Nitrogen-doped carbon / wolfram diselenide nanosphere composite material, and preparation method and application thereof

Abstract

This invention relates to the field of batteries, and more particularly to a nitrogen-doped carbon / tungsten diselenide nanosphere composite material, its preparation method, and its applications. This invention achieves tight coupling between few-layer WSe2 nanosheets and a nitrogen-doped carbon framework through a process combining complexation-polymerization and subsequent selenization. The resulting material consists of nanosphere particles, providing more electrochemical active sites and shortening the zinc ion diffusion distance. By introducing a nitrogen-doped carbon framework, this invention effectively improves the overall conductivity of the composite material and suppresses the stacking and aggregation of WSe2 nanosheets during charge and discharge, thereby significantly improving rate performance and cycle stability.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more particularly to a nitrogen-doped carbon / tungsten diselenide nanosphere composite material, its preparation method, and its application. Background Technology

[0002] In recent years, lithium-ion batteries have been widely used in portable electronic devices, electric vehicles, and energy storage systems due to their high operating voltage, high specific energy, and long cycle life. However, lithium metal has drawbacks such as limited reserves, high cost, and safety concerns. Current battery development demands both low cost and high safety. Zinc, as an abundant metal, is much cheaper than lithium and has high safety, making zinc-ion batteries a promising alternative to lithium-ion batteries. However, with the increasing demand for high-power and long-life applications, traditional cathode materials are no longer sufficient to meet the requirements of applications that demand both high rate and high capacity.

[0003] Numerous significant studies have been reported on cathode materials for aqueous zinc-ion batteries, including organic compounds, vanadium-based compounds, manganese-based oxides, and Prussian blue analogues. While Prussian blue and organic compounds exhibit high output voltages, their poor conductivity and strong electrostatic interaction with zinc ions lead to poor charge-discharge capacity and cycle stability. Metal oxides, with their abundant resources, good environmental compatibility, and high theoretical specific capacity, are ideal electrode materials for metal batteries. However, metal oxides suffer from severe polarization, slow reaction rates, low battery efficiency, and poor cycle stability. Transition metal dichalcogenides (TMDs), due to their high theoretical specific capacity and layered structure, are considered promising new anode materials. TMDs possess a unique two-dimensional layered structure with weak van der Waals forces between layers, which can accommodate intercalated ions, making them highly suitable for secondary battery technologies using large amounts of hydrated metal ions. Tungsten diselenide (WSe2) has an interlayer spacing of 1.3 nm, theoretically enabling the realization of hydrated Zn. 2+ Insertion and desorption between its layers. However, bulk WSe2 generally suffers from insufficient intrinsic conductivity, significant volume effect during charge and discharge, and easy stacking and aggregation of nanosheets during cycling, which limits its rate performance and cycle stability.

[0004] Therefore, developing a novel composite material that is structurally stable, easy to process, and can achieve tight coupling between few-layer WSe2 nanosheets and nitrogen-doped carbon framework is of great significance for obtaining zinc-ion battery cathode materials with excellent rate performance and long cycle stability. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a nitrogen-doped carbon / tungsten diselenide nanosphere composite material, its preparation method, and its applications.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of this invention is to provide a method for preparing a nitrogen-doped carbon / tungsten diselenide nanosphere composite material, comprising the steps of:

[0008] S1. Disperse the structure-directing agent and surfactant in an ethanol solution, add dopamine hydrochloride and tungsten source to carry out a complexation-polymerization reaction to obtain a tungsten-polydopamine precursor;

[0009] S2. The tungsten-polydopamine precursor is mixed with a selenium source and then heat-treated under an inert atmosphere to obtain the nitrogen-doped carbon / tungsten diselenide nanosphere composite material NC / WSe2.

[0010] Preferably, the mass ratio of the structure-directing agent, the surfactant, the dopamine hydrochloride, and the tungsten source is 42-50:6-10:6-10:30-46; and the mass ratio of the tungsten source to the selenium source is 10-20:80-90.

[0011] Preferably, in step S1, the structure directing agent is polyethylene-polypropylene glycol block copolymer F127.

[0012] Preferably, in step S1, the surfactant is hexadecyltrimethylammonium bromide.

[0013] Preferably, in step S1, the complexation-polymerization reaction includes: reacting at room temperature for 2-3 hours, centrifuging and washing the product, and drying at 60-80°C after washing.

[0014] Preferably, in step S1, the tungsten source includes at least one of sodium tungstate, ammonium tungstate, and tungsten ethoxide.

[0015] Preferably, in step S2, the heat treatment includes: heating to 600-800°C at a rate of 5-10°C / min, and sintering in an argon or nitrogen atmosphere for 3-6 hours.

[0016] A second aspect of the present invention is to provide a nitrogen-doped carbon / tungsten diselenide nanosphere composite material prepared by the above preparation method, comprising: a nitrogen-doped carbon framework and tungsten diselenide nanosheets, wherein the tungsten diselenide nanosheets are dispersed and embedded in the nitrogen-doped carbon framework to form a three-dimensional nanosphere structure.

[0017] A third aspect of the present invention is to provide a nitrogen-doped carbon / tungsten diselenide nanosphere composite material prepared by the above preparation method, or the application of the above nitrogen-doped carbon / tungsten diselenide nanosphere composite material in the positive electrode of a zinc-ion battery.

[0018] A fourth aspect of the present invention is to provide a zinc-ion battery, comprising: a positive electrode, a counter electrode made of a sheet of metallic zinc, a separator made of a glass microfiber membrane, and a ZnSO4 electrolyte;

[0019] The preparation of the positive electrode includes: mixing the nitrogen-doped carbon / tungsten diselenide nanosphere composite material NC / WSe2 obtained by the above preparation method, a conductive agent, a binder and N-methylpyrrolidone, coating it onto a copper foil, drying it and pressing it into a sheet to obtain the positive electrode sheet.

[0020] Preferably, the mass ratio of the nitrogen-doped carbon / tungsten diselenide nanosphere composite material NC / WSe2, the conductive agent, and the binder is 6-8:2.5-1.5:1.5-0.5.

[0021] Preferably, the conductive agent includes at least one of Super P, carbon nanotubes, acetylene black, and graphene.

[0022] Preferably, the adhesive comprises at least one of polyvinylidene fluoride and sodium alginate.

[0023] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0024] This invention achieves tight coupling between few-layer WSe2 nanosheets and a nitrogen-doped carbon framework through a process combining complexation-polymerization and subsequent selenization. The resulting material consists of nanospheres that provide more electrochemical active sites and shorten the zinc ion diffusion distance. By introducing a nitrogen-doped carbon framework, this invention effectively improves the overall conductivity of the composite material and suppresses the stacking and aggregation of WSe2 nanosheets during charge and discharge, thereby significantly improving rate performance and cycle stability. Attached Figure Description

[0025] Figure 1 The XRD patterns of the precursor W-PDA and the composite material NC / WSe2 in the embodiments of the present invention are shown below.

[0026] Figure 2 This is a SEM image of NC / WSe2 in an embodiment of the present invention;

[0027] Figure 3 The rate performance curve of NC / WSe2 as the positive electrode of zinc-ion battery in the embodiments of the present invention;

[0028] Figure 4 This is a cycle performance curve of NC / WSe2 as the positive electrode of a zinc-ion battery in an embodiment of the present invention;

[0029] Figure 5 Cycle performance curves of commercially available WSe2 as the positive electrode of zinc-ion batteries in the test examples of this invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0033] Example

[0034] This embodiment provides a method for preparing nitrogen-doped carbon / tungsten diselenide nanosphere composite materials, the steps of which include:

[0035] S1. 960 mg of the structure-directing agent polyethylene-polypropylene glycol block copolymer F127 and 200 mg of the surfactant cetyltrimethylammonium bromide CTBA were dispersed in 44 mL of ethanol solution (water to ethanol volume ratio of 10:1). 200 mg of dopamine hydrochloride PDA and 600 mg of NaWO4·2H2O were added, and the mixture was stirred at room temperature for 2 h to obtain a yellow suspension. The obtained product was centrifuged and washed several times with water and ethanol, and dried at 60 °C for 12 h to obtain the tungsten-polydopamine precursor W-PDA.

[0036] S2. Place 600 mg of selenium powder in the upstream of a tube furnace and 100 mg of W-PDA precursor in the downstream. Under a nitrogen atmosphere, heat the furnace to 600 °C at a rate of 5 °C / min and sinter for 4 h. After natural cooling, the nitrogen-doped carbon / tungsten diselenide nanosphere composite material NC / WSe2 is obtained.

[0037] X-ray diffraction (XRD) was used to verify the crystallinity and phase structure of the prepared material. Scanning electron microscopy (SEM) was used to examine the particle morphology and size of the prepared NC / WSe2.

[0038] Figure 1 The XRD pattern of NC / WSe2 obtained in Example 1 of this invention is shown in the figure. As can be seen from the figure, the XRD pattern of W-PDA shows a (010) peak at 25.18°, which belongs to the polymerization reaction. The main diffraction peak of NC / WSe2 is at 23.74°, which also belongs to the (010) peak. At the same time, new diffraction peaks are added at 13.94° and 54.12°, which correspond to the (002) and (110) peak planes of WSe2, proving the formation of NC / WSe2 (JCPDS No. 38-1388).

[0039] Figure 2 The image shows a SEM image of NC / WSe2 prepared in Example 1 of this invention. It can be seen that the NC / WSe2 prepared in this example has a morphology of nanospheres with a diameter of about 800 nm and the particle size is relatively uniform.

[0040] Detection Examples

[0041] The NC / WSe2 obtained in the examples was used as the positive electrode material to prepare a battery and its electrochemical performance was tested. The steps included: adding NC / WSe2 active material (70wt%), acetylene black (20wt%), and polyvinylidene fluoride (10wt%) to 700μL NMP and stirring evenly to form a slurry; coating the slurry onto copper foil and vacuum drying at 60°C overnight; and then pressing the slurry to obtain a positive electrode sheet with a loading of approximately 1.7 mg / cm³. 2 Subsequently, a coin cell was assembled using a zinc sheet as the counter electrode, a glass microfiber membrane as the separator, and a 1.0 mol / L ZnSO4 aqueous solution as the electrolyte. The resulting active material loading was approximately 1.2 mg / cm³. 2 A battery was prepared using commercially available WSe2 as the positive electrode active material according to the above method as a comparison. The cycle performance and rate performance of the prepared material were tested using an electrochemical workstation within a voltage range of 0-1.8V. The test results are shown in Table 1 and... Figure 3-5 As shown.

[0042] Table 1

[0043]

[0044] Figure 3 The results show that the average discharge specific capacities of NC / WSe2 at current densities of 2.0, 5.0, 8.0, 12.0, 15.0, and 20.0 A / g are 148.53, 124.80, 105.38, 94.67, 89.67, 85.35, and 80 mAh / g, respectively. When the current density is restored to 2.0 A / g, the specific capacity can still be restored to 141.29 mAh / g, indicating that the NC / WSe2 electrode material has excellent rate performance.

[0045] Figure 4 This indicates that when the NC / WSe2 material prepared in this embodiment is used as the positive electrode of a zinc-ion battery, it achieves a performance of 5.0 A·g -1 After 2500 cycles, the coulomb efficiency approaches 100%.

[0046] In summary, this invention effectively improves the rate performance and cycle stability of zinc-ion batteries by constructing three-dimensional nanospheres tightly coupled with a nitrogen-doped porous carbon framework as the cathode material. The method of this invention is simple, controllable, and suitable for the preparation of high-performance zinc storage materials.

[0047] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a nitrogen-doped carbon / tungsten diselenide nanosphere composite material, characterized in that the steps include... include: S1. Disperse the structure-directing agent and surfactant in an ethanol solution, add dopamine hydrochloride and tungsten source to carry out a complexation-polymerization reaction to obtain a tungsten-polydopamine precursor; S2. The tungsten-polydopamine precursor is mixed with a selenium source and then heat-treated under an inert atmosphere to obtain the nitrogen-doped carbon / tungsten diselenide nanosphere composite material NC / WSe2.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the structure-directing agent, the surfactant, the dopamine hydrochloride, and the tungsten source is 42-50:6-10:6-10:30-46; the mass ratio of the tungsten source to the selenium source is 10-20:80-90.

3. The preparation method according to claim 1, characterized in that, In step S1, the structure directing agent is polyethylene-polypropylene glycol block copolymer F127.

4. The preparation method according to claim 1, characterized in that, In step S1, the surfactant is hexadecyltrimethylammonium bromide.

5. The preparation method according to claim 1, characterized in that, In step S1, the complexation-polymerization reaction includes: reacting at room temperature for 2-3 hours, centrifuging and washing the product, and drying at 60-80°C after washing.

6. The preparation method according to claim 1, characterized in that, In step S1, the tungsten source includes at least one of sodium tungstate, ammonium tungstate, and tungsten ethoxide.

7. The preparation method according to claim 1, characterized in that, In step S2, the heat treatment includes: heating to 600-800°C at a rate of 5-10°C / min, and sintering in an argon or nitrogen atmosphere for 3-6 hours.

8. A nitrogen-doped carbon / tungsten diselenide nanosphere composite material prepared by the preparation method according to any one of claims 1-7, characterized in that, include: A nitrogen-doped carbon framework and tungsten diselenide nanosheets are formed, wherein the tungsten diselenide nanosheets are dispersed and embedded in the nitrogen-doped carbon framework to form a three-dimensional nanosphere structure.

9. The application of a nitrogen-doped carbon / tungsten diselenide nanosphere composite material prepared by any one of claims 1-7 or the nitrogen-doped carbon / tungsten diselenide nanosphere composite material as described in claim 8 in the cathode of a zinc-ion battery.

10. A zinc-ion battery, characterized in that, include: The positive electrode, the counter electrode made of zinc sheet, the separator made of glass microfiber membrane, and the ZnSO4 electrolyte; The preparation of the positive electrode includes: mixing nitrogen-doped carbon / tungsten diselenide nanosphere composite material NC / WSe2 obtained by the preparation method according to any one of claims 1-7, a conductive agent, a binder and N-methylpyrrolidone, coating the mixture onto a copper foil, drying it and pressing it into a sheet to obtain the positive electrode sheet.

Images