JP6034200B2 - Redox flow secondary battery - Google Patents

Description

  The present invention relates to a redox flow secondary battery.

  The redox flow secondary battery stores and discharges electricity, and belongs to a large stationary battery used for leveling the amount of electricity used. A redox flow secondary battery has a positive electrode electrolyte solution (positive electrode cell) containing a positive electrode and a positive electrode active material and a negative electrode electrolyte solution (negative electrode cell) containing a negative electrode and a negative electrode active material separated by a diaphragm. Charging and discharging is performed using an oxidation-reduction reaction, and an electrolytic solution containing the both active materials is circulated from a storage tank to an electrolytic layer to be used.

  As the active material contained in the electrolytic solution, for example, iron-chromium-based, chromium-bromine-based, zinc-bromine-based, vanadium-based utilizing a difference in charge, or the like is used.

  In particular, vanadium-based batteries have the advantages such as high electromotive force, fast electrode reaction of vanadium ions, small amount of hydrogen generated as a side reaction, and high output.

In addition, the diaphragm is devised so as not to mix the electrolyte containing the active material of both electrodes. However, the conventional diaphragm has problems such as being easily oxidized and having a sufficiently low electric resistance. In order to increase the current efficiency, the permeation of each active material ion contained in each cell electrolyte (contamination of the electrolyte in the bipolar electrolyte) is prevented as much as possible, and protons (H ⁺ ) that carry charges are sufficient. An ion exchange membrane that is easy to permeate and excellent in ion selective permeability is required.

In this vanadium secondary battery, vanadium divalent (V ²⁺ ) / 3 valent (V ³⁺ ) in the negative electrode cell and vanadium tetravalent (V ⁴⁺ ) / 5 valent (V ⁵⁺ ) in the positive electrode cell. ) Redox reaction. Therefore, since the electrolyte solution of the positive electrode cell and the negative electrode cell is the same kind of metal ion species, even if the electrolyte solution is mixed through the diaphragm, it is regenerated normally by charging, so compared to other types of metal species Hard to be a big problem. However, since active materials that are wasted increase and current efficiency decreases, active material ions should not permeate freely as much as possible.

  Conventionally, there are batteries that use various types of diaphragms (sometimes simply abbreviated as “membranes” in this specification). For example, the ionic differential pressure and osmotic pressure of an electrolyte can be freely used as a driving force. A battery using a porous film to pass through has been reported. For example, Patent Document 1 discloses a polytetrafluoroethylene (PTFE) porous film, a polyolefin (PO) -based porous film, a PO-based nonwoven fabric, and the like as such a porous film.

  Citation 2 discloses a composite membrane that combines a porous membrane and a hydrous polymer so that both electrolytes do not move due to a pressure difference between cells.

  Citation 3 discloses that a cellulose or ethylene-vinyl alcohol copolymer film is used as a nonporous hydrophilic polymer film having a hydrophilic hydroxyl group.

  Cited Document 4 describes that the use of a polysulfone membrane (anion exchange membrane) as a hydrocarbon ion exchange resin results in a current efficiency of 80% to 88.5% and excellent radical oxidation resistance. ing.

  Citation 5 discloses a method in which a fluorine-based or polysulfone-based ion exchange membrane is used as a diaphragm, and in order to increase the current efficiency, expensive platinum is supported on the positive electrode porous carbon to increase the reaction efficiency.

Cited Document 6 discloses an iron-chromium redox flow battery in which a hydrophilic resin is applied to pores of a porous film such as polypropylene (PP). Examples of this document include an example of a membrane in which both surfaces of a 100 μm-thick PP porous membrane are coated with a fluorine-based ion exchange resin (manufactured by DuPont, trademark Nafion) with a thickness of several μm. Here, Nafion, - a repeating unit represented _{by, - - (CF 2 -CF 2} ) (CF 2 -CF (-O- (CF 2 CFXO) n - (CF 2) m -SO 3 H) )-, A copolymer containing X = CF ₃ , n = 1, m = 2.

  Cited Document 7 describes an example of a vanadium type battery that uses a two-layer liquid-permeable porous carbon electrode having a specific surface lattice, and reduces the cell electrical resistance as much as possible by increasing the efficiency by devising from the electrode side. It is disclosed.

Cited Document 8 discloses a cross-linked polymer copolymerized with an anion exchange type styrenic group and divinylbenzene having a pyridinium group (using cation N ⁺ ) having low resistance and excellent proton permeability. An example of a vanadium redox flow battery used as a diaphragm is disclosed.

  Reference 9 uses a membrane having a structure in which a cationic ion exchange membrane (fluorine polymer or other hydrocarbon polymer) and an anion ion exchange membrane (polysulfone polymer) are alternately laminated. An example in which ion selective permeability is improved by a method in which the cation exchange membrane side is in contact with the positive electrode electrolyte side is disclosed.

  In Cited Document 10, a vinyl heterocyclic compound having two or more hydrophilic groups on a porous substrate made of a porous PTFE resin as a membrane having excellent chemical resistance, low resistance and excellent ion selective permeability. An example of use of an anion exchange membrane formed by combining a crosslinked polymer having a repeating unit (such as vinylpyrrolidone having an amino group) is disclosed. As for the principle, when a metal cation with a large ion diameter and charge amount is subjected to a potential difference, the cations on each cam surface are electrically repelled and the metal cation permeates through the membrane, but the ion diameter is also small. It is described that the monovalent proton (H +) can easily diffuse and permeate a diaphragm having a cation, so that the electric resistance is reduced.

JP 2005-158383 A Japanese Patent Publication No. 6-105615 JP-A-62-226580 JP-A-6-188005 JP-A-5-242905 JP-A-6-260183 JP-A-9-92321 JP-A-10-208767 Japanese Patent Laid-Open No. 11-260390 JP 2000-235849 A

However, the composite membrane disclosed in Cited Document 2 has a high electrical resistance, and each ion is not as diffuse as a porous membrane, but has a problem that it freely diffuses. The film disclosed in the cited document 3 also has the same problem as described above and is inferior in oxidation resistance.
The battery disclosed in the cited document 4 still has insufficient current efficiency, and is inferior in oxidation resistance deterioration resistance in a sulfuric acid electrolyte over a long period of time. Moreover, it is described in the comparative example of the document that the current efficiency as a Teflon (registered trademark) -based ion exchange membrane is 64.8 to 78.6%, which has a problem in performance.
Also in the cited document 5, the same problem as described above cannot be solved, and there is a problem that a large facility is expensive in terms of price.
The film disclosed in the cited document 6 is described that the internal resistance increases unless the thickness of the coating film is made extremely thin (several μm). Further, there is no description of any device for improving ion selective permeability.
The battery disclosed in Cited Document 8 has insufficient current efficiency and also has problems with long-term use due to oxidative degradation.
The film disclosed in the cited document 9 has a problem that the electric resistance becomes high.
In the results shown in the example of the cited document 10, the internal resistance (electrical resistance) of the film cannot be said to be sufficiently low, and oxidation resistance deterioration becomes a problem in long-term use.

Conventional vanadium-based redox flow battery electrolyte (separation) membranes consist of a cell in which the majority of vanadium ion ions, which are the active material of the electrolyte solution of both electrodes, and a high-valence ion group. In each of the majority of cells (negative electrode side, positive electrode side), diffusion / transmission to the counter electrode (cell) is suppressed, and proton (H ⁺ ) is selectively selected in accordance with the intended charge / discharge operation. It is used for the purpose of making it permeate. However, at present, the performance is not sufficient.
As membrane base materials mainly composed of hydrocarbon-based resins, porous membranes that are not simply ion-selective by simply isolating the electrolyte containing the electrolyte that plays the main role in both cells, and those that are not ion-selective (non-porous) A hydrophilic membrane substrate, a porous membrane in which a hydrophilic membrane substrate is embedded or coated, and the like are used. Further, a so-called cation exchange membrane having various anion groups, or a composite membrane in which a cation exchange resin is coated or embedded in pores of a porous membrane substrate, similarly, an anion exchange membrane in which the membrane itself has a cation group, Similarly, a composite membrane in which an anion exchange resin is coated or embedded on a porous membrane base material, a laminated type of the two, and the like are used as a diaphragm, and researches that make use of the respective characteristics are being conducted.
As the diaphragm, an ion-exchange resin diaphragm that sufficiently satisfies the two contradictory properties of electrical resistance (mainly dependent on proton permeability) and metal ion (polyvalent cation) permeability blocking, which is the main active material. Has not been developed so far. Fluorine ion exchange resins are also excellent in proton (H ⁺ ) permeability and have not been fully studied for contradictory properties of suppressing the transmission of active material ions. An electrolyte membrane for a redox flow battery that sufficiently satisfies oxidation resistance (hydroxy radical resistance) has not been developed.

In view of the above circumstances, the present invention has excellent ion selective permeability that can suppress the ion permeability of the active material without deteriorating proton (H ⁺ ) permeability, has low electrical resistance, An object of the present invention is to provide an electrolyte membrane for a redox flow secondary battery excellent in efficiency and a redox flow secondary battery using the same.

  As a result of intensive studies to solve the above problems, the present inventors are excellent in including a fluorine-based polymer electrolyte polymer having a specific equivalent mass EW (dry mass in grams per equivalent of ion-exchange groups). The present inventors have found that an electrolyte membrane for a redox flow secondary battery and a redox flow secondary battery using the same having excellent ion selective permeability, low electric resistance and excellent current efficiency can be achieved. I let you.

That is, the present invention is as follows.
[1]
A positive electrode cell chamber including a positive electrode made of a carbon electrode;
A negative electrode cell chamber including a negative electrode made of a carbon electrode;
An electrolyte membrane as a diaphragm for separating and separating the positive electrode cell chamber and the negative electrode cell chamber;
Having an electrolytic cell containing
The positive electrode cell chamber contains a positive electrode electrolyte containing an active material, and the negative electrode cell chamber contains a negative electrode electrolyte containing an active material,
A redox flow secondary battery that charges and discharges based on a valence change of an active material in the electrolyte solution,
The electrolyte membrane includes an ion exchange resin composition mainly composed of a fluorine-based polymer electrolyte polymer,
A redox flow secondary battery in which an equivalent mass EW (dry mass in grams per equivalent of ion-exchange groups) of the fluoropolymer electrolyte polymer is 300 to 1300 g / eq.
[2]
The redox flow secondary battery according to [1], wherein the fluorine-based polymer electrolyte polymer includes a polymer having a structure represented by the following formula (1).
_{^{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF (CF 2 -O- (CFR 1) b - (CFR 2) c -X 3)] g - (1)
(Wherein, X ¹ and X ² each independently represents one or more selected from the group consisting of a halogen atom and a C 1-3 perfluoroalkyl group. X ³ represents COOZ, SO _3. Z, PO ₃ Z ₂ or PO ₃ HZ represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or an amine (NH ₄ , NH ₃ R ₁ , NH ₂ R ₁ R ₂ , NHR ₁ R ₂ R ₃ , NR ₁ R ₂ R ₃ R ₄ ), wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently any one selected from the group consisting of an alkyl group and an arene group. Wherein X ³ is PO ₃ Z ₂ , Z may be the same or different, and R ¹ and R ² are each independently a halogen atom, having 1 to 10 carbon atoms. One selected from the group consisting of perfluoroalkyl groups and fluorochloroalkyl groups .a and g shows the above, 0 ≦ a <1,0 <g ≦ 1, a + g = 1 .c represents an integer of .b 0 to 8 indicating the number satisfying is 0 or 1.)
[3]
The redox flow according to [1] above, wherein the fluoropolymer electrolyte polymer includes a polymer having a repeating unit represented by the following formula (2) and a repeating unit represented by the following formula (3). Secondary battery.
(In the formula, Q ¹ is a perfluoroalkylene group which may have an etheric oxygen atom, and Q ² is a perfluoroalkylene which may have a single bond or an etheric oxygen atom. R ^f1 is a perfluoroalkyl group which may have an etheric oxygen atom, X is an oxygen atom, a nitrogen atom or a carbon atom, and a is a case where X is an oxygen atom 0, 1 when X is a nitrogen atom, 2 when X is a carbon atom, Y is a fluorine atom or a monovalent perfluoro organic group, s is 0 or 1, and R ^f2 is a perfluoroalkyl group, Z is a fluorine atom or a monovalent perfluoro organic group, and t is an integer of 0 to 3.)
[4]
The redox flow secondary battery according to [3], further including a repeating unit based on tetrafluoroethylene.
[5]
The redox flow secondary battery according to [1], wherein the fluorine-based polymer electrolyte polymer includes a copolymer including a repeating unit based on the following monomer A and a repeating unit based on the following monomer B.
Monomer A: Perfluoromonomer B giving a polymer having a repeating unit containing a ring structure in the main chain by radical polymerization B: CF ₂ = CF— (OCF ₂ CFY ¹ ) _m —O _p — (CF ₂ ) _n —SO ₂ Perfluorovinyl ether represented by Y ² (wherein Y ¹ is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, n is an integer of 1 to 12, and p is 0) Or 1 and m + p> 0, Y ² is OH or NHSO ₂ Z, and Z is a C 1-6 perfluoroalkyl group which may contain an etheric oxygen atom.
[6]
The redox flow secondary battery according to the above [5], wherein the repeating unit based on the monomer A is any one or more repeating units represented by the following formula (5).
(In the formula, n is an integer of 1 to 4, R ^f is a perfluoroalkyl group or perfluoroalkoxy group having 1 to 8 carbon atoms, and X ¹ and X ² are each independently a fluorine atom or trifluoromethyl. In addition, when n is 2 or more in (CX ¹ X ² ) _n , the combination of X ¹ and X ² may be different for each carbon).
[7]
The fluorine-based polyelectrolyte polymer is a copolymer obtained by copolymerizing any of the following compounds (A) to (F) as a comonomer, and is crosslinked by reacting a polymer unit based on the comonomer. The redox flow secondary battery according to any one of the above [1] to [6].
(A) A perfluoro unsaturated compound having two double bonds.
(B) Perfluoroethene or perfluoro (alkyl vinyl ether) having a bromine atom.
(C) Polyfluoroethene or polyfluoro (alkyl vinyl ether) having a carboxylic acid group, a carboxylic acid group or a carboxylic acid ester group.
(D) Polyfluoroethene or polyfluoro (alkyl vinyl ether) having a hydroxyl group.
(E) Perfluoroethene or perfluoro (alkyl vinyl ether) having a cyano group.
(F) Perfluoroethene or perfluoro (alkyl vinyl ether) having a cyanate group.
[8]
The redox flow secondary battery according to any one of [1] to [7], wherein the electrolyte membrane has an equilibrium water content of 5 to 80 mass%.
[9]
The redox flow secondary battery according to any one of [1] to [8], wherein the electrolyte membrane has a reinforcing material made of a fluorine-based microporous membrane.
[10]
Redox in any one of said [1]-[9] in which the said ion exchange resin composition contains 0.1-200 mass parts polyazole type compound with respect to 100 mass parts of said fluoropolymer electrolyte polymers. Flow secondary battery.
[11]
The polyazole compound comprises a polymer of a heterocyclic compound containing one or more nitrogen atoms in the ring, and a polymer of a heterocyclic compound containing one or more nitrogen atoms and oxygen and / or sulfur in the ring. The redox flow secondary battery according to [10], wherein the redox flow secondary battery is one or more selected from the group consisting of:
[12]
The polyazole compound is selected from the group consisting of a polyimidazole compound, a polybenzimidazole compound, a polybenzobisimidazole compound, a polybenzoxazole compound, a polyoxazole compound, a polythiazole compound, and a polybenzothiazole compound. The redox flow secondary battery according to the above [10] or [11], which is one or more selected.
[13]
The redox flow secondary battery according to any one of the above [10] to [12], wherein the fluorine-based polymer electrolyte polymer and the polyazole-based compound form an ionic bond in at least a part thereof.
[14]
The ion exchange resin composition according to any one of [1] to [13], wherein the ion exchange resin composition includes at least one selected from the group consisting of a Ce-based additive, a Co-based additive, and a Mn-based additive. Redox flow secondary battery.
[15]
The above [1] to [14], wherein the ion exchange resin composition contains 0.1 to 20 parts by mass of a polyphenylene ether resin and / or a polyphenylene sulfide resin with respect to 100 parts by mass of the fluoropolymer electrolyte polymer. The redox flow secondary battery according to any one of the above.
[16]
The redox flow secondary battery according to any one of the above [1] to [15], wherein the redox flow secondary battery is a vanadium-based redox flow secondary battery using a sulfuric acid electrolyte containing vanadium as a positive electrode and a negative electrode electrolyte. Next battery.

  The electrolyte membrane for a redox flow secondary battery of the present invention has excellent ion selective permeability. Therefore, it has high proton (hydrogen ion) permeability, low electrical resistance, can suppress the permeation of active material ions in the electrolytic solution, and further exhibits high current efficiency.

An example of the schematic diagram of the redox flow secondary battery in this embodiment is shown.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following this embodiment.

The redox flow secondary battery in this embodiment is
A positive electrode cell chamber including a positive electrode made of a carbon electrode;
A negative electrode cell chamber including a negative electrode made of a carbon electrode;
An electrolyte membrane as a diaphragm for separating and separating the positive electrode cell chamber and the negative electrode cell chamber;
Having an electrolytic cell containing
The positive electrode cell chamber contains a positive electrode electrolyte containing an active material, and the negative electrode cell chamber contains a negative electrode electrolyte containing an active material,
A redox flow secondary battery that charges and discharges based on a valence change of an active material in the electrolyte solution,
The electrolyte membrane includes an ion exchange resin composition mainly composed of a fluorine-based polymer electrolyte polymer,
The equivalent mass EW of the fluoropolymer electrolyte polymer is 300 to 1300 g / eq.

  FIG. 1 shows an example of a schematic diagram of a redox flow secondary battery in the present embodiment. The redox flow secondary battery 10 in this embodiment includes a positive electrode cell chamber 2 including a positive electrode 1 made of a carbon electrode, a negative electrode cell chamber 4 including a negative electrode 3 made of a carbon electrode, the positive electrode cell chamber 2, and the negative electrode cell. An electrolytic cell 6 including an electrolyte membrane 5 as a diaphragm that separates and separates the chamber 4 from the chamber 4, the positive electrode cell chamber 2 containing a positive electrode electrolyte containing an active material, and the negative electrode cell chamber 4 containing an active material. Includes negative electrode electrolyte. The positive electrode electrolyte and the negative electrode electrolyte containing the active material are stored, for example, by the positive electrode electrolyte tank 7 and the negative electrode electrolyte tank 8, and are supplied to each cell chamber by a pump or the like. In addition, the current generated by the Redox flow secondary battery may be converted from direct current to alternating current via the AC / DC converter 9.

The redox flow secondary battery according to the present embodiment has a liquid-permeable porous collector electrode (for negative electrode and positive electrode) arranged on both sides of the diaphragm, sandwiched by pressing, and partitioned by the diaphragm. Is a positive electrode cell chamber and the other is a negative electrode cell chamber, and the thickness of both cell chambers is secured by a spacer.
In the case of a vanadium-based redox flow secondary battery, a positive electrode electrolyte composed of a sulfuric acid electrolyte containing vanadium tetravalent (V ⁴⁺ ) and pentavalent (V ⁵⁺ ) in the positive electrode cell chamber, The battery is charged and discharged by circulating a negative electrode electrolyte containing vanadium trivalent (V ³⁺ ) and divalent (V ²⁺ ). At this time, at the time of charging, V ⁴⁺ is oxidized to V ⁵⁺ because vanadium ions emit electrons in the positive electrode cell chamber, and V ³⁺ is changed to V ² by electrons returning through the outer path in the negative cell chamber. Reduced to ⁺ . In this oxidation-reduction reaction, protons (H ⁺ ) are excessive in the positive electrode cell chamber, while protons (H ⁺ ) are insufficient in the negative electrode cell chamber. The diaphragm selectively moves excess protons in the positive electrode cell chamber to the negative electrode chamber, thereby maintaining electrical neutrality. The reverse reaction proceeds during discharge. The current efficiency (%) at this time is expressed as a ratio (%) obtained by dividing the discharge power amount by the charge power amount. Both power amounts depend on the internal resistance of the battery cell, the ion selectivity of the diaphragm, and other current losses. To do. A decrease in internal resistance improves voltage efficiency, and an improvement in ion selectivity and other reductions in current loss improve current efficiency, and thus are important indicators for redox flow secondary batteries.

  The electrolyte membrane for a redox flow secondary battery in the present embodiment includes an ion exchange resin composition mainly composed of a fluorine-based polymer electrolyte polymer having a specific equivalent mass EW.

  In this embodiment, “mainly” means that the corresponding component is contained in the resin composition in an amount of preferably 50 to 100% by mass, more preferably 80 to 100% by mass, and still more preferably 90 to 100% by mass. Say.

[Fluoropolymer electrolyte polymer]
The fluorine-based polymer electrolyte polymer in the present embodiment may include a polymer having a structure represented by the following formula (1) (hereinafter also referred to as “polymer A”).
_{^{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF (CF 2 -O- (CFR 1) b - (CFR 2) c -X 3)] g - (1)
In the formula, X ¹ and X ² each independently represent one or more selected from the group consisting of a halogen atom and a C 1-3 perfluoroalkyl group. X ³ represents COOZ, SO ₃ Z, PO ₃ Z ₂ or PO ₃ HZ. Z represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or an amine (NH ₄ , NH ₃ R ₁ , NH ₂ R ₁ R ₂ , NHR ₁ R ₂ R ₃ , NR ₁ R ₂ R ₃ R ₄ ). R ₁ , R ₂ , R ₃ and R ₄ each independently represents one or more selected from the group consisting of an alkyl group and an arene group. Here, when X ³ is PO ₃ Z ₂ , Z may be the same or different. R ¹ and R ² each independently represent one or more selected from the group consisting of a halogen atom, a C 1-10 perfluoroalkyl group and a fluorochloroalkyl group. a and g are numbers satisfying 0 ≦ a <1, 0 <g ≦ 1, and a + g = 1. b shows the integer of 0-8. c represents 0 or 1;

X ¹ and X ² each independently represent one or more selected from the group consisting of a halogen atom and a C 1 to C 3 perfluoroalkyl group. Here, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. X ¹ and X ² are preferably a fluorine atom or a C 1 to C 3 perfluoroalkyl group from the viewpoint of chemical stability of the polymer.

X ³ represents COOZ, SO ₃ Z, PO ₃ Z ₂ or PO ₃ HZ. In the present specification, X ³ is also referred to as an ion exchange group.

Z represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or an amine (NH ₄ , NH ₃ R ₁ , NH ₂ R ₁ R ₂ , NHR ₁ R ₂ R ₃ , NR ₁ R ₂ R ₃ R ₄ ). Here, it does not specifically limit as an alkali metal atom, A lithium atom, a sodium atom, a potassium atom, etc. are mentioned. Moreover, it does not specifically limit as an alkaline-earth metal atom, A calcium atom, a magnesium atom, etc. are mentioned. R ₁ , R ₂ , R ₃ and R ₄ each independently represent one or more selected from the group consisting of an alkyl group and an arene group. Here, when X ³ is PO ₃ Z ₂ , Z may be the same or different. X ³ is preferably SO ₃ Z from the viewpoint of chemical stability of the polymer.

R ¹ and R ² each independently represent one or more selected from the group consisting of a halogen atom, a C 1-10 perfluoroalkyl group and a fluorochloroalkyl group. Here, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

  a and g are numbers satisfying 0 ≦ a <1, 0 <g ≦ 1, and a + g = 1. b shows the integer of 0-8. c represents 0 or 1;

  The polymer A is preferably a perfluorocarbon sulfonic acid resin (PFSA resin) because the effects of the present invention tend to become more prominent. The PFSA resin in this embodiment has a main chain composed of a Teflon (registered trademark) skeleton chain, a perfluorocarbon as a side chain, and one to two or more sulfonic acid groups in each side chain (some of which are partially salted). It may be in the form of

The polymer A in this embodiment is
- and a repeating unit represented by formula, - (CF ₂ -CF ₂₎
Equation _{(2): CF 2 = CF-} (CF 2 CFXO) n - [A] ( wherein, X represents F or a perfluoroalkyl group having 1 to 3 carbon atoms, n represents an integer of 0 to 5 [A] is (CF ₂ ) _m —W (m represents an integer of 0 to 6. However, n and m are not 0 at the same time. W represents SO ₃ H.) or formula (3) _{: CF 2 = CF- (CF 2} ) P -CF (-O- (CF 2) K -W) or _{CF 2 = CF- (CF 2)} P -CF (- (CF 2) L -O- (CF ₂ ) _m -W) (wherein P represents an integer of 0 to 5, k represents an integer of 1 to 5, L represents an integer of 1 to 5, and m represents an integer of 0 to 6). However, k and L may be the same or different, and P, K and L are not 0 at the same time.)
It is preferable to consist of.

PFSA resin, - a repeating unit represented _{by, - - (CF 2 -CF 2} ) (CF 2 -CF (- (CF 2 CFXO) n - (CF 2) m -SO 3 H)) - Table Repeating unit (wherein, X represents F or CF ₃ , n represents an integer of 0 to 5, m represents an integer of 0 to 12, provided that n and m are not 0 at the same time). It is more preferable that the copolymer contains When the PFSA resin is a copolymer having the above structure and has a predetermined equivalent mass EW, the obtained electrolyte membrane has sufficient hydrophilicity and has high resistance to radical species generated by oxidative degradation. There is a tendency.

Furthermore, _{n in the} repeating unit represented by the above-described — (CF ₂ —CF (— (CF ₂ CFXO) _n — (CF ₂ ) _m —SO ₃ H)) — of the PFSA resin is 0, and m is 1 what is 6 integer, or _{CF 2 = CF- (CF 2)} P -CF of the formula _{(3) (-O- (CF 2} ) K -W) and CF ₂ = CF- (CF _{2 ) P -CF (- (CF 2} ) L -O- (CF 2) if it contains repeating units of both _m -W), equivalent weight EW is low, a tendency that hydrophilicity of the electrolyte membrane obtained is high is there.

The polymer A in the present embodiment is preferably a perfluorocarbon sulfonic acid resin (PFSA) having a structure represented by the following formula (4) because the effects of the present invention tend to become more prominent.
_{- [CF 2 CF 2] a} - [CF 2 -CF ((- (CF 2) m -X 4)] g - (4)
(In the formula, a and g represent a number satisfying 0 ≦ a <1, 0 <g ≦ 1, a + g = 1, m represents an integer of 1 to 6, and X ⁴ represents SO ₃ H.)

(Method for producing polymer A)
The polymer A in this embodiment can be obtained, for example, by producing a resin precursor and then hydrolyzing it.
In the case of a PFSA resin, for example, a PFSA resin precursor composed of a copolymer of a fluorinated vinyl ether compound represented by the following general formula (5) and a fluorinated olefin monomer represented by the following general formula (6) is added with water. It is obtained by decomposing.

_{CF 2 = CF- (CF 2 CFXO} ) n - [A] (5)
(In the formula, X represents F or a perfluoroalkyl group having 1 to 3 carbon atoms, n represents an integer of 0 to 5, and A represents (CF ₂ ) _m —W or CF ₂ = CF— (CF the _{- ((CF 2) L -O-} (CF 2) m -W) - 2) P -CF ((O- (CF 2) K -W) or _{CF 2 = CF- (CF 2)} P -CF P represents an integer of 0 to 12, m represents an integer of 0 to 6 (where n and m are not 0 at the same time), k represents an integer of 1 to 5, and L represents 1 to 5 (However, n and L or K are not 0 simultaneously.) W represents a functional group that can be converted to SO ₃ H by hydrolysis.)
CF ₂ = CFZ (6)
(In the formula, Z represents H, Cl, F, a perfluoroalkyl group having 1 to 3 carbon atoms, or a cyclic perfluoroalkyl group that may contain oxygen.)

The W shown a functional group capable of conversion to SO ₃ H by hydrolysis in the above formula (5) is not particularly _{limited, SO 2 F, SO 2 Cl} , SO 2 Br are preferred. In the above formula, it is more preferable that X = CF ₃ , W = SO ₂ F, and Z = F. Among them, n = 0, m = 0 to 6 (however, n and m are not 0 at the same time), and X = CF ₃ , W = SO ₂ F, and Z = F are highly hydrophilic. It is particularly preferable because it tends to obtain a solution with high resin concentration.

  The resin precursor in this embodiment can be synthesized by a known means. For example, in a polymerization method using a peroxide of a radical generator, a vinyl fluoride compound having the above ion exchange group precursor and tetrafluoroethylene (TFE) using a polymerization solvent such as a fluorinated hydrocarbon Polymerization by filling and dissolving fluorinated olefin gas (solution polymerization), Polymerization using vinyl fluoride compound itself as polymerization solvent without using solvents such as fluorine-containing hydrocarbons (bulk polymerization) , Using a surfactant aqueous solution as a medium, a method of polymerizing by filling and reacting a vinyl fluoride compound and a fluorinated olefin gas (emulsion polymerization), an aqueous solution of a co-emulsifier such as a surfactant and alcohol, A method of polymerization (emulsion polymerization) and suspension by filling a gas of vinyl fluoride compound and fluorinated olefin, emulsifying and reacting them. A method of polymerization by reacting filled suspending fluoride vinyl compound and the fluorinated olefin gas in an aqueous solution of Jozai (suspension) and the like are known.

  In the present embodiment, any of those prepared by any of the polymerization methods described above can be used. Moreover, the polymer of a block shape or a taper shape obtained by adjusting superposition | polymerization conditions, such as the supply amount of TFE gas, may be sufficient.

  Further, the resin precursor is obtained by treating an impure terminal generated in the resin molecular structure during the polymerization reaction or a portion that is structurally susceptible to oxidation (CO group, H bond portion, etc.) under a fluorine gas by a known method, The portion may be fluorinated.

  The molecular weight of the resin precursor is 0.05 to 50 (melt flow index (MFI) value measured according to ASTM: D1238 (measurement conditions: temperature 270 ° C., load 2160 g). g / 10 minutes). The preferable range of MFI of the precursor resin is 0.1 to 30 (g / 10 minutes), and the more preferable range is 0.5 to 20 (g / 10 minutes).

The resin precursor is extruded with a nozzle or die using an extruder, and then subjected to hydrolysis treatment, or is a product produced when polymerized, that is, a dispersed liquid, or a powdered product that is precipitated and filtered. Then, hydrolysis treatment is performed. The shape of the resin precursor is not particularly limited, but from the viewpoint of increasing the treatment speed in the hydrolysis treatment and acid treatment described later, it is in the form of pellets of 0.5 cm ³ or less, or in the form of dispersed liquid or powder particles. Among them, it is preferable to use a powdery product after polymerization. From the viewpoint of cost, an extruded film-like resin precursor may be used.

  The resin precursor obtained as described above and molded as necessary is subsequently immersed in a basic reaction liquid and hydrolyzed. The basic reaction solution used for the hydrolysis treatment is not particularly limited, but is an aqueous solution of an amine compound such as dimethylamine, diethylamine, monomethylamine and monoethylamine, or hydroxide of an alkali metal or alkaline earth metal. An aqueous solution of the product is preferable, and an aqueous solution of sodium hydroxide and potassium hydroxide is particularly preferable. When the alkali metal or alkaline earth metal hydroxide is used, the content is not particularly limited, but is preferably 10 to 30% by mass with respect to the entire reaction solution. More preferably, the reaction solution further contains a swellable organic compound such as methyl alcohol, ethyl alcohol, acetone and DMSO. The content of the swellable organic compound is preferably 1 to 30% by mass with respect to the entire reaction solution.

  The resin precursor is hydrolyzed in the basic reaction liquid, then sufficiently washed with warm water and the like, and then acid-treated. The acid used for the acid treatment is not particularly limited, but preferred are mineral acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as oxalic acid, acetic acid, formic acid and trifluoroacetic acid, and a mixture of these acids and water. Is more preferable. Moreover, the said acids may be used independently or may use 2 or more types together. The basic reaction solution used in the hydrolysis treatment may be removed in advance before the acid treatment, for example, by treatment with a cation exchange resin.

By the acid treatment, the resin precursor is protonated to generate ion exchange groups. For example, W of the PFSA resin precursor is protonated by acid treatment to become SO ₃ H. The fluorine-based polymer electrolyte polymer obtained by the hydrolysis and acid treatment can be dispersed or dissolved in a protic organic solvent, water, or a mixed solvent of both.

  The fluorine-based polymer electrolyte polymer in the present embodiment is a polymer having a repeating unit represented by the following formula (7) and a repeating unit represented by the following formula (8) (hereinafter referred to as “polymer B”). May also be included.).

In the formula, Q ¹ is a perfluoroalkylene group which may have an etheric oxygen atom, and Q ² is a perfluoroalkylene group which may have a single bond or an etheric oxygen atom. R ^f1 is a perfluoroalkyl group which may have an etheric oxygen atom, X is an oxygen atom, a nitrogen atom or a carbon atom, and a is 0 when X is an oxygen atom. 1 when X is a nitrogen atom, 2 when X is a carbon atom, Y is a fluorine atom or a monovalent perfluoro organic group, s is 0 or 1, and R ^f2 Is a perfluoroalkyl group, Z is a fluorine atom or a monovalent perfluoro organic group, and t is an integer of 0-3. The single bond means that the carbon atom of CY and the sulfur atom of SO ₂ are directly bonded. An organic group means a group containing one or more carbon atoms.

  In the present embodiment, the repeating unit represented by the formula (7) is referred to as a unit (7). Repeating units represented by other formulas are also described in the same manner. The repeating unit means a unit derived from the monomer formed by polymerization of the monomer. The repeating unit may be a unit directly formed by a polymerization reaction, or may be a unit in which a part of the unit is converted into another structure by treating the polymer. In this embodiment, a compound represented by the formula (u1) is referred to as a compound (u1). The same applies to compounds represented by other formulas.

Unit (7):
When the perfluoroalkylene group of Q ¹ and Q ² has an etheric oxygen atom, the oxygen atom may be one or two or more. The oxygen atom may be inserted between the carbon atom-carbon atom bonds of the perfluoroalkylene group or may be inserted at the carbon atom bond terminal. The perfluoroalkylene group may be linear or branched, and is preferably linear. 1-6 are preferable and, as for carbon number of a perfluoroalkylene group, 1-4 are more preferable. If the number of carbon atoms is 6 or less, the boiling point of the raw fluorine-containing monomer is lowered, and distillation purification becomes easy. Moreover, if carbon number is 6 or less, the increase in the equivalent mass of the polymer B will be suppressed, and the fall of the proton conductivity of an electrolyte membrane will be suppressed.

Q ² is preferably a C 1-6 perfluoroalkylene group which may have an etheric oxygen atom. When Q ² is a perfluoroalkylene group having 1 to 6 carbon atoms which may have an etheric oxygen atom, the redox flow secondary battery was operated over a longer period than when Q ² was a single bond. In particular, the stability of the power generation performance is excellent. At least one of Q ¹ and Q ² is preferably a C 1-6 perfluoroalkylene group having an etheric oxygen atom. Since the fluorine-containing monomer having a C 1-6 perfluoroalkylene group having an etheric oxygen atom can be synthesized without undergoing a fluorination reaction with a fluorine gas, the yield is good and the production is easy.

The perfluoroalkyl group for R ^f1 may be linear or branched, and is preferably linear. 1-6 are preferable and, as for carbon number of a perfluoroalkyl group, 1-4 are more preferable. As the perfluoroalkyl group, a perfluoromethyl group, a perfluoroethyl group, and the like are preferable. When the unit (7) has two or more R ^{f1 s} , R ^f1 may be the same group or different groups.

The — (SO ₂ X (SO ₂ R ^f1 ) _a ) ⁻ H ⁺ group is an ionic group. _{- (SO 2 X (SO 2} R f1) a) - The H ⁺ group, a sulfonic acid group (-SO ₃ ^- H ⁺ group), a sulfonimide group _{(-SO 2 N (SO 2 R} f1) - H + group), or a sulfonmethide group _{(-SO 2 C (SO 2 R} f1) 2) - H + group).

  Y is preferably a fluorine atom or a linear perfluoroalkyl group having 1 to 6 carbon atoms which may have an etheric oxygen atom.

  As the unit (7), the unit (M1) is preferable, and the unit (M11), the unit (M12), or the unit (M13) is more preferable because the production of the polymer H is easy and industrial implementation is easy. preferable.

R ^F11 is a straight-chain perfluoroalkylene group having 1 to 6 carbon atoms which may have a single bond or an etheric oxygen atom, and R ^F12 is a straight chain having 1 to 6 carbon atoms. It is a chain perfluoroalkylene group.

Unit (8):
The perfluoroalkyl group for R ^f2 may be linear or branched. As for carbon number of a perfluoroalkyl group, 1-12 are preferable. If the number of carbon atoms is 12 or less, an increase in the equivalent mass of the polymer B can be suppressed, and a decrease in proton conductivity of the electrolyte membrane can be suppressed. Z is preferably a fluorine atom or a trifluoromethyl group.

  The unit (8) is preferably the unit (M2), more preferably the unit (M21) or the unit (M22) from the viewpoint that the production of the polymer B is easy and industrial implementation is easy.

  However, q is an integer of 1-12.

Other units:
The polymer B may further have a repeating unit (hereinafter referred to as another unit) based on another monomer described later. What is necessary is just to adjust suitably the ratio of another unit so that the equivalent mass of the polymer B may become the preferable range mentioned later.

  The other unit is preferably a repeating unit based on a perfluoromonomer, more preferably a repeating unit based on tetrafluoroethylene, from the viewpoint of mechanical strength and chemical durability of the electrolyte membrane. The proportion of repeating units based on tetrafluoroethylene is preferably 20 mol% or more of all repeating units (100 mol%) constituting the polymer B from the viewpoint of mechanical strength and chemical durability of the electrolyte membrane. 40 mol% or more is more preferable. The proportion of repeating units based on tetrafluoroethylene is preferably 92 mol% or less, more preferably 87 mol% or less, of all repeating units (100 mol%) constituting the polymer B from the viewpoint of the electric resistance of the electrolyte membrane. preferable.

  The polymer B may have one each of the unit (7), the unit (8), and other units, or may have two or more of each. The polymer B is preferably a perfluoropolymer from the viewpoint of chemical durability of the electrolyte membrane.

  When the ratio of the unit (8) in the polymer B is unit (8) / (unit (7) + unit (8)), 0.05 to 0.30 (molar ratio) is preferable, and 0.075 to 0.25 is more preferable, and 0.1 to 0.2 is more preferable. If the ratio of the unit (8) is 0.05 or more, the durability against repetition of the wet state and the dry state of the electrolyte membrane becomes high, and the solid polymer fuel cell can be stably operated over a long period of time. When the ratio of the unit (8) is 0.30 or less, the water content of the electrolyte membrane is not too high, and the mechanical strength of the electrolyte membrane can be maintained without the softening temperature and the glass transition temperature becoming too low. .

The weight average molecular weight of the polymer B is preferably 1 × 10 ⁴ to 1 × 10 ^7, more preferably 5 × 10 ^{4 to} 5 × 10 ⁶ , and even more preferably 1 × 10 ^{5 to} 3 × 10 ⁶ . If the weight average molecular weight of the polymer B is 1 × 10 ⁴ or more, the physical properties such as the degree of swelling hardly change over time, and the durability of the electrolyte membrane is sufficient. If the weight average molecular weight of the polymer B is 1 × 10 ⁷ or less, solutionization and molding are facilitated.

The weight average molecular weight of the polymer B can be evaluated by measuring the TQ value. The TQ value (unit: ° C.) is an index of the molecular weight of the polymer, and the extrusion amount when the polymer is melt-extruded under the condition of the extrusion pressure of 2.94 MPa using a nozzle having a length of 1 mm and an inner diameter of 1 mm is 100 mm. ^The temperature is ³ / sec. For example, a polymer having a TQ value of 200 to 300 ° C. corresponds to a weight average molecular weight of 1 × 10 ⁵ to 1 × 10 ⁶ although the composition of repeating units constituting the polymer differs.

(Method for producing polymer B)
The polymer B can be manufactured through the following processes, for example.
(I) A step of polymerizing the compound (u1), the compound (u2), and, if necessary, another monomer to obtain a precursor polymer having a —SO ₂ F group (hereinafter referred to as “polymer F”).

(II) A step of bringing the polymer F and fluorine gas into contact with each other as necessary to fluorinate unstable terminal groups of the polymer F.
(III) A step of converting the —SO ₂ F group of the polymer F into a sulfonic acid group, a sulfonimide group, or a sulfonemethide group to obtain a polymer B.

(I) Process:
As the compound (u1), the compound (m1) is preferable, and the compound (m11), the compound (m12), or the compound (m13) is more preferable.

  Compound (m1) can be produced, for example, by the following synthesis route.

  As the compound (u2), the compound (m2) is preferable, and the compound (m21) or the compound (m22) is more preferable.

  Compound (u2) can be produced, for example, by a known synthesis method such as the method described in Examples of US Pat. No. 3,291,843.

  Examples of other monomers include tetrafluoroethylene, chlorotrifluoroethylene, trifluoroethylene, vinylidene fluoride, vinyl fluoride, ethylene, propylene, perfluoro α-olefins (such as hexafluoropropylene), and (perfluoroethylene). Fluoroalkyl) ethylenes (such as (perfluorobutyl) ethylene), (perfluoroalkyl) propenes (such as 3-perfluorooctyl-1-propene), and compounds represented by the following formula (9): It is done.

_{CF 2 = CF- (OCF 2 CFY} 1) m -O p - (CF 2) n -SO 2 F ··· (9)
Here, Y ₁ is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, n is an integer of 1 to 12, p is 0 or 1, and m + p> 0.

  Of the other monomers, perfluoromonomer is preferable and tetrafluoroethylene is more preferable from the viewpoint of mechanical strength and chemical durability of the electrolyte membrane.

  Examples of the polymerization method include known polymerization methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Moreover, you may superpose | polymerize in a liquid or supercritical carbon dioxide. Polymerization is performed under conditions where radicals occur. Examples of the method for generating radicals include a method of irradiating radiation such as ultraviolet rays, γ rays, and electron beams, a method of adding a radical initiator, and the like.

  The polymerization temperature is usually 10 to 150 ° C. Examples of radical initiators include bis (fluoroacyl) peroxides, bis (chlorofluoroacyl) peroxides, dialkyl peroxydicarbonates, diacyl peroxides, peroxyesters, azo compounds, persulfates, and the like. Perfluoro compounds such as bis (fluoroacyl) peroxides are preferred from the viewpoint of obtaining a polymer F having few unstable terminal groups.

  As the solvent used in the solution polymerization method, a solvent having a boiling point of 20 to 350 ° C is preferable, and a solvent having a boiling point of 40 to 150 ° C is more preferable. Examples of the solvent include perfluorotrialkylamines (perfluorotributylamine, etc.), perfluorocarbons (perfluorohexane, perfluorooctane, etc.), hydrofluorocarbons (1H, 4H-perfluorobutane, 1H-perfluoro Hexane, etc.), hydrochlorofluorocarbons (3,3-dichloro-1,1,1,2,2-pentafluoropropane, 1,3-dichloro-1,1,2,2,3-pentafluoropropane, etc. .).

  In the solution polymerization method, a monomer, a radical initiator or the like is added to a solvent, and radicals are generated in the solvent to polymerize the monomer. The monomer may be added all at once, sequentially, or continuously.

  In the suspension polymerization method, water is used as a dispersion medium, a monomer, a nonionic radical initiator or the like is added to the dispersion medium, and radicals are generated in the dispersion medium to polymerize the monomer. Nonionic radical initiators include bis (fluoroacyl) peroxides, bis (chlorofluoroacyl) peroxides, dialkyl peroxydicarbonates, diacyl peroxides, peroxyesters, dialkyl peroxides, bis (Fluoroalkyl) peroxides, azo compounds and the like can be mentioned.

  The dispersion medium may contain the above-mentioned solvent as an auxiliary agent; a surfactant as a dispersion stabilizer that prevents aggregation of suspended particles; a hydrocarbon compound (hexane, methanol, etc.) as a molecular weight regulator.

(II) Process:
The unstable terminal group is a group formed by a chain transfer reaction, a group based on a radical initiator or the like, and specifically includes a —COOH group, a —CF═CF ₂ group, a —COF group, —CF ₂ H. Group. By fluorinating or stabilizing the unstable terminal group, the decomposition of the polymer H is suppressed, and the durability of the electrolyte membrane is improved.

  The fluorine gas may be diluted with an inert gas such as nitrogen, helium or carbon dioxide, or may be used as it is without being diluted. The temperature at which the polymer F and the fluorine gas are brought into contact is preferably from room temperature to 300 ° C, more preferably from 50 to 250 ° C, further preferably from 100 to 220 ° C, particularly preferably from 150 to 200 ° C. The contact time between the polymer F and the fluorine gas is preferably 1 minute to 1 week, and more preferably 1 to 50 hours.

(III) Process:
For example, when converting a —SO ₂ F group into a sulfonic acid group, the step (III-1) is performed. When converting a —SO ₂ F group into a sulfonimide group, the step (III-2) is performed.
(III-1) A step of hydrolyzing the —SO ₂ F group of the polymer F to form a sulfonate, converting the sulfonate into an acid form and converting it to a sulfonate group.
(III-2) A salt type sulfonimide group (—SO ₂ NMSO ₂ R ^f1 group) obtained by imidizing the —SO ₂ F group of the polymer F (where M is an alkali metal or a quaternary ammonium salt) And converting to an acid-type sulfonimide group (—SO ₂ NHSO ₂ R ^f1 group).

(III-1) Process:
The hydrolysis is performed, for example, by bringing the polymer F and the basic compound into contact in a solvent. Examples of the basic compound include sodium hydroxide and potassium hydroxide. Examples of the solvent include water, a mixed solvent of water and a polar solvent, and the like. Examples of the polar solvent include alcohols (methanol, ethanol, etc.), dimethyl sulfoxide and the like. The acidification is performed, for example, by bringing a polymer having a sulfonate into contact with an aqueous solution such as hydrochloric acid or sulfuric acid. Hydrolysis and acidification are usually performed at 0 to 120 ° C.

(III-2) Process:
The following method is mentioned as imidation.
(III-2-1) A method of reacting —SO ₂ F group with R ^f1 SO ₂ NHM.
(III-2-2) A method of reacting —SO ₂ F group with R ^f1 SO ₂ NH _{2 in} the presence of alkali metal hydroxide, alkali metal carbonate, MF, ammonia or primary to tertiary amine. .
(III-2-3) A method of reacting —SO ₂ F group with R ^f1 SO ₂ NMSi (CH ₃ ) ₃ .
Acidification is performed by treating a polymer having a salt-type sulfonimide group with an acid (sulfuric acid, nitric acid, hydrochloric acid, etc.).

In addition, the polymer B whose ionic group is a sulfonimide group includes the compound (u1 ′) obtained by converting the —SO ₂ F group of the compound (u1) into a sulfonimide group, the compound (u2), and as necessary. It can also be produced by polymerizing with other monomers. Compound (u1 ′) is obtained by adding chlorine or bromine to the unsaturated bond of compound (u1), converting the —SO ₂ F group into a sulfonimide group in the same manner as in step (III-2), It can manufacture by performing a dechlorination or a debromination reaction using.

The polymer B described above has units (7) and units (8), and therefore has low electrical resistance, a higher softening temperature than conventional polymers for electrolyte membranes, and flexibility. high. The reason is as follows.
The side chain of the unit (7) has two ionic groups, and the thermal mobility of the ionic group is suppressed as compared with a conventional polymer having one ionic group in the side chain. Therefore, it is thought that the softening temperature of the polymer B which has a unit (7) becomes high. Further, since the side chain of the unit (8) has an effect of enhancing the flexibility of the main chain of the polymer, the unit (7) has a unit (7) compared to a polymer having the unit (7) and not having the unit (8). ) And the unit (8) are considered to have high flexibility.

The fluorine-based polymer electrolyte polymer in the present embodiment may include a copolymer including a repeating unit based on the following monomer A and a repeating unit based on the following monomer B (hereinafter also referred to as “polymer C”). .
Monomer A: Perfluoromonomer B giving a polymer having a repeating unit containing a ring structure in the main chain by radical polymerization B: CF ₂ = CF— (OCF ₂ CFY ¹ ) _m —O _p — (CF ₂ ) _n —SO ₂ Perfluorovinyl ether represented by Y ^{2 wherein} Y ¹ is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, n is an integer of 1 to 12, and p is 0 or 1, m + p> 0, Y ² is OH or NHSO ₂ Z, and Z is a C 1-6 perfluoroalkyl group which may contain an etheric oxygen atom.

Although the ring structure in the polymer C is not particularly limited, for example, a ring structure represented by the following formula (10) is preferable. In the formula, n is an integer of 1 to 4, R ^f is a C 1-8 perfluoroalkyl group or perfluoroalkoxy group, and X ¹ and X ² are each independently a fluorine atom or a trifluoromethyl group. It is. Moreover, when (n) is 2 or more in (CX ¹ X ² ) n, the combination of X ¹ and X ² may be different for each carbon. In any ring structure, a 4- to 7-membered ring is preferable, and a 5-membered or 6-membered ring is particularly preferable in consideration of the stability of the ring.

  Examples of the monomer having a comonomer ring structure for obtaining the polymer C include perfluoro (2,2-dimethyl-1,3-dioxole) (hereinafter referred to as PDD), perfluoro (1,3-dioxole), Examples thereof include perfluoro (2-methylene-4-methyl-1,3-dioxolane) (hereinafter referred to as MMD), 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, and the like.

  As the cyclopolymerizable monomer of the comonomer for obtaining the polymer C, perfluoro (3-butenyl vinyl ether) (hereinafter referred to as BVE), perfluoro [(1-methyl-3-butenyl) vinyl ether], perfluoro Examples include fluoro (allyl vinyl ether), 1,1 ′-[(difluoromethylene) bis (oxy)] bis [1,2,2-trifluoroethene], and the like.

  Specific examples of the repeating unit based on the monomer having a cyclic structure or the cyclopolymerizable monomer described above include, for example, a repeating unit based on PDD is represented by formula (11), a repeating unit based on BVE is represented by formula (12), and MMD. The repeating unit based on is shown by Formula (13). As used herein, the term “perfluoropolymer having an aliphatic ring structure” refers to a perfluoropolymer containing a repeating unit having a ring structure that does not contain an unsaturated bond.

As the monomer having a sulfonic acid group, a sulfonimide group or a precursor group of these groups to be reacted with a monomer having a ring structure or a cyclopolymerizable monomer, perfluorovinyl ether having a —SO ₂ F group is preferably exemplified. _{Specifically, CF 2 = CF- (OCF 2} CFY 1) m -O p - (CF 2) n perfluorovinylether (wherein represented by -SO ₂ F, Y ¹ is a fluorine atom or a trifluoromethyl And m is an integer of 0 to 3, n is an integer of 1 to 12, p is 0 or 1, and m + p> 0. Among the perfluorovinyl ethers, compounds of the formulas (14) to (16) are preferable. Here, in formulas (14) to (16), q is an integer of 1 to 8, r is an integer of 1 to 8, and s is 2 or 3. When the polymerization is carried out using a monomer having —SO ₂ F group, it is usually converted into —SO ₃ H group or sulfonimide group by hydrolysis, acidification treatment or known reaction to obtain an electrolyte material. That, CF ₂ = CF- in the polymer as a electrolyte material ^{_{(OCF 2 CFY 1) m -O}} p - (CF 2) repeating units based on _n -Z (Z is a sulfonic acid group or a sulfonimide group) It is preferably included.

In addition to the above monomers, monomers represented by the following formulas (17) to (19) can also be used. However, in the formula, Y ^2, Y ³ are each a fluorine atom or a trifluoromethyl group, t, x is an integer of 0 to 2, u, v, w is an integer from 1 to 12. More specifically, monomers represented by the formulas (20) to (23) are exemplified.

Examples of the polymer C include perfluoro (3-butenyl vinyl ether), perfluoro (2,2-dimethyl-1,3-dioxole), perfluoro (1,3-dioxole), 2,2,4- A repeating unit based on a monomer selected from the group consisting of trifluoro-5-trifluoromethoxy-1,3-dioxole and perfluoro (2-methylene-4-methyl-1,3-dioxolane); and perfluoro (3 , 6-dioxa-4-methyl-7-octene) sulfonic acid _{(CF 2 = CFOCF 2 CF (} CF 3) O (CF 2) 2 SO 3 H) or perfluoro (3-oxa-4-pentene) sulfonic acid A polymer containing a repeating unit based on (CF ₂ = CFO (CF ₂ ) ₂ SO ₃ H) is preferable.

The polymer C is synthesized through a copolymerization step of the above-described cyclic monomer or cyclopolymerizable monomer and a monomer having a —SO ₂ F group as represented by, for example, the formulas (14) to (16). However, other radically polymerizable monomers such as tetrafluoroethylene may be copolymerized for adjusting the strength. When the polymer C is composed only of a repeating unit based on a monomer having a ring structure and a repeating unit based on a monomer having a sulfonic acid group or a sulfonimide group, the skeleton tends to be rigid, and the fuel cell membrane or catalyst This is because when used in a layer, the membrane and the catalyst layer may be fragile.

  The polymer C is excellent in water repellency by passing through a fluorination step after polymerization. When used as a cathode electrolyte of a redox flow secondary battery, the polymer C improves the output of the redox flow secondary battery for a long period of time. Although stable characteristics are shown, when copolymerizing other monomers, the content of the repeating unit based on the other monomers in the polymer is 35 by mass so as not to impair the excellent output characteristics. % Or less, and particularly preferably 20% or less.

Examples of the copolymerizable monomer include TFE, chlorotrifluoroethylene, vinylidene fluoride, hexafluoropropylene, trifluoroethylene, vinyl fluoride, and ethylene. Further, the compound represented by ^{_{CF 2 = CFOR f1, CH 2}} = CHR f2, CH 2 = CHCH 2 R f2 may be used. R ^f1 is a perfluoroalkyl group having 1 to 12 carbon atoms, may have a branched structure, and may contain an etheric oxygen atom. R ^f2 is a C 1-12 perfluoroalkyl group. Among these, the use of perfluoromonomer is preferable from the viewpoint of durability because the reaction with fluorine gas is easy. Of these, TFE is preferred because it is readily available and has high polymerization reactivity.

As the compound represented by CF ₂ ═CFOR ^f1 in the above monomer, a perfluorovinyl ether compound represented by CF ₂ ═CF— (OCF ₂ CFX) _y —O—R ^f4 is preferable. However, in the formula, y is an integer of 0 to 3, X is a fluorine atom or a trifluoromethyl group, and R ^f4 is a linear or branched perfluoroalkyl group having 1 to 12 carbon atoms (hereinafter referred to as the present invention). In the specification, R ^f4 is used interchangeably.) Especially, the compound represented by Formula (24)-(26) is mentioned preferably. However, in formula, a is an integer of 1-8, b is an integer of 1-8, c is 2 or 3.

  In order to increase the strength of the film using the polymer C, the number average molecular weight of the polymer C is preferably 5,000 or more, more preferably 10,000 or more, and even more preferably 20,000 or more. Moreover, since a moldability and the solubility to the solvent mentioned later may fall when molecular weight is too large, molecular weight is preferable 5000000 or less, and it is more preferable that it is 2000000 or less.

  The content of the repeating unit based on the monomer having a ring structure in the polymer C is preferably 0.5 to 80 mol%, 1 to 80 mol%, further 4 to 70 mol%, more preferably 10 to 70 mol%. More preferably. Even if a small amount of a repeating unit based on a monomer having a ring structure is contained, there is an effect of improving the durability, but if it is less than 0.5%, the effect may not easily appear. In addition, the greater the number of repeating units based on a monomer having a ring structure, the better the durability of the present polymer under severe conditions (for example, at high temperatures). On the other hand, if there are too many repeating units having a ring structure, the number of sulfonic acid groups in the polymer will decrease, and the ion exchange capacity will decrease and the conductivity may decrease.

  Moreover, when using the polymer C as an electrolyte membrane, the use temperature may become a high temperature of 100 degreeC or more especially. Therefore, the softening temperature of the electrolyte membrane is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, and particularly preferably 120 ° C. or higher. The softening temperature can be measured by a dynamic viscoelasticity measuring method. In this specification, the storage elastic modulus of the acidified film is measured under conditions of dynamic viscoelasticity measurement at 1 Hz and a temperature increase rate of 2 ° C./min. A tangent at 50 ° C. and a tangent at a storage elastic modulus of 5 × 10 7 Pa. The intersection with is the softening temperature. In addition, since some polymers are difficult to measure dynamic viscoelasticity, such polymers can be measured by the TMA method to obtain a softening temperature. In this case, the content of the repeating unit based on the monomer having a ring structure is preferably 20 mol% or more, more preferably 30 mol% or more, and particularly preferably 40 mol% or more.

  Furthermore, when the polymer C contains a repeating unit based on a copolymerizable monomer such as TFE, the repeating unit is preferably contained in an amount of 5 to 85 mol%. When it is less than 5 mol%, for example, when used as an electrolyte membrane, the toughness of the membrane may not be sufficient. When it is more than 85 mol%, the repeating unit having a ring structure and the sulfonic acid group in the polymer are decreased, and the effect expected in the present invention may not be exhibited. More preferably, it is 10-80 mol%, More preferably, it is 10-70 mol%. Further, in order to obtain a polymer having a high softening temperature, it is preferably 10 to 70 mol%, more preferably 10 to 60 mol%, and particularly preferably 10 to 50 mol%.

  The repeating unit having a sulfonic acid group or a sulfonimide group is preferably contained so that the ion exchange capacity of the polymer C is 0.7 to 2.5 meq / g dry resin, 0.9 to More preferably, it is contained so as to be 1.5 meq / g dry resin. If the ion exchange capacity is too low, the conductivity of the polymer as the electrolyte material will be low. If it is too high, the water repellency will be poor and the durability will be poor when used in a fuel cell, and the polymer strength may be insufficient. is there.

  As the polymerization for obtaining the polymer C, conventionally known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be employed. Polymerization is performed under conditions where radicals are generated, and a method of irradiating radiation such as ultraviolet rays, γ rays, electron beams, etc., and a method of adding a radical initiator used in normal radical polymerization are common. The polymerization temperature is usually about 20 to 150 ° C. Examples of radical initiators include bis (fluoroacyl) peroxides, bis (chlorofluoroacyl) peroxides, dialkyl peroxydicarbonates, diacyl peroxides, peroxyesters, azo compounds, and persulfates. Can be mentioned.

  In the solution polymerization, the boiling point of the solvent used is usually 20 to 350 ° C., preferably 40 to 150 ° C., from the viewpoint of handleability. Examples of the solvent that can be used include the same solvents as the fluorine-containing solvent exemplified as the preferred fluorine-containing solvent when the fluorination of the polymer C is performed in the fluorine-containing solvent. That is, a polyfluorotrialkylamine compound, a perfluoroalkane, a hydrofluoroalkane, a chlorofluoroalkane, a fluoroolefin having no double bond at the molecular chain end, a polyfluorocycloalkane, a polyfluorocyclic ether compound, a hydrofluoroether, Fluorine-containing low molecular weight polyether, t-butanol and the like can be mentioned. These may be used alone or in combination of two or more. In addition, polymerization can also be performed using liquid or supercritical carbon dioxide.

The fluorine-based polymer electrolyte polymer in the present embodiment is obtained by copolymerizing any one of the following compounds (A) to (F) as a comonomer, and reacting with a polymerization unit based on the comonomer to crosslink. It may be what was done.
(A) A perfluoro unsaturated compound having two double bonds.
(B) Perfluoroethene or perfluoro (alkyl vinyl ether) having a bromine atom.
(C) Polyfluoroethene or polyfluoro (alkyl vinyl ether) having a carboxylic acid group, a carboxylic acid group or a carboxylic acid ester group.
(D) Polyfluoroethene or polyfluoro (alkyl vinyl ether) having a hydroxyl group.
(E) Perfluoroethene or perfluoro (alkyl vinyl ether) having a cyano group.
(F) Perfluoroethene or perfluoro (alkyl vinyl ether) having a cyanate group.

  In the fluorinated polymer electrolyte polymer in the present embodiment, the crosslinking site for crosslinking the basic skeleton is usually introduced by copolymerizing a radically polymerizable fluorine-containing unsaturated compound having a crosslinking site. The fluorine-containing unsaturated compound preferably has a high fluorine content, and is particularly preferably a perfluoro compound. The polymer obtained by copolymerizing the fluorine-containing unsaturated compound can be crosslinked by heat treatment or the like. Moreover, you may mix a crosslinking agent as needed. Specific examples of the fluorine-containing unsaturated compound include the following six types.

  First, perfluorounsaturated compounds having two double bonds are exemplified, and specific examples include compounds of formulas 27 to 34. Among them, the compounds of the formulas 32 to 34 have double bonds with different reactivities, and even when the perfluorovinyloxy group side is polymerized, the polymerization reactivity of the other double bond is smaller than that. It can be easily introduced into the resin as a crosslinking site without reacting during polymerization.

  Here, in the formula, h is an integer of 2 to 8, i and j are each independently an integer of 1 to 5, k is an integer of 0 to 6, and r is an integer of 0 to 5. . Moreover, s is an integer of 1-8, t is an integer of 2-5, u is an integer of 0-5.

  Secondly, perfluoroethene or perfluoro (alkyl vinyl ether) having a bromine atom (the alkyl chain may contain an etheric oxygen atom), specifically, compounds of formulas 35 to 37, etc. Is preferred. In addition, in Formula 35-37 and Formula 38-40 mentioned later, v and w are the integers of 1-5 each independently.

Third, polyfluoroethene or polyfluoro (alkyl vinyl ether) having a carboxylic acid group, a carboxylic acid group, or a carboxylic acid ester group (such as an alkoxycarbonyl group) (the alkyl chain may contain an etheric oxygen atom) Specifically, compounds of formulas 38 to 40 are preferred. However, where, M is an alkyl group having 1 to 5 carbon atoms, a hydrogen atom, an alkali metal (lithium, potassium, sodium) atom or NH _4.

  Fourthly, polyfluoroethene having a hydroxyl group or polyfluoro (alkyl vinyl ether) (the alkyl chain may contain an etheric oxygen atom) is exemplified, and specifically, compounds of formulas 41 to 43 are exemplified. Preferably mentioned.

  Fifth, perfluoroethene having a cyano group or perfluoro (alkyl vinyl ether) (the alkyl chain may contain an etheric oxygen atom), specifically, compounds of formulas 44 to 48, etc. Is preferred.

  Sixth, polyfluoroethene having a cyanato group or polyfluoro (alkyl vinyl ether) (wherein the alkyl chain may contain an etheric oxygen atom), specifically, compounds of formulas 49 to 50, etc. Is preferred. However, in formula, Z is a hydrogen atom or a trifluoromethyl group.

  The crosslinking method of the fluorine-based polymer electrolyte polymer in the present embodiment is usually a method used for crosslinking of a polymer material, such as heating, radiation irradiation, electron beam irradiation, light irradiation, etc. Is preferable in terms of the availability of the apparatus and the ease of handling. In order to accelerate the crosslinking reaction, a method in which a radical initiator such as peroxide, a crosslinking agent such as triallyl isocyanurate, bisphenol, bisphenol AF, etc. is added and heated may be employed. You may add adjuvants, such as sodium carbonate, potassium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, calcium hydroxide, magnesium hydroxide, as needed.

When using a copolymer copolymerized with a compound having a cyano group as in formulas 44 to 48 or a compound having a cyanate group as in formulas 49 to 50, there is no need to add a separate catalyst. As necessary, as a curing catalyst, Lewis acids, proton acids, tetraphenyl tin, triphenyl tin hydroxide, transition metal salts of carboxylic acids such as (C ₇ F ₁₅ COO) ₂ Zn, ammonium salts of carboxylic acids, One or more selected from peroxides, amines, amidines, compounds having an imidoylamidine structure, and the like may be used.

  Moreover, the blocked amine compound which protected some or all of the active hydrogen of ammonia or an amine compound with the other functional group can also be added as a catalyst. If necessary, an acid-type treatment of the sulfonic acid group is performed after the crosslinking. The temperature of thermosetting is usually 100 to 400 ° C, preferably 150 to 350 ° C. The treatment time is preferably 0.1 minute to 2 days, particularly 0.5 minute to 3 hours. As a heating method, methods such as oven heating, hot pressing, infrared heating, and high-frequency heating are employed. In order to prevent deterioration of the polymer, treatment under an inert gas atmosphere such as nitrogen is also preferable.

  In this embodiment, the equivalent mass EW of the fluorine-based polymer electrolyte polymer (dry mass gram of the fluorine-based polymer electrolyte polymer per equivalent of ion-exchange groups) is adjusted to 300 to 1300 (g / eq). The upper limit of EW is preferably 1100 (g / eq), more preferably 900 (g / eq). The lower limit of EW is preferably 400 (g / eq), more preferably 450 (g / eq), and even more preferably 500 (g / eq). The smaller the EW, the higher the ionic conductivity, but the higher the solubility in hot water, it is preferable that the EW is adjusted within the appropriate range as described above.

  By adjusting the equivalent mass EW of the fluorine-based polymer electrolyte polymer to the above range, it is possible to impart excellent hydrophilicity to the ion exchange resin composition containing the same, and the electrolyte obtained using the resin composition Membranes have low electrical resistance and high hydrophilicity, many smaller clusters (small parts where ion exchange groups coordinate and / or adsorb water molecules), high oxidation resistance (hydroxyl radical resistance), low electricity It tends to exhibit resistance and good ion selective permeability.

  The equivalent mass EW of the fluoropolymer electrolyte polymer is preferably 300 g / eq or more from the viewpoint of hydrophilicity and water resistance of the film, and is preferably 1300 g / eq or less from the viewpoint of hydrophilicity and electric resistance of the film. preferable. In addition, when the EW of the fluoropolymer electrolyte polymer is close to the lower limit, the resin can be obtained by directly or indirectly partially cross-linking the molecules of the ion exchange groups on the side chain of the membrane. It may be modified to control solubility and excessive swelling.

Examples of the partial crosslinking reaction include a reaction between an ion exchange group and a functional group or main chain of another molecule, a reaction between ion exchange groups, an oxidation-resistant low molecular compound, an oligomer, or a high molecular substance. In some cases, it may be a reaction with a salt (including an ionic bond with a SO ₃ H group) forming substance. Examples of the oxidation-resistant low molecular weight compound, oligomer or polymer substance include polyhydric alcohols and organic diamines.

  When the partial crosslinking reaction is performed, the EW of the fluorine-based polymer electrolyte polymer may be low. That is, the water solubility should be reduced (water resistance improved) without sacrificing the ion exchange group (in other words, EW). The same applies when the fluorine-based polymer electrolyte polymer is in a low melt flow region (polymer region) and there are many intermolecular entanglements.

Moreover, the functional group (for example, SO ₂ F group) before hydrolysis of the fluorine-based polymer electrolyte polymer is partially imidized (including alkylimidation) partially (including intermolecular). Good.

  The equivalent mass EW of the fluorine-based polymer electrolyte polymer can be measured by subjecting the fluorine-based polymer electrolyte polymer to salt substitution and back titrating the solution with an alkaline solution.

  The equivalent mass EW of the fluorine-based polymer electrolyte polymer can be adjusted by the copolymerization ratio of the fluorine-based monomer, the selection of the monomer type, and the like.

Nafion is a fluorine-based resin described in Patent Document described above (Nafion: DuPont _{TM), - (CF 2 -CF 2)} - and repeating units represented by, - (CF ₂ -CF (- And a repeating unit represented by O— (CF ₂ CFXO) _n — (CF ₂ ) _m —SO ₃ H)) —, wherein X═CF ₃ , n = 1, and m = 2. , EW is known to be 893-1030. However, when Nafion is used as a material for the electrolyte membrane of a redox flow secondary battery, the hydrophilicity is insufficient, the electric resistance is high, the selective ion permeability and the current efficiency tend to deteriorate.

  The ionic conductivity of the electrolyte membrane in this embodiment at 110 ° C. and a relative humidity of 50% RH is 0.10 S / cm or more. The electrolyte membrane in the present embodiment preferably has an ionic conductivity at 40% RH of 0.10 S / cm or more, more preferably an ionic conductivity at 30% RH of 0.10 S / cm or more, and even more preferably at 20% RH. Ionic conductivity is 0.10 S / cm or more. The higher the ionic conductivity of the electrolyte membrane, the better. However, even if the ionic conductivity at 110 ° C. and relative humidity of 50% RH is 1.0 S / cm or less, usually sufficient performance is exhibited. When the ionic conductivity of the electrolyte membrane is within the above range, the electrical resistance is lowered and excellent current efficiency is exhibited.

  As content of the fluorine-type polymer electrolyte polymer contained in the ion exchange resin composition which forms the electrolyte membrane in this embodiment, Preferably it is about 33.3-100 mass%, More preferably, it is 40-100 mass%, More preferably, it is 50-99.5 mass%.

  The ion exchange resin composition forming the electrolyte membrane in this embodiment may contain any one or more selected from the group consisting of Ce-based additives, Co-based additives, and Mn-based additives. Good. When the ion exchange resin composition contains a Ce-based additive, it is considered that some of the ion exchange groups are ion-exchanged by cerium ions, cobalt ions, and / or manganese ions. As a result, ion selective permeability and acid resistance There is a tendency for the chemical deterioration property to improve.

The Ce-based additive is preferably one that forms + 3-valent and / or + 4-valent cerium ions in the solution. Examples of the salt containing + trivalent cerium ions include cerium nitrate, cerium carbonate, cerium acetate, cerium chloride, and cerium sulfate. Examples of the salt containing + tetravalent cerium ions include cerium sulfate (Ce (SO ₄ ) ₂ .4H ₂ O), diammonium cerium nitrate (Ce (NH ₄ ) ₂ (NO ₃ ) ₆ ), and tetraammonium cerium sulfate. (Ce (NH ₄ ) ₄ (SO ₄ ) ₄ .4H ₂ O) and the like. Further, an organometallic complex salt of cerium can be used, and examples of such an organometallic complex salt of cerium include cerium acetylacetonate (Ce (CH ₃ COCHCOCH ₃ ) ₃ .3H ₂ O). Among these, cerium nitrate and cerium sulfate are particularly preferable because they are water-soluble and easy to handle.

  The Ce-based additive content is a ratio of cerium ions to the number of ion-exchange groups in the electrolyte membrane, preferably 0.02 to 20%, more preferably 0.05 to 15%, and still more preferably 0.07. -10%. When the content of the Ce-based additive is 20% or less, the ion selective permeability tends to be good, and when it is 0.02% or more, the oxidation deterioration resistance (hydroxy radical resistance) tends to be improved. is there.

As the Co-based additive, those that form +2 and / or +3 valent cobalt ions in the solution are preferable. Examples of the salt containing +2 valent cobalt ions include cobalt nitrate, cobalt carbonate, cobalt acetate, cobalt chloride, and cobalt sulfate. Examples of the salt containing + trivalent cobalt ions include cobalt chloride (CoCl ₃ ) and cobalt nitrate (Co (NO ₃ ) ₂ ). An organometallic complex salt of cobalt can also be used, and examples of such an organometallic complex salt of cobalt include cobalt acetylacetonate (Co (CH ₃ COCHCOCH ₃ ) ₃ ). Among these, cobalt nitrate and cobalt sulfate are particularly preferable because they are water-soluble and easy to handle.

As the Mn-based additive, various compounds such as water-soluble manganese salts, water-insoluble manganese salts, and insoluble compounds such as oxides and hydroxides can be used. Manganese has a valence of +2 or +3. Examples of the salt containing +2 valent manganese ions include manganese acetate (Mn (CH ₃ COO) ₂ .4H ₂ O), manganese chloride (MnCl ₂ .4H ₂ O), manganese nitrate (Mn (NO ₃ ) _2. 6H ₂ O), manganese sulfate (MnSO ₄ .5H ₂ O), manganese carbonate (MnCO ₃ .nH ₂ O), and the like. Examples of the salt containing + trivalent manganese ions include manganese acetate (Mn (CH ₃ COO) ₃ .2H ₂ O). Further, an organometallic complex salt of manganese can also be used. Examples of such an organometallic complex salt of manganese include manganese acetylacetonate (Mn (CH ₃ COCHCOCH ₃ ) ₂ ) and the like.

  The content of the Co-based and / or Mn-based additive is a ratio of cobalt ions and / or manganese ions to the number of ion exchange groups in the electrolyte membrane, preferably 0.01 to 50%, more preferably 0.05. -30%, more preferably 0.07-20%. When the content of the Co-based and / or Mn-based additive is 50% or less, the ion selective permeability tends to be good, and when it is 0.01% or more, oxidation deterioration resistance (hydroxy radical resistance) Tend to improve.

  The ion-exchangeable resin composition in the present embodiment contains a polyazole compound in addition to or in addition to the above-described fluorine-based polymer electrolyte polymer, and a basic polymer (low molecular weight substance such as an oligomer). Including the above), the chemical stability (mainly oxidation resistance and the like) of the resin composition tends to increase. These compounds partially form an ion complex in the form of fine particles or close to molecular dispersion in the resin composition to form an ion cross-linked structure. In particular, when the EW of the fluorine-based polymer electrolyte polymer is low (300 to 500), the water resistance and electrical resistance, or the water-containing cluster diameter tends to be small. It is preferable from the viewpoint.

  In addition, the fluorine-based polymer electrolyte polymer is a partial salt (total ion-exchange group equivalent of 0.01 to 0.01) with an alkali metal, alkaline earth metal, or other radical-degradable transition metal (Ce compound, Mn compound, etc.). May be used alone or in combination with a basic polymer.

  The polyazole-based compound is selected from the group consisting of a polymer of a heterocyclic compound containing one or more nitrogen atoms in the ring and a polymer of a heterocyclic compound containing one or more nitrogen atoms and oxygen and / or sulfur in the ring. One or more selected may be mentioned. The structure of the heterocyclic ring is not particularly limited, but a 5-membered ring is preferable.

  The polyazole compound is at least one selected from the group consisting of polybenzimidazole compounds, polybenzobisimidazole compounds, polybenzoxazole compounds, polyoxazole compounds, polythiazole compounds, and polybenzothiazole compounds. Is mentioned.

  When the ion exchange resin composition contains a polyazole-based compound, the polyazole-based compound is preferably in a dispersed state that does not decrease the strength, and is preferably dispersed in a sea island-like mosaic state. Further, the polyazole compound may be present in a state of being ionized with various acids so that a partial surface of the film forms an ionic bond and the inside of the film is in an ionic (cation) state. In addition, a state in which at least a part of the ion exchange group of the fluorine-based polymer electrolyte polymer and at least a part of the polyazole compound are reacted in a form close to molecular dispersion (for example, ion-bonded, acid-base ion complex) More preferably, it is in a state of chemical bonding such as a state of forming s.

  Examples of the ionic bond include a state in which the sulfonic acid group of the PFSA resin is ionically bonded to a nitrogen atom in each reactive group such as an imidazole group, an oxazole group, and a thiazole group in the polyazole compound. When the state is controlled, the cluster diameter, which is an ion channel formed with the sulfonic acid group of the PFSA resin, can be controlled around water molecules. As a result, an electrolyte membrane having an excellent balance can be obtained without significantly sacrificing any of the contradictory performances regarding ion selective permeability, water resistance, and oxidation resistance without increasing the electrical resistance of the membrane. Therefore, the performance can be greatly improved as compared with the conventional one.

  The content of the polyazole compound with respect to the fluorine-based polymer electrolyte polymer is preferably 0.1 to 200 parts by mass, more preferably 0.1 to 200 parts by mass with respect to 100 parts by mass of the fluorine-based polymer electrolyte polymer. It is 5-150 mass parts, More preferably, it is 1-100 mass parts, Most preferably, it is 1-50 mass parts. By adjusting the content of the polyazole compound to the above range, while maintaining good electrical resistance, it has excellent water resistance, strength, high oxidation resistance, and ion selective permeability for a redox flow secondary battery. There is a tendency that an electrolyte membrane can be obtained. Alternatively, a polyazole compound may be activated by including or reacting a phosphoric acid compound (single or polyphosphoric acid or the like) and binding a part thereof to the polyazole compound.

  The ion-exchangeable resin composition in the present embodiment is a polyphenylene ether (PPE) resin and / or for the purpose of increasing the oxidation resistance (chemical durability) of the electrolyte membrane or for reducing the cluster diameter. You may contain polyphenylene sulfide (PPS) resin. As a method for adding the PPE / PPS resin, the PPE / PPS resin may be mixed by an extrusion method or an aqueous solvent dispersion of the PPE / PPS resin may be mixed with a stock solution dispersion of a resin composition mainly composed of a fluorine-based polymer electrolyte polymer. . The addition amount is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the fluorinated polymer electrolyte polymer. When the content of the PPE and / or PPS resin is 0.1 parts by mass or more, the above effects tend to be exhibited. When the content is 20 parts by mass or less, sufficient film strength tends to be obtained.

  The polyphenylene sulfide resin in the present embodiment is preferably a polyphenylene sulfide resin containing a paraphenylene sulfide skeleton of 70 mol% or more, preferably 90 mol% or more. The method for producing PPS is not particularly limited. Usually, a halogen-substituted aromatic compound, for example, p-dichlorobenzene is polymerized in the presence of sulfur and sodium carbonate, sodium sulfide in a polar solvent. Examples of the method include polymerization in the presence of sodium hydrogen sulfide and sodium hydroxide or hydrogen sulfide and sodium hydroxide or sodium aminoalkanoate, and self-condensation of p-chlorothiophenol. Among them, N-methylpyrrolidone, dimethyl, etc. A method of reacting sodium sulfide with p-dichlorobenzene in an amide solvent such as acetamide or a sulfone solvent such as sulfolane is suitable. Specifically, for example, US Pat. No. 2,513,188, Japanese Patent Publication No. 44-27671, Japanese Patent Publication No. 45-3368, Japanese Patent Publication No. 52-12240, Japanese Patent Publication No. Sho 61-225217, and US Patents. No. 3,274,165, British Patent No. 1160660, Japanese Patent Publication No. 46-27255, Belgian Patent No. 29437, JP-A-5-222196, etc. Obtained by the prior art method.

  PPS preferably has a melt viscosity at 320 ° C. (using a flow tester, 300 ° C., load 196 N, L / D (L: orifice length, D: orifice inner diameter) = 10/1 value held for 6 minutes) 1 to 10,000 poise, more preferably 100 to 10,000 poise.

  Furthermore, what introduce | transduced the acidic functional group into PPS can also be used suitably. The acidic functional group to be introduced is preferably a sulfonic acid group, a phosphoric acid group, a carboxylic acid group, a maleic acid group, a maleic anhydride group, a fumaric acid group, an itaconic acid group, an acrylic acid group, or a methacrylic acid group. Particularly preferred. The method for introducing the acidic functional group is not particularly limited, and is performed using a general method. For example, the introduction of a sulfonic acid group can be carried out under a known condition using a sulfonating agent such as sulfuric anhydride or fuming sulfuric acid. Hu, T .; Xu, W .; Yang, Y. et al. Fu, Journal of Applied Polymer Science, Vol. 91, E.E. Montoneri, Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 27, 3043-3051 (1989). Further, those in which the introduced acidic functional group is substituted with a metal salt or an amine salt are also preferably used. The metal salt is preferably an alkali metal salt such as sodium salt or potassium salt, or an alkaline earth metal salt such as calcium salt.

  Specific examples of the polyphenylene ether resin include, for example, poly (2,6-dimethyl-1,4-phenylene ether), poly (2-methyl-6-ethyl-1,4-phenylene ether), and poly (2-methyl -6-phenyl-1,4-phenylene ether), poly (2,6-dichloro-1,4-phenylene ether) and the like, and 2,6-dimethylphenol and other phenols (for example, 2,6- Polyphenylene ether copolymers such as copolymers with 3,6-trimethylphenol and 2-methyl-6-butylphenol are also included. Among them, poly (2,6-dimethyl-1,4-phenylene ether), a copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol is preferable, and poly (2,6-dimethyl-1 , 4-phenylene ether) is particularly preferred.

  The method for producing PPE is not particularly limited. For example, oxidative polymerization of 2,6-xylenol is performed using, for example, a complex of cuprous salt and amine described in US Pat. No. 3,306,874 as a catalyst. In addition, U.S. Pat. Nos. 3,306,875, 3,257,357, 3,257,358, Japanese Patent Publication Nos. 52-17880, 50-51197, and JP It can be easily produced by the method described in Japanese Patent Laid-Open No. 63-152628.

  In addition to the above-mentioned PPE alone, the polyphenylene ether resin contains polystyrene having atactic and syndiotactic stereoregularity (including atactic high impact polystyrene) in an amount of 1 to 100 parts by mass with respect to 100 parts by mass of the PPE component. What was mix | blended in the range of 400 mass parts can also be used suitably.

  Furthermore, as the polyphenylene ether resin, those obtained by introducing a reactive functional group into the various polyphenylene ethers listed above can be suitably used. Examples of the reactive functional group include an epoxy group, an oxazonyl group, an amino group, an isocyanate group, a carbodiimide group, and other acidic functional groups. Among them, the acidic functional group is more preferably used. The acidic functional group to be introduced is preferably a sulfonic acid group, a phosphoric acid group, a carboxylic acid group, a maleic acid group, a maleic anhydride group, a fumaric acid group, an itaconic acid group, an acrylic acid group, or a methacrylic acid group. Is particularly preferred.

  The weight average molecular weight of the polyphenylene ether resin is preferably 1,000 or more and 5,000,000 or less, more preferably 1,500 or more and 1,000,000 or less.

  As the fluorine-based polymer electrolyte polymer in the present embodiment, fluorine-based resins other than PFSA resins (resins containing carboxylic acid, phosphoric acid, etc. and other known fluorine-based resins) can be used. When two or more of these resins are used, they may be mixed in a solvent or dispersed in a medium, or resin precursors may be extruded and mixed.

  The equilibrium moisture content of the electrolyte membrane is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more. Moreover, as an upper limit, it is 80 mass% or less, More preferably, it is 50 mass% or less, More preferably, it is 40 mass% or less. When the equilibrium water content of the electrolyte membrane is 5% by mass or more, the electric resistance, current efficiency, oxidation resistance, and ion selective permeability of the membrane tend to be good. On the other hand, when the equilibrium moisture content is 50% by mass or less, the dimensional stability and strength of the membrane are improved, and the increase in water-soluble components tends to be suppressed. The equilibrium moisture content of the electrolyte membrane is based on a membrane obtained by forming a resin composition from a dispersion of water and an alcohol-based solvent and drying at 160 ° C. or lower, and the equilibrium is 23 ° C. and 50% relative humidity (RH). It is expressed as saturated water absorption (Wc).

  The equilibrium moisture content of the electrolyte membrane can be adjusted by the same method as that for EW described above.

  The electrolyte membrane in this embodiment may have a reinforcing material composed of a fluorine-based microporous membrane. The fluorine-based microporous membrane is not particularly limited as long as the affinity with the fluorine-based polymer electrolyte polymer is good, and examples thereof include a microporous membrane made of polytetrafluoroethylene (PTFE), which is stretched and porous. A polytetrafluoroethylene (PTFE) -based membrane is preferable. A reinforcing membrane in which an ion-exchange resin composition mainly composed of a fluorine-based polymer electrolyte polymer is embedded in this PTFE-based membrane with substantially no gap is the viewpoint of the strength of the thin film and the viewpoint of suppressing the dimensional change in the plane (longitudinal and lateral) directions. To more preferable. The reinforcing membrane is prepared by immersing an appropriate amount of a dispersion of an appropriate concentration of a solute having the above-mentioned components in an organic solvent or alcohol-water containing the above-described ion exchange resin composition in a porous membrane, It can be obtained by drying.

  The solvent used for producing the reinforcing membrane is not particularly limited, but a solvent having a boiling point of 250 ° C. or lower is preferable, a solvent having a boiling point of 200 ° C. or lower is more preferable, and a boiling point of 120 ° C. or lower is more preferable. It is a solvent. Among these, water and aliphatic alcohols are preferable, and specific examples include water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, and tert-butyl alcohol. The said solvent may be used by a single solvent, or may use 2 or more types together.

  Although the manufacturing method of the PTFE microporous membrane suitably used in the present embodiment is not particularly limited, it is preferably an expanded PTFE microporous membrane from the viewpoint of suppressing the dimensional change of the electrolyte membrane. The expanded PTFE microporous membrane is produced by a known method as disclosed in, for example, JP-A-51-30277, JP-A-1-01876 and JP-A-10-30031. be able to. Specifically, first, a liquid lubricant such as solvent naphtha and white oil is added to fine powder obtained by coagulating an aqueous PTFE emulsion polymerization dispersion, and paste extrusion is performed in a rod shape. Thereafter, this rod-like paste extrudate (cake) is rolled to obtain a PTFE green body. The green tape at this time is stretched at an arbitrary magnification in the longitudinal direction (MD direction) and / or the width direction (TD direction). At the time of stretching or after stretching, the liquid lubricant filled at the time of extrusion can be removed by overheating or extraction to obtain a stretched PTFE microporous membrane.

  Fluorine-based microporous membranes may be prepared by adding known additives such as non-fibrinated materials (for example, low molecular weight PTFE), ultraviolet absorbers, light stabilizers, antistatic agents, antifogging agents, and color pigments as necessary. You may contain in the range which does not impair the achievement and effect of this.

  The fluorine-based microporous membrane preferably has a pore distribution center (peak) in the pore diameter range of 0.08 μm to 5.0 μm, more preferably in the range of 0.1 to 4.0 μm. More preferably, it is in the range of 0.3 to 3.0 μm. Here, the pore distribution of the microporous membrane refers to a value measured by a bubble point half dry method using a bubble point method described in JIS-K-3832. Here, if the distribution center of the pore diameter is 0.08 μm or more, it can be easily filled with an additive or an electrolyte solution having a hydrogen peroxide suppressing effect and the like, and generation of voids in the electrolyte membrane can be suppressed. Since a sufficient filling rate of the electrolyte polymer can be secured, the processability tends to be excellent. If the distribution center of the pore diameter is 5.0 μm or less, the dimensional change of the electrolyte membrane can be suppressed, and a sufficient membrane reinforcing effect tends to be obtained.

  From the viewpoint of initial power generation characteristics, the distribution center of the pore distribution of the microporous membrane is preferably 0.1 μm or more, more preferably 0.3 μm or more, and preferably 0.5 μm or more. More preferably, it is particularly preferably 0.7 μm or more. From the viewpoint of the reinforcing effect of the membrane, the distribution center of the pore distribution of the microporous membrane is preferably 4.5 μm or less, more preferably 4.0 μm or less, and 3.5 μm or less. More preferably, it is particularly preferably 3.0 μm or less.

  The pore distribution of the fluorine-based microporous membrane is preferably such that the abundance of pores having a pore diameter of 0.08 μm to 5.0 μm in the microporous membrane is 0.5 or more (quantity ratio). Here, the “abundance of pores” of the microporous membrane means a pore diameter measurement range of 0.065 μm to 10.0 μm by a bubble point half dry method using a bubble point method described in JIS-K-3832. The ratio of the number of pores existing in the range of the pore diameter of 0.08 μm to 5.0 μm to the total number of pores of the microporous membrane measured. Adjusting the microporous membrane to have a pore size of 0.08 μm to 5.0 μm in an amount of 0.5 or more (quantity ratio), the pore size of the microporous membrane becomes relatively uniform. It becomes easy to uniformly fill the voids of the porous membrane with the fluorine-based polymer electrolyte polymer. As a result, when the fluorine-based polymer electrolyte polymer contains an additive, the additive can be uniformly dispersed in the membrane, so that voids are not easily generated in the membrane, and the electrolyte membrane tends to exhibit high chemical durability. is there. When the additive does not have proton conductivity, the pore diameter of the microporous membrane is adjusted to be about the same as or larger than the median diameter of the additive so that the pores of the microporous membrane are not blocked by the additive. be able to. This indicates that, as a result, proton conduction in the membrane tends to be performed smoothly without being disturbed, and it is possible to exhibit excellent effects such as improving the initial characteristics of the electrolyte membrane. It becomes.

  The abundance of pores having a pore diameter of 0.08 μm to 5.0 μm of the fluorine-based microporous membrane in the present embodiment is more preferably 0.7 or more, further preferably 0.8 or more, It is even more preferably 0.9 or more, and particularly preferably 1.

  Moreover, the abundance (quantity ratio) of pores having a pore diameter of 0.5 to 5.0 μm in the fluorine-based microporous membrane is preferably 0.5 or more, more preferably 0.7 or more, and still more preferably 0.8. 8 or more, even more preferably 0.9 or more, and particularly preferably 1.

  Furthermore, the abundance (quantity ratio) of pores having a pore diameter of 0.7 μm to 5.0 μm of the microporous membrane is preferably 0.5 or more, more preferably 0.7 or more, further preferably 0.8 or more. Even more preferably, it is 0.9 or more, and particularly preferably 1.

  The fluorine-based microporous membrane in the present embodiment preferably has at least two distribution centers in the pore distribution. When the pore distribution of the fluorine-based microporous membrane has two distribution centers, (i) the distribution center having a large pore diameter plays a role such as promotion of discharge of reaction product water and easy filling of the additive (ii) ) Since the distribution center with a small pore size has a part that plays a role of suppressing the volume swelling of the electrolyte by the mechanical strength of the microporous membrane, the electrolyte membrane including this microporous membrane is chemically durable. It tends to be easy to achieve both physical properties and physical durability.

  The pore size of the fluorine-based microporous membrane depends on the type of lubricant, the dispersibility of the lubricant, the stretch ratio of the microporous membrane, the lubricant extraction solvent, the heat treatment temperature, the heat treatment time, the extraction time, and the extraction temperature. The numerical value can be adjusted to the above range.

  In addition, the fluorine-based microporous membrane in the present embodiment may be a single layer or may be composed of multiple layers as necessary. From the standpoint that defects do not propagate even when defects such as voids and pinholes occur in each single layer, a multilayer is preferable. On the other hand, from the viewpoint of the filling properties of the electrolyte polymer and the additive, a single layer is preferable. Examples of the method for forming the microporous film into a multilayer include a method of bonding two or more single layers by thermal lamination, a method of rolling a plurality of cakes, and the like.

  Moreover, it is preferable that the elastic modulus of at least one of the machine flow direction (MD) at the time of manufacture and the direction perpendicular | vertical to this (TD) is 1000 MPa or less, and the fluorine microporous film in this embodiment is 500 MPa or less. More preferably, it is more preferably 250 MPa or less. By setting the elastic modulus of the microporous membrane to 1000 MPa or less, the dimensional stability of the electrolyte membrane is improved. Here, the elastic modulus of the microporous membrane refers to a value measured according to JIS-K7113.

  Proton conduction in the fluorinated polymer electrolyte polymer is made possible by the absorption of water by the fluorinated polymer electrolyte polymer and the hydration of the ion exchange groups. Therefore, the conductivity at the same humidity increases as the ion exchange group density increases and the ion exchange capacity increases. Also, the higher the humidity, the higher the conductivity.

  The fluorine-based polymer electrolyte polymer in the present embodiment exhibits high conductivity even under low humidity when the sulfone group density is high, but has a problem that it is extremely water-containing under high humidity. For example, in the operation of a redox flow secondary battery, starting and stopping are usually performed once or more once a day, but the electrolyte membrane repeats swelling and shrinking due to a change in humidity at that time. It is negative in terms of both performance and durability that the electrolyte membrane repeats such wet and dry dimensional changes. When the ion exchange capacity is high, the fluorine-based polymer electrolyte polymer in the present embodiment is easy to contain water, and when the film is formed as it is, the dimensional change in wet and dry is large. However, by using a microporous film having an elastic modulus of 1000 MPa or less, it is possible to relieve the stress due to the volume change of the film with the microporous film and suppress the dimensional change. On the other hand, if the elastic modulus of the microporous membrane is too small, the strength of the membrane tends to decrease. Accordingly, the elastic modulus of the fluorine-based microporous membrane is preferably 1 to 1000 MPa, more preferably 10 to 800 MPa, and further preferably 100 to 500 MPa.

  The fluorine-based microporous membrane in the present embodiment preferably has a porosity of 50% to 90%, more preferably 60% to 90%, still more preferably 60% to 85%, and 50% to 90%. 85% is particularly preferable. When the porosity is in the range of 50% to 90%, the ionic conductivity of the electrolyte membrane, the strength of the electrolyte membrane, and the suppression of dimensional change tend to be compatible. Here, the porosity of the microporous film refers to a value measured by a mercury porosimeter (for example, Shimadzu Corporation, trade name: Autopore IV 9520, initial pressure of about 20 kPa) by a mercury intrusion method.

  The porosity of the microporous membrane can be adjusted to the above range depending on the number of pores in the microporous membrane, the pore diameter, the pore shape, the draw ratio, the amount of liquid lubricant added, and the type of liquid lubricant. As a means for increasing the porosity of the microporous film, for example, a method of adjusting the addition amount of the liquid lubricant to 5 to 50% by mass can be mentioned. By adjusting the addition amount of the liquid lubricant within this range, the moldability of the resin constituting the microporous membrane is maintained and the plasticizing effect is sufficient. It can be highly fibrillated in the axial direction and can efficiently increase the draw ratio. On the other hand, examples of means for lowering the porosity include reducing the amount of liquid lubricant and decreasing the draw ratio.

  The fluorine-based microporous membrane in this embodiment preferably has a thickness of 0.1 μm to 50 μm, more preferably 0.5 μm to 30 μm, still more preferably 1.0 μm to 20 μm, and 2.0 μm. It is particularly preferable that it is ˜20 μm. When the film thickness is in the range of 0.1 μm to 50 μm, the polymer electrolyte polymer can fill the microporous membrane with pores, and the dimensional change of the electrolyte membrane tends to be suppressed. Here, the film thickness of the microporous membrane is determined by sufficiently allowing the membrane to stand in a constant temperature and humidity room of 50% RH, and then using a known film thickness meter (for example, trade name “B-1 manufactured by Toyo Seiki Seisakusho”). ") Means the value measured using.

  The value of the film thickness of the microporous film can be adjusted to the above range by the solid content of the cast solution, the amount of the extruded resin, the extrusion speed, and the stretching ratio of the microporous film.

  It is preferable that the fluorine-based microporous membrane in the present embodiment is further subjected to a heat setting treatment to reduce shrinkage. By performing this heat setting treatment, the shrinkage of the microporous membrane under a high temperature atmosphere can be reduced, and the dimensional change of the electrolyte membrane can be reduced. The heat setting is performed on the microporous film by, for example, relaxing the stress in the TD (width direction) direction in a temperature range below the melting point of the microporous film raw material with a TD (width direction) tenter. In the case of PTFE suitably used in the present embodiment, a preferable stress relaxation temperature range is 200 ° C to 420 ° C.

  In addition, the fluorine-based microporous film in the present embodiment may be subjected to surface treatment such as coating with a surfactant and chemical modification, as necessary, within a range that does not impair the problems and effects of the present invention. By performing the surface treatment, the surface of the microporous membrane can be hydrophilized, and the water content of the electrolyte membrane can be adjusted in addition to the effect of high filling of the polymer electrolyte polymer solution.

  The method for producing an electrolyte membrane (film formation method) in the present embodiment is not particularly limited, and a known extrusion method or cast film formation can be used. The electrolyte membrane may be a single layer or a multilayer (2 to 5 layers). In the case of a multilayer, it is possible to improve the performance of the electrolyte membrane by laminating films having different properties (for example, resins having different EW and functional groups). it can. In the case of a multilayer, it may be laminated at the time of extrusion film formation or casting, or the obtained respective films may be laminated.

  In addition, the electrolyte membrane formed by the above method is thoroughly washed with water (or treated with a dilute aqueous acidic solution such as hydrochloric acid, nitric acid, sulfuric acid or the like before washing with water if necessary) to remove impurities. The film is preferably heat-treated in air (preferably in an inert gas) at 130 to 200 ° C., preferably 140 to 180 ° C., more preferably 150 to 170 ° C. for 1 to 30 minutes. The heat treatment time is more preferably 2 to 20 minutes, further preferably 3 to 15 minutes, and particularly preferably about 5 to 10 minutes.

  One of the reasons for performing the above treatment is that the raw material-derived particles (between the primary particles and the secondary particles) and the molecules are not sufficiently entangled with each other in the state as they are at the time of film formation. For the purpose of entanglement of water, it is particularly useful for water resistance (especially lowering the hot water-dissolved component ratio), stabilizing the saturated water absorption rate of water, and generating stable clusters. It is also useful from the viewpoint of improving the film strength. This is particularly useful when the cast film forming method is used.

  Another reason is that by forming minute intermolecular cross-links between molecules of the fluorine-based polymer electrolyte polymer, it contributes to water resistance and stable cluster formation, and the cluster diameter is made uniform and It is estimated that there is an effect to make it smaller.

  Furthermore, the ion exchange group of the fluorine-based polyelectrolyte polymer in the resin composition reacts with an active reaction site (such as an aromatic ring) of other additives (including the resin) at least a part thereof. Therefore, it is presumed that minute cross-links are generated and stabilized (particularly due to the reaction of ion-exchange groups existing in the vicinity of other resin components that are dispersed additives). The degree of this cross-linking is preferably 0.001 to 5%, more preferably 0.1 to 3%, still more preferably 0.2 to 0.2% in terms of EW (degree of EW reduction before and after heat treatment). About 2%.

  In addition, when excessive treatment exceeding the upper limit of the above treatment conditions (time, temperature) is performed, defluorination, dehydrofluoric acid, desulfonic acid, thermal oxidation sites, etc. increase, and defects in the molecular structure occur. From that point of view, the oxidation degradation resistance tends to deteriorate during actual use as an electrolytic membrane. On the other hand, if it is less than the lower limit of the processing conditions, the effect of the above-described main processing may be insufficient.

The ion cluster present in the electrolyte membrane in the present embodiment has an appropriate molecular structure consisting of a hydrophobic portion forming a fluorinated hydrocarbon portion that forms the skeleton of the polymer electrolyte polymer molecule and a side chain bonded to the main chain. And a portion where a plurality of hydrophilic groups, which are ion-exchange groups located at the tip and forming the length portion, are gathered (via molecules), and water molecules, hydrogen bonds and other affinities coordinated around the portion. It consists of free water (also called free water) collected in the vicinity. Then, a plurality of large-sized channels (so-called ion clusters) and small-sized ion channels that connect the channels are formed. As a result, the ion channels continuously pass in the thickness direction of the membrane, and these ions (especially protons). Functions as a H ⁺ ) conduction path (channel).

The ion cluster diameter measured by the small angle X-ray method in 25 ° C. water of the electrolyte membrane in this embodiment is preferably 1.00 to 3.10 nm, more preferably 1.50 to 3.00 nm, and still more preferably 1. .70 to 2.95 nm, particularly preferably 2.00 to 2.75 nm. When the ion cluster diameter exceeds 3.10 nm, large ions are likely to be transmitted, which may cause a problem in ion selective permeability, and the strength of the membrane tends to decrease. On the other hand, when the ion cluster diameter is less than 1.00 nm, it becomes difficult for protons (H ⁺ ) coordinated with water molecules to pass through and the electrical resistance tends to increase.

The number of ion clusters (units / nm ³ ) per unit volume of the electrolyte membrane is preferably 0.06 to 0.25, more preferably 0.09 to 0.22, and still more preferably 0.12 to 0.00. 20. If the number of ion clusters per unit volume is too large, the film strength may decrease, and if it is too small, the electrical conductivity tends to deteriorate (membrane electrical resistance decreases).

The specific calculation method of the ion cluster diameter and the number of clusters is as follows.
Small-angle X-ray scattering measurement is performed in a state where the electrolyte membrane is impregnated with water at 25 ° C., and empty cell scattering correction and absolute intensity correction are performed on the obtained scattering profile. When the measurement is performed using a two-dimensional detector, the data is made one-dimensional by an annular average or the like, and the scattering angle dependence of the scattering intensity is obtained. Using the scattering angle dependence (scattering profile) of the scattering intensity obtained in this way, clusters were created according to the method described in Yasuhiro Hashimoto, Naoki Sakamoto, Hideki Iijima Polymer Sciences Vol.63 No.3 pp.116 2006 The diameter can be determined. In other words, assuming that the cluster structure is represented by a core-shell type hard sphere having a particle size distribution, the theoretical scattering formula based on this model is used to fit the region where scattering from clusters in the measured scattering profile is dominant. Thus, the average cluster diameter (cluster diameter) and the cluster number density can be obtained. In this model, the core portion corresponds to a cluster, and the core diameter is the cluster diameter. Note that the shell layer is virtual and the electron density of the shell layer is the same as that of the matrix portion. The thickness is 0.25 nm.

  The ion cluster diameter and the number of ion clusters of the electrolyte membrane can be adjusted by the polymer structure, polymer composition, film forming conditions, and the like.

  The electrolyte membrane in this embodiment has excellent ion selective permeability, low electrical resistance, excellent durability (mainly hydroxyl radical oxidation resistance), and was excellent as a diaphragm for redox flow secondary batteries. Demonstrate performance. In addition, each physical property in this specification can be measured according to the method described in the following Examples, unless otherwise specified.

  Next, the present embodiment will be described more specifically with reference to examples and comparative examples. However, the present embodiment is not limited to the following examples unless it exceeds the gist.

[Measuring method]
(Fluoropolymer electrolyte polymer)
(1) Melt flow index of PFSA resin precursor Based on ASTM: D1238, measurement was carried out under conditions of measurement: temperature 270 ° C. and load 2160 g.

(2) Equivalent mass EW of PFSA resin
0.3 g of PFSA resin was immersed in 30 mL of a saturated NaCl aqueous solution at 25 ° C. and left for 30 minutes with stirring. Subsequently, the free protons in the saturated NaCl aqueous solution were subjected to neutralization titration using 0.01N sodium hydroxide aqueous solution with phenolphthalein as an indicator. The PFSA resin component obtained after neutralization, in which the counter ion of the ion exchange group is in the state of sodium ion, was rinsed with pure water, further vacuum dried and weighed. The amount of sodium hydroxide required for neutralization is M (mmol), and the mass of the PFSA resin in which the counter ion of the ion exchange group is in a sodium ion state is W (mg). g / eq).
EW = (W / M) −22

(Polymer electrolyte membrane)

(3) Film thickness After the film sample was allowed to stand for 1 hour or longer in a room at 23 ° C. and 50% RH, the film was measured using a film thickness meter (trade name “B-1” manufactured by Toyo Seiki Seisakusho). The thickness was measured.

(4) Membrane equilibrium moisture content
A dispersion of PFSA resin was applied on a clear glass plate, dried at 150 ° C. for about 10 minutes, peeled to form a film of about 30 μm, and left in water at 23 ° C. for about 3 hours. Equilibrium water content was measured when left in a room at 50 ° C. and a relative humidity (RH) of 50% for 24 hours. As a standard dry film, an 80 ° C. vacuum dry film was used. The equilibrium moisture content was calculated from the change in mass of the membrane.

(5) Membrane water absorption
A dispersion of PFSA resin is applied on a clear glass plate, dried at 150 ° C. for about 10 minutes, peeled to form a film of about 30 μm, and left in water at 23 ° C. for about 3 hours. The maximum water content was measured when wiped off. As a standard dry film, an 80 ° C. vacuum dry film was used. The maximum water content was calculated from the change in mass of the membrane.

(Microporous membrane)
(6) Pore distribution The pore distribution of the microporous membrane was measured as follows. First, a microporous membrane sample was cut into a size of φ25 mm, and measurement was performed using a through pore distribution / gas, fluid permeability analyzer (manufactured by Xonics Corporation, apparatus name: Porometer 3G). The measurement of this apparatus is based on the bubble point method described in JIS-K-3832, and after the pore volume of the microporous membrane is first completely filled with a test liquid (porofil (registered trademark)) In this method, the pressure applied to the porous membrane is gradually increased to obtain the pore distribution from the surface tension of the test liquid, the pressure of the applied gas, and the supply flow rate (bubble point half-dry method). The pore distribution of the microporous membrane was measured with a pore measurement range: 0.065 μm to 10.0 μm, a flow rate gas: compressed air.
Moreover, the abundance of the pores was calculated by the following formula.
(Abundance of pores) = (Number of pores existing in a pore diameter range of 0.3 μm to 5.0 μm) / (Total number of pores of a microporous membrane existing in a pore diameter of 0.065 μm to 10.0 μm)

(7) Elastic modulus The membrane sample was cut into a rectangular film of 70 mm x 10 mm, and the elastic modulus was measured according to JIS K-7127.

(8) Porosity The porosity was measured by mercury porosimetry using a mercury porosimeter (manufactured by Shimadzu Corporation, trade name: Autopore IV 9520, initial pressure of about 20 kPa).

(9) Charging / discharging test Redox flow secondary batteries have liquid-permeable porous collector electrodes (for negative electrode and positive electrode) arranged on both sides of the diaphragm on both sides of the diaphragm. One was sandwiched and separated by a diaphragm, the positive electrode cell chamber, the other was the negative electrode cell chamber, and the thickness of both cell chambers was secured with a spacer. The positive electrode cell chamber is composed of a sulfuric acid electrolyte containing vanadium tetravalent (V ⁴⁺ ) and pentavalent (V ⁵⁺ ), and the negative electrode cell chamber is composed of vanadium trivalent (V ³⁺ ) and the same. A negative electrode electrolyte containing divalent (V ²⁺ ) was circulated to charge and discharge the battery. At this time, at the time of charging, V ⁴⁺ is oxidized to V ⁵⁺ because vanadium ions emit electrons in the positive electrode cell chamber, and V ³⁺ is changed to V ² by electrons returning through the outer path in the negative cell chamber. Reduced to ⁺ . In this oxidation-reduction reaction, protons (H ⁺ ) are excessive in the positive electrode cell chamber, while protons (H ⁺ ) are insufficient in the negative electrode cell chamber. The diaphragm selectively moves excess protons in the positive electrode cell chamber to the negative electrode chamber, thereby maintaining electrical neutrality. The reverse reaction proceeds during discharge. The battery efficiency (energy efficiency) and current efficiency (%) at this time are expressed as a ratio (%) obtained by dividing the discharge power amount by the charge power amount. Both power amounts are selectively permeated through the internal resistance of the battery cell and the diaphragm. And other current losses. The current efficiency (%) is expressed as a ratio (%) obtained by dividing the amount of discharged electricity by the amount of charged electricity, and both the amounts of electricity depend on the ion selective permeability of the diaphragm and other current losses. Battery efficiency is expressed as the product of current efficiency and voltage efficiency. A decrease in internal resistance, ie, cell electrical resistivity, improves voltage efficiency, and an improvement in ion selective permeability and other reductions in current loss improve current efficiency, and thus are important indicators in redox flow secondary batteries.
The charge / discharge experiment was performed using the battery obtained as described above. Use an aqueous electrolyte with a total vanadium concentration of 2 M / L and a total sulfate radical concentration of 4 M / L, and the thickness of the installed positive and negative electrode cell chambers is 5 mm, respectively, between the porous electrode and the diaphragm. Was used by sandwiching a felt made of carbon fiber having a thickness of 5 mm and a bulk density of about 0.1 g / cm ³ . The charge / discharge experiment was conducted at a current density of 80 mA / cm ² .
The cell electrical resistivity was determined by measuring the DC resistance value at an AC voltage of 10 mV and a frequency of 20 kHz at the start of discharge using the AC impedance method, and multiplying this by the electrode area.

(Examples 1-8)
(1) Preparation of PFSA resin precursor A 10% aqueous solution of C ₇ F ₁₅ COONH ₄ and pure water were charged into a stainless steel stirring autoclave, and after sufficient vacuum and nitrogen substitution, tetrafluoroethylene (CF ₂ = CF ₂ ) (hereinafter also abbreviated as “TFE”) Gas was introduced and the pressure was increased to 0.7 MPa at a cage pressure. Subsequently, polymerization was initiated by injecting an aqueous ammonium persulfate solution. In order to replenish the TFE consumed by the polymerization, the TFE gas is continuously supplied to keep the pressure of the autoclave at 0.7 MPa, which corresponds to 0.70 times in mass ratio with respect to the supplied TFE. The amount of CF ₂ ═CFCF ₂ O (CF ₂ ) ₂ —SO ₂ F is continuously supplied to perform polymerization, and the polymerization conditions are adjusted to the optimum ranges, respectively. Various perfluorocarbon sulfonic acid resin precursor powders Got. The MFI of the obtained PFSA resin precursor powder A1 was 0.8 (g / 10 min).

(2) Production of perfluorocarbon sulfonic acid resin and dispersion thereof The obtained PFSA resin precursor powder A1 was dissolved in an aqueous solution in which potassium hydroxide (15% by mass) and methyl alcohol (50% by mass) were dissolved. The hydrolysis treatment was performed by contact at 20 ° C. for 20 hours. Then, it was immersed in 60 degreeC water for 5 hours. Next, the treatment of immersing in a 2N aqueous hydrochloric acid solution at 60 ° C. for 1 hour was repeated 5 times by updating the aqueous hydrochloric acid solution every time, and then washed with ion-exchanged water and dried. Thereby, a polymer A of a PFSA resin having a sulfonic acid group (SO ₃ H) and a structure represented by the formula (1) was obtained. The EW of the obtained polymer A was 750 (g / eq).
The obtained PFSA resin was placed in a 5 L autoclave together with an aqueous ethanol solution (water: ethanol = 50: 50 (mass ratio)), sealed, heated to 160 ° C. with stirring with a blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to prepare a 5% by mass uniform PFSA resin dispersion. Next, 100 g of pure water was added to 100 g of these PFSA resin dispersions and stirred, and then the liquid was concentrated to a solid content concentration of 20% by mass while heating and stirring at 80 ° C.
The obtained PFSA resin dispersion was designated as dispersion (ASF1).

  Next, a polybenzimidazole (hereinafter also abbreviated as “PBI”) powder is dissolved in an alkaline aqueous solution (KOH 10% aqueous solution) and stirred while being uniformly mixed and dispersed in each of the PFSA resin dispersions. The mixture was uniformly mixed (in a solid component) so as to be 4 parts by mass with respect to 100 parts by mass of the PFSA resin component. Next, these are passed through a column packed with particulate cation exchange resin particles, and the alkali ion component is almost completely removed, and ionic bonds between at least some of the functional groups (sulfonic acid groups and alkaline nitrogen atoms) are formed. The resulting mixed dispersion was designated as ASBF1.

  In the same manner, polyphenylene sulfide (hereinafter also abbreviated as “PPS”) powder (manufactured by Chevron Phillips, model number P-4) is dissolved in an alkaline aqueous solution (KOH 10% aqueous solution). The mixture was stirred while being uniformly mixed and dispersed, and finally (in solid components), the mixture was uniformly mixed so as to be 10 parts by mass with respect to 100 parts by mass of the PFSA resin component. Next, these are passed through a column packed with particulate cation exchange resin particles, and the alkali ion component is almost completely removed, and ionic bonds between at least some of the functional groups (sulfonic acid groups and alkaline nitrogen atoms) are formed. This was designated as ASBF2 as a mixed dispersion.

(3) Production of Electrolyte Membrane The obtained dispersion (ASF1) and mixed dispersion (ASBF1 and ASBF2) were cast on a polyimide film as a carrier sheet by a known ordinary method, and 120 ° C. (20 Min.) Was applied to blow off the solvent almost completely and dried to obtain a film. This was further heat-treated in a hot air atmosphere at 160 ° C. for 10 minutes to obtain an electrolyte membrane having a thickness of 50 μm. The electrolyte membrane obtained from ASF1 was used as Example 1, the electrolyte membrane obtained from ASBF1 was used as Example 2, and the electrolyte membrane obtained from ASBF2 was used as the electrolyte membrane of Example 3.

The equilibrium water content of the obtained electrolyte membrane was ASF1 (19% by mass), ASBF1 (23% by mass), and ASBF2 (23% by mass).
The maximum water content of each electrolyte membrane in water at 25 ° C. for 3 hours was ASF1 (38 mass%), ASBF1 (34 mass%), and ASBF2 (34 mass%), respectively. Here, the maximum moisture content indicates the maximum value observed when measuring the equilibrium moisture content.
The ionic conductivity of the electrolyte membrane was ASF1 (0.14 S / cm), ASBF1 (0.12 S / cm), and ASBF2 (0.1 S / cm).

Furthermore, the electrolyte membrane of Examples 4-8 was obtained by performing the following process.
The electrolyte membrane of Example 1 was distilled from cerium nitrate (Example 4), cerium carbonate (Example 5), manganese acetate (Example 6), cobalt nitrate (Example 7), or manganese nitrate (Example 8). It was immersed in a 1% nitric acid aqueous solution dissolved in water, and stirred with a stirrer at room temperature for 40 hours to contain each metal ion in the electrolyte membrane. As a result of analyzing the nitric acid aqueous solution before and after immersion by inductively coupled plasma (ICP) emission analysis, the content of each metal ion in the electrolyte membrane (cerium ion, cobalt ion, manganese ion relative to the number of —SO ₃ — groups in the membrane) %) Were 10.2% (Example 4), 10.4% (Example 5), 25.1% (Example 6), 25.2% (Example 7), and 25.4, respectively. % (Example 8).

  Next, a charge / discharge test was performed using each electrolyte membrane as a diaphragm of a vanadium redox flow secondary battery. Each electrolyte membrane was sufficiently equilibrated in the electrolyte solution, and then a charge / discharge experiment was performed. After the electrolyte membrane was made stable, the cell electrical resistivity and current efficiency were measured. Table 1 shows the cell electrical resistivity / current efficiency of each film.

Example 9
(1) Production of PTFE microporous membrane 1 463 mL of hydrocarbon oil as an extruded liquid lubricating oil was added at 20 ° C. and mixed with 1 kg of PTFE fine powder having a number average molecular weight of 6.5 million.
Next, the round bar-like molded body obtained by extruding this mixture by paste extrusion was molded into a film shape by a calender roll heated to 70 ° C. to obtain a PTFE film. This film was passed through a hot air drying oven at 250 ° C. to evaporate and remove the extrusion aid, thereby obtaining an unfired film having an average thickness of 300 μm and a width of 150 mm.
Next, this unsintered PTFE film was stretched in the longitudinal direction (MD direction) at a stretching ratio of 6.6 times and wound up. Both ends of the obtained MD direction stretched PTFE film were sandwiched between clips, stretched in the width direction (TD direction) at a stretch ratio of 8 times, heat-set, and a stretched PTFE film having a thickness of 10 μm was obtained. The stretching temperature at this time was 290 ° C., and the heat setting temperature was 360 ° C. The produced PTFE microporous membrane was designated as microporous membrane 1. The distribution center of the pore distribution of the microporous membrane 1 was 1.29 μm.

(2) Preparation of electrolyte membrane The dispersion ASF1 was applied onto a base film using a bar coater (manufactured by Matsuo Sangyo, bar No. 200, WET film thickness 200 μm) (application area: width of about 200 mm × length of about 500 mm), the PTFE microporous membrane 1 (film thickness: 10 μm, porosity: 82%, sample size: width 200 mm × length 500 mm) is laminated on the dispersion while the dispersion is not completely dried. The dispersion and the microporous membrane were pressure-bonded from above the porous membrane using a rubber roller. At this time, after visually confirming that a part of the microporous membrane was filled with the dispersion, this membrane was dried in an oven at 90 ° C. for 20 minutes. Next, the dispersion liquid was laminated again in the same manner from above the PTFE microporous film of the obtained film to sufficiently fill the voids of the microporous film with the dispersion liquid, and this film was further subjected to an oven at 90 ° C. for 20 minutes. Dried. The “PTFE microporous membrane sufficiently impregnated with the dispersion” thus obtained was heat-treated in an oven at 170 ° C. for 1 hour to obtain an electrolyte membrane having a thickness of about 30 μm. The evaluation results of the electrolyte membrane are shown in Table 1.
The obtained electrolyte membrane had an equilibrium water content of 12% by mass.
The maximum water content of the electrolyte membrane in 25 ° C. water for 3 hours was 23% by mass. Here, the maximum moisture content indicates the maximum value observed when measuring the equilibrium moisture content.
The dimensional change of the electrolyte membrane was 14%

(Examples 10 to 15)
A PFSA resin precursor was produced by the same method as that described in Example 1 of JP2008-210793A. The MFI of the obtained PFSA resin precursor powder was 1.5 (g / 10 min).
Using the obtained PFSA resin precursor powder, a polymer B (EW: 960 g / eq) of PFSA resin was obtained by the same method as in Examples 1 to 9, and further, the same method as in Examples 1 to 9 As a result, an electrolyte membrane was obtained. The evaluation results of the electrolyte membrane are shown in Table 1.

(Examples 16 to 18)
Perfluoro (2,2-dimethyl-1,3-dioxole) (PDD) / CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF by a method similar to the method described in Example 1 of International Publication No. 2004-66426. A PFSA resin precursor of ₂ CF ₂ SO ₂ F (PSVE) copolymer was prepared. The MFI of the obtained PFSA resin precursor powder was 1.5 (g / 10 min).
Using the obtained PFSA resin precursor powder, a polymer C of PFSA resin (EW: 1000 g / eq) was obtained in the same manner as in Examples 1 to 9, and the same method as in Examples 1 to 9. As a result, an electrolyte membrane was obtained. The evaluation results of the electrolyte membrane are shown in Table 1.

(Examples 19 and 20)
The electrolyte membranes obtained in Example 16 and Example 17 were pressed at 150 ° C. with a surface pressure of 2 MPa using a flat plate press, and then thermally crosslinked at 220 ° C. for 2 hours. The MFI of the obtained PFSA resin was 1.0 (g / 10 min). The evaluation results of the electrolyte membrane are shown in Table 1.

(Reference Example 1)
An electrolyte membrane was obtained in the same manner as in Example 1 except that Nafion DE2021 (DuPont, 20% solution, EW1050) was used instead of the polymer A. The equilibrium water content of this membrane was 4% by mass.
When the dimensional change was measured using the obtained electrolyte membrane, it was 23%, and the dimensional change was large.
Moreover, as a result of conducting a charge / discharge test in the same manner as in the example, the current efficiency (%) / cell electrical resistivity (Ω · cm ² ) was 94.5 / 1.20. The level was lower than the example. This is presumably because the electrolyte membrane of Comparative Example 1 has low ion selective permeability. In addition, as a result of the endurance test, the results of 200 cycles of charge / discharge were also inferior in durability, with a current efficiency of 86.0% and an electric resistance of 1.30.

(Reference Example 2)
To 100 parts by mass of polypropylene having a weight average molecular weight of 4 × 10 ⁵ , 0.375 parts by mass of an antioxidant was added to obtain a polyolefin composition. 30 parts by mass of this polyolefin composition was put into a twin screw extruder (58 mmφ, L / D = 42, strong kneading type). Moreover, 70 mass parts of liquid paraffin was supplied from the side feeder of this twin-screw extruder, and it melt-kneaded at 200 rpm, and prepared the polyolefin solution in an extruder.
Subsequently, a melt-kneaded product was extruded at 220 ° C. from a T die installed at the tip of the extruder, and a sheet was formed while being taken up by a cooling roll. Next, the formed sheet was sequentially biaxially stretched 7 × 5 at 110 ° C. to obtain a stretched film. The obtained stretched membrane was washed with methylene chloride to extract and remove the remaining liquid paraffin, followed by drying and heat treatment to obtain a 12 μm thick polypropylene microporous membrane. The distribution center of the pore distribution of the microporous membrane was 0.05 μm.
An electrolyte membrane was prepared in the same manner as in Example 1 except that Nafion DE2021 (DuPont, 20% solution, EW1050) was used instead of the polymer A, and the polypropylene microporous membrane prepared above was used. Obtained. The equilibrium water content of this membrane was 4% by mass.
When the dimensional change was measured using the obtained electrolyte membrane, it was 5%.
In addition, as a result of conducting a charge / discharge test in the same manner as in the example, the current efficiency (%) / cell electrical resistivity (Ω · cm ² ) was 50 / 2.20. It was also a low level. In addition, as a result of endurance testing, the results of carrying out 200 cycles of charge / discharge were also inferior in durability, with a current efficiency of 25.0% and an electric resistance of 4.00.
Table 1 shows the results of Examples 1 to 20 and Reference Examples 1 and 2.

  The electrolyte membrane of the present invention has excellent ion selective permeability, low electrical resistance, and excellent durability (mainly hydroxyl radical oxidation resistance), and is industrially used as a diaphragm for redox flow secondary batteries. Has availability.

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Positive electrode cell chamber 3 Negative electrode 4 Negative electrode cell chamber 5 Electrolyte membrane 6 Electrolyzer 7 Positive electrode electrolyte tank 8 Negative electrode electrolyte tank 9 AC / DC converter 10 Redox flow secondary battery

Claims (14)

A positive electrode cell chamber including a positive electrode made of a carbon electrode;
A negative electrode cell chamber including a negative electrode made of a carbon electrode;
An electrolyte membrane as a diaphragm for separating and separating the positive electrode cell chamber and the negative electrode cell chamber;
Having an electrolytic cell containing
The positive electrode cell chamber contains a positive electrode electrolyte containing an active material, and the negative electrode cell chamber contains a negative electrode electrolyte containing an active material,
A redox flow secondary battery that charges and discharges based on a valence change of an active material in the electrolyte solution,
The electrolyte membrane includes an ion exchange resin composition mainly composed of a fluorine-based polymer electrolyte polymer,
The fluorine-based (dry weight grams per equivalent of ion exchange groups) equivalent weight EW of the polymer electrolyte polymer Ri is 300~1300g / eq der,
The equilibrium water content of the electrolyte membrane is 5 to 80% by mass,
The redox flow secondary battery in which the fluorine-based polymer electrolyte polymer includes a polymer having a structure represented by the following formula (1) .
_{^{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF (CF 2 -O- (CFR 1) b - (CFR 2) c -X 3)] g - (1)
( Wherein, X ¹ and X ² each independently represents one or more selected from the group consisting of a halogen atom and a C 1-3 perfluoroalkyl group. X ³ represents COOZ, SO _3. Z, PO ₃ Z ₂ or PO ₃ HZ represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or an amine (NH ₄ , NH ₃ R ₁ , NH ₂ R ₁ R ₂ , NHR ₁ R ₂ R ₃ , NR ₁ R ₂ R ₃ R ₄ ), wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently any one selected from the group consisting of an alkyl group and an arene group. Wherein X ³ is PO ₃ Z ₂ , Z may be the same or different, and R ¹ and R ² are each independently a halogen atom, having 1 to 10 carbon atoms. One selected from the group consisting of perfluoroalkyl groups and fluorochloroalkyl groups .A and g shows the above, 0 ≦ a <1,0 <g ≦ 1, a + g = 1 .c represents an integer of .b 0 to 8 indicating the number satisfying is 0 or 1.) A positive electrode cell chamber including a positive electrode made of a carbon electrode;
A negative electrode cell chamber including a negative electrode made of a carbon electrode;
An electrolyte membrane as a diaphragm for separating and separating the positive electrode cell chamber and the negative electrode cell chamber;
Having an electrolytic cell containing
The positive electrode cell chamber contains a positive electrode electrolyte containing an active material, and the negative electrode cell chamber contains a negative electrode electrolyte containing an active material,
A redox flow secondary battery that charges and discharges based on a valence change of an active material in the electrolyte solution,
The electrolyte membrane includes an ion exchange resin composition mainly composed of a fluorine-based polymer electrolyte polymer,
The fluoropolymer electrolyte polymer has an equivalent mass EW (dry mass in grams per equivalent of ion-exchange groups) of 300 to 1300 g / eq,
The equilibrium water content of the electrolyte membrane is 5 to 80% by mass,
The redox flow secondary battery in which the fluorine-based polymer electrolyte polymer includes a polymer having a repeating unit represented by the following formula (2) and a repeating unit represented by the following formula (3).
(Where Q ¹ Is a perfluoroalkylene group which may have an etheric oxygen atom, and Q ² Is a perfluoroalkylene group which may have a single bond or an etheric oxygen atom, and R ^f1 Is a perfluoroalkyl group which may have an etheric oxygen atom, X is an oxygen atom, a nitrogen atom or a carbon atom, a is 0 when X is an oxygen atom, and X is 1 for a nitrogen atom, 2 if X is a carbon atom, Y is a fluorine atom or a monovalent perfluoro organic group, s is 0 or 1, and R ^f2 Is a perfluoroalkyl group, Z is a fluorine atom or a monovalent perfluoro organic group, and t is an integer of 0-3. ) The redox flow secondary battery according to claim 2 , further comprising a repeating unit based on tetrafluoroethylene. A positive electrode cell chamber including a positive electrode made of a carbon electrode;
A negative electrode cell chamber including a negative electrode made of a carbon electrode;
An electrolyte membrane as a diaphragm for separating and separating the positive electrode cell chamber and the negative electrode cell chamber;
Having an electrolytic cell containing
The positive electrode cell chamber contains a positive electrode electrolyte containing an active material, and the negative electrode cell chamber contains a negative electrode electrolyte containing an active material,
A redox flow secondary battery that charges and discharges based on a valence change of an active material in the electrolyte solution,
The electrolyte membrane includes an ion exchange resin composition mainly composed of a fluorine-based polymer electrolyte polymer,
The fluoropolymer electrolyte polymer has an equivalent mass EW (dry mass in grams per equivalent of ion-exchange groups) of 300 to 1300 g / eq,
The equilibrium water content of the electrolyte membrane is 5 to 80% by mass,
The redox flow secondary battery in which the fluorine-based polymer electrolyte polymer includes a copolymer including a repeating unit based on the following monomer A and a repeating unit based on the following monomer B.
Monomer A: Perfluoromonomer that gives a polymer having a repeating unit containing a ring structure in the main chain by radical polymerization
Monomer B: CF ₂ = CF- (OCF ₂ CFY ¹ ) _m -O _p -(CF ₂ ) _n -SO ₂ Y ² Perfluorovinyl ether represented by
(Where Y ¹ Is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, n is an integer of 1 to 12, p is 0 or 1, and m + p> 0, Y ² Is OH or NHSO ₂ Z is a C 1-6 perfluoroalkyl group which may contain an etheric oxygen atom. ). The redox flow secondary battery according to claim 4 , wherein the repeating unit based on the monomer A is any one or more repeating units represented by the following formula (5).
(In the formula, n is an integer of 1 to 4, R ^f is a perfluoroalkyl group or perfluoroalkoxy group having 1 to 8 carbon atoms, and X ¹ and X ² are each independently a fluorine atom or trifluoromethyl. In addition, when n is 2 or more in (CX ¹ X ² ) _n , the combination of X ¹ and X ² may be different for each carbon). The fluorine-based polyelectrolyte polymer is a copolymer obtained by copolymerizing any of the following compounds (A) to (F) as a comonomer, and is crosslinked by reacting a polymer unit based on the comonomer. The redox flow secondary battery according to any one of claims 1 to 5 .
(A) A perfluoro unsaturated compound having two double bonds.
(B) Perfluoroethene or perfluoro (alkyl vinyl ether) having a bromine atom.
(C) Polyfluoroethene or polyfluoro (alkyl vinyl ether) having a carboxylic acid group, a carboxylic acid group or a carboxylic acid ester group.
(D) Polyfluoroethene or polyfluoro (alkyl vinyl ether) having a hydroxyl group.
(E) Perfluoroethene or perfluoro (alkyl vinyl ether) having a cyano group.
(F) Perfluoroethene or perfluoro (alkyl vinyl ether) having a cyanate group. The redox flow secondary battery according to any one of claims 1 to 6 , wherein the electrolyte membrane has a reinforcing material made of a fluorine-based microporous membrane. The redox flow according to any one of claims 1 to 7 , wherein the ion-exchange resin composition contains 0.1 to 200 parts by mass of a polyazole compound with respect to 100 parts by mass of the fluorine-based polymer electrolyte polymer. Secondary battery. The polyazole compound comprises a polymer of a heterocyclic compound containing one or more nitrogen atoms in the ring, and a polymer of a heterocyclic compound containing one or more nitrogen atoms and oxygen and / or sulfur in the ring. The redox flow secondary battery of Claim 8 which is 1 or more types selected from. The polyazole compound is selected from the group consisting of a polyimidazole compound, a polybenzimidazole compound, a polybenzobisimidazole compound, a polybenzoxazole compound, a polyoxazole compound, a polythiazole compound, and a polybenzothiazole compound. The redox flow secondary battery according to claim 8 or 9 , which is one or more selected. The redox flow secondary battery according to any one of claims 8 to 10 , wherein the fluorine-based polymer electrolyte polymer and the polyazole-based compound form an ionic bond in at least a part thereof. The redox according to any one of claims 1 to 11 , wherein the ion exchange resin composition includes at least one selected from the group consisting of a Ce-based additive, a Co-based additive, and a Mn-based additive. Flow secondary battery. The ion exchange resin composition comprises a polyphenylene ether resin and / or polyphenylene sulfide resin of the 0.1 to 20 parts by weight per 100 parts by weight fluoropolymer electrolyte polymer, any of claims 1 to 12 1 The redox flow secondary battery according to item. The redox flow secondary battery according to any one of claims 1 to 13 , wherein the redox flow secondary battery is a vanadium redox flow secondary battery in which a sulfuric acid electrolyte containing vanadium is used as a positive electrode and a negative electrode electrolyte. battery.