Proton exchange membrane and preparation method thereof

Abstract

The invention discloses a proton exchange membrane and a preparation method thereof, the proton exchange membrane is obtained on a substrate by casting slurry on the substrate, drying and post-processing, the slurry comprises perfluorosulfonic acid resin, thermoplastic polyurethane, a solvent and an acidic substance, and the acidic substance is at least one of acetic acid, fatty acid, phosphoric acid, silicic acid and tungstic acid. Compared with the prior art, the perfluorinated sulfonic acid resin solution is high in flowability, so that the film-forming property and the mechanical property are poor, and the perfluorinated sulfonic acid resin and the thermoplastic polyurethane are compounded, so that the diaphragm has excellent elasticity, the water absorption swelling bearing capacity of the diaphragm in a battery is improved, and the diaphragm has good film-forming property and good mechanical property; the elongation at break of the diaphragm is remarkably improved, the diaphragm has good chemical stability, and meanwhile, the proton conductivity of the diaphragm can be increased to a certain extent by introducing an acidic material.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery diaphragms, and specifically relates to a proton exchange membrane and a preparation method thereof. Background Art

[0002] At present, the global energy development and the coordination issue between energy and environment have become the focus of attention of all mankind and are also key topics for China's economic development. Since the 1990s, with the intensification of the energy crisis and the prominence of environmental pollution problems, the global attention to environmental protection and green technologies has been continuously increasing. According to the global energy development trend in the next 50 years, the energy structure will still be mainly based on fossil fuels, supplemented by renewable energy and new energy. Developing economical, efficient, and clean energy (including renewable and non-renewable energy) will be the core issue of energy science and technology in the 21st century. As the fourth-generation large-scale power generation method following thermal power, hydropower, and nuclear power, fuel cell technology can effectively alleviate the energy crisis and contribute to sustainable economic development. Due to its advantages such as high energy efficiency, low pollution, and low noise, it has become a research hotspot in the current energy field.

[0003] A proton exchange membrane fuel cell (PEMFC) is a power generation device that uses hydrogen as fuel and oxygen as an oxidant, and its core component is the proton exchange membrane. This proton exchange membrane not only provides a one-way transmission channel for protons but also can isolate the fuel and the oxidant. To achieve the efficient operation of the proton exchange membrane fuel cell, the proton exchange membrane must have high proton conductivity, excellent chemical and mechanical stability. Currently, perfluorosulfonic acid proton exchange membranes are the most widely used, and the Nafion series membranes produced by DuPont are the most representative. However, Nafion membranes still have problems such as high production difficulty and high cost, and the synthesis and sulfonation processes of perfluorinated materials are complex, and hydrolysis and degradation are likely to occur during film formation, affecting the membrane performance and increasing the production cost. To overcome these disadvantages, domestic scholars have proposed various modification methods, including inorganic doping, adding support materials, heat treatment, crosslinking, blending, in-situ polymerization, self-assembly, etc., but still cannot completely solve the above technical problems. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a proton exchange membrane.

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

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

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

[0008] A proton exchange membrane, comprising: perfluorosulfonic acid resin (PFSA) and thermoplastic polyurethane (TPU). By mass, the ratio of perfluorosulfonic acid resin (PFSA) to thermoplastic polyurethane (TPU) is (1 - 20):(1 - 20).

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

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

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

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

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

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

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

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

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

[0018] The preparation method of the above proton exchange membrane includes: casting the slurry on a substrate, drying, and post - treating to obtain a proton exchange membrane on the substrate. The post - treatment includes: soaking successively in sulfuric acid, hydrogen peroxide, and water.

[0019] In the above technical solution, the drying includes: first drying at 50 - 80 °C for 10 - 14 h, and then drying at 100 - 130 °C for 1 - 2 h.

[0020] In the above technical solution, the post-treatment includes: soaking in sulfuric acid at 50 - 80 °C for 1.5 - 3 h, soaking in hydrogen peroxide at 50 - 70 °C for 0.5 - 2 h, washing, then soaking in water at 50 - 70 °C for 0.5 - 2 h, and finally drying at 60 - 90 °C for 10 - 14 h.

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

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

[0023] In the above technical solution, by mass, 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.

[0024] In the above technical solution, by mass, 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.

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

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

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

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

[0029] In the above technical solution, the method for obtaining the perfluorosulfonic acid resin (PFSA) solution is: mixing perfluorosulfonic acid resin (PFSA) and the first solvent, and stirring until homogeneous at 140 - 160 °C.

[0030] In the above technical solution, the method for obtaining the thermoplastic polyurethane (TPU) solution is: mixing thermoplastic polyurethane (TPU), the second solvent and the acidic substance, and stirring until homogeneous at 20 - 40 °C.

[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 above technical solution, the first solvent is one or a mixture of two of N - methylpyrrolidone (NMP) and N,N - dimethylformamide (DMF), and the second solvent is one or a mixture of two of N - methylpyrrolidone (NMP) and N,N - dimethylformamide (DMF).

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

[0035] Application of perfluorosulfonic acid resin, thermoplastic polyurethane and acidic substance in synergistically improving the proton conductivity of the proton exchange membrane, and 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 the hydrolysis stability of the proton exchange membrane.

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

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] The perfluorosulfonic acid resin (PFSA) solution has high fluidity, so its film-forming property and mechanical properties are poor. In the present invention, by compounding perfluorosulfonic acid resin (PFSA) and thermoplastic polyurethane (TPU), the diaphragm has excellent elasticity, increasing the ability of the diaphragm to withstand water absorption and swelling in the battery, bringing good film-forming properties and good mechanical properties to the diaphragm, significantly improving the elongation at break of the diaphragm, and having good chemical stability; at the same time, an acidic substance is introduced to provide acid-base pairs and then form hydrogen bonds, providing a proton channel, which can increase the proton conductivity of the diaphragm to a certain extent. Description of the Drawings

[0040] Figure 1 SEM image of the proton exchange membrane prepared in Example 1 at 200X;

[0041] Figure 2 SEM image of the proton exchange membrane prepared in Example 1 at 1KX;

[0042] Figure 3 SEM image of the proton exchange membrane prepared in Example 1 at 15KX;

[0043] Figure 4 SEM image of the proton exchange membrane prepared in Example 1 at 5KX. Detailed Embodiments

[0044] The technical solutions of the present invention will be further described below with specific embodiments.

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

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

[0047] N-methylpyrrolidone (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 AG, Germany;

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

[0053] Electrochemical workstation, CHI660E, Deerns 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: Immerse a membrane with a pre-dried mass of Wo (g) in deionized water at 80 °C for 48 h, take out the immersed membrane and dry it at 80 °C for 8 h, and measure its mass as Wt (g). The hydrolysis stability value Wc of the proton exchange membrane is calculated by the following formula:

[0057]

[0058] Water absorption rate: Dry the membrane in an oven at 80 °C ± 2 °C for 24 hours, take it out and air-dry it to room temperature, and measure the mass of the membrane as m 0 (g). Then immerse the membrane in distilled water at 80 °C for 8 h, remove the water on the surface of the membrane with filter paper, and measure the mass of the membrane as m 1 (g) within 30 seconds. The water absorption rate Δm value is calculated by the following formula:

[0059]

[0060] Make the membrane into a rectangular spline with a length of 65 mm and a width of 15 mm. Use a Shimadzu tensile machine in Japan, set the tensile speed to 5 mm / min, and the original gauge length to 20 mm, for testing mechanical properties and elongation at break:

[0061] The mechanical property (tensile strength) is calculated by the following formula:

[0062] σ 1 = p / (b × d), where σ1 is the tensile strength (MPa), p is the maximum load (N), b is the width of the rectangular spline (mm), d is the thickness of the rectangular spline (mm), and the thickness is measured by a thickness gauge.

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

[0064] Among them, e is the elongation at break, l 0 is the length of the rectangular spline, and l a is the length of the rectangular spline at break.

[0065] Proton conductivity: Test under the conditions of 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 "membrane" is one of the proton exchange membranes prepared in Examples 1 to 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, deionized water is used.

[0068] Examples 1 - 7

[0069] A method for preparing a proton exchange membrane, comprising: casting a slurry onto a substrate (a 20 cm × 20 cm glass plate), drying (first drying at 80 °C for 12 h, then drying at 120 °C for 1.5 h), and performing post-treatment to obtain a proton exchange membrane on the substrate, wherein the post-treatment is: soaking in sulfuric acid (sulfuric acid concentration is 1 mol / L) at 60 °C for 2 h, soaking in hydrogen peroxide (hydrogen peroxide concentration is 3 wt%) at 60 °C for 2 h, washing three times with water, then soaking in water at 60 °C for 2 h, and finally drying at 80 °C 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 °C at a rotation speed of 150 r / min for 1 h until homogeneous to obtain a slurry. The perfluorosulfonic acid resin (PFSA) solution is a mixture of perfluorosulfonic acid resin (PFSA) and a first solvent, and the thermoplastic polyurethane (TPU) solution is a mixture of thermoplastic polyurethane (TPU), a second solvent, and an acidic substance. By mass fraction, 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 is: mixing perfluorosulfonic acid resin (PFSA) and a first solvent, stirring in a high-temperature reactor at 150 °C at a rotation speed of 500 r / min for 4 h until homogeneous to obtain a perfluorosulfonic acid resin (PFSA) solution. By mass fraction, 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-methylpyrrolidone (NMP).

[0072] A method for obtaining a thermoplastic polyurethane (TPU) solution is: mixing thermoplastic polyurethane (TPU), a second solvent, and an acidic substance, stirring in a magnetic stirrer at 30 °C at a rotation speed of 150 r / min for 1 h until homogeneous to obtain a thermoplastic polyurethane (TPU) solution. By mass fraction, the ratio of thermoplastic polyurethane (TPU), acidic substance, and the second solvent in the thermoplastic polyurethane (TPU) solution is 5:1:50, the second solvent is N-methylpyrrolidone (NMP), and the acidic substance is acetic acid.

[0073] The value of X is shown in Table 1, and 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 preparation method of a pure PFSA proton exchange membrane includes: mixing 5 g of PFSA and 95 g of NMP, stirring in a high-temperature reaction kettle at 150 °C at a rotation speed of 600 r / min for 4 h to obtain a slurry, casting the slurry on a 20 cm × 20 cm glass plate, drying at 80 °C for 10 h first, then drying at 120 °C for 1.5 h, taking out the membrane, soaking it in 1 mol / L sulfuric acid at 80 °C for 2 h, then soaking it in hydrogen peroxide (concentration 3 wt%) at 60 °C for 1 h, taking out, washing with deionized water, soaking in deionized water at 60 °C for 1 h, and finally drying at 80 °C for 12 h to obtain a pure PFSA proton exchange membrane.

[0079] Comparative Example 2

[0080] A preparation method of a hybrid separator is basically the same as that of Comparative Example 1, the difference being only that: the slurries are 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 in a high-temperature reaction kettle at 150 °C at a rotation speed of 600 r / min for 4 h to obtain the slurry of Comparative Example 2.

[0082] Comparative Example 3

[0083] A preparation method of a composite separator is basically the same as that of Example 1, the difference being only that: the slurries are 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, the difference being only that: no acidic substance is added to the thermoplastic polyurethane (TPU) solution of Comparative Example 3. By mass, the ratio of thermoplastic polyurethane (TPU) to the second solvent is 5:50. By mass, 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.

[0085] Perform performance tests on the proton exchange membranes prepared in Examples 1 to 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, as shown in Table 2.

[0086] Table 2

[0087]

[0088]

[0089] As can be seen from Table 2, TPU was added in Examples 1-7 and Comparative Example 3, resulting in a significant improvement in the elongation at break, indicating that TPU can endow the separator with excellent elastic properties. At the same time, adding TPU can also improve the tensile strength of the separator to a certain extent, increasing the possibility of its practical application. By comparing Comparative Example 1 and Comparative Example 2, it can be found that the proton conductivity of Comparative Example 2 has increased, indicating that adding acetic acid provides acid-base pairs, which is beneficial to the proton transfer efficiency between membranes. Through comprehensive analysis, the performance of Example 7 is the best.

[0090] Figures 1 to 4 SEM image of the proton exchange membrane prepared in Example 1. Through Figures 1 to 4 it can be seen that the surface of the proton exchange membrane obtained from the slurry containing TPU and acetic acid is uneven, indicating that some pores have appeared inside, which is beneficial to the proton transfer in the separator; at the same time, circular holes can also be seen on the surface at high magnification, further proving the above view, which also provides strong evidence for the proton conduction function of the separator.

[0091] The above provides 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 equivalent substitution that can be made by those skilled in the art without creative efforts falls within the protection scope of the present invention.

Claims

1. A proton exchange membrane, characterized in that: include: The ratio of the perfluorosulfonic acid resin to the thermoplastic polyurethane is (1-20): (1-20) by weight.

2. The proton exchange membrane according to claim 1, characterized in that The thickness of the proton exchange membrane is 50 to 60 microns.

3. A slurry, characterized in that: include: Perfluorosulfonic acid resin, thermoplastic polyurethane, solvent and acidic substance, calculated by weight, the ratio of perfluorosulfonic acid resin to thermoplastic polyurethane is (1-20):(1-20), and the ratio of thermoplastic polyurethane to acidic substance is (3-7):(1-2).

4. The slurry according to claim 3, characterized in that The acidic substance is at least one of acetic acid, fatty acid, phosphoric acid, silicic acid and tungstic acid.

5. The method for preparing a proton exchange membrane according to any one of claims 1 to 2, characterized in that: include: The slurry of claim 4 is cast on a substrate, dried, and post-processed to obtain a proton exchange membrane on the substrate, wherein the post-processing comprises: soaking in sulfuric acid, hydrogen peroxide, and water in sequence.

6. The method for preparing the slurry according to any one of claims 3 to 4, characterized in that: include: The perfluorosulfonic acid resin solution and the thermoplastic polyurethane solution are mixed until uniform to obtain a slurry, wherein the perfluorosulfonic acid resin solution is a mixture of a perfluorosulfonic acid resin and a first solvent, and the thermoplastic polyurethane solution is a mixture of a thermoplastic polyurethane, a second solvent and an acidic substance. The ratio of the perfluorosulfonic acid resin in the perfluorosulfonic acid resin solution to the thermoplastic polyurethane in the thermoplastic polyurethane solution is (1-20):(1-20) by weight, and the ratio of the thermoplastic polyurethane in the thermoplastic polyurethane solution to the acidic substance is (3-7):(1-2) by weight.

7. The preparation method according to claim 6, characterized in that: In terms of mass fractions, the ratio of thermoplastic polyurethane, acidic substance and second solvent in the thermoplastic polyurethane solution is (3-7):(1-2):(50-60).

8. Application of perfluorosulfonic acid resin and thermoplastic polyurethane to synergistically improve the tensile strength, hydrolytic stability and / or elongation at break of proton exchange membrane.

9. Application of perfluorosulfonic acid resin, thermoplastic polyurethane and acidic substance to synergistically improve the 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.

10. Application of perfluorosulfonic acid resin and thermoplastic polyurethane to synergistically reduce the water absorption rate of proton exchange membrane.

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