Nonaqueous electrolyte secondary battery laminated separator, nonaqueous electrolyte secondary battery member, and nonaqueous electrolyte secondary battery

Abstract

To provide a laminated separator for a nonaqueous electrolyte secondary battery excellent in heat resistance.SOLUTION: The laminated film has a heated tensile modulus of not less than 0.25, the heated tensile modulus being a stress-versus-elongation slope in a region where an elongation percentage is 50% to 200% in a tensile test in which the laminated film is elongated at a rate of 10mm / min in an MD direction in an atmosphere at 120 °C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminate separator for a non-aqueous electrolyte secondary battery, a member for a non-aqueous electrolyte secondary battery, and 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, etc., and recently development has been progressing for use as batteries for automobiles.

[0003] As the separator, which is a component of the non-aqueous electrolyte secondary battery, a laminate separator formed by laminating two or more layers, such as a laminate separator formed by laminating a porous layer such as a heat-resistant layer on one or both sides of a polyolefin porous film, has conventionally been used. Furthermore, in recent years, with the trend toward higher battery capacities, there has been an increasing demand for laminate separators with high voltage resistance. As a laminate separator that meets this demand, a laminate separator has been developed that has the following characteristics (a) and (b), as described in Patent Document 1: (a) A porous layer is laminated on one or both sides of a polyolefin porous film; (b) The porous layer includes an aramid resin that is a block copolymer having a structure in which some aromatic rings are linked together by sulfonyl bonds, more specifically, a structure having a block with many sulfonyl groups and a block with few sulfonyl groups, and a filler. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-42995 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional laminated separators such as the laminated separator described in Patent Document 1 have room for improvement in terms of heat resistance, such as shape retention in high-temperature environments. [Means for solving the problem]

[0006] One aspect of the present invention is a laminate separator for a non-aqueous electrolyte secondary battery, which is formed by laminating two or more layers, The laminate separator for a non-aqueous electrolyte secondary battery has a heat tensile modulus of 0.25 or more in a region of elongation from 50% to 200% in a tensile test. (Here, the tensile test is a test in which the laminated separator for a non-aqueous electrolyte secondary battery is stretched in the MD direction at a rate of 10 mm / min in an atmosphere of 120°C, and the stress (unit: N) applied at that time is measured. the elongation rate is a ratio [unit: %] of the elongation amount [unit: mm] in the MD direction of the laminate separator for a nonaqueous electrolyte secondary battery to the length [unit: mm] in the MD direction of the laminate separator for a nonaqueous electrolyte secondary battery before the elongation, The heat tensile modulus is the slope of an approximate line obtained by using the least squares method in the elongation range of 50% to 200% for a stress-strain curve obtained by plotting the elongation on the X axis and the stress on the Y axis. [Effects of the Invention]

[0007] The laminate separator according to one aspect of the present invention exhibits an effect of excellent heat resistance, such as shape retention in a high-temperature environment. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of the present invention will be described below, but the present invention is not limited thereto. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less."

[0009] [Embodiment 1: Laminated separator for non-aqueous electrolyte secondary battery] The laminate separator for a non-aqueous electrolyte secondary battery according to Embodiment 1 of the present invention is a laminate separator for a non-aqueous electrolyte secondary battery formed by laminating two or more layers, and has a heat tensile modulus of 0.25 or more in a region of elongation from 50% to 200% in a tensile test. Hereinafter, the laminate separator for a non-aqueous electrolyte secondary battery according to Embodiment 1 of the present invention will be simply referred to as a "laminated separator." (Here, the tensile test is a test in which the laminated separator for a non-aqueous electrolyte secondary battery is stretched in the MD direction at a rate of 10 mm / min in an atmosphere of 120°C, and the stress (unit: N) applied at that time is measured. the elongation rate is a ratio [unit: %] of the elongation amount [unit: mm] in the MD direction of the laminate separator for a nonaqueous electrolyte secondary battery to the length [unit: mm] in the MD direction of the laminate separator for a nonaqueous electrolyte secondary battery before the elongation, The heat tensile modulus is the slope of an approximate line obtained by using the least squares method in the elongation range of 50% to 200% for a stress-strain curve obtained by plotting the elongation on the X axis and the stress on the Y axis. In this specification, "MD (Machine Direction)" refers to the conveyance direction in the manufacture of a laminate separator. In addition, when the conveyance direction of a laminate separator is unknown, the longitudinal direction of the laminate separator (cylindrical type: winding direction, zigzag type: folding direction) is used as the MD direction.

[0010] <Tensile test> In one embodiment of the present invention, the tensile test is not particularly limited as long as it involves stretching the laminated separator in the MD direction at a rate of 10 mm / min in an atmosphere of 120°C and measuring the stress (unit: N) applied during this stretching. The tensile test can be carried out, for example, by a method in accordance with JIS K7127. Specifically, the tensile test can be carried out by the method described in the examples.

[0011] The tensile test may be performed using the laminate separator as is, or a measurement sample having a predetermined shape and a structure formed by stacking two or more layers of the laminate separator may be obtained from the laminate separator, and the measurement sample may be used as the measurement sample. The method for obtaining the measurement sample is not particularly limited, and examples include a method in which a part of the laminate separator is cut out or punched out and the part is used as the measurement sample.

[0012] The shape and size of the measurement sample are not particularly limited. Here, from the viewpoint of avoiding breakage near the ends of the measurement sample and enabling accurate stress measurement during a tensile test, it is preferable that the measurement sample have a dumbbell shape. The dumbbell shape has wide portions near the ends and a narrow portion in the center, and the curvature of the portion that transitions from the wide end portion to the narrow portion in the center is gentle. Examples of the dumbbell shape include the shape specified as dumbbell No. 3 in JIS K6251.

[0013] The elongation amount and elongation percentage in the tensile test may be measured based on the length of the laminate separator or the measurement sample in the MD direction, or based on the distance between benchmark lines provided on the laminate separator or the measurement sample. Two benchmark lines are provided perpendicular to a direction parallel to the MD direction and equidistant from the center of the laminate separator or the measurement sample. When the measurement sample is dumbbell-shaped, the benchmark lines are preferably provided in the narrow central portion of the dumbbell-shaped measurement sample, from the viewpoint of accurately measuring the elongation amount and elongation percentage.

[0014] Here, the length in the MD direction of the laminate separator or the measurement sample before the elongation, or the distance between the benchmark lines, is defined as X0 [mm]. Furthermore, the length in the MD direction of the laminate separator or the measurement sample after a predetermined time has elapsed since the start of the tensile test, or the distance between the benchmark lines, is defined as X1 [mm]. In this case, the elongation amount [mm] after a predetermined time has elapsed since the start of the tensile test is calculated according to the following formula (1), and the elongation percentage [%] is calculated according to the following formula (2). Elongation [mm] = X1 [mm] - X0 [mm] (1) Elongation [%] = (X1 [mm] - X0 [mm]) / X0 [mm] (2) The method for measuring the stress is not particularly limited and can be carried out by any known method. During the tensile test, the stress may be measured every time the elongation amount increases by a predetermined amount, for example, 0.02 mm.

[0015] <Heat tensile modulus> In one embodiment of the present invention, the thermal tensile modulus is the slope of an approximate line obtained by using the least squares method in the elongation range of 50% to 200% on a stress-strain curve obtained by plotting the elongation on the X axis and the stress on the Y axis. Specifically, the slope is the ratio of stress to elongation.

[0016] Typically, when the laminate separator is heated due to heat generated by an excessive voltage, the layer with the lower heat resistance among the two or more layers is altered, causing the layer to change into a state that does not allow charge carriers to pass through, thereby ensuring the safety of the nonaqueous electrolyte secondary battery. For example, when the layer with the lower heat resistance contains a resin and has pores, the resin constituting the layer melts, causing the pores to close. The layer with the lower heat resistance is a layer that is prone to shrinkage due to heat.

[0017] On the other hand, during the deterioration, the easily shrinkable layer shrinks, and at the same time, stress is applied in the in-plane direction to other layers that are less likely to shrink due to heat than the easily shrinkable layer, causing these other layers to shrink as well, resulting in the entire laminate separator shrinking. As a result, a short circuit may occur in the nonaqueous electrolyte secondary battery. The shrinkage of the entire laminate separator corresponds to plastic deformation.

[0018] Furthermore, even if the easily-shrinkable layer shrinks, the other layers maintain their shape because the degree of shrinkage is smaller than that of the easily-shrinkable layer. Thus, the other layers have resistance to stress applied in the in-plane direction due to shrinkage in the easily-shrinkable layer, in other words, resistance to plastic deformation of the easily-shrinkable layer caused by the stress. When the resistance is large, the other layers shrink less, making it difficult for the entire laminated separator to shrink. As a result, the laminated separator has high shape retention when heated and excellent heat resistance.

[0019] Here, the ambient temperature of 120°C in the tensile test is the temperature at which the easily shrinkable layer, which is altered by heat generated by excessive voltage in a laminate separator constituting a typical nonaqueous electrolyte secondary battery, typically softens. Therefore, the easily shrinkable layer softens due to the stress applied in the tensile test, and therefore undergoes significant plastic deformation. Furthermore, the other layer laminated on the easily shrinkable layer undergoes small plastic deformation while resisting the plastic deformation of the easily shrinkable layer. Furthermore, the region of elongation from 50% to 200% in the tensile test corresponds to the region in which the laminate separator undergoes plastic deformation. Therefore, the thermal tensile coefficient is a parameter that represents the resistance of the other layer to the plastic deformation of the easily shrinkable layer caused by the stress, and a larger thermal tensile coefficient indicates a larger resistance.

[0020] As described above, the larger the heat tensile coefficient, i.e., the greater the resistance, the better the laminate separator's shape retention during heating and the better its heat resistance. From this perspective, the heat tensile coefficient is 0.25 or greater, and a higher value is preferable, specifically, 0.26 or greater. The upper limit of the heat tensile coefficient is not particularly limited and may be, for example, 0.35 or less, or 0.40 or less.

[0021] <Structure of laminated separator> The configuration of the laminate separator is not particularly limited as long as it is a configuration in which two or more layers are laminated. The laminate separator may have a configuration in which one layer is laminated on one or both sides of another layer. Hereinafter, the one layer will be referred to as "Layer A," and the other layer will be referred to as "Layer B." Layer A is, for example, a polyolefin porous film. Layer B is, for example, a porous layer. Therefore, the laminate separator is, for example, a laminate separator having a structure in which a porous layer is laminated on one or both sides of a polyolefin porous film. Hereinafter, the laminate separator will be described as a laminate separator having a configuration in which Layer B is laminated on one or both sides of Layer A. Hereinafter, Layer A and Layer B correspond to at least one of the two or more layers.

[0022] (Layer A) The term "polyolefin porous film" used below refers to the polyolefin porous film when Layer A is a polyolefin porous film. A polyolefin porous film has many interconnected pores inside, allowing gases and liquids to pass from one side to the other. The polyolefin porous film can serve as a substrate for a laminated separator. The polyolefin porous film can melt when the battery generates heat, rendering the laminated separator porous, thereby imparting a shutdown function to the laminated separator.

[0023] Here, the term "polyolefin porous film" refers to a porous film mainly composed of a polyolefin resin. Furthermore, "mainly composed of a polyolefin resin" means that the proportion of polyolefin resin in the porous film is 50% by volume or more, preferably 90% by volume or more, and more preferably 95% by volume or more of the total material constituting the porous film.

[0024] The polyolefin resin, which is the main component of the polyolefin porous film, is not particularly limited, and examples thereof include homopolymers and copolymers obtained by polymerizing monomers such as thermoplastic resins, such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and / or 1-hexene. Homopolymers include polyethylene, polypropylene, and polybutene, while copolymers include ethylene-propylene copolymers. The polyolefin porous film may be a layer containing one of these polyolefin resins alone, or a layer containing two or more of these polyolefin resins. Among these, polyethylene is more preferred because it can prevent (shut down) excessive current flow at lower temperatures, and high-molecular-weight polyethylene composed mainly of ethylene is particularly preferred. The polyolefin porous film may contain components other than polyolefins as long as their functionality is not impaired.

[0025] 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 more preferred, and the weight-average molecular weight is 5×10 5 ~15×10 6 It is more preferable that the polyolefin resin contains a high molecular weight component having a weight average molecular weight of 1,000,000 or more, since this improves the strength of the polyolefin porous film and the laminate separator for a non-aqueous electrolyte secondary battery.

[0026] The polyolefin porous film may have a multilayer structure consisting of two or more layers. For example, a multilayer structure of the polyolefin porous film may be a laminate of a layer mainly composed of polyethylene and a layer mainly composed of polypropylene. The number of layers is not particularly limited, and the film may be two layers composed of polyethylene and polypropylene, or three layers composed of a combination of polyethylene and polypropylene. The multilayer structure of polyethylene and polypropylene makes it possible to achieve both shutdown properties and heat resistance.

[0027] The polyolefin porous film may have a crosslinked structure. The crosslinked structure can be introduced, for example, by using a silane-modified polyolefin. A polyolefin porous film having a crosslinked structure has excellent heat resistance, and therefore, by combining it with Layer B, 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 Layer B.

[0028] The thickness of Layer A is preferably 3 to 20 μm, more preferably 4 to 15 μm, and even more preferably 4.5 to 15 μm. If the thickness is 3 μm or more, the strength of the laminated separator can be ensured. Furthermore, when Layer A is a polyolefin porous film, if the thickness is 3 μm or more, the required functions (shutdown function, etc.) can be sufficiently obtained. If the thickness is 20 μm or less, a thin laminated separator can be obtained.

[0029] The pore size of the pores in the polyolefin porous film is preferably 0.1 μm or less, and more preferably 0.06 μm or less, which allows for sufficient ion permeability and further prevents particles constituting the electrode from entering.

[0030] The weight per unit area of ​​the layer A, i.e., the weight per unit area, is usually 2 to 20 g / m 2 so as to increase the gravitational energy density and volumetric energy density of the battery. 2 It is preferable that the density is 2.5 to 12 g / m 2It is more preferable that:

[0031] The air permeability of Layer A is preferably 30 to 500 s / 100 mL, more preferably 50 to 300 s / 100 mL, in Gurley value, which allows the laminated separator to have sufficient ion permeability.

[0032] The porosity of the polyolefin porous film is preferably 20 to 80% by volume, more preferably 30 to 75% by volume, which increases the amount of electrolyte retained and enables the flow of excessive current to be reliably prevented (shut down) at a lower temperature.

[0033] The method for producing a polyolefin porous film is not particularly limited and may be a known method, such as a method described in Japanese Patent No. 5476844 in which a filler is added to a thermoplastic resin, the film is formed, and then the filler is removed.

[0034] Specifically, for example, when a polyolefin porous film is formed from a polyolefin resin containing ultra-high molecular weight polyethylene and a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, it is preferably produced by a method including the following steps (1) to (4) from the viewpoint of production costs: (1) A step of kneading 100 parts by weight of ultra-high molecular weight polyethylene, 5 to 200 parts by weight of a low-molecular weight polyolefin having a weight-average molecular weight of 10,000 or less, and 100 to 400 parts by weight of an inorganic filler such as calcium carbonate to obtain a polyolefin-based resin composition; (2) forming a sheet from the polyolefin resin composition; (3) a step of removing the inorganic filler from the sheet obtained in step (2); (4) A step of stretching the sheet obtained in step (3). In addition, the methods described in the above-mentioned patent documents may also be used.

[0035] Furthermore, commercially available products having the above-mentioned characteristics may be used as the polyolefin porous film.

[0036] (Layer B) At least one of the two or more layers may be a heat-resistant layer, for example, Layer B. In this specification, a heat-resistant layer refers to a layer having a higher melting temperature than the layers constituting the laminate separator other than Layer B, such as Layer A.

[0037] At least one of the two or more layers, for example, Layer B, may be a layer containing a resin. The resin is not particularly limited and may be, for example, 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 resin may be a single resin or a mixture of two or more resins. For example, when a mixture of a heat-resistant polyamide resin and an adhesive (meth)acrylate resin and / or fluorine-containing resin is used as the resin, Layer B can be obtained that exhibits both heat resistance and adhesiveness. In this case, the form of the (meth)acrylate resin and / or fluorine-containing resin is not particularly limited and may be in the form of particles, may be present in a mixture with the polyamide resin, or may be segregated on the surface of Layer B.

[0038] The polyolefin is not particularly limited, and examples thereof include polyethylene, polypropylene, polybutene, and ethylene-propylene copolymer.

[0039] The (meth)acrylate resin is not particularly limited, and examples thereof include methyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate.

[0040] The fluorine-containing resin is not particularly limited, and examples thereof 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.

[0041] The polyamide resin is not particularly limited, and examples thereof include aramid resins such as aromatic polyamides and wholly aromatic polyamides.

[0042] The polyester resin is not particularly limited, and examples thereof include aromatic polyesters and liquid crystal polyesters. The aromatic polyester is not particularly limited, and examples thereof include polyarylates.

[0043] Examples of the water-soluble polymer include polyvinyl alcohol, polyethylene glycol, cellulose ether, sodium alginate, polyacrylic acid, polyacrylamide, and polymethacrylic acid.

[0044] The aramid resin is not particularly limited, and examples thereof include a block copolymer having a block A mainly composed of a unit represented by the following formula (3) and a block B mainly composed of a unit represented by the following formula (4). -(NH-Ar 1 -NHCO-Ar 2 -CO)- (3) -(NH-Ar 3 -NHCO-Ar 4-CO)- (4) (In formulas (3) and (4), Ar 1 , Ar 2 , Ar 3 and Ar 4 may be different for each unit, and Ar 1 , Ar 2 , Ar 3 and Ar 4 are each independently a divalent group having one or more aromatic rings, and all Ar 1 More than 50% of the compounds have a structure in which two aromatic rings are connected by a sulfonyl bond, and all Ar 3 Less than 50% of the compounds have a structure in which two aromatic rings are connected by a sulfonyl bond, and all Ar 1 and Ar 3 Of these, 10-70% have a structure in which two aromatic rings are linked by a sulfonyl bond. Of all the units contained in the block A in the block copolymer, the proportion of units of formula (3) is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more. The entire block A, excluding the terminals, is represented by units of formula (3). Of all the units contained in the block B, the proportion of units of formula (4) is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more. The entire block B, excluding the terminals, is represented by units of formula (4).

[0045] In the formula (3) and the formula (4), Ar 1 , Ar 2 , Ar 3 and Ar 4 may be different for each unit. 1 , Ar 2 , Ar 3 and Ar 4 are each independently a divalent group having one or more aromatic rings.

[0046] In this specification, the term "aromatic ring" refers to a cyclic compound that satisfies Hückel's rule. Examples of aromatic rings include benzene, naphthalene, anthracene, azulene, pyrrole, pyridine, furan, and thiophene. The aromatic ring may be composed only of carbon atoms and hydrogen atoms. The aromatic ring may be a benzene ring or a condensed ring of two or more benzene rings (e.g., naphthalene, anthracene, etc.).

[0047] In the block A, at least a part of Ar 1 has a structure in which two aromatic rings are connected by a sulfonyl bond. 3 may have a structure in which two aromatic rings are connected by a sulfonyl bond. 1 and Ar 3 Among these, Ar has a structure in which two aromatic rings are connected by a sulfonyl bond. 1 and Ar 3 The lower limit of the proportion is 10% or more, preferably 30% or more, more preferably 35% or more, and even more preferably 40% or more. The upper limit of this proportion is 70% or less, preferably 65% ​​or less, and more preferably 60% or less.

[0048] In the block A, all Ar 1 Among these, Ar has a structure in which two aromatic rings are connected by a sulfonyl bond. 1 The proportion of Ar in the block A is 50% or more, preferably 80% or more, and more preferably 90% or more. 1 However, it may have a structure in which two aromatic rings are linked by a sulfonyl bond.

[0049] In the block B, all Ar 3 Among these, Ar has a structure in which two aromatic rings are connected by a sulfonyl bond. 3 The proportion of Ar in the block B is 50% or less, preferably 20% or less, and more preferably 10% or less. 3 may have a structure other than the structure in which two aromatic rings are connected by a sulfonyl bond.

[0050] Therefore, it can be said that the block A has a relatively large amount of sulfonyl groups, and the block B has a relatively small amount of sulfonyl groups. By using a block copolymer having these two types of blocks as the resin, it is possible to obtain a layer B that can achieve both high voltage resistance and adhesiveness, and a laminate separator including the layer B.

[0051] The structure in which the two aromatic rings are linked by a sulfonyl bond is not particularly limited, and examples thereof include 4,4'-diphenylsulfonyl, 3,4'-diphenylsulfonyl, and 3,3'-diphenylsulfonyl.

[0052] Examples of structures other than the structure in which the two aromatic rings are linked by a sulfonyl bond are not particularly limited, and include, for example, the structures shown below.

[0053] [ka]

[0054] At least a portion of the units of formula (3) contained in block A may be 4,4'-diphenylsulfonyl terephthalamide. In this case, the lower limit of the proportion of 4,4'-diphenylsulfonyl terephthalamide among the units of formula (3) contained in block A is preferably 50% or more, more preferably 80% or more, and even more preferably 90% or more. 4,4'-diphenylsulfonyl terephthalamide is easy to handle, and the monomer is readily available.

[0055] At least a portion of the units of formula (4) contained in block B may be paraphenylene terephthalamide. In this case, the lower limit of the proportion of paraphenylene terephthalamide among the units of formula (4) contained in block B is preferably 50% or more, more preferably 80% or more, and even more preferably 90% or more. Paraphenylene terephthalamide is easy to handle, and the monomer is readily available.

[0056] The block copolymer may have a structure composed of units other than those represented by formulas (3) and (4), such as a polyimide skeleton.

[0057] The number of blocks contained in the block copolymer is not particularly limited. The block copolymer may have, for example, a diblock structure such as block A-block B, or a triblock structure such as block A-block B-block A or block B-block A-block B. The block copolymer may also have a tetrablock structure such as block A-block B-block A-block B. Of the above structures, a triblock structure of block B-block A-block B is preferred as the structure of the block copolymer.

[0058] The number of units of formula (3) contained in block A in one molecule of the block copolymer is preferably 10 to 1,000, more preferably 20 to 300. When the number of units of formula (3) is within the above-mentioned range, a sufficiently large number of sulfonyl groups is contained in the molecule, thereby enhancing the high-voltage resistance of Layer B and a laminate separator including Layer B. The number of units of formula (4) contained in block B in one molecule of the block copolymer is preferably 10 to 500, more preferably 15 to 200. When the number of units of formula (4) is within the above-mentioned range, the adhesion of Layer B to other layers such as Layer A or to electrodes is enhanced.

[0059] Here, the number of units of the formula (3) and the formula (4) described as a preferred value is the number in the molecule corresponding to the mode of the molecular weight distribution of the block copolymer. The molecular weight distribution of the block copolymer can be experimentally determined, for example, by gel permeation chromatography.

[0060] The molecular weight of the block copolymer, expressed as an intrinsic viscosity, is preferably 0.5 to 5 dL / g, more preferably 0.8 to 2.5 dL / g. When the molecular weight is within the above range, good coatability when forming Layer B (described below) and strength of the obtained Layer B and the laminate separator including Layer B can be achieved at the same time.

[0061] When Layer B contains the block copolymer, the content thereof is preferably 10 to 80% by weight, and more preferably 30 to 60% by weight, based on 100% by weight of Layer B. When the content is within the above range, Layer B and a laminate separator including Layer B can be provided with sufficient high-voltage resistance due to the electron-withdrawing properties of the sulfonyl group of the block copolymer.

[0062] From the viewpoint of suitably increasing the heat tensile modulus, it is preferable to select a combination of components with high affinity between the components of Layer A and Layer B. By selecting a combination of components with high affinity, the interaction, i.e., the bond, between Layer A and Layer B is strengthened, and the adhesion between Layer A and Layer B can be improved. Here, if the adhesion between Layer A and Layer B is high, when one of Layer A and Layer B shrinks, the other of Layer A and Layer B will have high resistance to the shrinkage. Therefore, by selecting a combination of components with high affinity, the resistance can be improved, and as a result, the heat tensile modulus can be suitably increased and controlled within a suitable range of 0.25 or more.

[0063] The combination of components with high affinity is not particularly limited, and examples thereof include selecting a polyolefin as a component of Layer A and then selecting an aramid resin containing the block copolymer having the following characteristics as a component of Layer B. It has the same structure as block A and contains a large amount of homopolymers and cyclic components (described below) that have low reactivity with terminal monomers and other polymers. Hereinafter, a homopolymer having the same structure as the block A and low reactivity with monomers and other polymers at its terminals will be referred to as a "homopolymer A." Furthermore, an aramid resin containing the block copolymer and having the above characteristics will be referred to as a "modified aramid resin."

[0064] Here, selecting a polyolefin as a constituent component of Layer A means, for example, selecting the polyolefin porous film as Layer A. Selecting the modified aramid resin as a constituent component of Layer B means, for example, selecting a porous layer containing the modified aramid resin as Layer B.

[0065] The homopolymer A is a by-product that can be generated during the preparation of the block copolymer. Specifically, the homopolymer A has a structure in which the terminal group is a carboxy group: C(═O)—OH.

[0066] Furthermore, during the preparation of the block copolymer, a homopolymer having the same structure as block B but low reactivity at its terminals with monomers and other polymers may also be produced as another by-product. Hereinafter, a homopolymer having the same structure as block B but low reactivity at its terminals with monomers and other polymers will be referred to as "homopolymer B." Homopolymer A has a higher affinity with polyolefins than homopolymer B and a block copolymer consisting of block A and block B.

[0067] Furthermore, a part of the homopolymer A can be converted into a cyclic component by condensation of both ends. Thus, the aramid resin containing the block copolymer can contain the cyclic component in addition to the homopolymer A. Here, the cyclic component also has high affinity with polyolefins, similar to the homopolymer A.

[0068] Therefore, since the modified aramid resin contains a large amount of homopolymer A and the cyclic component, it has a high affinity with polyolefin. Therefore, when Layer A of the laminate separator is the polyolefin porous film and Layer B is a porous layer containing the modified aramid resin, the heat tensile modulus of the laminate separator can be controlled within a suitable range of 0.25 or more.

[0069] Since the homopolymer A has a terminal carboxy group, the modified aramid resin contains many carboxy groups, which are polar functional groups, and has improved affinity with non-aqueous electrolytes. Therefore, a laminate separator including Layer B containing the modified aramid resin can improve the rate characteristics of a non-aqueous electrolyte secondary battery including the laminate separator.

[0070] Furthermore, homopolymer A and the cyclic component have a higher affinity for solvents commonly used in the coating liquid, such as N-methyl-2-pyrrolidone (hereinafter referred to as "NMP"), than homopolymer B and a block copolymer consisting of block A and block B. Therefore, homopolymer A and the cyclic component have a high solubility in the solvent. Therefore, when forming layer B, the block copolymer consisting of block A and block B and homopolymer B first precipitate to form a network structure, and then homopolymer A precipitates near the network structure. This type of precipitation results in a layer B with large pores, resulting in reduced air permeability for layer B and for a laminate separator comprising layer B. Therefore, a laminate separator comprising layer B containing a modified aramid resin has a low air permeability value and is also excellent in terms of air permeability.

[0071] At least one of the two or more layers, for example, Layer B, may contain a filler. When Layer B contains a filler, the content of the filler in Layer B is preferably 20 to 90 wt %, and more preferably 30 to 80 wt %, when the weight of Layer B, i.e., the entire weight of the layers including the filler, is taken as 100 wt %. When the content of the filler is within the above range, Layer B and a laminated separator including Layer B can have sufficient ion permeability.

[0072] The filler types include organic fillers, inorganic fillers, and mixtures thereof.

[0073] Examples of the organic filler include styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, methyl acrylate, and the like, alone or in copolymers of two or more thereof; fluororesins such as polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, and polyvinylidene fluoride; melamine resin; urea resin; polyolefin; and polymethacrylate. The organic fillers may be used alone or in combination of two or more. Among these organic fillers, polytetrafluoroethylene powder is preferred in terms of chemical stability. Furthermore, polyolefin may be used as the organic filler to improve the shutdown property of the laminated separator for nonaqueous electrolyte secondary batteries. When polyolefin is used as the organic filler, shutdown property can be imparted to Layer B.

[0074] Examples of the inorganic filler include inorganic materials such as metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates, and sulfates. Specific examples include powders of aluminum oxide (e.g., alumina), boehmite, silica, titania, magnesia, barium titanate, barium sulfate, magnesium hydroxide, aluminum hydroxide, and calcium carbonate; as well as minerals such as mica, zeolite, kaolin, and talc. The inorganic fillers may be used alone or in combination. Among these inorganic fillers, aluminum oxide is preferred in terms of chemical stability.

[0075] The shape of the filler may be substantially spherical, plate-like, columnar, needle-like, whisker-like, fibrous, etc., and any of these particles may be used. Approximately spherical particles are preferred because they are more likely to form uniform pores.

[0076] The average particle size of the filler is preferably 0.01 to 1 μm, and more preferably 0.01 to 0.8 μm. Fillers with an average particle size of 0.01 μm or more tend to enlarge the pores in Layer B, thereby preventing a decrease in ion permeability even when the separator is compressed in a battery. Furthermore, irregularities are more likely to form on the surface of Layer B, improving the slipperiness of the separator. On the other hand, when the average particle size of the filler is 1 μm or less, the heat resistance of the separator can be improved and the separator can be made thinner. To achieve both of these properties, fillers with different average particle sizes may be used in combination, or a filler with a wide particle size distribution may be used. In this specification, the "average particle size of the filler" refers to the volume-based average particle size (D50) of the filler. D50 refers to the particle size 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.).

[0077] Layer B may contain components other than the resin and 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.

[0078] Examples of the additives include flame retardants, antioxidants, surfactants, and waxes. If Layer B is prone to static electricity, adding an antistatic agent can suppress the static electricity of Layer B. Furthermore, adding a flame retardant and / or a crosslinking agent can further improve the safety and heat resistance of the separator.

[0079] (Physical properties of Layer B and laminated separator, etc.) The air permeability of the laminate separator is preferably 500 s / 100 mL or less, more preferably 300 s / 100 mL or less, in Gurley value. The air permeability of Layer B is preferably 400 s / 100 mL or less, more preferably 200 s / 100 mL or less, in Gurley value. If the air permeability of the laminate separator and / or Layer B is within the above range, it can be said that the laminate separator has sufficient ion permeability.

[0080] For example, when the laminated separator is composed only of Layer A and Layer B, the air permeability of Layer B is calculated as YX, where X is the air permeability of Layer A and Y is the air permeability of the laminated separator. When Layer B is a porous layer containing a resin, the air permeability of Layer B can be adjusted, for example, by the intrinsic viscosity of the resin and the basis weight of Layer B. Generally, as the intrinsic viscosity of the resin decreases, the Gurley value of the porous layer containing the resin tends to decrease. Furthermore, as the basis weight of the porous layer decreases, the Gurley value of the porous layer tends to decrease.

[0081] The weight per unit area of ​​Layer B, i.e., the basis weight, is 0.6 to 2.5 g / m from the viewpoint of controlling the air permeability within a suitable range. 2 It is preferable that the density is 0.8 to 2.0 g / m 2It is more preferable that:

[0082] The upper limit of the thickness of Layer B is preferably 10 μm or less, more preferably 7 μm or less, and even more preferably 5 μm or less, and the lower limit of the thickness of Layer B is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 0.6 μm or more.

[0083] Layer B may be provided on one side of layer A or on both sides of layer A. Furthermore, one layer B and the other layer B provided on both sides of layer A may have the same film thickness, basis weight, and porosity, or may be different from each other.

[0084] The laminate separator may have at least one layer of the two or more layers, Layer C, which is different from Layer A and Layer B. Examples of Layer C are not particularly limited and include known layers such as an adhesive layer, a heat-resistant porous layer different from Layer B, a slippery layer intended to improve the slipperiness of the separator, a layer containing organic particles such as polyolefins intended to provide shutdown properties, an antistatic layer, and a protective layer. For example, the laminate separator may include Layer C, in addition to Layer A and Layer B, as necessary, as long as the objectives of the present invention are not impaired. A heat-resistant porous layer different from Layer B means that the type of resin and filler, the filler loading amount, etc., are different from those of Layer B. When Layer C is a heat-resistant porous layer different from Layer B, the resin, filler, and filler loading amount exemplified for Layer B can be applied to Layer C. The slippery layer is a layer containing an antiblocking agent or a layer containing a filler, and the slipperiness of the separator can be improved by providing surface irregularities.

[0085] Layer C can be provided on one or both sides of the laminated separator. When the laminated separator has Layer B on both sides of Layer A, Layer C can be provided on Layer B on both sides, or on Layer B on one side. When the laminated separator has Layer B on only one side of Layer A, Layer C can be provided on Layer B, or on the side of Layer A that is not provided with Layer B. Layer C can be provided in the outermost layer of the laminated separator.

[0086] 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-based 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-based resins that can be used include those described in paragraphs

[0017] to

[0022] of JP 2017-168419 A. The acrylic resins and PVDF-based resins may be used alone or in combination. The adhesive layer may further contain a filler in addition to the components that contribute to adhesiveness. The filler may be the same as the filler added to Layer B. 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 be formed in a dot or stripe pattern by pattern coating. The adhesive layer fixes the separator to the electrode via the adhesive layer, improving the handling and heat resistance of the electrode laminate. Furthermore, the adhesive layer may be formed in a particle, dot, or stripe pattern to prevent a decrease in the ion permeability of the laminate separator.

[0087] <Laminate separator manufacturing method> For example, the components constituting Layer B, such as the resin and the filler, are dissolved or dispersed in a solvent to form a coating liquid, which can be used to form Layer B on one or both sides of Layer A to produce the laminated separator. Examples of methods for forming the coating liquid include mechanical stirring, ultrasonic dispersion, high-pressure dispersion, and media dispersion. Examples of solvents that can be used include N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide.

[0088] The laminated separator can be produced, for example, by preparing the coating liquid described above, applying the coating liquid to Layer A, and drying the coating liquid to form Layer B on Layer A.

[0089] The coating liquid can be applied to Layer A by any known coating method such as with a knife, blade, bar, gravure, or die.

[0090] The solvent (dispersion medium) is generally removed by drying. Drying methods include natural drying, air drying, heat drying, and reduced pressure drying, but any method can be used as long as it can sufficiently remove the solvent (dispersion medium). Alternatively, the solvent (dispersion medium) contained in the paint may be replaced with another solvent before drying. Specific examples of methods for replacing the solvent (dispersion medium) with another solvent and then removing it include replacing it with a low-boiling point poor solvent such as water, alcohol, or acetone, precipitating it, and then drying it.

[0091] (Method for controlling the heat tensile modulus) In the aforementioned method for producing a laminate separator, the laminate separator according to one embodiment of the present invention can be produced by controlling the heat tensile coefficient to a large value of 0.25 or greater. The method for controlling the heat tensile coefficient to a large value of 0.25 or greater is not particularly limited, and examples include a method of increasing the number of strong bonds between the two or more layers to improve adhesion. A specific example of a method for increasing the number of strong bonds is selecting a combination of components that have high affinity between the components of Layer A and Layer B. A more specific example of this method includes a method in which the polyolefin porous film is used as Layer A and a coating liquid containing the modified aramid resin and, optionally, the filler is used as the coating liquid.

[0092] A method for preparing the modified aramid resin will be described below. First, examples of the method for preparing the aramid resin containing the block copolymer include the methods shown in 1. and 2 below. By using these methods, an aramid resin containing a block copolymer having a diblock structure of block A-block B can be prepared. Furthermore, an aramid resin containing a block copolymer having other block structures can also be prepared by applying the following procedures and production conditions. 1.NH2-Ar 1 -NH2 and X-(O=)C-Ar 2 A dicarboxylic acid halide represented by -C(=O)-X (X is a halogen atom such as F, Cl, Br, or I) is used as a monomer and polymerized according to a known aromatic polyamide polymerization method, thereby synthesizing block A having a unit of formula (4). 2. After the synthesis of Block A is completed, NH2-Ar 3 -NH2 and X-(O=)C-Ar 4A dicarboxylic acid halide represented by -C(=O)-X (X is a halogen atom such as F, Cl, Br, or I) is used as a monomer and polymerized according to a known aromatic polyamide polymerization method. This synthesizes block B having the unit of formula (5) linked to block A.

[0093] A modified aramid resin that can be suitably used for producing the laminate separator can be prepared by a method that satisfies the production conditions (i) and (ii) below in the method according to the procedures shown in 1. and 2. Hereinafter, the method that satisfies the production conditions (i) and (ii) below in the method according to the procedures shown in 1. and 2. will be referred to as a "method for preparing a modified aramid resin." (i) In the synthesis of block A described in 1 above, the water content of the solvent used is set to be higher than that in conventional methods for producing the block copolymer, for example, preferably 400 ppm or more, more preferably 450 ppm or more. (ii) In the synthesis of block A shown in 1 above, the charge ratio, which is the molar ratio of the diamine to the dicarboxylic acid halide, is set to a range close to 1.00, for example, preferably 0.99 to 1.01, more preferably 0.995 to 1.005.

[0094] Here, the aramid resin containing the block copolymer produced by the methods shown in 1. and 2. above may contain homopolymer A, homopolymer B and the cyclic component as by-products.

[0095] When the condition (i) is satisfied, in step 1, the terminal group of block A, C(═O)-X (X is a halogen atom such as F, Cl, Br, or I), reacts with water molecules (HO), converting the terminal group into a carboxy group, C(═O)-OH, which is easily converted into a carboxy group. Here, the carboxy group corresponds to a group with low reactivity with monomers and other polymers. This increases the amount of homopolymer A contained in the block copolymer. Furthermore, since part of homopolymer A becomes the cyclic component, the content of the cyclic component also increases when the content of homopolymer A is high.

[0096] Therefore, when the above condition (i) is satisfied, a modified aramid resin having a high content of homopolymer A and the cyclic component can be suitably prepared.

[0097] On the other hand, when the condition (i) is satisfied, the C(═O)—X group, which is the reaction site, is likely to become a carboxy group that has low reactivity with monomers and other polymers during the polymerization reaction that produces block A. Therefore, when the condition (i) is satisfied, the degree of polymerization of block A decreases, and the weight-average molecular weight of the resulting modified aramid resin is likely to decrease. Here, if the weight-average molecular weight of the modified aramid resin is low, the modified aramid resin has high solubility in solvents and is difficult to precipitate in the method for producing the laminate separator, so that layer B may not be formed, and the laminate separator may not be produced.

[0098] However, when the charge ratio is close to 1.00, the number of monomers that become terminal groups of block A decreases, and the degree of polymerization of block A increases, resulting in a higher weight-average molecular weight of the resulting modified aramid resin. Thus, by satisfying condition (ii), even when condition (i) is satisfied, the weight-average molecular weight of the resulting modified aramid resin can be increased to a level that allows layer B to be suitably formed and the laminate separator to be suitably produced. Therefore, the method for preparing a modified aramid resin can prepare a modified aramid resin that can be suitably used in producing the laminate separator.

[0099] Although aramid resin has been used as an example to explain a method for increasing the number of strong bonds between layers in two or more layers, any method for increasing the affinity between Layer A and Layer B can be applied to materials other than aramid resin. For example, it is believed that the affinity between Layer A and Layer B can be increased by subjecting the surface of Layer A to an activation treatment and by providing a filler contained in Layer B with a functional group that has a high affinity for Layer A through a coupling treatment or the like.

[0100] [Embodiment 2: Nonaqueous electrolyte secondary battery member, Embodiment 3: Nonaqueous electrolyte secondary battery] The nonaqueous electrolyte secondary battery member according to the second embodiment of the present invention comprises a positive electrode, the nonaqueous electrolyte secondary battery laminate separator according to the first embodiment of the present invention, and a negative electrode arranged in this order. The nonaqueous electrolyte secondary battery according to the third embodiment of the present invention includes the nonaqueous electrolyte secondary battery laminate separator according to the first embodiment of the present invention.

[0101] Therefore, the nonaqueous electrolyte secondary battery member according to one embodiment of the present invention provides an excellent safety by suitably preventing short circuits caused by separator contraction due to heat generated during operation. Furthermore, the nonaqueous electrolyte secondary battery according to one embodiment of the present invention provides an excellent safety by suitably preventing short circuits.

[0102] A nonaqueous electrolyte secondary battery according to one embodiment of the present invention typically has a structure in which a negative electrode and a positive electrode face each other with the laminated separator interposed therebetween. In the nonaqueous electrolyte secondary battery, a battery element in which the structure is impregnated with an electrolyte is sealed in an exterior material. For example, the nonaqueous electrolyte secondary battery is a lithium ion secondary battery that generates electromotive force by doping and dedoping lithium ions.

[0103] <Positive electrode> The positive electrode may be, 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 current collector. The active material layer may further contain a conductive agent.

[0104] The positive electrode active material may be, for example, a material that can be doped and dedoped with lithium ions.

[0105] Examples of such materials include lithium composite oxides containing at least one transition metal, such as V, Ti, Cr, Mn, Fe, Co, Ni, and Cu. Examples of lithium composite oxides include lithium composite oxides having a layered structure, lithium composite oxides having a spinel structure, and solid-solution lithium-containing transition metal oxides composed of lithium composite oxides having both a layered structure and a spinel structure. Other examples include lithium cobalt composite oxides and lithium nickel composite oxides. Furthermore, examples of these lithium composite oxides in which a portion of the transition metal atoms that constitute the main component of the lithium composite oxides has been substituted 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, are also included.

[0106] Examples of the lithium composite oxide in which a portion of the transition metal atoms that constitute the main component of the lithium composite oxide are substituted with other elements include a lithium cobalt composite oxide having a layered structure represented by the following formula (5), a lithium nickel composite oxide represented by the following formula (6), a lithium manganese composite oxide having a spinel structure represented by the following formula (7), and a solid solution lithium-containing transition metal oxide represented by the following formula (8).

[0107] Li x (Co 1-a M 1 a ) 1-x ]O2...Equation (5) (In formula (5), M 1 is at least one metal 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, and satisfies -0.1≦x≦0.30, 0≦a≦0.5. Li y (Ni 1-b M 2b ) 1-y O2···Formula (6) (In Formula (6), M 2 is at least one metal 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, and satisfies -0.1 ≦ y ≦ 0.30, 0 ≦ b ≦ 0.5.) Li z Mn 2-c M 3 c O4···Formula (7) (In Formula (7), M 3 is at least one metal 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, and satisfies 0.9 ≦ z, 0 ≦ c ≦ 1.5.) Li 1+w M 4 d M 5 e O2···Formula (8) (In Formula (8), M 4 and M 5 are at least one metal selected from the group consisting of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mg, and Ca, and satisfy 0 < w ≦ 1 / 3, 0 ≦ d ≦ 2 / 3, 0 ≦ e ≦ 2 / 3, w + d + e = 1.) Specific examples of the lithium composite oxide represented by the above Formulas (5) to (8) 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 0.33Mn 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 Ni 0.36 Co 0.08 Mn 0.49 Examples include O2.

[0108] Lithium composite oxides other than those represented by formulas (5) to (8) can also be preferably 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 Examples include O2.

[0109] Materials other than lithium composite oxides that can be preferably used as the positive electrode active material include, for example, phosphates having an olivine structure, such as phosphates having an olivine structure represented by the following formula (9).

[0110] Li v (M 6 f M 7 g M 8 h M 9 i ) j PO4...Equation (9) (In formula (9), M 6 is Mn, Co, or Ni, and M 7is Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, or Mo, and M 8 is a transition metal or main group element, optionally excluding elements of groups VIA and VIIA, and M 9 is a transition metal or a main group element, optionally excluding elements of Groups VIA and VIIA, and satisfies 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. The positive electrode active material preferably has a coating layer on the surface of the lithium metal composite oxide particles constituting the positive electrode active material. 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, and among these, metal composite oxides are preferably used.

[0111] The metal composite oxide is preferably an oxide having lithium ion conductivity. Examples of such metal composite oxides include metal composite oxides of Li and at least one element selected from the group consisting of Nb, Ge, Si, P, Al, W, Ta, Ti, S, Zr, Zn, V, and B. When the positive electrode active material has a coating layer, the coating layer suppresses side reactions at the interface between the positive electrode active material and the electrolyte under high voltage, thereby achieving a longer life for the resulting secondary battery. Furthermore, the formation of a high-resistance layer at the interface between the positive electrode active material and the electrolyte is suppressed, thereby achieving a higher output for the resulting secondary battery.

[0112] Examples of the conductive agent include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fiber, and baked organic polymer compounds.

[0113] Examples of the binder include polyvinylidene fluoride, vinylidene fluoride copolymers, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, ethylene-tetrafluoroethylene copolymers, vinylidene fluoride-tetrafluoroethylene copolymers, vinylidene fluoride-trifluoroethylene copolymers, vinylidene fluoride-trichloroethylene copolymers, vinylidene fluoride-vinyl fluoride copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, thermoplastic resins such as thermoplastic polyimide, polyethylene, and polypropylene, acrylic resins, and styrene-butadiene rubber. The binder also functions as a thickener.

[0114] Examples of the positive electrode current collector include conductive materials such as Al, Ni, stainless steel, etc. Among them, Al is more preferable because it can be easily processed into a thin film and is inexpensive.

[0115] Examples of methods for producing a sheet-like positive electrode include a method in which a positive electrode active material, a conductive agent, and a binder that constitute a positive electrode mixture are pressure-molded on a positive electrode current collector; and a method in which a positive electrode active material, a conductive agent, and a binder are made into a paste using an appropriate organic solvent to obtain a positive electrode mixture, and then the positive electrode mixture is applied to a positive electrode current collector and dried to obtain a sheet-like positive electrode mixture, which is then pressed to adhere to the positive electrode current collector.

[0116] <Negative electrode> The negative electrode may be, 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 current collector. The active material layer may further contain a conductive agent.

[0117] Examples of the negative electrode active material include carbon 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.

[0118] Examples of carbon materials that can be used as the negative electrode active material include graphite such as natural graphite and artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fiber, and fired organic polymer compounds.

[0119] Examples of oxides that can be used as the negative electrode active material include oxides represented by 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 represented by the formula V such as V2O5 and VO2 x O y (where x and y are positive real numbers); oxides of vanadium such as Fe3O4, Fe2O3, and FeO, with the formula Fe x O y (where x and y are positive real numbers); oxides of iron, 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 general 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;

[0120] Examples of sulfides that can be used as the negative electrode active material include those represented by the formula Ti, such as Ti2S3, TiS2, and TiS. x S y (where x and y are positive real numbers); 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 Fe x S y (where x and y are positive real numbers); iron sulfides such as Mo2S3 and MoS2 with the formula Mo x S y (where x and y are positive real numbers) Molybdenum sulfides such as SnS2 and SnS with the formula SnS xSulfide of tin represented by (where x is a positive real number); Sulfide of tungsten such as WS2 x Sulfide of tungsten represented by (where x is a positive real number); Sulfide of antimony such as Sb2S3 x S y Sulfide of antimony represented by (where x and y are positive real numbers); Formulas such as Se5S3, SeS2, SeS x S y Sulfide of selenium represented by (where x and y are positive real numbers); can be mentioned.

[0121] As nitrides that can be used as negative electrode active materials, for example, Li3N, Li 3-x A x Lithium-containing nitrides such as N (where A is either or both of Ni and Co, and 0 < x < 3).

[0122] These carbon materials, oxides, sulfides, and nitrides may be used alone or in combination of two or more. Also, these carbon materials, oxides, sulfides, and nitrides may be either crystalline or amorphous. These carbon materials, oxides, sulfides, and nitrides are mainly supported on the negative electrode current collector and used as an electrode.

[0123] Also, as metals that can be used as negative electrode active materials, lithium metal, silicon metal, tin metal, etc. can be mentioned.

[0124] In addition, composite materials containing Si or Sn as the first constituent element and, in addition, the second and third constituent elements can be mentioned. The second constituent element is, for example, at least one of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium, and zirconium. The third constituent element is, for example, at least one of boron, carbon, aluminum, and phosphorus.

[0125] Particularly, 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.

[0126] Examples of the negative electrode current collector include Cu, Ni, stainless steel, etc. Among them, Cu is more preferable, particularly in lithium ion secondary batteries, because it is difficult to form an alloy with lithium and it can be easily processed into a thin film.

[0127] Examples of methods for producing a sheet-like negative electrode include a method of press-molding a negative electrode active material that will become a negative electrode mixture onto a negative electrode current collector, a method of forming a negative electrode active material into a paste using an appropriate organic solvent to obtain a negative electrode mixture, applying the negative electrode mixture to a negative electrode current collector, drying the mixture, and then pressing the resulting sheet-like negative electrode mixture to adhere it to the negative electrode current collector. The paste preferably contains the conductive agent and the binder.

[0128] <Nonaqueous electrolyte> The non-aqueous electrolyte may be, for example, a non-aqueous electrolyte prepared by dissolving a lithium salt in an organic solvent. 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, and Li2B 10 Cl 10 , LiBOB (here, BOB stands for bis(oxalato)borate), lithium salts of lower aliphatic carboxylic acids, LiAlCl4, etc. These may be used alone or as a mixture of two or more. Among them, it is preferable to use a lithium salt containing at least one selected from the group consisting of fluorine-containing LiPF6, LiAsF6, LiSbF6, LiBF4, LiSO3F, LiCF3SO3, LiN(SO2CF3)2, and LiC(SO2CF3)3.

[0129] 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. esters 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-propane sultone; or organic solvents such as these with a fluoro group introduced therein (organic solvents in which one or more hydrogen atoms have been replaced with fluorine atoms).

[0130] It is preferable to mix two or more of the organic solvents and use them as a mixed solvent. Among them, a mixed solvent containing a carbonate is preferred, and a mixed solvent of a cyclic carbonate and an acyclic carbonate and a mixed solvent of a cyclic carbonate and an ether are more preferred. As a mixed solvent 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, being resistant to deterioration even when used at high voltages and for long periods of time, and being difficult to decompose even when graphite materials such as natural graphite and artificial graphite are used as the negative electrode active material.

[0131] Furthermore, it is preferable to use a nonaqueous electrolyte solution containing a fluorine-containing lithium salt such as LiPF6 and an organic solvent having a fluorine substituent, as this increases the safety of the resulting nonaqueous electrolyte secondary battery. A mixed solvent containing dimethyl carbonate and an ether having a fluorine substituent, such as pentafluoropropyl methyl ether or 2,2,3,3-tetrafluoropropyl difluoromethyl ether, is more preferable, as it has a high capacity retention rate even when discharged at a high voltage.

[0132] <Members for non-aqueous electrolyte secondary batteries and methods for manufacturing non-aqueous electrolyte secondary batteries> As a method for producing a member for a non-aqueous electrolyte secondary battery, for example, there can be mentioned a method in which a positive electrode, a laminated separator for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention, and a negative electrode are arranged in this order.

[0133] The following method can be used to manufacture a nonaqueous electrolyte secondary battery. First, a nonaqueous electrolyte secondary battery component is placed in a container that will serve as the housing of the nonaqueous electrolyte secondary battery. Next, the container is filled with a nonaqueous electrolyte, and then the container is sealed while reducing the pressure. This completes the manufacture of a nonaqueous electrolyte secondary battery.

[0134] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0135] An embodiment of the present invention may include the following features.

[0136] [1] A laminate separator for a non-aqueous electrolyte secondary battery, comprising two or more layers stacked together, A laminated separator for a non-aqueous electrolyte secondary battery, which has a heat tensile modulus of 0.25 or more in a region of elongation from 50% to 200% in a tensile test. (Here, the tensile test is a test in which the laminated separator for a non-aqueous electrolyte secondary battery is stretched in the MD direction at a rate of 10 mm / min in an atmosphere of 120°C, and the stress (unit: N) applied at that time is measured. the elongation rate is a ratio [unit: %] of the elongation amount [unit: mm] in the MD direction of the laminate separator for a nonaqueous electrolyte secondary battery to the length [unit: mm] in the MD direction of the laminate separator for a nonaqueous electrolyte secondary battery before the elongation, The heat tensile modulus is the slope of an approximate line obtained by using the least squares method in the elongation range of 50% to 200% for a stress-strain curve obtained by plotting the elongation on the X axis and the stress on the Y axis. [2] The laminate separator for a non-aqueous electrolyte secondary battery according to [1], which has a structure in which a porous layer is laminated on one or both sides of a polyolefin porous film. [3] The laminate separator for a non-aqueous electrolyte secondary battery according to [1] or [2], wherein at least one layer of the two or more layers is a heat-resistant layer. [4] The laminate separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [3], wherein at least one layer of the two or more layers is a layer containing 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. [5] The laminate separator for a non-aqueous electrolyte secondary battery according to [4], wherein the polyamide resin is an aramid resin. [6] The aramid resin comprises a block A mainly composed of a unit represented by the following formula (3): -(NH-Ar 1 -NHCO-Ar 2 -CO)- (3) Block B mainly composed of a unit represented by the following formula (4), -(NH-Ar 3 -NHCO-Ar 4 -CO)- (4) The laminate separator for a non-aqueous electrolyte secondary battery according to [5], which is a block copolymer having the following structure: During the ceremony, Ar 1 , Ar 2 , Ar 3 and Ar 4 may be different for each unit, Ar 1 , Ar 2 , Ar 3 and Ar 4 are each independently a divalent group having one or more aromatic rings, All Ar 1 More than 50% of these have a structure in which two aromatic rings are connected by a sulfonyl bond. All Ar 3 Of these, 50% or less have a structure in which two aromatic rings are connected by a sulfonyl bond, All Ar 1 and Ar 3 Among these, 10 to 70% have a structure in which two aromatic rings are linked by a sulfonyl bond. [7] The laminate separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [6], wherein at least one of the two or more layers contains a filler, and the content of the filler in the layer containing the filler is 20 to 90% by weight, where the weight of the entire layer containing the filler is 100% by weight. [8] The laminate separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [7], further comprising an adhesive layer in addition to the two or more layers. [9] A member for a non-aqueous electrolyte secondary battery, comprising a positive electrode, the laminate separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [8], and a negative electrode, arranged in this order.

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

[0137] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0138] [Methods for measuring various physical properties] In the examples and comparative examples described below, the various physical properties were measured by the following methods.

[0139] <Film thickness> The thickness of the polyolefin porous film was measured using a high-precision digital length measuring machine (VL-50) manufactured by Mitutoyo Corporation.

[0140] <Weight per unit area> A square sample of 8 cm x 8 cm was cut out from the polyolefin porous film. The weight of this sample was measured and designated as W1 (g). The basis weight of the polyolefin porous film was calculated according to the following formula (10). Weight of polyolefin porous film (g / m 2 )=W1(g) / (0.08×0.08) (10) An 8 cm x 8 cm square sample was cut out from the laminated separator. The weight of this sample was measured and designated as W2 (g). The weight per unit area of ​​the laminated separator was calculated according to the following formula (11). Weight of laminated separator (g / m 2 )=W2(g) / (0.08×0.08) (11) The weight per unit area of ​​the porous layer was calculated by subtracting the weight per unit area of ​​the polyolefin porous film from the weight per unit area of ​​the laminated separator.

[0141] <Heat tensile modulus> A tensile test was performed on the laminated separator in accordance with JIS K7127 standard, in which the laminated separator was stretched in the MD direction at a rate of 10 mm / min in an atmosphere of 120°C. The stress [N] and elongation [mm] applied to the laminated separator were measured, and the elongation percentage [%] and heat tensile modulus were calculated based on the measurement results. Specifically, the heat tensile modulus was calculated by a method consisting of the following steps (a) to (e). (a) The separator was punched out into a shape (gauge length 20 mm, width 5 mm) specified in dumbbell No. 3 according to JIS K6251, with the MD direction being the longitudinal direction. The resulting laminated separator having the shape specified in dumbbell No. 3 was used as a measurement sample. (b) The measurement sample obtained in step (a) was stretched in the MD direction at a rate of 10 mm / min in an atmosphere at 120°C, and the stress [N], which is the load applied to the measurement sample, and the elongation [mm] were measured until the measurement sample completely broke. The stress measurement was carried out every time the elongation increased by 0.02 mm. More specifically, the stress, which is the load applied at that time, was measured every time the elongation increased by 0.02 mm. Specifically, the elongation after a predetermined time from the start of the elongation was calculated using the following formula (1), where X1 [mm] is the gauge length after the predetermined time from the start of the elongation, and X0 is the gauge length before the elongation, i.e., 20 mm. Elongation [mm] = X1 [mm] - X0 [mm] (1) (c) The elongation amount obtained in step (b) was converted into an elongation percentage (unit: %) by dividing the elongation amount by the gauge length before elongation in step (b), i.e., 20 mm. Specifically, the elongation percentage after a predetermined time has elapsed since the start of elongation was calculated using the following formula (2), where X1 [mm] is the gauge length after the predetermined time has elapsed since the start of elongation, and X0 is the gauge length before elongation, i.e., 20 mm. Elongation [%] = (X1 [mm] - X0 [mm]) / X0 [mm] (2) The calculated elongation values ​​were plotted on the X-axis (horizontal axis) and the stress was plotted on the Y-axis (vertical axis) to obtain a stress-strain curve. (d) A straight line was created by the least squares method within the X of the stress-strain curve obtained in step (c), i.e., the elongation range of 50 to 200%, and the slope of the straight line was calculated. The calculated slope was defined as the thermal tensile modulus.

[0142] <Heating shape retention rate> A laminated separator was cut into an 80mm x 80mm square to prepare a sample, and a 60mm square line was drawn on the surface of the porous layer constituting the sample, inside the outer edge of the 80mm square, to prepare a measurement sample. The measurement sample was sandwiched between paper and placed in an oven heated to 150°C. After one hour, the measurement sample was removed from the oven, and the length of the line drawn in the MD direction and the length of the line drawn in the TD direction of the measurement sample were measured using digital calipers. The measured length of the line drawn in the MD direction of the measurement sample after heating was defined as D. MD (mm). MD Using the above, the value (unit: %) represented by the following formula (12) was calculated as the "heated shape retention rate."

[0143] (D MD / 60)×100 (12) Here, it can be said that a heated shape retention rate of 85% or more means that the laminated separator has excellent heat resistance.

[0144] [Production Example 1: Preparation of Coating Liquid] Coating liquid (1) was prepared according to the following procedure: The aramid resin contained in coating liquid (1) was 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. 4241 g of NMP was charged into the flask. 326.1 g of calcium chloride 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%). Water was added to the calcium chloride solution in such a manner that the moisture content of the calcium chloride solution would be 450 ppm. The calcium chloride used was previously dried in a vacuum at 200°C for 2 hours. 3. While maintaining the temperature of the polymerization system at 40°C, 141.76 g of 4,4'-diaminodiphenyl sulfone (DDS) was added and completely dissolved. 4. The temperature of the polymerization system was cooled to 25°C. While maintaining the temperature of the polymerization system at 25±2°C, a total of 115.67 g of terephthalic acid dichloride (TPC) was added in three portions. The reaction was carried out for 1 hour to synthesize Block A1 consisting of poly(4,4'-diphenylsulfonylterephthalamide). The molar ratio of DDS to TPC was 1.002. 5. 61.74 g of paraphenylenediamine (PPD) 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 113.08 g of TPC was added in three portions. The reaction was allowed to proceed for 1.5 hours, allowing the poly(paraphenylene terephthalamide) block B1 to extend on both sides of the block A1. The molar ratio of PPD to TPC was 1.025. 7. The polymerization system was aged for 1 hour while maintaining the temperature at 20±2°C. In this way, an aramid polymerization liquid (1) was obtained. In the block copolymer contained in the aramid polymerization liquid (1), block A1 accounted for 50% of the entire molecules, and block B1 accounted for the remaining 50% of the entire molecules. The aramid polymerization liquid (1) contained an aramid resin containing the block copolymer. 8. Alumina (average particle size: 13 nm) was added to the aramid polymerization liquid (1) and mixed so that the weight ratio of the aramid resin containing the block copolymer to alumina was 1:1. 9. NMP as a diluent and calcium carbonate as a neutralizer were added to the mixture obtained in step 8 so that the solid content was 4% by weight. The "solid content" here refers to the content of aramid resin and alumina. The solution was stirred for 20 minutes to dilute and neutralize it. The neutralized solution was degassed under reduced pressure to prepare a slurry coating solution (1).

[0145] [Production Example 2: Preparation of Coating Liquid] A slurry coating liquid (2) was prepared by carrying out the same operations as in 1. to 9. of Production Example 1, except that in 8. the weight ratio of aramid resin to alumina was changed to 3:1.

[0146] [Production Example 3: Preparation of coating liquid] Coating liquid (3) was prepared according to the following procedure: The aramid resin contained in coating liquid (3) 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. 4241 g of NMP was charged into the flask. 326.1 g of calcium chloride 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%). Water was added to the calcium chloride solution in such a manner that the moisture content of the calcium chloride solution would be 450 ppm. The calcium chloride used was previously dried in a vacuum at 200°C for 2 hours. 3. While maintaining the temperature of the polymerization system at 40°C, 141.61 g of DDS was added and completely dissolved. 4. The temperature of the polymerization system was cooled to 25°C. While maintaining the temperature of the polymerization system at 25±2°C, a total of 116.13 g of TPC was added in three portions. The reaction was allowed to proceed for 1 hour to synthesize Block A2, which consisted of poly(4,4'-diphenylsulfonylterephthalamide). The molar ratio of DDS to TPC was 0.997. 5. 61.67g of PPD was added to the flask and allowed to dissolve completely for 1 hour. 6. While maintaining the temperature of the polymerization system at 25±2°C, a total of 112.96 g of TPC was added in three portions. The reaction was allowed to proceed for 1.5 hours, allowing the poly(paraphenylene terephthalamide) block B2 to extend on both sides of the block A2. The molar ratio of PPD to TPC was 1.025. 7. The polymerization system was aged for 1 hour while maintaining the temperature at 20±2°C. In this way, an aramid polymerization liquid (3) was obtained. In the block copolymer contained in the aramid polymerization liquid (3), 50% of the entire molecule was occupied by block A2, and the remaining 50% of the entire molecule was occupied by block B2. The aramid polymerization liquid (3) contained an aramid resin containing the block copolymer. 8. Alumina (average particle size: 13 nm) was added to the aramid polymerization liquid (3) and mixed so that the weight ratio of the aramid resin containing the block copolymer to alumina was 1:1. 9. NMP as a diluent and calcium carbonate as a neutralizer were added to the mixture obtained in step 8 so that the solid content was 4% by weight. The "solid content" here refers to the content of aramid resin and alumina. The solution was stirred for 20 minutes to dilute and neutralize it. The neutralized solution was degassed under reduced pressure to prepare a slurry coating solution (3).

[0147] [Manufacturing Example 4] A slurry coating liquid (4) was prepared by carrying out the same operations as in 1. to 9. of Production Example 3, except that in 8. the weight ratio of aramid resin to alumina was changed to 3:1.

[0148] [Manufacturing Example 5] Coating liquid (5) was prepared according to the following procedure: The aramid resin contained in coating liquid (5) 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. 4241 g of NMP was charged into the flask. 326.1 g of calcium chloride 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%). Water was added to the calcium chloride solution in such a manner that the moisture content of the calcium chloride solution would be 450 ppm. The calcium chloride used was previously dried in a vacuum at 200°C for 2 hours. 3. While maintaining the temperature of the polymerization system at 40°C, 141.70 g of DDS was added and completely dissolved. 4. The temperature of the polymerization system was cooled to 25°C. While maintaining the temperature of the polymerization system at 25±2°C, a total of 115.86 g of TPC was added in three portions. The reaction was allowed to proceed for 1 hour to synthesize block A3 consisting of poly(4,4'-diphenylsulfonylterephthalamide). The molar ratio of DDS to TPC was 1.00. 5. 61.71 g of PPD was added to the flask and allowed to dissolve completely for 1 hour. 6. While maintaining the temperature of the polymerization system at 25±2°C, a total of 113.03 g of TPC was added in three portions. The reaction was allowed to proceed for 1.5 hours, allowing block B3 (poly(paraphenylene terephthalamide)) to extend on both sides of block A3. The molar ratio of PPD to TPC was 1.025. 7. The polymerization system was aged for 1 hour while maintaining the temperature at 20±2°C. In this way, an aramid polymerization liquid (5) was obtained. In the block copolymer contained in the aramid polymerization liquid (5), 50% of the entire molecule was occupied by block A3, and the remaining 50% of the entire molecule was occupied by block B3. The aramid polymerization liquid (5) contained an aramid resin containing the block copolymer. 8. Alumina (average particle size: 13 nm) was added to the aramid polymerization liquid (5) and mixed in such a way that the weight ratio of the aramid resin containing the block copolymer to alumina was 2:1. 9. NMP as a diluent and calcium carbonate as a neutralizer were added to the mixture obtained in step 8 so that the solid content was 4% by weight. The "solid content" here refers to the content of aramid resin and alumina. The solution was stirred for 20 minutes to dilute and neutralize it. The neutralized solution was degassed under reduced pressure to prepare a slurry coating solution (5).

[0149] [Manufacturing Example 6] Coating liquid (6) was prepared according to the following procedure: The aramid resin contained in coating liquid (6) 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. 4234 g of NMP was charged into the flask. 325.5 g of calcium chloride 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%). Water was added to the calcium chloride solution in a manner calculated to give a moisture content of 450 ppm. The calcium chloride used was previously dried in a vacuum at 200°C for 2 hours. 3. While maintaining the temperature of the polymerization system at 40°C, 94.01 g of DDS was added and completely dissolved. 4. The temperature of the polymerization system was cooled to 25°C. While maintaining the temperature of the polymerization system at 25±2°C, a total of 77.25 g of TPC was added in three portions. The reaction was allowed to proceed for 1 hour to synthesize block A4 consisting of poly(4,4'-diphenylsulfonylterephthalamide). The molar ratio of DDS to TPC was 0.995. 5. 95.53 g of PPD was added to the flask and allowed to dissolve completely for 1 hour. 6. While maintaining the temperature of the polymerization system at 25±2°C, a total of 173.29 g of TPC was added in three portions. The reaction was allowed to proceed for 1.5 hours, allowing block B4 (poly(paraphenylene terephthalamide)) to extend on both sides of block A4. The molar ratio of PPD to TPC was 1.035. 7. The polymerization system was aged for 1 hour while maintaining the temperature at 20±2°C. In this way, an aramid polymerization liquid (6) was obtained. In the block copolymer contained in the aramid polymerization liquid (6), block A4 accounted for 30% of the entire molecule, and block B4 accounted for the remaining 70% of the entire molecule. The aramid polymerization liquid (6) contained an aramid resin containing the block copolymer. 8. Alumina (average particle size: 13 nm) was added to the aramid polymerization liquid (6) and mixed in such a way that the weight ratio of the aramid resin containing the block copolymer to alumina was 1:1. 9. NMP as a diluent and calcium carbonate as a neutralizer were added to the mixture obtained in step 8 so that the solid content was 4% by weight. The "solid content" here refers to the content of aramid resin and alumina. The solution was stirred for 20 minutes to dilute and neutralize it. The neutralized solution was degassed under reduced pressure to prepare a slurry coating solution (6).

[0150] [Comparative Manufacturing Example 1] Coating liquid (7) was prepared according to the following procedure: The aramid resin contained in coating liquid (7) 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. 4202 g of NMP was charged into the flask. 365.9 g of calcium chloride 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%). Water was added to the calcium chloride solution in a manner calculated to give a moisture content of 300 ppm. The calcium chloride used was previously dried in a vacuum at 200°C for 2 hours. 3. While maintaining the temperature of the polymerization system at 40°C, 141.97 g of DDS was added and completely dissolved. 4. The temperature of the polymerization system was cooled to 16°C. While maintaining the temperature of the polymerization system at 16±2°C, a total of 114.25 g of TPC was added in three portions. The reaction was allowed to proceed for 1 hour to synthesize Block A5, which consisted of poly(4,4'-diphenylsulfonylterephthalamide). The molar ratio of DDS to TPC was 1.016. 5. 61.83 g of PPD was added to the flask and allowed to dissolve completely for 1 hour. 6. While maintaining the temperature of the polymerization system at 18±2°C, a total of 114.03 g of TPC was added in three portions. The reaction was allowed to proceed for 1.5 hours, allowing block B5 (poly(paraphenylene terephthalamide)) to extend on both sides of block A5. The molar ratio of PPD to TPC was 1.018. 7. The polymerization system was aged for 1 hour while maintaining the temperature at 20±2°C. In this way, an aramid polymerization liquid (7) was obtained. In the block copolymer contained in the aramid polymerization liquid (7), 50% of the entire molecule was occupied by block A5, and the remaining 50% of the entire molecule was occupied by block B5. The aramid polymerization liquid (7) contained an aramid resin containing the block copolymer. 8. Alumina (average particle size: 13 nm) was added to the aramid polymerization liquid (7) and mixed in such a way that the weight ratio of the aramid resin containing the block copolymer to alumina was 1:1. 9. NMP as a diluent and calcium carbonate as a neutralizer were added to the mixture obtained in step 8 so that the solid content was 4% by weight. The "solid content" here refers to the content of aramid resin and alumina. The solution was stirred for 20 minutes to dilute and neutralize it. The neutralized solution was degassed under reduced pressure to prepare a slurry coating solution (7).

[0151] [Example 1] Porous film (Porous polyethylene film, thickness: 9 μm, weight: 5 g / m 2 While conveying the porous film, the slurry coating liquid (1) prepared in Production Example 1 was coated on one side (surface) of the porous film. As a result, a coating film was formed on one side of the porous film. Then, while conveying the porous film on which the coating film was formed, the coating film and the porous film were passed through a precipitation tank set at 50°C and a relative humidity of 70%, and the coating film was exposed to air containing water vapor at 50°C and a relative humidity of 70%. This caused a block copolymer to precipitate on one side (surface) of the porous film, forming a coating layer. Next, a laminate consisting of the porous film and the coating layer precipitated on one side of the porous film was washed with water to remove calcium chloride and the solvent from the coating layer. The laminate was then dried to obtain a laminate separator (1) in which a porous layer was formed on one side of the porous film.

[0152] [Example 2] A laminated separator (2) was obtained by carrying out the same operation as in Example 1, except that the slurry coating liquid (2) prepared in Production Example 2 was used instead of the slurry coating liquid (1).

[0153] [Example 3] A laminated separator (3) was obtained by carrying out the same operation as in Example 1, except that the slurry coating liquid (3) prepared in Production Example 3 was used instead of the slurry coating liquid (1).

[0154] [Example 4] A laminated separator (4) was obtained by carrying out the same operation as in Example 1, except that the slurry coating liquid (4) prepared in Production Example 4 was used instead of the slurry coating liquid (1).

[0155] [Example 5] A laminated separator (5) was obtained by carrying out the same operation as in Example 1, except that the slurry coating liquid (5) prepared in Production Example 5 was used instead of the slurry coating liquid (1).

[0156] [Example 6] A laminated separator (6) was obtained by carrying out the same operation as in Example 1, except that the slurry coating liquid (6) prepared in Production Example 6 was used instead of the slurry coating liquid (1).

[0157] [Comparative Example 1] The same operation as in Example 1 was carried out, except that the slurry coating liquid (7) prepared in Comparative Production Example 1 was used instead of the slurry coating liquid (1), to obtain a comparative laminated separator (1).

[0158] [result] Table 1 below shows the heat tensile modulus, the porous layer weight and the heat shape retention rate of the laminated separators (1) to (6) described in Examples 1 to 6 and Comparative Example 1 and the comparative laminated separator (1).

[0159] [Table 1]

[0160] As shown in Table 1, the laminate separators (1) to (6) described in Examples 1 to 6 had a large heat tensile coefficient of 0.25 or more, while the comparative laminate separator (1) described in Comparative Example 1 had a heat tensile coefficient of less than 0.25. Therefore, the laminate separators (1) to (6) described in Examples 1 to 6 correspond to a laminate separator according to one embodiment of the present invention.

[0161] Furthermore, as shown in Table 1, the laminated separators (1) to (6) described in Examples 1 to 6 have a high heat shape retention rate of 85% or more, and are superior in heat resistance to the comparative laminated separator (1) described in Comparative Example 1.

[0162] As described above, it has been demonstrated that the laminated separator according to one embodiment of the present invention has excellent heat resistance. [Industrial Applicability]

[0163] The laminate separator according to one embodiment of the present invention has excellent heat resistance, and therefore, the laminate separator can be used to manufacture non-aqueous electrolyte secondary batteries that are excellent in safety because it effectively prevents short circuits caused by separator contraction due to heat generated during operation.

Claims

1. A laminate separator for a non-aqueous electrolyte secondary battery, comprising two or more layers stacked together, A laminated separator for a non-aqueous electrolyte secondary battery, which has a heat tensile modulus of 0.25 or more in a region of elongation from 50% to 200% in a tensile test. (Here, the tensile test is a test in which the laminated separator for a non-aqueous electrolyte secondary battery is stretched in the MD direction at a rate of 10 mm / min in an atmosphere of 120° C., and the stress (unit: N) applied at that time is measured. the elongation rate is a ratio [unit: %] of the amount of elongation [unit: mm] in the MD direction of the laminate separator for a nonaqueous electrolyte secondary battery to the length [unit: mm] in the MD direction of the laminate separator for a nonaqueous electrolyte secondary battery before the elongation, The heat tensile modulus is the slope of an approximate line obtained by using the least squares method in the elongation range of 50% to 200% for a stress-strain curve obtained by plotting the elongation on the X axis and the stress on the Y axis.

2. 2. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1, which has a structure in which a porous layer is laminated on one or both sides of a polyolefin porous film.

3. 2. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1, wherein at least one layer of the two or more layers is a heat-resistant layer.

4. 2. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1, wherein at least one layer of the two or more layers is a layer containing 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.

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

6. The aramid resin comprises a block A mainly composed of a unit represented by the following formula (3): -(NH-Ar １ -NHCO-Ar ２ -CO)- (3) A block B mainly composed of a unit represented by the following formula (4): -(NH-Ar ３ -NHCO-Ar ４ -CO)- (4) The laminate separator for a non-aqueous electrolyte secondary battery according to claim 5, which is a block copolymer having the formula: During the ceremony, Ar １ , Ar ２ , Ar ３ and Ar ４ may be different for each unit, Ar １ , Ar ２ , Ar ３ and Ar ４ are each independently a divalent group having one or more aromatic rings, All Ar １ More than 50% of these have a structure in which two aromatic rings are linked by a sulfonyl bond, All Ar ３ 50% or less of the above have a structure in which two aromatic rings are connected by a sulfonyl bond, All Ar １ and Ar ３ Among these, 10 to 70% have a structure in which two aromatic rings are linked by a sulfonyl bond.

7. 2. The laminate separator for a nonaqueous electrolyte secondary battery according to claim 1, wherein at least one layer of the two or more layers contains a filler, and the content of the filler in the layer containing the filler is 20 to 90% by weight, where the weight of the entire layer containing the filler is 100% by weight.

8. 2. The laminate separator for a non-aqueous electrolyte secondary battery according to claim 1, wherein at least one layer of the two or more layers is an adhesive layer.

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

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

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