Ion exchange membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of polymeric membranes, in particular to an ion exchange membrane and a preparation method and application thereof. The ion exchange membrane provided by the invention is obtained by reacting polyarylether containing pyridyl and cyano with a protonation reagent. Polyarylether containing pyridyl and cyano is adopted as a raw material, the polymer is endowed with alkaline sites by utilizing the pyridyl, the pyridyl is subjected to protonation by soaking in a protonation reagent, the protonated pyridyl is generated, and the ion exchange membrane is endowed with high proton conductivity. Moreover, the strongly polar cyano group can enhance the acting force between molecular chains and improve the rigidity of the molecular chains to inhibit swelling of the membrane, so that the chemical stability and the dimensional stability of the ion exchange membrane material are improved, and meanwhile, the mechanical property of the ion exchange membrane material can be improved. The ion exchange membrane has a wide application prospect in flow batteries such as a vanadium flow battery and an iron-chromium flow battery.

Description

An ion exchange membrane, its preparation method and application Technical Field

[0001] This invention relates to the field of polymer membrane technology, specifically to an ion exchange membrane, its preparation method, and its application. Background Technology

[0002] Flow batteries are among the most promising energy storage technologies currently available. Their power and capacity can be independently designed, offering advantages such as design flexibility, large capacity, safety, and environmental friendliness. They are suitable for large-scale energy storage and can be applied to renewable energy generation and storage, emergency power systems, backup power stations, and peak shaving and valley filling in power systems. In flow batteries, the separator is a key component, its function being to conduct ions while isolating the positive and negative electrolytes. Its performance directly affects the battery's efficiency and lifespan. Therefore, an ideal separator needs to possess low sheet resistance (high ionic conductivity), low active material permeability (high selectivity), and good chemical stability and mechanical strength.

[0003] Currently, perfluorinated ion exchange membranes (such as Nafion membranes) are widely used membrane materials due to their excellent conductivity and chemical stability. However, their high cost and limited ability to block vanadium ions lead to reduced coulombic efficiency and capacity decay, limiting their application in large-scale energy storage.

[0004] To reduce costs, non-fluorinated ion exchange membranes have become a research hotspot. These membranes mainly include sulfonated polymer membranes and quaternized polymer membranes, such as sulfonated or quaternized polyaryletherketones and polyarylethersulfones. These membranes improve ion conductivity by introducing ion exchange groups (such as sulfonic acid groups and quaternary ammonium groups). However, increasing the ion exchange capacity often leads to excessive swelling of the membrane in the aqueous electrolyte, resulting in decreased mechanical properties, reduced selectivity, and poorer chemical stability, making it difficult to maintain stable performance during long-term operation. Summary of the Invention

[0005] To address the technical problems of excessive swelling and decreased stability in existing non-fluorinated ion exchange membranes due to increased ion conductivity, this invention provides an ion exchange membrane, its preparation method, and its applications. The ion exchange membrane prepared by this invention simultaneously possesses low swelling, high ion selectivity, good chemical stability, and excellent battery performance. Furthermore, its preparation method is simple and environmentally friendly, showing promise for large-scale industrialization.

[0006] This invention imparts ion exchange capability by simultaneously introducing pyridine and cyano groups into the polyaryl ether backbone and protonating the pyridine groups using a protonating agent. The strong polarity of the cyano group and its synergistic effect with the polyaryl ether backbone effectively suppresses excessive swelling of the membrane in the aqueous electrolyte, improving the membrane's dimensional stability and mechanical strength. The protonated pyridine group provides a highly efficient ion transport channel, ensuring proton conductivity. While maintaining high ion conductivity, the swelling degree of the membrane is significantly reduced, thus resolving the contradiction between ion conductivity and swelling stability in traditional non-fluorinated ion exchange membranes.

[0007] The first objective of this invention is to provide an ion exchange membrane, which is obtained by mixing a polyarylene ether containing pyridine and cyano groups with a solvent, performing a film-forming treatment, sequentially immersing it in a protonating reagent for a protonation reaction, and then immersing it in a sulfuric acid solution for sulfate ion exchange treatment; the protonating reagent is an acid; the chemical structural formula of the polyarylene ether containing pyridine and cyano groups is as follows: In the formula, y = 0.2~1.0, n = 50~1000; Ar1 ​​is selected from any one of the following groups: Ar2 is Ar3 is selected from any one of the following groups: Ar4 is selected from any one of the following groups: .

[0008] Preferably, n = 100 to 500.

[0009] Preferably, the method for preparing polyaryl ethers containing pyridinyl and cyano groups is as follows: under a protective atmosphere, bisphenol containing an Ar3 structure, 2,6-difluorobenzonitrile, and a dihaloaromatic monomer undergo a polycondensation reaction under alkaline catalysis to obtain polyaryl ethers containing pyridinyl and cyano groups; the bisphenol containing an Ar3 structure is 4,4'-phenyl(pyridin-4-yl)methylene)bisphenol, bisphenol A, hexafluorobisphenol A, biphenyl, hydroquinone, 4,4'-dihydroxybenzophenone, or 9,9-bis(4-hydroxyphenyl)anthrone; the dihaloaromatic monomer is 4,4'-difluoroxylenone or 4,4'-difluorodiphenyl sulfone.

[0010] Preferably, the molar ratio of bisphenol containing the Ar3 structure, 2,6-difluorobenzonitrile, and dihaloaromatic monomer is 5:2 to 4:1 to 2.

[0011] Preferably, the specific preparation method of polyarylene ethers containing pyridine and cyano groups is as follows: Under a protective atmosphere, bisphenol containing Ar3 structure, 2,6-difluorobenzonitrile, dihaloaromatic monomer and base are dissolved in a second solvent, and polycondensation reaction is carried out at 140℃~180℃ to obtain polyarylene ethers containing pyridine and cyano groups.

[0012] Preferably, the bisphenol containing the Ar3 structure is 4,4'-phenyl(pyridin-4-yl)methylene)diphenol.

[0013] Preferably, the second solvent is 1-methyl-2-pyrrolidone, N,N-dimethylacetamide, or dimethyl sulfoxide.

[0014] Preferably, the protonating agent is at least one of phosphoric acid, sulfuric acid, hydrochloric acid, methanesulfonic acid, and trifluoromethanesulfonic acid.

[0015] Preferably, the mass concentration of the protonating agent is 1 wt.% to 100 wt.%; more preferably, the mass concentration of the protonating agent is 40 wt.% to 50 wt.%.

[0016] Preferably, the concentration of the sulfuric acid solution is 2 mol / L to 5 mol / L.

[0017] The second objective of this invention is to provide a method for preparing an ion exchange membrane, comprising the following steps: dissolving a polyarylene ether containing pyridinyl and cyano groups in a first solvent and casting it into a membrane to obtain a base membrane; immersing the base membrane in a protonating reagent to perform a protonation reaction to protonate the pyridinyl groups, thereby obtaining a protonated membrane; and immersing the protonated membrane in a sulfuric acid solution to replace the anions in the protonated membrane with sulfate ions, thereby obtaining an ion exchange membrane.

[0018] Preferably, the base is sodium carbonate or potassium carbonate; the first solvent is N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, chloroform, 1,1,2,2-tetrachloroethane, dimethyl sulfoxide, or sulfolane.

[0019] Preferably, the protonation reaction is carried out at a temperature of 25°C to 160°C for a time of 2 hours to 24 hours. More preferably, the protonation reaction is carried out at a temperature of 25°C to 40°C.

[0020] Preferably, a third objective of the present invention is to provide the application of ion exchange membranes as separators in flow batteries.

[0021] Preferably, the flow energy storage battery includes, but is not limited to, vanadium redox flow batteries and iron-chromium redox flow batteries.

[0022] Compared with existing technologies, this invention has the following technical advantages: The ion exchange membrane of this invention is obtained by protonation and ion exchange treatment of polyaryl ethers containing pyridine and cyano groups. By simultaneously introducing pyridine and cyano groups into the polyaryl ether backbone, the strongly polar cyano group enhances the intermolecular forces of the polyaryl ether molecular chains through dipole-dipole interactions and conjugation with the aromatic rings of the backbone, forming a more compact network structure. This effectively suppresses excessive water absorption and swelling of the ion exchange membrane in aqueous electrolytes, endowing the ion exchange membrane with excellent dimensional stability and mechanical strength. Simultaneously, the protonated pyridine group provides effective ion transport sites, ensuring proton conductivity. Furthermore, the dense structure enhanced by the cyano group significantly blocks the transmembrane permeation of active substances such as vanadium ions. While ensuring high ion conductivity, it significantly reduces the swelling degree of the ion exchange membrane, thus resolving the contradiction between ion conductivity and swelling stability in traditional non-fluorinated ion exchange membranes.

[0023] The polyarylene backbone of this invention has excellent chemical inertness, and the introduced cyano and protonated pyridinyl groups also exhibit good stability under strong acidic oxidizing conditions, enabling the ion exchange membrane to maintain stable performance during long-term battery operation and extend battery life.

[0024] This invention synthesizes polyarylene ethers containing pyridinyl and cyano groups through a one-step condensation polymerization process and adopts a post-protonation process, which completely avoids the highly toxic chloromethylation reagents used in the preparation of traditional quaternary ammonium membranes. The synthesis route is short, the conditions are mild, and the environment is environmentally friendly, and it has the potential for large-scale industrial production. Attached Figure Description

[0025] Figure 1 shows the 1H NMR spectrum of the polyarylene containing pyridyl and cyano groups prepared in Example 1.

[0026] Figure 2 shows the 1H NMR spectrum of the polyarylene containing pyridyl and cyano groups prepared in Example 2.

[0027] Figure 3 shows the 1H NMR spectrum of the pyridine-containing polyarylether ketone prepared in Comparative Example 1.

[0028] Figure 4 shows the swelling ratio of the ion exchange membranes prepared in Example 1, Example 2 and Comparative Example 1.

[0029] Figure 5 shows the sheet resistance of the ion exchange membranes prepared in Example 1, Example 2 and Comparative Example 1.

[0030] Figure 6 shows the tensile strength of the base membrane and ion exchange membrane prepared in Examples 1, 2 and Comparative Example 1.

[0031] Figure 7 shows the cycling data of the ion exchange membrane prepared in Example 1 in a vanadium redox flow battery.

[0032] Figure 8 shows the battery energy efficiency of the ion exchange membranes prepared in Examples 1, 2 and Comparative Example 1 after oxidation testing. Detailed Implementation

[0033] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0034] It should be noted that the full English name of 4,4'-phenyl(pyridin-4-yl)methylene)diphenol is 4,4'-DihydroxytriphenylMethane, abbreviated as PyDP; the full English name of 2,6-difluorobenzonitrile is 2,6-Difluorobenzonitrile, abbreviated as 2,6-DFBN; the full English name of 4,4'-difluorodiphenylmethanone is 4,4′-Difluorodiphenylmethanone, abbreviated as DFK; and the Chinese name of NMP is N-methylpyrrolidone.

[0035] Example 1: A method for preparing an ion exchange membrane, comprising the following steps: Step 1: Preparation of polyarylene ethers containing pyridinyl and cyano groups: In a three-necked flask equipped with a mechanical stirrer, a water separator, and nitrogen inlet and outlet, 6.3655 g of PyDP, 1.0021 g of 2,6-DFBN, and 2.3580 g of DFK were added sequentially. Then, 1.9348 g of K2CO3, 5 mL of 1-methyl-2-pyrrolidone, and 5 mL of toluene were added. Under nitrogen protection, the mixture was refluxed at 140°C for 4 hours to remove water. Subsequently, the toluene was distilled off, and the reaction temperature was raised to 160°C and maintained for 10 hours. After the reaction was completed, the polymer solution was poured into water to precipitate the polymer. The obtained polymer was washed four times with hot water and then dried to obtain polyarylene ethers containing pyridinyl and cyano groups. The specific synthetic route is as follows:

[0036] .

[0037] In the structural formula of the polyaryl ether containing pyridinyl and cyano groups, n is 200. The 1H NMR spectrum of the polyaryl ether containing pyridinyl and cyano groups is shown in Figure 1, indicating the successful synthesis of the polyaryl ether containing pyridinyl and cyano groups. The term "Chemical shift" in Figure 1 refers to this process.

[0038] Step 2: Preparation of ion exchange membrane: Weigh 0.5 g of polyarylene ether containing pyridinyl and cyano groups into a 10 mL centrifuge tube, add 3.65 mL of N-methylpyrrolidone to prepare a casting solution, and centrifuge the casting solution to remove impurities and perform vacuum degassing. Use a 500 μm scraper to cast the centrifuged casting solution onto a glass plate, dry at 70°C for 4 h, and then immerse the cast glass plate in distilled water to obtain a base membrane with a thickness of 30 μm to 40 μm, denoted as PyPENK 4:6 virgin.

[0039] PyPENK 4:6 virgin was protonated in 50 wt.% phosphoric acid at 40 °C for 4 h to obtain an ion exchange membrane containing protonated pyridinyl and cyano groups, denoted as PyPENK 4:6 phosphoric acid doped membrane.

[0040] The PyPENK 4:6 phosphate-doped membrane was immersed in a 3M sulfuric acid solution for 24 hours to allow the phosphate molecules in the PyPENK 4:6 phosphate-doped membrane to be exchanged for sulfuric acid molecules, thus obtaining a PyPENK 4:6 ion exchange membrane, denoted as PyPENK4:6. The ion exchange membrane was then stored in 3M sulfuric acid for later use.

[0041] Example 2 describes a method for preparing an ion exchange membrane, which is basically the same as the method in Example 1, except that the molar ratio of 2,6-DFBN monomer to DFK monomer is 6:4, yielding a polyarylene ether containing pyridinyl and cyano groups; the specific synthetic route is as follows: .

[0042] In the structural formula of the polyaryl ether containing pyridinyl and cyano groups, n is 230. The 1H NMR spectrum of the polyaryl ether containing pyridinyl and cyano groups is shown in Figure 2, indicating the successful synthesis of the polyaryl ether containing pyridinyl and cyano groups. The term "Chemical shift" in Figure 2 refers to this process.

[0043] Weigh 0.5 g of a polyarylene ether containing pyridinyl and cyano groups into a 10 mL centrifuge tube, add 3.65 mL of N-methylpyrrolidone to prepare a casting solution, and centrifuge the solution to remove impurities and perform vacuum degassing. Use a 500 μm scraper to cast the centrifuged casting solution onto a glass plate, dry at 70°C for 4 h, and then immerse the cast glass plate in distilled water to obtain a base film with a thickness of 30 μm–40 μm, denoted as PyPENK 6:4 virgin.

[0044] PyPENK 4:6 virgin was protonated in 50 wt.% phosphoric acid at 40 °C for 4 h to obtain an ion exchange membrane containing protonated pyridinyl and cyano groups, denoted as PyPENK 4:6 phosphoric acid doped membrane.

[0045] The PyPENK 6:4 phosphate-doped membrane was immersed in a 3M sulfuric acid solution for 24 hours to allow the phosphate molecules in the PyPENK 6:4 phosphate-doped membrane to be exchanged for sulfuric acid molecules, thus obtaining a PyPENK 6:4 ion exchange membrane, denoted as PyPENK6:4. The ion exchange membrane was then stored in 3M sulfuric acid for later use.

[0046] Comparative Example 1 describes a method for preparing an ion exchange membrane that is basically the same as the method for preparing an ion exchange membrane in Example 1, except that 2,6-DFBN monomer was not added.

[0047] Step 1: Preparation of pyridine-containing polyaryl ethers: In a three-necked flask equipped with a mechanical stirrer, a water separator, and nitrogen inlet and outlet, 6.3655 g of PyDP, 2.3580 g of DFK, 1.9348 g of K2CO3, 5 mL of 1-methyl-2-pyrrolidone, and 5 mL of toluene were added sequentially. Under nitrogen protection, the mixture was refluxed at 140°C for 4 hours to remove water. The toluene was then distilled off, and the reaction temperature was raised to 160°C and maintained for 10 hours. After the reaction was complete, the polymer solution was poured into water to precipitate the polymer. The obtained polymer was washed four times with hot water and then dried to obtain the pyridine-containing polyaryl ether. The specific synthetic route is shown below:

[0048] .

[0049] In the structural formula of the pyridine-containing polyaryl ether, n is 210. The 1H NMR spectrum of the pyridine-containing polyaryl ether is shown in Figure 3, indicating the successful synthesis of the pyridine-containing polyaryl ether. The term "Chemical shift" in Figure 3 refers to this process.

[0050] Step 2: Preparation of ion exchange membrane: Weigh 0.5 g of pyridine-containing polyarylene ether into a 10 mL centrifuge tube, add 3.65 mL of N-methylpyrrolidone to prepare a casting solution, and centrifuge the casting solution to remove impurities and perform vacuum degassing. Use a 500 μm scraper to cast the centrifuged casting solution onto a glass plate, dry at 70°C for 4 h, and then immerse the cast glass plate in distilled water to obtain a base membrane with a thickness of 30 μm to 40 μm, denoted as PyPEK virgin.

[0051] PyPEK-40 virgin was protonated in 50 wt.% phosphoric acid at 40 °C for 4 h to obtain an ion exchange membrane containing protonated pyridine groups, denoted as PyPEK-40 phosphoric acid doped membrane.

[0052] The PyPEK-40 phosphoric acid-doped membrane was immersed in a sulfuric acid solution with a concentration of 3M for 24 hours to exchange the phosphoric acid molecules in the PyPEK-40 phosphoric acid-doped membrane into sulfuric acid molecules, obtaining the PyPEK-40 ion exchange membrane, denoted as PyPEK-40, and the ion exchange membrane was stored in 3M sulfuric acid for later use.

[0053] Test 1.

[0054] In Figure 4, the Chinese name of Swelling ratio is swelling rate. PyPEK-40 is the PyPEK-40 ion exchange membrane prepared in Comparative Example 1. PyPENK 4:6 is the PyPENK 4:6 ion exchange membrane prepared in Example 1. PyPENK 6:4 is the PyPENK 6:4 ion exchange membrane prepared in Example 2.

[0055] As shown in Figure 4, the swelling rate of the PyPEK-40 ion exchange membrane prepared in Comparative Example 1 is 33.58%. The swelling rate of the PyPENK 4:6 ion exchange membrane prepared in Example 1 is 27.99%. The swelling rate of the PyPENK 6:4 ion exchange membrane prepared in Example 2 is 22.57%. Thus, it can be seen that as the cyano group increases, the swelling rate decreases. This is because the strongly polar cyano group can increase the cohesive force of the molecular chain, enhance the chain rigidity, thereby restricting the swelling of the membrane and having better membrane size stability.

[0056] Test 2.

[0057] In Figure 5, the Chinese name of Area resistance is surface resistance. PyPEK-40 is the PyPEK-40 ion exchange membrane prepared in Comparative Example 1. PyPENK 4:6 is the PyPENK 4:6 ion exchange membrane prepared in Example 1. PyPENK 6:4 is the PyPENK 6:4 ion exchange membrane prepared in Example 2. Nafion212 is a commercial Nafion membrane.

[0058] As shown in Figure 5, the resistance of the PyPEK-40 ion exchange membrane in the vanadium electrolyte is 0.37 Ω·cm 2 ; the resistance of the PyPENK 4:6 ion exchange membrane in the vanadium electrolyte is 0.23 Ω·cm 2 ; the resistance of the PyPENK 6:4 ion exchange membrane in the vanadium electrolyte is 0.21 Ω·cm 2 . Compared with the PyPEK-40 ion exchange membrane of Comparative Example 1, the surface resistances of the cyano group-containing PyPENK 4:6 ion exchange membrane and PyPENK 6:4 ion exchange membrane are lower. This indicates that the ion exchange membranes prepared in the embodiments of the present invention are more suitable for application in vanadium redox flow batteries.

[0059] Test 3.

[0060] In Figure 6, the Chinese name of Ultimate tensile strength is tensile strength. PyPEK virgin is the PyPEK-based membrane prepared in Comparative Example 1, and PyPEK-40 is the PyPEK-40 ion exchange membrane prepared in Comparative Example 1; PyPENK 4:6 virgin is the PyPENK 4:6-based membrane prepared in Example 1, and PyPENK 4:6 is the PyPENK 4:6 ion exchange membrane prepared in Example 1; PyPENK 6:4 virgin is the PyPENK 6:4-based membrane prepared in Example 2, and PyPENK 6:4 is the PyPENK 6:4 ion exchange membrane prepared in Example 2.

[0061] As shown in Figure 6, the change in the tensile strength of the PyPEK-based membrane of Comparative Example 1 and the protonated PyPEK-40 ion exchange membrane is relatively large. Compared with the change in the tensile strength of the PyPEK-based membrane of Comparative Example 1 before and after protonation, the change in the tensile strength of the PyPENK 4:6-based membrane of Example 1 before and after protonation is smaller; the change in the tensile strength of the PyPENK 6:4-based membrane of Example 2 before and after protonation is smaller. This is mainly because the strongly polar cyano group enhances the intermolecular interaction force, and the molecular chain is more rigid, which is very beneficial to maintaining the high mechanical strength of the ion exchange membrane after protonation.

[0062] Test 4.

[0063] The ion exchange membranes of Examples 1 to 2 and the ion exchange membrane of Comparative Example 1 were respectively immersed in a 1.5 M VO 2+ solution for 20 days to test the cycle stability of the ion exchange membrane.

[0064] In Figure 7, the Chinese name of Cycle number is cycle period, and the Chinese name of Efficienfy is efficiency; as shown in Figure 7, within 1000 cycles, the PyPENK 4:6 ion exchange membrane prepared in Example 1 exhibited good cycle stability, indicating that the ion exchange membrane prepared in the embodiments of the present invention is suitable for use in vanadium redox flow batteries.

[0065] In Figure 8, Current Density refers to current density, and EE refers to energy efficiency. PyPEK-40 before is the PyPEK-40 ion exchange membrane prepared in Comparative Example 1 before immersion, and PyPEK-40 after is the PyPEK-40 ion exchange membrane prepared in Comparative Example 1 after immersion. PyPENK 4:6 before is the PyPENK 4:6 ion exchange membrane prepared in Example 1 before immersion, and PyPENK 4:6 after is the PyPENK 4:6 ion exchange membrane prepared in Example 1 after immersion. PyPENK 6:4 before is the PyPENK 6:4 ion exchange membrane prepared in Example 2 before immersion, and PyPENK 6:4 after is the PyPENK 6:4 ion exchange membrane prepared in Example 2 after immersion.

[0066] As shown in Figure 8, the battery performance of the anion exchange membranes prepared in Comparative Example 1, Example 1 and Example 2 is compared before and after oxidation. The battery energy efficiency (EE) of the cyano-containing PyPENK 4:6 ion exchange membrane and the PyPENK 6:4 ion exchange membrane is more stable, while the energy efficiency of the cyano-free PyPEK-40 membrane shows a significant decrease.

[0067] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0068] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. An ion exchange membrane, characterized in that, The ion exchange membrane is obtained by mixing a polyarylene ether containing pyridine and cyano groups with a solvent, followed by a film-forming treatment, and then sequentially immersing it in a protonating reagent for protonation reaction, and finally immersing it in a sulfuric acid solution for sulfate ion exchange treatment; the protonating reagent is an acid; the chemical structural formula of the polyarylene ether containing pyridine and cyano groups is as follows: In the formula, y = 0.2~1.0, n = 50~1000; Ar1 ​​is selected from any one of the following groups: Ar2 is Ar3 is selected from any one of the following groups: Ar4 is selected from any one of the following groups: 。 2. The ion exchange membrane according to claim 1, characterized in that, The preparation method of polyaryl ethers containing pyridinyl and cyano groups is as follows: Under a protective atmosphere, bisphenol containing an Ar3 structure, 2,6-difluorobenzonitrile, and dihaloaromatic monomers undergo a condensation reaction under alkaline catalysis to obtain polyaryl ethers containing pyridinyl and cyano groups; the bisphenol containing an Ar3 structure is 4,4'-phenyl(pyridin-4-yl)methylene)bisphenol, bisphenol A, hexafluorobisphenol A, biphenyl, hydroquinone, 4,4'-dihydroxybenzophenone, or 9,9-bis(4-hydroxyphenyl)anthrone; the dihaloaromatic monomer is 4,4'-difluoroxylenone or 4,4'-difluorodiphenyl sulfone.

3. The ion exchange membrane according to claim 2, characterized in that, The molar ratio of bisphenol containing the Ar3 structure, 2,6-difluorobenzonitrile, and dihaloaromatic monomers is 5:2 to 4:1 to 2.

4. The ion exchange membrane according to claim 3, characterized in that, The bisphenol containing the Ar3 structure is 4,4'-phenyl(pyridin-4-yl)methylene)diphenol.

5. The ion exchange membrane according to claim 1, characterized in that, The protonating agent is at least one of phosphoric acid, sulfuric acid, hydrochloric acid, methanesulfonic acid, and trifluoromethanesulfonic acid; the mass concentration of the protonating agent is 1 wt.% to 100 wt.%; and the concentration of the sulfuric acid solution is 2 mol / L to 5 mol / L.

6. A method for preparing an ion exchange membrane according to any one of claims 1 to 5, characterized in that, The process includes the following steps: dissolving a polyarylene ether containing pyridinyl and cyano groups in a first solvent and casting it into a film to obtain a base film; immersing the base film in a protonating reagent to perform a protonation reaction to protonate the pyridinyl groups, thereby obtaining a protonated film; and immersing the protonated film in a sulfuric acid solution to replace the anions in the protonated film with sulfate ions, thereby obtaining an ion exchange membrane.

7. The method for preparing the ion exchange membrane according to claim 6, characterized in that, The base is sodium carbonate or potassium carbonate; the first solvent is N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, chloroform, 1,1,2,2-tetrachloroethane, dimethyl sulfoxide, or sulfolane.

8. The method for preparing the ion exchange membrane according to claim 6, characterized in that, The temperature range for the protonation reaction is 25℃ to 160℃.

9. The application of the ion exchange membrane according to any one of claims 1 to 5 as a separator in a flow battery.

10. The application of the ion exchange membrane according to claim 9 as a separator in a flow battery, characterized in that, The flow battery is either a vanadium redox flow battery or an iron-chromium redox flow battery.

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