CN108807957A - Anode material of lithium-ion battery lacks layer rhenium disulfide nanometer sheet/hollow carbon sphere and preparation method thereof - Google Patents

Abstract

The invention discloses a few-layer rhenium disulfide nanosheet/hollow carbon sphere as a negative electrode material of a sodium ion battery and a preparation method thereof. The negative electrode material is formed by attaching rhenium disulfide nanosheets to the inner and outer carbon shells of porous hollow carbon spheres, using ammonium perrhenate as a precursor, thioacetamide as a sulfur source, hydrazine hydrate as a reducing agent, and porous hollow carbon The ball is a rhenium disulfide growth framework, and the negative electrode material is obtained. The negative electrode material prepared by the present invention uses hollow porous carbon nanospheres with uniform particle size as the skeleton, and the rhenium disulfide sheet structure is evenly dispersed on the carbon shell. The use of porous hollow carbon spheres limits the size of rhenium disulfide nanosheets. The number of growth layers is between 2 and 7. This few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite not only has many sodium intercalation active sites, but also has high conductivity, and the internal cavity can also buffer the volume. effect, prevent the flakes from falling off and maintain the stability of the structure, and there is no obvious agglomeration of rhenium disulfide nanosheets.

Description

Few-layer rhenium disulfide nanosheets/hollow carbon spheres as anode material for sodium-ion batteries and its preparation preparation method

technical field

The invention belongs to the technical field of sodium ion battery material synthesis, and in particular relates to a few-layer ReS ₂ nanosheet/hollow carbon sphere composite material (ReS ₂ /C) and a preparation method thereof.

Background technique

The initial research on sodium-ion batteries was almost simultaneous with that of lithium-ion batteries. With the large-scale use of lithium-ion batteries in electronic devices and the potential demand for electric vehicles and large-scale grid energy storage, people's concerns about lithium reserves in the earth's crust are gradually increasing. Considering the similar chemical properties of sodium ions and lithium ions and the abundant reserves of sodium in the earth's crust, research on sodium-ion batteries has been revived in recent years. Compared with lithium-ion batteries, sodium-ion batteries have obvious advantages in the following aspects: 1. The reserve of sodium in the earth's crust is more than 1000 times that of lithium, and it is widely distributed, and the mining cost is low; 2. Compared with lithium-ion batteries, The half-cell potential of the sodium-ion battery is 0.3-0.4V higher, and the choice of electrolyte is wider; 3. The sodium battery has relatively stable electrochemical performance and is safer to use. However, sodium-ion batteries also have some inherent disadvantages: 1. The relative atomic mass of sodium is much greater than that of lithium (23.0 vs 6.9), which leads to the theoretical mass specific capacity of sodium-ion batteries being smaller than that of lithium-ion batteries; 2. The radius of sodium ions is much larger Due to the radius of lithium ions, it is more difficult to find suitable sodium ion intercalation materials, which leads to the theoretical volume specific capacity of sodium ion batteries is also smaller than that of lithium ion batteries. At present, research on sodium-ion batteries is progressing rapidly. However, most of them are still focused on finding suitable sodium ion intercalation materials, studying the sodium ion intercalation mechanism, and improving the specific capacity and cycle performance of batteries.

Carbon materials have extremely rich morphology, structure, and pore size distribution, which have a very important impact on the storage performance of sodium ions. So far, the electrochemical sodium storage properties of various carbon materials have been widely studied, from zero-dimensional carbon dots, to one-dimensional carbon nanotubes, carbon fibers, two-dimensional graphene, and then to three-dimensional carbon materials with various morphologies. Although its specific capacity is higher than that of graphite, it is generally still lower than 300 mA hg ^-1 . Although the specific capacity of carbon materials can be improved to a certain extent by modifying the carbon materials by compounding elements, the results are not particularly impressive. Layered titanate compounds are another well-studied intercalation anode material for Na-ion batteries. They have attracted attention due to their low sodium intercalation potential and the fact that almost zero strain occurs when sodium ions are intercalated. But this type of material also faces a series of problems: poor electrical conductivity and low theoretical specific capacity. Most of the experimental results show that its specific capacity is lower than 200 mA hg ^-1 . At present, the most studied are various metal oxides and sulfides. For example, self-supporting MoS ₂ -graphene paper was synthesized by acid exfoliation, and steel-ion batteries were assembled. Compared with pure MoS ₂ , the cycle characteristics of this composite material were greatly improved. Comparing the theoretical specific capacities of different metal oxides and sulfides, it can be seen that based on a similar reaction mechanism, since the atomic weight of sulfur is greater than that of oxygen, the theoretical specific capacity of the oxide is generally greater than that of the corresponding sulfide for the same transition metal. However, both materials suffer from severe volume expansion effects.

Contents of the invention

The purpose of the present invention is to propose a sodium-ion battery negative electrode material with few layers of rhenium disulfide nanosheets/hollow carbon spheres and a preparation method thereof.

The technical solution that realizes the object of the present invention is:

A sodium-ion battery negative electrode material, the negative electrode material is formed by attaching rhenium disulfide nanosheets to the inner and outer carbon shells of porous hollow carbon spheres.

Wherein, the diameter of the hollow carbon sphere is 410±5nm, the thickness of the carbon shell is 28±2nm, and the number of rhenium disulfide nanosheets is between 2 and 7.

The preparation method of above-mentioned sodium ion battery negative electrode material, comprises the steps:

Dissolve ammonium perrhenate and thioacetamide in water, ultrasonically add a certain amount of hydrazine hydrate and mix evenly, and add hollow porous carbon nanospheres to ultrasonically disperse in the above solution, perform hydrothermal reaction, and centrifuge wash after the reaction is completed to obtain After the solid phase is dried, the dried product is calcined at a high temperature under the protection of a hydrogen/argon atmosphere to obtain a few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C).

In the above steps, ammonium perrhenate is used as a precursor, thioacetamide is used as a sulfur source, hydrazine hydrate is used as a reducing agent, and porous hollow carbon spheres are used as a rhenium disulfide growth framework, wherein ammonium perrhenate, thioacetamide, The mass ratio of hydrazine hydrate to porous hollow carbon spheres is 1:1~2:0.5~1:0.6~1, the hydrothermal temperature in the reaction is 80~145°C, the reaction time is 1~5 h, and calcined under the protection of hydrogen/argon, The calcination temperature is 400~800℃, and the calcination time is 2~6 h.

Compared with prior art, the advantage of the present invention is:

The few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite material prepared by the present invention uses hollow porous carbon nanospheres with uniform particle size as the skeleton, and the rhenium disulfide sheet structure is uniformly dispersed on the carbon shell, and the porous hollow carbon The use of spheres limits the number of growth layers of rhenium disulfide nanosheets between 2 and 7. This few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite not only has many sodium intercalation active sites, but also has a high The electrical conductivity, the internal cavity can also buffer the volume effect, prevent the flakes from falling off and maintain the stability of the structure, and there is no obvious agglomeration of the rhenium disulfide nanosheets.

Description of drawings

Figure 1 is a transmission electron microscope image of the prepared hollow porous carbon nanospheres.

Fig. 2 is a transmission electron microscope image of the few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C) prepared under the conditions of implementation 2.

Fig. 3 is a high-magnification image after ultrathin sectioning of the few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C) prepared under the conditions of implementation 2.

Fig. 4 is the transmission electron micrograph of the product obtained by reducing the quality of thioacetamide, hydrazine hydrate and carbon spheres under the conditions of implementation 4.

Fig. 5 is an XRD pattern of the few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C) prepared under the conditions of Embodiment 2.

Figure 6 is the long-term cycle performance diagram of the few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C) prepared under the conditions of implementation 2 (current density is 0.4 A g ^-1 ).

Fig. 7 is a charge-discharge cycle performance graph of different rates of the few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C) prepared under the conditions of implementation 2.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in detail below in conjunction with the embodiments and accompanying drawings.

The invention uses hollow porous carbon nanospheres as templates to synthesize a few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite material through a hydrothermal method. Few-layer rhenium disulfide nanosheets/hollow carbon spheres (ReS ₂ /C) exhibit more sodium intercalation active sites, lower sodium ion transport resistance and good electrical conductivity, which is conducive to the rapid transport of sodium ions and electrons. By embedding rhenium disulfide nanosheets on the carbon shells of hollow carbon spheres, the accumulation of rhenium disulfide can be reduced, thereby reducing the number of layers of rhenium disulfide, shortening the diffusion path of sodium ions, reducing the transport resistance of sodium ions and increasing intercalation. It would be a good way to increase the electrochemical performance of sodium active sites. In addition, the carbon shell improves the electrical conductivity of the composite. At the same time, the rhenium disulfide grown inside the carbon shell can prevent its structure from falling off during charging and discharging, and the internal space can also buffer the volume effect during the intercalation/desodiumization process, which is conducive to the stability of the structure during the cycle, so that the material has Good rate performance and cycle stability enable the active material to be effectively protected in high current and long cycle. Therefore, the nano-hollow composite material (ReS ₂ /C) formed by embedding the carbon shells of few-layer ReS ₂ nanosheets into the grown hollow carbon spheres is a promising anode material for sodium ions.

1. Preparation of hollow porous carbon nanospheres:

Add 50 mL of absolute ethanol, 5 mL of deionized water, and 1 mL of ammonia water into the beaker in turn and perform magnetic stirring. At the same time, add 0.4 mL of tetraethyl orthosilicate to the above mixture, stir the mixture for a period of time, and weigh Add 0.2 g of resorcinol and 0.2 g of formaldehyde to the above mixed solution in sequence, and stir magnetically for 24 h at a water bath temperature of 30 °C. After the reaction was completed, it was centrifuged and washed to obtain a solid phase and then dried. Under the protection of argon, the dried product was calcined at 600°C for 5 hours at a heating rate of 2°C/min, and then the calcined product was placed in a water bath at 60°C. Etching with 2 M sodium hydroxide solution for 12 h. Finally, the etched product is centrifuged and washed, and the obtained solid phase is dried to obtain hollow porous carbon nanospheres. The obtained porous hollow carbon spheres had a particle size of 420 nm and a wall thickness of 28 nm.

The water bath temperature is 30 ℃ and the reaction time of magnetic stirring is 24 h. The hollow porous carbon spheres prepared under this condition have uniform particle size, stable structure and high yield. It provides a good source for the subsequent preparation of porous hollow carbon shells embedded with few-layer _ReS2 nanosheets. It has a good skeleton effect.

2. Preparation of negative electrode materials:

Example 1:

Dissolve 0.3 g of ammonium perrhenate and 0.3 g of thioacetamide solid in 70 mL of deionized water, ultrasonically, and at the same time add 0.15 g of hydrazine hydrate to mix evenly, and add 0.18 g of hollow porous carbon nanospheres to ultrasonically disperse in the above solution, Hydrothermal reaction at 80 °C for 1 h, after the reaction was completed, centrifuged and washed to obtain a solid phase and then dried, the dried product was calcined at 400 °C for 2 h under the protection of hydrogen/argon at a heating rate of 2 °C/min, and obtained Few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C).

Example 2:

Preparation of few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C)

Dissolve 0.3 g of ammonium perrhenate and 0.45 g of thioacetamide solid in 70 mL of deionized water, ultrasonically, and at the same time add 0.24 g of hydrazine hydrate to mix evenly, and add 0.24 g of hollow porous carbon nanospheres to ultrasonically disperse in the above solution, Hydrothermal reaction at 120 °C for 3 h, after the reaction was completed, centrifuged and washed to obtain a solid phase and then dried, the dried product was calcined at 600 °C for 4 h under the protection of hydrogen/argon at a heating rate of 2 °C/min, and obtained Few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C).

Example 3:

Preparation of few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C)

Dissolve 0.3 g of ammonium perrhenate and 0.6 g of thioacetamide solid in 70 mL of deionized water, ultrasonically, and at the same time add 0.3 g of hydrazine hydrate to mix evenly, and add 0.3 g of hollow porous carbon nanospheres to ultrasonically disperse in the above solution, Hydrothermal reaction at 145 °C for 5 h, after the reaction was completed, centrifuged and washed to obtain a solid phase and then dried, the dried product was calcined at 800 °C for 6 h at a heating rate of 2 °C/min under the protection of hydrogen/argon to obtain Few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C).

Example 4:

Dissolve 0.3 g of ammonium perrhenate and 0.15 g of thioacetamide solid in 70 mL of deionized water, ultrasonically, and at the same time add 0.05 g of hydrazine hydrate to mix evenly, and add 0.1 g of hollow porous carbon nanospheres to ultrasonically disperse in the above solution, Hydrothermal reaction at 145 °C for 5 h, after the reaction was completed, centrifuged and washed to obtain a solid phase and then dried, the dried product was calcined at 800 °C for 6 h under the protection of hydrogen/argon at a heating rate of 2 °C/min and at a high temperature of 6 h. The product of the hollow carbon spheres is substantially unsupported rhenium disulfide nanosheets.

3. Material performance verification:

Under the conditions of embodiment 2, the few-layer rhenium disulfide nanosheets/hollow carbon spheres of the optimal sodium ion battery negative electrode material can be obtained, and the following are the material characterizations of the selected embodiment 2:

Figure 1 is a transmission electron microscope image of the prepared hollow porous carbon nanospheres. It can be seen from the figure that the prepared product has a hollow structure inside, that is, the inner silicon dioxide is completely etched, the surface of the shell is rough and porous, and the hollow spherical shell is intact with uniform particle size and uniform dispersion. The hollow mesoporous carbon nanospheres have a diameter of ~410 nm and a carbon wall thickness of 30 nm.

Fig. 2 is a transmission electron microscope image of the prepared few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C). It can be seen from the figure that the prepared product is a few-layer rhenium disulfide nanosheet embedded in the carbon shell of the hollow porous carbon nanosphere. uniform.

Fig. 3 is a high-resolution transmission electron microscope image of a few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite material (ReS ₂ /C) after ultrathin sectioning. It can be seen from the figure that few-layer ReS ₂ nanosheets are embedded and grown on the inner shell of carbon spheres, forming a few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C).

Fig. 4 is a transmission electron micrograph of the product obtained by reducing the mass of thioacetamide (0.15 g), hydrazine hydrate (0.05 g) and carbon spheres (0.1 g) in Example 4. It can be seen from the figure that the quality of thioacetamide, hydrazine hydrate and carbon spheres is reduced, and basically no rhenium disulfide nanosheets are loaded on the hollow mesoporous carbon spheres.

Fig. 5 is an XRD pattern of a few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite material (ReS ₂ /C).

The few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C) prepared in Example 2 of the present invention was assembled into a button sodium ion battery.

Figure 6 and Figure 7 are the electrochemical performance diagram, long-term cycle performance diagram (current density 0.4 A g ^-1 ) and rate of the prepared few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite (ReS ₂ /C) performance graph.

Figure 6 shows the long-term cycle performance diagram of the electrode material at a constant current density of 0.4 _A g ^-1 . After 1000 cycles, the reversible The specific capacity is 209 mA hg ^-1 .

Figure 7 is the graph of charge-discharge cycle performance at different rates. The material was discharged at a current density of 0.2 A g ^-1 , 0.4 A g ^-1 , 0.8 A g ^-1 , 1 A g ^-1 , and 2 A g ^-1 . Then return to discharge at a current density of 0.2 A g ^-1 , and cycle charge and discharge for 9 cycles respectively. When the current density reaches 2 A g ^-1 , the discharge specific capacity can still reach 108 mA hg ^-1 . Finally, when the current density returns to 0.2 A g ^-1 , the specific discharge capacity can be restored to the original 352 mA hg ^-1 , indicating excellent rate capability.

In a word, the present invention has the characteristics of cheap raw materials, simple and environmentally friendly process, large output and excellent performance, and provides a simple method for preparing few-layer rhenium disulfide nanosheets/hollow carbon sphere nanocomposites (ReS ₂ /C), and has large-scale application potential. The few-layer rhenium disulfide nanosheet/hollow carbon sphere nanocomposite material (ReS ₂ /C) can be used as an electrode material for a sodium ion battery.

Claims (9)

1. A negative electrode material for a sodium ion battery, characterized in that, the negative electrode material is formed by attaching rhenium disulfide nanosheets to the inner and outer carbon shells of porous hollow carbon spheres. 2. The negative electrode material according to claim 1, characterized in that the hollow carbon spheres have a diameter of 410±5nm. 3. The negative electrode material according to claim 1, characterized in that the thickness of the carbon shell is 28±2nm. 4. The negative electrode material according to claim 1, wherein the number of rhenium disulfide nanosheets is between 2 and 7. 5. the preparation method of sodium ion battery negative electrode material as claimed in claim 1-4, is characterized in that, comprises the steps: Dissolve ammonium perrhenate and thioacetamide in water, add hydrazine hydrate, mix evenly by ultrasonic, add hollow porous carbon nanospheres, continue ultrasonic dispersion, the mixed solution undergoes hydrothermal reaction, and centrifuges and washes after the reaction is completed. After the solid phase is obtained, it is dried, and the dried product is calcined at a high temperature under the protection of a hydrogen/argon atmosphere to obtain the negative electrode material. 6. The method according to claim 5, wherein the mass ratio of ammonium perrhenate, thioacetamide, hydrazine hydrate and porous hollow carbon spheres is 1:1~2:0.5~1:0.6~1. 7. The method according to claim 5, wherein the hydrothermal reaction temperature is 80-145°C, and the reaction time is 1-5h. 8. The method according to claim 5, wherein the calcination temperature is 400-800° C., and the calcination time is 2-6 h. 9. The application of the sodium ion battery negative electrode material according to claims 1-4.