Positive electrode active material for non-aqueous electrolyte secondary batteries and method for producing the same

Abstract

To provide a positive electrode active material for a non-aqueous electrolyte secondary battery that is excellent in output characteristics in a non-aqueous electrolyte secondary battery.SOLUTION: A positive electrode active material for a non-aqueous electrolyte secondary battery includes particles including lithium transition metal composite oxide having a layer structure, and an aluminum compound having an average particle diameter of 1 nm or more and less than 500 nm. The positive electrode active material for a non-aqueous electrolyte secondary battery has a volume average particle diameter of 1 μm or more and 8 μm or less, a specific surface area of 1.4 m2 / g or more, and an angle of difference of 6° or more, which is obtained by subtracting the angle of fall from the angle of repose measured by a powder characteristic measuring instrument.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a positive electrode active material for non-aqueous electrolyte secondary batteries and a method for producing the same. [Background technology]

[0002] High power output characteristics are required for positive electrode active materials in non-aqueous electrolyte secondary batteries used in large power equipment such as electric vehicles. To obtain high power output characteristics, positive electrode active materials having a structure of secondary particles formed by the aggregation of many primary particles are considered effective. In this regard, lithium-containing transition metal composite oxides in which the ratio of lithium to oxygen differs between the surface and the interior of the secondary particles have been proposed (see, for example, Patent Document 1). Furthermore, lithium transition metal oxides with an alumina coating layer on the surface have also been proposed (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-99410 [Patent Document 2] Special Publication No. 2016-538694 [Overview of the project] [Problems that the invention aims to solve]

[0004] One aspect of this disclosure aims to provide a positive electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the same, which exhibits excellent output characteristics in a non-aqueous electrolyte secondary battery. [Means for solving the problem]

[0005] The first embodiment is a positive electrode active material for a non-aqueous electrolyte secondary battery comprising particles containing a lithium transition metal composite oxide and an aluminum compound having an average particle size of 1 nm or more and less than 500 nm. The positive electrode active material for the non-aqueous electrolyte secondary battery has a volume average particle size of 1 μm or more and 8 μm or less, and a specific surface area of ​​1.4 m². 2 It is 1 / g or more.

[0006] The second embodiment is a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: preparing particles containing a lithium transition metal composite oxide; and mixing the particles containing the lithium transition metal composite oxide with an aluminum compound having an average particle size of 1 nm or more and less than 500 nm to obtain a mixture. The particles containing the lithium transition metal composite oxide have a volume average particle size of 1 μm or more and 8 μm or less, and a specific surface area of ​​1.3 m². 2 It is 1 / g or more. [Effects of the Invention]

[0007] According to one aspect of this disclosure, it is possible to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that has excellent output characteristics in a non-aqueous electrolyte secondary battery, and a method for producing the same. [Brief explanation of the drawing]

[0008] [Figure 1] This is an example of a scanning electron microscope (SEM) image of the positive electrode active material according to Example 1. [Figure 2] This is an example of an SEM image of the positive electrode active material related to Reference Example 1. [Modes for carrying out the invention]

[0009] In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved. Furthermore, the content of each component in a composition refers to the total amount of multiple substances present in the composition, unless otherwise specified, if multiple substances corresponding to each component exist in the composition. Moreover, the upper and lower limits of the numerical ranges described herein can be arbitrarily selected and combined. Embodiments of the present invention will be described in detail below. However, the embodiments shown below are illustrative examples of positive electrode active materials for non-aqueous electrolyte secondary batteries and methods for producing the same, for embodying the technical concept of the present invention, and the present invention is not limited to the positive electrode active materials for non-aqueous electrolyte secondary batteries and methods for producing the same shown below.

[0010] Cathode active material for non-aqueous electrolyte secondary batteries The positive electrode active material for non-aqueous electrolyte secondary batteries contains particles containing lithium transition metal composite oxide and an aluminum compound with an average particle size of 1 nm or more and less than 500 nm, with a volume average particle size of 1 μm or more and 8 μm or less, and a specific surface area of ​​1.4 m². 2 The concentration is 1 / g or more. The positive electrode active material for non-aqueous electrolyte secondary batteries can be efficiently manufactured, for example, by the manufacturing method for the positive electrode active material for non-aqueous electrolyte secondary batteries described later.

[0011] The positive electrode active material for non-aqueous electrolyte secondary batteries (hereinafter also simply referred to as "positive electrode active material") has a relatively small particle size and a large specific surface area, which allows it to achieve excellent output characteristics, such as reduced DC resistance in low-temperature environments, when used in the construction of a non-aqueous electrolyte secondary battery. Furthermore, because it contains an aluminum compound, it exhibits excellent flowability as a powder despite its large specific surface area, resulting in good process flowability and excellent productivity in the manufacturing process. This can be attributed, for example, to the increased steric hindrance between particles caused by the inclusion of an aluminum compound, which suppresses aggregation.

[0012] From the viewpoint of output characteristics in a non-aqueous electrolyte secondary battery, the positive electrode active material may have a volume-average particle size of 1 μm or more and 8 μm or less, preferably 1.2 μm or more, 1.5 μm or more, 2 μm or more, 2.5 μm or more, 3 μm or more, or 3.5 μm or more, and preferably 6 μm or less, 5 μm or less, 4.7 μm or less, or 4.5 μm or less. In one embodiment, the volume-average particle size may be 2 μm or more and 6 μm or less. The volume-average particle size of the positive electrode active material is determined as the particle size corresponding to 50% of the volume accumulation from the small diameter side in the volume-based cumulative particle size distribution. The volume-based cumulative particle size distribution is measured, for example, by a laser diffraction particle size distribution analyzer.

[0013] From the perspective of output characteristics in non-aqueous electrolyte secondary batteries, the positive electrode active material should have a specific surface area of ​​1.4 m² as measured by the BET method. 2 It may be 1.7 m or more, preferably 1.7 m 2 / g or more, 1.9m2 2.0 m / g or more 2 2.5 m / g or more, or 2 it may be 4.0 m / g or more. Further, the specific surface area may be, for example, 4.0 m 2 / g or less, preferably 3.8 m 2 / g or less, 3.3 m 2 / g or less, or 3.0 m 2 / g or less. In one embodiment, the specific surface area of the positive electrode active material may be, for example, 1.7 m 2 / g or more and 3.8 m 2 / g or less, preferably 1.7 m 2 / g or more and 3.3 m 2 / g or less, or 1.9 m 2 / g or more and 3.0 m 2 / g or less. The specific surface area measured by the BET method is measured by the one-point method using nitrogen gas based on the BET (Brunauer Emmett Teller) theory.

[0014] From the viewpoint of fluidity, the angle of repose of the positive electrode active material as a powder may be, for example, less than 70°, preferably 68° or less, or 67° or less. The lower limit of the angle of repose may be, for example, 50° or more, or 60° or more. Further, from the viewpoint of fluidity, the angle of collapse of the positive electrode active material as a powder may be, for example, less than 68°, preferably 66° or less, or 61° or less. The lower limit of the angle of collapse may be, for example, 40° or more, or 45° or more. Furthermore, from the viewpoint of fluidity, the difference angle obtained by subtracting the angle of collapse from the angle of repose of the positive electrode active material may be, for example, 3° or more, preferably 6° or more, or 8° or more. The upper limit of the difference angle may be, for example, 25° or less, or 20° or less.

[0015] Here, "angle of repose (θ1)" refers to the inclination angle when the positive electrode active material powder is deposited on the measurement table. A common method for depositing the positive electrode active material powder is the injection method. "Disintegration angle (θ2)" refers to the inclination angle measured after applying a predetermined impact force to the measurement table following the measurement of the angle of repose (θ1). For measuring the angle of repose (θ1) and the disintegration angle (θ2), a powder properties analyzer (e.g., Powder Tester®; manufactured by Hosokawa Micron Corporation) can be used.

[0016] The specific methods for measuring the angle of repose (θ1) and the angle of collapse (θ2) are as follows.

[0017] [Method for measuring the angle of repose] The powder to be measured was dropped from a funnel of a predetermined height onto a horizontal substrate (measuring table). The base angle was calculated from the diameter and height of the resulting conical deposit, and this base angle was defined as the angle of repose. Generally, the measurement can be performed in accordance with JIS-R9301-2-2.

[0018] [Method for measuring collapse angle] The angle of repose of a cone-shaped sediment is measured, and then the cone-shaped sediment is collapsed by applying a predetermined impact three times to a measuring table. The base angle is then calculated from the diameter and height of the cone-shaped sediment, and this base angle is defined as the collapse angle. Here, the predetermined impact is the impact adopted by the measuring device used, and is specific to that device and constant.

[0019] [Method for measuring the difference angle] The angle difference was calculated using the following formula. Angle of repose (°) - Angle of collapse (°) = Difference angle (°)

[0020] Lithium transition metal composite oxides The lithium transition metal composite oxide particles constituting the positive electrode active material (hereinafter also simply referred to as "lithium transition metal composite oxide particles") may be, for example, secondary particles formed by the aggregation of multiple primary particles containing lithium transition metal composite oxide. The output characteristics of a non-aqueous electrolyte secondary battery constructed using a positive electrode active material containing lithium transition metal composite oxide particles are improved when these particles have a predetermined volume-average particle size and specific surface area. Therefore, in one embodiment, the positive electrode active material may consist of lithium transition metal composite oxide particles having a predetermined volume-average particle size and specific surface area.

[0021] The volume-average particle size (D50) of the lithium transition metal composite oxide particles may be, for example, 1 μm or more and 8 μm or less, preferably 1.2 μm or more, 1.5 μm or more, 2 μm or more, 2.5 μm or more, 3 μm or more, or 3.5 μm or more, and also preferably 6 μm or less, 5 μm or less, 4.7 μm or less, or 4.5 μm or less. In one embodiment, the volume-average particle size may be 2 μm or more and 6 μm or less. When the volume-average particle size of the lithium transition metal composite oxide particles is within the above range, the fluidity as a positive electrode active material is good, and the output characteristics may be further improved when constructing a non-aqueous electrolyte secondary battery. Here, the volume-average particle size of the lithium transition metal composite oxide particles is determined as the particle size corresponding to 50% of the volume accumulation from the small diameter side in the volume-based cumulative particle size distribution, similar to the positive electrode active material.

[0022] The positive electrode active material consists of lithium transition metal composite oxide particles and aluminum compound nanoparticles. Therefore, the volume-average particle size of the lithium transition metal composite oxide particles can be approximately the same as the volume-average particle size of the positive electrode active material.

[0023] Lithium transition metal composite oxide particles are formed by the aggregation of multiple primary particles. The average particle size D is determined based on electron microscopy observation of the primary particles. SEM For example, the particle size is 0.1 μm or more and 1.5 μm or less, preferably 0.12 μm or more, and more preferably 0.15 μm or more. Also, the average particle size D based on electron microscope observation of primary particles. SEMThe particle size is preferably 1.2 μm or less, and more preferably 1.0 μm or less. When the average particle size based on electron microscope observation of primary particles is within the above range, the output may be improved when constructing a non-aqueous electrolyte secondary battery.

[0024] The specific surface area of ​​lithium transition metal composite oxide particles, as measured by the BET method, is 1.3 m² from the viewpoint of output characteristics in non-aqueous electrolyte secondary batteries. 2 It may be 1.5 m or more, preferably 1.5 m 2 / g or more, 1.7m 2 / g or more, or 1.9m 2 It may be greater than or equal to / g. Also, the specific surface area is, for example, 3.9m². 2 It may be less than or equal to / g, preferably 3.5m 2 / g or less, 3.3m 2 / g or less, or 2.8m 2 It may be less than or equal to / g. When the specific surface area of ​​the lithium transition metal composite oxide particles is within the above range, the output characteristics may be further improved, and the effect of improving fluidity when aluminum compounds are added may be greater.

[0025] The positive electrode active material consists of secondary particles, which are particles containing lithium transition metal composite oxides, and nanoparticles of aluminum compounds. Therefore, the specific surface area of ​​the lithium transition metal composite oxide particles may be approximately the same as the specific surface area of ​​the positive electrode active material, or it may be between 80% and 110% of the specific surface area of ​​the positive electrode active material.

[0026] Lithium transition metal composite oxide particles are secondary particles formed by the aggregation of multiple primary particles and may have voids within them. This makes it easy to achieve a predetermined specific surface area, which may further improve the output characteristics in non-aqueous electrolyte secondary batteries. The presence of voids within lithium transition metal composite oxide particles can be evaluated, for example, from their cross-sectional image. Cross-sectional images of particles can be obtained, for example, using a scanning electron microscope (SEM).

[0027] When lithium transition metal composite oxide particles have internal voids, the degree of these voids can be evaluated, for example, by the porosity. Porosity is an indicator of the proportion of space formed inside secondary particles composed of lithium transition metal composite oxides, and is measured by cross-sectional observation of the secondary particles. The porosity of lithium transition metal composite oxide particles may be, for example, 15% to 50% or 20% to 50%. By controlling the porosity within this range, even with the same specific surface area, the contact area with the electrolyte can be increased, making it possible to obtain a positive electrode active material with superior output characteristics. This results in a secondary battery with improved power density per unit volume. The porosity of lithium transition metal composite oxide particles is preferably 25% to 45%, 27% or more, 29% or more, or 30% or more, 40% or less, or 38% or less.

[0028] The porosity of secondary particles can be measured by observing an arbitrary cross-section of the secondary particles using a scanning electron microscope (SEM) and performing image analysis. Specifically, multiple secondary particles are embedded in resin or the like, and cross-sectional samples are prepared by processes such as cross-section polishing, making it possible to observe the cross-section of the secondary particles using a scanning electron microscope. Then, 100 secondary particles are arbitrarily selected whose cross-sectional size is within ±1 μm of the volume-average particle size (D50) of the lithium transition metal composite oxide particles. For each secondary particle, image analysis software (e.g., HALCON; MVTec) is used to detect the voids (spaces) within the secondary particle in white and the dense areas within the contour of the secondary particle in black. The total area of ​​the white areas and the total area of ​​the black areas of the 100 selected secondary particles are calculated, and the porosity can be calculated by calculating the ratio of the area of ​​the space to the cross-sectional area of ​​the secondary particle [white area / (white area + black area)]. The porosity of the secondary particles of the positive electrode active material for non-aqueous electrolyte secondary batteries containing aluminum compounds is equivalent to that of the secondary particles (matrix material) made of lithium transition metal composite oxides.

[0029] The lithium transition metal composite oxide constituting the positive electrode active material may, for example, contain lithium (Li) and nickel (Ni) in its composition and have a layered structure. The lithium transition metal composite oxide may contain at least lithium (Li) and nickel (Ni), and may further contain cobalt (Co). Furthermore, the lithium transition metal composite oxide may further contain at least one first metallic element selected from the group consisting of aluminum (Al) and manganese (Mn). Furthermore, lithium transition metal composite oxides may further contain, in addition to these, at least one secondary metallic element selected from the group consisting of magnesium (Mg), calcium (Ca), titanium (Ti), zirconium (Zr), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), iron (Fe), copper (Cu), silicon (Si), tin (Sn), bismuth (Bi), gallium (Ga), yttrium (Y), samarium (Sm), erbium (Er), cerium (Ce), neodymium (Nd), lanthanum (La), cadmium (Cd), and lutetium (Lu). The secondary metallic element may be at least one selected from the group consisting of zirconium (Zr), titanium (Ti), magnesium (Mg), tantalum (Ta), niobium (Nb), molybdenum (Mo), and tungsten (W).

[0030] In lithium transition metal composite oxides, the ratio of moles of nickel to the total number of moles of metal elements other than lithium may be greater than 0, preferably 0.33 or higher. The ratio of moles of nickel to the total number of moles of metal elements other than lithium may be 0.4 or higher, or 0.45 or higher. Furthermore, the ratio of moles of nickel to the total number of moles of metal elements other than lithium may be less than 1, preferably 0.95 or lower, 0.8 or lower, or 0.6 or lower. When the ratio of moles of nickel is within the above range, it is possible to achieve both high-voltage charge / discharge capacity and cycle characteristics in a non-aqueous electrolyte secondary battery.

[0031] When the lithium transition metal composite oxide contains cobalt, the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium may be, for example, greater than 0, preferably 0.01, more preferably 0.02 or more, 0.05 or more, 0.1 or more, or 0.15 or more. Furthermore, the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium may be less than 1, preferably 0.6 or less, 0.4 or less, or 0.35 or less. Also, the ratio of the number of moles of cobalt to the total number of moles of metal elements other than lithium may be 0.33 or less, 0.3 or less, or 0.25 or less. When the ratio of the number of moles of cobalt is within the above range, sufficient charge and discharge capacity at high voltage can be achieved in a non-aqueous electrolyte secondary battery.

[0032] When a lithium transition metal composite oxide contains at least one of manganese and aluminum, the ratio of the total number of moles of manganese and aluminum to the total number of moles of metal elements other than lithium may be, for example, greater than 0, preferably 0.01 or more, more preferably 0.05 or more, 0.1 or more, or 0.15 or more. Furthermore, the ratio of the total number of moles of manganese and aluminum to the total number of moles of metal elements other than lithium may be, for example, 0.6 or less, preferably 0.35 or less. Also, the ratio of the total number of moles of manganese and aluminum to the total number of moles of metal elements other than lithium may be 0.33 or less, or 0.3 or less. When the ratio of the total number of moles of manganese and aluminum is within the above-mentioned range, both charge / discharge capacity and safety can be achieved in a non-aqueous electrolyte secondary battery.

[0033] In lithium transition metal composite oxides, the ratio of moles of lithium to the total number of moles of metal elements other than lithium may be, for example, 0.95 or more, preferably 1.0 or more, 1.03 or more, or 1.05 or more. Alternatively, the ratio of moles of lithium to the total number of moles of metal elements other than lithium may be, for example, 1.5 or less, preferably 1.3 or less, 1.25 or less, or 1.2 or less. When the ratio of moles of lithium is 0.95 or more, the interfacial resistance generated at the interface between the positive electrode surface and the non-aqueous electrolyte in a non-aqueous electrolyte secondary battery using a positive electrode active material containing the resulting lithium transition metal composite oxide tends to improve the output of the non-aqueous electrolyte secondary battery. On the other hand, when the ratio of moles of lithium is 1.5 or less, the initial discharge capacity tends to improve when the positive electrode active material is used as the positive electrode of a non-aqueous electrolyte secondary battery.

[0034] When the lithium transition metal composite oxide contains nickel, cobalt, and manganese, the ratio of moles of nickel, cobalt, and manganese may be, for example, nickel:cobalt:manganese = (0.33 to 0.95):(0.02 to 0.6):(0.01 to 0.35), preferably (0.33 to 0.8):(0.05 to 0.35):(0.05 to 0.35). When the lithium transition metal composite oxide contains nickel, cobalt, manganese, and aluminum, the ratio of moles of nickel, cobalt, and (manganese + aluminum) may be, for example, nickel:cobalt:(manganese + aluminum) = (0.33 to 0.95):(0.02 to 0.6):(0.01 to 0.35), preferably (0.33 to 0.8):(0.05 to 0.35):(0.05 to 0.35).

[0035] When the lithium transition metal composite oxide contains at least one second metal element, the ratio of the total molar number of the second metal element to the total molar number of the metal elements other than lithium may be, for example, greater than 0, preferably 0.001 or more, or 0.003 or more. Also, the ratio of the total molar number of the second metal element to the total molar number of the metal elements other than lithium may be, for example, 0.05 or less, preferably 0.02 or less, or 0.015 or less. When particularly containing tungsten as the second metal element, by setting the ratio of the molar number of tungsten to the total molar number of the metal elements other than lithium to be 0.05 or more and 0.15 or less, there is a tendency to form particles with a higher porosity.

[0036] The lithium transition metal composite oxide may have a composition represented by the following formula (1), for example. The lithium transition metal composite oxide may have a layered structure and may have a hexagonal crystal structure. Li p Ni x Co y M 1 z M 2 w O 2+α (1)

[0037] Here, p, x, y, z, w, and α satisfy 1.0 ≤ p ≤ 1.3, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ w ≤ 0.05, x + y + z + w = 1, and -0.1 ≤ α ≤ 0.1. x, y, z, and w may satisfy 0 < x < 1, 0 ≤ y ≤ 0.6, 0 ≤ z ≤ 0.6, and 0 ≤ w ≤ 0.05, may satisfy 0.33 ≤ x ≤ 0.95, 0.01 ≤ y ≤ 0.6, 0 ≤ z ≤ 0.35, and 0 ≤ w ≤ 0.05, and may satisfy 0.33 ≤ x ≤ 0.8, 0.02 ≤ y ≤ 0.35, 0.05 ≤ z ≤ 0.35, and 0 ≤ w ≤ 0.02.

[0038] M 1 may represent at least one of Mn and Al. M 2This may represent at least one selected from the group consisting of Mg, Ca, Ti, Zr, Nb, Ta, Cr, Mo, W, Fe, Cu, Si, Sn, Bi, Ga, Y, Sm, Er, Ce, Nd, La, Cd, and Lu, and may represent at least one selected from the group consisting of Zr, Ti, Mg, Ta, Nb, Mo, and W.

[0039] The content of lithium transition metal composite oxide particles in the positive electrode active material may be, for example, 80% by mass or more, preferably 90% by mass or more, or 95% by mass or more. The upper limit of the content of lithium transition metal composite oxide particles in the positive electrode active material may be, for example, less than 100% by mass, preferably 99% by mass or less, or 98% by mass or less.

[0040] Aluminum compounds The positive electrode active material may contain an aluminum compound in addition to lithium transition metal composite oxide particles. The aluminum compound in the positive electrode active material may exist independently of the lithium transition metal composite oxide particles, or at least a portion of the aluminum compound particles may be attached to the surface of the lithium transition metal composite oxide particles. From the viewpoint of the fluidity of the positive electrode active material as a powder, the attachment of the aluminum compound particles to the surface of the lithium transition metal composite oxide particles is preferably by physical adsorption. Physical adsorption may be by van der Waals forces, for example. Furthermore, from the viewpoint of the fluidity of the positive electrode active material as a powder, it is preferable that the attachment of the aluminum compound particles to the surface of the lithium transition metal composite oxide particles does not involve a chemical reaction between the aluminum compound and the lithium transition metal composite oxide. The chemical reaction between the aluminum compound and the lithium transition metal composite oxide is promoted by, for example, heat treatment or mechanochemical treatment of a mixture of the aluminum compound and the lithium transition metal composite oxide. Therefore, the positive electrode active material may be an unheat-treated product containing the aluminum compound and the lithium transition metal composite oxide. Here, "non-heat-treated material" means a mixture containing an aluminum compound and a lithium transition metal composite oxide that is obtained without heat treatment at a temperature of 300°C or higher, or 200°C or higher, for, for, for 2 hours or more, or for 30 minutes or more. Because the positive electrode active material is a non-heat-treated material, the effect of improving fluidity by mixing in an aluminum compound may be more pronounced.

[0041] Examples of aluminum compounds constituting the positive electrode active material include aluminum oxide (e.g., Al2O3), aluminum hydroxide, aluminum chloride, aluminum nitrate, and aluminum nitride, and it is preferable to include at least one selected from the group consisting of these. Including a specific aluminum compound may further improve the fluidity of the positive electrode active material as a powder while minimizing the influence on the output characteristics and the viscosity of the slurry containing the positive electrode active material.

[0042] The average particle size of the aluminum compound may be, for example, 1 nm or more and less than 500 nm, preferably 2 nm or more, 5 nm or more, or 10 nm or more, from the viewpoint of the fluidity of the positive electrode active material as a powder. Alternatively, the average particle size may be 300 nm or less, 100 nm or less, or 50 nm or less. When the average particle size of the aluminum compound is within the above range, process fluidity tends to be improved more efficiently.

[0043] From the viewpoint of output characteristics in a non-aqueous electrolyte secondary battery, the content of the aluminum compound in the positive electrode active material may be, for example, 2 mol% or less, preferably 1.8 mol% or less, or 1.5 mol% or less, per mole of lithium transition metal composite oxide. Furthermore, from the viewpoint of the fluidity of the positive electrode active material as a powder, the content of the aluminum compound in the positive electrode active material may be, for example, 0.01 mol% or more, preferably 0.05 mol% or more, or 0.1 mol% or more, per mole of lithium transition metal composite oxide. In one embodiment, the content of the aluminum compound in the positive electrode active material may be 0.01 mol% or more and 2 mol% or less per mole of lithium transition metal composite oxide.

[0044] Tungsten compounds The positive electrode active material may further contain a tungsten compound, or it may contain particles of the tungsten compound. The inclusion of a tungsten compound in the positive electrode active material can, for example, effectively suppress the increase in viscosity of the slurry containing the positive electrode active material. In particular, the volume-average particle size of the lithium transition metal composite oxide particles is 4.7 μm or less, and the specific surface area is 1.3 m². 2When the concentration is greater than or equal to / g, the effect of suppressing viscosity increase tends to be greater. The tungsten compound in the positive electrode active material may exist independently of the lithium transition metal composite oxide particles, or at least a portion of the tungsten compound may be attached to the surface of the lithium transition metal composite oxide particles. Alternatively, at least a portion of the tungsten compound may react with lithium and be included in the positive electrode active material in the form of lithium tungstate. From the viewpoint of the fluidity of the slurry containing the positive electrode active material, physical adsorption is preferred for the attachment of the tungsten compound to the surface of the lithium transition metal composite oxide particles.

[0045] As the tungsten compound constituting the positive electrode active material, tungsten oxide (e.g., WO3) is preferred. In some cases, including a specific tungsten compound can more effectively suppress the increase in viscosity of the slurry containing the positive electrode active material.

[0046] The average particle size of the tungsten compound may be, for example, 0.05 μm to 2 μm, preferably 0.25 μm or more, or 0.50 μm or more, from the viewpoint of suppressing the viscosity increase of the slurry containing the positive electrode active material. The average particle size may also preferably be 1.7 μm or less, or 1.5 μm or less. Here, the average particle size of the tungsten compound is measured as the volume-average particle size using a laser diffraction particle size distribution analyzer (SALD-3100, manufactured by Shimadzu Corporation).

[0047] The tungsten compound content in the positive electrode active material may be, for example, 0.1 mol% to 2 mol% per mole of lithium transition metal composite oxide. From the viewpoint of output characteristics in a non-aqueous electrolyte secondary battery, the tungsten compound content in the positive electrode active material may preferably be 1.8 mol% or less, or 1.5 mol% or less, per mole of lithium transition metal composite oxide. Furthermore, from the viewpoint of suppressing viscosity increase of the slurry containing the positive electrode active material, the tungsten compound content in the positive electrode active material may preferably be 0.2 mol% or more, or 0.3 mol% or more, per mole of lithium transition metal composite oxide.

[0048] metal compounds In one embodiment, the positive electrode active material may contain other metal compounds instead of aluminum compounds. Examples of other metal compounds include tungsten compounds, titanium compounds, zirconium compounds, silicon compounds, magnesium compounds, etc., and may contain at least one selected from the group consisting of these. From the viewpoint of balancing fluidity and output characteristics, it is preferable that the other metal compound contains at least one selected from the group consisting of tungsten compounds, titanium compounds, silicon compounds, and magnesium compounds, and it is more preferable to include at least one tungsten compound when considering the slurry viscosity during positive electrode fabrication. The other metal compound may be, for example, an oxide, hydroxide, nitride, etc. The average particle size of the other metal compound may be, for example, 0.01 μm or more and 2 μm or less. The content of the other metal compound in the positive electrode active material may be, for example, 0.1 mol% or more and 2 mol% or less per mole of lithium transition metal composite oxide.

[0049] Method for producing positive electrode active material for non-aqueous electrolyte secondary batteries A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery may include a preparation step of preparing particles containing a lithium transition metal composite oxide, and a mixing step of mixing the particles containing the lithium transition metal composite oxide with an aluminum compound having an average particle size of 1 nm or more and less than 500 nm to obtain a mixture. The prepared particles containing the lithium transition metal composite oxide may have a volume average particle size of 1 μm or more and 8 μm or less, and a specific surface area of ​​1.3 m². 2 It may be 1 / g or more.

[0050] Preparation process In the preparation step, particles containing the desired lithium transition metal composite oxide (hereinafter also simply referred to as "lithium transition metal composite oxide particles") are prepared. The lithium transition metal composite oxide particles may be prepared by purchasing or other means, or by manufacturing them using methods for producing lithium transition metal composite oxides as described later. The details and preferred embodiments of the lithium transition metal composite oxide particles to be prepared are the same as those described for lithium transition metal composite oxide particles in relation to positive electrode active materials for non-aqueous electrolyte secondary batteries.

[0051] Mixing process In the mixing step, lithium transition metal composite oxide particles and an aluminum compound are mixed to obtain a mixture. The resulting mixture may be a positive electrode active material for a non-aqueous electrolyte secondary battery. The mixing of lithium transition metal composite oxide particles and the aluminum compound may be carried out by dry mixing using, for example, a high-speed shear mixer. The mixing temperature may be, for example, 10°C to 100°C, and preferably 25°C to 60°C.

[0052] The average particle size of the aluminum compound used in the mixing process may be, for example, 1 nm or more and less than 500 nm. Details of the aluminum compound and preferred embodiments are as previously described.

[0053] The amount of aluminum compound mixed with lithium transition metal composite oxide particles in the mixing step may be, for example, 2 mol% or less per mole of lithium transition metal composite oxide, preferably 1.8 mol% or less, or 1.5 mol% or less. The amount of aluminum compound mixed in the mixing step may be, for example, 0.01 mol% or more per mole of lithium transition metal composite oxide, preferably 0.05 mol% or more, or 0.1 mol% or more.

[0054] The method for producing the positive electrode active material may further include mixing lithium transition metal composite oxide particles and a tungsten compound. The mixing of lithium transition metal composite oxide particles and the tungsten compound may be carried out simultaneously with the mixing of lithium transition metal composite oxide particles and an aluminum compound, or it may be carried out separately and sequentially. From the viewpoint of fluidity, it is preferable to mix with the aluminum compound first, and then with the tungsten compound. The mixing of lithium transition metal composite oxide particles and the tungsten compound may be carried out by dry mixing using, for example, a high-speed shear mixer. The mixing temperature may be, for example, 10°C to 100°C, and preferably 25°C to 60°C.

[0055] The average particle size of the tungsten compound used in mixing with lithium transition metal composite oxide particles may be, for example, 0.05 μm or more and 2 μm or less. Details of the tungsten compound and preferred embodiments are as previously described.

[0056] The amount of tungsten compound mixed with lithium transition metal composite oxide particles may be, for example, 0.1 mol% to 2 mol% per mole of lithium transition metal composite oxide. Preferably, the amount of tungsten compound may be 1.8 mol% or less, or 1.5 mol% or less, 0.2 mol% or more, or 0.3 mol% or more per mole of lithium transition metal composite oxide.

[0057] The method for producing the positive electrode active material may further include a drying step, a granulation step, and the like after the mixing step.

[0058] The method for producing the positive electrode active material preferably does not include a heat treatment step in which a mixture containing lithium transition metal composite oxide particles and an aluminum compound is heat-treated. By omitting the heat treatment step, the fluidity of the positive electrode active material can be maintained well. Here, a heat treatment step means maintaining a temperature of, for example, 300°C or higher, or 200°C or higher, for, for, for 2 hours or more, or for 30 minutes or more, for the mixture containing lithium transition metal composite oxide particles and an aluminum compound. Therefore, in this specification, obtaining the mixture at a temperature of, for example, 150°C or lower does not constitute heat treatment.

[0059] Method for producing lithium transition metal composite oxides Lithium transition metal composite oxide particles used in a method for producing positive electrode active materials can be produced by, for example, the following method. The method for producing lithium transition metal composite oxide may include a composite oxide preparation step of preparing a composite oxide containing nickel, and a synthesis step of mixing the nickel-containing composite oxide with a lithium compound and heat-treating it to obtain a lithium transition metal composite oxide containing lithium and nickel and having a layered structure. The produced lithium transition metal composite oxide may contain secondary particles formed by the aggregation of multiple primary particles containing lithium transition metal composite oxide.

[0060] Complex oxide preparation process In the composite oxide preparation step, a nickel-containing composite oxide (hereinafter also simply referred to as "nickel composite oxide") is prepared. The prepared nickel composite oxide may contain secondary particles formed by the aggregation of multiple primary particles containing nickel composite oxide. The nickel composite oxide may be prepared by purchase or other means, or it may be manufactured by the nickel composite oxide manufacturing method described later. Details of the prepared nickel composite oxide will be described later.

[0061] Synthesis process The synthesis process includes mixing the prepared nickel composite oxide with a lithium compound to obtain a lithium mixture, and heat-treating the lithium mixture to obtain a lithium transition metal composite oxide having a layered structure containing lithium and nickel. In the synthesis process, the lithium transition metal composite oxide may be obtained by the diffusion of lithium contained in the lithium compound into the nickel composite oxide.

[0062] Methods for mixing nickel composite oxides and lithium compounds include, for example, dry mixing of the nickel composite oxide and lithium compound using a stirring mixer, and wet mixing of a nickel composite oxide slurry using a ball mill or similar mixer. Examples of lithium compounds include lithium hydroxide, lithium nitrate, lithium carbonate, and mixtures thereof.

[0063] The ratio of moles of lithium to the total number of moles of metal elements other than lithium in a lithium mixture (also called the lithium ratio) may be, for example, 0.9 to 1.3, and preferably 1 to 1.2. When the lithium ratio is 0.9 or higher, the formation of by-products tends to be suppressed. Furthermore, when the lithium ratio is 1.3 or lower, the increase in the amount of alkaline components present on the surface of the lithium mixture is suppressed, and the adsorption of moisture due to the deliquescent properties of the alkaline components is suppressed, which tends to improve handling properties.

[0064] In the mixing of nickel composite oxide and lithium compound, in addition to the lithium compound, a compound containing at least one secondary metallic element selected from the group consisting of magnesium, calcium, titanium, zirconium, niobium, tantalum, chromium, molybdenum, tungsten, iron, copper, silicon, tin, bismuth, gallium, yttrium, samarium, erbium, cerium, neodymium, lanthanum, cadmium, and lutetium may be further mixed. Examples of compounds containing the secondary metallic element include hydroxides, oxides, and carbonates. The secondary metallic element may be at least one selected from the group consisting of zirconium, titanium, magnesium, tantalum, niobium, molybdenum, and tungsten. It is preferable to include tungsten as the secondary metallic element because it tends to produce particles with higher porosity and thus enable the construction of batteries with higher output characteristics.

[0065] The heat treatment temperature in the synthesis process may be, for example, 650°C to 990°C, preferably 700°C to 730°C, or 760°C to 760°C. Alternatively, the heat treatment temperature may be 960°C or lower, 940°C or lower, or 920°C or lower. The heat treatment of the mixture may be performed at a single temperature, but from the viewpoint of particle control, it is preferable to perform it at multiple temperatures. When heat treatment is performed at multiple temperatures, for example, it is desirable to maintain a first temperature for a predetermined time, then further increase the temperature, and maintain a second temperature for a predetermined time. The first temperature is, for example, 650°C to 850°C, preferably 700°C to 820°C, and the second temperature is, for example, 730°C to 960°C, preferably 760°C to 920°C. A heat treatment temperature of 650°C or higher tends to suppress the increase in unreacted lithium. A heat treatment temperature of 990°C or lower tends to suppress the decomposition of the resulting lithium transition metal composite oxide. Furthermore, from the viewpoint of obtaining a lithium transition metal composite oxide with high porosity, it is preferable to heat-treat at a temperature of 800°C to 980°C for 8 hours or more, and more preferable to heat-treat at a temperature of 810°C to 920°C for 8 hours or more, and the heat-treat time may be, for example, 20 hours or less. The heat-treat time, as the time for holding the highest temperature, may be, for example, 2 hours or more, preferably 4 hours or more, or 6 hours or more. The heat-treat time may also be, for example, 20 hours or less, preferably 18 hours or less, or 12 hours or less, and if heat treatment is performed at multiple temperatures, each may be 1 hour or more and 19 hours or less. The atmosphere for heat treatment may be in the presence of oxygen, preferably an atmosphere containing 10% to 100% by volume of oxygen.

[0066] In the method for producing lithium transition metal composite oxides, after the synthesis process, the resulting heat-treated product may be subjected to treatments such as coarse crushing, pulverization, or dry sieving as needed.

[0067] Method for producing nickel complex oxides A method for producing nickel composite oxides may include, for example, a first solution preparation step of preparing a first solution containing nickel ions and, if necessary, cobalt ions; a second solution preparation step of preparing a second solution containing a complex ion forming factor; a liquid medium preparation step of preparing a liquid medium having a pH in the range of 10 to 13.5; a crystallization step of obtaining a reaction solution in which the pH is maintained in the range of 10 to 13.5 while supplying the first solution and the second solution separately and simultaneously to the liquid medium; a composite hydroxide recovery step of obtaining a nickel-containing composite hydroxide from the reaction solution; and a composite hydroxide heat treatment step of heat-treating the obtained composite hydroxide to obtain a nickel composite oxide. For details on how to obtain such a composite oxide, see, for example, Japanese Patent Application Publication No. 2003-292322, Japanese Patent Application Publication No. 2011-116580 (US Patent Application Publication No. 2012 / 270107), etc.

[0068] First solution preparation step In the first solution preparation step, a first solution containing nickel ions and, if necessary, cobalt ions is prepared. The first solution is prepared by dissolving a predetermined amount of salt containing each metal element in water, according to the composition of the target nickel composite oxide. Examples of salts include nitrates, sulfates, and hydrochlorides. When preparing the first solution, an acidic substance (e.g., an aqueous sulfuric acid solution) may be added to the water. This may make it easier to dissolve the salts containing each metal element. In the preparation of the first solution, a basic substance may be added to adjust the pH. The total number of moles of metal elements such as nickel in the first solution may be set appropriately according to the average particle size of the target nickel composite oxide. Here, the total number of moles of metal elements means the total number of moles of nickel and cobalt if the first solution contains nickel and cobalt, and the total number of moles of nickel, cobalt, and manganese if the first solution contains nickel, cobalt, and manganese.

[0069] The first solution may further contain, in addition to nickel ions, at least one of cobalt ions, aluminum ions, and manganese ions. Furthermore, the first solution may further contain, in addition to these, ions of at least one secondary metallic element selected from the group consisting of magnesium, calcium, titanium, zirconium, niobium, tantalum, chromium, molybdenum, tungsten, iron, copper, silicon, tin, bismuth, gallium, yttrium, samarium, erbium, cerium, neodymium, lanthanum, cadmium, and lutetium. The secondary metallic element may be at least one selected from the group consisting of zirconium, titanium, magnesium, tantalum, niobium, molybdenum, and tungsten.

[0070] The concentration of metal ions such as nickel and cobalt in the first solution may be, for example, 1.0 mol / L or more and 2.6 mol / L or less in total for each metal ion. Preferably, the concentration of metal ions may be 1.5 mol / L or more, or 1.7 mol / L or more. Alternatively, the concentration of metal ions may be 2.2 mol / L or less, or 2.0 mol / L or less. When the metal ion concentration of the first solution is 1.0 mol / L or more, a sufficient amount of crystallized material can be obtained per reaction vessel, thus improving productivity. On the other hand, when the metal ion concentration of the first solution is 2.6 mol / L or less, it is suppressed that the concentration exceeds the saturation concentration of the metal salt at room temperature, and the decrease in the metal ion concentration in the solution due to the precipitation of metal salt crystals is suppressed.

[0071] Second solution preparation step In the second solution preparation step, a second solution containing a complex ion forming factor is prepared. The second solution contains a complex ion forming factor that can form complex ions with the metal ions contained in the first solution. For example, if the complex ion forming factor is ammonia, an aqueous ammonia solution can be used as the second solution. The ammonia content in the aqueous ammonia solution may be, for example, 5% by mass or more and 25% by mass or less. Preferably, the ammonia content may be 10% by mass or more, or 12% by mass or more. Preferably, the ammonia content may be 20% by mass or less, or 18% by mass or less.

[0072] Liquid medium preparation process In the liquid medium preparation step, a liquid medium with a pH in the range of 10 to 13.5 is prepared. The liquid medium is adjusted, for example, by using a predetermined amount of water and a basic solution such as an aqueous sodium hydroxide solution in a reaction vessel to create a solution with a pH of 10 to 13.5. By adjusting the pH of the solution to 10 to 13.5, fluctuations in the pH of the reaction solution during the initial stages of the reaction can be suppressed.

[0073] Crystallization process In the crystallization step, the first and second solutions are supplied to the liquid medium separately and simultaneously while maintaining the pH of the reaction solution within a range of 10 to 13.5. This allows for the production of nickel-containing composite hydroxide particles from the reaction solution. In addition to the first and second solutions, a basic solution may be supplied to the liquid medium simultaneously. This makes it easy to maintain the pH of the reaction solution within a range of 10 to 13.5.

[0074] In the crystallization step, it is preferable to supply each solution so as to maintain the pH of the reaction solution within a range of 10 to 13.5. For example, the pH of the reaction solution can be maintained within a range of 10 to 13.5 by adjusting the supply amount of the second solution according to the supply amount of the first solution. If the pH of the reaction solution is 10 or higher, the amount of impurities contained in the resulting composite hydroxide (e.g., non-metallic sulfates and nitrates in the reaction solution) is sufficiently reduced, and the decrease in capacity of the final product, the non-aqueous electrolyte secondary battery, tends to be suppressed. Also, if the pH is 13.5 or lower, the generation of fine secondary particles is suppressed, and the handling properties of the resulting composite hydroxide may be improved. The pH of the reaction solution to be maintained is preferably 10.5 or higher, or 10.9 or higher, and preferably 11.7 or lower, or 11.3 or lower. The temperature of the reaction solution may be controlled to be within a range of, for example, 25°C to 80°C, preferably 40°C to 75°C, or 50°C to 70°C. The atmosphere during the crystallization process can be a low-oxidizing atmosphere, for example, the oxygen concentration can be maintained at 10% by volume or less.

[0075] In the crystallization step, the concentration of nickel ions in the reaction solution may be maintained in a range of, for example, 10 ppm to 1000 ppm, preferably 10 ppm to 100 ppm. If the nickel ion concentration is 10 ppm or higher, the complex hydroxide will precipitate sufficiently. If the nickel ion concentration is 1000 ppm or lower, the amount of nickel eluted will be small, thus suppressing deviation from the desired composition. The nickel ion concentration can be adjusted, for example, when using an aqueous ammonia solution as the second solution (complex ion forming solution), by supplying the second solution so that the ammonium ion concentration in the reaction solution is between 1000 ppm and 15000 ppm.

[0076] The supply time for the first solution may be, for example, 6 hours or more and 60 hours or less, preferably 8 hours or more, or 10 hours or more. Alternatively, the supply time for the first solution may be preferably 42 hours or less, 24 hours or less, or 18 hours or less. A supply time of 6 hours or more tends to result in a slower deposition rate of the composite hydroxide, thus yielding a nickel composite oxide with higher smoothness. A supply time of 60 hours or less can further improve productivity.

[0077] The value obtained by taking the total number of moles of nickel, etc. supplied in the first solution throughout the entire crystallization process as the denominator and the total number of moles of nickel, etc. supplied in the first solution per hour as the numerator, may be, for example, 0.015 or more and 0.125 or less, preferably 0.020 or more, or 0.050 or more, and preferably 0.10 or less. If it is 0.015 or more, productivity can be further improved. If it is 0.125 or less, there is a tendency to obtain nickel composite oxides with a larger specific surface area.

[0078] A method for producing nickel composite oxides may include a seed generation step prior to the crystallization step. In the seed generation step, for example, a portion of the prepared first solution is supplied to a liquid medium to generate a nickel-containing composite hydroxide in the liquid medium, for example, as a seed crystal. That is, the liquid medium used in the crystallization step may be a seed solution containing a nickel-containing composite hydroxide. The temperature in the seed generation step can be, for example, 40°C to 80°C. The atmosphere in the seed generation step can be a low-oxidizing atmosphere, and for example, the oxygen concentration can be maintained at 10% by volume or less.

[0079] If composite hydroxide particles are generated in the liquid medium before the crystallization process, one of the pre-generated composite hydroxide particles becomes a seed crystal that constitutes one of the composite hydroxide particles obtained after the crystallization process. This allows the total number of secondary composite hydroxide particles obtained after the crystallization process to be controlled by the number of pre-generated composite hydroxide particles. For example, supplying a large amount of the first solution beforehand increases the number of composite hydroxide particles generated, which tends to reduce the average particle size of the secondary composite hydroxide particles after the crystallization process.

[0080] In the crystallization process, the first solution and the second solution may be supplied to the liquid medium continuously or intermittently. The first solution may be supplied continuously throughout the entire supply time of the first solution in the crystallization process. Here, "continuously throughout the entire supply time" means that there is almost no period of time during which the solution is not supplied. Furthermore, "almost no period of time of time of time of supply" means that the period of time during which the solution is not supplied is less than 1% of the total supply time.

[0081] Composite hydroxide recovery process In the complex hydroxide recovery process, the nickel-containing complex hydroxide is separated and recovered from the reaction solution. The complex hydroxide can be recovered from the reaction solution by, for example, separating the resulting precipitate using commonly used separation methods such as filtration or centrifugation. The resulting precipitate may be subjected to treatments such as washing with water, filtration, or drying. The composition ratio of metal elements in the complex hydroxide may be approximately the same as the composition ratio of metal elements other than lithium in lithium transition metal complex oxides obtained using these as raw materials.

[0082] Composite hydroxide heat treatment process In the composite hydroxide heat treatment process, the resulting composite hydroxide is heat-treated to obtain a nickel composite oxide. The heat treatment dehydrates the composite hydroxide, generating the nickel composite oxide. The nickel composite oxide may be a precursor to a lithium transition metal composite oxide, or a precursor to a positive electrode active material.

[0083] The heat treatment temperature may be, for example, 105°C to 900°C, preferably 300°C to 500°C. The heat treatment time may be, for example, 5 hours to 30 hours, preferably 10 hours to 20 hours. The heat treatment atmosphere may be an oxygen-containing atmosphere or an air atmosphere.

[0084] In nickel composite oxides, the ratio of moles of nickel to the total number of moles of metal elements contained in the nickel composite oxide may be, for example, greater than 0 and less than 1. The ratio of moles of nickel to the total number of moles of metal elements may preferably be 0.33 or more. The ratio of moles of nickel to the total number of moles of metal elements may be 0.4 or more, or 0.45 or more. Furthermore, the ratio of moles of nickel to the total number of moles of metal elements may preferably be 0.95 or less, 0.8 or less, or 0.6 or less.

[0085] Nickel composite oxides may contain cobalt in their composition. When nickel composite oxides contain cobalt in their composition, the ratio of the number of moles of cobalt to the total number of moles of metal elements contained in the nickel composite oxide may be greater than 0 and less than 1. The ratio of the number of moles of cobalt to the total number of moles of metal elements is preferably 0.01 or more, 0.02 or more, 0.05 or more, 0.1 or more, or 0.15 or more. Furthermore, the ratio of the number of moles of cobalt to the total number of moles of metal elements is preferably 0.6 or less. The ratio of the number of moles of cobalt to the total number of moles of metal elements may be 0.4 or less, 0.35 or less, 0.33 or less, 0.3 or less, or 0.25 or less.

[0086] Nickel composite oxides may contain at least one of manganese and aluminum in their composition. When nickel composite oxides contain at least one of manganese and aluminum in their composition, the ratio of the total number of moles of manganese and aluminum to the total number of moles of metal elements contained in the nickel composite oxide may be, for example, greater than 0, preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, and particularly preferably 0.15 or more. The ratio of the total number of moles of manganese and aluminum to the total number of moles of metal elements may also be, for example, 0.6 or less, preferably 0.35 or less. The ratio of the total number of moles of manganese and aluminum to the total number of moles of metal elements may be 0.33 or less, or 0.3 or less.

[0087] Nickel composite oxides may contain at least one secondary metal element in their composition. When nickel composite oxides contain at least one secondary metal element in their composition, the ratio of the total number of moles of the secondary metal element to the total number of moles of the metal element contained in the nickel composite oxide may be, for example, greater than 0, 0.001 or more, or 0.003 or more. The ratio of the total number of moles of the secondary metal element to the total number of moles of the metal element may also be, for example, 0.05 or less, 0.02 or less, 0.015 or less, or 0.01 or less.

[0088] Nickel composite oxides may have a composition represented by, for example, the following formula (2). Ni q Co r M 1 s M 2 t O 2+β (2)

[0089] In formula (2), M 1 represents at least one of Mn and Al. M 2 represents at least one selected from the group consisting of Mg, Ca, Ti, Zr, Nb, Ta, Cr, Mo, W, Fe, Cu, Si, Sn, Bi, Ga, Y, Sm, Er, Ce, Nd, La, Cd, and Lu. q, r, s, t, and β satisfy 0 < q < 1, 0 ≤ r ≤ 0.6, 0 ≤ s ≤ 0.6, 0 ≤ t ≤ 0.02, -0.1 ≤ β ≤ 1.1, and q + r + s + t = 1. Preferably, 0.33 ≤ q ≤ 0.95, 0.02 ≤ r ≤ 0.35, 0.01 ≤ s ≤ 0.35, and 0 ≤ t ≤ 0.015. Also preferably, M 2 is at least one selected from the group consisting of Zr, Ti, Mg, Ta, Nb, Mo, and W.

[0090] The tap density of the nickel composite oxide may be 1.3 g / cm 3 or less, preferably 1.15 g / cm 3 or less, more preferably 1 g / cm 3 or less, still more preferably 0.96 g / cm 3 or less. Also, the tap density of the nickel composite oxide may be greater than 0 g / cm 3 preferably 0.2 g / cm 3 or more, or 0.4 g / cm 3 or more. When the tap density of the nickel composite oxide is 1.3 g / cm 3The following conditions tend to result in lithium transition metal composite oxides with larger specific surface areas: When the ratio of moles of nickel to the total number of moles of metal elements in the nickel composite oxide is 0.5 or higher, the lithium transition metal composite oxide obtained by reacting a mixture of nickel composite oxide, lithium compound, and tungsten compound tends to have higher porosity particles, leading to improved power characteristics.

[0091] The particle size of the nickel composite oxide may be between 1 μm and 8 μm, preferably between 2 μm and 2.5 μm or 3 μm. Alternatively, the particle size of the nickel composite oxide may be between 6 μm and 5 μm or 4 μm. A particle size of 1 μm to 8 μm tends to result in lithium transition metal composite oxide particles with a larger specific surface area when satisfying the above-mentioned tap density range.

[0092] Electrodes for non-aqueous electrolyte secondary batteries The electrode for a non-aqueous electrolyte secondary battery comprises a current collector and a positive electrode active material layer disposed on the current collector and containing the positive electrode active material described above. A non-aqueous electrolyte secondary battery equipped with such an electrode can achieve excellent output characteristics.

[0093] The density of the positive electrode active material layer is, for example, 2.6 g / cm³. 3 More than 3.9g / cm 3 The following may be the case, preferably 2.8 g / cm³ 3 More than 3.8g / cm 3 Below, 3.1g / cm 3 More than 3.7g / cm 3 The following, or 3.2 g / cm³ 3 More than 3.6g / cm 3 The following may apply: The density of the positive electrode active material layer is calculated by dividing the mass of the positive electrode active material layer by the volume of the positive electrode active material layer. Here, the density of the positive electrode active material layer can be adjusted by applying pressure after the electrode composition described later is applied to the current collector.

[0094] Examples of materials for the current collector include aluminum, nickel, and stainless steel. The positive electrode active material layer can be formed by applying an electrode composition obtained by mixing the above-mentioned positive electrode active material, conductive additive, binder, etc., with a solvent onto the current collector, and then performing drying, pressurizing, etc. Examples of conductive additives include natural graphite, artificial graphite, and acetylene black. Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, and polyamide acrylic resin. Examples of solvents include N-methyl-2-pyrrolidone (NMP).

[0095] Nonaqueous electrolyte secondary battery A non-aqueous electrolyte secondary battery comprises the above-mentioned electrodes for a non-aqueous electrolyte secondary battery. In addition to the electrodes for a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery is configured to include a negative electrode for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte, a separator, etc. For the negative electrode, non-aqueous electrolyte, separator, etc. in a non-aqueous electrolyte secondary battery, for example, those described in Japanese Patent Publication No. 2002-075367, Japanese Patent Publication No. 2011-146390, Japanese Patent Publication No. 2006-12433 (the entire disclosures of these are incorporated herein by reference), etc., can be used as appropriate.

[0096] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and it goes without saying that any configuration that is substantially identical to the technical idea described in the claims of this disclosure and produces similar effects is included within the technical scope of this disclosure. [Examples]

[0097] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the following, the volume-average particle size was evaluated using a laser diffraction particle size distribution analyzer (SALD-3100, Shimadzu Corporation). The specific surface area was evaluated using a BET specific surface area analyzer (Macsorb, Mountec Co., Ltd.) by nitrogen gas adsorption method (single-point method). The porosity was evaluated using the scanning electron microscope (SEM) and image analysis software (e.g., HALCON, MVTec Co., Ltd.) described above.

[0098] Example 1 Preparation of each solution A first solution (combined concentration of nickel ions, cobalt ions, and manganese ions of 1.7 mol / L) was prepared by dissolving nickel sulfate solution, cobalt sulfate solution, and manganese sulfate solution in water in a molar ratio of 35:35:30 for each metal element, and mixing them. The total number of moles of metal elements in the first solution was set to 350 moles. A 25 wt% sodium hydroxide aqueous solution was prepared as a basic solution. A 12.5 wt% ammonia aqueous solution was prepared as the second solution (complex ion forming solution).

[0099] Preparation of the liquid medium 30 liters of water were prepared in a reaction vessel, and an aqueous sodium hydroxide solution was added to bring the pH to 12.5. Nitrogen gas was introduced to replace the nitrogen in the reaction vessel, and the liquid medium was prepared as the pre-reaction solution.

[0100] Seed generation process While stirring the liquid medium, 10 moles of the first solution were added to the liquid medium to precipitate a composite hydroxide containing nickel, cobalt, and manganese.

[0101] Crystallization process The remaining 340 moles of the first solution, an aqueous sodium hydroxide solution, and the second solution were supplied to the reaction solution over 12 hours while stirring, maintaining a pH of approximately 10.9 to 11.3 and an ammonium ion concentration of approximately 4000 ppm. This allowed for the precipitation of a composite hydroxide containing nickel, cobalt, and manganese. The temperature of the reaction solution was controlled to approximately 60°C. The precipitate was washed with water, filtered, separated, and then dried to obtain a composite hydroxide containing nickel, cobalt, and manganese (hereinafter also referred to as nickel-cobalt composite hydroxide). The nickel-cobalt composite hydroxide was heat-treated at 320°C for 16 hours under an atmospheric environment to recover a transition metal composite oxide containing nickel, cobalt, and manganese (hereinafter also referred to as composite oxide). The volume-average particle size was 4.7 μm, and the tap density was 0.86 g / cm³. 3 A composite oxide was obtained.

[0102] Synthesis process The obtained composite oxide was mixed with lithium carbonate, zirconium(IV) oxide, and tungsten(VI) oxide in a molar ratio of Li:(Ni+Co+Mn):Zr:W=1.19:1:0.005:0.003 to obtain a lithium mixture. The obtained lithium mixture was heat-treated in an atmospheric environment. The heat treatment was performed at a first temperature of 780°C for 2 hours and a second temperature of 910°C for 4 hours to obtain a heat-treated product. The obtained heat-treated product was pulverized and passed through a dry sieve to obtain a composition formula Li 1.19 Ni 0.35 Co 0.35 Mn 0.30 Zr 0.005 W 0.003 A lithium transition metal composite oxide represented by O2 was obtained.

[0103] The resulting lithium transition metal composite oxide matrix has a volume-average particle size of 4.4 μm and a specific surface area of ​​2.06 m². 2 The void ratio was 30% per gram.

[0104] Mixing process The lithium transition metal composite oxide obtained above was mixed with aluminum oxide (Al2O3: manufactured by CABOT; average particle size 20 to 30 nm) as an aluminum compound, in a molar ratio of (Ni+Co+Mn):Al = 1:0.005 relative to the lithium transition metal composite oxide, and then mixed using a high-speed shear mixer. After that, the mixture was passed through a dry sieve to obtain the positive electrode active material of Example 1.

[0105] The volume-average particle size of the positive electrode active material obtained in Example 1 was 4.4 μm, and the specific surface area was 2.26 m². 2 The void ratio was 30% per gram.

[0106] The positive electrode active material obtained in Example 1 was observed using a scanning electron microscope (Hitachi High-Technologies SU8230) at an acceleration voltage of 1.5 kV, and scanning electron microscope (SEM) images were acquired. The results are shown in Figure 1.

[0107] Comparative Example 1 In the crystallization process, the pH of the reaction solution was maintained at approximately 11.3 to 11.7, the ammonium ion concentration was set to approximately 6000 ppm, the temperature of the reaction solution was controlled to approximately 45°C, and the supply time of the first solution in the crystallization process was set to 18 hours. Except for these other factors, the procedure was the same as in Example 1, resulting in a volume-average particle size of 3.4 μm and a tap density of 1.46 g / cm³. 3 A composite oxide containing nickel, cobalt, and manganese was obtained. A lithium transition metal composite oxide of Comparative Example 1 was obtained in the same manner as the synthesis process of Example 1, except that the obtained composite oxide was used.

[0108] The obtained lithium transition metal composite oxide was used as the positive electrode active material for Comparative Example 1. The volume-average particle size of the positive electrode active material for Comparative Example 1 was 3.1 μm, and the specific surface area was 1.09 m². 2 The void ratio was 5% per gram.

[0109] Example 2 In the mixing process, tungsten oxide (WO3: manufactured by Nippon Shinkinzoku Co., Ltd.; average particle size 1000 nm) was further added as a tungsten compound in addition to the aluminum compound, and the mixture was formulated with the lithium transition metal composite oxide in a molar ratio of (Ni+Co+Mn):Al:W = 1:0.005:0.005, except that the process was the same as in Example 1 to obtain the positive electrode active material of Example 2.

[0110] The volume-average particle size of the positive electrode active material obtained in Example 2 was 4.4 μm, and the specific surface area was 2.29 m². 2 The void ratio was 30% per gram.

[0111] Example 3 In the synthesis process, the lithium transition metal composite oxide of Example 3 was obtained in the same manner as in Example 2, except that the second temperature of the heat treatment was changed from 910°C to 950°C.

[0112] The volume-average particle size of the positive electrode active material obtained in Example 3 was 4.3 μm, and the specific surface area was 1.43 m². 2 The void ratio was 17% per gram.

[0113] Example 4 In the synthesis process, the lithium transition metal composite oxide of Example 4 was obtained in the same manner as in Example 2, except that the second temperature of the heat treatment was changed from 910°C to 880°C.

[0114] The volume-average particle size of the positive electrode active material obtained in Example 4 was 3.9 μm, and the specific surface area was 2.90 m². 2 The void ratio was 31% per gram.

[0115] Example 5 In the synthesis process, the lithium transition metal composite oxide of Example 5 was obtained in the same manner as in Example 2, except that the second temperature of the heat treatment was changed from 910°C to 860°C.

[0116] The volume-average particle size of the positive electrode active material obtained in Example 5 was 3.9 μm, and the specific surface area was 3.33 m². 2 The void ratio was 31% per gram.

[0117] Example 6 In the synthesis process, the lithium transition metal composite oxide of Example 5 was obtained in the same manner as in Example 2, except that the second temperature of the heat treatment was changed from 910°C to 840°C.

[0118] The volume-average particle size of the positive electrode active material obtained in Example 6 was 3.9 μm, and the specific surface area was 3.84 m². 2 The void ratio was 32% per gram.

[0119] Reference example 1 Except for omitting the mixing step, the lithium transition metal composite oxide obtained in Example 1 was used as the cathode active material in Reference Example 1, following the same procedure as in Example 1. SEM images were also acquired in the same manner as in Example 1. The results are shown in Figure 2.

[0120] Reference example 2 In the mixing process, tungsten oxide (WO3: manufactured by Nippon Shinkinzoku Co., Ltd.; average particle size 1000 nm) was used as a tungsten compound instead of the aluminum compound, and was blended with the lithium transition metal composite oxide in a molar ratio of (Ni+Co+Mn):W=1:0.005, in the same manner as in Example 1, to obtain the positive electrode active material of Reference Example 2.

[0121] The volume-average particle size of the positive electrode active material obtained in Reference Example 2 was 4.4 μm, and the specific surface area was 2.07 m². 2 The void ratio was 30% per gram.

[0122] Reference example 3 In the mixing process, titanium oxide (TiO2: manufactured by Nippon Aerosil Co., Ltd.; average particle size 20 to 40 nm) was added as a titanium compound instead of the aluminum compound, in a molar ratio of (Ni+Co+Mn):Ti=1:0.003 to the lithium transition metal composite oxide. The cathode active material of Reference Example 3 was obtained in the same manner as in Example 1.

[0123] The volume-average particle size of the positive electrode active material obtained in Reference Example 3 was 4.4 μm, and the specific surface area was 2.13 m². 2 The void ratio was 30% per gram.

[0124] Reference example 4 In the mixing process, zirconium oxide (ZrO2: manufactured by TECNAN; average particle size 20 to 30 nm) was added as a zirconium compound instead of the aluminum compound, in a molar ratio of (Ni+Co+Mn):Zr=1:0.002 to the lithium transition metal composite oxide. The cathode active material of Reference Example 4 was obtained in the same manner as in Example 1.

[0125] The volume-average particle size of the positive electrode active material obtained in Reference Example 4 was 4.4 μm, and the specific surface area was 2.21 m². 2 The void ratio was 30% per gram.

[0126] Reference example 5 In the mixing process, silicon dioxide (SiO2: manufactured by Nippon Aerosil Co., Ltd.; average particle size 40 to 50 nm) was added as a silicon compound instead of the aluminum compound, in a molar ratio of (Ni+Co+Mn):Si=1:0.005 to the lithium transition metal composite oxide. Otherwise, the cathode active material of Reference Example 5 was obtained in the same manner as in Example 1.

[0127] The volume-average particle size of the positive electrode active material obtained in Reference Example 5 was 4.4 μm, and the specific surface area was 2.16 m². 2 The void ratio was 30% per gram.

[0128] Example 7 In the mixing process, aluminum oxide (Al2O3: manufactured by CABOT; average particle size 20 to 30 nm) was replaced with aluminum oxide (Al2O3: manufactured by Aldrich; average particle size 200 to 300 nm) as an aluminum compound, and was blended with the lithium transition metal composite oxide in a molar ratio of (Ni+Co+Mn):Al = 1:0.005. The cathode active material of Example 7 was obtained in the same manner as in Example 1.

[0129] The volume-average particle size of the positive electrode active material obtained in Example 7 was 4.4 μm, and the specific surface area was 2.33 m². 2 The void ratio was 30% per gram.

[0130] Example 8 In the mixing process, instead of aluminum oxide (Al2O3; manufactured by CABOT; average particle size 20 to 30 nm), aluminum oxide (Al2O3; manufactured by Sumitomo Chemical Co., Ltd.; average particle size 500 nm) as an aluminum compound was blended with the lithium transition metal composite oxide so that (Ni + Co + Mn):Al = 1:0.005 (molar ratio). In the same manner as in Example 1, the positive electrode active material of Example 8 was obtained.

[0131] The volume average particle size of the obtained positive electrode active material of Example 8 was 4.4 μm, the specific surface area was 2.07 m 2 / g, and the porosity was 30%.

[0132] Reference Example 6 A first solution (concentration of nickel ions, cobalt ions, and manganese ions combined was 1.7 mol / L) was prepared by dissolving nickel sulfate solution, cobalt sulfate solution, and manganese sulfate solution in water so that the molar ratio of the metal elements was 50:20:30 and mixing them. In the same manner as in Example 1, a composite oxide with a volume average particle size of 4.2 μm and a tap density of 1.05 g / cm 3 was obtained. Also, in the synthesis process, in the same manner as in Example 1 except that Li:(Ni + Co + Mn):Zr:W = 1.14:1:0.005:0.003 (molar ratio) and heat treatment was performed at 840 °C for 8 hours, a lithium transition metal composite oxide represented by the composition formula Li 1.14 Ni 0.5 Co 0.2 Mn 0.3 Zr 0.005 W 0.003 O2 was obtained. The volume average particle size of the obtained lithium transition metal composite oxide as the base material was 3.9 μm, the specific surface area was 2.09 m 2 / g, and the porosity was 31%.

[0133] Example 9 To the lithium transition metal composite oxide obtained as Reference Example 6, aluminum oxide (Al2O3; manufactured by CABOT; average particle size 20 to 30 nm) as an aluminum compound and tungsten oxide (WO3; manufactured by Nippon Shinyaku Co., Ltd.; average particle size 1000 nm) as a tungsten compound were blended so that (Ni + Co + Mn):Al:W = 1:0.005:0.005 (molar ratio) with respect to the lithium transition metal composite oxide, and then mixed with a high-speed shear mixer. Thereafter, the positive electrode active material of Example 9 was obtained by passing through a dry sieve.

[0134] The volume average particle size of the obtained positive electrode active material of Example 9 was 4.1 μm, the specific surface area was 2.35 m 2 / g, and the porosity was 31%.

[0135] Comparative Example 2 A first solution (total concentration of nickel ions, cobalt ions and manganese ions: 1.7 mol / L) was prepared by dissolving nickel sulfate solution, cobalt sulfate solution and manganese sulfate solution in water so that the molar ratio of metal elements was 50:20:30. Except for this, in the same manner as Comparative Example 1, a composite oxide having a volume average particle size of 3.1 μm and a tap density of 1.33 g / cm 3 was obtained. Further, in the synthesis step, except that the obtained composite oxide was heat-treated at 860 °C for 8 hours, in the same manner as Comparative Example 1, the positive electrode active material of Comparative Example 2 was obtained.

[0136] The volume average particle size of the obtained positive electrode active material of Comparative Example 2 was 3.0 μm, the specific surface area was 1.27 m 2 / g, and the porosity was 5%.

[0137] Comparative Example 3 Using the composite oxide obtained in Comparative Example 2, in the synthesis step, lithium carbonate, zirconium(IV) oxide and tungsten(VI) oxide were mixed so that Li:(Ni + Co + Mn):Zr:W = 1.12:1:0.005:0.01 (molar ratio), and heat-treated at 920 °C for 8 hours in an air atmosphere to obtain a composition formula Li 1.12 Ni 0.5 Co 0.2 Mn 0.3Zr 0.005 W 0.01 A lithium transition metal composite oxide represented by O2 was obtained.

[0138] The lithium transition metal composite oxide obtained in Comparative Example 3 had a volume-average particle size of 3.3 μm and a specific surface area of ​​1.12 m². 2 The void ratio was 5% per gram.

[0139] Example 10 In Example 9, the positive electrode active material of Example 10 was obtained in the same manner as in Example 9, except that the mixture was prepared in the synthesis step to be Li:(Ni+Co+Mn):Zr:W=1.16:1:0.005:0.01 (molar ratio) and heat-treated at 860°C for 8 hours.

[0140] The volume-average particle size of the positive electrode active material obtained in Example 10 was 3.7 μm, and the specific surface area was 2.79 m². 2 The void ratio was 36% per gram.

[0141] [Table 1]

[0142] Evaluation of process fluidity Approximately 50g of each of the positive electrode active materials obtained above was weighed and placed into a powder properties analyzer (Powder Tester®; manufactured by Hosokawa Micron Corporation). The angle of repose and decay angle were then automatically measured, and the difference angle was calculated. The results are shown in Table 2.

[0143] Evaluation of the viscosity of the positive electrode mixture slurry Using each of the positive electrode active materials obtained above, positive electrode mixture slurries were prepared as follows, and the viscosity of the positive electrode mixture slurries was evaluated.

[0144] Preparation of cathode mixture slurry A cathode mixture slurry was prepared by dispersing 89.5 parts by mass of cathode active material, 5 parts by mass of acetylene black as a conductive additive, 5 parts by mass of polyvinylidene fluoride (PVDF) as a binder, and 0.5 parts by mass of polyvinylpyrrolidone (PVP) as a dispersant in N-methyl-2-pyrrolidone (NMP).

[0145] Evaluation of relative viscosity The viscosity of the cathode mixture slurry prepared as described above was measured immediately after preparation and 6 hours after preparation using an E-type viscometer (Thermo Scientic; HAAKE Viscotester 550). As shown in the formula below, the viscosity increase was defined as the value obtained by dividing the viscosity of the cathode mixture slurry 6 hours after preparation by the viscosity immediately after preparation. (Slurry viscosity after 6 hours) / (Slurry viscosity immediately after preparation)

[0146] The obtained viscosity increase rates were evaluated as relative viscosity increase rates for Examples 1 to 8 and Reference Examples 1 to 5, with the viscosity increase rate of Comparative Example 1 set to 1. For Reference Example 6, Examples 9 and 10, and Comparative Example 3, the viscosity increase rate was evaluated as relative viscosity increase rates with the viscosity increase rate of Comparative Example 2 set to 1. The results are shown in Tables 2 and 3.

[0147] Fabrication of evaluation batteries Using the positive electrode active material obtained above, an evaluation battery was fabricated according to the following procedure.

[0148] Fabrication of the positive electrode A positive electrode slurry was prepared by dispersing 92 parts by mass of positive electrode active material, 3 parts by mass of acetylene black, and 5 parts by mass of polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone (NMP). The obtained positive electrode slurry was applied to aluminum foil to be used as a current collector, dried, compressed and molded using a roll press, and then cut to a predetermined size to produce a positive electrode.

[0149] Fabrication of the negative electrode A negative electrode slurry was prepared by dispersing and dissolving 97.5 parts by weight of artificial graphite, 1.5 parts by weight of carboxymethylcellulose (CMC), and 1.0 part by weight of SBR (styrene-butadiene rubber) in pure water. The obtained negative electrode slurry was applied to a current collector made of copper foil, dried, compressed and molded using a roll press, and then cut to a predetermined size to produce a negative electrode.

[0150] After attaching lead electrodes to the positive and negative electrode current collectors, a separator was placed between the positive and negative electrodes, and these were then placed in a laminated pouch. Next, this was vacuum-dried at 65°C to remove moisture adsorbed on each component. After that, an electrolyte solution was injected into the laminated pouch under an argon atmosphere and sealed to fabricate an evaluation battery. The electrolyte solution used was a mixture of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) in a volume ratio of 3:7, with lithium hexafluoride phosphate (LiPF6) dissolved in it to a concentration of 1 mol / L. The resulting evaluation battery was placed in a constant temperature bath at 25°C and aged with a weak current, after which the following evaluation was performed.

[0151] Evaluation of output characteristics (DC internal resistance measurement) The DC internal resistance was measured on evaluation batteries after aging. After constant current charging to a depth of charge of 50% at a full charge voltage of 4.2V, the evaluation batteries were placed in an environment of -25°C and pulse discharge was performed with a specific current i for 10 seconds, and the voltage V at 10 seconds was measured. The intersection points were plotted with current i on the x-axis and voltage V on the y-axis, and the slope of the line connecting the intersection points was defined as the DC internal resistance (DC-IR). The currents i were set to 0.02A, 0.04A, 0.06A, 0.08A, and 0.10A. A low DC-IR indicates good output characteristics.

[0152] The obtained DC internal resistances were evaluated as relative DC internal resistances for Examples 1 to 8, Comparative Example 1, and Reference Examples 2 to 5, with the DC internal resistance of Reference Example 1 set to 1. For Examples 9, 10, and Comparative Examples 2 and 3, the DC internal resistances were evaluated as relative DC internal resistances with the DC internal resistance of Reference Example 6 set to 1. The results are shown in Tables 2 and 3.

[0153] [Table 2]

[0154] [Table 3]

[0155] Tables 1 to 3 show that increasing the specific surface area of ​​particles with a volume-average particle size of 4.4 μm or less improves output characteristics. Furthermore, mixing these particles with metal compounds tends to improve process fluidity, and in particular, when aluminum oxide and tungsten oxide are mixed, it was confirmed that the handling properties, including the viscosity of the slurry containing the positive electrode active material, are efficiently improved.

Claims

1. The material comprises particles containing a lithium transition metal composite oxide having a layered structure, and an aluminum compound having an average particle size of 1 nm or more and less than 500 nm. The volume-average particle size is between 1 μm and 8 μm, and the specific surface area is 1.4 m². ２ A positive electrode active material for non-aqueous electrolyte secondary batteries, having a concentration of 1 / g or more, and a difference angle of 6° or more obtained by subtracting the decay angle from the angle of repose as measured by a powder properties measuring instrument.

2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, further comprising a tungsten compound.

3. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 2, wherein the content of the tungsten compound is 0.1 mol% or more and 2 mol% or less relative to the lithium transition metal composite oxide.

4. The lithium transition metal composite oxide comprises lithium and nickel in its composition as a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3.

5. The particles containing the lithium transition metal composite oxide have internal voids, as described in any one of claims 1 to 4.

6. The specific surface area is 1.7 m². ２ / g or more 3.3m ２ A positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the amount is less than or equal to / g.

7. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, wherein the content of the aluminum compound is 2 mol% or less relative to the lithium transition metal composite oxide.

8. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein the content of the aluminum compound is 0.01 mol% or more relative to the lithium transition metal composite oxide.

9. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 8, wherein the volume-average particle size is 2 μm or more and 6 μm or less.

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