A membrane electrode and its preparation method, a flow battery

Abstract

This invention provides a membrane electrode and its preparation method, as well as a flow battery. The membrane electrode includes: a separation membrane; a first coating layer covering at least a portion of the surface of one side of the separation membrane; and a second coating layer covering at least a portion of the surface of the separation membrane away from the first coating layer. The first coating layer includes a first catalyst and a first electrode material, and the second coating layer includes a second catalyst and a second electrode material. The first catalyst and the second catalyst are different. The porosity of the separation membrane is 30%–50%, and the pore size is 20–100 nm. By setting coatings containing different catalysts on both sides of the separation membrane, a dual-catalyst membrane electrode is formed, reducing the mass transfer distance of the electrolyte charge-discharge reaction on both sides of the membrane. The catalysts on both sides of the separation membrane have a catalytic effect on the positive and negative electrode reactions, which can improve the reaction activity of the positive and negative electrodes respectively, thereby improving the charge-discharge coulombic efficiency, energy efficiency, and cycle stability of the flow battery.

Description

Technical Field

[0001] This application belongs to the field of flow battery technology, specifically relating to a membrane electrode and its preparation method, and a flow battery. Background Technology

[0002] Flow batteries, with their advantages of high safety, long cycle life, and large energy storage capacity, have broad application prospects in large-scale energy storage. Among them, the membrane electrode assembly (MEA), as the core component of a flow battery, plays a crucial role in battery performance. However, in existing flow battery MEAs, during proton transport and diffusion, the distance between the electrode and the membrane causes the conduction resistance to increase significantly with increasing distance. This results in the charging and discharging reactions mainly concentrated on the surface of the electrode materials on both sides of the membrane, limiting the reactive region.

[0003] Therefore, developing a membrane electrode suitable for flow batteries that can address the impact of mass transfer resistance on battery charge-discharge performance and improve energy conversion efficiency is a problem that needs to be solved. Summary of the Invention

[0004] The purpose of this application is to provide a membrane electrode and its preparation method, as well as a flow battery, in order to solve the problem of unsatisfactory energy conversion efficiency caused by mass transfer resistance in existing flow batteries.

[0005] The first embodiment of this application provides a membrane electrode, comprising:

[0006] Separation membrane;

[0007] A first coating is applied to at least a portion of the surface of one side of the separation membrane;

[0008] A second coating is applied to at least a portion of the surface of the separation membrane on the side away from the first coating;

[0009] The first coating comprises a first catalyst and a first electrode material, and the second coating comprises a second catalyst and a second electrode material; the first catalyst is different from the second catalyst.

[0010] The separation membrane has a porosity of 30% to 50% and a pore size of 20 to 100 nm.

[0011] In some embodiments, the first coating has a first thickness H1, the second coating has a second thickness H2, and the separation membrane has a third thickness H3, satisfying:

[0012] 7%≤(H1+H2) / H3≤25%.

[0013] In some embodiments, the first thickness H1 satisfies: 5μm≤H1≤12μm.

[0014] In some embodiments, the second thickness H2 satisfies: 5μm≤H2≤12μm.

[0015] In some embodiments, the third thickness H3 satisfies: 50μm≤H3≤76μm.

[0016] In some embodiments, the mass ratio of the first catalyst to the first electrode material is (10~40):(60~90).

[0017] In some embodiments, the mass ratio of the second catalyst to the second electrode material is (10~40):(60~90).

[0018] In some embodiments, the separation membrane includes at least one of perfluorosulfonic acid membrane, sulfonated polyether ether ketone membrane, polystyrene sulfonic acid membrane, polyimide sulfonic acid membrane, polybenzimidazole membrane, quaternized polyarylether ketone membrane, and alkyl sulfonate imidazole polysulfone.

[0019] In some embodiments, the first catalyst includes at least one of CeO2 and SnO2.

[0020] In some embodiments, the second catalyst includes at least one of Cu nanoparticles, Bi nanoparticles, Bi2O3, TiO2, and In.

[0021] In some embodiments, the first electrode material includes at least one of carbon black, carbon nanotubes, carbon nanofibers, carbon nanospheres, graphene, and noble metal powder.

[0022] In some embodiments, the second electrode material includes at least one of carbon black, carbon nanotubes, carbon nanofibers, carbon nanospheres, graphene, and noble metal powder.

[0023] In some embodiments, the first coating further includes a first adhesive, and the second coating further includes a second adhesive;

[0024] The mass ratio of the first catalyst, the first electrode material and the first binder is (10~40):(40~85):(5~10).

[0025] The mass ratio of the second catalyst, the second electrode material and the second binder is (10~40):(40~85):(5~10).

[0026] In some embodiments, the first adhesive comprises at least one of polytetrafluoroethylene and perfluorosulfonic acid ionomers.

[0027] In some embodiments, the second adhesive comprises at least one of polytetrafluoroethylene and perfluorosulfonic acid ionomer.

[0028] The second embodiment of this application provides a method for preparing a membrane electrode, which is used to prepare the membrane electrode in any of the above embodiments, and includes the following steps:

[0029] The first catalyst, the first electrode material, and the first binder are added to the first solvent to obtain the first slurry;

[0030] The second catalyst, the second electrode material, and the second binder are added to the second solvent to obtain the second slurry;

[0031] A separation membrane is provided, and the first slurry is coated on one side of the separation membrane to obtain a first coating;

[0032] The second slurry is coated onto the side of the separation membrane away from the first coating to obtain a second coating.

[0033] In some embodiments, the mass ratio of the first catalyst, the first electrode material and the first binder is (10~40):(40~85):(5~10).

[0034] In some embodiments, the mass ratio of the second catalyst, the second electrode material, and the second binder is (10~40):(40~85):(5~10).

[0035] In some embodiments, the solid content in the first slurry is 3-5%.

[0036] In some embodiments, the solid content in the second slurry is 3-5%.

[0037] In some embodiments, the first solvent includes at least one of acetone, deionized water, ethylene glycol dimethyl ether, ethanol, isopropanol, ethylene glycol, glycerol, acetonitrile, dimethyl sulfoxide, dimethylformamide, and N-methyl-2-pyrrolidone.

[0038] In some embodiments, the second solvent includes at least one of acetone, deionized water, ethylene glycol dimethyl ether, ethanol, isopropanol, ethylene glycol, glycerol, acetonitrile, dimethyl sulfoxide, dimethylformamide, and N-methyl-2-pyrrolidone.

[0039] The third embodiment of this application provides a flow battery, including the membrane electrode of any of the above embodiments, or including the membrane electrode prepared by the preparation method of any of the above embodiments.

[0040] This application forms a dual-catalyst membrane electrode by setting coatings containing different catalysts on both sides of the separation membrane. This reduces the mass transfer distance of the electrolyte charge-discharge reaction on both sides of the membrane, thereby reducing the mass transfer resistance. The catalysts on both sides of the separation membrane have a catalytic effect on the positive and negative electrode reactions, which can improve the reaction activity of the positive and negative electrodes respectively, improve the selectivity of the electrode reaction, and suppress the occurrence of side reactions such as hydrogen evolution to a certain extent. At the same time, it can also reduce the cross-migration and permeation of ions in the positive and negative electrolytes, and improve the charge-discharge coulombic efficiency, energy efficiency and cycle stability of the flow battery. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0043] Figure 1 This is a schematic diagram of a membrane electrode structure provided in an embodiment of this application;

[0044] Figure 2 A schematic diagram illustrating the fabrication process of a membrane electrode according to an embodiment of this application;

[0045] Figure 3 This is an exploded structural diagram of a flow battery provided in an embodiment of this application;

[0046] Figure 4 A scanning electron microscope image of the membrane electrode provided in Embodiment 1 of this application;

[0047] Figure 5 The energy dispersive spectroscopy (EDS) spectrum of the membrane electrode provided in Embodiment 1 of this application;

[0048] Figure 6 Impedance test results of the membrane electrode provided in Embodiment 1 and Comparative Example 1 of this application;

[0049] Figure 7 The graph shows the electrical performance test results of the flow batteries provided in Example 1 and Comparative Example 1 of this application;

[0050] Figure 8 The graph shows the electrical performance test results of the flow batteries provided in Example 2 and Comparative Example 2 of this application.

[0051] Explanation of reference numerals in the attached figures:

[0052] 11-Separation membrane, 12-First coating, 13-Second coating, 100-Membrane electrode, 200-Carbon felt, 300-Gluconate pad, 400-Electrode plate, 500-End plate, 600-Charge / discharge device, 700-First storage bottle, 800-Second storage bottle. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0054] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for mutual communication; they can refer to a direct connection, an indirect connection through an intermediate medium, or an indirect connection through a pipe or conduit; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. In the description of this application, "multiple" means two or more, unless otherwise expressly and specifically limited. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features.

[0055] Electrodes in flow batteries typically employ electrochemically stable conductive materials, such as carbon fiber felt in vanadium-based flow batteries and iron-chromium batteries. However, due to the influence of proton transport and diffusion rates, the conduction resistance increases with the distance from the membrane. The applicant's research has revealed that the charge-discharge reactions in flow batteries mainly concentrate on the surfaces of the electrode materials on both sides of the membrane. By combining the membrane and electrodes to create a "sandwich" structure integrated catalyst-coated membrane (CCM), the mass transfer distance can be shortened, reducing mass transfer resistance to some extent. Furthermore, introducing a catalyst into the electrode material can accelerate the kinetics of the electrode reaction, thereby improving the overall voltage and energy efficiency of the battery.

[0056] The first embodiment of this application provides a membrane electrode 100, such as... Figure 1 As shown, it includes:

[0057] Separation membrane 11;

[0058] The first coating 12 is applied to at least a portion of the surface of one side of the separation membrane 11;

[0059] The second coating 13 is applied to at least a portion of the surface of the separation membrane 11 on the side away from the first coating 12;

[0060] The first coating 12 includes a first catalyst and a first electrode material, and the second coating 13 includes a second catalyst and a second electrode material; the first catalyst and the second catalyst are different.

[0061] The separation membrane 11 has a porosity of 30%~50% and a pore size of 20~100nm.

[0062] It is understood that the porosity of the separation membrane 11 can be any value or a range between any two of 30%, 35%, 40%, 45%, and 50%, and the pore size (unit: nm) can be any value or a range between any two of 20, 40, 60, 80, and 100. The first catalyst and the second catalyst are the positive electrode catalyst and the negative electrode catalyst, respectively. By forming a membrane electrode 100 by providing coatings containing electrode materials and positive and negative electrode catalysts on both sides of the separation membrane 11, the contact between the catalyst layer and the electrolyte can be improved, the mass transfer distance can be shortened, and the reaction rate of electrochemical active materials in the flow battery and the energy efficiency of the battery can be enhanced. Introducing electrode materials into the catalyst layer can improve the conductivity of the membrane electrode 100 and increase the voltage efficiency of the battery. The membrane electrode 100 provided in this application can achieve a near-zero mass transfer distance between the electrodes on both sides of the membrane, significantly reducing the impact of mass transfer resistance on the charge and discharge performance of the battery. It also has a catalytic effect on the positive and negative electrode reactions, which can improve the reaction activity of the positive and negative electrodes respectively, improve the selectivity of the electrode reaction, and suppress side reactions such as hydrogen evolution to a certain extent, thereby improving the charge and discharge energy efficiency of the flow battery. By controlling the porosity and pore size of the separation membrane 11 to meet the above-mentioned value range, it can be ensured that the separation membrane 11 reduces the cross-migration and permeation of ions in the positive and negative electrolytes, further improving the charge and discharge coulombic efficiency, energy efficiency and cycle stability of the flow battery.

[0063] In some embodiments, the first coating 12 has a first thickness H1, the second coating 13 has a second thickness H2, and the separation membrane 11 has a third thickness H3, satisfying the following:

[0064] 7%≤(H1+H2) / H3≤25%.

[0065] It is understood that the value of (H1+H2) / H3 can be any value or a range between any two of the following: 7%, 10%, 13%, 16%, 19%, 22%, and 25%. When the thicknesses of the first coating 12, the second coating 13, and the separation membrane 11 satisfy the above relationship, it can be ensured that the formed membrane electrode 100 has both good conductivity and mass transfer resistance controlled within an ideal range.

[0066] In some embodiments, the first thickness H1 satisfies: 5μm≤H1≤12μm.

[0067] It is understandable that the value of H1 (unit: μm) can be any value of 5, 7, 9, 11, 12 or a range between any two values.

[0068] In some embodiments, the second thickness H2 satisfies: 5μm≤H2≤12μm.

[0069] It is understandable that the value of H2 (unit: μm) can be any value of 5, 7, 9, 11, 12 or a range between any two values.

[0070] In some embodiments, the third thickness H3 satisfies: 50μm≤H3≤76μm.

[0071] It is understood that the value of H3 (unit: μm) can be any value among 50, 55, 60, 65, 70, and 76, or a range between any two values. When H1, H2, and H3 satisfy the above value range, it can be further ensured that the formed membrane electrode 100 has both good conductivity and mass transfer resistance controlled within an ideal range.

[0072] In some embodiments, the mass ratio of the first catalyst to the first electrode material is (10~40):(60~90).

[0073] When the mass ratio of the first catalyst to the first electrode material meets the above-mentioned range, the first coating 12 can simultaneously possess good reactivity and electrical conductivity.

[0074] In some embodiments, the mass ratio of the second catalyst to the second electrode material is (10~40):(60~90).

[0075] When the mass ratio of the second catalyst to the second electrode material meets the above-mentioned range, the second coating 13 can simultaneously possess good reactivity and electrical conductivity.

[0076] In some embodiments, the separation membrane 11 can be at least one of a cation exchange membrane, an anion exchange membrane, a zwitterion membrane, a porous membrane, and a self-made ion exchange membrane or ion conduction membrane. The cation exchange membrane includes perfluorosulfonic acid membranes (Nafion), sulfonated polyether ether ketone membranes (SPEEK), polystyrene sulfonate membranes (PSS), and polyimide sulfonate membranes (SPI), among which perfluorosulfonic acid membranes are the most widely used due to their good chemical stability and conductivity, and can be used as a preferred separation membrane 11. The anion exchange membrane includes polybenzimidazole membranes (PBI) and quaternized polyarylene ether ketone membranes (AEMs), among others. The zwitterion membrane includes alkyl sulfonate imidazole polysulfone (PSf-MI-PS), among others. The porous membrane includes nanofiltration membranes, among others.

[0077] In some embodiments, the first catalyst comprises at least one of CeO2 and SnO2. The metals in CeO2 and SnO2 exhibit multivalent states and can exist in strongly acidic environments. Since the first catalyst is a positive electrode catalyst, its introduction facilitates the positive electrode reaction (e.g., VO2+) in the flow battery. 2+ / VO2 + It improves the reaction kinetics of redox pairs, and its morphology increases the electrochemical active surface area, providing more active sites for the reaction. At the same time, it accelerates charge transfer and vanadium ion diffusion, reduces polarization, and thus promotes redox reactions and enhances the performance of flow batteries.

[0078] In some embodiments, the second catalyst includes at least one of Cu nanoparticles, Bi nanoparticles, Bi₂O₃, TiO₂, and In. These substances possess high hydrogen evolution overpotentials and can stably provide electrocatalytic activity in strongly acidic environments. Since the second catalyst is a negative electrode catalyst, its introduction can reduce charge transfer resistance, thereby promoting the electron transfer process of the negative electrode reaction in the flow battery. Its morphology increases the electrochemical surface area of ​​the electrode, providing more active sites, and the high hydrogen evolution reaction potential can effectively suppress the occurrence of side reactions such as the negative electrode hydrogen evolution reaction. Preferably, the second catalyst can be Bi₂O₃. In iron-chromium flow batteries, Bi₂O₃ can catalyze the electrochemical overpotential of Cr₂O₃. 3+ / Cr 2+ It exhibits superior performance in inhibiting hydrogen evolution reaction while simultaneously undergoing redox reactions.

[0079] In some embodiments, the first electrode material includes at least one of carbon black, carbon nanotubes, carbon nanofibers, carbon nanospheres, graphene, and noble metal powder.

[0080] In some embodiments, the second electrode material includes at least one of carbon black, carbon nanotubes, carbon nanofibers, carbon nanospheres, graphene, and noble metal powder.

[0081] It is understood that the first electrode material and the second electrode material can be the same or different. The noble metal can be at least one of platinum, gold, palladium, iridium, etc. These electrode materials possess good electrical conductivity and the characteristic of being stable in a strong acid environment. Coating these materials as positive and negative electrode materials on both sides of the separation membrane 11 can, on the one hand, directly support the redox reaction of the electrochemically active substances in the solution, and on the other hand, serve as a catalyst support, improving the conductivity of the catalyst and giving the composite coating formed with the catalyst a higher specific surface area, thereby improving the catalytic efficiency of the catalyst and preventing the cross-penetration of ions in the positive and negative electrode electrolytes.

[0082] In some embodiments, the first coating 12 further includes a first adhesive, and the second coating 13 further includes a second adhesive;

[0083] The mass ratio of the first catalyst, the first electrode material and the first binder is (10~40):(40~85):(5~10).

[0084] The mass ratio of the second catalyst, the second electrode material and the second binder is (10~40):(40~85):(5~10).

[0085] It is understandable that by adding a binder, the electrode material and the catalyst can be more uniformly and firmly fixed in their respective coatings. When the mass ratio of the first catalyst, the first electrode material, and the first binder meets the above-mentioned values, the first coating 12 has good adhesion and catalytic performance; when the mass ratio of the second catalyst, the second electrode material, and the second binder meets the above-mentioned values, the second coating 13 has good adhesion and catalytic performance.

[0086] In some embodiments, the first adhesive comprises at least one of polytetrafluoroethylene and perfluorosulfonic acid ionomer.

[0087] In some embodiments, the second adhesive comprises at least one of polytetrafluoroethylene and perfluorosulfonic acid ionomer.

[0088] It is understandable that the first adhesive and the second adhesive can be the same or different.

[0089] The second embodiment of this application provides a method for preparing a membrane electrode 100, which is used to prepare the membrane electrode 100 in any of the above embodiments, and includes the following steps:

[0090] The first catalyst, the first electrode material, and the first binder are added to the first solvent to obtain the first slurry;

[0091] The second catalyst, the second electrode material, and the second binder are added to the second solvent to obtain the second slurry;

[0092] A separation membrane 11 is provided, and a first slurry is coated on one side of the separation membrane 11 to obtain a first coating 12;

[0093] The second slurry is coated on the side of the separation membrane 11 away from the first coating 12 to obtain the second coating 13.

[0094] By adding a first catalyst, a first electrode material, and a first binder to a first solvent, and adding a second catalyst, a second electrode material, and a second binder to a second solvent, a uniformly dispersed composite slurry can be formed. This allows the solutes in both the first and second slurries to form a uniform coating after application, while also ensuring a good interfacial structure at the catalyst / ionomer interface. The rheological properties and pH value of the solvent both affect the catalyst dispersibility and the interaction between the catalyst and the ionomer. Appropriately adjusting the solvent polarity can improve the performance of the membrane electrode 100, and solvents with lower dielectric constants can help the perfluorosulfonic acid membrane form a good proton transport structure, thereby further improving its proton conductivity.

[0095] In some embodiments, the method of coating the first slurry on one side of the separation membrane 11 and the method of coating the second slurry on the side of the separation membrane 11 away from the first coating 12 are as follows: Figure 2 As shown, the coating methods include: direct coating, dip coating, spray coating, blade coating, transfer coating, electro-spray coating, vacuum deposition, screen printing, inkjet printing, and roller coating. Among these, screen printing, inkjet printing, and roller coating are suitable for large-scale production.

[0096] Furthermore, when the coating method is spraying, the coating steps include:

[0097] The separation membrane 11 is placed on a heating plate and heated, and the temperature is controlled to be maintained at 85℃~100℃;

[0098] The first slurry is dispersed into a mist and sprayed onto one side of the separation membrane 11 using a spray gun device to form a first coating 12.

[0099] The second slurry is dispersed into a mist and sprayed onto the other side of the separation membrane 11 using a spray gun device to form a second coating 13.

[0100] By controlling the heating plate to maintain a specific temperature, the risk of film deformation can be reduced while ensuring rapid solvent evaporation.

[0101] In some embodiments, the first catalyst comprises at least one of CeO2 and SnO2. The second catalyst comprises at least one of Cu nanoparticles, Bi nanoparticles, TiO2, and In. The first electrode material comprises at least one of carbon black, carbon nanotubes, carbon nanofibers, carbon nanospheres, graphene, and noble metal powder. The second electrode material comprises at least one of carbon black, carbon nanotubes, carbon nanofibers, carbon nanospheres, graphene, and noble metal powder. The second binder comprises at least one of polytetrafluoroethylene and perfluorosulfonic acid ionomers. The first binder comprises at least one of polytetrafluoroethylene and perfluorosulfonic acid ionomers.

[0102] In some embodiments, the mass ratio of the first catalyst, the first electrode material and the first binder is (10~40):(40~85):(5~10).

[0103] In some embodiments, the mass ratio of the second catalyst, the second electrode material, and the second binder is (10~40):(40~85):(5~10).

[0104] It is understood that when the mass ratio of the first catalyst, the first electrode material, and the first binder meets the above-mentioned values, the first coating 12 has good adhesion and catalytic performance; when the mass ratio of the second catalyst, the second electrode material, and the second binder meets the above-mentioned values, the second coating 13 has good adhesion and catalytic performance.

[0105] In some embodiments, the solid content in the first slurry is 3-5%.

[0106] It is understandable that the solid content in the first slurry can be any value of 3%, 4%, or 5%, or a value within any two of these values.

[0107] In some embodiments, the solid content in the second slurry is 3-5%.

[0108] It is understandable that the solid content in the second slurry can be any two values ​​from 3%, 4%, and 5%, or any value within a range between two values. If the solid content of the slurry is too low, excessive solvent will cause the membrane to swell and deform, damaging the mechanical strength of the membrane, and will also lead to uneven catalyst distribution. If the solid content of the slurry is too high, the coating structure will be loose and easy to fall off, affecting the operational stability of the membrane electrode 100. When the solid content in the first and second slurries meets the above-mentioned value range, the first coating 12 formed by the first slurry and the second coating 13 formed by the second slurry can have good mechanical strength, uniformity, and adhesion.

[0109] In some embodiments, the first solvent includes at least one of acetone, deionized water, ethylene glycol dimethyl ether, ethanol, isopropanol, ethylene glycol, glycerol, acetonitrile, dimethyl sulfoxide, dimethylformamide, and N-methyl-2-pyrrolidone.

[0110] In some embodiments, the second solvent includes at least one selected from acetone, deionized water, ethylene glycol dimethyl ether, ethanol, isopropanol, ethylene glycol, glycerol, acetonitrile, dimethyl sulfoxide, dimethylformamide, and N-methyl-2-pyrrolidone.

[0111] The third embodiment of this application provides a flow battery, including the membrane electrode 100 in any of the above embodiments, or including the membrane electrode 100 prepared by the preparation method in any of the above embodiments.

[0112] like Figure 3 As shown, specifically, the flow battery includes a membrane electrode 100, a carbon felt 200, a rubber pad 300, an electrode plate 400, and an end plate 500. The carbon felt 200, the rubber pad 300, the electrode plate 400, and the end plate 500 are each in two sets and are arranged symmetrically about the membrane electrode 100.

[0113] Two sets of carbon felt 200 are respectively covered on at least part of the surface on both sides of the membrane electrode 100, serving as an electronic conductor between the membrane electrode 100 and the electrode plate 400, as well as an ion diffusion region in the electrode reaction, and also as a transverse conductive layer for the positive and negative electrode electrolyte inlet and outlet channels.

[0114] Two sets of rubber pads 300 are respectively covered on at least a portion of the surface of two sets of carbon felts 200 to buffer the contact pressure between the membrane electrode 100, the carbon felt 200 and the electrode plate 400.

[0115] Two sets of electrode plates 400 are respectively covered on at least part of the surface of two sets of rubber pads 300. The surface of the electrode plate 400 near the rubber pad 300 is provided with a flow channel for the electrolyte to enter and exit the electrode plate 400, so as to guide the electrolyte, thereby promoting the uniform distribution of reactants and increasing the effective reaction area of ​​the dual catalytic membrane electrode 100.

[0116] Two sets of end plates 500 are respectively covered on at least a portion of the surfaces of two sets of electrode plates 400, for fixing the membrane electrode 100, carbon felt 200, rubber pad 300 and electrode plate 400 disposed between the two sets of end plates 500.

[0117] When the flow battery is working, such as Figure 3 As shown, the two sets of electrode plates 400 are electrically connected through the charge-discharge device 600. The end plate 500 located on the positive electrode side of the membrane electrode 100 is connected to the first storage bottle 700 containing the positive electrolyte, and the end plate 500 located on the negative electrode side of the membrane electrode 100 is connected to the second storage bottle 800 containing the negative electrolyte, thus forming a circuit.

[0118] The following description, in conjunction with specific embodiments, illustrates the membrane electrode 100 and its preparation method, as well as the flow battery provided in this application:

[0119] Example 1

[0120] This embodiment provides a dual-catalyst-membrane electrode 100, which is used to construct an all-vanadium redox flow battery system.

[0121] Preparation of the first slurry on the positive electrode side of membrane electrode 100: Weigh 500 mg of Vulcan XC72R carbon black and 50 mg of CeO2 positive electrode catalyst and place them in a beaker. Add 5 mL of deionized water and 50 mL of isopropanol solution to the beaker, and then add 54 μL of Nafion membrane solution (5wt%) as a binder. Sonicate in an ice bath for 30 min to disperse the slurry evenly.

[0122] Preparation of the second slurry on the negative electrode side of membrane electrode 100: Weigh 500 mg of Vulcan XC72R carbon black and 50 mg of Bi2O3 negative electrode catalyst and place them in a beaker. Add 50 mL of deionized water and 100 mL of isopropanol solution to the beaker, and then add 54 μL of Nafion membrane solution (5wt%) as a binder. Sonicate in an ice bath for 30 min to disperse the slurry evenly.

[0123] Preparation of the dual-catalyst membrane electrode 100: A commercially available Nafion 212 membrane was cut into a 6cm × 8cm rectangle. The membrane was immersed in 5% H2O2 solution and 1M H2SO4 at 80℃ for 1 hour to remove organic contaminants. It was then rinsed with deionized water to remove residual acid and dried at 70℃ for 12 hours. Before spraying, the surface of the heating plate was cleaned alternately with ethanol and deionized water. The pretreated membrane was then placed on the heating plate, and the temperature was maintained at 85℃ to allow the slurry solvent to evaporate quickly. Using a spray gun, the air pump was turned on, and the spraying height was adjusted. The gun was moved evenly, slowly, and regularly in a zigzag pattern, and the first and second slurries were dispersed into a mist and sprayed onto both sides of the membrane surface in small amounts using gas pressure. Finally, the membrane was dried in a 70℃ oven for 12 hours to obtain the dual-catalyst membrane electrode 100.

[0124] The fabricated membrane electrode 100 was scanned by electron microscopy, and the results are as follows: Figure 4 As shown; and energy dispersive spectroscopy (EDS) analysis was performed on the fabricated membrane electrode 100, the results of which are as follows. Figure 5 As shown, the prepared membrane electrode 100 has positive and negative electrode catalysts uniformly loaded on both sides.

[0125] The aforementioned dual-catalyst-membrane electrode 100 is assembled with carbon felt 200, rubber pad 300, electrode plate 400, and end plate 500 to form a flow battery, such as... Figure 3As shown, the positive electrode electrolyte is 3M H2SO4 + 2M VO2SO4. 2+ The solution, the negative electrode electrolyte is 3M H2SO4 + 2M V 3+ Solution.

[0126] Comparative Example 1

[0127] This comparative example uses a commercially available Nafion 212 membrane as the ion exchange membrane, and is assembled with carbon felt 200, rubber pad 300, electrode plate 400 and end plate 500 to form a flow battery. The positive and negative electrode electrolytes of the flow battery are the same as those in Example 1.

[0128] The membrane electrode 100 provided in Example 1 and the Nafion 212 membrane provided in Comparative Example 1 were subjected to EIS electrochemical impedance spectroscopy (EIS) tests. The test procedures were performed in accordance with ASTM G106-89 (2023), "Standard Implementation Procedure for Electrochemical Impedance Measurement Algorithms and Equipment Validation." The test results are as follows: Figure 6 As shown. According to Figure 6 As can be seen, the introduction of the dual-catalyst-membrane electrode 100 provided in Example 1 reduces the sheet resistance of the membrane and increases the overall voltage efficiency of the battery (Note: the blank control group was tested with 3M H2SO4 solution under conditions without ion exchange membrane).

[0129] The flow batteries provided in Example 1 and Comparative Example 1 were subjected to electrical performance tests. The test steps included:

[0130] 1. Assemble a single battery, connect the positive and negative electrolyte storage tanks respectively, and connect the charge / discharge test platform;

[0131] 2. Set the parameters and perform a constant power 10W charge and discharge test. Set the charging cutoff voltage to 1.58V, the discharging cutoff voltage to 1V, and the number of cycles to 100. Start the charge and discharge test platform to perform the test.

[0132] Test results are as follows Figure 7 As shown in Table 1.

[0133] Table 1

[0134]

[0135] according to Figure 7 As shown in Table 1, the membrane electrode 100 provided in Example 1 has stable physicochemical properties and high electrochemical activity when used in a vanadium redox flow battery. The flow battery prepared in Example 1 shows significant improvements in capacity retention, energy efficiency, and coulombic efficiency compared to Comparative Example 1, which only uses an ion-exchange membrane. Under constant power of 10W and with the water bath temperature maintained at 35℃, after 100 cycles, the average energy efficiency was 84.19%, the average coulombic efficiency was 96.71%, and the capacity retention reached 105.95%.

[0136] Example 2

[0137] This embodiment provides a dual-catalyst-membrane electrode 100, which is used to construct an iron-chromium redox flow battery system.

[0138] Preparation of the first slurry on the positive electrode side of membrane electrode 100: Weigh 500 mg of Vulcan XC72R carbon black and 50 mg of SnO2 positive electrode catalyst and place them in a beaker. Add 50 mL of deionized water and 100 mL of isopropanol solution to the beaker, and then add 54 μL of Nafion membrane solution (5wt%) as a binder. Sonicate in an ice bath for 30 min to disperse the slurry evenly.

[0139] Preparation of the second slurry on the negative electrode side of membrane electrode 100: Weigh 500 mg of Vulcan XC72R carbon black and 50 mg of Bi2O3 negative electrode catalyst and place them in a beaker. Add 50 mL of deionized water and 100 mL of isopropanol solution to the beaker, and then add 54 μL of Nafion membrane solution (5wt%) as a binder. Sonicate in an ice bath for 30 min to disperse the slurry evenly.

[0140] Preparation of the dual-catalyst membrane electrode 100: Commercially available Nafion 212 membranes were cut into 6cm × 8cm rectangles. The membranes were immersed in 5% H₂O₂ solution and 1M H₂SO₄ at 80℃ for 1 hour to remove organic contaminants. They were then rinsed with deionized water to remove residual acid and dried at 70℃ for 12 hours. Before spraying, the surface of the heating plate was cleaned alternately with ethanol and deionized water. The pretreated membrane was then placed on the heating plate, maintaining a temperature of 85℃. Further, using a spray gun, the air pump was turned on, and the spraying height was adjusted. The gun was moved evenly, slowly, and regularly in a zigzag pattern, using gas pressure to disperse the prepared positive and negative electrode catalyst slurries into a mist and spray them onto both sides of the membrane. Finally, the membrane was dried in a 70℃ oven for 12 hours to obtain the dual-catalyst membrane electrode 100.

[0141] The aforementioned dual-catalyst-membrane electrode 100 is assembled with carbon felt 200, rubber pad 300, electrode plate 400, and end plate 500 to form a flow battery, such as... Figure 3 As shown, both the positive and negative electrode electrolytes are composed of 1 M FeCl2 + 1 M CrCl3 + 3 M HCl solution.

[0142] Comparative Example 2

[0143] This comparative example uses a commercially available Nafion 212 membrane as the ion exchange membrane and assembles it with carbon felt 200, rubber pad 300, electrode plate 400 and end plate 500 to form a flow battery. The positive and negative electrolytes of the flow battery are the same as those in Example 2.

[0144] The flow batteries provided in Example 2 and Comparative Example 2 were subjected to electrical performance tests, and the test results are as follows: Figure 8 As shown in Table 2.

[0145] Table 2

[0146]

[0147] according to Figure 8 As shown in Table 2, the flow battery prepared in Example 2 exhibits significantly improved performance in terms of capacity retention, energy efficiency, and coulombic efficiency compared to Comparative Example 2, which only uses an ion exchange membrane. Under constant power testing conditions of 10W, after 100 cycles, the average capacity retention reached 91.52%, the average coulombic efficiency was 99.41%, the average energy efficiency was 71.14%, and the average discharge specific energy was 8.47Wh / L.

[0148] The membrane electrode 100 and its preparation method, as well as the flow battery, provided in the embodiments of this application have been described in detail above. Specific examples have been used in this application to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A membrane electrode, characterized by, A membrane electrode for a flow battery comprises: a separation membrane (11); a first coating layer (12) coated on at least part of the surface of one side of the separation membrane (11); a second coating layer (13) coated on at least part of the surface of the side of the separation membrane (11) away from the first coating layer (12); wherein the first coating layer (12) comprises a first catalyst and a first electrode material; the first catalyst comprises at least one of CeO2 and SnO2, the first electrode material comprises at least one of carbon black, carbon nanotube, carbon nanofiber, nanometer carbon sphere, graphene and noble metal powder, and the mass ratio of the first catalyst to the first electrode material is (10-40):(60-85) so that the first electrode material serves as a carrier of the first catalyst; the second coating layer (13) comprises a second catalyst and a second electrode material; the second catalyst comprises at least one of Cu nanoparticles, Bi nanoparticles, Bi2O3, TiO2 and In, the second electrode material comprises at least one of carbon black, carbon nanotube, carbon nanofiber, nanometer carbon sphere, graphene and noble metal powder, and the mass ratio of the second catalyst to the second electrode material is (10-40):(60-85) so that the second electrode material serves as a carrier of the second catalyst; the porosity of the separation membrane (11) is 30%-50% and the pore size is 20-100 nm; the first coating layer (12) has a first thickness H1, the second coating layer (13) has a second thickness H2, and the separation membrane (11) has a third thickness H3, and the following condition is met: 7%≤(H1+H2) / H3≤25%.

2. The membrane electrode according to claim 1, wherein the first thickness H1 meets: 5 μm≤H1≤12 μm; and / or, the second thickness H2 meets: 5 μm≤H2≤12 μm; and / or, the third thickness H3 meets: 50 μm≤H3≤76 μm.

3. The membrane electrode of claim 1, wherein the separation membrane (11) comprises at least one of a perfluorosulfonic acid membrane, a sulfonated polyether ether ketone membrane, a polystyrene sulfonic acid membrane, a polyimide sulfonic acid membrane and a polybenzimidazole membrane.

4. The membrane electrode of claim 1, wherein the first coating layer (12) comprises a first adhesive, and the second coating layer (13) further comprises a second adhesive; wherein the mass ratio of the first catalyst, the first electrode material and the first adhesive is (10-40):(60-85):(5-10); the mass ratio of the second catalyst, the second electrode material and the second adhesive is (10-40):(60-85):(5-10).

5. The membrane electrode of claim 4, wherein the first adhesive comprises at least one of polytetrafluoroethylene and perfluorosulfonic acid ionomer; the second adhesive comprises at least one of polytetrafluoroethylene and perfluorosulfonic acid ionomer.

6. A method for producing a membrane electrode as claimed in any one of claims 1 to 5, characterized in that comprising the following steps: adding a first catalyst, a first electrode material and a first adhesive into a first solvent to obtain a first slurry; adding a second catalyst, a second electrode material and a second adhesive into a second solvent to obtain a second slurry; A separation film (11) is provided, the first slurry is coated on one side of the separation film (11) to obtain a first coating layer (12); The second slurry is coated on the side of the separation film (11) away from the first coating layer (12) to obtain a second coating layer (13).

7. The method of claim 6, wherein, The mass ratio of the first catalyst, the first electrode material and the first binder is (10-40):(60-85):(5-10); The mass ratio of the second catalyst, the second electrode material and the second binder is (10-40):(60-85):(5-10); The solid content in the first slurry is 3-5%; The solid content in the second slurry is 3-5%.

8. The method of claim 6, wherein, The first solvent comprises at least one of acetone, deionized water, ethylene glycol dimethyl ether, ethanol, isopropyl alcohol, ethylene glycol, glycerol, acetonitrile, dimethyl sulfoxide, dimethyl formamide and N-methyl-2-pyrrolidone; and / or, The second solvent comprises at least one of acetone, deionized water, ethylene glycol dimethyl ether, ethanol, isopropyl alcohol, ethylene glycol, glycerol, acetonitrile, dimethyl sulfoxide, dimethyl formamide and N-methyl-2-pyrrolidone.

9. A flow battery comprising a membrane electrode (100), characterized in that The membrane electrode (100) is the membrane electrode (100) of any one of claims 1-5, or the membrane electrode (100) is prepared by the method of any one of claims 7-8.

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