JP2013056801A - Lithium composite metal oxide, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium composite metal oxide which is useful for a nonaqueous electrolyte secondary battery capable of showing a high capacity.SOLUTION: Concerning this lithium composite metal oxide represented by formula (A), in powder X-ray diffractometry using CuK α-line, a crystal structure includes a structure belonging to a hexagonal system and a space group R-3m, and a lattice constant a calculated based on the hexagonal system and the space group is ≤2.87 Å. LiNiO(A) (wherein, 1.05≤x≤1.30 and -0.1≤δ≤0.1 are satisfied.).

Description

  The present invention relates to a lithium composite metal oxide used for a positive electrode active material for a non-aqueous electrolyte secondary battery.

  Lithium composite metal oxide is used as a positive electrode active material in nonaqueous electrolyte secondary batteries such as lithium secondary batteries. Lithium secondary batteries have already been put into practical use as small power sources for mobile phones and notebook computers, and are also being applied to medium and large power sources for automobiles and power storage.

As a conventional lithium composite metal oxide, Patent Document 1 has a hexagonal system, space group R-3m, which is called a layered rock salt structure, and a lattice constant a calculated based on the crystal system and the space group. Is a lithium composite metal oxide for a positive electrode material for a lithium secondary battery, which has a lattice constant c of 14.19 具体 and a composition formula of LiNiO ₂ .

Japanese Patent No. 3167518

  However, the non-aqueous electrolyte secondary battery obtained by using the above-described conventional lithium composite metal oxide as a positive electrode active material is not sufficient in applications requiring high capacity, that is, in automobile applications or power storage applications. Absent. An object of the present invention is to provide a lithium composite metal oxide useful for a nonaqueous electrolyte secondary battery capable of exhibiting a high capacity, and a method for producing the same.

  As a result of various investigations in view of the above circumstances, the present inventors have found that the following inventions meet the above-mentioned object, and have reached the present invention.

<1> A lithium composite metal oxide represented by the formula (A),
In powder X-ray diffraction measurement using CuKα rays, the crystal structure includes a structure belonging to the hexagonal system and the space group R-3m, and the lattice constant a calculated based on the crystal system and the space group is 2. Lithium composite metal oxide which is 87% or less.
Li _x NiO _{2 ± δ} (A)
(Here, 1.05 ≦ x ≦ 1.30 and −0.1 ≦ δ ≦ 0.1.)
<2> The lithium composite metal oxide according to <1>, wherein the lattice constant c is in the range of 14.19 to 14.22 and the lattice volume is in the range of 100.5 to ^{3 and} 101.5 to ³ .
<3> The lithium composite metal oxide according to <1> or <2>, wherein a value (c / a) obtained by dividing the lattice constant c by the lattice constant a is 4.94 or more and 4.97 or less.
<4> A positive electrode comprising the lithium composite metal oxide according to any one of <1> to <3> as a positive electrode active material.
<5> A nonaqueous electrolyte secondary battery comprising the positive electrode according to <4>.
<6> A method for producing a lithium composite metal oxide comprising the following steps (1), (2), (3) and (4) in this order.
(1) A step of producing a coprecipitate by bringing an aqueous solution containing Ni and an alkali containing Li into contact to obtain a coprecipitate slurry. (2) Solid-liquid separation of the obtained coprecipitate slurry is performed as a solid. (3) The mixture obtained by mixing the obtained solid and lithium compound is held at a temperature of 300 ° C. or higher and 550 ° C. or lower and fired to obtain the first lithium composite metal oxide. Step (4) A mixture obtained by mixing the obtained first lithium composite metal oxide and the lithium compound is held at a temperature of 600 ° C. or higher and 800 ° C. or lower and calcined to produce a second lithium composite metal oxide. <7> In the step (3), the lithium composite according to <6>, wherein a lithium compound is added in an amount of 1.0 mol times or more and 2.0 mol times or less in terms of Li with respect to the amount of charged Ni. A method for producing a metal oxide.
<8> The production method according to <6> or <7>, wherein in the step (4), a lithium compound is added in an amount of 1.0 mol times or more and 2.0 mol times or less in terms of Li with respect to the charged Ni amount. .

  ADVANTAGE OF THE INVENTION According to this invention, the lithium composite metal oxide which can give the nonaqueous electrolyte secondary battery which shows a high capacity | capacitance compared with the conventional lithium secondary battery is provided.

The present invention is a lithium composite metal oxide represented by the following formula (A), and in powder X-ray diffraction measurement using CuKα rays, the crystal structure belongs to the hexagonal system, space group R-3m. The present invention relates to a lithium composite metal oxide including a structure and having a lattice constant “a” calculated based on the crystal system and the space group of 2.87% or less.
Li _x NiO _{2 ± δ} (A)
(Here, 1.05 ≦ x ≦ 1.30 and −0.1 ≦ δ ≦ 0.1.)

  The crystal structure (crystal system) and space group of the lithium composite metal oxide of the present invention are measured by powder X-ray diffraction measurement using CuKα as a radiation source and a measurement range of diffraction angle 2θ of 10 ° or more and 90 ° or less, Based on the results, Rietveld analysis (for example, “Practice of X-ray powder analysis—Introduction to Rietveld method”, published on February 10, 2002, edited by the Japan Society for Analytical Chemistry, X-ray Analysis Research Roundtable) The lattice constant is a value calculated on the basis of the crystal structure (crystal system) and the space group.

  In the lithium composite metal oxide of the present invention, when the lattice constant a exceeds 2.87%, the capacity of the positive electrode using the lithium composite metal oxide as a positive electrode active material is not sufficient. In order to obtain a higher capacity positive electrode, the lattice constant a is more preferably 2.84 to 2.87.

  Further, in the formula (A), when x corresponding to the Li / Ni molar ratio is less than 1.05, the obtained nonaqueous electrolyte secondary battery has insufficient cycle characteristics, and x is 1.30. If it exceeds, the capacity is not sufficient. In order to improve the cycle characteristics, x is preferably 1.05 or more and 1.25 or less, and more preferably 1.06 or more and 1.10 or less.

  Further, δ in the oxygen amount (2 ± δ) in the formula (A) is in the range of −0.1 or more and 0.1 or less.

In the lithium composite metal oxide of the present invention, in order to obtain a positive electrode of a higher capacity, it is preferable that the lattice constant c is equal to or less than 14.22Å least 14.19A, the lattice volume of 100.5A ³ or more 101.5Å It is preferably ³ or less.

  In the lithium composite metal oxide of the present invention, in order to obtain a higher capacity positive electrode, the value (c / a) obtained by dividing the lattice constant c by the lattice constant a is 4.94 or more and 4.97 or less. preferable.

As a method for producing the lithium composite metal oxide of the present invention, a production method including the following steps (1), (2), (3) and (4) in this order can be mentioned.
(1) A step of producing a coprecipitate by bringing an aqueous solution containing Ni and an alkali containing Li into contact to obtain a coprecipitate slurry. (2) Solid-liquid separation of the obtained coprecipitate slurry is performed as a solid. (3) Step of obtaining a calcined product by maintaining a mixture obtained by mixing the obtained solid content and the lithium compound at a temperature of 300 ° C. or higher and 550 ° C. or lower (4) And a step of maintaining a mixture obtained by mixing the lithium compound at a temperature of 600 ° C. or higher and 800 ° C. or lower.

  Hereinafter, each step will be described.

In the step (1), the aqueous solution containing Ni dissolves water-soluble compounds such as water-soluble genus salts such as nitrates, sulfates, acetates and oxalates and water-soluble halides such as chlorides in water. Can be adjusted. When the raw material containing Ni is an oxide, hydroxide, or metal material that is sparingly soluble in water, these raw materials can be dissolved in an aqueous solution containing an acid to obtain an aqueous solution containing Ni. .
Among these, an aqueous solution obtained by dissolving Ni nitrate in water is preferable.

In the step (1), as the alkali source, one or more anhydrides selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate and ammonium carbonate and / or Alternatively, one or more hydrates or aqueous ammonia can be used, and these are usually dissolved in water and used as an aqueous solution. The concentration of alkali in the aqueous solution is usually about 0.1 to 20M, preferably about 0.5 to 10M.
From the viewpoint of increasing the crystal purity of the lithium composite metal oxide, it is preferable to use an anhydride and / or hydrate of lithium hydroxide as the alkali.
In the step (1), when an anhydride and / or hydrate of lithium hydroxide is used as the alkali, the coprecipitate slurry contains lithium.

  As a method of contact (liquid phase mixing) in step (1), a method of adding an alkaline aqueous solution to an aqueous solution containing Ni and mixing, a method of adding an aqueous solution containing Ni to an alkaline aqueous solution and mixing, and water A method of adding and mixing an aqueous solution containing Ni and an aqueous alkaline solution can be mentioned. In mixing these, it is preferable to involve stirring. Among the above contact methods, the method of adding and mixing an aqueous solution containing Ni to the alkaline aqueous solution can be preferably used because it is easy to maintain the pH change. In this case, as the aqueous solution containing Ni is added to and mixed with the alkaline aqueous solution, the pH of the mixed solution tends to decrease, but this pH is 9 or more, preferably 10 or more. An aqueous solution containing Ni is preferably added while adjusting.

  The water used as the solvent for the aqueous solution containing Ni and the aqueous alkaline solution is preferably pure water and / or ion-exchanged water. In addition, an organic solvent other than water, such as alcohol, a pH adjuster, or the like may be included as long as the effects of the present invention are not impaired.

  Next, as step (2), the coprecipitate slurry is subjected to solid-liquid separation to obtain a solid content. Examples of the method for obtaining a solid content by solid-liquid separation from the coprecipitate slurry include filtration, centrifugation, and solvent distillation. Since the method is simple, a method using filtration is preferably used.

  Drying is usually performed by heat treatment, but may be performed by air drying, vacuum drying, or the like. As the drying atmosphere, air, oxygen, nitrogen, argon, or a mixed gas thereof can be used, but an air atmosphere is preferable. When drying is performed by heat treatment, it is usually performed at 50 to 300 ° C, preferably about 100 to 200 ° C.

Next, as the step (3), a mixture obtained by mixing the solid content obtained above and the lithium compound is held at a temperature of 300 to 550 ° C. and fired to obtain a first lithium composite metal compound.
Examples of the lithium compound include one or more anhydrides and / or one or more hydrates selected from the group consisting of lithium hydroxide, lithium chloride, lithium nitrate, and lithium carbonate, and have high reactivity. Therefore, lithium hydroxide is preferably used.

  In the step (3), the firing temperature is 300 ° C. or higher and 550 ° C. or lower in the sense that it is easy to produce a uniform product.

  Next, in step (4), the mixture obtained by mixing the first lithium composite metal compound obtained above and the lithium compound is held at a temperature of 600 ° C. or higher and 800 ° C. or lower and fired to obtain second lithium. A composite metal compound is obtained. Examples of the lithium compound include one or more anhydrides and / or one or more hydrates selected from the group consisting of lithium hydroxide, lithium chloride, lithium nitrate, and lithium carbonate, and have high reactivity. Therefore, lithium hydroxide is preferably used.

  The second lithium composite metal compound obtained in the step (4) includes a crystal structure including a structure belonging to a hexagonal system and a space group R-3m, and a lattice constant a of 2.87２ or less. . In step (4), if the firing temperature is lower than 600 ° C., it is difficult to obtain a structure belonging to the space group R-3m, and if it exceeds 800 ° C., the resulting nonaqueous electrolyte secondary battery is This is not preferable because the capacity is not sufficient.

  Next, the mixing method in the said process (3) and process (4) is demonstrated. The mixing method of the lithium compound and the solid content or the first lithium composite metal compound may be either dry mixing or wet mixing, and is preferably dry mixing from the viewpoint of simplicity. Examples of the mixing device include stirring and mixing, a V-type mixer, a W-type mixer, a ribbon mixer, a drum mixer, a ball mill, and the like.

  In the step (3), it is easy to obtain a uniform first lithium composite metal compound. Therefore, it is preferable to add the lithium compound 1.0 times or more and 2.0 times or less with respect to the charged Ni amount ratio.

  In step (4), in order to increase the capacity of the non-aqueous electrolyte secondary battery obtained by using the second lithium composite metal compound, the lithium compound is added in an amount of 1.0 to 2.0 times the Ni content ratio. It is preferable to add.

In the above step (3) or step (4), if necessary, a filtration and drying step may be added after the baked product is washed with water.
In the step (3) or step (4), an oxygen atmosphere is preferable as the firing atmosphere. Here, the oxygen atmosphere refers to an atmosphere containing 50% or more of oxygen.

  The electrode having the lithium composite metal oxide of the present invention as a positive electrode active material is suitable as a positive electrode for a non-aqueous electrolyte secondary battery.

  Using the lithium composite metal oxide of the present invention, for example, a positive electrode for a non-aqueous electrolyte secondary battery can be produced as follows.

  The positive electrode is manufactured by supporting a positive electrode mixture containing the positive electrode active material, a conductive material and a binder on a positive electrode current collector. A carbon material can be used as the conductive material, and examples of the carbon material include graphite powder, carbon black (for example, acetylene black), and a fibrous carbon material. Since carbon black is fine and has a large surface area, adding a small amount to the positive electrode mixture can improve the conductivity inside the positive electrode and improve the charge / discharge efficiency and output characteristics. This reduces the binding property between the positive electrode mixture and the positive electrode current collector, and causes an increase in internal resistance. Usually, the ratio of the conductive material in the positive electrode mixture is 5 to 20 parts by weight with respect to 100 parts by weight of the positive electrode active material. When a fibrous carbon material such as graphitized carbon fiber or carbon nanotube is used as the conductive material, this ratio can be lowered.

  As the binder, a thermoplastic resin can be used. Specifically, polyvinylidene fluoride (hereinafter sometimes referred to as PVdF), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), and four fluorine. Fluorine resins such as fluorinated ethylene / hexafluoropropylene / vinylidene fluoride copolymer, hexafluoropropylene / vinylidene fluoride copolymer, tetrafluoroethylene / perfluorovinyl ether copolymer; polyethylene, polypropylene, etc. A polyolefin resin. Moreover, you may use these 2 types or more in mixture. Further, by using a fluororesin and a polyolefin resin as a binder, the ratio of the fluororesin to the positive electrode mixture is 1 to 10% by weight, and the ratio of the polyolefin resin is 0.1 to 2% by weight, A positive electrode mixture excellent in binding property with the positive electrode current collector can be obtained.

  As the positive electrode current collector, a conductor such as Al, Ni, and stainless steel can be used, but Al is preferable because it is easy to process into a thin film and is inexpensive. Examples of the method of supporting the positive electrode mixture on the positive electrode current collector include a method of pressure molding, and a method of pasting using an organic solvent, applying onto the positive electrode current collector, drying and pressing to fix the positive electrode current collector. It is done. When making a paste, a paste made of a positive electrode active material, a conductive material, a binder, and an organic solvent is prepared. Examples of the organic solvent include amine solvents such as N, N-dimethylaminopropylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; ketone solvents such as methyl ethyl ketone; ester solvents such as methyl acetate; dimethylacetamide, N-methyl- And amide solvents such as 2-pyrrolidone (hereinafter sometimes referred to as NMP).

  Examples of the method of applying the positive electrode mixture to the positive electrode current collector include a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method, and an electrostatic spray method. A positive electrode can be manufactured by the method mentioned above.

  As a method for manufacturing a non-aqueous electrolyte secondary battery using the above positive electrode, a case of manufacturing a lithium secondary battery will be described as an example. That is, the electrode group obtained by laminating and winding the separator, the negative electrode, and the positive electrode can be manufactured by being impregnated with an electrolytic solution after being housed in a battery can.

  As the shape of the electrode group, for example, a cross-section when the electrode group is cut in a direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, a rectangle with rounded corners, or the like. The shape can be mentioned. In addition, examples of the shape of the battery include a paper shape, a coin shape, a cylindrical shape, and a square shape.

  The negative electrode only needs to be capable of doping and dedoping lithium ions at a lower potential than the positive electrode, and an electrode in which a negative electrode mixture containing a negative electrode material is supported on a negative electrode current collector, and an electrode made of a negative electrode material alone Can be mentioned. Examples of the negative electrode material include carbon materials, chalcogen compounds (oxides, sulfides, and the like), nitrides, metals, and alloys that can be doped and dedoped with lithium ions at a lower potential than the positive electrode. Moreover, you may use these negative electrode materials in mixture.

The negative electrode material is exemplified below. Specific examples of the carbon material include graphite such as natural graphite and artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and organic polymer compound fired bodies. Examples oxide, _{specifically,} (wherein, x represents a positive real number) SiO 2, SiO, etc. formula SiO _x oxides of silicon represented by; TiO _2, TiO, etc. by the formula TiO _x (wherein, x Is an oxide of titanium represented by a positive real number; an oxide of vanadium represented by a formula VO _x (where x is a positive real number) such as V ₂ O ₅ and VO ₂ ; Fe ₃ O ₄ , Fe ₂ O ₃ , FeO, etc. Iron oxide represented by the formula FeO _x (where x is a positive real number); SnO ₂ , SnO, etc. represented by the formula SnO _x (where x is a positive real number) An oxide of tin; an oxide of tungsten represented by a general formula WO _x (where x is a positive real number) such as WO ₃ and WO ₂ ; lithium and titanium such as Li ₄ Ti ₅ O ₁₂ and LiVO ₂ ; Or a composite metal oxide containing vanadium. Specific examples of the sulfide include titanium sulfide represented by the formula TiS _x (where x is a positive real number) such as Ti ₂ S ₃ , TiS ₂ , and TiS; V ₃ S ₄ , VS _2, Vanadium sulfide represented by the formula VS _x (where x is a positive real number), such as VS; FeS _x (where x is a positive real number), such as Fe ₃ S ₄ , FeS ₂ , FeS Iron sulfide; molybdenum sulfide represented by the formula MoS _x (where x is a positive real number) such as Mo ₂ S ₃ , MoS ₂ ; SnS _x such as SnS _2, SnS where x is A sulfide of tin represented by a positive real number; a sulfide of tungsten represented by WS _{2 and the} like WS _x (where x is a positive real number); and a formula SbS _x such as Sb ₂ S ₃ (where x is antimony represented by a positive real _{number); Se 5 S 3, SeS} 2, SeS formula SeS _x (wherein such, Sulfide selenium represented by a positive real number); and the like. Specific examples of the nitride include lithium-containing nitrides such as Li ₃ N, Li _3-x A _x N (where A is Ni and / or Co, and 0 <x <3). Can be mentioned. These carbon materials, oxides, sulfides, and nitrides may be used in combination, and may be crystalline or amorphous. Further, these carbon materials, oxides, sulfides and nitrides are mainly carried on the negative electrode current collector and used as electrodes.

Specific examples of the metal include lithium metal, silicon metal, and tin metal. Examples of the alloy include lithium alloys such as Li—Al, Li—Ni, and Li—Si; silicon alloys such as Si—Zn; Sn—Mn, Sn—Co, Sn—Ni, Sn—Cu, and Sn—La. And tin alloys such as Cu ₂ Sb and La ₃ Ni ₂ Sn ₇ . These metals and alloys are mainly used alone as electrodes (for example, used in a foil shape).

  Among the negative electrode materials, from the viewpoint of high potential flatness, low average discharge potential, good cycle characteristics, and the like, a carbon material mainly composed of graphite such as natural graphite or artificial graphite is preferably used. The shape of the carbon material may be any of a flake shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, or an aggregate of fine powder.

  The negative electrode mixture may contain a binder as necessary. Examples of the binder include thermoplastic resins, and specific examples include PVdF, thermoplastic polyimide, carboxymethyl cellulose, polyethylene, and polypropylene.

  Examples of the negative electrode current collector include conductors such as Cu, Ni, and stainless steel, and Cu may be used because it is difficult to form an alloy with lithium and it is easy to process into a thin film. The method of supporting the negative electrode mixture on the negative electrode current collector is the same as in the case of the positive electrode. The method is a method of pressure molding, pasted using a solvent, etc., coated on the negative electrode current collector, dried, pressed and pressed. The method of doing is mentioned.

  As the separator, for example, a material having a form such as a porous membrane, a nonwoven fabric, a woven fabric made of a polyolefin resin such as polyethylene and polypropylene, a fluororesin, a nitrogen-containing aromatic polymer, and the like can be used. Moreover, it is good also as a separator using 2 or more types of the said material, and the said material may be laminated | stacked. Examples of the separator include separators described in JP 2000-30686 A, JP 10-324758 A, and the like. The thickness of the separator is preferably about 5 to 200 μm, and preferably about 5 to 40 μm, as long as the mechanical strength is maintained because the volume energy density of the battery is increased and the internal resistance is reduced.

  The separator preferably has a porous film containing a thermoplastic resin. In a non-aqueous electrolyte secondary battery, normally, when an abnormal current flows in the battery due to a short circuit between the positive electrode and the negative electrode, the function of shutting down the current and preventing the excessive current from flowing (shut down) It is preferable to have. Here, the shutdown is performed by closing the micropores of the porous film in the separator when the normal use temperature is exceeded. After the shutdown, even if the temperature in the battery rises to a certain high temperature, it is preferable to maintain the shutdown state without breaking the film due to the temperature. Examples of such a separator include a laminated film in which a heat-resistant porous layer and a porous film are laminated. By using the film as a separator, the heat resistance of the secondary battery in the present invention can be further increased. . Here, the heat-resistant porous layer may be laminated on both surfaces of the porous film.

  Hereinafter, a laminated film in which the heat resistant porous layer and the porous film are laminated to each other will be described.

  In the laminated film, the heat resistant porous layer is a layer having higher heat resistance than the porous film, and the heat resistant porous layer may be formed of an inorganic powder or may contain a heat resistant resin. When the heat resistant porous layer contains a heat resistant resin, the heat resistant porous layer can be formed by an easy technique such as coating. Examples of the heat resistant resin include polyamide, polyimide, polyamideimide, polycarbonate, polyacetal, polysulfone, polyphenylene sulfide, polyether ketone, aromatic polyester, polyether sulfone, and polyetherimide. Is preferably polyamide, polyimide, polyamideimide, polyethersulfone and polyetherimide, more preferably polyamide, polyimide or polyamideimide. Even more preferred are nitrogen-containing aromatic polymers such as aromatic polyamides (para-oriented aromatic polyamides, meta-oriented aromatic polyamides), aromatic polyimides, aromatic polyamideimides, and particularly preferred are aromatic polyamides and production surfaces. Particularly preferred is para-oriented aromatic polyamide (hereinafter sometimes referred to as para-aramid). Examples of the heat resistant resin include poly-4-methylpentene-1 and cyclic olefin polymers. By using these heat resistant resins, the heat resistance of the laminated film, that is, the thermal film breaking temperature of the laminated film can be further increased. Among these heat-resistant resins, when using a nitrogen-containing aromatic polymer, because of the polarity in the molecule, compatibility with the electrolyte, that is, the liquid retention in the heat-resistant porous layer may be improved, The rate of impregnation of the electrolytic solution during the production of the nonaqueous electrolyte secondary battery is also high, and the charge / discharge capacity of the nonaqueous electrolyte secondary battery is further increased.

  The thermal film breaking temperature of such a laminated film depends on the type of heat-resistant resin, and is selected and used according to the use scene and purpose of use. More specifically, as the heat resistant resin, the cyclic olefin polymer is used at about 400 ° C. when the nitrogen-containing aromatic polymer is used, and at about 250 ° C. when poly-4-methylpentene-1 is used. When using, the thermal film breaking temperature can be controlled to about 300 ° C., respectively. In addition, when the heat resistant porous layer is made of an inorganic powder, the thermal film breaking temperature can be controlled to, for example, 500 ° C. or higher.

  The para-aramid is obtained by condensation polymerization of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid halide, and the amide bond is in the para position of the aromatic ring or an oriented position equivalent thereto (for example, 4,4 ′ -Substantially consisting of repeating units bonded in the opposite direction, such as biphenylene, 1,5-naphthalene, 2,6-naphthalene, etc., in an orientation extending coaxially or in parallel. Specifically, poly (paraphenylene terephthalamide), poly (parabenzamide), poly (4,4′-benzanilide terephthalamide), poly (paraphenylene-4,4′-biphenylenedicarboxylic acid amide), poly ( Para-aligned or para-oriented such as paraphenylene-2,6-naphthalenedicarboxylic acid amide), poly (2-chloro-paraphenylene terephthalamide), paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer Examples include para-aramid having a structure according to the type.

  The aromatic polyimide is preferably a wholly aromatic polyimide produced by condensation polymerization of an aromatic dianhydride and a diamine. Specific examples of the dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic Examples include acid dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride. Specific examples of the diamine include oxydianiline, paraphenylenediamine, benzophenonediamine, 3,3′-methylenedianiline, 3,3′-diaminobenzophenone, 3,3′-diaminodiphenylsulfone and 1,5. -Naphthalenediamine. Moreover, a polyimide soluble in a solvent can be preferably used. Examples of such a polyimide include a polycondensate polyimide of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and an aromatic diamine.

  As the above-mentioned aromatic polyamideimide, those obtained from condensation polymerization using aromatic dicarboxylic acid and aromatic diisocyanate, those obtained from condensation polymerization using aromatic diacid anhydride and aromatic diisocyanate Is mentioned. Specific examples of the aromatic dicarboxylic acid include isophthalic acid and terephthalic acid. A specific example of the aromatic dianhydride is trimellitic anhydride. Specific examples of the aromatic diisocyanate include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, orthotolylene diisocyanate, and m-xylene diisocyanate.

  In order to further enhance the ion permeability, the heat-resistant porous layer is preferably a thin heat-resistant porous layer having a thickness of 1 to 10 μm, more preferably 1 to 5 μm, and particularly 1 to 4 μm. The heat-resistant porous layer has fine pores, and the size (diameter) of the pores is usually 3 μm or less, preferably 1 μm or less. Moreover, when a heat resistant porous layer contains a heat resistant resin, a heat resistant porous layer can also contain the below-mentioned filler.

  In the laminated film, the porous film preferably has fine pores and has a shutdown function. In this case, the porous film contains a thermoplastic resin. The size of the micropores in the porous film is usually 3 μm or less, preferably 1 μm or less. The porosity of the porous film is usually 30 to 80% by volume, preferably 40 to 70% by volume. In the nonaqueous electrolyte secondary battery, when the normal use temperature is exceeded, the porous film containing the thermoplastic resin can close the micropores by softening the thermoplastic resin constituting the porous film.

  What is necessary is just to select the thermoplastic resin which does not melt | dissolve in the electrolyte solution in a nonaqueous electrolyte secondary battery. Specific examples include polyolefin resins such as polyethylene and polypropylene, and thermoplastic polyurethane resins, and a mixture of two or more of these may be used. In order to soften and shut down at a lower temperature, it is preferable to contain polyethylene. Specific examples of the polyethylene include polyethylene such as low density polyethylene, high density polyethylene, and linear polyethylene, and ultra high molecular weight polyethylene having a molecular weight of 1,000,000 or more. In order to further increase the puncture strength of the porous film, the thermoplastic resin constituting the film preferably contains at least ultra high molecular weight polyethylene. In addition, in terms of production of the porous film, the thermoplastic resin may preferably contain a wax made of polyolefin having a low molecular weight (weight average molecular weight of 10,000 or less).

  Moreover, the thickness of the porous film in a laminated | multilayer film is 3-30 micrometers normally, More preferably, it is 3-25 micrometers. In the present invention, the thickness of the laminated film is usually 40 μm or less, preferably 30 μm or less. Moreover, when the thickness of the heat resistant porous layer is A (μm) and the thickness of the porous film is B (μm), the value of A / B is preferably 0.1 or more and 1 or less.

  Moreover, when the heat resistant porous layer contains a heat resistant resin, the heat resistant porous layer may contain one or more fillers. The filler may be selected from organic powder, inorganic powder, or a mixture thereof as the material thereof. The average particle size of the particles constituting the filler is preferably 0.01 to 1 μm or less.

  Examples of the organic powder include styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, and methyl acrylate, or a copolymer of two or more types; polytetrafluoroethylene, 4 fluorine, and the like. Fluorine resin such as fluorinated ethylene-6 fluorinated propylene copolymer, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, etc .; powder made of organic matter such as melamine resin; urea resin; polyolefin resin; Can be mentioned. The organic powder may be used alone or in combination of two or more. Among these organic powders, polytetrafluoroethylene powder is preferable from the viewpoint of chemical stability.

  Examples of the inorganic powder include powders made of inorganic substances such as metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates, sulfates, etc. Among these, they are made of inorganic substances having low conductivity. Powder is preferably used. Specific examples include powders made of alumina, silica, titanium dioxide, calcium carbonate, or the like. The inorganic powder may be used alone or in combination of two or more. Among these inorganic powders, alumina powder is preferable from the viewpoint of chemical stability. Here, it is more preferable that all of the particles constituting the filler are alumina particles, and it is even more preferable that all of the particles constituting the filler are alumina particles, and part or all of them are substantially spherical alumina particles. It is embodiment which is. Incidentally, when the heat-resistant porous layer is formed from an inorganic powder, the inorganic powder exemplified above may be used, and may be mixed with a binder as necessary.

  The filler content when the heat-resistant porous layer contains a heat-resistant resin depends on the specific gravity of the filler material. For example, when all of the particles constituting the filler are alumina particles, When the total weight is 100 parts by weight, the weight of the filler is usually 5 to 95 parts by weight, preferably 20 to 95 parts by weight, and more preferably 30 to 90 parts by weight. These ranges can be appropriately set depending on the specific gravity of the filler material.

  Examples of the shape of the filler include a substantially spherical shape, a plate shape, a columnar shape, a needle shape, a whisker shape, and a fibrous shape, and any particle can be used. Spherical particles are preferred. Examples of the substantially spherical particles include particles having a particle aspect ratio (long particle diameter / short particle diameter) of 1 or more and 1.5 or less. The aspect ratio of the particles can be measured by an electron micrograph.

  In the present invention, from the viewpoint of ion permeability, the separator preferably has an air permeability of 50 to 300 seconds / 100 cc, more preferably 50 to 200 seconds / 100 cc in terms of air permeability by the Gurley method. preferable. Moreover, the porosity of a separator is 30-80 volume% normally, Preferably it is 40-70 volume%. The separator may be a laminate of separators having different porosity.

In the secondary battery, the electrolytic solution usually contains an electrolyte and an organic solvent. Examples of the electrolyte include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (COCF ₃ ), Li (C ₄ F ₉ SO ₃ ), LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , LiBOB (where BOB is bis (oxalato) borate). ), Lithium salts such as lower aliphatic carboxylic acid lithium salts and LiAlCl _4, and a mixture of two or more of these may be used. The lithium salt is usually selected from the group consisting of LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ and LiC (SO ₂ CF ₃ ) ₃ containing fluorine among them. Those containing at least one selected are used.

In the electrolytic solution, examples of the organic solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, 1,2-di ( Carbonates such as methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, 2-methyl Ethers such as tetrahydrofuran; esters such as methyl formate, methyl acetate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; N, N-dimethylformamide, N, N-dimethylacetate Amides such as amides; Carbamates such as 3-methyl-2-oxazolidone; Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propane sultone, or those obtained by further introducing a fluorine substituent into the above organic solvent Usually, two or more of these are used in combination. Among them, a mixed solvent containing carbonates is preferable, and a mixed solvent of cyclic carbonate and acyclic carbonate and a mixed solvent of cyclic carbonate and ether are more preferable. The mixed solvent of cyclic carbonate and non-cyclic carbonate has a wide operating temperature range, excellent load characteristics, and is hardly decomposable even when a graphite material such as natural graphite or artificial graphite is used as the negative electrode active material. In this respect, a mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferable. Further, in view of particularly excellent safety improving effect is obtained, it is preferable to use an electrolytic solution containing an organic solvent having a lithium salt and a fluorine substituent containing fluorine such as LiPF _6. A mixed solvent containing ethers having fluorine substituents such as pentafluoropropyl methyl ether and 2,2,3,3-tetrafluoropropyl difluoromethyl ether and dimethyl carbonate has excellent high-current discharge characteristics, preferable.

A solid electrolyte may be used instead of the above electrolytic solution. As the solid electrolyte, for example, an organic polymer electrolyte such as a polyethylene oxide polymer compound, a polymer compound containing at least one of a polyorganosiloxane chain or a polyoxyalkylene chain can be used. Moreover, what is called a gel type which hold | maintained the non-aqueous electrolyte in the high molecular compound can also be used. The _{Li 2 S-SiS 2, Li} 2 S-GeS 2, Li 2 S-P 2 S 5, Li 2 S-B 2 S 3, Li 2 S-SiS 2 -Li 3 PO 4, Li 2 S-SiS _An inorganic solid electrolyte containing a sulfide such as _2- Li ₂ SO ₄ may be used. Using these solid electrolytes, safety may be further improved. In the nonaqueous electrolyte secondary battery of the present invention, when a solid electrolyte is used, the solid electrolyte may serve as a separator, and in that case, the separator may not be required.

  Next, the present invention will be described in more detail with reference to examples. The evaluation of the lithium composite metal oxide (positive electrode active material), the charge / discharge test, and the cycle test were performed as follows.

(1) Preparation of positive electrode for charge / discharge test A mixture of a positive electrode active material and a conductive material (a mixture of acetylene black and graphite at 9: 1 (weight ratio)) was combined with PVdF (N-methyl-2- Pyrrolidone was used as the organic solvent.) Was added to the composition of active material: conductive material: binder (PVdF) = 87: 10: 3 (weight ratio) and kneaded to obtain a paste, The paste was applied to an Al foil having a thickness of 40 μm and vacuum-dried at 150 ° C. for 8 hours to obtain a positive electrode.

(2) Production of non-aqueous electrolyte secondary battery (coin cell) for charge / discharge test Using the positive electrode obtained in (1), with the Al foil surface facing down on the lower lid of the coin cell (manufactured by Hosen Co., Ltd.) A positive electrode is placed thereon, and a laminated film separator (a heat-resistant porous layer is laminated on a polyethylene porous film (thickness: 16 μm)) is placed thereon, and an electrolytic solution (ethylene carbonate (hereinafter, sometimes referred to as EC) may be placed here. .), Dimethyl carbonate (hereinafter sometimes referred to as DMC) and ethyl methyl carbonate (hereinafter sometimes referred to as EMC) in a 30:35:35 (volume ratio) mixed solution of 1 mol / liter of LiPF _6. 300 μl of a solution dissolved so as to be (hereinafter sometimes referred to as LiPF ₆ / EC + DMC + EMC) was injected. Next, using metallic lithium as the negative electrode, the metallic lithium is placed on the upper side of the laminated film separator, covered with a gasket, and caulked with a caulking machine to produce a non-aqueous electrolyte secondary battery (coin-type battery R2032). did.
The battery was assembled in a glove box in an argon atmosphere. Moreover, the manufacturing method of the said laminated film separator is mentioned later.

(3) Charge / Discharge Test Using the above coin-type battery, a charge / discharge test was performed under the following conditions. The 0.2C discharge capacity in the charge / discharge test was determined as follows.

<Charge / discharge test>
Test temperature 25 ° C
Charging maximum voltage 4.8V, charging time 10 hours, charging current 0.3 mA / cm ²
Discharge minimum voltage 1.5V, discharge time 10 hours, discharge current 0.3 mA / cm ²

(4) Preparation of positive electrode (tablet electrode) for cycle test The positive electrode active material was dried at 120 ° C. for 12 hours. 5 mg each of the positive electrode active material and acetylene black were weighed and mixed in an agate mortar, and further 0.5 mg of PTFE was added and molded into a tablet shape to obtain a tablet-shaped molded body. The tablet-shaped molded body was placed on a SUS plate, Al meshes were stacked, sandwiched between SUS plates, the tablet-shaped molded body and Al mesh were pressure-bonded, and dried at 120 ° C. for 12 hours to obtain a tablet electrode.
(5) Production of non-aqueous electrolyte secondary battery for cycle test In the glove box, a tablet electrode is placed at the center of the lower part of the HS flat cell (manufactured by Hosen Co., Ltd.), and the electrolyte (LiPF ₆ / EC + DMC (5: 5) 0.1 ml) was added dropwise. A separator (two sheets) and glass filter paper were immersed in the electrolytic solution, and then placed on the tablet electrode, and a metal lithium foil was placed thereon. Then, a battery was fabricated by placing a convex presser, putting a spring, placing an upper lid, and tightening with a thumbscrew.
(6) Cycle test A cycle test was carried out under the following conditions using the above battery. The charge capacity, discharge capacity, and cycle maintenance rate in the cycle test were determined as follows.

<Cycle test>
Test temperature 30 ° C
Maximum charging voltage 4.8V, charging current 0.1mA / cm ²
Discharge minimum voltage 2.2V, discharge current 0.1mA / cm ²
Initial charge / discharge efficiency (%) = discharge capacity at the first cycle (mAh / g) / charge capacity at the first cycle (mAh / g)
Cycle retention rate (%) = 50th cycle discharge capacity (mAh / g) / 1st cycle discharge capacity (mAh / g)

(7) Evaluation of lithium composite metal oxide Composition analysis of lithium composite metal oxide After the powder was dissolved in hydrochloric acid, it was measured using an inductively coupled plasma emission spectrometry (SPS3000 manufactured by SII).

2. Measurement of BET Specific Surface Area of Lithium Composite Metal Oxide 1 g of the powder to be measured was dried in a nitrogen atmosphere at 150 ° C. for 15 minutes, and then measured using a Micromeritics Flowsorb II2300.

3. Evaluation of crystal structure (crystal system and space group) of lithium composite oxide by X-ray diffraction method, calculation of lattice constant Sample powder was filled in a glass sample plate, and a Rigaku rotary cathode X-ray diffractometer RU-200B was used. The measurement was performed under the following measurement conditions.
Measurement condition source: CuKα
Voltage: 40 kV
Current: 200 mA
Measurement range (2θ): 10 ° to 87 °

From the obtained X-ray diffraction profile, the crystal structure (crystal system and space group) of the sample was specified, and the lattice constant was calculated.

Comparative Example 1
1. Production and Evaluation of Lithium Composite Metal Oxide Lithium hydroxide monohydrate and nickel hydroxide were weighed so that the molar ratio of Li: Ni was 1.02: 1 and mixed with a mortar to obtain a mixture. . Next, the mixture is put into a firing container, and fired by holding it in an oxygen atmosphere at 700 ° C. for 20 hours using an electric furnace, cooled to room temperature to obtain a fired product F ¹ , pulverized, and fired. The product is put in a firing container, and is fired by holding it in an oxygen atmosphere at 750 ° C. for 20 hours using an electric furnace. The product is cooled to room temperature to obtain a fired product F ² , which is pulverized and powdered lithium composite to obtain a metal oxide G ^1. When X-ray powder diffraction measurement of G ¹ was performed and analysis was performed, it was found that the lithium composite metal oxide G ¹ was hexagonal and space group R-3m. In X-ray diffraction measurement, the obtained peak was analyzed based on hexagonal crystal and space group R-3m, and the lattice constant was calculated. As a result, the lattice constant a was 2.877Å, the lattice constant c was 14.196Å, the lattice volume was 101.7Å ³ , and the value obtained by dividing the lattice constant c by the lattice constant a (c / a) was 4.934. It was. The results are summarized in Table 1.

When the composition analysis of G ¹ was performed, the molar ratio of Li: Ni was 1.02: 1.00, and the BET specific surface area was 0.9 m ² / g. The results are summarized in Table 1.

2. Charge / Discharge Test of Nonaqueous Electrolyte Secondary Battery A coin-type battery was prepared using the G ¹ and a charge / discharge test was performed. As a result, the discharge capacity at 0.2C was 251 mAh / g.
3. Cycle test of non-aqueous electrolyte secondary battery A battery was produced using G ¹ and subjected to a cycle test. As a result, the charge capacity in the first cycle was 240 mAh / g, and the discharge capacity in the first cycle was 197 mAh. / G, and the initial charge / discharge efficiency was 82%. Further, the discharge capacity at the 50th cycle was 121 mAh / g, and the cycle retention rate was not sufficient at 60%.

Example 1
1. Production and Evaluation of Transition Metal Composite Hydroxide 72.7 g (corresponding to 0.25 mol) of nickel nitrate (II) as a water-soluble salt of Ni was weighed and dissolved in 500 ml of pure water to obtain an aqueous solution containing Ni. . Further, 60 g of anhydrous lithium hydroxide was weighed and dissolved in 1000 ml of pure water to obtain an alkali metal aqueous solution. Next, the alkali metal aqueous solution is charged into the reaction vessel, and further, an aqueous solution containing Ni is charged at a rate of 250 ml per hour using a liquid feed pump, thereby carrying out coprecipitation, and depositing the precipitate. The mixture was stirred and stirred for 24 hours with a stirring blade while introducing air into the reaction vessel to obtain a coprecipitate slurry. Further, the obtained coprecipitate slurry was subjected to solid-liquid separation to obtain a coprecipitate Q ^1.

2. Amount Li (mol) were weighed so that the 1.0-fold to Ni amount charged manufacture of the lithium composite metal oxide and Evaluation of Q ^1, lithium hydroxide monohydrate (mol), distilled water 150ml The mixture was stirred, dispersed, and dried at 100 ° C. for 6 hours to obtain a mixture B ¹ . The mixture is then placed in an alumina firing vessel, fired at 400 ° C. for 20 hours in an oxygen atmosphere using an electric furnace, cooled to room temperature, ground, washed with distilled water, filtered, and dried at 100 ° C. 12 hours to obtain a lithium composite hydroxide C ^1. The lithium composite hydroxide and lithium hydroxide monohydrate were charged, weighed so that the Li amount (mol) was 2.0 times the Ni amount (mol), poured into 200 ml of distilled water, and dissolved by stirring. Thereafter, the fired product was added, dispersed, and dried at 100 ° C. for 12 hours to obtain a mixture D ¹ . The mixture is then placed in an alumina firing vessel, fired at 650 ° C. for 20 hours in an oxygen atmosphere using an electric furnace, cooled to room temperature, ground, washed with distilled water, filtered, and dried 6 hours at 100 ° C., to obtain a powdered lithium composite metal oxide E ^1. Conducted a powder X-ray diffraction measurement of said E ^1, was subjected to analysis, the lithium composite metal oxide E ¹ is hexagonal, it was found that a space group R-3m. In X-ray diffraction measurement, the obtained peak was analyzed based on hexagonal crystal and space group R-3m, and the lattice constant was calculated. As a result, the lattice constant a was 2.863 Å, the lattice constant c was 14.202 Å, the lattice volume was 100.8 Å ³ , and the value (c / a) obtained by dividing the lattice constant c by the lattice constant a was 4.960. It was. The results are summarized in Table 1.

When the composition analysis of E ¹ was performed, the molar ratio of Li: Ni was 1.07: 1.00, and the BET specific surface area was 4.4 m ² / g. The results are summarized in Table 1.

3. Charge / Discharge Test of Nonaqueous Electrolyte Secondary Battery A coin-type battery was prepared using E ¹ and subjected to a charge / discharge test. As a result, the discharge capacity at 0.2C was as high as 303 mAh / g.
4). Cycle test of non-aqueous electrolyte secondary battery A battery was prepared using E ¹ and subjected to a cycle test. As a result, the charge capacity of the first cycle was 211 mAh / g, and the discharge capacity of the first cycle was 193 mAh. / G, and the initial charge / discharge efficiency was as high as 91%. In addition, the discharge capacity at the 50th cycle was 154 mAh / g, and the cycle retention rate was 80%, which was higher than the cycle retention rate of Comparative Example 1.

Example 2
1. Production of lithium composite metal oxide Lithium hydroxide monohydrate was charged, weighed so that the Li amount (mol) was 2.0 times the Ni amount (mol), poured into 200 ml of distilled water, and dissolved by stirring. The coprecipitate Q ² obtained by the same operation as in Example 1 was added, dispersed, and dried at 100 ° C. for 12 hours to obtain a mixture B ² . The mixture is then placed in an alumina firing vessel, fired at 550 ° C. for 20 hours in an oxygen atmosphere using an electric furnace, cooled to room temperature, ground, washed with distilled water, filtered, and dried 6 hours at 100 ° C., to obtain a powdered lithium composite metal oxide C ^2. When the powder X-ray diffraction measurement of the C ² was performed and analyzed, it was found that the lithium composite metal oxide C ² was a hexagonal crystal and a space group R-3m. In X-ray diffraction measurement, the obtained peak was analyzed based on hexagonal crystal and space group R-3m, and the lattice constant was calculated. As a result, the lattice constant a was 2.865 Å, the lattice constant c was 14.199 Å, the lattice volume was 101.0 Å ³ , and the value obtained by dividing the lattice constant c by the lattice constant a (c / a) was 4.955. It was. The results are summarized in Table 1.

When the composition analysis of C ² was performed, the molar ratio of Li: Ni was 1.22: 1.00, and the BET specific surface area was 10.4 m ² / g. The results are summarized in Table 1.

2. Charge / Discharge Test of Nonaqueous Electrolyte Secondary Battery A coin-type battery was prepared using C ² and a charge / discharge test was performed. As a result, the discharge capacity at 0.2C was as high as 349 mAh / g.

Example 3
1. Except that the production firing temperature of the lithium composite metal oxide and 600 ° C. is performed in the same manner as in Example 2 to give a powdered lithium composite metal oxide C ^3. When the powder X-ray diffraction measurement of the C ³ was performed and analyzed, it was found that the lithium composite metal oxide C ³ was hexagonal and space group R-3m. In X-ray diffraction measurement, the obtained peak was analyzed based on hexagonal crystal and space group R-3m, and the lattice constant was calculated. As a result, the lattice constant a was 2.866 Å, the lattice constant c was 14.202 Å, the lattice volume was 101.1 Å ³ , and the value obtained by dividing the lattice constant c by the lattice constant a (c / a) was 4.955. It was. The results are summarized in Table 1.

When the composition analysis of C ³ was performed, the molar ratio of Li: Ni was 1.21: 1.00, and the BET specific surface area was 3.9 m ² / g. The results are summarized in Table 1.

2. Charge / Discharge Test of Nonaqueous Electrolyte Secondary Battery A coin-type battery was prepared using C ³ and subjected to a charge / discharge test. As a result, the discharge capacity at 0.2C was as high as 322 mAh / g.

(Reference example)
Production Example of Laminated Film Separator (1) Production of Slurry Coating Liquid After 272.7 g of calcium chloride was dissolved in 4200 g of NMP, 132.9 g of paraphenylenediamine was added and completely dissolved. To the obtained solution, 243.3 g of terephthalic acid dichloride was gradually added and polymerized to obtain para-aramid, which was further diluted with NMP to obtain a para-aramid solution (A) having a concentration of 2.0% by weight. To 100 g of the obtained para-aramid solution, 2 g of alumina powder (a) (manufactured by Nippon Aerosil Co., Ltd., Alumina C, average particle size 0.02 μm) and 2 g of alumina powder (b) (Sumitomo Chemical Co., Ltd. Sumiko Random, AA03, average particles) 4 g in total as a filler is added and mixed, treated three times with a nanomizer, filtered through a 1000 mesh wire net, and degassed under reduced pressure to produce a slurry coating solution (B) did. The weight of alumina powder (filler) with respect to the total weight of para-aramid and alumina powder is 67% by weight.

(2) Production and Evaluation of Laminated Film As the porous film, a polyethylene porous film (film thickness 12 μm, air permeability 140 seconds / 100 cc, average pore diameter 0.1 μm, porosity 50%) was used. The polyethylene porous film was fixed on a PET film having a thickness of 100 μm, and the slurry-like coating liquid (B) was applied onto the porous film by a bar coater manufactured by Tester Sangyo Co., Ltd. The coated porous membrane on the PET film is integrated and immersed in water, which is a poor solvent, to deposit a para-aramid porous membrane (heat-resistant porous layer), and then the solvent is dried to form a heat-resistant porous membrane. A laminated film 1 in which a layer and a porous film were laminated was obtained. The thickness of the laminated film 1 was 16 μm, and the thickness of the para-aramid porous film (heat resistant porous layer) was 4 μm. The air permeability of the laminated film 1 was 180 seconds / 100 cc, and the porosity was 50%. When the cross section of the heat resistant porous layer in the laminated film 1 was observed with a scanning electron microscope (SEM), a relatively small micropore of about 0.03 to 0.06 μm and a relatively large micropore of about 0.1 to 1 μm. It was found to have The laminated film was evaluated by the following method.

<Evaluation of laminated film>
(A) Thickness measurement The thickness of the laminated film and the thickness of the porous film were measured in accordance with JIS standards (K7130-1992). Moreover, as the thickness of the heat resistant porous layer, a value obtained by subtracting the thickness of the porous film from the thickness of the laminated film was used.
(B) Measurement of air permeability by Gurley method The air permeability of the laminated film was measured by a digital timer type Gurley type densometer manufactured by Yasuda Seiki Seisakusho Co., Ltd. based on JIS P8117.
(C) Porosity A sample of the obtained laminated film was cut into a 10 cm long square and the weight W (g) and thickness D (cm) were measured. The weight of each layer in the sample (Wi (g)) (i is an integer from 1 to n) is obtained, and from the true specific gravity (true specific gravity i (g / cm ³ )) of the material of each layer, The volume of each layer was determined, and the porosity (volume%) was determined from the following formula.
Porosity (volume%) = 100 × {1− (W1 / true specific gravity 1 + W2 / true specific gravity 2 + ·· + Wn / true specific gravity n) / (10 × 10 × D)}

  According to the present invention, it is possible to obtain a non-aqueous electrolyte secondary battery exhibiting a higher capacity than that of a conventional lithium secondary battery, and the secondary battery is particularly used in applications requiring high capacity, that is, an automobile. It is extremely useful for a non-aqueous electrolyte secondary battery for power use or power storage.

Claims (8)

A lithium composite metal oxide represented by the formula (A),
In powder X-ray diffraction measurement using CuKα rays, the crystal structure includes a structure belonging to the hexagonal system and the space group R-3m, and the lattice constant a calculated based on the crystal system and the space group is 2. Lithium composite metal oxide, characterized by being 87 mm or less.
Li _x NiO _{2 ± δ} (A)
(Here, 1.05 ≦ x ≦ 1.30 and −0.1 ≦ δ ≦ 0.1.) There lattice constant c to 14.22Å following range of 14.19A, lithium mixed metal oxide according to claim 1, the lattice volume is in the range of 100.5A ³ or 101.5A ³ or less.   The lithium composite metal oxide according to claim 1 or 2, wherein a value (c / a) obtained by dividing the lattice constant c by the lattice constant a is 4.94 or more and 4.97 or less.   A positive electrode comprising the lithium composite metal oxide according to claim 1 as a positive electrode active material.   A non-aqueous electrolyte secondary battery comprising the positive electrode according to claim 4. A method for producing a lithium composite metal oxide comprising the following steps (1), (2), (3) and (4) in this order:
(1) A step of producing a coprecipitate by bringing an aqueous solution containing Ni and an alkali containing Li into contact to obtain a coprecipitate slurry. (2) Solid-liquid separation of the obtained coprecipitate slurry is performed as a solid. (3) The mixture obtained by mixing the obtained solid and lithium compound is held at a temperature of 300 ° C. or higher and 550 ° C. or lower and fired to obtain the first lithium composite metal oxide. Step (4) A mixture obtained by mixing the obtained first lithium composite metal oxide and the lithium compound is held at a temperature of 600 ° C. or higher and 800 ° C. or lower and calcined to produce a second lithium composite metal oxide. The process of getting things   The method for producing a lithium composite metal oxide according to claim 6, wherein in the step (3), a lithium compound is added in an amount of 1.0 mol times or more and 2.0 mol times or less in terms of Li with respect to the charged Ni amount.   The process according to claim 6 or 7, wherein in step (4), a lithium compound is added in an amount of 1.0 mol times or more and 2.0 mol times or less in terms of Li with respect to the amount of charged Ni.