WO2020091062A1 - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

The purpose of the present invention is to achieve a non-aqueous electrolyte secondary battery that has excellent charging capacity after high-rate discharge. This non-aqueous electrolyte secondary battery comprises: a porous layer that includes a resin and an inorganic filler that has a thermal expansion coefficient of no more than 11 ppm/̊C, the rate at which the temperature of the surface of the porous layer increases being 0.93̊C/sec–1.25̊C/sec; a positive electrode; a negative electrode; and a non-aqueous electrolyte that contains 0.5–300 ppm of a prescribed additive.

Description

Non-aqueous electrolyte secondary battery

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

Non-aqueous electrolyte secondary batteries, especially lithium-ion secondary batteries, are widely used as batteries for personal computers, mobile phones, personal digital assistants, etc. due to their high energy density, and recently they have been used in consumer products such as electric tools and vacuum cleaners. The battery is being developed as a vehicle battery and a vehicle battery.

As non-aqueous electrolyte secondary batteries, for example, non-aqueous electrolyte secondary batteries described in Patent Documents 1 and 2 are known.

Patent No. 5569515 JP, 2009-146822, A

However, the above-mentioned conventional technology 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 an object thereof is to realize a non-aqueous electrolyte secondary battery having an 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, a negative electrode, and a non-aqueous electrolyte, and heats the inorganic filler at −40 ° C. to 200 ° C. The expansion layer has a coefficient of expansion of 11 ppm / ° C. or less, and the porous layer is impregnated with a solution containing propylene carbonate, a polyoxyalkylene nonionic surfactant and water in a weight ratio of 85: 12: 3, and then has a frequency of 2455 MHz. Of the temperature of the porous layer surface increased from 0.93 ° C./second to 1.25 ° C./second measured from the start of irradiation to 15 seconds after irradiation with the microwave of 1800 W. The non-aqueous electrolyte contains 0.5 ppm or more and 300 ppm or less of an additive having an ionic conductivity reduction rate L represented by the following formula (A) of 1.0% or more and 6.0% or less.
L = (LA-LB) / LA ... (A)
(In the formula (A), LA was prepared by dissolving LiPF ₆ in a mixed solvent containing ethylene carbonate, ethylmethyl carbonate and diethyl carbonate in a volume ratio of 3: 5: 2 such that the concentration thereof was 1 mol / L. The ionic conductivity (mS / cm) of the reference electrolytic solution is represented, and LB represents the ionic conductivity (mS / cm) of the electrolytic solution prepared by dissolving the additive in the reference electrolytic solution in an amount of 1.0% by weight. .)
Further, the non-aqueous electrolyte secondary battery according to Aspect 2 of the present invention is the same as in Aspect 1, except that the porous layer is laminated on one side or both sides of the polyolefin porous film.

Further, in the non-aqueous electrolyte secondary battery according to Aspect 3 of the present invention, in the Aspect 1 or 2, the porous layer has a polyolefin, a (meth) acrylate resin, a fluorine-containing resin, a polyamide resin, a polyester resin. It includes a resin selected from the group consisting of resins and water-soluble polymers.

Further, in the non-aqueous electrolyte secondary battery according to Aspect 4 of the present invention, in the Aspect 3, the polyamide resin is an aramid resin.

The nonaqueous electrolyte secondary battery according to Aspect 5 of the present invention is the nonaqueous electrolyte secondary battery according to any one of Aspects 1 to 4, wherein the nonaqueous electrolyte solution contains an electrolyte containing lithium.

Further, in the non-aqueous electrolyte secondary battery according to Aspect 6 of the present invention, in any one of Aspects 1 to 5, the non-aqueous electrolyte contains an aprotic polar solvent.

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

It is a figure which shows an example of the temperature change of the porous layer surface.

An embodiment of the present invention will be described below, but the present invention is not limited to this. The present invention is not limited to each configuration described below, various modifications are possible within the scope shown in the claims, and the technical means disclosed in different embodiments are appropriately combined. The obtained embodiments are also included in the technical scope of the present invention. Unless otherwise specified in the present 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 containing an inorganic filler and a resin, a positive electrode, a negative electrode and a non-aqueous electrolyte, and the inorganic filler at −40 ° C. to 200 ° C. The thermal expansion coefficient is 11 ppm / ° C. or less, and the porous layer is impregnated with a solution containing propylene carbonate, a polyoxyalkylene type nonionic surfactant and water in a weight ratio of 85: 12: 3, and then the frequency is increased. The temperature rising rate of the surface of the porous layer from the start of irradiation to 15 seconds after the start of irradiation was 0.93 ° C./sec or more and 1.25 ° C./sec or less, which was measured while irradiating the microwave of 2455 MHz with an output of 1800 W. The non-aqueous electrolyte contains 0.5 ppm or more and 300 ppm or less of an additive having an ionic conductivity reduction rate L represented by the following formula (A) of 1.0% or more and 6.0% or less.
L = (LA-LB) / LA ... (A)
In formula (A), LA is a reference in which LiPF ₆ is dissolved in a mixed solvent containing ethylene carbonate, ethylmethyl carbonate and diethyl carbonate in a volume ratio of 3: 5: 2 so that the concentration becomes 1 mol / L. Represents the ionic conductivity (mS / cm) of the working electrolyte solution, and LB represents the ionic conductivity (mS / cm) of the electrolyte solution prepared by dissolving 1.0% by weight of the additive in the reference electrolyte solution.

In this way, the thermal expansion coefficient of the inorganic filler contained in the porous layer and the temperature rising rate of the porous layer surface are adjusted to an appropriate range, and the ionic conductivity decrease rate and the content of the additive contained in the non-aqueous electrolyte are included. Adjust the amount to a specific range. As a result, the flow of ions in the non-aqueous electrolyte secondary battery including them can be adjusted to a suitable value, and as a result, the charge capacity of the non-aqueous electrolyte secondary battery after high rate discharge can be maintained high.

[Porous layer]
In one embodiment of the present invention, the porous layer may be disposed between the polyolefin porous film and at least one of the positive electrode and the negative electrode as a member constituting the non-aqueous electrolyte secondary battery. 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 the active material layer of at least one of the positive electrode and the negative electrode. Alternatively, the porous layer may be arranged between the polyolefin porous film and at least one of the positive electrode and the negative electrode so as to be in contact with them. The porous layer arranged between the polyolefin porous film and at least one of the positive electrode and the negative electrode may be one layer or two or more layers. The porous layer is preferably an insulating porous layer containing a resin.

When a porous layer is laminated on one side of a polyolefin porous film described below which is a separator for a non-aqueous electrolyte secondary battery, the porous layer is preferably a surface facing the positive electrode in the polyolefin porous film. To be laminated. More preferably, the porous layer is laminated on the surface in contact with the positive electrode.

It is considered that the charge capacity after high rate discharge is affected by the denseness of the porous layer. The less dense the porous layer is, the more easily lithium ions permeate, so that the charge capacity after high rate discharge is improved. On the other hand, the denser the porous layer, the less likely lithium ions will permeate.

The factor affecting the compactness of such a porous layer is the void structure of the porous layer. The void structure of the porous layer may include the area of the inner wall of the void, the degree of bending of the void, and the like. It is considered that the smaller the area of the inner wall of the voids and the degree of waviness of the voids, the lower the density of the porous layer, and conversely, the greater the area of the inner wall of the voids and the degree of waviness of the voids, the higher the density of the porous layer. Be done.

The present inventors focused on the temperature rising rate of the surface of the porous layer as a parameter reflecting the denseness of the porous layer. The lower the denseness of the porous layer, the smaller the rate of temperature rise on the surface of the porous layer. On the other hand, the higher the denseness of the porous layer, the higher the temperature rising rate on the surface of the porous layer.

The porous layer in one embodiment of the present invention is impregnated with a solution containing propylene carbonate, a polyoxyalkylene type nonionic surfactant and water in a weight ratio of 85: 12: 3, and then a microwave having a frequency of 2455 MHz is used. The temperature increase rate of the surface of the porous layer measured from 15 seconds after the start of irradiation was 0.93 ° C./sec or more and 1.25 ° C./sec or less, which was measured while irradiating with an output of 1800 W. The rate of temperature rise on the surface of the porous layer is preferably 0.95 ° C./sec or more, more preferably 0.97 ° C./sec or more. The rate of temperature rise on the surface of the porous layer is preferably 1.23 ° C./sec or less, more preferably 1.20 ° C./sec or less.

FIG. 1 is a diagram showing an example of the temperature change on the surface of the porous layer. The temperature increase rate from the start of irradiation to 15 seconds later corresponds to the slope at which the contribution ratio (R ² ) when the curve in the area surrounded by the solid line in FIG. 1 is linearly approximated is maximized.

If the rate of temperature rise on the surface of the porous layer is 1.25 ° C / sec or less, the denseness of the porous layer is not too high. That is, the flow path of the lithium ion does not become too long, and the flow path does not have too many branches. Therefore, since lithium ions easily pass through the porous layer, the charge capacity of the non-aqueous electrolyte secondary battery after high rate discharge can be improved. Further, when the temperature rising rate is 0.93 ° C./sec or more, the porous layer has a certain degree of denseness, so that strength and safety are secured.

In the present specification, the polyoxyalkylene type nonionic surfactant means a polymer having an oxyalkylene group and acting as a nonionic surfactant. The polyoxyalkylene type nonionic surfactant is not particularly limited as long as it can promote the penetration of the solution into the inside of the porous layer. The heat generated by the polyoxyalkylene nonionic surfactant is insignificant compared to water, so it is considered that the difference in the structure of the polyoxyalkylene nonionic surfactant does not significantly affect the calorific value. This is because. Examples of the polyoxyalkylene type nonionic surfactant include polyoxyalkylene alkyl ethers, polyoxyalkylene tridecyl ethers, polyoxyalkylene polycyclic phenyl ethers, polyoxyalkylene aryl ethers, and compounds represented by the following formula (1). The compound etc. which are mentioned can be used.

(In the formula, m = 5 to 10 and n = 10 to 25, and the arrangement of each repeating unit may be block, random or alternating.)
The compound represented by the formula (1) can also be referred to as an ethylene oxide / propylene oxide copolymer. As a specific example of the polyoxyalkylene type nonionic surfactant composed of the compound, a commercially available SN wet 980 (manufactured by San Nopco Ltd.) can be mentioned. The SN wet 980 is composed of a compound represented by the formula (1) in which the average value of m is 7 and the average value of n is 19.

Also, the porous layer contains an inorganic filler having a thermal expansion coefficient of 11 ppm / ° C. or less at −40 ° C. to 200 ° C. In the present specification, the inorganic filler means a filler composed of an inorganic material. The coefficient of thermal expansion of the inorganic filler can affect the uniformity of the distribution of the constituents and voids in the porous layer, and the uniformity of the degree of void deformation during battery operation. It is considered that this is because the thermal expansion coefficient of the inorganic filler may affect whether or not the distribution of the constituent components and voids during the formation of the porous layer can be easily made uniform. The more evenly distributed the voids and constituents in the porous layer, or the higher the uniformity of void deformation during battery operation, the easier lithium ions permeate through the porous layer. Therefore, the charge capacity of the non-aqueous electrolyte secondary battery after high rate discharge tends to be improved.

If the coefficient of thermal expansion of the inorganic filler at −40 ° C. to 200 ° C. is 11 ppm / ° C. or less, a porous layer in which voids and constituent components are uniformly distributed can be obtained. In addition, the voids in the porous layer are less likely to be deformed during battery operation. Therefore, since lithium ions easily pass through the porous layer, the charge capacity of the non-aqueous electrolyte secondary battery after high rate discharge can be improved.

The coefficient of thermal expansion is preferably larger than 0 ppm / ° C, more preferably 1 ppm / ° C or more. When the porous layer is deformed due to heat generation during the operation of the non-aqueous electrolyte secondary battery, stress concentrates on the contact portion between the inorganic filler and the binder resin forming the porous layer, so that the inside of the porous layer The void structure may change irreversibly, and as a result, the battery characteristics may be adversely affected. When the coefficient of thermal expansion is within the above range, such adverse effects can be avoided.

The lower limit of the content of the inorganic filler in the porous layer is preferably 50% by weight or more, and 70% by weight or more with respect to the total weight of the inorganic filler and the resin constituting the porous layer. More preferably, it is more preferably 90% by weight or more. On the other hand, the upper limit value of the content of the inorganic filler in the porous layer is preferably 99% by weight or less, and more preferably 98% by weight or less. The content of the inorganic filler is preferably 50% by weight or more from the viewpoint of heat resistance. Further, the content of the inorganic filler is preferably 99% by weight or less from the viewpoint of adhesion between the inorganic fillers. Further, by containing the inorganic filler, the slipperiness and heat resistance of the separator or the like having the porous layer can be improved.

It is preferable that the inorganic filler is a filler that is stable in the non-aqueous electrolyte and electrochemically stable. From the viewpoint of ensuring the safety of the battery, the inorganic filler is preferably a filler having a heat resistant temperature of 150 ° C. or higher.

The inorganic filler is preferably an inorganic filler containing oxygen element. In the present specification, the inorganic filler containing an oxygen element means a filler composed of an inorganic material containing an oxygen element. Examples of the inorganic substance containing an oxygen element include, but are not limited to, barium zirconate titanate, calcium titanate, aluminum titanate, and borosilicate glass.

Furthermore, it is preferable that the atomic composition percentage of oxygen in the inorganic filler containing oxygen element is 60 at% or more. When the atomic composition percentage of oxygen is 60 at% or more, the inorganic fillers repel each other and are easily dispersed. Therefore, the inorganic fillers are less likely to interact with each other, and the constituent components can be dispersed more uniformly. Therefore, the rate of temperature rise on the surface of the porous layer can also be adjusted by controlling the atomic composition percentage of oxygen contained in the inorganic filler.

The shape of the inorganic filler may change depending on the method for producing the inorganic filler and / or the dispersion condition of the inorganic filler when producing a coating liquid for forming the porous layer. The shape of the inorganic filler is any shape, such as a spherical shape, an oval shape, a rectangular shape, or a shape such as a gourd shape obtained by heat-sealing particles having a spherical shape, or an indefinite shape having no specific shape. Good. From the viewpoint of ion permeability and liquid retention of the porous layer, the shape of the inorganic filler is more preferably a gourd shape or an amorphous shape.

The resin contained in the porous layer is preferably insoluble in the electrolytic solution of the battery and is electrochemically stable in the usage range of the battery. Examples of the resin include polyolefin; (meth) acrylate resin; fluorine-containing resin; polyamide resin; polyimide resin; polyester resin; rubbers; resin having a melting point or glass transition temperature of 180 ° C. or higher; water-soluble polymer Polycarbonate, polyacetal, polyether ether ketone, etc .;

Among the above resins, polyolefins, polyester resins, (meth) acrylate resins, fluorine-containing resins, polyamide resins and water-soluble polymers are preferable.

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

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

Specific examples of the aramid resin include poly (paraphenylene terephthalamide), poly (metaphenylene isophthalamide), poly (parabenzamide), poly (metabenzamide), poly (4,4′-benzanilide terephthalate). Amide), poly (paraphenylene-4,4′-biphenylenedicarboxylic acid amide), poly (metaphenylene-4,4′-biphenylenedicarboxylic acid amide), poly (paraphenylene-2,6-naphthalenedicarboxylic acid amide), Poly (metaphenylene-2,6-naphthalenedicarboxylic acid amide), poly (2-chloroparaphenylene terephthalamide), paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer, metaphenylene terephthalamide / 2 , 6-diclosure Paraphenylene terephthalamide copolymer and the like. Of these, poly (paraphenylene terephthalamide) is more preferable.

As the polyester resin, aromatic polyester such as polyarylate and liquid crystal polyester are preferable.

Examples of rubbers include styrene-butadiene copolymer and its hydride, methacrylic acid ester copolymer, acrylonitrile-acrylic acid ester copolymer, styrene-acrylic acid ester copolymer, ethylene propylene rubber, polyvinyl acetate and the like. Can be mentioned.

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

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

Examples of the fluorine-containing resin include polyvinylidene fluoride (PVDF), polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer Coalescence, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-trichloroethylene copolymer, vinylidene fluoride-vinyl fluoride copolymer, vinylidene fluoride-hexafluoro Examples thereof include propylene-tetrafluoroethylene copolymer and ethylene-tetrafluoroethylene copolymer. Among them, when the porous layer is arranged facing the positive electrode, it is easy to maintain various performances such as rate characteristics and resistance characteristics of the non-aqueous electrolyte secondary battery even if oxidative deterioration occurs during battery operation. Fluorine-containing resins are preferred.

The porous layer in the present embodiment is preferably arranged between the separator for non-aqueous electrolyte secondary battery and the positive electrode active material layer included in the positive electrode. In the following description regarding the physical properties of the porous layer, when a non-aqueous electrolyte secondary battery, a porous layer arranged between the separator for the non-aqueous electrolyte secondary battery and the positive electrode active material layer provided in the positive electrode. Refers to at least the physical properties of.

The average thickness of the porous layer is preferably in the range of 0.5 μm to 10 μm, and preferably in the range of 1 μm to 5 μm, from the viewpoint of securing adhesiveness to the electrode and high energy density. Is more preferable.

When the thickness of the porous layer is 0.5 μm or more per layer, an internal short circuit due to damage of the non-aqueous electrolyte secondary battery can be sufficiently suppressed, and the amount of the electrolyte retained in the porous layer can be suppressed. Will be sufficient.

On the other hand, when the film thickness of the porous layer exceeds 10 μm per layer, the lithium ion permeation resistance increases in the non-aqueous electrolyte secondary battery, so the positive electrode may deteriorate when the cycle is repeated. Therefore, in the non-aqueous electrolyte secondary battery, the rate characteristics and the cycle characteristics may deteriorate. In addition, since the distance between the positive electrode and the negative electrode increases, the internal volume efficiency of the non-aqueous electrolyte secondary battery may decrease.

The basis weight per unit area of the porous layer can be appropriately determined in consideration of the strength, film thickness, weight and handling property of the porous layer. The basis weight per unit area of the porous layer is preferably 0.5 to 20 g / m ² and more preferably 0.5 to 10 g / m ² per porous layer.

By setting the basis 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 basis weight of the porous layer exceeds the above range, the non-aqueous electrolyte secondary battery tends to be heavy.

The porosity of the porous layer is preferably 20 to 90% by volume, and more preferably 30 to 80% by volume so that sufficient ion permeability can be obtained. The pore size of the pores of the porous layer is preferably 1.0 μm or less, more preferably 0.5 μm or less. By setting the pore diameters to these sizes, the non-aqueous electrolyte secondary battery can obtain sufficient ion permeability.

[Method for producing porous layer]
The porous layer can be formed by using the coating liquid obtained by dissolving or dispersing the resin in the solvent and dispersing the inorganic filler. The solvent can be said to be a solvent for dissolving the resin and a dispersion medium for dispersing the resin or the inorganic filler. Examples of the method for forming the coating liquid include a mechanical stirring method, an ultrasonic dispersion method, a high pressure dispersion method, and a media dispersion method.

The method for forming the porous layer is, for example, a method in which the coating liquid is directly applied to the surface of the base material and then the solvent is removed; after the coating liquid is applied to an appropriate support, the solvent is removed to form a porous layer. To form a porous layer, press-bond the porous layer and the base material, and then peel off the support; after applying the coating liquid to an appropriate support, press-contact the base material on the coated surface, and then the support And a method of removing the solvent after removing the substrate; and a method of removing the solvent after dip coating by dipping the substrate in the coating solution.

Preferably, the solvent does not adversely affect the base material, dissolves the resin uniformly and stably, and disperses the inorganic filler uniformly and stably. Examples of the solvent include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, acetone and water.

The coating liquid may appropriately contain a dispersant, a plasticizer, a surfactant, a pH adjuster and the like as components other than the resin and the inorganic filler.

Note that, in addition to the polyolefin porous film described later, other films, a positive electrode, a negative electrode, and the like can be used as the base material.

As a method for applying the coating liquid to the substrate, a conventionally known method can be adopted, and specific examples thereof include a gravure coater method, a dip coater method, a bar coater method and a die coater method. ..

-The method of removing the solvent is generally drying. Further, the solvent contained in the coating liquid may be replaced with another solvent before drying.

The shear viscosity of the coating liquid is preferably 1 Pa · s or less, more preferably 0.5 Pa · s or less. When the shear viscosity is high, the constituent components are likely to interact with each other, and the resulting porous layer is likely to have high denseness. When the shear viscosity of the coating liquid is 1 Pa · s or less, the denseness of the porous layer does not become too high, and the constituent components can be dispersed more uniformly. Therefore, by controlling the shear viscosity of this coating liquid, the temperature rising rate of the surface of the porous layer can be controlled. Further, this makes it possible to control the permeation of lithium ions.

In addition, in this specification, the shear viscosity refers to continuous shear in an interval 1 having a shear rate of 0.1 to 1000 [1 / sec] and an interval 2 having a shear rate of 1000 to 0.1 [1 / sec]. This refers to the shear viscosity at a shear rate of 0.4 [1 / sec] at interval 2 when the viscosity is measured.

[Non-aqueous electrolyte]
The non-aqueous electrolyte in one embodiment of the present invention contains an additive having an ionic conductivity decrease rate L represented by the following formula (A) of 1.0% or more and 6.0% or less, 0.5 ppm to 300 ppm. contains.
L = (LA-LB) / LA ... (A)
In formula (A), LA is a reference in which LiPF ₆ is dissolved in a mixed solvent containing ethylene carbonate, ethylmethyl carbonate and diethyl carbonate in a volume ratio of 3: 5: 2 so that the concentration becomes 1 mol / L. The ionic conductivity (mS / cm) of the electrolyte for use is shown. LB represents the ionic conductivity (mS / cm) of the electrolytic solution prepared by dissolving 1.0% by weight of the additive in the reference electrolytic solution.

The additive is not particularly limited as long as it is a compound that satisfies the ionic conductivity reduction rate L represented by the formula (A) of 1.0% or more and 6.0% or less. Examples of such a compound include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethyl phosphate, vinylene carbonate, propane sultone, 2,6-dione. -Tert-butyl-4-methylphenol, 6- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t-butyldibenzo [d , F] [1,3,2] dioxaphosphine, tris (2,4-di-tert-butylphenyl) phosphate, 2- [1- (2-hydroxy-3,5-di-tert-) Pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl acrylate, dibutylhydroxytoluene and the like can be mentioned.

The non-aqueous electrolytic solution contains an electrolyte and an organic solvent. Examples of the electrolyte include an electrolyte containing lithium. As the electrolyte containing lithium, for _{example, 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, Examples thereof include metal salts such as Li ₂ B ₁₀ Cl ₁₀ , lithium salts of lower aliphatic carboxylic acids and lithium salts such as LiAlCl ₄ . The electrolyte may be used alone or in combination of two or more kinds.

Examples of the organic solvent that constitutes the non-aqueous electrolytic solution include carbonates, ethers, esters, nitriles, amides, carbamates and sulfur-containing compounds, and fluorine groups introduced into these organic solvents. An aprotic polar solvent such as a fluorine-containing organic solvent may be used. The organic solvent may be used alone or in combination of two or more.

Like the reference electrolyte, the organic solvent is preferably a mixed solvent containing a cyclic compound such as ethylene carbonate and a chain compound such as ethylmethyl carbonate and diethyl carbonate. The mixed solvent contains the cyclic compound and the chain compound preferably in a volume ratio of 2: 8 to 4: 6, more preferably in a volume ratio of 2: 8 to 3: 7, and particularly preferably. Is included in a volume ratio of 3: 7. The mixed solvent in which the cyclic compound and the chain compound are mixed at a volume ratio of 3: 7 is an organic solvent that is generally used in the non-aqueous electrolyte solution of the non-aqueous electrolyte secondary battery.

The additive in one embodiment of the present invention reduces the ionic conductivity of the reference electrolyte solution. The following reasons can be considered as reasons why the reduction of the charge capacity after high-rate discharge can be suppressed by adding the additive to the non-aqueous electrolyte solution. By adding the additive, the dissociation degree of ions in the non-aqueous electrolyte may be reduced. This can reduce the depletion of ions at the interface between the separator and the electrode during charge / discharge, particularly when the battery is operated at high speed. Therefore, it is considered that the reduction of the charge capacity after the high rate discharge can be suppressed.

From the viewpoint of reducing the depletion of ions near the electrodes, the non-aqueous electrolyte solution contains the additive in an amount of 0.5 ppm or more, preferably 20 ppm or more, and more preferably 45 ppm or more.

On the other hand, when the content of the additive is excessively large, the degree of dissociation of ions in the entire non-aqueous electrolyte solution is excessively reduced, which is considered to hinder the flow of ions in the entire non-aqueous electrolyte secondary battery. Be done. Therefore, on the contrary, the battery characteristics such as the charge capacity after high rate discharge may be deteriorated. From the viewpoint of suppressing inhibition of ion flow in the entire non-aqueous electrolyte secondary battery, the non-aqueous electrolyte contains the additive in an amount of 300 ppm or less, preferably 250 ppm or less, and 180 ppm or less. Is more preferable.

Here, in the non-aqueous electrolyte secondary battery according to the embodiment of the present invention, the degree of ion dissociation in the vicinity of the positive electrode during repeated charging and discharging, particularly when the battery is operated at a high speed, It is strongly influenced by the amount of additives.

Therefore, the nonaqueous electrolyte secondary battery according to the embodiment of the present invention can suitably reduce the degree of dissociation of ions near the positive electrode regardless of the type of the nonaqueous electrolyte. That is, regardless of the type and amount of the electrolyte contained in the non-aqueous electrolytic solution, and the type of the organic solvent contained, the addition of 0.5 ppm or more and 300 ppm or less of the additive causes dissociation of ions near the positive electrode. The degree can be suitably reduced. As a result, it is possible to suppress a decrease in charge capacity after high rate discharge.

The method for controlling the content of the additive in the non-aqueous electrolytic solution to be 0.5 ppm or more and 300 ppm or less is not particularly limited, but, for example, in the method for manufacturing a non-aqueous electrolytic solution secondary battery described later, non-aqueous electrolytic Examples include a method of pre-dissolving the additive in the non-aqueous electrolyte solution to be injected into the container that will be the housing of the liquid secondary battery, so that the content of the additive is 0.5 ppm or more and 300 ppm or less. it can.

[Positive electrode]
The positive electrode in one embodiment of the present invention is not particularly limited as long as it is generally used as the positive electrode of a non-aqueous electrolyte secondary battery. For example, a positive electrode sheet having a structure in which an active material layer containing a positive electrode active material and a binder is formed on a positive electrode current collector can be used as the positive electrode. The active material layer may further contain a conductive agent.

The positive electrode active material includes, for example, a material capable of being doped / dedoped with metal ions such as lithium ions or sodium ions. Specific examples of the material include a lithium composite oxide containing at least one transition metal such as V, Mn, Fe, Co, and Ni.

Examples of the conductive agent include natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers and carbonaceous materials such as organic polymer compound fired bodies. The conductive agent may be used alone or in combination of two or more kinds.

Examples of the binder include fluororesin such as polyvinylidene fluoride (PVDF), acrylic resin, and styrene-butadiene rubber. 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 easily processed into a thin film and is inexpensive.

The positive electrode sheet may be produced, for example, by pressure molding a positive electrode active material, a conductive agent and a binder on a positive electrode current collector; a positive electrode active material, a conductive agent and a binder using an appropriate organic solvent. Is applied to a positive electrode current collector, dried, and then pressed to fix it to the positive electrode current collector; and the like.

[Negative electrode]
The negative electrode in one embodiment of the present invention is not particularly limited as long as it is generally used as a negative electrode of a non-aqueous electrolyte secondary battery. For example, a negative electrode sheet having a structure in which an active material layer containing a negative electrode active material and a binder is formed on a negative electrode current collector can be used as the negative electrode. The active material layer may further contain a conductive agent.

As the negative electrode active material, for example, a material capable of doping / dedoping metal ions such as lithium ions or sodium ions can be mentioned. Examples of the material include a carbonaceous material and the like. Examples of the carbonaceous material include natural graphite, artificial graphite, cokes, carbon black and pyrolytic carbons.

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

Examples of the method for producing the negative electrode sheet include a method in which the negative electrode active material is pressure-molded on the negative electrode current collector; the negative electrode active material is made into a paste using an appropriate organic solvent, and then the paste is used as the negative electrode current collector. And the like, and then pressurizing and fixing to the negative electrode current collector; and the like. The paste preferably contains the conductive agent and the binder.

[Polyolefin porous film]
The non-aqueous electrolyte secondary battery in one embodiment of the present invention may include a polyolefin porous film. Below, a polyolefin porous film may only be called a "porous film." The porous film contains a polyolefin-based resin as a main component and has a large number of pores connected to the inside thereof, so that a gas and a liquid can pass from one surface to the other surface. The porous film alone can serve as a separator for a non-aqueous electrolyte secondary battery. It can also be a base material of the laminated separator for a non-aqueous electrolyte secondary battery in which the above-mentioned porous layer is laminated.

On at least one surface of the polyolefin porous film, a laminate in which the porous layer is laminated, in the present specification, also referred to as "non-aqueous electrolyte secondary battery laminated separator" or "laminated separator" .. Further, the separator for a non-aqueous electrolyte secondary battery in one embodiment of the present invention may further include other layers such as an adhesive layer, a heat resistant layer, and a protective layer, in addition to the polyolefin porous film.

The proportion of polyolefin in the porous film is 50% by volume or more of the entire porous film, more preferably 90% by volume or more, and further preferably 95% by volume or more. Further, it is more preferable that the polyolefin contains a high molecular weight component having a weight average molecular weight of 5 × 10 ⁵ to 15 × 10 ⁶ . In particular, when the polyolefin contains a high molecular weight component having a weight average molecular weight of 1,000,000 or more, the strength of the separator for a non-aqueous electrolyte secondary battery is improved, which is more preferable.

The polyolefin, which is a thermoplastic resin, is specifically a homopolymer obtained by polymerizing monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene and 1-hexene. Alternatively, a copolymer may be used. Examples of the homopolymer include polyethylene, polypropylene and polybutene. Examples of the copolymer include ethylene-propylene copolymer.

Among these, polyethylene is more preferable because it can block excessive current from flowing at lower temperatures. Note that 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, ultrahigh molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more is more preferable.

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

The basis weight per unit area of the porous film can be appropriately determined in consideration of strength, film thickness, weight and handleability. However, the basis weight is preferably 4 to 20 g / m ² , and preferably 4 to 12 g / m ² so that the weight energy density and the volume energy density of the non-aqueous electrolyte secondary battery can be increased. More preferably, it is more preferably 5 to 10 g / m ² .

The air permeability of the porous film is preferably 30 to 500 sec / 100 mL in Gurley value, and more preferably 50 to 300 sec / 100 mL. When the porous film has the above-mentioned air permeability, sufficient ion permeability can be obtained. The air permeability of the laminated separator for a non-aqueous electrolyte secondary battery in which the above-mentioned porous layer is laminated on the porous film is preferably 30 to 1000 sec / 100 mL in terms of Gurley value, and is 50 to 800 sec / 100 mL. Is more preferable. Since the laminated separator for a non-aqueous electrolyte secondary battery has the above-mentioned air permeability, it is possible to obtain sufficient ion permeability in the non-aqueous electrolyte secondary battery.

The porosity of the porous film is preferably 20 to 80% by volume so as to increase the holding amount of the electrolytic solution and to surely prevent the flow of an excessive current at a lower temperature. It is more preferably 30 to 75% by volume. The pore size of the pores of the porous film is 0.3 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. Is preferable, and 0.14 μm or less is more preferable.

[Method for producing polyolefin porous film]
The method for producing the porous film is not particularly limited. For example, a sheet-shaped polyolefin resin composition is prepared by kneading a polyolefin resin, a pore-forming agent such as an inorganic filler and a plasticizer, and optionally an antioxidant and the like and then extruding the kneaded product. After removing the pore-forming agent from the sheet-shaped polyolefin resin composition with an appropriate solvent, the polyolefin resin composition from which the pore-forming agent has been removed may be stretched to produce a polyolefin porous film. it can.

The above-mentioned inorganic filler is not particularly limited, and examples thereof include inorganic fillers, specifically calcium carbonate and the like. The plasticizer is not particularly limited, and examples thereof include low molecular weight hydrocarbons such as liquid paraffin.

Specifically, a method including the following steps can be mentioned.
(A) a step of kneading an ultrahigh molecular weight polyethylene, a low molecular weight polyethylene having a weight average molecular weight of 10,000 or less, a pore forming agent such as calcium carbonate or a plasticizer, and an antioxidant to obtain a polyolefin resin composition,
(B) a step of rolling the obtained polyolefin resin composition with a pair of rolling rollers and gradually cooling it while pulling it with a take-up roller having a different speed ratio to form a sheet,
(C) A step of removing the pore forming agent from the obtained sheet with a suitable solvent.
(D) A step of stretching the sheet from which the pore forming agent has been removed at an appropriate stretching ratio.

[Method for producing laminated separator for non-aqueous electrolyte secondary battery]
Examples of the method for producing a laminated separator for a non-aqueous electrolyte secondary battery in one embodiment of the present invention include, for example, in the above-mentioned “method for producing a porous layer”, as the base material to which the coating liquid is applied, The method of using a polyolefin porous film can be mentioned.

In other words, the porous layer is laminated on one side or both sides of the polyolefin porous film to obtain a non-aqueous electrolyte secondary battery laminated separator.

[Method for producing non-aqueous electrolyte secondary battery]
As a method for manufacturing the non-aqueous electrolyte secondary battery according to the embodiment of the present invention, a conventionally known manufacturing method can be adopted. For example, by arranging the positive electrode, the polyolefin porous film, and the negative electrode in this order, a member for a non-aqueous electrolyte secondary battery is formed. Here, the porous layer may be present between the polyolefin porous film and at least one of the positive electrode and the negative electrode. Then, the member for a non-aqueous electrolyte secondary battery is put in a container which is a casing of the non-aqueous electrolyte secondary battery. After filling the inside of the container with the non-aqueous electrolyte, the container is sealed while reducing the pressure. Thereby, the non-aqueous electrolyte secondary battery according to the embodiment of the present invention can be manufactured.

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.

[Measuring method]
Various measurements in Examples and Comparative Examples were performed by the following methods.

(1) Film thickness (unit: μm)
The thicknesses of the non-aqueous electrolyte secondary battery separator and the porous layer were measured using a high precision digital length measuring machine (VL-50) manufactured by Mitutoyo Corporation. The film thickness of the porous layer was a value obtained by subtracting the film thickness of the part where the porous layer was not formed from the film thickness of the part where the porous layer was formed in each laminate.

(2) Shear viscosity The shear viscosities of the coating solutions used in Examples 1 to 5 and Comparative Examples 1 to 4 were continuously measured using a rheometer (MCR301 manufactured by Anton Paar Co.) under the following conditions at intervals 1 and 2. It was measured. The shear viscosity at a shear rate of 0.4 [1 / sec] in this interval 2 was adopted.
Jig used: cone plate (CP-50-1), measurement position: 1 mm, measurement temperature: 25 ° C
Shear rate in interval 1: 0.1-1000 [1 / sec],
Shear rate at interval 2: 1000 to 0.1 [1 / sec].

(3) Atomic Composition Percentage of Oxygen Included in Inorganic Filler The calculation method of the atomic composition percentage [at%] of oxygen contained in the inorganic filler of Example 1 is shown below.
Chemical formula: BaTi _0.8 Zr _0.2 O ₃
Ba: Ti: Zr: O = 1: 0.8: 0.2: 3
Atomic composition percentage of oxygen [at%] = 3 / (1 + 0.8 + 0.2 + 3) × 100 = 60 [at%]
With respect to the inorganic fillers used in Examples 2 to 5 and Comparative Examples 1 to 4, the atomic composition percentage of oxygen was calculated by the same calculation method.

(4) Measurement of Separator Temperature Change Behavior During Microwave Irradiation A 4 cm × 4 cm test piece was prepared from the non-aqueous electrolyte secondary battery laminates of Examples 1 to 5 and Comparative Examples 1 to 4 produced as described below. I cut it out. The test piece was impregnated with a solution containing propylene carbonate, SN Wet 980 (manufactured by San Nopco Ltd.) and water in a weight ratio of 85: 12: 3. Thereafter, these test pieces were spread on a Teflon (registered trademark) sheet (size: 12 cm × 10 cm). The test piece was folded in half so that an optical fiber type thermometer (Neoptix Reflex thermometer manufactured by Astec Co., Ltd.) coated with Teflon (registered trademark) was sandwiched between the porous layer surfaces. After that, in order to surely bring the thermometer into contact with the surface of the porous layer, a PTFE plate was placed on the test piece except for 1 mm around the thermometer to prevent floating.

Next, after fixing a test piece impregnated with the solution in a microwave irradiator equipped with a turntable (manufactured by Micro Electronics Co., Ltd., 9 kW microwave oven, frequency 2455 MHz) in a state of sandwiching a thermometer, The test piece was irradiated with microwave at 1800 W for 2 minutes.

The temperature change of the test piece during microwave irradiation was measured every 0.2 seconds with the optical fiber thermometer.

The slope at which the contribution ratio is maximum in the linear approximation of the temperature of the porous layer surface and the microwave irradiation time from the start of microwave irradiation to 15 seconds is the temperature rise rate of the porous layer surface (° C / sec. ).

(5) Measurement of Thermal Expansion Coefficient The thermal expansion coefficient (ppm / ° C.) of the inorganic fillers used in Examples 1 to 5 and Comparative Examples 1 to 4 at −40 ° C. to 200 ° C. was measured using TMA402 F1 Hyperion (made by NETZSCH). Was measured under the following conditions.
Measurement atmosphere: helium, measurement load: 0.02 N, heating rate: 5 ° C./min, reference sample: quartz, measurement method: compression mode.

(6) Reduction rate of ionic conductivity (%)
By dissolving LiPF _{6 in a} mixed solvent prepared by mixing ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in a volume ratio of 3: 5: 2 so that the concentration becomes 1 mol / L, a reference electrolyte solution is obtained. Got Each additive was added to the reference electrolyte solution to be 1% and dissolved, and then the ionic conductivity (mS / cm) was measured. The ionic conductivity was measured using an electric conductivity meter (ES-71) manufactured by Horiba Ltd.
The ionic conductivity decrease rate is represented by the following formula (A).

L = (LA-LB) / LA ... (A)
L: reduction rate of ionic conductivity (%),
LA: ionic conductivity (mS / cm) before adding the additive,
LB: Ionic conductivity (mS / cm) after adding the additive.

(7) Battery Characteristics of Non-Aqueous Electrolyte Secondary Battery A non-aqueous electrolyte secondary battery assembled as described below was subjected to CC at 25 ° C. in a voltage range of 4.1 to 2.7 V and a charging current value of 0.2 C. -CV charging (final current condition 0.02C), CC discharge with a discharge current value of 0.2C was set as one cycle, and four cycles of initial charge / discharge were performed at 25 ° C.

Note that the current value for discharging the rated capacity based on the discharge capacity of 1 hour rate in 1 hour is 1C. CC-CV charging is a charging method in which charging is performed with a set constant current, and after reaching a predetermined voltage, the current is reduced while maintaining the voltage. CC discharge is a method of discharging to a predetermined voltage with a set constant current. The same applies to the following.

For the non-aqueous electrolyte secondary battery subjected to the initial charging / discharging, CC-CV charging with a charging current value of 1C (end current condition 0.02C) and discharging current values of 0.2C, 1C, 2C were performed in this order. The discharge was carried out. Charging / discharging was performed for 3 cycles at 55 ° C. for each rate. At this time, the voltage range was set to 2.7V to 4.2V. At this time, the charge capacity at the time of 1C charge of the 3rd cycle at the time of 2C discharge rate characteristic measurement was measured, and it was set as the charge capacity after high rate discharge. The designed capacity of the non-aqueous electrolyte secondary batteries manufactured in Examples and Comparative Examples was 20.5 mAh.

[Example 1]
<Production of porous layer>
(Production of coating liquid)
As an inorganic filler, barium titanate zirconate (manufactured by Sakai Chemical Industry Co., Ltd., BTZ-01-8020), as a binder resin, vinylidene fluoride-hexafluoropropylene copolymer (manufactured by Arkema Ltd .: trade name "KYNAR2801"), solvent As a mixture, N-methyl-2-pyrrolidone (manufactured by Kanto Chemical Co., Inc.) was mixed in the following manner.

First, 10 parts by weight of vinylidene fluoride-hexafluoropropylene copolymer was added to 90 parts by weight of barium zirconate titanate to obtain a mixture. Next, the solvent was added to the obtained mixture so that the concentration of solids (barium zirconate titanate and vinylidene fluoride-hexafluoropropylene copolymer) was 40% by weight, and the mixture was mixed. Obtained. The resulting mixed liquid was stirred and mixed using a rotation / revolution mixer (Awatori Kentaro made by Shinky Co., Ltd.) and a thin film swivel type high speed mixer (Filmix made by Primix Co., Ltd.) to obtain a uniform coating liquid. ..

(Production of porous layer)
The obtained coating liquid was applied to one surface of a polyethylene porous film (thickness 12 μm, porosity 44%), which is a separator for a non-aqueous electrolyte secondary battery, by a doctor blade method. The obtained coating film was dried at 80 ° C. to form the porous layer 1 on one surface of the non-aqueous electrolyte secondary battery separator. Thus, a laminate 1 including the separator for non-aqueous electrolyte secondary battery and the porous layer 1 was obtained. At this time, the doctor blade clearance was adjusted so that the basis weight of the porous layer 1 was 7 g / m ² . Table 1 shows the measurement results of various physical properties of the coating liquid, the inorganic filler, and the laminate 1.

<Preparation of non-aqueous electrolyte secondary battery>
(Preparation of positive electrode)
A commercially available positive electrode manufactured 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 applied to the commercially available positive electrode so that the size of the part where the positive electrode active material layer was formed was 40 mm × 35 mm, and the part where the width of 13 mm was not formed and the positive electrode active material layer was not formed remained on the outer periphery thereof. It was cut out and used as the positive electrode of the non-aqueous electrolyte secondary battery described later. The positive electrode active material layer had a thickness of 58 μm and a density of 2.50 g / cm ³ .

(Preparation of negative electrode)
A commercially available negative electrode manufactured by applying graphite / styrene-1,3-butadiene copolymer / sodium carboxymethyl cellulose (weight ratio 98/1/1) to a copper foil was used. A copper foil was applied to the commercially available negative electrode so that the size of the part where the negative electrode active material layer was formed was 50 mm × 40 mm, and the part where the width of 13 mm was not formed and the negative electrode active material layer was not formed remained on the outer periphery thereof. It was cut out to obtain a negative electrode for a non-aqueous electrolyte secondary battery described later. The negative electrode active material layer had a thickness of 49 μm and a density of 1.40 g / cm ³ .

(Preparation of non-aqueous electrolyte)
LiPF ₆ was dissolved in a mixed solvent in which ethylene carbonate, ethylmethyl carbonate, and diethyl carbonate were mixed at a volume ratio of 3: 5: 2 so that the concentration thereof was 1 mol / L, to obtain an electrolytic solution stock solution 1. The electrolytic solution stock solution 1 is an aprotic polar solvent electrolytic solution containing Li ⁺ ions.

Addition liquid 1 was obtained by adding diethyl carbonate to 10.3 mg of dibutylhydroxytoluene (BHT, ionic conductivity reduction rate: 5.3%) to dissolve to 5 mL. The non-aqueous electrolyte solution 1 was obtained by mixing 300 μL of the additive solution 1 and 1700 μL of the electrolyte solution stock solution 1. Table 2 shows the content of the additive in the non-aqueous electrolyte solution 1.

(Assembly of non-aqueous electrolyte secondary battery)
Using the positive electrode, the negative electrode, the laminate 1, and the nonaqueous electrolytic solution 1, a nonaqueous electrolytic solution secondary battery 1 was manufactured by the method described below.

A non-aqueous electrolyte secondary battery member 1 was obtained by stacking the positive electrode, the laminate 1 with the porous layer facing the positive electrode side, and the negative electrode in this order in a laminate pouch. At this time, the positive electrode and the negative electrode were arranged such that the entire main surface of the positive electrode active material layer of the positive electrode was included in the range of the main surface of the negative electrode active material layer of the negative electrode. That is, the positive electrode and the negative electrode were arranged such that the entire main surface of the positive electrode active material layer of the positive electrode overlaps the main surface of the negative electrode active material layer of the negative electrode.

Next, the non-aqueous electrolyte secondary battery member 1 was placed in a prefabricated bag in which an aluminum layer and a heat seal layer were laminated. Further, 0.23 mL of the non-aqueous electrolyte solution 1 was put in this bag. Then, the inside of the bag was depressurized and the bag was heat-sealed to manufacture the non-aqueous electrolyte secondary battery 1.

After that, the charge capacity of the non-aqueous electrolyte secondary battery 1 obtained by the above method after high rate discharge was measured. The results are shown in Table 2.

[Example 2]
<Preparation of non-aqueous electrolyte secondary battery>
(Preparation of non-aqueous electrolyte)
LiPF ₆ was dissolved in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 3: 7 so that the concentration thereof was 1 mol / L, to obtain an electrolytic solution stock solution 2.

Addition liquid 2 was obtained by adding diethyl carbonate to 10.0 mg of vinylene carbonate (VC, reduction rate of ionic conductivity: 1.3%) to make 5 mL. 200 μL of the additive solution 2 and 1800 μL of the electrolytic solution stock solution 2 were mixed, and 900 μL of the electrolytic solution stock solution 2 was added to 100 μL of the mixed solution of the additive solution 2 and the electrolytic solution stock solution 2 to obtain an additive solution 3. A non-aqueous electrolyte solution 2 was prepared by mixing 50 μL of the additive solution 3 and 1950 μL of the electrolyte solution stock solution 2. Table 2 shows the content of the additive in the non-aqueous electrolyte solution 2.

(Assembly 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 the non-aqueous electrolyte 2 was used instead of the non-aqueous electrolyte 1.

After that, the charge capacity of the non-aqueous electrolyte secondary battery 2 obtained by the above method after high rate discharge was measured. The results are shown in Table 2.

[Example 3]
<Production of Laminated Body Comprising Non-Aqueous Electrolyte Secondary Battery Separator and Porous Layer>
In the same manner as in Example 1 except that calcium titanate (D50 = 0.3 μm manufactured by Toyoshima Seisakusho) was used as the inorganic filler, instead of the porous layer 1 on one surface of the separator for a non-aqueous electrolyte secondary battery. The porous layer 2 was formed. As a result, a laminate 2 including the separator for non-aqueous electrolyte secondary battery and the porous layer 2 was obtained. Table 1 shows the measurement results of various physical properties of the coating liquid, the inorganic filler, and the laminate 2.

<Preparation of non-aqueous electrolyte secondary battery>
(Preparation of non-aqueous electrolyte)
LiPF ₆ was dissolved in a mixed solvent prepared by mixing ethylene carbonate, ethylmethyl carbonate and diethyl carbonate in a volume ratio of 4: 4: 2 so that the concentration thereof was 1 mol / L, to obtain an electrolytic solution stock solution 3. It was

Diethyl carbonate was added to 11.2 mg of pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (Irg.1010, ionic conductivity reduction rate: 4.0%), and dissolved. It was made to be 5 mL and the addition liquid 4 was obtained. 90 μL of the additive solution 4 and 1910 μL of the electrolytic solution stock solution 3 were mixed to obtain a non-aqueous electrolytic solution 3. Table 2 shows the content of the additive in the non-aqueous electrolyte solution 3.

(Assembly of non-aqueous electrolyte secondary battery)
A non-aqueous electrolyte secondary was prepared in the same manner as in Example 1 except that the laminate 2 was used instead of the laminate 1 and the non-aqueous electrolyte 3 was used instead of the non-aqueous electrolyte 1. A battery 3 was produced.

After that, the charge capacity of the non-aqueous electrolyte secondary battery 3 obtained by the above method after high rate discharge was measured. The results are shown in Table 2.

[Example 4]
<Preparation of non-aqueous electrolyte secondary battery>
(Preparation of non-aqueous electrolyte)
90 μL of the additive solution 4 and 1910 μL of the electrolytic solution stock solution 1 were mixed to obtain a non-aqueous electrolytic solution 4. Table 2 shows the content of the additive in the non-aqueous electrolyte solution 4.

(Assembly of non-aqueous electrolyte secondary battery)
A non-aqueous electrolyte secondary was prepared in the same manner as in Example 1 except that the laminate 2 was used instead of the laminate 1 and the non-aqueous electrolyte 4 was used instead of the non-aqueous electrolyte 1. Battery 4 was produced.

After that, the charge capacity of the non-aqueous electrolyte secondary battery 4 obtained by the above method after high rate discharge was measured. The results are shown in Table 2.

[Example 5]
<Production of Laminated Body Comprising Non-Aqueous Electrolyte Secondary Battery Separator and Porous Layer>
In the same manner as in Example 1, except that aluminum titanate (D50 = 0.9 μm manufactured by Toyoshima Seisakusho) was used as the inorganic filler, one side of the separator for a non-aqueous electrolyte secondary battery was replaced with a porous layer 1 instead of the porous layer 1. The quality layer 3 was formed. Thereby, a laminate 3 including the separator for non-aqueous electrolyte secondary battery and the porous layer 3 was obtained. Table 1 shows the measurement results of various physical properties of the coating liquid, the inorganic filler, and the laminate 3.

<Preparation of non-aqueous electrolyte secondary battery>
(Preparation of non-aqueous electrolyte)
LiPF ₆ was dissolved in a mixed solvent prepared by mixing ethylene carbonate, ethylmethyl carbonate and diethyl carbonate in a volume ratio of 2: 5: 3 so that the concentration thereof was 1 mol / L, to obtain an electrolytic solution stock solution 4. It was 90 μL of the additive solution 4 and 1910 μL of the electrolytic solution stock solution 4 were mixed to form a non-aqueous electrolytic solution 5. Table 2 shows the content of the additive in the non-aqueous electrolyte solution 5.

(Assembly of non-aqueous electrolyte secondary battery)
A non-aqueous electrolyte secondary was prepared in the same manner as in Example 1 except that the laminate 3 was used instead of the laminate 1 and the non-aqueous electrolyte 5 was used instead of the non-aqueous electrolyte 1. A battery 5 was produced.

After that, the charge capacity of the non-aqueous electrolyte secondary battery 5 obtained by the above method after high rate discharge was measured. The results are shown in Table 2.

[Comparative Example 1]
<Preparation of non-aqueous electrolyte secondary battery>
(Preparation of non-aqueous electrolyte)
Diethyl carbonate was added to and dissolved in 9.7 mg of tris- (4-t-butyl-2,6-di-methyl-3-hydroxybenzyl) isocyanurate (Cyanox 1790, ionic conductivity reduction rate: 6.1%). 5 mL was added to obtain Additive Liquid 5. 90 μL of the additive solution 5 and 1910 μL of the electrolytic solution stock solution 1 were mixed to obtain a non-aqueous electrolytic solution 6. Table 2 shows the content of the additive in the non-aqueous electrolyte solution 6.

(Assembly of non-aqueous electrolyte secondary battery)
A non-aqueous electrolyte secondary was prepared in the same manner as in Example 1 except that the laminate 2 was used instead of the laminate 1 and the non-aqueous electrolyte 6 was used instead of the non-aqueous electrolyte 1. A battery 6 was produced.

After that, the charge capacity of the non-aqueous electrolyte secondary battery 6 obtained by the above method after high rate discharge was measured. The results are shown in Table 2.

[Comparative Example 2]
<Production of Laminated Body Comprising Non-Aqueous Electrolyte Secondary Battery Separator and Porous Layer>
As the inorganic filler, except that borax (manufactured by Wako Pure Chemical Industries, Ltd.) that passed through a sieve having an opening of 53 μm was used, the porous layer 1 was formed on one surface of the separator for the non-aqueous electrolyte secondary battery in the same manner as in Example 1. Instead, the porous layer 4 was formed. Thereby, a laminate 4 of the separator for non-aqueous electrolyte secondary battery and the porous layer 4 was obtained. Table 1 shows the measurement results of various physical properties of the coating liquid, the inorganic filler, and the laminate 4.

<Preparation of non-aqueous electrolyte secondary battery>
(Assembly of non-aqueous electrolyte secondary battery)
A non-aqueous electrolyte secondary was prepared in the same manner as in Example 1 except that the laminate 4 was used instead of the laminate 1 and the non-aqueous electrolyte 4 was used instead of the non-aqueous electrolyte 1. Battery 7 was produced.

After that, the charge capacity of the non-aqueous electrolyte secondary battery 7 obtained by the above method after high rate discharge was measured. The results are shown in Table 2.

[Comparative Example 3]
<Production of Laminated Body Comprising Non-Aqueous Electrolyte Secondary Battery Separator and Porous Layer>
A porous layer 5 was used instead of the porous layer 1 on one surface of the separator for a non-aqueous electrolyte secondary battery in the same manner as in Example 1 except that alumina (AKP3000 manufactured by Sumitomo Chemical Co., Ltd.) was used as the inorganic filler. Formed. Thereby, a laminate 5 of the separator for non-aqueous electrolyte secondary battery and the porous layer 5 was obtained. Table 1 shows the measurement results of various physical properties of the coating liquid, the inorganic filler, and the laminate 5.

<Preparation of non-aqueous electrolyte secondary battery>
(Assembly of non-aqueous electrolyte secondary battery)
A non-aqueous electrolyte secondary was prepared in the same manner as in Example 1 except that the laminate 5 was used instead of the laminate 1 and the non-aqueous electrolyte 4 was used instead of the non-aqueous electrolyte 1. A battery 8 was produced.

After that, the charge capacity of the non-aqueous electrolyte secondary battery 8 obtained by the above method after high rate discharge was measured. The results are shown in Table 2.

[Comparative Example 4]
<Preparation of non-aqueous electrolyte secondary battery>
(Assembly of non-aqueous electrolyte secondary battery)
A non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the laminate 2 was used instead of the laminate 1 and the electrolytic solution stock solution 1 was used instead of the non-aqueous electrolyte solution 1. 9 was produced.

After that, the charge capacity of the non-aqueous electrolyte secondary battery 9 obtained by the above method after high rate discharge was measured. The results are shown in Table 2.

As shown in Tables 1 and 2, the non-aqueous electrolyte secondary batteries of Examples 1 to 5 were superior to the non-aqueous electrolyte secondary batteries of Comparative Examples 1 to 4 in charge capacity after high rate discharge. I found out that In the non-aqueous electrolyte secondary batteries of Examples 1 to 5, the inorganic filler has a thermal expansion coefficient of 1 ppm / ° C. or more and 11 ppm / ° C. or less, and the temperature rising rate of the porous layer surface is 0.93 ° C. / 0.5 ppm or more and 300 ppm or less of an additive having a ionic conductivity reduction rate of 1.0% or more and 6.0% or less in the nonaqueous electrolytic solution contains. On the other hand, in Comparative Example 1, the ionic conductivity decrease rate of the additive exceeds 6.0%. In Comparative Example 2, the coefficient of thermal expansion of the inorganic filler exceeds 11 ppm / ° C, and the rate of temperature rise on the surface of the porous layer is less than 0.93 ° C / sec. In Comparative Example 3, the rate of temperature rise on the surface of the porous layer exceeds 1.25 ° C / sec. Comparative Example 4 contains no additive.

The non-aqueous electrolyte secondary battery according to the embodiment of the present invention maintains a high charge capacity after high rate discharge. Therefore, it can be suitably used for various applications, particularly as a battery for consumer use such as an electric power tool and a vacuum cleaner, and an on-vehicle battery that requires high-rate discharge.

Claims (6)

1. A porous layer containing an inorganic filler and a resin, a positive electrode, a negative electrode and a non-aqueous electrolyte,
   The thermal expansion coefficient of the inorganic filler at −40 ° C. to 200 ° C. is 11 ppm / ° C. or less,
   The porous layer was impregnated with a solution containing propylene carbonate, a polyoxyalkylene-type nonionic surfactant and water in a weight ratio of 85: 12: 3, and then was irradiated with a microwave having a frequency of 2455 MHz at an output of 1800 W. The measured rate of temperature rise on the surface of the porous layer from the start of irradiation to 15 seconds later is 0.93 ° C./sec or more and 1.25 ° C./sec or less,
   The non-aqueous electrolyte contains 0.5 ppm or more and 300 ppm or less of an additive having an ionic conductivity decrease rate L represented by the following formula (A) of 1.0% or more and 6.0% or less. Water electrolyte secondary battery.
   L = (LA-LB) / LA ... (A)
   (In the formula (A), LA was prepared by dissolving LiPF ₆ in a mixed solvent containing ethylene carbonate, ethylmethyl carbonate and diethyl carbonate in a volume ratio of 3: 5: 2 such that the concentration thereof was 1 mol / L. The ionic conductivity (mS / cm) of the reference electrolytic solution is represented, and LB represents the ionic conductivity (mS / cm) of the electrolytic solution prepared by dissolving the additive in the reference electrolytic solution in an amount of 1.0% by weight. .)
2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the porous layer is laminated on one side or both sides of a polyolefin porous film.
3. The porous layer contains a resin selected from the group consisting of a polyolefin, a (meth) acrylate resin, a fluorine-containing resin, a polyamide resin, a polyester resin, and a water-soluble polymer. The non-aqueous electrolyte secondary battery described.
4. The non-aqueous electrolyte secondary battery according to claim 3, wherein the polyamide resin is an aramid resin.
5. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the non-aqueous electrolyte contains an electrolyte containing lithium.
6. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte contains an aprotic polar solvent.

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