A high-temperature fuel cell proton exchange membrane, its preparation method and application

Abstract

This invention belongs to the field of polymer electrolyte membrane material technology, and specifically relates to a high-temperature fuel cell proton exchange membrane, its preparation method, and its application. The high-temperature fuel cell proton exchange membrane provided by this invention undergoes ion exchange, washing, and drying in an alkaline solution to obtain a mixture of products S1 and S2; the mixture of S1 and S2 is then subjected to a phosphonylation reaction in a solvent at 70℃~120℃ to obtain a casting solution; the composite film (Ⅰ) obtained by casting and drying the casting solution is immersed in a heated acidic solution, washed, and dried to obtain a composite film (Ⅱ); the composite film (Ⅱ) is then immersed in a heated phosphoric acid solution and removed to obtain the final product; this high-temperature fuel cell proton exchange membrane can maintain good proton conductivity, high proton conductivity and high peak power density, high tensile strength, and high phosphoric acid retention rate (i.e., phosphoric acid is not easily lost) even under the condition of low phosphoric acid adsorption.

Description

Technical Field

[0001] This invention belongs to the field of polymer electrolyte membrane material technology, and specifically relates to a high-temperature fuel cell proton exchange membrane, its preparation method, and its application. Background Technology

[0002] Under high temperature and low humidity conditions, high-temperature proton exchange membranes (PTMs) function to transfer protons, block electrons, and prevent gas diffusion. High-performance, long-life high-temperature fuel cells require PTMs with good mechanical properties and high proton transport rates. Commercially available PTMs require phosphoric acid doping as a proton conductor. While this increases phosphoric acid adsorption and thus improves the proton conductivity of the polymer membrane, the plasticizing effect of phosphoric acid weakens the intermolecular forces between the polymer backbone, reducing the mechanical properties of the polymer membrane and consequently decreasing the durability of the high-temperature fuel cell. Furthermore, the phosphoric acid doped within the polymer membrane is prone to loss under high temperature and low humidity conditions. This loss disrupts the hydrogen bond network in the polymer structure, hindering proton transport. Simultaneously, phosphoric acid can cause catalyst deactivation in the membrane electrode assembly, affecting cell lifespan. Introducing basic groups to increase phosphoric acid doping improves proton conductivity but negatively impacts the mechanical properties and phosphoric acid retention rate of the high-temperature PTM.

[0003] In order to address the above problems to some extent, existing technologies have provided high-temperature proton exchange membranes prepared using amphoteric copolymers. For example, the high-temperature proton exchange membrane provided in "An Amphoteric Copolymer, a High-Temperature Proton Exchange Membrane, Its Preparation Method and Application" (ZL202410779044.2) has both good mechanical and electrochemical properties. However, as the battery industry places higher demands on product performance, the conductor content (doping content of phosphoric acid as a proton conductor) of the high-temperature proton exchange membrane prepared using amphoteric copolymers is still relatively high, and the proton conductor is still prone to loss, which still affects the proton conductivity and tensile strength. Therefore, it is very necessary to prepare a high-temperature fuel cell proton exchange membrane that can solve the problems of high conductor content and easy loss of proton conductors in high-temperature proton exchange membranes made of amphoteric copolymers. Summary of the Invention

[0004] To address the shortcomings of the prior art, the present invention aims to provide a high-temperature fuel cell proton exchange membrane, its preparation method, and its application. The high-temperature fuel cell proton exchange membrane prepared by this method solves the problems of high conductor content and easy loss of proton conductors in high-temperature proton exchange membranes.

[0005] To solve the above-mentioned technical problems, the present invention provides a high-temperature fuel cell proton exchange membrane. This high-temperature fuel cell proton exchange membrane is prepared by separately performing ion exchange on polymer (I) and polymer (II) in an alkaline solution, washing and drying them separately, then mixing them and performing a phosphonylation reaction in a solvent at 70℃~120℃; then casting and drying the phosphonylation reaction product to obtain a membrane, which is subsequently immersed in a heated acidic solution (preferably HCl solution) and a heated phosphoric acid solution, and then removed; wherein the mass ratio of polymer (I) to polymer (II) is 60~90:10~40. Polymer (Ⅰ) is Ar is: , , or ; Polymer (II) is .

[0006] The inventors of this invention discovered that both polymer (I) and polymer (II) undergo ion exchange reactions when immersed in an alkaline solution. After the ion exchange reaction, polymer (II) is added to polymer (I) and subjected to a phosphonylation reaction in a solvent at 70°C to 120°C to obtain a casting solution. The casting solution is then cast and dried to obtain a semi-interpenetrating network structure film. This is because:

[0007] Polymers (I) and (II) form a hydrogen bond network by protons generated through self-ionization under high temperature and low humidity conditions. A small amount of phosphoric acid is doped into the composite high-temperature proton exchange membrane, which on the one hand constructs a dense and interconnected proton transport channel, and on the other hand improves the mechanical properties of the polymer membrane. Furthermore, the tertiary amine groups of polymer (I) anchor the proton conductor with phosphoric acid through strong ion-pair interactions, while the semi-interpenetrating structure effectively traps the phosphoric acid proton conductor. This dual effect effectively mitigates the loss of proton conductors within the membrane, thus enhancing the electrochemical performance of the polymer membrane.

[0008] The proton exchange membrane of a high-temperature fuel cell exhibits good proton conductivity, high proton conductor retention, high peak power density, and high tensile strength under low phosphoric acid adsorption conditions.

[0009] Preferably, the phosphoric acid adsorption capacity of the proton exchange membrane in the high-temperature fuel cell is 89%~150%, and the tensile strength is 28MPa~45MPa.

[0010] Preferably, at 140°C, the proton conduction is 40 mS / cm. -1 ~60mS cm -1 Peak power density is 360mW / cm³ -2 ~600mWcm -2 .

[0011] Preferably, the solvent is one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, or N-methylpyrrolidone, and the solvent used in the phosphonylation reaction is one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, or N-methylpyrrolidone.

[0012] Preferably, the viscosity of polymer (I) is 0.5 dL / g to 3.5 dL / g; the number-average molecular weight of polymer (II) is 200 Da to 2000 Da; and the thickness of the composite film (I) is 10 μm to 30 μm.

[0013] This invention also provides a method for preparing a proton exchange membrane for a high-temperature fuel cell, comprising the following preparation steps: Polymer (Ⅰ) and polymer (Ⅱ) were subjected to ion exchange reactions in alkaline solutions, and then washed and dried to obtain S1 and S1, respectively. S1 and S2 are mixed, and then a solvent is added to the mixture of S1 and S2 to dissolve them. A phosphonylation reaction is carried out at 70℃~120℃ to obtain a casting solution. The casting solution is then cast and dried to obtain a composite film (Ⅰ). Composite film (II) was obtained by immersing composite film (Ⅰ) in HCl solution, followed by washing and drying. The composite membrane (II) was immersed in a phosphoric acid solution and then removed to obtain a proton exchange membrane for a high-temperature fuel cell. Polymer (Ⅰ) is Ar is: , , or ; Polymer (II) is .

[0014] Preferably, the composite film (I) is soaked in an HCl solution at a temperature of 60℃~90℃ for 5h~24h, and then vacuum dried at a temperature of 50℃~100℃ after soaking in the HCl solution; the composite film (II) is soaked in an 80wt%~90wt% phosphoric acid solution and kept at 90~110℃ for 8~16h, and then taken out and left to stand at 20℃~30℃ for 24h~48h.

[0015] Preferably, the preparation steps of the polymer (Ⅰ) are as follows: N-methyl-4-piperidinone monomer and aromatic ring-containing monomer were mixed at a molar ratio of 1.0~1.5:1 and dissolved in a solvent. Then, an organic strong acid catalyst was added and the mixture was subjected to Friedel-Crafts reaction polycondensation at 0℃~5℃ for 5h~10h to obtain a terpolymer. The terpolymer was first precipitated by a poor solvent, then washed with water and ethanol, and then dried to obtain polymer (Ⅰ). The organic strong acid catalyst includes trifluoroacetic acid and trifluoromethanesulfonic acid in a molar ratio of 1:1 to 20; the molar ratio of aromatic ring monomer to organic strong acid catalyst is 1:1 to 30; the aromatic ring monomer is at least one of biphenyl, 2,2'-dihydroxybiphenyl, p-terphenyl, m-terphenyl or o-terphenyl; the undesirable solvent is at least one of water, methanol, ethanol or n-propanol.

[0016] Preferably, the preparation steps of the polymer (II) are as follows: p-Cresol, aniline and paraformaldehyde were mixed in a molar ratio of 1:1:2 and then synthesized into a monocyclic benzoxazine monomer via the Mannich reaction at 80℃~100℃. Linear benzoxazine polymers were prepared by thermally initiated ring-opening polymerization of benzoxazine monomers at 150℃~220℃. The linear benzoxazine polymer was modified by introducing organophosphonic acid groups through phosphorylation and hydrolysis to obtain polymer (II).

[0017] This invention provides the application of a high-temperature fuel cell proton exchange membrane in the preparation of high-temperature fuel cells.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: Polymer (I) contains a rigid aromatic tertiary amine structure, and polymer (II) provides phosphonylation reaction sites. They are compounded at a mass ratio of 60-90:10-40. First, the two polymers are treated separately with an alkaline solution for ion exchange to activate nucleophilic groups and remove impurities, yielding products S1 and S2. After mixing, they undergo phosphonylation in a solvent at 70-120°C, covalently grafting phosphonic acid groups onto the polymer backbone to form intrinsic fixed proton jumping sites, while simultaneously constructing a semi-interpenetrating polymer network. After casting and drying, a film is obtained, which is then immersed in a heated acidic solution to protonate the tertiary amine into a quaternary ammonium salt form and displace residual alkali metal ions. Finally, it is immersed in a heated phosphoric acid solution, forming strong ion pairs through ion exchange, firmly anchoring the phosphoric acid molecules within the film. This technical approach fundamentally changes the traditional high-temperature membrane model that relies on large amounts of free phosphoric acid to construct proton channels. Covalent phosphonic acid groups provide a continuous hydrogen-bonded network independent of free phosphoric acid, maintaining high proton conductivity even with low phosphoric acid adsorption. The ion-pair interaction between the tertiary amine and phosphoric acid, along with the physical trapping effect of the semi-interpenetrating network, forms a dual binding mechanism, greatly suppressing proton conductor loss. Simultaneously, the low phosphoric acid content avoids excessive plasticization of the polymer matrix, and combined with the structural reinforcement effect of the semi-interpenetrating network, gives the membrane high tensile strength. Furthermore, the low phosphoric acid adsorption reduces poisoning of the electrode catalyst layer, which is beneficial for improving peak power density. Therefore, this approach fundamentally solves the problem of high phosphoric acid doping content and easy loss in traditional high-temperature proton exchange membranes, achieving a synergistic improvement in both electrochemical and mechanical properties. Attached Figure Description

[0019] Figure 1 S1 prepared in Example 1 of the present invention 1 H-NMR spectrum.

[0020] Figure 2 S1 prepared in Example 1 of the present invention 31 P-NMR spectrum.

[0021] Figure 3 S2 prepared in Example 1 of the present invention 1 H-NMR spectrum. Detailed Implementation

[0022] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0023] It should be noted that when numerical ranges are involved in this invention, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in Examples 1 to 7, preferred embodiments are described in this invention to avoid redundancy. However, this invention is not limited to these, but can be implemented in other ways within the scope of the technical solutions defined in the appended claims. All raw materials, reagents, instruments, and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0024] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] The aromatic ring monomer is at least one of biphenyl, 2,2'-dihydroxybiphenyl, p-terphenyl, m-terphenyl or o-terphenyl; the following examples preferably use p-terphenyl, o-terphenyl or m-terphenyl.

[0026] The unsuitable solvent is at least one of water, methanol, ethanol or n-propanol, with water being preferred in the following examples.

[0027] Example 1 A method for preparing a proton exchange membrane for a high-temperature fuel cell includes the following steps: (1) Preparation of polymer (II) Toluene (25 mL), p-cresol (25 mmol), aniline (25 mmol), and paraformaldehyde (50 mmol) were added to a single-necked flask and reacted by the Mannich reaction at 90 °C for 10 h. The resulting mixture was cooled to room temperature and precipitated with anhydrous ethanol. The precipitate was washed several times with anhydrous ethanol and then dried in an oven at 50 °C to obtain a white byproduct, namely the monocyclic benzoxazine monomer.

[0028] A 5% casting solution was prepared by dissolving the monocyclic benzoxazine monomer in dimethyl sulfoxide. The casting solution was then coated onto a glass plate and the film was cured by gradually increasing the temperature. A linear benzoxazine polymer was prepared by thermally initiated ring-opening polymerization at 150℃~220℃.

[0029] 1.0 g of linear benzoxazine polymer was dissolved in 30 mL of N-methylpyrrolidone and stirred at 80 °C until completely dissolved. At 0 °C, 6 mmol of POCl3 and 6 mmol of pyridine were added dropwise to the flask, and the reaction was stopped after 12 h. Then, 60 mL of deionized water was added dropwise to the flask, and the entire mixture was poured into 400 mL of deionized water. The mixture was stirred for 3 days, and the reactants were then separated from the water. The product was washed with a large amount of deionized water and ethanol, and dried in an oven at 80 °C to obtain polymer (II), which has a number-average molecular weight of 200 Da.

[0030] (2) Preparation method of polymer (Ⅰ) To a three-necked flask, 7.2 mmol of p-terphenyl, 7.92 mmol of N-methyl-4-piperidinone, and 10 mL of dichloromethane were added and stirred at 0 °C for 3 h. Then, 0.72 mL of trifluoroacetic acid and 6 mL of trifluoromethanesulfonic acid were added and stirred at 0 °C for 5 h. The mixture was then stirred at 25 °C for 24 h. The solid was collected by sedimentation in water, washed with ethanol, and dried to obtain a terpolymer. The product was stirred in 1 mol / L NaOH solution at 80 °C for 24 h, then washed with water and ethanol, and dried under vacuum at 100 °C for 24 h. The viscosity of polymer (I) was 2 dL / g.

[0031] (3) High-temperature fuel cell proton exchange membrane Polymer (II) (0.1 g) and polymer (I) (0.9 g) were weighed and immersed in 1 mol / L NaOH solution, respectively. The mixture was stirred at high temperature to obtain products S1 and S2. Products S1 and S2 were mixed and dissolved in 10 mL of dimethyl sulfoxide. The mixture was stirred at 80 °C for 12 h until completely dissolved to obtain a casting solution. The casting solution was cast onto a glass plate, and the solvent was evaporated at 70 °C to obtain a 25 μm thick M1 film (composite film (I)). The composite film (I) obtained by casting and drying the casting solution was immersed in an HCl solution at 60 °C–90 °C for 5–24 h. After washing and drying at 50 °C–100 °C, composite film (II) was obtained. Composite film (II) was placed in an 85 wt% phosphoric acid solution and immersed at 100 °C for 12 h. It was then removed and allowed to stand at 20 °C–30 °C for 24–48 h to obtain a high-temperature proton exchange membrane.

[0032] Example 2 The difference between Example 2 and Example 1 is that in step (3), polymer (II) (0.2g) and polymer (I) (0.8g) are blended to prepare a composite membrane, while the other steps are the same as in Example 1.

[0033] Example 3 The difference between Example 3 and Example 1 is that in step (3), polymer (II) (0.3g) and polymer (I) (0.7g) are blended to prepare a composite membrane, while the other steps are the same as in Example 1.

[0034] Example 4 The difference between Example 4 and Example 1 is that in step (3), polymer (II) (0.4g) and polymer (I) (0.6g) are blended to prepare a composite membrane.

[0035] Example 5 A method for preparing a proton exchange membrane for a high-temperature fuel cell includes the following steps: (1) Preparation of polymer (II) Toluene (25 mL), p-cresol (25 mmol), aniline (25 mmol), and paraformaldehyde (50 mmol) were added to a single-necked flask and reacted by the Mannich reaction at 80 °C for 10 h. The resulting mixture was cooled to room temperature and precipitated with anhydrous ethanol. The precipitate was washed several times with anhydrous ethanol and then dried in an oven at 50 °C to obtain a white byproduct, namely the monocyclic benzoxazine monomer.

[0036] A 5% casting solution was prepared by dissolving the monocyclic benzoxazine monomer in dimethyl sulfoxide. The casting solution was then coated onto a glass plate and the film was cured by gradually increasing the temperature. A linear benzoxazine polymer was prepared by thermally initiated ring-opening polymerization at 150°C.

[0037] 1.0 g of linear benzoxazine polymer was dissolved in 30 mL of N-methylpyrrolidone and stirred at 80 °C until completely dissolved. At 0 °C, 6 mmol of POCl3 and 6 mmol of pyridine were added dropwise to the flask, and the reaction was stopped after 12 h. Then, 60 mL of deionized water was added dropwise to the flask, and the entire mixture was poured into 400 mL of deionized water. The mixture was stirred for 3 days, and the reactants were then separated from the water. The product was washed with a large amount of deionized water and ethanol, and dried in an oven at 80 °C to obtain polymer (II), which has a number-average molecular weight of 200 Da.

[0038] (2) Preparation method of polymer (Ⅰ) To a three-necked flask, add m-terphenyl (7.2 mmol), N-methyl-4-piperidinone (7.2 mmol), and dichloromethane (10 mL), and stir at 0 °C for 3 h. Then add trifluoroacetic acid (5.2 mL) and trifluoromethanesulfonic acid (6 mL), and stir at 0 °C for 8 h. Then stir at 25 °C for 24 h. The solid settles in water, is washed with ethanol, and dried to obtain a terpolymer. Stir the product in 1 mol / L NaOH solution at 80 °C for 24 h, then wash with water and ethanol, and dry under vacuum at 100 °C for 24 h. The viscosity of polymer (I) is 1.5 dL / g.

[0039] (3) High-temperature fuel cell proton exchange membrane 3) Weigh out polymer (II) (0.1g) and polymer (I) (0.9g) and immerse them separately in 1 mol / L NaOH solution. Stir at high temperature to obtain products S1 and S2. Mix products S1 and S2 and dissolve them in 10 mL of dimethylacetamide. Stir at 70℃ for 12 h until completely dissolved to obtain casting solution. Cast the casting solution onto a glass plate and evaporate the solvent at 70℃ to obtain a 30 μm thick M1 film (composite film (I)). Immerse the composite film (I) obtained by casting and drying the casting solution in HCl solution at 60℃~90℃ for 5h~24h. After washing and drying at 50℃~100℃, composite film (II) is obtained. Composite film (II) is placed in 85wt% phosphoric acid solution and immersed at 100℃ for 12h. After removal, it is allowed to stand at 20℃~30℃ for 24h~48h to obtain a high-temperature proton exchange membrane.

[0040] Example 6 A method for preparing a proton exchange membrane for a high-temperature fuel cell includes the following steps: (1) Preparation of polymer (II) Toluene (25 mL), p-cresol (25 mmol), aniline (25 mmol), and paraformaldehyde (50 mmol) were added to a single-necked flask and reacted by the Mannich reaction at 100 °C for 10 h. The resulting mixture was cooled to room temperature and precipitated with anhydrous ethanol. The precipitate was washed several times with anhydrous ethanol and then dried in an oven at 50 °C to obtain a white byproduct, namely the monocyclic benzoxazine monomer.

[0041] A 5% casting solution was prepared by dissolving the monocyclic benzoxazine monomer in dimethyl sulfoxide. The casting solution was then coated onto a glass plate and the film was cured by gradually increasing the temperature. A linear benzoxazine polymer was prepared by thermally initiated ring-opening polymerization at 220°C.

[0042] 1.0 g of linear benzoxazine polymer was dissolved in 30 mL of N-methylpyrrolidone and stirred at 80 °C until completely dissolved. At 0 °C, 6 mmol of POCl3 and 6 mmol of pyridine were added dropwise to the flask, and the reaction was stopped after 12 h. Then, 60 mL of deionized water was added dropwise to the flask, and the entire mixture was poured into 400 mL of deionized water. The mixture was stirred for 3 days, and the reactants were then separated from the water. The product was washed with a large amount of deionized water and ethanol, and dried in an oven at 80 °C to obtain polymer (II), which has a number average molecular weight of 1000 Da.

[0043] (2) Preparation method of polymer (Ⅰ) To a three-necked flask, add o-terphenyl (4.8 mmol), N-methyl-4-piperidinone (7.2 mmol), and dichloromethane (10 mL), and stir at 0 °C for 3 h. Then add trifluoroacetic acid (0.26 mL) and trifluoromethanesulfonic acid (6 mL), and stir at 0 °C for 8 h. Then stir at 25 °C for 24 h. The solid is obtained by sedimentation in water, washed with ethanol, and dried to obtain a terpolymer. Stir the product in 1 mol / L NaOH solution at 80 °C for 24 h, then wash with water and ethanol, and dry under vacuum at 100 °C for 24 h. The viscosity of polymer (I) is 3.5 dL / g.

[0044] (3) High-temperature fuel cell proton exchange membrane Polymer (II) (0.1g) and polymer (I) (0.9g) were weighed and soaked separately in 1 mol / L NaOH solution. The mixture was stirred at high temperature to obtain products S1 and S2. Products S1 and S2 were mixed and dissolved in 10 mL of dimethylformamide. The mixture was stirred at 120℃ for 12 h until completely dissolved, yielding a casting solution. The casting solution was cast onto a glass plate, and the solvent was evaporated at 70℃ to obtain a 10 μm thick M1 film (composite film (I)). The composite film (I) obtained by casting and drying the casting solution was soaked in an HCl solution at 60℃~90℃ for 5 h~24 h. After washing and drying at 50℃~100℃, composite film (II) was obtained. Composite film (II) was placed in a 90wt% phosphoric acid solution and soaked at 100℃ for 12 h. It was then removed and allowed to stand at 20℃~30℃ for 24 h~48 h to obtain a high-temperature proton exchange membrane.

[0045] Example 7 A method for preparing a proton exchange membrane for a high-temperature fuel cell includes the following steps: (1) Preparation of polymer (II) Toluene (25 mL), p-cresol (25 mmol), aniline (25 mmol), and paraformaldehyde (50 mmol) were added to a single-necked flask and reacted by the Mannich reaction at 100 °C for 10 h. The resulting mixture was cooled to room temperature and precipitated with anhydrous ethanol. The precipitate was washed several times with anhydrous ethanol and then dried in an oven at 50 °C to obtain a white byproduct, namely the monocyclic benzoxazine monomer.

[0046] A 5% casting solution was prepared by dissolving the monocyclic benzoxazine monomer in dimethyl sulfoxide. The casting solution was then coated onto a glass plate and the film was cured by gradually increasing the temperature. A linear benzoxazine polymer was prepared by thermally initiated ring-opening polymerization at 220°C.

[0047] 1.0 g of linear benzoxazine polymer was dissolved in 30 mL of N-methylpyrrolidone and stirred at 80 °C until completely dissolved. At 0 °C, 6 mmol of POCl3 and 6 mmol of pyridine were added dropwise to the flask, and the reaction was stopped after 12 h. Then, 60 mL of deionized water was added dropwise to the flask, and the entire mixture was poured into 400 mL of deionized water. The mixture was stirred for 3 days, and the reactants were then separated from the water. The product was washed with a large amount of deionized water and ethanol, and dried in an oven at 80 °C to obtain polymer (II), which has a number-average molecular weight of 2000 Da.

[0048] (2) Preparation method of polymer (Ⅰ) To a three-necked flask, add o-terphenyl (7.2 mmol), N-methyl-4-piperidinone (7.2 mmol), and dichloromethane (10 mL), and stir at 0 °C for 3 h. Then add trifluoroacetic acid (1.5 mL) and trifluoromethanesulfonic acid (17.32 mL), and stir at 0 °C for 8 h. Then stir at 25 °C for 24 h. The solid settles in water, is washed with ethanol, and dried to obtain a terpolymer. Stir the product in 1 mol / L NaOH solution at 80 °C for 24 h, then wash with water and ethanol, and dry under vacuum at 100 °C for 24 h. The viscosity of polymer (I) is 3 dL / g.

[0049] (3) High-temperature fuel cell proton exchange membrane Polymer (II) (0.1 g) and polymer (I) (0.9 g) were weighed and immersed in 1 mol / L NaOH solution, respectively. The mixture was stirred at high temperature to obtain products S1 and S2. Products S1 and S2 were mixed and dissolved in 10 mL of dimethylformamide. The mixture was stirred at 120 °C for 12 h until completely dissolved, yielding a casting solution. The casting solution was cast onto a glass plate, and the solvent was evaporated at 70 °C to obtain a 10 μm thick M1 film (composite film (I)). The composite film (I) obtained by casting and drying the casting solution was immersed in an HCl solution at 60 °C–90 °C for 5–24 h. After washing and drying at 50 °C–100 °C, composite film (II) was obtained. Composite film (II) was placed in an 80 wt% phosphoric acid solution and immersed at 100 °C for 12 h. It was then removed and allowed to stand at 20 °C–30 °C for 24–48 h to obtain a high-temperature proton exchange membrane.

[0050] All of the above Examples 1 to 7 can prepare high-temperature fuel cell proton exchange membranes. The high-temperature fuel cell proton exchange membranes prepared in Examples 1 to 4 are preferred for experimental verification.

[0051] (0) Structural confirmation Figure 1 S1 prepared in Example 1 of the present invention 1 H-NMR spectrum, by Figure 1 It can be seen that polymer (Ⅰ) was successfully prepared.

[0052] Figure 2 S1 prepared in Example 1 of the present invention 31 p-NMR spectrum, through Figure 2 It can be concluded that polymer (Ⅰ) was successfully prepared.

[0053] Figure 3 S2 prepared in Example 1 of the present invention 1 H-NMR spectrum, through Figure 3 It can be concluded that polymer (II) was successfully prepared.

[0054] (ii) Performance Testing The high-temperature proton exchange membranes from Examples 1 to 4 were used to prepare membrane electrodes using a three-in-one method. The electrodes were then assembled in a battery fixture and polarization curves were tested. The results are shown in Table 1.

[0055] Table 1 shows the polarization curve test results of the high-temperature proton exchange membranes in Examples 1 to 4. Comparing Examples 1 to 4, it can be seen that as the proportion of polymer (II) increases, the phosphoric acid adsorption of the high-temperature proton exchange membrane gradually decreases, the tensile strength first increases and then decreases, the phosphoric acid retention first increases and then decreases, the proton conductivity first increases and then decreases, and the peak power density first increases and then decreases. This is because, although the polymer (II) crosslinking network helps to enhance the interaction between the copolymer and phosphoric acid, it also has a certain negative impact on the intermolecular forces of the copolymer. The phosphoric acid adsorption is affected by the content of the basic polymer. This invention, by introducing a polymer (II) crosslinking network, improves the mechanical properties, phosphoric acid retention rate, and peak power density of the high-temperature proton exchange membrane while maintaining a comparable level (Example 2) or significantly improving it (Examples 1, 3, and 4).

[0056] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A proton exchange membrane for a high-temperature fuel cell, characterized in that, The high-temperature fuel cell proton exchange membrane is prepared by performing ion exchange on polymer (I) and polymer (II) in an alkaline solution, washing and drying them separately, mixing them and performing a phosphonylation reaction in a solvent at 70℃~120℃; then casting and drying the phosphonylation reaction product to obtain a membrane, which is then sequentially immersed in a heated acidic solution and a heated phosphoric acid solution. Polymer (Ⅰ) is Ar is: , , or ; Polymer (II) is The mass ratio of polymer (Ⅰ) to polymer (Ⅱ) is 60~90:10~40.

2. The high-temperature fuel cell proton exchange membrane according to claim 1, characterized in that, The phosphoric acid adsorption capacity of the proton exchange membrane in high-temperature fuel cells is 89%~150%, and the tensile strength is 28MPa~45MPa.

3. The high-temperature fuel cell proton exchange membrane according to claim 1, characterized in that, At 140℃, proton conduction is 40 mS / cm. -1 ~60mS cm -1 Peak power density is 360 mW / cm³ -2 ~600mWcm -2 .

4. The high-temperature fuel cell proton exchange membrane according to claim 1, characterized in that, The solvent is one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide or N-methylpyrrolidone, and the solvent used in the phosphonylation reaction is one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide or N-methylpyrrolidone.

5. The method for preparing a high-temperature fuel cell proton exchange membrane according to any one of claims 1 to 4, characterized in that, The preparation steps include the following: Polymer (I) and polymer (II) were subjected to ion exchange reactions in alkaline solutions, and then washed and dried to obtain S1 and S1, respectively. S1 and S2 are mixed, and then a solvent is added to the mixture of S1 and S2 to dissolve them. A phosphonylation reaction is carried out at 70℃~120℃ to obtain a casting solution. The casting solution is cast and dried to obtain a composite film (Ⅰ), wherein the mass ratio of polymer (Ⅰ) to polymer (Ⅱ) is 60~90:10~40. Composite film (II) was obtained by immersing composite film (Ⅰ) in HCl solution, followed by washing and drying. The composite membrane (II) was immersed in a phosphoric acid solution and then removed to obtain a proton exchange membrane for a high-temperature fuel cell. Polymer (Ⅰ) is Ar is: , , or ; Polymer (II) is .

6. The method for preparing a high-temperature fuel cell proton exchange membrane according to claim 5, characterized in that, The composite film (Ⅰ) is soaked in an HCl solution at a temperature of 60℃~90℃ for 5h~24h, and then vacuum dried at a temperature of 50℃~100℃ after soaking in the HCl solution; the composite film (Ⅱ) is soaked in an 80wt%~90wt% phosphoric acid solution and kept at 90~110℃ for 8~16h, and then taken out and left to stand at 20℃~30℃ for 24h~48h.

7. The method for preparing a high-temperature fuel cell proton exchange membrane according to claim 1, characterized in that, The preparation steps of the polymer (Ⅰ) are as follows: N-methyl-4-piperidinone monomer and aromatic ring-containing monomer were mixed at a molar ratio of 1.0~1.5:1 and dissolved in a solvent. Then, an organic strong acid catalyst was added and the mixture was subjected to Friedel-Crafts reaction polycondensation at 0℃~5℃ for 5h~10h to obtain a terpolymer. The terpolymer was first precipitated by a poor solvent, then washed with water and ethanol, and then dried to obtain polymer (Ⅰ). The organic strong acid catalyst includes trifluoroacetic acid and trifluoromethanesulfonic acid in a molar ratio of 1:1 to 20; the molar ratio of aromatic ring monomer to organic strong acid catalyst is 1:1 to 30; the aromatic ring monomer is at least one of biphenyl, 2,2'-dihydroxybiphenyl, p-terphenyl, m-terphenyl or o-terphenyl; the undesirable solvent is at least one of water, methanol, ethanol or n-propanol.

8. The application of the high-temperature fuel cell proton exchange membrane according to claim 1 in the preparation of high-temperature fuel cells.

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