WO2021125250A1

WO2021125250A1 - Polymer membrane and nonaqueous electrolyte battery

Info

Publication number: WO2021125250A1
Application number: PCT/JP2020/047072
Authority: WO
Inventors: 俊充田中; 有紀太田; 真緒 ▲高▼山; 能久乾
Original assignee: 株式会社クラレ
Priority date: 2019-12-18
Filing date: 2020-12-17
Publication date: 2021-06-24

Abstract

The present invention relates to a polymer membrane for nonaqueous electrolyte batteries, said polymer membrane containing a polyvinyl acetal resin that has a hydroxyl group amount of from 56% by mole to 90% by mole.

Description

Polymer membrane and non-aqueous electrolyte battery

The present invention relates to polymer membranes and non-aqueous electrolyte batteries.

In recent years, with the spread of mobile terminals such as mobile phones, notebook computers, pad-type information terminal devices, electric vehicles, hybrid vehicles, etc., various non-aqueous electrolyte batteries have been developed. , Development is being carried out with an emphasis on increasing capacity.

For example, it has been studied to use a silicon-based negative electrode active material having a larger theoretical capacity per mass than a conventional carbon-based negative electrode active material as the negative electrode active material to increase the energy density (Patent Document 1). Further, it has been studied to use metallic lithium having a theoretical capacity of 3861.7 mAh / g as the negative electrode active material (Patent Document 2).

Further, as a positive electrode active material, a lithium-sulfur secondary battery using sulfur having a theoretical capacity of 1672 mAh / g has been developed (Patent Document 3).

Along with the increase in output and capacity of batteries, higher safety is also required.

Regarding the improvement of safety, an all-solid-state battery using a solid electrolyte is being studied. For example, Patent Document 4 discloses, as an organic solid electrolyte, a polymer electrolyte containing polyvinyl acetal and an ionic dissociable salt as main components and substantially composed of only solid content (Patent Document 4).

Further, as a non-aqueous electrolyte battery, a battery using a gel-like polymer electrolyte in which a polymer compound holds an electrolytic solution is also being studied. For example, Patent Document 5 discloses a secondary battery including a polymer electrolyte containing polyvinyl acetal, a solvent, and an electrolyte salt.

Japanese Unexamined Patent Publication No. 2018-20602 Japanese Unexamined Patent Publication No. 2017-16904 International Publication No. 2016/068043 Japanese Patent No. 362030 Japanese Patent No. 4466416

When a silicon-based negative electrode active material is used for high output and high capacity, the silicon-based negative electrode active material has a large expansion and contraction during charging and discharging, so that the electrodes are liable to crack or have defects due to charging and discharging, and the battery life. And stability may decrease. Further, when metallic lithium is used, dendrites (dendritic Li) are formed on the lithium negative electrode thin film during charging, which may cause an internal short circuit and ignition. Further, when sulfur is used as the positive electrode active material, the reaction intermediate product may elute and the battery life may be shortened.

All-solid-state batteries can impart flame retardancy and thermal / chemical stability to the electrolyte, so it is easy to ensure safety and durability, but higher output, higher capacity, and longer battery life. It is difficult to achieve both, and it cannot be said that the all-solid-state battery has sufficiently high ionic conductivity as compared with the liquid-based battery.

Therefore, an object of the present invention is to provide a polymer film for a non-aqueous electrolyte battery, which has high ionic conductivity and can contribute to extending the life of the battery.

The present inventors have repeated detailed studies in order to solve the above-mentioned problems, and have completed the present invention. That is, the present invention includes the following preferred embodiments.
[1] A polymer film for a non-aqueous electrolyte battery containing a polyvinyl acetal-based resin having a hydroxyl group content of 56 to 90 mol%.
[2] When immersed in diethyl carbonate at 60 ° C. for 1 hour, the following formula:

[In the formula, A represents the mass (g) of the polymer film before immersion, and B represents the dry mass (g) of the polymer film after immersion].
The polymer membrane according to the above [1], wherein the dissolution rate calculated by the above method is 7% or less.
[3] When immersed in a solution in which lithium bis (fluorosulfonyl) imide was dissolved in 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide at a concentration of 1 mol / L at 25 ° C. for 24 hours, the following Formula:

[In the formula, C represents the mass (g) of the polymer film before immersion, and D represents the mass (g) of the polymer film after immersion].
The polymer film according to the above [1] or [2], wherein the swelling rate calculated by the above method is 20% or more.
[4] The polymer film according to any one of [1] to [3] above, wherein the polyvinyl acetal resin has a hydroxyl group content of 62 to 90 mol%.
[5] When immersed in a solution in which lithium bis (fluorosulfonyl) imide was dissolved in 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide at a concentration of 1 mol / L at 25 ° C. for 24 hours, the following Formula:

[In the formula, C represents the mass (g) of the polymer film before immersion, and D represents the mass (g) of the polymer film after immersion].
The polymer film according to the above [4], wherein the swelling rate calculated by the above method is 40% or more.
[6] The polymer film for a non-aqueous electrolyte battery according to the above [1], wherein the polyvinyl acetal-based resin has a crosslinked structure.
[7] When immersed in diethyl carbonate at 60 ° C. for 1 hour, the following formula:

[In the formula, A represents the mass (g) of the polymer film before immersion, and B represents the dry mass (g) of the polymer film after immersion].
The polymer membrane according to the above [6], wherein the dissolution rate calculated by the above method is 2% or less.
[8] When immersed in a solution in which lithium bis (fluorosulfonyl) imide was dissolved in 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide at a concentration of 1 mol / L at 25 ° C. for 24 hours, the following Formula:

[In the formula, C represents the mass (g) of the polymer film before immersion, and D represents the mass (g) of the polymer film after immersion].
The polymer film according to the above [6] or [7], wherein the swelling rate calculated by the above method is 20% or more.
[9] The polymer membrane according to any one of [6] to [8] above, wherein the crosslinked structure is a structure derived from a crosslinking agent having a reactive group for a hydroxyl group.
[10] The polymer membrane according to any one of [1] to [9] above, wherein the polyvinyl acetal-based resin is at least one selected from the group consisting of polyvinyl butyral, polyvinyl nonanal and polyvinyl octanal.
[11] The polymer film according to any one of [1] to [10] above, wherein the polyvinyl acetal-based resin has a degree of polymerization of 250 to 5,000.
[12] The polymer film according to any one of [1] to [11] above, wherein the degree of saponification of the polyvinyl acetal resin is 90 mol% or more.
[13] A non-aqueous electrolyte battery comprising the polymer membrane according to any one of the above [1] to [12].

According to the present invention, it is possible to provide a polymer film for a non-aqueous electrolyte battery, which has high ionic conductivity and can contribute to extending the life of the battery.

Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention.

The polymer membrane of the present invention is a polymer membrane for non-aqueous electrolyte batteries, and contains a polyvinyl acetal-based resin having a hydroxyl group content of 56 to 90 mol%.

(Polyvinyl acetal resin)
The polyvinyl acetal-based resin contained in the polymer film of the present invention has a hydroxyl group content of 56 to 90 mol%, preferably 58 to 90 mol%, more preferably 60 to 90 mol%, still more preferably 62 to 90 mol%. Have. When the amount of hydroxyl groups of the polyvinyl acetal-based resin is less than 56 mol%, the solubility of the polyvinyl acetal-based resin in the electrolytic solution becomes high, and the polyvinyl acetal-based resin is easily dissolved in the electrolytic solution. As a result, the polymer film is easily affected by the electrolytic solution, the mechanical strength of the polymer film is lowered, and the life of the battery containing the polymer film is easily shortened. Further, the polymer film is easily dissolved in the electrolytic solution, which may cause a decrease in battery safety. Further, when the amount of hydroxyl groups of the polyvinyl acetal resin exceeds 90 mol%, in addition to industrial difficulty in synthesis, the swelling property of the polymer film is also lowered, and the ionic conductivity cannot be sufficiently enhanced. .. In addition, the solubility of the polyvinyl acetal-based resin in an organic solvent is lowered, and the film-forming property of the polymer film is lowered.

It is not clear why a polymer membrane containing a polyvinyl acetal resin having a hydroxyl group amount within the above range has high ionic conductivity and can contribute to extending the life of a battery, but for example, high electrolytic solution resistance. It is considered that the present invention has swellability, mechanical strength, and the like, and the present invention is not limited to the mechanism described later, but the following reasons can be considered. When the polyvinyl acetal resin contained in the polymer film has many hydroxyl groups, hydrogen bonds between the hydroxyl groups result in a partially crystalline film, which enhances the strength of the gel-like polymer film swollen with the electrolytic solution. Therefore, it is considered that the mechanical stability can be improved. Further, since the number of hydroxyl groups is large, the solubility in an organic solvent can be reduced and the electrolytic solution resistance can be improved. Further, it is considered that the large number of hydroxyl groups makes it easy to promote the dissociation of the lithium salt in the non-aqueous electrolyte battery and enhance the ionic conductivity. Further, since the resin has an acetalized structure, even when there are many hydroxyl groups, the acetal group acts as a spacer between the polymer chains due to steric hindrance due to the acetal group, and the polymer film is swollen by the electrolytic solution. Can be promoted. As a result, it is considered that high ionic conductivity can be achieved.

The amount of hydroxyl groups in the polyvinyl acetal-based resin is preferably 58 mol% or more, more preferably 60 mol% or more, still more preferably 62 mol% or more, still more preferably, from the viewpoint of easily improving the chemical stability of the polymer film. Is 63 mol% or more, particularly preferably 67 mol% or more, particularly more preferably 70 mol% or more, and extremely preferably 73 mol% or more. Further, the amount of the hydroxyl group is preferably 89 mol% or less from the viewpoint of easily increasing the swelling rate of the polymer film and easily improving the ionic conductivity and easily improving the production efficiency of the polymer film. It is preferably 88 mol% or less, still more preferably 85 mol% or less, and even more preferably 80 mol% or less. The amount of hydroxyl groups in the polyvinyl acetal resin can be calculated by the method described in Examples.

Here, the amount of hydroxyl groups of the polyvinyl acetal-based resin is desired by a method of adjusting the amount of the raw material polyvinyl alcohol resin with respect to aldehyde when synthesizing the polyvinyl acetal-based resin, a method of adjusting the saponification degree of the raw material polyvinyl alcohol, or the like. It can be adjusted to a range.

The degree of acetalization of the polyvinyl acetal-based resin is preferably 10 to 38 mol%, more preferably 10 to 35 mol%, still more preferably 10 to 38 mol%, in terms of the total acetalization degree regardless of whether acetalization of a single aldehyde or a mixed aldehyde is used. Is 10 to 34 mol%, even more preferably 11 to 32 mol%, particularly preferably 11 to 30 mol%, and most preferably 12 to 30 mol%. When the degree of acetalization is at least the above lower limit, it is easy to improve the low solubility of the polymer membrane in the electrolytic solution (electrolyte resistance) and the electrochemical stability (oxidation-reduction resistance). When the degree of acetalization is not more than the above upper limit, the swelling of the polymer membrane containing the polyvinyl acetal resin due to the electrolytic solution is appropriately increased, and the ionic conductivity of the non-aqueous electrolyte battery containing the polymer film is likely to be improved. The degree of acetalization can be calculated by, for example, the method described in Examples. The degree of acetalization of the polyvinyl acetal-based resin is adjusted to the above desired range by a method of adjusting the amount of aldehyde with respect to the raw material polyvinyl alcohol resin when synthesizing the polyvinyl acetal-based resin, a method of adjusting the degree of saponification of the raw material polyvinyl alcohol, or the like. can do.

The amount of acetyl group in the polyvinyl acetal resin is preferably 10 mol% or less, more preferably 5 mol% or less, still more preferably 1 mol% or less. The amount of the acetyl group is preferably 0.1 mol% or more. When the amount of the acetyl group is not more than the above upper limit, it is easy to prevent the polyvinyl acetal resin from being dissolved in the electrolytic solution, and it is easy to improve the electrochemical stability (oxidation-reduction resistance) and the mechanical strength. Further, if it is equal to or higher than the above lower limit, the affinity of the residual ester group derived from the resin manufacturing process for the organic solvent is likely to be lowered, and the solubility and swelling degree in the organic solvent are likely to be lowered. It is easy to stabilize the slurry. The amount of acetyl group can be calculated by, for example, the method described in Examples. The amount of acetyl groups in the polyvinyl acetal-based resin can be adjusted to the above-mentioned desired range by a method of adjusting the saponification degree of the raw material polyvinyl alcohol.

The degree of polymerization of the polyvinyl acetal resin is preferably 250 or more, more preferably 300 or more, still more preferably 1,000 or more, and particularly preferably 1,500 or more. The degree of polymerization is preferably 5,000 or less, more preferably 4,000 or less, still more preferably 3,000 or less, and even more preferably 2,000 or less. When the degree of polymerization is not more than the above upper limit, the resin has good solubility in a solvent and a homogeneous film can be easily obtained. Further, when it is at least the above lower limit, the film forming property is good and the electrolytic solution resistance can be easily obtained. The degree of polymerization can be measured according to JIS-K6726. The degree of polymerization of the polyvinyl acetal-based resin can be adjusted to the above-mentioned desired range by a method of adjusting the degree of polymerization of the raw material polyvinyl alcohol resin (or the raw material polyvinyl acetate resin).

The saponification degree of the polyvinyl acetal resin is preferably 90 mol% or more, more preferably 95 mol% or more, and further preferably 99 mol% or more. When the saponification degree is equal to or higher than the above lower limit, the affinity of the residual ester group derived from the resin manufacturing process with respect to the organic solvent is likely to be lowered, and the solubility in the organic solvent and the degree of swelling are likely to be lowered. It is easy to stabilize the slurry. The upper limit of the saponification degree is preferably 99.9 mol% or less. In the present specification, the saponification degree of the polyvinyl acetal-based resin means the saponification degree of the polyvinyl alcohol-based resin before acetalization, and can be measured according to JIS-K6726.

Examples of the polyvinyl acetal-based resin include a resin obtained by acetalizing a polyvinyl alcohol-based resin.

The polyvinyl alcohol-based resin mainly has a structural unit derived from vinyl alcohol and a structural unit derived from vinyl ester, but a configuration derived from a monomer other than these structural units as long as the effect of the present invention is not impaired. It may include units. Other monomers include α-olefins such as ethylene, propylene, 1-butene, isobutene and 1-hexene; acrylic acid, methacrylic acid, crotonic acid, phthalic acid, phthalic anhydride, maleic acid and maleine anhydride. Unsaturated acids such as acids, itaconic acids, itaconic acids anhydride and salts thereof or alkyl esters thereof having 1 to 18 carbon atoms; acrylamide, N-alkylacrylamide having 1 to 18 carbon atoms, N, N-dimethylacrylamide, 2- Acrylamides such as acrylamide propanesulfonic acid and its salts, acrylamidepropyldimethylamine and its acid salts or quaternary salts thereof; methacrylamide, N-alkylmethacrylicamide having 1 to 18 carbon atoms, N, N-dimethylmethacrylate, 2 -Methylamides such as methacrylamide propanesulfonic acid and its salts, methacrylicamide propyldimethylamine and its salts or quaternary salts thereof; N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide. Vinyl cyanide such as acrylonitrile and methacrylonitrile; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether and n-butyl vinyl ether; allyl acetate; propyl allyl ether, butyl allyl ether, hexyl Allyl ethers such as allyl ethers; vinyl halides such as vinyl chloride, vinyl fluoride, vinyl bromide; vinylidene halides such as vinylidene chloride and vinylidene fluoride; vinylsilanes such as trimethoxyvinylsilane; polyoxyalkylene allyl Compounds having an oxyalkylene group such as ether; isopropenyl acetate; 3-butene-1-ol, 4-pentene-1-ol, 5-hexene-1-ol, 7-octen-1-ol, 9-decene- Hydroxy group-containing α-olefins such as 1-ol and 3-methyl-3-buten-1-ol; derived from fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride, etc. Compounds having a carboxyl group; ethylene sulfonic acid, allylsulfonic acid, metaallylsulfonic acid, monomers having a sulfonic acid group derived from 2-acrylamide-2-methylpropanesulfonic acid, etc .; vinyloxyethyltrimethylammonium chloride, Vinyloxybutyltrimethylammonium Lolide, vinyloxyethyl dimethylamine, vinyloxymethyl diethylamine, N-acrylamide methyl trimethyl ammonium chloride, N-acrylamide ethyl trimethyl ammonium chloride, N-acrylamide dimethylamine, allyl trimethyl ammonium chloride, methallyl trimethyl ammonium chloride, dimethyl allyl amine, allyl Examples thereof include compounds having a cationic group derived from ethylamine and the like. Among these, α-olefins such as ethylene, propylene, 1-butene, isobutene and 1-hexene; N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide from the viewpoint of availability and copolymerizability. N-vinylamides such as: methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether and other vinyl ethers; allyl acetate; propyl allyl ether, butyl allyl ether, hexyl allyl ether and the like. Classes; monomers having an oxyalkylene group such as polyoxyalkylene allyl ether; 3-butene-1-ol, 4-pentene-1-ol, 5-hexene-1-ol, 7-octen-1-ol, Hydroxy group-containing α-olefins such as 9-decene-1-ol and 3-methyl-3-butene-1-ol are preferable. These monomers can be used alone or in combination of two or more.

The content of the structural units derived from other monomers other than the structural units derived from vinyl alcohol and the structural units derived from vinyl ester is usually 20 with respect to the total number of moles of the structural units constituting the polyvinyl alcohol-based resin. It is mol% or less, preferably 10 mol% or less, and more preferably 5 mol% or less.

The polyvinyl alcohol-based resin can be produced by a known method, for example, a method of saponifying a resin obtained by polymerizing vinyl alcohol and the above-mentioned monomer in a solvent such as alcohol. Examples of the solvent used in this method include lower alcohols such as methanol and ethanol, and methanol can be preferably used. The solvent used for the saponification reaction preferably contains a solvent such as acetone, methyl acetate, ethyl acetate, and benzene in an amount of, for example, 40% by mass or less based on the total amount of the solvent used, in addition to the above-mentioned lower alcohol. You may be doing it. As the catalyst used in the saponification reaction, an alkali metal hydroxide such as potassium hydroxide or sodium hydroxide, an alkali catalyst such as sodium methoxyde, or an acid catalyst such as mineral acid is used. The temperature of the saponification reaction is not particularly limited, but is preferably in the range of 20 to 60 ° C. The vinyl alcohol-based resin obtained by the saponification reaction is washed and then dried.

The saponification degree of the polyvinyl alcohol-based resin is preferably 90 mol% or more, more preferably 95 mol% or more, and further preferably 99 mol% or more. When the saponification degree is equal to or higher than the above lower limit, the affinity of the residual ester group derived from the resin manufacturing process with respect to the organic solvent is likely to be lowered, the solubility in the organic solvent and the degree of swelling are likely to be lowered, and the slurry at the time of resin manufacturing is likely to be lowered. Is easy to stabilize. The upper limit of the saponification degree is preferably 99.9 mol% or less. As described above, the saponification degree of the polyvinyl acetal-based resin in the present specification is the saponification degree of the polyvinyl alcohol-based resin before acetalization.

The polyvinyl acetal-based resin can be produced, for example, by acetalizing the polyvinyl alcohol-based resin with an aldehyde. The acetalization method is not particularly limited, and examples thereof include a precipitation method and a solid-liquid reaction method. In the precipitation method, for example, water or acetone is used as a solvent, the raw material polyvinyl alcohol-based resin is dissolved in water or acetone, and a catalyst such as acid is added to carry out an acetalization reaction, and the produced polyvinyl acetal-based resin is produced. Is a method of precipitating and neutralizing the acid used as a catalyst to obtain a solid powder. The solid-liquid reaction method is a method in which the reaction can be carried out in the same manner as the precipitation method, except that a solvent in which the raw material polyvinyl alcohol-based resin is not dissolved is used. Regardless of which method is used, the obtained polyvinyl acetal-based resin powder contains impurities such as unreacted aldehydes and salts generated by neutralization. Therefore, the impurities are soluble in order to remove these impurities. A high-purity polyvinyl acetal-based resin can be obtained by extraction or evaporative removal using a different solvent.

Examples of the aldehyde used for acetalization include aliphatic aldehydes such as formaldehyde, acetaldehyde, propyl aldehyde, n-butyl aldehyde (1-butanal), sec-butyl aldehyde, octyl aldehyde, dodecyl aldehyde, and nonyl aldehyde; cyclohexanecarbaldehyde. , Cyclooctanecarbaldehyde, trimethylcyclohexanecarbaldehyde, cyclopentylaldehyde, dimethylcyclohexanecarbaldehyde, methylcyclohexanecarbaldehyde, methylcyclopentylaldehyde and other alicyclic aldehydes; α-campolenealdehyde, ferlandral, cyclocitral, trimethyltetra Terpen-based aldehydes such as hydrobenzaldehyde, α-pyronenaldehyde, miltenal, dihydromiltenal, and camphenilan aldehyde; aromatics such as benzaldehyde, naphthaldehyde, anthralaldehyde, phenylacetaldehyde, tolualdehyde, dimethylbenzaldehyde, cuminaldehyde, and benzylaldehyde. Group aldehydes; unsaturated aldehydes such as cyclohexene aldehydes, dimethylcyclohexene aldehydes, and acrolein; aldehydes having heterocycles such as furfural and 5-methylfurfural; hemiacetals such as glucose and glucosamine; having amino groups such as 4-aminobutylaldehyde. Examples include aldehydes. These aldehydes can be used alone or in combination of two or more. Also, instead of aldehyde or in combination with aldehyde, aliphatic ketones such as 2-propanone, methyl ethyl ketone, 3-pentanone and 2-hexanone; aliphatic alicyclic ketones such as cyclopentanone and cyclohexanone; and acetophenone, benzophenone and the like. It is also possible to use the aromatic ketone of. The aldehyde used for acetalization is preferably a fat from the viewpoint that it is easy to increase the free volume between the polymer chains due to the steric disorder of the acetal group, and as a result, it is easy to improve the swelling property by the electrolytic solution and improve the ionic conductivity. Group aldehydes, more preferably aliphatic aldehydes having 4 to 12 carbon atoms, even more preferably aliphatic aldehydes having 4 to 9 carbon atoms, even more preferably butyl aldehydes (butanal, butyral), nonyl aldehydes (nonanal), and octyl aldehydes. (Octanar). Therefore, the polyvinyl acetal-based resin is also preferably a polyvinyl acetal-based resin acetalized with an aliphatic aldehyde, and more preferably a polyvinyl acetal-based resin acetalized with an aliphatic aldehyde having 4 to 12 carbon atoms. A polyvinyl acetal-based resin acetalized with an aliphatic aldehyde having 4 to 9 carbon atoms is more preferable. The polyvinyl acetal-based resin is even more preferably at least one selected from the group consisting of polyvinyl butyral, polyvinyl nonanal and polyvinyl octanal.

As the acid catalyst, a known acid can be used, and examples thereof include inorganic acids such as sulfuric acid, hydrochloric acid and nitric acid, and organic acids such as paratoluenesulfonic acid. The acid catalyst is usually used in an amount such that the acid concentration in the final system of the acetalization reaction is 0.5 to 5.0% by mass, but the acid catalyst is not limited to this concentration. A predetermined amount of these acid catalysts may be added at one time, but in the case of the precipitation method, the polyvinyl acetal-based resin having relatively fine particles is added in an appropriate number of times in order to precipitate and precipitate. Is preferable. On the other hand, in the case of the solid-liquid reaction method, it is preferable to add a predetermined amount at the beginning of the reaction from the viewpoint of reaction efficiency.

In a preferred embodiment of the present invention, the polyvinyl acetal-based resin contained in the polymer film of the present invention has a crosslinked structure. The cross-linked structure is not particularly limited as long as it is a structure for cross-linking polyvinyl acetal-based resins with each other, but is preferably a structure derived from a cross-linking agent having a reactive group for a hydroxyl group, and more preferably an addition reaction with a hydroxyl group and / or. It is a structure derived from a cross-linking agent that undergoes a ring-opening reaction. When a cross-linking agent that undergoes an addition reaction or a ring-opening reaction with a hydroxyl group is used as the cross-linking agent, these cross-linking agents do not generate desorbed substances such as water during the cross-linking reaction. It is preferable because it is easy to prevent the mixture from being mixed inside the non-aqueous electrolyte battery. The polyvinyl acetal-based resin may have a cross-linked structure derived from one kind of cross-linking agent, or may have a cross-linked structure derived from two or more kinds of cross-linking agents. In the preferred embodiment, it is possible to provide a polymer film for a non-aqueous electrolyte battery, which has high mechanical strength and electrolytic solution resistance.

When the polyvinyl acetal resin contained in the polymer film of the present invention has a crosslinked structure, the crosslinking agent having a reactive group for a hydroxyl group (hereinafter, also referred to as “hydroxyl reactive group”) has a reactive group for a hydroxyl group. The cross-linking agent having at least one is not particularly limited, but for example, a compound having two or more hydroxyl-reactive groups, a compound having at least one hydroxyl-reactive group and at least one ethylenically unsaturated group, and the like can be used. Can be mentioned. Examples of the hydroxyl group reactive group include an isocyanate group, an epoxy group, a carboxyl group, an acid anhydride group, an aldehyde group, an acyl group and the like. The hydroxyl group-reactive group is preferably a group that does not generate desorbed substances such as water during the reaction with the hydroxyl group. Since such a cross-linking agent having a hydroxyl-reactive group does not generate an elimination product during the reaction with the uncross-linked polyvinyl acetal-based resin, impurities are not contained in the obtained polymer film. When a cross-linking agent having a hydroxyl group-reactive group that does not generate a desorbed product during the reaction with an uncrosslinked polyvinyl acetal resin is used, impurities such as desorbed products generated by the reaction react with an electrolytic solution, an active material, or the like. It is easy to prevent this from happening, and the possibility of affecting the battery can be reduced. From this point of view, the cross-linking agent is preferably a cross-linking agent that undergoes an addition reaction and / or a ring-opening reaction with a hydroxyl group, and is more preferably selected from the group consisting of an isocyanate group, an epoxy group and an acid anhydride group. A cross-linking agent having at least one hydroxyl group-reactive group.

When the cross-linking agent has at least one hydroxyl group-reactive group selected from the group consisting of, for example, an isocyanate group and an acid anhydride group, the cross-linking agent can be said to be a cross-linking agent that undergoes an addition reaction with a hydroxyl group. The cross-linking agent that undergoes an addition reaction with a hydroxyl group refers to a cross-linking agent that is added to an uncrosslinked polyvinyl acetal-based resin without the cross-linking agent being accompanied by an elimination reaction of water or the like. Further, when the cross-linking agent has, for example, at least one epoxy group as a hydroxyl-reactive group, it can be said that the cross-linking agent is a cross-linking agent that undergoes a ring-opening (ring-opening addition) reaction with the hydroxyl group.

The cross-linking agent is preferably a compound having two or more hydroxyl-reactive groups and / or a compound having at least one hydroxyl-reactive group and at least one ethylenically unsaturated group. When the cross-linking agent is a compound having two or more hydroxyl-reactive groups, one hydroxyl-reactive group of the cross-linking agent reacts with the hydroxyl group of the polyvinyl acetal-based resin before cross-linking, and the other hydroxyl-reactive group Reacts with another hydroxyl group of another polyvinyl acetal-based resin, whereby the polyvinyl acetal-based resin contains a crosslinked structure. Such cross-linking agents preferably include polyfunctional isocyanates, isocyanuric acid derivatives, polyfunctional epoxides, acid anhydrides and the like. Examples of the polyfunctional epoxide include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, diethylene glycol diglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and tripropylene. Examples thereof include glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether and their polymers, and triglycidyl isocyanurate. Examples of the polyfunctional isocyanate include hexamethylene diisocyanate, toluene 2,4-diisocyanate, 1,6-diisocyanate hexane, isofornyl diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenyl polyisocyanate. Examples of the acid anhydride include succinic anhydride, glutanic anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic acid anhydride, and cyclopentanetetracarboxylic acid dianhydride. Examples include phenylsuccinic anhydride and phenylsuccinic anhydride.

When the cross-linking agent is a compound having at least one hydroxyl-reactive group and at least one ethylenically unsaturated group, at least one hydroxyl-reactive group of the cross-linking agent is a hydroxyl group of the polyvinyl acetal resin before cross-linking. A cross-linking agent having an ethylenically unsaturated group is incorporated into the polyvinyl acetal-based resin. Next, the crosslinked structure can be introduced into the polyvinyl acetal-based resin by photocrosslinking (photopolymerizing) the ethylenically unsaturated groups with each other by photocrosslinking. The ethylenically unsaturated group is not particularly limited as long as it is a photocrosslinkable group, and for example, a (meth) acryloyl group, a vinyl group, an allyl group, a propagyl group, a butenyl group, an ethynyl group, a maleimide group, a nadiimide group, and the like. Examples thereof include (meth) acryloyloxy group and (meth) acryloylamide group, which are preferably (meth) acryloyl group, (meth) acryloyloxy group and (meth) acryloylamide group from the viewpoint of reactivity in photocrosslinking. ..

In one aspect of the present invention in which the polyvinyl acetal resin has a crosslinked structure, the polymer membrane of the present invention may contain a crosslinking accelerator. As the cross-linking accelerator, for example, an acid catalyst such as sulfuric acid, hydrochloric acid or acetic acid, a metal hydride such as sodium hydride, or a base such as a metal alkoxide such as sodium methoxide or sodium ethoxide can be used.

When the polyvinyl acetal resin has a cross-linked structure and the polymer film contains a cross-linking accelerator, the content thereof can be appropriately adjusted according to the type of the cross-linking agent contained in the polymer film and the amount thereof. With respect to 100 parts by mass of the cross-linking agent, 0.1 to 30 parts by mass is preferable, 0.5 to 10 parts by mass is more preferable, and 0.5 to 8 parts by mass is further preferable. When the content of the polymerization initiator is within this range, the electrolytic solution elution resistance of the polymer film can be further enhanced.

In one aspect of the present invention in which the polyvinyl acetal resin has a crosslinked structure, the polymer film of the present invention may contain a polymerization initiator. As the polymerization initiator, for example, when ultraviolet rays are used as active energy rays, photopolymerization initiators such as benzoin-based, acetophenone-based, thioxanthone-based, phosphine oxide-based and peroxide-based, sulfonium salt-based, and iodonium salt-based are used. be able to.

When the polyvinyl acetal resin has a crosslinked structure and the polymer film contains a polymerization initiator, the content thereof can be appropriately adjusted according to the type and amount of the crosslinked agent contained in the polymer film. With respect to 100 parts by mass of the cross-linking agent, 0.1 to 30 parts by mass is preferable, 0.5 to 10 parts by mass is more preferable, and 0.5 to 8 parts by mass is further preferable. When the content of the polymerization initiator is within this range, the electrolytic solution elution resistance of the polymer film can be further enhanced.

When the polyvinyl acetal resin has a crosslinked structure and the polymer film contains a photopolymerization initiator, the polymer film may further contain a photosensitizer. Photosensitizers include xanthone compounds such as xanthone, thioxanthone (eg, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, etc.); anthracene, alkoxy group-containing anthracene (eg, dibutoxyanthracene, etc.); Examples include phenothiazine and rubrene.

When the polyvinyl acetal resin has a crosslinked structure and the polymer film contains a photopolymerization initiator and a photosensitizer, the polymerization reaction of the polymerizable liquid crystal contained in the composition can be further promoted. The amount of the photosensitizer added can be appropriately adjusted according to the type and amount of the photopolymerization initiator and the cross-linking agent, but is preferably 0.1 to 30 parts by mass with respect to 100 parts by mass of the cross-linking agent. 5 to 10 parts by mass is more preferable, and 0.5 to 8 parts by mass is further preferable.

In one aspect of the present invention in which the polyvinyl acetal-based resin has a crosslinked structure, the polyvinyl acetal-based resin contained in the polymer film has a crosslinked structure, for example, a hydroxyl group-reactive group that does not generate desorbed substances during the crosslinking reaction. Having a cross-linked structure derived from the cross-linking agent has means that, for example, using a Fourier-converted infrared spectrophotometer or the like, disappearance of peaks derived from functional groups (for example, isocyanate group or epoxy group) involved in cross-linking and cross-linking are performed. It can be confirmed by the appearance of a peak derived from a group formed later (for example, an amide group or an ether group).

In one aspect of the present invention in which the polyvinyl acetal-based resin has a cross-linked structure, the amount of the cross-linking agent added to the polyvinyl acetal-based resin contained in the polymer film of the present invention is the electrolyte resistance elution resistance and mechanical stability of the polymer film. From the viewpoint of properties, it is preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass, based on the total amount of the polyvinyl acetal-based resin having a crosslinked structure contained in the crosslinked polymer film. That is all. The amount of the cross-linking agent added in the above embodiment is preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, from the viewpoint of swelling property and ionic conductivity of the polymer membrane. Even more preferably, it is 15% by mass or less. The amount of the cross-linking agent added may be calculated by measuring the amount of the cross-linked structure in the polyvinyl acetal-based resin contained in the polymer film, or from the charging ratio when producing the polyvinyl acetal-based resin having the cross-linked structure. It may be calculated.

In one aspect of the present invention in which the polyvinyl acetal-based resin has a crosslinked structure, the present invention is not limited to the mechanism described later, but the polyvinyl acetal-based resin contained in the polymer film has many hydroxyl groups and has many hydroxyl groups. It is considered that having the crosslinked structure makes it possible to further increase the strength of the polymer film in the gel state swollen with the electrolytic solution and improve the mechanical stability. Further, it is considered that the solubility in an organic solvent can be further reduced by having a large number of hydroxyl groups and a crosslinked structure. Further, it is considered that the large number of hydroxyl groups facilitates the dissociation of the lithium salt in the non-aqueous electrolyte battery and further enhances the ionic conductivity. Further, since the resin has an acetalized structure, even when there are many hydroxyl groups, the acetal group acts as a spacer between the polymer chains due to steric hindrance due to the acetal group, and the polymer film is swollen by the electrolytic solution. Is considered to be easier to promote. As a result, it is considered that high electrolytic solution resistance, swelling property, and mechanical strength can be easily enhanced, and ionic conductivity can be imparted while enhancing mechanical stability.

In one aspect of the present invention in which the polyvinyl acetal resin has a crosslinked structure, the amount of hydroxyl groups in the polyvinyl acetal resin is preferably 58 mol% or more, more preferably 58 mol% or more, from the viewpoint of easily improving the chemical stability of the polymer film. It is 60 mol% or more, more preferably 62 mol% or more, still more preferably 65 mol% or more. The amount of the hydroxyl group is preferably 89 mol% or less, more preferably, from the viewpoint of easily increasing the swelling rate of the polymer film, easily improving the ionic conductivity, and easily improving the production efficiency of the polymer film. Is 88 mol% or less, more preferably 85 mol% or less, still more preferably 82 mol% or less. When the polyvinyl acetal-based resin has a crosslinked structure, the amount of hydroxyl groups in the polyvinyl acetal-based resin is the amount of hydroxyl groups in the polyvinyl acetal-based resin after cross-linking. Therefore, if some of the hydroxyl groups of the polyvinyl acetal-based resin before cross-linking contribute to the cross-linking reaction and do not exist as hydroxyl groups after cross-linking, the amount of the groups is not included in the amount of hydroxyl groups of the polyvinyl acetal-based resin after cross-linking. .. Here, the amount of hydroxyl groups of the polyvinyl acetal-based resin contained in the polymer film of the present invention in the above aspect is determined by using a solution containing the resin when the polyvinyl acetal-based resin contained in the polymer film is dissolved in a solvent for NMR measurement. It can be calculated using a nuclear magnetic resonance spectroscope as a measurement sample. Even when no solution is used, the amount of hydroxyl groups can be calculated relatively using an IR spectrophotometer or the amount of hydroxyl groups for the polyvinyl acetal-based resin before cross-linking, and the amount of cross-linking agent added and the reaction rate can be used to calculate the amount of polyvinyl after cross-linking. It is also possible to calculate the amount of hydroxyl groups in the acetal resin. For example, the amount of hydroxyl groups of the polyvinyl acetal-based resin contained in the polymer film may be calculated by the method described in Examples.

(Polymer membrane)
The polymer film of the present invention is a film containing the above-mentioned polyvinyl acetal resin. The polymer film of the present invention may contain one kind of polyvinyl acetal-based resin, or may contain two or more kinds of polyvinyl acetal-based resins. When the polymer film contains two or more kinds of polyvinyl acetal-based resins, it may contain polyvinyl acetal-based resins having different acetalization degree, acetyl group amount, hydroxyl group amount, degree of polymerization and / or monomer component and the like. The thickness of the polymer film may be appropriately set according to the purpose of using the polymer film, but from the viewpoint of mechanical strength, it is preferably 0.01 μm or more, more preferably 0.01 μm or more in the state before swelling by the electrolytic solution. Is 0.08 μm or more, more preferably 0.3 μm or more. From the viewpoint of ionic conductivity, it is preferably 60 μm or less, more preferably 40 μm or less, and further preferably 20 μm or less. The thickness of the polymer film can be determined by ellipsometry, transmission measurement, reflectance measurement, optical film thickness measurement method such as laser microscope, film thickness measurement method using X-ray such as fluorescent X-ray, X-CT, constant pressure. It can be measured by using a film thickness measurement, a stylus type surface shape measurement method such as SPM, or the like. In one aspect of the present invention, the polyvinyl acetal-based resin contained in the polymer film may have a crosslinked structure.

The polymer membrane of the present invention containing a polyvinyl acetal-based resin having a hydroxyl group content of 56 to 90 mol% has low electrolyte solubility. In the present specification, having low solubility in an electrolytic solution means that the solubility in an organic solvent contained in the electrolytic solution is low, and the polyvinyl acetal-based resin contained in the polymer film is difficult to elute by contact with the organic solvent. Represents. The solubility of the electrolytic solution can be evaluated by, for example, using diethyl carbonate as an organic solvent and measuring the elution rate with respect to the solvent. Specifically, when the polymer membrane of the present invention was immersed in diethyl carbonate at 60 ° C. for 1 hour, the following formula:

[In the formula, A represents the mass (g) before immersion of the polymer film, and B represents the mass (g) after immersion of the polymer film]
The elution rate calculated by the above method is preferably 7% or less, more preferably 6% or less, still more preferably 5% or less, still more preferably 4.5% or less. When the elution rate when immersed in diethyl carbonate is not more than the above upper limit, the solubility of the polymer membrane in the electrolytic solution tends to be lowered. The lower limit of the above elution rate may be 0% or more because it is preferable that it does not substantially elute into diethyl carbonate. Here, the mass of B after immersion in the polymer film is the dry mass of the polymer film after immersion. Therefore, for example, when the polymer membrane swells in diethyl carbonate under the above conditions, after removing diethyl carbonate by drying, the dry mass of the polymer membrane after immersion is measured to calculate the elution rate. The elution rate can be adjusted within the above range by adjusting the hydroxyl group weight, molecular weight, presence / absence and type of crosslinked structure of the polyvinyl acetal resin.

The polymer film of the present invention containing a polyvinyl acetal-based resin having a hydroxyl group content of 56 to 90 mol% has an appropriate swelling property with respect to an electrolytic solution. By swelling the polymer film in the electrolytic solution and holding the electrolytic solution, it is easy to suppress the leakage of the electrolytic solution, and it is easy to improve the ionic conductivity. Specifically, the polymer film of the present invention was placed in 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide at a concentration of 1 mol / L of lithium bis (fluorosulfonyl) imide at 25 ° C. for 24 hours. When immersed in the dissolved solution, the following formula:

[In the formula, C represents the mass (g) of the polymer film before immersion, and D represents the mass (g) of the polymer film after immersion].
The swelling rate calculated by is preferably 20% or more, more preferably 25% or more, further preferably 30% or more, still more preferably 40% or more, particularly preferably 43% or more, and particularly more preferably 45% or more. , Very preferably 50% or more, very more preferably 53% or more. Here, the mass of D after immersion in the polymer film is the mass of the swollen polymer film after immersion, and is the mass of the swollen polymer film containing the above solution incorporated in the polymer film. Is. When the swelling rate is at least the above lower limit, the lithium ion conductivity of the polymer film can be more easily improved. The upper limit of the swelling rate is not particularly limited, but from the viewpoint of designing the battery, it is preferably 125% or less, more preferably 100% or less, still more preferably 75% or less. The swelling rate can be adjusted within the above range by adjusting the hydroxyl group weight, molecular weight, presence / absence and type of crosslinked structure of the polyvinyl acetal resin.

In a preferred embodiment of the present invention, the polyvinyl acetal-based resin contains a polyvinyl acetal-based resin having a hydroxyl group content of 62 to 90 mol%. The polymer membrane of the present invention containing the polyvinyl acetal-based resin has lower electrolyte solubility. When the polymer membrane of the present invention in this embodiment was immersed in diethyl carbonate at 60 ° C. for 1 hour, the following formula:

[In the formula, A represents the mass (g) before immersion of the polymer film, and B represents the mass (g) after immersion of the polymer film]
The elution rate calculated by the above method is preferably 7% or less, more preferably 6% or less, still more preferably 5% or less, still more preferably 4.5% or less. When the elution rate when immersed in diethyl carbonate is not more than the above upper limit, the solubility of the polymer membrane in the electrolytic solution is likely to be lowered. The lower limit of the above elution rate may be 0% or more because it is preferable that it does not substantially elute into diethyl carbonate.

The polymer film of the present invention containing a polyvinyl acetal-based resin having a hydroxyl group amount of 62 to 90 mol%, which is one aspect of the present invention, has more appropriate swelling property with respect to an electrolytic solution. By swelling the polymer film in the electrolytic solution and holding the electrolytic solution, it becomes easier to suppress the leakage of the electrolytic solution, and it becomes easier to improve the ionic conductivity. Specifically, the polymer film of the present invention was placed in 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide at a concentration of 1 mol / L of lithium bis (fluorosulfonyl) imide at 25 ° C. for 24 hours. When immersed in the dissolved solution, the following formula:

[In the formula, C represents the mass (g) of the polymer film before immersion, and D represents the mass (g) of the polymer film after immersion].
The swelling rate calculated by the above is preferably 40% or more, more preferably 43% or more, further preferably 45% or more, still more preferably 50% or more, and particularly preferably 53% or more. When the swelling rate is at least the above lower limit, the lithium ion conductivity of the polymer film can be more easily improved. The upper limit of the swelling rate is not particularly limited, but from the viewpoint of designing the battery, it is preferably 125% or less, more preferably 100% or less, still more preferably 75% or less.

In one aspect of the present invention in which a polyvinyl acetal-based resin having a hydroxyl group content of 56 to 90 mol% has a crosslinked structure, the polymer membrane containing the polyvinyl acetal-based resin has high electrolytic solution resistance. In the present specification, having electrolyte resistance means that the electrolyte solution has lower solubility in an organic solvent, and the polyvinyl acetal resin contained in the polymer film is less likely to elute due to contact with the organic solvent. Represents that. The resistance to the electrolytic solution can also be evaluated by, for example, using diethyl carbonate as an organic solvent and measuring the elution rate with respect to the solvent. Specifically, when the polymer membrane in one embodiment of the present invention in which the polyvinyl acetal resin has a crosslinked structure is immersed in diethyl carbonate at 60 ° C. for 1 hour, the following formula:

[In the formula, A represents the mass (g) before immersion of the polymer film, and B represents the mass (g) after immersion of the polymer film]
The elution rate calculated by is preferably 2% or less, more preferably 1.5% or less, still more preferably 1.2% or less, still more preferably 1.0% or less, and particularly preferably 0.8% or less. Is. The lower limit of the above elution rate may be 0% or more because it is preferable that it does not substantially elute into diethyl carbonate. When the elution rate when immersed in diethyl carbonate is not more than the above upper limit, it is easy to improve the electrolytic solution resistance of the polymer membrane.

In one aspect of the present invention in which a polyvinyl acetal-based resin having a hydroxyl group content of 56 to 90 mol% has a crosslinked structure, the polymer membrane containing the polyvinyl acetal-based resin has an appropriate swelling property with respect to an electrolytic solution. By swelling the polymer film in the electrolytic solution and holding the electrolytic solution, it is easy to suppress the leakage of the electrolytic solution, and it is easy to improve the ionic conductivity. Specifically, the polymer film of the present invention in the above embodiment is subjected to 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) at a concentration of 1 mol / L of lithium bis (fluorosulfonyl) imide at 25 ° C. for 24 hours. When immersed in a solution dissolved in imide, the following formula:

[In the formula, C represents the mass (g) of the polymer film before immersion, and D represents the mass (g) of the polymer film after immersion].
The swelling rate calculated by the above method is preferably 20% or more, more preferably 25% or more, still more preferably 30% or more. Here, the mass of D after immersion in the polymer film is the mass of the swollen polymer film after immersion, and is the mass of the swollen polymer film containing the above solution incorporated in the polymer film. Is. When the swelling rate is at least the above lower limit, the lithium ion conductivity of the polymer film can be more easily improved. The upper limit of the swelling rate is not particularly limited, but from the viewpoint of designing the battery, it is preferably 125% or less, more preferably 100% or less, still more preferably 75% or less, still more preferably 60% or less.

In one embodiment of the present invention in which a polyvinyl acetal-based resin having a hydroxyl group content of 56 to 90 mol% has a crosslinked structure, the polymer film containing the polyvinyl acetal-based resin can easily increase the mechanical strength. The polymer film of the present invention is immersed in a solution in which lithium bis (fluorosulfonyl) imide is dissolved in 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide at a concentration of 1 mol / L at 25 ° C. for 24 hours. The swollen polymer film thus obtained was used as a measurement sample and measured at 25 ° C. and 500 mm / min according to JIS K 7162-1B, preferably 580 kgf / cm ² or more, more preferably 600 kgf / cm ² or more, and further. It preferably has a tensile strength of 620 kgf / cm ² or more, even more preferably 640 kgf / cm ² or more, and particularly preferably 660 kgf / cm ^{2 or more.} The upper limit of the tensile strength is not particularly limited, for example 4,000kgf / cm ² or less, 3,500kgf / cm ² or less, may be 2,500kgf / cm ² or less and the like.

The amount of the above-mentioned specific polyvinyl acetal-based resin contained in the polymer film of the present invention is preferably 50% by mass or more, more preferably 50% by mass or more, based on the total mass of the polymer film, from the viewpoint of swellability to the electrolytic solution. Is 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The upper limit of the amount of the above-mentioned specific polyvinyl acetal-based resin contained in the polymer film of the present invention is not particularly limited, and may be 100% by mass or less.

The polymer film of the present invention may or may not contain other components in addition to the above-mentioned polyvinyl acetal-based resin. Other components that can be contained in the polymer membrane of the present invention include, for example, a cross-linking agent, a surfactant, a defoaming agent, a release agent, an anti-blocking agent, an adhesive, a metal scavenger, and the like. The content of the other component may be appropriately selected depending on the purpose of blending the component, but from the viewpoint of ionic conductivity, it is preferably 15% by mass or less, more preferably 15% by mass or less, based on the total mass of the polymer membrane. Is 10% by mass or less, more preferably 5% by mass or less. When the polymer membrane of the present invention further contains a cross-linking agent, the cross-linking agent may be contained in the polymer membrane of the present invention as a structure for cross-linking the above-mentioned polyvinyl acetal-based resin.

The method for producing the polymer film of the present invention containing the polyvinyl acetal-based resin is not particularly limited, but for example, a polyvinyl acetal-based resin solution containing the polyvinyl acetal-based resin and at least one solvent is demolded as necessary. The polymer film of the present invention can be produced by coating on the applied base material, drying the coating film, and peeling off the base material. Further, each member such as the positive electrode, the negative electrode, the separator, and the current collector used in the battery may be directly coated with the polyvinyl acetal resin solution of the present invention and dried to prepare a film.

Also in one aspect of the present invention in which the polyvinyl acetal resin having a hydroxyl group content of 56 to 90 mol% has a crosslinked structure, the method for producing the polymer film containing the polyvinyl acetal resin is not particularly limited, but for example, before crosslinking. A polyvinyl acetal resin solution containing a polyvinyl acetal resin, at least one solvent, and a cross-linking agent is applied onto a base material which has been subjected to a mold release treatment, if necessary, and the coating film is dried, and then the coating film is dried. The polymer film of the present invention according to the above embodiment can be produced by cross-linking the polyvinyl acetal resin by heating and / or irradiating with energy rays or the like and peeling off the base material. Further, the cross-linking agent may be contained later by a coat or the like. Further, the polyvinyl acetal-based resin solution may contain a polymerization initiator and a photosensitizer. A polymer film may be produced using a solution containing the crosslinked polyvinyl acetal resin. Further, each member such as the positive electrode, the negative electrode, the separator, and the current collector used in the battery is directly coated with the solution containing the polyvinyl acetal resin of the present invention or the solution containing the cross-linking agent and the polyvinyl acetal resin before cross-linking. The film may be prepared by drying and, if necessary, performing a cross-linking reaction by heating and / or irradiation with energy rays or the like.
The cross-linking conditions may be appropriately adjusted depending on the cross-linking agent used and the base material. For example, the cross-linking agent has a heat-reactive group such as an isocyanate group, an epoxy group, a carboxyl group, or an acid anhydride group (hereinafter, When a heat-reactive cross-linking agent (also referred to as a heat-reactive cross-linking agent) is used, the cross-linked structure can be introduced into the polyvinyl acetal resin by heating at a temperature of preferably 60 to 180 ° C., more preferably 70 to 150 ° C. Further, for example, when a cross-linking agent having a photo-cross-linking group such as a (meth) acrylate group (hereinafter, also referred to as a photo-crosslinking cross-linking agent) is used as the cross-linking agent, a mercury lamp or the like is used for the dry coating film described later. By irradiating with ultraviolet rays, a crosslinked structure can be introduced into the polyvinyl acetal resin.

The solvent for dissolving the polyvinyl acetal-based resin is not particularly limited as long as it is a solvent capable of dissolving the polyvinyl acetal-based resin. Examples of solvents include cyclic amide solvents such as N-alkylpyrrolidone such as N-methylpyrrolidone, N-ethylpyrrolidone, N-methyl-α-methylpyrrolidone, N-ethyl-α-methylpyrrolidone; N, N- Amido solvents such as dimethylformamide, N, N-dimethylacetamide; cyclic ether solvents such as tetrahydrofuran, dioxane, morpholin, N-methylmorpholin; sulfoxide solvents such as dimethyl sulfoxide; sulfone solvents such as sulfolane and the like can be mentioned. .. These solvents can be used alone or in combination of two or more. Among these, a cyclic amide solvent is preferable. When the cyclic amide solvent is used, the polyvinyl acetal resin can be sufficiently dissolved and the viscosity of the obtained polyvinyl acetal resin solution can be reduced, so that the coatability of the polyvinyl acetal resin solution is improved. It is easy to improve the uniformity of the obtained polymer film.

The content of the polyvinyl acetal resin contained in the polyvinyl acetal resin solution is preferably 1 to 30% by mass, more preferably 3 to 20% by mass, and particularly preferably 5 to 5 to 30% by mass, based on the total amount of the polyvinyl acetal resin solution. It is 10% by mass. When the content of the polyvinyl acetal-based resin is at least the above lower limit, the coatability is good and the film is easily formed. Further, when it is not more than the above upper limit, it is easy to prepare a polyvinyl acetal-based resin solution.

(Non-aqueous electrolyte battery)
The polymer membrane of the present invention is a polymer membrane for non-aqueous electrolyte batteries. The present invention also provides a non-aqueous electrolyte battery containing the polymer membrane of the present invention. The polymer membrane of the present invention has high ionic conductivity when used in a portion of a non-aqueous electrolyte battery that comes into contact with an electrolytic solution, and can contribute to the safety and long life of the battery. Therefore, the polymer film of the present invention can be used as a component that comes into contact with at least one member of the positive electrode, the negative electrode, and the separator. The polymer membrane of the present invention is not limited in its state as long as it is a membrane containing the above-mentioned specific polyvinyl acetal-based resin, and when used in a non-aqueous electrolyte battery, it swells with an electrolytic solution or the like. It may be in a gel state or a gel state film. The polymer membrane of the present invention, preferably the polymer membrane in one embodiment of the present invention in which the polyvinyl acetal resin has a crosslinked structure, is not particularly limited in purpose as long as it is used in a non-aqueous electrolyte battery, and is not limited to an electrolyte. It can also be used in the above applications. In a non-aqueous electrolyte battery, the polymer film of the present invention, preferably a polyvinyl acetal resin having a crosslinked structure, preferably has at least a part of the polymer film in contact with an electrolytic solution. It is used as a component, more preferably as an electrolyte, and even more preferably as a gel electrolyte.

The non-aqueous electrolyte battery of the present invention (sometimes referred to simply as a "battery") includes at least the polymer film of the present invention, electrodes (negative electrode and positive electrode), and an electrolytic solution. The non-aqueous electrolyte battery of the present invention may further include a separator. Examples of the non-aqueous electrolyte battery of the present invention include a lithium ion battery, a lithium metal battery, a sodium ion battery, a potassium ion battery, a magnesium battery, a lithium sulfur battery, an all-solid-state lithium battery, a metal air battery, and a lithium ion capacitor. Be done.

The positive electrode and the negative electrode contained in the non-aqueous electrolyte battery include a cured body and a current collector of the positive electrode or the negative electrode active material, respectively. The cured product may contain a binder (for example, a binder resin) if necessary.

As the negative electrode active material, a material conventionally used as a negative electrode active material for non-aqueous electrolyte batteries can be used, and examples thereof include amorphous carbon, artificial graphite, natural graphite (graphite), and mesocarbon microbeads ( MCMB), pitch-based carbon fibers, carbon black, activated carbon, carbon fibers, hard carbon, soft carbon, mesoporous carbon, carbonaceous materials such as conductive polymers such as polyacene, represented by _{SiO x} , SnO _x , LiTIO _x Composite metal oxides and other metal oxides, lithium metals, lithium-based metals such as lithium alloys _{, metal compounds such as TiS 2} and LiTiS ₂ , composite materials of metal oxides and carbonaceous materials, magnesium, iron, zinc , Metals such as aluminum and the like.

As the positive electrode active material, for example, a material conventionally used as a positive electrode active material of a non-aqueous electrolyte battery can be used, and examples thereof include TiS ₂ , TiS ₃ , amorphous MoS ₃ , and Cu _2. Transition metal oxides such as V ₂ O ₃ , amorphous V ₂ O-P ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ , LiCo O ₂ , LiNiO ₂ _{, LiMnO 2} , LiMn ₂ _{O 4,} etc. lithium-containing composite metal _{_{_{_{oxides, P 2 -Na 2/3 Ni 1/3 Mn}}}} 2/3 O 2, NaCrO 2, Na 2/3 [Fe 1/2 Mn 1/2] O 2, NaMnO, Na x Sodium-containing composite metal oxides such as CoO ₂ , potassium-containing composite metal oxides such as K ₂ Mn [Fe (CN) ₆ ], K _x MnO ₂ , K _x Fe _0.5 Mn _0.5 O ₂ , KFeSO ₄ F, etc. , Mo ₃ S, MgTi ₂ S ₄ , V ₂ O ₅ , NVO, MgFeSiO ₄ , carbon paper, carbon material, sulfur-based and the like. These positive electrode active materials can be used alone or in combination of two or more.

The positive electrode and the negative electrode contained in the non-aqueous electrolyte battery may further contain a conductive auxiliary agent. The conductive auxiliary agent is used to increase the output of the non-aqueous electrolyte battery, and can be appropriately selected depending on the case where it is used for the positive electrode or the negative electrode. Examples thereof include graphite, acetylene black, and carbon black. , Ketjen black, vapor-grown carbon fiber and the like. Among these, acetylene black is preferable from the viewpoint that the obtained non-aqueous electrolyte battery can easily increase the output.

When the positive electrode and / or the negative electrode contains a conductive auxiliary agent, the content of the conductive auxiliary agent is preferably 0.1 to 15 parts by mass, more preferably 1 to 10 parts by mass, based on 100 parts by mass of the active material. More preferably, it is 3 to 10 parts by mass. When the content of the conductive auxiliary agent is in the above range, there is a sufficient conductive auxiliary effect without lowering the battery capacity.

As the binder, a material conventionally used as a negative electrode active material of a non-aqueous electrolyte battery can be used, and examples thereof include SBR, NBR, acrylic rubber, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinylidene fluoride, and acrylic type. , Polyamide-imide type, polyvinylcor type and the like.

The binder used for the negative electrode and the positive electrode is particularly a polymer compound having a vinyl alcohol-based material or a copolymer containing vinyl acetal and / or vinyl ester, which is the same material as the polymer film of the present invention. It is expected that the electrode position will be displaced from the polymer film of the present invention and the productivity will be improved by preventing the active material from falling off. Therefore, it is more preferable to use the same kind of material as the polymer film of the present invention as the binder. On the other hand, from the viewpoint of the balance between availability and productivity improvement, it is one of the preferred embodiments to use an SBR emulsion.

In addition to the binder, the active material, and the conductive auxiliary agent, the positive electrode and / or the negative electrode may be added with a flame retardant aid, a thickener, a defoaming agent, a leveling agent, an adhesion imparting agent, etc., if necessary. Can include agents.

As the separator, a material conventionally used as a separator for a non-aqueous electrolyte battery can be used, and examples thereof include a porous film made of polyolefins such as polypropylene and polyethylene, fluororesin, cellulose, and polyamides. Examples thereof include non-woven fabrics, and those obtained by laminating them can also be used.

For the electrode, a composition containing a positive electrode or negative electrode active material, a binder resin, and one or more kinds of solvents (hereinafter, also referred to as a slurry composition) is applied to a current collector, and the solvent is removed by drying or the like. Obtainable. Further, the electrode may be rolled after drying.

The current collector is not particularly limited as long as it is made of a conductive material, and examples thereof include metal materials such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum. These current collectors can be used alone or in combination of two or more. Among the current collectors, aluminum is preferable as the positive electrode current collector, and copper is preferable as the negative electrode current collector from the viewpoint of the adhesiveness of the active material and the discharge capacity.

The method of applying the slurry composition to the current collector is not particularly limited, and examples thereof include an extrusion coater, a reverse roller, a doctor blade, and an applicator. The coating amount of the slurry composition is appropriately selected according to the desired thickness of the cured product derived from the slurry composition.

Examples of the electrode rolling method include a mold press and a roll press. The press pressure is preferably 1 to 40 MPa from the viewpoint of easily increasing the battery capacity.

The thickness of the current collector is preferably 1 to 20 μm, more preferably 2 to 15 μm. The thickness of the cured product is preferably 10 to 400 μm, more preferably 20 to 300 μm. The thickness of the electrode is preferably 20 to 200 μm.

The electrolyte solution contained in the non-aqueous electrolyte battery of the present invention may contain an electrolyte salt, an organic solvent and / or an additive, or may be a solid electrolyte, an ionic liquid, or an ionic liquid containing an electrolyte salt. The electrolyte salt may be solid, liquid, or gel as long as it is used in a normal non-aqueous electrolyte battery, and exhibits a function as a battery depending on the type of the negative electrode active material and the positive electrode active material. You can select the one as appropriate. Specific electrolyte salt, for _{_{_{example, LiClO 4, LiBF 6, LiPF}}} 6, LiTFSA, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 Cl 10, LiAlC l4, LiCl, LiBr, LiB (C ₂ H ₅ ) ₄ , CF ₃ SO ₃ Li, CH ₃ SO ₃ Li, LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, lower aliphatic lithium carboxylate, NaPF ₆ , NaTFSA, NaFSI, KFSI, KPF ₆ , Mg (TFSA) ₂ , Mg [N (CF ₃ SO ₂ ) ₂ ] _{2, and the} like.

The solvent contained in the electrolytic solution is not particularly limited, and specific examples thereof include carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, and vinylene carbonate; γ-butyl lactone and the like. Solvents; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, diethylene glycol diethyl ether; sulfoxides such as dimethylsulfoxide; 1,3-dioxolane Oxoranes such as 4-methyl-1,3-dioxolane; Nitrogen-containing compounds such as acetonitrile and nitromethane; Organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate and the like. Inorganic acid esters such as triethyl phosphate, dimethyl carbonate, diethyl carbonate; diglimes; triglimes; sulfolanes; oxazolidinones such as 3-methyl-2-oxazolidinone; 1,3-propanesulton, 1,4-butanesulton , Naphthaltons and the like, and these can be used alone or in combination of two or more. When a gel-like electrolytic solution is used, a nitrile-based polymer, an acrylic-based polymer, a fluorine-based polymer, an alkylene oxide-based polymer, or the like can be added as a gelling agent.

The additive contained in the electrolytic solution is not particularly limited, and examples thereof include VC, VEC, FEC, and LiFSI.

The solid electrolyte is not particularly limited _{, and is sulfide-based such as Li 2} _{SP 2} S ₅ , LGPS, LSiPSCl, LSiSnPS, oxide-based such as LLTO, LATP, LLZO, LAGP, LIPON, and polymer such as PEO-LiTFSI. Examples thereof include a system, a complex system such as LiBH ₄ , LiBH _4- _{LiI, LiBH 4-} LiNH ₂ , LiBH _4- P ₂ S _5, and a hydride system such as crosobolan and carboran.

The ionic liquid used as the electrolytic solution is not particularly limited, and is, for example, ammonium-based, pyrrolidinium-based, pyridinium-based, imidazolium-based, piperidinium-based, pyrazolium-based, oxazolium-based, pyridadinium-based, phosphonium-based, sulfonium-based, triazolium-based, and and one or more cations selected from among the mixture _{^{_{^{_{^{BF 4 -, PF 6 -,}}}}}} AsF 6 -, SbF 6 -, AlCl 4 -, HSO 4 -, ClO 4 -, CH 3 SO 3 -, (F ₅ _O2) 2 ^N - is selected from among _{_{_{_{^{-, (C 2 F 5 SO}}}}} 2) 2 N -, (C 2 F 5 SO 2) (CF 3 SO 2) N - and _(CF ₃ SO ₂₎ 2 N Examples thereof include compounds containing one or more types of anions selected from at least one.

The method for manufacturing the non-aqueous electrolyte battery is not particularly limited, and for example, the following manufacturing method is exemplified. For example, the polymer film of the present invention is independently produced, and a laminate that is laminated so as to be in contact with the negative electrode and / or the positive electrode is wound or folded according to the shape of the battery and placed in a battery container to contain an electrolytic solution. Inject and seal. Further, each member such as the positive electrode, the negative electrode, and the separator used for the battery is directly coated with the polyvinyl acetal-based resin solution of the present invention, and dried to form a film to prepare a battery by the method as described above. May be good. The shape of the battery may be any of known coin type, button type, sheet type, cylindrical type, square type, flat type and the like.

The non-aqueous electrolyte battery of the present invention is useful for various applications. For example, it is very useful as a battery used in a mobile terminal that requires miniaturization, thinning, weight reduction, and high performance. Further, it can be suitably used for batteries of equipment requiring flexibility, for example, winding type dry batteries and laminated type batteries.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples. In addition,% in an Example is related to mass unless otherwise specified. First, the measurement method and the evaluation method are shown below.

<Analysis of polyvinyl acetal resin>
The degree of polymerization, the degree of saponification, the degree of acetalization, the amount of acetyl groups, and the amount of hydroxyl groups of the polyvinyl acetal-based resins used in Examples and Comparative Examples were measured according to the methods shown below. Regarding the polyvinyl acetal-based resins used in Examples and Comparative Examples, the degree of polymerization, the degree of saponification, the degree of acetalization, and the amount of acetyl groups are values that do not change depending on the manufacturing process of the polymer film, and therefore the polyvinyl used as a raw material. The value measured for the acetal-based resin may be used as the value for the polyvinyl acetal-based resin contained in the polymer film. When the polyvinyl acetal-based resin does not have a crosslinked structure, the amount of hydroxyl groups does not change depending on the polymer film manufacturing process. Therefore, the value measured for the polyvinyl acetal-based resin used as the raw material is the polymer. It may be a value for the polyvinyl acetal resin contained in the film. When the polyvinyl acetal resin has a crosslinked structure, the degree of polymerization, the degree of saponification, the degree of acetalization, and the amount of acetyl groups and the amount of hydroxyl groups, which are values that do not change depending on the manufacturing process of the polymer film, are the values before cross-linking used as raw materials. The value measured for the polyvinyl acetal-based resin of the above may be used as the value for the cross-linked polyvinyl acetal-based resin contained in the polymer film. The amount of hydroxyl groups in the polyvinyl acetal-based resin after cross-linking was measured by the method described later.

(A) Degree of polymerization and degree of saponification According to JIS-K6726, the degree of polymerization and saponification of polyvinyl alcohol (resin before acetalization of polyvinyl acetal resin) was measured and used as the degree of polymerization and saponification of polyvinyl acetal resin. ..

(B) Degree of Acetalization A polyvinyl acetal-based resin is dissolved in dimethyl sulfoxide-d6 (DMSO-d6) containing 0.03% by volume of tetramethylsilane, which is a standard sample, and used as a measuring instrument by a nuclear magnetic resonance spectrometer ( It was measured using "AVance 600" (manufactured by Bruker) under the conditions of a resonance frequency of 1H 600 MHz and a temperature of 25 ° C. Peak intensity derived from the methyl group (0.87 ppm) of the vinyl acetal unit and peak derived from the methylene group (1.14 to 1.94 ppm) in the main chain of the vinyl alcohol unit, the vinyl ester unit, and the vinyl acetal unit. The degree of acetalization was determined from the strength.

(C) Acetyl Group Amount Polypolyacetal-based resin is dissolved in dimethyl sulfoxide-d6 (DMSO-d6) containing 0.03% by volume of tetramethylsilane, which is a standard sample, and used as a measuring instrument by a nuclear magnetic resonance spectrometer (c). It was measured using "AVance 600" (manufactured by Bruker) under the conditions of a resonance frequency of 1H 600 MHz and a temperature of 25 ° C. The peak intensity derived from the methyl group (1.94 ppm) of the vinyl ester unit and the peak derived from the methylene group (0.87 to 1.70 ppm) in the main chain of the vinyl alcohol unit, the vinyl ester unit, and the vinyl acetal unit. The amount of acetyl group was determined from the strength.

(D) Amount of hydroxyl group From the degree of acetalization and the amount of acetyl groups calculated above, the amount of hydroxyl group was calculated according to the following formula.

When a polyvinyl acetal-based resin having a crosslinked structure was used, the amount of hydroxyl groups in the polyvinyl acetal-based resin before cross-linking was calculated according to the above formula.

<Analysis of polymer membrane>
(E) Elution rate The polymer films obtained in Examples and Comparative Examples were punched into a circular shape of φ14 mm using a punching machine, immersed in 5 g of diethyl carbonate, allowed to stand at 60 ° C. for 1 hour, and then taken out. The drying treatment was carried out under the condition of 80 ° C. for 3 hours. The mass of the obtained film after immersion and drying was measured, and the mass change rate after immersion and drying was calculated from the following formula and used as the elution rate.

[In the formula, A represents the mass (g) of the polymer film before immersion, and B represents the dry mass (g) of the polymer film after immersion].

(F) Swelling rate The polymer films obtained in Examples and Comparative Examples are punched into a circular shape of φ14 mm using a punching machine, immersed in an electrolytic solution at 25 ° C. for 24 hours, and then the polymer film is taken out and the polymer film is taken out. After wiping off the solution adhering to the surface with a waste cloth, the mass of the polymer film after immersion was measured, and the rate of change in mass after immersion was calculated by the following formula and used as the degree of swelling (%). Lithium bis (fluorosulfonyl) imide (LiFSI) dissolved in 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide (EMI-FSI) in the electrolytic solution (1M-LiFSI, EMI-FSI, Kishida) (Manufactured by Chemical Co., Ltd.) was used.

[In the formula, C represents the mass (g) of the polymer film before immersion, and D represents the mass (g) of the polymer film after immersion].

(G) Ion Conductivity Measurement Using a gel electrolyte obtained by impregnating the polymer films obtained in Examples and Comparative Examples with 350 μL of an electrolytic solution (mol / L LiFSI EMI-FSI, manufactured by Kishida Chemical Co., Ltd.), the working electrode. A triode cell was prepared using platinum as the reference electrode and Li metal as the reference electrode and the counter electrode. Using an impedance measuring device (potential / galvanostat (SI1287, manufactured by Solartron) and frequency response analyzer (FRA, manufactured by Solartron)), AC impedance measurement was performed in the range of amplitude 10 mV and measurement frequency 0.01 to 1 MHz. ^{, Ion conductivity (Scm -1} ) was calculated from the obtained resistance and thickness.

(H) Measurement of piercing strength The polymer films obtained in Examples and Comparative Examples were cut into 2 cm squares, and a cylinder with a texture analyzer (XT Plus, manufactured by EKO Instruments) had a temperature of 25 ° C., a piercing speed of 2 mm / s, and a diameter of 1 mm. Measurements were made using a type probe.
Further, the piercing strength of the film cut into 2 cm squares and swollen under the same conditions as the above-mentioned measurement of the swelling rate was measured in the same manner.

(I) Cycle test (cell preparation)
The preparation solution (polyvinyl acetal resin solution) for producing the polymer films obtained in Examples and Comparative Examples was applied to a separator so as to have a film thickness of 1 to 2 μm. The polymer membrane with a separator was dried under reduced pressure at 40 ° C. for 12 hours, and then cut into a size of 5.1 × 5.0 cm. Next, the negative electrode with Cu current collector foil (natural graphite + SiO hoop 10.3 mg / cm ² , 1.45 g · cm ³ , manufactured by Yayama) was 4.8 x 4.5 cm, and the positive electrode with Al current collector foil (LCO positive electrode plate). 25.3 mg / cm ² single-sided specification, manufactured by Yayama) was cut out to a size of 4.9 x 4.7 cm and a lead tab was attached, and then these two electrodes were used to cut out a polymer film with a separator to the above size. I sandwiched it. After installing the sandwiched material in the aluminum laminate pack and so that the lead tab comes out of the aluminum laminate pack, the electrolytic solution (ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) = A laminate cell was prepared by encapsulating 350 μl of 1/1/1, 1.0 M LiPF _{6) under reduced pressure.}
(Calculation method of cycle characteristics)
The prepared cell was placed in a constant temperature bath at 25 ° C., and AC impedance was measured with an impedance measuring device (potential / galvanostat (SI1287, manufactured by Solartron) and frequency response analyzer (FRA, manufactured by Solartron)). After 5 cycles, the cell was resealed, and when the discharge capacity in the 1st cycle was E and the discharge capacity in the 100th cycle was F, the discharge capacity retention rate was calculated by the following formula and used as the cycle characteristics. ..
Cycle characteristics (%) = F / E x 100

(J) Thickness The thickness of the polymer film was measured using a thickness measuring device (constant pressure thickness measuring device PG-02J, manufactured by Teflock Co., Ltd.).

When using a polyvinyl acetal-based resin having a crosslinked structure, the following was further measured.

<Analysis of Polymer Membrane- (k) Reaction Rate>
A polyvinyl acetal-based resin film was prepared by applying the polyvinyl acetal-based resin solution prepared in Examples and Comparative Examples onto the release-treated polyethylene terephthalate film and drying the film. The prepared film was used as a measurement sample and measured by the ATR method using a Fourier transform infrared spectrophotometer (FT / IR6600, manufactured by JASCO Corporation).
When a cross-linking agent having an ethylenically unsaturated bond is used, the reaction rate is calculated from the reduction rate of the absorption peak of ^{810 cm -1 derived from the double bond.} When a cross-linking agent having an isocyanate group is used, the reaction rate is calculated from the reduction rate of the absorption peak of ^{2300 cm-1 derived from the isocyanate group.} When a cross-linking agent having an epoxy group is used, the reaction rate is calculated from the reduction rate of the absorption peak of ^{910 cm -1 derived from the epoxy group.} The formula for calculating the reaction rate is as follows.
Reaction rate [%] = {(absorption intensity at each wave number before cross-linking-absorption intensity at each wave number after cross-linking) / absorption intensity at each wave number before cross-linking} × 100

<Analysis of Polymer Membrane- (l) Amount of Hydroxyl Group in Polyvinyl Acetal Resin after Crosslinking>
The amount of hydroxyl groups in the polyvinyl acetal-based resin after cross-linking was calculated by the following formula from the acetalization degree and the amount of acetyl groups measured for the polyvinyl acetal-based resin before cross-linking and the above reaction rate.
Amount of hydroxyl group (after cross-linking) [mol%] = 100-degree of acetalization [mol%] -amount of acetyl group [mol%]-(amount of cross-linking agent added [mol%] x reaction rate [%] / 100)

<Analysis of polymer membrane- (m) Mechanical properties>
A sheet of polyvinyl acetal resin was prepared by applying the polyvinyl acetal resin solution prepared in Examples and Comparative Examples onto the release-treated polyethylene terephthalate film and drying the film. After obtaining a test piece according to JIS K 7162-1B from the obtained sheet, the tensile strength was determined using a tensile tester (Autograph AG5000B, manufactured by Shimadzu Corporation) under the conditions of 500 mm / min and 25 ° C. It was measured. In addition, a tensile test was also carried out on the membrane swollen under the same conditions as described above.

<Example 1>
(Polyvinyl acetal resin solution (1))
To a three-necked flask equipped with a reflux condenser and a thermometer, 150 g of acetone, 100 g of water, and 12.3 g of 1-butanal were added, and polyvinyl alcohol (saponification degree 99 mol%, average degree of polymerization 1700) was added while stirring with a magnetic stirrer. 50 g was added over 1 minute. A mixed solution of 50 g of water and 21.2 g of 47 mass% sulfuric acid was added dropwise from a dropping funnel over 5 minutes, the temperature was raised to 30 ° C., and the reaction was carried out for 5 hours. A 1 mol / L aqueous sodium hydroxide solution was added until the pH reached 8, and then the solid was removed by filtration. The solid substance was washed 5 times with a mixed solvent having a mass ratio of acetone and water of 1: 1 and then dried at 120 ° C. and a pressure of 0.005 MPa for 6 hours to obtain a polyvinyl acetal resin (1). .. The amount of acetyl group, degree of acetalization and amount of hydroxyl group of the obtained polyvinyl acetal resin were measured by the above method.
95 parts by mass of N-methylpyrrolidone (NMP) is added to 5 parts by mass of the obtained polyvinyl acetal resin (1), and the mass of the polyvinyl acetal resin (1) is based on the mass of the polyvinyl acetal resin solution. A polyvinyl acetal-based resin solution (1) in an amount of 5% by mass was obtained.

(Polymer membrane (1))
The polyvinyl acetal-based resin solution (1) obtained above is applied on a release-treated polyethylene terephthalate film using a baker-type applicator (SA-201, manufactured by Tester Sangyo Co., Ltd.), and then at 80 ° C. for 3 The polymer film (1) was obtained by drying for a time. The thickness of the obtained polymer film (1) was 23 μm.

The elution rate, swelling rate, and piercing strength were measured using the polymer film obtained above. The results are shown in the table.

The polymer film (1) was transferred to a glove box (manufactured by Miwa Seisakusho) in an argon gas atmosphere. A tripolar cell was prepared using the prepared polymer membrane (1), and ionic conductivity was measured. The results are shown in the table.

A laminate cell was prepared using the above polymer film (1), and a charge / discharge test was carried out at a rate of 0.2 C for 100 cycles. The results are shown in the table.

<Example 2>
In the preparation of the polyvinyl acetal-based resin of Example 1, the polyvinyl acetal-based resin (2) was obtained in the same manner as in Example 1 except that 10 g of 1-butarnal was used instead of 12.3 g of 1-butanal. It was. Using the obtained polyvinyl acetal-based resin (2), a polyvinyl acetal-based resin solution (2) was prepared in the same manner as in Example 1, and the polymer was used in the same manner as in Example 1. A film (2) (thickness 16 μm) was obtained.

Using the polymer membrane (2) obtained above, elution rate, swelling rate, puncture strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 1. The results are shown in the table.

<Example 3>
In the preparation of the polyvinyl acetal-based resin of Example 1, the polyvinyl acetal-based resin (3) was the same as in Example 1 except that 4.4 g of 1-butarnal was used instead of 12.3 g of 1-butanal. Got Using the obtained polyvinyl acetal-based resin (3), a polyvinyl acetal-based resin solution (3) was prepared in the same manner as in Example 1, and the polymer was used in the same manner as in Example 1. A film (3) (thickness 19 μm) was obtained.

Using the polymer membrane (3) obtained above, elution rate, swelling rate, piercing strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 1. The results are shown in the table.

<Example 4>
In the preparation of the polyvinyl acetal-based resin of Example 1, the polyvinyl acetal-based resin (4) was the same as in Example 1 except that 18.8 g of 1-nonanal was used instead of 12.3 g of 1-butanal. Got Using the obtained polyvinyl acetal-based resin (4), a polyvinyl acetal-based resin solution (4) was prepared in the same manner as in Example 1, and the polymer was used in the same manner as in Example 1. A film (4) (thickness 20 μm) was obtained.

Using the polymer membrane (4) obtained above, elution rate, swelling rate, piercing strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 1. The results are shown in the table.

<Example 5>
To a three-necked flask equipped with a reflux condenser and a thermometer, 150 g of acetone, 100 g of water, and 18.8 g of 1-nonanaal were added, and polyvinyl alcohol (saponification degree 99 mol%, average degree of polymerization 2400) was added while stirring with a magnetic stirrer. 50 g was added over 1 minute. A mixed solution of 50 g of water and 21.2 g of 47 mass% sulfuric acid was added dropwise from a dropping funnel over 5 minutes, the temperature was raised to 30 ° C., and the reaction was carried out for 5 hours. A 1 mol / L aqueous sodium hydroxide solution was added until the pH reached 8, and then the solid was removed by filtration. The solid substance was washed 5 times with a mixed solvent having a mass ratio of acetone and water of 1: 1 and then dried at 120 ° C. and a pressure of 0.005 MPa for 6 hours to obtain a polyvinyl acetal resin (5). .. 95 parts by mass of NMP is added to 5 parts by mass of the obtained polyvinyl acetal resin (5), and the mass of the polyvinyl acetal resin (5) is 5% by mass with respect to the mass of the polyvinyl acetal resin solution. An acetal-based resin solution (5) was obtained. Using the resin solution, a polymer film (5) (thickness 19 μm) was obtained in the same manner as in Example 1.

Using the polymer membrane (5) obtained above, elution rate, swelling rate, piercing strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 1. The results are shown in the table.

<Example 6>
In the preparation of the polyvinyl acetal-based resin of Example 1, the polyvinyl acetal-based resin (6) was the same as in Example 1 except that 25.3 g of 1-octanal was used instead of 12.3 g of 1-butanal. Got Using the obtained polyvinyl acetal-based resin (6), a polyvinyl acetal-based resin solution (6) was prepared in the same manner as in Example 1, and the polymer was used in the same manner as in Example 1. A film (6) (thickness 18 μm) was obtained.

Using the polymer membrane (6) obtained above, elution rate, swelling rate, puncture strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 1. The results are shown in the table.

<Example 7>
In the preparation of the polyvinyl acetal-based resin of Example 1, the polyvinyl acetal-based resin (7) was the same as in Example 1 except that 13.3 g of 1-octanal was used instead of 12.3 g of 1-butanal. Got Using the obtained polyvinyl acetal-based resin (7), a polyvinyl acetal-based resin solution (7) was prepared in the same manner as in Example 1, and the polymer was used in the same manner as in Example 1. A film (7) (thickness 17 μm) was obtained.

Using the polymer membrane (7) obtained above, elution rate, swelling rate, puncture strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 1. The results are shown in the table.

<Comparative example 1>
In the preparation of the polyvinyl acetal-based resin of Example 1, the polyvinyl acetal-based resin (8) was the same as in Example 1 except that 29.2 g of 1-butanol was used instead of 12.3 g of 1-butanal. Got Using the obtained polyvinyl acetal-based resin (8), a polyvinyl acetal-based resin solution (8) was prepared in the same manner as in Example 1, and the polymer was used in the same manner as in Example 1. A film (8) (thickness 20 μm) was obtained.

Using the polymer membrane (8) obtained above, elution rate, swelling rate, piercing strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 1. The results are shown in the table.

<Comparative example 2>
In the preparation of the polyvinyl acetal-based resin of Example 1, the polyvinyl acetal-based resin (9) was the same as in Example 1 except that 19.2 g of 1-butanol was used instead of 12.3 g of 1-butanal. Got Using the obtained polyvinyl acetal-based resin (9), a polyvinyl acetal-based resin solution (9) was prepared in the same manner as in Example 1, and the polymer was used in the same manner as in Example 1. A film (9) (thickness 17 μm) was obtained.

Using the polymer membrane (9) obtained above, elution rate, swelling rate, puncture strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 1. The results are shown in the table.

<Comparative example 3>
5 parts by mass of polyvinyl formal (manufactured by Tokyo Chemical Industry Co., Ltd.) is dissolved in 95 parts by mass of NMP to prepare a polyvinyl acetal-based resin solution (10), and the resin solution is used to prepare a polymer film in the same manner as in Example 1. (10) (thickness 18 μm) was obtained.

Using the polymer membrane (10) obtained above, the elution rate, swelling rate, piercing strength and ionic conductivity were measured in the same manner as in Example 1. In the puncture test, the membrane could not retain its pre-swelling shape and the puncture test could not be performed. Therefore, the cycle characteristics could not be implemented. The results are shown in the table.

<Comparative example 4>
A 10% by mass aqueous solution of polyvinyl alcohol (saponification degree 99%, PVA-117, manufactured by Kuraray) was prepared, and a polymer film (11) (thickness 10 μm) was obtained in the same manner as in Example 1.

Using the polymer film (11) obtained above, the elution rate, swelling rate, and piercing strength were carried out in the same manner as in Example 1. Although the ionic conductivity was measured, the polymer membrane (11) did not swell in the electrolytic solution, the ionic conductivity was 0 Scm- ¹ , and the ionic conductivity was not shown. Therefore, the cycle test was not conducted.

<Comparative example 5>
A 10% by mass aqueous solution of polyvinyl alcohol (saponification degree 80%, PVA-417, manufactured by Kuraray) was prepared, and a polymer film (12) (thickness 10 μm) was obtained in the same manner as in Example 1.

Using the polymer membrane (12) obtained above, elution rate, swelling rate, puncture strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 1. The results are shown in the table.

<Comparative Example 6>
A fluorine-based resin solution was obtained by adding 95 parts by mass of NMP to 5 parts by mass of polyvinylidene fluoride (PVDF; manufactured by HSV900 Kynar). Using the resin solution, a polymer film (13) (thickness 23 μm) was obtained in the same manner as in Example 1.

Using the polymer membrane (13) obtained above, elution rate, swelling rate, puncture strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 1. The results are shown in the table.

<Comparative Example 7>
In Example 1, a cycle test was similarly carried out using a polyethylene terephthalate film that had been release-treated without coating the polymer film (1). The results are shown in the table.

<Example 8>
(Polyvinyl acetal resin solution (15))
To a three-necked flask equipped with a reflux condenser and a thermometer, 150 g of acetone, 100 g of water, and 12.3 g of 1-butanal were added, and polyvinyl alcohol (saponification degree 99 mol%, average degree of polymerization 1700) was added while stirring with a magnetic stirrer. 50 g was added over 1 minute. A mixed solution of 50 g of water and 21.2 g of 47 mass% sulfuric acid was added dropwise from a dropping funnel over 5 minutes, the temperature was raised to 30 ° C., and the reaction was carried out for 5 hours. A 1 mol / L aqueous sodium hydroxide solution was added until the pH reached 8, and then the solid was removed by filtration. The solid was washed 5 times with a mixed solvent having a mass ratio of acetone and water of 1: 1 and then dried at 120 ° C. and a pressure of 0.005 MPa for 6 hours to obtain a polyvinyl acetal resin. 89.7 parts by mass of the obtained polyvinyl acetal resin, 5 parts by mass of a photocrosslinkable cross-linking agent (a) (2-isocyanatoethyl acrylate), and 0.15 parts of a photopolymerization initiator (1-hydroxycyclohexylphenylketone). A polyvinyl acetal resin solution (15) containing a polyvinyl acetal resin having an acryloyl group by adding parts by mass and N-methylpyrrolidone (NMP), mixing, and heating and stirring at 80 ° C. for 2 hours (solid content:). About 5% by mass) was obtained.

(Polymer membrane (15))
The polyvinyl acetal-based resin solution (15) obtained above is applied on a release-treated polyethylene terephthalate film using a baker-type applicator (SA-201, manufactured by Tester Sangyo Co., Ltd.), and then at 80 ° C. for 3 A polymer film was obtained by drying for a time. Next, the obtained polymer film was irradiated with ultraviolet light at 24 mW for 60 seconds using a high-pressure mercury lamp (TOSCURE401, manufactured by Toshiba Corporation) and crosslinked to obtain a polymer film (15). The thickness of the obtained polymer film (15) was 18 μm.

Using the polymer membrane obtained above, IR measurement was performed to calculate the isocyanate reaction rate and the acrylate reaction rate. In addition, the amount of hydroxyl groups in the polyvinyl acetal-based resin after cross-linking was calculated. Furthermore, the elution rate, swelling rate, and tensile strength were measured using the polymer membrane obtained above. The results are shown in the table.

The polymer film (15) was transferred to a glove box (manufactured by Miwa Seisakusho) in an argon gas atmosphere. A tripolar cell was prepared using the prepared polymer membrane (15), and ionic conductivity was measured. The results are shown in the table.

A laminate cell was prepared using the above polymer film (15), and a charge / discharge test was carried out at a rate of 0.2 C for 100 cycles. The results are shown in the table.

<Example 9>
A polyvinyl acetal resin was obtained in the same manner as in Example 8 except that 24.3 g of nonanal was used instead of 12.3 g of 1-butanal in the preparation of the polyvinyl acetal resin of Example 8. Using the obtained polyvinyl acetal-based resin, a polyvinyl acetal-based resin solution (16) was prepared in the same manner as in Example 8, and the polymer film (16) was prepared in the same manner as in Example 8 using the resin solution. ) (Thickness 18 μm) was obtained.

Using the polymer membrane (16) obtained above, the reaction rate, elution rate, swelling rate, tensile strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 8. The results are shown in the table.

<Example 10>
A polyvinyl acetal resin was obtained in the same manner as in Example 8 except that 20.1 g of octanal was used instead of 12.3 g of 1-butanal in the preparation of the polyvinyl acetal resin of Example 8. Using the obtained polyvinyl acetal-based resin, a polyvinyl acetal-based resin solution (17) was prepared in the same manner as in Example 8, and the polymer film (17) was prepared in the same manner as in Example 8 using the resin solution. ) (Thickness 15 μm) was obtained.

Using the polymer membrane (17) obtained above, the reaction rate, elution rate, swelling rate, tensile strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 8. The results are shown in the table.

<Example 11>
In the preparation of the polyvinyl acetal-based resin solution of Example 8, the same procedure as in Example 8 except that the heat-reactive cross-linking agent (b) (hexamethylene diisocyanate) was used instead of the cross-linking agent (a). , Polyvinyl acetal resin solution (18) was obtained. In the preparation of the polymer film using the resin solution, a polymer film (18) (thickness 16 μm) was obtained in the same manner as in Example 8 except that UV treatment was not performed.

Using the polymer membrane (18) obtained above, the reaction rate, elution rate, swelling rate, tensile strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 8. The results are shown in the table.

<Example 12>
A polyvinyl acetal resin was obtained in the same manner as in Example 11 except that 24.3 g of nonanal was used instead of 12.3 g of 1-butanal in the preparation of the polyvinyl acetal resin of Example 11. Using the obtained polyvinyl acetal-based resin, a polyvinyl acetal-based resin solution (19) was prepared in the same manner as in Example 11, and the polymer film (19) was prepared in the same manner as in Example 11 using the resin solution. ) (Thickness 17 μm) was obtained.

Using the polymer membrane (19) obtained above, the reaction rate, elution rate, swelling rate, tensile strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 8. The results are shown in the table.

<Example 13>
A polyvinyl acetal resin was obtained in the same manner as in Example 11 except that 20.1 g of octanal was used instead of 12.3 g of 1-butanal in the preparation of the polyvinyl acetal resin of Example 11. Using the obtained polyvinyl acetal-based resin, a polyvinyl acetal-based resin solution (20) was prepared in the same manner as in Example 11, and the polymer film (20) was prepared in the same manner as in Example 11 using the resin solution. ) (Thickness 21 μm) was obtained.

Using the polymer membrane (20) obtained above, the reaction rate, elution rate, swelling rate, tensile strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 8. The results are shown in the table.

<Example 14>
In the preparation of the polyvinyl acetal-based resin solution of Example 8, a photo-crosslinkable cross-linking agent (c) (acrylic acid (3,4-epoxycyclohexyl) methyl) was used instead of the cross-linking agent (a), and a polymerization initiator was used. A polyvinyl acetal-based resin solution (21) was obtained in the same manner as in Example 8 except that 0.25 parts by mass of sodium ethoxydo was used. In the preparation of the polymer film using the resin solution, a polymer film (21) (thickness 18 μm) was obtained in the same manner as in Example 8 except that the drying temperature was set to 100 ° C.

Using the polymer membrane (21) obtained above, the reaction rate, elution rate, swelling rate, tensile strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 8. The results are shown in the table.

<Comparative Example 8>
In the preparation of the polyvinyl acetal-based resin of Example 11, the polymer film (22) (thickness) was the same as in Example 11 except that 29.2 g of 1-butyral was used instead of 12.3 g of 1-butyral. 18 μm) was obtained.

Using the polymer membrane (22) obtained above, the reaction rate, elution rate, swelling rate, tensile strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 8. The results are shown in the table.

<Comparative Example 9>
In the preparation of the polymer film of Example 11, the polymer film (23) (thickness) was the same as in Example 11 except that polyvinyl alcohol (PVA-117, manufactured by Kuraray) was used instead of the polyvinyl acetal resin. 18 μm) was obtained.

Using the polymer membrane (23) obtained above, the reaction rate, elution rate, swelling rate, tensile strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 8. The results are shown in the table.

<Comparative Example 10>
A polymer film (24) (thickness 18 μm) was obtained in the same manner as in Example 11 except that the amount of the cross-linking agent (b) added in Example 11 was 10% by mass.

Using the polymer membrane (24) obtained above, the reaction rate, elution rate, swelling rate, tensile strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 8. The results are shown in the table.

<Comparative Example 11>
A fluorine-based resin solution was obtained by adding 95 parts by mass of NMP to 5 parts by mass of polyvinylidene fluoride (PVDF; manufactured by HSV900 Kynar). Using the resin solution, a polymer film (25) (thickness 18 μm) was obtained in the same manner as in Example 8.

Using the polymer membrane (25) obtained above, elution rate, swelling rate, tensile strength, ionic conductivity measurement and cycle test were carried out in the same manner as in Example 8. The results are shown in the table.

It was confirmed that the polymer films of Examples 1 to 14 containing the polyvinyl acetal-based resin having a hydroxyl group content of 56 to 90 mol% had high Li ion conductivity and high ionic conductivity. It was also confirmed that the battery using the polymer film has high cycle characteristics.

The polymer films of Examples 1 to 7 containing a polyvinyl acetal-based resin having a hydroxyl group content of 56 to 90 mol% (preferably 62 to 90 mol%) have a low elution rate and have electrolytic solution resistance, and are films. The piercing strength was also high. Since the polymer membranes of Examples 1 to 7 also have high ionic conductivity, it was confirmed that inserting the polymer membrane into the battery can contribute to the improvement of cycle characteristics. On the other hand, it was confirmed that the polymer films of Comparative Examples 1 to 3 having a hydroxyl group content of less than 56 mol% had a high elution rate and could not stably retain their shape in the electrolytic solution. Further, it was found that the polymer film of Comparative Example 4 did not correspond to a polyvinyl acetal-based resin because it was not acetalized, and was not a film that had no ionic conductivity and could be incorporated into a battery. Further, the polymer film of Comparative Example 5 was a film of polyvinyl alcohol that was not acetalized but swelled in the electrolytic solution, but it was confirmed that the ionic conductivity was low because the swelling property was low. In addition, the piercing strength of the film was low, and the cycle characteristics of the battery containing the film were also low. The batteries containing the polymer films of Comparative Examples 6 and 7, which are not the films of the polyvinyl acetal resin, were also inferior in cycle characteristics to the batteries containing the polymer film of the present invention.

The polymer membranes of Examples 8 to 14 containing a polyvinyl acetal-based resin having a hydroxyl group content of 56 to 90 mol% and a crosslinked structure have electrolytic solution resistance due to a low elution rate, and are contained in the electrolytic solution. The film shape retention was high, and the tensile strength of the film was also high. Further, it was confirmed that the batteries containing the polymer films of Examples 8 to 14 have high ionic conductivity and excellent cycle characteristics. It is considered that this is because the polymer film has high mechanical strength and electrolyte resistance, and the collapse of the electrode due to expansion and contraction of the active material is suppressed. On the other hand, it was confirmed that the polymer film of Comparative Example 8 containing the polyvinyl acetal-based resin having a hydroxyl group content of less than 56 mol% had a high elution rate and could not retain its shape in the electrolytic solution for a long period of time. .. Further, it was confirmed that the battery containing the polymer film of Comparative Example 8 had insufficient cycle characteristics, which caused the polymer film to have low mechanical strength and electrolyte resistance, and the electrode collapsed due to expansion and contraction of the active material. It is probable that it could not be suppressed. Further, the polymer membrane of Comparative Example 9 containing the modified polyvinyl alcohol having a hydroxyl group content of 90 mol% or more did not show swelling property to the electrolytic solution, and the ionic conductivity could not be measured. The polymer membrane of Comparative Example 10 containing a polyvinyl acetal-based resin having a low hydroxyl group content of less than 56 mol% has a low elution rate and electrolyte resistance, but has low swelling property and low mechanical strength. The cycle characteristics of the battery containing the polymer film were also poor. It was confirmed that the polymer film of Comparative Example 11 had a lower tensile strength and poorer cycle characteristics than the polymer film containing the specific polyvinyl acetal-based resin of the present invention.

Claims

A polymer membrane for non-aqueous electrolyte batteries containing a polyvinyl acetal-based resin having a hydroxyl group content of 56 to 90 mol%.
When immersed in diethyl carbonate at 60 ° C. for 1 hour, the following formula:

[In the formula, A represents the mass (g) of the polymer film before immersion, and B represents the dry mass (g) of the polymer film after immersion].
The polymer membrane according to claim 1, wherein the dissolution rate calculated by the above method is 7% or less.
When immersed in a solution of lithium bis (fluorosulfonyl) imide in 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide at a concentration of 1 mol / L at 25 ° C. for 24 hours, the following formula:

[In the formula, C represents the mass (g) of the polymer film before immersion, and D represents the mass (g) of the polymer film after immersion].
The polymer membrane according to claim 1 or 2, wherein the swelling rate calculated by the above method is 20% or more.
The polymer film according to any one of claims 1 to 3, wherein the polyvinyl acetal resin has a hydroxyl group content of 62 to 90 mol%.
When immersed in a solution of lithium bis (fluorosulfonyl) imide in 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide at a concentration of 1 mol / L at 25 ° C. for 24 hours, the following formula:

[In the formula, C represents the mass (g) of the polymer film before immersion, and D represents the mass (g) of the polymer film after immersion].
The polymer membrane according to claim 4, wherein the swelling rate calculated by the above method is 40% or more.
The polymer film for a non-aqueous electrolyte battery according to claim 1, wherein the polyvinyl acetal-based resin has a crosslinked structure.
When immersed in diethyl carbonate at 60 ° C. for 1 hour, the following formula:

[In the formula, A represents the mass (g) of the polymer film before immersion, and B represents the dry mass (g) of the polymer film after immersion].
The polymer membrane according to claim 6, wherein the dissolution rate calculated by the above method is 2% or less.
When immersed in a solution of lithium bis (fluorosulfonyl) imide in 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide at a concentration of 1 mol / L at 25 ° C. for 24 hours, the following formula:

[In the formula, C represents the mass (g) of the polymer film before immersion, and D represents the mass (g) of the polymer film after immersion].
The polymer membrane according to claim 6 or 7, wherein the swelling rate calculated by the above method is 20% or more.
The polymer membrane according to any one of claims 6 to 8, wherein the crosslinked structure is a structure derived from a crosslinking agent having a reactive group for a hydroxyl group.
The polymer membrane according to any one of claims 1 to 9, wherein the polyvinyl acetal-based resin is at least one selected from the group consisting of polyvinyl butyral, polyvinyl nonanal, and polyvinyl octanal.
The polymer film according to any one of claims 1 to 10, wherein the degree of polymerization of the polyvinyl acetal resin is 250 to 5,000.
The polymer film according to any one of claims 1 to 11, wherein the degree of saponification of the polyvinyl acetal resin is 90 mol% or more.
A non-aqueous electrolyte battery comprising the polymer membrane according to any one of claims 1 to 12.