Positive electrode active material for nonaqueous electrolyte secondary battery

Abstract

To provide a positive electrode active material for a nonaqueous electrolyte secondary battery, which is capable of achieving both high output characteristics and high durability.SOLUTION: A positive electrode active material includes a lithium-transition metal composite oxide in which a ratio D50 / DSEM of a 50% particle size D50 in volume-based cumulative particle size distribution to an average particle size DSEM based on electron microscopic observation is 1 or more and 4 or less, the lithium-transition metal composite oxide having a layered structure. A ratio of the number of moles of nickel to the total number of moles of metals other than lithium in a composition of the lithium-transition metal composite oxide is 0.6 or more and less than 0.8. The positive electrode active material satisfies at least one of the following aspects: (i) the disorder of nickel element in the lithium-transition metal composite oxide determined by X-ray diffractometry is 2.0% or less; (ii) a ratio D90 / D10 of a 90% particle size D90 to a 10% particle size D10 in volume-based cumulative particle size distribution is 2.3 or less; and (iii) D50 is 1 μm or more and 5.5 μm or less.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a positive electrode active material for a non-aqueous electrolyte secondary battery. [Background technology]

[0002] Positive electrode active materials for nonaqueous electrolyte secondary batteries used in large power equipment such as electric vehicles are required to have both high output power and high durability. To achieve high output power, it is effective to use a positive electrode active material having a secondary particle structure in which many primary particles are aggregated, to form hollow structures within the secondary particles to increase the BET ratio, or to reduce the primary particle size of the aggregated secondary particles. However, such positive electrode active materials can suffer from cracks in the secondary particles due to pressure treatment during electrode formation and expansion and contraction during charge and discharge, leaving room for improvement in durability. In relation to the above, a positive electrode active material in which the number of primary particles constituting one secondary particle is reduced has been proposed (see, for example, Patent Document 1). Also, a positive electrode active material in which primary particles are monodispersed has been proposed (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-243949 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-355824 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the case of conventional positive electrode active materials, it has sometimes been impossible to achieve both high output characteristics and high durability. An object of one embodiment of the present disclosure is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that can achieve both high output characteristics and high durability. [Means for solving the problem]

[0005] Specific means for solving the above problems are as follows, and the present invention includes the following aspects. The first aspect is an average particle size D based on electron microscope observation. SEM is 1 μm or more and 7 μm or less, and the 50% particle size D in the cumulative particle size distribution based on the volume 50 Average particle size D based on electron microscope observation SEM Ratio to D 50 / D SEM is 1 or more and 4 or less, and the 90% particle size D in the cumulative particle size distribution based on the volume 90 10% particle size D 10 Ratio to D 90 / D 10 The positive electrode active material for a non-aqueous electrolyte secondary battery includes a lithium transition metal composite oxide particle group having a saturation ratio of 4 or less, the lithium transition metal composite oxide containing nickel in its composition and having a layered structure.

[0006] A second aspect is an electrode for a non-aqueous electrolyte secondary battery, comprising: a current collector; and a positive electrode active material layer disposed on the current collector and containing the positive electrode active material. A third aspect is a non-aqueous electrolyte secondary battery comprising the electrode. [Effects of the Invention]

[0007] According to one embodiment of the present disclosure, it is possible to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that can achieve both high output characteristics and high durability. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 1. [Figure 2] FIG. 10 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 3. [Figure 3] FIG. 10 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 4. [Figure 4]FIG. 10 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 5. [Figure 5] FIG. 10 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 6. [Figure 6] FIG. 2 is a diagram showing an example of an SEM image of lithium transition metal composite oxide particles according to Comparative Example 1. [Figure 7] 10 is a diagram showing an example of an SEM image of lithium transition metal composite oxide particles according to Comparative Example 2. FIG. [Figure 8] FIG. 10 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 7. [Figure 9] FIG. 10 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 8. [Figure 10] FIG. 10 is a diagram showing an example of an SEM image of lithium transition metal composite oxide particles according to Comparative Example 3. [Figure 11] FIG. 10 is a diagram showing an example of an SEM image of lithium transition metal composite oxide particles according to Comparative Example 4. [Figure 12] FIG. 10 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 10. [Figure 13] FIG. 10 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 11. [Figure 14] FIG. 12 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 12. [Figure 15] 10 is a diagram showing an example of an SEM image of lithium transition metal composite oxide particles according to Comparative Example 5. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present disclosure will be described based on embodiments. However, the embodiments shown below are intended to embody the technical concept of the present invention and are not intended to limit the present invention to the following. In this specification, the content of each component in a composition means the total amount of the multiple substances present in the composition when multiple substances corresponding to each component are present in the composition, unless otherwise specified.

[0010] [Cathode active material for non-aqueous electrolyte secondary batteries] The positive electrode active material for a non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure (hereinafter also simply referred to as the "positive electrode active material") has an average particle size D SEM is 1 μm or more and 7 μm or less, and the 50% particle size D in the cumulative particle size distribution based on the volume 50 The ratio D to the average particle size based on electron microscope observation 50 / D SEM is 1 or more and 4 or less, and the 90% particle size D in the cumulative particle size distribution based on the volume 90 10% particle size D 10 Ratio to D 90 / D 10 The lithium transition metal composite oxide particles have a molecular weight of 4 or less, and the lithium transition metal composite oxide constituting the particle groups contains nickel in its composition and has a layered structure.

[0011] The positive electrode active material has an average particle size D SEM is 1 μm or more and 7 μm or less, and D 50 D SEM Ratio to D 50 / D SEM is between 1 and 4, and the ratio D 90 / D 10 The composite oxide particles (hereinafter simply referred to as "composite oxide particles") contain lithium transition metal composite oxide particles having a D of 4 or less. 50 / D SEM When D is 1 or more and 4 or less, it means that the composite oxide particle is a particle consisting of a single particle or a particle consisting of a few primary particles (hereinafter, also simply referred to as "single particle"), and there are few contact grain boundaries between the primary particles.90 / D 10 A value of 4 or less means that the cumulative particle size distribution based on the volume of the composite oxide particles is narrow and the particle sizes are uniform. These characteristics enable the material to achieve both high output characteristics and high durability.

[0012] Compared to positive electrode active materials containing conventional single-particle lithium transition metal composite oxide particles with secondary particles consisting of a large number of agglomerated primary particles, positive electrode active materials containing single-particle lithium transition metal composite oxide particles exhibit excellent durability by suppressing the decrease in capacity retention rate due to the disconnection of the lithium ion conductive path caused by the grain boundary dissociation of the secondary particles during charge / discharge cycles, and the increase in the diffusion resistance of lithium ions. On the other hand, a three-dimensional grain boundary network like that of a positive electrode active material made of agglomerated particles is hardly formed, making it impossible to design a high output power using grain boundary conduction, and therefore output characteristics tend to be insufficient. In order to improve output characteristics, the particle size of the single particles (D SEM However, if the particle size is too small, the interaction between particles increases, which tends to significantly worsen the packing of the electrode plate, and the reduced powder flowability can significantly worsen handling. On the other hand, a certain particle size is necessary to obtain a particularly practical energy density, but if the particle size is increased, it is thought that the power output deficiency tends to become more pronounced.

[0013] The lithium transition metal composite oxide particles of one embodiment according to the present disclosure have a more uniform particle size than conventional single particles. This prevents unevenness in charge / discharge depth among particles due to current concentration on some particles even when charging / discharging at a high current density. This is thought to prevent local degradation due to cycling while also suppressing an increase in resistance due to current concentration.

[0014] Furthermore, the uniform particle size of the lithium transition metal composite oxide particles with few grain boundaries prevents the particles from collapsing even when pressed under high pressure during electrode fabrication, which is thought to enable the voids between the particles to be homogenized. Furthermore, when a battery is constructed, the voids between the particles are filled with electrolyte, forming paths for lithium ions to diffuse. The uniform size of these diffusion paths is thought to reduce unevenness in charge and discharge behavior among particles. This suggests that even lithium transition metal composite oxide particles with few contact boundaries between primary particles can achieve excellent output characteristics while ensuring electrode plate packing.

[0015] Furthermore, when synthesizing single particles, a high heat treatment temperature is generally required to grow the particles. In particular, in compositions with a high Ni ratio, high-temperature sintering can cause Ni elements to become mixed into the Li site, a phenomenon known as disorder. Disorder inhibits the diffusion of Li ions in the composite oxide particles, creating resistance and resulting in reduced charge / discharge capacity at practical current densities and reduced output characteristics, so it is desirable to suppress it. By suppressing disorder, better capacity and output characteristics can be achieved in single particles.

[0016] The composite oxide particles that make up the positive electrode active material have an average particle size D SEM From the viewpoint of durability, it is 1 μm or more and 7 μm or less, and from the viewpoint of power density and electrode plate packing, when the range of x is 0.3≦x<0.6, it is preferably 1.1 μm or more, more preferably 1.3 μm or more, and preferably 4 μm or less, and more preferably 2 μm or less. When the range of x is 0.6≦x≦0.95, it is preferably 1.1 μm or more, more preferably 1.3 μm or more, and preferably 5 μm or less, and more preferably 4 μm or less.

[0017] Average particle size D based on electron microscope observation SEM is obtained by observing particles using a scanning electron microscope (SEM) at magnifications ranging from 1,000 to 10,000 times depending on the particle size, selecting 100 particles whose particle outlines can be confirmed, calculating the equivalent spherical diameter of the selected particles using image processing software, and then calculating the arithmetic mean of the obtained equivalent spherical diameters.

[0018] The composite oxide particles have a 50% particle size D in the cumulative particle size distribution based on volume. 50 Average particle size D based on electron microscope observation SEM Ratio to D 50 / D SEM is between 1 and 4. D 50 / D SEM When the value is 1, it indicates a single particle, and the closer it is to 1, the fewer the number of primary particles it consists of. 50 / D SEM From the viewpoint of durability, 50 / D SEM is preferably 1 or more and less than 4, and from the viewpoint of power density, is preferably 3 or less, and particularly preferably 2.5 or less.

[0019] The 50% particle size D 50 is, for example, 1 μm or more and 21 μm or less, and from the viewpoint of output density, is preferably 1.5 μm or more, more preferably 3 μm or more, and is preferably 8 μm or less, more preferably 5.5 μm or less.

[0020] 50% particle size D 50 is determined as the particle size corresponding to the cumulative 50% from the small diameter side in the cumulative particle size distribution on a volume basis measured under wet conditions using a laser diffraction particle size distribution analyzer. Similarly, the 90% particle size D 90 and 10% particle size D 10 are calculated as the particle diameters corresponding to 90% and 10% cumulatively from the small diameter side, respectively.

[0021] The composite oxide particles have a 90% particle size D 90 10% particle size D 10 The ratio of D to D indicates the spread of particle size distribution, and the smaller the value, the more uniform the particle size. 90 / D 10 is 4 or less, and from the viewpoint of power density, it is preferably 3 or less, and more preferably 2.5 or less. 90 / D 10 The lower limit is, for example, 1.2 or more.

[0022] The lithium transition metal composite oxide contains nickel in its composition and has a layered structure. Examples of such lithium transition metal composite oxides include lithium nickel composite oxide and lithium nickel cobalt manganese composite oxide. Among them, the lithium transition metal composite oxide preferably has a composition represented by the following formula (1): Li p Ni x Co y M 1 z O 2+α (1) In formula (1), p, x, y, z, and α satisfy the following conditions: 1.0≦p≦1.3, 0.3≦x≦0.95, 0≦y≦0.4, 0≦z≦0.5, x+y+z=1, −0.1≦α≦0.1; and M 1 represents at least one of Mn and Al.

[0023] The lithium transition metal composite oxide particles may be doped with an element other than the elements constituting the lithium transition metal composite oxide. Examples of the doped element include B, Na, Mg, Si, P, S, K, Ca, Ti, V, Cr, Zn, Sr, Y, Zr, Nb, Mo, In, Sn, Ba, La, Ce, Nd, Sm, Eu, Gd, Ta, W, and Bi. Compounds used for doping with these elements include oxides and fluorides containing at least one element selected from the group consisting of these elements, as well as Li composite oxides thereof. The doping amount can be, for example, 0.005 mol % to 10 mol % of the lithium transition metal composite oxide particles.

[0024] The lithium transition metal composite oxide particles may also have a core particle containing a lithium transition metal composite oxide and an attachment disposed on the surface of the core particle. The attachment may be disposed on at least a portion of the surface of the core particle, preferably occupying at least 1% of the surface area of the core particle. The composition of the attachment is appropriately selected depending on the purpose, and examples thereof include oxides and fluorides containing at least one element selected from the group consisting of B, Na, Mg, Si, P, S, K, Ca, Ti, V, Cr, Zn, Sr, Y, Zr, Nb, Mo, In, Sn, Ba, La, Ce, Nd, Sm, Eu, Gd, Ta, W, and Bi, as well as Li composite oxides thereof. The content of the attachment may be, for example, 0.03% by mass to 10% by mass, preferably 0.1% by mass to 2% by mass, in the lithium transition metal composite oxide particles.

[0025] The lithium transition metal composite oxide contains nickel in its composition. From the viewpoint of initial efficiency in nonaqueous electrolyte secondary batteries, the lithium transition metal composite oxide preferably has a disorder of nickel element determined by X-ray diffraction of 4.0% or less, more preferably 2.0% or less, and even more preferably 1.5% or less. Here, disorder of nickel element refers to a chemical disorder of the transition metal ions (nickel ions) that should occupy the original sites. In lithium transition metal composite oxides with a layered structure, this is typically the interchange of lithium ions that should occupy the site represented by 3b in Wyckoff notation (3b site, hereinafter the same) with transition metal ions that should occupy the 3a site. The smaller the disorder of nickel element, the better the initial efficiency, and therefore the better.

[0026] The disorder of nickel element in lithium transition metal composite oxide can be determined by X-ray diffraction. For lithium transition metal composite oxide, X-ray diffraction spectrum is measured using CuKα radiation. The composition model is Li 1-d Ni dUse MeO₂ (where Me is a transition metal other than nickel in the lithium transition metal composite oxide), and based on the obtained X-ray diffraction spectrum, perform structure optimization by Rietveld analysis. Let the percentage of d calculated as a result of the structure optimization be the value of the disorder of the nickel element.

[0027] When the lithium transition metal composite oxide has a composition represented by the formula (1), in one embodiment of the present invention, depending on the value of x in the formula (1), the range of a, D SEM , D 50 , D 90 and D 10 The range of the particle size represented by, and the more preferable range of the disorder of the nickel element may vary, and they are exemplified below.

[0028] In the formula (1), when 0.3 ≦ x < 0.8 is satisfied for x, from the viewpoint of the output density, D 50 / D SEM is preferably 1 or more and 2 or less.

[0029] In the formula (1), when 0.3 ≦ x < 0.6 is satisfied for x, from the viewpoint of the output density, it is preferable to satisfy at least one of the following aspects. (i) The disorder of the nickel element determined by the X-ray diffraction method of the lithium transition metal composite oxide particles is preferably 1.5% or less from the viewpoint of the charge-discharge capacity. (ii) D 90 / D 10 is preferably 3.0 or less, and more preferably 2.5 or less. (iii) D 50 is preferably 1 μm or more and 5.5 μm or less, and more preferably 1 μm or more and 3 μm or less from the viewpoint of the electrode plate filling property. (iv) p in the formula (1) preferably satisfies 1.1 < p < 1.2.

[0030] In the formula (1), when 0.6 ≦ x < 0.8 is satisfied for x, from the viewpoint of the output density, it is preferable to satisfy at least one of the following aspects. (i) From the viewpoint of charge / discharge capacity, the disorder of the nickel element in the lithium transition metal composite oxide particles determined by X-ray diffraction is preferably 2.0% or less. (ii)D 90 / D 10 is preferably 2.3 or less. (iii)D 50 From the viewpoint of electrode plate packing, the thickness is preferably 1 μm or more and 5.5 μm or less.

[0031] In the formula (1), when x satisfies 0.8≦x<0.95, it is preferable that at least one of the following aspects is satisfied from the viewpoint of power density. (i) From the viewpoint of charge / discharge capacity, the disorder of the nickel element in the lithium transition metal composite oxide particles determined by X-ray diffraction is preferably 4.0% or less. (ii)D 90 / D 10 is preferably 3.0 or less. (iii)D 50 From the viewpoint of electrode plate packing, the thickness is preferably 1 μm or more and 5.5 μm or less.

[0032] [Method of manufacturing positive electrode active material] The lithium transition metal composite oxide particles contained in the positive electrode active material according to the present disclosure can be produced by a production method including mixing a lithium compound and an oxide having a desired composition to obtain a raw material mixture, and heat-treating the obtained raw material mixture. The heat-treated product obtained after the heat treatment may be subjected to a crushing treatment, or may be subjected to a treatment such as washing with water to remove unreacted materials, by-products, etc. Furthermore, it may be subjected to a further treatment such as dispersion treatment or classification treatment.

[0033] Methods for obtaining an oxide having a desired composition include a method in which raw material compounds (hydroxides, carbonates, etc.) are mixed according to the target composition and decomposed into an oxide by heat treatment, and a co-precipitation method in which a solvent-soluble raw material compound is dissolved in a solvent, and precursor precipitates are obtained according to the target composition by adjusting the temperature, pH, adding a complexing agent, etc., and the precursors are then heat-treated to obtain an oxide. Hereinafter, an example of a method for producing a positive electrode active material will be described, taking as an example the case where the lithium transition metal composite oxide is represented by formula (1).

[0034] The method for obtaining the raw material mixture preferably includes obtaining a composite oxide containing nickel, cobalt, and at least one of manganese and aluminum by a coprecipitation method, and mixing the obtained composite oxide with a lithium compound such as lithium carbonate or lithium hydroxide.

[0035] A method for obtaining a composite oxide by coprecipitation can include a seed generation step of adjusting the pH of a mixed aqueous solution containing metal ions in a desired composition to obtain seed crystals, a crystallization step of growing the generated seed crystals to obtain a composite hydroxide having desired properties, and a step of heat-treating the obtained composite hydroxide to obtain a composite oxide. For details of the method for obtaining a composite oxide, see JP 2003-292322 A, JP 2011-116580 A, etc.

[0036] The composite oxide obtained by the coprecipitation method has a particle size distribution index, D 90 / D 10 is, for example, 3 or less, preferably 2 or less. 50 is, for example, 12 μm or less, preferably 6 μm or less, more preferably 4 μm or less, and is, for example, 1 μm or more, preferably 2 μm or more.

[0037] The content ratio of nickel, cobalt, manganese and aluminum in the composite oxide, Ni / Co / (Mn+Al), can be, for example, 1 / 1 / 1, 6 / 2 / 2, 8 / 1 / 1, or the like.

[0038] The raw material mixture preferably contains a lithium compound in addition to the composite oxide. Examples of the lithium compound include lithium carbonate, lithium hydroxide, and lithium oxide. The particle size of the lithium compound used is D 50The average particle size is, for example, 0.1 μm or more and 100 μm or less, and preferably 2 μm or more and 20 μm or less. The lithium content in the raw material mixture, as Li / (Ni+Co+Mn+Al), can be, for example, 1.0 or more and 1.3 or less, and preferably 1.2 or less. The composite oxide and the lithium compound can be mixed, for example, using a high-speed shear mixer.

[0039] The resulting raw material mixture is heat-treated to obtain lithium transition metal composite oxide particles. The heat treatment temperature is, for example, 700°C to 1100°C. The heat treatment may be performed at a single temperature or at multiple temperatures. When heat-treating at multiple temperatures, for example, a first heat treatment may be performed in the range of 700°C to 925°C, followed by a second heat treatment in the range of 930°C to 1100°C. A third heat treatment may also be additionally performed in the range of 700°C to 850°C.

[0040] The heat treatment time is, for example, 1 to 40 hours, and when heat treatment is performed at multiple temperatures, each time can be 1 to 10 hours. The heat treatment atmosphere may be air or an oxygen atmosphere.

[0041] The heat-treated product may be subjected to crushing, dispersion, classification, etc., thereby obtaining the desired lithium transition metal composite oxide particles.

[0042] Alternatively, the heat-treated product may be subjected to crushing, dispersion, classification, etc., followed by further mixing with a lithium compound to obtain a mixture, followed by additional heat treatment. When a lithium compound is further mixed, the lithium content in the mixture may be, for example, 1.05 or more and 1.3 or less, preferably 1.1 or more and 1.2 or less, as expressed as Li / (Ni+Co+Mn+Al). The temperature of the additional heat treatment may be in the range of 850°C to 1000°C, preferably 870°C to 950°C, and is preferably lower than the heat treatment temperature of the raw material mixture. The heat treatment time for the additional heat treatment may be, for example, 2 hours to 15 hours. After the additional heat treatment, crushing, dispersion, classification, etc. may be performed.

[0043] [Nonaqueous electrolyte secondary battery electrode] The electrode for a non-aqueous electrolyte secondary battery includes a current collector and a positive electrode active material layer disposed on the current collector and containing the positive electrode active material for a non-aqueous electrolyte secondary battery. A non-aqueous electrolyte secondary battery including such an electrode can achieve high durability and high output characteristics.

[0044] Examples of materials for the current collector include aluminum, nickel, and stainless steel. The positive electrode active material layer can be formed by applying a positive electrode mixture obtained by mixing the above-mentioned positive electrode active material, a conductive material, a binder, and the like with a solvent onto the current collector, followed by drying and pressure treatments. Examples of conductive materials include natural graphite, artificial graphite, and acetylene black. Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, and polyamide acrylic resin.

[0045] [Non-aqueous electrolyte secondary battery] The non-aqueous electrolyte secondary battery includes the above-mentioned electrodes for a non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery is configured to include, in addition to the electrodes for a non-aqueous electrolyte secondary battery, a negative electrode for a non-aqueous secondary battery, a non-aqueous electrolyte, a separator, etc. For the negative electrode, non-aqueous electrolyte, separator, etc. of the non-aqueous electrolyte secondary battery, those for non-aqueous electrolyte secondary batteries described in, for example, JP 2002-075367 A, JP 2011-146390 A, JP 2006-12433 A (the disclosures of which are incorporated herein by reference in their entirety) can be appropriately used. [Example]

[0046] Hereinafter, examples of the present invention will be described in detail.

[0047] First, the methods for measuring physical properties in the following Examples and Comparative Examples will be described. D 10 , D 50 and D 90For the above, a laser diffraction particle size distribution analyzer (SALD-3100 manufactured by Shimadzu Corporation) was used to measure the volume-based cumulative particle size distribution, and the particle sizes were determined corresponding to the cumulative size from the smallest diameter side. Average particle size D based on electron microscope observation SEM In the image observed at 1000 to 10,000 times magnification using a scanning electron microscope (SEM), 100 particles whose particle outlines could be confirmed were selected, and the spherical equivalent diameter of the selected particles was calculated using image processing software (ImageJ), and the particle diameter was determined as the arithmetic mean of the obtained spherical equivalent diameters.

[0048] The disorder value of the nickel element (Ni disorder amount) was determined by the X-ray diffraction method according to the following procedure. The obtained lithium transition metal composite oxide particles were subjected to X-ray diffraction spectroscopy using CuKα radiation (tube current 200 mA, tube voltage 45 kV). Based on the obtained X-ray diffraction spectrum, a composition model was established. 1-d Ni d Structural optimization of the lithium transition metal composite oxide, MeO2 (Me is a transition metal other than nickel in the lithium transition metal composite oxide), was performed by Rietveld analysis using Rietan2000 software. The percentage of d calculated as a result of the structural optimization was taken as the amount of Ni disorder.

[0049] Example 1 (Seed generation process) First, 10 kg of water was placed in a reaction tank and stirred until the ammonium ion concentration was adjusted to 1.8% by mass. The temperature inside the tank was set to 25°C, and nitrogen gas was circulated to maintain the oxygen concentration in the reaction tank space at 10% by volume or less. A 25% by mass aqueous solution of sodium hydroxide was added to the water in the reaction tank to adjust the pH value of the solution in the tank to 13.5 or higher. Next, a nickel sulfate solution, a cobalt sulfate solution, and a manganese sulfate solution were mixed together to prepare a mixed aqueous solution in a molar ratio of 1:1:1. The mixed aqueous solution was added until the solute amount reached 4 moles, and seeds were generated while controlling the pH value of the reaction solution to 12.0 or higher with a sodium hydroxide solution.

[0050] (Crystallization process) After the seed generation step, the temperature inside the tank was maintained at 25°C or higher until the end of the crystallization step. A mixed aqueous solution of 1200 moles of solute was also prepared, and was simultaneously added to the reaction tank over a period of 5 hours or more, together with the aqueous ammonia solution, while maintaining the ammonium ion concentration in the solution at 2000 ppm or higher, to prevent new seed generation. During the reaction, the pH value of the reaction solution was controlled to be maintained at 10.5 to 12.0 using a sodium hydroxide solution. Sampling was carried out sequentially during the reaction, and the D of the composite hydroxide particles was measured. 50 The addition was stopped when the particle size reached approximately 4.5 μm. The product was then washed with water, filtered, and dried to obtain composite hydroxide particles. The obtained hydroxide precursor was heat-treated at 300°C for 20 hours in an air atmosphere to obtain composite hydroxide particles with a composition ratio of Ni / Co / Mn=0.33 / 0.33 / 0.33. 10 = 3.4 μm, D 50 = 4.5 μm, D 90 = 6.0 μm, D 90 / D 10 = 1.8.

[0051] (synthesis process) The resulting composite oxide was mixed with lithium carbonate so that Li / (Ni+Co+Mn) = 1.15 to obtain a raw material mixture. The resulting raw material mixture was fired in air at 925°C for 7.5 hours, and then at 1030°C for 6 hours to obtain a sintered body. The resulting sintered body was crushed, dispersed in a resin ball mill for 10 minutes, and then dry-sieved to obtain a powder. The resulting powder was classified into three groups: large, medium, and small using a dry classifier, and the medium particles were separated. The ratio of medium particles after classification to before classification was 46 wt%. From the above, the average particle size D based on electron microscope observation SEM is 3.6 μm, and D 10 = 3.7 μm, D 50 = 5.1 μm, D 90 =6.7μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 1.4, and the ratio D 90 / D 10 is 1.8, the Ni disorder amount is 0.3%, and the composition formula is Li 1.15 Ni 0.33 Co 0.33 Mn 0.33 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 1.

[0052] Example 2 The timing at which the addition of the mixed aqueous solution in the crystallization step in Example 1 was completed was determined based on the D 50 The same conditions were used except that the change was made when the thickness of the film reached approximately 3.0 μm. The film had a composition ratio of Ni / Co / Mn=0.33 / 0.33 / 0.33, and D 10 = 2.2 μm, D 50 = 3.0 μm, D 90 = 4.1 μm, D 90 / D 10 A composite oxide with a Li / (Ni+Co+Mn) ratio of 1.9 was obtained. The composite oxide and lithium carbonate were mixed to obtain a raw material mixture with a Li / (Ni+Co+Mn) ratio of 1.05. The raw material mixture was fired in air at 925°C for 7.5 hours, and then at 1030°C for 6 hours to obtain a sintered body. The sintered body was crushed, dispersed in a resin ball mill for 30 minutes, and then dry-sieved to obtain a powder. The powder was mixed with lithium carbonate to obtain a Li / (Ni+Co+Mn) ratio of 1.17, and then fired in air at 700°C for 10 hours to obtain a sintered body. The sintered body was crushed, dispersed in a resin ball mill for 30 minutes, and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 1.2 μm, and D 10 = 1.4 μm, D 50 = 3.2 μm, D 90 =5.1μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 2.7, and the ratio D 90 / D 10 is 3.6, the Ni disorder amount is 1.7%, and the composition formula is: Li 1.17 Ni 0.33Co 0.33 Mn 0.33 The lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1.

[0053] Example 3 A composite oxide was obtained under the same conditions as in Example 2. The composite oxide and lithium carbonate were mixed so that Li / (Ni+Co+Mn) = 1.05 to obtain a raw material mixture. The resulting raw material mixture was fired in air at 925°C for 7.5 hours, and then at 1030°C for 6 hours to obtain a sintered body. The resulting sintered body was crushed, dispersed in a resin ball mill for 30 minutes, and then dry-sieved to obtain a powder. The resulting powder and lithium carbonate were mixed so that Li / (Ni+Co+Mn) = 1.17, and then fired in air at 900°C for 10 hours to obtain a sintered body. The resulting sintered body was crushed, dispersed in a resin ball mill for 30 minutes, and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 1.2 μm, and D 10 = 1.5 μm, D 50 = 3.3 μm, D 90 =5.1μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 2.8, and D in the particle size distribution 90 / D 10 The ratio is 3.4, the amount of Ni disorder is 0.9%, and the composition formula is Li 1.17 Ni 0.33 Co 0.33 Mn 0.33 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 2.

[0054] Example 4 A composite oxide was obtained under the same conditions as in Example 2. The composite oxide and lithium carbonate were mixed to obtain a raw material mixture such that Li / (Ni+Co+Mn) = 1.05. The raw material mixture was then fired in air at 925°C for 7.5 hours and then at 1030°C for 6 hours to obtain a sintered body. The sintered body was then crushed, dispersed in a resin ball mill for 30 minutes, and dry-sieved to obtain a powder. The powder was then mixed with lithium carbonate to obtain a Li / (Ni+Co+Mn) = 1.17 and fired in air at 900°C for 10 hours to obtain a sintered body. The sintered body was then crushed and dispersed twice using a jet mill, adjusting the feed pressure to 0.4 MPa and the crushing pressure to 0.55 MPa to prevent the primary particles from being crushed. The dispersion was then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 1.4 μm, and D 10 = 1.1 μm, D 50 = 1.9 μm, D 90 =2.8μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 1.4, and D in the particle size distribution 90 / D 10 The ratio is 2.5, the amount of Ni disorder is 1.0%, and the composition formula is Li 1.17 Ni 0.33 Co 0.33 Mn 0.33 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 3.

[0055] Example 5 The timing at which the addition of the mixed aqueous solution in the crystallization step in Example 1 was completed was determined based on the D 50 The same conditions were used except that the thickness was changed when the thickness reached 9.9 μm. The composition ratio of Ni / Co / Mn was 0.33 / 0.33 / 0.33, and D 10 = 8.6 μm, D 50 = 9.9 μm, D 90 = 12.7 μm, D 90 / D 10A composite oxide with a Li / (Ni+Co+Mn) ratio of 1.5 was obtained. The composite oxide and lithium carbonate were mixed to obtain a raw material mixture with a Li / (Ni+Co+Mn) ratio of 1.05. The raw material mixture was fired in air at 925°C for 7.5 hours, and then at 1080°C for 6 hours to obtain a sintered body. The sintered body was crushed, dispersed in a resin ball mill for 10 minutes, and then dry-sieved to obtain a powder. The powder was mixed with lithium carbonate to obtain a Li / (Ni+Co+Mn) ratio of 1.14, and then fired in air at 900°C for 10 hours to obtain a sintered body. The sintered body was crushed, dispersed in a resin ball mill for 10 minutes, and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 6.8 μm, and D 10 = 7.6 μm, D 50 = 10.4 μm, D 90 =16.4μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 1.5, and D in the particle size distribution 90 / D 10 The ratio is 2.2, the amount of Ni disorder is 1.1%, and the composition formula is Li 1.14 Ni 0.33 Co 0.33 Mn 0.33 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 4.

[0056] Example 6 A composite oxide was obtained under the same conditions as in Example 2. The obtained composite oxide and lithium carbonate were mixed so that Li / (Ni+Co+Mn) = 1.05 to obtain a raw material mixture. The obtained raw material mixture was fired in air at 925°C for 7.5 hours, and then at 1030°C for 6 hours to obtain a sintered body. The obtained sintered body was crushed, dispersed in a resin ball mill for 10 minutes, and then dry-sieved to obtain a powder. The obtained powder and lithium carbonate were mixed so that Li / (Ni+Co+Mn) = 1.14, and then fired in air at 900°C for 10 hours to obtain a sintered body. The obtained sintered body was crushed, dispersed in a resin ball mill for 10 minutes, and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 1.25 μm, and D 10 = 2.7 μm, D 50 = 4.5 μm, D 90 = 6.7 μm, mean particle size of primary particles D SEM D against 50 Ratio of D 50 / D SEM is 3.6, and D in the particle size distribution 90 / D 10 The ratio is 2.5, the amount of Ni disorder is 1.0%, and the composition formula is Li 1.14 Ni 0.33 Co 0.33 Mn 0.33 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 5.

[0057] (Comparative Example 1) During the crystallization reaction in Example 1, the seed slurry separately prepared in the seed generation step was added to the reaction tank multiple times, and the timing of finishing adding the mixed aqueous solution was adjusted to the D of the composite hydroxide particles. 50 The same conditions were used except that the change was made when the thickness reached 5.0 μm. The composition ratio of Ni / Co / Mn was 0.33 / 0.33 / 0.33, and D 10 = 2.4 μm, D 50 = 5.0 μm, D 90 = 12.2 μm, D 90 / D 10 A composite oxide with a Li / (Ni+Co+Mn) ratio of 5.1 was obtained. The composite oxide and lithium carbonate were mixed to obtain a raw material mixture such that Li / (Ni+Co+Mn) was 1.05. The raw material mixture was fired in air at 925°C for 7.5 hours, and then at 1030°C for 6 hours to obtain a sintered body. The sintered body was crushed, dispersed in a resin ball mill for 10 minutes, and then dry-sieved to obtain a powder. The powder was mixed with lithium carbonate to obtain a Li / (Ni+Co+Mn) ratio of 1.14, and then fired in air at 900°C for 10 hours to obtain a sintered body. The sintered body was crushed, dispersed in a resin ball mill for 10 minutes, and then dry-sieved to obtain a powder. From the above, the average particle size D SEMis 3.65 μm, and D 10 = 2.5 μm, D 50 = 7.0 μm, D 90 = 13.5 μm, D relative to the average particle size of primary particles 50 Ratio of D 50 / D SEM is 1.9, and D in the particle size distribution 90 / D 10 The ratio is 5.4, the amount of Ni disorder is 0.9%, and the composition formula is Li 1.14 Ni 0.33 Co 0.33 Mn 0.33 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 6.

[0058] (Comparative Example 2) A composite oxide was obtained under the same conditions as in Example 2. The obtained composite oxide and lithium carbonate were mixed so that Li / (Ni+Co+Mn)=1.15 to obtain a raw material mixture. The obtained raw material mixture was fired in air at 950°C for 15 hours to obtain a sintered body. The obtained sintered body was crushed, subjected to a dispersion treatment in a resin ball mill for 10 minutes, and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 0.49 μm, and D 10 = 3.0 μm, D 50 = 4.4 μm, D 90 =7.6μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 9.0, and D in particle size distribution 90 / D 10 The ratio is 2.5, the amount of Ni disorder is 0.9%, and the composition formula is Li 1.15 Ni 0.33 Co 0.33 Mn 0.33 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 7.

[0059] Example 7 The nickel sulfate solution, cobalt sulfate solution, and manganese sulfate solution in Example 1 were changed to a mixed aqueous solution with a molar ratio of 6:2:2, and the timing of finishing the addition of the mixed aqueous solution in the crystallization step was changed to D 50 The same conditions were used except that the Ni / Co / Mn composition ratio was changed when the D 10 = 4.0 μm, D 50 = 4.7 μm, D 90 = 6.2 μm, D 90 / D 10 A composite oxide with a Li / (Ni+Co+Mn) ratio of 1.6 was obtained. The composite oxide and lithium hydroxide monohydrate were mixed to obtain a raw material mixture such that Li / (Ni+Co+Mn) was 1.06. The raw material mixture was fired in an oxygen stream at 870°C for 7 hours, and then at 970°C for 7 hours to obtain a sintered body. The sintered body was crushed and dispersed for 10 minutes in a resin ball mill to obtain a powder. The powder was then added to a rotary blade-type high-speed stirring mixer and 10% by mass of water relative to the powder, and stirred at 2000 rpm to dissolve residual alkali at the grain boundaries and perform a dispersion treatment. The mixture was then dried at 350°C and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 3.7 μm, and D 10 = 3.4 μm, D 50 = 5.4 μm, D 90 =7.7μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 1.5, and D in the particle size distribution 90 / D 10 The ratio is 2.3, the amount of Ni disorder is 1.5%, and the composition formula is Li 1.06 Ni 0.60 Co 0.20 Mn 0.20 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 8.

[0060] Example 8 A composite oxide was obtained under the same conditions as in Example 7. The obtained composite oxide and lithium hydroxide monohydrate were mixed so that Li / (Ni+Co+Mn) = 1.17 to obtain a raw material mixture. The obtained raw material mixture was fired in air at 930°C for 10 hours to obtain a sintered body. The obtained sintered body was crushed and dispersed for 10 minutes in a resin ball mill to obtain a powder. The powder and 10% by mass of water relative to the powder were then added to a rotary blade-type high-speed stirring mixer and stirred at 2000 rpm to dissolve residual alkali at the grain boundaries, thereby performing a dispersion treatment. The mixture was then dried at 350°C and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 3.2 μm, and D 10 = 3.6 μm, D 50 = 6.1 μm, D 90 =9.2μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 1.9, and D in the particle size distribution 90 / D 10 The ratio is 2.6, the amount of Ni disorder is 1.2%, and the composition formula is Li 1.17 Ni 0.60 Co 0.20 Mn 0.20 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 9.

[0061] Example 9 A composite oxide was obtained under the same conditions as in Example 7. The obtained composite oxide and lithium carbonate were mixed so that Li / (Ni+Co+Mn) = 1.17 to obtain a raw material mixture. The obtained raw material mixture was fired in air at 930°C for 10 hours to obtain a sintered body. The obtained sintered body was crushed and dispersed for 10 minutes in a resin ball mill to obtain a powder. The powder and 10% by mass of water relative to the powder were then added to a rotary blade-type high-speed stirring mixer and stirred at 2000 rpm to dissolve residual alkali at the grain boundaries, thereby performing a dispersion treatment. The mixture was then dried at 350°C and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 3.1 μm, and D10 = 3.8 μm, D 50 = 6.3 μm, D 90 =9.6μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 2.0, and D in the particle size distribution 90 / D 10 The ratio is 2.5, the amount of Ni disorder is 2.2%, and the composition formula is Li 1.17 Ni 0.60 Co 0.20 Mn 0.20 The lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1.

[0062] (Comparative Example 3) A composite oxide was obtained under the same conditions as in Example 7. The obtained composite oxide and lithium hydroxide monohydrate were mixed so that Li / (Ni+Co+Mn) = 1.17 to obtain a raw material mixture. The obtained raw material mixture was fired in air at 810°C for 10 hours to obtain a sintered body. The obtained sintered body was crushed, subjected to a dispersion treatment in a resin ball mill for 10 minutes, and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 0.4 μm, and D 10 = 3.2 μm, D 50 = 4.7 μm, D 90 = 7.5 μm, mean particle size of primary particles D SEM D against 50 Ratio of D 50 / D SEM is 11.8, and D in particle size distribution 90 / D 10 The ratio is 2.3, the amount of Ni disorder is 1.0%, and the composition formula is Li 1.17 Ni 0.60 Co 0.20 Mn 0.20 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 10.

[0063] Comparative Example 4 A composite oxide was obtained under the same conditions as in Example 7. The obtained composite oxide and lithium hydroxide monohydrate were mixed so that Li / (Ni+Co+Mn) = 1.17 to obtain a raw material mixture. The obtained raw material mixture was fired in air at 930°C for 10 hours to obtain a sintered body. The obtained sintered body was crushed, subjected to a dispersion treatment in a resin ball mill for 10 minutes, and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 3.2 μm, and D 10 = 4.1 μm, D50 = 9.6 μm, D 90 =23.4μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 3.0, and D in the particle size distribution 90 / D 10 The ratio is 5.7, the amount of Ni disorder is 1.3%, and the composition formula is Li 1.17 Ni 0.60 Co 0.20 Mn 0.20 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 11.

[0064] Example 10 The mixing ratio of the nickel sulfate solution, the cobalt sulfate solution, and the manganese sulfate solution in Example 1 was changed to 8:1:1 in molar ratio to obtain a mixed aqueous solution, and the timing at which the introduction of the mixed aqueous solution in the crystallization step was completed was adjusted to the D of the composite hydroxide particles. 50 The same conditions were used except that the change was made when the thickness reached 4.7 μm. The composition ratio of Ni / Co / Mn was 0.80 / 0.10 / 0.10, and D 10 = 3.4 μm, D 50 = 4.6 μm, D 90 = 6.1 μm, D 90 / D 10A composite oxide with a Li / (Ni+Co+Mn) ratio of 1.8 was obtained. The composite oxide and lithium hydroxide monohydrate were mixed to obtain a raw material mixture with a Li / (Ni+Co+Mn) ratio of 1.04. The raw material mixture was fired in an oxygen stream at 780°C for 5 hours, then at 1000°C for 10 hours, and then at 780°C for another 5 hours to obtain a sintered body. The sintered body was crushed and dispersed in a resin ball mill for 10 minutes to obtain a powder. The powder was then added to a rotary blade-type high-speed stirring mixer and 10% by mass of water relative to the powder, and stirred at 2000 rpm to dissolve residual alkali at the grain boundaries and perform a dispersion treatment. The mixture was then dried at 350°C and dry-sieved to obtain a powder. From the above, the average particle size D SEM is 3.1 μm, and D 10 = 3.7 μm, D 50 = 7.1 μm, D 90 =12.0μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 2.3, and D in the particle size distribution 90 / D 10 The ratio is 3.2, the amount of Ni disorder is 1.7%, and the composition formula is Li 1.04 Ni 0.80 Co 0.10 Mn 0.10 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 12.

[0065] Example 11 A composite oxide was obtained under the same conditions as in Example 10. The obtained composite oxide and lithium hydroxide monohydrate were mixed so that Li / (Ni+Co+Mn) = 1.04 to obtain a raw material mixture. The obtained raw material mixture was fired in an oxygen stream at 780°C for 5 hours and then at 950°C for 10 hours to obtain a sintered body. The obtained sintered body was crushed and dispersed for 10 minutes in a resin ball mill to obtain a powder. The powder and 10% by mass of water relative to the powder were then added to a rotary blade-type high-speed stirring mixer and stirred at 2000 rpm to dissolve residual alkali at the grain boundaries, thereby performing a dispersion treatment. The mixture was then dried at 350°C and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 2.5 μm, and D 10 = 3.0 μm, D 50 = 5.3 μm, D 90 =8.2μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 2.1, and D in particle size distribution 90 / D 10 The ratio is 2.7, the Ni disorder amount is 2.3%, and the composition formula is Li 1.04 Ni 0.80 Co 0.10 Mn 0.10 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 13.

[0066] Example 12 A composite oxide was obtained under the same conditions as in Example 10. The composite oxide obtained and lithium hydroxide monohydrate were mixed so that Li / (Ni+Co+Mn) = 1.04 to obtain a raw material mixture. The resulting raw material mixture was fired in an oxygen stream at 780°C for 5 hours, and then at 1000°C for 10 hours to obtain a sintered body. The resulting sintered body was crushed and dispersed for 10 minutes in a resin ball mill to obtain a powder. The powder and 10% by mass of water relative to the powder were then added to a rotary blade-type high-speed stirring mixer and stirred at 2000 rpm to dissolve residual alkali at the grain boundaries, thereby performing a dispersion treatment. The mixture was then dried at 350°C and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 3.0 μm, and D 10 = 3.7 μm, D 50 = 6.6 μm, D 90 =9.6μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 2.2, and D in the particle size distribution 90 / D 10 The ratio is 2.6, the amount of Ni disorder is 4.2%, and the composition formula is Li 1.04 Ni 0.80 Co0.10 Mn 0.10 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 14.

[0067] (Comparative Example 5) The mixed aqueous solution in Example 1 was changed to a mixed solution of nickel sulfate solution and cobalt sulfate solution in a molar ratio of 80:15, and the timing of finishing the addition of the mixed solution in the crystallization step was adjusted to the D 50 The same conditions were used except that the thickness was changed when the thickness reached 4.6 μm. The composition ratio of Ni / Co was 0.80 / 0.15, and D 10 = 3.4 μm, D 50 = 4.6 μm, D 90 = 6.1 μm, D 90 / D 10 A composite oxide with a Ni / Co / Al ratio of 0.80 / 0.15 / 0.05 was obtained. The composite oxide and aluminum oxide were mixed to a composition ratio of Ni / Co / Al of 0.80 / 0.15 / 0.05, and lithium hydroxide monohydrate was mixed to a composition ratio of Li / (Ni+Co+Al) of 1.04, to obtain a raw material mixture. The raw material mixture was fired in air at 710°C for 5 hours to obtain a sintered body. The sintered body was crushed, dispersed in a resin ball mill for 10 minutes, and then dry-sieved to obtain a powder. From the above, the average particle size D SEM is 0.3 μm, and D 10 = 4.5 μm, D 50 = 5.8 μm, D 90 =7.4μm, average particle size D SEM D against 50 Ratio of D 50 / D SEM is 19.3, and D in particle size distribution 90 / D 10 The ratio is 1.6, the amount of Ni disorder is 1.0%, and the composition formula is Li 1.04 Ni 0.80 Co 0.15 MnAl 0.05 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 15.

[0068] [evaluation] Using the lithium transition metal composite oxide obtained above as the positive electrode active material, a battery for evaluation was fabricated in the following manner.

[0069] (Preparation of positive electrode) A positive electrode mixture was prepared by dispersing 96 parts by weight of the positive electrode active material, 3 parts by weight of acetylene black, and 1 part by weight of polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone (NMP). The resulting positive electrode mixture was applied to an aluminum foil current collector, dried, compressed in a roll press, and then cut to a specified size to fabricate a positive electrode.

[0070] (Preparation of negative electrode) A negative electrode mixture was prepared by dispersing 96 parts by weight of the negative electrode active material and 4 parts by weight of PVDF in NMP. The resulting negative electrode mixture was applied to a copper foil current collector, dried, and then compression-molded using a roll press. The negative electrode was then cut to a predetermined size to produce a negative electrode.

[0071] (Preparation of evaluation battery) After attaching lead electrodes to the positive and negative current collectors, a separator was placed between the positive and negative electrodes, and the resulting assembly was housed in a bag-shaped laminate pack. This was then vacuum dried at 65°C to remove moisture adsorbed to each component. An electrolyte solution was then injected into the laminate pack under an argon atmosphere and sealed. The resulting battery was placed in a thermostatic chamber at 25°C and aged using a weak current. The electrolyte used was a mixture of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) in a volume ratio of 3:7, with lithium hexafluorophosphate (LiPF6) dissolved to a concentration of 1 mol / L.

[0072] (Charge / discharge test) The test batteries obtained above were evaluated for power density and durability as follows. (power density) The test battery was discharged to a 50% SOC and held at 25°C for 2 hours. The battery was then discharged at a constant current from the 50% SOC state, and the DC resistance was measured at 10 seconds to calculate the power density. The lower limit voltage for discharge was set to 2.7V.

[0073] (durability) A charge-discharge cycle test was carried out at a temperature of 60°C with a current density of 2.0 mA / cm. 2 The battery was charged to a maximum charging voltage of 4.2 V at a constant current of 2.0 mA / cm 2 A total of 1000 such cycles were performed. The discharge capacity was measured for each cycle, and the durability (%) was calculated using the formula: (discharge capacity at the 1000th cycle / discharge capacity at the 1st cycle) × 100. The evaluation results are summarized in Table 1.

[0074] [Table 1]

[0075] As shown in Table 1, the positive electrode active materials of Examples 1 to 12 exhibit superior power density and durability compared to Comparative Examples 1 to 5. Among them, when the range of x is 0.3≦x<0.6, Examples 1, 3, and 5 exhibit superior power density, and Example 4 exhibits particularly superior power density. When the range of x is 0.6≦x<0.8, Example 8 exhibits superior power density, and Example 7 exhibits particularly superior power density. When the range of x is 0.8≦x<0.95, Example 10 exhibits superior power density, and Example 11 exhibits particularly superior power density. [Industrial Applicability]

[0076] A non-aqueous electrolyte secondary battery including an electrode for a non-aqueous electrolyte secondary battery using the positive electrode active material of the present disclosure has excellent power density and durability, and can therefore be suitably used in large power equipment such as electric vehicles.

Claims

1. 50% particle size D in cumulative particle size distribution based on volume ５０ Average particle size D based on electron microscope observation ＳＥＭ Ratio D to ５０ / D ＳＥＭ is 1 or more and 4 or less, and the lithium transition metal composite oxide has a layered structure, the ratio of the number of moles of nickel to the total number of moles of metals other than lithium in the composition of the lithium transition metal composite oxide is 0.6 or more and less than 0.8; A positive electrode active material that satisfies at least one of the following aspects: (i) The lithium transition metal composite oxide has a nickel element disorder of 2.0% or less as determined by X-ray diffraction. (ii) 90% particle size D in the cumulative particle size distribution based on volume ９０ 10% particle size D in the cumulative particle size distribution based on volume １０ Ratio D to ９０ / D １０ is 2.3 or less. (iii) the D ５０ is 1 μm or more and 5.5 μm or less.

2. 2. The positive electrode active material according to claim 1, wherein the lithium transition metal composite oxide contains cobalt in its composition, and the ratio of the number of moles of cobalt to the total number of moles of metals other than lithium is 0.2 or less.

3. 3. The positive electrode active material according to claim 1, wherein the lithium transition metal composite oxide contains at least one of manganese and aluminum in its composition, and the ratio of the total number of moles of manganese and aluminum to the total number of moles of metals other than lithium is 0.2 or less.

4. 4. The positive electrode active material according to claim 1, wherein the lithium transition metal composite oxide has a ratio of the number of moles of lithium to the total number of moles of metals other than lithium of 1.0 or more and 1.3 or less.

5. 5. The positive electrode active material according to claim 1, wherein the lithium transition metal composite oxide has a ratio of the number of moles of oxygen atoms to the total number of moles of metals other than lithium of 1.9 or more and 2.1 or less.

6. The above D ５０ The above D ＳＥＭ Ratio D to ５０ / D ＳＥＭ The positive electrode active material according to claim 1 , wherein R is 1 or more and 3 or less.

7. The above D ９０ is 2.8 μm or more and 16.4 μm or less, The above D １０ The positive electrode active material according to claim 1 , wherein the average particle size is 1.1 μm or more and 7.6 μm or less.

8. An electrode for a non-aqueous electrolyte secondary battery, comprising: a current collector; and a positive electrode active material layer disposed on the current collector and containing the positive electrode active material according to claim 1 .

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