JPWO2014034415A1 - Ion exchange membrane for vanadium redox battery, composite, and vanadium redox battery - Google Patents

Abstract

An object of the present invention is to provide a material exhibiting outstanding performance as an ion exchange membrane for a vanadium redox battery, which is excellent in high energy efficiency and long-term charge / discharge cycle durability. A composite ion exchange membrane comprising an ion exchange resin layer containing a hydrophilic component and a hydrophobic component and a porous material layer, wherein the ion exchange resin layer is formed on one or both sides of the composite ion exchange membrane. A composite ion exchange membrane for a vanadium redox battery, wherein the composite ion exchange membrane is disposed as an outermost layer, and the thickness of at least one outermost layer of the ion exchange resin layer is 5 to 50 µm.

Description

  The present invention relates to an ion exchange membrane comprising an ion exchange resin and a porous substrate, and is particularly useful for a vanadium redox battery.

In recent years, new secondary batteries excellent in energy efficiency and environmental performance have attracted attention. In particular, in order to store natural energy such as sunlight and wind power, a large secondary battery is strongly demanded. Among these, the redox flow battery is excellent in charge / discharge cycle resistance and safety, and is optimal for a large-sized secondary battery.

  A redox flow battery is generally a battery that obtains energy by causing a redox reaction of vanadium in a vanadium sulfate solution by circulation of a pump. In this redox flow battery, a cation exchange membrane or an anion exchange membrane is used in order to maintain the ion balance between both electrodes.

As anion exchange membrane, Selemion APS manufactured by Asahi Glass Co., Ltd. is used. However, since an anion exchange membrane needs to pass ions having a large ion radius such as sulfate anion, there is a problem that resistance is high.

  In addition to ion conductivity, the ion exchange membrane must have characteristics such as prevention of permeation of the electrolyte and mechanical strength. Examples of such an ion exchange membrane include a membrane containing a perfluorocarbon sulfonic acid polymer introduced with a sulfonic acid group represented by Nafion (registered trademark) manufactured by DuPont of the United States, and a neoceptor manufactured by Tokuyama. A membrane containing a crosslinked polystyrene sulfonate is used.

A membrane containing a perfluorocarbon sulfonic acid polymer such as Nafion has advantages of excellent chemical durability, high proton conductivity, and low cell resistance. However, Nafion also has a problem of poor ion permeation selectivity. Specifically, vanadium ions are also allowed to pass during charging / discharging, so that the amount of active material in the electrolytic solution is reduced and the charging / discharging cycle is significantly deteriorated. In addition, there are problems of high cost and large environmental load at the time of disposal.

  On the other hand, a membrane containing a polystyrenesulfonic acid cross-linked product such as Neoceptor has advantages such as low cost, difficulty in passing vanadium ions, and excellent ion permeation selectivity. However, there are also problems in chemical durability and heat resistance, such as sulfonic acid groups being eliminated during hydrolysis and heat generation.

  Thus, several methods have been proposed for achieving both high energy efficiency and high durability in the ion exchange membrane for vanadium redox batteries. For example, in Patent Document 1 and Patent Document 2, a sulfonic acid group is introduced into an aromatic polymer to improve mechanical strength and heat resistance. However, most of these techniques are optimized for fuel cell applications, and few techniques optimized for redox flow battery applications have been developed.

In Patent Document 3, a method of reinforcing an ion exchange membrane with a synthetic resin fabric is proposed, but there is no track record of using it for a vanadium redox battery, and the thickness of the composite membrane exceeds 100 μm. It is expected to be difficult to achieve both efficiency and high durability.

In Non-Patent Document 1, sulfonated polyether ether ketone is used for redox flow battery applications, and charge / discharge characteristics superior to Nafion are reported. However, even with these methods, energy efficiency and voltage efficiency are insufficient.

Special table hei 11-502245 Japanese Patent Laid-Open No. 2004-1063 JP-A-8-12775

Journal of Power Sources (China) 2011, 195, p. 4380-4383

  Accordingly, an object of the present invention is to provide an ion exchange membrane for a vanadium-based redox battery that is low in resistance and excellent in durability in a long-term charge / discharge cycle.

  The inventors of the present invention have intensively studied to achieve the above object, and as a result, are a composite ion exchange membrane comprising an ion exchange resin layer comprising a hydrophilic segment and a hydrophobic segment and a porous material layer, wherein the hydrophilic segment and It has been found that the above object is achieved by a specific composite membrane in which an ion exchange resin layer composed of a hydrophobic segment is disposed on one or both sides of a composite ion exchange membrane and the thickness thereof is 5 to 50 μm.

The present invention has the following configuration.
1. A composite ion exchange membrane comprising an ion exchange resin layer containing a hydrophilic component and a hydrophobic component and a porous material layer, wherein the ion exchange resin layer is disposed as an outermost layer on one or both sides of the composite ion exchange membrane A composite ion exchange membrane for vanadium redox batteries, wherein the outermost layer thickness of at least one surface of the ion exchange resin layer is 5 to 50 µm.
2. 2. The composite ion exchange membrane for vanadium redox battery according to 1, wherein the composite ion exchange membrane contains at least two ion exchange resin layers having different ion exchange capacities.

3. The composite ion exchange membrane for vanadium redox battery according to 1-2, wherein the strength of the porous material is 1.00 MPa or more.
4). In the composite ion exchange membrane, the ion exchange resin is filled in the porous material and the ion exchange resin layer and the ion exchange resin in the porous material are both represented by the following general formula (1) and 4. The composite ion exchange membrane for vanadium redox battery according to 1 to 3, comprising an acidic ionic group as the hydrophilic component.

(1)
Where X is a monovalent or divalent group, any of a nitrile group, an amide group, an ester group or a carboxyl group, Z is an O atom or S atom, and Ar ′ is a divalent aromatic group. Indicates.

5. In the composite ion exchange membrane, the ion exchange resin layer and the ion exchange resin in the porous material are both represented by the following general formula (2) as a hydrophilic constituent and by the following general formula (3) as a hydrophobic constituent. 5. The composite ion exchange membrane for vanadium-based redox batteries according to 4, characterized by containing the constituents represented.

(2)

(3)
m and n represent copolymerization ratios of the general formula (2) and the general formula (3), m + n = 100, and 20 ≦ m ≦ 70 and 30 ≦ n ≦ 80. Y represents a sulfone group or a carbonyl group, X represents H or a monovalent cation species, Z represents an O atom, an S atom, or a direct bond, and W represents a divalent aromatic group.

6). 6. The vanadium system according to 5, wherein the composite ion exchange membrane has a constituent represented by the following general formula (4) as a hydrophilic constituent and a constituent represented by the following general formula (5) as a hydrophobic constituent. Ion exchange membrane for redox batteries.

(4)

(5)
m and n represent the copolymerization ratio of the general formula (4) and the general formula (5), m + n = 100, and 20 ≦ m ≦ 70 and 30 ≦ n ≦ 80. X represents H or a monovalent cationic species.

7). In the porous material, the porous substrate is selected from the group consisting of synthetic fiber fabric, chemical fiber fabric, natural fiber fabric, synthetic fiber nonwoven fabric, chemical fiber nonwoven fabric, paper, porous film, porous metal plate, and porous ceramic plate. 2. The composite ion exchange membrane for vanadium redox battery according to 1, which is any one of the above.
8). A composite for vanadium redox battery, comprising the ion exchange membrane according to any one of claims 1 to 7 and an electrode.
A vanadium-based redox battery comprising the composite according to 9.8.

  A composite ion exchange membrane comprising an ion exchange resin layer containing a hydrophilic component and a hydrophobic component of the present invention and a layer in which a porous material is filled with an ion exchange resin, the hydrophilic segment and the hydrophobic segment Vanadium-based redox battery having a high energy efficiency and excellent long-term charge / discharge cycle durability with a specific composition in which an ion exchange resin layer is disposed on one or both sides of a composite ion exchange membrane and has a thickness of 5 to 50 μm It is possible to provide a material that exhibits outstanding performance as an ion exchange membrane.

FIG. 1 shows a schematic diagram of a vanadium redox flow battery. FIG. 2 is a diagram illustrating the first embodiment. FIG. 3 is a diagram showing a second embodiment. FIG. 4 is a diagram showing a third embodiment. FIG. 5 shows the fourth embodiment. FIG. 6 shows the fifth embodiment.

Hereinafter, the present invention will be described in detail. The present invention provides an ion exchange membrane for a vanadium-based redox battery that has high energy efficiency and excellent durability in a long-term charge / discharge cycle. That is, an ion exchange resin containing a hydrophilic component and a hydrophobic component is combined with a porous material, and a layer made of only the ion exchange resin is arranged on one or both sides of the composite ion exchange membrane, and its thickness is 5 By setting it to ˜50 μm, it is possible to achieve both the reinforcement effect by the porous material and the resistance reduction effect by the ion exchange resin layer.

  The polymer or the composition constituting the composite ion exchange membrane for vanadium redox battery of the present invention is not limited in the polymer structure as long as it has two or more polymer compositions having different sulfonic acid group contents. The hydrophilic component is a polymer structure containing an ionic group such as a sulfonic acid group, a phosphonic acid group, or a carboxylic acid group. Examples of these polymers include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Polyesters, polyamides such as nylon 6, nylon 6,6, nylon 6,10 and nylon 12, acrylate resins such as polymethyl methacrylate, polymethacrylates, polymethyl acrylate and polyacrylates, polyacryl Acid resins, polymethacrylic acid resins, polyethylene, polypropylene, various polyolefins including polystyrene and diene polymers, polyurethane resins, cellulose resins such as cellulose acetate and ethyl cellulose, polyrelays , Aromatic hydrocarbons such as aramid, polycarbonate, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyethersulfone, polyetheretherketone, polyetherimide, polyimide, polyamideimide, polybenzimidazole, polybenzoxazole, polybenzthiazole There is no particular limitation as long as it is a polymer in which an ionic group as described above is introduced into a polymer, a fluororesin such as polytetrafluoroethylene or polyvinylidene fluoride, an epoxy resin, a phenol resin, a novolac resin, or a benzoxazine resin. . Of the ionic groups, sulfonic acid groups having the highest degree of acid dissociation are preferred. In these compositions, if necessary, for example, antioxidants, heat stabilizers, lubricants, tackifiers, plasticizers, crosslinking agents, viscosity modifiers, antistatic agents, antibacterial agents, antifoaming agents. Further, various additives such as a dispersant and a polymerization inhibitor may be included.

More preferred is an aromatic hydrocarbon polymer exhibiting high current efficiency, low resistance, heat resistance and high mechanical strength. Specifically, polyarylate, aramid, polycarbonate, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyethersulfone, polyetheretherketone, polyetherimide, polyimide, polyamideimide, polybenzimidazole, polybenzoxazole, and polybenzthiazole. Preferably exemplified. A polymer or composition obtained by sulfonating these polymers is more preferable.

More preferred are sulfonated polymers or compositions such as polyarylate, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyethersulfone, polyetheretherketone, polyetherimide, and polyimide. In the case of these polymers or compositions, since the polymer structure is more rigid, it exhibits better heat resistance and mechanical strength.

In order to suppress low resistance and vanadium ion permeation, it is preferable to make the minute gaps between the polymer structures as small as possible. Therefore, it is not preferable to introduce a bulky structure that causes steric hindrance between polymer structures, for example, a long-chain aliphatic group such as a t-butyl group or a fluorenyl group, and brings about physical interaction between polymer structures. It is preferable to introduce such a functional group. As a functional group which brings about a physical interaction, polar functional groups other than an ionic group are preferable, and among them, a nitrile group, an amide group, an ester group, and a carboxyl group are preferable. Furthermore, a nitrile group is most preferred from the viewpoint of hydrolysis resistance and strength of physical interaction. Therefore, the hydrocarbon polymer preferably has a hydrophobic component represented by the following general formula (1).

(1)
Where X is a monovalent or divalent group, any of a nitrile group, an amide group, an ester group or a carboxyl group, Z is an O atom or S atom, and Ar ′ is a divalent aromatic group. Indicates.

More preferably, the hydrocarbon-based polymer includes the following general formula (2) as a hydrophilic constituent and a constituent represented by the general formula (3) as a hydrophobic constituent. By having a benzonitrile structure in the polymer structure, the dimensional stability in the electrolytic solution is excellent, and the toughness of the film is also high, so that both high current efficiency and low resistance can be achieved.

(2)

(3)
m and n represent copolymerization ratios of the general formula (2) and the general formula (3), m + n = 100, and 20 ≦ m ≦ 70 and 30 ≦ n ≦ 80. Y represents a sulfone group or a carbonyl group, X represents H or a monovalent cation species, Z represents an O atom, an S atom, or a direct bond, and W represents a divalent aromatic group.

The most preferable hydrocarbon-based polymer includes the following general formula (4) as a hydrophilic constituent and a constituent represented by the general formula (5) as a hydrophobic constituent. By having a biphenyl structure and a benzonitrile structure, the film has excellent dimensional stability in the electrolytic solution and high toughness of the film, so that both high current efficiency and low resistance can be achieved.

(4)

(5)
In the above general formula (4) and general formula (5), m and n represent the copolymerization ratio of general formula (4) and general formula (5), m + n = 100, 20 ≦ m ≦ 70, 30 ≦ Compositions in the range of n ≦ 80 are preferred.
X represents H or a monovalent cation species.

The polymer or composition constituting the composite ion exchange membrane for a vanadium redox battery of the present invention may be a block polymer comprising the components of the above general formula (2) and general formula (3). It is preferable to use a block polymer because it has excellent dimensional stability in the electrolytic solution and improves the vanadium ion permeation suppression effect due to the microphase separation structure of the hydrophilic segment and the hydrophobic segment.

The composite ion exchange membrane for vanadium redox batteries of the present invention may contain structural units other than the above general formulas (2) and (3) and the sulfonic acid group-containing component. At this time, it is preferable that structural units other than those represented by the general formula (2) and the general formula (3) are 50% by mass or less of the sulfonic acid group-containing component. By setting it to 50% by mass or less, the characteristics of the ion exchange membrane for vanadium redox battery of the present invention can be utilized.

In the composite ion exchange membrane for vanadium-based redox battery of the present invention, in order to develop the reinforcement effect by the porous material and the resistance reduction effect by the ion exchange resin layer, ion exchange containing a hydrophilic component and a hydrophobic component The resin layer is preferably disposed on the outermost layer on one or both sides of the porous material, and more preferably disposed on the outermost layer on both surfaces. By disposing the ion exchange resin layer on the outermost layer on one or both sides of the porous material, the interface resistance between the electrolytic solution and the ion exchange membrane can be sufficiently lowered.

In the ion exchange resin layer containing a hydrophilic component and a hydrophobic component, the thickness of each layer is preferably 5 to 50 μm, and more preferably 10 to 30 μm. By setting the thickness of the ion exchange resin layer within the above range, it is possible to satisfy all of the resistance reduction of the composite ion exchange membrane, the permeation suppression of vanadium ions, and the durability against long-term charge / discharge cycles. When the thickness of the ion exchange resin layer is 50 μm or more, vanadium ion permeation suppression and long-term charge / discharge cycle durability are improved, but the membrane resistance of the composite ion exchange membrane is remarkably increased. Although all the above performances can be satisfied even when the thickness is 5 μm or less, the thickness is preferably 5 μm or more because of easy thickness control.

The filling rate of the ion exchange resin in the porous material is preferably 10 to 100%, more preferably 50 to 100%. By filling the porous material with an ion exchange resin within the above range, the membrane resistance of the composite ion exchange membrane can be lowered by lowering the interface resistance between the porous material and the electrolytic solution. When the filling rate of the ion exchange resin in the porous material is less than 100%, the surface of the porous material needs to be subjected to a hydrophilic treatment.

The thickness of the porous material layer filled with the ion exchange resin is preferably 5 to 100 μm, more preferably 7 to 70 μm, and further preferably 10 to 50 μm. By making the thickness of the porous material layer filled with the ion exchange resin within the above range, it is possible to satisfy all of the resistance to the composite ion exchange membrane, the suppression of permeation of vanadium ions, and the durability against the long-term charge / discharge cycle. . When it is out of the above range, one characteristic is improved, but the other characteristic is remarkably deteriorated.

In the composite ion exchange membrane of the present invention, ion exchange resins having different sulfonic acid group contents are layered, and the number thereof is preferably 2 or more and 5 or less, more preferably 2 or more and 3 layers. It has the following structure.

In a composite ion exchange membrane having a two-layer structure, when the ion exchange resin layer that is the outermost layer on one side is the A layer and the ion exchange resin layer filled with the porous material is the B layer, for example, as a hydrophobic component In the case where the sulfonic acid group is contained in the ion exchange resin constituting the A layer and the B layer as the hydrophilic component as the general formula (1), the composition in which the sulfonic acid group content is A layer <B layer Things are preferred. The resistance of the B layer increases because the porous material is insulative, but this increase can be offset by increasing the sulfonic acid group content. In that case, vanadium permeation | transmission suppression can also be made compatible by using an ion exchange resin with little sulfonic acid group content for A layer.

As described above, the polymer structure to be used is not limited, but it is preferable to use a polymer having the structure of the general formula (2) as the hydrophilic constituent and the polymer having the general formula (3) as the hydrophobic constituent. At that time, in the general formulas (2) and (3), a composition in which the A layer is in the range of 20 ≦ m ≦ 33 and the B layer is in the range of 30 ≦ m ≦ 65 is preferable. By setting m of the A layer within the above range, permeation of vanadium ions can be suppressed. When m of the A layer is larger than 33, the swellability with respect to the electrolytic solution and the vanadium ion permeability are too large, and the current efficiency tends to be lowered. On the other hand, by setting m of the B layer within the above range, a sufficiently low resistance can be exhibited when used as an ion exchange membrane for a vanadium redox battery. When m is less than 30, the resistance tends to be high when used as an ion exchange membrane for a vanadium redox battery. In addition, sulfonic acid group content can be calculated | required by titration mentioned later. More preferably, the A layer satisfies 26 ≦ m ≦ 33, and the B layer satisfies 35 ≦ m ≦ 55.

The composite ion exchange membrane having a three-layer structure preferably has a structure in which an ion exchange resin layer filled with a porous material is sandwiched between ion exchange resin layers containing a hydrophilic component and a hydrophobic component. When the ion exchange resin layer arranged as the outermost layer on both sides is the A layer and the ion exchange resin layer filled with the porous material is the B layer, in the general formula (1), the sulfonic acid group content is the A layer. <B layer is preferred. The polymer structure used and the range of m are the same as in the case of the two-layer structure.

  The IEC (ion exchange capacity) of the sulfonic acid group of each layer is preferably 0.5 meq / g or more and 2.0 or less for the A layer, and 2.0 or more and 3.0 meq / g or less for the B layer. Furthermore, the IEC of the A layer is 1.0 meq / g or more and 2.0 or less, and the IEC of the B layer is more preferably 1.8 or more and 2.5 meq / g or less. When the IEC of the A layer is 0.5 meq / g or less, the membrane resistance of the composite ion exchange membrane tends to increase. When the IEC of the B layer is 3.0 meq / g or more, the swelling property and vanadium ion permeability with respect to the electrolytic solution tend to be too large to be suitable for use. The difference in ion exchange capacity between layers having different ion exchange capacities is preferably 0.5 meq / g or more and 1.5 meq / g or less, more preferably 0.8 meq / g or more and 1.3 meq / g or less.

In addition, the hydrocarbon-based ion exchange membrane having a structure of two or more layers preferably has a logarithmic polymer viscosity of each layer measured by a method described later of 0.5 dl / g or more. When the logarithmic viscosity is smaller than 0.5 dl / g, the membrane tends to become brittle when molded as an ion exchange membrane. The logarithmic viscosity is more preferably 0.8 dl / g or more. On the other hand, when the logarithmic viscosity exceeds 5, problems in processability such as difficulty in dissolving the polymer occur, which is not preferable. As a solvent for measuring the logarithmic viscosity, polar organic solvents such as N-methylpyrrolidone and N, N-dimethylacetamide can be generally used. When the solubility in these is low, concentrated sulfuric acid is used. It can also be measured.

The method for producing the composite ion exchange membrane for vanadium redox battery of the present invention can be carried out by any known method. First, the method of impregnating the polymer in the porous material is not particularly limited, but any polymer solution or its melt is cast after placing or pressing the porous material after casting, and then casting again on the porous material. A method of casting a polymer solution or a melt thereof, a method of impregnation by passing a porous material in an arbitrary polymer solution or the melt thereof, and the like are preferable.

When the porous material is impregnated with the polymer, the viscosity of the polymer solution or the melt thereof needs to be 2.0 to 200000 mPa · s, preferably 5.0 to 150,000 mPa · s, more preferably 10 to 10 mpa · s. 100000 mPa · s. If it is less than 2.0 mPa · s, the impregnated solution flows down from the porous material, so that the polymer filling rate in the porous material decreases. When it exceeds 200,000 mPa · s, the solution is not impregnated in the porous material, and the remaining air adversely affects the characteristics of the composite membrane.

A method for laminating ion exchange resins having different amounts of sulfonic acid groups is not particularly limited, but it is preferable to perform lamination by adhesion or superposition. Overlaying refers to laminating a plurality of ion exchange membranes without using an adhesive or the like. Adhesion refers to bonding a plurality of ion exchange membranes with an adhesive ion exchange resin or the like, or solution casting in multiple layers. When superposing, a plurality of ion exchange membranes may be superposed in a state where water or an organic solvent is included on the surface. In the case of bonding, it can be carried out by any known method such as overcoating by solution casting, solution casting in multiple layers, and heating press.

  The most preferable method for forming the composite ion exchange membrane for vanadium redox batteries of the present invention is casting from a solution, and the solvent is removed from the cast solution to obtain an ion exchange membrane for vanadium redox batteries. it can. After impregnating a porous material with an ion exchange resin as described above, an ion exchange resin layer composed of a hydrophilic segment and a hydrophobic segment is formed by superposition or adhesion, and a composite ion exchange composed of two or more layers is formed. A membrane can be obtained. Aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, hexamethylphosphonamide, etc. Alternatively, an appropriate alcohol can be selected from alcohols such as methanol and ethanol, but is not limited thereto. A plurality of these solvents may be used as a mixture within a possible range. The compound concentration in the solution is preferably in the range of 0.1 to 50% by mass. If the compound concentration in the solution is less than 0.1% by mass, it tends to be difficult to obtain a good molded product, and if it exceeds 50% by mass, the workability tends to deteriorate. A method of obtaining a molded body from a solution can be performed using a conventionally known method. When the solvent is an organic solvent, the solvent is preferably distilled off by heating or drying under reduced pressure. At this time, it can be formed into various shapes such as a fiber shape, a film shape, a pellet shape, a plate shape, a rod shape, a pipe shape, a ball shape, and a block shape in a composite form with other compounds as necessary. . When combined with a compound having a similar dissolution behavior, it is preferable in that good molding can be achieved. The sulfonic acid group in the molded article thus obtained may contain a salt form with a cationic species, but it can be converted to a free sulfonic acid group by acid treatment as necessary. You can also.

The removal of the solvent is preferably by drying in view of the uniformity of the ion exchange membrane for vanadium redox batteries. Moreover, in order to avoid decomposition | disassembly and alteration of a compound or a solvent, it can also dry at the lowest temperature possible under reduced pressure. Further, when the viscosity of the solution is high, when the substrate or the solution is heated and cast at a high temperature, the viscosity of the solution is lowered and the casting can be easily performed. The thickness of the solution at the time of casting is not particularly limited, but is preferably 10 to 1000 μm. More preferably, it is 50-500 micrometers. If the thickness of the solution is less than 10 μm, the form as an ion exchange membrane for a vanadium redox battery tends to be not maintained, and if it is thicker than 1000 μm, a non-uniform ion exchange membrane tends to be easily formed. As a method for controlling the cast thickness of the solution, a known method can be used. For example, the thickness can be controlled by using a coating means such as an applicator or a doctor blade, or by adjusting the amount and concentration of the solution with a cast area constant using a glass petri dish or the like. The cast solution can obtain a more uniform film by adjusting the solvent removal rate. For example, when the solvent is removed by heating, the evaporation rate can be lowered by lowering the temperature in the first stage. When removing the solvent by immersing it in a non-solvent such as water, the solidification rate of the compound can be adjusted by leaving the cast solution in the air or in an inert gas for an appropriate period of time. it can.

The porosity of the porous material used for the composite ion exchange membrane for vanadium redox batteries of the present invention is preferably 20 to 90%, more preferably 40 to 90%. By using a porous material having a porosity in the above range, the polymer can be filled efficiently and the membrane resistance can be lowered sufficiently. Moreover, about the intensity | strength of a porous material, it is required that it is 1.00 MPa or more, and it is more preferable that it is 2.00 MPa or more. Thereby, sufficient strength can be obtained when the porous material is filled with the polymer. About thickness, it is preferable that it is 5-150 micrometers, It is more preferable that it is 10-80 micrometers, It is further more preferable that it is 20-60 micrometers. By setting the thickness within the above range, the membrane resistance of the layer in which the porous material is filled with the polymer can be lowered, and the handleability at the time of production is improved.

The pore size of the porous material used for the composite ion exchange membrane for vanadium redox battery of the present invention is preferably 0.05 μm or more and 10 μm or less, and more preferably 0.1 μm or more and 7 μm or less. By setting the pore size within the above range, the polymer can be easily filled into the porous material and the reinforcing effect of the porous material can be sufficiently exerted.

The form of the porous material used in the composite ion exchange membrane for vanadium redox battery of the present invention is as follows: synthetic fiber fabric, chemical fiber fabric, natural fiber fabric, synthetic fiber nonwoven fabric, chemical fiber nonwoven fabric, paper, porous film, porous metal plate A porous ceramic plate is preferable, and a synthetic fiber fabric, a synthetic fiber nonwoven fabric, a chemical fiber nonwoven fabric, or a porous film is more preferable. By using the porous material in these forms, the impregnation of the polymer can be performed efficiently, and the handleability during the production becomes good.

The constituent components of the porous material used for the composite ion exchange membrane for vanadium redox batteries of the present invention are not particularly limited as long as they can withstand the usage environment of the vanadium redox batteries. Specifically, it is preferably a component having acid resistance and oxidation resistance. More preferably, a fluororesin such as polyolefin, polytetrafluoroethylene or polyvinylidene fluoride, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyethersulfone, polyetheretherketone, polyetherimide, polyimide, polyamideimide, polybenzimidazole, It is a porous material made of polybenzoxazole, polybenzthiazole or the like.

  A vanadium redox battery is a battery that charges and discharges by an oxidation-reduction reaction of vanadium having different valences. The ion exchange membrane is used as a diaphragm for adjusting the ion balance in the positive electrode and the negative electrode and preventing mixing of vanadium having different valences. The hydrocarbon ion exchange membrane for a vanadium redox battery having a structure of two or more layers according to the present invention may be used for a redox flow battery in which an aqueous electrolyte is charged and discharged by circulating a pump, or an aqueous electrolyte. Alternatively, a redox battery in which a carbon electrode is impregnated with vanadium hydrate may be used. A redox flow battery that charges and discharges aqueous electrolyte solution by circulating a pump has a diaphragm disposed between a pair of current collector plates facing each other with a gap interposed therebetween, for example. An electrode material is sandwiched between at least one of the diaphragms, and the electrode material includes an electrolytic cell having a structure including an electrolytic solution made of an aqueous solution containing an active material. The battery composite refers to an ion exchange membrane and an electrode material (3 and 5 in FIG. 1).

  Examples of the aqueous electrolyte include iron-chromium, titanium-manganese-chromium, chromium-chromium, iron-titanium, and the like, in addition to the vanadium electrolyte as described above, but the vanadium electrolyte is preferable. . In particular, the carbon electrode material assembly of the present invention uses a vanadium-based electrolyte having a viscosity of 0.005 Pa · s or more at 25 ° C. or a vanadium-based electrolyte containing 1.5 mol / l or more of vanadium ions. Useful for redox flow batteries.

EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example, this invention is not limited to these Examples. Various measurements were performed as follows.

Solution viscosity: The polymer powder was dissolved in N-methylpyrrolidone at a concentration of 0.5 g / dl, the viscosity was measured using an Ubbelohde viscometer in a constant temperature bath at 30 ° C., and the logarithmic viscosity ln [ta / tb] / Evaluation was made in c) (ta is the number of seconds that the sample solution was dropped, tb was the number of seconds that the solvent was dropped, and c was the polymer concentration).

Battery characteristics: A small cell having an electrode area of 10 cm ² of 10 cm in the vertical direction (liquid flow direction) and 1 cm in the width direction is formed, and charging and discharging are repeated at a constant current density, current efficiency, cell resistance, energy efficiency, voltage efficiency Was calculated as follows. Moreover, a 2.5 mol / l sulfuric acid aqueous solution of 1.5 mol / l vanadium oxysulfate was used for the positive electrode electrolyte, and a 2.5 mol / l sulfuric acid aqueous solution of 1.5 mol / l vanadium sulfate was used for the negative electrode electrolyte. It was. The amount of the electrolytic solution was excessively large with respect to the cell and the piping. The liquid flow rate was 6.2 ml per minute, and the measurement was performed at 30 ° C.

(A) Current efficiency: η _I
In a one-cycle test that starts with charging and ends with discharging, the current density is 100 mA / cm 2 (1600 mA) per electrode geometric area, and the amount of electricity required for charging up to 1.7 V is constant up to Q ₁ coulomb and 1.0 V. Let Q ₂ and Q ₃ coulomb be the amounts of electricity taken out by the current discharge and the subsequent constant voltage discharge at 1.2 V, respectively, and the current efficiency ηI is obtained by Equation 1.

(B) Cell resistance: R
The ratio of the amount of electricity taken out by discharge with respect to the theoretical amount of electricity Q _th necessary to completely reduce V ³⁺ in the negative electrode solution to V ²⁺ is taken as the charging rate, and the charging rate is obtained by Equation 2.

The charging voltage V _C50 and the discharging voltage V _D50 corresponding to the amount of electricity when the charging rate is 50% are obtained from the amount-voltage curve, respectively, and the cell resistance R (Ω · cm ² ) with respect to the electrode geometric area is obtained from Equation 3. .

(C) Voltage efficiency: η _V
Using the cell resistance R obtained by the above method, the voltage efficiency η _V is obtained by the simple method of Formula 74.

Here, E is a cell open circuit voltage of 1.432 V (measured value) when the charging rate is 50%, and I is a current value of 0.4 A in constant current charge / discharge.

(D) Energy efficiency: η _E
Using the current efficiency η _I and the voltage efficiency η _V described above, the energy efficiency η _E is obtained by Equation 5.

Long-term charge / discharge cycle durability: Constant current charge up to 1.6V with a current density of 100mA / cm2 per electrode geometric area (1600mA in total) for a 1.0V cell, then the current density from 1.6V 1. Perform constant current discharge at 100 mA / cm 2 per electrode geometric area (1600 mA in total).
The time when 0V is reached is defined as one cycle. This cycle is repeated until charge / discharge is impossible, and the number of cycles at that time is defined as redox flow battery durability.

NMR measurement: A polymer (sulfonic acid group is Na or K salt) was dissolved in a solvent, and ¹ H-NMR was measured at room temperature using UNITY-500 manufactured by VARIAN. Heavy dimethyl sulfoxide was used as the solvent. From the peak area value derived from the structural formula (4) and the peak area value derived from the structural formula (5), the molar ratio of the constituent components was calculated, and the values of m and n were calculated.

IEC: 100 mg of the dried ion exchange membrane was immersed in 50 ml of 0.01N NaOH aqueous solution and stirred at 25 ° C. overnight. Then, neutralization titration with 0.05N HCl aqueous solution was performed. For neutralization titration, a potentiometric titrator COMMITE-980 manufactured by Hiranuma Sangyo Co., Ltd. was used. The ion exchange capacity was calculated by the following formula.
Ion exchange capacity [meq / g] = (10-titration [ml]) / 2

Cross-sectional observation of composite ion exchange membrane: After embedding a composite ion-exchange membrane piece with a resin, a cross-sectional sample was prepared using a microtome. The prepared cross-sectional sample was observed and photographed with a differential interference microscope (OPTIPHOT manufactured by Nikon Corporation, objective lens 40 times) (FIGS. 2 and 3).
The composite ion-exchange membrane piece was cut and subjected to Pt sputtering was observed with a scanning electron microscope S-4500 manufactured by Hitachi at an acceleration voltage of 5 kV (FIG. 4).

Example 1
3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt (abbreviation: S-DCDPS) 5.000 g (0.01012 mole), 2,6-dichlorobenzonitrile (abbreviation: DCBN) 2.2215 g ( 0.01288 mole), 4,4'-biphenol 4.2846 g (0.02299 mole), potassium carbonate 3.4957 g (0.02529 mole) and 2.61 g of molecular sieves were weighed into a 100 ml four-necked flask and flushed with nitrogen. . After adding 30 ml of NMP and stirring at 150 ° C. for 1 hour, the reaction was continued by raising the reaction temperature to 195-200 ° C. and sufficiently increasing the viscosity of the system (about 5 hours). After standing to cool, the precipitated molecular sieve was removed and the mixture was precipitated in water as a strand. The obtained polymer was washed in boiling water for 1 hour and then dried. The logarithmic viscosity of the polymer was 1.24 dl / g, and in the above structural formula, m = 44 and n = 56. The polymer structural formula is shown below (hereinafter the structure is referred to as polymer 1). The IEC determined by titration after treating polymer 1 with 2M-sulfuric acid was 2.03 meq / g.

4.320 g (0.00875 mole) of 3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt (abbreviation: S-DCDPS) and 4,6-dichlorobenzonitrile (abbreviation: DCBN) Polymerization was conducted in the same manner as in Example 1 except that 1847 g (0.02426 mole), 4,4′-biphenol 6.1494 g (0.03300 mole), and potassium carbonate 5.0171 g (0.03630 mole). In the formula, a polymer having m = 26.5 and n = 73.5 was obtained. The logarithmic viscosity of the polymer was 1.58 dl / g. The polymer structural formula is shown below (hereinafter the structure is referred to as polymer 2). The IEC determined by titration after treating polymer 2 with 2M-sulfuric acid was 1.33 meq / g.

About each of the obtained polymer 1 and polymer 2, 10 g was dissolved in 67 ml of NMP. The prepared polymer 1 solution was cast to a glass plate on a hot plate to a thickness of about 330 μm. Next, Syntex Nano 6 (thickness 110 μm, porosity 90%, strength 1.14 MPa) manufactured by Mitsui Chemicals, Inc. was placed on the cast solution and dried by heating at 80 ° C. for 1 hour. After drying, the prepared polymer 2 solution was overcoated to a thickness of about 330 μm, similarly dried by heating, and then immersed in water overnight or longer. The resulting film was treated with boiling water for 1 hour in dilute sulfuric acid (6 ml of concentrated sulfuric acid, 300 ml of water) to remove the salt and convert it to acid, and then boiled with pure water for 1 hour to remove the free acid component. And then dried. By observing the cross section, it was confirmed that the ion exchange resin layer was disposed on one side of the porous material layer, and the composite ion exchange membrane was filled with the ion exchange resin in the porous material layer (FIG. 2). The thickness of the outermost ion exchange resin layer was 20 μm, and the thickness of the porous material layer was 45 μm.

The produced composite ion exchange membrane was sandwiched between carbon electrode materials (XF30A manufactured by Toyobo Co., Ltd.), and a cell as shown in FIG. 1 was assembled. A small cell having an electrode area of 10 cm ² of 10 cm in the vertical direction (liquid passing direction) and 1 cm in the width direction was prepared, and charge / discharge was repeated at a constant current density to evaluate the ion exchange membrane performance. A 3 mol / l sulfuric acid aqueous solution of 2 mol / l vanadium oxysulfate was used for the positive electrode electrolyte, and a 3 mol / l sulfuric acid aqueous solution of 2 mol / l vanadium sulfate was used for the negative electrode electrolyte. The amount of the electrolytic solution was excessively large with respect to the cell and the piping. The liquid flow rate was 6.2 ml per minute, and the measurement was performed at 30 ° C.

(Example 2)
A composite ion exchange membrane was prepared and battery performance was evaluated in the same manner as in Example 1 except that the porous material used was changed to Lydall's Solopor3P07A (thickness 20 μm, porosity 83%, strength 12 MPa). By observing the cross section, it was confirmed that the ion exchange resin layers were disposed on both sides of the porous material layer, and the composite ion exchange membrane was filled with the ion exchange resin in the porous material layer (FIG. 3). The thicknesses of the outermost ion exchange resin layers were 30 μm and 7 μm, respectively, and the thickness of the porous material layer was 13 μm.

(Example 3)
A composite ion exchange membrane was prepared in the same manner as in Example 1 except that the porous material used was changed to Sumitomo Electric's Poeflon HPW-045-30 (thickness 30 μm, porosity 60%). evaluated. By observing the cross section, it was confirmed that the ion exchange resin layer was a composite ion exchange membrane in which the ion exchange resin layer was disposed on both sides of the porous material layer and the ion exchange resin was filled in the porous material layer (FIG. 4). The thickness of the exchange resin layer was 20 μm, and the thickness of the porous material layer was 25 μm.

Example 4
5.000 g (0.01012 mole) of S-DCDPS, 1.4367 g (0.00833 mole) of DCBN, 3.6501 g (0.01959 mole) of 4,4′-biphenol, and 2.9800 g (0.02155 mole) of potassium carbonate. ), 2.61 g of the molecular sieve was weighed into a 100 ml four-necked flask and flushed with nitrogen. After adding 30 ml of NMP and stirring at 150 ° C. for 1 hour, the reaction was continued by raising the reaction temperature to 195-200 ° C. and sufficiently increasing the viscosity of the system (about 5 hours). After standing to cool, the precipitated molecular sieve was removed and the mixture was precipitated in water as a strand. The obtained polymer was washed in boiling water for 1 hour and then dried. The logarithmic viscosity of the polymer was 1.33 dl / g. In the above structural formula, m = 55 and n = 45. The polymer structural formula is shown below (hereinafter the structure is referred to as polymer 3). The IEC determined by titration after treating polymer 3 with 2M-sulfuric acid was 2.33 meq / g.

A composite ion exchange membrane was prepared in the same manner as in Example 3 except that the polymer filled in the porous substrate was polymer 3, the cast thickness of polymer 3 was 200 μm, and the cast thickness of polymer 1 was 200 μm. Evaluated. By observing the cross section, it was confirmed that the ion exchange resin layer was disposed on both sides of the porous material layer, and the composite ion exchange membrane was filled with the ion exchange resin in the porous material layer (FIG. 5). The thickness of the outermost ion exchange resin layer was 14 μm on one side, 8 μm on the other side, and the thickness of the porous material layer was 20 μm.

(Example 5)
Implementation was performed except that the porous material used was Lydoll Solupor 5P09B (thickness 38 μm, porosity 83%, strength 8 MPa), and the polymer filled in the porous substrate and the polymer arranged in the outermost layer were both polymer 1. A composite ion exchange membrane was prepared in the same manner as in Example 2, and the battery performance was evaluated. By observing the cross section, it was confirmed that the ion exchange resin layer was disposed on both surfaces of the porous material layer, and the composite ion exchange membrane was filled with the ion exchange resin in the porous material layer (FIG. 6). The thickness of the outermost ion exchange resin layer was 18 μm on one side, 7 μm on the other side, and the thickness of the porous material layer was 13 μm.

(Comparative Example 1)
4.4560 g (0.00902 mole) of 3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt (abbreviation: S-DCDPS) and 2,6-dichlorobenzonitrile (abbreviation: DCBN) of 3. Polymerization was conducted in the same manner as in Example 1 except that 1583 g (0.01831 mole), 4,4′-biphenol 5.0912 g (0.02732 mole), and potassium carbonate 4.1538 g (0.03005 mole). In the formula, a polymer with m = 33 and n = 67 was obtained. The logarithmic viscosity of the polymer was 1.58 dl / g. The polymer structural formula is shown below (hereinafter the structure is referred to as polymer 4). The IEC determined by titration after treating polymer 4 with 2M-sulfuric acid was 1.71 meq / g.

The ion exchange membrane performance was evaluated in the same manner as in Example 1 except that a single layer ion exchange membrane (30 μm) made of polymer 3 was sandwiched between carbon electrode materials (XF30A manufactured by Toyobo Co., Ltd.).
(Comparative Example 2)
Ion exchange membrane performance was evaluated in the same manner as in Example 1 except that a single-layer ion exchange membrane (30 μm) made of polymer 1 was sandwiched between carbon electrode materials (XF30A manufactured by Toyobo Co., Ltd.).
(Comparative Example 3)
Ion exchange membrane performance was evaluated in the same manner as in Example 1 except that a single-layer ion exchange membrane (30 μm) made of polymer 2 was sandwiched between carbon electrode materials (XF30A manufactured by Toyobo Co., Ltd.).
(Comparative Example 4)
Ion exchange membrane performance was evaluated in the same manner as in Example 1 except that Nafion 115CS manufactured by DuPont USA was sandwiched between carbon electrode materials (XF30A manufactured by Toyobo Co., Ltd.).

  Using the ion exchange membrane produced in Examples 1-3 and Comparative Examples 1-4, charging / discharging was repeatedly performed at 100 mA / cm <2>, and the initial performance and charging / discharging cycle durability were measured. As a result, it became as shown in Table 1.

  As is clear from the results in Table 1, the composite ion exchange membranes when the ion exchange resin layer and the packing layer on the porous substrate have different amounts of sulfonic acid groups (Examples 1 to 4), It has been shown that it exhibits very high current efficiency, low resistance, and excellent energy efficiency. In addition, as in Example 5, even when the ion exchange resin layer and the filling layer to the porous substrate are made of the same sulfonic acid group, long-term charge / discharge that is significantly longer than that of the uncomposite membrane (Comparative Examples 1 to 3) Improved cycle durability. Further, the same applies to Examples 1 to 3. These composite membranes showed higher energy efficiency than the perfluorosulfonic acid membrane (Comparative Example 4). Thus, a significant improvement in durability could be confirmed by providing a composite with a porous material and providing an outermost layer. In addition, the outermost ion exchange resin layer and the porous substrate filling layer are made of polymers with different sulfonic acid group contents, which not only provides durability, but also reduces the resistance of the composite ion exchange membrane and ion permeation. The selectivity was compatible.

A composite ion exchange membrane comprising an ion exchange resin layer containing a hydrophilic component and a hydrophobic component and a porous material layer, wherein the ion exchange resin layer is disposed as an outermost layer on one or both sides of the composite ion exchange membrane In the ion exchange resin layer, at least one outermost layer thickness is 5 to 50 μm, and the composite ion exchange membrane for vanadium redox battery has high energy efficiency and excellent durability for long-term charge / discharge cycles. In addition, it is possible to provide an ion exchange membrane for a vanadium redox battery and to contribute to improving the performance of the vanadium redox battery.

DESCRIPTION OF SYMBOLS 1 ... Current collecting plate, 2 ... Spacer, 3 ... Ion exchange membrane, 4a, b ... Liquid passage, 5 ... Electrode material,
6 ... Cathode solution tank, 7 ... Cathode solution tank, 8, 9 ... Pump

Claims (9)

A composite ion exchange membrane comprising an ion exchange resin layer containing a hydrophilic component and a hydrophobic component and a porous material layer, wherein the ion exchange resin layer is disposed as an outermost layer on one or both sides of the composite ion exchange membrane A composite ion exchange membrane for vanadium redox batteries, wherein the outermost layer thickness of at least one surface of the ion exchange resin layer is 5 to 50 µm. 2. The composite ion exchange membrane for vanadium-based redox batteries according to claim 1, wherein the composite ion exchange membrane contains at least two ion exchange resin layers having different ion exchange capacities.   The composite ion exchange membrane for vanadium redox battery according to claim 1, wherein the strength of the porous material is 1.00 MPa or more. In the composite ion exchange membrane, the ion exchange resin is filled in the porous material and the ion exchange resin layer and the ion exchange resin in the porous material are both represented by the following general formula (1) and The composite ion exchange membrane for a vanadium redox battery according to claim 1, wherein the hydrophilic constituent component includes an acidic ionic group.
(1)
Where X is a monovalent or divalent group, any of a nitrile group, an amide group, an ester group or a carboxyl group, Z is an O atom or S atom, and Ar ′ is a divalent aromatic group. Indicates. In the composite ion exchange membrane, the ion exchange resin layer and the ion exchange resin in the porous material are both represented by the following general formula (2) as a hydrophilic constituent and by the following general formula (3) as a hydrophobic constituent. The composite ion exchange membrane for vanadium-based redox batteries according to claim 4, comprising the constituents represented.
(2)
(3)
m and n represent copolymerization ratios of the general formula (2) and the general formula (3), m + n = 100, and 20 ≦ m ≦ 70 and 30 ≦ n ≦ 80. Y represents a sulfone group or a carbonyl group, X represents H or a monovalent cation species, Z represents an O atom, an S atom, or a direct bond, and W represents a divalent aromatic group. 6. The composite ion exchange membrane according to claim 5, wherein the composite ion exchange membrane has a structural component represented by the following general formula (4) as a hydrophilic structural component and a structural component represented by the following general formula (5) as a hydrophobic structural component. Ion exchange membrane for vanadium redox batteries.
(4)
(5)
m and n represent the copolymerization ratio of the general formula (4) and the general formula (5), m + n = 100, and 20 ≦ m ≦ 70 and 30 ≦ n ≦ 80. X represents H or a monovalent cationic species. In the porous material, the porous substrate is selected from the group consisting of synthetic fiber fabric, chemical fiber fabric, natural fiber fabric, synthetic fiber nonwoven fabric, chemical fiber nonwoven fabric, paper, porous film, porous metal plate, and porous ceramic plate. The composite ion exchange membrane for a vanadium redox battery according to claim 1, wherein the composite ion exchange membrane is any one of the above. A composite for vanadium redox battery, comprising the ion exchange membrane according to any one of claims 1 to 7 and an electrode. A vanadium redox battery comprising the composite according to claim 8.