Separator for non-aqueous secondary battery, and non-aqueous secondary battery

Abstract

A separator for a non-aqueous secondary battery, which comprises a porous substrate and an adhesive layer positioned on at least one surface of the porous substrate, the adhesive layer comprising a polyvinylidene fluoride resin, and the separator for a non-aqueous secondary battery comprising a nonionic surfactant having a cloud point of 30-85 DEG C (inclusive) and a molecular weight of 200-1500 (inclusive).

Description

Technical Field

[0001] The present disclosure relates to a separator for a nonaqueous secondary battery and a nonaqueous secondary battery. Background Art

[0002] Conventionally, it has been proposed to provide a porous layer containing a resin and a filler on one or both surfaces of a porous substrate for the purpose of improving the heat resistance of a separator or improving the adhesion between an electrode and a separator.

[0003] For example, a diaphragm is disclosed in which a heat-resistant layer comprising a polyvinylidene fluoride (PVDF) resin and an inorganic filler is formed on one side of a polyethylene microporous membrane as a porous substrate (see Japanese Patent Gazette No. 5657177). The diaphragm obtained by forming an adhesive layer comprising polyvinylidene fluoride on a porous substrate has the effect of suppressing the deformation of the battery cell caused by the expansion and contraction of the electrode accompanying the charge and discharge, and improving the reliability of the battery. By bonding the diaphragm to the electrode, the contraction during heating is suppressed. Thus, it helps to improve the safety of the battery. Summary of the invention

[0004] Problems to be solved by the invention

[0005] However, PVDF has the property of being easily charged. When an adhesive layer containing PVDF is provided on the outermost surface of the separator, it has the property of easily leading to a decrease in handling and a decrease in the yield rate due to easy adsorption of foreign matter. Therefore, it is necessary to implement appropriate static removal treatment during operation. In view of this situation, in a separator provided with an adhesive layer containing PVDF, antistatic treatment is considered to be one of the technical issues.

[0006] In order to solve the above-mentioned technical problems, a technique using a surfactant has been proposed in the past. However, the current situation is that the techniques disclosed so far have disadvantages such as causing an increase in the water content in the separator or a decrease in the performance of the battery cell.

[0007] An embodiment of the present disclosure aims to provide a non-aqueous secondary battery separator having an adhesive layer containing a polyvinylidene fluoride resin on at least one surface of a porous substrate so as to have adhesion to an electrode and suppress charge-up to improve handleability.

[0008] Another embodiment of the present disclosure aims to provide a non-aqueous secondary battery having good adhesion between a separator and an electrode and excellent battery characteristics.

[0009] Means for solving problems

[0010] Specific means for solving the problem include the following methods.

[0011] <1> A separator for a non-aqueous secondary battery, comprising: a porous substrate; and an adhesive layer located on at least one side of the porous substrate, wherein the adhesive layer comprises a polyvinylidene fluoride resin.

[0012] The nonaqueous secondary battery separator includes a nonionic surfactant having a cloud point of 30° C. to 85° C. and a molecular weight of 200 to 1500.

[0013] <2> like <1> In the non-aqueous secondary battery separator, the porous substrate comprises a polyolefin microporous membrane.

[0014] <3> like <2> The non-aqueous secondary battery separator is characterized in that the porous substrate has a heat-resistant layer on at least one side of the polyolefin microporous membrane, the heat-resistant layer contains an inorganic filler, and the content of the inorganic filler relative to the entire layer is 90% by mass or more.

[0015] <4> like <1> ~ <3> The nonaqueous secondary battery separator described in any one of the preceding claims comprises the adhesive layer on both surfaces of the porous substrate.

[0016] <5> like <1> ~ <4> The nonaqueous secondary battery separator described in any one of the preceding claims, wherein the adhesive layer includes a three-dimensional network structure of the polyvinylidene fluoride-based resin.

[0017] <6> like <1> ~ <5> The non-aqueous secondary battery separator according to any one of the preceding claims, wherein the content of the nonionic surfactant is 0.05 g / m 2 ~1.0g / m 2 .

[0018] <7> A non-aqueous secondary battery comprising: a positive electrode; a negative electrode; and <1> ~ <6> In any one of the above-described nonaqueous secondary battery separators, the nonaqueous secondary battery separator is disposed between the positive electrode and the negative electrode.

[0019] Effects of the Invention

[0020] According to one embodiment of the present disclosure, a nonaqueous secondary battery separator is provided, wherein an adhesive layer containing a polyvinylidene fluoride resin is provided on at least one surface of a porous substrate to have adhesion to an electrode, suppress charge-up, and improve handleability.

[0021] According to another embodiment of the present disclosure, a non-aqueous secondary battery having good adhesion between a separator and an electrode and excellent battery characteristics can be provided. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present invention will be described. It should be noted that these descriptions and examples are intended to illustrate the present invention and do not limit the scope of the present invention.

[0023] In the present specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended effect of the process can be achieved.

[0024] In this specification, the expression "(meth)acryl-" means "acryl-" or "methacryl-".

[0025] In this specification, regarding the separator for non-aqueous secondary battery, "long side direction" refers to the longitudinal direction of the separator manufactured in a long strip shape, and "width direction" refers to the direction perpendicular to the long side direction of the separator. The "long side direction" is also referred to as the "MD direction", and the "width direction" is also referred to as the "TD direction".

[0026] In this specification, the numerical range shown by "~" indicates a range including the numerical values ​​recorded before and after "~" as the minimum value and the maximum value, respectively. In the numerical range recorded in stages in this specification, the upper limit value or lower limit value recorded in one numerical range can be replaced by the upper limit value or lower limit value of the numerical range recorded in other stages. In addition, in the numerical range recorded in this specification, the upper limit value or lower limit value of the numerical range can be replaced by the value shown in the embodiment.

[0027] In the present specification, when a plurality of substances belonging to each component are present in the composition, the amount of each component in the composition refers to the total amount of the plurality of substances present in the composition unless otherwise specified.

[0028] In this specification, the so-called "total solid content" refers to the total mass of the components obtained by removing the solvent from the entire composition of the composition. In addition, the so-called "solid content" is a component obtained by removing the solvent as described above, for example, at 25°C, it can be solid or liquid.

[0029] In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0030] In this specification, "heat resistance" means a property that a material does not melt or decompose in a temperature range lower than 200°C.

[0031] <Separator for non-aqueous secondary batteries>

[0032] The non-aqueous secondary battery separator of the present disclosure has a porous substrate and an adhesive layer comprising a polyvinylidene fluoride resin disposed on at least one side of the porous substrate. The adhesive layer can also be disposed on both sides of the porous substrate. In addition, the non-aqueous secondary battery separator of the present disclosure includes a nonionic surfactant having a turbidity point of 30°C to 85°C and a molecular weight of 200 to 1500.

[0033] In the case of the non-aqueous secondary battery separator of the present disclosure, the separator has an adhesive layer comprising a polyvinylidene fluoride resin and a nonionic surfactant having a turbidity point and a molecular weight within a specific range, thereby suppressing charging, improving operability, and improving battery characteristics when the battery is made. Although the mechanism of action for achieving such an effect may not be clear, it is speculated as follows.

[0034] It has always been known that the technology of using surfactants and aqueous binders for the purpose of suppressing charging, but there is a tendency to increase the amount of water retained inside, which sometimes affects the battery performance. Therefore, it was found that the desired properties could not be obtained by simply using surfactants, and a technology for properly controlling the amount of water was needed. In view of this situation, the following insights were obtained: among a large number of surfactants, a specific nonionic surfactant can moderately suppress the affinity with water, that is, the property of surrounding water, and present the desired charging suppression.

[0035] The non-aqueous secondary battery separator of the present disclosure is achieved based on the above insights. In the case of having an adhesive layer containing a polyvinylidene fluoride resin, the separator contains a non-ionic surfactant whose cloud point and molecular weight meet a specific range, thereby achieving adhesion to the electrode and charge suppression. As a result, the separator has the advantages of excellent operability and excellent battery characteristics when made into a battery.

[0036] Hereinafter, the nonaqueous secondary battery separator (hereinafter, also simply referred to as “separator”) of the present disclosure will be described in detail.

[0037] (Nonionic surfactant)

[0038] The non-aqueous secondary battery separator of the present disclosure contains a nonionic surfactant having a cloud point of 30°C to 85°C and a molecular weight of 200 to 1500. By selecting a nonionic surfactant having a specific cloud point and molecular weight, the hydrophilicity of the separator will not become too high, the increase in the water content of the separator can be suppressed, and the charging can be suppressed.

[0039] In the non-aqueous secondary battery separator of the present disclosure, the nonionic surfactant may be included in any layer, and may be included in any layer of the porous substrate, the adhesive layer, and the heat-resistant layer described later. The nonionic surfactant may be included in at least one of the porous substrate, the adhesive layer, and the heat-resistant layer described later, preferably at least in the adhesive layer, and preferably most in the adhesive layer.

[0040] The cloud point of the nonionic surfactant is above 30°C and below 85°C. If the cloud point is below 30°C, it is not easy to dissolve. Therefore, it is difficult to impart the surfactant by preparing an aqueous solution and applying it, and the manufacturing adaptability is poor. As a result, it is also difficult to obtain a sufficient charge suppression effect. In addition, if the cloud point is higher than 85°C, the hydrophilicity becomes too high, which easily causes the water content of the separator to increase, and it is easy to damage the battery performance when the battery is made.

[0041] The lower limit of the cloud point of the nonionic surfactant is preferably 33° C. or higher, more preferably 35° C. or higher, and further preferably 38° C. or higher for the same reason as above. The upper limit of the cloud point of the nonionic surfactant is preferably 60° C. or lower, more preferably 50° C. or lower, and further more preferably 45° C. or lower for the same reason as above.

[0042] The cloud point is a value measured in accordance with JIS K 2269.

[0043] The molecular weight of the nonionic surfactant is 200 to 1500. If the molecular weight is lower than 200, the cloud point becomes low, and the lipophilicity is generally too high, so it is difficult to prepare an aqueous solution, and the manufacturing adaptability is poor as described above. As a result, it is also difficult to obtain a charge suppression effect. In addition, if the molecular weight is higher than 1500, from the perspective of steric hindrance, the surfactant molecules are not easy to be oriented on the surface of the adhesive layer, and it is difficult to obtain a sufficient antistatic effect.

[0044] The lower limit of the molecular weight of the nonionic surfactant is preferably 250 or more, more preferably 300 or more, and further more preferably 400 or more for the same reason as above. In addition, the upper limit of the molecular weight of the nonionic surfactant is preferably 1000 or less, more preferably 750 or less, and further more preferably 700 or less for the same reason as above.

[0045] The molecular weight can be determined from the chemical formula by arithmetic calculation based on the types and numbers of atoms constituting the nonionic surfactant.

[0046] The so-called nonionic surfactant refers to a nonionic surfactant that does not show ionicity even when dissolved in water but exhibits surface activity. The nonionic surfactant of the present disclosure is not particularly limited as long as it has the above-mentioned cloud point and molecular weight, and can be appropriately selected and used.

[0047] Specific examples of nonionic surfactants include those having alkylene oxide (C n H 2n -O-, n=2 or 3) chain alkylene oxide surfactants, etc.

[0048] Examples of the alkylene oxide surfactant include alkylene oxide alkyl ethers, etc. Examples of the alkylene oxide alkyl ethers include ethylene oxide alkyl ethers and propylene oxide alkyl ethers, and more preferably ethylene oxide alkyl ethers having 8 to 18 (preferably 10 to 16) carbon atoms in the alkyl moiety.

[0049] Specific examples of ethylene oxide alkyl ethers include polyoxyethylene (9) lauryl ether (cloud point 83°C, molecular weight 582, ethylene oxide units 9), polyoxyethylene (6) lauryl ether (cloud point 40°C, molecular weight 450, ethylene oxide units 6), polyoxyethylene (9) oleyl ether (cloud point 55°C, molecular weight 664, ethylene oxide units 9), and the like.

[0050] As the nonionic surfactant of the present disclosure, commercially available products may be used, for example, EMULGEN series manufactured by Kao Corporation (e.g., EMULGEN 108, EMULGEN 409PV, EMULGEN 707, EMULGEN 109P) and PLURONIC series manufactured by ADEKA Corporation (e.g., PLURONIC P-84, PLURONIC L-64).

[0051] The nonionic surfactant may be contained alone or in combination of two or more.

[0052] The content of the nonionic surfactant in the nonaqueous secondary battery separator of the present disclosure is preferably 0.05 g / m 2 More preferably 0.08 g / m 2 More preferably, 0.1 g / m 2 In addition, the content of the nonionic surfactant is preferably 1.0 g / m 2 Below, more preferably 0.7g / m 2 Below, more preferably 0.6 g / m 2 the following.

[0053] If the content of nonionic surfactant is 0.05g / m2 If the content of the nonionic surfactant is 1.0 g / m 2 Below, the moisture content of the separator will not become too high.

[0054] The content of nonionic surfactant in the separator for non-aqueous secondary batteries can be obtained by dissolving the separator in dimethyl sulfoxide and analyzing the soluble components by nuclear magnetic resonance (NMR). Specifically, the weight of the soluble components can be calculated by the difference in weight before and after the separator is dissolved in dimethyl sulfoxide. 1 H-NMR, 19 The weight ratio of the polyvinylidene fluoride resin to the nonionic surfactant was determined by F-NMR.

[0055] (Porous substrate)

[0056] The nonaqueous secondary battery separator of the present disclosure has a porous substrate.

[0057] The so-called porous substrate refers to a substrate having pores or voids inside. As such a substrate, microporous membranes; porous sheets formed of fibrous materials such as non-woven fabrics and paper-like sheets; and the like can be cited. In particular, from the perspective of thin film and high strength of the diaphragm, a microporous membrane is preferred. The so-called microporous membrane refers to the following membrane: a structure formed with a large number of micropores inside, and these micropores are connected, and gas or liquid can pass from one side of the surface to the other side.

[0058] The material constituting the porous substrate may be any material as long as it has electrical insulating properties, and may be an organic material or an inorganic material.

[0059] The porous substrate may be a single layer or a multilayer. The porous substrate preferably has a microporous membrane containing polyolefin (referred to as "polyolefin microporous membrane"). In the case where the porous substrate is a single layer, the porous substrate is preferably a polyolefin microporous membrane. In addition, in the case where the porous substrate is a multilayer, it is preferably a substrate having a polyolefin microporous membrane and a heat-resistant layer, and more preferably a substrate formed by a polyolefin microporous membrane and a heat-resistant layer coated on the polyolefin microporous membrane.

[0060] From the viewpoint of imparting a shutdown function to the porous substrate, the material constituting the porous substrate preferably includes a thermoplastic resin. The so-called shutdown function refers to the following function: when the battery temperature rises, the constituent material melts and blocks the pores of the porous substrate, thereby blocking the movement of ions and preventing thermal runaway of the battery. As thermoplastic resins, for example, polyesters such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene can be cited. From the viewpoint of imparting a shutdown function, the thermoplastic resin is preferably a resin having a flow elongation deformation temperature of less than 200°C.

[0061] As the polyolefin microporous membrane, a polyolefin microporous membrane having sufficient mechanical properties and ion permeability can be selected from polyolefin microporous membranes suitable for existing non-aqueous secondary battery separators. From the viewpoint of exhibiting the shutdown function, the polyolefin microporous membrane preferably contains polyethylene, and the polyethylene content is preferably 95% by mass or more.

[0062] From the viewpoint of imparting heat resistance to the extent that the film is not easily damaged when exposed to high temperature, the polyolefin microporous membrane is preferably a polyolefin microporous membrane comprising polyethylene and polypropylene. As such a polyolefin microporous membrane, a microporous membrane in which polyethylene and polypropylene are mixed in one layer can be cited. In such a microporous membrane, from the viewpoint of realizing both the shutdown function and heat resistance, it is preferred to contain more than 95% by mass of polyethylene and less than 5% by mass of polypropylene. In addition, from the viewpoint of realizing both the shutdown function and heat resistance, the polyolefin microporous membrane is also preferably a polyolefin microporous membrane of the following structure: having a laminated structure of more than 2 layers, at least 1 layer comprising polyethylene, and at least 1 layer comprising polypropylene.

[0063] The polyolefin contained in the polyolefin microporous membrane is preferably a polyolefin having a weight average molecular weight of 100,000 to 5,000,000. If the weight average molecular weight is 100,000 or more, sufficient mechanical properties can be ensured. On the other hand, if the weight average molecular weight is 5,000,000 or less, the shutdown properties are good and the membrane is easily formed.

[0064] The polyolefin microporous membrane can be manufactured, for example, by the following method. That is, the following method: a molten polyolefin resin is extruded from a T-die to form a sheet, which is then crystallized and stretched, and further heat-treated to form a microporous membrane. Alternatively, the following method: a polyolefin resin melted together with a plasticizer such as liquid paraffin is extruded from a T-die, cooled to form a sheet, stretched, and then the plasticizer is extracted and heat-treated to form a microporous membrane.

[0065] Examples of the porous sheet formed of a fibrous material include porous sheets such as nonwoven fabric and paper formed of a fibrous material of a thermoplastic resin.

[0066] (Heat-resistant layer)

[0067] The heat-resistant layer is a layer disposed on the polyolefin microporous membrane (preferably on the surface of the polyolefin microporous membrane).

[0068] The heat-resistant layer may be present only on one side of the polyolefin microporous membrane, or may be present on both sides of the polyolefin microporous membrane. If the heat-resistant layer is present on both sides of the polyolefin microporous membrane, the heat resistance of the diaphragm is more excellent, and the safety of the battery can be further improved. In addition, it is not easy to curl in the diaphragm, and the operability during the manufacture of the battery is excellent. If the heat-resistant layer is present only on one side of the polyolefin microporous membrane, the ion permeability of the diaphragm is more excellent. In addition, the thickness of the entire diaphragm can be suppressed, and a battery with higher energy density can be manufactured.

[0069] The heat-resistant layer is preferably a layer containing a binder resin and an inorganic filler.

[0070] The binder resin of the heat-resistant layer may be either a water-insoluble resin or a water-soluble resin.

[0071] Examples of the binder resin include polyvinylidene fluoride resins, wholly aromatic polyamides, polyamideimides, polyimides, polyethersulfones, polysulfones, polyetherketones, polyketones, polyetherimides, poly-N-vinylacetamide, polyacrylamide, copolymer polyether polyamides, fluorine-based rubbers, acrylic resins, styrene-butadiene copolymers, cellulose, and polyvinyl alcohol.

[0072] The binder resin may be a particulate resin, and examples thereof include resin particles such as polyvinylidene fluoride resin, fluorine-based rubber, and styrene-butadiene copolymer. The binder resin may also be a water-soluble resin such as cellulose and polyvinyl alcohol.

[0073] When a particulate resin or a water-soluble resin is used as the binder resin, the binder resin can be dispersed or dissolved in water to prepare a coating liquid, and the heat-resistant layer can be formed on the porous substrate by a dry coating method using the coating liquid.

[0074] As a binder resin, from the viewpoint of excellent heat resistance, it is preferably a heat-resistant resin comprising at least one selected from the group consisting of wholly aromatic polyamide, polyamide-imide and polyimide. Among them, from the viewpoint of durability, wholly aromatic polyamide is preferred. Wholly aromatic polyamide can be meta-type or para-type. Among wholly aromatic polyamides, meta-type wholly aromatic polyamide is preferred from the viewpoint of easy formation of a porous layer and excellent redox resistance in an electrode reaction. In wholly aromatic polyamide, a small amount of aliphatic monomers can also be copolymerized.

[0075] Specifically, as the wholly aromatic polyamide used as the binder resin, poly(meta-phenylene isophthalamide) or poly(para-phenylene terephthalamide) is preferred, and poly(meta-phenylene isophthalamide) is more preferred.

[0076] As a binder resin, from the viewpoint of the close adhesion between the heat-resistant layer and the adhesive layer, polyvinylidene fluoride resin (PVDF resin) is preferred. As PVDF resin, homopolymers of vinylidene fluoride (i.e., polyvinylidene fluoride); copolymers of vinylidene fluoride and other monomers (polyvinylidene fluoride copolymers); mixtures of polyvinylidene fluoride and polyvinylidene fluoride copolymers. As monomers copolymerizable with vinylidene fluoride, for example, tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, trichloroethylene, vinyl fluoride, trifluoroperfluoropropyl ether, ethylene, (meth)acrylic acid, methyl (meth)acrylate, (meth)acrylate, vinyl acetate, vinyl chloride, acrylonitrile, etc. can be mentioned. These monomers can be used alone or in combination of two or more. The weight average molecular weight (Mw) of the PVDF resin is preferably 600,000 to 3,000,000. The acid value of the PVDF resin is preferably 3 mgKOH / g to 20 mgKOH / g. The acid value of PVDF resin can be controlled by, for example, introducing carboxyl groups into PVDF resin. The introduction and amount of carboxyl groups into PVDF resin can be controlled by using monomers having carboxyl groups (e.g., (meth) acrylic acid, (meth) acrylic acid esters, maleic acid, maleic anhydride, maleic acid esters and fluorine-substituted products thereof) as polymerization components of PVDF resin and adjusting the polymerization ratio.

[0077] The inorganic filler is not particularly limited, and examples thereof include particles of metal hydroxides such as aluminum hydroxide, magnesium hydroxide, calcium hydroxide, chromium hydroxide, zirconium hydroxide, cerium hydroxide, nickel hydroxide, and boron hydroxide; particles of metal oxides such as silicon dioxide, aluminum oxide, zirconium oxide, magnesium oxide, and barium titanate; particles of carbonates such as calcium carbonate and magnesium carbonate; particles of sulfates such as barium sulfate and calcium sulfate; etc. As the inorganic filler, from the viewpoint of stability in the electrolyte and electrochemical stability, particles containing at least one kind selected from the group consisting of magnesium-based particles and barium-based particles are preferred.

[0078] The magnesium-based particles refer to inorganic fillers containing a magnesium compound, and specific examples thereof include magnesium hydroxide and magnesium oxide.

[0079] The barium-based particles refer to inorganic fillers containing a barium compound, and specific examples thereof include barium sulfate and barium titanate.

[0080] The inorganic filler may be a filler surface-modified with a silane coupling agent or the like.

[0081] The particle shape of the inorganic filler is not limited and may be any of spherical, elliptical, plate-like, needle-like, and amorphous. From the viewpoint of suppressing short circuit of the battery, the inorganic filler contained in the heat-resistant layer is preferably plate-like particles or unaggregated primary particles.

[0082] The average particle size of the inorganic filler is preferably 0.01 μm to 10 μm, with a lower limit of 0.1 μm being more preferred and an upper limit of 5 μm being more preferred.

[0083] The average particle size is a value measured using a laser diffraction particle size distribution measuring device, for example, Mastersizer 2000 manufactured by Sysmex. Specifically, the median particle size (D50) in the volume particle size distribution of a dispersion obtained by mixing and dispersing an inorganic filler, water (dispersion medium) and a nonionic surfactant (Triton X-100; dispersant) is taken as the average particle size.

[0084] As the porous substrate, it is preferred that at least one side of the polyolefin microporous membrane further comprises a heat-resistant layer containing an inorganic filler and the content of the inorganic filler relative to the heat-resistant layer as a whole is 90% by mass or more. The content of the inorganic filler relative to the heat-resistant layer as a whole is preferably 90% by mass or more and less than 100% by mass, and more preferably 95% by mass or more and less than 100% by mass.

[0085] The inorganic filler may be used alone or in combination of two or more.

[0086] The content of the inorganic filler in the heat-resistant layer is preferably 2.0 g / m 2 ~20.0g / m 2 If the content of inorganic filler is 2.0g / m 2 If the content of the inorganic filler is 20.0 g / m 2 Below, the heat-resistant layer is unlikely to be peeled off and fall off.

[0087] The heat-resistant layer may also contain additives such as a dispersant, a wetting agent, a defoamer, a pH adjuster, etc. in addition to the above-mentioned nonionic surfactant. The dispersant can improve the dispersibility, coating property or storage stability in the coating liquid for forming the heat-resistant layer. The wetting agent, the defoamer, and the pH adjuster can be added to the coating liquid for forming the heat-resistant layer for the purpose of, for example, improving the affinity with the polyolefin microporous membrane, suppressing the mixing of air into the coating liquid, or pH adjustment.

[0088] - Characteristics of heat-resistant layer -

[0089] In the separator of the present disclosure, the thickness of the heat-resistant layer is preferably 0.5 μm or more per side, more preferably 0.8 μm or more per side, from the viewpoint of the heat resistance or operability of the separator, and preferably 4.0 μm or less per side, more preferably 3.5 μm or less per side, from the viewpoint of the operability of the separator or the energy density of the battery. As for the thickness of the heat-resistant layer, whether the heat-resistant layer is present on only one side of the porous substrate or on both sides, the total thickness of the two sides is preferably 1.0 μm or more, more preferably 1.6 μm or more, preferably 8.0 μm or less, more preferably 7.0 μm or less.

[0090] The heat-resistant layer may be a porous layer having a plurality of pores. When the heat-resistant layer is a porous layer, the porosity is preferably 30% to 70%.

[0091] In the case where the porous substrate has a polyolefin microporous membrane and a heat-resistant layer, from the viewpoint of the bonding strength of the separator to the electrode, the peel strength between the polyolefin microporous membrane and the heat-resistant layer is preferably 5 N / m or more, more preferably 10 N / m or more, and further preferably 20 N / m or more. In addition, from the viewpoint of ion permeability, the peel strength is preferably 75 N / m or less, more preferably 60 N / m or less, and further preferably 50 N / m or less.

[0092] (Adhesive layer)

[0093] The non-aqueous secondary battery separator of the present disclosure has an adhesive layer containing a polyvinylidene fluoride resin on at least one surface of a porous substrate. The adhesive layer is responsible for bonding the separator to, for example, an electrode.

[0094] From the viewpoint of further achieving the effects of the present disclosure, the adhesive layer is preferably disposed on both surfaces of the porous substrate, rather than being disposed only on one surface of the porous substrate.

[0095] The adhesive layer contains a polyvinylidene fluoride-based resin.

[0096] As polyvinylidene fluoride resins, homopolymers of vinylidene fluoride (i.e., polyvinylidene fluoride); copolymers of vinylidene fluoride and other monomers (polyvinylidene fluoride copolymers); mixtures of polyvinylidene fluoride and polyvinylidene fluoride copolymers. As monomers copolymerizable with vinylidene fluoride, for example, tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, trichloroethylene, vinyl fluoride, trifluoroperfluoropropyl ether, ethylene, (meth)acrylic acid, methyl (meth)acrylate, (meth)acrylate, vinyl acetate, vinyl chloride, acrylonitrile, etc. can be mentioned. These monomers can be used alone or in combination of two or more.

[0097] From the viewpoint of obtaining mechanical strength capable of withstanding pressure and heat during battery production, the polyvinylidene fluoride copolymer is preferably a copolymer having 50 mol % or more of structural units derived from vinylidene fluoride.

[0098] The polyvinylidene fluoride copolymer is preferably a copolymer of vinylidene fluoride and tetrafluoroethylene, a copolymer of vinylidene fluoride and hexafluoropropylene, or a copolymer of vinylidene fluoride and trifluoroethylene, and more preferably a copolymer of vinylidene fluoride and hexafluoropropylene. The copolymer of vinylidene fluoride and hexafluoropropylene is preferably a copolymer containing 0.1 mol% to 10 mol% (preferably 0.5 mol% to 5 mol%) of a structural unit derived from hexafluoropropylene.

[0099] The weight average molecular weight of the polyvinylidene fluoride-based resin is preferably 1,000 to 5,000,000, more preferably 10,000 to 3,000,000, and even more preferably 50,000 to 2,000,000.

[0100] The polyvinylidene fluoride resin may also be included in the form of particles. The bonding layer may also be a layer having a structure in which polyvinylidene fluoride resin particles are attached to a porous substrate. The bonding layer containing polyvinylidene fluoride resin particles may also utilize the gaps between the polyvinylidene fluoride resin particles to allow gas or liquid to pass from one side to the other side. The so-called structure with polyvinylidene fluoride resin particles attached includes not only a method of maintaining the particle shape in the completed diaphragm, but also a method of melting a part of the particles and not maintaining the particle shape due to heat treatment or drying treatment in the manufacturing process.

[0101] The adhesive layer preferably has a three-dimensional network structure of a polyvinylidene fluoride resin. When the adhesive layer has a three-dimensional network structure, the ion permeability in the adhesive layer becomes good and uniform even after bonding to the electrode.

[0102] The three-dimensional network structure refers to a structure in which holes (spaces) spread three-dimensionally in various directions in three-dimensional space including left-right direction, up-down direction, front-back direction and oblique directions therebetween (for example, multiple particles are connected).

[0103] The three-dimensional network structure can be formed by dissolving a polyvinylidene fluoride resin in an organic solvent, applying a liquid containing the polyvinylidene fluoride resin to a porous substrate, immersing the porous substrate in a coagulation liquid containing a poor solvent for the polyvinylidene fluoride resin, washing with water, and drying.

[0104] Alternatively, a bonding layer having a three-dimensional network structure may be formed by using polyvinylidene fluoride resin particles.

[0105] However, the method of forming the three-dimensional network structure is not limited thereto.

[0106] That the adhesive layer has a three-dimensional network structure can be confirmed by cutting the completed separator along a plane parallel to the thickness direction and observing the adhesive layer in the cross section using a scanning electron microscope.

[0107] By making the adhesive layer attached to the heat-resistant layer or the porous substrate, the interface failure between the heat-resistant layer or the porous substrate and the adhesive layer is not likely to occur. In addition, by making the adhesive layer a structure in which the polyvinylidene fluoride resin particles are connected to each other, the toughness of the adhesive layer is excellent, and the cohesive failure of the adhesive layer is not likely to occur.

[0108] Adhesive layer can further include other resins except polyvinylidene fluoride resin according to the composition of positive or negative pole in the range of the effect that will not significantly damage the present disclosure.As other resins, for example, homopolymers or copolymers of fluorine-based rubber, acrylic resin, styrene-butadiene copolymer, vinyl nitrile compound (acrylonitrile, methacrylonitrile, etc.), carboxymethyl cellulose, hydroxyalkyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyether (polyethylene oxide, polypropylene oxide, etc.) can be cited.From the aspect of excellent oxidation resistance, adhesive layer preferably includes polyvinylidene fluoride resin and acrylic resin. In addition, from the viewpoint of adjusting the ion permeability of the adhesive layer, the adhesion of the adhesive layer to the electrode, the peel strength between the adhesive layer and the heat-resistant layer, and the operability of the adhesive layer in a well-balanced manner, the adhesive layer preferably comprises particles of a mixture of polyvinylidene fluoride resin and acrylic resin, or a mixture of first particles containing polyvinylidene fluoride resin (preferably greater than 50 mass % relative to the total solid content) and second particles containing acrylic resin (preferably greater than 50 mass % relative to the total solid content).

[0109] Examples of acrylic resins include poly(meth)acrylic acid, poly(meth)acrylic acid salts, poly(meth)acrylic acid esters, cross-linked poly(meth)acrylic acid, cross-linked poly(meth)acrylic acid salts, and cross-linked poly(meth)acrylic acid esters, and these may be modified.

[0110] As for the adhesive layer, from the viewpoint of well-balanced adjustment of the ion permeability of the adhesive layer, the adhesion of the adhesive layer to the electrode, the peel strength between the adhesive layer and the heat-resistant layer, and the operability of the adhesive layer, the content of the polyvinylidene fluoride resin relative to the entire layer is preferably greater than 50% by mass, more preferably greater than 70% by mass, and even more preferably greater than 90% by mass.

[0111] The adhesive layer may contain additives such as a dispersant such as a surfactant, a wetting agent, a defoaming agent, and a pH adjuster.

[0112] The adhesive layer can be formed by preparing a liquid containing a polyvinylidene fluoride resin for forming the adhesive layer, and imparting (e.g., coating) the liquid containing the polyvinylidene fluoride resin to the porous substrate. The adhesive layer can also be formed by, for example, preparing a resin particle dispersion containing polyvinylidene fluoride resin particles and coating the resin particle dispersion on the porous substrate.

[0113] The adhesive layer preferably has a thickness of 0.2 g / m2 per side from the viewpoint of adhesion to the electrode. 2 From the viewpoint of ion permeability, operability of the separator, or energy density of the battery, it is preferred that the thickness per side be 2.0 g / m 2 the following.

[0114] - Characteristics of diaphragm -

[0115] The thickness of the separator of the present disclosure is preferably 8.0 μm or more, more preferably 9.0 μm or more from the viewpoint of mechanical strength of the separator, and is preferably 20.0 μm or less, more preferably 15.0 μm or less from the viewpoint of battery energy density.

[0116] From the viewpoint of the mechanical strength of the separator or the short circuit resistance of the battery, the puncture strength of the separator of the present disclosure is preferably 150 g to 1000 g, more preferably 200 g to 600 g. The puncture strength of the separator is measured in the same manner as the puncture strength of the porous substrate.

[0117] The porosity of the separator of the present disclosure is preferably 30% to 60% from the viewpoint of adhesion to electrodes, operability of the separator, ion permeability, or mechanical strength.

[0118] The amount of water contained in the diaphragm of the present disclosure (based on mass) is preferably 1200 ppm or less, and more preferably 1000 ppm or less. The less the amount of water in the diaphragm, the more the reaction between the electrolyte and water can be suppressed when a battery is formed, and the generation of gas in the battery can be suppressed, so that the cycle characteristics of the battery are improved. From this point of view, the amount of water contained in the diaphragm is more preferably 800 ppm or less, more preferably 600 ppm or less, and particularly preferably 500 ppm or less.

[0119] From the viewpoint of the load characteristics of the battery, the membrane resistance of the separator of the present disclosure is preferably 0.5 ohm·cm 2 ~10ohm·cm 2 , more preferably 1 ohm·cm 2 ~8ohm·cm 2 .

[0120] From the viewpoint of the balance between mechanical strength and ion permeability, the Gurley value (JIS P8117:2009) of the separator of the present disclosure is preferably 50 to 800 sec / 100 mL, more preferably 80 to 500 sec / 100 mL, and even more preferably 100 to 400 sec / 100 mL.

[0121] In the case of the separator of the present disclosure, from the viewpoint of ion permeability, the difference between the Gurley value of the separator and the Gurley value of the porous substrate is preferably 20 seconds / 100 mL to 300 seconds / 100 mL. The difference between the Gurley value of the separator and the Gurley value of the porous substrate is more preferably 200 seconds / 100 mL or less, and further preferably 150 seconds / 100 mL or less.

[0122] From the viewpoint of mechanical strength and handling properties of the separator, the tensile strength of the separator of the present disclosure in both MD and TD is preferably 500 kgf / cm 2 More preferably, 700 kgf / cm 2 The upper limit is usually 3000kgf / cm 2 the following.

[0123] -Method for manufacturing diaphragm-

[0124] The separator of the present disclosure can be produced by a method comprising the steps of forming an adhesive layer containing a polyvinylidene fluoride resin on at least one surface of a porous substrate and attaching a nonionic surfactant.

[0125] The adhesive layer can be formed via the following process. That is, in this process, the polyvinylidene fluoride resin is dissolved in a mixed solvent formed by a solvent that can dissolve it (hereinafter, also referred to as a "good solvent") and a solvent that cannot dissolve it (hereinafter, also referred to as a "poor solvent"), and a polyvinylidene fluoride resin solution is made. After the solution is applied to at least one side of the substrate, it is immersed in a coagulation liquid formed by a mixed solvent and water as an example of a poor solvent. Thus, the polyvinylidene fluoride resin is solidified into a three-dimensional network structure, the coagulation liquid is washed with water, and the water is dried.

[0126] Here, the good solvent includes polar amide solvents such as N-methylpyrrolidone, dimethylacetamide, and dimethylformamide. The poor solvent includes water, methanol, ethanol, propanol, butanol, butanediol, ethylene glycol, propylene glycol, tripropylene glycol, etc. In addition, the mixed solvent does not necessarily need to contain a poor solvent, and can also be composed of only a good solvent.

[0127] Alternatively, the adhesive layer may be formed by applying the same polyvinylidene fluoride resin solution as above to at least one side of the substrate, drying the good solvent to precipitate the polyvinylidene fluoride resin in a three-dimensional network structure, and then removing the poor solvent by drying or extraction.

[0128] When coating is performed using a liquid obtained by dispersing an inorganic filler in a polyvinylidene fluoride resin solution, the mixed solvent can be dried and removed after coating to form an adhesive layer having a three-dimensional network structure.

[0129] The attachment of the nonionic surfactant can be achieved by applying an aqueous solution of the nonionic surfactant to a porous substrate formed with an adhesive layer. The application of the aqueous solution of the nonionic surfactant is preferably carried out after the polyvinylidene fluoride resin is precipitated in a three-dimensional network structure in the adhesive layer forming step, and is particularly preferably carried out after the dried adhesive layer is formed on the porous substrate. Here, the application of the aqueous solution of the nonionic surfactant can be achieved by known methods such as gravure coating and dip coating.

[0130] <Non-aqueous secondary battery>

[0131] The non-aqueous secondary battery of the present disclosure comprises a positive electrode, a negative electrode and a separator for the non-aqueous secondary battery of the present disclosure disposed between the positive electrode and the negative electrode. The non-aqueous secondary battery of the present disclosure is a non-aqueous secondary battery that obtains electromotive force by doping and dedoping lithium. Doping refers to absorption, loading, adsorption or embedding, and refers to the phenomenon that lithium ions enter the active material of an electrode such as a positive electrode.

[0132] The nonaqueous secondary battery of the present disclosure has excellent adhesion between the separator and the electrode, suppresses static electricity, and has excellent handleability, so the battery has excellent productivity and battery cycle characteristics (capacity retention rate).

[0133] The nonaqueous secondary battery of the present disclosure has a structure in which a battery element (a negative electrode and a positive electrode facing each other via a separator) is sealed in an outer packaging material together with an electrolyte. The nonaqueous secondary battery of the present disclosure is suitable for nonaqueous electrolyte secondary batteries, especially lithium ion secondary batteries.

[0134] Hereinafter, examples of the positive electrode, the negative electrode, the electrolyte solution, and the outer casing material included in the non-aqueous secondary battery of the present disclosure will be described.

[0135] As an embodiment of the positive electrode, an active material layer including a positive electrode active material and a binder resin is formed on a current collector. The active material layer may further include a conductive additive. As the positive electrode active material, for example, a transition metal oxide containing lithium can be cited, specifically, LiCoO2, LiNiO2, LiMn 1 / 2 Ni 1 / 2 O2、LiCo 1 / 3Mn 1 / 3 Ni 1 / 3 O2, LiMn2O4, LiFePO4, LiCo 1 / 2 Ni 1 / 2 O2、LiAl 1 / 4 Ni 3 / 4 O2, etc. Examples of binder resins include polyvinylidene fluoride resins and styrene-butadiene copolymers. Examples of conductive additives include carbon materials such as acetylene black, Ketjen black, and graphite powder. Examples of current collectors include aluminum foil, titanium foil, and stainless steel foil with a thickness of 5 μm to 20 μm.

[0136] In the non-aqueous secondary battery of the present disclosure, when the adhesive layer of the separator of the present disclosure contains a polyvinylidene fluoride resin, since the polyvinylidene fluoride resin has excellent oxidation resistance, the adhesive layer is arranged on the positive electrode side of the non-aqueous secondary battery, thereby making it easy to apply LiMn that can operate at a high voltage of 4.2V or more. 1 / 2 Ni 1 / 2 O2、LiCo 1 / 3 Mn 1 / 3 Ni 1 / 3 O2 and the like are used as positive electrode active materials.

[0137] As an embodiment of the negative electrode, there can be cited a structure in which an active material layer including a negative electrode active material and a binder resin is formed on a current collector. The active material layer may further include a conductive aid. As the negative electrode active material, there can be cited materials that can electrochemically absorb lithium, specifically, for example, carbon materials; alloys of lithium with silicon, tin, aluminum, etc.; Wood's alloy; and the like. As a binder resin, for example, polyvinylidene fluoride resins, styrene-butadiene copolymers, etc. can be cited. As a conductive aid, for example, carbon materials such as acetylene black, Ketjen black, and graphite powder can be cited. As a current collector, for example, copper foil, nickel foil, stainless steel foil, etc. with a thickness of 5μm to 20μm can be cited. In addition, metal lithium foil can also be used as the negative electrode instead of the above-mentioned negative electrode.

[0138] The electrolyte is a solution obtained by dissolving a lithium salt in a non-aqueous solvent. Examples of lithium salts include LiPF6, LiBF4, and LiClO4. Examples of non-aqueous solvents include cyclic carbonates such as ethylene carbonate, propylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, and vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and fluorinated carbonates thereof; cyclic esters such as γ-butyrolactone and γ-valerolactone; and the like, which can be used alone or in combination. As an electrolyte, a solution obtained by mixing cyclic carbonates and chain carbonates at a mass ratio of 20:80 to 40:60 (cyclic carbonate: chain carbonate) and dissolving lithium salts in a range of 0.5 mol / L to 1.5 mol / L is suitable.

[0139] Examples of the outer packaging material include metal cases, aluminum laminated film packaging, etc. The shape of the battery includes square, cylindrical, button, etc. The separator of the present disclosure is suitable for any shape.

[0140] As the manufacturing method of the non-aqueous secondary battery of the present disclosure, there can be cited: a manufacturing method including the steps of impregnating the diaphragm with an electrolyte and subjecting it to a hot pressing treatment (referred to as "wet hot pressing" in the present disclosure) to thereby bond it to the electrode; and a manufacturing method including the steps of subjecting the diaphragm to a hot pressing treatment (referred to as "dry hot pressing" in the present disclosure) without impregnating the diaphragm with an electrolyte to thereby bond it to the electrode.

[0141] In the case of the non-aqueous secondary battery of the present disclosure, the separator of the present disclosure can be disposed between the positive electrode and the negative electrode, and after winding in the length direction to produce a wound body, the wound body can be used to produce, for example, by the following production methods 1 to 3. In the present disclosure, the effect of the separator for the non-aqueous secondary battery of the present disclosure can be expected in production method 1 or 2, but production method 3 may also be used. The same is true when an element produced by sequentially stacking at least one layer of a positive electrode, a separator, and a negative electrode (so-called stacking method) is used instead of a wound body.

[0142] (Manufacturing method 1) After the wound body is dry-hot pressed to bond the electrode and the separator, it is placed in an outer packaging material (for example, an aluminum laminate film package, the same below), an electrolyte is injected into it, and the wound body is further wet-hot pressed from the top of the outer packaging material to bond the electrode and the separator and seal the outer packaging material.

[0143] (Manufacturing Method 2) After the wound body is dry-heat-pressed to bond the electrode and the separator, it is placed in an outer packaging material, an electrolyte is injected therein, and the outer packaging material is sealed.

[0144] (Manufacturing method 3) The wound body is housed in an outer packaging material, an electrolyte is injected therein, and the wound body is wet hot pressed from above the outer packaging material to bond the electrode and the separator and seal the outer packaging material.

[0145] As the conditions for hot pressing in the above-mentioned manufacturing methods 1 to 3, the pressing temperature of each of the dry hot pressing and the wet hot pressing is preferably 60° C. to 120° C., more preferably 70° C. to 100° C., and the pressing pressure is 1 cm 2 The load of the electrode is preferably 0.5 kg to 90 kg. The pressing time is preferably adjusted according to the pressing temperature and the pressing pressure, for example, within the range of 0.1 minute to 60 minutes.

[0146] In the above manufacturing method 1 or 2, the wound body may be subjected to room temperature pressurization (pressurization at room temperature) before dry hot pressing to temporarily bond the wound body. In the above manufacturing method 2, the wound body may be subjected to room temperature pressurization before being stored in the outer packaging material to temporarily bond the wound body.

[0147] Example

[0148] Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to the following examples as long as the gist of the invention is not exceeded.

[0149] [Determination of cloud point]

[0150] The measurement was conducted in accordance with JIS K 2269.

[0151] [Determination of the content of nonionic surfactant]

[0152] The content of the nonionic surfactant in the separator for non-aqueous secondary batteries is determined by dissolving the separator in dimethyl sulfoxide and analyzing the soluble components by nuclear magnetic resonance (NMR). Specifically, the weight of the soluble components is calculated by the difference in weight before and after the separator is dissolved in dimethyl sulfoxide, and the weight of the soluble components is calculated by using 1 H-NMR, 19 The weight ratio of the polyvinylidene fluoride resin to the nonionic surfactant was determined by F-NMR.

[0153] [Evaluation of charging properties]

[0154] The half-life method described in JIS L 1094 was used to measure the saturation voltage and half-life after applying a corona discharge of 10 kV for 3 minutes to the sample using a static honest meter (manufactured by SHISHIDO ELECTROSTATIC, LTD.) with the distance between the sample and the electrode set to 20 mm.

[0155] [Determination of moisture content]

[0156] The measurement was performed using a Karl Fischer moisture meter. Specifically, the membranes prepared in the following examples and comparative examples were used as samples, and after the samples were stored in a dry room with a dew point of -55°C for 1 hour, each sample was heated at 150°C for 15 minutes. The water discharged during this period was transported to the Karl Fischer moisture meter using dry air (dew point of -55°C) as a carrier gas, and the moisture content was measured using the coulometric method and divided by the sample weight to obtain the moisture content.

[0157] [Battery performance evaluation]

[0158] A composite layer of graphite / styrene butadiene rubber / carboxymethyl cellulose (=96.2 / 2.8 / 1.0 [mass ratio]) is formed on copper foil to form a negative electrode. In addition, a composite layer of lithium cobaltate / polyvinylidene fluoride / acetylene black (=94.0 / 3.0 / 3.0 [mass ratio]) is formed on aluminum foil to form a positive electrode. The obtained negative electrode and positive electrode are joined via a separator, placed in an aluminum laminate film package, and then an electrolyte is injected and sealed to obtain a battery. Here, the electrolyte is 1M (mol / L) LiPF6-ethylene carbonate / ethyl methyl carbonate (=3 / 7 [mass ratio]).

[0159] The battery performance was evaluated by the 10C constant current discharge capacity retention rate relative to the 0.1C constant current discharge capacity. The discharge cutoff voltage was set to 2.5 V. It should be noted that the charging was set to 0.1C, 4.2V constant current and constant voltage charging.

[0160] (Example 1)

[0161] An aqueous solution of EMULGEN 108 (manufactured by Kao Corporation), which is a nonionic surfactant with a cloud point of 40°C and a molecular weight of 450, was applied to both sides of a diaphragm (manufactured by SEMCORP, product model: ND7T211O, which is obtained by laminating a heat-resistant layer containing aluminum oxide particles and acrylic resin on one side of a polyethylene microporous membrane, and further laminating an adhesive layer having a three-dimensional network structure formed by a polyvinylidene fluoride-hexafluoropropylene copolymer on the surface and back side (the surface and the other side of the aforementioned heat-resistant layer) of a porous substrate) and then dried at 60°C for 10 minutes to produce a diaphragm. The amount of EMULGEN 108 attached to the diaphragm was 0.2 g / m 2 The produced separator was cut along a plane parallel to the thickness direction, and the adhesive layer in the cross section was observed using a scanning electron microscope, confirming that the adhesive layer had a three-dimensional network structure.

[0162] In addition, the produced separator was used as a sample, and the chargeability, moisture content, and battery performance were measured and evaluated. The obtained results are shown in Table 1.

[0163] (Example 2)

[0164] The amount of EMULGEN 108 applied in Example 1 was changed to 0.13 g / m 2 A separator was produced in the same manner as in Example 1 except for the above. The produced separator was used as a sample, and the chargeability, water content, and battery performance were measured and evaluated. The obtained results are shown in Table 1.

[0165] Furthermore, the separator was cut along a plane parallel to the thickness direction, and the adhesive layer in the cross section was observed using a scanning electron microscope. It was confirmed that the adhesive layer had a three-dimensional network structure.

[0166] (Example 3)

[0167] The amount of EMULGEN 108 applied in Example 1 was changed to 0.4 g / m 2 A separator was produced in the same manner as in Example 1 except for the above. The produced separator was used as a sample, and the chargeability, water content, and battery performance were measured and evaluated. The obtained results are shown in Table 1.

[0168] Furthermore, the separator was cut along a plane parallel to the thickness direction, and the adhesive layer in the cross section was observed using a scanning electron microscope. It was confirmed that the adhesive layer had a three-dimensional network structure.

[0169] (Example 4)

[0170] The amount of EMULGEN 108 applied in Example 1 was changed to 0.6 g / m2 A separator was produced in the same manner as in Example 1 except for the above. The produced separator was used as a sample, and the chargeability, water content, and battery performance were measured and evaluated. The obtained results are shown in Table 1.

[0171] Furthermore, the separator was cut along a plane parallel to the thickness direction, and the adhesive layer in the cross section was observed using a scanning electron microscope. It was confirmed that the adhesive layer had a three-dimensional network structure.

[0172] (Example 5)

[0173] A separator was prepared in the same manner as in Example 1 except that EMULGEN 108 in Example 1 was replaced with EMULGEN 409PV (manufactured by Kao Corporation) which is a nonionic surfactant having a cloud point of 55°C and a molecular weight of 664. The prepared separator was used as a sample, and the chargeability, moisture content, and battery performance were measured and evaluated. The results are shown in Table 1.

[0174] Furthermore, the separator was cut along a plane parallel to the thickness direction, and the adhesive layer in the cross section was observed using a scanning electron microscope. It was confirmed that the adhesive layer had a three-dimensional network structure.

[0175] (Comparative Example 1)

[0176] A separator was prepared in the same manner as in Example 1 except that EMULGEN 108 in Example 1 was replaced with EMULGEN 150 (manufactured by Kao Corporation) which is a nonionic surfactant having a cloud point higher than 100°C and a molecular weight of 2254. The prepared separator was used as a sample, and the chargeability, moisture content, and battery performance were measured and evaluated. The results are shown in Table 1.

[0177] (Comparative Example 2)

[0178] A separator was prepared in the same manner as in Example 1 except that EMULGEN 108 in Example 1 was replaced with EMULGEN 120 (manufactured by Kao Corporation) which is a nonionic surfactant having a cloud point of 98°C and a molecular weight of 758. The prepared separator was used as a sample, and the chargeability, moisture content, and battery performance were measured and evaluated. The results are shown in Table 1.

[0179] (Comparative Example 3)

[0180] A separator was produced in the same manner as in Example 1 except that the aqueous solution of EMULGEN 108 was not applied. The produced separator was used as a sample, and the chargeability, moisture content, and battery performance were measured and evaluated. The results are shown in Table 1.

[0181] [Table 1]

[0182]

[0183] As shown in Table 1, the embodiment using a specific nonionic surfactant with a cloud point of less than 85°C and a molecular weight of less than 1500 has less charge suppression, good operability, good water content in the diaphragm, and excellent battery performance compared to the comparative example not using the specific nonionic surfactant.

[0184] The entire disclosure of Japanese Patent Application No. 2022-060397 filed on March 31, 2022 is incorporated into this specification by reference.

[0185] All documents, patent applications, and technical standards described in this specification are incorporated into this specification by reference to the same extent as if each document, patent application, and technical standard was specifically and individually described.

Claims

1. A separator for a non-aqueous secondary battery, comprising: a porous substrate; and an adhesive layer located on at least one side of the porous substrate, the adhesive layer comprising a polyvinylidene fluoride resin, The nonaqueous secondary battery separator includes a nonionic surfactant having a cloud point of 30° C. to 85° C. and a molecular weight of 200 to 1500.

2. The non-aqueous secondary battery separator according to claim 1, wherein The porous substrate has a polyolefin microporous membrane.

3. The non-aqueous secondary battery separator according to claim 2, wherein: The porous substrate has a heat-resistant layer on at least one surface of the polyolefin microporous membrane. The heat-resistant layer contains an inorganic filler, and the content of the inorganic filler with respect to the entire layer is 90% by mass or more.

4. The nonaqueous secondary battery separator according to any one of claims 1 to 3, wherein The adhesive layer is provided on both surfaces of the porous substrate.

5. The nonaqueous secondary battery separator according to any one of claims 1 to 4, wherein The adhesive layer includes a three-dimensional network structure of the polyvinylidene fluoride-based resin.

6. The nonaqueous secondary battery separator according to any one of claims 1 to 5, wherein The content of the nonionic surfactant is 0.05 g / m 2 ~1.0g / m 2 .

7. A non-aqueous secondary battery comprising: positive electrode; negative electrode; and The nonaqueous secondary battery separator according to any one of claims 1 to 6, wherein the nonaqueous secondary battery separator is disposed between the positive electrode and the negative electrode.

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