Auxiliary cross-linking type polyarylpyridine anion exchange membrane as well as preparation method and application thereof

Abstract

The invention provides an auxiliary cross-linking type polyarylpyridine anion exchange membrane as well as a preparation method and application thereof, and the preparation method of the auxiliary cross-linking type polyarylpyridine anion exchange membrane comprises the following steps: condensing one or more aromatic compounds and 4-acetylpyridine to obtain a polymer intermediate; a halogenated alkenyl compound is introduced as a cross-linking agent in the quaternization process, and an auxiliary cross-linking agent is additionally added in the film scraping process. The participation of the auxiliary cross-linking agent can make up the defect of low cross-linking degree in the alkenyl free radical reaction process, and is beneficial to the construction of a two-dimensional membrane structure with stable cross-linking degree. The auxiliary crosslinking type polyarylpyridine anion exchange membrane disclosed by the invention has relatively strong mechanical property, excellent membrane framework stability, relatively strong chemical stability, relatively strong swelling resistance and relatively long service life; the auxiliary crosslinking type polyarylpyridine anion exchange membrane disclosed by the invention has good application prospects and large-scale popularization potential in the field of flow batteries.

Description

Technical Field

[0001] The present invention relates to anion exchange membrane technology, in particular to an auxiliary cross-linked polyarylpyridine anion exchange membrane, a preparation method and application thereof. Background Art

[0002] With the increasing development of liquid flow battery energy storage technology, important components such as anion exchange membranes are receiving increasing attention. In liquid flow batteries, anion exchange membranes play a role in selectively transferring anions and blocking the positive and negative electrolytes. Currently, anion exchange membranes are mainly based on a superacid-catalyzed polyaryl structure, which is then converted into a linear quaternary ammonium salt structure that provides stable ion exchange capacity through reactions such as quaternization. However, this polymer material easily absorbs water and swells in aqueous solution, resulting in poor dimensional stability and mechanical strength.

[0003] At present, in order to solve the problems of swelling and dimensional stability caused by the structure of anion exchange membranes, the method of adding cross-linking groups and constructing two-dimensional membranes is generally used. Commonly used cross-linking groups include alkenyl groups. For example, Chen Nanjun's team used aromatic structures such as terphenyl, bibenzyl and dimethylfluorene with N-methylpiperidone to obtain a high molecular polymer through superacid catalysis. 4-Chloromethylstyrene was introduced as a cross-linker in the quaternization process. Alkenyl free radical reaction occurred during the dissolution and film formation process to obtain a cross-linked two-dimensional membrane structure. This structure has excellent mechanical properties such as tensile strength, but the properties such as elongation at break are not outstanding and there is a lack of characterization of the degree of cross-linking of the anion exchange membrane (J.Membr.Sci., 2021, 638, 119685). Similarly, Li Sihan's team used structures such as terphenyl and methylfluorene with carbonyl compounds such as N-methylpiperidone and trifluoroacetophenone to obtain polymers through superacid catalysis. 4-Chloromethylstyrene was also introduced during the quaternization process, and cross-linking occurred through olefin radical reaction. The introduction of trifluoromethyl structure in this structure gave it strong alkali resistance and oxidation resistance, but there was also a lack of characterization of the degree of cross-linking.

[0004] The anion exchange membranes currently used in flow batteries have the following problems: 1) Some main chain structures are too rigid, resulting in poor mechanical properties of the ion exchange membrane; 2) The olefin radical crosslinking mode has a lower crosslinking degree than expected, and the water absorption rate and swelling coefficient are still high; 3) The olefin radical crosslinking has high requirements for the temperature and olefin concentration during the dissolution and scraping process, which greatly increases the difficulty of subsequent scale-up experiments and production of scraping membranes. Summary of the Invention

[0005] The purpose of the present invention is to address the above-mentioned problems and propose an auxiliary cross-linked polyarylpyridine anion exchange membrane. This anion exchange membrane forms a polymer backbone with excellent flexibility through the condensation of aromatic compounds and 4-acetylpyridine, and introduces alkenyl functional groups into the side chains through a quaternization reaction to construct cross-linking active sites. During the membrane formation process, the formation of a three-dimensional cross-linked network is promoted by adding an auxiliary cross-linking agent, and ultimately a membrane material with a high degree of cross-linking is obtained. This preparation method has the advantage of simple process. The ion exchange membrane obtained has outstanding mechanical strength, low swelling properties and good environmental adaptability, which can meet the requirements of liquid flow batteries.

[0006] To achieve the above object, the technical solution adopted by the present invention is: an auxiliary cross-linked polyarylpyridine anion exchange membrane, the general formula of which is shown in Formula 1:

[0007]

[0008] In Formula 1, Ar is independently selected from one or more of biphenyl, p-terphenyl, m-terphenyl, fluorene and dimethylfluorene;

[0009] R is one or more of methyl, methoxy and ethoxy;

[0010] R1 is independently selected from the structure of Formula 2 or Formula 3:

[0011]

[0012] In Formula 1 and Formula 3, 10≤m≤1000, 10≤n≤1000, 1≤a≤5, and m, n, and a are all positive integers.

[0013] Furthermore, the R is preferably a methyl group.

[0014] Furthermore, preferably, in Formula 1, Formula 2 and Formula 3, 100≤m≤1000, 100≤n≤1000, 1≤a≤5, and m, n, and a are all positive integers.

[0015] Furthermore, more preferred among Formula 1, Formula 2 and Formula 3 are: 600≤m≤1000, 300≤n≤1000, 2≤a≤4, and m, n, and a are all positive integers.

[0016] Another object of the present invention is to disclose a method for preparing an auxiliary cross-linked polyarylpyridine anion exchange membrane, comprising the following steps:

[0017] (1) reacting an aromatic compound and 4-acetylpyridine in dichloromethane under the catalytic action of a superacid catalyst at -10-25°C for 12-36 hours, then soaking in a sodium hydroxide aqueous solution, hardening, crushing, washing with deionized water, and drying to obtain a polymer intermediate;

[0018] (2) adding the polymer intermediate and the halogenated alkenyl compound to an organic solvent, reacting at 45-65° C. for 48-72 hours; adding iodomethane after the reaction, reacting at 20-35° C. for 24-48 hours; adding acetone after the reaction, precipitating a solid product, washing, and drying to obtain a membrane powder;

[0019] (3) Dissolve the membrane powder in an organic solvent, add an auxiliary crosslinking agent and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), stir evenly to obtain a viscous solution, apply the viscous solution on the base membrane, and use a scraper to scrape the base membrane to obtain a wet film, and dry it to obtain an auxiliary crosslinked polyarylpyridine anion exchange membrane.

[0020] The reaction principle of the auxiliary cross-linked polyarylpyridine anion exchange membrane is as follows:

[0021]

[0022] Furthermore, in step (1), the molar ratio of the aromatic compound to 4-acetylpyridine is 1:1.0-1.6.

[0023] Furthermore, in step (1), the molar ratio of the aromatic compound, dichloromethane and superacid catalyst is 1:5.5-8.5:8.5-13.

[0024] Furthermore, in step (1), the superacid catalyst is one or more of trifluoroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, acetic acid, pentafluoropropionic acid and tellurium pentafluoride.

[0025] Furthermore, in step (1), the aromatic compound is one or more of biphenyl, p-terphenyl, m-terphenyl, fluorene and dimethylfluorene.

[0026] Furthermore, in step (1), 1-1.5M sodium hydroxide ice water solution is used for soaking, hardening and crushing.

[0027] Furthermore, in step (1), the drying temperature is 80-85°C.

[0028] Furthermore, in step (2), the molar ratio of the repeating unit of the polymer intermediate, the haloalkenyl compound and methyl iodide is 1:0.1-0.6:2-4.

[0029] Furthermore, in step (2), the mass ratio of the repeating unit of the polymer intermediate to the organic solvent is 1:5.5-10.

[0030] Furthermore, in step (2), the volume ratio of the organic solvent to acetone is 1:4-10.

[0031] Furthermore, in step (2), the organic solvent is one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

[0032] Furthermore, in step (2), the structural formula of the haloalkenyl compound is as shown in Formula 4 and / or Formula 5:

[0033]

[0034] In Formula 5, 1≤a≤5, and a is a positive integer.

[0035] Furthermore, in step (2), the drying temperature is 45-55°C.

[0036] Furthermore, in step (2), deionized water is used for washing.

[0037] Furthermore, in step (3), the mass ratio of the membrane powder to the organic solvent is 1:4-7.

[0038] Furthermore, in step (3), the mass ratio of the membrane powder, the auxiliary cross-linking agent and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is 1:0.02-0.16:0.002-0.016.

[0039] Furthermore, in step (3), the organic solvent is one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

[0040] Furthermore, in step (3), the structure of the auxiliary cross-linking agent is as shown in Formula 6,

[0041]

[0042] In Formula 6, R is independently selected from one or more of methyl, methoxy and ethoxy.

[0043] Furthermore, in Formula 6, R is preferably a methyl group and / or a methoxy group.

[0044] Furthermore, in step (3), the auxiliary cross-linking agent is ethyl acetoacetate.

[0045] The inclusion of an auxiliary crosslinker can compensate for the low degree of crosslinking during the alkenyl radical reaction, facilitating the construction of a stable, two-dimensional membrane structure. 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU), an organic base, catalyzes the nucleophilic addition reaction between the auxiliary crosslinker and the terminal alkenyl group, promoting crosslinking.

[0046] Furthermore, in step (3), the membrane powder is dissolved in an organic solvent, an auxiliary cross-linking agent and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) are added, and the mixture is stirred at 35-40° C. to obtain a viscous solution.

[0047] Furthermore, in step (3), the viscous solution is coated on a PET base film preheated to 40-45° C. through a bottom glass plate, and a scraper provided with a coating machine is used to scrape the base film at a speed of 5-7 mm / s to obtain a wet film.

[0048] Furthermore, in step (3), the wet film thickness is 500-800 μm, and the film surface is flat.

[0049] Furthermore, in step (3), the drying step is performed at 60-65°C for 2-2.5 hours, and then at 90-95°C for 4-4.5 hours. Gradual heating helps the cross-linking reaction proceed smoothly. Direct heating at 90°C for a long time will cause the cross-linking reaction to proceed too quickly, resulting in local wrinkles and other phenomena.

[0050] Another object of the present invention is to disclose the application of an auxiliary cross-linked polyarylpyridine anion exchange membrane in the field of liquid flow batteries.

[0051] The present invention discloses an auxiliary cross-linked polyarylpyridine anion exchange membrane, its preparation method, and application. The present invention utilizes condensation of one or more aromatic compounds with 4-acetylpyridine to obtain a polymer intermediate, introduces a haloolefin compound as a cross-linking agent during quaternization, and adds an auxiliary cross-linking agent during the scraping process. Specifically, the present invention has the following advantages over the prior art:

[0052] 1) The auxiliary cross-linked polyarylpyridine anion exchange membrane of the present invention has dense ether-free polymer main chains and a high-polymerization degree aromatic skeleton, which ensures the dimensional stability of the anion exchange membrane.

[0053] 2) The introduction of the auxiliary alkenyl cross-linking form of the present invention can make up for the defect of low cross-linking degree in the alkenyl free radical reaction process, simply and quickly construct a planar two-dimensional membrane structure, suppress the water absorption rate of the anion exchange membrane, and reduce the swelling coefficient.

[0054] 3) The auxiliary cross-linked polyarylpyridine anion exchange membrane of the present invention, the introduction of a high-polymerization aromatic skeleton and a non-rigid carbon structure in 4-acetylpyridine, increases the flexibility of the side chain while ensuring the rigidity of the polymerized monomer, thereby enhancing the mechanical properties of the anion exchange membrane, such as tensile strength and elongation at break.

[0055] 4) The auxiliary alkenyl cross-linking form of the present invention avoids the problem of low cross-linking degree in the single alkenyl cross-linking mode and increases the possibility of high cross-linking degree anion exchange membrane.

[0056] The auxiliary cross-linked polyarylpyridine anion exchange membrane prepared by the present invention has advantages such as strong mechanical properties (tensile strength ≥40 MPa, elongation at break ≥70%), excellent membrane skeleton stability, strong chemical stability (immersion in Fenton reagent for 72 hours), strong resistance to swelling (swelling rate ≤15%), and long service life. The auxiliary cross-linked polyarylpyridine anion exchange membrane of the present invention has good application prospects and large-scale promotion potential in the field of liquid flow batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a graph showing the cycle number of coulombic efficiency, energy efficiency and voltage efficiency of the cross-linked polyarylpyridine anion exchange membrane prepared in Example 3 in the charge and discharge cycle test of the organic liquid flow battery. DETAILED DESCRIPTION

[0058] The present invention will be further described below with reference to the following examples. The following description of the technical features is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0059] In the present invention, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising" and similar meanings, as well as closed-ended "consisting of", "composed of" and similar meanings.

[0060] Unless otherwise stated, the units used in this specification are international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0061] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints A and B.

[0062] In this specification, the numerical range expressed using "above" or "below" means a numerical range including the number.

[0063] In this specification, the use of "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0064] In this specification, the use of "optional" or "optional" indicates that certain substances, components, execution steps, application conditions and other factors are used or not used.

[0065] In this specification, when "normal temperature" or "room temperature" is used, the temperature may be 15-25°C.

[0066] In this manual, the reagents or instruments used without indicating the manufacturer are all conventional products that can be obtained through commercial purchase.

[0067] Example 1

[0068] This embodiment discloses an auxiliary cross-linked polyarylpyridine anion exchange membrane, the preparation method and reaction principle of which are as follows:

[0069]

[0070] In the above formula, 600≤m≤800, 300≤n≤800.

[0071] Step (1) Synthesis of intermediate

[0072] To a 1L reactor, diphenyl (30.8g, 0.2mol), 4-acetylpyridine (29.07g, 0.24mol) and dichloromethane (70mL) were added, and trifluoroacetic acid (31.2g, 0.28mol) and trifluoromethanesulfonic acid (343.0g, 2.3mol) were slowly added dropwise. The reaction was carried out for 12h. The temperature was kept at 0-15°C throughout the above process. After the reaction was completed, the blue-purple viscous liquid obtained by the reaction was poured into 1L of 1M sodium hydroxide solution. After hardening and precipitation, it was crushed and washed with water, and then placed in an 80°C oven to obtain a white solid (49.25g, yield 95.7%) as a polymer intermediate.

[0073] 1 H NMR (400MHz, CDCl3, ppm) δ8.52(2H),7.8-7.2(10H),2.32(3H).

[0074] Step (2) Synthesis of membrane powder

[0075] To a 1L four-necked flask, the polymer intermediate (30.9 g, 0.12 mol) obtained in step (1), p-chloromethylstyrene (2.5 g, 0.06 mol) and dimethyl sulfoxide (264 g) were added. The mixture was reacted at 80°C for 48 h. Then, iodomethane (51.1 g, 0.36 mol) was added. The mixture was reacted at 35°C for 48 h. After the reaction was completed, acetone (1000 mL) was added. The precipitated material was washed with water and dried at 45°C to obtain a light yellow solid (45.74 g, yield 94.3%) as a membrane powder.

[0076] 1 H NMR (400MHz, DMSO-d6, ppm) δ9.02(4H),7.8-7.0(24H),6.70(1H),5.84(3H),5.22(1H),4.36(3H),2.33(6H).

[0077] Step (3) Preparation of anion exchange membrane

[0078] The membrane powder (25 g) obtained in step (2), dimethyl sulfoxide (110 g) and ethyl acetoacetate (2.41 g) were added to a 100 mL beaker, stirred and dissolved at 35-40 ° C, and DBU (0.25 g) was added after complete dissolution. After mixing, the homogeneous viscous solution was coated on a PET base film preheated to 40 ° C through the bottom glass plate, and the base film was scraped at a speed of 5 mm / s using the scraper provided by the coating machine to keep the thickness within 550-570 μm and the membrane surface flat. The membrane was dried at 60 ° C for 4 h, and then heated to 90 ° C for 6 h to obtain an auxiliary cross-linked polyarylpyridine anion exchange membrane with a thickness of 45 ± 2 μm.

[0079] Example 2

[0080] This embodiment discloses an auxiliary cross-linked polyarylpyridine anion exchange membrane, the preparation method and reaction principle of which are as follows:

[0081]

[0082] In the above formula, 800≤m≤1000, 300≤n≤400.

[0083] Step (1) Synthesis of intermediate

[0084] To a 1L reactor, p-terphenyl (46.2g, 0.2mol), 4-acetylpyridine (31.4g, 0.26mol) and dichloromethane (78mL) were added, and trifluoroacetic acid (32.5g, 0.28mol) and trifluoromethanesulfonic acid (346.0g, 2.3mol) were slowly added dropwise. The reaction was allowed to proceed for 24h. The temperature was maintained at 0-10°C throughout the entire process. After the reaction was completed, the blue-purple viscous liquid obtained by the reaction was poured into 1L of 1M sodium hydroxide solution. After hardening and precipitation, the solid was crushed and washed with water, and then dried in an 80°C oven to obtain a white solid (63.29g, 94.9% yield) as a polymer intermediate.

[0085] 1 H NMR (400MHz, CDCl3, ppm) δ8.53(2H),7.8-7.2(14H),2.32(3H).

[0086] Step (2) Synthesis of membrane powder

[0087] To a 1L four-necked flask, the polymer intermediate (39.9 g, 0.12 mol) obtained in step (1), 5-bromo-1-pentene (2.7 g, 0.018 mol) and dimethyl sulfoxide (352 g) were added. The mixture was reacted at 80°C for 48 h. Then, iodomethane (51.1 g, 0.36 mol) was added. The mixture was reacted at 35°C for 48 h. After the reaction was completed, acetone (1800 mL) was added. The precipitated material was washed with water and dried at 50°C to obtain a light yellow solid (54.54 g, yield 94.6%) as a membrane powder.

[0088] 1 H NMR (400MHz, DMSO-d6, ppm) δ8.98(4H),7.8-7.2(28H),5.80(0.3H),5.2-4.9(1.2H),4.38(5.1H),2.32(6H),2.11(1.2H).

[0089] Step (3) Preparation of anion exchange membrane

[0090] The membrane powder (25 g) obtained in step (2), dimethyl sulfoxide (144 g) and acetylacetone (0.47 g) were added to a 100 mL beaker, stirred and dissolved at 35-40 ° C, and DBU (0.05 g) was added after complete dissolution. After mixing evenly, the homogeneous viscous solution was coated on a PET base film preheated to 40 ° C through the bottom glass plate, and the base film was scraped at a speed of 5 mm / s using the scraper provided by the coating machine to keep the thickness within 660-680 μm and the membrane surface flat. The membrane was dried at 60 ° C for 4 h, then heated to 90 ° C and dried for 6 h to finally obtain an auxiliary cross-linked polyarylpyridine anion exchange membrane with a thickness of 45 ± 2 μm.

[0091] Example 3

[0092] This embodiment discloses an auxiliary cross-linked polyarylpyridine anion exchange membrane, the preparation method and reaction principle of which are as follows:

[0093]

[0094] In the above formula, 800≤m≤1000, 300≤n≤400.

[0095] Step (1) Synthesis of intermediate

[0096] To a 1L reactor, p-terphenyl (23.1g, 0.1mol), m-terphenyl (23.1g, 0.1mol), 4-acetylpyridine (31.4g, 0.26mol) and dichloromethane (78mL) were added, and trifluoroacetic acid (32.5g, 0.28mol) and trifluoromethanesulfonic acid (346.0g, 2.3mol) were slowly added dropwise. The reaction was continued for 24h. The temperature was kept at 0-10°C throughout the above process. After the reaction was completed, the blue-purple viscous liquid obtained by the reaction was poured into 1L of 1M sodium hydroxide solution. After hardening and precipitation, it was crushed and washed with water, and then dried in an 80°C oven to obtain a white solid (62.89g, yield 94.3%) as a polymer intermediate.

[0097] 1 H NMR (400MHz, CDCl3, ppm) δ8.53(2H),7.8-7.2(14H),2.32(3H).

[0098] Step (2) Synthesis of membrane powder

[0099] To a 1L four-necked flask, the polymer intermediate (39.9 g, 0.12 mol) obtained in step (1), p-chloromethylstyrene (2.8 g, 0.018 mol) and dimethyl sulfoxide (352 g) were added. The mixture was reacted at 80°C for 48 h. Then, iodomethane (51.1 g, 0.36 mol) was added. The mixture was reacted at 35°C for 48 h. After the reaction was completed, acetone (1800 mL) was added. The precipitated material was washed with water and dried at 50°C to obtain a light yellow solid (54.43 g, yield 95.1%) as a membrane powder.

[0100] 1 H NMR (400MHz, DMSO-d6, ppm) δ8.98(4H),8.0-7.2(29.2H),6.72(0.3H),5.88(0.9H),5.27(0.3H),4.38(5.1H),2.29(6H).

[0101] Step (3) Preparation of anion exchange membrane

[0102] The membrane powder (25 g) obtained in step (2), dimethyl sulfoxide (150 g) and dimethyl malonate (0.63 g) were added to a 100 mL beaker, stirred and dissolved at 35-40 ° C, and DBU (0.06 g) was added after complete dissolution. After mixing, the homogeneous viscous solution was coated on a PET base film preheated to 40 ° C through the bottom glass plate, and the base film was scraped at a speed of 5 mm / s using the scraper provided by the coating machine to keep the thickness within 660-680 μm and the membrane surface flat. The membrane was dried at 60 ° C for 4 h, and then heated to 90 ° C for 6 h to obtain an auxiliary cross-linked polyarylpyridine anion exchange membrane with a thickness of 45 ± 2 μm.

[0103] Example 4

[0104] This embodiment discloses an auxiliary cross-linked polyarylpyridine anion exchange membrane, the preparation method and reaction principle of which are as follows:

[0105]

[0106] In the above formula, 800≤m≤1000, 300≤n≤400.

[0107] Step (1) Synthesis of intermediate

[0108] To a 1L reactor, p-terphenyl (34.55g, 0.15mol), fluorene (8.2g, 0.05mol), 4-acetylpyridine (31.6g, 0.26mol) and dichloromethane (78mL) were added, and trifluoroacetic acid (32.1g, 0.28mol) and trifluoromethanesulfonic acid (346.0g, 2.3mol) were slowly added dropwise. The reaction was carried out for 24h. The temperature was kept at 10-15°C throughout the above process. After waiting for the reaction to complete, the reddish-purple viscous liquid obtained by the reaction was poured into 1L of 1M sodium hydroxide solution. After hardening and precipitation, it was crushed and washed with water, and then placed in an 80°C oven to obtain a white solid (60.63g, yield 95.5%) as a polymer intermediate.

[0109] 1 H NMR (400MHz, CDCl3, ppm) δ8.54(2H),7.92(0.5H),7.5-7.1(10H),4.12(0.5H),2.30(3H).

[0110] Step (2) Synthesis of membrane powder

[0111] To a 1L four-necked flask, the polymer intermediate (38.12 g, 0.12 mol) obtained in step (1), p-chloromethylstyrene (2.8 g, 0.018 mol) and dimethyl sulfoxide (360 g) were added. The mixture was reacted at 80°C for 48 h. Then, iodomethane (51.1 g, 0.36 mol) was added. The mixture was reacted at 35°C for 48 h. After the reaction was completed, acetone (1800 mL) was added. The precipitated material was washed with water and dried at 55°C to obtain a light yellow solid (51.87 g, yield 94.6%) as a membrane powder.

[0112] 1 H NMR (400MHz, DMSO-d6, ppm) δ8.89(2H),7.9-7.2(13.1H),6.72(0.16H),5.88(0.44H),5.26(0.14H),4.38(2.56),4.12(0.5H),2.27(3H).

[0113] Step (3) Preparation of anion exchange membrane

[0114] The membrane powder (25 g) obtained in step (2), dimethyl sulfoxide (128 g) and diethyl malonate (0.78) were added to a 100 mL beaker, stirred and dissolved at 35-40 ° C, and DBU (0.08 g) was added after complete dissolution. After mixing evenly, the homogeneous viscous solution was coated on a PET base film preheated to 40 ° C through the bottom glass plate, and the base film was scraped at a speed of 5 mm / s using the scraper provided by the coating machine to keep the thickness within 620-640 μm and the membrane surface flat. The membrane was dried at 60 ° C for 4 h, and then heated to 90 ° C for 6 h to obtain an auxiliary cross-linked polyarylpyridine anion exchange membrane with a thickness of 45 ± 2 μm.

[0115] Comparative Example 1

[0116] This comparative example discloses an anion exchange membrane, the preparation method and reaction principle of which are as follows:

[0117]

[0118] In the above formula, 600≤m≤800, 300≤n≤800.

[0119] The membrane powder (25 g) obtained in step (2) of Example 1 and dimethyl sulfoxide (110 g) were added to a 100 mL beaker, and the mixture was stirred and dissolved at 35-40° C. After complete dissolution, the homogeneous viscous solution was coated on a PET base film preheated to 40° C. through a bottom glass plate, and the base film was scraped at a speed of 5 mm / s using a scraper provided with the coating machine to keep the thickness within 550-570 μm and the membrane surface flat. The membrane was dried at 60° C. for 4 h, and then heated to 90° C. and dried for 6 h to obtain a cross-linked polyarylpyridine anion exchange membrane with a thickness of 45±2 μm.

[0120] Comparative Example 2

[0121] This comparative example discloses an anion exchange membrane, the preparation method and reaction principle of which are as follows:

[0122]

[0123] In the above formula, 800≤m≤1000, 300≤n≤400.

[0124] The membrane powder (25 g) obtained in step (2) of Example 2 and dimethyl sulfoxide (144 g) were added to a 100 mL beaker, and the mixture was stirred and dissolved at 35-40° C. After complete dissolution, the homogeneous viscous solution was coated on a PET base film preheated to 40° C. through a bottom glass plate, and the base film was scraped at a speed of 5 mm / s using a scraper provided with the coating machine to keep the thickness within 660-680 μm and the membrane surface flat. The membrane was dried at 60° C. for 4 h, and then heated to 90° C. and dried for 6 h to obtain a cross-linked polyarylpyridine anion exchange membrane with a thickness of 45±2 μm.

[0125] Comparative Example 3

[0126] This comparative example discloses an anion exchange membrane, the preparation method and reaction principle of which are as follows:

[0127]

[0128] In the above formula, 800≤m≤1000, 300≤n≤400.

[0129] The membrane powder (25 g) obtained in step (2) of Example 3 and dimethyl sulfoxide (150 g) were added to a 100 mL beaker, and the mixture was stirred and dissolved at 35-40 ° C. After complete dissolution, the homogeneous viscous solution was coated on a PET base film preheated to 40 ° C through the bottom glass plate, and the base film was scraped at a speed of 5 mm / s using the scraper provided by the coating machine to keep the thickness within 660-680 μm and the membrane surface flat. The membrane was dried at 60 ° C for 4 h, and then heated to 90 ° C for 6 h to obtain a cross-linked polyarylpyridine anion exchange membrane with a thickness of 45 ± 2 μm.

[0130] Comparative Example 4

[0131] This comparative example discloses an anion exchange membrane, the preparation method and reaction principle of which are as follows:

[0132]

[0133] In the above formula, 800≤m≤1000, 300≤n≤400.

[0134] The membrane powder (25 g) obtained in step (2) of Example 4 and dimethyl sulfoxide (128 g) were added to a 100 mL beaker, and the mixture was stirred and dissolved at 35-40 ° C. After complete dissolution, the homogeneous viscous solution was coated on a PET base film preheated to 40 ° C through the bottom glass plate, and the base film was scraped at a speed of 5 mm / s using the scraper provided by the coating machine to keep the thickness within 620-640 μm and the membrane surface flat. The membrane was dried at 60 ° C for 4 h, and then heated to 90 ° C for 6 h to obtain a cross-linked polyarylpyridine anion exchange membrane with a thickness of 45 ± 2 μm.

[0135] The auxiliary cross-linked polyarylpyridine anion exchange membranes of Examples 1-4 and the anion exchange membranes of Comparative Examples 1-4 were tested, and the test methods and results are as follows:

[0136] The tensile strength and elongation at break of the anion exchange membranes obtained in Examples 1-4 and Comparative Examples 1-4 were measured using a universal tensile testing machine. The data are shown in Table 1.

[0137] The swelling rate of the anion exchange membranes obtained in Examples 1-4 and Comparative Examples 1-4 was tested, and the data are shown in Table 1.

[0138] The swelling rate test method is as follows: put the membrane into a 60℃ oven to dry to constant weight, then soak it in pure water for 24 hours, take it out and wipe the surface moisture, the size is S1, then transfer it to a 60℃ oven to dry for 24 hours, take it out and the size is S2, the swelling rate is (S1-S2) / S 2* 100%

[0139] The gel fraction (GF) of the anion exchange membranes obtained in Examples 1-4 and Comparative Examples 1-4 was tested, and the data are shown in Table 1.

[0140] The gel fraction can be used to intuitively judge the degree of cross-linking. The test method is as follows: the anion exchange membrane is dried to a constant weight, with a mass of m1, and dissolved in dimethyl sulfoxide. After waiting for 24 hours to dissolve, the solution is filtered out and the insoluble matter is dried to a constant weight of m2. GF = m2 / m1*100%.

[0141] The conductivity of the anion exchange membranes obtained in Examples 1-4 and Comparative Examples 1-4 was measured, and the anion exchange membranes obtained in Examples 1-4 were immersed in Fenton's reagent for 72 hours to detect the change in conductivity before and after the oxidation resistance test. The specific data are shown in Table 1.

[0142] Table 1 Test data summary

[0143]

[0144] As shown in Table 1, by comparing Examples 1-4 with Comparative Examples 1-4, after the auxiliary cross-linking agent participates in cross-linking, the tensile strength of the film increases, while the elongation at break remains the same, indicating that cross-linking brings about an improvement in mechanical strength.

[0145] Comparison of the gel fractions of Examples 1-4 and Comparative Examples 1-4 shows that the crosslinking with the participation of the auxiliary crosslinking agent used in Examples 1-4 has a higher degree of crosslinking.

[0146] By comparing Examples 1-4 with Comparative Examples 1-4, it can be seen that the anion exchange membrane of the patented structure of the present invention has a lower swelling rate, indicating that it has higher skeleton stability and a more stable two-dimensional membrane structure.

[0147] By comparing Examples 1-4 with Comparative Examples 1-4, it can be seen that the conductivity of the anion exchange membrane of the patented structure of the present invention does not show a downward trend, indicating that the cross-linking method involving the auxiliary cross-linking agent does not affect the change of conductivity.

[0148] From the Fenton reagent immersion experiments in Examples 1-4, it can be seen that the anion exchange membrane with the patented structure of the present invention has a certain oxidation resistance.

[0149] Example 5

[0150] This embodiment discloses an application of an auxiliary cross-linked polyarylpyridine anion exchange membrane in the field of organic liquid flow batteries: the auxiliary cross-linked polyarylpyridine anion exchange membrane prepared in step (3) of Example 3 is assembled in a battery cell, the positive and negative electrolytes are 1.5M aqueous solution of formula 7 and 1.5M aqueous solution of formula 8, respectively, the supporting electrolyte is sodium chloride, and the constant power is 128mW / cm in a constant temperature box at 25°C. 2 Carry out cyclic charge and discharge test, such as Figure 1 As shown, the coulombic efficiency is 99.81% (constant current and constant voltage) and 99.90% (constant power), the voltage efficiency is 82.91% (constant current and constant voltage) and 83.89% (constant power), and the energy efficiency is 82.74% (constant current and constant voltage) and 83.81% (constant power). The overall battery efficiency is excellent, indicating that the anion exchange membrane with the patented structure of the present invention can be used in fields such as liquid flow batteries.

[0151]

[0152] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An auxiliary cross-linked polyarylpyridine anion exchange membrane, characterized in that: Its general formula is shown in Formula 1: In Formula 1, Ar is independently selected from one or more of biphenyl, p-terphenyl, m-terphenyl, fluorene and dimethylfluorene; R is one or more of methyl, methoxy and ethoxy; R1 is independently selected from the structure of Formula 2 or Formula 3: In Formula 1 and Formula 3, 10≤m≤1000, 10≤n≤1000, 1≤a≤5, and m, n, and a are all positive integers.

2. A method for preparing the auxiliary cross-linked polyarylpyridine anion exchange membrane according to claim 1, characterized in that: The following steps are involved: (1) reacting an aromatic compound and 4-acetylpyridine in dichloromethane under the catalytic action of a superacid catalyst at -10-25°C for 12-36 hours, then soaking in a sodium hydroxide aqueous solution, hardening, crushing, washing with deionized water, and drying to obtain a polymer intermediate; (2) adding the polymer intermediate and the halogenated alkenyl compound to an organic solvent, reacting at 45-65° C. for 48-72 hours; adding iodomethane after the reaction, reacting at 20-35° C. for 24-48 hours; adding acetone after the reaction, precipitating a solid product, washing, and drying to obtain a membrane powder; (3) Dissolve the membrane powder in an organic solvent, add an auxiliary crosslinking agent and 1,8-diazabicyclo[5.4.0]undec-7-ene, stir evenly to obtain a viscous solution, apply the viscous solution on the base film, and use a scraper to scrape the base film to obtain a wet film, and dry it to obtain an auxiliary crosslinked polyarylpyridine anion exchange membrane.

3. The method for preparing the auxiliary cross-linked polyarylpyridine anion exchange membrane according to claim 2, characterized in that: In step (1), the molar ratio of the aromatic compound to 4-acetylpyridine is 1:1.0-1.6; And / or, in step (1), the molar ratio of the aromatic compound, dichloromethane and superacid catalyst is 1:5.5-8.5:8.5-13.

4. The method for preparing the auxiliary cross-linked polyarylpyridine anion exchange membrane according to claim 2, characterized in that: In step (1), the superacid catalyst is one or more of trifluoroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, acetic acid, pentafluoropropionic acid and tellurium pentafluoride; And / or, in step (1), the aromatic compound is one or more of biphenyl, p-terphenyl, m-terphenyl, fluorene and dimethylfluorene.

5. The method for preparing the auxiliary cross-linked polyarylpyridine anion exchange membrane according to claim 2, characterized in that: In step (2), the molar ratio of the repeating unit of the polymer intermediate, the haloalkenyl compound and iodomethane is 1:0.1-0.6:2-4; And / or, in step (2), the mass ratio of the repeating unit of the polymer intermediate to the organic solvent is 1:5.5-10; And / or, in step (2), the volume ratio of the organic solvent to acetone is 1:4-10.

6. The method for preparing the auxiliary cross-linked polyarylpyridine anion exchange membrane according to claim 2, characterized in that: In step (2), the organic solvent is one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone; In step (2), the structure of the haloalkenyl compound is shown in Formula 4 and / or Formula 5: In Formula 5, 1≤a≤5, and a is a positive integer.

7. The method for preparing the auxiliary cross-linked polyarylpyridine anion exchange membrane according to claim 2, characterized in that: In step (3), the mass ratio of the membrane powder to the organic solvent is 1:4-7; And / or, in step (3), the mass ratio of the membrane powder, the auxiliary cross-linking agent and 1,8-diazabicyclo[5.4.0]undec-7-ene is 1:0.02-0.16:0.002-0.

016.

8. The method for preparing the auxiliary cross-linked polyarylpyridine anion exchange membrane according to claim 2, characterized in that: In step (3), the organic solvent is one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone; And / or, in step (3), the structure of the auxiliary cross-linking agent is as shown in Formula 6, In Formula 6, R is independently selected from one or more of methyl, methoxy and ethoxy.

9. The method for preparing the auxiliary cross-linked polyarylpyridine anion exchange membrane according to claim 2, characterized in that: In step (3), the membrane powder is dissolved in an organic solvent, an auxiliary cross-linking agent and 1,8-diazabicyclo[5.4.0]undec-7-ene are added, and the mixture is stirred at 35-40° C. to obtain a viscous solution. And / or, in step (3), the viscous solution is coated on a PET base film preheated to 40-45° C. through a bottom glass plate, and a scraper provided with a coating machine is used to scrape the base film at a speed of 5-7 mm / s to obtain a wet film; And / or, in step (3), the wet film thickness is 500-800 μm, and the film surface is flat; And / or, in step (3), the drying step is performed at 60-65°C for 2-2.5 hours, and then the temperature is raised to 90-95°C for drying for 4-4.5 hours.

10. Use of the auxiliary cross-linked polyarylpyridine anion exchange membrane according to claim 1 in the field of liquid flow batteries.

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