A two-dimensional flexible material composed of vanadium phosphate oxide and MXene and a preparation method and application thereof

Abstract

The application discloses a two-dimensional flexible material compounded by vanadium oxyphosphate and MXene and a preparation method and application thereof, and belongs to the technical field of functional nanomaterial preparation. The application first prepares multilayer vanadium oxyphosphate through a hydrothermal method, then fully mixes vanadium oxyphosphate which is stripped through a liquid phase with MXene and polyacrylonitrile to prepare a spinning liquid, adopts an electrostatic spinning method to obtain a polymer fiber film doped with vanadium oxyphosphate nanosheets, and further carries out calcination and carbonization treatment in an ammonia atmosphere to obtain a flexible porous vanadium-based nanofiber film material. The vanadium oxyphosphate film material prepared by the method has physical properties of rich active sites, high conductivity, sufficient ion transmission channels, good flexibility and excellent self-supporting structure, has the advantages of high activity, high capacity and high stability in energy storage application, and has an excellent application prospect. The preparation process of the application is simple, energy consumption is low, and the application is suitable for industrial large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of functional nanomaterial preparation technology, and more specifically, relates to a two-dimensional flexible material composed of vanadium oxyphosphate and MXene, its preparation method and application. Background Technology

[0002] The energy crisis remains a pressing global problem. The massive consumption of fossil fuels has led to their depletion, environmental pollution, and global warming. Developing new energy technologies can effectively solve the energy problem. Battery technology stores energy in the form of chemical energy, making it a green and efficient energy storage and conversion technology. Lithium-ion batteries, with their long cycle life, high energy density, low self-discharge, and environmental friendliness, are widely used in mobile energy devices such as mobile phones, computers, and electric vehicles, and are the most mature and widely applied energy conversion technology in the new energy field. Furthermore, fuel cells are a new energy technology that directly converts biomass energy into discharge energy. Compared to traditional batteries, this reduces the process of converting biomass energy into chemical energy, is not limited by the Carnot cycle, and greatly improves fuel utilization. Currently, fuel cell technology is already being used in new energy vehicles.

[0003] However, lithium-ion batteries still face many challenges, such as low lithium reserves, scarcity of cathode materials (e.g., nickel and cobalt), and high production costs. These are significant issues limiting the large-scale application of this technology. In this context, sodium-ion batteries (SIBs) have attracted widespread attention due to their abundant sodium metal reserves, lower production costs, and similar advantages to lithium-ion batteries in terms of ion insertion / extraction mechanisms, making them a strong candidate for future replacements of lithium-ion batteries.

[0004] MXene is a two-dimensional transition metal carbide / nitride that is widely used as an electrode material in emerging ion batteries due to its desirable properties. These properties include a large and tunable interlayer space, excellent hydrophilicity, superior conductivity, compositional diversity, and rich surface chemistry, making MXene a promising candidate not only as an electrode material but also as another component in emerging batteries.

[0005] Vanadium oxyphosphate is a vanadium-based compound. Vanadium-based compounds have long been studied as cathode materials for ion batteries. The multiple oxidation states of vanadium give vanadium compounds outstanding structural diversity, and various open structures provide convenient pathways for ion diffusion. PO4 in phosphate... 3- The polyanionic framework has better thermal stability than layered oxides. In addition, the phosphate component hinders oxygen release during charging, thereby increasing battery safety.

[0006] Isopropanol (IPA) is an organic compound that can replace ethanol as a solvent in many cases. It is a good solvent and chemical raw material. In addition, it can also be used as a solvent in chemical stripping methods. It has the advantages of low cost, good quality and easy control. Summary of the Invention

[0007] The technical problem this invention aims to solve is to provide a simple process for the large-scale preparation of a two-dimensional flexible material composed of vanadium oxyphosphate and MXene, exhibiting excellent electrochemical performance, using low-cost raw materials. The vanadium oxyphosphate and MXene composite possesses good performance characteristics for sodium (zinc) ion batteries, and can also be used as an active material to assemble flexible batteries. This addresses the problems of complex manufacturing processes, high costs, poor performance, and limited application range of commercial battery materials.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a two-dimensional flexible material composed of vanadium oxyphosphate and MXene includes the following steps:

[0010] (1) After thoroughly stirring vanadium pentoxide, phosphoric acid and deionized water, multilayer vanadium oxyphosphate was prepared by hydrothermal method.

[0011] (2) Add multilayer vanadium oxyphosphate to isopropanol, ultrasonically peel it into single-layer vanadium oxyphosphate, add single-layer MXene after peeling, and centrifuge to obtain MXene composite single-layer vanadium oxyphosphate dihydrate powder.

[0012] (3) Dissolve MXene composite monolayer vanadium phosphate dihydrate powder in N,N-dimethylformamide, then add polyacrylonitrile and stir to prepare a spinning solution, and obtain a spinning membrane by electrospinning.

[0013] (4) The spun film was calcined in a tube furnace under an ammonia atmosphere to obtain a two-dimensional flexible material composed of vanadium oxyphosphate and MXene.

[0014] Further, in step (1), the molar ratio of vanadium pentoxide to phosphoric acid is 1-3:15-25, and the specific conditions for the hydrothermal method are 60-150℃ for 6-18h.

[0015] Further, the specific method of ultrasonic stripping in step (2) is as follows: add 0.3-1.5g of multilayer vanadium oxyphosphate to 100-250mL of isopropanol solution and stir evenly, sonicate at room temperature until the yellow-green turbid solution becomes clear and the Tyndall effect appears.

[0016] Furthermore, in step (2), the mass ratio of multilayer vanadium oxyphosphate to MXene is 0.3-1.5:0.1-2.5.

[0017] Further, the specific method for preparing the spinning solution in step (3) is as follows: the mass ratio of polyacrylonitrile to MXene composite monolayer vanadium oxyphosphate dihydrate powder is 5-9:1-5, and the stirring time is more than 24 hours.

[0018] Further, the electrospinning in step (3) specifically involves using a 5-10 mL syringe, setting the electrospinning voltage to 5-15 kV, and setting the feed rate to 0.5-1.2 mL / h. -1 .

[0019] Furthermore, the specific calcination conditions in step (4) are as follows: calcination at 300–700℃ for 1–5 hours under an ammonia atmosphere, with a heating rate of 2–10℃ / min. -1 .

[0020] The two-dimensional flexible material composed of vanadium oxyphosphate and MXene is prepared by any of the methods described.

[0021] The application of the two-dimensional flexible material composed of vanadium oxyphosphate and MXene in energy storage and conversion, metal-ion batteries or supercapacitors.

[0022] In the aforementioned application, the two-dimensional flexible material composed of vanadium oxyphosphate and MXene is used as a cathode material for ion batteries.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) Compared with the existing methods for preparing two-dimensional flexible materials, the material prepared by this method has a very strong universality. It has the characteristics of high temperature resistance and can maintain the integrity of the structure during high temperature carbonization. At the same time, it also has good flexibility and can still recover after being bent at large angles multiple times. In practical use, it can be used in various ion batteries, thus greatly improving the application range of the material.

[0025] (2) The method of this invention is simple and efficient, and the obtained material has a high two-dimensional area (micrometer level) and an extremely high specific surface area. The raw material utilization rate is high during the experiment, and no surfactant is required to fully composite the monolayer MXene with vanadium oxyphosphate nanosheets. Therefore, no post-processing is required after the material is synthesized.

[0026] (3) This invention, through calcination and carbonization, endows the fiber membrane with a porous structure. This structure provides a larger surface area and more active sites for ions in electrochemical applications. In application, the two-dimensional flexible material obtained by this method can be directly used as the positive electrode of a battery without any substrate or binder, and it exhibits good capacity contribution. Furthermore, the two-dimensional flexible material obtained by this method is bendable, showing broad application prospects in pouch batteries. Attached Figure Description

[0027] Figure 1 These are scanning electron microscope (SEM) images of the multilayer vanadium oxyphosphate dihydrate nanosheets at different magnifications in Example 1 of this invention.

[0028] Figure 2 These are scanning electron microscope (SEM) images of MXene composite monolayer vanadium oxyphosphate dihydrate nanosheets at different magnifications in Example 1 of this invention.

[0029] Figure 3 The XRD patterns are of the multilayer vanadium oxyphosphate dihydrate nanosheets and the MXene composite single-layer vanadium oxyphosphate dihydrate nanosheets in Example 1 of this invention.

[0030] Figure 4 This is an EDS (Electronic Data Sequencing) image of the MXene composite monolayer vanadium oxyphosphate dihydrate nanosheets in Example 1 of this invention.

[0031] Figure 5 These are scanning electron microscope (SEM) images of the MXene composite monolayer vanadium oxyphosphate dihydrate nanosheet fiber membrane at different magnifications in Example 2 of this invention.

[0032] Figure 6 The images show different bending conditions and surface views after bending of the MXene composite monolayer vanadium oxyphosphate dihydrate nanosheet fiber membrane in Example 2 of this invention.

[0033] Figure 7 The diagram shows the performance of a sodium-ion battery using the MXene composite monolayer vanadium oxyphosphate dihydrate nanosheet fiber membrane as the positive electrode in Example 3 of this invention.

[0034] Figure 8 The graph shows the performance of a zinc-ion battery using the MXene composite monolayer vanadium oxyphosphate dihydrate nanosheet fiber membrane as the positive electrode in Example 4 of this invention. Detailed Implementation

[0035] The present invention will be further described below with reference to specific embodiments.

[0036] Example 1: Preparation of MXene composite monolayer vanadium oxyphosphate dihydrate powder

[0037] Add 0.5-2.0 g of V₂O₅ and 5-15 mL of phosphoric acid to 10-40 mL of deionized water, place on a stirring table, and stir vigorously at 4000-8000 rpm for 2-4 hours to obtain a bright yellow viscous liquid. Pour the stirred solution into a hydrothermal reactor and react at 60-150℃ for 6-18 hours. After hydrothermal treatment, centrifuge to obtain a yellow-green multilayered vanadium oxyphosphate dihydrate VOP powder. Figure 1 ).

[0038] Weigh 0.3-1.5g of the above powder and add it to 100-250mL of isopropanol solution. Stir well with a glass rod, then sonicate at room temperature for 3-10 hours to perform liquid-phase exfoliation of the multilayer vanadium oxyphosphate until the yellow-green turbid solution becomes clear and the Tyndall effect is observed. Then add 0.1-2.5g of monolayer MXene. After centrifugation, a dark green MXene composite monolayer vanadium oxyphosphate dihydrate powder (VOP / MXene) is obtained. Figure 2 As shown, monolayer MXene and monolayer vanadium oxyphosphate nanosheets are combined to form nanoflowers. XRD tests were performed on multilayer vanadium oxyphosphate dihydrate powder samples and MXene-composite monolayer vanadium oxyphosphate dihydrate powder samples. Figure 3 The former is a pure sample, which can be matched with the VOPO4·2H2O standard card, while the latter is an MXene-VOPO4·2H2O composite sample. The shift in the XRD peak position proves that MXene and the pure sample undergo a recombination reaction in the exfoliation solution. Meanwhile, Figure 4 The EDS test results of the medium sample also indicate that the two are fully composite.

[0039] Example 2: Preparation of MXene composite monolayer vanadium oxyphosphate dihydrate nanosheet fiber membrane

[0040] The monolayer vanadium oxyphosphate dihydrate powder obtained in Example 1 was dissolved in N,N-dimethylformamide and stirred thoroughly at room temperature to form a green solution. Polyacrylonitrile (PAN) was added to the solution and stirred thoroughly for 24-48 hours to prepare a spinning solution. Using electrospinning technology, a polymer fiber membrane of MXene composite monolayer vanadium oxyphosphate nanosheets was obtained. After drying the fiber membrane overnight, it was transferred to a tube furnace and calcined at a heating rate of 2-10°C per minute to 500-900°C for 1-5 hours under an ammonia atmosphere to obtain a carbonized fiber membrane. Figure 5 ).like Figure 6 As shown, the fiber membrane structure remains intact after high-temperature carbonization, and it can still recover its original shape after being bent at different angles, demonstrating good flexibility.

[0041] Example 3: Preparation of Sodium-ion Batteries

[0042] The two-dimensional flexible film composed of vanadium oxide and MXene obtained in Example 2 was cut into 1*1cm squares, vacuum dried, and used as the positive electrode. The negative electrode was a sodium metal sheet, and the electrolyte was prepared at 1.0-2.0 mol / L. -1 A button cell was assembled using a NaCF3SO3 solution (diglyme solvent) and a glass fiber separator. The assembled cells were then tested for performance in a battery testing cabinet (Shenzhen Xinwei CT-4008). The operating voltage was 0.01–3.0V. Figure 7As shown, sodium-ion batteries using this thin film as the positive electrode have high discharge capacity and are a good positive electrode material for sodium-ion batteries.

[0043] Example 4: Preparation of Zinc-ion Batteries

[0044] The two-dimensional flexible film composed of vanadium oxide and MXene obtained in Example 2 was cut into 1*1cm squares, vacuum dried, and used as the positive electrode. The negative electrode was a zinc sheet, and the electrolyte was 1.0-3.0 mol / L. -1 Zinc trifluoromethanesulfonate (solvent: deionized water) and glass fiber separator were used to assemble button batteries. The assembled batteries were then tested for performance in a battery testing cabinet (Shenzhen Xinwei CT-4008) with an operating voltage of 0.01–3.0V. Figure 8 As shown, zinc-ion batteries using this thin film as the positive electrode can undergo long-term charge-discharge at low current densities and exhibit good stability, making it a good positive electrode material for zinc-ion batteries.

Claims

1. A method for preparing a two-dimensional flexible material composed of vanadium oxyphosphate and MXene, characterized in that, Includes the following steps: (1) After thoroughly stirring vanadium pentoxide, phosphoric acid and deionized water, multilayer vanadium oxyphosphate was prepared by hydrothermal method. (2) Add multilayer vanadium oxyphosphate to isopropanol, and ultrasonically peel it into single-layer vanadium oxyphosphate. After peeling, add single-layer MXene, and centrifuge to obtain MXene composite single-layer vanadium oxyphosphate dihydrate powder; the mass ratio of multilayer vanadium oxyphosphate to single-layer MXene is 0.3-1.5:0.1-2.

5. (3) Dissolve MXene composite monolayer vanadium oxyphosphate dihydrate powder in N,N-dimethylformamide, then add polyacrylonitrile and stir to prepare a spinning solution, and obtain a spinning film by electrospinning; the mass ratio of polyacrylonitrile to MXene composite monolayer vanadium oxyphosphate dihydrate powder is 5-9:1-5, and the stirring time is more than 24 hours. (4) The spun film is calcined in a tube furnace under an ammonia atmosphere to obtain a two-dimensional flexible material composed of vanadium oxyphosphate and MXene. The specific calcination conditions are: calcination at 300-700℃ for 1-5 hours under an ammonia atmosphere, with a heating rate of 2-10℃ / min. -1 .

2. The method for preparing a two-dimensional flexible material composed of vanadium oxyphosphate and MXene according to claim 1, characterized in that, In step (1), the molar ratio of vanadium pentoxide to phosphoric acid is 1-3:15-25, and the specific conditions for the hydrothermal method are 60-150℃ for 6-18h.

3. The method for preparing the two-dimensional flexible material composed of vanadium oxyphosphate and MXene according to claim 1, characterized in that, The specific method for ultrasonic stripping in step (2) is as follows: add 0.3-1.5g of multilayer vanadium oxyphosphate to 100-250mL of isopropanol solution and stir evenly. Ultrasound at room temperature until the yellow-green turbid solution becomes clear and the Tyndall effect appears.

4. The method for preparing a two-dimensional flexible material composed of vanadium oxyphosphate and MXene according to claim 1, characterized in that, The electrospinning in step (3) specifically involves using a 5-10 mL syringe, setting the electrospinning voltage to 5-15 kV, and setting the feed rate to 0.5-1.2 mL / h. -1 .

5. The two-dimensional flexible material composed of vanadium oxyphosphate and MXene prepared by the method according to any one of claims 1-4.

6. The application of the two-dimensional flexible material composed of vanadium oxyphosphate and MXene as described in claim 5 in energy storage and conversion, metal-ion batteries or supercapacitors.

7. The application according to claim 6, characterized in that, The two-dimensional flexible material composed of vanadium oxyphosphate and MXene is used as a cathode material for metal-ion batteries.

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