Single-atom dispersed cu, zn co-doped carbon sheet flexible material and preparation method and application thereof

Abstract

The application discloses a single-atom dispersed Cu and Zn co-doped carbon sheet flexible material and a preparation method and application thereof, and the preparation method comprises the following steps: soaking a flexible carbon cloth in a nitric acid solution and performing hydrothermal treatment to obtain an active flexible carbon cloth with oxygen-containing functional groups grafted on the surface; adding copper salt and zinc salt solutions into a dimethyl imidazole solution, uniformly mixing, then adding the active flexible carbon cloth, and standing and reacting to obtain a precursor flexible carbon cloth; and performing vacuum calcination on the precursor flexible carbon cloth to obtain the single-atom dispersed Cu and Zn co-doped carbon sheet flexible material. The raw material used in the application is easy to obtain, the process is simple, the conditions are easy to control, the thickness of the modification layer can be controlled, the specific surface area and physical strength of the carbon cloth can be significantly improved, the copper atom doping amount is high, and therefore the controllable modification layer thickness and atomic-level metal doping are realized, and the application is suitable for the application of energy storage devices such as supercapacitors, lithium ion batteries and fuel cells.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energy storage material preparation, and relates to a single-atom-dispersed Cu and Zn co-doped carbon sheet flexible material and a preparation method and application thereof. BACKGROUND

[0002] The aqueous zinc ion battery using zinc metal as the negative electrode has the advantages of low cost, high safety and high energy density, because the zinc metal has low cost, high theoretical capacity and low redox potential, and water is thermodynamically stable and non-toxic as the electrolyte. However, similar to most alkali metal ion batteries, the zinc ion battery inevitably faces the problem of dendrite growth, which seriously affects the further development of the aqueous zinc ion battery.

[0003] In recent years, the problem of dendrite growth has been alleviated by using a mild neutral / weak acid electrolyte, but the high roughness and unevenness of the commercial zinc foil lead to zinc plating in the area with high local current density, further aggravating the growth of zinc dendrites. Therefore, it is necessary to homogenize the electric field distribution on the zinc anode to promote the uniform and orderly nucleation of zinc ions to avoid the growth of zinc dendrites. In addition, due to the freedom from the limitations of traditional battery applications, flexible wearable electronic devices have received extensive attention and welcome in recent years. Under such circumstances, flexible carbon cloth materials with various morphologies and properties are expected to achieve zinc dendrite inhibition and high stability of the zinc anode.

[0004] Various pure carbon materials such as graphene and carbon nanotubes are currently the most common electrode active materials, which have good cycle stability and excellent conductivity, but some of the carbon materials used at present lack sufficient three-dimensional space, leading to the vertical growth of zinc dendrites and further causing device short circuit. A large number of studies have shown that a layer of zincophilic metal modified on the carbon material can inhibit zinc dendrites, but the metal layer modified by electrodeposition is generally thick, several microns thick, and has the problems of loose combination, excessive metal and metal aggregation; the method of loading metal particles by hydrothermal growth is time-consuming and is not conducive to large-scale application. SUMMARY

[0005] In view of the problems in the prior art, the application provides a single-atom-dispersed Cu and Zn co-doped carbon sheet flexible material and a preparation method and application thereof, so as to solve the technical problems that the metal layer modified carbon material prepared in the prior art has a thick metal layer on the surface, the metal layer is not tightly combined, the metal particles are easy to aggregate, and the time is long.

[0006] The application is realized by the following technical scheme:

[0007] The preparation method of the single-atom-dispersed Cu and Zn co-doped carbon sheet flexible material comprises the following steps:

[0008] S1: The flexible carbon cloth is immersed in nitric acid solution for hydrothermal treatment to obtain an active flexible carbon cloth with oxygen-containing functional groups grafted on its surface.

[0009] S2: Add copper salt and zinc salt solutions to dimethylimidazole solution, mix well, then add the active flexible carbon cloth, let it stand to react, and obtain the precursor flexible carbon cloth.

[0010] S3: The precursor flexible carbon cloth is calcined under vacuum to obtain the single-atom dispersed Cu and Zn co-doped carbon sheet flexible material.

[0011] Preferably, in step S1, the flexible carbon cloth is one of carbon fiber cloth, carbon paper, or flexible three-dimensional graphene.

[0012] Preferably, in step S1, the hydrothermal treatment temperature is 70–90°C, the solvothermal time is 8–12 h, and the concentration of the nitric acid solution is 7–14 mol / L.

[0013] Preferably, in step S2, the zinc salt is one or two of zinc nitrate hexahydrate, anhydrous zinc acetate, or zinc acetate dihydrate, and the copper salt is copper nitrate and / or copper acetate.

[0014] Preferably, in step S2, copper salt and zinc salt solutions are added to dimethylimidazole solution to form a mixed solution of salt solution and dimethylimidazole solution, wherein the concentration of salt solution is 0.025-0.05 mol / L and the concentration of dimethylimidazole is 0.25-0.5 mol / L.

[0015] Preferably, in step S2, the concentration ratio of copper salt to zinc salt in the salt solution is (1-2):(1-4).

[0016] Preferably, in step S2, the copper salt and zinc salt solutions are mixed evenly with the dimethylimidazole solution by ultrasonic treatment, wherein the ultrasonic frequency is 28-40 kHz and the ultrasonic time is 1-5 min.

[0017] Preferably, in step S3, vacuum calcination is performed under an argon or nitrogen atmosphere, the calcination temperature is 700-900℃, and the calcination time is 2-4 hours.

[0018] A flexible Cu-Zn co-doped carbon sheet material with single-atom dispersion was prepared by the method described above.

[0019] The above-mentioned single-atom dispersed Cu and Zn co-doped carbon sheet flexible material is used in aqueous zinc-ion batteries.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] This invention provides a method for preparing a single-atom dispersed Cu / Zn co-doped carbon sheet flexible material. First, the flexible carbon cloth is activated in nitric acid solution to obtain an active flexible carbon cloth with oxygen-containing functional groups grafted on its surface. Then, Zn / Cu-ZIF is grown on the surface of the activated flexible carbon cloth. Next, the flexible carbon cloth with Zn / Cu-ZIF grown on it is used as a precursor and subjected to vacuum calcination to carbonize the ZIF framework, finally obtaining a Zn / Cu co-doped carbon sheet. This carbon sheet is a nitrogen-doped carbon sheet, i.e., the product is N / Zn / Cu@CCs. This invention modifies flexible carbon cloth by introducing Zn / Cu-ZIF as a porous carbon precursor, resulting in N, Cu, and Zn co-doped flexible carbon cloth. This improves upon the shortcomings of a single carbon substrate. During preparation, Zn and Cu are grown in situ on the flexible carbon cloth substrate, and further high-temperature carbonization yields porous carbon fibers. The rich three-dimensional porous structure can accommodate zinc dendrites grown during the charge-discharge process. Furthermore, the zinc-loving, atomically monodisperse metal particles generated after Zn / Cu-ZIF carbonization have strong zinc-binding ability, which can homogenize zinc ion deposition. The nitrogen element in the material can lower the nucleation barrier. This invention selects Zn-MOF with a low boiling point as a template, while simultaneously loading high-boiling-point active metal particles. In the subsequent high-temperature treatment process, porous carbon containing atomically dispersed metals is formed. The raw materials used in this invention are readily available, the process is simple, and the conditions are easy to control. The thickness of the modification layer can be controlled, and the specific surface area and physical strength of the carbon cloth can be significantly improved. Moreover, the copper atom doping amount is high, thereby achieving controllable modification layer thickness and atomic-level metal doping. It is suitable for applications in energy storage devices such as supercapacitors, lithium-ion batteries, and fuel cells.

[0022] Furthermore, in step S1, the flexible carbon cloth is one of carbon fiber cloth, carbon paper, or flexible three-dimensional graphene, which can effectively improve the electrical conductivity of the material, provide a three-dimensional structure, and physically inhibit the growth of zinc dendrites.

[0023] Furthermore, in step S1, the hydrothermal treatment temperature is 70–90°C, the solvothermal time is 8–12 h, and the concentration of the nitric acid solution is 7–14 mol / L, which allows oxygen-containing functional groups to be loaded onto the carbon substrate material, which is beneficial for the subsequent growth of MOF.

[0024] Furthermore, in step S2, the zinc salt is one or two of zinc nitrate hexahydrate, anhydrous zinc acetate, or zinc acetate dihydrate, and the copper salt is copper nitrate and / or copper acetate, which can be used as zinc and copper sources to ensure that atomic-level doped copper and zinc are formed in the subsequent carbonization process.

[0025] Furthermore, in step S2, copper salt and zinc salt solutions are added to dimethylimidazole solution to form a mixed solution of salt solution and dimethylimidazole solution. The concentration of the salt solution is 0.025-0.05 mol / L, and the concentration of the dimethylimidazole is 0.25-0.5 mol / L. Controlling this concentration range can effectively control the thickness of the obtained metal modification layer.

[0026] Furthermore, in step S2, the concentration ratio of copper salt to zinc salt in the salt solution is (1-2):(1-4), which can control the ratio of metallic zinc and metallic copper in the product.

[0027] Furthermore, in step S2, the copper salt and zinc salt solutions are mixed evenly with the dimethylimidazole solution by ultrasonic treatment. The ultrasonic frequency is 28-40 kHz and the ultrasonic time is 1-5 min, which allows the zinc salt and copper salt to be fully dissolved and mixed, and to undergo a coordination reaction with dimethylimidazole, so that the product Zn / Cu-ZIF can be distributed on the flexible carbon cloth.

[0028] Furthermore, in step S3, vacuum calcination is performed under an argon or nitrogen atmosphere at a temperature of 700-900°C for 2-4 hours, which can carbonize the precursor. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic flowchart of a method for preparing a single-atom dispersed Cu and Zn co-doped carbon sheet flexible material according to the present invention.

[0031] Figure 2 SEM images of N / Zn / Cu@CCs obtained in Examples 1(a), 2(b), 3(c) and 5(d) of this invention;

[0032] Figure 3 TEM image of N / Zn / Cu@CCs prepared in Example 1;

[0033] Figure 4 The results show a comparison of the cycle stability of pure carbon substrate (a), bare zinc (b), and Zn / Cu@N-CCs (c) prepared in Example 1 of this invention for use in aqueous zinc-ion batteries. Detailed Implementation

[0034] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0035] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0036] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0037] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0038] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0039] like Figure 1 As shown, this invention provides a method for preparing a single-atom dispersed Cu and Zn co-doped carbon sheet flexible material, comprising the following steps:

[0040] S1: Flexible carbon cloth and 60 mL of nitric acid solution were placed in a 100 mL polytetrafluoroethylene liner and hydrothermally treated in an oven to grow oxygen-containing active groups on the flexible carbon cloth substrate. After hydrothermal treatment, the flexible carbon cloth was immersed in deionized water until the solution became neutral. Then it was dried at 60 °C to obtain the active flexible carbon cloth substrate.

[0041] The concentration of the nitric acid solution is 7–14 mol / L, the solvothermal temperature is 70–90℃, the solvothermal time is 8–12 h, and the deionized water soaking is performed 5 times, with an interval of 0.5–2 h between each soaking.

[0042] S2: Weigh out copper salt and zinc salt according to the molar ratio and prepare aqueous solutions, denoted as solution A; weigh out a certain concentration of dimethylimidazole solution and prepare an aqueous solution, denoted as solution B. Quickly pour solution A into solution B and mix by ultrasonication to obtain a mixed solution, denoted as solution C.

[0043] The zinc salt is one or two of zinc nitrate hexahydrate, anhydrous zinc acetate, or zinc acetate dihydrate, and the copper salt is copper nitrate and / or copper acetate.

[0044] Preferably, in the mixed solution, the concentration of the metal salt is 0.025–0.05 mol / L, the concentration ratio of the copper salt to the zinc salt is (1–2):(1–4), and the concentration of the dimethylimidazole is 0.25–0.5 mol / L.

[0045] Preferably, the ultrasonic frequency is 28–40 kHz and the ultrasonic time is 1–5 min.

[0046] S3: Place the treated flexible carbon cloth substrate in the prepared solution C and let it stand for 2-4 hours. After a period of time, ZIF containing Zn and Cu elements grows in situ on the flexible carbon cloth substrate (Zn / Cu-ZIF@CCs). Wash repeatedly with deionized water to remove the precipitates that have not grown on the substrate. Then, dry the Zn / Cu-ZIF@CCs in a forced-air drying oven at 60°C to obtain the precursor flexible carbon cloth Zn / Cu-ZIF@CCs.

[0047] S4: The precursor flexible carbon cloth Zn / Cu-ZIF@CCs is transferred to a tube furnace for vacuum calcination. Further, the flexible carbon cloth obtained by high-temperature carbonization is immersed in hydrochloric acid solution to remove residual metal particles from the surface, then washed repeatedly with deionized water, and then dried in a forced-air drying oven at 60°C for 4 hours to obtain N / Zn / Cu@CCs. This material is a Zn and Cu co-doped carbon fiber cloth, which is a nitrogen-doped carbon fiber cloth.

[0048] The vacuum calcination atmosphere is either argon or nitrogen, the heating rate is 2-5°C, the calcination temperature is 700-900°C, and the holding time is 2-4 hours.

[0049] The concentration of hydrochloric acid is 0.1–1 mol / L, and the soaking time in hydrochloric acid is 12–24 h.

[0050] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0051] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0052] Example 1

[0053] A method for preparing a single-atom dispersed Cu and Zn co-doped flexible carbon sheet material includes the following steps:

[0054] (1) Flexible commercial carbon fiber cloth and 60 mL of 7 mol / L nitric acid solution were placed in a 100 mL polytetrafluoroethylene-lined reactor and hydrothermally treated in an oven at 80 °C for 12 h. After hydrothermal treatment, the flexible carbon cloth was immersed in deionized water, with the water changed every 2 h, and the process was repeated 5 times. Then it was dried at 60 °C to obtain an active flexible carbon cloth substrate.

[0055] (2) Solution A was prepared with a salt concentration of 0.025 mol / L and a copper salt to zinc salt concentration ratio of 1:4. Specifically, 0.02 mol / L Zn(COO)₂·2H₂O and 0.005 mol / L Cu(COO)₂ were weighed and dissolved in 100 mL of deionized water to obtain solution A; 0.5 mol / L 2-methylimidazole was weighed and dissolved in 100 mL of deionized water, and this solution was denoted as solution B. Then, solution B was quickly poured into solution A and sonicated at a frequency of 40 kHz for 1 min to obtain mixed solution C.

[0056] (3) Arrange the treated activated carbon in solution C, ensuring that the solution submerges the carbon cloth substrate. After standing for 3 hours, take it out and rinse it several times with deionized water to remove excess precipitates on the surface. Then, put the carbon cloth precursor into an oven and dry it overnight at 60°C.

[0057] (4) High-temperature carbonization treatment: Under a nitrogen atmosphere, the pre-oxidized fiber cloth was heated from room temperature to 900℃ at a heating rate of 5℃ / min and held for 2 hours. The resulting flexible material of Cu and Zn co-doped carbon sheets with single-atom dispersion was immersed in 0.1mol / L hydrochloric acid solution for 12 hours to remove residual metals on the surface. Then, the carbon fiber cloth was washed with deionized water until neutral. The result was a flexible three-dimensional carbon fiber cloth (N / Zn / Cu@CCs) co-doped with N, Cu and Zn elements. The corresponding product reference is available. Figure 2 a.

[0058] Example 2

[0059] A method for preparing a single-atom dispersed Cu and Zn co-doped flexible carbon sheet material includes the following steps:

[0060] (1) Flexible commercial carbon fiber cloth and 60 mL of 7 mol / L nitric acid solution were placed in a 100 mL polytetrafluoroethylene liner and hydrothermally treated in an oven at 70 °C for 12 h. After hydrothermal treatment, the flexible carbon cloth was immersed in deionized water, with the water changed every 2 h, and the process was repeated 5 times. Then it was dried at 60 °C to obtain an active flexible carbon cloth substrate.

[0061] (2) Solution A was prepared with a salt concentration of 0.025 mol / L and a copper salt to zinc salt concentration ratio of 2:3. 0.015 mol / L Zn(COO)₂·2H₂O and 0.01 mol / L Cu(COO)₂ were weighed and dissolved in 100 mL of deionized water to obtain solution A. 0.5 mol / L 2-methylimidazole was weighed and dissolved in 100 mL of deionized water, and this solution was designated as solution B. Then, solution B was quickly poured into solution A, and the mixture was sonicated at 38 kHz for 3 min to obtain mixed solution C.

[0062] (3) Place the treated activated carbon cloth substrate in solution C, ensuring that the solution submerges the carbon cloth substrate. After standing for 3 hours, remove it and rinse it several times with deionized water to remove excess precipitates on the surface. Then, put the carbon cloth precursor into an oven and dry it overnight at 60°C.

[0063] (4) High-temperature carbonization treatment: Under a nitrogen atmosphere, the pre-oxidized fiber cloth was heated from room temperature to 800℃ at a heating rate of 5℃ / min and held for 2 hours. The resulting flexible material of Cu and Zn co-doped carbon sheets with single-atom dispersion was immersed in 0.5mol / L hydrochloric acid solution for 12 hours to remove residual metals on the surface. Then, the carbon fiber cloth was washed with deionized water until neutral. The result was a flexible three-dimensional carbon fiber cloth (N / Zn / Cu@CCs) doped with N, Cu and Zn elements. The corresponding product reference is available. Figure 2 b.

[0064] Example 3

[0065] A method for preparing a single-atom dispersed Cu and Zn co-doped flexible carbon sheet material includes the following steps:

[0066] (1) Flexible commercial carbon fiber cloth and 60 mL of 14 mol / L nitric acid solution were placed in a 100 mL polytetrafluoroethylene liner and hydrothermally treated in an oven at 80 °C for 10 h. After hydrothermal treatment, the flexible carbon cloth was immersed in deionized water, with the water changed every 2 h, and the process was repeated 5 times. Then it was dried at 60 °C to obtain an active flexible carbon cloth substrate.

[0067] (2) Solution A was prepared with a salt concentration of 0.04 mol / L and a copper salt to zinc salt concentration ratio of 1:3. Specifically, 0.03 mol / L of anhydrous Zn(COO)2 and 0.01 mol / L of Cu(COO)2 were weighed and dissolved in 100 mL of deionized water to obtain solution A; 0.4 mol / L of 2-methylimidazole was weighed and dissolved in 100 mL of deionized water, and this solution was denoted as solution B. Then, solution B was quickly poured into solution A and sonicated at a frequency of 28 kHz for 1 min to obtain mixed solution C.

[0068] (3) Place the treated activated carbon cloth substrate in solution C, let it stand for 2 hours, then take it out and rinse it with deionized water several times to remove excess precipitates on the surface. Then put the carbon cloth precursor into an oven and dry it overnight at 60°C.

[0069] (4) High-temperature carbonization treatment: Under a nitrogen atmosphere, the pre-oxidized fiber cloth was heated from room temperature to 700℃ at a heating rate of 2℃ / min and held for 4h. The resulting flexible material of Cu and Zn co-doped carbon sheets with single-atom dispersion was immersed in 0.1mol / L hydrochloric acid solution for 12h to remove residual metals on the surface. Then, the carbon fiber cloth was washed with deionized water until neutral. The result was a flexible three-dimensional carbon fiber cloth (N / Zn / Cu@CCs) doped with N, Cu and Zn elements. The corresponding product reference is available. Figure 2 c.

[0070] Example 4

[0071] A method for preparing a single-atom dispersed Cu and Zn co-doped flexible carbon sheet material includes the following steps:

[0072] (1) Flexible commercial carbon fiber cloth and 60 mL of 10 mol / L nitric acid solution were placed in a 100 mL polytetrafluoroethylene liner and hydrothermally treated in an oven at 90 °C for 8 h. After hydrothermal treatment, the flexible carbon cloth was immersed in deionized water, with the water changed every 2 h, and the process was repeated 5 times. Then it was dried at 60 °C to obtain an active flexible carbon cloth substrate.

[0073] (2) Solution A was prepared with a salt concentration of 0.025 mol / L and a copper salt to zinc salt concentration ratio of 2:3. Specifically, 0.015 mol / L Zn(NO)3·6H2O and 0.01 mol / L Cu(NO3)2 were weighed and dissolved in 100 mL of deionized water to obtain solution A; 0.4 mol / L 2-methylimidazole was weighed and dissolved in 100 mL of deionized water, and this was recorded as solution B. Then, solution B was quickly poured into solution A, and the mixture was sonicated at a frequency of 35 kHz for 3 min to obtain mixed solution C.

[0074] (3) Place the treated activated carbon cloth substrate in solution C, ensuring that the solution submerges the carbon cloth substrate. After standing for 2 hours, remove it and rinse it several times with deionized water to remove excess precipitates on the surface. Then, put the carbon cloth precursor into an oven and dry it overnight at 60°C.

[0075] (4) High-temperature carbonization treatment: Under nitrogen atmosphere, the pre-oxidized fiber cloth is heated from room temperature to 900℃ at a heating rate of 2℃ / min and kept at that temperature for 3h. The resulting flexible material of Cu and Zn co-doped carbon sheets with single-atom dispersion is immersed in 0.5mol / L hydrochloric acid solution for 15h to remove residual metal on the surface. Then, the carbon fiber cloth is washed with deionized water until neutral, resulting in a flexible three-dimensional carbon fiber cloth (N / Zn / Cu@CCs) doped with N, Cu and Zn elements.

[0076] Example 5

[0077] A method for preparing a single-atom dispersed Cu and Zn co-doped flexible carbon sheet material includes the following steps:

[0078] (1) Flexible carbon cloth, three-dimensional graphene, and 60 mL of 12 mol / L nitric acid solution were placed in a 100 mL polytetrafluoroethylene liner and subjected to hydrothermal treatment in an oven. The solvothermal temperature was controlled at 70 °C and the solvothermal time was 12 h. After hydrothermal treatment, the flexible carbon cloth was immersed in deionized water, and the water was changed every 2 h, repeated 5 times. Then it was dried at 60 °C to obtain the active flexible carbon cloth substrate.

[0079] (2) Solution A was prepared with a salt concentration of 0.05 mol / L and a copper salt to zinc salt concentration ratio of 1:4. Specifically, 0.01 mol / L Zn(COO)2·2H2O and 0.04 mol / L Cu(COO)2 were weighed and dissolved in 100 mL of deionized water to obtain solution A; 0.25 mol / L 2-methylimidazole was weighed and dissolved in 100 mL of deionized water, and this solution was denoted as solution B. Then, solution B was quickly poured into solution A and sonicated at a frequency of 40 kHz for 1 min to obtain mixed solution C.

[0080] (3) Insert the treated activated carbon cloth substrate into solution C, ensuring that the solution submerges the carbon cloth substrate. After standing for 4 hours, remove it and rinse it several times with deionized water to remove excess precipitates on the surface. Then, put the carbon cloth precursor into an oven and dry it overnight at 60°C.

[0081] (4) High-temperature carbonization treatment: Under a nitrogen atmosphere, the pre-oxidized fiber cloth was heated from room temperature to 800℃ at a heating rate of 2℃ / min and held for 4 hours. The resulting flexible material of Cu and Zn co-doped carbon sheets with single-atom dispersion was immersed in 0.1mol / L hydrochloric acid solution for 24 hours to remove residual metals on the surface. Then, the carbon fiber cloth was washed with deionized water until neutral. The result was a flexible three-dimensional carbon fiber cloth (N / Zn / Cu@CCs) doped with N, Cu and Zn elements. For specific products, see [link to product description]. Figure 2 d.

[0082] Figure 2 SEM images of different N / Zn / Cu@CCs prepared for the examples, by... Figure 2 It can be seen that the modified layer has a sheet-like structure, and the thickness of the modified layer of N-Zn / Cu@CCs prepared with different ratios and different reaction times is different. The modified layer is thinner when the concentration is lower and the reaction time is shorter.

[0083] Figure 3 TEM images of N / Zn / Cu@CCs prepared in Example 1, by Figure 3 It can be seen that the size of the metal particles is approximately 10 nm, which is atomically dispersed.

[0084] Figure 4 The cycling stability of different N / Zn / Cu@CCs prepared for the examples was determined by... Figure 3 It is evident that samples doped with atomically dispersed Cu and Zn exhibit the best cycle stability. This is because the flexible carbon substrate provides a three-dimensional space to accommodate zinc dendrites. The controllable thickness of the decorative layer and the introduction of atomically dispersed metallic zinc and copper as sites for zinc ion deposition effectively improve the shortcomings of pure carbon materials as anodes in zinc-ion batteries.

[0085] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a single-atom dispersed Cu and Zn co-doped carbon sheet flexible material, characterized in that, Includes the following steps: S1: The flexible carbon cloth is immersed in nitric acid solution for hydrothermal treatment to obtain an active flexible carbon cloth with oxygen-containing functional groups grafted on its surface. S2: Add copper salt and zinc salt solutions to dimethylimidazole solution, mix well, then add the active flexible carbon cloth, let it stand to react, and obtain the precursor flexible carbon cloth. S3: Vacuum calcination is performed on the precursor flexible carbon cloth to obtain the single-atom dispersed Cu and Zn co-doped carbon sheet flexible material. In step S1, the hydrothermal treatment temperature is 70~90℃, the solvothermal time is 8~12h, and the concentration of the nitric acid solution is 7~14mol / L; In step S2, copper salt and zinc salt solutions are added to dimethylimidazole solution to form a mixed solution of salt solution and dimethylimidazole solution. The concentration of the salt solution is 0.025~0.05 mol / L, and the concentration of the dimethylimidazole solution is 0.25~0.5 mol / L. In step S2, the concentration ratio of copper salt to zinc salt in the salt solution is (1~2):(1~4); In step S3, vacuum calcination is performed under an argon or nitrogen atmosphere at a temperature of 700-900℃ for 2-4 hours.

2. The method for preparing a single-atom dispersed Cu and Zn co-doped carbon sheet flexible material according to claim 1, characterized in that, In step S1, the flexible carbon cloth is one of carbon fiber cloth, carbon paper, or flexible three-dimensional graphene.

3. The method for preparing a single-atom dispersed Cu and Zn co-doped carbon sheet flexible material according to claim 1, characterized in that, In step S2, the zinc salt is one or two of zinc nitrate hexahydrate, anhydrous zinc acetate, or zinc acetate dihydrate, and the copper salt is copper nitrate and / or copper acetate.

4. The method for preparing a single-atom dispersed Cu and Zn co-doped carbon sheet flexible material according to claim 1, characterized in that, In step S2, the copper salt and zinc salt solutions are mixed evenly with the dimethylimidazole solution by ultrasonic treatment. The ultrasonic frequency is 28~40KHz and the ultrasonic time is 1~5min.

5. A flexible Cu / Zn co-doped carbon sheet material with single-atom dispersion, characterized in that, It is prepared by the method described in any one of claims 1 to 4.

6. The application of the single-atom dispersed Cu and Zn co-doped carbon sheet flexible material as described in claim 5 in an aqueous zinc-ion battery.

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