JP2013112531A - Lithium metal composite oxide and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new lithium metal composite oxide capable of improving characteristics of lithium ion batteries.SOLUTION: In the lithium metal composite oxide, the half-value widths of diffraction peaks on (110) and (102) planes at Miller index hkl in X-ray diffraction are ≤0.20 and ≤0.14, respectively, the diffraction peak intensity ratio I(006)/I(102) of (006) and (102) planes is ≤0.44, and the diffraction peak intensity ratio I(101)/I(108) of (101) and (108) planes is ≥2.49.

Description

  The present invention relates to a lithium metal composite oxide, a method for producing the same, a positive electrode material for a lithium ion secondary battery containing the lithium metal composite oxide, and a lithium ion battery.

  In recent years, lithium ion batteries are widely used in various fields such as electronic devices and automobiles.

  A lithium ion secondary battery is usually formed by housing a positive electrode, a negative electrode, and a nonaqueous electrolyte in a battery case or the like. In particular, the positive electrode of a lithium ion battery is an important element that greatly affects the characteristics of the lithium ion battery, and positive electrode materials are actively developed for the purpose of improving the characteristics of the lithium ion battery (Patent Documents). See 1 and 2 etc.).

JP 2010-165507 A Japanese Patent No. 4707939

  It is an object of the present invention to provide a new lithium metal composite oxide and a method for producing the same that can improve the characteristics of a lithium ion battery.

  Furthermore, this invention makes it a subject to provide the positive electrode material and lithium ion secondary battery containing the said lithium metal complex oxide.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor found a new lithium metal composite oxide capable of improving the characteristics of a lithium ion battery and completed the present invention.

  That is, according to the present invention, the half-value widths of diffraction peaks on the (110) plane and the (102) plane in the mirror index hkl of X-ray diffraction are 0.20 or less and 0.14 or less, respectively (006) The diffraction peak intensity ratio I (006) / I (102) at the plane and the (102) plane is 0.44 or less, and the diffraction peak intensity ratio at the (101) plane and the (108) plane is I (101) / I. (108) is 2.49 or more, and relates to a lithium metal composite oxide.

  The present invention also provides a method for producing the above lithium metal composite oxide, wherein a mixture containing a lithium compound and a metal hydroxide and / or a metal oxide is defined by the following formula (i): It is related with the manufacturing method characterized by mixing so that a degree may become 0.90 or more, and baking the obtained mixed powder in oxidizing atmosphere.

Mixing degree = L ₂ / L ₁ (i)
(L ₁ : Standard deviation of histogram determined by image analysis of powder obtained by firing test mixture at 300 ° C. for 5 minutes in air atmosphere L ₂ : Mix test mixture using vertical granulator After that, the convergence value of the standard deviation of the histogram obtained by image analysis of the powder obtained by baking at 300 ° C. for 5 minutes in the air atmosphere)

  The present invention is also a method for producing the above lithium metal composite oxide, which is obtained by mixing a mixture containing a lithium compound, a metal hydroxide and / or a metal oxide using a vertical granulator. The present invention relates to a production method characterized by firing the mixed powder in an oxidizing atmosphere.

  Furthermore, this invention relates to the positive electrode material for lithium ion secondary batteries containing the lithium metal complex oxide obtained by the said lithium metal complex oxide or the said manufacturing method.

  Furthermore, this invention relates to the lithium ion secondary battery containing the said positive electrode material for lithium ion secondary batteries.

  By using the lithium metal composite oxide of the present invention, the characteristics of the lithium ion battery can be improved.

FIG. 1 shows an SEM image of the lithium metal composite oxide obtained in the example.

[Lithium metal composite oxide]
The lithium metal composite oxide of the present invention is characterized by an X-ray diffraction image.

  That is, the half width of the diffraction peak on the (110) plane in the Miller index hkl is 0.20 or less. The lower limit of the half width of the peak is not particularly limited, but is usually 0.08 or more.

  The half width of the diffraction peak at the (102) plane is 0.14 or less. The lower limit of the half width of the peak is not particularly limited, but is usually 0.08 or more.

  The diffraction peak intensity ratio I (006) / I (102) at the (006) plane and the (102) plane is 0.44 or less. The lower limit of the diffraction intensity ratio is not particularly limited, but is usually 0.30 or more.

  The diffraction peak intensity ratio I (101) / I (108) on the (101) plane and the (108) plane is 2.49 or more. The upper limit of the diffraction intensity ratio is not particularly limited, but is usually 3.50 or less.

The composition of the lithium metal composite oxide is not particularly limited, but the following general formula (I)
Li _{1 + x} MO ₂ (I)
(X is a number from 0 to 0.2, M is a metal element other than lithium, and preferably Mg, Ni, Mn, Co, Sc, Ti, V, W, Cr, Fe, Cu, A lithium metal composite oxide represented by (Zn, Y, Zr, Nb, Mo, Pd, Al, Sn, and Cd) is preferable.

Particularly preferred lithium metal composite oxides are:
_{(1) Li 1 + x Ni} 1-y-z Mn y Co z O 2 (I ')
(X is a number from 0 to 0.2, y is a number from 0.2 to 0.4, and z is a number from 0.2 to 0.4.)
(2) Li _{1 + x} Ni _1-y Co _y O ₂ (I ″)
(X is a number from 0 to 0.2, and y is a number from 0.05 to 0.5.)
(3) Li _{1 + x} Ni _1-yz Al _y Co _z O ₂ (I ′ ″)
(X is a number from 0 to 0.2, y is a number from 0.01 to 0.1, and z is a number from 0.1 to 0.3.)
_{(4) Li x Mn y M} z O 2 (I '''')
(M is one or more metal elements selected from transition metals, preferably Mg, Ni, Co, Sc, Ti, V, W, Cr, Fe, Cu, Zn, Y, Zr, Nb, Mo, At least one selected from the group consisting of Pd, Al, Sn and Cd, x is a number from 1.06 to 1.80, y is a number from 0.5 to 0.9, and z is The number is 0.1 to 0.5.)

The powder physical properties of the lithium metal composite oxide are not particularly limited, but the tap density is preferably 1.0 to 3.0 g / ml, particularly preferably 1.5 g / ml or more. The bulk density is preferably 0.6 to 1.2 g / ml, particularly preferably 0.7 g / ml or more. If the average particle size (D50) is too small, side reactions occur on the surface of the positive electrode and the cycle characteristics tend to deteriorate. If D50 is too large, diffusion of lithium is hindered and the rate characteristics and capacity tend to decrease. Therefore, it is preferably in the range of 1 to 30 μm, particularly preferably 3 to 20 μm. If the specific surface area according to the BET method is too large, the cycle characteristics tend to deteriorate. Moreover, since there exists a tendency for a rate characteristic and a capacity | capacitance to fall when too small, Preferably it is 0.1-3.0 m < ² > / g, More preferably, it is the range of 0.2-2.0 m < ² > / g.

[Method for producing lithium metal composite oxide]
Although there is no restriction | limiting in particular as a manufacturing method of the lithium metal complex oxide of this invention, The mixture (raw material) containing a lithium compound and a metal hydroxide and / or a metal oxide is defined to following formula (i) It is preferable to mix so that the degree of mixing is 0.90 or more, and the obtained mixed powder is fired in an oxidizing atmosphere, and mixing by a vertical granulator is particularly preferable.

Mixing degree = L ₂ / L ₁ (i)
(L ₁ : Standard deviation of histogram obtained by image analysis of powder obtained by baking test object mixture (raw material) at 300 ° C. for 5 minutes in air atmosphere L ₂ : Test target mixture (raw material) vertical (The convergence value of the standard deviation of the histogram obtained by image analysis of powder obtained by mixing for 5 minutes at 300 ° C. in an air atmosphere after mixing using a granulator)
The convergence value of the standard deviation is a standard deviation when sufficiently mixed using a vertical granulator, and is typically a standard when mixed for 10 minutes or more with a main blade at 700 rpm and a cross screw at 2500 rpm. It can be called a deviation.

  The method for producing the metal hydroxide and / or metal oxide is not particularly limited. For example, a metal salt such as a cobalt salt and a manganese salt in a reaction vessel in an inert gas atmosphere or in the presence of a reducing agent. It is preferable to use a so-called continuous coprecipitation method in which an aqueous metal salt solution containing a complexing agent, an alkali metal hydroxide, and an alkali metal hydroxide are continuously supplied, grown continuously and taken out continuously. By using the coprecipitation method, a metal hydroxide in which the metal is uniformly dissolved in a high density can be obtained, thereby improving the density and characteristics of the lithium metal composite oxide.

  The pH during the neutralization reaction is preferably in the range of 10 to 13, particularly 10 to 12. In the continuous method, in order to make the particle growth uniform, the pH change is preferably controlled within a range of ± 0.5, particularly ± 0.05. Although there is no restriction | limiting in particular in reaction temperature, The range of 30-80 degreeC, especially 40-60 degreeC is preferable. The metal ion concentration is preferably in the range of 0.7 to 2.0 mol / L, particularly 1.4 to 2.0 mol / L, in order to increase the density of the resulting hydroxide. The number of stirring during the reaction is not particularly limited, but it is preferably in the range of 1000 to 3000 rpm, particularly 1200 to 2000 rpm in order to obtain a sufficient polishing action between the particles and obtain high density particles.

  The firing temperature of the metal composite hydroxide and / or metal composite oxide and a lithium compound such as lithium hydroxide or lithium carbonate is not particularly limited, but is preferably 900 ° C. or higher and 1100 ° C. or lower, more preferably It is 900 degreeC or more and 1050 degrees C or less, Most preferably, it is 900 degreeC-1025 degreeC. When the firing temperature is lower than 900 ° C., the problem that the energy density (discharge capacity) and the high-rate discharge performance are lowered tends to occur. In a region below this, there may be a structural factor that hinders the movement of Li.

  On the other hand, when the firing temperature exceeds 1100 ° C., problems such as difficulty in obtaining a composite oxide having a target composition due to volatilization of Li, and problems in that battery performance deteriorates due to particle densification. Cheap. This is because when the temperature exceeds 1100 ° C., the primary particle growth rate increases and the crystal grains of the composite oxide become too large. In addition, the amount of Li deficiency increases locally. It may be caused by structural instability. By setting the firing temperature in the range of 900 ° C. or more and 1025 ° C. or less, a battery having a particularly high energy density (discharge capacity) and excellent charge / discharge cycle performance can be produced. The firing time is preferably 3 hours to 50 hours. When the firing time exceeds 50 hours, there is no problem in battery performance, but the battery performance tends to be substantially inferior due to volatilization of Li. If the firing time is less than 3 hours, the crystal growth is poor and the battery performance tends to be poor. In addition, it is also effective to perform temporary baking before the above baking. The temperature for such preliminary firing is preferably in the range of 300 to 900 ° C. for 1 to 10 hours. The oxidizing atmosphere may be an atmosphere containing oxygen, such as an air atmosphere.

[Positive electrode material for lithium ion secondary battery and lithium ion secondary battery]
The positive electrode material for a lithium ion battery of the present invention is characterized by containing the above lithium metal composite oxide. The positive electrode material for a lithium ion battery according to the present invention further includes a generally known positive electrode active material such as lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium cobalt manganese nickel oxide, etc., in accordance with the purpose. Can be added.

Further, the positive electrode material for a lithium ion battery of the present invention may further contain other compounds, and examples of other compounds include Group I compounds such as CuO, Cu ₂ O, Ag ₂ O, CuS, and CuSO ₄ . Group IV compounds such as TiS ₂ , SiO ₂ and SnO, Group V compounds such as V ₂ O ₅ , V ₆ O ₁₂ , VO _x , Nb ₂ O ₅ , Bi ₂ O ₃ and Sb ₂ O ₃ , CrO ₃ , _{cr 2 O 3, MoO 3,} MoS 2, WO 3, SeO VI group compound such as _2, VII group compound such as _{MnO 2, Mn 2 O 3,} Fe 2 O 3, FeO, Fe 3 O 4, Ni 2 O _{3, NiO, CoO 3, CoO} VIII group compound such as such as disulfide, polypyrrole, polyaniline, polyparaphenylene, polyacetylene, conductive polymer compounds such as polyacene-based material, pseudo-graphite It includes structures carbonaceous materials.

  When other compounds other than the positive electrode active material are used in combination with the positive electrode material, the use ratio of the other compounds is not limited as long as the effects of the present invention are not impaired. 1% to 50% by weight is preferable with respect to the total weight of the material, and more preferably 5% to 30% by weight.

  The lithium ion battery of the present invention is characterized by including the positive electrode material of the present invention. Usually, the positive electrode, a negative electrode for a nonaqueous electrolyte secondary battery (hereinafter also simply referred to as “negative electrode”), a nonaqueous electrolyte, In general, a separator for a nonaqueous electrolyte battery is provided between the positive electrode and the negative electrode. The nonaqueous electrolyte is preferably exemplified by a form in which an electrolyte salt is contained in a nonaqueous solvent.

  As the nonaqueous electrolyte, those generally proposed for use in lithium ion batteries and the like can be used. Non-aqueous solvents include propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, vinylene carbonate and other cyclic carbonates; γ-butyrolactone, γ-valerolactone and other cyclic esters; dimethyl carbonate, diethyl carbonate, ethylmethyl Chain carbonates such as carbonate; chain esters such as methyl formate, methyl acetate and methyl butyrate; tetrahydrofuran or derivatives thereof; 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4 -Ethers such as dibutoxyethane and methyldiglyme; nitriles such as acetonitrile and benzonitrile; dioxolane or derivatives thereof; ethylene sulfide, sulfolane, sultone or derivatives thereof alone or Although the mixture of 2 or more types etc. can be mentioned, it is not limited to these.

Examples of the electrolyte salt include LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiSCN, LiBr, LiI, Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ , NaClO ₄ , NaI, NaSCN, NaBr, KClO ₄ , KSCN Inorganic ion salts containing one of lithium (Li), sodium (Na) or potassium (K), LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , (CH ₃ ) ₄ NBF ₄ , (CH ₃ ) ₄ NBr _{, (C 2 H 5) 4} NClO 4, (C 2 H 5) 4 NI, (C 3 H 7) 4 NBr, (n-C 4 H 9) 4 NClO _{, (N-C 4 H 9} ) 4 NI, (C 2 H 5) 4 N-maleate, (C 2 H 5) 4 N-benzoate, (C 2 H 5) 4 N-phtalate, lithium stearyl sulfonate, Examples include organic ionic salts such as lithium octyl sulfonate and lithium dodecylbenzene sulfonate, and these ionic compounds can be used alone or in admixture of two or more.

Furthermore, by mixing and using an inorganic ion salt such as LiBF ₄ or LiPF ₆ and a lithium salt having a perfluoroalkyl group such as LiN (C ₂ F ₅ SO ₂ ) ₂ , the viscosity of the electrolyte is further lowered. Therefore, the low temperature characteristics can be further enhanced, which is more desirable.

  The concentration of the electrolyte salt in the nonaqueous electrolyte is preferably 0.1 mol / liter to 5 mol / liter, more preferably 1 mol / liter to 2.5 in order to reliably obtain a battery having high battery characteristics. Mol / liter.

  The positive electrode preferably includes a positive electrode active material containing the lithium metal composite oxide according to the present invention as a main constituent component. For example, the lithium metal composite oxide according to the present invention further includes a conductive agent and a binder. Accordingly, after mixing with a filler to make a positive electrode material, this positive electrode material is applied to a foil, a lath plate or the like as a current collector, or subjected to pressure bonding, and heated at a temperature of about 50 ° C. to 250 ° C. for about 2 hours. Thus, it is suitably manufactured. The content of the positive electrode active material with respect to the positive electrode is usually 80% by weight to 99% by weight, and preferably 85% by weight to 97% by weight.

  The negative electrode has a negative electrode material as a main component. Any negative electrode material that can occlude and release lithium ions may be selected. For example, lithium metal, lithium alloy (lithium metal-containing alloys such as lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and wood alloy), lithium composite oxide (lithium-titanium) In addition to silicon nitride, alloys capable of occluding and releasing lithium, carbon materials (for example, graphite, hard carbon, low-temperature fired carbon, amorphous carbon, etc.) can be used. Among these, graphite has a working potential very close to that of metallic lithium, so that when lithium salt is employed as the electrolyte salt, self-discharge can be reduced, and irreversible capacity in charge / discharge can be reduced, so that graphite is preferable. For example, artificial graphite and natural graphite are preferable. In particular, graphite in which the surface of the negative electrode material is modified with amorphous carbon or the like is desirable because it generates less gas during charging.

Below, the analysis result by X-ray diffraction etc. of the graphite which can be used suitably is shown;
Lattice spacing (d002) 0.333 to 0.350 nm
a-axis direction crystallite size La 20 nm or more c-axis direction crystallite size Lc 20 nm or more true density 2.00 to 2.25 g / cm ³
It is also possible to modify graphite by adding a metal oxide such as tin oxide or silicon oxide, phosphorus, boron, amorphous carbon or the like. In particular, by modifying the surface of graphite by the above-described method, it is possible to suppress the decomposition of the electrolyte and improve the battery characteristics, which is desirable. In addition to graphite, lithium metal-containing alloys such as lithium metal, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and wood alloys can be used in combination. Graphite in which lithium is inserted by chemical reduction can also be used as the negative electrode material. The content of the negative electrode material with respect to the negative electrode is usually 80% to 99% by weight, and preferably 90% to 98% by weight.

  It is desirable that the positive electrode active material powder and the negative electrode material powder have an average particle size of 100 μm or less. In particular, the powder of the positive electrode active material is desirably 10 μm or less for the purpose of improving the high output characteristics of the battery. In order to obtain the powder in a predetermined shape, a pulverizer or a classifier is used. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling air flow type jet mill or a sieve is used. At the time of pulverization, wet pulverization in the presence of water or an organic solvent such as hexane may be used. There is no particular limitation on the classification method, and a sieve, an air classifier, or the like is used as needed for both dry and wet methods.

  As described above, the positive electrode material and the negative electrode material, which are main components of the positive electrode and the negative electrode, have been described in detail. In addition to the main component, the positive electrode and the negative electrode include a conductive agent, a binder, a thickener, a filler, and the like. However, it may be contained as another component.

  The conductive agent is not limited as long as it is an electron conductive material that does not adversely affect the battery performance. Usually, natural graphite (such as scaly graphite, scaly graphite, earthy graphite), artificial graphite, carbon black, acetylene black, A conductive material such as ketjen black, carbon whisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) powder, metal fiber, and conductive ceramic material can be included as one kind or a mixture thereof. .

Among these, as the conductive agent, acetylene black is desirable from the viewpoints of electron conductivity and coatability. The addition amount of the conductive agent is preferably 0.1% by weight to 50% by weight, and particularly preferably 0.5% by weight to 30% by weight with respect to the total weight of the positive electrode or the negative electrode. In particular, it is desirable to use acetylene black by pulverizing into ultrafine particles of 0.1 to 0.5 μm because the required carbon amount can be reduced. These mixing methods are physical mixing, and the ideal is uniform mixing. Therefore, powder mixers such as V-type mixers, S-type mixers, crackers, ball mills, and planetary ball mills can be mixed dry or wet.
Examples of the binder include thermoplastic resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyethylene, and polypropylene, ethylene-propylene-genter polymer (EPDM), sulfonated EPDM, and styrene butadiene rubber. A polymer having rubber elasticity such as (SBR) or fluororubber can be used as one kind or a mixture of two or more kinds. The addition amount of the binder is preferably 1 to 50% by weight, particularly preferably 2 to 30% by weight, based on the total weight of the positive electrode or the negative electrode.
In particular, the positive electrode according to the present invention preferably contains 1% by weight or more of a conductive carbon material with respect to the positive electrode active material and a binder having ion conductivity by containing an electrolytic solution. In the case of using LiPF ₆ as the electrolyte and ethylene carbonate, diethylene carbonate, dimethyl carbonate or the like as the solvent as the electrolyte, the “binder having ion conductivity by containing the electrolyte” Of the binders, poly (vinylidene fluoride) (PVdF) and polyethylene (polyethylene oxide) can be suitably used.

  As said thickener, polysaccharides, such as carboxymethylcellulose and methylcellulose, can be normally used as 1 type, or 2 or more types of mixtures. Moreover, it is desirable that the thickener having a functional group that reacts with lithium, such as a polysaccharide, be deactivated by a treatment such as methylation. The addition amount of the thickener is preferably 0.5 to 10% by weight, particularly preferably 1 to 2% by weight, based on the total weight of the positive electrode or the negative electrode.

  As the filler, any material that does not adversely affect the battery performance may be used. Usually, olefin polymers such as polypropylene and polyethylene, amorphous silica, alumina, zeolite, glass, carbon and the like are used. The addition amount of the filler is preferably 30% by weight or less with respect to the total weight of the positive electrode or the negative electrode.

  The positive electrode and the negative electrode are obtained by mixing main constituent components (a positive electrode active material in the case of the positive electrode and a negative electrode material in the case of the negative electrode), a conductive agent and a binder in a solvent such as N-methylpyrrolidone and toluene. A slurry is prepared, and the slurry is preferably prepared by applying the slurry onto a current collector described in detail below and drying. About the application method, for example, it is desirable to apply to any thickness and any shape using means such as roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coater, etc. It is not limited.

  The current collector may be anything as long as it is an electronic conductor that does not adversely affect the constructed battery. For example, as a current collector for positive electrode, aluminum, titanium, stainless steel, nickel, calcined carbon, conductive polymer, conductive glass, etc. are used for the purpose of improving adhesion, conductivity and oxidation resistance. A material obtained by treating the surface of copper or copper with carbon, nickel, titanium, silver or the like can be used. In addition to copper, nickel, iron, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., the negative electrode current collector is adhesive, conductive, anti-reduction For the purpose of the property, the thing which processed the surface of copper etc. with carbon, nickel, titanium, silver, etc. can be used. The surface of these materials can be oxidized.

  Regarding the shape of the current collector, a film shape, a sheet shape, a net shape, a punched or expanded material, a lath body, a porous body, a foamed body, a formed body of fiber groups, and the like are used in addition to the foil shape. The thickness is not particularly limited, but a thickness of 1 to 500 μm is used. Among these current collectors, as the positive electrode, an aluminum foil excellent in oxidation resistance is used, and as the negative electrode, reduction resistance and electric conductivity are excellent, and an inexpensive copper foil, nickel foil, iron foil, and It is preferable to use an alloy foil containing a part thereof. Furthermore, a foil having a rough surface surface roughness of 0.2 μmRa or more is preferable, whereby the adhesion between the positive electrode active material or the negative electrode material and the current collector is excellent. Therefore, it is preferable to use an electrolytic foil because it has such a rough surface. In particular, an electrolytic foil that has been subjected to a cracking treatment is most preferable. Furthermore, when the double-sided coating is applied to the foil, it is desirable that the surface roughness of the foil is the same or nearly equal.

  As the separator for a nonaqueous electrolyte battery, it is preferable to use a porous film or a nonwoven fabric exhibiting excellent rate characteristics alone or in combination. Examples of the material constituting the separator for a nonaqueous electrolyte battery include polyolefin resins typified by polyethylene and polypropylene, polyester resins typified by polyethylene terephthalate and polybutylene terephthalate, polyvinylidene fluoride, and vinylidene fluoride-hexa. Fluoropropylene copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, fluorine Vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride - tetrafluoroethylene - hexafluoropropylene copolymer, vinylidene fluoride - ethylene - can be mentioned tetrafluoroethylene copolymer.

  The porosity of the non-aqueous electrolyte battery separator is preferably 98% by volume or less from the viewpoint of strength. Further, the porosity is preferably 20% by volume or more from the viewpoint of discharge capacity.

  The separator for a nonaqueous electrolyte battery may be a polymer gel composed of a polymer such as acrylonitrile, ethylene oxide, propylene oxide, methyl methacrylate, vinyl acetate, vinyl pyrrolidone, polyvinylidene fluoride, and an electrolyte.

  Use of the non-aqueous electrolyte in the gel state as described above is preferable in that it has an effect of preventing leakage. Further, when the separator for a nonaqueous electrolyte battery is used in combination with a polymer film such as a porous film or a nonwoven fabric as described above, the electrolyte retention is preferably improved. That is, by forming a film in which the surface of the polyethylene microporous membrane and the microporous wall are coated with a solvophilic polymer having a thickness of several μm or less, and holding the electrolyte in the micropores of the film, Gels.

  Examples of the solvophilic polymer include polyvinylidene fluoride, an acrylate monomer having an ethylene oxide group or an ester group, an epoxy monomer, a polymer having a monomer having an isocyanate group, and the like crosslinked. The monomer can be subjected to a crosslinking reaction using a radical initiator in combination with heating or ultraviolet rays (UV), or using an actinic ray such as an electron beam (EB).

  For the purpose of controlling strength and physical properties, the solvophilic polymer can be used by blending a physical property modifier in a range that does not interfere with the formation of a crosslinked product. Examples of the physical property modifier include inorganic fillers {metal oxides such as silicon oxide, titanium oxide, aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, and iron oxide; metal carbonates such as calcium carbonate and magnesium carbonate}. , Polymers {polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc.} and the like. The amount of the physical property modifier added is usually 50% by weight or less, preferably 20% by weight or less, based on the crosslinkable monomer.

  The lithium ion battery according to the present invention is suitable by, for example, injecting an electrolyte before or after laminating a separator for a nonaqueous electrolyte battery, a positive electrode, and a negative electrode, and finally sealing with an exterior material. It is produced. In addition, in a battery in which a power generation element in which a positive electrode and a negative electrode are laminated via a separator for a nonaqueous electrolyte battery is wound, the electrolyte is preferably injected into the power generation element before and after the winding. As the injection method, it is possible to inject at normal pressure, but a vacuum impregnation method and a pressure impregnation method can also be used.

  Examples of the battery exterior material include nickel-plated iron, stainless steel, aluminum, and a metal-resin composite film. For example, a metal resin composite film having a configuration in which a metal foil is sandwiched between resin films is preferable. Specific examples of the metal foil include, but are not limited to, aluminum, iron, nickel, copper, stainless steel, titanium, gold, silver, and the like. In addition, as the resin film on the battery outer side, a resin film having excellent piercing strength such as polyethylene terephthalate film and nylon film can be heat-sealed as the resin film on the battery inner side such as polyethylene film and nylon film. Preferred is a film having solvent resistance.

  The configuration of the battery is not particularly limited, and a coin battery or a button battery having a positive electrode, a negative electrode, and a single-layer or multi-layer separator, a cylindrical battery having a positive electrode, a negative electrode, and a roll separator, and a square battery Examples include batteries and flat batteries.

Hereinafter, the present invention will be described in more detail with reference to examples. Incidentally, each embodiment, _{L 2} in the comparative example, vertical granulator (Powrex Corp., VG-10) main blade with a 700 rpm, after mixing 10 minutes at a cross screw 2500 rpm, baked 5 minutes at 300 ° C. air atmosphere It is the standard deviation of the histogram calculated | required by the image analysis of the powder obtained by doing this. For image analysis, the sample powder was scraped using a glass cell for XRD measurement and a slide glass, and an image obtained by photographing the cross section using a digital camera was image analysis software (Image J ver. 1, manufactured by National Institutes of Health, USA). 44). The average particle size, tap density, bulk density, and X-ray diffraction image were measured as follows.
Measurement conditions of powder physical properties (1) Average particle size Using a Horiba LA-950, the secondary particle size of the powder was measured. The measurement conditions followed the operating procedure manual.
(2) Tap density / bulk density Tap density: The mass of a 20 mL cell was measured [A], and the sample was naturally dropped into the cell and filled. The weight [B] and filling volume [D] of the cell after tapping 200 times were measured using a “TAPDENSER KYT3000” manufactured by Seishin Enterprise Co., Ltd. with a 4 cm spacer, and the tap density was determined by the following formula.
Tap density = (B−A) / D g / ml
Bulk density (bulk density): Sample particles were naturally dropped and filled in a specific container, and the mass (g) / volume (ml) was calculated from the mass (g) and volume (ml) at this time.
(3) X-ray diffraction image Using RINT2200V / PC manufactured by Rigaku Corporation, X-ray diffraction measurement using CuKα rays was performed. Measurement conditions were set such that the step width was 0.03, the measurement time was 1.0, the current value was 40 mA, the voltage was 40 kV, and the measurement angle was 10.0 to 70.0 °. For the calculation of the half width and peak intensity ratio, Rigaku Jade5 is used, the number of data is set to 15 in the peak search, the parabolic filter is selected, the peak top is selected as the peak position definition, and the threshold is 3. 00, peak intensity% cutoff is 0.10, BG determination range is 1.0, BG averaging points are 7, angle range is 10.0-70.0, variable filter length and Kα2 peak are removed, A peak search was performed on the existing peak list by selecting delete. Next, Pearson-VII is selected as the setting for peak separation, Kα2 with peak is selected, exponent is 1.5, Lorentz is 0.5, asymmetry is 0.0, initial half width is half width curve Selection, peak search was selected as the initial position, three-dimensional polynomial BG was selected as the type of BG, and the current profile was selected to be refined. The refinement was repeated until the value of R became constant, and the analysis result when the value of R became constant was adopted. From the analysis results, the half width of the diffraction peak at the (110) plane is the half width of the diffraction peak near 65 °, and the half width of the diffraction peak at the (102) plane is that of the diffraction peak near 38.4 °. I read the half width. Similarly, I (006) / I (102) is obtained from (the intensity of the diffraction peak near 37.9 °) / (the intensity of the diffraction peak near 38.4 °), and I (101) / I (108) is It was determined from (intensity of diffraction peak around 36.7 °) / (intensity of diffraction peak around 64.4 °).
Example Ni _0.33 Co _0.33 Mn _0.33 OH produced according to the method of Japanese Patent Application Laid-Open No. 2002-201028 and lithium carbonate are so prepared that the metal: Li (atomic ratio) is 1: 1.07. And mixed so that the degree of mixing was 0.90.

Subsequently, the obtained mixed powder was baked at 925 ° C. for 10 hours in an oxygen-containing atmosphere to obtain Li _1.07 Ni _0.33 Co _0.33 Mn _0.33 O ₂ (D50: 5.1 μm, tap density). : 1.34 g / ml, bulk density: 0.74 g / ml, BET surface area: 1.21 g / m ² ). An SEM image of the obtained powder is shown in FIG.

Similarly, Li _1.03 Ni _0.46 Co _0.20 Mn _0.34 O ₂ (mixing degree 0.97, D50: 5.4 μm, tap density: 1.80 g / ml, bulk density: 1. 08 g / ml, BET surface area: 0.56 g / m ² ), Li _1.03 Ni _0.805 Co _0.155 Al _0.04 O ₂ (mixing degree 0.95, D50: 15.1 μm, tap density: 2 .40 g / ml, bulk density: 1.65 g / ml, BET surface area: 0.27 g / m ² ), Li [Li _0.545 Ni _0.20 Co _0.10 Mn _0.70 ] O ₂ (degree of mixing 0) .93, D50: 6.4 μm, tap density: 1.00 g / ml, bulk density: 0.57 g / ml, BET surface area: 1.68 g / m ² ).
Comparative Examples Each lithium metal composite oxide was prepared under the same conditions as in Example 1 except that the mixing was performed under conditions where the degree of mixing was less than 0.90.

  Table 1 shows the powder physical properties and X-ray diffraction analysis results of the examples and comparative examples.

Evaluation method of battery characteristics (1)
The lithium metal composite oxides obtained in Examples 1 to 3 and Comparative Examples 1 to 3, the conductive agent (acetylene black) and the binder (polyvinylidene fluoride) were mixed at a weight ratio of 90: 5: 5, respectively. -Methyl-2-pyrrolidone was added and kneaded and dispersed to prepare a slurry. The slurry was applied to an aluminum foil using a Baker type applicator and dried at 60 ° C. for 3 hours and 120 ° C. for 12 hours. A positive electrode plate was obtained by punching the dried electrode into a 2 cm ² area. Moreover, the bipolar evaluation cell which makes these positive electrode materials a positive electrode was created. The evaluation cell was produced by attaching lithium metal to a stainless steel plate as a negative electrode plate. A solution in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3: 7 was dissolved in lithium hexafluorophosphate so as to be 1 mol / liter, and the separator was infiltrated into the separator. A polypropylene separator was used as the separator. A positive electrode plate, a separator, and a negative electrode plate were sandwiched between stainless plates and sealed with an exterior material to form a bipolar evaluation cell. Using the obtained bipolar evaluation cell, initial charge capacity, initial discharge capacity, initial charge / discharge efficiency, 1C discharge capacity, 5C discharge capacity and 10C discharge capacity were measured. The charge capacity was constant current and constant voltage charge with a current of 0.2 C and a voltage of 4.3 V, and the charge termination condition was when the current value attenuated to 100 μA. The discharge capacity was a constant current discharge with a current of 0.5 C and a final voltage of 3.0 V. The measurement results are shown in Table 2.
Battery characteristics evaluation method (2)
The lithium metal composite oxide obtained in Example 4 and Comparative Example 4 and a conductive agent (acetylene black) / binder (polyvinylidene fluoride) were mixed at a weight ratio of 88: 6: 6, respectively, and N-methyl-2 -Pyrrolidone was added and kneaded and dispersed to prepare a slurry. The slurry was applied to an aluminum foil using a Baker type applicator and dried at 60 ° C. for 3 hours and 120 ° C. for 12 hours. A positive electrode plate was obtained by punching the dried electrode into a 2 cm ² area. Moreover, the bipolar evaluation cell which makes these positive electrode materials a positive electrode was created. The evaluation cell was produced by attaching lithium metal to a stainless steel plate as a negative electrode plate. A solution in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3: 7 was dissolved in lithium hexafluorophosphate so as to be 1 mol / liter, and the separator was infiltrated into the separator. A polypropylene separator was used as the separator. A positive electrode plate, a separator, and a negative electrode plate were sandwiched between stainless plates and sealed with an exterior material to form a bipolar evaluation cell. Using the obtained bipolar evaluation cell, initial charge capacity, initial discharge capacity, initial charge / discharge efficiency, 0.1C discharge capacity, 0.2C discharge capacity, 0.5C discharge capacity and 1C discharge capacity were measured. The charge capacity was constant current and constant voltage charge with a current of 0.05 C and a voltage of 4.8 V, and the charge termination condition was when the current value attenuated to 0.02 C. The discharge capacity was a constant current discharge with a current of 0.05 C and a final voltage of 2.0 V. The measurement results are shown in Table 2.

  From the above results, it can be seen that the battery characteristics are improved by using the lithium metal composite oxide of the present invention. In particular, in Example 1 and Example 3, the 5C discharge capacity and the 10C discharge capacity are significantly improved, and it can be seen that the improvement of the battery characteristics at high load was achieved.

Claims (5)

  The half-value widths of diffraction peaks on the (110) plane and the (102) plane at the Miller index hkl of X-ray diffraction are 0.20 or less and 0.14 or less, respectively (006) plane and (102) plane The diffraction peak intensity ratio I (006) / I (102) is 0.44 or less, and the diffraction peak intensity ratio I (101) / I (108) on the (101) plane and (108) plane is 2. Lithium metal composite oxide characterized by being 49 or more. A method for producing a lithium metal composite oxide according to claim 1,
A lithium compound and a mixture containing a metal hydroxide and / or a metal oxide are mixed so that the degree of mixing defined by the following formula (i) is 0.90 or more, and the obtained mixed powder is obtained. A manufacturing method characterized by firing in an oxidizing atmosphere.
Mixing degree = L ₂ / L ₁ (i)
L ₁ : Standard deviation of histogram obtained by image analysis of powder obtained by baking test object mixture at 300 ° C. for 5 minutes in air atmosphere L ₂ : After mixing test object mixture using vertical granulator Convergence value of histogram standard deviation obtained by image analysis of powder obtained by baking at 300 ° C. for 5 minutes in air A method for producing a lithium metal composite oxide according to claim 1,
A production method comprising mixing a lithium compound, a metal hydroxide and / or a metal oxide using a vertical granulator, and firing the obtained mixed powder in an oxidizing atmosphere.   The positive electrode material for lithium ion secondary batteries containing the lithium metal complex oxide of Claim 1, or the lithium metal complex oxide obtained by the manufacturing method of Claim 2 or 3.   The lithium ion secondary battery containing the positive electrode material for lithium ion secondary batteries of Claim 4.