JP2023085143A - Lithium metal composite oxide, positive electrode active material for lithium secondary battery, positive electrode for lithium secondary battery and lithium secondary battery - Google Patents

Abstract

To provide a lithium metal composite oxide, a positive electrode active material for lithium secondary batteries, and a positive electrode for lithium secondary batteries, which can increase the initial charge-discharge efficiency of lithium secondary batteries.SOLUTION: A lithium metal composite oxide having a layered structure contains at least Ni, Li and an element X. The element X is one or more elements selected from the group consisting of Co, Mn, Al, Fe, Cu, Ti, Mg, W, Mo, Nb, Zn, Sn, Zr, Ga, V, B, Si, S and P. The lithium metal composite oxide satisfies (1) and (2) as follows: L/M≤0.03 (1) and A/B≤2.0 (2).SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a lithium metal composite oxide, a positive electrode active material for lithium secondary batteries, a positive electrode for lithium secondary batteries, and a lithium secondary battery.

A positive electrode active material for a lithium secondary battery is used for a positive electrode that constitutes a lithium secondary battery. A positive electrode active material for a lithium secondary battery contains a lithium metal composite oxide.

One of the battery characteristics of lithium secondary batteries is initial charge/discharge efficiency. When the initial charge/discharge efficiency is high, Li ions inserted during charging can be sufficiently used for discharging, resulting in a battery with high energy density. One of the reasons for lowering the initial charge/discharge efficiency is that Li ions are not used during discharge, that is, the movement of Li ions is inhibited.

For example, Patent Literature 1 describes a positive electrode active material that does not leave foreign substances or unreacted substances and has an appropriate composition. Specifically, Patent Document 1 focuses on the electronic environment around Li atoms in the positive electrode active material and discloses a positive electrode active material in which a singlet peak appears in the NMR spectrum obtained by ⁷ Li NMR measurement. It is disclosed that such a positive electrode active material is less likely to inhibit the movement of Li ions, so that the performance of the lithium secondary battery is less likely to deteriorate.

JP-A-2016-42462

As the application fields of lithium secondary batteries advance, there is a demand for provision of lithium secondary batteries with high energy density.
The present invention has been made in view of the above circumstances, and provides a lithium metal composite oxide, a positive electrode active material for lithium secondary batteries, and a positive electrode for lithium secondary batteries that can increase the initial charge and discharge efficiency of lithium secondary batteries. intended to A further object is to provide a lithium secondary battery using these.

One aspect of the present invention includes [1] to [9].
[1] A lithium metal composite oxide having a layered structure, containing at least Ni, Li and an element X, wherein the element X is Co, Mn, Al, Fe, Cu, Ti, Mg, W, Mo, A lithium metal composite oxide which is at least one element selected from the group consisting of Nb, Zn, Sn, Zr, Ga, V, B, Si, S and P and satisfies the following (1) and (2) .
0.0070≦L/M≦0.03 (1)
A/B≦2.5 (2)
(L is calculated from the signal having the maximum intensity among the peaks appearing in the range of -50 ppm to 50 ppm in the solid-state nuclear magnetic resonance spectrum of ⁷ Li of the lithium metal composite oxide obtained by nuclear magnetic resonance measurement. is the abundance (mol) of Li determined from the product of the abundance (% by mass) of Li and the amount (mol) of Li in the lithium metal composite oxide measured by ICP emission spectroscopy, and M is It is the total amount (mol) of metal elements other than Li in the lithium metal composite oxide measured by ICP emission spectroscopy.
A is the Li content ratio (% by mass) determined from the amount of one or both of LiOH and Li ₂ CO ₃ calculated by the neutralization titration method with respect to the total amount of the lithium metal composite oxide, and B is , with respect to the total amount of the lithium metal composite oxide, in the solid-state nuclear magnetic resonance spectrum of ⁷ Li of the lithium metal composite oxide obtained by nuclear magnetic resonance measurement, among the peaks appearing in the range of -50 ppm to 50 ppm, the maximum intensity is the abundance ratio (% by mass) of Li calculated from the signal having the peak of )
[2] The lithium metal composite oxide according to [1], wherein B is 0.2% by mass or less.
[3] The lithium metal composite oxide according to [1] or [2], wherein A is 0.4% by mass or less.
[4] The lithium metal composite oxide according to any one of [1] to [3], which satisfies the following compositional formula (I).
Li[Li _a (Ni _(1-yw) Al _w X1 _y ) _1-a ]O ₂ (I)
(In formula (I), X1 is selected from the group consisting of Mn, Co, Fe, Cu, Ti, Mg, W, Mo, Nb, Zn, Sn, Zr, Ga, V, B, Si, S and P and satisfies -0.1 ≤ a ≤ 0.2, 0 ≤ y ≤ 0.5, 0 < w ≤ 0.5, 0 < y + w ≤ 0.7.)
[5] The lithium metal composite oxide according to any one of [1] to [4], which has a BET specific surface area of 0.2 m ² /g or more.
[6] The lithium metal composite oxide according to any one of [1] to [5], which has a 50% cumulative volume particle size (D ₅₀ ) of 1 μm or more determined by particle size distribution measurement.
[7] A positive electrode active material for lithium secondary batteries, comprising the lithium metal composite oxide according to any one of [1] to [6].
[8] A positive electrode for a lithium secondary battery containing the positive electrode active material for a lithium secondary battery according to [7].
[9] A lithium secondary battery comprising the positive electrode for a lithium secondary battery according to [8].

According to the present invention, it is possible to provide a lithium metal composite oxide, a positive electrode active material for a lithium secondary battery, and a positive electrode for a lithium secondary battery that can increase the initial charge/discharge efficiency of a lithium secondary battery. Furthermore, a lithium secondary battery using these can be provided.

1 is a schematic diagram showing an example of a lithium secondary battery; FIG. 1 is a schematic diagram showing an example of an all-solid lithium secondary battery; FIG. 2 is a solid-state nuclear magnetic resonance spectrum of ⁷ Li of Example 2. FIG.

<Lithium metal composite oxide>
This embodiment is a lithium metal composite oxide having a layered structure.
Lithium metal composite oxide is hereinafter referred to as "LiMO".
LiMO contains at least Ni, Li and the element X. Element X is one selected from the group consisting of Co, Mn, Al, Fe, Cu, Ti, Mg, W, Mo, Nb, Zn, Sn, Zr, Ga, V, B, Si, S and P These are the above elements.
"Ni" refers to nickel atoms rather than nickel metal. “Co” and “Li” and the like similarly refer to cobalt atoms and lithium atoms and the like, respectively.

Li contained in LiMO has the following three types (α) to (γ).
(α) Li that can effectively contribute to charging and discharging during operation of the lithium secondary battery.
(β) Li that cannot contribute to charging and discharging during operation of the lithium secondary battery but does not hinder the movement of Li ions.
(γ) Li that cannot contribute to charging and discharging during the operation of the lithium secondary battery and hinders the movement of Li ions.

The more (α) and the less (β) and (γ), the better the battery that can be efficiently charged and discharged.
The present inventors considered that the Li (β) and (γ) are the cause of the decrease in the initial charge/discharge efficiency, and conceived of reducing the Li (β) and (γ). The present invention focuses on the magnetic environment that Li receives from surrounding metals, and relates to the idea of stipulating the amount of Li.

LiMO satisfies the following (1) and (2).
0.0070≦L/M≦0.03 (1)
A/B≦2.5 (2)

[Nuclear magnetic resonance measurement]
L and B are obtained by nuclear magnetic resonance measurement of LiMO.
In this embodiment, the nuclear magnetic resonance measurements are solid-state nuclear magnetic resonance measurements of ⁷ Li. Solid-state nuclear magnetic resonance measurements of ⁷ Li are hereinafter referred to as “ ⁷ Li-NMR”.

A solid-state nuclear magnetic resonance spectrum of ⁷ Li obtained by ⁷ Li-NMR is shown in FIG. 3 is a solid-state nuclear magnetic resonance spectrum of ⁷ Li of Example 2. FIG. In the solid-state nuclear magnetic resonance spectrum of ⁷ Li, a sharp Li peak appearing at −50 ppm to 50 ppm and a rather broad Li peak having a mass center in the range from 400 ppm to 1000 ppm are observed.
At this time, the sharp Li peak appearing in the range of −50 ppm to 50 ppm is the Li peak that is not magnetically affected by the paramagnetic metal.

Li, which constitutes a sharp Li peak near 0 ppm, is Li that is not magnetically affected by a paramagnetic metal, and oxides reacted with Li and element X, and residues of lithium compounds used as raw materials. to cause. That is, by analyzing sharp Li peaks appearing in the range of −50 ppm to 50 ppm, the amounts of Li in (β) and (γ) can be specified. A compound obtained by reacting Li with element X is referred to as Li—X oxide.

A Li—X oxide can be produced by firing at a high temperature when firing a mixture of a metal composite compound as a raw material and a lithium compound. The “high temperature” referred to here is, for example, 780° C. or higher. It can also be caused by firing a mixture containing excess lithium compounds.

Specifically, the Li—X oxide can be produced by alloying Li and the element X under high-temperature firing or in the presence of an excess lithium compound and phase-separating from the crystal structure of LiMO. The Li—X oxide can be unevenly distributed on the surface of LiMO as an oxide that does not belong to the crystal structure. Also, when LiMO contains secondary particles that are aggregates of primary particles, it may be unevenly distributed between the primary particles that make up the secondary particles. In this case, the unevenly distributed Li-X oxide does not hinder the movement of Li ions, but the Li contained in the Li-X oxide does not contribute much to charging and discharging compared to LiMO, which may lead to deterioration of battery performance. be.

Also, Li and the element X are consumed by the amount of the Li—X oxide formed. As a result, the composition of LiMO to be produced deviates from the charge ratio, making it difficult to obtain LiMO with the desired composition.

Li--X oxides are, for example, Li--Al oxides, Li--Zr oxides and Li--B oxides.

[ ⁷ Li-NMR measurement conditions]
Specifically, the measurement conditions of ⁷ Li-NMR are as follows.
When performing ⁷ Li-NMR, LiMO powder is packed in a measurement sample tube having an outer diameter of 4 mm and inserted into the apparatus. Using Bruker's AVANCE300 (the resonant frequency of ⁷ Li-NMR is 116.6 MHz) as a measurement device, under room temperature (actual measurement 24° C.), the rotation speed of magic angle spinning at 50 kHz, Hahn spin echo method. NMR is measured by

A 1 mol/L lithium chloride aqueous solution is used as a shift reference, and the shift position separately measured as an external standard is set to 0 ppm. In the measurement, the repetition waiting time between measurements is set to 0.5 seconds, and the number of times of integration is set to 2048 times.

The above method yields a solid-state nuclear magnetic resonance spectrum of ⁷ Li of LiMO. Waveform analysis is performed on the obtained spectrum to determine the peak with the maximum intensity among the peaks appearing in the range of -50 ppm to 50 ppm. The signal integral value of the determined peak, and the center of mass in the range of 400 ppm or more and 1000 ppm or less from the obtained spectrum, from the signal integral value of the peak obtained as a result of waveform separation of the slightly broad Li peak, the signal integral ratio Calculate Let the obtained signal integration ratio be Lw (% by mass). Lw (% by mass) is the ratio of Li not magnetically affected by the paramagnetic metal to the total Li in LiMO.
The signal integration ratio is (determined peak signal integration value)/(determined peak signal integration value+peak signal integration value obtained by waveform separation).

For the specific calculation method, the obtained solid ⁷ Li-NMR spectrum has a mass center in the range of 400 ppm or more and 1000 ppm or less. The waveform separation used separates into three peaks. The three peaks are peaks attributed to paramagnetic metal elements occupying all the 6 coordination sites near Li, 5 of the 6 coordination sites are paramagnetic metal elements, and the remaining 1 or Paramagnetic metal element is coordinated at 4 of the 6 coordination sites, and diamagnetic metal element is coordinated at the remaining 2 sites. It is a peak attributed to a thing. Since many spinning side bands are detected on the spectrum and the fitting results do not converge, waveform separation is performed after optimizing the signal width to 12 ppm for Li salts and 130 ppm for other components as constraint conditions.

The signal integral value is calculated from the peak area in the range surrounded by the peak curve from the peak start to the peak end of the peak and the baseline.
In this specification, the peak start is the rising point of the corresponding peak after peak separation, and the peak start means the point of contact between the corresponding peak and the baseline.
In this specification, the peak end is the point where the corresponding peak after peak separation ends. Peak end means the point of contact between the corresponding peak and the baseline.
In the present specification, the baseline means a line obtained by polynomial interpolation of the peak portion using data before and after the peak, which is clearly not the peak, in the solid-state nuclear magnetic resonance spectrum of LiMO ⁷ Li. .
Peak areas are automatically calculated using software.

[Measurement by ICP emission spectroscopy]
In this embodiment, "ICP emission spectroscopy" is described as "ICP".
ICP can measure the total amount of metal elements present in LiMO.

Analysis of LiMO by ICP is carried out by using an ICP emission spectrometer after dissolving LiMO powder in hydrochloric acid.

As the ICP emission spectrometer, for example, SPS3000 manufactured by SII Nanotechnology Co., Ltd. can be used.

(Calculation of L)
L (mol) is obtained by multiplying the total amount (mol) of Li elements contained in LiMO by the Lw (mass %) obtained above from the result of measurement by ICP. L means the amount of Li contained in LiMO that is not magnetically affected by the paramagnetic metal.

(Calculation of M)
M, which is the total amount (mol) of metal elements other than Li contained in LiMO, is determined from the results of the ICP measurement.

L and M obtained by the above method satisfy the following (1).
0.0070≦L/M≦0.03 (1)

(1) is preferably any one of the following (1)-1 to (1)-5.
0.0070≦L/M≦0.025 (1)-1
0.0070≦L/M≦0.020 (1)-2
0.0070≦L/M≦0.018 (1)-3
0.0070≦L/M≦0.016 (1)-4
0.0100≦L/M≦0.016 (1)-5

(Calculation of A)
A is calculated by the neutralization titration method.
Here, A is the Li content ratio (% by mass) determined from the amount of one or both of LiOH and Li ₂ CO ₃ calculated by the neutralization titration method with respect to the total amount of LiMO.

Either one or both of LiOH and Li ₂ CO ₃ are lithium compounds that remain unreacted when LiMO is produced. Hereinafter, either one or both of LiOH and Li ₂ CO ₃ will be referred to as the residual Li component. The residual Li component becomes resistance when the lithium secondary battery operates, and does not contribute to charging and discharging.

That is, by calculating A, the amount of (γ) can be specified.

[Neutralization titration method]
20 g of LiMO powder and 100 g of pure water are placed in a 100 ml beaker and stirred for 5 minutes. After stirring, the LiMO powder is filtered, 0.1 mol/L hydrochloric acid is added dropwise to 60 g of the remaining filtrate, and the pH of the filtrate is measured with a pH meter.
The titration amount of hydrochloric acid at pH = 8.3 ± 0.1 is Sml, and the titration amount of hydrochloric acid at pH = 4.5 ± 0.1 is Tml. Calculate lithium and lithium hydroxide concentrations.

In the formulas below, the molecular weights of lithium carbonate and lithium hydroxide are calculated by assuming that each atomic weight is H: 1.000, Li: 6.941, C: 12.000, and O: 16.000.

Lithium carbonate concentration (% by mass) =
{0.1 x (TS)/1000} x {73.882/(20 x 60/100)} x 100
Lithium hydroxide concentration (% by mass) =
{0.1×(2T−S)/1000}×{23.941/(20×60/100)}×100

(Calculation of B)
From the peaks appearing at -50 ppm or more and 50 ppm or less of the solid-state nuclear magnetic resonance spectrum of ⁷ Li of LiMO, the abundance ratio (% by mass) of Li that is not magnetically affected by the paramagnetic metal among Li contained in LiMO Calculate a certain Lw.

Lx, which is the abundance ratio (% by mass) of Li contained in LiMO, is determined from the results of the ICP measurement.

Let B be the product of Lw and Lx. B is calculated from the signal having the maximum intensity among the peaks appearing in the range of −50 ppm or more and 50 ppm or less in the solid-state nuclear magnetic resonance spectrum of ⁷ Li of LiMO obtained by nuclear magnetic resonance measurement for the total amount of LiMO. is the abundance ratio (% by mass) of Li.

A and B obtained by the above method satisfy the following (2).
A/B≦2.5 (2)

(2) is preferably any one of the following (2)-1 to (2)-10.
A/B≤2.1 (2)-1
A/B≤2.0 (2)-2
A/B≤1.9 (2)-3
A/B≤1.5 (2)-4
A/B≤1.0 (2)-5
0.1≦A/B≦2.1 (2)-6
0.2≦A/B≦2.0 (2)-7
0.3≦A/B≦1.9 (2)-8
0.3≦A/B≦1.5 (2)-9
0.3≦A/B≦1.0 (2)-10

LiMO that satisfies (1) and (2) means that the total amount of Li described in (β) and (γ) above is small, and the ratio of Li described in (γ) is small.
In this case, the aforementioned Li—X oxides and residual Li components are small, Li that can contribute to charge and discharge is present sufficiently, and LiMO with the desired composition is easily obtained. In addition, since the residual Li component is small and the resistance during operation of the lithium secondary battery is small, the initial charge/discharge efficiency is likely to be improved.

B preferably satisfies any one of the following (3)-1 to (3)-8.
B≦0.2% by mass (3)-1
B≦0.18% by mass (3)-2
B≦0.15% by mass (3)-3
B≦0.1% by mass (3)-4
0% by mass < B ≤ 0.2% by mass (3)-5
0 mass% ≤ B ≤ 0.18 mass% (3)-6
0 mass% ≤ B ≤ 0.15 mass% (3)-7
0% by mass ≤ B ≤ 0.1% by mass (3)-8

LiMO in which B satisfies the above range means that the abundance of (β) is smaller and that Li that can contribute to charge and discharge is present sufficiently.

A preferably satisfies any one of the following (4)-1 to (4)-8.
A ≤ 0.4% by mass (4)-1
A ≤ 0.2% by mass (4)-2
A ≤ 0.12% by mass (4)-3
A ≤ 0.08% by mass (4)-4
0% by mass ≤ A ≤ 0.4% by mass (4)-5
0% by mass ≤ A ≤ 0.4% by mass (4)-6
0% by mass ≤ A ≤ 0.12% by mass (4)-7
0% by mass ≤ A ≤ 0.08% by mass (4)-8

LiMO in which A satisfies the above range has a smaller amount of (γ), and the resistance during operation of the lithium secondary battery is small, so the initial charge/discharge efficiency is likely to be improved.

(compositional formula)
LiMO preferably satisfies the following formula (I).
Li[Li _a (Ni _(1-yw) Al _w X1 _y ) _1-a ]O ₂ (I)
(In formula (I), X1 is selected from the group consisting of Mn, Co, Fe, Cu, Ti, Mg, W, Mo, Nb, Zn, Sn, Zr, Ga, V, B, Si, S and P and satisfies -0.1 ≤ a ≤ 0.2, 0 ≤ y ≤ 0.5, 0 < w ≤ 0.5, 0 < y + w ≤ 0.7.)

In composition formula (I), a is preferably 0.001 or more, more preferably 0.0015 or more, and particularly preferably 0.002 or more, from the viewpoint of improving cycle characteristics. From the viewpoint of obtaining a lithium secondary battery with high initial efficiency, a is preferably 0.1 or less, more preferably 0.08 or less, and particularly preferably 0.06 or less.

The above upper limit and lower limit of a can be combined arbitrarily.
a preferably satisfies 0.001≦a≦0.1, and more preferably satisfies 0.002≦a≦0.06.

In the composition formula (I), from the viewpoint of obtaining a lithium secondary battery with high charge-discharge capacity, it is preferable to satisfy 0.01 < y + w < 0.6, and more preferably 0.01 < y + w ≤ 0.5. It is more preferable to satisfy 0<y+w≦0.25, and it is particularly preferable to satisfy 0.01<y+w≦0.2.

In composition formula (I), y is more preferably 0.05 or more, particularly preferably 0.08 or more, from the viewpoint of obtaining a lithium secondary battery with low battery internal resistance. From the viewpoint of obtaining a lithium secondary battery with high thermal stability, it is preferably 0.4 or less, particularly preferably 0.3 or less.
The upper limit and lower limit of y can be combined arbitrarily. Examples of combinations of y include 0.05≦y≦0.4 and 0.08≦y≦0.3.

In composition formula (I), w is more preferably 0.05 or more, particularly preferably 0.08 or more, from the viewpoint of improving cycle characteristics. Moreover, it is preferably 0.099 or less, more preferably 0.09 or less, and particularly preferably 0.095 or less.
The upper limit and lower limit of w can be combined arbitrarily.
w preferably satisfies 0.05≦w≦0.099.

The combination of a, y and w preferably satisfies 0.002≤a≤0.06, 0.08≤y≤0.3 and 0.05≤w≤0.099.

The composition analysis of LiMO can be performed by the method described in [Measurement by ICP emission spectroscopy] above.

(Layered structure)
The crystal structure of LiMO is a layered structure, and more preferably a hexagonal crystal structure or a monoclinic crystal structure.

The hexagonal crystal structure is: P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P61, P65, P62, P64, P63, P-6, P6/m, P63/m, P622, From P6122, P6522, P6222, P6422, P6322, P6mm, P6cc, P63cm, P63mc, P-6m2, P-6c2, P-62m, P-62c, P6/mmm, P6/mcc, P63/mcm and P63/mmc belong to any one space group selected from the group consisting of

The monoclinic crystal structure consists of P2, P21, C2, Pm, Pc, Cm, Cc, P2/m, P21/m, C2/m, P2/c, P21/c and C2/c. It belongs to any one space group selected from the group.

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

The crystal structure of LiMO can be calculated by powder X-ray diffraction measurement of LiMO using CuKα as a radiation source and measuring the diffraction angle 2θ within a range of 10° to 90°. Specifically, it can be confirmed by observation using a powder X-ray diffraction measurement device (for example, Ultima IV manufactured by Rigaku Corporation).

(BET specific surface area)
LiMO preferably has a BET specific surface area of 0.2 m ² /g or more. LiMO preferably has a BET specific surface area of 3.0 m ² /g or less. LiMO preferably has a BET specific surface area of 0.2 m ² /g or more and 3.0 m ² /g or less, more preferably 0.25 m ² /g or more and 2.5 m ² /g or less. It is particularly preferable to satisfy 30 m ² /g or more and 2.2 m ² /g or less.

The use of LiMO having a BET specific surface area equal to or higher than the above lower limit facilitates enhancing the output characteristics of the lithium secondary battery.
When LiMO having a BET specific surface area equal to or less than the above upper limit is used, the contact area between the LiMO and the electrolytic solution is less likely to increase, and gas due to the decomposition of the electrolytic solution is less likely to be generated.

[Measurement of BET specific surface area]
The BET specific surface area of the object to be measured can be measured by a BET specific surface area measuring device. As the BET specific surface area measuring device, for example, Macsorb (registered trademark) manufactured by Mountech Co., Ltd. can be used. When a powdery measurement object is measured, it is preferable to dry it at 105° C. for 30 minutes in a nitrogen atmosphere as a pretreatment. The object to be measured is LiMO.

(Particle size)
LiMO preferably satisfies a 50% cumulative volume particle size (D ₅₀ ) of 1 μm or more determined by particle size distribution measurement. LiMO preferably satisfies _D50 of 15 μm or less. LiMO preferably satisfies _D50 of 1 μm or more and 15 μm or less, more preferably 2 μm or more and 14 μm or less, and still more preferably 3 μm or more and 14 μm or less.

[Measurement of particle size]
"Cumulative volume particle size" is measured by a laser diffraction scattering method. Specifically, 0.1 g of LiMO powder is added to 50 ml of a 0.2% by mass sodium hexametaphosphate aqueous solution to obtain a dispersion in which the powder is dispersed. Next, the particle size distribution of the resulting dispersion is measured using a laser diffraction/scattering particle size distribution analyzer (eg, LA950, manufactured by Horiba, Ltd.) to obtain a volume-based cumulative particle size distribution curve.
In the obtained cumulative particle size distribution curve, the value of the particle size at the time of 50% accumulation from the microparticle side is the 50% cumulative volume particle size _D50 (μm).

In this specification, the battery performance of lithium secondary batteries is measured by the following method.

<Measurement of battery performance>
(Preparation of positive electrode for lithium secondary battery)
LiMO manufactured by the manufacturing method of this embodiment is used as a CAM. CAM, a conductive material, and a binder are added at a composition ratio of CAM:conductive material:binder=92:5:3 (mass ratio) and kneaded to prepare a pasty positive electrode mixture. N-methyl-2-pyrrolidone is used as an organic solvent when preparing the positive electrode mixture. Acetylene black is used as the conductive material. Polyvinylidene fluoride is used as the binder.

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 positive electrode area of this positive electrode for lithium secondary battery is 1.65 cm ² .

(Production of lithium secondary battery)
The following operations are performed in an argon atmosphere glove box.
Place the lithium secondary battery positive electrode prepared in (Preparation of positive electrode for lithium secondary battery) on the lower cover of coin battery R2032 parts (manufactured by Hosen Co., Ltd.) with the aluminum foil side facing down, A separator (polyethylene porous film) is placed thereon. 300 μl of electrolytic solution is injected here. The electrolytic solution used was obtained by dissolving LiPF ₆ at a ratio of 1.0 mol/l in a mixed solution of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate at a volume ratio of 30:35:35.

Next, using metallic lithium as the negative electrode, the negative electrode is placed on the upper side of the laminated film separator, the upper lid is placed via a gasket, and the lid is crimped with a crimping machine to produce a lithium secondary battery (coin type half cell R2032).

Using the lithium secondary battery produced by the above method, the initial discharge capacity and the initial charge capacity are measured by the following method, and the initial charge/discharge efficiency is calculated.

(Initial charge/discharge efficiency)
By allowing the lithium secondary battery to stand at room temperature for 12 hours, the separator and the positive electrode mixture layer are sufficiently impregnated with the electrolytic solution.
At a test temperature of 25° C., constant current and constant voltage charging and constant current discharging are performed with a current set value of 0.2 CA for both charging and discharging. The negative electrode is metal Li, the maximum charge voltage is 4.3V, and the minimum discharge voltage is 2.8V. The discharge capacity is measured, and the obtained value is defined as "initial discharge capacity" (mAh/g). The charge capacity is measured, and the obtained value is defined as "initial charge capacity" (mAh/g).
From the obtained charge capacity and discharge capacity, the initial charge/discharge efficiency is obtained based on the following formula.
Initial charge/discharge efficiency (%) = initial discharge capacity (mAh/g)/initial charge capacity (mAh/g) x 100

When the initial charge/discharge efficiency obtained by the above method is 82% or more, it is evaluated as "high initial charge/discharge efficiency".

<Method for Producing Lithium Metal Composite Oxide>
A method for producing LiMO is a method in which a step of producing a metal composite oxide, a step of mixing a metal composite oxide and a lithium compound to obtain a mixture, and a step of obtaining LiMO are carried out in this order.

[Manufacturing process of metal composite oxide]
First, a metal composite oxide containing Ni and the element X is prepared.
A metal composite oxide can be produced by a generally known batch coprecipitation method or continuous coprecipitation method. The method for producing the metal composite oxide containing Ni, Co and Al as metals will be described in detail below.

First, a nickel salt solution, a cobalt salt solution, an aluminum salt solution, and a complexing agent are reacted by a coprecipitation method, particularly a continuous method described in JP-A-2002-201028, to form Ni _(1-ab) Co A metal composite hydroxide represented by _a Al _b (OH) ₂ (wherein a+b=1) is produced.

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

As the cobalt salt that is the solute of the cobalt salt solution, for example, one or more of cobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate can be used.

As the aluminum salt that is the solute of the aluminum salt solution, for example, aluminum sulfate, sodium aluminate, or the like can be used.

The above metal salts are used in proportions corresponding to the composition ratio of Ni _(1-ab) Co _a Al _b (OH) ₂ . Also, water is used as a solvent.

Complexing agents are compounds capable of forming complexes with Ni, Co, and Al ions in aqueous solution. Examples include ammonium ion donors, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine.

Ammonium ion donors include ammonium salts such as ammonium hydroxide, ammonium sulfate, ammonium chloride, ammonium carbonate and ammonium fluoride.

The complexing agent may not be contained, and when the complexing agent is contained, the amount of the complexing agent contained in the mixed solution containing the nickel salt solution, the cobalt salt solution, the aluminum salt solution and the complexing agent is, for example, The mol ratio to the total number of mols of the metal salt 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 aluminum salt solution and the complexing agent, before the pH of the mixed solution changes from alkaline to neutral, Add an alkaline aqueous solution. Sodium hydroxide and potassium hydroxide can be used as the alkaline aqueous solution.

In addition, the value of pH in this specification is defined as the value measured when the temperature of the liquid mixture is 40 degreeC. The pH of the mixed solution is measured when the temperature of the mixed solution sampled from the reaction tank reaches 40°C.

If the temperature of the sampled mixture is lower than 40°C, the mixture is heated to 40°C and the pH is measured.

If the temperature of the sampled mixture is higher than 40°C, the pH is measured when the mixture is cooled to 40°C.

When the nickel salt solution, cobalt salt solution, and aluminum salt solution as well as the complexing agent are continuously supplied to the reactor, Ni, Co, and Al react to form Ni _(1-ab) Co _a Al. _b (OH) ₂ is produced.

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

In addition, during the reaction, the pH value in the reaction vessel is controlled, for example, within the range of pH 9 or more and pH 13 or less, preferably pH 11 or more and pH 13 or less.

The materials in the reaction vessel are appropriately agitated to mix.
The reactor used in the continuous co-precipitation process is an overflow-type reactor in which the formed reaction precipitate is overflowed and separated from the top of the reactor.

The inside of the reaction vessel may be an inert atmosphere. An inert atmosphere suppresses the aggregation of elements that are more easily oxidized than nickel, and a uniform metal composite hydroxide can be obtained.

Oxygen may also be introduced into the reaction vessel. A method of introducing oxygen into the reactor includes a method of bubbling an oxygen-containing gas. At this time, it is preferable to introduce oxygen gas while maintaining an inert atmosphere without introducing a large amount of oxygen. Increasing the amount of transition metal oxidation increases the specific surface area.

In addition to controlling the above conditions, various gases such as nitrogen, argon, inert gases such as carbon dioxide, air, oxidizing gases such as oxygen, or mixed gases thereof are supplied into the reaction vessel to obtain The oxidation state of the reaction products may be controlled.

As compounds that oxidize the resulting reaction product, peroxides such as hydrogen peroxide, peroxide salts such as permanganate, perchlorates, hypochlorites, nitric acid, halogens, ozone, etc. are used. can do.

Organic acids such as oxalic acid and formic acid, sulfites, hydrazine, and the like can be used as compounds for reducing the resulting reaction product.

After the above reaction, the resulting reaction product is washed with water and then dried to obtain a nickel-cobalt-aluminum metal composite hydroxide. In addition, if contaminants derived from the mixed solution remain only by washing the reaction product with water, the reaction product may optionally be washed with weak acid water, sodium hydroxide, or potassium hydroxide. It may be washed with an alkaline solution.

Furthermore, a nickel-cobalt-aluminum metal composite oxide, which is a metal composite oxide, can be prepared by oxidizing the nickel-cobalt-aluminum metal composite hydroxide.

The firing time for oxidation is preferably 1 hour or more and 30 hours or less, which is the total time from the start of temperature rise to the end of temperature retention. The heating rate in the heating step to reach the maximum holding temperature is preferably 180° C./hour or more, more preferably 200° C./hour or more, and particularly preferably 250° C./hour or more.

The maximum holding temperature in the present specification is the maximum holding temperature of the atmosphere inside the firing furnace in the firing process, and means the firing temperature in the firing process. In the case of the main firing step having a plurality of heating steps, the highest holding temperature means the highest temperature in each heating step.

The heating rate in this specification refers to the time from the start of temperature rise to the maximum holding temperature in the firing device, and the time from the start of temperature rise to the maximum holding temperature in the firing furnace of the firing device. calculated from the temperature difference.

[Step of obtaining a mixture]
After drying the metal composite oxide, it is mixed with a lithium compound.

As the lithium compound, one or more of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, and lithium oxide may be used in combination.
Among these lithium compounds, lithium hydroxide and lithium acetate can react with carbon dioxide in the air and contain several percent of lithium carbonate.

Preferably, the purity of the lithium compound satisfies 98% or higher.

The metal composite oxide may be dried prior to mixing with the lithium compound.
Drying conditions for the metal composite oxide are not particularly limited. Drying conditions are preferably conditions under which the metal composite oxide is not oxidized or reduced. Specifically, the drying conditions are such that the metal composite oxide is maintained as it is.

An inert gas such as nitrogen, helium, or argon may be used in the atmosphere during drying in order to create a condition in which the metal composite oxide is not oxidized or reduced.

After drying the metal composite oxide, it may be appropriately classified.

The lithium compound and metal composite oxide are used in consideration of the composition ratio of the final object. For example, when a nickel-cobalt-aluminum metal composite oxide is used as the metal composite oxide, the lithium compound and the metal composite oxide are LiNi _(1-abc) Co _a Al _b X _c O ₂ (wherein, It is used in a proportion corresponding to the composition ratio of a+b+c=1).
In LiMO, which is the final product, Li contained in the lithium compound and the metal element contained in the metal composite oxide are mixed at a ratio such that the molar ratio is 0.98 or more and 1.1 or less. It is easy to control (1) and (2) of LiMO within the preferred range of the present embodiment.

[Step of obtaining lithium metal composite oxide]
A lithium-nickel-cobalt-aluminum metal composite oxide is obtained as LiMO by firing a mixture of the nickel-cobalt-aluminum metal composite oxide and the lithium compound. For firing, dry air, an oxygen atmosphere, an inert atmosphere, or the like is used depending on the desired composition. In this embodiment, it is preferable to bake in an oxygen atmosphere.

The firing process may be a single firing or may have multiple firing steps.
When there are multiple firing steps, the step of firing at the highest temperature is referred to as main firing. Temporary sintering may be performed before main sintering at a temperature lower than that of main sintering. Further, after the main firing, post-baking may be performed in which the material is fired at a temperature lower than that of the main firing.

The firing temperature (maximum holding temperature) of the main firing is preferably 600° C. or higher, more preferably 610° C. or higher, and particularly preferably 620° C. or higher, from the viewpoint of promoting the growth of LiMO particles. From the viewpoint of preventing cracks from being formed in the LiMO particles and maintaining the particle strength, the temperature is preferably 1200° C. or lower, more preferably 1100° C. or lower, and particularly preferably 1000° C. or lower.

The upper limit and lower limit of the maximum holding temperature for main firing can be combined arbitrarily.
Examples of combinations include 600° C. or higher and 1200° C. or lower, 610° C. or higher and 1100° C. or lower, and 620° C. or higher and 1000° C. or lower.

The sintering temperature for the preliminary sintering or post-sintering may be lower than the sintering temperature for the main sintering, and may be, for example, in the range of 350° C. or higher and 800° C. or lower.

The holding temperature in firing may be appropriately adjusted according to the type and composition of the transition metal element used.

Moreover, the holding time at the holding temperature is preferably 0.1 hour or more and 20 hours or less, preferably 0.5 hour or more and 10 hours or less.

In the present embodiment, the temperature rising time from the start of temperature rising to the maximum holding temperature is preferably 2 hours or longer, more preferably 2.5 hours or longer, and particularly preferably 3 hours or longer. Further, the heating time is preferably 10 hours or less, more preferably 9 hours or less, and particularly preferably 8 hours or less.

The heating rate in the heating step is preferably 100° C./hour or more, more preferably 120° C./hour or more, and particularly preferably 150° C./hour or more. In addition, the heating rate in the heating step to reach the maximum holding temperature is preferably 350° C./hour or less, more preferably 300° C./hour or less, and particularly preferably 250° C./hour or less.
The rate of temperature rise in the heating process to reach the maximum holding temperature is calculated by dividing the difference between the temperature at which the heating is started and the holding temperature by the time required to reach the holding temperature.

As the firing atmosphere, air, oxygen, nitrogen, argon, or a mixed gas thereof can be used.

In this embodiment, the firing step is preferably performed in an oxygen-containing atmosphere.
When the mixture is continuously supplied into the firing furnace, the ratio of the mixture supply rate (kg/min) and the oxygen gas supply rate (Nm ³ /min) (oxygen gas supply rate/mixture supply rate) is preferably 20 or less, more preferably 10 or less, and particularly preferably 5 or less.

When firing a certain amount of mixed powder, the ratio of the total amount (Nm ³ ) of oxygen gas supplied into the furnace during firing to the amount (kg) of the mixture supplied (total amount of oxygen gas/mixture supply rate) is preferably 20 or less, more preferably 10 or less, and particularly preferably 5 or less.

LiMO that satisfies (1) and (2) can be obtained by adjusting the ratio of the total amount of oxygen gas to the supply rate of the mixture in the above range.

[Optional process]
- Crushing step The fired product obtained in the firing step may be appropriately crushed.

- Classification step The fired product obtained by the firing step may be classified as appropriate.

- Drying step The fired product obtained by the firing step may be dried. Drying conditions may be, for example, a temperature of 100° C. or higher and 750° C. or lower for 1 hour or longer and 20 hours or shorter.

- Washing step In the present embodiment, it is preferable to wash the fired product after firing with a cleaning liquid such as pure water or an alkaline cleaning liquid. When the drying step is carried out, washing may be performed after drying.

Examples of alkaline cleaning solutions include LiOH (lithium hydroxide), NaOH (sodium hydroxide), KOH ( _potassium hydroxide), _Li2CO3 (lithium carbonate), _{Na2CO3 (} sodium carbonate), and _{K2CO3 .} An aqueous solution of one or more anhydrides selected from the group consisting of (potassium carbonate) and (NH ₄ ) ₂ CO ₃ (ammonium carbonate) and an aqueous solution of the hydrate of said anhydride can be mentioned. Ammonia can also be used as the alkali.

In the washing step, the method of bringing the cleaning liquid and the fired product into contact includes a method of putting the fired product into each cleaning liquid and stirring, and a method of showering the fired product with each cleaning liquid as shower water. As a method of applying each cleaning solution as shower water to the fired product, after the fired product is put into the cleaning solution and stirred, the fired product is separated from each cleaning solution, and then each cleaning solution is used as shower water, after separation. A method of applying to the baked product can be mentioned.

In the present embodiment, the cleaning liquid pH in the cleaning step is preferably adjusted to 11.5 or higher, more preferably 11.8 or higher, and particularly preferably 12.0 or higher. The pH of the cleaning liquid when the baked product is put into the cleaning liquid and stirred is the value obtained by measuring the pH of the slurry whose temperature has been adjusted to 10° C. after 5 minutes have passed since the baking powder was added.
By controlling the pH of the cleaning liquid within the above range, the Li—X oxide and residual Li component can be removed from the fired powder, and the residual Li component can be removed more efficiently.

The temperature of the cleaning liquid used for cleaning is preferably 20° C. or lower, more preferably 15° C. or lower, and even more preferably 10° C. or lower. By controlling the temperature of the cleaning liquid within the above range so that the cleaning liquid does not freeze, excessive elution of lithium ions from the crystal structure of the baked product into the cleaning liquid during cleaning can be suppressed.

The baked product after washing may be dried as appropriate.

Through the above steps, LiMO is obtained.

<Positive electrode active material for lithium secondary battery>
The CAM of this embodiment contains LiMO produced by the method described above. In the CAM of the present embodiment, the content of LiMO with respect to the total mass (100 mass%) of the CAM is preferably 70-99 mass%, more preferably 80-98 mass%.

In this embodiment, the content ratio of LiMO with respect to the total mass of CAM is determined by SEM observation of CAM by irradiating the CAM with an electron beam at an acceleration voltage of 20 kV using a SEM (for example, JSM-5510 manufactured by JEOL Ltd.). Seek by. The magnification of the SEM photograph is adjusted so that 200 to 400 CAM particles of interest are present in the SEM photograph. As an example, the magnification may be 1000-30000 times.

<Lithium secondary battery>
Next, the configuration of a lithium secondary battery suitable for using the LiMO of the present embodiment as a CAM will be described.
Furthermore, a positive electrode for a lithium secondary battery (hereinafter sometimes referred to as a positive electrode) suitable for using the LiMO of the present embodiment as a CAM 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 the LiMO of the present embodiment as a CAM includes 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. have.

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 electrolyte disposed between the positive electrode and the negative electrode.

FIG. 1 is a schematic diagram showing an example of a lithium secondary battery. The cylindrical lithium secondary battery 10 of this embodiment is manufactured as follows.

First, as shown in 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 arranged as follows: 1 and the negative electrode 3 are stacked in this order and wound to form an electrode group 4 .

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 structure described above, and may have a layered structure 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.

Hereinafter, each configuration will be described in order.
(positive electrode)
The positive electrode can be manufactured by first preparing a positive electrode mixture containing CAM, a conductive material, and a binder, and supporting the positive electrode mixture on a positive electrode current collector.

(Conductive material)
A carbon material can be used as the conductive material of the positive electrode. Examples of carbon materials include graphite powder, carbon black (eg, acetylene black), and fibrous carbon materials.

The ratio of the conductive material in the positive electrode mixture is preferably 5 to 20 parts by mass with respect to 100 parts by mass of CAM.

(binder)
A thermoplastic resin can be used as the binder of the positive electrode. Examples of thermoplastic resins include polyimide resins; fluorine resins such as polyvinylidene fluoride (hereinafter sometimes referred to as PVdF) and polytetrafluoroethylene; polyolefin resins such as polyethylene and polypropylene; can be mentioned.

(Positive electrode current collector)
A strip-shaped member made of a metal material such as Al, Ni, or stainless steel can be used as the positive electrode current collector of the positive electrode.

As a method for supporting the positive electrode mixture on the positive electrode current collector, the positive electrode mixture is made into a paste using an organic solvent, the obtained positive electrode mixture paste is applied to at least one side of the positive electrode current collector and dried, A method of fixing by performing an electrode pressing process can be mentioned.

When the positive electrode mixture is made into a paste, an organic solvent that can be used includes N-methyl-2-pyrrolidone (hereinafter sometimes referred to as NMP).

Examples of the method for applying the positive electrode mixture paste to the positive electrode current collector include a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method, and an electrostatic spray method.
A positive electrode can be manufactured by the method mentioned above.

(negative electrode)
The negative electrode of the lithium secondary battery may be capable of doping and dedoping lithium ions at a potential lower than that of the positive electrode, and an electrode in which a negative electrode mixture containing a negative electrode active material is supported on a negative electrode current collector; An electrode consisting of a negative electrode active material alone can be mentioned.

(Negative electrode active material)
Examples of the negative electrode active material of the negative electrode include carbon materials, chalcogen compounds (oxides, sulfides, etc.), nitrides, metals, and alloys, which can be doped and undoped with lithium ions at a potential lower than that of the positive electrode. be done.

Examples of carbon materials that can be used as the negative electrode active material include graphite such as natural graphite or artificial graphite, cokes, carbon black, carbon fibers, and baked organic polymer compounds.

Examples of oxides that can be used as the negative electrode active material include oxides of silicon represented by _the formula SiO _x (where x is a positive real number _{) such as SiO 2 and} SiO; , x is a positive real number); metal composite oxides containing lithium and titanium, such as Li ₄ Ti ₅ O ₁₂ and LiVO ₂ ;

Metals that can be used as the negative electrode active material include lithium metal, silicon metal, and tin metal. As a material that can be used as a negative electrode active material, a material described in WO2019/098384A1 or US2020/0274158A1 may be used.

These metals and alloys are mainly used alone as electrodes after being processed into a foil shape, for example.

Among the above negative electrode active materials, the potential of the negative electrode hardly changes from the uncharged state to the fully charged state during charging (good potential flatness), the average discharge potential is low, and the capacity retention rate when repeatedly charged and discharged is low. A carbon material containing graphite as a main component, such as natural graphite or artificial graphite, is preferably used for reasons such as high (good cycle characteristics). The shape of the carbon material may be, for example, flaky such as natural graphite, spherical such as mesocarbon microbeads, fibrous such as graphitized carbon fiber, or aggregates of fine powder.

The negative electrode mixture may contain a binder, if necessary. Examples of binders include thermoplastic resins, and specific examples include PVdF, thermoplastic polyimide, carboxymethyl cellulose (hereinafter sometimes referred to as CMC), styrene-butadiene rubber (hereinafter sometimes referred to as SBR). some), polyethylene and polypropylene.

(Negative electrode current collector)
Examples of the negative electrode current collector that the negative electrode has include a belt-like member made of a metal material such as Cu, Ni, or stainless steel.

As a method for supporting the negative electrode mixture on such a negative electrode current collector, as in the case of the positive electrode, a method of pressure molding, a paste using a solvent etc. is applied or dried and then pressed on the negative electrode current collector. A method of crimping can be mentioned.

(separator)
As the separator of the lithium secondary battery, for example, a material having the form of a porous film, nonwoven fabric, or woven fabric made of a material such as a polyolefin resin such as polyethylene and polypropylene, a fluororesin, or a nitrogen-containing aromatic polymer is used. can be used. Moreover, the separator may be formed using two or more of these materials, or the separator may be formed by laminating these materials. Also, the separator described in JP-A-2000-030686 or US20090111025A1 may be used.

(Electrolyte)
An electrolytic solution that a lithium secondary battery has contains an electrolyte and an organic solvent.

Electrolytes contained in the electrolytic solution include lithium salts such as LiClO ₄ and LiPF ₆ , and mixtures of two or more of these may be used.

As the organic solvent contained in the electrolytic solution, carbonates such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate can be used.

As the organic solvent, it is preferable to use a mixture of two or more of these. Among them, a mixed solvent containing carbonates is preferable, and a mixed solvent of a cyclic carbonate and a non-cyclic carbonate and a mixed solvent of a cyclic carbonate and an ether are more preferable.

Further, as the electrolytic solution, it is preferable to use an electrolytic solution containing a fluorine-containing lithium salt such as LiPF ₆ and an organic solvent having a fluorine substituent, since the safety of the obtained lithium secondary battery is increased. As the electrolyte and organic solvent contained in the electrolytic solution, the electrolyte and organic solvent described in WO2019/098384A1 or US2020/0274158A1 may be used.

<All-solid lithium secondary battery>
Next, while explaining the configuration of the all-solid lithium secondary battery, the positive electrode used as the CAM of the all-solid lithium secondary battery using LiMO according to one embodiment of the present invention as the CAM, and the all-solid lithium secondary battery having the positive electrode The following battery will be explained.

FIG. 2 is a schematic diagram showing an example of the all-solid lithium secondary battery of this embodiment. The all-solid 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 outer package 200 that accommodates 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 material forming each member will be described later.

The laminate 100 may have an external terminal 113 connected to the positive current collector 112 and an external terminal 123 connected to the negative 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-state lithium secondary battery 1000 further includes 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 .

As 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) shapes.

The all-solid-state lithium secondary battery 1000 is illustrated as having one laminate 100 as an example, but the present embodiment 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 .

Hereinafter, each configuration will be described in order.

(positive electrode)
The positive electrode 110 of this embodiment has a positive electrode active material layer 111 and a positive electrode current collector 112 .

The positive electrode active material layer 111 includes the CAM and the solid electrolyte which are one embodiment of the present invention described above. Moreover, the positive electrode active material layer 111 may contain a conductive material and a binder.

(solid electrolyte)
As the solid electrolyte contained in the positive electrode active material layer 111 of the present embodiment, a solid electrolyte having lithium ion conductivity and used in known all-solid lithium secondary batteries can be employed. Examples of such solid electrolytes include inorganic electrolytes and organic electrolytes. Examples of inorganic electrolytes include oxide-based solid electrolytes, sulfide-based solid electrolytes, and hydride-based solid electrolytes. Examples of organic electrolytes include polymer-based solid electrolytes. Examples of each electrolyte include compounds described in WO2020/208872A1, US2016/0233510A1, US2012/0251871A1, and US2018/0159169A1, and examples thereof include the following compounds.

(Oxide solid electrolyte)
Examples of oxide-based solid electrolytes include perovskite-type oxides, NASICON-type oxides, LISICON-type oxides, and garnet-type oxides. Specific examples of each oxide include compounds described in WO2020/208872A1, US2016/0233510A1, and US2020/0259213A1, and examples thereof include the following compounds.

Perovskite oxides include Li—La—Ti-based oxides such as Li _a La _1-a TiO ₃ (0<a<1), Li _b La _1-b TaO ₃ (0<b<1) and the like. Examples thereof include Li—La—Ta-based oxides and Li—La—Nb-based oxides such as Li _c La _1-c NbO ₃ (0<c<1).

Examples of NASICON-type oxides include Li _1+d Al _d Ti _2-d (PO ₄ ) ₃ (0≦d≦1). The NASICON-type oxide is Li _m M ¹ _n M ² _o P _p O _q (where M ¹ is selected from the group consisting of B, Al, Ga, In, C, Si, Ge, Sn, Sb and Se). One or more selected elements ^M2 is one or more elements selected from the group consisting of Ti, Zr, Ge, In, Ga, Sn and Al m, n, o, p and q is an arbitrary positive number).

As the LISICON-type oxide, Li ₄ M ³ O ₄ —Li ₃ M ⁴ O ₄ (M ³ is one or more elements selected from the group consisting of Si, Ge, and Ti. M ⁴ is P is one or more elements selected from the group consisting of , As and V).

Garnet-type oxides include Li—La—Zr-based oxides such as Li ₇ La ₃ Zr ₂ O ₁₂ (also referred to as LLZ).

The oxide-based solid electrolyte may be a crystalline material or an amorphous material.

(Sulfide-based solid electrolyte)
Examples of sulfide solid electrolytes include Li ₂ SP ₂ S ₅ based compounds, Li ₂ S—SiS ₂ based compounds, Li ₂ S—GeS ₂ based compounds, Li ₂ S—B ₂ S ₃ based compounds, LiI- Si ₂ SP ₂ S ₅ based compounds, LiI-Li ₂ SP ₂ O ₅ based compounds, LiI-Li ₃ PO ₄ -P ₂ S ₅ based compounds and Li ₁₀ GeP ₂ S ₁₂ based compounds, etc. can be done.

In this specification, the expression "based compound" that refers to a sulfide-based solid electrolyte refers to a solid electrolyte that mainly contains raw materials such as "Li ₂ S" and "P ₂ S ₅ " described before "based compound". Used as a generic term for For example, Li ₂ SP ₂ S ₅ based compounds include solid electrolytes that mainly contain Li ₂ S and P ₂ S ₅ and further contain other raw materials. The ratio of Li ₂ S contained in the Li ₂ SP ₂ S ₅ based compound is, for example, 50 to 90% by mass with respect to the entire Li ₂ SP ₂ S ₅ based compound. The ratio of P ₂ S ₅ contained in the Li ₂ SP ₂ S ₅ based compound is, for example, 10 to 50% by mass with respect to the entire Li ₂ SP ₂ S ₅ based compound. In addition, the ratio of other raw materials contained in the Li ₂ SP ₂ S ₅ compound is, for example, 0 to 30% by mass with respect to the entire Li ₂ SP ₂ S ₅ compound. The Li ₂ SP ₂ S ₅ -based compound also includes solid electrolytes in which the mixing ratio of Li ₂ S and P ₂ S ₅ is varied.

Li ₂ SP ₂ S ₅ compounds include Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ -LiI, Li ₂ SP ₂ S ₅ -LiCl, Li ₂ SP _{2 S5 - LiBr} , _Li2SP2S5 - _{LiI - LiBr , Li2SP2S5} - _Li2O , _Li2SP2S5 - _Li2O -LiI and _Li2S- P ₂ S ₅ -Z _m S _n (m and n are positive numbers, Z is Ge, Zn or Ga).

Li ₂ S—SiS ₂ compounds include Li ₂ S—SiS ₂ , Li ₂ S—SiS ₂ —LiI, Li ₂ S—SiS ₂ —LiBr, Li ₂ S—SiS ₂ —LiCl, and Li ₂ S—SiS. ₂ - _{B2S3 -} LiI, _Li2S - _{SiS2 - P2S5} -LiI, _Li2S - _{SiS2 - P2S5 -} LiCl, Li2S _{- SiS2} - _Li3PO4 , Li _2S —SiS ₂ —Li ₂ SO ₄ and Li ₂ S—SiS ₂ —Li _x MO _y (x, y are positive numbers; M is P, Si, Ge, B, Al, Ga, or In; There is.) and so on.

Examples of Li ₂ S—GeS ₂ based compounds include Li ₂ S—GeS ₂ and Li ₂ S—GeS ₂ —P ₂ S ₅ .

The sulfide-based solid electrolyte may be a crystalline material or an amorphous material.

(Hydride solid electrolyte)
Examples of hydride solid electrolyte materials include LiBH ₄ , LiBH ₄ -3KI, LiBH ₄ -PI ₂ , LiBH ₄ -P ₂ S ₅ , LiBH ₄ -LiNH ₂ , 3LiBH ₄ -LiI, LiNH ₂ , Li ₂ AlH ₆ , Li( _NH2 ) _2I , _Li2NH , LiGd( _BH4 ) _3Cl , _Li2 ( _BH4 )( _NH2 ), _Li3 ( _NH2 )I and _Li4 ( _BH4 )( _NH2 ) ₃ etc. can be mentioned.

(Polymer solid electrolyte)
Examples of polymer-based solid electrolytes include organic polymer electrolytes such as polyethylene oxide-based polymer compounds and polymer compounds containing one or more selected from the group consisting of polyorganosiloxane chains and polyoxyalkylene chains. . In addition, a so-called gel type in which a non-aqueous electrolyte is held in a polymer compound can also be used.

Two or more kinds of solid electrolytes can be used in combination as long as the effects of the invention are not impaired.

(Conductive material and binder)
As the conductive material included in the positive electrode active material layer 111, the materials described in (Conductive material) can be used. Also, the ratio described in the above (Conductive material) can be similarly applied to the ratio of the conductive material in the positive electrode mixture. Further, as the binder contained in the positive electrode, the materials described in the above (Binder) can be used.

(Positive electrode current collector)
As the positive electrode current collector 112 included in the positive electrode 110, the material described in the above (Positive electrode current collector) can be used.

As a method for supporting the positive electrode active material layer 111 on the positive electrode current collector 112 , there is a method of pressure-molding the positive electrode active material layer 111 on the positive electrode current collector 112 . Cold pressing or hot pressing can be used for pressure molding.

Alternatively, a mixture of CAM, a solid electrolyte, a conductive material, and a binder is pasted using an organic solvent to form a positive electrode mixture, and the obtained positive electrode mixture is applied to at least one surface of the positive electrode current collector 112, dried, and pressed. The positive electrode current collector 112 may carry the positive electrode active material layer 111 by pressing and fixing.

Alternatively, a mixture of the CAM, the solid electrolyte, and the conductive material is pasted using an organic solvent to form a positive electrode mixture, and the obtained positive electrode mixture is applied to at least one surface of the positive electrode current collector 112, dried, and sintered. Thus, the positive electrode current collector 112 may support the positive electrode active material layer 111 .

As the organic solvent that can be used for the positive electrode mixture, the same organic solvent that can be used when the positive electrode mixture described above (Positive electrode current collector) is made into a paste can be used.

Examples of the method for applying the positive electrode mixture to the positive electrode current collector 112 include the methods described above in (Positive electrode current collector).

The positive electrode 110 can be manufactured by the method described above. Specific combinations of materials used for the positive electrode 110 include the CAM described in this embodiment and the combinations described in Table 1.

(negative electrode)
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. As the negative electrode active material, the negative electrode current collector, the solid electrolyte, the conductive material, and the binder, those described above can be used.

As a method for supporting the negative electrode active material layer 121 on the negative electrode current collector 122 , as in the case of the positive electrode 110 , there is a method of pressure molding, and a paste-like negative electrode mixture containing a negative electrode active material is applied onto the negative electrode current collector 122 . a method of applying a paste-like negative electrode mixture containing a negative electrode active material onto the negative electrode current collector 122, drying it, and then sintering it.

(Solid electrolyte layer)
The solid electrolyte layer 130 has the solid electrolyte described above.

The solid electrolyte layer 130 can be formed by depositing an inorganic solid electrolyte on the surface of the positive electrode active material layer 111 of the positive electrode 110 described above by sputtering.

Further, the solid electrolyte layer 130 can be formed by applying a paste mixture containing a solid electrolyte to the surface of the positive electrode active material layer 111 of the positive electrode 110 described above and drying the mixture. After drying, the solid electrolyte layer 130 may be formed by press molding and further pressing by cold isostatic pressing (CIP).

Laminate 100 is obtained by laminating negative electrode 120 on solid electrolyte layer 130 provided on positive electrode 110 as described above, using a known method, in such a manner that negative electrode active material layer 121 is in contact with the surface of solid electrolyte layer 130 . It can be manufactured by

In the lithium secondary battery configured as described above, since the LiMO of the present embodiment is used as the CAM, it is possible to provide a lithium secondary battery with high initial charge/discharge efficiency.

In addition, since the positive electrode having the structure described above has the LiMO having the structure described above as the CAM, the initial charge/discharge efficiency of the lithium secondary battery can be increased.

Furthermore, since the lithium secondary battery having the above configuration has the positive electrode described above, the secondary battery has high initial charge/discharge efficiency and a long life.

<Composition analysis>
The composition analysis of LiMO was performed by the method described in [Measurement by ICP Emission Spectroscopy] above.

<Measurement of battery performance>
The battery performance of the lithium secondary battery using LiMO was measured by the method described in <Measurement of Battery Performance> above. Specifically, the initial charge/discharge efficiency was measured.

<L/M>
Nuclear magnetic resonance measurement of LiMO was carried out by the method described in [Nuclear magnetic resonance measurement] above, and L was obtained by the method described in (Method for calculating L) above.
In addition, M of LiMO was determined by the method described in [Measurement by ICP Emission Spectroscopy].
L/M was calculated from the obtained L and M.

<B/A>
A of LiMO was determined by the method described in [Neutralization titration method] above.
LiMO was measured by the method described in [Nuclear magnetic resonance measurement] above, and B was obtained by the method described in (Method for calculating B) above.
B/A was calculated from the obtained A and B.

<Measurement of BET specific surface area>
The BET specific surface area of LiMO was measured by the method described in [Measurement of BET specific surface area] above.

<Measurement of particle size distribution>
The particle size distribution of LiMO was measured by the method described in [Measurement of particle size distribution] above.

<<Example 1>>
1. Production of LiMO1 After water was put into a reactor equipped with a stirrer and an overflow pipe, an aqueous sodium hydroxide solution was added and the liquid temperature was maintained at 50°C.

A nickel sulfate aqueous solution, a cobalt sulfate aqueous solution, and an aluminum sulfate aqueous solution were mixed at a ratio of 88:9:3 in atomic ratio of Ni, Co, and Al to prepare a mixed raw material solution.

Next, this mixed raw material liquid and an aqueous solution of ammonium sulfate were continuously added as a complexing agent into the reactor while stirring. An aqueous solution of sodium hydroxide was added dropwise at appropriate times so that the pH of the solution in the reaction tank was 11.6 (measured at a liquid temperature of 40° C.) to obtain particles of nickel-cobalt-aluminum composite hydroxide.

After washing the particles of nickel-cobalt-aluminum composite hydroxide, the particles were dehydrated in a centrifuge, isolated, and oxidized at 650° C. to obtain nickel-cobalt-aluminum composite oxide 1 . A composition analysis of the nickel-cobalt-aluminum composite oxide 1 revealed that the atomic ratio of Ni, Co, and Al was 88.3:8.8:2.9.

Nickel-cobalt-aluminum composite oxide 1 and lithium hydroxide monohydrate powder were weighed and mixed at a molar ratio of Li/(Ni+Co+Al)=1.06.

After that, it was calcined at 650° C. for 5 hours in an oxygen atmosphere. At this time, the heating rate from room temperature to the holding temperature was set to 100° C./hour, and the heating time was set to 6.3 hours for firing.
After that, in an oxygen atmosphere, the ratio of oxygen gas supply rate/mixture supply rate was set to 5, and main firing was performed at 720° C. for 6 hours. At this time, the heating rate from room temperature to the holding temperature was set to 120° C./hour, and the heating time was set to 5.8 hours for firing.

After that, pure water was added to the obtained baked powder so that the slurry pH became 12.0, and the mixture was stirred for 20 minutes. The filtered wet cake was dried to obtain LiMO1.

2. Evaluation of LiMO1 A composition analysis of LiMO1 was performed, and a = 0.015, y = 0.089, and w = 0.026. LiMO1 had a layered structure.

<<Example 2>>
1. Production of LiMO2 Except for changing the holding temperature of the main firing to 700 ° C., setting the heating rate from room temperature to the holding temperature at that time to 200 ° C./hour, and setting the heating time to 3.4 hours. LiMO2 was obtained by the same method as in Example 1.

2. Evaluation of LiMO2 A composition analysis of LiMO2 was performed, and a = 0.021, y = 0.088, and w = 0.024. LiMO2 had a layered structure.

FIG. 3 shows the solid-state nuclear magnetic resonance spectrum of ⁷ Li of LiMO2.

<<Example 3>>
1. Production of LiMO3 After water was put into a reactor equipped with a stirrer and an overflow pipe, an aqueous sodium hydroxide solution was added and the liquid temperature was maintained at 50°C.

An aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of aluminum sulfate were mixed in such a ratio that the atomic ratio of Ni, Co, and Al was 91:7:2 to prepare a mixed raw material solution.

Next, this mixed raw material liquid and an aqueous solution of ammonium sulfate were continuously added as a complexing agent into the reactor while stirring. An aqueous sodium hydroxide solution was added dropwise at appropriate times so that the pH of the solution in the reaction tank reached 12.2 (measured at a liquid temperature of 40° C.) to obtain particles of nickel-cobalt-aluminum composite hydroxide.
After washing the nickel-cobalt-aluminum composite hydroxide particles, the particles were dehydrated in a centrifuge, isolated, and dried at 120° C. to obtain nickel-cobalt-aluminum composite hydroxide 2 . A composition analysis of the nickel-cobalt-aluminum composite hydroxide 2 revealed that the atomic ratio of Ni, Co, and Al was 90.1:7.0:2.9.

Nickel-cobalt-aluminum composite oxide 2 and lithium hydroxide monohydrate powder were weighed and mixed at a molar ratio of Li/(Ni+Co+Al)=1.06.

After that, it was calcined at 650° C. for 5 hours in an oxygen atmosphere. At this time, the heating rate from room temperature to the holding temperature was set to 100° C./hour, and the heating time was set to 6.3 hours for firing.
After that, in an oxygen atmosphere, the ratio of oxygen gas supply rate/mixture supply rate was set to 5, and main firing was performed at 760° C. for 6 hours. At this time, the heating rate to the holding temperature was set to 300° C./hour, and the heating time was set to 1.9 hours.

After that, pure water was added to the obtained sintered powder so that the slurry pH was 12.0, and the slurry was washed with water for 20 minutes with stirring. The filtered wet cake was dried to obtain LiMO3.

2. Evaluation of LiMO3 A composition analysis of LiMO3 was performed, and a = 0.014, y = 0.074, and w = 0.024. LiMO3 had a layered structure.

<<Comparative Example 1>>
1. Production of LiMO4 Nickel-cobalt-aluminum composite oxide 1 and lithium hydroxide monohydrate powder were weighed and mixed at a molar ratio of Li/(Ni+Co+Al)=1.06.

After that, it was calcined at 650° C. for 5 hours in an oxygen atmosphere. At this time, the heating rate to the holding temperature was set to 100° C./hour, and the heating time was set to 6.3 hours.
After that, in an oxygen atmosphere, the ratio of oxygen gas supply rate/mixture supply rate was set to 5, and main firing was performed at 720° C. for 6 hours. At this time, the heating rate to the holding temperature was set to 100° C./hour, and the heating time was set to 7.0 hours to obtain LiMO4.

2. Evaluation of LiMO4 Composition analysis of LiMO4 revealed a = 0.047, y = 0.088, and w = 0.028. LiMO4 had a layered structure.

<<Comparative Example 2>>
1. Production of LiMO5 The same procedure as in Comparative Example 1 was performed except that nickel-cobalt-aluminum composite oxide 1 and lithium hydroxide monohydrate powder were weighed and mixed at a molar ratio of Li/(Ni+Co+Al)=1.00. LiMO5 was obtained by the method.

2. Evaluation of LiMO5 Composition analysis of LiMO5 revealed a = -0.005, y = 0.089, and w = 0.024. LiMO5 had a layered structure.

<<Comparative Example 3>>
1. Production of LiMO6 Nickel-cobalt-aluminum composite oxide 1 and lithium hydroxide monohydrate powder were weighed and mixed at a molar ratio of Li/(Ni+Co+Al)=1.02.
After that, it was calcined at 650° C. for 5 hours in an oxygen atmosphere. At this time, the heating rate to the holding temperature was set to 100° C./hour, and the heating time was set to 6.3 hours.

After that, in an oxygen atmosphere, the ratio of oxygen gas supply rate/mixture supply rate was set to 5, and main firing was performed at 720° C. for 6 hours. At this time, the heating rate to the holding temperature was set to 400° C./hour, and the heating time was set to 1.8 hours to obtain LiMO6.

2. Evaluation of LiMO6 Composition analysis of LiMO6 revealed a=0.04, y=0.089, and w=0.024. LiMO6 had a layered structure.

<<Comparative Example 4>>
Nickel-cobalt-aluminum composite oxide 1 and lithium hydroxide monohydrate powder were weighed and mixed at a molar ratio of Li/(Ni+Co+Al)=1.02.
Comparative Example 3 except that the holding temperature of the main firing was changed to 770 ° C., the temperature rising rate from room temperature to the holding temperature at that time was set to 300 ° C./hour, and the heating time was set to 7.5 hours. After obtaining a sintered powder by the same method as above, pure water was added to the obtained sintered powder so that the slurry pH was 11.4, and the slurry was washed with water for 20 minutes with stirring, and the filtered wet cake was dried to obtain LiMO7. .

2. Evaluation of LiMO7 Composition analysis of LiMO7 revealed a=−0.005, y=0.089, and w=0.024. LiMO7 had a layered structure.

For each LiMO produced in Examples 1-3 and Comparative Examples 1-4, L/M, A (% by mass), B (% by mass), B/A, BET specific surface area, particle size distribution and initial charge/discharge efficiency The results are listed in Table 4.

As shown in Table 4, when the LiMOs of Examples 1 to 3 satisfying (1) and (2) were used, the initial charge/discharge efficiency of the lithium secondary battery was as high as 84% or more.

1: Separator, 3: Negative electrode, 4: Electrode group, 5: Battery can, 6: Electrolyte solution, 7: Top insulator, 8: Sealing body, 10: Lithium secondary battery, 21: Positive electrode lead, 100: Laminate, 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 lithium secondary battery

Claims (9)

A lithium metal composite oxide having a layered structure, containing at least Ni, Li and element X,
The element X is selected from the group consisting of Co, Mn, Al, Fe, Cu, Ti, Mg, W, Mo, Nb, Zn, Sn, Zr, Ga, V, B, Si, S and P. is an element of more than a species,
A lithium metal composite oxide that satisfies the following (1) and (2).
0.0070≦L/M≦0.03 (1)
A/B≦2.5 (2)
(L is calculated from the signal having the maximum intensity among the peaks appearing in the range of -50 ppm to 50 ppm in the solid-state nuclear magnetic resonance spectrum of ⁷ Li of the lithium metal composite oxide obtained by nuclear magnetic resonance measurement. is the abundance (mol) of Li determined from the product of the abundance (% by mass) of Li and the amount (mol) of Li in the lithium metal composite oxide measured by ICP emission spectroscopy, and M is It is the total amount (mol) of metal elements other than Li in the lithium metal composite oxide measured by ICP emission spectroscopy.
A is the Li content ratio (% by mass) determined from the amount of one or both of LiOH and Li ₂ CO ₃ calculated by the neutralization titration method with respect to the total amount of the lithium metal composite oxide, and B is , with respect to the total amount of the lithium metal composite oxide, in the solid-state nuclear magnetic resonance spectrum of ⁷ Li of the lithium metal composite oxide obtained by nuclear magnetic resonance measurement, among the peaks appearing in the range of -50 ppm to 50 ppm, the maximum intensity is the abundance ratio (% by mass) of Li calculated from the signal having the peak of ) 2. The lithium metal composite oxide according to claim 1, wherein said B is 0.2% by mass or less. 3. The lithium metal composite oxide according to claim 1, wherein said A is 0.4% by mass or less. The lithium metal composite oxide according to any one of claims 1 to 3, which satisfies the following compositional formula (I).
Li[Li _a (Ni _(1-yw) Al _w X1 _y ) _1-a ]O ₂ (I)
(In formula (I), X1 is selected from the group consisting of Mn, Co, Fe, Cu, Ti, Mg, W, Mo, Nb, Zn, Sn, Zr, Ga, V, B, Si, S and P and satisfies -0.1 ≤ a ≤ 0.2, 0 ≤ y ≤ 0.5, 0 < w ≤ 0.5, 0 < y + w ≤ 0.7.) The lithium metal composite oxide according to any one of claims 1 to 4, having a BET specific surface area of 0.2 m ² /g or more. 6. The lithium metal composite oxide according to any one of claims 1 to 5, wherein the 50% cumulative volume particle size (D ₅₀ ) determined by particle size distribution measurement is 1 μm or more. A positive electrode active material for a lithium secondary battery, comprising the lithium metal composite oxide according to any one of claims 1 to 6. A positive electrode for lithium secondary batteries, comprising the positive electrode active material for lithium secondary batteries according to claim 7 . A lithium secondary battery comprising the positive electrode for a lithium secondary battery according to claim 8 .

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