WO2024128014A1 - Metal composite compound powder and method for producing positive electrode active material for lithium secondary battery - Google Patents

Abstract

Provided is a metal composite compound powder that contains at least Ni and an element M and satisfies formula (A).　L_A/L_av≥1.2 … (A) (In formula A, L_A represents the crystallite size calculated from a diffraction peak present in the 2θ=38.5±1° range in powder x-ray diffraction measurement using CuKα rays.　L_av represents the average crystallite size calculated by Rietveld analysis of the powder x-ray diffraction pattern in the 2θ=10°-90° range obtained by the powder x-ray diffraction measurement.)

Description

METAL COMPOSITE COMPOUND POWDER AND METHOD FOR PRODUCING POSITIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY

The present invention relates to a method for producing a metal complex compound powder and a positive electrode active material for a lithium secondary battery.
This application claims priority based on Japanese Patent Application No. 2022-201286, filed on December 16, 2022, the contents of which are incorporated herein by reference.

The positive electrode active material contained in the positive electrode of a lithium secondary battery can be obtained, for example, by mixing a lithium compound and a metal composite compound containing a metal element other than Li and baking the mixture.

As the applications of lithium secondary batteries expand, there is a demand for improving the battery performance of lithium secondary batteries. As a technique for improving the battery performance of lithium secondary batteries, attempts have been made to control the crystalline state of the metal complex compound that is the raw material for the positive electrode active material. Patent Document 1 discloses a metal complex compound in which the intensity ratio of the diffraction peaks is specified for two specific crystal planes. It has been shown that the lithium metal complex oxide obtained from the metal complex compound of Patent Document 1 has good battery characteristics.

JP-A-2015-003838

As the use of lithium secondary batteries advances, further improvements in metal composite compounds are required.

The present invention was made in consideration of these circumstances, and aims to provide a metal composite compound powder that can be used to produce a positive electrode active material with low charge transfer resistance. It also aims to provide a method for producing a positive electrode active material for lithium secondary batteries using such a metal composite compound powder.

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

[1] A metal composite compound powder containing at least Ni and an element M, the element M being one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si, and satisfying the following formula (A):
L _A / L _av ≧1.2 ... (A)
(In formula (A), L _A represents a crystallite diameter calculated from a diffraction peak present within a range of 2θ=38.5±1° in powder X-ray diffraction measurement using CuKα radiation.
L _av represents the average crystallite size calculated by Rietveld analysis of the powder X-ray diffraction pattern in the range of 2θ=10°-90° obtained by the powder X-ray diffraction measurement.)
[2] A metal composite compound powder containing at least Ni and an element M, the element M being one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si, and satisfying the following formula (B):
_L / L _av ≦3.2 ... (B)
(In formula (B), L _B represents a crystallite diameter calculated from a diffraction peak present within a range of 2θ=33.0±1° in powder X-ray diffraction measurement using CuKα radiation.
L _av represents the average crystallite size calculated by Rietveld analysis of the powder X-ray diffraction pattern in the range of 2θ=10°-90° obtained by the powder X-ray diffraction measurement.)
[3] The metal composite compound powder according to [1] or [2], which satisfies the following formula (C):
_L / L _≥ 1.2 ... (C)
(In formula (C), L _C represents a crystallite size calculated from a diffraction peak present within the range of 2θ=19.1±1° in the powder X-ray diffraction measurement.)
[4] The metal complex compound powder according to any one of [1] to [3], represented by the following composition formula (I).
Ni _(1-x-y) Co _x M _y O _z (OH) _2-α ... (I)
(The composition formula (I) satisfies 0≦x≦0.5, 0<y≦0.5, 0<x+y<1, 0≦z≦3, −0.5≦α≦2, and α-z<2, and M is one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.)
[5] The metal complex compound powder according to [4], wherein the composition formula (I) satisfies 0≦x≦0.1 and 0<x+y<0.6.
[6] The metal complex compound powder according to any one of [1] to [5], having a BET specific surface area of more than 10.0 m ² /g.
[7] The metal composite compound powder according to any one of [1] to [6], wherein _D50 , which is a 50% cumulative volume particle size, is 8 μm or more and 20 μm or less.
[8] A method for producing a positive electrode active material for a lithium secondary battery, comprising: a mixing step of mixing the metal composite compound powder according to any one of [1] to [7] with a lithium compound; and a firing step of firing the resulting mixture in an oxygen-containing atmosphere at a temperature of 500° C. or higher and 1000° C. or lower.

The present invention provides a metal composite compound powder that can be used to produce a positive electrode active material with low charge transfer resistance. It also provides a method for producing a positive electrode active material for lithium secondary batteries using such a metal composite compound powder.

FIG. 1 is a schematic diagram showing an example of a lithium secondary battery. FIG. 2 is a schematic diagram showing an example of an all-solid-state lithium secondary battery.

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

The term "powder" refers to a collection of fine particles. "Metal composite compound powder" refers to a powdered metal composite compound. Similarly, similar expressions that add "powder" to the name of a substance also refer to a powdered substance. Hereafter, "metal composite compound powder" will be abbreviated as "MCC (Metal Composite Compound)."

The term "CAM" means Cathode Active Material for lithium secondary batteries.

Unless otherwise specified, the expression indicating the atomic symbol of a metal indicates the element and not the metal itself, for example, "Ni" indicates a nickel atom.
In this specification, the metal elements include metalloid elements such as B and Si.

Regarding a numerical range, for example, "1-10 μm" 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."
The lithium secondary battery refers to a lithium ion secondary battery.

<Metal Complex Compound>
The MCC of this embodiment contains at least Ni and an element M. The element M is one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.
MCC is a hexagonal compound having a layered structure. The MCC may be a metal composite oxide or a metal composite hydroxide. The metal composite hydroxide may include a partially oxidized compound. The MCC is a hexagonal compound having a layered structure, and is preferably a metal composite oxide or a metal composite hydroxide.

　MCC may further contain Co in addition to Ni and element M.

Moreover, the MCC preferably contains Ni and an element M1. The element M1 is either or both of Mn and Al. That is, the MCC preferably contains either or both of Mn and Al as the element M.
The MCC may further contain Co in addition to Ni and element M1.

Furthermore, the MCC may further contain an element M2 in addition to Ni and element M1. The element M2 is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.
The MCC may further contain Co in addition to Ni, element M1 and element M2.

The inventors' research has revealed that when the crystal growth of MCC is biased toward a specific plane compared to conventional MCC, the charge transfer resistance of the resulting CAM is low. In the following explanation, "growth biased toward a specific plane" is referred to as "having anisotropy."

In this specification, the appropriate anisotropy of MCC is defined as the ratio of the crystallite diameter calculated from the diffraction peak of a specific plane to the average crystallite diameter of MCC. In this specification, the crystallite diameter calculated from the diffraction peak of a specific plane for the crystallites constituting MCC is used as a representative value for the specific plane, and the anisotropy of MCC is evaluated by normalizing the representative value with the average crystallite diameter of MCC.

　MCC satisfies the following formula (A) or formula (B).

L _A / L _av ≧1.2 ... (A)
(In formula (A), L _A represents a crystallite diameter calculated from a diffraction peak present within a range of 2θ=38.5±1° in powder X-ray diffraction measurement using CuKα radiation.
L _av represents the average crystallite size calculated by Rietveld analysis of the powder X-ray diffraction pattern in the range of 2θ=10°-90° obtained by the powder X-ray diffraction measurement.)

_L / L _av ≦3.2 ... (B)
(In formula (B), L _B represents a crystallite diameter calculated from a diffraction peak present within a range of 2θ=33.0±1° in powder X-ray diffraction measurement using CuKα radiation.
L _av represents the average crystallite size calculated by Rietveld analysis of the powder X-ray diffraction pattern in the range of 2θ=10°-90° obtained by the powder X-ray diffraction measurement.)

Moreover, it is preferable that the MCC satisfying the above formula (A) or (B) further satisfies the following formula (C).
_L / L _≥ 1.2 ... (C)
(In formula (C), L _C represents a crystallite size calculated from a diffraction peak present within the range of 2θ=19.1±1° in the powder X-ray diffraction measurement.)

L _A , L _B , L _C , and _Lav included in the formulas (A) to (C) are each determined by the following method.

[Calculation method of L _A , L _B , L _C , and _Lav ]
The powder X-ray diffraction measurement is carried out using an X-ray diffractometer, such as D8ADVANCE (manufactured by Bruker Corporation).

First, MCC is loaded onto a dedicated substrate and measurements are performed using a CuKα source at a diffraction angle 2θ = 10° to 90° with a sampling width of 0.02° to obtain a powder X-ray diffraction spectrum. The obtained powder X-ray diffraction spectrum is analyzed using integrated powder X-ray analysis software to identify the crystal structure.

The powder X-ray diffraction spectrum is analyzed using powder X-ray diffraction analysis software (DIFFRAC.EVA, manufactured by Bruker Corporation), and the crystallite size is calculated from the diffraction peaks present within the range of 2θ = 38.5 ± 1 °. The calculated crystallite size is designated as _LA . The diffraction peaks present within the range of 2θ = 38.5 ± 1 ° are the diffraction peaks on the (101) plane of MCC.

From the above analysis, the crystallite size is calculated from the diffraction peaks present within the range of 2θ = 33.0 ± 1 °. The calculated crystallite size is designated as L _B. The diffraction peaks present within the range of 2θ = 33.0 ± 1 ° are the diffraction peaks in the (100) plane of MCC.

From the above analysis, the crystallite size is calculated from the diffraction peaks present within the range of 2θ = 19.1 ± 1 °. The calculated crystallite size is designated as L _C. The diffraction peaks present within the range of 2θ = 19.1 ± 1 ° are the diffraction peaks of the (001) plane of MCC.

In addition, the powder X-ray diffraction pattern in the obtained powder X-ray diffraction spectrum is subjected to Rietveld analysis to calculate the average crystallite size _Lav . In the Rietveld analysis, the obtained powder X-ray diffraction pattern is refined by fitting the powder X-ray diffraction pattern by the nonlinear least squares method using the crystal structure model _of β-Ni(OH) 2, which is a hexagonal crystal system, as a parameter. The average crystallite size is calculated from the refined powder X-ray diffraction pattern. Examples of analysis software for Rietveld analysis include TOPAS, Rietan, JANA, JADE, etc. In this embodiment, TOPAS ver. 4.2 (manufactured by Bruker) is used as the analysis software for performing the Rietveld analysis.

L _A /L _{av is} preferably 1.3 or more, _and more preferably 1.4 or more, and is preferably 2.5 or less, and more preferably 2.3 or less.

The upper limit and lower limit of L _A /L _av can be combined in any desired manner. For example, L _A /L _av is preferably 1.2 to 2.5, more preferably 1.3 to 2.3, and even more preferably 1.4 to 2.3.

L _B /L _{av is} preferably 3.0 or less, _and more preferably 2.8 or less, and is preferably 1.4 or more, and more preferably 1.6 or more.

The upper limit and lower limit of L _B /L _av can be combined in any desired manner. For example, L _B /L _av may be 1.4-3.2, 1.6-3.0, 1.6-2.8, or 1.4-2.8.

L _C /L _av is preferably 1.3 or more. Also, L _C /L _av is preferably 2.5 or less, and more preferably 2.3 or less.

The upper limit and lower limit of L _C /L _av can be combined in any desired manner. For example, L _C /L _av is preferably 1.2 to 2.5, more preferably 1.2 to 2.3, and even more preferably 1.3 to 2.3.

L _A is preferably 60 Å or more, and more preferably 100 Å or more. L _A is preferably 300 Å or less, and more preferably 250 Å or less.

The upper limit and lower limit of L _A can be arbitrarily combined. L _A is preferably 60 to 300 Å, and more preferably 100 to 250 Å.

L _B is preferably 100 Å or more, and more preferably 150 Å or more. L _B is preferably 350 Å or less, and more preferably 300 Å or less.

The upper limit and lower limit of L _B can be arbitrarily combined. L _B is preferably 100 to 350 Å, and more preferably 150 to 300 Å.

L _C is preferably 100 Å or more, and more preferably 150 Å or more. L _C is preferably 350 Å or less, and more preferably 250 Å or less.

The upper limit and lower limit of L _C can be arbitrarily combined. L _C is preferably 100-350 Å, and more preferably 150-300 Å.

_Lav is preferably 50 Å or more, and more preferably 70 Å or more. _Lav is preferably 300 Å or less, and more preferably 200 Å or less.

The upper limit and lower limit of _Lav can be arbitrarily combined. _Lav is preferably 50-300 Å, and more preferably 70-200 Å.

MCC satisfying the above formula (A) indicates that the (101) plane direction in the hexagonal crystal structure grows anisotropically. In other words, L _A /L _av can be considered as a numerical value representing the crystallinity in the layer direction in the CAM of layered structure made from MCC. Therefore, MCC satisfying the above formula (A) is considered to have a high proportion of faces in the direction intersecting the lamination direction of the layered structure of the obtained CAM, that is, faces into which Li can be inserted. As a result, the charge transfer resistance of the lithium secondary battery is low.

MCC satisfying the above formula (B) shows that it does not grow anisotropically in the direction of the (100) plane in the hexagonal crystal structure. It is considered that MCC satisfying the above formula (B) is easy to diffuse internally when Li enters the layer of the obtained CAM. In addition, it is considered that the crystal of CAM obtained from MCC satisfying the above formula (B) is less likely to flatten in the direction intersecting the stacking direction of the layered structure and the ratio of the face into which _Li can be _inserted is less likely to become small compared with CAM obtained from MCC having the same volume and L B /L av exceeding 3.2. As a result, the charge transfer resistance of the lithium secondary battery is low.

　MCC that satisfies the above formula (C) indicates that the (001) plane in the hexagonal crystal structure has grown anisotropically. MCC that satisfies the above formula (A) or (B) and also satisfies the above formula (C) tends to result in a lower charge transfer resistance in the resulting lithium secondary battery.

For an MCC that satisfies the above formula (A) and formula (C), L _A /L _av and L _C /L _av may be the following combinations.
L _A /L _av is 1.2-2.5 and L _C /L _av is 1.2-2.3
L _A /L _av is 1.2-2.5 and L _C /L _av is 1.3-2.3

For an MCC that satisfies the above formula (B) and formula (C), L _B /L _av and L _C /L _av may be the following combinations.
L _B /L _av is 1.4-3.2 and L _C /L _av is 1.2-2.3
L _B /L _av is 1.6-3.0 and L _C /L _av is 1.2-2.3
L _AB /L _av is 1.6-3.0 and L _C /L _av is 1.3-2.3

[BET specific surface area]
The BET specific surface area of MCC is preferably greater than 10.0 m ² /g, more preferably 12.0 m ² /g or more, and even more preferably 14.0 m ² /g or more. The BET specific surface area of MCC is preferably 50.0 m ² /g or less, more preferably 40.0 m ² /g or less, and even more preferably 30.0 m ² /g or less.

The upper limit and lower limit of the BET specific surface area can be arbitrarily combined. The BET specific surface area is preferably more than 10.0 m ² /g and not more than 50.0 m ² /g, more preferably 12.0 to 40.0 m ² /g, and even more preferably 14.0 to 30.0 m ² /g.

If the BET specific surface area of MCC is equal to or greater than the lower limit above, in a lithium secondary battery using CAM obtained using MCC in the positive electrode, the surface area involved in the reaction is large, and charge transfer resistance is likely to be low. Also, if the BET specific surface area of MCC is equal to or less than the upper limit above, in a lithium secondary battery using CAM obtained using MCC in the positive electrode, excessive increase in the contact area between CAM and electrolyte is suppressed, a resistance layer caused by decomposition of the electrolyte is unlikely to form, and charge transfer resistance is likely to be low.

[Method for measuring BET specific surface area]
The BET specific surface area (unit: ^m2 /g) of MCC can be measured by a BET specific surface area measuring device after drying 1 g of MCC in a nitrogen atmosphere at 105°C for 30 minutes. As the BET specific surface area measuring device, for example, Macsorb (registered trademark) manufactured by Mountech Co., Ltd. can be used.

[50% cumulative volume particle size ( _D50 )]
The _D50 of the MCC is preferably 8 μm or more, more preferably 10 μm or more, and even more preferably more than 13 μm. The _D50 of the MCC is preferably 20 μm or less, and more preferably 18 μm or less.
When the _D50 of MCC is within the above range, the reaction between MCC and the lithium compound is likely to proceed uniformly, and the crystallinity of the CAM obtained by using MCC is unlikely to vary. As a result, the reaction in the CAM proceeds uniformly during operation of the lithium secondary battery, and the charge transfer resistance is likely to be low.

The upper limit and lower limit of _D50 can be combined in any desired manner. _D50 is preferably 8 to 20 μm, more preferably 10 μm to 20 μm, and even more preferably more than 13 μm to 18 μm or less.

[Method of measuring _D50 ]
The cumulative particle size distribution of MCC is determined on a volume basis and is measured using a measuring device that uses a laser diffraction scattering method as its measurement principle. For example, the measuring device may be MT3000II (manufactured by Microtrack Bell).

In the obtained cumulative particle size distribution curve based on volume, the particle size at which the cumulative volume ratio from the small particle side is 50% when the whole is taken as 100% is defined as D ₅₀ (μm).

[Composition formula]
The MCC is preferably represented by the following composition formula (I).
Ni _{(1-x-y) CoxMyOz} ( _OH ) _2-α ... ₍ I)
(In the composition formula (I), 0≦x≦0.5, 0<y≦0.5, 0<x+y<1, 0≦z≦3, −0.5≦α≦2, and α-z<2 are satisfied, and M is one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.)

Furthermore, the MCC represented by the composition formula (I) may be a powder of a metal composite hydroxide represented by the following composition formula (I)-1, where z = 0. The definition of M in the composition formula (I)-1 is the same as in the above composition formula (I).
Ni _1-x-y Co _x M _y (OH) _2-α ... (I)-1
(Composition formula (I)-1 satisfies 0≦x≦0.5, 0<y≦0.5, 0<x+y<1, and −0.5≦α<2.)

(x)
x preferably satisfies 0≦x≦0.1, more preferably satisfies 0≦x≦0.05, and even more preferably satisfies 0≦x<0.05. That is, the amount of Co in MCC is preferably 10 mol% or less, more preferably 5 mol% or less, and even more preferably less than 5 mol% based on the total amount of Ni, Co, and element M. MCC does not need to contain Co (x=0).

In general, it is known that MCC compositions with a relatively large amount of Co are easier to sinter during CAM production, making CAM production easier. In contrast, it has been confirmed that the MCC of this embodiment satisfies the above formula (A) or (B), making it easy to produce CAM even with a small amount of Co.

When x satisfies 0≦x≦0.1, it is preferable that composition formula (I) satisfies 0<x+y<0.6 from the viewpoint of reducing the charge transfer resistance.

(y)
From the viewpoint of reducing the charge transfer resistance, y is preferably 0.01 or more, more preferably 0.02 or more, and particularly preferably 0.03 or more. Also, y is preferably 0.40 or less, more preferably 0.30 or less, and even more preferably 0.10 or less.

The above upper limit and lower limit values of y can be combined in any desired manner.
The above composition formula (I) or the above composition formula (I)-1 preferably satisfies 0.01≦y≦0.40, more preferably satisfies 0.02≦y≦0.30, and further preferably satisfies 0.03≦y≦0.10.

From the viewpoint of reducing the charge transfer resistance, x+y is preferably 0.02 or more, and more preferably 0.05 or more. Furthermore, x+y is preferably less than 0.6, more preferably 0.3 or less, even more preferably 0.2 or less, and particularly preferably 0.1 or less.

The upper and lower limits of x+y can be combined in any combination. The composition formula (I) or the composition formula (I)-1 preferably satisfies 0<x+y<0.6, more preferably satisfies 0.02≦x+y≦0.3, even more preferably satisfies 0.05≦x+y≦0.2, and particularly preferably satisfies 0.05≦x+y≦0.1.

(z)
z is preferably 0.02 or more, more preferably 0.03 or more, and even more preferably 0.05 or more. z is preferably 2.8 or less, more preferably 2.6 or less, and even more preferably 2.4 or less.

The above upper and lower limits can be combined in any desired manner.
The above composition formula (I) preferably satisfies 0≦z≦2.8, more preferably satisfies 0.02≦z≦2.8, further preferably satisfies 0.03≦z≦2.6, and particularly preferably satisfies 0.05≦z≦2.4.

(α)
The value of α is preferably −0.45 or more, more preferably −0.40 or more, and even more preferably −0.35 or more. The value of α is preferably 1.8 or less, more preferably 1.6 or less, and even more preferably 1.4 or less. The upper and lower limits can be combined in any combination.

The above composition formula (I) or the above composition formula (I)-1 preferably satisfies -0.45≦α≦1.8, more preferably satisfies -0.40≦α≦1.6, and even more preferably satisfies -0.35≦α≦1.4.

In this embodiment, it is preferable that the composition formula (I) or the composition formula (I)-1 satisfies 0≦x≦0.1, 0.01≦y≦0.40, 0<x+y<0.6, 0≦z≦2.8, and -0.45≦α≦1.8.

From the viewpoint of reducing the charge transfer resistance, M is preferably one or more elements selected from the group consisting of Mn, Ti, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si, and more preferably one or more elements selected from the group consisting of Mn, Ti, Al, Zr, Nb, W, and B.

[Composition Analysis]
The composition of MCC is measured by dissolving MCC in hydrochloric acid and then using an ICP emission spectrometer such as Optima 7300 (manufactured by PerkinElmer Co., Ltd.).

MCC is evaluated by manufacturing a CAM using MCC as a raw material and then measuring the charge transfer resistance of the lithium secondary battery. The CAM using the MCC of this embodiment as a raw material facilitates the insertion of lithium ions during charging and the desorption of lithium ions during discharging. Therefore, a lithium secondary battery using such a CAM has a small charge transfer resistance, is easy to charge and discharge, and has excellent rate characteristics.

[Method of evaluating MCC]
The MCC is evaluated after a lithium secondary battery is produced by the following method.

[1. Preparation of lithium secondary battery]
(CAM Creation)
MCC and lithium hydroxide monohydrate powder are weighed and mixed in such a ratio that the molar ratio of Li contained in the lithium hydroxide monohydrate powder to the total amount of metal elements contained in MCC is Li/(Ni+Co+M)=1.05 to obtain a mixture. The obtained mixture is fired at 650°C for 5 hours in an oxygen atmosphere, and then fired at 750°C for 5 hours in an oxygen atmosphere to obtain a fired product. The fired product is mixed with pure water at 5°C to prepare a 50% by mass slurry, and the obtained slurry is stirred for 20 minutes. Then, the mixture is dried at 210°C for 10 hours in a nitrogen atmosphere to obtain a CAM.

(Preparation of positive electrode for lithium secondary battery)
The obtained CAM, a conductive material (acetylene black), and a binder (PVdF) are added and kneaded in a ratio of CAM:conductive material:binder=92:5:3 (mass ratio) to prepare a paste-like positive electrode mixture. When preparing the positive electrode mixture, N-methyl-2-pyrrolidone is used as an organic solvent.

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 .

(Preparation of Lithium Secondary Battery)
The following operations are carried out in a glove box under an argon atmosphere.
The positive electrode for lithium secondary battery prepared in [Preparation of positive electrode for lithium secondary battery] is placed on the bottom cover of a part for coin type battery R2032 (for example, manufactured by Hosen Co., Ltd.) with the aluminum foil side facing down, and a separator (polyethylene porous film) is placed on top of it. 300 μL of electrolyte is poured here. The electrolyte is a mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 30:35:35, with LiPF ₆ dissolved in a ratio of 1.0 mol/L.

Next, metallic lithium is used as the negative electrode, and the negative electrode is placed on top of the separator, with a lid placed over the gasket and crimped with a crimping machine to create a lithium secondary battery (coin-type (R2032) half cell).

2. Method for measuring charge transfer resistance
The lithium secondary battery prepared by the above method is left to stand at room temperature for 12 hours to allow the separator and the positive electrode mixture layer to be sufficiently impregnated with the electrolyte. The lithium secondary battery is used to perform electrochemical impedance (EIS) measurement of the battery, and the charge transfer resistance of the CAM is calculated from the obtained results.

First, the lithium secondary battery is charged and discharged at a constant current and constant voltage at a test temperature of 25°C with a current setting of 0.1 CA for both charging and discharging. The maximum charging voltage is 4.3 V and the minimum discharging voltage is 2.5 V. Next, the lithium secondary battery that has completed discharging is charged again at a constant current and constant voltage with a current setting of 0.1 CA up to the maximum charging voltage, and the voltage after charging is set to 100% SOC.

EIS measurements are performed at a test temperature of 25° C. and an SOC of 100%. Under conditions of an applied voltage of 0 V and an amplitude voltage of 10 mV, measurements are performed from a response frequency of 0.01 Hz to 10 ⁶ Hz, and the charge transfer resistance (Ω) of the CAM is determined from the size of the arc that appears at a response frequency of several hundred Hz to several 10 ⁻¹ Hz in a Cole-Cole plot created from the obtained measurement data. The charge transfer resistance of the CAM is determined using the Instant Fit function of the analysis software ZView2 manufactured by Solartron.

<Method of producing MCC>
The method for producing MCC includes a slurry preparation step and a separation step in this order.

The slurry preparation process is a process in which a first aqueous solution containing a raw material element including Ni, a second aqueous solution containing at least the element M, and an alkaline aqueous solution are supplied to a reaction tank to obtain a slurry containing a reaction precipitate. The second aqueous solution containing a raw material element may contain Co.

The separation process involves dehydrating the slurry to separate the reaction precipitate, and then drying the resulting reaction precipitate.

In the following description, the aqueous solution containing the first raw material element is abbreviated as the "first aqueous solution" and the aqueous solution containing the second raw material element is abbreviated as the "second aqueous solution." In addition, "Co" and "element M" may be collectively referred to as "other elements" in the sense that they are different from Ni.

The first aqueous solution is an aqueous solution in which the Ni content relative to the total amount of metal elements contained in the first aqueous solution is 70 mass % or more.
The second aqueous solution is an aqueous solution in which the content of the other elements relative to the total amount of the metal elements contained in the second aqueous solution is 70 mass % or more.
The first aqueous solution and the second aqueous solution may contain the same element or different elements, so long as the above content is satisfied.

[Slurry preparation process]
In the slurry preparation step, the first aqueous solution, the second aqueous solution, and the alkaline aqueous solution are each supplied into a reaction tank from different supply ports. As a result, nuclei originating from other elements contained in the second aqueous solution are generated in the reaction tank, and nickel ions contained in the first aqueous solution react with each other to generate a reaction precipitate. The generated reaction precipitate is a coprecipitate of Ni and other elements. As a result, in this step, a slurry containing a coprecipitate, which is a reaction precipitate, is obtained.

In this process, the ratio (S2/S1) of the supply amount S1 (unit: L/min) of the second aqueous solution supplied to the reaction tank to the supply amount S2 (unit: L/min) of the alkaline aqueous solution supplied to the reaction tank is set to 3.0-12.0.

S2/S1 is preferably 3.5 or more, and more preferably 4.0 or more. S2/S1 is preferably 11.0 or less, more preferably 10.0 or less, and even more preferably 9.8 or less. The above upper and lower limit values can be combined in any manner. Examples of S2/S1 include 3.5-11.0, 4.0-10.0, or 4.0-9.8.

By controlling S2/S1 within the above range, the distribution of the other elements and the alkaline aqueous solution in the reaction tank can be kept constant. This makes it easier for the nucleation of coprecipitates originating from the other elements contained in the second aqueous solution, the rate of crystal growth, and the orientation of crystal growth to become constant, resulting in an MCC that satisfies the above formula (A) or (B), and preferably satisfies the above formula (C).

The second aqueous solution may be supplied to the reaction tank from a plurality of supply ports. When the second aqueous solution is supplied from a plurality of supply ports, the total amount of the second aqueous solution at each supply port corresponds to the above S1. When a plurality of types of second aqueous solutions are used, the total amount of each second aqueous solution supplied corresponds to the above S1.
Similarly, the alkaline aqueous solution may be supplied to the reaction tank from a plurality of supply ports. When the alkaline aqueous solution is supplied from a plurality of supply ports, the total amount of the alkaline aqueous solution at each supply port corresponds to S2 above.

In the slurry preparation process, the solution temperature in the reaction tank is controlled within the range of, for example, 20-80°C, preferably 30-75°C.

In the slurry preparation step, the pH value of the slurry in the reaction vessel is preferably controlled within the range of, for example, 10 to 12.5. When the pH value is within the above range, MCC having a BET specific surface area and _D50 within the range of this embodiment can be obtained.

In this specification, the pH value is defined as the value measured when the temperature of the slurry is 40°C. Therefore, after sampling the slurry from the reaction tank, the slurry is heated or cooled as necessary, and the pH of the slurry is measured when it reaches 40°C.

In this process, in addition to the first aqueous solution, the second aqueous solution, and the alkaline aqueous solution, a complexing agent may be added to the reaction tank. The complexing agent used is a compound capable of forming a complex with nickel ions, cobalt ions, and ions of element M in an aqueous solution. Examples of the complexing agent include ammonium ion donors (ammonium hydroxide, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc.), hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracil diacetic acid, and glycine.

[Separation process]
After the above-mentioned slurry preparation process, the slurry is dehydrated to separate the coprecipitate, and the coprecipitate obtained is dried to obtain MCC. Examples of the method for dehydrating the slurry include centrifugation and suction filtration.

The obtained coprecipitate may be washed appropriately before drying. The coprecipitate is preferably washed with water. If impurities from the first aqueous solution or the second aqueous solution remain when the coprecipitate is simply washed with water, the coprecipitate may be washed with a weak acid water or an alkaline solution containing sodium hydroxide or potassium hydroxide, as necessary.

Below, as a more specific example, a manufacturing process for MCC containing Ni, Mn, and Al will be described. First, in a slurry preparation process, a slurry containing a metal composite hydroxide containing Ni, Mn, and Al is prepared. A metal composite hydroxide having a layered structure can be manufactured by a batch co-precipitation method or a continuous co-precipitation method.

When producing metal composite hydroxides by the continuous coprecipitation method, an example of a reaction vessel that can be used is an overflow type reaction vessel that separates the reaction precipitate that is formed.

When producing metal complex hydroxides by batch coprecipitation, examples of usable reaction tanks include reaction tanks without an overflow pipe, and devices equipped with a concentration tank connected to an overflow pipe and a mechanism for concentrating the overflowed reaction precipitate in the concentration tank and circulating it back to the reaction tank.

Specifically, a metal composite hydroxide represented by Ni _{(1-y) MnzAlw} (OH)2 (where z+w=y) is produced _by reacting an aqueous nickel salt solution, an aqueous manganese salt solution, an aqueous aluminum salt solution and a complexing agent using the continuous coprecipitation method described in _JP -A-2002-201028.

When producing a metal composite hydroxide, the nickel salt aqueous solution corresponds to the above-mentioned first aqueous solution, and the manganese salt aqueous solution and the aluminum salt aqueous solution correspond to the above-mentioned second aqueous solution. The first and second aqueous solutions may also be prepared by mixing the respective aqueous solutions. For example, the nickel salt aqueous solution, the manganese salt aqueous solution and the aluminum salt aqueous solution may be mixed to prepare the first aqueous solution, and the aluminum salt aqueous solution may be used as the second aqueous solution.

As the nickel salt that is the solute of the nickel salt aqueous solution, for example, at least one of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate can be used.

As the manganese salt, which is the solute of the manganese salt aqueous solution, for example, at least one of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate can be used.

The aluminum salt that is the solute of the aluminum salt aqueous solution can be, for example, aluminum sulfate or sodium aluminate.

The above metal salts are used in _a ratio corresponding to the composition ratio of the above Ni _{(1-y) MnzAlw} (OH) ₂ . That is, the amount of each metal salt is specified so that the molar ratio of Ni, Mn, and Al in the mixed solution containing the above metal salts is (1-y):z:w. Water is used as the solvent.

In the manufacturing process of the metal composite hydroxide, a complexing agent may or may not be used. When a complexing agent is used, the amount of the complexing agent contained in the mixed solution containing the nickel salt aqueous solution, the manganese salt aqueous solution, the aluminum salt aqueous solution, and the complexing agent is, for example, a molar ratio of the amount of the complexing agent to the total number of moles of the metal salts (nickel salt, manganese salt, and aluminum salt) that is greater than 0 and less than or equal to 2.0.

In the coprecipitation method, an alkaline aqueous solution is added in addition to the nickel salt aqueous solution, manganese salt aqueous solution, aluminum salt aqueous solution, and complexing agent. The alkaline aqueous solution is, for example, a sodium hydroxide aqueous solution.

When the nickel salt aqueous solution, manganese salt aqueous solution, and aluminum salt aqueous solution, as well as any complexing agent and alkaline aqueous solution, are continuously supplied to the reaction tank, Ni, Mn, and Al react to obtain a slurry in which Ni _{(1-y) MnzAlw} (OH) ₂ is generated. In this case, by setting the S2/S1 ratio within _the above-mentioned range, MCC satisfying the above formula (A) or (B) can be obtained.

Then, in the separation process, the coprecipitate is separated from the slurry and dried.

As a result of the above, MCC, which is a metal composite hydroxide, is obtained.
After drying, a sieving treatment may be carried out to adjust the _D50 of the metal composite hydroxide.

When MCC is a metal composite oxide, the metal composite oxide can be produced by heat treating the metal composite hydroxide in an oxygen-containing atmosphere.

In the heat treatment, the maximum holding temperature is preferably 350-800°C, and more preferably 400-700°C. The maximum holding temperature in the heat treatment means the highest holding temperature in the heat treatment. When the heat treatment is performed multiple times, the maximum holding temperature means the highest temperature among each heat treatment.

The heating time refers to the total time from the start of the temperature rise until the end of temperature maintenance after the maximum holding temperature is reached. The heating time is preferably 1 to 30 hours.

<Method of manufacturing positive electrode active material for lithium secondary battery>
The above-mentioned MCC can be used as a raw material to manufacture CAM.

The method for producing CAM includes a mixing step of mixing MCC with a lithium compound, and a firing step of firing the resulting mixture at a temperature of 500-1000°C in an oxygen-containing atmosphere. The method for producing CAM may also include a cleaning step of cleaning the resulting fired product after the firing step.

[Mixing process]
The MCC and the lithium compound are mixed.
As the lithium compound, one or more compounds selected from the group consisting of lithium carbonate, lithium hydroxide, and lithium hydroxide monohydrate can be used.

The lithium compound and MCC are mixed taking into account the composition ratio of the final product to obtain a mixture of the lithium compound and MCC.

[Firing process]
The resulting mixture is fired in an oxygen-containing atmosphere at a firing temperature of 500-1000° C. By firing the mixture, CAM crystals grow.

The firing temperature in this specification means the temperature of the atmosphere in the firing furnace, and refers to the maximum temperature that can be maintained (maximum maintenance temperature).
When the firing process has a plurality of firing stages, the firing temperature means the temperature of the stage in which firing is performed at the highest holding temperature among the firing stages.

The firing temperature is preferably 550-980°C, more preferably 600-960°C.

The time for which the firing temperature is maintained may be, for example, 0.1 to 20 hours, with 0.5 to 10 hours being preferred.

It is also preferable to perform the firing in an oxygen-containing atmosphere. Specifically, it is preferable to introduce oxygen gas and create an oxygen-containing atmosphere inside the firing furnace.

The heating rate is calculated from the time from when heating starts in the kiln until the maximum holding temperature is reached, and the temperature difference from the temperature when heating starts in the kiln to the maximum holding temperature.

For firing, a firing furnace such as a static firing furnace or a fluidized bed firing furnace is used. A static firing furnace is, for example, a tunnel furnace or a roller hearth kiln. A fluidized bed firing furnace is, for example, a rotary kiln.

[Cleaning process]
In this embodiment, the fired product may be washed with a washing liquid such as pure water or an alkaline washing liquid. After washing, the fired product may be appropriately dried.

The fired product is then appropriately washed, crushed and sieved to obtain CAM.

By using an MCC with the above configuration, it is possible to manufacture a CAM with low charge transfer resistance.

Furthermore, according to the above-mentioned CAM manufacturing method, by using the above-mentioned MCC as a raw material, it is possible to suitably manufacture a CAM with low charge transfer resistance.

<Lithium secondary battery>
A positive electrode for a lithium secondary battery suitable for use with the CAM obtained by the above-mentioned manufacturing method will be described. Hereinafter, the positive electrode for a lithium secondary battery may be referred to as a positive electrode.
Furthermore, a lithium secondary battery suitable for use as a positive electrode will be described.

An example of a suitable lithium secondary battery for use with CAM has a positive electrode, a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and an electrolyte placed between the positive electrode and the negative electrode.

FIG. 1 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 the partially enlarged view of FIG. 1, 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 stacked in the order of separator 1, positive electrode 2, separator 1, negative electrode 3, and then wound to form an electrode group 4.

As an example, the positive electrode 2 has a positive electrode active material layer 2a containing CAM and a positive electrode current collector 2b on one side of which the positive electrode active material layer 2a is formed. Such a positive electrode 2 can be manufactured by first preparing a positive electrode mixture containing CAM, a conductive material, and a binder, and then supporting the positive electrode mixture on one side of the positive electrode current collector 2b to form the positive electrode active material layer 2a.

The negative electrode 3 can be, for example, an electrode in which a negative electrode mixture containing a negative electrode active material (not shown) is supported on a negative electrode current collector, or an electrode made of a negative electrode active material alone, and can be manufactured in the same manner as the positive electrode 2.

Then, the electrode group 4 and an insulator (not shown) are placed in the battery can 5, the bottom of the can is sealed, the electrode group 4 is impregnated with an electrolyte solution 6, and the electrolyte is disposed between the positive electrode 2 and the negative electrode 3. Furthermore, the top of the battery can 5 is sealed with a top insulator 7 and a sealing body 8, thereby manufacturing a lithium secondary battery 10.

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

The shape of a lithium secondary battery having such an electrode group 4 can be any shape specified by IEC 60086, a standard for batteries established by the International Electrotechnical Commission (IEC), or JIS C 8500. Examples of shapes include a cylindrical shape or a rectangular shape.

Furthermore, the lithium secondary battery is not limited to the above-mentioned wound type configuration, but may be a laminated type configuration in which a laminated 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.

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

<All-solid-state lithium secondary battery>
The CAM obtained by the manufacturing method of this embodiment can be used as a CAM for an all-solid-state lithium secondary battery.

FIG. 2 is a schematic diagram showing an example of an all-solid-state lithium secondary battery. The all-solid-state lithium secondary battery 1000 shown in FIG. 2 has a laminate 100 having a positive electrode 110, a negative electrode 120, and a solid electrolyte layer 130, and an exterior body 200 that houses the laminate 100. The all-solid-state lithium secondary battery 1000 may also have a bipolar structure in which a CAM and a negative electrode active material are disposed on both sides of a current collector. A specific example of a bipolar structure is the structure 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 includes the above-mentioned CAM and solid electrolyte. The positive electrode active material layer 111 may also include 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. The negative electrode active material layer 121 may also 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, the all-solid-state lithium secondary battery 1000 may have a separator between the positive electrode 110 and the negative electrode 120.

The all-solid-state lithium secondary battery 1000 further includes an insulator (not shown) that insulates the laminate 100 from the exterior body 200, and a sealing body (not shown) that seals the opening 200a of the exterior body 200.

The exterior body 200 may be a container molded from a highly corrosion-resistant metal material such as aluminum, stainless steel, or nickel-plated steel. Alternatively, the exterior body 200 may be a container made of a laminate film processed into a bag shape with corrosion resistance applied to at least one side.

The shape of the all-solid-state lithium secondary battery 1000 can be, for example, a coin type, a button type, a paper type (or a sheet type), a cylindrical type, a square type, or a laminate type (pouch type).

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

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

The above describes preferred embodiments of the present invention, but the present invention is not limited to these examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

The present invention may further include the following aspects:

[21] An MCC containing at least Ni and the element M, wherein the L _A /L _av is 1.4-2.3.
[22] The MCC according to [21], wherein the L _A is 100-250 Å.
[23] An MCC containing at least Ni and the element M, wherein the L _B /L _av is 1.4 to 2.8.
[24] The MCC according to [23], wherein the L _B /L _av is 1.6 to 2.8.
[25] The MCC according to [23] or [24], wherein the L _B is 150-300 Å.
[26] The MCC according to any one of [21] to [25], wherein the L _C /L _av is 1.2 to 2.3.
[27] The MCC according to any one of [21] to [26], wherein the L _C /L _av is 1.3 to 2.3.
[28] The MCC according to [26] or [27], wherein the L _C is 100-350 Å.
[29] The MCC according to any one of [26] to [28], wherein the L _C is 150-300 Å.
[29] The MCC according to any one of [21] to [28], represented by the composition formula (I).
[30] The MCC according to [29], wherein the composition formula (I) satisfies 0≦x≦0.1 and 0<x+y<0.6.
[31] An MCC containing at least Ni and the element M1 and satisfying the formula (A).
[32] An MCC containing at least Ni and the element M1 and satisfying formula (B).
[33] The MCC according to any one of [21] to [32], wherein the BET specific surface area is 14.0 to 30.0 m ² /g.
[34] The MCC according to any one of [21] to [33], wherein the _D50 is greater than 13 μm and less than or equal to 18 μm.
[35] A method for producing CAM, comprising: a mixing step of mixing the MCC according to any one of [21] to [34] with a lithium compound; and a firing step of firing the resulting mixture at a temperature of 500-1000° C. in an oxygen-containing atmosphere.
[36] The MCC according to any one of [21] to [34], which is a hexagonal compound having a layered structure and is a metal composite oxide or a metal composite hydroxide.
[37] An MCC which is a hexagonal compound having a layered structure, and is a metal composite oxide or metal composite hydroxide, and contains at least Ni and the element M1, and in which the L _A /L _av is 1.2-2.5 and the L _C /L _av is 1.2-2.3.

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

[Powder X-ray diffraction measurement]
The _LA , _LB , _LC , and _Lav of the metal composite hydroxide obtained below were calculated by the above-mentioned [Method of calculating _LA , _LB , _LC , and _Lav ].

[BET specific surface area]
The BET specific surface area of the metal composite hydroxide obtained below was measured by the above-mentioned [Method for measuring BET specific surface area].

[Cumulative particle size distribution]
The _D50 of the metal composite hydroxide obtained below was measured by the above-mentioned method of [Method of measuring _D50 ].

[Composition Analysis]
The composition of the metal composite hydroxide produced by the method described below was analyzed by the method described above in [Composition Analysis].

[MCC Evaluation]
The metal composite hydroxide obtained as described below was heat-treated at 650° C. for 5 hours in an air atmosphere to obtain a metal composite oxide MCC. A lithium secondary battery was produced using the obtained MCC according to the above-mentioned [Method of Evaluating MCC], and the charge transfer resistance was measured and evaluated. When the charge transfer resistance was 70Ω or less, the charge transfer resistance was evaluated as low.

Example 1
(Slurry preparation process)
First, water was placed in a reaction vessel equipped with a stirrer and an overflow pipe, and then an aqueous sodium hydroxide solution was supplied thereto while maintaining the liquid temperature at 70°C.

A first aqueous solution 1 was prepared by mixing an aqueous nickel sulfate solution, an aqueous manganese sulfate solution, and an aqueous aluminum sulfate solution. At this time, the first aqueous solution 1 was adjusted so that the Ni content was 97.5 mass%, the Mn content was 2.0 mass%, and the Al content was 0.5 mass% relative to the total amount of metal elements contained in the first aqueous solution 1.

An aluminum sulfate aqueous solution was prepared as the second aqueous solution 1.

Next, the first aqueous solution 1 and the second aqueous solution 1 were continuously added to the reaction tank from different supply ports under stirring in such a ratio that the molar ratio of Ni, Mn, and Al in the reaction tank was 93.0:3.5:3.5. At the same time, an aqueous ammonium sulfate solution was added dropwise as a complexing agent, and an aqueous sodium hydroxide solution was added dropwise as an alkaline aqueous solution. At this time, the supply amount of the aqueous sodium hydroxide solution was adjusted so that the ratio S2/S1 of the supply amount S1 of the second aqueous solution 1 to the supply amount S2 of the aqueous sodium hydroxide solution was 6.4, and a slurry was obtained. The pH of the slurry in the reaction tank was 11.40.

(Separation process)
The obtained slurry was dehydrated using a centrifuge, washed, isolated, and dried at 105° C. to obtain metal composite hydroxide 1.

Example 2
A nickel sulfate aqueous solution and a manganese sulfate aqueous solution were mixed to prepare a first aqueous solution 2. At this time, the first aqueous solution 2 was adjusted so that the Ni content was 98.9 mass % and the Mn content was 1.1 mass % with respect to the total amount of metal elements contained in the first aqueous solution 2.

The first aqueous solution 2 and the second aqueous solution 1 were continuously added from different supply ports in such a ratio that the atomic ratio of Ni, Mn, and Al in the reaction tank was 93.0:1.0:6.0, the amount of sodium hydroxide aqueous solution supplied was adjusted to make the ratio S2/S1 8.3, and the pH of the slurry in the reaction tank was 10.96. Except for this, metal composite hydroxide 2 was obtained in the same manner as in Example 1.

Example 3
A nickel sulfate aqueous solution and a manganese sulfate aqueous solution were mixed to prepare a first aqueous solution 3. At this time, the first aqueous solution 3 was adjusted so that the Ni content was 93.6 mass % and the Mn content was 6.4 mass % with respect to the total amount of metal elements contained in the first aqueous solution 3.

The first aqueous solution 3 and the second aqueous solution 1 were continuously added from different supply ports in such a ratio that the atomic ratio of Ni, Mn, and Al in the reaction tank was 88.0:6.0:6.0, the amount of sodium hydroxide aqueous solution supplied was adjusted to make the ratio S2/S1 4.4, and the pH of the slurry in the reaction tank was 10.85. Except for this, metal composite hydroxide 3 was obtained in the same manner as in Example 1.

Example 4
A nickel sulfate aqueous solution and a manganese sulfate aqueous solution were mixed to prepare a first aqueous solution 4. At this time, the first aqueous solution 4 was adjusted so that the Ni content was 98.9 mass % and the Mn content was 1.1 mass % with respect to the total amount of metal elements contained in the first aqueous solution 4.

The first aqueous solution 4 and the second aqueous solution 1 were continuously added from different supply ports in such a ratio that the atomic ratio of Ni, Mn, and Al in the reaction tank was 93.0:1.0:6.0, the amount of sodium hydroxide aqueous solution supplied was adjusted to make the ratio S2/S1 6.4, and the pH of the slurry in the reaction tank was 11.04. Except for this, metal composite hydroxide 4 was obtained in the same manner as in Example 1.

Example 5
Metal composite hydroxide 5 was obtained in the same manner as in Example 1, except that the first aqueous solution 2 and the second aqueous solution 1 were continuously added from different supply ports in such a ratio that the atomic ratio of Ni, Mn, and Al in the reaction tank was 93.0:3.5:3.5, the supply amount of the sodium hydroxide aqueous solution was adjusted to make the ratio S2/S1 5.3, and the pH of the slurry in the reaction tank was 11.12.

<Comparative Example 1>
A nickel sulfate aqueous solution and a manganese sulfate aqueous solution were mixed to prepare a first aqueous solution 5. At this time, the first aqueous solution 5 was adjusted so that the Ni content was 98.9 mass % and the Mn content was 1.1 mass % with respect to the total amount of metal elements contained in the first aqueous solution 5.

The first aqueous solution 5 and the second aqueous solution 1 were continuously added from different supply ports in such a ratio that the atomic ratio of Ni, Mn, and Al in the reaction tank was 93.0:3.5:3.5, the amount of sodium hydroxide aqueous solution supplied was adjusted to make the ratio S2/S1 12.7, and the pH of the slurry in the reaction tank was 12.20. Except for this, a metal composite hydroxide 6 was obtained in the same manner as in Example 1.

The compositions, physical properties, and charge transfer resistance of the obtained metal composite hydroxides 1 to 6 are shown in Table 1. In the table, x and y indicate the values of x and y when the metal composite hydroxide is expressed by the following composition formula (I). The obtained metal composite hydroxides 1 to 6 were all hexagonal crystal compounds having a layered structure.
Ni _(1-x-y) Co _x M _y O _z (OH) _2-α ... (I)

As a result of the evaluation, the metal composite hydroxides of Examples 1 to 5, which satisfy the above formula (A) or (B), had low charge transfer resistance in lithium secondary batteries using CAM made from them as the positive electrode.

In contrast, it was found that the metal composite hydroxide of Comparative Example 1, which does not satisfy the above formula (A) or (B), had a higher charge transfer resistance in a lithium secondary battery than Examples 1 to 5. In Comparative Example 1, the ratio S2/S1 exceeds 12.0. Therefore, it is considered that the nucleation of the coprecipitate originating from the other elements contained in the second aqueous solution, the rate of crystal growth, and the orientation of crystal growth are difficult to be constant, and the obtained MCC did not satisfy the above formula (A) or (B).

Furthermore, from the results of the above Examples and Comparative Examples, it was confirmed that, for the same composition, the larger the L _A /L _av , the lower the charge transfer resistance.

1...separator, 2...positive electrode, 2a...positive electrode active material layer, 2b...positive electrode current collector, 3...negative electrode, 4...electrode group, 5...battery can, 6...electrolyte, 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, 123...external terminal, 130...solid electrolyte layer, 200...exterior body, 200a...opening, 1000...all-solid-state lithium secondary battery

Claims (8)

Contains at least Ni and an element M;
The element M is one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si;
A metal composite compound powder that satisfies the following formula (A):
L _A / L _av ≧1.2 ... (A)
(In formula (A), L _A represents a crystallite diameter calculated from a diffraction peak present within a range of 2θ=38.5±1° in powder X-ray diffraction measurement using CuKα radiation.
L _av represents the average crystallite size calculated by Rietveld analysis of the powder X-ray diffraction pattern in the range of 2θ=10°-90° obtained by the powder X-ray diffraction measurement.) Contains at least Ni and an element M;
The element M is one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si;
A metal complex compound powder that satisfies the following formula (B):
_L / L _av ≦3.2 ... (B)
(In formula (B), L _B represents a crystallite diameter calculated from a diffraction peak present within a range of 2θ=33.0±1° in powder X-ray diffraction measurement using CuKα radiation.
L _av represents the average crystallite size calculated by Rietveld analysis of the powder X-ray diffraction pattern in the range of 2θ=10°-90° obtained by the powder X-ray diffraction measurement.) The metal complex compound powder according to claim 1 or 2, which satisfies the following formula (C):
_L / L _≥ 1.2 ... (C)
(In formula (C), L _C represents a crystallite size calculated from a diffraction peak present within the range of 2θ=19.1±1° in the powder X-ray diffraction measurement.) 3. The metal complex compound powder according to claim 1, which is represented by the following composition formula (I):
Ni _(1-x-y) Co _x M _y O _z (OH) _2-α ... (I)
(The composition formula (I) satisfies 0≦x≦0.5, 0<y≦0.5, 0<x+y<1, 0≦z≦3, −0.5≦α≦2, and α-z<2, and M is one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.) The metal composite compound powder according to claim 4, wherein the composition formula (I) satisfies 0≦x≦0.1 and 0<x+y<0.6. The metal complex compound powder according to claim 1 or 2, having a BET specific surface area of more than 10.0 m ² /g. The metal complex compound powder according to claim 1 or 2, wherein _D50 , which is a 50% cumulative volume particle size, is 8 μm or more and 20 μm or less. A mixing step of mixing the metal composite compound powder according to claim 1 or 2 with a lithium compound;
and calcining the resulting mixture in an oxygen-containing atmosphere at a temperature of 500° C. or higher and 1000° C. or lower.

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