CN116490997A - Method for producing modified lithium nickel manganese cobalt composite oxide particles - Google Patents
Method for producing modified lithium nickel manganese cobalt composite oxide particles Download PDFInfo
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- CN116490997A CN116490997A CN202180074901.3A CN202180074901A CN116490997A CN 116490997 A CN116490997 A CN 116490997A CN 202180074901 A CN202180074901 A CN 202180074901A CN 116490997 A CN116490997 A CN 116490997A
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Abstract
The present invention provides LiNiMnCo composite oxide particles which can improve cycle characteristics when used as a positive electrode active material of a lithium secondary battery. The method for producing modified LiNiMnCo composite oxide particles is characterized by comprising a modification step in which the following general formula (1) is obtained: li (Li) x Ni y Mn z Co t M p O 1+x (1) (wherein x represents 0.98.ltoreq.x.ltoreq.1.20, y represents 0.30.ltoreq.y.ltoreq.1.00, z represents 0.ltoreq.z.ltoreq.0.50, t represents 0.ltoreq.t.ltoreq.0.50, p represents 0.ltoreq.p.ltoreq.0.05, y+z+t+p=1.00.) the present invention provides a composite oxide particle of LiNiMnCo and a titanium chelate compoundThe surface treatment liquid of the compound is contacted to obtain coated particles having a titanium chelate compound attached to the particle surfaces of the lithium nickel manganese cobalt composite oxide particles, and then the coated particles are subjected to a heat treatment to obtain modified LiNiMnCo composite oxide particles, the titanium chelate compound being represented by the following general formula (2): ti (R) 1 ) m L n (2) Titanium chelates or ammonium salts thereof are shown.
Description
Technical Field
The invention relates to a method for manufacturing modified lithium nickel manganese cobalt composite oxide particles.
Background
Currently, as a positive electrode active material of a lithium secondary battery, lithium cobaltate is used. However, cobalt is a rare metal, and thus a lithium nickel manganese cobalt composite oxide having a low cobalt content has been developed (for example, see patent documents 1 to 2).
It is known that a lithium secondary battery using 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, and has a higher capacity than lithium cobaltate (for example, refer to patent document 3).
However, even in these conventional methods, there is a problem in that the cycle characteristics of the lithium secondary battery using the lithium nickel manganese cobalt composite oxide as the positive electrode active material are deteriorated.
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 particle surfaces of a lithium nickel manganese cobalt composite oxide with a Ti-containing compound has been proposed (for example, see patent literature 4, patent literature 5, and the like).
As a method of coating the particle surface of the lithium nickel manganese cobalt composite oxide with the Ti-containing compound, patent documents 4 and 5 propose the following methods: an alkoxide monomer or oligomer formed from an organometallic compound such as Ti is mixed with an alcohol such as 2-propanol, a chelating agent such as acetylacetone is added thereto, and water is further added thereto to prepare a dispersion in which a precursor containing fine particles of Ti having an average particle size of 1 to 20nm is dispersed, and the surface of the particles of the lithium nickel manganese cobalt composite oxide is coated with the dispersion, followed by heat treatment.
Prior art literature
Patent literature
Patent document 1: WO 2004/092073
Patent document 2: japanese patent laid-open publication No. 2005-25975
Patent document 3: japanese patent application laid-open No. 2011-23120
Patent document 4: japanese patent laid-open publication 2016-24968
Patent document 5: japanese patent laid-open publication 2016-72071
Disclosure of Invention
Technical problem to be solved by the invention
In recent years, the application of lithium secondary batteries to the automotive field such as electric vehicles, hybrid vehicles, plug-in hybrid vehicles, and the like has been studied. Therefore, 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 demanded.
Accordingly, the present invention aims to: provided are lithium nickel manganese cobalt composite oxide particles which can improve cycle characteristics when used as a positive electrode active material for a lithium secondary battery.
Technical scheme for solving technical problems
The inventors of the present invention have conducted intensive studies in view of the above-described practical circumstances, and as a result, have found that a lithium secondary battery comprising a modified lithium nickel manganese cobalt composite oxide particle obtained by bringing a surface treatment liquid containing a titanium chelate compound represented by the general formula (1) or an ammonium salt thereof into contact with the surface treatment liquid and then performing a heat treatment, and using the modified lithium nickel manganese cobalt composite oxide particle as a positive electrode active material is excellent in cycle characteristics, and have completed the present invention.
Specifically, the present invention (1) provides a method for producing modified lithium nickel manganese cobalt composite oxide particles, comprising a modification step,
the modification step is a step of bringing lithium nickel manganese cobalt composite oxide particles represented by the following general formula (1) into contact with a surface treatment liquid containing a titanium chelate compound to obtain coated particles having the titanium chelate compound attached to the particle surfaces of the lithium nickel manganese cobalt composite oxide particles, and then subjecting the coated particles to a heat treatment to obtain modified lithium nickel manganese cobalt composite oxide particles,
Li x Ni y Mn z Co t M p O 1+x (1)
( In the formula (1), M represents 1 or more than 2 metal elements selected from Mg, al, ti, zr, cu, fe, sr, ca, V, mo, bi, nb, si, zn, ga, ge, sn, ba, W, na and K. x is 0.98.ltoreq.x.ltoreq.1.20, y is 0.30.ltoreq.y.ltoreq.1.00, z is 0.ltoreq.z.ltoreq.0.50, t is 0.ltoreq.t.ltoreq.0.50, p is 0.ltoreq.p.ltoreq.0.05, y+z+t+p=1.00. )
The titanium chelate compound is a titanium chelate compound represented by the following general formula (2) or an ammonium salt thereof.
Ti(R 1 ) m L n (2)
(in the formula (2), R 1 The alkoxy group, hydroxyl group, halogen atom, amino group or phosphine group may be the same or different when a plurality of the same are present. L represents a group derived from a hydroxycarboxylic acid, and when there are a plurality of groups, they may be the same or different. m represents a number of 0 to 3, n represents a number of 1 to 3, and m+n is 3 to 6. )
The present invention also provides (2) a method for producing modified lithium nickel manganese cobalt composite oxide particles of (1), comprising: the temperature of the heating treatment is 400-1000 ℃.
The present invention also provides (3) a method for producing modified lithium nickel manganese cobalt composite oxide particles of (1) or (2), characterized by comprising: l in the above general formula (2) is a monocarboxylic acid.
The present invention also provides (4) a method for producing modified lithium nickel manganese cobalt composite oxide particles of (1) or (2), characterized by comprising: l in the above general formula (2) is lactic acid.
The present invention also provides (5) a method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of (1) to (4), comprising the steps of: the pH of the surface treatment liquid is 7 or more.
The present invention also provides (6) a method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of (1) to (5), comprising the steps of: the titanium chelate compound in the coated particlesThe amount of adhesion is relative to every 1m 2 The lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) are 0.1 to 150mg in terms of Ti atoms.
The present invention also provides (7) a method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of (1) to (6), comprising the steps of: the amount of residual alkali in the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is 1.2 mass% or less.
The present invention also provides (8) a method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of (1) to (7), comprising the steps of: the residual alkali content in the modified lithium nickel manganese cobalt composite oxide particles is 1.2 mass% or less.
The present invention also provides (9) a method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of (1) to (8), comprising the steps of: in the modification step, the modification is carried out at a ratio of 1m 2 The Ti content of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is 0.1 to 150mg in terms of Ti atoms, and the surface modifying solution is added to the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) and mixed, and then the whole is dried.
The present invention also provides (10) a method for producing a positive electrode active material for a lithium secondary battery, characterized by comprising: comprising a step of mixing large particles having an average particle diameter of 7.5 to 30.0 [ mu ] m obtained by the production method according to any one of (1) to (9) with small particles having an average particle diameter of 0.5 to 7.5 [ mu ] m obtained by the production method according to any one of (1) to (9).
Effects of the invention
The present invention can provide lithium nickel manganese cobalt composite oxide particles which can improve cycle characteristics when used as a positive electrode active material for a lithium secondary battery.
Detailed Description
The present invention will be described below based on preferred embodiments.
The method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention comprises a modification step of bringing lithium nickel manganese cobalt composite oxide particles represented by general formula (1) into contact with a surface treatment liquid containing a titanium chelate compound represented by general formula (2) or an ammonium salt of a titanium chelate compound represented by general formula (2) to obtain coated particles in which these titanium chelate compounds are attached to the particle surfaces of the lithium nickel manganese cobalt composite oxide particles, and then subjecting the obtained coated particles to a heat treatment to obtain modified lithium nickel manganese cobalt composite oxide particles. Hereinafter, the titanium chelate compound represented by the general formula (2) and the ammonium salt of the titanium chelate compound represented by the general formula (2) are sometimes collectively referred to as "titanium chelate compound".
The method for producing a modified lithium nickel manganese cobalt composite oxide according to the present invention basically comprises the following steps (A) to (B).
(A) The working procedure comprises the following steps: and (3) a step of bringing 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, into contact with the surface treatment liquid containing the titanium chelate compound according to the present invention to obtain coated particles in which the titanium chelate compound is adhered to the surfaces of the lithium nickel manganese cobalt composite oxide particles.
(B) The working procedure comprises the following steps: and (c) a step of heating the coated particles obtained in the 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.
Hereinafter, the "modified lithium nickel manganese cobalt composite oxide particles (a)" and the "modified lithium nickel manganese cobalt composite oxide particles (B)" may be collectively referred to as "modified lithium nickel manganese cobalt composite oxide particles".
In the step (B), the coated particles are subjected to a heat treatment to obtain modified lithium nickel manganese cobalt composite oxide particles (a) and modified lithium nickel manganese cobalt composite oxide particles (B).
Regarding the modified lithium nickel manganese cobalt composite oxide particles (a), oxides containing Ti are present attached to the particle surfaces of the lithium nickel manganese cobalt composite oxide particles. The presence of the Ti-containing oxide adhered to the particle surface of the lithium nickel manganese cobalt composite oxide particles was confirmed by observing that Ti was unevenly distributed such as offset on the particle surface of the lithium nickel manganese cobalt composite oxide particles when the particle surface of the modified lithium nickel manganese cobalt composite oxide particles was analyzed at 10,000 ～ 30,000 times magnification by elemental mapping analysis of Ti by SEM-EDX.
On the other hand, 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 at 10,000 ～ 30,000 times magnification by elemental mapping analysis of Ti by SEM-EDX, ti could be observed in a state uniformly distributed as in Co, ni, mn, and the like. The inventors of the present invention speculate that since the modified lithium nickel manganese cobalt composite oxide particles (B) preferentially undergo a solid solution reaction of Ti, ti is contained in the lithium nickel manganese cobalt composite oxide particles by solid solution, and Ti is uniformly distributed on the particle surfaces of the lithium nickel manganese cobalt composite oxide particles as in Co, ni, mn, and the like.
(A) The step is a step of bringing the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) to be modified into contact with the surface treatment liquid containing the titanium chelate compound according to the present invention to obtain coated particles in which the titanium chelate compound is adhered to the surfaces of the lithium nickel manganese cobalt composite oxide particles. The titanium chelate compound on the particle surface of the lithium nickel manganese cobalt composite oxide particle may coat the entire particle surface of the lithium nickel manganese cobalt composite oxide particle, or may coat a part of the particle surface. Coating a portion of the particle surface means: the surface of the particles is exposed to a part of the surface of the coating object in addition to the titanium chelate compound.
In the step (a), the lithium nickel manganese cobalt composite oxide particles to be modified are lithium nickel manganese cobalt composite oxide particles represented by the following general formula (1).
Li x Ni y Mn z Co t M p O 1+x (1)
( Wherein M represents 1 or 2 or more metal elements selected from Mg, al, ti, zr, cu, fe, sr, ca, V, mo, bi, nb, si, zn, ga, ge, sn, ba, W, na and K. x is 0.98.ltoreq.x.ltoreq.1.20, y is 0.30.ltoreq.y.ltoreq.1.00, z is 0.ltoreq.z.ltoreq.0.50, t is 0.ltoreq.t.ltoreq.0.50, p is 0.ltoreq.p.ltoreq.0.05, y+z+t+p=1.00. )
X in the formula of the general formula (1) is more than or equal to 0.98 and less than or equal to 1.20. From the viewpoint of an initial capacity increase, x is preferably 1.00.ltoreq.x.ltoreq.1.10. In addition, y in the formula of the general formula (1) is 0.30.ltoreq.y < 1.00. From the viewpoint of being capable of having both the initial capacity and the cycle characteristics, y is preferably 0.50.ltoreq.y.ltoreq.0.95, and particularly preferably 0.60.ltoreq.y.ltoreq.0.90. In the formula (1), z is 0 < z.ltoreq.0.50. From the viewpoint of excellent safety, z is preferably 0.025.ltoreq.z.ltoreq.0.45. In addition, t is more than 0 and less than or equal to 0.50. From the viewpoint of excellent safety, t is preferably 0.025.ltoreq.t.ltoreq.0.45. y+z+t+p=1.00. The y/z is preferably (y/z) > 1, particularly preferably (y/z). Gtoreq.1.5, more preferably 3.ltoreq.y/z.ltoreq.38.
In the formula, M is a metal element contained in the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) as needed to improve battery performance such as cycle characteristics and safety, and as M, 1 or 2 or more metal elements selected from Mg, al, ti, zr, cu, fe, sr, ca, V, mo, bi, nb, si, zn, ga, ge, sn, ba, W, na and K may be mentioned. In the formula of the general formula (1), p is 0.ltoreq.p.ltoreq.0.05, and preferably 0.0001.ltoreq.p.ltoreq.0.045.
The lithium nickel manganese cobalt composite oxide particles to be modified are particles 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 obtained by monodispersing primary particles, or aggregated particles obtained by aggregating primary particles to form secondary particles. The average particle diameter of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is preferably 1.0 to 30.0 μm, particularly preferably 3.0 to 25.0 μm, in terms of a particle diameter (D50) of 50% by volume in the particle size distribution obtained by a laser diffraction/scattering method. 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 2.00m 2 Preferably 0.15 to 1.00m per gram 2 And/g. When the average particle diameter or BET specific surface area of the lithium nickel manganese cobalt composite oxide particles falls within the above range, the preparation and coating properties of the positive electrode mixture become easy, and an electrode having high filling properties can be obtained.
The amount of the residual alkali in the lithium nickel manganese cobalt composite oxide particles of the general formula (1) to be modified is preferably 1.2 mass% or less, and particularly preferably 1.0 mass% or less. By the amount of the residual alkali in the lithium nickel manganese cobalt composite oxide particles falling within the above range, the expansion and deterioration of the battery due to the gas generated by the residual alkali can be suppressed.
In the present invention, the residual alkali means an alkali component eluted into water when lithium nickel manganese cobalt composite oxide particles are dispersed in water at 25 ℃ with stirring. The residual alkali amount can be obtained as follows: 5g of lithium nickel manganese cobalt composite oxide particles and 100g of pure water were weighed into a beaker, dispersed at 25℃for 5 minutes using a magnetic stirrer, and then the dispersion was filtered, and the amount of alkali present in the obtained filtrate was titrated. The residual alkali amount is a value obtained by measuring the amount of lithium by titration and converting the lithium amount into lithium carbonate.
The lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) to be modified can be produced, for example, by performing a raw material mixing step of mixing a lithium source, a nickel source, a manganese source, a cobalt source, and an optionally added M source to prepare a raw material mixture, and then performing a firing step of firing the obtained raw material mixture.
As the lithium source, nickel source, manganese source, cobalt source, and M source involved in the raw material mixing step, for example, hydroxides, oxides, carbonates, nitrates, sulfates, organic acid salts, and the like thereof can be used. The average particle diameters of the lithium source, nickel source, manganese source, cobalt source and M source are 1.0 to 30.0. Mu.m, preferably 2.0 to 25.0. Mu.m, as determined by a laser light scattering method.
The nickel source, manganese source, and cobalt source involved in the raw material mixing step may be compounds containing nickel atoms, manganese atoms, and cobalt atoms. Examples of the compound containing a nickel atom, a manganese atom and a cobalt atom include a composite oxide, a composite hydroxide, a composite oxyhydroxide, and a composite carbonate, each of which contains these atoms.
As a method for preparing a compound containing a nickel atom, a manganese atom and a cobalt atom, a known method can be used. For example, in the case of composite hydroxides, the preparation can be carried out by means of the coprecipitation method. Specifically, the composite hydroxide can be coprecipitated by mixing an aqueous solution containing prescribed amounts of nickel atoms, cobalt atoms and manganese atoms, an aqueous solution of a complexing agent, and an aqueous solution of an alkali (see JP-A-10-81521, JP-A-10-81520, JP-A-10-29820, JP-A-2002-201028, etc.). In the case of the complex carbonate, there may be mentioned: a method in which a solution (solution a) containing nickel ions, manganese ions and cobalt ions and a solution (solution B) containing carbonate ions or bicarbonate ions are added to a reaction vessel to react (japanese patent application laid-open No. 2009-179545); or a method in which a solution (solution a) containing a nickel salt, a manganese salt and a cobalt salt and a solution (solution B) containing a metal carbonate or a metal hydrogencarbonate are added to a solution (solution C) containing the same anions as those of the nickel salt, the manganese salt and the cobalt salt in the solution a and the same anions as those of the metal carbonate or the metal hydrogencarbonate in the solution B, and reacted (japanese patent application laid-open No. 2009-179544). The compound containing a nickel atom, a manganese atom and a cobalt atom may be commercially available.
The average particle diameter of the compound containing nickel atoms, cobalt atoms and manganese atoms is 1.0 to 100. Mu.m, preferably 2.0 to 80.0. Mu.m, as determined by a laser light scattering method.
In the production of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1), a composite hydroxide containing a nickel atom, a cobalt atom and a manganese atom is preferably used as a nickel source, a manganese source and a cobalt source in view of good reactivity.
In the raw material mixing step, the molar ratio (Li/(ni+mn+co+m)) of Li atoms to the total number of moles (ni+mn+co+m) of Ni atoms, mn atoms, co atoms and M atoms in the nickel source, manganese source and cobalt source is 0.98 to 1.20, preferably 1.00 to 1.10, in terms of the mixing ratio of the lithium source to the nickel source, manganese source, cobalt source and M source added as needed, from the viewpoint of the discharge capacity becoming high.
In the raw material mixing step, the mixing ratio of the raw materials of the nickel source, the manganese source, the cobalt source, and the M source added as needed may be adjusted to the atomic molar ratio of nickel, manganese, cobalt, and M represented by the general formula (1).
The process for producing the lithium source, nickel source, manganese source, cobalt source and M source as raw materials is not limited, but in order to produce lithium nickel manganese cobalt composite oxide particles having high purity, it is preferable that the impurity content is as small as possible.
In the raw material mixing step, the lithium source, the nickel source, the manganese source, the cobalt source, and the M source added as needed may be mixed by any of dry and wet methods, but for ease of production, dry mixing is preferable.
In the case of dry mixing, it is preferable to perform the mixing mechanically for uniform mixing of the raw materials. Examples of the mixing device include a high-speed mixer, a super mixer, a vortex mixer, a Ai Liji mixer, a henschel mixer, a nodavizer mixer, a ribbon blender, a V-type mixer, a conical mixer, a jet mill, a cosmamizer, a paint mixer, a bead mill, and a ball mill. In laboratory scale mixing, it is sufficient to use a household mixer.
In the case of wet mixing, a media mill is preferably used as a mixing device in terms of being able to prepare a slurry in which the respective raw materials are uniformly dispersed. In addition, in the slurry after the mixing treatment, spray drying is preferably performed in view of excellent reactivity and obtaining a raw material mixture in which the raw materials are uniformly dispersed.
The firing step is a step of firing the raw material mixture obtained in the raw material mixing step to obtain a lithium nickel manganese cobalt composite oxide.
In the firing step, the raw material mixture is fired so that the firing temperature at the time of the raw material reaction is 600 to 1000 ℃, preferably 700 to 950 ℃. The reason for this is that when the firing temperature is less than 600 ℃, there is a tendency that a large amount of unreacted lithium remains due to insufficient reaction, while when the firing temperature exceeds 1000 ℃, there is a tendency that the lithium nickel manganese cobalt composite oxide formed at one time is decomposed.
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 or oxygen.
In the firing step, the firing may be performed in a multi-stage manner. By firing in a multistage manner, modified lithium nickel manganese cobalt composite oxide particles having more excellent cycle characteristics can be obtained. When the firing is performed in a plurality of stages, it is preferable to fire at 650 to 800 ℃ for 1 to 10 hours, and then heat the mixture to 800 to 950 ℃ to directly fire the mixture for 5 to 30 hours so that the temperature becomes higher than the firing temperature.
The lithium nickel manganese cobalt composite oxide thus obtained may be subjected to a plurality of firing steps, if necessary.
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 needed, the lithium source, the nickel source, the manganese source, the cobalt source, and the M source added as needed are sufficiently reacted at a mixing ratio of 0.98 to 1.20 in terms of a molar ratio (Li/(ni+mn+co+m)) of Li atoms to the total molar number (ni+mn+co+m) of Ni atoms, mn atoms, co atoms, and M atoms in the nickel source, the manganese source, the cobalt source, and the M source, and the lithium nickel manganese composite oxide particles having the residual alkali amount in the above range can be produced by firing the raw material at 700 ℃ or higher, preferably 750 to 1000 ℃ for 3 hours or higher, preferably 5 to 30 hours. In the present production method, the firing is performed in the aforementioned multi-stage manner, whereby lithium nickel manganese composite oxide particles having a further reduced residual alkali content can be produced.
(A) The surface treatment liquid in the step is obtained by dissolving or dispersing a titanium chelate compound, that is, a titanium chelate compound represented by the general formula (2) or an ammonium salt of a titanium chelate compound represented by the general formula (2), in water and/or an organic solvent.
(A) The titanium chelate compound involved in the step (2) is a titanium chelate compound represented by the following general formula.
Ti(R 1 ) m L n (2)
(wherein R is 1 The alkoxy group, hydroxyl group, halogen atom, amino group or phosphine group may be the same or different when a plurality of the same are present. L represents a group derived from hydroxycarboxylic acid, when there are pluralMay be the same or different. m represents a number of 0 to 3, n represents a number of 1 to 3, and m+n is 3 to 6. )
As R 1 The alkoxy group is preferably a straight-chain or branched alkoxy group having 1 to 4 carbon atoms. As R 1 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. As R 1 Examples of the amino group include methylamino, ethylamino, propylamino, isopropylamino, butylamino, isobutylamino, tert-butylamino, pentylamino and the like. As R 1 Examples of the phosphine include trimethylphosphine, triethylphosphine, tributylphosphine, tri-t-butylphosphine, and triphenylphosphine.
Examples of the group derived from a hydroxycarboxylic acid as the group L include 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 with a titanium atom. Examples of the group derived from a hydroxycarboxylic acid as the group represented by 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 hydroxycarboxylic acid are bidentate coordinated to a titanium atom. Among these, preferred are those in which an oxygen atom of a hydroxyl group in a hydroxycarboxylic acid and an oxygen atom of a carboxyl group in a hydroxycarboxylic acid are bidentate coordinated with a titanium atom. When m is 0, m+n is preferably 3, and when m is 1 to 3, m+n is preferably 4 or 5.
As a method for producing a titanium chelate compound, for example, a titanium alkoxide is diluted with a solvent to obtain a diluted solution, and the diluted solution is mixed with a hydroxycarboxylic acid to obtain a solution containing a titanium chelate compound (see WO 2019/138989). In the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, a solution containing a titanium chelate compound obtained by the above-described method for producing a titanium chelate compound may be directly used as a surface treatment liquid in the step (a). In addition, water may be added to the solution containing the titanium chelate compound to be used as the surface treatment liquid. Thus, as the surface treatment liquid, a dispersion or a solution of the titanium chelate compound in the aqueous solvent can be obtained.
Examples of the titanium alkoxide include tetramethoxytitanium (IV), tetraethoxytitanium (IV), tetra-n-propoxytitanium (IV), tetra-Isopropoxytitanium (IV), tetra-n-butoxytitanium (IV), and tetra-Isobutoxytitanium (IV).
Examples of the hydroxycarboxylic acid include monocarboxylic acids such as lactic acid, glycolic acid, glyceric acid and hydroxybutyric acid, dicarboxylic acids such as hydroxymalonic acid, malic acid and tartaric acid, and tricarboxylic acids such as citric acid and isocitric acid. Among these, lactic acid is preferable from the viewpoints of easy formation of a solution at room temperature, easy mixing with a titanium alkoxide diluent, and easy production of a titanium chelate compound.
Further, 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, when the diluent and the hydroxycarboxylic acid are mixed, or in order to obtain a titanium chelate compound efficiently with high productivity in a solution containing the titanium chelate compound, a ligand compound capable of coordinating with titanium may be added in addition to the hydroxycarboxylic acid. Examples of the ligand compound include compounds containing a halogen atom, amines having a functional group such as methylamino, ethylamino, propylamino, isopropylamino, butylamino, isobutylamino, t-butylamino, pentylamino, and the like, and phosphines such as trimethylphosphine, triethylphosphine, tributylphosphine, tri-t-butylphosphine, and triphenylphosphine.
As the ammonium salt of the titanium chelate compound, preferable is an ammonium salt of titanium lactate (Ti (OH) 2 [(OCH(CH 3 )COO － )] 2 (NH 4 + ) 2 )。
Titanium chelates and their ammonium salts are commercially available from Matsumoto Fine Chemical, and commercially available products can be used.
In addition, from the viewpoint of stability of the Ti solution and easiness in handling of the coating treatment, the Ti concentration in the surface treatment liquid in the step (A) is preferably 0.1 to 1500mmol/L, and more preferably 0.2 to 1000mmol/L in terms of Ti atoms.
In terms of suppressing elution of Li from the lithium nickel manganese cobalt composite oxide particles when the lithium nickel manganese cobalt composite oxide particles are brought into contact with the surface treatment liquid, the pH of the surface treatment liquid in the step (a) is preferably 7 or more, preferably 8 or more and 11 or less, and particularly preferably more than 8 and 10 or less. The pH of the surface treatment liquid may be adjusted to the above-described range by adding an acid or an alkali to the surface treatment liquid.
In the step (a), the method of bringing the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) into contact with the surface treatment liquid containing the titanium chelate compound is not particularly limited, and examples thereof include a method of mixing the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) with the surface treatment liquid containing the 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 in the form of powder, paste, or slurry. The mixture is in the form of powder, paste or slurry, and a mixture of any form can be obtained by adjusting the amount of the surface treatment liquid containing the titanium chelate compound to be added to the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1). 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 is a powdery mixture, and the mixture can be obtained by adding a small 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), and 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 is a slurry-like mixture, and the mixture can be obtained by adding a small amount of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) to a large liquid volume of the surface treatment liquid containing the titanium chelate compound.
The contacting of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) with the solution containing the titanium chelate compound may be a method in which the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) are immersed in the solution containing the titanium chelate compound.
Among these, in the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, as a method for bringing the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) into contact with a surface treatment liquid containing a titanium chelate compound, a method in which a mixture is made into a slurry form is preferable in view of enabling the titanium chelate compound to easily adhere to the entire surface of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1).
Preferably, the 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 solvent is completely dried directly, whereby coated particles in which the particle surfaces of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) are coated with the titanium chelate compound are obtained. The drying temperature at the time of drying is not particularly limited as long as the solvent evaporates, and is preferably 60 to 180 ℃, particularly preferably 90 to 150 ℃.
The drying may be performed entirely by a spray drying apparatus, a rotary evaporator, a fluidized bed drying and 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 preferably all dried by a spray drying apparatus in view of easy control of the coating amount of the titanium chelate compound.
(B) The step (a) is a step of heating the coated particles obtained in the step (a) to obtain a modified lithium nickel manganese cobalt composite oxide (a) or a modified lithium nickel manganese cobalt composite oxide (B).
In the modified lithium nickel manganese cobalt composite oxide particles (a), ti atoms are not mainly dissolved in the lithium nickel manganese cobalt composite oxide particles, but are present on the surfaces of the lithium nickel manganese cobalt composite oxide particles in the state of Ti-containing oxide. In the modified lithium nickel manganese cobalt composite oxide particles (a), a small amount of Ti atoms may be partially dissolved in the lithium nickel manganese cobalt composite oxide particles.
In the modified lithium nickel manganese cobalt composite oxide particles (B), ti atoms are thought to exist mainly in a state of being solid-dissolved in the inside of the particles of 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 are analyzed by elemental mapping analysis of Ti by SEM-EDX, ti atoms may be present on the surfaces of the lithium nickel manganese cobalt composite oxide particles in the form of oxides containing Ti, as long as Ti can be observed in a uniformly distributed state similar to Co, ni, mn, or the like.
Therefore, by analyzing the particle surface of the sample particles by elemental mapping analysis of Ti using SEM-EDX, it was possible to confirm whether the modified lithium nickel manganese cobalt composite oxide particles (a) or the modified lithium nickel manganese cobalt composite oxide particles (B) were. That is, in the case of the modified lithium nickel manganese cobalt composite oxide particles (a), when the particle surfaces of the sample particles were analyzed at 10,000 ～ 30,000 times magnification by elemental mapping analysis of Ti by SEM-EDX, it was observed that Ti bias and the like were unevenly distributed on the sample particle surfaces. In the case of the modified lithium nickel manganese cobalt composite oxide particles (B), when the particle surfaces of the sample particles were analyzed at 10,000 ～ 30,000 times magnification by elemental mapping analysis of Ti by SEM-EDX, it was observed that Ti was uniformly distributed on the sample particle surfaces.
In the present invention, the oxide containing Ti coating the particle surface of the lithium nickel manganese cobalt composite oxide particle means an oxide of Ti, a composite oxide containing Ti and 1 or 2 or more kinds selected from Li, ni, mn, co and M, and the like.
In the heating treatment in the step (B), the heating treatment temperature is 400 to 1000 ℃, preferably 450 to 950 ℃. The reason for this is that when the heat treatment temperature is less than 400 ℃, the titanium chelate compound for coating treatment cannot undergo sufficient decomposition and oxidation reaction, and that when the heat treatment temperature exceeds 1000 ℃, the solid solution reaction of Ti and lithium nickel manganese cobalt 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 interior, so that the amount of Ti in the vicinity of the particle surface is insufficient, and it is difficult to obtain the modification effect of the present invention.
In the heating treatment in the step (B), the time of the heating treatment is not critical in the present production method, and it is generally possible to obtain modified lithium nickel manganese cobalt composite oxide particles having sufficient performance for 1 hour or more, preferably 2 to 10 hours.
In the heating treatment in the step (B), the atmosphere of the heating treatment is preferably an oxidizing atmosphere such as air or oxygen.
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 brought into contact with the surface treatment liquid containing the titanium chelate compound, and then the solvent is completely dried directly, so that the coating amount (adhering amount) of the Ti-containing oxide in the modified lithium nickel manganese cobalt composite oxide particles (a) with respect to the lithium nickel manganese cobalt composite oxide particles and the solid solution amount (content) of the Ti in the modified lithium nickel manganese cobalt composite oxide particles (B) with respect to the lithium nickel manganese cobalt composite oxide particles can be expressed as the theoretical coating amount (adhering amount) and solid solution amount (content) obtained from the amounts of the lithium nickel manganese cobalt composite oxide particles and the Ti content in the surface treatment liquid containing the titanium chelate compound used.
In the step (A) of the modification step, it is preferable that the amount of Ti-containing oxide to be deposited is in the range of 1m for the purpose of easily controlling the coating amount and the solid solution amount of the titanium chelate compound 2 The Ti content in the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is 0.1 to 150mg, preferably 0.5 to 120mg in terms of Ti atom, and the surface modifying solution is added to the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) and mixed, and then dried in its entirety.
In the present invention, "every 1m 2 The Ti content "in terms of Ti atoms in the lithium nickel manganese cobalt composite oxide particles was determined by the following calculation formula.
k＝x×(1/t)
k: every 1m 2 Ti content (mg) in terms of Ti atom in the lithium nickel manganese cobalt composite oxide particles;
x: ti content (mg) in terms of Ti atom relative to 1g of the lithium nickel manganese cobalt composite oxide;
t: BET specific surface area (m) of lithium nickel manganese cobalt composite oxide particles 2 /g)。
In the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, the amount of Ti-containing oxide attached and the amount (content) of Ti solid solution in the obtained modified lithium nickel manganese cobalt composite oxide particles are set to 1m 2 The lithium nickel manganese cobalt composite oxide particles are 0.1 to 150mg, preferably 0.5 to 120mg in terms of Ti atom. When the modified lithium nickel manganese cobalt composite oxide particles (a) and/or the modified lithium nickel manganese cobalt composite oxide particles (B) are used as the positive electrode active material of the lithium secondary battery, the cycle characteristics are further improved by the amount of the Ti-containing oxide attached to the modified lithium nickel manganese cobalt composite oxide particles and the amount (content) of the Ti-containing oxide dissolved in the above-mentioned ranges, which is preferable. That is, in the method for producing a modified lithium nickel manganese cobalt composite oxide according to the present invention, the lithium nickel manganese cobalt composite oxide is prepared so as to be 1m each 2 The amount of the lithium nickel manganese cobalt composite oxide particles obtained is preferably adjusted in the step (a) by adjusting the amount of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) and the concentration of the titanium chelate compound in the surface treatment liquid and the amount of the surface treatment liquid to be contacted, in terms of Ti atoms, to 0.1 to 150mg, preferably 0.5 to 120mg.
In the present invention, "oxide containing Ti" is used every 1m 2 The amount of Ti atoms in the lithium nickel manganese cobalt composite oxide particles in terms of the amount of Ti atoms "was calculated by the following equation.
k’＝x×(1/t)
k': oxides containing Ti at every 1m 2 An adhesion amount (mg) in terms of Ti atoms in the lithium nickel manganese cobalt composite oxide particles;
x: ti content (mg) in terms of Ti atom relative to 1g of the lithium nickel manganese cobalt composite oxide;
t: BET specific surface area (m) of lithium nickel manganese cobalt composite oxide particles 2 /g)。
In addition, in view of suppressing expansion and deterioration of the battery due to gas generated by the residual alkali, the residual alkali amount 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 preferably 1.2 mass% or less, and more preferably 1.0 mass% or less.
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 suitable for use as a positive electrode active material for a lithium secondary battery, and a lithium secondary battery using the modified lithium nickel manganese cobalt composite oxide particles as a positive electrode active material has higher cycle characteristics than a lithium nickel manganese cobalt composite oxide particle using unmodified lithium nickel cobalt composite oxide particles having the same composition of Li, ni, mn, and Co.
Further, by mixing large particles of the modified lithium nickel manganese cobalt composite oxide obtained by the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention with small particles of the modified lithium nickel manganese cobalt composite oxide obtained by the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, the capacity per unit volume can be improved. In this case, from the viewpoint of increasing the capacity per unit volume, the average particle diameter of the large particles is preferably 7.5 to 30.0. Mu.m, more preferably 8.0 to 25.0. Mu.m, and the average particle diameter of the small particles is preferably 0.5 to 7.5. Mu.m, more preferably 1.0 to 7.0. Mu.m. In addition, from the viewpoint of further increasing the capacity per unit volume, it is preferable to use 0.65tonf/cm for the mixture 2 The compression density at the time of compression treatment was 2.7g/cm 3 The above is preferably 2.8 to 3.3g/cm 3 。
In the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, it is preferable that the large particles of the modified lithium nickel manganese cobalt composite oxide are modified lithium nickel manganese cobalt composite oxide particles (a) and the small particles of the modified lithium nickel manganese cobalt composite oxide are modified lithium nickel manganese cobalt composite oxide particles (B) in view of further improving cycle characteristics.
In the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, when the average particle diameter of the lithium nickel manganese cobalt composite oxide particles to which the titanium chelate compound is attached in the step (a) is small, the attached titanium chelate compound and the Ti-containing oxide as a thermal decomposition product thereof do not uniformly expand in volume on the particle surfaces of the lithium nickel manganese cobalt composite oxide particles, and are easily highly dispersed, and the reactivity of the Ti-containing oxide as a thermal decomposition product of the highly dispersed and attached titanium chelate compound with the lithium nickel manganese cobalt composite oxide particles becomes high on the lithium nickel manganese cobalt composite oxide particle surfaces. Therefore, in the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, in the case where the average particle diameter of the lithium nickel manganese cobalt composite oxide particles to which the titanium chelate compound is attached in the step (a) is small, the attached titanium chelate compound and the Ti-containing oxide as a heated decomposition product thereof are easily and uniformly dispersed further highly on the particle surface of the lithium nickel manganese cobalt composite oxide particles, and the reactivity of the Ti-containing oxide as a heated decomposition product of the highly dispersed and attached titanium chelate compound with the lithium nickel manganese cobalt composite oxide particles becomes high on the lithium nickel manganese cobalt composite oxide particle surface, and therefore even if the heating treatment temperature in the step (B) is the same, the modified lithium nickel manganese cobalt composite oxide particles (B) are easily produced in the case where the average particle diameter of the lithium nickel manganese cobalt composite oxide particles to which the titanium chelate compound is attached in the step (a) is small. In addition, when the heat treatment temperature in the step (B) is high, the reactivity of the Ti-containing oxide, which is the heat decomposition product of the attached titanium chelate compound, with the lithium nickel manganese cobalt composite oxide particles becomes high on the surfaces of the lithium nickel manganese cobalt composite oxide particles, and therefore, when the heat treatment temperature in the step (B) is high, the modified lithium nickel manganese cobalt composite oxide particles (B) are easily produced.
In other words, in the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, in the case where the average particle diameter of the lithium nickel manganese cobalt composite oxide particles to which the titanium chelate compound is attached in the step (a) is large, the attached titanium chelate compound and the Ti-containing oxide as a thermal decomposition product thereof are likely to be unevenly volume-expanded and dispersed on the particle surfaces of the lithium nickel manganese cobalt composite oxide particles, and the reactivity of the Ti-containing oxide as a thermal decomposition product of the titanium chelate compound attached by volume expansion with the lithium nickel manganese cobalt composite oxide particles becomes low on the lithium nickel manganese cobalt composite oxide particle surfaces, and therefore, even if the temperature of the heat treatment in the step (B) is the same, the modified lithium nickel manganese cobalt composite oxide particles (a) are likely to be produced in the case where the average particle diameter of the lithium nickel manganese cobalt composite oxide particles to which the titanium chelate compound is attached in the step (a) is large. Further, the lower the heat treatment temperature in the step (B), the lower the reactivity of the attached titanium chelate compound with the lithium nickel manganese cobalt composite oxide particles on the surfaces of the lithium nickel manganese cobalt composite oxide particles, and therefore the lower the heat treatment temperature in the step (B), the more easily the modified lithium nickel manganese cobalt composite oxide particles (a) are produced.
Accordingly, in the method for producing modified lithium nickel manganese cobalt composite oxide particles of the present invention, the modified lithium nickel manganese cobalt composite oxide particles (a) and the modified lithium nickel manganese cobalt composite oxide particles (B) can be produced by appropriately selecting the combination of the average particle diameter of the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) used in the step (a) and the heat treatment temperature in the step (B).
For example, in a preferred embodiment of the present invention, in the step (a), the modified lithium nickel manganese cobalt composite oxide particles (a) can be produced by using particles having an average particle diameter of 7.5 to 30.0 μm, preferably 8.0 to 25.0 μm, as the lithium nickel manganese cobalt composite oxide particles of the general formula (1), and performing the steps (a) and (B) at a heat treatment temperature of 750 ℃ to 1000 ℃ and preferably 750 ℃ to 900 ℃.
In addition, in the step (A), the modified lithium nickel manganese cobalt composite oxide particles (B) can be produced by using particles having an average particle diameter of 0.5 to 7.5 μm, preferably 1.0 to 7.0 μm as the lithium nickel manganese cobalt composite oxide particles of the general formula (1) and performing the steps (A) and (B) at a heat treatment temperature of 750 to 1000℃and preferably 750 to 900 ℃.
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 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, and sufficiently mixed with a household mixer to obtain a raw material mixture having a molar ratio of Li/(ni+mn+co) of 1.01. The nickel manganese cobalt composite hydroxide was used as a commercially available product.
Next, the resulting raw material mixture was fired at 700℃for 2 hours in an alumina pot in an atmosphere, followed by 10 hours at 850 ℃. After the firing, the fired product was pulverized and classified. The obtained fired product was measured by XRD, and as a result, it was confirmed to be a single-phase lithium nickel manganese cobalt composite oxide. The obtained sample had an average particle diameter of 10.2. Mu.m, and a BET specific surface area of 0.21m 2 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 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 a raw material mixture having a molar ratio of Li/(ni+mn+co) of 1.01. The nickel manganese cobalt composite hydroxide was used as a commercially available product.
Next, the resulting raw material mixture was fired at 700℃for 2 hours in an alumina pot in an atmosphere, followed by 10 hours at 850 ℃. After the firing, the fired product was pulverized and classified. The obtained fired product was measured by XRD, and as a result, it was confirmed to be a single-phase lithium nickel manganese cobalt composite oxide. The obtained sample had an average particle diameter of 5.4. Mu.m, and a BET specific surface area of 0.69m 2 Spherical lithium nickel manganese cobalt composite oxide particles (LiNi) 0.6 Mn 0.2 Co 0.2 O 2 )。
The physical properties of the lithium nickel manganese cobalt composite oxide sample (LNMC sample) obtained above are shown in table 1.
The average particle diameter, the amount of residual alkali, and the pressed density of the LNMC sample were measured as follows.
< average particle diameter >)
The average particle diameter was determined by a laser diffraction/scattering method.
< measurement of residual alkali >)
Regarding the residual alkali amount of the LNMC sample, 5g of the sample and 100g of ultrapure water were weighed into a beaker, and dispersed at 25℃for 5 minutes using a magnetic stirrer. Subsequently, the dispersion was filtered, 70ml of the filtrate was titrated with 0.1N-HCl using an automatic titration apparatus (model COMTITE-2500), and the amount of residual alkali present in the sample was calculated (the amount of lithium was measured and converted into a value of lithium carbonate).
< compression Density >
2.25g of the sample was weighed and put into a biaxial former having a diameter of 1.5cm, and a press was used to apply a pressure of 0.65tonf/cm 2 The height of the compressed article was measured in a state of 1 minute, and the compression density of the sample was calculated from the apparent volume of the compressed article calculated from the height and the mass of the sample measured.
TABLE 1
< preparation of surface treatment liquid >
Preparation of surface treatment liquid containing titanium lactate chelate
Titanium ammonium lactate (Ti (OH)) manufactured by Matsumoto Fine Chemical company 2 [(OCH(CH 3 )COO － )] 2 (NH 4 + ) 2 ) Aqueous solution (product name: TC-335, pH 4.4) was added with ammonia water to adjust the pH to 8.5, and a surface treatment solution containing a titanium lactate chelate compound was prepared at the concentration shown in Table 2 below.
TABLE 2
Examples 1 to 6
The LNMC sample and the surface treatment liquid were weighed in the proportions shown in table 3, and a slurry having a solid content concentration of 25 mass% was prepared.
Then, the coated particles were fed to a spray dryer having an outlet temperature of 120℃so that the slurry was fed at a rate of 65 g/min, to obtain coated particles in which a titanium lactate chelate compound was adhered to the particle surfaces of the LNMC sample.
Next, the coated particles were subjected to a heat treatment at 800 ℃ for 5 hours to obtain a modified LNMC sample (a) in which Ti oxide was adhered to the particle surfaces of the LNMC sample and a modified LNMC sample (B) in which Ti was dissolved in the LNMC sample.
The elemental mapping analysis of Ti was performed on the particle surfaces of the sample particles at a magnification of 20,000 times by using SEM-EDX (field emission scanning electron microscope SU-8220 manufactured by Hitachi high technology Co., ltd. And energy dispersive X-ray analysis device XFlash5060 FlattQUAD manufactured by BRUKER Co., ltd.) to confirm whether or not the sample was a modified LNMC sample having Ti oxide attached thereto or a modified LNMC sample having Ti dissolved in the LNMC sample. Since Ti was subjected to elemental mapping analysis of the particle surface of the sample particles by SEM-EDX and Ti was unevenly distributed by bias, it was confirmed that the modified lithium nickel manganese cobalt composite oxide particles (A) were obtained using LNMC sample 1 as the LNMC sample. On the other hand, since Ti was uniformly distributed as in Co, ni and Mn by performing elemental mapping analysis of Ti on the particle surface of the sample particles by SEM-EDX, it was confirmed that the modified lithium nickel manganese cobalt composite oxide particles (B) were obtained using LNMC sample 2 as the LNMC sample.
The SEM-EDX measurement conditions were as follows.
Acceleration voltage: 15kV, magnification: 20,000 times, operating distance: 9.5-11.5 mm, the measurement time is: and 6 minutes.
In addition, the residual alkali content of the modified LNMC sample was also measured in the same manner as in the LNMC sample.
The amount of the surface treatment liquid in Table 3 was such that the surface treatment was addedThe liquid becomes 1m each 2 The calculated value of the Ti content in the LNMC sample in terms of Ti atoms is obtained by the following calculation formula.
k＝x×(1/t)
k: every 1m 2 Ti content (mg) in terms of Ti atom in the LNMC sample;
x: ti content (mg) in terms of Ti atom relative to 1g of LNMC sample;
t: BET specific surface area (m 2 /g)。
Reference example 1
Using commercially available lithium cobalt oxide (LiCoO) 2 Average particle diameter 9.5 μm, BET specific surface area 0.37m 2 In the same manner as in examples 1 to 3, a modified Lithium Cobalt Oxide (LCO) sample having Ti oxide adhered to the particle surface thereof was obtained.
In addition, the residual alkali content of the modified LCO was also measured in the same manner as in the LNMC sample.
The amount of the surface treatment liquid added in Table 3 was 1m at the time of adding the surface treatment liquid 2 The calculated value of the Ti content in terms of Ti atoms in the LCO sample is obtained by the following equation.
k”＝x”×(1/t”)
k'. Every 1m 2 Ti content (mg) in terms of Ti atoms in the LCO sample;
x': ti content (mg) in terms of Ti atom relative to 1g of LCO sample;
t': BET specific surface area (m) of LCO sample 2 /g)。
TABLE 3
Battery performance tests were performed as follows.
< manufacturing of lithium Secondary Battery 1 >)
The modified LNMC sample obtained in the example was mixed with 95 mass%, 2.5 mass% of graphite powder, and 2.5 mass% of polyvinylidene fluoride to prepare a positive electrode agent, which was dispersed in N-methyl-2-pyrrolidone to prepare a kneaded paste. The paste was applied to an aluminum foil, dried, pressed, and punched into a disk having a diameter of 15mm, to obtain a positive electrode plate.
Using this positive electrode plate, button-type lithium secondary batteries were fabricated using each member such as a separator, a negative electrode, a positive electrode, a current collector, a mounting component, an external terminal, and an electrolyte. Wherein, the cathode uses metal lithium foil, and the electrolyte uses 1 mole LiPF 6 A liquid obtained by dissolving in 1 liter of a 1:1 mixture of ethylene carbonate and methyl ethyl carbonate.
Next, performance evaluation of the obtained lithium secondary battery was performed. The results are shown in Table 4. A lithium secondary battery was also produced in the same manner as in 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, and the same evaluation was performed. The results are also shown in Table 4.
< evaluation of Battery Performance 1 >)
The fabricated button lithium secondary battery was operated at room temperature under the following test conditions, and the following battery performances were evaluated.
(1) Test conditions for evaluation of cycle characteristics
First, the charge was carried out at 0.5C for 2 hours to 4.3V, and then at 4.3V for 3 hours, and constant current/constant voltage charge (CCCV charge) was carried out. Thereafter, constant current discharge (CC discharge) was performed at 0.2C to 2.7V, and charge and discharge were performed, and these operations were repeated 20 times as 1 cycle.
(2) Primary charge capacity and primary discharge capacity (weight per active material)
The charge capacity and discharge capacity of the 1 st cycle in the cycle characteristic evaluation were defined as the initial charge capacity and initial discharge capacity.
(3) Discharge capacity at 20 th cycle (weight of active substance unit)
The discharge capacity at the 20 th cycle in the cycle characteristic evaluation was taken as the 20 th cycle discharge capacity.
(4) Capacity maintenance rate
The capacity retention rate was calculated from the discharge capacities (unit active material weight) of the 1 st cycle and the 20 th cycle in the cycle characteristic evaluation by the following formula.
Capacity maintenance ratio (%) = (discharge capacity of 20 th cycle/discharge capacity of 1 st cycle) ×100
(5) Energy density maintenance rate
The energy density maintenance rate was calculated from the Wh capacity (weight of active material per unit) at the discharge of each of the 1 st cycle and the 20 th cycle in the cycle characteristic evaluation, using the following formula.
Energy density maintenance ratio (%) = (discharge Wh capacity of 20 th cycle/discharge Wh capacity of 1 st cycle) ×100
TABLE 4
< manufacturing 2 of lithium Secondary Battery >
Using the modified LNMC samples obtained in examples 1 to 6 and the LNMC sample before modification, the mixture having the composition shown in table 5 was prepared as a positive electrode active material sample by thoroughly mixing the mixture using a household mixer. The pressed density of the positive electrode active material sample was measured in the same manner as in the LNMC sample, and the results are shown in table 5.
TABLE 5
The positive electrode active material sample 95 mass%, graphite powder 2.5 mass% and polyvinylidene fluoride 2.5 mass% were mixed to prepare a positive electrode agent, which was dispersed in N-methyl-2-pyrrolidone to prepare a kneaded paste. The paste was applied to an aluminum foil. Drying, pressing, and stamping into disk with diameter of 15mm to obtain positive plate.
Using this positive electrode plate, button-type lithium secondary batteries were fabricated using each member such as a separator, a negative electrode, a positive electrode, a current collector, a mounting component, an external terminal, and an electrolyte. Wherein the method comprises the steps of The negative electrode was made of a metallic lithium foil, and the electrolyte was made of 1 mol LiPF 6 A liquid obtained by dissolving in 1 liter of a 1:1 mixture of ethylene carbonate and methyl ethyl carbonate.
Next, performance evaluation of the obtained lithium secondary battery was performed. The results are shown in Table 6.
< evaluation of Battery Performance 2 >
The fabricated button lithium secondary battery was operated at room temperature under the following test conditions, and the cycle characteristics, primary charge capacity, primary discharge capacity (weight per active material), capacity retention rate, and energy density retention rate were evaluated in the same manner as in the above-described battery performance evaluation 1. The discharge capacity per unit volume was further evaluated, and the results are shown in table 6. The modified LNMC samples of example 2 and example 5 were evaluated as positive electrode active material samples in the same manner. The results are shown in Table 6.
(6) Discharge capacity per unit volume
The discharge capacity per unit volume was determined from the initial discharge capacity and the electrode density by the following calculation formula.
Discharge capacity per unit volume (mAh/cm) 3 ) Discharge capacity (mAh/g) x electrode density (g/cm) at 1 st cycle 3 ) X 0.95 (ratio of active Material amount in cathode Material)
The mass and thickness of the electrode made of the sample to be measured were measured, and the thickness and mass of the current collector were subtracted from each other to obtain the density of the positive electrode material, and the electrode density was calculated. The positive electrode material was a mixture of 95 mass% of the positive electrode active material sample, 2.5 mass% of graphite powder, and 2.5 mass% of polyvinylidene fluoride, and the pressing pressure at the time of producing the electrode was 0.38ton/cm in terms of line pressure.
TABLE 6
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Claims (10)
1. A method for manufacturing modified lithium nickel manganese cobalt composite oxide particles is characterized in that:
comprises a modification procedure and a modification procedure,
the modification step is a step of bringing lithium nickel manganese cobalt composite oxide particles represented by the following general formula (1) into contact with a surface treatment liquid containing a titanium chelate compound to obtain coated particles having the titanium chelate compound attached to the particle surfaces of the lithium nickel manganese cobalt composite oxide particles, and then subjecting the coated particles to a heat treatment to obtain modified lithium nickel manganese cobalt composite oxide particles,
Li x Ni y Mn z Co t M p O 1+x (1)
in the formula (1), M represents 1 or more than 2 metal elements selected from Mg, al, ti, zr, cu, fe, sr, ca, V, mo, bi, nb, si, zn, ga, ge, sn, ba, W, na and K, x represents 0.98.ltoreq.x.ltoreq.1.20, y represents 0.30.ltoreq.y < 1.00, z represents 0 < z.ltoreq.0.50, t represents 0 < t.ltoreq.0.50, p represents 0.ltoreq.p.ltoreq.0.05, and y+z+t+p=1.00;
The titanium chelate compound is a titanium chelate compound represented by the following general formula (2) or an ammonium salt thereof,
Ti(R 1 ) m L n (2)
in the formula (2), R 1 When a plurality of the groups are present, L represents a group derived from a hydroxycarboxylic acid, and when a plurality of the groups are present, m represents a number of 0 to 3 inclusive, n represents a number of 1 to 3 inclusive, and m+n is 3 to 6.
2. The method for producing modified lithium nickel manganese cobalt composite oxide particles according to claim 1, wherein:
the temperature of the heating treatment is 400-1000 ℃.
3. The method for producing modified lithium nickel manganese cobalt composite oxide particles according to claim 1 or 2, characterized in that:
l in the general formula (2) is a monocarboxylic acid.
4. The method for producing modified lithium nickel manganese cobalt composite oxide particles according to claim 1 or 2, characterized in that:
l in the general formula (2) is lactic acid.
5. The method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of claims 1 to 4, wherein:
the pH of the surface treatment liquid is 7 or more.
6. The method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of claims 1 to 5, wherein:
The amount of the titanium chelate compound attached in the coated particles is relative to 1m 2 The lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) are 0.1 to 150mg in terms of Ti atoms.
7. The method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of claims 1 to 6, wherein:
the amount of residual alkali in the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) is 1.2 mass% or less.
8. The method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of claims 1 to 7, wherein:
the residual alkali content in the modified lithium nickel manganese cobalt composite oxide particles is 1.2 mass% or less.
9. The method for producing modified lithium nickel manganese cobalt composite oxide particles according to any one of claims 1 to 8, wherein:
in the modification step, the modification is carried out in a proportion of 1m 2 The Ti content of the lithium nickel manganese cobalt composite oxide particles shown in the general formula (1) is expressed by Ti atomsThe surface modifying liquid is added to the lithium nickel manganese cobalt composite oxide particles represented by the general formula (1) in an amount of 0.1 to 150mg in terms of the amount added, and the mixture is mixed and dried in its entirety.
10. A method for producing a positive electrode active material for a lithium secondary battery, characterized by comprising:
Comprising a step of mixing large particles having an average particle diameter of 7.5 to 30.0 [ mu ] m obtained by the production method according to any one of claims 1 to 9 with small particles having an average particle diameter of 0.5 to 7.5 [ mu ] m obtained by the production method according to any one of claims 1 to 9.
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| JP2020-185031 | 2020-11-05 | ||
| JP2021177454A JP7252298B2 (en) | 2020-11-05 | 2021-10-29 | Method for producing modified lithium-nickel-manganese-cobalt composite oxide particles |
| JP2021-177454 | 2021-10-29 | ||
| PCT/JP2021/040449 WO2022097653A1 (en) | 2020-11-05 | 2021-11-02 | Method of producing modified lithium nickel manganese cobalt composite oxide particles |
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