KR20210082495A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

An object of the present invention is to realize a non-aqueous electrolyte secondary battery having excellent discharge capacity recovery characteristics after a charge/discharge cycle. A non-aqueous electrolyte secondary battery according to the present invention includes a porous layer comprising an inorganic filler and a resin, a positive electrode plate having a number of bendings until the electrode active material layer is peeled off 130 times or more, and a negative electrode plate having a bending number of 1650 times or more. and, the porous layer has a value of a scratch test expressed by a specific formula in the range of 0.10 to 0.42.

Description

Non-aqueous electrolyte secondary battery

The present invention relates to a non-aqueous electrolyte secondary battery.

BACKGROUND ART Non-aqueous electrolyte secondary batteries such as lithium secondary batteries are widely used as batteries used in devices such as personal computers, mobile phones, and portable information terminals.

In devices equipped with lithium ion batteries, various types of electrical protection circuits are provided in chargers and battery packs to ensure normal and safe operation of the batteries. However, for example, if the lithium ion battery is continuously charged due to a failure or malfunction of these protection circuits, oxidation-reduction decomposition of the electrolyte on the surface of the positive electrode accompanied by heat generation, oxygen release due to decomposition of the positive electrode active material, and further to the negative electrode In some cases, precipitation of metallic lithium may occur. As a result, there is a risk of finally falling into a thermal runaway state, which in some cases may cause ignition or rupture of the battery.

In order to safely stop the battery before reaching such a dangerous thermal runaway state, a porous substrate containing polyolefin as a main component is currently used as a separator in most lithium ion batteries. The porous substrate containing the polyolefin as a main component has a shut-down function in which pores open in the porous substrate are blocked at about 130°C to 140°C when the internal temperature of the battery rises due to a certain defect.

On the other hand, since a porous substrate containing polyolefin as a main component has low heat resistance, it melts when exposed to a temperature higher than the temperature at which the shutdown function operates, as a result, a short circuit occurs inside the battery, and there is a risk of ignition or explosion of the battery. there was. Then, in order to improve the heat resistance of the said porous substrate, development of the separator which laminated|stacked the porous layer containing a filler and a resin on at least one surface of the said porous substrate is progressing.

As an example of such a separator, patent document 1 describes the separator for batteries formed with the porous layer containing boehmite (plate-shaped particle) as microparticles|fine-particles.

Japanese Patent Laid-Open No. 2008-4438 (published on January 10, 2008)

However, the prior art as described above has room for improvement in terms of the discharge capacity recovery characteristics of the battery after the charge/discharge cycle.

The present invention has been made in view of the above problems, and an object thereof is to realize a non-aqueous electrolyte secondary battery having excellent discharge capacity recovery characteristics of the battery after a charge/discharge cycle.

The non-aqueous electrolyte secondary battery according to the first aspect of the present invention has a porous layer containing an inorganic filler and a resin, and in accordance with the MIT test technique specified in JIS P 8115 (1994), a load of 1N and a bending angle of 45° In the test, the number of bending until the electrode active material layer is peeled is 130 or more positive electrode plate, and in the bending resistance test, the negative electrode plate is the number of bending until the electrode active material layer is peeled is 1650 or more, As for the said porous layer, the value represented by following formula (1) exists in the range of 0.10-0.42.

|1-T/M|····(1)

(In formula (1), T represents the distance to the critical load in the scratch test under a constant load of 0.1N in TD, and M is the scratch test under a constant load of 0.1N in MD. In this case, the distance to the critical load is indicated.)

Further, in the nonaqueous electrolyte secondary battery according to the second aspect of the present invention, in the first aspect, the porous layer is polyolefin, (meth)acrylate-based resin, fluorine-containing resin, polyamide-based resin, polyester-based resin and water-soluble One or more resins are selected from the group consisting of polymers.

Further, in the non-aqueous electrolyte secondary battery according to the third aspect of the present invention, in the second aspect, the polyamide-based resin is an aramid resin.

Further, in the nonaqueous electrolyte secondary battery according to Aspect 4 of the present invention, in any of Aspects 1 to 3, the porous layer is laminated on one or both surfaces of the polyolefin porous film.

Further, in the nonaqueous electrolyte secondary battery according to Embodiment 5 of the present invention, in any of Embodiments 1 to 4, the positive electrode plate contains a transition metal oxide, and the negative electrode plate contains graphite.

According to one aspect of the present invention, it is possible to realize a non-aqueous electrolyte secondary battery having excellent discharge capacity recovery characteristics of the battery after a charge/discharge cycle.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the outline of an MIT testing machine.
2 is a schematic diagram showing the structure of the porous layer in a porous layer containing an inorganic filler when the orientation of the inorganic filler is large (left figure) and when the orientation of the inorganic filler is small (right figure).
It is a figure which shows the apparatus in a scratch test, and its operation.
It is a figure which shows the critical load in the graph produced from the result of a scratch test, and the distance to a critical load.

One embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various modifications can be made within the scope shown in the claims, and the technical scope of the present invention is also applicable to embodiments obtained by appropriately combining technical means disclosed in other embodiments. are included in In addition, unless otherwise indicated in this specification, "A to B" which shows a numerical range means "A or more and B or less."

A non-aqueous electrolyte secondary battery according to an embodiment of the present invention includes a porous layer containing an inorganic filler and a resin, and in accordance with the MIT test technique specified in JIS P 8115 (1994), carried out under a load of 1N and a bending angle of 45° In the bending resistance test, a positive electrode plate having a number of bending times of 130 or more until the electrode active material layer is peeled off, and a negative electrode plate having a bending number of 1650 times or more until the electrode active material layer is peeled off in the folding resistance test, , The porous layer is characterized in that the value represented by the following formula (1) is in the range of 0.10 to 0.42.

|1-T/M|····(1)

(in formula (1), T represents the distance to the critical load in the scratch test under the constant load of 0.1N in TD (Transverse Direction), M is 0.1 in MD (Machine Direction) The distance to the critical load in the scratch test under a constant load of N is indicated.)

<Positive plate>

The positive electrode plate in the nonaqueous electrolyte secondary battery according to the embodiment of the present invention is not particularly limited as long as the number of times of bending measured in the bending resistance test is within a specific range as will be described later. For example, as the positive electrode active material layer, a sheet-shaped positive electrode plate in which a positive electrode mixture containing a positive electrode active material, a conductive agent, and a binder is supported on a positive electrode current collector is used. In addition, the positive electrode plate may support positive mix on both surfaces of a positive electrode collector, and may support positive mix on one side of a positive electrode collector.

As said positive electrode active material, the material which can dope/dedope lithium ion is mentioned, for example. As the material, a transition metal oxide is preferable. Specific examples of the transition metal oxide include lithium composite oxides containing at least one transition metal such as V, Mn, Fe, Co, and Ni.

Examples of the conductive agent include carbonaceous materials such as graphite (natural graphite, artificial graphite), cokes, carbon black, pyrolytic carbons, carbon fibers, and organic polymer compound fired bodies. One type of the said electrically conductive agent may be used and may be used combining two or more types.

Examples of the binder include polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, and tetrafluoroethylene-perfluoroalkylvinyl ether. of copolymers, ethylene-tetrafluoroethylene copolymers, vinylidene fluoride-hexafluoropropylene copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, thermoplastic polyimides, polyethylene and polypropylene Thermoplastic resins, such as an acrylic resin, and a styrene-butadiene rubber are mentioned. Moreover, the binder also has a function as a thickener.

As said positive electrode current collector, conductors, such as Al, Ni, and stainless steel, are mentioned, for example. Among them, Al is more preferable because it is easy to process into a thin film and is inexpensive.

<Negative plate>

The negative electrode plate in the non-aqueous electrolyte secondary battery according to the embodiment of the present invention is not particularly limited as long as the number of bendings measured in the bending resistance test is within a specific range as will be described later. For example, as the negative electrode active material layer, a sheet-shaped negative electrode in which a negative electrode mixture containing a negative electrode active material is supported on a negative electrode current collector is used. The sheet-shaped negative electrode plate preferably contains the conductive agent and the binder. Further, the negative electrode plate may support the negative electrode mixture on both surfaces of the negative electrode current collector, or the negative electrode mixture may support the negative electrode mixture on one side of the negative electrode current collector.

As said negative electrode active material, the material which can dope/dedope lithium ion, lithium metal, a lithium alloy, etc. are mentioned, for example. As said material, a carbonaceous material etc. are mentioned, for example. Examples of the carbonaceous material include graphite (natural graphite, artificial graphite), cokes, carbon black, and pyrolytic carbons. As the conductive agent and the binder, those described as the conductive agent and the binder that can be contained in the positive electrode active material layer can be used.

Examples of the anode current collector include Cu, Ni, and stainless steel, and in particular, in a lithium ion secondary battery, it is difficult to form an alloy with lithium, and Cu is more preferable because it is easy to process into a thin film.

<Number of bends>

The positive electrode plate and the negative electrode plate in one embodiment of the present invention have a specific range in the number of bendings until the active material layer is peeled in the bending resistance test conducted in accordance with the MIT test technique specified in JIS P 8115 (1994). to be. The bending resistance test is performed under a load of 1N and a bending angle of 45°. In a non-aqueous electrolyte secondary battery, expansion and contraction of the active material may occur during a charge/discharge cycle. The more the number of bendings until the electrode active material layer is peeled off, as measured by the fold resistance test, the more the adhesion between the components (active material, conductive agent, and binder) contained in the electrode active material layer, and the electrode active material layer and the current collector It shows that adhesiveness is easy to maintain. Therefore, deterioration of the non-aqueous electrolyte secondary battery in the course of the charge/discharge cycle is suppressed.

In the bending resistance test, the positive electrode plate has a bending frequency of 130 or more until the electrode active material layer is peeled off, and is preferably 150 or more. Further, in the bending resistance test, the number of bendings until the electrode active material layer is peeled off of the negative electrode plate is 1650 times or more, preferably 1800 times or more, and more preferably 2000 times or more.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the outline of the MIT tester used for the MIT test technique. The x-axis represents the horizontal direction, and the y-axis represents the vertical direction. An overview of the MIT testing technique is described below. One end in the longitudinal direction of the test piece is sandwiched between the spring-loaded clamps, and the other end is clamped by sandwiching the bending clamp. A spring-loaded clamp is connected to the weight. In the bending resistance test, the load by this weight is 1N. As a result, the test piece is in a state in which tension is applied in the longitudinal direction. In this state, the longitudinal direction of the test piece is parallel to the vertical direction. And the test piece is bent by rotating a bending clamp. In the bending resistance test, the bending angle at this time is 45°. That is, the test piece is bent at 45° left and right. In addition, the speed of bending the test piece is 175 reciprocations/min.

<Method for manufacturing positive plate and negative plate>

As a manufacturing method of a sheet-shaped positive electrode plate, For example, a method of press-molding a positive electrode active material, a electrically conductive agent, and a binder on a positive electrode electrical power collector; A method in which the positive electrode active material, the conductive agent and the binder are made into a paste using an appropriate organic solvent, the paste is coated on the positive electrode current collector, and then pressed in a wet state or after drying to adhere to the positive electrode current collector, etc. can be heard

Similarly, as a manufacturing method of a sheet-shaped negative electrode plate, For example, a method of press-molding a negative electrode active material on a negative electrode collector; A method in which the negative electrode active material is made into a paste using an appropriate organic solvent, the paste is coated on the negative electrode current collector, and then pressed in a wet state or after drying to adhere to the negative electrode current collector, and the like. The paste preferably contains the conductive agent and the binder.

Here, by adjusting the pressurization time, the pressure or the pressurization method, the number of bending described above can be controlled. As for the time to pressurize, 1-3600 second is preferable, More preferably, it is 1-300 second. Pressurization may be performed by restraining the positive electrode plate or the negative electrode plate. In this specification, the pressure by restraint is also called restraint pressure. As for the restraint pressure, 0.01-10 MPa is preferable, More preferably, it is 0.01-5 MPa. Moreover, you may pressurize in the state which wet the positive electrode plate or a negative electrode plate using an organic solvent. Thereby, the adhesiveness of the components contained in the electrode active material layer inside, and the adhesiveness of an electrode active material layer and an electrical power collector can be improved. Examples of the organic solvent include carbonates, ethers, esters, nitriles, amides, carbamates and sulfur-containing compounds, and fluorine-containing organic solvents in which fluorine groups are introduced into these organic solvents. can

<Porous layer>

In one embodiment of the present invention, the porous layer is a member constituting the non-aqueous electrolyte secondary battery, and may be disposed between the polyolefin porous film and at least one of a positive electrode plate and a negative electrode plate. The porous layer may be formed on one side or both sides of the polyolefin porous film. Alternatively, the porous layer may be formed on at least one active material layer of the positive electrode plate and the negative electrode plate. Alternatively, the porous layer may be disposed between the polyolefin porous film and at least any one of a positive electrode plate and a negative electrode plate to be in contact with them. The number of porous layers arrange|positioned between a polyolefin porous film and at least any one of a positive electrode plate and a negative electrode plate may be one, and two or more layers may be sufficient as it. It is preferable that a porous layer is an insulating porous layer containing resin.

When a porous layer is laminated|stacked on the single side|surface of a polyolefin porous film, the said porous layer, Preferably, it is laminated|stacked on the surface which opposes the positive electrode plate in a polyolefin porous film. More preferably, the porous layer is laminated on the surface in contact with the positive electrode plate.

The porous layer in one Embodiment of this invention contains an inorganic filler and resin. The porous layer has a plurality of pores therein, has a structure in which these pores are connected, and is a layer in which gas or liquid can pass from one side to the other. In addition, when the porous layer in one embodiment of the present invention is used as a member constituting a laminated separator for a nonaqueous electrolyte secondary battery to be described later, the porous layer is the outermost layer of the laminated separator, and may be a layer in contact with the electrode. have.

It is preferable that resin contained in the porous layer in one Embodiment of this invention is insoluble in the electrolyte solution of a battery, and is electrochemically stable in the usage range of the battery. As said resin, specifically, For example, polyolefin; (meth)acrylate-based resin; fluorine-containing resin; polyamide-based resin; polyimide-based resin; polyester-based resin; rubber; a resin having a melting point or glass transition temperature of 180°C or higher; water-soluble polymers; Polycarbonate, polyacetal, polyether ether ketone, etc. are mentioned.

Among the above-mentioned resins, polyolefin, (meth)acrylate-based resin, fluorine-containing resin, polyamide-based resin, polyester-based resin and water-soluble polymer are preferable.

As polyolefin, polyethylene, polypropylene, polybutene, an ethylene-propylene copolymer, etc. are preferable.

Examples of the fluorine-containing resin include polyvinylidene fluoride (PVDF), polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoro Alkyl 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, ethylene-tetrafluoroethylene copolymer, etc., and among the said fluorine-containing resin, a fluorine-containing rubber whose glass transition temperature is 23 degrees C or less can be raised.

As the polyamide-based resin, aramid resins such as aromatic polyamide and wholly aromatic polyamide are preferable.

As an aramid resin, specifically, for example, poly (paraphenylene terephthalamide), poly (metaphenylene isophthalamide), poly (parabenzamide), poly (metabenzamide), poly (4,4') -benzanilide terephthalamide), poly(paraphenylene-4,4'-biphenylenedicarboxylic acid amide), poly(metaphenylene-4,4'-biphenylenedicarboxylic acid amide), poly (paraphenylene-2,6-naphthalenedicarboxylic acid amide), poly(metaphenylene-2,6-naphthalenedicarboxylic acid amide), poly(2-chloroparaphenylene terephthalamide), paraphenylene Terephthalamide/2,6-dichloroparaphenyleneterephthalamide copolymer, metaphenyleneterephthalamide/2,6-dichloroparaphenyleneterephthalamide copolymer, etc. are mentioned. Among these, poly(paraphenylene terephthalamide) is more preferable.

As polyester-type resin, aromatic polyesters, such as polyarylate, and liquid crystal polyester are preferable.

As rubbers, a styrene-butadiene copolymer and its hydride, a methacrylic acid ester copolymer, an acrylonitrile-acrylic acid ester copolymer, a styrene-acrylic acid ester copolymer, ethylene propylene rubber, polyvinyl acetate, etc. are mentioned.

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

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

In addition, the number of resin contained in the porous layer in one Embodiment of this invention may be one, and two or more types of resin mixture may be sufficient as it.

Among the above resins, when the porous layer is disposed to face the positive electrode plate, it is easy to maintain various performances such as rate characteristics and resistance characteristics of the non-aqueous electrolyte secondary battery even if oxidative deterioration occurs during battery operation. Therefore, the fluorine-containing resin is preferable

The porous layer in one Embodiment of this invention contains an inorganic filler. The lower limit of the content is preferably 50% by weight or more, more preferably 70% by weight or more, and more preferably 90% by weight, based on the total weight of the filler and the resin constituting the porous layer in the embodiment of the present invention. % or more is more preferable. On the other hand, it is preferable that it is 99 weight% or less, and, as for the upper limit of content of an inorganic filler in the porous layer in one Embodiment of this invention, it is more preferable that it is 98 weight% or less. It is preferable from a heat resistant viewpoint that content of the said filler is 50 weight% or more, and it is preferable from a viewpoint of adhesiveness between fillers that content of the said filler is 99 weight% or less. By containing an inorganic filler, the slidability and heat resistance of the separator containing the said porous layer can be improved. The inorganic filler is not particularly limited as long as it is stable to the non-aqueous electrolyte and electrochemically stable. From the viewpoint of securing the safety of the battery, a filler having a heat resistance temperature of 150°C or higher is preferable.

Although the said inorganic filler is not specifically limited, Usually, it is an insulating filler. The inorganic filler is preferably an inorganic substance containing at least one element selected from the group consisting of an aluminum element, a zinc element, a calcium element, a zirconium element, a silicon element, a magnesium element, a barium element, and a boron element, preferably is an inorganic substance containing elemental aluminum. Moreover, the inorganic filler, Preferably, the oxide of the said metal element is included.

Specifically, as the inorganic filler, titanium oxide, alumina (Al ₂ O ₃ ), zinc oxide (ZnO), calcium oxide (CaO), zirconia (ZrO ₂ ), silica, magnesia, barium oxide, boron oxide, mica, Wollastonite, attapulgite, boehmite (alumina monohydrate), etc. are mentioned. As said inorganic filler, 1 type of filler may be used independently and may be used combining two or more types of fillers.

It is preferable that the inorganic filler in the porous layer in one Embodiment of this invention contains an alumina and a plate-shaped filler. Examples of the plate-shaped filler include one or more fillers selected from the group consisting of zinc oxide (ZnO), mica, and boehmite among the oxides of the metal elements listed above.

It is preferable that the volume average particle diameter of the said inorganic filler is the range of 0.01 micrometer - 10 micrometers from a viewpoint of ensuring favorable adhesiveness and slidability, and the moldability of a laminated body. As the lower limit, 0.05 micrometer or more is more preferable, and 0.1 micrometer or more is still more preferable. As the upper limit, 5 micrometers or less are more preferable, and 1 micrometer or less is still more preferable.

The shape of the said inorganic filler is arbitrary, and is not specifically limited. The shape of the inorganic filler may be a particle shape, for example, a spherical shape; oval shape; plate shape; rod shape; irregular shape; fiber shape; a shape in which single particles of a spherical or columnar shape are heat-sealed, such as a peanut shape and/or a tetrapot shape; Any of these may be used. From the viewpoint of preventing a short circuit of the battery, the inorganic filler is preferably plate-shaped particles and/or non-agglomerated primary particles. In addition, from the viewpoint of ion permeation, the shape of the inorganic filler is a resinous shape having a lump, a concave part, a constriction part, a raised or expanded part, and a coral shape, in which the particles in the porous material are unlikely to be tightly packed and voids are easily formed between particles. , or an irregular shape such as a cluster shape; fiber shape; It is preferable that single particles are heat-sealed, such as a peanut shape and/or a tetrapod shape. It is particularly preferable that the shape of the inorganic filler is a shape in which single particles of a spherical or columnar shape are thermally fused, such as a peanut shape and/or a tetrapod shape.

A filler can improve slidability by forming fine unevenness|corrugation on the surface of a porous layer. When the filler is plate-shaped particles and/or non-agglomerated primary particles, the unevenness formed on the surface of the porous layer by the filler becomes finer, and the adhesion between the porous layer and the electrode becomes better.

It is preferable that it is 10 % - 50 %, and, as for the oxygen atomic mass percentage of the metal oxide which comprises an inorganic filler contained in the porous layer in one Embodiment of this invention, it is more preferable that it is 20 % - 50 %. In this specification, "oxygen atom mass percentage" means what showed the mass ratio of the oxygen atom in the said metal oxide with respect to the total mass of the whole metal oxide in percentage. For example, in the case of zinc oxide, since the molecular weight of zinc oxide (ZnO) is 65.4+16.0=81.4 from the atomic weight of zinc: 65.4 and the atomic weight of oxygen: 16.0, the oxygen atomic mass percentage in zinc oxide is 16.0/81.4× 100 = 20 (%).

If the oxygen atomic mass percentage of the metal oxide is within the above range, the affinity of the inorganic filler with the solvent or dispersion medium in the coating liquid used in the method for producing a porous layer described later is appropriately maintained, and between the inorganic fillers is appropriately selected. can be kept at a distance. Thereby, the dispersibility of a coating liquid can be made favorable and, as a result, the above-mentioned Formula (1) can be controlled in an appropriate prescribed range.

The porous layer in one Embodiment of this invention may contain other components other than the inorganic filler and resin mentioned above. As said other component, surfactant, wax, binder resin, etc. are mentioned, for example. Moreover, it is preferable that content of the said other component is 0 weight% - 50 weight% with respect to the weight of the whole porous layer.

The average film thickness of the porous layer in one embodiment of the present invention is preferably in the range of 0.5 µm to 10 µm per porous layer from the viewpoint of ensuring electrode adhesion and high energy density, and 1 µm to It is more preferable that it is the range of 5 micrometers.

The weight per unit area of the porous layer can be appropriately determined in consideration of the strength, film thickness, weight, and handling properties of the porous layer. It is preferable that it is 0.5-20 g/m<^2> , and, as for the weight per unit area of a porous layer ^{, it is more preferable that it is 0.5-10 g/m<2> per one porous layer.}

By making the weight per unit area of the porous layer within these numerical ranges, the weight energy density and volume energy density of the nonaqueous electrolyte secondary battery can be increased. When the weight per unit area of the porous layer exceeds the above range, the non-aqueous electrolyte secondary battery tends to become heavy.

It is preferable that it is 20-90 volume%, and, as for the porosity of a porous layer, it is more preferable that it is 30-80 volume% so that sufficient ion permeability may be acquired. Moreover, it is preferable that it is 1.0 micrometer or less, and, as for the pore diameter of the pore which a porous layer has, it is more preferable that it is 0.5 micrometer or less. By making the pore diameter of the pores into these sizes, the nonaqueous electrolyte secondary battery can obtain sufficient ion permeability.

<T/M ratio of porous layer surface>

It is preferable that it is the range of 0.10-0.42, and, as for the porous layer in one Embodiment of this invention, it is more preferable that the value represented by the following formula (1) is the range of 0.10-0.30.

|1-T/M|····(1)

(In formula (1), T represents the distance to the critical load in the scratch test under a constant load of 0.1N in TD, and M is the scratch test under a constant load of 0.1N in MD. In this case, the distance to the critical load is indicated.)

The ratio of the distance (T) to the critical load in TD and the distance (M) to the critical load in MD measured by the scratch test mentioned above shows the orientation of the inorganic filler in a porous layer is an indicator Here, the schematic diagram of the aspect of the inorganic filler in a porous layer when the said orientation is high (anisotropy) and when the said orientation is low (isotropic) is shown in FIG. The left figure of FIG. 2 is a schematic diagram which shows the structure of the said porous layer in the case where the orientation of an inorganic filler in a porous layer containing an inorganic filler is large and shows anisotropy, The right figure of FIG. 2 is the orientation of an inorganic filler It is a schematic diagram which shows the structure of the said porous layer in the case of showing this small isotropy.

The value represented by the formula (1) is a value indicating the anisotropy of the distance to the critical load in the scratch test, and the closer the value is to zero, the more isotropic the distance to the critical load. Hereinafter, the value represented by Formula (1) is also simply called "Formula (1)".

The "scratch test" in the present specification is, as shown in FIG. 3, a constant load is applied to the indenter, and the porous membrane is moved in the horizontal direction in a state in which the surface layer of the porous membrane to be measured is compressed in the thickness direction. , is a test to measure the stress generated at a certain indenter moving distance. The state in which the surface layer of the porous film was compressively deformed in the thickness direction, that is, is a state in which an indenter was pressed into the porous film. This test is specifically carried out by the method shown below:

(1) A laminate which is a laminated porous film obtained by laminating a porous layer to be measured on a porous substrate is cut to a size of 20 mm x 60 mm. Thereafter, the cut laminate 3 is bonded to a 30 mm x 70 mm glass preparat as the substrate 2 with an aqueous glue, and dried at a temperature of 25° C. for one day and one night to prepare a test sample. In addition, at the time of the said bonding, it is made so that a bubble does not enter between the laminated body and the glass-made preparaton.

(2) The test sample produced in the step (1) is installed in a microscratch test apparatus. In a state in which a vertical load of 0.1 N is applied on the test sample by the diamond indenter 1 in the test apparatus, the table in the test apparatus is directed toward the TD of the laminate at a rate of 5 mm/min. Move a distance of 10 mm at a speed. In the meantime, the frictional force, which is the stress generated between the diamond indenter and the test sample, is measured.

(3) A curve graph showing the relationship between the displacement of the stress measured in the step (2) and the movement distance of the table is prepared, and from the curve graph, as shown in FIG. 4 , the critical load value in TD and the distance to the critical load is calculated.

(4) The moving direction of the table is changed to MD, the above-described steps (1) to (3) are repeatedly performed, and the critical load value and the distance to the critical load in MD are calculated.

In addition, about the measurement conditions other than the conditions mentioned above in the said scratch test, it implements on the conditions similar to the method of JIS R 3255.

The distance to the critical load value calculated in the scratch test is an index of (a) the plastic deformation easiness of the surface layer of the laminated porous film, and (b) the transferability of the shear stress to the surface opposite to the measurement surface. When the distance to the critical load value is long, in the laminated porous film to be measured, (a') the surface layer portion is less likely to be plastically deformed, and (b') the shear stress transferability to the surface opposite to the measurement surface is low. That is, it indicates that the stress is difficult to transmit.

Moreover, it is thought that the distance to the critical load in TD direction and MD direction is strongly influenced by the structural factor of the laminated porous film shown below.

(i) Orientation state of resin to MD in a laminated porous film

(ii) Orientation state of resin in TD in a laminated porous film

(iii) contact state of resin orientated in the MD direction and TD direction in the thickness direction of a laminated porous film

When the above-mentioned formula (1) is larger than 0.42, since the anisotropy of the internal structure of the porous layer becomes excessively high, the length of the ion permeation channel inside the porous layer becomes long. As a result, in the nonaqueous electrolyte secondary battery incorporating the porous layer, the ion permeation resistance of the porous layer increases, and the resistance of the separator in the nonaqueous electrolyte secondary battery increases. On the other hand, when Formula (1) mentioned above is less than 0.10, it is thought that the structure of a porous layer becomes the structure which has excessively high isotropy. When the structure of the porous layer has excessively high isotropy, in the nonaqueous electrolyte secondary battery incorporating the porous layer, the electrolyte storage capacity of the porous layer during battery operation tends to be excessively high. As a result, the electrolyte supply capability of the separator base material and the electrode that come into contact with the porous layer and supply the electrolyte to the porous layer regulates the flow of the electrolyte throughout the nonaqueous electrolyte secondary battery. As a result, the resistance of the separator in the non-aqueous electrolyte secondary battery increases.

<Central particle size (D50)>

As for the porous layer in one Embodiment of this invention, it is preferable that the range of the central particle diameter (D50) of an inorganic filler is 0.1 micrometer - 11 micrometers, It is more preferable that it is the range of 0.1 micrometer - 10 micrometers, 0.1 micrometer - It is more preferable that it is in the range of 5 micrometers, and it is especially preferable that it is 0.5 micrometer.

Although the method of measuring the central particle diameter of an inorganic filler is not specifically limited, For example, it measures by the method as described in an Example.

When the central particle diameter of an inorganic filler is larger than 11 micrometers, since the film thickness of a heat-resistant layer increases and nonuniformity generate|occur|produces, nonuniformity arises also in the ion permeation of a porous layer. As a result, the resistance of the separator in the nonaqueous electrolyte secondary battery incorporating the porous layer tends to increase. On the other hand, since the viscosity of the coating liquid containing an inorganic filler becomes high when the central particle diameter of an inorganic filler is less than 0.1 micrometer, there exists a possibility of expressing dilatency. As a result, the coating liquid becomes poor in coating performance, and the coating nonuniformity to a porous layer may generate|occur|produce. Further, since the central particle size of the inorganic filler is small, the amount of the binder required for binding the inorganic filler increases. As a result, in the nonaqueous electrolyte secondary battery incorporating the porous layer, the ion permeation resistance of the porous layer increases, and the resistance of the separator in the nonaqueous electrolyte secondary battery increases.

<BET specific surface area>

It is preferable that the BET specific surface area per unit area of an inorganic filler is 100 m<^2> /g or less, as for the porous layer in one Embodiment of this invention, It is more preferable that it is ^{50 m<2> /g or less, It may be 10 m<2>} /g or less.

Although the method of measuring the BET specific surface area per unit area of an inorganic filler is not specifically limited, For example, the method including the process shown to the following (1)-(3) is mentioned.

(1) A step of pre-treating the filler by vacuum drying at 80°C for 8 hours.

(2) A step of measuring an adsorption/desorption isotherm by nitrogen by a static solution method.

(3) A step of calculating the specific surface area of the filler by the BET method.

In addition, in the measurement of the specific surface area of a filler, although the apparatus and measuring apparatus which perform a pre-processing are not specifically limited, For example, BELPREP-vacII (made by Microtrac Bell Corporation) is a measuring apparatus as a pre-processing apparatus. BELSORP-mini (manufactured by Microtrac Bell Corporation) can be used.

In addition, the measurement conditions at the time of measuring the specific surface area of a filler are not specifically limited, A person skilled in the art can set suitably.

When the BET specific surface area per unit area of the inorganic filler ^{is larger than 100 m 2} /g, the filler oil supply property increases due to the increase of the BET specific surface area, and accordingly, the properties of the porous layer as a coating solution decrease, and poor coatability there is a risk of becoming As a result, the resistance of the separator in the non-aqueous electrolyte secondary battery incorporating the porous layer tends to increase.

<Method for producing porous layer>

Although it does not specifically limit as a manufacturing method of the porous layer in one Embodiment of this invention, For example, using the process in any one of the processes (1)-(3) shown below on a base material, the said inorganic The method of forming the porous layer containing a filler and the said resin is mentioned. In the case of the process (2) and the process (3) shown below, a porous layer can be manufactured by further drying after depositing the said resin and removing a solvent. The state in which the said inorganic filler is disperse|distributed and the said resin is melt|dissolved may be sufficient as the coating liquid in process (1)-(3). In addition, the solvent is a solvent for dissolving the resin, and can also be referred to as a dispersion medium for dispersing the resin or the inorganic filler.

(1) The process of forming a porous layer by coating the coating liquid containing the said inorganic filler and the said resin on a base material, and drying and removing the solvent in the said coating liquid.

(2) After coating the coating solution containing the inorganic filler and the resin on the surface of the substrate, the substrate is immersed in a precipitation solvent, which is a poor solvent for the resin, to precipitate the resin, and a porous layer process to form.

(3) After coating the coating solution containing the inorganic filler and the resin on the surface of the base material, using a low-boiling organic acid to make the coating solution acidic to precipitate the resin, thereby forming a porous layer forming process.

Other films, positive electrode plates, negative electrode plates, etc. can be used for the base material in addition to the polyolefin porous film described later.

The solvent is preferably a solvent that does not adversely affect the substrate, uniformly and stably dissolves the resin, and uniformly and stably disperses the inorganic filler. Examples of the solvent include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, acetone and water.

It is preferable to use isopropyl alcohol or t-butyl alcohol as said precipitation solvent, for example.

In the said step (3), para-toluenesulfonic acid, acetic acid, etc. can be used as a low boiling point organic acid, for example.

The coating amount of the porous layer (i.e., the weight per unit area) is preferably ^{0.5 to 20 g/m 2} in terms of solid content per layer of the porous layer, usually from the viewpoint of adhesion to the electrode or electrode sheet and ion permeability. , more preferably 0.5 to 10 g/m ² , and still more preferably 0.5 g/m ² to 1.5 g/m ² . That is, it is preferable to adjust the quantity of the said coating liquid apply|coated on the said base material so that the coating amount (weight per unit area) of the porous layer obtained may become the above-mentioned range.

As a method of controlling the orientation of the porous layer in one embodiment of the present invention, that is, the above-mentioned formula (1), as described below, used for the production of the porous layer, containing an inorganic filler and a resin Controlling the coating shear rate at the time of coating the solid content concentration of a coating liquid, and a coating liquid on a base material, etc. are mentioned.

Although the suitable solid content concentration of the said coating liquid may change according to the kind of filler, etc., it is generally preferable that it is more than 20 weight% and 40 weight% or less. It is preferable that the said solid content concentration is the above-mentioned range from the point which can maintain the viscosity of the said coating liquid appropriately, and, as a result, can control the above-mentioned Formula (1) to an appropriate prescribed range.

The coating shear rate when the coating solution is applied onto the substrate may vary depending on the type of filler, etc., but in general, it is preferably 2 (1/s) or more, and 4 (1/s) to 50 (1). /s) is more preferable.

Here, for example, as the inorganic filler, a shape in which spherical or columnar single particles such as a peanut shape and/or a tetrapod shape are thermally fused, a spherical shape, an oval shape, a plate shape, a rod shape, or an irregular shape having a shape In the case of using an inorganic filler, if the coating shear rate is increased, high shear force is applied to the inorganic filler, so that the anisotropy tends to increase. On the other hand, when the said coating shearing rate is made small, since a shear force does not apply to an inorganic filler, there exists a tendency for isotropic orientation.

On the other hand, when the inorganic filler is a long-fiber diameter inorganic filler such as wollastonite with a long fiber diameter, if the coating shear rate is increased, the long fibers may become entangled with each other, or the long fibers may get caught on the blade of the doctor blade. For this reason, it becomes a scattered orientation, and there exists a tendency for anisotropy to become low. On the other hand, when the coating shear rate is reduced, the long fibers do not become entangled with each other and do not get caught on the blade of the doctor blade, so that the orientation becomes easier and the anisotropy tends to increase.

<Separator for non-aqueous electrolyte secondary battery>

A separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention includes a polyolefin porous film.

In addition, the separator for nonaqueous electrolyte secondary batteries according to an embodiment of the present invention may further include other layers such as an adhesive layer, a heat-resistant layer, and a protective layer in addition to the polyolefin porous film.

<Polyolefin Polyolefin Film>

The nonaqueous electrolyte secondary battery in one embodiment of the present invention may include a polyolefin porous film. Hereinafter, a polyolefin porous film may be simply called a "porous film." The porous film has a polyolefin-based resin as a main component, has many pores connected therein, and allows gas and liquid to pass from one surface to the other. The porous film may be a separator for a non-aqueous electrolyte secondary battery alone. Moreover, it can become a porous base material in the laminated separator for nonaqueous electrolyte secondary batteries in which the above-mentioned porous layer was laminated|stacked.

A laminate in which the porous layer is laminated on at least one surface of the polyolefin porous film is also referred to as a “laminated separator for a non-aqueous electrolyte secondary battery” or a “laminated separator” in the present specification.

The proportion of the polyolefin in the porous film is 50% by volume or more of the entire porous film, more preferably 90% by volume or more, still more preferably 95% by volume or more. Further, it is more preferable that the polyolefin contains a high molecular weight component having a weight average molecular weight of 5×10 ⁵ to 15×10 ^{6 .} In particular, when the polyolefin contains a high molecular weight component having a weight average molecular weight of 1,000,000 or more, since the strength of the separator for nonaqueous electrolyte secondary batteries is improved, it is more preferable.

As said polyolefin which is a thermoplastic resin, the homopolymer or copolymer formed by superposing|polymerizing monomers, such as ethylene, propylene, 1-butene, 4-methyl-1- pentene, and 1-hexene, is specifically mentioned, for example. As said homopolymer, polyethylene, polypropylene, and polybutene are mentioned, for example. Moreover, as said copolymer, an ethylene-propylene copolymer is mentioned, for example.

Among these, since it can prevent the flow of an excessive current at a lower temperature, polyethylene is more preferable. In addition, preventing this excessive current from flowing is also called shutdown. Examples of the polyethylene include low-density polyethylene, high-density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), and ultra-high molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more. Among them, ultra-high molecular weight polyethylene having a weight average molecular weight of 1 million or more is more preferable.

It is preferable that the film thickness of a porous film is 4-40 micrometers, It is more preferable that it is 5-30 micrometers, It is still more preferable that it is 6-15 micrometers.

The weight per unit area of the porous film can be appropriately determined in consideration of strength, film thickness, weight, and handling properties. However, in order to increase the weight energy density and volume energy density of the non-aqueous electrolyte secondary battery, the weight per unit area ^{is preferably 4 to 20 g/m 2} , more preferably 4 to 12 g/m ² , and 5 to 10 g It is more preferably /m ^{2 .}

It is preferable that it is 30-500 sec/100 mL in Gurley value, and, as for the air permeability of a porous film, it is more preferable that it is 50-300 sec/100 mL. When a porous film has the said air permeability, sufficient ion permeability can be acquired. The air permeability of the laminated separator for nonaqueous electrolyte secondary batteries in which the above-mentioned porous layer is laminated on a porous film is preferably 30 to 1000 sec/100 mL, more preferably 50 to 800 sec/100 mL, in terms of Gurley value. When the laminated separator for nonaqueous electrolyte secondary batteries has the said air permeability, sufficient ion permeability can be acquired in a nonaqueous electrolyte secondary battery.

The porosity of the porous film is preferably 20 to 80% by volume, and preferably 30 to 75% by volume, so as to obtain a function of reliably preventing excessive current from flowing at a lower temperature while increasing the amount of holding of the electrolytic solution. more preferably. In addition, the pore diameter of the pores of the porous film is preferably 0.3 µm or less, more preferably 0.14 µm or less so that sufficient ion permeability can be obtained and the inflow of particles to the positive electrode plate and the negative electrode plate can be prevented. Do.

<Manufacturing method of polyolefin porous film>

The manufacturing method of the said polyolefin porous film is not specifically limited. For example, a sheet-shaped polyolefin resin composition is produced by extruding after kneading a polyolefin-based resin, an inorganic filler and a pore-forming agent such as a plasticizer, and optionally an antioxidant. A polyolefin porous film can be manufactured by removing the said pore former from the said sheet-like polyolefin resin composition with a suitable solvent, and then extending|stretching the polyolefin resin composition from which the said pore former was removed.

It does not specifically limit as said inorganic filler, An inorganic filler, specifically calcium carbonate, etc. are mentioned. It does not specifically limit as said plasticizer, Low molecular weight hydrocarbons, such as liquid paraffin, are mentioned.

Specifically, a method including a process as shown below is mentioned.

(A) a step of kneading ultra-high molecular weight polyethylene, low molecular weight polyethylene having a weight average molecular weight of 10,000 or less, a pore former such as calcium carbonate or a plasticizer, and an antioxidant to obtain a polyolefin resin composition;

(B) a step of rolling the obtained polyolefin resin composition with a pair of rolling rollers, cooling stepwise while pulling with a winding roller having a different speed ratio, and forming a sheet;

(C) removing the pore-forming agent from the obtained sheet with an appropriate solvent;

(D) A step of stretching the sheet from which the hole former has been removed at an appropriate draw ratio.

<Method for manufacturing a laminated separator for non-aqueous electrolyte secondary battery>

As the manufacturing method of the laminated separator for nonaqueous electrolyte secondary batteries in one embodiment of the present invention, for example, in the above-mentioned "Manufacturing method of a porous layer", the above-mentioned polyolefin porous film is used as the base material to which the coating solution is applied. how to use it.

<Non-aqueous electrolyte>

The non-aqueous electrolyte that may be included in the non-aqueous electrolyte secondary battery according to the embodiment of the present invention is not particularly limited as long as it is a non-aqueous electrolyte generally used in the non-aqueous electrolyte secondary battery. As the non-aqueous electrolyte, for example, a non-aqueous electrolyte obtained by dissolving a lithium salt in an organic solvent can be used. Examples of the lithium salt include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ , LiC(CF ₃ SO ₂ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , a lower aliphatic carboxylate lithium salt, and LiAlCl ₄ , and the like. As for the said lithium salt, only 1 type may be used and it may use it in combination of 2 or more type.

Examples of the organic solvent constituting the non-aqueous electrolyte include carbonates, ethers, esters, nitriles, amides, carbamates and sulfur-containing compounds, and fluorine-containing compounds obtained by introducing a fluorine group into these organic solvents. An organic solvent etc. are mentioned. As for the said organic solvent, only 1 type may be used and it may use it in combination of 2 or more types.

<Method for manufacturing non-aqueous electrolyte secondary battery>

As a method of manufacturing the nonaqueous electrolyte secondary battery according to one embodiment of the present invention, for example, the following method is mentioned. First, the positive electrode plate, the porous layer, the non-aqueous electrolyte secondary battery separator, and the negative electrode plate are arranged in this order to form a non-aqueous electrolyte secondary battery member. Thereafter, the non-aqueous electrolyte secondary battery member is placed in a container serving as a housing of the non-aqueous electrolyte secondary battery, and the container is then filled with the non-aqueous electrolyte, and sealed while depressurizing. Thereby, the non-aqueous electrolyte secondary battery according to an embodiment of the present invention can be manufactured.

As described above, the nonaqueous electrolyte secondary battery according to the embodiment of the present invention includes a separator for a nonaqueous electrolyte secondary battery comprising a polyolefin porous film, a porous layer, a positive electrode plate, and a negative electrode plate. In particular, the nonaqueous electrolyte secondary battery according to the embodiment of the present invention satisfies the requirements of (i) to (iii) below.

(i) In the porous layer, the value represented by the following formula (1) is in the range of 0.10 to 0.42.

|1-T/M|····(1)

(In formula (1), T represents the distance to the critical load in the scratch test under a constant load of 0.1N in TD, and M is the scratch test under a constant load of 0.1N in MD. In this case, the distance to the critical load is indicated.)

(ii) The number of times of bending of the positive electrode plate until the electrode active material layer is peeled is 130 or more. (iii) The number of times of bending of the negative electrode plate until the electrode active material layer is peeled is 1650 or more.

According to the requirement of (i), in the nonaqueous electrolyte secondary battery according to the embodiment of the present invention, the distribution of lithium ions in the porous layer is maintained uniformly because the porous layer has a uniform and dense structure. And, according to the requirements of (ii) and (iii), the whole electrode tends to follow the expansion and contraction of the active material isotropically. Therefore, the adhesiveness of the components contained in the inside of an electrode active material layer, and the adhesiveness of an electrode active material layer and an electrical power collector are maintained easily.

Therefore, in the non-aqueous electrolyte secondary battery satisfying the requirements of (i) to (iii), (a) the lithium ion permeability is good because the distribution of lithium ions in the porous layer is uniform, and (b) Since the above-mentioned adhesiveness is easily maintained, deterioration of the nonaqueous electrolyte secondary battery in the process of a charge/discharge cycle is suppressed. Therefore, it is thought that the discharge capacity recovery characteristic of the battery is improved even after the charge/discharge cycle (for example, after 100 cycles).

This invention is not limited to each embodiment mentioned above, Various changes are possible within the range shown in the claim, The embodiment obtained by combining the technical means disclosed in each other embodiment suitably is also included in the technical scope of this invention. .

Example

Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

[How to measure]

Each measurement in an Example and a comparative example was performed by the following method.

(1. Fracture resistance test)

A test piece having a length of 105 mm and a width of 15 mm was cut out from the positive electrode plate or the negative electrode plate obtained in the following Examples and Comparative Examples. According to the MIT test technique, a fold resistance test was performed using this test piece.

The bending resistance test was performed using an MIT type bending resistance tester (manufactured by Yasuda Seimitsu Kikai), in accordance with the MIT test technique stipulated in JIS P 8115 (1994), load: 1N, bending part R: 0.38 mm, bending speed 175 reciprocating/min. It was carried out by fixing one end of the test piece and bending it at an angle of 45 degrees from side to side.

Thereby, the number of bendings until the electrode active material layer was peeled from the positive electrode plate or the negative electrode plate was measured. The number of bendings here is the number of reciprocating bending displayed on the counter of the MIT type bending resistance tester.

(2. Scratch Test)

The T/M ratio of the critical load value and the distance to the critical load was measured in the scratch test shown below. Measurement conditions other than those described below were measured under the same conditions as those of JIS R 3255. In addition, the microscratch test apparatus (made by CSEM Instruments) was used as a measuring apparatus.

(1) A laminate obtained by laminating the porous layers prepared in Examples and Comparative Examples on a porous substrate was cut to a size of 20 mm x 60 mm. Thereafter, on the entire surface of the cut laminate on the separator side, that is, on the porous substrate side, arabic Yamato aqueous liquid paste (manufactured by Yamato Co., Ltd.) diluted 5 times with water was added to about ^{1.5 g/m 2 in weight per unit area.} It was applied thinly in a small amount. Next, the surface to which the aqueous liquid paste was applied was bonded onto a 30 mm x 70 mm glass preparat, and then dried at a temperature of 25°C for one day and one night to prepare a test sample. In addition, at the time of the said bonding, it was made so that a bubble did not flow in between the laminated body and the glass preparat.

(2) The test sample produced in the step (1) was installed in a microscratch testing apparatus (manufactured by CSEM Instruments). In the state in which a vertical load of 0.1 N magnitude was applied on the test sample with a diamond indenter (vertical angle of 120°, a cone with a tip radius of 0.2 mm) in the test apparatus, the table in the test apparatus, A distance of 10 mm was moved at a rate of 5 mm/min toward the TD of the laminate. In the meantime, the stress generated between the diamond indenter and the test sample, that is, frictional force was measured.

(3) A curve graph showing the relationship between the displacement of the stress measured in the step (2) and the moving distance of the table was prepared. The distance to the critical load value and critical load in TD was computed from the said curve graph.

(4) The moving direction of the table was changed to MD, and steps (1) to (3) described above were repeated to calculate the critical load value and the distance to the critical load in MD.

(3. Film thickness (unit: μm))

The thickness of the porous layer, the porous base material, the positive electrode active material layer, and the negative electrode active material layer was measured using a high-precision digital measuring instrument (VL-50) manufactured by Mitsutoyo Corporation. In addition, the thickness of the positive electrode active material layer is calculated by subtracting the thickness of the aluminum foil as the current collector from the thickness of the positive electrode plate, and the thickness of the negative electrode active material layer is calculated by subtracting the thickness of the copper foil as the current collector from the thickness of the negative electrode plate. calculated. In addition, the thickness of a porous layer was computed by subtracting the thickness of an uncoated part from the thickness of the coating part of each laminated body. In addition, a coating part points out the part in which the porous layer is formed, and an uncoated part points out the part in which a porous layer is not formed.

(4. Particle size distribution)

The volume-based particle size distribution of the filler was calculated by measuring D10, D50, and D90 using a laser diffraction particle size distribution meter SALD2200 manufactured by Shimadzu Corporation. Here, the particle diameter of the value used as 50% of the integrated distribution by volume basis, the particle diameter of the value used as 10%, and the particle diameter of the value used as 90% are referred to as D50, D10, and D90, respectively. In addition, D50 is also called a center particle diameter.

(5. Specific Surface Area)

The specific surface area of the filler was measured using BELSORP-mini (manufactured by Microtrac Bell Corporation). For the filler which vacuum-dried at the pretreatment temperature of 80 degreeC for 8 hours, the adsorption-desorption isotherm by nitrogen was measured using the regular use method, and it computed by the BET method. Various conditions in the dosage method are as follows: adsorption temperature; 77K, adsorbate; nitrogen, saturated vapor pressure; actual value, adsorbate cross-sectional area; 0.162 nm ² , equilibrium waiting time (waiting time after reaching an adsorption equilibrium state (a state in which the pressure change during adsorption/desorption becomes less than or equal to a predetermined value)); 500sec. In addition, the pore volume was computed by the MP method and the BJH method, and BELPREP-vacII (made by Microtrac Bell Corporation) was used as a pretreatment apparatus.

(6. Measurement of discharge recovery capacity after 100 cycles of charging and discharging)

<6-1. Initial charge/discharge>

For the new non-aqueous electrolyte secondary batteries prepared in Examples and Comparative Examples, which did not undergo a charge/discharge cycle, a voltage range of 2.7 to 4.1V, a charge current value of 0.2C, CC-CV charging (final current condition of 0.02C), Discharge current value: CC discharge of 0.2 C was set as 1 cycle, and initial charging/discharging of 4 cycles was performed at 25 degreeC. Here, 1C is a current value for discharging the rated capacity according to the discharge capacity at the rate of 1 hour in 1 hour. In addition, CC-CV charging is a charging method in which charging is performed at a set constant current, and after reaching a predetermined voltage, the current is reduced while maintaining the voltage. In addition, CC discharge is a method of discharging from a set constant current to a predetermined voltage. The meaning of these terms is the same in this specification.

<6-2. Cycle Test>

A non-aqueous electrolyte secondary battery after initial charging and discharging, voltage range: 2.7 to 4.2V, charging current value: 1C CC-CV charging (final current condition: 0.02C), discharging current value: 10C CC discharging as one cycle, 100 Charging and discharging of the cycle was performed at 55°C.

<6-3. Discharge recovery capacity test after 100 cycles of charging and discharging>

For a non-aqueous electrolyte secondary battery subjected to 100 cycles of charging and discharging, voltage range: 2.7V to 4.2V, charging current value: CC-CV charging at 1C (final current condition: 0.02C), discharging current value: CC discharge at 0.2C was set as 1 cycle, and 3 cycles of charging and discharging were performed at 55°C. The discharge capacity of the 3rd cycle was made into the discharge recovery capacity. In Table 1 mentioned later, the said discharge recovery capacity is shown as "discharge recovery capacity after 100 cycles".

The discharge recovery capacity test is a test method that discharges at a low rate (0.2 C) after 100 charge/discharge cycles, and more accurately checks the discharge capacity, and the degree of deterioration of the discharge performance of the entire battery, particularly the discharge of the electrode You can check the degree of degradation of performance.

[Example 1]

[Production of porous layer and laminate]

(Porous substrate (layer A))

A porous substrate was prepared using polyethylene, which is a polyolefin.

That is, 70 parts by weight of ultra-high molecular weight polyethylene powder (340M, manufactured by Mitsui Chemicals Co., Ltd.) and 30 parts by weight of polyethylene wax having a weight average molecular weight of 1000 (FNP-0115, manufactured by Nippon Seiro Co., Ltd.) were mixed to obtain mixed polyethylene. got it With respect to 100 parts by weight of the obtained mixed polyethylene, an antioxidant (Irg1010, manufactured by Ciba Specialty Chemicals) 0.4 parts by weight, an antioxidant (P168, manufactured by Ciba Specialty Chemicals, Ltd.) 0.1 parts by weight and stear 1.3 parts by weight of sodium acid was added, and calcium carbonate (manufactured by Maruo Calcium, Ltd.) having an average particle diameter of 0.1 µm was added so that the proportion to the total volume was 38 vol%. After mixing this composition with a Henschel mixer with a powder state, the polyethylene resin composition was obtained by melt-kneading with a twin-screw kneader. Next, this polyethylene resin composition was rolled as a pair of rolls whose surface temperature was set to 150 degreeC, and the sheet|seat was produced. Calcium carbonate was dissolved and removed by immersing this sheet in the hydrochloric acid aqueous solution prepared by mix|blending 0.5 weight% of nonionic surfactant with 4 mol/L hydrochloric acid. Then, the sheet|seat was extended|stretched 6 times at 105 degreeC, and the polyethylene porous base material (layer A) was produced. The porous substrate had a porosity of 53%, a weight per unit area of 7 g/m ² , and a thickness of 16 µm.

(Porous layer (B layer))

(Preparation of coating solution)

As the inorganic filler 1, hexagonal plate-shaped zinc oxide having an oxygen atomic mass percentage of 20% (manufactured by Sakai Chemical Co., Ltd., trade name: XZ-100F) was used. D50, D10, and D90 of the inorganic filler 1 were 0.4 µm, 0.2 µm, and 2.1 µm, respectively. In addition, the BET specific surface area per unit area of the inorganic filler 1 was 7.3 m ² /g.

As the binder resin, a vinylidene fluoride-hexafluoropropylene copolymer (Arkema Corporation: trade name "KYNAR2801") was used.

The inorganic filler, vinylidene fluoride-hexafluoropropylene copolymer and solvent (N-methyl-2-pyrrolidinone manufactured by Kanto Chemical Co., Ltd.) were mixed in the following ratio. That is, 10 parts by weight of the vinylidene fluoride-hexafluoropropylene copolymer is mixed with respect to 90 parts by weight of the inorganic filler, and the concentration of solid content (inorganic filler and vinylidene fluoride-hexafluoropropylene copolymer) in the resulting mixed solution. The solvent was mixed so that it became 37 wt%. The obtained liquid mixture was stirred and mixed with a thin film swirl type high-speed mixer (Primix Co., Ltd. Filmic (registered trademark)) to obtain a uniform coating liquid 1.

(Manufacture of porous layer and laminated body)

The obtained coating solution 1 was coated on one side of the layer A by a doctor blade method at a coating shear rate of 3.9 (1/s) to form a coating film on one side of the layer A. Then, the B layer was formed on the single side|surface of the said A layer by drying the said coating film over 20 minutes at 65 degreeC. Thereby, the laminated body 1 (laminated separator) in which the B layer was laminated|stacked on the single side|surface of the A-layer was obtained. The weight per unit area of the layer B was 7 g/m ² , and the thickness was 4 μm.

[Production of non-aqueous electrolyte secondary battery]

(positive plate)

A positive electrode plate in which a positive electrode mixture of LiNi _0.5 Mn _0.3 Co _0.2 O ₂ /conductive agent/PVDF (weight ratio: 92/5/3) was laminated on one side of a positive electrode current collector (aluminum foil) was obtained. A restraining pressure (0.7 MPa) was applied to this positive plate at room temperature for 30 seconds.

The positive electrode plate was cut so that the portion on which the positive electrode active material layer was laminated had a size of 45 mm × 30 mm, and a portion where the positive electrode active material layer was not laminated with a width of 13 mm on the outer periphery remained to obtain a positive electrode plate 1. The thickness of the positive electrode active material layer was 38 µm.

(negative plate)

A negative electrode mixture of natural graphite/styrene-1,3-butadiene copolymer/sodium carboxymethylcellulose (weight ratio 98/1/1) having an average particle diameter (D50) of 15 μm on a volume basis is used as the negative electrode current collector (copper foil). A negative electrode plate laminated on one side was obtained. A restraining pressure (0.7 MPa) was applied to the negative electrode plate at room temperature for 30 seconds.

Negative electrode plate 1 was obtained by cutting the negative electrode plate so that the portion on which the negative electrode active material layer was laminated had a size of 50 mm x 35 mm, and the outer periphery had a width of 13 mm to leave a portion where the negative electrode active material layer was not laminated. The thickness of the negative electrode active material layer was 38 µm.

(Production of non-aqueous electrolyte secondary battery)

Using the positive electrode plate 1, the negative electrode plate 1, and the laminate 1, a non-aqueous electrolyte secondary battery was manufactured by the method shown below.

Member 1 for nonaqueous electrolyte secondary batteries was obtained by laminating|stacking (arranging) the said positive electrode plate 1, the laminated body 1, and the negative electrode plate 1 in this order in a laminated pouch. At this time, the positive electrode plate 1 and the negative electrode plate 1 were arranged such that the entire main surface of the positive electrode active material layer of the positive electrode plate 1 was included in the range of the main surface of the negative electrode active material layer of the negative electrode plate 1. That is, the positive electrode plate 1 and the negative electrode plate 1 were arranged such that the entire main surface of the positive electrode active material layer of the positive electrode plate 1 overlaps the main surface of the negative electrode active material layer of the negative electrode plate 1. Moreover, the surface of the porous layer side of the laminated body 1 was made to face the positive electrode active material layer of the positive electrode plate 1.

Next, the non-aqueous electrolyte secondary battery member 1 was placed in a previously prepared bag in which an aluminum layer and a heat-sealing layer were laminated, and 0.23 mL of the non-aqueous electrolyte was placed in the bag. The non-aqueous electrolyte is prepared by dissolving ethylene carbonate, ethylmethyl carbonate, and diethyl carbonate in a mixed solvent obtained by mixing 3:5:2 (volume ratio) so that _{the concentration of LiPF 6} is 1 mol/L. prepared. And the nonaqueous electrolyte secondary battery 1 was produced by heat-sealing the said bag while depressurizing the inside of a bag.

Thereafter, the battery characteristics of the non-aqueous electrolyte secondary battery 1 obtained by the method described above were measured. The results are shown in Table 1.

[Example 2]

[Production of porous layer and laminate]

As the inorganic filler 2, a mixture of spherical alumina (manufactured by Sumitomo Chemical Co., Ltd., trade name: AA03) and mica (manufactured by Wako Pure Chemical Industries, Ltd., trade name: non-swellable synthetic mica) was used. The mixture was prepared by mixing 50 parts by weight of spherical alumina and 50 parts by weight of mica in a mortar. The oxygen atomic mass percentage of the inorganic filler 2 was 45%. In addition, D50, D10, and D90 of the inorganic filler 2 were 4.2 micrometers, 0.5 micrometers, and 11.5 micrometers, respectively. In addition, the BET specific surface area per unit area of the inorganic filler 2 was 4.5 m ² /g.

The coating liquid was produced as follows. That is, while mixing 10 parts by weight of the vinylidene fluoride-hexafluoropropylene copolymer with respect to 90 parts by weight of the inorganic filler, the concentration of the solid content (inorganic filler + vinylidene fluoride-hexafluoropropylene copolymer) in the resulting mixed solution The solvent was mixed so that it became 30 wt%. The obtained mixed solution was stirred and mixed with a thin film swirl type high-speed mixer to obtain a uniform coating solution 2.

Inorganic filler 1 used for the production of the porous layer (layer B) was changed to the inorganic filler 2, the coating solution 1 was changed to the coating solution 2, and the coating shear rate was changed to 7.9 (1/s), It carried out similarly to Example 1, and obtained the laminated body 2.

[Production of non-aqueous electrolyte secondary battery]

A non-aqueous electrolyte secondary battery 2 was obtained in the same manner as in Example 1 except that the laminate 2 was used instead of the laminate 1.

Then, the battery characteristics of the nonaqueous electrolyte secondary battery 2 obtained by the above-mentioned method were measured. The results are shown in Table 1.

[Example 3]

[Production of porous layer and laminate]

As the inorganic filler 3, wollastonite having an oxygen atomic mass percentage of 42% (manufactured by Hayashi Kasei Co., Ltd., trade name: Wollastonite VM-8N) was used. D50, D10, and D90 of the inorganic filler 3 were 10.6 micrometers, 2.4 micrometers, and 25.3 micrometers, respectively. In addition, the BET specific surface area per unit area of the inorganic filler 3 was 1.3 m ² /g.

The coating liquid was produced as follows. That is, while mixing 10 parts by weight of the vinylidene fluoride-hexafluoropropylene copolymer with respect to 90 parts by weight of the inorganic filler, the concentration of the solid content (inorganic filler + vinylidene fluoride-hexafluoropropylene copolymer) in the resulting mixed solution The solvent was mixed so that it became 40 wt%. The obtained mixed solution was stirred and mixed with a thin film swirl type high-speed mixer to obtain a uniform coating solution 3.

Inorganic filler 1 used for the production of the porous layer (layer B) was changed to the inorganic filler 3, the coating solution 1 was changed to the coating solution 3, and the coating shear rate was changed to 7.9 (1/s), except that It carried out similarly to Example 1, and obtained the laminated body 3.

[Production of non-aqueous electrolyte secondary battery]

A non-aqueous electrolyte secondary battery 3 was obtained in the same manner as in Example 1 except that the laminate 3 was used instead of the laminate 1.

Thereafter, the battery characteristics of the non-aqueous electrolyte secondary battery 3 obtained by the method described above were measured. The results are shown in Table 1.

[Example 4]

[Production of porous layer and laminate]

As the inorganic filler 4, a mixture of α-alumina (manufactured by Sumitomo Chemical Co., Ltd., trade name: AKP3000) and hexagonal plate-shaped zinc oxide (manufactured by Sakai Chemical Co., Ltd., trade name: XZ-1000F) was used. The mixture was prepared by mixing 99 parts by weight of α alumina and 1 part by weight of hexagonal plate-shaped zinc oxide in a mortar. The oxygen atomic mass percentage of the inorganic filler 4 was 47%. In addition, D50, D10, and D90 of the inorganic filler 4 were 0.8 micrometer, 0.4 micrometer, and 2.2 micrometer, respectively. In addition, the BET specific surface area per unit area of the inorganic filler 4 was 4.5 m ² /g.

The coating liquid was produced as follows. That is, while mixing 10 parts by weight of the vinylidene fluoride-hexafluoropropylene copolymer with respect to 90 parts by weight of the inorganic filler, the concentration of the solid content (inorganic filler + vinylidene fluoride-hexafluoropropylene copolymer) in the resulting mixed solution The solvent was mixed so that it became 40 wt%. The obtained mixed solution was stirred and mixed with a thin film swirl type high-speed mixer to obtain a uniform coating solution 4.

Inorganic filler 1 used for the production of the porous layer (layer B) was changed to the inorganic filler 4, the coating solution 1 was changed to the coating solution 4, and the coating shear rate was changed to 39.4 (1/s), except that It carried out similarly to Example 1, and obtained the laminated body 4.

(positive plate)

A positive electrode plate in which a positive electrode mixture of LiNi _0.5 Mn _0.3 Co _0.2 O ₂ /conductive agent/PVDF (weight ratio: 92/5/3) was laminated on one side of a positive electrode current collector (aluminum foil) was obtained. While the positive electrode plate was wetted with diethyl carbonate, a restraining pressure (0.7 MPa) was applied at room temperature for 30 seconds.

A positive electrode plate 2 was obtained by cutting the positive electrode plate so that the portion where the positive electrode active material layer was laminated had a size of 45 mm × 30 mm, and a portion where the positive electrode active material layer was not laminated was left with a width of 13 mm on the outer periphery. The thickness of the positive electrode active material layer was 37 µm.

[Production of non-aqueous electrolyte secondary battery]

A non-aqueous electrolyte secondary battery 4 was obtained in the same manner as in Example 1 except that the laminate 4 was used instead of the laminate 1 and the positive electrode plate 2 was used as the positive electrode plate.

Then, the battery characteristics of the nonaqueous electrolyte secondary battery 4 obtained by the above-mentioned method were measured. The results are shown in Table 1.

[Example 5]

(positive plate)

A positive electrode plate in which a positive electrode mixture (LiCoO ₂ /conductive agent/PVDF (weight ratio: 100/5/3)) was laminated on one side of a positive electrode current collector (aluminum foil) was obtained. While the positive electrode plate was wetted with diethyl carbonate, a restraining pressure (0.7 MPa) was applied at room temperature for 30 seconds.

A positive electrode plate 3 was obtained by cutting the positive electrode plate so that the portion on which the positive electrode active material layer was laminated had a size of 45 mm × 30 mm, and a portion where the positive electrode active material layer was not laminated was left with a width of 13 mm on the outer periphery. The thickness of the positive electrode active material layer was 38 µm.

[Production of non-aqueous electrolyte secondary battery]

A non-aqueous electrolyte secondary battery 5 was obtained in the same manner as in Example 1 except that the laminate 4 was used instead of the laminate 1 and the positive electrode plate 3 was used as the positive electrode plate.

Thereafter, the battery characteristics of the non-aqueous electrolyte secondary battery 5 obtained by the method described above were measured. The results are shown in Table 1.

[Example 6]

(negative plate)

A negative electrode mixture in which a negative electrode mixture of natural graphite/styrene-1,3-butadiene copolymer/carboxymethylcellulose sodium (weight ratio 98/1/1) was laminated on one side of a negative electrode current collector (copper foil) was obtained. The negative electrode plate was wetted with diethyl carbonate, and a restraining pressure (0.7 MPa) was applied at room temperature for 30 seconds.

Negative electrode plate 2 was obtained by cutting the negative electrode plate so that the portion on which the negative electrode active material layer was laminated had a size of 50 mm × 35 mm, and a portion where the negative electrode active material layer was not laminated was left with a width of 13 mm on the outer periphery. The thickness of the negative electrode active material layer was 37 µm.

[Production of non-aqueous electrolyte secondary battery]

A non-aqueous electrolyte secondary battery 6 was obtained in the same manner as in Example 1 except that the laminate 4 was used instead of the laminate 1 and the negative electrode plate 2 was used as the negative electrode plate.

Then, the battery characteristics of the nonaqueous electrolyte secondary battery 6 obtained by the above-mentioned method were measured. The results are shown in Table 1.

[Example 7]

(negative plate)

A negative electrode plate in which a negative electrode mixture of artificial spheroidal graphite/conductive agent/PVDF (weight ratio 85/15/7.5) was laminated on one side of a negative electrode current collector (copper foil) was obtained. While this negative electrode plate was wetted with diethyl carbonate, a restraining pressure (0.7 MPa) was applied at room temperature for 30 seconds.

Negative electrode plate 3 was obtained by cutting the negative electrode plate so that the portion on which the negative electrode active material layer was laminated had a size of 50 mm × 35 mm, and the outer periphery had a width of 13 mm to leave a portion where the negative electrode active material layer was not laminated. The thickness of the negative electrode active material layer was 36 µm.

[Production of non-aqueous electrolyte secondary battery]

A non-aqueous electrolyte secondary battery 7 was obtained in the same manner as in Example 1 except that the laminate 4 was used instead of the laminate 1 and the negative electrode plate 3 was used as the negative electrode plate.

Thereafter, the battery characteristics of the non-aqueous electrolyte secondary battery 7 obtained by the method described above were measured. The results are shown in Table 1.

[Comparative Example 1]

[Production of porous layer and laminate]

As the inorganic filler 5, borax (manufactured by Wako Pure Chemical Industries, Ltd.) having an oxygen atomic mass percentage of 71% was used. D50, D10, and D90 of the inorganic filler 5 were 27 µm, 6.3 µm, and 111 µm, respectively. In addition, the BET specific surface area per unit area of the inorganic filler 5 was 2.5 m ² /g.

The coating liquid was produced as follows. That is, while mixing 10 parts by weight of the vinylidene fluoride-hexafluoropropylene copolymer with respect to 90 parts by weight of the inorganic filler, the concentration of the solid content (inorganic filler + vinylidene fluoride-hexafluoropropylene copolymer) in the resulting mixed solution The solvent was mixed so that it became 40 wt%. The obtained mixed solution was stirred and mixed with a thin film swirl type high-speed mixer to obtain a uniform coating solution 5.

Inorganic filler 1 used for the production of the porous layer (layer B) was changed to the inorganic filler 5, the coating solution 1 was changed to the coating solution 5, and the coating shear rate was changed to 7.9 (1/s), It carried out similarly to Example 1, and obtained the laminated body 5.

[Production of non-aqueous electrolyte secondary battery]

A non-aqueous electrolyte secondary battery 8 was obtained in the same manner as in Example 1 except that the laminate 5 was used instead of the laminate 1.

Then, the battery characteristics of the nonaqueous electrolyte secondary battery 8 obtained by the above-mentioned method were measured. The results are shown in Table 1.

[Comparative Example 2]

(positive plate)

A positive electrode plate in which a positive electrode mixture of LiNi _0.5 Mn _0.3 Co _0.2 O ₂ /conductive agent/PVDF (weight ratio: 92/5/3) was laminated on one side of a positive electrode current collector (aluminum foil) was obtained.

The positive electrode plate was cut so that the portion on which the positive electrode active material layer was laminated had a size of 45 mm × 30 mm, and had a width of 13 mm on the outer periphery to leave a portion on which the positive electrode active material layer was not laminated, so that the positive electrode plate 4 was obtained. The thickness of the positive electrode active material layer was 38 µm.

[Production of non-aqueous electrolyte secondary battery]

A non-aqueous electrolyte secondary battery 9 was obtained in the same manner as in Example 1 except that the laminate 4 was used instead of the laminate 1 and the positive electrode plate 4 was used as the positive electrode plate.

Then, the battery characteristics of the nonaqueous electrolyte secondary battery 9 obtained by the above-mentioned method were measured. The results are shown in Table 1.

[Comparative Example 3]

(negative plate)

A negative electrode mixture in which a negative electrode mixture of natural graphite/styrene-1,3-butadiene copolymer/carboxymethylcellulose sodium (weight ratio 98/1/1) was laminated on one side of a negative electrode current collector (copper foil) was obtained.

The negative electrode plate was cut so that the portion on which the negative electrode active material layer was laminated had a size of 50 mm × 35 mm, and the width was 13 mm on the outer periphery to leave a portion where the negative electrode active material layer was not laminated, so that the negative electrode plate 4 was obtained. The thickness of the negative electrode active material layer was 38 µm.

[Production of non-aqueous electrolyte secondary battery]

A non-aqueous electrolyte secondary battery 10 was obtained in the same manner as in Example 1 except that the laminate 4 was used instead of the laminate 1 and the negative electrode plate 4 was used as the negative electrode plate.

Then, the battery characteristics of the nonaqueous electrolyte secondary battery 10 obtained by the above-mentioned method were measured. The results are shown in Table 1.

In addition, in Table 1, in Examples 2 and 4-7, and the "inorganic filler" column of Comparative Examples 2-3, two types of compounds and numerical value are described. The numerical value represents parts by weight of the compound. For example, in Example 2, it _{is described as "Al 2} O ₃ /mica 50/50", _{which indicates that 50 parts by weight of Al 2} O ₃ and 50 parts by weight of mica were used.

[conclusion]

As shown in Table 1, it was found that the nonaqueous electrolyte secondary batteries of Examples 1 to 7 had excellent discharge capacity recovery characteristics after charge and discharge cycles compared to the nonaqueous electrolyte secondary batteries of Comparative Examples 1 to 3. In the nonaqueous electrolyte secondary batteries of Examples 1 to 7, the number of bendings until the electrode active material layer of the positive electrode plate is peeled off is 130 or more, and the number of bending until the electrode active material layer of the negative electrode plate is peeled is 1650 times or more and the value expressed by |1-T/M| of the porous layer is in the range of 0.10 to 0.42. On the other hand, in Comparative Example 1, |1-T/M| exceeds 0.42. In Comparative Example 2, the number of times of bending until the electrode active material layer of the positive electrode plate is peeled off is less than 130 times. In Comparative Example 3, the number of bendings until the electrode active material layer of the negative electrode plate was peeled off was less than 1650 times.

Since the non-aqueous electrolyte secondary battery according to the embodiment of the present invention has excellent discharge capacity recovery characteristics after a charge/discharge cycle, it is suitably used as a battery for use in personal computers, mobile phones, portable information terminals, etc., and as an on-vehicle battery. can

1: diamond indenter
2: Substrate
3: Laminate

Claims (5)

A porous layer comprising an inorganic filler and a resin;
In accordance with the MIT test technique stipulated in JIS P 8115 (1994), in the bending resistance test conducted at a load of 1N and a bending angle of 45°, the positive electrode plate in which the number of bending until the electrode active material layer is peeled off is 130 or more;
In the bending resistance test, the number of bending until the electrode active material layer is peeled is provided with a negative electrode plate of 1650 times or more,
The porous layer is a non-aqueous electrolyte secondary battery having a value represented by the following formula (1) in the range of 0.10 to 0.42.
|1-T/M|····(1)
(In formula (1), T represents the distance to the critical load in the scratch test under a constant load of 0.1 N in TD, and M is the scratch test under a constant load of 0.1 N in MD. In this case, the distance to the critical load is indicated.) The non-water according to claim 1, wherein the porous layer contains at least one resin selected from the group consisting of polyolefin, (meth)acrylate-based resin, fluorine-containing resin, polyamide-based resin, polyester-based resin, and water-soluble polymer. electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to claim 2, wherein the polyamide-based resin is an aramid resin. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the porous layer is laminated on one or both surfaces of the polyolefin porous film. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the positive electrode plate contains a transition metal oxide, and the negative electrode plate contains graphite.

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