WO2018105481A1 - Method for producing positive electrode active material for lithium secondary batteries - Google Patents

Abstract

This method for producing a positive electrode active material for lithium secondary batteries produces a positive electrode active material for lithium secondary batteries, which contains a lithium composite metal compound. This method comprises: a spray mixing step which includes heating of a composite metal compound powder that contains nickel, cobalt and manganese, the production of a mixed powder by spraying an alkaline solution, in which a tungsten compound is dissolved, onto the composite metal compound powder, thereby mixing the composite metal compound powder with the tungsten compound, and subsequent cooling of the mixed powder; and a step wherein a lithium salt and the mixed powder are mixed with each other and then fired, thereby producing a lithium composite metal compound.

Description

Method for producing positive electrode active material for lithium secondary battery

The present invention relates to a method for producing a positive electrode active material for a lithium secondary battery.
This application claims priority based on Japanese Patent Application No. 2016-237694 filed in Japan on December 7, 2016, the contents of which are incorporated herein by reference.

The lithium composite oxide is used as a positive electrode active material for a lithium secondary battery. Lithium secondary batteries have already been put into practical use not only for small power sources for mobile phones and notebook computers, but also for medium and large power sources for automobiles and power storage.

In order to improve the performance of the lithium secondary battery such as battery capacity, a lithium composite metal compound containing lithium, nickel, cobalt, and manganese is used as the positive electrode active material for the lithium secondary battery. Furthermore, in order to achieve low battery resistance and long life, it is useful to contain tungsten in the positive electrode active material for a lithium secondary battery. For example, Patent Document 1 describes a technique of adding an alkaline solution in which a tungsten compound is dissolved after primary firing of a lithium composite metal compound. Patent Document 2 describes a method of dry-adding tungsten oxide to a precursor of a lithium composite metal compound. Patent Document 3 describes a method of preparing a slurry solution containing a precursor of a lithium composite metal compound and tungsten oxide and spray drying the slurry solution.

JP 2012-79464 A JP 2014-197556 A JP 2011-228292 A

In order to achieve low battery resistance and long life, it is useful to include tungsten in the positive electrode active material for a lithium secondary battery. However, the methods described in Patent Documents 1 to 3 have a problem in that when tungsten is added, the tungsten aggregates and segregates, resulting in a foreign substance derived from tungsten.
This invention is made | formed in view of the said situation, Comprising: It aims at providing the manufacturing method of the positive electrode active material for lithium secondary batteries by which segregation of tungsten was suppressed.

That is, the present invention includes the following [1] to [6].
[1] A method for producing a positive electrode active material for a lithium secondary battery containing a lithium composite metal compound, comprising heating a composite metal compound powder containing nickel, cobalt and manganese, and an alkaline solution in which a tungsten compound is dissolved Spraying the composite metal compound powder to produce a mixed powder by mixing the composite metal compound powder and the tungsten compound, and then cooling the mixed powder; and a lithium salt; And a step of mixing the mixed powder and firing to produce a lithium composite metal compound, and a method for producing a positive electrode active material for a lithium secondary battery.
[2] The method for producing a positive electrode active material for a lithium secondary battery according to [1], wherein the lithium composite metal compound is represented by the following composition formula (I).
Li [Lix (Ni (1-yzw) CoyMnzMw) 1-x] O ₂ (I)
(In the composition formula (I), −0.1 ≦ x ≦ 0.2, 0 <y ≦ 0.5, 0 <z ≦ 0.8, 0 ≦ w ≦ 0.1, y + z + w <1, M is Fe , Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, and V represent one or more metals selected from the group.
[3] The lithium secondary battery according to [1] or [2], wherein the content of tungsten contained in the positive electrode active material for a lithium secondary battery is 1.0 mol% or less with respect to the total molar amount of the transition metal. A method for producing a positive electrode active material.
[4] The method for producing a positive electrode active material for a lithium secondary battery according to any one of [1] to [3], wherein in the spray mixing step, the tungsten compound is tungsten oxide.
[5] The method for producing a positive electrode active material for a lithium secondary battery according to any one of [1] to [4], wherein in the spray mixing step, the alkaline solution contains lithium hydroxide.
[6] The positive electrode for a lithium secondary battery according to any one of [1] to [5], wherein the temperature of the composite metal compound powder when spraying the alkaline solution in the spray mixing step is 100 ° C. or higher. A method for producing an active material.

According to the present invention, it is possible to provide a method for producing a positive electrode active material for a lithium secondary battery in which segregation of tungsten is suppressed.

It is a schematic block diagram which shows an example of a lithium ion secondary battery. It is a schematic block diagram which shows an example of a lithium ion secondary battery. It is a SEM image of the mixed powder after the dry mixing of the comparative example 2. It is a SEM image of the mixed powder after spray mixing of Example 3.

<Method for producing positive electrode active material for lithium secondary battery>
The method for producing a positive electrode active material for a lithium secondary battery according to the present embodiment includes heating a composite metal compound powder containing nickel, cobalt, and manganese, and converting the alkaline solution in which the tungsten compound is dissolved into the composite metal compound powder. Spraying and mixing the composite metal compound powder and the tungsten compound to produce a mixed powder, and thereafter cooling the mixed powder; a lithium salt; and the mixture powder. Mixing and firing to produce a lithium composite metal compound.
In the method for producing a positive electrode active material for a lithium secondary battery, first, a metal other than lithium, that is, an essential metal composed of Ni, Co, and Mn, and Fe, Cr, Cu, Ti, B, Mg, Al , W, Mo, Nb, Zn, Sn, Zr, Ga, and V, it is preferable to prepare a composite metal compound containing any one or more arbitrary metals, and to fire the composite metal compound with an appropriate lithium salt . The composite metal compound is preferably a composite metal hydroxide or a composite metal oxide.
In more detail, the manufacturing method of the positive electrode active material for lithium secondary batteries of this embodiment is equipped with the manufacturing process of the composite metal compound which has the said spray mixing process, and the manufacturing process of lithium metal complex oxide.
Hereinafter, each process of the manufacturing method of the positive electrode active material for lithium secondary batteries of this embodiment is demonstrated.

[Production process of composite metal compound]
The manufacturing process of the composite metal compound includes metals other than lithium, that is, essential metals composed of Ni, Co, and Mn, and Fe, Cr, Cu, Ti, B, Mg, Al, W, Mo, Nb, Zn , Sn, Zr, Ga and V, a step of preparing a composite metal compound containing any one or more arbitrary metals.

The composite metal compound can be produced by a generally known batch coprecipitation method or continuous coprecipitation method. Hereinafter, the manufacturing method will be described in detail by taking a composite metal hydroxide containing nickel, cobalt and manganese as an example.

First, a nickel salt solution, a cobalt salt solution, a manganese salt solution, and a complexing agent are reacted by a coprecipitation method, in particular, a continuous method described in JP-A-2002-201028, and Ni _x Co _y Mn _z (OH) ₂ A composite metal hydroxide represented by the formula (where x + y + z = 1) is produced.

Although it does not specifically limit as nickel salt which is the solute of the said nickel salt solution, For example, any one of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate can be used. As the cobalt salt that is a solute of the cobalt salt solution, for example, any one of cobalt sulfate, cobalt nitrate, and cobalt chloride can be used. As the manganese salt that is a solute of the manganese salt solution, for example, any one of manganese sulfate, manganese nitrate, and manganese chloride can be used. The above metal salt is used in a proportion corresponding to the composition ratio of Ni _x Co _y Mn _z (OH) ₂ . That is, the amount of each metal salt is defined so that the molar ratio of nickel, cobalt, and manganese in the mixed solution containing the metal salt is x: y: z. Moreover, water is used as a solvent.

The complexing agent is capable of forming a complex with nickel, cobalt, and manganese ions in an aqueous solution. For example, an ammonium ion supplier (ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc.), hydrazine, Examples include ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracil diacetic acid, and glycine.

The complexing agent may not be contained. 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 manganese salt solution and the complexing agent is, for example, The molar ratio with respect to the total number of moles of the metal salt is greater than 0 and 2.0 or less.

During the precipitation, an alkali metal hydroxide (for example, sodium hydroxide or potassium hydroxide) is added if necessary to adjust the pH value of the aqueous solution.

When the complexing agent is continuously supplied to the reaction vessel in addition to the nickel salt solution, the cobalt salt solution, and the manganese salt solution, nickel, cobalt, and manganese react to form Ni _x Co _y Mn _z (OH) _2. Is manufactured. During the reaction, the temperature of the reaction vessel is controlled within a range of, for example, 20 ° C. to 80 ° C., preferably 30 to 70 ° C. The pH value in the reaction vessel (when measured at 40 ° C.) is controlled, for example, within the range of pH 9 to pH 13, preferably pH 11-13. The substance in the reaction vessel is appropriately stirred.

The inside of the reaction tank may be an inert atmosphere. When the inert atmosphere is used, it is possible to suppress aggregation of elements that are more easily oxidized than nickel and to obtain a uniform composite metal hydroxide.

Also, the inside of the reaction vessel may be in an appropriate oxygen-containing atmosphere or in the presence of an oxidizing agent while maintaining an inert atmosphere. By moderately oxidizing the transition metal, the form of the composite metal hydroxide is controlled, and the size and dispersion of the voids inside the secondary particles in the positive electrode material produced using the composite metal hydroxide are controlled. It becomes possible. At this time, the oxygen and the oxidizing agent in the oxygen-containing gas need only have sufficient oxygen atoms to oxidize the transition metal. By introducing appropriate oxygen atoms into the reaction tank, an inert atmosphere in the reaction tank can be maintained.

In order to create an oxygen-containing atmosphere in the reaction tank, an oxygen-containing gas may be introduced into the reaction tank. The oxygen concentration (volume%) with respect to the volume of the oxygen-containing gas in the oxygen-containing gas is preferably 1 or more and 15 or less. In order to improve the uniformity of the solution in the reaction vessel, an oxygen-containing gas may be bubbled. Examples of the oxygen-containing gas include oxygen gas, air, or a mixed gas of these and an oxygen-free gas such as nitrogen gas. From the viewpoint of easy adjustment of the oxygen concentration in the oxygen-containing gas, a mixed gas is preferable among the above.

In order to bring the inside of the reaction vessel into the presence of an oxidizing agent, an oxidizing agent may be added to the reaction vessel. Examples of the oxidizing agent include hydrogen peroxide, chlorate, hypochlorite, perchlorate, and permanganate. Hydrogen peroxide is preferably used from the viewpoint of hardly bringing impurities into the reaction system.

After the above reaction, the obtained reaction precipitate is washed with water and then dried to isolate nickel cobalt manganese hydroxide as a composite metal compound containing nickel, cobalt and manganese. Moreover, you may wash | clean with the weak acid water and the alkaline solution containing sodium hydroxide and potassium hydroxide as needed. In the above example, nickel cobalt manganese composite hydroxide is manufactured, but nickel cobalt manganese composite oxide may be prepared. In preparing the nickel cobalt manganese composite oxide, for example, a step of bringing the coprecipitate slurry into contact with an oxidizing agent or a step of heat treating the nickel cobalt manganese composite hydroxide may be performed.

The BET specific surface area of the obtained composite metal compound powder containing nickel, cobalt, and manganese is preferably 15 to 90 m ² / g, and the average particle size is preferably 2.0 to 15 μm.
Here, the BET specific surface area was determined by drying 1 g of a composite metal compound powder containing nickel, cobalt, and manganese in a nitrogen atmosphere at 105 ° C. for 30 minutes, and then a BET specific surface area meter (Macsorb (registered trademark) manufactured by Mountec). It is the value measured using.
The average particle diameter is a value measured by the following method. Using a laser diffraction particle size distribution analyzer (LA-950, manufactured by HORIBA, Ltd.), 0.1 g of a composite metal compound powder containing nickel, cobalt, and manganese was put into 50 ml of a 0.2 mass% sodium hexametaphosphate aqueous solution, A dispersion in which the powder is dispersed is obtained. The particle size distribution of the obtained dispersion is measured to obtain a volume-based cumulative particle size distribution curve. In the obtained cumulative particle size distribution curve, the value of the particle diameter (D ₅₀ ) viewed from the fine particle side when 50% is accumulated is defined as the average particle diameter of the composite metal compound containing nickel, cobalt, and manganese.

-Spray mixing process In the spray mixing process, the composite metal compound powder containing nickel, cobalt, and manganese obtained in the above process is heated, and an alkali solution in which a tungsten compound is dissolved is sprayed on the composite metal compound powder, and the composite metal is sprayed. A compound powder and a tungsten compound are mixed to produce a mixed powder. Thereafter, the mixed powder is cooled.

In the spray mixing process, the tungsten compound is dissolved in an alkaline solution. The dissolution method is not particularly limited, and for example, a tungsten compound may be added and dissolved while stirring the solution using a reaction vessel equipped with a stirring device. From the viewpoint of suppressing the generation of tungsten-derived foreign matter, the tungsten compound is preferably completely dissolved in an alkaline solution and uniformly dispersed.

The foreign substance derived from tungsten in this specification is an aggregate of tungsten produced by segregation of the tungsten compound when the tungsten compound is added to the composite metal compound.

The concentration of the tungsten compound in the alkaline solution is preferably 0.5 to 15% by mass, and more preferably 2.0 to 6.0% by mass with respect to the total mass of the alkaline solution. If the concentration of the tungsten compound is 15% by mass or more, the tungsten compound may be left undissolved. When the concentration of the tungsten compound is 15% by mass or less, the tungsten compound can be completely dissolved in the alkaline solution and uniformly dispersed.

Next, the composite metal compound powder containing nickel, cobalt, and manganese obtained in the above step is heated, and an alkaline solution in which a tungsten compound is dissolved is sprayed on the composite metal compound powder, and the nickel, cobalt, and manganese are added. The mixed metal compound powder and the tungsten compound are mixed to produce a mixed powder. That is, while heating and stirring the composite metal compound powder containing nickel, cobalt, and manganese obtained in the above step, an alkaline solution in which a tungsten compound is dissolved is sprayed on the composite metal compound powder, and the nickel, cobalt, and A mixed powder is produced by mixing a composite metal compound powder containing manganese and a tungsten compound.
The composite metal compound powder is preferably heated to a temperature higher than the temperature at which the solvent of the alkaline solution evaporates. Specifically, the temperature at which the composite metal compound powder is heated is appropriately set according to the boiling point of the solvent of the alkaline solution contained in the alkaline solution and the spraying conditions of the alkaline solution.
More specifically, the lower limit of the temperature of the composite metal compound powder is preferably 100 ° C. or higher, and more preferably 105 ° C. or higher. The upper limit of the temperature of a composite metal compound powder is not specifically limited, For example, 150 degrees C or less, 130 degrees C or less, 120 degrees C or less is mentioned.
The upper limit value and the lower limit value can be arbitrarily combined. For example, the temperature of the composite metal compound powder is preferably 100 ° C. or higher and 150 ° C. or lower, and more preferably 105 ° C. or higher and 150 ° C. or lower.

In the spray mixing step, an alkaline solution in which a tungsten compound is dissolved is sprayed on the heated composite metal compound powder to mix the composite metal compound and the tungsten compound. The supply amount (L / min) at the time of spraying the alkaline solution, the discharge pressure (MPa), the nozzle diameter of the nozzle that discharges the alkaline solution, and the like are appropriately set depending on the specifications of the heating spray device used.
For example, the supply amount during spraying of the alkaline solution is 1.0 to 3.0 L / h, the discharge pressure is 0.05 MPa to 1.0 MPa, the nozzle diameter is 30 to 200 μm, and about 10 to 600 minutes. Spray mixing is preferred.
The temperature of the alkaline solution in the spraying process is preferably 20 to 90 ° C.

The tungsten compound used in the spray mixing step is not particularly limited as long as it is soluble in an alkaline solution, and tungsten oxide, ammonium tungstate, sodium tungstate, and lithium tungstate can be used. In the present embodiment, it is particularly preferable to use tungsten oxide.

In the spray mixing process, the above tungsten compound is dissolved in an alkaline solution and used. As the alkaline solute used in the alkaline solution, ammonia or lithium hydroxide can be used. In this embodiment, it is preferable to use lithium hydroxide. The solvent used in the alkaline solution may be any liquid that dissolves the solute, and includes water.

After spray mixing under the above conditions, the mixed powder is cooled to about room temperature (for example, 25 ° C.).

In the method for producing a positive electrode active material for a lithium secondary battery according to this embodiment, a composite metal compound that is a precursor of a positive electrode active material for a lithium secondary battery is heated, and an alkali solution in which a tungsten compound is dissolved is spray mixed. By this step, the alkaline solution adheres to the surface of the composite metal compound, and at the same time, the solvent of the alkaline solution evaporates instantly and can be mixed with the composite metal compound without aggregation of tungsten particles. For this reason, the positive electrode active material for lithium secondary batteries in which the generation of foreign substances derived from tungsten is suppressed can be produced.

[Process for producing lithium composite metal oxide]
A mixed powder of the composite metal compound and the tungsten compound (hereinafter referred to as “mixed powder”) is mixed with a lithium salt. As the lithium salt, any one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, lithium oxide, or a mixture of two or more can be used.

The lithium salt and the mixed powder are used in consideration of the composition ratio of the final target product. In the spray mixing step, when a lithium hydroxide aqueous solution is used as the alkaline solution, the amount of lithium charged (added amount) is the total amount of lithium in the lithium hydroxide used in the spray mixing step and the lithium salt. To do. For example, when nickel-cobalt-manganese composite hydroxide is used, the lithium salt and the mixed powder are used at a ratio corresponding to the composition ratio of LiNi _x Co _y Mn _z O ₂ (where x + y + z = 1).
The lithium salt and the mixed powder have a molar ratio (Li / Me) of lithium in the lithium compound to all transition metal elements (Me) in the mixed powder containing nickel exceeding 1. May be mixed.

A lithium-tungsten-nickel cobalt manganese composite oxide is obtained by firing a mixture of a lithium salt and the mixed powder. For the firing, dry air, an oxygen atmosphere, an inert atmosphere, or the like is used according to a desired composition, and a plurality of heating steps are performed if necessary.

Although there is no restriction | limiting in particular as a calcination temperature of the said mixed powder and lithium compounds, such as lithium hydroxide and lithium carbonate, It is preferable that it is 600 degreeC or more and 1100 degrees C or less, and it is 750 degreeC or more and 1050 degrees C or less. More preferably, it is 800 ° C. or higher and 1025 ° C. or lower. By setting the firing temperature to 600 ° C. or higher, the charge capacity can be increased. By setting the firing temperature to 1100 ° C. or lower, Li volatilization can be prevented, and a lithium-tungsten-nickel cobalt manganese composite oxide having a target composition can be obtained.

Calcination time is preferably 3 hours to 50 hours. When the firing time exceeds 50 hours, the battery performance tends to be substantially inferior due to volatilization of lithium. That is, when the firing time is 50 hours or less, lithium can be prevented from volatilizing. If the firing time is less than 3 hours, the crystal growth is poor and the battery performance tends to be poor. That is, when the firing time is 3 hours or more, the crystal development is good and the battery performance is good. In addition, it is also effective to perform temporary baking before the above baking. The temperature for such preliminary firing is preferably in the range of 300 to 850 ° C. for 1 to 10 hours.

The time from the start of temperature rise to the firing temperature is preferably 0.5 hours or more and 20 hours or less. A more uniform lithium-tungsten-nickelcobalt-manganese composite oxide can be obtained when the time from the start of temperature rise to the firing temperature is within this range. Moreover, it is preferable that the time from reaching the firing temperature to the end of the temperature holding is 0.5 hours or more and 20 hours or less. When the time from reaching the firing temperature to the end of the temperature holding is within this range, the development of crystals progresses better, and the battery performance can be further improved.

The lithium metal composite oxide obtained by firing is appropriately classified after pulverization, and is used as a positive electrode active material applicable to a lithium secondary battery.

<Positive electrode active material for lithium secondary battery>
In this embodiment, it is preferable that the positive electrode active material for lithium secondary batteries to be produced contains a compound represented by the following composition formula (I).
Li [Lix (Ni (1-yzw) CoyMnzMw) 1-x] O ₂ (I)
(In the composition formula (I), −0.1 ≦ x ≦ 0.2, 0 <y ≦ 0.5, 0 <z ≦ 0.8, 0 ≦ w ≦ 0.1, y + z + w <1, M is Fe , Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, and V represent one or more metals selected from the group.

In the present embodiment, when the positive electrode active material for a lithium secondary battery produced is composed of only the lithium composite metal compound represented by the composition formula (I), it is represented by M in the composition formula (I). Of these metals, W (tungsten) must be included.
In the present embodiment, the produced positive electrode active material for a lithium secondary battery is a lithium composite metal compound represented by the above composition formula (I), and the metal represented by M in the composition formula (I) Among these, when the lithium composite metal compound not containing W (tungsten) is included, the lithium composite metal compound represented by the composition formula (I) and the tungsten compound are included.

In the present embodiment, the tungsten content contained in the positive electrode active material for a lithium secondary battery is preferably 0.01 mol% or more and 1.0 mol% or less with respect to the total molar amount of the transition metal, 0.1 mol% It is more preferably 0.9 mol% or less and particularly preferably 0.2 mol% or more and 0.8 mol% or less. When the tungsten content contained in the positive electrode active material for a lithium secondary battery is 0.01 mol% or more and 1.0 mol% or less, a reduction in battery resistance is expected.

From the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having high cycle characteristics, x in the composition formula (I) is preferably more than 0, more preferably 0.01 or more, and 0.02 or more. More preferably. Further, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having higher initial Coulomb efficiency, x in the composition formula (I) is preferably 0.1 or less, and more preferably 0.08 or less. More preferably, it is 0.06 or less.
The upper limit value and the lower limit value of x can be arbitrarily combined. For example, x exceeds 0 and is preferably 0.1 or less, more preferably 0.01 or more and 0.08 or less, and further preferably 0.02 or more and 0.06 or less.
In the present specification, “high cycle characteristics” means that the discharge capacity retention ratio is high.

Further, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having a high discharge capacity, y in the composition formula (I) is preferably 0.10 or more, more preferably 0.20 or more, and 0 More preferably, it is 30 or more. Further, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having high thermal stability, y in the composition formula (I) is preferably 0.49 or less, and more preferably 0.48 or less. More preferably, it is 0.47 or less.
The upper limit value and the lower limit value of y can be arbitrarily combined. For example, y is preferably 0.10 or more and 0.49 or less, more preferably 0.20 or more and 0.48 or less, and further preferably 0.30 or more and 0.47 or less.

From the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having a high discharge capacity at a high current rate, z in the composition formula (I) is preferably 0.05 or more, and preferably 0.10 or more. More preferably, it is more preferably 0.20 or more. Further, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having a high discharge capacity, z in the composition formula (I) is preferably 0.35 or less, more preferably 0.30 or less, and 0 More preferably, it is .25 or less.
The upper limit value and lower limit value of z can be arbitrarily combined. For example, z is preferably 0.05 or more and 0.35 or less, more preferably 0.10 or more and 0.30 or less, and further preferably 0.20 or more and 0.25 or less.

Further, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having high cycle characteristics, w in the composition formula (I) is preferably 0.01 or more, more preferably 0.03 or more, and 0 More preferably, it is 0.05 or more. Further, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having high storage characteristics at a high temperature (for example, in an environment of 60 ° C.), w in the composition formula (I) is preferably 0.09 or less. It is more preferably 08 or less, and further preferably 0.07 or less.
The upper limit value and the lower limit value of w can be arbitrarily combined. For example, w is preferably 0.01 or more and 0.09 or less, more preferably 0.03 or more and 0.08 or less, and further preferably 0.05 or more and 0.07 or less.

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

Further, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery with high cycle characteristics, M in the composition formula (I) is one or more selected from the group consisting of Ti, B, Mg, Al, W, and Zr. From the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having high thermal stability, it is at least one metal selected from the group consisting of B, Al, W, and Zr. It is preferable.

(BET specific surface area)
In the present embodiment, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having a high discharge capacity at a high current rate, the BET specific surface area (m ² / g) of the positive electrode active material is 0.1 m ² / g or more. Is preferably 0.5 m ² / g or more, and more preferably 1.0 m ² / g or more. Further, from the viewpoint of reducing the hygroscopicity of the positive electrode active material, the BET specific surface area (m ² / g) of the positive electrode active material is preferably 4.0 m ² / g or less, preferably 3.8 m ² / g or less. More preferably, it is 2.6 m ² / g or less.
The upper limit value and the lower limit value of the BET specific surface area (m ² / g) of the positive electrode active material can be arbitrarily combined. For example, the BET specific surface area (m ² / g) is preferably 0.1 m ² / g or more and 4.0 m ² / g or less, and is 0.5 m ² / g or more and 3.8 m ² / g or less. Is more preferably 1.05 m ² / g or more and 2.6 m ² / g or less.

The BET specific surface area in the present embodiment is measured using a Macsorb (registered trademark) manufactured by Mountec Co., Ltd. after drying 1 g of the positive electrode active material powder in a nitrogen atmosphere at 105 ° C. for 30 minutes.

(Layered structure)
The crystal structure of the positive electrode active material is a layered structure, and more preferably a hexagonal crystal structure or a monoclinic crystal structure.

The hexagonal crystal structures are 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, P6 mm, P6 cc, 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.

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

Among these, from the viewpoint of obtaining a positive electrode active material for a lithium secondary battery having a high discharge capacity, the crystal structure is a hexagonal crystal structure belonging to the space group R-3m or a single crystal belonging to C2 / m. Particularly preferred is an oblique crystal structure.

<Lithium secondary battery>
Next, while explaining the configuration of the lithium secondary battery, a positive electrode using the positive electrode active material for a lithium secondary battery of the present embodiment as a positive electrode active material of the lithium secondary battery, and a lithium secondary battery having the positive electrode explain.

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

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

First, as shown in FIG. 1A, a pair of separators 1 having a strip shape, a strip-like positive electrode 2 having a positive electrode lead 21 at one end, and a strip-like negative electrode 3 having a negative electrode lead 31 at one end, a separator 1, a positive electrode 2, and a separator 1 and negative electrode 3 are laminated in this order and wound to form electrode group 4.

Next, as shown in FIG. 1B, after the electrode group 4 and an insulator (not shown) are accommodated in the battery can 5, the bottom of the can is sealed, the electrode group 4 is impregnated with the electrolytic solution 6, the positive electrode 2, the negative electrode 3, An electrolyte is placed between the two. Furthermore, the lithium secondary battery 10 can be manufactured by sealing the upper part of the battery can 5 with the top insulator 7 and the sealing body 8.

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

Moreover, as a shape of the lithium secondary battery having such an electrode group 4, a shape defined by IEC 60086 or JIS C 8500 which is a standard for a battery defined by the International Electrotechnical Commission (IEC) can be adopted. . For example, cylindrical shape, square shape, etc. can be mentioned.

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

Hereafter, each structure is demonstrated in order.
(Positive electrode)
The positive electrode of this embodiment can be manufactured by first adjusting 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)
As the conductive material included in the positive electrode of the present embodiment, a carbon material can be used. Examples of the carbon material include graphite powder, carbon black (for example, acetylene black), and a fibrous carbon material. Since carbon black is fine and has a large surface area, by adding a small amount to the positive electrode mixture, the conductivity inside the positive electrode can be improved and the charge / discharge efficiency and output characteristics can be improved. 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 reduced, which causes an increase in internal resistance.

The proportion 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. When a fibrous carbon material such as graphitized carbon fiber or carbon nanotube is used as the conductive material, this ratio can be lowered.

(binder)
As the binder included in the positive electrode of the present embodiment, a thermoplastic resin can be used.
This thermoplastic resin is sometimes referred to as polyvinylidene fluoride (hereinafter referred to as PVdF).
), Polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride copolymer, propylene hexafluoride / vinylidene fluoride copolymer, tetrafluoroethylene Fluorine resins such as fluorinated ethylene / perfluorovinyl ether copolymers; Polyolefin resins such as polyethylene and polypropylene.

These thermoplastic resins may be used as a mixture of two or more. By using a fluororesin and a polyolefin resin as a binder, the ratio of the fluororesin to the total mass of the positive electrode mixture is 1% by mass to 10% by mass, and the ratio of the polyolefin resin is 0.1% by mass to 2% by mass In addition, a positive electrode mixture having both high adhesion to the positive electrode current collector and high bonding strength inside the positive electrode mixture can be obtained.

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

Examples of the method of supporting the positive electrode mixture on the positive electrode current collector include a method of pressure-molding the positive electrode mixture on the positive electrode current collector. Also, the positive electrode mixture is made into a paste using an organic solvent, and the resulting positive electrode mixture paste is applied to at least one surface side of the positive electrode current collector, dried, pressed and fixed, whereby the positive electrode current collector is bonded to the positive electrode current collector. A mixture may be supported.

When the positive electrode mixture is made into a paste, usable organic solvents include amine solvents such as N, N-dimethylaminopropylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; ketone solvents such as methyl ethyl ketone; methyl acetate And amide solvents such as dimethylacetamide and N-methyl-2-pyrrolidone (hereinafter sometimes referred to as NMP).

Examples of the method of 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 included in the lithium secondary battery of this embodiment is only required to be able to dope and dedope lithium ions at a lower potential than 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 of the negative electrode active material alone.

(Negative electrode active material)
Examples of the negative electrode active material possessed by the negative electrode include carbon materials, chalcogen compounds (oxides, sulfides, etc.), nitrides, metals, and alloys that can be doped and dedoped with lithium ions at a lower potential than the positive electrode. It is 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 organic polymer compound fired bodies.

The oxide can be used as an anode active _material, (wherein, x represents a positive real number) SiO 2, SiO, etc. formula SiO _x oxides of silicon represented _by; TiO 2, TiO, etc. formula TiO _x (wherein , X is a positive real number); oxide of titanium represented by formula VO _x (where x is a positive real number) such as V ₂ O ₅ and VO ₂ ; 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) Oxide of tin; tungsten oxide represented by general formula WO _x (where x is a positive real number) such as WO ₃ and WO ₂ ; lithium and titanium such as Li ₄ Ti ₅ O ₁₂ and LiVO ₂ Or a composite metal oxide containing vanadium; It is possible.

Examples of sulfides that can be used as the negative electrode active material 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 , VS _2, VS and other vanadium sulfides represented by the formula VS _x (where x is a positive real number); Fe ₃ S ₄ , FeS ₂ , FeS and other formulas FeS _x (where x is a positive real number) Iron sulfide represented; Mo ₂ S ₃ , MoS _{2 and the} like MoS _x (where x is a positive real number) Molybdenum sulfide; SnS _2, SnS and other formula SnS _x (where, a sulfide of tin represented by x is a positive real number; a sulfide of tungsten represented by a formula WS _x (where x is a positive real number) such as WS ₂ ; a formula SbS _x such as Sb ₂ S ₃ (here And x is a positive real number) antimony sulfide; Se ₅ S ₃ , selenium sulfide represented by the formula SeS _x (where x is a positive real number) such as SeS ₂ and SeS.

Examples of the nitride that can be used as the negative electrode active material include Li ₃ N and Li _3-x A _x N (where A is one or both of Ni and Co, and 0 <x <3). And lithium-containing nitrides.

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

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

Alloys that can be used as the negative electrode active material include lithium alloys such as Li—Al, Li—Ni, Li—Si, Li—Sn, and Li—Sn—Ni; silicon alloys such as Si—Zn; Sn—Mn, Sn -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 negative electrode active materials, the potential of the negative electrode hardly changes from the uncharged state to the fully charged state at the time of charging (potential flatness is good), the average discharge potential is low, and the capacity retention rate when repeatedly charged and discharged is For reasons such as high (good cycle characteristics), carbon materials containing graphite as a main component, such as natural graphite and artificial graphite, are preferably used. The shape of the carbon material may be any of a flake shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, or an aggregate of fine powder.

The negative electrode mixture may contain a binder as necessary. Examples of the binder include thermoplastic resins, and specific examples include PVdF, thermoplastic polyimide, 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, and stainless steel. In particular, it is preferable to use Cu as a forming material and process it into a thin film from the viewpoint that it is difficult to make an alloy with lithium and it is easy to process.

As a method of supporting the negative electrode mixture on such a negative electrode current collector, as in the case of the positive electrode, a method using pressure molding, pasting with a solvent, etc., applying to the negative electrode current collector, drying and pressing. The method of crimping is mentioned.

(Separator)
Examples of the separator included in the lithium secondary battery of the present embodiment include a porous film, a nonwoven fabric, a woven fabric, and the like made of a material such as a polyolefin resin such as polyethylene and polypropylene, a fluororesin, and a nitrogen-containing aromatic polymer. A material having the following can be used. Moreover, a separator may be formed by using two or more of these materials, or a separator may be formed by laminating these materials.

In the present embodiment, the separator allows the electrolyte to permeate well when the battery is used (during charging / discharging). Therefore, the air resistance according to the Gurley method defined in JIS P 8117 is 50 seconds / 100 cc or more, 300 seconds / 100 cc. Or less, more preferably 50 seconds / 100 cc or more and 200 seconds / 100 cc or less.

Further, 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 with respect to the volume of the separator. The separator may be a laminate of separators having different porosity.

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

The electrolyte contained in the electrolyte includes 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 (SO ₂ CF ₃ ) (COCF ₃ ), Li (C ₄ F ₉ SO ₃ ), LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , LiBOB (where BOB is bis (oxalato) borate LiFSI (here, FSI is bis (fluorosulfonyl) imide), lithium salt such as lower aliphatic carboxylic acid lithium salt, LiAlCl _4, and a mixture of two or more of these May be used. Among them, as the electrolyte, 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 preferable to use one containing one kind.

Examples of the organic solvent contained in the electrolyte include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, and 1,2-di- Carbonates such as (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, 2- Ethers such as methyltetrahydrofuran; Esters such as methyl formate, methyl acetate and γ-butyrolactone; Nitriles such as acetonitrile and butyronitrile; N, N-dimethylformamide, N, N-dimethyla Amides such as toamide; carbamates such as 3-methyl-2-oxazolidone; sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propane sultone, or those obtained by further introducing a fluoro group into these organic solvents ( One obtained by substituting one or more hydrogen atoms in the organic solvent with fluorine atoms can be used.

It is preferable to use a mixture of two or more of these as the organic solvent. Of these, a mixed solvent containing carbonates is preferable, and a mixed solvent of cyclic carbonate and acyclic carbonate and a mixed solvent of cyclic carbonate and ethers are more preferable. As a mixed solvent of a cyclic carbonate and an acyclic carbonate, a mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferable. The electrolyte using such a mixed solvent has a wide operating temperature range, hardly deteriorates even when charged and discharged at a high current rate, hardly deteriorates even when used for a long time, and natural graphite as an active material of the negative electrode. Even when a graphite material such as artificial graphite is used, it has many features that it is hardly decomposable.

Further, as the electrolytic solution, it is preferable to use an electrolytic solution containing a lithium salt containing fluorine such as LiPF ₆ and an organic solvent having a fluorine substituent because the safety of the obtained lithium secondary battery is increased. A mixed solvent containing ethers having fluorine substituents such as pentafluoropropyl methyl ether and 2,2,3,3-tetrafluoropropyl difluoromethyl ether and dimethyl carbonate is capable of capacity even when charging / discharging at a high current rate. Since the maintenance rate is high, it is more preferable.

A solid electrolyte may be used instead of the above electrolytic solution. As the solid electrolyte, for example, an organic polymer electrolyte such as a polyethylene oxide polymer compound, a polymer compound containing at least one of a polyorganosiloxane chain or a polyoxyalkylene chain can be used. Moreover, what is called a gel type which hold | maintained the non-aqueous electrolyte in the high molecular compound can also be used. Also Li ₂ S—SiS ₂ , Li ₂ S—GeS ₂ , Li ₂ S—P ₂ S ₅ , Li ₂ S—B ₂ S ₃ , Li ₂ S—SiS ₂ —Li ₃ PO ₄ , Li ₂ S—SiS _{2 -Li 2 SO 4, Li 2} S-GeS 2 -P 2 S 5 inorganic solid electrolytes containing a sulfide, and the like, may be used a mixture of two or more thereof. By using these solid electrolytes, the safety of the lithium secondary battery may be further improved.

In the lithium secondary battery of this embodiment, when a solid electrolyte is used, the solid electrolyte may serve as a separator, and in that case, the separator may not be required.

Since the positive electrode active material having the above-described configuration uses the above-described lithium-containing composite metal oxide of the present embodiment, the life of the lithium secondary battery using the positive electrode active material can be extended.

Moreover, since the positive electrode having the above-described configuration has the above-described positive electrode active material for a lithium secondary battery according to this embodiment, the life of the lithium secondary battery can be extended.

Furthermore, since the lithium secondary battery having the above-described configuration has the above-described positive electrode, it becomes a lithium secondary battery having a longer life than before.

Next, the embodiment of the present invention will be described in more detail with reference to examples.

In this example, evaluation of the positive electrode active material for a lithium secondary battery was performed as follows.

[Evaluation of segregation of tungsten]
3 g of a positive electrode active material powder for a lithium secondary battery was sampled, and a reflection electron image of the positive electrode active material for a lithium ion secondary battery was measured using a field emission scanning electron microscope (ULTRA PLUS manufactured by ZEISS). Images of 10 different fields of view were obtained at an acceleration voltage of 15 kV and a magnification of 500. In the obtained image, particles having a contrast different from that of the active material were regarded as segregation of tungsten, and the presence or absence of segregation of tungsten was evaluated.

[BET specific surface area measurement]
After 1 g of the positive electrode active material powder for lithium secondary battery or nickel cobalt manganese composite metal hydroxide powder was dried at 105 ° C. for 30 minutes in a nitrogen atmosphere, a BET specific surface area meter (Macsorb (registered trademark) manufactured by Mountec Co., Ltd.) was used. And measured.

[Measurement of average particle size]
The average particle diameter was measured by using a laser diffraction particle size distribution analyzer (LA-950, manufactured by Horiba, Ltd.), 0.2 g by mass of 0.1 g of a positive electrode active material powder or a composite metal compound powder for a lithium secondary battery. The solution was poured into 50 ml of an aqueous sodium hexametaphosphate solution to obtain a dispersion in which the powder was dispersed. The particle size distribution of the obtained dispersion was measured to obtain a volume-based cumulative particle size distribution curve. In the obtained cumulative particle size distribution curve, the value of the particle diameter (D ₅₀ ) viewed from the fine particle side at 50% accumulation was taken as the average particle diameter of the positive electrode active material for lithium secondary batteries.

[Composition analysis]
The composition analysis of the lithium metal composite oxide powder produced by the method described below is performed by dissolving the obtained lithium metal composite oxide powder in hydrochloric acid and then using an inductively coupled plasma emission spectrometer (SII Nanotechnology, Inc.). Manufactured by SPS3000).

<Example 1>
≪Manufacture of positive electrode active material 1 for lithium secondary battery≫
[Production method of spray liquid]
After water was put in a tank equipped with a stirrer, an aqueous lithium hydroxide solution and tungsten oxide were added to obtain an alkaline aqueous solution in which tungsten oxide was dissolved. At this time, the tungsten oxide concentration in the alkaline aqueous solution was 2.8% by mass with respect to the mass of the entire alkaline aqueous solution.

Spray mixing step Nickel cobalt manganese composite metal hydroxide powder (Ni _0.55 Co _0.21 Mn _0.24 (OH) ₂ ) (BET specific surface area: 86.3 m ² / g, D ₅₀ : 3.4 μm) While being heated and mixed at 105 ° C., an alkaline aqueous solution in which the tungsten compound obtained above was dissolved was sprayed for 1 hour. Thereafter, the mixture was cooled to obtain a mixed powder 1. The spraying conditions at this time are as follows.
{Spraying conditions}
Nozzle diameter: 45 μm
Discharge pressure: 0.6 MPaG
Flow rate: 1.9L / h
Nickel cobalt manganese composite metal hydroxide powder amount: 4100g
Alkaline aqueous solution amount: 1850 g

[Production process of lithium composite metal oxide]
The mixed powder 1 and the lithium carbonate powder were weighed and mixed so that Li / (Ni + Co + Mn) = 1.07, and then subjected to primary firing at 760 ° C. for 5 hours in an air atmosphere. Secondary firing was performed at 850 ° C. for 10 hours to obtain a target positive electrode active material 1 for a lithium secondary battery. The positive electrode active material 1 for a lithium secondary battery had a BET specific surface area of 3.8 m ² / g and D ₅₀ of 2.7 μm.

≪Evaluation of cathode active material 1 for lithium secondary battery≫
When the composition analysis of the obtained positive electrode active material 1 for lithium secondary batteries was performed, it was Li: Ni: Co: Mn: W by molar ratio = 1.07: 0.55: 0.21: 0.24: 0. 0.005.
Furthermore, no segregated material was observed in the positive electrode active material 1 for lithium secondary batteries, and no foreign substance derived from tungsten was observed.

<Example 2>
≪Manufacture of positive electrode active material 2 for lithium secondary battery≫
[Production method of spray liquid]
After water was put in a tank equipped with a stirrer, an aqueous lithium hydroxide solution and tungsten oxide were added to obtain an alkaline aqueous solution in which tungsten oxide was dissolved. The tungsten oxide concentration in the alkaline aqueous solution at this time was 5.6% by mass with respect to the total mass of the alkaline aqueous solution.

Spray mixing step Nickel cobalt manganese composite metal hydroxide powder (Ni _0.31 Co _0.33 Mn _0.36 (OH) ₂ ) (BET specific surface area: 37.2 m ² / g, D ₅₀ : 4.0 μm) While being heated to 105 ° C. and mixed, an alkaline aqueous solution in which the tungsten compound obtained above was dissolved was sprayed for 0.5 hour. Thereafter, the mixture was cooled to obtain a mixed powder 2. The spraying conditions at this time are as follows.
The spraying conditions at this time are as follows.
{Spraying conditions}
Nozzle diameter: 45 μm
Discharge pressure: 0.6 MPaG
Flow rate: 1.9L / h
Nickel cobalt manganese composite metal hydroxide powder amount: 4100g
Alkaline solution amount: 950 g

[Production process of lithium composite metal oxide]
The mixed powder 2 and the lithium carbonate powder were weighed and mixed so that Li / (Ni + Co + Mn) = 1.10, and then subjected to primary firing at 690 ° C. for 5 hours in an air atmosphere. Secondary firing was performed at 950 ° C. for 6 hours to obtain the target positive electrode active material 2 for a lithium secondary battery. The positive electrode active material 2 for a lithium secondary battery had a BET specific surface area of 2.4 m ² / g and a D ₅₀ of 3.6 μm.

≪Evaluation of cathode active material 2 for lithium secondary battery≫
When the composition analysis of the obtained positive electrode active material 2 for lithium secondary batteries was performed, it was Li: Ni: Co: Mn: W by molar ratio = 1.10: 0.32: 0.33: 0.35: 0. 0.005.
Furthermore, no segregated material was observed in the positive electrode active material 2 for a lithium secondary battery, and no foreign substance derived from tungsten was confirmed.

<Example 3>
≪Manufacture of positive electrode active material 3 for lithium secondary battery≫
[Production method of spray liquid]
After water was put in a tank equipped with a stirrer, an aqueous lithium hydroxide solution and tungsten oxide were added to obtain an alkaline aqueous solution in which tungsten oxide was dissolved. At this time, the tungsten oxide concentration in the alkaline aqueous solution was 2.8% by mass with respect to the mass of the entire alkaline aqueous solution.

Spray mixing step Nickel cobalt manganese composite metal hydroxide powder (Ni _0.31 Co _0.33 Mn _0.36 (OH) ₂ ) (BET specific surface area: 37.9 m ² / g, D ₅₀ : 3.3 μm) While being heated to 105 ° C. and mixed, an alkaline aqueous solution in which the tungsten compound obtained above was dissolved was sprayed for 1 hour. Thereafter, the mixture was cooled to obtain a mixed powder 3. The spraying conditions at this time are as follows.
{Spraying conditions}
Nozzle diameter: 45 μm
Discharge pressure: 0.6 MPaG
Flow rate: 1.9L / h
Nickel cobalt manganese composite metal hydroxide powder amount: 4100g
Alkaline aqueous solution amount: 1900g

[Production process of lithium composite metal oxide]
The mixed powder 3 and the lithium carbonate powder were weighed and mixed so that Li / (Ni + Co + Mn) = 1.10, and then subjected to primary firing at 690 ° C. for 5 hours in an air atmosphere. Secondary firing was performed at 950 ° C. for 6 hours to obtain the target positive electrode active material 3 for a lithium secondary battery. The positive electrode active material 3 for a lithium secondary battery had a BET specific surface area of 2.4 m ² / g and D ₅₀ of 3.4 μm.

≪Evaluation of positive electrode active material 3 for lithium secondary battery≫
When the composition analysis of the obtained positive electrode active material 3 for lithium secondary batteries was performed, it was Li: Ni: Co: Mn: W by molar ratio = 1.10: 0.32: 0.33: 0.36: 0. 0.005.
Furthermore, no segregated material was observed in the positive electrode active material 3 for lithium secondary batteries, and no foreign substance derived from tungsten was observed.

<Example 4>
<< Manufacture of cathode active material 4 for lithium secondary battery >>
[Production method of spray liquid]
After water was put in a tank equipped with a stirrer, an aqueous lithium hydroxide solution and tungsten oxide were added to obtain an alkaline aqueous solution in which tungsten oxide was dissolved. At this time, the tungsten oxide concentration in the alkaline aqueous solution was 2.8% by mass with respect to the mass of the entire alkaline aqueous solution.

Spray mixing step Nickel cobalt manganese composite metal hydroxide powder (Ni _0.31 Co _0.33 Mn _0.36 (OH) ₂ ) (BET specific surface area: 29.8 m ² / g, D ₅₀ : 4.0 μm) While being heated to 105 ° C. and mixed, an alkaline aqueous solution in which the tungsten compound obtained above was dissolved was sprayed for 1 hour. Thereafter, the mixture was cooled to obtain a mixed powder 4. The spraying conditions at this time are as follows.
{Spraying conditions}
Nozzle diameter: 45 μm
Discharge pressure: 0.6 MPaG
Flow rate: 1.9L / h
Nickel cobalt manganese composite metal hydroxide powder amount: 4100g
Alkaline aqueous solution amount: 1900g

[Production process of lithium composite metal oxide]
After the mixed powder 4 and the lithium carbonate powder were weighed and mixed so that Li / (Ni + Co + Mn) = 1.10, the mixture was performed at 690 ° C. for 4 hours in an air atmosphere and continuously at 955 ° C. for 6 hours. Time firing was performed to obtain the target positive electrode active material 4 for a lithium secondary battery. The positive electrode active material 4 for lithium secondary battery had a BET specific surface area of 1.8 m ² / g and a D ₅₀ of 3.7 μm.

<< Evaluation of Positive Electrode Active Material 4 for Lithium Secondary Battery >>
When the composition analysis of the obtained positive electrode active material 4 for lithium secondary batteries was performed, it was Li: Ni: Co: Mn: W at a molar ratio of 1.11: 0.32: 0.33: 0.35: 0. 0.005.
Furthermore, no segregated material was observed in the positive electrode active material 4 for lithium secondary batteries, and no foreign substance derived from tungsten was observed.

<Example 5>
<< Manufacture of cathode active material 5 for lithium secondary battery >>
[Production method of spray liquid]
After water was put in a tank equipped with a stirrer, an aqueous lithium hydroxide solution and tungsten oxide were added to obtain an alkaline aqueous solution in which tungsten oxide was dissolved. The tungsten oxide concentration in the alkaline aqueous solution at this time was 2.3% by mass with respect to the mass of the entire alkaline aqueous solution.

Spray mixing step Nickel cobalt manganese composite metal hydroxide powder (Ni _0.87 Co _0.10 Mn _0.02 Al _0.01 (OH) ₂ ) (BET specific surface area: 20.6 m ² / g, D ₅₀ : 10.4 μm) was heated to 105 ° C. and mixed with an alkaline aqueous solution in which the tungsten compound obtained above was dissolved for 2.5 hours. Thereafter, the mixture was cooled to obtain a mixed powder 5. The spraying conditions at this time are as follows.
{Spraying conditions}
Nozzle diameter: 45 μm
Discharge pressure: 0.6 MPaG
Flow rate: 1.9L / h
Nickel cobalt manganese composite metal hydroxide powder amount: 9000 g
Alkaline aqueous solution amount: 4700 g

[Production process of lithium composite metal oxide]
The mixed powder 5 and the lithium carbonate powder were weighed and mixed so that Li / (Ni + Co + Mn) = 1.02, then subjected to primary firing at 760 ° C. for 5 hours in an oxygen atmosphere, and then an oxygen atmosphere Then, secondary firing was performed at 760 ° C. for 10 hours to obtain a target positive electrode active material 5 for a lithium secondary battery. The positive electrode active material 5 for a lithium secondary battery had a BET specific surface area of 0.26 m ² / g and a D ₅₀ of 10.9 μm.

≪Evaluation of cathode active material 5 for lithium secondary battery≫
When the composition analysis of the obtained positive electrode active material 5 for lithium secondary batteries was conducted, it was Li: Ni: Co: Mn: Al: W by molar ratio = 0.99: 0.89: 0.09: 0.02. : 0.02: 0.004.
Furthermore, no segregated material was observed in the positive electrode active material 5 for lithium secondary batteries, and no foreign substance derived from tungsten was confirmed.

<Comparative Example 1>
<< Manufacture of cathode active material 6 for lithium secondary battery >>
Nickel cobalt manganese composite metal hydroxide powder (Ni _0.55 Co _0.21 Mn _0.24 (OH) ₂ ) (BET specific surface area: 82.6 m ² / g, D ₅₀ : 3.6 μm) and tungsten oxide The powder was weighed so that W per 1 mol of transition metal was 0.005 mol, and dry-mixed for 1 hour to obtain mixed powder 6.

After the mixed powder 6 and the lithium carbonate powder were weighed and mixed so that Li / (Ni + Co + Mn) = 1.07, primary firing was performed at 760 ° C. for 5 hours in an air atmosphere, and then the air atmosphere Then, secondary firing was performed at 850 ° C. for 10 hours to obtain a target positive electrode active material 6 for a lithium secondary battery. The positive electrode active material 6 for a lithium secondary battery had a BET specific surface area of 3.2 m ² / g and a D ₅₀ of 3.2 μm.

≪Evaluation of cathode active material 6 for lithium secondary battery≫
When the composition analysis of the obtained positive electrode active material 6 for lithium secondary batteries was performed, it was Li: Ni: Co: Mn: W at a molar ratio of 1.07: 0.55: 0.21: 0.24: 0. 0.005.
Furthermore, segregated material was observed in the positive electrode active material 6 for lithium secondary batteries, and foreign substances derived from tungsten were confirmed.

<Comparative example 2>
≪Manufacture of positive electrode active material 7 for lithium secondary battery≫
[Production process of composite metal compound]
Nickel cobalt manganese composite metal hydroxide powder (Ni _0.31 Co _0.33 Mn _0.36 (OH) ₂ ) (BET specific surface area: 37.2 m ² / g, D ₅₀ : 4.0 μm), tungsten oxide The powder was weighed so that W per 1 mol of transition metal was 0.005 mol, and dry-mixed for 1 hour to obtain mixed powder 7.

[Production process of lithium composite metal oxide]
The mixed powder 7 obtained in the above process was heat-treated. Specifically, primary firing was performed at 690 ° C. for 5 hours in an air atmosphere, and then secondary firing was performed at 950 ° C. for 6 hours.

The mixed powder 7 and the lithium carbonate powder were weighed and mixed so that Li / (Ni + Co + Mn) = 1.10, and then subjected to primary firing at 690 ° C. for 5 hours in an air atmosphere. The target positive electrode active material 7 for lithium secondary batteries was obtained by performing secondary baking for 6 hours at 925 degreeC. The positive electrode active material 7 for a lithium secondary battery had a BET specific surface area of 2.2 m ² / g and a D ₅₀ of 3.8 μm.

≪Evaluation of positive electrode active material 7 for lithium secondary battery≫
When the composition analysis of the obtained positive electrode active material 7 for lithium secondary batteries was conducted, it was Li: Ni: Co: Mn: W by molar ratio = 1.10: 0.32: 0.33: 0.35: 0. 0.005.
Furthermore, segregated material was observed in the positive electrode active material 7 for the lithium secondary battery, and foreign substances derived from tungsten were confirmed.

<Comparative Example 3>
<< Manufacture of cathode active material 8 for lithium secondary battery >>
Nickel cobalt manganese composite metal hydroxide powder (Ni _0.87 Co _0.10 Mn _0.02 Al _0.01 (OH) ₂ ) (BET specific surface area: 20.6 m ² / g, D ₅₀ : 10.4 μm) The tungsten oxide powder was weighed so that W per 1 mol of the transition metal was 0.004 mol, and dry-mixed for 1 hour to obtain a mixed powder 8.

[Production process of lithium composite metal oxide]
The mixed powder 8 and the lithium carbonate powder were weighed and mixed so that Li / (Ni + Co + Mn) = 1.02, then subjected to primary firing at 760 ° C. for 5 hours in an oxygen atmosphere, and then an oxygen atmosphere Then, secondary firing was performed at 760 ° C. for 10 hours to obtain a target positive electrode active material 8 for a lithium secondary battery. The BET specific surface area of the positive electrode active material 8 for a lithium secondary battery was 0.28 m ² / g, and D ₅₀ was 10.6 μm.

≪Evaluation of cathode active material 8 for lithium secondary battery≫
When composition analysis of the obtained positive electrode active material 8 for lithium secondary batteries was conducted, Li: Ni: Co: Mn: Al: W in molar ratio was 0.99: 0.89: 0.09: 0.02. : 0.02: 0.004.
Furthermore, segregated material was observed in the positive electrode active material 8 for the lithium secondary battery, and foreign substances derived from tungsten were confirmed.

<Comparative example 4>
≪Production of positive electrode active material 9 for lithium secondary battery≫
Nickel cobalt manganese composite metal hydroxide powder (Ni _0.55 Co _0.21 Mn _0.24 (OH) ₂ ) (BET specific surface area: 84.0 m ² / g, D ₅₀ : 3.5 μm), lithium carbonate The powder was weighed and mixed so that Li / (Ni + Co + Mn) = 1.07, and then subjected to primary firing at 760 ° C. for 10 hours in an air atmosphere. The obtained composite metal compound powder 9 and tungsten oxide The powder was dry mixed for 1 hour. Then, secondary firing was performed at 850 ° C. for 10 hours in an oxygen atmosphere to obtain the target positive electrode active material 9 for a lithium secondary battery. The positive electrode active material 9 for a lithium secondary battery had a BET specific surface area of 3.5 m ² / g and D ₅₀ of 3.0 μm.

≪Evaluation of cathode active material 9 for lithium secondary battery≫
When the composition analysis of the obtained positive electrode active material 9 for lithium secondary batteries was performed, it was Li: Ni: Co: Mn: W at a molar ratio of 1.07: 0.56: 0.21: 0.24: 0. 0.005.
Furthermore, segregated material was observed in the positive electrode active material 9 for lithium secondary batteries, and foreign substances derived from tungsten were confirmed.

Table 1 summarizes the manufacturing conditions for Examples 1 to 5 and Comparative Examples 1 to 4. In Table 1 below, “W” means tungsten.

As described in the above results, in Examples 1 to 5 to which the present invention was applied, no segregated material derived from tungsten was observed, and the generation of foreign matters could be suppressed. On the other hand, in Comparative Examples 1 to 4 to which the present invention was not applied, segregated materials derived from tungsten were observed, and foreign matters were generated.

FIG. 2 shows an SEM photograph of the mixed powder after dry mixing in Comparative Example 2, and FIG. 3 shows an SEM photograph of the mixed powder after spray mixing in Example 3. In Comparative Example 2 in which the present invention was not applied, segregated material derived from tungsten was confirmed at the position indicated by reference numeral 20 in FIG. On the other hand, in Example 3 to which the present invention was applied, segregated material derived from tungsten was not confirmed after the mixing of tungsten.

According to the present invention, it is possible to provide a method for producing a positive electrode active material for a lithium secondary battery in which segregation of tungsten is suppressed.

DESCRIPTION OF SYMBOLS 1 ... Separator, 2 ... Positive electrode, 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, 31 ... Negative electrode lead

Claims (6)

1. A method for producing a positive electrode active material for a lithium secondary battery comprising a lithium composite metal compound,
   Heating a composite metal compound powder containing nickel, cobalt, and manganese, spraying an alkaline solution of a tungsten compound on the composite metal compound powder, mixing the composite metal compound powder and the tungsten compound, and mixing powder A spray mixing step comprising producing and then cooling the mixed powder;
   A step of mixing a lithium salt and the mixed powder and baking to produce a lithium composite metal compound;
   The manufacturing method of the positive electrode active material for lithium secondary batteries which has this.
2. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the lithium composite metal compound is represented by the following composition formula (I).
   Li [Lix (Ni (1-yzw) CoyMnzMw) 1-x] O ₂ (I)
   (In the composition formula (I), −0.1 ≦ x ≦ 0.2, 0 <y ≦ 0.5, 0 <z ≦ 0.8, 0 ≦ w ≦ 0.1, y + z + w <1, M is Fe , Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, and V represent one or more metals selected from the group.
3. The production of a positive electrode active material for a lithium secondary battery according to claim 1 or 2, wherein the tungsten content contained in the positive electrode active material for a lithium secondary battery is 1.0 mol% or less with respect to the total molar amount of the transition metal. Method.
4. The method for producing a positive electrode active material for a lithium secondary battery according to any one of claims 1 to 3, wherein the tungsten compound is tungsten oxide in the spray mixing step.
5. The method for producing a positive electrode active material for a lithium secondary battery according to any one of claims 1 to 4, wherein in the spray mixing step, the alkaline solution contains lithium hydroxide.
6. The method for producing a positive electrode active material for a lithium secondary battery according to any one of claims 1 to 5, wherein in the spray mixing step, a temperature of the composite metal compound powder when spraying the alkaline solution is 100 ° C or higher. .

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