KR102538460B1 - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

An object of the present invention is to provide a non-aqueous electrolyte secondary battery having excellent charge capacity after high-rate discharge. A non-aqueous electrolyte secondary battery according to one aspect of the present invention includes a porous layer containing an inorganic filler and a resin, and positive and negative electrode plates having a capacitance per 900 mm 2 of measurement area in a predetermined range, and the surface of the porous layer The aspect ratio of the projected image of the inorganic filler and the peak intensity ratio (I _(hkl) /I _(abc) ) of orthogonal arbitrary diffraction surfaces (hkl) and (abc) when measured by the wide-angle X-ray diffraction method are determined are in range

Description

Non-aqueous electrolyte secondary battery

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

Since non-aqueous electrolyte secondary batteries, particularly lithium ion secondary batteries, have high energy density, they are widely used as batteries used in personal computers, mobile phones, personal digital assistants, etc., and are recently being developed as in-vehicle batteries.

As a non-aqueous electrolyte secondary battery, for example, a separator for non-aqueous secondary batteries in which a porous layer containing a plate-shaped inorganic filler as described in Patent Document 1 and having a porosity of 60 to 90% is laminated on at least one side of a porous substrate. A non-aqueous electrolyte secondary battery having a is known.

Japanese Unexamined Patent Publication No. 2010-108753

However, the prior art as described above has room for improvement in terms of charge capacity after high-rate discharge.

The present invention has been made in view of the above problems, and its object is to realize a non-aqueous electrolyte secondary battery having excellent charge capacity after high-rate discharge.

A non-aqueous electrolyte secondary battery according to aspect 1 of the present invention includes a porous layer containing an inorganic filler and a resin, a positive electrode plate having a capacitance per 900 mm2 of measurement area of 1 nF or more and 1000 nF or less, and capacitance per 900 mm2 of measurement area. Equipped with a negative electrode plate of 4 nF or more and 8500 nF or less, the aspect ratio of the projected image of the inorganic filler on the surface of the porous layer is in the range of 1.4 to 4.0, and the porous layer is measured by wide-angle X-ray diffraction. , peak intensities of arbitrary diffraction surfaces (hkl) and (abc) orthogonal to each other, I _(hkl) and I _(abc) satisfy the following formula (1), and the peak intensity ratio calculated by the following formula (2) The range of the maximum value is the range of 1.5 to 300.

I _(hkl) >I _(abc) … (One),

I _(hkl) /I _(abc) … (2).

Further, in the nonaqueous electrolyte secondary battery according to aspect 2 of the present invention, in the aspect 1, the porous layer is a polyolefin, a (meth)acrylate-based resin, a fluorine-containing resin, a polyamide-based resin, or a polyester-based resin and at least one resin selected from the group consisting of water-soluble polymers.

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 non-aqueous electrolyte secondary battery according to aspect 4 of the present invention, in any one of aspects 1 to 3, the porous layer is laminated on one side or both sides of a polyolefin porous film.

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

The non-aqueous electrolyte secondary battery according to one embodiment of the present invention is excellent in charge capacity after high-rate discharge of the battery.

1 is a schematic diagram showing the structure of a porous layer containing an inorganic filler, when the orientation of the inorganic filler is large (left drawing) and when the orientation of the inorganic filler is small (right drawing).
2 is a schematic view showing a projected image of an inorganic filler on the surface of a porous layer in one embodiment of the present invention.
3 is a schematic diagram showing a measurement target electrode, which is a measurement target of capacitance, in an embodiment of the present application.
4 is a schematic diagram showing a probe electrode used for measuring capacitance in an embodiment of the present application.

One embodiment of the present invention is described below, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various changes are possible within the scope indicated in the claims, and the technical scope of the present invention also applies to embodiments obtained by appropriately combining technical means disclosed in other embodiments. included in In addition, unless otherwise specified in this specification, “A to B” representing 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 described later, a positive electrode plate and a negative electrode plate described later. In addition, the non-aqueous electrolyte secondary battery according to one embodiment of the present invention may further include a polyolefin porous film described later.

Members constituting the non-aqueous electrolyte secondary battery according to one embodiment of the present invention will be described in detail below.

[Porous layer]

The porous layer in one embodiment of the present invention is a porous layer containing an inorganic filler and a resin, and a projection image of the inorganic filler on the surface of the porous layer (hereinafter sometimes referred to as "the surface of the porous layer") The aspect ratio of is in the range of 1.4 to 4.0, and the peak intensities I (hkl) and I of arbitrary diffraction surfaces (hkl) and (abc ₎ orthogonal to each other, measured by wide-angle X-ray diffraction, of the porous layer _(abc) satisfies the following formula (1), and the range of the maximum value of the peak intensity ratio calculated by the following formula (2) is the range of 1.5 to 300.

I _(hkl) >I _(abc) … (One),

I _(hkl) /I _(abc) … (2).

In one embodiment of the present invention, the porous layer, as a member constituting the non-aqueous electrolyte secondary battery, may be disposed between a 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 one of the positive electrode plate and the negative electrode plate so as to be in contact with them. The porous layer disposed between the polyolefin porous film and at least either one of the positive electrode plate and the negative electrode plate may be one layer or two or more layers. It is preferable that a porous layer is an insulating porous layer containing resin.

When the porous layer is laminated on one side of the polyolefin porous film, the porous layer is preferably laminated on the surface facing the positive electrode plate in the polyolefin porous film. More preferably, the porous layer is laminated on a surface in contact with the positive electrode plate.

The above-mentioned "aspect ratio of the projected image of the inorganic filler on the surface of the porous layer" and the above-mentioned "maximum value of the peak intensity ratio calculated by formula (2)" are all indexes indicating the orientation of the inorganic filler in the porous layer. am. Here, the schematic diagram of the aspect of the inorganic filler in the porous layer when the said orientation is high and the said orientation is low is shown in FIG. The left figure of FIG. 1 is a schematic diagram showing the structure of the porous layer containing inorganic fillers when the orientation of the fillers is large and the anisotropy is high, and the right figure of FIG. 1 is the orientation of the inorganic fillers. It is a schematic diagram showing the structure of the said porous layer in case this is small and anisotropy is low.

The porous layer in one embodiment of the present invention contains an inorganic filler and a resin. The porous layer is a layer that has a large number of pores inside and has a structure in which these pores are connected, allowing gas or liquid to pass from one side to the other side. In addition, when the porous layer in one embodiment of the present invention is used as a member constituting a multilayer separator for non-aqueous electrolyte secondary batteries described later, the porous layer is an electrode plate as the outermost layer of the multilayer separator for non-aqueous electrolyte secondary batteries It can be a layer in contact with

It is preferable that the resin contained in the porous layer in one embodiment of the present invention is insoluble in the electrolyte solution of the battery and is electrochemically stable within the usage range of the battery. As said resin, it is polyolefin, for example specifically,; (meth)acrylate-based resins; fluorine-containing resins; 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 resins described above, polyolefins, (meth)acrylate-based resins, fluorine-containing resins, polyamide-based resins, polyester-based resins, and water-soluble polymers are preferable.

As the polyolefin, polyethylene, polypropylene, polybutene, ethylene-propylene copolymer and the like are preferable.

As the fluorine-containing resin, 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 above fluorine-containing resins, fluorine-containing rubbers having a glass transition temperature of 23°C or lower are exemplified.

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), para A phenylene terephthalamide/2,6-dichloroparaphenylene terephthalamide copolymer, a metaphenylene terephthalamide/2,6-dichloroparaphenylene terephthalamide copolymer, etc. are mentioned. Among these, poly(paraphenylene terephthalamide) is more preferable.

As the polyester-based resin, aromatic polyesters such as polyarylates and liquid crystal polyesters are preferable.

Examples of rubbers include styrene-butadiene copolymers and hydrides thereof, methacrylic acid ester copolymers, acrylonitrile-acrylic acid ester copolymers, styrene-acrylic acid ester copolymers, ethylene propylene rubber, and polyvinyl acetate.

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

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

In addition, one type of resin contained in the porous layer in one Embodiment of this invention may be sufficient as it, and a resin mixture of 2 or more types may be sufficient as it.

Among the above resins, when the porous layer is disposed facing 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 degradation occurs during battery operation, so fluorine-containing resins is preferable

The porous layer in one embodiment of the present invention contains an inorganic filler. The lower limit of its content is preferably 50% by weight or more, more preferably 70% by weight or more, and more preferably 90% by weight or more with respect to the total weight of the filler and the resin constituting the porous layer in one embodiment of the present invention. it 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 a porous layer in one Embodiment of this invention, it is more preferable that it is 98 weight% or less. It is preferable from a viewpoint of heat resistance that content of the said filler is 50 weight% or more, and it is preferable from an adhesive viewpoint between fillers that content of the said filler is 99 weight% or less. By containing an inorganic filler, the slipperiness|lubricacy 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 battery safety, 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 aluminum element, zinc element, calcium element, zirconium element, silicon element, magnesium element, barium element and boron element, preferably Preferably, it is an inorganic material containing an aluminum element. In addition, the inorganic filler preferably contains an oxide of the above element.

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

It is preferable that the inorganic filler in the porous layer in one embodiment of the present invention contains 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 above elements.

The volume average particle diameter of the inorganic filler is preferably in the range of 0.01 µm to 10 µm from the viewpoint of ensuring good adhesion and sliding properties and moldability of the laminate. As the lower limit, 0.05 μm or more is more preferable, and 0.1 μm or more is still more preferable. As its upper limit, 5 micrometers or less is more preferable, and 1 micrometer or less is still more preferable.

The shape of the inorganic filler is arbitrary and is not particularly limited. The shape of the inorganic filler may be particulate, for example, spherical; oval shape; platy; rod shape; irregular shape; fibrous; It may be any of; shape in which spherical or columnar single particles are heat-sealed, such as a peanut shape and/or a tetrapod shape. From the viewpoint of preventing a short circuit of the battery, the inorganic filler is preferably plate-shaped particles and/or non-aggregated primary particles. In addition, from the viewpoint of ion permeation, the shape of the inorganic filler is a dendrite or coral-like shape in which the particles in the porous body are difficult to be closely packed and voids are easily formed between the particles, and have lumps, concave portions, constrictions, ridges or swelling. , or indefinite shapes such as clusters; fibrous; It is preferable to have a shape in which single particles are heat-sealed, such as a peanut shape and/or a tetrapod shape. The shape of the inorganic filler is particularly more preferably a shape in which spherical or columnar single particles such as a peanut shape and/or a tetrapod shape are heat-sealed.

The filler can improve the slipperiness by forming fine irregularities on the surface of the porous layer. When the filler is plate-shaped particles and/or non-aggregated primary particles, the filler is formed on the surface of the porous layer. The irregularities to be formed become finer, and the adhesion between the porous layer and the electrode plate becomes better.

The oxygen atomic mass percentage of the oxide of the element constituting the inorganic filler contained in the porous layer in one embodiment of the present invention is preferably 10% to 50%, and more preferably 20% to 50%. do. In this specification, "oxygen atom mass percentage" means the mass ratio of oxygen atoms in the oxide to the total mass of the entire oxide of the element expressed as a percentage. For example, in the case of zinc oxide, from the atomic weight of zinc: 65.4, the atomic weight of oxygen: 16.0, since the molecular weight of zinc oxide (ZnO) is 65.4+16.0=81.4, the atomic mass percentage of oxygen in zinc oxide is 16.0/81.4× 100 = 20 (%).

When the oxygen atomic mass percentage of the oxide of the element is in the above-mentioned range, affinity between the solvent or dispersion medium in the coating solution used in the method for producing a porous layer described later and the inorganic filler is suitably maintained, and the inorganic filler is separated. You can keep it at an appropriate distance. This makes it possible to improve the dispersibility of the coating solution, and as a result, the "aspect ratio of the projected image of the inorganic filler on the surface of the porous layer" and the "orientation degree of the porous layer" can be controlled within an appropriate stipulated range. .

The aspect ratio of the inorganic filler itself included in the porous layer in one embodiment of the present invention is in the thickness direction in a SEM image observed from vertically above the arrangement surface in a state where the inorganic filler is disposed on a plane. It is expressed as the average value of the ratio of the length of the minor axis to the length of the major axis of 100 non-overlapping particles. In addition, in this specification, the length of a major axis is also called a major axis diameter, and the length of a minor axis is also called a minor axis diameter. The aspect ratio of the inorganic filler itself is preferably 1 to 10, more preferably 1.1 to 8, still more preferably 1.2 to 5. When the aspect ratio of the inorganic filler itself is in the above-mentioned range, when the porous layer in one embodiment of the present invention is formed by the method described later, in the porous layer obtained, the orientation of the filler or the surface of the porous layer The distribution uniformity of the filler can be controlled within a desirable range.

The porous layer in one embodiment of the present invention may contain other components other than the above-mentioned inorganic filler and resin. 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 adhesiveness with the electrode plate and high energy density, and 1 It is more preferably in the range of μm to 5 μm.

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 porous layer.

By setting the weight per unit area of the porous layer within these numerical ranges, the weight energy density and volume energy density of the non-aqueous 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 can be obtained. 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 setting the pore size of the pores to these sizes, the non-aqueous electrolyte secondary battery can obtain sufficient ion permeability.

<Aspect ratio of the projected image of the inorganic filler on the surface of the porous layer>

In the porous layer in one embodiment of the present invention, the aspect ratio of the projected image of the inorganic filler on the surface of the porous layer is in the range of 1.4 to 4.0, preferably in the range of 1.5 to 2.3. Here, the said aspect ratio uses a scanning electron microscope (SEM), and takes the SEM image which is an electron micrograph of the surface directly above a porous layer, that is, from vertically upward, and shoots the projected image of an inorganic filler from the photograph. It is a value obtained by creating and calculating the length ratio of the length of the major axis/short axis of the projected image of the inorganic filler. That is, the said aspect ratio shows the shape of the said inorganic filler observed when observing the inorganic filler in the surface of a porous layer from the direction directly above a porous layer.

Moreover, the schematic diagram of the projected image of the inorganic filler created from the SEM image of the surface of the porous layer mentioned above is shown in FIG.

As a specific measuring method of the said aspect ratio, the method including the process shown to the following (1) - (4) is mentioned, for example. In addition, the "surface" of a porous layer means the surface of a porous layer observable by SEM from right above a porous layer.

(1) In a laminate formed by laminating a porous layer on a substrate, SEM surface observation at an acceleration voltage of 5 kV using a field emission scanning electron microscope JSM-7600F manufactured by Nippon Electronics from directly above the porous side of the laminate ( A step of obtaining a SEM image by performing a reflection electron image).

(2) Place an OHP film on the SEM image obtained in step (1), create a projection image projected along the particle outline of the inorganic filler printed on the SEM image, and photograph the projection image with a digital still camera process.

(3) Incorporating the data of the photograph obtained in step (2) into a computer, using image analysis free software IMAGE J published by the National Institutes of Health (NIH), each of the 100 filler particles Step of calculating the aspect ratio of Here, the filler particles are approximated to an elliptical shape one by one, the major axis diameter and the minor axis diameter are calculated, and a value obtained by dividing the major axis diameter by the minor axis diameter is taken as an aspect ratio.

(4) The process of calculating the average value of the aspect ratio of the projected image of each particle obtained in step (3), and using the value as the aspect ratio of the projected image of the inorganic filler on the surface of the porous layer.

The aspect ratio of the projected image of the inorganic filler on the surface of the porous layer is an index showing the distribution uniformity of the inorganic filler in the porous layer, particularly on the surface. As for the thing whose aspect ratio is close to 1, the shape and distribution of the constituent material on the surface of a porous layer are uniform, and it is easy to fill densely. On the other hand, the large aspect ratio indicates that the arrangement of the components in the surface structure of the porous layer becomes non-uniform, and as a result, the shape of the openings on the surface of the porous layer and the uniformity of distribution are reduced.

When the aspect ratio is greater than 4.0, the uniformity of the shape and distribution of the porous layer, particularly the surface opening thereof, is excessively reduced. It is thought that a location where the electrolyte storage capacity is lowered occurs, and as a result, the rate characteristics of the non-aqueous electrolyte secondary battery are lowered. On the other hand, when the aspect ratio is less than 1.4, the distribution of the inorganic filler on the surface of the porous layer, in particular, becomes an excessively uniform structure, and as a result, the surface opening area of the porous layer becomes small. In a non-aqueous electrolyte secondary battery, it is considered that the electrolyte storage capacity of the porous layer during battery operation is reduced, and as a result, the battery rate characteristics of the non-aqueous electrolyte secondary battery are lowered.

<Orientation degree of porous layer>

The porous layer in one embodiment of the present invention is I _(hkl) , which is the peak intensity of arbitrary diffraction surfaces (hkl) and (abc) orthogonal to each other in the porous layer measured by a wide-angle X-ray diffraction method. ₎ and I _(abc) satisfy the following formula (1), and the range of the maximum value of the peak intensity ratio calculated by the following formula (2) is preferably in the range of 1.5 to 300, and in the range of 1.5 to 250 is more preferable.

I _(hkl) >I _(abc) … (One),

I _(hkl) /I _(abc) … (2).

Hereinafter, in this specification, the maximum value of the peak intensity ratio calculated by the formula (2) is also referred to as "the degree of orientation of the porous layer."

The method for measuring the peak intensities I _(hkl) and I _(abc) and the peak intensity ratio I _(hkl) /I _(abc) is not particularly limited. For example, the following (1) to (3) ) can be mentioned.

(1) A step of preparing a sample for measurement by cutting out a laminate (laminated porous film) formed by laminating a porous layer on a substrate into a square having a side of 2 cm.

(2) The sample for measurement obtained in step (1) was placed in an Al holder with the porous layer side in the sample as the measurement surface, and the X-ray profile was measured by wide-angle X-ray diffraction (2θ-θ scan method). process of measuring. In addition, the device and measurement conditions for measuring the X-ray profile are not particularly limited, but, for example, Rigaku Denki Co., Ltd. RU-200R (rotating large cathode type) is used as the device, CuKα rays are used as the X-ray source, , output can be measured at 50KV-200mA and scan speed 2°/min.

(3) Based on the X-ray profile obtained in step (2), peak intensities I _{(hkl) of arbitrary diffraction planes (hkl) and (abc)} orthogonal to each other in the wide-angle X-ray diffraction measurement of the porous layer, and When I _(abc) satisfies the above formula (1), the peak intensity ratio calculated by the above formula (2) is calculated, and the maximum value of the peak intensity ratio, that is, the step of calculating the degree of orientation of the porous layer.

In addition, in calculating the degree of orientation of the porous layer, it is important that both the direction in the horizontal direction and the direction in the normal direction with respect to the substrate surface are determined by using diffraction surfaces orthogonal to each other.

The maximum value of the peak intensity ratio represented by the formula (2) is an index showing the degree of orientation inside the porous layer. The thing with a small peak intensity ratio represented by said Formula (2) shows that the degree of orientation in the internal structure of a porous layer is low, and the thing with a large peak intensity ratio expressed by said Formula (2) has a degree of orientation in the internal structure of a porous layer indicates high.

When the maximum value of the peak intensity ratio represented by the above formula (2) is greater than 300, the anisotropy of the internal structure of the porous layer becomes excessively high, and the length of the ion permeation channel inside the porous layer becomes long. As a result, the above In a non-aqueous electrolyte secondary battery in which a porous layer is inserted, it is considered that the ion permeation resistance of the porous layer increases and the battery rate characteristic of the non-aqueous electrolyte secondary battery is lowered.

On the other hand, when the maximum value of the peak intensity ratio represented by the above formula (2) is less than 1.5, compared to a case using a porous layer having a peak intensity ratio of 1.5 or more, in a non-aqueous electrolyte secondary battery in which the porous layer is inserted, from the electrode Supplied ions are permeated at high speed. Therefore, the supply of ions from the electrodes becomes rate-limiting (i.e., ions are depleted from the surface of the electrodes), and the limiting current, which is a battery operating current value condition, becomes small. As a result, it is considered that the battery rate characteristics of the non-aqueous electrolyte secondary battery are lowered.

<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 any one of the process (1)-(3) shown below on a base material, A method of forming an inorganic filler and a porous layer containing the above resin is exemplified. In the case of the process (2) and process (3) shown below, after precipitating the said resin, it is further dried and a porous layer can be manufactured by removing a solvent. The coating liquid in steps (1) to (3) may be in a state in which the inorganic filler is dispersed and the resin is dissolved. In addition, the said solvent can also be said to be a solvent which dissolves resin, and also a dispersion medium which disperse|distributes resin or an 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 base material, the base material is immersed in a precipitation solvent that is a poor solvent for the resin to precipitate the resin to form a porous layer. forming process.

(3) After coating the coating solution containing the inorganic filler and the resin on the surface of the base material, the resin is precipitated by making the liquid of the coating solution acidic using a low-boiling point organic acid to form a porous layer. process to do.

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 uniformly and stably dissolves the resin and uniformly and stably disperses the inorganic filler without adversely affecting the substrate. Examples of the solvent include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, acetone and water.

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

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

In addition, as described below, as a method for controlling the orientation of the porous layer in one embodiment of the present invention, that is, the "aspect ratio of the projected image of the inorganic filler on the surface of the porous layer" and the "orientation degree of the porous layer" Similarly, adjusting the solid content concentration of the coating liquid containing the said inorganic filler and the said resin used for manufacture of a porous layer, and the coating shear rate at the time of coating the said coating liquid on a base material is mentioned.

A suitable solid content concentration of the coating solution may change depending on the type of filler or the like, but is generally preferably greater than 20% by weight and less than or equal to 40% by weight. When the solid content concentration is within the above-mentioned range, the viscosity of the coating solution is appropriately maintained, and as a result, the "aspect ratio of the projected image of the inorganic filler on the surface of the porous layer" and the "orientation degree of the porous layer" are within the above-mentioned suitable range. It is preferable because it can be controlled with

The coating shear rate at the time of coating the coating liquid on the substrate may vary depending on the type of filler or the like, but is generally preferably 2 (1/s) or more, and 4 (1/s) to 50 ( 1/s) is more preferable.

Here, for example, the inorganic filler has a shape in which spherical or columnar single particles such as peanuts and/or tetrapods are heat-sealed, spherical, elliptical, plate, rod, or irregular. In the case of using an inorganic filler, when the coating shear rate is increased, high shear force is applied to the inorganic filler, so the anisotropy tends to increase. On the other hand, when the coating shear rate is reduced, the shear force is not applied to the inorganic filler, so it tends to be isotropically oriented.

On the other hand, when the inorganic filler is a long fiber diameter inorganic filler such as wollastonite having a long fiber diameter, when the coating shear rate is increased, the long fibers are entangled with each other or the long fibers are not caught on the blade of the doctor blade. Therefore, there is a tendency that the orientation is disturbed and the anisotropy is lowered. On the other hand, if the coating shear rate is reduced, the long fibers do not become entangled with each other and do not catch on the blade of the doctor blade, so orientation becomes easier and the anisotropy tends to increase.

[Positive plate, negative plate]

The positive electrode plate in one embodiment of the present invention has a capacitance per 900 mm 2 of measurement area of 1 nF or more and 1000 nF or less, and the negative electrode plate has a capacitance per 900 mm 2 of measurement area of 4 nF or more and 8500 nF or less.

<capacitance>

In this specification, "measurement area" refers to a measurement object (positive electrode or negative electrode plate) in the measurement electrode (upper (main) electrode, probe electrode) of the LCR meter in the capacitance measurement method described later. It means the area of the point in contact with Therefore, the value of the capacitance per measurement area X mm 2 means that in an LCR meter, the measurement target and the measurement electrode are brought into contact so that the area of the measurement electrode is X mm 2 at the location where the two overlap, and the capacitance is measured. means the measured value in one case.

In the present invention, the capacitance of the positive electrode plate is a value measured by bringing a measuring electrode (probe electrode) into contact with the surface of the positive electrode plate on the positive electrode active material layer side in the method for measuring the capacitance of the electrode plate described later, and is mainly The polarization state of the positive electrode active material layer of the positive electrode plate is shown.

In the present invention, the capacitance of the negative electrode plate is a value measured by contacting the measuring electrode to the surface of the negative electrode plate on the negative electrode active material layer side in the method for measuring the capacitance of the electrode plate described later, and is mainly a value of the negative electrode plate. represents the polarization state of the negative electrode active material layer.

In a non-aqueous electrolyte secondary battery, ions as charge carriers are released from the negative electrode plate during discharge. The said ion passes through the separator for non-aqueous electrolyte secondary batteries, and is then introduce|transduced into the positive electrode plate. At this time, the ions are solvated by the electrolyte solvent in the negative electrode plate and on the surface of the negative electrode plate, and desolvated in the positive electrode plate and on the surface of the positive electrode plate. In addition, the said ion is Li ⁺ when a non-aqueous electrolyte secondary battery is a lithium ion secondary battery, for example.

Therefore, the degree of solvation of ions described above is influenced by the polarization state of the negative electrode active material layer of the negative electrode plate. Further, the degree of desolvation of ions described above is influenced by the polarization state of the positive electrode active material layer of the positive electrode plate.

Therefore, the above-described solvation and desolvation can be appropriately promoted by controlling the capacitance of the negative electrode plate and the positive electrode plate in an appropriate range, that is, by adjusting the polarization state of the negative electrode active material layer and the positive electrode active material layer to a suitable state. there is. In this way, the permeability of ions as charge carriers can be improved, and the discharge output characteristics of the non-aqueous electrolyte secondary battery can be improved, particularly when a discharge current of a large current with a time rate of 10 C or more is applied. From the above viewpoint, in the negative electrode plate of the non-aqueous electrolyte secondary battery according to one embodiment of the present invention, the capacitance per 900 mm 2 of measurement area is 4 nF or more and 8500 nF or less, preferably 4 nF or more and 3000 nF or less , more preferably 4 nF or more and 2600 nF or less. In addition, the lower limit of the capacitance may be 100 nF or more, 200 nF or more, or 1000 nF or more.

Specifically, when the capacitance per 900 mm 2 of measurement area of the negative electrode is less than 4 nF, the negative electrode has low polarizability, so it hardly contributes to the above-mentioned promotion of solvation. Therefore, in the non-aqueous electrolyte secondary battery in which the negative electrode plate is inserted, no improvement in output characteristics occurs. On the other hand, when the capacitance per 900 mm of measurement area of the negative electrode is greater than 8500 nF, the polarization power of the negative electrode becomes too high, so the affinity between the inner wall of the void of the negative electrode and ions becomes too high. Therefore, movement (release) of ions from the negative electrode plate is inhibited. Therefore, in a non-aqueous electrolyte secondary battery in which the negative electrode plate is inserted, its output characteristics are rather deteriorated.

From the above viewpoint, the positive electrode plate according to one embodiment of the present invention has a capacitance per 900 mm 2 of 1 nF or more and 1000 nF or less, preferably 2 nF or more and 600 nF or less, and preferably 2 nF or more and 400 nF or less. it is more preferable Further, the lower limit of the capacitance may be 3 nF or more.

Specifically, in the positive electrode plate, when the capacitance per 900 mm 2 of measurement area is less than 1 nF, the polarization power of the positive electrode plate is low, so it hardly contributes to the desolvation. Therefore, in the non-aqueous electrolyte secondary battery in which the positive electrode plate is inserted, no improvement in output characteristics occurs. On the other hand, in the positive electrode plate, when the capacitance per 900 mm 2 of measurement area is larger than 1000 nF, the polarization power of the positive electrode plate is too high, so the desolvation proceeds excessively. Therefore, the solvent for moving inside the positive electrode plate is desolvated, and the affinity between the inner wall of the pores inside the positive electrode plate and the desolvated ions becomes too high. Therefore, movement of ions inside the positive electrode plate is inhibited. Therefore, in a non-aqueous electrolyte secondary battery in which the positive electrode plate is inserted, its output characteristics are rather deteriorated.

<Capacitance control method>

The capacitance of the positive electrode plate and the negative electrode plate can be controlled by adjusting the surface areas of the positive electrode active material layer and the negative electrode active material layer, respectively. Specifically, for example, by scraping the surfaces of the positive electrode active material layer and the negative electrode active material layer with sandpaper or the like, the surface area can be increased, thereby increasing the capacitance. Alternatively, the capacitance of the positive electrode plate and the negative electrode plate can be controlled by adjusting the relative permittivity of materials constituting each of the positive electrode plate and the negative electrode plate. The dielectric constant can be adjusted by changing the shape, porosity, and distribution of voids in each of the positive electrode plate and the negative electrode plate. In addition, the dielectric constant can also be adjusted by adjusting the material constituting each of the positive electrode plate and the negative electrode plate.

<Method of measuring capacitance>

In one embodiment of the present invention, the capacitance of the electrode plate (positive electrode plate or negative electrode plate) per 900 mm 2 of measurement area is CV: 0.010 V, SPEED: SLOW2, AVG: 8, CABLE: 1m, OPEN: All, SHORT: All DCBIAS set to 0.00V, and measured under the condition of frequency: 300KHz.

In this capacitance measurement, the capacitance of the electrode plate before being inserted into the non-aqueous electrolyte secondary battery is measured. The capacitance is a unique value determined by the shape (surface area) of the solid insulating material (electrode plate), the constituent material, the shape of the pores, the porosity, and the distribution of the pores. Therefore, the capacitance of the electrode plate after being inserted into the non-aqueous electrolyte secondary battery also becomes a value equal to the capacitance value measured before being inserted into the non-aqueous electrolyte secondary battery.

Alternatively, the positive electrode plate and the negative electrode plate may be taken out from the battery after being inserted into the non-aqueous electrolyte secondary battery and passed through a charge/discharge history, and the capacitance of the positive electrode plate and the negative electrode plate may be measured. Specifically, for example, for a non-aqueous electrolyte rechargeable battery, after taking out an electrode laminate (non-aqueous electrolyte secondary battery member) from an exterior member, and then unfolding this, one electrode plate (positive electrode plate or negative electrode plate) is taken out. do. A sample piece is obtained by cutting this electrode plate into the same size as the electrode plate to be measured in the capacitance measuring method described above. Thereafter, the test piece is washed several times (for example, three times) in diethyl carbonate (hereinafter sometimes referred to as DEC). The cleaning described above is performed by adding a test piece to the DEC, cleaning the DEC, replacing the DEC with a new DEC, and repeating the process of cleaning the test piece several times (for example, three times), and the electrolyte solution and the electrolyte solution adhering to the surface of the electrode plate. It is a process to remove decomposition products, lithium salts, etc. After sufficiently drying the obtained washed electrode plate, it is used as an electrode to be measured. The type of exterior member and laminated structure of the battery to be taken out is not limited.

<Orientation of inorganic filler in porous layer and capacitance of electrode plate>

As described above, the aspect ratio of the projected image of the inorganic filler on the surface of the porous layer is in the range of 1.4 to 4.0, and I _(hkl) and I when the porous layer is measured by a wide-angle X-ray diffraction method ₍ When _abc) satisfies the above formula and the range of the maximum value of the peak intensity ratio calculated by the above formula (2) is in the range of 1.5 to 300 (condition 1), the porous layer has a structure that easily holds the electrolyte solution , and also, since the movement path of ions as charge carriers is optimized, the permeability of ions is promoted.

Further, when the capacitance per 900 mm 2 of the measurement area of the positive electrode plate is 1 nF or more and 1000 nF or less, and the capacitance per 900 mm 2 of the measurement area of the negative electrode plate is 4 nF or more and 8500 nF or less (condition 2), the polarization of the electrode active material layer When this is appropriate, desolvation and solvation of ions, which are charge carriers, are promoted, and permeability of the ions is improved.

When the degree of orientation of the inorganic filler in the porous layer satisfies condition 1 above and the electrode plate satisfies condition 2 above, the pores of the porous layer take on a suitable dense structure, and the permeability of ions as charge carriers and the electrolyte solution Both support properties are achieved, and the polarization of the electrode active material layer is appropriate. Therefore, solvation and desolvation of ions as charge carriers also proceed smoothly. As a result, the unevenness of the capacity in the direction of the electrode surface due to the high-rate discharge is suppressed, that is, the unevenness in the concentration of ions as charge carriers is eliminated. This makes it possible to correct surface direction non-uniformity at the time of refilling, that is, to re-uniform. As a result, it is considered that the charge capacity of the battery after high-rate discharge can be improved.

The charge capacity of the non-aqueous electrolyte secondary battery according to one embodiment of the present invention at 1C charge after high-rate discharge (10C discharge) is preferably 14.5 mAh or more, and more preferably 15 mAh or more.

Note that the charge capacity at 1C charge after high-rate discharge (10C discharge) is a value measured by the measurement method described in Examples.

<positive plate>

The positive electrode plate in one embodiment of the present invention is not particularly limited as long as the capacitance per 900 mm 2 of measurement area is within the above range. For example, as the positive electrode active material layer, a sheet-like 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. Further, the positive electrode plate may support the positive electrode mixture on both surfaces of the positive electrode current collector, or may support the positive electrode mixture on one side of the positive electrode current 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 transition metal oxides include transition metals such as V, Mn, Fe, Co, and Ni, and/or lithium composite oxides containing at least one oxide of the transition metal. .

Examples of the conductive agent include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and fired bodies of organic polymer compounds. As for the said electrically conductive agent, only 1 type may be used, and you may use it in combination of 2 or more types.

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

Examples of the positive electrode current collector include conductors such as Al, Ni, and stainless steel. Among them, Al is more preferable because it is easy to process into a thin film and is inexpensive.

Examples of the manufacturing method of the sheet-like positive electrode plate include a method in which a positive electrode active material, a conductive agent and a binder are pressure-molded on a positive electrode current collector; a method in which a positive electrode active material, a conductive agent and a binder are formed into a paste using an appropriate organic solvent, then the paste is applied to the positive electrode current collector, and then dried and pressed to adhere to the positive electrode current collector; etc. can be mentioned.

<negative plate>

The negative electrode plate in one embodiment of the present invention is not particularly limited as long as the capacitance per 900 mm 2 of measurement area is within the above range. For example, as the negative electrode active material layer, a sheet-shaped negative electrode plate in which a negative electrode mixture containing a negative electrode active material, a conductive agent, and a binder is supported on a negative electrode current collector is used. Further, the negative electrode plate may support the negative electrode mixture on both surfaces of the negative electrode current collector, or may support the negative electrode mixture on one side of the negative electrode current collector.

As the conductive agent and the binder, those described as the conductive agent and binder included in the positive electrode active material layer can be used.

Examples of the negative electrode active material include materials capable of doping and undoping lithium ions, lithium metal, and lithium alloys. Specific examples of the material include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and organic polymer compound fired bodies; and chalcogen compounds such as oxides and sulfides that perform dope and undope of lithium ions at a potential lower than that of the positive electrode. Among the negative electrode active materials, those containing graphite are preferred, and graphite materials such as natural graphite and artificial graphite are used as the main component because a large energy density is obtained when combined with a positive electrode due to high potential flatness and low average discharge potential. A carbonaceous material made of is more preferable. Moreover, the said negative electrode active material may have graphite as a main component, and may also contain silicon.

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

As a manufacturing method of the sheet-like negative electrode plate, for example, a method of press-molding a negative electrode active material on a negative electrode current collector; a method in which a negative electrode active material is formed into a paste using an appropriate organic solvent, then the paste is applied to the negative electrode current collector, and then dried and then pressurized to adhere to the negative electrode current collector; etc. can be mentioned. The paste preferably includes the conductive agent and the binder.

[Polyolefin Porous Film]

The non-aqueous electrolyte secondary battery in one embodiment of the present invention may be equipped with a polyolefin porous film. Below, a polyolefin porous film may be simply called a "porous film." The porous film has a polyolefin-based resin as a main component, has a large number of pores connected therein, and allows gases and liquids to pass from one side to the other side. The said porous film can become a separator for non-aqueous electrolyte rechargeable batteries independently. In addition, it can serve as a base material for a laminated separator for a non-aqueous electrolyte secondary battery in which the porous layer described above is laminated.

A laminate formed by laminating the porous layer on at least one surface of the polyolefin porous film is also referred to as a "laminated separator for non-aqueous electrolyte rechargeable batteries" or a "laminated separator" in the present specification. In addition, the separator for nonaqueous electrolyte rechargeable batteries in one embodiment of the present invention may further include other layers such as an adhesive layer, a heat resistance layer, and a protective layer in addition to the polyolefin porous film.

The ratio of the polyolefin to the porous film is 50 vol% or more of the entire porous film, more preferably 90 vol% or more, and still more preferably 95 vol% or more. Moreover, it is more preferable that the said polyolefin contains the high molecular weight component whose weight average molecular weight is 5x10 ^<5> -15x10 ^<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 non-aqueous electrolyte secondary battery separator is improved, it is more preferable.

Specific examples of the polyolefin, which is a thermoplastic resin, include homopolymers or copolymers obtained by polymerizing monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene and 1-hexene. there is. As said homopolymer, polyethylene, a polypropylene, and a polybutene are mentioned, for example. Moreover, as said copolymer, an ethylene-propylene copolymer is mentioned, for example.

Among these, polyethylene is more preferable because it can prevent an excessive current from flowing at a lower temperature. Further, blocking the flow of this excessive current is also referred to as shutdown. Examples of the polyethylene include low-density polyethylene, high-density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), and ultrahigh molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more. Among these, ultra-high molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more is more preferable.

The film thickness of the porous film is preferably 4 to 40 μm, more preferably 5 to 30 μm, still more preferably 6 to 15 μm.

The weight per unit area of the porous film can be appropriately determined in consideration of strength, film thickness, weight, and handling properties. However, 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 in order to increase the gravimetric energy density and volume energy density of the non-aqueous electrolyte secondary battery. /m 2 is more preferable.

It is preferable that it is 30-500 sec/100mL in Gurley value, and, as for the air permeability of a porous film, it is more preferable that it is 50-300sec/100mL. Sufficient ion permeability can be obtained when a porous film has the said air permeability. It is preferable that it is 30-1000sec/100mL in Gurley value, and, as for the air permeability of the multilayer separator for non-aqueous electrolyte rechargeable batteries which laminated|stacked the above-mentioned porous layer on the porous film, it is more preferable that it is 50-800sec/100mL. The laminated separator for non-aqueous electrolyte secondary batteries can obtain sufficient ion permeability in a non-aqueous electrolyte secondary battery by having the said air permeability.

The porosity of the porous film is preferably 20 to 80% by volume, and more preferably 30 to 75% by volume so that the function of reliably preventing excessive current from flowing at a lower temperature can be obtained while increasing the retention amount of the electrolyte solution. desirable. 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 particles can be prevented from entering the positive electrode and the negative electrode. .

<Method for producing porous polyolefin 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 resin, a pore forming agent such as an inorganic filler and a plasticizer, and optionally an antioxidant or the like. After removing the pore forming agent from the sheet-like polyolefin resin composition with an appropriate solvent, a polyolefin porous film can be produced by stretching the polyolefin resin composition from which the pore forming agent has been removed.

It does not specifically limit as said inorganic filler, An inorganic filler, specifically, a calcium carbonate etc. are mentioned. The plasticizer is not particularly limited, and low molecular weight hydrocarbons such as liquid paraffin are exemplified.

Specifically, a method including a step as shown below is exemplified.

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

(B) a step of forming a sheet by rolling the obtained polyolefin resin composition with a pair of rolling rollers and gradually cooling it while drawing it with a take-up roller having a different speed ratio;

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

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

[Method of Manufacturing Laminated Separator for Non-aqueous Electrolyte Secondary Battery]

As a manufacturing method of the multilayer separator for non-aqueous electrolyte secondary batteries in one embodiment of the present invention, for example, in the "manufacturing method of a porous layer" described above, as a base material to which the coating solution is applied, the polyolefin porous film described above You can see how to use .

[Non-aqueous electrolyte]

The non-aqueous electrolyte that can be contained in the non-aqueous electrolyte secondary battery according to one embodiment of the present invention is not particularly limited as long as it is a non-aqueous electrolyte that is generally used in non-aqueous electrolyte secondary batteries. 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 , lower aliphatic carboxylic acid lithium salt and LiAlCl ₄ . As for the said lithium salt, only one type may be used, and you may use it in combination of 2 or more types.

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. The said organic solvent may use only 1 type, and may use it in combination of 2 or more types.

[Method for Manufacturing Non-Aqueous Electrolyte Secondary Battery]

As a method for manufacturing a nonaqueous secondary battery according to an embodiment of the present invention, a conventionally known manufacturing method can be employed. For example, a member for non-aqueous electrolyte rechargeable batteries is formed by arranging a positive electrode plate, a polyolefin porous film, and a negative electrode plate in this order. Here, the porous layer may exist between the polyolefin porous film and at least one of the positive electrode plate and the negative electrode plate. Next, the member for non-aqueous electrolyte secondary batteries is placed in a container used as a housing of the non-aqueous electrolyte secondary battery. After filling the inside of the container with the non-aqueous electrolyte solution, it is sealed while reducing the pressure. Thereby, the non-aqueous electrolyte secondary battery according to one embodiment of the present invention can be manufactured.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[measurement method]

Each measurement in Examples and Comparative Examples was performed by the following method.

(1) Film thickness (Unit: μm)

The film thickness of the polyolefin porous film and the porous layer, and the thickness of the positive electrode plate and the negative electrode plate were measured using a high-precision digital measuring instrument (VL-50) manufactured by Mitutoyo Corporation. The thickness of the electrode active material layer was obtained by subtracting the thickness of the uncoated portion from the thickness of the coated portion of each electrode plate.

(2) Measuring the aspect ratio of the projected image of the inorganic filler on the surface of the porous layer

SEM surface observation (reflection electron image) from the porous layer side of the multilayer body of the polyolefin porous film and porous layer produced in Examples and Comparative Examples using a JSM-7600F field emission scanning electron microscope manufactured by Nippon Electronics at an acceleration voltage of 5 kV. was performed to obtain an electron micrograph (SEM image).

An OHP film was placed on the obtained SEM image, a projection image projected along the particle contour of the inorganic filler was created, and the projection image was photographed with a digital still camera. The data of the obtained photograph is introduced into a computer, and using image analysis free software IMAGE J published by the National Institutes of Health (NIH), the aspect ratio of each of 100 particles is calculated, and the average is calculated. It was set as the aspect ratio of the projected image of the inorganic filler on the surface of the porous layer in the porous layer (hereinafter also referred to as a surface filler aspect ratio). Here, each filler particle was approximated to an elliptical shape, the major axis diameter and the minor axis diameter were calculated, and the value obtained by dividing the major axis diameter by the minor axis diameter was used as the aspect ratio per filler.

(3) Measurement of the maximum value of the peak intensity ratio (I _(hkl) /I _(abc) )

The multilayer body of the porous polyolefin film and the porous layer prepared in Examples and Comparative Examples was cut into a square having a side of 2 cm to obtain a sample for measurement. The obtained sample for measurement was placed in an Al holder with the porous layer in the sample as a measurement surface, and the X-ray profile was measured by a wide-angle X-ray diffraction method (2θ-θ scan method). As an apparatus, an RU-200R (rotating large cathode type) manufactured by Rigaku Denki Co., Ltd. was used, CuKα rays were used as an X-ray source, and output was measured at 50 KV-200 mA and a scan speed of 2°/min. Based on the obtained X-ray profile, the peak intensities I (hkl) and I (abc) of orthogonal arbitrary diffraction surfaces ( _hkl ) and ( _{abc) in the wide-angle X-ray diffraction measurement of the porous layer are expressed by the following formula (1)} ), the peak intensity ratio calculated by I _(hkl) /I _(abc) was calculated, and the maximum value of the peak intensity ratio was calculated.

I _(hkl) >I _(abc) … (One).

(4) Measurement of capacitance of electrode plate

The capacitance per measurement area of 900 mm 2 of the positive electrode plate and negative electrode plate obtained in Examples and Comparative Examples was measured using an LCR meter manufactured by Hioki Denki (model number: IM3536). At this time, the measurement conditions were set to CV: 0.010V, SPEED: SLOW2, AVG: 8, CABLE: 1m, OPEN: All, SHORT: All DCBIAS 0.00V, and frequency: 300KHz. The absolute value of the measured capacitance was taken as the capacitance.

From the electrode plate to be measured, a portion where a 3 cm × 3 cm square electrode active material layer was formed and a portion where a 1 cm × 1 cm square electrode active material layer was not formed were integrally cut out. A tab lead having a length of 6 cm and a width of 0.5 cm was ultrasonically welded to a portion of the cut electrode plate where the electrode active material layer was not formed to obtain an electrode plate for measuring capacitance (FIG. 3). A tab lead made of aluminum was used for the tab lead of the positive electrode plate, and a tab lead made of nickel was used for the tab lead of the negative electrode plate.

From the current collector, a 5 cm x 4 cm square and a 1 cm x 1 cm square as a site for tab lead welding were cut out as one body. A tab lead having a length of 6 cm and a width of 0.5 cm was ultrasonically welded to the cut portion of the current collector for welding the tab lead to obtain a probe electrode (electrode for measurement) (FIG. 4). An aluminum probe electrode with a thickness of 20 μm was used as the probe electrode for measuring the capacitance of the positive electrode plate, and a copper probe electrode with a thickness of 20 μm was used for the probe electrode for measuring the capacitance of the negative electrode plate. .

A laminate was produced by overlapping the probe electrode and a portion (square portion of 3 cm x 3 cm) where the electrode active material layer of the electrode plate for measurement was formed. The obtained laminate was sandwiched between two sheets of silicone rubber, and further pinched between two SUS plates from above each silicone rubber at a pressure of 0.7 MPa to obtain a laminate used for measurement. The tab lead was taken out from the laminated body used for measurement, and the voltage terminal and current terminal of the LCR meter were connected from the side closer to the electrode plate of the tab lead.

(5) Measurement of the porosity of the positive electrode active material layer

The porosity of the positive electrode active material layer included in positive electrode plate 1 in Example 1 below was measured using the method described below. The porosity of the positive electrode active material layer included in the other positive electrode plates in the following examples and comparative examples was also measured by the same method.

A positive electrode plate in which a positive electrode mixture (LiNi _0.5 Mn _0.3 Co _0.2 O ₂ /conductive agent/PVDF (weight ratio: 92/5/3)) is supported on one side of a positive electrode current collector (aluminum foil) is coated with 14.5 cm2 (4.5 cm×3 cm+ It was cut to a size of 1 cm × 1 cm). The cut out positive electrode plate had a mass of 0.215 g and a thickness of 58 µm. When the positive electrode current collector was cut out to the same size, the mass was 0.078 g and the thickness was 20 μm.

The positive electrode active material layer density ρ was calculated as (0.215-0.078)/{(58-20)/10000×14.5} = 2.5 g/cm 3 .

The true density of the materials constituting the positive electrode mixture was 4.68 g/cm 3 for LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , 1.8 g/cm 3 for the conductive agent, and 1.8 g/cm 3 for PVDF.

The porosity ε of the positive electrode active material layer calculated based on the following formula using these values was 40%.

ε=[1-{2.5×(92/100)/4.68+2.5×(5/100)/1.8+2.5×(3/100)/1.8}]×100=40%

(6) Measurement of the porosity of the negative electrode active material layer

The porosity of the negative electrode active material layer included in the negative electrode plate 1 in Example 1 below was measured using the method described below. The porosity of the negative electrode active material layer of the other negative electrode plates in the following Examples and Comparative Examples was also measured by the same method.

A negative electrode plate in which a negative electrode mixture (graphite/styrene-1,3-butadiene copolymer/sodium carboxymethylcellulose (weight ratio: 98/1/1)) is supported on one side of a negative electrode current collector (copper foil) is coated with 18.5 cm2 (5 cm × It was cut to a size of 3.5 cm + 1 cm × 1 cm). The cut negative plate had a mass of 0.266 g and a thickness of 48 µm. When the negative electrode current collector was cut out to the same size, the mass was 0.162 g and the thickness was 10 μm.

The negative electrode active material layer density ρ was calculated as (0.266-0.162)/{(48-10)/10000×18.5} = 1.49 g/cm 3 .

The true densities of the materials constituting the negative electrode mixture were 2.2 g/cm 3 for graphite, 1 g/cm 3 for styrene-1,3-butadiene copolymer, and 1.6 g/cm 3 for sodium carboxymethylcellulose.

The porosity ε of the negative electrode active material layer calculated based on the following formula using these values was 31%.

ε=[1-{1.49×(98/100)/2.2+1.49×(1/100)/1+1.49×(1/100)/1.6}]×100=31%

(7) Charge capacity after high-rate discharge of non-aqueous electrolyte secondary battery

The charge capacity at 1C charge after high-rate discharge (10C discharge) of the non-aqueous electrolyte secondary batteries manufactured in Examples and Comparative Examples was measured by the methods shown in the following steps (A) to (B).

(A) Initial charge and discharge test

Voltage range for the new non-aqueous electrolyte secondary battery that has not undergone charge-discharge cycles manufactured in Examples and Comparative Examples; 2.7 to 4.1 V, CC-CV charging at a charging current value of 0.2 C (end current condition: 0.02 C), and CC discharging at a discharging current value of 0.2 C were set as one cycle, and four cycles of initial charge and discharge were performed at 25 ° C.

In addition, the current value for discharging the rated capacity by the discharge capacity at the rate of 1 hour in 1 hour is 1C. In addition, CC-CV charging is a charging method in which charging is performed with a set constant current, and after reaching a predetermined voltage, the voltage is maintained while reducing the current. In addition, CC discharge is a method of discharging up to a predetermined voltage at a set constant current. These are also the same below.

(B) Charge capacity (mAh) at 1C charge after high-rate discharge (10C discharge)

CC-CV charging with a charging current value of 1C (end current condition: 0.02C) and discharging current values of 0.2C, 1C, 5C, and 10C were performed in this order for the non-aqueous electrolyte secondary battery that had undergone the initial charging and discharging. For each rate, charging and discharging were performed at 55°C in 3 cycles. At this time, the voltage range was 2.7V to 4.2V.

At this time, the charge capacity at the time of 1C charge at the 3rd cycle at the time of measuring the 10C discharge rate characteristics was measured, and it was set as the charge capacity (mAh) after high-rate discharge. In addition, the design capacity of the non-aqueous electrolyte secondary battery manufactured in Examples and Comparative Examples was 20.5 mAh.

[Example 1]

<Manufacture of polyolefin porous film>

A polyolefin porous film was produced using polyethylene. Specifically, 70 parts by weight of ultra-high molecular weight polyethylene powder (340M, manufactured by Mitsui Chemical Co., Ltd.) and 30 parts by weight of polyethylene wax (FNP-0115, manufactured by Nihon Seiro Co., Ltd.) having a weight average molecular weight of 1000 were mixed and mixed. obtained polyethylene. 0.4 parts by weight of an antioxidant (Irg1010, manufactured by Ciba Specialty Chemicals, Inc.), 0.1 part by weight of an antioxidant (P168, manufactured by Ciba Specialty Chemicals, Inc.) and 1.3 parts by weight of sodium stearate with respect to 100 parts by weight of the obtained blended polyethylene. Furthermore, calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) having an average particle diameter of 0.1 µm was added so that the proportion to the total volume was 38 vol%. A polyethylene resin composition was obtained by mixing this composition as a powder with a Henschel mixer and then melt-kneading it with a twin screw kneader. Next, a sheet was produced by rolling this polyethylene resin composition with a pair of rolls whose surface temperature was set to 150°C. The sheet was immersed in an aqueous hydrochloric acid solution prepared by blending 0.5% by weight of a nonionic surfactant in 4 mol/L hydrochloric acid to dissolve and remove calcium carbonate. Then, the sheet was stretched 6 times at 105°C to produce a polyolefin porous film. The porosity of the polyolefin porous film was 53%, the weight per unit area was 7 g/m 2 , and the film thickness was 16 μm. This polyolefin porous film was used as polyolefin porous film 1.

<Manufacture of porous layer>

(Manufacture of coating solution)

As the inorganic filler 1, hexagonal plate-like zinc oxide (trade name: XZ-100F, manufactured by Sakai Chemical Industry Co., Ltd.) having an oxygen atomic mass percentage of 20% was used.

As the resin, a vinylidene fluoride-hexafluoropropylene copolymer (manufactured by Arkema Co., Ltd.; trade name "KYNAR2801") was used.

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

(Manufacture of porous layer)

The obtained coating liquid was applied to one side of the polyolefin porous film 1 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 polyolefin porous film 1. After that, the porous layer 1 was formed on one side of the polyolefin porous film 1 by drying the coating film at 65°C for 20 minutes. Thus, a laminate 1 of the polyolefin porous film 1 and the porous layer 1 was obtained. The weight per unit area of the porous layer 1 was 7 g/m 2 , and the thickness was 4 μm. Using the obtained layered product 1, the aspect ratio of the projected image of the inorganic filler on the surface of the porous layer and the maximum value of the peak intensity ratio were measured. The results are shown in Table 1.

<Production of non-aqueous electrolyte secondary battery>

(Manufacture of positive electrode plate)

A positive electrode plate prepared by applying LiNi _0.5 Mn _0.3 Co _0.2 O ₂ /conductive agent/PVDF (weight ratio 92/5/3) to an aluminum foil was used. An aluminum foil was cut out of the positive electrode plate so that the size of the portion where the positive electrode active material layer was formed was 45 mm × 30 mm, and a portion having a width of 13 mm on the outer periphery where the positive electrode active material layer was not formed remained, to obtain positive electrode plate 1. . The thickness of the positive electrode active material layer was 58 μm, and the density was 2.50 g/cm 3 .

(Manufacture of negative plate)

A negative electrode plate prepared by applying graphite/styrene-1,3-butadiene copolymer/sodium carboxymethylcellulose (weight ratio 98/1/1) to a copper foil was used. The negative electrode plate 1 was formed by cutting the copper foil so that the size of the portion on which the negative electrode active material layer was formed was 50 mm × 35 mm, and a portion having a width of 13 mm on the outer circumference of the negative electrode plate was not formed on the negative electrode active material layer. did The negative electrode active material layer had a thickness of 49 μm and a density of 1.40 g/cm 3 .

(Assembly of non-aqueous electrolyte secondary battery)

A non-aqueous electrolyte secondary battery was manufactured by the method shown below using the said positive electrode plate, the said negative electrode plate, and the said laminated body 1.

Inside the laminated pouch, member 1 for non-aqueous electrolyte rechargeable batteries was obtained by laminating (arranging) the positive electrode plate 1, the laminate 1 in which the porous layer was opposed to the positive electrode side, and the negative electrode plate 1 in this order. At this time, the positive electrode plate 1 and the negative electrode plate 1 were disposed such that all of the main surfaces of the positive electrode active material layer of the positive electrode plate 1 were included in the range of the main surface of the negative electrode active material layer of the negative electrode plate 1 (overlapping with the main surface). .

Then, the member 1 for non-aqueous electrolyte secondary batteries was put into a previously produced bag formed by laminating an aluminum layer and a heat seal layer, and further, 0.25 mL of non-aqueous electrolyte was put into this bag. In the non-aqueous electrolyte solution, LiPF ₆ is dissolved in a mixed solvent obtained by mixing ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate at a ratio of 3:5:2 (volume ratio) so that the concentration is 1 mol/L. It was prepared. Then, the non-aqueous electrolyte secondary battery 1 was produced by heat-sealing the bag while depressurizing the inside of the bag.

[Example 2]

<Manufacture of laminate of polyolefin porous film and porous layer>

As a raw material for the inorganic filler 2, Zirkondioxid/Calciumoxid (ZrO ₂ /CaO = 95/5) fused (manufactured by Ceram) having an oxygen atomic mass percentage of 26% was used. The Zirkondioxid/Calciumoxid (ZrO ₂ /CaO = 95/5) fused (manufactured by Ceram) was pulverized by performing vibration mill pulverization using a 3.3 L alumina pot and 15 mmφ alumina balls for 4 hours to obtain a pulverized product. The pulverized product was used as inorganic filler 2. Here, Zirkondioxid/Calciumoxid (ZrO ₂ /CaO = 95/5) fused forms a solid solution obtained by melting 295 parts by weight of ZrO and 5 parts by weight of CaO.

In place of the inorganic filler 1 used for the production of the porous layer, the above-described inorganic filler 2 was used to prepare a coating solution 2, and the coating solution 2 was coated on one side of the polyolefin porous film 1 at a shear rate of 7.9 (1/s). Except having coated and forming the porous layer 2, it carried out similarly to Example 1, and obtained the laminated body 2 of the polyolefin porous film 1 and the porous layer 2. Using the obtained layered product 2, the aspect ratio of the projected image of the inorganic filler 2 on the surface of the porous layer and the maximum value of the peak intensity ratio were measured. The results are shown in Table 1.

<Production of non-aqueous electrolyte secondary battery>

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

[Example 3]

<Manufacture of laminate of polyolefin porous film and porous layer>

As raw materials for the inorganic filler 3, α-alumina (manufactured by Sumitomo Chemical Co., Ltd., trade name: AKP3000) and hexagonal plate-like zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., trade name: XZ-1000F) were used. A mixture of 99 parts by weight of α-alumina and 1 part by weight of hexagonal plate-shaped zinc oxide mixed in a mortar (oxygen atom mass percentage: 47%) was used as inorganic filler 3. While mixing 10 parts by weight of the vinylidene fluoride-hexafluoropropylene copolymer with respect to 90 parts by weight of the inorganic filler 3, the concentration of the solid content (inorganic filler and vinylidene fluoride-hexafluoropropylene copolymer) in the mixture obtained. A coating solution 3 was prepared by mixing a solvent so that the coating solution 3 was applied to one side of the polyolefin porous film 1 at a coating shear rate of 39.4 (1/s) to form a porous layer 3. Other than that, it carried out similarly to Example 1, and obtained the laminated body 3 of the polyolefin porous film 1 and the porous layer 3. Using the obtained layered product 3, the aspect ratio of the projected image of the inorganic filler 3 on the surface of the porous layer and the maximum value of the peak intensity ratio were measured. The results are shown in Table 1.

<Production of non-aqueous electrolyte secondary battery>

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

[Example 4]

<Manufacture of laminate of polyolefin porous film and porous layer>

As raw materials for the inorganic filler 4, spherical alumina (product name: AA03, manufactured by Sumitomo Chemical Co., Ltd.) and mica (product name: non-swellable synthetic mica, manufactured by Wako Pure Chemical Industries, Ltd.) were used. A mixture of 50 parts by weight of spherical alumina and 50 parts by weight of mica in a mortar (oxygen atomic mass percentage: 45%) was used as inorganic filler 4. While mixing 10 parts by weight of the vinylidene fluoride-hexafluoropropylene copolymer with respect to 90 parts by weight of the inorganic filler 4, the concentration of the solid content (inorganic filler and vinylidene fluoride-hexafluoropropylene copolymer) in the mixture obtained. Coating solution 4 was prepared by mixing a solvent so that the content of the coating solution 4 was applied to one side of the polyolefin porous film 1 at a coating shear rate of 7.9 (1/s) to form a porous layer 4. Other than that, it carried out similarly to Example 1, and obtained the laminated body 4 of the polyolefin porous film 1 and the porous layer 4. Using the obtained layered product 4, the aspect ratio of the projected image of the inorganic filler 4 on the surface of the porous layer and the maximum value of the peak intensity ratio were measured. The results are shown in Table 1.

<Production of non-aqueous electrolyte secondary battery>

A non-aqueous electrolyte secondary battery 4 was produced in the same manner as in Example 1, except that laminate 4 was used instead of laminate 1.

[Example 5]

<Manufacture of laminate of polyolefin porous film and porous layer>

As the inorganic filler 5, wollastonite having an oxygen atomic mass percentage of 41% (manufactured by Hayashi Kasei Co., Ltd., trade name: wollastonite VM-8N) was used. While mixing 10 parts by weight of the vinylidene fluoride-hexafluoropropylene copolymer with respect to 90 parts by weight of the inorganic filler 5, the concentration of the solid content (inorganic filler and vinylidene fluoride-hexafluoropropylene copolymer) in the mixture obtained. A coating solution 5 was prepared by mixing a solvent so that the coating solution 5 was applied to one side of the polyolefin porous film 1 at a coating shear rate of 7.9 (1/s) to form a porous layer 5. Other than that, it carried out similarly to Example 1, and obtained the laminated body 5 of the polyolefin porous film 1 and the porous layer 5. Using the obtained layered product 5, the aspect ratio of the projected image of the inorganic filler 5 on the surface of the porous layer and the maximum value of the peak intensity ratio were measured. The results are shown in Table 1.

<Production of non-aqueous electrolyte secondary battery>

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

[Example 6]

<Manufacture of laminate of polyolefin porous film and porous layer>

Laminate 3 similar to Example 3 was used.

<Production of non-aqueous electrolyte secondary battery>

(Manufacture of positive electrode plate)

The surface of the positive electrode active material layer side of the same positive electrode plate as positive electrode plate 1 was polished three times using an abrasive cloth sheet manufactured by Nagatsuka Kogyo Co., Ltd. (model number TYPE AA GRIT No100) to obtain positive electrode plate 2. The positive electrode active material layer of the positive electrode plate 2 had a thickness of 38 μm and a porosity of 40%.

(Manufacture of negative plate)

As the negative electrode plate, the negative electrode plate 1 was used.

(Assembly of non-aqueous electrolyte secondary battery)

A non-aqueous electrolyte secondary battery 6 was produced in the same manner as in Example 1, except that laminate 3 was used instead of laminate 1 and positive electrode plate 2 was used instead of positive electrode plate 1.

[Example 7]

<Manufacture of laminate of polyolefin porous film and porous layer>

Laminate 3 similar to Example 3 was used.

<Production of non-aqueous electrolyte secondary battery>

(Manufacture of positive electrode plate)

The surface of the positive electrode active material layer side of the same positive electrode plate as positive electrode plate 1 was polished 5 times using an abrasive cloth sheet manufactured by Nagatsuka Kogyo Co., Ltd. (model number TYPE AA GRIT No100) to obtain positive electrode plate 3. The positive electrode active material layer of the positive electrode plate 3 had a thickness of 38 μm and a porosity of 40%.

(Manufacture of negative plate)

As the negative electrode plate, the negative electrode plate 1 was used.

(Assembly of non-aqueous electrolyte secondary battery)

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

[Example 8]

<Manufacture of laminate of polyolefin porous film and porous layer>

Laminate 3 similar to Example 3 was used.

<Production of non-aqueous electrolyte secondary battery>

(Manufacture of positive electrode plate)

As the positive electrode plate, the positive electrode plate 1 above was used.

(Manufacture of negative plate)

The surface of the negative electrode active material layer side of the same negative electrode plate as negative electrode plate 1 was polished three times using an abrasive cloth sheet manufactured by Nagatsuka Kogyo Co., Ltd. (model number TYPE AA GRIT No100) to obtain negative electrode plate 2. The negative electrode active material layer of the negative electrode plate 2 had a thickness of 38 μm and a porosity of 31%.

(Assembly of non-aqueous electrolyte secondary battery)

A non-aqueous electrolyte secondary battery 8 was produced in the same manner as in Example 1, except that laminate 3 was used instead of laminate 1 and negative electrode plate 2 was used instead of negative electrode plate 1.

[Example 9]

<Manufacture of laminate of polyolefin porous film and porous layer>

Laminate 3 similar to Example 3 was used.

<Production of non-aqueous electrolyte secondary battery>

(Manufacture of positive electrode plate)

As the positive electrode plate, the positive electrode plate 1 above was used.

(Manufacture of negative plate)

The surface of the negative electrode active material layer side of the same negative electrode plate as negative electrode plate 1 was polished 7 times using an abrasive cloth sheet manufactured by Nagatsuka Kogyo Co., Ltd. (model number TYPE AA GRIT No100) to obtain negative electrode plate 3. The negative electrode active material layer of the negative electrode plate 3 had a thickness of 38 μm and a porosity of 31%.

(Assembly of non-aqueous electrolyte secondary battery)

A non-aqueous electrolyte secondary battery 9 was produced in the same manner as in Example 1, except that laminate 3 was used instead of laminate 1 and negative electrode plate 3 was used instead of negative electrode plate 1.

[Comparative Example 1]

<Manufacture of laminate of polyolefin porous film and porous layer>

As the inorganic filler 6, borax having an oxygen atomic mass percentage of 71% (manufactured by Wako Pure Chemical Industries, Ltd.) was used. While mixing 10 parts by weight of vinylidene fluoride-hexafluoropropylene copolymer with respect to 90 parts by weight of inorganic filler 6, concentration of solid content (inorganic filler and vinylidene fluoride-hexafluoropropylene copolymer) in the mixture obtained Coating solution 6 was prepared by mixing a solvent so that the coating solution 6 was applied to one side of the polyolefin porous film 1 at a coating shear rate of 7.9 (1/s) to form a porous layer 6. Other than that, it carried out similarly to Example 1, and obtained the laminated body 6 of the polyolefin porous film 1 and the porous layer 6. Using the obtained layered product 6, the aspect ratio of the projected image of the inorganic filler 6 on the surface of the porous layer and the maximum value of the peak intensity ratio were measured. The results are shown in Table 1.

<Production of non-aqueous electrolyte secondary battery>

A non-aqueous electrolyte secondary battery 10 was produced in the same manner as in Example 1, except that laminate 6 was used instead of laminate 1.

[Comparative Example 2]

<Manufacture of laminate of polyolefin porous film and porous layer>

As the inorganic filler 7, hexagonal plate-shaped zinc oxide (trade name: XZ-100F, manufactured by Sakai Chemical Industry Co., Ltd.) having an oxygen atomic mass percentage of 20% was used. What produced the coating solution 7 using the inorganic filler 7, and formed the porous layer 7 by coating the coating solution 7 on one side of the polyolefin porous film 1 at a coating shear rate of 0.4 (1/s) by a doctor blade method. Other than that, it carried out similarly to Example 1, and obtained the laminated body 7 of the polyolefin porous film 1 and the porous layer 7. Using the obtained layered product 7, the aspect ratio of the projected image of the inorganic filler 7 on the surface of the porous layer and the maximum value of the peak intensity ratio were measured. The results are shown in Table 1.

<Production of non-aqueous electrolyte secondary battery>

A non-aqueous electrolyte secondary battery 11 was produced in the same manner as in Example 1, except that laminate 7 was used instead of laminate 1.

[Comparative Example 3]

<Manufacture of laminate of polyolefin porous film and porous layer>

As the inorganic filler 8, attapulgite having an oxygen atomic mass percentage of 48% (manufactured by Hayashi Kasei Co., Ltd., trade name: ATTAGEL#50) was used. While mixing 10 parts by weight of the vinylidene fluoride-hexafluoropropylene copolymer with respect to 90 parts by weight of the inorganic filler 8, the concentration of the solid content (inorganic filler and vinylidene fluoride-hexafluoropropylene copolymer) in the mixture obtained. Coating solution 8 was prepared by mixing the solvent so that 17% by weight was obtained, and the coating solution 8 was coated on one side of the polyolefin porous film 1 by a doctor blade method at a coating shear rate of 1.3 (1/s) to form a porous layer. Except having formed 8, it carried out similarly to Example 1, and obtained the laminated body 8 of the polyolefin porous film 1 and the porous layer 8. Using the obtained layered product 8, the aspect ratio of the projected image of the inorganic filler 8 on the surface of the porous layer and the maximum value of the peak intensity ratio were measured. The results are shown in Table 1.

<Production of non-aqueous electrolyte secondary battery>

A non-aqueous electrolyte secondary battery 12 was produced in the same manner as in Example 1, except that laminate 8 was used instead of laminate 1.

[Comparative Example 4]

<Manufacture of laminate of polyolefin porous film and porous layer>

As the inorganic filler 9, mica having an oxygen atomic mass percentage of 44% (manufactured by Wako Pure Chemical Industries, Ltd., trade name: non-swellable mica) was used. While mixing 10 parts by weight of the vinylidene fluoride-hexafluoropropylene copolymer with respect to 90 parts by weight of the inorganic filler 9, the concentration of the solid content (inorganic filler and vinylidene fluoride-hexafluoropropylene copolymer) in the mixture obtained. Coating solution 9 was prepared by mixing the solvent so that 20% by weight was obtained, and the coating solution 9 was coated on one side of the polyolefin porous film 1 at a coating shear rate of 0.4 (1/s) by a doctor blade method to form a porous layer 9. Except having formed, it carried out similarly to Example 1, and obtained the laminated body 9 of the polyolefin porous film 1 and the porous layer 9. Using the obtained laminate 9, the aspect ratio of the projected image of the inorganic filler 9 on the surface of the porous layer and the maximum value of the peak intensity ratio were measured. The results are shown in Table 1.

<Production of non-aqueous electrolyte secondary battery>

A non-aqueous electrolyte secondary battery 13 was produced in the same manner as in Example 1, except that laminate 9 was used instead of laminate 1.

[Comparative Example 5]

<Manufacture of laminate of polyolefin porous film and porous layer>

Laminate 3 similar to Example 3 was used.

<Production of non-aqueous electrolyte secondary battery>

(Manufacture of positive electrode plate)

The surface of the positive electrode active material layer side of the same positive electrode plate as positive electrode plate 1 was polished 10 times using an abrasive cloth sheet manufactured by Nagatsuka Kogyo Co., Ltd. (model number TYPE AA GRIT No100) to obtain positive electrode plate 4. The positive electrode active material layer of the positive electrode plate 4 had a thickness of 38 μm and a porosity of 40%.

(Manufacture of negative plate)

As the negative electrode plate, the negative electrode plate 1 was used.

(Assembly of non-aqueous electrolyte secondary battery)

A non-aqueous electrolyte secondary battery 14 was produced in the same manner as in Example 1, except that laminate 3 was used instead of laminate 1 and positive electrode plate 4 was used instead of positive electrode plate 1.

[Comparative Example 6]

<Manufacture of laminate of polyolefin porous film and porous layer>

Laminate 3 similar to Example 3 was used.

<Production of non-aqueous electrolyte secondary battery>

(Manufacture of positive electrode plate)

As the positive electrode plate, the positive electrode plate 1 above was used.

(Manufacture of negative plate)

The surface of the negative electrode active material layer side of the same negative electrode plate as negative electrode plate 1 was polished 10 times using an abrasive cloth sheet manufactured by Nagatsuka Kogyo Co., Ltd. (model number TYPE AA GRIT No100) to obtain negative electrode plate 4. The negative electrode active material layer of the negative electrode plate 4 had a thickness of 38 μm and a porosity of 31%.

(Assembly of non-aqueous electrolyte secondary battery)

A non-aqueous electrolyte secondary battery 15 was produced in the same manner as in Example 1, except that laminate 3 was used instead of laminate 1 and negative electrode plate 4 was used instead of negative electrode plate 1.

[Evaluation results of non-aqueous electrolyte secondary batteries 1 to 15]

Table 1 shows the results of measuring the charge capacities of the non-aqueous electrolyte secondary batteries 1 to 15 obtained in Examples and Comparative Examples after high-rate discharge.

[conclusion]

From the description in Table 1, the aspect ratio of the projected image of the inorganic filler on the surface of the porous layer is in the range of 1.4 to 4.0, and the maximum value of the peak intensity ratio (I _(hkl) / I _(abc) ) is in the range of 1.5 to 300, The non-aqueous electrolyte secondary battery obtained in Examples 1 to 9, wherein the capacitance per 900 mm of measurement area of the positive electrode plate is 1 nF or more and 1000 nF or less, and the capacitance of the negative electrode plate is 4 nF or more and 8500 nF or less of 4 nF or more and 8500 nF or less, It was shown that the batteries obtained in Comparative Examples 1 to 6 had higher charge capacities after high-rate discharge than non-aqueous electrolyte secondary batteries that did not satisfy any of the conditions.

The non-aqueous electrolyte secondary battery according to the present invention is excellent in charge capacity after high-rate discharge. Therefore, the non-aqueous electrolyte secondary battery of the present invention can be widely used in the field of manufacturing non-aqueous electrolyte secondary batteries.

Claims (5)

A porous layer containing an inorganic filler and a resin;
A positive electrode plate having a capacitance per 900 mm 2 of measurement area of 1 nF or more and 1000 nF or less;
A negative electrode plate having a capacitance per 900 mm 2 of measurement area of 4 nF or more and 8500 nF or less,
The aspect ratio of the projected image of the inorganic filler on the surface of the porous layer is in the range of 1.4 to 4.0,
Peak intensities I (hkl) and I (abc) of arbitrary diffraction surfaces ( _hkl ) and (abc) orthogonal to each other, measured by wide-angle X-ray diffraction, of the porous layer satisfy the following formula (1 ₎ do,
A non-aqueous electrolyte secondary battery in which the range of the maximum value of the peak intensity ratio calculated by the following formula (2) is in the range of 1.5 to 300.
I _(hkl) >I _(abc) … (One)
I _(hkl) /I _(abc) … (2) The method according to claim 1, wherein the porous layer contains at least one resin selected from the group consisting of polyolefins, (meth)acrylate-based resins, fluorine-containing resins, polyamide-based resins, polyester-based resins, and water-soluble polymers. , non-aqueous 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 side or both sides of a polyolefin porous film. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the positive electrode plate contains a transition metal oxide and the negative electrode plate contains graphite.

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