WO2016006075A1 - Redox flow battery - Google Patents

Redox flow battery Download PDF

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Publication number
WO2016006075A1
WO2016006075A1 PCT/JP2014/068409 JP2014068409W WO2016006075A1 WO 2016006075 A1 WO2016006075 A1 WO 2016006075A1 JP 2014068409 W JP2014068409 W JP 2014068409W WO 2016006075 A1 WO2016006075 A1 WO 2016006075A1
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WO
WIPO (PCT)
Prior art keywords
flow battery
electrode electrolyte
redox flow
positive electrode
negative electrode
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PCT/JP2014/068409
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French (fr)
Japanese (ja)
Inventor
昌 山内
洋成 出口
嵐 黄
俊博 宮▲崎▼
昭介 山之内
Original Assignee
日新電機 株式会社
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Application filed by 日新電機 株式会社 filed Critical 日新電機 株式会社
Priority to JP2016532366A priority Critical patent/JP6172394B2/en
Priority to PCT/JP2014/068409 priority patent/WO2016006075A1/en
Priority to CN201480078666.7A priority patent/CN106463751B/en
Publication of WO2016006075A1 publication Critical patent/WO2016006075A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a redox flow battery.
  • a redox flow battery uses a strongly acidic electrolyte.
  • a strongly acidic electrolytic solution an electrolytic solution containing a vanadium redox substance has been put into practical use. Since the metal redox ions in the strongly acidic electrolyte are stably dissolved even at a relatively high concentration, the energy density of the battery can be increased.
  • the ion-conducting carriers are H + ions or OH ⁇ ions. Since both the mobility of H + ions and the mobility of OH ⁇ ions are relatively high, the strongly acidic electrolyte has high conductivity. This increases the battery efficiency as a result of the reduced battery resistance.
  • Patent Document 1 discloses a composite membrane of a hydrophilic membrane and a porous membrane as a diaphragm for a redox flow battery.
  • the hydrophilic film is composed of a cellulose polymer or an ethylene-vinyl alcohol copolymer.
  • the porous film is made of tetrafluoroethylene or vinyl chloride.
  • Patent Document 2 discloses a weakly acidic electrolytic solution.
  • Patent Document 3 discloses a cation exchange membrane as a diaphragm used in a power storage battery having an electrolyte having a pH of 2 or more and 8 or less. This cation exchange membrane is obtained by graft-polymerizing styrene sulfonate on a resin film substrate having an ethylene-vinyl alcohol copolymer as a matrix.
  • Patent Document 4 discloses an ion-permeable diaphragm having a microporous membrane. This ion-permeable diaphragm is excellent in characteristics required for electrolysis of alkaline water, and is also useful for a battery using an aqueous electrolyte.
  • Patent Document 5 discloses a negative electrode in which a copolymer of chloromethylstyrene and divinylbenzene is filled in the pores of a porous substrate made of polyolefin, and a quaternary ammonium group is introduced into the copolymer. An ion exchange membrane is disclosed.
  • Patent Documents 1 to 5 described above describe anion exchange using a non-porous substrate made of an ethylene-vinyl alcohol copolymer in a redox flow battery using an electrolytic solution having a pH in the range of 2 to 8. There is no suggestion of a configuration using a membrane as a diaphragm.
  • An object of the present invention is to provide a redox flow battery having a diaphragm suitable for use of an electrolytic solution having a pH in the range of 2 or more and 8 or less.
  • the non-porous substrate is preferably an ethylene-vinyl alcohol copolymer film having a specific gravity of 1.17 or more and 1.23 or less.
  • the non-porous substrate is preferably a uniaxial or biaxially stretched ethylene-vinyl alcohol copolymer film.
  • a graft ratio of the anion exchange membrane is 15% or more and 47% or less.
  • the thickness of the non-porous substrate is preferably 15 ⁇ m or more and 50 ⁇ m or less.
  • the monomer preferably includes a vinylbenzyltrimethylammonium salt.
  • the positive electrode electrolyte preferably contains an iron redox material and citric acid or lactic acid.
  • the redox flow battery includes a charge / discharge cell 11, a first tank 23 that stores a positive electrode electrolyte 22, and a second tank 33 that stores a negative electrode electrolyte 32. Further, the redox flow battery includes a first supply pipe 24 that supplies the positive electrode electrolyte 22 to the charge / discharge cell 11 and a second supply pipe 34 that supplies the negative electrode electrolyte 32 to the charge / discharge cell 11.
  • the inside of the charge / discharge cell 11 is partitioned into a positive electrode side cell 21 and a negative electrode side cell 31 by a diaphragm 12.
  • a positive electrode 21a and a positive electrode side current collecting plate 21b are arranged in contact with each other.
  • a negative electrode 31 a and a negative electrode current collector 31 b are arranged in contact with each other.
  • the positive electrode 21a and the negative electrode 31a are made of, for example, carbon felt.
  • the positive electrode side current collector plate 21b and the negative electrode side current collector plate 31b are made of, for example, a glassy carbon plate.
  • the positive electrode side current collector plate 21 b and the negative electrode side current collector plate 31 b are electrically connected to the charge / discharge device 10.
  • the redox flow battery is provided with a temperature adjusting device for adjusting the temperature around the charge / discharge cell 11 as necessary.
  • a first tank 23 is connected to the positive electrode side cell 21 via a first supply pipe 24 and a first recovery pipe 25.
  • the first supply pipe 24 is equipped with a first pump 26.
  • the positive electrolyte solution 22 in the first tank 23 is supplied to the positive electrode side cell 21 through the first supply pipe 24.
  • the positive electrode electrolyte 22 in the positive electrode side cell 21 is recovered to the first tank 23 through the first recovery pipe 25.
  • the positive electrode electrolyte 22 circulates between the first tank 23 and the positive electrode side cell 21.
  • the second tank 33 is connected to the negative electrode side cell 31 via a second supply pipe 34 and a second recovery pipe 35.
  • the second supply pipe 34 is equipped with a second pump 36.
  • the negative electrolyte solution 32 in the second tank 33 is supplied to the negative electrode side cell 31 through the second supply pipe 34.
  • the negative electrode electrolyte 32 in the negative electrode side cell 31 is recovered in the second tank 33 through the second recovery pipe 35.
  • the negative electrode electrolyte 32 circulates between the second tank 33 and the negative electrode side cell 31.
  • the first gas pipe 13a is connected to the first tank 23 and the second tank 33.
  • the first gas pipe 13 a supplies the inert gas supplied from the inert gas generator into the positive electrode electrolyte 22 in the first tank 23 and the negative electrode electrolyte 32 in the second tank 33. Thereby, the contact with the positive electrode electrolyte solution 22 and the negative electrode electrolyte solution 32, and oxygen in air
  • the oxygen concentration in the gas phase in the first tank 23 and the second tank 33 is kept substantially constant by adjusting the supply amount of the inert gas.
  • nitrogen gas is used as the inert gas.
  • the inert gas examples include carbon dioxide gas, argon gas, and helium gas in addition to nitrogen gas.
  • the inert gas supplied to the first tank 23 and the second tank 33 is exhausted through the exhaust pipe 14.
  • a water seal portion 15 that seals the front end opening of the exhaust pipe 14 is provided at the distal end of the exhaust pipe 14 on the discharge side. The water seal 15 prevents the air from flowing back into the exhaust pipe 14 and keeps the pressure in the first tank 23 and the second tank 33 constant.
  • the redox flow battery according to this embodiment includes a case 41.
  • the case 41 surrounds the charge / discharge cell 11, the first tank 23, and the second tank 33.
  • the case 41 is connected to the second gas pipe 13b.
  • the second gas pipe 13 b supplies the inert gas supplied from the inert gas generator to the periphery of the charge / discharge cell 11. Thereby, the contact with the charging / discharging cell 11 and oxygen in air
  • the oxygen concentration in the case 41 is kept substantially constant by adjusting the supply amount of the inert gas.
  • an oxidation reaction is performed in the positive electrode electrolyte solution 22 in contact with the positive electrode 21a, and a reduction reaction is performed in the negative electrode electrolyte solution 32 in contact with the negative electrode 31a. That is, the positive electrode 21a emits electrons and the negative electrode 31a receives electrons.
  • the positive collector plate 21b supplies the electrons discharged from the positive electrode 21a to the charging / discharging device 10.
  • the negative electrode current collector 31b supplies the electrons received from the charge / discharge device 10 to the negative electrode 31a.
  • a reduction reaction is performed in the positive electrode electrolyte 22 in contact with the positive electrode 21a, and an oxidation reaction is performed in the negative electrode electrolyte 32 in contact with the negative electrode 31a. That is, the positive electrode 21a receives electrons and the negative electrode 31a emits electrons. At this time, the positive collector plate 21b supplies the electrons received from the charge / discharge device 10 to the positive electrode 21a.
  • the diaphragm 12 suppresses permeation of the active material between the positive electrode side cell 21 and the negative electrode side cell 31.
  • the diaphragm 12 is composed of an anion exchange membrane.
  • the diaphragm 12 transmits the anions in the negative electrode side cell 31 to the positive electrode side cell 21 during charging, and transmits the anions in the positive electrode side cell 21 to the negative electrode side cell 31 during discharge.
  • the anion exchange membrane is obtained by graft polymerization of a monomer having an anion exchangeable substituent (hereinafter sometimes simply referred to as a monomer) on a non-porous substrate made of an ethylene-vinyl alcohol copolymer. That is, the main chain of the polymer constituting the anion exchange membrane is composed of an ethylene-vinyl alcohol copolymer, and the graft chain of the polymer is composed of a polymer of a monomer having an anion exchangeable substituent.
  • a monomer having an anion exchangeable substituent hereinafter sometimes simply referred to as a monomer
  • the non-porous substrate made of ethylene-vinyl alcohol copolymer can be selected from commercially available films or sheets.
  • the thickness of the non-porous substrate made of an ethylene-vinyl alcohol copolymer is preferably 15 ⁇ m or more and 50 ⁇ m or less.
  • the non-porous substrate made of an ethylene-vinyl alcohol copolymer is preferably an ethylene-vinyl alcohol copolymer film having a specific gravity of 1.17 or more and 1.23 or less. This specific gravity is measured in accordance with JIS Z8807: 2012. Specifically, the specific gravity can be measured using a specific gravity bottle.
  • the ethylene content of the ethylene-vinyl alcohol copolymer is preferably 20 mol% or more, for example, from the viewpoint that the strength as the diaphragm 12 is easily secured.
  • the ethylene content of the ethylene-vinyl alcohol copolymer is preferably 50 mol% or less from the viewpoint of hydrophilicity.
  • the non-porous substrate may contain an additive such as a plasticizer, for example.
  • non-porous substrate made of an ethylene-vinyl alcohol copolymer an unstretched or stretched film is preferably used.
  • the non-porous substrate made of an ethylene-vinyl alcohol copolymer is preferably a uniaxial or biaxially stretched ethylene-vinyl alcohol copolymer film.
  • Examples of the anion-exchangeable substituent of the monomer include a primary to tertiary amino group, a quaternary ammonium group, a pyridyl group, an imidazole group, a quaternary pyridinium group, and a quaternary imidazolium group.
  • Examples of the counter ion of the substituent that the monomer has include a halide ion, an inorganic oxoacid anion, an organic acid anion, an organic sulfonate anion, a hydroxide ion, a bicarbonate ion, and a carbonate ion.
  • the anion exchangeable substituent of the monomer may include an aryl group.
  • a vinylbenzyl trialkylammonium salt is used as the monomer having a substituent containing an aryl group.
  • the vinyl benzyl trialkyl ammonium salt include vinyl benzyl trimethyl ammonium salt, vinyl benzyl triethyl ammonium salt, and vinyl benzyl triethanol ammonium salt.
  • the monomer preferably includes a vinyl benzyl trimethyl ammonium salt.
  • the graft ratio of the anion exchange membrane is preferably 15% or more and 47% or less.
  • the graft ratio of the anion exchange membrane is calculated by the following formula (A) when the mass of the non-porous substrate is W0 and the mass of the anion exchange membrane is W1.
  • the diaphragm 12 (anion exchange membrane) is manufactured through a polymerization process.
  • a graft chain is introduced using a monomer into a radical active site generated on the non-porous substrate.
  • the radical active site can be generated by, for example, radical polymerization initiator, ionizing radiation irradiation, ultraviolet irradiation, ultrasonic irradiation, plasma irradiation, or the like.
  • the polymerization step using ionizing radiation has the advantage that the production process is simple, safe and has a low environmental impact.
  • ionizing radiation examples include ⁇ rays, ⁇ rays, ⁇ rays, electron rays, X rays and the like.
  • ionizing radiations for example, ⁇ rays emitted from cobalt 60, electron beams emitted from an electron beam accelerator, X-rays, and the like are preferable from the viewpoint of easy industrial use.
  • Irradiation with ionizing radiation is preferably performed in an inert gas atmosphere such as nitrogen gas, neon gas, or argon gas from the viewpoint of suppressing the reaction between radical active sites and oxygen.
  • the absorbed dose of ionizing radiation is, for example, in the range of 1 to 300 kGy.
  • the graft ratio can be changed by adjusting the absorbed dose of ionizing radiation.
  • a solution containing the monomer is brought into contact with the non-porous substrate in which radical active sites are generated.
  • the radical polymerization reaction can be promoted by shaking or heating the non-porous substrate immersed in the solution containing the monomer.
  • the solvent of the solution containing the monomer for example, water, alcohols such as methanol and ethanol, and hydrophilic solvents such as hydrophilic ketones such as acetone can be used.
  • a mixed solvent obtained by mixing plural kinds of hydrophilic solvents may be used.
  • the solvent to be used preferably contains water as the main component, more preferably water, from the viewpoints of cost reduction of the production process, reduction of environmental burden, and improvement of process safety.
  • water for example, ion exchange water, pure water, ultrapure water, or the like can be used.
  • the concentration of the monomer in the solution containing the monomer is, for example, in the range of 3% by mass to 35% by mass, and more preferably 5% by mass to 30% by mass.
  • the monomer concentration is 5% by mass or more, it is easy to increase the graft ratio.
  • the monomer concentration is 35% by mass or less, the formation of a monomer homopolymer is suppressed.
  • the time for which the solution containing the monomer is brought into contact with the non-porous substrate in which the radical active site is generated is, for example, in the range of 30 minutes to 48 hours.
  • the contact between the non-porous base material in which the radical active site is generated and the solution containing the monomer is also preferably performed in an inert gas atmosphere such as nitrogen gas, neon gas, argon gas, etc., as in the case of irradiation with ionizing radiation.
  • the anion exchange membrane is washed with water in the washing step.
  • an acid may be used as necessary.
  • the pH of the positive electrode electrolyte 22 and the pH of the negative electrode electrolyte 32 are in the range of 2 or more and 8 or less.
  • an aqueous solution containing an active material capable of performing a redox reaction within the above pH range is used.
  • the pH of the positive electrode electrolyte 22 and the pH of the negative electrode electrolyte 32 are 2 or more, corrosion resistance is easily ensured.
  • the pH of the positive electrode electrolyte 22 and the pH of the negative electrode electrolyte 32 are 8 or less, for example, the solubility of the active material is easily ensured.
  • active materials examples include iron redox materials, titanium redox materials, chromium redox materials, manganese redox materials, and copper redox materials.
  • the “redox substance” described in the present application refers to a metal ion, a metal complex ion, or a metal generated by a metal redox reaction.
  • the active material is preferably contained in the electrolytic solution as a metal complex in order to suppress precipitation within the above pH range.
  • the chelating agent for forming the metal complex is capable of forming a complex with the active material, and examples thereof include amines, citric acid, lactic acid, aminocarboxylic chelating agents, and polyethyleneimine.
  • the cathode electrolyte 22 contains an iron redox material and an acid.
  • the acid is citric acid or lactic acid.
  • iron functions as an active material. For example, oxidation from iron (II) to iron (III) occurs during charging, and reduction from iron (III) to iron (II) occurs during discharging. Is presumed to occur.
  • the positive electrode electrolyte 22 contains the acid described above, so that a practical electromotive force can be easily obtained.
  • the concentration of the iron redox substance (iron ions) in the positive electrode electrolyte 22 is preferably 0.2 mol / L or more, more preferably 0.3 mol / L or more, from the viewpoint of increasing the energy density. More preferably 0.4 mol / L or more.
  • the concentration of the iron redox substance (iron ions) in the positive electrode electrolyte 22 is preferably 1.0 mol / L or less.
  • the molar ratio of the acid to the iron redox substance in the positive electrode electrolyte 22 is preferably in the range of 1 or more and 4 or less.
  • the molar ratio is 1 or more, the electrical resistance of the positive electrode electrolyte 22 becomes lower, so that the Coulomb efficiency and the utilization rate of the positive electrode electrolyte 22 can be easily increased.
  • the molar ratio is 4 or less, both economic efficiency and practicality can be easily achieved.
  • the pH of the positive electrode electrolyte 22 is preferably in the range of 1 or more and 7 or less, more preferably 2 or more and 5 or less, for example, since it is easy to ensure the solubility of the iron redox material and the acid. Is within the range.
  • the pH is a value measured at 20 ° C., for example.
  • the positive electrode electrolyte 22 may contain, for example, an inorganic acid salt or various chelating agents as necessary.
  • the negative electrode electrolyte 32 is an electrolyte containing a redox material of titanium and an acid.
  • the acid is citric acid or lactic acid.
  • titanium functions as an active material. For example, reduction from titanium (IV) to titanium (III) occurs during charging, and oxidation from titanium (III) to titanium (IV) occurs during discharging. Is presumed to occur.
  • the negative electrode electrolyte solution 32 is complexed by containing the above acid, and the potential of about 0.2 V is lowered, so that a practical electromotive force is easily obtained.
  • the concentration of the titanium redox material (titanium ions) in the negative electrode electrolyte 32 is preferably 0.2 mol / L or more, more preferably 0.3 mol / L or more, from the viewpoint of increasing the energy density. More preferably 0.4 mol / L or more.
  • the concentration of the titanium redox substance (titanium ions) in the negative electrode electrolyte solution 32 is preferably 1.0 mol / L or less.
  • the molar ratio of the acid to the redox substance of titanium in the negative electrode electrolyte solution 32 is preferably in the range of 1 or more and 4 or less.
  • the molar ratio is 1 or more, the electric resistance of the negative electrode electrolyte 32 becomes lower, so that the Coulomb efficiency and the utilization factor of the negative electrode electrolyte 32 are easily increased.
  • the molar ratio is 4 or less, both economic efficiency and practicality can be easily achieved.
  • the pH of the negative electrode electrolyte solution 32 is preferably in the range of 1 or more and 7 or less because, for example, it is easy to ensure the solubility of the redox material of titanium and the acid.
  • the pH of the negative electrode electrolyte solution 32 is more preferably in the range of 2 or more and 5 or less.
  • the negative electrode electrolyte 32 may contain, for example, an inorganic acid salt or various chelating agents as necessary.
  • the positive electrode electrolyte 22 and the negative electrode electrolyte 32 can be prepared by a known method. It is preferable that the water used for the positive electrode electrolyte 22 and the negative electrode electrolyte 32 has a purity equal to or higher than that of distilled water.
  • the amount of dissolved oxygen in the negative electrode electrolyte solution 32 in the second tank 33 is preferably set to 1.5 mg / L or less.
  • the dissolved oxygen amount is more preferably 1.0 mg / L or less.
  • the oxygen concentration in the case 41 is preferably 10% by volume or less.
  • the oxygen concentration in the gas phase in the second tank 33 is preferably 1% by volume or less.
  • the dissolved oxygen amount in the positive electrode electrolyte solution 22 in the first tank 23 may also be set to 1.5 mg / L or less, or may be set to 1.0 mg / L or less.
  • the oxygen concentration in the gas phase in the first tank 23 may also be set to 1% by volume or less.
  • the current efficiency is calculated by substituting the amount of electricity (A) for charging in a predetermined cycle and the amount of electricity (B) for discharging in a predetermined cycle into the following equation (1).
  • Current efficiency (%) B / A ⁇ 100 (1)
  • One charge / discharge of the redox flow battery is referred to as one cycle.
  • the current efficiency is preferably maintained at 90% or more from the first cycle to the ninth cycle, for example.
  • the anion exchange membrane of the present embodiment uses a non-porous substrate, and the non-porous substrate is made of a relatively inexpensive ethylene-vinyl alcohol copolymer. That is, the anion exchange membrane of this embodiment can avoid using an expensive resin material or requiring special processing like a porous substrate. Therefore, it is advantageous from the viewpoint of promoting further spread of the redox flow battery by reducing the cost of the equipment.
  • the positive electrode electrolyte solution 22 and the negative electrode electrolyte solution 32 have a pH in the range of 2 or more and 8 or less.
  • This redox flow battery has an anion exchange membrane as the diaphragm 12 of the positive electrode electrolyte 22 and the negative electrode electrolyte 32.
  • the anion exchange membrane is obtained by graft polymerization of a monomer having an anion exchangeable substituent on a non-porous substrate made of an ethylene-vinyl alcohol copolymer.
  • This anion exchange membrane is suitable as a diaphragm for a redox flow battery in which the pH of the positive electrode electrolyte 22 and the negative electrode electrolyte 32 is in the range of 2 to 8.
  • non-porous substrate made of an ethylene-vinyl alcohol copolymer for example, an ethylene-vinyl alcohol copolymer film having a specific gravity of 1.17 or more and 1.23 or less can be used.
  • the non-porous substrate made of an ethylene-vinyl alcohol copolymer for example, a uniaxial or biaxially stretched ethylene-vinyl alcohol copolymer film can be used.
  • the graft ratio of the anion exchange membrane is preferably 15% or more and 47% or less. When the graft ratio of the anion exchange membrane is 15% or more, anions are easily transmitted. When the graft ratio of the anion exchange membrane is 47% or less, permeation of the redox material is easily suppressed. Therefore, suitable battery performance is easily exhibited.
  • the thickness of the non-porous substrate made of an ethylene-vinyl alcohol copolymer is preferably 15 ⁇ m or more and 50 ⁇ m or less. In this case, for example, the mechanical strength of the diaphragm 12 can be easily obtained, and the anion permeability can be easily secured.
  • the anion exchange membrane of the present embodiment suitably suppresses permeation of iron ions in a positive electrode electrolyte containing an iron redox material and citric acid or lactic acid. For this reason, the redox flow battery of this embodiment can improve battery life, for example, in a redox flow battery containing a redox-based substance of iron as a positive electrode electrolyte and citric acid or lactic acid. This is advantageous.
  • the embodiment may be modified as follows.
  • the anion exchange membrane may include a support having higher permeability of ions serving as ion-conducting carriers than the anion exchange membrane. That is, the diaphragm 12 may be a laminate having an anion exchange membrane and a support that supports the membrane.
  • the shape, arrangement, or number of the charge / discharge cells 11 included in the redox flow battery and the capacities of the first tank 23 and the second tank 33 may be changed according to performance required for the redox flow battery. Further, the supply amount of the positive electrode electrolyte 22 and the negative electrode electrolyte 32 to the charge / discharge cell 11 can also be set according to, for example, the capacity of the charge / discharge cell 11. For example, the case 41 may be omitted in the case of an electrolyte having a small influence of oxygen concentration.
  • an anion exchange membrane obtained by graft-polymerizing vinylbenzyltrimethylammonium chloride on a biaxially stretched ethylene-vinyl alcohol copolymer film was obtained.
  • the obtained anion exchange membrane was taken out of the bag, washed with water, and dried.
  • the graft ratio of the anion exchange membranes was in the range of 26 to 28%.
  • permeability of the ion in electrolyte solution was measured as follows. First, the opening of the glass container containing the electrolytic solution was sealed with an anion exchange membrane. As the electrolytic solution, 0.2 mol / L iron (II) -citric acid complex aqueous solution was used.
  • a beaker containing 100 mL of distilled water was prepared, and the anion exchange membrane attached to the glass container was immersed in distilled water, and the distilled water was stirred for 48 hours using a stirrer.
  • the iron ion concentration in distilled water was measured. This iron ion concentration was converted into a concentration per 1 cm 2 of an anion exchange membrane area, 1 mol of an electrolyte solution, and 1 hour, and the converted value was defined as a transmittance.
  • the lower limit of measurable iron ion concentration is 0.2 mg / L, and this value is 1.87 ⁇ 10 ⁇ 8 when converted to transmittance.
  • the transmittance of the anion exchange membrane obtained in Production Example 1 was 3.01 ⁇ 10 ⁇ 7 .
  • the transmittance was also obtained in the same manner for a commercially available ion exchange membrane that did not use an ethylene-vinyl alcohol copolymer substrate.
  • a commercially available ion exchange membrane a commercially available product (trade name: Neocepta AHA, manufactured by Astom Corp.) was used.
  • the transmittance of the commercial product was 5.13 ⁇ 10 ⁇ 7 .
  • Example 1 ⁇ Redox flow battery> The redox flow battery shown in FIG. 1 was used. As a positive electrode and a negative electrode, the electrode area was set to 10 cm 2 using carbon felt (trade name: GFA5, manufactured by SGL). As the current collector plate, pure titanium having a thickness of 1.0 mm was used. As the diaphragm, the anion exchange membrane obtained in Production Example 1 was used.
  • a glass container with a capacity of 30 mL was used as the first tank and the second tank. Silicone tubes were used as the supply tubes, the recovery tubes, the gas tubes, and the exhaust tubes.
  • a micro tube pump MP-1000, manufactured by Tokyo Rika Kikai Co., Ltd.
  • PFX200 manufactured by Kikusui Electronics Co., Ltd.
  • the oxygen concentration in the ambient atmosphere of the charge / discharge cell was adjusted to 1% or less by supplying nitrogen from the second gas pipe into the case.
  • the supply of nitrogen gas from the second gas pipe was continued during the subsequent charge / discharge test.
  • the amount of dissolved oxygen was measured using a dissolved oxygen meter (“B-506” manufactured by Iijima Electronics Co., Ltd.).
  • the oxygen concentration was measured using an oxygen concentration meter (“XPO-318” manufactured by Shin Cosmos Electric Co., Ltd.).
  • ⁇ Charge / discharge test> In the charge / discharge test, first, charging was performed at a constant current for 60 minutes. Next, the battery was discharged at a constant current with a final discharge voltage of 0V. From the first cycle to the third cycle of charge / discharge, the constant current is set to 50 mA, from the fourth cycle to the sixth cycle of charge / discharge, the constant current is set to 100 mA, and from the seventh cycle to the ninth cycle of charge / discharge. The constant current was 200 mA.
  • Example 2 For the current efficiency, an average value in the first to third cycles, an average value in the fourth to sixth cycles, and an average value in the seventh to ninth cycles were calculated.
  • Example 2 a charge / discharge test was performed in the same manner as in Example 1 except that the diaphragm was changed.
  • Example 2 a biaxially stretched ethylene-vinyl alcohol copolymer film was used as an unstretched ethylene-vinyl alcohol copolymer film (trade name: Eval film EF-F50, thickness 50 ⁇ m, size 80 ⁇ 80 mm, specific gravity 1.19.
  • An anion exchange membrane was obtained in the same manner as in Example 1 except that the product was changed to Kuraray Co., Ltd.
  • the graft ratio of the anion exchange membranes was in the range of 26 to 29%.
  • the transmittance of the anion exchange membrane of Example 2 was measured in the same manner as the method described in the above (Comparison of transmittance of ions in electrolytic solution) column, and was 9.89 ⁇ 10 ⁇ 7 . Similar to Example 1, the results of calculating the current efficiency are shown in Table 1.
  • Example 3 In Example 3, a charge / discharge test was performed in the same manner as in Example 1 except that the diaphragm was changed. In Example 3, an anion exchange membrane was prepared in the same manner as in Example 1 except that the biaxially stretched ethylene-vinyl alcohol copolymer film was changed to a uniaxially stretched ethylene-vinyl alcohol copolymer film described below. Obtained.
  • the uniaxially stretched ethylene-vinyl alcohol copolymer film of Example 3 is an unstretched ethylene-vinyl alcohol copolymer film (trade name: Eval Film EF-F50, thickness 50 ⁇ m, specific gravity 1.19, manufactured by Kuraray Co., Ltd.).
  • Example 4 In Example 4, a charge / discharge test was performed in the same manner as in Example 1 except that the diaphragm was changed.
  • Example 4 was the same as Example 1 except that the concentration of vinylbenzyltrimethylammonium chloride in the aqueous solution to be reacted with the biaxially stretched ethylene-vinyl alcohol copolymer film was changed from 6% by mass to 8% by mass.
  • An anion exchange membrane was obtained.
  • the graft ratio of the anion exchange membranes was in the range of 44 to 47%.
  • the transmittance of the anion exchange membrane of Example 4 was measured in the same manner as the method described in the above (Comparison of transmittance of ions in electrolytic solution) column, and was 9.33 ⁇ 10 ⁇ 7 . Similar to Example 1, the results of calculating the current efficiency are shown in Table 1.
  • Comparative example In the comparative example, a charge / discharge test was performed and current efficiency was calculated in the same manner as in Example 1 except that a commercially available ion exchange membrane (trade name: Neocepta AHA, manufactured by Astom Co., Ltd.) was used as the diaphragm of the redox flow battery. did. The results are shown in Table 1.
  • the ion exchange membranes of Examples 1 to 4 have the same performance as the ion exchange membrane of the comparative example as a diaphragm of the redox flow battery.
  • Table 2 shows the transmittances of Examples 1 to 4 and Comparative Example.

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Abstract

The pHs of the positive electrode electrolyte solution and the negative electrode electrolyte solution used in this redox flow battery are within the range of from 2 to 8 (inclusive). An anion-exchange membrane is used as a separation membrane between the positive electrode electrolyte solution and the negative electrode electrolyte solution. The anion-exchange membrane is obtained by graft-polymerizing a monomer having an anion-exchangeable substituent to a non-porous base that is formed of an ethylene-vinyl alcohol copolymer.

Description

レドックスフロー電池Redox flow battery
　本発明は、レドックスフロー電池に関する。 The present invention relates to a redox flow battery.
　一般的にレドックスフロー電池では強酸性の電解液が用いられる。強酸性の電解液の例としては、バナジウムのレドックス系物質を含有する電解液が実用化されている。強酸性の電解液中における金属レドックスイオンは、比較的高濃度であっても安定して溶解されるため、電池のエネルギー密度を高くすることができる。また、強酸性の電解液では、イオン伝導のキャリアはＨ＋イオン又はＯＨ－イオンとなる。Ｈ＋イオンの移動度及びＯＨ－イオンの移動度はいずれも比較的高いため、強酸性の電解液は高い導電率を有する。これにより、電池の抵抗が小さくなる結果、電池の効率は高まる。ところが、レドックスフロー電池を構成する部品には、強酸性の電解液に耐え得る耐薬品性が求められる。レドックスフロー電池の部品としては、例えば、正極電解液と負極電解液の間の隔膜が挙げられる。特許文献１には、レドックスフロー電池用の隔膜として、親水性膜と多孔質膜との複合膜が開示されている。親水性膜は、セルロース系ポリマーやエチレン－ビニルアルコール共重合体から構成されている。多孔質膜は、テトラフルオロエチレンや塩化ビニルから構成されている。 In general, a redox flow battery uses a strongly acidic electrolyte. As an example of a strongly acidic electrolytic solution, an electrolytic solution containing a vanadium redox substance has been put into practical use. Since the metal redox ions in the strongly acidic electrolyte are stably dissolved even at a relatively high concentration, the energy density of the battery can be increased. In the case of a strongly acidic electrolyte, the ion-conducting carriers are H + ions or OH − ions. Since both the mobility of H + ions and the mobility of OH − ions are relatively high, the strongly acidic electrolyte has high conductivity. This increases the battery efficiency as a result of the reduced battery resistance. However, chemicals that can withstand a strongly acidic electrolyte are required for the components constituting the redox flow battery. As a component of a redox flow battery, for example, a diaphragm between a positive electrode electrolyte and a negative electrode electrolyte can be cited. Patent Document 1 discloses a composite membrane of a hydrophilic membrane and a porous membrane as a diaphragm for a redox flow battery. The hydrophilic film is composed of a cellulose polymer or an ethylene-vinyl alcohol copolymer. The porous film is made of tetrafluoroethylene or vinyl chloride.
　一方、特許文献２には、弱酸性の電解液が開示されている。弱酸性の電解液を用いる場合では、強酸性の電解液を用いる場合よりも、正極電解液と負極電解液の間の隔膜に求められる耐薬品性は緩和される。また、特許文献３には、電解液のｐＨが２以上、８以下の電力貯蔵電池に用いられる隔膜としての陽イオン交換膜が開示されている。この陽イオン交換膜は、エチレン－ビニルアルコール共重合体をマトリックスとする樹脂フィルム基材にスチレンスルホン酸塩をグラフト重合したものである。 On the other hand, Patent Document 2 discloses a weakly acidic electrolytic solution. In the case of using a weakly acidic electrolytic solution, the chemical resistance required for the diaphragm between the positive and negative electrolytic solutions is relaxed compared to the case of using a strongly acidic electrolytic solution. Patent Document 3 discloses a cation exchange membrane as a diaphragm used in a power storage battery having an electrolyte having a pH of 2 or more and 8 or less. This cation exchange membrane is obtained by graft-polymerizing styrene sulfonate on a resin film substrate having an ethylene-vinyl alcohol copolymer as a matrix.
　なお、特許文献４には、微多孔膜を備えるイオン透過性隔膜が開示されている。このイオン透過性隔膜は、アルカリ水の電解に要求される特性に優れるものであり、水系電解液を使用する電池にも有用とされている。また、特許文献５には、ポリオレフィンからなる多孔質基材の細孔内に、クロロメチルスチレンとジビニルベンゼンとの共重合体を充填し、その共重合体に第四級アンモニウム基を導入した陰イオン交換膜が開示されている。 Note that Patent Document 4 discloses an ion-permeable diaphragm having a microporous membrane. This ion-permeable diaphragm is excellent in characteristics required for electrolysis of alkaline water, and is also useful for a battery using an aqueous electrolyte. Patent Document 5 discloses a negative electrode in which a copolymer of chloromethylstyrene and divinylbenzene is filled in the pores of a porous substrate made of polyolefin, and a quaternary ammonium group is introduced into the copolymer. An ion exchange membrane is disclosed.
特開昭６２－２２３９８４号公報Japanese Patent Laid-Open No. 62-223984 特開昭５６－４２９７０号公報JP 56-42970 A 国際公開第２０１４／０３０２３０号International Publication No. 2014/030230 特開２０１４－１２８８９号公報JP 2014-12889 A 特開２００９－１４４０４１号公報JP 2009-144041 A
　レドックスフロー電池において、ｐＨが２以上、８以下の範囲内の電解液を用いた場合、電池の部品に求められる耐薬品性が緩和されるため、高価な材料の使用を回避することが可能となる。したがって、設備の低コスト化が実現可能となるため、レドックスフロー電池の更なる普及を促進するという観点で有利である。 In the redox flow battery, when an electrolyte solution having a pH in the range of 2 or more and 8 or less is used, the chemical resistance required for the battery parts is alleviated, so that the use of expensive materials can be avoided. Become. Therefore, it is possible to reduce the cost of the equipment, which is advantageous from the viewpoint of promoting further popularization of the redox flow battery.
　本発明は、ｐＨが２以上、８以下の範囲内の電解液を用いたレドックスフロー電池において、好適な隔膜を見出すことでなされたものである。上述した特許文献１～５は、ｐＨが２以上、８以下の範囲内の電解液を用いたレドックスフロー電池において、エチレン－ビニルアルコール共重合体製の非多孔質基材を用いた陰イオン交換膜を隔膜として用いる構成について示唆していない。 The present invention has been made by finding a suitable diaphragm in a redox flow battery using an electrolytic solution having a pH in the range of 2 or more and 8 or less. Patent Documents 1 to 5 described above describe anion exchange using a non-porous substrate made of an ethylene-vinyl alcohol copolymer in a redox flow battery using an electrolytic solution having a pH in the range of 2 to 8. There is no suggestion of a configuration using a membrane as a diaphragm.
　本発明の目的は、ｐＨが２以上、８以下の範囲内の電解液を用いる場合に好適な隔膜を有するレドックスフロー電池を提供することにある。 An object of the present invention is to provide a redox flow battery having a diaphragm suitable for use of an electrolytic solution having a pH in the range of 2 or more and 8 or less.
　上記の目的を達成するために、本発明の一態様では、ｐＨが２以上、８以下の範囲内の正極電解液及び負極電解液が用いられるレドックスフロー電池であって、エチレン－ビニルアルコール共重合体製の非多孔質基材に陰イオン交換性の置換基を有するモノマーをグラフト重合してなる陰イオン交換膜を、正極電解液と負極電解液の間の隔膜として有するレドックスフロー電池を提供する。 In order to achieve the above object, according to one embodiment of the present invention, there is provided a redox flow battery using a positive electrode electrolyte and a negative electrode electrolyte having a pH in the range of 2 or more and 8 or less, wherein the ethylene-vinyl alcohol copolymer is used. Provided is a redox flow battery having an anion exchange membrane formed by graft polymerization of a monomer having an anion exchangeable substituent on a non-porous substrate made of coalescence as a diaphragm between a positive electrode electrolyte and a negative electrode electrolyte. .
　前記レドックスフロー電池において、前記非多孔質基材は、比重が１．１７以上、１．２３以下のエチレン－ビニルアルコール共重合体フィルムであることが好ましい。
　前記レドックスフロー電池において、前記非多孔質基材は、一軸又は二軸延伸エチレン－ビニルアルコール共重合体フィルムであることが好ましい。 In the redox flow battery, the non-porous substrate is preferably an ethylene-vinyl alcohol copolymer film having a specific gravity of 1.17 or more and 1.23 or less.
In the redox flow battery, the non-porous substrate is preferably a uniaxial or biaxially stretched ethylene-vinyl alcohol copolymer film.
　前記レドックスフロー電池において、前記陰イオン交換膜のグラフト率は、１５％以上、４７％以下であることが好ましい。
　前記レドックスフロー電池において、前記非多孔質基材の厚みは、１５μｍ以上、５０μｍ以下であることが好ましい。 In the redox flow battery, it is preferable that a graft ratio of the anion exchange membrane is 15% or more and 47% or less.
In the redox flow battery, the thickness of the non-porous substrate is preferably 15 μm or more and 50 μm or less.
　前記レドックスフロー電池において、前記モノマーは、ビニルベンジルトリメチルアンモニウム塩を含むことが好ましい。
　前記レドックスフロー電池において、前記正極電解液は、鉄のレドックス系物質と、クエン酸又は乳酸とを含有することが好ましい。 In the redox flow battery, the monomer preferably includes a vinylbenzyltrimethylammonium salt.
In the redox flow battery, the positive electrode electrolyte preferably contains an iron redox material and citric acid or lactic acid.
本発明の実施形態のレドックスフロー電池を示す概略図である。It is the schematic which shows the redox flow battery of embodiment of this invention.
　以下、本発明の実施形態に係るレドックスフロー電池について説明する。
　＜レドックスフロー電池の構造＞
　図１に示すように、レドックスフロー電池は、充放電セル１１と、正極電解液２２を貯蔵する第１タンク２３と、負極電解液３２を貯蔵する第２タンク３３とを備える。さらに、レドックスフロー電池は、正極電解液２２を充放電セル１１に供給する第１供給管２４と、負極電解液３２を充放電セル１１に供給する第２供給管３４とを備える。 Hereinafter, the redox flow battery according to the embodiment of the present invention will be described.
<Structure of redox flow battery>
As shown in FIG. 1, the redox flow battery includes a charge / discharge cell 11, a first tank 23 that stores a positive electrode electrolyte 22, and a second tank 33 that stores a negative electrode electrolyte 32. Further, the redox flow battery includes a first supply pipe 24 that supplies the positive electrode electrolyte 22 to the charge / discharge cell 11 and a second supply pipe 34 that supplies the negative electrode electrolyte 32 to the charge / discharge cell 11.
　充放電セル１１の内部は、隔膜１２によって正極側セル２１と負極側セル３１とに仕切られている。
　正極側セル２１には、正極２１ａと正極側集電板２１ｂとが互いに接触した状態で配置されている。負極側セル３１には、負極３１ａと負極側集電板３１ｂとが互いに接触した状態で配置されている。正極２１ａ及び負極３１ａは、例えばカーボン製のフェルトから構成される。正極側集電板２１ｂ及び負極側集電板３１ｂは、例えばガラス状カーボン板から構成される。正極側集電板２１ｂ及び負極側集電板３１ｂは、充放電装置１０に電気的に接続されている。レドックスフロー電池には、充放電セル１１周辺の温度を調節する温度調節装置が必要に応じて設けられる。 The inside of the charge / discharge cell 11 is partitioned into a positive electrode side cell 21 and a negative electrode side cell 31 by a diaphragm 12.
In the positive electrode side cell 21, a positive electrode 21a and a positive electrode side current collecting plate 21b are arranged in contact with each other. In the negative electrode side cell 31, a negative electrode 31 a and a negative electrode current collector 31 b are arranged in contact with each other. The positive electrode 21a and the negative electrode 31a are made of, for example, carbon felt. The positive electrode side current collector plate 21b and the negative electrode side current collector plate 31b are made of, for example, a glassy carbon plate. The positive electrode side current collector plate 21 b and the negative electrode side current collector plate 31 b are electrically connected to the charge / discharge device 10. The redox flow battery is provided with a temperature adjusting device for adjusting the temperature around the charge / discharge cell 11 as necessary.
　正極側セル２１には、第１供給管２４及び第１回収管２５を介して第１タンク２３が接続されている。第１供給管２４には、第１ポンプ２６が装備されている。第１ポンプ２６の作動により、第１タンク２３内の正極電解液２２は、第１供給管２４を通じて正極側セル２１に供給される。このとき、正極側セル２１内の正極電解液２２は、第１回収管２５を通じて第１タンク２３に回収される。このように正極電解液２２は、第１タンク２３と正極側セル２１との間を循環する。 A first tank 23 is connected to the positive electrode side cell 21 via a first supply pipe 24 and a first recovery pipe 25. The first supply pipe 24 is equipped with a first pump 26. By the operation of the first pump 26, the positive electrolyte solution 22 in the first tank 23 is supplied to the positive electrode side cell 21 through the first supply pipe 24. At this time, the positive electrode electrolyte 22 in the positive electrode side cell 21 is recovered to the first tank 23 through the first recovery pipe 25. Thus, the positive electrode electrolyte 22 circulates between the first tank 23 and the positive electrode side cell 21.
　負極側セル３１には、第２供給管３４及び第２回収管３５を介して第２タンク３３が接続されている。第２供給管３４には、第２ポンプ３６が装備されている。第２ポンプ３６の作動により、第２タンク３３内の負極電解液３２は、第２供給管３４を通じて負極側セル３１に供給される。このとき、負極側セル３１内の負極電解液３２は、第２回収管３５を通じて第２タンク３３に回収される。このように負極電解液３２は、第２タンク３３と負極側セル３１との間を循環する。 The second tank 33 is connected to the negative electrode side cell 31 via a second supply pipe 34 and a second recovery pipe 35. The second supply pipe 34 is equipped with a second pump 36. By the operation of the second pump 36, the negative electrolyte solution 32 in the second tank 33 is supplied to the negative electrode side cell 31 through the second supply pipe 34. At this time, the negative electrode electrolyte 32 in the negative electrode side cell 31 is recovered in the second tank 33 through the second recovery pipe 35. Thus, the negative electrode electrolyte 32 circulates between the second tank 33 and the negative electrode side cell 31.
　第１タンク２３及び第２タンク３３には、第１ガス管１３ａが接続されている。第１ガス管１３ａは、不活性ガス発生装置から供給される不活性ガスを、第１タンク２３内の正極電解液２２中及び第２タンク３３内の負極電解液３２中に供給する。これにより、正極電解液２２及び負極電解液３２と大気中の酸素との接触が抑制される。第１タンク２３内及び第２タンク３３内の気相中の酸素濃度は、不活性ガスの供給量を調整することで、略一定に保たれる。 The first gas pipe 13a is connected to the first tank 23 and the second tank 33. The first gas pipe 13 a supplies the inert gas supplied from the inert gas generator into the positive electrode electrolyte 22 in the first tank 23 and the negative electrode electrolyte 32 in the second tank 33. Thereby, the contact with the positive electrode electrolyte solution 22 and the negative electrode electrolyte solution 32, and oxygen in air | atmosphere is suppressed. The oxygen concentration in the gas phase in the first tank 23 and the second tank 33 is kept substantially constant by adjusting the supply amount of the inert gas.
　不活性ガスとしては、例えば窒素ガスが用いられる。なお、使用できる不活性ガスの例としては、窒素ガス以外に、例えば、二酸化炭素ガス、アルゴンガス、ヘリウムガスが挙げられる。第１タンク２３及び第２タンク３３に供給された不活性ガスは、排気管１４を通じて排気される。排気管１４の排出側の先端には、排気管１４の先端開口を水封する水封部１５が設けられている。水封部１５は、排気管１４内に大気が逆流することを防止するとともに、第１タンク２３内及び第２タンク３３内の圧力を一定に保つ。 For example, nitrogen gas is used as the inert gas. Examples of the inert gas that can be used include carbon dioxide gas, argon gas, and helium gas in addition to nitrogen gas. The inert gas supplied to the first tank 23 and the second tank 33 is exhausted through the exhaust pipe 14. A water seal portion 15 that seals the front end opening of the exhaust pipe 14 is provided at the distal end of the exhaust pipe 14 on the discharge side. The water seal 15 prevents the air from flowing back into the exhaust pipe 14 and keeps the pressure in the first tank 23 and the second tank 33 constant.
　本実施形態のレドックスフロー電池は、ケース４１を備えている。ケース４１は、充放電セル１１、第１タンク２３、及び第２タンク３３を取り囲む。ケース４１には、第２ガス管１３ｂが接続されている。第２ガス管１３ｂは、不活性ガス発生装置から供給される不活性ガスを充放電セル１１の周囲に供給する。これにより、充放電セル１１と大気中の酸素との接触が抑制される。ケース４１内の酸素濃度は、不活性ガスの供給量を調整することで、略一定に保たれる。 The redox flow battery according to this embodiment includes a case 41. The case 41 surrounds the charge / discharge cell 11, the first tank 23, and the second tank 33. The case 41 is connected to the second gas pipe 13b. The second gas pipe 13 b supplies the inert gas supplied from the inert gas generator to the periphery of the charge / discharge cell 11. Thereby, the contact with the charging / discharging cell 11 and oxygen in air | atmosphere is suppressed. The oxygen concentration in the case 41 is kept substantially constant by adjusting the supply amount of the inert gas.
　充電時には、正極２１ａに接触する正極電解液２２中で酸化反応が行われるとともに、負極３１ａに接触する負極電解液３２中で還元反応が行われる。すなわち、正極２１ａは電子を放出するとともに、負極３１ａは電子を受け取る。このとき、正極側集電板２１ｂは、正極２１ａから放出された電子を充放電装置１０に供給する。負極側集電板３１ｂは、充放電装置１０から受け取った電子を負極３１ａに供給する。 At the time of charging, an oxidation reaction is performed in the positive electrode electrolyte solution 22 in contact with the positive electrode 21a, and a reduction reaction is performed in the negative electrode electrolyte solution 32 in contact with the negative electrode 31a. That is, the positive electrode 21a emits electrons and the negative electrode 31a receives electrons. At this time, the positive collector plate 21b supplies the electrons discharged from the positive electrode 21a to the charging / discharging device 10. The negative electrode current collector 31b supplies the electrons received from the charge / discharge device 10 to the negative electrode 31a.
　放電時には、正極２１ａに接触する正極電解液２２中で還元反応が行われるとともに、負極３１ａに接触する負極電解液３２中で酸化反応が行われる。すなわち、正極２１ａは電子を受け取るとともに、負極３１ａは電子を放出する。このとき、正極側集電板２１ｂは、充放電装置１０から受け取った電子を正極２１ａに供給する。 At the time of discharging, a reduction reaction is performed in the positive electrode electrolyte 22 in contact with the positive electrode 21a, and an oxidation reaction is performed in the negative electrode electrolyte 32 in contact with the negative electrode 31a. That is, the positive electrode 21a receives electrons and the negative electrode 31a emits electrons. At this time, the positive collector plate 21b supplies the electrons received from the charge / discharge device 10 to the positive electrode 21a.
　＜隔膜１２（陰イオン交換膜）の構成＞
　隔膜１２は、正極側セル２１と負極側セル３１との間において活物質の透過を抑制する。隔膜１２は陰イオン交換膜から構成されている。隔膜１２は、充電時には、負極側セル３１中の陰イオンを正極側セル２１へ透過させるとともに、放電時には、正極側セル２１中の陰イオンを負極側セル３１へ透過させる。 <Configuration of diaphragm 12 (anion exchange membrane)>
The diaphragm 12 suppresses permeation of the active material between the positive electrode side cell 21 and the negative electrode side cell 31. The diaphragm 12 is composed of an anion exchange membrane. The diaphragm 12 transmits the anions in the negative electrode side cell 31 to the positive electrode side cell 21 during charging, and transmits the anions in the positive electrode side cell 21 to the negative electrode side cell 31 during discharge.
　陰イオン交換膜は、エチレン－ビニルアルコール共重合体製の非多孔質基材に陰イオン交換性の置換基を有するモノマー（以下、単にモノマーという場合がある。）をグラフト重合したものである。すなわち、陰イオン交換膜を構成するポリマーの主鎖は、エチレン－ビニルアルコール共重合体から構成され、そのポリマーのグラフト鎖は陰イオン交換性の置換基を有するモノマーの重合体から構成される。 The anion exchange membrane is obtained by graft polymerization of a monomer having an anion exchangeable substituent (hereinafter sometimes simply referred to as a monomer) on a non-porous substrate made of an ethylene-vinyl alcohol copolymer. That is, the main chain of the polymer constituting the anion exchange membrane is composed of an ethylene-vinyl alcohol copolymer, and the graft chain of the polymer is composed of a polymer of a monomer having an anion exchangeable substituent.
　エチレン－ビニルアルコール共重合体製の非多孔質基材としては、市販のフィルム又はシートから選択して用いることができる。エチレン－ビニルアルコール共重合体製の非多孔質基材の厚みは、１５μｍ以上、５０μｍ以下であることが好ましい。エチレン－ビニルアルコール共重合体製の非多孔質基材は、比重が１．１７以上、１．２３以下のエチレン－ビニルアルコール共重合体フィルムであることが好ましい。この比重は、ＪＩＳ　Ｚ８８０７：２０１２に準拠して測定される。具体的には、比重瓶を用いて比重を測定することができる。エチレン－ビニルアルコール共重合体のエチレン含量は、隔膜１２としての強度が容易に確保されるという観点から、例えば２０ｍｏｌ％以上であることが好ましい。エチレン－ビニルアルコール共重合体のエチレン含量は、親水性の観点から、５０ｍｏｌ％以下であることが好ましい。なお、非多孔質基材には、例えば、可塑剤等の添加剤が含有されていてもよい。 The non-porous substrate made of ethylene-vinyl alcohol copolymer can be selected from commercially available films or sheets. The thickness of the non-porous substrate made of an ethylene-vinyl alcohol copolymer is preferably 15 μm or more and 50 μm or less. The non-porous substrate made of an ethylene-vinyl alcohol copolymer is preferably an ethylene-vinyl alcohol copolymer film having a specific gravity of 1.17 or more and 1.23 or less. This specific gravity is measured in accordance with JIS Z8807: 2012. Specifically, the specific gravity can be measured using a specific gravity bottle. The ethylene content of the ethylene-vinyl alcohol copolymer is preferably 20 mol% or more, for example, from the viewpoint that the strength as the diaphragm 12 is easily secured. The ethylene content of the ethylene-vinyl alcohol copolymer is preferably 50 mol% or less from the viewpoint of hydrophilicity. The non-porous substrate may contain an additive such as a plasticizer, for example.
　エチレン－ビニルアルコール共重合体製の非多孔質基材としては、無延伸又は延伸フィルムが好適に用いられる。エチレン－ビニルアルコール共重合体製の非多孔質基材は、一軸又は二軸延伸エチレン－ビニルアルコール共重合体フィルムであることが好ましい。 As the non-porous substrate made of an ethylene-vinyl alcohol copolymer, an unstretched or stretched film is preferably used. The non-porous substrate made of an ethylene-vinyl alcohol copolymer is preferably a uniaxial or biaxially stretched ethylene-vinyl alcohol copolymer film.
　モノマーの有する陰イオン交換性の置換基としては、例えば、１～３級アミノ基、４級アンモニウム基、ピリジル基、イミダゾール基、４級ピリジニウム基、及び４級イミダゾリウム基が挙げられる。モノマーの有する置換基の対イオンとしては、例えば、ハロゲン化物イオン、無機オキソ酸アニオン、有機酸アニオン、有機スルホン酸アニオン、水酸化物イオン、炭酸水素イオン、炭酸イオン等が挙げられる。 Examples of the anion-exchangeable substituent of the monomer include a primary to tertiary amino group, a quaternary ammonium group, a pyridyl group, an imidazole group, a quaternary pyridinium group, and a quaternary imidazolium group. Examples of the counter ion of the substituent that the monomer has include a halide ion, an inorganic oxoacid anion, an organic acid anion, an organic sulfonate anion, a hydroxide ion, a bicarbonate ion, and a carbonate ion.
　モノマーの有する陰イオン交換性の置換基は、アリール基を含んでいてもよい。アリール基を含む置換基を有するモノマーは、例えば、ビニルベンジルトリアルキルアンモニウム塩が用いられる。ビニルベンジルトリアルキルアンモニウム塩としては、例えば、ビニルベンジルトリメチルアンモニウム塩、ビニルベンジルトリエチルアンモニウム塩、及びビニルベンジルトリエタノールアンモニウム塩が挙げられる。モノマーは、ビニルベンジルトリメチルアンモニウム塩を含むことが好ましい。 The anion exchangeable substituent of the monomer may include an aryl group. As the monomer having a substituent containing an aryl group, for example, a vinylbenzyl trialkylammonium salt is used. Examples of the vinyl benzyl trialkyl ammonium salt include vinyl benzyl trimethyl ammonium salt, vinyl benzyl triethyl ammonium salt, and vinyl benzyl triethanol ammonium salt. The monomer preferably includes a vinyl benzyl trimethyl ammonium salt.
　陰イオン交換膜のグラフト率は、１５％以上、４７％以下であることが好ましい。陰イオン交換膜のグラフト率は、非多孔質基材の質量をＷ０、陰イオン交換膜の質量をＷ１とした場合、下記式（Ａ）により算出される。 The graft ratio of the anion exchange membrane is preferably 15% or more and 47% or less. The graft ratio of the anion exchange membrane is calculated by the following formula (A) when the mass of the non-porous substrate is W0 and the mass of the anion exchange membrane is W1.
　グラフト率（％）＝１００×（Ｗ１－Ｗ０）／Ｗ０　・・・（Ａ）
　隔膜１２（陰イオン交換膜）は、重合工程を通じて製造される。重合工程では、非多孔質基材に生成させたラジカル活性点に、モノマーを用いてグラフト鎖を導入する。ラジカル活性点は、例えば、ラジカル重合開始剤、電離放射線の照射、紫外線の照射、超音波の照射、プラズマの照射等により生成することができる。ラジカル活性点を生成する方法の中でも、電離放射線の照射を用いた重合工程は、製造プロセスが簡単、安全、かつ環境へ負荷も小さいという利点を有する。 Graft ratio (%) = 100 × (W1-W0) / W0 (A)
The diaphragm 12 (anion exchange membrane) is manufactured through a polymerization process. In the polymerization step, a graft chain is introduced using a monomer into a radical active site generated on the non-porous substrate. The radical active site can be generated by, for example, radical polymerization initiator, ionizing radiation irradiation, ultraviolet irradiation, ultrasonic irradiation, plasma irradiation, or the like. Among the methods for generating radical active sites, the polymerization step using ionizing radiation has the advantage that the production process is simple, safe and has a low environmental impact.
　電離放射線としては、例えばα線、β線、γ線、電子線、Ｘ線等が挙げられる。電離放射線の中でも、工業的に利用し易いという観点から、例えばコバルト６０から放射されるγ線、電子線加速器から放射される電子線、Ｘ線等が好適である。 Examples of ionizing radiation include α rays, β rays, γ rays, electron rays, X rays and the like. Among the ionizing radiations, for example, γ rays emitted from cobalt 60, electron beams emitted from an electron beam accelerator, X-rays, and the like are preferable from the viewpoint of easy industrial use.
　電離放射線の照射は、ラジカル活性点と酸素との反応を抑制するという観点から、窒素ガス、ネオンガス、アルゴンガス等の不活性ガス雰囲気下で行うことが好ましい。電離放射線の吸収線量は、例えば１～３００ｋＧｙの範囲とされる。電離放射線の吸収線量を調整することで、グラフト率を変更することができる。 Irradiation with ionizing radiation is preferably performed in an inert gas atmosphere such as nitrogen gas, neon gas, or argon gas from the viewpoint of suppressing the reaction between radical active sites and oxygen. The absorbed dose of ionizing radiation is, for example, in the range of 1 to 300 kGy. The graft ratio can be changed by adjusting the absorbed dose of ionizing radiation.
　重合工程では、ラジカル活性点の生成した非多孔質基材に、モノマーを含む溶液を接触させる。この接触では、モノマーを含む溶液中に浸漬した非多孔質基材を振とうしたり、加熱したりすることで、ラジカル重合反応を促進することが可能である。 In the polymerization step, a solution containing the monomer is brought into contact with the non-porous substrate in which radical active sites are generated. In this contact, the radical polymerization reaction can be promoted by shaking or heating the non-porous substrate immersed in the solution containing the monomer.
　モノマーを含む溶液の溶媒としては、例えば、水、メタノール、エタノール等のアルコール、アセトン等の親水性ケトン等の親水性溶媒を使用することができる。複数種の親水性溶媒を混合した混合溶媒を用いてもよい。使用する溶媒は、製造プロセスのコスト低減、環境負荷の低減、及びプロセスの安全性の向上の観点から、水を主成分とすることが好ましく、より好ましくは水である。水としては、例えば、イオン交換水、純水、超純水等を用いることができる。 As the solvent of the solution containing the monomer, for example, water, alcohols such as methanol and ethanol, and hydrophilic solvents such as hydrophilic ketones such as acetone can be used. A mixed solvent obtained by mixing plural kinds of hydrophilic solvents may be used. The solvent to be used preferably contains water as the main component, more preferably water, from the viewpoints of cost reduction of the production process, reduction of environmental burden, and improvement of process safety. As water, for example, ion exchange water, pure water, ultrapure water, or the like can be used.
　モノマーを含む溶液におけるモノマーの濃度調整により、グラフト率を変更することが可能である。モノマーを含む溶液中におけるモノマーの濃度は、例えば３質量％以上、３５質量％以下の範囲であり、より好ましくは５質量％以上、３０質量％以下である。モノマーの濃度が５質量％以上の場合、グラフト率を高めることが容易となる。モノマーの濃度が３５質量％以下の場合、モノマーの単独重合体の生成が抑制される。 It is possible to change the graft ratio by adjusting the monomer concentration in the solution containing the monomer. The concentration of the monomer in the solution containing the monomer is, for example, in the range of 3% by mass to 35% by mass, and more preferably 5% by mass to 30% by mass. When the monomer concentration is 5% by mass or more, it is easy to increase the graft ratio. When the monomer concentration is 35% by mass or less, the formation of a monomer homopolymer is suppressed.
　ラジカル活性点の生成した非多孔質基材に、モノマーを含む溶液を接触させる時間は、例えば３０分以上、４８時間以下の範囲とされる。
　ラジカル活性点の生成した非多孔質基材とモノマーを含む溶液との接触についても、電離放射線の照射と同様に、窒素ガス、ネオンガス、アルゴンガス等の不活性ガス雰囲気下で行うことが好ましい。 The time for which the solution containing the monomer is brought into contact with the non-porous substrate in which the radical active site is generated is, for example, in the range of 30 minutes to 48 hours.
The contact between the non-porous base material in which the radical active site is generated and the solution containing the monomer is also preferably performed in an inert gas atmosphere such as nitrogen gas, neon gas, argon gas, etc., as in the case of irradiation with ionizing radiation.
　重合工程後、陰イオン交換膜は、洗浄工程において水で洗浄される。洗浄工程では、必要に応じて酸を用いてもよい。
　＜電解液＞
　正極電解液２２のｐＨ及び負極電解液３２のｐＨは、２以上、８以下の範囲内である。 After the polymerization step, the anion exchange membrane is washed with water in the washing step. In the washing step, an acid may be used as necessary.
<Electrolyte>
The pH of the positive electrode electrolyte 22 and the pH of the negative electrode electrolyte 32 are in the range of 2 or more and 8 or less.
　正極電解液２２及び負極電解液３２として、上記ｐＨの範囲内で酸化還元反応を行うことのできる活物質を含む水溶液が用いられる。正極電解液２２のｐＨ及び負極電解液３２のｐＨが２以上であることで、耐食性が確保され易くなる。正極電解液２２のｐＨ及び負極電解液３２のｐＨが８以下であることで、例えば、活物質の溶解性が確保され易くなる。 As the positive electrode electrolyte 22 and the negative electrode electrolyte 32, an aqueous solution containing an active material capable of performing a redox reaction within the above pH range is used. When the pH of the positive electrode electrolyte 22 and the pH of the negative electrode electrolyte 32 are 2 or more, corrosion resistance is easily ensured. When the pH of the positive electrode electrolyte 22 and the pH of the negative electrode electrolyte 32 are 8 or less, for example, the solubility of the active material is easily ensured.
　活物質としては、例えば、鉄のレドックス系物質、チタンのレドックス系物質、クロムのレドックス系物質、マンガンのレドックス系物質、及び銅のレドックス系物質が挙げられる。本出願で記載する「レドックス系物質」とは、金属の酸化還元反応で生成する金属イオン、金属錯イオン又は金属のことを言う。 Examples of active materials include iron redox materials, titanium redox materials, chromium redox materials, manganese redox materials, and copper redox materials. The “redox substance” described in the present application refers to a metal ion, a metal complex ion, or a metal generated by a metal redox reaction.
　活物質は、上記ｐＨの範囲内における析出を抑制するために、金属錯体として電解液中に含有されることが好適である。金属錯体を形成するためのキレート剤としては、活物質と錯体を形成し得るものであって、例えば、アミン、クエン酸、乳酸、アミノカルボン系キレート剤、及びポリエチレンイミンが挙げられる。 The active material is preferably contained in the electrolytic solution as a metal complex in order to suppress precipitation within the above pH range. The chelating agent for forming the metal complex is capable of forming a complex with the active material, and examples thereof include amines, citric acid, lactic acid, aminocarboxylic chelating agents, and polyethyleneimine.
　以下、正極電解液２２及び負極電解液３２の一例の詳細について説明する。
　正極電解液２２は、鉄のレドックス系物質と、酸とを含有する。酸は、クエン酸又は乳酸である。 Hereinafter, details of an example of the positive electrode electrolyte 22 and the negative electrode electrolyte 32 will be described.
The cathode electrolyte 22 contains an iron redox material and an acid. The acid is citric acid or lactic acid.
　正極電解液２２中では、鉄が活物質として機能し、例えば、充電時には、鉄（II）から鉄（III）への酸化が起こり、放電時には、鉄（III）から鉄（II）への還元が起こると推測される。正極電解液２２は、上記の酸を含有することにより、実用的な起電力が得られ易くなっている。 In the positive electrode electrolyte 22, iron functions as an active material. For example, oxidation from iron (II) to iron (III) occurs during charging, and reduction from iron (III) to iron (II) occurs during discharging. Is presumed to occur. The positive electrode electrolyte 22 contains the acid described above, so that a practical electromotive force can be easily obtained.
　正極電解液２２中における鉄のレドックス系物質（鉄イオン）の濃度は、エネルギー密度を高めるという観点から、好ましくは０．２モル／Ｌ以上であり、より好ましくは０．３モル／Ｌ以上であり、さらに好ましくは０．４モル／Ｌ以上である。正極電解液２２中における鉄のレドックス系物質（鉄イオン）の濃度は、好ましくは１．０モル／Ｌ以下である。 The concentration of the iron redox substance (iron ions) in the positive electrode electrolyte 22 is preferably 0.2 mol / L or more, more preferably 0.3 mol / L or more, from the viewpoint of increasing the energy density. More preferably 0.4 mol / L or more. The concentration of the iron redox substance (iron ions) in the positive electrode electrolyte 22 is preferably 1.0 mol / L or less.
　正極電解液２２中の鉄のレドックス系物質に対する上記酸のモル比は、１以上、４以下の範囲内であることが好ましい。前記モル比が１以上の場合、正極電解液２２の電気抵抗がより低くなるため、クーロン効率及び正極電解液２２の利用率を高めることが容易となる。前記モル比が４以下の場合、経済性と実用性の両立が容易となる。 The molar ratio of the acid to the iron redox substance in the positive electrode electrolyte 22 is preferably in the range of 1 or more and 4 or less. When the molar ratio is 1 or more, the electrical resistance of the positive electrode electrolyte 22 becomes lower, so that the Coulomb efficiency and the utilization rate of the positive electrode electrolyte 22 can be easily increased. When the molar ratio is 4 or less, both economic efficiency and practicality can be easily achieved.
　正極電解液２２のｐＨは、例えば、鉄のレドックス系物質及び上記酸の溶解性を確保し易いことから、１以上、７以下の範囲内であることが好ましく、より好ましくは２以上、５以下の範囲内である。なお、ｐＨは、例えば２０℃で測定される値である。 The pH of the positive electrode electrolyte 22 is preferably in the range of 1 or more and 7 or less, more preferably 2 or more and 5 or less, for example, since it is easy to ensure the solubility of the iron redox material and the acid. Is within the range. The pH is a value measured at 20 ° C., for example.
　正極電解液２２には、必要に応じて、例えば、無機酸の塩、又は各種キレート剤を含有させることもできる。
　負極電解液３２は、チタンのレドックス系物質と酸とを含有する電解液である。酸は、クエン酸又は乳酸である。 The positive electrode electrolyte 22 may contain, for example, an inorganic acid salt or various chelating agents as necessary.
The negative electrode electrolyte 32 is an electrolyte containing a redox material of titanium and an acid. The acid is citric acid or lactic acid.
　負極電解液３２中では、チタンが活物質として機能し、例えば、充電時には、チタン（IV）からチタン（III）への還元が起こり、放電時には、チタン（III）からチタン（IV）への酸化が起こると推測される。負極電解液３２は、上記の酸を含有することにより、錯体化し、約０．２Ｖ電位が下がるため、実用的な起電力が得られ易くなっている。 In the negative electrode electrolyte 32, titanium functions as an active material. For example, reduction from titanium (IV) to titanium (III) occurs during charging, and oxidation from titanium (III) to titanium (IV) occurs during discharging. Is presumed to occur. The negative electrode electrolyte solution 32 is complexed by containing the above acid, and the potential of about 0.2 V is lowered, so that a practical electromotive force is easily obtained.
　負極電解液３２中におけるチタンのレドックス系物質（チタンイオン）の濃度は、エネルギー密度を高めるという観点から、好ましくは０．２モル／Ｌ以上であり、より好ましくは０．３モル／Ｌ以上であり、さらに好ましくは０．４モル／Ｌ以上である。負極電解液３２中におけるチタンのレドックス系物質（チタンイオン）の濃度は、好ましくは１．０モル／Ｌ以下である。 The concentration of the titanium redox material (titanium ions) in the negative electrode electrolyte 32 is preferably 0.2 mol / L or more, more preferably 0.3 mol / L or more, from the viewpoint of increasing the energy density. More preferably 0.4 mol / L or more. The concentration of the titanium redox substance (titanium ions) in the negative electrode electrolyte solution 32 is preferably 1.0 mol / L or less.
　負極電解液３２中のチタンのレドックス系物質に対する上記酸のモル比は、１以上、４以下の範囲内であることが好ましい。前記モル比が１以上の場合、負極電解液３２の電気抵抗がより低くなるため、クーロン効率及び負極電解液３２の利用率を高めることが容易となる。前記モル比が４以下の場合、経済性と実用性の両立が容易となる。 The molar ratio of the acid to the redox substance of titanium in the negative electrode electrolyte solution 32 is preferably in the range of 1 or more and 4 or less. When the molar ratio is 1 or more, the electric resistance of the negative electrode electrolyte 32 becomes lower, so that the Coulomb efficiency and the utilization factor of the negative electrode electrolyte 32 are easily increased. When the molar ratio is 4 or less, both economic efficiency and practicality can be easily achieved.
　負極電解液３２のｐＨは、例えば、チタンのレドックス系物質及び上記酸の溶解性を確保し易いことから、１以上、７以下の範囲内であることが好ましい。負極電解液３２のｐＨは、２以上、５以下の範囲内であることがより好ましい。 The pH of the negative electrode electrolyte solution 32 is preferably in the range of 1 or more and 7 or less because, for example, it is easy to ensure the solubility of the redox material of titanium and the acid. The pH of the negative electrode electrolyte solution 32 is more preferably in the range of 2 or more and 5 or less.
　負極電解液３２には、必要に応じて、例えば、無機酸の塩、又は各種キレート剤を含有させることもできる。
　正極電解液２２及び負極電解液３２は、公知の方法で調製することができる。正極電解液２２及び負極電解液３２に用いる水は、蒸留水と同等又はそれ以上の純度を有していることが好ましい。 The negative electrode electrolyte 32 may contain, for example, an inorganic acid salt or various chelating agents as necessary.
The positive electrode electrolyte 22 and the negative electrode electrolyte 32 can be prepared by a known method. It is preferable that the water used for the positive electrode electrolyte 22 and the negative electrode electrolyte 32 has a purity equal to or higher than that of distilled water.
　以上のように構成されたレドックスフロー電池では、第２タンク３３内の負極電解液３２中の溶存酸素量が１．５ｍｇ／Ｌ以下に設定されることが好ましい。溶存酸素量は、１．０ｍｇ／Ｌ以下であることがより好ましい。さらに、ケース４１内の酸素濃度は１０体積％以下であることが好ましい。加えて、第２タンク３３内の気相中の酸素濃度は１体積％以下であることが好ましい。 In the redox flow battery configured as described above, the amount of dissolved oxygen in the negative electrode electrolyte solution 32 in the second tank 33 is preferably set to 1.5 mg / L or less. The dissolved oxygen amount is more preferably 1.0 mg / L or less. Furthermore, the oxygen concentration in the case 41 is preferably 10% by volume or less. In addition, the oxygen concentration in the gas phase in the second tank 33 is preferably 1% by volume or less.
　なお、第１タンク２３内の正極電解液２２中の溶存酸素量についても１．５ｍｇ／Ｌ以下に設定されてもよいし、１．０ｍｇ／Ｌ以下に設定されてもよい。また、第１タンク２３内の気相中の酸素濃度についても１体積％以下に設定されてもよい。 Note that the dissolved oxygen amount in the positive electrode electrolyte solution 22 in the first tank 23 may also be set to 1.5 mg / L or less, or may be set to 1.0 mg / L or less. The oxygen concentration in the gas phase in the first tank 23 may also be set to 1% by volume or less.
　＜レドックスフロー電池の作用＞
　ｐＨが２以上、８以下の範囲内の正極電解液２２及び負極電解液３２を用いたレドックスフロー電池は、上述した陰イオン交換膜を隔膜１２として有するため、レドックス系物質である金属イオンの透過が好適に抑制され、良好な電流効率が発揮される。 <Action of redox flow battery>
Since the redox flow battery using the positive electrode electrolyte solution 22 and the negative electrode electrolyte solution 32 having a pH in the range of 2 or more and 8 or less has the above-described anion exchange membrane as the diaphragm 12, the permeation of metal ions which are redox substances is performed. Is suitably suppressed, and good current efficiency is exhibited.
　電流効率は、所定のサイクル目の充電の電気量（Ａ）と所定のサイクル目の放電の電気量（Ｂ）とを下記式（１）に代入することで算出される。
　電流効率（％）＝Ｂ／Ａ×１００　・・・（１）
　なお、レドックスフロー電池の充放電１回を１サイクルという。 The current efficiency is calculated by substituting the amount of electricity (A) for charging in a predetermined cycle and the amount of electricity (B) for discharging in a predetermined cycle into the following equation (1).
Current efficiency (%) = B / A × 100 (1)
One charge / discharge of the redox flow battery is referred to as one cycle.
　電流効率は、例えば、１サイクル目から９サイクル目まで９０％以上に維持されることが好ましい。
　本実施形態の陰イオン交換膜は、非多孔質基材を用いるものであり、その非多孔質基材は、比較的安価なエチレン－ビニルアルコール共重合体製である。すなわち、本実施形態の陰イオン交換膜は、高価な樹脂材料を用いたり、多孔質基材のように特殊な加工を要したりすることを回避することが可能である。したがって、設備の低コスト化によって、レドックスフロー電池の更なる普及を促進するという観点で有利である。 The current efficiency is preferably maintained at 90% or more from the first cycle to the ninth cycle, for example.
The anion exchange membrane of the present embodiment uses a non-porous substrate, and the non-porous substrate is made of a relatively inexpensive ethylene-vinyl alcohol copolymer. That is, the anion exchange membrane of this embodiment can avoid using an expensive resin material or requiring special processing like a porous substrate. Therefore, it is advantageous from the viewpoint of promoting further spread of the redox flow battery by reducing the cost of the equipment.
　以上説明した本実施形態によれば、以下の効果を奏する。
　（１）本実施形態のレドックスフロー電池では、正極電解液２２及び負極電解液３２のｐＨが２以上、８以下の範囲内である。このレドックスフロー電池は、陰イオン交換膜を、正極電解液２２と負極電解液３２の隔膜１２として有する。陰イオン交換膜は、エチレン－ビニルアルコール共重合体製の非多孔質基材に陰イオン交換性の置換基を有するモノマーをグラフト重合したものである。この陰イオン交換膜は、正極電解液２２及び負極電解液３２のｐＨが２以上、８以下の範囲内のレドックスフロー電池の隔膜として好適である。 According to this embodiment described above, the following effects are obtained.
(1) In the redox flow battery of this embodiment, the positive electrode electrolyte solution 22 and the negative electrode electrolyte solution 32 have a pH in the range of 2 or more and 8 or less. This redox flow battery has an anion exchange membrane as the diaphragm 12 of the positive electrode electrolyte 22 and the negative electrode electrolyte 32. The anion exchange membrane is obtained by graft polymerization of a monomer having an anion exchangeable substituent on a non-porous substrate made of an ethylene-vinyl alcohol copolymer. This anion exchange membrane is suitable as a diaphragm for a redox flow battery in which the pH of the positive electrode electrolyte 22 and the negative electrode electrolyte 32 is in the range of 2 to 8.
　（２）エチレン－ビニルアルコール共重合体製の非多孔質基材としては、例えば、比重が１．１７以上、１．２３以下のエチレン－ビニルアルコール共重合体フィルムを用いることができる。 (2) As the non-porous substrate made of an ethylene-vinyl alcohol copolymer, for example, an ethylene-vinyl alcohol copolymer film having a specific gravity of 1.17 or more and 1.23 or less can be used.
　（３）エチレン－ビニルアルコール共重合体製の非多孔質基材としては、例えば、一軸又は二軸延伸エチレン－ビニルアルコール共重合体フィルムを用いることができる。
　（４）陰イオン交換膜のグラフト率は、１５％以上、４７％以下であることが好ましい。陰イオン交換膜のグラフト率が１５％以上の場合、陰イオンが透過し易くなる。陰イオン交換膜のグラフト率が４７％以下の場合、レドックス系物質の透過が抑制され易くなる。したがって、好適な電池性能が発揮され易くなる。 (3) As the non-porous substrate made of an ethylene-vinyl alcohol copolymer, for example, a uniaxial or biaxially stretched ethylene-vinyl alcohol copolymer film can be used.
(4) The graft ratio of the anion exchange membrane is preferably 15% or more and 47% or less. When the graft ratio of the anion exchange membrane is 15% or more, anions are easily transmitted. When the graft ratio of the anion exchange membrane is 47% or less, permeation of the redox material is easily suppressed. Therefore, suitable battery performance is easily exhibited.
　（５）エチレン－ビニルアルコール共重合体製の非多孔質基材の厚みは、１５μｍ以上、５０μｍ以下であることが好ましい。この場合、例えば、隔膜１２の機械的な強度が得られ易くなるとともに、陰イオンの透過性が確保され易くなる。 (5) The thickness of the non-porous substrate made of an ethylene-vinyl alcohol copolymer is preferably 15 μm or more and 50 μm or less. In this case, for example, the mechanical strength of the diaphragm 12 can be easily obtained, and the anion permeability can be easily secured.
　（６）本実施形態の陰イオン交換膜は、鉄のレドックス系物質と、クエン酸又は乳酸とを含有する正極電解液において、鉄イオンの透過を好適に抑制する。このため、本実施形態のレドックスフロー電池は、特に、正極電解液として鉄のレドックス系物質と、クエン酸又は乳酸とを含有するレドックスフロー電池において、例えば、電池寿命を向上することが可能である点で有利である。 (6) The anion exchange membrane of the present embodiment suitably suppresses permeation of iron ions in a positive electrode electrolyte containing an iron redox material and citric acid or lactic acid. For this reason, the redox flow battery of this embodiment can improve battery life, for example, in a redox flow battery containing a redox-based substance of iron as a positive electrode electrolyte and citric acid or lactic acid. This is advantageous.
　（変更例）
　前記実施形態は以下のように変更されてもよい。
　・前記陰イオン交換膜は、イオン伝導のキャリアとなるイオンの透過性が前記陰イオン交換膜よりも高い支持体を備えていてもよい。すなわち、隔膜１２は、陰イオン交換膜と、それを支持する支持体とを有する積層体であってもよい。 (Example of change)
The embodiment may be modified as follows.
The anion exchange membrane may include a support having higher permeability of ions serving as ion-conducting carriers than the anion exchange membrane. That is, the diaphragm 12 may be a laminate having an anion exchange membrane and a support that supports the membrane.
　・レドックスフロー電池の有する充放電セル１１の形状、配置、又は数や第１タンク２３及び第２タンク３３の容量はレドックスフロー電池に求められる性能等に応じて変更されてもよい。また、充放電セル１１に対する正極電解液２２及び負極電解液３２の供給量についても、例えば充放電セル１１の容量等に応じて設定することができる。また、例えば、酸素濃度の影響の小さい電解液の場合には、ケース４１を省略してもよい。 The shape, arrangement, or number of the charge / discharge cells 11 included in the redox flow battery and the capacities of the first tank 23 and the second tank 33 may be changed according to performance required for the redox flow battery. Further, the supply amount of the positive electrode electrolyte 22 and the negative electrode electrolyte 32 to the charge / discharge cell 11 can also be set according to, for example, the capacity of the charge / discharge cell 11. For example, the case 41 may be omitted in the case of an electrolyte having a small influence of oxygen concentration.
　次に、実施例及び比較例により本発明をさらに詳細に説明する。
　（製造例１）
　二軸延伸エチレン－ビニルアルコール共重合体フィルム（商品名：エバールフィルムＥＦ－ＸＬ１５、厚み１５μｍ、寸法８０×８０ｍｍ、比重１．１７、株式会社クラレ製）を袋に密封した後、その袋中を窒素置換した。これに電子線を加速電圧７５０ｋＶ、吸収線量５０ｋＧｙの条件で照射した後、袋中にビニルベンジルトリメチルアンモニウムクロリド（商品名：シグマ－アルドリッチ社製、４－ビニルベンジルトリメチルアンモニウムクロリド）の６質量％水溶液を２０ｍＬ注入した。次に、袋を５０℃の恒温槽中で２時間振とうした。これにより、二軸延伸エチレン－ビニルアルコール共重合体フィルムにビニルベンジルトリメチルアンモニウムクロリドをグラフト重合した陰イオン交換膜（隔膜）を得た。 Next, the present invention will be described in more detail with reference to examples and comparative examples.
(Production Example 1)
A biaxially stretched ethylene-vinyl alcohol copolymer film (trade name: Eval film EF-XL15, thickness 15 μm, dimensions 80 × 80 mm, specific gravity 1.17, manufactured by Kuraray Co., Ltd.) was sealed in a bag, Replaced with nitrogen. This was irradiated with an electron beam under conditions of an acceleration voltage of 750 kV and an absorbed dose of 50 kGy, and then a 6% by mass aqueous solution of vinylbenzyltrimethylammonium chloride (trade name: 4-vinylbenzyltrimethylammonium chloride, manufactured by Sigma-Aldrich) in a bag. 20 mL was injected. Next, the bag was shaken in a constant temperature bath at 50 ° C. for 2 hours. As a result, an anion exchange membrane (diaphragm) obtained by graft-polymerizing vinylbenzyltrimethylammonium chloride on a biaxially stretched ethylene-vinyl alcohol copolymer film was obtained.
　得られた陰イオン交換膜を袋から取り出し、水等で洗浄した後に乾燥させた。
　この手順で複数の陰イオン交換膜を作成した結果、陰イオン交換膜のグラフト率は、２６～２８％の範囲内であった。 The obtained anion exchange membrane was taken out of the bag, washed with water, and dried.
As a result of producing a plurality of anion exchange membranes by this procedure, the graft ratio of the anion exchange membranes was in the range of 26 to 28%.
　（電解液中のイオンの透過率の比較）
　上記製造例１で得られた陰イオン交換膜について、電解液中のイオンの透過率を次のように測定した。まず、電解液を入れたガラス製容器の開口を陰イオン交換膜で密封した。電解液としては、０．２モル／Ｌの鉄（II）－クエン酸錯体水溶液を用いた。 (Comparison of transmittance of ions in electrolyte)
About the anion exchange membrane obtained by the said manufacture example 1, the transmittance | permeability of the ion in electrolyte solution was measured as follows. First, the opening of the glass container containing the electrolytic solution was sealed with an anion exchange membrane. As the electrolytic solution, 0.2 mol / L iron (II) -citric acid complex aqueous solution was used.
　１００ｍＬの蒸留水を入れたビーカーを準備し、上記のガラス製容器に取り付けた陰イオン交換膜を蒸留水中に浸漬した状態で、スターラーを用いて蒸留水を４８時間撹拌した。次に、蒸留水中の鉄イオン濃度を測定した。この鉄イオン濃度を、陰イオン交換膜の面積１ｃｍ２当たり、かつ電解液の濃度１モル当たり、かつ１時間当たりの濃度に換算し、その換算値を透過率とした。なお、鉄イオン濃度の測定可能な下限値は、０．２ｍｇ／Ｌであり、この値を透過率に換算すると１．８７×１０－８である。 A beaker containing 100 mL of distilled water was prepared, and the anion exchange membrane attached to the glass container was immersed in distilled water, and the distilled water was stirred for 48 hours using a stirrer. Next, the iron ion concentration in distilled water was measured. This iron ion concentration was converted into a concentration per 1 cm 2 of an anion exchange membrane area, 1 mol of an electrolyte solution, and 1 hour, and the converted value was defined as a transmittance. The lower limit of measurable iron ion concentration is 0.2 mg / L, and this value is 1.87 × 10 −8 when converted to transmittance.
　製造例１で得られた陰イオン交換膜の透過率は、３．０１×１０－７であった。
　なお、エチレン－ビニルアルコール共重合体の基材を用いていない市販のイオン交換膜についても、同様に透過率を求めた。市販のイオン交換膜としては、市販品（商品名：ネオセプタＡＨＡ、アストム社製）を用いた。市販品の透過率は、５．１３×１０－７であった。 The transmittance of the anion exchange membrane obtained in Production Example 1 was 3.01 × 10 −7 .
The transmittance was also obtained in the same manner for a commercially available ion exchange membrane that did not use an ethylene-vinyl alcohol copolymer substrate. As a commercially available ion exchange membrane, a commercially available product (trade name: Neocepta AHA, manufactured by Astom Corp.) was used. The transmittance of the commercial product was 5.13 × 10 −7 .
　このように、製造例１で得られた陰イオン交換膜は、市販品のイオン交換膜と同様に鉄イオンの透過を抑制できることが分かる。
　（実施例１）
　＜レドックスフロー電池＞
　図１に示されるレドックスフロー電池を用いた。正極及び負極としては、カーボンフェルト（商品名：ＧＦＡ５、ＳＧＬ社製）を用いて電極面積を１０ｃｍ２に設定した。集電板としては、厚み１．０ｍｍの純チタンを用いた。隔膜としては、製造例１で得られた陰イオン交換膜を用いた。 Thus, it turns out that the anion exchange membrane obtained in Production Example 1 can suppress the permeation of iron ions in the same manner as a commercially available ion exchange membrane.
(Example 1)
<Redox flow battery>
The redox flow battery shown in FIG. 1 was used. As a positive electrode and a negative electrode, the electrode area was set to 10 cm 2 using carbon felt (trade name: GFA5, manufactured by SGL). As the current collector plate, pure titanium having a thickness of 1.0 mm was used. As the diaphragm, the anion exchange membrane obtained in Production Example 1 was used.
　第１タンク及び第２タンクとしては、容量３０ｍＬのガラス容器を用いた。各供給管、各回収管、各ガス管及び排気管としては、シリコーン製のチューブを用いた。各ポンプとしては、マイクロチューブポンプ（ＭＰ－１０００、東京理化器械株式会社製）を用いた。充放電装置としては、充放電バッテリテストシステム（ＰＦＸ２００、菊水電子工業株式会社製）を用いた。 A glass container with a capacity of 30 mL was used as the first tank and the second tank. Silicone tubes were used as the supply tubes, the recovery tubes, the gas tubes, and the exhaust tubes. As each pump, a micro tube pump (MP-1000, manufactured by Tokyo Rika Kikai Co., Ltd.) was used. As the charge / discharge device, a charge / discharge battery test system (PFX200, manufactured by Kikusui Electronics Co., Ltd.) was used.
　＜鉄（II）－クエン酸錯体水溶液の調製＞
　蒸留水５０ｍＬに０．０４モル（８．４ｇ）のクエン酸を溶解させた。この水溶液に、０．０１モル（０．４ｇ）のＮａＯＨを添加することで、ｐＨを２に調整した。この水溶液に、０．０２モル（４．０ｇ）のＦｅＣｌ・４Ｈ２Ｏを溶解させた。次に、この水溶液に、全量が１００ｍＬとなるように蒸留水を加えた。これにより、鉄（II）－クエン酸錯体の濃度が０．２モル／Ｌの水溶液を得た。 <Preparation of aqueous solution of iron (II) -citric acid complex>
0.04 mol (8.4 g) of citric acid was dissolved in 50 mL of distilled water. The pH was adjusted to 2 by adding 0.01 mol (0.4 g) of NaOH to this aqueous solution. In this aqueous solution, 0.02 mol (4.0 g) of FeCl.4H 2 O was dissolved. Next, distilled water was added to the aqueous solution so that the total amount became 100 mL. As a result, an aqueous solution having an iron (II) -citrate complex concentration of 0.2 mol / L was obtained.
　＜チタン（IV）－クエン酸錯体水溶液の調製＞
　蒸留水３０ｍＬに０．０４モル（８．４ｇ）のクエン酸を溶解させた。この水溶液に、２８質量％アンモニア水を３．６ｇ（０．０６モルのアンモニアに相当）添加した後、０．０６モル（２．４ｇ）のＮａＯＨを添加することで、ｐＨを５に調整した。この水溶液に、チタンの濃度が１６質量％のＴｉＣｌ４水溶液を６ｇ（０．０２モルのチタンに相当）添加した。次に、この水溶液に、全量が１００ｍＬとなるように蒸留水を加えて６０℃に加温しながら透明になるまで撹拌した。これにより、チタン（IV）－クエン酸錯体の濃度が０．２モル／Ｌの水溶液を得た。 <Preparation of aqueous solution of titanium (IV) -citric acid complex>
0.04 mol (8.4 g) of citric acid was dissolved in 30 mL of distilled water. After adding 3.6 g (equivalent to 0.06 mol of ammonia) of 28% by mass ammonia water to this aqueous solution, the pH was adjusted to 5 by adding 0.06 mol (2.4 g) of NaOH. . To this aqueous solution, 6 g (corresponding to 0.02 mol of titanium) of a TiCl 4 aqueous solution having a titanium concentration of 16 mass% was added. Next, distilled water was added to this aqueous solution so that the total amount became 100 mL, and it stirred until it became transparent, heating at 60 degreeC. As a result, an aqueous solution having a titanium (IV) -citrate complex concentration of 0.2 mol / L was obtained.
　＜酸素濃度の調整＞
　正極電解液として鉄（II）－クエン酸錯体水溶液を用いるとともに、負極電解液としてチタン（IV）－クエン酸錯体水溶液を用いた。第１ガス管から窒素ガスを供給することで、各電解液のバブリングを行い、各電解液中の溶存酸素量を０．８ｍｇ／Ｌ（飽和酸素濃度の約１０％）以下に調整した。なお、第１ガス管からの窒素ガスの供給は、以降の充放電試験中においても継続した。 <Adjustment of oxygen concentration>
An iron (II) -citrate complex aqueous solution was used as the positive electrode electrolyte, and a titanium (IV) -citrate complex aqueous solution was used as the negative electrode electrolyte. By supplying nitrogen gas from the first gas pipe, each electrolyte solution was bubbled, and the amount of dissolved oxygen in each electrolyte solution was adjusted to 0.8 mg / L (about 10% of the saturated oxygen concentration) or less. The supply of nitrogen gas from the first gas pipe was continued during the subsequent charge / discharge test.
　次に、第２ガス管からケース内に窒素を供給することで、充放電セルの周囲雰囲気の酸素濃度を１％以下に調整した。なお、第２ガス管からの窒素ガスの供給は、以降の充放電試験中においても継続した。 Next, the oxygen concentration in the ambient atmosphere of the charge / discharge cell was adjusted to 1% or less by supplying nitrogen from the second gas pipe into the case. The supply of nitrogen gas from the second gas pipe was continued during the subsequent charge / discharge test.
　溶存酸素量は、溶存酸素計（飯島電子工業株式会社製、“Ｂ－５０６”）を用いて測定した。酸素濃度は、酸素濃度計（新コスモス電機株式会社製、“ＸＰＯ－３１８”）を用いて測定した。 The amount of dissolved oxygen was measured using a dissolved oxygen meter (“B-506” manufactured by Iijima Electronics Co., Ltd.). The oxygen concentration was measured using an oxygen concentration meter (“XPO-318” manufactured by Shin Cosmos Electric Co., Ltd.).
　＜充放電試験＞
　充放電試験は、まず、充電を定電流で６０分間行った。次に、定電流で、放電終止電圧を０Ｖとして放電した。充放電の１サイクル目から３サイクル目までは、定電流を５０ｍＡとし、充放電の４サイクル目から６サイクル目までは、定電流を１００ｍＡとし、充放電の７サイクル目から９サイクル目までは、定電流を２００ｍＡとした。 <Charge / discharge test>
In the charge / discharge test, first, charging was performed at a constant current for 60 minutes. Next, the battery was discharged at a constant current with a final discharge voltage of 0V. From the first cycle to the third cycle of charge / discharge, the constant current is set to 50 mA, from the fourth cycle to the sixth cycle of charge / discharge, the constant current is set to 100 mA, and from the seventh cycle to the ninth cycle of charge / discharge. The constant current was 200 mA.
　充放電を行う際のレドックス反応は、以下のように推定される。
　正極：鉄（II）－クエン酸錯体　⇔　鉄（III）－クエン酸錯体＋ｅ－
　負極：チタン（IV）－クエン酸錯体＋ｅ－　⇔　チタン（III）－クエン酸錯体
　実施例１では、隔膜の性能に依存し易い評価項目である電流効率を算出した。その結果を表１に示す。 The redox reaction at the time of charging / discharging is estimated as follows.
Positive electrode: Iron (II) -citric acid complex 鉄 Iron (III) -citric acid complex + e −
Negative electrode: Titanium (IV) -citric acid complex + e −チ タ ン Titanium (III) -citric acid complex In Example 1, the current efficiency, which is an evaluation item that easily depends on the performance of the diaphragm, was calculated. The results are shown in Table 1.
　電流効率は、１～３サイクル目の平均値と、４～６サイクル目の平均値と、７～９サイクル目の平均値とを算出した。
　（実施例２）
　実施例２では、隔膜を変更した以外は実施例１と同様に充放電試験を行った。実施例２では、二軸延伸エチレン－ビニルアルコール共重合体フィルムを、無延伸エチレン－ビニルアルコール共重合体フィルム（商品名：エバールフィルムＥＦ－Ｆ５０、厚み５０μｍ、寸法８０×８０ｍｍ、比重１．１９、株式会社クラレ製）に変更した以外は、実施例１と同様にして陰イオン交換膜を得た。複数の陰イオン交換膜を作成した結果、陰イオン交換膜のグラフト率は、２６～２９％の範囲内であった。実施例２の陰イオン交換膜における透過率を上記（電解液中のイオンの透過率の比較）欄で述べた方法と同様に測定した結果、９．８９×１０－７であった。実施例１と同様に、電流効率を算出した結果を表１に示す。 For the current efficiency, an average value in the first to third cycles, an average value in the fourth to sixth cycles, and an average value in the seventh to ninth cycles were calculated.
(Example 2)
In Example 2, a charge / discharge test was performed in the same manner as in Example 1 except that the diaphragm was changed. In Example 2, a biaxially stretched ethylene-vinyl alcohol copolymer film was used as an unstretched ethylene-vinyl alcohol copolymer film (trade name: Eval film EF-F50, thickness 50 μm, size 80 × 80 mm, specific gravity 1.19. An anion exchange membrane was obtained in the same manner as in Example 1 except that the product was changed to Kuraray Co., Ltd. As a result of producing a plurality of anion exchange membranes, the graft ratio of the anion exchange membranes was in the range of 26 to 29%. The transmittance of the anion exchange membrane of Example 2 was measured in the same manner as the method described in the above (Comparison of transmittance of ions in electrolytic solution) column, and was 9.89 × 10 −7 . Similar to Example 1, the results of calculating the current efficiency are shown in Table 1.
　（実施例３）
　実施例３では、隔膜を変更した以外は実施例１と同様に充放電試験を行った。実施例３では、二軸延伸エチレン－ビニルアルコール共重合体フィルムを、以下に説明する一軸延伸エチレン－ビニルアルコール共重合体フィルムに変更した以外は、実施例１と同様にして陰イオン交換膜を得た。実施例３の一軸延伸エチレン－ビニルアルコール共重合体フィルムは、無延伸エチレン－ビニルアルコール共重合体フィルム（商品名：エバールフィルムＥＦ－Ｆ５０、厚み５０μｍ、比重１．１９、株式会社クラレ製）を１６０℃に加熱した状態で幅寸法を１．３倍に一軸延伸したフィルム（寸法８０×８０ｍｍ、比重１．２３）である。複数の陰イオン交換膜を作成した結果、陰イオン交換膜のグラフト率は、１５～１８％の範囲内であった。実施例３の陰イオン交換膜における透過率を上記（電解液中のイオンの透過率の比較）欄で述べた方法と同様に測定した結果、２．６４×１０－７であった。実施例１と同様に、電流効率を算出した結果を表１に示す。 (Example 3)
In Example 3, a charge / discharge test was performed in the same manner as in Example 1 except that the diaphragm was changed. In Example 3, an anion exchange membrane was prepared in the same manner as in Example 1 except that the biaxially stretched ethylene-vinyl alcohol copolymer film was changed to a uniaxially stretched ethylene-vinyl alcohol copolymer film described below. Obtained. The uniaxially stretched ethylene-vinyl alcohol copolymer film of Example 3 is an unstretched ethylene-vinyl alcohol copolymer film (trade name: Eval Film EF-F50, thickness 50 μm, specific gravity 1.19, manufactured by Kuraray Co., Ltd.). It is a film (size 80 × 80 mm, specific gravity 1.23) that is uniaxially stretched 1.3 times in width while being heated to 160 ° C. As a result of producing a plurality of anion exchange membranes, the graft ratio of the anion exchange membranes was in the range of 15 to 18%. The transmittance of the anion exchange membrane of Example 3 was measured in the same manner as described in the above-mentioned column (Comparison of transmittance of ions in the electrolytic solution), and was found to be 2.64 × 10 −7 . Similar to Example 1, the results of calculating the current efficiency are shown in Table 1.
　（実施例４）
　実施例４では、隔膜を変更した以外は実施例１と同様に充放電試験を行った。実施例４では、二軸延伸エチレン－ビニルアルコール共重合体フィルムと反応させる水溶液中のビニルベンジルトリメチルアンモニウムクロリドの濃度を６質量％から８質量％に変更した以外は、実施例１と同様にして陰イオン交換膜を得た。複数の陰イオン交換膜を作成した結果、陰イオン交換膜のグラフト率は、４４～４７％の範囲内であった。実施例４の陰イオン交換膜における透過率を上記（電解液中のイオンの透過率の比較）欄で述べた方法と同様に測定した結果、９．３３×１０－７であった。実施例１と同様に、電流効率を算出した結果を表１に示す。 Example 4
In Example 4, a charge / discharge test was performed in the same manner as in Example 1 except that the diaphragm was changed. Example 4 was the same as Example 1 except that the concentration of vinylbenzyltrimethylammonium chloride in the aqueous solution to be reacted with the biaxially stretched ethylene-vinyl alcohol copolymer film was changed from 6% by mass to 8% by mass. An anion exchange membrane was obtained. As a result of producing a plurality of anion exchange membranes, the graft ratio of the anion exchange membranes was in the range of 44 to 47%. The transmittance of the anion exchange membrane of Example 4 was measured in the same manner as the method described in the above (Comparison of transmittance of ions in electrolytic solution) column, and was 9.33 × 10 −7 . Similar to Example 1, the results of calculating the current efficiency are shown in Table 1.
　（比較例）
　比較例では、イオン交換膜の市販品（商品名：ネオセプタＡＨＡ、アストム社製）をレドックスフロー電池の隔膜として用いた以外は、実施例１と同様に、充放電試験を行い、電流効率を算出した。その結果を表１に示す。 (Comparative example)
In the comparative example, a charge / discharge test was performed and current efficiency was calculated in the same manner as in Example 1 except that a commercially available ion exchange membrane (trade name: Neocepta AHA, manufactured by Astom Co., Ltd.) was used as the diaphragm of the redox flow battery. did. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
 　表１に示すように、実施例１～４のイオン交換膜は、レドックスフロー電池の隔膜として比較例のイオン交換膜と同様の性能を有する。
Figure JPOXMLDOC01-appb-T000001
 As shown in Table 1, the ion exchange membranes of Examples 1 to 4 have the same performance as the ion exchange membrane of the comparative example as a diaphragm of the redox flow battery.
　表２には、実施例１～４及び比較例の透過率を示す。 Table 2 shows the transmittances of Examples 1 to 4 and Comparative Example.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002

Claims (7)

  1. 　ｐＨが２以上、８以下の範囲内の正極電解液及び負極電解液が用いられるレドックスフロー電池であって、
    　エチレン－ビニルアルコール共重合体製の非多孔質基材に陰イオン交換性の置換基を有するモノマーをグラフト重合してなる陰イオン交換膜を、正極電解液と負極電解液の間の隔膜として有することを特徴とするレドックスフロー電池。     A redox flow battery in which a positive electrode electrolyte and a negative electrode electrolyte in a pH range of 2 or more and 8 or less are used,
    An anion exchange membrane formed by graft polymerization of a monomer having an anion exchangeable substituent on a non-porous substrate made of an ethylene-vinyl alcohol copolymer is used as a diaphragm between the positive electrode electrolyte and the negative electrode electrolyte. A redox flow battery.
  2. 　前記非多孔質基材は、比重が１．１７以上、１．２３以下のエチレン－ビニルアルコール共重合体フィルムである、請求項１に記載のレドックスフロー電池。 The redox flow battery according to claim 1, wherein the non-porous substrate is an ethylene-vinyl alcohol copolymer film having a specific gravity of 1.17 or more and 1.23 or less.
  3. 　前記非多孔質基材は、一軸又は二軸延伸エチレン－ビニルアルコール共重合体フィルムである、請求項１又は請求項２に記載のレドックスフロー電池。 The redox flow battery according to claim 1 or 2, wherein the non-porous substrate is a uniaxial or biaxially stretched ethylene-vinyl alcohol copolymer film.
  4. 　前記陰イオン交換膜のグラフト率は、１５％以上、４７％以下である、請求項１から請求項３のいずれか一項に記載のレドックスフロー電池。 The redox flow battery according to any one of claims 1 to 3, wherein a graft ratio of the anion exchange membrane is 15% or more and 47% or less.
  5. 　前記非多孔質基材の厚みは、１５μｍ以上、５０μｍ以下である、請求項１から請求項４のいずれか一項に記載のレドックスフロー電池。 The redox flow battery according to any one of claims 1 to 4, wherein the non-porous substrate has a thickness of 15 µm or more and 50 µm or less.
  6. 　前記モノマーは、ビニルベンジルトリメチルアンモニウム塩を含む、請求項１から請求項５のいずれか一項に記載のレドックスフロー電池。 The redox flow battery according to any one of claims 1 to 5, wherein the monomer includes a vinylbenzyltrimethylammonium salt.
  7. 　前記正極電解液は、鉄のレドックス系物質と、クエン酸又は乳酸とを含有する、請求項１から請求項６のいずれか一項に記載のレドックスフロー電池。 The redox flow battery according to any one of claims 1 to 6, wherein the positive electrode electrolyte contains an iron redox substance and citric acid or lactic acid.
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