Polymer electrolyte membrane, film electrode assembly, redox flow battery cell, redox flow battery, and wound body

Abstract

To provide a polymer electrolyte membrane which yields a redox flow battery cell having current efficiency and voltage efficiency in a good balance, and having high power efficiency; a film electrode assembly; a redox flow battery cell; a redox flow battery; and a wound body.SOLUTION: A polymer electrolyte membrane comprises a nitrogen-containing fluoropolymer or a salt thereof containing a unit expressed by [CF2-CF(-(OCF2CXF)a-O-(CF2)b-SO2-NH-R1-(NR2-R3-)c-NR4R5)] (where a is 0 to 2, b is 1 to 4, c is 0 to 2, X is -F or -CF3, R1 and R3 are a divalent aliphatic hydrocarbon group of C1 to 10 or a divalent aromatic hydrocarbon group of C6 to 12, R2 is H, a monovalent aliphatic hydrocarbon group of C1 to 10, or a monovalent aromatic hydrocarbon group of C6 to 12, and R4 and R5 are H, a monovalent aliphatic hydrocarbon group of C1 to 10, or a monovalent aromatic hydrocarbon group of C6 to 10), and a structure unit expressed by [CFX-CF2] (where X is -F or -CF3), and has a mass per unit area of 100 g / m2 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a polymer electrolyte membrane, a membrane electrode assembly, a cell for a redox flow battery, a redox flow battery, and a wound body. [Background technology]

[0002] A redox flow battery is a secondary battery that stores and discharges electricity. A redox flow battery has a structure in which a positive electrode electrolyte (positive electrode cell) containing a positive electrode and a positive electrode redox active material and a negative electrode electrolyte (negative electrode cell) containing a negative electrode and a negative electrode redox active material are separated by a diaphragm, and charging and discharging are performed by utilizing the oxidation-reduction reaction of both redox active materials. A large capacity can be achieved by distributing the electrolyte containing both redox active materials from a storage tank to an electrolytic cell.

[0003] Examples of redox active materials contained in the electrolyte include iron / chromium, chromium / bromine, zinc / bromine, and vanadium, which utilizes the difference in electric charge. In particular, vanadium-based redox flow batteries have the advantages of high electromotive force, fast electrode reaction of vanadium ions, low amount of hydrogen generated as a side reaction, and high output, and therefore their development is being actively pursued. In vanadium-based redox flow batteries, the divalent (V 2+ ) / 3V(V 3+ ) and the tetravalent (V 4+ ) / 5V(V 5+ ) oxidation-reduction reaction. If the redox active material passes through, the stored charge is neutralized and the current efficiency decreases, so it is desirable for the membrane to suppress the permeation of the redox active material as much as possible. In order to suppress the permeation of the redox active material and achieve high power efficiency, a polymer electrolyte membrane is used.

[0004] Patent Document 1 discloses that by alternately laminating cation-exchange base layers and anion-exchange base layers, the initial power efficiency is excellent.

[0005] Patent Document 2 discloses that the use of a membrane containing a sulfonated polymer and a heterocyclic molecule containing multiple nitrogen atoms results in low proton area specificity and excellent vanadium ion permeation selectivity.

[0006] Patent Document 3 discloses that the use of a polymer electrolyte membrane having an internal crossover prevention layer, which is a metal layer formed by reducing a cationic metal, results in excellent discharge capacity, current efficiency, voltage efficiency, and power efficiency.

[0007] Patent Document 4 discloses that by using a redox flow battery membrane including a first ion exchange resin layer, an anion exchange resin layer containing an anion exchange compound, and a second ion exchange resin layer in this order, curling is suppressed and power efficiency is excellent.

[0008] In producing the above-mentioned membrane, there is a technique for preparing a polymer solution and forming the membrane. For example, Patent Document 5 discloses a 5% by mass solution of a fluororesin having acidic groups dissolved in a solvent having a mass ratio of ethanol and water of 50:50. Patent Document 6 discloses that a thin film having high strength, good adhesion to a substrate, and good chemical resistance can be obtained by using a polymer electrolyte solution in which a fluororesin having acidic groups is dissolved in a solvent containing a hydrophilic, high-boiling-point polar solvent.

[0009] On the other hand, there is a technique for producing the above-mentioned membrane by co-extrusion of two kinds of polymers to form a membrane. For example, Patent Document 7 discloses that by co-extruding a perfluorosulfonic acid polymer precursor with an incompatible polymer, a multilayer film having a perfluorosulfonic acid polymer precursor layer with reduced thickness supported on an incompatible polymer layer can be formed, and a proton exchange membrane with reduced thickness can be obtained. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 11-260390 [Patent Document 2] International Patent Publication No. 2017 / 155648 [Patent Document 3] International Patent Publication No. 2016 / 163773 [Patent Document 4] International Patent Publication No. 2021 / 215126 [Patent Document 5] Japanese Patent Application Publication No. 07-296634 [Patent Document 6] JP 2004-164854 A [Patent Document 7] International Patent Publication No. 2013 / 091073 Summary of the Invention [Problem to be solved by the invention]

[0011] It is expected that excellent battery characteristics can be obtained by making the polymer electrolyte membrane thinner. According to the techniques disclosed in Patent Documents 5 and 6, in order to dissolve in a solvent, an acidic group is introduced into the molecular structure of the polymer, so there are limitations on the molecular structure of the polymer. It was found that nitrogen-containing fluoropolymers having amino groups and sulfonamide moieties have low solubility in solvents and it is difficult to prepare a coating solution. As shown in Patent Document 7, it has been difficult to obtain a thin film by the technique of forming a film by co-extrusion of two types of polymers.

[0012] Therefore, an object of the present invention is to provide a polymer electrolyte membrane, a membrane electrode assembly, a cell for a redox flow battery, a redox flow battery, and a wound body, which can provide a cell for a redox battery having a well-balanced excellent current efficiency and voltage efficiency and high power efficiency. [Means for solving the problem]

[0013] The present inventors have found that the above-mentioned problems can be solved by setting the mass per unit area of ​​the nitrogen-containing fluoropolymer membrane within a specific range.

[0014] Embodiments of the present invention include the following aspects. <1> The present invention includes a nitrogen-containing fluoropolymer membrane containing a nitrogen-containing fluoropolymer or a salt thereof, the nitrogen-containing fluoropolymer comprising a structural unit represented by the following formula (1-1) and a structural unit represented by the following formula (1-2): The mass per unit area of ​​the nitrogen-containing fluoropolymer is 100 g / m 2 The polymer electrolyte membrane is as follows: -[CF2-CF(-(OCF2CXF) a -O-(CF2) b -SO2-NH-R 1 -(NR 2 -R 3 -) c -NR 4 R 5 )]-...Formula (1-1) (In the formula, a is an integer between 0 and 2, b is an integer between 1 and 4, c is an integer between 0 and 2, X is -F or -CF3; R 1 and R 3 may be the same or different, and each represents a substituted or unsubstituted divalent aliphatic hydrocarbon group having from 1 to 10 carbon atoms, or a substituted or unsubstituted divalent aromatic hydrocarbon group having from 6 to 12 carbon atoms, R 2 is a hydrogen atom, a substituted or unsubstituted monovalent aliphatic hydrocarbon group having from 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having from 6 to 12 carbon atoms, R 4 and R 5 may be the same or different and are a hydrogen atom, a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms. -[CFX-CF2]-...Formula (1-2) (In the formula, X is -F or -CF3.) <2> In the nitrogen-containing fluoropolymer, the ratio of the structural unit represented by the formula (1-1) is 1 mol % or more and 50 mol % or less based on the total monomer units, and the ratio of the structural unit represented by the formula (1-2) is 50 mol % or more and 99 mol % or less based on the total monomer units. <1> The polymer electrolyte membrane according to claim 1. <3> The nitrogen-containing fluoropolymer membrane; At least one porous material layer is laminated on each of the substrate and the substrate. <1> or <2> The polymer electrolyte membrane according to claim 1. <4> The porosity of the porous material layer is 40% or more and 90% or less. <3> The polymer electrolyte membrane according to claim 1. <5> <1> ~ <4> 2. A membrane electrode assembly comprising the polymer electrolyte membrane according to claim 1 and at least one electrode joined together. <6> For redox flow batteries, <1> ~ <4> 2. The polymer electrolyte membrane according to claim 1 . <7> For redox flow batteries, <5> The membrane electrode assembly according to claim 1 . <8> The present invention relates to a battery comprising a first electrolyte solution including a first redox active material, a second electrolyte solution including a second redox active material, a first electrode in contact with the first electrolyte solution, a second electrode in contact with the second electrolyte solution, and a diaphragm disposed between the first electrolyte solution and the second electrolyte solution, the diaphragm being: <1> ~ <4> 2. A cell for a redox flow battery, comprising the polymer electrolyte membrane according to claim 1. <9> The first electrolytic solution and the second electrolytic solution are acidic. <8> The cell for a redox flow battery according to claim 1. <10> The first electrolytic solution and the second electrolytic solution are in contact with the nitrogen-containing fluoropolymer membrane in the polymer electrolyte membrane; <9> The cell for a redox flow battery according to claim 1. <11> The membrane is joined to at least one electrode. <8> ~ <10> 2. The cell for a redox flow battery according to claim 1 . <12> At least one selected from the group consisting of the first electrode and the second electrode is a carbon electrode. <8> ~ <11> 2. The cell for a redox flow battery according to claim 1 . <13> At least one selected from the group consisting of the first redox active material and the second redox active material is at least one selected from the group consisting of a metal-based redox active material, a non-metal-based redox active material, and an organic redox active material; <8> ~ <12> 2. The cell for a redox flow battery according to claim 1 . <14> <8> ~ <13> 13. A redox flow battery comprising a redox flow battery cell according to any one of claims 1 to 12, wherein the redox flow battery cell is a laminate. <15> <1> ~ <4> 2. A rolled body obtained by rolling the polymer electrolyte membrane according to claim 1. <16> The width of the polymer electrolyte membrane is 50 mm or more and 5,000 mm or less. <15> The wound body according to claim 1. <17> The length of the polymer electrolyte membrane is 100 mm or more. <15> or <16> The wound body according to claim 1. Effect of the Invention

[0015] According to the present invention, it is possible to provide a polymer electrolyte membrane, a membrane electrode assembly, a cell for a redox flow battery, a redox flow battery, and a wound body, which can provide a cell for a redox battery having a well-balanced excellent current efficiency and voltage efficiency and high power efficiency. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing an example of a cell for a redox flow battery. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Below, we will explain in detail the form for implementing the present invention (hereinafter referred to as the "present embodiment"). However, the present invention is not limited to the following description and can be implemented in various modifications within the scope of its gist.

[0018] A numerical range indicated using "~" indicates a range including the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range of a certain stage can be arbitrarily combined with the upper limit or lower limit of a numerical range of another stage.

[0019] The "liquid composition" may be either a solution or a dispersion, but is preferably a solution.

[0020] In this embodiment, The present invention includes a nitrogen-containing fluoropolymer membrane containing a nitrogen-containing fluoropolymer or a salt thereof, the nitrogen-containing fluoropolymer comprising a structural unit represented by the following formula (1-1) and a structural unit represented by the following formula (1-2): The mass per unit area of ​​the nitrogen-containing fluoropolymer is 100 g / m 2 The present invention relates to a polymer electrolyte membrane comprising: -[CF2-CF(-(OCF2CXF) a -O-(CF2) b -SO2-NH-R 1 -(NR 2 -R 3 -) c -NR 4 R 5 )]-...Formula (1-1) (In the formula, a is an integer between 0 and 2, b is an integer between 1 and 4, c is an integer between 0 and 2, X is -F or -CF3; R 1 and R 3may be the same or different, and each represents a substituted or unsubstituted divalent aliphatic hydrocarbon group having from 1 to 10 carbon atoms, or a substituted or unsubstituted divalent aromatic hydrocarbon group having from 6 to 12 carbon atoms, R 2 is a hydrogen atom, a substituted or unsubstituted monovalent aliphatic hydrocarbon group having from 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having from 6 to 12 carbon atoms, R 4 and R 5 may be the same or different and are a hydrogen atom, a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms. -[CFX-CF2]-...Formula (1-2) (In the formula, X is -F or -CF3.) According to the present embodiment, it is possible to provide a polymer electrolyte membrane, a membrane electrode assembly, a cell for a redox flow battery, a redox flow battery, and a wound body, which can provide a cell for a redox battery having a well-balanced excellent current efficiency and voltage efficiency and high power efficiency.

[0021] In the nitrogen-containing fluoropolymer, the following moiety in the structural unit represented by formula (1-1) can undergo a morphological change in a liquid as shown below. [ka] (wherein * is a binding site, A - is an anion species, and C + is a cationic species.) That is, under acidic conditions, the terminal amine is protonated and the resin acts as an anion exchange resin, whereas under basic conditions, the terminal amine salt is deprotonated and the resin acts as a cation exchange resin. When the polymer electrolyte membrane according to the present embodiment is used as a separator in a redox flow battery, the nitrogen-containing fluoropolymer is placed under acidic conditions when it comes into contact with the negative electrode electrolyte, so that the negative electrode electrolyte V 3+ , V 2+During charging and discharging, the positive electrode side does not allow cations such as SO4 - to the negative electrode side, and the membrane as a whole functions as an anion exchange resin. In addition, by setting the mass per unit area of ​​the nitrogen-containing fluoropolymer membrane within a predetermined range, the nitrogen-containing fluoropolymer membrane can be formed thin, which is thought to reduce the resistance between the electrodes and result in excellent battery performance. As described above, the polymer electrolyte membrane according to this embodiment has the above-mentioned properties, and therefore, when used as a diaphragm of a redox flow cell, it can exhibit excellent battery performance.

[0022] [Polymer electrolyte membrane] The polymer electrolyte membrane according to this embodiment includes a nitrogen-containing fluoropolymer membrane that includes a nitrogen-containing fluoropolymer containing a structural unit represented by formula (1-1) and a structural unit represented by formula (1-2) or a salt thereof. Furthermore, the polymer electrolyte membrane according to this embodiment may be a single layer of nitrogen-containing fluoropolymer membrane, or may be a laminate comprising at least one nitrogen-containing fluoropolymer membrane (hereinafter also referred to as "layer L1" when made into a laminate) and at least one porous material layer (hereinafter also referred to as "layer S1").

[0023] (Nitrogen-containing fluoropolymer membrane) The mass per unit area of ​​the nitrogen-containing fluoropolymer membrane is 100 g / m 2 Within this range, a polymer electrolyte membrane having an excellent balance between current efficiency and voltage efficiency, i.e., excellent power efficiency, can be obtained. The mass per unit area of ​​the nitrogen-containing fluoropolymer membrane is preferably 100 g / m or less. 2 0.1g / m or less 2 More preferably, it is 50 g / m 2 Less than 0.2g / m 2 More preferably, it is 25 g / m 2 Less than 0.5g / m 2 That's all.

[0024] The nitrogen-containing fluoropolymer membrane contains a nitrogen-containing fluoropolymer or a salt thereof that contains a structural unit represented by formula (1-1) and a structural unit represented by formula (1-2) (hereinafter also referred to as nitrogen-containing fluoropolymer (1)).

[0025] -[CF2-CF(-(OCF2CXF) a -O-(CF2) b -SO2-NH-R 1 -(NR 2 -R 3 -) c -NR 4 R 5 )]-...Formula (1-1)

[0026] -[CFX―CF2]-...Formula (1-2)

[0027] -[CF2-CF(-(OCF2CXF) a -O-(CF2) b -SO3H)]-...Formula (1-3)

[0028] In the nitrogen-containing fluoropolymer, the following moiety in the structural unit represented by formula (1-1) can undergo a morphological change in a liquid as shown below. [ka] (wherein * is a binding site, A - is an anion species, and C + is a cationic species.) In other words, under acidic conditions, the terminal amine is protonated and the resin acts as an anion exchange resin. On the other hand, under basic conditions, the terminal amine salt is deprotonated and the resin acts as a cation exchange resin. Because of these characteristics, the resin can be used as a membrane for a redox flow cell to achieve excellent battery performance.

[0029] -[CF2-CF(-(OCF2CXF) a -O-(CF2) b -SO2-NH-R 1 -(NR 2 -R 3 -)c -NR 4 R 5 )]-...Formula (1-1) In formula (1-1), the various numbers and substituents are as follows. a is an integer of 0 or more and 2 or less, preferably an integer of 1 or more and 2 or less, and more preferably 1. b is an integer of 1 or more and 4 or less, preferably an integer of 1 or more and 3 or less, and more preferably 2. c is an integer of 0 or more and 2 or less, preferably an integer of 0 or more and 1 or less, and more preferably 0.

[0030] X is -F or -CF3, preferably -CF3. R 1 and R 3 may be the same or different and are each a substituted or unsubstituted divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 12 carbon atoms.

[0031] The divalent aliphatic hydrocarbon group may be linear, branched, or cyclic. The number of carbon atoms in the divalent aliphatic hydrocarbon group is preferably 2 to 8, more preferably 2 to 6, and even more preferably 2 to 4. Examples of the divalent aliphatic hydrocarbon group include an ethylene group, a 1,3-propanediyl group, a 1,2-propanediyl group, a 1,4-butanediyl group, a 1,3-butanediyl group, and a 1,2-butanediyl group.

[0032] The number of carbon atoms in the divalent aromatic hydrocarbon group is preferably 6 or more and 10 or less, more preferably 6 or more and 8 or less, and even more preferably 6. Examples of the divalent aromatic hydrocarbon group include a phenylene group and a naphthylene group.

[0033] R 2 is a hydrogen atom, a substituted or unsubstituted monovalent aliphatic hydrocarbon group having from 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having from 6 to 12 carbon atoms.

[0034] R 4 and R 5 may be the same or different and are a hydrogen atom, a substituted or unsubstituted monovalent aliphatic hydrocarbon group having from 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having from 6 to 10 carbon atoms. R 4 and R 5 R is preferably a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and more preferably an unsubstituted monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms. 4 and R 5 The number of carbon atoms in the monovalent aliphatic hydrocarbon group in R is preferably 1 to 4. 4 and R 5 In the above formula, examples of the monovalent aliphatic hydrocarbon group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and a tert-butyl group.

[0035] In the case of a substituted aliphatic hydrocarbon group or a substituted aromatic hydrocarbon group, the substituent is not particularly limited, but examples thereof include halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms, nitrile groups (-CN), alkoxy groups (-OR a ), alkyl carbonate group (-OCOR a ), alkyl ester group (-COR a ), acyl group (-COR a ), sulfide group (-SR a ), sulfoxide group (-SOR a ), sulfonic group (-SO2R a ), and urethane groups (-NHCOR a ) etc. a is an aliphatic hydrocarbon group having 1 to 10 carbon atoms or an aromatic hydrocarbon group having 6 to 10 carbon atoms. When it is an aliphatic hydrocarbon group, the substituent may be an aromatic hydrocarbon group having 6 to 10 carbon atoms, and when it is an aromatic hydrocarbon group, the substituent may be an aliphatic hydrocarbon group having 1 to 10 carbon atoms. When it has a substituent, the substituent may be one type alone or multiple types.

[0036] In the formula (1-1), it is preferable that a=1, b=2, and X=-CF3, or a=0, b=2, and X=-F.

[0037] In the nitrogen-containing fluoropolymer, the proportion of the structural unit represented by formula (1-1) relative to the total monomer units is preferably 1 mol% or more and 50 mol% or less, preferably 5 mol% or more and 30 mol% or less, more preferably 10 mol% or more and 25 mol% or less, and even more preferably 13 mol% or more and 22 mol% or less.

[0038] -[CFX―CF2]-...Formula (1-2) In the formula, X is -F or -CF3, preferably -F.

[0039] In the nitrogen-containing fluoropolymer, the proportion of the structural unit represented by formula (1-2) relative to the total monomer units is preferably 50 mol% or more and 99 mol% or less, preferably 70 mol% or more and 95 mol% or less, more preferably 75 mol% or more and 90 mol% or less, and even more preferably 78 mol% or more and 87 mol% or less.

[0040] -[CF2-CF(-(OCF2CXF) a -O-(CF2) b -SO3H)]-...Formula (1-3) In the formula, a, b, and X are defined the same as a, b, and X in the above formula (1-1).

[0041] In the nitrogen-containing fluoropolymer, the proportion of the structural unit represented by formula (1-3) relative to the total monomer units is preferably 0 mol% or more and 10 mol% or less, more preferably 0 mol% or more and 5 mol% or less, and preferably 0 mol% or more and 3 mol% or less.

[0042] The nitrogen-containing fluoropolymer containing the structural unit represented by formula (1-1) and the structural unit represented by formula (1-2) may be a salt thereof. The salt may be a salt of the nitrogen-containing fluoropolymer and an amine compound present in the liquid composition, or may be another basic substance. As described above, the structural unit represented by formula (1-1) is amphoteric, and therefore may be a salt of an acidic substance.

[0043] The content of the nitrogen-containing fluoropolymer (1) is preferably from 0.1 to 40 mass %, more preferably from 0.3 to 30 mass %, and even more preferably from 0.5 to 20 mass %, based on the total amount of the liquid composition.

[0044] The method for producing the nitrogen-containing fluoropolymer (1) is not particularly limited, but it can be produced, for example, by the following method. The method for producing the nitrogen-containing fluoropolymer (1) according to this embodiment is, for example, The method includes a step of reacting a fluoropolymer containing a structural unit represented by the following formula (1-1a) and a structural unit represented by the following formula (1-2) (hereinafter also referred to as "fluoropolymer F") with a compound represented by the following formula (1-1b). -[CF2-CF(-(OCF2CXF) a -O-(CF2) b -SO2-F]-...Formula (1-1a) (In the formula, the various numbers and substituents are defined as in formula (1-1).) -[CFX―CF2]-...Formula (1-2) H2N-R 1 -(NR 2 -R 3 -) c -NR 4 R 5 (1-1b)

[0045] The above reaction forms a sulfonamide moiety -SO2-NH-, and nitrogen-containing fluoropolymer (1) is obtained. The reaction conditions are appropriately set. The compound represented by formula (1-1b) is added to a solvent such as dimethyl sulfoxide (DMSO), and the solid fluoropolymer F is impregnated with the mixed solution to obtain nitrogen-containing fluoropolymer (1) having a structural unit represented by formula (1-1) introduced therein.

[0046] In order to obtain a nitrogen-containing fluoropolymer having a structural unit represented by formula (1-3), the compound represented by formula (1-1b) is reacted with the fluoropolymer F in a molar amount smaller than the F-SO2- group contained in the structural unit represented by formula (1-1a), and the remaining F-SO2- group can be introduced by hydrolysis during the reaction of the fluoropolymer F with the compound represented by formula (1-1b).

[0047] (Porous material layer) The porous material layer is preferably a porous membrane made of a neutral material having no ion exchange group. Examples of the neutral material include polyolefins such as polytetrafluoroethylene (PTFE), polyethylene, and polypropylene. More specifically, examples of the porous membrane include a PTFE porous membrane, a polyolefin porous membrane, and a polyolefin nonwoven fabric.

[0048] The porosity of the porous material layer is preferably 40% or more and 95% or less. This porosity allows the electrolyte to pass through easily, making the polymer electrolyte membrane easier to use as a separator for a redox flow battery. The porosity of the porous material layer is preferably 45% or more and 90% or less, more preferably 50% or more and 85% or less. The porosity is expressed as the mass of the porous material layer, M (g), and the volume of the porous material layer, V (cm 3 ) and the true density D (g / cm 3 ) into the following formula. The volume V of the porous material layer is calculated by measuring the film thickness of the porous material before it is composited with the polymer 20 times and calculating the average value and the area. In the case of PTFE, the true density is 2.18 g / cm 3It is calculated from the following formula. Porosity (%) = {1-(M / (V D))} x 100

[0049] The average pore size of the porous material layer is preferably 0.001 to 10 μm, more preferably 0.01 to 5 μm, and further preferably 0.05 to 1 μm. The average pore size can be measured by a method in accordance with ASTM (American Society for Testing and Materials) F316-86.

[0050] The mass per unit area of ​​the porous material layer is preferably 1 g / m 2 More than 200g / m 2 More preferably, it is 3 g / m or less. 2 More than 100g / m 2 More preferably, it is 15 g / m or less. 2 More than 50g / m 2 The following is the result.

[0051] The thickness of the porous material layer is preferably 1 to 100 μm, more preferably 5 to 80 μm, and further preferably 10 to 50 μm.

[0052] In the polymer electrolyte membrane according to the present embodiment, the orientation ratio OR in the membrane plane direction measured by wide-angle X-ray scattering measurement is preferably 1.0 or more and less than 1.1. When the orientation ratio OR in the membrane plane direction is in this range, the dimensional change of the membrane when immersed in an electrolyte becomes isotropic, and therefore the variation in the membrane performance tends to be stabilized. The orientation ratio OR in the membrane plane direction is preferably 1.00 or more and 1.08 or less, more preferably 1.00 or more and 1.05 or less, and even more preferably 1.00 or more and 1.03 or less.

[0053] The orientation ratio OR in the film surface direction is measured by wide-angle X-ray scattering measurement.

[0054] As described below, a polymer electrolyte membrane having an orientation ratio OR in the membrane plane direction within the above-mentioned range can be obtained by applying a nitrogen-containing fluoropolymer liquid composition to obtain a nitrogen-containing fluoropolymer membrane.

[0055] The total thickness of the polymer electrolyte membrane according to this embodiment is preferably 0.01 μm or more and 200 μm or less, more preferably 0.1 μm or more and 150 μm or less, even more preferably 0.3 μm or more and 100 μm or less, and even more preferably 0.5 μm or more and 50 μm or less.

[0056] The method for producing the polymer electrolyte membrane according to this embodiment is not particularly limited, but for example, the membrane can be produced by the following method. A method for producing a polymer electrolyte membrane includes, for example, A liquid composition preparation step of dissolving the nitrogen-containing fluoropolymer (1) in a solvent; and a film-forming step of applying the liquid composition obtained in the liquid composition preparation step onto a substrate to form a nitrogen-containing fluoropolymer film;

[0043]

[0057] (Liquid composition preparation process) The nitrogen-containing fluoropolymer or a salt thereof is as shown in the above nitrogen-containing fluoropolymer (1).

[0058] 〔solvent〕 The solvent may be a polar or non-polar solvent, but is preferably a polar solvent.

[0059] The solvent preferably contains an aprotic polar solvent, such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), diglyme, or cyclohexanone.

[0060] The proportion of the aprotic polar solvent in the solvent is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and still more preferably 90% by mass or more and 100% by mass or less.

[0061] The boiling point of the solvent is preferably 140° C. or higher from the viewpoint of increasing the solubility of the nitrogen-containing fluoropolymer (1) in the solvent by heating. The boiling point of the solvent is preferably 145° C. or higher and 210° C. or lower, more preferably 150° C. or higher and 205° C. or lower, and even more preferably 160° C. or higher and 205° C. or lower.

[0062] In the dissolving step, the solvent preferably contains an aprotic polar solvent having a boiling point of 140° C. or higher. Examples of the aprotic polar solvent and the preferred range of the boiling point are as described above.

[0063] In the dissolving step, the ratio of the aprotic polar solvent is preferably 50% by mass or more and 100% by mass or less with respect to the total amount of the solvent, more preferably 70% by mass or more and 100% by mass or less, even more preferably 80% by mass or more and 100% by mass or less, and even more preferably 90% by mass or more and 100% by mass or less with respect to the total amount of the solvent.

[0064] The solid content concentration in the nitrogen-containing fluoropolymer liquid composition is preferably 0.1 to 40 mass %, more preferably 0.3 to 30 mass %, and preferably 0.5 to 20 mass %, based on the total amount of the liquid composition. Here, the solid content concentration refers to non-volatile components such as the nitrogen-containing fluoropolymer in the nitrogen-containing fluoropolymer liquid composition.

[0065] It is preferable to use an amine compound or an ammonium salt.

[0066] [Amine Compound] The amine compound preferably has a boiling point of 140°C or more and 220°C or less. By containing an amine compound having a boiling point in this range, a nitrogen-containing fluoropolymer liquid composition exhibiting excellent film-forming properties can be obtained. In addition, when a nitrogen-containing fluoropolymer liquid composition containing an amine compound having a boiling point in this range is spread on a substrate and dried to obtain a film of the polymer, the boiling point being in this range makes it possible to suppress the occurrence of cracks, bubbles, etc., and obtain a uniform film. This effect is presumably expressed by appropriately controlling the volatilization of the amine compound during film formation from the liquid composition. Incidentally, by having a boiling point in this range, the liquid composition can be stirred at a high temperature during production, so that the nitrogen-containing fluoropolymer (1) can be dissolved in a solvent. The boiling point of the amine compound is preferably 145 to 210°C, more preferably 150 to 205°C, and even more preferably 160 to 205°C. Incidentally, the boiling point means the boiling point at a pressure of 0.101 MPa.

[0067] The amine compound may have at least one amino group. The number of amino groups in the amine compound is preferably 1 to 4, more preferably 1 to 3, and further preferably 1 to 2. The amine compound is preferably a diamine compound. The amino group in the amine compound may be any of a primary amino group, a secondary amino group, and a tertiary amino group. From the viewpoint of increasing the solubility of the nitrogen-containing fluoropolymer (1) in a solvent, the diamine compound preferably contains a primary amino group and a tertiary amino group.

[0068] The amine compound is preferably, for example, a compound represented by the following formula (2). H2N-R 21 -NR 22 R 23 ...Equation (2) (In the formula, R 21 is a substituted or unsubstituted divalent aliphatic hydrocarbon group having from 1 to 10 carbon atoms, or a substituted or unsubstituted divalent aromatic hydrocarbon group having from 6 to 12 carbon atoms, R 22 and R23 may be the same or different and are a hydrogen atom, a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms.

[0069] R 22 , and R 23 R is preferably a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and more preferably an unsubstituted monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms. 14 , and R 15 The number of carbon atoms in the monovalent aliphatic hydrocarbon group in R is preferably 1 to 4. 4 and R 5 In the above formula, examples of the monovalent aliphatic hydrocarbon group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and a tert-butyl group.

[0070] R 21 In the above, the divalent aliphatic hydrocarbon group may be linear, branched, or cyclic. The number of carbon atoms in the divalent aliphatic hydrocarbon group is preferably 2 or more and 8 or less, more preferably 2 or more and 6 or less, and even more preferably 2 or more and 4 or less. Examples of the divalent aliphatic hydrocarbon group include an ethylene group, a 1,3-propanediyl group, a 1,2-propanediyl group, a 1,4-butanediyl group, a 1,3-butanediyl group, and a 1,2-butanediyl group.

[0071] The number of carbon atoms in the divalent aromatic hydrocarbon group is preferably 6 or more and 10 or less, more preferably 6 or more and 8 or less, and even more preferably 6. Examples of the divalent aromatic hydrocarbon group include a phenylene group and a naphthylene group.

[0072] Suitable amine compounds include, for example, N,N-diethylethylenediamine (DEEDA, bp = 146 ° C, CAS No. = 100-36-7), N,N-diethyl-1,3-propanediamine (DEPDA, bp = 171 ° C, CAS No. = 104-78-9), N,N-dibutylethylenediamine (DBEDA, bp = 214 ° C, CAS No. = 3529-09-7), and N,N-dibutyl-1,3-propanediamine (DBPDA, bp = 205 ° C, CAS No. = 102-83-0). Note that bp means boiling point. These amine compounds have a larger number of nitrogen atoms per mass than general monoamines, so that the solubility of the nitrogen-containing fluoropolymer (1) in the solvent can be increased.

[0073] In the dissolving step, from the viewpoint of increasing the solubility of the nitrogen-containing fluoropolymer, it is preferable to add 1 part by mass or more of the amine compound to 100 parts by mass of the nitrogen-containing fluoropolymer. The amount of the amine compound added is preferably 5 parts by mass or more and 10,000 parts by mass or less, more preferably 10 parts by mass or more and 1,000 parts by mass or less, to 100 parts by mass of the nitrogen-containing fluoropolymer.

[0074] In the dissolving step, the ratio of the amine compound to be added is preferably 0.1 molar parts or more relative to 1 molar part of the structural unit represented by formula (1-1). The ratio of the amine compound to be added is preferably 1 molar part or more, more preferably 2 molar parts or more, and even more preferably 2 molar parts or more and 20 molar parts or less relative to 1 molar part of the structural unit represented by formula (1-1).

[0075] [Ammonium salt] The nitrogen-containing fluoropolymer liquid composition according to the present embodiment preferably contains an ammonium salt. By containing an ammonium salt, a nitrogen-containing fluoropolymer liquid composition exhibiting excellent film-forming properties can be obtained. In addition, when the liquid composition of the nitrogen-containing fluoropolymer containing an ammonium salt is spread on a substrate and dried to obtain a film of the polymer, the occurrence of cracks, bubbles, etc. can be suppressed, and a uniform film can be obtained. This effect is presumably exhibited because the ammonium salt does not volatilize when forming a film from the liquid composition.

[0076] The ammonium group in the ammonium salt may be any one of a primary ammonium group, a secondary ammonium group, a tertiary ammonium group, and a quaternary ammonium group. From the viewpoint of increasing the solubility of the nitrogen-containing fluoropolymer (1) in a solvent, the ammonium salt preferably contains a quaternary ammonium group.

[0077] The ammonium salt preferably contains an ammonium cation represented by the following formula (3). R 21 R 22 R 23 R 24 N + ...Equation (3)

[0078] In formula (3), R 21 , R 22 , R 23 , and R 24 is a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms, R 21 , R 22 , R 23 , and R 24 may be linked to each other to form a ring structure containing an N element. The monovalent aliphatic hydrocarbon group preferably has 1 to 4 carbon atoms. 21 , R 22 , R 23 , and R 24In the above formula, examples of the monovalent aliphatic hydrocarbon group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and a tert-butyl group. The monovalent aromatic hydrocarbon group preferably has 6 to 8 carbon atoms. 21 , R 22 , R 23 , and R 24 In the above formula, examples of the monovalent aromatic hydrocarbon group include a phenyl group and a naphthyl group.

[0079] When the aliphatic hydrocarbon group or aromatic hydrocarbon group is substituted, the substituent is a hydroxyl group, an acetoxy group, a halogen group, a sulfonic acid group, or a phosphonic acid group.

[0080] It is preferable that the ammonium cation represented by formula (3) includes at least one ammonium cation selected from the group consisting of ammonium cations represented by the following formula (3-1), ammonium cations represented by the following formula (3-2), ammonium cations represented by the following formula (3-3), and ammonium cations represented by the following formula (3-4). (CH3)4N + ...Formula (3-1) (CH3CH2)4N + ...Formula (3-2) (CH3CH2CH2)4N + ...Formula (3-3) (CH3CH2CH2CH2)4N + ...Formula (3-4) (CH3)3N + -(CH2)2-OH...Formula (3-5)

[0081] The anion species of the ammonium salt is hydroxy anion.

[0082] Examples of the ammonium salt include tetramethylammonium hydroxide and tetraethylammonium hydroxide.

[0083] In the dissolving step, from the viewpoint of increasing the solubility of the nitrogen-containing fluoropolymer, it is preferable to add 1 part by mass or more of the ammonium salt to 100 parts by mass of the nitrogen-containing fluoropolymer. The amount of the amine compound added is preferably 5 parts by mass or more and 10,000 parts by mass or less, more preferably 10 parts by mass or more and 1,000 parts by mass or less, to 100 parts by mass of the nitrogen-containing fluoropolymer.

[0084] In the dissolving step, the ratio of the ammonium salt to be added is preferably 0.1 molar parts or more relative to 1 molar part of the structural unit represented by formula (1-1). The ratio of the ammonium salt to be added is preferably 1 molar part or more, more preferably 2 molar parts or more, and even more preferably 2 molar parts or more and 20 molar parts or less relative to 1 molar part of the structural unit represented by formula (1-1).

[0085] The maximum temperature by heating in the dissolving step is more than 100° C. and not more than 210° C. The maximum temperature by heating is preferably 120° C. or more and 210° C. or less, more preferably 140° C. or more and 210° C. or less, and even more preferably 160° C. or more and 210° C. or less.

[0086] The heating time in the dissolving step is not particularly limited, but may be from 1 hour to 48 hours.

[0087] The pressure in the dissolving step is preferably 10 atm or less. The pressure in the dissolving step is preferably 8 atm or less, more preferably 5 atm or less, and further preferably 5 atm or less and 1 atm or more.

[0088] (film formation process) In the film-forming step, the nitrogen-containing fluoropolymer liquid composition is applied onto a substrate to form a nitrogen-containing fluoropolymer film. The substrate is not particularly limited, and may be a release sheet when a monolayer membrane of a nitrogen-containing fluoropolymer membrane is obtained, or may be a porous membrane that becomes the above-mentioned porous layer when a polymer electrolyte membrane having a laminate structure is obtained.

[0089] The coating method is not particularly limited, and may be spray coating or gravure coating.

[0090] The polymer electrolyte membrane according to the present embodiment can be used as a diaphragm in applications such as redox flow batteries, fuel cells, salt electrolysis, alkaline water electrolysis, and carbon dioxide reduction electrolysis. Among these, the polymer electrolyte membrane according to the present embodiment is preferably used for redox flow batteries, and more preferably used as a diaphragm for redox flow batteries. More specifically, it is used, for example, as a cell for a redox flow battery.

[0091] [Redox flow battery cells] The redox flow battery cell includes a first electrolytic solution, a second electrolytic solution, a first electrode, and a diaphragm. The first electrolytic solution includes a first redox active material. The second electrolytic solution includes a second redox active material. The first electrode is in contact with the first electrolytic solution. The diaphragm is disposed between the second electrode in contact with the second electrolytic solution, the first electrolytic solution, and the second electrolytic solution. The polymer electrolyte membrane according to the present embodiment is used as the diaphragm. In addition to the above-mentioned configuration, the redox flow battery cell may include a bipolar plate, a frame, a compressible seal, a conductive additive, or a balancing cell.

[0092] FIG. 1 is a schematic diagram showing an example of a cell for a redox flow battery. The redox flow battery cell 10 has an electrolytic cell 6 including a cell chamber 2 containing a first electrode 1 (positive electrode in FIG. 1), a cell chamber 4 containing a second electrode 3 (negative electrode in FIG. 1), and a diaphragm 5 isolating and separating the cell chamber 2 from the cell chamber 4. The cell chamber 2 contains a first electrolyte solution containing a first redox active material, and the cell chamber 4 contains a second electrolyte solution containing a second redox active material.

[0093] In the redox flow battery cell according to this embodiment, the first and second electrolytic solutions are preferably acidic. In addition, the first and second electrolytic solutions are preferably in contact with the nitrogen-containing fluoropolymer membrane in the polymer electrolyte membrane. Since the first and second electrolytic solutions are acidic, the polymer electrolyte membrane according to this embodiment used as the separator 5 is positively charged and functions as an anion exchange membrane.

[0094] When a polymer electrolyte membrane formed by laminating at least one nitrogen-containing fluoropolymer membrane and one porous material layer is used as the diaphragm 5, it is preferable that a surface of the nitrogen-containing fluoropolymer membrane is in contact with the second electrolyte solution containing a second redox active material filled in the cell chamber 4.

[0095] It is preferable that the diaphragm 5 and at least one electrode are joined together. By joining the electrodes, the distance between the electrodes can be shortened, the electrical resistance is reduced, and the battery performance is improved.

[0096] The electrolytes containing the redox active material are stored in, for example, electrolyte tanks 7 and 8, respectively, and supplied to each cell chamber by a pump or the like. Furthermore, the current generated by the redox flow battery cell may be converted from DC to AC via AC / DC converter 9, or may be converted from AC to DC via AC / DC converter 9 and used to fill the redox flow battery cell. The redox flow battery cell of this embodiment is preferably a redox flow secondary battery cell.

[0097] (electrolyte) The electrolyte contains a redox active material. The redox active material is a material having redox activity that is directly related to electromotive force in a cell for a redox flow battery. Examples of the redox active material include a metal-based redox active material, a non-metal-based redox active material, and an organic redox active material. The redox active material may be a neutral compound or an ionic compound.

[0098] The metal-based redox active material is a material containing at least one metal atom, and may contain a plurality of metal atoms of the same kind or a plurality of different metals. The metal atoms used in the metal-based redox active material are not particularly limited, but may include aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, tin, lead, and cerium, and among these, titanium, vanadium, chromium, manganese, iron, and cerium are preferred. In addition, from the viewpoint of making the first redox active material and the second redox active material of the same kind, vanadium, iron, copper, and tin are preferred, vanadium and iron are more preferred, and vanadium is particularly preferred.

[0099] The metal-based redox active material may have an active material ligand. Examples of the active material ligand include cyanide ion, acetylacetone, ethylenediamine, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, carbon monoxide, bipyridine, bipyrazine, ethylene glycol, propylene glycol, ethanedithiol, butanedithiol, terpyridine, diethylenetriamine, triazacyclononane, tris(hydroxymethyl)aminomethane, ascorbic acid, citric acid, glycolic acid, gluconic acid, acetic acid, formic acid, benzoic acid, malic acid, maleic acid, phthalic acid, sarcosinic acid, salicylic acid, oxalic acid, urea, aminophenolate, and lactic acid. These active material ligands may be used alone or in combination.

[0100] Non-metallic redox active materials include, but are not limited to, chlorine, bromine, sulfur, polysulfides, and the like.

[0101] Examples of organic redox active materials include, but are not limited to, viologen, derivatives thereof, and compounds having a viologen structure in a polymer side chain, 2,2,6,6-tetramethyl-1-piperidinyloxy radical, derivatives thereof, and compounds having a 2,2,6,6-tetramethyl-1-piperidinyloxy radical structure in a polymer side chain, ferrocene, derivatives thereof, and compounds having a ferrocene structure in a polymer side chain, quinone, derivatives thereof, and compounds having a quinone structure in a polymer side chain, anthraquinone, derivatives thereof, and compounds having an anthraquinone structure in a polymer side chain, quinoxaline, derivatives thereof, and compounds having a quinoxaline structure in a polymer side chain, and the like.

[0102] These redox active materials may be used alone or in combination of two or more kinds.

[0103] When the redox active material is used in a cell for a redox flow battery, the redox active material used in the electrolyte of the positive electrode and the redox active material used in the electrolyte of the negative electrode can be combined according to the desired characteristics. The combination of the redox active materials is not particularly limited, but includes combinations such as vanadium / vanadium, iron / iron, lead / lead, copper / copper, iron / chromium, chromium / bromine, zinc / bromine, polysulfide / bromine, zinc / cerium, zinc / nickel, zinc / cerium, zinc / iodine, titanium / manganese, vanadium / cerium, and vanadium / manganese. Among these, vanadium / vanadium, iron / iron, iron / chromium, chromium / bromine, zinc / bromine, and titanium / manganese are preferred because they provide a high electromotive force and are excellent in stability during charging and discharging, and vanadium / vanadium, iron / iron, and zinc / bromine are more preferred, with vanadium / vanadium being particularly preferred.

[0104] When the redox active materials of both the positive electrode and the negative electrode are vanadium, the battery is also referred to as a vanadium redox flow battery cell or a vanadium redox flow battery. In addition, when the redox active materials of the positive and negative electrodes are both vanadium, VO 2+ / VO2 +, and at the negative electrode, V 2+ / V 3+ Charging and discharging are performed by utilizing an oxidation-reduction reaction using the redox couple. During charging, the oxidation-reduction reaction causes an excess of protons (H+) in the positive electrode cell chamber, while the negative electrode cell chamber has a shortage of protons (H+). The diaphragm selectively transfers the excess protons in the positive electrode cell chamber to the negative electrode chamber, maintaining electrical neutrality. During discharging, the reverse reaction occurs, maintaining electrical neutrality.

[0105] Examples of the solvent used in the electrolyte include water, alcohols, nitriles, esters, ketones, ethers, aliphatic hydrocarbons, aromatic hydrocarbons, etc. Among these, water is preferred from the viewpoint of improving safety during operation of the redox flow battery cell.

[0106] More specifically, examples of the solvent include alcohols such as methanol, ethanol, propanol, butanol, hexanol, cyclohexanol, ethylene glycol, diethylene glycol, and glycerol, nitriles such as acetonitrile, propionitrile, and benzonitrile, esters such as ethyl acetate and butyl acetate, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, ethers such as diethyl ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether, aliphatic hydrocarbons such as pentane, hexane, cyclohexane, heptane, octane, chloroform, dichloromethane, and tetrachloromethane, and aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene, dichlorobenzene, phenol, and cresol. These solvents may be used alone or in combination.

[0107] The electrolytic solution may further contain an electrolyte. The electrolyte is a substance that dissociates into ions in the electrolytic solution and improves the electrical conductivity of the electrolytic solution. Examples of the electrolyte include, but are not limited to, sulfuric acid, hydrochloric acid, nitric acid, acetic acid, phosphoric acid, sodium hydroxide, potassium hydroxide, calcium hydroxide, and sodium acetate. These electrolytes may be used alone or in combination.

[0108] The electrolyte may further contain additives depending on the desired properties of the electrolyte. Examples of additives include ethylene glycol, diethylene glycol, polyethylene glycol, glycerol, mannitol, sorbitol, pentaerythritol, tris(hydroxymethyl)aminomethane, corn starch, corn syrup, gelatin, glycerol, guar gum, pectin, surfactants, etc. These additives may be used alone or in combination.

[0109] (electrode) The electrodes include, for example, metal electrodes and carbon electrodes. Examples of materials for the metal electrode include aluminum, gold, silver, copper, chromium, molybdenum, nickel, thallium, titanium, iridium, zinc, tin, composites of these metals, etc. The shape of the metal electrode is not particularly limited, but examples include plate-like, lattice-like, mesh-like (diamond-like, tortoiseshell-like), linear, rod-like, etc.

[0110] Examples of carbon electrodes include glassy carbon electrodes, pyrolytic carbon electrodes, carbon felt electrodes, carbon paper electrodes, carbon foam electrodes, carbon cloth electrodes, carbon knit electrodes, carbon nanofiber sheet electrodes, and activated carbon fiber sheet electrodes. In the case of carbon electrodes for applications in which liquid or gas is circulated inside the electrode, it is preferable that the electrodes have continuous voids, and it is more preferable that the electrodes are porous bodies having continuous voids. Examples of carbon electrodes having continuous voids include carbon felt electrodes, carbon paper electrodes, carbon foam electrodes, carbon cloth electrodes, carbon knit electrodes, carbon nanofiber sheet electrodes, and activated carbon fiber sheet electrodes. Among these, carbon felt, carbon paper, and carbon foam are preferable, and carbon foam is more preferable, from the viewpoint of reducing resistance due to high flexibility and large surface area. It is preferable that the carbon foam has a structure in which the carbon portion is three-dimensionally continuous. It is preferable that the carbon foam has a linear portion and a bonding portion that bonds the linear portion, since it can have high flexibility and a large surface area.

[0111] Examples of commercially available carbon felt and carbon paper include SIGRACELL (registered trademark) KFD series, GFA series, GFD series, SGL series, and SIGRACET (registered trademark) series manufactured by SGL CARBON, carbon felt manufactured by Toyobo Co., Ltd. (e.g., XF30A, BW-309), CARBORON (registered trademark) GF series manufactured by Nippon Carbon Co., Ltd. (e.g., GF-20, GF-3F), TORAYCA (trademark) TGP series manufactured by Toray Industries, Inc., PYROFIL (trademark) series and GRAFIL (trademark) series manufactured by Mitsubishi Chemical Corporation, VGCF (registered trademark) sheet manufactured by Showa Denko K.K., carbon felt and graphite felt manufactured by MERSEN, etc. These may be subjected to activation treatment such as oxidation as necessary. Carbon foam can be produced by known methods (WO 2018 / 096895, WO 2018 / 168741, WO 2020 / 045645).

[0112] <Membrane electrode assembly> The membrane electrode assembly in this embodiment has a structure in which a polymer electrolyte membrane and at least one electrode are joined together. The membrane electrode assembly is preferably a structure in which a polymer electrolyte membrane and two electrodes are joined together. With this membrane electrode assembly, the process of assembling an electrode, a polymer electrolyte membrane, and an electrode in this order is not required when assembling a cell for a redox flow battery.

[0113] The polymer electrolyte membrane and the electrodes can be bonded together by using a hot press and / or a hot roll press. The temperature during bonding is preferably from room temperature to 250° C., more preferably from room temperature to 200° C., even more preferably from room temperature to 170° C., and still more preferably from room temperature to 150° C.

[0114] The pressure during bonding is preferably 0.01 MPa or more and 100 MPa or less, more preferably 0.05 MPa or more and 50 MPa or less, even more preferably 0.08 MPa or more and 20 MPa or less, and still more preferably 0.1 MPa or more and 10 MPa or less.

[0115] The time for bonding is preferably from 0.01 seconds to 10 hours, more preferably from 0.1 seconds to 5 hours, even more preferably from 0.5 seconds to 2 hours, and still more preferably from 1 second to 1 hour.

[0116] The atmosphere during bonding is not particularly limited, but may be any of air, nitrogen, and argon.

[0117] The membrane electrode assembly according to this embodiment can be used for various applications, but is preferably used in a cell for a redox flow battery and a redox flow battery.

[0118] [Redox flow battery] A redox flow battery has a structure in which redox flow battery cells are stacked. When stacked, electricity can be passed between the individual redox flow battery cells via bipolar plates. Examples of materials for the bipolar plate include carbon, graphite, metals, and materials containing dispersed carbon particles, carbon fibers, metal particles, metal fibers, graphene, and carbon nanotubes. The bipolar plate may have various flow paths, which may improve the contact between the electrodes and the electrolyte. The flow paths are not particularly limited, and examples thereof include serpentine, interdigitated, parallel, multi-parallel, discontinuous, and combinations of the above flow paths.

[0119] By using the redox flow battery cell and the redox flow battery of the present embodiment, it is possible to provide a mechanism for smoothing the supply and demand of power and stabilizing the fluctuating power obtained from renewable energy sources such as solar energy and wind energy. More specifically, it is possible to provide integration of power obtained from renewable energy sources, power peak load shifting, stabilization of the power grid, baseload power, energy arbitrage, support for weak power grids, frequency regulation, and any combination of the above. It can also be used as a power source for remote camps, forward operating bases, power transmission and distribution telecommunications, remote sensors, etc. that do not use a power grid. The cell for a redox flow battery and the redox flow battery of this embodiment can be equipped with a control system and a power conditioning unit. The control system may be used to control the operation of various valves, pumps, circuits, sensors, mitigation devices, other electronic / hardware control devices, safety protection devices, and the like. By using the power conditioning unit, the voltage and current of the input power can be converted to an optimal form for the redox flow battery cell and / or the redox flow battery, and the voltage and current of the output power can be converted to an optimal form for any application. For example, when the redox flow battery cell and / or the redox flow battery is connected to a power grid, in a charging cycle, the power conditioning unit can convert the input AC power into DC power of a suitable voltage and current. In addition, in a discharging cycle, the redox flow battery cell and / or the redox flow battery generates DC power, and the power conditioning unit can convert the DC power into AC power of a suitable voltage and frequency for sending to the power grid.

[0120] [Rolled body] The wound body according to the present embodiment is formed by winding a polymer electrolyte membrane. The wound body may have a core tube. The polymer electrolyte membrane according to the present embodiment may be formed into a wound body, which allows easy operation during the production of the polymer electrolyte membrane and during the production of a cell for a redox flow battery using the polymer electrolyte membrane.

[0121] In the wound body, the width of the polymer electrolyte membrane is preferably 50 mm or more and 5,000 mm or less, and the length of the polymer electrolyte membrane in the wound body is preferably 100 mm or more. EXAMPLES

[0122] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples.

[0123] In the examples and comparative examples, various measurements were carried out as follows.

[0124] <Equivalent weight (EW) measurement> A polymer electrolyte membrane in which the counter ions of the ion exchange groups are in the proton state, approximately 2 to 20 cm 2The sample was immersed in 30 ml of saturated NaCl aqueous solution at 25°C and left for 30 minutes while stirring. Next, the protons in the saturated NaCl aqueous solution were neutralized by titration using 0.01N sodium hydroxide aqueous solution with phenolphthalein as an indicator. The polymer electrolyte membrane obtained after neutralization, in which the counter ions of the ion exchange groups were in a state of sodium ions, was rinsed with pure water, further vacuum dried, and weighed. The amount of sodium hydroxide required for neutralization was M (mmol), and the weight of the polymer electrolyte membrane in which the counter ions of the ion exchange groups were sodium ions was W (mg), and the equivalent weight EW (g / eq) was calculated from the following formula. EW=(W / M)-22

[0125] <Melt flow rate (MFR) measurement method> The MFR of the polymer was measured using a MELT INDEXER TYPE C-5059D (manufactured by Toyo Seiki Co., Ltd., Japan) at 270°C and a load of 2.16 kg according to JIS K 7210: 2014. The mass of the extruded polymer was expressed in grams per 10 minutes.

[0126] <Infrared absorption measurement of nitrogen-containing fluoropolymer> The nitrogen-containing fluoropolymer liquid composition was applied to a germanium sample stage (10 mmφ) for IR measurement and dried for 20 minutes at 120° C. to obtain a sample for analysis. IR transmission measurement of this sample (microscopic FT-IR device LUMOS; manufactured by Bruker Japan Co., Ltd.) was performed under the following conditions. Aperture size: 124μm x 124μm Wavenumber resolution: 4cm -1 Number of times: 32 In addition, the measurement was performed at 980 cm -1 It is desirable to select a sample thickness where the peak is not saturated (Abs is 1 or less) and where the influence of interference fringes is minimal.

[0127] <Confirmation of sulfonamide bond> The nitrogen-containing fluoropolymer was heated in 2 mol / L hydrochloric acid at 90°C for 3 hours, and then taken out and dried at room temperature for 6 hours. The hydrochloric acid-treated polymer was measured using a transmission infrared spectrometer (Frontier, manufactured by PerkinElmer) and the peak wave number due to -SO2-NH- in the obtained infrared spectrum was 1380 ± 5 cm -1 The presence or absence of the -SO2-NH- group was confirmed based on the presence or absence of an infrared absorption peak.

[0128] <Sulfonamide ratio> The hydrolysis rate of the nitrogen-containing fluoropolymer was calculated by the following method. The infrared spectrum of the nitrogen-containing fluoropolymer was differentiated twice to reveal a peak at 980 ± 5 cm due to COC. -1 Peak wave number for absolute value of peak height -SO3-derived 1050±5cm -1 The ratio of the absolute values ​​of the peak heights of Next, the polymer with -SO2F groups at the side chain ends, which was used as a raw material in the production of the nitrogen-containing fluoropolymer, was contacted with an aqueous solution of potassium hydroxide (15% by mass) and methyl alcohol (50% by mass) at 80°C for 20 hours for hydrolysis. It was then heated at 90°C for 3 hours in a 25% by volume aqueous solution of ethylenediamine, and after removal, it was washed with water until the pH of the washing water was 8 or less, and dried at room temperature for 6 hours. This treatment completely hydrolyzed the nitrogen-containing fluoropolymer, and all of the -SO2-NH- groups in the polymer were modified to -SO3- groups. The infrared spectrum of the hydrolyzed polymer was differentiated twice, and a peak wavenumber of 980±5 cm originating from COC was found. -1 Peak wave number for absolute value of peak height -SO3-derived 1050±5cm -1 The ratio of the absolute values ​​of the peak heights of The hydrolysis rate was calculated according to the following formula. Hydrolysis rate [mol%] = (980±5cm of nitrogen-containing fluoropolymer -1 Absolute value of peak height of 1050±5cm -1 Ratio of absolute peak heights of hydrolyzed polymer to 980±5cm -1 Absolute value of peak height of 1050±5cm-1 (ratio of absolute peak heights of each peak) × 100

[0129] <Mass per unit area> (Measurement of mass per unit area of ​​nitrogen-containing fluoropolymer membrane in polymer electrolyte with porous material layer) The mass m1 (g) of the porous membrane forming the porous material layer was measured immediately after drying the porous membrane in an oven (manufactured by Espec Corp., "PHH-202") at 100°C for 10 minutes and removing the porous membrane from the oven. The mass m2 (g) of the polymer electrolyte membrane formed on the porous membrane with a nitrogen-containing fluoropolymer membrane was measured immediately after drying the polymer electrolyte membrane in an oven (manufactured by Espec Corp., "PHH-202") at 100°C for 10 minutes and removing the polymer electrolyte membrane from the oven. The area of ​​the porous membrane was defined as S (m 2 ) and calculate the mass per unit area X (basis weight: g / m2) based on the following formula: 2 ) was calculated. X = (m2-m1) / S(g / m 2 )

[0130] <Redox flow battery cell evaluation (RFB evaluation)> For the evaluation of the redox flow battery cell, a cell was used that was composed of a Viton (trademark) rubber gasket, a polyvinylidene chloride flow path frame, a graphite bipolar plate (material: "G347" manufactured by Tokai Carbon Co., Ltd.) equipped with a copper electrode terminal, and an acrylic resin end plate. The diaphragm prepared in the examples and comparative examples was cut to 50 x 90 mm and used. The thickness of the Viton (trademark) rubber gasket was adjusted so that the compression rate of the electrode (ratio of thickness before and after compression) was 50%. The electrode was cut to 20 x 25 mm and used. The diaphragm, two electrodes, and cell components were assembled in the following order: acrylic resin end plate, graphite bipolar plate with copper electrode terminal, Viton (trademark) rubber gasket, polyvinylidene chloride flow frame, electrode, diaphragm, electrode, Viton (trademark) rubber gasket, graphite bipolar plate with copper electrode terminal, and acrylic resin end plate, and fastened with stainless steel bolts. A Viton (trademark) rubber gasket was also installed between the polyvinylidene chloride flow frame and the diaphragm. 7 mL of vanadium sulfate solution with a vanadium ion concentration of 1.6 M, vanadium ion valence of 3.5, and sulfate ion concentration of 4.5 M was added to the electrolyte tank and circulated at a flow rate of 7 mL / min. The charge / discharge test was performed by a constant current method using a charge / discharge power supply device "PFX2011" (product name, manufactured by Kikusui Electronics Co., Ltd.) and a control unit "PFX2121" (product name, manufactured by Kikusui Electronics Co., Ltd.). The voltage range is 1.00 to 1.55 V, and the current density is 80 mA / cm 2 It was decided.

[0131] <Current efficiency> The current efficiency was determined by dividing the discharge capacity after 10 charge / discharge cycles by the charge capacity.

[0132] <Voltage efficiency> The voltage efficiency was determined by dividing the average discharge voltage after 10 charge / discharge cycles by the average charge voltage.

[0133] <Power efficiency> The power efficiency was calculated by dividing the amount of discharged power after 10 charge / discharge cycles by the amount of charged power.

[0134] [Production of raw polymers] <Production Example F1> A fluoropolymer F1 was synthesized containing the following structural units and having an EW of 910: -[CF2-CF-(OCF2CF(CF3)-O-(CF2)2-SO2-F]- -[CF2-CF2]-

[0135] First, a fluoropolymer of CF2=CF2 (hereinafter, TFE) and CF2=CFOCF2CF(CF3)O(CF2)2-SO2F (hereinafter, S monomer) was polymerized as follows.

[0136] 580g of CF2ClCFCl2 (hereinafter, CFC113) and 280g of CF2=CFOCF2CF(CF3)O(CF2)2-SO2F were charged into a 1-liter stainless steel autoclave, and then purged with nitrogen and then with TFE. After the temperature was set to 35°C and the TFE pressure was set to 0.157MPaG, 0.55g of a CFC113 solution containing 5wt% of (n-C3F7COO-)2 was added, and polymerization was carried out for about 3.5 hours. During this time, TFE was fed from outside the system so that the TFE pressure was constant. After purging TFE from the obtained polymerization liquid, CFC113 was distilled off at 90°C and normal pressure, and then the remaining S monomer was distilled off at 90°C under reduced pressure. Furthermore, it was dried under reduced pressure at 150°C for 2 days to obtain 10.5g of fluoropolymer F1.

[0137] The resulting fluoropolymer F1 had an MFR of 20 g / 10 min and contained 18 mol % of repeating units of SO3H group-containing monomers.

[0138] For fluoropolymer F1, the following samples were prepared and the EW was measured. The fluoropolymer F1 thus obtained was contacted with an aqueous solution of potassium hydroxide (15% by mass) and methyl alcohol (50% by mass) at 80° C. for 20 hours to carry out hydrolysis treatment. Thereafter, the polymer was immersed in water at 60° C. for 5 hours. Next, the polymer was immersed in a 2N aqueous hydrochloric acid solution at 60° C. for 1 hour for 5 times, with the aqueous hydrochloric acid solution being renewed each time. The polymer was then washed with ion-exchanged water and dried to obtain a fluoropolymer FA1.

[0139] This fluoropolymer FA1 was placed in a 5 L autoclave together with an aqueous ethanol solution (water:ethanol = 50.0:50.0 (mass ratio)), sealed, and heated to 160 ° C. with stirring using a blade and held for 5 hours. The autoclave was then naturally cooled to produce a uniform fluoropolymer FA1 solution with a solid content concentration of 5 mass %.

[0140] 500g of water was added to 500g of the fluoropolymer FA1 solution, and the solution was concentrated under reduced pressure to a solid content concentration of 15% by mass at 80° C. Addition of 500g of water and concentration under reduced pressure to a solid content concentration of 15% by mass at 80° C. were repeated until the amount of ethanol contained was 0.1% by mass or less. After that, 500g of water was added to the obtained liquid after concentration under reduced pressure, and the solution was concentrated under reduced pressure at 80° C. to produce a fluoropolymer solution FA2 with a solid content concentration of 30% by mass.

[0141] Fluoropolymer solution FA2 (100 g) and a stirrer were placed in a polypropylene container, and acetic acid (12 g, Fujifilm Wako Pure Chemical Industries, special reagent grade) was added while stirring with a magnetic stirrer (Koike Precision Machinery Manufacturing Co., Ltd., "HE-20GA") until the mixture was homogenous. Next, 1-propanol (12 g, Fujifilm Wako Pure Chemical Industries, special reagent grade) was added, and the mixture was stirred at 25°C for 12 hours, resulting in a transparent and homogenous fluoropolymer solution FB1.

[0142] The obtained fluoropolymer solution FB1 was applied (coating area: width about 250 mm × length about 400 mm) onto a substrate film, Kapton (registered trademark) film (Toray-DuPont, 300 mm × 600 mm), using a blade coater (MTI, "EQ-Se-KTQ-250", film thickness after heat treatment 50 μm), and then dried for 5 minutes at room temperature, 5 minutes in a 60 ° C. oven (Espec, "PHH-202"), and 10 minutes in a 120 ° C. oven (Espec, "PHH-202"). The obtained film was heat-treated for 20 minutes in a 150 ° C. oven (Espec, "PHH-202"), cooled to room temperature, and peeled off from the Kapton film to obtain a polymer electrolyte membrane C1 with a film thickness of 50 μm. This polymer electrolyte membrane was measured by the above-mentioned EW measurement method, and the EW was 910.

[0143] [Production of nitrogen-containing fluoropolymers] <Manufacturing example AP1> Polymer F1 was freeze-pulverized using a freeze-pulverizer (JFC-2000, manufactured by Japan Analytical Industry Co., Ltd.) to obtain polymer powder FP1. Dimethyl sulfoxide (DMSO: 293.4 g) was added to a 1 L PP container, and N,N-dimethylethylenediamine (DMEDA: 97.8 g) was added at 25°C, and the mixture was stirred until it became uniform. The above polymer powder (FP1: 10 g) was added to the diamine solution, and the mixture was stirred at 25°C. After 168 hours, the powder was filtered, washed with ethanol, and then vacuum dried at 40°C for 12 hours to obtain a powdered nitrogen-containing fluoropolymer AP1. The nitrogen-containing fluoropolymer AP1 was subjected to the above-mentioned IR measurement to measure the sulfonamidation rate. Using this sulfonamidation rate and the monomer ratio obtained from the EW measurement, the ratio of the monomer represented by formula (1-1), the monomer represented by formula (1-2), and the monomer represented by formula (1-3) was calculated.

[0144] <Manufacturing example AP3> Powdered nitrogen-containing fluoropolymer AP3 was obtained in the same manner as in Production Example AP1, except that the diamine compound, N,N-diethylethylenediamine (DEEDA), was added in the amount shown in Table 1, and the final amount of solvent was set to the value shown in Table 1. For the nitrogen-containing fluoropolymer AP3, the molar ratios of various monomers were calculated in the same manner as in Production Example AP1.

[0145] <Manufacturing example AP4> A powdery nitrogen-containing fluoropolymer AP4 was obtained in the same manner as in Production Example AP1, except that the diamine compound was N,N-diethyl-1,3-propanediamine (DEPDA) in the amount shown in Table 1 and the final amount of solvent was the value shown in Table 1. For the nitrogen-containing fluoropolymer AP4, the molar ratios of various monomers were calculated in the same manner as in Production Example AP1.

[0146] [Table 1]

[0147] [Production of liquid composition of nitrogen-containing fluoropolymer] <Production Example AS1> 10 g of nitrogen-containing fluoropolymer AP1 was placed in a 300 mL two-neck flask equipped with a Dimroth condenser together with 80 g of dimethylacetamide (DMAc) and 10 g of N,N-diethyl-1,3-propanediamine (DEPDA), and the temperature was raised to 165°C while stirring with a blade and maintained for 8 hours. The flask was then naturally cooled, and the liquid composition was subjected to pressure filtration to produce a uniform nitrogen-containing fluoropolymer liquid composition AS1 (solution) with a solid content concentration of 10.0 mass%.

[0148] <Manufacturing examples AS2, AS3> Except for changing the nitrogen-containing fluoropolymer AP1 to a polymer shown in Table 2, a liquid composition (solution) of a nitrogen-containing fluoropolymer was prepared in the same manner as in Production Example AS1.

[0149] [Table 2]

[0150] [Production Example E1: Production of Carbon Foam Electrode] Carbon foam electrodes were prepared in the following manner. A 1.2 mm thick SUS plate was placed around the melamine resin foam (dimensions: 400 mm x 400 mm x 40 mm) as a spacer, sandwiched between 10 mm thick graphite plates from above and below, and introduced into a vacuum heat press (Kitagawa Seiki Co., Ltd., KVHC-II). Next, while decompressing and evacuating with a vacuum pump, the temperature inside the press was raised to 360°C at a heating rate of 5°C / min and held for 5 minutes. During the temperature rise and while held at 360°C, pressing was performed at a pressure of 3.0 MPa. After that, the temperature inside the machine was lowered to 50°C, the vacuum pump was stopped, and the pressing was released. The obtained pressed sample was placed in a heat treatment furnace (ULVAC, 6-L14), and while evacuating the furnace and supplying nitrogen gas into the furnace at a flow rate of 2 L / min, the temperature inside the furnace was raised to 1100°C at a heating rate of 5°C / min and held for 1 hour. After that, the temperature inside the furnace was lowered to room temperature, and the vacuum pump was stopped. The obtained heat-treated sample was placed in a mesh belt type electric furnace set at an internal temperature of 330°C and supplied with dry air at a flow rate of 1 L / min, and held for 1 hour to produce a carbon foam electrode.

[0151] <Example 1> As a coating liquid, a nitrogen-containing fluoropolymer liquid composition SA1 was applied (coating area: width approx. 250 mm x length approx. 400 mm) onto a substrate film, Kapton (registered trademark) film (Toray-DuPont Co., Ltd., 300 mm x 600 mm), using a blade coater (MTI Corporation, "EQ-Se-KTQ-250", wet film thickness 100 μm). After leaving to stand for 1 minute at room temperature, a hydrophilic PTFE membrane filter (Advantec Corporation, product name: H010A090C, pore size: 0.10 μm, porosity: 71%, mass per unit area: 22 g / m) was applied from above the coating liquid. 2The specimen was then dried for 20 minutes in an oven (Espec Corp., "PHH-202") at 100°C. After cooling to room temperature, it was peeled off from the Kapton film, revealing a mass per unit area of ​​4.3 g / m. 2 A polymer electrolyte membrane having a nitrogen-containing fluoropolymer membrane of the above formula was obtained. The obtained polymer electrolyte membrane was used to evaluate a cell for a redox flow battery. The electrodes of the battery cells were all carbon foam electrodes produced in Production Example E1. The results of the cell evaluation for a redox flow battery are shown in Table 3.

[0152] <Examples 2 and 3> A polymer electrolyte membrane having a nitrogen-containing fluoropolymer membrane with a basis weight shown in Table 3 was obtained in the same manner as in Example 1, except that the coating liquid was a liquid composition shown in Table 3. The obtained polymer electrolyte membrane was used to perform a redox flow battery cell evaluation. The electrodes of the battery cells were all carbon foam electrodes produced in Production Example E1. The results of the redox flow battery cell evaluation are shown in Table 3.

[0153] <Comparative Example 1> A redox flow battery cell evaluation was performed on a commercially available polymer electrolyte membrane (Nafion115, thickness 50 μm, extrusion molding). The electrodes of the battery cells were all carbon foam electrodes produced in Production Example E1. The results of the redox flow battery cell evaluation are shown in Table 4.

[0154] [Table 3]

[0155] [Table 4]

[0156] As described above, it is understood that the polymer electrolyte membrane according to this embodiment makes it possible to obtain a redox battery cell having a well-balanced excellent current efficiency and voltage efficiency, and also having high power efficiency. [Explanation of symbols]

[0157] Reference Signs List 1...first electrode, 2...cell chamber, 3...second electrode, 4...cell chamber, 5...diaphragm, 6...electrolytic cell, 7...electrolyte tank, 8...electrolyte tank, 9...DC converter, 10...cell for redox flow battery

Claims

1. The present invention includes a nitrogen-containing fluoropolymer membrane containing a nitrogen-containing fluoropolymer or a salt thereof, the nitrogen-containing fluoropolymer comprising a structural unit represented by the following formula (1-1) and a structural unit represented by the following formula (1-2): The mass per unit area of ​​the nitrogen-containing fluoropolymer is 100 g / m 2 The polymer electrolyte membrane is as follows: - [CF 2 - CF(-(OCF 2 CXF) a - O-(CF 2 ) b - SO 2 - NH-R 1 -(NR 2 - R 3 -) c - NR 4 R 5 )]-... Formula (1-1) (In the formula, a is an integer of 0 to 2, b is an integer of 1 to 4, c is an integer between 0 and 2, X is -F or -CF 3 and R 1 and R 3 may be the same or different, and each represents a substituted or unsubstituted divalent aliphatic hydrocarbon group having from 1 to 10 carbon atoms, or a substituted or unsubstituted divalent aromatic hydrocarbon group having from 6 to 12 carbon atoms, R 2 represents a hydrogen atom, a substituted or unsubstituted monovalent aliphatic hydrocarbon group having from 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having from 6 to 12 carbon atoms, R 4 and R 5 may be the same or different, and each is a hydrogen atom, a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms. - [CFX-CF 2 ]-・・・Formula (1-2) (Wherein, X is -F or -CF 3 It is.)

2. 2. The polymer electrolyte membrane according to claim 1, wherein the ratio of the structural unit represented by the formula (1-1) to the total monomer units in the nitrogen-containing fluoropolymer is 1 mol % or more and 50 mol % or less, and the ratio of the structural unit represented by the formula (1-2) to the total monomer units is 50 mol % or more and 99 mol % or less.

3. The nitrogen-containing fluoropolymer membrane; 2. The polymer electrolyte membrane according to claim 1, wherein at least one of the first layer and the second layer is a porous material layer.

4. The polymer electrolyte membrane according to claim 3 , wherein the porosity of the porous material layer is from 40% to 90%.

5. A membrane electrode assembly comprising the polymer electrolyte membrane according to any one of claims 1 to 4 and at least one electrode joined together.

6. The polymer electrolyte membrane according to any one of claims 1 to 4, which is for use in a redox flow battery.

7. The membrane electrode assembly according to claim 5 , which is for a redox flow battery.

8. A cell for a redox flow battery comprising: a first electrolytic solution containing a first redox active material; a second electrolytic solution containing a second redox active material; a first electrode in contact with the first electrolytic solution; a second electrode in contact with the second electrolytic solution; and a diaphragm disposed between the first electrolytic solution and the second electrolytic solution, wherein the diaphragm is the polymer electrolyte membrane according to any one of claims 1 to 4.

9. The redox flow battery cell according to claim 8 , wherein the first electrolyte solution and the second electrolyte solution are acidic.

10. 10. The cell for a redox flow battery according to claim 9, wherein the first electrolyte and the second electrolyte are in contact with the nitrogen-containing fluoropolymer membrane in the polymer electrolyte membrane.

11. 9. The cell for a redox flow battery according to claim 8, wherein the membrane and at least one electrode are joined together.

12. 9. The cell for a redox flow battery according to claim 8, wherein at least one selected from the group consisting of the first electrode and the second electrode is a carbon electrode.

13. 9. The cell for a redox flow battery according to claim 8, wherein the at least one selected from the group consisting of the first redox active material and the second redox active material is at least one selected from the group consisting of a metal-based redox active material, a non-metal-based redox active material, and an organic redox active material.

14. A redox flow battery, comprising the redox flow battery cell according to claim 8 , stacked together.

15. A rolled body obtained by rolling the polymer electrolyte membrane according to any one of claims 1 to 4.

16. 16. The wound body according to claim 15, wherein the polymer electrolyte membrane has a width of 50 mm or more and 5,000 mm or less.

17. 16. The wound body according to claim 15, wherein the length of the polymer electrolyte membrane is 100 mm or more.

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