(2) Slowly add a certain amount of alcohol solvent to the stannate solution in step (1), stir at room temperature 25°C for a certain period of time, centrifuge, wash and dry, and obtain a white precursor product A;

(3) Disperse the white precursor product A obtained in step (2) in deionized water, ultrasonically disperse, add Tris (Tris) to adjust the pH value of the solution, then add dopamine hydrochloride, and continue stirring at room temperature for a certain period of time Centrifuged, washed and dried to obtain a black product B;

(4) Get selenium powder or sulfur powder and the black product B in the above-mentioned step (3) and be placed in tube furnace, heat treatment under inert gas protection, obtain nitrogen-selenium co-doped carbon-coated tin selenide composite material or Nitrogen-sulfur co-doped carbon-coated stannous sulfide composites.

Following as preferred technical scheme of the present invention:

In step (1), the stannate is sodium stannate trihydrate (Na ₂ SnO ₃ 3H ₂ O) or potassium stannate trihydrate (K ₂ SnO ₃ 3H ₂ O), and the concentration of stannate is 0.01 -0.03 mol L ^-1 .

In step (2), described alcohol solvent is any one in monohydric alcohols such as absolute methanol, dehydrated ethanol, Virahol, and is (1-2) with the volume ratio of deionized water in step 1: 1. The stirring time is 6-48h, and the drying condition is: place in a vacuum oven at 50-80°C for 12-24h.

In step (3), the ratio of the amount of white precursor product A to deionized water is 50-150mg: 80mL, preferably 100mg: 80mL, every 100mg of white precursor product A corresponds to 80mL deionized water, and the pH of the solution is 8.0-9.0, the mass of dopamine hydrochloride is 0.5-3 times the mass of the white precursor product A used, the stirring time is 12-48h, and the drying condition is: place in a vacuum oven at 50-80°C for 12-24h.

In step (4), the quality of the selenium powder or sulfur powder is 1-3 times the quality of the black product B used, the inert gas is one of nitrogen or argon, the heat treatment temperature is 500-700 °C, and the heating rate is 1-5°C/min, holding time 2-4h.

The carbon-coated tin-based chalcogenide composite material has a typical core-shell structure, and its particle diameter is about 110-150nm, wherein the thickness of the surface carbon layer is about 10-30nm, and the middle part is SnSe or SnS.

The obtained carbon-coated tin-based chalcogenide composite material is used as the negative electrode material of the sodium ion battery, mixed with conductive carbon black (Super P) and binder (CMC) to obtain a slurry, and coated on the metal copper foil current collector to obtain Negative electrode, with glass fiber as separator, metallic sodium as counter electrode, 1mol L ^-1 NaClO ₄ diglyme solution as electrolyte, and complete battery assembly in a glove box filled with argon. After the assembled sodium-ion battery was left standing for 24 hours, a constant current charge-discharge test was performed with a voltage window of 0.01-3.0V. The specific capacity, rate performance and long-term cycle performance of the negative electrode of the battery were tested in a constant temperature environment of 25±1°C.

Compared with prior art, the beneficial effect of the present invention is:

(1) The present invention synthesizes tin dioxide through a simple and easy-to-operate room temperature precipitation method. Compared with the existing tin dioxide that needs urea and hydrothermal conditions to synthesize, the particle size is smaller and uniform, and the yield is larger and stable. Simultaneously, the reaction conditions are simple, which is beneficial to reduce energy consumption.

(2) In the synthesis of carbon-coated tin-based chalcogenide composite materials, the present invention uses tin dioxide as a precursor and adopts a one-step heat treatment method, compared with the existing method of first carbonizing and then selenizing (or vulcanizing) , does not need argon-hydrogen mixed gas, only ordinary inert atmosphere can be realized, the operation is safe, the conditions are simple, and energy is saved.

(3) The prepared carbon-coated tin-based chalcogenide composite material has a stable structure, and the surface double heteroatom-doped carbon layer has more defects and active sites than the pure carbon layer, which greatly improves the overall electrical conductivity of the material and adsorption capacity for sodium ions. At the same time, the carbon layer can also effectively buffer the stress change of the internal SnSe or SnS during the process of intercalating sodium, relieve the volume expansion, and make the material have better electrochemical performance and cycle stability, which has excellent application prospects in the field of energy storage.

Description of drawings

Fig. 1 is the scanning electron microscope picture of the nitrogen-selenium co-doped carbon-coated tin selenide composite material prepared in embodiment 1;

Fig. 2 is the transmission electron microscope picture of the nitrogen-selenium co-doped carbon-coated tin selenide composite material prepared in embodiment 1;

3 is an X-ray diffraction pattern of the nitrogen-selenium co-doped carbon-coated tin selenide composite material prepared in Example 1.

FIG. 4 is a rate performance diagram of a sodium ion battery of the nitrogen-selenium co-doped carbon-coated tin selenide composite material prepared in Example 1. FIG.

5 is a constant current charge and discharge diagram of a sodium ion battery prepared in Example 1 with nitrogen and selenium co-doped carbon-coated tin selenide composite material.

FIG. 6 is a diagram of the sodium ion battery cycle performance of the nitrogen-selenium co-doped carbon-coated tin selenide composite material prepared in Example 1.

Detailed ways

The content of the present invention will be further described below through specific embodiments. It should be noted that the specific implementation examples are not intended to limit the scope of the present invention. Under the condition of no substantial technical content contribution, conventional transformations by those skilled in the art are also regarded as the applicable scope of the present invention, and all are within the scope of the present invention. within the scope of protection.

Example 1

(1) Weigh 2 mmol of sodium stannate trihydrate (Na ₂ SnO ₃ 3H ₂ O) and dissolve it in 100 mL of deionized water, stir until clear, then slowly add 150 mL of absolute ethanol, the solution appears white turbidity, continue stirring for 24 hours; Centrifuge at a speed of 6000r min ^-1 to obtain a white product, wash it three times with deionized water and absolute ethanol, and dry it in a vacuum oven at 60°C for 12 hours to obtain tin dioxide (SnO ₂ ) nanoparticles;

(2) Weigh 100mg of the above SnO ₂ and dissolve it in 80mL of deionized water, ultrasonically disperse for 15min, then add 100mg of Tris buffer substance to make the pH of the solution ~8.5, then add 200mg of dopamine hydrochloride, and stir for ^24h ; The black product was obtained by centrifugation at a rotating speed, washed three times with deionized water and absolute ethanol, and dried in a vacuum oven at 60°C for 12 hours to obtain polydopamine-coated tin dioxide (SnO ₂ @PDA);

(3) Weigh 50mg of SnO ₂ @PDA and 100mg of selenium powder, place them in the downstream and upstream of the tube furnace respectively, pass in nitrogen, raise the temperature to 600°C at a heating rate of 2°C min ^-1 and hold it for 2h, then cool naturally to a room temperature of 25° C. to obtain a nitrogen-selenium co-doped carbon-coated tin selenide composite material.

Example 2

(1) Weigh 2 mmol of potassium stannate trihydrate (K ₂ SnO ₃ 3H ₂ O) and dissolve it in 100 mL of deionized water, stir until clear, then slowly add 150 mL of absolute ethanol, the solution appears white turbidity, continue stirring for 24 hours; Centrifuge at a speed of 6000r min ^-1 to obtain a white product, wash it three times with deionized water and absolute ethanol, and dry it in a vacuum oven at 60°C for 12h to obtain _SnO2 nanoparticles;

(2) Weigh 100mg of the above SnO ₂ and dissolve it in 80mL of deionized water, ultrasonically disperse for 15min, then add 100mg of Tris buffer substance to make the pH of the solution ~8.5, then add 200mg of dopamine hydrochloride, and stir for ^24h ; The black product was obtained by centrifugation at a rotating speed, washed three times with deionized water and absolute ethanol, and dried in a vacuum oven at 60°C for 12 hours to obtain SnO ₂ @PDA;

(3) Weigh 50mg of SnO ₂ @PDA and 100mg of selenium powder, place them in the downstream and upstream of the tube furnace respectively, pass in nitrogen, raise the temperature to 600°C at a heating rate of 2°C min ^-1 and hold it for 2h, then cool naturally to a room temperature of 25° C. to obtain a nitrogen-selenium co-doped carbon-coated tin selenide composite material.

Example 3

(1) Weigh 2mmol Na ₂ SnO ₃ 3H ₂ O and dissolve it in 100mL deionized water, stir until clear, then slowly add 150mL isopropanol, the solution appears white turbidity, continue stirring for ^24h ; The white product was obtained by centrifugation at a rotating speed, washed three times with deionized water and absolute ethanol, and dried in a vacuum oven at 60°C for 12 hours to obtain SnO ₂ nanoparticles;

(2) Weigh 100mg of the above SnO ₂ and dissolve it in 80mL of deionized water, ultrasonically disperse for 15min, then add 100mg of Tris buffer substance to make the pH of the solution ~8.5, then add 200mg of dopamine hydrochloride, and stir for ^24h ; The black product was obtained by centrifugation at a rotating speed, washed three times with deionized water and absolute ethanol, and dried in a vacuum oven at 60°C for 12 hours to obtain SnO ₂ @PDA;

(3) Weigh 50mg of SnO ₂ @PDA and 100mg of selenium powder, place them in the downstream and upstream of the tube furnace respectively, pass in nitrogen, raise the temperature to 600°C at a heating rate of 2°C min ^-1 and hold it for 2h, then cool naturally to a room temperature of 25° C. to obtain a nitrogen-selenium co-doped carbon-coated tin selenide composite material.

Example 4

(1) Weigh 2mmol Na ₂ SnO ₃ ·3H ₂ O and dissolve it in 100mL deionized water, stir until clear, then slowly add 150mL absolute ethanol, the solution appears white turbidity, continue stirring for ^24h ; The white product was obtained by centrifugation under lower pressure, and washed three times with deionized water and absolute ethanol respectively, and dried in a vacuum oven at 60°C for 12 hours to obtain SnO ₂ nanoparticles;

(2) Weigh 100 mg of the above SnO ₂ and dissolve it in 80 mL of deionized water, ultrasonically disperse for 15 min, then add 100 mg of Tris buffer substance to make the pH of the solution ~8.5, then add 300 mg of dopamine hydrochloride, and stir for ²⁴ h; The black product was obtained by centrifugation at a rotating speed, washed three times with deionized water and absolute ethanol, and dried in a vacuum oven at 60°C for 12 hours to obtain SnO ₂ @PDA;

(3) Weigh 50mg of SnO ₂ @PDA and 100mg of selenium powder, place them in the downstream and upstream of the tube furnace respectively, pass in nitrogen, raise the temperature to 600°C at a heating rate of 2°C min ^-1 and hold it for 2h, then cool naturally to a room temperature of 25° C. to obtain a nitrogen-selenium co-doped carbon-coated tin selenide composite material.

Example 5

(1) Weigh 2mmol Na ₂ SnO ₃ ·3H ₂ O and dissolve it in 100mL deionized water, stir until clear, then slowly add 150mL absolute ethanol, the solution appears white turbidity, continue stirring for ^24h ; The white product was obtained by centrifugation under lower pressure, and washed three times with deionized water and absolute ethanol respectively, and dried in a vacuum oven at 60°C for 12 hours to obtain SnO ₂ nanoparticles;

(2) Weigh 100 mg of the above-mentioned SnO ₂ and dissolve it in 80 mL of deionized water, ultrasonically disperse for 15 h, then add 100 mg of Tris buffer substance to make the pH of the solution ~8.5, then add 200 mg of dopamine hydrochloride, and stir for ²⁴ h; The black product was obtained by centrifugation at a rotating speed, washed three times with deionized water and absolute ethanol, and dried in a vacuum oven at 60°C for 12 hours to obtain SnO ₂ @PDA;

(3) Weigh 50mg of SnO ₂ @PDA and 100mg of sulfur powder, place them in the downstream and upstream of the tube furnace respectively, pass in nitrogen, raise the temperature to 600°C at a heating rate of 2°C min ^-1 and keep it for 2h, then cool naturally to a room temperature of 25° C. to obtain a nitrogen-sulfur co-doped carbon-coated stannous sulfide composite material.

Performance Testing

The carbon-coated tin-based chalcogenide composite material prepared in Examples 1-5 above was used as the negative electrode material of the sodium ion battery, and assembled into a sodium ion battery for constant current charge and discharge tests. Figure 4 shows the rate performance test results of Example 1. It can be seen from the figure that the sodium ion battery operates at 0.1A g ^-1 , 0.2A g ^-1 , 0.5Ag ^-1 , 1A g ^-1 , 2A g ^-1 , The capacity at the current density of 5A g ^-1 and 10A g ^-1 is 562.6mA h g ^-1 , 503.9mA h g ^-1 , 421.6mA h g ^-1 , 390.9mA h g ^-1 , 352.2mAh g ^-1 , 301.0mA h g ^{-1 1} and 285.3mA h g ^-1 , showing excellent rate performance. Figure 5 shows the constant current charge and discharge curves of the electrode at a current density of 0.1A g ^-1 , and its first cycle Coulombic efficiency is as high as 89.9%. From the cycle performance diagram in Figure 6, it can be seen that the Na-ion battery still has a capacity retention rate of 83.8% after 100 cycles at a current density of 1A g ^-1 , showing excellent cycle stability.

The carbon-coated tin-based chalcogenide composite material in Examples 1-5 is used as the negative electrode material of the sodium-ion battery after being assembled into a sodium-ion battery, and the discharge capacities at different current densities are shown in Table 1:

Table 1

It can be seen from the table that changing the types of stannate (Example 2) and alcohol solvent (Example 3) has no significant impact on the electrochemical performance of the final product compared with the comparison sample (Example 1). Increasing the amount of dopamine hydrochloride (Example 4) slightly decreases the capacity of the final product, which is due to the decrease of high-capacity SnSe content due to the increase of carbon content in the material. After changing the last step of selenization into vulcanization (Example 5), the capacity of the material is significantly improved. This is mainly because although SnS and SnSe are all layered materials, the sodium storage mechanism is also similar, but the relative atomic mass ratio of S Se is small, so the theoretical sodium storage capacity of SnS is higher than that of SnSe.

Claims (10)

1. a preparation method of carbon-coated tin-based chalcogenide composite material, is characterized in that, comprises the following steps: Step 1: dissolving stannate in deionized water to prepare a stannate solution, and continuously stirring; Step 2: Add an alcohol solvent to the stannate solution in Step 1, centrifuge after stirring, wash and dry, and obtain a white precursor product A; Step 3: Disperse the white precursor product A obtained in step 2 in deionized water, ultrasonically disperse, add trishydroxymethylaminomethane, adjust the pH value of the solution, then add dopamine hydrochloride, centrifuge after stirring, wash and dry, and obtain the black product B ; Step 4: Take the selenium powder or sulfur powder and the black product B in the above step 3 and place them in a tube furnace, heat treatment under the protection of an inert gas to obtain a nitrogen-selenium co-doped carbon-coated tin selenide composite material or nitrogen-sulfur Co-doped carbon-coated stannous sulfide composites. 2. preparation method according to claim 1, is characterized in that, in step 1, described stannate is sodium stannate trihydrate or potassium stannate trihydrate, and the stannate in described stannate solution The concentration is 0.01-0.03 mol L ^-1 . 3. The preparation method according to claim 1, characterized in that, in step 2, the alcohol solvent is any one of anhydrous methanol, absolute ethanol, and isopropanol monohydric alcohols; The volume ratio of the alcohol solvent to the deionized water in step 1 is (1-2):1. 4. preparation method according to claim 1 is characterized in that, in step 2, the time of stirring is 6-48 h. 5. The preparation method according to claim 1, characterized in that, in step 2, the drying condition is: place in a vacuum oven at 50-80°C for 12-24 h. 6. the preparation method according to claim 1, is characterized in that, in step 3, the ratio of the consumption of described white precursor product A and deionized water is 50 ~ 150 mg: 80 mL; Adjust the pH value of the solution to 8.0-9.0; The mass of the dopamine hydrochloride is 0.5-3 times the mass of the white precursor product A used. 7. preparation method according to claim 1, is characterized in that, in step 3, the time of stirring is 12-48 h; The drying conditions are: place in a vacuum oven at 50-80 °C for 12-24 h. 8. preparation method according to claim 1, is characterized in that, in step 4, the quality of described selenium powder or sulfur powder is 1-3 times of the quality of black product B used; The inert gas is one of nitrogen or argon; The heat treatment temperature is 500-700 °C, the heating rate is 1-5 °C/min, and the holding time is 2-4 h. 9. The nitrogen-selenium co-doped carbon-coated stannous selenide composite material or the nitrogen-sulfur co-doped carbon-coated stannous sulfide composite material prepared by the preparation method according to any one of claims 1-8. 10. The application of the nitrogen-selenium co-doped carbon-coated tin selenide composite material or the nitrogen-sulfur co-doped carbon-coated stannous sulfide composite material according to claim 9 as an electrode material for a sodium-ion battery.

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