Separator for non-aqueous secondary batteries and non-aqueous secondary batteries

Abstract

To provide a separator for a non-aqueous secondary battery which has an adhesive layer containing a polyvinylidene fluoride-based resin provided on at least one surface of a porous base material, has adhesion to an electrode, suppresses charging and enhances handling property.SOLUTION: A separator for a non-aqueous secondary battery has a porous base material, and an adhesive layer containing a polyvinylidene fluoride-based resin on at least one surface of the porous base material, and contains a nonionic surface active agent having a cloud point of 30°C or higher and 85°C or lower and a molecular weight of 200 or more and 1,500 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a separator for non-aqueous secondary batteries and a non-aqueous secondary battery. [Background technology]

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

[0003] For example, a separator has been disclosed in which a heat-resistant layer containing polyvinylidene fluoride (PVDF) resin and inorganic filler is formed on one side of a porous substrate, which is a polyethylene microporous membrane (see Patent Document 1). A separator in which an adhesive layer containing polyvinylidene fluoride is formed on a porous substrate has the effect of suppressing cell deformation due to the expansion and contraction of electrodes during charging and discharging, thereby improving the reliability of the battery. The separator adheres to the electrodes, suppressing shrinkage when heated. This contributes to improving the safety of the battery. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 5657177 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, PVDF has a tendency to become electrically charged, and when an adhesive layer containing PVDF is provided on the outermost surface of a separator, it can easily lead to reduced transportability and decreased yield due to the attraction of foreign matter. Therefore, it was necessary to apply appropriate static discharge treatment during handling. In light of this situation, antistatic measures are considered one of the technical challenges for separators equipped with an adhesive layer containing PVDF.

[0006] In response to the above technical problems, a technique using a surfactant has been proposed conventionally. However, the techniques disclosed so far have the drawback of causing an increase in the moisture content in the separator or a decrease in cell performance.

[0007] The problem to be solved by one embodiment of the present disclosure is to provide a separator for a non-aqueous secondary battery that has an adhesive layer containing a polyvinylidene fluoride-based resin on at least one side of a porous substrate, has adhesiveness to an electrode, suppresses charging, and has improved handling properties. The problem to be solved by another embodiment of the present disclosure is to provide a non-aqueous secondary battery having excellent battery characteristics while having adhesiveness between the separator and the electrode.

Means for Solving the Problems

[0008] Specific means for solving the problems include the following aspects. <1> A separator for a non-aqueous secondary battery, comprising a porous substrate and an adhesive layer containing a polyvinylidene fluoride-based resin on at least one side of the porous substrate, and containing a nonionic surfactant having a cloud point of 30°C or higher and 85°C or lower and a molecular weight of 200 or higher and 1500 or lower.

[0009] <2> The separator for a non-aqueous secondary battery according to <1>, wherein the porous substrate has a polyolefin microporous membrane.

[0010] <3> The separator for a non-aqueous secondary battery according to <2>, wherein the porous substrate has a heat-resistant layer containing an inorganic filler on at least one side of the polyolefin microporous membrane and having a content of the inorganic filler in the entire layer of 90% by mass or more.

[0011] <4> The separator for a non-aqueous secondary battery according to any one of <1> to <3>, having the adhesive layer on both sides of the porous substrate.

[0012] <5> The adhesive layer includes a three-dimensional network structure of the polyvinylidene fluoride resin. <1> ~ <4> This is a separator for non-aqueous secondary batteries as described in any one of the following.

[0013] <6> The content of the nonionic surfactant is 0.05 g / m 2 ~1.0g / m 2 That is <1> ~ <5> This is a separator for non-aqueous secondary batteries as described in any one of the following.

[0014] <7> A positive electrode, a negative electrode, and a device placed between the positive electrode and the negative electrode, <1> ~ <6> A non-aqueous secondary battery comprising a separator for non-aqueous secondary batteries described in any one of the above. [Effects of the Invention]

[0015] According to one embodiment of the present disclosure, a separator for a non-aqueous secondary battery is provided which has adhesive properties to an electrode, suppresses static charge, and improves handling properties, by providing an adhesive layer containing a polyvinylidene fluoride-based resin on at least one side of a porous substrate. Other embodiments of the present disclosure provide a non-aqueous secondary battery that has good adhesion between the separator and the electrode while exhibiting excellent battery characteristics. [Modes for carrying out the invention]

[0016] Embodiments of the present invention will be described below. These descriptions and examples are illustrative of the present invention and do not limit its scope.

[0017] In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended function is achieved.

[0018] In this specification, the term "(meth)acrylic" means "acrylic" or "methacrylic".

[0019] In this specification, with respect to separators for non-aqueous secondary batteries, "longitudinal direction" means the longitudinal direction of a separator manufactured in a long shape, and "width direction" means the direction perpendicular to the longitudinal direction of the separator. The "longitudinal direction" is also referred to as the "MD direction," and the "width direction" is also referred to as the "TD direction."

[0020] In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages within this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this specification, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples.

[0021] Furthermore, in this specification, the amount of each component in a composition means the total amount of multiple substances corresponding to each component present in the composition, unless otherwise specified.

[0022] In this specification, "total solids" refers to the total mass of the components of the composition excluding the solvent. Furthermore, "solids" refers to the components excluding the solvent, and may be solid or liquid at 25°C, for example.

[0023] In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0024] In this specification, "heat resistance" means the property of not melting or decomposing at temperatures below 200°C.

[0025] <Separator for non-aqueous secondary batteries> The separator for non-aqueous secondary batteries of this disclosure comprises a porous substrate and an adhesive layer containing a polyvinylidene fluoride resin disposed on at least one side of the porous substrate. The adhesive layer may be disposed on both sides of the porous substrate. The separator for non-aqueous secondary batteries of this disclosure also contains a nonionic surfactant having a cloud point of 30°C to 85°C and a molecular weight of 200 to 1500.

[0026] The separator for non-aqueous secondary batteries disclosed herein has an adhesive layer containing a polyvinylidene fluoride resin and contains a nonionic surfactant with a cloud point and molecular weight within a specific range, thereby suppressing static charge, improving handling properties, and further enhancing battery characteristics when used as a battery. The mechanism by which these effects are achieved is not entirely clear, but it is presumed to be as follows. While techniques using surfactants or water-based binders to suppress static charge have been known for some time, these tend to increase the amount of water retained internally, which can affect battery performance. Therefore, it has become clear that simply using surfactants or similar substances is not sufficient to obtain the desired properties, and that techniques for appropriately controlling the amount of water are necessary. In light of these circumstances, we have found that certain nonionic surfactants, among many surfactants, can appropriately suppress their affinity for water, i.e., their water-holding properties, while still exhibiting the desired static charge suppression. The separator for non-aqueous secondary batteries described herein was achieved based on the above findings. When an adhesive layer containing a polyvinylidene fluoride resin is provided, the separator contains a nonionic surfactant whose cloud point and molecular weight satisfy a specific range, thereby achieving both adhesion to the electrode and antistatic properties. As a result, the separator has the advantages of excellent handling properties and excellent battery characteristics when used as a battery.

[0027] The separator for non-aqueous secondary batteries described herein (hereinafter also simply referred to as "separator") will be described in detail below.

[0028] (Nonionic surfactant) The separator for non-aqueous secondary batteries of this 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 can not become too high, the increase in the moisture content of the separator can be suppressed, and static charge can be inhibited.

[0029] In the separator for non-aqueous secondary batteries of this disclosure, the nonionic surfactant may be contained in any of the layers, including the porous substrate, the adhesive layer, and the heat-resistant layer described later. The nonionic surfactant may be contained in at least one of the porous substrate, the adhesive layer, and the heat-resistant layer described later, preferably in at least the adhesive layer, and most preferably in the adhesive layer.

[0030] The cloud point of nonionic surfactants is between 30°C and 85°C. If the cloud point is lower than 30°C, dissolution becomes difficult, making it difficult to apply the surfactant by preparing an aqueous solution and coating it, resulting in poor manufacturing suitability. As a result, it is difficult to obtain a sufficient antistatic effect. Furthermore, if the cloud point exceeds 85°C, the hydrophilicity becomes too high, which easily causes an increase in the moisture content of the separator, and can impair the battery performance when used as a battery. For the same reasons as above, the cloud point of the nonionic surfactant is preferably 30°C to 60°C, more preferably 35°C to 50°C, and even more preferably 35°C to 45°C.

[0031] The cloud point is a value measured in accordance with JIS K 2269.

[0032] The molecular weight of nonionic surfactants is between 200 and 1500. If the molecular weight is lower than 200, the cloud point becomes low, and the lipophilicity is generally too high, making it difficult to prepare aqueous solutions and resulting in poor manufacturing suitability as described above. As a result, it is difficult to obtain an antistatic effect. Furthermore, if the molecular weight is higher than 1500, from the standpoint of steric hindrance, the surfactant molecules have difficulty oriented on the adhesive layer surface, making it difficult to obtain a sufficient antistatic effect. For the same reasons as above, the molecular weight of the nonionic surfactant is preferably 200 to 1000, more preferably 300 to 750, and even more preferably 400 to 670.

[0033] The molecular weight of a nonionic surfactant can be determined by arithmetic calculation from its chemical formula, based on the types and number of atoms that make up the surfactant.

[0034] A nonionic surfactant is a nonionic surfactant that does not exhibit ionic properties when dissolved in water but still exhibits surface activity. The nonionic surfactants in this disclosure are not particularly limited as long as they have the above-mentioned cloud point and molecular weight, and can be appropriately selected and used.

[0035] A specific example of a nonionic surfactant is alkylene oxide (C n H 2n Examples include alkylene oxide surfactants having an -O-, n=2 or 3) chain.

[0036] Examples of the alkylene oxide-based surfactant include alkylene oxide ethers. Examples of alkylene oxide alkyl ethers include ethylene oxide alkyl ethers and propylene oxide alkyl ethers, with ethylene oxide alkyl ethers having 8 to 18 (preferably 10 to 16) carbon atoms in the alkyl group being more preferred.

[0037] 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), and polyoxyethylene(9) oleyl ether (cloud point 55°C, molecular weight 664, ethylene oxide units 9).

[0038] The nonionic surfactant of the present disclosure may use commercially available products that are on the market. For example, the Emulgen series manufactured by Kao Corporation (e.g., Emulgen 108, Emulgen 409PV, Emulgen 707, Emulgen 109P), and the Pluronic series manufactured by ADEKA Corporation (e.g., Pluronic P-84, Pluronic L-64) can be mentioned.

[0039] The nonionic surfactant may be contained alone or in combination of two or more kinds. As the content of the nonionic surfactant in the separator for non-aqueous secondary batteries of the present disclosure, 0.05 g / m 2 or more and 1.0 g / m 2 or less is preferable, and 0.1 g / m 2 or more and 0.7 g / m 2 or less is more preferable, and 0.1 g / m 2 or more and 0.5 g / m 2 or less is even more preferable. When the content of the nonionic surfactant is 0.05 g / m 2 or more, a good antistatic effect is easily obtained. Also, when the content of the nonionic surfactant is 1.0 g / m 2 or less, the moisture content of the separator does not become too high.

[0040] 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) method. Specifically, the weight of the soluble components is determined by the weight difference before and after dissolving the separator in dimethyl sulfoxide, 1 1H-NMR, 19 and it can be calculated by determining the weight ratio of the polyvinylidene fluoride-based resin and the nonionic surfactant by 19F-NMR.

[0041] (Porous substrate) The separator for non-aqueous secondary batteries of the present disclosure has a porous substrate. A porous substrate refers to a substrate that has voids or cavities inside. Examples of such substrates include microporous membranes; porous sheets made of fibrous materials such as nonwoven fabrics and paper-like sheets; and microporous membranes are particularly preferred from the viewpoint of thinning and increasing the strength of separators. A microporous membrane refers to a membrane that has a large number of fine pores inside, in which these fine pores are connected, and which allows gas or liquid to pass from one side to the other.

[0042] The materials constituting the porous substrate may be either organic or inorganic materials, as long as they possess electrical insulating properties.

[0043] The porous substrate may be single-layer or multi-layer. Preferably, the porous substrate has a microporous membrane containing polyolefin ("polyolefin microporous membrane"). If the porous substrate is single-layer, it is preferable that the porous substrate is a polyolefin microporous membrane. If the porous substrate is multi-layer, a substrate having a polyolefin microporous membrane and a heat-resistant layer is preferred, and a substrate consisting of a polyolefin microporous membrane and a heat-resistant layer coated on the polyolefin microporous membrane is more preferable.

[0044] From the viewpoint of providing a shutdown function to the porous substrate, it is preferable that the materials constituting the porous substrate include a thermoplastic resin. The shutdown function refers to the function that, when the battery temperature rises, the constituent materials melt and block the pores of the porous substrate, thereby blocking ion movement and preventing thermal runaway of the battery. Examples of thermoplastic resins include polyesters such as polyethylene terephthalate; and polyolefins such as polyethylene and polypropylene. From the viewpoint of providing a shutdown function, it is preferable that the thermoplastic resin has a flow-stretch deformation temperature of less than 200°C.

[0045] As the polyolefin microporous membrane, one with sufficient mechanical properties and ion permeability should be selected from among the polyolefin microporous membranes that have been applied to conventional non-aqueous secondary battery separators. From the viewpoint of exhibiting a shutdown function, the polyolefin microporous membrane preferably contains polyethylene, and the polyethylene content is preferably 95% by mass or more.

[0046] From the viewpoint of providing heat resistance sufficient to prevent easy rupture when exposed to high temperatures, polyolefin microporous membranes containing polyethylene and polypropylene are preferred. Examples of such polyolefin microporous membranes include those in which polyethylene and polypropylene are mixed in a single layer. In such microporous membranes, from the viewpoint of achieving both shutdown function and heat resistance, it is preferable to include 95% by mass or more of polyethylene and 5% by mass or less of polypropylene. Furthermore, from the viewpoint of achieving both shutdown function and heat resistance, polyolefin microporous membranes having a laminated structure of two or more layers, where at least one layer contains polyethylene and at least one layer contains polypropylene, are also preferred.

[0047] The polyolefin contained in the polyolefin microporous membrane is preferably one with a weight-average molecular weight of 100,000 to 5,000,000. A weight-average molecular weight of 100,000 or more ensures sufficient mechanical properties. On the other hand, a weight-average molecular weight of 5,000,000 or less provides good shutdown properties and facilitates membrane formation.

[0048] Polyolefin microporous membranes can be manufactured, for example, by the following methods: extruding molten polyolefin resin from a T-die to form a sheet, crystallizing it, stretching it, and then heat-treating it to create a microporous membrane; or extruding molten polyolefin resin together with a plasticizer such as liquid paraffin from a T-die, cooling it to form a sheet, stretching it, extracting the plasticizer, and then heat-treating it to create a microporous membrane.

[0049] Examples of porous sheets made of fibrous material include nonwoven fabrics made of thermoplastic resin fibers, and porous sheets made of paper.

[0050] The heat-resistant layer is a layer placed on top of the polyolefin microporous film (preferably on the surface of the polyolefin microporous film). The heat-resistant layer may be present on only one side of the porous substrate or on both sides. When the heat-resistant layer is present on both sides of the porous substrate, the heat resistance of the separator is improved, further enhancing the safety of the battery. Additionally, curling of the separator is less likely to occur, resulting in superior handling during battery manufacturing. When the heat-resistant layer is present on only one side of the porous substrate, the ion permeability of the separator is improved. Furthermore, the overall thickness of the separator can be reduced, allowing for the manufacture of batteries with higher energy density.

[0051] The heat-resistant layer is preferably a layer containing a binder resin and an inorganic filler.

[0052] The binder resin for the heat-resistant layer may be either a water-insoluble resin or a water-soluble resin. Examples of binder resins include polyvinylidene fluoride resins, fully aromatic polyamides, polyamide-imides, polyimides, polyethersulfones, polysulfones, polyetherketones, polyketones, polyetherimides, poly-N-vinylacetamide, polyacrylamide, copolymerized polyether polyamides, fluororubbers, acrylic resins, styrene-butadiene copolymers, cellulose, and polyvinyl alcohol.

[0053] The binder resin may be a particulate resin, such as polyvinylidene fluoride resin, fluororubber, or styrene-butadiene copolymer resin particles. The binder resin may also be a water-soluble resin such as cellulose or polyvinyl alcohol. When using particulate resin or water-soluble resin as the binder resin, a coating solution can be prepared by dispersing or dissolving the binder resin in water, and a heat-resistant layer can be formed on a porous substrate by a dry coating method using this coating solution.

[0054] As the binder resin, a heat-resistant resin containing at least one selected from the group consisting of all-aromatic polyamides, polyamide-imides, and polyimides is preferred from the viewpoint of excellent heat resistance. Among these, all-aromatic polyamides are preferred from the viewpoint of durability. The all-aromatic polyamide may be meta-type or para-type. Among all-aromatic polyamides, meta-type all-aromatic polyamides are preferred from the viewpoint of easily forming a porous layer and having excellent oxidation-reduction resistance in electrode reactions. A small amount of aliphatic monomer may be copolymerized in the all-aromatic polyamide.

[0055] As for the all-aromatic polyamide used as the binder resin, polymetaphenylene isophthalamide or polyparaphenylene terephthalamide are preferred, and polymetaphenylene isophthalamide is more preferred.

[0056] From the viewpoint of adhesion between the heat-resistant layer and the adhesive layer, polyvinylidene fluoride resins (PVDF resins) are preferred as binder resins. Examples of PVDF resins include homopolymers of vinylidene fluoride (i.e., polyvinylidene fluoride); copolymers of vinylidene fluoride with other monomers (polyvinylidene fluoride copolymers); and mixtures of polyvinylidene fluoride and polyvinylidene fluoride copolymers. Examples of monomers copolymerizable with vinylidene fluoride include tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, trichloroethylene, vinyl fluoride, trifluoroperfluoropropyl ether, ethylene, (meth)acrylic acid, methyl (meth)acrylate, (meth)acrylic acid esters, vinyl acetate, vinyl chloride, and acrylonitrile. These monomers may be used individually or in combination of two or more. The PVDF resin preferably has a weight-average molecular weight (Mw) of 600,000 to 3,000,000. The PVDF resin preferably has an acid value of 3 mg KOH / g to 20 mg KOH / g. The acid value of the PVDF resin can be controlled, for example, by introducing carboxyl groups into the PVDF resin. The introduction of carboxyl groups into the PVDF resin and the amount introduced 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 derivatives thereof) as polymerization components of the PVDF resin and adjusting the polymerization ratio.

[0057] There are no particular restrictions on the inorganic filler, and examples 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 silica, alumina, zirconia, magnesium oxide, and barium titanate; particles of carbonates such as calcium carbonate and magnesium carbonate; and particles of sulfates such as barium sulfate and calcium sulfate. From the viewpoint of stability with respect to the electrolyte and electrochemical stability, it is preferable that the inorganic filler contains at least one selected from the group consisting of magnesium-based particles and barium-based particles. Magnesium-based particles refer to inorganic fillers containing magnesium compounds, specifically including magnesium hydroxide, magnesium oxide, and the like. Barium-based particles refer to inorganic fillers containing barium compounds, specifically including barium sulfate, barium titanate, and the like. The inorganic filler may be surface-modified with a silane coupling agent or the like.

[0058] There are no limitations on the particle shape of the inorganic filler; it may be spherical, elliptical, plate-shaped, needle-shaped, or irregularly shaped. From the viewpoint of suppressing short circuits in the battery, the inorganic filler contained in the heat-resistant layer is preferably plate-shaped or non-aggregated primary particles.

[0059] The average particle size of the inorganic filler is preferably 0.01 μm to 10 μm. The lower limit is more preferably 0.1 μm, and the upper limit is more preferably 5 μm. The average particle size is a value measured using a laser diffraction particle size distribution analyzer, for example, the MasterSizer 2000 manufactured by Sysmex Corporation. Specifically, the average particle size is defined as the central particle size (D50) in the volume particle size distribution of a dispersion liquid obtained by mixing and dispersing an inorganic filler, water (dispersion medium), and a nonionic surfactant (Triton X-100; dispersant).

[0060] As a porous substrate, a substrate having a heat-resistant layer containing an inorganic filler on at least one side of a polyolefin microporous membrane, wherein the inorganic filler content relative to the entire layer is 90% by mass or more, is preferred. The inorganic filler content relative to the entire layer 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.

[0061] Inorganic fillers may be used individually or in combination of two or more types. The inorganic filler content in the heat-resistant layer is 2.0 g / m². 2 ~20.0g / m 2 Preferably, the inorganic filler content is 2.0 g / m².2 The above results in superior heat resistance of the separator. The inorganic filler content is 20.0 g / m². 2 The following conditions make it less likely for the heat-resistant layer to peel off and fall off.

[0062] The heat-resistant layer may contain additives other than the nonionic surfactant mentioned above, such as dispersants, wetting agents, defoamers, and pH adjusters. Dispersants can improve the dispersibility, coating properties, or storage stability of the coating solution used to form the heat-resistant layer. Wetting agents, defoamers, and pH adjusters can be added to the coating solution used to form the heat-resistant layer, for example, to improve compatibility with the polyolefin microporous membrane, to suppress air entrapment in the coating solution, or to adjust the pH.

[0063] - Properties of the heat-resistant layer - In the separator of this 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 heat resistance or handling properties 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 handling properties of the separator or energy density of the battery. The total thickness of the heat-resistant layer on both sides, whether the heat-resistant layer is on only one side or on both sides of the porous substrate, is preferably 1.0 μm or more, more preferably 1.6 μm or more, preferably 8.0 μm or less, and more preferably 7.0 μm or less.

[0064] The heat-resistant layer may be a porous layer having multiple pores. If the heat-resistant layer is a porous layer, the porosity is preferably 30% to 70%.

[0065] When the porous substrate has a polyolefin microporous membrane and a heat-resistant layer, 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 even more preferably 20 N / m or more, from the viewpoint of the adhesion strength of the separator to the electrode. Furthermore, from the viewpoint of ion permeability, the peel strength is preferably 75 N / m or less, more preferably 60 N / m or less, and even more preferably 50 N / m or less.

[0066] (Adhesive layer) The separator for non-aqueous secondary batteries of this disclosure has an adhesive layer containing a polyvinylidene fluoride resin on at least one side of a porous substrate. The adhesive layer is responsible for bonding the separator to, for example, an electrode.

[0067] The adhesive layer is not only placed on one side of the porous substrate, but is preferably placed on both sides of the porous substrate, in order to better achieve the effects of this disclosure.

[0068] The adhesive layer contains a polyvinylidene fluoride-based resin. Examples of polyvinylidene fluoride-based resins include polyvinylidene fluoride homopolymers (i.e., polyvinylidene fluoride); copolymers of polyvinylidene fluoride with other monomers (polyvinylidene fluoride copolymers); and mixtures of polyvinylidene fluoride and polyvinylidene fluoride copolymers. Examples of monomers copolymerizable with polyvinylidene fluoride include tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, trichloroethylene, vinyl fluoride, trifluoroperfluoropropyl ether, ethylene, (meth)acrylic acid, methyl (meth)acrylate, (meth)acrylic acid esters, vinyl acetate, vinyl chloride, and acrylonitrile. These monomers may be used individually or in combination of two or more.

[0069] From the viewpoint of obtaining mechanical strength that can withstand the pressure and heat during battery manufacturing, polyvinylidene fluoride copolymers are preferred that have 50 mol% or more of constituent units derived from vinylidene fluoride.

[0070] Preferably, the polyvinylidene fluoride copolymer is a copolymer of vinylidene fluoride and tetrafluoroethylene, a copolymer of vinylidene fluoride and hexafluoropropylene, or a copolymer of vinylidene fluoride and trifluoroethylene, with the copolymer of vinylidene fluoride and hexafluoropropylene being more preferred. The copolymer of vinylidene fluoride and hexafluoropropylene is preferably one containing 0.1 mol% to 10 mol% (preferably 0.5 mol% to 5 mol%) of hexafluoropropylene-derived structural units.

[0071] The weight-average molecular weight of the polyvinylidene fluoride resin is preferably 10 to 5 million, more preferably 10,000 to 3 million, and even more preferably 50,000 to 2 million.

[0072] The polyvinylidene fluoride resin may be included in the form of particles. The adhesive layer may be a layer having a structure in which particles of polyvinylidene fluoride resin are attached to a porous substrate. The adhesive layer containing particles of polyvinylidene fluoride resin may allow gas or liquid to pass from one side to the other through gaps present between the particles of polyvinylidene fluoride resin. The structure in which particles of polyvinylidene fluoride resin are attached includes not only the form in which the particle shape is maintained in the finished separator, but also the form in which the particles are partially melted due to heat treatment or drying treatment during the manufacturing process and do not maintain their particle shape.

[0073] The adhesive layer preferably has a three-dimensional network structure made of polyvinylidene fluoride resin. Having a three-dimensional network structure in the adhesive layer ensures that the ion permeability within the adhesive layer remains good and uniform even after adhesion to the electrode.

[0074] A three-dimensional network structure refers to a structure in which pores (spaces) extend three-dimensionally in various directions in three-dimensional space, including the left-right, up-down, front-back, and diagonal directions in between (for example, multiple particles are connected).

[0075] A three-dimensional network structure can be formed by dissolving a polyvinylidene fluoride resin in an organic solvent, applying the polyvinylidene fluoride resin-containing solution to a porous substrate, immersing it in a coagulation solution containing a poor solvent of polyvinylidene fluoride resin, washing it with water, and drying it. Furthermore, by using polyvinylidene fluoride-based resin particles, it is possible to form an adhesive layer having a three-dimensional network structure. However, the methods for forming the three-dimensional network structure are not limited to these.

[0076] The presence of a three-dimensional network structure in the adhesive layer can be confirmed by cutting the completed separator in a plane parallel to the thickness direction and observing the adhesive layer on the cut surface with a scanning electron microscope.

[0077] Because the adhesive layer is attached to the heat-resistant layer or porous substrate, interfacial fracture between the heat-resistant layer or porous substrate and the adhesive layer is less likely to occur. Furthermore, because the adhesive layer has a structure in which polyvinylidene fluoride resin particles are interconnected, the adhesive layer has excellent toughness and is less prone to cohesive fracture.

[0078] The adhesive layer may further contain other resins besides polyvinylidene fluoride resins, in accordance with the composition of the positive or negative electrode, to the extent that it does not significantly impair the effects of the present disclosure. Examples of other resins include fluororubber, acrylic resins, styrene-butadiene copolymers, homopolymers or copolymers of vinyl nitrile compounds (acrylonitrile, methacrylonitrile, etc.), carboxymethylcellulose, hydroxyalkylcellulose, polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, and polyethers (polyethylene oxide, polypropylene oxide, etc.). The adhesive layer preferably contains polyvinylidene fluoride resins and acrylic resins in terms of excellent oxidation resistance. Furthermore, the adhesive layer preferably contains particles of a mixture of polyvinylidene fluoride resin and acrylic resin, or a mixture of first particles containing polyvinylidene fluoride resin (preferably more than 50% by mass of the total solids) and second particles containing acrylic resin (preferably more than 50% by mass of the total solids), from the viewpoint of balancing the ion permeability of the adhesive layer, the adhesion of the adhesive layer to the electrodes, the peel strength between the adhesive layer and the heat-resistant layer, and the handling properties of the adhesive layer.

[0079] 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, which may be modified.

[0080] From the viewpoint of balancing the ion permeability of the adhesive layer, the adhesion of the adhesive layer to the electrodes, the peel strength between the adhesive layer and the heat-resistant layer, and the handling properties of the adhesive layer, the polyvinylidene fluoride resin content of the entire layer is preferably more than 50% by mass, more preferably 70% by mass or more, and even more preferably 90% by mass or more.

[0081] The adhesive layer may contain additives such as dispersants (including surfactants), wetting agents, defoamers, and pH adjusters.

[0082] The adhesive layer can be formed by preparing a polyvinylidene fluoride-based resin-containing liquid for forming the adhesive layer and applying (e.g., coating) the polyvinylidene fluoride-based resin-containing liquid onto a porous substrate. Alternatively, the adhesive layer may be formed by preparing a resin particle dispersion liquid containing polyvinylidene fluoride-based resin particles and coating the resin particle dispersion liquid onto a porous substrate. The adhesive layer should have a density of 0.2 g / m² per side, from the viewpoint of adhesion to the electrode. 2 The above is preferred, and from the viewpoint of ion permeability, separator handling, or battery energy density, 2.0 g / m² per side is preferred. 2 The following are preferable.

[0083] -Separator Characteristics- The thickness of the separator in this disclosure is preferably 8.0 μm or more, more preferably 9.0 μm or more, from the viewpoint of the mechanical strength of the separator, and preferably 20.0 μm or less, more preferably 15.0 μm or less, from the viewpoint of the energy density of the battery.

[0084] The puncture strength of the separator according to this disclosure is preferably 150g to 1000g, and more preferably 200g to 600g, from the viewpoint of the mechanical strength of the separator or the short-circuit resistance of the battery. The method for measuring the puncture strength of the separator is the same as the method for measuring the puncture strength of a porous substrate.

[0085] The porosity of the separator according to this disclosure is preferably 30% to 60% from the viewpoint of adhesion to the electrode, handling of the separator, ion permeability, or mechanical strength.

[0086] The moisture content (by mass) of the separator in this disclosure is preferably 1200 ppm or less, and more preferably 1000 ppm or less. The lower the moisture content of the separator, the more the reaction between the electrolyte and water is suppressed when it is used to construct a battery, thereby suppressing gas generation within the battery and improving the battery's cycle characteristics. From this viewpoint, the moisture content of the separator is more preferably 800 ppm or less, even more preferably 600 ppm or less, and particularly preferably 500 ppm or less.

[0087] The film resistance of the separator in this disclosure is 0.5 ohm·cm from the viewpoint of the battery load characteristics. 2 ~10 ohms·cm 2 Preferably, 1 ohm·cm 2 ~8 ohms·cm 2 This is preferable.

[0088] The Gaale value (JIS P8117:2009) of the separator in this disclosure is preferably 50 seconds / 100 mL to 800 seconds / 100 mL, more preferably 80 seconds / 100 mL to 500 seconds / 100 mL, and even more preferably 100 seconds / 100 mL to 400 seconds / 100 mL, from the viewpoint of balancing mechanical strength and ion permeability.

[0089] From the viewpoint of ion permeability, the separator of this disclosure preferably has a difference of 20 seconds / 100 mL to 300 seconds / 100 mL between the Gaarle value of the separator and the Gaarle value of the porous substrate. More preferably, the difference between the Gaarle value of the separator and the Gaarle value of the porous substrate is 200 seconds / 100 mL or less, and even more preferably 150 seconds / 100 mL or less.

[0090] The tensile strengths of the separators in the MD and TD of this disclosure are both 500 kgf / cm², from the viewpoint of the mechanical strength or handling properties of the separators. 2 The above is preferable, and 700 kgf / cm² 2 The above is preferable. The upper limit is usually 3000 kgf / cm². 2 The following applies:

[0091] -Method for manufacturing a separator- The separator of this disclosure is manufactured by a method comprising the steps of forming an adhesive layer containing a polyvinylidene fluoride resin on at least one side of a porous substrate, and attaching a nonionic surfactant. The adhesive layer can be formed through the following steps. Specifically, in this step, a polyvinylidene fluoride resin solution is prepared by dissolving the polyvinylidene fluoride resin in a mixed solvent consisting of a solvent that dissolves the polyvinylidene fluoride resin (hereinafter also referred to as the "good solvent") and a solvent that does not dissolve it (hereinafter also referred to as the "poor solvent"). After coating at least one side of the substrate with this solution, it is immersed in a solidification solution consisting of the mixed solvent and water, which is an example of a poor solvent. This solidifies the polyvinylidene fluoride resin into a three-dimensional network structure, after which the solidification solution is washed with water and the water is dried. Here, good solvents include polar amide solvents such as N-methylpyrrolidone, dimethylacetamide, and dimethylformamide. Poor solvents include water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, and tripropylene glycol. Furthermore, the mixed solvent does not necessarily need to contain a poor solvent and may consist only of good solvents. Furthermore, the adhesive layer can also be formed by applying a polyvinylidene fluoride resin solution, similar to the one described above, to at least one side of the substrate, drying the good solvent to precipitate the polyvinylidene fluoride resin into a three-dimensional network structure, and then removing the poor solvent by drying or extraction. Furthermore, when coating using a polyvinylidene fluoride-based resin solution in which an inorganic filler is dispersed, a three-dimensional network-like adhesive layer can be formed by drying and removing the mixed solvent after coating. The adhesion of a nonionic surfactant can be achieved by applying an aqueous solution of the nonionic surfactant to a porous substrate on which an adhesive layer has been formed. The application of the aqueous solution of the nonionic surfactant is preferably carried out after the polyvinylidene fluoride resin has been deposited into a three-dimensional network structure during the adhesive layer formation process, and is particularly preferable to be carried out after the adhesive layer has been formed on the porous substrate after drying. Here, the application of the aqueous solution of the nonionic surfactant can be achieved by known methods such as gravure coating and dip coating.

[0092] <Non-aqueous secondary battery> The non-aqueous secondary battery of this disclosure comprises a positive electrode, a negative electrode, and a separator for the non-aqueous secondary battery of this disclosure, as described above, disposed between the positive and negative electrodes. The non-aqueous secondary battery of this disclosure is a non-aqueous secondary battery that obtains electromotive force by doping and dedoping of lithium. Doping means absorption, support, adsorption, or insertion, and refers to the phenomenon in which lithium ions enter the active material of an electrode such as a positive electrode.

[0093] The non-aqueous secondary battery of this disclosure is superior in battery productivity and battery cycle characteristics (capacity retention rate) because the separator of this disclosure has excellent adhesion to the electrodes, suppresses static charge, and has excellent handling properties.

[0094] The non-aqueous secondary battery of this disclosure has a structure in which, for example, a battery element in which a negative electrode and a positive electrode face each other via a separator is sealed together with an electrolyte in an outer casing. The non-aqueous secondary battery of this disclosure is suitable for non-aqueous electrolyte secondary batteries, particularly lithium-ion secondary batteries.

[0095] The following describes examples of the forms of the positive electrode, negative electrode, electrolyte, and outer casing material of the non-aqueous secondary battery of this disclosure.

[0096] An example of a positive electrode embodiment is a structure in which an active material layer containing a positive electrode active material and a binder resin is molded on a current collector. The active material layer may further contain a conductive additive. Examples of positive electrode active materials include lithium-containing transition metal oxides, specifically LiCoO2, LiNiO2, and LiMn 1 / 2 Ni 1 / 2 O2, LiCo 1 / 3 Mn 1 / 3 Ni 1 / 3 O2, LiMn2O4, LiFePO4, LiCo 1 / 2 Ni 1 / 2 O2, Lial 1 / 4 Ni 3 / 4Examples include O2. 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.

[0097] In the non-aqueous secondary battery of this disclosure, when the adhesive layer of the separator of this disclosure contains a polyvinylidene fluoride resin, the polyvinylidene fluoride resin has excellent oxidation resistance, so by placing the adhesive layer on the positive electrode side of the non-aqueous secondary battery, LiMn capable of operating at a high voltage of 4.2V or higher can be used as the positive electrode active material. 1 / 2 Ni 1 / 2 O2, LiCo 1 / 3 Mn 1 / 3 Ni 1 / 3 O2 and similar substances are easy to apply.

[0098] An example of a negative electrode embodiment is a structure in which an active material layer containing a negative electrode active material and a binder resin is molded on a current collector. The active material layer may further contain a conductive additive. Examples of negative electrode active materials include materials that can electrochemically absorb lithium, specifically carbon materials; alloys of silicon, tin, aluminum, etc. with lithium; Wood's alloys; 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 copper foil, nickel foil, and stainless steel foil with a thickness of 5 μm to 20 μm. Alternatively, metallic lithium foil may be used as the negative electrode instead of the above-mentioned negative electrode.

[0099] 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; linear carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and their fluorine-substituted derivatives; and cyclic esters such as γ-butyrolactone and γ-valerolactone. These may be used individually or in combination. A suitable electrolyte is a solution obtained by mixing a cyclic carbonate and a linear carbonate in a mass ratio (cyclic carbonate:linear carbonate) of 20:80 to 40:60 and dissolving a lithium salt in a concentration of 0.5 mol / L to 1.5 mol / L.

[0100] Examples of outer packaging materials include metal cans and aluminum laminate film packs. While batteries can take various shapes such as rectangular, cylindrical, and coin-shaped, the separator of this disclosure is suitable for any of these shapes.

[0101] The manufacturing methods for non-aqueous secondary batteries according to this disclosure include a manufacturing method that includes impregnating a separator with an electrolyte and performing a heat press treatment (hereinafter referred to as "wet heat press") to adhere it to an electrode; and a manufacturing method that includes performing a heat press treatment (hereinafter referred to as "dry heat press") without impregnating the separator with an electrolyte and adhering it to an electrode.

[0102] The non-aqueous secondary battery of this disclosure can be manufactured by placing the separator of this disclosure between the positive electrode and the negative electrode, winding it in the longitudinal direction to produce a wound body, and then using this wound body, for example, by the following manufacturing methods 1 to 3. In this disclosure, the effects of the separator for non-aqueous secondary batteries of this disclosure described above are expected to be more pronounced in manufacturing method 1 or 2, but manufacturing method 3 may also be used. The same applies when using an element manufactured by stacking the positive electrode, separator, and negative electrode in that order in at least one layer each (so-called stack method) instead of a wound body.

[0103] (Manufacturing method 1) After dry heat pressing the wound body to bond the electrodes and separators, it is placed in an outer packaging material (for example, an aluminum laminate film pack; the same applies hereinafter), an electrolyte is injected into it, and the wound body is further wet heat pressed over the outer packaging material to bond the electrodes and separators and seal the outer packaging material. (Manufacturing method 2) After bonding the electrodes and separators to the wound body using dry heat pressing, the body is placed in an outer casing, an electrolyte solution is injected, and the outer casing is sealed. (Manufacturing method 3) The wound body is placed in an outer material, an electrolyte is injected therein, and the wound body is wet-heat-pressed from above the outer material to bond the electrodes to the separator and seal the outer material.

[0104] The conditions for the heat pressing in the above manufacturing methods 1 to 3 are as follows: For dry heat pressing and wet heat pressing, the press temperature is preferably 60°C to 120°C, more preferably 70°C to 100°C, and the press pressure is 1 cm at the electrode. 2 The load per press is preferably between 0.5 kg and 90 kg. The pressing time is preferably adjusted according to the pressing temperature and pressing pressure, for example, within a range of 0.1 minutes to 60 minutes.

[0105] In manufacturing method 1 or 2 described above, the winding may be temporarily bonded by applying room temperature press (pressure at room temperature) before dry heat pressing. In manufacturing method 2 described above, the winding may be temporarily bonded by applying room temperature press before being placed in the outer material. [Examples]

[0106] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the spirit of the invention.

[0107] [Measurement of cloud point] Measurements were taken in accordance with JIS K 2269.

[0108] [Evaluation of electrostatic properties] The half-life was measured using the half-life method described in JIS L 1094. Specifically, the separators prepared in the following examples and comparative examples were used as samples, and the saturation voltage and half-life were measured after applying a 10kV, 3-minute corona discharge to the sample using a static honestometer (manufactured by Shishido Electrostatics Co., Ltd.) with a distance of 20mm between the sample and the electrode.

[0109] [Moisture content measurement] The moisture content was measured using a Karl Fischer moisture meter. Specifically, the separators prepared in the following examples and comparative examples were used as samples. The samples were stored in a dry room with a dew point of -55°C for 1 hour, and then each sample was heated at 150°C for 15 minutes. The moisture released during this time was transported to the Karl Fischer moisture meter using dry air (dew point -55°C) as the carrier gas, and the amount of moisture was measured by the coulometric method. The moisture content was then determined by dividing the result by the weight of the sample.

[0110] [Battery performance evaluation] A composite layer of graphite / styrene-butadiene rubber / carboxymethylcellulose (=96.2 / 2.8 / 1.0 [mass ratio]) was formed on copper foil to serve as the negative electrode. A composite layer of lithium cobaltate / polyvinylidene fluoride / acetylene black (=94.0 / 3.0 / 3.0 [mass ratio]) was formed on aluminum foil to serve as the positive electrode. The resulting negative and positive electrodes were joined via a separator, placed in an aluminum laminate film pack, and then sealed after injecting the electrolyte. The electrolyte used was 1 M (mol / L) LiPF6-ethylene carbonate / ethyl methyl carbonate (=3 / 7 [mass ratio]). Battery performance was evaluated by the retention rate of the 10C constant current discharge capacity relative to the 0.1C constant current discharge capacity. The discharge cutoff voltage was set to 2.5V. Charging was performed using constant current / constant voltage charging at 0.1C and 4.2V.

[0111] (Example 1) A separator was fabricated by laminating a heat-resistant layer containing alumina particles and an acrylic resin onto one side of a polyethylene microporous membrane, and then laminating a three-dimensional network adhesive layer made of polyvinylidene fluoride-hexafluoropropylene copolymer onto both sides of the porous substrate (the front and the other side of the heat-resistant layer). An aqueous solution of Emulgen 108 (manufactured by Kao Corporation), a nonionic surfactant with a cloud point of 40°C and a molecular weight of 450, was applied to both sides of the separator (SEMCORP, product model number: ND7T211O). The separator was then dried at 60°C for 10 minutes. The amount of Emulgen 108 deposited on the separator was 0.2 g / m². 2 The fabricated separator was cut along a plane parallel to its thickness, and the adhesive layer on the cut surface was observed with a scanning electron microscope to confirm that it had a three-dimensional network structure. Furthermore, Table 1 shows the results of measuring and evaluating the electrostatic properties, moisture content, and battery performance of the fabricated separators as samples.

[0112] (Example 2) In Example 1, the amount of emulsion 108 applied was 0.13 g / m². 2 The separator was fabricated in the same manner as in Example 1, except for the change made to [specific component]. The electrostatic properties, moisture content, and battery performance of the fabricated separator were measured and evaluated, and the results are shown in Table 1. Furthermore, by cutting the separator in a plane parallel to its thickness and observing the adhesive layer on the cut surface with a scanning electron microscope, it was confirmed that the adhesive layer has a three-dimensional network structure.

[0113] (Example 3) In Example 1, the amount of emulsion 108 applied was 0.4 g / m². 2 The separator was fabricated in the same manner as in Example 1, except for the change made to [specific component]. The electrostatic properties, moisture content, and battery performance of the fabricated separator were measured and evaluated, and the results are shown in Table 1. Furthermore, by cutting the separator in a plane parallel to its thickness and observing the adhesive layer on the cut surface with a scanning electron microscope, it was confirmed that the adhesive layer has a three-dimensional network structure.

[0114] (Example 4) In Example 1, the amount of emulsion 108 applied was 0.6 g / m². 2 The separator was fabricated in the same manner as in Example 1, except for the change made to [specific component]. The electrostatic properties, moisture content, and battery performance of the fabricated separator were measured and evaluated, and the results are shown in Table 1. Furthermore, by cutting the separator in a plane parallel to its thickness and observing the adhesive layer on the cut surface with a scanning electron microscope, it was confirmed that the adhesive layer has a three-dimensional network structure.

[0115] (Example 5) Separators were prepared in the same manner as in Example 1, except that Emulgen 108 was replaced with Emulgen 409PV (manufactured by Kao Corporation), a nonionic surfactant with a cloud point of 55°C and a molecular weight of 664. The electrostatic properties, moisture content, and battery performance of the prepared separators were measured and evaluated, and the results are shown in Table 1. Furthermore, by cutting the separator in a plane parallel to its thickness and observing the adhesive layer on the cut surface with a scanning electron microscope, it was confirmed that the adhesive layer has a three-dimensional network structure.

[0116] (Comparative Example 1) Separators were prepared in the same manner as in Example 1, except that Emulgen 108 was replaced with Emulgen 150 (manufactured by Kao Corporation), a nonionic surfactant with a cloud point of over 100°C and a molecular weight of 2254. The electrostatic properties, moisture content, and battery performance of the prepared separators were measured and evaluated, and the results are shown in Table 1.

[0117] (Comparative Example 2) Separators were prepared in the same manner as in Example 1, except that Emulgen 108 was replaced with Emulgen 120 (manufactured by Kao Corporation), a nonionic surfactant with a cloud point of 98°C and a molecular weight of 758. The electrostatic properties, moisture content, and battery performance of the prepared separators were measured and evaluated, and the results are shown in Table 1.

[0118] (Comparative Example 3) Separators were prepared in the same manner as in Example 1, except that the aqueous solution of Emulgen 108 was not applied. The electrostatic properties, moisture content, and battery performance of the prepared separators were measured and evaluated, and the results are shown in Table 1.

[0119] [Table 1]

[0120] As shown in Table 1, the examples using a specific nonionic surfactant with a cloud point of 85°C or less and a molecular weight of 1500 or less showed less static charge, better handling properties, better moisture content in the separator, and superior battery performance compared to the comparative example that did not use the specific nonionic surfactant.

Claims

1. Porous substrate and An adhesive layer containing a polyvinylidene fluoride resin is provided on at least one side of the porous substrate, It has, A separator for non-aqueous secondary batteries, comprising a nonionic surfactant having a cloud point of 30°C to 85°C and a molecular weight of 200 to 1500.

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

3. The separator for a non-aqueous secondary battery according to claim 2, wherein the porous substrate has a heat-resistant layer on at least one side of the polyolefin microporous membrane, the inorganic filler content of the entire layer being 90% by mass or more.

4. A separator for a non-aqueous secondary battery according to any one of claims 1 to 3, wherein the adhesive layer is provided on both sides of the porous substrate.

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

6. The content of the nonionic surfactant is 0.05 g / m ２ ~1.0 g / m ２ A separator for a non-aqueous secondary battery according to any one of claims 1 to 5.

7. Positive electrode and, The negative electrode and, Displaced between the positive electrode and the negative electrode, the separator for a non-aqueous secondary battery according to any one of claims 1 to 6, A non-aqueous secondary battery equipped with [a specific feature].

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