JPH10162853A - Diaphragm for redox flow battery and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diaphragm on which a metallic ion permeating quantity is reduced and which has high charging-discharging efficiency and is excellent in durability by using a copolymer of a monomer unit having substantially no unsaturated bond introduced from an aliphatic hydrocarbon monomer and a styrene monomer unit as matrix resin. SOLUTION: Resin obtained by adding hydrogen by copolymerizing a styrene monomer and butadiene, is used as matrix resin of an ion exchange memberane. By being constituted in this way, a diaphragm particularly excellent in durability more than a diaphragm in which matrix resin having an unsaturated bond such as a styrene-butadiene copolymer is made to exist, is obtained. Though the content of respective constitutive units is not particularly limited, it is desirable that a unit on the basis of a styrene monomer is set to 10 to 80wt.% to a copolymer, and desirably, molecular weight of the copolymer is also set to a range of 50,000 to 500,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane for a redox flow battery having excellent durability, and more particularly to a membrane for a vanadium redox flow battery.

[0002]

2. Description of the Related Art In a redox flow battery, a positive electrode and a negative electrode battery active materials are passed through a liquid permeable electrolytic cell having a positive electrode chamber and a negative electrode chamber in which a positive electrode and a negative electrode are separated by a diaphragm, and a redox reaction is utilized. To perform charging and discharging. In general, a membrane having an ion function, for example, an ion exchange membrane is used as a diaphragm for the purpose of preventing permeation of metal ions. Various kinds of metals are considered to be used as the battery active material, but recently, a vanadium-based redox flow battery using vanadium as the battery active material (Japanese Patent Application Laid-Open No. Sho 62-62).
186473) has been proposed.

[0003] This battery is excellent in electromotive force, battery capacity, and the like as compared with the iron / chromium-based redox flow battery that has been conventionally studied. Even if the positive and negative electrode solutions are mixed with each other, they have the advantage that they can be easily regenerated by charging.

[0004]

Generally, an ion exchange membrane is used as a membrane for a redox flow battery. In a normal ion exchange membrane, a resin composition of a resin that functions as a matrix without introducing ion exchange groups (hereinafter simply referred to as a matrix resin) and an ion exchange resin is attached to a porous substrate. Is widely known. Here, as the matrix resin, for example,
Styrene-butadiene copolymer and acrylonitrile-butadiene copolymer.

When an ion exchange membrane containing such a matrix resin is used as a membrane for a redox flow battery, the redox flow battery uses an oxidizing substance such as pentavalent vanadium ion or 3 Valent iron ions and the like act on the matrix resin in the ion-exchange membrane to cause a change in the ion-exchange resin portion, causing problems such as partial separation of the ion-exchange resin portion from the substrate. In particular, pentavalent vanadium ions have a strong oxidizing power, and there is a serious problem in durability when using a general ion exchange membrane as a membrane.

Accordingly, as a membrane having oxidation resistance, a perfluoro membrane or a polysulfone membrane (JP-A-6-18)
No. 8005) has been proposed.

[0007] However, the new membrane proposed above does not satisfy all the required functions, and when used as an industrial redox flow battery membrane, has a small amount of permeation of metal ions, There has been a demand for an inexpensive diaphragm having high charge / discharge efficiency, particularly excellent durability.

[0008]

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies in view of the above-mentioned problems, and as a result, as a matrix resin, have substantially no unsaturated bonds derived from aliphatic hydrocarbon monomers. The present inventors have found that the above problems can be solved by using a copolymer of a monomer unit and a styrene-based monomer unit, and have led to the present invention.

That is, according to the present invention, a copolymer of a monomer unit having substantially no unsaturated bond derived from an aliphatic hydrocarbon monomer and a styrene monomer unit, Provided is a redox flow battery membrane comprising an ion exchange membrane in which a resin composition comprising an ion exchange resin is adhered to a porous substrate.

[0010] The membrane for a redox flow battery of the present invention comprises:
It is possible to use a copolymer of a monomer unit having substantially no unsaturated bond derived from an aliphatic hydrocarbon-based monomer and a styrene-based monomer unit as a matrix resin of an ion exchange membrane. This is a characteristic, and by doing so, a membrane having particularly excellent durability can be obtained as compared with a membrane in which a matrix resin having an unsaturated bond such as a styrene-butadiene copolymer is present.

In the present invention, the copolymer of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon-based monomer and a styrene-based monomer unit includes Known compounds consisting of structural units can be used without any limitation. As the styrene-based monomer constituting the copolymer, styrene or a styrene-substituted product obtained by introducing a substituent such as a halogen group, an alkyl group or a haloalkyl group into an aromatic ring or a vinyl group of the styrene is not limited at all. Used without. Such styrene substitutes include, for example, vinyl toluene, vinyl xylene, chlorostyrene, chloromethylstyrene, α-methylstyrene,
α-halogenated styrene, α, β, β′-trihalogenated styrene and the like.

On the other hand, the aliphatic hydrocarbon-based monomer which is another component of the copolymer is an unsaturated aliphatic hydrocarbon, preferably an unsaturated aliphatic hydrocarbon having 2 to 9 carbon atoms. Is used without particular limitation. In that case, as the unsaturated aliphatic hydrocarbon, specifically, ethylene,
It is preferable to use olefins such as propylene and butylene and conjugated diolefins such as butadiene and isoprene.
In the present invention, the copolymer used as the matrix resin is a monomer unit derived from an aliphatic hydrocarbon-based monomer, in a state where the copolymer constitutes the monomer unit It has substantially no unsaturated bond. Therefore, when an aliphatic hydrocarbon-based monomer having a plurality of unsaturated bonds such as the conjugated diolefin is used as a copolymer component, the copolymer is further subjected to a hydrogenation treatment after the copolymerization. It is necessary to eliminate unsaturated bonds remaining in the unit based on the formula (1). In addition, as a form of copolymerization,
Any type such as a so-called AB type diblock type, an ABA type triblock type, or a random type may be used. Further, it may contain a small amount of a third monomer such as divinylbenzene, methacrylic acid, and acrylic acid.

In the present invention, a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer most preferably used and a monomer based on a styrene monomer Examples of the copolymerization with a unit include a resin obtained by copolymerizing a styrene monomer and butadiene, and further hydrogenating the obtained copolymer. When the copolymer having an unsaturated bond is subjected to a hydrogenation treatment, some unsaturated bonds may remain in the obtained copolymer.
Usually, the number of such remaining unsaturated bonds is preferably within 5%, preferably within 2%, of the total number of unsaturated bonds before the hydrogenation treatment.

In a copolymer of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon-based monomer and a unit based on a styrene-based monomer, the copolymer contains Although the amount is not particularly limited, the unit based on the styrene monomer is 10% based on the total weight of the copolymer.
It is preferably set to 80% by weight. The molecular weight of the copolymer is not particularly limited, but is usually 1,0.
00 to 1,000,000, preferably 50,000 to 5
Preferably, it is in the range of 00,000.

In the film of the present invention, as a component of the resin composition, a monomer unit having substantially no unsaturated bond derived from such an aliphatic hydrocarbon monomer and a styrene monomer unit are used. Confirmation that the copolymer is used as a matrix resin can be performed, for example, by the following method. That is, the film of the present invention can be carried out by extracting the resin by Soxhlet extraction or the like with an organic solvent such as acetone or tetrahydrofuran, and analyzing the resin by infrared spectroscopy. The copolymer, when measured by infrared spectroscopy, carbon in the vicinity of 1450 cm ^-1 - there is a peak derived from a hydrogen bond, 1600 cm around ^-1, there is a peak derived from aromatic around 1500 cm ^-1 I do. On the other hand, around 1640 cm ^-1 , 970 cm
^It exhibits such characteristics that a peak derived from the carbon-carbon double bond of the alkene does not substantially exist near ^-1 .

In the membrane for a redox flow battery of the present invention, a copolymer of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer and a styrene monomer unit is used. And a resin composition comprising an ion-exchange resin is used by being attached to a substrate. Such a membrane
As long as it has the above configuration, it may be obtained by any method, but is usually obtained by the following method. That is, a monomer having substantially no unsaturated bond derived from a monomer having a functional group into which an ion exchange group can be introduced or an ion exchange group, a crosslinking agent, a polymerization initiator and an aliphatic hydrocarbon monomer. This is a method in which a mixture comprising a copolymer of a monomer unit and a styrene-based monomer unit is adhered to a substrate, molded and polymerized, and then, if necessary, an ion exchange group is introduced.

Here, as a monomer having a functional group into which an ion exchange group can be introduced or an ion exchange group, a monomer used in the production of a conventionally known ion exchange membrane can be used without any particular limitation. You. Specifically, styrene,
Α, β, vinyltoluene, vinylxylene, acenaphrene, vinylnaphthalene, α-halogenated styrene, etc.
β'-trihalogenated styrene, chlorostyrenes and the like. Particularly in the case of a membrane for a cationic redox flow battery, α-halogenated vinyl sulfonic acid,
α, β, β′-halogenated vinyl sulfonic acid, methacrylic acid, acrylic acid, styrene sulfonic acid, vinyl sulfonic acid, maleic acid, itaconic acid, styrene phosphonylic acid, maleic anhydride, vinyl phosphoric acid, and their salts; Esters and the like are used. In the case of a diaphragm for an anionic redox flow battery, vinyl pyridine, methyl vinyl pyridine, ethyl vinyl pyridine, vinyl pyrrolidone, vinyl carbazole, vinyl imidazole, amino styrene, alkyl amino styrene, dialkyl amino styrene, trialkyl amino styrene ,
Methyl vinyl ketone, chloromethyl styrene, acrylamide, acrylamide, oxime, styrene, vinyltoluene and the like are used.

As the cross-linking agent, a conventionally known monomer used in the production of an ion exchange membrane is used without any particular limitation. Specifically, for example, m-, p-, o-
Examples include divinyl compounds such as divinylbenzene, divinyl sulfone, butadiene, chloroprene, isoprene, divinylnaphthalene, diallylamine, triallylamine, and divinylpyridines, and trivinyl compounds such as trivinylbenzenes.

Further, as the polymerization initiator, conventionally known polymerization initiators are used without any particular limitation, and may be appropriately selected according to the base material used and the molding conditions. For example, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butylperoxy-2-ethylhexanoate, lauryl peroxide, stearyl peroxide, methyl isobutyl ketone peroxide,
Cyclohexane peroxide, o-methylbenzoyl peroxide, 2,4,4-trimethylpentylperoxy-phenoxyacetate, α-cumylperoxy neodecanoate, di-tert-butylperoxy-
Hexahydroterephthalate, tert-butylperoxybenzoate, diisopropylbenzene hydroperoxide, di-tert-butylperoxide,
1,1-bis-tert-butylperoxy-3,3
5-trimethylcyclohexane or the like is used.

In the present invention, a mixture of the above-mentioned monomer having a functional group into which an ion-exchange group can be introduced or an ion-exchange group, a crosslinking agent, a polymerization initiator and the matrix resin may be added, if necessary. As a monomer having a functional group capable of introducing an ion exchange group and a monomer copolymerizable with a crosslinking agent, for example, styrene, acrylonitrile,
Ethyl styrene, vinyl chloride, acrolein, methyl vinyl ketone, maleic anhydride, salts or esters thereof, itaconic acid, salts or esters thereof, and the like may be appropriately mixed. Further, a plasticizer such as dioctyl phthalate, dibutyl phthalate, tributyl phosphate, tributyl acetyl citrate or an aliphatic acid or an alcohol ester of an aromatic acid, and even a solvent for diluting the monomer may be appropriately added. good.

In the present invention, the mixing ratio of each of the above-mentioned components is not particularly limited, but is generally 100 parts by weight of a functional group capable of introducing an ion exchange group or 100 parts by weight of a monomer having an ion exchange group. On the other hand, 1 to 100 parts by weight of a crosslinking agent, copolymerization of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile It is preferable to blend the coalescing in the range of 2 to 200 parts by weight and the polymerization initiator in the range of 0.1 to 30 parts by weight based on 100% by weight of the total monomers.

The monomer mixture obtained as described above is adhered to a substrate and polymerized. Here, as the base material, those which use polyvinyl chloride, polyolefin or the like as a material resin, which has been conventionally used as a base material for an ion exchange membrane, are used without any limitation. As a shape, a woven fabric, a nonwoven fabric, a net, or a porous sheet thereof can be used without limitation.

The thickness of these substrates is not particularly limited, but is in the range of 10 to 200 μm, especially 50 to 10 μm.
Those having a thickness of 0 μm are preferred.

When the monomer mixture is adhered to the above-mentioned base material and then polymerized, the temperature is generally raised from normal temperature under pressure, but the rate of temperature rise is not particularly limited and may be appropriately determined. Just choose. These polymerization conditions also depend on the type of polymerization initiator involved, the composition of the monomer mixture, and the type of base material, and cannot be determined unequivocally, but are optimal for the performance of a redox flow battery diaphragm. May be appropriately selected in consideration of the above. In addition, as a method of attaching the paste-like material to the base material, a known method such as coating, impregnation, or dipping may be appropriately adopted.

The film-like polymer obtained by polymerization as described above may be converted, if necessary, to a known polymer such as sulfonation.
Chlorosulfonation, chloromethylation and amination, quaternary ammonium basification, quaternary pyridinium basification,
A desired ion-exchange group can be introduced by a treatment such as phosphonium conversion, sulfonium conversion, hydrolysis, and protonation to obtain a membrane for a redox flow battery.
The introduction amount of these ion exchange groups is not particularly limited,
Generally, it is suitable that the ion exchange capacity is in the range of 1 to 10 mmol / g-dry membrane, preferably 2 to 6 mmol / g-dry membrane. Further, the thickness of the ion exchange membrane is related to desired charge / discharge efficiency, electric resistance, mechanical strength, durability, and the like, but is generally 10 to 200 μm, preferably 50 to 200 μm.
Preferably, it is in the range of 120 μm.

In the present invention, the ion exchange membrane obtained as described above is used as a membrane for a redox flow battery. The term “redox flow battery” used here refers to a method in which a battery active material of a positive electrode and a negative electrode is passed through a liquid-permeable electrolytic cell having a positive electrode chamber and a negative electrode chamber in which a positive electrode and a negative electrode are separated by a diaphragm, and utilizing an oxidation-reduction reaction It performs charging and discharging. Battery active material combinations include iron / chromium,
Vanadium / vanadium-based, chromium / bromine-based, vanadium / titanium-based, vanadium / iron, zinc / iron-based and the like are considered. In particular, the membrane for redox flow batteries of the present invention is a battery system containing vanadium and has excellent durability.

[0027]

The membrane for a redox flow battery according to the present invention can be prepared by using a copolymer of a monomer unit based on acrylonitrile and a specific aliphatic hydrocarbon-based unit as a matrix resin constituting the membrane. Extremely excellent durability can be imparted without lowering the charge / discharge efficiency.

[0028]

EXAMPLES Examples of the present invention and comparative examples are shown below, but the present invention is not limited to these examples.

Example 1 100 parts by weight of styrene, 5 parts by weight of divinylbenzene, 20 parts by weight of acrylonitrile, 10 parts of chloromethylstyrene
Parts by weight, 20 parts by weight of dibutyl phthalate, 3 parts by weight of benzoyl peroxide, and a styrene-butadiene copolymer 10 having a hydrogenation rate of 98% as a matrix resin.
A paste-like mixture obtained by mixing parts by weight was applied to a polyvinyl chloride cloth, coated with a polyester film as a release material, and then subjected to heat polymerization at 100 ° C. for 3 hours.

Next, the obtained membrane-like polymer was immersed in a 1: 1 mixture of 98% concentrated sulfuric acid and chlorosulfonic acid having a purity of 90% or more at 40 ° C. for 60 minutes to prepare a cationic redox flow. A battery diaphragm was obtained. This membrane for redox flow batteries has an ion exchange capacity of 2.8 mmol / g-
The dried film had a thickness of 100 μm. This redox flow battery membrane was subjected to Soxhlet extraction at 40 ° C. for 3 days using tetrahydrofuran as a solvent, and the obtained extract was analyzed by infrared spectroscopy. as a result,
1450cm carbon around ^-1 - there is a peak derived from a hydrogen bond, 1600 cm around ^-1, there is a peak derived from aromatic near 1500 cm ^-1, on the one hand, 1640C
In the vicinity of m ^-1 and 970 cm ^-1 , substantially no peak derived from the carbon-carbon double bond of the alkene was observed.

Next, the obtained redox flow battery membrane was used as a positive electrode solution at 2 mol / l VOSO ₄ +2 mo.
1 / l sulfuric acid mixed solution was used as a negative electrode solution at 2 mol / l of V
Charge / discharge was performed at a current density of 60 mA / cm ² using a mixed solution of ₂ (SO ₄ ) ₃ +2 mol / l sulfuric acid, and the charge / discharge efficiency was determined. The results are shown in Table 1. Further, as an accelerated test, 0.2 mol / l of 5
It was immersed in a vanadium sulfate solution for one month. No change was observed in the immersion film. Table 1 shows the results of measuring the charge / discharge efficiency of the immersion film.

Comparative Example 1 A styrene-butadiene copolymer not subjected to a hydrogenation treatment was used as the matrix resin under the same conditions as in Example 1 except that the ion exchange capacity was 2.8 mmol / g-dry membrane,
A membrane for a cation-type redox flow battery having a thickness of 100 μm was obtained. This redox flow battery membrane was also subjected to Soxhlet extraction under the same conditions as in Example 1, and the resulting extract was subjected to infrared spectroscopy. As a result, a peak derived from a carbon-hydrogen bond was found at around 1450 cm ^−1. Exists, 1600
cm around ^-1, there is a peak derived from aromatic ring in the vicinity of 1500 cm ^-1, further, 1640 cm around ^-1, 970c
A peak derived from the carbon-carbon double bond of the alkene was present near m ^-1 .

The charge / discharge efficiency of this film was measured under the same conditions as in Example 1, and the results are shown in Table 1. In addition, as a result of immersion under the same conditions as in Example 1 to examine the durability, the resin component was partially peeled off. Table 1 shows the charge / discharge efficiency of the immersion film.

Example 2 100 parts by weight of 4-vinylpyridine, 6 parts by weight of styrene,
6 parts by weight of divinylbenzene having a purity of about 57%, 20 parts by weight of dioctyl phthalate, 3 parts by weight of benzoyl peroxide, and a hydrogenation rate of 98% as a matrix resin
A styrene-butadiene copolymer was mixed with 15 parts by weight of a paste-like mixture, and the mixture was applied to a polyvinyl chloride woven fabric, and a polyester film was coated as a release material.
Heat polymerization was performed at 70 ° C. for 10 hours. Next, the obtained membrane polymer was subjected to methylation at 30 ° C. for 24 hours using a 40% by weight hexane solution of methyl iodide, and the ion exchange capacity was 3.0 mmol / g-dry membrane, thickness. 110μ
m was obtained for the anion-type redox flow battery. This membrane for redox flow batteries was subjected to Soxhlet extraction at 40 ° C. for 3 days using tetrahydrofuran as a solvent, and the obtained extract was analyzed using infrared spectroscopy. As a result, the carbon in the vicinity of 1450 cm ^-1 - there is a peak derived from a hydrogen bond, 1600 cm around ^-1, 150
There is a peak derived from aromatic around 0 cm ^-1, on the one hand, 1640 cm around ^-1, in the vicinity of ^970cm-1, alkene carbon - peak attributable to carbon double bond was not substantially observed .

Table 1 shows the charge / discharge efficiency of the redox flow battery membrane. Further, in order to examine the durability, as an accelerated test, the sample was immersed in a 1 mol / l pentavalent vanadium sulfate solution at 60 ° C. Even after three months, no change was observed in the film itself. Table 1 shows the charge / discharge efficiency of the immersion film.

Comparative Example 2 Styrene not hydrogenated as a matrix resin
Under the same conditions as in Example 2 except that the butadiene copolymer was used, a diaphragm for an anion-type redox flow battery having an ion exchange capacity of 3.0 mmol / g-dry membrane and a thickness of 110 μm was obtained. The charge / discharge efficiency of this film was measured under the same conditions as in Example 1, and the results are shown in Table 1. Further, in order to examine the durability, the same immersion was performed under the same conditions as in Example 2. When taken out after 3 months and observed, peeling was observed in a part of the resin. Table 1 also shows the charge / discharge efficiency of the immersion film.

Example 3 100 parts by weight of styrene, 5 parts by weight of divinylbenzene, 20 parts by weight of acrylonitrile, 10 parts of chloromethylstyrene
Parts by weight, dioctyl phthalate 20 parts by weight, benzoyl peroxide 3 parts by weight, and a styrene-isoprene copolymer 1 having a hydrogenation rate of 98% as a matrix resin 1
A paste-like mixture obtained by mixing 5 parts by weight was applied to a polyvinyl chloride woven fabric, and a polyester film was coated as a release material, followed by heat polymerization at 100 ° C. for 4 hours.

Next, the obtained membrane-like polymer was immersed in a 1: 1 mixture of 98% concentrated sulfuric acid and chlorosulfonic acid having a purity of 90% or more at 40 ° C. for 60 minutes to obtain a cationic redox flow. A battery diaphragm was obtained. This membrane for redox flow batteries had an ion exchange capacity of 2.8 mmol / g-dry membrane and a thickness of 120 μm. This membrane for a redox flow battery was treated with tetrahydrofuran as a solvent,
Soxhlet extraction was performed at 0 ° C. for 3 days, and the obtained extract was analyzed using infrared spectroscopy. As a result, 145
0cm carbon around ^-1 - there is a peak derived from a hydrogen bond, 1600 cm around ^-1, there is a peak derived from aromatic ring in the vicinity of 1500 cm ^-1, on the one hand, 1640 cm around ^-1, around 970cm ^-1 For, substantially no peak derived from the carbon-carbon double bond of the alkene was observed.

Next, the charging / discharging efficiencies of the obtained redox flow battery membrane are shown in Table 1 for the comparative examples. Furthermore,
In order to examine the durability, the same immersion was performed under the same conditions as in Example 1. Even after one month, no change was observed in the film itself. Table 1 also shows the charge / discharge efficiency of the immersion film.

Comparative Example 3 Styrene not hydrogenated as a matrix resin
Under the same conditions as in Example 3 except that the butadiene copolymer was used, a membrane for a cation-type redox flow battery having an ion exchange capacity of 2.8 mmol / g-dry membrane and a thickness of 120 μm was obtained. The charge / discharge efficiency of this film was measured under the same conditions as in Example 1, and the results are shown in Table 1. Further, in order to examine the durability, the same immersion was performed under the same conditions as in Example 1. One month later, when taken out and observed, peeling was observed in a part of the resin. Table 1 also shows the charge / discharge efficiency of the immersion film.

[0041]

[Table 1]

Claims (3)

[Claims] 1. A copolymer of a monomer unit having substantially no unsaturated bond derived from an aliphatic hydrocarbon-based monomer and a styrene-based monomer unit, and an ion-exchange resin. A membrane for a redox flow battery comprising an ion exchange membrane in which a resin composition is adhered to a substrate. 2. The membrane for a redox flow battery according to claim 1, wherein the redox flow battery is a vanadium-based redox flow battery. 3. It has a substantially unsaturated bond derived from a functional group into which an ion exchange group can be introduced or a monomer having an ion exchange group, a crosslinking agent, a polymerization initiator, and an aliphatic hydrocarbon monomer. A mixture comprising a copolymer of a monomer unit and a styrene-based monomer unit which is not to be adhered to a base material and molded and polymerized, and then, if necessary, an ion exchange group is introduced. A method for producing a membrane for a redox flow battery according to claim 1.