Ionomer and preparation method therefor, membrane electrode, and fuel cell

Abstract

The present application provides an ionomer and a preparation method therefor, a membrane electrode, and a fuel cell. The structure of the ionomer comprises anions, and the polarizability of the anions is greater than or equal to 3.5x10-24 cm3. In embodiments of the present application, the polarizability of the anions represents the level of difficulty of an electron cloud of the anions in producing an induced dipole under the action of an external electric field. The higher the polarizability, the more easily the electron cloud of the anions generates stronger induced dipole interaction with polar alcohol molecules, thereby enhancing the solvation effect. In the embodiments of the present application, the polarizability of the anions is greater than or equal to 3.5×10-24 cm3. The anions have relatively high polarizability, and can form relatively strong induced dipole interaction with alcohol solvent molecules. Such interaction helps break the cohesion between ionomer molecules, making it easier for the ionomer molecules to disperse into a solvent, thereby improving the solubility of the ionomer in an alcohol solvent.

Description

An ionomer and its preparation method, membrane electrode and fuel cell

[0001] This application claims priority to Chinese Patent Application No. 202510339039.4, filed with the Chinese Patent Office on March 20, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, specifically to an ionomer and its preparation method, a membrane electrode, and a fuel cell. Background Technology

[0003] Catalyst slurry is a key material in fuel cell manufacturing, primarily used in the preparation of the membrane electrode assembly (MEA). The catalyst slurry is a mixture of catalyst, ionomer, and alcohol solvents, which, after coating and drying, forms the catalytic layer of the electrode. Ionomer is a polymer containing ionic groups; in the MEA components of fuel cells and electrolyzers, it mainly acts as a binder in the ion exchange membrane and catalytic layer, and also plays a synergistic role in ion exchange. As an important component of the catalyst slurry, the ionomer material needs to be fully soluble or dispersed in the alcohol solvent to ensure the formation of a stable catalyst slurry. Technical issues

[0004] However, the Ionomer materials in the current anion exchange system of fuel cells generally suffer from solubility problems. Ionomers are either only slightly soluble or completely soluble in alcohol solvents, which cannot guarantee the stability of the catalyst slurry and ultimately affects the manufacturability of fuel cells. Technical solutions

[0005] This application provides an ionomer for use in fuel cells. The ionomer has an anionic structure, and the polarizability of the anionic anion is greater than or equal to 3.5 × 10⁻⁶. -24 cm 3 .

[0006] This application also provides a method for preparing an ionomer, comprising the following steps:

[0007] Provide a first monomer and a second monomer, wherein the first monomer is a monomer containing a nitrogen-containing heterocycle, and the second monomer includes a monomer containing a linear structure and / or a monomer containing a branched structure;

[0008] The first monomer and the second monomer are mixed to cause the first monomer and the second monomer to undergo a polymerization reaction to generate a polymer;

[0009] The polymer was subjected to quaternization and ion exchange treatment in sequence to obtain an ionomer;

[0010] The ionomers include anions with a polarizability greater than or equal to 3.5 × 10⁻⁶. -24 cm 3 .

[0011] This application also provides a catalyst slurry, comprising: a catalyst, an alcohol solvent, and the above-described ionomer or an ionomer prepared by the above-described method.

[0012] This application also provides a membrane electrode comprising the above-described ionomer or an ionomer prepared by the above-described method.

[0013] This application also provides a fuel cell comprising the above-described ionomer or an ionomer prepared by the above-described method. Beneficial effects

[0014] The ionomer of this application comprises anions with a polarizability greater than or equal to 3.5 × 10⁻⁶. -24 cm 3 In the embodiments of this application, the polarizability of the anion represents the ease with which the electron cloud of the anion forms an induced dipole under the action of an applied electric field; the higher the polarizability, the more easily the electron cloud of the anion generates a stronger induced dipole interaction with polar alcohol molecules, thereby enhancing the solvation effect. In the embodiments of this application, the polarizability of the anion is greater than or equal to 3.5 × 10⁻⁶. -24 cm 3 Anions have high polarizability and can form strong induced dipole interactions with alcohol solvent molecules. This interaction helps to break the cohesive forces between ionomer molecules, making it easier for ionomer molecules to disperse into the solvent, thereby improving the solubility of ionomers in alcohol solvents. Embodiments of the present invention

[0015] In the description of this application, unless otherwise expressly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0016] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, where the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, where the first feature is at a lower horizontal level than the second feature.

[0017] In the description of this embodiment, the terms "upper," "lower," "left," "right," "front," and "rear," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used for distinction in description and have no special meaning.

[0018] In related technologies, the solubility problem of Ionomer materials in anion exchange systems is common. Ionomers are only slightly soluble or cannot be dissolved in alcohol solvents, which needs further improvement.

[0019] To address the aforementioned problems, this application provides an ionomer for use in fuel cells. The ionomer's structure includes anions, and the polarizability of the anions is greater than or equal to 3.5 × 10⁻⁶. -24 cm 3 In the embodiments of this application, the polarizability of the anion represents the ease with which the electron cloud of the anion forms an induced dipole under the action of an applied electric field; the higher the polarizability, the more easily the electron cloud of the anion generates a stronger induced dipole interaction with polar alcohol molecules, thereby enhancing the solvation effect. In the embodiments of this application, the polarizability of the anion is greater than or equal to 3.5 × 10⁻⁶. -24 cm 3 Anions have high polarizability and can form strong induced dipole interactions with alcohol solvent molecules. This interaction helps to break the cohesive forces between ionomer molecules, making it easier for ionomer molecules to disperse into the solvent, thereby improving the solubility of ionomers in alcohol solvents.

[0020] In one embodiment, the polarizability of the anion is 3.5 × 10⁻⁶. -24 cm 3 -11×10 -24 cm 3 Optionally, the polarizability of the anion can be 3.5 × 10⁻⁶. -24 cm 34.5×10 -24 cm 3 5.5×10 -24 cm 3 6.5×10 -24 cm 3 7.0×10 -24 cm 3 8.5×10 -24 cm 3 9.0×10 -24 cm 3 10.5×10 -24 cm 3 11×10 -24 cm 3 The range between any one or any two of the following is not limited here. In this embodiment, if the polarizability of the anion is too low, it is easy to reduce the induced dipole interaction between the anion and the polar alcohol molecule, and the effect of the anion in improving the solubility of the ionomer in alcohol solvents is not ideal; if the polarizability of the anion is too high, it is easy to cause the anion to be unstable in the electric field or chemical environment, and the anion is more likely to decompose or undergo side reactions, reducing the chemical stability of the ionomer.

[0021] In one embodiment, the anion includes at least one selected from trifluoroacetate ions, citrate ions, and thiocyanate ions. In this embodiment, the polarizability of the trifluoroacetate ion is 4.0 × 10⁻⁶. -24 cm 3 –6.0×10 -24 cm 3 Trifluoroacetate ions possess strong polarizability, and their electron cloud more readily engages with polar alcohol molecules to form stronger induced dipole interactions, thereby enhancing solvation. Furthermore, the trifluoromethyl group in the trifluoroacetate ion is a strongly polar group; its strong electron-withdrawing effect delocalizes the negative charge of the trifluoroacetate ion, enhancing its interaction with polar solvents such as alcohols. The hydrogen bonding between the trifluoroacetate ion and alcohols promotes solvent penetration and ion cluster formation, thus facilitating the dissolution of the ionomer. Additionally, the relatively large size and dispersed charge distribution of the trifluoroacetate ion weaken the electrostatic attraction between the anion and the ionomer backbone, reducing ion pair formation, decreasing the crystallization tendency of the ionomer in alcohols, and improving its stability in alcohols. The polarizability of the citrate ion is 7.0 × 10⁻⁶. -24 cm 3 –8.5×10 -24 cm 3Citrate ions possess strong polarizability, and their electron cloud more readily engages with polar alcohol molecules to form stronger induced dipole interactions, thus enhancing solvation. Furthermore, citrate ions have multiple carboxyl groups, which can form strong hydrogen bonds with alcohol solvents. This hydrogen bond network enhances the "cage effect" of the solvent, facilitating the dispersion and dissolution of the ionomer in the solvent and stabilizing the dissolved ionomer. Additionally, the relatively large size of the citrate ion disrupts the regularity of the ionomer molecular chains and interferes with their close packing, reducing the crystallinity of the ionomer. This allows the molecular chains to be more easily penetrated and dissolved by solvent molecules, improving the solubility and stability of the ionomer in alcohol solvents. The polarizability of thiocyanate ions is 9.0 × 10⁻⁶. -24 cm 3 –10.5×10 -24 cm 3 Thiocyanate ions have strong polarizability, and their electron cloud is more likely to generate stronger induced dipole interactions with polar alcohol molecules, thereby enhancing solvation. In addition, thiocyanate ions are a strongly polar group with a high dipole moment, which can increase the polarity of the ionomer, thereby enhancing the interaction between the ionomer and alcohol solvents. Furthermore, the nitrogen and sulfur atoms in thiocyanate ions can form hydrogen bonds with hydroxyl groups in alcohol solvents, which can significantly improve the solubility of the ionomer in alcohol solvents.

[0022] In this embodiment, trifluoroacetate ions not only improve the solubility of the ionomer in alcohol solvents but also enhance the electrochemical performance of the fuel cell. Specifically, the weak ion-pair effect of trifluoroacetate ions reduces the energy barrier for ion migration, thereby increasing the conductivity of the ionomer. Furthermore, when the catalyst is mixed with the ionomer to prepare a membrane electrode assembly, the hydrophobic group -CF3 of the trifluoroacetate ion reduces the coverage of water molecules on the catalyst surface, exposing more active sites. This allows the fuel cell to generate more current within the same electrode area, thus increasing the power output of the fuel cell. Additionally, the strong electron-withdrawing effect of trifluoroacetate ions reduces the electron density of the ionomer backbone, inhibiting oxidative degradation caused by free radical attacks such as OH, and improving the chemical stability of the ionomer. Moreover, trifluoroacetate ions can interact with -COO through -CF3. - The synergistic effect of these components achieves a hydrophobic-hydrophilic balance, thereby optimizing the swelling ratio of the ionomer and reducing the generation of microcracks in the membrane electrode. Therefore, when ionomers containing trifluoroacetate ions are applied to fuel cells, the electrochemical performance of the fuel cells can be improved.

[0023] In this embodiment, citrate ions not only improve the solubility of the ionomer in alcohol solvents but also enhance the electrochemical performance of the fuel cell. Specifically, the hydrophilicity of citrate ions allows them to interact with water molecules, forming a hydrogen bond network. This network facilitates the formation of continuous hydrophilic channels within the ionomer, providing a low-resistance path for proton transport, reducing the tortuosity of proton transport, and improving proton conductivity and the electrochemical performance of the fuel cell.

[0024] In this embodiment, thiocyanate ions not only improve the solubility of the ionomer in alcohol solvents but also enhance the electrochemical performance of the fuel cell. Specifically, the ion mobility of thiocyanate ions is 7.9 × 10⁻⁶. -4 cm 2 At / V·s, thiocyanate ions exhibit high ion mobility, which can reduce the resistance of ionomers, improve proton transport efficiency, and allow current to pass through the ionomers more easily, thus enhancing the conductivity of fuel cells. Furthermore, thiocyanate ions possess lone pairs of electrons, enabling them to form dynamic coordination bonds with metal ions in the catalyst. These thiocyanate ions can rapidly exchange coordination between different metal ions, promoting the dynamic recombination of ion clusters in the ionomers. This results in more flexible and varied ion cluster structures, facilitating ion diffusion and transport within the ionomers and increasing ion mobility. The dynamic cross-linking effect of thiocyanate ions can also enhance the elastic modulus of the ionomer network, mitigating mechanical fatigue caused by swelling. Furthermore, as a component of the catalyst layer, the ionomer, through the dynamic coordination of thiocyanate ions, can enhance the interfacial compatibility between the electrolyte and the catalyst layer, allowing ions to transport more smoothly between them. Additionally, the strong coordination ability of thiocyanate ions can inhibit the dissolution of metal ions from the catalyst, while simultaneously adsorbing onto the surface of the catalyst's metal atoms. This adsorption optimizes the catalyst's ability to adsorb oxygen molecules, making it easier for oxygen molecules to undergo reduction reactions on the catalyst surface, lowering the activation energy barrier and activation overpotential of the oxygen reduction reaction. This allows the fuel cell to generate a larger current at the same output voltage, improving the fuel cell's energy conversion efficiency. Therefore, thiocyanate ions, through their high ion mobility, dynamic coordination, and strong coordination ability, enhance the electrochemical performance of fuel cells.

[0025] In one embodiment, the ionomer structure further includes a nitrogen-containing heterocyclic cation, with the anion attached to the nitrogen-containing heterocyclic cation. In this embodiment, the nitrogen-containing heterocyclic cation typically exhibits high chemical stability and can remain stable in acidic or alkaline environments. The attachment of the anion to the relatively stable nitrogen-containing heterocyclic cation reduces anion degradation, further ensuring the chemical stability of the ionomer.

[0026] In one embodiment, the ionomer has a structure as shown in Formula 1:

[0027] Where A represents a nitrogen-containing heterocyclic cation, Ar1 represents a linear structural unit, M- represents an anion, and X is the molar percentage of the linear structural unit in the ionomer.

[0028] In one embodiment, the ionomer has a structure as shown in Formula 2:

[0029] Wherein, A represents a nitrogen-containing heterocyclic cation, Ar1 represents a linear structural unit, Ar2 represents a branched structural unit with at least three active sites, M- represents an anion, X is the molar percentage of the linear structural unit in the ionomer, and Y is the molar percentage of the branched structural unit in the ionomer.

[0030] In one embodiment, the linear structural unit Ar1 in Formula 1 and / or Formula 2 includes at least one of a biphenyl group, a p-terphenyl group, a meta-terphenyl group, and a tetraphenyl group.

[0031] In one embodiment, the branched structural unit Ar2 in Formula 2 includes at least one of the following: 1,3,5-triphenylphenyl group, triphenylmethane group, 9,10-benzophenanthrene group, tetraphenylmethane group, triphenylene group, 9,9'-diphenylfluorene group, 9,9'-spirodifluorene group, 9,9'-bifluorene group, 9,9'-bicarbazole group, 4,4-bis(9-carbazole)biphenyl group, 2,2'-bi-9,9'-spirobis[9H-fluorene] group, and triphenylamine group.

[0032] In one embodiment, in Formula 1, 0 < X ​​≤ 100%; optionally, X can be any one or any two of 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc.

[0033] In one embodiment, in Equation 2, 0 < Y ≤ 100%, and X + Y ≤ 100%. Optionally, Y can be any one or any two of 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc.

[0034] In one embodiment, the structure of Formula 1 is one or more of the following:

[0035] In one embodiment, the structure of Formula 2 is one or more of the following:

[0036] This application also provides a method for preparing an ionomer, comprising the following steps:

[0037] S1. Provide a first monomer and a second monomer, wherein the first monomer is a monomer containing a nitrogen-containing heterocycle, and the second monomer includes a monomer containing a linear structure and / or a monomer containing a branched structure;

[0038] S2. Mix the first monomer and the second monomer to cause the first monomer and the second monomer to undergo a polymerization reaction to generate a polymer;

[0039] S3. The polymer is subjected to quaternization and ion exchange treatment in sequence to obtain an ionomer;

[0040] The ionomers include anions with a polarizability greater than or equal to 3.5 × 10⁻⁶. -24 cm 3 In the embodiments of this application, the polarizability of the anion represents the ease with which the electron cloud of the anion forms an induced dipole under the action of an applied electric field; the higher the polarizability, the more easily the electron cloud of the anion generates a stronger induced dipole interaction with polar alcohol molecules, thereby enhancing the solvation effect. In the embodiments of this application, the polarizability of the anion is greater than or equal to 3.5 × 10⁻⁶. -24 cm 3 Anions have high polarizability and can form strong induced dipole interactions with alcohol solvent molecules. This interaction helps to break the cohesive forces between ionomer molecules, making it easier for ionomer molecules to disperse into the solvent, thereby improving the solubility of ionomers in alcohol solvents.

[0041] In one embodiment, the first monomer is selected from piperidinone monomers or quinine cycloketone monomers, the structure of the piperidinone monomer is shown in Formula 3, and the structure of the quinine cycloketone monomer is shown in Formula 4:

[0042] R1 and R2 are each independently selected from one of methyl, ethyl, propyl, butyl, pentyl, and cyclopropyl; R3 is selected from one of hydrogen atom, alkyl, alkenyl, alkynyl, and aromatic ring.

[0043] In one embodiment, the piperidone monomer comprises one or more of the following structures:

[0044] In one embodiment, the quinine cycloketone monomer comprises one or more of the following structures.

[0045] In one embodiment, the monomer containing a linear structure includes one or more of biphenyl, para-terphenyl, meta-terphenyl, and tetraphenyl.

[0046] In one embodiment, the monomer containing a branched structure includes one or more of the following: 1,3,5-triphenylbenzene, triphenylmethane, 9,10-benzophenanthrene, tetraphenylmethane, triphenylene, 9,9'-diphenylfluorene, 9,9'-spirobifluorene, 9,9'-bifluorene, 9,9'-bicarbazole, 4,4-bis(9-carbazole)biphenyl, 2,2'-bi-9,9'-spirobis[9H-fluorene], 9-(9H-fluorene-9-yl)anthracene, and triphenylamine.

[0047] In one embodiment, step S2 specifically includes:

[0048] S21. Add the first monomer and the second monomer to solvent A to obtain the first mixture;

[0049] S22. Add an acidic catalyst to the mixture at a temperature not exceeding 0°C to obtain a reaction solution;

[0050] S23. The reaction solution is subjected to polymerization reaction at a temperature of 0℃~30℃ to obtain the first mixture;

[0051] S24. Filter, wash and dry the mixture to obtain the polymer.

[0052] In this embodiment, the acid catalyst can lower the activation energy of the polymerization reaction, thereby accelerating the polymerization process between monomers. Furthermore, controlling the polymerization temperature between 0°C and 30°C can, on the one hand, reduce the decomposition or deactivation of the acid catalyst at high temperatures; on the other hand, it allows for precise control of the reaction progress, reducing the risk of runaway reactions caused by excessively rapid reactions.

[0053] In one embodiment, the acid catalyst includes one or more of methanesulfonic acid, pentafluoropropionic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and heptafluorobutyric acid.

[0054] In one embodiment, solvent A includes one or more of dichloromethane, trichloromethane, chloroform, and tetrahydrofuran.

[0055] In one embodiment, step S3 specifically includes:

[0056] S31. Add the polymer and quaternizing agent to solvent B to obtain a second mixture;

[0057] S32. The second mixture is subjected to a quaternization reaction at a temperature of 30℃~100℃ to obtain a second mixture. The mixture is then filtered, washed, and dried to obtain the quaternized polymer.

[0058] S33. The quaternized polymer is subjected to an ion exchange reaction with an ion exchange reagent at a temperature of 20℃~100℃, and then filtered, washed and dried to obtain the ionomer.

[0059] In this embodiment, the temperature of the quaternization reaction can be any one or any two of 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C, and is not limited herein. The temperature of the ion exchange reaction can be any one or any two of 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C, and is not limited herein.

[0060] In one embodiment, the quaternizing agent includes one or more of the following: methyl trifluoroacetate, methyl p-toluenesulfonate, iodomethane, bromopropane, iodoethane, iodopropane, iodobutane, iodopentane, iodohexane, bromoethane, bromobutane, bromopentane, bromohexane, bromocyclohexane, bromocyclopentane, methyl methanesulfonate, ethyl methanesulfonate, propyl methanesulfonate, butyl methanesulfonate, propyl ethanesulfonate, ethyl ethanesulfonate, but-3-yn-1-yl methanesulfonate, allyl sulfonate, methyl benzenesulfonate, methyl nitrobenzenesulfonate, methyl trifluoromethanesulfonate, ethyl trifluoromethanesulfonate, ethyl toluenesulfonate, cyclobutyl toluene-4-sulfonate, butyl toluenesulfonate, neopentyl benzenesulfonate, tetrahydro-2H-pyran-4-yl methanesulfonate, and cyclohexyl p-toluenesulfonate.

[0061] In one embodiment, solvent B includes one or more of dimethyl sulfoxide, tetrahydrofuran, N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and acetonitrile.

[0062] In one embodiment, the ion exchange reagent includes one or more of potassium trifluoroacetate, sodium trifluoroacetate, potassium citrate, sodium citrate, potassium thiocyanate, and sodium thiocyanate.

[0063] This application also provides a catalyst slurry, comprising: a catalyst, an alcohol solvent, and the aforementioned ionomer or an ionomer prepared by the aforementioned method. In this embodiment, the ionomer has an anionic structure, and the polarizability of the anion is greater than or equal to 3.5 × 10⁻⁶. -24 cm 3 Anions have high polarizability and can form strong induced dipole interactions with alcohol solvent molecules. This interaction helps to break the cohesive forces between ionomer molecules, making it easier for ionomer molecules to disperse into the solvent, thereby improving the solubility of ionomers in alcohol solvents and thus improving the stability of catalyst slurry.

[0064] In this embodiment, the type of catalyst is not limited, and the catalyst may include at least one of Pt / C, Pt and Pt-M / C, wherein M is selected from one or two of Co, Mo, W, Ru and Pd.

[0065] In this embodiment, the type of alcohol solvent is not limited, and the alcohol solvent may include ethanol, propanol, isopropanol, or a mixture of ethanol and dimethyl sulfoxide.

[0066] This application also provides a membrane electrode comprising the above-described ionomer or an ionomer prepared by the above-described method.

[0067] This application also provides a fuel cell comprising the above-described ionomer or an ionomer prepared by the above-described method.

[0068] The above solution will be further described below with reference to specific embodiments. The preferred embodiments of this application are detailed below:

[0069] Example 1

[0070] (1) Add 0.135 mol of p-terphenyl and 0.36 mol of N-methyl-4-piperidinone to 100 ml of dichloromethane and mix well to obtain the first mixture;

[0071] (2) Add 22.8 ml of trifluoroacetic acid and 240 ml of trifluoromethanesulfonic acid dropwise to the first mixture at 0℃. After the addition is complete, carry out an oligomerization reaction at 5℃ for 1.5 h, and then carry out a high-polymerization reaction at 15℃ for 3 h. After the polymerization reaction is completed, the reaction product is discharged into pure water through an extruder, filtered, washed with pure water, and dried to obtain the polymer.

[0072] (3) Add 0.1 mol of the polymer obtained in step (2), 0.12 mol of the acid-binding agent triethylamine and 0.15 mol of the quaternizing agent bromopropane to 200 ml of dimethyl sulfoxide, mix well to obtain a second mixture, react the second mixture at 80 °C for 15 h, after the reaction is completed, precipitate the reaction product with ethyl acetate, filter, wash with ethyl acetate, dry to obtain the quaternized polymer.

[0073] (4) Mix 0.1 mol of the quaternized polymer obtained in step (3) with 1 liter of 1 mol / L potassium trifluoroacetate aqueous solution to allow the quaternized polymer to undergo an ion exchange reaction with potassium trifluoroacetate. After the reaction is complete, wash with pure water and dry to obtain an ionomer. The ionomer includes the following structure:

[0074] Example 2

[0075] The difference between Example 2 and Example 1 is as follows:

[0076] In step (4), potassium trifluoroacetate is replaced with potassium citrate, and the rest is the same as in Example 1;

[0077] The ionomer obtained in Example 2 has the following structure:

[0078] Example 3

[0079] The difference between Example 3 and Example 1 is as follows:

[0080] In step (4), potassium trifluoroacetate is replaced with potassium thiocyanate, and the rest is the same as in Example 1;

[0081] The ionomer obtained in Example 3 has the following structure:

[0082] Example 4

[0083] The difference between Example 4 and Example 1 is as follows:

[0084] In step (1), N-methyl-4-piperidinone is replaced with 3-quinone, and the rest is the same as in Example 1;

[0085] The ionomer obtained in Example 4 has the following structure:

[0086] Example 5

[0087] The difference between Example 5 and Example 1 is:

[0088] Step (1) is as follows: 0.135 mol of p-terphenyl, 0.015 mol of triphenylmethane and 0.36 mol of N-methyl-4-piperidinone are added to 100 ml of dichloromethane and mixed evenly to obtain the first mixture.

[0089] The rest is the same as in Example 1;

[0090] The ionomer obtained in Example 5 has the following structure:

[0091] Example 6

[0092] The difference between Example 6 and Example 5 is as follows:

[0093] In step (4), potassium trifluoroacetate is replaced with potassium thiocyanate, and the rest is the same as in Example 5;

[0094] The ionomer obtained in Example 6 has the following structure:

[0095] Comparative Example 1

[0096] The difference between Comparative Example 1 and Example 1 is as follows:

[0097] Step (4) was not performed;

[0098] The corresponding change in step (3) is as follows: 0.1 mol of the polymer obtained in step (2), 0.12 mol of the acid-binding agent triethylamine and 0.15 mol of the quaternizing agent bromopropane are added to 200 mL of dimethyl sulfoxide and mixed evenly to obtain a second mixture. The second mixture is reacted at 80 °C for 15 h. After the reaction is completed, the reaction product is precipitated with ethyl acetate as a precipitant, filtered, washed with ethyl acetate, and dried to obtain the ionomer.

[0099] The rest is the same as in Example 1.

[0100] Comparative Example 2

[0101] The difference between Comparative Example 2 and Example 1 is as follows:

[0102] In step (4), potassium trifluoroacetate is replaced with potassium bicarbonate, wherein the polarizability of bicarbonate ions is approximately 3.3 × 10⁻⁶. -24 cm 3 The rest is the same as in Example 1.

[0103] Comparative Example 3

[0104] The difference between Comparative Example 3 and Example 1 is as follows:

[0105] In step (4), potassium trifluoroacetate is replaced with sodium carbonate, wherein the polarizability of carbonate ions is approximately 3.0 × 10⁻⁶. -24 cm 3 The rest is the same as in Example 1.

[0106] Comparative Example 4

[0107] The difference between Comparative Example 4 and Example 1 is as follows:

[0108] In step (4), potassium trifluoroacetate is replaced with sodium tetrafluoroborate, wherein the polarizability of the tetrafluoroborate ion is approximately 2.5 × 10⁻⁶. -24 cm 3 The rest is the same as in Example 1.

[0109] Test methods

[0110] (I) Ionomer solubility and stability test

[0111] At 50°C, the ionomers obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were dissolved in a solvent containing ethanol and dimethyl sulfoxide to obtain a mixture. The volume ratio of ethanol to dimethyl sulfoxide was 1:1, and the mass ratio of ionomer to solvent was 1:5. The solubility and stability of the mixture within 24 hours were observed at room temperature. The test results are shown in Table 1 below.

[0112] Table 1

[0113] (II) Catalyst Slurry Stability Test

[0114] Catalyst slurries were prepared by blending the ionomers obtained in Examples 1 to 6 and Comparative Examples 1 to 4 with a platinum catalyst and ethanol. The mass ratio of ionomer, platinum catalyst, and ethanol was 0.5:1:2. The stability of the catalyst slurry was observed at room temperature for 24 hours. The test results are shown in Table 2 below.

[0115] Table 2

[0116] (III) Conductivity test of ionomer solution

[0117] Test steps

[0118] (1) Dissolve the ionomers obtained from Examples 1 to 6 and Comparative Examples 1 to 4 in water to obtain a 20 wt% mixture;

[0119] (2) Keep the mixture at a constant temperature to the test temperature (e.g., 25°C);

[0120] (3) The electrode was calibrated using a KCl standard solution with known conductivity (0.1 mol / L, conductivity 1.288 S / m at 25 °C);

[0121] (4) Immerse the four-electrode probe vertically into the mixture to ensure that the electrodes are completely covered and no air bubbles adhere to it;

[0122] (5) Record the resistance value after the reading of the ion conductivity test device stabilizes (repeat the measurement 3 times and take the average value);

[0123] (6) Calculate the conductivity using the formula σ=L / R·A, where R is the solution resistance (Ω), L is the electrode spacing (cm), and A is the electrode area (cm²). 2 ), where σ is the conductivity (S / cm), and the test results are shown in Table 3 below.

[0124] (iv) Polarization performance test

[0125] The polarization properties of the ionomer were tested in the nickel ferrite anode-platinum carbon cathode catalytic system at 70℃@2M KOH, and the test results are shown in Table 3 below.

[0126] Table 3

[0127] According to the test results in Tables 1 and 2, the ionomers provided in the examples exhibit good solubility and stability in alcohol solvents, and the catalyst slurry containing the ionomers from the examples of this application also shows good stability. The polarizability of the anions in the examples of this application is greater than or equal to 3.5 × 10⁻⁶. -24 cm3 Anions have high polarizability and can form strong induced dipole interactions with alcohol solvent molecules. This interaction helps to break the cohesive forces between ionomer molecules, making it easier for ionomer molecules to disperse into the solvent, thereby improving the solubility of ionomers in alcohol solvents. Applying the ionomers of the embodiments of this application to catalyst slurries can improve the stability of the catalyst slurry.

[0128] According to the test results in Table 3, the ionomer provided in the examples has relatively low resistance and relatively high conductivity. When the ionomer provided in the examples is applied to a fuel cell, the fuel cell achieves a conductivity of 0.5 A / cm. 2 Current density and 1A / cm 2 The fuel cell exhibits relatively low polarization voltage at various current densities, indicating good polarization performance. In this embodiment, the anion polarizability is greater than or equal to 3.5 × 10⁻⁶. -24 cm 3 It can effectively improve the electrical conductivity of ionomers and enhance the electrochemical performance of fuel cells.

[0129] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An ionomer for use in a fuel cell, said ionomer comprising an anion having a polarizability greater than or equal to 3.5 × 10⁻⁶. -24 cm 3 .

2. The ionomer according to claim 1, wherein, The polarizability of the anion is 3.5 × 10⁻⁶. -24 cm 3 -11×10 -24 cm 3 .

3. The ionomer according to claim 1 or 2, wherein, The anion includes at least one of trifluoroacetate ion, citrate ion, and thiocyanate ion.

4. The ionomer according to any one of claims 1-3, wherein, The structure of the ionomer also includes a nitrogen-containing heterocyclic cation, and the anion is connected to the nitrogen-containing heterocyclic cation.

5. The ionomer according to claim 4, wherein, The ionomer has a structure as shown in Formula 1 or Formula 2: In Formula 1, A represents the nitrogen-containing heterocyclic cation, Ar1 represents the linear structural unit, M- represents the anion, and X is the molar percentage of the linear structural unit in the ionomer. In Formula 2, A represents the nitrogen-containing heterocyclic cation, Ar1 represents a linear structural unit, Ar2 represents a branched structural unit with at least three active sites, M- represents the anion, X is the molar percentage of the linear structural unit in the ionomer, and Y is the molar percentage of the branched structural unit in the ionomer.

6. The ionomer according to claim 5, wherein, The linear structural unit Ar1 includes at least one of the following: a biphenyl group, a para-terphenyl group, a meta-terphenyl group, and a tetraphenyl group; and / or The branched structural unit Ar2 includes at least one of the following: 1,3,5-triphenylphenyl group, triphenylmethane group, 9,10-benzophenanthrene group, tetraphenylmethane group, triphenylene group, 9,9'-diphenylfluorene group, 9,9'-spirodifluorene group, 9,9'-bifluorene group, 9,9'-bicarbazole group, 4,4-bis(9-carbazole)biphenyl group, 2,2'-bi-9,9'-spirobis[9H-fluorene] group, and triphenylamine group; and / or In Equation 1, 0 < X ​​≤ 100%; and / or In Equation 2, 0 < Y ≤ 100%, and X + Y ≤ 100%.

7. The ionomer according to claim 5 or 6, wherein, The structure of Formula 1 is one or more of the following:

8. The ionomer according to any one of claims 5-7, wherein, The structure of Formula 2 is one or more of the following:

9. A method for preparing an ionomer, comprising the following steps: A first monomer and a second monomer are provided, wherein the first monomer is a monomer containing a nitrogen-containing heterocycle, and the second monomer includes a monomer containing a linear structure and / or a monomer containing a branched structure; The first monomer and the second monomer are mixed to cause the first monomer and the second monomer to undergo a polymerization reaction to generate a polymer; The polymer was subjected to quaternization and ion exchange treatments in sequence to obtain the ionomer. The ionomer comprises an anion, and the polarizability of the anion is greater than or equal to 3.5 × 10⁻⁶. -24 cm 3 .

10. The preparation method according to claim 9, wherein, The first monomer is selected from piperidone monomers or quinine cyclic ketone monomers, wherein the structure of the piperidone monomer is shown in Formula 3 and the structure of the quinine cyclic ketone monomer is shown in Formula 4. R1 and R2 are each independently selected from one of methyl, ethyl, propyl, butyl, pentyl, and cyclopropyl; R3 is selected from one of hydrogen atom, alkyl, alkenyl, alkynyl, and aromatic ring.

11. The preparation method according to claim 9 or 10, wherein, The monomers containing linear structures include one or more of biphenyl, para-terphenyl, meta-terphenyl, and tetraphenyl.

12. The preparation method according to any one of claims 9-11, wherein, The branched monomers include one or more of the following: 1,3,5-triphenylbenzene, triphenylmethane, 9,10-benzophenanthrene, tetraphenylmethane, triphenylene, 9,9'-diphenylfluorene, 9,9'-spirodifluorene, 9,9'-bifluorene, 9,9'-bicarbazole, 4,4-bis(9-carbazole)biphenyl, 2,2'-bi-9,9'-spirobis[9H-fluorene], 9-(9H-fluorene-9-yl)anthracene, and triphenylamine.

13. The preparation method according to claim 10, wherein, The piperidone monomer comprises one or more of the following structures: and / or The quinine cyclic ketone monomer includes one or more of the following structures:

14. The preparation method according to any one of claims 9 to 13, wherein, The step of mixing the first monomer and the second monomer to cause the first monomer and the second monomer to undergo a polymerization reaction to generate a polymer specifically includes: The first monomer and the second monomer are added to solvent A to obtain a first mixture; An acid catalyst is added to the mixture at a temperature not exceeding 0°C to obtain a reaction solution; The reaction solution was subjected to a polymerization reaction at a temperature of 0℃ to 30℃ to obtain a first mixture; The mixture is filtered, washed, and dried to obtain the polymer.

15. The preparation method according to claim 14, wherein, Solvent A includes one or more of dichloromethane, trichloromethane, chloroform, and tetrahydrofuran; and / or The acid catalyst includes one or more of methanesulfonic acid, pentafluoropropionic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and heptafluorobutyric acid.

16. The preparation method according to any one of claims 9 to 15, wherein, The step of sequentially subjecting the polymer to quaternization and ion exchange treatments to obtain the ionomer specifically includes: The polymer and the quaternizing agent are added to solvent B to obtain a second mixture; The second mixture was subjected to a quaternization reaction at a temperature of 30℃ to 100℃ to obtain a second mixture, which was then filtered, washed, and dried to obtain a quaternized polymer. The quaternized polymer was subjected to an ion exchange reaction with an ion exchange reagent at a temperature of 20°C to 100°C. The mixture was then filtered, washed, and dried to obtain the ionomer.

17. The preparation method according to claim 16, wherein, The quaternizing agent comprises one or more of the following: methyl trifluoroacetate, methyl p-toluenesulfonate, iodomethane, bromopropane, iodoethane, iodopropane, iodobutane, iodopentane, iodohexane, bromoethane, bromobutane, bromopentane, bromohexane, bromocyclohexane, bromocyclopentane, methyl methanesulfonate, ethyl methanesulfonate, propyl methanesulfonate, butyl methanesulfonate, propyl ethanesulfonate, ethyl ethanesulfonate, but-3-yn-1-yl methanesulfonate, allyl sulfonate, methyl benzenesulfonate, methyl nitrobenzenesulfonate, methyl trifluoromethanesulfonate, ethyl trifluoromethanesulfonate, ethyl toluenesulfonate, cyclobutyl toluene-4-sulfonate, butyl toluenesulfonate, neopentyl benzenesulfonate, tetrahydro-2H-pyran-4-yl methanesulfonate, and cyclohexyl p-toluenesulfonate; and / or Solvent B comprises one or more of dimethyl sulfoxide, tetrahydrofuran, N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and acetonitrile; and / or The ion exchange reagent includes one or more of potassium trifluoroacetate, sodium trifluoroacetate, potassium citrate, sodium citrate, potassium thiocyanate, and sodium thiocyanate.

18. A catalyst slurry, comprising: Catalyst, alcohol solvent and ionomer according to any one of claims 1 to 8 or ionomer prepared by the method according to any one of claims 9 to 17.

19. A membrane electrode comprising the ionomer according to any one of claims 1 to 8 or the ionomer prepared by the method according to any one of claims 9 to 17.

20. A fuel cell comprising an ionomer as described in any one of claims 1 to 8 or an ionomer shell prepared by the method of any one of claims 9 to 17.