Ionomer and preparation method thereof, membrane electrode and fuel cell

Abstract

The invention provides an ionomer and a preparation method thereof, 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 3.5 * 10 <-24 > cm < 3 >. In the embodiment of the invention, the polarizability of the anion represents the difficulty degree of induced dipole of the electron cloud of the anion under the action of an external electric field; the higher the polarizability is, the higher the electron clouds of the anions are, the stronger induced dipole interaction with the polar alcohol molecules is achieved, and therefore the solvation effect is enhanced. According to the embodiment of the invention, the polarizability of the anion is greater than or equal to 3.5 * 10 <-24 > cm < 3 >, the anion has high polarizability and can form strong induced dipole interaction with alcohol solvent molecules, and the interaction force is beneficial to breaking cohesion among ionomer molecules, so that the ionomer molecules can be more easily dispersed into the solvent, and the ionomer molecules can be more easily dispersed into the solvent. Therefore, the solubility of the ionomer in the alcohol solvent is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an ionomer and a preparation method thereof, a membrane electrode and a fuel cell. Background Art

[0002] Catalyst slurry is a key material in fuel cell manufacturing, primarily used to prepare the membrane electrode of fuel cells. The catalyst slurry is a mixture of components such as catalysts, ionomers, and alcohol solvents. After coating and drying, it forms the catalytic layer of the electrode. Ionomer is a polymer containing ionic groups. In the membrane electrode components of fuel cells and electrolyzers, it primarily serves 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 when mixed with it to ensure the formation of a stable catalyst slurry.

[0003] However, the ionomer materials used in the anion exchange system of current fuel cells generally have solubility problems. Ionomers dissolve in alcohol solvents in small amounts or not at all, making it impossible to ensure the stability of the catalyst slurry, which ultimately affects the manufacturability of the fuel cell. Summary of the Invention

[0004] The embodiments of the present invention provide an ionomer and a preparation method thereof, a membrane electrode, and a fuel cell, which can improve the technical problem that the ionomer is slightly soluble or not soluble in alcohol solvents.

[0005] In a first aspect, an embodiment of the present invention provides an ionomer for use in a fuel cell, wherein the structure of the ionomer includes anions, and the polarizability of the anions is greater than or equal to 3.5×10 -24 cm 3 .

[0006] In one embodiment, the polarizability of the anion is 3.5×10 -24 cm 3 -11×10 -24 cm 3 .

[0007] In one embodiment, the anion comprises at least one of trifluoroacetate ion, citrate ion, and thiocyanate ion; and / or

[0008] The structure of the ionomer further includes a nitrogen-containing heterocyclic cation, and the anion is connected to the nitrogen-containing heterocyclic cation.

[0009] In one embodiment, the ionomer has a structure as shown in Formula 1 or Formula 2:

[0010]

[0011] Wherein, in the formula 1, A represents the nitrogen-containing heterocyclic cation, Ar1 represents a linear structural unit, M- represents the anion, and X is the molar ratio of the linear structural unit in the ionomer;

[0012]

[0013] Wherein, in the formula 2, A represents the nitrogen-containing heterocyclic cation, Ar1 represents a linear structural unit, Ar2 represents a branched structural unit having at least three active sites, M- represents the anion, X is the molar ratio of the linear structural unit in the ionomer, and Y is the molar ratio of the branched structural unit in the ionomer.

[0014] In one embodiment, the linear structural unit Ar1 includes at least one of a biphenyl group, a p-terphenyl group, a m-terphenyl group, and a quaternary group; and / or

[0015] The branched structural unit Ar2 includes at least one of a 1,3,5-triphenylphenyl group, a triphenylmethane group, a 9,10-triphenylene group, a tetraphenylmethane group, a triptycene group, a 9,9'-diphenylfluorene group, a 9,9'-spirobifluorene group, a 9,9'-bifluorene group, a 9,9'-bicarbazole group, a 4,4-di(9-carbazole)biphenyl group, a 2,2'-bi-9,9'-spirobi[9H-fluorene] group, and a triphenylamine group; and / or

[0016] In Formula 1, 0<X≤100%; and / or

[0017] In Formula 2, 0<Y≤100%, and X+Y≤100%.

[0018] In one embodiment, the structure of Formula 1 is one or more of the following:

[0019]

[0020]

[0021] The structure of Formula 2 is one or more of the following:

[0022]

[0023]

[0024] In a second aspect, an embodiment of the present invention provides a method for preparing an ionomer, comprising the following steps:

[0025] Providing 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;

[0026] mixing the first monomer and the second monomer so as to polymerize the first monomer and the second monomer to generate a polymer;

[0027] The polymer is sequentially subjected to quaternization treatment and ion exchange treatment to obtain the ionomer;

[0028] The structure of the ionomer includes anions, and the polarizability of the anions is greater than or equal to 3.5×10 - 24 cm 3 .

[0029] In one embodiment, the first monomer is selected from a piperidone monomer or a quinuclidine monomer. The structure of the piperidone monomer is shown in Formula 3, and the structure of the quinuclidine monomer is shown in Formula 4:

[0030]

[0031] wherein R1 and R2 are each independently selected from one of methyl, ethyl, propyl, butyl, pentyl, and cyclopropyl; R3 is selected from one of hydrogen, alkyl, alkenyl, alkynyl, and aromatic ring; and / or

[0032] The monomer containing a linear structure includes one or more of biphenyl, p-terphenyl, m-terphenyl, and quaterphenyl; and / or

[0033] The monomer containing a branched structure includes one or more of 1,3,5-triphenylbenzene, triphenylmethane, 9,10-triphenylene, tetraphenylmethane, triptycene, 9,9'-diphenylfluorene, 9,9'-spirobifluorene, 9,9'-bifluorene, 9,9'-bicarbazole, 4,4-di(9-carbazole)biphenyl, 2,2'-bi-9,9'-spirobi[9H-fluorene], 9-(9H-fluoren-9-yl)anthracene, and triphenylamine.

[0034] In one embodiment, the piperidone monomer comprises one or more of the following structures:

[0035]

[0036] and / or

[0037] The quinuclidine monomer includes one or more of the following structures:

[0038]

[0039] In one embodiment, the step of mixing the first monomer and the second monomer so as to polymerize the first monomer and the second monomer to generate a polymer specifically includes:

[0040] adding the first monomer and the second monomer into solvent A to obtain a first mixed solution;

[0041] adding an acid catalyst to the mixed solution at a temperature not greater than 0° C. to obtain a reaction solution;

[0042] The reaction solution is subjected to a polymerization reaction at a temperature of 0° C. to 30° C. to obtain a first mixture;

[0043] The mixture is filtered, washed, and dried to obtain the polymer.

[0044] In one embodiment, the step of sequentially subjecting the polymer to quaternization treatment and ion exchange treatment to obtain the ionomer specifically includes:

[0045] adding the polymer and the quaternizing agent into solvent B to obtain a second mixed solution;

[0046] quaternizing the second mixed solution at a temperature of 30° C. to 100° C. to obtain a second mixture, filtering, washing, and drying to obtain a quaternized polymer;

[0047] The quaternized polymer is subjected to an ion exchange reaction with an ion exchange reagent at a temperature of 20° C. to 100° C., and the reaction is filtered, washed, and dried to obtain the ionomer.

[0048] In one embodiment, the solvent A comprises one or more of dichloromethane, chloroform, chloroform, and tetrahydrofuran; and / or

[0049] The acid catalyst includes one or more of methanesulfonic acid, pentafluoropropionic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and heptafluorobutyric acid; and / or

[0050] The quaternizing agent comprises one or more of methyl trifluoroacetate, methyl p-toluenesulfonate, iodomethane, propyl bromide, ethyl iodide, propyl iodide, butyl iodide, pentane iodide, hexane iodide, ethyl bromide, butyl bromide, pentane bromide, hexane bromide, cyclohexane bromide, cyclopentane bromide, methyl methanesulfonate, ethyl methanesulfonate, propyl methanesulfonate, butyl methanesulfonate, propyl ethanesulfonate, ethyl ethanesulfonate, but-3-yn-1-yl methanesulfonate, allyl allylsulfonate, methyl benzenesulfonate, methyl nitrobenzenesulfonate, methyl trifluoromethanesulfonate, ethyl trifluoromethanesulfonate, ethyl toluenesulfonate, cyclobutyl toluene-4-sulfonate, butyl toluenesulfonate, neopentylbenzenesulfonate, tetrahydro-2H-pyran-4-yl methanesulfonate, and cyclohexyl p-toluenesulfonate; and / or

[0051] The solvent B comprises one or more of dimethyl sulfoxide, tetrahydrofuran, N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and acetonitrile; and / or

[0052] The ion exchange reagent includes one or more of potassium trifluoroacetate, sodium trifluoroacetate, potassium citrate, sodium citrate, potassium thiocyanate, and sodium thiocyanate.

[0053] In a third aspect, an embodiment of the present invention provides a catalyst slurry comprising: a catalyst, an alcohol solvent, and the ionomer as described above or the ionomer prepared by the method as described above.

[0054] In a fourth aspect, an embodiment of the present invention provides a membrane electrode, comprising the ionomer as described above or the ionomer prepared by the method as described above.

[0055] In a fifth aspect, an embodiment of the present invention provides a fuel cell, comprising the ionomer as described above or the ionomer prepared by the method as described above.

[0056] Beneficial effects of the embodiments of the present invention:

[0057] In an embodiment of the present invention, the structure of the ionomer includes anions, and the polarizability of the anions is greater than or equal to 3.5×10 -24 cm 3 In the embodiments of the present application, the polarizability of the anion indicates the difficulty of the anion's electron cloud to generate an induced dipole under the action of an external electric field; the higher the polarizability, the easier it is for the anion's electron cloud to generate a stronger induced dipole interaction with polar alcohol molecules, thereby enhancing the solvation effect. The polarizability of the anion in the embodiments of the present application is greater than or equal to 3.5×10 -24 cm 3 The anion has a high polarizability and can form a strong induced dipole interaction with the alcohol solvent molecules. This interaction force helps to break the cohesive force between the ionomer molecules, making the ionomer molecules easier to disperse into the solvent, thereby improving the solubility of the ionomer in alcohol solvents. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0059] In the related art, ionomer materials of anion exchange systems generally have solubility problems. Ionomers are only slightly soluble or not soluble at all in alcohol solvents, which needs further improvement.

[0060] To solve the above problems, the present invention provides an ionomer for use in a fuel cell. The ionomer structure includes anions, and the polarizability of the anions is greater than or equal to 3.5×10 -24 cm 3 In the embodiments of the present application, the polarizability of the anion indicates the difficulty of the anion's electron cloud to generate an induced dipole under the action of an external electric field; the higher the polarizability, the easier it is for the anion's electron cloud to generate a stronger induced dipole interaction with polar alcohol molecules, thereby enhancing the solvation effect. The polarizability of the anion in the embodiments of the present application is greater than or equal to 3.5×10 -24 cm 3 The anion has a high polarizability and can form a strong induced dipole interaction with the alcohol solvent molecules. This interaction force helps to break the cohesive force between the ionomer molecules, making the ionomer molecules easier to disperse into the solvent, thereby improving the solubility of the ionomer in alcohol solvents.

[0061] In one embodiment, the polarizability of the anion is 3.5×10 -24 cm 3 -11×10 -24 cm 3 Alternatively, the polarizability of the anion can be 3.5×10 -24 cm 3 , 4.5×10 -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 3In this embodiment, if the polarizability of the anion is too low, the induced dipole interaction between the anion and the polar alcohol molecule is easily reduced, and the effect of the anion in improving the solubility of the ionomer in the alcohol solvent is not ideal; if the polarizability of the anion is too high, the anion is easily unstable in the electric field or chemical environment, and the anion is more likely to decompose or undergo side reactions, thereby reducing the chemical stability of the ionomer.

[0062] In one embodiment, the anion includes at least one of trifluoroacetate ion, citrate ion, and thiocyanate ion. In this embodiment, the polarizability of trifluoroacetate ion is 4.0×10 -24 cm 3 –6.0×10 -24 cm 3 The trifluoroacetate ion has a strong polarizability, and its electron cloud is more likely to produce stronger induced dipole interactions with polar alcohol molecules, thereby enhancing solvation. In addition, the trifluoroacetate ion contains a trifluoromethyl group, which is a highly polar group. The strong electron-withdrawing effect of the trifluoromethyl group delocalizes the negative charge of the trifluoroacetate ion, enhancing the interaction between the trifluoroacetate ion and polar solvents such as alcohol solvents. The hydrogen bonding between the trifluoroacetate ion and alcohol solvents can promote solvent penetration and the formation of ion clusters, thereby promoting the dissolution of the ionomer. In addition, the trifluoroacetate ion is large in size and has a dispersed charge distribution, which can weaken the electrostatic attraction between the anion and the ionomer backbone, reduce ion pair formation, reduce the crystallization tendency of the ionomer in alcohol solvents, and improve the stability of the ionomer in alcohol solvents. The polarizability of the citrate ion is 7.0×10 -24 cm 3 –8.5×10 -24 cm 3 The citrate ion has a strong polarizability, and the electron cloud of the citrate ion is more likely to produce stronger induced dipole interactions with polar alcohol molecules, thereby enhancing the solvation effect. In addition, the citrate ion has multiple carboxyl groups, which can form strong hydrogen bonds with alcohol solvents. This hydrogen bond network can enhance the solvent's "cage effect", help the ionomer to disperse and dissolve in the solvent, and stabilize the dissolved ionomer. In addition, the citrate group is large in size, which can destroy the regularity of the ionomer molecular chain and interfere with the close stacking of the molecular chain, reducing the crystallinity of the ionomer, making the molecular chain more easily penetrated and dissolved by solvent molecules, and improving the solubility and stability of the ionomer in alcohol solvents. The polarizability of the thiocyanate ion is 9.0×10 -24 cm 3 –10.5×10 -24 cm 3The thiocyanate ion has a strong polarizability, and the electron cloud of the thiocyanate ion is more likely to produce a stronger induced dipole interaction with polar alcohol molecules, thereby enhancing the solvation effect; in addition, the thiocyanate ion is a strong polar group with a high dipole moment, which can increase the polarity of the ionomer, thereby enhancing the interaction between the ionomer and the alcohol solvent. In addition, the nitrogen and sulfur atoms in the thiocyanate ion can form hydrogen bonds with the hydroxyl groups in the alcohol solvent, which can significantly improve the solubility of the ionomer in the alcohol solvent.

[0063] In this embodiment, trifluoroacetate ions can not only improve the solubility of ionomers in alcohol solvents, but also improve the electrochemical performance of fuel cells. Specifically, the weak ion pair effect of trifluoroacetate ions can reduce the energy barrier of ion migration and improve the conductivity of ionomers. In addition, when the catalyst is mixed with the ionomer to prepare a membrane electrode, the hydrophobic group -CF of trifluoroacetate can reduce the coverage of water molecules on the catalyst surface, exposing more active sites on the catalyst. Under the same electrode area, the fuel cell can generate more current, thereby improving the power output of the fuel cell. In addition, the strong electron-withdrawing effect of trifluoroacetate ions can reduce the electron density of the ionomer backbone, inhibit the oxidative degradation caused by free radical attacks such as OH, and improve the chemical stability of the ionomer. In addition, trifluoroacetate ions can achieve a hydrophobic-hydrophilic balance through the synergistic effect of -CF and -COO-, thereby optimizing the swelling rate 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 cell can be improved.

[0064] In this embodiment, the citrate ions not only increase the solubility of the ionomer in alcohol solvents but also enhance the electrochemical performance of the fuel cell. Specifically, the hydrophilicity of the citrate ions enables them to interact with water molecules, forming a hydrogen bond network. This hydrogen bond network helps form 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.

[0065] In this embodiment, the thiocyanate ion can not only improve the solubility of the ionomer in the alcohol solvent, but also improve the electrochemical performance of the fuel cell. Specifically, the ion mobility of the thiocyanate ion is 7.9×10 -4 cm 2 / V·s, thiocyanate ions have a high ion mobility, which can reduce the resistance of the ionomer and improve the proton transfer efficiency. The current can pass through the ionomer more easily, thereby improving the conductivity of the fuel cell. In addition, thiocyanate ions have lone pairs of electrons and can form dynamic coordination bonds with the metal ions of the catalyst. Thiocyanate ions can quickly exchange coordination between different metal ions, promote the dynamic reorganization of the ion clusters of the ionomer, make the structure of the ion clusters more flexible and changeable, facilitate the diffusion and transport of ions in the ionomer, and improve the ion mobility. The dynamic cross-linking effect of thiocyanate ions can also enhance the elastic modulus of the ionomer network and alleviate the mechanical fatigue of the ionomer caused by swelling. Furthermore, as a component of the catalyst layer, the dynamic coordination of thiocyanate ions can enhance the interfacial compatibility between the electrolyte and the catalyst layer in the battery, allowing ions to transfer more smoothly between the electrolyte and the catalyst layer. Furthermore, the strong coordination ability of thiocyanate ions can inhibit the dissolution of metal ions from the catalyst, while allowing them to adsorb on the surface of the metal atoms of the catalyst. This adsorption of thiocyanate ions can optimize the catalyst's adsorption capacity for oxygen molecules, making oxygen molecules more susceptible to reduction reactions on the catalyst surface, reducing the activation energy barrier and activation overpotential of the oxygen reduction reaction. This allows the fuel cell to generate a higher current at the same output voltage, improving the fuel cell's energy conversion efficiency. Therefore, thiocyanate ions improve the electrochemical performance of fuel cells through their higher ion mobility, dynamic coordination, and strong coordination ability.

[0066] In one embodiment, the ionomer structure further includes a nitrogen-containing heterocyclic cation, and the anion is linked to the nitrogen-containing heterocyclic cation. In this embodiment, the nitrogen-containing heterocyclic cation generally has high chemical stability and can remain stable in acidic or alkaline environments. The anion linked to the relatively stable nitrogen-containing heterocyclic cation can reduce the degradation of the anion, further ensuring the chemical stability of the ionomer.

[0067] In one embodiment, the ionomer has a structure as shown in Formula 1:

[0068]

[0069] Wherein, A represents a nitrogen-containing heterocyclic cation, Ar1 represents a linear structural unit, M- represents an anion, and X is the molar ratio of the linear structural unit in the ionomer.

[0070] In one embodiment, the ionomer has a structure as shown in Formula 2:

[0071]

[0072] Wherein, A represents the nitrogen-containing heterocyclic cation, Ar1 represents a linear structural unit, Ar2 represents a branched structural unit having at least three active sites, M- represents the anion, X is the molar ratio of the linear structural unit in the ionomer, and Y is the molar ratio of the branched structural unit in the ionomer.

[0073] 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 m-terphenyl group, and a quaterphenyl group.

[0074] In one embodiment, the branched structural unit Ar2 in Formula 2 includes at least one of a 1,3,5-triphenylphenyl group, a triphenylmethane group, a 9,10-triphenylene group, a tetraphenylmethane group, a triptycene group, a 9,9'-diphenylfluorene group, a 9,9'-spirobifluorene group, a 9,9'-bifluorene group, a 9,9'-bicarbazole group, a 4,4-di(9-carbazole)biphenyl group, a 2,2'-bi-9,9'-spirobi[9H-fluorene] group, and a triphenylamine group.

[0075] In one embodiment, in Formula 1, 0<X≤100%; optionally, X can be any one of 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc., or a range between any two of them.

[0076] In one embodiment, in Formula 2, 0<Y≤100%, and X+Y≤100%. Optionally, Y can be any one of 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc., or a range between any two of them.

[0077] In one embodiment, the structure of Formula 1 is one or more of the following:

[0078]

[0079]

[0080] In one embodiment, the structure of Formula 2 is one or more of the following:

[0081]

[0082]

[0083] The present application also provides a method for preparing an ionomer, comprising the following steps:

[0084] S1. Providing 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;

[0085] S2, mixing the first monomer and the second monomer so that the first monomer and the second monomer undergo a polymerization reaction to generate a polymer;

[0086] S3, sequentially subjecting the polymer to quaternization treatment and ion exchange treatment to obtain an ionomer;

[0087] The structure of the ionomer includes anions, and the polarizability of the anions is greater than or equal to 3.5×10 -24 cm 3 In the embodiments of the present application, the polarizability of the anion indicates the difficulty of the anion's electron cloud to generate an induced dipole under the action of an external electric field; the higher the polarizability, the easier it is for the anion's electron cloud to generate a stronger induced dipole interaction with polar alcohol molecules, thereby enhancing the solvation effect. The polarizability of the anion in the embodiments of the present application is greater than or equal to 3.5×10 - 24 cm 3 The anion has a high polarizability and can form a strong induced dipole interaction with the alcohol solvent molecules. This interaction force helps to break the cohesive force between the ionomer molecules, making the ionomer molecules easier to disperse into the solvent, thereby improving the solubility of the ionomer in alcohol solvents.

[0088] In one embodiment, the first monomer is selected from a piperidone monomer or a quinuclidinone monomer. The structure of the piperidone monomer is shown in Formula 3, and the structure of the quinuclidinone monomer is shown in Formula 4:

[0089]

[0090] Wherein, 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.

[0091] In one embodiment, the piperidinone monomer comprises one or more of the following structures:

[0092]

[0093] In one embodiment, the quinuclidinone monomer comprises one or more of the following structures:

[0094]

[0095] In one embodiment, the monomer containing a linear structure includes one or more of biphenyl, p-terphenyl, m-terphenyl, and quaterphenyl.

[0096] In one embodiment, the monomer containing a branched structure includes one or more of 1,3,5-triphenylbenzene, triphenylmethane, 9,10-triphenylene, tetraphenylmethane, triptycene, 9,9'-diphenylfluorene, 9,9'-spirobifluorene, 9,9'-bifluorene, 9,9'-bicarbazole, 4,4-di(9-carbazole)biphenyl, 2,2'-bi-9,9'-spirobi[9H-fluorene], 9-(9H-fluoren-9-yl)anthracene, and triphenylamine.

[0097] In one embodiment, step S2 specifically includes:

[0098] S21, adding the first monomer and the second monomer to solvent A to obtain a first mixed solution;

[0099] S22, adding an acid catalyst to the mixed solution at a temperature not greater than 0° C. to obtain a reaction solution;

[0100] S23, performing a polymerization reaction on the reaction solution at a temperature of 0° C. to 30° C. to obtain a first mixture;

[0101] S24, filtering, washing, and drying the mixture to obtain a polymer.

[0102] In this embodiment, the acid catalyst can reduce the activation energy of the polymerization reaction, thereby accelerating the polymerization process between monomers. Furthermore, the polymerization reaction temperature is controlled between 0°C and 30°C. This not only reduces the decomposition or deactivation of the acid catalyst at high temperatures, but also allows for precise control of the reaction progress, reducing the risk of runaway reactions due to overly rapid reactions.

[0103] In one embodiment, the acid catalyst includes one or more of methanesulfonic acid, pentafluoropropionic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and heptafluorobutyric acid.

[0104] In one embodiment, solvent A includes one or more of dichloromethane, chloroform, chloroform, and tetrahydrofuran.

[0105] In one embodiment, step S3 specifically includes:

[0106] S31, adding the polymer and the quaternizing agent to solvent B to obtain a second mixed solution;

[0107] S32, subjecting the second mixed solution to a quaternization reaction at a temperature of 30° C. to 100° C. to obtain a second mixture, filtering, washing, and drying to obtain a quaternized polymer;

[0108] S33, conducting an ion exchange reaction between the quaternized polymer and an ion exchange reagent at a temperature of 20° C. to 100° C., filtering, washing, and drying to obtain an ionomer.

[0109] In this embodiment, the temperature of the quaternization reaction can be any one of 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc., or a range between any two thereof, and is not limited thereto. The temperature of the ion exchange reaction can be any one of 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc., or a range between any two thereof, and is not limited thereto.

[0110] In one embodiment, the quaternizing agent includes one or more of 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 allylsulfonate, methyl benzenesulfonate, methyl nitrobenzenesulfonate, methyl trifluoromethanesulfonate, ethyl trifluoromethanesulfonate, ethyl toluenesulfonate, cyclobutyl toluene-4-sulfonate, butyl toluenesulfonate, neopentylbenzenesulfonate, tetrahydro-2H-pyran-4-yl methanesulfonate, and cyclohexyl p-toluenesulfonate.

[0111] 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.

[0112] 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.

[0113] The present application also provides a catalyst slurry, comprising: a catalyst, an alcohol solvent, and the ionomer as described above or an ionomer prepared by the method as described above. In this embodiment, the structure of the ionomer includes anions, and the polarizability of the anions is greater than or equal to 3.5×10 -24 cm 3 The anion has a high polarizability and can form a strong induced dipole interaction with the alcohol solvent molecules. This interaction force helps to break the cohesive force between the ionomer molecules, making the ionomer molecules easier to disperse into the solvent, thereby improving the solubility of the ionomer in the alcohol solvent and further improving the stability of the catalyst slurry.

[0114] 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 one or two selected from Co, Mo, W, Ru and Pd.

[0115] 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.

[0116] The present application also provides a membrane electrode, comprising the ionomer as described above or the ionomer prepared by the method as described above.

[0117] The present application also provides a fuel cell, comprising the ionomer as described above or the ionomer prepared by the method as described above.

[0118] The above solution is further described below with reference to specific implementation examples. The preferred embodiments of the present application are described in detail as follows:

[0119] Example 1

[0120] (1) adding 0.135 mol of p-terphenyl and 0.36 mol of N-methyl-4-piperidone to 100 ml of dichloromethane and mixing them uniformly to obtain a first mixed solution;

[0121] (2) adding 22.8 ml of trifluoroacetic acid and 240 ml of trifluoromethanesulfonic acid dropwise to the first mixed solution at 0° C., and then carrying out oligomerization at 5° C. for 1.5 h, and then carrying out polymerization at 15° C. for 3 h. After the polymerization reaction is completed, the reaction product is discharged from an extruder into pure water, filtered, washed with pure water, and dried to obtain a polymer;

[0122] (3) 0.1 mol of the polymer obtained in step (2), 0.12 mol of an acid-binding agent, triethylamine, and 0.15 mol of a quaternizing agent, bromopropane, were added to 200 ml of dimethyl sulfoxide, and the mixture was uniformly mixed to obtain a second mixed solution. The second mixed solution was reacted at 80° C. for 15 h. After the reaction was completed, the reaction product was precipitated using a precipitant, ethyl acetate, filtered, washed with ethyl acetate, and dried to obtain a quaternized polymer.

[0123] (4) 0.1 mol of the quaternized polymer obtained in step (3) was stirred and mixed with 1 liter of a 1 mol / L potassium trifluoroacetate aqueous solution to allow the quaternized polymer to undergo an ion exchange reaction with the potassium trifluoroacetate. After the reaction, the ionomer was washed with pure water and dried to obtain an ionomer. The ionomer comprises the following structure:

[0124]

[0125] Example 2

[0126] The difference between Example 2 and Example 1 is that:

[0127] In step (4), potassium trifluoroacetate was replaced with potassium citrate, and the rest was the same as in Example 1;

[0128] The ionomer obtained in Example 2 includes the following structure:

[0129]

[0130] Example 3

[0131] The difference between Example 3 and Example 1 is that:

[0132] In step (4), potassium trifluoroacetate was replaced with potassium thiocyanate, and the rest was the same as in Example 1;

[0133] The ionomer obtained in Example 3 includes the following structure:

[0134]

[0135] Example 4

[0136] The difference between Example 4 and Example 1 is that:

[0137] In step (1), N-methyl-4-piperidone was replaced with 3-quinidone, and the rest was the same as in Example 1;

[0138] The ionomer obtained in Example 4 includes the following structure:

[0139]

[0140] Example 5

[0141] The difference between Example 5 and Example 1 is that:

[0142] Step (1) is: adding 0.135 mol of p-terphenyl, 0.015 mol of triphenylmethane and 0.36 mol of N-methyl-4-piperidone to 100 ml of dichloromethane, mixing well, to obtain a first mixed solution;

[0143] The rest is the same as in Example 1;

[0144] The ionomer obtained in Example 5 includes the following structure:

[0145]

[0146] Example 6

[0147] The difference between Example 6 and Example 5 is that:

[0148] In step (4), potassium trifluoroacetate was replaced with potassium thiocyanate, and the rest was the same as in Example 5;

[0149] The ionomer obtained in Example 6 includes the following structure:

[0150]

[0151] Comparative Example 1

[0152] The difference between Comparative Example 1 and Example 1 is:

[0153] Step (4) was not performed;

[0154] The corresponding variation of step (3) is as follows: 0.1 mol of the polymer obtained in step (2), 0.12 mol of an acid-binding agent, triethylamine, and 0.15 mol of a quaternizing agent, bromopropane, are added to 200 mL of dimethyl sulfoxide, mixed evenly to obtain a second mixed solution, and the second mixed solution is reacted at 80° C. for 15 h. After the reaction is completed, the reaction product is precipitated using a precipitant, ethyl acetate, filtered, washed with ethyl acetate, and dried to obtain an ionomer;

[0155] The rest is the same as in Example 1.

[0156] Comparative Example 2

[0157] The difference between Comparative Example 2 and Example 1 is:

[0158] In step (4), potassium trifluoroacetate is replaced with potassium bicarbonate, wherein the polarizability of bicarbonate ion is about 3.3×10 -24 cm 3 , the rest is the same as in Example 1.

[0159] Comparative Example 3

[0160] The difference between Comparative Example 3 and Example 1 is:

[0161] In step (4), potassium trifluoroacetate is replaced with sodium carbonate, wherein the polarizability of carbonate ion is about 3.0×10 -24 cm 3 , the rest is the same as in Example 1.

[0162] Comparative Example 4

[0163] The difference between Comparative Example 4 and Example 1 is:

[0164] In step (4), potassium trifluoroacetate is replaced with sodium tetrafluoroborate, wherein the polarizability of tetrafluoroborate ion is about 2.5×10 -24 cm 3 , the rest is the same as in Example 1.

[0165] Test Method

[0166] (1) Ionomer solubility and stability test

[0167] 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 mixed solution. The volume ratio of ethanol to dimethyl sulfoxide was 1:1, and the mass ratio of ionomer to solvent was 1:5. The solubility of the mixed solution and the stability of the mixed solution within 24 hours were observed at room temperature. The test results are shown in Table 1 below:

[0168] Table 1

[0169]

[0170]

[0171] (2) Catalyst slurry stability test

[0172] The ionomers obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were blended with a metal platinum catalyst and ethanol to prepare a catalyst slurry. The mass ratio of ionomer, metal platinum catalyst and ethanol was 0.5:1:2. The slurry stability of the catalyst slurry was observed at room temperature for 24 hours. The test results are shown in Table 2 below:

[0173] Table 2

[0174] sample stability Example 1 Homogeneous stability Example 2 Homogeneous stability Example 3 Homogeneous stability Example 4 Homogeneous stability Example 5 Homogeneous stability Example 6 Homogeneous stability Comparative Example 1 Separation and sedimentation Comparative Example 2 Separation and sedimentation Comparative Example 3 Separation and sedimentation Comparative Example 4 Separation and sedimentation

[0175] (3) Conductivity test of ionomer solution

[0176] Test steps

[0177] (1) dissolving the ionomers obtained in Examples 1 to 6 and Comparative Examples 1 to 4 in water to obtain a 20 wt % mixed solution;

[0178] (2) Keeping the mixed solution at a constant temperature to the test temperature (e.g., 25°C);

[0179] (3) Calibrate the electrode using a KCl standard solution of known conductivity (0.1 mol / L, conductivity 1.288 S / m at 25°C);

[0180] (4) Immerse the four-electrode probe vertically into the mixed solution to ensure that the electrodes are completely covered and there are no bubbles attached;

[0181] (5) After the reading of the ionic conductivity test device stabilizes, record the resistance value (repeat the measurement three times and take the average value);

[0182] (6) Conductivity was calculated according to 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 (cm). 2 ), σ is the conductivity (S / cm), and the test results are shown in Table 3 below.

[0183] (4) Polarization performance test

[0184] The polarization performance of the ionomer was tested in an anode nickel ferrite-cathode platinum carbon catalyst system at 70°C @ 2M KOH. The test results are shown in Table 3 below.

[0185] Table 3

[0186]

[0187]

[0188] According to the test results in Table 1 and Table 2, the ionomer provided in the embodiment has good solubility and stability in alcohol solvents, and the catalyst slurry containing the ionomer of the embodiment of the present application also has good stability. The polarizability of the anion of the embodiment of the present application is greater than or equal to 3.5×10 -24 cm 3 The anion has a high polarizability and can form a strong induced dipole interaction with the alcohol solvent molecules. This interaction force helps to break the cohesive force between the ionomer molecules, making the ionomer molecules easier to disperse into the solvent, thereby improving the solubility of the ionomer in the alcohol solvent. Applying the ionomer of the embodiment of the present application to the catalyst slurry can improve the stability of the catalyst slurry.

[0189] According to the test results in Table 3, the ionomer provided in the embodiment has relatively low resistance and relatively high conductivity. When the ionomer provided in the embodiment is applied to a fuel cell, the fuel cell has a high conductivity at 0.5 A / cm 2 The current density and 1A / cm 2 The polarization voltage is relatively low at a current density of 1000 nm, and the polarization performance of the fuel cell is good. The polarization rate of the anion in the embodiment of the present application is greater than or equal to 3.5×10 -24 cm 3 It can effectively improve the electrical conductivity of the ionomer and improve the electrochemical performance of the fuel cell.

[0190] The embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. An ionomer, used in a fuel cell, characterized in that: The structure of the ionomer includes anions, and the polarizability of the anions is greater than or equal to 3.5×10 -24 cm 3 .

2. The ionomer according to claim 1, characterized in that The polarizability of the anion is 3.5×10 -24 cm 3 -11×10 -24 cm 3 .

3. The ionomer according to claim 1 or 2, characterized in that The anion comprises at least one of trifluoroacetate ion, citrate ion, and thiocyanate ion; and / or The structure of the ionomer further includes a nitrogen-containing heterocyclic cation, and the anion is connected to the nitrogen-containing heterocyclic cation.

4. The ionomer according to claim 3, characterized in that The ionomer has a structure as shown in Formula 1 or Formula 2: Wherein, in the formula 1, A represents the nitrogen-containing heterocyclic cation, Ar1 represents a linear structural unit, M- represents the anion, and X is the molar ratio of the linear structural unit in the ionomer; Wherein, in the formula 2, A represents the nitrogen-containing heterocyclic cation, Ar1 represents a linear structural unit, Ar2 represents a branched structural unit having at least three active sites, M- represents the anion, X is the molar ratio of the linear structural unit in the ionomer, and Y is the molar ratio of the branched structural unit in the ionomer.

5. The ionomer according to claim 4, characterized in that The linear structural unit Ar1 includes at least one of a biphenyl group, a p-terphenyl group, a m-terphenyl group, and a quaternary group; and / or The branched structural unit Ar2 includes at least one of a 1,3,5-triphenylphenyl group, a triphenylmethane group, a 9,10-triphenylene group, a tetraphenylmethane group, a triptycene group, a 9,9'-diphenylfluorene group, a 9,9'-spirobifluorene group, a 9,9'-bifluorene group, a 9,9'-bicarbazole group, a 4,4-di(9-carbazole)biphenyl group, a 2,2'-bi-9,9'-spirobi[9H-fluorene] group, and a triphenylamine group; and / or In Formula 1, 0<X≤100%; and / or In Formula 2, 0<Y≤100%, and X+Y≤100%.

6. The ionomer according to claim 5, characterized in that The structure of Formula 1 is one or more of the following: And / or the structure of Formula 2 is one or more of the following:

7. A method for preparing an ionomer, characterized in that: The following steps are involved: Providing 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; mixing the first monomer and the second monomer so as to polymerize the first monomer and the second monomer to generate a polymer; The polymer is sequentially subjected to quaternization treatment and ion exchange treatment to obtain the ionomer; The structure of the ionomer includes anions, and the polarizability of the anions is greater than or equal to 3.5×10 -24 cm 3 .

8. The preparation method according to claim 7, characterized in that The first monomer is selected from a piperidone monomer or a quinuclidine monomer. The structure of the piperidone monomer is shown in Formula 3, and the structure of the quinuclidine monomer is shown in Formula 4: wherein R1 and R2 are each independently selected from one of methyl, ethyl, propyl, butyl, pentyl, and cyclopropyl; R3 is selected from one of hydrogen, alkyl, alkenyl, alkynyl, and aromatic ring; and / or The monomer containing a linear structure includes one or more of biphenyl, p-terphenyl, m-terphenyl, and quaterphenyl; and / or The monomer containing a branched structure includes one or more of 1,3,5-triphenylbenzene, triphenylmethane, 9,10-triphenylene, tetraphenylmethane, triptycene, 9,9'-diphenylfluorene, 9,9'-spirobifluorene, 9,9'-bifluorene, 9,9'-bicarbazole, 4,4-di(9-carbazole)biphenyl, 2,2'-bi-9,9'-spirobi[9H-fluorene], 9-(9H-fluoren-9-yl)anthracene, and triphenylamine.

9. The preparation method according to claim 8, characterized in that The piperidone monomer includes one or more of the following structures: and / or The quinuclidine monomer includes one or more of the following structures:

10. The preparation method according to any one of claims 7 to 9, characterized in that: The step of mixing the first monomer and the second monomer so as to polymerize the first monomer and the second monomer to generate a polymer specifically includes: adding the first monomer and the second monomer into solvent A to obtain a first mixed solution; adding an acid catalyst to the mixed solution at a temperature not greater than 0° C. to obtain a reaction solution; The reaction solution is subjected to a polymerization reaction at a temperature of 0° C. to 30° C. to obtain a first mixture; The mixture is filtered, washed, and dried to obtain the polymer.

11. The preparation method according to claim 10, characterized in that: The solvent A comprises one or more of dichloromethane, chloroform, chloroform, and tetrahydrofuran; and / or The acid catalyst includes one or more of methanesulfonic acid, pentafluoropropionic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and heptafluorobutyric acid.

12. The preparation method according to any one of claims 7 to 9, characterized in that: The step of sequentially subjecting the polymer to quaternization treatment and ion exchange treatment to obtain the ionomer specifically comprises: adding the polymer and the quaternizing agent into solvent B to obtain a second mixed solution; quaternizing the second mixed solution at a temperature of 30° C. to 100° C. to obtain a second mixture, filtering, washing, and drying to obtain a quaternized polymer; The quaternized polymer is subjected to an ion exchange reaction with an ion exchange reagent at a temperature of 20° C. to 100° C., and the reaction is filtered, washed, and dried to obtain the ionomer.

13. The preparation method according to claim 12, characterized in that The quaternizing agent comprises one or more of 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, neopentylbenzenesulfonate, tetrahydro-2H-pyran-4-yl methanesulfonate, and cyclohexyl p-toluenesulfonate; and / or The 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.

14. A catalyst slurry, characterized in that include: A catalyst, an alcohol solvent, and the ionomer according to any one of claims 1 to 6 or the ionomer prepared by the method according to any one of claims 7 to 13.

15. A membrane electrode, characterized in that: The invention relates to an ionomer according to any one of claims 1 to 6 or an ionomer prepared by the method according to any one of claims 7 to 13.

16. A fuel cell, characterized in that: The invention relates to an ionomer according to any one of claims 1 to 6 or an ionomer prepared by the method according to any one of claims 7 to 13.

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