JP6499442B2 - Positive electrode active material for lithium ion battery and method for producing positive electrode active material for lithium ion battery - Google Patents

Description

  The present invention relates to a positive electrode active material for lithium ion batteries and a method for producing a positive electrode active material for lithium ion batteries.

As a positive electrode active material for a lithium secondary battery, there is Li (Ni, Co, Mn) O ₂ , and various composition ratios of Ni, Co, and Mn are set according to required battery characteristics. Among these, the composition containing a large amount of Ni satisfies the three requirements of capacity, output, and safety in a well-balanced manner, so that application to electric vehicle applications has begun.

  Various techniques have been studied for producing a positive electrode active material for a lithium secondary battery. For example, Patent Document 1 includes a lithium compound, at least one transition metal compound selected from V, Cr, Mn, Fe, Co, Ni, and Cu, and As, Ge, P, Pb, A step of pulverizing a compound having at least one element selected from the group consisting of Sb, Si and Sn in a liquid medium, and preparing a slurry in which these are uniformly dispersed, and a spray drying step of spray drying the slurry And a method for producing a lithium transition metal-based compound powder for a lithium secondary battery positive electrode material, including a firing step of firing the obtained spray-dried body at 950 ° C. or higher in an oxygen-containing gas atmosphere.

  Further, Patent Document 2 discloses a lithium compound, one or more transition metal compounds containing at least Mn, Ni, and Co, and an additive for suppressing grain growth and sintering during firing in a liquid medium. By a production method comprising at least a slurry preparation step for pulverizing and obtaining a slurry in which these are uniformly dispersed, a spray drying step for spray-drying the obtained slurry, and a firing step for firing the obtained spray-dried powder Mixing the obtained lithium-containing transition metal composite oxide powder A with lithium-containing transition metal composite oxide powder B having a layered structure and containing at least Ni and Co as transition metals and Li A method for producing a positive electrode active material for a lithium secondary battery is disclosed.

Further, in Patent Document 3, Li ₂ CO ₃ , MnCO ₃ , and CoCO ₃ are weighed, ethanol is added thereto, mixed with a ball mill, dried, heat-treated, and then ethanol is added again. A method for producing a positive electrode active material for a lithium secondary battery that is pulverized for a time by a ball mill is disclosed.

WO2011 / 083861 JP 2009-32647 A JP-A-4-106875

The production methods described in Patent Documents 1 and 2 are such that the Li compound is uniformly coated on the surface of the transition metal compound as compared with the conventional dry production method (Example 2 of Patent Document 3). Alternatively, the transition metal compound and Li are blended intimately, and as a result, the electrode using the powder obtained by firing the powder after spray drying is less likely to cause gelation due to residual Li and may have fewer defective products. However, in these spraying methods, as in Example 1 of Patent Document 1 and Example 1 of Patent Document 2, for example, a Li compound, a Ni compound, a Co compound, a Mn compound, and an additive are individually added. In the past, a method of blending and spraying was used. In this case, there are Ni compounds, Co compounds, and Mn compounds with large particle diameters, so in the active material powder after firing, there are Ni-rich, Co-rich, and Mn-rich spots inside the particles and / or on the particle surfaces. It has occurred. This is because, in particular, a compound having a large amount of Ni ²⁺ such as lithium nickel cobalt manganese oxide and a compound having a Ni ³⁺ which is formed by reacting a Ni-rich portion with Li have optimum firing conditions. Different. For this reason, there has been a problem that the battery characteristics are not optimized as compared with a single transition metal such as LiNiO ₂ or LiCoO ₂ . In order to solve this, in Patent Document 2, etc., wet pulverization is performed before spraying, but the transition metal compound in a state of not being well blended remains on the surface of the media used in the wet pulverization. However, since these are peeled off from the media and entered into the slurry, Ni-rich, Co-rich, and Mn-rich portions are also produced in the particles and / or on the particle surface in the firing after spray drying, resulting in a battery. The phenomenon in which the characteristics are not optimized remains, and it cannot be said that the phenomenon has been solved sufficiently.

  In general, as the Ni composition ratio increases, the charge / discharge capacity tends to increase, but on the other hand, the capacity retention rate when repeatedly charged / discharged, so-called cycle characteristics, tends to deteriorate, so that it is particularly high. There has always been a need for improved cycle characteristics in electric vehicle applications that require capacity and need to be charged and discharged at high temperatures and high currents. When improvement of cycle characteristics is required, if a step of pulverizing the positive electrode active material (or its precursor or its intermediate) is entered during the manufacturing process of the positive electrode active material for lithium ion batteries, the resulting fine particles are The electrolytic solution was decomposed more violently than the normal particles, and from this, there was room for improvement in the cycle characteristics of the positive electrode active material for lithium ion batteries of Patent Document 1 and Patent Document 2.

  Then, this invention makes it a subject to provide the manufacturing method of the positive electrode active material for lithium ion batteries with which cycling characteristics become favorable, and the positive electrode active material for lithium ion batteries.

  As a result of various studies to solve such problems, the present inventor has a predetermined composition, and controls variation in the abundance ratio of doped metal elements in the particles, that is, variation between particles. Thus, it was found that a positive electrode active material with improved cycle characteristics can be obtained.

In one aspect, the present invention completed based on the above knowledge has a composition formula: Li _a Ni _x Co _y Mn _z M _b O ₂
(In the above formula, M is at least one selected from an element group containing Mg and Al, or two or more, and 0.9 <a <1.2, 0.5 ≦ x ≦ 1.0, 0 < (b <0.1, x + y + z + b = 1.0)
And a coefficient of variation (A) of the metal element M between the particles is 0.20 or less.

  In one embodiment of the positive electrode active material for a lithium ion battery of the present invention, the coefficient of variation (A) of the metal element M is 0.15 or less.

  In another embodiment of the positive electrode active material for a lithium ion battery of the present invention, the coefficient of variation (B) of Ni, Co, and Mn between particles is 0.15 or less.

  In still another embodiment of the positive electrode active material for a lithium ion battery of the present invention, the coefficient of variation (B) of Ni, Co, and Mn between particles is 0.12 or less.

  In another aspect of the present invention, (I) a lithium salt, (II) Ni, Mn, and Co, and at least one or two or more metal elements M selected from an element group including Mg and Al, A lithium metal salt solution slurry having a solid average particle size of 5 μm or more, and spray-drying the lithium metal salt solution slurry to form a composite of lithium metal salts A method for producing a positive electrode active material for a lithium ion battery, comprising: obtaining a body powder; and firing the powder.

  In one embodiment of the method for producing a positive electrode active material for a lithium ion battery of the present invention, the spray drying is performed using a micro mist dryer.

  In another embodiment of the method for producing a positive electrode active material for a lithium ion battery of the present invention, the metal salt is a nitrate.

  In still another embodiment of the method for producing a positive electrode active material for a lithium ion battery of the present invention, the lithium salt is lithium carbonate.

In still another embodiment of the method for producing a positive electrode active material for a lithium ion battery according to the present invention, the positive electrode active material for a lithium ion battery has a composition formula: Li _a Ni _x Co _y Mn _z M _b O ₂
(In the above formula, M is at least one selected from an element group containing Mg and Al, or two or more, and 0.9 <a <1.2, 0.5 ≦ x ≦ 1.0, 0 < (b <0.1, x + y + z + b = 1.0)
It is represented by

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the positive electrode active material for lithium ion batteries from which cycling characteristics become favorable, and the positive electrode active material for lithium ion batteries can be provided.

In an Example, it is a mapping image which shows the particle | grains observed in order to evaluate a variation coefficient.

(Configuration of positive electrode active material for lithium ion battery)
The positive electrode active material for a lithium ion battery of the present invention is
Composition formula: Li _a Ni _x Co _y Mn _z M _b O ₂
(In the above formula, M is at least one selected from an element group containing Mg and Al, or two or more, and 0.9 <a <1.2, 0.5 ≦ x ≦ 1.0, 0 < (b <0.1, x + y + z + b = 1.0)
It is represented by
The ratio of lithium to all metals in the positive electrode active material for a lithium ion battery is 0.9 to 1.2. If the ratio is less than 0.9, it is difficult to maintain a stable crystal structure. This is because the high capacity cannot be secured.
On the other hand, when the nickel ratio is less than 0.5, the absolute amount of oxygen necessary for firing 1 mol of the positive electrode active material is small, and the effect of the oxidizing agent in the metal salt cannot be sufficiently obtained.

The metal element M is a trace element added to improve cycle characteristics. The coefficient of variation of the metal element M is controlled by the manufacturing method described later. If b is 0.1 or more in the composition M _b of the metal element M, battery characteristics may be poor. Therefore, the composition of the metal element M is controlled so that the composition M _{b is} 0 <b <0.1. The metal element M includes Mg and Al, and is further selected from an element group including Zr, Ti, Fe, Zn, and the like. The metal element M is preferably Mg and / or Al. The metal element M is more preferably Mg.

In _a positive electrode active material for a lithium ion battery represented by a composition formula: Li _a Ni _x Co _y Mn _z M _b O ₂ , the variation in the abundance ratio (variation between particles) of the metal element to be doped is controlled. Thus, a positive electrode active material with improved cycle characteristics can be obtained. In particular, a metal element that is a trace element usually has a large coefficient of variation, but in the present invention, attention is paid to variations in the metal element M that is the trace element. Al or Mg added in a small amount is contained in the particles or exists in the form of coating the particles, and has an effect of suppressing the deterioration of the crystals due to the use of the battery. Therefore, it is also preferable that variation in the main composition of nickel, manganese, and cobalt is suppressed (in bulk) in the entire positive electrode active material, but it is more important that the trace elements are present uniformly in each particle. The present invention has found the importance of suppressing the variation between particles of such trace elements, and from this point of view, the positive electrode active material for a lithium ion battery of the present invention is a metal between particles. The variation coefficient (A) of the element M is controlled to 0.20 or less. By controlling the coefficient of variation (A), which is an indicator of the variation in the abundance ratio (variation between particles) of the trace amount of the metal element M to be doped to 0.20 or less, the trace amount of the metal element M to be doped Can exist uniformly among the respective particles of the positive electrode active material, and the cycle characteristics of the positive electrode active material become good. The coefficient of variation (A) of the metal element M between the particles is preferably 0.15 or less, and typically 0.02 to 0.20. In the present invention, the coefficient of variation of the metal element M indicates the coefficient of variation of the one kind of element when the metal element M is composed of one kind of element. For this reason, “the coefficient of variation (A) of the metal element M between particles is 0.20 or less” indicates that the coefficient of variation of the one kind of element is 0.20 or less. The variation coefficient of the metal element M indicates the variation coefficient of each type of element when the metal element M is composed of a plurality of types of elements. Therefore, “the coefficient of variation (A) of the metal element M between the particles is 0.20 or less” indicates that the coefficient of variation for each element type is 0.20 or less.

  The positive electrode active material for a lithium ion battery of the present invention preferably has a coefficient of variation (B) of Ni, Co and Mn between particles of 0.15 or less. According to such a configuration, Ni, Co, and Mn between the particles can exist uniformly between the particles of the positive electrode active material, and the cycle characteristics and the discharge capacity of the positive electrode active material are improved. In addition, the positive electrode active material for a lithium ion battery of the present invention has a coefficient of variation (A) of the metal element M between particles such as Al and Mg added in a small amount as described above is controlled to 0.20 or less. In addition, the coefficient of variation (B) of Ni, Co, and Mn between particles is controlled to 0.15 or less. The concentration of Ni, Co, and Mn between particles is about 10 times or more the concentration of metal element M between particles such as Al and Mg added in a small amount. The coefficient of variation between the metal element M having such a concentration difference and Ni, Co, and Mn is controlled to the same level, and the cycle characteristics of the positive electrode active material become very good. The variation coefficient (B) of Ni, Co and Mn between particles is more preferably 0.12 or less, still more preferably 0.10 or less, even more preferably 0.05 or less, and even more preferably 0.03 or less. It is typically 0.01 to 0.15.

In addition, the coefficient of variation of metal elements Mg, Al, Ni, Mn, and Co between particles in the present invention is obtained using an electron beam probe microanalyzer: EPMA (JEOL Ltd .: JXA-8500F). As a specific method of calculating the coefficient of variation, first, a cross-sectional SEM is performed on the positive electrode material powder to obtain an image of the particles, and then element mapping is performed using the electron probe microanalyzer. The acceleration voltage at the time of EPMA measurement is 15.0 keV, and the irradiation current is 2.0 × 10 ⁻⁸ A. Subsequently, 20 particles having a particle diameter of 7 μm or more are arbitrarily selected from the obtained mapping image, and the composition ratio is calculated from the intensity of the electron probe microanalyzer at the center portion. From these, the coefficient of variation of the metal elements metal elements Mg, Al, Ni, Mn, and Co is calculated by the following equation.
Coefficient of variation of metal element Mg = (standard deviation of Mg composition (for 20 points)) / (average value of Mg composition (for 20 points))
Coefficient of variation of metal element Al = (standard deviation of Al composition (for 20 points)) / (average value of Al composition (for 20 points))
Coefficient of variation of metal element Ni = (standard deviation of Ni composition (for 20 points)) / (average value of Ni composition (for 20 points))
Coefficient of variation of metal element Mn = (standard deviation of Mn composition (for 20 points)) / (average value of Mn composition (for 20 points))
Coefficient of variation of metal element Co = (standard deviation of Co composition (for 20 points)) / (average value of Co composition (for 20 points))
In addition, when adding Mg and Al simultaneously, a variation coefficient is calculated | required by said formula about each element.

(Method for producing positive electrode active material for lithium ion battery)
The manufacturing method of the positive electrode active material for lithium ion batteries which concerns on embodiment of this invention is demonstrated.
First, an aqueous solution of a metal salt containing Ni, Mn and Co and at least one or more metal elements M selected from an element group containing Mg and Al is prepared. As the metal salt, nitrates, hydroxides, carbonates, oxyhydroxides, and the like can be used. Among these, nitrates are more preferable because they have a large action as an oxidizing agent. At this time, each metal contained in the metal salt solution is adjusted to have a desired molar ratio. Thereby, the molar ratio of each metal in the positive electrode active material is determined. The metal element M is an element that is doped to improve cycle characteristics, and is at least one or more selected from the group of elements including Mg and Al. The metal element M can be appropriately selected as necessary.

  Next, as a lithium source, for example, lithium carbonate is suspended in pure water, and then the above-described metal salt solution of metal is added to prepare a lithium metal salt solution slurry. At this time, the average particle diameter of the slurry can be adjusted to 5 μm or more by using a lithium source (for example, lithium carbonate) having an average particle diameter of 5 μm or more as a raw material. By setting the average particle size of the solid content of the slurry to 5 μm or more, the average particle size of the solid content becomes large. For this reason, the particle size of the dried powder and the calcined powder obtained based on the particles is increased, and the effect of improving the TAP density of the calcined powder is obtained.

Next, the lithium metal salt solution slurry is spray-dried to obtain a lithium metal salt composite powder. For spray drying, a micro mist dryer is preferably used. A micro mist dryer is a spray dryer that uses a pulverizer, and thinly spreads a lithium metal salt solution slurry by a high-speed air stream in multiple paths and causes them to collide at a predetermined collision focal point, thereby generating shock waves. A mist of μm to several tens of μm can be formed. As the atomizer, for example, a device provided with a three-fluid nozzle or a four-fluid nozzle is preferable. The atomization apparatus provided with the three-fluid nozzle or the four-fluid nozzle is provided with two liquid and gas system paths symmetrically with respect to the nozzle edge. .
The produced mist is dried in a drying chamber in a micro mist dryer to produce a dry powder of a lithium metal salt composite having an average particle size of 30 to 60 μm mainly composed of the compound on the right side of the above formula.
Thus, at least the following effects can be obtained by using the micro mist dryer:
(1) A large amount of single micron droplets can be sprayed.
(2) The average droplet diameter can be controlled by changing the gas-liquid ratio.
(3) The particle size distribution of the particles becomes sharp, and the variation in the particle size is satisfactorily suppressed.
(4) Nozzle clogging that has occurred in the external mixing method is suppressed, enabling continuous spraying for a long time.
(5) The necessary spray amount can be easily obtained by adjusting the edge length.
(6) Drying and powder dispersion can be performed simultaneously, and the production efficiency is improved.

  Next, the dry powder is filled in a baking container of a predetermined size so as to have a predetermined thickness, and baking is performed, for example, by heating and holding at 700 to 1000 ° C. for 2 to 18 hours in an air atmosphere. Thus, a positive electrode active material powder is obtained. At this time, oxygen may be blown into the air atmosphere as necessary. Although the timing of blowing can be set arbitrarily, it is particularly preferable to blow in the latter half of the firing process in which the nitrate radical has disappeared.

  According to the production method of the present invention, a positive electrode active material for a lithium ion battery having good cycle characteristics can be produced. This is achieved by mixing, spray-drying, and mixing Ni, Co, and Mn compounds in a solution. It does not require a conventional process such as wet grinding with media, and Ni-rich, Co-rich, and Mn-rich parts do not appear in the powder after firing (that is, a metal required by an electron probe microanalyzer). By spraying a slurry having a solid content with an average particle diameter of 5 μm or more only by atomization with a micromist dryer, the variation coefficient (A) of the element M is 0.20 or less). When the crushed powder was used as a positive electrode active material for a lithium ion battery, good cycle characteristics could be obtained.

  In the present invention, “pulverization” means that the secondary particles are aggregated into individual primary particles, or the tertiary aggregation formed by the secondary particles is solved. That is, “pulverization” indicates that only the powder of primary particles to secondary particles is used. In this respect, the “pulverization” is different from “pulverization” in which the original primary particles themselves are broken or made into finer particles. When pulverization is performed, finer particles than the original primary particles appear, and the cathode material causes deterioration of cycle characteristics. Therefore, in the present invention, “pulverization” is performed instead of “pulverization”.

  Examples for better understanding of the present invention and its advantages are provided below, but the present invention is not limited to these examples.

(Examples 1 to 11)
-Production of slurry-
First, nitric acid (60% aqueous solution), metallic nickel, metallic cobalt, and metallic manganese were prepared, and Mg and Al were further added as metallic elements M to dissolve these five kinds of metals in nitric acid (this solution is referred to as “ Liquid I ”). Separately, lithium carbonate was dispersed in water and stirred and mixed at 45 Hz. Next, the liquid I was dripped at about 2 L / min in the water in which this lithium carbonate was disperse | distributed, and the slurry containing Li, Ni, Co, Mn, Mg, and Al was produced. Moreover, the average particle diameter of this slurry was controlled to 5 micrometers or more by using lithium carbonate with an average particle diameter of 5 micrometers or more as a raw material. The average particle size of the solid content of the slurry was observed using Microtrack (wet particle size distribution measuring device) manufactured by Nikkiso Co., Ltd.

-Spray drying-
The slurry obtained by the raw material mixing was sprayed so that the G / S was 2000 by adjusting the supply air temperature and the exhaust gas temperature using a micro mist dryer having a three-fluid nozzle. At this time, the supply air temperature was 320 ° C., and the exhaust temperature was 165 ° C.

-Firing and crushing-
The powder obtained by drying was calcined at 900 ° C. for 2 hours using a roller hearth kiln, then cooled to 750 ° C. and calcined at that temperature for 2 hours. The mass after firing was crushed using a roll mill and a pulverizer to obtain an active material powder.

(Comparative Examples 1-3)
In the production of the slurry, an active material powder was obtained in the same manner as in the example except that the metal elements Mg and Al were not added.

(Comparative Examples 4-6)
In order to produce an active material powder in which Mg and Al are not uniformly dispersed, the following steps were performed. That is, in the preparation of the slurry, the slurry was prepared in the same manner as in the example without adding the metal elements Mg and Al. Subsequently, dry spraying was performed in the same manner as in the example. Then, after dry-mixing Mg and Al to the obtained dry powder, active material powder was obtained by performing baking and crushing like an Example.

(Comparative Examples 7-9, 11, 13)
In the preparation of the slurry, Li compound (LiOH, Li ₂ CO ₃ ), Ni compound (NiO), Co compound (Co ₃ O ₄ ), Mn compound (Mn ₂ O ₃ ), Mg compound (MgO), and Al compound ( A slurry was prepared using Al ₂ O ₃ ) as a raw material and wet-mixed in a solvent. Then, active material powder was obtained by performing spray drying, baking, and crushing similarly to the Example.

(Comparative Examples 10 and 12)
In the production of the slurry, an active material powder was produced in the same manner as in the example except that the addition amounts of the metal elements Mg and Al were large.

(Evaluation)
-Composition-
The obtained positive electrode powder was confirmed to have a layered structure by XRD diffraction, and the contents of Li, Ni, Mn, Co and metal elements Mg and Al were measured by ICP and ion chromatography. From the analysis results, a, x, y, z, and b in the case where the product is expressed by a chemical formula of Li _a Ni _x Co _y Mn _z M _b O ₂ were obtained. Each obtained ratio was described in Tables 1-3.

-Coefficient of variation-
About the obtained positive electrode powder, electron beam probe microanalyzer: EPMA (JEOL Ltd .: JXA-8500F) was used to determine the coefficient of variation of metallic elements Mg, Al, and Ni, Mn, Co between particles. It was. As a specific calculation method of the coefficient of variation, first, a cross-sectional SEM was performed on the obtained positive electrode powder to obtain an image of particles, and then element mapping was performed using the electron beam probe microanalyzer. The acceleration voltage during EPMA measurement was 15.0 keV and the irradiation current was 2.0 × 10 ⁻⁸ A. Subsequently, in the obtained mapping image, 20 particles having a particle size of 7 μm or more are selected, the composition ratio is calculated from the electron probe microanalyzer intensity at the center, and finally the average is obtained from the data of the 20 points. The coefficient of variation of the metal elements metal elements Mg, Al, Ni, Mn, and Co was calculated by the following formula.
Coefficient of variation of metal element Mg = (standard deviation of Mg composition (for 20 points)) / (average value of Mg composition (for 20 points))
Coefficient of variation of metal element Al = (standard deviation of Al composition (for 20 points)) / (average value of Al composition (for 20 points))
Coefficient of variation of metal element Ni = (standard deviation of Ni composition (for 20 points)) / (average value of Ni composition (for 20 points))
Coefficient of variation of metal element Mn = (standard deviation of Mn composition (for 20 points)) / (average value of Mn composition (for 20 points))
Coefficient of variation of metal element Co = (standard deviation of Co composition (for 20 points)) / (average value of Co composition (for 20 points))
In addition, when adding Mg and Al simultaneously, the variation coefficient was calculated | required by the said formula about each element.

  FIG. 1 shows an example of particles having a particle diameter of 7 μm or more for collecting 20 points of data in the mapping image. The composition of the central portion of the particle having a size larger than that of the periphery as shown by a circle in FIG. 1 is measured. Although there were singular points where only a large amount (or few) of Al was detected, if these values were outside the range of the average value ± (3 × standard deviation), it was judged as an outlier, and the coefficient of variation Such singular points are excluded when calculating.

-Battery characteristics-
The electrode for battery characteristic evaluation was applied to an Al foil by kneading an organic solvent NMP (N-methylpyrrolidone) at a ratio of active material: binder: conductive material = 96: 2: 2 and pressed after drying. And produced. Using these, a 2032 type coin battery for evaluation with Li as the counter electrode was prepared, 1M LiPF ₆ was used as the electrolyte, and ethylene carbonate (EC) and dimethyl carbonate (DMC) were used as the electrolyte in a volume ratio of 1: 1. What was melt | dissolved so that it might become was used, charge was performed in constant current constant voltage mode, voltage was set to 4.3V, and discharge was performed in constant current mode and voltage was set to 3.0V. The initial capacity and initial efficiency (discharge amount / charge amount) were confirmed by charging / discharging at 0.1 C, and the battery characteristics (cycle characteristics: capacity retention after repeating 20 cycles of charging / discharging at 55 ° C.) were evaluated. .
Tables 1 to 3 show the test conditions and evaluation results of Examples 1 to 11 and Comparative Examples 1 to 13. Table 4 shows the composition ratio of Example 1 and the coefficient of variation calculated using the composition ratio. In Table 4, “Sigma” indicates the composition deviation value (for 20 points) of Al, Ni, Mn, Mg, and Co, and the coefficient of variation was calculated as follows using the Sigma:
Coefficient of variation = Sigma / Average

(Evaluation results)
Examples 1 to 11 all had good battery characteristics.
Comparative Examples 1 to 3 did not contain the metal element M, and the battery characteristics were poor.
In Comparative Examples 4 to 9, since the coefficient of variation of the metal element M exceeded 0.20, the battery characteristics were poor.
In Comparative Examples 10 to 13, in the composition ratio (M _b ) of the metal element M, b was 0.1 or more, and thus the battery characteristics were poor.

Claims (8)

Composition formula: Li _a Ni _x Co _y Mn _z M _b O ₂
(In the above formula, M is at least one selected from an element group containing Mg and Al, or two or more, and 0.9 <a <1.2, 0.5 ≦ x ≦ 1.0, 0 < (b <0.1, x + y + z + b = 1.0)
Represented by
The positive electrode active material for lithium ion batteries whose coefficient of variation (A) of the metallic element M between particles is 0.20 or less.   The positive electrode active material for a lithium ion battery according to claim 1, wherein the coefficient of variation (A) of the metal element M is 0.15 or less.   The positive electrode active material for a lithium ion battery according to claim 1 or 2, wherein the coefficient of variation (B) of Ni, Co, and Mn between the particles is 0.15 or less.   The positive electrode active material for a lithium ion battery according to claim 1 or 2, wherein the coefficient of variation (B) of Ni, Co, and Mn between the particles is 0.12 or less. (I) a lithium salt;
(II) a metal salt containing Ni, Mn and Co, and at least one or more metal elements M selected from the element group containing Mg and Al;
And preparing a lithium metal salt solution slurry having an average particle size of solids of 5 μm or more, and
Obtaining a lithium metal salt composite powder by spray drying the lithium metal salt solution slurry; and
Firing the powder;
A method for producing a positive electrode active material for a lithium ion battery, comprising :
The positive electrode active material for a lithium ion battery has a composition formula: Li _a Ni _x Co _y Mn _z M _b O ₂
(In the above formula, M is at least one selected from an element group containing Mg and Al, or two or more, and 0.9 <a <1.2, 0.5 ≦ x ≦ 1.0, 0 < (b <0.1, x + y + z + b = 1.0)
Represented by
The coefficient of variation (A) of the metal element M between the particles is 0.20 or less.
A method for producing a positive electrode active material for a lithium ion battery .   The manufacturing method of the positive electrode active material for lithium ion batteries of Claim 5 which performs the said spray drying using a micro mist dryer.   The method for producing a positive electrode active material for a lithium ion battery according to claim 5 or 6, wherein the metal salt is a nitrate.   The said lithium salt is lithium carbonate, The manufacturing method of the positive electrode active material for lithium ion batteries as described in any one of Claims 5-7.