JP2023062215A - Separator for non-aqueous electrolyte battery - Google Patents

Abstract

To provide a separator for a non-aqueous electrolyte battery capable of forming a non-aqueous electrolyte battery having excellent battery capacity retention even when the film thickness is thin, and the non-aqueous electrolyte battery.SOLUTION: A separator for a non-aqueous electrolyte battery includes a non-woven fabric and a porous membrane made of a polyvinyl alcohol-based resin, and at least a part of the porous membrane exists between fibers constituting the non-woven fabric, and at least one surface of the separator has a contact angle of 35° or more and a film thickness of 1 to 15 μm.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. Therefore, most of the separators that constitute non-aqueous electrolyte batteries are made of heat-resistant porous membranes (porous films). has been proposed (Patent Document 1).

On the other hand, if the thickness of the separator made of a porous film is reduced, the amount of active material can be increased, and the battery capacity can be increased. For this reason, the need for thinner separators has increased in recent years.

Patent No. 5944808

However, according to the studies of the present inventors, repeated charging and discharging of a battery containing a separator formed by thinning an affinity porous sheet as in Patent Document 1 tends to cause micro-short circuits, and the battery capacity tends to decrease. It was found that a sufficient capacity retention rate could not be obtained.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a separator for a non-aqueous electrolyte battery and a non-aqueous electrolyte battery that can form a non-aqueous electrolyte battery having excellent capacity retention even if the film thickness is thin.

As a result of intensive studies to solve the above problems, the present inventors have found that a non-aqueous electrolyte battery separator having a thickness of 1 to 15 μm, which includes a non-woven fabric and a porous film made of a polyvinyl alcohol-based resin, At least part of the is present between the fibers constituting the nonwoven fabric, and the contact angle of at least one surface of the separator is adjusted to 35 ° or more, the above problems can be solved.

[1] A non-aqueous electrolyte battery separator comprising a non-woven fabric and a porous film made of a polyvinyl alcohol-based resin, wherein at least part of the porous film exists between fibers constituting the non-woven fabric, and at least one of the separators A separator for a non-aqueous electrolyte battery, wherein the contact angle of the surface of the non-aqueous electrolyte battery is 35° or more and the film thickness is 1 to 15 μm.
[2] The separator for non-aqueous electrolyte batteries according to [1], which has an air permeability of 50 to 500 seconds.
[3] Peel strength _Pa when the separator is crimped to a negative electrode comprising natural graphite, SBR and CMC at a ratio of 98:1:1 under conditions of 25 ° C. and a linear pressure of 40 kg / cm, _Pa , which is the ratio of the peel strength _Pb when the separator is pressed against a positive electrode containing NCM, Ketjenblack, carbon black, and PVDF in a ratio of 92:2.5:2.5:3 /P _b is 0.9 to 40, and P _a and P _b exceed 0 N/m.
[4] Under conditions of 25° C. and a press pressure of 5 MPa, the peel strength is 2 N/m or less when one surface and the other surface of the separator are overlapped and pressed for 8 hours. 3].
[5] Any one of [1] to [4], wherein the separator is elongated and has a tensile strength of 500 kgf/cm ² or more, whichever is lower between tensile strength in the longitudinal direction and tensile strength in the transverse direction. The separator for a non-aqueous electrolyte battery according to any one of the above.
[6] The separator for a non-aqueous electrolyte battery according to any one of [1] to [5], wherein the separator has a moisture content of 1% or less after being dried at 100° C. for 1 hour.
[7] The polyvinyl alcohol resin is at least one selected from the group consisting of ethylene-vinyl alcohol resin and polyvinyl acetal resin, for a non-aqueous electrolyte battery according to any one of [1] to [6]. separator.
[8] The separator for nonaqueous electrolyte batteries according to any one of [1] to [7], which has a film shrinkage rate of 2% or less at 150°C.
[9] The non-aqueous electrolyte battery separator according to any one of [1] to [8], wherein the non-woven fabric has a melting point of 300° C. or higher.
[10] The non-aqueous electrolyte battery separator according to any one of [1] to [9], wherein the non-woven fabric comprises molten liquid crystal-forming polyester fibers.
[11] A nonaqueous electrolyte battery comprising the separator for a nonaqueous electrolyte battery according to any one of [1] to [10].

INDUSTRIAL APPLICABILITY The separator for non-aqueous electrolyte batteries of the present invention can form a non-aqueous electrolyte battery having excellent capacity retention even when the film thickness is thin. Therefore, the separator for non-aqueous electrolyte batteries of the present invention can be suitably used for non-aqueous electrolyte batteries.

4 is an SEM image of the surface of the separator obtained in Example 2. FIG. 4 is an SEM image of the surface of the separator obtained in Comparative Example 2. FIG.

[Separator for non-aqueous electrolyte battery]
The non-aqueous electrolyte battery separator of the present invention includes a non-woven fabric and a porous membrane made of a polyvinyl alcohol-based resin, and at least part of the porous membrane exists between fibers constituting the non-woven fabric. Further, the separator for a non-aqueous electrolyte battery of the present invention is thinned to a thickness of 1 to 15 μm, and the contact angle of at least one surface of the separator is 35° or more. In this specification, the "non-aqueous electrolyte battery separator" may be simply referred to as "separator", and the "porous membrane made of polyvinyl alcohol-based resin" may be referred to as "resin porous membrane".

The inventor of the present invention found that even when the separator is thinned, if the porous resin membrane is present between the fibers of the non-woven fabric and the contact angle of at least one surface of the separator is adjusted to 35° or more, a surprising result can be obtained. In addition, it was found that a decrease in battery capacity due to repeated charging and discharging of a battery containing the separator can be effectively suppressed. It is presumed that this is due to the following reasons. That is, a non-woven fabric or a separator having a low air permeability is likely to have through holes and micro short circuits, so that short circuits and Li dendrites are likely to occur when the battery is repeatedly charged and discharged. This phenomenon is also likely to be accelerated by the expansion and contraction of the active material during charging and discharging. However, if the contact angle of at least one surface of the separator is 35° or more, the nonwoven fabric and the porous resin membrane are combined from the surface portion of the separator to the inside. More specifically, the nonwoven fabric is present. Part of the constituent fibers are present on the surface of the separator, and a resin porous membrane exists between the fibers of the nonwoven fabric from the surface to the inside, so that the strength is high and the formation of micropores is effectively suppressed. It is estimated that Therefore, the separator of the present invention can form a non-aqueous electrolyte battery having excellent capacity retention even if the film thickness is thin.

<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 urethane fibers. Among these fibers, polyester fibers such as polyethylene terephthalate fiber, polybutylene terephthalate fiber, polytrimethylene terephthalate fiber, and molten liquid crystal-forming polyester fiber are preferred. In particular, from the viewpoint of easily increasing the strength of the separator and the capacity retention rate of the battery, the nonwoven fabric should contain at least one selected from the group consisting of polyamide fibers, molten liquid crystal forming polyester fibers, and polyethylene terephthalate fibers. is preferred, and polyamide fibers and/or liquid crystal-forming polyester fibers are more preferred.

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 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, preferably 15 μm or less, more preferably 13 μm or less, and even more preferably. is 9 μm or less. When the fiber diameter of the nonwoven fabric is at least the above lower limit, the mechanical properties of the obtained separator can be easily improved. , it is easy to increase the capacity retention rate of the battery.

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 It is 40 g/m ² or less, more preferably 30 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, internal resistance is easy to reduce as the basis weight of a nonwoven fabric is below said upper limit.

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.

In the separator of the present invention, the thickness of the nonwoven fabric is preferably 1 μm or more, more preferably 2 μm or more, still more preferably 3 μm or more, preferably 20 μm or less, more preferably 17 μm or less, still more preferably 15 μm or less, and even more preferably. is 13 μm or less, particularly preferably 11 μm or less. When the thickness of the nonwoven fabric is at least the above lower limit, it is easy to increase the capacity retention rate and electrolyte holding capacity of the battery. 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.

<Porous membrane>
The separator of the present invention includes a porous film made of polyvinyl alcohol-based resin. Polyvinyl alcohol-based resins include, for example, polyvinyl alcohol, ethylene-vinyl alcohol resin, polyvinyl acetal resin, and the like. These polyvinyl alcohol-based resins can be used alone or in combination of two or more. In addition, the porous membrane indicates a membrane having a large number of pores inside and outside the membrane.

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 strength and water resistance of the separator and the capacity retention rate of the battery are likely to be improved. Since it can have hydrophilicity, it becomes easier to process the separator.

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

Examples of polyvinyl alcohol include those obtained by saponifying a resin obtained by polymerizing vinyl alcohol and optionally 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. Polyvinyl alcohol obtained by the saponification reaction is dried after washing.

The polyvinyl acetal resin can be produced, for example, by acetalizing the polyvinyl alcohol 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 raw material polyvinyl alcohol 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. , the acid used as a catalyst is neutralized 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 polyvinyl alcohol as a raw material 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 viewpoint of easily increasing 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.

Among the polyvinyl alcohol-based resins, at least one selected from the group consisting of ethylene-vinyl alcohol resins and polyvinyl acetal resins is preferable from the viewpoint of facilitating an increase in the capacity retention of a battery containing a separator and an easiness in reducing the water content. .

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-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine, allyl Examples include compounds having cationic groups derived from trimethylammonium chloride, methallyltrimethylammonium chloride, dimethylallylamine, allylethylamine, and the like. 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 amount of hydroxyl groups in the polyvinyl alcohol resin is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 20 mol% or more, still more preferably 30 mol%, based on the vinyl group unit of the polyvinyl alcohol resin. % or more, preferably 100 mol % or less, more preferably 90 mol % or less, still more preferably 80 mol % or less. When the amount of hydroxyl groups is within the above range, it is easy to increase the affinity with the electrolytic solution and the capacity retention of the battery, and to reduce the air permeability. 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 affinity with the electrolytic solution and the capacity retention rate of the battery are likely to be increased, and the air permeability is likely to be reduced. The degree of saponification can be measured according to JIS-K6726.

In one embodiment of the present invention, when polyvinyl alcohol is used as the polyvinyl alcohol-based resin, the degree of saponification is preferably 50 mol% or more, more preferably 55 mol% or more, still more preferably 60 mol% or more, and particularly preferably is 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 swellability with respect to the electrolytic solution is high, the capacity retention rate of the battery is easily increased, and the apparent air permeability 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 affinity with the electrolytic solution and the capacity retention rate of the battery are likely to be increased, and the air permeability is likely to be 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, preferably 5000 or less, more preferably 3000 or less, and further Preferably it is 2500 or less. When the viscosity-average degree of polymerization is at least the above lower limit, the strength of the separator is likely to be increased, and the capacity retention 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.

The resin porous membrane may contain other additives in addition to the polyvinyl alcohol-based resin and the surfactant. Examples of other additives include polymer compounds other than polyvinyl alcohol resins, inorganic fine powders such as cross-linking agents, antioxidants, UV absorbers, lubricants, antifoaming agents and antiblocking agents, and organic substances. The content of other additives is usually 10% by mass or less, preferably 5% by mass or less, relative to the mass of the porous resin membrane.

The content of the porous resin membrane in the separator of the present invention is preferably 5% by mass or more, more preferably 8% by mass or more, still more preferably 10% by mass or more, and preferably 50% by mass, relative to the mass of the separator. % or less, more preferably 45 mass % or less, and still more preferably 40 mass % or less. When the content of the porous resin membrane in the separator is at least the above lower limit, the strength of the separator and the capacity retention of the obtained battery are likely to be improved, and the adhesiveness and liquid absorption to the electrode are likely to be enhanced. When the content of the porous resin membrane in the separator is equal to or less than the above upper limit, the air permeability can be easily reduced. The content of the porous resin membrane may be calculated by subtracting the mass of the nonwoven fabric alone from the mass of the separator. sulfoxide, etc.), and subtracting the mass after dissolution from the mass before dissolution; can be calculated. The content of the porous resin membrane can be calculated, for example, by the method described in Examples.

<Separator for non-aqueous electrolyte battery>
The separator of the present invention includes the nonwoven fabric and the porous membrane made of the polyvinyl alcohol resin, at least a part of the porous membrane exists between the fibers constituting the nonwoven fabric, and the contact angle of one surface is 35. ° or more. Such a separator can have an optimum amount of resin porous membrane from the viewpoint of strength in the voids of the nonwoven fabric extending from the surface part of the separator to the inside, so that even a thin film of 1 to 15 μm has an excellent capacity retention rate. can form a battery. In this specification, compositing does not mean that the surface of the nonwoven fabric is covered (or coated) with the porous resin membrane, but that the porous resin membrane exists (or penetrates) between the fibers (or voids) that make up the nonwoven fabric. indicates that the

FIG. 1 is an image of one surface of a separator according to one embodiment of the present invention (corresponding to Example 2) taken using a scanning electron microscope (SEM). As shown in the SEM image, the separator of the present invention has a contact angle of 35° or more on the surface because some fibers of the nonwoven fabric are present on the surface portion and a resin porous membrane is present between the fibers. can be. In the separator of the present invention, a porous resin membrane may partially exist on the surface of the nonwoven fabric as long as the contact angle is within the range of the present invention.

On the other hand, if the contact angle of the separator surface is less than 35°, the entire surface or most of the surface of the nonwoven fabric tends to be coated with the porous resin film, resulting in low surface strength, especially the film thickness. If the layer is thin, the battery capacity tends to decrease due to repeated charging and discharging.

The contact angle of at least one surface of the separator of the present invention is preferably 36° or more, more preferably 37° or more, still more preferably 38° or more, even more preferably 39° or more, and particularly preferably 40° or more. . When the contact angle is at least the above lower limit, the porous resin membrane and the non-woven fabric tend to be sufficiently combined from the surface, so that the capacity retention of the obtained battery is likely to be improved. The contact angle of at least one surface of the separator of the present invention is preferably 70° or less, more preferably 65° or less, even more preferably 60° or less, and particularly preferably 55° or less. When the contact angle is equal to or less than the above upper limit, the affinity with the electrolytic solution is high, and the adhesiveness with the electrode is also enhanced, so the capacity retention rate can be easily increased, and the productivity of the battery is also excellent. Moreover, from the viewpoint of film homogeneity, it is more preferable that the contact angles on both surfaces of the separator are within the above range. The contact angle herein is the contact angle to propylene carbonate. Specifically, after dividing a 6 cm × 15 cm separator into 10 equal parts, the contact angle at each point was measured by the droplet method using a contact angle meter, and the values were averaged. For example, the method described in the Examples. can be measured by The contact angle can be obtained by manufacturing the separator by the method described in the section [Method for producing a separator for non-aqueous electrolyte batteries], especially by a method including a dewatering process, or by changing the type of non-woven fabric or polyvinyl alcohol resin (for example, this It can be adjusted by adopting the preferable one of the invention).

The film thickness of the separator of the present invention is 1 to 15 μm. Since the contact angle of at least one surface of the separator of the present invention is adjusted within the above range, even a thin film having a thickness of 1 to 15 μm can have excellent capacity retention. The film thickness of the separator of the present invention is preferably 14 μm or less, more preferably 13 μm or less, still more preferably 12 μm or less, even more preferably 11 μm or less, particularly preferably 10 μm or less, and even more preferably 9 μm or less. It is 2 μm or more, more preferably 3 μm or more. When the thickness of the separator is at least the above lower limit, the capacity retention of the battery containing the separator can be easily increased, and when the thickness of the separator is at most the above upper limit, the amount of active material in the battery can be increased. It is easy to increase the battery capacity. 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 separator of the present invention has a specific air permeability because the polyvinyl alcohol-based resin exists between the fibers constituting the nonwoven fabric. The air permeability of the separator of the present invention is preferably 50 seconds or more, more preferably 80 seconds or more, still more preferably 100 seconds or more, even more preferably 110 seconds or more, particularly preferably 120 seconds or more, and preferably 500 seconds or more. seconds or less, more preferably 400 seconds or less, and even more preferably 300 seconds or less. When the air permeability is at least the above lower limit, even if the film thickness is thin, it is easy to increase the capacity retention rate and the liquid absorption of the electrolytic solution of the resulting battery. 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 according to JIS P8117, for example, by the method described in Examples. The air permeability can be adjusted, for example, by appropriately changing the size (or basis weight) of the pores of the nonwoven fabric, the content of the porous resin membrane, the pore size of the porous resin membrane, and the like.

In one embodiment of the present invention, _Cx , which is the ratio of the contact angle on one side of the separator of the present invention (contact angle _Cx ) to the contact angle on the other side (contact angle _Cy ) / _Cy is preferably 0.8 or more, more preferably 0.85 or more, still more preferably 0.90 or more, particularly preferably 0.95 or more, preferably 1.2 or less, more preferably 1.2 or more. It is 15 or less, more preferably 1.1 or less, and particularly preferably 1.05 or less. When the contact angle ratio C _x /C _y is within the above range, it is easy to increase the capacity retention of the resulting battery. The contact angle of the separator surface can be measured by the method described above, for example, by the method described in Examples.

In one embodiment of the present invention, a negative electrode comprising natural graphite, SBR (styrene-butadiene rubber) and CMC (carboxymethylcellulose) at a ratio of 98:1:1 under the conditions of 25° C. and linear pressure of 40 kg/cm, The peel strength P _a when the separator of the present invention is crimped, and the ratio of NCM (nickel-cobalt-manganese ternary material), Ketjenblack, carbon black and PVDF (polyvinylidene fluoride) to 92:2.5: The ratio P _a /P _{b, which is the ratio of the peel strength P b when} the separator of the present invention is pressure-bonded to the positive electrode having a ratio of 2.5:3, is preferably 0.9 or more, more preferably It is 1.0 or more, more preferably 1.5 or more, preferably 40 or less, more preferably 30 or less, still more preferably 20 or less, and particularly preferably 14 or less. However, P _a and P _b exceed 0 N/m. When the peel strength ratio P _a /P _b is within the above range, it is easy to increase the capacity retention of the battery including the separator and to reduce the water content of the separator. Peel strengths P _a and P _b are obtained by laminating the electrode surface of the pressure-bonded separator and the stainless steel plate using double-sided tape, and measuring the 180° peel strength with a 50 N load cell at a peel width of 10 mm and a peel speed of 100 mm/ It is obtained by measuring under the conditions of min, and can be measured, for example, by the method described in Examples. The peel strength ratio P _a /P _b can be adjusted by appropriately changing the amount of hydroxyl groups in the resin constituting the porous resin membrane.

In one embodiment of the present invention, under conditions of 25 ° C. and a press pressure of 5 MPa, the peel strength P _c when one surface and the other surface of the separator of the present invention are overlapped and pressed for 8 hours is preferably 2 N/m or less, more preferably 1.0 N/m or less, still more preferably 0.5 N/m or less, even more preferably 0.3 N/m or less, particularly preferably 0.1 N/m or less, and even more preferably It is 0.01 N/m or less. When the peel strength P _c is equal to or less than the above upper limit, the surface of the separator is easily peeled off when unwinding the rolled separator, and battery characteristics and productivity are easily improved. The peel strength P _c can be measured by the same method as P _a and P _b by bonding one side of the two separators pressed under the above conditions to a stainless steel plate using a double-sided tape, for example, described in the Examples. can be measured by the method of The peel strength _Pc can be adjusted by appropriately changing the amount of hydroxyl groups in the resin constituting the nonwoven fabric or the porous resin membrane.

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% or less (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. After drying the separator at 100° C. for 1 hour, the water content can be measured at a temperature of 120° C. using a moisture measuring device, for example, by the method described in Examples. The water content of the separator can be adjusted by appropriately changing the amount of hydroxyl groups in the non-woven fabric or the polyvinyl alcohol resin. For example, the water content tends to decrease as the amount of hydroxyl groups in the polyvinyl alcohol resin decreases.

In one embodiment of the present invention, the separator of the present invention preferably has a film shrinkage at 150° C. of 2% or less, more preferably 1.5% or less, still more preferably 1.0% or less, and even more preferably 0%. 0.5% or less, particularly preferably 0.1% or less. When the film shrinkage rate is equal to or less than the above upper limit, it is easy to improve the heat resistance. 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. The film shrinkage rate may be adjusted by appropriately changing the type of nonwoven fabric.

In one embodiment of the present invention, the separator of the present invention is elongated, and of the tensile strength in the longitudinal direction and the tensile strength in the transverse direction, the lower tensile strength is preferably 500 kgf/cm ² or more, and more It is preferably 600 kgf/cm ² or more, more preferably 800 kgf/cm ² or more, and particularly preferably 1,000 kgf/cm ² or more. When the lower tensile strength is equal to or higher than the above lower limit, durability is likely to be improved. The upper limit of the lower tensile strength is usually 10,000 kgf/cm ² or less, preferably 5,000 kgf/cm ² or less. In this specification, the longitudinal direction indicates the MD direction, which is the machine flow direction during separator production, and the lateral direction indicates the TD direction, which is perpendicular to the machine flow direction during separator production. Tensile strength can be measured using a tensile tester using a test piece of JIS K 7162-1B, for example, by the method described in Examples. The tensile strength may be adjusted by appropriately changing, for example, the type of nonwoven fabric, the content of the porous resin membrane, the thickness of the separator, the contact angle of the surface, and the like.

In one embodiment of the present invention, the puncture strength of the separator of the present invention is preferably 200 g/mm ² or more, more preferably 300 g/mm ² or more, still more preferably 350 g/mm ² or more, still more preferably 400 g/mm ² or more. When the puncture strength is at least the above lower limit, the strength of the separator is likely to be increased, and the capacity retention rate of the battery is likely to be increased. The upper limit of the puncture strength is usually 5,000 g/mm ² or less, preferably 3,000 g/mm ² or less. The puncture strength can be measured using a texture analyzer at a temperature of 25° C., for example, by the method described in Examples. The puncture strength may be adjusted by appropriately changing, for example, the type of nonwoven fabric, the content of the porous resin membrane, the thickness of the separator, the contact angle of the surface, and the like.

Even if the separator of the present invention is a thin film, the obtained battery can have an excellent capacity retention rate. The capacity retention rate (also referred to as discharge capacity retention rate) of the battery comprising the separator of the present invention is preferably 81% or higher, more preferably 83% or higher, still more preferably 85% or higher, and still more preferably 87% or higher. , particularly preferably 88% or more, particularly more preferably 89% or more. The capacity retention rate can be measured, for example, by the method described in Examples.

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 containing a laminate of a plurality of nonwoven fabrics and a porous membrane made of a polyvinyl alcohol-based resin, preferably a separator in which the laminate and a resin porous membrane are combined. . Further, other layers such as a functional layer may be laminated on the separator as long as the contact angle of at least one surface of the separator satisfies 35° or more and 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 polyvinyl alcohol resin in a water-containing solvent to obtain a porous film-forming solution; a step (II) of impregnating the nonwoven fabric; a step (III) of deliquoring the resin-impregnated nonwoven fabric; and a step (IV) of solidifying the polyvinyl alcohol-based resin in the deliquored resin-impregnated nonwoven fabric with a coagulating liquid. is preferred.

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

In a mixed solvent containing water and an organic solvent, the mixing ratio of water and the organic solvent (water/organic solvent) is preferably 3/97 to 70/30, more preferably 5/95 to 65 by volume. /35. By using a mixed solvent containing water and an organic solvent at a ratio within the above range, it is possible to easily prepare a porous film-forming solution containing a polyvinyl alcohol-based resin having a solid content concentration suitable for forming a separator.

The solid content concentration of the polyvinyl alcohol resin in the porous film-forming solution is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass. When the solid content concentration of the polyvinyl alcohol-based resin is within the above range, the handleability of the porous film-forming solution is good, and the separator is easily formed.

In step (I), the solution for forming a porous film is obtained by mixing, preferably stirring and mixing, a polyvinyl alcohol resin, water, and optionally an organic solvent and other additives to dissolve the polyvinyl alcohol resin. be done. 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.

Step (II) is a step of impregnating the nonwoven fabric with the porous membrane forming solution. Examples of the impregnation method include a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, an immersion method, and a brush coating method. The immersion method is preferable from the viewpoint that it is easy to penetrate between them. The solution temperature during impregnation is preferably 20 to 100°C, more preferably 25 to 80°C. By including the impregnation step, at least part of the porous resin membrane can be present between the fibers (or voids) constituting the nonwoven fabric of the obtained separator.

Step (III) is a step of removing liquid from the resin-impregnated nonwoven fabric obtained by impregnation. In the dewatering step, the porous film-forming solution existing on (or adhering to) the surface of the nonwoven fabric is removed. The dewatering method is performed by using a device such as a knife coater, bar coater, applicator, roll coater, squeeze roll, nip roll, etc., and providing at least a clearance between the coating part or the dewatering part of the device and the surface of the nonwoven fabric. Instead, it is preferable to remove the liquid along the surface of the nonwoven fabric (or along the direction perpendicular to the film thickness direction of the nonwoven fabric) while the coating part or the liquid removing part of the apparatus is in contact with the surface of the nonwoven fabric. preferable. By removing liquid in this way, it is easy to adjust the contact angle within the above range of the present invention. The solution temperature during deliquoring is preferably 0 to 70°C, more preferably 5 to 60°C. By including such a dewatering step, after step (IV), the fibers constituting the nonwoven fabric and the porous resin membrane are combined from the surface to the inside without covering the entire surface of the nonwoven fabric with the porous resin membrane. The contact angle of the separator surface can be adjusted within the above range of the present invention. 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 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, it is easy to remove the porous film-forming solution existing on (or adhering to) the surface of the nonwoven fabric. Easy to adjust within the above range. More specifically, in this embodiment, a clearance between the device and the substrate surface (substrate It is preferable to remove liquid along a direction perpendicular to the film thickness direction at a position where the clearance to the surface of the resin-impregnated nonwoven fabric is equal to or less than the film thickness of the resin-impregnated nonwoven fabric. The clearance to the base material surface is not particularly limited as long as it is equal to or less than the film thickness of the resin-impregnated nonwoven fabric, and can be appropriately selected according to the film thickness of the resin-impregnated nonwoven fabric. It is below. When the clearance is equal to or less than the above upper limit, the contact angle is easily adjusted within the above range of the present invention, and the smaller the clearance, the larger the contact angle tends to be.

In another embodiment of the present invention, the conveyed resin-impregnated nonwoven fabric may be deliquored by, for example, squeeze rolls. In the case of deliquoring using a squeeze roll or the like, the deliquoring can be performed while the rolls are in contact with both surfaces of the resin-impregnated nonwoven fabric, so the contact angle of the resulting separator surface can be easily adjusted within the above range of the present invention. In addition, the contact angle and the content of the porous resin membrane to be supported can be adjusted by adjusting the distance between the rolls, the pressure applied between the rolls, the angle of the rolls, and the like. By using such a deliquoring method, production by a roll-to-roll system becomes possible, and productivity can be improved. Moreover, the contact angle on both sides of the separator can be efficiently adjusted within the range of the present invention without using a base material. 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 squeeze roll, a coagulating liquid described later, and a drying zone, and wound up. methods and the like.

Step (IV) is a step of solidifying the polyvinyl alcohol-based resin in the drained resin-impregnated nonwoven fabric with a solidifying 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, it is preferred that the resin-impregnated nonwoven fabric placed on the substrate is immersed in the coagulation liquid together, and the substrate is peeled off after coagulation. Moreover, in the embodiment by the roll-to-roll method, a method of conveying the resin-impregnated nonwoven fabric conveyed by a roll through a coagulating liquid is preferable.

The coagulating liquid is not particularly limited as long as it is a solvent capable of coagulating the porous film forming solution, for example, a poor solvent for the polyvinyl alcohol-based resin. Examples of the coagulating liquid include water and a mixed solvent of water and an organic solvent. Examples of organic solvents miscible with water 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, it is easy to obtain a porous film made of polyvinyl alcohol resin, and it is easy to adjust the air permeability to the above range of the present invention.

In the production method of the present invention, the immersion time of the porous membrane forming solution in the coagulation liquid is, for example, 0.1 second to 30 minutes, preferably 1 second or longer, more preferably 3 seconds or longer, preferably 25 minutes or less, more preferably 20 minutes or less. When the immersion time is equal to or longer than the above lower limit, the polyvinyl alcohol-based resin is easily solidified sufficiently, and pores having a desired pore diameter are easily 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.

Through step (IV), a non-woven fabric containing a wet film of polyvinyl alcohol-based resin is obtained. 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 and the amount of solvent contained in the wet film, etc., so that the solvent can be removed as quickly as possible without damaging the obtained porous film (for example, cracking due to stress concentration). can be determined as appropriate. 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 is excellent in capacity retention (or discharge capacity retention) even if the thickness of the separator is thin. Furthermore, since the film thickness of the separator is thin, 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 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.

Methods for measuring physical properties of separators (porous membranes) obtained in Examples and Comparative Examples described later are shown below.

[Thickness]
The film thicknesses of the separators obtained in Examples and Comparative Examples were 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 resin was measured according to JIS K 6726.

[SEM image]
SEM imaging was performed using the following equipment.
Device Keyence VE-8800
Accelerating voltage 8kV
Magnification 1000x

[Porous membrane content]
The content of the porous membrane was calculated by subtracting the mass of the nonwoven fabric alone from the mass of the separators obtained in Examples and Comparative Examples.

[Measurement of degree of saponification and viscosity-average degree of polymerization]
The degree of saponification of the polyvinyl alcohol resin was measured according to JIS-K6726.

[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

[Contact angle]
The separators obtained in Examples and Comparative Examples were cut into 6 cm×15 cm pieces, and the cut separators were divided into 10 equal parts. It was measured under the following conditions by a droplet method using a goniometer. The average value of the values obtained by measuring at each location was evaluated as the contact angle of the separator.
(Measurement condition)
Measuring device: DM700, manufactured by Kyowa Interface Science Co., Ltd. Temperature: 25°C
Solvent: propylene carbonate (PC)
Drop volume: 1.5 μl
Measurement time: After 1000ms

[Puncture Strength]
The separators obtained in Examples and Comparative Examples were cut into 2 cm squares, and measured with a texture analyzer (XT Plus, manufactured by EKO Instruments) at a temperature of 25°C, at a puncture speed of 2 mm/s, using a φ1 mm cylindrical probe. did

[Peel strength]
Under the conditions of 25° C. and a linear pressure of 40 kg/cm, a negative electrode containing natural graphite, SBR and CMC at a ratio of 98:1:1 and NCM, Ketjenblack, carbon rack and PVDF at 92:2.5: The separators obtained in Examples and Comparative Examples were press-bonded to the positive electrodes having a ratio of 2.5:3. Next, the electrode surface of the crimped sample and the stainless steel plate are laminated using a double-sided tape (Nichiban double-sided tape), and a 50 N load cell (manufactured by Imada Co., Ltd.) is used to measure 180 ° peel strength (peeling width 10 mm, peeling speed 100 mm/min) was measured. P _a is the peel strength from the negative electrode, P _b is the peel strength from the positive electrode, and the peel strength ratio P _a /P _b was calculated.
Also, under the conditions of 25 ° C. and a press pressure of 5 MPa, two separators obtained in Examples and Comparative Examples were used, and one surface and the other surface of the separator were overlapped and pressed for 8 hours. The intensity _Pc was also performed in the same manner as above. At that time, one separator surface and the stainless steel plate were pasted together using a double-sided tape (Nichiban double-sided tape).

[Tensile strength]
The tensile strength of the separators obtained in Examples and Comparative Examples was calculated using a tensile tester under the following conditions using test pieces according to JIS K 7162-1B. The tensile strength was measured in both the MD and TD directions of the separator.
(Measurement condition)
Measuring device: Autograph AG5000B, manufactured by Shimadzu Corporation Temperature: 25°C
Distance between chucks: 70mm
Test speed: 500 mm/min Test piece: Dumbbell type (test part width 10 mm), test piece thickness 10 μm

[Water content]
The separators obtained in Examples and Comparative Examples were dried at 100° C. for 1 hour, and the water content was measured under the following conditions.
(Measurement condition)
Measuring device: Karl Fischer moisture measuring device, manufactured by Mitsubishi Chemical Analytech Temperature: 120°C

[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 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 soaked and impregnated by soaking the nonwoven fabric with the solution, and then the resin-impregnated nonwoven fabric is placed on a glass plate placed on a horizontal table, and the resin-impregnated nonwoven fabric is Excess liquid was removed using an applicator (T101, manufactured by Matsuo Sangyo Co., Ltd.). The liquid removal is performed by setting the clearance between the coating portion of the applicator and the glass plate surface (also referred to as the clearance to the glass plate surface) to 5 μm, while bringing the coating portion of the applicator into contact with the surface of the resin-impregnated nonwoven fabric. along the surface. Then, the whole glass plate substrate was immersed in a water bath at 40° C. for 10 minutes to solidify. Next, the nonwoven fabric containing the wet film of ethylene-vinyl alcohol resin was taken out from the water tank, peeled off from the base material, air-dried, and then 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 ethylene-vinyl alcohol resin was obtained. The content of the porous resin membrane in the separator was 35% by mass with respect to the mass of the separator.

[Example 2]
The molten liquid crystal forming polyester nonwoven fabric was changed to a molten liquid crystal forming polyester nonwoven fabric having a basis weight of 8.0 g/m ² , a thickness of 15 µm, an average fiber diameter of 2.5 µm to 3 µm, and a melting point of 350°C. A separator was obtained in the same manner as in Example 1, except that the clearance for the was set to 10 μm. The content of the porous resin membrane in the separator was 27% by mass with respect to the mass of the separator.
FIG. 1 shows an SEM image of the surface of the obtained non-aqueous electrolyte battery separator. As shown in the SEM image, it was confirmed that fibers constituting the non-woven fabric were present on the surface of the separator, and a porous membrane made of ethylene-vinyl alcohol resin was present between the fibers.

[Example 3]
The molten liquid crystal forming polyester nonwoven fabric was changed to a molten liquid crystal forming polyester nonwoven fabric having a basis weight of 8.0 g/m ² , a thickness of 19 µm, an average fiber diameter of 2.5 µm to 3 µm, and a melting point of 350°C. A separator was obtained in the same manner as in Example 1, except that the clearance for the was set to 10 μm. The content of the porous resin membrane in the separator was 37% by mass with respect to the mass of the separator.

[Example 4]
(1) Preparation of Porous Film Forming Solution Polyvinyl butyral resin powder ("Mowital B60T" manufactured by Kuraray, degree of saponification 96-99 mol%, amount of hydroxyl groups 24-27 mol%) was added to dimethyl sulfoxide 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.), impregnated by soaking the non-woven fabric with the solution, then placing the resin-impregnated non-woven fabric on a glass plate placed on a horizontal table, and removing excess liquid from the resin-impregnated non-woven fabric with an applicator ( T101, manufactured by Matsuo Sangyo Co., Ltd.) was used to remove liquid. The liquid removal was performed along the surface of the glass plate while keeping the coating portion of the applicator in contact with the surface of the resin-impregnated nonwoven fabric by setting the clearance to the surface of the glass plate to 5 μm. Then, the whole glass plate substrate was immersed in a water bath at 25° C. for 10 minutes to solidify. Next, the nonwoven fabric containing the wet film of polyvinyl butyral resin was taken out from the water bath, peeled off from the base material, air-dried, and then dried at 100° C. for 1 hour.
After that, rolling was performed in the same manner as in Example 1 to obtain a separator. The content of the porous resin membrane in the separator was 26% by mass with respect to the mass of the separator.

[Example 5]
The molten liquid crystal forming polyester nonwoven fabric was changed to a molten liquid crystal forming polyester nonwoven fabric having a basis weight of 8.0 g/m ² , a thickness of 15 µm, an average fiber diameter of 2.5 µm to 3 µm, and a melting point of 350°C. A separator was obtained in the same manner as in Example 4, except that the clearance to the was set to 10 μm. The content of the porous resin membrane in the separator was 25% by mass with respect to the mass of the separator.

[Example 6]
A separator was obtained in the same manner as in Example 5, except that the nonwoven fabric was changed to polyethylene terephthalate (basis weight: 6.2 g/m ² , thickness: 9 µm, melting point: 255°C). The content of the porous resin membrane in the separator was 29% by mass with respect to the mass of the separator.

[Example 7]
A separator was obtained in the same manner as in Example 2, except that the nonwoven fabric was changed to polyethylene terephthalate (basis weight: 6.2 g/m ² , thickness: 9 m, melting point: 255°C). The content of the porous resin membrane in the separator was 31% by mass with respect to the mass of the separator.

[Comparative Example 1]
The molten liquid crystal forming polyester nonwoven fabric was changed to a molten liquid crystal forming polyester nonwoven fabric having a basis weight of 8.0 g/m ² , a thickness of 15 µm, an average fiber diameter of 2.5 µm to 3 µm, and a melting point of 350°C. A separator was obtained in the same manner as in Example 1 except that a clearance was provided between the coated portion of the applicator and the surface of the resin-impregnated nonwoven fabric so that the two did not contact each other by setting the clearance to 20 μm. . The content of the porous resin membrane in the separator was 30% by mass with respect to the mass of the separator.

[Comparative Example 2]
The same as in Example 1, except that the clearance between the coated portion of the applicator and the surface of the resin-impregnated nonwoven fabric was provided to prevent contact between the two by setting the clearance to the surface of the glass plate to 20 μm when removing the liquid. A separator was obtained by the method of The content of the porous resin membrane in the separator was 36% by mass with respect to the mass of the separator. FIG. 2 shows an SEM image of the surface of the obtained non-aqueous electrolyte battery separator. As shown in the SEM image, it was confirmed that only a porous film made of ethylene-vinyl alcohol resin was present on the surface of the separator. That is, it was found that the separator obtained in Comparative Example 2 had the porous membrane covering the surface of the nonwoven fabric.

[Comparative Example 3]
(1) Preparation of Porous Film Forming Solution A polyvinyl alcohol-based aqueous solution (manufactured by Kuraray Co., Ltd., Clastomer, saponification degree 97 to 98 mol%, hydroxyl group content 24 to 85 mol%, solid content concentration 10% by mass), polyethylene glycol (molecular weight 1000, manufactured by Fuji Film Wako Pure Chemical) was added to polyvinyl alcohol resin in an amount of 42 parts by weight to prepare a solution for forming a porous film.
(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.), impregnated by soaking the non-woven fabric with the solution, and then placing the resin-impregnated non-woven fabric on a glass plate placed on a horizontal table to remove excess liquid from the resin-impregnated non-woven fabric. was removed using an applicator (T101, manufactured by Matsuo Sangyo Co., Ltd.). The liquid removal was performed by setting a clearance of 20 μm with respect to the surface of the glass plate to provide a clearance between the coating portion of the applicator and the surface of the resin-impregnated nonwoven fabric so that they would not come into contact with each other. Then, the whole glass plate substrate was immersed in an isopropyl alcohol bath at 20° C. for 20 minutes to solidify. Next, the nonwoven fabric containing the wet film was taken out from the water bath, peeled off from the substrate, air-dried, and then dried at 100° C. for 1 hour.
After that, rolling was performed in the same manner as in Example 1 to obtain a separator. The content of the porous resin membrane in the separator was 25% by mass with respect to the mass of the separator.

[Comparative Example 4]
A separator was obtained in the same manner as in Example 1, except that the molten liquid crystal-forming polyester nonwoven fabric was not used.

[Comparative Example 5]
The same as in Example 7, except that the clearance between the coated portion of the applicator and the surface of the resin-impregnated nonwoven fabric was provided to prevent contact between the two by setting the clearance to the surface of the glass plate to 20 μm when removing the liquid. A separator was obtained by the method of The content of the porous resin membrane in the separator was 35% by mass with respect to the mass of the separator.

[Comparative Example 6]
A separator was obtained in the same manner as in Comparative Example 3, except that the molten liquid crystal-forming polyester nonwoven fabric was not used.

[Comparative Example 7]
A commercially available PE separator (9 μm) is placed on a glass plate placed on a horizontal table, alumina is applied with an applicator (T101, manufactured by Matsuo Sangyo Co., Ltd., clearance for PE separator 5 μm), and hot at 50 ° C. After drying on the plate for 1 hour, the surface opposite to the coated surface was similarly coated with alumina to prepare a heat-resistant coated separator.

[Comparative Example 8]
Using the commercially available PE separator used in Comparative Example 7, alumina was applied only on one side with an applicator (T101, manufactured by Matsuo Sangyo Co., Ltd., clearance for PE separator 100 μm), and then placed on a hot plate at 50 ° C. for 3 hours. After drying, a heat-resistant coated separator was produced.

Film thickness, contact angle, air permeability, peel strength ratio Pa/Pb, peel strength P _c , puncture strength, tensile strength (MD direction and TD direction) of the separators obtained in Examples 1 to 7 and Comparative Examples 1 to 8 ), moisture content, film shrinkage, and capacity retention of the battery are shown in Table 5. Table 5 also shows the type of resin and the type of nonwoven fabric that constitute the porous membrane. In Table 5, EVOH indicates ethylene-vinyl alcohol resin (copolymer), PVB indicates polyvinyl butyral, and PVA indicates polyvinyl alcohol. Heat-resistant PE indicates polyethylene coated with a heat-resistant resin. Also, PL indicates a melt liquid crystal-forming polyester.

As shown in Table 5, it was confirmed that the separators for non-aqueous electrolyte batteries obtained in Examples 1-7 had significantly higher battery capacity retention than those of Comparative Examples 1-8.
Therefore, the non-aqueous electrolyte battery separator of the present invention can form a non-aqueous electrolyte battery having excellent battery capacity retention even if the film thickness is thin.

Claims (11)

A non-aqueous electrolyte battery separator comprising a non-woven fabric and a porous membrane made of a polyvinyl alcohol-based resin, wherein at least part of the porous membrane exists between fibers constituting the non-woven fabric, and at least one surface of the separator A separator for a non-aqueous electrolyte battery, having a contact angle of 35° or more and a film thickness of 1 to 15 μm. 2. The separator for nonaqueous electrolyte batteries according to claim 1, which has an air permeability of 50 to 500 seconds. Under the conditions of 25° C. and a linear pressure of 40 kg/cm, the peel strength _Pa when the separator was pressed against a negative electrode containing natural graphite, SBR and CMC in a ratio of 98:1:1, NCM, Ket P _a / _P b is the ratio of the peel strength P _b when the separator is pressure-bonded to the positive electrode containing chain black, carbon black and PVDF in a ratio of 92: 2.5: 2.5: 3 is 0.9 to 40, and P _a and P _b exceed 0 N/m. Any one of claims 1 to 3, wherein the peel strength is 2 N/m or less when one surface and the other surface of the separator are overlapped and pressed for 8 hours under conditions of 25° C. and a press pressure of 5 MPa. The separator for non-aqueous electrolyte batteries according to . The separator according to any one of claims 1 to 4, wherein the separator has a long shape, and the tensile strength in the longitudinal direction and the tensile strength in the transverse direction is 500 kgf/cm ² or more, which is the lower one. Separator for water electrolyte batteries. 6. The separator for a non-aqueous electrolyte battery according to claim 1, wherein said separator has a water content of 1% or less after being dried at 100° C. for 1 hour. 7. The non-aqueous electrolyte battery separator according to claim 1, wherein said polyvinyl alcohol resin is at least one selected from the group consisting of ethylene-vinyl alcohol resin and polyvinyl acetal resin. 8. The separator for non-aqueous electrolyte batteries according to claim 1, wherein the film shrinkage at 150° C. is 2% or less. The non-aqueous electrolyte battery separator according to any one of claims 1 to 8, wherein said non-woven fabric has a melting point of 300°C or higher. 10. The non-aqueous electrolyte battery separator according to claim 1, wherein said non-woven fabric comprises molten liquid crystal-forming polyester fibers. A nonaqueous electrolyte battery comprising the separator for a nonaqueous electrolyte battery according to any one of claims 1 to 10.

Images