Positive electrode active material for lithium secondary battery and lithium secondary battery

Abstract

To impart excellent cycle characteristics to a lithium secondary battery using lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material.SOLUTION: A positive electrode active material for lithium secondary battery consists of lithium-nickel-manganese-cobalt composite oxide particles in which Ti is contained in lithium-nickel-manganese-cobalt composite oxide particles expressed by the following general formula (1): LixNiyMnzCotMpO1+x(1) (in the formula, M denotes one or more kinds of metal elements selected from Al, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na, and K, x denotes 0.98≤x≤1.20, y denotes 0.30≤y<1.00, z denotes 0<z≤0.50, t denotes 0<t≤0.50, p denotes 0≤p≤0.05, and y+z+t+p=1) in a solid solution state, where the particle has a first region in which atom mol% of Ti is 4.0 at% or more and a second region in which atom mol% of Ti is less than 4.0 at%, and is a single phase in X-ray diffraction analysis.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery. [Background technology]

[0002] Lithium cobalt oxide has traditionally been used as the positive electrode active material for lithium secondary batteries. However, because 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).

[0003] It is known that lithium secondary batteries that use a lithium nickel manganese cobalt composite oxide as a positive electrode active material can reduce costs by adjusting the atomic ratio of nickel, manganese, and cobalt contained in the composite oxide, and also have a higher capacity than lithium cobalt oxide (see, for example, Patent Document 3).

[0004] However, even with these conventional techniques, the lithium secondary battery using the lithium nickel manganese cobalt composite oxide as the positive electrode active material still has the problem of deterioration in cycle characteristics.

[0005] As a method for improving the cycle characteristics of a lithium secondary battery using a lithium nickel manganese cobalt composite oxide as a positive electrode active material, a method of coating the particle surface of the lithium nickel manganese cobalt composite oxide with a Ti-containing compound has been proposed (see, for example, Patent Document 4 and Patent Document 5).

[0006] Patent Documents 4 and 5 propose a method for coating the particle surfaces of a lithium nickel manganese cobalt composite oxide with a Ti-containing compound, in which an alkoxide monomer or oligomer made of an organometallic compound such as Ti is mixed with an alcohol such as 2-propanol, a chelating agent such as acetylacetone is added, and water is further added to prepare a dispersion in which a precursor of Ti-containing fine particles having an average particle size of 1 to 20 nm is dispersed, the particle surfaces of the lithium nickel manganese cobalt composite oxide are coated with the dispersion, and then a heat treatment is performed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2004 / 092073 Pamphlet [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-25975 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-23120 [Patent Document 4] Japanese Patent Application Laid-Open No. 2016-24968 [Patent Document 5] Japanese Patent Application Laid-Open No. 2016-72071 Summary of the Invention [Problem to be solved by the invention]

[0008] In recent years, lithium secondary batteries have been considered for use in the automotive field, such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles. For this reason, further improvements in the cycle characteristics of lithium secondary batteries that use lithium nickel manganese cobalt composite oxide as the positive electrode active material are required.

[0009] Therefore, an object of the present invention is to provide a positive electrode active material using a lithium nickel manganese cobalt composite oxide. To provide a positive electrode active material for a lithium secondary battery that can impart excellent cycle characteristics to the lithium secondary battery and a lithium secondary battery having excellent cycle characteristics.

Means for Solving the Problems

[0010] As a result of intensive studies in view of the above circumstances, the present inventors have found that lithium nickel manganese cobalt composite oxide particles in which Ti is dissolved in lithium nickel manganese cobalt composite oxide particles represented by the general formula (1), and from the surface in the depth direction, a region in which Ti is dissolved at a predetermined atomic mol% or more and a region in which the solid solution amount of Ti is less than the predetermined atomic mol%, and a lithium secondary battery using, as a positive electrode active material, lithium nickel manganese cobalt composite oxide particles that are single-phase in X-ray diffraction analysis has excellent cycle performance, and have completed the present invention.

[0011] That is, the present invention (1) is the following general formula (1): Li x Ni y Mn z Co t M p O 1+x (1) (In the formula, M represents one or more metal elements selected from Al, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na, and K. x represents 0.98 ≦ x ≦ 1.20, y represents 0.30 ≦ y < 1.00, z represents 0 < z ≦ 0.50, t represents 0 < t ≦ 0.50, p represents 0 ≦ p ≦ 0.05, and y + z + t + p = 1.) It consists of lithium nickel manganese cobalt composite oxide particles in which Ti is dissolved and contained in lithium nickel manganese cobalt composite oxide particles represented by The lithium nickel manganese cobalt composite oxide particles have a first region in which the atomic mol% of Ti with respect to the total of Ni, Co, and Ti is 4.0 at% or more and a second region in which the atomic mol% of Ti with respect to the total of Ni, Co, and Ti is less than 4.0 at% in the depth direction from the surface. the first region is formed to a depth of 15 nm or more from the surface of the lithium nickel manganese cobalt composite oxide particle, The ratio (A / B) of the atomic mole % of Ti to the total of Ni, Co, and Ti at a depth of 0 nm from the surface of the lithium nickel manganese cobalt composite oxide particles to the atomic mole % of Ti to the total of Ni, Co, and Ti at a depth of 330 nm from the surface of the particles is 10.0 or more. the law of nature, The lithium nickel manganese cobalt composite oxide represented by the general formula (1) is a single phase in X-ray diffraction analysis. To do so, The present invention provides a positive electrode active material for a lithium secondary battery, characterized by:

[0012] The present invention (2) also provides a positive electrode active material for a lithium secondary battery according to (1), characterized in that the content of Ti is, in atomic terms, 0.01 to 5.00 mol % as Ti relative to the total amount of Ni, Mn, Co, and M in the lithium nickel manganese cobalt composite oxide particles.

[0013] The present invention (3) also provides a positive electrode active material for a lithium secondary battery according to (1) or (2), characterized in that the content of residual alkali is 1.20 mass % or less.

[0014] The present invention (4) also provides a positive electrode active material for a lithium secondary battery according to any one of (1) to (3), characterized in that the atomic molar percentage of Ti relative to the total of Ni, Co, and Ti on the particle surface is 6.0 at% or more.

[0017] In addition, the present invention ( 5 ) A mixture of large particles having an average particle diameter of 7.5 to 30.0 μm and small particles having an average particle diameter of 0.50 to 7.5 μm (1) to ( 4 ) a positive electrode active material for a lithium secondary battery.

[0018] In addition, the present invention ( 6 ) is characterized in that the mixing ratio of the large particles to the small particles is 7:13 to 19:1 by mass ratio ( 5) a positive electrode active material for a lithium secondary battery.

[0019] In addition, the present invention ( 7 ) the mixture has a viscosity of 0.65 tonf / cm 2 The compression density when compressed is 2.7 g / cm 3 It is characterized by the above ( 5 ) or ( 6 ) Positive electrode active material for lithium secondary batteries.

[0022] The present invention (8) also provides (1) to ( 7 The present invention provides a lithium secondary battery characterized by using any one of the positive electrode active materials for lithium secondary batteries. [Effects of the Invention]

[0023] According to the positive electrode active material for lithium secondary batteries of the present invention, it is possible to impart excellent cycle characteristics to lithium secondary batteries that use a lithium nickel manganese cobalt composite oxide as a positive electrode active material, and further, by using the positive electrode active material for lithium secondary batteries of the present invention, it is possible to obtain lithium secondary batteries with excellent cycle characteristics. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is an X-ray diffraction diagram of the positive electrode active material sample obtained in Example 1. [Figure 2] 1 is an X-ray diffraction diagram of the positive electrode active material sample obtained in Example 2. [Figure 3] FIG. 10 is an X-ray diffraction diagram of the positive electrode active material sample obtained in Comparative Example 3. [Figure 4] FIG. 2 is a graph showing the change in atomic mole percentage of Ti in the depth direction of the positive electrode active material sample obtained in Example 1. [Figure 5] FIG. 2 is a graph showing the change in atomic mole percentage of Ti in the depth direction of the positive electrode active material sample obtained in Comparative Example 1. [Figure 6] 1 shows secondary electron images and Ti element mapping images obtained by analyzing the positive electrode active material samples obtained in Example 2 and Comparative Example 3 by SEM-EDX analysis. [Embodiments for Carrying out the Invention]

[0025] The positive electrode active material for a lithium secondary battery of the present invention has the following general formula (1): Li x Ni y Mn z Co t M p O 1+x (1) (In the formula, M represents one or more metal elements selected from Al, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na, and K. x represents 0.98 ≦ x ≦ 1.20, y represents 0.30 ≦ y < 1.00, z represents 0 < z ≦ 0.50, t represents 0 < t ≦ 0.50, p represents 0 ≦ p ≦ 0.05, and y + z + t + p = 1.) It consists of lithium nickel manganese cobalt composite oxide particles in which Ti is solid-dissolved and contained in lithium nickel manganese cobalt composite oxide particles represented by The lithium nickel manganese cobalt composite oxide particles have a first region in the depth direction from the surface where the atomic mole% of Ti with respect to the total of Ni, Co, and Ti is 4.0 at% or more, and a second region where the atomic mole% of Ti with respect to the total of Ni, Co, and Ti is less than 4.0 at%. In X-ray diffraction analysis, it is a single-phase lithium nickel manganese cobalt composite oxide represented by the general formula (1). It is a positive electrode active material for a lithium secondary battery, characterized by the above.

[0026] The positive electrode active material for a lithium secondary battery of the present invention is a lithium nickel manganese cobalt composite oxide particle in which Ti is incorporated by solid-solving it into a lithium nickel manganese cobalt composite oxide particle represented by general formula (1). That is, the positive electrode active material for a lithium secondary battery of the present invention is a lithium nickel manganese cobalt composite oxide particle represented by general formula (1) in which Ti is solid-solubilized. The positive electrode active material for a lithium secondary battery of the present invention has, in the depth direction from the particle surface of the lithium nickel manganese cobalt composite oxide particle, a first region in which the amount of Ti in solid solution is a predetermined mol % or more, and a second region following the first region in which the amount of Ti in solid solution is less than the predetermined mol %. The positive electrode active material for a lithium secondary battery of the present invention is an aggregate of lithium nickel manganese cobalt composite oxide particles that are single-phase in X-ray diffraction analysis.

[0027] Therefore, the positive electrode active material for a lithium secondary battery of the present invention is distinguishable from those in which Ti oxide is present and adhered to the surface of the lithium nickel manganese cobalt composite oxide particle of the core particle. When Ti oxide is present on the surface of the lithium nickel manganese cobalt composite oxide particles of the core particles, Ti oxide is detected as a different phase in addition to the lithium nickel manganese cobalt composite oxide of the core particles when subjected to X-ray diffraction analysis, although this depends on the amount of Ti oxide attached. In contrast, in the lithium nickel manganese cobalt composite oxide particles in which Ti is contained as a solid solution in the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) according to the positive electrode active material for lithium secondary batteries of the present invention, a different phase of Ti oxide is not substantially detected when subjected to X-ray diffraction analysis. That is, the positive electrode active material for lithium secondary batteries of the present invention is a single-phase lithium nickel manganese cobalt oxide represented by the general formula (1) in X-ray diffraction analysis. The composite oxide particles are

[0028] In addition, when an oxide containing Ti adheres to the particle surface of lithium nickel manganese cobalt composite oxide particles and is present, when the particle surface of the lithium nickel manganese cobalt composite oxide particles is analyzed by elemental mapping analysis of Ti by SEM-EDX at a magnification of 10,000 to 30,000 times, Ti is observed to be unevenly distributed such as unevenly distributed on the particle surface of the lithium nickel manganese cobalt composite oxide particles. On the other hand, in the lithium nickel manganese cobalt composite oxide particles in which Ti is dissolved and contained in the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) according to the positive electrode active material for a lithium secondary battery of the present invention, when the particle surface of the lithium nickel manganese cobalt composite oxide particles is analyzed by elemental mapping analysis of Ti by SEM-EDX at a magnification of 10,000 to 30,000 times, Ti is observed to be uniformly distributed in the same manner as Co, Ni, Mn, etc.

[0029] In the positive electrode active material for a lithium secondary battery of the present invention, the lithium nickel manganese cobalt composite oxide particles in which Ti is dissolved are composite oxides containing lithium, nickel, manganese and cobalt, and are represented by the following general formula (1). Li x Ni y Mn z Co t M p O 1+x (1) (In the formula, M represents one or more metal elements selected from Al, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na and K. x represents 0.98 ≦ x ≦ 1.20, y represents 0.30 ≦ y < 1.00, z represents 0 < z ≦ 0.50, t represents 0 < t ≦ 0.50, p represents 0 ≦ p ≦ 0.05, and y + z + t + p = 1.)

[0030] In the formula of general formula (1), x satisfies 0.98 ≦ x ≦ 1.20. In terms of achieving a high initial capacity, it is preferably 1.00 ≦ x ≦ 1.10. Also, in the formula of general formula (1), y satisfies 0.30 ≦ y < 1.00. In terms of achieving both a high initial capacity and good cycle characteristics, it is preferably 0.50 ≦ y ≦ 0.95, and particularly preferably 0.60 ≦ y ≦ 0.90. Further, in the formula of general formula (1), z satisfies 0 < z ≦ 0.50. In terms of excellent safety, it is preferably 0.025 ≦ z ≦ 0.45. Also, t satisfies 0 < t ≦ 0.50. In terms of excellent safety, it is preferably 0.025 ≦ t ≦ 0.45. y + z + t + p = 1. y / z is preferably (y / z) > 1, particularly preferably (y / z) ≧ 1.5, and more preferably 3 ≦ (y / z) ≦ 38.

[0031] In addition, M in the formula is a metal element that is optionally incorporated into the lithium nickel manganese cobalt composite oxide represented by general formula (1) for the purpose of improving battery performance such as cycle characteristics and safety. Examples of M include one or more metal elements selected from Al, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na, and K. In the formula of general formula (1), p satisfies 0 ≦ p ≦ 0.050, preferably 0.0001 ≦ p ≦ 0.045.

[0032] In the positive electrode active material of the lithium secondary battery of the present invention, the lithium nickel manganese cobalt composite oxide particles containing Ti in solid solution have a first region containing Ti in solid solution at a predetermined molar percentage or more and a second region having a molar percentage of Ti in solid solution less than a predetermined value, in the depth direction from the surface of the lithium nickel manganese cobalt composite oxide particles.

[0033] The first region is represented by the following formula: Atomic molar percentage of Ti with respect to the total of Ni, Co, and Ti = (Ti / (Ni + Co + Ti)) × 100 (In the formula, Ni, Co, and Ti are all in terms of the number of moles in atomic conversion.) This is a region in which the percentage (atomic mole %) of the number of moles of Ti in atomic terms to the total number of moles of Ni, Co, and Ti in atomic terms calculated by the formula (1) is 4.0 at % or more.

[0034] The first region is preferably formed to a depth of at least 5 nm from the surface of the lithium nickel manganese cobalt composite oxide particle, more preferably 10 nm or more, and even more preferably 15 nm or more. The upper limit of the formation range of the first region is 100 nm or less, preferably 60 nm or less, and even more preferably 50 nm or less, in the depth direction. By forming the first region in this range, lithium ion conductivity in the second region is maintained, while elution of transition metals from the interior of the lithium nickel manganese cobalt composite oxide particle is suppressed, improving cycle characteristics.

[0035] The second region is represented by the formula: Atomic mole % of Ti relative to the total of Ni, Co, and Ti=(Ti / (Ni+Co+Ti))×100 (In the formula, Ni, Co, and Ti are all expressed as moles in atomic terms.) This is a region where the percentage (atomic mole %) of the number of moles of Ti in atomic terms to the total number of moles of Ni, Co, and Ti in atomic terms calculated by the formula (1) is less than 4.0 at %. The second region is a region that does not contain Ti, or even if it contains Ti, the percentage (atomic mole %) of the number of moles of Ti in atomic terms to the total number of moles of Ni, Co, and Ti in atomic terms is less than 4.0 at %.

[0036] The second region is formed from the boundary with the first region in the depth direction to the center of the particle, thereby maintaining lithium ion conductivity in the second region and suppressing the elution of transition metals from the inside of the lithium nickel manganese cobalt composite oxide particle, thereby improving cycle characteristics.

[0037] In the present invention, the first and second regions are determined by X-ray photoelectron spectroscopy (XPS) analysis in which lithium nickel manganese cobalt composite oxide particles are etched with argon from the surface in the depth direction, and the element peaks of Ni, Co, and Ti are measured in the depth direction.The region where the atomic mole percentage of Ti relative to the total of Ni, Co, and Ti is 4.0 at% or more is determined to be the first region, and the region where the atomic mole percentage is less than 4.0 at% is determined to be the second region.

[0038] In the lithium secondary battery positive electrode active material of the present invention, the lithium nickel manganese cobalt composite oxide particles containing Ti as a solid solution preferably have an atomic mole % of Ti relative to the total of Ni, Co, and Ti on the particle surface of 6.0 at% or more, more preferably 6.5 to 95.0 at%, even more preferably 7.0 to 50.0 at%, and even more preferably 10.0 to 30.0 at%. When the atomic mole % of Ti on the surface of the lithium nickel manganese cobalt composite oxide particles is within the above range, elution of transition metals from the interior of the lithium nickel manganese cobalt composite oxide particles is suppressed, improving cycle characteristics while maintaining lithium ion conductivity. The atomic mole % of Ti relative to the total of Ni, Co, and Ti on the particle surface is determined by X-ray photoelectron spectroscopy (XPS) analysis, in which the lithium nickel manganese cobalt composite oxide particles are etched with argon from the surface in the depth direction, and the elemental peaks of Ni, Co, and Ti are measured in the depth direction. The atomic mole % of Ti relative to the total of Ni, Co, and Ti on the particle surface is calculated based on the analytical value at 0 nm in the depth direction, as determined by the following formula: Atomic mole % of Ti relative to the total of Ni, Co, and Ti=(Ti / (Ni+Co+Ti))×100 (In the formula, Ni, Co, and Ti are all expressed as moles in atomic terms.) This is the value calculated as follows.

[0039] In the positive electrode active material for a lithium secondary battery of the present invention, the content of Ti in the lithium nickel manganese cobalt composite oxide particles containing Ti as a solid solution is, in atomic terms, Ni, Mn The amount of Ti is preferably 0.01 to 5.00 mol %, and particularly preferably 0.02 to 4.50 mol %, relative to the total amount (mol) of Ni, Co, and M. When the amount of Ti in the solid solution is within the above range, both initial capacity and cycle characteristics can be achieved. Note that the content of Ti in the lithium nickel manganese cobalt composite oxide particles refers to the percentage of the total moles of Ti, in atomic terms, contained in the entire lithium nickel manganese cobalt composite oxide particles relative to the total amount (mol) of Ni, Mn, Co, and M, in atomic terms, contained in the entire lithium nickel manganese cobalt composite oxide particles.

[0040] In the positive electrode active material for a lithium secondary battery of the present invention, the ratio (A / B) of "the atomic molar percentage (A) of Ti relative to the total of Ni, Co, and Ti at a depth of 0 nm" to "the atomic molar percentage (B) of Ti relative to the total of Ni, Co, and Ti at a depth of 330 nm" of the lithium nickel manganese cobalt composite oxide particles containing Ti as a solid solution is 10.0 or more, preferably 10.5 to 150.0, particularly preferably 11.0 to 120.0, and even more preferably 15.0 to 40.0, from the viewpoint of suppressing elution of transition metals from the interior of the lithium nickel manganese cobalt composite oxide particles and improving cycle characteristics.

[0041] The positive electrode active material for a lithium secondary battery of the present invention is a granular product of lithium nickel manganese cobalt composite oxide particles containing Ti as a solid solution. The lithium nickel manganese cobalt composite oxide particles containing Ti as a solid solution may be single particles in which primary particles are monodispersed, or may be aggregated particles in which primary particles are aggregated to form secondary particles.

[0042] The positive electrode active material for a lithium secondary battery of the present invention has an average particle size of 0.50 to 30.0 μm, preferably 1.0 to 25.0 μm, and particularly preferably 1.5 to 20.0 μm, as calculated as the 50% particle size (D50) converted into volume in the particle size distribution determined by a laser diffraction / scattering method. The positive electrode active material for a lithium secondary battery of the present invention also has a BET specific surface area of ​​preferably 0.05 to 2.00 m. 2 / g, particularly preferably 0.15 to 1.00 m 2 When the average particle size or BET specific surface area of ​​the positive electrode active material for a lithium secondary battery of the present invention is within the above range, the preparation and coating properties of the positive electrode mixture become easy, and furthermore, an electrode with high packing properties can be obtained.

[0043] Furthermore, the residual alkali content of the positive electrode active material for a lithium secondary battery of the present invention is preferably 1.20% by mass or less, particularly preferably 1.00% by mass or less. When the residual alkali content of the positive electrode active material for a lithium secondary battery of the present invention is within the above range, it is possible to suppress expansion and deterioration of the battery caused by gas generation due to the residual alkali.

[0044] In the present invention, the residual alkali refers to the alkali component eluted into water when the positive electrode active material for a lithium secondary battery of the present invention is stirred and dispersed in water at 25°C. The amount of residual alkali is determined by weighing 5 g of the positive electrode active material for a lithium secondary battery of the present invention and 100 g of pure water into a beaker, dispersing them at 25°C for 5 minutes with a magnetic stirrer, filtering the dispersion, and subjecting the amount of alkali present in the obtained filtrate to neutralization titration. The amount of residual alkali is a value obtained by measuring the amount of lithium by titration and converting it into lithium carbonate.

[0045] The method for producing the positive electrode active material for a lithium secondary battery of the present invention is not particularly limited, but the positive electrode active material for a lithium secondary battery of the present invention is suitably produced, for example, by the method for producing the positive electrode active material for a lithium secondary battery of the present invention described below.

[0046] The method for producing a positive electrode active material for a lithium secondary battery of the present invention comprises reacting a compound represented by the following general formula (1): Li x Ni y Mn z Co t M p O 1+x (1) (In the formula, M represents one or more metal elements selected from Mg, Al, Ti, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na, and K. x satisfies 0.98 ≤ x ≤ 1.20, y satisfies 0.30 ≤ y < 1.00, z satisfies 0 < z ≤ 0.50, t satisfies 0 < t ≤ 0.50, p satisfies 0 ≤ p ≤ 0.05, and y + z + t + p = 1.) (The lithium nickel manganese cobalt composite oxide particles represented by the following formula are dry-mixed with an oxide containing Ti, and the oxide containing Ti is adhered to the particle surface of the lithium nickel manganese cobalt oxide particles to obtain oxide-attached composite oxide particles containing Ti. Then, the oxide-attached composite oxide particles containing Ti are heat-treated at 750°C or higher and 1000°C or lower. This is a method for producing a positive electrode active material for a lithium secondary battery.) The lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) according to the method for producing a positive electrode active material for a lithium secondary battery of the present invention are produced, for example, by performing a raw material mixing step of mixing a lithium source, a nickel source, a manganese source, a cobalt source, and an M source added as needed to prepare a raw material mixture, and then a firing step of firing the obtained raw material mixture.)

[0047] As the lithium source, nickel source, manganese source, cobalt source, and M source added as needed in the raw material mixing step, for example, their hydroxides, oxides, carbonates, nitrates, sulfates, organic acid salts, etc. are used. The average particle diameters of the lithium source, nickel source, manganese source, cobalt source, and M source are average particle diameters determined by the laser scattering method, and are 0.50 to 30.0 μm, preferably 1.0 to 25.0 μm.)

[0048] 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. Examples of the compounds containing nickel atoms, manganese atoms, and cobalt atoms include composite oxides, composite hydroxides, composite oxyhydroxides, composite carbonates, etc. containing these atoms.)

[0049] 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. Examples of the compounds containing nickel atoms, manganese atoms, and cobalt atoms include composite oxides, composite hydroxides, composite oxyhydroxides, composite carbonates, etc. containing these atoms.)

[0050] A known method can be used to prepare a compound containing nickel, manganese, and cobalt atoms. For example, a composite hydroxide can be prepared by a coprecipitation method. Specifically, a composite hydroxide can be coprecipitated by mixing an aqueous solution containing predetermined amounts of nickel, cobalt, and manganese atoms, an aqueous solution of a complexing agent, and an aqueous alkali solution (see JP-A-10-81521, JP-A-10-81520, JP-A-10-29820, JP-A-2002-201028, etc.). In the case of composite carbonates, examples include a method in which a solution containing nickel ions, manganese ions, and cobalt ions (Liquid A) and a solution containing carbonate ions or bicarbonate ions (Liquid B) are added to a reaction vessel to carry out the reaction (Japanese Patent Laid-Open No. 2009-179545), or a method in which a solution containing nickel salt, manganese salt, and cobalt salt (Liquid A) and a solution containing metal carbonate or metal bicarbonate (Liquid B) are added to a solution containing the same anions as the nickel salt, manganese salt, and cobalt salt in Liquid A and the same anions as the metal carbonate or metal bicarbonate in Liquid B (Liquid C) to carry out the reaction (Japanese Patent Laid-Open No. 2009-179544). The compound containing nickel atoms, manganese atoms, and cobalt atoms may be commercially available.

[0051] The average particle size of the compound containing nickel atoms, cobalt atoms, and manganese atoms is 0.50 to 100 μm, preferably 1.0 to 80.0 μm, as determined by a laser scattering method.

[0052] In producing the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1), it is preferable to use a composite hydroxide containing nickel atoms, cobalt atoms, and manganese atoms as the nickel source, manganese source, and cobalt source, in terms of improving reactivity.

[0053] In the raw material mixing step, the mixing ratio of the lithium source, nickel source, manganese source, cobalt source, and the M source added as needed is such that the molar ratio of Li atoms to the total number of moles of Ni atoms, Mn atoms, Co atoms, and M atoms (Ni+Mn+Co+M) in the nickel source, manganese source, and cobalt source (Li / (Ni+Mn+Co+M)) is 0.98 to 1.20, and particularly preferably 1.00 to 1.10, in terms of increasing the discharge capacity.

[0054] In the raw material mixing step, the mixing ratio of the respective raw materials, that is, the nickel source, the manganese source, the cobalt source, and the M source added as needed, may be adjusted so as to achieve the atomic molar ratio of nickel, manganese, cobalt, and M represented by the general formula (1) above.

[0055] The manufacturing history of the raw materials, lithium source, nickel source, manganese source, cobalt source and M source, is not important, but in order to produce high-purity lithium-nickel-manganese-cobalt composite oxide particles, it is preferable that the impurity content be as low as possible.

[0056] In the raw material mixing step, the lithium source, nickel source, manganese source, cobalt source, and the M source to be added as needed can be mixed by either a dry method or a wet method, but dry mixing is preferred because it is easier to produce.

[0057] In the case of dry mixing, it is preferable to use a mechanical means to mix the raw materials uniformly. Examples of mixing devices include high-speed mixers, super mixers, turbosphere mixers, Eirich mixers, Henschel mixers, Nauta mixers, ribbon blenders, V-type mixers, conical blenders, jet mills, cosmomizers, paint shakers, bead mills, and ball mills. At the laboratory level, a household mixer is sufficient.

[0058] In the case of wet mixing, it is preferable to use a media mill as a mixing device, since it is possible to prepare a slurry in which each raw material is uniformly dispersed. Furthermore, it is preferable to spray dry the slurry after the mixing process, from the viewpoint of obtaining a raw material mixture with excellent reactivity and in which each raw material is uniformly dispersed.

[0059] The calcination step is a step in which the raw material mixture obtained by the raw material mixing step is calcined to obtain a lithium nickel manganese cobalt composite oxide.

[0060] In the calcination step, the calcination temperature when calcining the raw material mixture to react the raw materials is 600 to 1000° C., preferably 700 to 950° C. The reason for this is that if the calcination temperature is less than 600° C., the reaction tends to be insufficient and a large amount of unreacted lithium tends to remain, while if the calcination temperature exceeds 1000° C., the lithium nickel manganese cobalt composite oxide that has been produced tends to decompose. 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 or oxygen gas.

[0061] Furthermore, in the calcination step, the calcination may be performed in multiple stages. By performing the calcination in multiple stages, lithium nickel manganese cobalt composite oxide particles with even more excellent cycle characteristics can be obtained. When performing the calcination in multiple stages, it is preferable to perform the calcination at a temperature in the range of 650 to 800°C for 1 to 10 hours, and then further increase the temperature to 800 to 950°C, which is higher than the calcination temperature, and continue calcining at that temperature for 5 to 30 hours.

[0062] The lithium nickel manganese cobalt composite oxide thus obtained may be mixed with other materials as required. It may be subjected to several firing steps.

[0063] Furthermore, a lithium nickel manganese composite oxide having a residual alkali content within the above range can be produced by, in the raw material mixing step of the lithium source, nickel source, manganese source, cobalt source, and optionally added M source, adjusting the mixing ratio so that the molar ratio of Li atoms to the total number of moles of Ni atoms, Mn atoms, Co atoms, and M atoms (Ni + Mn + Co + M) in the nickel source, manganese source, cobalt source, and M source (Li / (Ni + Mn + Co + M)) is 0.98 to 1.20, and subjecting the nickel source, manganese source, cobalt source, and optionally added M source to a calcination reaction at 700°C or higher, preferably 750 to 1000°C, for 3 hours or longer, preferably 5 to 30 hours, to thoroughly react the lithium source, nickel source, manganese source, cobalt source, and optionally added M source. In this production method, by carrying out the calcination in the multistage manner described above, a lithium nickel manganese cobalt composite oxide having an even reduced residual alkali content can be produced.

[0064] The residual alkali in the positive electrode active material for a lithium secondary battery of the present invention and the method for measuring it are as described above for the lithium nickel manganese cobalt composite oxide particles. The residual alkali refers to the alkaline component eluted into water when the positive electrode active material for a lithium secondary battery is stirred and dispersed in water at 25°C. The amount of residual alkali is determined by weighing 5 g of the positive electrode active material for a lithium secondary battery and 100 g of pure water into a beaker, dispersing the mixture with a magnetic stirrer at 25°C for 5 minutes, filtering the dispersion, and subjecting the amount of alkali present in the resulting filtrate to neutralization titration. The amount of residual alkali is determined by measuring the amount of lithium by titration and converting it into lithium carbonate.

[0065] Examples of the oxide containing Ti in the method for producing a positive electrode active material for a lithium secondary battery of the present invention include TiO2, Ti2O3, Ti n O 2n-1 Examples include oxides of Ti such as those (n=3 to 9) and composite oxides containing Ti and one or more selected from Mg, Li, Ni, Mn, Co, and M. Of these, oxides of Ti, particularly TiO2, are preferred because of their enhanced effect in improving cycle characteristics.

[0066] The average particle size of the oxide containing Ti is 100 μm or less, preferably 0.01 to 10.0 μm, in terms of the particle size at 50% of the volume (D50) determined by a laser diffraction / scattering method, since this allows Ti to be efficiently incorporated into the particle surface of the lithium nickel manganese cobalt composite oxide particles by solid solution in the shell layer.

[0067] The Ti-containing oxide may be an aggregate of primary particles that form secondary particles. In the method for producing a positive electrode active material for a lithium secondary battery of the present invention, the lithium nickel manganese cobalt composite oxide particles and the Ti-containing oxide are mixed in a dry manner, so that the aggregated Ti-containing oxide is finely crushed during mixing, and the finely divided Ti-containing oxide can be attached to the particle surfaces of the lithium nickel manganese cobalt composite oxide particles.

[0068] When an aggregated Ti-containing oxide is used, the primary particle size of the Ti-containing oxide is preferably 2.0 μm or less, and more preferably 0.001 to 1.0 μm, as the average particle size of the primary particles determined from a scanning electron microscope photograph, in order to efficiently attach the Ti-containing oxide to the particle surfaces of the lithium nickel manganese cobalt composite oxide particles.

[0069] In the method for producing a positive electrode active material for a lithium secondary battery according to the present invention, the amount of the oxide containing Ti mixed into the lithium nickel manganese cobalt composite oxide particles is, in atomic terms, 0.01 to 5.00 mol %, preferably 0.02 to 4.50 mol %, as Ti relative to the total amount (mol) of Ni, Mn, Co, and M in the lithium nickel manganese cobalt composite oxide particles, and this allows the initial capacity and cycle characteristics to be both within preferred ranges. This is preferable in that it can be

[0070] Then, by dry mixing the lithium nickel manganese cobalt composite oxide particles represented by general formula (1) with an oxide containing Ti, the oxide containing Ti is adhered to the particle surface of the lithium nickel manganese cobalt composite oxide particles represented by general formula (1), and Ti-containing oxide-adhered composite oxide particles can be obtained, i.e., lithium nickel manganese cobalt composite oxide particles represented by general formula (1) having the oxide containing Ti adhered and distributed on the particle surface.

[0071] Examples of equipment used in the mixing process include high-speed mixers, super mixers, turbosphere mixers, Henschel mixers, Nauta mixers, ribbon blenders, and V-type mixers. The mixing process is not limited to the mechanical means exemplified above. At the laboratory level, a household mixer or a laboratory mill is also sufficient.

[0072] In the method for producing a positive electrode active material for a lithium secondary battery of the present invention, the Ti-containing oxide-attached composite oxide particles are then heat-treated at 750° C. or higher and 1000° C. or lower, preferably 755 to 975° C., and particularly preferably 760 to 950° C. This heat treatment results in lithium nickel manganese cobalt composite oxide particles having a Ti-containing oxide solid solution therein, the lithium nickel manganese cobalt composite oxide particles having, from the surface to the depth direction, a region (first region) containing dissolved Ti at a predetermined atomic mol % or higher and a region (second region) in which the dissolved Ti content is less than the predetermined atomic mol %, and which is single-phase in X-ray diffraction analysis and is represented by the general formula (1).

[0073] In the method for producing a positive electrode active material for a lithium secondary battery of the present invention, the heat treatment time is not critical, and a positive electrode active material for a lithium secondary battery with satisfactory performance can be obtained if the heat treatment time is usually 1 hour or more, preferably 2 to 10 hours. The heat treatment atmosphere is preferably an oxidizing atmosphere such as air or oxygen gas.

[0074] In the method for producing a positive electrode active material for a lithium secondary battery of the present invention, as described above, the Ti-containing oxide-attached composite oxide particles are heat-treated to obtain the positive electrode active material for a lithium secondary battery of the present invention. Furthermore, in the method for producing a positive electrode active material for a lithium secondary battery of the present invention, after the heat treatment, pulverization, classification, granulation, etc. may be performed as necessary.

[0075] The positive electrode active material for a lithium secondary battery of the present invention is preferably a mixture of large particles having an average particle diameter of 7.5 to 30.0 μm and small particles having an average particle diameter of 0.50 to 7.5 μm, in terms of increasing capacity per volume. The average particle diameter of the large particles is 7.5 to 30.0 μm, preferably 8.0 to 25.0 μm, and particularly preferably 8.5 to 20.0 μm. The average particle diameter of the small particles is 0.5 to 7.5 μm, preferably 1.0 to 7.0 μm, and particularly preferably 1.5 to 6.5 μm. The mixing ratio of the large particles to the small particles is preferably 7:13 to 19:1, and particularly preferably 1:1 to 9:1, by mass. The mixture of the large particles and the small particles has a viscosity of 0.65 tonf / cm 2 The compression density when compressed is 2.7 g / cm 3 or more, preferably 2.8 to 3.3 g / cm 3 , more preferably 2.9 to 3.3 g / cm 3 In addition, when the positive electrode active material for a lithium secondary battery according to the present invention is a mixture of large particles and small particles, the mixture can be obtained, for example, by separately producing large particles having an average particle size of 7.5 to 30.0 μm, preferably 8.0 to 25.0 μm, and particularly preferably 8.5 to 20.0 μm, and small particles having an average particle size of 0.5 to 7.5 μm, preferably 1.0 to 7.0 μm, and particularly preferably 1.5 to 6.5 μm, and then mixing the obtained large particles and small particles at a predetermined mixing ratio.

[0076] 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. The 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.

[0077] The positive electrode of the lithium secondary battery of the present invention is formed, for example, by applying a positive electrode mixture to a positive electrode current collector and drying the mixture. The positive electrode mixture comprises a positive electrode active material, a conductive agent, a binder, and, if necessary, a filler. The lithium secondary battery of the present invention has the positive electrode uniformly coated with the positive electrode active material for lithium secondary batteries of the present invention. Therefore, the lithium secondary battery of the present invention has high battery performance, and in particular, excellent cycle characteristics.

[0078] The content of the positive electrode active material contained in the positive electrode mixture for the lithium secondary battery of the present invention is preferably 70 to 100 mass %, particularly preferably 90 to 98 mass %.

[0079] The positive electrode current collector for the lithium secondary battery of the present invention is not particularly limited as long as it is an electron conductor that does not undergo chemical changes in the constructed battery. Examples include stainless steel, nickel, aluminum, titanium, calcined carbon, and aluminum or stainless steel surfaces that have been surface-treated with carbon, nickel, titanium, or silver. These materials may be used after oxidizing their surfaces, or the current collector surface may be roughened by surface treatment. Examples of the current collector form include foil, film, sheet, net, punched material, lath, porous material, foam, fiber group, and nonwoven fabric molded body. The thickness of the current collector is not particularly limited, but is preferably 1 to 500 μm.

[0080] The conductive agent for the lithium secondary battery of the present invention is not particularly limited as long as it is an electron-conductive material that does not undergo chemical changes in the constructed battery. Examples include graphite (e.g., natural graphite and artificial graphite); carbon black (e.g., carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black); conductive fibers (e.g., carbon fiber and metal fiber); metal powders (e.g., carbon fluoride, aluminum, and nickel powder); conductive whiskers (e.g., zinc oxide and potassium titanate); conductive metal oxides (e.g., titanium oxide); and conductive materials such as polyphenylene derivatives. Examples of natural graphite include scaly graphite, flake graphite, and amorphous graphite. These can be used alone or in combination. The conductive agent is incorporated in an amount of 1 to 50% by mass, preferably 2 to 30% by mass, of the positive electrode mixture.

[0081] Examples of binders for the lithium secondary battery of the present invention include starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkylvinyl ether ter copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer or its (Na+) ion crosslinked product, ethylene Ethylene-methacrylic acid copolymer or its (Na+) ion crosslinked product, ethylene-acrylic methyl methacrylate copolymer or its (Na+) ion crosslinked product, ethylene-methyl methacrylate copolymer Polymers or their (Na+) ion crosslinked bodies, polysaccharides such as polyethylene oxide, thermoplastics Examples of suitable binders include acrylic resins and polymers having rubber elasticity, which can be used alone or in combination of two or more. 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 in the positive electrode mixture is 1 to 50 mass %, preferably 5 to 15 mass %.

[0082] The filler in the lithium secondary battery of the present invention suppresses volume expansion of the positive electrode in the positive electrode mixture and is added as needed. Any fibrous material that does not undergo chemical changes in the constructed battery can be used as the filler, and examples of such materials include fibers of olefin polymers such as polypropylene and polyethylene, glass, and carbon. The amount of filler added is not particularly limited, but is preferably 0 to 30 mass % in the positive electrode mixture.

[0083] The negative electrode of the lithium secondary battery of the present invention is formed by applying a negative electrode material to a negative electrode current collector and drying it. The negative electrode current collector of the lithium secondary battery of the present invention is not particularly limited as long as it is an electron conductor that does not undergo chemical changes in the constructed battery. Examples of the negative electrode current collector include stainless steel, nickel, copper, titanium, aluminum, calcined carbon, copper or stainless steel surfaces surface-treated with carbon, nickel, titanium, or silver, and aluminum-cadmium alloys. These materials may also be used after oxidizing their surfaces, or the current collector surface may be roughened by surface treatment. Examples of the current collector form include foils, films, sheets, nets, punched materials, laths, porous materials, foamed materials, fiber clusters, and nonwoven fabric molded bodies. The thickness of the current collector is not particularly limited, but is preferably 1 to 500 μm.

[0084] The negative electrode material for the lithium secondary battery of the present invention is not particularly limited. For example, carbonaceous materials, metal composite oxides, lithium metal, lithium alloys, silicon-based alloys, tin-based alloys, metal oxides, conductive polymers, chalcogen compounds, Li-Co-Ni-based materials, Li4Ti5O 12 , lithium niobate, silicon oxide (SiO x : 0.5 ≦ x ≦ 1.6), etc. can be mentioned. Examples of the carbonaceous material include graphitizable carbon materials, graphite-based carbon materials, etc. Examples of the metal composite oxide include Sn p (M 1 ) 1-p (M 2 ) q O r (where M 1 represents one or more elements selected from Mn, Fe, Pb, and Ge, and M 2 represents one or more elements selected from Al, B, P, Si, Group 1, Group 2, Group 3 of the periodic table, and halogen elements, and 0 < p ≦ 1, 1 ≦ q ≦ 3, 1 ≦ r ≦ 8 are shown.).), compounds such as Li t Fe2O3 (0 ≦ t ≦ 1), Li t WO2 (0 ≦ t ≦ 1), etc. can be mentioned. Examples of the metal oxide include GeO, GeO2, SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, Bi2O3, Bi2O4, Bi2O5, etc. Examples of the conductive polymer include polyacetylene, poly-p-phenylene, etc.

[0085] The separator for the lithium secondary battery of the present invention is an insulating thin film having high ion permeability and a predetermined mechanical strength. Sheets or nonwoven fabrics made of olefin polymers such as polypropylene, glass fibers, or polyethylene are used because of their resistance to organic solvents and hydrophobicity. The pore size of the separator may be within a range generally useful for batteries, for example, 0.01 to 10 μm. The thickness of the separator may be within a range generally used for batteries, for example, 5 to 300 μm. When a solid electrolyte such as a polymer is used as the electrolyte described below, the solid electrolyte may also serve as the separator.

[0086] The non-aqueous electrolyte containing a lithium salt in the lithium secondary battery of the present invention is composed of a non-aqueous electrolyte and a lithium salt. The non-aqueous electrolyte in the lithium secondary battery of the present invention may be a non-aqueous electrolyte solution, an organic solid electrolyte, or an inorganic solid electrolyte. The non-aqueous electrolyte solution may be, for example, Examples of the solvent include a solvent obtained by mixing one or more aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, diethyl ether, 1,3-propane sultone, methyl propionate, and ethyl propionate.

[0087] Examples of the organic solid electrolyte for the lithium secondary battery of the present invention include polyethylene derivatives, polyethylene oxide derivatives or polymers containing the same, polypropylene oxide derivatives or polymers containing the same, phosphate ester polymers, polymers containing ionically dissociable groups such as polyphosphazene, polyaziridine, polyethylene sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polyhexafluoropropylene, and mixtures of polymers containing ionically dissociable groups with the above-mentioned nonaqueous electrolyte solutions.

[0088] The inorganic solid electrolyte for the lithium secondary battery of the present invention can be a Li nitride, halide, oxyacid salt, sulfide, or the like, and examples thereof include LiN, LiI, LiNI, LiN-LiI-LiOH, LiSiO, LiSiO-LiI-LiOH, LiSiS, LiSiO, LiSiO-LiI-LiOH, P2S, LiS, or LiS-P2S, LiS-SiS, LiS-GeS, LiS-GaS, LiS-B2S, LiS-P2S-X, LiS-SiS-X, LiS-GeS-X, LiS-GaS-X, LiS-B2S-X (wherein X is at least one selected from LiI, B2S, and Al2S3), and the like.

[0089] Furthermore, when the inorganic solid electrolyte is amorphous (glass), oxygen-containing compounds such as lithium phosphate (Li3PO4), lithium oxide (Li2O), lithium sulfate (Li2SO4), phosphorus oxide (P2O5), and lithium borate (Li3BO3), Li3PO 4-u N 2u / 3 (u is 0 <u<4)、Li4SiO 4-u N 2u / 3 (u is 0 <u<4)、Li4GeO 4-u N 2u / 3 (u is 0 <u<4)、Li3BO 3-u N 2u / 3A compound containing nitrogen such as (0 < u < 3) can be incorporated into the inorganic solid electrolyte. By adding this oxygen-containing compound or nitrogen-containing compound, the gaps in the amorphous skeleton formed can be widened, the hindrance to the movement of lithium ions can be reduced, and the ionic conductivity can be further improved.

[0090] As the lithium salt according to the lithium secondary battery of the present invention, those that dissolve in the above non-aqueous electrolyte are used. For example, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiB 10 Cl 10 , LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylic acid, lithium tetraphenylborate, salts obtained by mixing one or more of imides, etc. can be mentioned.

[0091] In addition, for the purpose of improving discharge, charge characteristics, and flame retardancy, the following compounds can be added to the non-aqueous electrolyte. For example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, triamide hexaline acid, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinone and N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, polyethylene glycol, pyrrole, 2-methoxyethanol, aluminum trichloride, conductive poly mer electrode active material monomers, triethylene phosphonamide, trialkyl phosphine, morpholine, aryl compounds having a carbonyl group, hexamethylphosphoric triamide and 4-alkylmorpholine, bicyclic tertiary amines, oils, phosphonium salts and tertiary sulfonium salts, phosphazenes, carbonates, etc. can be mentioned. In addition, a halogen-containing solvent, for example, carbon tetrachloride, ethylene trifluoride can be included in the electrolyte to make the electrolyte non-flammable. Also, carbon dioxide gas can be included in the electrolyte to make it suitable for high-temperature storage.

[0092] The lithium secondary battery of the present invention is a lithium secondary battery that has little cycle degradation even when charge and discharge are repeated and has a high energy density retention rate, and the shape of the battery may be any shape such as button, sheet, cylinder, square, coin type, etc.

[0093] The applications of the lithium secondary battery of the present invention are not particularly limited. For example, they include electronic devices such as notebook computers, laptop computers, pocket word processors, mobile phones, cordless handsets, portable CD players, radios, liquid crystal televisions, backup power supplies, electric shavers, memory cards, video movies, etc., consumer electronic devices such as automobiles, electric vehicles, drones, game devices, and power tools.

Examples

[0094] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. <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 = 6:2:2 (molar ratio), average particle size 9.8 μm) were weighed and thoroughly mixed using a household mixer to obtain a raw material mixture with a Li / (Ni + Mn + Co) molar ratio of 1.01. A commercially available nickel manganese cobalt composite hydroxide was used. Next, the obtained raw material mixture was fired in an alumina crucible at 700 °C for 2 hours and then at 850 °C for 10 hours in an air atmosphere. After the firing was completed, the fired product was pulverized and classified. As a result of measuring the obtained fired product by XRD, it was confirmed that it was a single-phase lithium nickel manganese cobalt composite oxide. Also, the obtained product had an average particle size of 10.2 μm, a BET specific surface area of 0.21 m 2 / g, and was spherical lithium nickel manganese cobalt composite oxide particles (LiNi 0.6 Mn 0.2 Co 0.2 O2) with secondary aggregation.

[0095] <LNMC Sample 2> 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: 3.7 μm) were weighed and thoroughly mixed using a household mixer to obtain a raw material mixture with a molar ratio of Li / (Ni + Mn + Co) of 1.01. The nickel manganese cobalt composite hydroxide used was commercially available. Next, the obtained raw material mixture was fired in an alumina crucible at 700 °C for 2 hours and then at 850 °C for 10 hours in an air atmosphere. After the firing was completed, the fired product was pulverized and classified. As a result of measuring the obtained fired product by XRD, it was confirmed that it was a single-phase lithium nickel manganese cobalt composite oxide. Also, the obtained product had an average particle size of 5.4 μm, a BET specific surface area of 0.69 m 2 / g, and was spherical lithium nickel manganese cobalt composite oxide particles (LiNi 0.6 Mn 0.2 Co 0.2 O2) with secondary aggregation.

[0096] The physical properties of the lithium nickel manganese cobalt composite oxide sample (LNMC sample) obtained above are shown in Table 1. Note that the average particle size, residual alkali amount, and tap density of the LMNC sample were measured as follows. <Average particle size> Determined by laser diffraction / scattering method. <Measurement of residual alkali amount> 5 g of the sample and 100 g of ultrapure water were weighed into a beaker and dispersed at 25 °C for 5 minutes using a magnetic stirrer. Next, this dispersion was filtered, and 70 ml of the filtrate was titrated with 0.1 N-HCl using an automatic titrator (model COMTITE-XXXXX) to calculate the residual alkali amount (value obtained by measuring the lithium amount and converting it to lithium carbonate) present in the sample. <Tap density> [[ID=三十二]]2.25 g of the sample was weighed and placed into a biaxial former with a diameter of 1.5 cm, and using a press, at 0.65 tonf / cm 2 It should be noted that the "XXXXX" in the automatic titrator model in the translation of item needs to be filled in according to the actual model number in the original text. Also, the unit "tonf / cm" in item might need further clarification or correction depending on the correct unit in the original text.The height of the compressed product was measured while applying a pressure of 1000 kJ / min for 1 minute, and the compressed density of the sample was calculated from the apparent volume of the compressed product calculated from the height and the mass of the sample taken.

[0097] [Table 1]

[0098] Example 1 29.9 g of LNMC sample 1 was taken, to which 0.0618 g of titanium oxide (TiO2) was added, and the mixture was thoroughly mixed in a laboratory mill to obtain TiO2-attached composite oxide particles. The obtained TiO2-attached composite oxide particles were then calcined at 800°C for 5 hours, followed by heat treatment, pulverization, and classification to obtain a positive electrode active material sample in which 0.25 mol% of Ti was dissolved relative to the total amount of Ni, Mn, and Co in LNMC sample 1. The average particle diameter (D50) of the obtained positive electrode active material was 10.2 μm, and the BET specific surface area was 0.21 m 2 / g. The residual alkali content and pressed density were also measured in the same manner as for the LNMC sample, and the results are shown in Table 2. The titanium oxide used was an aggregate of secondary particles formed by the aggregation of primary particles. The particle size (D50) calculated as 50% by volume using a laser diffraction / scattering method was 0.38 μm, and the average particle size of the primary particles measured using SEM images was 0.035 μm. The average particle size of the primary particles was determined by randomly selecting 30 particles from the scanning electron microscope, measuring the minor axis and major axis of each particle, calculating half of the sum of the two, and averaging the values ​​of the 30 particles. In addition, X-ray diffraction analysis was performed on the obtained positive electrode active material sample using Cu-Kα radiation as a radiation source. No diffraction peaks due to TiO2 or other phases such as LiTiO2 and Li2TiO3 were observed, confirming that the sample was a single-phase lithium-nickel-manganese-cobalt composite oxide particle. The X-ray diffraction pattern of the positive electrode active material sample is shown in Figure 1. In addition, the particle surface of the positive electrode active material sample was observed at a magnification of 20,000 times using SEM-EDX (Hitachi Elemental mapping analysis of Ti was performed using a High Technologies SU-8220 field emission scanning electron microscope and a Bruker XFlash 5060 FlatQUAD energy dispersive X-ray analyzer, and confirmed that Ti was uniformly distributed, similar to Co, Ni, and Mn. From the results of X-ray diffraction analysis, Ti element mapping analysis, and X-ray photoelectron spectroscopy (XPS) analysis described below, it was confirmed that Ti was present as a solid solution inside the particles of the positive electrode active material sample.

[0099] Example 2 29.9 g of LNMC sample 2 was taken, to which 0.144 g of titanium oxide (TiO2) was added, and the mixture was thoroughly mixed in a laboratory mill to obtain TiO2-attached composite oxide particles. The obtained TiO2-attached composite oxide particles were then calcined at 800°C for 5 hours, followed by heat treatment, pulverization, and classification to obtain a positive electrode active material sample in which 0.58 mol% of Ti was dissolved relative to the total amount of Ni, Mn, and Co in LNMC sample 2. The average particle diameter (D50) of the obtained positive electrode active material was 4.0 μm, and the BET specific surface area was 0.69 m 2 / g. The residual alkali content and pressed density were also measured in the same manner as for the LNMC sample, and the results are shown in Table 2. In addition, X-ray diffraction analysis was performed on the obtained positive electrode active material sample using Cu-Kα radiation as a radiation source. No diffraction peaks due to TiO2 or other phases such as LiTiO2 and Li2TiO3 were observed, confirming that the sample was a single-phase lithium-nickel-manganese-cobalt composite oxide particle. The X-ray diffraction pattern of the positive electrode active material sample is shown in Figure 2. In addition, the particle surface of the positive electrode active material sample was observed at a magnification of 20,000 times using SEM-EDX (Hitachi Elemental mapping analysis of Ti was performed using a High Technologies SU-8220 field emission scanning electron microscope and a Bruker XFlash 5060 FlatQUAD energy dispersive X-ray analyzer, and confirmed that Ti was uniformly distributed, similar to Co, Ni, and Mn. The results of X-ray diffraction analysis, Ti elemental mapping analysis (Figure 6), and X-ray photoelectron spectroscopy (XPS) analysis, which will be described later, confirmed that Ti was present as a solid solution inside the particles of the positive electrode active material sample.

[0100] [Table 2]

[0101] 1) The amount of Ti charged in Examples 1 and 2 was calculated as a percentage of the amount of Ti in atomic terms relative to the total amount of Ni, Mn, Co, and M in atomic terms in the LNMC sample, which was determined from the amount of TiO2 charged.

[0102] (Comparative Example 1) Lithium carbonate (average particle size 5.7 μm), nickel manganese cobalt composite hydroxide (Ni:Mn:Co = 6:2:2 (molar ratio), average particle size 9.8 μm), and titanium oxide (TiO2) were weighed and thoroughly mixed in a household mixer to obtain a raw material mixture with a Li / (Ni + Mn + Co) molar ratio of 1.01 and 0.25 mol % of Ti attached relative to the total amount of Ni, Mn, and Co in the nickel manganese cobalt composite hydroxide. Note that a commercially available nickel manganese cobalt composite hydroxide was used. The resulting raw material mixture was then fired in an alumina pot at 700°C for 2 hours, followed by 10 hours at 850°C in an air atmosphere. After firing, the fired product was crushed and classified. The resulting product had an average particle size of 10.4 μm and a BET specific surface area of ​​0.31 m. 2 / g. The residual alkali content and pressed density were also measured in the same manner as for the LNMC sample, and the results are shown in Table 3. In addition, the obtained positive electrode active material sample was subjected to X-ray diffraction analysis using Cu-Kα radiation as the radiation source. No diffraction peaks due to TiO2 or other phases such as LiTiO2 or Li2TiO3 were observed.

[0103] (Comparative Example 2) Lithium carbonate (average particle size 5.7 μm), nickel manganese cobalt composite hydroxide (Ni:Mn:Co = 6:2:2 (molar ratio), average particle size 3.7 μm), and titanium oxide (TiO₂) were weighed and thoroughly mixed using a household mixer to obtain a raw material mixture with a molar ratio of Li / (Ni + Mn + Co) of 1.01 and 0.58 mol% of Ti attached as Ti with respect to the total amount of Ni, Mn, and Co in the nickel manganese cobalt composite hydroxide. A commercially available nickel manganese cobalt composite hydroxide was used. Next, the obtained raw material mixture was fired in an alumina pot at 700 °C for 2 hours, followed by firing at 850 °C for 10 hours in an air atmosphere. After the firing was completed, the fired product was pulverized and classified. The obtained product had an average particle size of 4.0 μm and a BET specific surface area of 0.70 m 2 / g. Also, the residual alkali amount and the pressure density were measured in the same manner as for the LNMC sample. The results are shown in Table 3. In addition, X-ray diffraction analysis was performed on the obtained positive electrode active material sample using Cu-Kα rays as the radiation source. Diffraction peaks due to TiO₂ and diffraction peaks of heterogeneous phases such as LiTiO₂ and Li₂TiO₃ were not observed.

[0104]

Table 3

[0105] 1) The Ti charge amounts in Comparative Example 1 and Comparative Example 2 were calculated as the percentage of the amount of Ti in atomic conversion with respect to the total amount of Ni, Mn, Co, and M in the LNMC sample in atomic conversion determined from the charged amount of TiO₂.

[0106] <State of Ti distribution> The positive electrode active material samples obtained in the examples were subjected to X-ray photoelectron spectroscopy (XPS) analysis (apparatus name: ULVAC-PHI Corporation QuanteraSXM) by etching the surface with argon in the depth direction, and measuring the Ti peak, Ni peak, and Co peak in the depth direction. The atomic mole percent of Ti relative to the total of Ni, Co, and Ti on the particle surface and inside the particle of the positive electrode active material sample ((Ti / (Ni + Co + Ti)) × 100) was calculated. The atomic mole percent of Ti relative to the total of Ni, Co, and Ti on the particle surface, the formation depth of the first region, and the ratio (A / B) of the atomic mole percent of Ti relative to the total of Ni, Co, and Ti at 0 nm in the depth direction to the atomic mole percent of Ti at 330 nm in the depth direction (B) were also calculated. The results are shown in Table 4. 4 and 5 are graphs showing the change in "atomic mole % of Ti relative to the total of Ni, Co, and Ti ((Ti / (Ni+Co+Ti))×100)" in the depth direction of the positive electrode active materials obtained in Example 1 and Comparative Example 1, respectively. The etching conditions are as follows: X-ray source: (monochrome Al-Kα) Ion species: Ar+ Output: 25W Accelerating voltage: 15 kV Etching rate: 2.2 to 2.4 nm / min (SiO2 equivalent) Orbital of the measured element Co:2p 3 / 2 Ni:2p 3 / 2 Ti:2p

[0107] [Table 4]

[0108] 1) The atomic mole % of Ti on the particle surface is the value of "(Ti / (Ni+Co+Ti))×100" calculated from the measurement value at 0 nm in the depth direction in X-ray photoelectron spectroscopy (XPS) analysis. 2) The "first region" was determined by X-ray photoelectron spectroscopy (XPS) of a sample, etching it with argon from the surface in the depth direction, and measuring the element peaks of Ni, Co, and Ti in the depth direction. When the atomic mole percentage of Ti relative to the total of Ni, Co, and Ti ((Ti / (Ni+Co+Ti)) x 100) was 4.0 at% or more, it was determined to be in the first region. When the atomic mole percentage of Ti relative to the total of Ni, Co, and Ti ((Ti / (Ni+Co+Ti)) x 100) was less than 4.0 at%, it was determined to be in the second region. 3) "A / B" indicates the ratio (A / B) of "the atomic mole % of Ti relative to the total of Ni, Co, and Ti at a depth of 330 nm ((Ti / (Ni+Co+Ti))×100)(A)" to "the atomic mole % of Ti relative to the total of Ni, Co, and Ti at a depth of 0 nm ((Ti / (Ni+Co+Ti))×100)(B)".

[0109] (Comparative Example 3) A positive electrode active material sample was obtained in the same manner as in Example 2, except that instead of performing heat treatment by firing the obtained TiO2-attached composite oxide particles at 800°C for 5 hours, the obtained TiO2-attached composite oxide particles were heat treated by firing at 600°C for 5 hours. Ti was attached in an amount of 0.58 mol% relative to the total amount of Ni, Mn, and Co in LNMC sample 2. The average particle diameter (D50) of the obtained positive electrode active material was 3.9 μm, and the BET specific surface area was 0.88 m 2 / g. The residual alkali content and pressed density were also measured in the same manner as for the LNMC sample, and the results are shown in Table 5. Furthermore, X-ray diffraction analysis was performed on the obtained positive electrode active material sample using Cu-Kα radiation as the radiation source. No diffraction peaks other than those of the lithium nickel manganese cobalt composite oxide were observed. The X-ray diffraction pattern of the positive electrode active material sample is shown in Figure 3. The reason that no diffraction peaks other than those of the lithium nickel manganese cobalt composite oxide were observed is thought to be because the amount of Ti oxide added was small. In addition, the particle surface of the positive electrode active material sample was observed at a magnification of 20,000 times using SEM-EDX (Hitachi This was confirmed by elemental mapping analysis of Ti using a High Technologies SU-8220 field emission scanning electron microscope and a Bruker XFlash 5060 FlatQUAD energy dispersive X-ray analyzer. Ti was found to be unevenly distributed. The results of elemental mapping analysis of Ti confirmed that Ti was not dissolved inside the particles of the positive electrode active material sample, but was present as Ti oxide on the particle surface (Figure 6).

[0110] Comparative Example 4 29.9 g of LiCoO2 sample (LCO sample) was collected, to which 0.0612 g of titanium oxide (TiO2) was added, and the mixture was thoroughly mixed in a laboratory mill to obtain TiO2-attached LCO particles. The obtained TiO2-attached LCO particles were then fired at 900°C for 5 hours, followed by heat treatment, pulverization, and classification to obtain a positive electrode active material sample in which 0.25 mol% of Ti was dissolved relative to the amount of Co in the LCO sample. The average particle diameter (D50) of the obtained positive electrode active material was 8.3 μm, and the BET specific surface area was 0.37 m 2 / g. The residual alkali content and pressed density were also measured in the same manner as for the LNMC sample, and the results are shown in Table 5. Furthermore, X-ray diffraction analysis was performed on the obtained positive electrode active material sample using Cu-Kα radiation as a radiation source. No diffraction peaks attributable to TiO2 or other phases such as LiTiO2 and Li2TiO3 were observed, confirming that the sample was a single-phase lithium-cobalt composite oxide particle.

[0111] [Table 5]

[0112] 1) The amount of Ti charged in Comparative Example 3 was calculated as a percentage of the amount of Ti in atomic terms relative to the total amount of Ni, Mn, Co, and M in atomic terms in the LNMC sample, which was determined from the amount of TiO2 charged. The amount of Ti charged in Comparative Example 4 was calculated as a percentage of the amount of Ti in atomic terms relative to the amount of Co in atomic terms in the LCO sample, which was determined from the amount of TiO2 charged. Note: "-" in the table indicates that the measurement was not performed.

[0113] The battery performance test was carried out as follows. <Preparation of lithium secondary battery 1> 95% by mass of the positive electrode active material samples obtained in Examples 1 and 2 and Comparative Examples 1 to 4, 2.5% by mass of graphite powder % by mass and 2.5% by mass of polyvinylidene fluoride to form a positive electrode material. The mixture was dispersed in 2-pyrrolidinone to prepare a kneaded paste, which was then applied to aluminum foil, dried, pressed, and punched into a disk with a diameter of 15 mm to obtain a positive electrode plate.

[0114] Using this positive electrode plate, a coin-type lithium secondary battery was fabricated using components such as a separator, negative electrode, positive electrode, current collector, mounting hardware, external terminals, and electrolyte. Metallic lithium foil was used for the negative electrode, and the electrolyte was prepared by dissolving 61 moles of LiPF in 1 liter of a 1:1 mixture of ethylene carbonate and methyl ethyl carbonate.

[0115] Next, the performance of the obtained lithium secondary battery was evaluated. The results are shown in Tables 6 and 7. Lithium secondary batteries were fabricated in the same manner using LNMC sample 1 (Comparative Example 5) and LNMC sample 2 (Comparative Example 6) as the positive electrode active material, and similar evaluations were performed. The results are shown in Tables 6 and 7.

[0116] <Battery performance evaluation 1> The produced coin-type lithium secondary battery was operated at room temperature under the following test conditions, and the following battery performance was evaluated. (1) Test conditions for cycle characteristics evaluation First, the battery was charged to 4.3 V at 0.5 C over 2 hours, and then maintained at 4.3 V for 3 hours (constant current / constant voltage charging (CCCV charging)). Subsequently, the battery was discharged to 2.7 V at a constant current (CC discharge) of 0.2 C or 1.0 C. This cycle counts as one cycle, and a total of 30 cycles were performed. The discharge capacity was measured after each cycle. The first, second, tenth, twentieth, and thirtieth cycles were CC discharged at 0.2 C, while the remaining cycles were CC discharged at 1.0 C. (2) Initial charge capacity, initial discharge capacity (per weight of active material) The charge capacity and discharge capacity in the first cycle in the cycle characteristic evaluation were defined as the initial charge capacity and initial discharge capacity. (3) Discharge capacity at 30th cycle (per weight of active material) The discharge capacity at the 30th cycle in the cycle characteristic evaluation was taken as the 30th cycle discharge capacity. (4) Capacity maintenance rate The capacity retention rate was calculated from the discharge capacities (per weight of active material) at the first and 30th cycles in the cycle characteristic evaluation using the following formula. Capacity retention rate (%) = (discharge capacity at 30th cycle / discharge capacity at 1st cycle) x 100 (5) Energy density maintenance rate The energy density retention rate was calculated from the Wh capacity (per active material weight) during discharge in each of the 1st and 30th cycles in the cycle characteristic evaluation using the following formula. Energy density retention rate (%) = (30th cycle discharge Wh capacity / 1st cycle discharge Wh capacity)×100

[0117] [Table 6]

[0118] [Table 7]

[0119] <Fabrication of lithium secondary battery 2> The positive electrode active material samples and LNMC samples obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were thoroughly mixed in a household mixer to prepare mixtures having the compositions shown in Table 8, which were used as positive electrode active material samples. The pressed densities of the positive electrode active material samples were measured in the same manner as for the LNMC samples, and the results are shown in Table 8.

[0120] [Table 8]

[0121] A positive electrode agent was prepared by mixing 95% by mass of a positive electrode active material sample, 2.5% by mass of graphite powder, and 2.5% by mass of polyvinylidene fluoride, and then dispersed in N-methyl-2-pyrrolidinone to prepare a kneaded paste. The kneaded paste was applied to aluminum foil, dried, pressed, and punched into a 15 mm diameter disk to obtain a positive electrode plate. Using this positive electrode plate, a coin-type lithium secondary battery was fabricated using components such as a separator, negative electrode, positive electrode, current collector, mounting hardware, external terminals, and electrolyte. Metallic lithium foil was used for the negative electrode, and the electrolyte was prepared by dissolving 61 moles of LiPF in 1 liter of a 1:1 mixture of ethylene carbonate and methyl ethyl carbonate. The performance of the resulting lithium secondary battery was then evaluated, and the results are shown in Table 9.

[0122] <Battery performance evaluation 2> The coin-type lithium secondary battery thus prepared was operated at room temperature under the following test conditions, and the cycle characteristics were evaluated, including the initial charge capacity, the initial discharge capacity (per active material weight), and the charge capacity at the 30th cycle. The discharge capacity (per weight of active material), capacity retention rate, and energy density retention rate at the 30th cycle were evaluated in the same manner as in Battery Performance Evaluation 1. The discharge capacity per volume was also evaluated, and the results are shown in Table 9. The positive electrode active material samples of Examples 1 and 2 were also evaluated in the same manner. The results are shown in Table 9. (6) Discharge capacity per volume The discharge capacity per volume was calculated from the initial discharge capacity and the electrode density using the following formula. Discharge capacity per volume (mAh / cm 3 ) = 1st cycle discharge capacity (mAh / g) × Electrode density (g / cm 3 ) x 0.95 (ratio of active material in coating agent) The electrode density was calculated by measuring the mass and thickness of the electrode prepared from the sample to be measured, and subtracting the thickness and mass of the current collector from this to obtain the density of the positive electrode material. The positive electrode material consisted of 95% by mass of the positive electrode active material sample, 2.5% by mass of graphite powder, and polyvinyl fluoride. The electrode was made using a mixture of 2.5 mass% ethylenediamine and a linear pressure of 0.38 ton / cm. The value was m.

[0123] [Table 9]

Claims

1. The following general formula (1): Li ｘ Ni ｙ Mn ｚ Co ｔ M ｐ O １＋ｘ (1) (In the formula, M represents one or more metal elements selected from Al, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na, and K. x represents 0.98≦x≦1.20, y represents 0.30≦y<1.00, z represents 0<z≦0.50, t represents 0<t≦0.50, p represents 0≦p≦0.05, and y+z+t+p=1.) The present invention comprises lithium nickel manganese cobalt composite oxide particles containing Ti as a solid solution in lithium nickel manganese cobalt composite oxide particles represented by the formula: The lithium nickel manganese cobalt composite oxide particles have, in a depth direction from the surface, a first region in which the atomic mole % of Ti relative to the total of Ni, Co, and Ti is 4.0 at% or more, and a second region in which the atomic mole % of Ti relative to the total of Ni, Co, and Ti is less than 4.0 at%, the first region is formed to a depth of 15 nm or more from the surface of the lithium nickel manganese cobalt composite oxide particle, the ratio (A / B) of the atomic mol % (B) of Ti relative to the total of Ni, Co, and Ti at a depth of 330 nm from the surface of the lithium nickel manganese cobalt composite oxide particle to the atomic mol % (A) of Ti relative to the total of Ni, Co, and Ti at a depth of 0 nm from the surface of the lithium nickel manganese cobalt composite oxide particle is 10.0 or more; The lithium nickel manganese cobalt composite oxide is a single-phase lithium nickel manganese cobalt composite oxide represented by the general formula (1) in an X-ray diffraction analysis. A positive electrode active material for a lithium secondary battery, characterized by:

2. 2. The positive electrode active material for lithium secondary batteries according to claim 1, wherein the content of Ti is, in atomic terms, 0.01 to 5.00 mol % as Ti relative to the total amount of Ni, Mn, Co, and M in the lithium nickel manganese cobalt composite oxide particles.

3. 2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the content of residual alkali is 1.20 mass % or less.

4. 2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the atomic mole % of Ti relative to the total of Ni, Co and Ti on the particle surface is 6.0 at % or more.

5. 2. The positive electrode active material for a lithium secondary battery according to claim 1, which is a mixture of large particles having an average particle diameter of 7.5 to 30.0 μm and small particles having an average particle diameter of 0.50 to 7.5 μm.

6. 6. The positive electrode active material for a lithium secondary battery according to claim 5, wherein the mixing ratio of the large particles to the small particles is 7:13 to 19:1 by mass.

7. The mixture has a viscosity of 0.65 tonf / cm ２ The compression density when compressed is 2.7 g / cm ３ 6. The positive electrode active material for a lithium secondary battery according to claim 5, wherein the positive electrode active material is any one of the above.

8. A lithium secondary battery, characterized by using the positive electrode active material for lithium secondary batteries according to claim 1 or 5.

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