JP2011228219A - Electrolyte for magnesium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte for magnesium secondary battery suitable for manufacturing a magnesium secondary battery having a large discharge capacity (mAh/g) per unit mass and capable of substituting for a lithium secondary battery having a risk of firing or explosion.SOLUTION: A polymer electrolyte for magnesium secondary battery has a glass transition temperature of 150°C or above, ion-exchange capacity of 1-5 meq/g, an aromatic group, a sulfonic acid group and/or its metal salt. A magnesium secondary battery using it is also provided.

Description

  The present invention relates to an electrolyte for a magnesium secondary battery, and a magnesium secondary battery using the electrolyte.

  2. Description of the Related Art In recent years, secondary batteries using lithium have been widely used with downsizing and high functionality of electronic devices and the spread of electric vehicles. However, lithium is limited in terms of resources, and there are problems such as risk of ignition and explosion.

  Therefore, a secondary battery using a metal instead of lithium has been studied. For example, a secondary battery using magnesium or aluminum is expected in terms of safety and high capacity. Among them, magnesium is an abundant element on the earth, and can be obtained inexpensively and stably, and has an energy capacity per unit volume larger than that of lithium. Moreover, when used for a secondary battery, magnesium is much safer than lithium. For these reasons, the magnesium secondary battery is highly expected as an innovative secondary battery.

  However, magnesium secondary batteries still have many technical problems to be solved. For example, there is a problem that the actual performance is far from the theoretically expected performance because the polarity of magnesium ions is high and the diffusion in the electrolyte is slow.

  For this reason, various electrolytes for magnesium secondary batteries have been disclosed so far. For example, Patent Document 1 discloses an electrolytic solution produced by heat-treating metal magnesium, a halogenated hydrocarbon, an aluminum halide, and a quaternary ammonium salt in an ether organic solvent. Patent Document 2 discloses a nonaqueous electrolytic solution comprising an electrolyte containing a magnesium salt and trifluoromethanesulfonic acid or bistrifluoromethanesulfonylimide represented by a predetermined chemical formula.

JP 2009-064730 A JP 2007-280627 A

  The inventors of the present invention provided a new electrolyte for a magnesium secondary battery in place of the above electrolyte and produced a magnesium secondary battery having a large discharge capacity (mAh / g) per unit mass.

  As a result of intensive studies by the present inventors to solve the above problems, it was found that a magnesium secondary battery not only having excellent safety but also having a large capacity per unit mass can be obtained by using a specific polymer electrolyte. The present invention has been reached.

  That is, the magnesium secondary battery electrolyte that can solve the above-described problems includes a polymer electrolyte having a glass transition temperature of 150 ° C. or higher and an ion exchange capacity of 1 to 5 meq / g. .

  In the present invention, it is preferable that the polymer electrolyte has an aromatic group, a sulfonic acid group and / or a metal salt thereof, or the metal salt is a magnesium salt.

  The present invention also includes a magnesium secondary battery using the above magnesium secondary battery electrolyte.

  By using the magnesium secondary battery electrolyte of the present invention, a magnesium secondary battery having a large discharge capacity (mAh / g) per unit mass can be obtained.

(Polymer electrolyte characteristics)
The electrolyte for a magnesium secondary battery according to the present invention includes a polymer electrolyte having a glass transition temperature of 150 ° C. or higher and an ion exchange capacity of 1 to 5 meq / g.

  When the glass transition temperature of the polymer electrolyte is less than 150 ° C., safety at high temperatures may be lowered. The glass transition temperature of the polymer electrolyte is preferably 200 ° C. or higher, and preferably 300 ° C. or lower.

  When the ion exchange capacity of the polymer electrolyte is less than 1 meq / g, the transportability of magnesium ions may be lowered, and the battery performance may be lowered. When the ion exchange capacity exceeds 5 meq / g, shape retention may be poor when the polymer electrolyte is used to form a membrane, which may make it difficult to manufacture a battery. The ion exchange capacity of the polymer electrolyte is preferably 1.5 meq / g or more, and preferably 2.5 meq / g or less.

(Polymer electrolyte structure)
The structure of the polymer electrolyte of the present invention is not particularly limited as long as it has the above-mentioned characteristics. However, an aromatic group, a sulfonic acid group and / or a metal salt thereof (hereinafter simply referred to as “ It may preferably be referred to as an “ion exchange group”. Examples of such a polymer electrolyte include aromatic hydrocarbon polymers having an ion exchange group.

  An aromatic hydrocarbon polymer has an aromatic ring in the polymer main chain, and this aromatic ring is a single bond, an ether bond, a sulfone bond, an imide bond, a heterocyclic bond, an ester bond, an amide bond, a urethane bond, A non-fluorinated or partially fluorinated ion-conducting polymer having a structure bonded with at least one linking group selected from a sulfide bond, a carbonate bond, and a ketone bond.

  Examples of the aromatic hydrocarbon polymer having such a structure include polyarylene polymers such as poly (p-phenylene) and poly (m-phenylene); polysulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene oxide, and polyether sulfone. Polyarylene (thio) ether polymers such as polyether ketones (polyether ketone, polyether ketone ketone, polyether ether ketone, polyether ether ketone ketone, polyether ketone ether ketone ketone, polyether ketone sulfone); polyimide , Polyphenylquinoxaline, polybenzoxazole, polybenzthiazole, polybenzimidazole, aromatic polyester, aromatic polyamide, aromatic polyureta , Aromatic polycarbonates, polyaryl ketone.

  The polymer electrolyte may be composed of one of these aromatic hydrocarbon polymers or a combination of two or more. In particular, aromatic hydrocarbon polymers include polyarylene polymers such as poly (p-phenylene) and poly (m-phenylene); polysulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene oxide, polyether sulfone, polyether ketone. A polyarylene (thio) ether-based polymer such as a polyarylene; preferably the polyarylene / polyarylene (thio) ether copolymer-based polymer, and may have a side chain composed of an aromatic group or an aliphatic group. Good.

  The polymer electrolyte of the present invention is constituted by the aromatic hydrocarbon polymer having a sulfonic acid group and / or a metal salt thereof. The ion exchange group may be held at any position of the aromatic hydrocarbon polymer, for example, on the aromatic ring constituting the polymer main chain, on the aromatic group constituting the polymer side chain, or on the aliphatic group The aspect which has an ion exchange group on the top is mentioned.

  As the metal salt of the sulfone group possessed by the aromatic hydrocarbon polymer of the present invention, a cation salt other than proton is preferable. Examples of such cations include monovalent cations such as alkali metal ions such as lithium, sodium and potassium and monoammonium salts; divalent cations such as alkaline earth metal ions such as magnesium and calcium. Of these, magnesium ions are preferred.

  The metal salt of the sulfone group may be composed of a single type of salt selected from the group of these cationic salts, or may be composed of a plurality of types of salts in combination of two or more types. When constituted, it is preferable that at least a magnesium salt is contained.

  When the metal salt of the sulfone group is a polyvalent cation such as an alkaline earth metal ion such as magnesium or calcium, the polyvalent cation forms a salt with a plurality of sulfonic acid groups in the polymer electrolyte. May be. Moreover, you may form a salt with both the sulfonic acid group in a polymer electrolyte, and free ions, such as a chloride ion, a nitrate ion, and a perchlorate ion.

  In the polymer electrolyte of the present invention, all the ion exchange groups may be composed of sulfonic acid groups, or part or all may be composed of metal salts of sulfonic acid groups.

  The polymer electrolyte used in the present invention is not limited to the above-mentioned aromatic hydrocarbon polymer homopolymer or random copolymer, but also a segmented block copolymer, a polymer having a long-chain or short-chain branch (for example, a comb type). The ion exchange group may be held in a higher order structure such as a polymer or a star polymer. In particular, when a copolymer that can form a co-continuous structure by phase separation of a hydrophilic part and a hydrophobic part, such as a segmented block copolymer, is used as an aromatic hydrocarbon polymer, the durability of the polymer electrolyte and magnesium This is preferable in terms of improving ion conductivity. Examples of such a segmented block copolymer include a copolymer of a hydrophilic segment having an ion exchange group and a hydrophobic segment having no ion exchange group. Such a segmented block copolymer can be obtained, for example, by polymerizing an oligomer constituting the segment directly or via another compound.

  The molecular weight of the polymer electrolyte is not particularly limited, but it is preferable that the number average molecular weight measured by using gel permeation chromatography with polyethylene glycol as a standard is in the range of 10,000 to 500,000. If it is less than 10,000, when manufacturing a polymer electrolyte membrane using a polymer electrolyte, the physical properties of the membrane may deteriorate. The larger the molecular weight, the better from the viewpoint of mechanical properties, but if it is too large, when producing a polymer electrolyte membrane using a polymer electrolyte, the concentration of the solvent solution of the polymer electrolyte must be reduced, There may be problems with solvent removal.

  The logarithmic viscosity of the polymer electrolyte is preferably in the range of 0.1 to 10.0 dL / g, and more preferably in the range of 0.3 to 5.0 dL / g. If the logarithmic viscosity is less than 0.1 dL / g, it may be difficult to form a film. On the other hand, if the logarithmic viscosity exceeds 10.0 dL / g, the viscosity of the film-forming solution may become too high or the concentration may become too low, making film formation difficult. The logarithmic viscosity is a value measured at 30 ° C. by the method described later.

(Polymer electrolyte production method)
The polymer electrolyte according to the present invention may be produced by any method. Examples thereof include a method of introducing an ion exchange group into an aromatic hydrocarbon polymer, a method of polymerizing a monomer component having an ion exchange group, and the like.

  Among the methods for introducing ion exchange groups into an aromatic hydrocarbon polymer, in particular, as a method for introducing ion exchange groups onto the aromatic ring of an aromatic hydrocarbon polymer, for example, an aromatic having a skeleton as described above A method of introducing a suitable sulfonating agent by reacting with a hydrocarbon polymer while appropriately selecting reaction conditions depending on the polymer may be mentioned. As such a sulfonating agent, for example, concentrated sulfuric acid or fuming sulfuric acid (for example, Solid State Ionics, 106, P219 (1998)) reported as an example of introducing a sulfonic acid group into an aromatic hydrocarbon polymer. , Chlorosulfuric acid (for example, J. Polym. Sci., Polym. Chem., 22, P295 (1984)), sulfuric anhydride complex (for example, J. Polym. Sci., Polym. Chem., 22, P721 (1984)). , J. Polym. Sci., Polym. Chem., 23, P1231 (1985)), and sulfonating agents described in Japanese Patent No. 2884189. These sulfonating agents may be used alone or in combination of two or more.

  Examples of a method for polymerizing a monomer component having an ion exchange group to obtain an aromatic hydrocarbon polymer having an ion exchange group include, for example, a diamine containing an aromatic diamine having an ion exchange group and an aromatic tetracarboxylic acid. A method of polymerizing an acid dianhydride to obtain an ion exchange group-containing polyimide; polymerizing a dicarboxylic acid containing an aromatic dicarboxylic acid having an ion exchange group, and an aromatic diamine diol, an aromatic diamine dithiol, or an aromatic tetramine To obtain ion-exchange group-containing polybenzoxazole, ion-exchange-group-containing polybenzthiazole, or ion-exchange-group-containing polybenzimidazole; polysulfone, polyethersulfone, or polyether by polymerizing aromatic dihalide and aromatic diol In obtaining ketones, aromatic dimers having ion exchange groups A method using an aromatic diol having rides and ion-exchange groups. The use of aromatic dihalides having ion exchange groups tends to increase the degree of polymerization more easily than the use of aromatic diols having ion exchange groups, and the heat of aromatic hydrocarbon polymers having ion exchange groups. It is preferable because stability is increased.

  When the ion exchange group of the polymer electrolyte is a sulfonic acid group, the method for converting the sulfonic acid group into a metal salt is not particularly limited. For example, the polymer electrolyte is added to an aqueous solution containing a cation. The method of immersing is mentioned. Further, when the ion exchange group of the polymer electrolyte is a metal salt of a sulfonic acid group and the metal salt is converted to another metal salt, the method for converting the metal salt is not particularly limited. For example, the polymer electrolyte is once treated with a strong acid to form a sulfonic acid group, and then immersed in an aqueous solution containing other cations to react the sulfonic acid group with another metal ion compound. .

  The outline of the polymer electrolyte used in the present invention and the production method thereof have been described above. In the following, particularly preferred embodiments of the electrolyte and the production method thereof will be described more specifically.

(Preferred examples of polymer electrolyte)
The polymer electrolyte of the present invention is particularly preferably an ion-exchange group-containing aromatic hydrocarbon polymer having a repeating unit represented by the general formula 1.

[In General Formula 1, X represents a —S (═O) ₂ — group or —C (═O) — group, Y represents H or a metal ion, Z ¹ represents either an O or S atom, Z ² is, O atom, S atom, -CH ₂ - group, -C (CH _{3) 2} - group, -C (CF _{3) 2} - group, -S (= O) ₂ - group, -C (= O) -A group, a cyclohexylene group, or a direct bond, R represents an alkyl group having 1 to 4 carbon atoms, n1 represents an integer of 1 or more, and n3 represents an integer of 0 to 4, respectively. ]

In General Formula 1, when X is a —S (═O) ₂ — group, the solubility of the polymer electrolyte in the solvent is improved. When X is a —C (═O) — group, the softening temperature of the polymer electrolyte can be lowered to further enhance the bonding property with the electrode, or photocrosslinking property can be imparted to the polymer electrolyte. Y is preferably an H atom or an alkaline earth metal such as magnesium. If Y is an H atom, it is easily decomposed by heat in the production process of the polymer electrolyte membrane. Therefore, Y is formed as an alkali metal salt such as sodium or potassium at the time of molding such as production of the electrolyte membrane. It is preferable to convert Y into H atoms by treatment, or to make Y into magnesium by further acting a magnesium ion compound. When Z ¹ is an O atom, there are advantages such as little coloring of the polymer and easy availability of raw materials. When Z ¹ is an S atom, the oxidation resistance of the polymer electrolyte is improved. When Z ² is an O atom or an S atom, the bondability between the polymer electrolyte and the electrode is further improved. When Z ² is a direct bond, the dimensional stability of the polymer electrolyte membrane is improved. When Z ² is a sulfone group or a carbonyl group, the durability of the polymer electrolyte is improved. n1 is preferably in the range of 1-30. When n1 is 2 or more, Z ² may be composed of different bonding groups. In n1 is 3 or more, and Z ² is the case of the O atoms, bonding between the polymer electrolyte membrane and the electrode is particularly enhanced. When n3 is 0, it is easy to obtain a high molecular weight polymer. When n3 is 1 to 2, the durability of the polymer electrolyte is improved.

  The polymer electrolyte of the present invention is preferably an ion-exchange group-containing aromatic hydrocarbon polymer containing a repeating unit represented by the general formula 1 and a repeating unit represented by the general formula 2. Such an aromatic hydrocarbon-based polymer has an appropriate softening temperature, and is well bonded to an electrode (catalyst layer) when a polymer electrolyte membrane is formed.

[In General Formula 2, Ar ¹ represents a divalent aromatic group, Z ³ represents either an O atom or an S atom, Z ⁴ represents an O atom, an S atom, a —CH ₂ — group, —C (CH _{3) 2} - group, -C (CF _{3) 2} - group, -S (= O) ₂ - group, -C (= O) - group, cyclohexylene group, either a direct bond, R is the number of carbon atoms 1 to 4 alkyl groups, n2 represents an integer of 1 or more, and n3 represents an integer of 0 to 4, respectively. ]

In the general formula 2, when Z ³ is an O atom, there are advantages such that the coloring of the polymer is small and the raw materials are easily available. When Z ³ is an S atom, the oxidation resistance of the polymer electrolyte is improved. When Z ⁴ is an O atom or an S atom, the bondability of the polymer electrolyte is further improved. When Z ⁴ is a direct bond, the dimensional stability of the polymer electrolyte membrane is improved. When Z ⁴ is a sulfone group or a carbonyl group, the durability of the polymer electrolyte is improved. n2 is preferably in the range of 1 to 30, and when n2 is 2 or more, Z ⁴ may be composed of different linking groups. When n2 is 3 or more and Z ⁴ is an O atom, the bondability between the polymer electrolyte membrane and the electrode is particularly improved. When n3 is 0, a polymer is easily obtained. When n3 is 1 to 2, durability is improved.

Ar ¹ in the general formula 2 is preferably a divalent aromatic group having an electron-withdrawing group. The electron-withdrawing group may be a known electron-withdrawing group, and is not particularly limited. For example, sulfo group such as sulfone group, sulfonyl group, sulfonic acid group, sulfonic acid ester group, sulfonic acid amide group, sulfonic acid imide group and derivatives thereof; carboxyl group such as carboxyl group and carboxylic acid ester group and derivatives thereof; carbonyl A cyano group; a halogen group; a perfluoroalkyl group such as a trifluoromethyl group; a nitro group; a phosphine group. These electron withdrawing groups may be used alone or in combination of two or more.

Ar ¹ is preferably represented by General Formulas 3 to 6. In the case of general formula 3, the solubility of the polymer can be increased. In the case of the general formula 4, the softening temperature of the polymer can be lowered to enhance the bonding property with the electrode, or the photocrosslinking property can be imparted. In the case of the general formulas 5 and 6, the swelling of the polymer can be reduced. Such an effect is larger in the general formula 6. Of the general formulas 3 to 6, the general formula 6 is most preferable.

The polymer electrolyte used in the present invention contains a repeating unit represented by the general formula 1 in addition to a repeating unit represented by the general formula 2, and both Z ¹ and Z ² in the general formula 1 are O atoms. More preferably, it is configured using an ion-exchange group-containing aromatic hydrocarbon polymer in which n1 is 3 or more. The polymer electrolyte membrane obtained using such an aromatic hydrocarbon-based polymer has particularly improved bondability with the electrode.

Moreover, it is more preferable that both Z ³ and Z ⁴ in the general formula 2 are O atoms, and n2 is 3 or more. The polymer electrolyte membrane obtained by using such an aromatic hydrocarbon polymer further improves the bondability with the electrode.

  When the polymer electrolyte of the present invention is an ion exchange group-containing aromatic hydrocarbon polymer mainly composed of a repeating unit represented by the general formula 1 and a repeating unit represented by the general formula 2, each repeating unit Is preferably in the range of 7:93 to 70:30. The molar ratio of 7:93 means that when the number of moles of the repeating unit represented by the general formula 1 is 7, the number of moles of the repeating unit represented by the general formula 2 is 93. When the number of repeating units represented by the general formula 1 is larger than the molar ratio of 70:30, the shape retention when the polymer electrolyte membrane is formed may be unfavorable. If the repeating unit represented by the general formula 1 is less than the molar ratio of 7:93, it is not preferable because the magnesium ion conductivity is lowered and the resistance is increased when the polymer electrolyte membrane is formed. The molar ratio is more preferably in the range of 10:90 to 50:50, and still more preferably in the range of 10:90 to 40:60.

  The polymer electrolyte of the present invention is more preferably an ion-exchange group-containing aromatic hydrocarbon polymer containing a repeating unit represented by general formula 7 in addition to general formula 1 and general formula 2. . By using such an aromatic hydrocarbon polymer, it is possible to improve the form stability of the membrane when it is used as a polymer electrolyte membrane.

[In General Formula 7, X represents a —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, and Z ⁵ represents either an O atom or an S atom. Represents. ]

The reason why it is preferable that X, Y, and Z ^{5 in the} general formula 7 are the above-described embodiments is the same as the reason described for X, Y, and Z ¹ in the general formula ¹ , respectively.

Such an aromatic hydrocarbon-based polymer has a bonding property between a polymer electrolyte membrane and an electrode, and a membrane when Z ¹ and Z ² in formula 1 are O atoms or S atoms and n1 is 1. This is preferable because the morphological stability becomes better. Further, when Z ³ and Z ⁴ in the general formula 2 are O atoms or S atoms and n2 is 1, the bondability between the polymer electrolyte membrane and the electrode and the morphological stability of the membrane are further improved. This is preferable.

  In addition to the repeating units represented by the general formulas 1, 2, and 7, the polymer electrolyte of the present invention further contains an ion-exchange group-containing aromatic hydrocarbon system containing a repeating unit represented by the general formula 8. More preferably, it is a polymer. By using such an aromatic hydrocarbon polymer, the bondability between the polymer electrolyte membrane and the electrode and the morphological stability of the membrane can be greatly improved.

[In General Formula 8, Ar ² represents a divalent aromatic group, and Z ⁶ represents either an O atom or an S atom. ]

In General Formula 8, it is preferable that Z ⁶ is the above-described aspect, and a preferable specific aspect of Ar ² is the same as the reason described for Z ³ and Ar ¹ in General Formula 2, respectively.

When the polymer electrolyte of the present invention is an ion exchange group-containing aromatic hydrocarbon polymer having all the repeating units represented by the general formulas 1, 2, 7, and 8, mol% of the respective repeating units. , And the mol% of other repeating units preferably satisfy the following formulas 1 to 3.
0.9 ≦ (n3 + n4 + n5 + n6) / (n3 + n4 + n5 + n6 + n7)
≦ 1.0 (Formula 1)
0.05 ≦ (n3 + n4) / (n3 + n4 + n5 + n6)
≦ 0.7 (Formula 2)
0.01 ≦ (n4 + n6) / (n3 + n4 + n5 + n6)
≦ 0.95 (Formula 3)

(In the above formula, n3 is the mol% of the repeating unit represented by the general formula 7, n4 is the mol% of the repeating unit represented by the general formula 1, and n5 is the mol of the repeating unit represented by the general formula 8. %, N6 represents the mol% of the repeating unit represented by the general formula 2, and n7 represents the mol% of the other repeating unit.)

  If (n3 + n4 + n5 + n6) / (n3 + n4 + n5 + n6 + n7) is smaller than 0.9, good characteristics may not be obtained when a polymer electrolyte membrane is obtained. More preferred is a range of 0.95 to 1.0.

  If (n3 + n4) / (n3 + n4 + n5 + n6) is smaller than 0.05, sufficient magnesium ion conductivity may not be obtained when a polymer electrolyte membrane is obtained. On the other hand, if it is greater than 0.7, the swellability of the polymer electrolyte membrane may be remarkably increased.

  (N3 + n4) / (n3 + n4 + n5 + n6) is preferably in the range of 0.07 to 0.5, and more preferably in the range of 0.1 to 0.4.

  When (n4 + n6) / (n3 + n4 + n5 + n6) is smaller than 0.01, the bondability between the polymer electrolyte membrane and the electrode may be lowered. When it is larger than 0.95, the swelling property of the polymer electrolyte membrane may become too large. The range of 0.05-0.8 is more preferable, and the range of 0.4-0.8 is more preferable.

  In the aromatic hydrocarbon polymer, the bonding mode of each repeating unit represented by each general formula is not particularly limited, and examples thereof include random bonding, alternating bonding, and bonding in a continuous block structure. It is done. The aromatic hydrocarbon-based polymer may be composed of a single bonding mode or a combination of two or more bonding modes.

(Preferred example of production method of polymer electrolyte)
The ion-exchange group-containing aromatic hydrocarbon polymer having a repeating unit represented by the above general formula 1 or the like is a monomer represented by the following general formulas 9 to 11 (for example, (activated) dihalogen aromatic compound, aromatic Diols, aromatic dithiols, dinitroaromatic compounds, etc.) can be produced by a known method (for example, a polymerization reaction by a known aromatic nucleophilic substitution reaction in the presence of a basic compound). Further, it is preferable to further use a monomer represented by the general formula 12 because physical properties such as film form stability are improved.

In the general formulas 9 to 12, Z ⁷ and Z ¹⁰ are each independently any one of Cl atom, F atom, I atom, Br atom and nitro group, and Z ⁸ and Z ¹¹ are each independently OH group. , SH group, -O-NH-C (= O) -R group, -S-NH-C (= O) -R group. R represents an aromatic or aliphatic hydrocarbon group. X, Y, Z ² , n1, and Ar ¹ are the same as X, Y, Z ² , n1, and Ar ¹ , respectively.

  Specific examples of the monomer represented by the general formula 9 include 3,3′-disulfo-4,4′-dichlorodiphenyl sulfone, 3,3′-disulfo-4,4′-difluorodiphenyl sulfone, 3,3 ′. -Disulfo-4,4'-dichlorodiphenyl ketone, 3,3'-disulfo-4,4'-difluorodiphenyl ketone, 3,3'-disulfobutyl-4,4'-dichlorodiphenyl sulfone, 3,3'-disulfobutyl Dihalogen aromatic compounds such as -4,4'-difluorodiphenyl sulfone, 3,3'-disulfobutyl-4,4'-dichlorodiphenyl ketone, 3,3'-disulfobutyl-4,4'-difluorodiphenyl ketone, and these In which the sulfonic acid group forms a salt with a cation. Specific examples of the cation are as described above.

  Examples of the compound represented by the general formula 9 in which the sulfonic acid group is a salt include sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone, 3,3′-disulfone Sodium salt-4,4′-difluorodiphenylsulfone, sodium 3,3′-disulfonate-4,4′-dichlorodiphenylketone, sodium 3,3′-disulfonate-4,4′-difluorodiphenylketone, 3, 3′-potassium disulfonate-4,4′-dichlorodiphenylsulfone, 3,3′-potassium disulfonate-4,4′-difluorodiphenylsulfone, 3,3′-potassium disulfonate-4,4′-dichlorodiphenyl Examples thereof include ketones and potassium 3,3′-disulfonate-4,4′-difluorodiphenyl ketone.

  Specific examples of the monomer represented by the general formula 10 include 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, 2,2- Bis (3-methyl-4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) methane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, bis (4-hydroxyphenyl) sulfide (4,4 ′ -Thiobisphenol), 4,4'-dihydroxydiphenyl ether, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4'-dihydroxydiphenylsulfone (bisphenol S), terminal hydroxyl group-containing phenylene ether oligomer (the following general formula Aromatic diols such as those having a structure represented by 13; 4 Examples include aromatic dithiols such as 4′-thiobisbenzenethiol and 4,4′-oxybisbenzenethiol, and in particular, bis (4-hydroxyphenyl) sulfide and 1,1-bis (4-hydroxyphenyl). Cyclohexane, terminal hydroxyl group-containing phenylene ether oligomer, and 4,4′-thiobisbenzenethiol are preferred.

[In General Formula 13, n is an integer of 1 or more, and a mixture of plural kinds of components with different n may be used. ]

  The monomer represented by the general formula 10 increases the flexibility of the polymer electrolyte membrane, and brings about effects such as prevention of breakage against deformation and improvement in bondability with an electrode due to a decrease in glass transition temperature.

  Examples of the monomer represented by the general formula 11 include monomers having a leaving group in a nucleophilic substitution reaction such as halogen or nitro group and an electron-withdrawing group that activates the same aromatic ring. Specifically, 2,6-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-difluorobenzonitrile, 4,4′-dichlorodiphenyl sulfone, 4,4′- Examples include, but are not limited to, activated dihalogen aromatic compounds such as difluorodiphenyl sulfone, 4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone, and decafluorobiphenyl. In addition, other aromatic dihalogen compounds, aromatic dinitro compounds, aromatic dicyano compounds and the like that are active in aromatic nucleophilic substitution can also be used.

  Examples of the monomer represented by the general formula 12 include 4,4′-biphenol, 4,4′-dimercaptobiphenol, 3,3 ′, 5,5′-tetramethyl-4-hydroxybiphenyl, 3,3 Examples include aromatic diols such as' -dimethyl-4-hydroxybiphenyl, and 4,4'-biphenol is particularly preferable.

  In the present invention, other various activated dihalogen aromatic compounds, dinitro aromatic compounds, bisphenol compounds, and bisthiophenol compounds can be used in combination with the monomers represented by the general formulas 9 to 12 as monomers. Examples of the bisphenol compound or bisthiophenol compound include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, and bis (4-hydroxyphenyl). Sulfone, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) butane, 3,3-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxy) -3,5-dimethylphenyl) propane, bis (4-hydroxy-3,5-dimethylphenyl) methane, bis (4-hydroxy-2,5-dimethylphenyl) methane, bis (4-hydroxyphenyl) phenylmethane, Hydroquinone, resorcin, bis (4-hydroxyphenyl) ketone, 1,4-ben Njichioru, 1,3 benzenedithiol, phenolphthalein, 10- (2,5-dihydroxyphenyl) -9,10-dihydro-9-oxa-10-phosphatonin phenanthrene-10-oxide, and the like. In addition, various aromatic diols or various aromatic dithiols that can be used for polymerization of polyarylene ether compounds by aromatic nucleophilic substitution reaction may be used.

(Polymer electrolyte deposition method)
The method for producing a polymer electrolyte membrane for a magnesium secondary battery using the polymer electrolyte of the present invention is not particularly limited. For example, a solvent solution of the polymer electrolyte is cast on a support, Subsequently, it can manufacture by removing a solvent. Hereinafter, a suitable method for forming a polymer electrolyte will be described in detail.

(Step of obtaining a cast film)
The solvent used in this step is not particularly limited as long as it can uniformly dissolve or disperse the polymer electrolyte, and may be appropriately selected according to the structure of the polymer electrolyte, but is a polar solvent. It is preferable that the solvent is an aprotic polar solvent. Examples of the aprotic polar solvent include N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, N-morpholine-N-oxide, and hexamethylene. Examples include phosphonamide, dimethyl sulfoxide, sulfolane, γ-butyrolactone, and diphenyl sulfone. In particular, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide are preferable. These solvents may be used alone or in combination of two or more. The boiling point of the solvent is preferably in the range of 100 to 300 ° C. If it is lower than 100 ° C., the form may be deteriorated during film formation, which is not preferable. If it exceeds 300 ° C., a large amount of energy may be required for production of the polymer electrolyte membrane, and it may be difficult to control the solvent content in the polymer electrolyte membrane to an appropriate range.

  The solid content concentration of the solvent solution of the polymer electrolyte can be appropriately determined depending on the molecular weight of the polymer electrolyte, the temperature at the time of casting, and the like, and specifically, it is preferably in the range of 5 to 50% by mass. . If it is less than 5% by mass, it may take time to remove the solvent in the subsequent step, and the form of the film may be deteriorated, or the solvent content in the film may not be appropriately controlled. If it exceeds 50% by mass, the viscosity of the solvent solution becomes too high and handling may be difficult. More preferably, it is 5-30 mass%.

  The viscosity of the solvent solution of the polymer electrolyte is not particularly limited, but is preferably within a range where it can be cast on the support satisfactorily. More preferably, the viscosity is in the range of 1 to 1000 Pa · s at the casting temperature.

  As a method for casting the polymer electrolyte solution onto the support, a known method can be used, but it is preferable to cast a solution having a constant concentration so as to have a constant thickness. For example, using a doctor blade, applicator, or the like to push the solution into a gap of a certain gap to make the casting thickness constant, or by using a slot die or the like, the polymer electrolyte solution is supplied at a constant speed for casting. A method is mentioned. The casting on the support may be performed in a batch manner, but it is preferable to perform the casting continuously because the productivity is good.

  The support for casting the polymer electrolyte solution is not particularly limited as long as it does not dissolve in the solvent used to dissolve or disperse the polymer electrolyte, but is preferably flat and flexible. . For example, resin films such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyarylate, polyamide, polyimide, polyamideimide, polyaramid, and polybenzazole, and inorganic compounds such as silica, titania, and zirconia are coated on the surface. Or a film made of a metal such as stainless steel. From the viewpoints of heat resistance and solvent resistance, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyarylate, polyamide, polyimide, and polyaramid are preferable, and polyethylene terephthalate is more preferable from the viewpoint of cost and quality.

(Solvent removal process)
In this step, the solvent is removed from the cast film. One of the techniques for removing the solvent is to heat the cast film of the polymer electrolyte to evaporate the solvent. In this case, the content of the solvent in the electrolyte membrane obtained after removing the solvent by heating is preferably 10 to 50% by mass. If it is less than 10% by mass, the polymer electrolyte membrane and the support may be too firmly bonded and cannot be peeled off. Moreover, even if it can peel, a wrinkle and a tear may arise and a form may worsen. If it is more than 50% by mass, the expansibility of the electrolyte membrane may increase. A more preferable range is 15 to 30% by mass.

  As another method for removing the solvent, the polymer electrolyte casting membrane is brought into contact with a poor solvent which is mixed with the solvent used for preparing the casting membrane and does not dissolve the polymer electrolyte. And a method of forming a polymer electrolyte membrane.

  As the poor solvent to be used, an appropriate solvent may be used according to the structure of the polymer electrolyte and the kind of the solvent used in the casting process. Examples thereof include water, alcohols, ketones, ethers, low molecular hydrocarbons, halogen-containing solvents, and mixtures thereof. When the solvent used in the casting process is miscible with water, it is preferable to use water as the poor solvent.

  Examples of the contacting method include immersing the cast film in a poor solvent, or holding the cast film in the poor solvent vapor, and a combination of these methods can also be performed.

  When the casting film is immersed in a poor solvent, the temperature of the poor solvent is preferably not less than the melting point of the poor solvent and not more than the boiling point. When the poor solvent is water, the temperature is preferably 20 to 70 ° C, more preferably 20 to 50 ° C. When the temperature is high, the solvent removal efficiency is improved, but the film morphology may be deteriorated. Further, when the temperature is low, the solvent removal efficiency is lowered, and the productivity may be lowered.

  In the case where the cast film is held in the poor solvent vapor, the treatment temperature is preferably not lower than the melting point of the poor solvent and not higher than the boiling point of the solvent to be removed. When the poor solvent is water, the temperature is preferably 20 to 70 ° C, and more preferably 20 to 50 ° C. When the temperature is high, the solvent removal efficiency is improved, but the film morphology may be deteriorated. Further, when the temperature is low, the solvent removal efficiency is lowered, and the productivity may be lowered. The vapor pressure of the poor solvent in the atmosphere is preferably 10 to 100%, more preferably 50 to 99% with respect to the saturated vapor pressure at the temperature. When the vapor pressure of the poor solvent is high, the solvent removal efficiency is improved, but the film morphology may be deteriorated. Further, when the vapor pressure of the poor solvent is low, the solvent removal efficiency is lowered, and productivity may be lowered.

  Thus, when removing a solvent by contact with a poor solvent, the solvent extraction process described later may or may not be performed.

  In addition, content of the solvent of an electrolyte membrane can be calculated | required with the following method.

<Measurement method of residual solvent amount>
The solvent adhering to the electrolyte membrane is wiped off with a filter paper, left in a room at 23 ° C. and 50% RH for 1 hour, dissolved in deuterated dimethyl sulfoxide, and accumulated using Varian 400-MR manufactured by Varian. The ¹ H-NMR spectrum is measured 128 times at 25 ° C. It is obtained by calculating the residual solvent amount for the electrolyte membrane from the integral value of the peak for the polymer electrolyte and the solvent, which has been assigned in advance. If the electrolyte membrane does not dissolve in deuterated dimethyl sulfoxide, the solvent is extracted from the electrolyte membrane with a Soxhlet extractor using water, and the solvent concentration in the water is determined by gas chromatography to determine the residual solvent. Calculate the amount. When the solvent does not dissolve in water, the amount of residual solvent is calculated by gas chromatography in the same manner as described above except that another solvent is used.

  The heating temperature at the time of heating to evaporate the solvent in the cast film is preferably 300 ° C. or lower, or lower than the boiling point of the solvent, and more preferably 200 ° C. or lower. When the heating temperature exceeds 300 ° C., the solvent removal efficiency is improved, but the solvent or polymer electrolyte may be decomposed or altered, or the shape of the resulting polymer electrolyte membrane may be deteriorated (quality deteriorates). is there. Moreover, about the minimum of heating temperature, 50 degreeC is preferable. If the heating temperature is less than 50 ° C., it may be difficult to remove the solvent sufficiently. The heating method can be performed by any known method such as hot air, infrared rays, and microwaves. Moreover, you may carry out in inert gas atmosphere, such as nitrogen.

(Solvent extraction process)
In the present invention, the polymer electrolyte membrane obtained through the solvent removal step is brought into contact with a poor solvent that is miscible with the solvent used to prepare the cast membrane and does not dissolve the polymer electrolyte, thereby The amount of the solvent in the electrolyte membrane can be adjusted by extracting the solvent remaining in the electrolyte membrane.

  As a poor solvent used at this process, what is necessary is just to use an appropriate thing according to the kind of electrolyte membrane and the solvent used at the casting process. For example, water, alcohol, ketone, ether, low molecular hydrocarbon, halogen-containing solvent and the like can be mentioned. When the solvent used in the casting process is miscible with water, it is preferable to use water as the poor solvent.

  The method of extracting the solvent in the electrolyte membrane with a poor solvent is not particularly limited, but it is preferable to carry out so that the poor solvent uniformly contacts the electrolyte membrane. For example, a method of immersing the electrolyte membrane in a poor solvent and a method of applying or spraying the poor solvent to the electrolyte membrane can be mentioned. These methods may be performed in two or more times or in combination.

  The temperature of the poor solvent is preferably not lower than the melting point and not higher than the boiling point of the poor solvent to be used. When the poor solvent is water, it is preferably in the range of 20 to 70 ° C, more preferably 20 to 50 ° C. When the temperature is high, the extraction efficiency of the solvent is improved, but the form and performance of the membrane may be lowered. Further, when the temperature is low, the extraction efficiency of the solvent is lowered, and the productivity may be lowered.

  In this step, the content of the solvent in the electrolyte membrane is preferably 2.0% by mass or less by contact with the poor solvent. When it is larger than 2.0% by mass, the shape retention of the electrolyte membrane may be deteriorated. In addition, although it does not specifically limit about the minimum of the content rate of a solvent, It is preferable that it is 0.3 mass%. If it is less than 0.3% by mass, production problems such as peeling of the film from the support may occur in the subsequent steps.

(Ion exchange group conversion process)
When the ion exchange group of the polymer electrolyte membrane obtained through the above steps is a metal salt of a sulfonic acid group, an acidic component solution having a pKa of 3 or less (hereinafter simply referred to as “acidic solution”) And the step of converting the salt of the ion exchange group possessed by the polymer electrolyte membrane having a solvent content of 2.0 mass% or less into protons.

  The acidic solution having a pKa of 3 or less used in this step is at least selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, perchloric acid, methanesulfonic acid, trifluoroacetic acid, sulfonimide, oxo acid and the like. An aqueous solution in which one kind of acidic component is dissolved may be mentioned, and the pKa of the acidic component is preferably equal to or smaller than the ion exchange group salt of the polymer electrolyte. The acidic component is preferably sulfuric acid, hydrochloric acid, methanesulfonic acid, or trifluoroacetic acid, and more preferably sulfuric acid. Although the density | concentration of the acidic component in an acidic solution is not specifically limited, For example, the range of 1-75 mass% is preferable. If the concentration is less than 1% by mass, a large amount of acidic solution is required for conversion to protons, which may cause a problem in productivity. When the concentration exceeds 75% by mass, the dissociation degree of the acidic component in the acidic solution may decrease, and the conversion efficiency may decrease.

  Note that the polymer electrolyte membrane converted into the sulfonic acid group may be treated with an arbitrary metal ion compound and converted into a metal salt again at an arbitrary stage. In particular, when the ion exchange group of the polymer electrolyte membrane obtained through the above steps is a salt of a metal other than magnesium, and when obtaining a magnesium salt of a sulfonic acid group from such a polymer electrolyte membrane, a sulfone group is used. When most of the acid group salts are converted to sulfonic acid groups and then treated with a magnesium compound, it is preferable because ion exchange can be performed uniformly to the inside of the membrane.

  The method for converting the salt of the ion exchange group of the polymer electrolyte membrane into protons using an acidic solution is not particularly limited, but it is preferable that the acidic solution be uniformly contacted with the electrolyte. For example, a method of immersing the electrolyte membrane in an acidic solution and a method of applying or spraying the acidic solution to the electrolyte membrane can be mentioned. These methods may be performed in two or more times or in combination.

(Washing process)
When acidic components or free metal ions remain in the polymer electrolyte membrane by contact with the acidic solution, the polymer electrolyte is brought into contact with a poor solvent of the polymer electrolyte membrane that can dissolve the acidic components. You may perform operation which removes the acidic component in a film | membrane. Examples of the poor solvent used include water, alcohols, ketones, ethers, low molecular hydrocarbons, and halogen-containing solvents. When the acidic component is dissolved in water, it is preferable to use water.

  The content of the acidic component in the polymer electrolyte membrane is preferably 1% by mass or less, and more preferably 0.1% by mass or less. If the content of the acidic component is large, the acidic component may be eluted, causing corrosion and chemical damage.

  The method for bringing the poor solvent into contact with the polymer electrolyte membrane is not particularly limited, and the method may be the same as the method for extracting the solvent in the electrolyte with the poor solvent.

(Support by support)
In the film formation method of the present invention, after the solvent removal step, the electrolyte membrane may be peeled off from the support and the subsequent steps (solvent extraction step or ion exchange group conversion step) may be performed. It is preferable to perform all the steps included in the method in a state where the film is supported by the support (in other words, the film is not peeled off from the support). When the membrane is peeled off from the support, the polymer electrolyte membrane may be deteriorated in shape, such as wrinkles or irregularities in the polymer electrolyte membrane.

(Characteristics of polymer electrolyte membrane)
The thickness of the polymer electrolyte membrane of the present invention is preferably 40 μm or less, more preferably 35 μm or less (more preferably 30 μm or less). If the thickness of the polymer electrolyte membrane is larger than 40 μm, it tends to be difficult to obtain a balance between characteristics, form (quality), and productivity. The lower limit of the thickness of the polymer electrolyte membrane is 1 μm (more preferably 3 μm). When the thickness of the polymer electrolyte membrane is less than 1 μm, it becomes difficult to handle the polymer electrolyte membrane, and a short circuit or the like may occur when a magnesium secondary battery is manufactured.

  The electrolyte membrane of the present invention may be a porous body. The method for obtaining the porous body is not particularly limited, and any method can be used. For example, when removing the solvent from the cast film, the cast film is brought into contact with the poor solvent, or particles that are soluble in the poor solvent and insoluble in the solvent are added to the electrolyte solution. A porous body can be obtained by dissolving with.

  In the case of a porous body, the porosity is preferably 10 to 90% by volume, and more preferably 20 to 80% by volume. When the porosity is large, it may be difficult to maintain the shape, and when the porosity is small, the performance as an electrolyte membrane may be deteriorated. The size of the pores is preferably in the range of 0.001 to 1 μm as an average, and more preferably in the range of 0.005 to 0.5 μm. If the pores are large, it may be difficult to maintain the shape, and if the pores are small, the performance as an electrolyte membrane may be reduced.

  The shape of the polymer electrolyte membrane obtained by the above method is not particularly limited, and may be any form such as a sheet or a roll. In addition, the support used in producing the polymer electrolyte membrane may not be peeled off, but it is preferable to peel after the production and to laminate the polymer electrolyte membrane with another support because the workability is improved. Another support includes a resin film having an adhesive layer. Examples of such a resin film include, but are not limited to, those made of crystallized polyolefin, amorphous polyolefin, polyester, and the like. Examples of the adhesive layer include, but are not limited to, an acrylic resin adhesive, a polyethylene-vinyl alcohol adhesive, a silicone adhesive, a modified polyolefin resin adhesive, and the like. The new support can be laminated on one or both sides of the polymer electrolyte membrane. When laminating a new support only on one side of the polymer electrolyte membrane, it is preferable to wrap the polymer electrolyte membrane on the inside because it is less affected by changes in humidity during transportation and storage. . The support may be peeled off when using the polymer electrolyte membrane.

(Electrolyte for magnesium secondary battery)
The electrolyte for a magnesium secondary battery of the present invention preferably includes an electrolyte solution in addition to the polymer electrolyte. For example, an embodiment in which a polymer electrolyte is impregnated with an electrolyte solution can be mentioned. The method of impregnating the polymer electrolyte with the electrolyte solution is not particularly limited, and a method of immersing the polymer electrolyte membrane obtained through the above steps in the electrolyte solution or the electrolyte solution in the polymer electrolyte membrane The method of apply | coating or spraying is mentioned. The content of the electrolyte solution in the polymer electrolyte is preferably 1 to 99% by mass, and more preferably 10 to 90% by mass.

  The electrolyte is not particularly limited, and examples thereof include magnesium salts such as magnesium perchlorate, magnesium chloride, magnesium trifluoromethanesulfonate, and bis (trifluorosulfonyl) imidomagnesium. The solvent for dissolving or dispersing the electrolyte is not particularly limited, and examples thereof include propylene carbonate, ethylene carbonate, dimethyl carbonate, dimethoxyethane, and ionic liquid. The magnesium salt concentration in the electrolyte solution is preferably in the range of dissolution, and is preferably 40% by weight or less (more preferably 25% by weight or less).

(Magnesium secondary battery)
The magnesium secondary battery of the present invention may be configured using any positive electrode or negative electrode as long as the polymer electrolyte (membrane) is used as the electrolyte. Further, the shape is not limited. For example, a magnesium secondary battery in which a mixture of manganese oxide, graphite, and polyvinylidene chloride is used as the positive electrode, a magnesium plate is used as the negative electrode, and the positive electrode and the negative electrode are stacked on both sides of the polymer electrolyte membrane, respectively.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to these examples, and can be implemented with appropriate modifications within a range that can be adapted to the above and the gist described below. These are all included in the technical scope of the present invention. In the following examples and comparative examples, “parts” and “%” mean parts by mass and mass%, respectively.

  First, the logarithmic viscosity, residual solvent amount, Tg, ion exchange capacity, metal ion concentration of the polymer electrolyte (membrane) produced according to the examples and comparative examples, and the measurement method of the charge / discharge test of the magnesium secondary battery will be described below. To do.

<Logarithmic viscosity of polymer electrolyte>
The polymer electrolyte was dissolved in N-methylpyrrolidone at a concentration of 0.5 g / dL, and the viscosity was measured using a Ubbelohde viscometer in a constant temperature bath at 30 ° C., and the logarithmic viscosity ln [ta / tb] / c (Ta is the drop time of the sample solution, tb is the drop time of the solvent only, and c is the polymer concentration of the sample solution [unit: g / dL]).

<Measurement of residual solvent>
The solvent of the polymer electrolyte is wiped off with a filter paper, left in a room at 23 ° C. and 50% RH for 1 hour, dissolved in deuterated dimethyl sulfoxide, and a total number of times of 128 times using a Varian Varian 400-MR. ¹ H-NMR spectrum was measured at 25 ° C. The residual solvent amount with respect to the polymer electrolyte was calculated from the integral value of the peak with respect to the polymer electrolyte and the solvent previously assigned.

<Tg of polymer electrolyte>
Using a Rheogel-E4000 manufactured by UBM, for a 5 mm wide polymer electrolyte (membrane), the storage elastic modulus (E1) and loss elastic modulus (T1) in tensile mode were increased from room temperature to 250 ° C. at 2 ° C./min. E2) was measured. The temperature at which tan δ determined as the ratio of the loss elastic modulus (E2) to the storage elastic modulus (E1) has a maximum value was defined as Tg.

<Ion exchange capacity of polymer electrolyte>
The polymer electrolyte (membrane) was dried at 110 ° C. for 1 hour, allowed to stand overnight at room temperature in a nitrogen atmosphere, weighed, then stirred with an aqueous sodium hydroxide solution, and then subjected to ion exchange capacity by back titration with an aqueous hydrochloric acid solution. Asked.

<Metal ion concentration of polymer electrolyte>
Metal ions in the polymer electrolyte were quantified by inductively coupled plasma optical emission spectrometry.

<Charge / discharge test of magnesium secondary battery>
For the magnesium secondary battery, a charge / discharge cycle test was performed at a constant current of 0.5 mA / cm ² and a turn-back voltage of 0 V and 2 V, and the discharge capacity at the time of two cycles was measured.

Example 1
<Manufacture of polymer electrolyte>
The reactor was charged with 778 parts of sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (S-DCDPS), 374 parts of 2,6-dichlorobenzonitrile (DCBN), 4,4′-biphenol (BP ) 723 parts, potassium carbonate 547 parts, and N-methyl-2-pyrrolidone (NMP) 4910 parts were added and reacted at 200 ° C. for 16 hours in a nitrogen atmosphere. After allowing to cool, the polymer was precipitated in water as a strand, and the resulting polymer was washed 5 times with 10 L of water and then dried to obtain a polymer electrolyte. The logarithmic viscosity of this polymer electrolyte was 1.42 dL / g.

<Manufacture of polymer electrolyte membrane>
A 24% polymer electrolyte solution was prepared using NMP as a solvent. Next, an electrolyte solution was continuously cast on a non-adhesive polyethylene terephthalate film as a support with a blade coater at a temperature of 25 ° C. so as to have a thickness of 200 μm, and then dried at 80 ° C. for 60 minutes. Was removed. The residual amount of NMP was 21%.

  The obtained polymer electrolyte membrane was immersed in water at 0 ° C. for 20 minutes without peeling from the support to extract the solvent. The residual amount of NMP was 0.2%.

  Tg measurement was performed on the polymer electrolyte membrane after solvent extraction, but no Tan δ peak was present. Even when the temperature increased (250 ° C.), E1 and E2 hardly decreased, and Tg was 250 ° C. or higher. Further, the ion exchange capacity of the polymer electrolyte membrane was 2.0 meq / g.

  After solvent extraction, the polymer electrolyte membrane is immersed in a 20% sulfuric acid aqueous solution (pKa = −3.0) at 30 ° C. for 30 minutes without peeling off the support, and then the polymer electrolyte membrane is not peeled off from the support. After immersing in pure water at 30 ° C. for 15 minutes, it was further immersed in pure water at 30 ° C. for 15 minutes. Thereafter, the substrate is immersed in a 2 mol / L magnesium sulfate aqueous solution at 30 ° C. for 60 minutes without peeling off the polymer electrolyte membrane from the support, and then in pure water at 30 ° C. for 15 minutes without peeling off the polymer electrolyte membrane from the support. After soaking, it was further soaked in another 30 ° C. pure water for 15 minutes. Thereafter, the polymer electrolyte membrane was air-dried at 30 ° C. for 10 minutes without removing the polymer electrolyte membrane from the support to obtain a 30 μm thick polymer electrolyte membrane laminated on the support. The Mg ion concentration in the electrolyte membrane was 0.9 meq / g.

<Manufacture of electrolyte for magnesium secondary battery>
The obtained polymer electrolyte membrane was cut into a circle having a diameter of 16 mm, dried at 120 ° C. for 1 hour to remove moisture, and then dried into 20% magnesium perchlorate-containing propylene carbonate (electrolyte solution) under a dry nitrogen atmosphere. It was immersed for 1 hour at room temperature to produce an electrolyte for a magnesium secondary battery containing an electrolyte solution.

<Manufacture of magnesium secondary battery>
A circular pellet having a diameter of 15 mm and a thickness of 200 μm obtained by mixing manganese oxide, graphite and polyvinylidene chloride in a ratio of 80: 18: 2 as a positive electrode, and a circular magnesium plate having a diameter of 15 mm and a thickness of 1 mm as a negative electrode, respectively. Used, superimposed on both sides of the electrolyte membrane obtained through the above steps, put in the positive electrode can with the positive electrode facing down, and further overlapped and fitted the insulating gasket and negative electrode cup, coin type of outer diameter 18mm, height 2mm A magnesium ion secondary battery was produced.

  When the charging / discharging test of the obtained magnesium secondary battery was done, the discharge capacity was 120 mAh / g.

(Example 2)
<Manufacture of polymer electrolyte membrane>
In the same manner as in Example 1, a 24% polymer electrolyte solution using NMP as a solvent was prepared. Next, an electrolyte solution was continuously cast on a non-adhesive polyethylene terephthalate film as a support at a temperature of 25 ° C. with a blade coater so as to have a thickness of 250 μm, and then 25 ° C. and a relative humidity of 90% (saturated steam). The film was continuously exposed for 1 minute in an atmosphere where the water vapor pressure was 90%) and then immersed in water at 25 ° C. for 10 minutes every 3 minutes to obtain a film from which the solvent was removed. Thereafter, the polymer electrolyte membrane is immersed in a 20% sulfuric acid aqueous solution (pKa = −3.0) at 30 ° C. for 30 minutes without peeling the polymer electrolyte membrane from the support, and then the polymer electrolyte membrane is not peeled off from the support 30. After dipping in pure water at 15 ° C. for 15 minutes, it was further immersed in pure water at 30 ° C. for 15 minutes. Thereafter, the substrate is immersed in a 2 mol / L magnesium sulfate aqueous solution at 30 ° C. for 60 minutes without peeling off the polymer electrolyte membrane from the support, and then in pure water at 30 ° C. for 15 minutes without peeling off the polymer electrolyte membrane from the support. After dipping, it was further dipped in another 30 ° C. pure water for 15 minutes to obtain a polymer electrolyte membrane having a thickness of 40 μm laminated on the support. The Mg ion concentration in the electrolyte membrane was 1.0 meq / g.

<Manufacture of electrolyte for magnesium secondary battery>
The obtained polymer electrolyte membrane was cut into a circle having a diameter of 16 mm, and after being immersed in a 10% aqueous solution of propylene carbonate, a 20% aqueous solution of propylene carbonate, and propylene carbonate in this order for 30 minutes, respectively, to remove water, In a dry nitrogen atmosphere, it was immersed in 20% magnesium perchlorate-containing propylene carbonate (electrolyte solution) at room temperature for 1 hour to produce an electrolyte for a magnesium secondary battery containing the electrolyte solution.

<Manufacture of magnesium secondary battery>
A coin-type magnesium ion secondary battery was produced in the same manner as in Example 1 except that the electrolyte membrane obtained through the above steps was used.

  When the charging / discharging test of the obtained magnesium secondary battery was done, the discharge capacity was 125 mAh / g.

(Comparative Example 1)
A magnesium ion secondary battery was fabricated in the same manner as in Example 1 except that a circular polypropylene porous film having a film thickness of 25 μm, an average pore diameter of 0.1 μm, and a diameter of 16 mm was used instead of the polymer electrolyte of Example 1. When the charge / discharge test was conducted, the discharge capacity was 5 mAh / g.

  The magnesium secondary battery electrolyte of the present invention includes a polymer electrolyte having a glass transition temperature of 150 ° C. or higher and an ion exchange capacity of 1 to 5 meq / g. An ion secondary battery can be provided and greatly contributes to the industrial world.

Claims (4)

  An electrolyte for a magnesium secondary battery, comprising a polymer electrolyte having a glass transition temperature of 150 ° C. or higher and an ion exchange capacity of 1 to 5 meq / g.   The electrolyte for a magnesium secondary battery according to claim 1, wherein the polymer electrolyte has an aromatic group, a sulfonic acid group and / or a metal salt thereof.   The electrolyte for a magnesium secondary battery according to claim 2, wherein the metal salt is a magnesium salt.   The magnesium secondary battery using the electrolyte for magnesium secondary batteries as described in any one of Claims 1-3.