A cross-linked polymer containing high-density imidazole, its preparation method and application in fuel cells

Abstract

A cross-linked polymer containing high-density imidazole, its preparation method and application in fuel cells. The present invention belongs to the technical field of high-temperature proton exchange membranes for fuel cells. The purpose of the present invention is to solve the technical problem that existing high-temperature proton exchange membranes cannot take into account both high proton conductivity and high dimensional stability. The present invention uses aromatic compounds as monomers and prepares a cross-linked membrane with high-density imidazole groups through a one-step method of superacid-catalyzed Friedel-Crafts hydroxyalkylation reaction. The introduction of a cross-linking agent containing imidazole groups increases the imidazole content in the cross-linked membrane. The polymer membrane achieves a better balance between dimensional stability and phosphoric acid doping amount. At the same time, the method of the present invention simplifies the preparation process of the cross-linked membrane, which is conducive to the commercial application of the cross-linked membrane in the field of high-temperature proton exchange membranes. The phosphoric acid-doped cross-linked membrane based on the present invention can be used as a high-temperature proton exchange membrane in the field of fuel cells and exhibits excellent comprehensive performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature proton exchange membranes for fuel cells (HT-PEMFCs), and in particular relates to a cross-linked polymer containing high-density imidazole, a preparation method thereof, and application in fuel cells. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) offer advantages such as cleanliness, high efficiency, rapid startup, and long lifespan, holding great promise for applications in fuel cell vehicles, mobile power supplies, and unmanned aerial vehicles (UAVs). Compared to low-temperature PEMFCs, high-temperature PEMFCs offer advantages such as simplified hydrothermal management, high electrode reaction kinetics, and strong tolerance to carbon monoxide. Consequently, high-temperature PEMs have attracted considerable attention in recent years. Phosphoric acid (PA)-doped polybenzimidazole (PBI) membranes exhibit numerous excellent properties at high temperatures, making them a promising candidate for high-performance high-temperature proton exchange membrane (HT-PEM) materials.

[0003] The proton conductivity of phosphoric acid-doped polymer membranes is closely related to the phosphoric acid doping level (PU) of the membrane. This means that proton conductivity increases with increasing PU. However, higher PU levels can lead to significant dimensional swelling of the membrane. Furthermore, due to the plasticizing effect of PA on the membrane, the mechanical strength of the membrane decreases significantly with increasing PU, particularly at high temperatures. This can significantly impact the membrane's battery performance. Therefore, developing membrane materials that can maintain excellent dimensional stability and mechanical strength at high PU levels is a key issue in the research of phosphoric acid-doped proton exchange membranes and a prerequisite for the development of proton exchange membrane fuel cells with excellent battery performance.

[0004] Polybenzimidazole (PBI), a currently commercialized high-temperature proton exchange membrane material, still has several inherent drawbacks. First, the raw material 3,3'-diaminobenzidine used to synthesize PBI is expensive and carcinogenic. Second, PBI typically uses polyphosphoric acid or Eaton's reagent as a polymerization solvent, resulting in high polymerization temperatures, typically above 190°C, and the polymerization process requires inert gas protection. Therefore, the development of high-temperature proton exchange membrane materials that can replace PBI has become a research hotspot. Superacid-catalyzed polymerization is a type of reaction that uses superacids as catalysts to polymerize electrophilic monomers with electron-rich monomers. This reaction offers advantages such as mild reaction conditions, the absence of metal catalysts, the need for precise stoichiometric ratios, and the ability to produce high molecular weight, narrowly distributed polymers. Therefore, polymers prepared using superacid-catalyzed polymerization are ideal candidates for HT-PEMFCs. However, linear polymers prepared using superacid-catalyzed polymerization still lack the ability to achieve a good balance between phosphoric acid doping and dimensional stability.

[0005] Previous research indicates that cross-linked films can reduce dimensional swelling after acid doping, thereby improving their dimensional stability. Conventional cross-linked films typically require the preparation of a linear polymer to be cross-linked, followed by the addition of a cross-linking agent during the film-making process. This complex preparation process is also often accompanied by challenges. The introduction of the cross-linking agent reduces the relative content of imidazole groups in the film, while the cross-linked structure tightly packs the polymer backbone, reducing the film's free volume. These two factors reduce the amount of phosphoric acid doping, leading to reduced proton conductivity and battery performance. Summary of the Invention

[0006] The purpose of the present invention is to solve the technical problem that existing high-temperature proton exchange membranes (HT-PEMFCs) cannot achieve both high proton conductivity and high dimensional stability, and to provide a cross-linked polymer containing high-density imidazole, a preparation method thereof, and an application in fuel cells.

[0007] The purpose of the present invention is to achieve through the following technical solutions:

[0008] One of the purposes of the present invention is to provide a cross-linked polymer containing high-density imidazole, wherein the cross-linked polymer containing high-density imidazole has the general structural formula:

[0009]

[0010] Wherein, Ar is selected from one of Formulas 101 to 109:

[0011]

[0012] R1 is selected from imidazolyl or alkylimidazole; R2 is selected from -CH3 or -H, and n=80-1000.

[0013] It is further defined that R1 is selected from one of Formula 201 to Formula 207:

[0014]

[0015] A second object of the present invention is to provide a method for preparing a cross-linked polymer containing high-density imidazole, wherein the preparation method is carried out according to the following steps:

[0016] S1: dissolving aromatic monomers and imidazole monomers in dichloromethane, then adding a superacid catalyst, reacting for a certain time, washing to remove the acid, and vacuum drying to obtain a flexible linear polymer;

[0017] S2: The flexible linear polymer is redissolved in the above-mentioned superacid catalyst to obtain a polymer solution, and then the imidazole monomer is added again to form a film at high temperature. The film is then boiled in water and vacuum-dried to obtain a cross-linked polymer containing high-density imidazole.

[0018] It is further defined that the molar ratio of the aromatic monomer to the imidazole monomer in S1 is 1:(1-5).

[0019] It is further defined that the superacid catalyst in S1 is a mixed acid of trifluoroacetic acid and methanesulfonic acid or a mixed acid of trifluoroacetic acid and trifluoromethanesulfonic acid.

[0020] It is further defined that the volume ratio of methanesulfonic acid or trifluoromethanesulfonic acid to trifluoroacetic acid is 1:(0.2-4).

[0021] It is further defined that the ratio of the super acid catalyst to the aromatic monomer in S1 is (200-2500) mL:1 mol.

[0022] It is further defined that the ratio of dichloromethane to aromatic monomer in S1 is (40-500) mL:1 mol.

[0023] It is further defined that the aromatic monomer in S1 is selected from one of the aromatic compounds based on Formula 101 to Formula 109:

[0024]

[0025] It is further defined that the imidazole monomer in S1 is selected from one of the aldehyde imidazoles based on Formula 201 to Formula 207:

[0026]

[0027] It is further defined that the reaction in S1 lasts for 2 to 36 hours.

[0028] It is further defined that in S1, the viscous liquid obtained by the reaction is washed and deacidified by sinking it into an alkaline aqueous solution.

[0029] Furthermore, the alkaline aqueous solution is an aqueous solution of ammonia, sodium bicarbonate, sodium carbonate or sodium hydroxide.

[0030] It is further defined that the concentration of the alkaline aqueous solution is 1 to 2M.

[0031] It is further defined that the solid content of the polymer solution in S2 is 2 to 15%.

[0032] It is further defined that the molar ratio of the imidazole monomer added again in S2 to the aromatic monomer in S1 is (0.2-3):1.

[0033] It is further defined that the high temperature in S2 is 60 to 180°C.

[0034] It is further defined that the boiling temperature in S2 is 60-100° C. and the boiling time is 2-24 h.

[0035] It is further defined that the cross-linking degree of the high-density imidazole-containing cross-linked polymer obtained in S2 is 1 to 80%.

[0036] A third object of the present invention is to provide a method for preparing a cross-linked polymer containing high-density imidazole, wherein the preparation method is carried out according to the following steps:

[0037] The aromatic monomer and imidazole monomer are dissolved in dichloromethane, and then a superacid catalyst is added. The reaction is carried out for a certain time, and the superacid catalyst is added again to dilute to a certain solid content to obtain a polymer solution. Subsequently, the imidazole monomer is added again and a film is formed at a high temperature. The film is then boiled in water and vacuum dried to obtain a cross-linked polymer containing high-density imidazole.

[0038] It is further defined that the molar ratio of the aromatic monomer to the imidazole monomer added for the first time is 1:(1-5).

[0039] It is further defined that the superacid catalyst is a mixed acid of trifluoroacetic acid and methanesulfonic acid or a mixed acid of trifluoroacetic acid and trifluoromethanesulfonic acid.

[0040] It is further defined that the volume ratio of methanesulfonic acid or trifluoromethanesulfonic acid to trifluoroacetic acid is 1:(0.2-4).

[0041] It is further defined that the ratio of the super acid catalyst to the aromatic monomer added for the first time is (200-2500) mL:1 mol.

[0042] It is further defined that the ratio of dichloromethane to aromatic monomer is (40-500) mL:1 mol.

[0043] It is further defined that the aromatic monomer is selected from one of the aromatic compounds based on Formula 101 to Formula 109:

[0044]

[0045] It is further defined that the imidazole monomer is selected from one of the aldehyde imidazoles based on Formula 201 to Formula 207:

[0046]

[0047] It is further limited to react for 2 to 36 hours.

[0048] It is further defined that the certain solid content is 2 to 15%.

[0049] It is further defined that the molar ratio of the re-added imidazole monomer to the aromatic monomer is (0.2-3):1.

[0050] It is further defined that the high temperature is 60 to 180°C.

[0051] It is further defined that the boiling temperature is 60-100°C and the boiling time is 2-24 hours.

[0052] It is further defined that the cross-linking degree of the high-density imidazole-containing cross-linked polymer obtained in S2 is 1 to 80%.

[0053] A fourth object of the present invention is to provide a method for preparing a high-temperature proton exchange membrane, the preparation method being as follows:

[0054] The cross-linked polymer membrane containing high-density imidazole is immersed in a phosphoric acid solution for doping to obtain a high-temperature proton exchange membrane.

[0055] It is further defined that the phosphoric acid concentration is 20 to 90 wt %, the doping temperature is 25 to 120° C., and the doping time is 4 to 24 hours.

[0056] A fifth object of the present invention is to provide a high-temperature proton exchange membrane prepared according to the above method.

[0057] A sixth object of the present invention is to provide an application of the high-temperature proton exchange membrane prepared by the above method in a fuel cell.

[0058] Compared with the prior art, the present invention has the following significant effects:

[0059] The present invention addresses the problems existing in current high-temperature proton exchange membrane materials. Using flexible aromatic compounds as monomers, a cross-linked membrane with a high density of imidazole groups is prepared through a one-step process catalyzed by superacid Friedel-Crafts hydroxyalkylation. The specific advantages are as follows:

[0060] (1) Because the crosslinking agent itself contains imidazole groups and the crosslinking sites are on the aromatic monomer, the introduction of the crosslinker does not reduce the content of imidazole groups but rather increases it. The high density of imidazole groups enables a high phosphoric acid doping level, and the crosslinked structure limits further membrane swelling. Therefore, the crosslinked membrane can achieve a high phosphoric acid doping level while maintaining good dimensional stability, achieving a good balance between dimensional stability and phosphoric acid doping level in the polymer membrane.

[0061] (2) The present invention prepares the cross-linked membrane by a one-pot method of superacid-catalyzed Friedel-Crafts hydroxyalkylation reaction, which eliminates the step of preparing the linear polymer to be cross-linked, simplifies the preparation process of the cross-linked membrane, and is conducive to the commercial application of the cross-linked membrane in the field of high-temperature proton exchange membranes.

[0062] (3) The cross-linked film prepared by the flexible aromatic monomer of the present invention has good film-forming properties, overcoming the disadvantage that the rigid aromatic monomer cannot be used to prepare the cross-linked film. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 This is a photograph showing the solubility of the cross-linked film obtained in Example 2 in NPM;

[0064] Figure 2 This is a photograph showing the solubility of the cross-linked film obtained in Example 3 in NPM;

[0065] Figure 3 This is a photograph showing the solubility of the cross-linked film obtained in Example 4 in NPM;

[0066] Figure 4 is a graph showing the phosphoric acid retention rate of the phosphoric acid-doped membrane based on the cross-linked membrane of Examples 2-4 in Example 5;

[0067] Figure 5 is the proton conductivity of the phosphoric acid-doped membrane based on the cross-linked membrane of Examples 2-4 in Example 5;

[0068] Figure 6 This is a battery performance characterization diagram of the phosphoric acid-doped membrane based on the cross-linked membrane of Examples 2-4 in Example 5. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0070] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0071] As used in the following examples, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0072] When amount, concentration or other value or parameter are represented with the range of scope, preferred range or a series of upper preferred value and lower preferred value limit, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, and no matter whether this scope is disclosed separately.For example, when disclosing scope "1 to 5", described scope should be interpreted as including scope "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc.When numerical range is described in this article, unless otherwise stated, otherwise this scope is intended to include its end value and all integers and fractions within the scope.In this application specification and claims, range limitation can be combined and / or interchanged, and if these ranges are not otherwise stated, include all subranges contained therein.

[0073] The indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirement (i.e. the number of times they appear). Therefore, "a" or "an" should be interpreted as including one or at least one, and elements or components in the singular also include plural forms, unless the quantity clearly refers to only the singular form.

[0074] The term "one embodiment" or "embodiment" of the present invention refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it necessarily refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0075] The endpoints of the ranges and any values ​​disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0076] Example 1: The preparation method of the cross-linked polymer containing high-density imidazole is carried out according to the following steps:

[0077] S1: Weigh 0.5856g of imidazole-2-carboxaldehyde and 0.7829g of biphenyl (Formula 101) and place them in a 50mL single-necked flask. Add 6mL of dichloromethane to the flask, stir evenly, and then drop 4mL of trifluoroacetic acid and 2mL of trifluoromethanesulfonic acid into the flask. React at room temperature for 24 hours. The reaction system becomes viscous. Then sink it into a 1M sodium bicarbonate aqueous solution, wash the acid clean, and then wash the polymer with deionized water until the deionized water is neutral. Finally, place the polymer in a vacuum oven and dry it at 120°C for 24 hours to obtain a flexible linear polymer.

[0078] S2: Weigh 0.35 g of a flexible linear polymer and dissolve it in 10 mL of a mixed acid of trifluoroacetic acid and trifluoromethanesulfonic acid (v / v = 1 / 4). Then, add 0.1448 g of imidazole-2-carboxaldehyde monomer to the polymer solution and stir evenly. Pour the solution onto a clean glass plate and form a film at 100°C. The film is peeled off the glass plate. The resulting film is boiled in deionized water at 80°C for 12 h, and then dried under vacuum at 120°C for 12 h to obtain a transparent cross-linked film with a thickness of 60 μm. The cross-linked film cannot be completely dissolved in NMP.

[0079] Example 2: The preparation method of the cross-linked polymer containing high-density imidazole is carried out according to the following steps:

[0080] 0.5856 g of imidazole-2-carboxaldehyde and 0.7829 g of biphenyl (Formula 101) were weighed and placed in a 50 mL single-necked flask. 6 mL of dichloromethane was added to the flask. After stirring, 4 mL of a mixed acid of trifluoroacetic acid and 2 mL of trifluoromethanesulfonic acid was added dropwise to the flask. The mixture was reacted at room temperature for 24 h. The reaction system was viscous. 12 mL of a mixed acid of trifluoroacetic acid and trifluoromethanesulfonic acid (v / v=1 / 4) was added again to dilute the mixture to a solid content of 8%. Subsequently, 0.4878 g of imidazole-2-carboxaldehyde monomer was stirred again. The solution was poured onto a clean glass plate and formed into a film at 100° C. The film was peeled off from the glass plate. The resulting film was boiled in deionized water at 80° C. for 12 h and then dried under vacuum at 120° C. for 12 h to obtain a transparent cross-linked film having a thickness of 71 μm. The cross-linked film could not be completely dissolved in NMP (see Figure 1 ).

[0081] Example 3: The preparation method of the cross-linked polymer containing high-density imidazole is carried out according to the following steps:

[0082] 0.5856 g of imidazole-2-carboxaldehyde and 0.7829 g of biphenyl (Formula 101) were weighed and placed in a 50 mL single-necked flask. 6 mL of dichloromethane was added to the flask. After stirring, 4 mL of a mixed acid of trifluoroacetic acid and 2 mL of trifluoromethanesulfonic acid was added dropwise to the flask. The mixture was reacted at room temperature for 24 h. The reaction system was viscous. 12 mL of a mixed acid of trifluoroacetic acid and trifluoromethanesulfonic acid (v / v=1 / 4) was added again to dilute the mixture to a solid content of 8%. Subsequently, 0.7318 g of imidazole-2-carboxaldehyde monomer was stirred again. The solution was poured onto a clean glass plate and formed into a film at 100° C. The film was peeled off from the glass plate. The resulting film was boiled in deionized water at 80° C. for 12 h and then dried under vacuum at 120° C. for 12 h to obtain a transparent cross-linked film having a thickness of 75 μm. The cross-linked film could not be completely dissolved in NMP (see Figure 2 ).

[0083] Example 4: The preparation method of the cross-linked polymer containing high-density imidazole is carried out according to the following steps:

[0084] 0.5856 g of imidazole-2-carboxaldehyde and 0.7829 g of biphenyl (Formula 101) were weighed and placed in a 50 mL single-necked flask. 6 mL of dichloromethane was added to the flask. After stirring, 4 mL of a mixed acid of trifluoroacetic acid and 2 mL of trifluoromethanesulfonic acid was added dropwise to the flask. The mixture was reacted at room temperature for 24 h. The reaction system was viscous. 12 mL of a mixed acid of trifluoroacetic acid and trifluoromethanesulfonic acid (v / v=1 / 4) was added again to dilute the mixture to a solid content of 8%. Subsequently, 0.9757 g of imidazole-2-carboxaldehyde monomer was stirred again. The solution was poured onto a clean glass plate and formed into a film at 100° C. The film was peeled off from the glass plate. The resulting film was boiled in deionized water at 80° C. for 12 h and then dried under vacuum at 120° C. for 12 h to obtain a transparent cross-linked film having a thickness of 70 μm. The cross-linked film could not be completely dissolved in NMP (see Figure 3 ).

[0085] Comparative Example:

[0086] 0.5856 g of imidazole-2-carboxaldehyde and 1.6429 g of (Formula 1010) monomer were weighed and placed in a 50 mL single-necked flask. 6 mL of dichloromethane was added to the flask and stirred. After stirring, 4 mL of a mixed acid of trifluoroacetic acid and 2 mL of trifluoromethanesulfonic acid was added dropwise to the flask. The mixture was reacted at room temperature for 24 h. The reaction system became viscous. 12 mL of a mixed acid of trifluoroacetic acid and trifluoromethanesulfonic acid (v / v = 1 / 4) was added to dilute the mixture to a solid content of 12%. Subsequently, 0.7318 g of imidazole-2-carboxaldehyde monomer was stirred again. The solution was poured onto a clean glass plate and placed at 100° C. After the solvent dried, the polymer was found to be fragmented and could not form a continuous film, making it unsuitable for performance testing. The structure of the monomer represented by Formula 1010 is as follows:

[0087]

[0088] Example 5, Preparation method of high temperature proton exchange membrane The preparation method is as follows:

[0089] The cross-linked membranes obtained in Examples 1 to 4 were doped with phosphoric acid at a concentration of 65 wt %, a doping time of 12 hours, and a doping temperature of 40°C. After doping, the membranes were removed, and excess phosphoric acid on the membrane surface was wiped off with filter paper. The membranes were then dried in a vacuum oven at 100°C for 12 hours to remove moisture, thereby obtaining phosphoric acid-doped cross-linked membranes, i.e., high-temperature proton exchange membranes.

[0090] The performance of the cross-linked membrane before and after doping with phosphoric acid is tested as follows (commercial o-PBI is used as a comparison):

[0091] (1) Determination of the crosslinking degree (C) of the crosslinked film before doping

[0092] The degree of crosslinking was determined by measuring the insoluble gel content of the crosslinked film. The calculation formula is as follows:

[0093] C(%)=W u / W

[0094] Among them, W u and W represent the insoluble gel mass and cross-linked membrane mass of the cross-linked membrane in organic solvent, respectively. The results are shown in Table 1.

[0095] (2) Measurement of phosphoric acid doping (PU)

[0096] The PU was calculated by weighing the mass of the membrane before and after immersion in phosphoric acid according to the following formula:

[0097] PU(%)=[(W d -W u ) / W u ]*100%

[0098] Among them, W u and W d They represent the mass of undoped and doped films respectively. The results are shown in Table 1.

[0099] (3) Measurement of area swelling rate and volume swelling rate (S% and V%)

[0100] By measuring the area and volume of the membrane before and after immersion in phosphoric acid, S% and V% were calculated according to the following formula:

[0101] S(%)=[(S d -S u ) / S u ]*100%

[0102] V(%)=[(V d -V u ) / V u ]*100%

[0103] Among them, S u and S d Represent the area of ​​undoped and doped films, V u and V d They represent the volumes of undoped and doped films, respectively. The results are shown in Table 1.

[0104] (4) Phosphoric acid retention rate of phosphoric acid-doped membrane

[0105] The phosphoric acid-doped membranes obtained in Examples 2 to 4 were weighed and placed in a constant temperature and humidity chamber at 80°C and 40% relative humidity. The membranes were taken out every 12 hours, the surface phosphoric acid was wiped dry, and the membranes were weighed again. The ratio of the membrane mass to the initial membrane mass was the phosphoric acid retention rate. The results are shown in FIG. Figure 4 shown.

[0106] (5) Proton conductivity of phosphoric acid-doped membranes

[0107] The phosphoric acid-doped films obtained in Examples 2 to 4 were cut into 1 cm × 4 cm strips for conductivity testing. The tests were conducted without humidification at a temperature of 120 to 200°C. The results are shown in Figure 2. Figure 5 shown.

[0108] (6) Battery performance of phosphoric acid-doped membrane

[0109] The phosphoric acid-doped membranes obtained in Examples 2 to 4 were assembled into membrane electrodes for battery performance testing. First, platinum-carbon catalyst was evenly sprayed on carbon paper to form a gas diffusion electrode, with a platinum loading of 1 mg / cm 2 Then, the phosphoric acid-doped membrane was sandwiched between two gas diffusion electrodes to form a sandwich structure, and an effective test area of ​​9 cm was prepared. 2 The battery performance test was carried out under non-humidified conditions and atmospheric pressure, with a test temperature of 160°C. The results are as follows Figure 6 shown.

[0110] Table 1: Phosphoric acid doping content and dimensional stability of the film

[0111] Sample film Phosphoric acid doping amount (%) Area swelling rate (%) Volume swelling rate (%) Crosslinking degree (%) Example 1 309 41 78 18 Example 2 301 39 75 20 Example 3 288 33 67 33 Example 4 275 29 60 41 o-PBI 210 35 68 -

[0112] The above results show that the phosphoric acid doping content is high and the doped membrane has good dimensional stability. The proton conductivity of the doped membrane at 180°C and non-humidified conditions is 100-210 mS / cm, indicating that the polymer membrane has good proton transport capacity. The peak power density of the H2 / O2 fuel cell at 160°C and non-humidified conditions is 400-1000 mW / cm 2 .

[0113] The foregoing are merely preferred embodiments of the present invention. These embodiments are all different implementations based on the overall concept of the present invention. The scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A cross-linked polymer containing high-density imidazole, characterized in that: Its general structural formula is: ； Wherein, Ar is selected from one of Formula 101 to Formula 109: ； R1 is selected from one of Formula 201 to Formula 207: ； R2 is selected from -CH3 or -H, n=80~1000.

2. The method for preparing a cross-linked polymer containing high-density imidazole according to claim 1, characterized in that: Follow these steps: S1: dissolving aromatic monomers and imidazole monomers in dichloromethane, then adding a superacid catalyst, reacting for a certain time, washing to remove the acid, and vacuum drying to obtain a flexible linear polymer; S2: The flexible linear polymer is redissolved in the above-mentioned superacid catalyst to obtain a polymer solution, and then the imidazole monomer is added again to form a film at high temperature. The film is then boiled in water and vacuum-dried to obtain a cross-linked polymer containing high-density imidazole.

3. The method according to claim 2, characterized in that The molar ratio of the aromatic monomer to the imidazole monomer in S1 is 1:(1-5), the superacid catalyst in S1 is a mixed acid of trifluoroacetic acid and methanesulfonic acid or a mixed acid of trifluoroacetic acid and trifluoromethanesulfonic acid, the ratio of the superacid catalyst to dichloromethane and the aromatic monomer in S1 is (200-2500) mL:(40-500) mL:1 mol, the reaction in S1 is carried out for 2-36 hours, the viscous liquid obtained by the reaction is washed and deacidified in S1 by sinking it into an alkaline aqueous solution, the solid content of the polymer solution in S2 is 2-15%, the molar ratio of the imidazole monomer added again in S2 to the aromatic monomer in S1 is (0.2-3):1, the high temperature in S2 is 60-180°C, and the cross-linking degree of the obtained high-density imidazole-containing cross-linked polymer is 1-80%.

4. The method for preparing a cross-linked polymer containing high-density imidazole according to claim 1, wherein: Follow these steps: The aromatic monomer and imidazole monomer are dissolved in dichloromethane, and then a superacid catalyst is added. The reaction is carried out for a certain time, and the superacid catalyst is added again to dilute to a certain solid content to obtain a polymer solution. Subsequently, the imidazole monomer is added again and a film is formed at a high temperature. The film is then boiled in water and vacuum dried to obtain a cross-linked polymer containing high-density imidazole.

5. The method according to claim 4, characterized in that The molar ratio of the aromatic monomer to the first added imidazole monomer is 1:(1-5), the superacid catalyst is a mixed acid of trifluoroacetic acid and methanesulfonic acid or a mixed acid of trifluoroacetic acid and trifluoromethanesulfonic acid, the ratio of the first added superacid catalyst to dichloromethane and the aromatic monomer is (200-2500) mL:(40-500) mL:1 mol, the reaction is carried out for 2-36 hours, the solid content is 2-15%, the molar ratio of the second added imidazole monomer to the aromatic monomer is (0.2-3):1, the high temperature is 60-180°C, and the cross-linking degree of the obtained high-density imidazole-containing cross-linked polymer is 1-80%.

6. A method for preparing a high-temperature proton exchange membrane, characterized in that: The preparation method is as follows: The cross-linked polymer membrane containing high-density imidazole according to claim 1 is immersed in a phosphoric acid solution for doping to obtain a high-temperature proton exchange membrane.

7. The method according to claim 6, characterized in that The phosphoric acid concentration is 20~90wt%, the doping temperature is 25~120℃, and the doping time is 4~24h.

8. A high-temperature proton exchange membrane prepared by the method according to claim 6 or 7.

9. Use of the high-temperature proton exchange membrane prepared by the method according to claim 6 or 7 in a fuel cell.

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