Zinc-bromine flow battery negative electrode material and preparation method and application thereof

Abstract

This invention provides a zinc-bromine flow battery anode material, its preparation method, and its application, belonging to the field of zinc-bromine flow batteries. The preparation method involves first adding a molybdenum source solution dropwise to a mixed aqueous solution containing zinc and copper sources, then adding a fluorine source and a pH buffer to adjust the pH to 6.5-7.5 to obtain a hydrothermal precursor solution. A carbon felt is then immersed in the hydrothermal precursor solution for a hydrothermal reaction, followed by washing and drying to obtain an intermediate carbon felt. This intermediate carbon felt is then impregnated in a modification solution containing a sulfonated polymer and an organozirconium crosslinking agent, and dried to obtain the zinc-bromine flow battery anode material. The preparation method of this invention, through optimized synthesis processes and the introduction of elemental doping and chemical coupling interfaces, produces a zinc-bromine flow battery anode material that can effectively suppress hydrogen evolution side reactions and enhance electrode interface stability while inhibiting zinc dendrite growth; simultaneously, it can significantly improve the energy efficiency and cycle stability of zinc-bromine flow batteries.

Description

Technical Field

[0001] This invention relates to the field of zinc-bromine flow battery technology, and in particular to a zinc-bromine flow battery negative electrode material, its preparation method, and its application. Background Technology

[0002] Zinc-bromine flow batteries, with their high cost-effectiveness, excellent safety, and environmental friendliness, have demonstrated significant application advantages in large-scale energy storage scenarios such as grid peak shaving and renewable energy consumption. As the core site for zinc deposition and stripping, the performance of the anode directly determines the battery's cycle stability, safety, and energy efficiency. Zinc metal, with its natural advantages of high theoretical specific capacity (820 mAh / g), high crustal abundance (approximately 70 mg / kg), and low cost (approximately US$2 / kg), not only supports the economic viability of the system but also avoids the resource scarcity problem of traditional lithium-ion battery anodes, making it an ideal anode material for large-scale energy storage.

[0003] However, with the increasing demands for large-scale and long-life energy storage systems from the "dual-carbon" target, the performance bottleneck of zinc anodes is becoming increasingly prominent, mainly facing the following technical challenges: First, there is the problem of zinc dendrite growth: Zinc is prone to non-uniform nucleation in aqueous electrolytes, leading to Zn dendrite growth. 2+ Excessive local deposition leads to dendrite formation; the continuous growth of dendrites not only punctures the diaphragm, causing a micro-short circuit risk, but also causes irreversible loss of active materials, significantly shortening cycle life. Secondly, there is a serious hydrogen evolution side reaction: due to the low standard electrode potential of zinc, its thermodynamic instability in aqueous environments is high, easily inducing hydrogen evolution; this not only reduces coulombic efficiency, but the generated hydrogen gas may also cause electrode structure deformation and electrolyte pH imbalance, accelerating performance degradation. Finally, there is also the defect of insufficient interfacial stability: Zn... 2+ During the deposition process, the zinc-bromine redox flow battery readily reacts with electrolyte components to generate insulating byproducts, forming an unstable passivation layer and increasing charge transport impedance. These factors collectively hinder the industrialization of zinc-bromine redox flow batteries.

[0004] In the prior art, Chinese patent CN117832517A discloses a technical solution for preparing nickel, tin, and cobalt oxide-modified carbon felt using a two-step calcination method. This solution aims to alleviate the zinc dendrite growth problem to some extent by introducing zinc-loving active sites to guide the uniform deposition of zinc. However, this technical approach is relatively simple, focusing only on dendrite suppression, without targeted optimization for suppressing hydrogen evolution side reactions and improving interface stability. It also lacks a multi-component synergistic regulation mechanism, making it difficult to comprehensively solve the complex technical challenges faced by the anode of zinc-bromine flow batteries. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a method for preparing a zinc-bromine flow battery anode material. By synergistically modifying a carbon felt substrate, a zinc-bromine flow battery anode material with comprehensive functions is prepared, which can effectively suppress hydrogen evolution side reactions and enhance electrode interface stability while inhibiting zinc dendrite growth. At the same time, through the synergistic regulation of multiple modification strategies, the energy efficiency and cycle stability of the zinc-bromine flow battery are significantly improved.

[0006] The present invention also provides a zinc-bromine flow battery anode material prepared by the aforementioned method.

[0007] The present invention also provides the application of the zinc-bromine flow battery negative electrode material.

[0008] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing a zinc-bromine flow battery negative electrode material includes the following steps: Step S01: Under stirring conditions, the molybdenum source aqueous solution is added dropwise to a mixed aqueous solution containing zinc and copper sources, followed by the addition of a fluorine source and a pH buffer to adjust the pH value to 6.5-7.5, thereby obtaining a hydrothermal precursor solution. Step S02: Immerse the carbon felt in the hydrothermal precursor solution for hydrothermal reaction. After the reaction is completed, the product is washed and vacuum dried to obtain the intermediate carbon felt. Step S03: Impregnate the intermediate carbon felt into a modification solution containing sulfonated polymer and organozirconium crosslinking agent. After impregnation, vacuum dry to obtain the zinc-bromine flow battery anode material.

[0009] Preferably, in step S01, the zinc source is one of zinc nitrate, zinc acetate, and zinc sulfate; The copper source is one of copper nitrate, copper chloride, or copper acetate; The molybdenum source is either ammonium molybdate or sodium molybdate; The fluorine source is either sodium fluoride or ammonium fluoride; The pH buffer is one of hexamethylenetetramine, ammonia, or urea.

[0010] Preferably, in step S01, the molar concentration of the molybdenum source in the aqueous solution of the molybdenum source is 0.0075-0.1 mol / L; and the concentration of the zinc source in the mixed aqueous solution containing the zinc source and the copper source is 0.05-0.5 mol / L.

[0011] Preferably, in step S01, the molar concentration of the zinc source in the hydrothermal precursor solution is 0.042-0.42 mol / L; The molar ratio of zinc, copper, and molybdenum sources in the hydrothermal precursor solution is 1:0.02-0.10:0.01-0.05; The molar ratio of zinc source, fluorine source and pH buffer in the hydrothermal precursor solution is 1:1-2:1-2.

[0012] Preferably, in step S02, the ratio of the carbon felt area to the hydrothermal precursor liquid volume is 8-13 cm². 2 100mL; The hydrothermal reaction temperature is 90-140℃, and the hydrothermal reaction time is 4-10h.

[0013] Preferably, in step S03, the sulfonated polymer is one of sulfonated polyether ether ketone, perfluorosulfonic acid resin, and sulfonated polysulfone; The organozirconium crosslinking agent is one of zirconium isopropoxide, zirconium n-butoxide, and zirconium acetylacetonate; The solvent used in the modification solution is one of N,N-dimethylformamide, N-methylpyrrolidone, or dimethyl sulfoxide.

[0014] Preferably, in step S03, the concentration of the sulfonated polymer in the modifying solution is 0.5-5.0 wt%. The mass ratio of organozirconium crosslinking agent to sulfonated polymer in the modification solution is 1:10-50.

[0015] Preferably, in step S03, the mass ratio of the intermediate carbon felt to the modifying liquid is 0.45-0.7:100; The soaking time is 10-60 minutes.

[0016] A zinc-bromine flow battery anode material is prepared using the aforementioned preparation method.

[0017] A zinc-bromine flow battery uses the aforementioned zinc-bromine flow battery negative electrode material as the negative electrode of the zinc-bromine flow battery.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The preparation method of the zinc-bromine flow battery negative electrode material of the present invention introduces an organic zirconium crosslinking agent and a sulfonated polymer to construct a stable chemical coupling interface in step S03. Utilizing the strong electrophilicity of zirconium ions, coordination bonding and condensation reactions occur between the hydroxyl groups of fluorinated zinc hydroxide in the intermediate carbon felt and the sulfonic acid groups in the sulfonated polymer. The zirconium atoms act as molecular bridges, anchoring the polymer layer to the surface of the intermediate carbon felt through chemical bonds, achieving a transformation from physical adsorption to chemical coupling. This significantly enhances the negative electrode's resistance to electrolyte erosion and peeling, improving battery safety, stability, and energy efficiency. Simultaneously, the chemical coupling interface acts as a regulating valve for the zinc ion flow, controlling the charge distribution at the negative electrode interface to achieve a smooth distribution of the zinc ion flow. Combined with the three-dimensional physical steric hindrance provided by the carbon felt framework, the internal copper-molybdenum components further suppress the tip growth of zinc dendrites and the occurrence of hydrogen evolution side reactions.

[0019] 2. The preparation method of the zinc-bromine flow battery negative electrode material of the present invention significantly improves the performance of the zinc-bromine flow battery by optimizing process parameters. The mass ratio of the organozirconium crosslinking agent to the sulfonated polymer plays a decisive role in the crosslinking density and structural stability of the chemical coupling interface. The inventors' research found that when the mass ratio of the organozirconium crosslinking agent to the sulfonated polymer is too high, excessive crosslinking increases the brittleness of the polymer modification layer, leading to microcracks in the negative electrode, interlayer delamination, and blockage of Zn. 2+ The transmission channel is obstructed, increasing impedance and reducing battery performance. When the mass ratio is too low, there are insufficient zirconium ion coordination centers, making it impossible to construct enough chemical anchoring sites between the organic polymer and the zinc hydroxide fluoride in the intermediate carbon felt. This leads to easy swelling and detachment of the polymer layer, resulting in the loss of its function in inhibiting zinc dendrites and protecting active sites, thus causing a decrease in energy efficiency and a shortened cycle life. An appropriate mass ratio can introduce a suitable amount of zirconium-based crosslinking sites, constructing a stable chemical coupling interface that balances mechanical toughness and ion selectivity, synergistically regulating zinc dendrite growth and hydrogen evolution side reactions.

[0020] 3. The preparation method of the zinc-bromine flow battery negative electrode material of the present invention adopts a fine batch synthesis strategy in step S01, which involves first mixing zinc and copper ions, then slowly adding a molybdenum source at a rate of 1-5 mL / min, and finally adding a fluorine source and a buffer while adjusting the pH to 6.5-7.5. This overcomes the defect of local rapid precipitation of molybdate caused by conventional one-time mixing, and ensures that the three metal cations of zinc, copper, and molybdenum are uniformly dispersed and form a complex system in the liquid phase. At the same time, this batch process successfully induces copper and molybdenum atoms to enter the lattice of fluorinated zinc hydroxide to form solid solution doping, thereby avoiding the precipitation of independent impurity phases. This ensures the uniformity of element doping and obtains a structurally stable fluorinated zinc hydroxide phase, rather than a single zinc oxide or zinc hydroxide. Finally, through the hydrothermal reaction in step S02, a copper-molybdenum dual-doped fluorinated zinc hydroxide loading with uniform morphology and pure phase is achieved on the carbon felt surface.

[0021] 4. The preparation method of the zinc-bromine flow battery negative electrode material of the present invention significantly improves the electronic conductivity of zinc hydroxide fluoride through co-doping with Cu and Mo elements, and endows the material with excellent zinc affinity properties, which can effectively reduce the nucleation overpotential of zinc and inhibit the growth of zinc dendrites in the negative electrode of zinc-bromine flow battery; at the same time, zinc hydroxide fluoride itself has stable chemical properties, and the highly electronegative F atoms in its lattice can effectively weaken the binding effect between zinc ions and water molecules, reduce the penetration and direct contact of free water molecules in the electrolyte to the electrode interface, thereby significantly reducing the occurrence of hydrogen evolution side reactions; in addition, the introduction of Mo element with high hydrogen evolution overpotential forms a synergistic effect with the highly electronegative F atoms in the lattice of zinc hydroxide fluoride, jointly constructing an efficient hydrogen protection barrier.

[0022] 5. This invention prepares a zinc-bromine flow battery anode material with simple processing steps and stable structure by optimizing the synthesis process and introducing elemental doping and chemical coupling interfaces, significantly improving the overall electrochemical performance of the zinc-bromine flow battery. Experimental results show that at 80 mA / cm²... 2 After 200 cycles at a given current density, the anode material exhibits excellent efficiency indicators, with a coulombic efficiency of 98.3-98.8%, a voltage efficiency of 79.5-81.9%, and an energy efficiency of 78.5-80.5%. These data confirm that the anode material possesses good chemical stability, can significantly improve the energy conversion efficiency and cycle life of zinc-bromine flow batteries, and has broad prospects for practical applications.

[0023] 6. The preparation method of the zinc-bromine flow battery negative electrode material of the present invention has simple process steps, mild conditions, is easy to control and environmentally friendly, and has the potential for large-scale industrial production. Attached Figure Description

[0024] Figure 1 The image shows a scanning electron microscope (SEM) image of the zinc-bromine flow battery anode material prepared in Example 1.

[0025] Figure 2 The image shows the zinc deposition SEM image of the zinc-bromine flow battery anode material prepared in Example 1 at a charging capacity of 540 mAh.

[0026] Figure 3 The graph shows the long-cycle energy efficiency of a zinc-bromine flow battery assembled using the negative electrode material prepared in Example 1.

[0027] Figure 4 This is a comparative trend chart showing the test data of batteries assembled using Examples 1-4 and Comparative Examples 1-6 after 200 cycles. Detailed Implementation

[0028] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0029] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0030] This invention provides a method for preparing a negative electrode material for a zinc-bromine flow battery, comprising the following steps: Step S01: Under stirring conditions, the molybdenum source aqueous solution is added dropwise to a mixed aqueous solution containing zinc and copper sources, followed by the addition of a fluorine source and a pH buffer to adjust the pH value to 6.5-7.5, thereby obtaining a hydrothermal precursor solution. Step S02: Immerse the carbon felt in the hydrothermal precursor solution for hydrothermal reaction. After the reaction is completed, the product is washed and vacuum dried to obtain the intermediate carbon felt. Step S03: The intermediate carbon felt is impregnated in a modification solution containing sulfonated polymer and organozirconium crosslinking agent. After impregnation, it is vacuum dried to obtain the zinc-bromine flow battery negative electrode material.

[0031] In this embodiment of the invention, step S01 overcomes the defect of conventional one-time mixing causing rapid local precipitation of molybdate by first mixing zinc and copper ions, then adding molybdenum source, and finally adding fluorine source and pH buffer and adjusting pH to 6.5-7.5 through a batch synthesis strategy. This ensures that the three metal cations of zinc, copper, and molybdenum are uniformly dispersed and form a complex system in the liquid phase. At the same time, this batch process successfully induces copper and molybdenum atoms to enter the lattice of fluorinated zinc hydroxide to form solid solution doping and avoid the precipitation of independent impurity phases, thereby ensuring the uniformity of element doping and obtaining a structurally stable fluorinated zinc hydroxide phase, rather than a single zinc oxide or zinc hydroxide. Finally, through the hydrothermal reaction in step S02, a copper-molybdenum dual-doped fluorinated zinc hydroxide loading with uniform morphology and pure phase is achieved on the carbon felt surface.

[0032] In this embodiment of the invention, step S03 constructs a stable chemical coupling interface by introducing an organic zirconium crosslinking agent and a sulfonated polymer. Utilizing the strong electrophilicity of zirconium ions, coordination and condensation reactions occur between the hydroxyl groups of zinc hydroxide fluoride in the intermediate carbon felt and the sulfonic acid groups in the sulfonated polymer. Zirconium atoms act as molecular bridges, anchoring the polymer layer to the surface of the intermediate carbon felt through chemical bonds, achieving a transformation from physical adsorption to chemical coupling. This significantly enhances the negative electrode's resistance to electrolyte erosion and peeling, improving battery safety, stability, and energy efficiency. Simultaneously, the chemical coupling interface acts as a regulating valve for the zinc ion flow, controlling the charge distribution at the negative electrode interface to achieve a smooth distribution of the zinc ion flow. Combined with the three-dimensional physical steric hindrance provided by the carbon felt framework, this, along with the internal copper-molybdenum components, further suppresses the tip growth of zinc dendrites and the occurrence of hydrogen evolution side reactions.

[0033] The aforementioned technologies work together synergistically to produce a zinc-bromine flow battery anode material that can effectively suppress hydrogen evolution side reactions and enhance electrode interface stability while inhibiting zinc dendrite growth. At the same time, it can also significantly improve the energy efficiency and cycle stability of the zinc-bromine flow battery.

[0034] Preferably, in step S01, the zinc source is one of zinc nitrate, zinc acetate, and zinc sulfate; the copper source is one of copper nitrate, copper chloride, and copper acetate; the molybdenum source is one of ammonium molybdate and sodium molybdate; the fluorine source is one of sodium fluoride and ammonium fluoride; and the pH buffer is one of hexamethylenetetramine, ammonia, and urea. Preferably, in step S01, the molar concentration of the molybdenum source in the aqueous solution of the molybdenum source is 0.0075-0.1 mol / L; and the concentration of the zinc source in the mixed aqueous solution containing the zinc source and the copper source is 0.05-0.5 mol / L. Preferably, in step S01, the dropping rate of the molybdenum source aqueous solution is 1-5 mL / min.

[0035] Preferably, in step S01, the molar concentration of the zinc source in the hydrothermal precursor solution is 0.042-0.42 mol / L; the molar ratio of the zinc source, copper source, and molybdenum source in the hydrothermal precursor solution is 1:0.02-0.10:0.01-0.05; and the molar ratio of the zinc source, fluorine source, and pH buffer in the hydrothermal precursor solution is 1:1.0-2.0:1.0-2.0.

[0036] Preferably, in step S02, the ratio of the carbon felt area to the hydrothermal precursor liquid volume is 8-13 cm². 2 100mL.

[0037] Preferably, in step S02, the hydrothermal reaction temperature is 90-140℃ and the hydrothermal reaction time is 4-10h; the vacuum drying temperature is 60-80℃ and the vacuum drying time is 8-12h.

[0038] Preferably, in step S03, the sulfonated polymer is one of sulfonated polyether ether ketone, perfluorosulfonic acid resin, and sulfonated polysulfone; the organozirconium crosslinking agent is one of zirconium isopropoxide, zirconium n-butoxide, and zirconium acetylacetonate; and the solvent used in the modification solution is one of N,N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0039] Preferably, in step S03, the concentration of the sulfonated polymer in the modification solution is 0.5-5.0 wt%; the mass ratio of the organozirconium crosslinking agent to the sulfonated polymer in the modification solution is 1:10-50.

[0040] Preferably, in step S03, the mass ratio of the intermediate carbon felt to the modification liquid is 0.45-0.7:100.

[0041] Preferably, in step S03, the impregnation time is 10-60 min; the vacuum drying temperature is 60-100℃, and the vacuum drying time is 6-10 h.

[0042] The present invention also provides a zinc-bromine flow battery anode material prepared by the aforementioned method.

[0043] This invention also provides a zinc-bromine flow battery, which uses the zinc-bromine flow battery negative electrode material as the negative electrode of the zinc-bromine flow battery.

[0044] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described below in conjunction with some specific embodiments.

[0045] Example 1 This embodiment provides a method for preparing a negative electrode material for a zinc-bromine flow battery, the specific steps of which are as follows: (1) Dissolve 20 mmol zinc nitrate and 0.4 mmol copper nitrate in 100 mL deionized water to obtain a zinc-copper solution; at the same time, dissolve 1 mmol ammonium molybdate in 20 mL deionized water to obtain a molybdenum solution. Then, under stirring conditions at room temperature, slowly add the molybdenum solution to the zinc-copper solution at a flow rate of 1 mL / min; after the addition is complete and the mixture is homogeneous, add 20 mmol sodium fluoride and 20 mmol hexamethylenetetramine to the system, continue stirring and adjust the pH of the system to the range of 6.5-7.5 with 0.1 mol / L sodium hydroxide solution or 0.1 mol / L dilute nitric acid solution to obtain a homogeneous hydrothermal precursor solution; (2) Place 12cm 2 The carbon felt was immersed in the hydrothermal precursor solution prepared above and transferred together to the hydrothermal reactor. It was sealed and kept at 90°C for 8 hours for hydrothermal in-situ growth treatment. After the reaction was completed, it was naturally cooled to room temperature. The product was taken out and repeatedly washed with deionized water. Then it was placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain the intermediate carbon felt. (3) 1g of sulfonated polyether ether ketone and 0.1g of zirconium isopropoxide were added sequentially to 98.9g of N,N-dimethylformamide. After stirring evenly, 0.6g of intermediate carbon felt was completely immersed in the modification solution and kept immersed for 10min. After immersion, the intermediate carbon felt was taken out and then placed in a vacuum drying oven and dried at 60℃ for 10h. The zinc-bromine flow battery negative electrode material was finally obtained and recorded as the sample of Example 1.

[0046] This embodiment also provides a zinc-bromine flow battery anode material prepared by the aforementioned method.

[0047] Example 2 This embodiment provides a method for preparing a negative electrode material for a zinc-bromine flow battery, the specific steps of which are as follows: (1) Dissolve 5 mmol zinc sulfate and 0.15 mmol copper acetate in 100 mL deionized water to obtain a zinc-copper solution; at the same time, dissolve 0.15 mmol sodium molybdate in 20 mL deionized water to obtain a molybdenum solution. Then, under stirring conditions at room temperature, slowly add the molybdenum solution to the zinc-copper solution at a flow rate of 2 mL / min; after the addition is complete and the mixture is homogeneous, add 10 mmol ammonium fluoride and 9 mmol ammonia water (concentration 25 wt%) to the system, continue stirring and adjust the pH of the system to the range of 6.5-7.5 with 0.1 mol / L sodium hydroxide solution or 0.1 mol / L dilute nitric acid solution to obtain a homogeneous hydrothermal precursor solution; (2) 15.6cm 2 The carbon felt was immersed in the aforementioned hydrothermal precursor solution and transferred together into a hydrothermal reactor. It was then sealed and kept at 130°C for 10 hours for in-situ hydrothermal growth. After the reaction was complete, it was allowed to cool naturally to room temperature. The product was then removed and repeatedly washed with deionized water, subsequently placed in a vacuum drying oven and dried at 80°C for 8 hours to obtain the intermediate carbon felt. (3) 0.5g of sulfonated polysulfone and 0.01g of zirconium isopropoxide were added sequentially to 99.49g of dimethyl sulfoxide and stirred evenly. Then, 0.7g of intermediate carbon felt was completely immersed in the modification solution and kept immersed for 40min. After the immersion was completed, the intermediate carbon felt was taken out and then placed in a vacuum drying oven and dried at 80℃ for 8h. The zinc-bromine flow battery negative electrode material was finally obtained and recorded as the sample of Example 2.

[0048] This embodiment also provides a zinc-bromine flow battery anode material prepared by the aforementioned method.

[0049] Example 3 This embodiment provides a method for preparing a negative electrode material for a zinc-bromine flow battery, the specific steps of which are as follows: (1) Dissolve 50 mmol zinc acetate and 5 mmol copper chloride in 100 mL deionized water to obtain a zinc-copper solution; at the same time, dissolve 0.5 mmol sodium molybdate in 20 mL deionized water to obtain a molybdenum solution. Then, under stirring conditions at room temperature, slowly add the molybdenum solution to the zinc-copper solution at a flow rate of 3 mL / min; after the addition is complete and the mixture is homogeneous, add 75 mmol sodium fluoride and 100 mmol urea to the system, continue stirring and adjust the pH of the system to the range of 6.5-7.5 with 0.1 mol / L sodium hydroxide solution or 0.1 mol / L dilute nitric acid solution to obtain a homogeneous hydrothermal precursor solution; (2) 9.6cm 2The carbon felt was immersed in the aforementioned hydrothermal precursor solution and transferred together into a hydrothermal reactor. It was then sealed and kept at 140°C for 4 hours for in-situ hydrothermal growth. After the reaction was complete, it was allowed to cool naturally to room temperature. The product was then removed and repeatedly washed with deionized water, subsequently placed in a vacuum drying oven and dried at 70°C for 10 hours to obtain the intermediate carbon felt. (3) 3g of perfluorosulfonic acid resin and 0.15g of n-butoxide zirconium were added to 96.85g of N-methylpyrrolidone in sequence. After stirring evenly, 0.45g of intermediate carbon felt was completely immersed in the modification solution and kept immersed for 60min. After the immersion was completed, the intermediate carbon felt was taken out and then placed in a vacuum drying oven and dried at 100℃ for 6h. The zinc bromine flow battery negative electrode material was finally obtained and recorded as the sample of Example 3.

[0050] This embodiment also provides a zinc-bromine flow battery anode material prepared by the aforementioned method.

[0051] Example 4 This embodiment provides a method for preparing a negative electrode material for a zinc-bromine flow battery, the specific steps of which are as follows: (1) Dissolve 40 mmol zinc nitrate and 3.2 mmol copper chloride in 100 mL deionized water to obtain a zinc-copper solution; at the same time, dissolve 2 mmol ammonium molybdate in 20 mL deionized water to obtain a molybdenum solution. Then, under stirring conditions at room temperature, slowly add the molybdenum solution to the zinc-copper solution at a flow rate of 5 mL / min; after the addition is complete and the mixture is homogeneous, add 64 mmol ammonium fluoride and 60 mmol hexamethylenetetramine to the system, continue stirring and adjust the pH of the system to the range of 6.5-7.5 with 0.1 mol / L sodium hydroxide solution or 0.1 mol / L dilute nitric acid solution to obtain a homogeneous hydrothermal precursor solution; (2) 9.6cm 2 The carbon felt was immersed in the aforementioned hydrothermal precursor solution and transferred together into a hydrothermal reactor. It was then sealed and kept at 100°C for 6 hours for in-situ hydrothermal growth. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The product was then removed and repeatedly washed with deionized water. It was subsequently placed in a vacuum drying oven and dried at 76°C for 11 hours to obtain the intermediate carbon felt. (3) 5g of sulfonated polyether ether ketone and 0.17g of zirconium acetylacetonate were added to 94.83g of dimethyl sulfoxide in sequence. After stirring evenly, 0.5g of intermediate carbon felt was completely immersed in the modification solution and kept immersed for 30min. After the immersion was completed, the intermediate carbon felt was taken out and then placed in a vacuum drying oven and dried at 70℃ for 7h. The zinc bromine flow battery negative electrode material was finally obtained and recorded as the sample of Example 4.

[0052] This embodiment also provides a zinc-bromine flow battery anode material prepared by the aforementioned method.

[0053] Comparative Example 1 This comparative example adopts the technical solution of Example 1. The difference between this example and Example 1 is that in step (1), zinc nitrate, copper nitrate, ammonium molybdate, sodium fluoride and hexamethylenetetramine are added to 120 mL of deionized water at one time and mixed and dissolved. All other steps are the same as in Example 1. The final product is recorded as the sample of Comparative Example 1.

[0054] Comparative Example 2 This comparative example adopts the technical solution of Example 1. The difference between this example and Example 1 is that copper nitrate is not added in step (1). All other steps are the same as in Example 1. The final product is recorded as the sample of Comparative Example 2.

[0055] Comparative Example 3 This comparative example adopts the technical solution of Example 1. The difference between this example and Example 1 is that ammonium molybdate is not added in step (1). All other steps are the same as in Example 1. The final product is recorded as the sample of Comparative Example 3.

[0056] Comparative Example 4 This comparative example adopts the technical solution of Example 1. The difference between this example and Example 1 is that no organic zirconium crosslinking agent is added in step (3). All other steps are the same as in Example 1. The final product is recorded as the sample of Comparative Example 4.

[0057] Comparative Example 5 This comparative example adopts the technical solution of Example 1. The difference between this example and Example 1 is that the mass ratio of zirconium isopropoxide to sulfonated polyether ether ketone in step (3) is 1:5. This value is not within the range of process parameters in all examples. All other steps are the same as in Example 1. The final product is recorded as Comparative Example 5 sample.

[0058] Comparative Example 6 This comparative example adopts the technical solution of Example 1. The difference between this example and Example 1 is that the mass ratio of zirconium isopropoxide to sulfonated polyether ether ketone in step (3) is 1:100. This value is not within the range of process parameters in all examples. All other steps are the same as in Example 1. The final product is recorded as Comparative Example 6 sample.

[0059] Battery fixture assembly and performance testing: To systematically evaluate the electrochemical performance of the negative electrode materials prepared in Examples 1-4 and Comparative Examples 1-6, single zinc-bromine flow batteries were assembled and tested according to the following steps: First, the flow channels of the graphite plate were cleaned with deionized water and dried. Then, the battery components were stacked and assembled. A gasket was fixed on the graphite plate, and the cut carbon felt positive electrode material was placed in the center of the gasket, covered with a microporous polyolefin separator. Next, a gasket and the negative electrode material prepared according to this invention were placed on the other side of the separator. Finally, the components were aligned and the clamps were tightened with bolts to ensure sealing and accurate flow field alignment. After assembly, the flow circulation system was connected and an electrolyte (composed of 2M zinc bromide + 4M ammonium chloride + 0.5M 1-methyl-1-ethylpyrrolidine bromide) was injected to ensure uniform circulation of the electrolyte within the flow channels. Subsequently, the charge / discharge current density was 80 mA / cm². 2 Electrochemical performance tests were conducted under a discharge cutoff voltage of 0.6V. The average coulombic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) data of the batteries obtained from each example and comparative example after 200 cycles are summarized in Table 1.

[0060] Table 1. Summary of battery performance after 200 cycles for each embodiment and comparative example.

[0061] Figure 1 The image shows a scanning electron microscope (SEM) image of the zinc-bromine flow battery anode material prepared in Example 1. The image clearly shows a continuous micron-sized fiber surface exhibiting regular and dense longitudinal groove textures. The overall coating morphology is dense, uniform, and without peeling, indicating that the fiber surface is completely covered by a dense composite layer. This composite coating layer consists of an in-situ grown copper-molybdenum dual-doped zinc hydroxide fluoride phase and a sulfonated polymer locked by zirconium ions. The surface possesses both a fine granular texture and a smooth glaze-like characteristic, reflecting a deep integration of the inorganic crystals and the cross-linked polymer. This tight coating structure provides abundant zinc-loving active sites, thus providing solid morphological support for uniform zinc deposition and interfacial stability. Figure 2 The charged-state SEM characterization results show a uniform and dense zinc deposition morphology, with no needle-like or dendritic structures observed. This indicates that the negative electrode system can reduce the nucleation overpotential and effectively induce uniform zinc deposition.

[0062] Combined with Table 1, Figure 3 and Figure 4Data analysis showed that the anode materials prepared in Examples 1-4 exhibited excellent electrochemical stability and energy conversion efficiency after 200 cycles in a zinc-bromine flow battery. Specifically, the charge transfer efficiency (CE) of all examples was ≥98.3% (98.8% in Example 4), indicating highly reversible charge transfer and significant suppression of hydrogen evolution side reactions; the energy conversion efficiency (VE) was ≥79.5% (81.9% in Example 2), reflecting that the material effectively reduced the nucleation overpotential of zinc deposition; and the energy conversion efficiency (EE) was ≥78.5% (80.5% in Example 2), confirming the stability of the material performance and the overall high efficiency of energy conversion. The performance differences among the examples revealed the regulatory mechanism of process parameters on the charge transfer and catalytic activity of the material, while the overall excellent performance fully verified the reliability of the preparation process and the structural stability of the material.

[0063] The performance test data shows that the coulombic efficiency (CE) of the example group is as high as 98.3%-98.8%, significantly better than that of the comparative group. On the one hand, the anode material prepared by this invention has excellent electronic conductivity and zinc affinity, which can effectively reduce the zinc nucleation overpotential, achieve uniform zinc deposition, and significantly inhibit zinc dendrite growth. On the other hand, relying on the synergistic effect of the highly electronegative F atoms and the high hydrogen evolution overpotential Mo element in the material, the interaction between zinc ions and water molecules can be weakened, reducing the penetration of free water molecules into the electrode interface, thereby significantly inhibiting the hydrogen evolution side reaction. Secondly, the VE of the example group is 79.5%-81.9%, which is also better than that of the comparative group (68.1%-77.3%). This reveals that the solid solution doping of Cu / Mo elements significantly improves the catalytic activity and reduces the zinc nucleation overpotential, significantly reducing the charge transfer impedance and polarization loss. Ultimately, the EE of the example group reached 78.5%-80.5%, a significant leap compared to the comparative example (28.0%-70.5%), confirming that the negative electrode material designed in this invention can significantly suppress dendrites, prevent exfoliation, and resist hydrogen evolution, thereby greatly reducing energy loss during the energy conversion process.

[0064] Comparing Example 1 with Comparative Examples 1-3, it can be seen that the performance of the zinc-bromine flow battery is significantly influenced by the synthesis strategy and elemental doping in step (1). Comparative Example 1 employs a one-time mixing strategy, which easily leads to rapid local precipitation of molybdate, resulting in uneven elemental doping and the formation of impurity phases. This makes the chemical properties of zinc hydroxide fluoride unstable, making it difficult to effectively weaken the binding force between zinc ions and water molecules, exacerbating the hydrogen evolution side reaction, and ultimately causing the battery's CE and EE to be significantly lower than in Example 1. Comparative Example 2 did not introduce a copper source, resulting in limited improvement in the conductivity of the negative electrode material, a significant reduction in zinc affinity, and difficulty in achieving uniform zinc deposition. Comparative Example 3 lacks Mo, an element with a high hydrogen evolution overpotential, and cannot form a synergistic hydrogen-resistant effect with the strongly electronegative F atoms in the crystal lattice. Its weakening effect on the binding force between zinc ions and water molecules is limited, and it cannot effectively suppress the penetration of free water molecules from the electrolyte to the electrode interface, resulting in a relatively severe hydrogen evolution side reaction. Therefore, employing stepwise fine synthesis supplemented by copper-molybdenum dual-element doping is key to improving battery energy efficiency.

[0065] In Comparative Example 4, due to the absence of an organozirconium crosslinking agent, only unstable physical adsorption occurred between the sulfonated polyether ether ketone and the intermediate carbon felt. In Comparative Example 5, when the mass ratio of zirconium isopropoxide to sulfonated polyether ether ketone was too high, excessive crosslinking occurred at the interface, leading to increased brittleness of the polymer modification layer and blockage of Zn. 2+ The transmission channel increases impedance and reduces battery performance. In Comparative Example 6, when the proportion of organic zirconium crosslinking agent is too low, due to insufficient zirconium ion coordination centers, it is difficult to construct a sufficiently dense chemical coupling site at the interface. The polymer layer is prone to swelling and detachment, losing its function of inhibiting zinc dendrites and protecting active sites, resulting in decreased energy efficiency and shortened cycle life. Comparing Example 1 and Comparative Examples 4-6, it can be seen that the technical solution of the present invention constructs a stable chemical coupling interface on the carbon felt surface by optimizing process parameters. Its performance indicators are far superior to the physical adsorption of Comparative Example 4, the over-crosslinking of Comparative Example 5, and the under-crosslinking state of Comparative Example 6. Compared with the interface defects caused by unstable physical adsorption or proportion imbalance, the chemical coupling interface loaded on the carbon felt achieves strong chemical anchoring through the coordination bonding of zirconium ions. This chemical coupling interface has higher erosion resistance and can achieve a smooth distribution of zinc ion flow between the carbon felt and the zinc deposition layer. Combined with the three-dimensional physical steric hindrance provided by the carbon felt skeleton, it works synergistically with the internal copper-molybdenum components to further inhibit the tip growth of zinc dendrites and the occurrence of hydrogen evolution side reactions.

[0066] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0067] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a negative electrode material for a zinc-bromine flow battery, characterized in that, Includes the following steps: Step S01: Under stirring conditions, the molybdenum source aqueous solution is added dropwise to a mixed aqueous solution containing zinc and copper sources, followed by the addition of a fluorine source and a pH buffer to adjust the pH value to 6.5-7.5, thereby obtaining a hydrothermal precursor solution. Step S02: Immerse the carbon felt in the hydrothermal precursor solution for hydrothermal reaction. After the reaction is completed, the product is washed and vacuum dried to obtain the intermediate carbon felt. Step S03: Impregnate the intermediate carbon felt into a modification solution containing sulfonated polymer and organozirconium crosslinking agent. After impregnation, vacuum dry to obtain the zinc-bromine flow battery anode material.

2. The method for preparing the zinc-bromine flow battery negative electrode material according to claim 1, characterized in that, In step S01, the zinc source is one of zinc nitrate, zinc acetate, and zinc sulfate. The copper source is one of copper nitrate, copper chloride, or copper acetate; The molybdenum source is either ammonium molybdate or sodium molybdate; The fluorine source is either sodium fluoride or ammonium fluoride; The pH buffer is one of hexamethylenetetramine, ammonia, or urea.

3. The method for preparing the zinc-bromine flow battery negative electrode material according to claim 1, characterized in that, In step S01, the molar concentration of molybdenum source in the aqueous solution of molybdenum source is 0.0075-0.1 mol / L; the concentration of zinc source in the mixed aqueous solution containing zinc source and copper source is 0.05-0.5 mol / L.

4. The method for preparing the zinc-bromine flow battery negative electrode material according to claim 1, characterized in that, In step S01, the molar concentration of the zinc source in the hydrothermal precursor solution is 0.042-0.42 mol / L; The molar ratio of zinc, copper, and molybdenum sources in the hydrothermal precursor solution is 1:0.02-0.10:0.01-0.05; The molar ratio of zinc source, fluorine source and pH buffer in the hydrothermal precursor solution is 1:1-2:1-2.

5. The method for preparing the zinc-bromine flow battery negative electrode material according to claim 1, characterized in that, In step S02, the ratio of the carbon felt area to the hydrothermal precursor liquid volume is 8-13 cm². 2 100mL; The hydrothermal reaction temperature is 90-140℃, and the hydrothermal reaction time is 4-10h.

6. The method for preparing the zinc-bromine flow battery negative electrode material according to claim 1, characterized in that, In step S03, the sulfonated polymer is one of sulfonated polyether ether ketone, perfluorosulfonic acid resin, and sulfonated polysulfone. The organozirconium crosslinking agent is one of zirconium isopropoxide, zirconium n-butoxide, and zirconium acetylacetonate; The solvent used in the modification solution is one of N,N-dimethylformamide, N-methylpyrrolidone, or dimethyl sulfoxide.

7. The method for preparing the zinc-bromine flow battery negative electrode material according to claim 1, characterized in that, In step S03, the concentration of the sulfonated polymer in the modification solution is 0.5-5.0 wt%. The mass ratio of organozirconium crosslinking agent to sulfonated polymer in the modification solution is 1:10-50.

8. The method for preparing the zinc-bromine flow battery negative electrode material according to claim 1, characterized in that, In step S03, the mass ratio of the intermediate carbon felt to the modification liquid is 0.45-0.7:100; The soaking time is 10-60 minutes.

9. A zinc-bromine flow battery negative electrode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. A zinc-bromine flow battery, wherein the zinc-bromine flow battery negative electrode material of claim 9 is used as the negative electrode of the zinc-bromine flow battery.

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