JP7222866B2 - Lithium metal composite oxide powder, positive electrode active material for lithium secondary battery, positive electrode, and lithium secondary battery - Google Patents

Description

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

A lithium metal composite oxide powder is used as a positive electrode active material for lithium secondary batteries.
Lithium secondary batteries have already been put to practical use not only as small-sized power sources for mobile phones and notebook computers, but also as medium- or large-sized power sources for automobiles and power storage.

The particle shape of the lithium metal composite oxide powder affects the filling properties during pressing when used as a positive electrode active material.

For example, Patent Document 1 describes a positive electrode active material for a lithium secondary battery having secondary particles with an average circularity of 0.05 or more and 0.6 or less. Patent Literature 1 describes that when the circularity of the secondary particles is within the above range, the contact with the conductive aid is improved and high-power charging/discharging becomes possible. In Patent Document 1, when the average circularity is 1, it means that the positive electrode active material is a sphere (perfect sphere), and the smaller the average circularity, the more distant the shape of the positive electrode active material is from the spherical shape. It is stated that

JP 2008-186753 A

In the positive electrode active material for lithium secondary batteries as described in Patent Document 1, there is room for improvement from the viewpoint of improving volumetric capacity and volumetric capacity retention rate.
An object of the present invention is to provide a lithium metal composite oxide powder, a positive electrode active material for a lithium secondary battery, a positive electrode, and a lithium secondary battery having high volume capacity and volume capacity retention rate.

That is, the present invention includes the following inventions [1] to [8].
[1] A lithium metal composite oxide powder composed of secondary particles formed by agglomeration of primary particles and single particles existing independently of the secondary particles, and having the following composition formula ( 1) and characterized by satisfying the following requirements (A), (B) and (C).
Li[Li _x (Ni _(1-yzw) Co _y Mn _z M _w ) _1-x ]O ₂ (1)
(where M is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga and V; -0. satisfy 1≦x≦0.2, 0<y≦0.4, 0≦z≦0.4, and 0≦w≦0.1.)
(A) The BET specific surface area of the lithium metal composite oxide powder is less than 2 m ² /g.
(B) The lithium metal composite oxide powder has two or more peaks in the number-based circularity distribution of the circularity determined by the following formula (2).
Circularity=4πS/L ² (2)
(S is the projected area of the projected image of the particle, and L is the perimeter of the particle.)
(C) The lithium metal composite oxide powder has an average particle diameter _D50 of 2 μm or more and 20 μm or less.
[2] The lithium metal composite oxide powder according to [1], which has an average circularity of 0.4 or more and 0.8 or less.
[3] In the circularity distribution, the circularity has a first peak in the circularity range of 0.4 or more and 0.7 or less, and the circularity is 0.75 or more and 0.95 or less. The lithium metal composite oxide powder according to [1] or [2], which has 2 peaks.
[4] The lithium metal composite oxide powder according to [3], wherein the circularity distribution has a standard deviation of circularity distribution of 0.1 or more and 0.4 or less.
[5] The lithium metal composite oxide powder according to [3] or [4], wherein the first peak is a peak derived from single particles and the second peak is a peak derived from secondary particles. .
[6] The lithium metal composite oxide powder according to any one of [1] to [5], containing single particles having an average particle size of 1.0 μm or more and 5.0 μm or less.
[7] A positive electrode active material for a lithium secondary battery, containing the lithium metal composite oxide powder according to any one of [1] to [6].
[8] A positive electrode comprising the positive electrode active material for a lithium secondary battery according to [7].
[9] A lithium secondary battery having the positive electrode according to [8].

According to the present invention, it is possible to provide a lithium metal composite oxide powder, a positive electrode active material for a lithium secondary battery, a positive electrode, and a lithium secondary battery having high volume capacity and high volume capacity retention rate.

1 is a schematic configuration diagram showing an example of a lithium ion secondary battery; FIG. 1 is a schematic configuration diagram showing an example of a lithium ion secondary battery; FIG. 4 is a graph showing an example of the circularity distribution of a lithium metal composite oxide powder containing secondary particles alone. 4 is a graph showing an example of the circularity distribution of a lithium metal composite oxide powder containing single particles alone. 4 is a graph showing an example of the circularity distribution of the lithium metal composite oxide powder of the present embodiment. It is a schematic diagram for demonstrating the effect at the time of applying this embodiment. It is a schematic diagram for demonstrating the effect when this embodiment is not applied.

In the present invention, the "primary particles" are particles that do not have grain boundaries in appearance when observed in a field of view of 5000 to 20000 times using a scanning electron microscope or the like, and are secondary particles. Constituent particles are meant.
In the present invention, "secondary particles" are particles formed by aggregation of the primary particles.
In the present invention, the term "single particle" means a particle that exists independently of the secondary particles, has no grain boundary in appearance, and has a particle diameter of, for example, 0.5 μm or more.
In the present invention, the term "particles" is meant to include either or both of single particles and secondary particles.

<Lithium metal composite oxide powder>
This embodiment is a lithium metal composite oxide powder composed of secondary particles formed by agglomeration of primary particles and single particles existing independently of the secondary particles.
The lithium metal composite oxide powder of this embodiment is represented by the following compositional formula (1) and satisfies the following requirements (A), (B) and (C).
Li[Li _x (Ni _(1-yzw) Co _y Mn _z M _w ) _1-x ]O ₂ (1)
(where M is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga and V; -0. satisfy 1≦x≦0.2, 0<y≦0.4, 0≦z≦0.4, and 0≦w≦0.1.)
(A) The BET specific surface area of the lithium metal composite oxide powder is less than 2 m ² /g.
(B) The lithium metal composite oxide powder has two or more peaks in the number-based circularity distribution of the circularity determined by the following formula (2).
Circularity=4πS/L ² (2)
(S is the projected area of the projected image of the particle, and L is the perimeter of the particle.)
(C) The lithium metal composite oxide powder has an average particle diameter _D50 of 2 μm or more and 20 μm or less.

<<Composition formula (1)>>
The positive electrode active material of this embodiment is represented by the following compositional formula (1).
Li[Li _x (Ni _(1-yzw) Co _y Mn _z M _w ) _1-x ]O ₂ (1)
(where M is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, La and V, - satisfy 0.1≦x≦0.2, 0≦y≦0.4, 0≦z≦0.4, and 0≦w≦0.1.)

From the viewpoint of obtaining a lithium secondary battery with good cycle characteristics, x in the composition formula (1) is preferably greater than 0, more preferably 0.01 or more, and even more preferably 0.02 or more. . From the viewpoint of obtaining a lithium secondary battery with a higher initial coulombic efficiency, x in the composition formula (I) is preferably 0.1 or less, more preferably 0.08 or less, and 0.06. More preferably:
The upper limit and lower limit of x can be combined arbitrarily.
In this embodiment, it is preferable that 0<x≦0.1.
As used herein, “good cycle characteristics” means characteristics in which the amount of decrease in battery capacity is small due to repeated charging and discharging, and means that the ratio of capacity at remeasurement to initial capacity is less likely to decrease.

Further, from the viewpoint of obtaining a lithium secondary battery with low battery internal resistance, y in the composition formula (1) is preferably greater than 0, more preferably 0.005 or more, and 0.01 or more. is more preferable, and 0.05 or more is particularly preferable. Moreover, from the viewpoint of obtaining a lithium secondary battery with high thermal stability, y in the composition formula (1) is more preferably 0.35 or less, and even more preferably 0.33 or less.
The upper limit and lower limit of y can be combined arbitrarily.
In this embodiment, it is preferable that 0<y≦0.4.

In the present embodiment, it is more preferable that 0<x≦0.1 and 0<y≦0.4 in the composition formula (1).

Also, from the viewpoint of obtaining a lithium secondary battery with high cycle characteristics, z in the composition formula (1) is preferably 0.01 or more, more preferably 0.02 or more, and 0.1 or more. It is even more preferable to have In addition, from the viewpoint of obtaining a lithium secondary battery with high storage stability at high temperatures (for example, in an environment of 60° C.), z in the composition formula (1) is preferably 0.39 or less, and is 0.38 or less. is more preferable, and 0.35 or less is even more preferable.
The upper limit and lower limit of z can be combined arbitrarily.

In addition, from the viewpoint of obtaining a lithium secondary battery with low battery internal resistance, w in the composition formula (1) is preferably greater than 0, more preferably 0.0005 or more, and 0.001 or more. is more preferred. Also, from the viewpoint of obtaining a lithium secondary battery with a large discharge capacity at a high current rate, w in the composition formula (1) is preferably 0.09 or less, more preferably 0.08 or less, and 0 It is more preferably 0.07 or less.
The upper limit and lower limit of w can be combined arbitrarily.

Further, from the viewpoint of obtaining a lithium secondary battery with a large battery capacity, in the present embodiment, y + z + w in the composition formula (1) is preferably less than 0.5, more preferably 0.48 or less, and 0.46 or less. More preferred.

M in the composition formula (1) is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, La and V. represents

Moreover, from the viewpoint of obtaining a lithium secondary battery with high cycle characteristics, M in the composition formula (1) is one or more elements selected from the group consisting of Ti, Mg, Al, W, B, and Zr. is preferred, and one or more elements selected from the group consisting of Al and Zr are more preferred. Moreover, from the viewpoint of obtaining a lithium secondary battery with high thermal stability, it is preferably one or more elements selected from the group consisting of Ti, Al, W, B, and Zr.

≪Requirements (A)≫
The lithium metal composite oxide powder of the present embodiment has a BET specific surface area of less than 2 m ² /g, preferably 1.7 m ² /g or less, more preferably 1.5 m ² /g or less, and 1.4 m ² /g. g or less is particularly preferred.
In the present embodiment, the BET specific surface area is a value obtained by drying 1 g of lithium metal composite oxide powder in a nitrogen atmosphere at 105° C. for 30 minutes and then measuring it using Macsorb (registered trademark) manufactured by Mountech (unit: : m ² /g).

It is presumed that the lithium metal composite oxide powder of the present embodiment can improve the volume capacity and the volume capacity retention rate by setting the BET specific surface area to the upper limit value or less.

≪Requirement (B)≫
The lithium metal composite oxide powder of this embodiment has two or more peaks in the circularity distribution.

・Measurement of Circularity Distribution Circularity distribution of the lithium metal composite oxide powder to be measured is measured. The circularity distribution in the present embodiment is a circularity distribution based on the number of circularities obtained by the following equation (2).
First, an SEM image of the lithium metal composite oxide powder is taken to obtain a particle image which is a projected image of the lithium metal composite oxide powder particles. Next, the circularity calculated by the following formula (2) is measured for each particle that constitutes the lithium metal composite oxide powder. The obtained circularity is plotted on the horizontal axis and the number of particles is plotted on the vertical axis to obtain the circularity distribution of the lithium metal composite oxide powder. The degree of circularity shown in the following formula (2) means that the closer the numerical value is to 1, the better the circularity.
Circularity=4πS/L ² (2)
(S is the projected area of the projected image of the particle, and L is the perimeter of the particle.)

The circularity distribution can be measured by, for example, using an image taken using a scanning cell microscope (SEM) or a transmission electron microscope (TEM), and a method of performing image analysis, a commercially available particle image analysis device, especially a flow and a method using a particle image analyzer of the formula.

The lithium metal composite oxide powder of this embodiment has two or more peaks in the circularity distribution obtained by the above method. Here, the “peak” is divided into 20 so that the circularity is evenly spaced every 0.05 between 0 and 1.0 in the circularity distribution in which the horizontal axis is the circularity and the vertical axis is the number of particles. When the data range of is set, the number of particles changes from an increase to a decrease from the low circularity side to the high circularity side.
In the evaluation of the circularity distribution, a data range obtained by dividing the circularity between 0 and 1.0 into 20 or more may be set.

In this embodiment, it is preferable to measure the circularity distribution a plurality of times to confirm that peaks appear with good reproducibility. In addition, it is determined that a portion with no reproducibility is derived from noise and is not treated as a peak.

The average circularity is preferably 0.4 or more and 0.8 or less, more preferably 0.45 or more and 0.75 or less, and particularly preferably 0.48 or more and 0.70 or less. The average circularity can be calculated by dividing the sum of the circularities of all particles by the total number of particles.

In the present embodiment, in the circularity distribution in which the horizontal axis is the circularity and the vertical axis is the number of particles, the circularity has a first peak in the circularity range of 0.4 or more and 0.7 or less. It is preferable to have the second peak in the circularity range of 0.75 or more and 0.95 or less.

In the present embodiment, the lithium metal composite oxide powder preferably has a circularity distribution standard deviation of 0.1 or more, more preferably 0.15 or more in the circularity distribution from the viewpoint of increasing the volumetric capacity. More preferably, it is 0.18 or more. In addition, from the viewpoint of enhancing the handleability of the lithium metal composite oxide powder, it is preferably 0.4 or less, more preferably 0.35 or less, and even more preferably 0.30 or less.

In the present embodiment, it is preferable that the first peak is a peak derived from single particles, and the second peak is a peak derived from secondary particles. The lithium metal composite oxide powder of this embodiment is composed of secondary particles and single particles. Since the secondary particles are formed by agglomerating the primary particles, they have a nearly spherical particle shape. Therefore, among the peaks observed in the circularity distribution, the second peak may be a peak derived from secondary particles. Also, the first peak may be a peak derived from a single particle that is another component. The particles from which the first peak and the second peak are derived are determined from the images taken when calculating the circularity of each particle.

2A to 2C show circularity distributions of lithium metal composite oxides having different particle existence modes.
FIG. 2A is a graph showing an example of a circularity distribution of a lithium metal composite oxide powder containing secondary particles alone.
FIG. 2B is a graph showing an example of a circularity distribution of a lithium metal composite oxide powder containing single particles alone.
FIG. 2C is a graph showing an example of the circularity distribution of the lithium metal composite oxide powder of this embodiment.

As shown in FIG. 2A, the lithium metal composite oxide powder containing secondary particles alone may have a circularity peak in the range of 0.8 to 0.9. Secondary particles are aggregates of primary particles, and most of the secondary particles are spherical particles. For this reason, in the lithium metal composite oxide powder containing only secondary particles, a single peak may be observed in the range of high circularity as shown in FIG. 2A.
In addition, the lithium metal composite oxide powder containing secondary particles alone may contain a small amount of primary particles generated by cracking of the secondary particles, but the amount of primary particles is very small. Therefore, it is considered that no peak derived from primary particles is observed.

As shown in FIG. 2B, in the circularity distribution of the lithium composite metal oxide containing single particles alone, no sharp peak is observed, and the overall peak may be broad. This is presumed to be due to the fact that in single grains, large and well-developed crystal planes tend to appear on the grain surface.

FIG. 2C shows an example of the circularity distribution of the lithium metal composite oxide powder of this embodiment. When composed of secondary particles formed by aggregation of primary particles and single particles existing independently of the secondary particles, the first peak derived from the single particles and the secondary particles At least two of the second peaks from are sometimes observed.
In this embodiment, the circularity distribution may have two or more peaks, and may have three or more peaks. When particles with different particle shapes (eg, ellipsoidal particles, plate-like particles, fibrous particles) are contained, multiple peaks derived from the circularity of each particle may be observed.

In the lithium metal composite oxide powder of the present embodiment, the abundance ratio of the single particles and the secondary particles is preferably 1 to 60/99 to 40. The mixing ratio is the mass ratio of the particles.

≪Requirement (C)≫
The lithium metal composite oxide powder of the present embodiment has an average particle diameter _D50 of 2 μm or more and 20 μm or less, preferably 3 μm or more and 18 μm or less, more preferably 4 μm or more and 15 μm or less.

In the lithium metal composite oxide powder of the present embodiment, the average particle size of single particles is preferably 1 μm or more, more preferably 1.1 μm or more, and even more preferably 1.2 μm or more.
Moreover, the upper limit of the average particle size of the single particles is not particularly limited. For example, the average particle size of single particles may be 5.0 μm or less, 4.0 μm or less, or 3.0 μm or less.

.. Average particle size of single particles and secondary particles First, the lithium metal composite oxide powder is placed on a conductive sheet attached on a sample stage, and JSM-5510 manufactured by JEOL Ltd. is used to increase the accelerating voltage. A 20 kV electron beam is irradiated and SEM observation is performed. 50 single particles or secondary particles are arbitrarily extracted from the image (SEM photograph) obtained by SEM observation, and for each single particle or secondary particle, the projected image of the single particle or secondary particle is projected from a certain direction. The distance between the drawn parallel lines (unidirectional diameter) is measured as the particle size of the single particles or secondary particles. The arithmetic average value of the particle sizes of the obtained single particles or secondary particles is the average single particle size or average secondary particle size of the lithium metal composite oxide powder. The n number for calculating the average particle size is 50 or more.

..Average particle size _D50
Measured by laser diffraction scattering method. First, 0.1 g of lithium metal composite oxide powder is put into 50 ml of 0.2% by mass sodium hexametaphosphate aqueous solution to obtain a dispersion liquid in which the powder is dispersed.
Next, the particle size distribution of the resulting dispersion is measured using a Microtrac MT3300EXII (laser diffraction scattering particle size distribution analyzer) manufactured by Microtrac Bell Co., Ltd. to obtain a volume-based cumulative particle size distribution curve.

Then, in the obtained cumulative particle size distribution curve, the value of the particle diameter at the point where the cumulative volume from the small particle side reaches 50% is _D50 (μm).

(Layered structure)
In the present embodiment, the crystal structure of the lithium metal composite oxide powder is a layered structure, and more preferably a hexagonal crystal structure or a monoclinic crystal structure.

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

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

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

The lithium metal composite oxide powder of the present embodiment can be used as a positive electrode active material to improve the electrode density when an electrode is produced. FIG. 3 shows a schematic diagram when the lithium metal composite oxide powder of the present embodiment is press-filled. In FIGS. 3 and 4, particles with a high degree of circularity are exemplified as secondary particles, and particles with a low degree of circularity are exemplified as single particles. FIG. 3 shows a state in which a positive electrode mixture containing secondary particles 56 , single particles 57 , a conductive agent 58 and a binder 59 is applied onto a current collector 55 . When the positive electrode mixture is pressed and fixed onto the current collector, the pressure causes friction between the secondary particles 56 and the single particles 57, and the secondary particles 56 are cracked, resulting in cracked secondary particles. (56A) occurs. The cracked secondary particles 56A and single particles 57 are moved and rearranged so as to fill up the gaps by pressurization. In other words, it is presumed that the single particles 57 enter the gaps between the split secondary particles 56A, the contact areas between the secondary particles (reference numerals 56 and 56A) and the single particles 57 increase, and the gaps decrease. This is thought to improve the density of the electrodes.

In addition, it is presumed that the presence of the single particles 57 increases the friction with the secondary particles 56 and promotes particle cracking. In addition, since the particles in which the single particles 57 and the secondary particles 56 are split have a low degree of circularity, it is thought that the particles move due to pressure, and even if they are rearranged, voids of a certain size or less remain. For this reason, it is presumed that depletion of the electrolytic solution is less likely to occur even when the battery is repeatedly charged and discharged. It is presumed that due to such action, the lithium metal composite oxide powder of the present embodiment containing secondary particles and single particles has a high volume capacity and a high volume capacity retention rate.

On the other hand, FIG. 4 shows a case where an electrode is manufactured using a lithium composite metal oxide powder that does not contain single particles but has secondary particles alone as a positive electrode active material. A positive electrode mixture containing secondary particles 61 , a binder 62 , and a conductive agent 63 is applied onto a current collector 60 . When the positive electrode mixture is pressed and fixed onto the current collector, if there are split secondary particles 61A and unsplit secondary particles, the particles are sufficiently moved and rearranged by the pressure. It is thought that there is no progress and a gap is generated. If this embodiment is not applied, it is considered that the density of the electrodes cannot be improved because the gap cannot be filled.

<Method for Producing Lithium Metal Composite Oxide Powder>
The lithium metal composite oxide powder of the present embodiment can be produced by production method 1 or production method 2 below.

≪Manufacturing method 1≫
In producing the lithium metal composite oxide powder of the present embodiment, first, metals other than lithium, that is, containing at least Ni, Co, Mn, Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb , Zn, Sn, Zr, Ga, La and V, and sintering the metal composite compound with an appropriate lithium salt and an inert melting agent. is preferred. As the metal composite compound, a metal composite hydroxide or a metal composite oxide is preferable. An example of a method for producing a lithium metal composite oxide powder will be described below by dividing it into a metal composite compound production process and a lithium metal composite oxide production process.

(Manufacturing process of metal composite compound)
A metal complex compound can be produced by a generally known batch coprecipitation method or continuous coprecipitation method. The method for producing the metal composite hydroxide containing nickel, cobalt and manganese as metals will be described in detail below.

In production method 1, in the step of producing a metal composite compound, a metal composite compound that ultimately forms single particles and a metal composite compound that forms secondary particles are respectively produced. Hereinafter, the metal composite compound that finally forms single particles may be referred to as "single particle precursor". Also, the metal composite compound that finally forms secondary particles may be referred to as a "secondary particle precursor".

First, a nickel salt solution, a cobalt salt solution, a manganese 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 _a Co _b Mn _c (OH). ₂ A metal composite hydroxide represented by (a+b+c=1 in the formula) 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 manganese salt that is the solute of the manganese salt solution, for example, one or more of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate can be used. The above metal salts are used _in a proportion corresponding to the composition ratio of _the above _NiaCobMnc (OH) ₂ . Also, water is used as a solvent.

The complexing agent is one capable of forming a complex with ions of nickel, cobalt, and manganese in an aqueous solution. ammonium salt of ), hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine.

During precipitation, alkali metal hydroxides (eg sodium hydroxide, potassium hydroxide) are added, if necessary, to adjust the pH value of the aqueous solution.

When the nickel salt solution, cobalt salt solution, and manganese salt solution as well as the complexing agent are continuously supplied to the _reaction tank, nickel, cobalt, and manganese react to _{form NiaCobMnc} (OH) _2. is manufactured. During the reaction, the temperature of the reaction vessel is controlled within the range of, for example, 20° C. or higher and 80° C. or lower, preferably 30 to 70° C., and the pH value in the reaction vessel is, for example, pH 9 or higher and pH 13 or lower, preferably pH 11 or higher and pH 13 or lower. Controlled within the range, the material in the reactor is appropriately agitated. The reactor is of the overflow type for separation of the reaction sediment formed.

In production method 1, a first co-precipitation tank for producing single particle precursors and a second co-precipitation tank for forming secondary particle precursors are used.
A single particle precursor can be produced by appropriately controlling the concentration of the metal salt supplied to the first coprecipitator, the stirring speed, the reaction temperature, the reaction pH, the firing conditions described later, and the like.

Specifically, the temperature of the reaction tank is, for example, preferably 30° C. or higher and 80° C. or lower, more preferably controlled within the range of 40 to 70° C., and within the range of ±20° C. with respect to the second reaction tank described later. is more preferable. In addition, the pH value in the reaction tank is preferably controlled within the range of pH 10 or more and pH 13 or less, and more preferably within the range of pH 11 or more and pH 12.5 or less. It is more preferable to have a pH higher than that of the second reaction tank, and particularly preferably a pH higher than that of the second reaction tank.

In addition, the secondary particle precursor can be produced by appropriately controlling the concentration of the metal salt supplied to the second coprecipitation tank, the stirring speed, the reaction temperature, the reaction pH, and the calcination conditions described later.
Specifically, the temperature of the reaction vessel is, for example, preferably 20° C. or higher and 80° C. or lower, more preferably controlled within the range of 30 to 70° C., and the range of ±20° C. with respect to the second reaction vessel described later. is more preferable. In addition, the pH value in the reaction tank is preferably controlled within the range of pH 10 or more and pH 13 or less, and more preferably within the range of pH 11 or more and pH 12.5 or less. It is more preferable to have a pH lower than that of the second reaction tank, and particularly preferably a pH lower than that of the second reaction tank.

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 may be supplied into the reaction vessel. . In addition to gases, other substances that promote an oxidized state include oxides such as hydrogen peroxide, peroxide salts such as permanganate, perchlorates, hypochlorites, nitric acid, halogens, and ozone. be able to. In addition to gases, organic acids such as oxalic acid and formic acid, sulfites, hydrazine, and the like can be used as agents that promote a reduced state.

After the above reaction, each of the reaction precipitates obtained is washed with water and then dried to isolate nickel-cobalt-manganese hydroxide (single particle precursor, secondary particle precursor) as a nickel-cobalt-manganese composite compound. do. Moreover, you may wash|clean with alkaline solution containing weak acid water, sodium hydroxide, or potassium hydroxide as needed.
In addition, in the above example, a nickel-cobalt-manganese composite hydroxide is produced, but a nickel-cobalt-manganese composite oxide may be prepared.

(Manufacturing process of lithium metal composite oxide)
After drying the metal composite oxide or metal composite hydroxide as a single particle precursor or a secondary particle precursor, it is mixed with a lithium salt. By mixing the single particle precursors and the secondary particle precursors at a predetermined mass ratio during mixing, the existence ratio of the resulting single particles and secondary particles can be roughly controlled.
In the process after mixing, the single particle precursor and the secondary particle precursor are aggregated or separated, and there are also secondary particles based on the single particle precursor or single particles based on the secondary particle precursor. However, by adjusting the mixing ratio of the single particle precursor and the secondary particle precursor and the conditions of the steps after the mixing, the ratio of the single particles and the secondary particles in the finally obtained lithium metal composite oxide powder can be improved. The abundance ratio can be controlled.

In the present embodiment, the drying conditions are not particularly limited. ), conditions under which metal composite hydroxides are oxidized (hydroxides are oxidized to oxides), conditions under which metal composite oxides are reduced (oxides are reduced to hydroxides ) may be used. Inert gases such as nitrogen, helium and argon may be used for non-oxidizing/reducing conditions, and oxygen or air may be used for hydroxide oxidizing conditions. As for the conditions for reducing the metal composite oxide, a reducing agent such as hydrazine or sodium sulfite may be used in an inert gas atmosphere. As the lithium salt, one or a mixture of two or more of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, and lithium oxide may be used.

After drying the metal composite oxide or metal composite hydroxide as the single particle precursor or the secondary particle precursor, classification may be carried out as appropriate. The above lithium salt and metal composite hydroxide are used in consideration of the composition ratio of the final product. For example, when nickel-cobalt-manganese composite hydroxide is used, the lithium salt and the metal composite hydroxide are used in a proportion corresponding to the composition ratio of LiNi _a Co _b Mn _c O ₂ (where a + b + c = 1). . A lithium-nickel-cobalt-manganese composite oxide is obtained by calcining a mixture of the nickel-cobalt-manganese metal composite hydroxide and the lithium salt. For firing, dry air, an oxygen atmosphere, an inert atmosphere, or the like is used depending on the desired composition, and if necessary, a plurality of heating steps are performed.

By adjusting the holding temperature in the firing, the average particle size of the single particles and the average particle size of the secondary particles of the obtained lithium metal composite oxide can be controlled within the preferred range of the present embodiment.
The holding temperature in firing may be appropriately adjusted according to the type of transition metal element and precipitant used.
Specifically, the holding temperature can be in the range of 200° C. or higher and 1150° C. or lower, preferably 300° C. or higher and 1050° C. or lower, and more preferably 500° C. or higher and 1000° C. or lower.

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. The rate of temperature increase up to the holding temperature is usually 50° C./hour or more and 400° C./hour or less, and the temperature drop rate from the holding temperature to room temperature is usually 10° C./hour or more and 400° C./hour or less. As the firing atmosphere, air, oxygen, nitrogen, argon, or a mixed gas thereof can be used.

The lithium metal composite oxide obtained by sintering is pulverized and then appropriately classified to obtain a positive electrode active material that can be applied to lithium secondary batteries.

<<Manufacturing method 2>>
For the lithium metal composite oxide powder of the present embodiment, a first lithium metal composite oxide powder composed of single particles and a second lithium metal composite oxide powder composed of secondary particles are produced. and mixing the first and second lithium metal composite oxide powders.

In the case of producing any of the first and second lithium metal composite oxide powders, first, metals other than lithium, that is, containing at least Ni, Co, Mn, Fe, Cu, Ti, Mg, Al, W , B, Mo, Nb, Zn, Sn, Zr, Ga, La, and V. A metal composite compound containing any one or more arbitrary elements is prepared, and the metal composite compound is subjected to a first lithium metal composite oxidation The powder is preferably calcined with a suitable lithium salt and an inert solvent. When producing the second lithium metal composite oxide powder, it is preferable to calcine the metal composite compound with an appropriate lithium salt.

As the metal composite compound, a metal composite hydroxide or a metal composite oxide is preferable. An example of a method for producing a lithium metal composite oxide powder will be described below by dividing it into a metal composite compound production process and a lithium metal composite oxide production process.

(Manufacturing process of metal composite compound)
A metal complex compound can be produced by a generally known batch coprecipitation method or continuous coprecipitation method. The method for producing the metal composite hydroxide containing nickel, cobalt and manganese as metals will be described in detail below.

First, a nickel salt solution, a cobalt salt solution, a manganese 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 _a Co _b Mn _c (OH). ₂ A metal composite hydroxide represented by (a+b+c=1 in the formula) is produced.

The nickel salt, which is the solute of the nickel salt solution, the cobalt salt, which is the solute of the cobalt salt solution, and the manganese salt, which is the solute of the manganese salt solution, are the same as those in the production method 1 above. Also, water is used as a solvent.

The explanation about the complexing agent and precipitation is the same as the explanation in the production method 1 above.

After the above reaction, the obtained reaction precipitate is washed with water and then dried to isolate nickel-cobalt-manganese hydroxide as a nickel-cobalt-manganese composite compound. Moreover, you may wash|clean with the alkaline solution containing weak acid water, sodium hydroxide, or potassium hydroxide as needed.
In addition, in the above example, a nickel-cobalt-manganese composite hydroxide is produced, but a nickel-cobalt-manganese composite oxide may be prepared.

(Manufacturing process of lithium metal composite oxide)
After drying the metal composite oxide or metal composite hydroxide, it is mixed with a lithium salt. Moreover, when manufacturing the first lithium metal composite oxide powder, it is preferable to mix an inert melting agent at the same time as this mixing.
Firing an inert melting agent-containing mixture comprising a metal complex oxide or metal hydroxide, a lithium salt and an inert melting agent results in firing the mixture in the presence of the inert melting agent. By firing in the presence of an inert melting agent, it is possible to suppress the formation of secondary particles due to sintering of primary particles. Also, the growth of single grains can be promoted.

In the present embodiment, the explanations regarding the drying conditions and classification are the same as in the production method 1.

When producing the first lithium metal composite oxide powder, the reaction of the mixture can be promoted by firing the mixture in the presence of an inert melting agent. The inert melting agent may remain in the lithium metal composite oxide powder after firing, or may be removed by washing with water or the like after firing. In the present embodiment, it is preferable to wash the lithium composite metal oxide after firing with water or the like.

By adjusting the holding temperature in the sintering, the particle size of the single particles or the average particle size of the secondary particles of the resulting lithium metal composite oxide can be controlled within the preferred range of the present embodiment.
The holding temperature in the firing may be appropriately adjusted according to the type of transition metal element used and the type and amount of precipitant and inert melting agent.
Specifically, the holding temperature can be in the range of 200° C. or higher and 1150° C. or lower, preferably 300° C. or higher and 1050° C. or lower, and more preferably 500° C. or higher and 1000° C. or lower.

In particular, when the first lithium metal composite oxide powder is produced, the holding temperature of the second lithium metal composite oxide powder is preferably 30° C. or higher, more preferably 50° C. or higher. ° C. or more is more preferable.

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. The rate of temperature increase up to the holding temperature is usually 50° C./hour or more and 400° C./hour or less, and the temperature drop rate from the holding temperature to room temperature is usually 10° C./hour or more and 400° C./hour or less. As the firing atmosphere, air, oxygen, nitrogen, argon, or a mixed gas thereof can be used.

By mixing the obtained first and second lithium metal composite oxide powders in a predetermined ratio, the lithium metal composite oxide powder of the present embodiment can be obtained.

The lithium metal composite oxide obtained by sintering is pulverized and then appropriately classified to obtain a positive electrode active material that can be applied to lithium secondary batteries.

The inert melting agent that can be used in this embodiment is not particularly limited as long as it hardly reacts with the mixture during firing. In the present embodiment, one or more elements selected from the group consisting of Na, K, Rb, Cs, Ca, Mg, Sr and Ba (hereinafter referred to as "A") are fluorides and A chlorides. , A carbonate, A sulfate, A nitrate, A phosphate, A hydroxide, A molybdate and A tungstate. .

Fluorides of A include NaF (melting point: 993° C.), KF (melting point: 858° C.), RbF (melting point: 795° C.), CsF (melting point: 682° C.), CaF ₂ (melting point: 1402° C.), MgF ₂ (melting point: 1263° C.), SrF ₂ (melting point: 1473° C.) and BaF ₂ (melting point: 1355° C.).

Chlorides of A include NaCl (melting point: 801°C), KCl (melting point: 770°C), RbCl (melting point: 718°C), CsCl (melting point: 645°C), CaCl ₂ (melting point: 782°C), MgCl ₂ (melting point: 714° C.), SrCl ₂ (melting point: 857° C.) and BaCl ₂ (melting point: 963° C.).

Carbonates of A include Na ₂ CO ₃ (melting point: 854° C.), K ₂ CO ₃ (melting point: 899° C.), Rb ₂ CO ₃ (melting point: 837° C.), Cs ₂ CO ₃ (melting point: 793° C.). , CaCO ₃ (melting point: 825° C.), MgCO ₃ (melting point: 990° C.), SrCO ₃ (melting point: 1497° C.) and BaCO ₃ (melting point: 1380° C.).

Sulfates of A include Na ₂ SO ₄ (melting point: 884° C.), K ₂ SO ₄ (melting point: 1069° C.), Rb ₂ SO ₄ (melting point: 1066° C.), Cs ₂ SO ₄ (melting point: 1005° C.). , CaSO ₄ (melting point: 1460° C.), MgSO ₄ (melting point: 1137° C.), SrSO ₄ (melting point: 1605° C.) and BaSO ₄ (melting point: 1580° C.).

Nitrates of A include NaNO ₃ (melting point: 310° C.), KNO ₃ (melting point: 337° C.), RbNO ₃ (melting point: 316° C.), CsNO ₃ (melting point: 417° C.), Ca(NO ₃ ) ₂ (melting point: 417° C.). : 561°C), Mg( _NO3 ) ₂ , Sr( _NO3 ) ₂ (melting point: 645°C) and Ba( _NO3 ) ₂ (melting point: 596°C).

Phosphates of A include Na ₃ PO ₄ , K ₃ PO ₄ (melting point: 1340° C.), Rb ₃ PO ₄ , Cs ₃ PO ₄ , Ca ₃ (PO ₄ ) ₂ , Mg ₃ (PO ₄ ) ₂ ( 1184° C.), Sr ₃ (PO ₄ ) ₂ (melting point: 1727° C.) and Ba ₃ (PO ₄ ) ₂ (melting point: 1767° C.).

As the hydroxide of A, NaOH (melting point: 318°C), KOH (melting point: 360°C), RbOH (melting point: 301°C), CsOH (melting point: 272°C), Ca(OH) ₂ (melting point: 408°C ), Mg(OH) ₂ (melting point: 350° C.), Sr(OH) ₂ (melting point: 375° C.) and Ba(OH) ₂ (melting point: 853° C.).

Molybdates of A include Na ₂ MoO ₄ (melting point: 698° C.), K ₂ MoO ₄ (melting point: 919° C.), Rb ₂ MoO ₄ (melting point: 958° C.), Cs ₂ MoO ₄ (melting point: 956° C.). ), CaMoO ₄ (melting point: 1520° C.), MgMoO ₄ (melting point: 1060° C.), SrMoO ₄ (melting point: 1040° C.) and BaMoO ₄ (melting point: 1460° C.).

_Tungstates of A include _Na2WO4 (melting point: 687°C), _{K2WO4 , Rb2WO4} , _{Cs2WO4 , CaWO4} , _MgWO4 , _SrWO4 and _{BaWO4 .} .

In this embodiment, two or more of these inert melting agents can be used. When two or more are used, the melting point may be lowered. Among these inert melting agents, as an inert melting agent for obtaining a lithium metal composite oxide powder with higher crystallinity, any one of carbonates and sulfates of A, chlorides of A, or A combination is preferred. Moreover, A is preferably either one or both of sodium (Na) and potassium (K). That is, among the above, particularly preferred inert melting agents are one or more selected from the group consisting _of NaCl, _KCl , _Na2CO3 , _{K2CO3 , Na2SO4 ,} and _K2SO4 . .

In this embodiment, the amount of the inert melting agent present during firing may be appropriately selected. For example, the amount of the inert melting agent present during firing is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the lithium compound. Further, if necessary, an inert melting agent other than the inert melting agents listed above may be used together. Examples of the melting agent include ammonium salts such as _NH4Cl and _NH4F .

<Lithium secondary battery>
Next, a positive electrode using the positive electrode active material for a lithium secondary battery containing the positive electrode active material powder of the present embodiment and a lithium secondary battery having this positive electrode will be described while describing the configuration of the lithium secondary battery.

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

1A and 1B are schematic diagrams showing an example of the lithium secondary battery of this embodiment. The cylindrical lithium secondary battery 10 of this embodiment is manufactured as follows.

First, as shown in FIG. 1A, 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, as shown in FIG. 1B, 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 electrolyte solution 6, and the positive electrode 2 and the negative electrode 3 are separated. Place the electrolyte between 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.

As for the shape of the electrode group 4, for example, the cross-sectional shape when the electrode group 4 is cut in the direction perpendicular to the winding axis is a columnar shape such as 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, shapes such as a cylindrical shape and 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 of the present embodiment can be manufactured by first preparing a positive electrode mixture containing a positive electrode active material, 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 of the present embodiment. Examples of carbon materials include graphite powder, carbon black (eg, acetylene black), and fibrous carbon materials. Since carbon black is fine particles and has a large surface area, adding a small amount of carbon black to the positive electrode mixture can increase the conductivity inside the positive electrode and improve the charge-discharge efficiency and output characteristics. Both the binding force between the positive electrode mixture and the positive electrode current collector and the binding force inside the positive electrode mixture are lowered, which rather causes an increase in internal resistance.

The ratio of the conductive material in the positive electrode mixture is preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. If a fibrous carbon material such as graphitized carbon fiber or carbon nanotube is used as the conductive material, this ratio can be lowered.

(binder)
A thermoplastic resin can be used as the binder of the positive electrode of the present embodiment.
This thermoplastic resin is polyvinylidene fluoride (hereinafter sometimes referred to as PVdF).
), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), ethylene tetrafluoride/propylene hexafluoride/vinylidene fluoride copolymer, propylene hexafluoride/vinylidene fluoride copolymer, tetrafluoride fluororesins such as ethylene chloride/perfluorovinyl ether copolymers; polyolefin resins such as polyethylene and polypropylene;

These thermoplastic resins may be used in combination of two or more. A fluororesin and a polyolefin resin are used as a binder, and the ratio of the fluororesin to the entire positive electrode mixture is 1% by mass or more and 10% by mass or less, and the ratio of the polyolefin resin is 0.1% by mass or more and 2% by mass or less. It is possible to obtain a positive electrode mixture having both high adhesion to the current collector and high bonding strength inside the positive electrode mixture.

(Positive electrode current collector)
As the positive electrode current collector included in the positive electrode of the present embodiment, a strip-shaped member made of a metal material such as Al, Ni, or stainless steel can be used. Among them, it is preferable to use Al as a forming material and process it into a thin film because it is easy to process and inexpensive.

As a method for supporting the positive electrode mixture on the positive electrode current collector, there is a method of pressure-molding the positive electrode mixture on the positive electrode current collector. In addition, the positive electrode mixture is made into a paste using an organic solvent, and the obtained positive electrode mixture paste is applied to at least one side of a positive electrode current collector, dried, and pressed to adhere, thereby forming a positive electrode on the positive electrode current collector. A mixture may be supported.

When the positive electrode mixture is made into a paste, organic solvents that can be used include amine-based solvents such as N,N-dimethylaminopropylamine and diethylenetriamine; ether-based solvents such as tetrahydrofuran; ketone-based solvents such as methyl ethyl ketone; ester solvents such as dimethylacetamide; amide solvents such as dimethylacetamide and N-methyl-2-pyrrolidone (hereinafter sometimes referred to as NMP);

Examples of methods for applying the positive electrode mixture paste to the positive electrode current collector include slit die coating, screen coating, curtain coating, knife coating, gravure coating, and electrostatic spraying.

A positive electrode can be manufactured by the method mentioned above.
(negative electrode)
The negative electrode included in the lithium secondary battery of the present embodiment may be capable of doping and dedoping lithium ions at a potential lower than that of the positive electrode, and the negative electrode mixture containing the negative electrode active material is supported on the negative electrode current collector. and an electrode composed solely of the negative electrode active material.

(Negative electrode active material)
Examples of the negative electrode active material that the negative electrode has include carbon materials, chalcogen compounds (oxides, sulfides, etc.), nitrides, metals, or alloys that 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 and artificial graphite, cokes, carbon black, pyrolytic carbons, 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); V ₂ O ₅ , VO _2, etc. Vanadium oxide represented by the formula VO _x (where x is a positive real number); Fe ₃ O ₄ , Fe ₂ O ₃ , FeO, etc. Iron oxide represented by the formula FeO _x (where x is a positive real number); SnO ₂ , SnO, etc. represented by the formula SnO _x (where x is a positive real number) oxides of tin such as WO ₃ and WO ₂ ; oxides of tungsten represented by the general formula WO _x (where x is a positive real number); lithium and titanium such as Li ₄ Ti ₅ O ₁₂ and LiVO ₂ or a composite metal oxide containing vanadium;

Sulfides that can be used as negative electrode active materials include titanium sulfides represented by the formula TiS _x (where x is a positive real number) such as Ti ₂ S ₃ , TiS ₂ and TiS; V ₃ S ₄ and VS. _2, Vanadium sulfide represented by _the formula VS _x (where x is a positive real number) _such as _{VS ;} Molybdenum sulfide represented by the formula MoS _x (where x is a positive real number) such as Mo ₂ S ₃ and MoS ₂ ; SnS _{2 and} SnS etc. Formula SnS _x (where, sulfides of tin represented by the formula _{WS x} (where x is a positive real number); sulfides _of tungsten represented by the formula WS _x (where x is a positive real number) _; selenium sulfide represented _by the formula SeS _x (where x is a positive real number), such as _Se5S3 , _SeS2 , SeS, etc.; can be mentioned.

Nitrides that can be used as negative electrode active materials include Li ₃ N and Li _3-x A _x N (where A is either one or both of Ni and Co, and 0<x<3). Lithium-containing nitrides such as

These carbon materials, oxides, sulfides and nitrides may be used alone or in combination of two or more. Moreover, these carbon materials, oxides, sulfides and nitrides may be either crystalline or amorphous.

Metals that can be used as the negative electrode active material include lithium metal, silicon metal, and tin metal.

Alloys that can be used as negative electrode active materials include lithium alloys such as Li—Al, Li—Ni, Li—Si, Li—Sn, and Li—Sn—Ni; silicon alloys such as Si—Zn; - tin alloys such as Co, Sn-Ni, Sn-Cu, Sn-La; alloys such as Cu ₂ Sb, La ₃ Ni ₂ Sn ₇ ;

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. Binders may include thermoplastic resins, specifically PVdF, thermoplastic polyimides, carboxymethyl cellulose, polyethylene and polypropylene.

(Negative electrode current collector)
Examples of the negative electrode current collector of the negative electrode include a band-shaped member made of a metal material such as Cu, Ni, or stainless steel. Among them, it is preferable to use Cu as a forming material and process it into a thin film because it is difficult to form an alloy with lithium and is easy to process.

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 or the like is applied to the negative electrode current collector, dried and then pressed. A method of crimping can be mentioned.

(separator)
The separator of the lithium secondary battery of the present embodiment may be in the form of a porous film, nonwoven fabric, or woven fabric made of a material such as a polyolefin resin such as polyethylene or polypropylene, a fluororesin, or a nitrogen-containing aromatic polymer. 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.

In the present embodiment, the separator has a permeation resistance of 50 seconds/100 cc or more and 300 seconds/100 cc according to the Gurley method defined in JIS P 8117 in order to allow the electrolyte to pass through the separator well when the battery is used (during charging and discharging). It is preferably 50 seconds/100 cc or more and 200 seconds/100 cc or less.

The porosity of the separator is preferably 30% by volume or more and 80% by volume or less, more preferably 40% by volume or more and 70% by volume or less. The separator may be a laminate of separators with different porosities.

(Electrolyte)
The electrolytic solution of the lithium secondary battery of this embodiment contains an electrolyte and an organic solvent.

Electrolytes contained in the electrolytic solution include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN ( _{SO2CF3 )} ( _COCF3 ) _, Li( _C4F9SO3 ), _LiC ( _{SO2CF3 ) 3} , _Li2B10Cl10 , LiBOB (where _BOB is _bis (oxalato)borate ), LiFSI (where FSI is bis(fluorosulfonyl)imide), lower aliphatic carboxylic acid lithium salts, _LiAlCl4 and other lithium salts, and mixtures of two or more thereof may be used. Among them, the electrolyte is at least selected from the group consisting of LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(SO ₂ CF ₃ ) ₂ and LiC(SO ₂ CF ₃ ) ₃ containing fluorine. It is preferred to use one containing one.

Examples of the organic solvent contained in the electrolytic solution include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, 1,2-di (Methoxycarbonyloxy) carbonates such as ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropylmethyl ether, 2,2,3,3-tetrafluoropropyldifluoromethyl ether, tetrahydrofuran, 2- ethers such as methyltetrahydrofuran; esters such as methyl formate, methyl acetate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; - Carbamates such as 2-oxazolidone; Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide, 1,3-propanesultone, or those obtained by further introducing a fluoro group into these organic solvents (one of the hydrogen atoms of the organic solvent above substituted with a fluorine atom) 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. A mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferable as the mixed solvent of the cyclic carbonate and the non-cyclic carbonate. The electrolyte using such a mixed solvent has a wide operating temperature range, does not easily deteriorate even when charging and discharging at a high current rate, does not easily deteriorate even after long-term use, and uses natural graphite as an active material for the negative electrode. , and has many features of being resistant to decomposition even when graphite materials such as artificial graphite are used.

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. Mixed solvents containing fluorine-substituted ethers such as pentafluoropropylmethyl ether and 2,2,3,3-tetrafluoropropyldifluoromethyl ether and dimethyl carbonate do not retain their capacity even when charged and discharged at a high current rate. It is more preferable because of its high retention rate.

A solid electrolyte may be used in place of the above electrolytic solution. Examples of solid electrolytes that can be used include organic polymer electrolytes such as polyethylene oxide polymer compounds and polymer compounds containing at least one 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. Li ₂ S—SiS ₂ , Li ₂ S—GeS ₂ , Li ₂ SP ₂ S ₅ , Li ₂ S—B ₂ S ₃ , Li ₂ S—SiS ₂ —Li ₃ PO ₄ , Li ₂ S—SiS Inorganic solid electrolytes containing sulfides such as ₂ - _{Li 2} SO ₄ and Li ₂ S--GeS ₂ --P ₂ S ₅ may be mentioned, and mixtures of two or more of these may be used. By using these solid electrolytes, the safety of the lithium secondary battery can sometimes be improved.

Moreover, in the lithium secondary battery of the present embodiment, when a solid electrolyte is used, the solid electrolyte may serve as a separator, in which case the separator may not be required.

EXAMPLES Next, the present invention will be described in more detail by way of examples.

<Composition analysis>
The composition analysis of the lithium metal composite oxide powder produced by the method described below was performed by dissolving the obtained lithium composite metal compound powder in hydrochloric acid and then using an inductively coupled plasma emission spectrometer (manufactured by SII Nanotechnology Co., Ltd. , SPS3000).

<BET specific surface area measurement>
After drying 1 g of the lithium metal composite oxide powder at 105° C. for 30 minutes in a nitrogen atmosphere, it was measured using Macsorb (registered trademark) manufactured by Mountech (unit: m ² /g).

<Measurement of average particle diameter _D50 >
0.1 g of lithium metal composite oxide powder was put into 50 ml of 0.2% by mass sodium hexametaphosphate aqueous solution to obtain a dispersion liquid in which the powder was dispersed. Next, the particle size distribution of the resulting dispersion was measured using a Microtrac MT3300EXII (laser diffraction scattering particle size distribution analyzer) manufactured by Microtrac Bell Co., Ltd. to obtain a volume-based cumulative particle size distribution curve. Then, in the obtained cumulative particle size distribution curve, when the whole is 100%, the value of the particle diameter at the point where the cumulative volume from the fine particle side becomes 50% is defined as the 50% cumulative volume particle size D ₅₀ (μm). asked.

<Measurement of average particle size of single particles and secondary particles>
The lithium metal composite oxide powder was placed on a conductive sheet pasted on a sample stage, and an electron beam was irradiated at an acceleration voltage of 20 kV using JSM-5510 manufactured by JEOL Ltd. for SEM observation. When the lithium composite metal oxide powder was placed on the conductive sheet, the amount of powder placed on the conductive sheet was adjusted so that independent particles were not observed overlapping each other. 50 single particles or secondary particles are arbitrarily extracted from the image (SEM photograph) obtained by SEM observation, and for each single particle or secondary particle, a parallel line drawn from a certain direction sandwiches the projected image. The distance between lines (unidirectional diameter) was measured as the particle size of single particles or secondary particles.
The arithmetic average value of the particle sizes of the obtained single particles or secondary particles was taken as the average single particle size or average secondary particle size of the lithium metal composite oxide powder.

<Measurement of circularity>
The SEM surface image is taken into a computer, and using image analysis software Image J, binarization processing is performed at the intermediate value between the maximum luminance and the minimum luminance in the SEM image, and the lithium composite metal oxide powder, that is, single particles or A binarized image was obtained by converting the secondary particles to black and the portions other than the single particles or secondary particles to white. Circularity was measured for each of the black portions corresponding to the single particles or secondary particles in the binarized image.

[Method for measuring the number of peaks in circularity distribution]
In the circularity distribution with the circularity of each particle obtained by the above method on the horizontal axis and the number of particles on the vertical axis, the circularity is between 0 and 1.0 at equal intervals every 0.05. When the data range of 20 divisions was set to , the number of points (peaks) where the number of particles changed from an increase to a decrease was measured from the low circularity side to the high circularity side.

[Calculation of average circularity]
The average circularity was calculated as follows.
Average circularity of lithium composite metal oxide powder = sum of observed circularity of all particles/number of all observed particles

[Calculation of Circularity of First and Second Peaks] The average circularity of single particles or secondary particles was calculated as follows.
Average Circularity of Single Particles = Sum of Observed Circularities of Single Particles/Number of Observed Single Particles Average Circularity of Secondary Particles = Sum of Observed Circularities of Secondary Particles/Number of Observed Secondary Particles Alternatively, the average circularity of the secondary particles is calculated, and the peaks derived from particles with a low average circularity are called the first peak and the second peak. When there are two or more peaks, they are called third and fourth peaks.

<Calculation of circularity distribution standard deviation>
A circularity distribution standard deviation was calculated from the circularity distribution. Specifically, it was calculated as follows.

In the formula below, n is the total number of data and means the number of particles. The average value x ⁻ means the average circularity. x _i means the circularity of each particle.

[Production of lithium secondary battery]
・Preparation of positive electrode for lithium secondary battery A positive electrode active material for a lithium secondary battery, a conductive material (acetylene black), and a binder (PVdF) obtained by the manufacturing method described later are combined into a positive electrode active material for a lithium secondary battery: conductive material. : Binder = 92:5:3 (mass ratio), and kneaded to prepare a pasty positive electrode mixture. N-methyl-2-pyrrolidone was used as an organic solvent when preparing the positive electrode mixture.

The resulting positive electrode mixture was applied to an Al foil having a thickness of 40 μm as a current collector, dried at 60° C. for 3 hours, pressed at a linear pressure of 200 kN/m, and vacuum-dried at 150° C. for 8 hours. Thus, a positive electrode for a lithium secondary battery was obtained. The electrode area of this positive electrode for a lithium secondary battery was 1.65 cm ² . Moreover, the mass of the obtained positive electrode for lithium secondary batteries was measured, and the density of the positive electrode mixture layer (positive electrode density) was calculated.

- Production of lithium secondary battery (coin-shaped cell) The following operations were performed in a glove box in a dry air atmosphere.
Place the positive electrode prepared in "Preparation of positive electrode for lithium secondary battery" on the lower lid of coin cell (manufactured by Hosen Co., Ltd.) for coin battery R2032 with the aluminum foil side facing down, and then place the laminated film separator on top of it. (A heat-resistant porous layer was laminated (thickness: 16 µm) on a polyethylene porous film). 300 μL of electrolytic solution was injected here. The electrolytic solution used was prepared by dissolving LiPF ₆ to 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 top lid is placed through a gasket, and the lithium secondary battery (coin type battery R2032. (sometimes referred to as "battery").

・Charging and discharging test [measurement of initial volume capacity density and 50 cycle volume capacity density retention rate]
Using the coin-shaped battery produced in "Production of lithium secondary battery (coin-shaped cell)", the initial volume capacity density and the 50-cycle volume capacity density retention rate were evaluated in a 50-cycle test under the conditions shown below. Then, the volume capacity density retention rate after 50 times was calculated by the following formula. It should be noted that the higher the volume capacity density retention ratio after 50 cycles, the better the life characteristics of the battery.
Initial volume capacity density (mAh/cc) = 1st discharge capacity x positive electrode density Volume capacity density after 50 times (mAh/cc) = 50th discharge capacity x positive electrode density Volume capacity density retention rate after 50 times (% ) = volumetric capacity density after 50 times/initial volumetric capacity density × 100
Hereinafter, the volume capacity density retention rate after 50 cycles may be referred to as "cycle retention rate".

[Cycle test conditions]
Test temperature: 25°C
Charging conditions: maximum voltage during charging 4.3 V, charging time 6.0 hours, charging current 0.2 CA Pause time after charging: 10 minutes Discharging conditions: minimum voltage during discharging 2.5 V, discharging time 6.0 hours, Discharge current 0.2CA Post-discharge rest time: 10 minutes In this test, the step of sequentially performing charging, charging rest, discharging, and discharging rest was counted as one step.

≪Measurement of initial volume capacity density≫
The initial volume capacity density was measured by the following method.
A lithium secondary battery (coin-type cell) was produced using the positive electrode active material obtained by the method described below. For the positive electrode, a positive electrode active material, a conductive material (acetylene black), and a binder (PVdF) obtained by the method described later are combined into a positive electrode active material for a lithium secondary battery: conductive material: binder = 92: 5: 3 (mass ratio ) were added and kneaded to prepare a pasty positive electrode mixture.

<<Example 1>>
1. Production of Positive Electrode Active Material A1 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 kept at 55°C.

An aqueous nickel sulfate solution, an aqueous cobalt sulfate solution, an aqueous manganese sulfate solution, and an aqueous aluminum sulfate solution were prepared so that the atomic ratio of nickel atoms, cobalt atoms, manganese atoms, and aluminum atoms was 0.90:0.07:0.02:0.01. Mixed raw material liquid 1 was prepared by mixing as follows.

Next, this mixed raw material solution and an aqueous solution of ammonium sulfate were continuously added as a complexing agent into the reactor with stirring. An aqueous sodium hydroxide solution is added dropwise so that the pH of the solution in the reaction tank becomes 12.4 to obtain nickel-cobalt-manganese-aluminum composite hydroxide particles. , was isolated and dried at 105°C to obtain nickel-cobalt-manganese-aluminum composite hydroxide 1.

Nickel-cobalt-manganese-aluminum composite hydroxide particles 1, lithium hydroxide monohydrate powder, and potassium sulfate powder were mixed with Li/(Ni+Co+Mn+Al)=1.10, K ₂ SO ₄ /(LiOH+K ₂ SO ₄ )=0.1. (mol/mol), and then fired at 840° C. for 10 hours in an oxygen atmosphere to obtain a lithium metal composite oxide powder. The powder and pure water adjusted to a liquid temperature of 5 ° C. are mixed so that the ratio of the powder mass to the total amount is 0.3, and the prepared slurry is stirred for 20 minutes and then dehydrated. Furthermore, after rinsing with pure water having a liquid temperature adjusted to 5° C., the mass of which is twice the mass of the powder, the powder was isolated and dried at 150° C. to obtain a positive electrode active material A1.

2. Production of Positive Electrode Active Material B1 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 kept at 50°C.

Next, this mixed raw material solution 1 and an aqueous solution of ammonium sulfate were continuously added as a complexing agent into the reactor with stirring. An aqueous solution of sodium hydroxide is added dropwise at appropriate times so that the pH of the solution in the reaction tank becomes 11.9 to obtain nickel-cobalt-manganese-aluminum composite hydroxide particles. , was isolated and dried at 105°C to obtain nickel-cobalt-manganese-aluminum composite hydroxide 2.

Nickel-cobalt-manganese-aluminum composite hydroxide particles 2 and lithium hydroxide monohydrate powder were weighed and mixed so that Li/(Ni+Co+Mn+Al)=1.03, and then mixed at 760° C. for 10 hours in an oxygen atmosphere. It was calcined to obtain a positive electrode active material B1.

3. Production of Positive Electrode Active Material C1 The positive electrode active material A1 and the positive electrode active material B1 were weighed and mixed in a mass ratio of 20:80 to obtain a positive electrode active material C1.

4. Evaluation of Positive Electrode Active Material C1 Table 2 shows the analysis results of the positive electrode active material C1, and the measurement results of the volume capacity density and the 50-cycle volume capacity density retention rate.

<<Example 2>>
1. Production of Positive Electrode Active Material A2 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 kept at 55°C.

A nickel sulfate aqueous solution, a cobalt sulfate aqueous solution, and a manganese sulfate aqueous solution are mixed so that the atomic ratio of nickel atoms, cobalt atoms, and manganese atoms is 0.88:0.08:0.04, and a mixed raw material solution 2 is obtained. prepared.

Next, this mixed raw material solution ammonium aqueous solution was continuously added as a complexing agent into the reaction tank while stirring. An aqueous solution of sodium hydroxide is added dropwise at appropriate times so that the pH of the solution in the reaction tank becomes 11.8 to obtain nickel-cobalt-manganese-aluminum composite hydroxide particles. , was isolated and dried at 105° C. to obtain nickel-cobalt-manganese composite hydroxide 1.

Nickel-cobalt-manganese composite hydroxide particles 1, lithium hydroxide monohydrate powder and potassium sulfate powder were mixed with Li/(Ni+Co+Mn)=1.10, K ₂ SO ₄ /(LiOH+K ₂ SO ₄ )=0.1 ( mol/mol), and then fired at 840° C. for 10 hours in an oxygen atmosphere to obtain a lithium metal composite oxide powder. The powder and pure water adjusted to a liquid temperature of 5 ° C. are mixed so that the ratio of the powder mass to the total amount is 0.3, and the prepared slurry is stirred for 20 minutes and then dehydrated. Furthermore, after rinsing with pure water having a liquid temperature adjusted to 5° C., the mass of which is twice the mass of the powder, the powder was isolated and dried at 150° C. to obtain a positive electrode active material A2.

2. Production of Positive Electrode Active Material B2 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 45°C.

Next, this mixed raw material solution 2 and an aqueous solution of ammonium sulfate were continuously added as a complexing agent into the reactor with stirring. An aqueous solution of sodium hydroxide is added dropwise at appropriate times so that the pH of the solution in the reaction tank becomes 11.5 to obtain nickel-cobalt-manganese-aluminum composite hydroxide particles. , was isolated and dried at 105°C to obtain nickel-cobalt-manganese composite hydroxide 2.

Nickel-cobalt-manganese composite hydroxide particles 2 and lithium hydroxide monohydrate powder are weighed and mixed so that Li/(Ni + Co + Mn) = 1.03, and then fired at 790 ° C. for 10 hours in an oxygen atmosphere. Then, a positive electrode active material B2 was obtained.

3. Production of Positive Electrode Active Material C2 The positive electrode active material A2 and the positive electrode active material B2 were weighed and mixed so as to have a mass ratio of 20:80 to obtain a positive electrode active material C2.

4. Evaluation of Positive Electrode Active Material C2 Table 2 shows the analysis results of the positive electrode active material C2, and the measurement results of the volume capacity density and the 50-cycle volume capacity density retention rate.

<<Example 3>>
1. Production of positive electrode active material A3 Nickel-cobalt-manganese composite hydroxide particles 1, lithium hydroxide monohydrate powder, and potassium sulfate powder were mixed with Li/(Ni+Co+Mn)=1.15, K ₂ SO ₄ /(LiOH+K ₂ SO ₄ )=0.1 (mol/mol), and then fired at 840° C. for 10 hours in an oxygen atmosphere to obtain a lithium metal composite oxide powder. The powder and pure water adjusted to a liquid temperature of 5 ° C. are mixed so that the ratio of the powder mass to the total amount is 0.3, and the prepared slurry is stirred for 20 minutes and then dehydrated. Furthermore, after rinsing with pure water having a liquid temperature adjusted to 5° C., the mass of which is twice the mass of the powder, the powder was isolated and dried at 150° C. to obtain a positive electrode active material A3.

3. Production of Positive Electrode Active Material C3 The positive electrode active material A3 and the positive electrode active material B2 were weighed and mixed at a mass ratio of 25:75 to obtain a positive electrode active material C3.

4. Evaluation of Positive Electrode Active Material C3 Table 2 shows the analysis results of the positive electrode active material C3, and the measurement results of the volume capacity density and the 50-cycle volume capacity density retention rate.

<<Comparative Example 1>>
1. Production of Positive Electrode Active Material B3 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.

Next, this mixed raw material solution 2 and an aqueous solution of ammonium sulfate were continuously added as a complexing agent into the reactor with stirring. An aqueous sodium hydroxide solution is added dropwise so that the pH of the solution in the reaction tank becomes 12.5 to obtain nickel-cobalt-manganese-aluminum composite hydroxide particles, which are washed, dehydrated in a centrifuge, washed, and dehydrated. , was isolated and dried at 105°C to obtain nickel-cobalt-manganese composite hydroxide 3.

Nickel-cobalt-manganese composite hydroxide particles 3 and lithium hydroxide monohydrate powder are weighed and mixed so that Li/(Ni + Co + Mn) = 1.05, and then fired at 760 ° C. for 10 hours in an oxygen atmosphere. Then, a positive electrode active material B3 was obtained.

2. Evaluation of Positive Electrode Active Material B3 Table 2 shows the analysis results of the positive electrode active material B3, and the measurement results of the volume capacity density and the 50-cycle volume capacity density retention rate.

<<Comparative Example 2>>
1. Manufacture of Positive Electrode Active Material C4 The positive electrode active material B2 and the positive electrode active material B3 were weighed and mixed so as to have a mass ratio of 80:20 to obtain a positive electrode active material C4.
2. Evaluation of Positive Electrode Active Material C4 Table 2 shows the analysis results of the positive electrode active material C4, and the measurement results of the volume capacity density and the 50-cycle volume capacity density retention rate.

<<Comparative Example 3>>
1. Evaluation of Positive Electrode Active Material B2 Table 1 shows the analysis results of the positive electrode active material B2, and the measurement results of the volume capacity density and the 50-cycle volume capacity density retention rate.

<<Comparative Example 4>>
1. Evaluation of Positive Electrode Active Material A3 Table 2 shows the analysis results of the positive electrode active material A3, and the measurement results of the volume capacity density and the 50-cycle volume capacity density retention rate.

Table 1 summarizes the composition, BET specific surface area, D ₅₀ , number of circularity distribution peaks, and average circularity.
Table 2 shows the first peak circularity, second peak circularity, circularity distribution standard deviation, particles derived from the first peak, particles derived from the second peak, single particle average particle size, electrode density, initial The volumetric capacity density and the 50-cycle volumetric capacity density retention ratio are described together.

As shown in the above results, it was confirmed that the positive electrode active materials of Examples 1 to 3 to which the present invention was applied had high volumetric capacity densities and high 50-cycle volumetric capacity density retention rates.

DESCRIPTION OF SYMBOLS 1... Separator, 2... Positive electrode, 3... Negative electrode, 4... Electrode group, 5... Battery can, 6... Electrolytic solution, 7... Top insulator, 8... Sealing body, 10... Lithium secondary battery, 21... Positive electrode lead, 31 …negative lead

Claims (7)

Step 1 of obtaining a first lithium metal composite oxide powder;
Step 2 of obtaining a second lithium metal composite oxide powder;
mixing the first lithium metal composite oxide powder and the second lithium metal composite oxide powder so that the mixing ratio (mass ratio) is 1 to 60/99 to 40; A method for producing a lithium metal composite oxide powder represented by the following compositional formula (1) ,
The step 1 is
A step of obtaining a first metal composite compound, and a step of mixing the obtained first metal composite compound, a lithium compound, and an inert melting agent , and firing at a holding temperature A of 200° C. or higher and 1150° C. or lower. ,
The step of obtaining the first metal complex compound includes the step of supplying an aqueous solution of a metal salt containing at least nickel, an alkali metal hydroxide, and a complexing agent to a first coprecipitation tank; Adjusting the temperature of the tank to 30 ° C. or higher and 80 ° C. or lower, and adjusting the pH value in the first coprecipitation tank to 10 or higher and 13 or lower,
The step 2 is
A step of obtaining a second metal composite compound, a step of mixing the obtained second metal composite compound and a lithium compound, and firing at a holding temperature B of 200 ° C. or higher and 1150 ° C. or lower,
The step of obtaining the second metal complex compound includes the step of supplying an aqueous solution of a metal salt containing at least nickel, an alkali metal hydroxide, and a complexing agent to a second coprecipitation tank; Adjusting the temperature of the tank to 30 ° C. or higher and 80 ° C. or lower and adjusting the pH value in the second coprecipitation tank to 10 or higher and 13 or lower,
The pH of the first co-precipitation tank is higher than the pH of the second co-precipitation tank,
A method for producing a lithium metal composite oxide powder, wherein the holding temperature A is higher than the holding temperature B by 30° C. or more.
Li[Li _x (Ni _(1-yzw) Co _y Mn _z M _w ) _1-x ]O ₂ (1)
(where M is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga and V; -0. satisfy 1≦x≦0.2, 0<y≦0.4, 0≦z≦0.4, and 0≦w≦0.1.) 2. The method for producing a lithium metal composite oxide powder according to claim 1, wherein said first co-precipitation tank and said second co-precipitation tank are co-precipitation tanks equipped with a stirrer and an overflow pipe. 3. The method for producing a lithium metal composite oxide powder according to claim 1 , wherein said complexing agent is an aqueous solution of ammonium sulfate. The method for producing a lithium metal composite oxide powder according to any one of claims 1 to 3 , wherein step 1 includes a step of washing with water after firing. 5. The method for producing a lithium metal composite oxide powder according to claim 4 , wherein said washing step includes a step of washing twice or more. A step of obtaining a lithium metal composite oxide powder by the method for producing a lithium metal composite oxide powder according to any one of claims 1 to 5 , and manufacturing a positive electrode using the obtained lithium metal composite oxide powder. A method for manufacturing a positive electrode for a lithium secondary battery, comprising the step of: A step of obtaining a positive electrode for a lithium secondary battery by the method for producing a positive electrode for a lithium secondary battery according to claim 6 ; and a step of producing a lithium secondary battery using the obtained positive electrode for a lithium secondary battery. A method for manufacturing a lithium secondary battery, comprising:

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