MOF-based carbon fiber felt for flow battery electrode as well as preparation method and application of MOF-based carbon fiber felt

Abstract

The invention discloses an MOF-based carbon fiber felt for a flow battery electrode as well as a preparation method and application thereof, the preparation method comprises the following steps: S1, soaking a pre-oxidized felt in a metal salt solution, adding a 2-methylimidazole solution into the metal salt solution, standing and reacting for 2-48 hours at the temperature of 20-100 DEG C, taking out and drying to obtain an MOF-based pre-oxidized felt; and S2, performing carbonization, graphitization and activation treatment on the MOF-based pre-oxidized felt in sequence to obtain the MOF-based carbon fiber felt for the flow battery electrode. The preparation process is low in energy consumption and high in industrial feasibility, the prepared MOF-based carbon fiber felt has a high specific surface area and a hierarchical pore structure, when the MOF-based carbon fiber felt is applied to a flow battery electrode, the flow battery can have low resistance and high electrocatalytic activity, and the electrochemical performance of the flow battery can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid flow batteries, and in particular relates to a MOF-based carbon fiber felt for liquid flow battery electrodes, a preparation method and an application thereof. Background Art

[0002] Renewable energy sources such as solar energy, wind energy, hydropower, and biomass energy have non-steady-state characteristics of volatility and intermittence, and are affected by factors such as weather conditions. Energy storage technology has the natural advantage of peak load regulation, which can effectively improve the grid's ability to accept clean energy and solve the grid security and stability issues brought about by large-scale clean energy access.

[0003] Liquid flow batteries have the advantages of high energy conversion efficiency, large storage capacity, freedom of site selection, deep discharge, long service life, safety and environmental protection, etc., and are considered to be one of the most promising large-scale energy storage technologies. Among them, polyacrylonitrile-based carbon fiber felt is a key material for liquid flow batteries, providing reactive sites for electrochemical reactions. Currently, commercial carbon fiber felt materials are mainly used for refractory and heat-insulating materials. Their specifications and surface properties are not processed and produced for liquid flow battery electrode materials, so it is difficult to meet the performance requirements of liquid flow batteries. If it is used directly for liquid flow battery electrodes, there are a series of problems such as strong hydrophobicity of the material surface, poor wetting with the electrolyte, poor electrocatalytic activity, and irreversibility.

[0004] Therefore, it is necessary to develop carbon fiber felt materials for electrodes to meet the needs of flow batteries, and it is expected to further improve the energy efficiency and energy density of flow battery products, which is of great significance to accelerate the development of advanced electrochemical energy storage technology and the diversification of clean energy research and development. MOF materials are assembled from metal ions and organic ligands. They have extremely high specific surface area, rich active sites, adjustable pore structure, good stability, and easy modification and functionalization. Combined with carbon fiber felt materials, multi-level pore structure composite electrode materials can be prepared. Chinese Patent Publication No. CN111146449A proposes a method for preparing an electrode material and its use, comprising the steps of placing carbon felt in an aqueous solution of cobalt nitrate and soaking for 4 to 8 minutes; adding an aqueous solution of dimethylimidazole to the solution in which the carbon felt is soaked, and standing the solution at room temperature for reaction for 11 to 13 hours to obtain a MOF carbon felt composition; taking out the MOF carbon felt composition and drying it; and carbonizing the MOF carbon felt composition in a high-temperature vacuum tube furnace at 800°C for 1 hour under the protection of high-purity nitrogen, and then naturally cooling the composition to room temperature to obtain the electrode material; this technology grows MOF on a carbon felt material and performs secondary carbonization to obtain a composite electrode for a microbial fuel cell, but there are problems in that the energy consumption of the secondary carbonization of the carbon felt is too high and that the organic components of the MOF affect the electrode performance. Summary of the invention

[0005] In view of the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a MOF-based carbon fiber felt for liquid flow battery electrodes, a preparation method and an application thereof. By in-situ growing MOF on the pre-oxidation felt and simultaneously completing the carbonization of the pre-oxidation felt and MOF, a large amount of energy consumption can be saved while carbonizing the MOF material into a porous carbon particle structure, thereby obtaining a MOF-based carbon fiber felt for liquid flow battery electrodes having a porous structure on the surface. The MOF-based carbon fiber felt has a high specific surface area and a multi-level pore structure, has low resistance and high electrocatalytic activity, and can effectively improve the electrochemical performance of the liquid flow battery.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A first aspect of the present invention provides a method for preparing a MOF-based carbon fiber felt for a flow battery electrode, comprising the following steps:

[0008] S1, soaking the pre-oxidized felt in a metal salt solution, adding a 2-methylimidazole solution to the metal salt solution, standing the mixture for a reaction at a temperature of 20 to 100° C. for 2 to 48 hours, taking it out and drying it to obtain a MOF-based pre-oxidized felt;

[0009] S2, the MOF-based pre-oxidized felt is sequentially subjected to carbonization, graphitization and activation treatment to obtain the MOF-based carbon fiber felt.

[0010] Preferably, in step S1:

[0011] The pre-oxidized felt is one or more of nano-polyacrylonitrile-based pre-oxidized felt, micron-polyacrylonitrile-based pre-oxidized felt, general-grade asphalt-based pre-oxidized felt, mesophase asphalt-based pre-oxidized felt, and viscose-based pre-oxidized felt; and / or

[0012] The metal salt is one or more of zinc nitrate, zinc sulfate, zinc chloride, zinc acetate, cobalt nitrate, cobalt sulfate, cobalt chloride and cobalt acetate; and / or

[0013] The solvent used for the metal salt solution is one or more of methanol, water, ethanol and dimethylformamide; and / or

[0014] The solvent used in the 2-methylimidazole solution is one or more of methanol, water, ethanol and dimethylformamide.

[0015] Preferably, in step S1:

[0016] The concentration of the metal salt solution is 10-60 g / L; and / or

[0017] The concentration of the 2-methylimidazole solution is 15 to 120 g / L; and / or

[0018] The volume ratio of the 2-methylimidazole solution to the metal salt solution is 1:(0.5-2).

[0019] Preferably, in step S1:

[0020] The preoxidized felt is immersed in the metal salt solution for 5 to 60 minutes; and / or

[0021] The temperature of the static reaction is 25 to 70° C., and the static reaction time is 6 to 24 hours; and / or

[0022] The drying temperature is 40-100° C., and the drying time is 2-20 hours.

[0023] Preferably, the preoxidized felt is immersed in the metal salt solution for 10 to 30 minutes.

[0024] Preferably, in step S2:

[0025] The carbonization treatment is carried out in a nitrogen atmosphere at 500-1600° C. for 0.3-4 hours; and / or

[0026] The graphitization treatment is carried out in a nitrogen atmosphere at 1800-3000° C., and the graphitization time is 0.3-4 hours; and / or

[0027] The activation treatment is carried out in an activation gas atmosphere at 500-1500° C., and the activation time is 0.5-5 hours.

[0028] Preferably, during the carbonization process, the carbonization temperature is 750-1500° C. and the carbonization time is 1-3 hours; and / or

[0029] During the graphitization treatment, the graphitization temperature is 2000-2600° C. and the graphitization time is 1-3 hours; and / or

[0030] During the activation treatment, the activation gas is carbon dioxide or water vapor, the activation temperature is 600-1200° C., and the activation time is 1-4 hours.

[0031] The second aspect of the present invention provides a MOF-based carbon fiber felt for a flow battery electrode prepared according to the method for preparing a MOF-based carbon fiber felt for a flow battery electrode according to the first aspect of the present invention, wherein the MOF-based carbon fiber felt for a flow battery electrode has a specific surface area of ​​300 to 500 m 2 / g, and the porosity is above 90%.

[0032] The third aspect of the present invention provides an application of MOF-based carbon fiber felt for liquid flow battery electrodes prepared according to the preparation method of MOF-based carbon fiber felt for liquid flow battery electrodes described in the first aspect of the present invention in liquid flow battery electrodes.

[0033] Preferably, the flow battery electrode is made of MOF-based carbon fiber felt at a current density of 120 mA / cm 2 When the energy efficiency is ≥83%, the voltage efficiency is ≥84%, and the coulombic efficiency is ≥95%; and / or

[0034] The flow battery electrode is made of MOF-based carbon fiber felt at a current density of 200 mA / cm 2 When the energy efficiency is ≥80%, the voltage efficiency is ≥81%, and the coulombic efficiency is ≥94%.

[0035] The MOF-based carbon fiber felt for flow battery electrodes provided by the present invention and its preparation method and application have the following beneficial effects:

[0036] 1. The present invention uses pre-oxidation felt as a raw material and grows MOF in situ on the pre-oxidation felt. The carbonization process of the pre-oxidation felt and MOF can be completed simultaneously in the subsequent carbonization process. Compared with growing MOF on carbon felt and then performing secondary carbonization on the carbon felt, a lot of energy consumption can be saved, and the MOF material can be carbonized into a porous carbon particle structure;

[0037] 2. The present invention utilizes MOF to modify the pre-oxidized felt material, and after carbonization, a rough porous structure is formed on the surface of the carbon fiber felt, which forms a composite multi-level porous structure with the porous structure of the carbon fiber felt itself, which can enhance the infiltration of the electrolyte, increase the electrochemical reaction site, and improve the electrocatalytic activity;

[0038] 3. The preparation process of the present invention has low energy consumption and high industrial feasibility. The prepared MOF-based carbon fiber felt has a high specific surface area and a multi-level pore structure. When used as a flow battery electrode, it can enable the flow battery to have lower resistance and higher electrocatalytic activity, which can effectively improve the electrochemical performance of the flow battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0040] Figure 1 The present invention is a schematic flow chart of the method for preparing MOF-based carbon fiber felt for liquid flow battery electrodes. DETAILED DESCRIPTION

[0041] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with embodiments.

[0042] Combination Figure 1 As shown, a method for preparing a MOF-based carbon fiber felt for a flow battery electrode of the present invention comprises the following steps:

[0043] S1, soaking the pre-oxidized felt in a metal salt solution, adding a 2-methylimidazole solution to the metal salt solution, standing the mixture for a reaction at a temperature of 20 to 100° C. for 2 to 48 hours, taking it out and drying it to obtain a MOF-based pre-oxidized felt;

[0044] Specifically, the pre-oxidized felt with a thickness of 3 to 6 mm is soaked in a metal salt solution for 5 to 60 minutes (here, the metal salt solution can immerse the pre-oxidized felt), so that the metal salt is evenly distributed in the porous structure of the pre-oxidized felt; the pre-oxidized felt is one or more of nano-polyacrylonitrile-based pre-oxidized felt, micro-polyacrylonitrile-based pre-oxidized felt, general-grade asphalt-based pre-oxidized felt, mesophase asphalt-based pre-oxidized felt, and viscose-based pre-oxidized felt; the metal salt is one or more of zinc nitrate, zinc sulfate, zinc chloride, zinc acetate, cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt acetate; the solvent used for the metal salt solution is one or more of methanol, water, ethanol, and dimethylformamide; the concentration of the metal salt solution is 10 to 60 g / L. In a specific embodiment, the soaking time of the pre-oxidized felt in the metal salt solution is 10 to 30 minutes.

[0045] Then, add 2-methylimidazole solution to the metal salt solution in which the pre-oxidized felt is soaked, and the reaction is allowed to stand at a temperature of 20 to 100°C for 2 to 48 hours, and then the MOF-based pre-oxidized felt is obtained after being taken out and dried. The concentration of the 2-methylimidazole solution is 15 to 120 g / L, and the solvent used for the 2-methylimidazole solution is one or more of methanol, water, ethanol, and dimethylformamide. The volume ratio of the 2-methylimidazole solution to the metal salt solution is 1: (0.5 to 2). In a specific embodiment, the temperature of the standing reaction is 25 to 70°C, and the standing reaction time is 6 to 24 hours. When drying, the drying temperature is 40 to 100°C, and the drying time is 2 to 20 hours.

[0046] S2, the MOF-based pre-oxidized felt is sequentially subjected to carbonization, graphitization and activation treatment to obtain MOF-based carbon fiber felt for flow battery electrodes.

[0047] Specifically, the MOF-based pre-oxidized felt is sequentially carbonized and graphitized in a nitrogen atmosphere to obtain a MOF-based carbon fiber felt, which is then activated to obtain a MOF-based carbon fiber felt for a flow battery electrode; specifically, the MOF-based pre-oxidized felt is carbonized in a nitrogen atmosphere at 500-1600°C for 0.3-4h; then, it is graphitized in a nitrogen atmosphere at 1800-3000°C for 0.3-4h; then, it is activated in an activated gas atmosphere at 500-1500°C for 0.5-5h to finally obtain a MOF-based carbon fiber felt for a flow battery electrode. In a specific embodiment, during the carbonization treatment, the carbonization temperature is 750-1500°C, and the carbonization time is 1-3 hours; during the graphitization treatment, the graphitization temperature is 2000-2600°C, and the graphitization time is 1-3 hours; during the activation treatment, the activation gas is carbon dioxide or water vapor, the activation temperature is 600-1200°C, and the activation time is 1-4 hours.

[0048] In the above preparation process, the MOF on the MOF-based preoxidation felt and the preoxidation felt are carbonized at the same time, and a rough porous structure is formed on the surface of the carbon fiber felt, which forms a composite multi-level pore structure with the porous structure of the carbon fiber felt itself. The MOF-based carbon fiber felt for flow battery electrodes has a high specific surface area and a multi-level pore structure, and its specific properties are: the specific surface area is 300-500m 2 / g, and the porosity is above 90%.

[0049] When the MOF-based carbon fiber felt for flow battery electrode is used in the flow battery electrode, the electrode made of the MOF-based carbon fiber felt for flow battery electrode has a current density of 120 mA / cm 2 When the energy efficiency is ≥83%, the voltage efficiency is ≥84%, and the coulombic efficiency is ≥95%; the electrode made of MOF-based carbon fiber felt for the flow battery electrode has a current density of 200mA / cm 2 When the energy efficiency is ≥80%, the voltage efficiency is ≥81%, and the coulombic efficiency is ≥94%.

[0050] The MOF-based carbon fiber felt for liquid flow battery electrodes of the present invention, as well as its preparation method and application are further introduced below with reference to specific examples.

[0051] Example 1

[0052] The preparation method of a MOF-based carbon fiber felt for a flow battery electrode of this embodiment adopts the following steps:

[0053] (1) A 5 mm thick micron polyacrylonitrile-based pre-oxidized felt was immersed in 500 ml of a methanol solution containing 20 g of zinc nitrate for 15 min to uniformly distribute the zinc nitrate in the porous structure of the pre-oxidized felt.

[0054] (2) Add 500 mL of a methanol solution containing 45 g of 2-methylimidazole to the metal salt solution in which the pre-oxidized felt is soaked, and allow to react at 30° C. for 8 h. Take out and dry at 60° C. for 12 h to obtain a MOF-based pre-oxidized felt.

[0055] (3) The MOF-based preoxidized felt obtained in step (2) was carbonized for 2 h in a nitrogen atmosphere at 800°C, graphitized for 2 h in a nitrogen atmosphere at 2200°C, and activated for 2 h in a carbon dioxide atmosphere at 800°C to obtain a MOF-based MOF-based carbon fiber felt for flow battery electrodes, having a specific surface area of ​​323.6 m 2 / g, and the porosity is 91.1%.

[0056] The MOF-based carbon fiber felt prepared above was cut into 6 cm × 6 cm pieces as electrodes to assemble into a single cell, and the charge and discharge performance was tested: at a current density of 120 mA / cm 2 When the current density is increased to 200mA / cm 2 When the power consumption is 2.5W, the energy efficiency is 80.9%, the voltage efficiency is 84.1%, and the coulombic efficiency is 96.2%.

[0057] Example 2

[0058] The preparation method of a MOF-based carbon fiber felt for a flow battery electrode of this embodiment adopts the following steps:

[0059] (1) A 4 mm thick nano-polyacrylonitrile-based pre-oxidized felt was immersed in 500 mL of an aqueous solution containing 17 g of zinc sulfate for 18 min to allow the zinc sulfate to be evenly distributed in the porous structure of the pre-oxidized felt.

[0060] (2) Add 400 mL of an aqueous solution containing 40 g of 2-methylimidazole to the metal salt solution in which the pre-oxidized felt is soaked, and allow to react at 50° C. for 20 h. Take out and dry at 80° C. for 6 h to obtain a MOF-based pre-oxidized felt.

[0061] (3) The MOF-based preoxidized felt obtained in step (2) was carbonized for 1 h in a nitrogen atmosphere at 1200° C., graphitized for 2 h in a nitrogen atmosphere at 2100° C., and activated for 1.5 h in a water vapor atmosphere at 700° C. to obtain a MOF-based carbon fiber felt for flow battery electrodes, the specific surface area of ​​which was 455.2 m 2 / g, and the porosity is 93.2%.

[0062] The MOF-based carbon fiber felt prepared above was cut into 6 cm × 6 cm pieces as electrodes to assemble into a single cell, and the charge and discharge performance was tested: at a current density of 120 mA / cm 2When the current density is increased to 200mA / cm 2 When the power consumption is 2.5W, the energy efficiency is 80.1%, the voltage efficiency is 85.1%, and the coulombic efficiency is 94.2%.

[0063] Example 3

[0064] The preparation method of a MOF-based carbon fiber felt for a flow battery electrode of this embodiment adopts the following steps:

[0065] (1) A 5 mm thick micron polyacrylonitrile-based / general-grade asphalt-based mixed preoxidized felt was immersed in 500 mL of an ethanol solution containing 20 g of cobalt nitrate for 22 min to uniformly distribute the cobalt nitrate in the porous structure of the preoxidized felt.

[0066] (2) Add 800 mL of ethanol solution containing 60 g of 2-methylimidazole to the solution of the pre-oxidized felt, and let it stand at 40° C. for 15 h. Then, take it out and dry it at 50° C. for 18 h to obtain the MOF-based pre-oxidized felt.

[0067] (3) The MOF-based preoxidized felt obtained in step (2) was carbonized for 2 h in a nitrogen atmosphere at 1000° C., graphitized for 2 h in a nitrogen atmosphere at 2200° C., and activated for 1 h in a carbon dioxide atmosphere at 900° C. to obtain a MOF-based carbon fiber felt for flow battery electrodes, the specific surface area of ​​which was 341.3 m 2 / g, and the porosity is 91.5%.

[0068] The MOF-based carbon fiber felt prepared above was cut into 6 cm × 6 cm pieces as electrodes to assemble into a single cell, and the charge and discharge performance was tested: at a current density of 120 mA / cm 2 When the current density is increased to 200mA / cm 2 When the power consumption is 2.04W, the energy efficiency is 82.6%, the voltage efficiency is 84.8%, and the coulombic efficiency is 97.4%.

[0069] Example 4

[0070] The preparation method of a MOF-based carbon fiber felt for a flow battery electrode of this embodiment adopts the following steps:

[0071] (1) A 3 mm thick micron / nano polyacrylonitrile-based mixed preoxidized felt was immersed in 500 mL of a dimethylformamide solution containing 12 g of cobalt nitrate and 10 g of zinc nitrate for 25 min to uniformly distribute the cobalt nitrate in the porous structure of the preoxidized felt.

[0072] (2) Add 500 mL of dimethylformamide solution containing 30 g of 2-methylimidazole to the solution of the pre-oxidized felt, and let it stand at 60° C. for 10 h. Take it out and dry it at 90° C. for 2 h to obtain the MOF-based pre-oxidized felt.

[0073] (3) The MOF-based preoxidized felt obtained in step (2) was carbonized for 1 h in a nitrogen atmosphere at 1300° C., graphitized for 1.5 h in a nitrogen atmosphere at 2300° C., and activated for 1.2 h in a carbon dioxide atmosphere at 950° C. to obtain a MOF-based carbon fiber felt for flow battery electrodes, the specific surface area of ​​which was 388.4 m 2 / g, and the porosity is 92.4%.

[0074] The MOF-based carbon fiber felt prepared above was cut into 6 cm × 6 cm pieces as electrodes to assemble into a single cell, and the charge and discharge performance was tested: at a current density of 120 mA / cm 2 When the current density is increased to 200mA / cm 2 When the energy efficiency is 82.0%, the voltage efficiency is 83.5%, and the coulombic efficiency is 98.2%.

[0075] Example 5

[0076] The preparation method of a MOF-based carbon fiber felt for a flow battery electrode of this embodiment adopts the following steps:

[0077] (1) A 5 mm thick micron / nano polyacrylonitrile-based mixed pre-oxidized felt was immersed in 500 mL of a methanol solution containing 10 g of zinc nitrate and 10 g of zinc sulfate for 12 min to uniformly distribute the cobalt nitrate in the porous structure of the pre-oxidized felt.

[0078] (2) Add 750 mL of a methanol solution containing 60 g of 2-methylimidazole to the solution of the pre-oxidized felt, and allow to react at 25° C. for 16 h. Take out and dry at 60° C. for 15 h to obtain a MOF-based pre-oxidized felt.

[0079] (3) The MOF-based preoxidized felt obtained in step (2) was carbonized for 2 h in a nitrogen atmosphere at 1200° C., graphitized for 1.2 h in a nitrogen atmosphere at 2150° C., and activated for 2.5 h in a water vapor atmosphere at 800° C. to obtain a MOF-based carbon fiber felt for flow battery electrodes, the specific surface area of ​​which was 362.9 m 2 / g, and the porosity is 91.8%.

[0080] The MOF-based carbon fiber felt prepared above was cut into 6 cm × 6 cm pieces as electrodes to assemble into a single cell, and the charge and discharge performance was tested: at a current density of 120 mA / cm 2When the current density is increased to 200mA / cm 2 When the power consumption is 2.5W, the energy efficiency is 80.3%, the voltage efficiency is 81.9%, and the coulombic efficiency is 98.1%.

[0081] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for preparing MOF-based carbon fiber felt for flow battery electrodes, characterized in that: The following steps are involved: S1, soaking the pre-oxidized felt in a metal salt solution, adding a 2-methylimidazole solution to the metal salt solution, standing the mixture for a reaction at a temperature of 20 to 100° C. for 2 to 48 hours, taking it out and drying it to obtain a MOF-based pre-oxidized felt; S2, the MOF-based pre-oxidized felt is sequentially subjected to carbonization, graphitization and activation treatment to obtain MOF-based carbon fiber felt for flow battery electrodes.

2. The method for preparing MOF-based carbon fiber felt for flow battery electrodes according to claim 1, characterized in that: In step S1: The pre-oxidized felt is one or more of nano-polyacrylonitrile-based pre-oxidized felt, micron-polyacrylonitrile-based pre-oxidized felt, general-grade asphalt-based pre-oxidized felt, mesophase asphalt-based pre-oxidized felt, and viscose-based pre-oxidized felt; and / or The metal salt is one or more of zinc nitrate, zinc sulfate, zinc chloride, zinc acetate, cobalt nitrate, cobalt sulfate, cobalt chloride and cobalt acetate; and / or The solvent used for the metal salt solution is one or more of methanol, water, ethanol and dimethylformamide; and / or The solvent used in the 2-methylimidazole solution is one or more of methanol, water, ethanol and dimethylformamide.

3. The method for preparing MOF-based carbon fiber felt for flow battery electrodes according to claim 2, characterized in that: In step S1: The concentration of the metal salt solution is 10-60 g / L; and / or The concentration of the 2-methylimidazole solution is 15 to 120 g / L; and / or The volume ratio of the 2-methylimidazole solution to the metal salt solution is 1:(0.5-2).

4. The method for preparing MOF-based carbon fiber felt for flow battery electrodes according to claim 1, characterized in that: In step S1: The preoxidized felt is immersed in the metal salt solution for 5 to 60 minutes; and / or The temperature of the static reaction is 25 to 70° C., and the static reaction time is 6 to 24 hours; and / or The drying temperature is 40-100° C., and the drying time is 2-20 hours.

5. The method for preparing MOF-based carbon fiber felt for flow battery electrodes according to claim 4, characterized in that: The preoxidized felt is immersed in the metal salt solution for 10 to 30 minutes.

6. The method for preparing MOF-based carbon fiber felt for flow battery electrodes according to claim 1, characterized in that: In step S2: The carbonization treatment is carried out in a nitrogen atmosphere at 500-1600° C. for 0.3-4 hours; and / or The graphitization treatment is carried out in a nitrogen atmosphere at 1800-3000° C., and the graphitization time is 0.3-4 hours; and / or The activation treatment is carried out in an activation gas atmosphere at 500-1500° C., and the activation time is 0.5-5 hours.

7. The method for preparing MOF-based carbon fiber felt for flow battery electrodes according to claim 6, characterized in that: During the carbonization treatment, the carbonization temperature is 750-1500° C. and the carbonization time is 1-3 hours; and / or During the graphitization treatment, the graphitization temperature is 2000-2600° C. and the graphitization time is 1-3 hours; and / or During the activation treatment, the activation gas is carbon dioxide or water vapor, the activation temperature is 600-1200° C., and the activation time is 1-4 hours.

8. A MOF-based carbon fiber felt for flow battery electrodes prepared according to the method for preparing MOF-based carbon fiber felt for flow battery electrodes according to any one of claims 1 to 7, characterized in that: The specific surface area of ​​the MOF-based carbon fiber felt for the flow battery electrode is 300 to 500 m 2 / g, and the porosity is above 90%.

9. Use of MOF-based carbon fiber felt for flow battery electrodes prepared according to the method for preparing MOF-based carbon fiber felt for flow battery electrodes according to any one of claims 1 to 7 in flow battery electrodes.

10. The use according to claim 9, characterized in that: The flow battery electrode is made of MOF-based carbon fiber felt at a current density of 120 mA / cm 2 When the energy efficiency is ≥83%, the voltage efficiency is ≥84%, and the coulombic efficiency is ≥95%; and / or The flow battery electrode is made of MOF-based carbon fiber felt at a current density of 200 mA / cm 2 When the energy efficiency is ≥80%, the voltage efficiency is ≥81%, and the coulombic efficiency is ≥94%.

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