Multilayer composite proton exchange membrane as well as preparation method and application thereof

Abstract

The invention discloses a multilayer composite proton exchange membrane and a preparation method and application thereof.The multilayer composite proton exchange membrane comprises a base membrane, two para-aramid fiber coatings and two perfluorosulfonic acid coatings, the two para-aramid fiber coatings are the first para-aramid fiber coating and the second para-aramid fiber coating, and the perfluorosulfonic acid coatings are the perfluorosulfonic acid coatings. The two perfluorosulfonic acid coatings comprise a first perfluorosulfonic acid coating and a second perfluorosulfonic acid coating, the multi-layer composite proton exchange membrane is of an interlayer structure, and the interlayer structure sequentially comprises the first perfluorosulfonic acid coating, a first para-aramid fiber coating, a base membrane, a second para-aramid fiber coating and the second perfluorosulfonic acid coating from top to bottom. Each layer of para-aramid coating comprises para-aramid and ceramic, and each layer of perfluorosulfonic acid coating comprises perfluorosulfonic acid resin. The multi-layer composite proton exchange membrane prepared by the invention has relatively high proton conductivity and also has relatively excellent hydrogen barrier property.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery separators, and in particular relates to a multilayer composite proton exchange membrane and a preparation method and application thereof. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) use hydrogen as fuel to directly convert chemical energy into electrical energy, offering advantages such as high energy conversion rates and fast startup. The PEM is the core of PEMFCs, primarily isolating the anode and cathode gases and transferring protons. Currently, the most widely used PEM on the market is perfluorinated PEM, which is widely used as a diaphragm material due to its excellent electrochemical properties and thermal stability. However, the mechanical properties and proton conductivity of existing PEMs need to be improved. Summary of the Invention

[0003] In view of the deficiencies in the prior art, the present invention aims to provide a multilayer composite proton exchange membrane.

[0004] Another object of the present invention is to provide a method for preparing the multilayer composite proton exchange membrane.

[0005] The purpose of the present invention is achieved through the following technical solutions.

[0006] A multilayer composite proton exchange membrane comprises: a base membrane, two layers of para-aramid coatings, and two layers of perfluorosulfonic acid coatings, wherein the two layers of para-aramid coatings are a first para-aramid coating and a second para-aramid coating, and the two layers of perfluorosulfonic acid coatings are a first perfluorosulfonic acid coating and a second perfluorosulfonic acid coating, wherein:

[0007] The multilayer composite proton exchange membrane is a sandwich structure, which comprises, from top to bottom, a first perfluorosulfonic acid coating, a first para-aramid coating, a base membrane, a second para-aramid coating, and a second perfluorosulfonic acid coating.

[0008] Each layer of the para-aramid coating comprises: para-aramid and ceramic, and in each layer of the para-aramid coating, the ratio of para-aramid to ceramic is (5-20):(0.5-5) by weight.

[0009] Each layer of the perfluorosulfonic acid coating comprises: perfluorosulfonic acid resin,

[0010] Calculated by weight, the ratio of para-aramid, ceramic and perfluorosulfonic acid resin in the multilayer composite proton exchange membrane is (5-20): (0.5-5): (60-140).

[0011] In the above technical solution, in each layer of para-aramid coating, the ratio of para-aramid to ceramic is preferably (12-18):(1.2-2) by mass.

[0012] In the above technical solution, in the multilayer composite proton exchange membrane, the ratio of para-aramid, ceramic and perfluorosulfonic acid resin is preferably (12-18): (1.2-2): (100-135) by mass.

[0013] In the above technical solution, the ceramic is one or a mixture of several of alumina, boehmite, magnesium hydroxide and silicon dioxide.

[0014] In the above technical solution, the thickness of the multilayer composite proton exchange membrane is 20 to 80 μm, the thickness of each para-aramid coating layer is 0.1 to 5.5 μm, and the thickness of each perfluorosulfonic acid coating layer is 4 to 40 μm.

[0015] In the above technical solution, the base film, the para-aramid coating and the perfluorosulfonic acid coating have the same area.

[0016] In the above technical solution, the first para-aramid coating and the second para-aramid coating are the same or different.

[0017] In the above technical solution, the first perfluorosulfonic acid coating and the second perfluorosulfonic acid coating are the same or different.

[0018] The preparation method of the above-mentioned multilayer composite proton exchange membrane includes: coating a para-aramid slurry on both sides of a base membrane (the para-aramid slurries coated on the base membrane are the same or different), extracting, and dehydrating to obtain a first para-aramid coating and a second para-aramid coating on both sides of the base membrane to obtain a para-aramid coated diaphragm, and casting a perfluorosulfonic acid (PFSA) solution on both sides of the para-aramid coated diaphragm (the perfluorosulfonic acid solutions cast on both sides of the para-aramid coated diaphragm are the same or different) to form a first perfluorosulfonic acid coating and a second perfluorosulfonic acid coating to obtain (defined as) a multilayer composite proton exchange membrane, wherein the para-aramid slurry includes: para-aramid and ceramic, and the ratio of para-aramid to ceramic is (5-20): (0.5-5) by mass; the perfluorosulfonic acid solution includes: perfluorosulfonic acid resin and a second solvent, and the concentration of perfluorosulfonic acid resin in the perfluorosulfonic acid solution is 2-5.5wt%.

[0019] In the above technical solution, the para-aramid slurry also includes: a first solvent and calcium chloride as a pore-forming agent. The ratio of para-aramid, calcium chloride and the first solvent is (4.5-5.95): (2-4): (90-93.5) by mass.

[0020] In the above technical solution, the first solvent is one or a mixture of hexamethylphosphoramide, dimethylacetamide, N-methylpyrrolidone and tetramethylurea.

[0021] In the above technical solution, the second solvent is one or a mixture of N-methylpyrrolidone (NMP), dimethyl sulfoxide and dimethylformamide.

[0022] In the above technical solution, the method of casting a perfluorosulfonic acid (PFSA) solution includes: casting the perfluorosulfonic acid (PFSA) solution in a container, placing a para-aramid coated membrane on the liquid surface of the perfluorosulfonic acid (PFSA) solution in the container (at this time, the first para-aramid coating of the para-aramid coated membrane is in contact with the perfluorosulfonic acid solution in the container), heating for the first time, casting the perfluorosulfonic acid (PFSA) solution on the upper surface of the second para-aramid coating of the para-aramid coated membrane in the container, heating for the second time to obtain a second perfluorosulfonic acid coating on the upper surface of the second para-aramid coating, and post-treating to obtain a multilayer composite proton exchange membrane, wherein the post-treatment uses sulfuric acid and hydrogen peroxide.

[0023] In the above technical solution, the temperature of the first heating is 60-90° C., and the time of the first heating is 0.5-1.5 h.

[0024] In the above technical solution, the second heating includes: drying at 60-90°C for 8-12 hours, and then drying at 110-130°C for 1-3 hours.

[0025] In the above technical solution, the post-treatment includes: first soaking in sulfuric acid at 50-90°C for 0.5-3h, then soaking in hydrogen peroxide at 50-90°C for 0.5-3h, washing, and drying.

[0026] In the post-treatment method, the concentration of the sulfuric acid is 0.5 to 1.2 mol / L.

[0027] In the post-treatment method, the concentration of the hydrogen peroxide is 2.5-3.5 wt %.

[0028] In the post-treatment method, the washing is: first washing with water at room temperature of 20-25°C, and then soaking in water at 50-90°C for 0.5-3h.

[0029] In the above technical solution, the extraction includes: passing through extraction liquids with extractant concentrations from high to low, the extraction liquids with extractant concentrations from high to low are the first extraction liquid, the second extraction liquid, the third extraction liquid and the fourth extraction liquid, the first extraction liquid, the second extraction liquid and the third extraction liquid are each a mixture of an extractant and water, the fourth extraction liquid is water, the concentration of the extractant in the first extraction liquid is 65-80wt%, the concentration of the extractant in the second extraction liquid is 40-60wt%, the concentration of the extractant in the third extraction liquid is 20-40wt%, and the extractant is N-methylpyrrolidone (NMP).

[0030] In the above technical solution, the dehydration treatment is drying at 50-60°C for 6-12 minutes.

[0031] In the above technical solution, the method for preparing the para-aramid slurry comprises the following steps:

[0032] Step 1: Calcium chloride and a first solvent are mixed at -2 to 3° C. (the process of preparing the para-aramid slurry is carried out at this temperature), and stirred until the calcium chloride is uniformly dispersed in the first solvent. P-phenylenediamine and terephthaloyl chloride are added, and stirred until the p-phenylenediamine and terephthaloyl chloride are uniformly dispersed in the first solvent, so that the p-phenylenediamine and terephthaloyl chloride react to form para-aramid, thereby obtaining a para-aramid solution, wherein the ratio of the first solvent, calcium chloride, p-phenylenediamine and terephthaloyl chloride is (90 to 93.5): (2 to 4): (1.5 to 2): (3 to 4) by mass;

[0033] Step 2: mixing the para-aramid solution and ceramics until uniform to obtain a para-aramid slurry, wherein the ratio of para-aramid to ceramics in the para-aramid solution is (5-20):(0.5-5) by mass.

[0034] In the above technical solution, the method for preparing a perfluorosulfonic acid (PFSA) solution includes: mixing a perfluorosulfonic acid resin (powder) and a second solvent until uniform to obtain the perfluorosulfonic acid (PFSA) solution, wherein the ratio of the perfluorosulfonic acid resin (powder) to the second solvent is (2 to 5.5): (94.5 to 98) by mass.

[0035] In the method for preparing a perfluorosulfonic acid (PFSA) solution, a perfluorosulfonic acid resin (powder) and a second solvent are mixed and stirred at 140-160° C. until the mixture is uniform.

[0036] Application of perfluorosulfonic acid resin and para-aramid in improving the tensile strength and proton conductivity of proton exchange membranes.

[0037] Application of perfluorosulfonic acid resin and para-aramid in improving the hydrolytic stability of proton exchange membrane.

[0038] Application of perfluorosulfonic acid resin and para-aramid in improving the hydrogen barrier performance of proton exchange membrane.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention coats para-aramid slurry on both sides of the base membrane, forming a layer of para-aramid coating on each side of the base membrane to obtain a para-aramid coating membrane. The para-aramid coating membrane has good hydrophilicity, so that the perfluorosulfonic acid coating and the para-aramid coating are better combined. The multi-layer composite proton exchange membrane prepared by the present invention has high proton conductivity and excellent hydrogen barrier performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is the water contact angle of PE film;

[0042] Figure 2 is the water contact angle of the para-aramid coated separator;

[0043] Figure 3 This is a SEM image of the multilayer composite proton exchange membrane prepared in Example 4;

[0044] Figure 4 Graphs of hydrogen permeation tests at a sweep rate of 4 mV / s for a membrane electrode formed of the multilayer composite proton exchange membrane of Example 4, a membrane electrode formed of the PFSA&PE membrane of Comparative Example 2, and a membrane electrode formed of a standard membrane. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further described below with reference to specific embodiments.

[0046] The information of the raw materials involved in the following examples and comparative examples is as follows:

[0047] Perfluorosulfonic acid resin (powder), purity 98%, Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.

[0048] N-Methylpyrrolidone (NMP), purity 99.5%, Tianjin Hengxing Chemical Reagent Manufacturing Co., Ltd.

[0049] Calcium chloride, purity 99%, Tianjin Hengxing Chemical Reagent Manufacturing Co., Ltd.;

[0050] p-Phenylenediamine, purity 99.9%, Zhejiang Yanyi New Energy Technology Co., Ltd.;

[0051] Terephthaloyl chloride, purity 99.9%, Zhejiang Yanyi New Energy Technology Co., Ltd.;

[0052] Silicon dioxide (as ceramic), 99.9% purity, Zhejiang Yanyi New Energy Technology Co., Ltd.;

[0053] The models and manufacturers of the equipment involved in the following examples and comparative examples are as follows:

[0054] Contact angle tester, GM-YF-JCJ-027, White Oulin, Switzerland;

[0055] Scanning electron microscope, Sigma 300, Carl Zeiss, Germany;

[0056] Japan Shimadzu stretching machine, AGS-X (100N);

[0057] Electrochemical workstation, CHI660E, Shanghai Chenhua Instrument Co., Ltd.

[0058] Hydrolytic stability value: A pre-dried membrane with a mass of Wo (g) is immersed in deionized water at 80°C for 48 hours. The membrane is then taken out and dried at 80°C for 8 hours. The mass of the membrane is then measured as Wt (g). The hydrolytic stability value Wc is calculated using the following formula:

[0059]

[0060] Water absorption rate: Dry the membrane in an oven at 80℃±2℃ for 24 hours. After drying for 24 hours, measure the mass of the membrane as m0 (g). Then soak the membrane in distilled water at 80℃ for 8 hours. Use filter paper to remove water on the membrane surface. Measure the mass of the membrane as m1 (g) within 30 seconds. The water absorption rate Δm is calculated by the following formula:

[0061]

[0062] Mechanical properties (tensile strength): The diaphragm was made into a rectangular strip with a length of 65 mm and a width of 15 mm. A universal tensile testing machine was used with a tensile speed of 5 mm / min and an original gauge length of 20 mm. The mechanical properties were calculated using the following formula:

[0063] σ1=p / (b×d), where σ1 is tensile strength (MPa), p is maximum load (N), b is width of rectangular spline (mm), and d is thickness of rectangular spline (mm). The thickness is measured by a thickness gauge.

[0064] Proton conductivity test: The test was conducted at a temperature of 25° C. and a humidity of 100% RH.

[0065] Fuel cell hydrogen permeability test: First, the catalyst (Pt / C) (catalyst (Pt / C) was purchased from Shengernuo Energy Mall, JM 20% platinum carbon) was broken up and evenly dispersed using a slurry crusher, and then 1.65g of the evenly dispersed catalyst, 0.35g of 5wt% Nafion solution and 8g of isopropanol were evenly dispersed using a homogenizer to obtain a first mixed solution. Finally, an ultrasonic sprayer was used to support the first mixed solution on the diaphragm, and a hot press was used to press the catalyst-supported diaphragm and carbon paper (carbon paper manufacturer: Toray, Japan, model: TGP-H-060) to obtain a membrane electrode (the diaphragm is one of the multilayer composite proton exchange membrane of Example 4, the PFSA&PE diaphragm of Comparative Example 2, and the standard membrane). On a fuel cell test bench (manufacturer: Beit New Energy, model: NBT-PEM-100W), an electrochemical workstation CHI660E was used to test the hydrogen permeation current of the membrane electrode (MEA) using linear sweep voltammetry (LSV). In the voltage range of 0.1~0.5V, the -1A disturbance voltage was applied at a dynamic scan rate of 100 sq ft, H2 (100% RH) was introduced into the anode of the fuel cell test bench (the anode provided with the fuel cell test bench) at a flow rate of 200 sccm, and N2 (100% RH) was introduced into the cathode of the fuel cell test bench (the cathode provided with the fuel cell test bench) at a flow rate of 200 sccm.

[0066] The standard membrane is a purchased standard sample, manufacturer: Shengernuo Energy Mall, model: SMEA1223.

[0067] The following examples and comparative examples: The concentration of H2O2 in hydrogen peroxide is 3wt%.

[0068] In the following embodiments and comparative examples: water is deionized water.

[0069] In the following examples and comparative examples, the base film is a PE film, and the thickness of the PE film is 9 μm.

[0070] Examples 1 to 6

[0071] A multilayer composite proton exchange membrane comprises: a base membrane, two layers of para-aramid coatings and two layers of perfluorosulfonic acid coatings, wherein the two layers of para-aramid coatings are a first para-aramid coating and a second para-aramid coating, and the two layers of perfluorosulfonic acid coatings are a first perfluorosulfonic acid coating and a second perfluorosulfonic acid coating, wherein: the multilayer composite proton exchange membrane is a sandwich structure, and the sandwich structure is, from top to bottom, the first perfluorosulfonic acid coating, the first para-aramid coating, the base membrane, the second para-aramid coating and the second perfluorosulfonic acid coating, and each layer of para-aramid coating comprises: para-aramid and ceramic, and the ceramic is silicon dioxide In each para-aramid coating layer, the ratio of para-aramid to ceramic is 10:1, by mass. Each perfluorosulfonic acid coating layer includes perfluorosulfonic acid resin. In the multilayer composite proton exchange membrane, the ratio of para-aramid to ceramic to perfluorosulfonic acid resin is X, by mass. The thickness of the multilayer composite proton exchange membrane is C μm. The thickness of each para-aramid coating layer is A μm (the first para-aramid coating layer and the second para-aramid coating layer are the same thickness). The thickness of each perfluorosulfonic acid coating layer is B μm (the first perfluorosulfonic acid coating layer and the second perfluorosulfonic acid coating layer are the same thickness). The areas of the base membrane, para-aramid coating, and perfluorosulfonic acid coating are the same. The values ​​of X, A, B, and C are shown in Table 1.

[0072] The preparation method of the above-mentioned multi-layer composite proton exchange membrane includes: coating a para-aramid slurry on both sides of a base membrane, extracting (passing through extractants with decreasing extractant concentrations, the extractant is N-methylpyrrolidone (NMP), and the extractants with decreasing extractant concentrations are, in sequence, a first extractant, a second extractant, a third extractant, and a fourth extractant, the first extractant, the second extractant, and the third extractant are each a mixture of extractant and water, the fourth extractant is water, the extractant concentration in the first extractant is 80wt%, the extractant concentration in the second extractant is 50wt%, and the extractant concentration in the third extractant is 30wt%), drying in a 55°C oven for 8 minutes for dehydration treatment, obtaining a first para-aramid coating on one side of the base membrane and a second para-aramid coating on the other side of the base membrane, i.e., obtaining a para-aramid coated diaphragm.

[0073] Perfluorosulfonic acid (PFSA) solution was cast on both sides of the para-aramid coated membrane: in the same container, the perfluorosulfonic acid (PFSA) solution was cast on the substrate (glass plate) of the container, and the para-aramid coated membrane was placed on the liquid surface of the perfluorosulfonic acid (PFSA) solution in the container. At this time, the first para-aramid coating of the para-aramid coated membrane was parallel to and in contact with the liquid surface of the perfluorosulfonic acid (PFSA) solution in the container, and the membrane was heated for the first time (heated in an 80°C oven for 1 hour), and then the perfluorosulfonic acid (PFSA) solution was cast on the second para-aramid coating of the para-aramid coated membrane in the container. The upper surface of the layer was heated for the second time (dried in an oven at 80°C for 10 hours, then dried at 120°C for 1.5 hours), and a first perfluorosulfonic acid coating was obtained on the lower surface of the first para-aramid coating. A second perfluorosulfonic acid coating was obtained on the upper surface of the second para-aramid coating, and post-treated (first soaked in sulfuric acid at 60°C (the concentration of sulfuric acid was 1 mol / L) for 2 hours, then soaked in hydrogen peroxide at 60°C for 2 hours, taken out, washed with water at room temperature of 20-25°C, then soaked in water at 60°C for 2 hours, taken out, and dried at 60°C for 12 hours) to obtain a multilayer composite proton exchange membrane.

[0074] The first para-aramid coating and the second para-aramid coating are formed using the same para-aramid slurry. The method for preparing the para-aramid slurry includes the following steps:

[0075] Step 1: Calcium chloride (as a pore-forming agent) and a first solvent are mixed at 0° C. and stirred until the calcium chloride is uniformly dispersed in the first solvent. Paraphenylenediamine and terephthaloyl chloride are added and stirred until the paraphenylenediamine and terephthaloyl chloride are uniformly dispersed in the first solvent, so that the paraphenylenediamine and terephthaloyl chloride react to form para-aramid, thereby obtaining a para-aramid solution. The ratio of the first solvent, calcium chloride, paraphenylenediamine, and terephthaloyl chloride is 92:2.6:1.8:3.6 by mass, and the first solvent is N-methylpyrrolidone.

[0076] Step 2: Mix the para-aramid solution and the ceramic until uniformly mixed to obtain a para-aramid slurry. The ratio of the para-aramid to the ceramic in the para-aramid solution is 10:1 by mass.

[0077] The perfluorosulfonic acid (PFSA) solution used to form the first perfluorosulfonic acid coating and the second perfluorosulfonic acid coating is the same. The method for preparing the perfluorosulfonic acid (PFSA) solution includes: mixing a perfluorosulfonic acid resin (powder) and a second solvent, stirring in a high-temperature reactor at 150°C and a speed of 500 r / min for 4 hours until uniform, to obtain a perfluorosulfonic acid (PFSA) solution, wherein the ratio of the perfluorosulfonic acid resin (powder) to the second solvent is 5:95 by mass (the concentration of the perfluorosulfonic acid resin in the perfluorosulfonic acid solution is 5wt%), and the second solvent is N-methylpyrrolidone (NMP).

[0078] Table 1

[0079] Multilayer composite proton exchange membrane X A(μm) B (μm) C (μm) Example 1 5：0.5：89 0.5 20 50 Example 2 10：1：89 1 20 51 Example 3 15：1.5：89 1.5 20 52 Example 4 15：1.5：111.25 1.5 25 62 Example 5 15：1.5：133.5 1.5 30 72 Example 6 10：1：111.25 1 25 61

[0080] Comparative Example 1

[0081] A method for preparing a PFSA membrane comprises: casting 60 g of the perfluorosulfonic acid (PFSA) solution in Example 1 on a glass plate, placing the plate in an oven and drying it at 80° C. for 10 hours, heating the plate to 120° C. and drying it at 120° C. for 1.5 hours, soaking the plate in 60° C. sulfuric acid (sulfuric acid concentration is 1 mol / L) for 1 hour, then soaking the plate in 80° C. hydrogen peroxide for 1 hour, removing the plate, washing the plate with water at room temperature, then soaking the plate in 80° C. water for 1 hour, removing the plate, and drying the plate at 60° C. for 12 hours to obtain a PFSA membrane with a thickness of 38 μm.

[0082] Comparative Example 2

[0083] A preparation method of a PFSA&PE membrane, comprising: immersing a PE membrane in 3 mol / L sulfuric acid for hydrophilic treatment for 3 hours to obtain a hydrophilic membrane, casting 25 g of the perfluorosulfonic acid (PFSA) solution in Example 1 on a glass plate of the container in the same container, placing the hydrophilic membrane at the liquid level of the perfluorosulfonic acid (PFSA) solution in the container, heating it in an oven at 80°C for 1 hour, obtaining an A coating on the lower surface of the hydrophilic membrane, and then casting 25 g of the perfluorosulfonic acid (PFSA) solution in Example 1 on a glass plate of the container. The other side of the hydrophilic membrane cast in the container was dried in an oven at 80°C for 10 hours, then heated to 120°C and dried at 120°C for 1.5 hours to obtain a B coating on the upper surface of the hydrophilic membrane. Post-treatment: soak in sulfuric acid at 60°C (the concentration of sulfuric acid is 1 mol / L) for 2 hours, then soak in hydrogen peroxide at 60°C for 2 hours, take out, wash with water at room temperature, and then soak in water at 60°C for 2 hours, take out, and dry at 60°C for 12 hours to obtain a PFSA&PE membrane with a thickness of 60 μm.

[0084] Comparative Example 3

[0085] A method for preparing a multi-layer composite proton exchange membrane comprises: coating the para-aramid slurry of Example 1 on one side on a base membrane, extracting (passing through extractants with decreasing extractant concentrations, wherein the extractant is N-methylpyrrolidone (NMP), and the extractants with decreasing extractant concentrations are sequentially a first extractant, a second extractant, a third extractant, and a fourth extractant, wherein the first extractant, the second extractant, and the third extractant are each a mixture of an extractant and water, and the fourth extractant is water, wherein the concentration of the extractant in the first extractant is 80 wt %, the concentration of the extractant in the second extractant is 50 wt %, and the concentration of the extractant in the third extractant is 30 wt %), drying in an oven at 55° C. for 8 minutes for dehydration treatment, and forming a single-sided proton exchange membrane on the base membrane. A single-sided aramid coating (the thickness of the single-sided aramid coating is 1.5 μm) is formed to obtain a single-sided aramid coating diaphragm. In the same container, the perfluorosulfonic acid (PFSA) solution in Example 1 is cast on the substrate (glass plate) of the container, and the single-sided aramid coating diaphragm is placed in it. The membrane is heated in an 80°C oven for 1 hour to form a single-sided perfluorosulfonic acid coating (the thickness of the single-sided perfluorosulfonic acid coating is 30 μm) on the single-sided aramid coating diaphragm. Post-treatment (first soaking in 60°C sulfuric acid (the concentration of sulfuric acid is 1 mol / L) for 2 hours, then soaking in 60°C hydrogen peroxide for 2 hours, taking out, washing with water at room temperature, then soaking in 60°C water for 2 hours, taking out, and drying at 60°C for 12 hours) to obtain a multilayer composite proton exchange membrane.

[0086] Comparative Example 4

[0087] A multilayer composite proton exchange membrane for a methanol fuel cell is prepared according to Example 1 of the invention patent publication number CN 117039073 A.

[0088] The test parameters of the multilayer composite proton exchange membranes prepared in Examples 1 to 6, the PFSA membrane prepared in Comparative Example 1, the PFSA&PE membrane prepared in Comparative Example 2, the multilayer composite proton exchange membrane prepared in Comparative Example 3, and the multilayer composite proton exchange membrane for methanol fuel cells prepared in Comparative Example 4 are shown in Table 2.

[0089] Table 2

[0090]

[0091] As shown in Table 2, in Examples 1 to 6, the multilayer composite proton exchange membranes prepared in Examples 4 and 5 exhibit excellent mechanical properties, proton conductivity (proton conductivity) and hydrolytic stability, and the water absorption rate is also slightly improved. By comparing Comparative Examples 1 to 2, it can be seen that the PFSA membrane prepared in Comparative Example 1 has low mechanical properties and poor hydrolytic stability. The introduction of a hydrophilic membrane in Comparative Example 2 can greatly improve the mechanical properties, but the hydrolytic stability is less improved, and the proton conductivity is lower than that in Comparative Example 1. Comparative Example 2 and Examples 1 to 6 show that the introduction of a para-aramid coating membrane effectively improves the hydrolytic stability and the proton conductivity. This proves that the present invention achieves the advantages of good mechanical properties, high proton conductivity, good water absorption and good hydrolytic stability through the synergistic effect of PPTA, PE and PFSA. Compared with Comparative Example 4, the multilayer composite proton exchange membranes prepared in Examples 1 to 6 have more excellent proton conductivity and mechanical properties.

[0092] Figure 1 is the water contact angle of PE film, Figure 2 is the water contact angle of the para-aramid coating membrane. It can be seen that the para-aramid coating membrane ( Figure 2 The water contact angle of the "PPTA coating membrane" is smaller than that of the PE membrane, which proves that the hydrophilicity of the para-aramid coating membrane is higher than that of the PE membrane, which is more conducive to combining with the perfluorosulfonic acid coating.

[0093] Figure 3 This is the SEM of the multilayer composite proton exchange membrane prepared in Example 4. Figure 3 It can be observed that the surface of the multi-layer composite proton exchange membrane is relatively smooth and has no cracks.

[0094] pass Figure 4 It can be seen that the membrane electrode formed by the standard membrane ( Figure 4 The "Standard Sample" in the hydrogen permeation test has a large current density of 8.5mA / cm 2 , mainly due to the hydrogen permeating the membrane and reacting with the anode, forming a path resulting in a larger current density, the membrane electrode prepared by the PFSA&PE membrane of Comparative Example 2 ( Figure 4 The "PFSA&PE") has a lower current density of only 2mA / cm 2 , proving that less hydrogen permeates the PFSA&PE membrane of Comparative Example 2, and the membrane electrode prepared by the multilayer composite proton exchange membrane of Example 4 ( Figure 4 The "PFSA & PPTA / PE" has a lower current density (1.24mA / cm 2 ), the multilayer composite proton exchange membrane of Example 4 has more excellent hydrogen barrier performance.

[0095] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative labor falls within the scope of protection of the present invention.

Claims

1. A multilayer composite proton exchange membrane, characterized in that: include: A base film, two layers of para-aramid coatings and two layers of perfluorosulfonic acid coatings, wherein the two layers of para-aramid coatings are a first para-aramid coating and a second para-aramid coating, and the two layers of perfluorosulfonic acid coatings are a first perfluorosulfonic acid coating and a second perfluorosulfonic acid coating, wherein: The multilayer composite proton exchange membrane is a sandwich structure, which comprises, from top to bottom, a first perfluorosulfonic acid coating, a first para-aramid coating, a base membrane, a second para-aramid coating, and a second perfluorosulfonic acid coating. Each layer of the para-aramid coating comprises: para-aramid and ceramic, and in each layer of the para-aramid coating, the ratio of para-aramid to ceramic is (5-20):(0.5-5) by weight. Each layer of the perfluorosulfonic acid coating comprises: perfluorosulfonic acid resin, Calculated by weight, the ratio of para-aramid, ceramic and perfluorosulfonic acid resin in the multilayer composite proton exchange membrane is (5-20): (0.5-5): (60-140).

2. The multilayer composite proton exchange membrane according to claim 1, characterized in that The thickness of the multilayer composite proton exchange membrane is 20-80 μm, the thickness of each para-aramid coating layer is 0.1-5.5 μm, and the thickness of each perfluorosulfonic acid coating layer is 4-40 μm.

3. The method for preparing a multilayer composite proton exchange membrane according to claim 1 or 2, wherein: include: The para-aramid slurry is coated on both sides of the base membrane, extracted, and dehydrated to obtain a first para-aramid coating and a second para-aramid coating on both sides of the base membrane to obtain a para-aramid coated diaphragm, and a perfluorosulfonic acid solution is cast on both sides of the para-aramid coated diaphragm to form a first perfluorosulfonic acid coating and a second perfluorosulfonic acid coating to obtain a multilayer composite proton exchange membrane, wherein the para-aramid slurry includes: para-aramid and ceramic, and the ratio of para-aramid to ceramic is (5-20):(0.5-5) by mass; the perfluorosulfonic acid solution includes: perfluorosulfonic acid resin and a second solvent, and the concentration of perfluorosulfonic acid resin in the perfluorosulfonic acid solution is 2-5.5wt%.

4. The preparation method according to claim 3, characterized in that The method for casting a perfluorosulfonic acid solution comprises: casting the perfluorosulfonic acid solution in a container, placing a para-aramid coated diaphragm on the liquid surface of the perfluorosulfonic acid solution in the container, heating for the first time, casting the perfluorosulfonic acid solution on the upper surface of a second para-aramid coating of the para-aramid coated diaphragm in the container, heating for the second time, obtaining a second perfluorosulfonic acid coating on the upper surface of the second para-aramid coating, and post-processing to obtain a multilayer composite proton exchange membrane, wherein the post-processing uses sulfuric acid and hydrogen peroxide.

5. The preparation method according to claim 3, characterized in that The para-aramid slurry further comprises: a first solvent and calcium chloride as a pore-forming agent, and the ratio of the para-aramid, calcium chloride and the first solvent is (4.5-5.95): (2-4): (90-93.5) by mass.

6. The preparation method according to claim 5, characterized in that Extraction is used to remove the pore former.

7. Application of perfluorosulfonic acid resin and para-aramid in improving the tensile strength of proton exchange membrane.

8. Application of perfluorosulfonic acid resin and para-aramid in improving the hydrolysis stability of proton exchange membrane.

9. Application of perfluorosulfonic acid resin and para-aramid in improving the hydrogen barrier performance of proton exchange membrane.

10. Application of perfluorosulfonic acid resin and para-aramid in improving the proton conductivity of proton exchange membrane.

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