WO2023090452A1 - Precursor powder, positive electrode active material powder, positive electrode active material powder production method, positive electrode, and lithium secondary battery - Google Patents

Abstract

A precursor powder used as a precursor of a positive electrode active material for a lithium secondary battery, said precursor powder having a plurality of particles with pores, and a filling compound with which the pores are filled, wherein the particles have a layered structure and are composed of a metal complex compound including at least Ni, the filling compound is one or both of a water-soluble tungsten compound and a water-soluble molybdenum compound, and the precursor powder satisfies formula (1).　(1) 10≤(P1-P2)/P1×100<100... (P1: the maximum peak value, in the pore diameter distribution of the washed precursor powder, of the log differential pore volume in an area in which the pore diameter is at most 10 nm. P2: the value, in the pore diameter distribution of the precursor powder, of the log differential pore volume at the pore diameter of the peak exhibiting P1.)

Description

Precursor powder, positive electrode active material powder, method for producing positive electrode active material powder, positive electrode and lithium secondary battery

The present invention relates to a precursor powder, a positive electrode active material powder, a method for producing the positive electrode active material powder, a positive electrode, and a lithium secondary battery.
This application claims priority based on Japanese Patent Application No. 2021-189152 filed on November 22, 2021, the contents of which are incorporated herein.

Lithium metal composite oxide is used as a positive electrode active material for lithium secondary batteries. The positive electrode active material is usually in powder form.

In recent years, studies have been conducted to improve the performance (battery characteristics) of the positive electrode active material by adding another compound to the lithium metal composite oxide. As such a positive electrode active material, for example, a mixture of lithium metal composite oxide powder and lithium tungstate is known (see, for example, Patent Document 1).

JP-A-2016-225277

As the application field of lithium secondary batteries advances, there is a demand for further improvements in the cycle retention rate. The positive electrode active material described in Patent Document 1 has room for improvement in terms of cycle retention rate.

The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a precursor powder that can be used as a precursor of a positive electrode active material and can produce a positive electrode active material having a high cycle retention rate. do. Another object of the present invention is to provide a positive electrode active material powder having a high cycle retention rate and a method for producing a positive electrode active material powder having a high cycle retention rate. A further object of the present invention is to provide a positive electrode and a lithium secondary battery containing such a positive electrode active material powder and having an excellent cycle retention rate.

In order to solve the above problems, one aspect of the present invention includes the following aspects.

[1] A precursor powder used as a precursor of a positive electrode active material for a lithium secondary battery, comprising a plurality of particles having pores and a filling compound filled in the pores, the particles has a layered structure and is composed of a metal composite compound containing at least Ni, the filling compound is either or both of a water-soluble tungsten compound and a water-soluble molybdenum compound, and satisfies the following formula (1) precursor powder.
10≦(P1−P2)/P1×100<100 (1)
(P1 (cm ³ /g) is a washed precursor powder obtained by washing the precursor powder for 20 minutes with water that is 20 times the weight of the precursor powder, followed by solid-liquid separation and drying. P2 (cm ³ /g) is the maximum peak value of the log differential pore volume in the region with a pore size of 10 nm or less in the pore size distribution of the precursor powder. The pore size distribution is the value of the log differential pore volume at the pore size of The pore size distribution is the nitrogen desorption isotherm obtained by measuring the precursor powder or the washed precursor powder at liquid nitrogen temperature, - Obtained by analysis using the Joyner-Halenda (BJH) method.)

[2] The precursor powder according to [1], wherein the P2 is 0.8 cm ³ /g or less.

[3] The precursor powder according to [1] or [2], wherein the total pore volume obtained from the pore size distribution of the precursor powder is 0.005 to 0.15 cm ³ .

[4] The metal complex compound contains an element X, and the element X is Co, Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, S and P, and the atomic weight ratio between Ni and the element X contained in the metal composite compound and the sum of W and Mo contained in the filling compound is represented by the following formula The precursor powder according to any one of [1] to [3], which satisfies (2).
[Ni]: [X]: [W + Mo] = (1-a): a: b (2)
(Formula (2) satisfies 0.01≦a≦0.5 and 0.0015≦b≦0.03.)

[5] In a volume-based cumulative particle size distribution curve obtained by laser diffraction particle size distribution measurement, _D50 , which is the particle size at which the cumulative volume ratio from the small particle size side is 50%, is 3 to 20 μm [1] The precursor powder according to any one of [4] to [4].

[6] The precursor powder according to any one of [1] to [5], which has a BET specific surface area of 1 to 40 m ² /g.

[7] A positive electrode active material powder used in a lithium secondary battery, comprising a plurality of particles having pores and a filling compound filled in the pores, the particles having a layered structure. and a positive electrode comprising a lithium metal composite oxide containing at least Ni, the filling compound being either one or both of a water-soluble tungsten compound and a water-soluble molybdenum compound, and having a peak satisfying the following formula (3): Active material powder.
P3≧0.003 (3)
(P3 (cm ³ /g) is the washed powder obtained by washing the positive electrode active material powder for 20 minutes using water that is 20 times the weight of the positive electrode active material powder, and drying after solid-liquid separation. is the maximum peak value of the log differential pore volume in the pore size distribution of 10 nm or less in the pore size distribution of.The pore size distribution is the nitrogen desorption obtained by measuring the washed powder at liquid nitrogen temperature It is obtained by analyzing the isotherm by the Barrett-Joyner-Halenda (BJH) method.)

[8] The positive electrode active material powder according to [7], wherein the elution ratio, which is the total eluted molar amount of W and Mo with respect to the positive electrode active material powder, is 10 to 60%, as measured by the following measuring method.
(Measuring method)
The positive electrode active material powder is precisely weighed to obtain a sample, and the sample is washed for 20 minutes with water having a mass ratio of 20 times that of the sample, followed by solid-liquid separation to obtain a filtrate. The filtrate is subjected to ICP analysis, and the total eluted molar amount of W and Mo eluted in the filtrate is determined based on the analysis results. The elution ratio is obtained from the total molar amount of W and Mo in the sample and the total eluted molar amount.

[9] The particles include secondary particles in which the primary particles of the lithium metal composite oxide are aggregated, and the secondary particles are observed with a scanning electron microscope (SEM). The positive electrode active material powder according to [7] or [8], wherein the required number of primary particles per 1 μm ² is 10 to 50.

[10] The lithium metal composite oxide contains an element X, and the element X is Co, Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B , S and P, and the sum of Li, Ni, and the element X contained in the lithium metal composite oxide, and W and Mo contained in the filling compound The positive electrode active material powder according to any one of [7] to [9], wherein the atomic weight ratio of: satisfies the following formula (4).
[Li]: [Ni]: [X]: [W + Mo] = c: (1-a): a: b (4)
(Formula (4) satisfies 0.9≦c≦1.2, 0.01≦a≦0.5, and 0.0015≦b≦0.03.)

[11] In the volume-based cumulative particle size distribution curve obtained by laser diffraction particle size distribution measurement, _D50 , which is the particle size at which the cumulative volume ratio from the small particle size side is 50%, is 3 to 20 μm. The positive electrode active material powder according to any one of [10].

[12] The positive electrode active material powder according to any one of [7] to [11], which has a BET specific surface area of 2 m ² /g or less.

[13] Diffraction within the range of 2θ = 44.6 ± 2° with respect to the half width B of the diffraction peak of the diffraction peak within the range of 2θ = 18.7 ± 2° in powder X-ray diffraction measurement using CuKα rays The positive electrode active material powder according to any one of [7] to [12], wherein the ratio C/B to the peak half width C is 0.54 to 0.68.

[14] A step of mixing the precursor powder according to any one of [1] to [6] with a lithium compound to obtain a mixture; In the obtaining step, the precursor powder and the lithium are at a molar ratio of 0.90 to 1.20 for Li constituting the lithium compound with respect to the total amount of metal elements constituting the particles of the precursor powder. A method for producing a positive electrode active material powder, wherein the firing temperature in the step of mixing with a compound and firing is 740 to 920°C.

[15] A positive electrode comprising the positive electrode active material powder according to any one of [7] to [13].

[16] A lithium secondary battery having the positive electrode according to [15].

According to the present invention, it is possible to provide a precursor powder that is used as a precursor of a positive electrode active material and that enables production of a positive electrode active material with a high cycle maintenance rate. Further, it is possible to provide a positive electrode active material powder having a high cycle retention rate and a method for producing a positive electrode active material powder having a high cycle retention rate. Further, it is possible to provide a positive electrode and a lithium secondary battery containing such a positive electrode active material powder and having excellent cycle retention rate.

FIG. 1 is an SEM image of precursor powder 1 obtained in Example 1. FIG. FIG. 2 is an SEM-EDX image showing the distribution of W in the same field of view as in FIG. 3 is an SEM image of CAM powder 1 obtained in Example 1. FIG. FIG. 4 is an SEM-EDX image showing the distribution of W in the same field of view as in FIG. FIG. 5 is a schematic diagram showing how CAM particles grow during the production of CAM powder using the precursor powder described above. FIG. 6 is a schematic diagram showing how particles grow during production of LiMO particles using MCC particles that do not have a filling compound in their pores. FIG. 7 is a schematic diagram showing an example of a lithium secondary battery. FIG. 8 is a schematic diagram showing an example of the all-solid lithium secondary battery of the embodiment. 9 is an SEM photograph of CAM powder 1. FIG. FIG. 10 is an SEM photograph of CAM powder CB1. 11 is an SEM image of the precursor powder 4. FIG. FIG. 12 is an SEM-EDX image showing the distribution of Mo in the same field of view as in FIG. 13 is an SEM image of CAM powder 4. FIG. FIG. 14 is an SEM-EDX image showing the distribution of Mo in the same field of view as in FIG. FIG. 15 shows the measurement results for the precursor powder 1. FIG. FIG. 16 shows measurement results for CAM powder 1. FIG. FIG. 17 shows measurement results for the precursor powder CA1. FIG. 18 shows measurement results for CAM powder CB1. FIG. 19 shows the measurement results for precursor powder 5. FIG. 20 shows the measurement results for CAM powder 5. FIG.

<Definition of terms>
The terms used in this specification are defined as follows.

The term "MCC" means Metal Composite Compound.

The term "LiMO" means lithium metal composite oxide. LiMO is not included in the above MCC (MCC does not include LiMO).

The term "CAM" means a cathode active material for lithium secondary batteries.

Expressions that indicate the symbol of a metal element (for example, "Ni") indicate an element rather than a single metal unless otherwise specified.

The term "powder" means a collection of fine particles. Therefore, "positive electrode active material powder" (CAM powder), which is a combination of the term "powder" and the positive electrode active material, means powdery CAM. A similar expression in which "powder" is attached to the name of a substance also means a powdery substance.

The term "primary particles" means particles that do not appear to have grain boundaries when observed in a field of view of 10,000 times using a scanning electron microscope or the like.

The term "secondary particles" refers to particles in which the above primary particles are aggregated. That is, secondary particles are aggregates of primary particles.

Regarding the numerical range, for example, when “1 to 10 μm” is described, it means a numerical range from 1 μm to 10 μm including the lower limit (1 μm) and the upper limit (10 μm), that is, “1 μm or more and 10 μm or less”. .

<Measurement method>
Each value evaluated in this specification is obtained by measuring as follows.

[Cycle maintenance rate]
"Cycle retention rate" is measured using the following (measurement of cycle retention rate) using a lithium secondary battery obtained by the following (production of positive electrode for lithium secondary battery) and (production of lithium secondary battery (coin-type half cell)): method). When the value of cycle maintenance rate exceeds 80%, it is evaluated as "high cycle maintenance rate". A battery with a high cycle retention rate is preferable because it suppresses a decrease in capacity after repeated charging and discharging.

(Preparation of positive electrode for lithium secondary battery)
CAM powder, a conductive material (acetylene black), and a binder (PVdF) are added and kneaded so as to have a composition of CAM powder: conductive material: binder = 92:5:3 (mass ratio), thereby forming a paste. A positive electrode mixture is prepared. N-methyl-2-pyrrolidone is used as an organic solvent when preparing the positive electrode mixture.

The obtained positive electrode mixture is applied to an Al foil having a thickness of 40 μm as a current collector and vacuum-dried at 150° C. for 8 hours to obtain a positive electrode for a lithium secondary battery. The electrode area of this positive electrode for a lithium secondary battery is 1.65 cm ² .

(Fabrication of lithium secondary battery (coin-type half cell))
The following operations are performed in an argon atmosphere glove box.

Place the positive electrode for the lithium secondary battery described above on the lower lid of the coin-type battery R2032 part (manufactured by Hosen Co., Ltd.) with the aluminum foil side facing down, and place a polyethylene porous film separator on top of it. . 300 μl of electrolytic solution is injected here. As the electrolyte, a liquid obtained by dissolving LiPF ₆ to 1 mol/l in a mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate at a volume ratio of 30:35:35 is used.

Next, using metallic lithium as the negative electrode, place it on the upper side of the separator, cover it with a gasket, and crimp it with a crimping machine to make it a lithium secondary battery (coin-type half cell R2032, hereinafter referred to as "coin-type half cell"). There is.).

(Method for measuring cycle maintenance rate)
The resulting coin-shaped half-cell is allowed to stand at room temperature for 12 hours, so that the separator and the positive electrode mixture layer are sufficiently impregnated with the electrolytic solution. Next, as an initial charge/discharge treatment, constant current and constant voltage charge was performed by performing constant current charge at 0.2 CA to 4.3 V and then constant voltage charge at 4.3 V, followed by discharging at room temperature to 2.5 V at 0.2 CA. A constant current discharge is performed, and these charge/discharge operations are repeated four times.

After that, after performing constant-current and constant-voltage charging in which constant-current charging is performed at room temperature to 4.3 V at 0.5 CA and then constant-voltage charging at 4.3 V, constant-current discharging is performed at room temperature at 1 CA to 2.5 V. conduct. The discharge capacity at this time is measured, and the obtained value is defined as the "first cycle discharge capacity" (mAh/g).

The constant current constant voltage charge and the constant current discharge are combined to form the first charge/discharge cycle, and the charge/discharge cycle is repeated under the same conditions. After that, the discharge capacity (mAh/g) at the 50th cycle is measured.

Using the measured discharge capacity at the 1st cycle and the discharge capacity at the 50th cycle, the cycle retention rate is calculated from the following formula.
Cycle retention rate (%) = [discharge capacity at 50th cycle]/[discharge capacity at 1st cycle] x 100

[Cumulative particle size distribution]
The "cumulative particle size distribution" of each powder is obtained on a volume basis, and is measured using a measuring device based on the principle of laser diffraction scattering. For the measuring device, for example, MT3000II (manufactured by Microtrac Bell) can be used. The measurement range of the particle size distribution is 0.02 μm or more and 20 μm or less.

In the obtained volume-based cumulative particle size distribution curve, D ₅₀ (μm) is the particle size at which the cumulative volume ratio from the small particle size side is 50% when the whole is taken as 100%. More specifically, in a volume-based cumulative particle size distribution curve with a measurement range of 0.02 μm or more and 20 μm or less, when the entire measurement range is 100%, the particle volume ratio accumulated from the lower limit of the measurement range is The particle diameter at 50% is defined as D ₅₀ (μm).

[BET specific surface area]
The "BET specific surface area" of each powder is measured using the BET multipoint method from the nitrogen adsorption isotherm in the process of measuring the pore distribution described later. As a measuring device, for example, a specific surface area pore size distribution measuring device (BELSORP-mini (manufactured by Microtrack Bell Co., Ltd.)) can be used.

[Composition analysis]
The composition of each powder, MCC, and LiMO is measured using an ICP emission spectrometer after dissolving each powder in acid or alkali according to the element to be measured. As an ICP emission spectrometer, for example, Optima7300 (manufactured by PerkinElmer Co., Ltd.) can be used.

[Powder X-ray diffraction measurement]
Powder X-ray diffraction measurement is performed using an X-ray diffractometer. As an X-ray diffractometer, for example, D8ADVANCE (manufactured by Bruker Corporation) can be used.

First, each powder is filled on a dedicated substrate and measured using a CuKα radiation source under the conditions of a diffraction angle 2θ = 10 ° to 90 ° and a sampling width of 0.02 ° to obtain a powder X-ray diffraction spectrum. . From the spectrum obtained, the crystal structure is identified using integrated powder X-ray analysis software.

Using powder X-ray diffraction analysis software (manufactured by Bruker Corporation, DIFFRAC.EVA), the half-value width B of the diffraction peak within the range of 2θ = 18.7 ± 2 ° from the powder X-ray diffraction spectrum and 2θ = 44.6 ± Calculate the half-value width C of the diffraction peak within the range of 2°. The diffraction peak within the range of 2θ = 18.7 ± 2° is the diffraction peak in the (003) plane of LiMO contained in the CAM, and the diffraction peak within the range of 2θ = 44.6 ± 2° is the diffraction peak in the CAM. Diffraction peaks in the (104) plane of the contained LiMO.

[Number of primary particles constituting secondary particles (per unit area)]
The number of primary particles constituting the secondary particles is obtained by observing the secondary particles with a scanning electron microscope (SEM) and randomly selecting 5 visual fields from the obtained SEM image at a magnification of 10000 times. In each field of view, the number of primary particles on the surface of the secondary particles is counted, the number of primary particles per unit area of 1 μm ² is measured, and the average number of primary particles is calculated. A scanning electron microscope (manufactured by JEOL Ltd., JSM-5510) can be used for the measurement.

[Pore size distribution]
The "pore size distribution" of the particles constituting each powder can be obtained by analyzing the nitrogen desorption isotherm obtained by measuring the powder at liquid nitrogen temperature using the Barrett-Joyner-Halenda (BJH) method. As a nitrogen desorption isotherm measuring device, for example, BELSORP-mini (manufactured by Microtrac Bell Co., Ltd.) can be used.

First, 5 g of each powder is subjected to vacuum degassing treatment at 105° C. for 8 hours using a vacuum heat treatment apparatus (BELSORP-vacII, manufactured by Microtrack Bell Co., Ltd.). After the treatment, the nitrogen adsorption amount of each powder at the liquid nitrogen temperature (77 K) is measured using the above-mentioned measuring device, and a nitrogen adsorption isotherm and a nitrogen desorption isotherm are created.

In the nitrogen adsorption isotherm and the nitrogen desorption isotherm, the horizontal axis is the ratio between the adsorption equilibrium pressure and the saturated vapor pressure (relative pressure (ρ / ρ0)), and the vertical axis is the standard state (STP; Standard Temperature and Pressure). It is a curve obtained by plotting the nitrogen adsorption amount (cm ³ (STP)/g).

The obtained nitrogen desorption isotherm is analyzed by the BJH method to determine the pore size distribution in the pore size range of 2 nm or more and 200 nm or less. The pore size distribution is obtained by dividing the differential pore volume dV by the logarithmic differential value d (logD) of the pore size D. The horizontal axis is the pore size (nm, logarithmic scale) and the vertical axis is the log differential Distribution obtained by plotting as pore volume (cm ³ /g).

<Precursor powder>
The precursor powder of the present embodiment is used as a CAM precursor and has a plurality of particles having pores of a predetermined size and a filling compound that fills the pores.

The particles have a layered structure and consist of MCC containing at least Ni. The particles constituting the precursor powder may be hereinafter referred to as "MCC particles".

The crystal structure of the precursor preferably belongs to any one of the hexagonal, trigonal, orthorhombic, and monoclinic crystal systems, and particularly preferably belongs to the hexagonal or trigonal system. For example, it preferably belongs to the space group P-3m1. The crystal structure of the precursor can be confirmed by powder X-ray diffraction measurement.

The filling compound is either one or both of a tungsten compound (W compound) and a molybdenum compound (Mo compound). The fill compound is lithium ion conductive and water soluble. Such W compounds include Li ₂ WO ₄ and Li ₄ WO ₅ . _Moreover , _{Li2MoO4 , Li4MoO5} is mentioned as such Mo compound.

The MCC particles and the filling compound filled in the pores of the MCC particles constitute particulate precursors (precursor particles). That is, an MCC particle is a single secondary particle formed by agglomeration of MCC primary particles and having pores. A precursor particle is a single particle containing MCC particles and a filling compound. A precursor powder is an aggregate of a plurality of precursor particles.

Moreover, the precursor powder satisfies the following formula (1).
10≦(P1−P2)/P1×100<100 (1)

Here, P1 (cm ³ /g) is the washed precursor powder obtained by washing the precursor powder for 20 minutes with water that is 20 times the weight of the precursor powder, followed by solid-liquid separation and drying. is the maximum peak value of the log differential pore volume in the pore size distribution of 10 nm or less. As used herein, “washing” refers to an operation of stirring the precursor powder with water to dissolve and remove contaminants present on the particle surfaces and between the particles of the precursor powder.

"Maximum peak value" refers to the maximum value among the peak values of a plurality of peaks present in the above region. If there is no peak in the region with a pore diameter of 10 nm or less, it is evaluated as having no P1.

As mentioned above, the filling compound is water soluble. Therefore, by washing the precursor powder under the above conditions, the obtained washed precursor powder is in a state in which the filling compound is removed from the pores, and the pores buried by the filling compound are exposed. That is, the washed precursor powder can be pseudo-aggregated with MCC particles.

The nm-order pores are too small for the gaps formed between the MCC particles. Therefore, it can be determined that the peak appearing in the region with a pore diameter of 10 nm or less corresponds to the size of the pores formed in the MCC particles. The peak indicating P1 indicates the presence of pores possessed by MCC particles.

P1 may be 0.02 cm ³ /g or more, or may be 0.032 cm ³ /g or more. Also, P1 may be 0.9 cm ³ /g or less, or may be 0.8 cm ³ /g or less. The upper limit and lower limit of P1 can be combined arbitrarily. For example, P1 may be 0.02-0.9 cm ³ /g, or 0.032-0.8 cm ³ /g.

P2 (cm ³ /g) is the value of the log differential pore volume at the pore diameter of the peak showing P1 in the pore diameter distribution of the precursor powder before washing. For example, in the pore size distribution of the CAM powder before washing, when the pore size of the peak indicating P3 in the washed CAM powder is 4 nm, P4 is the log differential pore size at the pore size of 4 nm in the CAM powder before washing. volume value. In the precursor powder, the pores of the MCC particles are filled with a filling compound. Therefore, P2 is smaller than P1 (P1>P2).

P2 may be 0.001 cm ³ /g or more, or may be 0.002 cm ³ /g or more. Also, P2 may be 0.8 cm ³ /g or less, 0.7 cm ³ /g or less, or 0.6 cm ³ /g or less. The upper limit and lower limit of P2 can be combined arbitrarily. For example, P2 may be 0.001 to 0.8 cm ³ /g, may be 0.002 to 0.7 cm ³ /g, may be 0.002 to 0.6 cm ³ /g. good.

“(P1−P2)/P1×100” in formula (1) defined by P1 and P2 above is the maximum peak of the log differential pore volume in the region with a pore diameter of 10 nm or less before and after washing the precursor powder. It represents the change rate (%) of the value. As represented by formula (1), the precursor powder has a maximum peak value change rate of 10% or more and less than 100% before and after washing.

The rate of change is preferably 15% or more, more preferably 25% or more, even more preferably 35% or more, and particularly preferably 45% or more. Further, the rate of change may be 99% or less, or may be 98% or less. The upper limit and lower limit of the rate of change can be arbitrarily combined. The rate of change may be 15-99%, 25-99%, 35-99%, or 45-98%.

"(P1−P2)/P1×100" is, in other words, the fine pores possessed by the MCC particles when focusing on the fine pores having a pore diameter of 10 nm or less among the pores possessed by the MCC particles. Represents an approximation of the fill factor of the fill compound. The fine pores of the MCC particles are filled with a filling compound in a range of 10% by volume or more and less than 100% by volume.

Further, the total pore volume obtained from the pore size distribution of the precursor powder (total pore volume of the precursor powder) is preferably 0.005 to 0.15 cm ³ /g.

The total pore volume of the precursor powder may be 0.006 cm ³ /g or more, or 0.008 cm ³ /g or more. Also, the total pore volume of the precursor powder may be 0.05 cm ³ /g or less, or may be 0.02 cm ³ /g or less. The upper limit and lower limit of the total pore volume can be combined arbitrarily. For example, the total pore volume of the precursor powder may be 0.006-0.05 cm ³ /g, or 0.008-0.02 cm ³ /g.

In the precursor powder that satisfies formula (1) and preferably has a total pore volume within the above range, the pores of the MCC particles are filled with a sufficient amount of the filling compound. By using such a precursor powder, it is possible to produce a CAM powder with excellent cycle retention rate. Details will be described later.

(MCC particles)
The MCC forming the MCC particles preferably contains the element X in addition to Ni. Element X is at least one element selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, S and P. . Element X is preferably at least one element selected from the group consisting of Co, Mn, Al, Ti, Mg, Nb, and Zr.

In the precursor powder, the total amount ([W+Mo] ) and the atomic weight ratio preferably satisfies the following formula (2).
[Ni]: [X]: [W + Mo] = (1-a): a: b (2)
(Formula (2) satisfies 0.01≦a≦0.5 and 0.0015≦b≦0.03.)

That is, when the total of [Ni] and [X] is 100 mol%, the precursor powder has a ratio of [Ni] to the total of [Ni] and [X] of 50 to 99 mol% (0.5 ≤ 1-a ≤ 0.99), and the ratio of [X] to the sum of [Ni] and [X] is 1 to 50 mol% (0.01 ≤ a ≤ 0.5).

Also, the ratio of the sum of [W] and [Mo] to the sum of [Ni] and [X] is 0.15 to 3 mol% (0.0015≤b≤0.03).

a may be 0.02 or more, or may be 0.04 or more. Also, a may be 0.40 or less, or may be 0.30 or less. The upper limit and lower limit of a can be combined arbitrarily. For example, 0.02≦a≦0.40 or 0.04≦a≦0.30.

b may be 0.002 or more, or may be 0.003 or more. Also, b may be 0.02 or less, or may be 0.015 or less. The upper limit and lower limit of b can be combined arbitrarily. For example, 0.002≦b≦0.02 or 0.003≦b≦0.015.

That is, in the above formula (2), 0.02 ≤ a ≤ 0.40 and 0.0015 ≤ b ≤ 0.02 may be satisfied, and 0.04 ≤ a ≤ 0.30 and 0.003 ≤ b ≤ 0.015.

The ratio of the total amount of [Ni] and [X] contained in MCC and [W] and [Mo] contained in the filling compound (a, b above) can be obtained by the following method.

First, when it is known that the MCC constituting the precursor particles does not contain W and Mo as the element X, [W] and [Mo] of the precursor powder measured by the method described in [Composition analysis] can be employed as the total amount of [W] and [Mo] contained in the filling compound. Therefore, [Ni][X][W+Mo] can be obtained from the ICP analysis result of the precursor powder obtained by the above [composition analysis], and the above a and b can be obtained.

In addition, when it is known or unknown that the MCC constituting the precursor particles contains at least one of W and Mo as the element X, a and b are obtained by the following method.

First, by the method described in [Composition analysis] above, [Ni] contained in the precursor powder, the total amount X of elements corresponding to element X other than W and Mo, and the total amount A of W and Mo demand. The total amount A includes both the total amount B of W and Mo to be treated as element X of the MCC and the total amount of W and Mo constituting the filling compound.

Next, the precursor powder is precisely weighed to obtain a sample, the sample is washed for 20 minutes with water having a mass ratio of 20 times that of the sample, solid-liquid separation is performed, and the mass of the sample after solid-liquid separation is The filling compound is removed from the precursor powder by performing solid-liquid separation while passing twice as much water. The obtained powder is dried by vacuum drying at 120° C. for 10 hours to obtain a dried product. The dried product is measured by the method described in [Composition analysis] above to confirm the presence or absence of W or Mo. When W or Mo is confirmed, the total amount B of [W] and [Mo] to be treated as the element X of MCC is obtained.

By subtracting the total amount B from the total amount A, [W + Mo] can be obtained. By summing the total amount X and the total amount B, [X] can be obtained. From the obtained [Ni][X][W+Mo], the above a and b can be obtained.

MCC is preferably a hydroxide represented by the following compositional formula (I).
Ni _(1-xy) Co _x M _y (OH) _2-α Formula (I)
(In composition formula (I), 0 ≤ x ≤ 0.3, 0 < y ≤ 0.3, 0 < x + y ≤ 0.5, and −0.5 ≤ α < 0.5, M is Mn, It is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, S and P.)

M is preferably at least one element selected from the group consisting of Mn, Al, Ti, Mg, and Nb.

(x)
x may be 0. x is preferably 0.01 or more, more preferably 0.015 or more, and particularly preferably 0.02 or more. Also, x is preferably 0.30 or less, more preferably 0.25 or less, and particularly preferably 0.10 or less.

The above upper limit and lower limit of x can be combined arbitrarily.
The composition formula (I) preferably satisfies 0 ≤ x ≤ 0.25, more preferably 0.015 ≤ x ≤ 0.20, particularly 0.02 ≤ x ≤ 0.10 preferable.

(y)
y is preferably 0.01 or more, more preferably 0.015 or more, and particularly preferably 0.02 or more. Moreover, y is preferably 0.30 or less, more preferably 0.25 or less, and particularly preferably 0.15 or less.

The above upper limit and lower limit of y can be combined arbitrarily.
The above composition formula (I) preferably satisfies 0.01≦y≦0.30, more preferably satisfies 0.015≦y≦0.20, and satisfies 0.02≦y≦0.15 is particularly preferred.

(α)
α is preferably −0.45 or more, more preferably −0.30 or more, and particularly preferably −0.20 or more. α is preferably 0.45 or less, more preferably 0.30 or less, and particularly preferably 0.20 or less. The above upper limit and lower limit can be combined arbitrarily.

The preferred range of x+y is the same as the preferred range of a in formula (2) above.

The composition formula (I) preferably satisfies −0.45≦α≦0.45, more preferably −0.30≦α≦0.30, and −0.20≦α≦0.20. is particularly preferred.

The above composition formula (I) preferably satisfies 0≦x≦0.25, 0.01≦y≦0.30, and −0.45≦α≦0.45. Moreover, it is particularly preferable that the composition formula (I) satisfies 0.02≦x≦0.10, 0.02≦y≦0.15, and −0.20≦α≦0.20.

(Powder characteristics)
The D ₅₀ of the precursor powder is preferably 3-20 μm, more preferably 4-18 μm, even more preferably 7-17 μm. When the _D50 of the precursor powder is 3 μm or more, the amount of pores in the MCC particles increases, and the cycle retention rate of the lithium secondary battery using the CAM powder obtained from the precursor powder tends to improve. In addition, when the _D50 of the precursor powder is 20 μm or less, the precursor powder easily reacts with the lithium compound in the step of firing which will be described later, and a uniform crystal structure is generated throughout the precursor particles. The capacity of a lithium secondary battery using the obtained CAM powder is likely to be improved.

Also, the BET specific surface area of the precursor powder is preferably 1 to 40 m ² /g, more preferably 1.5 to 35 m ² /g, even more preferably 1.5 to 10 m ² /g. When the BET specific surface area of the precursor powder is 1 m ² /g or more, the amount of pores in the MCC particles increases, and the precursor powder easily reacts uniformly with the lithium compound in the firing step described later. Further, when the BET specific surface area of the precursor powder is 40 m ² /g or less, the pores of the MCC particles are easily filled with the W compound and the Mo compound, and the cycle maintenance of the lithium secondary battery using the obtained CAM powder is achieved. Easy to improve rate.

<Method for producing precursor powder>
The method for producing the precursor powder includes the steps of producing MCC particles, mixing a basic solution in which a filling compound is dissolved and the MCC particles to obtain a slurry, and solid-liquid separation of the precursor powder dispersed in the slurry. and a step of drying after removing by the operation or evaporation operation of the solution.

(Step of producing MCC particles)
MCC, which constitutes the MCC particles, is a metal composite hydroxide having a layered structure, and contains Ni and the element X at a molar ratio represented by the following formula (I′), for example.
Ni: X = (1-a): a (I')
(In formula (I′), X represents the element X and satisfies 0.01≦a≦0.5.)

The manufacturing process of MCC particles containing Ni, Co and Mn will be described below as an example. First, a metal composite hydroxide containing Ni, Co and Mn is prepared. A metal composite hydroxide having a layered structure can be produced by a generally known batch coprecipitation method or continuous coprecipitation method.

Specifically, by the continuous coprecipitation method described in JP-A-2002-201028, a nickel salt solution, a cobalt salt solution, a manganese salt solution and a complexing agent are reacted to obtain Ni _(1-xy) A metal composite hydroxide represented by Co _x Mn _y (OH) ₂ (x and y are the same as x and y in formula (I) above) is produced.

The nickel salt that is the solute of the nickel salt solution is not particularly limited, but at least one of nickel sulfate, nickel nitrate, nickel chloride and nickel acetate can be used.

At least one of cobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate can be used as the cobalt salt that is the solute of the cobalt salt solution.

At least one of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate can be used as the manganese salt that is the solute of the manganese salt solution.

The above metal salts are used in proportions corresponding to the composition ratio of Ni _(1-xy) Co _x Mn _y (OH) ₂ . That is, the amount of each metal salt is defined so that the molar ratio of Ni, Co and Mn in the mixed solution containing the metal salt corresponds to (1-xy):x:y. Also, water is used as a solvent.

The complexing agent is one capable of forming complexes with nickel ions, cobalt ions and manganese ions in an aqueous solution. etc.), hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid and uracil diacetic acid and glycine.

A complexing agent may or may not be used in the manufacturing process of the metal composite hydroxide. When a complexing agent is used, the amount of the complexing agent contained in the mixture containing the nickel salt solution, cobalt salt solution, manganese salt solution and complexing agent is, for example, metal salts (nickel salts, cobalt salts and manganese salts). is greater than 0 and 2.0 or less.

In the coprecipitation method, in order to adjust the pH value of the mixed solution containing the nickel salt solution, the cobalt salt solution, the manganese salt solution, and the complexing agent, the mixed solution is added before the pH of the mixed solution changes from alkaline to neutral. to which is added an aqueous solution of alkali metal hydroxide. The alkali metal hydroxide is, for example, sodium hydroxide, and is used as an aqueous sodium hydroxide solution.

When the nickel salt solution, cobalt salt solution, and manganese salt solution, as well as the complexing agent and the aqueous alkali metal hydroxide solution are continuously supplied to the reaction vessel, Ni, Co, and Mn react to form Ni _{(1- xy)} Co _x Mn _y (OH) ₂ is produced.

During the reaction, the temperature of the reaction vessel is controlled, for example, within the range of 20-80°C, preferably 30-70°C.

Also, during the reaction, the pH value of the reaction solution in the reaction tank is controlled within the range of pH 9-13, for example. For the pH of the reaction solution, a value measured at a solution temperature of 40°C is adopted.

The reaction precipitate formed in the reaction tank is neutralized while stirring. The neutralization time of the reaction precipitate is, for example, 1 to 20 hours.

For the reaction tank used in the continuous coprecipitation method, an overflow type reaction tank can be used to separate the formed reaction precipitate.

When producing a metal composite hydroxide by a batch coprecipitation method, the reaction tank includes a reaction tank without an overflow pipe and a thickening tank connected to the overflow pipe, and the overflowed reaction precipitate is removed in the thickening tank. Apparatus having a mechanism for concentrating and recirculating to the reaction vessel, etc., may be mentioned.

An inert gas is preferably supplied into the reaction vessel, and various gases such as nitrogen, argon, or mixed gases thereof are supplied into the reaction vessel. The above P1, BET specific surface area, and total pore volume of the precursor powder can be controlled by the inert gas flow rate.

In addition, by appropriately controlling the concentration of the metal salt supplied to the reaction tank, the reaction temperature, the reaction pH, etc., P1 above and P3 described later can be controlled within the range of the present embodiment.

After the above reaction, isolate the neutralized reaction precipitate. For isolation, for example, a method of dehydrating a slurry containing a reaction precipitate (that is, a coprecipitate slurry) by centrifugation, suction filtration, or the like is used.

Wash and dehydrate the isolated reaction precipitate. Washing of the reaction precipitate is preferably carried out using water or an alkaline washing solution. The reaction precipitate is preferably washed with an alkaline washing solution, more preferably with an aqueous sodium hydroxide solution.

After washing, further dehydration and drying yields a metal composite hydroxide containing Ni, Co, and Mn. After drying, a sieving treatment may be performed to adjust the particle size of the metal composite hydroxide.

MCC particles can be produced by the above steps. By carrying out the coprecipitation method under the above conditions, the total pore volume is 0.01 to 0.2 cm ³ /g, and in the pore size distribution, the log differential showing the maximum peak value in the region with a pore size of 10 nm or less MCC particles with a pore volume of 0.02-0.4 cm ³ /g can be obtained.

When the total pore volume of the MCC particles is within the above range, either one or both of the W compound and the Mo compound are likely to be uniformly filled into the pores of the MCC particles, and a lithium secondary battery using the obtained CAM powder is produced. cycle maintenance rate is easy to improve. The total pore volume of MCC particles is more preferably 0.015 cm ³ /g or more. The total pore volume of the MCC particles is preferably 0.18 cm ³ /g or less, particularly preferably 0.12 cm ³ /g or less.

After washing the reaction precipitate, the following (step of obtaining a slurry) may be continued without performing dehydration treatment and drying treatment.

(Step of obtaining slurry)
Next, a basic solution in which the filler compound is dissolved is mixed with the obtained MCC particles to obtain a slurry.

The basic solution is obtained by mixing either or both of _WO3 and _MoO3 , _LiOH.H2O as a base, and water. Alternatively, it can be obtained by mixing one or both of Li ₂ WO ₄ and Li ₂ MO ₄ , LiOH.H ₂ O as a base, and water. The pH of basic solutions at 25±2° C. is greater than 10 (pH>10).

The basic solution may contain NaOH in addition to LiOH as a base, or may contain NaOH instead of LiOH, but it is preferable to use only LiOH.

In a basic solution, either one or both of _WO3 and _MoO3 react with LiOH. By using the basic aqueous solution in this step, one or both of water-soluble Li ₂ WO ₄ and Li ₄ WO ₅ can be obtained from the basic aqueous solution containing W, and from the basic aqueous solution containing Mo, the water-soluble Either or both of Li ₂ MoO ₄ and Li ₄ MoO ₅ , ie the filling compounds described above, result.

A slurry is obtained by mixing the obtained basic solution and MCC particles. The water content of the slurry may be 20% by mass or more, or may be 21% by mass or more. The water content of the slurry may be 70% by mass or less. That is, the water content of the obtained slurry may be 20 to 70% by mass, or may be 21 to 70% by mass.

　Since the pH of the basic solution is greater than 10, the MCC particles in the slurry are difficult to dissolve in the basic solution, and the pores of the MCC particles are easily maintained. Therefore, while the MCC particles are dispersed in the slurry, the basic solution penetrates into the pores of the MCC particles. This fills the pores with a water-soluble filling compound.

It is preferable that the slurry is held for 5 minutes or longer. By keeping it as a slurry for this amount of time, the pores are sufficiently filled with the filling compound.

In this step, by adjusting the concentration and water content of the slurry and the ratio of the MCC particles contained in the slurry and the filling compound contained in the basic solution, the amount of the filling compound filled in the pores is adjusted, and the above The value of P2 can be controlled within the range of this embodiment. Moreover, the above P4 of the finally obtained CAM powder can be controlled within the range of the present embodiment.

(Drying process)
The precursor powder is then removed from the slurry and dried.
When the water content of the slurry is 20 to 30% by mass, the water may be removed by evaporation directly from the slurry to take out the precursor powder.

When the water content of the slurry exceeds 30% by mass, the slurry may be filtered to separate the solid content (solid-liquid separation), and water may be evaporated from the obtained solid content to take out the precursor powder.

Heating, pressure reduction, air blowing, and combinations thereof can be appropriately adopted as the drying method.

As a result, the precursor powder described above is obtained.

FIG. 1 is an SEM image of the precursor powder obtained in Example 1, which will be described later. The precursor powder shown in FIG. 1 has a compound containing Li and W as a filling compound. FIG. 2 is an SEM-EDX image in the same field of view as in FIG. 1, which is a W mapping image. In FIG. 2, the amount of W is indicated by the shade of color, and the white portion indicates that W does not exist, and the darker colored portion indicates that relatively more W is present. In each mapping image illustrated in the present specification, the abundance of an element is similarly indicated by the shade of color.

As shown in FIG. 1, pores can be confirmed in the precursor particles that make up the precursor powder. In the cross section of the particle, the white striped portions correspond to the pores.

In addition, as shown in FIG. 2, it can be confirmed that W exists even inside the precursor particles.

<CAM powder>
The CAM powder of the present embodiment is used in a lithium secondary battery and has a plurality of particles having pores of a predetermined size and a filling compound that fills the pores. As the filling compound, the same compounds as the filling compound contained in the precursor powder described above can be exemplified.

The particles that make up the CAM powder are made of LiMO that has a layered structure and contains at least Ni. These particles are hereinafter sometimes referred to as "LiMO particles". The LiMO particles and the filling compound that fills the pores of the LiMO particles constitute particulate CAMs (CAM particles). That is, a LiMO particle is a single secondary particle formed by aggregation of LiMO primary particles and having pores. A CAM particle is a single particle containing a LiMO particle and a filling compound. CAM powder is an aggregate of multiple CAM particles.

Moreover, the CAM powder has a peak that satisfies the following formula (3).
P3≧0.003 (3)

Here, P3 (cm ³ /g) is the pore size distribution of the washed powder obtained by washing the CAM powder for 20 minutes with water that is 20 times the mass of the CAM powder, followed by solid-liquid separation and drying. , is the maximum peak value of the log differential pore volume in the region with a pore diameter of 10 nm or less. If there is no peak in the region with a pore diameter of 10 nm or less, it is evaluated as having no P3.

As mentioned above, the filling compound is water soluble. Therefore, by washing the CAM powder under the above conditions, the obtained washed powder is in a state in which the filling compound is removed from the pores, and the pores buried by the filling compound are exposed. In other words, the washed powder can be considered as an aggregate of LiMO particles in a pseudo manner.

The nm-order pores are too small for the gaps formed between the LiMO particles. Therefore, it can be determined that the peak appearing in the region with a pore diameter of 10 nm or less corresponds to the size of the pores formed in the LiMO particles. The peak indicating P3 indicates the presence of pores possessed by the LiMO particles.

P3 may be 0.004 cm ³ /g or more, or 0.006 cm ³ /g or more. Also, P3 may be 0.06 cm ³ /g or less, or may be 0.05 cm ³ /g or less. The upper limit and lower limit of P3 can be combined arbitrarily. For example, P3 may be 0.004-0.06 cm ³ /g, or 0.006-0.05 cm ³ /g.

Also, in the pore size distribution of the CAM powder before washing, the maximum peak value of the log differential pore volume in the region with a pore size of 10 nm or less is defined as P4 (cm ³ /g). For example, in the pore size distribution of the CAM powder before washing, when the pore size of the peak indicating P1 in the washed precursor powder is 4 nm, P2 is the log differential at the pore size of 4 nm in the precursor powder before washing. is the pore volume value.

　In the CAM powder, the pores of the LiMO particles are filled with a filling compound. Therefore, P4 is smaller than P3 (P3>P4).

P4 may be 0.0005 cm ³ /g or more, or may be 0.0010 cm ³ /g or more. Also, P4 may be 0.020 cm ³ /g or less, or may be 0.015 cm ³ /g or less. The upper limit and lower limit of P4 can be combined arbitrarily. For example, P4 may be 0.0005-0.020 cm ³ /g, or 0.0010-0.015 cm ³ /g.

The CAM powder preferably satisfies the following formula (5).
50≦(P3−P4)/P3×100<100 (5)

“(P3−P4)/P3×100” in formula (5) defined by P3 and P4 above is the maximum peak value of the log differential pore volume in the region with a pore diameter of 10 nm or less before and after washing the CAM powder. represents the rate of change (%). As represented by the formula (5), the CAM powder has a maximum peak value change rate of 50% or more and less than 100% before and after washing.

The rate of change may be 60% or more, or 65% or more. Further, the rate of change may be 99% or less, or may be 98% or less. The upper limit and lower limit of the rate of change can be arbitrarily combined. For example, the rate of change may be 60-99%, or 65-98%.

“(P3−P4)/P3×100” is, in other words, when focusing on fine pores having a pore diameter of 10 nm or less among the pores possessed by the LiMO particles, for the fine pores possessed by the LiMO particles Represents an approximation of the fill factor of the fill compound. The fine pores of the LiMO particles are filled with a filling compound in a range of 50% by volume or more and less than 100% by volume.

The ratio of the total elution molar amount of [W] and [Mo] to the CAM powder (elution ratio) can be evaluated by the following method.

A sample is obtained by accurately weighing the CAM powder, and the sample is washed for 20 minutes using water that is 20 times the sample in terms of mass ratio, followed by solid-liquid separation to obtain the filtrate. The filtrate is subjected to ICP analysis, and the total eluted molar amount of [W] and [Mo] eluted in the filtrate is determined based on the analysis results. From the total molar amount of [W] and [Mo] obtained by ICP analysis of the sample (CAM powder) and the total molar amount of eluted [W] and [Mo], the elution ratio is determined.

The elution ratio determined by the above method corresponds to the total molar amount of the filling compound eluted from the pores by washing with water.

The CAM powder preferably has an elution ratio of 10 to 60%, more preferably 15 to 50%, as measured by the above method.

The LiMO particles that constitute the CAM powder include secondary particles that are aggregated LiMO primary particles. The number of primary particles constituting the secondary particles is preferably 10 to 50 per 1 μm ² , more preferably 20 to 40 per 1 μm ² .

(LiMO particles)
The LiMO constituting the LiMO particles further contains the element X described above.

In the CAM powder, the atomic weight ratio of [Li], [Ni], and [X] contained in LiMO and [W] and [Mo] contained in the filling compound must satisfy the following formula (4). is preferred.
[Li]: [Ni]: [X]: [W + Mo] = c: (1-a): a: b (4)
(Formula (4) satisfies 0.9≦c≦1.2, 0.01≦a≦0.5, and 0.0015≦b≦0.03.)

That is, the CAM powder has a ratio of [Ni] of 50 to 99 mol% (0.5 ≤ 1-a ≤ 0.99) when the total of [Ni] and [X] is 100 mol%, The proportion of [X] is 1 to 50 mol % (0.01≦a≦0.5).

Also, the ratio of the total of [Li] to the total of [Ni] and [X] is 90 to 120 mol% (0.9≤c≤1.2).

Furthermore, the ratio of the sum of [W] and [Mo] to the sum of [Ni] and [X] is 0.15 to 3 mol% (0.0015≤b≤0.03).

c may be 0.98 or more, or may be 1.00 or more. Also, c may be 1.15 or less, or may be 1.10 or less. The upper limit and lower limit of c can be combined arbitrarily. For example, 0.98≦c≦1.15 or 1.00≦c≦1.10.

The preferred range of a is the same as a described for the MCC particles of the precursor powder.

The preferred range of b is the same as b described for the MCC particles of the precursor powder.

That is, in the above formula (4), 0.98 ≤ c ≤ 1.15, 0.02 ≤ a ≤ 0.40 and 0.0020 ≤ b ≤ 0.02 may be satisfied, and 1.00 ≤ c ≤1.10, 0.04≤a≤0.30 and 0.003≤b≤0.015.

LiMO may be a compound represented by the following compositional formula (II).
Li[Li _d (Ni _(1-e) X _e ) _1-d ]O ₂ (II)
(In formula (II), X represents the element X and satisfies −0.1≦d≦0.2 and 0<e≦0.5.)

From the viewpoint of obtaining a lithium secondary battery with a high cycle retention rate, d in the formula (II) is -0.1 or more, more preferably -0.05 or more, and more preferably more than 0. . Further, from the viewpoint of obtaining a lithium secondary battery with a higher initial coulombic efficiency, d in the formula (II) is 0.2 or less, preferably 0.08 or less, and 0.06 or less. is more preferred.

The upper limit and lower limit of d can be combined arbitrarily. Combinations include, for example, d being -0.1 to 0.2, more than 0 to 0.2 or less, -0.05 to 0.08, more than 0 to 0.06 or less.

From the viewpoint of suppressing an increase in the resistance of the battery after repeated charge-discharge cycles, e in the formula (II) is preferably greater than 0 and 0.01 or more, and more preferably 0.02 or more. preferable. From the viewpoint of obtaining a lithium secondary battery with a high initial capacity, e in the formula (II) is 0.2 or less, preferably 0.1 or less, and more preferably 0.05 or less. .

The upper limit and lower limit of e can be combined arbitrarily. Combinations include, for example, e greater than 0 and 0.2 or less, 0.01 to 0.1, 0.02 to 0.05, and the like.

That is, in formula (II), d may be -0.1 to 0.2 and e may be more than 0 and 0.2 or less, d is more than 0 and 0.2 or less and e is more than 0 It may be 0.2 or less, d may be -0.05 to 0.08 and e may be 0.01 to 0.1, d is more than 0 and 0.06 or less and e is 0.06 or less. 02 to 0.05.

From the viewpoint of obtaining a lithium secondary battery with a high cycle retention rate, the element X is one or more elements selected from the group consisting of Co, Mn, Ti, Mg, Al, W, Nb, B and Zr. is preferred, and one or more elements selected from the group consisting of Co, Mn, Al, W, Nb and B are more preferred.

The crystal structure of LiMO is a layered rock salt structure, and more preferably a hexagonal crystal structure or a monoclinic crystal structure. The crystal structure of LiMO is identified based on the diffraction angle and peak intensity of the obtained X-ray diffraction spectrum obtained by obtaining the powder X-ray diffraction spectrum by powder X-ray diffraction measurement.

The hexagonal crystal structure is composed of P3, P3 ₁ , P3 ₂ , R3, P-3, R-3, P312, P321, P3 ₁ 12, P3 ₁ 21, P3 ₂ 12, P3 ₂ 21, R32, P3m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P6 ₁ , P6 ₅ , P6 ₂ , P6 ₄ , P6 ₃ , P-6, P6/m, P6 ₃ /m, P622, P6 ₁ 22, P6 ₅ 22, P6 ₂ 22, P6 ₄ 22, P6 ₃ 22, P6mm, P6cc, P6 ₃ cm, P6 ₃ mc, P- It belongs to any one space group selected from the group consisting of 6m2, P-6c2, P-62m, P-62c, P6/mmm, P6/mcc, P6 ₃ /mcm, and P6 ₃ /mmc.

The monoclinic crystal structures are P2, P2 ₁ , C2, Pm, Pc, Cm, Cc, P2/m, P2 ₁ /m, C2/m, P2/c, P2 ₁ /c, and C2 It belongs to any one space group selected from the group consisting of /c.

Among these, in order to obtain a lithium secondary battery with a high discharge capacity, the crystal structure is a hexagonal crystal structure assigned to the space group R-3m, or a monoclinic crystal assigned to C2 / m. A structure is particularly preferred.

The CAM powder has half of the diffraction peak (003 plane) within the range of 2θ = 18.7 ± 2° in the powder X-ray diffraction spectrum obtained by measuring by the method described in [Powder X-ray diffraction measurement] above. The ratio C/B between the value width B and the half-value width C of the diffraction peak (104 plane) within the range of 2θ=44.6±2° is preferably 0.54 to 0.68. That is, the C/B of the CAM powder is preferably 0.55-0.66.

A CAM powder having a C/B ratio of 0.54 to 0.68 grows moderately anisotropically in the normal direction of the (003) plane (that is, in the c-axis direction), and lithium ions are absorbed and desorbed from the CAM powder. easier. Therefore, a CAM powder in which C/B satisfies the above relationship can improve battery performance.

(Powder characteristics)
The _D50 of the CAM powder shows a value comparable to the _D50 of the precursor powder used for production. The D ₅₀ of the CAM powder is preferably 3-20 μm, more preferably 4-18 μm, even more preferably 7-17 μm. When the _D50 of the CAM powder is 3 μm or more, the pores of the LiMO particles are relatively increased, so that the cycle retention rate of the lithium secondary battery tends to be improved. Further, when the _D50 of the CAM powder is 20 μm or less, the pores of the LiMO particles are likely to come into contact with the electrolytic solution, and the initial capacity of the lithium secondary battery is likely to be improved.

The BET specific surface area of the CAM powder is preferably 2 m ² /g or less, more preferably 0.1 to 2 m ² /g, and even more preferably 0.2 to 1.5 m ² /g. , 0.25 to 1.0 m ² /g. When the BET specific surface area of the CAM powder is equal to or higher than the above lower limit, the CAM powder easily comes into contact with the electrolytic solution and improves the battery capacity. Further, when the BET specific surface area of the CAM powder is equal to or less than the upper limit, the decomposition reaction of the electrolytic solution, which is a side reaction in the lithium secondary battery, is unlikely to occur.

　CAM powder has fine pores that satisfy the above formula (3). When the CAM powder is used for the positive electrode of a lithium secondary battery, the water-soluble filling compound filled in the pores of the CAM particles constituting the CAM powder is considered to partially dissolve in the electrolyte solution, which is a polar solvent. Pores appear in the CAM particles when the filling compound dissolves.

　The fine pores of the CAM particles are expected to buffer the strain caused by the volume expansion and contraction of the CAM particles during charging and discharging of the lithium secondary battery, and suppress the damage of the particles. Also, it is believed that CAM particles with small pores are more effective at buffering than CAM particles with relatively large pores.

Furthermore, since the W compound and Mo compound used as the filling compound have high lithium ion conductivity, it is possible to suppress the decrease in capacity.

As a result, the CAM powder of the present embodiment can realize a lithium secondary battery with excellent cycle retention rate.

<Method for producing CAM powder>
A method for producing a CAM powder includes the steps of mixing a precursor powder and a lithium compound to obtain a mixture, and firing the mixture.

(Step of obtaining a mixture)
At least one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, lithium oxide, lithium chloride and lithium fluoride can be used as the lithium compound. Among these, any one of lithium hydroxide, lithium hydroxide hydrate and lithium carbonate or a mixture thereof is preferred. When lithium hydroxide or lithium hydroxide hydrate contains lithium carbonate, the content of lithium carbonate in lithium hydroxide or lithium hydroxide hydrate is preferably 5% by mass or less.

Before the step of obtaining the mixture, the precursor powder, which is a metal composite hydroxide, may be heat-treated in the range of 400 to 700°C to obtain a metal composite oxide. The heating temperature can be maintained for 0.5 to 10 hours. Air, oxygen, or a mixed gas of nitrogen can be used as the heating atmosphere.

　The lithium compound and the precursor powder are mixed in consideration of the composition ratio of the final target. Specifically, the lithium compound and the precursor powder are mixed at a ratio that satisfies the above formula (4).

That is, in the step of obtaining a mixture, the precursor powder is prepared at a molar ratio of 0.90 to 1.20 for Li constituting the lithium compound with respect to the total amount of metal elements constituting the particles of the precursor powder (precursor particles). A body powder and a lithium compound are mixed.

(Baking process)
The firing temperature is 740-920°C. When the firing temperature is 740° C. or higher, the normal direction of the (003) plane in the crystal structure (that is, the c-axis direction) grows moderately anisotropically, and the C/B is within the range of the present embodiment. can be obtained. Moreover, when the firing temperature is 920° C. or lower, it is possible to obtain a CAM powder in which the pores are filled with either one or both of the W compound and the Mo compound.

The firing temperature is preferably 750°C or higher, more preferably 760°C or higher, even more preferably 780°C or higher, even more preferably 790°C or higher, and particularly preferably 800°C or higher. Also, the firing temperature is preferably 910° C. or lower, more preferably 900° C. or lower.

The upper limit and lower limit of the firing temperature can be combined arbitrarily. For example, the firing temperature is preferably 750 to 920°C, more preferably 760 to 910°C, even more preferably 780 to 900°C, and particularly preferably 800 to 900°C.

Also, the firing temperature may be 760 to 920°C, 780 to 920°C, 790 to 920°C, or 800 to 920°C.

The firing temperature in this specification means the temperature of the atmosphere in the firing furnace, and also the highest temperature held in the firing process (hereinafter sometimes referred to as the maximum held temperature). When the firing process includes a plurality of heating steps, the temperature at the highest holding temperature in each heating step is taken as the firing temperature.

The holding time for firing is preferably 3 to 30 hours, more preferably 4 to 20 hours. If the holding time in firing exceeds 30 hours, the volatilization of lithium tends to substantially deteriorate the battery performance. When the holding time in the firing is less than 3 hours, the crystal growth is poor and the battery performance tends to be poor.

The heating rate in the heating process to reach the maximum holding temperature is preferably 80°C/hour or more, more preferably 100°C/hour or more, and particularly preferably 120°C/hour or more. The rate of temperature increase in the heating process to reach the maximum holding temperature is calculated from the time from the time the temperature starts to rise until the temperature reaches the holding temperature in the baking apparatus.

The firing process may have multiple firing stages with different firing temperatures. For example, it is preferable to have a first firing stage and a second firing stage that fires at a higher temperature than the first firing stage. Furthermore, it may have firing stages with different firing temperatures and firing times.

Air, oxygen, nitrogen, or a mixed gas of these is used as the firing atmosphere, and multiple firing steps are carried out if necessary. It is particularly preferable to use oxygen gas as the firing atmosphere.

The mixture of the precursor powder and the lithium compound may be calcined before performing the calcination step. In the present embodiment, calcination means calcination at a temperature lower than the calcination temperature in the calcination step. The firing temperature during temporary firing is, for example, in the range of 400°C or higher and lower than 700°C. The calcination may be performed multiple times.

The sintering apparatus used for sintering is not particularly limited, and for example, either a continuous sintering furnace or a fluidized sintering furnace may be used. Continuous firing furnaces include tunnel furnaces or roller hearth kilns. A rotary kiln may be used as the fluidized kiln.

By using the above-mentioned precursor powder and setting the firing conditions to the above-mentioned range, 1 μm
The number of primary particles per ² and C/B can be within the range of this embodiment.

FIG. 3 is an SEM image of the CAM powder obtained in Example 1, which will be described later. The CAM powder shown in FIG. 3 is produced using the precursor powder shown in FIGS. 4 is an SEM-EDX image in the same field of view as in FIG. 3, which is a W mapping image.

As shown in Fig. 3, pores can be confirmed in the CAM particles that make up the CAM powder. In the cross section of the particle, the white striped portions correspond to the pores.

In addition, as shown in FIG. 4, it can be confirmed that W exists even inside the CAM particles.

FIG. 5 is a schematic diagram showing how CAM particles grow during the production of CAM powder using the precursor powder described above. FIG. 6 is a schematic diagram showing how particles grow during production of LiMO particles using MCC particles that do not have a filling compound in their pores.

As shown in FIG. 5, when the precursor powder described above is mixed with a lithium compound and fired, the precursor particles A1 in the precursor powder react with the lithium compound (not shown), resulting in CAM particles B1 in the CAM powder. is obtained. Specifically, MCC forming the primary particles AP1 in the precursor particles A1 reacts with a lithium compound (not shown) to produce LiMO forming the primary particles BP1. The primary particles BP1 constitute CAM particles B1.

Here, in the precursor particles A1, the pores are filled with the filling compound F. Therefore, when the primary particles AP1 and the lithium compound react, the filling compound F positioned between the primary particles AP1 inhibits the coalescence of the primary particles AP1 and inhibits the growth of the primary particles BP1.

As a result, the primary particles BP1 in the CAM particles B1 are less likely to grow from the primary particles AP1 in the precursor particles A1, and tend to be small particles.

In addition, the filling compound F filled in the pores of the precursor particles A1 retains the pores during firing. Therefore, compared to the pores of the precursor particles A1, the pores of the CAM particles B1 are less likely to change in diameter even if the overall volume is reduced, and are equivalent in size to the pores of the precursor particles A1. easy to become.

Similarly, as shown in FIG. 6, when MCC particles A2 having no filling compound in pores are mixed with a lithium compound and fired, MCC constituting primary particles AP2 in MCC particles A2 and not shown It reacts with the lithium compound to produce LiMO, which constitutes the primary particles BP2. The primary particles BP2 constitute LiMO particles B2.

Here, when the primary particles AP2 and the lithium compound react, there is no substance that inhibits the coalescence of the primary particles AP2. Therefore, when the MCC particles A2 are fired, the primary particles AP2 are united.

As a result, the primary particles BP2 in the LiMO particles B2 tend to grow from the primary particles AP2 in the MCC particles A2 and become relatively large particles.

In addition, fine pores between the primary particles disappear as the primary particles BP2 coalesce. Therefore, relatively large pores tend to remain in the obtained LiMO particles B2 as compared with the pores of the MCC particles A2.

As described above, the CAM powder that satisfies the above (3) is obtained by firing the mixture of the precursor powder and the lithium compound.

A positive electrode active material with a high cycle retention rate can be produced from the precursor powder having the above configuration.

In addition, the positive electrode active material powder having the above configuration can realize a battery with a high cycle retention rate when used for the positive electrode of a lithium secondary battery.

According to the method for producing the positive electrode active material powder having the configuration described above, it is possible to easily produce a positive electrode active material powder that has a high cycle retention rate when used for the positive electrode of a lithium secondary battery.

<Lithium secondary battery>
Next, the configuration of a lithium secondary battery that uses CAM powder will be described.
Furthermore, a positive electrode for a lithium secondary battery (hereinafter sometimes referred to as a positive electrode) suitable for use of CAM powder will be described.
Furthermore, a lithium secondary battery suitable for use as a positive electrode will be described.

An example of a lithium secondary battery suitable for using CAM powder has a positive electrode and a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and an electrolytic solution placed between the positive electrode and the negative electrode.

An example of a lithium secondary battery has a positive electrode and a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and an electrolytic solution placed between the positive electrode and the negative electrode.

FIG. 7 is a schematic diagram showing an example of a lithium secondary battery. For example, a cylindrical lithium secondary battery 10 is manufactured as follows.

First, as shown in FIG. 7, a pair of strip-shaped separators 1, a strip-shaped positive electrode 2 having a positive electrode lead 21 at one end, and a strip-shaped negative electrode 3 having a negative electrode lead 31 at one end are arranged as follows: 1 and the negative electrode 3 are stacked in this order and wound to form an electrode group 4 .

The positive electrode 2 can be manufactured by first preparing a positive electrode mixture containing CAM powder, a conductive material, and a binder, and supporting the positive electrode mixture on a positive electrode current collector.

Examples of the negative electrode 3 include an electrode in which a negative electrode mixture containing a negative electrode active material (not shown) is supported on a negative electrode current collector, and an electrode composed solely of a negative electrode active material. can be manufactured in

Next, after housing the electrode group 4 and an insulator (not shown) in the battery can 5, the can bottom is sealed, the electrode group 4 is impregnated with the electrolytic solution 6, and the electrolyte is arranged between the positive electrode 2 and the negative electrode 3. . Further, by sealing the upper portion of the battery can 5 with the top insulator 7 and the sealing member 8, the lithium secondary battery 10 can be manufactured.

The shape of the electrode group 4 is, for example, a columnar shape such that the cross-sectional shape of the electrode group 4 cut in the direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, or a rectangle with rounded corners. can be mentioned.

In addition, as the shape of the lithium secondary battery having such an electrode group 4, a shape defined by IEC60086, which is a standard for batteries defined by the International Electrotechnical Commission (IEC), or JIS C 8500 can be adopted. . For example, a shape such as a cylindrical shape or a rectangular shape can be mentioned.

Further, the lithium secondary battery is not limited to the wound type configuration described above, and may have a layered configuration in which a layered structure of a positive electrode, a separator, a negative electrode, and a separator is repeatedly stacked. Examples of laminated lithium secondary batteries include so-called coin-type batteries, button-type batteries, and paper-type (or sheet-type) batteries.

For the positive electrode, separator, negative electrode and electrolyte that constitute the lithium secondary battery, for example, the configurations, materials and manufacturing methods described in [0113] to [0140] of WO2022/113904A1 can be used.

<All-solid lithium secondary battery>
The CAM powder of this embodiment can be used as a CAM for an all-solid lithium secondary battery.

FIG. 8 is a schematic diagram showing an example of an all-solid lithium secondary battery. The all-solid lithium secondary battery 1000 shown in FIG. 8 has a laminate 100 having a positive electrode 110, a negative electrode 120, and a solid electrolyte layer 130, and an exterior body 200 housing the laminate 100. Moreover, the all-solid lithium secondary battery 1000 may have a bipolar structure in which a CAM and a negative electrode active material are arranged on both sides of a current collector. Specific examples of bipolar structures include structures described in JP-A-2004-95400.

The positive electrode 110 has a positive electrode active material layer 111 and a positive electrode current collector 112 . The positive electrode active material layer 111 contains the above-described CAM and solid electrolyte. Moreover, the positive electrode active material layer 111 may contain a conductive material and a binder.

The negative electrode 120 has a negative electrode active material layer 121 and a negative electrode current collector 122 . The negative electrode active material layer 121 contains a negative electrode active material. Further, the negative electrode active material layer 121 may contain a solid electrolyte and a conductive material.

The laminate 100 may have an external terminal 113 connected to the positive electrode current collector 112 and an external terminal 123 connected to the negative electrode current collector 122 . In addition, all-solid lithium secondary battery 1000 may have a separator between positive electrode 110 and negative electrode 120 .

The all-solid lithium secondary battery 1000 further has an insulator (not shown) for insulating the laminate 100 and the exterior body 200 and a sealing body (not shown) for sealing the opening 200 a of the exterior body 200 .

For the exterior body 200, a container molded from a highly corrosion-resistant metal material such as aluminum, stainless steel, or nickel-plated steel can be used. Moreover, as the exterior body 200, a container in which a laminated film having at least one surface subjected to corrosion-resistant processing is processed into a bag shape can also be used.

Examples of the shape of the all-solid lithium secondary battery 1000 include coin-shaped, button-shaped, paper-shaped (or sheet-shaped), cylindrical, rectangular, and laminated (pouch-shaped).

The all-solid-state lithium secondary battery 1000 is illustrated as having one laminate 100 as an example, but is not limited to this. The all-solid-state lithium secondary battery 1000 may have a configuration in which the laminate 100 is used as a unit cell and a plurality of unit cells (laminate 100 ) are sealed inside the exterior body 200 .

For all-solid-state lithium secondary batteries, for example, the configurations, materials and manufacturing methods described in [0151] to [0181] of WO2022/113904A1 can be used.

The positive electrode as described above contains the CAM powder of the present embodiment and is therefore excellent in cycle retention.

In addition, since the lithium secondary battery as described above has the above positive electrode, it has excellent cycle retention rate.

As one aspect, the present invention also includes the following aspects.

<1> A precursor powder used as a precursor of a positive electrode active material for lithium secondary batteries,
a plurality of particles having pores;
a filling compound filled in the pores;
The particles have a layered structure and are made of MCC containing at least Ni,
the filling compound is either or both of a water-soluble tungsten compound and a water-soluble molybdenum compound;
A precursor powder that satisfies the following formula (A1).
15≦(P1−P2)/P1×100≦99 (A1)

<2> The precursor powder according to <1>, wherein the P2 is 0.6 cm ³ /g or less.

<3> The precursor powder according to <1> or <2>, wherein the total pore volume of the precursor powder is 0.008 to 0.02 cm ³ .

<4> the MCC contains the element X,
The atomic weight ratio between the Ni and the element X contained in the MCC and the sum of W and Mo contained in the filling compound is any one of <1> to <3> that satisfies the following formula (A2) A precursor powder as described in .
[Ni]: [X]: [W + Mo] = (1-a): a: b ... (A2)
(Formula (A2) satisfies 0.04≦a≦0.30 and 0.003≦b≦0.015.)

<5> The precursor powder according to any one of <1> to <4>, wherein the MCC is a hydroxide represented by the following compositional formula (IA).
Ni _1-xy Co _x M _y (OH) _2-α Formula (IA)
(In the composition formula (I), 0.02 ≤ x ≤ 0.10, 0.02 ≤ y ≤ 0.15, and -, -0.20 ≤ α ≤ 0.20 are satisfied, and M is Mn, Fe, One or more elements selected from the group consisting of Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, S and P.)

<6> The precursor powder according to any one of <1> to <5>, wherein the _D50 is 7 to 17 μm.

<7> The precursor powder according to any one of <1> to <6>, which has a BET specific surface area of 1.5 to 10 m ² /g.

<8> A CAM powder used in a lithium secondary battery,
a plurality of particles having pores;
a filling compound filled in the pores;
The particles have a layered structure and are made of LiMO containing at least Ni,
the filling compound is either or both of a water-soluble tungsten compound and a water-soluble molybdenum compound;
A CAM powder having a peak that satisfies the following formula (A3).
0.006≦P3≦0.05 (A3)

<9> The CAM powder according to <8>, which satisfies the following formula (A5).
65≦(P3−P4)/P3×100≦98 (A5)
(P4 (cm ³ /g) in the above formula (A5) is the same as P4 in the above formula (5).)

<10> The CAM powder according to <8> or <9>, wherein the elution rate is 10 to 60%.

<11> The particles include secondary particles in which the LiMO primary particles are aggregated,
The CAM powder according to any one of <8> to <10>, wherein the number of primary particles per 1 μm ² obtained from an SEM image of the secondary particles at a magnification of 10,000 is 20 to 40.

<12> The LiMO contains the element X,
The atomic weight ratio of Li, Ni, and element X contained in the LiMO and the sum of W and Mo contained in the filling compound is any one of <8> to <11> that satisfies the following formula (A4): CAM powder according to claim 1.
[Li]: [Ni]: [X]: [W + Mo] = c: (1-a): a: b (A4)
(Formula (A4) satisfies 1.00≦c≦1.10, 0.04≦a≦0.30, and 0.003≦b≦0.015.)

<13> The CAM powder according to any one of <8> to <12>, wherein the LiMO is a compound represented by the following composition formula (II-A).
Li[Li _d (Ni _(1-e) X _e ) _1-d ]O ₂ (II-A)
(In formula (II-A), X represents element X and satisfies 0<d≦0.06 and 0.02≦e≦0.05.)

<14> The CAM powder according to any one of <8> to <13>, wherein the D ₅₀ is 7 to 17 μm.

<15> The CAM powder according to any one of <8> to <14>, which has a BET specific surface area of 0.25 to 1.0 m ² /g.

<16> The CAM powder according to any one of <8> to <15>, wherein the C/B is 0.55 to 0.66.

Although the preferred embodiments according to the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to such examples. The various shapes, combinations, etc., of the constituent members shown in the above examples are merely examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

Although the present invention will be described below with reference to examples, the present invention is not limited to these examples.

[Composition analysis]
The composition analysis of each powder produced by the below-described method was performed by the method of [Composition analysis] described above.

[BET specific surface area]
The BET specific surface area of each powder was measured by the method of [BET specific surface area] described above.

[Cumulative particle size distribution]
The cumulative particle size distribution of each powder was measured by the method of [Cumulative particle size distribution] described above.

[Powder X-ray diffraction measurement]
The powder X-ray diffraction (XRD) measurement of the precursor powder and the CAM powder was performed by the method of [Powder X-ray diffraction measurement] described above.

[Number of Primary Particles Constituting Secondary Particles]
The number of primary particles composing the CAM powder was measured by the above-described [Number of primary particles composing secondary particles (per unit area)].

[Pore size distribution]
The pore size distribution of each particle was measured by the method of [pore size distribution] described above.

P1 was obtained by washing each precursor powder obtained by the method described later with water of 20 times the mass of the precursor powder for 20 minutes, filtering, and vacuum drying at 120° C. for 10 hours. The obtained precursor powder was measured by the method of [pore size distribution] described above, and obtained based on the definition of P1.

P2 was obtained based on the definition of P2 by measuring each precursor powder obtained by the method described below by the above-described [pore size distribution] method.

P3 was obtained by washing each CAM powder obtained by the method described below for 20 minutes with water having a mass 20 times the mass of the precursor powder, filtering, and drying by vacuum drying at 120° C. for 10 hours. The powder was measured by the method of [pore size distribution] described above, and obtained based on the definition of P3.

P4 is obtained based on the definition of P4 in the pore size distribution of the CAM powder obtained by measuring each CAM powder obtained by the method described below by the method of [pore size distribution] described above.

[Evaluation of battery performance]
Regarding the performance of the produced CAM powder, the battery performance was evaluated according to the method described in [Cycle maintenance rate] above.

(Example 1)
A metal composite hydroxide 1 having a composition of Ni _0.96 Co _0.02 Mn _0.02 (OH) ₂ was obtained by a known coprecipitation method using an aqueous solution of nickel sulfate, cobalt sulfate and manganese sulfate. rice field.

It was confirmed that the metal composite hydroxide 1 had a peak assigned to the space group P-3m1 in the powder XRD measurement using Cu-Kα rays, and had a layered structure.

The metal composite hydroxide 1 had a _D50 of 10.1 μm, a BET specific surface area of 8.0 m ² /g, and a total pore volume of 0.024 cm ³ /g as measured by a nitrogen adsorption method.

The metal composite hydroxide 1 has a log differential pore volume peak in a region of 10 nm or less in the pore size distribution calculated by the method described in [Pore size distribution] above, and the pore size of the peak is 3. 9 nm, and the peak value was 0.08 cm ³ /g.

3.7 g of LiOH·H ₂ O and 9.4 g of WO ₃ were added to 100 g of pure water and stirred to obtain a basic solution in which Li and W were dissolved at Li/W = 2.2 (molar ratio). 1 was prepared. The dissolved amount of W per 100 g of water in the solution was calculated to be 7.4 g. The pH of the basic solution 1 was 12.1 (measurement temperature 25°C ± 2°C).

The basic solution 1 was added to the metal composite hydroxide 1 to prepare a slurry (water content 50% by mass) with a metal composite hydroxide 1 concentration of 50% by mass, and stirred for 5 minutes. The slurry was filtered to obtain a wet cake with a water content of 15% by mass. Precursor powder 1 was obtained by heating and drying the wet cake at 120° C. for 10 hours.

According to the elemental analysis of the precursor powder 1, W/(Ni+Co+Mn), which is the ratio of the substance amount of W to the substance amounts of Ni, Co, and Mn, was 0.7 mol%. That is, the composition ratio (molar ratio) of the precursor powder 1 is [Ni]:[Co]:[Mn]:[W]=96 mol%:2 mol%:2 mol%:0.7 mol%, and the formula (2 ), a=0.04 and b=0.007.

Lithium hydroxide monohydrate was weighed so that the amount (molar ratio) of Li to the total amount of Ni, Co and Mn contained in the precursor powder 1 was 1.06. A mixture was obtained by mixing precursor powder 1 and lithium hydroxide monohydrate.

The resulting mixture was then fired at a firing temperature of 800°C for 5 hours in an oxygen atmosphere to obtain CAM powder 1.

The composition ratio (molar ratio) of the CAM powder 1 is Li/(Ni+Co+Mn)=1.06, and [Ni]:[Co]:[Mn]:[W]=96mol%:2mol%:2mol%:0. 0.7 mol %, and in formula (4), a=0.04, b=0.007, and c=1.06. It was confirmed that the particles of CAM powder 1 had a layered structure. The filler compound contained in precursor powder 1 and CAM powder 1 was a W compound containing Li and W.

(Example 2)
By adding 7.4 g of LiOH·H ₂ O and 18.7 g of WO ₃ to 100 g of pure water and further stirring, a basic solution was obtained in which Li and W were dissolved at Li/W = 2.2 (molar ratio). Solution 2 was prepared. The dissolved amount of W per 100 g of water in the solution was calculated to be 14.4 g. The pH of the basic solution 2 was 12.0 (measurement temperature 25°C ± 2°C).

Precursor powder 2 and CAM powder 2 were obtained in the same manner as in Example 1, except that basic solution 2 was added to metal composite hydroxide 1 to prepare slurry.

According to the elemental analysis of the precursor powder 2, W/(Ni+Co+Mn), which is the ratio of the substance amount of W to the substance amounts of Ni, Co, and Mn, was 1.4 mol%. That is, the composition ratio (molar ratio) of the precursor powder 2 is [Ni]:[Co]:[Mn]:[W]=96 mol%:2 mol%:2 mol%:1.4 mol%, and the formula (2 ), a=0.04 and b=0.014.

The composition ratio (molar ratio) of the CAM powder 2 is Li/(Ni+Co+Mn)=1.06, and [Ni]:[Co]:[Mn]:[W]=96mol%:2mol%:2mol%:1. 0.4 mol %, and in formula (4), a=0.04, b=0.014, and c=1.06. It was confirmed that the particles of CAM powder 2 had a layered structure. The filler compound contained in precursor powder 2 and CAM powder 2 was a W compound containing Li and W.

(Example 3)
6.5 g of NaOH and 17.8 _g of WO3 are added to 100 g of pure water, and further stirred to prepare a basic solution 3 in which Na and W are dissolved at Na/W = 2.1 (molar ratio). bottom. The dissolved amount of W per 100 g of water in the solution was calculated to be 14.1 g. The pH of the basic solution 3 was 12.0 (measurement temperature 25°C ± 2°C).

In the same manner as in Example 1, except that the slurry was adjusted by adding the basic solution 3 to the metal composite hydroxide 1, and the moisture content of the wet cake after filtration of the slurry was adjusted to 10% by mass. A precursor powder 3 and a CAM powder 3 were obtained.

According to the elemental analysis of the precursor powder 3, W/(Ni+Co+Mn), which is the ratio of the substance amount of W to the substance amounts of Ni, Co, and Mn, was 0.8 mol%. That is, the composition ratio (molar ratio) of the precursor powder 3 is [Ni]:[Co]:[Mn]:[W]=96 mol%:2 mol%:2 mol%:0.8 mol%, and the formula (2 ), a=0.04 and b=0.008.

The composition ratio (molar ratio) of the CAM powder 3 is Li/(Ni+Co+Mn)=1.06, and [Ni]:[Co]:[Mn]:[W]=96mol%:2mol%:2mol%:0. 8 mol %, and in formula (4), a = 0.04, b = 0.008, and c = 1.06. It was confirmed that the particles of CAM powder 3 had a layered structure. The filler compound contained in precursor powder 3 and CAM powder 3 was a W compound containing Li and W.

(Example 4)
0.6 g of LiOH·H ₂ O and 14.9 g of Li ₂ MoO ₄ were added to 100 g of pure water, and further stirred to dissolve Li and Mo at Li/Mo=2.2 (molar ratio). A basic solution 4 was prepared. The amount of dissolved Mo per 100 g of water in the solution was calculated to be 8.2 g. The pH of the basic solution 4 was 11.9 (measurement temperature 25°C ± 2°C).

14.4 g of the basic solution 4 is added to 100 g of the metal composite hydroxide 1, and 22 g of pure water is added and mixed to obtain a slurry having a mass concentration of the metal composite hydroxide 1 of 74% by mass (moisture content 26% by mass) was prepared.

The slurry was vacuum-dried at 50°C for 2 hours to obtain a wet cake. Furthermore, the precursor powder 4 was obtained by heating the wet cake at 120° C. for 10 hours.

According to the elemental analysis of the precursor powder 4, Mo/(Ni+Co+Mn), which is the ratio of the substance amount of Mo to the substance amounts of Ni, Co, and Mn, was 1.0 mol%. That is, the composition ratio (molar ratio) of the precursor powder 4 is [Ni]:[Co]:[Mn]:[Mo]=96 mol%:2 mol%:2 mol%:1.0 mol%, and the formula (2 ), a=0.04 and b=0.010.

A CAM powder 4 was obtained in the same manner as in Example 1 except that the precursor powder 4 was used.

The composition ratio (molar ratio) of the CAM powder 4 is Li/(Ni+Co+Mn)=1.06, and [Ni]:[Co]:[Mn]:[Mo]=96mol%:2mol%:2mol%:1. 0 mol %, and in formula (4), a = 0.04, b = 0.010, and c = 1.06. It was confirmed that the particles of CAM powder 4 had a layered structure. The filler compounds contained in precursor powder 4 and CAM powder 4 were Mo compounds containing Li and Mo.

(Comparative example 1)
Metal composite hydroxide 1 to which no basic solution was added was used as precursor powder C1.

Lithium hydroxide monohydrate was weighed so that the amount (molar ratio) of Li to 1 of the total amount of Ni, Co and Mn contained in the precursor powder C1 was 1.06.

Also, WO ₃ was weighed in an amount such that the ratio (mol %) of W to the total amount 1 of Ni, Co and Mn contained in the precursor powder C1 was 0.7 mol %.

Precursor powder C1, lithium hydroxide monohydrate and _WO3 were mixed to obtain a mixture. The composition ratio (molar ratio) of the resulting mixture was [Ni]:[Co]:[Mn]:[W]=96 mol %:2 mol %:2 mol %:0.7 mol %. The resulting mixture was fired at 800° C. for 5 hours in an oxygen atmosphere to obtain CAM powder C1.

The composition ratio (molar ratio) of the CAM powder C1 is Li/(Ni+Co+Mn)=1.06, and [Ni]:[Co]:[Mn]:[W]=96mol%:2mol%:2mol%:0. 0.7 mol %, and in formula (4), a=0.04, b=0.007, and c=1.06. It was confirmed that the particles of CAM powder C1 had a layered structure.

The CAM powder C1 washed under the above conditions had a peak pore size of 18.4 nm and a peak value of 0.012 cm ³ /g. The washed CAM powder C1 did not have a log differential pore volume peak in the region of 10 nm or less, and the maximum peak value P3 could not be evaluated.

Also, since there was no peak indicating the maximum peak value P3, the maximum peak value P4 could not be read in the pore size distribution of the CAM powder C1.

(Comparative example 2)
A CAM powder corresponding to the invention described in JP-A-2019-40675 was produced. Specifically, it was produced by the following method.
6.0 g of Li ₂ WO ₄ was added to 100 g of pure water and stirred to prepare a basic solution 5 in which Li and W were dissolved at Li/W=2.0 (molar ratio). The amount of dissolved W per 100 g of water in the aqueous solution was calculated to be 4.2 g. The pH of the basic solution 5 was 8.6 (measurement temperature 25°C ± 2°C).

While mixing 100 g of metal composite hydroxide 1, 4.5 g of basic solution 5 was sprayed to obtain a mixture of metal composite hydroxide 1 and basic solution 5. The resulting mixture was dried at 120° C. for 10 hours to obtain precursor powder C2.

　From the elemental analysis of the precursor powder C2, W/(Ni + Co + Mn), which is the ratio of the substance amount of W to the substance amounts of Ni, Co, and Mn, was 0.10 mol%. That is, the composition ratio (molar ratio) of the precursor powder C2 is [Ni]:[Co]:[Mn]:[W]=96 mol%:2 mol%:2 mol%:0.10 mol%, and the formula (2 ), a=0.04 and b=0.010.

Lithium hydroxide monohydrate was weighed so that the amount (molar ratio) of Li to the total amount of Ni, Co and Mn contained in the precursor powder C2 was 1.06. A mixture was obtained by mixing precursor powder C2 and lithium hydroxide. The resulting mixture was fired at 800° C. for 5 hours in an oxygen atmosphere to obtain CAM powder C2. The composition ratio (molar ratio) of the CAM powder C2 is Li/(Ni+Co+Mn)=1.06, and [Ni]:[Co]:[Mn]:[W]=96mol%:2mol%:2mol%:0. .10 mol %, and in formula (4), a = 0.04, b = 0.010 and c = 1.06. It was confirmed that the particles of CAM powder C2 had a layered structure. The filler compound contained in precursor powder C2 and CAM powder C2 was a W compound containing Li and W.

The CAM powder C2 washed under the above conditions had a peak pore size of 24.3 nm and a peak value of 0.018 cm ³ /g. The washed CAM powder C2 did not have a log differential pore volume peak in the region of 10 nm or less, and P3 could not be evaluated.

Also, since there is no peak indicating P3, P4 of CAM powder C2 could not be read.

Tables 1 and 2 show the evaluation results of the precursor powders of Examples 1-4 and Comparative Examples 1-2. Tables 3 and 4 show the evaluation results of the CAM powders of Examples 1-4 and Comparative Examples 1-2.

As a result of the evaluation, it was confirmed that Examples 1 to 4 using the precursor powder of the present embodiment exhibit superior cycle retention rates compared to Comparative Example 1 in which no filling compound was added to the precursor.

FIG. 9 is an SEM photograph of CAM powder 1. FIG. 10 is an SEM photograph of CAM powder C1.

As is clear from FIGS. 9 and 10, the primary particles forming the CAM particles of the CAM powder of the example are smaller than the primary particles forming the CAM particles of the CAM powder of the comparative example.

FIG. 11 is an SEM image of the precursor powder 4. FIG. 12 is an SEM-EDX image in the same field of view as in FIG. 11, which is a mapping image of Mo.

As shown in FIG. 11, pores can be confirmed in the precursor particles. In the particle cross section shown in FIG. 11, black striped portions correspond to pores.

In addition, as shown in FIG. 12, it can be confirmed that Mo exists even inside the precursor particles.

FIG. 13 is an SEM image of CAM powder 4. FIG. 14 is an SEM-EDX image in the same field of view as in FIG. 13, which is a mapping image of Mo.

As shown in FIG. 13, pores can be confirmed in the CAM particles. In the particle cross section, white striped portions also correspond to pores.

In addition, as shown in FIG. 14, it can be confirmed that Mo exists even inside the CAM particles.

15 and 16 are diagrams showing changes in pore size distribution before and after washing with water for the precursor powder 1 and the CAM powder 1 produced in Example 1. FIG. 15 shows the measurement results for the precursor powder 1, and FIG. 16 shows the measurement results for the CAM powder 1. FIG.

　In Figures 15 and 16, the broken line indicates the pore size distribution of the powder before washing, and the solid line indicates the pore size distribution of the powder after washing.

As shown in FIG. 15, the peak indicating P2 in the precursor powder 1 greatly changes to indicate P1 by washing. In addition, as shown in FIG. 16, in the CAM powder 1, after washing, similarly to the precursor powder 1, the peak in the region with a pore diameter of 10 nm or less grows large.

17 and 18 are diagrams showing changes in the pore size distribution of the precursor powder C1 and the CAM powder C1 produced in Comparative Example 1 before and after washing with water. FIG. 17 shows the measurement results for the precursor powder C1, and FIG. 18 shows the measurement results for the CAM powder C1.

　In Figures 17 and 18, the broken line indicates the pore size distribution of the powder before washing, and the solid line indicates the pore size distribution of the powder after washing.

As shown in FIG. 17, in the precursor powder C1, almost no change was observed in the maximum peak value before and after washing, indicating that the pores of the precursor powder C1 did not change by washing alone. Moreover, as shown in FIG. 18, in the CAM powder C1, after washing, a peak appears in the region of pore diameters exceeding 10 nm. The pores of the MCC particles of the precursor powder C1 were not filled with a filling compound, suggesting that the primary particles coalesced during firing to grow grains.

(Example 5)
A metal composite hydroxide 2 having a composition of Ni _0.91 Co _0.07 Mn _0.02 (OH) ₂ is obtained by a known coprecipitation method using an aqueous solution of nickel sulfate, cobalt sulfate and manganese sulfate. rice field.

It was confirmed that metal composite hydroxide 2 has a peak assigned to space group P-3m1 in powder XRD measurement using Cu-Kα rays, and has a layered structure.

The metal composite hydroxide 2 had a _D50 of 4.6 μm, a BET specific surface area of 36.1 m ² /g, and a total pore volume of 0.16 cm ³ /g as measured by a nitrogen adsorption method.

The metal composite hydroxide 2 has a log differential pore volume peak in a region with a pore diameter of 10 nm or less in the pore diameter distribution calculated by the method described in [Pore diameter distribution] above, and the pore diameter of the peak was 4.3 nm and the peak value was 0.823 cm ³ /g.

0.40 g of LiOH·H ₂ O and 16.5 g of Li ₂ WO ₄ were added to 100 g of pure water and stirred to obtain a base in which Li and W were dissolved at Li/W = 2.2 (molar ratio). A sexual solution 6 was prepared. The dissolved amount of W per 100 g of water in the solution was calculated to be 11.5 g. The pH of the basic solution 6 was 12.0 (measurement temperature 25°C ± 2°C).

19.5 g of basic solution 6 was added to 100 g of metal composite hydroxide 2, and 56 g of pure water was further added and mixed to prepare a slurry having a mass concentration of metal composite hydroxide 1 of 57% by mass. .

The slurry was vacuum-dried at 50°C for 2 hours to obtain a wet cake. Furthermore, the precursor powder 5 was obtained by heating the wet cake at 120° C. for 10 hours.

According to the elemental analysis of the precursor powder 5, W/(Ni+Co+Mn), which is the ratio of the substance amount of W to the substance amounts of Ni, Co, and Mn, was 1.0 mol%. That is, the composition ratio (molar ratio) of the precursor powder 4 is [Ni]:[Co]:[Mn]:[W]=91 mol%:7 mol%:2 mol%:1.0 mol%, and the formula (2 ), a=0.09 and b=0.010.

A CAM powder 5 was obtained in the same manner as in Example 1 except that the precursor powder 5 was used.

The composition ratio (molar ratio) of the CAM powder 5 is Li/(Ni+Co+Mn)=1.06, and [Ni]:[Co]:[Mn]:[W]=91 mol%:7 mol%:2 mol%:1. 0 mol %, and in formula (4), a = 0.09, b = 0.010, and c = 1.06. It was confirmed that the particles of CAM powder 5 had a layered structure.

(Comparative Example 3)
Metal composite hydroxide 2 to which no basic solution was added was used as precursor powder C3.

Lithium hydroxide monohydrate was weighed so that the amount (molar ratio) of Li to 1 of the total amount of Ni, Co and Mn contained in the precursor powder C3 was 1.06. A mixture was obtained by mixing precursor powder C3 and lithium hydroxide. The resulting mixture was fired at 800° C. for 5 hours in an oxygen atmosphere to obtain CAM powder C3.

The composition ratio (molar ratio) of CAM powder C3 is Li/(Ni + Co + Mn) = 1.06, [Ni]: [Co]: [Mn] = 91 mol%: 7 mol%: 2 mol%, and the formula (4 ), a=0.09, b=0 and c=1.06. It was confirmed that the particles of CAM powder C3 had a layered structure.

The CAM powder C3 washed under the above conditions had a peak pore size of 50.6 nm and a peak value of 0.016 cm ³ /g. CAM powder C3 after washing did not have a log differential pore volume peak in the region of 10 nm or less, and P3 could not be evaluated.

Also, since there is no peak indicating P3, P4 of CAM powder C2 could not be read.

Tables 5 and 6 show the evaluation results of the precursor powders of Example 5 and Comparative Example 3. Tables 7 and 8 show the evaluation results of the CAM powders of Example 5 and Comparative Example 3.

As a result of the evaluation, it was confirmed that Example 5 using the precursor powder of the present embodiment exhibited an excellent cycle retention rate compared to Comparative Example 3 in which no filling compound was added to the precursor.

19 and 20 are diagrams showing changes in pore size distribution before and after washing with water for precursor powder 5 and CAM powder 5 produced in Example 5. 19 shows the measurement results for the precursor powder 5, and FIG. 20 shows the measurement results for the CAM powder 5. FIG.

　In Figures 19 and 20, the broken line indicates the pore size distribution of the powder before washing, and the solid line indicates the pore size distribution of the powder after washing.

As shown in FIG. 19, the peak indicating P2 in the precursor powder 5 greatly changes to indicate P1 due to washing. Moreover, as shown in FIG. 20 , in the CAM powder 5 , after washing, similarly to the precursor powder 5 , a large peak grows in the region of pore diameters of 10 nm or less.

From the above results, it was confirmed that the present invention is useful.

DESCRIPTION OF SYMBOLS 1... Separator, 2... Positive electrode, 3... Negative electrode, 4... Electrode group, 5... Battery can, 6... Electrolytic solution, 7... Top insulator, 8... Sealing body, 10... Lithium secondary battery, 21... Positive electrode lead, 31 Negative electrode lead 100 Laminated body 110 Positive electrode 111 Positive electrode active material layer 112 Positive electrode current collector 113 External terminal 120 Negative electrode 121 Negative electrode active material layer 122 Negative electrode current collector DESCRIPTION OF SYMBOLS 123... External terminal 130... Solid electrolyte layer 200... Exterior body 200a... Opening part 1000... All-solid-state lithium secondary battery

Claims (16)

A precursor powder used as a precursor of a positive electrode active material for a lithium secondary battery,
a plurality of particles having pores;
a filling compound filled in the pores;
The particles have a layered structure and are composed of a metal composite compound containing at least Ni,
the filling compound is either or both of a water-soluble tungsten compound and a water-soluble molybdenum compound;
A precursor powder that satisfies the following formula (1).
10≦(P1−P2)/P1×100<100 (1)
(P1 (cm ³ /g) is the washed precursor powder obtained by washing the precursor powder for 20 minutes with water that is 20 times the weight of the precursor powder, followed by solid-liquid separation and drying. is the maximum peak value of the log differential pore volume in the pore size distribution of 10 nm or less.
P2 (cm ³ /g) is the value of the log differential pore volume at the pore diameter of the peak showing P1 in the pore diameter distribution of the precursor powder.
The pore size distribution is obtained by analyzing the nitrogen desorption isotherm obtained by measuring the precursor powder or the washed precursor powder at liquid nitrogen temperature by the Barrett-Joyner-Halenda (BJH) method. . ) 2. The precursor powder according to claim 1, wherein said P2 is 0.8 cm ^<3> /g or less. 3. The precursor powder according to claim 1, wherein the total pore volume obtained from the pore size distribution of the precursor powder is 0.005 to 0.15 cm ³ . The metal complex compound contains the element X,
The element X is at least one element selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, S and P. can be,
4. Any one of claims 1 to 3, wherein the atomic weight ratio between Ni and the element X contained in the metal composite compound and the sum of W and Mo contained in the filling compound satisfies the following formula (2) Precursor powder as described.
[Ni]: [X]: [W + Mo] = (1-a): a: b (2)
(Formula (2) satisfies 0.01≦a≦0.5 and 0.0015≦b≦0.03.) In the volume-based cumulative particle size distribution curve obtained by laser diffraction particle size distribution measurement, _D50 , which is the particle size at which the cumulative volume ratio from the small particle size side is 50%, is 3 to 20 μm. Precursor powder according to any one of claims 1 to 3. 6. The precursor powder according to any one of claims 1 to 5, which has a BET specific surface area of 1 to 40 m ² /g. A positive electrode active material powder used in a lithium secondary battery,
a plurality of particles having pores;
a filling compound filled in the pores;
The particles have a layered structure and are made of a lithium metal composite oxide containing at least Ni,
the filling compound is either or both of a water-soluble tungsten compound and a water-soluble molybdenum compound;
A positive electrode active material powder having a peak that satisfies the following formula (3).
P3≧0.003 (3)
(P3 (cm ³ /g) is the washed powder obtained by washing the positive electrode active material powder for 20 minutes using water that is 20 times the weight of the positive electrode active material powder, and drying after solid-liquid separation. is the maximum peak value of the log differential pore volume in the pore size distribution of 10 nm or less.
The pore size distribution is obtained by analyzing the nitrogen desorption isotherm obtained by measuring the washed powder at liquid nitrogen temperature by the Barrett-Joyner-Halenda (BJH) method. ) 8. The positive electrode active material powder according to claim 7, wherein the elution ratio, which is the total eluted molar amount of W and Mo with respect to the positive electrode active material powder, measured by the following measuring method is 10 to 60%.
(Measuring method)
The positive electrode active material powder is precisely weighed to obtain a sample, and the sample is washed for 20 minutes with water having a mass ratio of 20 times that of the sample, followed by solid-liquid separation to obtain a filtrate. The filtrate is subjected to ICP analysis, and the total eluted molar amount of W and Mo eluted in the filtrate is determined based on the analysis results. The elution ratio is obtained from the total molar amount of W and Mo in the sample and the total eluted molar amount. The particles include secondary particles in which the primary particles of the lithium metal composite oxide are aggregated,
9. The number of the primary particles per 1 μm ² obtained by observing the secondary particles with a scanning electron microscope (SEM) and obtaining an SEM image with a magnification of 10000 times is 10 to 50. positive electrode active material powder. The lithium metal composite oxide contains element X,
The element X is at least one element selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, S and P. can be,
10. The atomic weight ratio of Li, Ni, and the element X contained in the lithium metal composite oxide and the sum of W and Mo contained in the filling compound satisfies the following formula (4). The positive electrode active material powder according to any one of items 1 and 2.
[Li]: [Ni]: [X]: [W + Mo] = c: (1-a): a: b (4)
(Formula (4) satisfies 0.9≦c≦1.2, 0.01≦a≦0.5, and 0.0015≦b≦0.03.) In the volume-based cumulative particle size distribution curve obtained by laser diffraction particle size distribution measurement, _D50 , which is the particle size at which the cumulative volume ratio from the small particle size side is 50%, is 3 to 20 μm. The positive electrode active material powder according to any one of items 1 and 2. The positive electrode active material powder according to any one of claims 7 to 11, having a BET specific surface area of 2 m ² /g or less. In the powder X-ray diffraction measurement using CuKα rays, half of the diffraction peak within the range of 2θ = 44.6 ± 2 ° with respect to the half width B of the diffraction peak of the peak within the range of 2θ = 18.7 ± 2 ° The positive electrode active material powder according to any one of claims 7 to 12, wherein the ratio C/B to the price range C is 0.54 to 0.68. A step of mixing the precursor powder according to any one of claims 1 to 6 and a lithium compound to obtain a mixture;
calcining the mixture,
In the step of obtaining the mixture, the precursor powder having a molar ratio of 0.90 to 1.20 of Li constituting the lithium compound with respect to the total amount of metal elements constituting the particles of the precursor powder. and the lithium compound,
The method for producing a positive electrode active material powder, wherein the firing temperature in the firing step is 740 to 920°C. A positive electrode comprising the positive electrode active material powder according to any one of claims 7 to 13. A lithium secondary battery having the positive electrode according to claim 15.

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