Lamination separator for non-aqueous electrolyte secondary battery

Abstract

To provide a lamination separator for a non-aqueous electrolyte secondary battery capable of improving ion permeability after pressurization.SOLUTION: In a lamination separator for a non-aqueous electrolyte secondary battery, a porous layer is laminated on one face or both faces of a polyolefin porous film. The lamination separator satisfies the following conditions 1 and 3 or conditions 2 and 3. Condition 1: The porous layer contains fillers of which the average particle diameter is 1 μm or more. Condition 2: An uneven space capacity of a surface of the porous layer is 0.4 mL / m2 or more. Condition 3: It leads (porosity of porous layer-porosity of polyolefin porous film)÷porosity of lamination separator for non-aqueous electrolyte secondary battery≤0.6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Non-aqueous electrolyte secondary batteries (especially lithium ion secondary batteries) have high energy density and are widely used as batteries for personal computers, mobile phones, personal digital assistants, etc. Recently, development has also progressed for use as automotive batteries.

[0003] Separators, which are components of non-aqueous electrolyte secondary batteries, have also been improved to improve the performance of non-aqueous electrolyte secondary batteries. For example, Patent Document 1 discloses a separator for electrochemical elements having a separator layer (I) made of a microporous membrane and a porous separator layer (II) mainly containing a filler. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2008-123988 Summary of the Invention [Problem to be solved by the invention]

[0005] It is known that non-aqueous electrolyte secondary batteries experience an increase in internal pressure due to the expansion of electrodes (especially the negative electrode) during charging. In recent years, as the capacity of non-aqueous electrolyte secondary batteries has increased, batteries have become larger and electrodes made of next-generation materials (such as Si negative electrodes, Li metal negative electrodes, and sulfur positive electrodes) have begun to be used. Due to these changes, the increase in internal pressure during charging of next-generation non-aqueous electrolyte secondary batteries is greater than that of conventional non-aqueous electrolyte secondary batteries. In other words, in next-generation non-aqueous electrolyte secondary batteries, the pressure on the separator is greater, and the separator is pushed in by the expansion of the electrodes to a greater extent.

[0006] Under such a premise, the conventional technology described in Patent Document 1 has a problem in that ion permeability decreases after pressure is applied.

[0007] An object of one embodiment of the present invention is to provide a laminated separator for a non-aqueous electrolyte secondary battery that can improve ion permeability after pressure is applied. [Means for solving the problem]

[0008] The present invention includes the following aspects. <1> A laminate separator for a non-aqueous electrolyte secondary battery, comprising a polyolefin porous film and a porous layer laminated on one or both sides thereof, A laminated separator for a non-aqueous electrolyte secondary battery that satisfies the following conditions 1 and 3: Condition 1: The porous layer contains filler having an average particle size of 1 μm or more. Condition 3: (porosity of the porous layer−porosity of the polyolefin porous film)÷porosity of the laminated separator for a non-aqueous electrolyte secondary battery≦0.6. <2> The porous layer contains one or more resins selected from the group consisting of polyolefins, (meth)acrylate resins, fluorine-containing resins, polyamide resins, polyester resins, and water-soluble polymers. <1> 2. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1. <3> The porous layer contains an aramid resin. <2> 2. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1. <4> A laminate separator for a non-aqueous electrolyte secondary battery, comprising a polyolefin porous film and a porous layer laminated on one or both sides thereof, A laminated separator for a non-aqueous electrolyte secondary battery that satisfies the following conditions 2 and 3: Condition 2: The porous layer has a surface unevenness space volume of 0.4 mL / m 2 That's all. Condition 3: (porosity of the porous layer−porosity of the polyolefin porous film)÷porosity of the laminated separator for a non-aqueous electrolyte secondary battery≦0.6. <5> The porous layer contains one or more resins selected from the group consisting of polyolefins, (meth)acrylate resins, fluorine-containing resins, polyamide resins, polyester resins, and water-soluble polymers. <4> 2. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1. <6> The porous layer contains an aramid resin. <5> 2. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1. <7> A positive electrode and <1> ~ <6> a laminated separator for a non-aqueous electrolyte secondary battery according to any one of the above items and a negative electrode, Components for non-aqueous electrolyte secondary batteries. <8> <1> ~ <6> The laminated separator for a non-aqueous electrolyte secondary battery according to any one of the preceding items is provided. Nonaqueous electrolyte secondary battery. <9> <7> The non-aqueous electrolyte secondary battery member according to claim 1, Nonaqueous electrolyte secondary battery. [Effects of the Invention]

[0009] An object of one embodiment of the present invention is to provide a laminated separator for a non-aqueous electrolyte secondary battery that can improve ion permeability after pressure is applied. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram illustrating the volume of uneven spaces on the surface of a porous layer in one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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 the configurations described below, 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. In this specification, unless otherwise specified, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B."

[0012] As used herein, "MD (MD direction)" refers to the longitudinal direction of a continuously manufactured long-shaped product. As used herein, "TD (TD direction)" refers to the direction perpendicular to MD of a continuously manufactured long-shaped product. MD and TD are concepts of the manufacturing process, but manufactured products may exhibit different physical properties in MD and TD (such as the orientation of constituent components or constituent molecules). Based on such physical properties, MD and TD can be identified even for products that have left the manufacturing process.

[0013] In this specification, a laminate separator for a nonaqueous electrolyte secondary battery may be simply referred to as a “laminated separator.” In this specification, a parameter given by “(porosity of porous layer−porosity of polyolefin porous film) / porosity of laminate separator” may be simply referred to as a “porosity parameter.”

[0014] A laminate separator for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention has a porous layer laminated on one or both sides of a polyolefin porous film. The laminate separator satisfies condition 1 and / or condition 2, and condition 3, among the following conditions 1 to 3. In one embodiment, the laminate separator satisfies all of conditions 1 to 3. Such a laminate separator has excellent ion permeability after pressure is applied, and can maintain ion permeability at or above a certain standard even after pressure is applied. Condition 1: The porous layer contains filler particles with an average particle size of 1 μm or more. Condition 2: The volume of the uneven space on the surface of the porous layer is 0.4 mL / m2 That's all. Condition 3: The porosity parameter is 0.6 or less.

[0015] The porous layer and the polyolefin porous film, which are elements constituting the laminated separator, will be described in detail below.

[0016] [1. Porous layer] [1.1. General characteristics of porous layers] The porous layer usually contains a binder resin and a filler. Each of these elements will be described in detail below.

[0017] [1.1.1. Binder resin] The porous layer may contain a binder resin, examples of which include polyolefin, (meth)acrylate resin, fluorine-containing resin, polyamide 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, and nitrogen-containing aromatic resin.

[0018] Examples of polyolefins include polyethylene, polypropylene, polybutene, and ethylene-propylene copolymers.

[0019] Examples of fluorine-containing resins 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. Fluorine-containing rubbers having a glass transition temperature of 23°C or lower are also examples of fluorine-containing resins.

[0020] Examples of polyamides include aliphatic polyamides, semi-aromatic polyamides, and fully aromatic polyamides.

[0021] Examples of polyester resins include aromatic polyesters (such as polyarylates) and liquid crystal polyesters.

[0022] Examples of rubbers include styrene-butadiene copolymers and hydrogenated products thereof, methacrylic acid ester copolymers, acrylonitrile-acrylic acid ester copolymers, styrene-acrylic acid ester copolymers, ethylene propylene rubber, and polyvinyl acetate.

[0023] Examples of resins having a melting point or glass transition temperature of 180° C. or higher include polyphenylene ether, polysulfone, polyethersulfone, polyphenylene sulfide, polyetherimide, polyamideimide, and polyetheramide.

[0024] Examples of water-soluble polymers include polyvinyl alcohol, polyethylene glycol, cellulose ether, sodium alginate, polyacrylic acid, polyacrylamide, and polymethacrylic acid.

[0025] Examples of nitrogen-containing aromatic resins include aromatic polyamides, aromatic polyimides, aromatic polyamideimides, polybenzimidazole, polyurethane, and melamine resins. Examples of aromatic polyamides include wholly aromatic polyamides (aramid resins) and semi-aromatic polyamides. Examples of wholly aromatic polyamides include para-aramids and meta-aramids. Among the above-mentioned nitrogen-containing aromatic resins, wholly aromatic polyamides are preferred, and para-aramids are more preferred.

[0026] As used herein, para-aramid refers to a wholly aromatic polyamide in which the amide bond is located at the para position of the aromatic ring or a position equivalent thereto. A position equivalent to the para position refers to an orientation in which the amide bonds are located in opposite directions across the aromatic ring, on the same axis, or parallel to the aromatic ring. Examples of such orientations include the 4- and 4'-positions of the biphenylene ring, the 1- and 5-positions of the naphthalene ring, and the 2- and 6-positions of the naphthalene ring.

[0027] 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), paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer, poly(4,4'-diphenylsulfonyl terephthalamide), and paraphenylene terephthalamide / 4,4'-diphenylsulfonyl terephthalamide copolymer. All of the resins given as specific examples are para-aramids having a para-oriented structure or a structure similar to the para-oriented structure. Among the above-mentioned para-aramids, one or more types selected from the group consisting of poly(paraphenylene terephthalamide) and paraphenylene terephthalamide / 4,4'-diphenylsulfonyl terephthalamide copolymer are preferred because they are easy to produce and handle.

[0028] The porous layer may contain only one type of binder resin, or may contain two or more types of binder resin.

[0029] When the porous layer contains a binder resin, the binder resin does not have to contain a fluorine-containing resin. The porous layer may contain a binder resin, but the binder resin does not have to contain polyvinylidene fluoride.

[0030] [1.1.2. Filler] The filler material is not particularly limited, and examples of the filler include organic fillers and inorganic fillers.

[0031] Examples of organic filler materials include homopolymers or copolymers of monomers such as styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, and methyl acrylate; fluorine-containing materials (such as polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, and polyvinylidene fluoride); melamine resins; urea resins; polyolefins; polymethacrylates; and polyurethanes. One or more organic fillers may be used, or two or more may be used. From the viewpoint of chemical stability, one or more selected from the group consisting of polystyrene, polymethyl methacrylate, polyurethane, and polytetrafluoroethylene are preferred. Also from the viewpoint of chemical stability, one or more selected from the group consisting of polystyrene and polymethyl methacrylate are more preferred.

[0032] Examples of inorganic filler materials include inorganic substances. Examples of such materials include metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates, and sulfates. More specific examples include powders of aluminum oxide (alumina), boehmite, silica, titania, magnesia, barium titanate, barium sulfate, aluminum hydroxide, magnesium hydroxide, and calcium carbonate. Further specific examples include powders of minerals such as mica, zeolite, kaolin, and talc. Only one type of inorganic filler may be used, or two or more types may be used. From the viewpoint of chemical stability, one or more types selected from the group consisting of aluminum oxide, silica, and boehmite are preferred.

[0033] Examples of the shape of the filler include substantially spherical, plate-like, columnar, needle-like, whisker-like, and fibrous shapes. A substantially spherical filler is preferred because it is easy to form uniform pores.

[0034] In one embodiment, the filler may be heat-resistant particles. Heat-resistant particles do not substantially fuse together even in a high-temperature environment (e.g., 200°C). On the other hand, non-heat-resistant particles fuse together with other particles or the polyolefin porous film in a high-temperature environment. Non-heat-resistant particles may be blended to achieve the same function as a binder resin. However, heat-resistant particles are not usually expected to achieve such a function.

[0035] The filler may be used alone or in combination of two or more types.

[0036] In one embodiment, the porous layer contains a filler having an average particle size of 1 μm or more. This condition is referred to as condition 1 in this specification. When two or more types of fillers are contained in the porous layer, condition 1 can be said to be satisfied if at least one of the fillers has an average particle size of 1 μm or more. The average particle size of the filler is the particle size at which the cumulative frequency reaches 50% in the volume-based particle size distribution.

[0037] The content of filler having an average particle size of 1 μm or more in the porous layer is preferably 10 wt % or more, and more preferably 15 wt % or more, based on 100 wt % of the weight of the porous layer. A porous layer containing filler having an average particle size of 1 μm or more in the above range has improved compression characteristics, and can therefore have excellent ion permeability and low resistance after compression. There is no particular upper limit to the content of filler having an average particle size of 1 μm or more in the porous layer, but it is preferably 80 wt % or less, and more preferably 70 wt % or less, based on 100 wt % of the weight of the porous layer.

[0038] [1.1.2.1. First Filler and / or Second Filler (Optional Configuration)] The porous layer preferably contains a first filler and / or a second filler. The first filler and the second filler have different average particle sizes, with the first filler having a smaller average particle size than the second filler. The inclusion of the first filler and / or the second filler in the porous layer increases the porosity of the porous layer, making the porous layer more easily compressible when pressure is applied. This is thought to reduce compression of the polyolefin porous film and reduce the increase in air permeability (Gurley value) upon compression. Furthermore, the inclusion of the first filler and / or the second filler in the porous layer also reduces the air permeability (Gurley value) when uncompressed.

[0039] The upper limit of the average particle size of the first filler is preferably 0.03 μm or less, more preferably 0.025 μm or less, and even more preferably 0.02 μm or less. The lower limit of the average particle size of the first filler is, for example, 0.001 μm or more or 0.005 μm or more.

[0040] The lower limit of the average particle size of the second filler is preferably 1 μm or more, more preferably 1.5 μm or more, and the upper limit of the average particle size of the second filler is, for example, 10 μm or less, 8 μm or less, or 6 μm or less.

[0041] The average particle size of the first filler and the second filler is the particle size at which the cumulative frequency reaches 50% in the volume-based particle size distribution.

[0042] A porous layer containing a first filler and / or a second filler having an average particle size within the above range can easily keep the volume of the recessed and protruding spaces, which will be described later, within a suitable range.

[0043] The lower limit of the weight fraction of the second filler relative to the total weight of the first filler and the second filler is preferably 30% by weight or more, more preferably 35% by weight or more, and even more preferably 40% by weight or more. The upper limit of the weight fraction of the second filler is, for example, 90% by weight or less or 85% by weight or less.

[0044] The first filler and the second filler may be primary particles or secondary particles. When the first filler and / or the second filler are secondary particles, the average particle size of the first filler and / or the second filler is the average particle size of the secondary particles.

[0045] Therefore, the following categories 1a and 1b satisfy the above-mentioned preferable conditions for the first filler: The following category 1c may satisfy the above-mentioned preferable conditions for the first filler. Category 1a: The first filler is a primary particle that does not form a secondary particle, and the average particle size of the primary particles is 0.03 μm or less. Category 1b: The first filler is a secondary particle, and the average particle size of the secondary particle is 0.03 μm or less. Category 1c: The first filler is a secondary particle, and the average particle size of the primary particles that make up the secondary particle is 0.03 μm or less.

[0046] Similarly, the following categories 2a and 2b satisfy the above-mentioned preferable conditions for the second filler: The following category 2c may satisfy the above-mentioned preferable conditions for the second filler. Category 2a: The second filler is a primary particle that does not form a secondary particle, and the average particle size of the primary particles is 1 μm or more. Category 2b: The second filler is a secondary particle, and the average particle size of the secondary particles is 1 μm or more. Category 2c: The second filler is a secondary particle, and the average particle size of the primary particles that make up the secondary particle is 1 μm or more.

[0047] The porous layer containing the first and second fillers described above can reduce the increase in air permeability (Gurley value) during compression. An example of a method for measuring the increase in air permeability (Gurley value) during compression is as follows. 1. As described in the examples of the present application, the air permeability (Gurley value) of the laminated separator is measured after being pressurized at 20 MPa in accordance with JIS P8117. 2. Similarly, in accordance with JIS P8117, measure the air permeability (Gurley value) of the laminated separator before applying a pressure of 20 MPa. 3. Calculate the increase in air permeability during compression using the formula below. Increase in air permeability during compression (s / 100mL) = Gurley value after compression (s / 100mL) - Gurley value before compression (s / 100mL)

[0048] [1.1.3. Composition of Porous Layer] The lower limit of the weight fraction of the filler relative to the total weight of the porous layer is preferably 10% by weight or more, more preferably 30% by weight or more, and even more preferably 40% by weight or more. The upper limit of the weight fraction of the filler is, for example, 80% by weight or less, 70% by weight or less, or 60% by weight or less.

[0049] The lower limit of the weight fraction of the binder resin relative to the total weight of the porous layer is preferably 20% by weight or more, more preferably 30% by weight or more, and even more preferably 40% by weight or more. The upper limit of the weight fraction of the binder resin is, for example, 90% by weight or less, 70% by weight or less, or 60% by weight or less.

[0050] The content of inorganic substances in the porous layer is, for example, 75% by weight or less, 70% by weight or less, or 65% by weight or less. The porous layer may not contain inorganic substances. The inorganic substances referred to here mainly refer to inorganic fillers. Organic fillers and binder resins are not included in inorganic substances. That is, the porous layer may not contain inorganic fillers, or the porous layer may contain only binder resins and organic fillers.

[0051] [1.2. Characteristics of the porous layer] In one embodiment, the porous layer has a surface roughness void volume of 0.4 mL / m 2 This is the end of the procedure. This condition will be referred to as condition 2 in this specification.

[0052] The uneven void volume will be described with reference to the exemplary Fig. 1. In the example of Fig. 1, a porous layer 10 contains a filler 5.

[0053] The porous layer 10 preferably has a surface with irregularities. The volume per unit area of ​​the space enclosed by these irregularities and one or more predetermined planes is referred to as the irregular spatial volume. In FIG. 1, the total volume per unit area of ​​the vertical line portion V is the irregular spatial volume. The one or more predetermined planes can be set, for example, based on the load curve of the porous layer surface. In one embodiment, the one or more predetermined planes are a plane passing through a point where the area load ratio is 10% and parallel to the in-plane direction, and a plane passing through a point where the area load ratio is 80% and parallel to the in-plane direction. In this case, the volume per unit area of ​​the space enclosed by the two planes and the irregularities on the substrate layer surface is the irregular spatial volume. The load curve of the porous layer surface is generated using a laser microscope and analytical software. For an example of a specific method for measuring the irregular spatial volume of a porous layer, see the examples in this application.

[0054] The lower limit of the volume of the uneven space on the porous layer surface is 0.4 mL / m 2 More preferably, 0.5 mL / m 2 The upper limit of the volume of the uneven space on the surface of the porous layer is, for example, 2.5 mL / m 2 Below, 2.0mL / m 2 or less than 1.5 mL / m 2 The following is the result.

[0055] The average pore diameter of the porous layer is preferably 38.0 nm or less, more preferably 36.0 nm, and even more preferably 35.0 nm. The average pore diameter of the porous layer is, for example, 25.0 nm or more, 28.0 nm or more, or 29.0 nm or more. An example of a method for measuring the average pore diameter of the porous layer is shown below. 1. Using a PMI Perm Porometer (model: CFP-1500A) and test liquid (PMI GalWick), obtain the following two curves. Pressure-flow curve when immersed in test liquid Pressure-flow curve: half the flow measured in dry conditions 2. Based on the pressure at the intersection of the curves obtained in step 1, calculate the average pore diameter (nm) using the following formula. ·Average pore diameter (nm)=4cosθ×rP×1000 During the ceremony, r: Surface tension of the test liquid (mN / m) P: Pressure at the intersection of the two curves (Pa) θ: Contact angle between the porous layer and the test liquid (°)

[0056] The lower limit of the irregularity height of the porous layer is, for example, 0.5 μm or more or 0.7 μm or more. The upper limit of the irregularity height of the porous layer is, for example, 3.0 μm or less or 2.5 μm or less. If the irregularity height is within the above range, the irregularity space volume can be easily kept within the above range. The irregularity height of the porous layer is the average height of the protruding peaks where the area coverage ratio of the porous layer is 0% to 10%.

[0057] The porosity of the porous layer is preferably 50% by volume or more, more preferably 55% by volume or more, and even more preferably 65% ​​by volume or more. The upper limit of the porosity of the porous layer can be, for example, 90% by volume or less or 85% by volume or less. The porosity of the porous layer can be calculated from the weight ratio and true density of each material constituting the porous layer.

[0058] 2. Method for producing porous layer For example, the porous layer can be formed by using a coating liquid in which a binder resin, a filler, and optionally other components are dissolved or dispersed in a solvent. Specifically, the porous layer can be formed by applying the coating liquid to a polyolefin porous film and drying it.

[0059] Examples of methods for preparing the coating liquid include mechanical stirring, ultrasonic dispersion, high-pressure dispersion, and media dispersion. Examples of solvents for the coating liquid include N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide.

[0060] Examples of methods for applying the coating liquid include knife, blade, bar, gravure, and die.

[0061] The drying method is not limited to a specific means as long as the solvent can be sufficiently removed. Examples of drying methods include natural drying, air drying, heat drying, and reduced pressure drying. The solvent contained in the coating liquid may be replaced with another solvent before drying. A specific example of such a drying method is a method in which the solvent contained in the coating liquid is replaced with a low-boiling point poor solvent such as water, alcohol, or acetone, and a porous layer is precipitated, followed by drying.

[0062] When preparing the coating liquid, it is preferable to carry out high-pressure dispersion. According to such a production method, the dispersibility of the filler is improved, making it easier to keep the porosity and surface irregularity volume of the obtained porous layer within the above-mentioned range. The lower limit of the pressure in high-pressure dispersion is preferably 1 MPa or more, more preferably 5 MPa or more. The upper limit of the pressure in high-pressure dispersion is preferably 100 MPa or less, more preferably 70 MPa or less. If the pressure in high-pressure dispersion is within the above-mentioned range, it is easy to produce a porous layer that exhibits the above-mentioned effects.

[0063] High-pressure dispersion is a dispersion method that disperses components by utilizing the shear force generated when a high-pressure fluid flows through a narrow gap at high speed, or the collision force generated when a high-speed fluid hits a wall, etc. High-pressure dispersion can be performed, for example, using a high-pressure homogenizer.

[0064] Before coating the polyolefin porous film with coating liquid, it is preferable to impregnate the polyolefin porous film with solvent.According to this manufacturing method, the coating liquid is hardly impregnated into the inside of the polyolefin porous film, so that the pores of the polyolefin porous film are prevented from being blocked by the porous layer.As a result, the air permeability of the obtained porous layer is reduced, and it is easy to manufacture the porous layer having the porosity and the space volume of the uneven surface in the above-mentioned range, and it is easy to control the porosity of the whole laminated separator within the range described below.

[0065] The solvent that is impregnated into the polyolefin porous film is preferably the same as the solvent of the coating liquid.For example, when the solvent of the coating liquid is N-methyl-2-pyrrolidone, it is preferable to impregnate the polyolefin porous film with N-methyl-2-pyrrolidone before applying the coating liquid.The surface of the polyolefin porous film that is applied with the coating liquid and the surface of the polyolefin porous film that is applied with the solvent are different surfaces.

[0066] A preferred method for depositing the porous layer is to spray a poor solvent and saturate the air in the deposition tank with poor solvent vapor to cause deposition. This manufacturing method makes it easier to keep the porosity and surface irregularity volume of the resulting porous layer within the above-mentioned ranges. The lower limit of the time the coating liquid is allowed to reside in the deposition tank is preferably 1 second or more, more preferably 5 seconds or more. The upper limit of the time the coating liquid is allowed to reside in the deposition tank is preferably 60 seconds or less, more preferably 50 seconds or less. If the time the coating liquid is allowed to reside in the deposition tank is within the above-mentioned range, it is easy to produce a porous layer that exhibits the above-mentioned effects. Spraying the poor solvent can be carried out, for example, using a two-fluid nozzle.

[0067] [3. Polyolefin Porous Film] The laminate separator includes a polyolefin porous film, which has numerous interconnected pores inside, allowing gas and liquid to pass from one side of the polyolefin porous film to the other.

[0068] The polyolefin porous film may provide the laminate separator with a shutdown function, which is a function that melts when the battery generates heat, making the laminate separator non-porous.

[0069] The polyolefin porous film is mainly composed of a polyolefin resin. In this specification, "mainly composed of a polyolefin resin" means that the proportion of the polyolefin resin in the polyolefin porous film is 50% by volume or more of the total material constituting the polyolefin porous film. This proportion is preferably 90% by volume or more, and more preferably 95% by volume or more.

[0070] The polyolefin resin, which is the main component of the polyolefin porous film, is not particularly limited. Examples include polymers obtained by polymerizing monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene. The polyolefin resin may be a homopolymer or a copolymer. Examples of homopolymers include polyethylene, polypropylene, and polybutene. Examples of copolymers include an ethylene-propylene copolymer. Furthermore, in order to enhance the compression resistance of the substrate, the polyolefin resin may contain a silane-crosslinkable silane-modified polyolefin. The polyolefin porous film may contain only one type of polyolefin resin, or two or more types.

[0071] For the purpose of imparting a shutdown function to the polyolefin porous film, the polyolefin resin is more preferably polyethylene, and particularly preferably high-molecular-weight polyethylene. The polyolefin porous film may contain components other than polyolefins as long as the function is not impaired.

[0072] Examples of polyethylene include low-density polyethylene, high-density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), and ultra-high molecular weight polyethylene. Among these, ultra-high molecular weight polyethylene is preferred. In addition, polyethylene having a weight-average molecular weight of 5×10 5 ~15×10 6More preferred is polyethylene containing a high molecular weight component having a weight average molecular weight of 1,000,000 or more. If a high molecular weight component having a weight average molecular weight of 1,000,000 or more is contained, the strength of the polyolefin porous film and the laminate separator will be improved.

[0073] The lower limit of the thickness of the polyolefin porous film is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 9 μm or more. The upper limit of the thickness of the polyolefin porous film is preferably 20 μm or less, more preferably 15 μm or less. If the thickness is 5 μm or more, the functions required of the polyolefin porous film, such as the shutdown function, can be sufficiently obtained. If the thickness is 20 μm or less, a thin laminated separator can be obtained.

[0074] The pore size of the polyolefin porous film is preferably 0.1 μm or less, more preferably 0.06 μm or less. If the pore size is within the above range, sufficient ion permeability can be obtained. In addition, the intrusion of particles constituting the electrode can be successfully prevented.

[0075] The lower limit of the weight per unit area of ​​polyolefin porous film is 4 g / m 2 More than 5g / m is preferable. 2 More preferably, the upper limit of the weight per unit area is 20 g / m 2 Less than 12 g / m is preferred 2 The following is more preferable: If the basis weight is within the above range, the weight energy density and volume energy density of the battery can be increased.

[0076] The lower limit of the air permeability (Gurley value) of the polyolefin porous film is preferably 30 s / 100 mL or more, more preferably 50 s / 100 mL or more. The upper limit of the air permeability (Gurley value) is preferably 500 s / 100 mL or less, more preferably 300 s / 100 mL or less. If the air permeability (Gurley value) is in the above range, the laminated separator can obtain sufficient ion permeability.

[0077] The lower limit of the porosity of the polyolefin porous film is preferably 40% by volume or more, more preferably 45% by volume or more, and even more preferably 50% by volume or more. The upper limit of the porosity is preferably 80% by volume or less, more preferably 75% by volume or less. If the porosity is within the above range, the amount of electrolyte retained can be increased. In addition, the shutdown function can be activated at a lower temperature.

[0078] 4. Method for producing polyolefin porous film The method for producing the polyolefin porous film is not particularly limited. An example of the production method that can control the porosity of the polyolefin porous film is shown below.

[0079] The method for producing a polyolefin porous film includes the following steps 1 to 4. 1. A polyolefin resin and, optionally, a pore-forming agent are added to a kneader and melt-kneaded to obtain a polyolefin resin composition. 2. The polyolefin resin composition is stretched in the MD direction while being cooled to obtain a primary sheet. 3. The primary sheet is stretched in the TD direction. 4. Heat set at a specific temperature for a specific time.

[0080] In step 1, the amount of polyolefin resin used is preferably 6 to 45% by weight, and more preferably 9 to 36% by weight, when the weight of the resulting polyolefin resin composition is taken as 100% by weight.

[0081] Examples of pore-forming agents include inorganic fillers and plasticizers. Examples of inorganic fillers include inorganic fillers, a specific example of which is calcium carbonate. Examples of plasticizers include low-molecular-weight hydrocarbons such as liquid paraffin.

[0082] In addition to the pore-forming agent, known additives may be optionally used within the range that does not impair the effects of the present invention. Examples of known additives include antioxidants, fillers, and dispersing aids. Examples of fillers include alumina.

[0083] In step 2, examples of the method for obtaining the primary sheet include sheet forming methods such as inflation processing, calendar processing, T-die extrusion processing, and skiff method.

[0084] The sheet molding temperature in the sheet molding method (such as the T-die extrusion temperature in T-die extrusion processing) is preferably 200°C or higher and 280°C or lower, more preferably 220°C or higher and 260°C or lower.

[0085] The stretching temperature in step 2 is preferably 120°C or higher and 160°C or lower, and more preferably 130°C or higher and 155°C or lower.

[0086] Examples of the method for cooling the polyolefin resin composition in step 2 include a method of contacting it with a refrigerant (such as cold air or cooling water) and a method of contacting it with a cooling roll. Preferably, it is a method of contacting it with a cooling roll.

[0087] When the polyolefin resin composition and the primary sheet contain a pore-forming agent, the pore-forming agent is removed by washing with a washing liquid between steps 2 and 3 or after step 3.

[0088] The washing liquid is a solvent capable of removing the pore-forming agent, examples of which include aqueous hydrochloric acid, heptane, and dichloromethane.

[0089] The stretching temperature during stretching in the TD direction in step 3 is preferably 80° C. or more and 120° C. or less, more preferably 80° C. or more and 115° C. or less. The stretching ratio during stretching in the TD direction in step 3 is preferably 2 times or more and 12 times or less, more preferably 4 times or more and 10 times or less.

[0090] In step 3, the upper limit of the stretching speed when stretching in the TD direction is preferably 12 m / min or less, more preferably 10 m / min or less. The lower limit of the stretching speed is preferably 0.5 m / min or more, more preferably 1 m / min or more. By stretching at a stretching speed within the above range, the primary sheet is more likely to be stretched uniformly during stretching, and anisotropy is less likely to occur in the pores, making it possible to produce a polyolefin porous film in which pores are more uniformly and more densely distributed.

[0091] The heat setting in step 4 is preferably carried out at a temperature of 110° C. or more and 140° C. or less, more preferably 115° C. or more and 135° C. or less. The heat setting is preferably carried out for a time of 20 seconds or more and less than 20 minutes, more preferably 21 seconds or more and 15 minutes or less. By carrying out the heat setting for a long time of 20 seconds or more in step 4, a polyolefin porous film in which voids are distributed more uniformly and more densely can be produced.

[0092] By controlling the stretching speed in the TD direction to 12 m / min or less in step 3 and controlling the heat setting time to 20 seconds or more in step 4, the porosity of the polyolefin porous film can be controlled within a preferred range.

[0093] [5. Laminated separator for non-aqueous electrolyte secondary batteries] The laminated separator has a porous layer laminated on one or both sides of a polyolefin porous film. In addition to the polyolefin porous film and the porous layer, the laminated separator may have other layers as needed. Examples of such layers include an adhesive layer and a protective layer.

[0094] The thickness of the laminate separator is preferably 25 μm or less, more preferably 20 μm or less, and the thickness of the porous layer is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less.

[0095] [5.1. Characteristics of laminated separator] In one embodiment, the laminate separator has a porosity parameter of 0.6 or less. This condition is referred to herein as condition 3. The porosity parameter is a value given by (porosity of porous layer - porosity of polyolefin porous film) ÷ porosity of the laminate separator for non-aqueous electrolyte secondary batteries.

[0096] To reduce the porosity parameter, the numerator should be small and the denominator should be large. To reduce the numerator, the difference between the porosity of the porous layer and that of the polyolefin porous film should not be large. To increase the denominator, the porosity of the laminate separator as a whole should be increased. In summary, if both the porous layer and the polyolefin porous film are configured to have high porosity, the porosity parameter can be adjusted to 0.6 or less.

[0097] The porous layer and the porous polyolefin film having a high porosity can be obtained by the methods described above. Alternatively, commercially available products having a high porosity can be used.

[0098] The suitable porosity of the porous layer and the polyolefin porous film is as described above. The lower limit of the porosity of the laminate separator is preferably 40% by volume or more, more preferably 45% by volume or more, and even more preferably 50% by volume or more. The upper limit of the porosity of the laminate separator can be, for example, 70% by volume or less, 65% by volume or less, or 60% by volume or less.

[0099] The porosity of each of the porous layer, the polyolefin porous film, and the laminate separator is calculated based on the film thickness, the basis weight (weight per unit area), the weight ratio of the constituent materials, and the true density of the constituent materials, specifically according to the following formula (see the examples of the present application for more detailed conditions): Porosity (volume%) = [1-{A × (W a ÷d a +W b ÷d b +W c ÷d c +…+W n ÷d n )÷t}]×100 During the ceremony, t: target film thickness (cm) A: Weight of the target (g / cm 2 ) a, b, c..., n: Materials that make up the object. There are n types in total. ·W a , W b , W c …, W n : Weight ratio of each material (W a +W b +W c +…+W n =1) ·d a , d b , d c …, d n : True density of each material (g / cm 3 )

[0100] 6. Manufacturing method of laminated separator A laminated separator including a polyolefin porous film and a porous layer can be manufactured by applying a coating liquid for forming a porous layer to a polyolefin porous film and drying it. Specifically, a laminated separator can be manufactured by using a polyolefin porous film as the substrate in the porous manufacturing method described in Section [2].

[0101] 7. Non-aqueous electrolyte secondary battery components and non-aqueous electrolyte secondary batteries A nonaqueous electrolyte secondary battery member including the laminated separator for a nonaqueous electrolyte secondary battery according to one embodiment of the present invention is also one embodiment of the present invention. The nonaqueous electrolyte secondary battery member according to one embodiment of the present invention comprises a positive electrode, the above-described laminated separator for a nonaqueous electrolyte secondary battery, and a negative electrode arranged in this order. A nonaqueous electrolyte secondary battery including the laminated separator for a nonaqueous electrolyte secondary battery according to one embodiment of the present invention is also one embodiment of the present invention. The nonaqueous electrolyte secondary battery includes the above-described laminated separator for a nonaqueous electrolyte secondary battery. A nonaqueous electrolyte secondary battery typically includes a nonaqueous electrolyte secondary battery member. In a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery member impregnated with an electrolyte is typically enclosed in an exterior material. The nonaqueous electrolyte secondary battery may be a lithium ion secondary battery that generates electromotive force by doping and dedoping of lithium ions.

[0102] [7.1 Positive electrode] For example, a positive electrode sheet may be used as the positive electrode. In the positive electrode sheet, an active material layer containing a positive electrode active material and a binder is formed on a current collector. The active material layer may further contain a conductive agent.

[0103] Examples of positive electrode active materials include materials capable of doping and dedoping lithium ions. Examples of such materials include lithium composite oxides containing one or more transition metals, such as V, Ti, Cr, Mn, Fe, Co, Ni, and Cu. Examples of lithium composite oxides include lithium composite oxides with a layered structure, lithium composite oxides with a spinel structure, and solid-solution lithium-containing transition metal oxides (composed of lithium composite oxides with both layered and spinel structures). Further examples of lithium composite oxides include lithium cobalt composite oxide and lithium nickel composite oxide. Furthermore, examples of lithium composite oxides include materials in which some of the transition metal atoms in the lithium composite oxide are replaced with other elements, such as Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mg, Ca, Ga, Zr, Si, Nb, Mo, Sn, and W.

[0104] Examples of lithium composite oxides in which some of the transition metal atoms contained in the lithium composite oxide are substituted with other elements include substances represented by the following formulas (A) to (D). Formula (A) is a lithium cobalt composite oxide having a layered structure. Formula (B) is a lithium nickel composite oxide. Formula (C) is a lithium manganese composite oxide having a spinel structure. Formula (D) is a solid solution lithium-containing transition metal oxide.

[0105] Li x (Co 1-a M 1 a ) 1-x ]O2···(A) In formula (A), M 1 is one or more metals selected from the group consisting of Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, and W. x satisfies -0.1≦x≦0.30. a satisfies 0≦a≦0.5.

[0106] Li y (Ni 1-b M 2 b ) 1-y ]O2···(B) In formula (B), M 2 is one or more metals selected from the group consisting of Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, and W. y satisfies -0.1≦y≦0.30. b satisfies 0≦b≦0.5.

[0107] Li z Mn 2-c M 3 c O4···(C) In formula (C), M 3 is one or more metals selected from the group consisting of Na, K, B, F, Al, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, and W. z satisfies 0.9≦z. c satisfies 0≦c≦1.5.

[0108] Li 1+w M 4 d M 5 e O2···(D) In formula (D), M 4 and M 5 are one or more metals selected from the group consisting of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mg, and Ca. w, d, and e satisfy 0 < w ≤ 1 / 3, 0 ≤ d ≤ 2 / 3, 0 ≤ e ≤ 2 / 3, and w + d + e = 1.

[0109] Specific examples of the lithium composite oxide represented by formulas (A) to (D) include LiCoO2, LiNiO2, LiMnO2, LiNi 0.8 Co 0.2 O2, LiNi 0.5 Mn 0.5 O2, LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2, LiMn2O4, LiMn 1.5 Ni 0.5 O4, LiMn 1.5 Fe 0.5 O4, LiCoMnO4, Li 1.21 Ni 0.20 Mn 0.59 O2, Li 1.22 Ni 0.20 Mn 0.58 O2, Li 1.22 Ni 0.15 Co 0.10 Mn 0.53 O2, Li 1.07 Ni 0.35 Co 0.08 Mn 0.50 O2, Li 1.07 Ni0.36 Co 0.08 Mn 0.49 O2 is one example.

[0110] Of course, lithium composite oxides other than those represented by formulas (A) to (D) can also be suitably used as the positive electrode active material. Examples of such lithium composite oxides include LiNiVO4, LiV3O6, Li 1.2 Fe 0.4 Mn 0.4 O2 is one example.

[0111] In addition to lithium composite oxides, other examples of materials that can be suitably used as positive electrode active materials include phosphates having an olivine structure, such as those represented by the following formula (E):

[0112] Li v (M 6 f M 7 g M 8 h M 9 i ) j PO4···(E) In formula (E), M 6 is Mn, Co or Ni. 7 is Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb or Mo. 8 is a transition metal or main group element (in any configuration, M 8 are not elements of groups VIA and VIIA). 9 is a transition metal or main group element (in any configuration, M 9 (a) is not a group VIA or VIIA element. a to f satisfy the following conditions: 1.2 ≥ a ≥ 0.9, 1 ≥ b ≥ 0.6, 0.4 ≥ c ≥ 0, 0.2 ≥ d ≥ 0, 0.2 ≥ e ≥ 0, 1.2 ≥ f ≥ 0.9.

[0113] The positive electrode active material preferably has a coating layer on its surface. For example, particles of lithium metal composite oxide preferably have a coating layer on their surface. Examples of materials constituting the coating layer include metal composite oxides, metal salts, boron-containing compounds, nitrogen-containing compounds, silicon-containing compounds, and sulfur-containing compounds.

[0114] Among the above, metal composite oxides are preferred. Examples of metal composite oxides include metal composite oxides having lithium ion conductivity. Examples of metal composite oxides having lithium ion conductivity include metal composite oxides of Li and one or more elements selected from the group consisting of Nb, Ge, Si, P, Al, W, Ta, Ti, S, Zr, Zn, V, and B.

[0115] The presence of the coating layer can suppress side reactions at the positive electrode active material-electrolyte interface under high voltage, thereby extending the life of the secondary battery. Furthermore, the presence of the coating layer can suppress the formation of a high-resistance layer at the positive electrode active material-electrolyte interface, thereby increasing the output of the secondary battery.

[0116] Examples of the conductive agent include carbonaceous materials, such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fiber, and fired organic polymer compounds.

[0117] Examples of binders include polyvinylidene fluoride, vinylidene fluoride copolymer, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-trichloroethylene copolymer, vinylidene fluoride-vinyl fluoride copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, thermoplastic resin (thermoplastic polyimide, polyethylene, polypropylene, etc.), acrylic resin, and styrene-butadiene rubber. The binder may also function as a thickener.

[0118] Examples of the positive electrode current collector include conductors such as Al, Ni, stainless steel, etc. Among these, Al is preferred because it can be easily processed into a thin film and is inexpensive.

[0119] Examples of methods for producing a sheet-shaped positive electrode include the following. A manufacturing method in which a positive electrode active material, a conductive agent, and a binder are pressure-molded onto a positive electrode current collector to form a positive electrode mixture on the positive electrode current collector. A manufacturing method in which a paste-like positive electrode mixture is applied to a positive electrode current collector, dried, and the resulting sheet-like positive electrode mixture is then pressed to adhere to the positive electrode current collector. The paste-like positive electrode mixture is prepared by mixing a positive electrode active material, a conductive agent, a binder, and an appropriate organic solvent.

[0120] [7.2. Negative electrode] For example, a negative electrode sheet may be used as the negative electrode. In the negative electrode sheet, an active material layer containing a negative electrode active material and a binder is formed on a current collector. The active material layer may further contain a conductive agent.

[0121] Examples of negative electrode active materials include materials that can be doped and dedoped with lithium ions at a lower potential than the positive electrode. Specific examples of such materials include carbon materials, chalcogen compounds (oxides, sulfides, etc.), nitrides, metal materials, and alloys.

[0122] Examples of carbon materials include graphite (natural graphite, artificial graphite, etc.), cokes, carbon black, pyrolytic carbons, carbon fiber, and fired organic polymer compounds.

[0123] Examples of oxides include SiO2, SiO, and the like, which have the formula SiO x Silicon oxides represented by the formula TiO2, TiO, etc. (x is a positive real number) x Titanium oxide (x is a positive real number), such as V2O5 or VO2, is represented by the formula V x O y Vanadium oxides (x and y are positive real numbers) represented by the formula Fe x O y Iron oxide (x and y are positive real numbers); SnO2, SnO, etc., with the formula SnO x Tin oxide (x is a positive real number); WO3, WO2, etc., with the formula WO x Tungsten oxide (x is a positive real number) represented by Li4Ti5O 12 and composite metal oxides containing lithium and titanium or vanadium, such as LiVO2.

[0124] Examples of sulfides include Ti2S3, TiS2, TiS, etc. x S y Titanium sulfides (x and y are positive real numbers); V3S4, VS2, VS, etc., with the formula VS x Vanadium sulfides (x is a positive real number) are represented by the formula Fe3S4, FeS2, FeS, etc. x S y Iron sulfides (x and y are positive real numbers) with the formula Mo x S y Molybdenum sulfides (x and y are positive real numbers) are represented by the formula SnS, SnS, etc. xTin sulfide represented by (x is a positive real number); WS such as WS2 x Tungsten sulfide represented by (x is a positive real number); Sb such as Sb2S3 x S y Antimony sulfide represented by (x and y are positive real numbers); formulas containing Se such as Se5S3, SeS2, SeS x S y Selenium sulfide represented by (x and y are positive real numbers) can be mentioned.

[0125] Examples of nitrides include Li3N, Li 3-x A x Lithium-containing nitrides such as N (A is one or more selected from the group consisting of Ni and Co, and 0 < x < 3) can be mentioned.

[0126] The negative electrode active material may contain only one of the materials exemplified above, or may contain two or more. The materials exemplified above may be crystalline or amorphous. The materials exemplified above are mainly supported on the negative electrode current collector and used as an electrode.

[0127] Examples of metal materials include lithium metal, silicon metal, and tin metal.

[0128] Further examples of the negative electrode active material include composite materials. This composite material contains Si or Sn as the first constituent element, and further contains a second constituent element and a third constituent element. Examples of the second constituent element include one or more selected from the group consisting of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium, and zirconium. Examples of the third constituent element include one or more selected from the group consisting of boron, carbon, aluminum, and phosphorus.

[0129] In particular, since high battery capacity and excellent battery characteristics can be obtained, as the metal material, silicon or tin alone (which may contain trace amounts of impurities), SiO v (0 < v ≤ 2), SnO w(0≦w≦2), Si—Co—C composite material, Si—Ni—C composite material, Sn—Co—C composite material, and Sn—Ni—C composite material are preferred.

[0130] Examples of negative electrode current collectors include Cu, Ni, and stainless steel. In particular, Cu is preferred for lithium-ion secondary batteries because it is difficult to form an alloy with Li and is easy to process into a thin film.

[0131] Examples of methods for producing a sheet-shaped negative electrode include the following. A manufacturing method in which a negative electrode active material, a conductive agent, and a binder are pressure-molded onto a negative electrode current collector to form a negative electrode mixture on the negative electrode current collector. A manufacturing method in which a paste-like negative electrode mixture is applied to a negative electrode current collector, dried, and the resulting sheet-like negative electrode mixture is then pressed to adhere to the negative electrode current collector. The paste-like negative electrode mixture is prepared by mixing a negative electrode active material, a conductive agent, a binder, and an appropriate organic solvent.

[0132] [7.3.Nonaqueous electrolyte] An example of the non-aqueous electrolyte is a non-aqueous electrolyte in which a lithium salt is dissolved in an organic solvent.

[0133] Examples of lithium salts include LiClO4, LiPF6, LiAsF6, LiSbF6, LiBF4, LiSO3F, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(COCF3), Li(C4F9SO3), LiC(SO2CF3)3, Li2B 10 Cl 10, LiBOB (here, BOB stands for bis(oxalato)borate), lithium salts of lower aliphatic carboxylic acids, and LiAlCl4. Only one type of lithium salt may be used, or two or more types may be used. Preferably, the lithium salt includes a fluorine-containing lithium salt. More preferably, the lithium salt includes one or more types selected from the group consisting of LiPF6, LiAsF6, LiSbF6, LiBF4, LiSO3F, LiCF3SO3, LiN(SO2CF3)2, and LiC(SO2CF3)3.

[0134] Examples of organic solvents include carbonates (propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, 1,2-di(methoxycarbonyloxy)ethane, etc.); ethers (1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, etc.); , 2-methyltetrahydrofuran, etc.); esters (methyl formate, methyl acetate, γ-butyrolactone, etc.); nitriles (acetonitrile, butyronitrile, etc.); amides (N,N-dimethylformamide, N,N-dimethylacetamide, etc.); carbamates (3-methyl-2-oxazolidone, etc.); sulfur-containing compounds (sulfolane, dimethyl sulfoxide, 1,3-propane sultone, etc.); and organic solvents in which one or more hydrogen atoms of these organic solvents have been substituted with fluorine atoms.

[0135] The organic solvent is preferably a mixed solvent of two or more kinds. Preferably, the organic solvent is a mixed solvent containing carbonates. More preferably, the organic solvent is a mixed solvent of a cyclic carbonate and an acyclic carbonate, or a mixed solvent of a cyclic carbonate and an ether. Among mixed solvents of a cyclic carbonate and an acyclic carbonate, a mixed solvent containing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate is preferred. A nonaqueous electrolyte using such a mixed solvent has the advantages of a wide operating temperature range, resistance to deterioration even when used at high voltages, resistance to deterioration even when used for long periods of time, and resistance to decomposition with respect to a graphite negative electrode.

[0136] Another preferred example is a non-aqueous electrolyte solution that combines a fluorine-containing lithium salt (such as LiPF6) with an organic solvent having a fluorine substituent. Such a non-aqueous electrolyte solution enhances the safety of the resulting non-aqueous electrolyte secondary battery. More preferred examples include: Still another suitable example is a mixed solvent containing ethers having a fluorine substituent (e.g., pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether) and dimethyl carbonate. A nonaqueous electrolyte solution containing such a mixed solvent has a high capacity retention rate even when discharged at a high voltage.

[0137] 8. Materials for Non-aqueous Electrolyte Secondary Batteries and Methods for Manufacturing Non-aqueous Electrolyte Secondary Batteries An example of a method for producing a member for a non-aqueous electrolyte secondary battery is a method in which a positive electrode, a laminated separator for a non-aqueous electrolyte secondary battery, and a negative electrode are arranged in this order.

[0138] An example of a method for producing a non-aqueous electrolyte secondary battery includes the following steps. 1. Place the non-aqueous electrolyte secondary battery components in a container. 2. Fill the container with non-aqueous electrolyte. 3. Seal the container while reducing the pressure. [Example]

[0139] [Measurement method] (1) Average particle size of filler The particle size at which the cumulative frequency reaches 50% in the volume-based particle size distribution was taken as the average particle size of the filler.

[0140] (2) Weight per unit area The basis weights of the polyolefin porous film, the porous layer and the laminated separator were calculated according to the following procedure. 1. An 8 cm x 8 cm square sample was cut out from a polyolefin porous film. The weight of the sample was measured and designated as W1 (g). The basis weight of the polyolefin porous film was calculated according to the following formula. -Polyolefin porous film weight (g / m 2 )=W1÷(0.08×0.08) 2. An 8 cm x 8 cm square sample was cut out from the laminated separator. The weight of the sample was measured and recorded as W2 (g). The basis weight of the laminated separator was calculated using the following formula. -Laminated separator weight (g / m 2 )=W2÷(0.08×0.08) 3. The basis weight of the porous layer was calculated according to the following formula. · Basis weight of porous layer = Basis weight of laminated separator - Basis weight of polyolefin porous film

[0141] (3) Porosity For each of the porous layer, the polyolefin porous film and the laminate separator, calculation was carried out using the following formula. Porosity (volume%) = [1-{A × (W a ÷d a +W b ÷d b +W c ÷d c +…+W n ÷d n )÷t}]×100 During the ceremony, t: target film thickness (cm) A: Weight of the target (g / cm 2 ) a, b, c..., n: Materials that make up the object. There are n types in total. ·W a , W b , W c …, W n : weight ratio of each material, where W a +W b +W c …+W n =1. ·d a , d b , d c …, d n : True density of each material (g / cm 3 ). The true density of the filler was based on the product information. The true density of the resin was based on K Xiao et al., J. Mater. Sci. 27 (1992) 3065. The true density of the polyolefin porous film was measured using the helium gas substitution method. Specifically, the polyolefin porous film was cut into 4-6 mm square pieces, vacuum-dried at 30°C or below for 17 hours, and then measured using a dry automatic density meter (AccuPyc II 1340, Micromeritics).

[0142] (4) Volume of uneven spaces on the porous layer surface The volume of the uneven space on the surface of the porous layer was measured by the following procedure. 1. With the polyolefin porous film side of the laminated separator in close contact with the stage, the porous layer side was observed. A laser microscope (VK-X3000, Keyence Corporation) and measurement software (VK-X3000 Observation Application, Keyence Corporation) were used for the observation. The measurement conditions were: measurement software mode: simple measurement mode, scan mode: laser confocal, observation magnification: 150x. 2. After setting the reference plane, a load curve for the porous layer surface was created based on the microscope observation data. Analysis software (Multi-file analysis application, Keyence Corporation) was used to create the load curve. The analysis range was set to the central part of the field of view where lens aberrations are minimal. 3. The core region is defined as the area where the areal load ratio is 10% to 80%. The space volume (mL / m) in the core region 2 ) was defined as the volume of uneven space on the surface of the porous layer.

[0143] (5) Physical properties after applying 20 MPa pressure (5.1) Thickness and air permeability (Gurley value) of laminated separator The film thickness and air permeability of the laminated separator after compression at 20 MPa were measured according to the following procedure. 1. A 6cm x 6cm square sample was cut out from the laminated separator. 2. The sample cut out in step 1 was sandwiched between aluminum plates and pressed using a hydraulic compression molding machine under the following conditions: 20 MPa, 35°C, and 5 minutes. 3. The membrane thickness and air permeability of the laminated separator after pressing obtained in step 2 were measured. The membrane thickness was measured using a high-precision digital length measuring machine (VL-50, Mitutoyo Corporation). The air permeability was measured in accordance with JIS P8117.

[0144] (5.2) Thickness and air permeability (Gurley value) of porous layer The film thickness and air permeability of the porous layer after compression at 20 MPa were calculated according to the following formulas. · Thickness of porous layer after compression at 20 MPa = Thickness of laminated separator after compression at 20 MPa (μm) - Thickness of substrate after compression at 20 MPa (μm) Air permeability of porous layer after compression at 20 MPa = Air permeability of laminated separator after compression at 20 MPa (s / 100 mL) - Air permeability of substrate after compression at 20 MPa (s / 100 mL)

[0145] (5.3) Air permeability per thickness of porous layer The air permeability per film thickness of the porous layer after applying a pressure of 20 MPa was calculated according to the following formula. Air permeability per film thickness of porous layer after pressurization at 20 MPa = Air permeability of porous layer after pressurization at 20 MPa (s / 100 mL) ÷ Film thickness of porous layer after compression at 20 MPa (μm)

[0146] (5.4) Resistance of laminated separator The resistance of the laminated separator after compression at 20 MPa was measured according to the following procedure. 1. 23 circular measurement samples (diameter: 17 mm) were cut out from the laminated separator pressed under the same conditions as in (5.1). 2. The components for the 2032-type coin cell were prepared. These consisted of an upper cover, a lower cover, a gasket, two circular spacers (diameter: 15.5 mm, thickness: 0.5 mm), and a wave washer. 3. The bottom cover, spacer, measurement sample, and spacer were placed in this order. A gasket was then placed to secure the measurement sample, and a wave washer was placed on top of the spacer. The number of measurement samples placed between the two spacers was 5, 8, or 10. Two such coin cells were prepared for each type. 4. An electrolyte (Kishida Chemical Co., Ltd.) was poured into the cell. The electrolyte was a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) (EC / DMC / EMC = 30 / 35 / 35 (volume ratio)) in which LiPF6 was dissolved. The LiPF6 concentration was 0.1M. 5. The cell was left standing under a pressure of approximately -80 kPa for 10 minutes to allow the measurement sample to be impregnated with the electrolyte. Next, a lid was placed on the cell and sealed using a coin cell crimper to obtain a sample cell. Steps 3 to 5 were performed in a glove box filled with argon gas and with a dew point temperature of -80°C or lower. 6. The sample cell was placed in a thermostatic bath at 25°C and left for 24 hours. Next, the impedance curve of the sample cell was measured using an AC impedance measuring device. The measurement conditions were amplitude: 5 mV, frequency: 1 MHz to 10 kHz. The intercept on the real axis of the impedance curve was taken as the resistance component. 7. The measured resistance component was plotted against the number of measurement samples. The obtained plot was linearly approximated to determine the slope. The value obtained by multiplying the slope by the area of ​​the spacer was used as the resistance (Ω cm) of the laminated separator. 2 ) where the area of ​​the spacer is (1.55 cm ÷ 2) 2 ×π=1.88cm 2 It was.

[0147] [Synthesis Example] Aramid polymer solution 1 was synthesized by the following procedure. The aramid resin contained in aramid polymer solution 1 is a block copolymer having a poly(4,4'-diphenylsulfonyl terephthalamide) block. 1. A 5 L separable flask equipped with a stirring blade, a thermometer, a nitrogen inlet, and a powder addition port was thoroughly dried. 2. 4217 g of N-methyl-2-pyrrolidone was placed in a flask. 324.22 g of calcium chloride (vacuum dried at 200°C for 2 hours) was then added to the flask, and the temperature was raised to 100°C. This allowed the calcium chloride to completely dissolve, yielding a calcium chloride solution (7.14 wt%). The moisture content of the calcium chloride solution was adjusted to 400 ppm. 3. While the temperature of the polymerization system was maintained at 100°C, 140.66 g of 4,4'-diaminodiphenyl sulfone was added and completely dissolved. 4. The temperature of the polymerization system was cooled to 20°C. While maintaining the temperature of the polymerization system at 25±2°C, a total of 114.06 g of terephthalic acid dichloride was added in three portions. The reaction was carried out for 1 hour to synthesize Block 1 consisting of poly(4,4'-diphenylsulfonylterephthalamide). 5. 61.26 g of paraphenylenediamine was added to the flask and allowed to dissolve completely over 1 hour. 6. While maintaining the temperature of the polymerization system at 25±2°C, a total of 113.88 g of terephthalic acid dichloride was added in three portions. The reaction was carried out for 1.5 hours, allowing block 2 made of poly(paraphenylene terephthalamide) to extend on both sides of block 1. 7. The polymerization system was aged for 1 hour while maintaining the temperature at 20±2°C. Next, the mixture was stirred under reduced pressure for 1 hour to remove air bubbles. In this way, aramid polymerization liquid 1 was obtained. In the block copolymer contained in aramid polymerization liquid 1, block 1 accounted for 50% of the entire molecule, and block 2 accounted for the remaining 50% of the entire molecule.

[0148] [Manufacturing example] Coating liquid 1, which is a raw material for the porous layer, was prepared by the following procedure. 1. 52.5 g of Filler 1 (aluminum oxide A, average particle size: 0.013 μm), 36.89 g of Filler 2 (aluminum oxide B, average particle size: 1.8 μm), 15.29 g of calcium carbonate, and 1172 g of N-methyl-2-pyrrolidone were weighed and placed in a plastic cup. 2. The resulting mixture was dispersed using a homogenizer (10,000 rpm) for 5 minutes. 3. To the resulting dispersion, 750 g of aramid polymerization solution 1 (obtained in Synthesis Example) was added. 4. The resulting mixture was dispersed using a homogenizer (10,000 rpm) for 10 minutes. 5. The resulting mixture was passed through a high-pressure disperser (Gaulin homogenizer) twice to further disperse the mixture. The pressure was 50 MPa. In this way, Coating Solution 1 was prepared. The solid content of Coating Solution 1 was 7% by weight.

[0149] Example 1 The laminated separator 1 was produced by the following procedure. The separator was produced while a raw roll of polyolefin porous film was being conveyed by a machine. 1. A polyolefin porous film (polyethylene porous film, thickness: 10.8 μm, porosity: 55%) was unwound from a roll. 2. One side of the polyolefin porous film was impregnated with N-methyl-2-pyrrolidone. An impregnation roll was used for the impregnation. In this process, the same liquid as the solvent for Coating Solution 1 was impregnated into one side of the polyolefin porous film. 3. Coating liquid 1 was applied to the other surface of the polyolefin porous film. A bar coater was used for coating. The amount of coating liquid 1 applied was such that the basis weight of the porous layer was 1.9 g / m. 2 In this step, Coating Liquid 1 was applied to the surface opposite to the surface impregnated with N-methyl-2-pyrrolidone in Step 2. 4. The polyolefin porous film was introduced into a deposition tank to deposit a porous layer. Water and air were sprayed into the deposition tank from a two-fluid nozzle, thereby adjusting the relative humidity to 100%. The temperature of the deposition tank was set to room temperature. 5. The polyolefin porous film was introduced into a water washing device and washed with ion-exchanged water to remove N-methyl-2-pyrrolidone and calcium chloride. 6. The polyolefin porous film was dried with hot air to remove moisture, and thus a laminated separator 1 was obtained.

[0150] [Example 2, Comparative Examples 1 and 2] Laminated separator 2 and comparative laminated separators 1 and 2 were obtained in the same manner as in Example 1. However, the following changes were made as shown in Table 1. Filler 2 material and average particle size Weight ratio of block copolymer:filler 1:filler 2 in coating liquid Thickness and porosity of polyolefin porous film (polyethylene porous film)

[0151] 〔result〕 The results are shown in Table 1. [Table 1] JPEG2025167743000003.jpg19342

[0152] As shown in Table 1, the laminated separators according to the examples and comparative examples differed in whether or not they satisfied the following conditions 1 to 3. Condition 1: The average particle size of filler 2 is 1 μm or more Condition 2: The volume of the uneven space on the porous layer surface is 0.4 mL / m 2 End Condition 3: Porosity parameter is 0.6 or less

[0153] The laminated separators of Examples 1 and 2 all satisfied conditions 1 to 3. The laminated separator of Comparative Example 1 satisfied conditions 1 and 2, but did not satisfy condition 3. This is because the porosity of the polyolefin porous film used was low. The laminated separator of Comparative Example 2 satisfied condition 3, but did not satisfy conditions 1 and 2. This is because, under the production conditions of the Examples, it was difficult to increase the spatial volume of the irregularities on the porous layer surface without incorporating a filler with a large particle size (however, depending on the production conditions, there is room to increase the spatial volume of the irregularities on the porous layer surface without incorporating a filler with a large particle size).

[0154] When comparing the physical properties after applying a pressure of 20 MPa, the laminate separators according to the Examples had a lower air permeability (Gurley value) per thickness of the porous layer and a lower resistance of the laminate separator than the laminate separators according to the Comparative Examples. As is clear from Table 1, regardless of which Example or Comparative Example was selected, a significant difference was observed in at least one of the air permeability per thickness of the porous layer and the resistance of the laminate separator.

[0155] At first glance, the difference in resistance between the laminate separators according to Examples 1 and 2 and the laminate separator according to Comparative Example 2 appears small. However, in next-generation nonaqueous electrolyte secondary batteries, it is expected that the laminate separator will be repeatedly compressed due to expansion of the electrodes accompanying charge and discharge. Therefore, if the nonaqueous electrolyte secondary battery is used for a long period of time, it is expected that the difference in resistance after compression will become even greater.

[0156] These results suggest that the laminate separator according to one embodiment of the present invention has excellent ion permeability after pressure is applied. [Industrial Applicability]

[0157] The present invention can be used in non-aqueous electrolyte secondary batteries and the like.

Claims

1. A laminate separator for a non-aqueous electrolyte secondary battery, comprising a polyolefin porous film and a porous layer laminated on one or both sides thereof, A laminated separator for a non-aqueous electrolyte secondary battery, which satisfies the following conditions 1 and 3: Condition 1: The porous layer contains filler having an average particle size of 1 μm or more. Condition 3: (porosity of the porous layer−porosity of the polyolefin porous film) / porosity of the laminated separator for a non-aqueous electrolyte secondary battery≦0.

6.

2. the porous layer contains one or more resins selected from the group consisting of polyolefins, (meth)acrylate resins, fluorine-containing resins, polyamide resins, polyester resins, and water-soluble polymers; The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1 .

3. The porous layer contains an aramid resin. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 2 .

4. A laminate separator for a non-aqueous electrolyte secondary battery, comprising a polyolefin porous film and a porous layer laminated on one or both sides thereof, A laminated separator for a non-aqueous electrolyte secondary battery that satisfies the following conditions 2 and 3: Condition 2: The porous layer has a surface unevenness space volume of 0.4 mL / m ２ That's all. Condition 3: (porosity of the porous layer−porosity of the polyolefin porous film) / porosity of the laminated separator for a non-aqueous electrolyte secondary battery≦0.

6.

5. the porous layer contains one or more resins selected from the group consisting of polyolefins, (meth)acrylate resins, fluorine-containing resins, polyamide resins, polyester resins, and water-soluble polymers; The laminate separator for a non-aqueous electrolyte secondary battery according to claim 4 .

6. The porous layer contains an aramid resin. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 5 .

7. A positive electrode, the laminate separator for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 6, and a negative electrode are laminated in this order. Components for non-aqueous electrolyte secondary batteries.

8. The laminate separator for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6 is provided. Non-aqueous electrolyte secondary battery.

9. The nonaqueous electrolyte secondary battery member according to claim 7 is provided. Non-aqueous electrolyte secondary battery.

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