Non-aqueous electrolyte secondary battery shrapnel, non-aqueous electrolyte secondary battery components, non-aqueous electrolyte secondary battery

Abstract

To provide a separator with excellent heat resistance and battery performance for a non-aqueous electrolyte battery.SOLUTION: The separator for a non-aqueous electrolyte secondary battery includes a mixed layer containing a porous substrate and a heat-resistant resin. The porous substrate has a polyolefin porous film. A weight ratio (W1 / W0) of W1, the weight of the heat-resistant resin, to W0, the weight of the porous substrate, in the mixed layer is 0.07 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a separator for a non-aqueous electrolyte secondary battery, a component for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery. [Background technology]

[0002] Non-aqueous electrolyte secondary batteries, such as lithium-ion batteries, are currently widely used as batteries in devices such as personal computers, mobile phones, and portable information terminals, as well as in automotive batteries.

[0003] As a separator for the aforementioned non-aqueous electrolyte secondary battery, a separator is known in which a portion of the resin constituting the heat-resistant layer laminated on a porous film mainly composed of polyolefin is impregnated into a portion of the porous film to improve heat resistance (for example, Patent Documents 1 to 3). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2013-511818 [Patent Document 2] Japanese Patent Publication No. 2013-46998 [Patent Document 3] International Publication No. 2019 / 107219 Brochure [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in the conventional separator, the degree to which the resin constituting the heat-resistant layer penetrates the porous film is suppressed in order to ensure good shutdown characteristics and prevent an excessive increase in resistance. As a result, the separator has problems with insufficient heat resistance, especially in regions with low basis weight, and there is room for improvement in terms of safety. Furthermore, the conventional separator also has room for improvement in battery performance, such as ion permeability and coin cell resistance maintenance.

[0006] One aspect of the present invention aims to provide a separator for non-aqueous electrolyte secondary batteries that has superior heat resistance compared to conventional separators, as well as superior battery performance such as ion permeability and coin cell resistance maintenance. [Means for solving the problem]

[0007] The inventors have discovered that the heat resistance of the separator can be further improved by increasing the degree of penetration of the resin constituting the heat-resistant layer into the porous film. Furthermore, the inventors have also discovered that the ion permeability and resistance, which were predicted to deteriorate significantly, did not deteriorate as much as predicted, leading to the present invention.

[0008] One aspect of the present invention includes the inventions described in [1] to

[10] below. [1] A porous substrate comprising a porous film mainly composed of a polyolefin resin and a mixed layer containing a heat-resistant resin, A separator for a non-aqueous electrolyte secondary battery, wherein the weight ratio (W1 / W0) of the weight W1 of the heat-resistant resin in the mixed layer to the weight W0 of the porous substrate is 0.07 or more. [2] A separator for a non-aqueous electrolyte secondary battery as described in [1], wherein the shutdown temperature is 150°C or higher. [3] A separator for a non-aqueous electrolyte secondary battery according to [1] or [2], wherein a heat-resistant layer containing the heat-resistant resin is laminated on the mixed layer. [4] The heat-resistant layer further comprises a filler, as described in [3], for a non-aqueous electrolyte secondary battery separator. [5] The separator for a non-aqueous electrolyte secondary battery according to [4], wherein the content of the filler is 20% by weight or more and 90% by weight or less with respect to the total weight of the heat-resistant layer. [6] The heat-resistant layer is a separator for a non-aqueous electrolyte secondary battery according to any one of [3] to [5], wherein the value expressed by the following formula (1) is 5% or more. Brightness X1 (%) - Brightness X2 (%) ... Formula (1) (Here, the luminance X1 is the average value of the luminance at a point from the interface of the heat-resistant layer in contact with the mixed layer to a depth of 20% of the thickness of the heat-resistant layer. The luminance X2 is the average value of the luminance at a point from the outermost surface of the heat-resistant layer to a depth of 20% of the thickness of the heat-resistant layer. (The average value of the luminance of the entire heat-resistant layer is 100%). [7] The separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [6], having an air permeability of 500 sec / 100 mL or less. [8] The separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [7], wherein the heat-resistant resin is an aramid resin. [9] A member for a non-aqueous electrolyte secondary battery, in which a positive electrode, the separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [8], and a negative electrode are arranged in this order.

[10] A non-aqueous electrolyte secondary battery including the separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [8].

Advantages of the Invention

[0009] The separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention has better heat resistance than conventional separators, and also has excellent battery performance such as ion permeability and coin cell resistance maintenance.

Brief Description of the Drawings

[0010] [Figure 1] It is a schematic diagram showing an outline of the structure of an example of a heat-resistant layer further including a filler in an embodiment of the present invention.

Modes for Carrying Out the Invention

[0011] One embodiment of the present invention is described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more, B or less".

[0012] In this specification, the MD direction (Machine Direction) refers to the direction in which the sheet-like polyolefin resin composition and the porous film are transported in the porous film manufacturing method described later. The TD direction (Transverse Direction) refers to the direction parallel to the surface of the sheet-like polyolefin resin composition and the porous film, and perpendicular to the MD direction.

[0013] [Embodiment 1: Separator for non-aqueous electrolyte secondary battery] A separator for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention (hereinafter simply referred to as "separator") includes a porous substrate having a porous film mainly composed of a polyolefin resin and a mixed layer containing a heat-resistant resin, wherein the weight ratio (W1 / W0) of the weight W1 of the heat-resistant resin in the mixed layer to the weight W0 of the porous substrate is 0.07 or more.

[0014] The aforementioned "mixed layer" can be formed, for example, by the heat-resistant resin penetrating from one or both surfaces of the porous substrate. For example, if the heat-resistant resin penetrates a portion of the porous substrate, the separator will have a mixed layer and a portion consisting only of the porous substrate. In this specification, the portion of the separator consisting only of the porous substrate will be referred to as the "residual porous substrate." On the other hand, if the heat-resistant resin penetrates all of the porous substrate, for example, the separator will have a mixed layer and will not have a residual porous substrate.

[0015] The weight ratio in the mixed layer (hereinafter simply referred to as "weight ratio") is a parameter representing the content of the heat-resistant resin in the mixed layer. The separator comprises a porous substrate containing more of the heat-resistant resin than conventional separators.

[0016] In the separator, the mixed layer contains a specific amount or more of heat-resistant resin and has the aforementioned weight ratio. As a result, the heat resistance of the porous substrate is improved, and consequently, the heat resistance of the entire separator for non-aqueous electrolyte secondary batteries is also improved.

[0017] Furthermore, if the mixed layer has the aforementioned weight ratio, it is predicted that if the pores in the porous substrate are blocked by the heat-resistant resin, the ion permeability will decrease significantly and the resistance will increase greatly. However, contrary to this prediction, it was found that the separator maintains good ion permeability and good resistance even in this case. This is presumed to be because, in the separator, the heat-resistant resin is contained along the fibrils of the polyolefin resin constituting the porous substrate, making it difficult for the pores in the porous substrate to be blocked. As a result, it is believed that the separator maintains good ion permeability and good resistance.

[0018] The aforementioned "weight ratio" is preferably 0.07 or higher, and more preferably 0.10 or higher, from the viewpoint of suitably improving the heat resistance of the separator. On the other hand, if the mixed layer contains an excess amount of heat-resistant resin, the pores in the porous substrate may be blocked by the heat-resistant resin. For this reason, the aforementioned "weight ratio" is preferably 0.70 or lower, and more preferably 0.50 or lower.

[0019] Examples of methods for calculating the aforementioned "weight ratio" include those shown in (a) to (d) below. (a) If the separator has a heat-resistant layer laminated to it, the heat-resistant layer is removed. (b) If the separator obtained in (a) above, or the separator without a heat-resistant layer, does not contain a residual porous substrate, the weight of the mixed layer shall be measured and set as W2. If these separators do contain a residual porous substrate, the total weight of the mixed layer and the residual porous substrate shall be measured and set as W2. The difference between W2 measured in (c)(b) and the weight of the porous substrate: W0 (W2-W0) is calculated and taken as the weight of the heat-resistant resin in the mixed layer: W1. (d) The weight ratio (W1 / W0) is calculated from the weight W0 of the porous substrate and W1 calculated in (c).

[0020] In (c), the weight W0 of the porous substrate may be measured in advance before forming the mixed layer. Alternatively, the weight W0 of the porous substrate may be measured after the mixed layer has been washed with a cleaning solution to remove the heat-resistant resin. In addition, in (b) to (d), the value of the basis weight may be used instead of the actual weight.

[0021] The cleaning solution is not particularly limited as long as it dissolves the heat-resistant resin but does not dissolve the polyolefin. The cleaning solution may be, for example, hydrochloric acid and concentrated sulfuric acid.

[0022] [Porous base material] A porous substrate in one embodiment of the present invention is described below. Hereinafter, when simply referred to as "porous substrate," it means a porous substrate that does not contain heat-resistant resin.

[0023] The porous substrate comprises a polyolefin porous film. The polyolefin porous film is a porous film mainly composed of a polyolefin resin. "Mainly composed of a polyolefin resin" means that the proportion of the polyolefin resin in the porous film is 50 volume% or more, preferably 90 volume% or more, and more preferably 95 volume% or more of the total material constituting the porous film.

[0024] The porous substrate has numerous interconnected pores inside, allowing gases and liquids to pass from one side to the other.

[0025] The thickness of the porous substrate is preferably 5 to 20 μm, more preferably 7 to 15 μm, and even more preferably 8 to 15 μm. If the thickness is 5 μm or more, the functions required of the separator (such as shutdown function) can be sufficiently obtained. If the thickness is 20 μm or less, the separator can be made thinner.

[0026] The aforementioned polyolefin resin has a weight-average molecular weight of 5 × 10 5 ~15×10 6 It is more preferable that the polyolefin resin contains high molecular weight components. In particular, it is more preferable that the polyolefin resin contains high molecular weight components with a weight-average molecular weight of 1 million or more, because this improves the strength of the resulting porous substrate and the separator for non-aqueous electrolyte secondary batteries containing the porous substrate.

[0027] The polyolefin resin is not particularly limited, but examples include homopolymers or copolymers obtained by polymerizing one or more monomers selected from monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene.

[0028] Examples of the aforementioned homopolymers include polyethylene, polypropylene, and polybutene. Examples of the aforementioned copolymers include ethylene-propylene copolymers.

[0029] Polyethylene is more preferred as the polyolefin resin. Examples of polyethylene include low-density polyethylene, high-density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), and ultra-high molecular weight polyethylene with a weight-average molecular weight of 1 million or more. Of these, ultra-high molecular weight polyethylene with a weight-average molecular weight of 1 million or more is even more preferred.

[0030] The weight per unit area of ​​the porous substrate, i.e., the basis weight, is typically 2 to 20 g / m², in order to increase the gravimetric energy density and volumetric energy density of the battery. 2 Preferably, it is 5-12 g / m 2 It is preferable that it be so.

[0031] From the viewpoint of exhibiting sufficient ion permeability, the air permeability of the porous substrate is preferably 30 to 500 sec / 100 mL in Gaarle values, and more preferably 50 to 300 sec / 100 mL.

[0032] The porosity of the porous substrate is preferably 20% to 80% by volume, and more preferably 30% to 75% by volume, in order to increase the amount of electrolyte that can be held and to obtain the function of reliably preventing (shutting down) excessive current flow at a lower temperature.

[0033] The pore size of the pores in the porous substrate is preferably 0.1 μm or less, and more preferably 0.06 μm or less, from the viewpoint of sufficient ion permeability and preventing the entry of particles constituting the electrodes.

[0034] [Method for manufacturing porous substrates] In one embodiment of the present invention, the method for manufacturing the porous substrate can be a known method and is not particularly limited. For example, as described in Japanese Patent No. 5476844, a method can be used in which a filler is added to a thermoplastic resin, a film is formed, and then the filler is removed.

[0035] Specifically, for example, when a porous polyolefin film is formed from a polyolefin resin containing ultra-high molecular weight polyethylene and low molecular weight polyolefin with a weight-average molecular weight of 10,000 or less, it is preferable from the viewpoint of manufacturing cost to manufacture it by a method including the following steps (1) to (4).

[0036] (1) A step of kneading 100 parts by weight of ultra-high molecular weight polyethylene, 5 to 200 parts by weight of low molecular weight polyolefin with a weight-average molecular weight of 10,000 or less, and 100 to 400 parts by weight of an inorganic filler such as calcium carbonate to obtain a polyolefin resin composition. (2) A step of forming a sheet using a polyolefin resin composition, (3) A step to remove the inorganic filler from the sheet obtained in step (2), (4) A step of stretching the sheet obtained in step (3). In addition, methods described in the aforementioned patent documents may be used.

[0037] Alternatively, commercially available polyolefin porous films having the above-described characteristics may be used.

[0038] [Mixed layer] In one embodiment of the present invention, the mixed layer is a layer containing the porous substrate and the heat-resistant resin. Therefore, the mixed layer includes the polyolefin resin, which is a component of the porous substrate, and the heat-resistant resin.

[0039] In one embodiment of the present invention, the entire porous substrate may be included in the mixed layer, or a portion of the porous substrate may be included in the mixed layer. More specifically, the separator may or may not include the residual porous substrate. Furthermore, the mixed layer can be formed by impregnating the heat-resistant resin from one or both sides of the porous substrate, as described below. Here, for example, when the mixed layer is formed by impregnating the heat-resistant resin from one side of the porous substrate, the separator may have a mixed layer on the side of the porous substrate corresponding to the side into which the heat-resistant resin was impregnated, and a residual porous substrate on the side of the surface opposite to that side. Furthermore, for example, when the mixed layer is formed by impregnating the heat-resistant resin from both sides of the porous substrate, the separator may have two mixed layers on the sides corresponding to the sides of the porous substrate into which the heat-resistant resin was impregnated, and a residual porous substrate in the central part of the separator.

[0040] The volume percentage of the mixed layer is expressed as the proportion of the total volume of the porous substrate that is contained in the mixed layer. From the viewpoint of improving the heat resistance of the separator, the volume percentage of the mixed layer is preferably 5.0 volume% or more, and more preferably 7.0 volume% or more, of the total volume of the porous substrate. Furthermore, the upper limit of the volume of the mixed layer is 100 volume% of the total volume of the porous substrate, and from the viewpoint of the ion permeability and resistance value of the separator, it is preferably 55 volume% or less, and more preferably 40 volume% or less.

[0041] The heat-resistant resin is a resin that has superior heat resistance compared to polyolefin. In one embodiment of the present invention, the heat resistance of the separator can be improved by having the mixed layer.

[0042] Preferably, the heat-resistant resin is insoluble in the battery electrolyte and is electrochemically stable within the battery's operating range.

[0043] Examples of the heat-resistant resins include nitrogen-containing aromatic polymers; (meth)acrylate resins; fluoropolymer resins; polyester resins; rubbers; resins with a melting point or glass transition temperature of 180°C or higher; water-soluble polymers; polycarbonates, polyacetals, polyetheretherketones, etc.

[0044] Examples of nitrogen-containing aromatic polymers include aromatic polyamides, aromatic polyimides, aromatic polyamide-imides, polybenzimidazoles, polyurethanes, and melamine resins. Examples of aromatic polyamides include fully aromatic polyamides (aramid resins) and semi-aromatic polyamides. Examples of aromatic polyamides include para-aramids and meta-aramids. Among the nitrogen-containing aromatic polymers mentioned above, fully aromatic polyamides are preferred, and para-aramids are more preferred.

[0045] In this specification, "para-aramid" refers to a fully aromatic polyamide in which the amide bond is located at the para position or a similar orientation position of the aromatic ring. A para-like orientation position is an orientation position located on the opposite side of the aromatic ring, on the same axis, or parallel to it. Examples of such orientation positions include the 4th and 4' positions of the biphenylene ring, the 1st and 5th positions of the naphthalene ring, and the 2nd and 6th positions of the naphthalene ring.

[0046] Specific examples of para-aramids include poly(paraphenylene terephthalamide), poly(parabenzamide), poly(4,4'-benzanilide terephthalamide), poly(paraphenylene-4,4'-biphenylenedicarboxylic acid amide), poly(paraphenylene-2,6-naphthalenedicarboxylic acid amide), poly(2-chloro-paraphenylene terephthalamide), and paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer. Among the above-mentioned para-aramids, poly(paraphenylene terephthalamide) is preferred because it is easy to manufacture and handle.

[0047] Examples of fluororesins include polyvinylidene fluoride (PVDF), polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-trichloroethylene copolymer, vinylidene fluoride-vinyl fluoride copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, and ethylene-tetrafluoroethylene copolymer, as well as fluororubber, which has a glass transition temperature of 23°C or lower among the aforementioned fluororesins.

[0048] Preferred polyester resins include aromatic polyesters such as polyarylate and liquid crystal polyesters.

[0049] Examples of rubbers include styrene-butadiene copolymers and their hydrogenates, methacrylic acid ester copolymers, acrylonitrile-acrylic acid ester copolymers, styrene-acrylic acid ester copolymers, ethylene propylene rubber, and polyvinyl acetate.

[0050] Examples of resins with a melting point or glass transition temperature of 180°C or higher include polyphenylene ether, polysulfone, polyethersulfone, polyphenylene sulfide, polyetherimide, polyamideimide, and polyetheramide.

[0051] Examples of water-soluble polymers include polyvinyl alcohol, polyethylene glycol, cellulose ether, sodium alginate, polyacrylic acid, polyacrylamide, and polymethacrylic acid.

[0052] Furthermore, the heat-resistant resin may be of one type only, or two or more types may be used in combination.

[0053] The molecular weight of the heat-resistant resin, expressed as an intrinsic viscosity, is preferably 1.0 to 2.5 dL / g, and more preferably 1.2 to 2.0 dL / g. If the molecular weight of the heat-resistant resin is less than 1.0 dL / g, improvement in the heat resistance of the mixed layer may not be observed, and if the molecular weight of the heat-resistant resin exceeds 2.5 dL / g, it may not penetrate well into the substrate.

[0054] It is preferable that the weight, air permeability, porosity, and pore diameter of the mixed layer are within the same range as the preferred range of weight, air permeability, porosity, and pore diameter of the porous substrate.

[0055] [Method for manufacturing a mixed layer] The method for manufacturing the mixed layer is not particularly limited, and for example, one method involves applying a coating liquid containing the heat-resistant resin to one or both sides of the porous substrate, allowing the coating liquid to penetrate at least a portion of the interior of the porous substrate, and then removing the solvent contained in the coating liquid.

[0056] In this case, the coating liquid may be allowed to penetrate the entire interior of the porous substrate, or it may be allowed to penetrate only a part of the interior of the porous substrate. When the coating liquid is allowed to penetrate the entire interior of the porous substrate, it means that there is no residual porous substrate present. When the coating liquid is allowed to penetrate only a part of the interior of the porous substrate, it means that there is residual porous substrate present.

[0057] Here, the coating liquid that does not penetrate into the interior of the porous substrate can form a coating layer on one or both sides of the mixed layer. Then, by removing the solvent contained in the coating liquid, a heat-resistant layer, described later, can be formed on one or both sides of the mixed layer. Therefore, the separator may be in a form in which the heat-resistant layer is laminated on the mixed layer.

[0058] Before applying the coating liquid to one or both sides of the porous substrate, one or both sides of the porous substrate may be subjected to a hydrophilic treatment as necessary.

[0059] The coating liquid may contain fillers, as described below, which may be included in the heat-resistant layer. The coating liquid can usually be prepared by dissolving the heat-resistant resin in a solvent.

[0060] When forming a heat-resistant layer containing the filler on the mixed layer, the coating solution can usually be prepared by dissolving the heat-resistant resin in a solvent and dispersing the filler in the solvent. In this case, the solvent also serves as a dispersion medium for dispersing the filler.

[0061] Furthermore, the heat-resistant resin may be formed into an emulsion using the aforementioned solvent.

[0062] The solvent is not particularly limited, as long as it does not adversely affect the porous substrate, dissolves the heat-resistant resin uniformly and stably, and, if it contains a filler, disperses the filler uniformly and stably. Examples of the solvent include water and organic solvents. The solvent may be used alone or in combination of two or more types.

[0063] The coating solution can be formed by any method as long as it satisfies the conditions such as the amount of resin solids (resin concentration) and the amount of fine particles necessary to obtain the mixed layer and the heat-resistant layer. Specific examples of methods for forming the coating solution include mechanical stirring, ultrasonic dispersion, high-pressure dispersion, and media dispersion. Furthermore, the coating solution may contain additives other than the heat-resistant resin and fine particles, such as dispersants, plasticizers, surfactants, and pH adjusters, as long as they do not impair the objectives of the present invention. The amount of additives added should not impair the objectives of the present invention.

[0064] Conventional methods known as the application method for the coating liquid can be employed, specifically, for example, the gravure coater method, the dip coater method, the bar coater method, and the die coater method.

[0065] The most common method for removing the solvent is drying. Alternatively, the solvent contained in the coating solution may be replaced with another solvent before drying.

[0066] In one embodiment of the present invention, for example, by employing one or more of the following manufacturing conditions (A) to (C), the penetration of the coating liquid into the porous substrate can be promoted, and the mixed layer can be suitably manufactured. (A) When applying the coating liquid to the porous substrate, for example, a high-pressure bar is used, and the applied load per unit width of the coating bar is preferably 250 N / m or more, more preferably 300 N / m or more, to apply the coating liquid to the porous substrate. cloth Apply to the surface. Note that the applied load is applied to the land portion (coating bar). engineering Coating in the area between the liquid inlet and outlet. engineering It is calculated as the product of the liquid pressure and the wetted surface area of ​​the land. (B) The solvent is removed by drying, and the drying conditions are controlled so that the drying time is preferably 10 seconds or more, more preferably 20 seconds or more. (C) The content of the heat-resistant resin in the coating liquid is preferably controlled to 2.0 to 10.0% by weight, more preferably to 4.5 to 8.0% by weight.

[0067] As a method for suppressing the penetration of the heat-resistant resin into the interior of the porous substrate, a bottom impregnation method is known, in which the coating liquid is applied to one side of the porous substrate, and the side opposite to the side to which the coating liquid is applied is impregnated with a solvent such as N-methyl-2-pyrrolidone (NMP). In one embodiment of the present invention, as described above, the heat-resistant resin may be penetrated into the entire interior of the porous substrate. Therefore, the mixed layer can be suitably manufactured by applying the coating liquid to one side of the porous substrate without employing methods such as the bottom impregnation method. When the heat-resistant resin is to be penetrated into a part of the interior of the porous substrate, the bottom impregnation method or the like may be used as appropriate.

[0068] [Heat-resistant layer] As described above, the separator for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention may include a heat-resistant layer laminated on the mixed layer.

[0069] The heat-resistant layer includes the heat-resistant resin. The heat-resistant layer may also include a filler. The filler may be organic fine particles or inorganic fine particles. Therefore, when the heat-resistant layer includes the filler, the heat-resistant layer to The heat-resistant resin contained herein is contained between the fillers and between the fillers. The aforementioned It also functions as a binder resin that binds the mixed layer. Furthermore, insulating fine particles are preferred for the filler. In addition, the filler has constituent materials, particle size and specific surface area. of One or more of these may be two or more different types of fillers used in combination.

[0070] Examples of organic materials constituting the organic fine particles include styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, methyl acrylate, etc., either individually or in copolymers of two or more; fluorine-based resins such as polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, and polyvinylidene fluoride; melamine resin; urea resin; polyolefin; and polymethacrylate. The organic fine particles may be used individually or in mixtures of two or more. In terms of chemical stability, organic fine particles composed of polytetrafluoroethylene are preferred.

[0071] Examples of inorganic materials constituting the inorganic fine particles include metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates, and sulfates. Specific examples of the inorganic materials include powders of aluminum oxide (such as alumina), boehmite, silica, titania, magnesia, barium titanate, aluminum hydroxide, and calcium carbonate; as well as minerals such as mica, zeolite, kaolin, and talc. The inorganic fine particles may be used individually or as a mixture of two or more types. In terms of chemical stability, inorganic fine particles composed of aluminum oxide are preferred.

[0072] The filler can take the form of approximately spherical, plate-like, columnar, needle-like, whisker-like, or fibrous particles, and any of these particles can be used. Approximately spherical particles are preferred because they easily form uniform pores.

[0073] The average particle size of the filler is preferably 0.01 to 1 μm. In this specification, "average particle size of the filler" means the volume-based average particle size (D50) of the filler. D50 means the particle size at which the cumulative distribution based on volume accounts for 50%. D50 can be measured, for example, using a laser diffraction particle size analyzer (Shimadzu Corporation, product names: SALD2200, SALD2300, etc.).

[0074] The filler content in the heat-resistant layer is preferably 20 to 90% by weight, and more preferably 40 to 80% by weight, relative to the total weight of the heat-resistant layer. If the filler content is within the above range, a heat-resistant layer with sufficient ion permeability can be obtained.

[0075] The air permeability of the heat-resistant layer is preferably 400 sec / 100 mL or less, and more preferably 200 sec / 100 mL or less, according to the Gurley value.

[0076] The heat-resistant layer preferably has a value of 5% or more, and more preferably 7% or more, represented by the following formula (1). The upper limit of the value is not particularly limited, but for example, it is 60% or less, preferably 50% or less, and more preferably 11% or less. Brightness X1 (%) - Brightness X2 (%) ... Formula (1) Here, luminance X1 is the average value of luminance at a point from the interface of the heat-resistant layer in contact with the mixed layer to a depth of 20% of the thickness of the heat-resistant layer. Brightness X2 is the average brightness value at a point from the outermost surface of the heat-resistant layer to a depth of 20% of the thickness of the heat-resistant layer. The average brightness of the entire heat-resistant layer is 100%. Here, the outermost part of the heat-resistant layer refers to the surface facing the interface in the heat-resistant layer that is in contact with the mixed layer.

[0077] The value represented by formula (1) above represents the concentration bias of the substance constituting the heat-resistant layer in the thickness direction of the heat-resistant layer. The substance constituting the heat-resistant layer is the heat-resistant resin and the heat-resistant layer If it contains a filler, then it is that filler. If the value is within the preferred range described above, the heat-resistant layer contains more of the material constituting the heat-resistant layer in the region close to the mixed layer than in the region farther away from the mixed layer. In that case, more of the heat-resistant resin (or the heat-resistant resin and the filler), which is the material constituting the heat-resistant layer, has migrated to the region of the heat-resistant layer close to the mixed layer. As a result, it is considered that the mixed layer contains a suitable amount of the heat-resistant resin for imparting sufficient heat resistance to the separator.

[0078] The average value of the luminance can be measured by the same method as described in the later-described examples.

[0079] [Method for manufacturing a heat-resistant layer] The heat-resistant layer can be formed at the same time as the mixed layer. That is, the method for manufacturing the heat-resistant layer is the same as the method for manufacturing the mixed layer described above.

[0080] When the coating liquid contains the filler, the filler typically has a particle size larger than the pore size of the voids in the porous substrate. Therefore, when manufacturing the heat-resistant layer and the mixed layer, the filler is deposited on the mixed layer without penetrating into the interior of the porous substrate. Thus, after the solvent is removed, a filler-rich layer with a high filler content may be formed on the mixed layer. Here, the filler-rich layer is part of the heat-resistant layer. In other words, the heat-resistant layer may have a configuration comprising the filler-rich layer on the mixed layer, and on the filler-rich layer, a layer made of the heat-resistant resin, or a layer containing a small amount of filler.

[0081] Therefore, the separator may have a structure in which the filler-rich layer exists between the mixed layer and the layer made of the heat-resistant resin, or a layer containing a small amount of filler, even if it does contain filler.

[0082] Here, an example of the structure of a heat-resistant layer further containing the filler will be explained with reference to Figure 1. The separator shown in Figure 1 has a structure in which a heat-resistant layer 5 is laminated on a mixed layer in a laminate 1 consisting of a residual porous substrate and a mixed layer. Here, the filler 7 contained in the heat-resistant layer 5 is distributed in large quantities near the mixed layer in the laminate 1. On the other hand, the filler 7 is distributed in small quantities at positions far from the mixed layer in the laminate 1. Therefore, the separator shown in Figure 1 has a structure in which the filler-rich layer exists between the mixed layer and the layer with a low filler content.

[0083] Furthermore, arrow L10 in Figure 1 represents the total thickness of the heat-resistant layer 5, and the lengths of arrows L11 and L12 are both 20% of the length of arrow L10. Therefore, in the heat-resistant layer 5 shown in Figure 1, luminance X1 is the average luminance of the shaded area, and luminance X2 is the average luminance of the area with intersecting shaded lines.

[0084] [Physical properties of separators for non-aqueous electrolyte secondary batteries] The shutdown temperature of the separator is preferably 150°C or higher.

[0085] The method for measuring the shutdown temperature is not particularly limited. The shutdown temperature can be measured, for example, by the method shown in the embodiment.

[0086] The film thickness of the separator is preferably 5.0 μm to 45 μm, and more preferably 6 μm to 25 μm.

[0088] The permeability of the separator is preferably 500 sec / 100 mL or less in Gaarle values, and more preferably 300 sec / 100 mL or less. When the permeability is within the above range, the separator can be said to have sufficient ion permeability.

[0089] The separator may optionally include another porous layer other than the residual porous substrate, the mixed layer, and the heat-resistant layer, to the extent that it does not impair the objectives of the present invention. Examples of the other porous layer include known porous layers such as another heat-resistant layer, an adhesive layer, and a protective layer.

[0090] [Embodiment 2: Nonaqueous electrolyte secondary battery member, Embodiment 3: Nonaqueous electrolyte secondary battery] The component for a non-aqueous electrolyte secondary battery according to Embodiment 2 of the present invention is configured such that a positive electrode, a separator for a non-aqueous electrolyte secondary battery according to Embodiment 1 of the present invention, and a negative electrode are arranged in this order.

[0091] The non-aqueous electrolyte secondary battery according to Embodiment 3 of the present invention includes a separator for a non-aqueous electrolyte secondary battery according to Embodiment 1 of the present invention.

[0092] The non-aqueous electrolyte secondary battery according to Embodiment 3 of the present invention is a non-aqueous secondary battery that obtains electromotive force by doping and dedoping lithium, and may comprise a non-aqueous electrolyte secondary battery component in which a positive electrode, a separator for a non-aqueous electrolyte secondary battery according to Embodiment 1 of the present invention, and a negative electrode are stacked in this order. Note that the components of the non-aqueous electrolyte secondary battery other than the separator for a non-aqueous electrolyte secondary battery are not limited to those described below.

[0093] The non-aqueous electrolyte secondary battery according to Embodiment 3 of the present invention typically has a structure in which a battery element impregnated with electrolyte is sealed within an outer casing, with the negative electrode and positive electrode facing each other via a separator for non-aqueous electrolyte secondary batteries according to Embodiment 1 of the present invention. The non-aqueous electrolyte secondary battery is preferably a lithium-ion secondary battery. Doping refers to the phenomenon in which lithium ions enter the active material of an electrode such as the positive electrode.

[0094] The non-aqueous electrolyte secondary battery component according to Embodiment 2 of the present invention is equipped with a separator for non-aqueous electrolyte secondary batteries according to Embodiment 1 of the present invention. Therefore, the non-aqueous electrolyte secondary battery component according to Embodiment 2 of the present invention has the effect of having excellent heat resistance and the effect of being able to manufacture a non-aqueous electrolyte secondary battery with excellent resistance. The non-aqueous electrolyte secondary battery according to Embodiment 3 of the present invention is equipped with a separator for non-aqueous electrolyte secondary batteries according to Embodiment 1 of the present invention. Therefore, the non-aqueous electrolyte secondary battery according to Embodiment 3 of the present invention has the effect of having excellent heat resistance and resistance.

[0095] <Positive electrode> The positive electrode in the non-aqueous electrolyte secondary battery component and the non-aqueous electrolyte secondary battery according to one embodiment of the present invention is not particularly limited as long as it is generally used as a positive electrode in a non-aqueous electrolyte secondary battery. For example, a positive electrode sheet having a structure in which an active material layer containing a positive electrode active material and a binder is molded on a current collector can be used as the positive electrode. The active material layer may further contain a conductive agent.

[0096] Examples of the positive electrode active material include materials that can be doped and dedoped with lithium ions. Specifically, examples of such materials include lithium composite oxides containing at least one transition metal such as V, Mn, Fe, Co, and Ni.

[0097] Examples of the conductive agent include carbonaceous materials such as natural graphite, artificial graphite, coke, carbon black, pyrolytic carbons, carbon fibers, and calcined organic polymer compounds. The conductive agent may be used alone or in combination of two or more types.

[0098] Examples of the binder include fluorine-based resins such as polyvinylidene fluoride, acrylic resins, and styrene-butadiene rubber. The binder also functions as a thickening agent.

[0099] Examples of current collectors include conductors such as Al, Ni, and stainless steel. Among these, Al is more preferred because it is easy to process into a thin film and is inexpensive.

[0100] Examples of methods for manufacturing a sheet-shaped positive electrode include a method of pressurizing a positive electrode active material, a conductive agent, and a binder on a positive electrode current collector; a method of making a paste from the positive electrode active material, a conductive agent, and a binder using a suitable organic solvent, applying the paste to a positive electrode current collector, drying it, and then pressing it to fix it to the positive electrode current collector; and so on.

[0101] <Negative electrode> The negative electrode in the non-aqueous electrolyte secondary battery component and the non-aqueous electrolyte secondary battery according to one embodiment of the present invention is not particularly limited as long as it is generally used as a negative electrode in a non-aqueous electrolyte secondary battery. For example, a negative electrode sheet having a structure in which an active material layer containing a negative electrode active material and a binder is molded on a current collector can be used as the negative electrode. The active material layer may further contain a conductive agent.

[0102] Examples of the negative electrode active material include materials that can be doped and dedoped with lithium ions, lithium metal, or lithium alloy. Examples of such materials include carbonaceous materials. Examples of carbonaceous materials include natural graphite, artificial graphite, coke, carbon black, and pyrolytic carbons.

[0103] Examples of the current collector include Cu, Ni, and stainless steel. In particular, Cu is more preferred in lithium-ion secondary batteries because it is difficult to form alloys with lithium and is easy to process into thin films.

[0104] Examples of methods for manufacturing a sheet-shaped negative electrode include a method of pressurizing the negative electrode active material on a negative electrode current collector; a method of making the negative electrode active material into a paste using a suitable organic solvent, coating the paste onto the negative electrode current collector, drying it, and then pressing it to fix it to the negative electrode current collector; and so on. The paste preferably contains the conductive agent and the binder.

[0105] <Non-aqueous electrolyte> In the non-aqueous electrolyte secondary battery according to an embodiment of the present invention, the non-aqueous electrolyte is not particularly limited as long as it is a non-aqueous electrolyte generally used in non-aqueous electrolyte secondary batteries. For example, a non-aqueous electrolyte obtained by dissolving a lithium salt in an organic solvent can be used. Examples of the lithium salt include LiClO4, LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, Li2B 10 Cl 10 , lithium salts of lower aliphatic carboxylic acids, LiAlCl4, and the like. Only one kind of the lithium salt may be used, or two or more kinds may be used in combination.

[0106] Examples of the organic solvent constituting the non-aqueous electrolyte include carbonates, ethers, esters, nitriles, amides, carbamates, sulfur-containing compounds, and fluorine-containing organic solvents obtained by introducing a fluorine group into these organic solvents. Only one kind of the organic solvent may be used, or two or more kinds may be used in combination.

Examples

[0107] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0108] [Measurement methods for various physical properties] The measurements of various physical properties in Examples and Comparative Examples were performed by the following methods.

[0109] [Areal weight] The porous substrates used in Examples and Comparative Examples were cut into squares with a side length of 8 cm to obtain samples, and the weight W a [g] of this sample was measured. Using the measured value of W a , the areal weight [g / m 2 of the porous substrate was calculated according to the following formula (2). Areal weight of porous substrate = (W a) / (0.08×0.08)...Equation (2) The separator was cut into a square with sides of 8 cm to serve as a sample, and the weight of this sample was measured W. b [g] was measured. Furthermore, by applying and then peeling off a release tape to the surface of the sample on which the heat-resistant layer was formed, the heat-resistant layer was separated from the separator, and a laminate consisting of a residual porous substrate and a mixed layer was obtained. Weight W of the laminate c [g] was measured. The measured W b and W c Using the value of , the weight of the laminate [g / m²] is calculated according to the following formula (3). 2 The following was calculated. Furthermore, the weight of the heat-resistant layer was calculated according to formula (4) below. Weight of laminate = (W c ) / (0.08×0.08)...Equation (3) Weight basis weight of heat-resistant layer = (W b -W c ) / (0.08×0.08)...Equation (4) [Weight ratio in the mixed layer] Using the "weight basis weight of the porous substrate" and the "weight basis weight of the laminate" measured by the method described above, the "weight ratio in the mixed layer" was measured according to the following formula (5). Weight ratio in the mixed layer = {(weight of the laminate) - (weight of the porous substrate)} / (weight of the porous substrate) ... Equation (5) [Shutdown temperature] A 17.5 mmΦ film was cut from the separator obtained in the examples and comparative examples. After impregnating the film with an electrolyte, the film was sandwiched between two stainless steel (SUS) electrodes and fixed with clips to create a measurement cell. As the electrolyte, a non-aqueous electrolyte was used, prepared by dissolving LiBF4 in a mixed solvent of ethylene carbonate:diethyl carbonate = 50 vol%:50 vol% so that the concentration of LiBF4 was 1.0 mol / L. The terminals of an impedance analyzer were connected to both electrodes of the measurement cell. Then, the measurement cell was placed inside an oven, and the resistance value of the measurement cell at 1 kHz was measured while the temperature inside the oven was raised at a rate of 15°C / min. The temperature at which the measured resistance value reached its maximum value (but not more than 30000 Ω) was defined as the shutdown temperature (SD temperature).

[0110] [Average brightness of the heat-resistant layer] The following methods were used to measure the average brightness of the entire heat-resistant layer, with the average brightness of the heat-resistant layer being set to 100%, at a point from the interface of the heat-resistant layer in contact with the mixed layer to a depth of 20% of the thickness of the heat-resistant layer: Brightness X1[%], and at a point from the outermost surface of the heat-resistant layer, i.e., the surface facing the interface in contact with the mixed layer, to a depth of 20% of the thickness of the heat-resistant layer: Brightness X2[%]. 1. The separator was electron-stained with ruthenium tetroxide. 2. Epoxy resin was filled into the pores of the separator and allowed to harden. 3. The separator was cut perpendicular to the MD direction using the ion milling method (IB-19520 (manufactured by JEOL)). 4. The exposed cross-section was observed and imaged using a scanning electron microscope (SEM). At this time, the magnification was adjusted to the maximum magnification that allowed the entire cross-section of the heat-resistant layer and porous substrate, and the epoxy resin layer, to be included in the same field of view. An S-4800 (Hitachi High-Tech) SEM was used, and observation was performed using a backscattered electron detector under an acceleration voltage of 2kV. 5. For the obtained image, the brightness was output for each pixel. The obtained brightness was averaged in the in-plane direction. 6. A luminance profile was created by plotting the average luminance value in the in-plane direction along the thickness direction. This profile was normalized so that the average luminance value for the entire heat-resistant layer was 100%, and the average luminance value for the epoxy resin region was 0%. 7. A moving average of the brightness for 5 pixels was calculated for each pixel in the direction from the heat-resistant layer to the mixed layer. 8. The interface between the heat-resistant layer and the mixed layer was defined as the position where the slope of the moving average was at its maximum negative value, near the interface between the heat-resistant layer and the mixed layer. 9. Separately from steps 7 and 8, a moving average of the brightness for 5 pixels was calculated for each pixel in the direction from the epoxy resin outside the heat-resistant layer toward the heat-resistant layer. 10. The interface between the epoxy resin and the heat-resistant layer was defined as the position where the slope of the moving average was at its maximum positive value, near the interface between the epoxy resin and the heat-resistant layer. 11. The region sandwiched between the interfaces set in steps 8 and 10 was defined as the heat-resistant layer. X1 was defined as the average brightness from 0% to 20% in the thickness direction from the interface between the heat-resistant layer and the mixed layer. X2 was defined as the average brightness from 0% to 20% in the thickness direction from the interface between the epoxy resin and the heat-resistant layer.

[0111] Using the measured luminance values ​​X1[%] and X2[%], the value expressed by the following formula (1) was calculated. (Brightness X1[%]) - (Brightness X2[%]) ... Formula (1) [Air permeability] The air permeability (Gare value) of the separator was measured in accordance with JIS P8117. Subsequently, a release tape was applied to the surface of the separator on which the heat-resistant layer was formed, and then peeled off, thereby separating the heat-resistant layer from the separator and obtaining a laminate consisting of a residual porous substrate and a mixed layer. The air permeability of the laminate was measured in accordance with JIS P8117.

[0112] [Coin cell resistance] A 17 mmΦ film was cut from the separator obtained in the examples and comparative examples. After impregnating the film with an electrolyte, the film was sandwiched between two stainless steel (SUS) electrodes and fixed with clips to create a measurement cell. As the electrolyte, a non-aqueous electrolyte was used, prepared by dissolving LiPF6 in a mixed solvent of ethylene carbonate:dimethyl carbonate:ethyl methyl carbonate = 30 vol%:35 vol%:35 vol% so that the concentration of LiPF6 was 0.5 mol / L. The terminals of an impedance analyzer were connected to both electrodes of the measurement cell. Subsequently, the prepared coin cell was placed in a constant temperature bath set to 25°C. Then, measurements were taken using a Solartron AC impedance analyzer FRA (SI1260) and potentiostat (SI1287) at a frequency of 1 MHz to 0.1 Hz and a voltage amplitude of 10 mV. Coincell The liquid resistance r0 was determined.

[0113] [ Heating dimensional retention rate ] The separators obtained in the examples and comparative examples were cut into squares with dimensions of 8 cm in the MD direction and 8 cm in the TD direction. A square frame with dimensions of 6 cm in the MD direction and 6 cm in the TD direction was drawn 1 cm inward from each edge of the square. After folding an A5 size sheet of paper (copy paper) in half, the cut-out separator was placed inside, and the paper was stapled to obtain a sample.

[0114] The sample was placed inside an oven with an internal temperature of 200°C and left to stand for 1 hour. After that, the sample was removed from the oven, and the length of the width in the MD direction of the square frame described in the sample was measured. MD [cm] and width length in the TD direction: D TD [cm] was measured. The measured D MD and D TD Using the values ​​of , according to equations (6) and (7), the MD and TD directions when heated at 200°C Maintaining heating dimensions The rate was calculated. In the MD direction Heating dimensional retention rate[%]= (D MD / 6) ×100...Equation (6) In the TD direction Heating dimensional retention rate [%]= (D TD / 6) ×100...Equation (7) [Manufacturing Example 1: Preparation of Aramid Resin] Poly(paraphenylene terephthalamide), a type of aramid resin, was synthesized by the following method. A 3L separable flask equipped with a stirring blade, thermometer, nitrogen inlet, and powder addition port was used as the synthesis vessel. 2200g of NMP was placed in the thoroughly dried separable flask. 151.07g of calcium chloride powder was added to this, and the temperature was raised to 100°C to completely dissolve it, obtaining solution A. The calcium chloride powder used was pre-dried under vacuum at 200°C for 2 hours.

[0115] Next, the temperature of solution A was returned to room temperature, and 68.23 g of paraphenylenediamine was added and completely dissolved to obtain solution B. While maintaining the temperature of solution B at 20°C ± 2°C, 124.97 g of terephthalic acid dichloride was added in four portions at approximately 10-minute intervals to obtain solution C. Then, solution C was aged for 1 hour while continuing to stir at 150 rpm and maintaining the temperature at 20°C ± 2°C. As a result, an aramid polymerization solution containing 6% by weight of poly(paraphenylene terephthalamide) was obtained.

[0116] [Manufacturing Example 2: Preparation of Coating Solution (1)] 100 g of the aramid polymerization solution was weighed into a flask, and 6.0 g of alumina A (average particle size: 13 nm) was added to obtain dispersion A1. In dispersion A1, the weight ratio of poly(paraphenylene terephthalamide) to alumina A was 1:1. Next, NMP was added to dispersion A1 so that the solid content was 4.5% by weight, and the mixture was stirred for 240 minutes to obtain dispersion B2. Here, "solid content" refers to the total weight of poly(paraphenylene terephthalamide) and alumina A. Next, 0.73 g of calcium carbonate was added to dispersion B1 and stirred for 240 minutes to neutralize dispersion B1. The neutralized dispersion B1 was degassed under reduced pressure to prepare a slurry-like coating solution (1).

[0117] [Manufacturing Example 3: Preparation of Coating Solution (2)] 100 g of the aramid polymerization solution was weighed into a flask, and 6.0 g of alumina A (average particle size: 13 nm) and 6.0 g of alumina B (average particle size: 640 nm) were added to obtain dispersion A2. In dispersion A2, the weight ratio of poly(paraphenylene terephthalamide), alumina A, and alumina B was 1:1:1. Next, NMP was added to dispersion A2 so that the solid content was 6.0% by weight, and the mixture was stirred for 240 minutes to obtain dispersion B2. Here, "solid content" refers to the total weight of poly(paraphenylene terephthalamide), alumina A, and alumina B. Next, 0.73 g of calcium carbonate was added to dispersion B2 and the mixture was stirred for 240 minutes to neutralize dispersion B2. The neutralized dispersion B2 was degassed under reduced pressure to prepare a slurry-like coating solution (2).

[0118] [Example 1] As a porous substrate, a polyolefin porous film made of polyethylene (thickness: 10.5 μm, air permeability: 92 sec / 100 mL, basis weight: 5.40 g / m²) is used. 2A coating solution (1) was used. The coating solution (1) was applied to one side of a porous substrate using a high-pressure bar, applying a load of 327 N / m per width of the coating bar to the porous substrate, under the conditions of clearance: 0.05 mm and coating speed: 20 mm / min, to obtain a coated material. The obtained coated material was left to stand for 1 minute in an atmosphere of 50°C and 70% relative humidity to precipitate poly(paraphenylene terephthalamide). Next, the coated material with the precipitated poly(paraphenylene terephthalamide) was immersed in deionized water to remove calcium chloride and solvent from the coated material. Next, the coated material from which calcium chloride and solvent had been removed was dried at 80°C to obtain a separator (1) for a non-aqueous electrolyte secondary battery.

[0119] [Example 2] A separator (2) for a non-aqueous electrolyte secondary battery was obtained by the same method as in Example 1, except for (i) and (ii) below. (i) Coating liquid (2) was used instead of coating liquid (1). (ii) The coating liquid was applied to the porous substrate by applying a load of 327 N / m per width of the coating bar to the porous substrate using a high-pressure bar, under the conditions of clearance: 0.06 mm and coating speed: 20 mm / min.

[0120] [Example 3] A separator (3) for a non-aqueous electrolyte secondary battery was obtained by the same method as in Example 1, except for (iii) and (iv) below. (iii) The use of coating liquid (2) instead of coating liquid (1). (iv) The coating liquid was applied to the porous substrate by applying a load of 327 N / m per width of the coating bar to the porous substrate using a high-pressure bar, under the conditions of clearance: 0.08 mm and coating speed: 20 mm / min.

[0121] [Comparative Example 1] A separator (4) for a non-aqueous electrolyte secondary battery was obtained by the same method as in Example 1, except for (v) to (vii) below. (v) As a porous substrate, a polyolefin porous film made of polyethylene (thickness: 10.8 μm, air permeability: 91 sec / 100 mL, basis weight: 5.52 g / m²) 2 ) used. (vi) The coating liquid was applied to the porous substrate using a normal bar, with an applied load of 94 N / m per width of the coating bar applied to the porous substrate, under the conditions of clearance: 0.07 mm and coating speed: 20 mm / min. (vii) The coating is carried out while impregnating the surface of the porous substrate opposite to the surface to which the coating liquid is applied with NMP.

[0122] [Comparative Example 2] A separator (5) for a non-aqueous electrolyte secondary battery was obtained by the same method as in Example 1, except for (viii) and (ix) below. (viii) As a porous substrate, a polyolefin porous film made of polyethylene (thickness: 10.8 μm, air permeability: 94 sec / 100 mL, basis weight: 5.56 g / m²) 2 ) used. ( ix The coating liquid was applied to the porous substrate using a barcoder for manual application, without applying any substantial load to the porous substrate, under the conditions of clearance: 0.05 mm and coating speed: 5 mm / min.

[0123] [result] The physical properties of the separators (1) to (5) for non-aqueous electrolyte secondary batteries produced in Examples 1 to 3 and Comparative Examples 1 and 2 were measured using the method described above. The results are shown in Tables 1 and 2 below.

[0124] [Table 1]

[0125] [Table 2]

[0126] As shown in Table 2, the non-aqueous electrolyte secondary battery separators (1) to (3) manufactured in Examples 1 to 3 have a "weight ratio in the mixed layer" of 0.07 or higher. On the other hand, the non-aqueous electrolyte secondary battery separators (4) and (5) manufactured in Comparative Examples 1 and 2 have a "weight ratio in the mixed layer" of less than 0.07.

[0127] Non-aqueous electrolyte secondary battery separators (1) to (3) are compared to non-aqueous electrolyte secondary battery separators (4) and (5) at 200°C. Heating dimensional retention rate The values ​​were large, indicating superior heat resistance. Furthermore, the non-aqueous electrolyte secondary battery separators (1) to (3) had air permeability and coin cell resistance values ​​equivalent to those of non-aqueous electrolyte secondary battery separators (4) and (5), indicating good ion permeability and coin cell resistance maintenance.

[0128] In summary, the separator for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention has excellent heat resistance and also excellent battery performance such as ion permeability and coin cell resistance maintenance, due to having a "weight ratio in the mixed layer" of 0.07 or more. [Industrial applicability]

[0129] A separator for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention can be suitably used even in environments where high heat resistance is required. [Explanation of Symbols]

[0130] 1: Laminate consisting of a residual porous substrate and a mixed layer 5: Heat resistant layer 7: Filler

Claims

1. It comprises a porous substrate having a porous film mainly composed of polyolefin resin and a mixed layer containing a heat-resistant resin, The weight W of the heat-resistant resin in the mixed layer １ The weight W of the porous substrate ０ Weight ratio (W １ / W ０ ) is 0.07 or higher, The heat-resistant resin is a nitrogen-containing aromatic polymer. A separator for a non-aqueous electrolyte secondary battery, wherein the porous substrate has an air permeability of 30 to 92 sec / 100 mL.

2. A separator for a non-aqueous electrolyte secondary battery according to claim 1, wherein the shutdown temperature is 150°C or higher.

3. A separator for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein a heat-resistant layer containing the heat-resistant resin is laminated on the mixed layer.

4. The separator for a non-aqueous electrolyte secondary battery according to claim 3, wherein the heat-resistant layer further comprises a filler.

5. The separator for a non-aqueous electrolyte secondary battery according to claim 4, wherein the content of the filler is 20% by weight or more and 90% by weight or less with respect to the total weight of the heat-resistant layer.

6. The heat-resistant layer has a value of 5% or more represented by the following formula (1), as described in any one of claims 3 to 5, for a separator for a non-aqueous electrolyte secondary battery. Brightness X １ (%) - Brightness X ２ (%) ・・(1) (Here, luminance X １ This refers to the average brightness at a point from the interface of the heat-resistant layer in contact with the mixed layer to a depth of 20% of the thickness of the heat-resistant layer. Brightness X ２ This refers to the average brightness at a point from the outermost surface of the heat-resistant layer to a depth of 20% of the thickness of the heat-resistant layer. The average brightness of the entire heat-resistant layer is 100%.

7. A separator for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, wherein the air permeability is 500 sec / 100 mL or less.

8. A separator for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein the heat-resistant resin is an aramid resin.

9. A component for a non-aqueous electrolyte secondary battery, comprising a positive electrode, a separator for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 8, and a negative electrode, arranged in this order.

10. A non-aqueous electrolyte secondary battery comprising a separator for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 8.

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