A proton exchange membrane and a preparation method and application thereof

Abstract

This invention belongs to the field of fuel cells, specifically relating to a proton exchange membrane, its preparation method, and its application. In preparing the proton exchange membrane, an epoxy-based cage-like polysilsesquioxane is used as the crosslinking agent. The crosslinking agent is mixed with other raw materials, coated, and dried to form intermediate product A. Intermediate product A is then immersed in a first phosphoric acid solution and heat-treated at 60-80°C in air for a certain time to obtain intermediate product B. Intermediate product B is then immersed in a second phosphoric acid solution and heat-treated at 150-200°C in an inert atmosphere for a certain time to obtain the proton exchange membrane. The epoxy-based cage-like polysilsesquioxane possesses a high-temperature resistant cage structure. Combined with the subsequent two-stage heat treatment process, this improves the mechanical properties of the proton exchange membrane, reduces the possibility of phosphoric acid loss, and enhances the proton conductivity of the proton exchange membrane over a wide temperature range.

Description

Technical Field

[0001] This invention belongs to the field of fuel cells, specifically relating to a proton exchange membrane, its preparation method, and its application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are highly efficient energy conversion devices that can directly convert the chemical energy of fuel into electrical energy without combustion. Based on temperature, PEMFCs can be divided into high-temperature proton exchange membrane fuel cells (HT-PEMFCs) and low-temperature proton exchange membrane fuel cells (LT-PEMFCs).

[0003] As a core component of PEMFCs, the proton exchange membrane plays a decisive role in the operating temperature and electrochemical performance of fuel cells. Traditional high-temperature proton exchange membranes mainly operate at temperatures of 100~200℃. Due to the plasticizing effect of phosphoric acid and the loss of phosphoric acid at high temperatures, the proton conductivity of the proton exchange membrane does not show a significant improvement in molecular dynamics when operating at 240℃, thus affecting the electrochemical performance of the fuel cell. Summary of the Invention

[0004] In view of the defects and deficiencies of the existing technology, the present invention provides, in a first aspect, a method for preparing a proton exchange membrane; in a second aspect, a proton exchange membrane; and in a third aspect, a battery.

[0005] In a first aspect, the present invention provides a method for preparing a proton exchange membrane, comprising the following steps:

[0006] Step 1: Mix epoxy-based cage-like polysilsesquioxane and organic solvent to obtain solution A; mix polybenzimidazole, anhydrous lithium chloride and organic solvent and heat and stir under an oxygen-free atmosphere to obtain solution B;

[0007] Step 2: Mix solution A and solution B and heat and stir in an anaerobic atmosphere to obtain casting solution;

[0008] Step 3: The casting solution is coated onto the substrate and dried under vacuum to obtain intermediate product A;

[0009] Step 4: Immerse intermediate product A in a primary phosphoric acid solution, and then heat-treat it at 60-80°C in air for a certain period of time to obtain intermediate product B;

[0010] Step 5: The second phosphoric acid solution is brushed onto both sides of the intermediate product B, and then heat-treated at 150~200℃ for a certain time under an inert atmosphere to obtain the proton exchange membrane.

[0011] Preferably, the epoxy-based cage-like polysilsesquioxane has the following structural formula:

[0012] .

[0013] Preferably, the polybenzimidazole comprises any one or more of N-PBI (poly-2,2-(p-naphthyl)-5,5′-dibenzimidazole), m-PBI (poly-2,2-(m-phenylene)-5,5′-dibenzimidazole), p-PBI (poly-2,2-(p-phenylene)-5,5′-dibenzimidazole), OPBI (ether-bonded polybenzimidazole), AmPBI (amino-polybenzimidazole), BPPBI (pyridyl-polybenzimidazole), and PBIOH (hydroxyl-bonded polybenzimidazole).

[0014] Preferably, the organic solvents in solution A and solution B are one or more of N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, and tetrahydrofuran.

[0015] Preferably, the mass ratio of epoxy-based cage-like polysilsesquioxane to organic solvent in solution A is 1:20~100.

[0016] Preferably, the mass ratio of polybenzimidazole, anhydrous lithium chloride, and organic solvent in solution B is 1:0.05~0.25:20~25.

[0017] Preferably, in step 2, the mass ratio of epoxy-based cage-like polysilsesquioxane and polybenzimidazole in solution A and solution B is 1:4~20.

[0018] Preferably, in step 1, solution A is obtained by mixing epoxy-based cage-like polysilsesquioxane and organic solvent and stirring at room temperature for 3-5 hours; solution B is obtained by mixing polybenzimidazole, anhydrous lithium chloride and organic solvent and stirring at 70-80°C for 3-5 hours.

[0019] Preferably, in step 2, the heating temperature is 50~80℃ and the heating time is 0.5~1h.

[0020] Preferably, in step 3, the coating thickness is 200~1200μm.

[0021] Preferably, in step 3, the drying temperature is 120~150℃; the drying time is 8~12h.

[0022] Preferably, between steps 3 and 4, the intermediate product A is left to stand in air for 24-36 hours.

[0023] Preferably, in step 4, the heat treatment time is 36~72h.

[0024] In step 5, the mass ratio of the diphosphoric acid solution and intermediate product B used for each brushing is 1:0.25~0.35.

[0025] Preferably, in step 5, the heat treatment time is 2 to 12 hours.

[0026] Preferably, in steps 4 and 5, the mass fraction of the first phosphoric acid solution and the second phosphoric acid solution is 75% to 85%.

[0027] Preferably, in step 4, intermediate product A is completely immersed in the first phosphoric acid solution.

[0028] Preferably, in step 5, the inert gas providing the inert atmosphere is nitrogen or argon.

[0029] Secondly, the present invention provides a proton exchange membrane prepared by the above-described preparation method.

[0030] Thirdly, the present invention provides a battery comprising the above-described proton exchange membrane.

[0031] Compared with the prior art, the present invention has the following significant advantages:

[0032] (1) In the preparation of proton exchange membranes in this invention, epoxy-based cage-like polysilsesquioxane is selected as the crosslinking agent. Firstly, the cage-like structure has a larger free volume, which can adsorb more phosphoric acid and reduce the possibility of subsequent phosphoric acid loss. Secondly, epoxy-based cage-like polysilsesquioxane has good high-temperature resistance and good compatibility with polybenzimidazole. The two can be fully crosslinked during heat treatment, which further improves the mechanical properties of the proton exchange membrane. Thirdly, the combination of epoxy-based cage-like polysilsesquioxane and two-stage heat treatment process can further reduce the possibility of phosphoric acid loss and improve the proton conductivity of the proton exchange membrane in a wide temperature range.

[0033] (2) The preparation process provided by the present invention is simple and controllable, which is conducive to large-scale production and promotion. Attached Figure Description

[0034] Figure 1 Fourier transform infrared spectra of intermediate product A, epoxy-coated polysilsesquioxane (G-POSS), and polybenzimidazole (PBI) obtained in step 3 of Example 1.

[0035] Figure 2 The graph shows the proton conductivity of the proton exchange membranes prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 4.

[0036] Figure 3 The mechanical properties of the proton exchange membranes prepared in Example 1, Comparative Examples 1, 2, and 4 are shown in the test graph. Detailed Implementation

[0037] The present invention provides the following specific technical solutions.

[0038] In a first aspect, the present invention provides a method for preparing a proton exchange membrane, comprising the following steps:

[0039] Step 1: Mix epoxy-based cage-like polysilsesquioxane and organic solvent to obtain solution A; mix polybenzimidazole, anhydrous lithium chloride and organic solvent and heat and stir under an oxygen-free atmosphere to obtain solution B;

[0040] Step 2: Mix solution A and solution B and heat and stir in an anaerobic atmosphere to obtain casting solution;

[0041] Step 3: The casting solution is coated onto the substrate and dried under vacuum to obtain intermediate product A;

[0042] Step 4: Immerse intermediate product A in a primary phosphoric acid solution, and then heat-treat it at 60-80°C in air for a certain period of time to obtain intermediate product B;

[0043] Step 5: The second phosphoric acid solution is brushed onto both sides of the intermediate product B, and then heat-treated at 150~200℃ for a certain time under an inert atmosphere to obtain the proton exchange membrane.

[0044] Through research, the inventors discovered that, firstly, the proton exchange membrane prepared using epoxy-based cage-like polysilsesquioxane as a crosslinking agent possesses a large free volume, with ample unoccupied space. This allows the proton exchange membrane to adsorb more phosphoric acid during the first-stage immersion in phosphoric acid, reducing the impact of phosphoric acid loss on battery performance during operation. Secondly, epoxy-based cage-like polysilsesquioxane exhibits excellent high-temperature resistance and is a cage-type polysilsesquioxane molecule with a three-dimensional nanoscale organic / inorganic hybrid structure. It has good compatibility with polybenzimidazole (PBI), and the two are fully crosslinked during heat treatment, further improving the mechanical properties of the proton exchange membrane. Thirdly, the two-stage heat treatment process provided by this invention allows for full crosslinking of polybenzimidazole and the crosslinking agent, further enhancing the mechanical properties of the proton exchange membrane. Furthermore, the cage-like structure of the epoxy-based cage-like polysilsesquioxane can lock in the doped phosphoric acid during crosslinking, reducing the possibility of phosphoric acid loss and further improving the proton conductivity of the proton exchange membrane over a wide temperature range.

[0045] Further research by the inventors revealed that by brushing the second phosphoric acid solution onto both sides of intermediate product B, the swelling of intermediate product B at 150-200°C can be avoided, and the proton exchange membrane can be re-adsorbed with a small amount of phosphoric acid, thereby improving the proton conduction performance at high temperatures.

[0046] Preferably, the epoxy-based cage-like polysilsesquioxane has the following structural formula:

[0047] .

[0048] The reaction process of the epoxy-based cage-like polysilsesquioxane and the polybenzimidazole is as follows:

[0049] .

[0050] Preferably, the polybenzimidazole comprises any one or more of N-PBI (poly-2,2-(p-naphthyl)-5,5′-dibenzimidazole), m-PBI (poly-2,2-(m-phenylene)-5,5′-dibenzimidazole), p-PBI (poly-2,2-(p-phenylene)-5,5′-dibenzimidazole), OPBI (ether-bonded polybenzimidazole), AmPBI (amino-polybenzimidazole), BPPBI (pyridyl-polybenzimidazole), and PBIOH (hydroxyl-bonded polybenzimidazole).

[0051] Preferably, the organic solvents in solution A and solution B are one or more of N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, and tetrahydrofuran.

[0052] Preferably, the mass ratio of epoxy-based cage-like polysilsesquioxane to organic solvent in solution A is 1:20~100.

[0053] Preferably, the mass ratio of polybenzimidazole, anhydrous lithium chloride, and organic solvent in solution B is 1:0.05~0.25:20~25.

[0054] The above ratios are the preferred ranges given by the inventors after multiple studies. Proton exchange membranes prepared within this range exhibit good ductility and uniform texture. In practical applications, the above ratios can be adjusted according to ambient temperature and humidity. In specific embodiments of the present invention, the mass ratio of epoxy-based cage-like polysilsesquioxane to organic solvent in solution A can be 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, and 1:100; the mass ratio of polybenzimidazole, anhydrous lithium chloride, and organic solvent in solution B can be 1:0.05:20, 1:0.1:21, 1:0.15:22, 1:0.2:23, and 1:0.25:25.

[0055] Preferably, in step 2, the mass ratio of epoxy-based cage-like polysilsesquioxane and polybenzimidazole in solution A and solution B is 1:4~20.

[0056] The inventors discovered that polybenzimidazole itself possesses excellent thermal stability, chemical stability, and flame retardancy. The proton exchange membrane prepared by reacting excess polybenzimidazole with epoxy-based cage-like polysilsesquioxane not only inherits the excellent properties of polybenzimidazole but also exhibits a more uniform and dense structure, which is beneficial for improving the proton conductivity of the proton exchange membrane and preventing gas permeation. In practical applications, the mass ratio of epoxy-based cage-like polysilsesquioxane to polybenzimidazole in solution C can be 1:4, 1:8, 1:12, 1:16, or 1:20.

[0057] Preferably, in step 1, solution A is obtained by mixing epoxy-based cage-like polysilsesquioxane and organic solvent and stirring at room temperature for 3-5 hours; solution B is obtained by mixing polybenzimidazole, anhydrous lithium chloride and organic solvent and stirring at 70-80°C for 3-5 hours.

[0058] In practice, the stirring time of the epoxy-coated polysilsesquioxane and organic solvent can be adjusted according to the actual operating conditions. Stirring is sufficient until the epoxy-coated polysilsesquioxane dissolves in the organic solvent.

[0059] Preferably, in step 2, the heating temperature is 50~80℃ and the heating time is 0.5~1h.

[0060] Preferably, in step 3, the coating thickness is 200~1200μm.

[0061] Preferably, in step 3, the drying temperature is 120~150℃; the drying time is 8~12h.

[0062] Preferably, between steps 3 and 4, the intermediate product A is left to stand in air for 24-36 hours.

[0063] The inventors discovered through research that placing the intermediate product in the air for a certain period of time allows the anhydrous lithium chloride in product A to absorb moisture from the air, which is beneficial to improving the efficiency of subsequent proton exchange membrane adsorption of phosphoric acid.

[0064] Preferably, in step 4, the soaking time is 36~72h.

[0065] In step 5, the mass ratio of the diphosphoric acid solution and intermediate product B used for each brushing is 1:0.25~0.35.

[0066] Preferably, in step 5, the heat treatment time is 2 to 12 hours.

[0067] Preferably, in steps 4 and 5, the mass fraction of the first phosphoric acid solution and the second phosphoric acid solution is 75% to 85%.

[0068] Preferably, in step 4, intermediate product A is completely immersed in the first phosphoric acid solution.

[0069] The inventors discovered that completely immersing intermediate product A in the first phosphoric acid solution in step 4 helps intermediate product A to fully absorb phosphoric acid and improves the doping efficiency of phosphoric acid.

[0070] Preferably, in step 5, the inert gas providing the inert atmosphere is nitrogen or argon.

[0071] Secondly, the present invention provides a proton exchange membrane prepared by the above-described preparation method.

[0072] Thirdly, the present invention provides a battery comprising the above-described proton exchange membrane.

[0073] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0074] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0075] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0076] Example 1:

[0077] A method for preparing a proton exchange membrane includes the following steps:

[0078] Step 1: Add 0.1g of epoxy-coated polysilsesquioxane to 2mL of dimethyl sulfoxide solution and stir at room temperature for 5h to obtain solution A; add 0.4g of polybenzimidazole and 0.1g of anhydrous lithium chloride to 8mL of dimethyl sulfoxide, heat treat in an oxygen-free atmosphere at 70℃ in an oil bath and stir for 5h to obtain solution B.

[0079] Step 2: Mix solution A and solution B and heat-treat to 70°C in an oxygen-free atmosphere, stirring until homogeneous to obtain casting solution.

[0080] Step 3: The casting solution is scraped onto a flat glass plate to a thickness of 700 μm. The glass plate is then transferred to a vacuum drying oven, heated from 80°C to 150°C and kept at that temperature for 8 hours to obtain intermediate product A.

[0081] Step 4: Place intermediate product A in air for 48 hours.

[0082] Step 5: The intermediate product A after step 4 is completely immersed in a phosphoric acid solution with a mass fraction of 85% and heat-treated at 70°C for 48 hours. The resulting film is the intermediate product B.

[0083] Step 6: Place intermediate product B in a high-temperature container, then drop an 85% phosphoric acid solution onto one side of intermediate product B and brush it evenly. Turn intermediate product B over and drop the 85% phosphoric acid solution onto the other side of intermediate product B again and brush it evenly. The mass ratio of phosphoric acid solution to intermediate product B is 1:0.3 each time. Then place the intermediate product B coated with phosphoric acid solution in an argon atmosphere and heat treat it at 180°C for 4 hours. The resulting membrane is the proton exchange membrane.

[0084] Figure 1 The Fourier transform infrared spectra of intermediate product A, epoxy-coated polysilsesquioxane (G-POSS), and polybenzimidazole (PBI) obtained in step 3 of Example 1 are shown below. Figure 1 It can be observed that the Fourier transform infrared curve of intermediate product A is at 910 cm⁻¹ -1 The presence of an epoxy group peak indicates that the epoxy group reacted with the imidazole group, successfully forming a proton exchange membrane.

[0085] Comparative Example 1:

[0086] A method for preparing a proton exchange membrane includes the following steps:

[0087] Step 1: Add 0.1g of epoxy-coated polysilsesquioxane to 2mL of dimethyl sulfoxide and stir at room temperature for 5h to obtain solution A; add 0.4g of polybenzimidazole and 0.1g of anhydrous lithium chloride to 8mL of dimethyl sulfoxide, heat treat in an oxygen-free atmosphere at 70℃ in an oil bath and stir for 5h to obtain solution B.

[0088] Step 2: Mix solution A and solution B and heat-treat to 70°C in an oxygen-free atmosphere, stirring until homogeneous to obtain casting solution.

[0089] Step 3: The casting solution is scraped onto a flat glass plate, and then the glass plate is transferred to a vacuum drying oven. The temperature is increased from 80°C to 150°C and kept at that temperature for 8 hours to obtain intermediate product A.

[0090] Step 4: Place intermediate product A in air for 48 hours.

[0091] Step 5: Immerse the intermediate product A, which has been treated in step 4, completely in a phosphoric acid solution with a mass fraction of 85% for 48 hours. The resulting membrane is the proton exchange membrane.

[0092] Comparative Example 2:

[0093] A method for preparing a proton exchange membrane includes the following steps:

[0094] Step 1: Add 0.1g of epoxy-coated polysilsesquioxane to 2mL of dimethyl sulfoxide and stir at room temperature for 5h to obtain solution A; add 0.4g of polybenzimidazole and 0.1g of anhydrous lithium chloride to 8mL of dimethyl sulfoxide, heat treat in an oxygen-free atmosphere at 70℃ in an oil bath and stir for 5h to obtain solution B.

[0095] Step 2: Mix solution A and solution B and heat-treat to 70°C in an oxygen-free atmosphere, stirring until homogeneous to obtain casting solution.

[0096] Step 3: The casting solution is scraped onto a flat glass plate, and then the glass plate is transferred to a vacuum drying oven. The temperature is increased from 80°C to 150°C and kept at that temperature for 8 hours to obtain intermediate product A.

[0097] Step 4: Place intermediate product A in air for 48 hours.

[0098] Step 5: The intermediate product A after step 4 is completely immersed in a phosphoric acid solution with a mass fraction of 85% and heat-treated at 70°C for 48 hours. The resulting film is the intermediate product B.

[0099] Step 6: Place intermediate product B in a high-temperature container, then drop an 85% phosphoric acid solution onto one side of intermediate product B and brush it evenly. Turn intermediate product B over and drop the 85% phosphoric acid solution onto the other side of intermediate product B again and brush it evenly. The mass ratio of phosphoric acid solution to intermediate product B dropped each time is 1:0.3. Then place the intermediate product B coated with phosphoric acid solution in an argon atmosphere and heat-treat it at 70°C for 4 hours. The resulting membrane is the proton exchange membrane.

[0100] Comparative Example 3:

[0101] A method for preparing a proton exchange membrane includes the following steps:

[0102] Step 1: Add 0.1g of epoxy-coated polysilsesquioxane to 2mL of dimethyl sulfoxide and stir at room temperature for 5h to obtain solution A; add 0.4g of polybenzimidazole and 0.1g of anhydrous lithium chloride to 8mL of dimethyl sulfoxide, heat treat in an oxygen-free atmosphere at 70℃ in an oil bath and stir for 5h to obtain solution B.

[0103] Step 2: Mix solution A and solution B and heat-treat to 70°C in an oxygen-free atmosphere, stirring until homogeneous to obtain casting solution.

[0104] Step 3: The casting solution is scraped onto a flat glass plate, and then the glass plate is transferred to a vacuum drying oven. The temperature is increased from 80°C to 150°C and kept at that temperature for 8 hours to obtain intermediate product A.

[0105] Step 4: Place intermediate product A in air for 48 hours.

[0106] Step 5: The intermediate product A, which was treated in step 4, was completely immersed in a phosphoric acid solution with a mass fraction of 85% and heat-treated at 180°C. After 10 hours, it was observed that the intermediate product A swelled and dissolved in the phosphoric acid solution, making it impossible to conduct subsequent experiments and tests.

[0107] Comparative Example 4:

[0108] A method for preparing a proton exchange membrane includes the following steps:

[0109] Step 1: Add 0.1g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) to 2mL of dimethyl sulfoxide and stir at room temperature for 5h to obtain solution A; add 0.4g of polybenzimidazole and 0.1g of anhydrous lithium chloride to 8mL of dimethyl sulfoxide, heat treat in an oil bath at 70℃ under an oxygen-free atmosphere and stir for 5h to obtain solution B.

[0110] Step 2: Mix solution A and solution B and heat-treat to 70°C in an oxygen-free atmosphere, stirring until homogeneous to obtain casting solution.

[0111] Step 3: The casting solution is scraped onto a flat glass plate, and then the glass plate is transferred to a vacuum drying oven. The temperature is increased from 80°C to 150°C and kept at that temperature for 8 hours to obtain intermediate product A.

[0112] Step 4: Place intermediate product A in air for 48 hours.

[0113] Step 5: The intermediate product A after step 4 is completely immersed in a phosphoric acid solution with a mass fraction of 85% and heat-treated at 70°C for 48 hours. The resulting film is the intermediate product B.

[0114] Step 6: Place intermediate product B in a high-temperature container, then drop an 85% phosphoric acid solution onto one side of intermediate product B and brush it evenly. Turn intermediate product B over and drop the 85% phosphoric acid solution onto the other side of intermediate product B again and brush it evenly. The mass ratio of phosphoric acid solution to intermediate product B is 1:0.3 each time. Then place the intermediate product B coated with phosphoric acid solution in an argon atmosphere and heat treat it at 180°C for 4 hours. The resulting membrane is the proton exchange membrane.

[0115] Example 2:

[0116] A method for preparing a proton exchange membrane includes the following steps:

[0117] Step 1: Add 0.1g of epoxy-coated polysilsesquioxane to 2mL of N,N-dimethylformamide and stir at room temperature for 5h to obtain solution A; add 1g of polybenzimidazole and 0.05g of anhydrous lithium chloride to 23mL of N,N-dimethylformamide, heat treat in an anaerobic atmosphere at 80℃ in an oil bath and stir for 3h to obtain solution B.

[0118] Step 2: Mix solution A and solution B and heat-treat them to 80°C in an oxygen-free atmosphere, stirring until the mixture is homogeneous to obtain the casting solution.

[0119] Step 3: The casting solution is scraped onto a flat glass plate, and then the glass plate is transferred to a vacuum drying oven. The temperature is increased from 80°C to 150°C and kept at that temperature for 12 hours to obtain intermediate product A.

[0120] Step 4: Place intermediate product A in air for 48 hours.

[0121] Step 5: Immerse intermediate product A, which has been treated in step 4, in a 75% phosphoric acid solution and heat-treat it at 60°C for 72 hours. The resulting film is intermediate product B.

[0122] Step 6: Place intermediate product B in a high-temperature container, then drop a 75% phosphoric acid solution onto one side of intermediate product B and brush it evenly. Turn intermediate product B over and drop another 75% phosphoric acid solution onto the other side of intermediate product B and brush it evenly. The mass ratio of phosphoric acid solution to intermediate product B dropped each time is 0.35. Then place the intermediate product B coated with phosphoric acid solution in an argon atmosphere at 200°C for 12 hours. The resulting membrane is the proton exchange membrane.

[0123] Example 3:

[0124] A method for preparing a proton exchange membrane includes the following steps:

[0125] Step 1: Add 0.02g of epoxy-based cage-like polysilsesquioxane to 2mL of tetrahydrofuran and stir at room temperature for 5h to obtain solution A; add 0.4g of polybenzimidazole and 0.07g of anhydrous lithium chloride to 10mL of tetrahydrofuran, heat treat in an oxygen-free atmosphere at 70℃ in an oil bath and stir for 3h to obtain solution B.

[0126] Step 2: Mix solution A and solution B and heat-treat to 70°C in an oxygen-free atmosphere, stirring until homogeneous to obtain casting solution.

[0127] Step 3: The casting solution is scraped onto a flat glass plate, and then the glass plate is transferred to a vacuum drying oven. The temperature is increased from 80°C to 130°C and kept at that temperature for 8 hours to obtain intermediate product A.

[0128] Step 4: Place intermediate product A in air for 48 hours.

[0129] Step 5: Immerse intermediate product A, which has been treated in step 4, in a phosphoric acid solution with a mass fraction of 80% and heat-treat it at 80°C for 72 hours. The resulting film is intermediate product B.

[0130] Step 6: Place intermediate product B in a high-temperature container, then drop an 80% phosphoric acid solution onto one side of intermediate product B and brush it evenly. Turn intermediate product B over and drop the 80% phosphoric acid solution onto the other side of intermediate product B again and brush it evenly. The mass ratio of phosphoric acid solution to intermediate product B dropped each time is 1:0.25. Then place the intermediate product B coated with phosphoric acid solution in an argon atmosphere at 150°C for 12 hours. The resulting membrane is the proton exchange membrane.

[0131] Figure 2 The graphs show the proton conductivity of the proton exchange membranes prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 4. Figure 2 It can be seen that the proton conductivity of the proton exchange membrane prepared in Example 1 is higher than that of the proton exchange membrane prepared in Comparative Example 1. In the range of 100~250℃, the proton conductivity of the proton exchange membrane prepared in Example 1 is significantly improved, which proves that the proton exchange membrane prepared by the two-stage heat treatment process provided by the present invention has a better proton conductivity. Based on the trend of the proton conductivity curve, it can be reasonably inferred that the applicable temperature range of the proton exchange membrane prepared in Example 1 can also be significantly improved.

[0132] The proton conductivity of the proton exchange membrane prepared in Comparative Example 2 was lower than that of the proton exchange membrane prepared in Example 1. The inventors speculate that the reason is that the heat treatment temperature of the proton exchange membrane prepared in Comparative Example 2 was lower, which led to incomplete cross-linking reaction of the proton exchange membrane and easy loss of doped phosphoric acid, thus affecting its proton conductivity.

[0133] The proton conductivity of the proton exchange membrane prepared in Comparative Example 4 was lower than that of the proton exchange membrane prepared in Example 1. The inventors speculate that the reason is that the crosslinking agent used in preparing the proton exchange membrane of Comparative Example 4 does not contain a cage structure, which reduces the confinement and capture performance of phosphoric acid. Therefore, the proton conductivity of the proton exchange membrane prepared in Comparative Example 4 is the worst compared with that of Example 1, Comparative Example 1, and Comparative Example 2.

[0134] Depend on Figure 2It can be clearly observed that within the main operating temperature range of 100~200℃, the proton conductivity of the proton exchange membrane prepared in Example 1 is much higher than that of the proton exchange membranes prepared in Comparative Examples 1, 2 and 4, with the proton conductivity increasing by several times. This further demonstrates that the proton exchange membrane prepared by the process provided by the present invention has superior electrochemical performance.

[0135] Figure 3 The mechanical property test curves of the proton exchange membranes prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 4 are provided by [the relevant authority / organization]. Figure 3 It can be clearly seen that the proton exchange membrane prepared in Example 1 has the best mechanical properties, and its elongation at break and tensile strength are far superior to those of the proton exchange membranes prepared in Comparative Examples 1, 2 and 4.

[0136] The inventors speculate that the reasons may be as follows: the proton exchange membrane prepared in Comparative Example 1 did not undergo two-stage heat treatment, resulting in incomplete crosslinking and poor mechanical properties; although the proton exchange membrane prepared in Comparative Example 2 underwent two-stage heat treatment, its tensile strength increased, but the low heat treatment temperature led to a decrease in its elongation at break; the crosslinking agent used in Comparative Example 4 did not contain a cage structure, and the crosslinking agent may not have further crosslinked after heat treatment, so the mechanical properties of the proton exchange membrane prepared in Comparative Example 4 were similar to those in Comparative Example 1.

[0137] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a proton exchange membrane, characterized in that, Includes the following steps: Step 1: Mix epoxy-based cage-like polysilsesquioxane and organic solvent to obtain solution A; mix polybenzimidazole, anhydrous lithium chloride and organic solvent and heat and stir under an oxygen-free atmosphere to obtain solution B; Step 2: Mix solution A and solution B and heat and stir in an anaerobic atmosphere to obtain casting solution; Step 3: The casting solution is coated onto the substrate and dried under vacuum to obtain intermediate product A; Step 4: Immerse intermediate product A in a primary phosphoric acid solution, and then heat-treat it at 60-80°C for 36-72 hours in air atmosphere to obtain intermediate product B; Step 5: The second phosphoric acid solution is brushed onto both sides of the intermediate product B, and then heat-treated at 150~200℃ for 2~12h under an inert atmosphere to obtain the proton exchange membrane.

2. The method for preparing a proton exchange membrane as described in claim 1, characterized in that, The structural formula of the epoxy-based cage-like polysilsesquioxane is as follows: 。 3. The method for preparing a proton exchange membrane as described in claim 1, characterized in that, In step 5, the mass ratio of the diphosphoric acid solution and intermediate product B used for each brushing is 1:0.25~0.

35.

4. A method for preparing a proton exchange membrane as described in claim 1 or 2, characterized in that, The polybenzimidazole includes any one or more of N-PBI, m-PBI, p-PBI, OPBI, AmPBI, BPPBI, and PBIOH.

5. A method for preparing a proton exchange membrane as described in claim 1 or 3, characterized in that, The organic solvents in both solution A and solution B are one or more of N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, and tetrahydrofuran; the mass ratio of epoxy-based cage-like polysilsesquioxane to organic solvent in solution A is 1:20~100; the mass ratio of polybenzimidazole, anhydrous lithium chloride, and organic solvent in solution B is 1:0.05~0.25:20~25; and the mass fraction of both the first phosphoric acid solution and the second phosphoric acid solution is 75%~85%.

6. A method for preparing a proton exchange membrane as described in claim 1 or 2, characterized in that, In step 2, the mass ratio of epoxy-based cage-like polysilsesquioxane and polybenzimidazole in solution A and solution B is 1:4~20.

7. The method for preparing a proton exchange membrane as described in claim 1, characterized in that, In step 1, solution A is obtained by mixing epoxy-based cage-like polysilsesquioxane and organic solvent and stirring at room temperature for 3-5 hours; solution B is obtained by mixing polybenzimidazole, anhydrous lithium chloride and organic solvent and stirring at 70-80℃ for 3-5 hours.

8. The method for preparing a proton exchange membrane as described in claim 1, characterized in that, In step 2, the heating temperature is 50~80℃ and the heating time is 0.5~1h; in step 3, the drying temperature is 120~150℃ and the drying time is 8~12h; between step 3 and step 4, the intermediate product A is left to stand in the air for 24-36h.

9. A proton exchange membrane, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. A battery, characterized in that, Includes the proton exchange membrane as described in claim 9.

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