Nonaqueous electrolyte secondary battery laminated separator

Abstract

To provide a laminated separator for a nonaqueous electrolyte secondary battery capable of improving cycle characteristics of a built-in battery.SOLUTION: According to an embodiment of the present invention, there is provided a polyolefin vesicular film laminated film including: The nonaqueous electrolyte secondary battery laminated separator has an average coefficient of linear expansion of not less than 3.0 * 10 - 6 [1 / K] in a TD direction at a temperature in a range of 30 °C. to 50 °C.SELECTED DRAWING: None

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 a high energy density and are therefore widely used as batteries for personal computers, mobile phones, personal digital assistants, and automotive applications. Lithium ion batteries generally include a separator between the positive electrode and the negative electrode. Various separators have been proposed for the purpose of improving battery performance (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2006-299612 Summary of the Invention [Problem to be solved by the invention]

[0004] The separator disclosed in Patent Document 1 still has room for improvement in the cycle characteristics of the battery in which it is incorporated.

[0005] An object of one aspect of the present invention is to provide a laminate separator for a non-aqueous electrolyte secondary battery that can improve the cycle characteristics of the battery in which it is incorporated. [Means for solving the problem]

[0006] 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, The laminated separator for a non-aqueous electrolyte secondary battery has an average linear expansion coefficient in the TD direction at 30 to 50°C of 3.0 × 10-6 [1 / K] or more, Laminated separator for non-aqueous electrolyte secondary batteries. <2> The laminated separator for a non-aqueous electrolyte secondary battery has an average linear expansion coefficient in the MD direction at 30 to 50°C of -8.0 × 10 -6 [1 / K] or more, <1> 2. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1. <3> the porous layer contains a filler, The filler is an inorganic filler and / or an organic filler. <1> or <2> 2. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1. <4> The content of the filler is 30 to 99% by weight, assuming that the weight of the porous layer is 100% by weight. <3> 2. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1. <5> The porous layer contains one or more resins selected from the group consisting of polyolefins, (meth)acrylate resins, fluorine-containing resins, polyamide resins, polyimide resins, polyamideimide resins, polyester resins, and water-soluble polymers. <1> ~ <4> 10. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 9. <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. Non-aqueous electrolyte secondary battery. <9> <7> The non-aqueous electrolyte secondary battery member according to claim 1, Non-aqueous electrolyte secondary battery. [Effects of the Invention]

[0007] According to one aspect of the present invention, there is provided a laminate separator for a non-aqueous electrolyte secondary battery that can improve the cycle characteristics of a battery in which it is incorporated. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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."

[0009] 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.

[0010] In this specification, a laminate separator for a non-aqueous electrolyte secondary battery may be simply referred to as a "separator." In this specification, the average linear expansion coefficient in the TD direction at 30 to 50°C may be simply referred to as the "TD average linear expansion coefficient." In this specification, the average linear expansion coefficient in the MD direction at 30 to 50°C may be simply referred to as the "MD average linear expansion coefficient."

[0011] [1. Laminated separator for non-aqueous electrolyte secondary batteries] [1.1. Average linear expansion coefficient in the transverse direction at 30 to 50°C] Research by the present inventors has revealed that a separator whose average coefficient of linear expansion in the TD direction at 30 to 50°C is adjusted to a certain value or higher can improve the cycle characteristics (such as the discharge capacity retention rate after cycling) of a battery in which it is incorporated. While not intending to be bound by theory, a separator with such characteristics is more likely to expand in the TD direction at higher temperatures in the temperature range associated with charge and discharge (usually 30 to 50°C). Therefore, it is believed that the separator deforms appropriately during charge and discharge, enabling it to follow the expansion and contraction of the electrodes, thereby improving the cycle characteristics of the battery.

[0012] To produce a separator with such properties, it is preferable to stretch the separator in the TD direction after forming the porous layer in the manufacturing process. For example, if the separator is stretched in the TD direction at a low stretch ratio after forming the porous layer, the TD average linear expansion coefficient tends to increase. Furthermore, if the separator is contracted again in the TD direction after this stretching, the TD average linear expansion coefficient tends to further increase. For more specific examples, see Section [3].

[0013] Incidentally, it is considered that the residual stress in the separator caused by the formation of the porous layer is adjusted by performing TD stretching after the formation of the porous layer. Therefore, there is technical significance in performing TD stretching after the formation of the porous layer, and it is considered that the TD average linear expansion coefficient cannot be adjusted even if a porous layer is formed on one or both sides of a polyolefin porous film that has been TD stretched in advance.

[0014] [1.2. Separator properties] The separator's TD average linear expansion coefficient is 3.0 x 10 -6 [1 / K] or more. The TD average linear expansion coefficient is 5.0×10 -6 That's it, 10.0 x 10 -6 That's it, 20.0 x 10 -6 That's it, 40.0 x 10 -6 Above, 50.0 x 10 -6 That's it, 75.0 x 10 -6 or more than 100.0×10 -6A battery incorporating a separator that satisfies this condition has excellent cycle characteristics. The upper limit of the TD average linear expansion coefficient is, for example, 500.0 × 10 -6 or less or 250.0×10 -6 It can be the following:

[0015] In this specification, the TD average linear expansion coefficient is a value obtained by converting the amount of change in the length of a test piece in the TD direction per 1°C, calculated from the slope of the line connecting the point at 30°C and the point at 50°C on the linear expansion coefficient curve, into a value per mm of the test piece in the TD direction before the test. The TD average linear expansion coefficient can be calculated using the following formula. TD average linear expansion coefficient (1 / K)=[{L(T 50 )-L(T 30 )}÷20]÷L0 L0: Length of the test piece in the TD direction before the test (mm) L(T 30 ): Change in length of test piece in TD direction at 30℃ (mm) L(T 50 ): Change in length of test piece in TD direction at 50℃ (mm)

[0016] The MD average linear expansion coefficient of the separator is -10.0×10 -6 [1 / K] or more, -8.0×10 -6 or greater than or -7.0×10 -6 A battery incorporating a separator that satisfies this condition has excellent cycle characteristics. The upper limit of the MD average linear expansion coefficient is, for example, 150.0 × 10 -6 or less or 100.0 x 10 -6 It can be the following:

[0017] In this specification, the MD average linear expansion coefficient is a value obtained by converting the amount of change in the length of a test piece in the MD direction per 1°C, calculated from the slope of the line connecting the point at 30°C and the point at 50°C on the linear expansion coefficient curve, into a value per mm of the length in the MD direction of the test piece before the test. The MD average linear expansion coefficient is calculated using the following formula. MD average linear expansion coefficient (1 / K)=[{L'(T 50 )-L'(T30 )}÷20]÷L'0 L'0: Length of the test piece in the MD direction before the test (mm) L'(T 30 ): Change in length of test piece in MD direction at 30℃ (mm) L'(T 50 ): Change in length of test piece in MD direction at 50℃ (mm)

[0018] The linear expansion curve is a graph with the temperature on the horizontal axis and the linear expansion coefficient of the separator on the vertical axis. The linear expansion curve is determined by thermomechanical analysis based on JIS K7197. For specific examples of the measurement method, see the examples below.

[0019] The discharge capacity retention rate of a battery incorporating the separator after 200 cycles is preferably 85% or more, more preferably 90% or more. If the discharge capacity retention rate is within the above range, it can be said that the cycle characteristics of a battery incorporating the separator are improved. For the method of measuring the discharge capacity retention rate after cycle testing, see the Examples described below.

[0020] The separator preferably has an air permeability of 500 s / 100 mL or less, more preferably 400 s / 100 mL or less, and even more preferably 300 s / 100 mL or less, in terms of Gurley value. If the separator has an air permeability within the above-mentioned range, it can be said that the separator has sufficient ion permeability.

[0021] The withstand voltage of the separator is preferably 1.65 kV / mm or more, and more preferably 1.70 kV / mm or more.

[0022] The porosity of the separator is preferably 20 to 80% by volume, more preferably 30 to 70% by volume, and even more preferably 40 to 60% by volume, so as to increase the amount of electrolyte retained and to provide the function of reliably preventing the flow of excessive current at lower temperatures.

[0023] 2. Structure of Laminated Separator for Non-Aqueous Electrolyte Secondary Battery The separator is a laminate separator in which a porous layer is laminated on one or both sides of a polyolefin porous film. When a porous layer is provided on both sides of the polyolefin porous film, the thickness, basis weight, porosity, etc. of one porous layer and the other porous layer may be the same or different.

[0024] [2.1.Polyolefin porous film] In this specification, the term "polyolefin porous film" refers to a film mainly composed of a polyolefin resin. Furthermore, "mainly composed of a polyolefin resin" means that the proportion of the polyolefin resin in the polyolefin 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 materials constituting the polyolefin porous film.

[0025] A polyolefin porous film is composed primarily of a polyolefin resin and has numerous interconnected pores inside, allowing gases and liquids to pass from one side to the other.

[0026] The polyolefin has a weight average molecular weight of 5×10 5 ~15×10 6 In particular, it is more preferable that the polyolefin contains a high molecular weight component having a weight average molecular weight of 1,000,000 or more, since this improves the strength of the laminate separator for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention.

[0027] Examples of the polyolefin include homopolymers and copolymers obtained by polymerizing monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene.

[0028] Examples of the homopolymer include polyethylene, polypropylene, and polybutene, and examples of the copolymer include ethylene-propylene copolymer.

[0029] Among these, polyethylene is preferred as the polyolefin because it can prevent excessive current from flowing at a lower temperature. This "preventing excessive current from flowing" is also called "shutdown."

[0030] Examples of the polyethylene include low-density polyethylene, high-density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), ultra-high molecular weight polyethylene having a weight-average molecular weight of 1,000,000 or more, etc. Among these, ultra-high molecular weight polyethylene having a weight-average molecular weight of 1,000,000 or more is more preferred as the polyethylene.

[0031] The basis weight of the polyolefin porous film can be appropriately determined in consideration of the strength, thickness, weight, and handleability. However, in order to increase the weight energy density and volume energy density of the nonaqueous electrolyte secondary battery, the basis weight is preferably 2 to 20 g / m. 2 It is preferable that the density is 2 to 12 g / m 2 More preferably, it is 3 to 10 g / m 2 It is more preferable that:

[0032] The polyolefin porous film preferably has an air permeability of 30 to 500 s / 100 mL, more preferably 50 to 300 s / 100 mL, in terms of Gurley value. When the polyolefin porous film has an air permeability within the above range, the polyolefin porous film can obtain sufficient ion permeability.

[0033] The porosity of the polyolefin 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 obtain the function of reliably preventing excessive current flow at lower temperatures.

[0034] In addition, the pore size of the pores in the polyolefin porous film is preferably 0.3 μm or less, and more preferably 0.14 μm or less, so as to obtain sufficient ion permeability and prevent particles from entering the positive electrode and negative electrode.

[0035] The lower limit of the thickness of the polyolefin porous film is preferably 4 μm or more, more preferably 5 μm or more, and even more preferably 6 μm or more. The upper limit of the thickness of the polyolefin porous film is preferably 29 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less.

[0036] The polyolefin porous film may have a multilayer structure consisting of two or more layers. An example of a polyolefin porous film having a multilayer structure is a film in which a layer mainly composed of polyethylene and a layer mainly composed of polypropylene are laminated together. The number of layers included in the multilayer structure is not particularly limited. For example, the film may have a two-layer structure consisting of a polyethylene layer and a polypropylene layer, or a three-layer structure consisting of one or more polyethylene layers and one or more polypropylene layers. The multilayer structure consisting of a polyethylene layer and a polypropylene layer can achieve both shutdown property and heat resistance.

[0037] The polyolefin porous film may have a crosslinked structure. The crosslinked structure can be introduced, for example, by using a silane-modified polyolefin. The polyolefin porous film having a crosslinked structure has excellent heat resistance. Therefore, when a polyolefin porous film having a Chinese structure is combined with a porous layer, the heat resistance of the laminate separator for a non-aqueous electrolyte secondary battery can be further improved. The crosslinked structure may be formed between the polyolefin porous film and the porous layer.

[0038] [2.2. Porous Layer] The porous layer typically contains a binder resin. The binder resin is preferably a resin that is insoluble in the battery's electrolyte and is electrochemically stable under the conditions of use of the battery. In one embodiment, the porous layer contains a filler in addition to the binder resin.

[0039] (binder resin) Examples of the resin include polyolefins; (meth)acrylate resins; aromatic resins; fluorine-containing resins; polyamide resins; polyimide resins; polyamideimide resins; polyester resins; rubbers; resins with a melting point or glass transition temperature of 180°C or higher; water-soluble polymers; polycarbonate; polyacetal; and polyether ether ketone.

[0040] Of the above-mentioned resins, one or more resins selected from the group consisting of polyolefins, (meth)acrylate resins, fluorine-containing resins, aromatic resins, polyamide resins, polyester resins, polyamideimide resins, and water-soluble polymers are preferred.

[0041] The resin is more preferably an aromatic resin. Among aromatic resins, nitrogen-containing aromatic resins are particularly preferred. Furthermore, among nitrogen-containing aromatic resins, aramid resins, which will be described later, are most preferred. Nitrogen-containing aromatic resins have nitrogen-mediated bonds, such as amide bonds, and therefore have excellent heat resistance. Therefore, when the resin is a nitrogen-containing aromatic resin, the heat resistance of the porous layer can be suitably improved. As a result, the heat resistance of a laminate separator for a nonaqueous electrolyte secondary battery including the porous layer can be improved.

[0042] The polyolefin is preferably polyethylene, polypropylene, polybutene, an ethylene-propylene copolymer, or the like.

[0043] Examples of the fluorine-containing resin include polyvinylidene fluoride (PVDF), polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-trichloroethylene copolymer, vinylidene fluoride-vinyl fluoride copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, and ethylene-tetrafluoroethylene copolymer, as well as fluorine-containing rubbers having a glass transition temperature of 23°C or lower among the fluorine-containing resins.

[0044] The polyamide resin is preferably a polyamide resin that falls under the category of nitrogen-containing aromatic resin, and is particularly preferably an aramid resin such as an aromatic polyamide or a wholly aromatic polyamide.

[0045] 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 Examples of such copolymers include poly(2-chloroparaphenylene terephthalamide), poly(2,6-dichloroparaphenylene terephthalamide), poly(2,6-dichloroparaphenylene terephthalamide), poly(2,6-dichloroparaphenylene terephthalamide), poly(4,4'-diphenylsulfonyl terephthalamide), and poly(4,4'-diphenylsulfonyl terephthalamide).

[0046] Among the above-mentioned aramid resins, one or more 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.

[0047] As the polyester resin, aromatic polyesters such as polyarylates and liquid crystal polyesters are preferred.

[0048] Examples of the 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.

[0049] Examples of the resin having a melting point or glass transition temperature of 180° C. or higher include polyphenylene ether, polysulfone, polyethersulfone, polyphenylene sulfide, polyetherimide, polyamideimide, and polyetheramide.

[0050] The polyamideimide is preferably an aromatic polyamideimide. Examples of the aromatic polyamideimide include wholly aromatic polyamideimide and semi-aromatic polyamideimide. The aromatic polyamideimide is preferably wholly aromatic polyamideimide.

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

[0052] The resin may be one type of resin alone or a combination of two or more types of resins. For example, a combination of a polyamide resin, which has excellent heat resistance, and a (meth)acrylate resin and / or a fluorine-containing resin, which have adhesive properties, can be used to obtain a porous layer that has both heat resistance and adhesive properties. In this case, the form in which the (meth)acrylate resin or the fluorine-containing resin is present is not particularly limited. These resins may be, for example, in the form of particles, may be present in a mixed state with the polyamide resin, or may be unevenly distributed on the surface of the porous layer. The resin content in the porous layer is preferably 25 to 80% by weight, and more preferably 30 to 70% by weight, assuming the total weight of the porous layer to be 100% by weight.

[0053] (filler) The material constituting the filler is not particularly limited. The filler may be composed of only one type of filler, or may be composed of two or more types of fillers each made of a different material. The filler may be an inorganic filler or an organic filler.

[0054] 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, preferred inorganic fillers are fillers made of inorganic oxides such as silica, calcium oxide, magnesium oxide, titanium oxide, alumina, mica, zeolite, aluminum hydroxide, magnesium hydroxide, barium sulfate, and boehmite, more preferred are fillers made of calcium oxide, magnesium oxide, magnesium hydroxide, barium sulfate, alumina, or boehmite, and even more preferred are fillers made of magnesium hydroxide, barium sulfate, alumina, or boehmite.

[0055] Examples of the organic filler include homopolymers of monomers such as styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, and methyl acrylate, or copolymers of two or more of these monomers; fluororesins such as polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, and polyvinylidene fluoride; melamine resins; urea resins; polyolefins; and polymethacrylates. One type of organic filler may be used alone, or two or more types may be mixed and used. Among these organic fillers, polytetrafluoroethylene powder is preferred in terms of chemical stability. Furthermore, polyolefins are preferred from the viewpoint of improving the shutdown property of laminated separators for nonaqueous electrolyte secondary batteries. When polyolefins are used as the organic filler, shutdown property can be imparted to the porous layer.

[0056] The shape of the filler is not particularly limited and may be, for example, spherical, elliptical, plate-like, rod-like, or irregular, and among these, the shape of the filler is preferably spherical.

[0057] The average particle diameter 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. Fillers with an average particle diameter of 1 μm or more have the following advantages: (i) they can easily increase the pore size of the porous layer, thereby preventing a decrease in ion permeability even when the separator is compressed in a battery; and (ii) they can easily form irregularities on the surface of the porous layer, thereby improving the slipperiness of the separator. Fillers with an average particle diameter of less than 1 μm have the advantages of improving the heat resistance of the separator and enabling the separator to be made thinner. To achieve both of these advantages, two or more fillers with different average particle diameters may be used, or a filler with a wide particle size distribution may be used. In this specification, the "average particle diameter of the filler" refers to the volume-based average particle diameter (D50) of the filler. D50 refers to the particle diameter at which the cumulative distribution on a volume basis is 50%. D50 can be measured, for example, using a laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation, trade names: SALD2200, SALD2300, etc.).

[0058] The upper limit of the filler content in the porous layer is preferably 99% by weight or less, more preferably 90% by weight or less, even more preferably 80% by weight or less, and particularly preferably 70% by weight or less, assuming the total weight of the porous layer to be 100% by weight. If the filler content satisfies this range, the weight of the porous layer can be adjusted to an appropriate range. The lower limit of the filler content in the porous layer is preferably 30% by weight or more, more preferably 40% by weight or more. If the filler content satisfies this range, functions such as heat resistance can be easily exhibited sufficiently.

[0059] The basis weight of one side of the porous layer, i.e., the weight per unit area, can be appropriately determined in consideration of the strength, film thickness, weight, and handleability of the porous layer. The upper limit of the basis weight of one side of the porous layer is 3.0 g / m 2 Preferably, it is 2.5 g / m or less. 2 More preferably, it is 2.0 g / m or less. 2The lower limit of the basis weight of one surface of the porous layer is not particularly limited, but is preferably 0.4 g / m 2 It is preferable that the content is 0.45 g / m or more. 2 More preferably, it is 0.5 g / m or more. 2 More preferably, it is equal to or greater than this.

[0060] The air permeability of the porous layer is preferably 30 to 50 s / 100 mL, more preferably 40 to 75 s / 100 mL, in terms of Gurley value. If the air permeability of the porous layer is within the above range, it can be said that the porous layer has sufficient ion permeability.

[0061] The porosity of the porous layer is preferably 20 to 90% by volume, more preferably 30 to 50% by volume, so as to obtain sufficient ion permeability.

[0062] 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 these sizes, a nonaqueous electrolyte secondary battery including the porous layer can obtain sufficient ion permeability.

[0063] The lower limit of the thickness of the porous layer is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. The upper limit of the thickness of the porous layer is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less. If the thickness of the porous layer is within the above range, the function of the porous layer (such as imparting heat resistance) can be fully exhibited, and the thickness of the entire separator can be reduced.

[0064] The porous layer may contain components other than the resin and the filler, provided that the purpose of the present invention is not impaired. Examples of the other components include additives commonly used in separators for nonaqueous electrolyte secondary batteries. The other components may be one type or a mixture of two or more types.

[0065] Examples of the additives include flame retardants, antioxidants, surfactants, antistatic agents, crosslinking agents, and waxes. Adding an antistatic agent can reduce static buildup even in porous layers that are prone to static buildup. Adding a flame retardant and / or a crosslinking agent can further improve the safety and heat resistance of the separator.

[0066] [2.3. Other Layers] The laminated separator may further include other layers different from the polyolefin porous film and the porous layer, provided that the objectives of the present invention are not impaired. The other layers are not particularly limited and include known layers. Specific examples include an adhesive layer, a heat-resistant porous layer different from the porous layer, a slip layer intended to improve the slippage of the separator, a layer containing organic particles such as polyolefins for providing shutdown properties, an antistatic layer, a protective layer, etc. A heat-resistant porous layer different from the porous layer refers to a layer that differs from the porous layer in at least one element, such as the type of resin or filler or the filler content. When the other layer is a heat-resistant porous layer different from the porous layer, the type of resin or filler and the filler content contained in this heat-resistant porous layer may be the same as those described in the porous layer section. The slip layer may be a layer containing an antiblocking agent and / or a filler, and the provision of surface irregularities can improve the slippage of the separator.

[0067] The other layer may be provided on one or both sides of the laminated separator. When the laminated separator has a porous layer on both sides of the polyolefin porous film, the other layer may be provided on both porous layers, or on only one of the porous layers. When the laminated separator has a porous layer on only one side of the polyolefin porous film, the other layer may be provided on the porous layer, or on the side of the polyolefin porous film that does not have a porous layer, or on both of them. The other layer may be provided on the outermost layer of the laminated separator.

[0068] In this specification, the term "adhesive layer" refers to a layer having adhesive properties. The adhesive layer may be provided on the surface of the laminated separator that contacts the electrode. Examples of components contained in the adhesive layer that contribute to adhesiveness include acrylic resins and PVDF resins. Examples of acrylic resins that can be used include those described in paragraphs 0072 to 0088 of JP 2024-006988 A. Examples of PVDF resins that can be used include those described in paragraphs 0017 to 0022 of JP 2017-168419 A. Acrylic resins and PVDF resins may each be used alone or in combination of two or more. The adhesive layer may further contain a filler in addition to the components that contribute to adhesiveness. Fillers similar to those that can be used in the porous layer may be used. The state of the adhesive layer is not particularly limited; the components that contribute to adhesiveness may be present in particulate form or as a homogeneous coating layer. The adhesive layer may also be formed into a dotted or striped pattern by pattern coating. The adhesive layer fixes the separator to the electrode via the adhesive layer, improving the handling properties and heat resistance of the electrode laminate. The adhesive layer in the form of particles, dots, or stripes can suppress a decrease in ion permeability due to the adhesive layer.

[0069] 3. Manufacturing method of laminated separator for non-aqueous electrolyte secondary battery [3.1. Adjustment Factors for TD Average Linear Expansion Coefficient] The separator's TD average linear expansion coefficient is 3.0 x 10 -6 An example of a manufacturing condition for achieving a coefficient of thermal expansion of [1 / K] or more is stretching and shrinkage after the formation of the porous layer. Generally, the larger the stretch ratio in TD stretching, the larger the TD average linear expansion coefficient tends to be. Furthermore, if TD shrinkage is performed after TD stretching, the TD average linear expansion coefficient tends to be larger.

[0070] The stretching ratio in TD stretching is preferably 0.5% or more, more preferably 1% or more, even more preferably 5% or more, and particularly preferably 10% or more. The upper limit of the stretching ratio in TD stretching can be 20% or less, or 15% or less. If the stretching ratio is set to a low ratio within the above range, it is easy to prevent the porous layer stretched by stretching from cracking. In this specification, "stretching ratio is X%" means that if the length before stretching is 100%, the length after stretching is 100+X%.

[0071] The shrinkage ratio of TD shrinkage is usually equal to or less than the stretching ratio of TD stretching, preferably equal to or less than 8%, more preferably equal to or less than 6%, and even more preferably equal to or less than 4%. In this specification, "the shrinkage ratio is X%" means that if the length before shrinkage is 100%, the length after shrinkage is 100-X%.

[0072] However, the numerical ranges of the preferred manufacturing conditions described above are merely examples. A person skilled in the art would be able to appropriately set the TD stretching conditions and TD shrinkage conditions to achieve a TD average linear expansion coefficient of 3.0×10 -6 As a result, if one or more of the above-mentioned preferable conditions are not satisfied, the TD average linear expansion coefficient can be adjusted to 3.0 × 10 -6 It is possible to obtain a separator that is [1 / K] or higher.

[0073] [3.2. MD average linear expansion coefficient control factors] The MD average linear expansion coefficient of the separator can be adjusted by the same means as the TD average linear expansion coefficient. For example, a separator with an MD average linear expansion coefficient within a suitable range can be produced by stretching and shrinking the porous layer after formation.

[0074] [3.3. Method for producing polyolefin porous film] Examples of methods for producing a polyolefin porous film include the following. First, a polyolefin resin, a pore-forming agent such as an inorganic filler or a plasticizer, and optionally an antioxidant, etc. are kneaded to obtain a polyolefin resin composition. The polyolefin resin composition is then extruded to produce a sheet-like polyolefin resin composition. The pore-forming agent is then removed from the sheet-like polyolefin resin composition using an appropriate solvent. The polyolefin resin composition from which the pore-forming agent has been removed is then stretched to produce a polyolefin porous film.

[0075] The inorganic filler is not particularly limited, and examples thereof include fillers, specifically calcium carbonate, etc. The plasticizer is not particularly limited, and examples thereof include low molecular weight hydrocarbons such as liquid paraffin.

[0076] An example of a method for producing a polyolefin porous film includes a method including the steps shown below.

[0077] (i) a step of kneading an ultra-high molecular weight polyethylene having a weight-average molecular weight of 1 million or more, a low-molecular weight polyethylene having a weight-average molecular weight of 10,000 or less, a pore-forming agent such as calcium carbonate or a plasticizer, and an antioxidant to obtain a polyolefin-based resin composition; (ii) a step of gradually cooling the obtained polyolefin-based resin composition and forming it into a sheet; (iii) a step of removing the pore-forming agent from the obtained sheet with an appropriate solvent; and (iv) a step of stretching the sheet from which the pore-forming agent has been removed at an appropriate stretch ratio.

[0078] [3.4. Method for manufacturing porous layer] A porous layer can be formed by using a coating liquid in which the resin described in Section [2] is dissolved or dispersed in a solvent. Also, a porous layer containing a resin and a filler can be formed by using a coating liquid obtained by dissolving or dispersing a resin in a solvent and dispersing a filler therein.

[0079] The solvent may be a solvent that dissolves the resin. Alternatively, the solvent may be a dispersion medium that disperses the resin or filler. Examples of methods for forming the coating liquid include mechanical stirring, ultrasonic dispersion, high-pressure dispersion, and media dispersion.

[0080] Methods for forming a porous layer include, for example, a method in which a coating liquid is directly applied to the surface of a polyolefin porous film, and then the solvent is removed; a method in which a coating liquid is applied to a suitable support, and then the solvent is removed to form a porous layer, and the porous layer and the polyolefin porous film are pressed together, and then the support is peeled off; a method in which a coating liquid is applied to a suitable support, and then a polyolefin porous film is pressed onto the coated surface, and then the support is peeled off, and then the solvent is removed; and a method in which a polyolefin porous film is immersed in a coating liquid to perform dip coating, and then the solvent is removed.

[0081] The solvent is preferably one that does not adversely affect the polyolefin porous film, dissolves the resin uniformly and stably, and disperses the filler uniformly and stably. Examples of the solvent include one or more solvents selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, acetone, water, etc.

[0082] The coating liquid may contain, as appropriate, components other than the resin and filler, such as a dispersant, a plasticizer, a surfactant, and a pH adjuster.

[0083] The coating liquid can be applied to the polyolefin porous film by a conventionally known method, and specific examples thereof include a gravure coater method, a dip coater method, a bar coater method, and a die coater method.

[0084] When the coating liquid contains an aramid resin, the aramid resin can be precipitated by applying humidity to the coating surface, thereby forming a porous layer.

[0085] Examples of methods for removing the solvent from the coating liquid applied to the polyolefin porous film include methods for removing the solvent from the coating film, which is a film of the coating liquid, by ventilation drying, heat drying, etc.

[0086] Furthermore, by changing the amount of solvent in the coating liquid, the porosity and average pore size of the resulting porous layer can be adjusted.

[0087] The suitable solid content of the coating liquid may vary depending on the type of filler, but is generally preferably more than 3% by weight and not more than 40% by weight.

[0088] The coating shear rate when applying the coating liquid to the polyolefin porous film may vary depending on the type of filler, but is generally preferably 2 (1 / s) or more, and more preferably 4 (1 / s) to 50 (1 / s).

[0089] 4. Non-aqueous electrolyte secondary battery components and non-aqueous electrolyte secondary batteries A nonaqueous electrolyte secondary battery member according to one aspect of the present invention includes a positive electrode, the separator described above, and a negative electrode arranged in this order. The nonaqueous electrolyte secondary battery according to one aspect of the present invention includes the separator described above or the nonaqueous electrolyte secondary battery member described above.

[0090] The shape of the nonaqueous electrolyte secondary battery is not particularly limited, and may be a thin plate (paper) type, a disk type, a cylinder type, a prismatic type such as a rectangular parallelepiped, or the like. The nonaqueous electrolyte secondary battery is, for example, a nonaqueous electrolyte secondary battery that generates electromotive force by doping and dedoping lithium, and includes a nonaqueous electrolyte secondary battery member formed by laminating a positive electrode, the above-mentioned separator, and a negative electrode in this order. Note that the components of the nonaqueous electrolyte secondary battery other than the above-mentioned separator are not limited to the components described below.

[0091] The nonaqueous electrolyte secondary battery typically has a structure in which a battery element, in which a negative electrode and a positive electrode are opposed to each other with the separator interposed therebetween and an electrolyte is impregnated, is sealed in an exterior material. Note that "doping" refers to occlusion, support, adsorption, or insertion, and refers to the phenomenon in which lithium ions enter the active material of an electrode such as a positive electrode.

[0092] The nonaqueous electrolyte secondary battery member includes the separator described above, and therefore when incorporated into a nonaqueous electrolyte secondary battery, can suppress the occurrence of micro-short circuits in the nonaqueous electrolyte secondary battery and improve its safety. Furthermore, the nonaqueous electrolyte secondary battery includes the separator described above, and therefore is suppressed from the occurrence of micro-short circuits and has excellent safety.

[0093] [4.1. Positive electrode] The positive electrode is not particularly limited as long as it is generally used as a positive electrode for an electrochemical element. 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.

[0094] The positive electrode active material may be, for example, a material capable of doping and dedoping metal ions such as lithium ions or sodium ions. Specific examples of such materials include lithium-containing composite metal oxides containing lithium (Li) and at least one transition metal selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, and Al. Examples of such lithium-containing composite metal oxides include LiCoO2, LiNiO2, LiMn2O4, Li2MnO3, and LiNi x Mn y Co 1-x-y O2[0 <x+y<1]、LiNi x Co y Al 1-x-y O2[0 <x+y<1]、LiCr 0.5 Mn 0.5Examples include O2, LiFePO4, Li2FeP2O7, LiMnPO4, LiFeBO3, Li3V2(PO4)3, Li2CuO2, Li2FeSiO4, and Li2MnSiO4.

[0095] Examples of the conductive agent include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black (e.g., acetylene black), pyrolytic carbons, fibrous carbon materials, and baked organic polymer compounds. The conductive agent may be used alone or in combination of two or more. The proportion of the conductive agent in the positive electrode mixture is preferably 5 to 20 parts by mass per 100 parts by mass of the positive electrode active material. When a fibrous carbon material such as graphitized carbon fiber or carbon nanotubes is used as the conductive agent, this proportion can be reduced.

[0096] Thermoplastic resins can be used as the binder. Examples include fluororesins such as PVdF, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymers, hexafluoropropylene-vinylidene fluoride copolymers, and tetrafluoroethylene-perfluorovinyl ether copolymers, as well as acrylic resins, styrene-butadiene rubber, polyimide resins, and polyolefin resins. The binder also functions as a thickener. Two or more of these thermoplastic resins may be mixed. By using a fluororesin and a polyolefin resin as binders and setting the ratio of the fluororesin to the total positive electrode mixture to between 1% and 10% by mass and the ratio of the polyolefin resin to between 0.1% and 2% by mass, a positive electrode mixture with high adhesion to the positive electrode current collector and high internal bonding strength can be obtained.

[0097] Examples of the positive electrode current collector include conductors such as Al, Ni, stainless steel, etc. Among these, Al is more preferred because it can be easily processed into a thin film and is inexpensive.

[0098] Examples of methods for producing a positive electrode sheet include a method of pressurizing a positive electrode active material, a conductive agent, and a binder (positive electrode mixture) onto a positive electrode current collector; a method of forming the positive electrode mixture into a paste using an appropriate organic solvent, applying the paste to a positive electrode current collector, drying it, and then pressurizing it to adhere it to the positive electrode current collector.

[0099] Examples of organic solvents that can be used in the above method include amine solvents such as N,N-dimethylaminopropylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; ketone solvents such as methyl ethyl ketone; ester solvents such as methyl acetate; and amide solvents such as dimethylacetamide and NMP.

[0100] Examples of methods for applying the positive electrode mixture paste to the positive electrode current collector include slit die coating, screen coating, curtain coating, knife coating, gravure coating, and electrostatic spraying.

[0101] [4.2. Negative electrode] The negative electrode is not particularly limited as long as it is generally used as a negative electrode for an electrochemical element. 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.

[0102] Examples of the negative electrode active material include materials that can be doped and dedoped with metal ions such as lithium ions or sodium ions. Examples of such materials include carbonaceous materials, chalcogen compounds (oxides, sulfides, etc.), nitrides, metals, and alloys that can be doped and dedoped with lithium ions at a lower potential than the positive electrode. Examples of carbonaceous materials include natural graphite, artificial graphite, cokes, carbon black, and pyrolytic carbons.

[0103] Oxides that can be used as negative electrode active materials include SiO2, SiO, and the like, which are compounds of the formula SiO x(where x is a positive real number); oxides of silicon such as TiO2 and TiO with the formula TiO x (where x is a positive real number); oxides of titanium, such as V2O5 and VO2, with the formula VO x (where x is a positive real number) oxides of vanadium; Fe3O4, Fe2O3, FeO, etc., with the formula FeO x (where x is a positive real number) Iron oxides such as SnO2 and SnO with the formula SnO x (where x is a positive real number); tin oxides such as WO3 and WO2 with the formula WO x (where x is a positive real number) is the oxide of tungsten; Li4Ti5O 12 and composite metal oxides containing lithium, such as LiVO2, and titanium or vanadium.

[0104] Sulfides that can be used as negative electrode active materials include Ti2S3, TiS2, TiS, and other sulfides with the formula TiS x (where x is a positive real number); titanium sulfides such as V3S4, VS2, and VS, with the formula VS x (where x is a positive real number) Vanadium sulfides such as Fe3S4, FeS2, and FeS, with the formula FeS x (where x is a positive real number) Iron sulfides such as Mo2S3 and MoS2 with the formula MoS x (where x is a positive real number) Molybdenum sulfides such as SnS2 and SnS with the formula SnS x (where x is a positive real number); tin sulfides such as WS2 with the formula WS x (where x is a positive real number) tungsten sulfides such as Sb2S3 with the formula SbS x (where x is a positive real number) Antimony sulfides such as Se5S3, SeS2, and SeS with the formula SeS x (where x is a positive real number) and selenium sulfide.

[0105] Nitrides that can be used as negative electrode active materials include Li3N and Li 3-x A xExamples thereof include lithium-containing nitrides such as N (where A is either or both of Ni and Co, and 0 < x < 3).

[0106] These carbonaceous materials, oxides, sulfides, and nitrides may be used alone or in combination of two or more. Further, these carbonaceous materials, oxides, sulfides, and nitrides may be either crystalline or amorphous.

[0107] Examples of metals that can be used as the negative electrode active material include lithium metal, silicon metal, and tin metal.

[0108] Examples of alloys that can be used as the negative electrode active material include lithium alloys such as Li-Al, Li-Ni, Li-Si, Li-Sn, and Li-Sn-Ni; silicon alloys such as Si-Zn; tin alloys such as Sn-Mn, Sn-Co, Sn-Ni, Sn-Cu, and Sn-La; and alloys such as Cu2Sb and La3Ni2Sn7.

[0109] These metals and alloys are mainly used alone as electrodes, for example, after being processed into foil form. Among the above negative electrode active materials, carbonaceous materials mainly composed of graphite such as natural graphite and artificial graphite are preferably used. This is because the potential of the negative electrode hardly changes (good potential flatness) from the uncharged state to the fully charged state during charging, the average discharge potential is low, and the capacity retention rate during repeated charge and discharge is high (good cycle characteristics). The shape of the carbonaceous material may be, for example, flaky like natural graphite, spherical like mesocarbon microbeads, fibrous like graphitized carbon fibers, or an aggregate of fine powder.

[0110] Examples of the negative electrode current collector include Cu, Ni, and stainless steel. Cu is more preferable because it is difficult to form an alloy with lithium and is easy to process into a thin film.

[0111] Examples of methods for producing a negative electrode sheet include a method of press-molding a negative electrode active material onto a negative electrode current collector, a method of forming a paste of a negative electrode active material using an appropriate organic solvent, applying the paste to a negative electrode current collector, drying, and then pressing to adhere it to the negative electrode current collector, etc. The paste preferably contains the conductive agent and the binder described above.

[0112] The negative electrode sheet may contain a binder as needed. Examples of the binder include thermoplastic resins, such as PVdF, thermoplastic polyimide, carboxymethyl cellulose, and polyolefin resins.

[0113] [4.3.Nonaqueous electrolyte] The non-aqueous electrolyte is not particularly limited as long as it is a non-aqueous electrolyte generally used in electrochemical elements, such as non-aqueous electrolyte secondary batteries. For example, a non-aqueous electrolyte obtained by dissolving a lithium salt in an organic solvent can be used as the non-aqueous electrolyte. Examples of lithium salts include LiClO4, LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, LiN(SO2C2F5)2, LiN(SO2CF3)(COCF3), Li(C4F9SO3), Li2B 10 Cl 10 Examples of the lithium salt include LiBOB (here, BOB stands for bis(oxalato)borate), LiFSI (here, FSI stands for bis(fluorosulfonyl)imide), lithium salts of lower aliphatic carboxylic acids, and LiAlCl4. The lithium salts may be used alone or in combination of two or more. Among these, it is preferable to use an electrolyte containing at least one fluorine-containing material selected from the group consisting of LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(SO2CF3)2, and LiC(SO2CF3)3.

[0114] Examples of organic solvents include carbonates such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, and 1,2-di(methoxycarbonyloxy)ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran. Examples of suitable organic solvents include ethers such as methyl formate, methyl acetate, and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; carbamates such as 3-methyl-2-oxazolidone; sulfur-containing compounds such as sulfolane, dimethyl sulfoxide, and 1,3-propanesultone; and solvents obtained by further introducing fluoro groups into these organic solvents (solvents in which one or more hydrogen atoms in the organic solvent are substituted with fluorine atoms). These organic solvents may be used alone or in combination. Among these, mixed solvents containing carbonates are preferred, with mixed solvents of cyclic carbonates and acyclic carbonates and mixed solvents of cyclic carbonates and ethers being more preferred. Mixed solvents of cyclic carbonates and acyclic carbonates are preferably mixed solvents containing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. An electrolyte solution using such a mixed solvent has many advantages, including a wide operating temperature range, resistance to deterioration even when charged and discharged at a high current rate, resistance to deterioration even when used for a long period of time, and resistance to decomposition even when a graphite material such as natural graphite or artificial graphite is used as the active material of the negative electrode.

[0115] [4.4. Manufacturing method of non-aqueous electrolyte secondary battery] The nonaqueous electrolyte secondary battery can be manufactured by a conventionally known manufacturing method. For example, the nonaqueous electrolyte secondary battery member is formed by arranging a positive electrode, the separator, and a negative electrode in this order. Next, the nonaqueous electrolyte secondary battery member is placed in a container that will serve as the casing of the nonaqueous electrolyte secondary battery. The container is then filled with a nonaqueous electrolyte and sealed under reduced pressure. This completes the manufacture of the nonaqueous electrolyte secondary battery. [Example]

[0116] [Physical property measurement and evaluation test] (1) Average linear expansion coefficient in the TD direction at 30 to 50°C A linear expansion coefficient curve was measured by thermomechanical analysis based on JIS K7197, with the horizontal axis representing temperature and the vertical axis representing the linear expansion coefficient of the separator. The specific measurement conditions were as follows: Test equipment: TMA / SS6100 (Hitachi High-Tech Science Corporation) Probe diameter: 3.4mm Load: 30mN (tensile load applied in the TD direction) Temperature profile: 30-150°C, rising at 10°C / min - Test piece size: 5mm (MD direction) x 10mm (TD direction)

[0117] From the obtained linear expansion coefficient curve, the TD average linear expansion coefficient was calculated based on the following formula: This formula is the change in the length of the test piece in the TD direction per 1°C, calculated from the slope of the line connecting the point at 30°C and the point at 50°C on the linear expansion coefficient curve, converted into a value per mm of the test piece's length in the TD direction before the test. TD average linear expansion coefficient [1 / K]=[{L(T 50 )-L(T 30 )}÷20]÷10 L(T 30 ): Change in length of test piece in TD direction at 30℃ L(T 50 ): Change in length of test piece in TD direction at 50℃ (2) Average linear expansion coefficient in the MD direction at 30 to 50°C The MD average linear expansion coefficient was calculated using the following formula in the same manner as for the TD average linear expansion coefficient. However, the size of the test specimen was changed to 5 mm (TD) × 10 mm (MD). This formula is the change in the length of the test specimen in the MD direction per degree Celsius, calculated from the slope of the line connecting the points at 30°C and 50°C on the linear expansion coefficient curve, converted into a value per mm of the test specimen's MD length before the test. MD average linear expansion coefficient [1 / K]=[{L(T 50 )-L(T 30 )}÷20]÷10 L(T 30 ): Change in length of test piece in MD direction at 30℃ L(T 50 ): Change in length of test piece in MD direction at 50℃

[0118] (3) Discharge capacity retention rate after cycling First, a non-aqueous electrolyte secondary battery for testing, incorporating a separator, was fabricated according to the following procedure. 1. Thickness: 49.9 μm, Density: 2.97 g / cm 3 The positive electrode active material layer was composed of, by weight, LiNi 0.78 Co 0.19 Al 0.03 The ratio of O2:conductive material:polyvinylidene fluoride was 92:4:4. 2. Thickness: 71.2 μm, Density: 1.45 g / cm 3 A negative electrode having a void volume of 41.3 μL was prepared. The composition of the negative electrode active material layer was artificial graphite:styrene butadiene rubber:carboxymethyl cellulose=96.5:2.0:1.5 in weight ratio. 3. The negative electrode, separator, and positive electrode were laminated in this order to prepare a member for a non-aqueous electrolyte secondary battery. 4. The nonaqueous electrolyte secondary battery components were placed in a bag consisting of a laminated aluminum layer and a heat-sealed layer, and a nonaqueous electrolyte was poured into the bag. The amount of nonaqueous electrolyte poured was 2.8 times the total void volume of the electrodes and the laminated separator. The nonaqueous electrolyte consisted of a mixed solvent of ethylene carbonate: ethyl methyl carbonate: diethyl carbonate = 3:5:2 (volume ratio), in which 1 wt% vinylene carbonate and 1 mol / L LiPF6 were dissolved. 5. The bag was heat-sealed while the pressure inside the bag was reduced, thereby completing a non-aqueous electrolyte secondary battery for testing.

[0119] Next, the discharge capacity of the fabricated battery was measured according to the following procedure: The discharge capacity before and after the cycle was compared to calculate the discharge capacity retention rate. 1. An initial charge / discharge cycle was performed under the following conditions: temperature: 25°C, voltage range: 2.7 to 4.2 V, current value: 0.1 C (charging) or 0.2 C (discharging). Here, 1 C is the current value at which the rated capacity is discharged in 1 hour based on the hourly rate of discharge capacity. 2. The non-aqueous electrolyte secondary battery was aged by performing 10 cycles of charge and discharge at a temperature of 25°C, a voltage range of 2.7 to 4.2V, and a current value of 1C (when charging) or 5C (when discharging). 3. One charge / discharge cycle was performed at a temperature of 25°C, a voltage range of 2.7 to 4.2V, and a current value of 0.2C (when charging) or 0.2C (when discharging). 4. 200 charge / discharge cycles were performed under the following conditions: temperature: 45°C, voltage range: 2.7 to 4.2 V, current value: 1 C (charging) or 5 C (discharging). The discharge capacity (mAh) after each cycle was divided by the discharge capacity (mAh) at the first cycle, and this was taken as the capacity retention rate after each cycle.

[0120] [Synthesis Example 1] Coating liquid (1) was prepared according to the following procedure: The aramid resin contained in coating liquid (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. 4177 g of N-methyl-2-pyrrolidone was placed in a flask. 366.29 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 (8.00 wt%). The moisture content of the calcium chloride solution was adjusted to 300 ppm. 3. While maintaining the temperature of the polymerization system at 100°C, 141.119 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 226.911 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. 61.460 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 123.059 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, an aramid polymerization liquid (1) was obtained. In the block copolymer contained in the aramid polymerization liquid (1), block 1 accounts for 50% of the entire molecule, and block 2 accounts for the remaining 50% of the entire molecule. 8. Alumina (average particle size: 13 nm) was added to the aramid polymerization liquid (1) and mixed so that the weight ratio of aramid resin to alumina was 1:1. 9. The mixture obtained in step 8 was diluted with N-methyl-2-pyrrolidone to a solids content of 6% by weight, and stirred for 240 minutes. The "solids content" here refers to the total weight of the aramid resin and alumina. 10. Calcium carbonate was added to the mixed solution obtained in step 9 and stirred for 240 minutes to neutralize the solution. This neutralized solution was degassed under reduced pressure to prepare a slurry coating solution (1).

[0121] Example 1 A laminated separator for a non-aqueous electrolyte secondary battery was produced by the following procedure: The separator was produced while a raw sheet of polyolefin porous film was being conveyed by a machine. 1. Polyolefin porous film (polyethylene porous film, thickness: 12 μm, weight: 7.0 g / m 2 The coating liquid (1) was applied to one surface of the substrate (1), thereby forming a coating film of the coating liquid (1). 2. The polyolefin porous film was placed in a precipitation tank adjusted to a temperature of 50°C and a relative humidity of 70%. The coated film was exposed to water vapor to precipitate a block copolymer. 3. The coating liquid (1) was applied to the surface of the polyolefin porous film that had not been coated with the coating liquid (1) in step 1. This formed a coating film of the coating liquid (1). 4. The polyolefin porous film was placed in an immersion tank filled with a mixture of ion-exchanged water and NMP at a weight ratio of 2:3. The block copolymer was precipitated by contacting the coating film with the mixture. 5. The polyolefin porous film having the block copolymer-containing porous layers formed on both sides was washed with water to remove calcium chloride and N-methyl-2-pyrrolidone. 6. The polyolefin porous film having the block copolymer-containing porous layers formed on both sides thereof was dried. 7. Using a tenter, the polyolefin porous film was stretched in the TD direction. The stretching conditions were as follows: preheating chamber temperature: 50°C, stretching chamber temperature: 60°C, heat setting chamber temperature: 133°C, and stretch ratio: 14%. In this way, a separator (1) was obtained.

[0122] [Examples 2 to 4, Comparative Example 1] The stretching conditions and shrinkage conditions in step 7 of Example 1 were changed as shown in Table 1. In Example 4, the polyolefin porous film was shrunk in the TD direction in the heat setting chamber. In this way, separators (2) to (4) and comparative separator (1) were obtained.

[0123] 〔result〕 The results are shown in Table 1. [Table 1]

[0124] From Table 1, it can be seen that there is a correlation between the TD average linear expansion coefficient and the capacity retention rate after cycling. The separator according to the example has a TD average linear expansion coefficient of 3.0×10 -6 [1 / K] or more, and the capacity retention rate after 200 cycles was as high as 85% or more. The separator according to the comparative example had a TD average linear expansion coefficient of 3.0 × 10 -6 [1 / K], and the capacity retention rate after 200 cycles was as low as less than 85%.

[0125] From the results of the Examples and Comparative Examples, it can be seen that there are two factors that affect the TD average linear expansion coefficient: · Stretching ratio in TD stretching: The larger the stretching ratio in TD stretching after forming the porous layer, the larger the TD average linear expansion coefficient tends to be (see Examples 1 to 3). · TD shrinkage: If TD stretching is performed after the porous layer is formed and then TD shrinkage is further performed, the TD average linear expansion coefficient tends to increase (see Examples 1 and 4). [Industrial Applicability]

[0126] 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, The laminated separator for a non-aqueous electrolyte secondary battery has an average linear expansion coefficient in the TD direction at 30 to 50° C. of 3.0×10 －６ [1 / K] or more, Laminated separator for non-aqueous electrolyte secondary batteries.

2. The laminated separator for a non-aqueous electrolyte secondary battery has an average linear expansion coefficient in the MD direction at 30 to 50° C. of −8.0×10 －６ [1 / K] or more, The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1 .

3. the porous layer contains a filler, The filler is an inorganic filler and / or an organic filler. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1 .

4. The content of the filler is 30 to 99% by weight, where the weight of the porous layer is 100% by weight. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 3 .

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

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. Nonaqueous electrolyte secondary battery.

9. The nonaqueous electrolyte secondary battery member according to claim 7 is provided. Nonaqueous electrolyte secondary battery.

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