JP7252298B2 - Method for producing modified lithium-nickel-manganese-cobalt composite oxide particles - Google Patents

Description

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

Conventionally, lithium cobalt oxide 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 with a low cobalt content have been developed (see, for example, Patent Documents 1 and 2).

A lithium secondary battery that uses a lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material can be reduced in cost by adjusting the atomic ratio of nickel, manganese, and cobalt contained in the composite oxide. It is known to have a higher capacity than lithium cobalt oxide (see, for example, 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 the problem of deterioration in cycle characteristics.

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

WO 2004/092073 pamphlet JP-A-2005-25975 Japanese Unexamined Patent Application Publication No. 2011-23120 JP 2016-24968 A JP 2016-72071 A

In recent years, the use of lithium secondary batteries in the field of automobiles, such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles, has been investigated. For this reason, lithium secondary batteries using lithium-nickel-manganese-cobalt composite oxide as a positive electrode active material are required to further improve cycle characteristics.

Accordingly, an object of the present invention is to provide lithium-nickel-manganese-cobalt composite oxide particles that can improve cycle characteristics when used as a positive electrode active material for lithium secondary batteries.

The inventors of the present invention have made intensive studies in view of the above circumstances, and found that the lithium-manganese-cobalt composite oxide particles represented by the general formula (1) are converted into titanium chelates represented by a specific general formula or ammonium salts thereof. The modified lithium nickel manganese cobalt composite oxide particles are obtained by heat treatment after contact with the surface treatment liquid containing The inventors have found that the battery has excellent cycle characteristics, and have completed the present invention.

That is, the present invention (1) is represented by the following general formula (1):
_{LixNiyMnzCotMpO1 + x ( 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, where x is 0.98≤x≤1.20, y is 0.50≤y≤0.95 , z is 0.025≤z≤0.45 , t is 0.025 ≤ t ≤ 0.45 , p is 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 liquid containing a titanium chelate compound to obtain coated particles in which the titanium chelate compound is attached to the surface of the lithium-nickel-manganese-cobalt composite oxide particles. and then heat-treating the coated particles to obtain modified lithium-nickel-manganese-cobalt composite oxide particles,
The titanium chelate compound has the following general formula (2):
Ti(R ¹ ) _m L _n (2)
(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group, or a phosphine, and when there are multiple groups, they may be the same or different. L is derived from a hydroxycarboxylic acid. represents a group, and when there is more than one, they 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; be.)
A titanium chelate or its ammonium salt represented by
the surface treatment liquid containing the titanium chelate compound has a pH of 8 or more and 11 or less;
A method for producing modified lithium-nickel-manganese-cobalt composite oxide particles characterized by

The present invention (2) also provides the method for producing modified lithium-nickel-manganese-cobalt composite oxide particles according to (1), wherein the temperature of the heat treatment is 400 to 1000°C. .

Further, the present invention (3) is the modified lithium-nickel-manganese-cobalt composite oxide particles of (1) or (2), wherein L in the general formula (2) is a monovalent carboxylic acid. It is intended to provide a manufacturing method of.

Further, the present invention (4) provides the method for producing modified lithium-nickel-manganese-cobalt composite oxide particles of (1) or (2), wherein L in the general formula (2) is lactic acid. It provides.

Further, in the present invention ( 5 ), the amount of the titanium chelate compound attached to the coated particles is 0.00 in terms of Ti atoms per 1 m ² of the lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1). Provided is a method for producing modified lithium-nickel-manganese-cobalt composite oxide particles according to any one of (1) to ( 4 ), wherein the particles are 1 to 150 mg.

In addition, the present invention ( 6 ) is 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 (1). The present invention provides a method for producing modified lithium-nickel-manganese-cobalt composite oxide particles according to any one of (5) to ( 5 ).

Further, the present invention ( 7 ) is characterized in that the residual alkali content in the modified lithium-nickel-manganese-cobalt composite oxide particles is 1.2% by mass or less. A method for producing modified lithium-nickel-manganese-cobalt composite oxide particles according to the above.

Further, according to the present invention (8), in the reforming step,
The surface treatment liquid is added in an amount such that the Ti content per 1 m ² of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is 0.1 to 150 mg in terms of Ti atoms. adding to and mixing with the lithium-nickel-manganese-cobalt composite oxide particles represented by formula (1), and drying the entire amount;
A method for producing modified lithium-nickel-manganese-cobalt composite oxide particles according to any one of (1) to (7), characterized by:

In addition, the present invention ( 9 ) comprises particles having a large average particle diameter of 7.5 to 30.0 μm obtained by the production method according to any one of (1) to ( 8 ), and (1) to ( 8) A method for producing a positive electrode active material for a lithium secondary battery, comprising a step of mixing particles having a small average particle size of 0.5 to 7.5 μm obtained by the production method according to any one of ). It provides

According to the present invention, it is possible to provide lithium-nickel-manganese-cobalt composite oxide particles that can improve cycle characteristics when used as a positive electrode active material for lithium secondary batteries.

The present invention will be described below 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 mixed with the titanium chelate represented by the general formula (2) or the general Lithium-nickel-manganese-cobalt composite oxide particles are brought into contact with a surface treatment liquid containing an ammonium salt of a titanium chelate represented by formula (2) to obtain coated particles in which these titanium chelate compounds are attached to the particle surfaces, and then and a modifying step of obtaining modified lithium-nickel-manganese-cobalt composite oxide particles by heat-treating the obtained coated 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) may be collectively referred to as "titanium chelate compound".

The method for producing a modified lithium-nickel-manganese-cobalt composite oxide of the present invention basically comprises the following steps (A) and (B).
(A) Step: 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 treated with a surface treatment liquid containing the titanium chelate compound according to the present invention. to obtain coated particles in which a titanium chelate compound is attached to the surfaces of the lithium-nickel-manganese-cobalt composite oxide particles.
(B) step: The coated particles obtained by performing the (A) step are heat-treated to obtain modified lithium-nickel-manganese-cobalt composite oxide particles (A) or modified lithium-nickel-manganese-cobalt composite oxide particles ( B).
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 It is sometimes described as "matter particles".

In step (B), the coated particles are heat-treated 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 presence of the Ti-containing oxide adhering to the particle surface of the lithium-nickel-manganese-cobalt composite oxide particles means that the particle surface of the modified lithium-nickel-manganese-cobalt composite oxide particles is increased by 10,000 to 30,000 times. When analyzed by elemental mapping analysis of Ti by SEM-EDX at an magnification of be.
On the other hand, in the modified lithium-nickel-manganese-cobalt composite oxide particles (B), the particle surface of the modified lithium-nickel-manganese-cobalt composite oxide particles was examined by SEM-EDX at a magnification of 10,000 to 30,000 times. When analyzed by elemental mapping analysis, Ti is observed to be uniformly distributed like Co, Ni, Mn, and the like. The present inventors have found that in the modified lithium-nickel-manganese-cobalt composite oxide particles (B), the dissolution reaction of Ti proceeds preferentially, and Ti is contained in the lithium-nickel-manganese-cobalt composite oxide particles in a solid solution state. Therefore, it is assumed that Ti is uniformly distributed on the particle surface of the lithium-nickel-manganese-cobalt composite oxide particles in the same manner as Co, Ni, Mn, and the like.

In the step (A), the lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1) to be modified are brought into contact with the surface treatment liquid containing the titanium chelate compound according to the present invention to obtain lithium-nickel-manganese-cobalt. This is a step of obtaining coated particles in which a titanium chelate compound is attached to the surfaces of composite oxide particles. The titanium chelate compound on the particle surface of the lithium-nickel-manganese-cobalt composite oxide particles may coat the entire particle surface of the lithium-nickel-manganese-cobalt composite oxide particles, or may coat a part of the particle surface. There may be. The phrase "partially covering the particle surface" refers to a state in which the particle surface has a portion where the surface of the object to be coated is exposed in addition to the titanium chelate compound.

In the step (A), the lithium-nickel-manganese-cobalt composite oxide particles to be modified have the following general formula (1):
_{LixNiyMnzCotMpO1 + x ( 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, where x is 0.98≦x≦1.20, y is 0.30≦y<1.00, z is 0<z≦0.50, and t is 0 <t ≤ 0.50, p indicates 0 ≤ p ≤ 0.05, and y + z + t + p = 1.00.)
Lithium-nickel-manganese-cobalt composite oxide particles represented by

x in the general formula (1) satisfies 0.98≦x≦1.20. x preferably satisfies 1.00≦x≦1.10 in terms of increasing the initial capacity. Moreover, y in the general formula (1) satisfies 0.30≦y<1.00. y is preferably 0.50 ≤ y ≤ 0.95, and particularly preferably 0.60 ≤ y ≤ 0.90, in terms of achieving both initial capacity and cycle characteristics. Moreover, z in the general formula (1) satisfies 0<z≦0.50. z is preferably 0.025≦z≦0.45 from the viewpoint of excellent safety. Also, t satisfies 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 included in 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. It is a metal element, M is Mg, Al, Ti, Zr, Cu, Fe, Sr, Ca, V, Mo, Bi, Nb, Si, Zn, Ga, Ge, Sn, Ba, W, Na and K One or two or more metal elements selected from p in the general formula (1) satisfies 0≦p≦0.05, preferably 0.0001≦p≦0.045.

The lithium-nickel-manganese-cobalt composite oxide particles to be modified are particles of the 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 the primary particles are monodispersed, or aggregated particles in which the primary particles are aggregated to form secondary particles. good. The average particle size of the lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1) is the particle size (D50) at 50% volume conversion in the particle size distribution determined by the laser diffraction/scattering method, preferably 1. 0 to 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. is g. When the average particle size or BET specific surface area of the lithium-nickel-manganese-cobalt composite oxide particles is within the above range, the positive electrode mixture can be easily prepared and coated, and an electrode with high fillability can be obtained.

The amount of residual alkali in the lithium-nickel-manganese-cobalt composite oxide particles of 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 lithium-nickel-manganese-cobalt composite oxide particles is within the above range, expansion and deterioration of the battery caused by gas generation due to residual alkali can be suppressed.

In the present invention, the residual alkali indicates an alkali component eluted into water when the lithium-nickel-manganese-cobalt composite oxide particles are stirred and dispersed in water at 25°C. The amount of residual alkali is obtained 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. with a magnetic stirrer for 5 minutes, and then filtering this dispersion. It is determined by neutralization titration of the amount of alkali present in the filtrate. The amount of residual 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 prepared, for example, by mixing a lithium source, a nickel source, a manganese source, a cobalt source, and an M source to be added as necessary. It is produced by performing a raw material mixing step of preparing a raw material mixture and then a firing step of firing the obtained raw material mixture.

As the lithium source, nickel source, manganese source, cobalt source and M source related to the raw material mixing step, for example, hydroxides, oxides, carbonates, nitrates, sulfates, organic acid salts and the like of these are used. The average particle size 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. Preferably.

The nickel source, manganese source and cobalt source in the raw material mixing step may be compounds containing nickel atoms, manganese atoms and cobalt atoms. Compounds containing nickel atoms, manganese atoms and cobalt atoms include, for example, composite oxides, composite hydroxides, composite oxyhydroxides and composite carbonates containing these atoms.

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, a composite hydroxide can be prepared by a coprecipitation method. Specifically, 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 solution of an alkali, a composite hydroxide can be coprecipitated ( See JP-A-10-81521, JP-A-10-81520, JP-A-10-29820, 2002-201028, etc.). In the case of composite carbonates, a solution containing nickel ions, manganese ions and cobalt ions (solution A) and a solution containing carbonate ions or bicarbonate ions (solution B) are added to the reaction vessel to initiate the reaction. (JP 2009-179545 A), or a solution containing a nickel salt, a manganese salt and a cobalt salt (solution A), and a solution containing a metal carbonate or a metal hydrogen carbonate (solution B), the A A solution (solution C) containing the same anions as the anions of the nickel salt, the manganese salt and the cobalt salt in the liquid and the same anions as the anions of the metal carbonate or the metal hydrogen carbonate in the liquid B and a method of carrying out the reaction (Japanese Patent Application Laid-Open No. 2009-179544). Moreover, the compounds containing nickel atoms, manganese atoms and cobalt atoms may be commercially available products.

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

In the production of the lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1), composite hydroxides containing nickel atoms, cobalt atoms and manganese atoms can be used as the nickel source, manganese source and cobalt source. , is preferable in terms of good reactivity.

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 necessary is such that the discharge capacity is increased, so that the nickel source, the manganese source, and the cobalt source include The molar ratio of Li atoms (Li/(Ni+Mn+Co+M)) to the total number of moles of atoms, Mn atoms, Co atoms and M atoms (Ni+Mn+Co+M) is 0.98 to 1.20, preferably 1.00 to 1.10. be.

Further, 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 necessary is determined by the nickel, manganese, cobalt and M should be adjusted so that the atomic molar ratio of

In addition, although the production history of the raw material lithium source, nickel source, manganese source, cobalt source and M source does not matter, in order to produce high-purity lithium-nickel-manganese-cobalt composite oxide particles, the impurity content should be as low as possible is preferably less.

In the raw material mixing step, the means for mixing the lithium source, the nickel source, the manganese source, the cobalt source, and the optionally added M source may be either a dry method or a wet method. is preferred.

In the case of dry mixing, it is preferable to use mechanical means so that the raw materials are uniformly mixed. Examples of mixing devices include high-speed mixers, super mixers, turbosphere mixers, Eirich mixers, Henschel mixers, Nauta mixers, ribbon blenders, V-type mixers, conical blenders, jet mills, cosmomizers, paint shakers, and bead mills. , a ball mill, and the like. At the laboratory level, a home 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 in which each raw material is uniformly dispersed and has excellent reactivity.

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

In the firing step, the firing temperature for firing the raw material mixture to react the raw materials is 600 to 1000°C, preferably 700 to 950°C. The reason for this is that if the firing temperature is less than 600°C, the reaction tends to be insufficient and a large amount of unreacted lithium tends to remain. because there is a tendency

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

Moreover, in the firing process, the firing may be performed in a multistage manner. By carrying out the firing in multiple stages, it is possible to obtain modified lithium-nickel-manganese-cobalt composite oxide particles with even better cycle characteristics. When firing in multiple stages, after firing in the range of 650 to 800 ° C. for 1 to 10 hours, the temperature is further raised to 800 to 950 ° C. so that the temperature is higher than the firing temperature, and the firing is performed for 5 to 30 hours. is preferred.

The lithium-nickel-manganese-cobalt composite oxide obtained in this way may be subjected to a plurality of firing steps, if necessary.

In addition, the lithium-nickel-manganese composite oxide particles having a residual alkali amount in the above range are mixed in the raw material mixing step of the lithium source, the nickel source, the manganese source, the cobalt source, and the M source added as necessary. , the molar ratio of Li atoms to the total number of moles of Ni atoms, Mn atoms, Co atoms and M atoms (Ni + Mn + Co + M) in the cobalt source and M source (Li / (Ni + Mn + Co + M)) is 0.98 to 1.20. 700° C. or higher, preferably 750 to 1000° C., for 3 hours or longer, preferably 5 to 30 hours. It can be produced by reacting with the M source to be added. In this production method, the calcination is performed in the above-described multistage manner, whereby lithium-nickel-manganese composite oxide particles with a further reduced amount of residual alkali can be produced.

(A) The surface treatment liquid according to the step is 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), water and / or an organic It is dissolved or dispersed in a solvent.

(A) The titanium chelate according to the step has the following general formula (2):
Ti(R ¹ ) _m L _n (2)
(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group, or a phosphine, and when there are multiple groups, they may be the same or different. L is derived from a hydroxycarboxylic acid. represents a group, and when there is more than one, they 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; be.)
is a titanium chelate represented by

The alkoxy group for R ¹ is preferably a linear or branched alkoxy group having 1 to 4 carbon atoms. A halogen atom for R ¹ includes a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the amino group for R ¹ include methylamino group, ethylamino group, propylamino group, isopropylamino group, butylamino group, isobutylamino group, tert-butylamino group, pentylamino group and the like. Phosphines for R ¹ include, for example, trimethylphosphine, triethylphosphine, tributylphosphine, tris-tert-butylphosphine, triphenylphosphine and the like.

The hydroxycarboxylic acid-derived group for L includes a group in which an oxygen atom of a hydroxyl group in a hydroxycarboxylic acid or an oxygen atom of a carboxyl group in a hydroxycarboxylic acid is coordinated to a titanium atom. In addition, examples of the group derived from hydroxycarboxylic acid for L include a group in which an oxygen atom of a hydroxyl group in a hydroxycarboxylic acid and an oxygen atom of a carboxyl group in a hydroxylcarboxylic acid are bidentately coordinated to a titanium atom. be done. Among these, the oxygen atom of the hydroxyl group in the hydroxycarboxylic acid and the oxygen atom of the carboxyl group in the hydroxycarboxylic acid are preferably bidentate coordinated groups to the titanium atom. When m is 0, m+n is preferably 3, and when m is 1 or more and 3 or less, m+n is preferably 4 or 5.

As a method for producing a titanium chelate, for example, a titanium chelate-containing solution is obtained by diluting a titanium alkoxide with a solvent to obtain a diluted solution, and mixing the diluted solution with a hydroxycarboxylic acid (WO2019/138989 (see brochure). 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 above method for producing a titanium chelate can be used as it is as the surface treatment liquid in step (A). Alternatively, water may be added to a solution containing titanium chelate and used as a surface treatment solution. As a result, a dispersion or solution of titanium chelate in a water-containing solvent can be obtained as a surface treatment liquid.

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

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 isocitric acid. trivalent carboxylic acid, and the like. Among these, lactic acid is preferable from the viewpoint that it becomes a solution easily at room temperature, is easily mixed with the 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.

Further, when mixing a diluent with a hydroxycarboxylic acid, or in a solution containing a titanium chelate, for the purpose of efficiently obtaining a titanium chelate with high productivity, in addition to the hydroxycarboxylic acid, A ligand compound may be added. Examples of such ligand compounds include halogen atom-containing compounds, methylamino group, ethylamino group, propylamino group, isopropylamino group, butylamino group, isobutylamino group, t-butylamino group, pentylamino, and the like. and phosphines such as trimethylphosphine, 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.

Moreover, 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) is 0.1 to 1500 mmol/L, preferably 0.2 to 1000 mmol/L as Ti atoms. This is preferable from the viewpoint of facilitating the operability of the treatment.

The pH of the surface treatment liquid in the step (A) is 7 or more, preferably 8 or more and 11 or less, and particularly preferably 8 or more and 10 or less. It is preferable in that the elution of Li from the lithium-nickel-manganese-cobalt composite oxide particles is suppressed when the particles are brought into contact with each other. The pH of the surface treatment liquid can be adjusted by adding acid or alkali to the surface treatment liquid so that the pH falls 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. , a method of mixing the lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1) and a surface treatment liquid containing a titanium chelate compound. 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 powder, paste or slurry. There may be. When the mixture is in the form of powder, paste or slurry, 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) is adjusted. , can be obtained in any form. For example, 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 in the form of powder is the lithium-nickel-manganese represented by the general formula (1). Lithium-nickel-manganese-cobalt composite oxide particles obtained by adding a surface treatment liquid containing a titanium chelate compound in a small liquid volume to the cobalt composite oxide particles and represented by the general formula (1) When the mixture with the surface treatment liquid containing the titanium chelate compound is in the form of a slurry, the volume of the liquid is a large amount of the surface treatment liquid containing the titanium chelate compound, and the lithium nickel manganese represented by the general formula (1) is a small amount. It is obtained by adding cobalt composite oxide particles.

Further, the contact between the lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1) and the solution containing the titanium chelate compound causes the lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1) to or immersing in a solution containing a titanium chelate compound.

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

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, and then the entire amount of the solvent is dried as it is to obtain the general formula (1). It is preferable to obtain coated particles in which the surface of the lithium-nickel-manganese-cobalt composite oxide particles is coated with a titanium chelate compound. The drying temperature during drying is not particularly limited as long as it is a temperature at which the solvent evaporates, but is preferably 60 to 180°C, particularly preferably 90 to 150°C.

As for drying, total drying may be performed by a spray drying apparatus, a rotary evaporator, a fluidized bed drying coating apparatus, a vibration drying apparatus, or the like.

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 with a spray dryer to remove the solvent entirely. is preferable in that it becomes easy to control the coating amount of the titanium chelate compound.

In the step (B), the coated particles obtained in the step (A) are heat-treated to obtain a modified lithium-nickel-manganese-cobalt composite oxide (A) or a modified lithium-nickel-manganese-cobalt composite oxide (B). It is a process.

In the modified lithium-nickel-manganese-cobalt composite oxide particles (A), Ti atoms mainly do not form a solid solution in the lithium-nickel-manganese-cobalt composite oxide particles, but form lithium-nickel-manganese-cobalt oxides in the form of oxides containing Ti. It exists on the surface of the composite oxide particles. 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 lithium-nickel-manganese-cobalt composite oxide particles. In the modified lithium-nickel-manganese-cobalt composite oxide particles (B), when the particle surfaces of the modified lithium-nickel-manganese-cobalt composite oxide particles were analyzed by elemental mapping analysis of Ti using SEM-EDX, Ti was found to be Co. , Ni, Mn, etc., even if Ti atoms are present in the state of an oxide containing Ti on the surface of the lithium-nickel-manganese-cobalt composite oxide particles, as long as they are observed in a uniformly distributed state. good.

Therefore, whether the modified lithium-nickel-manganese-cobalt composite oxide particles (A) or the modified lithium-nickel-manganese-cobalt composite oxide particles (B) can be determined by SEM-EDX on the particle surface of the sample particles. Confirmed by analyzing with mapping analysis. That is, in the case of the modified lithium-nickel-manganese-cobalt composite oxide particles (A), the particle surface of the sample particles is analyzed by elemental mapping analysis of Ti by SEM-EDX at a magnification of 10,000 to 30,000 times. It is observed that Ti is unevenly distributed, such as unevenly distributed, on the surface of the sample particles. In the case of the modified lithium-nickel-manganese-cobalt composite oxide particles (B), the particle surface of the sample particles is analyzed by elemental mapping analysis of Ti by SEM-EDX at a magnification of 10,000 to 30,000 times. It is observed that Ti is uniformly distributed on the surface of the sample particles.

In the present invention, the oxide containing Ti coating the particle surface of the lithium-nickel-manganese-cobalt composite oxide particles is an oxide of Ti, Ti, and one selected from Li, Ni, Mn, Co and M. or a composite oxide containing two or more kinds.

In the heat treatment in step (B), the heat treatment temperature is 400 to 1000°C, preferably 450 to 950°C. The reason for this is that if the heat treatment temperature is less than 400°C, the titanium chelate for the coating treatment is not sufficiently decomposed and oxidized, and a sufficient effect cannot be obtained. The solid-solution reaction with the nickel-manganese-cobalt composite oxide particles progresses too much, and the solid-solution of Ti proceeds not only near the particle surface but also deep inside, so that the amount of Ti in the vicinity of the particle surface becomes insufficient, resulting in the reforming effect of the present invention. is difficult to obtain.

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

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

Further, in the method for producing 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 coated on a surface containing a titanium chelate compound. After contact with the treatment liquid, the entire amount of the solvent is dried as it is, so the coating amount of the oxide containing Ti on the lithium-nickel-manganese-cobalt composite oxide particles (A) with the modified lithium-nickel-manganese-cobalt composite oxide particles ( adhesion amount) and the solid solution amount (content) of Ti in the lithium-nickel-manganese-cobalt composite oxide particles in the modified lithium-nickel-manganese-cobalt composite oxide particles (B) is the amount of the lithium-nickel-manganese-cobalt composite oxide particles. It can be expressed as a theoretical coating amount (adhesion amount) and a solid solution amount (content) obtained from the Ti content in the surface treatment liquid containing the titanium chelate compound used.

In the (A) step of the reforming step, Ti per 1 m ² of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is adjusted so as to fall within the range of the adhesion amount of the oxide containing Ti described later. Lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1) are added to the surface treatment liquid in an amount such that the content is 0.1 to 150 mg, preferably 0.5 to 120 mg in terms of Ti atoms. It is preferable to add to the titanium chelate compound, mix it, and dry the entire amount because it becomes easy to control the coating amount and the solid solution amount of the titanium 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=x×(1/t)
k: Ti content (mg) in terms of Ti atoms per 1 m ² of lithium-nickel-manganese-cobalt composite oxide particles
x: Ti content (mg) in terms of Ti atoms per 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 modified lithium-nickel-manganese-cobalt composite oxide particles of the present invention, the adhesion amount of oxide containing Ti and the solid solution amount (content) of Ti in the obtained modified lithium-nickel-manganese-cobalt composite oxide particles is 0.1 to 150 mg, preferably 0.5 to 120 mg in terms of Ti atoms per 1 m ² of lithium-nickel-manganese-cobalt composite oxide particles. The adhesion amount of the oxide containing Ti in the modified lithium-nickel-manganese-cobalt composite oxide particles and the solid-solution amount (content) of Ti are within the above range, so that the modified lithium-nickel-manganese-cobalt composite oxide particles ( A) and/or the modified lithium-nickel-manganese-cobalt composite oxide particles (B) are preferable in that when they are used as the positive electrode active material of a lithium secondary battery, the cycle characteristics are further improved. That is, in the method for producing a modified lithium-nickel-manganese-cobalt composite oxide of the present invention, 0.1 to 150 mg, preferably 0.5, in terms of Ti atoms per 1 m ² of the obtained modified lithium-nickel-manganese-cobalt composite oxide particles. In the step (A), 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 liquid, and the surface treatment are adjusted to 120 mg. It is preferable to adjust the amount of liquid.

In the present invention, the "adhesion amount in terms of Ti atoms per 1 m ² of lithium-nickel-manganese-cobalt composite oxide particles of an oxide containing Ti" is obtained by the following formula.
k′=x×(1/t)
k′: Ti atom-equivalent adhesion amount (mg) per 1 m ² of lithium-nickel-manganese-cobalt composite oxide particles of an oxide containing Ti
x: Ti content (mg) in terms of Ti atoms per 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 addition, the amount of residual alkali in the modified lithium-nickel-manganese-cobalt composite oxide particles obtained by the method for producing modified lithium-nickel-manganese-cobalt composite oxide particles of the present invention is 1.2% by mass or less, preferably 1.2% by mass or less. The content of 0% by mass or less is preferable in that expansion and deterioration of the battery caused by gas generation due to residual alkali can be suppressed.

The modified lithium-nickel-manganese-cobalt composite oxide particles obtained by 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 for lithium secondary batteries, and the modified lithium-nickel-manganese-cobalt composite oxide particles are Lithium secondary batteries using high-quality lithium-nickel-manganese-cobalt composite oxide particles as a positive electrode active material are obtained by using lithium-nickel-manganese-cobalt composite oxide particles having the same composition of unmodified Li, Ni, Mn and Co. Cycle characteristics are improved compared to .

Further, the large particles of the modified lithium-nickel-manganese-cobalt composite oxide obtained by the method for producing the modified lithium-nickel-manganese-cobalt composite oxide particles of the present invention, and the modified lithium-nickel-manganese-cobalt composite oxide particles of the present invention. By mixing small particles of the modified lithium-nickel-manganese-cobalt composite oxide obtained by the manufacturing method, the capacity per volume can be improved. In this case, the average particle size of large particles is 7.5 to 30.0 μm, preferably 8.0 to 25.0 μm, and the average particle size of small particles is 0.5 to 7.5 μm, preferably 1.0 μm. A thickness of up to 7.0 μm is preferable from the viewpoint of improving the capacity per volume. In addition, when the mixture is compressed at 0.65 tonf/cm ² , the compression density is 2.7 g/cm ³ or more, preferably 2.8 to 3.3 g/cm ³ . is even higher, which is preferable.

In the method for producing modified lithium-nickel-manganese-cobalt composite oxide particles of the present invention, the large particles of the modified lithium-nickel-manganese-cobalt composite oxide are preferably the modified lithium-nickel-manganese-cobalt composite oxide particles (A). The small particles of the lithium-nickel-manganese-cobalt composite oxide are preferably the modified lithium-nickel-manganese-cobalt composite oxide particles (B) because the cycle characteristics are further improved.

In the method for producing modified lithium-nickel-manganese-cobalt composite oxide particles of the present invention, the smaller the average particle size of the lithium-nickel-manganese-cobalt composite oxide particles to which the titanium chelate compound is attached in the step (A), the greater the adhered titanium. A chelate compound and an oxide containing Ti, which is a thermal decomposition product thereof, are easily dispersed uniformly on the particle surface of the lithium-nickel-manganese-cobalt composite oxide particles without becoming bulky, and thermal decomposition of the titanium chelate compound adhered in a highly dispersed manner. The reactivity between the product oxide containing Ti and the lithium-nickel-manganese-cobalt composite oxide particles is enhanced on the surfaces 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 size of the lithium-nickel-manganese-cobalt composite oxide particles to which the titanium chelate compound is attached in the step (A), the better the adhesion. The resulting titanium chelate compound and its thermal decomposition product Ti-containing oxide are more likely to be uniformly and highly dispersed on the particle surface of the lithium-nickel-manganese-cobalt composite oxide particles, and thermal decomposition of the titanium chelate compound adhered in a highly dispersed manner. The product oxide containing Ti has high reactivity with the lithium-nickel-manganese-cobalt composite oxide particles on the surface of the lithium-nickel-manganese-cobalt composite oxide particles, so the heat treatment temperature in step (B) is the same. Even so, the smaller the average particle size of the lithium-nickel-manganese-cobalt composite oxide particles to which the titanium chelate compound is attached in the step (A), the easier it is to produce the modified lithium-nickel-manganese-cobalt composite oxide particles (B). Become. Further, when the heat treatment temperature in the step (B) is higher, the reactivity between the lithium-nickel-manganese-cobalt composite oxide particles and the lithium-nickel-manganese-cobalt composite oxide particles, which is the thermal decomposition product of the adhering titanium chelate compound, increases. Since the temperature increases on the surface of the cobalt composite oxide particles, the higher the heat treatment temperature in the step (B), the easier the formation of the modified lithium-nickel-manganese-cobalt composite oxide particles (B).
In other words, in the method for producing modified lithium-nickel-manganese-cobalt composite oxide particles of the present invention, the larger the average particle size of the lithium-nickel-manganese-cobalt composite oxide particles to which the titanium chelate compound is attached in step (A), The adhering titanium chelate compound and its thermal decomposition product Ti-containing oxide are unevenly bulky on the particle surface of the lithium-nickel-manganese-cobalt composite oxide particles and tend to disperse. Since the oxide containing Ti, which is a thermal decomposition product, has low reactivity with the lithium-nickel-manganese-cobalt composite oxide particles on the surface of the lithium-nickel-manganese-cobalt composite oxide particles, the heat treatment temperature in the step (B) is are the same, the larger the average particle size of the lithium-nickel-manganese-cobalt composite oxide particles to which the titanium chelate compound is attached in the step (A), the modified lithium-nickel-manganese-cobalt composite oxide particles (A) are produced. becomes easier. In addition, the lower the heat treatment temperature in the step (B), the lower the reactivity between the adhering titanium chelate compound and the lithium-nickel-manganese-cobalt composite oxide particles on the surface of the lithium-nickel-manganese-cobalt composite oxide particles. The lower the heat treatment temperature in step B), the easier the modified lithium-nickel-manganese-cobalt composite oxide particles (A) are produced.
Therefore, in the method for producing modified lithium-nickel-manganese-cobalt composite oxide particles of the present invention, the average particle size of the lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1) used in step (A) and (B ) By appropriately selecting the combination of heat treatment temperatures in the step, modified lithium-nickel-manganese-cobalt composite oxide particles (A) and modified lithium-nickel-manganese-cobalt composite oxide particles (B) can be produced separately. .

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 represented by the general formula (1) in the step (A). is 7.5 to 30.0 μm, preferably 8.0 to 25.0 μm. It can be produced by performing steps A) and (B).
In addition, the modified lithium-nickel-manganese-cobalt composite oxide particles (B) have an average particle diameter of 0.5 to 7.5 μm as the lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1) in the step (A). , Preferably, particles of 1.0 to 7.0 μm are used, and the heat treatment temperature in step (B) is 750 ° C. or higher and 1000 ° C. or lower, preferably 750 ° C. or higher and 900 ° C. or lower. It can be manufactured by performing

EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.
<Preparation of Lithium Nickel Manganese Cobalt Composite Oxide Particles (LNMC) Sample>
<LNMC sample 1>
Lithium carbonate (average particle size 5.7 μm) and nickel manganese cobalt composite hydroxide (Ni:Mn:Co=6:2:2 (molar ratio), average particle size 9.8 μm) were weighed and mixed with a home mixer. After thorough mixing, a raw material mixture having a Li/(Ni+Mn+Co) molar ratio of 1.01 was obtained. A commercially available nickel-manganese-cobalt composite hydroxide was used.
The resulting raw material mixture was then fired in an alumina bowl at 700° C. for 2 hours and then at 850° C. for 10 hours in an air atmosphere. After firing, the fired product was pulverized and classified. As a result of measuring the obtained fired product by XRD, it was confirmed to be a single-phase lithium-nickel-manganese-cobalt composite oxide. Further, the obtained particles had an average particle diameter of 10.2 μm, a BET specific surface area of 0.21 m ² /g, and secondary aggregated spherical lithium-nickel-manganese-cobalt composite oxide particles (LiNi _0.6 Mn _{0 .2} Co _0.2 O ₂ ).

<LNMC sample 2>
Lithium carbonate (average particle size 5.7 μm) and nickel manganese cobalt composite hydroxide (Ni:Mn:Co=6:2:2 (molar ratio), average particle size 3.7 μm) were weighed and mixed with a home mixer. After thorough mixing, a raw material mixture having a Li/(Ni+Mn+Co) molar ratio of 1.01 was obtained. A commercially available nickel-manganese-cobalt composite hydroxide was used.
The resulting raw material mixture was then fired in an alumina bowl at 700° C. for 2 hours and then at 850° C. for 10 hours in an air atmosphere. After firing, the fired product was pulverized and classified. As a result of measuring the obtained fired product by XRD, it was confirmed to be a single-phase lithium-nickel-manganese-cobalt composite oxide. Further, the obtained particles had an average particle diameter of 5.4 μm, a BET specific surface area of 0.69 m ² /g, and secondary aggregated spherical lithium-nickel-manganese-cobalt composite oxide particles (LiNi _0.6 Mn _{0 .2} Co _0.2 O ₂ ).

Table 1 shows various physical properties of the lithium-nickel-manganese-cobalt composite oxide sample (LNMC sample) obtained above.
The average particle size, residual alkali content and press density of the LNMC sample were measured as follows.
<Average particle size>
The average particle size was determined by a laser diffraction/scattering method.
<Measurement of residual alkali content>
Regarding the residual alkali amount of the LNMC sample, 5 g of the sample and 100 g of ultrapure water were weighed into a beaker and dispersed at 25° C. for 5 minutes using a magnetic stirrer. Next, this dispersion is filtered, and 70 ml of the filtrate is titrated with 0.1N-HCl using an automatic titrator (model COMTITE-2500) to measure the amount of residual alkali (the amount of lithium) present in the sample. converted into lithium carbonate) was calculated.
<Pressure density>
2.25 g of the sample was weighed out and placed in a double shaft former with a diameter of 1.5 cm, and a pressure of 0.65 tonf/cm ² was applied for 1 minute using a press to measure the height of the compressed product. , the compacted density of the sample was calculated from the apparent volume of the compact calculated from its height and the weight of the weighed sample.

<Preparation of surface treatment liquid>
<Preparation of Surface Treatment Liquid Containing Titanium Lactate Chelate>
Aqueous ammonia 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). In addition, the pH was adjusted to 8.5 to prepare a titanium lactate chelate-containing surface treatment liquid having the concentration shown in Table 2 below.

(Examples 1 to 6)
Using the LNMC sample and the surface treatment liquid, the ratios shown in Table 3 were obtained, and a slurry having a solid concentration of 25% by mass was prepared.
Then, the slurry was supplied to a spray dryer whose outlet temperature was set to 120° C. at a supply rate of 65 g/min to obtain coated particles in which the titanium lactate chelate adhered to the particle surfaces of the LNMC sample.
Next, the coated particles were heat-treated at 800 ° C. for 5 hours, and the modified LNMC sample (A) in which Ti oxide adhered to the particle surface of the LNMC sample and the modified LNMC sample containing Ti in a solid solution A LNMC sample (B) was obtained.
In addition, whether it is a modified LNMC sample to which Ti oxide is attached or a modified LNMC sample in which Ti is dissolved in the LNMC sample, the particle surface of the sample particle is examined with an SEM at a magnification of 20,000 times. - EDX (field emission scanning electron microscope SU-8220 manufactured by Hitachi High-Technologies Corporation and energy dispersive X-ray spectrometer XFlash5060FlatQUAD manufactured by BRUKER Corporation) was used to confirm elemental mapping analysis of Ti. As a result of elemental mapping analysis of Ti on the particle surface of the sample particles by SEM-EDX, the LNMC sample 1 was used as the LNMC sample, and Ti was unevenly distributed and unevenly distributed. It was confirmed that the particles were nickel-manganese-cobalt composite oxide particles (A). On the other hand, in the case of using LNMC sample 2 as the LNMC sample, as a result of elemental mapping analysis of Ti on the particle surface of the sample particles by SEM-EDX, Ti is uniformly distributed like Co, Ni and Mn. Therefore, it was confirmed that the particles were modified lithium-nickel-manganese-cobalt composite oxide particles (B).
The SEM-EDX measurement conditions are as follows.
Acceleration voltage: 15 kV, magnification: 20,000 times, working distance: 9.5 to 11.5 mm, measurement time: 6 minutes Also, for the modified LNMC sample, the amount of residual alkali was measured in the same manner as for the LNMC sample. It was measured.
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=x×(1/t)
k: Ti content (mg) in terms of Ti atoms per ^1m2 of LNMC sample
x: Ti content (mg) in terms of Ti atoms for 1 g of LNMC sample
t: BET specific surface area of LNMC sample (m ² /g)

(Reference example 1)
Using commercially available lithium cobalt oxide (LiCoO ₂ : average particle size 9.5 μm, BET specific surface area 0.37 m ² /g), in the same manner as in Examples 1 to 3, lithium cobalt oxide (LCO) sample particle surfaces A modified LCO sample with attached oxides of Ti was obtained.
The modified LCO was also measured for residual alkali content in the same manner as for the LNMC sample.
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″=x″×(1/t″)
k'': Ti content (mg) in terms of Ti atoms per ¹ m2 of LCO sample
x'': Ti content (mg) in terms of Ti atoms per 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 sample obtained in the example, 2.5% by mass of graphite powder, and 2.5% by mass of polyvinylidene fluoride are mixed to form a positive electrode agent, which is dispersed in N-methyl-2-pyrrolidinone. to prepare a kneaded paste. The kneaded paste was applied to an aluminum foil, dried, pressed and punched into a disk having a diameter of 15 mm to obtain a positive electrode plate.

Using this positive electrode plate, a coin-type lithium secondary battery was manufactured using members such as a separator, a negative electrode, a positive electrode, a collector plate, a mounting bracket, an external terminal, and an electrolytic solution. Among them, a metal lithium foil was used as the negative electrode, and a solution prepared by dissolving 1 mol of LiPF ₆ in 1 liter of a 1:1 mixed solution of ethylene carbonate and methyl ethyl carbonate was used as the electrolyte.
Next, performance evaluation of the obtained lithium secondary battery was performed. The results are shown in Table 4. In addition, the modified LCO sample prepared in Reference Example 1, the LNMC sample 1 (Comparative Example 1) and the LNMC sample 2 (Comparative Example 2) without modification were also prepared in the same manner as lithium secondary batteries. made an evaluation. The results are also shown in Table 4.

<Battery performance evaluation 1>
The prepared coin-type lithium secondary batteries were operated at room temperature under the following test conditions, and the following battery performances were evaluated.
(1) Test Conditions for Cycle Characteristic Evaluation First, charging was performed at 0.5 C to 4.3 V over 2 hours, and then constant current/constant voltage charging (CCCV charging) was performed to hold the voltage at 4.3 V for 3 hours. gone. After that, charge and discharge were performed by constant current discharge (CC discharge) to 2.7 V at 0.2 C, and these operations were regarded as one cycle, and 20 cycles were repeated.
(2) Initial charge capacity, initial discharge capacity (per weight of active material)
The charge capacity and discharge capacity at the first cycle in the cycle characteristic evaluation were defined as the initial charge capacity and the initial discharge capacity.
(3) 20th cycle discharge capacity (per weight of active material)
The discharge capacity at the 20th cycle in the cycle characteristic evaluation was defined as the 20th cycle discharge capacity.
(4) Capacity Retention Rate The capacity retention rate was calculated by the following formula from the discharge capacity (per active material weight) at the 1st cycle and the 20th cycle in the cycle characteristics evaluation.
Capacity retention rate (%) = (discharge capacity at 20th cycle/discharge capacity at 1st cycle) x 100
(5) Energy Density Retention Rate The energy density retention rate was calculated by the following formula from the Wh capacity (per active material weight) during discharge at the 1st cycle and the 20th cycle in the cycle characteristic evaluation.
Energy density maintenance rate (%) = (Discharge Wh capacity at 20th cycle/Discharge Wh capacity at 1st cycle) x 100

<Production of lithium secondary battery 2>
The modified LNMC samples obtained in Examples 1 to 6 and the LNMC samples before modification were thoroughly mixed in a home mixer to prepare a mixture having the composition shown in Table 5, and used as a positive electrode active material sample. . In addition, the press density of the positive electrode active material sample was measured in the same manner as for the LNMC sample, and the results are also shown in Table 5.

95% by mass of a positive electrode active material sample, 2.5% by mass of graphite powder, and 2.5% by mass of polyvinylidene fluoride were mixed to form 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, pressed and punched into a disk having a diameter of 15 mm to obtain a positive electrode plate.

Using this positive electrode plate, a coin-type lithium secondary battery was manufactured using members such as a separator, a negative electrode, a positive electrode, a collector plate, a mounting bracket, an external terminal, and an electrolytic solution. Among them, a metal lithium foil was used as the negative electrode, and a solution prepared by dissolving 1 mol of LiPF ₆ in 1 liter of a 1:1 mixed solution of ethylene carbonate and methyl ethyl carbonate was used as the electrolyte.
Next, performance evaluation of the obtained lithium secondary battery was performed. The results are also shown in Table 6.

<Battery performance evaluation 2>
The prepared coin-type lithium secondary battery was operated at room temperature under the following test conditions, and the cycle characteristics were evaluated. The capacity retention rate and the energy density retention rate were evaluated in the same manner as in the performance evaluation 1 of the battery. Furthermore, the discharge capacity per volume was also evaluated, and Table 6 shows the results. 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 also shown in Table 6.
(6) Discharge capacity per volume The discharge capacity per volume was obtained from the following formula using the initial discharge capacity and the electrode density.
Discharge capacity per volume (mAh/cm ³ ) = Discharge capacity at 1st cycle (mAh/g) x Electrode density (g/cm ³ ) x 0.95 (percentage of active material in positive electrode material)
The electrode density was calculated as the density of the positive electrode material by measuring the mass and thickness of the electrode produced from the sample to be measured, and subtracting the thickness and mass of the current collector from the measured mass and thickness. In addition, the positive electrode material is 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, and the press pressure during electrode production is a linear pressure of 0.38 ton/cm. and

Claims (9)

The following general formula (1):
_{LixNiyMnzCotMpO1 + x ( 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, where x is 0.98≤x≤1.20, y is 0.50≤y≤0.95, z is 0.025≤z≤0.45, t is 0.025 ≤ t ≤ 0.45, p is 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 liquid containing a titanium chelate compound to obtain coated particles in which the titanium chelate compound is attached to the surface of the lithium-nickel-manganese-cobalt composite oxide particles. and then heat-treating the coated particles to obtain modified lithium-nickel-manganese-cobalt composite oxide particles,
The titanium chelate compound has the following general formula (2):
Ti(R ¹ ) _m L _n (2)
(In the formula, R ¹ represents an alkoxy group, a hydroxyl group, a halogen atom, an amino group, or a phosphine, and when there are multiple groups, they may be the same or different. L is derived from a hydroxycarboxylic acid. represents a group, and when there is more than one, they 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; be.)
A titanium chelate or its ammonium salt represented by
the surface treatment liquid containing the titanium chelate compound has a pH of 8 or more and 11 or less;
A method for producing modified lithium-nickel-manganese-cobalt composite oxide particles, characterized by: The method for producing modified lithium-nickel-manganese-cobalt composite oxide particles according to claim 1, wherein the temperature of the heat treatment is 400 to 1000°C. 3. The method for producing modified lithium-nickel-manganese-cobalt composite oxide particles according to claim 1, wherein L in the general formula (2) is a monovalent carboxylic acid. 3. The method for producing modified lithium-nickel-manganese-cobalt composite oxide particles according to claim 1, wherein L in the general formula (2) is lactic acid. 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 ² of the lithium-nickel-manganese-cobalt composite oxide particles represented by the general formula (1). The method for producing modified lithium-nickel-manganese-cobalt composite oxide particles according to any one of claims 1 to 4. The improvement according to any one of claims 1 to 5, wherein 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. A method for producing high-quality lithium-nickel-manganese-cobalt composite oxide particles. The modified lithium-nickel-manganese-cobalt composite oxide according to any one of claims 1 to 6, wherein the amount of residual alkali in the modified lithium-nickel-manganese-cobalt composite oxide particles is 1.2% by mass or less. a method of manufacturing particles. In the reforming step,
The surface treatment liquid is added in an amount such that the Ti content per 1 m ² of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is 0.1 to 150 mg in terms of Ti atoms. adding to and mixing with the lithium-nickel-manganese-cobalt composite oxide particles represented by formula (1), and drying the entire amount;
The method for producing modified lithium-nickel-manganese-cobalt composite oxide particles according to any one of claims 1 to 7. 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 8, and obtained by the production method according to any one of claims 1 to 8. A method for producing a positive electrode active material for a lithium secondary battery, comprising a step of mixing small particles having an average particle size of 0.5 to 7.5 μm.