JP2023003220A - Separator for non-aqueous electrolyte battery - Google Patents

Abstract

To provide a separator for a non-aqueous electrolyte battery that can form a non-aqueous electrolyte battery having high heat resistance and excellent capacity retention ratio.SOLUTION: A separator for a non-aqueous electrolyte battery contains non-woven fabric and resin, and has a white index of 30 to 75.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte battery separator and a non-aqueous electrolyte battery including the non-aqueous electrolyte battery separator.

2. Description of the Related Art In recent years, various non-aqueous electrolyte batteries have been developed with the spread of mobile terminals such as mobile phones, laptop computers, and pad-type information terminal devices, electric vehicles, hybrid vehicles, and the like. Non-aqueous electrolyte batteries such as lithium-ion secondary batteries differ in form, capacity, performance, etc., depending _on their use. A structure in which a lithium salt such as LiBF ₄ , LiTFSI [lithium (bistrifluoromethylsulfonylimide)], or LiFSI [lithium (bisfluorosulfonylimide)] is contained in a container together with an electrolytic solution in which an organic liquid such as ethylene carbonate is dissolved. have.

Compared to water-based batteries, non-aqueous electrolyte batteries with the above structure are more susceptible to temperature rise due to external heat, overcharging, and smoke, fire, and explosion risks due to internal and external short circuits, etc., and are highly safe. gender is required. From the viewpoint of safety, a separator such as polypropylene having a shutdown function and a heat-resistant coated separator coated with aramid resin or the like are known. Also known is a separator composed of a heat-resistant porous film (porous film), for example, an affinity porous sheet in which a porous sheet such as a nonwoven fabric is coated with a heat-resistant resin (Patent Document 1).

Patent No. 5944808

However, according to the study of the present inventors, separators such as polypropylene and heat-resistant coated separators coated with aramid resin, etc., may cause film shrinkage under extremely high temperature conditions, and may not have sufficient heat resistance. It turns out there is. In addition, it has been found that when a battery using a separator such as that disclosed in Patent Document 1 is repeatedly charged and discharged, micro short-circuiting tends to occur, the battery capacity tends to decrease, and sufficient capacity retention cannot be obtained in some cases.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a separator for a non-aqueous electrolyte battery that has high heat resistance and is capable of forming a non-aqueous electrolyte battery with excellent capacity retention, and the non-aqueous electrolyte battery.

As a result of intensive studies aimed at solving the above problems, the present inventor found that the above problems can be solved by adjusting the white index to 30 to 75 in a non-aqueous electrolyte battery separator containing a nonwoven fabric and a resin. , completed the present invention. The present invention includes the following aspects.

[1] A non-aqueous electrolyte battery separator comprising a non-woven fabric and a resin and having a white index of 30 to 75.
[2] The separator for non-aqueous electrolyte batteries according to [1], which has a yellow index of -10 to 2.0.
[3] The nonwoven fabric is at least one selected from the group consisting of polyamide resin fibers, polyimide fibers, polyamideimide fibers, polyetherimide fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, and polyester fibers. The separator for non-aqueous electrolyte batteries according to [1] or [2], comprising:
[4] The non-aqueous electrolyte battery separator according to any one of [1] to [3], wherein the resin is a water-soluble resin.
[5] The nonaqueous electrolyte battery separator according to any one of [1] to [4], wherein the resin is a polyvinyl alcohol resin.
[6] The non-aqueous electrolyte battery separator according to [5], wherein the polyvinyl alcohol resin is at least one selected from the group consisting of polyvinyl alcohol resin, ethylene-vinyl alcohol resin, and polyvinyl acetal resin.
[7] The separator for non-aqueous electrolyte batteries according to any one of [1] to [6], wherein the resin exists as a porous film.
[8] The non-aqueous electrolyte battery separator according to any one of [1] to [7], which does not substantially contain a heat-resistant filler.
[9] A non-aqueous electrolyte battery comprising the separator for non-aqueous electrolyte batteries according to any one of [1] to [8].

INDUSTRIAL APPLICABILITY The separator for a non-aqueous electrolyte battery of the present invention can form a non-aqueous electrolyte battery having high heat resistance and excellent capacity retention. Therefore, the separator for non-aqueous electrolyte batteries of the present invention can be suitably used for non-aqueous electrolyte batteries.

[Separator for non-aqueous electrolyte battery]
The non-aqueous electrolyte battery separator of the present invention contains a non-woven fabric and a resin, and has a white index (also referred to as WI) of 30-75.

The present inventors found that adjusting the WI of the separator to 30 to 75 surprisingly improves the heat resistance of the separator and effectively suppresses the decrease in battery capacity caused by repeated charging and discharging of a battery containing the separator. I found what I can do. Although the reason is not clear, the numerical value of WI reflects the structural form of the composite based on the light diffusibility of the composite in which the nonwoven fabric and the resin are composited. It is presumed that the composite structure of (1) contributes to the improvement of the ability to prevent high-temperature heat shrinkage due to the nonwoven fabric of the separator and the improvement of the battery capacity retention ability due to the prevention of micro short circuits by the filling resin. In this specification, the separator for non-aqueous electrolyte batteries may be simply referred to as "separator".

<Nonwoven fabric>
The fiber material constituting the nonwoven fabric in the present invention is not particularly limited, and examples include polyolefin fibers, cellulose fibers, (meth)acrylic fibers, polyvinyl alcohol fibers, vinyl chloride fibers, styrene fibers, and polyester fibers. , polyamide fibers, polycarbonate fibers, and polyurethane fibers. Among these fibers, from the viewpoint of easily increasing the heat resistance of the separator, nonwoven fabrics include polyamide fiber, polyimide fiber, polyamideimide fiber, polyetherimide fiber, polyacrylonitrile fiber, polyvinyl alcohol fiber, and polyester. Preferably, it contains at least one selected from the group consisting of poly-based fibers, more preferably at least one selected from the group consisting of polyamide-based fibers, polyvinyl alcohol-based fibers and polyester-based fibers. , polyvinyl alcohol fibers and/or polyester fibers.

The polyvinyl alcohol-based fiber is preferably at least one selected from the group consisting of polyvinyl alcohol fiber, ethylene-vinyl alcohol fiber, and polyvinyl acetal fiber, from the viewpoint of easily increasing the battery capacity retention rate of the separator. Alcohol fibers are more preferred.

The polyvinyl alcohol fiber, the ethylene-vinyl alcohol fiber, and the polyvinyl acetal fiber are respectively the fiber made of the polyvinyl alcohol resin described in the <Resin> section, the ethylene-vinyl alcohol resin described in the <Resin> section, and fibers made of the polyvinyl acetal resin described in the <Resin> section.

The polyester fiber refers to a fiber made of a polyester resin, and the polyester resin refers to a polymer having an ester bond as the main bond in the main chain, such as a structural unit derived from a dicarboxylic acid and a structural unit derived from a diol. , and/or structural units derived from hydroxycarboxylic acid. In the present specification, the “structural unit derived from” may be simply referred to as “unit”. A unit may be called a hydroxycarboxylic acid unit or the like.

In the polyester-based resin, examples of the dicarboxylic acid constituting the dicarboxylic acid unit include aliphatic dicarboxylic acids such as malonic acid, succinic acid, adipic acid, azelaic acid, and sebacic acid; cyclohexanedicarboxylic acid, norbornene dicarboxylic acid, and tricyclodecane. Alicyclic dicarboxylic acids such as dicarboxylic acids; terephthalic acid, isophthalic acid, phthalic acid, biphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylketonedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalene dicarboxylic acids, aromatic dicarboxylic acids such as 2,7-naphthalenedicarboxylic acid; and ester-forming derivatives thereof. Among these, terephthalic acid and naphthalene dicarboxylic acid are preferable, and terephthalic acid is more preferable, from the viewpoint of easily increasing the heat resistance of the separator and the capacity retention of the battery. A dicarboxylic acid can be used individually or in combination of 2 or more types.

In the polyester-based resin, the diol constituting the diol unit includes, for example, ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, methylpentanediol, diethylene glycol, and 1,4-butylene glycol. Diol; cyclohexanedimethanol (eg, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol), norbornenedimethanol, tricyclodecanedimethanol and other cycloaliphatic diols; biphenol ( 4,4'-biphenol), aromatic diols such as hydroquinone, and the like. Among these, aliphatic diols such as ethylene glycol and aromatic diols such as 4,4'-biphenol are preferable from the viewpoint of easily increasing the heat resistance of the separator and the capacity retention of the battery. A diol can be used individually or in combination of 2 or more types.

In the polyester resin, the hydroxycarboxylic acid constituting the hydroxycarboxylic acid unit includes aliphatic hydroxycarboxylic acids such as 10-hydroxyoctadecanoic acid, lactic acid, hydroxyacrylic acid, 2-hydroxy-2-methylpropionic acid, and hydroxybutyric acid. alicyclic hydroxycarboxylic acids such as hydroxymethylcyclohexanecarboxylic acid, hydroxymethylnorbornenecarboxylic acid, and hydroxymethyltricyclodecanecarboxylic acid; hydroxybenzoic acid (e.g., parahydroxybenzoic acid), hydroxytoluic acid, hydroxynaphthoic acid (e.g., 6 -hydroxy-2-naphthoic acid), 3-(hydroxyphenyl)propionic acid, hydroxyphenylacetic acid, aromatic hydroxycarboxylic acids such as 3-hydroxy-3-phenylpropionic acid; and ester-forming derivatives thereof. . Among these, aromatic hydroxycarboxylic acids such as hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid are preferable from the viewpoint of easily increasing the heat resistance of the separator and the capacity retention of the battery. These hydroxycarboxylic acids can be used alone or in combination of two or more. Moreover, the polyester-based resin may contain structural units other than the dicarboxylic acid unit, the diol unit, and the hydroxycarboxylic acid unit.

In one embodiment of the present invention, the ratio of the dicarboxylic acid unit to the diol unit in the polyester resin is preferably 10:1 to 1:10, more preferably 5:1 to 1:5, still more preferably 2:1. to 1:2, particularly preferably 1.5:1 to 1.5.

In one embodiment of the present invention, polyester fibers include, for example, polyalkylene terephthalate fibers such as polyethylene terephthalate fiber, polytrimethylene terephthalate fiber, polybutylene terephthalate fiber, polylactic acid fiber, molten liquid crystal forming polyester fiber, and the like. Among these, the polyester fiber is preferably polyethylene terephthalate fiber and/or molten liquid crystal forming polyester fiber from the viewpoint of easily increasing the heat resistance of the separator.

The types of nonwoven fabrics include nonwoven fabrics formed by wet and dry processes, meltblown nonwoven fabrics, spunlaced nonwoven fabrics, thermal bonded nonwoven fabrics, and nonwoven fabrics formed by needle punching. Further, examples of the structure of the base fabric of the nonwoven fabric include plain weave and twill weave.

If necessary, the nonwoven fabric may be added with commonly used additives such as colorants, inorganic fillers, antioxidants, ultraviolet absorbers, and/or thermoplastic elastomers to the extent that the effects of the present invention are not impaired.

The molten liquid crystal-forming polyester constituting the molten liquid crystal-forming polyester fiber is a resin having excellent heat resistance and chemical resistance. In the present specification, the melt liquid crystal formability indicates the property of exhibiting optical anisotropy (liquid crystallinity) in the melt phase, and the melt liquid crystal formability polyester means a polyester exhibiting the melt liquid crystal formability. The "molten liquid crystal formability" can be identified by, for example, placing a sample on a hot stage, heating it in a nitrogen atmosphere, and observing light transmitted through the sample. The melt liquid crystal-forming polyester is composed of repeating structural units derived from, for example, an aromatic diol, an aromatic dicarboxylic acid, an aromatic hydroxycarboxylic acid, or the like. The structural unit derived from aromatic hydroxycarboxylic acid is not particularly limited in its chemical constitution. Further, the melt liquid crystal-forming polyester may contain structural units derived from an aromatic diamine, an aromatic hydroxyamine, or an aromatic aminocarboxylic acid to the extent that the effects of the present invention are not impaired. For example, preferred structural units include those shown in Table 1.

Each Y is independently a substituent capable of substituting within the range of 1 to the maximum substitutable number on an aromatic ring or a cyclo ring. Specifically, each Y is independently a hydrogen atom, a halogen atom (e.g. , a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), an alkyl group (e.g., a methyl group, an ethyl group, an isopropyl group, an alkyl group having 1 to 4 carbon atoms such as a t-butyl group, etc.), an alkoxy group (e.g., , methoxy group, ethoxy group, isopropoxy group, n-butoxy group, etc.), aryl group (e.g., phenyl group, naphthyl group, etc.), aralkyl group [benzyl group (phenylmethyl group), phenethyl group (phenylethyl group), etc. ], an aryloxy group (such as a phenoxy group), and an aralkyloxy group (such as a benzyloxy group).

More preferred structural units include structural units described in Examples (1) to (18) shown in Tables 2, 3 and 4 below. When the structural unit in the formula is a structural unit capable of exhibiting multiple structures, two or more of such structural units may be combined and used as a structural unit that constitutes the polymer.

Moreover, as Z, the substituent represented by the following formula is mentioned.

Among these, the melt liquid crystal-forming polyester used in the present invention has a structure in which parahydroxybenzoic acid and 6-hydroxy-2-naphthoic acid are main components, or parahydroxybenzoic acid and 6-hydroxy-2 - A configuration in which naphthoic acid, terephthalic acid and biphenol are the main components is preferred.

The nonwoven fabric containing a molten liquid crystal-forming polyester is preferably a meltblown nonwoven fabric obtained by a meltblowing method. A known method can be adopted for the melt blowing method. For example, the melted molten liquid crystal-forming polyester is discharged as a molten polymer from a plurality of nozzle holes arranged in a row, and the injection gas port provided adjacent to the orifice die. In this method, high-temperature, high-speed air is jetted from a nozzle to make the extruded molten polymer into fine fibers, and then the fiber stream is collected on a collector such as a conveyor net to produce a nonwoven fabric.

In the separator of the present invention, the average fiber diameter of the nonwoven fabric is preferably 0.1 μm or more, more preferably 0.3 μm or more, still more preferably 0.8 μm or more, even more preferably 1.0 μm or more, and particularly preferably 1.0 μm or more. It is 5 µm or more, preferably 15 µm or less, more preferably 13 µm or less, and still more preferably 9 µm or less. When the average fiber diameter of the nonwoven fabric is at least the above lower limit, the mechanical properties and heat resistance of the obtained separator can be easily improved. It suppresses the internal short circuit and makes it easy to increase the capacity retention rate of the battery. The average fiber diameter can be obtained, for example, by measuring the length from an electron microscope image.

In the separator of the present invention, the nonwoven fabric has a basis weight of preferably 1 g/m ² or more, more preferably 2 g/m ² or more, still more preferably 3 g/m ² or more, and preferably 45 g/m ² or less, more preferably 40 g/m ² or less, more preferably 30 g/m ² or less, even more preferably 20 g/m ² or less, and particularly preferably 15 g/m ² or less. When the basis weight of the nonwoven fabric is at least the above lower limit, the strength of the separator increases, and the capacity retention rate of the battery tends to increase. Moreover, it is easy to improve the heat resistance of the separator. When the basis weight of the nonwoven fabric is equal to or less than the above upper limit, it is easy to reduce the internal resistance.

In the separator of the present invention, the melting point of the nonwoven fabric is preferably 140° C. or higher, more preferably 200° C. or higher, still more preferably 250° C. or higher, even more preferably 300° C. or higher, particularly preferably 330° C. or higher. It is 650° C. or lower, more preferably 600° C. or lower, still more preferably 550° C. or lower. When the melting point of the nonwoven fabric is at least the above lower limit, the heat resistance of the separator can be easily increased, and when the melting point of the nonwoven fabric is at most the above upper limit, moldability can be easily enhanced. The melting point can be measured, for example, with a differential scanning calorimeter.

In the separator of the present invention, the thickness (film thickness) of the nonwoven fabric is preferably 1 µm or more, more preferably 2 µm or more, still more preferably 3 µm or more, even more preferably 4 µm or more, particularly preferably 5 µm or more, and particularly more preferably 7 µm. It is preferably 20 μm or less, more preferably 17 μm or less, even more preferably 15 μm or less, even more preferably 13 μm or less, and particularly preferably 11 μm or less. When the thickness of the nonwoven fabric is at least the above lower limit, the heat resistance of the separator and the capacity retention rate and electrolyte retention capacity of the battery can be easily increased. The amount can be increased, and it is easy to increase the battery capacity. The thickness of the nonwoven fabric can be measured with a thickness gauge, for example, by the method described in Examples.

The nonwoven fabric may be subjected to calender treatment or press treatment, if necessary, in order to improve the accuracy of thickness and homogeneity, and may be subjected to graft polymerization, plasma treatment, corona treatment, or the like depending on the purpose.

<Resin>
The separator of the present invention contains resin. Examples of resins include, but are not limited to, polyvinyl alcohol resins, polyolefin resins, vinyl resins, polycarbonate resins, polythiocarbonate resins, polyester resins, polyacetal resins, polyamide resins, polyimide resins, and polyamideimide. resin, polyetherimide resin, polyacrylonitrile resin, polyphenylene ether resin, polysulfone resin, polyphenylene sulfide resin, polyetherketone resin, thermoplastic elastomer, phenolic resin, amino resin (urea resin, melamine resins), furan-based resins, epoxy-based resins, polyurethane-based resins, silicone-based resins, diallyl phthalate-based resins, vinyl ester-based resins, furan-based resins, aniline-based resins, acetone-formaldehyde-based resins, alkyd-based resins, maleimide-based resins Resins, maleimide-cyanate ester resins, cyanate ester resins, benzoxazine resins, polybenzimidazole resins, polycarbodiimide resins, poly(meth)acrylic resins, styrene resins, rubber resins, fluorine resins A resin etc. are mentioned. Among these, the resin is preferably a water-soluble resin, and more preferably a polyvinyl alcohol-based resin, from the viewpoint of easily increasing the heat resistance of the separator and the capacity retention rate of the battery and of facilitating production. These resins can be used alone or in combination of two or more.

The polyvinyl alcohol-based resin is at least one selected from the group consisting of ethylene-vinyl alcohol resin, polyvinyl alcohol resin, and polyvinyl acetal resin, from the viewpoint of easily increasing the heat resistance of the separator and the capacity retention of the battery. preferable. These polyvinyl alcohol-based resins can be used alone or in combination of two or more.

Examples of ethylene-vinyl alcohol resins include those obtained by saponifying ethylene-vinyl ester copolymers such as ethylene-vinyl acetate copolymers. The ethylene content (ethylene modification amount) of the ethylene-vinyl alcohol resin is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 25 mol% or more, and more preferably 60 mol% or less, more preferably. is 55 mol % or less, more preferably 50 mol % or less. When the ethylene content is at least the above lower limit, the separator strength, water resistance, heat resistance, and battery capacity retention are likely to be improved. Since the resin can have moderate hydrophilicity, the separator can be easily processed.

In one embodiment of the present invention, the ethylene-vinyl alcohol resin contained in the separator of the present invention has an ethylene content from the viewpoint of easily increasing affinity with the electrolytic solution, strength, heat resistance, and capacity retention of the battery. It is preferably 5 to 60 mol % and has a saponification degree of 80 mol % or more.

The copolymerization form of the ethylene-vinyl alcohol resin is not particularly limited, and may be any of random copolymers, alternating copolymers, block copolymers, graft copolymers, and the like.

As the ethylene-vinyl alcohol resin in the present invention, a commercially available product or one prepared by a conventionally known method may be used.

Polyvinyl alcohol resins include those obtained by saponifying resins obtained by polymerizing vinyl alcohol and, if necessary, other monomers. For example, it can be produced by saponifying the resin dissolved in a solvent such as alcohol. Solvents used in this method include, for example, lower alcohols such as methanol and ethanol, and methanol can be preferably used. The alcohol used in the saponification reaction may contain solvents such as acetone, methyl acetate, ethyl acetate, and benzene, as long as the amount is, for example, 40% by mass or less. The catalyst used in the saponification reaction includes alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, alkali catalysts such as sodium methoxide, and acid catalysts such as mineral acids. The temperature of the saponification reaction is not particularly limited, but the range of 20 to 60°C is preferable. The polyvinyl alcohol resin obtained by the saponification reaction is dried after washing.

The polyvinyl acetal resin can be produced, for example, by acetalizing the polyvinyl alcohol resin with an aldehyde, and the method of acetalization 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 polyvinyl alcohol resin as a raw material is dissolved in water or acetone, a catalyst such as an acid is added to carry out an acetalization reaction, and the resulting polyvinyl acetal resin is precipitated. and neutralize 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 polyvinyl alcohol resin is not dissolved is used. Regardless of which method is used, the resulting polyvinyl acetal resin powder contains impurities such as unreacted aldehydes and salts generated by neutralization. A polyvinyl acetal resin with high purity can be obtained by extracting or removing by evaporation using a solvent.

Aldehydes used for acetalization include aliphatic aldehydes such as formaldehyde, acetaldehyde, propylaldehyde, n-butyraldehyde (1-butanol), sec-butyraldehyde, octylaldehyde, dodecylaldehyde; cyclohexanecarbaldehyde, cyclooctane; Alicyclic aldehydes such as carbaldehyde, trimethylcyclohexanecarbaldehyde, cyclopentylaldehyde, dimethylcyclohexanecarbaldehyde, methylcyclohexanecarbaldehyde, methylcyclopentylaldehyde; Terpene aldehydes such as α-pyronenaldehyde, myrtenal, dihydromyrtenal and camphenylaldehyde; aromatic aldehydes such as benzaldehyde, naphthaldehyde, anthraldehyde, phenylacetaldehyde, tolualdehyde, dimethylbenzaldehyde, cuminaldehyde and benzaldehyde; unsaturated aldehydes such as cyclohexenealdehyde, dimethylcyclohexenealdehyde and acrolein; aldehydes having a heterocyclic ring such as furfural and 5-methylfurfural; hemiacetals such as glucose and glucosamine; aldehydes having an amino group such as 4-aminobutyraldehyde; mentioned. These aldehydes can be used alone or in combination of two or more. Among these, aliphatic aldehydes such as n-butyraldehyde (1-butanol) are preferable from the viewpoints of affinity with the electrolytic solution of the separator and easy enhancement of the capacity retention of the battery. Aliphatic ketones such as 2-propanone, methyl ethyl ketone, 3-pentanone, and 2-hexanone; aliphatic ketones such as cyclopentanone and cyclohexanone; Group ketones and the like can also be used.

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

Polyvinyl alcohol-based resins contain, in addition to ethylene units, acetal units and vinyl alcohol units, monomers (also referred to as other monomers) that can be copolymerized with these units, as long as the effects of the present invention are not impaired. A derived structural unit may be included. Other monomers include α-olefins such as propylene, 1-butene, isobutene and 1-hexene; acrylic acid, methacrylic acid, crotonic acid, phthalic acid, phthalic anhydride, maleic acid, maleic anhydride, Unsaturated acids such as itaconic acid and itaconic anhydride, 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-acrylamide propane Acrylamides such as sulfonic acid and its salts, acrylamidopropyldimethylamine and its acid salts or its quaternary salts; methacrylamides such as amidopropanesulfonic acid and its salts, methacrylamidopropyldimethylamine and its acid salts or its quaternary salts; N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide and N-vinylacetamide; acrylonitrile , vinyl cyanides such as methacrylonitrile; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether; allyl acetate; propyl allyl ether, butyl allyl ether, hexyl allyl ether vinyl halides such as vinyl chloride, vinyl fluoride and vinyl bromide; vinylidene halides such as vinylidene chloride and vinylidene fluoride; vinylsilanes such as trimethoxyvinylsilane; compounds having an oxyalkylene group of; isopropenyl acetate; hydroxy group-containing α-olefins such as ol, 3-methyl-3-butene-1-ol; Acid; vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyldimethylamine, vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethyl Compounds having cationic groups derived from ammonium chloride, N-acrylamidodimethylamine, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, dimethylallylamine, allylethylamine, and the like. Among these, acrylic acid, methacrylic acid, crotonic acid, phthalic acid, phthalic anhydride, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, etc., are used from the viewpoint of easily increasing the heat resistance of the separator and the capacity retention rate of the battery. and salts thereof or alkyl esters thereof having 1 to 18 carbon atoms are preferred. These monomers can be used alone or in combination of two or more.

The content of structural units derived from other monomers is usually 20 mol% or less, preferably 10 mol% or less, and 5 mol% or less with respect to the total molar amount of the structural units constituting the polyvinyl alcohol-based resin. is more preferred.

The hydroxyl group content of the polyvinyl alcohol resin is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 20 mol% or more, and preferably 100 mol, based on the vinyl group unit of the polyvinyl alcohol resin. % or less, more preferably 90 mol % or less, still more preferably 85 mol % or less, still more preferably 80 mol % or less. When the amount of hydroxyl groups is within the above range, the heat resistance of the separator, the affinity with the electrolytic solution, and the capacity retention rate of the battery are likely to be increased, and the air permeability of the separator is likely to be reduced. The amount of hydroxyl groups can be measured, for example, by ¹ H-NMR. The vinyl group unit means a structural unit represented by the formula --(CH ₂ --C(R)H)--, where R represents H or a substituent.

The degree of saponification of the polyvinyl alcohol resin is preferably 50 mol % or more, more preferably 55 mol % or more, still more preferably 60 mol % or more, and preferably 100 mol % or less. When the degree of saponification is within the above range, the heat resistance of the separator, the affinity with the electrolytic solution, and the capacity retention of the battery can be easily increased, and the air permeability of the separator can be easily reduced. The degree of saponification can be measured according to JIS-K6726.

In one embodiment of the present invention, the degree of saponification when polyvinyl alcohol resin is used as the polyvinyl alcohol resin is preferably 50 mol% or more, more preferably 55 mol% or more, still more preferably 60 mol% or more, especially It is preferably 65 mol % or more, preferably 100 mol % or less, more preferably 99 mol % or less, still more preferably 98 mol % or less. When the degree of saponification is within the above range, the heat resistance of the separator and the swelling property against the electrolytic solution are enhanced, the capacity retention rate of the battery is easily increased, and the air permeability of the separator is easily reduced.

In one embodiment of the present invention, the degree of saponification when using ethylene-vinyl alcohol resin and/or polyvinyl acetal resin as the polyvinyl alcohol resin is preferably 70 mol% or more, more preferably 80 mol% or more, and further It is preferably 90 mol % or more, particularly preferably 95 mol % or more, and preferably 100 mol % or less. When the degree of saponification is within the above range, the heat resistance of the separator, the affinity with the electrolytic solution, and the capacity retention of the battery can be easily increased, and the air permeability of the separator can be easily reduced. The degree of saponification can be measured according to JIS-K6726. In this specification, the degree of saponification of polyvinyl acetal resin means the degree of saponification of polyvinyl alcohol resin before acetalization.

In one embodiment of the present invention, the viscosity average degree of polymerization of the polyvinyl alcohol resin is preferably 100 or more, more preferably 300 or more, still more preferably 400 or more, still more preferably 600 or more, preferably 5000 or less, It is more preferably 3000 or less, still more preferably 2500 or less. When the viscosity-average degree of polymerization is at least the above lower limit, the strength and heat resistance of the separator are likely to be increased, and the capacity retention rate of the battery is likely to be increased. Further, when the viscosity-average degree of polymerization is equal to or less than the above upper limit, it is easy to improve the film formability. The viscosity average degree of polymerization of the polyvinyl alcohol resin can be measured according to JIS-K6726, for example, by the method described in Examples.

In one embodiment of the present invention, the amount of resin supported in the separator of the present invention is preferably 1.3 g/m ² or more, more preferably 1.5 g/m ² or more, still more preferably 1.8 g/m ² Above, still more preferably 2.0 g/m ² or more, preferably 5.5 g/m ² or less, more preferably 5.0 g/m ² or less, even more preferably 4.5 g/m ² or less, still more preferably It is preferably 4.0 g/m ² or less, particularly preferably 3.5 g/m ² or less, and particularly preferably 3.0 g/m ² or less. When the supported amount of the resin is at least the above lower limit, the strength and heat resistance of the separator are likely to be improved, and internal short circuiting of the battery is likely to be suppressed. Furthermore, it is easy to improve the adhesiveness with the electrode and the liquid absorbency. When the supported amount of the resin is equal to or less than the above upper limit, the air permeability of the separator is likely to be reduced, and the capacity retention of the battery is likely to be increased. The supported amount of resin (g/m ² ) indicates the amount (g) of resin per 1 m ² of separator. In addition, the amount of resin supported (g/m ² ) may be calculated by subtracting the amount of nonwoven fabric alone (g/m ² ) from the amount of separator (g/m ² ). It can be calculated by the method of

In one embodiment of the present invention, the content of the resin in the separator of the present invention is preferably 5% by mass or more, more preferably 8% by mass or more, and still more preferably 10% by mass or more, relative to the mass of the separator. Still more preferably 15% by mass or more, particularly preferably 20% by mass or more, particularly more preferably 25% by mass or more, preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 45% by mass or less is. When the resin content in the separator is at least the above lower limit, the strength and heat resistance of the separator are likely to be improved, and internal short circuiting of the battery is likely to be suppressed. Furthermore, it is easy to improve the adhesiveness with the electrode and the liquid absorbency. When the content of the resin is equal to or less than the above upper limit, the air permeability of the separator is likely to be reduced, and the capacity retention rate of the battery is likely to be increased. The resin content may be calculated by subtracting the mass of the nonwoven fabric alone from the mass of the separator; It may be calculated by dissolving the resin with a stool and subtracting the mass after dissolution from the mass before dissolution; or by thermal analysis, for example, weight change using a thermogravimetric analyzer (TG).

The resin contained in the separator of the present invention preferably exists as a porous film (also referred to as a porous resin film). When the resin is present in the separator in the form of a porous resin membrane, that is, when the separator contains the porous resin membrane, the strength, heat resistance, and adhesiveness to the electrode of the separator can be easily increased, and the internal short circuit of the battery can be suppressed. and it is easy to increase the capacity retention rate. In addition, the porous membrane indicates a membrane having a large number of pores inside and outside the membrane.

The resin (preferably the porous resin membrane) may contain an additive (a). Examples of the additive (a) include polymer compounds other than the resin contained in the separator, inorganic fine powders such as cross-linking agents, antioxidants, ultraviolet absorbers, lubricants, antifoaming agents and antiblocking agents; Organic substances such as promoters (for example, polyethylene glycol) and the like are included. Additives (a) can be used alone or in combination of two or more. The content of the additive (a) is usually 10% by mass or less, preferably 5% by mass or less, more preferably 5% by mass or less, based on the mass of the resin containing the additive (that is, the total mass of the resin itself and the additive). It is 1% by mass or less. In one embodiment of the present invention, the content of the surfactant is preferably 5% by mass or less with respect to the mass of the resin containing the surfactant (that is, the total mass of the resin itself and the surfactant). , more preferably 3% by mass or less, still more preferably 1% by mass or less, particularly preferably 0.5% by mass or less, and most preferably 0.1% by mass or less.

<Separator for non-aqueous electrolyte battery>
The separator of the present invention contains the nonwoven fabric and the resin, and has a WI of 30-75. Therefore, a non-aqueous electrolyte battery having high heat resistance and excellent capacity retention can be formed. Further, the separator of the present invention can exhibit such effects even if it is a thin film. Therefore, the separator of the present invention can be suitably used for non-aqueous electrolyte batteries.

On the other hand, if the WI is outside the range of 30 to 75, micro short circuits tend to occur, and heat resistance and capacity retention tend to deteriorate.

WI is 30 or more, preferably 32 or more, more preferably 34 or more, still more preferably 36 or more, 75 or less, preferably 70 or less, more preferably 65 or less, still more preferably 60 or less, still more preferably 55 Below, it is particularly preferably 50 or less, and particularly more preferably 45 or less. When WI is at least the above lower limit, it is easy to suppress the internal short circuit of the battery, and it is easy to increase the capacity retention rate of the battery. When the WI is equal to or less than the above upper limit, the heat resistance of the separator is likely to be improved, and thus the film shrinkage rate is likely to be reduced. Furthermore, it is easy to increase the capacity retention rate of the battery. WI can be measured using a spectrophotometer in accordance with American Standards Test Methods E313, for example, by the method described in Examples. In addition, the separator of the present invention only needs to satisfy the above range of WI on at least one side (single side), preferably on both sides.

As described above, the numerical value of WI reflects the structural form of the composite material in which the nonwoven fabric and the resin are combined. This is advantageous from the viewpoint of improving the performance and battery capacity retention. In particular, the nonwoven fabric and the optimum amount of resin are combined from the surface of the nonwoven fabric to the inside. If the fabric has a composite structure (also referred to as an optimal composite structure) in which an optimum amount of resin is present between the fibers of the nonwoven fabric, the WI can satisfy a predetermined range.

In one embodiment of the present invention, the nonwoven fabric constituting the separator can exhibit a low WI value, and the porous resin membrane can exhibit a high WI value. In such an embodiment, although the nonwoven fabric alone exhibits a low WI value, the nonwoven fabric and the resin are combined to form an optimal composite structure, thereby increasing light diffusion and increasing the WI. It is believed that a range of 30-75 can be satisfied. On the other hand, even if a composite is formed, if the amount of resin carried is not optimal in relation to the nonwoven fabric, an optimal composite structure is not formed and WI cannot satisfy the predetermined range. Moreover, even if the supported amount of the resin is approximately the same, the WI may or may not satisfy the predetermined range. For example, when the nonwoven fabric surface is simply coated with a resin, the WI cannot satisfy the predetermined range. As described above, WI is considered to be an index mainly due to the composite structure of the separator. Surprisingly, the composite structure of the separator that satisfies the WI in a predetermined range improves the heat resistance and the capacity retention capacity of the battery. can contribute to In the present specification, the term "composite" refers to a state in which the nonwoven fabric surface is not simply coated (or coated) with a resin, but a state in which the resin exists (or penetrates) between the fibers (or voids) that make up the nonwoven fabric. indicates

In the separator of the present invention, WI is the method described in the section [Method for producing a separator for a non-aqueous electrolyte battery], in particular, the separator is produced by a method including a dewatering step, and the type and content of the nonwoven fabric or resin (or the supported amount), etc., can be adjusted within the range of 30 to 75 by, for example, adopting the preferred one of the present invention. The types of nonwoven fabric or resin include the average fiber diameter, basis weight, melting point, etc. of the nonwoven fabric, hydroxyl group amount, saponification degree, viscosity average degree of polymerization, etc. of the nonwoven fabric, thickness of the nonwoven fabric or resin, and the like. In one embodiment of the present invention, for example, WI tends to increase as the supported amount of the composite resin (preferably composite polyvinyl alcohol-based resin) increases.

The separator of the present invention preferably has a yellow index (sometimes referred to as YI) of -10 to 2.0. The present inventors have found that the heat resistance of the separator and the capacity retention of the resulting battery are improved when the WI of the separator is in the range of 30 to 75 and the YI is in the range of -10 to 2.0. I found it easy to improve. Although the reason is not clear, the following reasons are presumed. As mentioned above, WI can mainly depend on the composite structure of the separator, whereas YI can change depending on the type of nonwoven fabric, the type of resin, etc., especially the type of nonwoven fabric. be done. It is presumed that the separator having YI within the above range can include non-woven fabric or the like, which is particularly likely to exhibit heat resistance and battery capacity retention.

YI of the separator of the present invention is preferably −10 or more, more preferably −5.0 or more, still more preferably −2.5 or more, still more preferably −1.5 or more, and preferably 2.0 or less. , more preferably 1.5 or less, and still more preferably 1.0 or less. When YI is at least the above lower limit, the heat resistance of the separator can be easily increased, and when YI is at most the above upper limit, internal short circuiting of the obtained battery can be suppressed, and the capacity retention rate of the battery can be easily increased. . YI can be measured using a spectrophotometer according to American Standards Test Methods E313, for example, by the method described in Examples. In addition, YI is the method described in the section [Method for producing a separator for a non-aqueous electrolyte battery], in particular, the separator is produced by a method including a dewatering step, and the type and content (or supported amount) of the nonwoven fabric or resin ), etc., for example, by adopting the preferable one of the present invention, it can be adjusted to the range of -10 to 2.0.

Even if the separator of the present invention is a thin film, it can have excellent heat resistance and excellent battery capacity retention. The thickness (film thickness) of the separator of the present invention is preferably 25 μm or less, more preferably 20 μm or less, still more preferably 15 μm or less, even more preferably 14 μm or less, particularly preferably 12 μm or less, even more preferably 10 μm or less, and most preferably 10 μm or less. It is preferably 9 μm or less. When the thickness of the separator is at least the above lower limit, the capacity retention rate of the battery can be easily increased. Easy to raise. The thickness of the separator can be measured with a thickness gauge, for example, by the method described in Examples. The thickness of the separator can be adjusted, for example, by appropriately changing the thickness of the nonwoven fabric, the amount of resin supported, and the like.

In one embodiment of the present invention, the air permeability of the separator of the present invention is preferably 1 second or more, more preferably 5 seconds or more, still more preferably 10 seconds or more, still more preferably 20 seconds or more, and preferably It is 500 seconds or less, more preferably 400 seconds or less, still more preferably 300 seconds or less, still more preferably 100 seconds or less, and particularly preferably 80 seconds or less. When the air permeability is equal to or higher than the above lower limit, it is easy to increase the capacity retention of the battery and the liquid absorption of the electrolytic solution. In addition, since the adhesiveness between the separator and the electrode can be easily improved, misalignment between the separator and the electrode is less likely to occur in the battery manufacturing process. On the other hand, when the air permeability is equal to or less than the above upper limit, it tends to increase the liquid permeability of the electrolytic solution. In this specification, the air permeability indicates air permeability resistance, and the lower the value, the easier it is for air to pass through. The air permeability can be measured in accordance with JIS P8117, and the evaluation of the air permeability can be carried out five times at different locations for each sample, and the average value can be taken as the air permeability. It can be measured by the method described in . The air permeability can be adjusted, for example, by appropriately changing the pore size (or basis weight) of the nonwoven fabric, the resin content (or the supported amount), the pore size of the resin porous membrane, and the like.

In one embodiment of the present invention, the water content after drying the separator of the present invention at 100° C. for 1 hour is preferably 1% (10,000 ppm) or less, more preferably 0.8% (8,000 ppm or less). , more preferably 0.5% (5,000 ppm) or less, still more preferably 0.3% (3000 ppm) or less, and particularly preferably 0.11% (1100 ppm) or less. When the water content of the separator is equal to or less than the above upper limit, decomposition of the resin in the electrolytic solution is easily suppressed, and the capacity retention rate of the battery is easily increased. The lower limit of the water content is 0% or more. The water content can be measured using a moisture measuring device at a temperature of 120° C. after drying the separator at 100° C. for 1 hour. The water content of the separator can be adjusted by appropriately changing the amount of hydroxyl groups in the non-woven fabric or the resin, and tends to decrease as the amount of hydroxyl groups in the resin decreases, for example.

In one embodiment of the present invention, the separator of the present invention has a film shrinkage ratio at 150° C. of preferably 30% or less, more preferably 10% or less, even more preferably 5.0% or less, still more preferably 2.0. %, particularly preferably 1.5% or less, particularly more preferably 1.0% or less, even more preferably 0.5% or less, and most preferably 0.1% or less. When the film shrinkage rate is equal to or less than the above upper limit, heat resistance is likely to be exhibited. The lower limit of film shrinkage is usually 0% or more. The film shrinkage rate is the film shrinkage rate when heated at 150° C. for 1 hour, and can be calculated, for example, by the method described in Examples. In this specification, the heat resistance indicates the durability of the separator against heat, and can be evaluated, for example, by the above film shrinkage rate.

A battery comprising the separator of the present invention can exhibit excellent capacity retention. The capacity retention rate (also referred to as discharge capacity retention rate) of the battery comprising the separator of the present invention is preferably 90% or higher, more preferably 90.5% or higher, still more preferably 91% or higher, and still more preferably 91%. 0.5% or more, particularly preferably 92% or more, particularly more preferably 92.5% or more, most preferably 93% or more. The capacity retention rate of the battery can be measured, for example, by the method described in Examples. In the present specification, the term "excellent battery capacity retention" means that the battery has a high capacity retention.

The separator of the present invention may contain additives other than the nonwoven fabric and the resin. Other additives include, but are not particularly limited to, the additive (a) described above. Other additives, as described above, may be contained in the resin, preferably in the resin porous membrane, may be contained in the nonwoven fabric, or may be contained in a form independent of the nonwoven fabric or the resin. good too. The mass of other additives contained in the separator is usually 10% by mass or less, preferably 5% by mass or less, relative to the mass of the separator.
Since the separator of the present invention can exhibit sufficient heat resistance, in one embodiment of the present invention, the separator of the present invention preferably contains substantially no heat-resistant filler. The term "substantially free" means that the content of the heat-resistant filler is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less, and still more It is preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, particularly more preferably 0.01% by mass or less, and most preferably 0.001% by mass or less.

In the separator of the present invention, one nonwoven fabric may be used, or two or more nonwoven fabrics may be used to form a laminate. For example, it may be a separator comprising a laminate obtained by stacking a plurality of non-woven fabrics and a resin, or preferably a separator in which the laminate and a resin are combined. Further, other layers such as a functional layer may be laminated on the separator as long as the effects of the present invention are not impaired.

[Method for manufacturing separator for non-aqueous electrolyte battery]
The method for producing the separator of the present invention is not particularly limited, but the step (I) of dissolving the resin in a solvent to obtain a resin solution; the step (II) of impregnating the nonwoven fabric with the obtained resin solution; A method comprising the step (III) of removing liquid from the impregnated nonwoven fabric; and the step (IV) of coagulating the resin in the removed resin-impregnated nonwoven fabric with a coagulating liquid is preferred. When the resin in the resulting separator exists as a porous membrane, the resin solution may be referred to as a porous membrane forming solution.

In step (I), the solvent is not particularly limited as long as it can dissolve the resin, and examples thereof include water and organic solvents. Examples of organic solvents include, but are not limited to, alcoholic solvents such as methanol, ethanol, butanol, isopropanol, 1-propanol, 1-butanol, ethylene glycol; N-methylpyrrolidone, N-ethylpyrrolidone, N-methyl- Cyclic amide solvents such as N-alkylpyrrolidone such as α-methylpyrrolidone and N-ethyl-α-methylpyrrolidone; amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide; tetrahydrofuran, dioxane, morpholine cyclic ether solvents such as , N-methylmorpholine; sulfoxide solvents such as dimethylsulfoxide; sulfone solvents such as sulfolane. Among these, water, alcohol-based solvents, and sulfoxide-based solvents are preferable from the viewpoint of the solubility of resins (preferably polyvinyl alcohol-based resins). These organic solvents can be used alone or in combination of two or more.

In one embodiment of the present invention, when a mixed solvent containing water and an organic solvent is used as the solvent, the mixing ratio of water and the organic solvent (water/organic solvent) in the mixed solvent is preferably 3 by volume. /97 to 70/30, more preferably 5/95 to 65/35. By using a mixed solvent containing water and an organic solvent at a ratio within the above range, it is easy to prepare a resin solution containing a resin (preferably a polyvinyl alcohol-based resin) having a solid concentration suitable for forming a separator.

The solid content concentration of the resin in the resin solution is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass. When the solid content concentration of the resin is within the above range, the resin solution can be easily handled, and the separator can be easily formed.

In step (I), a resin solution is obtained by mixing, preferably stirring and mixing, a resin, a solvent, and optionally the aforementioned additives to dissolve the resin. The mixing temperature may be, for example, 20 to 100°C, preferably about 25 to 95°C, depending on the boiling point and solubility of the solvent. When a porous membrane formation accelerator is added as an additive, it is easy to promote the formation of a porous membrane as a phase separation component, reduce the air permeability of the obtained separator, and easily increase the capacity retention.

Step (II) is a step of impregnating a nonwoven fabric with a resin solution. Examples of impregnation methods include doctor blade method, dip method, reverse roll method, direct roll method, gravure method, extrusion method, immersion method, and brush coating method. The immersion method is preferable from the viewpoint that the WI and YI of the resulting separator easily satisfy the predetermined ranges described above. The solution temperature during impregnation is preferably 20 to 100°C, more preferably 25 to 80°C. By including the impregnation step, the resin is likely to exist between the fibers (or voids) constituting the nonwoven fabric of the obtained separator, and WI and YI are likely to satisfy the above predetermined ranges.

Step (III) is a step of removing liquid from the resin-impregnated nonwoven fabric obtained by impregnation. In the dewatering step, the resin solution existing on (or attached to) the surface of the nonwoven fabric is removed. The method of dewatering is, for example, using a device such as a blade coater, knife coater, bar coater, applicator, roll coater, squeeze roll, nip roll, etc., between the coating part or the dewatering part of the device and the surface of the nonwoven fabric, Preferably, at least no clearance is provided, and more preferably, along the surface of the nonwoven fabric (or along the direction perpendicular to the thickness direction of the nonwoven fabric) while the coating part or the draining part of the device is in contact with the surface of the nonwoven fabric. ) The method of deliquoring is preferred. By removing the liquid in this way, it is easy to adjust the WI and YI of the resulting separator within the predetermined ranges described above. The solution temperature during deliquoring is preferably 0 to 70°C, more preferably 5 to 60°C. By including such a dewatering step, after the step (IV), a separator in which the resin and the fibers constituting the nonwoven fabric are combined from the surface to the inside can be obtained without coating the entire surface of the nonwoven fabric with the resin. It is easy to adjust WI and YI of the separator within the predetermined range. In the present invention, liquid may be removed from at least one surface of the separator, but it is more preferable to remove liquid from both surfaces.

In one embodiment of the present invention, the conveyed resin-impregnated nonwoven fabric may be deliquored by, for example, a blade coater. In the deliquidation by a blade coater or the like, deliquidation can be performed while the blade is in contact with both surfaces of the resin-impregnated nonwoven fabric, so that the WI and YI of the obtained separator can be easily adjusted within the predetermined ranges described above. Also, by adjusting the pressure applied to the blade, the angle of the blade, and the like, WI, YI, and the amount (or content) of the resin to be carried can be adjusted. By using such a deliquoring method, production by a roll-to-roll system becomes possible, and productivity can be improved. Moreover, it is not necessary to use a base material, and WI and YI on both sides of the separator can be efficiently adjusted within the predetermined ranges described above. Specifically, as a roll-to-roll method, for example, a nonwoven fabric conveyed to a roll is conveyed through the porous film forming solution, a blade coater, a coagulating liquid described later, and a drying area, and then wound up. methods and the like.

In one embodiment of the present invention, the resin-impregnated nonwoven fabric is placed on a substrate, preferably on a substrate placed on a horizontal table, and the surface of the resin-impregnated nonwoven fabric opposite the substrate is deliquored as described above. may The base material is not particularly limited, and a base material containing a known resin may be used, or a glass substrate may be used. With such a method, the resin solution present (or attached) on the surface of the nonwoven fabric can be easily removed, and in particular, the removal of liquid on one side of the nonwoven fabric can reduce WI and YI within the above predetermined ranges on both sides of the separator. easy to adjust. More specifically, in this embodiment, a clearance between the device and the substrate surface (substrate It is preferable to perform liquid removal along a direction perpendicular to the thickness direction at a position where the clearance to the surface of the resin-impregnated nonwoven fabric is equal to or less than the thickness of the resin-impregnated nonwoven fabric. The clearance from the substrate surface is not particularly limited as long as it is equal to or less than the thickness of the resin-impregnated nonwoven fabric, and can be appropriately selected according to the thickness of the resin-impregnated nonwoven fabric. be. When the clearance is equal to or less than the above upper limit, it is easy to adjust the WI and YI of the separator to be obtained within the above predetermined range, and the smaller the clearance, the smaller the WI tends to be.

Step (IV) is a step of coagulating the resin in the drained resin-impregnated nonwoven fabric with a coagulating liquid. As a method of coagulating, for example, a method of immersing a dewatered, resin-impregnated nonwoven fabric in a coagulating liquid can be used. In one embodiment of the present invention, in a roll-to-roll method, a method of conveying a resin-impregnated nonwoven fabric conveyed by a roll through a coagulating liquid is preferred. Moreover, it is preferable to immerse the whole resin-impregnated nonwoven fabric placed on the base material in the coagulation liquid, and peel off the base material after coagulation.

The solidifying liquid is not particularly limited as long as it is a solvent capable of solidifying the resin solution, such as a poor solvent for the resin. Examples of the coagulating liquid include water, organic solvents, and mixed solvents of water and organic solvents. Examples of organic solvents include alcohol solvents such as methanol, ethanol, isopropanol and 1-propanol, and ketone solvents such as acetone and methyl ethyl ketone. These can be used singly or in combination of two or more.

The temperature of the coagulation liquid is preferably 0 to 70°C, more preferably 3 to 60°C, still more preferably 5 to 50°C. When the temperature of the coagulation liquid is within the above range, the resin, preferably a porous resin membrane, is easily formed between and/or on the fibers constituting the nonwoven fabric, and the air permeability is easily adjusted within the above range of the present invention.

In the production method of the present invention, the immersion time of the resin-impregnated nonwoven fabric in the coagulation liquid is, for example, 0.1 second to 30 minutes, preferably 1 second or longer, more preferably 3 seconds or longer, and preferably 25 minutes. 20 minutes or less, more preferably 20 minutes or less. When the immersion time is equal to or longer than the above lower limit, the resin tends to solidify sufficiently, and for example, when forming a porous resin membrane, pores having a desired pore diameter can easily be obtained. Further, when the immersion time is equal to or less than the above upper limit, excessive swelling in the coagulation liquid can be suppressed.

Step (IV) yields a nonwoven fabric comprising a wet film of resin. The obtained wet membrane may be subjected to a drying treatment to remove the solvent. The method of drying treatment is not particularly limited, and for example, natural drying; ventilation drying with warm air, hot air, or low humidity air; heat drying; reduced pressure/vacuum drying; A combination of these methods may be used. From the viewpoint of improving production efficiency without disturbing the pores and voids formed in the coagulation step, air drying is preferred. Drying conditions are determined according to the type of solvent used, the amount of solvent contained in the wet film, etc., and the solvent is removed as quickly as possible without damaging the resin, preferably the porous resin film (for example, cracking due to stress concentration). It may be determined appropriately so that it can be removed. For example, the drying temperature is generally 10 to 150°C, preferably 25 to 110°C, and the drying time is generally about 1 to 90 minutes.

Furthermore, in order to improve the smoothness of the separator, the separator from which the solvent has been removed may be subjected to a rolling treatment. Examples of the rolling method include methods such as die pressing and roll pressing.

[Non-aqueous electrolyte battery]
The present invention includes a non-aqueous electrolyte battery including the separator for a non-aqueous electrolyte battery of the present invention. Non-aqueous electrolyte batteries include, for example, lithium ion batteries, sodium ion batteries, lithium sulfur batteries, all-solid batteries, lithium ion capacitors, and lithium batteries. The non-aqueous electrolyte battery may be, for example, a non-aqueous electrolyte primary battery or a non-aqueous electrolyte secondary battery, preferably a non-aqueous electrolyte secondary battery. Since the non-aqueous electrolyte battery of the present invention contains the separator of the present invention, it has high heat resistance and is excellent in capacity retention (or discharge capacity retention). Furthermore, even if the thickness of the separator is thin, excellent heat resistance and capacity retention can be exhibited. As described above, in the non-aqueous electrolyte battery of the present invention, the film thickness of the separator can be reduced, so the amount of active material in the battery can be increased, and the battery capacity can be easily increased. Therefore, the non-aqueous electrolyte battery of the present invention has high heat resistance and can achieve both excellent capacity retention and high battery capacity.

In one embodiment of the present invention, the non-aqueous electrolyte battery of the present invention includes a positive electrode, a negative electrode and an electrolytic solution in addition to the separator of the present invention. The non-aqueous electrolyte battery of the present invention can be manufactured using known materials and techniques.

The non-aqueous electrolyte battery (sometimes simply referred to as "battery") of the present invention comprises at least the separator of the present invention, electrodes (a negative electrode and a positive electrode), and an electrolytic solution. Non-aqueous electrolyte batteries of the present invention include, for example, lithium ion batteries, lithium metal batteries, sodium ion batteries, potassium ion batteries, magnesium batteries, lithium sulfur batteries, all-solid lithium batteries, metal-air batteries, lithium ion capacitors, and the like. mentioned.

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

As the negative electrode active material, materials conventionally used as negative electrode active materials in non-aqueous electrolyte batteries can be used. Examples thereof include amorphous carbon, artificial graphite, natural graphite (graphite), mesocarbon microbeads ( MCMB), pitch-based carbon fiber, carbon black, activated carbon, carbon fiber, 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, other metal oxides, lithium metals, lithium 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 , and metals such as aluminum.

As the positive electrode active material, for example, materials conventionally used as positive electrode active materials for non-aqueous electrolyte batteries can be used, examples of which 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} and V ₆ O _{13 ;} Lithium-containing composite metal oxides such as LiNiCoMnO ₂ , 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 , sodium-containing complex metal oxides such as Na _x CoO ₂ , potassium-containing complex 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. Metal oxides, Mo ₃ S, MgTi ₂ S ₄ , V ₂ O ₅ , NVO, MgFeSiO ₄ , carbon paper, carbon materials, sulfur-based materials, and the like. These positive electrode active materials can be used alone or in combination of two or more.

The positive and negative electrodes contained in the non-aqueous electrolyte battery may further contain a conductive aid. The conductive aid is used to increase the output of the non-aqueous electrolyte battery, and can be appropriately selected according to the case of use for the positive electrode or the negative electrode. Examples thereof include graphite, acetylene black, and carbon black. , Ketjenblack, vapor-grown carbon fiber, and the like. Among these, acetylene black is preferably contained from the viewpoint that the output of the obtained non-aqueous electrolyte battery can be easily increased.

When the positive electrode and / or negative electrode contains a conductive aid, the content of the conductive aid 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 aid is within the above range, a sufficient conductive aid effect can be obtained without lowering the battery capacity.

As the binder, materials conventionally used as negative electrode active materials for non-aqueous electrolyte batteries can be used, examples of which include SBR, NBR, acrylic rubber, hydroxyethyl cellulose, carboxymethyl cellulose (CMC), and polyvinylidene fluoride. (PVDF), acrylic, polyamide-imide, and polyvinylcoal.

As the binder used for the negative electrode and the positive electrode, it is one of preferred embodiments to use an SBR-based emulsion from the viewpoint of the balance between availability and productivity improvement.

In addition to the binder, the active material, and the conductive aid, the positive electrode and/or the negative electrode may optionally contain a flame retardant aid, a thickener, an antifoaming agent, a leveling agent, an adhesion imparting agent, and the like. agent.

The electrode is formed by applying a composition containing a positive or negative electrode active material, a binder resin, and one or more solvents (hereinafter also referred to as a slurry composition) to a current collector, and removing the solvent by drying or the like. Obtainable. Also, 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 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, but examples thereof include an extrusion coater, reverse roller, doctor blade, applicator and the like. The application amount of the slurry composition is appropriately selected according to the desired thickness of the cured body derived from the slurry composition.

Examples of methods for rolling the electrode include methods such as die pressing and roll pressing. The pressing pressure is preferably 1 to 40 MPa from the viewpoint of easily increasing the battery capacity.

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

The electrolyte 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 functions as a battery depending on the type of negative electrode active material and positive electrode active material. You can choose one as appropriate. Specific electrolyte salts include, 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 , LiAlCl ₄ , LiCl, LiBr, LiB _{( C2H5} ) ₄ , _CF3SO3Li , _{CH3SO3Li , LiCF3SO3 , LiC4F9SO3 ,} Li _{( CF3SO2} )2N _, lithium _lower aliphatic carboxylate, _{NaPF 6} , NaTFSA, NaFSI, KFSI, _KPF6 , Mg(TFSA) ₂ , Mg(TFSA) ₂ , Mg[N _{(CF3SO2)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. Ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran and diethylene glycol diethyl ether; Sulfoxides such as dimethylsulfoxide; 1,3-dioxolane , 4-methyl-1,3-dioxolane and other oxolanes; nitrogen-containing compounds such as acetonitrile and nitromethane; organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate and ethyl propionate inorganic acid esters such as triethyl phosphate, dimethyl carbonate and diethyl carbonate; diglymes; triglymes; sulfolanes; oxazolidinones such as 3-methyl-2-oxazolidinone; , sultones such as naphthasultone, etc., and these can be used singly or in combination of two or more. When a gel electrolyte is used, a nitrile polymer, an acrylic polymer, a fluorine polymer, an alkylene oxide polymer, or the like can be added as a gelling agent.

Additives contained in the electrolytic solution are not particularly limited, and examples thereof include VC, VEC, FEC, and LiFSI.

The solid electrolyte is not particularly limited, and includes sulfides such as Li ₂ SP ₂ S ₅ , LGPS, LSiPSCl and LSiSnPS, oxides such as LLTO, LATP, LLZO, LAGP and LIPON, and polymers such as PEO-LiTFSI. complex systems such as LiBH ₄ , LiBH ₄ --LiI, LiBH ₄ --LiNH ₂ and LiBH ₄ --P ₂ S ₅ , and hydride systems such as closoborane and carborane.

The ionic liquid used as the electrolytic solution is not particularly limited, and for example, ammonium-based, pyrrolidinium-based, pyridinium-based, imidazolium-based, piperidinium-based, pyrazolium-based, oxazolium-based, pyridazinium-based, phosphonium-based, sulfonium-based, triazolium-based and One or more cations selected from the mixture and BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , AlCl ₄ ⁻ , HSO ₄ ⁻ , ClO ₄ ⁻ , CH ₃ SO ₃ ⁻ , (F _5O2 ) _2N- , _{( C2F5SO2} ) ^2N- _{, ( C2F5SO2} ⁾ _{( CF3SO2} ⁾ _N- ^and _{( CF3SO2 ) 2N-} and compounds containing one or more anions selected from at least one.

In the present invention, the shape of the non-aqueous electrolyte battery may be any 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 containing the separator of the present invention as a constituent member is highly safe, does not easily cause an increase in internal resistance, has an excellent capacity retention rate, and is an excellent battery such as a high battery capacity. have characteristics. The non-aqueous electrolyte battery of the present invention can be suitably used for various applications, for example, mobile terminals requiring miniaturization, thickness reduction, weight reduction and high performance, high capacity and high current. It is useful as a battery for use in large equipment such as electric vehicles that require performance such as charge/discharge characteristics.

EXAMPLES The present invention will be specifically described below with reference to Examples, but these are not intended to limit the scope of the present invention.

<Thickness>
The thickness of the separators obtained in Examples and Comparative Examples was measured using a thickness gauge (constant pressure thickness gauge PG-02J, manufactured by Teflock).

The thickness of the nonwoven fabric used in Examples and Comparative Examples was measured using a thickness meter B-1 (Toyo Seiki Seisakusho).

<Viscosity average degree of polymerization>
The viscosity-average degree of polymerization of the polyvinyl alcohol-based resins used in Examples and Comparative Examples was measured according to JIS K 6726.

<Amount of resin supported>
The amount (g/m ² ) of the resin supported was calculated by subtracting the amount (g/m ² ) of the nonwoven fabric alone from the amount (g/m ² ) of the separators obtained in Examples and Comparative Examples. The resin content (% by mass) was calculated using the amount of the separator (g/m ² ) and the supported amount of the resin (g/m ² ).

<White Index (WI) and Yellow Index (YI)>
The WI and YI of the separators obtained in Examples and Comparative Examples were measured as follows according to American Standards Test Methods E313.
Using a spectrophotometer (model number: CM-3500d, manufactured by KONICA MINOLTA), zero point calibration and white calibration were performed under the following conditions. As an underlay, a blackboard was placed on a laboratory bench, and one separator was placed thereon for measurement.
(WI, YI measurement conditions)
Measurement diameter: inner diameter 8 mm
Measurement: SCI (Specular Component Include)
UV: 100% (including UV components)
Light source 1: D65 (daylight, color temperature 6504k)
Observation field of view: 10° (CIE1964)
Display system: WI ASTE E313 whiteness
YI ASTE E313 yellowness manual average: 3 (number of times)
Standard deviation: SCI 0.20
Automatic average number of times: 3
Measurement waiting time: 0.0s

<Air Permeability>
The air permeability of the separators obtained in Examples and Comparative Examples was determined according to JIS P8117 under the following conditions. The air permeability was evaluated by measuring five times at different locations for each sample, and taking the average value as the air permeability.
(Measurement condition)
Measuring device: Oken type air permeability/smoothness tester (manufactured by Asahi Seiko Co., Ltd.)
Measurement time: 2 minutes

<Measurement of degree of saponification and viscosity average degree of polymerization>
According to JIS-K6726, the saponification degree and the viscosity-average degree of polymerization of the polyvinyl alcohol-based resins used in Examples and Comparative Examples were measured.

<Membrane shrinkage>
The separators obtained in Examples and Comparative Examples were punched into a diameter of 17 mm and heated at 150° C. for 1 hour. The film shrinkage ratio was calculated according to the following formula.
Film shrinkage ratio = (diameter before heating - diameter after heating) / diameter before heating x 100

<Battery capacity retention rate>
The separators obtained in Examples and Comparative Examples were cut into a size of 5.1×5.0 cm. Next, a positive electrode equivalent to that used in the peel strength test was cut into a size of 4.8 × 4.5 cm, and a negative electrode equivalent to that used in the peel strength test was cut into a size of 4.9 × 4.7 cm, respectively, and lead tabs were attached. rice field. A sheet of separator cut to the above size was sandwiched between these electrodes. The separator sandwiched between the electrodes was placed in an aluminum laminate pack so that the lead tab was outside the aluminum laminate pack. Next, 570 μl of an electrolytic solution (ethylene carbonate (EC)/ethyl methyl carbonate (EMC)/dimethyl carbonate (DMC)=1/1/1, 1.0 M LiPF ₆ ) was sealed in the aluminum laminate pack under reduced pressure. A laminate cell (non-aqueous electrolyte battery) for retention rate measurement was produced.
The laminate cell produced above was tested using a commercially available charge/discharge tester (TOSCAT3100, manufactured by Toyo System Co., Ltd.). In charging, constant current charging was performed at 0.2 C to 0.01 V against the lithium potential, and constant voltage charging at 0.01 V against the lithium potential was further carried out until the current reached 0.02 mA. In the discharge, constant current discharge was performed at 0.2 C to 1.5 V with respect to lithium potential. The laminate cell was placed in a constant temperature bath at 25° C., charged and discharged 100 times under the above conditions, and the capacity retention rate was calculated according to the following equation.
Capacity retention rate = discharge capacity at 100th cycle/discharge capacity at 1st cycle x 100

[Example 1]
(1) Preparation of Porous Film Forming Solution Polyvinyl alcohol-based aqueous solution (manufactured by Kuraray, product name “Clastomer AP20”, polyvinyl alcohol-polyacrylic acid copolymer resin, degree of saponification 97 to 98 mol%, viscosity average degree of polymerization 1700, Polyethylene glycol (molecular weight: 1000, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added in an amount of 42 parts by weight based on 100 parts by weight of the resin to form a porous film-forming solution. prepared. The solid content concentration of the porous film forming solution was 10% by mass.

(2) Preparation of porous film The solution for forming a porous film at 50°C obtained above was placed in a vat, and a molten liquid crystal forming polyester nonwoven fabric (manufactured by Kuraray, basis weight 4.1 g/m ² , thickness 10 µm, average fiber diameter) was obtained. 2.5 μm to 3 μm, melting point 350° C.) is rolled into the vat and soaked, impregnated by impregnating the nonwoven fabric with the solution, and then excess liquid is removed from both sides of the resin-impregnated nonwoven fabric using a blade coater. bottom. The liquid removal was performed along the nonwoven fabric surface without providing a clearance between the resin-impregnated nonwoven fabric surface and the liquid removal part of the blade. Then, it was rolled into an isopropyl alcohol bath at 20° C. and immersed for 20 minutes to solidify. Next, the nonwoven fabric containing the wet film was removed from the isopropyl alcohol bath, dried with hot air at 80°C, wound up, and dried at 100°C for 1 hour.

(3) Rolling The obtained separator was subjected to rolling treatment using a roll press (manufactured by Hosen Co., Ltd.) at 25° C. and a linear pressure of 40 kg/cm. Thus, a non-aqueous electrolyte battery separator including a non-woven fabric and a porous film made of polyvinyl alcohol resin was obtained. The thickness of the obtained separator was 8 μm.

[Example 2]
(1) Preparation of Porous Film Forming Solution Polyvinyl butyral resin powder ("Mowital B60T" manufactured by Kuraray, saponification degree 96-99 mol%, viscosity average polymerization degree 1700, hydroxyl group amount 24-27 mol%) was mixed with dimethyl sulfoxide. was dissolved at 70° C. for 3 hours to prepare a porous film-forming solution having a solid content concentration of 8% by mass.

(2) Preparation of porous film The solution for forming a porous film at 25°C obtained above was placed in a vat, and a molten liquid crystal-forming polyester nonwoven fabric (basis weight: 4.1 g/m ² , thickness: 10 µm, average fiber diameter: 2.5 µm) was obtained. ~3 μm, melting point 350° C.) was rolled into the vat and impregnated with the solution, and the excess liquid was removed from both sides of the resin-impregnated non-woven fabric using a blade coater. The liquid removal was performed along the nonwoven fabric surface without providing a clearance between the resin-impregnated nonwoven fabric surface and the liquid removal part of the blade. Then, it was rolled into a water bath at 25° C. and immersed for 10 minutes to solidify. Next, the nonwoven fabric containing the wet film of polyvinyl butyral resin was taken out from the water bath, dried with hot air at 80°C, wound up, and dried at 100°C for 1 hour.

(3) Rolling The same method as in Example 1 was used to obtain a non-aqueous electrolyte battery separator. The thickness of the obtained separator was 8 μm.

[Example 3]
(1) Preparation of Porous Film Forming Solution Ethylene-vinyl alcohol resin powder (manufactured by Kuraray, "E105B", ethylene modification amount 44 mol%, saponification degree 100 mol%, viscosity average polymerization degree 960, hydroxyl group amount 56 mol%) was dissolved in a mixed solvent of water and 1-propanol (water/1-propanol=40/60 volume ratio) at 70° C. for 3 hours to prepare a solution for forming a porous film having a solid concentration of 8% by mass.

(2) Preparation of Porous Film The porous film-forming solution obtained above, which was temperature-sensitive to 50° C., was placed in a vat, and a molten liquid crystal-forming polyester nonwoven fabric (manufactured by Kuraray Co., Ltd., weight per unit area: 4.1 g/m ² , thickness: 10 μm, Average fiber diameter 2.5 μm to 3 μm, melting point 350° C.) is rolled into the bat and immersed, impregnated by impregnating the nonwoven fabric with the solution, and then excess liquid is removed from both sides of the resin-impregnated nonwoven fabric using a blade coater. and drained. The liquid removal was performed along the nonwoven fabric surface without providing a clearance between the resin-impregnated nonwoven fabric surface and the liquid removal part of the blade. Then, it was rolled into a water bath at 40° C. and immersed for 10 minutes to solidify. Next, the nonwoven fabric containing the wet film of ethylene-vinyl alcohol resin was taken out from the water bath, dried with hot air at 80°C, wound up, and dried at 100°C for 1 hour.

(3) Rolling The same method as in Example 1 was used to obtain a non-aqueous electrolyte battery separator. The thickness was 8 μm.

[Example 4]
Vinylon (polyvinyl alcohol fiber, manufactured by Kuraray Co., Ltd., "Kuraray Vinylon VP": basis weight 3.2 g/m ² , thickness 11 μm, average fiber diameter 5.0 μm to 7.0 μm, melting point 200° C. or higher. ) A non-aqueous electrolyte battery separator was produced in the same manner as in Example 3, except that the non-woven fabric was used.

[Example 5]
Example 3, except that the molten liquid crystal-forming polyester nonwoven fabric was changed to polyethylene terephthalate nonwoven fabric (basis weight: 6.2 g/m ² , thickness: 9 µm, average fiber diameter: 6.0 µm to 8.0 µm, melting point: 255°C). A non-aqueous electrolyte battery separator was produced in the same manner.

[Comparative Example 1]
A commercially available PP separator (thickness: 9 μm) was used as the separator.

[Comparative Example 2]
As a separator, a commercially available aramid-coated heat-resistant separator (thickness: 10 μm) was used.

[Comparative Example 3]
A separator for a non-aqueous electrolyte battery was produced in the same manner as in Example 3, except that the solid content concentration of the porous film-forming solution was 5% by mass.

[Comparative Example 4]
A separator for a non-aqueous electrolyte battery was produced in the same manner as in Example 3, except that the solid content concentration of the porous film-forming solution was 18% by mass.

[Comparative Example 5]
A separator for a non-aqueous electrolyte battery was produced in the same manner as in Example 3, except that in the production of the porous membrane (2) above, the porous film was dried without being placed in a water bath (without solidification) after dewatering. The obtained separator was not a porous membrane but was a nonwoven fabric filled with a resin.

[Comparative Example 6]
As a separator, the molten liquid crystal forming polyester nonwoven fabric used in Example 1 was used.

[Comparative Example 7]
As a separator, the vinylon nonwoven fabric used in Example 4 was used.

[Comparative Example 8]
The polyethylene terephthalate nonwoven fabric used in Example 5 was used as the separator.

Using the non-aqueous electrolyte battery separators obtained in Examples and Comparative Examples, the thickness, resin loading, WI, YI, film shrinkage ratio, and battery capacity retention ratio were measured. Table 1 shows the results. In addition, in Table 1, with respect to the "amount of resin supported", the value of the resin content (% by mass) with respect to the mass of the separator is also shown in parentheses.

As shown in Table 1, the non-aqueous electrolyte battery separators obtained in Examples 1 to 5 have a low membrane shrinkage rate and a high capacity retention rate. On the other hand, the non-aqueous electrolyte battery separators obtained in Comparative Examples 1 and 2 have a significantly high film shrinkage rate, and the non-aqueous electrolyte battery separators obtained in Comparative Examples 3 to 8 have excellent battery performance. A short circuit occurs or the capacity retention of the battery is low. Therefore, the non-aqueous electrolyte battery separator of the present invention can form a battery having high heat resistance and excellent capacity retention.

Claims (9)

A nonaqueous electrolyte battery separator comprising a nonwoven fabric and a resin and having a white index of 30 to 75. 2. The separator for non-aqueous electrolyte batteries according to claim 1, wherein the yellow index is -10 to 2.0. The nonwoven fabric contains at least one selected from the group consisting of polyamide resin fibers, polyimide fibers, polyamideimide fibers, polyetherimide fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, and polyester fibers. The separator for non-aqueous electrolyte batteries according to claim 1 or 2, comprising: 4. The separator for non-aqueous electrolyte batteries according to claim 1, wherein said resin is a water-soluble resin. 5. The non-aqueous electrolyte battery separator according to claim 1, wherein said resin is a polyvinyl alcohol-based resin. 6. The non-aqueous electrolyte battery separator according to claim 5, wherein the polyvinyl alcohol-based resin is at least one selected from the group consisting of polyvinyl alcohol resin, ethylene-vinyl alcohol resin, and polyvinyl acetal resin. 7. The separator for non-aqueous electrolyte batteries according to claim 1, wherein said resin exists as a porous film. The separator for non-aqueous electrolyte batteries according to any one of claims 1 to 7, which contains substantially no heat-resistant filler. A nonaqueous electrolyte battery comprising the separator for a nonaqueous electrolyte battery according to any one of claims 1 to 8.