JP2019102225A - Separating membrane for redox flow battery and redox flow battery - Google Patents

Abstract

To provide a separating membrane for a redox flow battery, which is superior in proton permeability and which can serve to suppress the transmission of an active material, and to provide a redox flow battery superior in energy efficiency.SOLUTION: A separating membrane for a redox flow battery according to the present invention comprises: a resin layer including an ion-exchange resin; and a hydrophobic layer which is 110° or more in the contact angle with respect to water. At least one of outermost layers of the separating membrane of a redox flow battery is the hydrophobic layer. A redox flow battery according to the invention comprises an electrolytic cell including a positive electrode cell chamber having a positive electrode including a carbon electrode, a negative electrode cell chamber having a negative electrode including a carbon electrode, and a separating membrane for a redox flow battery which isolates the positive and negative electrode cell chambers from each other. The separating membrane for a redox flow battery has a resin layer including an ion-exchange resin, and a hydrophobic layer which is 110° or more in the contact angle with respect to water. At least one of the outermost layers of the separating membrane for a redox flow battery is the hydrophobic layer.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a redox flow battery diaphragm and a redox flow battery.

  The redox flow battery is one that stores and discharges electricity, and belongs to a large stationary battery used for leveling the amount of electricity used. The redox flow battery has a structure in which 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 are separated by a diaphragm. Charge and discharge are performed using the redox reaction of a substance. It is possible to increase the capacity by circulating the electrolytic solution containing both active materials from the storage tank to the electrolytic cell, which is suitable for the enlargement.

  As the active material contained in the electrolytic solution, for example, iron-chromium-based, chromium-bromine-based, zinc-bromine-based, vanadium-based that utilizes the difference in charge, and the like are used. In particular, vanadium-based secondary batteries have advantages such as high electromotive force, quick electrode reaction of vanadium ions, small amount of hydrogen generation as a side reaction, high output etc. .

  Further, the diaphragm is devised so that the electrolyte containing the active material of both electrodes does not mix. However, conventional diaphragms have problems such as being easily oxidized and not sufficiently low in electric resistance. In order to increase the current efficiency of the battery, it is required to prevent permeation of each active material contained in the cell electrolyte of both electrodes (contamination of the electrolyte in the bipolar electrolyte) as much as possible. A membrane having excellent ion selective permeability is required that easily transports protons easily.

The vanadium type redox flow battery, divalent vanadium in the negative cell and (V ²⁺⁾ / 3-valent (V ^3+), 4-valent vanadium in the positive cell (V ⁴⁺⁾ / 5-valent (V ⁵⁺⁾ It uses a redox reaction. As described above, since the electrolytes of the positive electrode cell and the negative electrode cell are metal ion species of the same type, even if the electrolyte solution is mixed through the diaphragm, it can be regenerated by the electrical process, compared with other metal species. It is hard to be a big problem. However, when the active material permeates, the stored charge is wasted and the current efficiency decreases, so it is desirable that the active material not permeate.

Conventionally, there are redox flow batteries that use various types of diaphragms (hereinafter, also simply referred to as "membranes"), for example, porous membranes that allow ion differential pressure and osmotic pressure of electrolyte solution to freely pass as driving force Batteries have been reported.
For example, in Patent Document 1, as a diaphragm for a redox flow battery, a polytetrafluoroethylene (hereinafter, also referred to as "PTFE") porous film, a polyolefin (hereinafter, also referred to as "PO")-based porous film, a PO-based non-woven fabric Etc. are disclosed.
Patent Document 2 discloses a composite membrane in which a porous membrane and a water-containing polymer are combined for the purpose of improving the charge / discharge energy efficiency of the redox flow battery and the mechanical strength of the membrane.
In Patent Document 3, for the purpose of improving charge / discharge energy efficiency of a redox flow battery, a cellulose or ethylene-vinyl alcohol copolymer as a nonporous hydrophilic polymer film having a hydrophilic hydroxyl group excellent in ion permeability It is disclosed to utilize the membrane of
In Patent Document 4, by using a polysulfone-based membrane (anion exchange membrane) as a hydrocarbon-based ion exchange resin, the current efficiency of the vanadium redox battery is 80% to 88.5%, and the radical oxidation resistance is also improved. It is described that it is excellent.
Patent Document 5 discloses a method of supporting expensive platinum on the porous carbon of a positive electrode to increase the current efficiency of a redox flow battery to increase the reaction efficiency. Trademark N117 and polysulfone based ion exchange membranes are described as diaphragms.
Patent Document 6 discloses an iron-chromium redox flow battery having a membrane obtained by applying a hydrophilic resin to the pores of a porous film such as polypropylene (hereinafter, also referred to as "PP"). An example of the document is an example of a membrane in which a fluorine-based ion exchange resin (manufactured by DuPont, registered trademark Nafion) is coated to a thickness of several μm on both surfaces of a porous PP film of 100 μm in thickness. Here, Nafion is a repeating unit represented by-(CF ₂ -CF ₂ )-and-(CF ₂ -CF (-O- (CF ₂ CFXO) _n- (CF ₂ ) _m -SO ₃ H) ) - in the repeating unit represented by in the copolymer containing a copolymer of _{X = CF 3, n = 1} , m = 2.
Patent Document 7 discloses a vanadium-based redox flow system in which the cell electrical resistance is reduced and the current efficiency is improved by improving the electrode, such as using a two-layer liquid-permeable porous carbon electrode having a specific surface lattice. An example of a secondary battery is disclosed.
Patent Document 8 discloses a cation exchange membrane (a fluorine-based polymer or another hydrocarbon-based polymer) and an anion exchange membrane (polysulfone) as a diaphragm for the purpose of reducing cell electric resistance and improving power efficiency and the like. There is disclosed a redox flow battery using a film formed by alternately laminating a system polymer and the like) and arranging a cation exchange film on the side in contact with the positive electrode electrolyte of the film.
In Patent Document 9, a vinyl heterocyclic compound having two or more hydrophilic groups on a porous base material made of a porous PTFE-based resin as a film having excellent chemical resistance, low resistance, and excellent ion selective permeability. A redox flow battery is disclosed that uses, as a diaphragm, an anion exchange membrane formed by combining a crosslinked polymer having a repeating unit (vinyl pyrrolidone having an amino group). Regarding the principle, when a potential difference is applied, the active material having a large ion diameter and a large charge amount is subject to electrical repulsion by cations in the surface layer of the diaphragm to inhibit membrane permeation, but the ion diameter is also small, It is described that the proton which is monovalent can diffuse and permeate easily through the diaphragm having a cation, so that the electric resistance is reduced.
In Patent Document 10, a solid polymer ion for a redox flow battery having an ion cluster diameter of 1.00 to 2.95 nm as a redox flow battery diaphragm having low proton permeation resistance and suppressing permeation of polyvalent metal cations. Exchange membranes have been proposed.
In patent document 11, in order to suppress permeation of the active material of a redox flow battery, the surface of a cation exchange membrane is chosen from the cation exchange membrane of high crosslinking degree, the anion exchange membrane of high crosslinking degree, a polyamine, and a hydrophobic polymer. It has been proposed to coat with different substances.

JP 2005-158383 A Japanese Examined Patent Publication No. 6-105615 Japanese Patent Application Laid-Open No. 62-226580 JP-A-6-188005 Unexamined-Japanese-Patent No. 5-242905 JP 6-260183 A JP 9-92321 A Japanese Patent Application Laid-Open No. 11-260390 Unexamined-Japanese-Patent No. 2000-235849 International Publication No. 2013/100079 Japanese Patent Application Laid-Open No. 60-160560

However, the battery disclosed in Patent Document 1 has a high internal resistance of the battery because the proton permeability of the diaphragm is low, and the current efficiency is insufficient because the permeation prevention of the active material is not sufficient.
The composite membrane disclosed in Patent Document 2 has a high internal resistance of the battery, and the current efficiency of the battery is low because the active material diffuses freely but not as much as the porous film. The film disclosed in Patent Document 3 also has the same problem as described above.
The battery disclosed in Patent Document 4 still has insufficient current efficiency. Although a battery using a PTFE-based ion exchange membrane is disclosed in the same document as a comparative example, its current efficiency is 64.8 to 78.6%, which is stated to be insufficient. .
The battery disclosed in Patent Document 5 also can not solve the same problems as above, and also has a problem that the large-sized equipment is expensive in terms of price.
The film disclosed in Patent Document 6 is described to increase internal resistance unless the thickness of the coating film is made extremely thin (several μm). Moreover, nothing is described about the device for improving ion selective permeability.
Since the battery disclosed in Patent Document 7 uses a polysulfone-based diaphragm, the ion selective permeability of the diaphragm is not sufficient, and the internal resistance and the current efficiency of the battery are not sufficient.
The membrane disclosed in Patent Document 8 has a problem that the internal resistance of the battery is high.
According to the results shown in the example of Patent Document 9, it can not be said that the internal resistance of the battery is sufficiently low.
The diaphragm for a redox flow battery disclosed in Patent Document 10 can not be said to be sufficiently permeable to protons from the viewpoint of obtaining a battery of higher output density, and the ion selective permeability is also insufficient.
The diaphragm for a redox flow battery disclosed in Patent Document 11 can not be said to be a sufficient effect of suppressing the permeation of metal ions, and nothing is described about a device for reducing the proton permeation resistance.

  The diaphragm for the conventional vanadium-based redox flow battery includes a cell (negative electrode side) having a large number of ions of low electric charge group of vanadium ion which is an active material of the electrolytic solution of both electrodes, and an ion group of high electric charge. In each of the majority of cells (positive electrode side), diffusion transfer of active material ions to the counter electrode (cell) is suppressed, and protons are selectively allowed to pass along with the intended charge / discharge operation. It is used for the purpose. However, at present, its performance is not sufficient.

  As a membrane base mainly made of hydrocarbon resin, a porous membrane having no ion selective permeability only for separating electrolytes of both cells, a hydrophilic membrane base having no ion selectivity (non-porous), A porous membrane in which a hydrophilic membrane substrate is embedded or coated is used. Also, a so-called cation exchange membrane in which the membrane itself has various anion groups, or a composite membrane in which a cation exchange resin is coated or embedded in the pores of a porous membrane base, 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 in a porous membrane substrate, a laminate type of the both, etc. are used as a diaphragm, and researches making use of their respective characteristics have been conducted.

  So far, diaphragms for redox flow batteries have been developed which fully satisfy two contradictory performances: suppression of battery internal resistance (depending on proton permeability of diaphragm) and inhibition of metal ion permeability as active material Absent. Also, in a Redox flow battery using a film that achieves low resistance and permeation inhibition of the active material, the amount of charge stored in the active material is taken out without waste, and internal resistance loss per unit of active material mass is also suppressed. Although the storage performance (energy efficiency) of the final battery is improved, a redox flow battery having sufficient energy efficiency has not been developed so far.

  With regard to the fluorine-based ion exchange resin, too, the device for the contradictory property of having excellent proton permeability and suppressing the permeation of the active material has not been sufficiently studied, and the low resistance and high current efficiency are sufficiently satisfied. A diaphragm for a redox flow battery and a high energy efficiency redox flow battery using the same have not been developed.

  In view of the above circumstances, the present invention has an object of providing a diaphragm for a redox flow battery excellent in proton permeability and suppressing permeation of an active material, and providing a redox flow battery excellent in energy efficiency. .

  MEANS TO SOLVE THE PROBLEM As a result of repeating earnestly examining in order to solve the said subject, the present inventors have a multilayer structure of at least 2 layers or more, and the contact angle with respect to water of at least one outermost layer is 110 degrees or more. It has been found that the above-mentioned problems can be fundamentally solved by the diaphragm.

That is, the present invention provides the following configurations.
[1]
A resin layer containing an ion exchange resin,
A hydrophobic layer having a contact angle to water of 110 ° or more,
A diaphragm for a redox flow battery having
A diaphragm for a redox flow battery, wherein at least one of the outermost layers of the diaphragm for a redox flow battery is the hydrophobic layer.
[2]
The diaphragm for a redox flow battery according to [1], wherein the hydrophobic layer has a void.
[3]
The diaphragm for a redox flow battery according to [1] or [2], wherein the hydrophobic layer contains fine particles.
[4]
The diaphragm for a redox flow battery according to [3], wherein an average particle diameter of the fine particles is 50 nm to 5 μm.
[5]
The diaphragm for a redox flow battery according to [3] or [4], wherein an amount of surface particles of the fine particles is 0.01 to 20 mg · cm ⁻² .
[6]
The diaphragm for a redox flow battery according to any one of [1] to [5], wherein the ion exchange resin contains a fluorine-based polymer electrolyte polymer.
[7]
An electrolytic cell comprising a positive electrode cell chamber having a positive electrode including a carbon electrode, a negative electrode cell chamber having a negative electrode including a carbon electrode, and a redox flow battery diaphragm separating and separating the positive electrode cell chamber and the negative cell chamber. Equipped
The membrane for a redox flow battery has a resin layer containing an ion exchange resin, and a hydrophobic layer having a contact angle to water of 110 ° or more,
The redox flow battery in which at least one of the outermost layers of the diaphragm for the redox flow battery is the hydrophobic layer.
[8]
An electrolytic cell comprising a positive electrode cell chamber having a positive electrode including a carbon electrode, a negative electrode cell chamber having a negative electrode including a carbon electrode, and a redox flow battery diaphragm separating and separating the positive electrode cell chamber and the negative cell chamber. Equipped
The membrane for a redox flow battery has a resin layer containing an ion exchange resin, and a hydrophobic layer having a contact angle to water of 110 ° or more,
At least one of the outermost layers of the redox flow cell diaphragm is the hydrophobic layer,
The vanadium-type redox flow battery in which the said hydrophobic layer contacts the electrolyte solution distribute | circulated to the said negative electrode.

The membrane for a redox flow battery of the present invention can easily transmit protons, so that the internal resistance of the battery can be suppressed, and a high current efficiency can be achieved because the permeation resistance of the active material is large.
In the redox flow battery using this diaphragm for a redox flow battery, high energy efficiency is achieved because both the loss of voltage due to the internal resistance and the loss of charge due to the movement of the active material are suppressed.

FIG. 1 is a schematic view illustrating a redox flow secondary battery according to an embodiment of the present invention. FIG. 2 is a SEM image of the surface of the diaphragm obtained in Example 1.

  Hereinafter, modes for carrying out the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail. The following present embodiment is an example for describing the present invention, and is not intended to limit the present invention to the following contents. The present invention can be implemented with various modifications within the scope of the gist.

The redox flow battery diaphragm of the present embodiment (hereinafter, also simply referred to as "diaphragm") has a resin layer containing an ion exchange resin, and a hydrophobic layer having a contact angle to water of 110 ° or more. It is a diaphragm, and at least one of the outermost layers of the diaphragm for the redox flow battery is the hydrophobic layer. With such a configuration, the diaphragm for a redox flow battery according to this embodiment can easily transmit protons, thereby suppressing the internal resistance of the battery, and achieving high current efficiency because the transmission resistance of the active material is large. Ru.
Although the mechanism by which the permeation of the active material is suppressed when at least one of the outermost layers is a hydrophobic layer is not clear, the following mechanism is expected.
In general, the magnitude of the contact angle to water at the surface of the membrane reflects the degree of hydrophobicity of the surface. When a highly hydrophobic surface is present in water, it is known that the water near the surface has a more organized structure (iceberg structure or hydrophobic hydration structure) than the bulk. When the diaphragm for a redox flow battery of this embodiment is used in water, it is considered that water molecules in the vicinity of the surface of the diaphragm form an iceberg structure.
The active material in the electrolyte of the redox flow battery is kept electrically stable by the orientation of the dipoles of water molecules. Since the water in the iceberg structure formed on the diaphragm surface is restricted in orientation by the organization, when the active material passes through it, the orientation of water molecules can not be changed, and it receives a large resistance.
On the other hand, protons have a transfer mechanism called the Grotthuss mechanism, and the movement of water molecules during diffusion is particularly small. For this reason, protons are less susceptible to the surface iceberg structure, and have high permeability to the redox flow cell diaphragm of the present embodiment.
For the above reasons, the diaphragm for a redox flow battery of the present embodiment is considered to easily transmit protons and to prevent transmission of the active material.

  In the present embodiment, the contact angle of the hydrophobic layer is 110 ° or more, preferably 120 ° or more, and more preferably 130 ° or more from the viewpoint described above.

(Measurement of contact angle)
In the redox flow cell diaphragm of the present embodiment, the contact angle of the hydrophobic layer to water can be measured by the following method.
First, the membrane for a redox flow battery cut out on a horizontal pedestal is fixed so that the measurement surface (i.e., the outermost hydrophobic layer) faces upward. Next, 6 μL of ion exchange water is dropped from the top of the fixed redox flow cell diaphragm. After 120 seconds of dripping, an image is acquired by a camera from the side, and a contact angle measurement value is obtained from the angle between the droplet surface and the film surface.

(Adjustment of contact angle)
The hydrophobic layer in the present embodiment can be easily formed using, for example, a material with high hydrophobicity. In addition, the contact angle to water can be adjusted by adjusting the material, porosity and the like of the hydrophobic layer. Moreover, after forming the resin layer in this embodiment, a structure may be changed by chemically processing the said surface, and a hydrophobic layer which a contact angle satisfy | fills the above-mentioned range may be formed.

In the present embodiment, the hydrophobic layer preferably has a void structure. A void in the hydrophobic layer means that there is a void inside the layer and the electrolyte can penetrate. The method of providing voids in the hydrophobic layer is not limited to the following, for example, a method of providing voids as particle gaps by forming a hydrophobic layer with fine particles, a method of attaching a porous film to an electrolyte membrane, filled hydrophobic After providing a layer, a method of providing a hole by a physical method, a method of providing a hydrophobic layer in which a substance soluble in a solvent is mixed, and extracting a soluble component by a solvent may be mentioned.
When the hydrophobic layer having a void has the above-described contact angle, the interface between the membrane and the water is generated in the void, so the actual surface area is increased as compared to a flat membrane (in the case of a hydrophobic layer having no void). As the actual surface area increases, the range in which the above-described water organization takes place tends to widen and the permeation of the active material can be suppressed more efficiently.
In the present embodiment, the porosity of the hydrophobic layer is preferably 5% to 95%. By setting the porosity to 5% or more, the permeability of protons can be secured and the membrane resistance can be reduced. In addition, by setting the porosity to 95% or less, the spread of water organization by the hydrophobic layer tends to be secured. From the same viewpoint, the porosity of the hydrophobic layer is more preferably 10% to 90%, and still more preferably 15% to 80%. The porosity can be calculated from the thickness of the hydrophobic layer and the density of particles constituting the hydrophobic layer. Specifically, a film in which the weight of the hydrophobic layer per unit area is appropriately adjusted is formed, and the thickness of the hydrophobic layer is measured. Here, the apparent hydrophobic layer density is calculated from (the weight of the hydrophobic layer per unit area) / (the thickness of the hydrophobic layer). The porosity can be determined by calculating (apparent hydrophobic layer density) / (density of particles constituting the hydrophobic layer) and taking the difference from 1. Specifically, it can be measured by the method described in the examples described later. Moreover, although the adjustment method of this porosity is not limited to the following, when forming a hydrophobic layer using microparticles | fine-particles, it adjusts by changing the particle size distribution of particle | grains, the shape of particle | grains, the quantity of a binder compound, etc. be able to. When the porous film is attached, it is determined depending on the porosity of the porous film and can be adjusted by a pressure bonding method or the like. When the holes are provided by a physical method, the diameter can be adjusted according to the diameter of the holes and the number of holes per unit area. Substances soluble in a solvent are mixed to form a hydrophobic layer, and when the solvent is extracted, adjustment can be made by changing the amount of the substance soluble in the solvent.

The hydrophobic layer preferably contains fine particles. By forming the hydrophobic layer with fine particles, the thickness of the outermost layer, the size of the air gap, the porosity and the like can be easily controlled.
When the hydrophobic layer is constituted by fine particles, a suitable binder may be used as long as the contact angle does not deviate from the above range. This prevents the surface layer from peeling off during use of the membrane and improves the durability. Although the material used as a binder is not specifically limited, By using ion exchange resin for a binder, since the permeability of ion can be maintained even when a void part is obstruct | occluded in part by a binder, it is preferable. Specific examples of the ion exchange resin that can be used as a binder will be described later.
The shape of the fine particles is not particularly limited, and may be spherical, elliptical, rod-like or the like. Moreover, the material which comprises microparticles | fine-particles can utilize arbitrary materials in the range which a contact angle does not remove | deviate from the said range. Specific examples thereof include, but are not limited to, polyphenylene sulfide, polytetrafluoroethylene, polyacrylamide, polyacrylonitrile, polycarbonate, polyurethane, polyethylene terephthalate and the like. Further, fine particles of different shapes and materials may be used as a mixture of two or more.

Moreover, it is preferable that the microparticles | fine-particles which comprise a hydrophobic layer have an average particle diameter of 50 nm or more and 5 micrometers or less. The average particle diameter is more preferably 50 nm or more and 2 μm or less, and still more preferably 80 nm or more and 1 μm or less. The average particle size of the fine particles can be measured, for example, by dispersing the fine particles in a suitable dispersion medium and using a dynamic light scattering method.
By setting the average particle diameter to 50 nm or more, clogging of the outermost layer with particles can be further suppressed. Further, by setting the average particle diameter to 5 μm or less, the actual surface area on the film surface can be more effectively increased, and the permeation of the active material is suppressed.

The surface particle amount (weight per unit surface area) of the fine particles constituting the hydrophobic layer is preferably 0.01 mg · cm ⁻² or more and 20 mg · cm ⁻² or less. By setting the concentration to 0.05 mg · cm ⁻² , the permeation suppression effect of the active material can be sufficiently obtained, and by setting the concentration to 5 mg · cm ⁻² or less, the influence on the proton permeability can be further reduced. For the same reason, more preferably 0.02 mg · cm ^-2 or more 10 mg · cm ^-2 or less, more preferably 0.05 mg · cm ^-2 or more 5 mg · cm ^-2 or less. The amount of surface particles can be adjusted to the above-mentioned range, for example, by casting a liquid in which the concentration of the fine particles forming the hydrophobic layer is appropriately adjusted. Moreover, the said surface particle amount can be measured by the method as described in the Example mentioned later. That is, the amount of surface particles of the hydrophobic layer can be calculated from the amount of particles in the fine particle dispersion and the coating thickness before drying. More specifically, when the amount of particles in the fine particle dispersion is adjusted to C (mg · cm ⁻³ ), coating is performed with a thickness a (μm) before drying to obtain Ca / 10,000 (mg · cm). A hydrophobic layer of ^-2 ) can be obtained. When using a dispersion in which the amount of particles in the particle dispersion is unknown, the solution is completely dried in an environment such as heating / decompression and the weight is measured to thereby quantify the amount of particles in the particle dispersion in advance. be able to. By adjusting the thickness before drying so that the amount of particles in the dispersion obtained here matches the amount of surface particles of the target hydrophobic layer, a hydrophobic layer in which the amount of surface particles is controlled can be obtained. Further, the amount of surface particles is a method of removing the hydrophobic layer from the surface and measuring the remaining membrane weight with respect to the diaphragm cut into a specific area, and a method of measuring the weight of fine particles constituting the removed hydrophobic layer Alternatively, it can be confirmed by separately preparing a film in which the hydrophobic layer is not formed and comparing the weight per unit area with the film in which the hydrophobic layer is formed.

(Ion exchange resin)
The resin layer in the present embodiment contains an ion exchange resin. The ion exchange resin is not particularly limited, but fluorine-based polymer electrolyte polymer, polyethersulfone resin, polyetheretherketone resin, phenol-formaldehyde resin, polystyrene resin, polytrifluorostyrene resin, trifluorostyrene resin, poly ( 2,3-Diphenyl-1,4-phenylene oxide) resin, poly (allyl ether ketone) resin, poly (allyl ether sulfone) resin, poly (phenyl quinosan phosphorus) resin, poly (benzyl silane) resin, polystyrene-grafting- Ethylene tetrafluoroethylene resin, polystyrene-graft-polyvinylidene resin, polystyrene-graft-tetrafluoroethylene resin, polyimide resin, polybenzimidazole resin, etc. There may be mentioned such as those obtained by introducing a sulfonic acid group or a carboxylic acid group, it is preferred to include a fluoropolymer electrolyte polymer. It is preferable that the said fluorine-type polymer electrolyte polymer has a structure represented by following formula (1).
_{^{- [CF 2 -CX 1 X 2}} ] a - [CF 2 -CF ((- O-CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - (CF ₂ ) _f −X ⁴ )] _g − (1)

X ^1, X ^2, X ³ in the formula ^{(1), R 1, R} 2 and a~g are respectively defined as follows.
Each of X ¹ , X ² and X ³ independently represents one or more selected from the group consisting of a halogen atom and a C 1 to C 3 perfluoroalkyl group. Although it does not specifically limit as said halogen atom, For example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom is mentioned. As X ¹ , X ² and X ³ , a fluorine atom or a perfluoroalkyl group having 1 to 3 carbon atoms is preferable from the viewpoint of chemical stability such as the resistance to oxidative degradation of a polymer.
X ⁴ represents COOZ, SO ₃ Z, PO ₃ Z ₂ or PO ₃ HZ. Hereinafter, X ⁴ is also referred to as “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 And R ₁ , R ₂ , R ₃ and R ₄ each independently represent at least one selected from the group consisting of an alkyl group and an arene group. When X ⁴ is PO ₃ Z ₂ , Z may be the same or different. It does not specifically limit as said alkali metal atom, For example, a lithium atom, a sodium atom, a potassium atom etc. are mentioned. Further, the alkaline earth metal atom is not particularly limited, and examples thereof include a calcium atom and a magnesium atom. As X ⁴ , SO ₃ Z is preferable from the viewpoint of chemical stability such as oxidation degradation resistance of the polymer.
Each of R ¹ and R ² independently represents one or more selected from the group consisting of a halogen atom, a C 1-10 perfluoroalkyl group and a fluorochloroalkyl group. Here, as a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned, for example.
a and g each represent a number satisfying 0 ≦ a <1, 0 <g ≦ 1, a + g = 1. b shows the integer of 0-8. c represents 0 or 1; d, e and f each independently represent an integer of 0 to 6 (provided that d, e and f are not simultaneously 0).

  The fluorine-based polymer electrolyte polymer in the present embodiment is preferably a perfluorocarbon sulfonic acid resin (hereinafter also referred to as “PFSA resin”) because the effects of the present embodiment tend to be more remarkable. In the PFSA resin in this embodiment, a perfluorocarbon as a side chain and one or more sulfonic acid groups in each side chain (possibly in the form of a salt in some cases) are included in the main chain consisting of a PTFE backbone chain. Or the like) is a bonded resin.

The PFSA resin is a repeating unit derived from a repeating unit represented by-(CF ₂ -CF ₂ )-and a compound represented by the following formula (2) or (3-1) or (3-2) It is preferable to contain

CF ₂ = CF (-O- (CF ₂ CFXO) _n- [A]) (2)
In (formula (2), X represents F or a perfluoroalkyl group having 1 to 3 carbon atoms, n is an integer of 0 to 5. [A] represents a (CF _{2) m} -SO ₃ H , Where m represents an integer of 0 to 6, provided that n and m do not simultaneously become 0.)

_{CF 2 = CF-O- (CF} 2) P -CFX (-O- (CF 2) K -SO 3 H) (3-1)
_{CF 2 = CF-O- (CF} 2) P -CFX (- (CF 2) L -O- (CF 2) m -SO 3 H) (3-2)
(In the formulas (3-1) and (3-2), X represents a C 1 to C 3 perfluoroalkyl group, P represents an integer of 0 to 12, and 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 do not simultaneously become 0.)

Further, the PFSA resin, - a repeating unit represented _{by, - - (CF 2 -CF 2} ) (CF 2 -CF (-O- (CF 2 CFXO) n - (CF 2) m -SO 3 H A repeating unit represented by the formula (wherein X represents F or CF ₃ , n represents an integer of 0 to 5 and m represents an integer of 0 to 12), provided that n and m are A copolymer containing not simultaneously 0.), which is represented by — (CF ₂ —CF (—O— (CF ₂ CFXO) _n — (CF ₂ ) _m —SO ₃ H)) — Repeating unit (in the formula, X represents CF ₃ , n represents 0 or 1 and m represents an integer of 0 to 12, provided that n and m do not simultaneously become 0) It is more preferable that it is a copolymer. When the PFSA resin is a copolymer having the above structure and has a predetermined equivalent mass EW to be described later, the obtained solid polymer electrolyte membrane has sufficient hydrophilicity and is a radical species generated by oxidative degradation. Resistance tends to increase.

Furthermore, _{n in the} repeating unit represented by-(CF ₂ -CF (-O- (CF ₂ CFXO) _n- (CF ₂ ) _m -SO ₃ H)) of the PFSA resin is 0, m Is an integer of 1 to 6, or -CF ₂ -CFX (-O- (CF) derived from the compound represented by the formula (3-1) and the compound represented by the formula (3-2) _{2) P -CFX (-O- (CF} 2) K -SO 3 H) - and _{-CF 2 -CFX (-O- (CF 2} ) P -CFX (- (CF 2) L -O- (CF 2 ) _m -SO ₃ H) - if it contains both the repeating units of, equivalent weight (EW) is low, there is a tendency that hydrophilicity of the resulting solid polymer ion exchange membrane is increased.

The fluorine-based polymer electrolyte polymer represented by the formula (1) in the present embodiment tends to be more remarkable in the effect of the present embodiment, and therefore, a PFSA resin having a structure represented by the following formula (4) It is more preferable that
-[CF ₂ CF ₂ ] _a- [CF ₂ -CF (-O-(CF ₂ ) _m- SO ₃ H)] _g- (4)
(In the formula (4), a and g each represents a number satisfying 0 ≦ a <1, 0 <g ≦ 1, a + g = 1, and m represents an integer of 1 to 6.)

  The fluorine-based polymer electrolyte polymer represented by the above formula (1) and the PFSA resin having a structure represented by the above formula (4) in the present embodiment are respectively represented by the above formulas (1) and (4) It is not particularly limited as long as it has the structure shown, and may include other structures.

The fluorine-based polymer electrolyte polymer represented by the above formula (1) and the PFSA resin having the structure represented by the above formula (4) in the present embodiment directly or partially between the molecules of the ion exchange group It may be indirectly partially crosslinked. The partial crosslinking is preferable from the viewpoint of controlling the solubility and the excessive swelling.
For example, even if the EW of the fluorine-based polymer electrolyte polymer is about 280 (g / eq), the water solubility of the fluorine-based polymer electrolyte polymer is reduced (water resistance is improved) by performing the partial crosslinking. be able to.
In addition, even when the fluorine-based polymer electrolyte polymer is in a low melt flow region (polymer region), intermolecular entanglement can be increased by the partial crosslinking, and solubility and excessive swelling can be reduced.
As the partial crosslinking reaction, for example, reaction of ion exchange group with functional group or main chain of another molecule, reaction of ion exchange groups, oxidation resistant low molecular weight compound, oligomer or polymer substance, etc. And a cross-linking reaction (covalent bond) of the following, and may optionally be a reaction with a salt (including an ionic bond with a SO ₃ H group) -forming substance. Examples of oxidation resistant low molecular weight compounds, oligomers or high molecular weight substances include polyhydric alcohols and organic diamines.

  The molecular weight of the fluorine-based polymer electrolyte polymer in this embodiment is not particularly limited, but it is 0 as a melt flow index (MFI) value measured according to ASTM: D1238 (measurement conditions: temperature 270 ° C., load 2160 g) .05 to 50 (g / 10 min) is preferable, 0.1 to 30 (g / 10 min) is more preferable, and 0.5 to 20 (g / 10 min) is further preferable preferable.

(EW of fluorinated polymer electrolyte polymer)
The equivalent mass EW (the dry mass gram of the fluorine-based polymer electrolyte polymer per equivalent of ion exchange groups) of the fluorine-based polymer electrolyte polymer in the present embodiment is preferably 300 to 1300 (g / eq), More preferably, it is 350-1000 (g / eq), More preferably, it is 400-900 (g / eq), Most preferably, it is 450-750 (g / eq).
In the fluorine-based polymer electrolyte polymer having the structure of the above formula (2), by adjusting its EW to the above range, in combination with its chemical structure, hydrophilicity excellent in the ion exchange resin composition containing it The resin layer obtained by using the resin composition has lower electric resistance and tends to further improve the battery performance. That is, the EW of the fluorine-based polymer electrolyte polymer is preferably 300 or more from the viewpoint of hydrophilicity and water resistance of the membrane, and is preferably 1300 or less from the viewpoint of hydrophilicity and electric resistance of the membrane.
The equivalent mass EW of the fluorine-based polymer electrolyte polymer can be measured by salt-substituting the fluorine-based polymer electrolyte polymer and back titration of the solution with an alkaline solution.
Said EW can be adjusted by the copolymerization ratio of the fluorine-type monomer which is a raw material of fluorine-type polymer electrolyte polymer, selection of a monomer kind, etc.

In addition, when the EW of the PFSA resin is near the above-mentioned lower limit value, the resin is partially modified by partial cross-linking reaction between molecules directly or indirectly between some of the ion exchange groups on the side chain of the resin. It may control the solubility or the excessive swelling. The partial crosslinking reaction is not limited to the following. For example, the reaction of an ion exchange group with a functional group or main chain of another molecule, or the reaction of ion exchange groups, a low molecular weight compound having low oxidation resistance, an oligomer or a polymer A crosslinking reaction (covalent bonding) via a substance or the like may be mentioned, and in some cases, it may be a reaction with a salt (including an ionic bond with a SO ₃ H group). Examples of the oxidation resistant low molecular weight compound, oligomer or high molecular substance include, but are not limited to, polyhydric alcohols and organic diamines.
When performing partial crosslinking reaction, the EW of the PFSA resin may be low. That is, the water solubility may be reduced (water resistance may be improved) without sacrificing the ion exchange group (in other words, EW). In addition, the same applies to the case where PFSA resin is a low melt flow region (polymer region) and there are many intermolecular entanglements.

(Additive)
In the diaphragm for a redox flow battery in the present embodiment, an additive may be added to any one or more layers for the purpose of improving chemical physical properties, physical physical properties, and the like. Specific examples of the additive in the present embodiment include, but are not limited to, polytetrafluoroethylene, polybenzimidazole, polyimide, polyamide imide, polypyridine, polypyrimidine, polyimidazole, polyvinyl pyridine, polyvinyl as an organic additive. As additives of inorganic substances such as imidazole, polyaniline, polyphenylene sulfide, Al ₂ O ₃ , B ₂ O ₃ , BaO, BaTiO ₃ , CaO, KTaO ₃ , LiNbO ₃ , MgO, P ₂ O ₅ , SiO, SiO ₂ , SnO _{2, SrO, TiO 2, V} 2 O 5, WO 3, Y 2 O 3, ZnO, metal oxides such as _{ZrO 2, Zr 2 O 3,} ZrSiO 4, BN, inorganic such as _{CaCl 2, Si 3 N 4,} TiN Etc. Also, two or more of these may be used simultaneously.

(Thickness of membrane)
The membrane for a redox flow battery of the present embodiment has at least one resin layer and a hydrophobic layer, and these may each be a laminate of two or more layers, and the redox flow battery of the present embodiment The diaphragm may further have another layer. Thus, although the diaphragm for redox flow batteries of this embodiment can take an appropriate thickness according to the form of utilization, it is preferable to generally have a thickness of 10 micrometers-200 micrometers. The handling property of the membrane tends to be secured at 10 μm or more, and the proton permeability tends to be secured at 200 μm or less.
Moreover, as for the thickness of the hydrophobic layer located in outermost layer, 0.1 micrometer-10 micrometers are preferable. When the thickness is 0.1 μm or more, a sufficient amount of the iceberg structure is formed, and the permeation of the active material tends to be suppressed. Further, by setting the thickness to 10 μm or less, when assembled as a redox flow battery, the air in the mechanism tends to be easily discharged. For the same reason, the thickness of the hydrophobic layer is more preferably 0.1 μm to 5 μm, and still more preferably 0.2 μm to 4 μm.

(Reinforcement of resin layer)
The resin layer in the present embodiment may be reinforced based on various known methods. Examples of known reinforcement methods include, but are not limited to, for example, reinforcement by addition of fibrillar PTFE (corresponding to JP-A-53-149881 (corresponding to US Pat. No. 4,218,542)) And JP-B-63-61 337 (corresponding to EP 94 679), reinforcement with a porous PTFE membrane subjected to stretching treatment (JP-B-5-75835 and JP-A-11-501964 (US See, Patents 5,599,614 and US Pat. No. 5,547,551)), reinforcement by addition of inorganic particles (Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ etc.) (See JP-A-6-111827, JP-A-9-219206 and US Pat. No. 5,523,181), reinforcement by cross-linking No. 000-188013), reinforcement by incorporating silica in a membrane by using a sol-gel reaction ((K. A. Mauritz, R. F. Storeyand, C. K. Jones, in Multiphase Polymer Materials: Blendsands) U.S. Ionomers, L. A. Utrackiand R. A. Weiss, Editors, ACS Symposium Series No. 395, p. 401, American Chemical Society, Washington, DC (1989)) and the like.

(Production method of diaphragm)
It does not specifically limit as a manufacturing method (film-forming method) of the diaphragm for redox flow batteries which concerns on this embodiment, For example, methods, such as extrusion molding, the cast film forming using a solution, etc., can be used.
Also, the method for forming the hydrophobic layer is not limited to the following, for example, a separately prepared hydrophobic layer is attached, or a solution or dispersion is cast on a resin layer, spray coating, gravure coating, etc. Method is mentioned.

(Redox flow battery)
The redox flow battery according to the present embodiment includes a positive electrode cell chamber having a positive electrode including a carbon electrode, a negative electrode cell chamber having a negative electrode including a carbon electrode, and a redox flow separating and separating the positive cell chamber and the negative cell chamber. A membrane for a battery, and the membrane for a redox flow battery has a resin layer containing an ion exchange resin, and a hydrophobic layer having a contact angle with water of 110 ° or more, and the redox flow At least one of the outermost layers of the battery diaphragm is the hydrophobic layer. That is, the redox flow battery diaphragm of the present embodiment described above can be preferably applied to the redox flow battery of the present embodiment, and the specific aspect to the preferred embodiment of the redox flow battery diaphragm in the redox flow battery of the present embodiment Is as described above.
The positive electrode cell chamber circulates a positive electrode electrolyte containing a positive electrode active material, and the negative electrode cell chamber circulates a negative electrode electrolyte containing a negative electrode active material, and the valences of the positive electrode active material and the negative electrode active material in the electrolytic solution Charge and discharge occur based on the change.

  FIG. 1 is an example of a schematic view of a redox flow battery according to the present embodiment. In this example, the redox flow secondary battery of the present embodiment includes: a positive electrode cell chamber 2 including a positive electrode 1 formed of a carbon electrode; a negative electrode cell chamber 4 including a negative electrode 3 formed of a carbon electrode; The cathode cell chamber 2 includes an electrolytic cell 6 including an electrolyte membrane 5 as a diaphragm for separating and separating the anode cell chamber 4 from each other, the cathode cell chamber 2 includes a cathode electrolyte containing an active material, and the anode cell chamber 4 It contains an anode electrolyte containing a substance. The positive electrode electrolyte and the negative 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 (arrows A and B). Also, the current generated by the redox flow battery may be converted from direct current to alternating current via the AC / DC converter 9.

  In the redox flow battery according to the present embodiment, although not shown in FIG. 1, liquid permeable and porous collector electrodes (for the negative electrode and for the positive electrode) are disposed on both sides of the diaphragm and pressed by pressing. It is possible to have a structure in which one of the two cell chambers is secured by a spacer, with one of the two cells separated by the diaphragm as the positive cell chamber and the other as the negative cell chamber.

In the case of a vanadium type redox flow battery, a positive electrode electrolyte composed of a sulfuric acid electrolyte containing tetravalent vanadium (V ⁴⁺ ) and pentavalent (V ⁵⁺ ) in the positive electrode cell chamber, and vanadium in the negative electrode cell chamber The battery is charged and discharged by flowing a negative electrode electrolyte containing trivalent (V ³⁺ ) and bivalent (V ²⁺ ). At this time, at the time of charging, V ^{4 +} is oxidized to V ^{5 +} in the positive electrode cell chamber because vanadium ions emit electrons, and V ^{3 +} is V ² by electrons returned through the outer path in the negative cell chamber. ^It is reduced to ⁺ . In this redox reaction, protons (H ⁺ ) become excessive in the positive electrode cell chamber, and the diaphragm selectively transfers the excess protons in the positive electrode cell chamber to the negative electrode chamber to maintain electrical neutrality. During discharge, the reverse reaction proceeds.

The storage performance in charge and discharge of the redox flow battery can be judged by energy efficiency. In a redox flow battery using a membrane that achieves both low internal resistance and permeation inhibition of the active material, the amount of charge stored in the active material is taken out without waste, and internal resistance loss per unit amount of charge is also suppressed Therefore, the storage performance (energy efficiency) of the final battery is improved. When the active material passes through the diaphragm during operation of the redox flow battery, ions whose charge number has changed due to charge can not contribute to discharge, and the current efficiency decreases. By using the diaphragm for a redox flow battery of the present embodiment, the permeation of the active material is suppressed, and therefore, it is possible to operate at high current efficiency.
On the other hand, the internal resistance of the redox flow battery depends on the proton permeability of the membrane, and the internal resistance of the battery is reduced by using a membrane with high proton permeability. When the internal resistance is reduced, the voltage required for charging decreases, and a higher voltage operation is possible for discharging.
As described above, the diaphragm for a redox flow battery of this embodiment achieves high current efficiency by suppressing permeation of the active material while keeping the internal resistance low, and the energy efficiency of the finally obtained redox flow battery is high.

In the case of a vanadium-type redox flow battery, it is known that the movement of V ^{2+ in the} anode cell chamber, in particular, to the cathode cell chamber reduces the current efficiency. Therefore, in the vanadium redox flow battery according to one aspect of the present embodiment, it is preferable that the hydrophobic layer be disposed toward the negative electrode chamber side. That is, the vanadium-type redox flow battery of this embodiment separates and separates a positive electrode cell chamber having a positive electrode including a carbon electrode, a negative electrode chamber having a negative electrode including a carbon electrode, the positive cell chamber and the negative cell chamber. A redox flow battery diaphragm, the redox flow battery diaphragm having a resin layer containing an ion exchange resin, and a hydrophobic layer having a contact angle with water of 110 ° or more, At least one of the outermost layers of the redox flow cell diaphragm is the hydrophobic layer, and the hydrophobic layer is in contact with the electrolyte solution flowing to the negative electrode. By being configured in this manner, the vanadium redox flow battery of the present embodiment exhibits high energy efficiency.

  Hereinafter, the present embodiment will be more specifically described by way of examples, but the present invention is not limited to the following examples. The evaluation method and the measurement method used in the present embodiment are as follows.

(EW of diaphragm for redox flow battery)
About 0.02 to 0.10 g of a diaphragm for a redox flow battery is immersed in 50 mL of 25 ° C. saturated aqueous NaCl solution (0.26 g / mL) and left for 10 minutes while stirring, then reagent special grade phenol manufactured by Wako Pure Chemical Industries, Ltd. Neutralization titration was carried out using a special grade 0.01 N sodium hydroxide aqueous solution manufactured by Wako Pure Chemical Industries, Ltd., using phthalein as an indicator. After the Na type ion exchange membrane obtained after neutralization was rinsed with pure water, it was vacuum dried and weighed. The equivalent weight of sodium hydroxide required for neutralization was M (mmol), the mass of the Na type ion exchange membrane was W (mg), and the equivalent mass EW (g / eq) was determined from the following equation.
EW = (W / M)-22
After repeating the above operation five times, except for the maximum value and the minimum value of the five calculated EW values, the three values are arithmetically averaged to obtain a measurement result.

Example 1
A solution was prepared by dispersing the polymer electrolyte in which m = 2 in the formula (4) in a mixed solvent of water and ethylene glycol. Here, the EW of the polyelectrolyte was 640, and the mass percent concentration of the polyelectrolyte was adjusted to be about 30%.
This was cast on a polyimide (PI) film using a blade coater so that the thickness after drying was about 30 μm.
The polyphenylene sulfide particle dispersion was prepared according to the method described in JP-A-2015-199875. Under the present circumstances, the polymer electrolyte solution (The polymer electrolyte used as m = 2 by said Formula (4) is used) used as a binder was added. The concentration of polyphenylene sulfide fine particles in the dispersion is 9 wt%, and the fine particle dispersion is coated on the cast film so that the amount of polyphenylene sulfide is 0.33 mg · cm ^−2. The thickness was adjusted and cast filmed.
After removing the residual solvent by washing the membrane with ion exchange water, heat treatment was performed at 170 ° C. to obtain a diaphragm for a redox flow battery.
Surface SEM images were obtained for the obtained films (FIG. 2). It was confirmed that a layer containing voids was formed on the surface by fine particles.

Comparative Example 1
A diaphragm for a redox flow battery was obtained in the same manner as in Example 1 except that no layer was formed of the polyphenylene sulfide fine particle dispersion.

(Contact angle measurement)
The contact angle to water of the outermost layer in the redox flow cell membrane was measured by the following method.
First, the diaphragm for a redox flow battery cut out on a horizontal pedestal was fixed so that the measurement surface faced upward. Subsequently, 6 microliters of ion-exchange water was dripped from on the fixed diaphragm for redox flow batteries. After dropping for 120 seconds, an image was obtained with a camera from the side, and the measured value of the contact angle was obtained from the angle between the droplet surface and the film surface.

(Measurement of surface particle amount of hydrophobic layer)
The surface particle amount of the hydrophobic layer was calculated by multiplying the amount of particles in the fine particle dispersion specified as the feed ratio by the coating thickness before drying.

(Measurement of average particle size)
The average particle sizes of the polyphenylene sulfide fine particles and the polytetrafluoroethylene fine particles used in the examples were measured by the dynamic light scattering method (DLS method). The solution used for cast film formation was diluted with water, and DLS measurement was performed on fine particles in the solution dispersion state. The particle size distribution was determined five times by the Marquardt method, and the average value of the peak top of the distribution was taken as the average particle size.

(Proton permeation resistance measurement of diaphragm for redox flow battery)
The proton permeation resistance of the redox flow cell membrane was evaluated as the internal resistance of the redox flow cell.
The membrane area was 10 cm ² , and both of the positive electrode tank and the negative electrode tank were assembled in a vanadium type redox flow battery with an electrolyte volume of 30 mL, and electrochemical impedance measurement was performed. Here, a carbon fiber non-woven fabric was used as the positive electrode / negative electrode material, and the vanadium ion concentration in both tanks was 1.6 M in all cases. The Nyquist diagram was created from the electrochemical impedance measurement results, and the resistance of the film was calculated from the real axis intersection point in the Nyquist diagram.

(Measurement of active material permeation suppression of diaphragm for redox flow battery)
The permeation suppression effect of the active material of the diaphragm for a redox flow battery was judged by the current efficiency of the redox flow battery.
A charge-discharge cycle test was conducted by assembling the same redox flow battery as described above. The test was performed by repeating charge and discharge at a current density of 70 mA · cm ⁻² .
The current efficiency is determined as the ratio of the amount of charge charged in each cycle to the amount of charge discharged.
The current efficiency in each cycle was calculated, and the efficiencies of 3 to 8 cycles were averaged to obtain the current efficiency of the film.

(Measurement of porosity of hydrophobic layer)
The porosity was calculated from the thickness of the hydrophobic layer and the density of the particles constituting the hydrophobic layer.
First, the thickness of the diaphragm was measured. In addition, a layer made of an electrolyte was prepared separately without providing a hydrophobic layer made of polyphenylene sulfide particles, and the thickness was measured. By taking these differences, the thickness of the hydrophobic layer was calculated. Here, the apparent hydrophobic layer density was calculated from (hydrophobic layer weight per unit area) / (hydrophobic layer thickness). Then, (apparent hydrophobic layer density) / (density of particles constituting the hydrophobic layer) was calculated, and the difference from 1 was taken to determine the porosity. In addition, about the density of the particle | grains which comprise a hydrophobic layer, the known value was used about the said particle | grains (a polyphenylene sulfide, polytetrafluoroethylene).

(Measurement result of internal resistance and current efficiency)
Table 1 shows the measurement results of Example 1 and Comparative Example 1.
It is understood that the current efficiency is improved without increasing the internal resistance, and in the membrane of the example, protons are easily transmitted and the transmission of the active material is suppressed.

Example 2
A diaphragm for a redox flow battery was obtained in the same manner as in Example 1 except that the EW of the polymer electrolyte was adjusted to 740. It was confirmed that a layer containing voids was formed on the surface by fine particles.

[Example 3]
A diaphragm for a redox flow battery was obtained in the same manner as in Example 2 except that the coating thickness was adjusted so that the amount of polyphenylene sulfide after drying was 0.55 mg · cm ⁻² . It was confirmed that a layer containing voids was formed on the surface by fine particles.

Example 4
A solution was prepared by dispersing the polymer electrolyte in which m = 2 in the formula (4) in a mixed solvent of water and ethylene glycol. Here, the EW of the polyelectrolyte was 740, and the mass percent concentration of the polyelectrolyte was adjusted to be about 30%.
This was cast on a polyimide (PI) film using a blade coater so that the thickness after drying was about 30 μm.
The polytetrafluoroethylene fine particle dispersion (manufactured by Sigma-Aldrich) was diluted with water and adjusted to have a concentration of 5% in the dispersion of polytetrafluoroethylene fine particles. Further, a polymer electrolyte solution (including a polymer electrolyte where m = 2 in the above formula (4)) as a binder was added to the dispersion. The fine particle dispersion was cast on the cast film so that the amount of polytetrafluoroethylene was 0.4 mg · cm ⁻² .
After removing the residual solvent by washing the membrane with ion exchange water, heat treatment was performed at 190 ° C. to obtain a diaphragm for a redox flow battery. It was confirmed that a layer containing voids was formed on the surface by fine particles.

Comparative Example 2
A diaphragm for a redox flow battery was obtained in the same manner as in Example 2 except that a layer of the polyphenylene sulfide fine particle dispersion was not formed.

(Energy efficiency of redox flow battery)
For Examples 2 to 4 and Comparative Example 2, the same redox flow battery as described above was assembled, and a charge and discharge cycle test was performed. The energy efficiency of each cycle was calculated, and the energy efficiencies of 3 to 8 cycles were averaged to obtain the energy efficiency of the redox flow battery.

(Measurement result of internal resistance and energy efficiency)
Table 2 shows the measurement results of Examples 2 to 4 and Comparative Example 2. About internal resistance, the result measured by the method similar to Example 1 about Example 2, 3 and Comparative Example 2 is shown.
It is understood that the redox flow battery of the example not only has a sufficiently low resistance, but also has high energy efficiency.

The membrane for a redox flow battery of the present invention has industrial applicability as a membrane having a low proton permeation resistance and capable of blocking the permeation of an active material.
A redox flow battery using this can be used as a battery with high energy efficiency.

DESCRIPTION OF SYMBOLS 1 positive electrode 2 positive electrode cell chamber 3 negative electrode 4 negative electrode cell chamber 5 diaphragm 6 electrolytic cell 7 positive electrode electrolyte tank 8 negative electrode electrolyte tank 9 AC / DC converter

Claims (8)

A resin layer containing an ion exchange resin,
A hydrophobic layer having a contact angle to water of 110 ° or more,
A diaphragm for a redox flow battery having
A diaphragm for a redox flow battery, wherein at least one of the outermost layers of the diaphragm for a redox flow battery is the hydrophobic layer.   The diaphragm for a redox flow battery according to claim 1, wherein the hydrophobic layer has a void.   The diaphragm for a redox flow battery according to claim 1, wherein the hydrophobic layer contains fine particles.   The diaphragm for a redox flow battery according to claim 3, wherein an average particle diameter of the fine particles is 50 nm to 5 μm. The diaphragm for a redox flow battery according to claim 3 or 4, wherein an amount of surface particles of the fine particles is 0.01 to 20 mg · cm- ² .   The diaphragm for a redox flow battery according to any one of claims 1 to 5, wherein the ion exchange resin contains a fluorine-based polymer electrolyte polymer. An electrolytic cell comprising a positive electrode cell chamber having a positive electrode including a carbon electrode, a negative electrode cell chamber having a negative electrode including a carbon electrode, and a redox flow battery diaphragm separating and separating the positive electrode cell chamber and the negative cell chamber. Equipped
The membrane for a redox flow battery has a resin layer containing an ion exchange resin, and a hydrophobic layer having a contact angle to water of 110 ° or more,
The redox flow battery in which at least one of the outermost layers of the diaphragm for the redox flow battery is the hydrophobic layer. An electrolytic cell comprising a positive electrode cell chamber having a positive electrode including a carbon electrode, a negative electrode cell chamber having a negative electrode including a carbon electrode, and a redox flow battery diaphragm separating and separating the positive electrode cell chamber and the negative cell chamber. Equipped
The membrane for a redox flow battery has a resin layer containing an ion exchange resin, and a hydrophobic layer having a contact angle to water of 110 ° or more,
At least one of the outermost layers of the redox flow cell diaphragm is the hydrophobic layer,
The vanadium-type redox flow battery in which the said hydrophobic layer contacts the electrolyte solution distribute | circulated to the said negative electrode.