Separator for non-aqueous electrolyte secondary battery

Abstract

To provide a separator for a non-aqueous electrolyte secondary battery that excels in both excellent ion permeability and compressive strength.SOLUTION: The separator for a non-aqueous electrolyte secondary battery includes a porous film and a porous layer laminated on both surfaces of the porous film. "60° gloss of the surface of one porous layer / 60° gloss of the surface of the other porous layer>1.15 (B)" is satisfied.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a separator for a non-aqueous electrolyte secondary battery (hereinafter also simply referred to as "separator"). [Background technology]

[0002] Non-aqueous electrolyte secondary batteries, in particular lithium ion secondary batteries, have a high energy density and are therefore widely used as batteries for personal computers, mobile phones, portable information terminals, and the like, and recently they have been developed as batteries for use in vehicles.

[0003] In recent years, with the expansion of applications of non-aqueous electrolyte secondary batteries, the separator is required to have heat resistance in order to further improve the safety of the battery. Here, for example, as described in Patent Document 1, a separator in which a heat-resistant porous layer is laminated on at least one side of a porous substrate is known to be a separator with excellent heat resistance. In addition, an example of Patent Document 1 describes a separator in which a heat-resistant porous layer is laminated on both sides of a porous substrate. As described in the example of Patent Document 1, a separator in which a heat-resistant porous layer is laminated on both sides of a porous substrate is known to be a separator with better heat resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-60777 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a separator in which a porous layer is laminated on both sides of a conventional porous substrate, the respective porous layers laminated on both sides of the porous substrate are generally porous layers having substantially the same or very similar properties. Here, the separator in which a porous layer is laminated on both sides of the conventional porous substrate has lower ion permeability than a separator in which a porous layer is laminated on one side of the porous substrate, and as a result, the rate characteristics of a non-aqueous electrolyte secondary battery including the separator may be deteriorated. On the other hand, it is known that the deterioration of the ion permeability can be prevented by adopting a porous layer with low air permeability as the porous layer laminated on both sides of the porous substrate. However, the separator in which the porous layer with low air permeability is laminated on both sides of the porous substrate has low compression resistance. Here, when the charge / discharge cycle is repeated in a non-aqueous electrolyte secondary battery, the electrodes expand and contract, and pressure is applied to the separator due to the expansion and contraction of the electrodes. If the separator has low compression resistance, the internal porous structure of the separator is likely to collapse due to the applied pressure, and as a result, the resistance of the separator is likely to increase. Therefore, a nonaqueous electrolyte secondary battery having a separator with low compression resistance may have an increased resistance value during repeated charge-discharge cycles, and may have deteriorated cycle characteristics.

[0006] As described above, in a conventional separator in which a porous layer is laminated on both sides of a porous substrate, there is a trade-off between ion permeability and compression resistance. Therefore, in a non-aqueous electrolyte secondary battery including a separator in which a porous layer is laminated on both sides of a conventional porous substrate, either the rate characteristic or the cycle characteristic is deteriorated, and there is a problem in that it is not possible to achieve both excellent rate characteristic and excellent cycle characteristic at the same time.

[0007] In order to solve the above problems, an object of the present invention is to provide a separator for a non-aqueous electrolyte secondary battery which is excellent in both ion permeability and compression resistance. [Means for solving the problem]

[0008] As a result of extensive research, the inventors have discovered that in a separator in which porous layers are laminated on both sides of a porous substrate (porous film), when there is a large difference in gloss between one side of the porous layer and the other side, it is possible to achieve both excellent ion permeability and excellent compression resistance, and have arrived at the present invention.

[0009] One aspect of the present invention is a separator for a non-aqueous electrolyte secondary battery, comprising a porous film containing a polyolefin resin as a main component and a porous layer laminated on both sides of the porous film, The porous layer contains a resin, A separator for a non-aqueous electrolyte secondary battery, wherein the 60° gloss of a surface of one of the porous layers and the 60° gloss of a surface of the other of the porous layers satisfy the following relationship (A) and (B): (60° gloss of one of the surfaces of the porous layer)>(60° gloss of the other of the surfaces of the porous layer) (A) (60° gloss of one of the surfaces of the porous layer) / (60° gloss of the other of the surfaces of the porous layer)>1.15 (B) Effect of the Invention

[0010] The separator for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention exhibits the effects of being excellent in both ion permeability and compression resistance. [Brief description of the drawings]

[0011] [Figure 1] In one embodiment of the present invention, (a) is a diagram showing an embodiment of one porous layer having a high 60° gloss on its surface, and (b) is a diagram showing an embodiment of the other porous layer having a low 60° gloss on its surface. [Diagram 2] 1 is a diagram showing the shape of an electrode used in a "pressure impedance test" described in an example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to each of the configurations described below, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in different embodiments. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more, B or less."

[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 is a separator for a non-aqueous electrolyte secondary battery comprising a porous film containing a polyolefin resin as a main component, and porous layers laminated on both sides of the porous film, wherein the porous layers contain a resin, and the 60° gloss of a surface of one of the porous layers and the 60° gloss of a surface of the other of the porous layers satisfy the following relationship (A) and (B): (60° gloss of one of the surfaces of the porous layer)>(60° gloss of the other of the surfaces of the porous layer) (A) (60° gloss of one of the surfaces of the porous layer) / (60° gloss of the other of the surfaces of the porous layer)>1.15 (B)

[0014] Hereinafter, the separator for a nonaqueous electrolyte secondary battery according to one embodiment of the present invention and the separator for a nonaqueous electrolyte secondary battery according to another embodiment of the present invention will be collectively referred to as the "separator of the present invention." Each member constituting the separator of the present invention will be described in detail below.

[0015] [Porous film] The porous film in one embodiment of the present invention is mainly composed of a polyolefin resin. Here, "mainly composed of a polyolefin resin" means that the proportion of the polyolefin resin in the porous film is 50% by weight or more, preferably 90% by weight or more, and more preferably 95% by weight or more of the total material constituting the porous film.

[0016] The porous film has many interconnected pores inside, allowing gases and liquids to pass from one surface to the other.

[0017] The thickness of the porous film is preferably 4 to 40 μm, and more preferably 5 to 20 μm. If the thickness of the porous film is 4 μm or more, internal short circuit of the battery can be sufficiently prevented. On the other hand, if the thickness of the porous film is 40 μm or less, the nonaqueous electrolyte secondary battery can be prevented from becoming large.

[0018] The polyolefin resin has a weight average molecular weight of 5×10 5 ~15×10 6 It is more preferable that the polyolefin resin contains a high molecular weight component having a weight average molecular weight of 1,000,000 or more. In particular, it is more preferable that the polyolefin resin contains a high molecular weight component having a weight average molecular weight of 1,000,000 or more, since the strength of the obtained porous film and the separator containing the porous film is improved.

[0019] The polyolefin resin is not particularly limited, but examples thereof include thermoplastic resins such as homopolymers or copolymers obtained by polymerizing monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene. Examples of the homopolymers include polyethylene, polypropylene, and polybutene. Examples of the copolymers include ethylene-propylene copolymers.

[0020] Among these, polyethylene is more preferable because it can prevent (shut down) an excessive current from flowing through the separator at a lower temperature. Examples of the polyethylene include low-density polyethylene, high-density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), and ultra-high molecular weight polyethylene having a weight-average molecular weight of 1,000,000 or more. Among these, the ultra-high molecular weight polyethylene is more preferable.

[0021] The weight per unit area of ​​the porous film can be appropriately determined in consideration of the strength, thickness, weight and handling properties. However, in order to increase the weight energy density and volume energy density of the nonaqueous electrolyte secondary battery, the weight per unit area is preferably 3 to 20 g / m. 2 is preferably 3 to 12 g / m 2 More preferably, the thickness is 3 to 10 g / m 2 It is even more preferable that:

[0022] From the viewpoint of obtaining sufficient ion permeability, the air permeability of the porous film is preferably 30 to 500 sec / 100 mL, and more preferably 50 to 300 sec / 100 mL, in terms of Gurley value.

[0023] The porosity of the porous film is preferably 20 to 80% by volume, more preferably 30 to 75% by volume, so as to increase the amount of electrolyte retained and to reliably prevent the flow of excessive current at a lower temperature. The pore size of the pores in the porous film is preferably 0.3 μm or less, more preferably 0.14 μm or less, so as to obtain sufficient ion permeability.

[0024] [Method of manufacturing porous film] The manufacturing method of the porous film is not particularly limited. For example, a polyolefin resin, a pore-forming agent such as an inorganic filler or a plasticizer, and optionally an antioxidant are kneaded and then extruded to prepare a sheet-shaped polyolefin resin composition. Then, the pore-forming agent is removed from the sheet-shaped polyolefin resin composition using a suitable solvent. Then, the polyolefin resin composition from which the pore-forming agent has been removed is stretched to produce the porous film.

[0025] The inorganic filler may be an inorganic filler, specifically, calcium carbonate, etc. The plasticizer may be a low molecular weight hydrocarbon such as liquid paraffin.

[0026] [Porous layer] The porous layer in one embodiment of the present invention is laminated on both sides of the porous film. Here, the embodiment of the porous layer will be described with reference to FIG. 1. FIG. 1 is a diagram showing (a) an embodiment of one porous layer having a high 60° gloss on the surface, and (b) an embodiment of the other porous layer having a low 60° gloss on the surface, in one embodiment of the present invention. Here, as shown in FIG. 1(a) and FIG. 1(b), in one embodiment of the present invention, the porous layer 2 is laminated on the porous film 1. Note that FIG. 1 shows only the porous film 1 and the porous layer 2 laminated on one side of the porous film 1. However, in the separator of the present invention, another porous layer is laminated on the surface of the porous film 1 opposite to the surface on which the porous layer 2 is laminated. The other porous layer is the other porous layer when the porous layer 2 is the one porous layer, and is the one porous layer when the porous layer 2 is the other porous layer. In addition, the "surface" of the porous layer 2 means the surface opposite to the surface of the porous layer 2 on the porous film 1 side.

[0027] As shown in FIG. 1(a), the one porous layer in one embodiment of the present invention has a smooth surface with few irregularities, and therefore the incident light 4 irradiated from the light source 3 is almost totally reflected by the surface. As a result, the incident light 4 is reflected, and the intensity of the reflected light 5, which has the same reflection angle (receiving angle) as the incident angle, is close to the intensity of the incident light 4, and the gloss of the porous layer 2 is high. On the other hand, as shown in FIG. 1(b), the other porous layer in one embodiment of the present invention has a rough surface, and therefore the incident light 4 irradiated from the light source 3 is diffusely reflected by the surface. As a result, the incident light 4 is reflected, and the intensity of the reflected light 5, which has the same reflection angle (receiving angle) as the incident angle, is lower than the intensity of the incident light 4, and the gloss of the porous layer 2 is low.

[0028] Here, the porous layer 2 is composed of a resin and, optionally, a filler. In the porous layer 2, a plurality of pores are formed by combining the resins. As a result, the porous layer 2 has a porous structure. By having the porous structure, the porous layer 2 is able to pass gas and liquid from one surface to the other surface.

[0029] It is generally known that when the three-dimensional network structure made of the resin constituting the porous layer 2 is sparse and / or when the resin or filler is a particle with a large particle diameter, the surface irregularities become large and the internal porous structure becomes a coarse structure. On the other hand, when the three-dimensional network structure made of the resin constituting the porous layer 2 is dense and when the resin or filler is a fine particle with a small particle diameter, the surface irregularities become small, the surface becomes smooth, and the internal porous structure becomes a dense structure.

[0030] Therefore, the one porous layer in one embodiment of the present invention has a high 60° gloss on the surface and a smooth surface with few irregularities, so that the internal porous structure is a dense structure. A porous layer with a dense porous structure is difficult to collapse under pressure, so that it has high compression resistance, but the pores are small, so that gas and liquid do not easily pass through, the air permeability value is large, and the ion permeability is low. In addition, the other porous layer in one embodiment of the present invention has a low 60° gloss on the surface and a surface with large irregularities, so that the internal porous structure is a rough structure. A porous layer with a rough porous structure has large pores, so that gas and liquid easily pass through, the air permeability value is small, and the ion permeability is high, but it is easy to collapse under pressure, so that the compression resistance is low. Therefore, in one embodiment of the present invention, one porous layer with a high 60° gloss on the surface has excellent compression resistance, but low ion permeability. The other porous layer, which has a low 60° gloss on the surface, has low compression resistance but is excellent in ion permeability.

[0031] In the separator of the present invention, the 60° gloss of the surface of one of the porous layers laminated on both sides of the porous film (hereinafter referred to as "gloss 1") and the 60° gloss of the surface of the other porous layer (hereinafter referred to as "gloss 2") satisfy the following relationship (A). (Glossiness 1)>(Glossiness 2) (A)

[0032] Satisfying the relationship (A) means that, in the separator of the present invention, of the porous layers laminated on both sides of the porous film, the porous layer having a greater 60° gloss on its surface is defined as "one porous layer", and the porous layer having a smaller 60° gloss on its surface is defined as "the other porous layer".

[0033] In the separator of the present invention, the "gloss level 1" and the "gloss level 2" satisfy the following relationship (B). (Glossiness 1) / (Glossiness 2)>1.15 (B)

[0034] Satisfying the relationship (B) means that "one porous layer" has a high "glossiness 1" and a dense porous structure, and "the other porous layer" has a low "glossiness 2" and a coarse porous structure. Thus, in the separator of the present invention, "one porous layer" having low ion permeability but high compression resistance and "the other porous layer" having high ion permeability but low compression resistance are laminated on each of both sides of the porous film.

[0035] Conventional separators in which porous layers are laminated on both sides of a porous film include the following two types of separators. A separator in which both of the porous layers have high ion permeability but low compression resistance (hereinafter referred to as "conventional separator 1"). A separator in which both of the porous layers have low ion permeability but high compression resistance (hereinafter, referred to as "conventional separator 2").

[0036] The separator of the present invention has an improved compression resistance of the entire separator by providing a "one porous layer" with high compression resistance compared to the conventional separator 1. Also, the separator of the present invention has an improved ion permeability of the entire separator by providing a "other porous layer" with high ion permeability compared to the conventional separator 2. As a result, the separator of the present invention, unlike the conventional separators 1 and 2, has the effect of being excellent in both ion permeability and compression resistance.

[0037] From the viewpoint of improving both the above-mentioned ion permeability and compression resistance, in the separator of the present invention that satisfies the requirement (B), the value of (gloss 1) / (gloss 2) is preferably 1.20 or more, and more preferably 1.25 or more.

[0038] The (glossiness 1) / (glossiness 2) value being excessively high means that in the separator of the present invention, the (glossiness 1) is excessively large or the (glossiness 2) is excessively small. Here, in the separator of the present invention, if the (glossiness 1) is excessively large, the ion permeability of the "one porous layer" may be excessively decreased, and the ion permeability of the entire separator may be decreased. In addition, in the separator of the present invention, if the (glossiness 2) is excessively small, the compression resistance of the "other porous layer" may be excessively decreased, and the compression resistance of the entire separator may be decreased. Therefore, it is more preferable that the (glossiness 1) and the (glossiness 2) are within a predetermined range in terms of preventing a decrease in compression resistance and a decrease in ion permeability. From the above viewpoint, the upper limit value of the (glossiness 1) is preferably 60% or less, more preferably 50% or less. Similarly, the lower limit value of the (glossiness 2) is preferably 5% or more, more preferably 10% or more.

[0039] From the viewpoint of preventing the aforementioned decrease in compression resistance and decrease in ion permeability, in the separator of the present invention that satisfies the requirement (B), the value of (gloss 1) / (gloss 2) is preferably 2.2 or less, and more preferably 2.0 or less.

[0040] The 60° gloss of the surface of the porous layer is the ratio of the intensity of reflected light having a reflection angle (reception angle) of 60° to the intensity of incident light when the surface of the porous layer is irradiated with incident light having an incidence angle of 60°. The 60° gloss of the surface of the porous layer is measured according to JIS Z8741, in which the incidence angle and reflection angle (reception angle) are set to 60°. Specifically, the 60° gloss of the surface of the porous layer can be measured, for example, by the method described in the Examples.

[0041] [resin] In one embodiment of the present invention, the porous layer contains a resin. When the porous layer contains a filler described below, the resin can function as a binder resin that bonds the fillers together, the filler and the positive electrode or the negative electrode, or the filler and the porous film.

[0042] In one embodiment of the present invention, the resin is preferably insoluble in the electrolyte of the battery and is electrochemically stable within the range of use of the battery. The resin is also preferably a heat-resistant resin.

[0043] The resin is not particularly limited. Specific examples of the resin include polyolefin, (meth)acrylate resin, fluorine-containing resin, polyamide resin, polyimide resin, polyester resin, rubber, resin with a melting point or glass transition temperature of 180° C. or higher, water-soluble polymer, polycarbonate, polyacetal, polyether ether ketone, etc. The resin may be one type or a mixture of two or more types of resins.

[0044] Among the specific examples of the resins, (meth)acrylate resins, fluorine-containing resins, polyamide resins and polyester resins are preferred.

[0045] Examples of polyamide resins include aromatic polyamides, preferably fully aromatic polyamides (aramid resins). Examples of polyester resins include polyarylates and liquid crystal polyesters. Examples of fluorine-containing resins include polyvinylidene fluoride resins. Examples of water-soluble polymers include polyvinyl alcohol, polyethylene glycol, cellulose ether, sodium alginate, polyacrylic acid, polyacrylamide, polymethacrylic acid, and the like.

[0046] Specific examples of the aramid resin include poly(paraphenylene terephthalamide), poly(metaphenylene isophthalamide), poly(parabenzamide), poly(metabenzamide), poly(4,4'-benzanilide terephthalamide), poly(paraphenylene-4,4'-biphenylenedicarboxylic acid amide), poly(metaphenylene-4,4'-biphenylenedicarboxylic acid amide), poly(paraphenylene-2,6-naphthalenedicarboxylic acid amide), poly(metaphenylene-2,6-naphthalenedicarboxylic acid amide), poly(para ... Examples of the poly(4,4'-diphenylsulfonyl terephthalamide) include poly(2-chloroparaphenylene terephthalamide), paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer, metaphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer, poly(4,4'-diphenylsulfonyl terephthalamide), paraphenylene terephthalamide / 4,4'-diphenylsulfonyl terephthalamide copolymer, etc. Among these, poly(paraphenylene terephthalamide) is more preferred.

[0047] The method for producing the resin is not particularly limited, and any conventionally known method can be used as appropriate.

[0048] [Filler] In one embodiment of the present invention, the porous layer may contain a filler, the content of which is preferably 30% by weight or more and 99% by weight or less, more preferably 40% by weight or more and 85% by weight or less, and even more preferably 40% by weight or more and 70% by weight or less, based on the total weight of the porous layer.

[0049] In one embodiment of the present invention, the material constituting the filler is not particularly limited. The filler may be composed of only one type of filler material, or may be composed of two or more types of fillers each having a different constituent material.

[0050] The filler may be an inorganic filler or an organic filler. Examples of the inorganic filler include fillers made of inorganic substances such as calcium carbonate, talc, clay, kaolin, silica, hydrotalcite, diatomaceous earth, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, aluminum hydroxide, boehmite, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, titanium nitride, alumina (aluminum oxide), aluminum nitride, mica, zeolite, and glass. Among these, the inorganic filler is preferably a filler made of an inorganic oxide such as silica, calcium oxide, magnesium oxide, titanium oxide, alumina, mica, zeolite, aluminum hydroxide, or boehmite, more preferably a filler made of calcium oxide, magnesium oxide, or alumina, and even more preferably a filler made of alumina. In addition, examples of the organic filler include fillers made of resin.

[0051] The shape of the filler is not particularly limited and may be, for example, spherical, elliptical, plate-like, rod-like, or irregular. Among these, the shape of the filler is preferably spherical.

[0052] The average particle size of the filler is preferably 0.01 μm or more and 10 μm or less, and more preferably 0.02 μm or more and 5 μm or less.

[0053] [Properties of porous layer] The thickness of the porous layer is preferably 0.5 to 15 μm, and more preferably 1 to 10 μm. When the thickness is within this range, it is suitable for preventing internal short circuits due to damage to the nonaqueous electrolyte secondary battery, for retaining the electrolyte in the porous layer, and for preventing deterioration of rate characteristics or cycle characteristics.

[0054] The weight per unit area of ​​the porous layer can be appropriately determined in consideration of the strength, film thickness, weight and handling property of the porous layer. The weight per unit area of ​​the porous layer is 0.5 to 20 g / m 2 It is preferable that the thickness is 0.5 to 10 g / m 2 By setting the weight per unit area within these numerical ranges, it is possible to increase the weight energy density and volume energy density of the nonaqueous electrolyte secondary battery.

[0055] The porosity of the porous layer is preferably 40% or more and 80% or less, and more preferably 50% or more and 70% or less. When the porosity is within the above range, the separator and the nonaqueous electrolyte secondary battery including the separator can obtain sufficient ion permeability.

[0056] The pores in the porous layer preferably have a pore size of 1.0 μm or less, more preferably 0.5 μm or less. By setting the pore size to this size, the separator and the nonaqueous electrolyte secondary battery including the separator can obtain sufficient ion permeability.

[0057] The porous layer may contain other components in addition to the resin and the filler. Examples of the other components include a surfactant and a wax. The content of the other components is preferably 0% by weight to 10% by weight based on the total weight of the porous layer.

[0058] In one embodiment of the present invention, it is preferable that the composition of the "one porous layer" and the composition of the "other porous layer" are substantially the same. Here, "substantially the same composition" means that the type of resin as a constituent material and the type of filler as an optional constituent material are the same between the "one porous layer" and the "other porous layer". In addition, the difference in the weight ratio (content) of the resin and the weight ratio (content) of the filler with respect to the weight of the entire porous layer between the "one porous layer" and the "other porous layer" is more preferably 30% or less, even more preferably 15% or less, and particularly preferably 0%. The difference in the weight ratio (content) of the resin and the weight ratio (content) of the filler being 0% means that the contents of the resin and the filler are the same.

[0059] [Method of manufacturing the porous layer] The method for producing the porous layer includes, for example, preparing a coating liquid by dissolving the resin in a solvent, applying the coating liquid to a substrate to form a coating layer, and then removing the solvent from the coating layer to form the porous layer. The substrate can be, for example, the porous film. In addition, when the porous layer contains the filler, the coating liquid can be prepared by dissolving the resin in a solvent and dispersing the filler.

[0060] The solvent (dispersion medium) is sufficient if it does not adversely affect the substrate such as a porous film and can dissolve the resin uniformly and stably, and if the filler is included, it is sufficient if it can disperse the filler uniformly and stably. Specific examples of the solvent include water; lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and t-butyl alcohol; acetone, toluene, xylene, hexane, N-methylpyrrolidone (NMP), N,N-dimethylacetamide, and N,N-dimethylformamide. The solvent may be used alone or in combination of two or more.

[0061] As long as the coating liquid can satisfy the conditions such as the resin solid content (resin concentration) necessary for obtaining a desired porous layer, and in the case of containing a filler, the conditions such as the amount of the filler, the forming method is not limited. Specific examples of the forming method include, for example, a mechanical stirring method, an ultrasonic dispersion method, a high-pressure dispersion method, a media dispersion method, and the like. Further, in the case of containing the filler, for example, a conventionally known disperser such as a three-one motor may be used to disperse the filler in the solvent. Further, the coating liquid may contain additives such as a dispersant, a plasticizer, a surfactant, and a pH adjuster in addition to the resin and the filler as long as the object of the present invention is not impaired.

[0062] The method of applying the coating liquid to the substrate is not particularly limited. For example, a sequential lamination method in which a porous layer is formed on one surface of the substrate and then a porous layer is formed on the other surface, a simultaneous lamination method in which porous layers are simultaneously formed on both surfaces of the substrate, and the like can be performed.

[0063] The method of applying the coating liquid to the substrate may be any method that can achieve the required basis weight and coating area. As the coating method, for example, a conventionally known method such as a gravure coater method can be used.

[0064] The method for forming the porous layer is not particularly limited, and examples thereof include the methods shown in the following (a) or (b).

[0065] (a) A method of immersing the coating layer in a precipitation liquid, precipitating the coating layer, then washing with water and drying to remove the solvent to form the porous layer (hereinafter referred to as the "immersion precipitation method").

[0066] (b) A method of exposing the substrate on which the coating layer is formed to air containing water vapor, precipitating the coating layer, then washing with water and drying to remove the solvent to form the porous layer (hereinafter referred to as the "humidity precipitation method").

[0067] In the immersion precipitation method, the method of immersing the coating layer in the precipitation liquid is not particularly limited. The coating layer and the substrate may be immersed together in the precipitation liquid, or only the coating layer may be immersed in the precipitation liquid.

[0068] The precipitating liquid may be a mixture of a solvent that cannot dissolve the resin and an organic solvent that can dissolve the resin. In the precipitating liquid, the precipitating rate of the resin can be controlled by adjusting the mixing ratio of the solvent that cannot dissolve the resin and the organic solvent. Specifically, when the mixing ratio of the organic solvent is small, the precipitating rate of the resin is high.

[0069] The solvent incapable of dissolving the resin is not particularly limited, and may be, for example, water, etc. The organic solvent is not particularly limited, and may be, for example, NMP, etc.

[0070] In the humidity precipitation method, the rate at which the resin is precipitated can be controlled by adjusting the temperature and humidity of the air containing water vapor. Specifically, the higher the temperature of the air containing water vapor, the faster the resin is precipitated. Also, the higher the humidity of the air containing water vapor, the faster the resin is precipitated.

[0071] Furthermore, in general, the immersion precipitation method provides a faster precipitation rate of the resin than the humidity precipitation method.

[0072] When the deposition rate of the resin is fast, the resin is deposited before the three-dimensional network structure made of the resin grows sufficiently, so that the resin forms a fine (dense) structure. Therefore, in the porous layer, the internal pore structure becomes a dense structure, and the surface becomes a smooth surface with few irregularities. Therefore, when the deposition rate of the resin is increased to form a porous layer using the above-mentioned method, the "glossiness 1" or the "glossiness 2" can be controlled to a large range in the obtained porous layer. On the other hand, when the deposition rate of the resin is decreased to form a porous layer, the three-dimensional network structure grows sufficiently, so that voids originating from the three-dimensional network structure are easily formed on the surface and inside of the porous layer. Therefore, in the porous layer, the internal pore structure becomes a rough structure due to the voids, and the surface irregularities become large. Therefore, when the deposition rate of the resin is decreased to form a porous layer using the above-mentioned method, the "glossiness 1" or the "glossiness 2" can be controlled to a small range in the obtained porous layer.

[0073] Therefore, the separator of the present invention can be produced by a method including the following steps (i) and (ii). (i) A step of forming the "one porous layer" on one side of the porous film by increasing the deposition rate of the resin. (ii) A step of forming the "other porous layer" on the other side of the porous film by slowing down the deposition rate of the resin.

[0074] A specific method for producing the separator of the present invention can include, for example, a method in which the "one porous layer" is formed on one side of the porous film by the immersion precipitation method, and the "other porous layer" is formed on the other side of the porous film by the humidity precipitation method.

[0075] When the step (i) and the step (ii) are performed, the step (i) may be performed first and then the step (ii), the step (ii) may be performed first and then the step (i), or the step (i) and the step (ii) may be performed simultaneously.

[0076] In the steps (i) and (ii), the operation of washing and drying the deposited coating layer may be performed in common. In other words, in the production of the separator of the present invention, after depositing the coating layer on both sides of the porous film, the coating layer or a laminate consisting of the coating layer and the porous film may be washed and dried in one go to form the porous layer on both sides of the porous film.

[0077] The conditions for forming the porous layer include, for example, the temperature and humidity of the air containing water vapor when the humidity deposition method is adopted, and the mixing ratio of the solvent that cannot dissolve the resin and the organic solvent in the deposition solution when the immersion deposition method is adopted. When the porous layer is formed on one side of each of the porous films, the "glossiness 1" and "glossiness 2" can be controlled within a suitable range by appropriately adjusting the type of the formation method and the formation conditions in the formation of each of the porous layers. As a result, the separator of the present invention can be suitably manufactured.

[0078] [Embodiment 3: Nonaqueous electrolyte secondary battery member, Embodiment 4: Nonaqueous electrolyte secondary battery] The nonaqueous electrolyte secondary battery member according to one embodiment of the present invention includes a positive electrode, a separator according to one embodiment of the present invention, and a negative electrode arranged in this order. The nonaqueous electrolyte secondary battery according to one embodiment of the present invention includes the separator according to one embodiment of the present invention.

[0079] The nonaqueous electrolyte secondary battery member, by including the separator, exhibits an effect of excellent rate characteristics and cycle characteristics in the nonaqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery, by including the separator, exhibits an effect of excellent rate characteristics and cycle characteristics.

[0080] A conventionally known manufacturing method can be used as the manufacturing method of the nonaqueous electrolyte secondary battery. For example, the nonaqueous electrolyte secondary battery member is formed by arranging a positive electrode, the separator, and a negative electrode in this order. Here, the porous layer of the separator is between the porous film and at least one of the positive electrode and the negative electrode. Next, the nonaqueous electrolyte secondary battery member is placed in a container that will become the housing of the nonaqueous electrolyte secondary battery. After filling the container with the nonaqueous electrolyte, the container is sealed while reducing the pressure. This allows the nonaqueous electrolyte secondary battery to be manufactured.

[0081] <Positive electrode> The positive electrode in one embodiment of the present invention is not particularly limited as long as it is generally used as a positive electrode of 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 formed on a positive electrode current collector can be used as the positive electrode. The active material layer may further contain a conductive agent.

[0082] The positive electrode active material may be, for example, a material capable of doping / dedoping metal ions such as lithium ions or sodium ions, etc. Examples of such materials include lithium composite oxides containing at least one transition metal such as V, Mn, Fe, Co, and Ni.

[0083] The conductive agent may be, for example, one or more selected from carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and baked organic polymer compounds.

[0084] Examples of the binder include fluorine-based resins such as polyvinylidene fluoride (PVDF), acrylic resins, and styrene-butadiene rubber.

[0085] The positive electrode current collector may be made of a conductor such as Al, Ni, or stainless steel.

[0086] Examples of methods for producing a positive electrode sheet include a method in which a positive electrode active material, a conductive agent, and a binder are pressure-molded on a positive electrode current collector.

[0087] <Negative electrode> The negative electrode in one embodiment of the present invention is not particularly limited as long as it is generally used as a negative electrode of 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 formed on a negative electrode current collector can be used as the negative electrode. The active material layer may further contain a conductive agent.

[0088] The negative electrode active material may be, for example, a material capable of doping / de-doping metal ions such as lithium ions or sodium ions, etc. Examples of such materials include carbonaceous materials such as natural graphite.

[0089] The negative electrode current collector may be made of, for example, Cu, Ni, stainless steel, or the like.

[0090] The negative electrode sheet can be produced, for example, by pressurizing and molding a negative electrode active material on a negative electrode current collector.

[0091] <Nonaqueous electrolyte> The nonaqueous electrolyte in one embodiment of the present invention is not particularly limited as long as it is a nonaqueous electrolyte generally used in nonaqueous electrolyte secondary batteries. For example, a nonaqueous electrolyte obtained by dissolving a lithium salt in an organic solvent can be used as the nonaqueous electrolyte. For example, LiClO 4 , LiPF 6 , LiAsF 6 , LiSbF 6 , LiBF4 , LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 , LiC(CF 3 SO 2 ) 3 , Li 2 B 10 Cl 10 , lower aliphatic carboxylic acid lithium salts and LiAlCl 4 One or more selected from the above can be mentioned.

[0092] Examples of the organic solvent constituting the nonaqueous electrolyte solution include one or more selected from carbonates, ethers, esters, nitriles, amides, carbamates, sulfur-containing compounds, and fluorine-containing organic solvents obtained by introducing a fluorine group into these organic solvents.

[0093] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0094] [summary] One embodiment of the present invention may include the following inventions [1] to [6]. [1] A separator for a non-aqueous electrolyte secondary battery, comprising a porous film containing a polyolefin resin as a main component and a porous layer laminated on both sides of the porous film, The porous layer contains a resin, A separator for a non-aqueous electrolyte secondary battery, wherein the 60° gloss of a surface of one of the porous layers and the 60° gloss of a surface of the other of the porous layers satisfy the following relationship (A) and (B): (60° gloss of one of the surfaces of the porous layer)>(60° gloss of the other of the surfaces of the porous layer) (A) (60° gloss of one of the surfaces of the porous layer) / (60° gloss of the other of the surfaces of the porous layer)>1.15 (B) [2] The porous layer contains a filler, The separator for a non-aqueous electrolyte secondary battery according to [1], wherein a content of the filler in the porous layer is 30% by weight or more and 99% by weight or less, based on a total weight of the porous layer. [3] The separator for a non-aqueous electrolyte secondary battery according to [1] or [2], wherein the resin is at least one selected from the group consisting of (meth)acrylate-based resins, fluorine-containing resins, polyamide-based resins, and polyester-based resins. [4] The separator for a non-aqueous electrolyte secondary battery according to [3], wherein the polyamide resin is an aramid resin. [5] A member for a non-aqueous electrolyte secondary battery, comprising a positive electrode, the separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [4], and a negative electrode, arranged in this order. [6] A non-aqueous electrolyte secondary battery comprising the separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [4].

[0095] The scope of the nonaqueous electrolyte secondary battery separator, nonaqueous electrolyte secondary battery member, and nonaqueous electrolyte secondary battery according to one embodiment of the present invention may include any combination of the features described in the above-mentioned configurations within the scope of the claims. EXAMPLES

[0096] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0097] [Measurement methods for various physical properties] Various physical properties in Examples 1 to 3 and Comparative Examples 1 and 2 were measured by the following methods.

[0098] [Total thickness of porous layer] The thicknesses (unit: μm) of the porous films and separators described in Examples 1 to 3 and Comparative Examples 1 and 2 were measured using a high-precision digital length measuring machine (Litematic VL-50B) manufactured by Mitutoyo Corporation. Then, the difference between the thickness of the separator and the thickness of the porous film was calculated, and the calculated value was taken as the total thickness (unit: μm) of the porous layers included in the separator. Here, the total thickness of the porous layers means the sum of the thicknesses of the porous layers formed on both sides (front and back) of the porous film in the separator.

[0099] [Air permeability per film thickness of porous layer] <Measurement and calculation of air permeability of porous layer> From the porous film and separator described in Examples 1 to 3 and Comparative Examples 1 and 2, a square of 60 mm x 60 mm in size was cut out to obtain a sample for measuring the air permeability of the porous film and the separator. The sample for measuring the air permeability of the porous film and the separator was placed in a digital type Oken type air permeability tester EGO1 manufactured by Asahi Seiko Co., Ltd., and the air permeability of the porous film and the separator was measured, respectively, to obtain the air permeability (A) (unit: s / 100 ml) of the porous film and the air permeability (B) (unit: s / 100 ml) of the separator. Then, the air permeability (C) (unit: s / 100 ml) of the porous layer was calculated from the measured values ​​of (A) and (B) according to the following formula. Air permeability of porous layer (C) = Air permeability of separator (B) - Air permeability of porous film (A)

[0100] <Calculation of air permeability per film thickness of porous layer> The air permeability (C) (unit: s / 100 ml) of the porous layer obtained by the above-mentioned method was divided by the film thickness (unit: μm) of the porous layer calculated by the method described in the "Film thickness of porous layer" column above to calculate the air permeability per unit film thickness of the porous layer (unit: (s / 100 ml) / μm).

[0101] [60° gloss of the surface of the porous layer (gloss 1, gloss 2)] The glossiness 1 and glossiness 2 of the separators produced in Examples 1 to 3 and Comparative Examples 1 and 2 described below were measured in accordance with JIS Z8741 with the incident angle and the receiving angle of 60° as follows. The specific method is shown below.

[0102] Each separator manufactured in Examples 1 to 3 and Comparative Examples 1 and 2 was cut into an A4 size to obtain a gloss measurement sample. Using a Handy Glossmeter PG-1M (manufactured by Nippon Denshoku Industries Co., Ltd.), a sheet of KB paper (manufactured by Kokuyo Co., Ltd., product number: KB-39N) was used as an underlay, and the A4 size gloss measurement sample was placed on top of it, and the surface gloss of each of the two porous layers constituting the separator was measured. The gloss measurement was performed with the incident angle and receiving angle set to 60°.

[0103] More specifically, the "glossiness" of one of the two porous layers was measured at seven arbitrary points on the surface by the above-mentioned method. The average value of the five "glossinesses" excluding the highest and lowest values ​​among the seven "glossinesses" obtained in the measurement was defined as the "MD glossiness" of the one porous layer. Similarly, the average value of the five "TD glossinesses" excluding the highest and lowest values ​​among the seven "TD glossinesses" obtained in the measurement was defined as the "surface glossiness" of the one porous layer. In addition, the same operation as the measurement and calculation operation for the one porous layer was performed on the other porous layer of the two porous layers, and the "surface glossiness" of the other porous layer was calculated. The larger "surface glossiness" of the "surface glossiness" of the one porous layer and the "surface glossiness" of the other porous layer was defined as the "glossiness 1", and the porous layer having the "glossiness 1" was defined as the "one porous layer". In addition, the smaller of the "surface glossiness" of the one porous layer and the "surface glossiness" of the other porous layer is defined as the "glossiness 2," and the porous layer having this "glossiness 2" is defined as the "other porous layer."

[0104] Next, the calculated "glossiness 1" and "glossiness 2" were used to calculate the value represented by the following formula (B). "Glossiness 1" / "Glossiness 2" (B)

[0105] [Pressure impedance] <Preparation of test cell> Test cells were produced by using the separators produced in Examples 1 to 3 and Comparative Examples 1 and 2 described below, respectively, according to the methods shown in 1. to 4. below. 1. Six separator pieces measuring 4.7 cm x 6.0 cm were cut out from the separator. 2. Two aluminum pieces were cut out from an aluminum foil with a thickness of 20 μm: one in the shape of a flag as shown in Figure 2(a) and the other in the shape of a flag as shown in Figure 2(b). Next, an aluminum tab with a sealant was welded to the rod part of each of the two cut aluminum pieces to create an aluminum electrode. 3. In a laminate pouch, the two aluminum electrodes prepared in step 2 were stacked, and the six separator pieces cut out in step 1 were placed between the two aluminum electrodes in the same orientation, and 250 μL of non-aqueous electrolyte was poured in. The non-aqueous electrolyte was a mixture of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 3:5:2, and LiPF 2 with a concentration of 1 mol / L was poured into the mixture. 6 A non-aqueous electrolyte having a composition obtained by dissolving the above was used. 4. The laminate pouch was heat-sealed while the pressure inside the laminate pouch was reduced, thereby producing a non-aqueous electrolyte secondary battery for testing, i.e., a test cell.

[0106] <Measurement of pressure impedance> Using the test cell prepared by the above method, pressure impedance measurement was carried out according to the following procedure: The device used for the measurement was an LCR meter (manufactured by Hioki E.E., product name: IM3536). 1. The test cell was sandwiched between a jig made of two iron plates, and a pressure of 10 MPa was applied using a hand press. The impedance of the test cell was measured under the following conditions: temperature: 25° C., frequency range: 200,000 to 20,000 Hz. 2.1. After the impedance measurement was performed on the test cell, a pressure of 10 MPa was applied using the hand press to bring the ultimate pressure to 20 MPa, and the impedance of the test cell was then measured under the same conditions as in 1. 3. Measurements were performed in 10 MPa increments until the ultimate pressure reached 50 MPa. Specifically, a further 10 MPa pressure was applied to the test cell after the impedance measurement in 2, using the hand press machine, to set the ultimate pressure to 30 MPa, and then the impedance measurement of the test cell was performed under the same conditions as in 1. Next, a further 10 MPa pressure was applied to the test cell, using the hand press machine, to set the ultimate pressure to 40 MPa, and then the impedance measurement of the test cell was performed under the same conditions as in 1. Finally, a further 10 MPa pressure was applied to the test cell, using the hand press machine, to set the ultimate pressure to 50 MPa, and then the impedance measurement of the test cell was performed under the same conditions as in 1. 4. For the impedance measurement results obtained at each pressure, the real axis value when the imaginary axis became 0 was calculated, and the calculated value was regarded as the resistance (unit: Ω) at that pressure. 5. Pressure (unit: MPa) was plotted on the X-axis, and resistance (unit: Ω) at that pressure was plotted on the Y-axis. A linear approximation was performed on the obtained plot using the least squares method, and the slope of the resulting straight line was calculated. The calculated slope of the straight line was taken as the value of pressure impedance (unit: Ω / MPa).

[0107] [Production Example 1: Preparation of Coating Fluid] As the resin constituting the porous layer, poly(paraphenylene terephthalamide) (hereinafter referred to as "PPTA"), which is a type of aramid resin, was synthesized by the following method.

[0108] A 3 L separable flask equipped with a stirring blade, a thermometer, a nitrogen inlet, and a powder addition port was used as a synthesis vessel. 2200 g of N-methyl-2-pyrrolidone (NMP) was charged into a thoroughly dried flask. 151.07 g of calcium chloride powder was added thereto, and the mixture was heated to 100°C to completely dissolve, obtaining an NMP solution of calcium chloride. The calcium chloride powder used was previously vacuum dried at 200°C for 2 hours.

[0109] Next, the temperature of the NMP solution of calcium chloride was returned to room temperature, and 68.23 g of paraphenylenediamine was added and completely dissolved to obtain solution A. While keeping the temperature of solution A at 20°C ± 2°C, 124.25 g of terephthalic acid dichloride was added to solution A in four portions at intervals of about 10 minutes to obtain solution B. Thereafter, while continuing stirring, solution B was aged for 1 hour while keeping the temperature at 20°C ± 2°C to obtain an aramid polymerization liquid containing 6 wt% of PPTA. The intrinsic viscosity of PPTA contained in the aramid polymerization liquid was 1.5 g / dL.

[0110] 100 parts by weight of the aramid polymerization liquid was weighed out in another flask, and 6.0 parts of alumina A (average particle size: 13 nm) was added to obtain a mixed liquid A. In the mixed liquid A, the weight ratio of PPTA to alumina A was 1:1. Next, NMP was added to the mixed liquid A so that the solid content was 4.5% by weight, and the mixture was stirred for 240 minutes to obtain a mixed liquid B. The "solid content" here refers to the total weight of PPTA and alumina A. Next, 0.73 parts of calcium carbonate was added to the mixed liquid B and the mixture was stirred for 240 minutes to neutralize the solution, thereby obtaining a neutralized liquid. Then, the neutralized liquid was degassed under reduced pressure to prepare a slurry coating liquid.

[0111] [Example 1] Porous film (Porous polyethylene film, thickness: 9μm, weight: 4.7g / m 2) was conveyed, a slurry coating liquid was applied to one side (front side) of the porous film, forming a coating film on one side of the porous film. Then, while conveying the porous film on which the coating film was formed, the coating film and the porous film were passed through a deposition tank set at 50°C and a relative humidity of 70%, and the coating film was exposed to air containing water vapor at 50°C and a relative humidity of 70%. As a result, PPTA was precipitated on one side (front side) of the porous film, forming a coating layer. Next, a slurry coating liquid was applied to the other side (rear side) of the porous film, forming another coating film. Then, while conveying the porous film on which the other coating film was formed, the other coating film and the porous film were passed through an immersion tank filled with a mixture of ion-exchanged water:NMP=40:60 (weight ratio). As a result, PPTA was precipitated on the other side (rear side) of the porous film, forming another coating layer. Next, the porous film and a laminate consisting of the coating layer and another coating layer deposited on both sides of the porous film were washed with water to remove calcium chloride and the solvent from the coating layer and the other coating layer. The laminate was then dried to form a porous layer on both sides of the porous film. As a result, a double-sided laminated separator wound body (1) was obtained in which a porous layer was laminated on both sides of the porous film. The double-sided laminated separator wound body (1) was used as a separator (1).

[0112] [Example 2] A double-sided laminated separator wound body (2) was obtained by the same operation as in Example 1, except that the mixture filled in the immersion tank was changed to ion-exchanged water:NMP=50:50 (weight ratio). The double-sided laminated separator wound body (2) was used as the separator (2).

[0113] [Example 3] A double-sided laminated separator wound body (3) was obtained by the same operation as in Example 1, except that the mixture filled in the immersion tank was changed to ion-exchanged water:NMP=60:40 (weight ratio). The double-sided laminated separator wound body (3) was used as the separator (3).

[0114] [Comparative Example 1] Instead of passing the other coating film and the porous film through the dipping tank, the other coating film and the porous film were passed through a deposition tank set at 50°C and a relative humidity of 70%, and the other coating film was exposed to air containing water vapor at 50°C and a relative humidity of 70%. Otherwise, the same operations as in Example 1 were performed to obtain a double-sided laminated separator wound body (4). The double-sided laminated separator wound body (4) was used as the separator (4).

[0115] [Comparative Example 2] While transporting the same porous film as the porous film used in Example 1, a slurry-like coating liquid was applied to one surface (the front surface) of the porous film to form a coating film on one surface of the porous film. Then, while transporting the porous film on which the coating film was formed, the coating film and the porous film were passed through a dipping tank filled with ion-exchanged water to deposit PPTA on one surface (the front surface) of the porous film and form a coating layer. Subsequently, the same operation was performed on the other surface (the back surface) of the porous film to deposit PPTA on the other surface (the back surface) of the porous film and form another coating layer. Next, the laminate composed of the porous film and the coating layers and another coating layer deposited on both surfaces of the porous film was washed with water to remove calcium chloride and the solvent from the coating layer and the other coating layer. Thereafter, the laminate was subjected to a drying treatment to form porous layers on both surfaces of the porous film. As a result, a double-sided laminated separator wound body (5) in which porous layers were laminated on both surfaces of the porous film was obtained. The double-sided laminated separator wound body (5) was used as the separator (5).

[0116] [Results] The physical properties of the separators (1) to (5) described in Examples 1 to 3 and Comparative Examples 1 and 2 were measured by the above-mentioned methods, and the results are shown in Table 1 below. In the separators (1) to (3), the porous layer formed by the method of exposing the coating film to air containing water vapor (humidity precipitation method) was the "other porous layer." In the separators (1) to (3), the porous layer formed by the method of passing the other coating film and the porous film through an immersion tank filled with a mixed liquid (immersion precipitation method) was the "one porous layer."

[0117] [Table 1]

[0118] As shown in Table 1, separators (1) to (3) produced in Examples 1 to 3 have (glossiness 1) and (glossiness 2) that satisfy the requirements (A) and (B) shown below, and therefore correspond to the separators of the present invention. On the other hand, separators (4) and (5) produced in Comparative Examples 1 and 2 do not correspond to the separators of the present invention, because (glossiness 1) and (glossiness 2) do not satisfy the requirement (B) shown below. (Glossiness 1)>(Glossiness 2) (A) (Glossiness 1) / (Glossiness 2)>1.15 (B)

[0119] The separators (1) to (3) have a smaller pressurized impedance value than the separator (4). Here, a smaller pressurized impedance value means that resistance is less likely to increase with pressure. Therefore, when the pressurized impedance value of the test cell is small, it is considered that the porous structure inside the separator constituting the test cell is less likely to collapse. Therefore, it was found that the separators (1) to (3) have a superior compression resistance than the separator (4). In addition, it was found that the separators (1) to (3) have a smaller air permeability value per thickness of the porous layer than the separator (5), and are superior in ion permeability. Therefore, it was found that the separators (1) to (3) are superior in both ion permeability and compression resistance, unlike the separators (4) and (5).

[0120] As described above, it has been found that the separator according to one embodiment of the present invention satisfies the requirements (A) and (B) above, and thereby exhibits the effects of being excellent in both ion permeability and compression resistance. [Industrial Applicability]

[0121] The separator according to one embodiment of the present invention can be used to manufacture a non-aqueous electrolyte secondary battery that has both excellent rate characteristics and excellent cycle characteristics. [Explanation of symbols]

[0122] 1. Porous film 2 Porous layer 3 light source 4 Incident light 5 Reflected light

Claims

1. A separator for a non-aqueous electrolyte secondary battery comprising a porous film containing a polyolefin resin as a main component and a porous layer laminated on both sides of the porous film, The porous layer contains a resin, A separator for a nonaqueous electrolyte secondary battery, wherein the 60° gloss of a surface of one of the porous layers and the 60° gloss of a surface of the other of the porous layers satisfy the following relationship (A) and (B): (60° gloss of the surface of one of the porous layers)>(60° gloss of the surface of the other of the porous layers) (A) (60° gloss of one of the surfaces of the porous layer) / (60° gloss of the other of the surfaces of the porous layer)>1.15 (B)

2. the porous layer includes a filler, 2 . The separator for a non-aqueous electrolyte secondary battery according to claim 1 , wherein a content of the filler in the porous layer is 30% by weight or more and 99% by weight or less based on a total weight of the porous layer.

3. 2. The separator for a non-aqueous electrolyte secondary battery according to claim 1, wherein the resin is at least one selected from the group consisting of (meth)acrylate-based resins, fluorine-containing resins, polyamide-based resins, and polyester-based resins.

4. 4. The separator for a non-aqueous electrolyte secondary battery according to claim 3, wherein the polyamide resin is an aramid resin.

5. A member for a non-aqueous electrolyte secondary battery, comprising a positive electrode, the separator for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, and a negative electrode, arranged in this order.

6. A non-aqueous electrolyte secondary battery comprising the separator for non-aqueous electrolyte secondary batteries according to any one of claims 1 to 4.

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