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 polyvinyl chloride-based resin particles and filler particles. The polyvinyl chloride-based resin particles contained in the adhesive porous layer have a glass transition temperature of 30-100° C.

Description

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

[0001] This disclosure relates to 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 polyvinyl chloride resin particles and filler particles disposed on one or both sides of the porous substrate, wherein the glass transition temperature of the polyvinyl chloride resin particles contained in the adhesive porous layer is 30°C to 100°C. <2> The separator for a non-aqueous secondary battery according to <1>, wherein the adhesive porous layer has a structure in which the polyvinyl chloride resin particles and the filler particles are connected and have voids between the particles. <3> The separator for a non-aqueous secondary battery according to <1> or <2>, wherein the adhesive porous layer comprises a filler layer containing the filler particles and in contact with the porous substrate, and a resin particle layer in which the polyvinyl chloride resin particles are attached to the filler layer. <4> The mass per unit area of ​​the polyvinyl chloride resin particles contained in the adhesive porous layer is 0.4 g / m² in total on both sides of the porous substrate. ２ ~5.0 g / m ２A separator for a non-aqueous secondary battery according to any one of <1> to <3>. <5> A separator for a non-aqueous secondary battery according to any one of <1> to <4>, wherein the average primary particle size of the polyvinyl chloride resin particles contained in the adhesive porous layer is 10 nm to 1000 nm. <6> A separator for a non-aqueous secondary battery according to any one of <1> to <5>, wherein the average primary particle size of the filler particles contained in the adhesive porous layer is 0.01 μm to 2 μm. <7> A separator for a non-aqueous secondary battery according to any one of <1> to <6>, 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. <8> The non-aqueous secondary battery separator according to any one of <1> to <7>, wherein the thermal shrinkage rate of the non-aqueous secondary battery separator when heat-treated at a temperature of 105°C for 60 minutes is 5% or less for both MD and TD. <9> The non-aqueous secondary battery separator according to any one of <1> to <8>, wherein the adhesive porous layer further contains a resin having carbonyl groups. <10> The non-aqueous secondary battery separator according to <9>, wherein the resin having carbonyl groups includes at least one selected from the group consisting of urethane resin, acrylic resin, polyamide, polyimide, polyester, polycarbonate, and polyvinyl acetate. <11> The non-aqueous secondary battery separator according to <9> or <10>, wherein the proportion of polyvinyl chloride resin in the total amount of polyvinyl chloride resin and resin having carbonyl groups contained in the adhesive porous layer is 20% to 80% by mass. <12> The non-aqueous secondary battery separator according to any one of <1> to <11>, wherein the thermal 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. <13> The non-aqueous secondary battery separator according to any one of <1> to <12>, wherein the adhesive porous layer further contains a surfactant. <14> The non-aqueous secondary battery separator according to <13>, wherein the surfactant includes at least one selected from the group consisting of nonionic surfactants and anionic surfactants.<15> 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 <14> 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] It is a schematic cross-sectional view of an example of the form (A) of the adhesive porous layer. It is a schematic cross-sectional view of an example of the form (B) of the adhesive porous layer. It is an 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 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 stepwise 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 numerically described stepwise range. Further, 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 the case where it cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0017] When referring to the amount of each component in a composition in this disclosure, if there are multiple substances corresponding to each component in the composition, unless otherwise specified, it refers to the total amount of those multiple substances present in the composition. In this disclosure, each component may contain multiple types of particles. If there are multiple types of particles corresponding to each component in the composition, the particle size of each component refers to the value for a mixture of those multiple particles present in the composition, unless otherwise specified.

[0018] In this 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 planar direction of the separator. In this disclosure, TD is also referred to as the "width direction".

[0019] In this disclosure, when the stacking relationship of each layer constituting the separator is expressed as "top" and "bottom," the layer closer to the porous substrate is referred to as "bottom," and the layer further away from the porous substrate is referred to as "top."

[0020] In this disclosure, the volume of the porous layer excluding the voids is referred to as the "solids volume."

[0021] In this disclosure, the process of impregnating a separator with an electrolyte solution and then performing a heat press treatment is referred to as "wet heat press," and the process of performing a heat press treatment without impregnating the separator with an electrolyte solution is referred to as "dry heat press."

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

[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 this disclosure) comprises a porous substrate and an adhesive porous layer containing polyvinyl chloride resin particles and filler particles disposed on one or both sides of the porous substrate.

[0024] The separator of this disclosure has an adhesive porous layer containing polyvinyl chloride resin particles 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 particles 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 particles and filler particles as the outermost layer of the separator on one side of a porous substrate, and having another layer on the other side of the porous substrate.

[0027] Form (3): A separator having an adhesive porous layer containing polyvinyl chloride resin particles 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 according to this disclosure has a glass transition temperature (Tg) of polyvinyl chloride resin particles contained in the adhesive porous layer of 30°C to 100°C. The adhesive porous layer of the separator according to this disclosure contains polyvinyl chloride resin particles and filler particles, and the Tg of the polyvinyl chloride resin particles is 30°C to 100°C, thereby achieving both air permeability (and therefore ion permeability) and adhesion to electrodes. If the Tg of the polyvinyl chloride resin particles is less than 30°C, the polyvinyl chloride resin particles may melt due to the heat generated during separator manufacturing, resulting in the particle shape not being maintained and a decrease in the air permeability of the adhesive porous layer and the separator. From the viewpoint of maintaining the particle shape of the polyvinyl chloride resin particles, the Tg of the polyvinyl chloride resin particles is 30°C or higher, preferably 35°C or higher, more preferably 40°C or higher, and even more preferably 45°C or higher. If the Tg of polyvinyl chloride resin particles exceeds 100°C, adhesion to the electrode is difficult to achieve. From the viewpoint of achieving adhesion to the electrode by applying heat to bond the separator to the electrode, the Tg of polyvinyl chloride resin particles is 100°C or lower, preferably 90°C or lower, more preferably 80°C or lower, and even more preferably 75°C or lower.

[0029] The glass transition temperature of polyvinyl chloride resin particles 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 polyvinyl chloride resin particles that form an adhesive porous layer, or polyvinyl chloride resin particles extracted from the adhesive porous layer of a separator.

[0030] The glass transition temperature of polyvinyl chloride resin particles can be controlled by adjusting the type of monomer and copolymerization ratio, using the FOX formula as a guideline.

[0031] From the viewpoint of excellent breathability, the adhesive porous layer of the separator of this disclosure preferably has a structure in which polyvinyl chloride resin particles and filler particles are linked and voids are present between the particles.

[0032] Examples of embodiments of the adhesive porous layer of the separator of this disclosure include the following embodiments (A) and (B). Embodiment (A) is preferred from the viewpoint of the separator achieving both breathability and adhesion to the electrode.

[0033] Form (A): An adhesive porous layer having a filler layer containing filler particles and in contact with a porous substrate, and a resin particle layer in which polyvinyl chloride resin particles are attached to the filler layer. Form (B): An adhesive porous layer in which polyvinyl chloride resin particles and filler particles are mixed.

[0034] Forms (A) and (B) will be described with reference to the drawings. Figure 1 is a schematic cross-sectional view of an example of form (A). Figure 2 is a schematic cross-sectional view of an example of form (B). Figures 1 and 2 are schematic cross-sectional views mainly for explaining the stacking order of layers, and the structure of each layer is abstracted or simplified. In Figures 1 and 2, layers having similar functions are denoted by the same reference numerals and described accordingly.

[0035] The separator 10A shown in Figure 1 is a separator in which an adhesive porous layer 50A is arranged on one side of a porous substrate 20. The adhesive porous layer 50A consists of a filler layer 30 and a resin particle layer 40. The filler layer 30 is a layer containing filler particles 32 and is in contact with the porous substrate 20. The resin particle layer 40 is a layer consisting of polyvinyl chloride resin particles 42 and is formed when the polyvinyl chloride resin particles 42 adhere to the filler layer 30.

[0036] The separator 10B shown in Figure 2 is a separator in which an adhesive porous layer 50B is placed on one side of a porous substrate 20. The adhesive porous layer 50B is a layer in which polyvinyl chloride resin particles 42 and filler particles 32 are mixed.

[0037] In form (A), the filler layer preferably contains filler particles and a binder resin. In form (A), it is preferable that in the filler layer, the filler particles are connected to each other by a binder resin and there are voids between the filler particles, and in the resin particle layer, the polyvinyl chloride resin particles are connected to each other and there are voids between the polyvinyl chloride resin particles.

[0038] In form (B), it is preferable that polyvinyl chloride resin particles connect filler particles, and that there are voids between the polyvinyl chloride resin particles and the filler particles.

[0039] In form (A), the mass ratio of polyvinyl chloride resin particles contained in the resin particle layer to filler particles contained in the filler layer is preferably polyvinyl chloride resin particles:filler particles = 80:20 to 20:80, more preferably 70:30 to 30:70, and even more preferably 60:40 to 40:60. When the mass ratio of polyvinyl chloride resin particles to filler particles is within the above range, the separator exhibits a good balance between breathability and adhesion to the electrode.

[0040] In form (B), the mass ratio of polyvinyl chloride resin particles to filler particles contained in the adhesive porous layer is preferably polyvinyl chloride resin particles:filler particles = 80:20 to 20:80, more preferably 70:30 to 30:70, and even more preferably 60:40 to 40:60. When the mass ratio of polyvinyl chloride resin particles to filler particles is within the above range, the separator exhibits a good balance between breathability and adhesion to the electrode.

[0041] From the viewpoint of adhesion of the separator to the electrode, the mass per unit area of ​​polyvinyl chloride resin particles contained in the adhesive porous layer is 0.4 g / m² for both forms (A) and (B), total on both sides of the porous substrate. ２ The above is preferable, and 0.5 g / m ２ The above is more preferable, 0.6 g / m ２ The above is even more preferable. From the viewpoint of separator permeability, the mass per unit area of ​​polyvinyl chloride resin particles contained in the adhesive porous layer is 5.0 g / m² in total on both sides of the porous substrate for both forms (A) and (B).２ The following is preferable: 3.0 g / m ２ The following is more preferable: 1.5 g / m ２ The following is even more preferable.

[0042] In both form (A) and form (B), in the separator in a state of adhesion to the electrode, some or all of the polyvinyl chloride resin particles contained in the adhesive porous layer may melt due to the heat applied to adhere the separator to the electrode, causing adjacent polyvinyl chloride resin particles to connect with each other, and some or all of them may not maintain their particle shape.

[0043] The details of the porous substrate and adhesive porous layer of the separator of this disclosure are described below.

[0044] [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 the like.

[0045] The material of the porous substrate is preferably an electrically insulating material.

[0046] 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.

[0047] 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.

[0048] As a porous substrate, from the viewpoint of imparting a shutdown function to the porous substrate, a porous substrate containing a microporous membrane containing a polyolefin (hereinafter referred to as "polyolefin microporous membrane") is preferred, and a porous substrate consisting solely of a polyolefin microporous membrane (i.e., a polyolefin microporous membrane) is more preferred.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] Examples of porous sheets made of fibrous material include porous sheets such as nonwoven fabrics and paper. Examples of fibrous material 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. 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.

[0056] 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.

[0057] - Characteristics of the porous substrate - From the perspective of mechanical strength, the thickness of the porous substrate is preferably 1 μm or more, more preferably 3 μm or more, and still more preferably 5 μm or more. From the perspective 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 still more preferably 8 μm or less. The thickness of the porous substrate is determined by measuring 20 points within a 10 cm square using a contact-type thickness gauge and averaging them.

[0058] From the perspective 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 still more preferably 90 seconds / 100 mL or more. From the perspective 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, still more preferably 180 seconds / 100 mL or less, and still more preferably 160 seconds / 100 mL or less. The air permeability of the porous substrate is measured and determined using a digital-type Oya permeability tester in accordance with JIS P8117:2009.

[0059] From the perspective of excellent electrolyte permeability and ion permeability, the porosity of the porous substrate is preferably 30% to 60%. The porosity ε (%) of the porous substrate is determined by the following formula. ε = {1 - Ws / (ds · t)} × 100 Here, Ws is the basis weight (g / m ２ ), ds is the true density (g / cm ３ ) of the porous substrate, and t is the thickness (μm) of the porous substrate. The basis weight is the mass per unit area.

[0060] [Adhesive porous layer] The adhesive porous layer is a layer disposed on the surface of the porous substrate and is the outermost layer of the separator. The adhesive porous layer has a large number of gaps or micropores and is a layer through which gas or liquid can pass from one surface to the other surface.

[0061] The adhesive porous layer contains at least polyvinyl chloride resin particles and filler particles. The adhesive porous layer may contain a polyvinyl chloride resin that is not in particle form, and may further contain a resin other than the polyvinyl chloride resin.

[0062] -Polyvinyl Chloride Resin Particles- The polyvinyl chloride resins that constitute polyvinyl chloride resin particles are described below. Polyvinyl chloride resins include homopolymers of vinyl chloride (also known as chloroethylene) (i.e., polyvinyl chloride) and copolymers of vinyl chloride and 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 largest number proportion among the monomers that make up the resin.

[0063] 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.

[0064] From the viewpoint of being able to form water-dispersible particles, polyvinyl chloride resins are preferably vinyl chloride-acrylic acid ester copolymers. Vinyl chloride-acrylic acid ester copolymers include alternating copolymers, random copolymers, block copolymers, and graft copolymers.

[0065] Examples of acrylic monomers in vinyl chloride-acrylic acid ester copolymers 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. Alkyl (meth)acrylate esters are preferred as the acrylic monomers. The alkyl group in the ester moiety of the alkyl (meth)acrylate ester is preferably a C1-C10 alkyl group, and more preferably a C1-C8 alkyl group. The acrylic monomers may be used individually or in combination of two or more.

[0066] From the viewpoint of adhesion to electrodes and the ability to form water-dispersible particles, the vinyl chloride-acrylic acid ester copolymer preferably has a vinyl chloride number ratio of 50% to 90% of the total monomers constituting the copolymer, more preferably 50% to 80%, and even more preferably 50% to 70%.

[0067] The polyvinyl chloride resin particles contained in the adhesive porous layer may be of one type or two or more types.

[0068] The average primary particle size of the polyvinyl chloride resin particles contained in the adhesive porous layer is preferably 10 nm to 1000 nm, more preferably 100 nm to 700 nm, and even more preferably 150 nm to 400 nm. When the average primary particle size of the polyvinyl chloride resin particles is 10 nm 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 polyvinyl chloride resin particles is more preferably 100 nm or more, and even more preferably 150 nm or more. When the average primary particle size of the polyvinyl chloride resin particles is 1000 nm 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 polyvinyl chloride resin particles is more preferably 700 nm or less, and even more preferably 400 nm or less.

[0069] The average primary particle size of polyvinyl chloride resin particles is determined by measuring the major axis of 100 randomly selected polyvinyl chloride resin particles observed using a scanning electron microscope (SEM) and averaging the major axes of these 100 particles. The sample used for SEM observation is polyvinyl chloride resin particles that form an adhesive porous layer, or polyvinyl chloride resin particles extracted from an adhesive porous layer.

[0070] From the viewpoint of adhesion of the separator to the electrode, the mass per unit area of ​​polyvinyl chloride resin particles contained in the adhesive porous layer should be 0.4 g / m² in total on both sides of the porous substrate. ２ The above is preferable, and 0.5 g / m ２ The above is more preferable, 0.6 g / m ２ The above is even more preferable. From the viewpoint of separator permeability, the mass per unit area of ​​polyvinyl chloride resin particles contained in the adhesive porous layer should be 5.0 g / m² in total on both sides of the porous substrate. ２ The following is preferable: 3.0 g / m ２ The following is more preferable: 1.5 g / m ２ The following is even more preferable.

[0071] The mass per unit area of ​​polyvinyl chloride resin particles contained in the adhesive porous layer is determined by cutting a separator into a 20 cm x 20 cm section, removing the polyvinyl chloride resin particles from the adhesive porous layer, measuring their mass, and then dividing the mass by the area.

[0072] The mass percentage of polyvinyl chloride resin particles 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.

[0073] When adhesive porous layers are present on both sides of a porous substrate, the type and / or content of polyvinyl chloride resin particles contained in one adhesive porous layer may be the same as or different from the type and / or content of polyvinyl chloride resin particles contained in the other adhesive porous layer.

[0074] - Filler particles - Examples of filler particles include inorganic particles and organic particles.

[0075] 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.

[0076] 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.

[0077] 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 50% to 95% by mass, more preferably 60% to 90% by mass, and even more preferably 70% to 85% by mass.

[0078] 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.

[0079] 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.

[0080] - 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.

[0081] 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.

[0082] The inorganic particles may be inorganic particles whose surface has been modified with a silane coupling agent or the like.

[0083] Inorganic particles may be used individually or in combination of two or more types.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] From the viewpoint of achieving a good balance between the permeability of the separator and adhesion to the electrodes, the mass ratio of inorganic particles to the total mass of the adhesive porous layer is preferably 50% to 95% by mass, more preferably 60% to 90% by mass, and even more preferably 70% to 85% by mass.

[0089] 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.

[0090] 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.

[0091] -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.

[0092] Organic particles may be used individually or in combination of two or more types.

[0093] -Binding Resin- When the adhesive porous layer is of form (A) and the filler particles are inorganic particles, it is preferable that the filler layer contains a binding resin for linking the inorganic particles. The binding resin may be a heat-resistant resin or a non-heat-resistant resin.

[0094] Examples of binder resins include acrylic resins, polyamide resins, butadiene-acrylonitrile resins, homopolymers or copolymers of vinyl nitrile compounds (acrylonitrile, methacrylonitrile, etc.), carboxymethylcellulose, hydroxyalkylcellulose, polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, and polyethers (polyethylene oxide, polypropylene oxide, etc.). These resins may be used individually or in combination of two or more.

[0095] Examples of heat-resistant resins include all-aromatic polyamides, polyamide-imides, polyimides, poly-N-vinylacetamides, polyacrylamides, copolymerized polyether polyamides, polyethersulfones, polysulfones, polyetherketones, and polyetherimides. These resins may be used individually or in combination of two or more types.

[0096] Among heat-resistant resins, all-aromatic polyamides are preferred from the viewpoint of durability. All-aromatic polyamides refer to polyamides whose main chain consists only of benzene rings and amide bonds. However, all-aromatic polyamides may also have small amounts of aliphatic monomers copolymerized into them. All-aromatic polyamides are also called aramids.

[0097] The all-aromatic polyamide may be meta-type or para-type. Among all-aromatic polyamides, meta-type all-aromatic polyamides are preferred from the viewpoint of easily forming porous layers and having excellent oxidation-reduction resistance in electrode reactions. Specifically, polymetaphenylene isophthalamide or polyparaphenylene terephthalamide are preferred, and polymetaphenylene isophthalamide is more preferred.

[0098] If the filler layer contains a heat-resistant resin, the heat-resistant resin content is preferably 85% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 95% to 100% by mass, relative to the total amount of resin contained in the filler layer.

[0099] When the filler layer contains a total aromatic polyamide, the total aromatic polyamide content is preferably 85% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 95% to 100% by mass, relative to the total amount of resin contained in the filler layer.

[0100] When filler layers are present on both sides of a porous substrate, the type or amount of heat-resistant resin contained in one filler layer may be the same as or different from the type or amount of heat-resistant resin contained in the other filler layer.

[0101] Examples of non-heat-resistant resins include butadiene polymers (e.g., butadiene homopolymers, styrene-butadiene copolymers) and acrylic resins (e.g., homopolymers or copolymers of acrylic monomers, copolymers of acrylic monomers and styrene monomers).

[0102] The amount of binder resin used is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, and even more preferably 3 to 5 parts by mass, per 100 parts by mass of inorganic particles.

[0103] -Other Resins- The adhesive porous layer may contain resins other than polyvinyl chloride resins. Examples of other resins include resins having carbonyl groups.

[0104] 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.

[0105] 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.

[0106] 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).

[0107] 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.

[0108] 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.

[0109] 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.

[0110] The polyvinyl chloride resin (particulate polyvinyl chloride resin and / or non-particulate polyvinyl chloride resin) and the resin having a carbonyl group may be separate polymers or copolymers. Copolymers include alternating copolymers, random copolymers, block copolymers, and graft copolymers.

[0111] The proportion of polyvinyl chloride resin (the sum of polyvinyl chloride resin in particulate form and polyvinyl chloride resin in non-particulate form) and the resin having a carbonyl group in the total amount of polyvinyl chloride resin 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.

[0112] The total mass percentage of polyvinyl chloride resin (particulate polyvinyl chloride resin and non-particulate polyvinyl chloride resin) and resin having a carbonyl group 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.

[0113] The total mass per unit area of ​​polyvinyl chloride resin (particulate polyvinyl chloride resin and non-particulate polyvinyl chloride resin) and resin containing carbonyl groups contained in the adhesive porous layer is 0.1 g / m² on both sides of the porous substrate, from the viewpoint of adhesion of the separator to the electrode. 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 ​​polyvinyl chloride resin (particulate polyvinyl chloride resin and non-particulate polyvinyl chloride resin) and resin having a carbonyl group contained in the adhesive porous layer should be 5.0 g / m² on both sides of the porous substrate, from the viewpoint of separator 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.

[0114] 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 ).

[0115] 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.

[0116] 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.

[0117] -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 polyvinyl chloride resin particles from the viewpoint of adhesion to electrodes, 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, the adhesive porous layer, by containing polyvinyl chloride resin particles and a surfactant, has good adhesion to both electrodes and porous substrates. 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.

[0118] 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.

[0119] 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).

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] -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.

[0125] - 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 ~5.0 g / m ２ More preferably, 1.0 g / m ２ ~4.0 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.

[0126] [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, even more preferably 9 μm or more, and still more preferably 10 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, even more preferably 15 μm or less, even more preferably 12 μm or less, and still more preferably 10 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.

[0127] 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 500 seconds / 100 mL or less, more preferably 450 seconds / 100 mL or less, even more preferably 400 seconds / 100 mL or less, even 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.

[0128] 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, even more preferably 10 seconds / 100 mL or more, and even more preferably 20 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.

[0129] 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.

[0130] 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).

[0131] 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 3% or less, and even more preferably 1% or less.

[0132] 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.

[0133] 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.

[0134] 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

[0135] [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.

[0136] As an example of a separator manufacturing method when the adhesive porous layer is of form (A), the following manufacturing method (A) can be cited.

[0137] A method for manufacturing a separator, comprising the steps of: applying a first coating solution containing a solvent, filler particles, and a binder resin to one or both sides of a porous substrate to form a first coating layer; immersing the porous substrate having the first coating layer in a solidifying solution to solidify the first coating layer, or drying and solidifying the first coating layer on the porous substrate to form a filler layer; applying a second coating solution containing water and polyvinyl chloride resin particles onto the filler layer to form a second coating layer; and drying the second coating layer on the filler layer to form a resin particle layer, thereby forming an adhesive porous layer having a filler layer and a resin particle layer on a porous substrate.

[0138] As an example of a separator manufacturing method when the adhesive porous layer is of form (B), the following manufacturing method (B) can be cited.

[0139] Manufacturing method (B): 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 to form an adhesive porous layer, thereby forming an adhesive porous layer on the porous substrate in which polyvinyl chloride resin particles and filler particles are mixed.

[0140] The manufacturing methods (A) and (B) will be explained below in order.

[0141] - Manufacturing Method (A) - Manufacturing Method (A) involves forming a filler layer by a wet coating method, and then forming a resin particle layer by a dry coating method.

[0142] The first coating solution is prepared by dispersing and dissolving filler particles and binder resin in a solvent. If necessary, other components besides filler particles and binder resin may be dissolved or dispersed in the first coating solution.

[0143] The solvent used in the preparation of the first coating solution includes a solvent that dissolves the binder resin (hereinafter also referred to as the "good solvent"). Examples of good solvents include polar amide solvents such as N-methylpyrrolidone, dimethylacetamide, and dimethylformamide.

[0144] The solvent used in preparing the first coating solution may contain a phase-separating agent that induces phase separation, from the viewpoint of forming a filler layer with a good porous structure. Therefore, the solvent used in preparing the first coating solution may be a mixed solvent of a good solvent and a phase-separating agent. It is preferable to mix the phase-separating agent with the good solvent in an amount that ensures a viscosity suitable for coating. Examples of phase-separating agents include water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, and tripropylene glycol.

[0145] When the solvent used to prepare the first coating solution is a mixed solvent of a good solvent and a phase separating agent, a mixed solvent containing 60% by mass or more of the good solvent and 5% to 40% by mass of the phase separating agent is preferred from the viewpoint of forming a good porous structure in the filler layer.

[0146] The resin concentration of the first coating solution is preferably 1% to 20% by mass, from the viewpoint of forming a good porous structure in the filler layer. When inorganic particles are used as filler particles, the inorganic particle concentration of the first coating solution is preferably 0.5% to 50% by mass, from the viewpoint of forming a good porous structure in the filler layer.

[0147] The first coating solution may contain dispersants such as surfactants, wetting agents, defoamers, pH adjusters, etc. These additives may remain in the filler 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.

[0148] Examples of means for applying the first coating solution to a porous substrate include Meyer bar, die coater, reverse roll coater, roll coater, and gravure coater. When forming a filler layer and an adhesive porous layer on both sides of a porous substrate, it is preferable from the viewpoint of productivity to apply the first coating solution to both sides of the porous substrate simultaneously.

[0149] The first coating layer is solidified by immersing the porous substrate on which the first coating layer is formed in a solidifying solution, thereby inducing phase separation in the first coating layer and solidifying the resin. Alternatively, the first coating layer on the porous substrate is dried and solidified. This yields a laminate consisting of a porous substrate and a filler layer.

[0150] The solidification solution generally contains the good solvent and phase separator used in the preparation of the first coating solution, along with water. From a production standpoint, it is preferable that the mixing ratio of the good solvent and phase separator match the mixing ratio of the mixed solvent used in the preparation of the first coating solution. A water content of 40% to 90% by mass in the solidification solution is preferable from the viewpoint of forming a good porous structure in the filler layer and from the viewpoint of the productivity of the filler layer. The temperature of the solidification solution is, for example, 20°C to 50°C.

[0151] After the first coating layer is solidified in the solidification solution, the laminate is removed from the solidification solution. Next, it is preferable to wash the laminate with water. Washing with water removes the solidification solution from the laminate. Washing with water is performed, for example, by transporting the laminate in a water bath. Next, the laminate may be dried, or the second coating solution may be applied without drying. Drying is performed, for example, by transporting the laminate in a high-temperature environment, blowing air on the laminate, or bringing the laminate into contact with a heat roll. The drying temperature is preferably 40°C to 80°C.

[0152] The second coating solution is prepared by dispersing polyvinyl chloride resin particles in water. If necessary, other components besides polyvinyl chloride resin particles may be dissolved or dispersed in the second coating solution.

[0153] The concentration of polyvinyl chloride resin particles in the second coating solution is preferably 1% to 20% by mass, from the viewpoint of coating properties and productivity of the resin particle layer.

[0154] The second coating solution may contain dispersants such as surfactants, wetting agents, defoamers, pH adjusters, etc. These additives may remain in the resin particle 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.

[0155] Examples of methods for applying the second coating solution onto the filler layer of the laminate include Meyer bar, die coater, reverse roll coater, roll coater, and gravure coater. When forming a resin particle layer and an adhesive porous layer on both sides of a porous substrate, it is preferable from the viewpoint of productivity to apply the second coating solution to both sides of the laminate simultaneously.

[0156] The second coating layer solidifies by drying (i.e., removing water) the second coating layer. Drying is performed, for example, by transporting the laminate in a high-temperature environment, blowing air onto the laminate, or bringing the laminate into contact with a heat roll. The drying temperature is set to a temperature that does not melt the polyvinyl chloride resin particles and maintains their particle shape. When transporting the laminate in a high-temperature environment, the ambient temperature is preferably 20°C or less above the glass transition temperature of the polyvinyl chloride resin particles in order to maintain the particle shape without melting the polyvinyl chloride resin particles.

[0157] - Manufacturing Method (B) - Manufacturing Method (B) involves forming an adhesive porous layer by a dry coating method.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.).

[0162] 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.

[0163] 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 a temperature that does not melt the polyvinyl chloride resin particles and maintains their particle shape. When transporting the porous substrate with the coating layer in a high-temperature environment, the ambient temperature is preferably at or below the glass transition temperature of the polyvinyl chloride resin particles + 20°C in order to maintain the particle shape without melting the polyvinyl chloride resin particles.

[0164] The separator of this disclosure may 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 compression or adhesive. A method for preparing the adhesive porous layer as an independent sheet is to apply manufacturing method (A) or manufacturing method (B) to form the adhesive porous layer on a release sheet.

[0165] <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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] 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).

[0174] 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.

[0175] 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.

[0176] 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.

[0177] 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.

[0178] 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.

[0179] 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.

[0180] 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.

[0181] In the following descriptions, synthesis, processing, and manufacturing were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0182] <Measurement Methods and Evaluation Methods> The measurement and evaluation methods applied to the examples and comparative examples are as follows.

[0183] [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.

[0184] [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.

[0185] [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.

[0186] [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).

[0187] [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).

[0188] [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).

[0189] [Coating amount of resin particles] Cut the separator into 20 cm x 20 cm pieces, remove the resin particles from the adhesive porous layer and measure their mass. Divide the mass by the area to determine the coating amount of resin particles (mass per unit area, g / m²). ２ ) was sought.

[0190] [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.

[0191] 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.

[0192] 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.

[0193] 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 85°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 11-15 and Comparative Examples 11-14, the heat-pressing conditions were a temperature of 75°C, a pressure of 1 MPa, and a time of 0.5 minutes.

[0194] 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.

[0195] 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.

[0196] [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 a temperature of 105°C or 130°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.

[0197] 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

[0198] [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.

[0199] [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%

[0200] <Manufacturing of Separators and Batteries> [Example 1] -Separator Preparation- A mixed solvent was prepared by mixing dimethylacetamide (DMAc) and tripropylene glycol (TPG) in a mass ratio of 95:5. Alumina particles and an acrylic resin were added to the mixed solvent and stirred to prepare a coating solution (1). The coating solution (1) had an acrylic resin concentration of 5% by mass, and the mass ratio of alumina particles to acrylic resin was 90:10.

[0201] A resin particle dispersion (1) was prepared in which vinyl chloride-acrylic acid ester copolymer particles were dispersed in water. The resin particle dispersion (1) had a resin particle concentration of 4% by mass.

[0202] A coating solution (1) was applied to one side of a polyethylene microporous membrane using a Meyer bar. Next, the membrane was immersed in a solidification solution (DMAc:TPG:water = 38:2:60 [mass ratio], liquid temperature 25°C) to solidify the coating layer. Then, it was washed in a water washing tank at a water temperature of 25°C and dried to form a filler layer on one side of the polyethylene microporous membrane. Next, a resin particle dispersion (1) was applied onto the filler layer using a Meyer bar and dried by transporting it in an atmosphere at a temperature of 60°C. In this way, a separator with an adhesive porous layer of form (A) on one side of a polyethylene microporous membrane was obtained.

[0203] Figure 3 shows an SEM image (magnification 10,000) of the surface of the adhesive porous layer of Example 1. The adhesive porous layer had a structure in which numerous polyvinyl chloride resin particles were attached to the filler layer.

[0204] - 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.

[0205] - 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.

[0206] -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.

[0207] [Examples 2-3] Separators were prepared in the same manner as in Example 1, except that at least one of the vinyl chloride-acrylic ester copolymer particles, the average primary particle size, the glass transition temperature, and the coating amount 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.

[0208] The separators of Examples 2 and 3 are each separators having an adhesive porous layer of form (A) on one side of a polyethylene microporous membrane. When the surface of the adhesive porous layer of the separators was observed with SEM, the adhesive porous layers of Examples 2 and 3 each had a structure in which a large number of polyvinyl chloride resin particles were attached to the filler layer.

[0209] [Example 4] - Preparation of Separator - A resin particle dispersion (1) was prepared in which vinyl chloride-acrylic acid ester copolymer particles were dispersed in water. A coating solution (2) was prepared by adding alumina particles, sodium hexametaphosphate, and ethanol to the resin particle dispersion (1). The coating solution (2) had a concentration of vinyl chloride-acrylic acid ester copolymer particles 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 alumina particles to vinyl chloride-acrylic acid ester copolymer particles of 50:50.

[0210] Using a Meyer bar, coating solution (2) was applied to one side of the polyethylene microporous membrane, and it was dried by transporting it in an atmosphere at a temperature of 60°C. In this way, a separator with an adhesive porous layer of form (B) on one side of the polyethylene microporous membrane was obtained. When the surface of the adhesive porous layer of the separator was observed with an SEM, the adhesive porous layer of Example 4 had a structure in which polyvinyl chloride resin particles and filler particles were mixed. Using the above separator, a non-aqueous secondary battery was fabricated in the same manner as in Example 1.

[0211] [Comparative Example 1] - Preparation of Separator - A resin particle dispersion (C1) was prepared in which polyvinyl chloride resin particles were dispersed in water. Ethanol was added to the resin particle dispersion (C1) to prepare a coating solution (C2). The coating solution (C2) had a resin particle concentration of 4% by mass and an ethanol concentration of 48%.

[0212] Using a Meyer bar, the coating solution (C2) was applied to both sides of the polyethylene microporous membrane, and it was dried by transporting it in an atmosphere at 60°C. In this way, a separator with resin layers on both sides of the polyethylene microporous membrane was obtained. When the surface of the resin layer was observed with an SEM, the polyvinyl chloride resin particles did not maintain their particle shape.

[0213] [Comparative Example 2] A separator was prepared in the same manner as in Comparative Example 1, except that the average primary particle size of the polyvinyl chloride resin particles, the glass transition temperature, and the coating amount were changed as shown in Table 1. When the surface of the resin layer was observed with an SEM, the polyvinyl chloride resin particles did not maintain their particle shape.

[0214] Table 1 shows the composition of the porous substrate and the adhesive porous layer, and Table 2 shows the physical properties and evaluation results of the separator. The amount of resin particles coated in Table 1 is the total for both sides of the porous substrate. The thickness of the adhesive porous layer in Table 1 is the total for both sides of the porous substrate. The abbreviations in Table 1 have the following meanings: ・PE: Polyethylene

[0215]

[0216]

[0000] [Example 11] - Preparation of separator - Acrylic resin and alumina particles were added to water and stirred to obtain a coating solution (11). The coating solution (11) contained 5% by mass of acrylic resin, and the mass ratio of alumina particles to acrylic resin was 90:10.

[0217] A resin particle dispersion (11) was prepared in which vinyl chloride-acrylic acid ester copolymer particles were dispersed in water. The resin particle dispersion (11) had a resin particle concentration of 10% by mass.

[0218] A coating solution (11) was applied to one side of a polyethylene microporous membrane using a Meyer bar and dried. In this way, a filler layer was formed on one side of the polyethylene microporous membrane. Next, a resin particle dispersion (11) was applied onto the filler layer using a Meyer bar, and dried by transporting it in an atmosphere at a temperature of 60°C to obtain a separator. Using this separator, a non-aqueous secondary battery was fabricated in the same manner as in Example 1.

[0219] The separator of Example 11 is a polyethylene microporous membrane with an adhesive porous layer of form (A) on one side. When the surface of the adhesive porous layer of the separator was observed with an SEM, it was found to have a structure in which a large number of polyvinyl chloride resin particles were attached to the filler layer.

[0220] [Example 12] A separator was prepared in the same manner as in Example 11, except that the amount of resin particle dispersion (11) used to form the resin particle layer was changed as shown in Table 4. Using this separator, a non-aqueous secondary battery was prepared in the same manner as in Example 1.

[0221] The separator of Example 12 is a polyethylene microporous membrane with an adhesive porous layer of form (A) on one side. When the surface of the adhesive porous layer of the separator was observed with an SEM, it was found to have a structure in which a large number of polyvinyl chloride resin particles were attached to the filler layer.

[0222] [Example 13] - Preparation of Separator - A mixed solvent was prepared by mixing dimethylacetamide (DMAc) and tripropylene glycol (TPG) in a mass ratio of 90:10. Magnesium hydroxide particles and meta-aramid (polymetaphenylene isophthalamide) were added to the mixed solvent and stirred to prepare a coating solution (12). The coating solution (12) had a meta-aramid concentration of 5% by mass, and the mass ratio of magnesium hydroxide particles to meta-aramid was 80:20.

[0223] A resin particle dispersion (11) was prepared in which vinyl chloride-acrylic acid ester copolymer particles were dispersed in water. The resin particle dispersion (11) had a resin particle concentration of 10% by mass.

[0224] A coating solution (12) was applied to both sides of a polyethylene microporous membrane using a Meyer bar. Next, the membrane was immersed in a solidification solution (DMAc:TPG:water = 36:4:60 [mass ratio], liquid temperature 25°C) to solidify the coating layer. Then, it was washed in a water washing tank at a water temperature of 25°C and dried. In this way, filler layers were formed on both sides of the polyethylene microporous membrane. Next, an equal amount of resin particle dispersion (11) was applied to the filler layers on both sides using a pair of Meyer bars, and dried by transporting it in an atmosphere at a temperature of 60°C to obtain a separator. Using this separator, a non-aqueous secondary battery was fabricated in the same manner as in Example 1.

[0225] The separator of Example 13 is a separator having adhesive porous layers of form (A) on both sides of a polyethylene microporous membrane. When the surface of the adhesive porous layer of the separator was observed with an SEM, it was found to have a structure in which a large number of polyvinyl chloride resin particles were attached to the filler layer.

[0226] [Example 14] A separator was prepared in the same manner as in Example 13, except that the amount of resin particle dispersion (11) used to form the resin particle layer was changed as shown in Table 4. Using this separator, a non-aqueous secondary battery was prepared in the same manner as in Example 1.

[0227] The separator of Example 14 is a separator having an adhesive porous layer of form (A) on both sides of a polyethylene microporous membrane. When the surface of the adhesive porous layer of the separator was observed with an SEM, it was found to have a structure in which a large number of polyvinyl chloride resin particles were attached to the filler layer.

[0228] [Example 15] A separator was prepared in the same manner as in Example 13, except that the average primary particle size, glass transition temperature, and coating amount of the vinyl chloride-acrylic acid ester copolymer particles used to form the resin particle layer were changed as shown in Table 4. Using this separator, a non-aqueous secondary battery was prepared in the same manner as in Example 1.

[0229] The separator of Example 15 is a separator having adhesive porous layers of form (A) on both sides of a polyethylene microporous membrane. When the surface of the adhesive porous layer of the separator was observed with an SEM, it was found to have a structure in which a large number of polyvinyl chloride resin particles were attached to the filler layer.

[0230] [Comparative Example 11] The polyethylene microporous membrane and filler layer laminate prepared in Example 11 was used as a separator.

[0231] [Comparative Example 12] The polyethylene microporous membrane and filler layer laminate prepared in Example 13 was used as a separator.

[0232] [Comparative Example 13] A separator was prepared in the same manner as in Example 13, except that the average primary particle size, glass transition temperature, and coating amount of the vinyl chloride-acrylic ester copolymer particles used to form the resin particle layer were changed as shown in Table 4. When the separator surface was observed with an SEM, the vinyl chloride-acrylic ester copolymer particles did not maintain their particle shape.

[0233] [Comparative Example 14] - Preparation of Separator - A resin particle dispersion (C1) was prepared in which polyvinyl chloride resin particles were dispersed in water. The resin particle dispersion (C1) had a resin particle concentration of 10% by mass.

[0234] A resin particle dispersion (C1) was coated onto both sides of a polyethylene microporous membrane using a pair of Meyer bars, and dried in an atmosphere at 60°C to obtain a separator. SEM observation of the separator surface revealed that the polyvinyl chloride resin particles did not maintain their particle shape.

[0235] Table 3 shows the composition of the porous substrate and filler layer of Examples 11-15 and Comparative Examples 11-14, Table 4 shows the composition of the resin particle layer of Examples 11-15 and Comparative Examples 11-14, and Table 5 shows the physical properties and evaluation results of the separators of Examples 11-15 and Comparative Examples 11-14. The abbreviations in Table 3 have the following meanings: PE: Polyethylene

[0236]

[0237]

[0238]

[0239] [Example 21] - Separator Production - A resin particle dispersion (21) was prepared in which vinyl chloride-acrylic ester copolymer particles (glass transition temperature 46°C) 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 4% 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

[0240] Using a pair of Meyer bars, an equal amount of coating liquid (21) 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 was obtained having adhesive porous layers on both sides of the polyethylene microporous membrane.

[0241] SEM observation of the surface of the adhesive porous layer revealed that resin particles were linking filler particles, and that there were voids between the resin particles and filler particles. Using this separator, a non-aqueous secondary battery was manufactured in the same manner as in Example 1.

[0242] [Example 22] A separator was manufactured in the same manner as in Example 21, except that the surfactant was changed to sodium dodecylbenzenesulfonate, an anionic surfactant, and the resin concentration was changed to 10% by mass. When the surface of the adhesive porous layer was observed with an SEM, it was found that the resin particles were linked to the filler particles, and that there were voids between the resin particles and the filler particles. Using this separator, a non-aqueous secondary battery was manufactured in the same manner as in Example 1.

[0243] Table 6 shows the composition of the porous substrate and adhesive porous layer of Examples 21-22, and Table 7 shows the physical properties and evaluation results of the separators of Examples 21-22. The coating amounts listed in Table 6 are the total for both sides of the porous substrate. The thickness of the adhesive porous layer listed in Table 6 is the total for both sides of the porous substrate.

[0244] The abbreviations in Table 6 have the following meanings: • PE: Polyethylene • VC-AAE: Vinyl chloride-acrylic acid copolymer

[0245]

[0246]

[0247] 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.

[0248] The disclosure of Japanese application number 2024-201828, 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.

[0249] 10A Separator 10B Separator 20 Porous substrate 30 Filler layer 32 Filler particles 40 Resin particle layer 42 Polyvinyl chloride resin particles 50A Adhesive porous layer 50B Adhesive porous layer

Claims

1. A separator for a non-aqueous secondary battery, comprising a porous substrate and an adhesive porous layer containing polyvinyl chloride resin particles and filler particles disposed on one or both sides of the porous substrate, wherein the glass transition temperature of the polyvinyl chloride resin particles contained in the adhesive porous layer is 30°C to 100°C.

2. The separator for a non-aqueous secondary battery according to claim 1, wherein the adhesive porous layer has a structure in which the polyvinyl chloride resin particles and the filler particles are connected and voids are present between the particles.

3. The separator for a non-aqueous secondary battery according to claim 1, wherein the adhesive porous layer comprises a filler layer containing the filler particles and in contact with the porous substrate, and a resin particle layer in which the polyvinyl chloride resin particles are attached to the filler layer.

4. The mass per unit area of ​​the polyvinyl chloride resin particles contained in the adhesive porous layer is 0.4 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.

5. The separator for a non-aqueous secondary battery according to claim 1, wherein the average primary particle size of the polyvinyl chloride resin particles contained in the adhesive porous layer is 10 nm to 1000 nm.

6. 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.

7. 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.

8. 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.

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

10. The separator for a non-aqueous secondary battery according to claim 9, 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.

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

12. 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.

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

14. The separator for a non-aqueous secondary battery according to claim 13, wherein the surfactant comprises at least one selected from the group consisting of nonionic surfactants and anionic surfactants.

15. 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 14 disposed between the positive electrode and the negative electrode, wherein electromotive force is obtained by doping and dedoping lithium ions.

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