JP7254531B2 - Positive electrode active material for lithium secondary battery, method for producing the same, and lithium secondary battery - Google Patents

Description

The present invention relates to a positive electrode active material for lithium secondary batteries, a method for producing the same, and a lithium secondary battery using the positive electrode active material.

Conventionally, lithium cobalt oxide has been used as a positive electrode active material for lithium secondary batteries. However, since cobalt is a rare metal, lithium-nickel-manganese-cobalt composite oxides with a low cobalt content have been developed (see, for example, Patent Documents 1 and 2).

Lithium secondary batteries that use lithium-nickel-manganese-cobalt composite oxide as the positive electrode active material can be made cheaper by adjusting the atomic ratio of nickel, manganese, and cobalt contained in the composite oxide. known (see, for example, Patent Document 3).

However, even with these prior art methods, a lithium secondary battery using a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material still has the problem of deterioration in cycle characteristics.

Further, Patent Document 4 proposes that the particle surface of a lithium-nickel-manganese-cobalt-based composite oxide is fluorine-coated, and that the fluorine-coated surface is provided with a spinel-like layer as a positive electrode active material. It is The lithium-nickel-manganese-cobalt-based composite oxide of Patent Document 4 is characterized in that the molar ratio of Mn atoms contained in the lithium-nickel-manganese-cobalt-based composite oxide is greater than the molar ratio of Ni atoms. It is not a so-called high-nickel lithium-nickel-manganese-cobalt composite oxide in which the molar ratio of Ni atoms is greater than the molar ratio of Mn atoms as in the present invention.

WO 2004/092073 pamphlet JP-A-2005-25975 Japanese Unexamined Patent Application Publication No. 2011-23120 Japanese translation of PCT publication No. 2015-533257

A high-nickel lithium-nickel-manganese-cobalt composite oxide with a high Ni content has a high capacity due to the high Ni content, and has a long life compared to LiNiO ₂ because part of the Ni is substituted. It is known to become

In lithium secondary batteries that use these high-nickel lithium-nickel-manganese-cobalt composite oxides as positive electrode active materials, there is a demand for improved performance toward higher capacity and higher energy. In addition to the improvement, there is a demand for a low average operating voltage drop and high energy density retention rate.

Accordingly, an object of the present invention is to provide a positive electrode active material for a lithium secondary battery using a high-nickel lithium-nickel-manganese-cobalt composite oxide in which the molar ratio of Ni atoms is higher than the molar ratio of Mn atoms, and which has a high capacity and excellent cycle characteristics. A positive electrode active material for a lithium secondary battery that is excellent, has a small decrease in average operating voltage, and can increase the energy density retention rate, an industrially advantageous manufacturing method thereof, and has high capacity, cycle characteristics, and average operating voltage To provide a lithium secondary battery with little decrease in energy density and high energy density retention rate.

As a result of intensive research in view of the above-mentioned circumstances, the present inventors have found that high-nickel lithium-nickel-manganese-cobalt composite oxide particles represented by a specific general formula and inorganic fluoride particles are used as positive electrode active materials. The inventors have found that the use of a positive electrode active material containing the mixture reduces the decrease in the cycle characteristics and average operating voltage of lithium secondary batteries and increases the energy density retention rate, thereby completing the present invention.

That is, the present invention (1) is represented by the following general formula (1):
Li _x Ni _y Mn _z Co _1-yz O _1+x (1)
(In the formula, x is 0.98≦x≦1.20, y is 0.50≦y<1.00, and z is 0<z≦0.50.)
and inorganic fluoride particles, wherein the inorganic fluoride particles are _MgF2 and AlF3 _. A positive electrode active material is provided.

Further, in the present invention (2), the F content in the inorganic fluoride particles is F relative to the total number of moles of Ni atoms, Mn atoms and Co atoms in the lithium nickel manganese cobalt composite oxide particles. The present invention provides the positive electrode active material for lithium secondary batteries according to (1), which is 0.05 to 2.00 mol % in terms of atoms.

Further, the present invention ( 3 ) is represented by the following general formula (1):
_{LixNiyMnzCo1 -yzO1 + x (} 1)
(Wherein, x is 0.98 ≤ x ≤ 1.20, y is 0.50 ≤ y < 1.00, z is 0 < z ≤ 0.50.) Lithium nickel manganese cobalt composite represented by A first step of mixing oxide particles and inorganic fluoride particles to obtain a mixture of lithium-nickel-manganese-cobalt composite oxide particles and inorganic fluoride particles , wherein the inorganic fluoride particles are composed of MgF ₂ and Disclosed is a method _for producing a cathode active material for a lithium secondary battery, which is AlF3 .

Moreover, the present invention ( 4 ) provides the method for producing a positive electrode active material for a lithium secondary battery according to ( 3 ), wherein the mixing treatment in the first step is performed by dry mixing.

In addition, the present invention ( 5 ) provides the method for producing a positive electrode active material for a lithium secondary battery according to ( 4 ), wherein the dry mixing treatment of the first step is performed in the presence of water. is.

Moreover, the present invention ( 6 ) provides the method for producing a positive electrode active material for a lithium secondary battery according to ( 3 ), wherein the mixing treatment in the first step is performed by wet mixing.

In addition, the present invention ( 7 ) is characterized by further comprising a second step of heat-treating the mixture of the lithium-nickel-manganese-cobalt composite oxide particles obtained by performing the first step and the inorganic fluoride particles (3 ) to (6) .

In addition, the present invention ( 8 ) provides the method for producing a positive electrode active material for lithium secondary batteries according to ( 7 ), wherein the temperature of the heat treatment in the second step is 200 to 1100°C. be.

Further, the present invention ( 9 ) provides a lithium secondary battery characterized by using the positive electrode active material for a lithium secondary battery of (1) or (2) as a positive electrode active material. .

According to the present invention, a positive electrode active material for a lithium secondary battery using a high-nickel lithium-nickel-manganese-cobalt composite oxide in which the molar ratio of Ni atoms is higher than the molar ratio of Mn atoms has high capacity, excellent cycle characteristics, A positive electrode active material for a lithium secondary battery that can further reduce the decrease in average operating voltage and increase the energy density retention rate, an industrially advantageous manufacturing method thereof, and have high capacity, cycle characteristics, and a decrease in average operating voltage. It is possible to provide a lithium secondary battery with a low energy density and a high energy density retention rate.

The present invention will be described below based on preferred embodiments.
A positive electrode active material for a lithium secondary battery of the present invention is a positive electrode active material for a lithium secondary battery containing a mixture of lithium-nickel-manganese-cobalt composite oxide particles and inorganic fluoride particles.

The lithium-nickel-manganese-cobalt composite oxide according to the positive electrode active material for lithium secondary batteries of the present invention is represented by the following general formula (1).
Li _x Ni _y Mn _z Co _1-yz O _1+x (1)
(In the formula, x is 0.98≦x≦1.20, y is 0.50≦y<1.00, and z is 0<z≦0.50.)

x in the general formula (1) satisfies 0.98≦x≦1.20. x satisfies 1.00≦x≦1.10 at the point where the initial discharge capacity is high. Moreover, y in the general formula (1) satisfies 0.50≦y<1.00. y preferably satisfies 0.50≦y≦0.95, particularly preferably 0.55≦y≦0.95, in terms of increasing the initial discharge capacity. Moreover, z in the general formula (1) satisfies 0<z≦0.50. z is preferably 0.05≦z≦0.45 from the viewpoint of excellent safety. y/z is preferably greater than 1, particularly preferably 1.2 or more, more preferably 1.5≤y/z≤99.

The lithium-nickel-manganese-cobalt composite oxide particles according to the positive electrode active material for lithium secondary batteries of the present invention are particles of the lithium-nickel-manganese-cobalt composite oxide represented by the general formula (1). The lithium-nickel-manganese-cobalt composite oxide particles may be single particles in which primary particles are monodispersed, or aggregated particles in which primary particles aggregate to form secondary particles. The average particle size of the lithium-nickel-manganese-cobalt composite oxide particles is the particle size (D50) of 50% in terms of volume in the particle size distribution determined by the laser diffraction/scattering method, preferably 1 to 30 μm, particularly preferably 3 to 25 μm. be. Also, the BET specific surface area of the lithium-nickel-manganese-cobalt composite oxide particles is preferably 0.05 to 2.00 m ² /g, particularly preferably 0.15 to 1.00 m ² /g. When the average particle size or BET specific surface area of the lithium-nickel-manganese-cobalt composite oxide particles is within the above range, the positive electrode mixture can be easily prepared and coated, and an electrode with high fillability can be obtained.

The lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1) are prepared by, for example, a raw material mixing step of mixing a lithium source, a nickel source, a manganese source and a cobalt source to prepare a raw material mixture. and a firing step of firing the mixture.

As the lithium source, nickel source, manganese source, and cobalt source used in the raw material mixing step, for example, hydroxides, oxides, carbonates, nitrates, sulfates, organic acid salts, and the like of these are used. The average particle size of the lithium source, nickel source, manganese source and cobalt source is preferably 1 to 30 μm, preferably 3 to 25 μm, as determined by a laser scattering method.

The nickel source, manganese source and cobalt source in the raw material mixing step may be compounds containing nickel atoms, manganese atoms and cobalt atoms. Compounds containing nickel atoms, manganese atoms and cobalt atoms include, for example, composite oxides, composite hydroxides, composite oxyhydroxides and composite carbonates containing these atoms.

As a method for preparing a compound containing a nickel atom, a manganese atom and a cobalt atom, a known method is used. For example, a composite hydroxide can be prepared by a coprecipitation method. Specifically, by mixing an aqueous solution containing predetermined amounts of nickel atoms, cobalt atoms, and manganese atoms, an aqueous solution of a complexing agent, and an aqueous solution of an alkali, a composite hydroxide can be coprecipitated ( See JP-A-10-81521, JP-A-10-81520, JP-A-10-29820, 2002-201028, etc.). In the case of composite carbonates, a solution containing nickel ions, manganese ions and cobalt ions (solution A) and a solution containing carbonate ions or bicarbonate ions (solution B) are added to the reaction vessel to initiate the reaction. (JP 2009-179545 A), or a solution containing a nickel salt, a manganese salt and a cobalt salt (solution A), and a solution containing a metal carbonate or a metal hydrogen carbonate (solution B), the A A solution (solution C) containing the same anions as the anions of the nickel salt, the manganese salt and the cobalt salt in the liquid and the same anions as the anions of the metal carbonate or the metal hydrogen carbonate in the liquid B and a method of carrying out the reaction (Japanese Patent Application Laid-Open No. 2009-179544). Further, the compounds containing nickel atoms, manganese atoms and cobalt atoms may be commercially available products.

The average particle size of the compound containing nickel atoms, cobalt atoms and manganese atoms is preferably 1 to 100 μm, preferably 5 to 80 μm, as determined by a laser scattering method.

In the production of the lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1), composite hydroxides containing nickel atoms, cobalt atoms and manganese atoms can be used as the nickel source, manganese source and cobalt source. , is preferable in terms of good reactivity.

In the raw material mixing step, the mixing ratio of the lithium source, the nickel source, the manganese source and the cobalt source is the total of Ni atoms, Mn atoms and Co atoms in the nickel source, manganese source and cobalt source in terms of increasing the discharge capacity. The molar ratio (Li/(Ni+Mn+Co)) of Li atoms to the number of moles (Ni+Mn+Co) is preferably 0.98 to 1.20, more preferably 1.00 to 1.10.

In addition, in the raw material mixing step, the mixing ratio of the raw materials of the nickel source, the manganese source and the cobalt source may be adjusted so as to achieve the atomic molar ratio of nickel, manganese and cobalt represented by the general formula (1). .

The production history of the raw material lithium source, nickel source, manganese source and cobalt source does not matter. is preferably

In the raw material mixing step, the means for mixing the lithium source, nickel source, manganese source and cobalt source may be either dry or wet, but dry mixing is preferred because of ease of production.

In the case of dry mixing, it is preferable to use mechanical means so that the raw materials are uniformly mixed. Examples of mixing devices include Ispeed mixer, super mixer, turbosphere mixer, Eirich mixer, Henschel mixer, Nauta mixer, ribbon blender, V-type mixer, conical blender, jet mill, cosmomizer, paint shaker, and bead mill. , a ball mill, and the like. At the laboratory level, a home mixer is sufficient.

In the case of wet mixing, it is preferable to use a media mill as a mixing device in that a slurry in which each raw material is uniformly dispersed can be prepared. Further, the slurry after the mixing treatment is preferably spray-dried from the viewpoint of obtaining a raw material mixture in which each raw material is uniformly dispersed and has excellent reactivity.

The firing step is a step of firing the raw material mixture obtained by performing the raw material mixing step to obtain a lithium-nickel-manganese-cobalt composite oxide.

In the firing step, the firing temperature for firing the raw material mixture and reacting the raw materials is 700 to 1100°C, preferably 750 to 1000°C. The reason for this is that if the firing temperature is less than 700°C, the reaction tends to be insufficient and a large amount of unreacted lithium tends to remain. because there is a tendency

The firing time in the firing step is 3 hours or more, preferably 5 to 30 hours. The firing atmosphere in the firing step is an oxidizing atmosphere of air and oxygen gas.

The lithium-nickel-manganese-cobalt composite oxide thus obtained may be subjected to a plurality of firing steps as required.

The inorganic fluoride particles related to the positive electrode active material for lithium secondary batteries of the present invention are insoluble or sparingly soluble in water. Examples of inorganic fluorides include MgF ₂ , AlF ₃ , TiF ₄ , ZrF ₄ , CaF ₂ , BaF ₂ , SrF ₂ , ZnF ₂ and LiF. As inorganic fluoride particles, _MgF2 and/or _AlF3 are preferred. The inorganic fluoride particles may be used singly or in combination of two or more.

Inorganic fluoride particles are particulate inorganic fluorides. The average particle size of the inorganic fluoride particles is preferably 0.01 to 30 μm, particularly preferably 0.1 to 20 μm, as determined by a laser diffraction/scattering method. When the average particle diameter of the inorganic fluoride particles is within the above range, problems are less likely to occur in the kneading step of preparing the positive electrode mixture and the coating step of applying the obtained positive electrode mixture to the positive electrode current collector. Become.

The content of the inorganic fluoride particles in the positive electrode active material for lithium secondary batteries of the present invention is relative to the total number of moles (Ni + Mn + Co) of Ni atoms, Mn atoms and Co atoms in the lithium nickel manganese cobalt composite oxide particles. is preferably 0.05 to 5.00 mol %, particularly preferably 0.10 to 2.00 mol %, in terms of F atoms. That is, the total mole number of Ni atoms, Mn atoms and Co atoms in terms of atoms in the lithium nickel manganese cobalt composite oxide particles (Ni + Mn + Co) contained in the positive electrode active material for lithium secondary batteries of the present invention The molar ratio ((F/(Ni + Mn + Co)) × 100) of "the number of moles of F atoms (F) in terms of atoms in the inorganic fluoride particles" is preferably 0.05 to 5.00 mol%, particularly preferably It is 0.10 to 2.00 mol %. When the content of the inorganic fluoride particles is within the above range, the effect of improving the cycle characteristics at high voltage while suppressing the decrease in the charge/discharge capacity of the lithium-nickel-manganese-cobalt composite oxide increases. When two or more kinds of inorganic fluoride particles are used as the inorganic fluoride particles, for example, when MgF ₂ and AlF ₃ are used in combination, Ni atoms, Mn atoms and The total amount of F atoms in terms of F atoms is preferably 0.05 to 5.00 mol%, particularly preferably 0.10 to 2.00 mol%, relative to the total moles of Co atoms (Ni+Mn+Co). adjust. When two or more kinds of inorganic fluoride particles are used as the inorganic fluoride particles, the total content of F atoms in terms of F atoms of the two or more inorganic fluoride particles is within the above range, so that the lithium nickel manganese cobalt composite The effect of improving characteristics such as cycle characteristics at high voltage, average operating voltage characteristics, and energy density retention rate increases while suppressing a decrease in charge-discharge capacity of the oxide.

In the positive electrode active material for a lithium secondary battery of the present invention, the inorganic fluoride particles may be present on the particle surface of the lithium-nickel-manganese-cobalt composite oxide particles, and are in a simple mixed state with the lithium-nickel-manganese-cobalt composite oxide particles. or both. That is, the positive electrode active material for a lithium secondary battery of the present invention may contain lithium-nickel-manganese-cobalt composite oxide particles and inorganic fluoride particles present on the surfaces of the lithium-nickel-manganese-cobalt composite oxide particles. Alternatively, it may be a simple mixture of lithium-nickel-manganese-cobalt composite oxide particles and inorganic fluoride particles, or it may contain a mixture of both forms. When the inorganic fluoride particles are present on the surface of the lithium-nickel-manganese-cobalt composite oxide particles, the inorganic fluoride particles are partially present on the surface of the lithium-nickel-manganese-cobalt composite oxide particles. , is preferable in that the lithium-nickel-manganese-cobalt composite oxide surface does not hinder the lithium-nickel-manganese-cobalt composite oxide.

The positive electrode active material for a lithium secondary battery of the present invention is preferably produced by a manufacturing method having a first step of mixing predetermined amounts of lithium-nickel-manganese-cobalt composite oxide particles and inorganic fluoride particles shown below. manufactured.

In the method for producing a positive electrode active material for a lithium secondary battery of the present invention, lithium-nickel-manganese-cobalt composite oxide particles and inorganic fluoride particles are mixed, and lithium-nickel-manganese-cobalt composite oxide particles and inorganic fluoride particles are mixed. A method for producing a positive electrode active material for a lithium secondary battery, comprising a first step of obtaining a mixture of

The lithium-nickel-manganese-cobalt composite oxide particles in the first step are the same as the lithium-nickel-manganese-cobalt composite oxide particles in the positive electrode active material for lithium secondary batteries of the present invention. That is, the lithium-nickel-manganese-cobalt composite oxide according to the first step is the lithium-nickel-manganese-cobalt composite oxide represented by the general formula (1). Moreover, the inorganic fluoride particles related to the first step are the same as the inorganic fluoride particles related to the positive electrode active material for lithium secondary batteries of the present invention.

In the first step, the mixing process can be either dry or wet.

In the first step, it is preferable to use a mechanical means as a dry mixing method because a uniform mixture can be obtained. The device used for dry mixing is not particularly limited as long as a homogeneous mixture can be obtained. Blenders, V-type mixers, conical blenders, jet mills, cosmomizers, paint shakers, bead mills, ball mills and the like can be mentioned. At the laboratory level, a home mixer is sufficient.

When the dry mixing process is performed in the first step, the dry mixing process can be performed in the presence of a small amount of water. By performing the dry mixing treatment in the presence of a small amount of water, the mixed state of the lithium-nickel-manganese-cobalt composite oxide particles and the inorganic fluoride particles is uniform compared to the case of performing the dry-mixing treatment in the absence of any water. becomes easier. However, when dry mixing is performed in the presence of a small amount of water in the first step, it is preferable to dry the mixture after the mixing and then perform a second step of heat-treating the resulting mixture to sufficiently remove the moisture. This is preferable in that deterioration of characteristics such as deterioration of discharge capacity and deterioration of cycle characteristics hardly occurs.

In the first step, when dry mixing treatment is performed in the presence of a small amount of water, the amount of water added is preferably 10 to 80% by mass with respect to the mixture of lithium nickel manganese cobalt composite oxide particles and inorganic fluoride particles. , particularly preferably 20 to 70% by mass.

When dry mixing is performed in the presence of water in the first step, the mixture is dried at 80 to 200° C. after the mixing, and then the resulting mixture is heat-treated in the second step.

In the first step, as a wet mixing method, lithium-nickel-manganese-cobalt composite oxide particles and inorganic fluoride particles are added to a water solvent so that the solid content is 10 to 80% by mass, preferably 20 to 80% by mass. 70% by mass, mixed by mechanical means to prepare a slurry, and then the slurry is dried in a still state, or the slurry is spray-dried to dry and the like to obtain a mixture of lithium-nickel-manganese-cobalt composite oxide particles and inorganic fluoride particles.

The device used for wet mixing is not particularly limited as long as a uniform slurry can be obtained. Equipment such as mills, attritors and high-intensity agitators are included. The wet mixing process is not limited to the mixing process by mechanical means exemplified above. In the wet mixing, a surfactant may be added to the slurry for mixing.

In the first step, when a dry mixing treatment is performed in the presence of a small amount of water or when a wet mixing treatment is performed, the second step may be performed following the first step to reduce the charge-discharge capacity due to moisture and the cycle. It is preferable in that it is possible to make it difficult to cause deterioration of characteristics such as deterioration of characteristics.

In the second step, the mixture of lithium-nickel-manganese-cobalt composite oxide particles and inorganic fluoride particles obtained by performing the first step is heat-treated. The temperature of the heat treatment in the second step is preferably 200-1100°C, particularly preferably 500-1000°C. When the temperature of the heat treatment is within the above range, moisture can be sufficiently removed, and deterioration of characteristics such as a decrease in charge/discharge capacity and a decrease in cycle characteristics can be made difficult to occur. The heat treatment time in the second step is preferably 1 to 10 hours, particularly preferably 2 to 7 hours. Moreover, the atmosphere of the heat treatment in the second step is preferably an oxidizing atmosphere such as air or oxygen gas.

Lithium-cobalt-based composite oxide, lithium-nickel-based composite oxide, lithium-manganese-based composite oxide, and iron phosphate are added to the positive electrode active material for a lithium secondary battery of the present invention in amounts that do not impair the effects of the present invention. Other positive electrode active materials, such as lithium and lithium vanadium phosphate, can also be contained and used as positive electrode active materials for lithium secondary batteries.

The lithium secondary battery of the present invention uses the positive electrode active material for lithium secondary batteries of the present invention as a positive electrode active material. A lithium secondary battery of the present invention comprises a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt.

The positive electrode of the lithium secondary battery of the present invention is formed, for example, by coating and drying a positive electrode material mixture on a positive electrode current collector. The positive electrode mixture is composed of a positive electrode active material, a conductive agent, a binder, a filler added as necessary, and the like. In the lithium secondary battery of the present invention, the positive electrode active material for a lithium secondary battery of the present invention is uniformly applied to the positive electrode. For this reason, the lithium secondary battery of the present invention has high battery performance, particularly excellent cycle characteristics, low average operating voltage drop and high maintenance, and high energy density retention rate.

The content of the positive electrode active material contained in the positive electrode mixture of the lithium secondary battery of the present invention is desirably 70 to 100% by mass, preferably 90 to 98% by mass.

The positive electrode current collector for the lithium secondary battery of the present invention is not particularly limited as long as it is an electronic conductor that does not cause a chemical change in the constructed battery. Examples include stainless steel, nickel, aluminum, and titanium. , calcined carbon, aluminum or stainless steel surface-treated with carbon, nickel, titanium or silver. The surface of these materials may be oxidized before use, or the surface of the current collector may be roughened by surface treatment. Examples of the form of the current collector include foil, film, sheet, net, punched material, lath, porous material, foam, fiber group, non-woven fabric, and the like. Although the thickness of the current collector is not particularly limited, it is preferably 1 to 500 μm.

The conductive agent for the lithium secondary battery of the present invention is not particularly limited as long as it is an electronically conductive material that does not cause chemical changes in the constructed battery. For example, graphite such as natural graphite and artificial graphite, carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, conductive fibers such as carbon fiber and metal fiber, Metal powders such as carbon fluoride, aluminum and nickel powders; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. Examples of graphite include flake graphite, flake graphite, earthy graphite, and the like. These can be used singly or in combination of two or more. The blending ratio of the conductive agent is 1 to 50% by mass, preferably 2 to 30% by mass, in the positive electrode mixture.

Examples of binders for the lithium secondary battery of the present invention include starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, regenerated cellulose, diacetylcellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, and polypropylene. , ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-per Fluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-penta Fluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetra Fluoroethylene copolymer, ethylene-acrylic acid copolymer or its (Na ⁺ ) ion crosslinked product, ethylene-methacrylic acid copolymer or its (Na ⁺ ) ion crosslinked product, ethylene-methyl acrylate copolymer or its (Na ⁺ ) ion cross-linked products, ethylene-methyl methacrylate copolymers or (Na ⁺ ) ion cross-linked products thereof, polysaccharides such as polyethylene oxide, thermoplastic resins, polymers having rubber elasticity, and the like. species or a combination of two or more species can be used. When using a compound containing a functional group that reacts with lithium, such as a polysaccharide, it is preferable to deactivate the functional group by adding a compound such as an isocyanate group. The blending ratio of the binder is 1 to 50% by mass, preferably 5 to 15% by mass in the positive electrode mixture.

The filler for the lithium secondary battery of the present invention suppresses volume expansion of the positive electrode in the positive electrode mixture, and is added as necessary. As the filler, any fibrous material can be used as long as it does not cause a chemical change in the constructed battery. The amount of the filler to be added is not particularly limited, but is preferably 0 to 30% by mass in the positive electrode mixture.

The negative electrode of the lithium secondary battery of the present invention is formed by coating and drying a negative electrode material on a negative electrode current collector. The negative electrode current collector for the lithium secondary battery of the present invention is not particularly limited as long as it is an electronic conductor that does not cause a chemical change in the constructed battery. Examples include stainless steel, nickel, copper, and titanium. , aluminum, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, or silver, and an aluminum-cadmium alloy. Further, the surface of these materials may be oxidized before use, or the surface of the current collector may be roughened by surface treatment. Examples of the form of the current collector include foil, film, sheet, net, punched material, lath, porous material, foam, fiber group, non-woven fabric, and the like. Although the thickness of the current collector is not particularly limited, it is preferably 1 to 500 μm.

The negative electrode material for the lithium secondary battery of the present invention is not particularly limited. materials, conductive polymers, chalcogen compounds, Li—Co—Ni materials, Li ₄ Ti ₅ O ₁₂ , lithium niobate, silicon oxide (SiOx: 0.5≦x≦1.6), and the like. Examples of carbonaceous materials include non-graphitizable carbon materials and graphite-based carbon materials. Examples of metal composite oxides include Sn _p (M ¹ ) _1-p (M ² ) _q O _r (wherein M ¹ represents one or more elements selected from Mn, Fe, Pb and Ge, M ² represents one or more elements selected from Al, B, P, Si, Groups 1, 2 and 3 of the periodic table and halogen elements, 0<p≦1, 1≦q≦3 , 1≦r≦8.), Li _t Fe ₂ O ₃ (0≦t≦1), and Li _t WO ₂ (0≦t≦1). As metal oxides _, GeO, _GeO2 , _SnO , _SnO2 , PbO, _{PbO2 , Pb2O3} , _Pb3O4 , _{Sb2O3 , Sb2O4 , Sb2O5 , Bi2O3} , Bi ₂ O ₄ , Bi ₂ O ₅ and the like. Examples of conductive polymers include polyacetylene and poly-p-phenylene.

As the separator for the lithium secondary battery of the present invention, an insulating thin film having a high ion permeability and a predetermined mechanical strength is used. Sheets and non-woven fabrics made of olefin polymers such as polypropylene, glass fibers, or polyethylene are used because of their organic solvent resistance and hydrophobicity. The pore size of the separator may generally be within a useful range for batteries, for example, 0.01 to 10 μm. The thickness of the separator may be within the range for general batteries, for example, 5 to 300 μm. In addition, when a solid electrolyte such as a polymer is used as the electrolyte described later, the solid electrolyte may also serve as a separator.

The lithium salt-containing non-aqueous electrolyte of the lithium secondary battery of the present invention comprises a non-aqueous electrolyte and a lithium salt. Non-aqueous electrolytes, organic solid electrolytes, and inorganic solid electrolytes are used as the non-aqueous electrolyte for the lithium secondary battery of the present invention. Non-aqueous electrolytes include, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyl Tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 3-methyl -Aprotic organic solvents such as 2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, diethyl ether, 1,3-propanesultone, methyl propionate, and ethyl propionate One type or a mixture of two or more types may be used.

Examples of the organic solid electrolyte for the lithium secondary battery of the present invention include polyethylene derivatives, polyethylene oxide derivatives or polymers containing these, polypropylene oxide derivatives or polymers containing these, phosphate ester polymers, polyphosphazenes, polyaziridines, and polyethylenes. Examples thereof include polymers containing ionic dissociation groups such as sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polyhexafluoropropylene, and mixtures of polymers containing ionic dissociation groups and the above non-aqueous electrolytes.

Li nitrides, halides, _oxysalts , sulfides and the like can be _used as _the inorganic solid electrolyte for the lithium secondary battery of the present invention. _3N —LiI—LiOH, LiSiO ₄ , LiSiO ₄ —LiI—LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ SiO ₄ —LiI—LiOH, P ₂ S ₅ , Li ₂ S or Li ₂ SP _2S5 , _Li2S -- _{SiS2 , Li2S --} GeS2 _{, Li2S} -- _{Ga2S3 , Li2S} -- _{B2S3 , Li2SP2S5} - _X , _Li2S -SiS ₂ -X, Li ₂ S-GeS ₂ -X, Li ₂ S-Ga ₂ S ₃ -X, Li ₂ S-B ₂ S ₃ -X, where X is LiI, B ₂ S ₃ , or at least one selected from Al ₂ S ₃ ), and the like.

Furthermore, when the inorganic solid electrolyte is amorphous (glass), lithium phosphate (Li ₃ PO ₄ ), lithium oxide (Li ₂ O), lithium sulfate (Li ₂ SO ₄ ), phosphorus oxide (P ₂ O ₅ ), compounds containing oxygen such _as lithium borate ( _Li3BO3 ), _{Li3PO4 -} uN2u _/3 (u is 0<u<4), _{Li4SiO4 -} uN2u _/3 (u is 0<u<4), _{Li4GeO4 - uN2u/3} (where u is 0<u<4), and _{Li3BO3 -} uN2u _/3 (where u is 0<u<3). The containing compound can be contained in the inorganic solid electrolyte. The addition of this oxygen-containing compound or nitrogen-containing compound widens the gaps in the formed amorphous skeleton, reduces hindrance to the movement of lithium ions, and further improves the ionic conductivity.

As _the lithium _salt for _the lithium secondary _battery of the present invention, one that dissolves in the above non _- aqueous electrolyte is used _{. SO3} , _{LiCF3CO2 , LiAsF6 , LiSbF6 , LiB10Cl10} , _LiAlCl4 , _{CH3SO3Li , CF3SO3Li} , ( _CF3SO2 ) _2NLi , lithium chloroborane, lower _aliphatic One or a mixture of two or more of lithium carboxylate, lithium tetraphenylborate, and imides may be used.

In addition, the following compounds can be added to the non-aqueous electrolyte for the purpose of improving discharge and charge characteristics and flame retardancy. For example, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones and N,N-substituted imidazolidines, ethylene glycol dialkyl ethers. , ammonium salt, polyethylene glycol, pyrrole, 2-methoxyethanol, aluminum trichloride, monomer of conductive polymer electrode active material, triethylenephosphonamide, trialkylphosphine, morpholine, aryl compound with carbonyl group, hexamethylphosphine Holic triamides and 4-alkylmorpholines, bicyclic tertiary amines, oils, phosphonium salts and tertiary sulfonium salts, phosphazenes, carbonates and the like. Moreover, in order to make the electrolyte nonflammable, the electrolyte may contain a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride. In addition, carbon dioxide gas can be contained in the electrolytic solution in order to make it suitable for high-temperature storage.

The lithium secondary battery of the present invention has a high capacity per volume, is a lithium secondary battery that is excellent in safety, cycle characteristics, and operating voltage. Any shape may be used.

Applications of the lithium secondary battery of the present invention are not particularly limited. Examples include electronic devices such as memory cards and video movies, and consumer electronic devices such as automobiles, electric vehicles, game devices, and electric tools.

EXAMPLES The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these Examples.
The average particle size of the examples was determined by a laser diffraction/scattering method.

<Preparation of Lithium Nickel Manganese Cobalt Composite Oxide Particles (LNMC) Sample>
<LNMC sample 1>
Lithium carbonate (average particle size 5.7 μm) and nickel-manganese-cobalt composite hydroxide (Ni:Mn:Co=8:1:1 (molar ratio), average particle size 11.3 μm) were weighed and mixed in a household mixer. to obtain a raw material mixture having a Li/(Ni+Mn+Co) molar ratio of 1.03. A commercially available nickel-manganese-cobalt composite hydroxide was used.
Next, the obtained raw material mixture was calcined in an alumina pot at 800° C. for 7 hours under an oxygen stream. After firing, the fired product was pulverized and classified. As a result of measuring the obtained sintered product by XRD, it was confirmed to be a single-phase lithium-nickel-manganese-cobalt composite oxide. Moreover, the obtained material was secondary aggregated spherical lithium-nickel-manganese-cobalt composite oxide particles (LiNi _0.8 Mn _0.1 C _0.1 O ₂ ) having an average particle diameter of 11.3 μm. .

<LNMC sample 2>
Lithium carbonate (average particle size 5.7 μm) and nickel-manganese-cobalt composite hydroxide (Ni:Mn:Co=5:3:2 (molar ratio), average particle size 4.0 μm) were weighed and mixed in a household mixer. to obtain a raw material mixture having a Li/(Ni+Mn+Co) molar ratio of 1.10. A commercially available nickel-manganese-cobalt composite hydroxide was used.
Next, the obtained raw material mixture was calcined in an alumina pot at 1000° C. for 10 hours in the air. After firing, the fired product was pulverized and classified. As a result of measuring the obtained sintered product by XRD, it was confirmed to be a single-phase lithium-nickel-manganese-cobalt composite oxide. Further, the obtained material was amorphous single-particle lithium-nickel-manganese-cobalt composite oxide particles (LiNi _0.5 Mn _0.3 Co _0.2 O ₂ ) having an average particle diameter of 9.8 μm. rice field.

<LNMC sample 3>
Lithium carbonate (average particle size 5.7 μm) and nickel-manganese-cobalt composite hydroxide (Ni:Mn:Co=6:2:2 (molar ratio), average particle size 11.2 μm) were weighed and mixed in a household mixer. to obtain a raw material mixture having a Li/(Ni+Mn+Co) molar ratio of 1.03. A commercially available nickel-manganese-cobalt composite hydroxide was used.
The resulting raw material mixture was then fired in an alumina pot at 850° C. for 10 hours in the air. After firing, the fired product was pulverized and classified. As a result of measuring the obtained fired product by XRD, it was confirmed to be a single-phase lithium-nickel-manganese-cobalt composite oxide. The obtained particles had an average particle diameter of 11.4 μm and were secondary aggregated spherical lithium-nickel-manganese-cobalt composite oxide particles (LiNi _0.6 Mn _0.2 Co _0.2 O ₂ ).

Table 1 shows various physical properties of the lithium-nickel-manganese-cobalt composite oxide sample (LNMC sample) obtained above. The average particle size was obtained by a laser diffraction/scattering method.

<Inorganic fluoride sample>
As an inorganic fluoride sample, a commercially available inorganic fluoride was pulverized and an inorganic fluoride having physical properties shown in Table 2 below was used.

(Example 1)
Using the LNMC sample 1 shown in Table 1, the LNMC sample 1 and the above MgF ₂ and AlF ₃ are weighed so that the inorganic fluoride is added in the amount shown in the first step of Table 3, and mixed well with a home mixer. bottom.
Next, the mixed powder was subjected to heat treatment (at 600° C. for 5 hours) shown in the second step in Table 3 in the atmosphere to prepare a positive electrode active material sample.

(Example 2)
Using the LNMC sample 1 shown in Table 1, the LNMC sample 1 and the above MgF ₂ and AlF ₃ are weighed so that the inorganic fluoride is added in the amount shown in the first step of Table 3, and mixed well with a home mixer. bottom.
Next, the mixed powder was subjected to the heat treatment (at 800° C. for 7 hours) shown in the second step in Table 3 under an oxygen stream to prepare a positive electrode active material sample.

(Example 3)
Using the LNMC sample 2 shown in Table 1, the LNMC sample 2 and the above MgF ₂ and AlF ₃ were weighed so that the amount of inorganic fluoride added in the first step of Table 3 was obtained, and water was added to make 50 A mass % slurry was prepared and thoroughly stirred and mixed with a stirrer.
Next, the slurry was spray-dried in a spray dryer adjusted to have an exhaust air temperature of 120° C. to obtain a dry powder.
Next, the dry powder was subjected to the heat treatment (at 600° C. for 5 hours) shown in the second step in Table 3 in the atmosphere to prepare a positive electrode active material sample.

(Comparative Examples 1 to 3)
Using the LNMC samples 1 and 2 described in Table 1, only the heat treatment shown in the second step of Table 3 was performed to obtain positive electrode active material samples. That is, no inorganic fluoride particles were mixed.

(Example 4)
Using the LNMC sample 1 shown in Table 1, the LNMC sample 1 and the above MgF ₂ and AlF ₃ are weighed so that the inorganic fluoride is added in the amount shown in the first step of Table 3, and mixed well with a home mixer. bottom.
Next, the mixed powder was subjected to a heat treatment (at 500° C. for 5 hours) shown in the second step in Table 3 in the atmosphere to prepare a positive electrode active material sample.

(Example 5)
Using the LNMC sample 1 described in Table 1, the heat treatment (600 ° C. for 5 hours) shown in the first step and the second step shown in Table 3 is performed in the same manner as in Example 1 to obtain a positive electrode active material sample. prepared.

(Example 6)
Using the LNMC sample 1 shown in Table 1, the heat treatment (700 ° C. for 5 hours) shown in the first step and the second step shown in Table 3 is performed in the same manner as in Example 1 to obtain a positive electrode active material sample. prepared.

１）無機フッ化物の添加量を、リチウムニッケルマンガンコバルト複合酸化物試料中のＮｉ＋Ｍｎ＋Ｃｏ原子の総量に対するＦ原子の量のモル％として表した。

1) The amount of inorganic fluoride added was expressed as mol % of the amount of F atoms with respect to the total amount of Ni+Mn+Co atoms in the lithium-nickel-manganese-cobalt composite oxide sample.

A battery performance test was conducted as follows.
<Production of lithium secondary battery>
95% by mass of the positive electrode active material obtained in Examples and Comparative Examples, 2.5% by mass of graphite powder, and 2.5% by mass of polyvinylidene fluoride were mixed to form a positive electrode agent, which was added to N-methyl-2-pyrrolidinone. A kneaded paste was prepared by dispersing. The kneaded paste was applied to an aluminum foil, dried, pressed and punched into a disk having a diameter of 15 mm to obtain a positive electrode plate.
Using this positive electrode plate, a coin-type lithium secondary battery was manufactured using members such as a separator, a negative electrode, a positive electrode, a collector plate, a mounting bracket, an external terminal, and an electrolytic solution. Among them, a metallic lithium foil was used as the negative electrode, and a solution prepared by dissolving 1 mol of LiPF ₆ in 1 liter of a 1:1 mixed solution of ethylene carbonate and methyl ethyl carbonate was used as the electrolyte.
Next, performance evaluation of the obtained lithium secondary battery was performed. The results are shown in Table 4.

<Battery performance evaluation>
The prepared coin-type lithium secondary batteries were operated at room temperature under the following test conditions, and the following battery performances were evaluated.
(1) Test Conditions for Cycle Characteristic Evaluation First, charging was performed at 0.5 C to 4.3 V over 2 hours, and then constant current/constant voltage charging (CCCV charging) was performed to hold the voltage at 4.3 V for 3 hours. gone. After that, charge and discharge were performed by constant current discharge (CC discharge) to 2.7 V at 0.2 C, and these operations were regarded as one cycle, and the discharge capacity was measured for each cycle. This cycle was repeated for 20 cycles.
(2) Initial charge capacity, initial discharge capacity (per weight of active material)
The charge capacity and discharge capacity at the first cycle in the cycle characteristic evaluation were defined as the initial charge capacity and the initial discharge capacity.
(3) Initial charge capacity, initial discharge capacity (per weight of active material)
The discharge capacity at the 20th cycle in the cycle characteristic evaluation was defined as the 20th cycle discharge capacity.
(4) Capacity Retention Rate The capacity retention rate was calculated by the following formula from the discharge capacity (per active material weight) at the 1st cycle and the 20th cycle in the cycle characteristics evaluation.
Capacity retention rate (%) = (discharge capacity at 20th cycle/discharge capacity at 1st cycle) x 100
(5) 2nd Cycle Average Operating Voltage, 20th Cycle Average Operating Voltage The average operating voltages during discharge at the 2nd and 20th cycles in the cycle characteristic evaluation were defined as the 2nd cycle average operating voltage and the 20th cycle average operating voltage. .
(6) Average operating voltage drop The average operating voltage drop (ΔV) was calculated by the following formula from the average operating voltage during discharge at the 2nd cycle and the 20th cycle in the cycle characteristics evaluation.
Average operating voltage drop (ΔV) = Average operating voltage at 2nd cycle - Average operating voltage at 20th cycle (7) Energy density retention rate Wh capacity during discharge at 1st cycle and 20th cycle in cycle characteristic evaluation From (per weight of active material), the energy density retention rate was calculated by the following formula.
Energy density maintenance rate (%) = (Discharge Wh capacity at 20th cycle/Discharge Wh capacity at 1st cycle) x 100

Claims (9)

The following general formula (1):
Li _x Ni _y Mn _z Co _1-yz O _1+x (1)
(In the formula, x is 0.98≦x≦1.20, y is 0.50≦y<1.00, and z is 0<z≦0.50.)
and inorganic fluoride particles, wherein the inorganic fluoride particles are _MgF2 and AlF3 _. Positive electrode active material. The F content in the inorganic fluoride particles is 0.05 to 2.0 in terms of F atoms with respect to the total number of moles of Ni atoms, Mn atoms and Co atoms in the lithium-nickel -manganese-cobalt composite oxide particles. 2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the content is 00 mol %. The following general formula (1):
_{LixNiyMnzCo1 -yzO1 + x (} 1)
(Wherein, x is 0.98 ≤ x ≤ 1.20, y is 0.50 ≤ y < 1.00, z is 0 < z ≤ 0.50.) Lithium nickel manganese cobalt composite represented by A first step of mixing oxide particles and inorganic fluoride particles to obtain a mixture of lithium-nickel-manganese-cobalt composite oxide particles and inorganic fluoride particles , wherein the inorganic fluoride particles are composed of MgF ₂ and A method for producing a positive _electrode active material for a lithium secondary battery, which is AlF3 . 4. The method for producing a positive electrode active material for a lithium secondary battery according to claim 3 , wherein the mixing treatment in said first step is performed by dry mixing. 5. The method of manufacturing a positive electrode active material for a lithium secondary battery according to claim 4 , wherein the dry mixing treatment of said first step is carried out in the presence of water. 4. The method for producing a positive electrode active material for a lithium secondary battery according to claim 3 , wherein the mixing treatment in the first step is performed by wet mixing. 7. The method according to any one of claims 3 to 6, further comprising a second step of heat-treating a mixture of lithium-nickel-manganese-cobalt composite oxide particles and inorganic fluoride particles obtained by performing the first step. A method for producing a positive electrode active material for a lithium secondary battery. 8. The method for producing a positive electrode active material for a lithium secondary battery according to claim 7 , wherein the temperature of the heat treatment in said second step is 200 to 1100.degree. 3. A lithium secondary battery, wherein the positive electrode active material for a lithium secondary battery according to claim 1 is used as a positive electrode active material.