Proton exchange membrane and method for producing the same

Abstract

The application discloses a kind of proton exchange membrane and preparation method thereof, the proton exchange membrane is casted by slurry on substrate, dry, post-processing, obtain on substrate, the slurry includes: perfluorosulfonic acid resin, thermoplastic polyurethane, solvent and acidic substance, the acidic substance is at least one of acetic acid, fatty acid, phosphoric acid, silicic acid and tungstic acid.Perfluorosulfonic acid resin solution fluidity is big, so film-forming property is poor, mechanical property is poor, the application is compounded by perfluorosulfonic acid resin and thermoplastic polyurethane, so that diaphragm has excellent elasticity, increase diaphragm in battery withstands the ability of water absorption swelling, bring good film-forming property and good mechanical property for diaphragm, significantly improve the elongation at break of diaphragm, with good chemical stability, while introducing acidic substance can increase the proton conductivity of diaphragm to some extent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery separators, and particularly relates to a proton exchange membrane and a preparation method thereof. BACKGROUND

[0002] At present, the global energy development and the coordination between energy and environment have become the focus of the whole human race, and are also the key issue of China's economic development. Since the 1990s, with the intensification of energy crisis and the prominent environmental pollution problem, the global attention to environmental protection and green technology has been continuously improved. According to the global energy development trend in the next 50 years, the energy structure will still be dominated by fossil fuels, supplemented by renewable energy and new energy. Developing economic and efficient, clean energy (including renewable and non-renewable energy) will be the core issue of energy technology in the 21st century. Fuel cell technology, as the fourth generation of large-scale power generation after thermal power, hydropower and nuclear power, can effectively alleviate the energy crisis and promote sustainable economic development, and has become a research hotspot in the current energy field due to its advantages of high energy efficiency, low pollution and low noise.

[0003] Proton exchange membrane fuel cell (PEMFC) is a power generation device using hydrogen as fuel and oxygen as oxidant, and the core component is proton exchange membrane. The proton exchange membrane not only provides a one-way transmission channel for protons, but also isolates the fuel and oxidant. In order to realize the efficient operation of the proton exchange membrane fuel cell, the proton exchange membrane must have high proton conductivity and excellent chemical and mechanical stability. At present, perfluorosulfonic acid proton exchange membrane is the most widely used, and the Nafion series membrane produced by DuPont Company is the most representative. However, the Nafion membrane still has problems such as high production difficulty and high cost, and the synthesis and sulfonation process of perfluorinated material is complex, which is easy to hydrolyze and degrade during film formation, affecting the performance of the membrane and increasing the production cost. In order to overcome these shortcomings, domestic scholars have proposed various modification methods, including inorganic doping, adding supporting materials, heat treatment, crosslinking, blending, in-situ polymerization, self-assembly, etc., but the above technical problems cannot be completely solved. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a proton exchange membrane.

[0005] Another purpose of the present application is to provide a preparation method of the above-mentioned proton exchange membrane.

[0006] Another purpose of the present application is to provide a slurry.

[0007] The purpose of the present application is achieved by the following technical solutions.

[0008] A proton exchange membrane comprises: a perfluorosulfonic acid resin (PFSA) and a thermoplastic polyurethane (TPU), wherein the ratio of the perfluorosulfonic acid resin (PFSA) and the thermoplastic polyurethane (TPU) is (1-20):(1-20) by mass fraction.

[0009] In the above technical solution, the ratio of the perfluorosulfonic acid resin (PFSA) and the thermoplastic polyurethane (TPU) is preferably (1.6-2.2):2 by mass fraction.

[0010] In the above technical solution, the ratio of the perfluorosulfonic acid resin (PFSA) and the thermoplastic polyurethane (TPU) is more preferably (2-2.2):2 by mass fraction.

[0011] In the above technical solution, the thickness of the proton exchange membrane is 50-60 microns.

[0012] A slurry comprises: a perfluorosulfonic acid resin (PFSA), a thermoplastic polyurethane (TPU), a solvent and an acidic substance, wherein the ratio of the perfluorosulfonic acid resin (PFSA) and the thermoplastic polyurethane (TPU) is (1-20):(1-20) by mass fraction, and the ratio of the thermoplastic polyurethane (TPU) and the acidic substance is (3-7):(1-2) by mass fraction.

[0013] In the above technical solution, the ratio of the perfluorosulfonic acid resin (PFSA) and the thermoplastic polyurethane (TPU) is preferably (1.6-2.2):2 by mass fraction.

[0014] In the above technical solution, the ratio of the perfluorosulfonic acid resin (PFSA) and the thermoplastic polyurethane (TPU) is more preferably (2-2.2):2 by mass fraction.

[0015] In the above technical solution, the solvent comprises N-methyl pyrrolidone (NMP) and / or N,N-dimethylformamide (DMF).

[0016] In the above technical solution, the ratio of the perfluorosulfonic acid resin (PFSA) and the solvent is (1-20):(130-160) by mass fraction.

[0017] In the above technical solution, the acidic substance is at least one of acetic acid, a fatty acid, phosphoric acid, silicic acid and tungstic acid.

[0018] A preparation method of the above proton exchange membrane comprises: casting the slurry on a substrate, drying, post-processing, obtaining a proton exchange membrane on the substrate, and the post-processing comprises: sequentially immersing in sulfuric acid, hydrogen peroxide and water.

[0019] In the technical scheme, the drying comprises: first drying for 10-14 hours at 50-80 DEG C, and then drying for 1-2 hours at 100-130 DEG C.

[0020] In the technical scheme, the post-treatment comprises: soaking in sulfuric acid at 50-80 DEG C for 1.5-3 hours, soaking in hydrogen peroxide at 50-70 DEG C for 0.5-2 hours, cleaning, soaking in water at 50-70 DEG C for 0.5-2 hours, and finally drying for 10-14 hours at 60-90 DEG C.

[0021] In the technical scheme, the concentration of the sulfuric acid is 0.5-1.2 mol / L, and the concentration of the hydrogen peroxide is 2.5-3.5 wt%.

[0022] The preparation method of the slurry comprises: mixing a perfluorosulfonic acid resin (PFSA) solution and a thermoplastic polyurethane (TPU) solution until uniform, wherein the perfluorosulfonic acid resin (PFSA) solution is a mixture of perfluorosulfonic acid resin (PFSA) and a first solvent, the thermoplastic polyurethane (TPU) solution is a mixture of thermoplastic polyurethane (TPU), a second solvent and an acidic substance, and the ratio of perfluorosulfonic acid resin (PFSA) in the perfluorosulfonic acid resin (PFSA) solution to thermoplastic polyurethane (TPU) in the thermoplastic polyurethane (TPU) solution is (1-20):(1-20) by mass fraction, and the ratio of thermoplastic polyurethane (TPU) to the acidic substance in the thermoplastic polyurethane (TPU) solution is (3-7):(1-2) by mass fraction.

[0023] In the technical scheme, the ratio of perfluorosulfonic acid resin (PFSA) in the perfluorosulfonic acid resin (PFSA) solution to thermoplastic polyurethane (TPU) in the thermoplastic polyurethane (TPU) solution is preferably (1.6-2.2):2 by mass fraction.

[0024] In the technical scheme, the ratio of perfluorosulfonic acid resin (PFSA) in the perfluorosulfonic acid resin (PFSA) solution to thermoplastic polyurethane (TPU) in the thermoplastic polyurethane (TPU) solution is more preferably (2-2.2):2 by mass fraction.

[0025] In the technical scheme, the perfluorosulfonic acid resin (PFSA) solution and the thermoplastic polyurethane (TPU) solution are mixed and stirred at 20-40 DEG C until uniform.

[0026] In the technical scheme, the perfluorosulfonic acid resin (PFSA) solution and the thermoplastic polyurethane (TPU) solution are mixed and stirred at 20-40 DEG C at a rotation speed of 100-200 r / min for 0.5-1 hour until uniform.

[0027] In the technical scheme, the ratio of the perfluorosulfonic acid resin (PFSA) and the first solvent in the perfluorosulfonic acid resin (PFSA) solution is (1-20):(80-100) by mass fraction, preferably (1-10):(80-100).

[0028] In the technical scheme, the ratio of the thermoplastic polyurethane (TPU), the acidic substance and the second solvent in the thermoplastic polyurethane (TPU) solution is (3-7):(1-2):(50-60) by mass fraction.

[0029] In the technical scheme, the method for obtaining the perfluorosulfonic acid resin (PFSA) solution is that the perfluorosulfonic acid resin (PFSA) and the first solvent are mixed and stirred at 140-160 DEG C until uniform.

[0030] In the technical scheme, the method for obtaining the thermoplastic polyurethane (TPU) solution is that the thermoplastic polyurethane (TPU), the second solvent and the acidic substance are mixed and stirred at 20-40 DEG C until uniform.

[0031] In the method for obtaining the perfluorosulfonic acid resin (PFSA) solution, the stirring speed is 400-600 r / min and the stirring time is 2.5-4 h.

[0032] In the method for obtaining the thermoplastic polyurethane (TPU) solution, the stirring speed is 100-200 r / min and the stirring time is 0.5-1.5 h.

[0033] In the technical scheme, the first solvent is a mixture of one or both of N-methyl pyrrolidone (NMP) and N,N-dimethylformamide (DMF), and the second solvent is a mixture of one or both of N-methyl pyrrolidone (NMP) and N,N-dimethylformamide (DMF).

[0034] Application of perfluorosulfonic acid resin and thermoplastic polyurethane in synergistically improving tensile strength and / or elongation at break of proton exchange membrane.

[0035] Application of perfluorosulfonic acid resin, thermoplastic polyurethane and acidic substance in synergistically improving proton conductivity of proton exchange membrane, wherein the acidic substance is at least one of acetic acid, fatty acid, phosphoric acid, silicic acid and tungstic acid.

[0036] Application of perfluorosulfonic acid resin and thermoplastic polyurethane in synergistically improving hydrolytic stability of proton exchange membrane.

[0037] Application of perfluorosulfonic acid resin and thermoplastic polyurethane in synergistically reducing water absorption of proton exchange membrane.

[0038] Compared with the prior art, the application has the beneficial effects that:

[0039] The perfluorosulfonic acid resin (PFSA) solution has large fluidity, and thus has poor film-forming property and poor mechanical property, the application makes the diaphragm have excellent elasticity by compounding the perfluorosulfonic acid resin (PFSA) and the thermoplastic polyurethane (TPU), increases the capacity of the diaphragm to bear water absorption swelling in the battery, brings good film-forming property and good mechanical property to the diaphragm, significantly improves the elongation at break of the diaphragm, and has good chemical stability; meanwhile, the acidic substance is introduced to provide acid-base pairs and form hydrogen bonds, and provide proton channels, so that the proton conductivity of the diaphragm can be increased to a certain extent. BRIEF DESCRIPTION OF DRAWINGS

[0040] Fig. 1 SEM of the proton exchange membrane prepared in example 1 under 200X;

[0041] Fig. 2 SEM of the proton exchange membrane prepared in example 1 under 1KX;

[0042] Fig. 3 SEM of the proton exchange membrane prepared in example 1 under 15KX;

[0043] Fig. 4 SEM of the proton exchange membrane prepared in example 1 under 5KX. DETAILED DESCRIPTION

[0044] The technical scheme of the application is further illustrated below in combination with specific examples.

[0045] The purchase sources of the medicines involved in the following examples and comparative examples are as follows:

[0046] Perfluorosulfonic acid resin (powder), purity 98%;

[0047] N-methyl pyrrolidone (NMP), purity 99.5%;

[0048] Thermoplastic polyurethane, purity AR;

[0049] Acetic acid, purity AR.

[0050] The models and manufacturers of the equipment involved in the following examples and comparative examples are as follows:

[0051] Scanning electron microscope, Sigma 300, Carl Zeiss Company, Germany;

[0052] Japan Shimadzu tensile machine, AGS-X (100N);

[0053] Electrochemical workstation, CHI660E, Dehn's Instrument Technology Co., Ltd.;

[0054] High-temperature reaction kettle, JHT-205KJ-C, Weihai Chaoyang Chemical Machinery Co., Ltd.

[0055] The test methods in the following examples are as follows:

[0056] Hydrolysis stability value: The film with a mass of Wo (g) dried in advance was soaked in deionized water at 80°C for 48 h, and the soaked film was taken out and dried at 80°C for 8 h, and its mass was tested as Wt (g). The hydrolysis stability value Wc of the proton exchange membrane was calculated by the following formula:

[0057]

[0058] Water absorption rate: The film was dried in an oven at 80°C ± 2°C for 24 hours, and then taken out and air-dried to room temperature. The mass of the film was measured as m0 (g). Then the film was soaked in distilled water at 80°C for 8 h, and the water on the surface of the film was removed with filter paper. The mass of the film was measured within 30 seconds as m1 (g). The water absorption rate Δm value was calculated by the following formula:

[0059]

[0060] The film was made into a rectangular sample with a length of 65 mm and a width of 15 mm. A Japanese Shimadzu tensile tester was used to test the mechanical properties and elongation at break, with a tensile speed of 5 mm / min and an original gauge length of 20 mm.

[0061] The mechanical properties (tensile strength) were calculated by the following formula:

[0062] σ1 = p / (b × d), where σ1 is the tensile strength (MPa), p is the maximum load (N), b is the width of the rectangular sample (mm), and d is the thickness of the rectangular sample (mm), which was measured by a thickness gauge.

[0063] The elongation at break was calculated by the following formula:

[0064] where e is the elongation at break, l0 is the length of the rectangular sample, and l a is the length of the rectangular sample at break.

[0065] Proton conductivity: The test was carried out at a temperature of 25°C and a humidity of 100% RH.

[0066] In the tests of hydrolysis stability value, water absorption rate, mechanical properties and proton conductivity, the "film" was one of the proton exchange membranes prepared in Examples 1-7, the pure PFSA proton exchange membrane prepared in Comparative Example 1, the hybrid separator prepared in Comparative Example 2, and the composite separator prepared in Comparative Example 3.

[0067] In the following examples, water is deionized water.

[0068] Examples 1-7

[0069] A method for preparing a proton exchange membrane, comprising: casting a slurry on a substrate (20 cm x 20 cm glass plate), drying (first drying at 80℃ for 12 h, and then drying at 120℃ for 1.5 h), post-treatment, to obtain a proton exchange membrane on the substrate, wherein the post-treatment comprises: soaking in sulfuric acid (the concentration of the sulfuric acid is 1 mol / L) at 60℃ for 2 h, soaking in hydrogen peroxide (the concentration of the hydrogen peroxide is 3 wt%) at 60℃ for 2 h, washing with water for three times, and then soaking in water at 60℃ for 2 h, and finally drying at 80℃ for 12 h.

[0070] A method for preparing a slurry, comprising: mixing a perfluorosulfonic acid resin (PFSA) solution and a thermoplastic polyurethane (TPU) solution, stirring in a magnetic stirrer at 30℃ and at a speed of 150 r / min for 1 h until uniform, to obtain the slurry, the perfluorosulfonic acid resin (PFSA) solution is a mixture of perfluorosulfonic acid resin (PFSA) and a first solvent, the thermoplastic polyurethane (TPU) solution is a mixture of thermoplastic polyurethane (TPU), a second solvent and an acidic substance, and the ratio of perfluorosulfonic acid resin (PFSA) in the perfluorosulfonic acid resin (PFSA) solution to thermoplastic polyurethane (TPU) in the thermoplastic polyurethane (TPU) solution is X.

[0071] A method for obtaining a perfluorosulfonic acid resin (PFSA) solution, comprising: mixing perfluorosulfonic acid resin (PFSA) and a first solvent, stirring in a high-temperature reaction kettle at 150℃ and at a speed of 500 r / min for 4 h until uniform, to obtain the perfluorosulfonic acid resin (PFSA) solution, and the ratio of perfluorosulfonic acid resin (PFSA) to the first solvent in the perfluorosulfonic acid resin (PFSA) solution is 3:95, and the first solvent is N-methyl pyrrolidone (NMP).

[0072] A method for obtaining a thermoplastic polyurethane (TPU) solution, comprising: mixing thermoplastic polyurethane (TPU), a second solvent and an acidic substance, stirring in a magnetic stirrer at 30℃ and at a speed of 150 r / min for 1 h until uniform, to obtain the thermoplastic polyurethane (TPU) solution, and the ratio of thermoplastic polyurethane (TPU) to the acidic substance to the second solvent in the thermoplastic polyurethane (TPU) solution is 5:1:50, the second solvent is N-methyl pyrrolidone (NMP), and the acidic substance is acetic acid.

[0073] X is shown in Table 1, and the proton exchange membranes of Examples 1-7 are obtained by changing the value of X.

[0074] Table 1

[0075]

[0076]

[0077] Comparative Example 1

[0078] A method for preparing a pure PFSA proton exchange membrane, comprising: mixing 5 g of PFSA and 95 g of NMP, stirring at 600 r / min in a high-temperature reaction kettle at 150℃ for 4 h to obtain a slurry, casting the slurry on a 20 cm x 20 cm glass plate, first drying at 80℃ for 10 h, then drying at 120℃ for 1.5 h, taking out the membrane, soaking in 1 mol / L sulfuric acid at 80℃ for 2 h, then soaking in hydrogen peroxide (concentration of 3 wt%) at 60℃ for 1 h, taking out, washing with deionized water, soaking in deionized water at 60℃ for 1 h, and finally drying at 80℃ for 12 h to obtain a pure PFSA proton exchange membrane.

[0079] Comparative Example 2

[0080] A method for preparing a hybrid separator, which is basically the same as Comparative Example 1, except that the slurry is different.

[0081] The method for preparing the slurry of Comparative Example 2 is: mixing 5 g of PFSA, 95 g of NMP and 0.05 g of acetic acid, stirring at 600 r / min in a high-temperature reaction kettle at 150℃ for 4 h to obtain the slurry of Comparative Example 2.

[0082] Comparative Example 3

[0083] A method for preparing a composite separator, which is basically the same as Example 1, except that the slurry is different.

[0084] The method for preparing the slurry of Comparative Example 3 is basically the same as the method for preparing the slurry of Example 1, except that the thermoplastic polyurethane (TPU) solution of Comparative Example 3 does not contain an acidic substance, the ratio of thermoplastic polyurethane (TPU) to the second solvent is 5:50 by mass fraction, and the ratio of perfluorosulfonic acid resin (PFSA) in the perfluorosulfonic acid resin (PFSA) solution to thermoplastic polyurethane (TPU) in the thermoplastic polyurethane (TPU) solution is 1:2 by mass fraction.

[0085] The performance of the proton exchange membranes prepared in Examples 1-7, the pure PFSA proton exchange membrane prepared in Comparative Example 1, the hybrid separator prepared in Comparative Example 2, and the composite separator prepared in Comparative Example 3 were tested, as shown in Table 2.

[0086] Table 2

[0087]

[0088]

[0089] From Table 2, it can be seen that TPU is added in Examples 1-7 and Comparative Example 3, which greatly improves the elongation at break, which shows that TPU can well impart the elastic properties of the separator. At the same time, the addition of TPU can also improve the tensile strength of the separator to a certain extent, increasing the possibility of its actual application. By comparing Comparative Example 1 with Comparative Example 2, it can be found that the proton conductivity of Comparative Example 2 is improved, which shows that the addition of acetic acid provides an acid-base pair, which is conducive to the transmission efficiency of protons between the membranes. Comprehensive analysis shows that the performance of Example 7 is the best.

[0090] Figs. 1-4 The SEM image of the proton exchange membrane prepared in Example 1 was prepared by Figs. 1-4 It can be seen that the proton exchange membrane obtained by using the slurry containing TPU and acetic acid has an uneven surface, which shows that some pores appear inside, which is conducive to the transmission of protons in the separator; at the same time, circular holes can also be seen on the surface under high magnification, which further proves the above point, which also provides strong evidence for the proton conduction function of the separator.

[0091] The above has made an exemplary description of the present application, it should be explained that, without departing from the core of the present application, any simple transformation, modification or other equivalent replacement which can not cost the creative labor of the person skilled in the art falls into the protection scope of the present application.

Claims

1. A method for producing a proton exchange membrane, characterized by, The method comprises: casting the slurry on a substrate, drying, and post-treatment to obtain a proton exchange membrane on the substrate, the post-treatment comprising: sequentially immersing in sulfuric acid, hydrogen peroxide and water; the slurry is composed of perfluorosulfonic acid resin, thermoplastic polyurethane, solvent and acidic substance, the ratio of perfluorosulfonic acid resin to thermoplastic polyurethane is (1-20):(1-20) by mass fraction, the ratio of thermoplastic polyurethane to acidic substance is (3-7):(1-2) by mass fraction, the acidic substance is at least one of fatty acid, phosphoric acid, silicic acid and tungstic acid, and the solvent comprises N-methylpyrrolidone and / or N,N-dimethylformamide.

2. The method of claim 1, wherein the proton exchange membrane is prepared by the steps of: The ratio of perfluorosulfonic acid resin to thermoplastic polyurethane is (1.6-2.2):2 by mass fraction.

3. The method of claim 1, wherein the proton exchange membrane is prepared by the steps of: The ratio of perfluorosulfonic acid resin to thermoplastic polyurethane is (2-2.2):2 by mass fraction.

4. The method of claim 1, wherein the proton exchange membrane is prepared by the steps of: The preparation method of the slurry comprises: mixing perfluorosulfonic acid resin solution and thermoplastic polyurethane solution uniformly to obtain the slurry, wherein the perfluorosulfonic acid resin solution is a mixture of perfluorosulfonic acid resin and a first solvent, the thermoplastic polyurethane solution is a mixture of thermoplastic polyurethane, a second solvent and an acidic substance, the ratio of perfluorosulfonic acid resin in the perfluorosulfonic acid resin solution to thermoplastic polyurethane in the thermoplastic polyurethane solution is (1-20):(1-20) by mass fraction, the ratio of thermoplastic polyurethane in the thermoplastic polyurethane solution to the acidic substance is (3-7):(1-2) by mass fraction, the first solvent is a mixture of one or both of N-methylpyrrolidone and N,N-dimethylformamide, and the second solvent is a mixture of one or both of N-methylpyrrolidone and N,N-dimethylformamide.

5. The method of claim 4, wherein the proton exchange membrane is prepared by the steps of: The ratio of thermoplastic polyurethane, acidic substance and second solvent in the thermoplastic polyurethane solution is (3-7):(1-2):(50-60) by mass fraction.

6. The proton exchange membrane obtained by the preparation method of claim 1.

7. The proton exchange membrane of claim 6, wherein, The thickness of the proton exchange membrane is 50-60 microns.

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