KR20230097043A - Method for producing modified lithium nickel manganese cobalt composite oxide particles - Google Patents

Abstract

(식 중, x는 0.98≤x≤1.20, y는 0.30≤y<1.00, z는 0<z≤0.50, t는 0<t≤0.50, p는 0≤p≤0.05를 나타내고, y+z+t+p=1.00임)
로 표시되는 리튬 니켈 망간 코발트 복합 산화물 입자를, 티타늄킬레이트 화합물을 포함하는 표면 처리액에 접촉시켜서, 해당 리튬 니켈 망간 코발트 복합 산화물 입자의 입자 표면에 티타늄킬레이트 화합물이 부착된 피복 입자를 얻고, 이어서 해당 피복 입자를 가열 처리함으로써, 개질 리튬 니켈 망간 코발트 복합 산화물 입자를 얻는 개질 공정을 갖고,
상기 티타늄킬레이트 화합물이, 하기 일반식 (2):

로 표시되는 티타늄킬레이트 또는 그의 암모늄염인 것을 특징으로 하는 개질 LiNiMnCo 복합 산화물 입자의 제조 방법.To provide a LiNiMnCo composite oxide particle capable of improving cycle characteristics when used as a positive electrode active material for a lithium secondary battery. The following general formula (1):

(In the formula, x represents 0.98≤x≤1.20, y represents 0.30≤y<1.00, z represents 0<z≤0.50, t represents 0<t≤0.50, p represents 0≤p≤0.05, and y+z+ t+p=1.00)
The lithium nickel manganese cobalt composite oxide particles represented by are brought into contact with a surface treatment solution containing a titanium chelate compound to obtain coated particles in which the titanium chelate compound adheres to the particle surfaces of the lithium nickel manganese cobalt composite oxide particles. a modification step of obtaining modified lithium nickel manganese cobalt composite oxide particles by heating the coated particles;
The titanium chelate compound has the following general formula (2):

A method for producing modified LiNiMnCo composite oxide particles, which is a titanium chelate represented by or an ammonium salt thereof.

Description

Method for producing modified lithium nickel manganese cobalt composite oxide particles

The present invention relates to a method for producing modified lithium nickel manganese cobalt composite oxide particles.

Conventionally, lithium cobaltate has been used as a positive electrode active material for lithium secondary batteries. However, since cobalt is a rare metal, lithium nickel manganese cobalt composite oxides having a low content of cobalt have been developed (see Patent Documents 1 and 2, for example).

A lithium secondary battery using a lithium nickel manganese cobalt composite oxide as a positive electrode active material can be reduced in cost and has a higher capacity than lithium cobaltate by adjusting the atomic ratio of nickel, manganese, and cobalt contained in the composite oxide. It is known (for example, refer to Patent Document 3).

However, even with these prior art methods, a lithium secondary battery using a lithium nickel manganese cobalt composite oxide as a positive electrode active material still has a problem of deterioration in cycle characteristics.

As a method for improving cycle characteristics of a lithium secondary battery using a lithium nickel manganese cobalt composite oxide as a positive electrode active material, a method of coating the particle surface of a lithium nickel manganese cobalt composite oxide with a Ti-containing compound has been proposed (for example, See Patent Document 4, Patent Document 5, etc.).

As a method for coating the particle surface of lithium nickel manganese cobalt composite oxide with a Ti-containing compound, Patent Documents 4 and 5 mix an alkoxide monomer or oligomer containing an organometallic compound such as Ti with an alcohol such as 2-propanol. After that, a chelating agent such as acetylacetone is added, and water is further added to prepare a dispersion in which precursors of fine particles having an average particle size of 1 to 20 nm containing Ti are dispersed, and lithium nickel manganese cobalt A method of coating the surface of a composite oxide particle and then performing a heat treatment has been proposed.

International Publication No. 2004/092073 Pamphlet Japanese Unexamined Patent Publication No. 2005-25975 Japanese Unexamined Patent Publication No. 2011-23120 Japanese Unexamined Patent Publication No. 2016-24968 Japanese Unexamined Patent Publication No. 2016-72071

Recently, lithium secondary batteries are being reviewed for use in automobile fields such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles. For this reason, in a lithium secondary battery using a lithium nickel manganese cobalt composite oxide as a positive electrode active material, further improvement in cycle characteristics is required.

Accordingly, an object of the present invention is to provide lithium nickel manganese cobalt composite oxide particles capable of improving cycle characteristics when used as a positive electrode active material for a lithium secondary battery.

The inventors of the present invention, as a result of intensive research in view of the above circumstances, found that lithium manganese cobalt composite oxide particles represented by the general formula (1) are a surface treatment solution containing a titanium chelate represented by a specific general formula or an ammonium salt thereof. and heat treatment to obtain modified lithium nickel manganese cobalt composite oxide particles, and a lithium secondary battery using the modified lithium nickel manganese cobalt composite oxide particles as a positive electrode active material has excellent cycle characteristics, The present invention has been completed.

That is, the present invention (1) is the following general formula (1):

(Wherein, M is selected from Mg, Al, Ti, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na and K Represents one or more metal elements that are x is 0.98≤x≤1.20, y is 0.30≤y<1.00, z is 0<z≤0.50, t is 0<t≤0.50, p is 0≤p≤ represents 0.05, and y+z+t+p=1.00)

The lithium nickel manganese cobalt composite oxide particles represented by are brought into contact with a surface treatment solution containing a titanium chelate compound to obtain coated particles in which the titanium chelate compound adheres to the particle surfaces of the lithium nickel manganese cobalt composite oxide particles. a modification step of obtaining modified lithium nickel manganese cobalt composite oxide particles by heating the coated particles;

The titanium chelate compound has the following general formula (2):

(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group or a phosphine, and when present in a plurality thereof, may be the same or different. L represents a group derived from hydroxycarboxylic acid, and a plurality of In this case, it may be the same or different. m represents a number of 0 or more and 3 or less, n represents a number of 1 or more and 3 or less, and m+n is 3 to 6)

A titanium chelate represented by or an ammonium salt thereof

It is to provide a method for producing modified lithium nickel manganese cobalt composite oxide particles characterized by.

In addition, the present invention (2) provides the method for producing modified lithium nickel manganese cobalt composite oxide particles of (1) characterized in that the temperature of the heat treatment is 400 to 1000°C.

In addition, the present invention (3) provides the method for producing modified lithium nickel manganese cobalt composite oxide particles according to (1) or (2), characterized in that L in the general formula (2) is a monovalent carboxylic acid.

Further, the present invention (4) provides the method for producing modified lithium nickel manganese cobalt composite oxide particles according to (1) or (2), characterized in that L in the general formula (2) is lactic acid.

In addition, the present invention (5) provides the method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of (1) to (4), characterized in that the surface treatment liquid has a pH of 7 or higher.

Further, in the present invention (6), the amount of adhesion of the titanium chelate compound on the coated particles is 0.1 to 150 mg in terms of Ti atom per 1 m 2 of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1). It is to provide a method for producing a modified lithium nickel manganese cobalt composite oxide particle according to any one of (1) to (5), characterized in that.

Further, the present invention (7) is any of the modified lithium nickel manganese of (1) to (6), characterized in that the amount of residual alkali in the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is 1.2% by mass or less. It is to provide a method for producing cobalt composite oxide particles.

Further, the present invention (8) is a method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of (1) to (7), characterized in that the amount of residual alkali in the modified lithium nickel manganese cobalt composite oxide particles is 1.2% by mass or less. is to provide

In addition, in the reforming step of the present invention (9),

The Ti content per 1 m 2 of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is an addition amount of 0.1 to 150 mg in terms of Ti atoms, and the surface modification liquid is represented by the general formula (1) Adding to the lithium nickel manganese cobalt composite oxide particles to be mixed, and drying the entire amount

It is to provide a method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of (1) to (8), characterized by:

Further, the present invention (10) provides large particles having an average particle diameter of 7.5 to 30.0 µm obtained by the production method according to any one of (1) to (9), and any one of (1) to (9). It is to provide a method for producing a positive electrode active material for a lithium secondary battery characterized by including a step of mixing small particles having an average particle diameter of 0.5 to 7.5 μm obtained by the production method described in .

ADVANTAGE OF THE INVENTION According to this invention, when used as a positive electrode active material of a lithium secondary battery, the lithium nickel manganese cobalt composite oxide particle which can improve cycling characteristics can be provided.

Hereinafter, the present invention will be described based on preferred embodiments.

In the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) are converted into a titanium chelate represented by the general formula (2) or the general formula (2). By contacting the surface treatment solution containing the ammonium salt of the indicated titanium chelate to obtain coated particles having these titanium chelate compounds adhered to the particle surfaces of the lithium nickel manganese cobalt composite oxide particles, and then heat-treating the obtained coated particles to modify It has a reforming process to obtain lithium nickel manganese cobalt composite oxide particles. Hereinafter, the titanium chelate represented by the general formula (2) and the ammonium salt of the titanium chelate represented by the general formula (2) are collectively referred to as "titanium chelate compounds" in some cases.

The method for producing the modified lithium nickel manganese cobalt composite oxide of the present invention basically has the following steps (A) to (B).

Step (A): The lithium nickel manganese cobalt composite oxide particles represented by the general formula (1), that is, the lithium nickel manganese cobalt composite oxide to be modified are brought into contact with a surface treatment solution containing a titanium chelate compound according to the present invention. , A step of obtaining coated particles in which a titanium chelate compound is adhered to the surface of lithium nickel manganese cobalt composite oxide particles.

Step (B): A step of heating the coated particles obtained in step (A) to obtain modified lithium nickel manganese cobalt composite oxide particles (A) or modified lithium nickel manganese cobalt composite oxide particles (B) described later.

In the following, "modified lithium nickel manganese cobalt composite oxide particles (A)" and "modified lithium nickel manganese cobalt composite oxide particles (B)" are collectively referred to as "modified lithium nickel manganese cobalt composite oxide particles". there is

In step (B), the coated particles are subjected to heat treatment to obtain modified lithium nickel manganese cobalt composite oxide particles (A) and modified lithium nickel manganese cobalt composite oxide particles (B).

The modified lithium nickel manganese cobalt composite oxide particles (A) are those in which an oxide containing Ti adheres to the particle surface of the lithium nickel manganese cobalt composite oxide particles. The fact that the Ti-containing oxide adheres to the particle surface of the lithium nickel manganese cobalt composite oxide particle indicates that the particle surface of the modified lithium nickel manganese cobalt composite oxide particle is examined by SEM-EDX at a magnification of 10,000 to 30,000 times. When analyzed by elemental mapping analysis of Ti, it is confirmed by observing that Ti is unevenly distributed on the particle surface of the lithium nickel manganese cobalt composite oxide particles.

On the other hand, in the modified lithium nickel manganese cobalt composite oxide particles (B), when the particle surface of the modified lithium nickel manganese cobalt composite oxide particles is analyzed by elemental mapping analysis of Ti by SEM-EDX at a magnification of 10,000 to 30,000 times , Ti is observed in a uniformly distributed state like Co, Ni, Mn, etc. The inventors of the present invention found that the solid solution reaction of Ti proceeds preferentially in the modified lithium nickel manganese cobalt composite oxide particles (B), and since Ti is contained in solid solution in the lithium nickel manganese cobalt composite oxide particles, Ti is lithium nickel manganese cobalt composite oxide. It is assumed that Co, Ni, Mn, etc. are uniformly distributed on the particle surface of the particles.

In the step (A), lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) to be modified are brought into contact with a surface treatment solution containing a titanium chelate compound according to the present invention to form lithium nickel manganese cobalt composite oxide particles. This is a step of obtaining coated particles with a titanium chelate compound attached to the surface. In addition, the titanium chelate compound on the particle surface of the lithium nickel manganese cobalt composite oxide particle may cover the entire particle surface of the lithium nickel manganese cobalt composite oxide particle or a part thereof. Covering a part of the particle surface means a state in which the particle surface has a portion where the surface of the object to be coated is exposed other than the titanium chelate compound.

In step (A), the lithium nickel manganese cobalt composite oxide particles to be modified have the following general formula (1):

(Wherein, M is selected from Mg, Al, Ti, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na and K Represents one or more metal elements that are x is 0.98≤x≤1.20, y is 0.30≤y<1.00, z is 0<z≤0.50, t is 0<t≤0.50, p is 0≤p≤ represents 0.05, and y+z+t+p=1.00)

It is a lithium nickel manganese cobalt composite oxide particle represented by

x in the formula of General Formula (1) is 0.98≤x≤1.20. It is preferable that x is 1.00 ≤ x ≤ 1.10 from the viewpoint of increasing the initial capacity. In addition, y in the formula of General Formula (1) is 0.30≤y<1.00. y is preferably 0.50 ≤ y ≤ 0.95, particularly preferably 0.60 ≤ y ≤ 0.90, from the viewpoint of achieving both initial capacity and cycle characteristics. In addition, z in the formula of General Formula (1) is 0<z≤0.50. z is preferably 0.025 ≤ z ≤ 0.45 from the viewpoint of excellent safety. Also, t is 0<t≤0.50. t is preferably 0.025≤t≤0.45 from the viewpoint of excellent safety. y+z+t+p=1.00. y/z is preferably (y/z)>1, particularly preferably (y/z)≥1.5, more preferably 3≤(y/z)≤38.

In addition, M in the formula is a metal element to be incorporated into the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) as necessary for the purpose of improving battery performance such as cycle characteristics and safety, M As, one or two selected from Mg, Al, Ti, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na and K More than one kind of metal element can be mentioned. In formula (1), p is 0 ≤ p ≤ 0.05, preferably 0.0001 ≤ p ≤ 0.045.

In addition, the lithium nickel manganese cobalt composite oxide particle to be modified is a granular material of a lithium nickel manganese cobalt composite oxide represented by the general formula (1). The lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) may be single particles in which primary particles are monodispersed, or may be aggregated particles in which primary particles aggregate to form secondary particles. The average particle diameter of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is the 50% volume conversion particle diameter (D50) in the particle size distribution determined by the laser diffraction/scattering method, and is preferably 1.0 to 1.0. 30.0 μm, particularly preferably 3.0 to 25.0 μm. The BET specific surface area of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is preferably 0.05 to 2.00 m 2 /g, particularly preferably 0.15 to 1.00 m 2 /g. When the average particle diameter or BET specific surface area of the lithium nickel manganese cobalt composite oxide particles is within the above range, the preparation and coating properties of the positive electrode mixture are facilitated, and an electrode with high fillability can be obtained.

The amount of residual alkali in the lithium nickel manganese cobalt composite oxide particles of the general formula (1) to be modified is preferably 1.2% by mass or less, particularly preferably 1.0% by mass or less. When the amount of residual alkali in the particles of the lithium nickel manganese cobalt composite oxide is within the above range, expansion and deterioration of the battery caused by gas generation due to the residual alkali can be suppressed.

In the present invention, residual alkali refers to an alkali component that is eluted into water when lithium nickel manganese cobalt composite oxide particles are stirred and dispersed in water at 25°C. Then, the amount of residual alkali was determined by weighing 5 g of lithium nickel manganese cobalt composite oxide particles and 100 g of pure water in a beaker, dispersing them at 25° C. for 5 minutes with a magnetic stirring bar, filtering the dispersion, and measuring the amount of alkali present in the obtained filtrate. It is obtained by neutralizing titration of the amount. In addition, the amount of the remaining alkali is a value obtained by measuring the amount of lithium by titration and converting it into lithium carbonate.

The lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) to be modified are, for example, a raw material for preparing a raw material mixture by mixing a lithium source, a nickel source, a manganese source, a cobalt source, and an M source added as needed It is manufactured by performing a mixing process and a sintering process of sintering the raw material mixture obtained subsequently.

As the lithium source, nickel source, manganese source, cobalt source, and M source according to the raw material mixing step, for example, these hydroxides, oxides, carbonates, nitrates, sulfates, organic acid salts, etc. are used. It is preferable that the average particle diameter of the lithium source, nickel source, manganese source, cobalt source, and M source is 1.0 to 30.0 μm, preferably 2.0 to 25.0 μm, as determined by a laser scattering method.

The nickel source, manganese source, and cobalt source according to the raw material mixing step may be compounds containing nickel atoms, manganese atoms, and cobalt atoms. As a compound containing a nickel atom, a manganese atom, and a cobalt atom, the composite oxide, composite hydroxide, composite oxyhydroxide, composite carbonate etc. which contain these atoms are mentioned, for example.

In addition, as a method for preparing a compound containing a nickel atom, a manganese atom, and a cobalt atom, a known method is used. For example, in the case of a composite hydroxide, it can be prepared by a coprecipitation method. Specifically, a composite hydroxide can be coprecipitated by mixing an aqueous solution containing predetermined amounts of nickel atoms, cobalt atoms, and manganese atoms, an aqueous solution of a complexing agent, and an aqueous alkali solution (Japanese Unexamined Patent Publication No. 10-81521). Japanese Patent Laid-Open No. 10-81520, Japanese Patent Laid-Open No. 10-29820, Japanese Patent Laid-Open No. 2002-201028, etc.). Further, in the case of a complex carbonate, a method in which a solution containing nickel ions, manganese ions, and cobalt ions (liquid A) and a solution containing carbonate ions or hydrogen carbonate ions (liquid B) are added to a reaction vessel to perform the reaction. (Japanese Unexamined Patent Publication No. 2009-179545), or a solution (liquid A) containing nickel salt, manganese salt and cobalt salt and a solution (liquid B) containing metal carbonate or metal hydrogen carbonate in the liquid A A method of reacting by adding to a solution (liquid C) containing the same anion as that of the nickel salt, manganese salt, and cobalt salt, and the same anion as that of the metal carbonate or metal hydrogencarbonate in the liquid B (Japanese Unexamined Patent Publication No. 2009-179544), etc. are mentioned. In addition, commercial items may be sufficient as the compound containing a nickel atom, a manganese atom, and a cobalt atom.

The average particle diameter of the compound containing nickel atoms, cobalt atoms and manganese atoms, determined by a laser scattering method, is 1.0 to 100 µm, preferably 2.0 to 80.0 µm.

In the production of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1), it is preferable to use composite hydroxides containing nickel atoms, cobalt atoms and manganese atoms as the nickel source, manganese source and cobalt source because the reactivity is It is desirable in that it becomes good.

In the raw material mixing step, the mixing ratio of the lithium source, the nickel source, the manganese source, the cobalt source, and the M source added as needed increases the discharge capacity, so the Ni atoms in the nickel source, manganese source, and cobalt source , the molar ratio of Li atoms (Li/(Ni+Mn+Co+M)) to the total number of moles of Mn atoms, Co atoms and M atoms (Ni+Mn+Co+M) is from 0.98 to 1.20, preferably from 1.00 to 1.20. It is 1.10.

In addition, in the raw material mixing step, the mixing ratio of each raw material of the nickel source, the manganese source, the cobalt source, and the M source added as needed is the nickel, manganese, cobalt, and M represented by the general formula (1) above. What is necessary is just to adjust it so that it may become an atomic molar ratio.

In addition, the manufacturing history of the lithium source, nickel source, manganese source, cobalt source, and M source as a raw material is irrelevant, but in order to produce high-purity lithium nickel manganese cobalt composite oxide particles, it is preferable that the impurity content is as low as possible.

In the raw material mixing step, as means for mixing the lithium source, nickel source, manganese source, cobalt source, and M source added as needed, either dry or wet method may be used, but dry mixing is preferable because production is easy. desirable.

In the case of dry mixing, it is preferable to perform by mechanical means so that raw materials may be mixed uniformly. As a mixing device, for example, a high-speed mixer, a super mixer, a turbo spare mixer, an Irish mixer, a Henschel mixer, a Nauta mixer, a ribbon blender, a V-type mixer, a conical blender, a jet mill, a cosmizer, a paint shaker, and a bead mill , a ball mill, and the like. Also, at the laboratory level, a household mixer is sufficient.

In the case of wet mixing, it is preferable to use a media mill as a mixing device in that a slurry in which each raw material is uniformly dispersed can be prepared. Further, the slurry after the mixing treatment is preferably spray-dried from the viewpoint of obtaining a raw material mixture having excellent reactivity and in which each raw material is uniformly dispersed.

The firing step is a step of obtaining a lithium nickel manganese cobalt composite oxide by firing the raw material mixture obtained by performing the raw material mixing step.

In the firing step, the firing temperature for firing the raw material mixture and reacting the raw materials is 600 to 1000°C, preferably 700 to 950°C. The reason for this is that when the firing temperature is less than 600 ° C, the reaction is insufficient and unreacted lithium tends to remain in a large amount. Because.

The firing time in the firing step is 3 hours or more, preferably 5 to 30 hours. In addition, the firing atmosphere in the firing process is an oxidizing atmosphere of air and oxygen gas.

In addition, in the firing step, firing may be performed in a multi-stage manner. By firing in a multi-stage manner, modified lithium nickel manganese cobalt composite oxide particles having further excellent cycle characteristics can be obtained. When firing in multiple stages, it is preferable to fire in the range of 650 to 800 ° C. for 1 to 10 hours, then raise the temperature to 800 to 950 ° C. so that the temperature is higher than the firing temperature, and then fire as it is for 5 to 30 hours.

The lithium nickel manganese cobalt composite oxide obtained in this way may be subjected to a plurality of firing steps as needed.

In addition, the lithium nickel manganese composite oxide particles having a residual alkali amount in the above range are a lithium source, a nickel source, a manganese source, a cobalt source, and an M source added as needed in the raw material mixing step, the nickel source, manganese source, and cobalt The molar ratio of Li atoms (Li/(Ni+Mn+Co+M)) to the total number of moles (Ni+Mn+Co+M) of Ni atoms, Mn atoms, Co atoms and M atoms in the circle and M circle is from 0.98 to 0.98. At a mixing ratio of 1.20, subject to a firing reaction at 700 ° C. or higher, preferably 750 to 1000 ° C. for 3 hours or more, preferably 5 to 30 hours, and a sufficient lithium source, nickel source, manganese source, cobalt source And it can be manufactured by reacting M source added as needed. In this production method, the firing is carried out in the above-described multi-stage manner, whereby lithium nickel manganese composite oxide particles in which the amount of residual alkali is further reduced can be produced.

(A) The surface treatment liquid according to the step dissolves a titanium chelate compound, that is, a titanium chelate represented by the general formula (2) or an ammonium salt of the titanium chelate represented by the general formula (2) in water and/or an organic solvent. or dispersed.

(A) Titanium chelate according to the process, the following general formula (2):

(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group or a phosphine, and when present in a plurality thereof, may be the same or different. L represents a group derived from hydroxycarboxylic acid, and a plurality of In this case, it may be the same or different. m represents a number of 0 or more and 3 or less, n represents a number of 1 or more and 3 or less, and m+n is 3 to 6)

It is a titanium chelate represented by

As the alkoxy group related to R ¹ , a linear or branched alkoxy group having 1 to 4 carbon atoms is preferable. As a halogen atom related to R ¹ , a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are exemplified. Examples of the amino group related to R ¹ include a methylamino group, an ethylamino group, a propylamino group, an isopropylamino group, a butylamino group, an isobutylamino group, a tert-butylamino group, and a pentylamino group. Examples of the phosphines related to R ¹ include trimethylphosphine, triethylphosphine, tributylphosphine, tris-tert-butylphosphine, and triphenylphosphine.

As the group derived from the hydroxycarboxylic acid related to L, a group formed by coordinating the oxygen atom of the hydroxyl group in the hydroxycarboxylic acid or the oxygen atom of the carboxyl group in the hydroxycarboxylic acid to the titanium atom is exemplified. can In addition, as a group derived from the hydroxycarboxylic acid related to L, the oxygen atom of the hydroxyl group in the hydroxycarboxylic acid and the oxygen atom of the carboxyl group in the hydroxyl carboxylic acid are doubled on the titanium atom. A group made for this can be mentioned. Among these, it is preferable that the oxygen atom of the hydroxyl group in hydroxycarboxylic acid and the oxygen atom of the carboxyl group in hydroxycarboxylic acid are a group formed by coordinating with a titanium atom in a bidentate manner. When m is 0, it is preferable that m+n is 3, and when m is 1 or more and 3 or less, it is preferable that m+n is 4 or 5.

Although it is a method for producing titanium chelate, for example, a solution containing titanium chelate is obtained by diluting titanium alkoxide with a solvent to obtain a diluted solution and mixing the diluted solution with hydroxycarboxylic acid (see pamphlet WO2019/138989). ). In the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, the solution containing the titanium chelate obtained by the method for producing titanium chelate can be used as a surface treatment liquid in step (A). In addition, water may be added to a solution containing titanium chelate and used as a surface treatment liquid. As a result, a dispersion or solution of titanium chelate in a water-containing solvent can be obtained as a surface treatment solution.

Examples of the titanium alkoxide include tetramethoxytitanium (IV), tetraethoxytitanium (IV), tetra-n-propoxytitanium (IV), tetraisopropoxytitanium (IV), tetra-n -butoxytitanium (IV) and tetraisobutoxytitanium (IV); and the like.

Examples of the hydroxycarboxylic acid include monovalent carboxylic acids such as lactic acid, glycolic acid, glyceric acid, and hydroxybutyric acid, divalent carboxylic acids such as tartronic acid, malic acid, and tartaric acid, citric acid, and isocitrate Trivalent carboxylic acids, such as these, etc. are mentioned. Among these, lactic acid is preferred from the viewpoint that it easily becomes a solution at room temperature, is easily mixed with a diluted titanium alkoxide solution, and can easily produce a titanium chelate.

As the solvent used as the diluent, alcohols such as methanol, ethanol, isopropanol, n-propanol, n-butanol, sec-butanol, tert-butanol, and n-pentane can be preferably used.

In addition, for the purpose of obtaining titanium chelate efficiently with high productivity when mixing the diluted solution and hydroxycarboxylic acid or in a solution containing titanium chelate, a ligand capable of coordinating to titanium in addition to hydroxycarboxylic acid A compound may be added. Examples of such ligand compounds include halogen atom-containing compounds, amines having functional groups such as methylamino group, ethylamino group, propylamino group, isopropylamino group, butylamino group, isobutylamino group, t-butylamino group, and pentylamino group, trimethyl and phosphines such as phosphine, triethylphosphine, tributylphosphine, tris-tert-butylphosphine, and triphenylphosphine.

As the ammonium salt of titanium chelate, titanium lactate ammonium salt (Ti(OH) ₂ [(OCH(CH ₃ )COO ^- ) ₂ (NH ₄ ⁺ ) ₂ ) is preferable.

In addition, some titanium chelates and their ammonium salts are commercially available from Matsumoto Fine Chemical Co., Ltd., and commercial products may be used.

In addition, the Ti concentration in the surface treatment solution according to the step (A), in terms of Ti atoms, is 0.1 to 1500 mmol/L, preferably 0.2 to 1000 mmol/L, so that the stability of the Ti solution and the operability of the coating treatment become easy. desirable from the point of view

(A) The pH of the surface treatment solution according to the step is 7 or more, preferably 8 or more and 11 or less, particularly preferably more than 8 and 10 or less, when the lithium nickel manganese cobalt composite oxide particles and the surface treatment solution come into contact. , which is preferable in that elution of Li from lithium nickel manganese cobalt composite oxide particles is suppressed. In addition, about the pH of the surface treatment liquid, the pH can be adjusted by adding acid or alkali to the surface treatment liquid so that it becomes a pH within the above range.

In the step (A), the method of contacting the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) with the surface treatment liquid containing the titanium chelate compound is not particularly limited, but, for example, the general formula A method of mixing the lithium nickel manganese cobalt composite oxide particles represented by (1) with a surface treatment solution containing a titanium chelate compound, and the like are exemplified. The mixture of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) and the surface treatment liquid containing the titanium chelate compound may be in the form of powder, paste or slurry. Whether the mixture is in powder form, paste form or slurry form, any form can be obtained by adjusting the addition amount of the surface treatment liquid containing the titanium chelate compound to the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1). can For example, the powdery mixture of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) and the surface treatment liquid containing the titanium chelate compound is the lithium nickel manganese cobalt composite oxide represented by the general formula (1) A surface treatment liquid obtained by adding a surface treatment liquid containing a titanium chelate compound in a small volume to particles, and containing lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) and a titanium chelate compound A mixture of in the form of a slurry is obtained by adding a small amount of lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) to a surface treatment liquid containing a large amount of titanium chelate compound by volume of the liquid.

Further, the contact of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) with the solution containing the titanium chelate compound results in the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1), the titanium chelate compound A method of immersing in a solution containing

Among these, in the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, a method in which lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) are brought into contact with a surface treatment liquid containing a titanium chelate compound. As a method, a method in which the mixture is in a slurry form is preferable in that the titanium chelate compound can be easily adhered to the entire surface of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1).

Lithium nickel manganese cobalt represented by general formula (1) is obtained by bringing lithium nickel manganese cobalt composite oxide particles represented by general formula (1) into contact with a surface treatment solution containing a titanium chelate compound, and then drying the entire amount of the solvent as it is. It is preferable to obtain coated particles in which the particle surfaces of composite oxide particles are coated with a titanium chelate compound. The drying temperature at the time of drying is not particularly limited as long as the solvent evaporates, but is preferably 60 to 180°C and particularly preferably 90 to 150°C.

In addition, regarding drying, you may perform whole-quantity drying by a spray drying apparatus, a rotary evaporator, a fluid bed dry-coating apparatus, a vibration drying apparatus, etc.

In the step (A), the slurry containing the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) and the surface treatment liquid containing the titanium chelate compound is dried by a spray drying device to remove the entire amount of the solvent. It is preferable in that it becomes easy to control the coating amount of the chelate compound.

Step (B) is a step of obtaining a modified lithium nickel manganese cobalt composite oxide (A) or a modified lithium nickel manganese cobalt composite oxide (B) by heating the coated particles obtained in step (A).

In the modified lithium nickel manganese cobalt composite oxide particles (A), Ti atoms are mainly not dissolved in the lithium nickel manganese cobalt composite oxide particles, and in the state of an oxide containing Ti, the surface of the lithium nickel manganese cobalt composite oxide particles exists in In addition, in the modified lithium nickel manganese cobalt composite oxide particles (A), a small amount of some Ti atoms may be dissolved inside the lithium nickel manganese cobalt composite oxide particles.

In the modified lithium nickel manganese cobalt composite oxide particles (B), Ti atoms are considered to exist mainly in a solid solution state inside the particles of the lithium nickel manganese cobalt composite oxide particles. Further, in the modified lithium nickel manganese cobalt composite oxide particles (B), when the particle surface of the modified lithium nickel manganese cobalt composite oxide particles was analyzed by elemental mapping analysis of Ti by SEM-EDX, Ti was found to be Co, Ni, Mn, etc. Similarly, as long as it is within the range observed in a uniformly distributed state, Ti atoms may exist in a Ti-containing oxide state on the surface of the lithium nickel manganese cobalt composite oxide particle.

Therefore, whether the particle is a modified lithium nickel manganese cobalt composite oxide particle (A) or a modified lithium nickel manganese cobalt composite oxide particle (B) is confirmed by analyzing the particle surface of the sample particle by elemental mapping analysis of Ti with SEM-EDX. That is, in the case of the modified lithium nickel manganese cobalt composite oxide particles (A), when the particle surfaces of the sample particles are analyzed by elemental mapping analysis of Ti by SEM-EDX at a magnification of 10,000 to 30,000 times, the surface of the sample particles It is observed that Ti exists in a non-uniform distribution such as uneven distribution. In addition, in the case of the modified lithium nickel manganese cobalt composite oxide particles (B), when the particle surfaces of the sample particles are analyzed by elemental mapping analysis of Ti by SEM-EDX at a magnification of 10,000 to 30,000 times, the surface of the sample particles It is observed that Ti exists in a uniform distribution.

In the present invention, the oxide containing Ti that coats the particle surface of the lithium nickel manganese cobalt composite oxide particles is an oxide of Ti, Ti, and one or two selected from Li, Ni, Mn, Co, and M. It represents a composite oxide containing more than one species.

In the heat treatment according to step (B), the heat treatment temperature is 400 to 1000°C, preferably 450 to 950°C. The reason for this is that when the heat treatment temperature is less than 400°C, sufficient decomposition and oxidation reaction of the titanium chelate for coating treatment are not performed, and sufficient effects cannot be obtained. This is because the solid solution reaction of the composite oxide particles proceeds excessively, and the solid solution of Ti proceeds not only in the vicinity of the particle surface but also in the depth, so that the amount of Ti in the vicinity of the particle surface is insufficient, making it difficult to obtain the modification effect of the present invention.

In the heat treatment according to step (B), the time of the heat treatment is not critical in the present production method, but is usually 1 hour or more, preferably 2 to 10 hours, and the modified lithium nickel manganese cobalt with satisfactory performance. Complex oxide particles can be obtained.

In the heat treatment according to step (B), the atmosphere of the heat treatment is preferably an oxidizing atmosphere such as air or oxygen gas.

Further, in the method for producing the modified lithium nickel manganese cobalt composite oxide particles of the present invention, in a preferred embodiment, the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) are prepared in a surface treatment solution containing a titanium chelate compound. in that the entire amount of the solvent is dried as it is after contact with the lithium nickel manganese cobalt composite oxide particle (A), the coating amount (adhesion amount) of the oxide containing Ti on the lithium nickel manganese cobalt composite oxide particle and the modified lithium The high amount (content) of Ti relative to the lithium nickel manganese cobalt composite oxide particles in the nickel manganese cobalt composite oxide particles (B) was determined from the amount of the lithium nickel manganese cobalt composite oxide particles and the Ti content in the surface treatment solution containing the titanium chelate compound used. It can be expressed as a theoretical coating amount (adhesion amount) and a high amount (content amount) obtained.

In the step (A) of the modification step, the Ti content per 1 m 2 of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is calculated in terms of Ti atoms so as to fall within the range of the amount of oxide containing Ti that is deposited, which will be described later. The above surface modification liquid is added in an amount of 0.1 to 150 mg, preferably 0.5 to 120 mg, to the lithium nickel manganese cobalt composite oxide particles represented by the above general formula (1), mixed, and dried. It is preferable in that it becomes easy to control the amount of coating and high amount of the chelate compound.

In the present invention, the "Ti content in terms of Ti atoms per 1 m 2 of lithium nickel manganese cobalt composite oxide particles" is obtained by the following formula.

k: Ti content (mg) in terms of Ti atoms per 1 m2 of lithium nickel manganese cobalt composite oxide particles

x: Ti content (mg) in terms of Ti atoms relative to 1 g of lithium nickel manganese cobalt composite oxide

t: BET specific surface area of lithium nickel manganese cobalt composite oxide particles (m 2 / g)

In the method for producing the modified lithium nickel manganese cobalt composite oxide particles of the present invention, the amount of oxide deposited with Ti and the high amount (content) of Ti in the obtained modified lithium nickel manganese cobalt composite oxide particles are lithium nickel manganese cobalt composite oxide particles 1 It is 0.1 to 150 mg, preferably 0.5 to 120 mg in terms of Ti atom per m 2 . The amount of oxide attached to Ti and the high amount (content) of Ti in the modified lithium nickel manganese cobalt composite oxide particles are within the above ranges, so that the modified lithium nickel manganese cobalt composite oxide particles (A) and/or the modified lithium nickel manganese cobalt composite When the oxide particle (B) is used as a positive electrode active material of a lithium secondary battery, it is preferable in that the cycle characteristics are further improved. That is, in the method for producing the modified lithium nickel manganese cobalt composite oxide of the present invention, the amount of the obtained modified lithium nickel manganese cobalt composite oxide particle is 0.1 to 150 mg, preferably 0.5 to 120 mg in terms of Ti atoms per 1 m 2 ( In step A), it is preferable to prepare the amount of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) to be brought into contact, the concentration of the titanium chelate compound in the surface treatment solution, and the amount of the surface treatment solution.

In the present invention, the "attachment amount in terms of Ti atoms per 1 m 2 of the lithium nickel manganese cobalt composite oxide particles of the oxide containing Ti" is obtained by the following formula.

k': Attachment amount (mg) in terms of Ti atoms per 1 m2 of lithium nickel manganese cobalt composite oxide particles of Ti-containing oxide

x: Ti content (mg) in terms of Ti atoms relative to 1 g of lithium nickel manganese cobalt composite oxide

t: BET specific surface area of lithium nickel manganese cobalt composite oxide particles (m 2 / g)

Further, the amount of residual alkali in the modified lithium nickel manganese cobalt composite oxide particles obtained by performing the method for producing the modified lithium nickel manganese cobalt composite oxide particles of the present invention is 1.2% by mass or less, preferably 1.0% by mass or less, attributable to the residual alkali. It is preferable in that expansion or deterioration of the battery caused by gas generation can be suppressed.

The modified lithium nickel manganese cobalt composite oxide particles obtained by performing the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention are suitably used as a positive electrode active material of a lithium secondary battery, and the modified lithium nickel manganese cobalt composite oxide particles are used as a positive electrode. A lithium secondary battery used as an active material has higher cycle characteristics than a case where lithium nickel manganese cobalt composite oxide particles having the same composition as unmodified Li, Ni, Mn, and Co are used.

Further, large particles of the modified lithium nickel manganese cobalt composite oxide obtained by performing the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, and modified lithium obtained by performing the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention By mixing small particles of nickel manganese cobalt composite oxide, the capacity per volume can be improved. In this case, when the average particle diameter of the large particles is 7.5 to 30.0 μm, preferably 8.0 to 25.0 μm, and the average particle diameter of the small particles is 0.5 to 7.5 μm, preferably 1.0 to 7.0 μm, the capacity per volume is improved. desirable from the point of view In addition, the press density when the mixture is compressed at 0.65 tonf/cm 2 is 2.7 g/cm 3 or more, preferably 2.8 to 3.3 g/cm 3 , from the standpoint of further increasing the capacity per volume.

In the method for producing the modified lithium nickel manganese cobalt composite oxide particles of the present invention, the modified lithium nickel manganese cobalt composite oxide particles (A) are preferably the large particles of the modified lithium nickel manganese cobalt composite oxide, and the modified lithium nickel manganese cobalt composite oxide particles (A) are preferred. The small particles of the oxide are preferably modified lithium nickel manganese cobalt composite oxide particles (B) in terms of further improving cycle characteristics.

In the method for producing the modified lithium nickel manganese cobalt composite oxide particles of the present invention, the smaller the average particle diameter of the lithium nickel manganese cobalt composite oxide particles to which the titanium chelate compound is deposited in step (A), the adhering titanium chelate compound or its The oxide containing Ti, which is a thermal decomposition product, does not uniformly increase in volume on the particle surface of the lithium nickel manganese cobalt composite oxide particles and is easily highly dispersed, and the oxide containing Ti, which is a thermal decomposition product of the titanium chelate compound adhered in a highly dispersed manner. The reactivity between the lithium nickel manganese cobalt composite oxide particles and the lithium nickel manganese cobalt composite oxide particles is increased on the surface of the lithium nickel manganese cobalt composite oxide particles. Therefore, in the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, the smaller the average particle diameter of the lithium nickel manganese cobalt composite oxide particles to which the titanium chelate compound is deposited in step (A), the smaller the adhering titanium chelate. A compound or an oxide containing Ti, which is a thermal decomposition product thereof, is more easily dispersed uniformly and highly dispersed on the particle surface of lithium nickel manganese cobalt composite oxide particles, and Ti, which is a thermal decomposition product of a titanium chelate compound adhered in a highly dispersed manner, Since the oxide has a higher reactivity with the lithium nickel manganese cobalt composite oxide particles on the surface of the lithium nickel manganese cobalt composite oxide particles, the titanium chelate compound is attached in the step (A) even if the heat treatment temperature in the step (B) is the same. The smaller the average particle diameter of the lithium nickel manganese cobalt composite oxide particles, the easier the modified lithium nickel manganese cobalt composite oxide particles (B) are to be formed. In addition, the higher the heat treatment temperature in the step (B), the higher the reactivity between the lithium nickel manganese cobalt composite oxide particles and the Ti-containing oxide, which is a thermal decomposition product of the attached titanium chelate compound, the lithium nickel manganese cobalt composite oxide particles Since it is higher on the surface, the higher the heat treatment temperature in the step (B), the easier it is to generate the modified lithium nickel manganese cobalt composite oxide particles (B).

In other words, in the method for producing the modified lithium nickel manganese cobalt composite oxide particles of the present invention, the larger the average particle diameter of the lithium nickel manganese cobalt composite oxide particles to which the titanium chelate compound is deposited in step (A), the larger the titanium chelate adhering. A compound or an oxide containing Ti, which is a thermal decomposition product of the compound, is non-uniformly bulky and easily dispersed on the particle surface of the lithium nickel manganese cobalt composite oxide particles, and Ti, which is a thermal decomposition product of the titanium chelate compound attached to the particle surface, Since the oxide has a lower reactivity with the lithium nickel manganese cobalt composite oxide particles on the surface of the lithium nickel manganese cobalt composite oxide particles, the titanium chelate compound is attached in the step (A) even if the heat treatment temperature in the step (B) is the same. The larger the average particle diameter of the lithium nickel manganese cobalt composite oxide particles, the more easily the modified lithium nickel manganese cobalt composite oxide particles (A) are formed. In addition, as the heat treatment temperature in step (B) is lowered, the reactivity between the adhering titanium chelate compound and the lithium nickel manganese cobalt composite oxide particles is lowered on the surface of the lithium nickel manganese cobalt composite oxide particles, so in step (B) The lower the heat treatment temperature, the easier the formation of the modified lithium nickel manganese cobalt composite oxide particles (A).

Therefore, in the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, the average particle diameter of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) used in step (A) in step (B) The modified lithium nickel manganese cobalt composite oxide particles (A) and the modified lithium nickel manganese cobalt composite oxide particles (B) can be produced separately by appropriately selecting a combination of heat treatment temperatures.

For example, in a preferred embodiment of the present invention, the modified lithium nickel manganese cobalt composite oxide particles (A) are lithium nickel manganese cobalt composite oxide particles of the general formula (1) in step (A), and have an average particle diameter Step (A) using particles of 7.5 to 30.0 μm, preferably 8.0 to 25.0 μm, and setting the heat treatment temperature in step (B) to 750° C. or more and 1000° C. or less, preferably 750° C. to 900° C. And (B) It can manufacture by performing a process.

In addition, the modified lithium nickel manganese cobalt composite oxide particles (B) are lithium nickel manganese cobalt composite oxide particles of the general formula (1) in step (A), and have an average particle diameter of 0.5 to 7.5 μm, preferably 1.0 to 7.0 μm. It can be produced by performing the above steps (A) and (B) using particles of, and setting the heat treatment temperature in the step (B) to 750 ° C. or more and 1000 ° C. or less, preferably 750 ° C. or more to 900 ° C. or less. .

Example

Hereinafter, the present invention will be described by examples, but the present invention is not limited thereto.

<Preparation of Lithium Nickel Manganese Cobalt Composite Oxide Particles (LNMC) Sample>

<LNMC sample 1>

Lithium carbonate (average particle diameter 5.7 μm) and nickel manganese cobalt composite hydroxide (Ni: Mn: Co = 6: 2: 2 (molar ratio), average particle diameter 9.8 μm) were weighed, thoroughly mixed with a household mixer, and Li / ( A raw material mixture having a molar ratio of Ni+Mn+Co) of 1.01 was obtained. In addition, a commercially available nickel-manganese-cobalt composite hydroxide was used.

Next, the obtained raw material mixture was fired in an air atmosphere at 700°C for 2 hours and then at 850°C for 10 hours in an alumina bowl. After completion of firing, the fired product was pulverized and classified. As a result of measuring the obtained fired product by XRD, it was confirmed that it was a single-phase lithium nickel manganese cobalt composite oxide. What was obtained was secondary agglomerated spherical lithium nickel manganese cobalt composite oxide particles (LiNi _0.6 Mn _0.2 Co _0.2 O ₂ ) with an average particle diameter of 10.2 μm and a BET specific surface area of 0.21 m 2 /g.

<LNMC sample 2>

Lithium carbonate (average particle diameter 5.7 μm) and nickel manganese cobalt composite hydroxide (Ni: Mn: Co = 6: 2: 2 (molar ratio), average particle diameter 3.7 μm) were weighed and sufficiently mixed with a household mixer to obtain Li / ( A raw material mixture having a molar ratio of Ni+Mn+Co) of 1.01 was obtained. In addition, a commercially available nickel-manganese-cobalt composite hydroxide was used.

Next, the obtained raw material mixture was fired in an air atmosphere at 700°C for 2 hours and then at 850°C for 10 hours in an alumina bowl. After completion of firing, the fired product was pulverized and classified. As a result of measuring the obtained fired product by XRD, it was confirmed that it was a single-phase lithium nickel manganese cobalt composite oxide. What was obtained was secondary agglomerated spherical lithium nickel manganese cobalt composite oxide particles (LiNi _0.6 Mn _0.2 Co _0.2 O ₂ ) with an average particle diameter of 5.4 μm and a BET specific surface area of 0.69 m 2 /g.

Table 1 shows the physical properties of the lithium nickel manganese cobalt composite oxide sample (LNMC sample) obtained above.

In addition, the average particle diameter of the LNMC sample, the amount of residual alkali, and the pressed density were measured as follows.

<Average Particle Size>

The average particle diameter was determined by a laser diffraction/scattering method.

<Measurement of Residual Alkali Amount>

Regarding the amount of residual alkali in the LNMC sample, 5 g of the sample and 100 g of ultrapure water were weighed in a beaker and dispersed at 25° C. for 5 minutes using a magnetic stirring bar. Next, this dispersion liquid was filtered, and 70 ml of the filtrate was titrated with 0.1 N-HCl with an automatic titrator (model COMTITE-2500), and the amount of remaining alkali present in the sample (value obtained by measuring the amount of lithium and converting it to lithium carbonate) ) was calculated.

<Pressed Density>

2.25 g of the sample was put into a twin-shaft molding machine with a weighing diameter of 1.5 cm, and the height of the compressed material was measured in a state where a pressure of 0.65 tonf / cm 2 was applied for 1 minute using a press machine, and the apparent volume of the compressed material calculated from the height was measured. From the mass of one sample, the pressed density of the sample was calculated.

<Preparation of surface treatment solution>

<Preparation of Surface Treatment Liquid Containing Titanium Lactate Chelate>

Ammonia water was added to an aqueous solution of titanium lactate ammonium salt (Ti(OH) ₂ [(OCH(CH ₃ )COO ^- ) ₂ (NH ₄ ⁺ ) ₂ ) manufactured by Matsumoto Fine Chemical Co., Ltd. (product name: TC-335, pH 4.4) to adjust the pH to 8.5. was adjusted so as to prepare a titanium lactate chelate-containing surface treatment solution having a concentration shown in Table 2 below.

(Examples 1 to 6)

Using the LNMC sample and surface treatment liquid, it was weighed so as to have the ratio shown in Table 3, and it was prepared so that it might become a slurry with a solid content concentration of 25 mass %.

Subsequently, the slurry was supplied at a feed rate of 65 g/min to a spray dryer with an outlet temperature set at 120° C. to obtain coated particles in which titanium lactate chelate adhered to the particle surfaces of the LNMC sample.

Subsequently, the coated particles were subjected to heat treatment at 800°C for 5 hours to obtain a modified LNMC sample (A) in which oxides of Ti adhered to the surface of the particles of the LNMC sample and a modified LNMC sample (B) in which Ti was dissolved and contained in the LNMC sample. got it

In addition, to determine whether the modified LNMC sample to which oxides of Ti are adhered or the modified LNMC sample in which Ti is dissolved and contained in the LNMC sample, the particle surfaces of the sample particles are examined by SEM-EDX (field emission manufactured by Hitachi High-Technologies Co., Ltd.) at a magnification of 20,000 times. It was confirmed by performing elemental mapping analysis of Ti using a scanning electron microscope SU-8220 and an energy dispersive X-ray analyzer XFlash5060FlatQUAD manufactured by BRUKER. The use of LNMC sample 1 as the LNMC sample is a modified lithium nickel manganese cobalt composite oxide particle ( A) has been confirmed. On the other hand, when LNMC sample 2 was used as the LNMC sample, as a result of elemental mapping analysis of Ti on the particle surface of the sample particle by SEM-EDX, Ti was uniformly distributed in the same way as Co, Ni, and Mn. It was confirmed that it was the nickel-manganese-cobalt composite oxide particle (B).

In addition, the measurement conditions of SEM-EDX are as follows.

Acceleration voltage: 15 kV, magnification: 20,000 times, walking distance: 9.5 to 11.5 mm, measurement time: 6 minutes

In addition, the amount of residual alkali was also measured for the modified LNMC sample in the same manner as for the LNMC sample.

In addition, the addition amount of the surface treatment liquid in Table 3 is a calculated value that becomes the Ti content in terms of Ti atoms per 1 m 2 of the LNMC sample when the surface treatment liquid is added, and was obtained by the following formula.

k: Ti content (mg) in terms of Ti atoms per 1 m2 of LNMC sample

x: Ti content in terms of Ti atom with respect to 1 g of LNMC sample (mg)

t: BET specific surface area of LNMC sample (m2/g)

(Reference Example 1)

Commercially available lithium cobalt oxide (LiCoO ₂ : average particle diameter: 9.5 μm, BET specific surface area: 0.37 m/g) was used, and in the same manner as in Examples 1 to 3, oxides of Ti were formed on the particle surfaces of lithium cobalt oxide (LCO) samples. An attached modified LCO sample was obtained.

In addition, for the modified LCO, the amount of residual alkali was measured in the same manner as for the LNMC sample.

In addition, the addition amount of the surface treatment liquid in Table 3 is a calculated value that becomes the Ti content in terms of Ti atoms per 1 m 2 of the LCO sample when the surface treatment liquid is added, and was obtained by the following formula.

k": Ti content (mg) in terms of Ti atoms per 1 m2 of LCO sample

x": Ti content (mg) in terms of Ti atom with respect to 1 g of LCO sample

t": BET specific surface area of LCO sample (m 2 / g)

A battery performance test was conducted as follows.

<Production of Lithium Secondary Battery 1>

95% by mass of the modified LNMC samples obtained in Examples, 2.5% by mass of graphite powder, and 2.5% by mass of polyvinylidene fluoride were mixed to make a positive electrode agent, which was dispersed in N-methyl-2-pyrrolidinone to prepare a kneaded paste. The kneaded paste was applied to an aluminum foil, dried and pressed, and then punched into a disc having a diameter of 15 mm to obtain a positive electrode plate.

Using this positive electrode plate, a coin-type lithium secondary battery was produced using each member such as a separator, negative electrode, positive electrode, current collector plate, mounting metal member, external terminal, and electrolyte solution. Among them, a metallic lithium foil was used as the negative electrode, and as the electrolyte, one obtained by dissolving 1 mole of LiPF ₆ in 1 liter of a 1:1 mixture of ethylene carbonate and methyl ethyl carbonate was used.

Subsequently, performance evaluation of the obtained lithium secondary battery was conducted. The results are shown in Table 4. In addition, lithium secondary batteries were prepared in the same manner for the modified LCO sample prepared in Reference Example 1, LNMC sample 1 (Comparative Example 1) and LNMC sample 2 (Comparative Example 2) without modification, and the same evaluation was performed. did The results are listed together in Table 4.

<Battery performance evaluation 1>

The produced coin-type lithium secondary battery was operated at room temperature under the following test conditions, and the following battery performance was evaluated.

(1) Test conditions for evaluation of cycle characteristics

First, charging was performed from 0.5 C to 4.3 V over 2 hours, and constant current/constant voltage charging (CCCV charging) was performed in which the voltage was maintained at 4.3 V for 3 hours. Thereafter, charge/discharge was performed by constant current discharge (CC discharge) at 0.2 C to 2.7 V, and these operations were repeated 20 cycles as one cycle.

(2) Initial charge capacity, initial discharge capacity (per weight of active material)

The first cycle charge capacity and discharge capacity in the evaluation of cycle characteristics were defined as the first charge capacity and the first discharge capacity.

(3) Discharge capacity at 20th cycle (per weight of active material)

The discharge capacity at the 20th cycle in the evaluation of cycle characteristics was taken as the discharge capacity at the 20th cycle.

(4) Capacity retention rate

From each discharge capacity (per active material weight) of the 1st cycle and the 20th cycle in evaluation of cycle characteristics, the capacity retention rate was calculated by the following formula.

Capacity retention rate (%) = (discharge capacity at the 20th cycle/discharge capacity at the 1st cycle) x 100

(5) Energy density retention rate

The energy density retention rate was calculated from the Wh capacity (per weight of active material) at each discharge of the 1st cycle and the 20th cycle in the evaluation of cycle characteristics by the following formula.

Energy density retention rate (%) = (discharge Wh capacity at the 20th cycle/discharge Wh capacity at the 1st cycle) x 100

<Production of lithium secondary battery 2>

Using the modified LNMC samples obtained in Examples 1 to 6 and the LNMC samples before modification, they were thoroughly mixed with a household mixer to prepare a mixture having the composition shown in Table 5, and used as a positive electrode active material sample. In addition, the pressed density of the positive electrode active material sample was measured in the same manner as in the above LNMC sample, and the results are shown in Table 5 together.

95% by mass of the positive electrode active material sample, 2.5% by mass of graphite powder, and 2.5% by mass of polyvinylidene fluoride were mixed to make a positive electrode agent, which was dispersed in N-methyl-2-pyrrolidinone to prepare a kneaded paste. The kneaded paste was applied to an aluminum foil, dried and pressed, and then punched into a disc having a diameter of 15 mm to obtain a positive electrode plate.

Using this positive electrode plate, a coin-type lithium secondary battery was produced using each member such as a separator, negative electrode, positive electrode, current collector plate, mounting metal member, external terminal, and electrolyte solution. Among them, a metallic lithium foil was used as the negative electrode, and as the electrolyte, one obtained by dissolving 1 mole of LiPF ₆ in 1 liter of a 1:1 mixture of ethylene carbonate and methyl ethyl carbonate was used.

Subsequently, performance evaluation of the obtained lithium secondary battery was conducted. The results are listed together in Table 6.

<Battery performance evaluation 2>

The fabricated coin-type lithium secondary battery was operated at room temperature under the following test conditions, cycle characteristics evaluation, initial charge capacity, initial discharge capacity (per weight of active material), initial charge capacity, initial discharge capacity (per weight of active material), capacity retention rate , energy density retention was evaluated in the same manner as in Performance Evaluation 1 of the battery. Further, the discharge capacity per volume was also evaluated, and the results are shown in Table 6. In addition, the modified LNMC samples of Examples 2 and 5 were used as positive electrode active material samples and evaluated in the same manner. The results are listed together in Table 6.

(6) Discharge capacity per volume

The discharge capacity per volume was determined by the following formula based on the initial discharge capacity and the electrode density.

Discharge capacity per volume (mAh/cm3) = discharge capacity at the first cycle (mAh/g) x electrode density (g/cm3) x 0.95 (ratio of active material amount in positive electrode material)

In addition, the electrode density was calculated as the density of the positive electrode material by measuring the mass and thickness of the electrode fabricated from the sample to be measured, subtracting the thickness and mass of the current collector from this. In addition, the positive electrode material was a mixture of 95% by mass of the positive electrode active material sample, 2.5% by mass of graphite powder, and 2.5% by mass of polyvinylidene fluoride.

Claims (10)

The following general formula (1):

(Wherein, M is selected from Mg, Al, Ti, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na and K Represents one or more metal elements that are x is 0.98≤x≤1.20, y is 0.30≤y<1.00, z is 0<z≤0.50, t is 0<t≤0.50, p is 0≤p≤ represents 0.05, and y+z+t+p=1.00)
The lithium nickel manganese cobalt composite oxide particles represented by are brought into contact with a surface treatment solution containing a titanium chelate compound to obtain coated particles in which the titanium chelate compound adheres to the particle surfaces of the lithium nickel manganese cobalt composite oxide particles. a modification step of obtaining modified lithium nickel manganese cobalt composite oxide particles by heating the coated particles;
The titanium chelate compound has the following general formula (2):

(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group or a phosphine, and when present in a plurality thereof, may be the same or different. L represents a group derived from hydroxycarboxylic acid, and a plurality of In this case, it may be the same or different. m represents a number of 0 or more and 3 or less, n represents a number of 1 or more and 3 or less, and m+n is 3 to 6)
Method for producing a modified lithium nickel manganese cobalt composite oxide particle, characterized in that the titanium chelate represented by or its ammonium salt. According to claim 1,
A method for producing modified lithium nickel manganese cobalt composite oxide particles, characterized in that the temperature of the heat treatment is 400 to 1000 ° C. According to claim 1 or 2,
A method for producing modified lithium nickel manganese cobalt composite oxide particles, characterized in that L in the general formula (2) is a monovalent carboxylic acid. According to claim 1 or 2,
A method for producing modified lithium nickel manganese cobalt composite oxide particles, wherein L in the general formula (2) is lactic acid. According to any one of claims 1 to 4,
Method for producing modified lithium nickel manganese cobalt composite oxide particles, characterized in that the pH of the surface treatment liquid is 7 or more. According to any one of claims 1 to 5,
The amount of the titanium chelate compound attached to the coated particles is 0.1 to 150 mg in terms of Ti atoms per 1 m of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1), Method for producing manganese-cobalt composite oxide particles. According to any one of claims 1 to 6,
A method for producing modified lithium nickel manganese cobalt composite oxide particles, characterized in that the amount of residual alkali in the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is 1.2% by mass or less. According to any one of claims 1 to 7,
A method for producing modified lithium nickel manganese cobalt composite oxide particles, wherein the amount of residual alkali in the modified lithium nickel manganese cobalt composite oxide particles is 1.2% by mass or less. According to any one of claims 1 to 8,
In the reforming process,
The Ti content per 1 m 2 of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is an addition amount of 0.1 to 150 mg in terms of Ti atoms, and the surface modification liquid is represented by the general formula (1) A method for producing modified lithium nickel manganese cobalt composite oxide particles, characterized in that the particles are added to the lithium nickel manganese cobalt composite oxide particles, mixed, and dried. Large particles having an average particle diameter of 7.5 to 30.0 µm obtained by the production method according to any one of claims 1 to 9, and an average particle diameter obtained by the production method according to any one of claims 1 to 9 A method for producing a positive electrode active material for a lithium secondary battery, comprising a step of mixing the small particles of 0.5 to 7.5 μm.