Proton conductive electrolyte material, method for producing proton conductive electrolyte material, and fuel cell

Abstract

This proton conductive electrolyte material has a chemical structure which comprises an acidic polymer (2) that contains an oxo acid group represented by -POx(OH)y (wherein x and y are each 1 or more), having a phosphorus atom, and at least one saturated hydrocarbon group in the main chain, and a basic polymer (3) that contains a basic functional group, while having at least one aromatic ring in the main chain, wherein an attractive interaction occurs between the oxo acid group and the basic functional group. This fuel cell is provided with the proton conductive electrolyte material. This method for producing a proton conductive electrolyte material includes: preparing a first solution by means of an acidic polymer and a mixed solvent; preparing a second solution in which a basic polymer is dissolved in a solvent; and preparing a mixed solution in which the first solution and the second solution are mixed. With respect to the preparation of the first or second solution, a mixed solvent which contains an inhibitor that is capable of inhibiting rapid aggregation of the oxo acid group and the basic functional group is prepared.

Description

Proton-conductive electrolyte material, method for manufacturing proton-conductive electrolyte material, and fuel cell CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Patent Application No. 2024-19064, filed on February 12, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a proton-conducting electrolyte material, a method for manufacturing the proton-conducting electrolyte material, and a fuel cell.

[0003] Conventionally, fuel cells (FCs) have been known to have a solid polymer structure in which an electrolyte membrane acting as a proton carrier is disposed between two electrodes, i.e., a hydrogen electrode and an oxygen electrode, which are arranged opposite to each other. The hydrogen electrode is also called a fuel electrode. In a fuel cell, hydrogen gas is supplied to the hydrogen electrode, and oxygen or air is supplied to the oxygen electrode, and electromotive force is generated by the following chemical reactions at each electrode: Hydrogen electrode: H ２ →2H ＋ +2e － Oxygen electrode: 2H ＋ +1 / 2O ２ +2e － →H ２ In recent years, in the field of fuel cells, efforts have been made to increase the temperature of FC systems in order to achieve both high output and cooling in order to popularize HDVs. HDV is an abbreviation for Heavy Duty Vehicle. For example, in the temperature range of 100°C to 150°C (hereinafter referred to as the "mid-temperature range"), which is higher than the conventional operating range of less than 100°C and is suitable for chemical reactions using hydrogen, water molecules are unlikely to exist because the temperature is above the boiling point of water. For this reason, it is difficult to achieve high proton conductivity in the mid-temperature range due to the presence of water, as with conventional electrolyte membranes. For this reason, a proton-conducting electrolyte membrane that achieves proton conduction without relying on water is needed in the mid-temperature range.

[0004] An electrolyte membrane for ensuring proton conductivity in the intermediate temperature range has been proposed, for example, in Patent Document 1. The proton-conducting electrolyte membrane described in Patent Document 1 has a membrane configuration in which an organic salt containing an oxoacid anion that exhibits an Arrhenius tendency even in the intermediate temperature range is mixed with a polymer electrolyte having an acidic functional group.

[0005] JP 2009-16344 A

[0006] In the medium-temperature range, for example, instead of water, acids with high boiling points, such as phosphoric acid or phosphonic acid, or ionic liquids are used as proton carriers. On the other hand, in fuel cells, water is generated during power generation, so water resistance is required for proton-conducting electrolyte membranes. To ensure high proton conductivity, it is desirable for the proton carrier to have high mobility in the carrier moiety that conducts protons. However, in this case, the proton carrier has a chemical structure that is easily soluble in water, which reduces water resistance. To ensure water resistance, it is desirable for the proton carrier to have a chemical structure in which the carrier moiety is strongly fixed by chemical bonds. However, in this case, the molecular mobility of the carrier moiety is significantly restricted, which reduces proton conductivity. Thus, there is a trade-off between water resistance and proton conductivity in the medium-temperature range for proton-conducting electrolyte membranes, and it is desirable to achieve both of these properties. The proton-conductive electrolyte membrane described in Patent Document 1 is a molten salt in which an organic salt dissolves in water, and therefore is not water-resistant and is limited to use at high temperatures and in an unhumidified environment. In addition, the proton conductivity at about 150°C is about 0.3 mS / cm, leaving room for improvement.

[0007] The present disclosure relates to a proton-conducting electrolyte material that can simultaneously achieve two properties: water resistance and proton conductivity in the medium temperature range; a method for producing the same; and a fuel cell using the same.

[0008] According to one aspect of the present disclosure, the proton-conducting electrolyte material is ｘ (OH) ｙThe polymer comprises an acidic polymer including an oxo acid group having a phosphorus atom represented by (x, y: 1 or more) and at least one saturated hydrocarbon group in the main chain, and a basic polymer including a basic functional group and at least one aromatic ring in the main chain, and has a chemical structure in which attractive interaction occurs between the oxo acid group and the basic functional group.

[0009] This proton-conducting electrolyte material is composed of an acidic polymer and a basic polymer. The acidic polymer is a flexible polymer containing at least one saturated hydrocarbon group in its main chain, while the basic polymer has at least one aromatic ring in its main chain and a structure that is more rigid than the acidic polymer. The acidic polymer is a flexible polymer containing oxoacid groups containing phosphorus atoms, and the high mobility of the proton carrier moiety ensures good proton conductivity. The basic polymer is also more rigid than the acidic polymer and contains basic functional groups. The basic functional groups have a chemical structure that generates attractive interactions with the oxoacid groups containing phosphorus atoms in the acidic polymer, thereby preventing the acidic polymer from dissolving in water. Therefore, this proton-conducting electrolyte material is capable of achieving both water resistance and good proton conductivity in the medium temperature range. Note that the notation "-" above indicates a bond (covalent bond).

[0010] According to another aspect of the present disclosure, a method for producing a proton-conducting electrolyte material includes: ｘ (OH) ｙ A method for producing a proton-conducting electrolyte material having an acidic polymer containing an oxo acid group having a phosphorus atom, represented by (x, y: 1 or more), and at least one saturated hydrocarbon group in its main chain, and a basic polymer containing a basic functional group and at least one aromatic ring in its main chain, the method comprising: preparing a first solution from the acidic polymer and a mixed solvent; preparing a second solution by dissolving the basic polymer in a solvent; and preparing a mixed solution by mixing the first solution and the second solution. In preparing the first solution, a mixed solvent is prepared containing an inhibitor that ionizes into monovalent cations and monovalent anions in the mixed solution and can inhibit rapid aggregation of the oxo acid group and the basic functional group.

[0011] This allows the production of the proton-conducting electrolyte material described above that combines water resistance and proton conductivity in the medium temperature range. Furthermore, an inhibitor that ionizes into monovalent cations and monovalent anions and inhibits the rapid aggregation of oxo acid groups and basic functional groups, i.e., an aggregation inhibitor, is added to the mixture of the first solution containing the acidic polymer and the second solution containing the basic polymer. This suppresses the generation of aggregates due to the neutralization reaction resulting from the mixing of the acidic polymer and the basic polymer, and allows the oxo acid groups and basic functional groups to react with each other, making it possible to produce a proton-conducting electrolyte material that contains a large number of acid-base paired chemical structures in the membrane.

[0012] According to another aspect of the present disclosure, a method for producing a proton-conducting electrolyte material includes: ｘ (OH) ｙ (x, y: 1 or more) and an oxoacid having a phosphorus atom, and at least one saturated hydrocarbon group in the main chain and an aromatic ring and an alkylene group (-(CH ２ ) ｚ a basic polymer having at least one aromatic ring in its main chain, a cationic group cationized by adding a hydrocarbon group to a basic functional group; and a first solution prepared by dissolving the acidic polymer in a solvent; a second solution prepared by dissolving the basic polymer in a solvent; and a mixed solution prepared by mixing the first and second solutions. In preparing the first or second solution, an inhibitor capable of inhibiting rapid aggregation due to reaction between the oxo acid group and the cationic group in the mixed solution is added to the first or second solution.

[0013] This allows the inhibitor to inhibit the reaction between the phosphorus atom-containing oxo acid group and the cationic group in the mixed solution and rapid aggregation, and similarly to the above-mentioned production method, a proton-conducting electrolyte material that has both water resistance and proton conductivity in the medium temperature range can be produced. ｘ (OH) ｙ Examples of the oxo acid group represented by (x, y: 1 or more) include a phosphonic acid group where x=1 and y=2.

[0014] According to another aspect of the present disclosure, there is provided a fuel cell comprising: ｘ (OH) ｙ The proton-conductive electrolyte material includes an acidic polymer including an oxo acid group having a phosphorus atom and at least one saturated hydrocarbon group in its main chain, and a basic polymer including a basic functional group and at least one aromatic ring in its main chain, and the proton-conductive electrolyte material has a chemical structure in which attractive interaction occurs between the oxo acid and the basic functional group.

[0015] This results in a fuel cell comprising the proton-conductive electrolyte material described above that has both water resistance and good proton conductivity in the medium temperature range.

[0016] 1 is a diagram showing an example of a proton-conducting electrolyte material according to the first embodiment; FIG. 2 is a diagram showing another example of a proton-conducting electrolyte material according to the first embodiment; FIG. 3 is a flowchart showing a method for producing a proton-conducting electrolyte membrane according to the first embodiment; FIG. 4 is an explanatory diagram showing the inhibition of attractive interactions between a basic group of a basic polymer and an oxo acid group, and the formation of ionic bonds between an acidic polymer and a basic polymer; FIG. 5 is a diagram showing measurement results of a proton-conducting electrolyte membrane according to the first embodiment using a Fourier transform infrared spectrophotometer (FT-IR); FIG. 6 is an explanatory diagram showing proton conductivity evaluation and a jig used therefor; FIG. 7 is a diagram showing measurement results of proton conductivity before and after a water resistance evaluation of a proton-conducting electrolyte membrane; FIG. 8 is an explanatory diagram showing the separation of phosphoric acid in a proton-conducting electrolyte membrane of a comparative example; FIG. 9 is a diagram showing evaluation results of a proton-conducting electrolyte membrane according to an example of the first embodiment; FIG. 10 is a diagram showing the results of an investigation into the relationship between the ionization rate of a basic functional group of a basic polymer in a proton-conducting electrolyte membrane according to an example of the first embodiment and the proton conductivity after a water resistance evaluation. 1 is a diagram showing the results of investigating the relationship between the molar percentage of acidic functional groups with respect to the sum of acidic functional groups and basic functional groups in a proton conducting electrolyte membrane according to an example of the first embodiment and the proton conductivity after water resistance evaluation. FIG. 2 is a diagram showing a proton conducting electrolyte material according to a second embodiment. FIG. 3 is a diagram showing ionic bonds in a proton conducting electrolyte membrane according to the second embodiment. FIG. 4 is a diagram showing evaluation results of a proton conducting electrolyte membrane according to an example of the second embodiment. FIG. 5 is a diagram showing the results of investigating the relationship between the molar percentage of acidic functional groups with respect to the sum of acidic functional groups and basic functional groups in a proton conducting electrolyte membrane according to an example of the second embodiment and the proton conductivity after water resistance evaluation. FIG. 6 is a flowchart showing a method for manufacturing a proton conducting electrolyte membrane according to the second embodiment. FIG. 7 is a diagram showing a proton conducting electrolyte material according to a third embodiment. FIG. 8 is a diagram showing ionic bonds in a proton conducting electrolyte membrane according to the third embodiment. FIG. 9 is a diagram showing evaluation results of a proton conducting electrolyte membrane according to an example of the third embodiment. FIG. 10 is a diagram showing the results of investigating the relationship between the molar percentage of acidic functional groups with respect to the sum of acidic functional groups and basic functional groups in a proton conducting electrolyte membrane according to an example of the third embodiment and the proton conductivity after water resistance evaluation.10 is a flowchart showing a method for manufacturing a proton-conductive electrolyte membrane according to a third embodiment.

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following embodiments, identical or equivalent parts will be denoted by the same reference numerals.

[0018] (First embodiment) [Proton-conducting electrolyte membrane] A proton-conducting electrolyte membrane 1 made of a proton-conducting electrolyte material according to a first embodiment will be described. The proton-conducting electrolyte membrane 1 is suitable for use in electrochemical devices requiring proton conduction, such as fuel cells, particularly those used in medium-temperature ranges. The proton-conducting electrolyte material according to this embodiment can also be used, for example, as an ionomer material for the catalyst layer in such electrochemical devices.

[0019] As shown in FIG. 1, the proton-conducting electrolyte membrane 1 comprises an acidic polymer 2 containing an oxoacid group having a phosphorus atom represented by the following formula (I) and at least one saturated hydrocarbon group in the main chain, and a basic polymer 3 containing a basic functional group and at least one aromatic ring in the main chain. Here, an oxoacid is an acid containing an oxygen atom in the molecule, and an acid is an acid that can be ionized to produce protons (H ＋ Therefore, the term "oxo acid group" as used herein refers to a functional group having an oxo acid unit and bonded to another unit.

[0020] -PO ｘ (OH) ｙ ...(I) In formula (I), x and y are 1 or more, and the symbol "-" represents a bond (covalent bond). Also, m, n, and l in Figure 1 are 1 or more. "Main chain" refers to the part corresponding to the central trunk of a chain compound (e.g., a polymer), and "side chain" refers to a functional group branching off from the main chain, a unit containing a functional group, a graft chain, etc. "Aromatic ring" refers to the cyclic skeleton of a compound having aromaticity, such as benzene, pyridine, or imidazole.

[0021] The proton-conducting electrolyte membrane 1 is flexible and has a chemical structure in which an acidic polymer 2 having oxo acid groups responsible for proton conduction forms an attractive interaction with a basic functional group in a rigid basic polymer 3. For example, as shown in FIG. 2 , the proton-conducting electrolyte membrane 1 has an acidic polymer 2 and a basic polymer 3 having cationized cationic groups in its main chain, and has a chemical structure in which the oxo acid groups of the acidic polymer 2 and the cationic groups of the basic polymer 3 are ionic-bonded. In other words, the proton-conducting electrolyte membrane 1 has a chemical structure in which an attractive interaction occurs between the oxo acid groups of the acidic polymer 2 and the basic functional groups of the basic polymer 3. The attractive interaction refers to a non-covalent bond such as a hydrogen bond or an ionic bond. Due to this interaction, the oxo acid groups of the acidic polymer 2 and the basic functional groups of the basic polymer 3 are in close proximity to each other.

[0022] [Acidic Polymer] The acidic polymer 2 is, for example, an acidic polymer having at least one saturated hydrocarbon group in the main chain and at least a phosphorus atom-based oxo acid group in the side chain of the saturated hydrocarbon group, as shown in the following chemical structural formula.

[0023] In the above chemical structural formula, R1 is a hydrocarbon group or an aromatic ring. R2 is a structure having at least one of a hydrocarbon group and an aromatic ring. For example, when R1 is a hydrocarbon group, the number of carbon atoms is set to 12 or less. -PO ｘ (OH) ｙ The subscript l (l) placed after the parentheses is a number equal to or greater than 1. l (l) is 1 when there is one phosphorus-atom-based oxo acid group, 2 when there are two phosphorus-atom-based oxo acid groups, and 3 when there are three phosphorus-atom-based oxo acid groups. In this specification, what is simply referred to as a "hydrocarbon group" may be either a saturated hydrocarbon group or an unsaturated hydrocarbon group, and may be linear or branched.

[0024] The acidic polymer 2 has one or more saturated hydrocarbon groups in its main chain, making it a more flexible polymer than the basic polymer 3. The acidic polymer 2 does not necessarily have R1 in its main chain. The acidic polymer 2 has a side chain branched from the saturated hydrocarbon group in its main chain, and the end of the side chain is a phosphorus atom-based oxo acid group. The oxo acid group interacts with the basic group of the basic polymer 3 and is responsible for proton conduction. The molecular weight of the acidic polymer 2 is, for example, a number average molecular weight (Mn) of 30,000 or more and 1,000,000 or less, determined by molecular weight calibration using standard polystyrene in gel permeation chromatography (GPC). The molecular weight of the acidic polymer 2 may be, for example, 30,000, 50,000, 70,000, 100,000, 120,000, or 150,000 or more, or 800,000, 600,000, 500,000, 400,000, 300,000, or 200,000 or less.

[0025] As the acidic polymer 2, for example, poly(p-styrenephosphonic acid) (hereinafter referred to as "PSPA") shown in the following chemical structural formula is preferably used, but is not limited to this. For example, the acidic polymer 2 may have a chemical structure in which a phosphorus atom-based oxo acid group (a phosphonic acid group in the case of PSPA) interacts with the basic functional group of the basic polymer 3, and for example, the position of the phosphonic acid group may be not only the p-position but also the o-position or the m-position. Note that a sulfonic acid group (-SO ３ In the case of an acidic polymer having a sulfonic acid group, the sulfonic acid group is converted into a sulfonic acid group by the reaction of RH and SO ３ It is separated into SO ３ Therefore, the acidic polymer 2 is selected from the group consisting of phosphonic acid groups (-PO ) that are stable even in the medium temperature range from the viewpoint of proton conductivity and durability. ３ H ２ , or -PO(OH) ２ The acidic polymer 2 is preferably a homopolymer having one type of monomer unit, but may also be a copolymer having two or more types of monomer units, and in the latter case, may be either a random polymer or a block polymer.

[0026] [Basic Polymer] The basic polymer 3 is, for example, a basic polymer having a monomer structure in which Z1, Z2, and at least one aromatic ring are contained in the main chain, and Z1 and Z2 are arranged on both sides of the aromatic ring, as shown in the following chemical structural formula:

[0027] In the above chemical structural formula, Z1 and Z2 are basic functional groups, and R3 to R6 are, for example, hydrocarbon groups or aromatic rings. For example, Z1 and Z2 are amino groups when the main chain of the basic polymer 3 contains an amine compound, imino groups when the main chain contains an imine compound, pyridyl groups when the main chain contains a pyridine compound, or imidazolyl groups when the main chain contains an imidazole compound. Furthermore, Z1 and Z2 are, for example, pyrazolyl groups when the main chain of the basic polymer 3 contains a pyrazole compound, pyrrolyl groups when the main chain contains a pyrrole compound, or triazolyl groups when the main chain contains a triazole compound. Examples of Z1 and Z2 include the functional groups described above, but are not limited to these, as long as they are functional groups exhibiting basicity. In other words, R4-Z1-R3 and R5-Z2-R6 represent, for example, an amine skeleton, imine skeleton, pyridine skeleton, imidazole skeleton, pyrazole skeleton, pyrrole skeleton, triazole skeleton, or the like, sandwiching the basic functional group described above.

[0028] The basic polymer 3 has a structure in which, for example, R4-Z1-R3 is bonded to one carbon atom of an aromatic ring, and R5-Z2-R6 is bonded to a carbon atom different from the carbon atom. The basic polymer 3 may have a structure in which, for example, one or more of R3 to R6 are absent, or none of them are present. Furthermore, in the basic polymer 3, the positional relationship between Z1 and Z2 sandwiching the aromatic ring is not limited to the p-position, but may be either the o-position or the m-position. Furthermore, in the basic polymer 3, at least one aromatic ring contained in the main chain may be separate from the basic functional group, or may be part of the basic functional group.

[0029] The basic polymer 3 has at least one aromatic ring in its main chain, which makes it more rigid than the acidic polymer 2 and serves as a base substrate to which the acidic polymer 2 binds through interaction. The molecular weight of the basic polymer 3 is preferably 200 or more, 500 or more, or 1,000 or more, and more preferably 2,000 or more, 5,000 or more, 10,000 or more, 20,000 or more, 40,000 or more, or 80,000 or more. The molecular weight is, for example, the number average molecular weight (Mn) determined by gel permeation chromatography (GPC) using standard polystyrene for molecular weight calibration.

[0030] For example, as shown in the following chemical structural formula, a polymer structure (hereinafter referred to as "PBI") having a monomer unit in which two benzimidazoles bonded in a linear chain to one benzene ring is preferably used as the basic polymer 3, but is not limited to this. In this case, the basic functional group in the basic polymer 3 is an imidazole skeleton.

[0031] In the above chemical structure, the unsaturated nitrogen atom contained in the imidazole skeleton is N ＋ Hereinafter, for convenience of explanation, PBI in which the unsaturated N atoms in the imidazole skeleton are cationized, i.e., not ionized, will be referred to as "PBI," and PBI in which at least a portion of the unsaturated N atoms in the imidazole skeleton are ionized will be referred to as "i-PBI."

[0032] The basic polymer 3 has a structure in which R7 is bonded to Z1, as shown in the following chemical structural formula.

[0033] In the above chemical structural formula, R7 is an alkyl group represented by the following formula (II), in which the carbon number z is 1 or more and 12 or less.

[0034] - (CH ２ ) ｚ－１ -CH ３...(II) This is to prevent situations where, if the number of carbon atoms in R7 exceeds 12, it becomes difficult to synthesize the basic polymer 3, the ion exchange capacity decreases, and the proton conductivity of the entire proton-conductive electrolyte membrane 1 decreases. － is a counter anion of the cationized Z1, and is an anion of a halogen such as F, Cl, Br, or I. The counter anion is derived from the halogen of the ionizing agent (e.g., alkyl halide) used to ionize the basic polymer 3. R7 is derived from the alkyl group of the ionizing agent. For example, methyl iodide (CH ３ When I) is used, R7 is a methyl group, AN － becomes iodine ions.

[0035] [Method for manufacturing proton-conductive electrolyte membrane] Next, a method for manufacturing the proton-conductive electrolyte membrane 1 according to the first embodiment will be described with reference to Fig. 3 and Fig. 4. Unless otherwise specified in the manufacturing steps below, temperature control is not required in the steps, and the steps are carried out at room temperature, for example.

[0036] First, in step S100 shown in FIG. 3, for example, PSPA is prepared as the acidic polymer 2.

[0037] Here, a synthesis example of PSPA is shown below.

[0038]

[0039] In a literature report (Org. Lett. 2011, 13(8), 2110-2113.), 4-diethyl styrenephosphonate monomer is synthesized by reacting p-styrylboronic acid with diethyl phosphite in the presence of 1,10-phenanthroline and copper(I) oxide as a catalyst. 4-Diethyl styrenephosphonate monomer can be synthesized in a similar manner to this reaction.

[0040] For example, 5.04 g (0.0210 mol) of 4-styrenephosphonic acid diethyl monomer and 3.1 mg (0.0085 mmol) of a reversible addition-fragmentation chain transfer (RAFT) agent are weighed out. Furthermore, for example, 1.5 mg (0.0091 mmol) of 2,2'-azoisobutyronitrile (AIBN) is weighed out and mixed with the above amounts of 4-styrenephosphonic acid diethyl monomer and RAFT agent in a round-bottom flask equipped with a stopcock to prepare a solution. Then, for example, nitrogen gas is bubbled through the solution for 30 minutes, and polymerization is carried out at atmospheric pressure using an oil bath at 85°C and 500 rpm while stirring. For example, the polymerization reaction is completely stopped after one hour by immersing the flask in liquid nitrogen.

[0041] As the RAFT agent, for example, 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid can be used.

[0042] For example, about 3 mL of tetrahydrofuran (THF) is added to the above reaction solution, and this polymer solution is dropped into about 100 mL of n-hexane to precipitate a powdery polymer (crudely purified poly(4-styrenediethylphosphonate)). The resulting polymer is separated by decantation and thoroughly dried by vacuum drying, and then re-dissolved in THF and dropped into n-hexane to precipitate the polymer. For example, the above-described polymer precipitation process is repeated about three times in total to remove unreacted monomers and low-molecular-weight oligomers, thereby obtaining purified poly(4-styrenediethylphosphonate).

[0043] The number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) of poly(diethyl 4-styrenephosphonate) are determined by gel permeation chromatography (GPC). Mw is the weight average molecular weight. Mn, Mw / Mn, and Mw are determined by a molecular weight calibration method using standard polystyrene and are found to be 122 kJ, 1.31, and 160 kJ, respectively. For example, a solvent containing THF as the main component is used as the eluent, and the flow rate is 1 mL / min and the temperature is 40°C, using a TSKgel column GMH manufactured by Tosoh Corporation. ＨＲ Measurements are performed with two -Ms linked together.

[0044] In the literature (Macromolecules, 2018, 51, 1120-1128), poly(4-styrenediethylphosphonate) is first reacted with bromotrimethylsilane. After the reaction, the alkyl groups of poly(4-styrenediethylphosphonate) are deprotected by dialysis using a methanol solvent to synthesize PSPA.

[0045] With reference to this reaction, for example, 1.0 g (4.2 mmol in monomer units) of poly(diethyl 4-styrenephosphonate) is dissolved in 8.6 mL of chloroform, 3.5 g (0.023 mol) of bromotrimethylsilane is added, and the mixture is placed in a 40°C oil bath and stirred overnight. This solution is concentrated, for example, by rotary evaporation, and then mixed with approximately 10 mL of methanol. The mixture is transferred to a cellulose dialysis tube and immersed in pure water for approximately one day for dialysis. For example, this dialysis is repeated about three times in total. The solution after dialysis is dried, for example, at 60°C, to obtain PSPA. The alkyl protecting group (-(CH ２ ) ｚ－１ -CH ３ The deprotection rate of the hydroxybenzoates (z: 1 or more and 12 or less) was measured by proton nuclear magnetic resonance spectroscopy ( １ When determined by H-NMR, it is estimated to be about 99% or more.

[0046] Examples of acidic polymers 2 other than PSPA include poly(4-(p-styryl)-1-butanephosphonic acid) (also known as poly(4-(4-vinylphenyl)butanephosphonic acid) or poly(4-(4-phosphonobutyl)styrene)) shown in the following chemical structural formula. Poly(4-(p-styryl)-1-butanephosphonic acid) can be synthesized by the method described in, for example, a patent document (publication number WO / 2023 / 120731). Hereinafter, for ease of explanation, poly(4-(p-styryl)-1-butanephosphonic acid) will be referred to as "PsbPA".

[0047] In step S110, a mixed solvent is prepared. Specifically, for example, pure water, n-propanol, and concentrated hydrochloric acid are prepared and mixed in a ratio of pure water:n-propanol:concentrated hydrochloric acid=20 wt %:60 wt %:20 wt % to prepare the mixed solvent.

[0048] In the next step S120, for example, PSPA is mixed with the mixed solvent to prepare a 3 wt % PSPA solution, and the solution is stirred at 1200 rpm using a stirrer until the mixing with the solution of the basic polymer 3 in step S140 is completed.

[0049] Next, in step S130, for example, i-PBI is prepared as the basic polymer 3, and the i-PBI is dissolved in dimethyl sulfoxide (DMSO) to prepare a 3 wt % i-PBI DMSO solution.

[0050] Here, an example of synthesizing i-PBI is shown below.

[0051]

[0052] First, for example, 2.01 g (0.65 mmol in monomer units) of a commercially available polybenzimidazole (PBI) dimethylacetamide (DMAc) solution (PBI concentration 10 wt%) is weighed out. Then, for example, 1.82 g and 1.10 g (7.7 mmol) of DMSO and iodomethane are weighed out, respectively, and mixed with the above amounts of 10 wt% PBI DMAc solution in a recovery flask to prepare a solution. Next, for example, this prepared solution is stirred at 40°C and 500 rpm in an oil bath at atmospheric pressure for approximately 5 days to carry out an ionization reaction.

[0053] For example, about 0.5 mL of DMSO is added to the reaction solution, and this polymer solution is dropped into about 200 mL of a mixed solvent of acetone / n-hexane (volume ratio 7 / 3) to precipitate a powdery polymer (crude i-PBI). For example, the resulting polymer is separated by suction filtration, thoroughly dried by vacuum drying, and then re-dissolved in DMSO, and the polymer is dropped into a mixed solvent of acetone / n-hexane (volume ratio 7 / 3) to precipitate the polymer. For example, this polymer precipitation process is repeated three times to remove unreacted iodomethane and obtain purified i-PBI.

[0054] The ionization rate of i-PBI was calculated by referring to the literature (Polym. Chem., 2011, 2, 1641-1643). １When measured by H-NMR, the ionization rate was found to be 91%.

[0055] Incidentally, i-PBI with different ionization rates can be synthesized by, for example, changing the amount of iodomethane used with PBI or the reaction time.

[0056] Instead of iodomethane, the DMAc solution of PBI can be mixed with, for example, bromoethane, 1-bromopropane, 1-chlorobutane, 1-bromobutane, 1-iodobutane, 1-bromohexane, 1-iodooctane, 1-bromodecane, etc. Additionally, instead of iodomethane, the DMAc solution of PBI can be mixed with, for example, 1-bromododecane, 1-iodododecane, ethyl 4-bromobutyrate, diethyl (3-bromopropyl)phosphonate, etc.

[0057] Then, in step S140, for example, a 3 wt % i-PBI DMSO solution is added dropwise to a 3 wt % PSPA solution being stirred. At this time, the 3 wt % i-PBI DMSO solution is added dropwise so that the ratio of acidic groups in PSPA to ionized or non-ionized basic groups in i-PBI is 90 mol %:10 mol %. Hereinafter, for ease of explanation, the solution obtained in step S140 will be simply referred to as the "polymer mixed solution."

[0058] Next, in step S150, the polymer mixture solution is placed in a polypropylene (PP) case, for example, and dried in stages. Specifically, a first drying step is performed in which the PP case containing the polymer mixture solution is placed in an incubator at 60°C, the PP case is covered with a beaker or the like to create a saturated steam environment for the polymer mixture solution, and the solution is allowed to stand in this state for seven days. This is followed by a second drying step in which the temperature in the incubator is raised to 70°C, for example, and the solution is allowed to stand for another day. Finally, a third drying step is performed in which the temperature in the incubator is raised to 80°C, for example, and the solution is allowed to stand for another two days.

[0059] At this time, the hydrochloric acid in the polymer mixed solution is ionized into monovalent cations and monovalent anions, and the cationized N of i-PBI is dissolved, as shown in FIG. ＋ and the counter anion I － To, H＋ and Cl － This inhibits aggregation due to the neutralization reaction caused by mixing the two polymer solutions, and thus the resulting generation of aggregated particles. In other words, hydrochloric acid functions as an inhibitor, i.e., an aggregation inhibitor. The first to third drying steps described above create an environment for gentle solvent evaporation, thereby suppressing the generation of aggregated particles due to neutralization, and gradually forming ionic bonds between the phosphonic acid groups of PSPA and the cationized imidazole skeleton of i-PBI.

[0060] Finally, in step S160, the polymer mixture obtained by evaporating the solvent through the first to third drying steps is spread using a scraper or the like to a thickness of a predetermined value or less, and is then hot-pressed under conditions of, for example, 170°C x 1 MPa x 1 min to form an electrolyte membrane.

[0061] The above-described manufacturing method can produce a proton-conducting electrolyte membrane 1 made of the proton-conducting electrolyte material of this embodiment. The above-described manufacturing method is not limited to the above-described example, and the order of each step may be changed within the possible range, or multiple steps may be performed in parallel. Furthermore, the material of the acidic polymer 2, the type, mixing ratio, and stirring speed of the mixed solvent to be added, the material of the basic polymer 3 and its solvent, and the molar ratio of the materials in the polymer mixed solution are merely examples and may be changed as appropriate.

[0062] Hereinafter, a sample of the proton-conductive electrolyte membrane 1 produced by the above-described production process will be referred to as "PSPA / i-PBI." Also, a sample of the proton-conductive electrolyte membrane 1 produced by the above-described production process using non-ionized PBI as the basic polymer 3 will be referred to as "PSPA / PBI."

[0063] The PSPA / i-PBI and PSPA / PBI obtained by the above-mentioned production method were measured by FT-IR to confirm the bonding state. As shown in FIG. 5, －１ A peak due to P—O stretching vibration is observed at the position of about 1048 cm －１At this position, a large peak is observed that is not observed in PSPA / PBI and is due to the ionic bond between the phosphonic acid group and the imidazole skeleton.

[0064] Examples and Comparative Examples Using PSPA as the acidic polymer 2 and i-PBI as the basic polymer 3, a circular PSPA / i-PBI having a diameter of 10 mm and a thickness of 0.1 mm was produced as Example 1 by the above-mentioned production method.

[0065] In addition, a circular PSPA / PBI film having a diameter of 10 mm and a thickness of 0.1 mm was prepared as Example 2 by the above-described manufacturing method using PSPA as the acidic polymer 2 and PBI as the basic polymer 3 .

[0066] On the other hand, as Comparative Example 1, only PSPA was subjected to a heat press similar to the molding process in Example 1 to prepare a circular sample having a diameter of 10 mm and a thickness of 0.1 mm.

[0067] The produced Examples 1 and 2 and Comparative Example 1 were subjected to a water resistance evaluation, which will be described later, and proton conductivity measurements were performed before and after the water resistance evaluation.

[0068] [Water Resistance Evaluation] Next, the water resistance evaluation will be described.

[0069] Various samples of the prepared proton-conductive electrolyte membrane were immersed in 20 ml of water in a sealed container, and the sealed container was left to stand in an incubator at 30°C for 2 hours. After that, the samples were removed from the sealed container and left to stand in an incubator at 60°C for 4 hours to dry. Hereinafter, this series of steps will be referred to as "water resistance test (A)." The weight of the sample was measured before and after the water resistance test (A), and the ratio of the weight after the water resistance test (A) to the weight before the water resistance test (A) was defined as the weight retention rate (%), and the weight retention rate was evaluated.

[0070] In Comparative Example 1, the film swelled at the time of the immersion step at 30° C. for 2 hours, and the film shape could not be maintained at all. In Comparative Example 1, in which the film was formed from PSPA alone, water resistance could not be ensured.

[0071] In Example 1, the weight before the water resistance test (A) was 22.3 mg, the weight after the water resistance test (A) was 21.5 mg, and the weight retention rate was 96.4%, indicating good water resistance. This result suggests that in the configuration of Example 1, due to the ionic bond between PSPA and i-PBI, most of the PSPA having hydrophilic phosphonic acid groups does not dissolve in water, and the weight and membrane shape are maintained.

[0072] Although Example 2 had poorer water resistance than Example 1, the weight before the water resistance test (A) was approximately 21.8 mg, the weight after the water resistance test (A) was approximately 15.9 mg, and the weight retention rate was approximately 72.9%, demonstrating improved water resistance compared to Comparative Example 1. This result, like Example 1, is due to the ionic bond between PSPA and PBI. The reason for the poorer water resistance than Example 1 is as follows: PBI does not have an ionized site, and therefore, in order to form an ionic bond, H must be bonded to the unsaturated N atom of the imidazole skeleton, resulting in ionization (protonation). However, this ionization is reversible and easily leads to deprotonation, resulting in less ion pair formation in Example 2 than in Example 1.

[0073] [Measurement of Proton Conductivity] A sample 10 of the produced proton-conducting electrolyte membrane 1 was set between the upper electrode 110 and the lower electrode 120 of an evaluation jig 100 shown in FIG. 6, for example, and a predetermined amplitude voltage and measurement frequency were set using a measuring instrument 200 to measure the proton conductivity σ expressed by the following formula (1).

[0074] σ=(1 / R)×(L / ((d / 2) ２ π)) ... (1)

[0075] In formula (1), R is the proton conduction resistance (Ω), L is the thickness (cm) of sample 10, and d is the diameter (cm) of the surface of sample 10 that comes into contact with evaluation jig 100. The measuring instrument 200 used was a potentio / galvanostat (VersaSTAT) manufactured by AMETEK Corporation. The proton conductivity measurement was performed with an amplitude voltage of ±20 mV and a measurement frequency of 0.1 to 1,000,000 Hz (10 points / decade).

[0076] The evaluation jig 100 has a structure in which, for example, carbon electrodes 110 and 120 have cylindrical protrusions 111 and 121 and plate portions 112 and 122, and the electrodes 110 and 120 can be fixed by fasteners 130 such as screws with the sample 10 sandwiched between the protrusions 111 and 121. The evaluation jig 100 has a structure in which the fasteners 130 are connected to connect the screw hole 113 of the upper electrode 110 and the screw hole 123 of the lower electrode 120 via, for example, a washer 131 made of an insulating material, so that they are not directly electrically connected. In the evaluation jig 100, the upper electrode 110 and the lower electrode 120 are connected to a measuring instrument 200 by wiring, and a sample setting portion consisting of the upper electrode 110, the lower electrode 120, the fasteners 130, and the washer 131 is placed in a constant temperature bath (not shown). This makes it possible to measure the electrical characteristics of the sample 10 in an environment of a predetermined temperature and humidity.

[0077] As shown in Figure 7, the proton conductivity of Example 1 under conditions of 20% RH and 120°C was 20 mS / cm before the water resistance test (A) and 7 mS / cm after the water resistance test (A). This result indicates that in a configuration in which the phosphonic acid group of the acidic polymer and the cationic group of the basic polymer are ionic bonded, the membrane shape is maintained due to improved water resistance, and good proton conductivity is maintained at the intermediate temperature range of 120°C. Furthermore, Example 1 showed roughly the same tendency as above in the intermediate temperature range of 100°C to 150°C.

[0078] In Example 2, the proton conductivity under conditions of a relative humidity of 20% RH and 120° C. was 20 mS / cm before the water resistance test (A) and 0.1 mS / cm after the water resistance test (A). Although Example 2 had a lower proton conductivity than Example 1, even after the water resistance test (A), it still exhibited proton conductivity at the same level as that described in Patent Document 1 (0.3 mS / cm).

[0079] Although not shown in FIG. 7, the proton conductivity of Comparative Example 1 under the conditions of a relative humidity of 20% RH and 120° C. was the highest result of 0.11 mS / cm before the water resistance test (A), but was not measurable after the water resistance test (A) because the membrane itself was dissolved.

[0080] Another possible comparative example is a structure (hereinafter referred to as "phosphate-PBI") in which a large number of phosphoric acids are bonded to the basic polymer PBI through acid-base interactions, as shown in Figure 8. However, the phosphate-PBI of the comparative example has a chemical structure in which, if some of the bonds between the phosphoric acid and PBI are broken by some chance, the individual phosphoric acids are independent, so that the phosphoric acid whose bond with the PBI is broken remains detached from the PBI. For this reason, it is difficult for the phosphate-PBI of the comparative example to maintain the interaction between the entire plurality of phosphoric acids and the PBI, and water resistance is not achieved.

[0081] On the other hand, Examples 1 and 2 have a chemical structure in which, even if one of the multiple bond sites between the phosphonic acid group of the acidic polymer 2 and the basic functional group of the basic polymer 3 breaks, the main chain of the acidic polymer 2 remains connected to the other bond sites. Therefore, Examples 1 and 2 are more likely to maintain the bond between the acidic polymer 2 and the basic polymer 3, ensuring better water resistance than the phosphoric acid-PBI of the comparative example. Furthermore, Example 1 forms an ion pair consisting of an acidic polymer 2 having a phosphonate anion and a basic polymer 3, which is an ionized organic cationic polymer that hardly ever returns to a deionized state. Therefore, Example 1 has a higher ion pair formation ability and ionic bond strength between the two polymers than Example 2, which forms an ion pair consisting of a similar acidic polymer 2 and a basic polymer 3 simply having a protonated basic functional group. In other words, Example 1 has a structure in which the acidic polymer 2 is less likely to peel off from the basic polymer 3 than Example 2. Therefore, Example 1 has better water resistance than Example 2.

[0082] Next, the ionization rate in i-PBI of the PSPA / i-PBI of Example 1 was changed, and the proton conductivity after the water resistance test (A) was measured, obtaining the results shown in Figures 9 and 10. Specifically, as shown in Figure 9, samples with ionization rates in i-PBI of 74% (No. 2), 91% (No. 1), and 94% (No. 3) were prepared, and the proton conductivity after the water resistance test (A) was measured.

[0083] The proton conductivities shown in FIGS. 9 to 11 were obtained by measurements in an environment at a relative humidity of 20% RH and a temperature of 120° C. The ionization rate is the proportion (%) of the basic functional groups of i-PBI that are cationized, and is 100% when all of the basic functional groups of the basic polymer 3 are cationized. The ionization rate in the proton-conducting electrolyte membrane 1 is not limited to the values ​​shown in FIGS. 9 and 10. For example, the ionization rate of the basic polymer 3 in the proton-conducting electrolyte membrane 1 may be 10% or more, 20% or more, 30% or more, 40% or more, or 50% or more, or may be 60% or more, 70% or more, 80% or more, or 90% or more.

[0084] In all of Samples No. 1 to No. 3 in Figure 9, the acidic functional group of the acidic polymer 2 (PSPA) is designated as A, and the basic functional group of the basic polymer 3 (i-PBI) is designated as B, with the molar ratio of their mixture being A / B = 90 mol%:10 mol%. Hereinafter, the molar ratio of the acidic functional groups of the acidic polymer 2 to the basic functional groups of the basic polymer 3 will be simply expressed as "A / B = X mol% / Y mol%" (X, Y: 0 to 100, X + Y = 100), as described above. The molar ratio of the acidic functional groups of the acidic polymer 2 to the basic functional groups of the basic polymer 3 can also be referred to as the "molar ratio of the acidic functional groups of the acidic polymer 2 to the basic functional groups of the basic polymer 3." Furthermore, the "acid group molar percentage" on the horizontal axis of Figure 11, which will be described later, corresponds to the molar ratio of the acidic functional groups of the acidic polymer 2 to the basic functional groups of the basic polymer 3. The acid group molar percentage in the proton-conducting electrolyte membrane 1 is not limited to only the values ​​shown in Figures 9 and 11. For example, the lower limit of the acid group molar percentage may be 10% or more, 20% or more, 30% or more, 40% or more, or 50% or more, or may be 60% or more, 70% or more, 80% or more, or 90% or more. The upper limit of the acid group molar percentage may be, for example, 99% or less, or may be 98% or less, 97% or less, 96% or less, or 95% or less.

[0085] The proton conductivities of Samples No. 1 to No. 3 in Example 1 after the water resistance test (A) were 7.2 mS / cm, 1.4 mS / cm, and 1.8 mS / cm, respectively. Furthermore, as shown in FIG. 10 , an approximate curve indicated by the dashed line was obtained by finite element analysis based on the plots of Samples No. 1 to No. 3 to determine the relationship between the ionization rate of the basic polymer 3 in Example 1 and the proton conductivity after the water resistance test (A). Considering the approximate curve based on the data of Samples No. 1 to No. 3, it is suggested that high proton conductivity can be achieved while ensuring water resistance in the medium temperature range as long as the ionization rate of the i-PBI in PSPA / i-PBI is at least within the range of 74% to 94%. Even if the ionization rate of the basic polymer 3 in PSPA / i-PBI is outside the above range, an ion pair consisting of the cationized acidic polymer 2 and the basic polymer 3 is formed, resulting in improved water resistance and proton conductivity compared to the acidic polymer 2 alone.

[0086] Furthermore, for the PSPA / i-PBI of Example 1, the compounding ratio of the acidic functional groups of PSPA to the basic functional groups of i-PBI, i.e., the mixing molar ratio, was changed, and the proton conductivity after the water resistance test (A) was measured. The results shown in FIG. 9 were obtained. Specifically, as shown in FIG. 9, Samples No. 4, No. 5, and No. 6 of Example 1 had A / B = 94 mol% / 6 mol%, A / B = 70 mol% / 30 mol%, and A / B = 50 mol% / 50 mol%, respectively. Samples No. 4, No. 5, and No. 6 had proton conductivities of 0.04 mS / cm, 1.2 mS / cm, and 0.09 mS / cm, respectively. Furthermore, as shown in FIG. 11, the relationship between the molar percentage of the acidic functional groups in Acidic Polymer 2 in Example 1 and the proton conductivity after the water resistance test (A) was observed for Sample No. The finite element method based on the data from four points, No. 3 to No. 6, yielded the approximate curve shown by the dashed line. These four points of data and the approximate curve suggest that high proton conductivity can be achieved while ensuring water resistance in the medium temperature range when the molar ratio of the acidic functional groups of PSPA to the basic functional groups of i-PBI in PSPA / i-PBI is within the range of 70% to 94%. Note that even if the molar ratio of the PSPA / i-PBI mixture is outside the above range, an ion pair consisting of a cationized acidic polymer 2 and a basic polymer 3 is formed, thereby achieving the effect of improving water resistance and proton conductivity compared to the acidic polymer 2 alone.

[0087] According to this embodiment, a proton-conducting electrolyte membrane 1 is provided, which includes an acidic polymer 2 having at least one saturated hydrocarbon group in its main chain and a phosphorus-atom-based oxo acid group in its side chain, and a basic polymer 3 having at least one aromatic ring and a basic functional group in its main chain. The proton-conducting electrolyte membrane 1 has a chemical structure in which the oxo acid group of the acidic polymer 2 interacts with the basic functional group of the basic polymer 3, thereby suppressing elution of the acidic polymer 2 even when exposed to water and ensuring water resistance. Furthermore, the proton-conducting electrolyte membrane 1 can maintain the interaction between the acidic polymer 2 and the basic polymer 3, thereby ensuring proton conductivity in the intermediate temperature range. This ensures both water resistance and proton conductivity in the intermediate temperature range. Thus, by using the proton-conducting electrolyte material according to this embodiment, it is possible to provide an electrolyte membrane that ensures both water resistance and proton conductivity in the intermediate temperature range in an electrochemical device requiring proton conduction.

[0088] (1) The proton-conducting electrolyte membrane 1 has an aromatic ring and an alkylene group (—(CH ２ ) ｚ -, z: 1 or more and 12 or less).

[0089] (2) The proton-conducting electrolyte membrane 1 has an imidazole skeleton in which the basic functional groups of the basic polymer 3 are arranged on the main chain.

[0090] (3) In the proton-conducting electrolyte membrane 1, the oxo acid of the acidic polymer 2 is a phosphonic acid group, and the basic functional group of the basic polymer 3 is a cationic group to which a hydrocarbon group has been added and which has been cationized, and the phosphonic acid group and the cationic group are ionic bonded. This strengthens the bond between the acidic polymer 2 and the basic polymer 3 in the proton-conducting electrolyte membrane 1, further improving water resistance. Examples of the cationic group include temporary cations such as a protonated imidazole skeleton, and an imidazole skeleton cationized by a quaternization reaction. From the viewpoint of improving water resistance, the basic polymer 3 preferably has a cationic group cationized by a quaternization reaction.

[0091] (4) The proton-conducting electrolyte membrane 1 has a basic polymer 3 in which the hydrocarbon group bonded to the basic functional group is —(CH ２ ) ｚ―１ -CH ３ (z: 1 or more and 12 or less), and has a halogen as a counter anion.

[0092] (5) A method for producing a proton-conducting electrolyte membrane 1 includes preparing a first polymer solution by dissolving an acidic polymer 2 in a solvent, preparing a second polymer solution by dissolving a basic polymer 3 in a solvent, and preparing a mixed solution by mixing the first and second polymer solutions. In preparing the first solution, an inhibitor is added to the solvent, which can inhibit rapid aggregation of the oxo acid groups and basic functional groups in the mixed solution, since the oxo acid groups and basic functional groups are ionized into monovalent cations and monovalent anions. The inhibitor temporarily binds to the cationic groups of the basic polymer 3, suppressing the neutralization reaction caused by the addition of the two acidic and basic polymer solutions. Furthermore, by slowly evaporating the inhibitor, stable ionic bonds are formed between the two polymers, enabling the production of a proton-conducting electrolyte membrane 1 that combines water resistance with proton conductivity in the medium temperature range.

[0093] (6) By constructing a fuel cell using the proton-conducting electrolyte membrane 1 described above, which has good water resistance while ensuring proton conductivity in the medium temperature range, the fuel cell can be used in the medium temperature range.

[0094] Second Embodiment Next, a proton conducting electrolyte membrane 1 according to a second embodiment will be described. In the proton conducting electrolyte membrane 1 according to this embodiment, as shown in FIG. 12, for example, an acidic polymer 2 has at least an aromatic ring and an alkylene group (—(CH ２ ) ｚ This embodiment differs from the first embodiment in that it has a structure having a spacer (-, z: 1 or more and 12 or less). This embodiment will mainly describe this difference. Note that the above "spacer" refers to a functional group that does not have chemical activity and is sandwiched between one functional group and another functional group. The same meaning applies to "spacer" hereinafter.

[0095] In this embodiment, the acidic polymer 2 has at least an aromatic ring and an alkylene group (—(CH ２ ) ｚ R8 in FIG. 12 is an alkylene group (-(CH ２ ) ｚ -, z: 1 or more and 12 or less). In the proton-conducting electrolyte membrane 1 of this embodiment, as shown in Fig. 13, the acidic polymer 2 is PsbPA, the basic polymer 3 is i-PBI, and the phosphonic acid group and the cationized imidazole skeleton of i-PBI form an ion pair. Hereinafter, the proton-conducting electrolyte membrane 1 of this embodiment shown in Fig. 13 will be referred to as "PsbPA / i-PBI."

[0096] For PsbPA / i-PBI, the ionization rate of i-PBI was fixed at 94%, and the compounding ratio, i.e., the mixing molar ratio A / B, was varied when the acidic functional group of PsbPA was A and the basic functional group of i-PBI was B. Various samples of the proton-conducting electrolyte membrane thus prepared were immersed in 20 ml of water in a sealed container, and the sealed container was left standing in an incubator at 60°C for 20 hours. The samples were then removed from the sealed container and left standing in an incubator at 60°C for 4 hours to dry. Hereinafter, this series of steps will be referred to as the "water resistance test (B)." The proton conductivity of these prepared samples was measured in an environment of 20% relative humidity and 120°C after the water resistance test (B), and the results shown in FIG. 14 were obtained.

[0097] Specifically, in the example shown in Figure 14, Samples No. 1, No. 2, No. 3, and No. 4 have A / B ratios of 94 mol% / 6 mol%, 90 mol% / 10 mol%, 80 mol% / 20 mol%, and 70 mol% / 30 mol%, respectively. Samples No. 1 to No. 4 had proton conductivities of 2.5 mS / cm, 7.9 mS / cm, 4.2 mS / cm, and 1.8 mS / cm, respectively, after the water resistance test (B).

[0098] When PsbPA was used as the acidic polymer 2, the relationship between the molar percentage of acidic functional groups in PsbPA and the proton conductivity after the water resistance test (B) was shown in Figure 15. Specifically, with the horizontal axis representing the molar percentage of acid groups (%) and the vertical axis representing the proton conductivity (mS / cm) after the water resistance test (B), an approximate curve was calculated using the finite element method based on the data for four samples No. 1 to No. 4, and the results shown by the dashed line in Figure 15 were obtained. These results suggest that when the ionization rate of i-PBI is 94% and the PsbPA / i-PBI blend molar ratio A / B is in the range of 70% to 94%, it is possible to ensure both water resistance and high proton conductivity in the medium temperature range.

[0099] Next, a method for producing the PsbPA / i-PBI proton-conducting electrolyte membrane 1 will be described. Unless otherwise specified in the following production steps, temperature control is not required in the step, and the step is carried out at room temperature, for example.

[0100] First, in step S210 shown in Figure 16, for example, PsbPA is prepared as the acidic polymer 2. 60 mg of PsbPA is weighed out and placed in a screw bottle, and DMSO is added dropwise to the screw bottle so that the total weight of the solution is 0.5 g. Next, for example, a stir bar is placed in the screw bottle containing the weighed PsbPA and DMSO, and the bottle is sealed with a lid. The mixture is then heated and stirred at 1500 rpm on a hot stirrer at 120°C for about half a day. After the PsbPA is completely dissolved, the mixture is returned to room temperature, yielding 0.5 g of a 12 wt% PsbPA DMSO solution as the acidic polymer solution.

[0101] In step S220, for example, i-PBI with an ionization rate of 94% is prepared as the basic polymer 3. 8 mg of i-PBI is weighed and placed in a screw bottle, and DMSO is added dropwise to the screw bottle so that the total solution weight becomes 0.07 g. The solution is then heated and stirred under the same conditions as in step S210. After the i-PBI is completely dissolved, the solution is returned to room temperature, yielding 0.07 g of a 12 wt % i-PBI DMSO solution. Then, 64 μg of 1.0 mol / L hydrochloric acid, which has been prepared in advance so that the molar ratio relative to the anionic group of i-PBI is 0.2, is added dropwise to the 12 wt % i-PBI DMSO solution, and the solution is stirred to obtain a basic polymer solution. This hydrochloric acid functions as an inhibitor, similar to the hydrochloric acid added during the preparation of the acidic polymer solution in the first embodiment.

[0102] Next, in step S230, for example, the 12 wt % PsbPA DMSO solution prepared in step S210 is stirred on a stirrer at 1500 rpm, and the 12 wt % i-PBI DMSO solution prepared in step S220 is added dropwise. Then, for example, one drop of ion-exchanged water, i.e., approximately 50 mg, is added dropwise to this mixed solution using a dropper. This ion-exchanged water serves to suppress the occurrence of aggregation between the acidic polymer and the basic polymer in the subsequent viscosity adjustment. Hereinafter, for ease of explanation, the solution obtained in step S230 will be simply referred to as the "polymer mixed solution."

[0103] Next, in step S240, for example, the lid of the screw bottle containing the polymer mixed solution is opened to leave it in an open state, and the solution is heated and stirred on a hot stirrer at 120°C at 1000 rpm for about 24 hours, and then returned to room temperature. The heating and stirring in step S240 is continued until the solids concentration reaches about 20 wt%, that is, until the polymer mixed solution reaches a viscosity range that allows it to be applied in the next step S250. In the above example, the heating and stirring is continued until the total weight of the solution reaches about 0.34 g.

[0104] Then, in step S250, the polymer mixed solution whose viscosity was adjusted in step S240 is applied using a desktop coater. Specifically, for example, a polyphenylene sulfide (PPS) sheet is prepared and attached to the glass plate of the desktop coater so that the water-repellent side of the PPS sheet becomes the coating surface. Next, for example, the coating surface of the PPS sheet is wiped and cleaned with ethanol, and the viscosity-adjusted polymer mixed solution is dripped onto it. If air bubbles are contained in the dripped polymer mixed solution, a degassing process is performed as appropriate, such as sucking up the air bubbles with a dropper and re-casting the sucked-up amount of polymer mixed solution. Then, for example, the gap between the coating surface of the PPS sheet and the wire bar of the desktop coater is adjusted to 200 μm, and the wire bar is moved at a speed of 9 mm / s to spread and coat the polymer mixed solution on the PPS sheet. The viscosity of the polymer mixed solution and the coating conditions of the desktop coater can be changed as appropriate.

[0105] Finally, in step S260, for example, the coated PPS sheet is pre-dried in the air for 6 hours, followed by a final drying step of 6 hours in a drying oven at 80°C. This stepwise drying step can prevent unintended rapid aggregation and separation of the acidic polymer and basic polymer on the PPS sheet. The membrane obtained by this drying step is then peeled off from the PPS sheet, producing the PsbPA / i-PBI proton-conducting electrolyte membrane 1.

[0106] The proton conducting electrolyte membrane 1 of this embodiment also provides the same effects as those of the first embodiment. In addition, the proton conducting electrolyte membrane 1 of this embodiment has an aromatic and alkylene group (-(CH ２ ) ｚ -, z: 1 or more and 12 or less) as a spacer, the effect of further improving water resistance can also be obtained.

[0107] A method for producing a proton-conducting electrolyte membrane 1 includes preparing a first polymer solution by dissolving an acidic polymer 2 in a solvent, preparing a second polymer solution by dissolving a basic polymer 3 in a solvent, and preparing a mixed solution by mixing the first and second polymer solutions. In preparing the second solution, an inhibitor capable of inhibiting rapid aggregation due to a reaction between the oxo acid groups of the acidic polymer 2 and the basic functional groups of the basic polymer 3 is added to the solvent. This allows the inhibitor to temporarily bind to the cationic groups of the basic polymer 3, suppressing the neutralization reaction caused by the addition of the two acidic and basic polymer solutions. This forms stable ionic bonds between the two polymers, making it possible to produce a proton-conducting electrolyte membrane 1 that is both water-resistant and has proton conductivity in the medium temperature range.

[0108] Third Embodiment Next, a proton conducting electrolyte membrane 1 according to a third embodiment will be described. In the proton conducting electrolyte membrane 1 according to this embodiment, as shown in FIG. 17, for example, an acidic polymer 2 has at least an aromatic ring and an alkylene group (—(CH ２ ) ｚ This embodiment differs from the first embodiment in that it has a structure having a hydroxyl group (-, z: 1 or more and 12 or less) and a plurality of oxo acid groups. In this embodiment, this difference will be mainly described.

[0109] In this embodiment, the acidic polymer 2 has at least an aromatic ring and an alkylene group (—(CH ２ ) ｚ The acidic polymer 2 has a structure having a side chain alkylene group (-(CH ２ ) ｚThe acidic polymer 2 has multiple oxo acid groups at the end of a hydrocarbon group to which a cation group (-, z: 1 to 12) and a methine group (>CH-) are bonded, and at least one oxo acid group forms an ion pair with a cationic group of the basic polymer. The subscript o (o) indicating the number of oxo acid groups in the acidic polymer 2 in Figure 17 is either 1 or 2. When o is 1, the total number of oxo acid groups per side chain containing an aromatic ring or an alkylene group is 2, and when o is 2, the total number of oxo acid groups is 3. The acidic polymer 2 is, for example, poly(8-(p-styryl)-1-octanediphosphonic acid) represented by the following chemical formula. Hereinafter, for ease of explanation, poly(4-(p-styryl)-1,1-octanediphosphonic acid) will be referred to simply as "PsodPA."

[0110] PsodPA can be synthesized, for example, by the following procedure. A phosphonate ester monomer is synthesized in a manner substantially similar to that described in a patent document (Publication No. WO / 2023 / 120731), except that 1,8-dibromooctane is used instead of 1,4-dibromobutane. Furthermore, a second phosphonate ester is introduced into the above phosphonate ester monomer with reference to the literature (Tetrahedron 2009, 65, 7498-7503 and Polym. Int. 2013, 62, 1717-1728). The resulting monomer is then polymerized and deprotected to synthesize PsodPA.

[0111] In this embodiment, the basic polymer 3 has two cationic groups cationized in the monomer unit, and these cationic groups form ion pairs with the oxo acid groups in the side chains of the acidic polymer 2. Note that R9 of the basic polymer 3 in FIG. 17 is an alkylene group (—(CH ２ ) ｚ -, z: 1 or more and 12 or less) and a methine group (>CH-).

[0112] As shown in Fig. 18, the proton-conducting electrolyte membrane 1 of this embodiment has PsodPA as the acidic polymer 2 and i-PBI as the basic polymer 3. Hereinafter, the proton-conducting electrolyte membrane 1 of this embodiment shown in Fig. 18 will be referred to as "PsodPA / i-PBI." PsodPA / i-PBI has a structure in which two cationized imidazole skeletons in the monomer of the basic polymer 3 and phosphonic acid groups in two monomers of the acidic polymer 2 are ionic-bonded.

[0113] For PsodPA / i-PBI, the ionization rate in i-PBI was fixed at 94%, and a plurality of samples were prepared by varying the compounding ratio, i.e., the mixing molar ratio A / B, where A is the acidic functional group of PsodPA and B is the basic functional group of i-PBI. Then, for these prepared samples, the proton conductivity was measured in an environment of a relative humidity of 20% RH and a temperature of 120°C after the water resistance test (B) described above, and the results shown in FIG. 19 were obtained.

[0114] Specifically, in the example shown in Figure 19, Samples No. 1, No. 2, No. 3, and No. 4 have A / B = 99 mol% / 1 mol%, A / B = 95 mol% / 5 mol%, A / B = 90 mol% / 10 mol%, and A / B = 85 mol% / 15 mol%, respectively. Samples No. 1 to No. 4 had proton conductivities of 3.2 mS / cm, 8.0 mS / cm, 19.2 mS / cm, and 7.4 mS / cm after the water resistance test (B), respectively, which are further improved compared to the first and second embodiments. This high proton conductivity is due to the fact that PsodPA has two phosphonic acid groups per monomer unit, and H ＋ The carrier density was improved, and the H ＋ This is thought to be due to the fact that the energy required for carrier exchange is reduced.

[0115] When PsodPA was used as the acidic polymer 2, the relationship between the molar percentage of acidic functional groups in PsodPA and the proton conductivity after the water resistance test (B) was shown in Figure 20. Specifically, with the horizontal axis representing the molar percentage of acid groups (%) and the vertical axis representing the proton conductivity (mS / cm) after the water resistance test (B), an approximate curve was calculated by the finite element method based on the data for four samples No. 1 to No. 4, and the results shown by the dashed line in Figure 20 were obtained. This result suggests that when the ionization rate of i-PBI is 94% and the PsodPA / i-PBI blend molar ratio A / B is at least in the range of 85% to 99%, it is possible to ensure both water resistance and high proton conductivity in the medium temperature range.

[0116] Next, a method for producing the PsodPA / i-PBI proton-conducting electrolyte membrane 1 will be described. Unless otherwise specified in the following production steps, temperature control is not required in the step, and the step is carried out at room temperature, for example.

[0117] First, in step S310 shown in FIG. 21 , for example, PsodPA is prepared as the acidic polymer 2, and lithium hydroxide (LiOH) is prepared as an inhibitor to suppress aggregation due to the reaction between the acidic polymer 2 and the basic polymer 3. LiOH is mixed in an equimolar ratio relative to the molar amount of phosphonic acid groups in the prepared PsodPA. Next, DMSO is prepared as a solvent, and an appropriate amount is weighed out to a weight ratio of PsodPA:DMSO = 8:92 and placed in a screw bottle. DMSO is then added dropwise to the screw bottle so that the total weight of the solution is 0.5 g. Next, for example, a stirrer is placed in the screw bottle containing the weighed PsodPA and DMSO, and the lid is closed and sealed. The mixture is then heated and stirred at 1500 rpm on a hot stirrer at 120 °C for approximately half a day. After the PsodPA is completely dissolved, the mixture is returned to room temperature to obtain an 8 wt % PsodPA DMSO solution as an acidic polymer solution.

[0118] At this time, in PsodPA, H in some of the OH groups of the phosphonic acid groups is substituted with Li by LiOH, and no more ionic bonds than necessary are formed from the time of mixing with i-PBI until film formation.

[0119] In step S320, for example, i-PBI with an ionization rate of 94% is prepared as the basic polymer 3, and DMSO is prepared as the solvent, and appropriate amounts are weighed out so that the weight ratio of i-PBI:DMSO is 12:88 and placed in a screw bottle. Then, the mixture is heated and stirred under the same conditions as in step S310, and after the i-PBI is completely dissolved, the mixture is returned to room temperature, thereby obtaining a 12 wt % i-PBI DMSO solution.

[0120] Next, in step S330, for example, the 8 wt% PsodPA DMSO solution prepared in step S310 is stirred on a stirrer at 1000 rpm, and the 12 wt% i-PBI DMSO solution prepared in step S320 is added dropwise. The 12 wt% i-PBI DMSO solution is added dropwise until the molar ratio of phosphonic acid groups in the acidic polymer solution to cationized imidazole skeletons in the basic polymer solution reaches 90:10. Then, for example, one drop of ion-exchanged water, i.e., approximately 50 mg, is added dropwise to this mixed solution using a dropper. This ion-exchanged water, as in the second embodiment, serves to suppress rapid aggregation due to the reaction between PsodPA and i-PBI. Hereinafter, for ease of explanation, the solution obtained in step S330 will be simply referred to as the "polymer mixed solution."

[0121] Next, in step S340, for example, the polymer mixed solution is transferred from a screw bottle containing the polymer mixed solution to a PP (polypropylene) container, and the container is left in an open state with the lid opened in a dryer set at 80°C for about 24 hours. This dries the mixed polymer and turns it into a film. Hereinafter, the mixed polymer filmed by this process will be simply referred to as a "film-formed polymer."

[0122] Then, in step S350, for example, 1.0 mol / L hydrochloric acid is prepared and heated to 60° C., and the membrane-forming polymer is immersed in the hydrochloric acid for 1 hour. In this process, Li substituted for the phosphonic acid group in PsodPA in the membrane-forming polymer is replaced with H by HCl, and PsodPA and i-PBI form an ionic bond.

[0123] Next, in step S360, pure water at 60°C is prepared, the membrane-forming polymer is removed from the hydrochloric acid, and the membrane-forming polymer is immersed in the pure water for 1 hour. In this washing process, the HCl and LiOH remaining in the membrane-forming polymer dissolve in the water and are removed from the membrane-forming polymer, while the PsodPA and i-PBI remain in the membrane-forming state because they are ionic bonds.

[0124] Finally, in step S370, the membrane-forming polymer is removed from the pure water and left to stand for about 1 hour in a dryer set at 60° C. This removes water from the membrane-forming polymer, and a proton-conducting electrolyte membrane 1 of PsodPA / i-PBI can be obtained.

[0125] The proton-conducting electrolyte membrane 1 of this embodiment also has the same effects as those of the first embodiment. The proton-conducting electrolyte membrane 1 of this embodiment has a plurality of oxo acid groups in the side chains of the acidic polymer 2, and thus has the effect of further improving water resistance.

[0126] The method for producing the proton-conducting electrolyte membrane 1 includes preparing a first polymer solution by dissolving an acidic polymer 2 in a solvent, preparing a second polymer solution by dissolving a basic polymer 3 in a solvent, and preparing a mixed solution by mixing the first and second polymer solutions. In preparing the first solution, an inhibitor is added to replace the H of the OH group in the oxo acid group in the side chain of the acidic polymer 2 with Li, thereby masking the H. This prevents rapid aggregation due to a reaction between the oxo acid group of the acidic polymer 2 and the basic functional group of the basic polymer 3 during the period from mixing the acidic polymer 2 with the basic polymer 3 to forming a membrane. After membrane formation, the inhibitor is removed, forming stable ionic bonds between the two polymers, enabling the production of a proton-conducting electrolyte membrane 1 that combines water resistance with proton conductivity in the medium temperature range.

[0127] (Other Embodiments) While the present disclosure has been described with reference to examples, it is understood that the present disclosure is not limited to those examples or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one, or less than one, are also within the scope and spirit of the present disclosure.

[0128] It goes without saying that in each of the above embodiments, the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle. Furthermore, in each of the above embodiments, when numerical values ​​such as the number, values, amounts, and ranges of the components of the embodiments are mentioned, they are not limited to the specific numbers unless they are specifically stated as essential or are clearly limited to a specific number in principle. Furthermore, in each of the above embodiments, when the shapes, positional relationships, etc. of the components are mentioned, they are not limited to the shapes, positional relationships, etc., unless they are specifically stated or are clearly limited to a specific shape, positional relationship, etc. in principle.

[0129] (Aspects of the present disclosure) The above-described present disclosure can be understood from the following aspects, for example. [First aspect] A proton-conducting electrolyte material comprising: -PO ｘ (OH) ｙ A proton-conducting electrolyte material comprising: an acidic polymer (2) containing an oxo acid group having a phosphorus atom represented by (x, y: 1 or more) and at least one saturated hydrocarbon group in the main chain; and a basic polymer (3) containing a basic functional group and at least one aromatic ring in the main chain, the proton-conducting electrolyte material having a chemical structure in which attractive interaction occurs between the oxo acid group and the basic functional group. [Second Aspect] The acidic polymer has an aromatic ring and an alkylene group (—(CH ２ ) ｚ[Third Aspect] The proton-conducting electrolyte material according to the first or second aspect, wherein the basic polymer has an imidazole skeleton in its main chain. [Fourth Aspect] The oxo acid group is —PO ｘ (OH) ｙ － (x, y: 1 or more), the basic functional group is a cationic group to which a hydrocarbon group is added and which is cationized, and the phosphonic acid group and the cationic group are ionic bonded. [Fifth Aspect] The proton-conducting electrolyte material according to any one of the first to third aspects, ２ ) ｚ The proton-conducting electrolyte material according to the fourth aspect, wherein the acidic polymer has at least two —PO ｘ (OH) ｙ － (x, y: 1 or more) and an aromatic ring and an alkylene group (—(CH ２ )—, z: 1 or more and 12 or less). ２ ) ｚ－１ -CH ３ (z: 1 or more and 12 or less), and has a halogen as a counter anion. ｘ (OH) ｙA method for producing a proton-conducting electrolyte material having an acidic polymer (2) containing an oxo acid group having a phosphorus atom and at least one saturated hydrocarbon group in its main chain, and a basic polymer (3) containing a basic functional group and at least one aromatic ring in its main chain, the method comprising: preparing a first solution from the acidic polymer and a mixed solvent; preparing a second solution by dissolving the basic polymer in a solvent; and preparing a mixed solution by mixing the first solution and the second solution, wherein in preparing the first solution, a mixed solvent is prepared containing an inhibitor that ionizes into monovalent cations and monovalent anions in the mixed solution and can inhibit rapid aggregation of the oxo acid group and the basic functional group. [Ninth Aspect] -PO ｘ (OH) ｙ (x, y: 1 or more) and at least one saturated hydrocarbon group in the main chain, and an aromatic ring and an alkylene group (-(CH ２ ) ｚ a basic polymer (3) having a main chain containing at least one aromatic ring and a cationic group cationized by adding a hydrocarbon group to a basic functional group, the basic polymer (3) comprising an acidic polymer (2) and a basic polymer (3) having at least one aromatic ring in a main chain, the method comprising: dissolving the acidic polymer in a solvent to prepare a first solution; dissolving the basic polymer in a solvent to prepare a second solution; and mixing the first solution and the second solution to prepare a mixed solution, wherein in preparing the first solution or the second solution, an inhibitor capable of inhibiting rapid aggregation due to reaction between the oxo acid group and the cationic group in the mixed solution is added to the first solution or the second solution. [Tenth Aspect] A fuel cell comprising: -PO ｘ (OH) ｙA fuel cell comprising: a proton-conducting electrolyte material having an acidic polymer (2) containing a phosphorus-containing oxoacid represented by (x, y: 1 or more) and at least one saturated hydrocarbon group in its main chain; and a basic polymer (3) containing a basic functional group and at least one aromatic ring in its main chain, wherein the proton-conducting electrolyte material has a chemical structure that generates an attractive interaction between the oxoacid and the basic functional group.

Claims

1. A proton-conducting electrolyte material comprising: -PO ｘ (OH) ｙ A proton-conducting electrolyte material comprising: an acidic polymer (2) containing an oxo acid group having a phosphorus atom and represented by (x, y: 1 or more) and at least one saturated hydrocarbon group in its main chain; and a basic polymer (3) containing a basic functional group and at least one aromatic ring in its main chain, the proton-conducting electrolyte material having a chemical structure in which attractive interaction occurs between the oxo acid group and the basic functional group.

2. The acidic polymer has an aromatic ring and an alkylene group (—(CH ２ ) ｚ 2. The proton-conducting electrolyte material according to claim 1, wherein the proton-conducting electrolyte material has at least one of the following: -, z: 1 or more and 12 or less.

3. The proton-conducting electrolyte material according to claim 1, wherein the basic polymer has an imidazole skeleton in the main chain.

4. The oxo acid group is -PO ｘ (OH) ｙ － (x, y: 1 or more), the basic functional group is a cationic group to which a hydrocarbon group is added and which is cationized, and the phosphonic acid group and the cationic group are ionic bonded to each other.

5. The acidic polymer has an aromatic ring and an alkylene group (—(CH ２ ) ｚ 5. The proton-conducting electrolyte material according to claim 4, wherein z is 0 or more and z is 1 or more and 12 or less.

6. The acidic polymer has at least two -PO ｘ (OH) ｙ － (x, y: 1 or more) and an aromatic ring and an alkylene group (—(CH ２ ) ｚ 5. The proton-conducting electrolyte material according to claim 4, wherein z is 0 or more and z is 1 or more and 12 or less.

7. The basic polymer is such that the hydrocarbon group is -(CH ２ ) ｚ－１ -CH ３ 5. The proton-conducting electrolyte material according to claim 4, wherein the alkyl group is represented by the formula (z: 1 or more and 12 or less), and the alkyl group has a halogen as a counter anion.

8. -PO ｘ (OH) ｙ 1. A method for producing a proton-conducting electrolyte material comprising: an acidic polymer (2) containing an oxo acid group having a phosphorus atom and at least one saturated hydrocarbon group in its main chain, and a basic polymer (3) containing a basic functional group and at least one aromatic ring in its main chain, the method comprising: preparing a first solution from the acidic polymer and a mixed solvent; preparing a second solution by dissolving the basic polymer in a solvent; and preparing a mixed solution by mixing the first solution and the second solution, wherein in preparing the first solution, a mixed solvent is prepared containing an inhibitor that ionizes into monovalent cations and monovalent anions in the mixed solution and can inhibit rapid aggregation of the oxo acid group and the basic functional group. 9.―PO ｘ (OH) ｙ (x, y: 1 or more) and at least one saturated hydrocarbon group in the main chain, and an aromatic ring and an alkylene group (-(CH ２ ) ｚ 1. A method for producing a proton-conducting electrolyte material having an acidic polymer (2) containing both an oxo acid group and an oxo group (x, z: 1 or more and 12 or less), and a basic polymer (3) containing a cationic group cationized by adding a hydrocarbon group to a basic functional group, and at least one aromatic ring in its main chain, the method comprising: preparing a first solution by dissolving the acidic polymer in a solvent; preparing a second solution by dissolving the basic polymer in a solvent; and preparing a mixed solution by mixing the first solution and the second solution, wherein in preparing the first solution or the second solution, an inhibitor capable of inhibiting rapid aggregation due to reaction between the oxo acid group and the cationic group in the mixed solution is added to the first solution or the second solution.

10. A fuel cell comprising: -PO ｘ (OH) ｙ A fuel cell comprising: a proton-conducting electrolyte material having an acidic polymer (2) containing an oxo acid group having a phosphorus atom and represented by (x, y: 1 or more) and at least one saturated hydrocarbon group in its main chain; and a basic polymer (3) containing a basic functional group and at least one aromatic ring in its main chain, wherein the proton-conducting electrolyte material has a chemical structure in which an attractive interaction occurs between the oxo acid group and the basic functional group.

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