JP6971193B2 - Alumina powder and a slurry containing it, an alumina porous membrane and a laminated separator provided with the alumina powder, a non-aqueous electrolytic solution secondary battery and a method for producing the same. - Google Patents

Description

The present invention relates to an alumina powder suitable for forming an alumina porous film. The present invention also relates to a slurry containing this alumina powder. Furthermore, the present invention relates to an alumina porous membrane containing the above alumina powder and a laminated separator provided with the alumina porous membrane. The present invention also relates to a non-aqueous electrolytic solution secondary battery including a positive electrode, a negative electrode or a separator provided with an alumina porous film, and a method for producing the same.

Non-aqueous electrolyte secondary batteries, particularly lithium ion secondary batteries, have a high energy density and are therefore used in small consumer devices such as mobile phones and personal computers. In recent years, in addition to these small devices, their application to automobile applications is accelerating.

The non-aqueous electrolytic solution secondary battery uses an organic solvent-based electrolytic solution, and has a positive electrode and a negative electrode. A general non-aqueous electrolytic solution secondary battery further has a separator arranged between the electrode plates for the purpose of electrically insulating the positive electrode and the negative electrode. For example, in a lithium ion secondary battery, a microporous sheet made of a polyolefin resin is used as a separator.

The separator made of a microporous sheet of polyolefin resin plays a role of maintaining the safety of the lithium ion secondary battery by the shutdown function of the separator when a short circuit occurs between the electrodes inside the battery. Specifically, the heat generated in the short-circuited portion closes the hole of the separator, and the lithium ion cannot move, and as a result, the battery function of the portion is lost. However, when the battery temperature suddenly exceeds, for example, 150 ° C. due to the heat generated momentarily by the short circuit, the separator may contract rapidly and the short-circuited portion between the positive electrode and the negative electrode may expand. In this case, the battery temperature may reach an abnormally overheated state of several hundred degrees Celsius or higher, which poses a problem in terms of safety.

Japanese Unexamined Patent Publication No. 2013-168361 (Patent Document 1) and WO2016 / 098579A1 (Patent Document 2) propose inorganic oxide powders having special protrusions. It has been shown that in the inorganic oxide porous membrane formed by using such an inorganic oxide powder, a sufficient void ratio can be maintained by the special protrusions of the inorganic oxide powder, so that ion permeability can be ensured.

Japanese Unexamined Patent Publication No. 2013-168361 WO2016 / 098579A1

To form an alumina porous film for a separator, a slurry containing alumina powder is usually applied to an object (for example, a base material), and the applied slurry is dried. Since the alumina powder has a high hardness, if the alumina powder having irregularities is used, the surface of the base material may be polished (polishability). In particular, the inorganic oxide powders of Patent Documents 1 and 2 have high polishability due to the shape having special protrusions, and the coating process is limited.

Further, from the viewpoint of ensuring the safety of the non-aqueous electrolyte secondary battery, it is important that the alumina porous film used in the non-aqueous electrolyte secondary battery has low reactivity with the electrolytic solution. Therefore, an alumina powder suitable for producing an alumina porous film having high surface chemical stability is desired. However, in Patent Documents 1 and 2, no consideration is given to the reactivity with the electrolytic solution.

An object of the present invention is to provide an alumina powder and an alumina slurry which are suitable for forming an alumina porous film having high surface chemical stability and have low abrasiveness. Another object of the present invention is to provide an alumina porous membrane having high surface chemical stability and a method for using the same, and a method for producing a non-aqueous electrolytic solution secondary battery having an alumina porous membrane having high surface chemical stability. It is to be.

The present invention includes the following aspects.
Aspect 1 of the present invention is
Alumina powder having an average three-dimensional particle unevenness of 3.5 or less and a pyridine-adsorbed BET specific surface area / nitrogen-adsorbed BET specific surface area ratio of 0.7 or less.

Aspect 2 of the present invention is the alumina powder according to Aspect 1, wherein the abundance ratio of the number of particles having a sphere equivalent diameter of less than 0.3 μm is 40% or less.

Aspect of the present invention 3, the nitrogen adsorption BET specific surface area of alumina powder according to embodiment 1 or 2 is 1m ² / g~15m ² / g.

Aspect 4 of the present invention is the alumina powder according to any one of Aspects 1 to 3 having an average particle size of 2.0 μm or less.

Aspect 5 of the present invention is an alumina slurry containing the alumina powder according to any one of aspects 1 to 4, a binder, and a solvent.

Aspect 6 of the present invention is an alumina porous membrane containing the alumina powder according to any one of aspects 1 to 4 and a binder.

Aspect 7 of the present invention is a laminated separator including the alumina porous membrane according to the aspect 6 and a separator having the alumina porous membrane on its surface.

Aspect 8 of the present invention is a non-aqueous electrolyte secondary battery in which the alumina porous membrane according to Aspect 6 is provided on at least one surface of a positive electrode, a negative electrode and a separator.

Aspect 9 of the present invention is a non-aqueous electrolytic solution secondary battery including a step of applying the alumina slurry according to the aspect 5 to at least one surface of a positive electrode, a negative electrode and a separator and then drying the alumina slurry to form a porous alumina film. It is a manufacturing method of.

According to the alumina powder of the present invention, an alumina slurry having low abrasiveness can be obtained, and an alumina porous film having high surface chemical stability can be formed. Further, by using the alumina powder of the present invention, an alumina porous film having high surface chemical stability, an alumina slurry having low abrasiveness suitable for producing the alumina porous film, a laminated separator containing the alumina porous film, and a laminated separator containing the alumina porous film, and It is possible to provide a non-aqueous electrolytic solution secondary battery containing the alumina porous membrane.

FIG. 1 is a schematic diagram for explaining the degree of three-dimensional particle unevenness. It is a schematic diagram for demonstrating the pore diameter in a coating film and the pore volume in a coating film.

Hereinafter, the present invention will be described in detail. In addition, when the expression "~" is used in this specification, it is used as an expression including numerical values before and after it.
The present invention includes an invention relating to an alumina powder, an alumina slurry, an alumina porous film, a laminated separator containing an alumina porous film, and a non-aqueous electrolytic solution secondary battery including the alumina porous film. These inventions will be described in sequence below.

<Alumina powder>
The alumina powder according to the present invention has an average three-dimensional particle unevenness of 3.5 or less and a ratio of pyridine adsorbed BET specific surface area / nitrogen adsorbed BET specific surface area of 0.7 or less (hereinafter, "the present invention". It may be referred to as "alumina powder" or simply "alumina powder").
Each of the provisions of the present invention will be described in detail below.

<Average 3D particle unevenness is 3.5 or less>
The alumina powder of the present invention has an average three-dimensional particle unevenness of 3.5 or less for the alumina particles constituting the alumina powder. That is, the shape of the alumina particles has relatively small irregularities.
The alumina powder according to the present invention has an average three-dimensional particle unevenness of preferably 3.0 or less, and more preferably 2.8 or less. Further, the average three-dimensional particle unevenness is preferably 2.0 or more, more preferably 2.2 or more, and particularly more preferably 2.4 or more.

Here, the "three-dimensional particle unevenness" is a parameter that serves as an index of the shape of each alumina particle constituting the alumina powder. The three-dimensional particle unevenness is defined by the following equation (1) based on ^{the particle volume V (μm 3} ) of the target particle and the volume La × Lb × Lc (μm ^{3) of the rectangular parallelepiped circumscribing the particle.} NS.
Three-dimensional particle unevenness = La × Lb × Lc ÷ V ・ ・ ・ ・ ・ (1)
Here, La means the major diameter of the particle, Lb means the middle diameter of the particle, Lc means the minor diameter of the particle, and La, Lb, and Lc are orthogonal to each other. FIG. 1 shows a schematic diagram for explaining the degree of three-dimensional particle unevenness. By calculating the three-dimensional particle unevenness from 100 or more particles using the above formula (1) and averaging the numbers, the "average three-dimensional particle unevenness" can be obtained as an index showing the characteristics of the particle shape. .. The "average three-dimensional particle unevenness" referred to here is an average value of the three-dimensional particle unevenness calculated by the equation (1) for each of an arbitrary 100 or more particles.

Since alumina is a relatively hard substance, when a slurry containing alumina powder is applied to an object (for example, a base material) in order to form an alumina porous film or the like, the alumina powder polishes the surface of the base material. There is. The larger the unevenness of the alumina particles, the higher the property of polishing the base material (this is called "polishability").
Since the alumina powder of the present invention is formed of alumina particles having relatively small irregularities, the polishability can be suppressed.

The particle volume V, the major axis La of the particles, the medium diameter Lb of the particles, and the minor axis Lc of the particles required to obtain the three-dimensional particle unevenness of the alumina particles are obtained by analyzing the stereoscopic image of the target particles. You can ask. To obtain a three-dimensional image of particles, a predetermined amount of alumina powder is dispersed in a particle fixing resin (epoxy resin, etc.), and an evaluation sample obtained by curing the particle fixing resin is cut at predetermined intervals by FIB processing. By repeating the acquisition of cross-sectional SEM images with a scanning electron microscope (SEM), a predetermined number of continuous cross-sectional SEM images (that is, continuous slice images) are obtained, and then the positions suitable for the obtained continuous slice images are obtained. It can be constructed by a general method of synthesizing while making corrections. A specific procedure for evaluating the degree of three-dimensional particle unevenness (a method for preparing a sample for a continuous slice image, a method for calculating V, La, Lb, and Lc by a three-dimensional quantitative analysis software) will be described in detail in Examples.

<The ratio of pyridine-adsorbed BET specific surface area / nitrogen-adsorbed BET specific surface area is 0.7 or less>
It is desirable that the alumina powder used for the alumina porous film for a non-aqueous electrolytic solution secondary battery has low reactivity with the electrolytic solution. The alumina powder of the present invention has a pyridine-adsorbed BET specific surface area / nitrogen-adsorbed BET specific surface area ratio (hereinafter sometimes referred to as “specific surface area ratio”) of 0.7 or less. A large specific surface area ratio indicates that a basic substance such as pyridine is more likely to be adsorbed on the surface of the alumina powder than a neutral substance such as nitrogen. That is, it is considered that the alumina powder having a large specific surface area ratio has a relatively high acidic property. It is presumed that the alumina powder of the present invention having a small specific surface area ratio has a lower acidic property and a lower reactivity with an electrolytic solution. However, the present invention is not limited to this estimation.

When the ratio of the specific surface area is small, the amount of gas generated by the contact between the alumina powder and the electrolytic solution can be reduced. Therefore, it is possible to suppress the deterioration of the cycle characteristics of the secondary battery due to the generation of gas in the battery. The ratio of the specific surface area of the alumina powder of the present invention is preferably 0.5 or less.
The pyridine-adsorbed BET specific surface area is determined by a multi-point method according to the method specified in JIS-Z8830 (2013) using a pyridine gas as an adsorbed gas using a specific surface area measuring device.

The alumina powder according to the present invention preferably further satisfies the following regulations.

<The proportion of particles with a sphere equivalent diameter of less than 0.3 μm is 40% or less>
The alumina powder of the present invention preferably contains 40% or less of fine particles having a sphere equivalent diameter of less than 0.3 μm. Here, the "sphere equivalent diameter" is one parameter of the alumina particle, and is the diameter d of the sphere having the same ^{volume as the particle volume V (μm 3) of the alumina powder, and is expressed by the following equation (2).} It is a value that satisfies.
V = 4π ÷ 3 × (d ÷ 2) ³・ ・ ・ ・ ・ (2)
Using the above formula (2), the "sphere equivalent diameter" can be calculated from 100 or more particles, and the abundance ratio of the number of particles less than 0.3 μm can be obtained.

When forming an alumina porous film using alumina powder, pores are formed by the voids between the alumina particles. In addition, fine alumina particles can enter between the alumina particles having a relatively large particle size. Therefore, when a large amount of fine alumina particles are contained, the voids formed between the alumina particles having a relatively large particle size are easily closed by the fine alumina particles, and the function as a porous film may be deteriorated. In other words, the alumina powder having a low content of fine particles is suitable for forming an alumina porous film. In particular, alumina powder having a low content of fine particles having a sphere equivalent diameter of less than 0.3 μm of 40% or less is preferable, and when an alumina porous film is formed, the void ratio is improved (that is, the ion permeability is improved). Can be made to.

The abundance ratio of the number of small particles having a sphere equivalent diameter of less than 0.3 μm is more preferably 35% or less, and particularly preferably 30% or less.
Ideally, the abundance ratio of the number of small particles having a sphere equivalent diameter of less than 0.3 μm is 0%, but it is actually difficult. Generally, the abundance ratio of the number of particles is 10% or more, and more realistically, 15% or more.

The particle volume V and the diameter d of the sphere required to obtain the equivalent diameter of the sphere can be obtained at the same time in the analysis of the three-dimensional image of the particles described above. The calculation method of V and d will be described in detail in Examples.

<Nitrogen adsorption BET specific surface area of 1m ² / g~15m ² / g>
Nitrogen adsorption BET specific surface area of the alumina powder of the present invention is preferably in the range of 1m ² / g~15m ² / g, more preferably from 2 to 10 m ² / g, and most preferably 3 to 8 m ² / g. When the nitrogen-adsorbed BET specific surface area is within this range, the binding property with the binder is improved when the alumina porous film is produced by the method described later, and a high-strength alumina porous film can be obtained. The specific surface area of nitrogen-adsorbed BET is determined by a one-point method according to the method specified in JIS-Z8830 (2013) using a specific surface area measuring device and using nitrogen gas as the adsorbed gas.

The preferred purity of alumina constituting the alumina powder of the present invention varies depending on the application.
The purity of alumina (hereinafter, may be referred to as alumina purity) is the ratio of aluminum oxide (% by mass) when the total of all the components contained in the alumina powder of the present invention is 100% by mass. Means.
The alumina purity (% by mass) of the alumina powder is 100, which is the sum of the mass of _{alumina and the mass of other oxides such as SiO 2} , Na ₂ O, MgO, CuO, Fe ₂ O ₃ and ZrO _2. It is calculated as (mass%) from the following formula. It should be noted that SiO ₂ , Na ₂ O, MgO, CuO, Fe ₂ O ₃ and ZrO _{2 and the} like are defined as impurities for the reference oxide (α-alumina).
Alumina purity (% by mass) = 100-total mass of impurities (% by mass)

The masses of the impurities SiO ₂ , Na ₂ O, MgO, CuO and Fe ₂ O ₃ are the contents of Si, Na, Mg, Cu and Fe obtained by measuring the evaluation sample by solid-state emission spectroscopy. _{The mass of ZrO 2} , which is the remaining impurity, is the content of Zr obtained by measuring the evaluation sample by the ICP emission method, and the content of Zr is the oxide corresponding to each element (SiO ₂ , Na ₂ O, MgO, It can be obtained by converting it into the mass of CuO, Fe ₂ O ₃ , ZrO _2).

In the case of alumina powder used for producing an alumina porous film for a secondary battery, the purity is preferably 90% by mass or more. That is, it is preferable that the impurities (oxides such as Si, Na, Mg, Cu, Fe, and Zr) contained in the alumina are 10% by mass or less. It is possible to suppress the deterioration of the electrical insulating property of the alumina porous membrane due to impurities, and it is possible to reduce the amount of metallic foreign matter mixed in which causes a short circuit.
The purity of the alumina powder is preferably 90% by mass or more, more preferably 99% by mass or more, and particularly preferably 99.9% by mass or more.

<Average particle size is 2.0 μm or less>
The average particle size of the alumina powder according to the present invention is preferably 2.0 μm or less, more preferably 1.5 μm or less, and most preferably 1.0 μm or less. The "average particle diameter" defined in the present specification means a particle diameter D50 (median diameter) corresponding to a cumulative percentage of 50% on a mass basis obtained by a laser diffraction method. When the average particle size of the alumina powder is 2.0 μm or less, an alumina porous film having an appropriate thickness can be formed, so that the energy density is maintained high when used in a non-aqueous electrolyte secondary battery. be able to. The average particle size of the alumina powder is preferably 0.1 μm or more, more preferably 0.2 μm or more, and most preferably 0.4 μm or more. When the average particle size of the alumina powder is 0.1 μm or more, the amount of binders added for binding the particles when forming the alumina porous film can be suppressed to an appropriate amount. Therefore, in the obtained alumina porous membrane, the ion permeability is less likely to be impaired by the binders, and the charge / discharge characteristics of the battery can be improved.

(Manufacturing method of alumina powder)
The method for producing the alumina powder of the present invention will be described below.
The alumina powder according to the present invention can be produced by using an alumina material produced by a known production method as a raw material for the alumina powder and pulverizing the alumina powder under appropriate conditions. In the present specification, the alumina material which is the raw material of the alumina powder may be referred to as "raw material alumina".

For example, it is effective to add an appropriate surface protective agent to pulverize the raw material alumina produced by a known method (for example, the Bayer process). As used herein, the term "surface protective agent" refers to an agent that appropriately protects the surface of the raw material alumina to suppress over-grinding during pulverization. The use of the surface protective agent facilitates the abundance ratio of the number of fine alumina particles (particles having a sphere equivalent diameter of less than 0.3 μm) within the preferable range (40% or less) specified in the present application.
Further, by using a surface protective agent at the time of pulverization, the raw material alumina can be quickly pulverized to the target particle size.

Further, depending on the type of the surface protective agent, it is also possible to protect the surface of the alumina powder after pulverization to impart preferable surface characteristics. For example, when the raw material alumina is pulverized with an appropriate surface protective agent, the reactivity of the pulverized alumina powder with the electrolytic solution can be reduced. Therefore, by using a surface protective agent when pulverizing the alumina powder, it is possible to obtain an alumina powder suitable for an alumina porous membrane for a non-aqueous electrolytic solution secondary battery.

Examples of the method for producing the raw material alumina include a Bayer method, an ammonium alum method, an aluminum underwater discharge method, an ammonium-aluminum-carbonate-hydrooxide method (AACH method), and an organic aluminum hydrolysis method (aluminum alkoxide method). In the case of the Bayer process, aluminum hydroxide obtained from bauxite can be calcined to produce raw material alumina. In this specification, aluminum hydroxide as a raw material for producing raw material alumina may be referred to as "raw material aluminum hydroxide".
The method for producing the raw material alumina using the Bayer process will be described in detail below.

The particle shape and particle size of the raw material aluminum hydroxide are not particularly limited, but usually aluminum hydroxide having an average particle diameter of about 10 μm to about 100 μm is used. A firing furnace such as a rotary kiln or a tunnel kiln can be used for firing the raw material aluminum hydroxide.
The firing temperature of the raw material aluminum hydroxide, the rate of temperature rise to the firing temperature, and the firing time are appropriately selected so as to obtain alumina having desired physical properties. The firing temperature of the raw material aluminum hydroxide is, for example, 1000 ° C. or higher and 1450 ° C. or lower, preferably 1000 ° C. or higher and 1350 ° C. or lower, and the heating rate when raising the temperature to this firing temperature is usually 30 ° C./hour or higher and 500 ° C. It is / hour or less, and the firing time of the raw material aluminum hydroxide is usually 0.5 hours or more and 24 hours or less, preferably 1 hour or more and 20 hours or less.

The raw material aluminum hydroxide may be fired in an atmosphere of an inert gas such as nitrogen gas or argon gas as well as in an atmospheric atmosphere, and the water vapor content may be fired by burning propane gas or the like. It may be fired in an atmosphere with high pressure. Normally, when firing in an atmosphere with a high partial pressure of water vapor, unlike in an atmospheric atmosphere, the obtained particles are easily baked due to the effect of the water vapor.
In this way, the raw material alumina can be produced using the Bayer process.

Next, a method for producing alumina powder from the raw material alumina will be described in detail.
Alumina powder can be obtained by pulverizing the raw material alumina produced by a known method.

The raw material alumina can be pulverized by a known method such as a vibration mill, a bead mill, a ball mill, or a jet mill, and may be pulverized in either a dry state or a wet state. For grinding, use an appropriate surface protectant. Thereby, the average three-dimensional particle unevenness and the number existence ratio of the equivalent sphere diameter of 0.3 μm can be easily controlled within a preferable range.
The crushing time is appropriately adjusted so as not to excessively crush. If the crushing time is too long, the alumina particles may be atomized too much, and the abundance ratio of the number of particles having a sphere equivalent diameter of 0.3 μm or less may increase.

As described above, a surface protective agent is used during pulverization. Suitable surface protective agents for limiting the average three-dimensional particle unevenness include monohydric alcohols such as methanol, ethanol, 1-propanol and 2-propanol; propylene glycol, polypropylene glycol, ethylene glycol and polyethylene glycol. Glycols such as; amines such as triethanolamine; higher fatty acids such as palmitic acid, stearic acid, oleic acid and the like. Each of these surface protectants may be used alone or in combination of two or more. Glycols, particularly propylene glycol, ethylene glycol, polypropylene glycol and polyethylene glycol are preferred.

The surface protectant may not only protect the surface of the alumina powder after grinding, but also have a function of inactivating the surface of the alumina powder. The function of inactivating the surface can reduce the reactivity of the alumina powder with the electrolytic solution. Such surface protectants include, for example, monohydric alcohols such as methanol, ethanol, 1-propanol and 2-propanol; glycols such as ethylene glycol, polyethylene glycol, propylene glycol and polypropylene glycol. From the viewpoint of low volatility, glycols, particularly ethylene glycol, polyethylene glycol, propylene glycol and polypropylene glycol are suitable.

The polyethylene glycol and polypropylene glycol used as the surface protective agent are not particularly limited in their molecular weights, but are preferably liquids having an average molecular weight of about 200 to 600 from the viewpoint of ease of addition.

The amount of the surface protective agent added is usually 0.01 to 2.0 parts by mass, preferably 0.05 to 1.0 parts by mass, and more preferably 0.1 to 0 parts by mass when the raw material alumina is 100 parts by mass. 5 parts by mass. If the amount of the surface protectant added is too large, the effect of the surface protectant is saturated. If the amount added is too small, the effect of the surface protectant will not be fully exhibited.

The alumina particles of the alumina powder thus obtained do not have special protrusions as disclosed in Patent Documents 1 and 2.

<Alumina slurry>
The alumina slurry according to the present invention contains the alumina powder according to the present invention, a binder, and a solvent.

(binder)
The binder has a function of binding the alumina particles to each other and adhering the alumina porous layer and the base material (for example, a separator, a negative electrode and / or a positive electrode) when forming the alumina porous film. A known binder can be used, and it is usually mainly composed of an organic substance.

Specific examples of the binder include fluororesins such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP); polyacrylic acid, polyacrylic acid methyl ester, and the like. Polyacrylic acid derivatives such as polyacrylic acid ethyl ester and polyacrylic acid hexyl ester; polymethacrylic acid derivatives such as polymethacrylic acid, polymethacrylic acid methyl ester, polymethacrylic acid ethyl ester and polymethacrylic acid hexyl ester; polyamide, polyimide, Polypolyamide, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyether sulfone, hexafluoropolypropylene, styrene butadiene rubber, carboxymethyl cellulose (hereinafter, CMC), polyacrylonitrile and its derivatives, polyethylene, polypropylene, aramid resin and the like or theirs. Examples include salt. These compounds may be used alone or in admixture of two or more, or may be used in combination with a copolymer described later.

The binder is selected from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid and hexadiene. It is also possible to use a copolymer of two or more kinds of materials to be used. These copolymers may be used alone or in admixture of two or more.

(Solvent (dispersion medium))
Known solvents can be used as suitable solvents for the alumina slurry, and specifically, water, alcohol, acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP). , Cyclohexane, xylene, cyclohexanone or a mixed solvent thereof can be used.

The blending amount of each component constituting the alumina slurry is not particularly limited as long as it can be appropriately applied to the base material or the support and an alumina porous film having desired characteristics can be formed. As an example of the blending amount, the binder may be 0.1 to 20 parts by mass and the solvent may be 10 to 500 parts by mass with respect to 100 parts by mass of the alumina powder according to the present invention.

Various additives may be further added to the alumina slurry in order to stabilize the dispersion of the alumina powder or to improve the coatability of the alumina slurry. Additives include, for example, dispersants, thickeners, leveling agents, antioxidants, defoamers, pH regulators containing acids or alkalis, and additives that have the function of suppressing side reactions such as electrolyte decomposition. Etc. are included. It is preferable that these additives are removed during the forming step of the porous alumina film and do not remain in the porous alumina film. When the additive remains in the alumina porous film, it is chemically and physically so that the additive does not significantly affect the battery reaction when the alumina porous film is used in a non-aqueous electrolyte secondary battery. It is desirable to select a stable additive. The content of the additive in the alumina slurry is preferably limited to an amount that does not significantly impair the characteristics of the alumina slurry and the alumina porous film formed from the alumina slurry. For example, it is preferably 10 parts by mass or less of the additive with respect to 100 parts by mass of alumina.

The alumina slurry containing the alumina powder is applied to a base material such as a positive electrode, a negative electrode, a separator, or a support in order to form an alumina porous film. Alumina usually has a higher hardness than the material (metal, resin, etc.) used for the base material or the like. If the alumina particles have irregularities, when the alumina slurry is applied to the substrate or the like, the irregularities may damage the surface of the substrate or the like and wear the substrate or the like. Therefore, in the case of an alumina slurry using alumina particles having large irregularities, it is necessary to pay sufficient attention so that wear is unlikely to occur when the slurry is applied to a substrate or the like.

However, the alumina powder of the present invention has an average three-dimensional particle unevenness of 3.5 or less, which is small (or small), and therefore, when the alumina slurry is applied to the surface of a substrate or the like, the alumina is used. Wear of the base material, etc. due to particles is unlikely to occur.

(Manufacturing method of alumina slurry)
The alumina slurry can be prepared by mixing the alumina powder according to the present invention, the binder, and the solvent in a predetermined blending amount, and then dispersing the alumina powder in the solvent by a known method. As a method for dispersing the alumina powder, for example, stirring with a stirrer such as a known planetary mixer, stirring with ultrasonic vibration, stirring using a bead mill, or the like can be used.

<Alumina porous membrane>
The alumina porous membrane according to the present invention contains the alumina powder of the present invention and a binder. Such an alumina porous membrane can be produced, for example, by using the alumina slurry according to the present invention.
Since alumina is a substance having high heat resistance and insulating properties, an alumina porous membrane containing alumina powder also has high heat resistance and insulating properties. Therefore, the alumina porous membrane of the present invention is suitable as an insulating porous membrane for protecting the separator used in the secondary battery from high heat and the like. In particular, it is suitable for being placed between the negative electrode and the separator. For example, it may be arranged on the surface of both sides of the separator facing the negative electrode. Further, it may be arranged on the surface (single side or both sides) of the negative electrode.

The volume-based porosity of the alumina porous membrane is preferably 20 to 90%, more preferably 30 to 70%. When the porosity of the alumina porous membrane is appropriate, it is possible to improve the ion permeability while ensuring the function as the insulating porous membrane when used in a secondary battery.

The average diameter (average pore diameter) of the pores of the alumina porous membrane is preferably 1 μm or less, more preferably 0.7 μm or less. Here, the "average pore diameter" refers to the median value (D50) of the pore diameter. In the present specification, it may be referred to as "average pore diameter D50". When the average pore diameter is appropriate, it is possible to improve the ion permeability when used in a secondary battery while ensuring the function as an insulating porous membrane.

When the alumina porous membrane has few fine pores, the ion permeability can be further improved when used in a secondary battery. The volume ratio of the pores having a pore diameter of 0.2 μm or less is preferably 30% by volume or less, more preferably 25% by volume or less. Further, the volume ratio of the pores having a pore diameter of more than 0.5 μm is preferably 10% by volume or more, more preferably 15% by volume or more.

The volume ratio (% by volume) of the pores having a pore diameter of 0.2 μm or less is “total of the pore volumes of the pores having a pore diameter of 0.2 μm or less” ÷ “pore volume of all the pores in the coating film”. It can be calculated by "total of" x 100. The volume ratio (% by volume) of the pores having a pore diameter of more than 0.5 μm is "the total of the pore volumes of the pores having a pore diameter of more than 0.5 μm" ÷ "the total of the pore volumes of all the pores in the coating film". It can be obtained by multiplying by 100.

The air permeability of the porous alumina film is preferably 10 seconds / 100 mL · μm or less, and more preferably 9 seconds / 100 mL · μm or less in terms of the galley value per 1 μm of the film thickness. When the gullet value of the alumina porous membrane is small (high air permeability), the ion permeability can be further improved when used in a secondary battery.

(Manufacturing method of porous alumina film)
The alumina porous film can be formed by applying the alumina slurry to the base material or the support and then removing the solvent (dispersion medium) in the alumina slurry.

<Laminate separator>
The laminated separator according to the present invention is provided with the alumina porous film of the present invention on the surface of the separator. That is, the laminated separator according to the present invention includes the above-mentioned alumina porous film and a separator having the alumina porous film on its surface. In the present specification, the "separator" broadly means a film that separates the positive electrode and the negative electrode of the battery, and includes a separator used for a secondary battery (for example, a non-aqueous electrolyte secondary battery). .. The alumina porous membrane can be laminated on one side or both sides of the separator.

The air permeability of the laminated separator is preferably 30 to 1000 seconds / 100 mL in terms of Gale value, and more preferably 50 to 800 seconds / 100 mL. Since the laminated separator has the air permeability, sufficient ion permeability can be obtained when the laminated separator is used as a member for a non-aqueous electrolytic solution secondary battery.

When the galley value of the laminated separator is small (high air permeability), it means that the porosity of the laminated separator is high and the laminated structure of the laminated separator is rough. If the galley value of the laminated separator is too small (the air permeability is too high), the strength of the separator may decrease, and the shape stability may be insufficient, especially at high temperatures. On the other hand, if the galley value of the laminated separator is too large (the air permeability is too low), sufficient ion permeability can be obtained when the laminated separator is used as a member for a non-aqueous electrolyte secondary battery. However, it may deteriorate the battery characteristics of the non-aqueous electrolyte secondary battery.

A separator suitable for a laminated separator is generally formed from a resin-made porous film. A separator suitable for the present application will be described in detail.

(Separator)
The separator is a film-like porous film arranged between the positive electrode and the negative electrode in a secondary battery, and is capable of transmitting gas and liquid from one surface to the other. The separator has a large number of pores inside thereof, and the pores are usually connected to each other.
The separator can be produced from a porous and film-like substrate (polyolefin-based porous substrate) containing a polyolefin-based resin as a main component.
The separator has a shutdown function by melting when the battery generates heat and making it non-perforated. The separator may be composed of one layer or may be formed of multiple layers.

The separator preferably has a piercing strength of 3N or more. If the puncture strength is too small, the positive and negative electrode active material particles are used in the case of stacking winding operation of positive and negative electrodes and separator in the battery assembly process, compression operation of winding group, or when external pressure is applied to the battery. There is a risk that the separator will be pierced and the positive and negative electrodes will be short-circuited. The puncture strength of the porous film is preferably 10 N or less, more preferably 8 N or less.

The film thickness of the separator may be appropriately determined in consideration of the film thickness of the non-aqueous electrolytic solution secondary battery member constituting the non-aqueous electrolytic solution secondary battery, and is preferably 4 to 40 μm, preferably 5 to 30 μm. It is more preferably 6 to 15 μm, and even more preferably 6 to 15 μm.

The volume-based porosity of the separator is preferably 20-80%, more preferably 30-75%. If the porosity of the separator is appropriate, the holding amount of the electrolytic solution can be increased, and when an excessive current flows, the current can be reliably blocked (shut down) at a lower temperature.
The average diameter (average pore diameter) of the pores of the separator is preferably 0.3 μm or less, more preferably 0.05 μm or more and 0.14 μm or less. Here, the "average pore diameter" refers to the median value (D50) of the pore diameter. In the present specification, it may be referred to as "average pore diameter D50". When the average pore size is appropriate, not only can the ion permeability of the separator be sufficiently maintained, but also various particles (for example, active material particles eluted and precipitated from the electrode plate during the charging / discharging process of the secondary battery, and alumina. Alumina particles that have fallen off from the porous film) can be prevented from entering the pores of the separator.

The proportion of the polyolefin-based resin contained in the separator is usually 50% by volume or more, preferably 90% by volume or more, and more preferably 95% by volume or more of the entire porous film. The polyolefin resin in the separator, it is preferable to contain the high molecular weight component having a weight average molecular weight ^{5 × 10 5 ~15 × 10 6} . In particular, it is preferable that a polyolefin component having a weight average molecular weight of 1 million or more is contained because the strength of the separator is increased.

Examples of the polyolefin-based resin suitable for the separator include high-molecular-weight homopolymers or copolymers obtained by polymerizing monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene. Can be done. The separator may include one layer (resin single layer film) or a plurality of layers (resin multilayer film) of the resin film of the polyolefin resin. As an example of a separator composed of a resin multilayer film, one layer of polyethylene film (PE film) is placed between two layers of polypropylene film (PP film), and these three layers are laminated (PP / PE / PP). There is a laminated film). In particular, high molecular weight polyethylene mainly composed of ethylene is preferable. The separator does not prevent the component other than the polyolefin from being contained as long as the function of the layer is not impaired.

The air permeability of the separator is usually in the range of 30 to 500 seconds / 100 mL in Gale value, preferably in the range of 50 to 300 seconds / 100 mL. If the air permeability of the separator is appropriate, sufficient ion permeability can be obtained.

The amount of grain of the separator is usually 4 to 20 g in that the strength, film thickness, handleability and weight, and the weight energy density and volume energy density of the battery when used as a separator for a secondary battery can be increased. / ^{m 2,} preferably 4～12G / ^{m 2,} 5 to 10 g / ^{m 2} is more preferable.

(Manufacturing method of laminated separator)
The laminated separator can be manufactured by forming an alumina porous film on the surface of the separator using an alumina slurry.
As an example of a method for producing a laminated separator, there is a method in which the alumina slurry is directly applied to the surface of the separator and then the solvent (dispersion medium) of the alumina slurry is removed.
As another example of the method for producing a laminated separator, an alumina slurry is applied to the surface of a support, the solvent (dispersion medium) of the alumina slurry is removed to form an alumina porous film, and then the alumina porous film is used as a separator. There is a method of crimping and peeling the support from the porous alumina film.

As yet another example of the method for manufacturing a laminated separator, an alumina slurry is applied to the surface of a support, the separator is pressure-bonded to the coated surface, the alumina slurry is transferred to the separator, and then the solvent (dispersion medium) of the alumina slurry is used. There is a way to remove it.
As another example of the method for producing a laminated separator, there is a method of immersing the separator in an alumina slurry to perform dip coating, and then removing the solvent (dispersion medium) of the alumina slurry.

When a laminated separator having an alumina porous film on both sides of the separator is manufactured, the alumina porous film may be formed on one surface of the separator and then the alumina porous film may be sequentially formed on the other surface. Alternatively, an alumina porous film may be formed on both sides of the separator at the same time.
If necessary, the surface of the separator may be hydrophilized before forming the porous alumina film on the surface of the separator.

The preferable conditions (weight, film thickness, coating method, solvent removal method) of the alumina porous film in the laminated separator will be described later.

The separator can be prepared by the following method.
The method for producing a separator containing a polyolefin resin as a main component is as follows, for example, when the porous film contains an ultra-high molecular weight polyolefin and a low molecular weight hydrocarbon having a weight average molecular weight of 10,000 or less. Is preferable.

That is, (1) a step of kneading an ultra-high molecular weight polyolefin, a low molecular weight hydrocarbon having a weight average molecular weight of 10,000 or less, and a pore-forming agent to obtain a polyolefin resin composition, and (2) rolling the polyolefin resin composition. A step of rolling with a roll to form a sheet (rolling step), a step of removing a pore-forming agent from the sheet obtained in (3) step (2), and a step of removing a pore-forming agent from the sheet obtained in (3) step (2), and a sheet obtained in (4) step (3). Can be obtained by a method including a step of stretching to obtain a porous film (separator). The operation of stretching the sheet in the above step (4) may be performed before the operation of removing the pore forming agent from the sheet in the above step (3).

Examples of the low molecular weight hydrocarbon include low molecular weight polyolefins such as polyolefin wax and low molecular weight polymethylene such as Fischer-Tropsch wax. The weight average molecular weights of the low molecular weight polyolefin and the low molecular weight polymethylene are preferably 200 or more and 3000 or less. When the weight average molecular weight is 200 or more, there is no possibility of evaporation during the production of the separator, and when the weight average molecular weight is 3000 or less, the mixture with the ultra-high molecular weight polyolefin is more uniformly formed, which is preferable.

Examples of the pore-forming agent include an inorganic filler and a plasticizer. Examples of the inorganic filler include an inorganic filler that can be dissolved in an acid-containing water-based solvent, an alkali-containing water-based solvent, or a water-based solvent mainly composed of water.

Examples of the inorganic filler that can be dissolved in an acid-containing aqueous solvent include calcium carbonate, magnesium carbonate, barium carbonate, zinc oxide, calcium oxide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium sulfate and the like. Calcium carbonate is preferable because it is inexpensive and it is easy to obtain fine powder. Examples of the inorganic filler that can be dissolved in an aqueous solvent containing an alkali include silicic acid and zinc oxide, and silicic acid is preferable because it is inexpensive and a fine powder can be easily obtained. Examples of the inorganic filler that can be dissolved in an aqueous solvent mainly composed of water include calcium chloride, sodium chloride, magnesium sulfate and the like.

Examples of the plasticizer include liquid paraffin and low molecular weight non-volatile hydrocarbon compounds such as mineral oil.

<Non-water electrolyte secondary battery>
The non-aqueous electrolytic solution secondary battery according to the present invention includes an electrode group including a positive electrode, a negative electrode and a separator, and a non-aqueous electrolytic solution, and further, the present invention is provided on at least one surface of the positive electrode, the negative electrode and the separator. It has an alumina porous film.
As the form of the electrode group suitable for the non-aqueous electrolyte secondary battery of the present invention, for example, an electrode group (laminated electrode group) formed by laminating a positive electrode, a negative electrode and a separator, a positive electrode, a negative electrode and a separator are laminated. , There is an electrode group (winding type electrode group) formed by winding the laminated body.

When the porosity of the alumina porous film used is high and the proportion of large pore diameters (for example, the volume proportion of pores having a pore diameter of more than 0.5 μm) is high, the lithium ion permeability is excellent and the lithium ion rectifying effect is obtained. Will also be good.
It is considered that the alumina powder having a small proportion of fine alumina particles having a sphere equivalent diameter of less than 0.3 μm can form an alumina porous film having a high void ratio and a high proportion of large pore diameters. By using such an alumina porous membrane, the battery characteristics of the non-aqueous electrolytic solution secondary battery can be improved.

Further, the alumina powder of the present invention has a pyridine-adsorbed BET specific surface area / nitrogen-adsorbed BET specific surface area ratio of 0.7 or less.
When a porous film obtained from an alumina powder having a small ratio is used for a non-aqueous electrolytic solution secondary battery, the reaction with the electrolytic solution of the non-aqueous electrolytic solution secondary battery is less likely to occur (in this way, the reaction with the electrolytic solution). Difficulty is referred to as "electrolyte solution stability of alumina porous film" in the present specification). When an alumina porous membrane having excellent electrolyte stability is used, deterioration of the electrolytic solution is suppressed, so that the cycle characteristics of the non-aqueous electrolytic solution secondary battery can be improved. Therefore, it is possible to manufacture a non-aqueous electrolyte secondary battery that maintains excellent electrical characteristics for a long period of time.

(Manufacturing method of non-aqueous electrolyte secondary battery)
The non-aqueous electrolytic solution secondary battery of the present invention includes a step of forming an alumina porous film on the surface of at least one of a electrode plate (positive electrode, negative electrode) and a separator. A specific embodiment includes a step of applying the above-mentioned alumina slurry to at least one surface of a positive electrode, a negative electrode and a separator, and then drying the alumina slurry to form an alumina porous film. The general positive electrode and negative electrode have an electrode mixture layer containing an electrode active material (positive electrode active material or negative electrode active material) and a binder on the surface thereof. When the alumina slurry is applied to the electrode plate (positive electrode or negative electrode), it can be applied on the electrode mixture layer contained in those electrodes.

The electrode group including the positive electrode, the negative electrode and the separator and the alumina porous film formed on the surface of any of the positive electrode, the negative electrode and the separator are stored in a battery container (for example, a battery can), and non-aqueous electrolysis is performed in the container. By injecting the liquid, a non-aqueous electrolyte secondary battery can be obtained.

As a more specific manufacturing method, a non-aqueous electrolytic solution secondary battery using a wound electrode group including a negative electrode having a porous alumina film formed on the surface thereof will be described as an example. An electrode mixture layer containing a negative electrode active material is formed on the surface of the negative electrode. An alumina slurry is applied on the electrode mixture layer and the alumina slurry is dried to form an alumina porous film on the surface of the negative electrode. One end of the negative electrode lead is joined to the lead joint portion of the negative electrode, and one end of the positive electrode lead is joined to the lead joint portion of the positive electrode. After laminating the positive electrode and the negative electrode via the separator, the laminated body is wound to form a wound electrode group. Insulating rings are arranged at the upper and lower parts of the wound electrode group and stored in the battery can. After injecting the electrolytic solution into the battery can, the opening of the battery can is closed with the battery lid.

The thickness of the alumina porous film is the thickness of the coated film in a wet state (wet) after coating, the weight ratio of the resin and the fine particles, the solid content concentration of the alumina slurry (sum of the resin concentration and the fine particle concentration), etc. Can be controlled by adjusting. As the support, for example, a resin film, a metal belt, a drum, or the like can be used.

The method of applying the alumina slurry to the electrode plate, separator or support may be any method as long as it can realize the required basis weight and coating area, and is not particularly limited. As a method for applying the alumina slurry, a conventionally known method can be adopted. Specifically, as such a method, for example, a gravure coater method, a small diameter gravure coater method, a reverse roll coater method, a transfer roll coater method, a kiss coater method, a dip coater method, a knife coater method, an air doctor blade coater method, and a blade. Examples thereof include a coater method, a rod coater method, a squeeze coater method, a cast coater method, a bar coater method, a die coater method, a screen printing method, and a spray coating method.

The solvent (dispersion medium) is generally removed by drying. Examples of the drying method include natural drying, blast drying, heat drying, vacuum drying and the like, but any method may be used as long as the solvent (dispersion medium) can be sufficiently removed. A normal drying device can be used for the above drying.
When heating is performed to remove the solvent (dispersion medium) from the coating film of the alumina slurry formed on the separator, in order to prevent the pores of the separator from shrinking and the air permeability from decreasing. It is desirable that the temperature is such that the air permeability of the separator does not decrease, specifically, 10 to 120 ° C, more preferably 20 to 80 ° C.

The film thickness of the alumina porous film formed by the above method is 0.5 to 15 μm when the separator is used as a base material and the alumina porous film is laminated on one side or both sides of the separator to form a laminated separator. It is preferably (per one side), more preferably 2 to 10 μm (per one side), and even more preferably 2 to 5 μm (per one side).

When the thickness of the alumina porous membrane is 1 μm or more (0.5 μm or more on one side), it is possible to sufficiently prevent an internal short circuit due to damage to the battery or the like in the laminated separator provided with the alumina porous membrane, and also. It is preferable in terms of maintaining the retention amount of the electrolytic solution in the alumina porous membrane. On the other hand, the total thickness of the alumina porous membrane of both sides is 30 μm or less (15 μm or less on one side), which suppresses an increase in the permeation resistance of ions such as lithium ions in the entire laminated separator provided with the alumina porous membrane. It is possible to prevent deterioration of the positive electrode and deterioration of rate characteristics and cycle characteristics when the charge / discharge cycle is repeated, and to prevent the secondary battery from becoming larger by suppressing the increase in the distance between the positive electrode and the negative electrode. It is preferable in terms of being able to do it.

In the following description of the physical properties of the alumina porous film, when the porous layers are laminated on both sides of the porous film, the alumina laminated on the surface of the porous film facing the positive electrode when used as a secondary battery. At least refers to the physical properties of the porous film.

The basis weight per unit area (per one side) of the alumina porous film can be appropriately determined in consideration of the strength, film thickness, weight, and handleability of the laminated separator. Typical basis weight is from 1 to 20 g / ^{m 2,} is preferably 4 to 15 g / ^{m 2,} and more preferably 4~12g / ^{m 2.} When the amount of the alumina porous film is within the above range, the weight energy density and the volumetric energy density of the non-aqueous electrolyte secondary battery having the laminated separator provided with the alumina porous film as a member can be increased, and the battery can be increased. It is preferable because the weight of the battery is reduced.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples.
In the examples, the physical characteristics of the alumina powder, the physical properties of the alumina porous film produced using the alumina powder, and the electrical characteristics of the non-aqueous electrolytic solution secondary battery provided with the alumina porous film were measured. The method for preparing the sample used for the measurement and the method for measuring the physical properties and electrical characteristics were as follows.

<Method for producing alumina powder>
The preparation conditions for each alumina powder are shown in Table 1 and are described in detail below.

(Alumina powder No. P1)
The aluminum hydroxide obtained by the Bayer process was calcined in a gas furnace ^{to obtain a raw material alumina having a BET specific surface area of 3.7 m 2} / g and an average particle size of 54 μm. A surface protective agent (propylene glycol) was added in an amount of 0.2% by mass to the raw material alumina and mixed, and then pulverized by a continuous bead mill with a classification mechanism described below to obtain α-phase alumina powder (No. P1). ..
(Continuous bead mill machine with classification mechanism)
・ Classification point (maximum particle size) = 3 μm ・ Crushed media: φ5 mm zirconia beads ・ Crushed media / alumina raw material mass ratio: 7
・ Supply of alumina raw material powder: Weight loss weight measurement type

(Alumina powder No. P2)
The aluminum hydroxide obtained by the Bayer process was calcined in a gas furnace ^{to obtain a raw material alumina having a BET specific surface area of 4.2 m 2} / g and an average particle size of 52 μm.
A surface protective agent (propylene glycol) was added and mixed in an amount of 0.2% by mass, and then pulverized by the following jet mill to obtain an alumina powder.
(Jet mill)
・ Equipment: PJM-280SP manufactured by Nippon Pneumatic Industries, Ltd.
-Supply rate of alumina raw material powder: 10 kg / h
・ Gauge pressure at the air supply port during crushing: 0.7 MPa

(Alumina powder No. P3)
The aluminum hydroxide obtained by the Bayer process was calcined in a gas furnace ^{to obtain a raw material alumina having a BET specific surface area of 3.7 m 2} / g and an average particle size of 54 μm. Alumina powder was obtained by pulverizing the raw material alumina with the following ball mill. No surface protective agent was added during pulverization.
(Ball mill)
・ Crushed media: φ30 mm alumina ball ・ Crushed media / alumina raw material mass ratio: 6
-Grinding time: particle size adjustment (average particle size D50 = 0.5 μm)

(Alumina powder No. P4)
It was prepared under the same conditions as Alumina Powder No. P1 except that no surface protective agent was added.

(Alumina powder No. P5)
Aluminum hydroxide obtained by the aluminum alkoxide method was calcined in a gas furnace ^{to obtain raw material alumina having a BET specific surface area of 4.0 m 2} / g and an average particle size of 7.8 μm. Alumina powder was obtained by pulverizing the raw material alumina with the following jet mill. No surface protective agent was added during pulverization.
(Jet mill)
・ Equipment: PJM-380SP manufactured by Nippon Pneumatic Industries, Ltd.
-Supply rate of alumina raw material powder: 15 kg / h
・ Gauge pressure at the air supply port during crushing: 0.7 MPa

<Physical characteristics of alumina powder>
The physical characteristics of the produced alumina powder were measured as follows. The measurement results are shown in Table 2.

(1. Average three-dimensional particle unevenness, number of particles with a sphere equivalent diameter of less than 0.3 μm)
2 parts by weight of a dispersant (polyester BYK-111 phosphate manufactured by Big Chemie) and 2 parts by weight of an alumina powder were dispersed in 100 parts by weight of an epoxy resin, and after vacuum degassing, 12 parts by weight of a curing agent was added. The obtained alumina-dispersed epoxy resin was poured into a silicone resin mold and cured.

The cured sample was fixed on a sample table for SEM, and a Pt-Pd thin film was deposited on the sample surface by a vacuum vapor deposition method. The thin-film vapor-deposited sample is set in FIB-SEM (FEI, HELIOS600), and the sample is processed by a focused ion beam (FIB) of gallium accelerated at an acceleration voltage of 30 kV to make a hole with a depth of 44.2 μm or more. , The cross section in any direction was exposed as the first observation surface. Since it is a three-dimensional measurement, the same result can be obtained regardless of the direction of the cross section. The first observation surface was SEM-observed at an acceleration voltage of 2.1 kV. The observation range (observation range) was 51.2 μm × 44.2 μm. After observing the first observation surface, the first observation surface was removed by a thickness of 50 nm by FIB processing to expose a new observation surface (second observation surface). The second observation surface was SEM-observed in the same manner as the first observation surface. By repeating this FIB processing and SEM observation, a series of SEM images were obtained for the observation surfaces arranged in parallel at 50 nm intervals in the sample. The scale of SEM observation was 50 nm / pix for the X-axis and the Y-axis, and 50 nm / pix for the Z-axis. Here, the X-axis is an axis parallel to the sample surface on the SEM observation surface, the Y-axis is the axis in the depth direction orthogonal to the sample surface on the SEM observation surface, the XY-plane is the SEM observation surface, and the Z-axis. Is the axis of the FIB cutting direction orthogonal to the SEM observation surface on the sample surface. This series of SEM images is processed by image analysis software (Visualization Sciences Group, Avizo ver. 6.0), and a sample is obtained for an observation portion corresponding to a rectangular parallelepiped of an observation range (51.2 μm × 44.2 μm) × 25 μm. A continuous slice image of was obtained.

Using the continuous slice image of this sample, a three-dimensional quantitative analysis (quantitative analysis of the three-dimensional structure) of the alumina particles contained in the sample was performed, and the three-dimensional particle unevenness and the equivalent sphere diameter were calculated. For the 3D quantitative analysis, the 3D-PRT particle analysis option of the quantitative analysis software TRI / 3D-BON-FCS (version: BON-FCS R10.01.10.29-H-64: manufactured by Ratoc System Engineering) was used. ..

In the three-dimensional quantitative analysis, first, the data of the continuous slice image was read by the quantitative analysis software TRI / 3D-PRT, and the median filter (3D, 3 × 3) was applied to remove the noise. Next, the three-dimensionally isolated particles were identified and labeled, respectively, to identify the particles to be measured. The region for performing the three-dimensional quantitative analysis (referred to as a “measurement region”) was a part of the above-mentioned observation portion (51.2 μm × 44.2 μm × 25 μm). The dimensions of the measurement area were about 48 μm × about 20 μm × about 20 μm. Particles that pass through the boundary surface of the measurement area were excluded from the measurement target.

For each of the measured particles, the particle volume V, the major axis La of the particle, the medium diameter Lb of the particle, and the minor axis Lc of the particle are obtained, and these are substituted into the following equations (1) and (2) to obtain the equivalent sphere diameter. d and the degree of three-dimensional particle unevenness were calculated, respectively. The average value of the obtained three-dimensional particle unevenness was calculated and shown in Table 2. Table 2 shows the abundance ratio of the number of particles having a sphere equivalent diameter d of less than 0.3 μm.
Three-dimensional particle unevenness = La × Lb × Lc ÷ V ・ ・ ・ ・ ・ (1)
V = 4π ÷ 3 × (d ÷ 2) ³・ ・ ・ ・ ・ (2)
When obtaining the average value of the sphere equivalent diameter d and the three-dimensional particle unevenness, it is necessary that the number of particles to be measured is 100 or more. As a result, the average value of the measured values can be substantially converged. In this example, the number of particles contained in the measurement region was about 1000 to 2000, and all the particles were measured and the average value was obtained.

(2. Nitrogen adsorption BET specific surface area)
As the specific surface area measuring device, "Flowsorb III 2310" manufactured by Shimadzu Corporation was used, and it was determined by the nitrogen adsorption method one-point method according to the method specified in JIS-Z8830 (2013). Each measurement condition was as follows.
・ Carrier gas: Nitrogen / helium mixed gas ・ Filled sample amount: 0.1 g
・ Sample pretreatment conditions: Treatment at 200 ° C for 20 minutes ・ Nitrogen adsorption temperature: Liquid nitrogen temperature (-196 ° C or less)
-Nitrogen desorption temperature: Room temperature (about 20 ° C)

(3. Ratio of pyridine-adsorbed BET specific surface area / nitrogen-adsorbed BET specific surface area)
The pyridine-adsorbed BET specific surface area was measured by a multi-point method using "BELSORP-18" manufactured by Microtrac Bell. Each measurement condition was as follows, and ^{the analysis range of the adsorption cross-sectional area of pyridine 0.285 nm 2} and the pyridine adsorption BET specific surface area was calculated under the conditions of P / P0 = 0.1 to 0.3.
・ Filled sample amount: 1g
・ Sample pretreatment conditions: Treatment at 150 ° C for 5 hours under vacuum ・ Pyridine constant temperature bath temperature: 80 ° C
-Pyridine adsorption temperature: 50 ° C
-Saturated vapor pressure: 9.607 kPa
-Initial introduction pressure: 0.267 kPa
・ Maximum suction pressure: P / P0 = 0.9
・ Adsorption equilibrium time: 300 seconds

By dividing the obtained pyridine-adsorbed BET specific surface area by the nitrogen-adsorbed BET specific surface area obtained by the above method, the "pyridine-adsorbed BET specific surface area / nitrogen-adsorbed BET specific surface area ratio" was obtained.

(4. Average particle size D50)
Using a laser particle size distribution measuring device [“Microtrack MT3300EXII” manufactured by Microtrac Bell Co., Ltd.], the average particle size was defined as the particle size D50 corresponding to a cumulative percentage of 50% on a mass basis by a laser diffraction method. At the time of measurement, a 0.2 mass% sodium hexametaphosphate aqueous solution was ultrasonically dispersed for 5 minutes, and the refractive index was 1.76.

(5. Ferrite polishing speed)
The ferrite polishing rate was measured in order to investigate the property (polishability) of the alumina powder to polish an object such as a base material. The ferrite polishing rate was measured only for alumina powder Nos. P1, P2 and P5. In the present specification, when the ferrite polishing rate is 20 μm or less, it is defined as “low polishability”.

Using a polishing machine (5627-56 type) manufactured by Marumoto Kogyo and a sample rotating machine (7705-2 type), ferrite is supplied to a buff cloth (NO-101 type manufactured by Marumoto Kogyo, 250 mmφ). The chip (6 mm × 1.5 mm × 12 mm) was polished, and the difference in thickness (μm) between before and after polishing was defined as the ferrite polishing rate. Here, the alumina-dispersed slurry was prepared by putting 35 g of alumina powder in 1750 mL of a 0.2 mass% sodium hexametaphosphate aqueous solution and ultrasonically dispersing it for 30 minutes. The polishing conditions were as follows.
Alumina-dispersed slurry dropping speed: 15 g / min.
・ Ferrite tip polishing area: 6 mm x 12 mm (72 mm ² )
・ Buff rotation speed: 400 rpm
・ Load: 400g
-Polishing time: 60 min.

(6. Gas generation amount)
In order to investigate the stability of the electrolytic solution, the amount of gas generated when the alumina powder was put into the electrolytic solution (gas generation amount) was measured. In the present specification, it is said that "the electrolyte stability is excellent" when the amount of gas generated is 60 mL or less.

After vacuum drying the alumina powder at 120 ° C. for 8 hours, 1 g of the alumina powder and 2 mg of the electrolytic solution are sealed in an aluminum laminate bag in a glove box kept at a dew point of -30 ° C or lower, and the filled aluminum laminate bag is filled. The mass of was measured. As the electrolytic solution, a LiPF ₆ solution manufactured by Kishida Chemical Co., Ltd. (1 mol / L, ethylene carbonate: ethylmethyl carbonate: diethyl carbonate = 30% by volume: 50% by volume: 20% by volume) was used. Before the heat treatment, the specific gravity and volume of the sealed aluminum laminated bag were measured by the Archimedes method, and then the aluminum laminated bag was heat-treated at 85 ° C. for 72 hours. The specific gravity and volume of the aluminum laminated bag after the heat treatment were measured by the Archimedes method, and the volume change before and after the heat treatment was calculated as the amount of gas generated.

In each physical property value in Table 2, those within the following range were regarded as "good". In Table 2, values outside the range below are underlined. Of the physical property values specified here, the "average three-dimensional particle unevenness" and the "pyridine-adsorbed BET specific surface area / nitrogen-adsorbed BET specific surface area ratio" are the essential physical property values for the alumina powder according to the present invention. Although shown, each of the other physical property values indicates a preferable physical property value in the alumina powder according to the present invention.
・ Average three-dimensional particle unevenness: 3.5 or less ・ Number of particles with sphere equivalent diameter less than 0.3 μm Presence ratio: 40% or less ・ Nitrogen adsorption BET specific surface area: 1 to 15 m ² / g
・ Ratio of pyridine-adsorbed BET specific surface area / nitrogen-adsorbed BET specific surface area: 0.7 or less ・ Average particle size D50: 2.0 μm or less ・ Ferrite polishing rate: 20 μm or less ・ Gas generation amount: 60 mL or less

<Method for producing porous alumina film>
Next, alumina porous films F1 to F4 were formed using alumina powder Nos. P1 to P4, respectively. The alumina porous film was formed on the surface of the base material (separator).
As the base material (separator), a polyethylene porous film (thickness: 12.4 μm, basis weight: 7.5 g / m ² , air permeability (Gare value): 184 seconds / 100 mL) was used. After pretreating one side of the substrate by corona discharge irradiation, an alumina porous film was formed on the treated surface by the following method.

CMC manufactured by Daicel FineChem Co., Ltd .; Part number 1110 (3 parts by weight), isopropyl alcohol (51.6 parts by weight), pure water (292 parts by weight) and alumina powder (100 parts by weight) are mixed and stirred in this order, and ultrasonic waves are used for 10 minutes. Dispersed. The obtained mixture was further dispersed for 21 minutes using CREAMICS (“CLM-0.8S” manufactured by M-Technique Co., Ltd.). The obtained dispersion was filtered through a mesh mesh having a mesh size of 10 μm to prepare an alumina slurry.

The slurry was gravure-coated on the treated surface of the base material pretreated by corona discharge irradiation using a desktop test coater manufactured by Yasui Seiki. The applied slurry was dried at a drying temperature of 50 ° C. to form an alumina porous film. The physical properties of the alumina porous film were measured using a laminated porous film (laminated separator) having an alumina porous film formed on the surface of the substrate.

<Physical characteristics of alumina porous membrane>
The physical characteristics of the prepared alumina porous membrane were measured as follows. The measurement results are shown in Table 3.

(1. Film thickness of alumina porous membrane)
The laminated porous film was measured with a high-precision digital measuring machine "VL-50A" manufactured by Mitutoyo Co., Ltd. The film thickness of the alumina porous film was calculated by subtracting the film thickness (12.4 μm) of the base material porous film from the measured film thickness of the laminated porous film.

(2. Metsuke amount of alumina porous film)
The laminated porous film is cut into a square of 8 cm × 8 cm, the weight W (g) is measured, and the grain amount (g / m ² ) = W / (0.08 m × 0.08 m) of the laminated porous film is first calculated. bottom. The basis weight of the porous substrate film (7.5 g / m ² ) was subtracted from this to calculate the basis weight of the porous alumina film.

(3. Porosity in the coating film (alumina porous film), volume ratio of pores, porosity, etc.)
After impregnating the laminated porous film with the epoxy resin, the epoxy resin was cured. After fixing the cured sample to the sample table, FIB processing is performed with FIB-SEM [manufactured by FEI (HELIOS600)] to remove the epoxy resin on the upper surface to expose the surface of the alumina porous film, and the surface thereof (alumina porous film). The surface) was observed by SEM at an acceleration voltage of 2.1 kV. After the observation, a new cross section was prepared by FIB processing with a thickness of 20 nm in the sample depth direction (thickness direction of the alumina porous membrane), and the cross section was observed by SEM. In this way, FIB processing and cross-sectional SEM observation were repeated at intervals of 20 nm to obtain a continuous slice image including the entire thickness of the alumina porous membrane, and image analysis software [Visualization Sciences Group Avizo ver. 6.0], a continuous slice image was obtained. The scale of SEM observation was 19.2 nm / pix for the X-axis and the Y-axis, and 20 nm / pix for the Z-axis. Here, the X-axis and the Y-axis are axes orthogonal to each other in a plane parallel to the surface of the alumina porous film, and the Z-axis is an axis orthogonal to the X-axis and the Y-axis and is an axis in the film thickness direction of the alumina porous film. Is.

Three-dimensional coating film was applied to the obtained continuous slice image using the quantitative analysis software TRI / 3D-BON-FCS (version: BON-FCS R.10.01.10.29-H-64: manufactured by Ratoc System Engineering). Quantitative analysis was performed to calculate the pore diameter, pore volume and porosity in the coating film.

In the three-dimensional quantitative analysis, first, the data of the continuous slice image is read by TRI / 3D-BON-FCS, a median filter (3D, 3 × 3) is applied, and then two gradations are performed by Auto-LW. The particle part and the void part were identified.
Noise is removed from the void portion identified by the above process under the conditions of 2D Ers Sml = 1, 3D Ers Sml = 5, and then the values of the Tickness parameter are set to MIL = 0.5, NdNd = 1.5, NdTm =. Calculation processing is performed under the condition of 2.0, and the pores in the coating film are defined by obtaining the minor axis Ticknes, the major axis Width, the distance between branch points Length, the total volume BV of the void portion, and the total volume TV of the analysis region. , The pore diameter, pore volume and porosity in the coating film were calculated by the following methods.

Here, the short-diameter Ticknes, the long-diameter Wide, and the distance between the branch points Length will be described with reference to FIG. "Minor diameter Ticknes" and "major diameter Width" mean the minor axis and the major axis in the cross section of the pores, respectively. "Distance between branch points" means the distance between adjacent branch points. The "branch point" is a point where two (or more) thin lines intersect when each pore is represented by a thin line.

(Pore diameter in the coating film (alumina porous film))
The pore diameter in the coating film was obtained from the following formula (3). The formula (3) is a formula for obtaining the average diameter (pore diameter) of the pores, and is intended to divide the sum of the short diameter (Thickness) and the major diameter (Wids) of the pores shown in FIG. 2 by 2. There is.
Pore diameter in the coating film = (Thickness + Wide) ÷ 2 ... (3)

(Pore volume in the coating film (alumina porous film))
The pore volume in the coating film was determined from the following formulas (4) and (5). Equation (4) is an equation for calculating the cross-sectional area (CS) of pores from the minor axis (Thickness) and the major axis (Wids). Equation (5) is an equation for calculating the pore volume from the obtained cross-sectional area and the length of the pores (distance between branch points (Length)).
CS = (Thickness ÷ 2) × (Width ÷ 2) × π ・ ・ ・ ・ ・ (4)
Pore volume in the coating film = CS × Length ・ ・ ・ ・ ・ (5)

(Porosity of coating film (alumina porous film))
The "void ratio" in the present invention is a parameter indicating the void in the alumina porous membrane, and can be obtained from the three-dimensional analysis of the alumina porous membrane in the analysis region. The following formula is obtained by dividing the total volume (BV) of the void portion by the total volume (TV) of the analysis region for the void portion identified by making two gradations into the particle portion and the void portion using three-dimensional analysis. This is the value specified in (6).
Porosity (% by volume) = BV ÷ TV x 100 ... (6)

(Pore distribution of coating film (alumina porous film))
The pore distribution in the coating film was obtained from the obtained pore diameter and pore volume in the coating film, and the volume ratio of the pores having a pore diameter of 0.2 μm or less (“pore volume of pores having a pore diameter of 0.2 μm or less”). "Total" ÷ "Total pore volume of all pores in the coating film" x 100 (volume%)) and volume ratio of pores with a pore diameter of more than 0.5 μm ("Fine with a pore diameter of more than 0.5 μm""Total pore volume of pores" ÷ "Total pore volume of all pores in the coating film" x 100 (% by volume)) was calculated. The measurement range of the pore distribution in the coating film was 17.6 μm × 11.3 μm × (observation depth) μm. Observation depth is determined according to the thickness of each sample (in terms of volume of the observation area, approximately 600~1000μm ³⁾ Approximately 3~5μm was.

(Average pore diameter D50)
The average pore diameter D50 was obtained from the pore distribution in the coating film (alumina porous film).

(4. Air permeability of alumina porous membrane)
In accordance with JIS P8117 (2009), the air permeability X (Gale value) (seconds / 100 mL) of the laminated porous film was measured with a Gale type densometer manufactured by Toyo Seiki Seisakusho Co., Ltd. The air permeability of the substrate (separator) (184 seconds / 100 mL at the galley value) is subtracted from the air permeability X (garle value) of the obtained laminated porous film, and the film thickness T (μm) of the alumina porous film is further reduced. The air permeability of the alumina porous film per 1 μm of the film thickness (Gale value per 1 μm of the film film) (seconds / 100 mL · μm) was determined by dividing by.
The air permeability of the alumina porous membrane per 1 μm of the film thickness can be obtained by the following formula.

Air permeability of alumina porous membrane per 1 μm film thickness = (X-184) ÷ T

Here, X is the air permeability (Gale value) (seconds / 100 mL) of the laminated porous film, and T is the film thickness (μm) of the alumina porous film.

In each physical property value in Table 3, those within the following range were regarded as "good". In Table 3, values outside the range below are underlined. It should be noted that each of the physical property values specified here indicates a range of preferable physical property values in the alumina porous membrane according to the present invention, and it is necessary that the alumina porous membrane according to the present invention always satisfies these physical characteristic values. Should not be understood.
Porosity: 20-90% by volume
-Average pore diameter D50: 1 μm or less-Volume ratio of pores with pore diameter 0.2 μm or less: 30% by volume or less-Volume ratio of pores with pore diameter over 0.5 μm: 10% by volume or more-Per 1 μm film thickness Air permeability (Gare value per 1 μm film thickness): 10 seconds / 100 mL · μm or less

<Method of manufacturing non-aqueous electrolyte secondary battery>
Next, a non-aqueous electrolytic solution secondary was used using a laminated separator (including a polyolefin porous membrane and an alumina porous membrane formed on the surface thereof) prepared for measuring the physical properties of the alumina porous membranes F1, F3, and F4. Batteries B1, B3 and B4 were prepared respectively. The conditions for producing the positive and negative electrodes contained in the non-aqueous electrolyte secondary batteries B1, B3, and B4, and the method for assembling the non-aqueous electrolyte secondary battery were as follows.

(Preparation of positive electrode)
A positive electrode was produced using a commercially available positive electrode material (aluminum foil on which a positive electrode active material layer was formed). _{In a commercially available positive electrode material, LiNi 0.5} Mn _0.3 Co _0.2 O ₂ / conductive material / PVDF (weight ratio 92/5/3) is coated on the surface of an aluminum foil as a positive electrode active material. The positive electrode material is processed so that the width of the positive electrode active material layer is 45 mm × 30 mm, and the portion where the positive electrode active material layer is not formed (the portion where the aluminum foil is exposed) has a width of 13 mm. It was used as a positive electrode. The thickness of the positive electrode active material layer formed on the positive electrode was 58 μm, the density was 2.50 g / cm ³ , and the positive electrode capacity of the positive electrode was 174 mAh / g.

(Manufacturing of negative electrode)
A negative electrode was produced using a commercially available negative electrode material (copper foil on which a negative electrode active material layer was formed). In a commercially available negative electrode material, graphite / styrene-1,3-butadiene copolymer / sodium carboxymethyl cellulose (weight ratio 98/1/1) is coated on the surface of a copper foil as a negative electrode active material. The negative electrode material is processed so that the width of the negative electrode active material layer is 50 mm × 35 mm and the width of the portion where the negative electrode active material layer is not formed (the portion where the copper foil is exposed) is 13 mm. The negative electrode was used. The thickness of the negative electrode active material layer formed on the negative electrode was 49 μm, the density was 1.40 g / cm ³ , and the negative electrode capacity of the negative electrode was 372 mAh / g.

(Assembly of non-aqueous electrolyte secondary battery)
A member for a secondary battery was obtained by laminating (arranging) a positive electrode, a laminated separator, and a negative electrode in this order in a laminated pouch. At this time, the laminated separator was arranged so that the layer of the alumina porous film faces the positive electrode side. Further, the positive electrode and the negative electrode were aligned so that the positive electrode active material layer of the positive electrode was entirely within the range of the main surface on which the negative electrode active material layer of the negative electrode was formed when observed in the stacking direction. The dimensions of the laminated separator were larger than those of the positive electrode and the negative electrode. The laminated separator was aligned with respect to the positive electrode and the negative electrode so that the laminated separator covered all of the positive electrode and the negative electrode when observed in the stacking direction.

Subsequently, the secondary battery member was placed in a bag in which an aluminum layer and a heat seal layer were laminated, and 0.25 mL of a non-aqueous electrolytic solution was further placed in this bag. As the non-aqueous electrolytic solution, _{an electrolytic solution at 25 ° C. in which LiPF 6} having a concentration of 1.0 mol / L was dissolved in a mixed solvent having a volume ratio of ethyl methyl carbonate, diethyl carbonate and ethylene carbonate at 50:20:30 was used. .. Then, the non-aqueous electrolyte secondary battery was produced by heat-sealing the bag while reducing the pressure inside the bag. The design capacity of the non-aqueous electrolyte secondary battery was set to 20.5 mAh.

<Electrical characteristics of non-aqueous electrolyte secondary battery>
The electrical characteristics of the prepared non-aqueous electrolyte secondary battery were measured as follows. The measurement results are shown in Table 4.

(1. Initial rate characteristics before cycle test)
For each of the non-aqueous electrolyte secondary batteries B1, B3, and B4, CC-CV charging with a voltage range of 2.7 to 4.1 V and a charging current value of 0.2 C (termination current condition 0.02 C). ) And CC discharge with a discharge current value of 0.2 C (the current value for discharging the rated capacity based on the discharge capacity of 1 hour rate in 1 hour is 1 C. The same shall apply hereinafter), and the initial charge of 4 cycles is set as 1 cycle. Discharge was performed at 25 ° C. Here, 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 the current is throttled. CC discharge is a method of discharging to a predetermined voltage with a set constant current.

After CC-CV charging (termination current condition 0.02C) with a charging current value of 1C to the non-aqueous electrolyte secondary battery that has been initially charged and discharged, the discharge current value (discharge rate) is changed. CC discharge was performed. The discharge current values were 0.2C, 1C, 5C, 10C, and 20C. Using the same non-aqueous electrolyte secondary battery with CC-CV charging and CC discharging as one cycle, the discharge current value is 0.2C x 3 cycles, 1C x 3 cycles, 5C x 3 cycles, 10C at 55 ° C. Charge / discharge tests of × 3 cycles and 20C × 3 cycles (15 cycles in total) were performed in this order.

The discharge capacity (0.2C discharge capacity) of the third cycle of the charge / discharge test conducted at the discharge current value of 0.2C and the discharge capacity (20C discharge capacity) of the third cycle of the charge / discharge test conducted at the discharge current value of 20C. The ratio with (20C discharge capacity / 0.2C discharge capacity) was calculated as the initial rate characteristic before the cycle test.

(Rate characteristics after 2.100 cycles)
The non-aqueous electrolyte secondary battery after the initial rate characteristic measurement before the cycle test is discharged with CC-CV charging (termination current condition 0.02C) with a voltage range of 2.7 to 4.2V and a charging current value of 1C. 100 cycles of charge and discharge were carried out at 55 ° C., with CC discharge having a current value of 10 C as one cycle.

CC-CV charging (termination current condition 0.02C) with a voltage range of 2.7V to 4.2V and a charging current value of 1C was performed on the non-aqueous electrolyte secondary battery that had been charged and discharged for 100 cycles. After that, CC discharge was performed while changing the discharge current value (discharge rate). The discharge current values were 0.2C, 1C, 5C, 10C, and 20C. Using the same non-aqueous electrolyte secondary battery with CC-CV charging and CC discharging as one cycle, the discharge current value is 0.2C x 3 cycles, 1C x 3 cycles, 5C x 3 cycles, 10C at 55 ° C. Charge / discharge tests of × 3 cycles and 20C × 3 cycles (15 cycles in total) were performed in this order.

The discharge capacity (0.2C discharge capacity) of the third cycle of the charge / discharge test conducted at the discharge current value of 0.2C and the discharge capacity (20C discharge capacity) of the third cycle of the charge / discharge test conducted at the discharge current value of 20C. The ratio with (20C discharge capacity / 0.2C discharge capacity) was calculated as the rate characteristic after 100 cycles.

In the present specification, when the initial rate characteristic test before the cycle test is 60% or more and the rate characteristic after 100 cycles is 20% or more, it is regarded as "excellent in battery characteristics".

In each measured value in Table 4, those within the following range were regarded as "good". In Table 4, values outside the range below are underlined. It should be noted that each measured value specified here indicates a range of preferable measured values in the non-aqueous electrolytic solution secondary battery according to the present invention, and the non-aqueous electrolytic solution secondary battery according to the present invention has these. It should not be understood that the physical properties must be met.
・ Initial rate characteristics before cycle test: 60% or more ・ Rate characteristics after 100 cycles: 20% or more

The experimental results in Tables 1 to 4 will be considered below.

Alumina powders No. P1 and P2 were alumina powders produced by the production method of the present invention using a surface protective agent, and all the physical property values were good. Therefore, the alumina porous films F1 and F2 formed by using these alumina powders have porosity, average pore diameter, volume ratio of pores having a pore diameter of 0.2 μm or less, and volume of pores having a pore diameter of more than 0.5 μm. All of the ratios were good. In addition, the non-aqueous electrolytic solution secondary battery B1 using the alumina porous membrane F1 had excellent electrical characteristics.

Alumina powders No. P1 and P2 had a small average three-dimensional particle unevenness, so that the ferrite polishing rate was low and the polishability was suppressed.

Further, since the alumina powders P1 and P2 have few particles having a sphere equivalent diameter of less than 0.3 μm, the alumina porous membranes F1 and F2 have a reduced volume ratio of pores having a pore diameter of 0.2 μm or less, and the pore diameter is 0. The volume ratio of pores over 5.5 μm increased. As a result, the galley values of the alumina porous films F1 and F2 per 1 μm of film thickness are reduced (that is, the air permeability per 1 μm of film thickness is increased and the Li ion permeability is improved), and the battery is excellent. It showed characteristics (eg, secondary battery B1).

Further, it can be said that the alumina powders P1 and P2 have a small amount of pyridine adsorbed (less acidic property) because the ratio of the pyridine-adsorbed BET specific surface area to the nitrogen-adsorbed BET specific surface area is small. Therefore, the amount of gas generated when the alumina powders P1 and P2 were put into the electrolytic solution was small, and the electrolytic solution stability was excellent. As a result, it is considered that the secondary battery provided with the alumina porous film formed from such alumina powder is unlikely to deteriorate in the electrolytic solution, and has excellent battery cycle characteristics (for example, formed from alumina powder P1). Secondary battery B1) equipped with the alumina porous film F1.

Alumina powders No. P3 and P4 are alumina powders produced without using a surface protective agent. Alumina powders No. P3 and P4 had a large proportion of particles having a sphere equivalent diameter of less than 0.3 μm. Therefore, the alumina porous membranes F3 and F4 formed by using these alumina powders have a large volume ratio of pores having a pore diameter of 0.2 μm or less, and a small volume ratio of pores having a pore diameter of more than 0.5 μm. .. As a result, the galley value of the alumina porous films F3 and F4 per 1 μm of film thickness increases (that is, the air permeability per 1 μm of film thickness decreases and the Li ion permeability decreases), and the secondary battery B3 , The battery characteristics of B4 were low.

Further, since the alumina powders No. P3 and P4 were produced without using a surface protective agent, the ratio of the pyridine-adsorbed BET specific surface area to the nitrogen-adsorbed BET specific surface area was large. In other words, it can be said that alumina powders No. P3 and P4 have a large amount of pyridine adsorbed (many acidic properties). Therefore, the amount of gas generated when the alumina powders P3 and P4 were put into the electrolytic solution was large, and the electrolytic solution stability was low. As a result, it is probable that the secondary batteries B3 and B4 provided with the alumina porous films F3 and F4 formed from the alumina powders P3 and P4 tended to deteriorate the electrolytic solution and had low battery cycle characteristics.

Alumina powder No. P5 had a large average three-dimensional particle unevenness, so that the ferrite polishing rate was high and the polishability was high.

Claims (12)

Alumina powder for forming an alumina porous film used in a non-aqueous electrolyte secondary battery.
The average three-dimensional particle asperity is 3.5 or less, and the ratio of pyridine adsorption BET specific surface area / nitrogen adsorption BET specific surface area of Ri der 0.7
Alumina powder for forming an alumina porous film containing glycols. The alumina powder for forming an alumina porous film according to claim 1, wherein the content of glycols is 0.01 to 2.0 parts by mass with respect to 100 parts by mass of the alumina powder. The alumina powder for forming an alumina porous film according to claim 1 or 2 , wherein the presence ratio of the number of particles having an equivalent sphere diameter of less than 0.3 μm is 40% or less. Porous alumina film forming alumina powder according to any one of claims 1 to 3 nitrogen adsorption BET specific surface area of 1m ² / g~15m ² / g. The alumina powder for forming an alumina porous film according to any one of claims 1 to 4 , wherein the average particle size is 2.0 μm or less. An alumina slurry containing the alumina powder for forming an alumina porous film according to any one of claims 1 to 5 , a binder, and a solvent. An alumina porous film containing the alumina powder for forming an alumina porous film according to any one of claims 1 to 5 and a binder. A laminated separator comprising the alumina porous membrane according to claim 7 and a separator having the alumina porous membrane on its surface. A non-aqueous electrolytic solution secondary battery in which the alumina porous film according to claim 7 is provided on at least one surface of a positive electrode, a negative electrode, and a separator. A method for manufacturing a non-aqueous electrolytic solution secondary battery, comprising a step of applying the alumina slurry according to claim 6 to at least one surface of a positive electrode, a negative electrode and a separator and then drying the alumina slurry to form an alumina porous film. The method for producing an alumina powder for forming an alumina porous film according to any one of claims 1 to 5.
A method for producing alumina powder, which comprises a step of mixing glycols and pulverizing the raw material alumina. Use of an alumina porous membrane containing the alumina powder according to any one of claims 1 to 5 for suppressing gas generation from the electrolytic solution of a non-aqueous electrolytic solution secondary battery.

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