Zinc dendrite-free deposition of carbon fiber negative electrode materials based on cu-zn-zif-8, batteries and methods thereof

Abstract

The application discloses a kind of zinc dendrite-free deposition carbon fiber negative materials based on Cu-Zn-ZIF-8 and battery and method, belong to the field of flow battery electrode material.The application covers a layer of Cu-Zn-ZIF-8 material on the surface of carbon fiber, to realize the uniform stable deposition of zinc ion, inhibit the generation of zinc dendrite.Cu-Zn-ZIF-8 is grown on the surface of carbon fiber by hydrothermal reaction, because it has higher binding energy between Zn atom, can reduce the nucleation barrier of Zn, promote Zn deposition.The method is simple, stable performance, carbon felt prepared by the method is used as the electrode material of zinc-based flow battery negative electrode, can enhance the mass transfer rate of zinc ion on the electrode surface, can also increase the nucleation site of Zn, significantly improve the deposition uniformity of zinc ion in the reduction process, inhibit the generation of zinc dendrite, widen the current density range of battery work, improve the service life and safety of zinc-based flow battery.

Description

Technical Field

[0001] This invention belongs to the field of flow battery electrode materials, specifically relating to a zinc-free dendrite-deposited carbon fiber anode material based on Cu-Zn-ZIF-8, its battery, and method. Background Technology

[0002] The use of renewable energy sources, primarily solar and wind power, is increasing. However, due to the intermittent and unstable nature of renewable energy, it is difficult for renewable energy power generation to completely replace traditional energy forms. Therefore, with the large-scale utilization of renewable energy, the demand for energy storage technology is also increasing. Among them, zinc-based flow batteries have outstanding advantages such as abundant raw materials, low cost, high flexibility, high safety, and high capacity, making them one of the solutions for large-scale energy storage.

[0003] However, unlike vanadium redox flow batteries, zinc-based flow batteries experience zinc plating and stripping during the redox reaction at the negative electrode. Uneven zinc deposition leads to the formation of zinc dendrites. These dendrites increase polarization losses, reduce battery efficiency and capacity, and in severe cases, can puncture the separator, causing a short circuit. The dendrite problem significantly impacts the lifespan and safety of zinc-based flow batteries. Therefore, mitigating the zinc dendrite problem is crucial for the large-scale application of zinc-based flow batteries. Summary of the Invention

[0004] The purpose of this invention is to address the common zinc dendrite problem in zinc-based flow batteries by providing a zinc dendrite-free carbon fiber anode material based on Cu-Zn-ZIF-8, along with its battery and method. This invention can reduce the zinc nucleation barrier, enhance zinc deposition uniformity, suppress zinc dendrite formation, improve the efficiency and capacity of zinc-based flow batteries, and significantly extend their lifespan.

[0005] The specific technical solution adopted in this invention is as follows:

[0006] In a first aspect, the present invention provides a zinc-free dendritic carbon fiber anode material based on Cu-Zn-ZIF-8, which is composed of Cu-Zn-ZIF-8 material and carbon fiber material. The Cu-Zn-ZIF-8 material is uniformly distributed in particulate form on the surface of the carbon fiber material and forms a uniform micro-nano pore structure.

[0007] Preferably, the carbon fiber material is carbon felt, graphite felt, carbon cloth, or carbon paper.

[0008] Secondly, the present invention provides a method for preparing zinc-free dendrite-deposited carbon fiber anode material based on Cu-Zn-ZIF-8, as detailed below:

[0009] Add an equal volume of 2-methylimidazolium methanol solution to a copper-zinc solution and stir until homogeneous to obtain a mixed solution. Immerse the pretreated carbon fiber material in the mixed solution and react fully at room temperature (preferably 25℃-30℃) for 12-48h (preferably 12-24h). After washing and drying, obtain a zinc-free dendrite-deposited carbon fiber anode material based on Cu-Zn-ZIF-8.

[0010] Preferably, in the copper-zinc solution, the copper ion concentration is 0.01-0.03M (more preferably 0.01M), the zinc ion concentration is 0.05-0.5M (more preferably 0.1-0.3M), and the solvent is methanol; the solute is one of the following combinations: zinc acetate, copper acetate or zinc nitrate, copper nitrate.

[0011] Preferably, the concentration of the 2-methylimidazolium methanol solution is 0.2-2M.

[0012] Preferably, the pretreatment process of the carbon fiber material is as follows: the carbon fiber material is soaked in a 68wt% concentrated nitric acid solution for 24 hours, and after soaking, it is washed with deionized water until the pH=7.

[0013] Preferably, the washing and drying process involves washing the solution with deionized water and methanol until the solution pH = 7, and then placing it in a vacuum drying oven and drying it at 40-80℃ (more preferably 50-70℃) for 6 hours.

[0014] Thirdly, the present invention provides a zinc-based flow battery, wherein the negative electrode of the battery is a zinc-free dendrite-deposited carbon fiber negative electrode material based on Cu-Zn-ZIF-8 as described in the first aspect or a zinc-free dendrite-deposited carbon fiber negative electrode material based on Cu-Zn-ZIF-8 obtained by any of the preparation methods described in the second aspect; and the positive electrode of the battery is a carbon fiber material.

[0015] Preferably, the thickness of the negative electrode is 0.7-6 mm (more preferably 1-2 mm), and the porosity is 75%-98% (more preferably 90%).

[0016] Preferably, the negative electrode electrolyte of the battery is a zinc oxide solution or a zinc ion solution, and the zinc concentration in the solution is 0.1-0.4M; the battery separator is one of an ion exchange membrane, a porous membrane, or a microporous membrane.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] This invention employs a zinc-dendritic-free carbon fiber anode material based on Cu-Zn-ZIF-8. This material has a higher binding energy with Zn atoms, significantly reducing the zinc nucleation barrier, improving the uniformity of zinc nucleation, and inducing uniform zinc ion deposition, thereby effectively suppressing zinc dendrite growth. Successful application of this material to the anode of zinc-based flow batteries can significantly improve battery efficiency and capacity, and broaden the battery's operating current density range. Simultaneously, using the anode material of this invention avoids the separator puncture problem caused by zinc dendrite formation, thus extending battery life and improving battery application safety. Furthermore, the preparation process of this invention is simple and low-cost, and the material performance is stable and reliable, providing a feasible solution for the application of zinc-based flow batteries in large-scale energy storage, and will promote the widespread application of zinc-based flow batteries in this field. Attached Figure Description

[0019] Figure 1 Electron micrograph of zinc-free dendrite-deposited carbon fiber anode material based on Cu-Zn-ZIF-8;

[0020] Figure 2 This is a comparison diagram of zinc nucleation overpotential between the examples and the comparative examples;

[0021] Figure 3 The images show scanning electron microscope (SEM) images of the example electrode and the comparative electrode at the end of charging in a zinc-based flow battery. Detailed Implementation

[0022] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific examples and accompanying drawings. However, this invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0023] This invention provides a zinc-free dendritic carbon fiber anode material based on Cu-Zn-ZIF-8. The material is mainly composed of Cu-Zn-ZIF-8 material and carbon fiber material. The Cu-Zn-ZIF-8 material is uniformly distributed in particulate form on the surface of the carbon fiber material, forming a uniform micro-nano pore structure.

[0024] In practical applications, carbon fiber materials can be made of carbon felt, graphite felt, carbon cloth, or carbon paper.

[0025] For the aforementioned zinc-free dendrite-deposited carbon fiber anode material based on Cu-Zn-ZIF-8, this invention provides a preparation method, the specific steps of which are as follows:

[0026] (1) Pretreatment of carbon fiber: The carbon fiber material was soaked in a 68wt% concentrated nitric acid solution for 24 hours. After soaking, it was washed with deionized water until the pH was 7.

[0027] (2) Solution preparation: Prepare a copper-zinc mixed solution, wherein the copper ion concentration is 0.01-0.03M, preferably 0.01M; the zinc ion concentration is 0.05-0.5M, preferably 0.1-0.3M; the solute is zinc acetate, copper acetate or zinc nitrate, copper nitrate, and the solvent is methanol.

[0028] (3) Add an equal volume of 2-methylimidazolium methanol solution to the copper-zinc mixed solution, stir until homogeneous, and obtain a mixed solution. The concentration of the 2-methylimidazolium methanol solution is 0.2-2M, preferably 0.4-1.2M.

[0029] (4) Immerse the carbon fiber material in the mixed solution and react at room temperature, preferably 25-30°C, for 12-48 hours, preferably 12-24 hours.

[0030] (5) Wash the reacted carbon fiber material with deionized water and methanol until pH=7.

[0031] (6) Place the carbon fiber material in a vacuum drying oven and dry it at 40-80℃, preferably 50-70℃, for 6 hours to obtain a zinc-free dendritic carbon fiber anode material based on Cu-Zn-ZIF-8.

[0032] Based on the aforementioned zinc-free dendrite-deposited carbon fiber anode material of Cu-Zn-ZIF-8, this invention also provides a zinc-based flow battery. In this battery, the zinc-free dendrite-deposited carbon fiber anode material of Cu-Zn-ZIF-8 serves as the battery anode; the battery cathode is ordinary carbon fiber, including carbon felt, graphite felt, carbon cloth, or carbon paper, etc.

[0033] In practical applications, the thickness of the negative electrode is 0.7-6 mm, preferably 1-2 mm; the porosity is 75%-98%, preferably 90%. The electrolyte of the battery negative electrode is a zinc oxide solution or a zinc ion solution, with a zinc concentration of 0.1-0.4 M; the battery separator is one of an ion exchange membrane, a porous membrane, or a microporous membrane.

[0034] Example

[0035] This invention provides a zinc-free dendrite-deposited carbon fiber anode material based on Cu-Zn-ZIF-8, the scanning electron microscope image of which is shown below. Figure 1 As shown in the figure, the surface of the carbon fiber is covered with granular Cu-Zn-ZIF-8 crystals. Specifically, the carbon fiber electrode material is a carbon cloth electrode material.

[0036] The raw materials for preparing the zinc-free dendritic deposition carbon fiber material based on Cu-Zn-ZIF-8 in this embodiment include: ordinary carbon cloth of type Carbon Energy WSO40, copper nitrate, zinc nitrate, 2-methylimidazole, deionized water, and concentrated nitric acid methanol. The specific preparation method is as follows:

[0037] (1) Soak the carbon cloth material in a 68wt% concentrated nitric acid solution for 24 hours. After soaking, wash with deionized water until pH=7.

[0038] (2) Prepare a 50ml copper-zinc mixed solution: the copper ion concentration is 0.01M; the zinc ion concentration is 0.05M; the solutes are zinc nitrate and copper nitrate, and the solvent is methanol.

[0039] (3) Add 50 ml of 2-methylimidazolium methanol solution with a concentration of 0.2 M to the copper-zinc mixed solution, stir well to obtain the mixed solution.

[0040] (4) Soak the carbon cloth in the mixed solution and react at room temperature for 24 hours.

[0041] (5) Wash the reacted carbon fibers with deionized water and methanol until pH=7.

[0042] (6) The carbon fiber was placed in a vacuum drying oven and dried at 50°C for 6 hours to obtain a zinc-free dendritic carbon fiber anode material based on Cu-Zn-ZIF-8.

[0043] Comparative Example

[0044] Raw carbon cloth without any treatment, model number Carbon Energy WS040.

[0045] The properties of the carbon cloth materials in the examples and comparative examples were measured using a three-electrode system. The working electrodes were two types of carbon cloth cut to 1cm x 1cm, the counter electrode was a platinum sheet electrode, the reference electrode was a mercuric oxide electrode, and the electrolyte was a zinc oxide solution with a concentration of 0.4 mol / L. The zinc nucleation overpotential of the two materials was measured under constant current deposition conditions, and the results are as follows: Figure 2 As shown.

[0046] The electrodes of the examples and comparative examples were respectively installed on the negative electrode of an alkaline zinc-iron flow battery. The positive electrode was a square ordinary carbon felt with a thickness of 3 mm, a size of 5 cm * 5 cm, and a porosity of 90%; the negative electrode was a stack of three layers of carbon cloth material from the examples or comparative examples, with a size of 5 cm * 5 cm. The positive electrode electrolyte was a sodium ferrocyanide solution with a concentration of 0.8 mol / L; the negative electrode electrolyte was a zinc oxide solution with a concentration of 0.4 mol / L; the separator was a Nafion 211 membrane manufactured by DuPont, with an 80 mA / cm² frequency. 2 The zinc deposition morphology on the negative electrode is as follows after charging at a current density for 24 minutes. Figure 3 As shown.

[0047] Figure 2The difference in nucleation overpotential between the examples and the comparative examples is shown. The nucleation overpotential of the examples (3mV) is reduced compared to that of the comparative examples (14mV), indicating that the energy barrier for zinc ion deposition on its electrode surface is lower, making it easier to achieve uniform nucleation and resulting in a more uniform zinc deposition effect, which can effectively prevent the formation of zinc dendrites.

[0048] Figure 3 The morphological differences of zinc deposition on the surfaces of the examples and comparative materials are shown. It can be seen that the zinc on the surface of the comparative example agglomerates into spheres and is relatively disordered and irregular, while the zinc deposition on the surface of the examples is more uniformly distributed, with a smoother morphology and is less prone to zinc dendrite formation, which can effectively improve the operational safety of zinc-based flow batteries.

[0049] This invention involves coating the surface of carbon fiber with a Cu-Zn-ZIF-8 material to achieve uniform and stable deposition of zinc ions and suppress the formation of zinc dendrites. Cu-Zn-ZIF-8 is grown on the carbon fiber surface via a hydrothermal reaction. Due to its higher binding energy with Zn atoms, it lowers the nucleation barrier of Zn and promotes Zn deposition. This method is simple and stable. Using the carbon felt prepared by this method as the electrode material for the negative electrode of a zinc-based flow battery enhances the mass transfer rate of zinc ions on the electrode surface and increases the number of Zn nucleation sites, significantly improving the deposition uniformity of zinc ions during the reduction process, suppressing the formation of zinc dendrites, widening the battery's operating current density range, and improving the lifespan and safety of the zinc-based flow battery.

[0050] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A zinc-free dendritic carbon fiber anode material based on Cu-Zn-ZIF-8, characterized in that, It is a composite material made of Cu-Zn-ZIF-8 and carbon fiber. The Cu-Zn-ZIF-8 material is uniformly distributed in particulate form on the surface of the carbon fiber material, forming a uniform micro-nano porous structure. The specific preparation method is as follows: An equal volume of 2-methylimidazolium methanol solution was added to a copper-zinc solution and stirred until homogeneous to obtain a mixed solution. The pretreated carbon fiber material was then immersed in the mixed solution and allowed to react fully at room temperature. After washing and drying, a zinc-free dendrite-deposited carbon fiber anode material based on Cu-Zn-ZIF-8 was obtained.

2. The zinc-free dendritic carbon fiber anode material based on Cu-Zn-ZIF-8 according to claim 1, characterized in that, The carbon fiber material is carbon felt, graphite felt, carbon cloth, or carbon paper.

3. A method for preparing zinc-free dendritic carbon fiber anode material based on Cu-Zn-ZIF-8, characterized in that, Specifically as follows: An equal volume of 2-methylimidazolium methanol solution was added to a copper-zinc solution and stirred until homogeneous to obtain a mixed solution. The pretreated carbon fiber material was then immersed in the mixed solution and allowed to react fully at room temperature. After washing and drying, a zinc-free dendrite-deposited carbon fiber anode material based on Cu-Zn-ZIF-8 was obtained.

4. The preparation method according to claim 3, characterized in that, The copper-zinc solution has a copper ion concentration of 0.01-0.03M and a zinc ion concentration of 0.05-0.5M, and the solvent is methanol; the solute is one of the following combinations: zinc acetate and copper acetate or zinc nitrate and copper nitrate.

5. The preparation method according to claim 3, characterized in that, The concentration of the 2-methylimidazolium methanol solution is 0.2-2M.

6. The preparation method according to claim 3, characterized in that, The pretreatment process of the carbon fiber material is as follows: the carbon fiber material is soaked in a 68 wt% concentrated nitric acid solution for 24 hours, and after soaking, it is washed with deionized water until pH=7.

7. The preparation method according to claim 3, characterized in that, The washing and drying process refers to washing with deionized water and methanol until the solution pH=7, followed by drying at 40-80℃ for 6 hours.

8. A zinc-based flow battery, characterized in that, The negative electrode of the battery is the zinc-free dendrite-deposited carbon fiber negative electrode material based on Cu-Zn-ZIF-8 as described in claim 1, or the zinc-free dendrite-deposited carbon fiber negative electrode material based on Cu-Zn-ZIF-8 obtained by any of the preparation methods described in claims 3-7; the positive electrode of the battery is a carbon fiber material.

9. A zinc-based flow battery according to claim 8, characterized in that, The thickness of the negative electrode is 0.7-6 mm, and the porosity is 75%-98%.

10. A zinc-based flow battery according to claim 8, characterized in that, The negative electrode electrolyte of the battery is a zinc oxide solution or a zinc ion solution, with a zinc concentration of 0.1-0.4M; the battery separator is an ion exchange membrane or a porous membrane.

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