Positive electrode active material for non-aqueous electrolyte secondary battery and method for manufacturing 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] The present disclosure relates to a positive electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the same. [Background technology]

[0002] High output power characteristics are required for positive electrode active materials for nonaqueous electrolyte secondary batteries used in large power equipment such as electric vehicles. A positive electrode active material having a secondary particle structure in which many primary particles aggregate is considered effective for achieving high output power characteristics. In this regard, lithium-containing transition metal composite oxides have been proposed in which the lithium to oxygen ratio differs between the surface and the interior of the secondary particles (see, for example, Patent Document 1). 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 Application Publication No. 2019-99410 [Patent Document 2] Special Publication No. 2016-538694 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one aspect of the present disclosure is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that exhibits excellent output characteristics in the non-aqueous electrolyte secondary battery, and a method for producing the same. [Means for solving the problem]

[0005] The first aspect is a positive electrode active material for a non-aqueous electrolyte secondary battery, which comprises 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 a 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 m 2 / g or more.

[0006] The second aspect is a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, which includes 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 m 2 / g or more. [Effects of the Invention]

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

[0008] [Figure 1] 2 is an example of a scanning electron microscope (SEM) image of the positive electrode active material according to Example 1. [Figure 2] 1 is an example of an SEM image of a positive electrode active material according to Reference Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this specification, the term "process" refers not only to an independent process, but also to a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. Furthermore, the content of each component in a composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified, when multiple substances corresponding to each component are present in the composition. Furthermore, the upper and lower limits of the numerical ranges described in this specification can be arbitrarily selected and combined. Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments described below are intended to exemplify a positive electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the same, in order to embody the technical concept of the present invention. The present invention is not limited to the positive electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the same described below.

[0010] Cathode active material for non-aqueous electrolyte secondary batteries The positive electrode active material for a non-aqueous electrolyte secondary battery includes 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, and has a volume average particle size of 1 μm or more and 8 μm or less and a specific surface area of ​​1.4 m 2 The positive electrode active material for a non-aqueous electrolyte secondary battery can be efficiently produced, for example, by a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, which will be described later.

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

[0012] From the viewpoint of output characteristics in a nonaqueous 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 cumulative volume from the smallest diameter side in the volume-based cumulative particle size distribution. The volume-based cumulative particle size distribution is measured, for example, using a laser diffraction particle size distribution analyzer.

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

[0014] From the viewpoint of fluidity, the positive electrode active material may have an angle of repose as a powder of, 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. From the viewpoint of fluidity, the positive electrode active material may have a collapse angle as a powder of, for example, less than 68°, preferably 66° or less, or 61° or less. The lower limit of the collapse angle may be, for example, 40° or more, or 45° or more. Furthermore, from the viewpoint of fluidity, the difference angle obtained by subtracting the collapse angle 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, the "angle of repose (θ1)" refers to the inclination angle when the powder of the positive electrode active material is deposited on the measurement table. A typical injection method can be used to deposit the powder of the positive electrode active material. Furthermore, the "angle of collapse (θ2)" refers to the inclination angle measured after applying a predetermined impact force to the measurement table after measuring the angle of repose (θ1). The angle of repose (θ1) and the angle of collapse (θ2) can be measured using, for example, a powder property measuring instrument (e.g., Powder Tester (registered trademark); manufactured by Hosokawa Micron Corporation).

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

[0017] [Method for measuring angle of repose] The powder to be measured was dropped onto a horizontal substrate (measurement table) from a funnel of a specified height, and the base angle was calculated from the diameter and height of the resulting cone-shaped deposit, and this base angle was taken as the angle of repose. Generally, it can be measured based on JIS-R9301-2-2.

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

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

[0020] Lithium transition metal composite oxide The particles containing a lithium transition metal composite oxide (hereinafter simply referred to as "lithium transition metal composite oxide particles") constituting the positive electrode active material may be, for example, secondary particles formed by aggregating a plurality of primary particles containing a lithium transition metal composite oxide. When the lithium transition metal composite oxide particles have a predetermined volume average particle size and specific surface area, the output characteristics of a nonaqueous electrolyte secondary battery constructed using a positive electrode active material containing the lithium transition metal composite oxide particles are improved. Therefore, in one embodiment, the positive electrode active material may be composed 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 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 flowability as a positive electrode active material is good, and the output characteristics may be further improved when a nonaqueous electrolyte secondary battery is constructed. Here, the volume average particle size of the lithium transition metal composite oxide particles is determined, as with the positive electrode active material, as the particle size corresponding to 50% of the cumulative volume from the small diameter side in the volume-based cumulative particle size distribution.

[0022] The positive electrode active material is composed of lithium transition metal composite oxide particles and nanoparticles of an aluminum compound, and therefore the volume average particle size of the lithium transition metal composite oxide particles may 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 based on electron microscope observation of the primary particles SEM is, for example, 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. SEMis preferably 1.2 μm or less, and more preferably 1.0 μm or less. If the average particle size of the primary particles as determined by electron microscope observation is within the above range, the output power of a non-aqueous electrolyte secondary battery may be improved when the battery is constructed.

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

[0025] The positive electrode active material is composed of secondary particles containing a lithium transition metal composite oxide and nanoparticles of an aluminum compound. Therefore, the specific surface area of ​​the lithium transition metal composite oxide particles may be approximately the same as that of the positive electrode active material, or may be 80% to 110% of that of the positive electrode active material.

[0026] The lithium transition metal composite oxide particles may be secondary particles formed by aggregating a plurality of primary particles and may have voids therein. This may facilitate achieving a predetermined specific surface area, which may further improve the output characteristics of non-aqueous electrolyte secondary batteries. The presence of voids in the lithium transition metal composite oxide particles can be evaluated, for example, from their cross-sectional images. Cross-sectional images of the particles can be obtained, for example, using a scanning electron microscope (SEM).

[0027] When lithium transition metal composite oxide particles have voids inside, the degree of voids can be evaluated, for example, by porosity. Porosity is an indicator of the proportion of voids formed inside secondary particles composed of lithium transition metal composite oxide and is measured by cross-sectional observation of the secondary particles. The porosity of the 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 a similar specific surface area, the contact area with the electrolyte can be increased, making it possible to obtain a positive electrode active material with better output characteristics. This results in a secondary battery with improved output density per volume. The porosity of the lithium transition metal composite oxide particles may preferably be 25% to 45%, or 27% to 29%, or 30% or more, or 40% to 38%.

[0028] The porosity of secondary particles can be measured by observing and analyzing the cross-sections of randomly selected secondary particles using a scanning electron microscope (SEM). Specifically, multiple secondary particles are embedded in a resin or other material, and a cross-section sample is prepared using a cross-section polisher or other processing method, allowing cross-section observation of the secondary particles using a scanning electron microscope. Then, 100 secondary particles with a cross-sectional size within ±1 μm of the volume average particle diameter (D50) of the lithium transition metal composite oxide particles are randomly selected. For each secondary particle, image analysis software (e.g., HALCON; manufactured by MVTec) is used to detect the voids (spaces) within the secondary particle as white and the dense areas within the secondary particle outline as black. The total area of ​​the white and black areas of the selected 100 secondary particles is calculated, and the porosity can be calculated by calculating the ratio of the void area 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 a non-aqueous electrolyte secondary battery containing an aluminum compound is equivalent to the porosity of the secondary particles (base material) made of a lithium transition metal composite oxide.

[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 metal element selected from the group consisting of aluminum (Al) and manganese (Mn). In addition, the lithium transition metal composite oxide may further contain at least one second metal 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 second metal 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 the lithium transition metal composite oxide, the ratio of the number of moles of nickel to the total number of moles of metal elements other than lithium may be, for example, greater than 0, preferably 0.33 or greater. The ratio of the number of moles of nickel to the total number of moles of metal elements other than lithium may be 0.4 or greater, or 0.45 or greater. Furthermore, the ratio of the number of moles of nickel to the total number of moles of metal elements other than lithium may be, for example, less than 1, preferably 0.95 or less, 0.8 or less, or 0.6 or less. When the ratio of the number of moles of nickel is within the above-mentioned range, it is possible to achieve both good charge / discharge capacity at high voltage and good cycle characteristics in a nonaqueous 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, and more preferably 0.02 or more, 0.05 or more, 0.1 or more, or 0.15 or more. 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, less than 1, preferably 0.6 or less, 0.4 or less, or 0.35 or less. 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-mentioned range, sufficient charge / discharge capacity at high voltages can be achieved in a nonaqueous electrolyte secondary battery.

[0032] When the 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 greater, more preferably 0.05 or greater, 0.1 or greater, or 0.15 or greater. 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. 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, a nonaqueous electrolyte secondary battery can achieve both high charge / discharge capacity and safety.

[0033] In the lithium transition metal composite oxide, the ratio of the number 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. The ratio of the number 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 nonaqueous electrolyte in a nonaqueous electrolyte secondary battery using a positive electrode active material containing the resulting lithium transition metal composite oxide is suppressed, thereby tending to improve the output of the nonaqueous 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 in a nonaqueous electrolyte secondary battery.

[0034] When the lithium transition metal composite oxide contains cobalt and manganese in addition to nickel, the molar ratio 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 cobalt, manganese, and aluminum in addition to nickel, the molar ratio 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. Further, 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<...>0000037<...>may represent at least one of Mn and Al. M 2may 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, or may represent at least one selected from the group consisting of Zr, Ti, Mg, Ta, Nb, Mo, and W.

[0039] The content of the 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 the 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 as aluminum compound particles independent of the lithium transition metal composite oxide particles, or at least a portion of the aluminum compound particles may adhere to the surfaces of the lithium transition metal composite oxide particles. From the viewpoint of the flowability of the positive electrode active material as a powder, the adhesion of the aluminum compound particles to the surfaces of the lithium transition metal composite oxide particles is preferably physical adsorption. Physical adsorption may be due to, for example, van der Waals forces. Furthermore, from the viewpoint of the flowability of the positive electrode active material as a powder, the adhesion of the aluminum compound particles to the surfaces of the lithium transition metal composite oxide particles is preferably not accompanied by 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, for example, by heat treatment, mechanochemical treatment, or the like, of a mixture of the aluminum compound and the lithium transition metal composite oxide. Therefore, the positive electrode active material may be a non-heat-treated product containing the aluminum compound and the lithium transition metal composite oxide. Here, the term "non-heat-treated product" means a product obtained without heat treatment of a mixture containing an aluminum compound and a lithium transition metal composite oxide at a temperature of 300° C. or higher, or 200° C. or higher, for example, 2 hours or longer, or 30 minutes or longer. When the positive electrode active material is non-heat-treated, the effect of improving fluidity by mixing an aluminum compound may be greater.

[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. The inclusion of a specific aluminum compound may further improve the fluidity of the positive electrode active material as a powder while reducing the effect on the output characteristics and the viscosity of the slurry containing the positive electrode active material.

[0042] From the viewpoint of fluidity as a powder of a positive electrode active material, the average particle size of the aluminum compound may be, for example, 1 nm or more and less than 500 nm, and preferably 2 nm or more, 5 nm or more, or 10 nm or more. The average particle size may be preferably 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] 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 the lithium transition metal composite oxide, from the viewpoint of output characteristics in a non-aqueous electrolyte secondary battery. Furthermore, 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 the lithium transition metal composite oxide, from the viewpoint of flowability of the positive electrode active material as a powder. In one embodiment, the content of the aluminum compound in the positive electrode active material may be 0.01 mol% or more to 2 mol% or less, per mole of the lithium transition metal composite oxide.

[0044] Tungsten Compounds The positive electrode active material may further contain a tungsten compound or may contain particles of the tungsten compound. When the positive electrode active material contains a tungsten compound, for example, it may be possible to effectively suppress an increase in viscosity of a slurry containing the positive electrode active material. In particular, when the volume average particle diameter of the lithium transition metal composite oxide particles is 4.7 μm or less and the specific surface area is 1.3 m, the positive electrode active material may contain a tungsten compound. 2 / g or more, 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. Furthermore, 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, the attachment of the tungsten compound to the surface of the lithium transition metal composite oxide particles is preferably physical adsorption.

[0045] The tungsten compound constituting the positive electrode active material is preferably tungsten oxide (e.g., WO3). By including a specific tungsten compound, an increase in viscosity of the slurry containing the positive electrode active material can sometimes be more effectively suppressed.

[0046] The average particle size of the tungsten compound may be, for example, 0.05 μm or more and 2 μm or less, preferably 0.25 μm or more or 0.50 μm or more, from the viewpoint of suppressing an increase in viscosity of a slurry containing the positive electrode active material. The average particle size may be preferably 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 content of the tungsten compound in the positive electrode active material may be, for example, 0.1 mol% or more and 2 mol% or less per mole of the lithium transition metal composite oxide. From the viewpoint of output characteristics of a nonaqueous electrolyte secondary battery, the content of the tungsten compound in the positive electrode active material may be preferably 1.8 mol% or less, or 1.5 mol% or less per mole of the lithium transition metal composite oxide. Furthermore, from the viewpoint of suppressing an increase in viscosity of a slurry containing the positive electrode active material, the content of the tungsten compound in the positive electrode active material may be preferably 0.2 mol% or more, or 0.3 mol% or more per mole of the lithium transition metal composite oxide.

[0048] metal compound In one embodiment, the positive electrode active material may contain another metal compound instead of an aluminum compound. Examples of the other metal compound include a tungsten compound, a titanium compound, a zirconium compound, a silicon compound, and a magnesium compound. The positive electrode active material may contain at least one metal compound selected from the group consisting of these compounds. From the viewpoint of achieving both fluidity and output characteristics, the other metal compound preferably contains at least one metal compound selected from the group consisting of a tungsten compound, a titanium compound, a silicon compound, and a magnesium compound. Considering the viscosity of the slurry during positive electrode preparation, the other metal compound more preferably contains at least one tungsten compound. The other metal compound may be, for example, an oxide, hydroxide, or nitride. 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 the lithium transition metal composite oxide.

[0049] Method for producing positive electrode active material for non-aqueous electrolyte secondary battery 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 a 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 a lithium transition metal composite oxide to be prepared 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 m 2 / g or more.

[0050] Preparation process In the preparation step, particles containing a desired lithium transition metal composite oxide (hereinafter 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 the like, or may be prepared by manufacturing using a lithium transition metal composite oxide manufacturing method described below. Details and preferred embodiments of the lithium transition metal composite oxide particles to be prepared are the same as those of the lithium transition metal composite oxide particles described in the positive electrode active material for non-aqueous electrolyte secondary batteries.

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

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

[0053] The amount of the aluminum compound mixed with the lithium transition metal composite oxide particles in the mixing step may be, for example, 2 mol% or less, preferably 1.8 mol% or less, or 1.5 mol% or less, relative to 1 mol of the lithium transition metal composite oxide. The amount of the aluminum compound mixed in the mixing step may be, for example, 0.01 mol% or more, preferably 0.05 mol% or more, or 0.1 mol% or more, relative to 1 mol of the lithium transition metal composite oxide.

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

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

[0056] The amount of the tungsten compound mixed with the lithium transition metal composite oxide particles may be, for example, 0.1 mol% or more and 2 mol% or less per mole of the lithium transition metal composite oxide. Preferably, the amount of the tungsten compound mixed may be 1.8 mol% or less, or 1.5 mol% or less, or 0.2 mol% or more, or 0.3 mol% or more per mole of the 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 a positive electrode active material preferably does not include a heat treatment step of heat-treating a mixture containing lithium transition metal composite oxide particles and an aluminum compound. The absence of a heat treatment step allows the fluidity of the positive electrode active material to be maintained at a temperature of, for example, 300°C or higher, or 200°C or higher, for example, 2 hours or longer, or 30 minutes or longer, for example. Therefore, in this specification, obtaining a mixture at a temperature of, for example, 150°C or lower does not constitute heat treatment.

[0059] Method for producing lithium transition metal composite oxide The lithium transition metal composite oxide particles used in the method for producing a positive electrode active material can be produced, for example, by the following production method. The method for producing a lithium transition metal composite oxide may include a composite oxide preparation step of preparing a nickel-containing composite oxide, and a synthesis step of mixing the nickel-containing composite oxide with a lithium compound and heat-treating the mixture 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 include secondary particles formed by aggregation of a plurality of primary particles containing the lithium transition metal composite oxide.

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

[0061] Synthesis process The synthesis step 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 containing lithium and nickel and having a layered structure. In the synthesis step, the lithium contained in the lithium compound may diffuse into the nickel composite oxide, thereby obtaining the lithium transition metal composite oxide.

[0062] Examples of methods for mixing the nickel composite oxide and the lithium compound include a method of dry mixing the nickel composite oxide and the lithium compound using a stirring mixer or the like, and a method of preparing a slurry of the nickel composite oxide and wet mixing it using a mixer such as a ball mill. Examples of the lithium compound include lithium hydroxide, lithium nitrate, lithium carbonate, and mixtures thereof.

[0063] The ratio of the number of moles of lithium to the total number of moles of metal elements other than lithium in the lithium mixture (also referred to as the lithium ratio) may be, for example, 0.9 or more and 1.3 or less, and preferably 1 or more and 1.2 or less. When the lithium ratio is 0.9 or more, the generation of by-products tends to be suppressed. Furthermore, when the lithium ratio is 1.3 or less, an increase in the amount of alkaline components present on the surface of the lithium mixture is suppressed, and moisture adsorption due to the deliquescence of the alkaline components is suppressed, which tends to improve handleability.

[0064] When mixing a nickel composite oxide with a lithium compound, in addition to the lithium compound, a simple substance, alloy, or compound containing at least one second metal 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 second metal element include hydroxides, oxides, and carbonates. The second metal element may be at least one selected from the group consisting of zirconium, titanium, magnesium, tantalum, niobium, molybdenum, and tungsten. When tungsten is included as the second metal element, it is preferable because it tends to result in particles with higher porosity and a battery with higher output characteristics.

[0065] The heat treatment temperature in the synthesis step may be, for example, 650°C or higher and 990°C or lower, and preferably 700°C or higher, 730°C or higher, or 760°C or higher. The heat treatment temperature may also be preferably 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 is preferably performed at multiple temperatures from the viewpoint of particle control. When performing heat treatment at multiple temperatures, it is desirable to, for example, hold the first temperature for a predetermined time, then further increase the temperature, and hold the second temperature for a predetermined time. The first temperature is, for example, 650°C or higher and 850°C or lower, preferably 700°C or higher and 820°C or lower, and the second temperature is, for example, 730°C or higher and 960°C or lower, preferably 760°C or higher and 920°C or lower. 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 a high porosity, heat treatment is preferably performed at 800°C or higher and 980°C or lower for 8 hours or longer, and more preferably at 810°C or higher and 920°C or lower for 8 hours or longer, and the heat treatment time may be, for example, 20 hours or shorter. The heat treatment time, as the time during which the maximum temperature is maintained, may be, for example, 2 hours or longer, preferably 4 hours or longer or 6 hours or longer. The heat treatment time may be, for example, 20 hours or shorter, preferably 18 hours or shorter or 12 hours or shorter, and when heat treatment is performed at multiple temperatures, each may be 1 hour or longer and 19 hours or shorter. The heat treatment may be performed in an atmosphere in the presence of oxygen, preferably an atmosphere containing 10% by volume or higher and 100% by volume or lower of oxygen.

[0066] In the method for producing a lithium transition metal composite oxide, after the synthesis step, the heat-treated product obtained may be subjected to treatments such as crushing, pulverization, dry sieving, etc., as required.

[0067] Method for producing nickel composite oxide The method for producing a nickel composite oxide may include, for example, a first solution preparation step of preparing a first solution containing nickel ions and, optionally, cobalt ions, a second solution preparation step of preparing a second solution containing a complex ion-forming agent, 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 separately and simultaneously supplying the first solution and the second solution to the liquid medium to obtain a reaction solution maintained at a pH in the range of 10 to 13.5, 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 of the method for obtaining such a composite oxide, see, for example, JP 2003-292322 A and JP 2011-116580 A (U.S. Patent Application Publication No. 2012 / 270107 A).

[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 facilitate the dissolution of the salt containing each metal element. When preparing the first solution, a basic substance may be further added to adjust the pH. The total number of moles of metal elements such as nickel in the first solution may be appropriately set according to the average particle size of the target nickel composite oxide. Here, the total number of moles of metal elements refers to the total number of moles of nickel and cobalt when the first solution contains nickel and cobalt, or the total number of moles of nickel, cobalt, and manganese when 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. The first solution may also contain, in addition to these, ions of at least one second metal 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 second metal element may be at least one element 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 terms of the total of all metal ions. The metal ion concentration may preferably be 1.5 mol / L or more, or 1.7 mol / L or more. The metal ion concentration may preferably be 2.2 mol / L or less, or 2.0 mol / L or less. When the metal ion concentration in the first solution is 1.0 mol / L or more, a sufficient amount of crystallized material is obtained per reaction vessel, thereby improving productivity. On the other hand, when the metal ion concentration in the first solution is 2.6 mol / L or less, the metal salt concentration is prevented from exceeding its saturation concentration at room temperature, and a 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 capable of forming a complex ion with the metal ion contained in the first solution. For example, when the complex ion-forming factor is ammonia, an aqueous ammonia solution can be used as the second solution. The content of ammonia contained in the aqueous ammonia solution may be, for example, 5% by mass or more and 25% by mass or less. The content of ammonia may preferably be 10% by mass or more, or 12% by mass or more. The content of ammonia may preferably 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 having a pH in the range of 10 to 13.5 is prepared. The liquid medium is adjusted to a pH of 10 to 13.5 by, for example, adding a predetermined amount of water and a basic solution such as an aqueous sodium hydroxide solution to a reaction vessel. Adjusting the pH of the solution to 10 to 13.5 can suppress pH fluctuations in the reaction solution at the initial stage of the reaction.

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

[0074] In the crystallization step, it is preferable to supply each solution so that the pH of the reaction solution is maintained in the range of 10 to 13.5. For example, the pH of the reaction solution can be maintained in the 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 (e.g., sulfate and nitric acid components other than metals contained in the reaction solution) contained in the obtained composite hydroxide is sufficiently reduced, and a decrease in the capacity of the non-aqueous electrolyte secondary battery, which is the final product, tends to be suppressed. Furthermore, if the pH is 13.5 or lower, the generation of minute secondary particles is suppressed, and the handleability of the obtained composite hydroxide may be improved. The pH of the reaction solution to be maintained may be preferably 10.5 or higher, or 10.9 or higher, and may also be preferably 11.7 or lower, or 11.3 or lower. The temperature of the reaction solution may be controlled to be, for example, in the range of 25°C to 80°C, preferably 40°C to 75°C, or 50°C to 70°C. The atmosphere in the crystallization step can be a low oxidizing atmosphere, and for example, the oxygen concentration can be maintained at 10% by volume or less.

[0075] In the crystallization step, the nickel ion concentration in the reaction solution may be maintained, for example, in the range of 10 ppm to 1000 ppm, and is preferably maintained in the range of 10 ppm to 100 ppm. If the nickel ion concentration is 10 ppm or higher, the composite hydroxide is sufficiently precipitated. If the nickel ion concentration is 1000 ppm or lower, the amount of nickel eluted is small, thereby preventing deviation from the target composition. For example, when an aqueous ammonia solution is used as the second solution (complex ion-forming solution), the nickel ion concentration can be adjusted by supplying the second solution so that the ammonium ion concentration in the reaction solution is 1000 ppm to 15000 ppm.

[0076] The time for supplying the first solution may be, for example, 6 hours or more and 60 hours or less, and may preferably be 8 hours or more or 10 hours or more. The time for supplying the first solution may preferably be 42 hours or less, 24 hours or less, or 18 hours or less. If the time is 6 hours or more, the precipitation rate of the composite hydroxide slows, and therefore, a nickel composite oxide with higher smoothness tends to be obtained. If the time is 60 hours or less, productivity can be further improved.

[0077] The value obtained by taking the total number of moles of nickel, etc. in the first solution supplied throughout the crystallization process as the denominator and the total number of moles of nickel, etc. in the first solution supplied 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. Also, if it is 0.125 or less, a nickel composite oxide with a larger specific surface area tends to be obtained.

[0078] The method for producing a nickel composite oxide may include a seed generation step prior to the crystallization step. In the seed generation step, for example, a part 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 seed crystals. That is, the liquid medium supplied to the crystallization step may be a seed solution containing a nickel-containing composite hydroxide. The temperature in the seed generation step may be, for example, 40°C to 80°C. The atmosphere in the seed generation step may be a low-oxidizing atmosphere, and the oxygen concentration may be maintained at, for example, 10% by volume or less.

[0079] If composite hydroxide particles are generated in advance in a liquid medium prior to the crystallization step, each composite hydroxide particle generated in advance serves as a seed crystal that constitutes one composite hydroxide particle obtained after the crystallization step. This allows the total number of secondary particles of the composite hydroxide obtained after the crystallization step to be controlled by the number of composite hydroxide particles generated in advance. For example, if a large amount of the first solution is supplied in advance, the number of composite hydroxide particles generated increases, and the average particle size of the secondary particles of the composite hydroxide after the crystallization step tends to be smaller.

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

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

[0082] Complex hydroxide heat treatment process In the composite hydroxide heat treatment step, the obtained composite hydroxide is heat treated to obtain a nickel composite oxide. The heat treatment dehydrates the composite hydroxide to produce a nickel composite oxide. The nickel composite oxide may be a precursor of a lithium transition metal composite oxide or a precursor of a positive electrode active material.

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

[0084] In the nickel composite oxide, the ratio of the number 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 the number of moles of nickel to the total number of moles of metal elements may preferably be 0.33 or greater. The ratio of the number of moles of nickel to the total number of moles of metal elements may be 0.4 or greater, or 0.45 or greater. Furthermore, the ratio of the number 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] The nickel composite oxide may contain cobalt in its composition. When the nickel composite oxide contains cobalt in its 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 may preferably be 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] The nickel composite oxide may contain at least one of manganese and aluminum in its composition. When the nickel composite oxide contains at least one of manganese and aluminum in its 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. Furthermore, the ratio of the total number of moles of manganese and aluminum to the total number of moles of metal elements is, 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] The nickel composite oxide may contain at least one type of second metal element in its composition. When the nickel composite oxide contains at least one type of second metal element in its composition, the ratio of the total number of moles of the second metal element to the total number of moles of the metal elements contained in the nickel composite oxide may be, for example, greater than 0, 0.001 or more, or 0.003 or more. Furthermore, the ratio of the total number of moles of the second metal element to the total number of moles of the metal elements may be, for example, 0.05 or less, 0.02 or less, 0.015 or less, or 0.01 or less.

[0088] The nickel composite oxide may have a composition represented by the following formula (2), for example. 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, even 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. The tap density of the nickel composite oxide is 1.3 g / cm 3When the ratio of the number of moles of nickel to the total number of moles of metal elements contained in the nickel composite oxide is 0.5 or more, the lithium transition metal composite oxide obtained by mixing and reacting the nickel composite oxide with the lithium compound and the tungsten compound tends to be obtained as particles with a higher porosity, and the output characteristics tend to be further improved.

[0091] The particle size of the nickel composite oxide may be 1 μm or more and 8 μm or less, and preferably 2 μm or more, 2.5 μm or more, or 3 μm or more. The particle size of the nickel composite oxide may be preferably 6 μm or less, 5 μm or less, or 4 μm or less. By making the particle size of the nickel composite oxide 1 μm or more and 8 μm or less, the obtained lithium transition metal composite oxide tends to have a larger specific surface area when the tap density range described above is satisfied.

[0092] Electrodes for non-aqueous electrolyte secondary batteries 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 including the above-described positive electrode active material. A non-aqueous electrolyte secondary battery including such an electrode can achieve excellent output characteristics.

[0093] The density of the positive electrode active material layer is, for example, 2.6 g / cm 3 More than 3.9g / cm 3 may be less than or equal to 2.8 g / cm 3 More than 3.8g / cm 3 Below, 3.1g / cm 3 More than 3.7g / cm 3 or less, or 3.2 g / cm 3 More than 3.6g / cm 3 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 to an electrode composition described later on a 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, a conductive additive, a binder, and the like together with a solvent onto the current collector, followed by drying and pressure treatment. 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 The nonaqueous electrolyte secondary battery includes the above-described electrodes for a nonaqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery is configured to include, in addition to the electrodes for a nonaqueous electrolyte secondary battery, a negative electrode for a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte, a separator, etc. For the negative electrode, nonaqueous electrolyte, separator, etc. of the nonaqueous electrolyte secondary battery, those for nonaqueous electrolyte secondary batteries described in, for example, JP 2002-075367 A, JP 2011-146390 A, JP 2006-12433 A (the entire disclosures of which are incorporated herein by reference) can be used as appropriate.

[0096] It should be noted that the present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and it goes without saying that any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

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

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

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

[0100] Seed generation process While stirring the liquid medium, the first solution was added to the liquid medium in an amount of 10 moles in total (molar number of moles of nickel, etc.) to precipitate a composite hydroxide containing nickel, cobalt, and manganese.

[0101] Crystallization process The remaining 340 moles of the first solution, the sodium hydroxide aqueous solution, and the second solution were added over 12 hours while stirring the reaction solution, so that the pH in the reaction solution was maintained at approximately 10.9 to 11.3 and the ammonium ion concentration was approximately 4000 ppm, thereby precipitating 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 subjected to heat treatment at 320°C for 16 hours in an air atmosphere, and recovered as 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 / cm. 3 A composite oxide of the above 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 air atmosphere. The heat treatment was carried out at a first temperature of 780°C for 2 hours and at a second temperature of 910°C for 4 hours to obtain a heat-treated product. The heat-treated product was pulverized and dry-sieved to obtain a lithium mixture with the 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 volume average particle size of the obtained lithium transition metal composite oxide as the base material was 4.4 μm and the specific surface area was 2.06 m 2 / g, and the porosity was 30%.

[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 in a high-speed shear mixer. The mixture was then dry-sieved to obtain the positive electrode active material of Example 1.

[0105] The resulting positive electrode active material of Example 1 had a volume average particle size of 4.4 μm and a specific surface area of ​​2.26 m 2 / g, and the porosity was 30%.

[0106] The positive electrode active material obtained in Example 1 was observed using a scanning electron microscope (Hitachi High-Technologies SU8230) at an accelerating voltage of 1.5 kV to obtain a scanning electron microscope (SEM) image. The results are shown in FIG.

[0107] Comparative Example 1 The same procedures as in Example 1 were carried out except that in the crystallization step, the pH of the reaction solution was maintained at about 11.3 to 11.7, the ammonium ion concentration was adjusted to about 6000 ppm, the temperature of the reaction solution was controlled to about 45°C, and the supply time of the first solution in the crystallization step was set to 18 hours, to obtain a volume average particle size of 3.4 μm and a tap density of 1.46 g / cm. 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 in 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 of Comparative Example 1. The volume average particle size of the positive electrode active material of Comparative Example 1 was 3.1 μm and the specific surface area was 1.09 m 2 / g, and the porosity was 5%.

[0109] Example 2 A positive electrode active material of Example 2 was obtained in the same manner as in Example 1, except that in the mixing step, tungsten oxide (WO: manufactured by Nippon New Metals Co., Ltd.; average particle size 1000 nm) was further added as a tungsten compound in addition to the aluminum compound, and was blended with the lithium transition metal composite oxide so that the molar ratio was (Ni+Co+Mn):Al:W=1:0.005:0.005.

[0110] The resulting positive electrode active material of Example 2 had a volume average particle size of 4.4 μm and a specific surface area of ​​2.29 m 2 / g, and the porosity was 30%.

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

[0112] The volume average particle size of the obtained positive electrode active material of Example 3 was 4.3 μm and the specific surface area was 1.43 m 2 / g and the porosity was 17%.

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

[0114] The resulting positive electrode active material of Example 4 had a volume average particle size of 3.9 μm and a specific surface area of ​​2.90 m 2 / g and the porosity was 31%.

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

[0116] The volume average particle size of the obtained positive electrode active material of Example 5 was 3.9 μm and the specific surface area was 3.33 m 2 / g and the porosity was 31%.

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

[0118] The resulting positive electrode active material of Example 6 had a volume average particle size of 3.9 μm and a specific surface area of ​​3.84 m 2 / g and the porosity was 32%.

[0119] Reference example 1 Except for not performing the mixing step, the lithium transition metal composite oxide serving as the base material obtained in Example 1 was used as the positive electrode active material of Reference Example 1 in the same manner as in Example 1. In addition, an SEM image was obtained in the same manner as in Example 1. The results are shown in FIG.

[0120] Reference example 2 A positive electrode active material of Reference Example 2 was obtained in the same manner as in Example 1, except that in the mixing step, tungsten oxide (WO: manufactured by Nippon New Metals 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 at a molar ratio of (Ni+Co+Mn):W=1:0.005.

[0121] The volume average particle size of the obtained positive electrode active material of Reference Example 2 was 4.4 μm and the specific surface area was 2.07 m 2 / g, and the porosity was 30%.

[0122] Reference example 3 A positive electrode active material of Reference Example 3 was obtained in the same manner as in Example 1, except that in the mixing step, titanium oxide (TiO: manufactured by Nippon Aerosil Co., Ltd.; average particle size 20 to 40 nm) was used as a titanium compound instead of the aluminum compound, and was blended with the lithium transition metal composite oxide at a molar ratio of (Ni+Co+Mn):Ti=1:0.003.

[0123] The resulting positive electrode active material of Reference Example 3 had a volume average particle size of 4.4 μm and a specific surface area of ​​2.13 m 2 / g, and the porosity was 30%.

[0124] Reference example 4 A positive electrode active material of Reference Example 4 was obtained in the same manner as in Example 1, except that in the mixing step, zirconium oxide (ZrO: manufactured by TECNAN Corporation; average particle size 20 to 30 nm) was used as a zirconium compound instead of the aluminum compound, and was blended with the lithium transition metal composite oxide at a molar ratio of (Ni+Co+Mn):Zr=1:0.002.

[0125] The resulting positive electrode active material of Reference Example 4 had a volume average particle size of 4.4 μm and a specific surface area of ​​2.21 m 2 / g, and the porosity was 30%.

[0126] Reference example 5 A positive electrode active material of Reference Example 5 was obtained in the same manner as in Example 1, except that in the mixing step, silicon dioxide (SiO: manufactured by Nippon Aerosil Co., Ltd.; average particle size 40 to 50 nm) was used as a silicon compound instead of the aluminum compound, and was blended with the lithium transition metal composite oxide at a molar ratio of (Ni+Co+Mn):Si=1:0.005.

[0127] The volume average particle size of the obtained positive electrode active material of Reference Example 5 was 4.4 μm and the specific surface area was 2.16 m 2 / g, and the porosity was 30%.

[0128] Example 7 A positive electrode active material of Example 7 was obtained in the same manner as in Example 1, except that in the mixing step, aluminum oxide (AlO: manufactured by CABOT Corporation; average particle size 20 to 30 nm) was replaced with aluminum oxide (AlO: manufactured by Aldrich Chemical Industries, Ltd.; average particle size 200 to 300 nm) as the aluminum compound, and the lithium transition metal composite oxide was blended in a molar ratio of (Ni+Co+Mn):Al=1:0.005.

[0129] The resulting positive electrode active material of Example 7 had a volume average particle size of 4.4 μm and a specific surface area of ​​2.33 m 2 / g, and the porosity was 30%.

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

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

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

[0133] Example 9 The lithium transition metal composite oxide obtained in Reference Example 6 was blended with aluminum oxide (Al2O3: manufactured by CABOT; average particle size 20 to 30 nm) as an aluminum compound and tungsten oxide (WO3: manufactured by Nippon New Metals Co., Ltd.; average particle size 1000 nm) as a tungsten compound in a molar ratio of (Ni+Co+Mn):Al:W=1:0.005:0.005 relative to the lithium transition metal composite oxide, and then mixed in a high-speed shear mixer. The resulting mixture was then dry-sieved to obtain the positive electrode active material of Example 9.

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

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

[0136] The volume average particle size of the obtained positive electrode active material of Comparative Example 2 was 3.0 μm and 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 the molar ratio of Li:(Ni+Co+Mn):Zr:W=1.12:1:0.005:0.01 was achieved, and the mixture was heat-treated at 920°C for 8 hours in an air atmosphere to produce a composite oxide having the 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 m 2 / g, and the porosity was 5%.

[0139] Example 10 The positive electrode active material of Example 10 was obtained in the same manner as in Example 9, except that in the synthesis step, the components were mixed so that 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 resulting positive electrode active material of Example 10 had a volume average particle size of 3.7 μm and a specific surface area of ​​2.79 m 2 / g and the porosity was 36%.

[0141] [Table 1]

[0142] Process flow evaluation Approximately 50 g of each of the positive electrode active materials obtained above was weighed and placed in a powder property measuring device (Powder Tester (registered trademark); manufactured by Hosokawa Micron Corporation). Thereafter, the angle of repose and the angle of collapse were automatically measured, and the difference angle was calculated. The results are shown in Table 2.

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

[0144] Preparation of positive electrode mixture slurry A positive electrode mixture slurry was prepared by dispersing 89.5 parts by mass of the positive electrode 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 thickening rate The viscosity of the positive electrode mixture slurry prepared above was measured immediately after the slurry preparation and 6 hours after the preparation using an E-type viscometer (manufactured by Thermo Scientific; HAAKE Viscotester550). The viscosity increase rate was calculated by dividing the viscosity of the positive electrode mixture slurry 6 hours after the preparation by the viscosity immediately after the preparation, as shown in the following formula. (Slurry viscosity after 6 hours) / (Slurry viscosity immediately after preparation)

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

[0147] Preparation of evaluation battery Using the positive electrode active material obtained above, a battery for evaluation was fabricated in the following manner.

[0148] Preparation of the positive electrode A positive electrode mixture slurry was prepared by dispersing 92 parts by weight of the positive electrode active material, 3 parts by weight of acetylene black, and 5 parts by weight of polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone (NMP). The resulting positive electrode mixture slurry was applied to an aluminum foil current collector, dried, and then compression-molded using a roll press. The resulting mixture was then cut to a predetermined size to fabricate a positive electrode.

[0149] Preparation of the negative electrode A negative electrode slurry was prepared by dissolving 97.5 parts by weight of artificial graphite, 1.5 parts by weight of carboxymethyl cellulose (CMC), and 1.0 part by weight of SBR (styrene butadiene rubber) in pure water. The resulting negative electrode slurry 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 specified size.

[0150] After attaching lead electrodes to the positive and negative electrode 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 poured into the laminate pack under an argon atmosphere and sealed to prepare a test 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 hexafluorophosphate (LiPF6) dissolved to a concentration of 1 mol / L. The test battery thus obtained was placed in a thermostatic chamber at 25°C and aged with a weak current. The following evaluations were then performed.

[0151] Evaluation of output characteristics (measurement of DC internal resistance) The DC internal resistance of the aged test battery was measured. After constant current charging to a charge depth of 50% at a full charge voltage of 4.2 V, the test battery was placed in a -25°C environment and pulse discharged at a specific current i for 10 seconds, and the voltage V at 10 seconds was measured. The current i was plotted on the horizontal axis and the voltage V on the vertical axis, and the intersection points were plotted. The slope of the line connecting the intersection points was taken as the DC internal resistance (DC-IR). The currents i were set to 0.02 A, 0.04 A, 0.06 A, 0.08 A, and 0.10 A. A low DC-IR indicates good output characteristics.

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

[0153] [Table 2]

[0154] [Table 3]

[0155] Tables 1 to 3 confirm 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 a metal compound with these particles 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 present invention 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 1 μm or more and 8 μm or less, and the specific surface area is 1.4 m ２ / g or more, and the difference angle obtained by subtracting the collapse angle from the repose angle measured with a powder property measuring instrument is 6° or more.

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

3. 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. 4. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the lithium transition metal composite oxide contains lithium and nickel in its composition.

5. 5. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the particles containing the lithium transition metal composite oxide have voids therein.

6. The specific surface area is 1.7 m ２ / g or more 3.3m ２ The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the SiO 2 content is 0.1 / g or less.

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

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

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

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