Porous polyethylene-based membrane / cross-linked poly (methylpiperidine-vinyl benzyl chloride) composite anion exchange membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of anion exchange membranes, and particularly relates to a porous polyethylene-based membrane / cross-linked poly (methylpiperidine-vinyl benzyl chloride) composite anion exchange membrane as well as a preparation method and application thereof. The invention provides a porous polyethylene-based membrane / cross-linked poly (methylpiperidine-vinyl benzyl chloride) composite anion exchange membrane, which is obtained by polymerizing a cyclic quaternary ammonium monomer in a porous polyethylene membrane, and the method is a one-pot method, is simple and rapid, and provides convenience for industrial large-scale production; the composite anion exchange membrane has excellent mechanical property, high ionic conductivity and high physical and chemical stability, is applied to preparation of fuel cells, has good electrochemical performance, meets the application requirements of the membrane in AEMFC, provides important reference for solving the key technical barrier hindering commercialized development of AEMFC, and is good in application progress.

Description

Technical Field

[0001] This invention belongs to the field of anion exchange membrane technology, specifically relating to porous polyethylene-based membrane / crosslinked poly(methylpiperidine@vinylbenzyl chloride) composite anion exchange membrane, its preparation method, and its applications. Background Technology

[0002] Fuel cells, as efficient and clean energy conversion devices, possess advantages such as high energy conversion efficiency and zero pollution, making them one of the important development directions in the future energy field. Among them, anion exchange membrane fuel cells (AEMFCs) have attracted widespread attention due to their advantages in low-temperature start-up, high power density, and fuel adaptability. However, as the core component of AEMFCs, the performance of anion exchange membranes (AEMs) directly affects the overall performance of the battery. Currently, traditional anion exchange membranes suffer from problems such as low ionic conductivity and poor stability, which limit the further development of AEMFCs. Therefore, developing a novel anion exchange membrane with high ionic conductivity and high stability is of great significance for promoting the commercialization of AEMFCs.

[0003] Generally, increasing the ion exchange capacity (IEC) of anion exchange membranes (AEMs) can achieve higher ion conductivity. However, paradoxically, increasing the IEC also brings serious negative effects to the anion exchange membrane, such as high water absorption and significant dimensional swelling, leading to a decrease in the mechanical properties of the AEM and the overall performance of the membrane electrode assembly. In addition, research on improving the ion conductivity and stability of AEMs mainly involves the following methods: (1) using polymers containing sulfone and ether bonds (such as polysulfone, polyphenylene ether, polyarylene ether, etc.) as the matrix material of AEMs or increasing the concentration of cationic groups in AEMs to improve the ion conductivity of AEMs; (2) crosslinking the polymer chains that conduct anions to restrict the slippage of molecular chains and improve the long-term stability of AEMs. However, the above methods have the following problems: (1) polymers containing sulfone and ether bonds are unstable under alkaline conditions and are susceptible to OH-. - (1) The attack of OH- makes it easier for degradation to occur, resulting in a decrease in the overall performance of AEMs; (2) The increase in the concentration of cationic groups in AEMs means that there are more cationic sites in AEMs that are easily attacked by OH-, which will bring serious negative effects such as high water absorption and large size swelling, resulting in a decrease in the mechanical properties of AEMs and the overall performance of membrane electrode assembly; (3) Simple cross-linking of polymer chains often limits ionic conductivity.

[0004] Given the problems existing in the application of anion exchange membranes in fuel cells, it is particularly important to develop anion exchange membrane with high ionic conductivity and high stability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a porous polyethylene-based membrane / crosslinked poly(methylpiperidine@vinylbenzyl chloride) composite anion exchange membrane, its preparation method, and its applications.

[0006] This invention provides a composite anion exchange membrane, which is prepared by polymerizing cyclic quaternary ammonium monomers and crosslinking agents in a porous polyethylene membrane;

[0007] The cyclic quaternary ammonium monomer is selected from at least one of 1-methyl-1-(4-vinylbenzyl)piperidine chloride, quaternized molecules of 4-vinylpyridine, and quaternized molecules of 4-vinylbenzyl chloride, and the mass ratio of the cyclic quaternary ammonium monomer to the crosslinking agent is 100:10-30.

[0008] Preferably, the mass ratio of cyclic quaternary ammonium monomer to crosslinking agent is 100:15-30.

[0009] Preferably, it is prepared by a method including the following steps:

[0010] Step 1: Mix the monomer with the crosslinking agent and the initiator to obtain the film-forming solution;

[0011] Step 2: Immerse the porous polyethylene membrane in the film-forming solution, and initiate the polymerization reaction by light irradiation to obtain the final product.

[0012] Preferably, in the film-forming solution, the mass ratio of monomer to solvent is 1-2:1-2; and / or, the mass ratio of monomer to initiator is 50-100:5-10.

[0013] Preferably, the crosslinking agent is selected from at least one of divinylbenzene, divinylisophthalate, 1,7-divinyl-1,1,3,3,5,5,7,7-octamethyltetrasiloxane, and divinylsilane; and / or, the initiator is selected from at least one of benzoin ether, diphenyl-2,4,6-trimethylphenylphosphooxy, and 1-hydroxycyclohexylphenyl ketone; and / or, the solvent of the film-forming solution is selected from at least one of ethanol, n-propanol, isopropanol, and n-butanol.

[0014] Preferably, the porous polyethylene-based membrane has a porosity of 40-50% and a thickness of 9-17 micrometers;

[0015] And / or, the porous polyethylene-based membrane is immersed in the film-forming solution until completely submerged.

[0016] Preferably, in step 2, the polymerization reaction takes 30-120 minutes, and the illumination conditions include 276-365nm and 300-500W.

[0017] This invention provides a method for preparing the composite anion exchange membrane according to any one of the above claims, comprising:

[0018] Cyclic quaternary ammonium monomers and crosslinking agents are polymerized in porous polyethylene membranes;

[0019] The cyclic quaternary ammonium monomer is selected from at least one of 1-methyl-1-(4-vinylbenzyl)piperidine chloride, quaternized molecules of 4-vinylpyridine, and quaternized molecules of 4-vinylbenzyl chloride, and the mass ratio of the cyclic quaternary ammonium monomer to the crosslinking agent is 100:10-30.

[0020] The present invention provides the use of the composite anion exchange membrane described in any of the above claims in the preparation of fuel cells.

[0021] The present invention provides a fuel cell comprising electrodes and a composite anion exchange membrane as described in any of the preceding claims.

[0022] This invention provides a porous polyethylene-based membrane / crosslinked poly(methylpiperidine@vinylbenzyl chloride) composite anion exchange membrane, which is obtained by polymerizing cyclic quaternary ammonium monomers in a porous polyethylene membrane. This method is a one-pot process, simple and rapid, providing convenience for large-scale industrial production. This composite anion exchange membrane has excellent mechanical properties, high ionic conductivity, and high physical and chemical stability. When applied to the preparation of fuel cells, it exhibits good electrochemical performance, meeting the application requirements of this type of membrane in AEMFCs. It provides an important reference for overcoming key technical barriers hindering the commercialization of AEMFCs, and its application is progressing well.

[0023] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions or alterations can be made without departing from the basic technical concept of the present invention.

[0024] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the preparation of PE / MVBPIP-DVB AEMs.

[0026] Figure 2 The monomers VBC, N-methylpiperidine, and synthesized MWBPIP 1 1H NMR spectrum; PMWBPIP (DVB without crosslinker) 1 ¹H NMR spectrum; where N-methylpiperidine: δ=2.07(3H,H) a ), δ=2.34(4H,H b ), δ=1.46(4H,H c), δ=1.33(2H,H d Monomer VBC: 1 HNMR(DMSO-d6): δ=5.82and 5.28(1H,H ab ), δ=6.70-6.77(1H,H) c ), δ=7.39-7.49(4H,H d and H e ), δ=4.76(2H,H f ); intermediate unit MVBPIP 1 HNMR (D2O): δ=5.80-5.91 (1H,H) a ), δ=5.30-5.38(1H,H) b ), δ=6.70-6.83(1H,H c ), δ=7.46-7.42(2H,H d ), δ=7.56-7.52(2H,H e ), δ=4.41(2H,H f ), δ=2.83-2.94(3H,H g ), δ=3.31-3.36(3H,H h ), δ=1.87-1.99(4H,H i ), δ=1.44-1.75(2H,H j ).

[0027] Figure 3 The images show the appearance of the PE / PMWBPIP-DVB composite film during its preparation process and the results of ultraviolet light transmittance measurements. Figure 3 Image a shows a comparison of the initial reaction of monomer VBC and N-methylpiperidine in ethyl acetate solution and the reaction at 60°C for 12 hours. Figure 3 b shows AEM images of the dried MWBPIP monomer powder, the MWBPIP monomer UV-initiated polymerization into polymer PMWBPIP, the PE porous base membrane, and the polymer-filled preparation. Figure 3 c represents a comparison of the transmittance of PE and PE / PMWBPIP-DVB-15% AEM in the visible light range; Figure 3 d represents the transmittance of PE / PMWBPIP-DV-15% AEM ultraviolet light range.

[0028] Figure 4 The image shows the SEM results of the PE / PMWBPIP-DVB composite membrane; where, Figure 4 a is a cross-sectional SEM image of the PE-based film; Figure 4 b is a surface SEM image of the PE base film; Figure 4c is a cross-sectional SEM image of PE / PMVPIP-DVB-15%; Figure 4 d is the surface SEM image of PE / PMVPIP-DVB-10%; Figure 4 e is a surface SEM image of PE / PMVPIP-DVB-15%; Figure 4 f is the surface SEM image of PE / PMVPIP-DVB-20%; Figure 4 g is a surface SEM image of PE / PMVPIP-DVB-25%; Figure 4 h represents a 30% surface SEM image; Figure 4 i represents the surface elemental distribution of the PE base film; Figure 4 k represents the surface element content distribution of the PE base film; Figure 4 j is the surface elemental distribution map of PE / PMVPIP-DVB-15%; Figure 4 l is a surface element content distribution diagram of PE / PMVPIP-DVB-15%.

[0029] Figure 5 The graph shows the XPS test results of the PE / PMWBPIP-DVB composite membrane; where, Figure 5 a represents the XPS full spectrum of PE-based film and PE / PMVBPIP-DVB-15% AEM; Figure 5 b is a comparison of the elemental content of PE base film and PE / PMVBPIP-DVB-15% AEM.

[0030] Figure 6 High-resolution XPS spectra of the PE / PMWBPIP-DVB composite membrane; among which, Figure 6 a is a high-resolution scan of the carbon element in the PE-based film; Figure 6 b is a high-resolution scan of the nitrogen element in the PE-based film; Figure 6 c is a high-resolution scan of the Cl element in the PE-based film; Figure 6 d is a high-resolution scan of C element in PE / PMVBPIP-DVB-15% AEM; Figure 6 e is a high-resolution scan of the N element in a PE / PMVBPIP-DVB-15% AEM. Figure 6 f is a high-resolution scan of Cl element from PE / PMVBPIP-DVB-15% AEM.

[0031] Figure 7 The image is a Fourier transform infrared (FTIR) spectrum; among which, Figure 7 a represents the infrared spectra of the intermediate monomer, the polymer PMVBPIP (without crosslinking agent DVB), and the prepared AEM. Figure 7 b is the FTIR spectrum of PE / PMVBPIP-DVB AEMs.

[0032] Figure 8 The graph shows the mechanical properties and thickness measurements; among them, Figure 8 a shows the stress-strain curves of PE-based films and PE / PMVBPIP-DVB AEMs; Figure 8 b is a diagram recording the stretching process of the PE base film; Figure 8 c is a diagram recording the tensile process of PE / PMVBPIP-DVB-15% AEMs; Figure 8 d represents the thickness and mass measurement results of the PE base film; Figure 8 e represents the thickness and quality measurement results of the PE base film; Figure 8 f is a high-performance verification record of PE / PMVBPIP-DVB-15% AEM.

[0033] Figure 9 The image shows the hydrophilicity test results of the PE / PMWBPIP-DVB composite membrane; among them, Figure 9 Figure a shows the water absorption rate of PE / PMVBPIP-DVBAEMs. Figure 9 Figure b shows the swelling ratio results of PE / PMVBPIP-DVB AEMs.

[0034] Figure 10 The figure shows the ionic conductivity characterization of the PE / PMWBPIP-DVB composite membrane; where, Figure 10 Figure a shows the ionic conductivity results of PE / PMVBPIP-DVBAEMs; Figure 10 b represents the Arrhenius curve of PE / PMVBPIP-DVB AEMs; Figure 10 c is a diagram of the ion transport mechanism of PE / PMVBPIP-DVB AEMs.

[0035] Figure 11 The image shows the results of an atomic force test experiment; in which, Figure 11 a is a height diagram of the PE base film at the 3-micrometer scale; Figure 11 b is the phase diagram of the PE-based film at the 3-micrometer scale; Figure 11 c represents the height of the PE-based film at the 500-nanometer scale; Figure 11 d represents the phase diagram of the PE-based film at the 500 nm scale; Figure 11 e is a height map of PE / PMVBPIP-DVB-15% AEM at the 3-micrometer scale; Figure 11 f is the phase diagram of PE / PMVBPIP-DVB-15% AEM at the 3-micrometer scale; Figure 11 g represents the height map of PE / PMVBPIP-DVB-15% AEM at the 500 nm scale; Figure 11 h represents the phase diagram of PE / PMVBPIP-DVB-15% AEM at the 500 nm scale; Figure 11 i is the height map of PE / PMVBPIP-DVB-15% AEM; Figure 11 j is the modulus distribution diagram of PE / PMVBPIP-DVB-15%AEM; Figure 11 k is the adhesion distribution diagram of PE / PMVBPIP-DVB-15% AEM.

[0036] Figure 12 This is a small-angle X-ray scattering (SAXS) spectrum; where, Figure 12 a is the SAXS spectrum of the PE-based film; Figure 12 b is the SAXS spectrum of PE / PMVBPIP-DVB AEMs.

[0037] Figure 13 The graph shows the solvent resistance stability test results of the PE / PMWBPIP-DVB composite film; where, Figure 13 Image a shows PE and PE / PMVBPIP-DVB AEMs immersed in DMSO solvent for 30 days; Figure 13 b represents the gel fraction of PE and PE / PMVBPIP-DVB AEMs; Figure 13 c represents the strength results for PE and PE / PMVBPIP-DVB AEMs.

[0038] Figure 14 The graph shows the results of thermal stability testing of the PE / PMWBPIP-DVB composite film; among them, Figure 14 a represents the thermogravimetric analysis (TGA) curves of PE and PE / PMVBPIP-DVB AEMs; Figure 14 b represents the thermogravimetric (DTG) curves of PE and PE / PMVBPIP-DVB AEMs.

[0039] Figure 15 The graph shows the results of the strong alkali resistance stability test of the PE / PMWBPIP-DVB composite membrane; among them, Figure 15 a is a graph showing the mass retention rate of PE / PMVBPIP-DVB AEMs; Figure 15 Figure b shows the ionic conductivity retention rate of PE and PE / PMVBPIP-DVB AEMs.

[0040] Figure 16 Comparison of FTIR spectra of PE / PMVBPIP-DVB-15% AEM (0 days and 60 days).

[0041] Figure 17 This is a diagram showing the performance structure of a fuel cell; where, Figure 17Figure a shows the performance results of an H2-O2 fuel cell prepared by PE / PMVBPIP-DVB-15% AEM at 60℃. Figure 17 Image b is a picture of MEA prepared by PE / PMVBPIP-DVB-15% AEM. Detailed Implementation

[0042] Unless otherwise specified, all reagents and materials used in the following examples and experimental cases are commercially available.

[0043] Example 1: Porous polyethylene-based membrane / crosslinked poly(methylpiperidine@vinylbenzyl chloride) composite anion exchange membrane and its preparation method

[0044] The preparation process of the porous polyethylene-based membrane / crosslinked poly(methylpiperidine@vinylbenzyl chloride) composite anion exchange membrane (PE / MVBPIP-DVB AEMs) in this embodiment is as follows: Figure 1 As shown, the specific steps are as follows:

[0045] 1. Preparation of the intermediate monomer 1-methyl-1-(4-vinylbenzyl)piperidinium chloride (MVBPIP)

[0046] The MVBPIP monomer was synthesized from 1-methylpiperidine and 4-vinylbenzyl chloride. Under nitrogen protection, equimolar amounts of 1 mol of 4-vinylbenzyl chloride (pre-treated with an alumina rapid separation column to remove polymerization inhibitors) and 1 mol of 1-methylpiperidine were added to a three-necked flask using ethyl acetate as solvent (50 mL). The apparatus was equipped with a reflux condenser and a booster stirrer, and the mixture was reacted in an oil bath at 60 °C for 12 h to obtain a white dispersion. This dispersion was washed three times with ethyl acetate, centrifuged, and the lower solid was dried in a vacuum drying oven at 40 °C for 8 h to obtain a dry white solid, which was the intermediate monomer MVBPIP.

[0047] 2. Preparation of PE / MVBPIP-DVB AEMs

[0048] A porous polyethylene (PE) membrane (50% porosity, 17 μm thickness, purchased from Shenzhen Xingyuan Material Technology Co., Ltd., product number 39201010.00) cut into small pieces was soaked in anhydrous ethanol for 24 hours to open the pores for later use. The white solid monomer MVBPIP prepared in the previous step was dissolved in anhydrous ethanol to prepare a monomer solution with a concentration of 50 wt%. Then, the crosslinking agent divinylbenzene (DVB, with the polymerization inhibitor removed using an alumina rapid separation column, the crosslinking agent being 15 wt% of the monomer mass) and the initiator benzoin ether (added at 10 wt% of the monomer mass) were added sequentially. After complete dissolution, a transparent film-forming solution was formed. A perforated PE membrane (10cm*10cm*17μm) was laid flat and immersed in a membrane-forming solution (25-50 ml). The membrane was then irradiated with UV light (365nm, 300W) for 30 min to initiate polymerization, causing the PMVBPIP polymer to crosslink and polymerize within the PE membrane, thus preparing a composite anion exchange membrane (PE / MVBPIP-DVB-15%). The prepared PE / MVBPIP-DVB membrane was then immersed in a nitrogen-saturated 2M NaOH aqueous solution, with the NaOH solution changed daily until Cl... - Completely replaced by OH - (Titrate the NaOH aqueous solution that soaks AEM with AgNO3 and HNO3 daily until no white precipitate is produced).

[0049] In other embodiments, the amount of crosslinking agent DVB can be adjusted to 10wt%, 20wt%, 25wt%, or 30wt% of the monomer mass, and the prepared AEM is named PE / MVBPIP-DVB-x%, where x is the mass fraction of the crosslinking agent, which are 10, 20, 25, or 30, respectively.

[0050] The technical solution of the present invention will be further explained through experiments below. The samples PE / MVBPIP-DVB-10%, PE / MVBPIP-DVB-15%, PE / MVBPIP-DVB-20%, PE / MVBPIP-DVB-25%, and PE / MVBPIP-DVB-30% tested in the following experimental examples were prepared by the methods described in the above embodiments.

[0051] Characterization of intermediate monomer MVBPIP and polymer PMVBPIP in Experimental Example 1

[0052] I. Experimental Methods

[0053] 1. Characterization of intermediate monomer MVBPIP

[0054] The monomers N-methylpiperidine, 4-vinylbenzyl chloride (VBC), and the synthesized intermediate monomer MWBPIP were dissolved in deuterated reagents and subjected to 1H NMR spectroscopy.

[0055] 2. Characterization of polymer PMVBPIP

[0056] To verify the feasibility of the UV-initiated polymerization process of this application, polymerization experiments were conducted under conditions with and without the crosslinking agent DVB. The polymerization products were dissolved in deuterated reagents and subjected to 1H NMR spectroscopy.

[0057] II. Experimental Results

[0058] 1. Characterization results of intermediate monomer MVBPIP

[0059] The monomers N-methylpiperidine, VBC, and the synthetic intermediate monomer MWBPIP 1 HNMR spectral results are as follows Figure 2 As shown. In the intermediate single-unit MVBPIP 1 In the HNMR spectrum, the aromatic ring protons belonging to the monomeric VBC produced double signals at chemical shifts of 7.56–7.52 ppm and 7.46–7.42 ppm, respectively, while multiple signals of the unsaturated olefin protons of VBC were observed at chemical shifts of 5.27 ppm, 5.88 ppm, and 6.70–6.83 ppm. Simultaneously, the characteristic signal of the methylene protons of VBC shifted from 4.76 ppm to 4.41 ppm due to the bonding with N-methylpiperidine. [1-3] Furthermore, the multiple signal peaks with chemical shifts at 3.31–3.36 ppm, 2.83–2.94 ppm, 1.87–1.99 ppm, and 1.44–1.75 ppm are attributed to the absorption peaks of the methylene proton adjacent to the nitrogen atom, the methyl proton adjacent to the nitrogen atom, and the methylene proton far from the nitrogen atom on the aromatic ring of N-methylpiperidine, respectively. These signals demonstrate that the intermediate MVBPIP was successfully synthesized by bonding VBC and N-methylpiperidine.

[0060] 2. Characterization results of polymer PMVBPIP

[0061] The characterization results of PMVBPIP are as follows: Figure 2 As shown. Proton NMR spectrum (NMR) 1 ¹H NMR analysis showed that after UV photoinitiation, the characteristic peaks of the monomer MVBPIP (vinyl proton signals: 5.27 ppm, 5.88 ppm, and 6.70-6.83 ppm) completely disappeared, and no residual double bond signal was detected. This result confirms that the MVBPIP monomer can be efficiently polymerized through UV photoinitiation to form the polymer PMVBPIP.

[0062] Example 2: Characterization of anion exchange membranes

[0063] I. Experimental Methods

[0064] The anion exchange membrane was characterized by visual observation, ultraviolet light transmittance analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR).

[0065] The ultraviolet (UV) transmittance of the thin film was measured using a UV-Vis spectrophotometer (UV-5200, Shanghai Yuanxi Instrument Co., Ltd.). The film was cut to a size of 40mm × 9mm and placed tightly against one side of a glass cuvette. The UV transmittance was then measured. A blank glass cuvette was used as a baseline control. The test parameters were as follows: scan range 190-1100nm; sampling interval 2.0s / sample; measurement method: transmittance.

[0066] II. Experimental Results

[0067] 1. Visual observation results

[0068] The original PE base film exhibits a white, opaque state due to its abundant microporous structure, which causes strong light scattering. Figure 3 (a-3b); After being impregnated with MWBPIP / DVB ethanol solution and polymerized under UV light for 30 min, the resulting PE / PMWBPIP-DVB composite film became transparent. This significant change in transparency confirms that the PMWBPIP-DVB polymer electrolyte has fully filled the pores of the PE base film, forming a composite material with a uniform phase structure.

[0069] 2. Results of ultraviolet light transmittance analysis

[0070] The results are as follows Figure 3 As shown in c-3d, in the visible light range (380nm-780nm), the PE-based film maintains extremely low light transmittance (<5%), while the AEM transmittance of the PE / PMWBPIP-DVB-15% prepared with pore filling is greatly increased to 60%-70%. This is mainly attributed to the good refractive index matching between the PE-based film and the PMWBPIP-DVB polymer, which significantly reduces interfacial light scattering. However, the refractive index difference between the filled polymer and the PE-based film increases after combining with water, thus inducing strong interfacial light scattering and significantly reducing the transmittance. Figure 3 c). In addition, Figure 3 As shown in d, PE / PMWBPIP-DVB maintains high transparency in the ultraviolet light range. This feature not only ensures that the monomers can react uniformly in the film thickness direction when ultraviolet light initiates polymerization, but also directly verifies the feasibility and effectiveness of the polymerization scheme of the present invention.

[0071] 3. SEM Analysis Results

[0072] The microstructure of PE / PMVBPIP-DVB AEMs was evaluated using high-magnification SEM images, and the results are as follows: Figure 4 As shown, the PE porous base membrane has a large number of micropores of about 100 nm evenly distributed on its surface, and the cross-section shows a large number of layered pores. In contrast, the PE / PMVBPIP-DVB composite membrane exhibits significantly different surface morphology characteristics: 1) the surface is smooth and dense, and the inherent fiber network structure and surface pores of the base membrane are not observed even at high magnification; 2) cross-sectional analysis shows that the layered pore structure is completely filled by the PMVBPIP-DVB polymer, with only a small number of closed micropores caused by the biaxial stretching process remaining. These morphological characteristics indicate that the PMVBPIP monomer solution can fully penetrate the three-dimensional channels of the base membrane under the synergistic effect of gravity, capillary action, and solution surface tension, and form a dense composite material after UV-initiated polymerization. PE / PMVBPIP-DVB membranes with different amounts of crosslinking agent are all densely filled, and the membrane with a higher degree of crosslinking (25%-30%) has a rougher surface. The dense structure of PE / PMVBPIP-DVB AEMs provides effective protection against gas leakage that could cause short circuits within the AEMFC.

[0073] In the SEM-EDS elemental distribution diagram, unlike the PE-based membrane where only C and O elements are uniformly distributed on the surface, the PE / PMVBPIP-DVB-15% AEM image shows a uniform distribution of O and N elements, with contents of 17.6% and 3.2%, respectively. N is a characteristic element of quaternary ammonium groups, and its increased content indicates that PMVBPIP-DVB has been successfully incorporated into the PE microporous membrane. Meanwhile, the significant increase in O elements is closely related to the absorption of moisture from the air by the hydrophilic polymer PMVBPIP-DVB within the PE-based membrane. These results confirm the effective filling of PMVBPIP-DVB in porous PE-based membranes.

[0074] 4. XPS Analysis Results

[0075] To further verify that PMVPIP-DVB has been successfully anchored within the micropores of PE, surface XPS spectral analysis was performed on the PE base film and PE / PMVPIP-DVB-15% AEM. The results are as follows: Figure 5 As shown. Compared to the PE-based film, the XPS spectrum of PE / PMVPIP-DVB-15% AEM shows new peaks for the characteristic elements N1s and Cl2P of the polymer PMVPIP, proving that the polymer PMVPIP-DVB is effectively introduced into the PE-based film. The high-resolution XPS spectrum of PE / PMVPIP-DVB-15% AEM shows ( Figure 6The high-resolution C1s scan curve fitting also revealed two sets of peaks at 284.80 eV and 286.1 eV, attributed to CC and CN, respectively. Furthermore, -NH2 (399 eV) and -NH3 were clearly observed in the N1s region of the PE / PMVPIP-DVB-15% spectrum. + The characteristic double peaks (401.3 eV) further confirm the presence of the PMVPIP-DVB polymer structure within the PE-based film.

[0076] 5. FTIR analysis results

[0077] Figure 7 The infrared spectra of the monomer, polymer, and prepared PE / PMVBPIP-DVB AEMs are shown. The intermediate monomer MVBPIP was prepared by the reaction of VBC and N-methylpiperidine, and its FTIR spectrum is located at 3030 cm⁻¹. -1 1601cm -1 And 1515cm -1 The absorption peak at 1266 cm⁻¹ originates from the aromatic ring in VBC. -1 And 823cm -1 The absorption peaks at 1630 cm⁻¹ are attributed to the CH rocking vibration and C-Cl stretching vibration of the -CH₂-Cl group in VBC, respectively. Notably, the stretching vibration (1630 cm⁻¹) of the C=C double bond in the VBC monomer, also attributed to the intermediate monomer MVBPIP, can still be observed in the spectrum. -1 This indicates that the olefin double bond structure was fully preserved during the bonding reaction between the piperidine group and VBC, and these unreacted C=C double bonds provided the necessary active sites for the subsequent UV-initiated polymerization reaction. Meanwhile, approximately 3362 cm⁻¹ -1 The broad peak at 1080 cm⁻¹ is related to the stretching vibration of the OH group in the hydrophilic N-methylpiperidine that absorbs water. -1 The absorption peak corresponds to the CN bending vibration of the ammonium group, indicating that the intermediate monomer MVBPIP was successfully prepared by N-methylpiperidine and VBC bonding.

[0078] After UV-initiated polymerization, MVBPIP monomers were polymerized at 1630 cm⁻¹. -1 The characteristic absorption peak of the C=C double bond at 719 cm⁻¹ completely disappeared in the polymer PMVBPIP spectrum, and no residual vinyl signal was observed in the FTIR spectrum of PE / PMVBPIP-DVB AEM. This result confirms the successful initiation of the UV-induced polymerization reaction and the efficient conversion of vinyl groups. FTIR structural characterization of PE / PMVBPIP-DVB AEMs shows that the peak at 719 cm⁻¹... -1 1465cm -1 2849cm -1And 2916cm -1 The characteristic peaks appearing at the same positions correspond to the -CH2- rocking vibration, shear vibration, and CH bond stretching vibration of the PE base film, respectively, while the peak at 3378 cm⁻¹ corresponds to the same position. -1 The appearance of the OH stretching vibration peak indicates enhanced membrane hydrophilicity, and these features collectively verify the successful filling of PMVBPIP-DVB in PE-based membranes. Although the FTIR spectra of samples with different degrees of crosslinking are generally similar, the changes in the intensity of the OH absorption peak reflect the regulatory effect of the degree of crosslinking on the hydrophilicity of the composite membrane. This finding provides an important basis for optimizing membrane performance.

[0079] The results of the above characterization experiments all demonstrate that the present invention has successfully prepared a composite anion exchange membrane (PE / MVBPIP-DVB).

[0080] Mechanical characterization analysis of composite anion exchange membrane in Experiment Example 3

[0081] I. Experimental Methods

[0082] Select the film to be tested and cut it into a 4cm × 1cm strip. Clamp the strip flat at both ends into the fixture of the universal testing machine (68TM-10, INSTRON Testing Equipment Trading Co., Ltd., USA). Set the gauge length to 20mm and adjust the speed at 10mm min. -1 Tensile tests were conducted at a certain speed, and the maximum stress and strain per unit area resisting fracture during the tensile process were recorded.

[0083] II. Experimental Results

[0084] Mechanical properties are one of the important performance indicators for evaluating the durability of an AEM in a fuel cell system. For example... Figure 8 As shown in Figure a, the PE porous base membrane exhibits excellent mechanical properties, with tensile strength and elongation at break reaching 162.5 MPa and 133.1%, respectively. The prepared PE / PMVBPIP-DVB AEMs all demonstrate higher mechanical properties than the PE base membrane (tensile strength > 186.1 MPa, elongation at break > 145.7%), far exceeding the requirements for practical applications of AEMFC. With increasing crosslinking degree, the tensile strength and elongation at break of PE / PMVBPIP-DVB AEMs increase simultaneously. This is because DVB enhances the interaction of polymer molecular chains, effectively distributing stress. Among them, the tensile strength of PE / PMVBPIP-DVB-15% AEM reaches the maximum value of this series of AEMs (206.6 MPa), and its elongation at break remains at 163.96%.

[0085] At the same time, through Figure 8The image records of the b-8c test process and the comparison of the film images after the test show that the PE / PMVBPIP-DVB-15% AEM exhibits very little stress whitening after stretching. This indicates that the PE microporous base film and the filled polymer are tightly bonded and share the stress tension, which is consistent with the current data conclusions.

[0086] The porous PE base film is only 17μm thick. After filling, the thickness of PE / PMVBPIP-DVB-15% AEM increases to 18μm, while its mass also increases to 2.5 times. This is further proof that the polymer PMVBPIP-DVB successfully and effectively fills the micropores of PE. Moreover, PE / PMVBPIP-DVB-15% AEM achieves a reduction in mass and thickness while maintaining the high strength of the film (e.g., ...). Figure 8 These characteristics (d-8e) perfectly align with the future development trend of fuel cells, which emphasizes both lightweight design and high performance. Furthermore, the PE / PMVBPIP-DVB-15% AEM material is soft and can recover its original shape after being rolled or folded at will. Figure 8 f) It can meet the requirements of various shapes and processes of AEMFC, and AEM is resistant to puncture by sharp substances, effectively resisting potential physical damage risks such as accidental impact, wear, and scratches, so as to ensure the overall safety of the fuel cell system.

[0087] The above experimental results show that the mechanical properties of the anion exchange membranes PE / MVBPIP-DVB-10%, PE / MVBPIP-DVB-15%, PE / MVBPIP-DVB-20%, PE / MVBPIP-DVB-25%, and PE / MVBPIP-DVB-30% provided by this invention are all superior to those of the PE porous base membrane. In particular, the PE / MVBPIP-DVB-15% AEM exhibits the best tensile strength and maintains a relatively good elongation at break.

[0088] Characterization and analysis of the hydrophilicity of the composite anion exchange membrane in Experiment Example 4

[0089] I. Experimental Methods

[0090] 1. Experiment on determination of water absorption (WU) and swelling ratio (SR)

[0091] To test the water absorption and swelling ratio of the film, the film was immersed in deionized water saturated with N2 at different temperatures (20℃, 40℃, 60℃, and 80℃) for 48 hours. After wiping off the moisture from the film surface, the mass and length of the wet film were measured using a high-precision analytical balance and a ruler. Subsequently, the film was dried in a forced-air drying oven to constant weight, and the dry weight and length of the film in the dried state were measured. The water absorption and swelling ratio (WU and SR) of the film were calculated using the following formulas:

[0092]

[0093] In the formula, m1 is the mass of the wet film at the test temperature, and m2 is the dry weight of the film.

[0094]

[0095] In the formula, l1 is the length of the wet film at the test temperature, and l2 is the length of the film in the dry state.

[0096] 3. Ion exchange capacity (IEC) and hydration number (λ) analysis and testing methods

[0097] Ion exchange capacity (IEC) was determined by back titration, by titrating the OH- ions exchanged and bound to the AEM membrane with hydrochloric acid. - This is used to characterize the number of exchangeable ions in a unit mass of AEM. The specific steps are as follows: After complete ion replacement, the membrane is immersed in N2-saturated deionized water and repeatedly rinsed until the surface is neutral as measured by a pH reagent. It is then dried in a 60℃ oven to constant weight. Afterward, a fixed mass of the membrane is immersed in 50 mL of 0.1 mol / L... -1 In an aqueous HCl solution, let stand for 72 hours until all OH groups in the film are removed. - Completely depleted by HCl. Take the HCl aqueous solution soaking the membrane and add phenolphthalein dropwise, using 0.01 mol L... -1 Titrate with a NaOH aqueous solution (standardized with potassium hydrogen phthalate) until a persistent pink color is obtained, and test the residual HCl content in the soaking solution. IEC (mmol g⁻¹) is calculated using the following formula:

[0098]

[0099] In the formula, C0 is the concentration of HCl aqueous solution, V0 is the volume of HCl aqueous solution used to soak the membrane, C1 is the concentration of NaOH aqueous solution, V1 is the volume of NaOH aqueous solution used to titrate the residual HCl, and m is the dry weight of the membrane to be tested.

[0100] The hydration number represents the number of water molecules that can associate with a single quaternary ammonium group, and can be calculated using the following formula:

[0101]

[0102] In the formula, WU is the water absorption rate of AEM at room temperature, and IEC is the ion exchange capacity measured at room temperature.

[0103] II. Experimental Results

[0104] 1. Results of water absorption rate test

[0105] The results of the water absorption test are as follows Figure 9As shown in Figure a, PE / PMVBPIP-DVB AEMs with different degrees of crosslinking all exhibited temperature dependence; that is, as the temperature increased from 20℃ to 80℃, the water absorption rate of the membrane continuously increased, with the PE / PMVBPIP-DVB-15% AEM reaching its maximum water absorption rate (24.19%) at 80℃. It can be seen that with the increase of crosslinking agent content, the water absorption rate of PE / PMVBPIP-DVB AEMs decreased significantly. This decrease is due to the increased amount of crosslinking agent leading to an increase in hydrophobic molecular chain segments, effectively inhibiting water penetration and adsorption. Simultaneously, the increased crosslinking density makes the internal matrix of the AEM more compact, also preventing water penetration. These two mechanisms together lead to a decrease in the water absorption rate of the AEM.

[0106] 2. Results of swelling rate experiment

[0107] High hydrophilicity helps improve the ionic conductivity of an atomizing element (AEM); however, excessive hydrophilicity can cause dimensional expansion of the AEM, thereby impairing its mechanical strength and negatively impacting the overall structure of the fuel cell. Therefore, ensuring a low swelling ratio is a crucial indicator for evaluating high-performance AEMs. The swelling ratio experimental results are as follows... Figure 9 As shown in b, the dimensional expansion of PE / PMVBPIP-DVB AEMs is suppressed with increasing DVB content, which is related to the amount of hydrophobic chains introduced by the crosslinking agent and the density of the AEM matrix. Furthermore, the dimensional expansion rate of PE / PMVBPIP-DVB AEMs increases with increasing temperature. This is because the increased temperature leads to intensified water molecule movement and polymer chain expansion, resulting in larger dimensions. However, the PE microporous membrane, as the base membrane, effectively limits excessive volume changes of the polymer within the pores, giving the composite membrane excellent dimensional stability. Among them, PE / PMVBPIP-DVB-15% exhibits the highest swelling rate (only 8.23%) at 80℃, meeting the application requirements of AEMFC.

[0108] 3. Results of ion exchange capacity experiment

[0109] The ion exchange capacity (IEC) values ​​of PE / PMVBPIP-DVB AEMs measured at 20 °C are shown in Table 1. The IEC values ​​of all membranes range from 0.98 to 1.55 meq g. -1Within the range, the PE / PMVBPIP-DVB-10% with the lowest degree of crosslinking exhibits the highest IEC value. Increased crosslinking degree leads to IEC showing the same trend as water absorption and swelling rate. In general, low-crosslinking PE / PMVBPIP-DVB AEMs result in relatively high IEC, water absorption, and swelling rate, and also have a higher capacity for bound water (this conclusion can be verified by data on the hydration number λ). The IEC values ​​of PE / PMVBPIP-DVB AEMs with different degrees of crosslinking remain generally at a low level. Furthermore, low-crosslinking PE / PMVBPIP-DVB AEMs, due to their loose internal structure and weaker inter-polymer chain interactions, exhibit higher water absorption and a larger hydration number (λ value), which will facilitate the transport of hydrated ions.

[0110] Table 1. IEC, WU and λ of PE / PMVBPIP-DVB AEMs at 20℃

[0111]

[0112] The above results show that by increasing the amount of crosslinking agent, the changes in IEC, water absorption rate and swelling rate are similar, all decreasing, indicating that the present invention needs to balance the influence of IEC and the hydrophilicity / hydrophobicity of the pores on membrane performance.

[0113] Experimental Example 4: Characterization and Analysis of Ion Conductivity

[0114] I. Experimental Methods

[0115] 1. Ionic conductivity (σ) test method

[0116] Within the operating temperature range of 20-80℃, the ionic conductivity (σ) of the AEM was evaluated using the two-point AC impedance method. Specifically, a film of fixed width was immersed in N2-saturated ultrapure water at different temperatures (20℃, 40℃, 60℃, and 80℃), and its two ends were fixed to both sides of a platinum electrode connected to an electrochemical workstation (CHI660E, Shanghai Chenhua Instrument Co., Ltd.). The bulk impedance of the film was then measured. In practice, the resistance was repeatedly tested until the value stabilized, and the conductivity was calculated using the following formula:

[0117]

[0118] In the formula, L is the electrode spacing, A represents the cross-sectional area of ​​the AEM, i.e., film thickness × width, and R is the bulk impedance of the film.

[0119] 2. Atomic Force Microscopy (AFM) Analysis Method

[0120] The thin film was flatly attached to a silicon substrate, and the microphase separation on the film surface was observed using an atomic force microscope (Icon, Bruker GmbH, Germany) in tapping mode.

[0121] 3. Small-angle X-ray scattering analysis (SXAS) test method

[0122] The alkalized membrane was immersed in N2-saturated deionized water for 24 hours to equilibrate. Then, the size of the micro-ionic domains composed of ion-conducting groups within the membrane was measured using a small-angle X-ray scattering analyzer (Xeuss 2.0, Cenopro, France). The ionic domain size is related to the Bragg spacing d and can be calculated using the following formula:

[0123]

[0124] In the formula, q is the scattering vector of the particles in the ion domain.

[0125] The scattering vector q is a key parameter describing the scattering phenomenon, and is defined as:

[0126]

[0127] In the formula, θ is the scattering angle and λ is the wavelength of the incident X-ray.

[0128] II. Experimental Results

[0129] 1. Results of ionic conductivity experiments

[0130] High ionic conductivity is a prerequisite for the practical application of AEMFCs. The ionic conductivity of PE / PMVBPIP-DVB AEMs was calculated using the AC bulk impedance measured by an electrochemical workstation, and the results are as follows: Figure 10 As shown in Figure a, at 80℃, the ionic conductivity of PE / PMVBPIP-DVB AEMs first increases and then decreases with increasing DVB content. Among them, PE / PMVBPIP-DVB-15% AEM exhibits outstanding ionic conductivity, achieving 158.73 mS / cm. -1 The highest ionic conductivity. This phenomenon stems from the multiple regulatory effects of crosslinking degree: moderate crosslinking (15% DVB) ensures sufficient hydration of piperidine groups (λ = 3.88) and constructs continuous ion transport channels by forming nanoscale microphase separation structures; while excessive crosslinking degree leads to: 1) decreased IEC value (reduced active sites); 2) restricted molecular chain movement (decreased water absorption); 3) excessive development of hydrophobic microdomains (…). Figure 10c) This impairs the connectivity of water clusters, forming "islands" for ion transport and hindering ion diffusion. It is noteworthy that the multi-layered microphase separation structure (PE-based membrane / polymer interface, polymer backbone / functional group interface) constructed by the pore-filling process synergistically works with the hydrophobic properties of DVB to achieve precise control of the hydrophilic / hydrophobic balance within the membrane. This provides a new approach to simultaneously achieving high conductivity and excellent mechanical stability.

[0131] The ionic conductivity of AEMs exhibits a temperature dependence, with the ionic conductivity of PE / PMVBPIP-DVB AEMs increasing with rising temperature. This phenomenon can be explained by two synergistic mechanisms: First, rising temperature provides a higher thermodynamic driving force for ion transport, allowing ions to gain sufficient energy to overcome migration barriers and significantly accelerating their movement. More importantly, when the temperature exceeds the glass transition temperature of the polymer matrix, the mobility of molecular chain segments is greatly enhanced, increasing the free volume fraction and promoting the ion diffusion rate. Furthermore, the change in ionic conductivity of PE / PMVBPIP-DVB AEMs is positively correlated with temperature, conforming to the Arrhenius equation. Based on the relationship between lnσ and 1000 / T, activation energy calculations reveal that the OH groups within PE / PMVBPIP-DVB AEMs... - The activation energy for ion transport is relatively small, ranging from 4.60 kJ / mol. -1 -9.32 kJ mol -1 Within the range ( Figure 10 b) This indicates that the ion transport resistance within PE / PMVBPIP-DVB AEMs is low, which may be related to the fact that the piperidine groups with side chains are more prone to swinging and aggregation.

[0132] 2. Atomic Force Analysis (AFM) Results

[0133] Using the tapping mode of AFM, the ion transport channels of PE / PMVBPIP-DVB-15% AEM were visually observed, and the results are as follows: Figure 11As shown in a-11k, the PE porous base membrane has interwoven fibers distributed on its surface, forming a typical porous structure, which is highly consistent with the conclusions of high-magnification SEM. Simultaneously, the light and dark zones shown in its phase diagram are due to the fibers and pores; the bright areas correspond to higher regions formed by fiber aggregation, while the dark areas originate from the height difference between the micropores and the surrounding fibers. The height image of PE / PMVBPIP-DVB-15% AEM reveals that no interwoven fiber distribution was observed on the surface of the PE base membrane, indicating that the polymer PMVBPIP-DVB effectively fills the pores inside the PE base membrane. Furthermore, the phase diagram of PE / PMVBPIP-DVB-15% AEM shows a clear hydrophilic-hydrophobic microphase separation structure, where dark areas represent hydrophilic domains formed by hanging piperidine quaternary ammonium salt clusters, and bright areas represent hydrophobic domains composed of the PE base membrane and the polymer backbone. Particularly significant is the wider and continuous distribution of the hydrophilic phase; these interconnected hydrophilic phases construct rapid ion transport channels, which will facilitate rapid ion transport within the AEM.

[0134] The adhesion and modulus force curves of AFM can further demonstrate the hydrophilic / hydrophobic microphase separation structure of PE / PMVBPIP-DVB-15% AEM. (AFM adhesion force distribution diagram of AEM) Figure 11 k) shows distinct light and dark zones. Because the PMVBPIP-DVB polymer with pendant piperidine quaternary ammonium groups fills the pores of the PE microporous membrane, electrostatic forces and hydrogen bonds easily form between the silicon needles and the hydrophilic piperidine quaternary ammonium groups, exhibiting strong adhesion, specifically shown as bright areas. This contrasts sharply with the low adhesion of the hydrophobic PE base membrane molecular chains and polymer backbone. AFM modulus distribution ( Figure 11 j) The distribution of adhesion forces is highly consistent with that of the PE molecular chains in the dark region and the benzene ring structure in the bright region, which contrasts with the piperidine ring, form a clear phase-separated structure. These results effectively verify the formation of the hydrophilic / hydrophobic phase separation structure within the PE / PMVBPIP-DVB AEM.

[0135] 3. SAXS analysis results

[0136] The size of the ion cluster structural domains formed by the pendant piperidine group clusters within the AEM was quantitatively characterized using SAXS. Figure 12As shown in a-12b, the PE-based membrane exhibits a homogeneous structure. After filling with the polymer PMVBPIP-DVB, it displays a distinct characteristic scattering peak, which is the characteristic ionomer band formed by hydrophilic quaternary ammonium group clusters. This characteristic scattering result, together with AFM characterization, confirms the existence of a significant microphase separation structure between the polymer molecular chains and ion clusters. The introduction of hydrophobic segments of the crosslinking agent can effectively regulate the size distribution of ion clusters within the membrane. SAXS data analysis calculated according to the Bragg equation (d = 2π / q) shows that the microphase separation structure of PE / PMVBPIP-DVB AEMs exhibits a significant crosslinking degree dependence (Table 2). The test results show that the ion cluster domain spacing (d-spacing) is distributed in the range of 42.78-46.37 nm. With the increase of DVB content, the Bragg spacing shows a decreasing trend (e.g., PE / PMVBPIP-DVB-30% decreases to 42.78 nm). This trend directly reflects the compression effect of the hydrophobic crosslinking network on the size of the hydrophilic ion clusters, jointly revealing the precise regulation effect of the crosslinking agent content on the microphase separation structure within the membrane.

[0137] Table 2 SAXS data for PE / PMVBPIP-DVB AEMs

[0138]

[0139] The above results show that among the composite anion exchange membranes provided by this invention, PE / PMVBPIP-DVB-15% has the highest ionic conductivity, especially under the test condition of 80℃, its ionic conductivity is significantly higher than that of other composite anion exchange membranes.

[0140] Stability Characterization Analysis of Experiment Example 5

[0141] I. Experimental Methods

[0142] 1. Solvent resistance test

[0143] To confirm the formation of an effective cross-linked network in PMVBPIP-DVB, gel fraction tests were performed on AEMs with different degrees of cross-linking. PMVBPIP polymerized without the addition of a cross-linking agent is soluble in DMSO. PE, PE / MVBPIP-DVB-10%, PE / MVBPIP-DVB-15%, PE / MVBPIP-DVB-20%, PE / MVBPIP-DVB-25%, and PE / MVBPIP-DVB-30% were immersed in DMSO for 30 days, and the remaining mass was tested periodically to assess the degree of effective cross-linking.

[0144] 2. Test of firmness using ultrasonic vibration method

[0145] The strength of the polymer within the micropores of PE directly affects the durability of the AEM (Alternating Electrode Imager). This experiment simulates the state of the AEM during actual use using rapid ultrasonic oscillation, thus providing a simple assessment of the bonding strength between the polymer and the PE substrate film. Specifically: After stabilizing in N2-saturated deionized water for 24 hours, a fixed-size portion of the film was dried and weighed. The film was then placed in a beaker and immersed in deionized water. The entire setup was subjected to rapid ultrasonic oscillation at 40 kHz in an ultrasonic cleaner (PS-60AD, Whale Control Instruments & Equipment Ningbo Co., Ltd.). The film was then removed, dried, and weighed again. The change in film mass before and after ultrasonication was compared to evaluate the strength of the polymer within the micropores.

[0146] 3. Thermogravimetric analysis (TGA) test method

[0147] Take 5-10 mg of the film sample and place it in a sample dish, using an empty sample dish as a control. Analyze the mass change curve with temperature using a Netzsch thermogravimetric analyzer (TG209, Netzsch Group, Germany). The experimental parameters are as follows: temperature range 40-600℃, N2 atmosphere protection, nitrogen flow rate 20 mL / min. -1 The heating rate is 10℃ / min. -1 .

[0148] 4. Oxidative stability test

[0149] To evaluate the oxidative stability of AEMs, PE / PMVBPIP-DVB AEMs with different degrees of crosslinking were tested in Fenton solution (3% H2O2, 2ppm Fe). 2+ The curve showing the change in mass retention rate in the figure.

[0150] 5. Stability test in alkaline environment

[0151] The composite anion exchange membrane prepared in this invention was accelerated alkalized with 1M NaOH solution at 20°C for 720 h, and then the mass retention rate, ionic conductivity and Fourier transform infrared spectrum were measured.

[0152] II. Experimental Results

[0153] 1. Solvent resistance

[0154] The results are as follows Figure 13As shown in a-13b, the PE-based membrane exhibits good solvent resistance, maintaining approximately 100% mass retention. In contrast, the gel fraction of PE / PMVBPIP-DVB AEMs ranges from 97.57% to 98.96%, fully demonstrating the formation of a stable cross-linked network in PMVBPIP-DVB. Photographs of PE / PMVBPIP-DVB AEMs immersed in DMSO solution for 30 days show that all samples maintain high transparency, with no whitening caused by polymer dissolution. This observation is corroborated by the high gel fraction (>97%) test data. These results indicate that the stable network structure constructed through cross-linking degree regulation can ensure the structural and performance reliability of AEMs during long-term use, providing an important guarantee for their application in harsh environments such as fuel cells.

[0155] 2. Results of ultrasonic vibration method

[0156] The interfacial bonding strength and mechanical durability of PE / PMVBPIP-DVB AEMs were further evaluated using an ultrasonic vibration method. Low-amplitude and high-frequency ultrasonic treatment generates heat, increases polymer chain fluidity, accelerates molecular chain diffusion and fusion, and can also cause molecular chain breakage, thereby damaging the material structure and intermolecular interactions. After continuous treatment of the sample with 40kHz high-frequency ultrasound for 10 minutes… Figure 13 c) AEMs with different degrees of crosslinking exhibited significantly different mass loss behaviors: the low-crosslinking PE / PMVBPIP-DVB-10% AEM retained 92.95% of its mass due to weaker intermolecular chain interactions; while the high-crosslinking PE / PMVBPIP-DVB-25% AEM, with its dense three-dimensional network structure, lost only 0.9% of its mass. Overall, even under these harsh ultrasonic conditions, all samples maintained a mass retention rate of over 90%, mainly attributed to: 1) the DVB crosslinking network firmly anchoring the polymer molecular chains within the PE pores; and 2) the strong interfacial interactions between the base film and the filling phase.

[38] The results confirm that the composite membrane possesses excellent resistance to mechanical fatigue, meeting the stringent requirements for material structural integrity during long-term operation of AEMFC, and providing key material assurance for improving the durability of the battery system.

[0157] 3. Results of thermogravimetric analysis

[0158] The curve of TGA-DTG shows ( Figure 14(a-14b) PE / PMVBPIP-DVB AEMs exhibit similar thermogravimetric curves, with the weight loss mainly occurring in three phases: 50℃-180℃ primarily due to the loss of water or solvent resulting in a slight decrease in mass; 180℃-330℃ due to the degradation of functional N-cyclic quaternary ammonium groups and side groups (benzene rings); and 330℃-500℃ primarily due to the breakage and degradation of the aliphatic backbone in the PMVBPIP-DVB polymer. At 450℃, the PE base film backbone undergoes thermal decomposition, exacerbating the mass loss. Overall, PE / PMVBPIP-DVB AEMs do not decompose thermally below 180℃, fully meeting the AEMFC operating temperature requirement (typically <80℃).

[0159] 4. Results of oxidative stability

[0160] The results are as follows Figure 15 As shown in Figure a, the mass retention rate of the samples increased with increasing crosslinking degree. Among them, the highly crosslinked PE / PMVBPIP-DVB-25% AEM exhibited the best antioxidant performance, maintaining a mass retention rate of 86.83% even after accelerated oxidation testing. This phenomenon is mainly attributed to the fact that the dense three-dimensional network structure formed by the high crosslinking density effectively inhibited the penetration and diffusion of free radicals. Overall, the oxidation stability of AEMs can be effectively improved by precisely controlling the crosslinking degree. The excellent antioxidant performance (mass retention rate ≥80.35%) exhibited by the PE / PMVBPIP-DVB AEMs series membrane materials provides an important guarantee for their long-term stable operation in fuel cell environments.

[0161] 5. Stability results in alkaline environments

[0162] Considering the strongly alkaline environment faced by AEM in fuel cells, the experiment used 1M NaOH solution for 720h accelerated alkalization testing at 20℃. Figure 15 (b) The results show that the synergistic effect of the fully carbon-chain PE base membrane and the sterically hindered cyclic quaternary ammonium groups endows the composite membrane with excellent alkali resistance: PE / PMVBPIP-DVB-30% AEM still retains 90.88% of its ionic conductivity after testing, and can withstand the long-term operation of AEMFC. It is noteworthy that PE / PMVBPIP-DVB-10% AEM exhibits a relatively low conductivity retention rate, which is closely related to the excessive swelling caused by its looser cross-linked network structure. The excessively high water absorption rate accelerates the OH- ionization process. - The penetration and degradation of quaternary ammonium groups.

[0163] By comparing the changes in FTIR spectra of PE / PMVBPIP-DVB-15% AEM before and after soaking in 1M NaOH solution for 60 days (20℃), it was found that ( Figure 16 Except for a slight decrease in the intensity of the characteristic absorption peaks, the positions and shapes of the characteristic peaks of all key functional groups remained stable, with no obvious peak shifts or new peak generation. This result verifies the excellent alkali resistance of the composite membrane at the molecular structure level.

[0164] The above results demonstrate that the composite anion exchange membrane provided by this invention exhibits high stability, including resistance to solvents, heat, oxidation, and strong alkalis.

[0165] Example 6: Characterization Analysis of Fuel Cells

[0166] I. Experimental Methods

[0167] The single-cell analysis and testing method and MEA assembly method are as follows:

[0168] The composite anion exchange membrane prepared in Example 1 was assembled into a membrane electrode assembly (MEA) and its single-cell performance was tested in an H2-O2 fuel cell system. The preparation process of the MEA assembly is as follows: the ionomer solution for preparing the MEA, Pt / C catalyst (40%), isopropanol, and deionized water were mixed in proportion and ultrasonically blended for 30 min. The mixture was then uniformly sprayed onto the surface of carbon paper with a catalyst loading of 0.5 mg / cm³. -2 The membrane electrode assembly (MEA) was fabricated by sandwiching the AEM between two sheets of carbon paper coated with catalyst and hot-pressing them at 60°C and 2 MPa for 2 min. Finally, the performance of the H2 / O2 fuel cell was evaluated using a fuel cell test station (Hephas Mini-L100, HEE Corporation) at 60°C with the following parameters: back pressure 0 MPa, H2 (anode) flow rate 250 mL / min. -1 The O2 (cathode) flow rate is 350 mL / min. -1 .

[0169] II. Experimental Results

[0170] Fuel cell test results as follows Figure 17 As shown, a single cell assembled with PE / PMVBPIP-DVB-15% AEM exhibited a high open-circuit voltage of 1.03V, confirming that the dense filling of the PE-based membrane pores by the PMVBPIP-DVB polymer effectively prevents gas cross-permeation. This cell achieved a power output of 120.20 mW / cm² in H₂-O₂ fuel cell testing. -2 Peak power density and 211.90 mA / cm² -2 The limiting current density, although these values ​​do not fully reflect the material itself, is 158.73 mS / cm. -1The high ionic conductivity of PE / PMVBPIP-DVB AEMs is primarily attributed to limitations in existing fuel cell assembly processes, including the influence of factors such as catalyst efficiency, slurry formulation, and electrode preparation technology. Nevertheless, these results sufficiently demonstrate the potential value of PE / PMVBPIP-DVB AEMs in fuel cell applications.

[0171] As can be seen from the above embodiments and experimental examples, the present invention provides a porous polyethylene-based membrane / crosslinked poly(methylpiperidine@vinylbenzyl chloride) composite anion exchange membrane, which is obtained by polymerizing cyclic quaternary ammonium monomers in a porous polyethylene membrane. This method is a one-pot process, which is simple and rapid, providing convenience for large-scale industrial production. The composite anion exchange membrane has excellent mechanical properties, high ionic conductivity, and high physical and chemical stability. When applied to the preparation of fuel cells, it exhibits good electrochemical performance, meeting the application requirements of this type of membrane in AEMFCs. It provides an important reference for solving key technical barriers hindering the commercialization of AEMFCs, and its application is progressing well.

Claims

1. A composite anion exchange membrane, characterized by, It is prepared by polymerization of a cyclic quaternary ammonium monomer and a crosslinking agent in a porous polyethylene film; The cyclic quaternary ammonium monomer is at least one selected from 1-methyl-1-(4-vinylbenzyl)piperidine chloride, quaternized molecules of 4-vinylpyridine, quaternized molecules of 4-vinylbenzyl chloride, and the mass ratio of the cyclic quaternary ammonium monomer to the crosslinking agent is 100:10-30.

2. The composite anion exchange membrane according to claim 1, characterized in that: The mass ratio of the cyclic quaternary ammonium monomer to the crosslinking agent is 100:15-30.

3. The composite anion exchange membrane according to claim 1 or 2, characterized in that, It is prepared by a method comprising the following steps: Step 1, mixing the monomer with the crosslinking agent and the initiator to obtain a film-forming solution; Step 2, immersing the porous polyethylene-based film in the film-forming solution, and initiating the polymerization reaction by light, to obtain the composite anion exchange film.

4. The composite anion exchange membrane according to claim 3, characterized in that: In the film-forming solution, the mass ratio of the monomer to the solvent is 1-2:1-2; and / or, the mass ratio of the monomer to the initiator is 50-100:5-10.

5. The composite anion exchange membrane according to claim 3, characterized in that: The crosslinking agent is at least one selected from divinylbenzene, divinyl isobenzoate, 1,7-divinyl-1,1,3,3,5,5,7,7-octamethyltetrasiloxane, and divinylsilane; and / or, the initiator is at least one selected from benzoin ethyl ether, diphenyl-2,4,6-trimethylphenyl phosphoroyl oxide, and 1-hydroxycyclohexyl phenone; and / or, the solvent of the film-forming solution is at least one selected from ethanol, n-propanol, isopropanol, and n-butanol.

6. The composite anion exchange membrane according to claim 3, characterized in that: The porosity of the porous polyethylene-based film is 40-50%, and the thickness is 9-17 microns; And / or, the porous polyethylene-based film is immersed in the film-forming solution until completely immersed.

7. The composite anion exchange membrane according to claim 3, characterized in that: In step 2, the time of the polymerization reaction is 30-120 minutes, and the light irradiation conditions include 276-365 nm and 300-500 W.

8. A method for producing the composite anion exchange membrane according to any one of claims 1 to 7, characterized in that it comprises the steps of It comprises: Polymerization of a cyclic quaternary ammonium monomer and a crosslinking agent in a porous polyethylene film; The cyclic quaternary ammonium monomer is at least one selected from 1-methyl-1-(4-vinylbenzyl)piperidine chloride, quaternized molecules of 4-vinylpyridine, quaternized molecules of 4-vinylbenzyl chloride, and the mass ratio of the cyclic quaternary ammonium monomer to the crosslinking agent is 100:10-30.

9. Use of the composite anion exchange film according to any one of claims 1-7 for preparing a fuel cell.

10. A fuel cell characterized by: It comprises an electrode and the composite anion exchange film according to any one of claims 1-7. It comprises an electrode and the composite anion exchange film according to any one of claims 1-7.

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