Separator for nonaqueous secondary battery, method for manufacturing separator for nonaqueous secondary battery, and nonaqueous secondary battery

Abstract

This separator for a nonaqueous secondary battery comprises a porous base material, and an adhesive porous layer that is disposed on one surface or both surfaces of the porous base material and contains a polyvinyl chloride-based resin and filler particles. The adhesive porous layer has a porous structure in which the filler particles are connected by the polyvinyl chloride-based resin and pile up.

Description

Separator for non-aqueous secondary batteries, method for manufacturing a separator for non-aqueous secondary batteries, and non-aqueous secondary batteries

[0001] This disclosure relates to a separator for non-aqueous secondary batteries, a method for manufacturing a separator for non-aqueous secondary batteries, and a non-aqueous secondary battery.

[0002] Organofluorine compounds have been used in a wide range of manufacturing and industrial applications due to their useful properties such as heat resistance, chemical resistance, and surfactant activity. In recent years, however, ecotoxicity and anthroptoxicity of organofluorine compounds have been reported, leading to stricter regulations on their manufacture and use worldwide.

[0003] Separators containing polyvinylidene fluoride resin are known for use in batteries. However, with the increasing restrictions on the manufacture and use of organofluorine compounds, there is an urgent need to develop separators with low or no polyvinylidene fluoride resin content.

[0004] Patent Document 1 discloses a separator for lithium-ion secondary batteries comprising a polyolefin resin (A), a resin (B), and a thermoplastic resin (C), wherein resin (B) is present on the surface of a microporous film formed of at least the polyolefin resin (A), and is selected from the group consisting of polyvinyl chloride, polycarbonate, polyamide, polybutylene terephthalate, and polyethylene terephthalate, and copolymerized with at least a portion of the polyolefin resin (A). Patent Document 2 discloses a separation membrane for lithium-ion secondary batteries comprising a porous polymer substrate with a porosity of 40% to 50%, and a porous coating layer containing small-particle inorganic particles with a D50 diameter of 10 nm to 100 nm, large-particle inorganic particles with a D50 diameter of 600 nm or more, and adhesive polymer particles with a D50 diameter of 200 nm or less, wherein the content of small-particle inorganic particles is 30 parts by mass or more per 100 parts by mass of the total inorganic particle content.

[0005] Japanese Patent Publication No. 2018-200788, Japanese Patent Publication No. 2023-516181

[0006] From the perspective of preventing internal short circuits in batteries, separators are required to have good adhesion to the electrodes. Separators containing polyvinylidene fluoride resin in the surface layer have excellent adhesion to the electrodes. However, there is a need for separators that have excellent adhesion to the electrodes even with a small amount of polyvinylidene fluoride resin in the surface layer, or even without polyvinylidene fluoride resin in the surface layer.

[0007] Furthermore, from the perspective of battery characteristics required for secondary batteries (e.g., cycle characteristics, rate characteristics), separators are required to have excellent ion permeability when immersed in electrolyte. The ion permeability of a separator can be evaluated using its air permeability in a dry state as an indicator; the better the air permeability, the better the ion permeability.

[0008] To improve the permeability (i.e., ion permeability) of a separator, the surface layer can be made porous. However, increasing the porosity of the surface layer tends to decrease its adhesion to the electrode. Achieving both permeability and adhesion to the electrode in a separator is not always easy.

[0009] This disclosure is made under the circumstances described above. The object of this disclosure is to provide a separator for non-aqueous secondary batteries that achieves both breathability and adhesion to electrodes.

[0010] The following embodiments are included as specific means for solving the above problems: <1> A separator for a non-aqueous secondary battery, comprising a porous substrate and an adhesive porous layer containing a polyvinyl chloride resin and filler particles disposed on one or both sides of the porous substrate, wherein the adhesive porous layer has a porous structure in which the filler particles are linked and stacked by the polyvinyl chloride resin. <2> The separator for a non-aqueous secondary battery according to <1>, wherein the glass transition temperature of the polyvinyl chloride resin contained in the adhesive porous layer is 40°C or less. <3> The mass per unit area of ​​the polyvinyl chloride resin contained in the adhesive porous layer is 0.1 g / m² in total for both sides of the porous substrate. ２ ~5.0 g / m ２A separator for a non-aqueous secondary battery according to <1> or <2>. <4> A separator for a non-aqueous secondary battery according to any one of <1> to <3>, wherein the average primary particle size of the filler particles contained in the adhesive porous layer is 0.01 μm to 2 μm. <5> A separator for a non-aqueous secondary battery according to any one of <1> to <4>, wherein the value obtained by subtracting the air permeability of the porous substrate from the air permeability of the separator for a non-aqueous secondary battery is 0 seconds / 100 mL to 200 seconds / 100 mL. <6> A separator for a non-aqueous secondary battery according to any one of <1> to <5>, wherein the heat shrinkage rate when the separator for a non-aqueous secondary battery is heat-treated at a temperature of 105 °C for 60 minutes is 5% or less for both MD and TD. <7> A separator for a non-aqueous secondary battery according to any one of <1> to <6>, wherein the adhesive porous layer further contains a resin having carbonyl groups. <8> The non-aqueous secondary battery separator according to <7>, wherein the resin having carbonyl groups comprises at least one selected from the group consisting of urethane resin, acrylic resin, polyamide, polyimide, polyester, polycarbonate, and polyvinyl acetate. <9> The non-aqueous secondary battery separator according to <7> or <8>, wherein the proportion of the polyvinyl chloride resin to the total amount of the polyvinyl chloride resin and the resin having carbonyl groups is 20% by mass to 80% by mass. <10> The non-aqueous secondary battery separator according to any one of <1> to <9>, wherein the heat shrinkage rate when the non-aqueous secondary battery separator is heat-treated at a temperature of 130°C for 60 minutes is 10% or less for both MD and TD. <11> The non-aqueous secondary battery separator according to any one of <1> to <10>, wherein the adhesive porous layer further contains a surfactant. <12> The separator for a non-aqueous secondary battery according to <11>, wherein the surfactant comprises at least one selected from the group consisting of nonionic surfactants and anionic surfactants.<13> A method for manufacturing a separator for a non-aqueous secondary battery according to any one of <1> to <12>, comprising: a step of applying a coating liquid containing water, polyvinyl chloride resin particles and filler particles to one or both sides of a porous substrate to form a coating layer; and a step of drying the coating layer on the porous substrate and melting the polyvinyl chloride resin particles to form an adhesive porous layer. A method for manufacturing a separator for a non-aqueous secondary battery. <14> A non-aqueous secondary battery comprising a positive electrode, a negative electrode, and a separator for a non-aqueous secondary battery according to any one of <1> to <12> disposed between the positive electrode and the negative electrode, and obtaining an electromotive force by doping and de-doping of lithium ions.

[0011] According to the present disclosure, a separator for a non-aqueous secondary battery that achieves both air permeability and adhesion to an electrode is provided.

[0012] SEM image of the surface of the adhesive porous layer of Example 1.

[0013] Hereinafter, embodiments of the present disclosure will be described. These descriptions and examples are illustrative of the embodiments and do not limit the scope of the embodiments.

[0014] In the present disclosure, a numerical range indicated by using "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described step by step. Also, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.

[0015] In the present disclosure, "A and / or B" is synonymous with "at least one of A and B". That is, "A and / or B" means that it may be only A, only B, or a combination of A and B.

[0016] In the present disclosure, the term "step" includes not only an independent step but also a step whose purpose is achieved even when it cannot be clearly distinguished from other steps.

[0017] When referring to the amount of each component in the composition in the present disclosure, when there are multiple substances corresponding to each component in the composition, unless otherwise specified, it means the total amount of the multiple substances present in the composition. The particles corresponding to each component in the present disclosure may include multiple types. When there are multiple types of particles corresponding to each component in the composition, the particle size of each component, unless otherwise specified, means the value for the mixture of the multiple types of particles present in the composition.

[0018] In the present disclosure, MD (Machine Direction) means the longitudinal direction in a separator manufactured in a long shape, and TD (Transverse Direction) means the direction perpendicular to MD in the plane direction of the separator. In the present disclosure, TD is also referred to as the "width direction".

[0019] In the present disclosure, when expressing the lamination relationship of each layer constituting the separator in terms of "upper" and "lower", the layer closer to the porous substrate is referred to as "lower", and the layer farther from the porous substrate is referred to as "upper".

[0020] In the present disclosure, the volume excluding the pores of the porous layer is referred to as the "solid volume".

[0021] In the present disclosure, performing a heat press treatment with the electrolyte infiltrated into the separator is referred to as "wet heat press", and performing a heat press treatment without the electrolyte infiltrated into the separator is referred to as "dry heat press".

[0022] In the present disclosure, the "monomer unit" of a polymer or resin means a constituent unit of the polymer or resin, which is a constituent unit formed by polymerization of a monomer. In the present disclosure, the notation "(meth)acrylic" means that it may be either "acrylic" or "methacrylic".

[0023] <Separator for non-aqueous secondary battery> The separator for non-aqueous secondary battery of the present disclosure (also simply referred to as "separator" in the present disclosure) includes a porous substrate and an adhesive porous layer containing a polyvinyl chloride-based resin and filler particles, which is disposed on one or both sides of the porous substrate.

[0024] The separator of this disclosure has an adhesive porous layer containing a polyvinyl chloride resin and filler particles on one or both sides of a porous substrate. Examples of embodiments of the separator of this disclosure include the following embodiments (1) to (3).

[0025] Form (1): A separator having an adhesive porous layer on both sides of a porous substrate, the outermost layer of which contains polyvinyl chloride resin and filler particles. In this separator, the adhesive porous layer on one side and the adhesive porous layer on the other side may be the same or different in form, components, and / or composition.

[0026] Form (2): A separator having an adhesive porous layer containing polyvinyl chloride resin and filler particles as the outermost layer of the separator on one side of a porous substrate, and another layer on the other side of the porous substrate.

[0027] Form (3): A separator having an adhesive porous layer containing polyvinyl chloride resin and filler particles as the outermost layer of the separator on one side of the porous substrate, and having no layer on the other side of the porous substrate (i.e., the surface of the porous substrate is exposed).

[0028] The adhesive porous layer of the separator of this disclosure has a porous structure in which filler particles are linked and stacked by a polyvinyl chloride resin, thereby achieving both breathability (and therefore ion permeability) and adhesion to electrodes.

[0029] Examples of the morphology of the adhesive porous layer include: a porous structure in which filler particles are bound to or trapped in a two-dimensional or three-dimensional network structure of fibrils containing polyvinyl chloride resin; a structure in which filler particles are bound to or trapped in a network-like microporous structure containing polyvinyl chloride resin; and a layered structure in which polyvinyl chloride resin connects many filler particles, forming voids between the filler particles.

[0030] The details of the porous substrate and adhesive porous layer of the separator of this disclosure will be described below.

[0031] [Porous Substrates] In this disclosure, a porous substrate means a substrate having voids or cavities inside. Examples of such substrates include microporous membranes; porous sheets made of fibrous material such as nonwoven fabrics and paper; and composite porous sheets obtained by laminating one or more other porous layers onto these microporous membranes or porous sheets.

[0032] The material of the porous substrate is preferably an electrically insulating material.

[0033] From the viewpoint of thinning the separator and increasing its strength, a microporous membrane is preferred as the porous substrate. A microporous membrane is a membrane that has a large number of fine pores inside, in which the fine pores are connected, and which allows gas or liquid to pass from one side to the other.

[0034] From the viewpoint of thermal dimensional stability, a composite porous substrate is preferred, which is a microporous membrane laminated with one or more porous heat-resistant layers. The porous heat-resistant layer is preferably a heat-resistant layer containing at least one of inorganic particles and a heat-resistant resin. In this disclosure, a heat-resistant resin refers to a resin with a melting point of 200°C or higher, or a resin that does not have a melting point but has a decomposition temperature of 200°C or higher. In other words, a heat-resistant resin in this disclosure is a resin that does not melt or decompose in the temperature range below 200°C.

[0035] The porous substrate preferably contains a thermoplastic resin in order to impart a shutdown function to the porous substrate. The shutdown function refers to the function that, when the battery temperature rises, melts the constituent material and blocks the pores of the porous substrate, thereby blocking ion movement and preventing thermal runaway of the battery. As the thermoplastic resin, a thermoplastic resin with a melting point of less than 200°C is preferred. Examples of thermoplastic resins include polyesters such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; and among these, polyolefins are preferred.

[0036] As a porous substrate, from the viewpoint of imparting a shutdown function to the porous substrate, a porous substrate containing a microporous membrane containing polyolefin (hereinafter referred to as "polyolefin microporous membrane") is preferred. Examples of porous substrates containing a polyolefin microporous membrane include a porous substrate consisting only of a polyolefin microporous membrane (i.e., a polyolefin microporous membrane) and a composite porous substrate in which a porous heat-resistant layer is arranged on one or both sides of the polyolefin microporous membrane. Here, the porous heat-resistant layer is preferably a heat-resistant layer containing at least one of inorganic particles and a heat-resistant resin.

[0037] Examples of polyolefin microporous membranes include those conventionally used in battery separators, and it is preferable to select one from among these that has sufficient mechanical properties and ion permeability.

[0038] From the viewpoint of exhibiting a shutdown function, a polyethylene-containing microporous membrane (hereinafter referred to as "polyethylene microporous membrane") is preferred among the polyolefin microporous membranes. The polyethylene content is preferably 95% by mass or more relative to the mass of the polyethylene microporous membrane.

[0039] From the viewpoint of possessing heat resistance that prevents the film from easily breaking when exposed to high temperatures, polyolefin microporous membranes containing polypropylene are preferred.

[0040] From the viewpoint of possessing both a shutdown function and heat resistance that prevents easy rupture when exposed to high temperatures, polyolefin microporous membranes containing polyethylene and polypropylene are preferred. Examples of polyolefin microporous membranes containing polyethylene and polypropylene include microporous membranes in which polyethylene and polypropylene are mixed in a single layer. In such microporous membranes, from the viewpoint of achieving both a 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. From the viewpoint of achieving both a shutdown function and heat resistance, polyolefin microporous membranes having a laminated structure of two or more layers, in which at least one layer contains polyethylene and at least one layer contains polypropylene, are also preferred.

[0041] The polyolefin used in the polyolefin microporous membrane is preferably one with a weight-average molecular weight (Mw) of 100,000 to 5,000,000. A polyolefin with an Mw of 100,000 or more provides sufficient mechanical properties to the microporous membrane. A polyolefin with an Mw of 5,000,000 or less exhibits good shutdown characteristics and facilitates the molding of the microporous membrane.

[0042] Methods for producing polyolefin microporous membranes include: a method in which molten polyolefin resin is extruded from a T-die to form a sheet, which is then crystallized, stretched, and subsequently heat-treated to form a microporous membrane; and a method in which molten polyolefin resin together with a plasticizer such as liquid paraffin is extruded from a T-die, which is then cooled to form a sheet, stretched, the plasticizer is extracted, and then heat-treated to form a microporous membrane.

[0043] Examples of porous sheets made of fibrous materials include nonwoven fabrics and porous sheets made of paper. Examples of fibrous materials include polyester such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; heat-resistant resins such as fully aromatic polyamides, polyamide-imides, polyimides, polyethersulfones, polysulfones, polyetherketones, and polyetherimides; and cellulose.

[0044] Examples of composite porous sheets include sheets in which a functional layer is laminated onto a porous sheet made of a microporous membrane or fibrous material. Such composite porous sheets are preferred from the viewpoint that further functionality can be added by the functional layer. Examples of functional layers include porous heat-resistant layers from the viewpoint of providing heat resistance to the composite porous sheet. Methods for compounding a microporous membrane or porous sheet with a functional layer include coating the functional layer onto the surface of the microporous membrane or porous sheet, joining the microporous membrane or porous sheet and the functional layer with an adhesive, and heat-pressing the microporous membrane or porous sheet and the functional layer.

[0045] An example of an embodiment of a composite porous sheet is a composite porous substrate comprising a polyolefin microporous membrane and a heat-resistant layer containing at least one of inorganic particles and a heat-resistant resin, disposed on one or both sides of the polyolefin microporous membrane. The heat-resistant layer is a porous layer. Examples of inorganic particles include metal oxide particles (silica, alumina, boehmite, titania, zirconia, magnesium oxide, barium oxide, etc.), metal hydroxide particles (magnesium hydroxide, aluminum hydroxide, calcium hydroxide, chromium hydroxide, zirconium hydroxide, cerium hydroxide, nickel hydroxide, boron hydroxide, etc.), metal sulfate particles (barium sulfate, calcium sulfate, etc.), metal carbonate particles (calcium carbonate, magnesium carbonate, barium carbonate, etc.), metal nitride particles (boron nitride, aluminum nitride, etc.), and clay mineral particles (calcium silicate, talc, etc.). The inorganic particles may also be inorganic particles whose surface has been modified with a silane coupling agent or the like. Examples of heat-resistant resins include all-aromatic polyamides, polyamide-imides, polyimides, polyethersulfones, polysulfones, polyetherketones, and polyetherimides.

[0046] When the above-mentioned composite porous substrate contains inorganic particles in the heat-resistant layer, it is preferable that the heat-resistant layer also contains a binder resin that binds the inorganic particles. The binder resin may be a heat-resistant resin or a non-heat-resistant resin. Examples of non-heat-resistant resins include butadiene polymers (e.g., butadiene homopolymers, styrene-butadiene copolymers) and acrylic resins (e.g., acrylic monomer homopolymers or copolymers, copolymers of acrylic monomers and styrene monomers).

[0047] One method for arranging a heat-resistant layer containing at least one of inorganic particles and a heat-resistant resin on one or both sides of a polyolefin microporous film is to apply a coating solution containing at least one of inorganic particles and a heat-resistant resin to one or both sides of the polyolefin microporous film.

[0048] In this disclosure, "porous substrate" is a term that includes "composite porous substrate".

[0049] The surface of the porous substrate may be subjected to various surface treatments, to the extent that they do not impair the properties of the porous substrate, in order to improve wettability with the coating liquid for forming an adhesive porous layer. Examples of surface treatments include corona treatment, plasma treatment, flame treatment, and ultraviolet irradiation treatment.

[0050] - Characteristics of Porous Substrate - From the viewpoint of mechanical strength, the thickness of the porous substrate is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. From the viewpoint of increasing the energy density of the battery, the thickness of the porous substrate is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. The thickness of the porous substrate is determined by measuring 20 points within a 10 cm square area using a contact-type thickness gauge and averaging the results.

[0051] From the viewpoint of suppressing internal short circuits in the battery, the air permeability of the porous substrate is preferably 50 seconds / 100 mL or more, more preferably 70 seconds / 100 mL or more, and even more preferably 90 seconds / 100 mL or more. From the viewpoint of excellent electrolyte permeability and ion permeability, the air permeability of the porous substrate is preferably 220 seconds / 100 mL or less, more preferably 200 seconds / 100 mL or less, and even more preferably 180 seconds / 100 mL or less. The air permeability of the porous substrate is measured and determined using a digital Ogane-type air permeability tester in accordance with JIS P8117:2009.

[0052] When the porous substrate is a porous substrate consisting only of a polyolefin microporous membrane (i.e., a polyolefin microporous membrane), the air permeability is preferably 50 seconds / 100 mL to 180 seconds / 100 mL, more preferably 70 seconds / 100 mL to 160 seconds / 100 mL or less, and even more preferably 90 seconds / 100 mL to 140 seconds / 100 mL. When the porous substrate is a composite porous substrate in which a porous heat-resistant layer is arranged on one or both sides of a polyolefin microporous membrane, the air permeability is preferably 90 seconds / 100 mL to 220 seconds / 100 mL, more preferably 100 seconds / 100 mL to 210 seconds / 100 mL or less, and even more preferably 110 seconds / 100 mL to 200 seconds / 100 mL.

[0053] The porosity of the porous substrate is preferably 30% to 60% from the viewpoint of excellent electrolyte permeability and ion permeability. The porosity ε (%) of the porous substrate is calculated by the following formula: ε = {1 - Ws / (ds・t)} × 100 where Ws is the basis weight (g / m) of the porous substrate. ２ ), ds is the true density (g / cm³) of the porous substrate. ３ ), t is the thickness of the porous substrate (μm). Basis weight is the mass per unit area.

[0054] [Adhesive Porous Layer] The adhesive porous layer is a layer placed on the surface of a porous substrate and is the outermost layer of the separator. The adhesive porous layer has numerous gaps or micropores, and is a layer through which gas or liquid can pass from one surface to the other.

[0055] The adhesive porous layer contains at least a polyvinyl chloride resin and filler particles. The adhesive porous layer may further contain resins other than polyvinyl chloride resin.

[0056] -Polyvinyl Chloride Resins- Polyvinyl chloride resins include homopolymers of vinyl chloride (also known as chloroethylene) (i.e., polyvinyl chloride) and copolymers of vinyl chloride with other monomers. Copolymers include alternating copolymers, random copolymers, block copolymers, and graft copolymers. In this disclosure, polyvinyl chloride resin means a resin in which vinyl chloride has the highest number proportion among the monomers constituting the resin.

[0057] It is preferable that the monomers other than vinyl chloride that constitute the polyvinyl chloride resin are monomers that do not contain fluorine atoms. Examples of monomers other than vinyl chloride include vinyl acetate, alkenes (e.g., ethene, propene, butene, pentene, hexene, etc.), dienes (e.g., butadiene, isoprene, etc.), styrene, α-methylstyrene, alkyl-substituted styrenes (e.g., 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, etc.), vinylidene chloride, acrylonitrile, (meth)acrylic acid, (meth)acrylic acid esters, urethane monomers, etc.

[0058] From the viewpoint of adhesion of the porous layer to the electrode, the polyvinyl chloride resin preferably has a polyvinyl chloride content of 50% to 100% of the total monomers constituting the polyvinyl chloride resin, more preferably 50% to 90%, even more preferably 50% to 80%, and even more preferably 50% to 70%.

[0059] The polyvinyl chloride resin contained in the adhesive porous layer may be one type or two or more types.

[0060] The polyvinyl chloride resin contained in the adhesive porous layer preferably has an average degree of polymerization of 500 to 1400, more preferably 550 to 1200, and even more preferably 600 to 1000. When the average degree of polymerization of the polyvinyl chloride resin is 500 or higher, the adhesive porous layer has excellent mechanical strength and is less likely to peel off from the electrode. From this viewpoint, the average degree of polymerization of the polyvinyl chloride resin is more preferably 550 or higher, and even more preferably 600 or higher. When the average degree of polymerization of the polyvinyl chloride resin is 1400 or lower, a porous structure is easily formed in the adhesive porous layer, and the permeability of the electrolyte and ion permeability in the adhesive porous layer are excellent. Furthermore, when the average degree of polymerization of the polyvinyl chloride resin is 1400 or lower, high mobility of the polymer chains when heated and ease of swelling in the electrolyte are ensured, so the adhesive porous layer adheres easily to the electrode by either dry heat pressing or wet heat pressing. Furthermore, if the average degree of polymerization of the polyvinyl chloride resin is 1400 or less, the viscosity of the coating liquid used to form the adhesive porous layer is relatively low, and the coating liquid has excellent applicability. From these viewpoints, it is more preferable that the average degree of polymerization of the polyvinyl chloride resin be 1200 or less, and even more preferable that it be 1000 or less.

[0061] The polyvinyl chloride resin may be in granular form when preparing the coating solution for forming the adhesive porous layer. For example, the coating solution may be prepared using water-dispersible polyvinyl chloride resin particles. However, the polyvinyl chloride resin particles must melt and not maintain their granular shape during the process of forming the adhesive porous layer. From the viewpoint of melting the polyvinyl chloride resin particles by heat application, the glass transition temperature (Tg) of the polyvinyl chloride resin particles and the polyvinyl chloride resin constituting those particles is preferably 40°C or lower, more preferably 35°C or lower, and even more preferably 30°C or lower. From the viewpoint of heat resistance of the battery, the Tg of the polyvinyl chloride resin particles and the polyvinyl chloride resin constituting those particles is preferably 20°C or higher, and more preferably 25°C or higher.

[0062] The glass transition temperature of polyvinyl chloride (PVC) resin particles and PVC resin is determined from the differential scanning calorimetry (DSC) curve obtained by differential scanning calorimetry (DSC). In the DSC curve, the intersection point of the low-temperature baseline and the tangent to the curve of the stepwise transition portion is defined as intersection point (1), and the intersection point of the high-temperature baseline and the tangent to the curve of the stepwise transition portion is defined as intersection point (2). The temperature midway between intersection point (1) and intersection point (2) is defined as the glass transition temperature. The sample used for DSC is PVC resin particles, which are the material that forms the adhesive porous layer, or PVC resin extracted from the adhesive porous layer of a separator.

[0063] The glass transition temperature of polyvinyl chloride resin particles and polyvinyl chloride resin can be controlled by adjusting the type of monomer and copolymerization ratio, using the FOX formula as a guideline.

[0064] From the viewpoint of adhesion of the separator to the electrode, the mass per unit area of ​​the polyvinyl chloride resin contained in the adhesive porous layer should be 0.1 g / m² in total on both sides of the porous substrate. ２ The above is preferable, and 0.2 g / m ２ The above is more preferable, 0.3 g / m ２The above is more preferable. The mass per unit area of the polyvinyl chloride resin contained in the adhesive porous layer is 5.0 g / m in total on both sides of the porous substrate from the viewpoint of the air permeability of the separator. ２ The following is preferable, and 4.0 g / m ２ The following is more preferable, and 3.0 g / m ２ The following is even more preferable.

[0065] The mass per unit area of the polyvinyl chloride resin contained in the adhesive porous layer is obtained by cutting out the separator into a size of 20 cm × 20 cm, peeling off the adhesive porous layer, removing the filler particles from the adhesive porous layer, measuring the mass of the remaining part of the adhesive porous layer, and dividing the mass by the area (400 cm ２ ).

[0066] The mass ratio of the polyvinyl chloride resin in the total resin of the adhesive porous layer is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and particularly preferably 100% by mass.

[0067] When the adhesive porous layers are on both sides of the porous substrate, the type and / or content of the polyvinyl chloride resin contained in one adhesive porous layer and the type and / or content of the polyvinyl chloride resin contained in the other adhesive porous layer may be the same or different.

[0068] - Other resins - The adhesive porous layer may contain other resins other than the polyvinyl chloride resin. Examples of other resins include acrylic resins, butadiene-acrylonitrile resins, homopolymers or copolymers of vinyl nitrile compounds (acrylonitrile, methacrylonitrile, etc.), carboxymethyl cellulose, hydroxyalkyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyethers (polyethylene oxide, polypropylene oxide, etc.), or mixtures of two or more of these. These resins may be used alone or in combination of two or more.

[0069] In one example of the embodiment, the mass percentage of other resins in the total resin of the adhesive porous layer is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less.

[0070] The adhesive porous layer preferably contains substantially no fluorine-containing resin. Examples of fluorine-containing resins include polyvinylidene fluoride resins and fluorine-based rubbers. Examples of polyvinylidene fluoride resins include homopolymers of vinylidene fluoride (i.e., polyvinylidene fluoride); copolymers of vinylidene fluoride with halogen-containing monomers such as hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, vinyl fluoride, and trichloroethylene; copolymers of vinylidene fluoride with monomers other than halogen-containing monomers; copolymers of vinylidene fluoride with halogen-containing monomers and monomers other than halogen-containing monomers; and mixtures thereof.

[0071] The statement that an adhesive porous layer is substantially free of fluorine-containing resin means that the mass percentage of fluorine-containing resin in the adhesive porous layer is 1% by mass or less. The mass percentage of fluorine-containing resin in the adhesive porous layer is preferably as low as possible, preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and particularly preferably 0% by mass. In other words, it is particularly preferable that the adhesive porous layer does not contain fluorine-containing resin.

[0072] -Resin having carbonyl groups- As an example of an embodiment of the adhesive porous layer, an adhesive porous layer containing a polyvinyl chloride resin and a resin having carbonyl groups as the resin is provided. According to this embodiment, a separator with excellent affinity between the porous substrate and the adhesive porous layer is provided. The adhesive porous layer contains a polyvinyl chloride resin from the viewpoint of adhesion to the electrode, and by further containing a resin having carbonyl groups, the affinity to the porous substrate (particularly a porous substrate containing polyolefin) is improved. As a result, the porous substrate and the adhesive porous layer are less likely to delaminate. Therefore, by containing a polyvinyl chloride resin and a resin having carbonyl groups, the adhesive porous layer has good adhesion to both the electrode and the porous substrate. According to this embodiment, as a result of the separator being less likely to delaminate, a battery that is less likely to cause internal short circuits is provided.

[0073] Examples of resins having a carbonyl group (-C(=O)-) include at least one selected from the group consisting of urethane resin, acrylic resin, polyamide, polyimide, polyester, polycarbonate, and polyvinyl acetate. These resins may be used individually or in combination of two or more.

[0074] As for the resin having a carbonyl group, at least one selected from the group consisting of urethane resins and acrylic resins is preferred, with urethane resin being more preferred, from the viewpoint of high affinity with porous substrates containing polyolefins.

[0075] Examples of urethane resins include polymers of polyols and polyisocyanates. Examples of polyols include diols (e.g., 1,4-butanediol), triols, tetraols, polyester polyols, polycarbonate polyols, polycaprolactone polyols, and polyether polyols. Examples of polyisocyanates include 4,4'-diphenylmethane diisocyanate (MDI), 2,6-toluene diisocyanate (TDI), 1,6-hexane diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI), and 3,3-dimethylbiphenyl-4,4'-diisocyanate (TODI).

[0076] Examples of acrylic resins include homopolymers and copolymers of acrylic monomers. Examples of acrylic monomers include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0077] As the acrylic monomer constituting the acrylic resin, alkyl (meth)acrylate is preferred. The alkyl group in the ester portion of the alkyl (meth)acrylate is preferably an alkyl group having 1 to 10 carbon atoms, and more preferably an alkyl group having 1 to 8 carbon atoms. The acrylic monomer may be used alone or in combination of two or more types.

[0078] When adhesive porous layers are present on both sides of a porous substrate, the type and / or content of the carbonyl group-containing resin in one adhesive porous layer and the type and / or content of the carbonyl group-containing resin in the other adhesive porous layer may be the same or different.

[0079] The polyvinyl chloride resin and the resin containing carbonyl groups may be separate polymers or copolymers. Copolymers include alternating copolymers, random copolymers, block copolymers, and graft copolymers.

[0080] The proportion of polyvinyl chloride resin in the total amount of polyvinyl chloride resin and resin having carbonyl groups is preferably 20% to 80% by mass, preferably 30% to 70% by mass, and more preferably 40% to 60% by mass, from the viewpoint of achieving both adhesion to electrodes and adhesion to porous substrates.

[0081] The total mass percentage of polyvinyl chloride resin and resin having carbonyl groups in the total resin of the adhesive porous layer is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and particularly preferably 100% by mass.

[0082] From the viewpoint of adhesion of the separator to the electrode, the total mass per unit area of ​​the polyvinyl chloride resin and the resin having carbonyl groups contained in the adhesive porous layer should be 0.1 g / m² on both sides of the porous substrate. ２ The above is preferable, and 0.2 g / m ２ The above is more preferable, 0.3 g / m ２ The above is even more preferable. The total mass per unit area of ​​the polyvinyl chloride resin and the resin having carbonyl groups contained in the adhesive porous layer should be 5.0 g / m² on both sides of the porous substrate, from the viewpoint of separator air permeability. ２ The following is preferable: 4.0 g / m ２ The following is more preferable: 3.0 g / m ２ The following is even more preferable.

[0083] The total mass per unit area of ​​polyvinyl chloride resin and carbonyl group-containing resin contained in the adhesive porous layer is calculated by cutting a separator to 20 cm x 20 cm, peeling off the adhesive porous layer, removing filler particles from the adhesive porous layer, measuring the mass of the remaining adhesive porous layer, and multiplying that mass by the area (400 cm²). ２ It is found by dividing by ).

[0084] - Filler particles - Examples of filler particles include inorganic particles and organic particles.

[0085] The average primary particle size of the filler particles contained in the adhesive porous layer is preferably 0.01 μm to 2 μm, more preferably 0.05 μm to 1 μm, and even more preferably 0.1 μm to 0.5 μm. When the average primary particle size of the filler particles is 0.01 μm or more, a porous structure is easily formed in the adhesive porous layer, and the permeability of the electrolyte and ion permeability in the adhesive porous layer are excellent. From this viewpoint, the average primary particle size of the filler particles is more preferably 0.05 μm or more, and even more preferably 0.1 μm or more. When the average primary particle size of the filler particles is 2 μm or less, the adhesive porous layer adheres easily to the electrode and is less likely to peel off from the electrode. From this viewpoint, the average primary particle size of the filler particles is more preferably 1 μm or less, and even more preferably 0.5 μm or less.

[0086] The average primary particle size of filler particles is determined by measuring the major axis of 100 randomly selected filler particles observed using a scanning electron microscope (SEM) and averaging the major axes of these 100 particles. The sample used for SEM observation is either filler particles that form an adhesive porous layer, or filler particles extracted from an adhesive porous layer.

[0087] From the viewpoint of achieving a good balance between the permeability of the separator and adhesion to the electrode, the mass ratio of filler particles to the mass of the adhesive porous layer is preferably 40% to 95% by mass, more preferably 45% to 90% by mass, and even more preferably 50% to 85% by mass.

[0088] From the viewpoint of achieving a good balance between the permeability of the separator and adhesion to the electrode, the volume ratio of filler particles to the solid content volume of the adhesive porous layer is preferably 10% to 90% by volume, more preferably 15% to 80% by volume, and even more preferably 20% to 70% by volume.

[0089] When adhesive porous layers are present on both sides of a porous substrate, the type and / or content of filler particles contained in one adhesive porous layer may be the same as or different from the type and / or content of filler particles contained in the other adhesive porous layer.

[0090] - Inorganic Particles - Examples of inorganic particles include metal oxide particles, metal hydroxide particles, metal sulfate particles, metal carbonate particles, metal nitride particles, and clay mineral particles.

[0091] Examples of metal oxides constituting metal oxide particles include silica (silicon dioxide), alumina (aluminum oxide), boehmite (alumina monohydrate), titania (titanium oxide), zirconia (zirconium oxide), magnesium oxide, and barium oxide, with alumina being preferred. Examples of metal hydroxides constituting metal hydroxide particles include magnesium hydroxide, aluminum hydroxide, calcium hydroxide, chromium hydroxide, zirconium hydroxide, cerium hydroxide, nickel hydroxide, and boron hydroxide, with magnesium hydroxide being preferred. Examples of metal sulfates constituting metal sulfate particles include barium sulfate and calcium sulfate, with barium sulfate being preferred. Examples of metal carbonates constituting metal carbonate particles include calcium carbonate, magnesium carbonate, and barium carbonate. Examples of metal nitrides constituting metal nitride particles include boron nitride and aluminum nitride. Examples of clay mineral particles include calcium silicate and talc.

[0092] The inorganic particles may be inorganic particles whose surface has been modified with a silane coupling agent or the like.

[0093] Inorganic particles may be used individually or in combination of two or more types.

[0094] As inorganic particles, at least one selected from the group consisting of metal oxide particles, metal hydroxide particles, and metal sulfate particles is preferred from the viewpoint of stability with respect to the electrolyte and electrochemical stability. Among these, at least one selected from the group consisting of alumina particles (aluminum oxide particles), magnesium hydroxide particles, and barium sulfate particles is more preferred.

[0095] There are no limitations on the particle shape of the inorganic particles; they may be spherical, elliptical, plate-shaped, needle-shaped, or irregularly shaped. From the viewpoint of suppressing internal short circuits in the battery, the inorganic particles contained in the adhesive porous layer are preferably plate-shaped particles or non-aggregated primary particles.

[0096] The average primary particle size of the inorganic particles contained in the adhesive porous layer is preferably 0.01 μm to 2 μm, more preferably 0.05 μm to 1 μm, and even more preferably 0.1 μm to 0.5 μm. When the average primary particle size of the inorganic particles is 0.01 μm or more, a porous structure is easily formed in the adhesive porous layer, and the permeability of the electrolyte and ion permeability in the adhesive porous layer are excellent. From this viewpoint, the average primary particle size of the inorganic particles is more preferably 0.05 μm or more, and even more preferably 0.1 μm or more. When the average primary particle size of the inorganic particles is 2 μm or less, the adhesive porous layer adheres easily to the electrode and is less likely to peel off from the electrode. From this viewpoint, the average primary particle size of the inorganic particles is more preferably 1 μm or less, and even more preferably 0.5 μm or less.

[0097] The average primary particle size of inorganic particles is determined by measuring the major axis of 100 randomly selected inorganic particles observed using a scanning electron microscope (SEM) and averaging the major axes of these 100 particles. The sample used for SEM observation is inorganic particles that form the adhesive porous layer, or inorganic particles extracted from the adhesive porous layer. There are no restrictions on the method of extracting inorganic particles from the adhesive porous layer. For example, such methods include immersing the adhesive porous layer peeled from the separator in an organic solvent that dissolves the binder resin to extract the inorganic particles; or heating the adhesive porous layer peeled from the separator to about 800°C to remove the binder resin and extract the inorganic particles.

[0098] From the viewpoint of achieving a good balance between the permeability of the separator and the adhesion to the electrode, the mass ratio of inorganic particles to the total mass of the adhesive porous layer is preferably 40% to 95% by mass, more preferably 45% to 90% by mass, and even more preferably 50% to 85% by mass.

[0099] From the viewpoint of achieving a good balance between the permeability of the separator and adhesion to the electrode, the volume ratio of inorganic particles to the solid content volume of the adhesive porous layer is preferably 10% to 90% by volume, more preferably 15% to 80% by volume, and even more preferably 20% to 70% by volume.

[0100] When adhesive porous layers are present on both sides of a porous substrate, the type and / or content of inorganic particles contained in one adhesive porous layer may be the same as or different from the type and / or content of inorganic particles contained in the other adhesive porous layer.

[0101] -Organic Particles- The adhesive porous layer may contain organic particles. Examples of organic particles include particles made of crosslinked polymers such as crosslinked poly(meth)acrylic acid, crosslinked poly(meth)acrylic acid ester, crosslinked polysilicone, crosslinked polystyrene, crosslinked polydivinylbenzene, styrene-divinylbenzene copolymer crosslinked product, melamine resin, phenolic resin, and benzoguanamine-formaldehyde condensate; and particles made of heat-resistant polymers such as polysulfone, polyacrylonitrile, aramid, and polyacetal. The resin constituting the organic particles may be a mixture, modified form, derivative, copolymer (random copolymer, alternating copolymer, block copolymer, graft copolymer) or crosslinked form of the above example materials.

[0102] Organic particles may be used individually or in combination of two or more types.

[0103] -Surfactant- As an example of an embodiment of the adhesive porous layer, an adhesive porous layer containing a surfactant is provided. According to this embodiment, a separator is provided that has excellent affinity between the porous substrate and the adhesive porous layer, and excellent cycle characteristics. The adhesive porous layer contains a polyvinyl chloride resin from the viewpoint of adhesion to the electrode, and by further containing a surfactant, the affinity to the porous substrate (particularly a porous substrate containing polyolefin) is improved. As a result, the porous substrate and the adhesive porous layer are less likely to delaminate. Therefore, by containing a polyvinyl chloride resin and a surfactant, the adhesive porous layer has good adhesion to both the electrode and the porous substrate. According to this embodiment, as a result of the separator being less likely to delaminate, a battery that is less prone to internal short circuits is provided. Furthermore, it is presumed that the adhesive porous layer containing a surfactant improves the cycle characteristics of the battery by acting on the properties of the interface where the porous substrate (particularly a porous substrate containing polyolefin) and the adhesive porous layer come into contact, and by acting on ion movement in the adhesive porous layer.

[0104] The surfactant may be a nonionic surfactant, anionic surfactant, cationic surfactant, or amphoteric surfactant. The surfactant may be used individually or in combination of two or more types.

[0105] Examples of nonionic surfactants include ether-based surfactants (e.g., polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene polyoxypropylene glycol), ester-based surfactants (e.g., glycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester), ester ether-based surfactants (e.g., fatty acid polyethylene glycol, fatty acid polyoxyethylene sorbitan), and alkanolamide-based surfactants (e.g., fatty acid alkanolamide). Examples of anionic surfactants include carboxylic acid-based surfactants (e.g., aliphatic monocarboxylates, polyoxyethylene alkyl ether carboxylates, N-acyl sarcosine salts, N-acyl glutamate salts), sulfonic acid-based surfactants (e.g., alkylbenzene sulfonates, alkylnaphthalene sulfonates, dialkyl sulfosuccinates, alkanesulfonates), sulfate-based surfactants (e.g., alkyl sulfates, polyoxyethylene alkyl ether sulfates), and phosphate-based surfactants (e.g., alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkylphenyl ether phosphates). Examples of cationic surfactants include alkylamine salt surfactants (e.g., monoalkylamine salts, dialkylamine salts, trialkylamine salts) and quaternary ammonium salt surfactants (e.g., alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, alkylbenzalkonium chloride). Examples of amphoteric surfactants include carboxybetaine surfactants (e.g., alkylbetaine, fatty acid amidopropyl betaine), glycine surfactants (e.g., alkyldiethylenetriaminoacetic acid), and amine oxide surfactants (e.g., alkylamine oxide).

[0106] As the surfactant, at least one selected from the group consisting of nonionic surfactants and anionic surfactants is preferred. Although the detailed mechanism is unknown, the adhesive porous layer containing nonionic and anionic surfactants improves the battery's cycle characteristics.

[0107] As a surfactant, a nonionic surfactant is preferred from the viewpoint of having excellent dispersibility of polyvinyl chloride resins and forming a good porous structure in the adhesive porous layer. When a nonionic surfactant is used, it is easy to control the value obtained by subtracting the air permeability of the porous substrate from the air permeability of the separator to 500 seconds / 100 mL or less.

[0108] The mass ratio of surfactant to the total mass of the adhesive porous layer is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, even more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more, from the viewpoint of increasing the affinity between the porous substrate and the adhesive porous layer and improving the battery cycle characteristics. The mass ratio of surfactant to the total mass of the adhesive porous layer is preferably 15% by mass or less, more preferably 12% by mass or less, even more preferably 10% by mass or less, even more preferably 8% by mass or less, even more preferably 5% by mass or less, and even more preferably 3% by mass or less, from the viewpoint of not having an unexpected effect on battery performance.

[0109] When adhesive porous layers are present on both sides of a porous substrate, the type and / or content of surfactant contained in one adhesive porous layer may be the same as or different from the type and / or content of surfactant contained in the other adhesive porous layer.

[0110] -Other Components- The adhesive porous layer may contain additives such as dispersants, thickeners, wetting agents, defoamers, and pH adjusters. Dispersants, thickeners, wetting agents, defoamers, and pH adjusters are added, for example, to the coating solution for forming the adhesive porous layer for the purpose of improving the dispersion stability of filler particles, improving film formation, improving compatibility with the porous substrate, suppressing air entrapment in the coating solution, or adjusting the pH.

[0111] - Characteristics of the Adhesive Porous Layer - The mass per unit area of ​​the adhesive porous layer is 0.6 g / m² in total for both sides of the porous substrate, from the viewpoint of adhesion to the electrode, thermal dimensional stability of the separator, and ion permeability of the layer. ２ ~6.0 g / m ２Preferably, it is 0.8 g / m ２ ~4.0 g / m ２ More preferably, 1.0 g / m ２ ~3.0 g / m ２ This is even more preferable. The mass per unit area of ​​the adhesive porous layer is determined by cutting the separator into a 20 cm x 20 cm piece, peeling off the adhesive porous layer and measuring its mass, and then dividing the mass by the area.

[0112] [Separator Characteristics] From the viewpoint of mechanical strength, the thickness of the separator is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 9 μm or more. From the viewpoint of the energy density of the battery, the thickness of the separator is preferably 20 μm or less, more preferably 18 μm or less, and even more preferably 17 μm or less. The thickness of the separator is determined by measuring 20 points within a 10 cm square area using a contact-type thickness gauge and averaging the results.

[0113] From the viewpoint of suppressing internal short circuits in the battery, the air permeability of the separator is preferably 100 seconds / 100 mL or more, more preferably 120 seconds / 100 mL or more, and even more preferably 150 seconds / 100 mL or more. From the viewpoint of ion permeability, the air permeability of the separator is preferably 400 seconds / 100 mL or less, more preferably 350 seconds / 100 mL or less, and even more preferably 300 seconds / 100 mL or less. The air permeability of the separator is measured and determined using a digital Ouken-type air permeability tester in accordance with JIS P8117:2009.

[0114] From the viewpoint of suppressing internal short circuits in the battery, the value obtained by subtracting the air permeability of the porous substrate from the air permeability of the separator is preferably 0 seconds / 100 mL or more, more preferably 5 seconds / 100 mL or more, and even more preferably 10 seconds / 100 mL or more. From the viewpoint of ion permeability, the value obtained by subtracting the air permeability of the porous substrate from the air permeability of the separator is preferably 200 seconds / 100 mL or less, more preferably 150 seconds / 100 mL or less, and even more preferably 120 seconds / 100 mL or less.

[0115] From the viewpoint of ion permeability, the porosity of the separator is preferably 30% to 60%. The porosity ε (%) of the separator is calculated using the following formula.

[0116] Here, for the separator's constituent material 1, constituent material 2, constituent material 3, ..., constituent material n, the mass per unit area of ​​each constituent material is W. １ , W ２、 W ３ ..., W ｎ (g / cm ２ ) and the true density of each constituent material is d １ d ２ d ３ , ..., d ｎ (g / cm ３ ) and the thickness of the separator is t (cm).

[0117] When the separator is heat-treated at 105°C for 60 minutes, the thermal shrinkage rate of MD and TD is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0118] When the separator is heat-treated at 130°C for 60 minutes, the thermal shrinkage rate of MD and TD is preferably 10% or less, more preferably 9% or less, and even more preferably 8% or less.

[0119] The thermal shrinkage rate of the separator is measured by the following method. Cut the separator into a rectangle with dimensions TD 60 mm x MD 180 mm to make a test specimen. Mark the specimen at points 20 mm and 170 mm from one end on the line that bisects TD (referred to as points A and B, respectively). Furthermore, mark the specimen at points 10 mm and 50 mm from one end on the line that bisects MD (referred to as points C and D, respectively). Attach a clip to the specimen (the clip should be placed between the end closest to point A and point A), and suspend it in an oven at a temperature of 105°C or 130°C for 60 minutes under no tension to perform heat treatment. Measure the lengths between A and B and between C and D before and after heat treatment, and calculate the thermal shrinkage rate using the following formula.

[0120] Thermal shrinkage rate of MD (%) = {(Length of AB before heat treatment - Length of AB after heat treatment) ÷ Length of AB before heat treatment} × 100 Thermal shrinkage rate of TD (%) = {(Length of CD before heat treatment - Length of CD after heat treatment) ÷ Length of CD before heat treatment} × 100

[0121] [Method for Manufacturing Separators] The separators of this disclosure can be manufactured, for example, by forming an adhesive porous layer on a porous substrate using a wet coating method or a dry coating method. In this disclosure, a wet coating method is a method of solidifying the coating layer in a solidifying liquid, and a dry coating method is a method of solidifying the coating layer by drying. A dry coating method is preferred for manufacturing the separators of this disclosure, and specifically, the following manufacturing method is preferred.

[0122] A method for manufacturing a separator, comprising the steps of: applying a coating liquid containing water, polyvinyl chloride resin particles, and filler particles to one or both sides of a porous substrate to form a coating layer; and drying the coating layer on the porous substrate and melting the polyvinyl chloride resin particles to form an adhesive porous layer.

[0123] The above manufacturing method will be described in detail below.

[0124] The coating solution is prepared by dispersing polyvinyl chloride resin particles and filler particles in water. If necessary, other components besides polyvinyl chloride resin particles and filler particles may be dissolved or dispersed in the coating solution. Examples of other components include resins having carbonyl groups and surfactants. The resins having carbonyl groups are preferably in the form of resin particles.

[0125] The concentration of polyvinyl chloride resin particles in the coating solution is preferably 1% to 20% by mass, from the viewpoint of coating properties and productivity of the adhesive porous layer. When inorganic particles are used as filler particles, the concentration of inorganic particles in the coating solution is preferably 0.5% to 50% by mass, from the viewpoint of forming a good porous structure in the adhesive porous layer.

[0126] The coating solution may contain dispersants, thickeners, wetting agents, defoamers, pH adjusters, etc. These additives may remain in the adhesive porous layer as long as they are electrochemically stable within the operating range of non-aqueous secondary batteries and do not inhibit reactions within the battery.

[0127] When the coating solution contains a resin having a carbonyl group and / or a surfactant, it exhibits good wettability to porous substrates (especially porous substrates containing polyolefins). In this case, the porous substrate may be one which has not undergone any hydrophilization treatment on its surface (e.g., corona treatment, plasma treatment, flame treatment, ultraviolet irradiation treatment, etc.).

[0128] Methods for applying coating liquid to porous substrates include Meyer bar, die coater, reverse roll coater, roll coater, and gravure coater. When forming an adhesive porous layer on both sides of a porous substrate, it is preferable from a productivity standpoint to apply the coating liquid to both sides of the porous substrate simultaneously.

[0129] The coating layer solidifies by drying (i.e., removing water) the coating layer. Drying is performed, for example, by transporting the porous substrate with the coating layer in a high-temperature environment, by blowing air onto the porous substrate with the coating layer, or by bringing the porous substrate with the coating layer into contact with a heat roll. The drying temperature is set to the temperature at which the polyvinyl chloride resin particles melt. When transporting the porous substrate with the coating layer in a high-temperature environment, the ambient temperature is preferably at or above the glass transition temperature of the polyvinyl chloride resin particles + 20°C in order to melt the polyvinyl chloride resin particles.

[0130] The separator of this disclosure can also be manufactured by preparing an adhesive porous layer as an independent sheet, and then layering this adhesive porous layer on a porous substrate and compounding it by heat bonding or adhesive. One method for preparing the adhesive porous layer as an independent sheet is to apply the above manufacturing method to form the adhesive porous layer on a release sheet.

[0131] <Non-aqueous secondary battery> The non-aqueous secondary battery of this disclosure is a non-aqueous secondary battery that obtains electromotive force by doping and dedoping of lithium ions, and comprises a positive electrode, a negative electrode, and a separator of this disclosure. Doping means absorption, support, adsorption, or insertion, and refers to the phenomenon in which lithium ions enter the active material of the electrode.

[0132] 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.

[0133] The non-aqueous secondary battery of this disclosure has good battery characteristics (e.g., cycle characteristics, rate characteristics) because the separator of this disclosure is permeable (and therefore ion permeable). The non-aqueous secondary battery of this disclosure has adhesive properties to the electrodes, so the electrodes and separator are less likely to detach and internal short circuits are less likely to occur.

[0134] 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.

[0135] 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 arranged 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, for example, LiCoO ２ LiNiO ２ LiMn １／２ Ni １／２ O ２ LiCo １／３ Mn １／３ Ni １／３ O ２ LiMn ２ O ４ LiFePO ４ LiCo １／２ Ni １／２ O ２ LiAl １／４ Ni ３／４ O ２ Examples 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] 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 arranged 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 ions, 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, graphite powder, and ultrafine carbon fibers. 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.

[0137] The electrolyte is preferably a solution of lithium salt dissolved in a non-aqueous solvent. Examples of lithium salts include LiPF4. ６ LiBF ４ LiClO ４ 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. As the electrolyte, a solution is preferred in which a cyclic carbonate and a linear carbonate are mixed in a mass ratio (cyclic carbonate:linear carbonate) of 20:80 to 40:60, and a lithium salt is dissolved in it at a concentration of 0.5 mol / L to 1.5 mol / L.

[0138] Examples of exterior materials include aluminum laminate film packs and metal cans. While batteries come in various shapes such as rectangular, cylindrical, and coin-shaped, the separator of this disclosure is suitable for any of these shapes.

[0139] The non-aqueous secondary battery of this disclosure can be manufactured by first creating a laminate in which the separator of this disclosure is placed between the positive electrode and the negative electrode, and then using this laminate by, for example, any of the following manufacturing methods (1) to (3).

[0140] Manufacturing method (1): After temporarily bonding the electrodes and separators by dry heat pressing the laminated material, it is placed in an outer packaging material (for example, an aluminum laminate film pack; the same applies hereinafter) and an electrolyte solution is injected into it. Next, the laminated material is wet heat pressed over the outer packaging material to bond the electrodes and separators and seal the outer packaging material.

[0141] Manufacturing method (2): The laminate is placed in an outer material and an electrolyte is injected into it. Next, the laminate is wet-heat-pressed from above the outer material to bond the electrodes to the separator and seal the outer material.

[0142] Manufacturing method (3): After the laminate is dry heat pressed to bond the electrodes and separator, it is placed in an outer casing and the electrolyte is injected therein. Next, the outer casing is sealed.

[0143] In manufacturing method (1) or manufacturing method (2), the press temperature of the wet heat press is preferably 50°C to 90°C, and more preferably 60°C to 80°C. The press pressure of the wet heat press is preferably 0.1 MPa to 2 MPa, and more preferably 0.5 MPa to 1.5 MPa. The press time of the wet heat press is preferably adjusted according to the press temperature and press pressure, for example, in the range of 1 minute to 12 hours.

[0144] In manufacturing method (1) or manufacturing method (3), the press temperature of the dry heat press is preferably 60°C to 90°C, and more preferably 70°C to 85°C. The press pressure of the dry heat press is preferably 0.5 MPa to 5 MPa, and more preferably 0.5 MPa to 3 MPa. The press time of the dry heat press is preferably adjusted according to the press temperature and press pressure, for example, in the range of 0.5 minutes to 1 hour.

[0145] When manufacturing a laminate with a separator placed between the positive electrode and the negative electrode, the method of placing the separator between the positive electrode and the negative electrode may be a method in which the positive electrode, separator, and negative electrode are stacked in that order in at least one layer each (the so-called stack method), or a method in which the positive electrode, separator, negative electrode, and separator are stacked in that order and wound in the length direction.

[0146] The separator and non-aqueous secondary battery of this disclosure will be described in more detail below with reference to examples. The materials, amounts used, proportions, processing procedures, etc., shown in the following examples can be modified as appropriate without departing from the spirit of this disclosure. Therefore, the scope of the separator and non-aqueous secondary battery of this disclosure should not be interpreted as being limited by the specific examples shown below.

[0147] In the following descriptions, synthesis, processing, and manufacturing were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0148] <Measurement Methods and Evaluation Methods> The measurement and evaluation methods applied to the examples and comparative examples are as follows.

[0149] [Thickness of Porous Substrate and Separator] The thickness of the porous substrate and separator was determined by measuring 20 arbitrary points within a 10 cm square area using a contact-type thickness gauge (Mitutoyo Corporation, LITEMATIC VL-50) and averaging the results. A cylindrical measuring terminal with a radius of 5 mm (Mitutoyo Corporation) was used, and a load of 0.01 N was applied during measurement.

[0150] [Thickness of the Adhesive Porous Layer] The thickness of the adhesive porous layer was determined by subtracting the thickness of the porous substrate from the thickness of the separator. This thickness is the total value for both sides of the porous substrate.

[0151] [Air permeability of porous substrate and separator] The air permeability (seconds / 100 mL) of the porous substrate and separator was measured in accordance with JIS P8117:2009 using a digital Ogane-type air permeability tester (Asahi Seiko Co., Ltd., model EG01). The difference in air permeability was calculated by subtracting the air permeability of the porous substrate from the air permeability of the separator.

[0152] [Average Primary Particle Size of Filler Particles] Filler particles used to form an adhesive porous layer were observed using a scanning electron microscope (SEM) to determine the average primary particle size. The major axis of 100 randomly selected filler particles on the SEM image was measured, and the average of the major axes of these 100 particles was taken as the average primary particle size (μm).

[0153] [Average Primary Particle Size of Resin Particles] The average primary particle size of resin particles was determined by observing the dried resin particle dispersion used for forming the adhesive porous layer using SEM. The major axis of 100 randomly selected resin particles on the SEM image was measured, and the average of the major axes of these 100 particles was defined as the average primary particle size (nm).

[0154] [Glass Transition Temperature of Resin Particles] Differential scanning calorimetry (DSC) was performed on a dry sample of a resin particle dispersion used to form an adhesive porous layer. A Q200 Differential Scanning Calorimeter (TA Instruments) was used as the DSC instrument, and the sample weight was 5 mg. The temperature was raised from -65°C to 150°C at a heating rate of 10°C / min, then quenched and reheated at the same heating rate to obtain a DSC curve. In the obtained DSC curve, the intersection point (1) between the low-temperature baseline and the tangent to the curve of the stepwise transition portion, and the intersection point (2) between the high-temperature baseline and the tangent to the curve of the stepwise transition portion were determined, and the temperature midway between intersection point (1) and intersection point (2) was defined as the glass transition temperature (Tg, °C).

[0155] [Amount of resin coating] Design coating amount (mass per unit area, g / m²) ２ )

[0156] [Adhesion to the electrode] 89.5 parts by mass of lithium cobalt oxide powder, which is the positive electrode active material, 4.5 parts by mass of acetylene black, which is a conductive additive, 6 parts by mass of polyvinylidene fluoride, which is a binder resin, and an appropriate amount of N-methyl-2-pyrrolidone were stirred and mixed in a double-arm mixer to prepare a slurry for the positive electrode. The slurry for the positive electrode was applied to one side of a 20 μm thick aluminum foil, dried, and then pressed to obtain a positive electrode having a positive electrode active material layer on one side.

[0157] A slurry for the negative electrode was prepared by mixing 300 parts by mass of artificial graphite, which is the negative electrode active material, 7.5 parts by mass of a water-soluble dispersion containing 40% by mass of a modified styrene-butadiene copolymer, which is the binder resin, 3 parts by mass of carboxymethylcellulose, which is the thickener, and an appropriate amount of water using a double-arm mixer. The slurry for the negative electrode was applied to one side of a 10 μm thick copper foil, dried, and then pressed to obtain a negative electrode having a negative electrode active material layer on one side.

[0158] The electrodes (positive and negative) were cut into rectangles measuring 15 mm wide x 70 mm long. The separator was cut into a rectangle measuring TD 18 mm x MD 74 mm. Release paper measuring 15 mm wide x 70 mm long was prepared. The separator was placed on top of the active material layer of the electrode (positive or negative), and then the release paper was placed on top of the separator to create a laminate.

[0159] The laminate was inserted into an aluminum laminate film pack, and the pack was heat-pressed in the direction of the laminate using a heat press (dry heat press) to bond the electrode (positive or negative electrode) to the separator. The heat-pressing conditions were a temperature of 75°C, a pressure of 1 MPa, and a time of 0.5 minutes. After heat-pressing, the laminate was removed from the pack, the release paper was peeled off, and a test specimen for dry adhesion was obtained. In Examples 21 to 23, the heat-pressing conditions were a temperature of 85°C, a pressure of 1 MPa, and a time of 0.5 minutes.

[0160] The laminate is inserted into an aluminum laminate film pack, and the electrolyte (1 mol / L LiBF) is added. ４ The electrolyte was impregnated into the laminate by injecting an electrolyte mixture of ethylene carbonate, propylene carbonate, and diethyl carbonate (mass ratio 1:1:1). Next, the laminate, still in its pack, was heat-pressed in the direction of the laminate using a heat press (wet heat press) to bond the electrodes (positive or negative electrode) to the separator. The heat-pressing conditions were a temperature of 70°C, a pressure of 1 MPa, and a time of 5 minutes. After heat-pressing, the laminate was removed from the pack, the release paper was peeled off, and a test specimen for wet adhesion was obtained.

[0161] The uncoated surface of the electrode of the test specimen was fixed to a metal plate with double-sided tape, and the metal plate was fixed to the lower chuck of a Tensilon (A&D Corporation, STB-1225S). At this time, the metal plate was fixed to the Tensilon so that the length direction of the test specimen (i.e., the MD of the separator) was in the direction of gravity. The separator was peeled off the electrode by about 2 cm from the lower end, and that end was fixed to the upper chuck, and a 180° peel test was performed. The tensile speed of the 180° peel test was set to 100 mm / min, and the load (N) from 10 mm to 30 mm after the start of measurement was taken at 0.4 mm intervals, and the average was calculated. Furthermore, the loads of 10 test specimens were averaged to determine the adhesive strength (N / 15 mm) between the electrode (positive or negative electrode) and the separator.

[0162] [Heat Shrinkage Rate of Separator] A rectangle of separator with dimensions TD 60 mm x MD 180 mm was cut out to form a test specimen. Marks were made on the test specimen at points 20 mm and 170 mm from one end, along the line that bisects TD (referred to as points A and B, respectively). Furthermore, marks were made at points 10 mm and 50 mm from one end, along the line that bisects MD (referred to as points C and D, respectively). A clip was attached to the test specimen (the clip was attached between the end closest to point A and point A), and the specimen was suspended in an oven at 105°C and heat-treated for 60 minutes under no tension. The lengths between A and B and between C and D were measured before and after the heat treatment, and the heat shrinkage rate was calculated using the following formula. The heat shrinkage rates of the three test specimens were then averaged.

[0163] Thermal shrinkage rate of MD (%) = {(Length of AB before heat treatment - Length of AB after heat treatment) ÷ Length of AB before heat treatment} × 100 Thermal shrinkage rate of TD (%) = {(Length of CD before heat treatment - Length of CD after heat treatment) ÷ Length of CD before heat treatment} × 100

[0164] [Affinity between porous substrate and adhesive porous layer] The affinity between the porous substrate and the adhesive porous layer was determined by the affinity of the coating solution to the porous substrate. Specifically, the coating solution was applied to both sides of the porous substrate using a pair of Meyer bars, and after 5 seconds, the spread of the coating solution was visually observed and determined as follows: G: The coating solution has spread over the entire surface of the porous substrate, and the surface of the porous substrate is not visible. NG: There are areas where the coating solution has not spread and the surface of the porous substrate is visible.

[0165] [Battery Cycle Characteristics (Capacity Retention Rate)] Ten non-aqueous secondary batteries, as described below, were prepared. The batteries underwent 300 charge-discharge cycles in an environment of 25°C. Charging was performed using constant current constant voltage charging at 3C / 4.2V, and discharging was performed using constant current discharge with a cutoff of 3C / 2.50V. The capacity retention rate (%) was calculated by dividing the discharge capacity at the 300th cycle by the initial discharge capacity. Furthermore, the average capacity retention rate (%) was calculated from the ten batteries, and the average values ​​were classified as follows: G1: Over 48% G2: 30% to 48% G3: Less than 30%

[0166] <Manufacturing of Separators and Batteries> [Example 1] -Separator Preparation- A resin particle dispersion (1) was prepared in which polyvinyl chloride resin particles were dispersed in water. A coating solution (1) was prepared by adding magnesium hydroxide particles, sodium hexametaphosphate, and ethanol to the resin particle dispersion (1). The coating solution (1) had a concentration of 4% by mass of polyvinyl chloride resin particles, a concentration of 0.03% by mass of sodium hexametaphosphate, and a concentration of 48% by mass of ethanol, with a mass ratio of magnesium hydroxide particles to polyvinyl chloride resin particles of 50:50.

[0167] Using a pair of Meyer bars, an equal amount of coating solution (1) was applied to both sides of the polyethylene microporous membrane, and the membrane was dried by transporting it in an atmosphere at a temperature of 60°C. In this way, a separator with an adhesive porous layer on both sides of the polyethylene microporous membrane was obtained.

[0168] Figure 1 shows an SEM image (magnification 10,000) of the surface of the adhesive porous layer of Example 1. The adhesive porous layer of Example 1 had a porous structure in which filler particles were linked by a polyvinyl chloride resin and the filler particles were stacked. The polyvinyl chloride resin did not maintain its particle shape.

[0169] - Preparation of the positive electrode - 89.5 parts by mass of lithium cobalt oxide powder, which is the positive electrode active material, 4.5 parts by mass of acetylene black, which is a conductive additive, 6 parts by mass of polyvinylidene fluoride, which is a binder resin, and an appropriate amount of N-methyl-2-pyrrolidone were stirred and mixed in a double-arm mixer to prepare a slurry for the positive electrode. The slurry for the positive electrode was applied to both sides of a 20 μm thick aluminum foil, dried, and then pressed to obtain a positive electrode having positive electrode active material layers on both sides.

[0170] - Preparation of the negative electrode - 300 parts by mass of artificial graphite, which is the negative electrode active material, 7.5 parts by mass of a water-soluble dispersion containing 40% by mass of a modified styrene-butadiene copolymer, which is the binder resin, 3 parts by mass of carboxymethylcellulose, which is the thickener, and an appropriate amount of water were mixed in a double-arm mixer to prepare a negative electrode slurry. The negative electrode slurry was applied to both sides of a 10 μm thick copper foil, dried, and then pressed to obtain a negative electrode having negative electrode active material layers on both sides.

[0171] -Battery Construction- The positive and negative electrodes were cut into 30mm x 50mm rectangles, and lead tabs were welded to each. The separator was cut into a TD35mm x MD55mm rectangle. These were stacked so that the positive and negative electrodes were alternated and a separator was sandwiched between them, creating a laminate consisting of 3 positive electrodes, 3 negative electrodes, and 5 separators. The laminate was inserted into an aluminum laminate film pack, and electrolyte (1 mol / L LiPF) was placed inside the pack. ６ - An electrolyte solution (ethylene carbonate:ethyl methyl carbonate [mass ratio 3:7]) was injected to impregnate the laminate. Next, the entire pack was heat-pressed in the direction of the laminate using a hot press (wet heat press) to bond the electrodes to the separator. The heat-pressing conditions were a press temperature of 70°C, a press pressure of 1 MPa, and a press time of 5 minutes. In this way, a non-aqueous secondary battery was obtained.

[0172] [Examples 2-4] Separators were prepared in the same manner as in Example 1, except that the amount of polyvinyl chloride resin coating was changed as shown in Table 1. Using each separator, a non-aqueous secondary battery was prepared in the same manner as in Example 1.

[0173] SEM observation of the surface of the adhesive porous layers revealed that the adhesive porous layers of Examples 2 to 4 each had a porous structure in which filler particles were linked by a polyvinyl chloride resin and the filler particles were stacked. The polyvinyl chloride resin did not maintain its particle shape.

[0174] [Comparative Example 1] A separator was prepared in the same manner as in Example 1, except that magnesium hydroxide particles were not used and the amount of polyvinyl chloride resin coating was changed as shown in Table 1.

[0175] SEM observation of the surface of the adhesive porous layer revealed that the adhesive porous layer of Comparative Example 1 was a dense coating in which the polyvinyl chloride resin did not maintain its particle shape.

[0176] Table 1 shows the composition of the porous substrates and adhesive porous layers of Examples 1-4 and Comparative Example 1, and Table 2 shows the physical properties and evaluation results of the separators of Examples 1-4 and Comparative Example 1. The amount of polyvinyl chloride resin coating listed in Table 1 is the total for both sides of the porous substrate. The thickness of the adhesive porous layer listed in Table 1 is the total for both sides of the porous substrate. The abbreviations in Table 1 have the following meanings: ・PE: Polyethylene

[0177]

[0178]

[0179] [Example 11] - Preparation of Separator - A resin particle dispersion (11) was prepared in which resin particles having a core-shell structure consisting of a polyvinyl chloride resin core and a urethane resin shell were dispersed in water. A coating solution (11) was prepared by adding magnesium hydroxide particles, sodium hexametaphosphate, and ethanol to the resin particle dispersion (11). The coating solution (11) had a resin particle concentration of 4% by mass, a sodium hexametaphosphate concentration of 0.03% by mass, and an ethanol concentration of 48% by mass, with a mass ratio of magnesium hydroxide particles to resin particles of 50:50.

[0180] Using a pair of Meyer burs, an equal amount of coating solution (11) was applied to both sides of the polyethylene microporous membrane, and the membrane was dried by transporting it in an atmosphere at a temperature capable of melting the resin particles. In this way, a separator with adhesive porous layers on both sides of the polyethylene microporous membrane was obtained. Using this separator, a non-aqueous secondary battery was fabricated in the same manner as in Example 1.

[0181] SEM observation of the surface of the adhesive porous layer revealed that it had a porous structure in which inorganic particles were linked together by resin. The resin did not maintain the particle shape.

[0182] [Examples 12-14] Separators were prepared in the same manner as in Example 11, except that the amount of resin coating was changed as shown in Table 3. Using each separator, a non-aqueous secondary battery was prepared in the same manner as in Example 1.

[0183] SEM observation of the surface of the adhesive porous layers revealed that the adhesive porous layers of Examples 12-14 each had a porous structure in which inorganic particles were linked by resin. The resin did not maintain the particle shape.

[0184] [Example 15] A separator was prepared in the same manner as in Example 11, except that the resin particles were changed to resin particles with a core-shell structure consisting of a polyvinyl chloride resin core and an acrylic resin shell. Using this separator, a non-aqueous secondary battery was prepared in the same manner as in Example 1.

[0185] SEM observation of the surface of the adhesive porous layer revealed a porous structure in which inorganic particles were linked by resin. The resin did not maintain the particle shape.

[0186] [Comparative Example 11] A coating solution was prepared in the same manner as in Example 11, except that the resin particles made of polyvinyl chloride resin and urethane resin were replaced with polyvinyl chloride resin particles, and magnesium hydroxide particles were not used. An attempt was made to coat an adhesive porous layer using this coating solution, but coating was not possible, and therefore a separator could not be manufactured.

[0187] Table 3 shows the composition of the porous substrates and adhesive porous layers of Examples 11-15 and Comparative Example 11, and Table 4 shows the physical properties and evaluation results of the separators of Examples 11-15 and Comparative Example 11. The amount of polyvinyl chloride resin coating listed in Table 3 is the total for both sides of the porous substrate. The thickness of the adhesive porous layer listed in Table 3 is the total for both sides of the porous substrate.

[0188] The abbreviations in Table 3 have the following meanings: • PE: Polyethylene • PVC: Polyvinyl chloride • PU: Urethane resin • AR: Acrylic resin

[0189]

[0190]

[0191] [Example 21] - Separator Production - A resin particle dispersion (21) was prepared in which resin particles having a core-shell structure consisting of a polyvinyl chloride resin core and a urethane resin shell were dispersed in water. A coating solution (21) was prepared by adding magnesium hydroxide particles and polyoxyethylene lauryl ether, a nonionic surfactant, to the resin particle dispersion (21). The composition of the coating solution (21) is as follows: - Resin concentration: 10% by mass - Mass ratio of resin to inorganic particles: resin:inorganic particles = 40:60 - Nonionic surfactant concentration: 3% by mass relative to the amount of resin

[0192] An equal amount of coating solution (21) was applied to both sides of the polyethylene microporous membrane using a pair of Meyer burs, and the membrane was dried by transporting it in an atmosphere at a temperature capable of melting the resin particles. In this way, a separator with adhesive porous layers on both sides of the polyethylene microporous membrane was obtained. Using this separator, a non-aqueous secondary battery was manufactured in the same manner as in Example 1.

[0193] SEM observation of the surface of the adhesive porous layer revealed that the adhesive porous layer had a porous structure in which inorganic particles were linked by resin, and the resin did not maintain the particle shape.

[0194] [Example 22] A separator was manufactured in the same manner as in Example 21, except that the nonionic surfactant was replaced with a polyoxyethylene alkyl ether and the resin concentration was changed to 12% by mass. When the surface of the adhesive porous layer was observed with an SEM, it was found that the adhesive porous layer was a porous structure in which inorganic particles were linked by the resin, and the resin did not maintain its particle shape. Using this separator, a non-aqueous secondary battery was manufactured in the same manner as in Example 1.

[0195] [Example 23] A separator was manufactured in the same manner as in Example 21, except that the surfactant was changed to sodium dodecylbenzenesulfonate, an anionic surfactant. When the surface of the adhesive porous layer was observed with an SEM, it was found that the adhesive porous layer had a porous structure in which inorganic particles were linked by resin, and the resin did not maintain its particle shape. Using this separator, a non-aqueous secondary battery was manufactured in the same manner as in Example 1.

[0196] Table 5 shows the composition of the porous substrates and adhesive porous layers of Examples 21 to 23, and Table 6 shows the physical properties and evaluation results of the separators of Examples 21 to 23. The coating amounts listed in Table 5 are the total for both sides of the porous substrate. The thickness of the adhesive porous layer listed in Table 5 is the total for both sides of the porous substrate.

[0197] The abbreviations in Table 5 have the following meanings: • PE: Polyethylene • PVC: Polyvinyl chloride • PU: Urethane resin

[0198]

[0199]

[0200] All documents, patent applications, and technical standards described herein are incorporated by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

[0201] The disclosure of Japanese application number 2024-201827, filed on November 19, 2024, is incorporated herein by reference in its entirety. The disclosure of Japanese application number 2024-201829, filed on November 19, 2024, is incorporated herein by reference in its entirety. The disclosure of Japanese application number 2024-201830, filed on November 19, 2024, is incorporated herein by reference in its entirety. The disclosure of Japanese application number 2025-019507, filed on February 7, 2025, is incorporated herein by reference in its entirety.

Claims

1. A separator for a non-aqueous secondary battery, comprising: a porous substrate; and an adhesive porous layer disposed on one or both sides of the porous substrate, the adhesive porous layer having a porous structure in which the filler particles are linked and stacked by the polyvinyl chloride resin.

2. The separator for a non-aqueous secondary battery according to claim 1, wherein the glass transition temperature of the polyvinyl chloride resin contained in the adhesive porous layer is 40°C or lower.

3. The mass per unit area of ​​the polyvinyl chloride resin contained in the adhesive porous layer is 0.1 g / m² in total for both sides of the porous substrate. ２ ~5.0 g / m ２ The separator for a non-aqueous secondary battery according to claim 1.

4. The separator for a non-aqueous secondary battery according to claim 1, wherein the average primary particle size of the filler particles contained in the adhesive porous layer is 0.01 μm to 2 μm.

5. The separator for a non-aqueous secondary battery according to claim 1, wherein the value obtained by subtracting the air permeability of the porous substrate from the air permeability of the separator for a non-aqueous secondary battery is 0 seconds / 100 mL to 200 seconds / 100 mL.

6. The separator for a non-aqueous secondary battery according to claim 1, wherein the thermal shrinkage rate when the separator for a non-aqueous secondary battery is heat-treated at a temperature of 105°C for 60 minutes is 5% or less for both MD and TD.

7. The separator for a non-aqueous secondary battery according to claim 1, wherein the adhesive porous layer further contains a resin having carbonyl groups.

8. The separator for a non-aqueous secondary battery according to claim 7, wherein the resin having a carbonyl group comprises at least one selected from the group consisting of urethane resin, acrylic resin, polyamide, polyimide, polyester, polycarbonate, and polyvinyl acetate.

9. The separator for a non-aqueous secondary battery according to claim 7, wherein the proportion of the polyvinyl chloride resin to the total amount of the polyvinyl chloride resin and the resin having a carbonyl group is 20% by mass to 80% by mass.

10. The separator for a non-aqueous secondary battery according to claim 1, wherein the thermal shrinkage rate when the separator for a non-aqueous secondary battery is heat-treated at a temperature of 130°C for 60 minutes is 10% or less for both MD and TD.

11. The separator for a non-aqueous secondary battery according to claim 1, wherein the adhesive porous layer further contains a surfactant.

12. The separator for a non-aqueous secondary battery according to claim 11, wherein the surfactant comprises at least one selected from the group consisting of nonionic surfactants and anionic surfactants.

13. A method for manufacturing a separator for a non-aqueous secondary battery according to any one of claims 1 to 12, comprising the steps of: applying a coating liquid containing water, polyvinyl chloride resin particles and filler particles to one or both sides of a porous substrate to form a coating layer; and drying the coating layer on the porous substrate and melting the polyvinyl chloride resin particles to form an adhesive porous layer.

14. A non-aqueous secondary battery comprising a positive electrode, a negative electrode, and a separator for a non-aqueous secondary battery according to any one of claims 1 to 12 disposed between the positive electrode and the negative electrode, wherein electromotive force is obtained by doping and dedoping lithium ions.

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