JPH10208767A - Diaphragm for vanadium-based redox flow cell and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion exchange membrane which is low in membrane resistance as a diaphragm, excellent in permeability of proton, low in permeability of vanadium ion and excellent in oxidation resistance by making cross- linking polymer having pyridinium group into a diaphragm for vanadium system redox flow cell. SOLUTION: Charging/discharging is performed by utilizing oxidation reduction reaction of V<2+> /V<3+> within a negative electrode liquid isolated via an ion exchange membrane and V<4+> /V<5+> within a positive electrode liquid. In this vanadium-based redox flow cell, a diaphragm for cell made of cross-linking polymer having pyridinium group is used as the ion exchange membrane. As the cross-linking polymer having this pyridinium group, ion exchange capacity 0.2 to 10mmol/g-dry membrane an overall dialysis coefficient ratio UH/UMg 50 or more of proton and magnesium ion are preferable. The cross-linking polymer is obtained by converting pyridyl group into the pyridinium group after pyridyl group vinyl polymerization monomer 100 pts.wt. cross-linking agent 1 to 100 pts.wt. monofunctional vinyl polymerization monomer or styrene system monomer 0 to 100 pts.wt. are copolymerized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm for separating a positive electrode solution and a negative electrode solution of a vanadium-based redox flow battery using vanadium as an electrolyte.

[0002]

2. Description of the Related Art In a redox flow battery, charge and discharge are repeated by utilizing a reversible oxidation-reduction reaction of a battery active material filled in or passed through a cathode chamber and an anode chamber separated by a diaphragm. Various battery systems have been proposed depending on the battery active material. For example, chromium-bromine-based, iron-chromium-based, vanadium-titanium-based, vanadium-vanadium-based, and the like. In a redox flow battery, these active materials are usually used as an electrolyte in the form of metal ions.

[0003] Among the battery systems using the above-mentioned battery active materials, those based on vanadium are particularly excellent in electromotive force, battery capacity and the like. And this is a redox of divalent (V ²⁺ ) / 3 (V ³⁺ ) of vanadium in the negative electrode chamber and a tetravalent (V ⁴⁺ ) / 5 pentavalent (V ⁵⁺ ) of vanadium in the positive electrode chamber. Since the reaction is utilized and the electrolytes in the positive electrode chamber and the negative electrode chamber are the same metal ion species, there is an advantage that the electrolyte can be easily regenerated by charging even if the electrolytes are mixed through the diaphragm.

[0004] In a redox flow battery, a diaphragm separates a positive electrode chamber and a negative electrode chamber to prevent mixing of electrolytes, and protons generated during charging and discharging move between the positive electrode chamber and the negative electrode chamber. It is required to have a proton permeability necessary for the formation. Therefore, application of an ion exchange membrane having excellent proton permeability as a diaphragm of a redox flow battery and having selective ion permeability in which the permeability of metal ions as a battery active material is suppressed has been proposed. For example, in the case of a diaphragm for the vanadium-based redox flow battery, it is necessary to suppress permeation of vanadium ions and selectively allow protons to permeate. That is, when vanadium is mixed between the two electrode chambers through the diaphragm, there occurs a problem that energy efficiency, that is, charge / discharge efficiency is reduced in a cycle of repeating charging and discharging. From the above requirements, various ion exchange membranes such as a polysulfone anion exchange membrane (JP-A-6-188005) have been proposed as a diaphragm for a vanadium redox flow battery. However,
The above document does not describe anything about the type of ion exchange group.

[0005] In addition, as a diaphragm in a redox flow battery, the membrane resistance (electrical resistance during charge / discharge) is low in relation to charge / discharge efficiency, or the contact with the electrolytic solution for a long period of time or the charge / discharge cycle is repeated. It is required that the membrane has excellent durability so that the performance of the membrane does not decrease. In particular, with respect to durability, since a redox flow battery contains a metal ion having strong oxidizing power as a battery active material, strong oxidation resistance is required.

[0006]

However, ion exchange membranes conventionally proposed as diaphragms for vanadium-based redox flow batteries use sulfonic acid type cation exchange membranes as ion exchange membranes. The oxidation resistance was not sufficient. In particular, a vanadium-based redox flow battery has a strong oxidizing power of pentavalent vanadium (V ⁵⁺ ), which is an active material of a positive electrode chamber, and thus a general ion exchange membrane is
Even when the battery is immersed only in such a solution of the positive electrode chamber, it is oxidized and deteriorated. Even when the battery is used as a battery, the charging / discharging efficiency is degraded with time or with repeated charging / discharging cycles. was there. For this reason, it has been desired for a diaphragm for a vanadium-based redox flow battery to increase charge / discharge efficiency and improve oxidation resistance so as to withstand long-term use for practical use.

In view of the above background, the present invention develops an ion exchange membrane having low membrane resistance, excellent proton permeability, low vanadium ion permeability, and excellent oxidation resistance as a membrane. The purpose is to:

[0008]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems. As a result, they have found that an ion-exchange membrane made of a crosslinked polymer having a specific ion-exchange group can solve the above problems as a diaphragm of a vanadium-based redox flow battery, and have completed the present invention.

That is, the present invention is a diaphragm for a vanadium redox flow battery comprising a crosslinked polymer having a pyridinium group.

The ion-exchange membrane made of the crosslinked polymer having a pyridinium group has a good charge / discharge efficiency because of a good suppression of the permeation of vanadium ions, and a high selective permeability of protons. It also shows high oxidation durability against vanadium (V), and is extremely suitable as a diaphragm for vanadium-based redox flow batteries.

On the other hand, a general anion exchange membrane having a quaternary ammonium form of an amino group as an ion exchange group is:
Oxidation resistance is not sufficient, and ion exchange groups are removed due to immersion in a vanadium solution or charge / discharge in a redox flow battery, and the charge / discharge efficiency gradually decreases.

In the present invention, the pyridinium group is a covalent valence tetravalent cation, that is, a pyridinium ion, in which an alkyl group or a hydrogen atom is coordinately bonded to a nitrogen atom of a pyridine ring. . Here, the alkyl group preferably has 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group. Further, the pyridine ring may have a substituent such as a methyl group or an ethyl group. The position of the nitrogen atom in the pyridine ring is not particularly limited, but 4-pyridyl is preferred.
In particular, an anion exchange membrane obtained by coordinating a hydrogen atom to a nitrogen atom of a pyridine ring is preferable as a diaphragm of a vanadium-based redox flow battery because it exhibits particularly high charge / discharge efficiency and oxidation resistance.

In the crosslinked polymer used in the present invention, the pyridinium group has an ion exchange capacity of 0.2 to 0.2.
10 mmol / g-dry film, preferably 2-6 mmol
/ G-amount of dry film is preferably introduced. Further, the crosslinked polymer into which these pyridinium groups are introduced may be any, but usually, it is generally composed of a polymer of a vinyl polymerizable monomer crosslinked by a crosslinking agent. It is a target. Here, when the polymer is not crosslinked, it is difficult to use it as a diaphragm for a vanadium-based redox flow battery due to poor oxidation resistance.

In the present invention, the anion exchange membrane used as a membrane for a vanadium-based redox flow battery is preferably 10 to 10 in consideration of easy handling and mechanical strength of the membrane.
It is preferred to have a thickness in the range of 200 μm, especially 50 to 120 μm. Further, as an index indicating the ion selectivity of the ion exchange membrane, U _H / U _Mg which is a ratio of the overall dialysis coefficient U of proton and magnesium ion is preferably 50 or more, and more preferably 100 or more.

In the present invention, as the crosslinked polymer having a pyridinium group, a polymer obtained by copolymerizing a polymerizable composition having the following composition, in which a pyridyl group is converted to a pyridinium group, is preferably used. it can. That is, based on 100 parts by weight of a vinyl polymerizable monomer having a pyridyl group, 1 to 100 parts by weight of a crosslinking agent, preferably 2 to 15 parts by weight, and 0 to 100 parts by weight of a monofunctional vinyl polymerizable monomer. , Preferably a polymerizable composition comprising 10 to 50 parts by weight.

Also, as a monofunctional vinyl polymerizable monomer,
The use of a specific amount of a styrene-based monomer is preferable because the durability of the obtained crosslinked polymer having a pyridinium group to a vanadium solution is further improved. That is, based on 100 parts by weight of a vinyl polymerizable monomer having a pyridyl group, 1 to 100 parts by weight of a crosslinking agent, preferably 2 to 15 parts by weight, and 10 to 100 parts by weight of a styrene monomer, preferably 20 to 60 parts by weight, more preferably 30 to 5 parts by weight
A polymerizable composition comprising 0 parts by weight can be suitably used.

The following compounds can be used as each monomer or copolymer described above. First, as the vinyl polymerizable monomer having a pyridyl group, a known compound having a pyridyl group and a vinyl group in a molecule can be used without any limitation. The compound that can be suitably used in the present invention can be represented by the following formula (1).

[0018]

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(Where R ¹ is a hydrogen atom, an alkyl group,
Or a vinyl group. Here, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group.
Are preferred. Specific examples of such a vinyl polymerizable monomer having a pyridyl group include 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, methylvinylpyridine, ethylvinylpyridine, divinylpyridine, and the like. .

As the cross-linking agent, a known compound having two or more vinyl polymerizable groups in the molecule can be used without any limitation, and a compound represented by the following formula (2) can be represented by a general formula. It can be suitably used.

[0021]

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(Where R ² and R ³ are the same or different hydrogen atoms, halogen atoms, or alkyl groups, and X is

[0023]

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Where n is 0 or 1. Here, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group.
Are preferred. Specific examples of such a crosslinking agent include m-divinylbenzene, p-divinylbenzene, o
-Divinylbenzene, butadiene, chloroprene, isoprene, trivinylbenzene, divinylnaphthalene, divinylbiphenyl and the like.

As the monofunctional vinyl polymerizable monomer, a known compound having one vinyl group in the molecule can be used without any limitation. Specific examples of such a monofunctional vinyl polymerizable monomer include olefins such as pentene, heptene, and octene; acrylic acid and its esters, methacrylic acid and its esters, acrylamide and its derivatives, methacrylamide and its derivatives, and acrylonitrile. , Methacrylonitrile and other acrylic monomers; maleic anhydride and its esters, maleamic acid and its derivatives, maleimide and its derivatives, and other maleic monomers; vinylcyclopropane, vinylnaphthalene, vinylfluorene, vinylphenanthrene And various monomers such as vinylanthracene and derivatives thereof.

The styrene monomer is styrene or a derivative thereof, and a compound represented by the general formula (3) can be preferably used.

[0027]

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(However, R ⁴ , R ⁵ and R ⁶ are the same or different, respectively, a hydrogen atom, a halogen atom, an alkyl group and a phenyl group.) Here, the alkyl group includes a methyl group, an ethyl group, 1-4 carbon atoms such as propyl, isopropyl and butyl groups
Are preferred. Such styrene monomers include styrene, α-methylstyrene, α-halogenated styrene, chlorostyrene, chloromethylstyrene, α,
β, β′-trihalogenated methylstyrene, vinyltoluene, vinylxylene, vinylbiphenyl and the like can be exemplified.

In the present invention, the diaphragm for a vanadium-based redox flow battery comprising a crosslinked polymer having a viridinium group may be produced by any production method. If a suitable production method is shown, a polymerizable composition containing a vinyl polymerizable monomer having a pyridyl group, a crosslinking agent, and a monofunctional vinyl polymerizable monomer used as needed is formed into a film and polymerized. After that, a method of converting a pyridyl group to a pyridinium group may be mentioned.

Here, the monomers and copolymers and the amounts used are as described above.

For the purpose of enhancing the film forming property of the polymerization of the diaphragm, a thickener or a plasticizer, and a polymerization initiator or the like may be added to initiate the vinyl polymerization of the polymerizable composition. . Specifically, a styrene-butadiene copolymer or an acrylonitrile-butadiene copolymer or a hydrogenated product thereof is used as a thickener, and an alcohol of an aromatic or aliphatic acid such as phthalic acid is used as a plasticizer. Esters and alkyl phosphate esters are exemplified. As the polymerization initiator, an organic peroxide or an azo compound-based thermally decomposable polymerization initiator is mainly used, but in the case of photopolymerization by irradiation of light such as ultraviolet light, the photopolymerization initiator is used. Can be used. Examples of the organic peroxide-based thermal decomposition type polymerization initiator include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and t-butylperoxy-2-.
Ethyl hexanoate, lauryl peroxide, stearyl peroxide, methyl isobutyl ketone peroxide, cyclohexane peroxide, o-methylbenzoyl oxide, 2,4,4-trimethylpentyl peroxy-phenoxy acetate, α-cumyl peroxy neodecano Ethate, di-t-butylperoxyhexahydroterephthalate, t-butylperoxybenzoate, diisopropylbenzene hydroperoxide, di-t-butylperoxide, 1,1-bis-
t-butylperoxy-3,3,5-trimethylcyclohexane and the like.

The paste-form polymerizable composition prepared with the above composition is formed and polymerized into a film. This molding polymerization is generally carried out by applying the polymerizable composition to a film-like base material and then performing a polymerization treatment such as heating.
As the base material, material resins such as polyvinyl chloride and polyolefin, which have been conventionally used as base materials for ion exchange membranes, are turned into fibers to form woven fabrics, nonwoven fabrics, nets, or films into porous sheets. Processed ones can be used. The thickness of the substrate is in the range of 10 to 200 μm, especially 50
１２０120 μm is preferred.

As a method for attaching the polymerizable composition to the substrate, for example, known methods such as coating, impregnation, and dipping can be used.
What is necessary is just to select suitably according to the material and shape of a base material, or the property of a polymerizable composition. The polymerizable composition adhered to the substrate is polymerized by a method of heating or a method of irradiating light such as ultraviolet rays or ionizing radiation depending on the type of the polymerization initiator to be blended. When the polymerization initiator is a thermal decomposition type polymerization initiator and is polymerized by heating, the polymerization is carried out by heating to a temperature not lower than the decomposition temperature of the added polymerization initiator. The polymerization temperature may be set in consideration of the heat resistance of the resin material. The polymerization time is between 5 and
It is preferable to adopt from a range of 16 hours. The film-like product made of the crosslinked polymer thus formed is then subjected to a treatment for converting the pyridyl group to a pyridinium group. As a method for converting to a pyridinium group, a known method is used without limitation. For example, when obtaining a pyridinium group in which an organic group such as an alkyl group is coordinated to a nitrogen atom of a pyridine ring, the film is dipped in a bath containing an alkyl halide such as methyl iodide. May be processed by the conventionally known quaternization method.

When a pyridinium group in which a hydrogen atom is coordinately bonded to a nitrogen atom of a pyridine ring is obtained, the film is immersed in an aqueous solution of a mineral acid such as hydrochloric acid or sulfuric acid. A method may be adopted. In that case, if an organic solvent is further mixed with the aqueous solution of mineral acids, the ion exchange capacity of the obtained ion exchange membrane increases, and when used as a diaphragm of a vanadium-based redox flow battery, the charge / discharge efficiency increases. It is more effective and effective. The organic solvent is not particularly limited as long as it is soluble in an aqueous solution of a mineral acid such as hydrochloric acid or sulfuric acid.Preferably, alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, Cellosolps such as ethylene glycol monoethyl ether, acetone,
Examples thereof include ketones such as ethyl methyl ketone, and cyclic ethers such as dioxane and tetrahydrofuran. The mixing amount of these organic solvents depends on the following immersion reaction conditions, but is at least 5% by weight, preferably at least 10% by weight.

On the other hand, the acid concentration of the aqueous solution of a mineral acid is preferably 0.5 mol / l or more even with a monobasic acid such as hydrochloric acid. By increasing the value, the protonation proceeds easily. Therefore, it is not necessary to strictly regulate the immersion bath temperature and the immersion treatment time, and a sufficient effect can be obtained by immersion treatment at room temperature for 3 hours or more. Further, in order to ensure the above-mentioned protonation treatment, it is possible to increase the immersion bath temperature. In this case, nonvolatile sulfuric acid is preferable as the mineral acid, and the immersion bath temperature is mixed with the immersion bath. It is desirable that the temperature be below the boiling point of the added organic compound solvent.

In the present invention, the anion exchange membrane obtained as described above is used as a diaphragm for a vanadium redox flow battery. Here, a vanadium-based redox flow battery refers to a sulfuric acid solution containing vanadium tetravalent / pentavalent as a positive electrode solution and a vanadium divalent / pentavalent / vanadium solution as a negative electrode solution in a positive electrode chamber and a negative electrode chamber in which a positive electrode and a negative electrode are separated by a diaphragm. A sulfuric acid solution containing trivalent is allowed to flow through a liquid permeable electrolytic cell, and charge and discharge are performed using an oxidation-reduction reaction.

[0037]

The anion exchange membrane of the present invention in which the pyridinium group is incorporated in the structure of the crosslinked polymer has a low membrane resistance and suppresses the permeation of vanadium ions as a diaphragm for a vanadium-based redox flow battery. And high charge and discharge efficiency. Furthermore, since it has excellent oxidation resistance as compared with the conventional ion exchange membrane, there is little reduction in charge / discharge efficiency due to repeated charge / discharge and contact with the electrolytic solution, and has an advantage that it can withstand long-term use. . Therefore, by using the diaphragm of the present invention, a high-performance vanadium-based redox flow battery can be provided, and the present invention is extremely useful in industry.

[0038]

The present invention will be described in more detail with reference to the following Examples, which by no means limit the scope of the present invention.

The measured values described in the examples were measured by the following methods.

Ion exchange capacity Chloride ion released when the chloride ion type was replaced with the nitrate ion type was quantified by the Mohr method.

U _H / U _Mg This value is an index indicating the ion selective permeability of the ion exchange membrane, and is the ratio of the total dialysis coefficient U of magnesium ions and protons. The larger the quantity, the higher the selective permeability of ions. The method for measuring U _Mg and U _H is as follows. 1mol / l sulfuric acid and 0.5mo as standard solution
A mixed solution of 1 / l magnesium sulfate is supplied to one side of the ion exchange membrane (effective membrane area A), and water is supplied to the other side of the ion exchange membrane. The amount (m) of magnesium ions and protons permeated to the water side was measured, and from the logarithmic concentration difference (△ C) between the two chambers,
It was determined by the following equation.

U = m / (A × ΔC) Battery performance of vanadium redox flow battery A mixed solution of 2 mol / l VOSO ₄ +2 mol / l sulfuric acid as a positive electrode solution and 2 mol / l V ₂ as a negative electrode solution
Using a mixed solution of (SO ₄ ) ₃ +2 mol / l sulfuric acid, charging and discharging were performed at a current density of 60 mA / cm ² , and the ratio of the total power obtained during discharging to the total power during charging was defined as the charging and discharging efficiency. And used as an index indicating battery performance.

Oxidation resistance of the ion exchange membrane As an accelerated deterioration test, the ion exchange membrane was heated to
/ L of sulfuric acid solution containing pentavalent vanadium, and after 3 days and 6 months, the ion exchange membrane was taken out, incorporated into the above vanadium redox flow battery as a diaphragm, and charge and discharge efficiency was measured under the same conditions as above. The oxidation durability of the ion exchange membrane was determined based on the measurement and the degree of decrease in charge / discharge efficiency.

Examples 1 to 16 According to the composition table shown in Table 1, various monomers and a copolymer were mixed to obtain a paste-like polymerizable composition. The obtained polymerizable composition was applied to a woven fabric made of polyvinyl chloride, coated with a polyester film as a release material, and then heated and polymerized at 75 ° C. for 6 hours.

Next, the obtained membrane copolymer was ionized by the following two ionization methods to obtain a membrane for a redox flow battery.

1) 40% by weight of methyl iodide and 6 of hexane
It was immersed in a 0 wt% mixed solution at 30 ° C. for 24 hours.

2) Sulfuric acid 10 wt% and acetone 40 w
It was immersed in an aqueous solution of t% at 35 ° C. for 5 hours.

The film thickness, ion exchange capacity, U _H / U _Mg , and charge / discharge efficiency of the thus obtained redox flow battery membrane were measured. Further, the charge / discharge efficiency after the accelerated deterioration test for examining the oxidation resistance was measured. Table 2 shows the results.

Comparative Example 1 A paste-like mixture obtained by mixing 100 parts by weight of styrene, 5 parts by weight of divinylbenzene having a purity of about 57%, and 2 parts by weight of benzoyl peroxide was applied to a woven fabric made of polyvinyl chloride. Was coated as a release material, and then heated and polymerized at 100 ° C. for 5 hours.

Next, the obtained film-form copolymer was immersed in a 1: 1 mixture of 98% concentrated sulfuric acid and chlorosulfonic acid having a purity of 90% or more for 60 minutes at 40 ° C. to obtain a sulfonic acid type cation. An exchange membrane was obtained.

The thickness of the sulfonic acid type cation exchange membrane,
The ion exchange capacity, U _H / U _Mg , and charge / discharge efficiency were measured.
Further, the charge / discharge efficiency after the accelerated deterioration test for examining the oxidation resistance was measured. Table 2 shows the results.

Comparative Example 2 Polysulfone (trade name: UDEL, manufactured by amoco) was dissolved in 1,1,2,2-tetrachloroethane, chloromethyl and anhydrous tin chloride were added, and the mixture was reacted at 110 ° C. for 4 hours. After that, precipitation and washing were performed with methyl alcohol to obtain a chloromethylated product.

The obtained chloromethylated product was dissolved in tetrachloroethane to obtain a 10% by weight solution. Next, this solution was cast on a glass plate and dried by heating at 50 ° C. for 2 hours to obtain a cast film having a thickness of 0.025 mm.

Next, the above-mentioned cast film was 1.2 mol / L.
Was immersed in a mixed solution of N, N, N ', N ¹ -tetramethyl-1,3-diaminopropane in methanol and dimethyl sulfoxide at 40 ° C. for 16 hours to obtain a fourth ion-exchange group.
A polysulfone-based anion exchange membrane having a quaternary ammonium base was obtained.

The thickness, ion exchange capacity, U _H / U _Mg , and charge / discharge efficiency of this polysulfone anion exchange membrane were measured. Further, the charge / discharge efficiency after the accelerated deterioration test for examining the oxidation resistance was measured. Table 2 shows the results.

Comparative Example 3 A paste-like mixture obtained by mixing 100 parts by weight of chloromethylstyrene, 5 parts by weight of divinylbenzene having a purity of about 57% and 2 parts by weight of benzoyl peroxide was applied to a woven fabric made of polyvinyl chloride. After coating with a polyester film as a release material, the mixture was heated and polymerized at 75 ° C for 6 hours.

Next, the obtained film-form copolymer was immersed in an aqueous solution of 10% by weight of trimethylamine and 20% by weight of acetone at 30 ° C. for 15 hours to aminate to obtain an anion exchange membrane.

The thickness, ion exchange capacity, U _H / U _Mg and charge / discharge efficiency of this anion exchange membrane were measured. Further, the charge / discharge efficiency after the accelerated deterioration test for examining the oxidation resistance was measured.
Table 2 shows the results.

[0059]

[Table 1]

[0060]

[Table 2]

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroki Hirayama 1-1, Mikage-cho, Tokuyama-shi, Yamaguchi Pref.

Claims (7)

[Claims] 1. A diaphragm for a vanadium redox flow battery comprising a crosslinked polymer having a pyridinium group. 2. The membrane according to claim 1, wherein the crosslinked polymer having a pyridinium group is an ion exchange capacity of 0.2 to 10 mmol / g-dry membrane. 3. The crosslinked polymer having a pyridinium group has a ratio of the overall dialysis coefficient of proton to magnesium ion (U _H
/ U _Mg ) is 50 or more. 4. The membrane according to claim 1, wherein the crosslinked polymer having a pyridinium group has a hydrogen atom coordinated to a nitrogen atom of a pyridine ring. 5. A crosslinked polymer having a pyridinium group comprising 100 parts by weight of a vinyl polymerizable monomer having a pyridyl group, 1 to 100 parts by weight of a crosslinking agent, and 0 to 100 parts by weight of a monofunctional vinyl polymerizable monomer. 2. The membrane according to claim 1, wherein the pyridyl group of the copolymer obtained by copolymerizing parts is converted to a pyridinium group. 6. A crosslinked polymer having a pyridinium group comprising 100 parts by weight of a vinyl polymerizable monomer having a pyridyl group, 1 to 100 parts by weight of a crosslinking agent, and a styrene monomer 10
2. The membrane according to claim 1, wherein the pyridyl group of the copolymer obtained by copolymerizing 〜100 parts by weight is converted to a pyridinium group. 7. A vinyl polymerizable monomer having a pyridyl group,
2. The method for producing a diaphragm according to claim 1, wherein a pyridyl group is converted into a pyridinium group after a polymerizable composition containing a crosslinking agent and optionally a monofunctional vinyl polymerizable monomer is subjected to molding polymerization. .