Amphoteric polymer material containing pyridinium cation and sulfonate, preparation method thereof and application in ion exchange membrane of all-vanadium redox flow battery

Abstract

The invention relates to the technical field of ion exchange membrane materials in energy storage batteries, in particular to an amphoteric polymer material containing pyridinium cations and sulfonate groups, a preparation method thereof and an application of the amphoteric polymer material in an ion exchange membrane of an all-vanadium redox flow battery, and the problem that the existing membrane material causes cross contamination of vanadium ions or poor ion conductivity is overcome. The polymer containing pyridinium cations and sulfonate groups is a poly(aryl-3-acetylpyridine) zwitterionic polymer. The first preparation method comprises: polymerizing an aromatic monomer with zwitterionic 3-acetylpyridine and non-ionized 3-acetylpyridine monomers in an organic solvent and acid catalysis to obtain the poly(aryl-3-acetylpyridine) zwitterionic polymer containing pyridinium cations and sulfonate groups; and the second preparation method comprises: polymerizing an aromatic monomer with 3-acetylpyridine, and then performing an ionization reaction with a sulfonating agent in an organic solvent and potassium carbonate as a catalyst to obtain the poly(aryl-3-acetylpyridine) zwitterionic polymer containing pyridinium cations and sulfonate groups.

Description

Technical Field

[0001] The invention relates to the technical field of ion exchange membrane materials in energy storage batteries, in particular to an amphoteric polymer material containing pyridinium cations and sulfonate groups, a preparation method thereof, and an application thereof in an ion exchange membrane of an all-vanadium liquid flow battery. Background Art

[0002] As an efficient and environmentally friendly energy storage technology, all-vanadium liquid flow battery is of great significance in coping with the volatility of renewable energy, improving grid stability and achieving carbon neutrality goals due to its advantages such as capacity independent of power design, long cycle life and high energy efficiency. Its key structural components include electrodes, bipolar plates, electrolytes and ion exchange membranes. However, the core component of all-vanadium liquid flow battery, ion exchange membrane, still faces challenges in its performance and cost. The ion exchange membrane for high-performance vanadium liquid flow battery should have high ion conductivity, low vanadium ion permeability, good chemical stability and low cost. At present, proton exchange membranes, such as commercial perfluorosulfonic acid membranes, have good conductivity and chemical stability, but the high vanadium ion permeability leads to lower coulombic efficiency. At the same time, the expensive cost limits its large-scale commercial application. Anion exchange membranes have improved in inhibiting vanadium ion cross-contamination, but their ionic conductivity in acidic environments is usually lower than that of proton exchange membranes.

[0003] In addition, the molecular skeletons of traditional aromatic polymer membrane materials include poly(arylethersulfone), poly(etherketone), etc. These materials are easily degraded in an acidic and highly oxidizing environment because of the ether bonds on their main chains. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an amphoteric polymer material containing pyridinium cations and sulfonate groups for preparing ion exchange membranes for all-vanadium liquid flow batteries, thereby overcoming the problem that existing membrane materials may cause cross-contamination of vanadium ions during use of the exchange membrane or may cause poor ion conductivity, and overcoming the problem that membrane materials are easily degraded in an acidic and highly oxidizing environment.

[0005] The technical solution adopted by the present invention to solve the technical problem is: an amphoteric polymer material containing pyridinium cations and sulfonate groups, wherein the polymer containing pyridinium cations and sulfonate groups is a poly(aryl-3-acetylpyridine) zwitterionic polymer, and its structural formula is shown in Formula 1.

[0006]

[0007] Formula 1,

[0008] In formula 1, the content of functionalized zwitterionic structural units x= 0~0.90, each structural unit contains both pyridinium cations and sulfonate group side chains, the number of methyl spacer groups contained in each sulfonic acid side chain n=0~4, and the content of non-functionalized aryl pyridine structural units 1-x=0.1~0.9.

[0009] The first preparation method of the above-mentioned amphoteric polymer material containing pyridinium cations and sulfonate groups is to prepare a poly (aryl-3-acetylpyridine) zwitterionic polymer containing pyridinium cations and sulfonate groups by polymerization reaction of aromatic monomers with zwitterionized 3-acetylpyridine and unionized 3-acetylpyridine monomers in an organic solvent and under the catalysis of an acid. The reaction formula is shown in Formula 2. Formula 2.

[0010] Specifically, during the preparation, the aromatic monomer Ar is stirred and dissolved in an organic solvent, and then 3-acetylpyridine and zwitterionized 3-acetylpyridine are added. After all the monomers are dissolved, a catalyst acid is added at a low temperature. After a period of reaction, the mixture is precipitated and soaked in water to remove excess acid, and then filtered, washed, and dried to obtain a poly (aryl-3-acetylpyridine) zwitterionic polymer containing pyridinium cations and sulfonate groups in formula 2.

[0011] Specifically, during the preparation process, the molar ratio of the aromatic monomer to the sum of the two 3-acetylpyridine monomers is 1:1.0-1:1.3, the molar ratio of 3-acetylpyridine to the zwitterionized 3-acetylpyridine monomer is 1:0-1:0.9, the molar ratio of the catalyst acid to the sum of the two 3-acetylpyridine monomers is 1:6-1:12, the concentration of the aromatic monomer in the organic solvent one is 0.8-2.5 mol / L, the low temperature is -10-10°C, the reaction time is 12-60h, the catalyst acid is any one of concentrated sulfuric acid, concentrated hydrochloric acid, trifluoromethanesulfonic acid, methanesulfonic acid or trifluoroacetic acid, and the organic solvent one is any one of dichloromethane, dichloroethane, tetrachloroethane or chloroform.

[0012] Specifically, the reaction formula for preparing the zwitterionized 3-acetylpyridine monomer is as shown in Formula 3:

[0013]

[0014] Formula 3,

[0015] In formula 3, 3-acetylpyridine is dissolved in organic solvent II, a sulfonating reagent is added, and then the mixture is refluxed, condensed and stirred for a period of time under heating conditions. The product is allowed to stand, filtered, washed at least twice with organic solvent II, and dried to obtain a solid powder, which is a zwitterionized 3-acetylpyridine monomer.

[0016] Specifically, in formula 3, the molar ratio of 3-acetylpyridine to the sulfonating agent is 1:1~1:2, the concentration of 3-acylpyridine in the second organic solvent is 0.5~1.8 mol / L, the reaction temperature is 40~65°C, the reaction time is 8~24h, the second organic solvent is one of ethyl acetate or acetonitrile, and the sulfonating agent is any one of 2-bromoethyl sodium sulfonate, 3-bromopropyl sodium sulfonate, 4-bromobutyl sodium sulfonate, 5-bromopentyl sodium sulfonate, 6-bromohexyl sodium sulfonate, 1,3-propane sultone or 1,4-butane sultone.

[0017] The second preparation method of the above-mentioned amphoteric polymer material containing pyridinium cations and sulfonate groups is to polymerize aromatic monomers with 3-acetylpyridine, and then use a sulfonating agent in an organic solvent three, with potassium carbonate as a catalyst, to perform a post-ionization reaction to obtain a poly (aryl-3-acetylpyridine) zwitterionic polymer containing pyridinium cations and sulfonate groups. The reaction formula is shown in Formula 4.

[0018] Formula 4.

[0019] Specifically, the preparation process includes:

[0020] Step 1: stirring and dissolving the aromatic monomer Ar in an organic solvent 1, then adding a certain amount of 3-acetylpyridine, and after all the monomers are dissolved, adding a catalyst acid at a low temperature, and after the reaction, settling and soaking in water to remove excess acid, and then filtering, washing, and drying to obtain a poly (aryl-3-acetylpyridine) polymer;

[0021] Step 2: dissolving the poly(aryl-3-acetylpyridine) polymer obtained in step 1 in organic solvent 3, adding potassium carbonate and a sulfonating agent, stirring and reacting under heating conditions, precipitating the product in ethyl acetate, and then washing with the solvent and water at least twice in sequence, and drying to obtain a poly(aryl-3-acetylpyridine) zwitterionic polymer containing pyridinium cations and sulfonate groups in formula 4.

[0022] Specifically, in step 1, the molar ratio of the aromatic monomer to the 3-acetylpyridine monomer is 1:1.0-1:1.3, the molar ratio of the catalyst acid to the sum of the two 3-acetylpyridine monomers is 1:6-1:12, the concentration of the aromatic monomer in the organic solvent 1 is 0.8-2.5 mol / L, the low temperature is -10-10°C, the reaction time is 12-60h, the catalyst acid is any one of sulfuric acid, hydrochloric acid, trifluoromethanesulfonic acid, methanesulfonic acid or trifluoroacetic acid, and the organic solvent 1 is any one of dichloromethane, dichloroethane, tetrachloroethane or chloroform;

[0023] In step 2, the mass ratio of the poly(aryl-3-acetylpyridine) polymer repeating unit to the sulfonating reagent is 1:0-1:0.9, the mass ratio of potassium carbonate to the sulfonating reagent is 1:1-1:1.1, the reaction temperature is 60-80°C, the reaction time is 12-48 h, the organic solvent three is any one of dimethyl sulfoxide or N-methylpyrrolidone, and the sulfonating reagent is any one of 2-bromoethyl sodium sulfonate, 3-bromopropyl sodium sulfonate, 4-bromobutyl sodium sulfonate, 5-bromopentyl sodium sulfonate, 6-bromohexyl sodium sulfonate, 1,3-propane sultone or 1,4-butane sultone.

[0024] The above-mentioned amphoteric polymer material containing pyridinium cations and sulfonate groups is used to prepare ion exchange membranes in all-vanadium liquid flow batteries.

[0025] The aromatic monomer Ar can be any one or more of the following structures:

[0026] .

[0027] The beneficial effects of the present invention are:

[0028] 1. The characteristic of this polymer material is that it introduces both cationic and anionic functional groups. When used as an ion exchange membrane for all-vanadium liquid flow batteries, it can effectively shield the cross-penetration of vanadium ions through the Donnan repulsion effect. The introduction of pyridinium cations effectively reduces the vanadium ion permeability of the membrane and improves the coulombic efficiency of the vanadium liquid flow battery. The introduction of sulfonic acid groups improves the ionic conductivity, reduces the ohmic loss of the battery, and improves the voltage efficiency, enabling it to selectively conduct hydrogen ions and maintain high ionic conductivity. In addition, the synergistic effect of the cationic and anionic groups in the zwitterionic membrane helps to form a stable ion channel and improve the dimensional stability of the exchange membrane in the electrolyte.

[0029] Second, the poly (aryl-3-acetylpyridine) zwitterionic polymer containing pyridinium cations and sulfonate groups can be prepared by two synthetic routes: pre-ionization and post-ionization. The preparation steps are few, the method is simple, and the yield is high. The ionization of the pyridinium group can be completed in the polymer structural unit and the sulfonic acid side chain can be introduced, thereby improving the ion selectivity of the polymer membrane material. In addition, the polymer skeleton is an aromatic skeleton without ether bonds, and has good mechanical properties and chemical stability.

[0030] 3. The preparation method of poly (aryl-3-acetylpyridine) zwitterionic polymer containing pyridinium cation and sulfonate provided by the present invention, the ion exchange capacity of such polymer can be regulated according to the ratio of the amount of zwitterionic 3-acetylpyridine and 3-acetylpyridine substance in the preparation method one, and can also be regulated by the ratio of the amount of poly (aryl-3-acetylpyridine) polymer repeating unit and sulfonated reagent in the preparation method two; the main chain of the polymer is polyaryl 3-acetylpyridine, which is an aromatic rigid polymer skeleton without ether bonds, and in addition to having good mechanical properties and chemical stability, it is also suitable for use in extreme environments;

[0031] 4. The amphoteric polyaryl 3-acetylpyridinium ionomer containing pyridinium cations and sulfonate groups provided by the present invention is soluble in dimethyl sulfoxide and can be used to prepare ion exchange membranes by a cast film method. The prepared ion exchange membranes have good ion conductivity, dimensional stability, vanadium resistance, and chemical stability, and perform well in vanadium liquid flow battery stacks. The preparation method is simple and the cost is low, and it can replace the current perfluorosulfonic acid type membrane materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A combined comparison diagram of the reaction formulas of two preparation methods of poly (aryl-3-acetylpyridine) zwitterionic polymers containing pyridinium cations and sulfonate groups as summarized in all embodiments of the present invention;

[0033] Figure 2a is the hydrogen nuclear magnetic resonance spectrum of the 3-acetylpyridine zwitterionic monomer in Example 1 of the present invention;

[0034] Figure 2b is a hydrogen nuclear magnetic resonance spectrum of the poly(biphenyl-3-acetylpyridine) amphoteric polymer in Example 1 of the present invention;

[0035] Figure 2c is a hydrogen nuclear magnetic resonance spectrum of the poly(biphenyl-3-acetylpyridine) polymer in Example 3 of the present invention;

[0036] Figure 3a This is a comparison chart of membrane surface resistance values ​​of the zwitterionic ion exchange membranes of Examples 1 and 3 of the present invention and several perfluorosulfonic acid membranes currently available on the market;

[0037] Figure 3b This is a comparison chart of the vanadium ion permeability results of the zwitterionic ion exchange membranes of Examples 1 and 3 of the present invention and several perfluorosulfonic acid membranes currently available on the market;

[0038] Figure 4a This is a comparison chart of the coulombic efficiency of the amphoteric ion exchange membrane of Example 3 of the present invention and the commercially available perfluorosulfonic acid membrane 1 in a vanadium liquid flow battery stack;

[0039] Figure 4b This is a comparison diagram of the voltage efficiency of the amphoteric ion exchange membrane of Example 3 of the present invention and the commercially available perfluorosulfonic acid membrane 1 in a vanadium liquid flow battery stack;

[0040] Figure 4c This is a comparison chart of the energy efficiency of the amphoteric ion exchange membrane of Example 3 of the present invention and the commercially available perfluorosulfonic acid membrane 1 in a vanadium redox flow battery stack. DETAILED DESCRIPTION

[0041] The present invention further illustrates the technical features by the following embodiments in combination with the accompanying drawings, but the protection scope of the present invention is not limited to the following embodiments.

[0042] In the examples, the sources of drugs and reagents are as follows:

[0043] Biphenyl (CAS No.: 92-52-4), Anaiji Chemical, 99%;

[0044] 3-Acetylpyridine (CAS No.: 350-03-8), Anaiji Chemical, 98%;

[0045] 1,3-Propane sultone (CAS No.: 1120-71-4), Anaiji Chemical, 98%;

[0046] Sodium 2-bromoethylsulfonate (CAS No. 4263-52-9), Anaiji Chemical, 98%;

[0047] 1,4-Butanesultone (CAS No.: 1633-83-6), Anaiji Chemical, 97%;

[0048] 9,9-Dimethylfluorene (CAS No. 4569-45-3), Anaiji Chemical, 98%;

[0049] Potassium carbonate (CAS No.: 584-08-7), Shanghai Lingfeng Chemical Reagent Co., Ltd., ≥99.0%;

[0050] Acetonitrile (CAS No.: 75-05-8), Shanghai Lingfeng Chemical Reagent Co., Ltd., ≥99.5%;

[0051] Dichloromethane (CAS No.: 75-09-2), Shanghai Lingfeng Chemical Reagent Co., Ltd., ≥99.5%;

[0052] Trifluoromethanesulfonic acid (CAS No.: 1493-13-6), Anaiji Chemical, 99%;

[0053] Ethyl acetate (CAS No.: 141-78-6) Shanghai Lingfeng Chemical Reagent Co., Ltd., ≥99.5%;

[0054] Dimethyl sulfoxide (CAS No.: 67-68-5) Shanghai Lingfeng Chemical Reagent Co., Ltd., ≥99.5%.

[0055] Embodiment 1:

[0056] Method 1 was used to prepare a poly(biphenyl-3-acetylpyridine) amphoteric polymer material with 3 side chain methylene spacer groups (n=1) and an IEC value of 1.58 mmol / g (x=0.6).

[0057] 1. In a 100 ml three-necked flask, 2.0000 g (16.5 mmol) of 3-acetylpyridine was stirred and dissolved in 20 ml of acetonitrile solvent, and then 4.0328 g (33 mmol) of 1,3-propanesultone was added and stirred at 60 ° C for 24 h under reflux condensation. Solid powder was precipitated during the reaction. After the reaction was completed, the product was filtered, washed with acetonitrile for 3 times, and then dried in a vacuum oven at 60 ° C for 24 h to obtain a white solid powder, which was zwitterionized 3-acetylpyridine monomer (n=1). The yield of the product was 93%. 1 H NMR (D2O) Figure 2a As shown;

[0058] 2. In a 100 ml three-necked flask, add 1.5421 g (10 mmol) of biphenyl, 1.8976 g (7.8 mmol) of zwitterionic 3-acetylpyridine monomer (n=1), and 0.6299 g of 3-acetylpyridine, then add 8 ml of dichloromethane and stir to dissolve, then slowly add 12 ml of trifluoromethanesulfonic acid dropwise under an ice bath, and the system is stirred at room temperature for 48 hours. After the reaction is completed, slowly pour the product into a large amount of water to precipitate to form a white fibrous solid, and let it stand for 24 hours. During this period, the water needs to be changed for soaking. Then the product is washed with water and dried to obtain a light yellow solid, which is poly (biphenyl-3-acetylpyridine) zwitterionic polymer with a yield of 91%. 1 H NMR (DMSO-d6) Figure 2b shown.

[0059] Embodiment 2:

[0060] Method 1 was used to prepare an amphoteric poly(terphenyl-3-acetylpyridine) ion exchange membrane with 4 side chain methylene spacers (n=2) and an IEC value of 1.41 mmol / g (n=0.7):

[0061] 1. In a 100 ml three-necked flask, 2.0000 g (16.5 mmol) of 3-acetylpyridine was stirred and dissolved in 20 ml of acetonitrile solvent, and then 4.4963 g (33 mmol) of 1,4-butanesulfonic acid lactone was added and stirred at 60 ° C for 24 h under reflux condensation. Solid powder was precipitated continuously during the reaction. After the reaction was completed, the product was filtered, washed repeatedly with acetonitrile for 3 times, and then dried in a vacuum oven at 60 ° C for 24 h to obtain a white solid powder, which was zwitterionized 3-acetylpyridine monomer (n=2), with a yield of 89%;

[0062] 2. Add 2.3031 g (10 mmol) of terphenyl, 2.3414 g (7.8 mmol) of zwitterionic 3-acetylpyridine monomer (n=2), and 0.4724 g of 3-acetylpyridine into a 100 ml three-necked flask, then add 8 ml of dichloromethane and stir to dissolve, then slowly add 12 ml of trifluoromethanesulfonic acid dropwise under an ice bath, and stir the system at room temperature for 48 h. After the reaction, slowly pour the product into a large amount of water to precipitate to form a white fibrous solid, and let it stand for 24 h. During this period, the water needs to be changed for soaking. Then, the product is washed with water and dried to obtain a light yellow solid, which is poly(terphenyl-3-acetylpyridine) zwitterionic polymer with a yield of 93%.

[0063] The material obtained in Example 2 was subjected to a further membrane preparation process, wherein 0.35 g of dried poly(terphenyl-3-acetylpyridine) zwitterionic polymer was dissolved in 15 ml of dimethyl sulfoxide to obtain a polymer solution, the polymer solution was coated on a glass plate, and then dried in an oven at 100° C. for 24 hours, the membrane was peeled off the glass plate, immersed in a 3 mol / L sulfuric acid solution for ion exchange, and the surface acid was washed off after being taken out to obtain a poly(terphenyl-3-acetylpyridine) zwitterionic ion exchange membrane (IEC=1.41 mmol / g).

[0064] Embodiment 3:

[0065] Method 2 was used to prepare a poly(biphenyl-3-acetylpyridine) zwitterionic ion exchange membrane with 3 side chain methylene spacers (n=1) and an IEC value of 1.39 mmol / g (x=0.5):

[0066] 1. Add 1.5421g (10 mmol) biphenyl and 1.5748g 3-acetylpyridine to a 100 ml three-necked flask, then add 5ml of dichloromethane and stir to dissolve, then slowly drop 11ml of trifluoromethanesulfonic acid in an ice bath, and stir the system at room temperature for 24h. After the reaction, slowly pour the product into a large amount of water to precipitate to form a white fibrous solid, and let it stand for 24h. During this period, the water needs to be changed for soaking. Then the product is washed with water and dried to obtain a white solid, which is poly (biphenyl-3-acetylpyridine) polymer, with a yield of 94%. 1 HNMR (DMSO-d6) Figure 2c shown.

[0067] 2. Add 1 g of poly (biphenyl-3-acetylpyridine) polymer and 30 ml of dimethyl sulfoxide into a 100 ml three-necked flask, stir to dissolve, then add 0.2364 g (1.9353 mmol) of 1,3-propanesultone and 0.2782 g (2.0127 mmol) of potassium carbonate, heat and stir at 80 ° C for 24 h, the product is precipitated in ethyl acetate, filtered, washed with ethyl acetate and water several times, and then dried to obtain a yellow solid product, i.e., poly (biphenyl-3-acetylpyridine) amphoteric polymer material, with a yield of 87%.

[0068] The material obtained in Example 3 was subjected to a further membrane preparation process, wherein 0.35 g of dried poly(biphenyl-3-acetylpyridine) zwitterionic polymer was dissolved in 15 ml of dimethyl sulfoxide to obtain a polymer solution, the polymer solution was coated on a glass plate, and then placed in an oven at 100° C. for drying for 24 hours. The membrane was peeled off from the glass plate, immersed in a 3 mol / L sulfuric acid solution for ion exchange, and then the surface acid was washed off after being taken out to obtain a poly(biphenyl-3-acetylpyridine) zwitterionic ion exchange membrane (n=1, IEC=1.39 mmol / g).

[0069] Embodiment 4:

[0070] Method 2 was used to prepare a poly(dimethylfluorene-3-acetylpyridine) zwitterionic ion exchange membrane with 2 side chain methylene spacers (n=0) and an IEC value of 1.05 mmol / g (x=0.4):

[0071] 1. Add 1.9428g (10mmol) of dimethylfluorene and 1.5748g of 3-acetylpyridine to a 100ml three-necked flask, then add 5ml of dichloromethane and stir to dissolve, then slowly add 11ml of trifluoromethanesulfonic acid dropwise under ice bath, and stir the system at room temperature for 24h. After the reaction, slowly pour the product into a large amount of water to precipitate to form a white fibrous solid, and let it stand for 24h. During this period, the water needs to be changed for soaking. Then the product is washed with water and dried to obtain a white solid, which is poly (dimethylfluorene-3-acetylpyridine) polymer with a yield of 88%.

[0072] 2. Add 1 g of poly (dimethylfluorene-3-acetylpyridine) polymer and 30 ml of dimethyl sulfoxide into a 100 ml three-necked flask, stir to dissolve, then add 0.2855 g (1.3404 mmol) of sodium bromoethane sulfonate and 0.1887 g (1.3672 mmol) of potassium carbonate, heat and stir at 80 ° C for 24 h, the product is precipitated in ethyl acetate, filtered, washed with ethyl acetate and water several times, and then dried to obtain a yellow solid product, i.e., poly (dimethylfluorene-3-acetylpyridine) amphoteric polymer material, with a yield of 85%.

[0073] The material obtained in Example 4 was subjected to a continuous membrane preparation process, wherein 0.35 g of dried poly(dimethylfluorene-3-acetylpyridine) amphoteric polymer material was dissolved in 15 ml of dimethyl sulfoxide to obtain a polymer solution, the polymer solution was coated on a glass plate, and then dried in an oven at 100° C. for 24 hours, the membrane was peeled off the glass plate, immersed in a 3 mol / L sulfuric acid solution for ion exchange, and the surface acid was washed off after being taken out to obtain a poly(dimethylfluorene-3-acetylpyridine) amphoteric ion exchange membrane (n=0, IEC=1.05 mmol / g).

[0074] The zwitterionic ion exchange membranes ZW60-P3AB and ZW50-P3AB in Examples 1 and 3 of the present invention have the following performance in terms of membrane area resistance: Figure 3a As shown in the experimental test results, the area resistance of commercially available perfluorosulfonic acid membranes (PFSA1, PFSA2, and PFSA3) is 0.29Ωcm 2 , 0.38Ωcm 2 and 0.34Ωcm 2 , while the area resistances of the zwitterionic ion exchange membranes ZW60-P3AB and ZW50-P3AB of the present invention are 0.17Ωcm 2 and 0.22Ωcm 2The resistance of the membrane is reduced by about 43% to 56%, which is significantly better than the commercially available perfluorosulfonic acid membrane, which means that it exhibits better performance in terms of conductivity. The membrane of the present invention adopts a specific zwitterionic side chain design, which can effectively reduce the resistance of the membrane while maintaining high ion conductivity. This structural design is significantly better than the single sulfonic acid group structure of the traditional perfluorosulfonic acid membrane, and improves the conductivity. Figure 3b The test results of ion permeability coefficient show that the amphoteric ion exchange membrane of the present invention shows significant advantages in blocking vanadium ions, which further proves its superiority in practical applications. The vanadium ion permeability coefficients of commercially available perfluorosulfonic acid membranes (PFSA1, PFSA2, and PFSA3) are 13.82×10 -9 cm 2 / s, 9.74×10 -9 cm 2 / s and 10.51×10 -9 cm 2 / s, while the vanadium ion permeability coefficients of the zwitterionic ion exchange membranes ZW60-P3AB and ZW50-P3AB of the present invention are 6.56×10 -9 cm 2 / s and 4.48×10 -9 cm 2 / s, which is about 33% to 68% lower than that of the commercially available perfluorosulfonic acid membrane. The results show that the membrane of the present invention is excellent in reducing the cross-permeation of vanadium ions, and can effectively reduce the efficiency reduction problem of vanadium flow batteries caused by electrolyte cross-contamination during long-term operation. The superior performance of the membrane of the present invention is attributed to its unique zwitterionic side chain design, which has significant advantages in improving ion selectivity and inhibiting vanadium ion migration.

[0075] Figure 4a , Figure 4b and Figure 4c The coulombic efficiency, voltage efficiency and energy efficiency of the membrane of the present invention (Example 3: ZW50-P3AB) in the vanadium flow battery stack are respectively shown, and compared with the commercially available perfluorosulfonic acid membrane (PFSA1). From the perspective of coulombic efficiency, the ZW50-P3AB of Example 3 maintains a level close to 100% at all current densities, showing extremely high ion selectivity and barrier capacity for vanadium ions, while the coulombic efficiency of the commercially available PFSA1 decreases at different current densities and further decreases with the increase in the number of cycles, especially at high current density, indicating that it has obvious cross-contamination problems during long-term operation; in terms of voltage efficiency, the ZW50-P3AB of Example 3 always maintains a high voltage efficiency, even at high current density (200mAcm -2), its efficiency is still significantly higher than that of the commercially available PFSA1, which indicates that the membrane of the present invention performs well in reducing resistance loss and improving electrochemical stability, and is helpful to improve the overall performance of the vanadium flow battery. The performance of energy efficiency further highlights the advantages of the membrane of the present invention. The ZW50-P3AB of Example 3 shows an energy efficiency significantly higher than that of the commercially available PFSA1 at different current densities and cycle numbers, especially under high current density and long-term cycle conditions, its advantages are more significant, which reflects that the membrane of the present invention can significantly improve the energy conversion efficiency of the battery system in practical applications. The membrane of the present invention shows superior comprehensive performance in the long-term operation of the vanadium flow battery, especially under high current density, and is superior to existing market products in terms of coulombic efficiency, voltage efficiency and energy efficiency. This performance improvement is attributed to the unique zwitterionic structure design of the membrane of the present invention, which not only effectively inhibits the cross-penetration of vanadium ions, but also significantly reduces the resistance of the membrane, providing an ideal technical solution for the development of high-efficiency vanadium flow batteries.

[0076] Various embodiments of the present invention have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Without departing from the scope and technical principles of the described embodiments, many modifications and changes are obvious to ordinary technicians in this technical field, and these modifications and changes should also be regarded as the scope of protection of the present invention.

Claims

1. An amphoteric polymer material containing pyridinium cations and sulfonate groups, characterized in that: The polymer containing pyridinium cations and sulfonate groups is a poly(aryl-3-acetylpyridine) zwitterionic polymer, and its structural formula is shown in Formula 1. Formula 1, In formula 1, the content of functionalized zwitterionic structural units x= 0~0.90, each structural unit contains both pyridinium cations and sulfonate group side chains, the number of methyl spacer groups contained in each sulfonic acid side chain n= 0~4, and the content of non-functionalized aryl pyridine structural units 1-x=0.1~0.

9.

2. A method for preparing the amphoteric polymer material containing pyridinium cations and sulfonate groups as claimed in claim 1, characterized in that: The poly(aryl-3-acetylpyridine) zwitterionic polymer containing pyridinium cation and sulfonate group is prepared by polymerization reaction of aromatic monomer with zwitterionized 3-acetylpyridine and unionized 3-acetylpyridine monomer in an organic solvent and under the catalysis of acid. The reaction formula is shown in Formula 2. Formula 2.

3. The method for preparing the amphoteric polymer material containing pyridinium cations and sulfonate groups according to claim 2, characterized in that: The aromatic monomer Ar is stirred and dissolved in an organic solvent, and then 3-acetylpyridine and zwitterionized 3-acetylpyridine are added. After all the monomers are dissolved, a catalyst acid is added at a low temperature. After a period of reaction, the mixture is precipitated and soaked in water to remove excess acid, and then filtered, washed and dried to obtain a poly (aryl-3-acetylpyridine) zwitterion polymer containing pyridinium cations and sulfonate groups in formula 2.

4. The method for preparing the amphoteric polymer material containing pyridinium cations and sulfonate groups according to claim 3, characterized in that: During the preparation process, the molar ratio of the aromatic monomer to the sum of the two 3-acetylpyridine monomers is 1:1.0-1:1.3, the molar ratio of 3-acetylpyridine to the zwitterionized 3-acetylpyridine monomer is 1:0-1:0.9, the molar ratio of the catalyst acid to the sum of the two 3-acetylpyridine monomers is 1:6-1:12, the concentration of the aromatic monomer in the organic solvent one is 0.8-2.5 mol / L, the low temperature is -10-10°C, the reaction time is 12-60 h, the catalyst acid is any one of concentrated sulfuric acid, concentrated hydrochloric acid, trifluoromethanesulfonic acid, methanesulfonic acid or trifluoroacetic acid, and the organic solvent one is any one of dichloromethane, dichloroethane, tetrachloroethane or chloroform.

5. The method for preparing the amphoteric polymer material containing pyridinium cations and sulfonate groups according to claim 4, characterized in that: The reaction formula for preparing the zwitterionized 3-acetylpyridine monomer is shown in Formula 3: Formula 3, In formula 3, 3-acetylpyridine is dissolved in organic solvent II, a sulfonating reagent is added, and then the mixture is refluxed, condensed and stirred for a period of time under heating conditions. The product is allowed to stand, filtered, washed at least twice with organic solvent II, and dried to obtain a solid powder, which is a zwitterionized 3-acetylpyridine monomer.

6. The method for preparing the amphoteric polymer material containing pyridinium cations and sulfonate groups according to claim 5, characterized in that: In formula 3, the molar ratio of 3-acetylpyridine to the sulfonating agent is 1:1-1:2, the concentration of 3-acylpyridine in the second organic solvent is 0.5-1.8 mol / L, the reaction temperature is 40-65°C, the reaction time is 8-24h, the second organic solvent is one of ethyl acetate or acetonitrile, and the sulfonating agent is any one of 2-bromoethyl sodium sulfonate, 3-bromopropyl sodium sulfonate, 4-bromobutyl sodium sulfonate, 5-bromopentyl sodium sulfonate, 6-bromohexyl sodium sulfonate, 1,3-propane sultone or 1,4-butane sultone.

7. A method for preparing the amphoteric polymer material containing pyridinium cations and sulfonate groups as claimed in claim 1, characterized in that: The aromatic monomer is polymerized with 3-acetylpyridine, and then a sulfonating agent is used in an organic solvent, potassium carbonate is used as a catalyst, and a post-ionization reaction is performed to obtain a poly (aryl-3-acetylpyridine) zwitterionic polymer containing pyridinium cations and sulfonate groups. The reaction formula is shown in Formula 4. Formula 4.

8. The method for preparing the amphoteric polymer material containing pyridinium cations and sulfonate groups according to claim 7, characterized in that it comprises: Step 1: stirring and dissolving the aromatic monomer Ar in an organic solvent 1, then adding a certain amount of 3-acetylpyridine, and after all the monomers are dissolved, adding a catalyst acid at a low temperature, and after the reaction, settling and soaking in water to remove excess acid, and then filtering, washing, and drying to obtain a poly (aryl-3-acetylpyridine) polymer; Step 2: dissolving the poly(aryl-3-acetylpyridine) polymer obtained in step 1 in organic solvent 3, adding potassium carbonate and a sulfonating agent, stirring and reacting under heating conditions, precipitating the product in ethyl acetate, and then washing with the solvent and water at least twice in sequence, and drying to obtain a poly(aryl-3-acetylpyridine) zwitterionic polymer containing pyridinium cations and sulfonate groups in formula 4.

9. The method for preparing the amphoteric polymer material containing pyridinium cations and sulfonate groups according to claim 8, characterized in that: In step 1, the molar ratio of the aromatic monomer to the 3-acetylpyridine monomer is 1:1.0-1:1.3, the molar ratio of the catalyst acid to the sum of the two 3-acetylpyridine monomers is 1:6-1:12, the concentration of the aromatic monomer in the organic solvent 1 is 0.8-2.5 mol / L, the low temperature is -10-10°C, the reaction time is 12-60h, the catalyst acid is any one of sulfuric acid, hydrochloric acid, trifluoromethanesulfonic acid, methanesulfonic acid or trifluoroacetic acid, and the organic solvent 1 is any one of dichloromethane, dichloroethane, tetrachloroethane or chloroform; In step 2, the mass ratio of the poly(aryl-3-acetylpyridine) polymer repeating unit to the sulfonating reagent is 1:0-1:0.9, the mass ratio of potassium carbonate to the sulfonating reagent is 1:1-1:1.1, the reaction temperature is 60-80°C, the reaction time is 12-48h, the organic solvent three is any one of dimethyl sulfoxide or N-methylpyrrolidone, and the sulfonating reagent is any one of 2-bromoethyl sodium sulfonate, 3-bromopropyl sodium sulfonate, 4-bromobutyl sodium sulfonate, 5-bromopentyl sodium sulfonate, 6-bromohexyl sodium sulfonate, 1,3-propane sultone or 1,4-butane sultone.

10. An application of the amphoteric polymer material containing pyridinium cations and sulfonate groups as claimed in claim 1, characterized in that: The amphoteric polymer material containing pyridinium cations and sulfonate groups is used for preparing ion exchange membranes in all-vanadium liquid flow batteries.

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