Separator for nonaqueous secondary battery, and nonaqueous secondary battery

Abstract

This separator for a nonaqueous secondary battery is provided with a porous layer containing a polyamide having: at least one among an alicyclic diamine unit and an alicyclic dicarboxylic acid unit; and at least one among an aromatic diamine unit and an aromatic dicarboxylic acid unit.

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] As a battery separator, a separator having a porous layer containing polyvinylidene fluoride resin is known. For example, Patent Document 1 discloses a separator for a non-aqueous secondary battery comprising a porous substrate and a porous layer containing polyvinylidene fluoride resin provided on one or both sides of the porous substrate.

[0003] International Publication No. 2017 / 082258

[0004] Because polyvinylidene fluoride resin exhibits excellent affinity with the binder resin of the electrode active material layer, a porous layer containing polyvinylidene fluoride resin in a separator exhibits excellent adhesion to the electrode.

[0005] However, in recent years, the ecotoxicity and anthroptoxicity of organofluorine compounds have been pointed out, and regulations on the manufacture and use of organofluorine compounds are being strengthened worldwide. Therefore, there is an urgent need to develop separators with a low content of polyvinylidene fluoride resin or those that do not contain polyvinylidene fluoride resin. Ideally, the separator should have excellent adhesion to electrodes even without containing polyvinylidene fluoride resin.

[0006] This disclosure was made under the circumstances described above. The object of this disclosure is to provide a separator for non-aqueous secondary batteries that exhibits excellent adhesion to electrodes by wet heat pressing.

[0007] The following embodiments are specific means for solving the aforementioned problems. Each formula is the same as the formula with the same number described later. <1> A separator for a non-aqueous secondary battery, comprising a porous layer containing a polyamide having at least one of an alicyclic diamine unit and an alicyclic dicarboxylic acid unit and at least one of an aromatic diamine unit and an aromatic dicarboxylic acid unit. <2> The separator for a non-aqueous secondary battery according to <1>, wherein the polyamide has at least one selected from the group consisting of an alicyclic diamine unit represented by formula (a1) and an alicyclic diamine unit represented by formula (a2), and / or at least one selected from the group consisting of an alicyclic dicarboxylic acid unit represented by formula (c1) and an alicyclic dicarboxylic acid unit represented by formula (c2). <3> The separator for a non-aqueous secondary battery according to <1> or <2>, wherein the polyamide has an aromatic diamine unit represented by formula (ra), and / or an aromatic dicarboxylic acid unit represented by formula (rc). <4> The separator for a non-aqueous secondary battery according to any one of <1> to <3>, wherein the polyamide further comprises at least one linear aliphatic constituent unit selected from the group consisting of linear aliphatic diamine units, linear aliphatic monoaminomonocarboxylic acid units, and linear aliphatic dicarboxylic acid units. <5> The separator for a non-aqueous secondary battery according to <4>, wherein the total proportion of the linear aliphatic constituent units to the total constituent units of the polyamide is 5 mol% to 50 mol%. <6> The separator for a non-aqueous secondary battery according to any one of <1> to <5>, wherein the glass transition temperature of the polyamide is 50°C to 200°C. <7> The separator for a non-aqueous secondary battery according to any one of <1> to <6>, wherein the porous layer further contains inorganic particles. <8> The separator for a non-aqueous secondary battery according to any one of <1> to <7>, wherein the air permeability is 100 seconds / 100 mL to 1000 seconds / 100 mL. <9> A separator for a non-aqueous secondary battery according to any one of <1> to <8>, wherein the porous layer substantially does not contain a fluorine-containing resin. <10> A separator for a non-aqueous secondary battery according to any one of <1> to <9>, comprising a porous substrate and the porous layer disposed on one or both sides of the porous substrate.<11> The separator for a non-aqueous secondary battery according to <10>, wherein the porous substrate comprises a polyolefin microporous membrane and an inorganic particle layer containing inorganic particles and a binder resin disposed on one or both sides of the polyolefin microporous membrane. <12> A non-aqueous secondary battery comprising a positive electrode, a negative electrode, the separator for a non-aqueous secondary battery according to any one of <1> to <11> disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte.

[0008] According to this disclosure, a separator for non-aqueous secondary batteries is provided that exhibits excellent adhesion to electrodes by wet heat pressing.

[0009] The embodiments of this disclosure are described below. These descriptions and embodiments are illustrative and do not limit the scope of the embodiments.

[0010] In this disclosure, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples.

[0011] In this disclosure, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" may be A alone, B alone, or a combination of A and B.

[0012] In this disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, provided that their objectives are achieved.

[0013] 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.

[0014] 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".

[0015] 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."

[0016] In this disclosure, the volume of the porous layer excluding the voids is referred to as the "solids volume."

[0017] 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."

[0018] In this disclosure, the term "(meth)acrylic" means that either "acrylic" or "methacrylic" may be used. In this disclosure, alkyl groups and alkylene groups include linear, branched, and cyclic groups unless otherwise specified. In this disclosure, organic groups, aromatic rings, linking groups, alkyl groups, alkylene groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, etc., may have hydrogen atoms in the group substituted with halogen atoms.

[0019] In this disclosure, when compounds are shown by structural formulas, the symbols representing carbon atoms and hydrogen atoms (C and H) in the hydrocarbon group and / or hydrocarbon chain may be omitted.

[0020] In this disclosure, the term "constituent unit" of a copolymer or resin means a unit formed by the polymerization of monomers and is synonymous with "monomer unit." A constituent unit in which an aromatic ring or alicyclic ring is included in the polymer main chain, and the linkage position of the aromatic ring or alicyclic ring to the polymer main chain is the meta position, is called a "meta-system constituent unit," and a constituent unit in which the linkage position of the aromatic ring or alicyclic ring to the polymer main chain is the para position is called a "para-system constituent unit."

[0021] <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 layer containing a polyamide having at least one of alicyclic diamine units and alicyclic dicarboxylic acid units and at least one of aromatic diamine units and aromatic dicarboxylic acid units.

[0022] In this disclosure, a polyamide having at least one of an alicyclic diamine unit and an alicyclic dicarboxylic acid unit and at least one of an aromatic diamine unit and an aromatic dicarboxylic acid unit is also referred to as "polyamide (S)". In this disclosure, a porous layer containing polyamide (S) is also referred to as "porous layer (S)".

[0023] The separator of this disclosure has at least a porous layer (S). The separator of this disclosure may consist only of a porous layer (S), or it may be a separator in which a porous layer (S) and another layer are laminated together.

[0024] An example of an embodiment of the separator of this disclosure is a separator comprising a porous substrate and a porous layer (S) disposed on one or both sides of the porous substrate. Examples of embodiments of this separator include the following embodiments (1) to (3).

[0025] Form (1): A separator having porous layers (S) on both sides of a porous substrate. In this separator, the porous layer (S) on one side and the porous layer (S) on the other side may be the same or different in terms of components and / or composition.

[0026] Embodiment (2): A separator having a porous layer (S) on one side of a porous substrate and another layer (for example, a resin layer that does not contain polyamide (S) but contains another resin) on the other side of the porous substrate.

[0027] Form (3): A separator having a porous layer (S) on one side of a porous substrate and no layer on the other side of the porous substrate (i.e., the surface of the porous substrate is exposed).

[0028] The separator of this disclosure exhibits excellent adhesion to electrodes by wet heat pressing. The mechanism is presumed to be as follows.

[0029] Conventionally, fully aromatic polyamides are known as resins that constitute the porous layer of separators. Since fully aromatic polyamides are heat-resistant resins, a porous layer containing fully aromatic polyamides functions as a heat-resistant layer. On the other hand, because fully aromatic polyamides have a high glass transition temperature, porous layers containing fully aromatic polyamides are difficult to thermocompress onto electrodes, and the porous layer has poor adhesion to electrodes. In contrast, the inventors of this disclosure have found that a polyamide (i.e., polyamide(S)) in which some of the aromatic constituent units of a fully aromatic polyamide are replaced with alicyclic constituent units adheres to electrodes by wet heat pressing. It is presumed that the polymer chains of polyamide(S) are flexible due to the presence of alicyclic constituent units and swell appropriately in the electrolyte. Furthermore, it is presumed that the glass transition temperature of polyamide(S) is relatively low due to the presence of alicyclic constituent units, and that the mobility of the polymer chains when heated is relatively high. It is presumed that due to these synergistic effects, a porous layer (S) containing polyamide(S) adheres well to electrodes by wet heat pressing.

[0030] The details of the polyamide (S), porous layer (S), and porous substrate are described below.

[0031] [Polyamide (S)] Polyamide (S) is a polyamide having at least one alicyclic structural unit selected from an alicyclic diamine unit and an alicyclic dicarboxylic acid unit, and at least one aromatic structural unit selected from an aromatic diamine unit and an aromatic dicarboxylic acid unit.

[0032] Examples of the alicyclic diamine unit include an alicyclic diamine unit represented by the following formula (a1) and an alicyclic diamine unit represented by the following formula (a2). Examples of the alicyclic dicarboxylic acid unit include an alicyclic dicarboxylic acid unit represented by the following formula (c1) and an alicyclic dicarboxylic acid unit represented by the following formula (c2).

[0033]

[0034] In formula (a1), n １ is an integer of 0 to 10, and n １ groups of R １ are each independently an alkyl group having 1 to 6 carbon atoms, n ２ is an integer of 0 to 10, n ２ groups of R ２ are each independently an alkyl group having 1 to 6 carbon atoms, X is a single bond, an oxygen atom or a divalent hydrocarbon group, and the two -NH- groups are each independently at the meta position or para position of X. In formula (a2), n １ is an integer of 0 to 10, n １ groups of R １ are each independently an alkyl group having 1 to 6 carbon atoms, and the two -NH- groups are at the meta position or para position relative to each other. In formula (c1), n １ is an integer of 0 to 10, n １ groups of R １ are each independently an alkyl group having 1 to 6 carbon atoms, n ２ is an integer of 0 to 10, n ２ groups of R ２ are each independently an alkyl group having 1 to 6 carbon atoms, X is a single bond, an oxygen atom or a divalent hydrocarbon group, and the two -CO- groups are each independently at the meta position or para position of X. In formula (c2), n １ is an integer of 0 to 10, n １ groups of R １Each of these is an alkyl group having 1 to 6 carbon atoms, and the two -CO- atoms are in the meta or para positions relative to each other.

[0035] In formula (a1), when two -NH- atoms are located at the meta position of X, the constituent unit is called a meta-alicyclic diamine unit represented by formula (a1). In formula (a1), when two -NH- atoms are located at the para position of X, the constituent unit is called a para-alicyclic diamine unit represented by formula (a1). In formula (a1), when one -NH- atom is located at the meta position of X and the other -NH- atom is located at the para position of X, the constituent unit is called a meta-para-alicyclic diamine unit represented by formula (a1). In formula (a2), when two -NH- atoms are located at the meta positions of each other, the constituent unit is called a meta-alicyclic diamine unit represented by formula (a2). In formula (a2), when two -NH- atoms are located at the para positions of each other, the constituent unit is called a para-alicyclic diamine unit represented by formula (a2). When two -CO- atoms are located at the meta position of X in formula (c1), the resulting unit is called a meta-alicyclic dicarboxylic acid unit represented by formula (c1). When two -CO- atoms are located at the para position of X in formula (c1), the resulting unit is called a para-alicyclic dicarboxylic acid unit represented by formula (c1). When one -CO- atom is located at the meta position of X and the other -CO- atom is located at the para position of X in formula (c1), the resulting unit is called a meta-para-alicyclic dicarboxylic acid unit represented by formula (c1). When two -CO- atoms are located at the meta positions of each other in formula (c2), the resulting unit is called a meta-alicyclic dicarboxylic acid unit represented by formula (c2). When two -CO- atoms are located at the para positions of each other in formula (c2), the resulting unit is called a para-alicyclic dicarboxylic acid unit represented by formula (c2).

[0036] Examples of aromatic diamine units include those represented by the following formula (ra). Examples of aromatic dicarboxylic acid units include those represented by the following formula (rc).

[0037]

[0038] In equation (ra), n １ n is an integer between 0 and 4, and１ Individual R １ Each of these is an alkyl group having 1 to 6 carbon atoms, and the two -NH- atoms are at the meta or para positions of each other. In formula (rc), n １ n is an integer between 0 and 4, and １ Individual R １ Each of these is an alkyl group having 1 to 6 carbon atoms, and the two -CO- atoms are in the meta or para positions relative to each other.

[0039] When two -NH- atoms are located at the meta position of each other in formula (ra), the resulting unit is called a meta-aromatic diamine unit represented by formula (ra). When two -NH- atoms are located at the para position of each other in formula (ra), the resulting unit is called a para-aromatic diamine unit represented by formula (ra). When two -CO- atoms are located at the meta position of each other in formula (rc), the resulting unit is called a meta-aromatic dicarboxylic acid unit represented by formula (rc). When two -CO- atoms are located at the para position of each other in formula (rc), the resulting unit is called a para-aromatic dicarboxylic acid unit represented by formula (rc).

[0040] In equation (a1), n １ n is an integer between 0 and 10, preferably between 0 and 4, more preferably 0, 1, or 2, and even more preferably 0 or 1. In formula (a1), n ２ is an integer between 0 and 10, preferably between 0 and 4, more preferably 0, 1, or 2, and even more preferably 0 or 1.

[0041] In equation (a2), n １ is an integer between 0 and 10, preferably between 0 and 4, more preferably 0, 1, or 2, and even more preferably 0 or 1.

[0042] In equation (c1), n １ n is an integer from 0 to 10, preferably an integer from 0 to 4, more preferably 0, 1, or 2, and even more preferably 0 or 1. In formula (c1), n ２is an integer between 0 and 10, preferably between 0 and 4, more preferably 0, 1, or 2, and even more preferably 0 or 1.

[0043] In equation (c2), n １ is an integer between 0 and 10, preferably between 0 and 4, more preferably 0, 1, or 2, and even more preferably 0 or 1.

[0044] In equation (ra), n １ is an integer between 0 and 4, preferably 0, 1, or 2, and more preferably 0 or 1.

[0045] In equation (rc), n １ is an integer between 0 and 4, preferably 0, 1, or 2, and more preferably 0 or 1.

[0046] R in equation (a1) １ and R ２ R in equation (a2) １ R in equation (c1) １ and R ２ R in equation (c2) １ R in formula (ra) １ Furthermore, R in formula (rc) １ Since the specific and preferred forms are the same, these substituents will be collectively referred to as "R" below.

[0047] The C1-C6 alkyl group related to R may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1-4, more preferably 1-3, and even more preferably 1 or 2. Examples of linear C1-C6 alkyl groups include methyl, ethyl, n-propyl, n-butyl, n-pentyl, and n-hexyl groups. Examples of branched C3-C6 alkyl groups include isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl, sec-hexyl, and tert-hexyl groups. Examples of cyclic alkyl groups with C3-C6 include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and polycyclic (e.g., bicyclic, tricyclic, spirocyclic) alkyl groups formed by linking these monocyclic alkyl groups.

[0048] Examples of divalent hydrocarbon groups relating to X in formulas (a1) and (c1) include alkylene groups having 1 to 18 carbon atoms. The number of carbon atoms in the alkylene group is preferably 1 to 12, more preferably 1 to 6, even more preferably 1 to 4, and particularly preferably 1. The alkylene group may be linear, branched, or cyclic. Examples of linear alkylene groups having 1 to 18 carbon atoms include methylene, ethylene, n-propylene, n-butylene, n-pentylene, n-hexylene, n-heptylene, n-octylene, n-nonylene, n-decylene, n-undecylene, n-dodecylene, tridecylene, n-tetradecylene, n-pentadecylene, n-hexadecylene, n-heptadecylene, and n-octadecylene. Examples of branched alkylene groups having 3 to 18 carbon atoms include isopropylene, isobutylene, sec-butylene, tert-butylene, isopentylene, neopentylene, tert-pentylene, isohexylene, sec-hexylene, tert-hexylene, isoheptylene, sec-heptylene, tert-heptylene, isooctylene, sec-octylene, tert-octylene, isononylene, sec-nonylene, tert-nonylene, isodecylene, sec-decylene, tert-decylene, isododecylene, sec-dodecylene, tert-dodecylene, tert-tetradecylene, and tert-pentadecylene. Examples of cyclic alkylene groups having 3 to 18 carbon atoms include cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, cycloheptylene, cyclooctylene, cyclononylene, and cyclodecylene.

[0049] From the viewpoint of suitability for the synthesis of polyamide (S), combinations of alicyclic diamine units and aromatic dicarboxylic acid units, and combinations of alicyclic dicarboxylic acid units and aromatic diamine units are preferred. Furthermore, from the viewpoint of increasing the solubility of polyamide (S) in organic solvents, combinations of meta-system components and para-system components are preferred. Specifically, the following combinations are preferred: • Combination of meta-alicyclic diamine units and para-system aromatic dicarboxylic acid units • Combination of para-alicyclic diamine units and meta-system aromatic dicarboxylic acid units • Combination of meta-alicyclic dicarboxylic acid units and para-system aromatic diamine units • Combination of para-alicyclic dicarboxylic acid units and meta-system aromatic diamine units

[0050] From the viewpoint of improving the synthetic suitability of polyamide (S) and its solubility in organic solvents, the following combinations are more preferable. - Combinations of a meta-alicyclic diamine unit represented by formula (a1) and a para-aromatic dicarboxylic acid unit represented by formula (rc) - Combinations of a para-alicyclic diamine unit represented by formula (a1) and a meta-aromatic dicarboxylic acid unit represented by formula (rc) - Combinations of a meta-alicyclic diamine unit represented by formula (a2) and a para-aromatic dicarboxylic acid unit represented by formula (rc) - Combinations of a para-alicyclic diamine unit represented by formula (a2) and a meta-aromatic dicarboxylic acid unit represented by formula (rc) - Combinations of a meta-alicyclic dicarboxylic acid unit represented by formula (c1) and a para-aromatic diamine unit represented by formula (ra) - Combinations of a para-alicyclic dicarboxylic acid unit represented by formula (c2) and a para-aromatic diamine unit represented by formula (ra)

[0051] From the viewpoint of improving the synthetic suitability of polyamide (S) and its solubility in organic solvents, the following combinations are even more preferable: • A combination of a meta-alicyclic diamine unit represented by formula (a1) and a para-aromatic dicarboxylic acid unit represented by formula (rc) • A combination of a para-alicyclic diamine unit represented by formula (a1) and a meta-aromatic dicarboxylic acid unit represented by formula (rc) • A combination of a meta-alicyclic dicarboxylic acid unit represented by formula (c1) and a para-aromatic diamine unit represented by formula (ra) • A combination of a para-alicyclic dicarboxylic acid unit represented by formula (c1) and a meta-aromatic diamine unit represented by formula (ra)

[0052] From the viewpoint of improving the synthetic suitability and solubility of polyamide (S) in organic solvents, the following combinations are particularly preferred: • A combination of a para-alicyclic diamine unit represented by formula (a1) and a meta-aromatic dicarboxylic acid unit represented by formula (rc) • A combination of a para-alicyclic dicarboxylic acid unit represented by formula (c1) and a meta-aromatic diamine unit represented by formula (ra)

[0053] From the viewpoint of controlling the glass transition temperature of polyamide (S) within an appropriate range, the total proportion of alicyclic structural units to the total amount of alicyclic structural units and aromatic structural units is preferably 25 mol% to 75 mol%, more preferably 35 mol% to 65 mol%, and even more preferably 45 mol% to 55 mol%.

[0054] The polyamide (S) preferably further has at least one linear aliphatic constituent unit selected from the group consisting of linear aliphatic diamine units, linear aliphatic monoaminomonocarboxylic acid units, and linear aliphatic dicarboxylic acid units. Having linear aliphatic constituent units results in a relatively low glass transition temperature for the polyamide (S).

[0055] The total proportion of linear aliphatic units in the total number of constituent units of polyamide (S) is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, even more preferably 20 mol% or more, and even more preferably 25 mol% or more, from the viewpoint of controlling the glass transition temperature of polyamide (S) within an appropriate range. The total proportion of linear aliphatic units in the total number of constituent units of polyamide (S) is preferably 55 mol% or less, more preferably 50 mol% or less, even more preferably 45 mol% or less, and even more preferably 40 mol% or less, from the viewpoint of controlling the glass transition temperature of polyamide (S) within an appropriate range and from the viewpoint of increasing solubility in organic solvents.

[0056] Examples of linear aliphatic constituent units include the linear aliphatic diamine unit represented by formula (e1), the linear aliphatic monoaminomonocarboxylic acid unit represented by formula (e2), and the linear aliphatic dicarboxylic acid unit represented by formula (e3).

[0057]

[0058] In equation (e1), n ​​is an integer between 4 and 18. Preferably, n is an integer between 6 and 16, more preferably between 8 and 14, and even more preferably between 10 and 12.

[0059] In equation (e2), n is an integer between 4 and 18. Preferably, n is an integer between 6 and 16, more preferably between 8 and 14, and even more preferably between 10 and 12.

[0060] In equation (e3), n is an integer between 4 and 18. Preferably, n is an integer between 6 and 16, more preferably between 8 and 14, and even more preferably between 10 and 12.

[0061] The types and composition of the constituent units of polyamide (S) can be determined by nuclear magnetic resonance (NMR) spectroscopy.

[0062] The ends of the polyamide (S) may be sealed or modified with end-capturing agents or molecular weight modifiers used during manufacturing.

[0063] The weight-average molecular weight (Mw) of the polyamide (S) is preferably between 5,000 and 200,000. When the Mw of the polyamide (S) is 5,000 or more, the relatively long polymer chains intertwine with the electrode or porous substrate, making delamination between the porous layer (S) and the electrode or porous substrate less likely. From this viewpoint, the Mw of the polyamide (S) is preferably 5,000 or more, more preferably 10,000 or more, and even more preferably 15,000 or more. When the Mw of the polyamide (S) is 200,000 or less, it swells easily in the electrolyte and the polymer chains have high mobility when heated, so the porous layer (S) adheres easily to the electrode by wet heat pressing. From this viewpoint, the Mw of the polyamide (S) is preferably 200,000 or less, more preferably 150,000 or less, and even more preferably 100,000 or less.

[0064] The weight-average molecular weight of polyamide (S) is measured by gel permeation chromatography (GPC). The eluent is 5 mM / L sodium trifluoroacetate-containing hexafluoroisopropanol, and the standard sample is polymethyl methacrylate.

[0065] The glass transition temperature (Tg) of polyamide (S) is preferably 50°C to 200°C. When the Tg of polyamide (S) is 200°C or lower, the mobility of the polymer chains is high when heated, making it easier for the porous layer (S) to adhere to the electrode by wet heat pressing. From this viewpoint, the Tg of polyamide (S) is preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 160°C or lower. When the Tg of polyamide (S) is 50°C or higher, it does not swell excessively in the electrolyte, and the pores of the porous layer (S) are less likely to become blocked, thus improving the battery's cycle characteristics. From this viewpoint, the Tg of polyamide (S) is preferably 50°C or higher, more preferably 80°C or higher, and even more preferably 100°C or higher.

[0066] The glass transition temperature (°C) of polyamide (S) is determined from the DSC curve obtained by differential scanning calorimetry (DSC). In the DSC curve, the point where the low-temperature baseline intersects with the tangent to the curve of the stepwise transition portion is called intersection (1), and the point where the high-temperature baseline intersects with the tangent to the curve of the stepwise transition portion is called intersection (2). The temperature midway between intersection (1) and intersection (2) is defined as the glass transition temperature.

[0067] The glass transition temperature of polyamide (S) can be controlled by adjusting the type of monomer and copolymerization ratio, using the FOX formula as a guide.

[0068] The polyamide (S) preferably has a melting point of 200°C or higher, or no melting point but a thermal decomposition temperature of 200°C or higher. In other words, the polyamide (S) preferably is a polyamide that does not melt or undergo thermal decomposition in the temperature range below 200°C. The polyamide (S) more preferably has no melting point and a thermal decomposition temperature of 450°C or higher, and even more preferably a thermal decomposition temperature of 500°C or higher.

[0069] The thermal decomposition temperature (°C) of polyamide (S) is the midpoint temperature of the mass change, determined by thermogravimetric analysis according to JIS K7120-1987 "Thermogravimetric Analysis Method for Plastics".

[0070] Polyamide (S) can be polymerized by known interfacial polymerization or solution polymerization methods.

[0071] [Porous layer (S)] In this disclosure, a porous layer means a layer having a large number of micropores inside, with a structure in which the micropores are connected, and through which a gas or liquid can pass from one surface to the other.

[0072] The porous layer (S) is a porous layer containing at least polyamide (S). The porous layer (S) may be a porous layer containing only polyamide (S), or a porous layer containing polyamide (S) and other materials.

[0073] -Polyamide (S)- The porous layer (S) contains polyamide (S). Details of polyamide (S) are as described above.

[0074] The mass percentage of polyamide (S) in the total resin contained in the porous layer (S) 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.

[0075] From the viewpoint of suppressing delamination between the electrode or the porous substrate, the volume ratio of polyamide (S) to the solid content volume of the porous layer (S) is preferably 50% to 100% by volume, more preferably 55% to 100% by volume, and even more preferably 60% to 100% by volume.

[0076] When porous layers (S) are present on both sides of a porous substrate, the type and / or content of polyamide (S) contained in one porous layer (S) and the type and / or content of polyamide (S) contained in the other porous layer (S) may be the same or different.

[0077] -Other Resins- The porous layer (S) may contain resins other than polyamide (S). Examples of other resins include fully aromatic polyamides, polyimides, polyamide-imides, acrylic resins, styrene-butadiene copolymers, butadiene-acrylonitrile resins, cellulose, polyvinylpyrrolidone, polyethers, polysulfones, polyethersulfones, polyketones, and polyetherketones. These resins may be used individually or in combination of two or more.

[0078] The mass percentage of other resins in the total resin contained in the porous layer (S) is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less.

[0079] The porous layer (S) 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.

[0080] The statement that the porous layer (S) is substantially free of fluorine-containing resin means that the mass ratio of fluorine-containing resin to the total mass of the porous layer (S) is 1% by mass or less. The mass ratio of fluorine-containing resin to the total mass of the porous layer (S) 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 porous layer (S) does not contain fluorine-containing resin.

[0081] - Inorganic Particles - The porous layer (S) may contain 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.

[0082] 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.

[0083] The inorganic particles may be inorganic particles whose surface has been modified with a silane coupling agent or the like.

[0084] Inorganic particles may be used individually or in combination of two or more types.

[0085] 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.

[0086] 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 porous layer (S) are preferably plate-shaped particles or non-aggregated primary particles.

[0087] The average primary particle size of the inorganic particles contained in the porous layer (S) is preferably 0.03 μm to 2 μm, more preferably 0.08 μm to 1.5 μm, and even more preferably 0.1 μm to 1 μm, from the viewpoint of forming a good porous structure without aggregation and suppressing delamination between the electrode or porous substrate.

[0088] 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 porous layer (S), or inorganic particles extracted from the porous layer (S). There are no restrictions on the method for extracting inorganic particles from the porous layer (S). For example, this method involves immersing the porous layer (S) peeled from the separator in an organic solvent that dissolves polyamide (S) to dissolve the polyamide (S) and extract the inorganic particles; or heating the porous layer (S) peeled from the separator to about 800°C to remove the polyamide (S) and extract the inorganic particles.

[0089] When the porous layer (S) contains inorganic particles, the volume ratio of inorganic particles to the solid content volume of the porous layer (S) is preferably 50 vol% or less, more preferably 45 vol% or less, and even more preferably 40 vol% or less, from the viewpoint of suppressing delamination between the electrode or porous substrate. When the porous layer (S) contains inorganic particles, the volume ratio of inorganic particles to the solid content volume of the porous layer (S) is preferably 5 vol% or more, more preferably 10 vol% or more, and even more preferably 15 vol% or more, from the viewpoint of forming a good porous structure in the porous layer (S) and the heat resistance of the separator.

[0090] When porous layers (S) are present on both sides of a porous substrate, the type and / or content of inorganic particles contained in one porous layer (S) may be the same as or different from the type and / or content of inorganic particles contained in the other porous layer (S).

[0091] Examples of the form of a porous layer (S) when the porous layer (S) contains inorganic particles include: a porous structure in which inorganic particles are bound or trapped in a two-dimensional or three-dimensional network of fibrils containing polyamide (S); a network-like microporous structure containing polyamide (S) in which inorganic particles are bound or trapped; and a layered structure in which polyamide (S) connects many inorganic particles, forming voids between the inorganic particles.

[0092] -Organic Particles- The porous layer (S) 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, fully aromatic polyamide, 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.

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

[0094] -Other Components- The porous layer (S) may contain additives such as surfactants, dispersants, wetting agents, defoamers, and pH adjusters. Surfactants and dispersants are added, for example, to the coating solution for forming the porous layer (S) to improve dispersibility, coating properties, or storage stability. Wetting agents, defoamers, and pH adjusters are added, for example, to the coating solution for forming the porous layer (S) to improve compatibility with the porous substrate, to suppress air entrapment in the coating solution, or to adjust the pH.

[0095] - Characteristics of the porous layer (S) - When the separator consists only of a porous layer (S), the thickness of the porous layer (S) is preferably 18 μm or less, more preferably 16 μm or less, and even more preferably 14 μm or less, from the viewpoint of the energy density of the battery. When the separator consists only of a porous layer (S), the thickness of the porous layer (S) is preferably 6 μm or more, more preferably 8 μm or more, and even more preferably 10 μm or more, from the viewpoint of mechanical strength.

[0096] When the porous layer (S) is present on both sides of the porous substrate, the thickness of the porous layer (S) is preferably 7 μm or less in total on both sides, more preferably 6 μm or less, and even more preferably 5 μm or less, from the viewpoint of the energy density of the battery. When the porous layer (S) is present on both sides of the porous substrate, the thickness of the porous layer (S) is preferably 1 μm or more in total on both sides, more preferably 2 μm or more, and even more preferably 3 μm or more, from the viewpoint of adhesion to the electrodes.

[0097] When the porous layer (S) is present on only one side of the porous substrate, the thickness of the porous layer (S) is preferably 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less, from the viewpoint of the energy density of the battery. When the porous layer (S) is present on only one side of the porous substrate, the thickness of the porous layer (S) is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more, from the viewpoint of adhesion to the electrode.

[0098] When a porous layer (S) is located on a porous substrate, the thickness of the porous layer (S) is obtained by subtracting the thickness of the porous substrate from the thickness of the flat film formed by laminating the porous layer (S) onto the porous substrate. The thickness of the flat film is determined by measuring the thickness at 20 points within a 10 cm square area using a contact-type thickness gauge and averaging these measurements.

[0099] If the separator consists only of a porous layer (S), the mass per unit area (i.e., basis weight) of the porous layer (S) is 3 g / m². ２ ~20g / m ２ Preferably, it is 5 g / m ２ ~18g / m ２ More preferably, 8 g / m ２ ~15g / m ２ That is even more preferable.

[0100] When a porous layer (S) is present on both sides of a porous substrate, the mass per unit area (i.e., basis weight) of the porous layer (S) is 1 g / m² in total for both sides. ２ ~8g / m ２ Preferably, it is 2 g / m ２ ~7g / m ２ More preferably, 3 g / m ２ ~6g / m ２ That is even more preferable.

[0101] When the porous layer (S) is present on only one side of the porous substrate, the mass per unit area (i.e., basis weight) of the porous layer (S) is 1 g / m². ２ ~6g / m ２ Preferably, it is 2 g / m ２ ~5g / m ２ More preferably, 3 g / m ２ ~4g / m ２ That is even more preferable.

[0102] When a porous layer (S) is located on a porous substrate, the mass per unit area (i.e., basis weight) of the porous layer (S) is the value obtained by subtracting the basis weight of the porous substrate from the basis weight of the flat film formed by laminating the porous layer (S) onto the porous substrate. The basis weight of the flat film is determined by cutting a 20 cm x 20 cm section, measuring its mass, and dividing the mass by the area.

[0103] From the viewpoint of ion permeability, the porosity of the porous layer (S) is preferably 20% to 70%. The porosity ε (%) of the porous layer (S) is determined by the following formula.

[0104]

[0105] Here, for the constituent material 1, constituent material 2, constituent material 3, ..., constituent material n of the porous layer (S), 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 porous layer (S) is t (cm).

[0106] [Porous Substrates] In this disclosure, a porous substrate means a substrate having voids or cavities inside. Examples of such substrates include microporous membranes; porous sheets made of fibrous material such as nonwoven fabrics and paper; and composite porous sheets obtained by laminating one or more other porous layers onto these microporous membranes or porous sheets.

[0107] The material of the porous substrate is preferably an electrically insulating material.

[0108] 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.

[0109] 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.

[0110] As a porous substrate, from the viewpoint of providing a shutdown function to the porous substrate, a porous substrate containing a polyolefin-containing microporous membrane (hereinafter referred to as "polyolefin microporous membrane") is preferred. Examples of porous substrates containing a polyolefin microporous membrane include a porous substrate consisting only of a polyolefin microporous membrane (i.e., a polyolefin microporous membrane) and a composite porous substrate (details will be described later) in which an inorganic particle layer is arranged on one or both sides of the polyolefin microporous membrane.

[0111] 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.

[0112] 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.

[0113] From the viewpoint of possessing heat resistance that prevents easy rupture when exposed to high temperatures, polyolefin microporous membranes containing polypropylene are preferred.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] Examples of porous sheets made of fibrous materials include nonwoven fabrics and porous sheets made of paper. Examples of fibrous materials include polyester such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; heat-resistant resins such as fully aromatic polyamides, polyamide-imides, polyimides, polyethersulfones, polysulfones, polyetherketones, and polyetherimides; and cellulose.

[0118] 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 thermal 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.

[0119] From the viewpoint of thermal dimensional stability and impact resistance, a composite porous substrate is preferred, which is a microporous membrane or porous sheet with an inorganic particle layer arranged on one or both sides. The inorganic particle layer is a porous layer. In this disclosure, "porous substrate" is a term that includes "composite porous substrate".

[0120] An example of an embodiment of a composite porous substrate is a composite porous substrate comprising a polyolefin microporous membrane and an inorganic particle layer disposed on one or both sides of the polyolefin microporous membrane. The inorganic particle layer is preferably a porous layer containing inorganic particles and a binder resin.

[0121] From the viewpoint of improving the heat resistance of the battery, the mass ratio of inorganic particles to the total mass of the inorganic particle layer is preferably 90% by mass or more, more preferably 92% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more.

[0122] Examples of inorganic particles included in the inorganic particle layer include metal oxide particles (silica, alumina, boehmite, titania, zirconia, magnesium oxide, barium oxide, etc.), metal hydroxide particles (magnesium hydroxide, aluminum hydroxide, calcium hydroxide, chromium hydroxide, zirconium hydroxide, cerium hydroxide, nickel hydroxide, boron hydroxide, etc.), metal sulfate particles (barium sulfate, calcium sulfate, etc.), metal carbonate particles (calcium carbonate, magnesium carbonate, barium carbonate, etc.), metal nitride particles (boron nitride, aluminum nitride, etc.), and clay mineral particles (calcium silicate, talc, etc.). The inorganic particles may also be inorganic particles whose surfaces have been modified with a silane coupling agent or the like.

[0123] The inorganic particle layer preferably also contains a binder resin that binds the inorganic particles together. The binder resin may be a heat-resistant resin or a non-heat-resistant resin. Examples of heat-resistant resins include all-aromatic polyamides, polyamide-imides, polyimides, polyethersulfones, polysulfones, polyetherketones, and polyetherimides. Examples of non-heat-resistant resins include butadiene polymers (e.g., butadiene homopolymers, styrene-butadiene copolymers) and acrylic resins (e.g., acrylic monomer homopolymers or copolymers, copolymers of acrylic monomers and styrene monomers).

[0124] The inorganic particle layer is a layer that is substantially free of polyamide (S). The inorganic particle layer being substantially free of polyamide (S) means that the mass ratio of polyamide (S) to the total mass of the inorganic particle layer is 1% by mass or less. Preferably, the mass ratio of polyamide (S) to the total mass of the inorganic particle layer is 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 inorganic particle layer does not contain polyamide (S).

[0125] One method for arranging an inorganic particle layer on one or both sides of a polyolefin microporous membrane is to coat one or both sides of the polyolefin microporous membrane with a coating solution containing inorganic particles and a binder resin.

[0126] Various surface treatments may be applied to the surface of the porous substrate to improve wettability with the coating liquid for forming the porous layer (S), provided that the properties of the porous substrate are not impaired. Examples of surface treatments include corona treatment, plasma treatment, flame treatment, and ultraviolet irradiation treatment.

[0127] - Characteristics of Porous Substrate - From the viewpoint of mechanical strength, the thickness of the porous substrate is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. From the viewpoint of increasing the energy density of the battery, the thickness of the porous substrate is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. The thickness of the porous substrate is determined by measuring the thickness at 20 points within a 10 cm square area using a contact-type thickness gauge and averaging these measurements.

[0128] From the viewpoint of suppressing internal short circuits in the battery, the air permeability of the porous substrate is preferably 80 seconds / 100 mL or more, more preferably 90 seconds / 100 mL or more, and even more preferably 100 seconds / 100 mL or more. From the viewpoint of excellent electrolyte permeability and ion permeability, the air permeability of the porous substrate is preferably 200 seconds / 100 mL or less, more preferably 180 seconds / 100 mL or less, and even more preferably 160 seconds / 100 mL or less. The air permeability of the porous substrate is the value measured using a Gurley densometer in accordance with JIS P8117:2009 "Paper and cardboard - Test methods for air permeability and air permeability resistance (intermediate region) - Gurley method".

[0129] When the porous substrate is a porous substrate consisting only of a polyolefin microporous membrane (i.e., a polyolefin microporous membrane), the air permeability is preferably 50 seconds / 100 mL to 180 seconds / 100 mL, more preferably 70 seconds / 100 mL to 160 seconds / 100 mL or less, and even more preferably 90 seconds / 100 mL to 140 seconds / 100 mL. When the porous substrate is a composite porous substrate in which an inorganic particle layer is arranged on one or both sides of a polyolefin microporous membrane, the air permeability is preferably 90 seconds / 100 mL to 220 seconds / 100 mL, more preferably 100 seconds / 100 mL to 210 seconds / 100 mL or less, and even more preferably 110 seconds / 100 mL to 200 seconds / 100 mL.

[0130] From the viewpoint 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 calculated by the following formula: ε = {1 - Ws / (ds・t)} × 100 where Ws is the mass per unit area (g / m²) of the porous substrate. ２ ), ds is the true density (g / cm³) of the porous substrate. ３ ), t is the thickness of the porous substrate (μm).

[0131] The average pore size of the porous substrate is preferably 50 nm or more, more preferably 60 nm or more, and even more preferably 70 nm or more, from the viewpoint of excellent electrolyte permeability and ion permeability. The average pore size of the porous substrate is preferably 140 nm or less, more preferably 130 nm or less, and even more preferably 120 nm or less, from the viewpoint of suppressing internal short circuits in the battery. The average pore size of the porous substrate is a value measured using a palm porometer in accordance with ASTM E1294-89.

[0132] [Separator Characteristics] From the viewpoint of mechanical strength, the thickness of the separator is preferably 6 μm or more, more preferably 8 μm or more, and even more preferably 10 μm or more. From the viewpoint of the energy density of the battery, the thickness of the separator is preferably 18 μm or less, more preferably 16 μm or less, and even more preferably 14 μm or less. The thickness of the separator is determined by measuring the thickness at 20 points within a 10 cm square area using a contact-type thickness gauge and averaging these measurements.

[0133] From the viewpoint of excellent electrolyte permeability and ion permeability, the average pore size of the separator is preferably 50 nm or more, more preferably 70 nm or more, and even more preferably 90 nm or more. From the viewpoint of suppressing internal short circuits in the battery, the average pore size of the separator is preferably 250 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less.

[0134] The average pore diameter (nm) of the separator is calculated using the following formula, assuming that all pores are cylindrical: X = 4V / S, where X is the average pore diameter of the separator and V is the pore diameter per meter of the separator. ２ This is the volume of voids per unit area, where S is the volume of 1 m of separator. ２ This is the surface area of ​​the void per unit area. Separator 1m ２ The void volume V per unit is calculated from the porosity of the separator. The porosity ε (%) of the separator is determined by the following formula.

[0135]

[0136] Here, for the constituent materials 1, 2, 3, ..., n of the separator, 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).

[0137] 1m Separator ２ The surface area S of the void is determined by the following method. First, the specific surface area (m²) of the separator is calculated. ２ The specific surface area (m²) is calculated from the amount of nitrogen gas adsorbed by applying the BET formula to the nitrogen gas adsorption method. ２ The mass per unit area of ​​the separator (g / m²) ２ ) multiplies by 1m ２ Calculate the surface area of ​​each void.

[0138] 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 150 seconds / 100 mL or more, and even more preferably 180 seconds / 100 mL or more. From the viewpoint of ion permeability, the air permeability of the separator is preferably 1000 seconds / 100 mL or less, more preferably 800 seconds / 100 mL or less, and even more preferably 500 seconds / 100 mL or less. The air permeability of the separator is the value measured using a Gurley densometer in accordance with JIS P8117:2009 "Paper and cardboard - Test methods for air permeability and air permeability resistance (intermediate region) - Gurley method".

[0139] [Method for Manufacturing Separators] The separators of this disclosure can be manufactured, for example, by forming a porous layer (S) 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 a coating layer in a solidifying liquid, and a dry coating method is a method of solidifying a coating layer by drying it. An example of an embodiment of the wet coating method is described below. Hereinafter, in the description of the method for manufacturing separators, the porous layer (S) will be simply referred to as the "porous layer".

[0140] The wet coating method involves applying a coating solution containing polyamide (S) onto a porous substrate, immersing it in a solidifying solution to solidify the coating layer, and then removing it from the solidifying solution, washing it with water, and drying it.

[0141] The coating solution for forming a porous layer is prepared by dissolving polyamide (S) in a solvent. Inorganic particles and other components are dispersed or dissolved in the coating solution as needed.

[0142] The solvent used in preparing the coating solution includes a solvent that dissolves polyamide (S) (hereinafter also referred to as a "good solvent"). Examples of good solvents include polar amide solvents such as N-methyl-2-pyrrolidone, dimethylacetamide, and dimethylformamide.

[0143] The solvent used in preparing the coating solution may contain a phase-separating agent to induce phase separation, from the viewpoint of forming a porous layer with a good porous structure. Therefore, the solvent used in preparing the 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.

[0144] When the solvent used to prepare the 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.

[0145] The polyamide concentration of the coating solution is preferably 1% to 20% by mass, from the viewpoint of forming a good porous structure. The inorganic particle concentration of the coating solution is preferably 0.5% to 50% by mass, from the viewpoint of forming a good porous structure.

[0146] The coating solution may contain surfactants, dispersants, wetting agents, defoamers, pH adjusters, etc. These additives may remain in the 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.

[0147] Methods for applying coating liquid to porous substrates include Meyer bar, die coater, reverse roll coater, roll coater, and gravure coater. When forming a 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.

[0148] The coating layer is solidified by immersing the porous substrate on which the coating layer is formed in a solidifying solution, thereby inducing phase separation in the coating layer and solidifying the resin. This results in a laminate consisting of a porous substrate and a porous layer.

[0149] The solidification solution generally contains the good solvent and phase separating agent used in the preparation of the coating solution, along with water. From a production standpoint, it is preferable that the mixing ratio of the good solvent and the phase separating agent match the mixing ratio of the mixed solvent used in the preparation of the coating solution. From the viewpoint of forming a porous structure and productivity, the water content in the solidification solution is preferably 40% to 90% by mass. The temperature of the solidification solution is, for example, 20°C to 50°C.

[0150] After the coating layer is solidified in the solidification solution, the laminate is removed from the solidification solution and washed with water. The solidification solution is removed from the laminate by washing with water. Further water is removed from the laminate by drying. Washing with water is performed, for example, by transporting the laminate in a water bath. Drying is performed, for example, by transporting the laminate in a high-temperature environment, by blowing air on the laminate, or by bringing the laminate into contact with a heat roll. The drying temperature is preferably 40°C to 80°C.

[0151] The separator of this disclosure may also be manufactured by a dry coating method. The dry coating method is a method of forming a porous layer on a porous substrate by coating a coating liquid onto a porous substrate and drying the coating layer to remove the solvent by evaporation.

[0152] The separator of this disclosure can also be manufactured by forming a porous layer (S) on a release sheet using the wet coating method or dry coating method described above, and then peeling the release sheet from the porous layer (S). In this case, a separator consisting only of the porous layer (S) is manufactured.

[0153] <Non-aqueous secondary battery> The non-aqueous secondary battery of this disclosure comprises a positive electrode, a negative electrode, a separator of this disclosure, and a non-aqueous electrolyte. Examples of non-aqueous secondary batteries of this disclosure include a non-aqueous secondary battery that obtains electromotive force by doping and dedoping of lithium ions, and a non-aqueous secondary battery that obtains electromotive force by dissolving and depositing metallic lithium. Doping means absorption, support, adsorption, or insertion, and refers to the phenomenon in which lithium ions enter the active material of the electrode.

[0154] 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 particularly suitable for lithium-ion secondary batteries.

[0155] The non-aqueous secondary battery of this disclosure exhibits excellent cycle characteristics because the separator of this disclosure has excellent adhesion to the electrode by wet heat pressing, resulting in smooth ion movement at the interface between the separator and the electrode. The non-aqueous secondary battery of this disclosure is less prone to internal short circuits because the separator of this disclosure has excellent adhesion to the electrode by wet heat pressing.

[0156] 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.

[0157] An example of a positive electrode embodiment is a configuration 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. Examples of lithium-containing transition metal oxides include LiCoO２ , 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 thereof include. Examples of the binder resin include polyvinylidene fluoride-based resins, styrene-butadiene copolymers, and the like. Examples of the conductive auxiliary agent include carbon materials such as acetylene black, Ketjen black, graphite powder, and ultrafine carbon fibers. Examples of the current collector include aluminum foil, titanium foil, stainless steel foil and the like having a thickness of 5 μm to 20 μm.

[0158] As an example of an embodiment of the negative electrode, there may be mentioned a configuration in which an active material layer containing a negative electrode active material and a binder resin is disposed on a current collector. The active material layer may further contain a conductive auxiliary agent. Examples of the negative electrode active material include materials capable of electrochemically intercalating lithium ions. Examples of such materials include carbon materials; alloys of lithium with silicon, tin, aluminum and the like; Wood's metal; and the like. Examples of the binder resin include polyvinylidene fluoride-based resins, styrene-butadiene copolymers, and the like. Examples of the conductive auxiliary agent include carbon materials such as acetylene black, Ketjen black, graphite powder, and ultrafine carbon fibers. Examples of the current collector include copper foil, nickel foil, stainless steel foil and the like having a thickness of 5 μm to 20 μm. Instead of the above negative electrode, metallic lithium foil may be used as the negative electrode.

[0159] The electrolytic solution is preferably a solution obtained by dissolving a lithium salt in a non-aqueous solvent. Examples of the lithium salt include LiPF ６ , LiBF ４ , LiClO ４Examples 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. Non-aqueous solvents may be used individually or in mixtures of two or more.

[0160] As the electrolyte, a solution is preferred in which cyclic carbonate and 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.

[0161] 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.

[0162] Examples of the manufacturing method for a non-aqueous secondary battery according to this disclosure include a manufacturing method having the following steps (1) to (3).

[0163] Process (1): A laminate is manufactured with a separator placed between the positive and negative electrodes. Process (2): The laminate is placed in an outer casing and an electrolyte is injected into it. Process (3): The laminate is wet-heat-pressed from above the outer casing to bond the electrodes and separator and seal the outer casing.

[0164] In step (1), 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 this 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 this order and wound in the length direction.

[0165] In step (3), the press temperature of the wet heat press is preferably 60°C to 100°C, and more preferably 70°C to 90°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.

[0166] 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.

[0167] In the following descriptions, synthesis, processing, and manufacturing were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0168] <Measurement Methods and Evaluation Methods> The measurement and evaluation methods applied to the examples and comparative examples are as follows.

[0169] [Thickness of Porous Substrate and Separator] The thickness of the porous substrate and separator was determined by measuring the thickness at 20 points within a 10 cm square area using a contact-type thickness gauge (LITEMATIC VL-50S, Mitutoyo Corporation) and averaging the results. A spherical measuring probe with a radius of 10 mm (Mitutoyo Corporation) was used as the measuring terminal, and a load of 0.19 N was applied during measurement.

[0170] [Air permeability of porous substrates and separators] The air permeability (seconds / 100 mL) of porous substrates and separators was measured using a G-B2C Gurley densometer (Toyo Seiki Seisakusho Co., Ltd.) in accordance with JIS P8117:2009 "Paper and cardboard - Test methods for air permeability and air permeability resistance (intermediate region) - Gurley method".

[0171] [Polyamide Constituent Units - Examples 1-4, Comparative Example 1] Polyamide used for forming porous layers was used as the sample. Powdered polyamide was added to a mixed solvent of deuterated trifluoroacetic acid and deuterated formic acid (volume ratio 1:1) and dissolved at 25°C. NMR was performed under the following conditions to identify the types and composition of the polyamide constituent units. • NMR apparatus: JNM-ECA600, JEOL Ltd. • Solution probe: ROYAL probe, JEOL Ltd. • Measurement temperature: 25°C １ H-NMR spectrum: 600 MHz, observation width 15 ppm, number of points 32 k, pulse repetition time 4 seconds

[0172] [Polyamide Constituent Units - Comparative Examples 2-3] Polyamide used for forming porous layers was used as the sample. Powdered polyamide was added to deuterated dimethyl sulfoxide with lithium chloride and dissolved at 100°C. NMR was performed under the following conditions to identify the types and composition of the polyamide constituent units. • NMR apparatus: JNM-ECA600, JEOL Ltd. • Solution probe: ROYAL probe, JEOL Ltd. • Measurement temperature: 100°C １ H-NMR spectrum: 600 MHz, observation width 15 ppm, number of points 32 k, pulse repetition time 4 seconds

[0173] [Weight-average molecular weight of polyamides - Examples 1-4, Comparative Example 1 -] Polyamides used to form porous layers were used as samples, and GPC was performed under the following conditions to measure the weight-average molecular weight (Mw). • Eluent: 5 mM / L sodium trifluoroacetate-containing hexafluoroisopropanol • Standard sample: Polymethyl methacrylate (EasiVial PM, Agilent Technologies, Inc.) • GPC instrument: HPLC-8320GPC EcoSEC, Tosoh Corporation • Column: TSK-gel SuperHM-M x 2 • Flow rate: 0.3 mL / min • Temperature: 40°C

[0174] [Weight-average molecular weight of polyamides - Comparative Examples 2-3 -] Polyamides used to form porous layers were used as samples, and GPC was performed under the following conditions to measure the weight-average molecular weight (Mw). • Eluent: 10 mMol / L LiCl-containing dimethylformamide • Standard sample: Polystyrene • GPC apparatus: CBM-40, SPD-20A, CTO-20A, SIL-20A, LC-20AD, DGU-20A, Shimadzu Corporation • Column: Shodex KD-806, KD-804, KD-802, Resonaq Corporation • Flow rate: 10 mL / min • Temperature: 40°C

[0175] [Glass Transition Temperature of Polyamide] Differential scanning calorimetry (DSC) was performed on polyamide used for forming porous layers as a sample. A Q200 Differential Scanning Calorimeter (TA Instruments) was used as the DSC instrument. 5 mg of sample was used. The sample was heated from -65°C to 200°C at a heating rate of 5°C / min, then quenched and reheated at the same heating rate to obtain a DSC curve. In the DSC curve, the intersection point (1) between the baseline on the low-temperature side and the tangent to the curve of the stepwise transition portion, and the intersection point (2) between the baseline on the high-temperature side 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).

[0176] [Solubility of Polyamide in DMAc] Polyamide used for forming porous layers was subjected to the following treatment. 20 g of powdered polyamide was added to 100 g of dimethylacetamide (DMAc) at a liquid temperature of 25°C, and the mixture was gently stirred for 1 hour using a magnetic stirring bar and a magnetic stirrer to prepare a polyamide solution. If insoluble matter was present, additional DMAc was added until the insoluble matter was eliminated. Solubility (mass%) was calculated using the following formula, and the solubility of polyamide in DMAc was classified as follows based on the solubility. Formula: Solubility (mass%) = 20 g of polyamide / (20 g of polyamide + 100 g of DMAc + mass of additional DMAc) × 100

[0177] A: Solubility of 10% by mass or more B: Solubility of less than 10% by mass, but 5% by mass or more C: Solubility of less than 5% by mass

[0178] [Average Primary Particle Size of Inorganic Particles] Inorganic particles used to form the porous layer were observed using a scanning electron microscope (SEM) to determine the average primary particle size. The major axis of 100 randomly selected inorganic 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).

[0179] [Wet Adhesion to Electrodes] A slurry for the positive electrode was prepared by stirring and mixing 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 in a double-arm mixer. 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.

[0180] 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 styrene-butadiene copolymer modified material, 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.

[0181] 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.

[0182] The laminate is inserted into an aluminum laminate film pack, and the electrolyte (1 mol / L LiBF) is added. ４The electrolyte (ethylene carbonate:propylene carbonate:diethyl carbonate [mass ratio 1:1:1]) was injected to impregnate the laminate. Next, the laminate, still in its pack, was heat-pressed in the direction of the laminate using a hot press (wet heat press) to bond the electrodes (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 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.

[0183] 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.

[0184] [Battery Cycle Characteristics] One hundred test secondary batteries, as described below, were prepared. The batteries underwent 100 charge-discharge cycles. Charging was performed using a constant current constant voltage charge of 1C / 4.2V, and discharging was performed using a constant current discharge with a cutoff of 1C / 2.75V. The capacity retention rate (%) was calculated by dividing the discharge capacity at the 100th cycle by the initial discharge capacity. Furthermore, the average value for all 100 batteries was calculated, and the average capacity retention rate was classified as follows.

[0185] A: 90% or more B: Less than 90%, 80% or more C: Less than 80%

[0186] <Manufacturing of Separators and Batteries> [Example 1] - Manufacturing of Separators - A mixed solvent was prepared by mixing dimethylacetamide (DMAc) and tripropylene glycol (TPG) in a mass ratio of 95:5. Polyamide was added to the mixed solvent and stirred to prepare coating solution (1). The polyamide concentration of coating solution (1) was set to 5% by mass. The constituent units and physical properties of the polyamide are shown in Table 1.

[0187] A pair of Meyer bars were used to apply equal amounts of coating solution (1) to both sides of the polyethylene microporous membrane. The coating amounts are shown in Table 1. 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. In this way, a separator having porous layers on both sides of the polyethylene microporous membrane was obtained. The thickness and air permeability of the polyethylene microporous membrane are shown in Table 1.

[0188] - Manufacturing 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.

[0189] - Manufacturing 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.

[0190] -Battery Manufacturing- 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 alternately arranged with a separator in between, creating a laminate consisting of 3 positive electrodes, 3 negative electrodes, and 5 separators. The laminate was placed in an aluminum laminate film pack, and electrolyte (1 mol / L LiBF) was placed inside the pack. ４ Ethylene carbonate:propylene carbonate (mass ratio 1:1) was injected, and the electrolyte was impregnated into the laminate. Then the pack was sealed. In this way, a non-aqueous secondary battery for testing was obtained.

[0191] [Example 2] A separator and a non-aqueous secondary battery were manufactured in the same manner as in Example 1, except that coating liquid (1) was replaced with coating liquid (2) described below.

[0192] -Coating Solution (2)- A mixed solvent was prepared by mixing DMAc and TPG in a mass ratio of 95:5. Polyamide and magnesium hydroxide particles (average primary particle size 0.8 μm) were added to the mixed solvent and stirred to prepare coating solution (2). The polyamide concentration of coating solution (2) was set to 5% by mass. The mixing amounts of magnesium hydroxide particles and polyamide were adjusted so that the volume ratio of magnesium hydroxide particles to the solid content volume of the porous layer was 35% by volume.

[0193] [Example 3] A separator and a non-aqueous secondary battery were manufactured in the same manner as in Example 1, except that the polyamide was replaced with a different polyamide. The constituent units and physical properties of the polyamide are shown in Table 1.

[0194] [Example 4] A separator and a non-aqueous secondary battery were manufactured in the same manner as in Example 1, except that the porous substrate was changed from a polyethylene microporous membrane to a composite porous substrate. The composite porous substrate is a polyethylene microporous membrane with a thickness of 8 μm and inorganic particle layers on both sides. The inorganic particle layer contains γ-alumina (average primary particle size 0.01 μm) and styrene-butadiene rubber, with a γ-alumina content of 97% by mass and a thickness of 1 μm per side. The thickness and air permeability of the composite porous substrate are shown in Table 1.

[0195] [Comparative Example 1] An attempt was made to manufacture a separator in the same manner as in Example 1, except that the polyamide was changed to a different polyamide. However, the solubility of the powdered polyamide in organic solvents was extremely low, and therefore it was not possible to prepare a coating solution with an appropriate polymer concentration, and thus it was not possible to manufacture a separator or a non-aqueous secondary battery.

[0196] [Comparative Example 2] A separator and a non-aqueous secondary battery were manufactured in the same manner as in Example 1, except that the polyamide was replaced with a different polyamide. The constituent units and physical properties of the polyamide are shown in Table 1.

[0197] [Comparative Example 3] A separator and a non-aqueous secondary battery were manufactured in the same manner as in Example 2, except that the polyamide was replaced with a different polyamide. The constituent units and physical properties of the polyamide are shown in Table 1.

[0198] Table 1 shows the composition of the porous substrate and porous layer, and Table 2 shows the physical properties and evaluation results of the separator. The coating amount of the porous layer listed in Table 1 is the total for both sides of the porous substrate. The abbreviations in Table 1 have the following meanings: PE: polyethylene, Me-PACM: constituent unit represented by the following structural formula, MPDA: constituent unit represented by the following structural formula, IA: constituent unit represented by the following structural formula, PA12: constituent unit represented by the following structural formula

[0199]

[0200]

[0201]

[0202] In the wet adhesion test, in Comparative Examples 2 and 3, the separator peeled off from the electrode immediately after the start of the test, and the value displayed on the testing machine was 0.00. In the wet adhesion test, in Examples 1 to 4, the porous layer (S) did not peel off from the electrode, but the porous layer (S) peeled off from the porous substrate of the separator. Therefore, the adhesive strength (N / 15mm) between the electrode and the porous layer (S) can be said to be higher than the value listed in Table 2.

[0203] 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.

[0204] The disclosure of Japanese application number 2025-028354, filed on 25 February 2025, is incorporated herein by reference in its entirety.

Claims

1. A separator for a non-aqueous secondary battery, comprising a porous layer containing a polyamide having at least one of an alicyclic diamine unit and an alicyclic dicarboxylic acid unit and at least one of an aromatic diamine unit and an aromatic dicarboxylic acid unit.

2. The separator for a non-aqueous secondary battery according to claim 1, wherein the polyamide has at least one selected from the group consisting of an alicyclic diamine unit represented by the following formula (a1) and an alicyclic diamine unit represented by the following formula (a2), and / or at least one selected from the group consisting of an alicyclic dicarboxylic acid unit represented by the following formula (c1) and an alicyclic dicarboxylic acid unit represented by the following formula (c2). In the formula (a1), n １ is an integer of 0 to 10, n １ R groups １ are each independently an alkyl group having 1 to 6 carbon atoms, n ２ is an integer of 0 to 10, n ２ R groups ２ are each independently an alkyl group having 1 to 6 carbon atoms, X is a single bond, an oxygen atom or a divalent hydrocarbon group, and the two -NH- groups are each independently at the meta position or para position of X. In the formula (a2), n １ is an integer of 0 to 10, n １ R groups １ are each independently an alkyl group having 1 to 6 carbon atoms, and the two -NH- groups are at the meta position or para position relative to each other. In the formula (c1), n １ is an integer of 0 to 10, n １ R groups １ are each independently an alkyl group having 1 to 6 carbon atoms, n ２ is an integer of 0 to 10, n ２ R groups ２ are each independently an alkyl group having 1 to 6 carbon atoms, X is a single bond, an oxygen atom or a divalent hydrocarbon group, and the two -CO- groups are each independently at the meta position or para position of X. In the formula (c2), n １ is an integer of 0 to 10, n １ R groups １ are each independently an alkyl group having 1 to 6 carbon atoms, and the two -CO- groups are at the meta position or para position relative to each other.

3. The separator for a non-aqueous secondary battery according to claim 1, wherein the polyamide has an aromatic diamine unit represented by the following formula (ra) and / or an aromatic dicarboxylic acid unit represented by the following formula (rc). In equation (ra), n １ n is an integer between 0 and 4, and １ Individual R １ Each of these is an alkyl group having 1 to 6 carbon atoms, and the two -NH- atoms are at the meta or para positions of each other. In formula (rc), n １ n is an integer between 0 and 4, and １ Individual R １ Each of these is an alkyl group having 1 to 6 carbon atoms, and the two -CO- atoms are in the meta or para positions relative to each other.

4. The separator for a non-aqueous secondary battery according to claim 1, wherein the polyamide further comprises at least one linear aliphatic constituent unit selected from the group consisting of linear aliphatic diamine units, linear aliphatic monoaminomonocarboxylic acid units, and linear aliphatic dicarboxylic acid units.

5. The separator for a non-aqueous secondary battery according to claim 4, wherein the total proportion of the linear aliphatic constituent units to the total constituent units of the polyamide is 5 mol% to 50 mol%.

6. The separator for a non-aqueous secondary battery according to claim 1, wherein the glass transition temperature of the polyamide is 50°C to 200°C.

7. The separator for a non-aqueous secondary battery according to claim 1, wherein the porous layer further contains inorganic particles.

8. The separator for a non-aqueous secondary battery according to claim 1, wherein the air permeability is 100 seconds / 100 mL to 1000 seconds / 100 mL.

9. The separator for a non-aqueous secondary battery according to claim 1, wherein the porous layer substantially does not contain a fluorine-containing resin.

10. A separator for a non-aqueous secondary battery according to claim 1, comprising a porous substrate and the porous layer disposed on one or both sides of the porous substrate.

11. The separator for a non-aqueous secondary battery according to claim 10, wherein the porous substrate comprises a polyolefin microporous membrane and an inorganic particle layer containing inorganic particles and a binder resin disposed on one or both sides of the polyolefin microporous membrane.

12. A non-aqueous secondary battery comprising a positive electrode, a negative electrode, a separator for a non-aqueous secondary battery according to any one of claims 1 to 11 disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte.

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