Metal acid compound dispersion

Abstract

The present invention provides a metal acid compound dispersion containing one or more metal M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum. The metal acid compound dispersion contains an organic acid and one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements. The metal acid compound dispersion has a D50 (on a volume integration basis) of 100 nm or less as measured by a dynamic light scattering.

Description

Metal acid compound dispersion

[0001] The present invention relates to a metal acid compound dispersion.

[0002] Metal oxide lithium compounds, which are composites of metal elements such as niobium, tantalum, molybdenum, and tungsten with lithium, an alkali metal element, are used in nonlinear optical materials, piezoelectric elements, nonlinear optical materials, battery materials, and the like. For example, in composite active material particles capable of reducing the battery resistance generated in all-solid-state lithium-ion batteries, lithium tantalate is cited as a lithium ion conductive oxide that coats at least a portion of the surface of the composite active material particles. For example, Patent Document 1 discloses a piezoelectric sensor in which a piezoelectric film layer containing lithium niobate powder is formed on a substrate layer of the piezoelectric sensor. In the piezoelectric sensor disclosed in Patent Document 1, the piezoelectric film layer is formed by spray-coating a mixture of lithium niobate powder and a sol-gel solution, followed by sintering.

[0003] Japanese Patent Publication No. 2023-63187

[0004] However, in the piezoelectric sensor disclosed in Patent Document 1, when a mixture of lithium niobate powder and a sol-gel solution is spray-coated, if the lithium niobate powder has low dispersibility or solubility in the solvent, it becomes difficult to form a uniform piezoelectric film layer. Also, if the storage stability of the mixture of lithium niobate powder and a solvent is poor, the spray-coating process becomes complicated.

[0005] In view of the above problems, the present invention provides a metal acid compound dispersion liquid having excellent storage stability.

[0006] The metal acid compound dispersion of the present invention, made to solve the above problems, is a metal acid compound dispersion containing one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum, and is characterized in that it contains one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and an organic acid, and the D50 (volume integrated basis) measured by the metal acid compound dispersion by dynamic light scattering is 100 nm or less. The metal acid compound dispersion of the present invention is a metal acid compound dispersion containing one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum, and is preferably excellent in terms of storage stability if it contains one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and an organic acid, and has a D50 (volume integrated basis) of 100 nm or less as measured by dynamic light scattering.

[0007] The metal acid compound dispersion of the present invention contains one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum. The metal species M is thought to exist in the metal acid compound dispersion of the present invention as an oxide or an ionic compound. Specifically, lanthanum, yttrium, cerium, and neodymium are thought to exist as trivalent metal cations coordinated with carboxylic acids such as acetic acid. Zirconium, on the other hand, is thought to exist as a tetravalent metal cation bonded with oxygen, carboxylic acids such as acetic acid, or (Zr ３ O ７ ) ２－ It is believed that niobium exists as an anion such as NbO ３－ , Nb ６ O １９ ２－Tantalum is thought to exist as an anion such as TaO, a polyoxometalate (polyacid) ion in which multiple niobium atoms are bonded to oxygen atoms, or a peroxo complex in which hydrogen peroxide is coordinated. ３－ , Ta ６ O １９ ２－ It is believed that molybdenum exists as an anion such as MoO, a polyoxometalate (polyacid) ion in which multiple tantalum atoms are bonded to oxygen atoms, or a peroxo complex in which hydrogen peroxide is coordinated. ４ ２－ It is believed that tungsten exists as an anion such as (W), a polyoxometalate (polyacid) ion in which multiple molybdenum atoms are bonded to oxygen atoms, or a peroxo complex in which hydrogen peroxide is coordinated. ２ O ７ ) ２－ Ya, (W １２ O １０ ) ８－ It is believed that titanium exists as an anion such as (Ti), a polyoxometalate (polyacid) ion in which multiple tungsten atoms are bonded to oxygen atoms, or a peroxo complex in which hydrogen peroxide is coordinated. ３ O ７ ) ２－ It is believed that aluminum exists as an anion such as [Al(OH)], a polyoxometalate (polyacid) ion in which multiple titanium atoms are bonded to oxygen atoms, or a peroxo complex in which hydrogen peroxide is coordinated. Aluminum also reacts with strong bases to form [Al(OH)]. ４ (H ２ O) ２ ] － anions such as Al dissolved in acid ３＋ cations such as Al coordinated to ethylenediaminetetraacetic acid ３＋ It is thought to exist as a cation.

[0008] Furthermore, the metal species M is not limited to one metal species selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum, but may be two or more metal species, or may be three or more metal species. For example, the metal species M may be two metal species, lanthanum and zirconium. Furthermore, the metal species M may be three metal species, lanthanum, zirconium, and tantalum.

[0009] The metal acid compound dispersion of the present invention contains one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements. That is, it is presumed that the metal acid in the metal acid compound dispersion of the present invention is present in the dispersion as ions in an ionic state with ions of one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements. It is believed that in the metal acid compound dispersion of the present invention, hydroxide ions are present as anions, while halide ions such as fluoride ions and chloride ions are almost absent, and the alkali metal elements and alkaline earth metal elements are present as cations.

[0010] Furthermore, the element X preferably contains lithium. Furthermore, the element X is not limited to only one alkali metal element, i.e., lithium, but is preferably two alkali metal elements, i.e., lithium and sodium, or lithium and potassium, or three alkali metal elements, i.e., lithium, sodium, and potassium. Furthermore, the element X may be one alkali metal element, i.e., sodium or potassium, or two alkali metal elements, i.e., sodium and potassium.

[0011] The metal acid compound dispersion of the present invention also contains an organic acid.

[0012] Examples of organic acids include carboxylic acids. Examples of carboxylic acids include saturated fatty acids, unsaturated fatty acids, hydroxy acids, aromatic carboxylic acids, dicarboxylic acids, tricarboxylic acids, oxocarboxylic acids, and carboxylic acid derivatives. Examples of saturated fatty acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, and stearic acid. Examples of unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and sorbic acid. Examples of hydroxy acids include lactic acid, malic acid, citric acid, tartaric acid, glycolic acid, hydroxybutyric acid, and glyceric acid. Examples of aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, melitic acid, and cinnamic acid. Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, and maleic acid. Examples of tricarboxylic acids include aconic acid. Examples of oxocarboxylic acids include pyruvate and oxaloacetate. Examples of carboxylic acid derivatives include amino acids and nitrocarboxylic acids. Examples of amino acids include alanine, arginine, and aspartic acid. Other examples of carboxylic acids include ethylenediaminetetraacetic acid. Alkali metal salts or alkaline earth metal salts of the organic acid may also be used. For example, sodium ethylenediaminetetraacetate and disodium ethylenediaminetetraacetate may be used.

[0013] Furthermore, the metal acid compound dispersion of the present invention preferably contains one or more organic acids selected from carboxylic acids, saturated fatty acids, hydroxy acids, citric acid, tartaric acid, lactic acid, acetic acid, and salts thereof. Organic acids that do not contain nitrogen atoms are preferred, for example, carboxylic acids, saturated fatty acids, and hydroxy acids are preferred, and it is more preferable to contain one or more selected from citric acid, tartaric acid, lactic acid, malic acid, acetic acid, and salts thereof. The organic acid also includes various isomers (structural isomers, optical isomers, etc.) of the above-mentioned compounds. Furthermore, the organic acid may be one or more organic acids of the above-mentioned compounds.

[0014] Furthermore, a D50 (volume-integrated basis) measured by dynamic light scattering of 100 nm or less is preferred from the viewpoints of high dispersibility, stability with little change over time, reactivity during reaction or compounding with other substances, and film uniformity during film formation. Furthermore, the particle diameter (D50) is preferably smaller, more preferably 50 nm or less, even more preferably 30 nm or less, particularly preferably 20 nm or less, even more particularly preferably 10 nm or less, even more particularly preferably 8 nm or less, even particularly preferably 6 nm or less, even more preferably 4 nm or less, even more preferably 2 nm or less, even more preferably 1 nm or less, even more preferably 0.6 nm or less, and most preferably greater than 0. Thus, a liquid having a D50 of 100 nm or less as measured using dynamic light scattering is defined as the "metal acid compound dispersion" of the present invention.

[0015] Here, dynamic light scattering is a method in which a solution such as a suspension is irradiated with light such as laser light, and the light scattering intensity from a group of particles undergoing Brownian motion is measured, and particle size and distribution are determined from the temporal fluctuations in this intensity. Specifically, particle size distribution is evaluated using a zeta potential, particle size, and molecular weight measurement system (manufactured by Otsuka Electronics Co., Ltd.: ELSZ-2000) in accordance with JIS Z 8828:2019 "Particle Size Analysis - Dynamic Light Scattering." Just before measurement, the solution to be measured is filtered through a filter with a 1 μm pore size to remove dust and other particles. D50 refers to the median diameter (D50), which is the particle size that represents the 50% integrated value of the integrated distribution curve. Furthermore, unless otherwise specified, in this specification, "particle diameter (D50)" includes both "initial particle diameter D50," which indicates the D50 of the metal acid compound dispersion of the present invention adjusted to a liquid temperature of 25°C immediately after production, and "aged particle diameter D50," which indicates the D50 of the metal acid compound dispersion of the present invention after it has been left to stand for one month from the day the metal acid compound dispersion of the present invention was produced in an incubator set at room temperature of 25°C. Furthermore, it is not possible to clearly observe whether the metal acid compound in the metal acid compound dispersion of the present invention is in a dissolved state in the solvent or exists as particles in the solvent. Therefore, the numerical value described as "particle diameter" in this specification means "the value measured as the particle diameter."

[0016] The metal acid compound dispersion of the present invention is a metal acid compound dispersion containing one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum, and is characterized in that it contains one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and an organic acid, and has a maximum transmittance of 70% T or more in a wavelength region of 400 nm to 760 nm. Here, the one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum, the one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and the organic acid in the metal acid compound dispersion of the present invention are as described above, and therefore detailed description thereof will be omitted.

[0017] The metal acid compound dispersion of the present invention preferably has a maximum transmittance in the wavelength region of 400 nm to 760 nm of 70% T or more, in terms of high dispersibility and excellent uniformity of the components in the liquid. The maximum transmittance in the wavelength region of 400 nm to 760 nm is more preferably 72% T or more, even more preferably 74% T or more, particularly preferably 76% T or more, especially preferably 78% T or more, even especially preferably 80% T or more, even especially preferably 85% T or more, even more preferably 90% T or more, even more preferably 95% T or more, especially more preferably 97% T or more, especially preferably 98% T or more, even especially preferably 99% T or more, and most preferably 100% T.

[0018] Furthermore, the metal acid compound dispersion liquid of the present invention may have a transmittance of 70% T or more at any one wavelength of 400 nm, 600 nm, or 750 nm. The transmittance at any one wavelength of 400 nm, 600 nm, or 750 nm, or at any two or more wavelengths, may be 72% T or more, 74% T or more, 76% T or more, 78% T or more, 80% T or more, 85% T or more, 90% T or more, 95% T or more, 97% T or more, 98% T or more, 99% T or more, or 100% T or more.

[0019] Furthermore, the metal acid compound dispersion liquid of the present invention may have a minimum transmittance in a wavelength region of 400 nm to 760 nm of 70% T or more. The minimum transmittance in the wavelength region of 400 nm to 760 nm may be 72% T or more, 74% T or more, 76% T or more, 78% T or more, 80% T or more, 85% T or more, 90% T or more, 95% T or more, 97% T or more, 98% T or more, 99% T or more, or 100% T or more.

[0020] Although the measured value of the transmittance may exceed 100%T due to measurement error or the like, since the theoretical upper limit is 100%, when the measured value exceeds 100%T, it is considered to be 100%T. Thus, a liquid in which the maximum value of the transmittance in the wavelength region of 400 nm to 760 nm of the metal acid compound dispersion of the present invention is 70%T or more is defined as the "metal acid compound dispersion" of the present invention. Furthermore, unless otherwise specified, in this specification, "transmittance" includes both "initial transmittance," which indicates the transmittance of the metal acid compound dispersion of the present invention adjusted to a liquid temperature of 25°C immediately after production, and "temporary transmittance," which indicates the transmittance of the metal acid compound dispersion of the present invention after being left to stand for one month from the day of production in an incubator set at room temperature of 25°C.

[0021] Here, the above-mentioned transmittance can be determined by measuring the ultraviolet-visible absorption spectrum (UV-Vis absorption spectrum) of the metal acid compound dispersion of the present invention in accordance with JIS K 0115, 2004 "General rules for absorptiometric analysis methods" under the following transmittance measurement conditions.

[0022] =Transmittance measurement conditions= Measuring device: Ultraviolet-visible-near-infrared spectrophotometer UH4150 (manufactured by Hitachi High-Tech Science Corporation) Measurement mode: Wavelength scan Data mode: %T (transmittance) Measurement wavelength range: 200 nm to 2000 nm Scan speed: 600 nm / min Sampling interval: 2 nm

[0023] In the present invention, the term "dispersion" is not limited to a dispersion in which a solute is dispersed or mixed in a solvent in a monomolecular state, but also includes aggregates in which a plurality of molecules are attracted to each other by intermolecular interactions, such as (1) polymer molecules, (2) solvated molecules, (3) molecular clusters, and (4) colloidal particles dispersed in a solvent.

[0024] The metal acid compound dispersion of the present invention may further contain hydrogen peroxide. In the method for producing a metal acid compound dispersion described below, the metal acid compound dispersion of the present invention may contain hydrogen peroxide because a complexation reaction of the metal species M proceeds by mixing and stirring hydrogen peroxide with a halide of one or more metal species M selected from the group consisting of one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum.

[0025] The method for detecting hydrogen peroxide in a metal oxide compound dispersion of the present invention can confirm the hydrogen peroxide content in the dispersion by, for example, using the standard addition method, measuring the relative absorbance intensity with respect to a standard solution of hydrogen peroxide. Specifically, the wavelength region in which a change in absorbance associated with peroxo complex formation is observed is identified from the UV-visible absorption spectra of a standard solution containing a known amount of hydrogen peroxide, e.g., 1% by mass, and a standard solution containing no added hydrogen peroxide. If the difference in absorbance between the standard solution containing no added hydrogen peroxide and a sample with an unknown hydrogen peroxide content in that wavelength region is less than 1%, it can be confirmed that the sample with an unknown hydrogen peroxide content is substantially free of hydrogen peroxide. If hydrogen peroxide is present in the dispersion, hydrogen peroxide reacts with, for example, a tantalum polyacid to form a peroxo complex. Therefore, the absence of hydrogen peroxide in the dispersion can be confirmed by checking the difference in absorbance with the standard solution containing no added hydrogen peroxide, as described above. In addition to the above-mentioned standard addition method, qualitative and quantitative analysis of hydrogen peroxide in the dispersion may be performed by, for example, using a commercially available hydrogen peroxide measurement kit, adding a reagent that undergoes a color reaction with hydrogen peroxide to the dispersion and measuring the color development, or by adding a reagent that undergoes a fluorescent reaction with hydrogen peroxide to the dispersion and measuring the luminescence.

[0026] The metal acid compound dispersion of the present invention may further contain ammonia and / or an organic nitrogen compound. The metal acid compound dispersion of the present invention may also contain an ionized alkaline aqueous solution, such as ammonia or an organic nitrogen compound. The contents of ammonia and organic nitrogen compound in the metal acid compound dispersion of the present invention are preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 1% by mass or less, based on 100% by mass of the metal acid compound dispersion of the present invention.

[0027] As will be explained in detail later in the method for producing the metal acid compound dispersion of the present invention, a halide of one or more metal species M selected from the group consisting of one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum is mixed and stirred with hydrogen peroxide, and the resulting mixture is reacted with ammonia and / or an alkaline compound such as an organic nitrogen compound to produce a precipitate. Therefore, the metal acid compound dispersion of the present invention contains ammonia and / or an organic nitrogen compound.

[0028] The method for measuring the ammonia content in the dispersion liquid is to add sodium hydroxide to the dispersion liquid, distill and separate the ammonia, and then quantify the ammonia content using an ion meter; ２ Examples of methods for quantifying the ammonia content include a method using a thermal conductivity meter, the Kjeldahl method, gas chromatography (GC), ion chromatography, and gas chromatography mass spectrometry (GC-MS). In particular, a method for quantifying the ammonia content using an ion meter is preferred.

[0029] Examples of organic nitrogen compounds include aliphatic amines, aromatic amines, amino alcohols, amino acids, polyamines, quaternary ammonium compounds, guanidine compounds, and azole compounds.

[0030] Examples of aliphatic amines include methylamine, dimethylamine, trimethylamine, ethylamine, methylethylamine, diethylamine, triethylamine, methyldiethylamine, dimethylethylamine, n-propylamine, di-n-propylamine, tri-n-propylamine, iso-propylamine, di-iso-propylamine, tri-iso-propylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, iso-butylamine, di-iso-butylamine, tri-iso-butylamine, tert-butylamine, n-pentaamine, n-hexylamine, cyclohexylamine, and piperidine.

[0031] Examples of aromatic amines include aniline, phenylenediamine, and diaminotoluene. Furthermore, examples of amino alcohols include methanolamine, ethanolamine, propanolamine, butanolamine, pentanolamine, dimethanolamine, diethanolamine, trimethanolamine, methylmethanolamine, methylethanolamine, methylpropanolamine, methylbutanolamine, ethylmethanolamine, ethylethanolamine, ethylpropanolamine, dimethylmethanolamine, dimethylethanolamine, dimethylpropanolamine, methyldimethanolamine, methyldiethanolamine, diethylmethanolamine, trishydroxymethylaminomethane, bis(2-hydroxyethyl)aminotris(hydroxymethyl)methane, and aminophenol. Furthermore, examples of amino acids include alanine, arginine, aspartic acid, and EDTA. Furthermore, examples of polyamines include polyamines and polyetheramines.

[0032] Examples of quaternary ammonium include alkylimidazolium, pyridinium, pyrrolidium, tetraalkylammonium, etc. Specific examples of alkylimidazolium include 1-methyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-propyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-methyl-2,3-dimethylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-propyl-2,3-dimethylimidazolium, and 1-butyl-2,3-dimethylimidazolium. Specific examples of pyridinium and pyrrolidium include N-butyl-pyridinium, N-ethyl-3-methyl-pyridinium, N-butyl-3-methyl-pyridinium, N-hexyl-4-(dimethylamino)-pyridinium, N-methyl-1-methylpyrrolidinium, and N-butyl-1-methylpyrrolidinium. Specific examples of tetraalkylammonium include tetramethylammonium, tetraethylammonium, tetrabutylammonium, and ethyl-dimethyl-propylammonium. Examples of anions that form salts with the above-mentioned cations include OH, － , Cl － ,Br － , I － , B.F. ４ － , HSO ４ － Examples include:

[0033] Examples of guanidine compounds include guanidine, diphenylguanidine, and ditolylguanidine. Examples of azole compounds include imidazole compounds and triazole compounds. Specific examples of imidazole compounds include imidazole, 2-methylimidazole, and 2-ethyl-4-methylimidazole. Specific examples of triazole compounds include 1,2,4-triazole, 1,2,4-triazole-3-methylcarboxylate, and 1,2,3-benzotriazole.

[0034] Here, the organic nitrogen compound is preferably an aliphatic amine because it has high volatility and low toxicity. Specifically, an aliphatic amine having 1 to 4 carbon atoms is more preferable, and an aliphatic amine having 1 to 2 carbon atoms is particularly preferable. Examples include methylamine and dimethylamine.

[0035] Furthermore, the organic nitrogen compound is preferably a quaternary ammonium, which not only has high solubility but also has high crystallization suppression and high solation suppression. For example, tetraalkylammonium salts are preferred, tetraalkylammonium hydroxide salts are more preferred, tetramethylammonium hydroxide and tetraethylammonium are particularly preferred, and tetramethylammonium hydroxide (TMAH) is also particularly preferred.

[0036] Furthermore, the organic nitrogen compound may be a mixture of two or more compounds selected from aliphatic amines, aromatic amines, amino alcohols, amino acids, polyamines, quaternary ammonium compounds, guanidine compounds, and azole compounds, rather than a single compound. For example, a mixture of two compounds, an aliphatic amine and a quaternary ammonium compound, is preferred because it can increase solubility while limiting the amount added so as not to increase toxicity.

[0037] Specific examples include mixtures of two organic nitrogen compounds such as methylamine and tetramethylammonium hydroxide (TMAH), dimethylamine and tetramethylammonium hydroxide (TMAH), and methylamine and dimethylamine, and mixtures of three organic nitrogen compounds such as methylamine, dimethylamine, and tetramethylammonium hydroxide (TMAH).

[0038] The content of the organic nitrogen compound present in the metal acid compound dispersion of the present invention can be measured by gas chromatography (GC), liquid chromatography (LC), mass spectrometry (MS), gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), etc. When a low-volatility organic nitrogen compound is contained, it is preferable to measure the content of the organic nitrogen compound by liquid chromatography (LC) or liquid chromatography-mass spectrometry (LC-MS).

[0039] The metal acid compound dispersion of the present invention may further contain a phosphorus compound and / or a chlorine compound.

[0040] Here, the phosphorus compound preferably contains at least one selected from inorganic phosphorus compounds, organic phosphorus compounds, and salts thereof.

[0041] Examples of inorganic phosphorus compounds include inorganic phosphoric acids, particularly phosphoric acids, phosphonic acids, and phosphinic acids. Specific examples of phosphoric acids include phosphoric acid (CAS No.: 7664-38-2), condensed phosphoric acid, pyrophosphoric acid (CAS No.: 2466-09-3), and polyphosphoric acid (CAS No.: 8071-16-1). Specific examples of phosphonic acids include phosphorous acid (CAS No.: 13598-36-2) and hypophosphorous acid (CAS No.: 6303-21-5). Specific examples of phosphinic acids include phosphinic acid (CAS No.: 6303-21-5).

[0042] Examples of organic phosphorus compounds include phosphate esters, organic phosphites, organic phosphonic acids, and organic phosphines. Specific examples of the organic phosphorus compound include methyl phosphate (CAS number: 52932-95-3), ethyl phosphate (CAS number: 37203-76-2), butyl phosphate (CAS number: 107-66-4), phenyl phosphate (CAS number: 701-64-4), dimethyl phosphate (CAS number: 813-78-5), diethyl phosphate (CAS number: 598-02-7), dibutyl phosphate (CAS number: 107-66-4), diphenyl phosphate (CAS number: 838-85-7), trimethyl phosphate (CAS number: 512-56-1), triethyl phosphate (CAS number: 78-40-0), tributyl phosphate (CAS number: 126-73-8), and triphenyl phosphate (CAS number: 115-86-6).

[0043] In addition, examples of organic phosphite ester acids and organic phosphonate esters include methylphosphonic acid (CAS number: 993-13-5), ethylphosphonic acid (CAS number: 6779-09-5), butylphosphonic acid (CAS number: 3321-64-0), phenylphosphonic acid (CAS number: 1571-33-1), dimethyl phosphite (dimethyl phosphonate) (CAS number: 868-85-9), diethyl phosphite (diethyl phosphonate) (CAS number : 762-04-9), dibutyl phosphite (dibutyl phosphonate) (CAS No.: 1809-19-4), diphenyl phosphite (diphenyl phosphonate) (CAS No.: 4712-55-4), trimethyl phosphite (CAS No.: 121-45-9), triethyl phosphite (CAS No.: 122-52-1), tributyl phosphite (CAS No.: 102-85-2), and triphenyl phosphite (CAS No.: 101-02-0).

[0044] Examples of the salts of inorganic phosphorus compounds and / or organic phosphorus compounds include ammonium salts of inorganic phosphorus compounds and / or organic phosphorus compounds, salts with organic nitrogen compounds, alkali metal salts, and alkaline earth metal salts.

[0045] An example of the organic phosphinic acids is triphenylphosphine (CAS number: 603-35-0).

[0046] Inorganic ammonium phosphate salts, salts with organic nitrogen compounds, alkali metal salts, and alkaline earth metal salts include ammonium phosphate, monoammonium phosphate (CAS No.: 7722-76-1), diammonium phosphate (CAS No.: 7783-28-0), sodium metaphosphate (CAS No.: 10361-03-2), potassium metaphosphate (CAS No.: 7790-53-6), and sodium hexametaphosphate (CAS No.: 10124-56-8). Examples of the polyphosphate include potassium hexametaphosphate, sodium pyrophosphate (CAS No.: 7722-88-5), potassium pyrophosphate (CAS No.: 7320-34-5), sodium polyphosphate (CAS No.: 68915-31-1), potassium polyphosphate, sodium tripolyphosphate (CAS No.: 7758-29-4), potassium tripolyphosphate (CAS No.: 13845-36-8), sodium ultrapolyphosphate, and potassium ultrapolyphosphate.

[0047] Furthermore, in the metal acid compound dispersion of the present invention, the phosphorus compound preferably contains one or more selected from phosphoric acid (CAS No.: 7664-38-2), condensed phosphoric acid, pyrophosphoric acid (CAS No.: 2466-09-3), polyphosphoric acid (CAS No.: 8071-16-1), phosphorous acid (CAS No.: 13598-36-2), hypophosphorous acid (CAS No.: 6303-21-5), ammonium phosphate, monoammonium phosphate (CAS No.: 7722-76-1), diammonium phosphate (CAS No.: 7783-28-0), ammonium pyrophosphate, and ammonium polyphosphate. Phosphorus compounds and salts of phosphoric acid are preferred for adjusting solutions to a pH closer to neutral. Conversely, condensed phosphoric acid compounds, or condensed phosphoric acid compounds such as pyrophosphoric acid, polyphosphoric acid, and salts of condensed phosphoric acid, are preferred for adjusting solutions to a high pH.

[0048] In this specification, "phosphoric acid" refers to orthophosphoric acid and does not include other phosphoric acids such as pyrophosphoric acid, polyphosphoric acid, and phosphorous acid. The phosphorus compound may form a compound with an alkali metal element or an alkaline earth metal element. For example, when the phosphorus compound contains a hydroxyl group (P-OH group), the phosphorus compound has a structure in which some or all of the hydrogen atoms in the hydroxyl group are substituted with an alkali metal element or an alkaline earth metal element.

[0049] Examples of chlorine compounds include hydrochloric acid (CAS No.: 7647-01-0), hypochlorous acid (CAS No.: 7790-92-3), chlorous acid (CAS No.: 13898-47-0), chloric acid (CAS No.: 7790-93-4), and perchloric acid (CAS No.: 7601-90-3).

[0050] Furthermore, the chlorine compound may be a salt of the above-mentioned chlorine compound, such as an ammonium salt, an amine salt, a quaternary ammonium salt, or a lithium salt, and preferably an ammonium salt or a lithium salt. Specific examples include ammonium chloride (CAS No.: 12125-02-9), ammonium perchlorate (CAS No.: 7790-98-9), lithium chloride (CAS No.: 7447-41-8), lithium perchlorate (CAS No.: 7791-03-9), methylamine hydrochloride (CAS No.: 593-51-1), and dimethylamine hydrochloride (CAS No.: 506-59-2).

[0051] In addition, if the inclusion of a chlorine compound in the metal acid compound dispersion of the present invention causes concern about corrosion or elution of the substrate depending on the material or type of the substrate to which the metal acid compound dispersion of the present invention is applied, it is preferable that the metal acid compound dispersion of the present invention does not contain a chlorine compound. For example, when the metal acid compound dispersion of the present invention is used for coating a positive electrode or positive electrode material for a lithium ion secondary battery described below, it is preferable that the metal acid compound dispersion of the present invention does not contain a chlorine compound.

[0052] The metal acid compound dispersion of the present invention is also characterized in that the metal species M content in the metal acid compound dispersion is from 0.01% by mass to 30% by mass in terms of metal species M atoms. If the metal species M content in the metal acid compound dispersion of the present invention is from 0.01% by mass to 30% by mass in terms of metal species M atoms, this is preferred in terms of achieving both practicality and stability of the metal acid compound dispersion, and is more preferably from 0.5% by mass to 25% by mass in terms of metal species M atoms, even more preferably from 1% by mass to 20% by mass in terms of metal species M atoms, particularly preferably from 1% by mass to 15% by mass in terms of metal species M atoms, even more particularly preferably from 3% by mass to 10% by mass in terms of metal species M atoms, and even more particularly preferably from 5% by mass to 10% by mass in terms of metal species M atoms.

[0053] The content of metal type M can be determined as follows.

[0054] When the metal species M contained in the metal acid compound dispersion of the present invention is one type of tantalum, the tantalum content in terms of Ta atoms in the metal acid compound dispersion of the present invention is the metal species M content in the metal acid compound dispersion of the present invention.

[0055] When the metal species M contained in the metal acid compound dispersion of the present invention is two types, lanthanum and zirconium, the sum of the lanthanum content in terms of La atoms and the zirconium content in terms of Zr atoms in the metal acid compound dispersion of the present invention is the content of the metal species M in the metal acid compound dispersion of the present invention.

[0056] Furthermore, when the metal species M contained in the metal acid compound dispersion of the present invention are three types, namely lanthanum, zirconium, and tantalum, the total of the lanthanum content in terms of La atoms, the zirconium content in terms of Zr atoms, and the tantalum content in terms of Ta atoms in the metal acid compound dispersion of the present invention is the content of the metal species M in the metal acid compound dispersion of the present invention.

[0057] Here, the content of the metal species M in the metal acid compound dispersion is calculated by diluting the dispersion appropriately with dilute hydrochloric acid as necessary, and measuring La mass% in terms of La atoms, Zr mass% in terms of Zr atoms, Nb mass% in terms of Nb atoms, Ta mass% in terms of Ta atoms, Mo mass% in terms of Mo atoms, W mass% in terms of W atoms, Ti mass% in terms of Ti atoms, Y mass% in terms of Y atoms, and Ce mass% in terms of Ce atoms using inductively coupled plasma atomic emission spectroscopy (ICP atomic emission spectroscopy (AG-5110, manufactured by Agilent Technologies)) in accordance with JIS K0116:2014. Furthermore, when the metal acid in the metal acid compound dispersion of the present invention is ionically bonded to an alkali metal or alkaline earth metal, for example, a lithium metal acid salt ionically bonded to lithium ions, the lithium content may be calculated by measuring Li mass% in terms of Li atoms, in the same manner as the content of the metal species M. By specifying the content of the metal species M and the content of lithium in the metal acid compound dispersion of the present invention, it is possible to specify the molar ratio Li / m of lithium (Li) to the metal species M(m) of the lithium metal oxide contained in the metal acid compound dispersion of the present invention. Note that the content of each element X of one or more elements X selected from the group consisting of alkali metal elements other than lithium and / or alkaline earth metal elements can also be calculated by measuring the mass % of each element X in terms of element X atoms, in the same manner as the content of the metal species M.

[0058] The metal acid compound dispersion of the present invention is characterized in that the organic acid content in the metal acid compound dispersion is 0.01% by mass or more and 30% by mass or less. The organic acid content in the metal acid compound dispersion of the present invention is preferably 0.01% by mass or more and 30% by mass or less, since the solution state has excellent stability over time. The organic acid content is more preferably 0.01% by mass or more and 20% by mass or less, even more preferably 0.01% by mass or more and 15% by mass or less, and particularly preferably 0.01% by mass or more and 10% by mass or less. When the metal acid compound dispersion of the present invention contains two or more organic acids, the organic acid content is the total content of the two or more organic acids contained.

[0059] The method for measuring the organic acid content in the metal acid compound dispersion of the present invention includes the steps of: １Examples of the method include H-NMR, gas chromatography (GC), liquid chromatography (LC), mass spectrometry (MS), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS). Of these, measurement of the organic acid content by liquid chromatography (LC) or liquid chromatography-mass spectrometry (LC-MS) is preferred.

[0060] １ The method for measuring the organic acid content in the metal acid compound dispersion of the present invention by H-NMR spectroscopy is as follows. Specifically, the organic acid content in the metal acid compound dispersion of the present invention can be determined by the following procedure using a nuclear magnetic resonance spectrometer (AVANCE NEO 600 manufactured by Bruker). A measurement sample is prepared by mixing 70 μL of a sample solution, 70 μL of a DSS-d6 deuterium oxide solution prepared by dissolving sodium 3-(trimethylsilyl)-1-propane-1,1,2,2,3,3-d6-sulfonate (hereinafter referred to as DSS-d6) in deuterium oxide, and 560 μL of deuterium oxide. The prepared measurement sample is subjected to the following measurement. １ According to the H-NMR spectrum measurement conditions, １ The H-NMR spectrum is measured.

[0061] = １ H-NMR spectrum measurement conditions = Magnetic field: 14.1 T (1H 600MHz) Spectrometer: AVANCE NEO 600 manufactured by Bruker Measurement and data processing software: TopSpin manufactured by Bruker NMR probe: Solvent probe (Type: PA BBO 600S3 BBF-H-D-05 Z SP) Solvent: Heavy water Internal sample for chemical shift value and organic acid amount: DSS-d6 Chemical shift value reference: The apex of the peak of DSS-d6 is set to 0.00 ppm. Spectral center (O1 value - SR value (chemical shift value)): 6 ppm or more and 6.4 ppm or less Radio frequency pulse intensity: The intensity is such that 15 μs results in a 90-degree pulse with respect to the peak of the irradiation center. Radio frequency pulse width: 15 μs Measurement interval: 84 μs (DW = 42 μs on the software) Number of measurement points: 32,768 points (TD = 65,536 on the software) Number of spectrum points (SI on the software): 65,536 points or more １ ​Obtained under H-NMR spectral measurement conditions １ The H-NMR spectrum is referred to as the "uncorrected spectrum."

[0062] The method for calculating the integral value is as described above. １ The FID data measured under H-NMR spectral measurement conditions is Fourier transformed using a window function with a full width at half maximum of 0.3 Hz, and then baseline correction is performed as described later. １ The H-NMR spectrum is obtained. １ A calculated spectrum is obtained from the H-NMR spectrum using the fitting method described below, and the range of the X-axis including the peak for which the integral value of the calculated spectrum is to be calculated is defined as the "integration range," and the sum of the spectral intensities at all points in the integration range is defined as the "integration value of the target sample." If there are multiple peaks for which the integral values ​​are to be calculated for one target sample, multiple integration ranges may be used.

[0063] The baseline correction method is wider than the integral range, and the X-axis range where the Y-axis values ​​on both sides of a certain X-axis range are close to 0 and the spectrum appears horizontal to the naked eye up to 0.1 ppm inside from both ends of that range is called the "baseline range." The number of baseline ranges is the same as the integral range. Point A is the point on the X-axis and Y-axis where the X-axis value of the uncorrected spectrum is closest to the value obtained by subtracting 0.01 ppm from the maximum value of the baseline range to the point closest to the maximum value of the baseline range, respectively, and Point B is the point on the X-axis and Y-axis where the X-axis value of the uncorrected spectrum is closest to the value obtained by adding 0.01 ppm to the minimum value of the baseline range, respectively. The straight line connecting Point A and Point B is called the "baseline." The curve obtained by subtracting the baseline Y-axis value from the Y-axis value of the uncorrected spectrum at each point between the minimum and maximum values ​​of the baseline range on the X-axis is called the "measured spectrum."

[0064] The method for determining the integral value from an experimentally measured spectrum is to take the sum of the Y-axis values ​​of all points from the point closest to the minimum value of the X-axis of the experimentally measured spectrum to the point closest to the maximum value as the integral value within that integration range.

[0065] When it is difficult to apply the above-mentioned method of finding an integral value from an actually measured spectrum due to reasons such as overlapping of multiple peaks, the integral value can be found by performing fitting as follows.

[0066] The range in which the Y-axis values ​​appear to be only those of the peak for which the integral value is to be calculated, without overlapping peaks, is called the "RMSD range." This RMSD range should be included in the integration range. If another peak for which the integral value is not to be calculated overlaps within one integration range, multiple RMSD ranges may be used for a single integration range to avoid the peak for which the integral value is not to be calculated. RMSD ranges for the same peak for which the integral value is to be calculated are included within the same integration range belonging to that peak. Also, overlapping ranges of RMSD ranges should not be included. Furthermore, the maximum ratio of RMSD to the sum of the Y-axis values ​​from the point closest to the minimum value to the point closest to the maximum value of the integration range is called the "RMSD reference value." The curve represented by the sum of the two pseudo-Voigt functions shown in equation (1) described later is called the "calculation spectrum." The mean squared error (hereinafter referred to as RMSD) is calculated for all points within the entire RMSD range for each of the four variables (total of eight variables): the chemical shift value at the peak center of the two pseudo-Voigt functions, the scaling constant, the full width at half maximum, and the ratio of the Lorentz function. The calculation spectrum is then fitted using the Excel Solver function so that the ratio of the RMSD to the sum of the Y-axis values ​​from the point closest to the minimum value to the point closest to the maximum value of the integral range is less than or equal to the RMSD reference value.

[0067]

[0068] In the above formula (1), x is １ In the H NMR spectrum, x0 is the chemical shift value on the x-axis, S is the chemical shift value at the peak top, η is the scaling factor to match the Y-axis value of the peak to the experimental value, η is the peak area ratio of the Lorentz function (first term) in the range from -∞ (negative infinity) to +∞ (positive infinity), Δ is the full width at half maximum of the peak, π is pi, ln represents the natural logarithm function, and exp represents the natural exponential function.

[0069] The aforementioned "pseudo-Voigt function" is based on "6. Profile Functions and Pattern Resolution Methods" in the Journal of the Crystallographic Society of Japan, 34, 86 (1992), "Special Feature: New Developments in Powder Diffraction."

[0070] In calculating the peak integral value of DSS-d6, the point C is the point on the X-axis and the Y-axis where the values ​​on the X-axis and the Y-axis are the averages of the values ​​on the X-axis and the Y-axis from the point closest to 0.04 ppm to the point closest to 0.05 ppm on the uncorrected spectrum, respectively, and the point D is the point on the X-axis and the Y-axis where the values ​​on the X-axis and the Y-axis are the averages of the values ​​on the X-axis and the Y-axis from the point closest to −0.05 ppm to the point closest to −0.04 ppm on the uncorrected spectrum, respectively. The line connecting points C and D is referred to as the "DSS-d6 baseline." At each point on the X-axis where the values ​​on the X-axis are chemical shift values ​​from −0.05 ppm to 0.05 ppm, the curve obtained by subtracting the values ​​on the Y-axis of the baseline from the values ​​on the Y-axis of the uncorrected spectrum is referred to as the "measured spectrum of DSS-d6." The sum of the Y-axis values ​​for all points in the measured spectrum of the reference reagent where the X-axis chemical shift value is between -0.05 ppm and 0.05 ppm is referred to as the "integral value of DSS-d6".

[0071] The weight concentration of the target sample can be calculated from the concentration of DSS-d6 and the amount added to the measurement sample, the molecular weight of DSS-d6 and the number of hydrogen atoms per molecule, the molecular weight of the target sample and the number of hydrogen atoms assigned to the peak obtained by calculating the integral value per molecule of the target sample, the integral value of the standard reagent, the integral value of the target sample, the volume of the target sample added to the measurement sample, and the specific gravity of the target sample.

[0072] Here, a method for determining the amount of lactic acid contained in the Ta lactate aqueous solution, which is the raw material in the examples described later, will be described below.

[0073] DSS-d6, used to determine the amount of lactic acid contained in an aqueous solution of lactate Ta, is dissolved in heavy water to a concentration of 10 g / L. In the aqueous solution of lactate Ta, there are two types of lactic acid: "lactic acid contained in the tantalum complex" and "free lactic acid" that is not contained in the tantalum complex.

[0074] First, a method for determining the amount of lactic acid contained in a tantalum complex will be described below.

[0075] The integral value of lactic acid contained in the tantalum complex is defined as follows: baseline range: 4.55 ppm to 8 ppm; integral range: 4.55 ppm to 6.55 ppm; RMSD range 1: 5.14 ppm to 6.55 ppm; RMSD range 2: 4.95 ppm to 5.00 ppm; RMSD range 3: 4.55 ppm to 4.58 ppm; and RMSD reference value: 0.002%, and the sum of the spectral intensities obtained using the above-described method is defined as the "integral value of lactic acid contained in the tantalum complex."

[0076] The weight concentration of lactic acid contained in the tantalum complex in the Ta lactate dispersion was calculated using the lactic acid contained in the tantalum complex as the target sample. The weight concentration of lactic acid contained in the tantalum complex in the Ta lactate dispersion was calculated to be 16.7% by mass based on the concentration of the DSS-d6 heavy water solution (10 g / L), the volume of the DSS-d6 heavy water solution in the measurement sample (70 μL), the molecular weight of DSS-d6 (224.35), the number of hydrogen atoms per molecule of DSS-d6 (9), the molecular weight of lactic acid (90.08), the integral value of the target sample, the integral value of the reference reagent, the volume of the tantalum acid compound dispersion in the measurement sample (70 μL), and the specific gravity of the tantalum acid compound dispersion (1.3274).

[0077] Next, a method for determining the amount of free lactic acid will be described below.

[0078] Free lactic acid is used as the target sample. 4.85 ppm to 4.93 ppm is defined as baseline range 1 for free lactic acid, 4.31 ppm to 4.4 ppm is defined as baseline range 2 for free lactic acid, and 4.05 ppm to 4.28 ppm is defined as baseline range 3 for free lactic acid. 4.85 ppm to 4.93 ppm is defined as integral range 1 for free lactic acid, 4.31 ppm to 4.4 ppm is defined as integral range 2 for free lactic acid, and 4.05 ppm to 4.28 ppm is defined as integral range 3 for free lactic acid. The sum of the three integral values ​​calculated from the measured spectrum obtained from baseline range 1 and integration range 1, the measured spectrum obtained from baseline range 2 and integration range 2, and the measured spectrum obtained from baseline range 3 and integration range 3 is defined as the "integral value of free lactic acid."

[0079] The weight concentration of free lactic acid in the lactic acid Ta dispersion was calculated using the following data: concentration of DSS-d6 deuterated aqueous solution 10 g / L, volume of DSS-d6 deuterated aqueous solution in the sample 70 μL, molecular weight of DSS-d6 224.35, number of hydrogen atoms in one molecule of DSS-d6 9, molecular weight of lactic acid 90.08, integral value of the target sample, integral value of the reference reagent, volume of tantalum acid compound dispersion in the sample 70 μL, and specific gravity of tantalum acid compound dispersion 1.3274. The weight concentration of free lactic acid was calculated to be 12.2 mass%.

[0080] The amount of lactic acid in the tantalum lactate aqueous solution is 28.9 mass % when the lactic acid content of the tantalum complex is 16.7 mass % and the free lactic acid content is 12.2 mass %.

[0081] Furthermore, the metal acid compound dispersion of the present invention is characterized in that the molar ratio x / m of the total amount of element X (x) to the total amount of metal species M (m) in the metal acid compound dispersion is 0.001 or more and 50 or less. A molar ratio x / m of the total amount of element X (x) to the total amount of metal species M (m) in the metal acid compound dispersion of the present invention is preferably 0.001 or more and 50 or less in terms of improved dispersibility and solubility in water, more preferably 0.001 or more and 40 or less, even more preferably 0.01 or more and 35 or less, and particularly preferably 0.5 or more and 35 or less. Note that the molar ratio x / m of the total amount of element X (x) to the total amount of metal species M (m) in the metal acid compound dispersion of the present invention may be 0.01 or more and 40 or less, or 0.5 or more and 40 or less.

[0082] The total amount (m) of the metal species M can be determined as follows.

[0083] When the metal species M contained in the metal acid compound dispersion of the present invention is tantalum alone, the number of moles of tantalum per liter of the metal acid compound dispersion of the present invention is the total amount (m) of the metal species M in the metal acid compound dispersion of the present invention.

[0084] When the metal species M contained in the metal acid compound dispersion of the present invention are two types, lanthanum and zirconium, the sum of the number of moles of lanthanum and the number of moles of zirconium per 1 L of the metal acid compound dispersion of the present invention is the total amount (m) of the metal species M in the metal acid compound dispersion of the present invention.

[0085] Furthermore, when the metal species M contained in the metal acid compound dispersion of the present invention are three types, namely lanthanum, zirconium, and tantalum, the sum of the number of moles of lanthanum, the number of moles of zirconium, and the number of moles of tantalum per 1 L of the metal acid compound dispersion of the present invention is the total amount (m) of the metal species M in the metal acid compound dispersion of the present invention.

[0086] The metal acid compound dispersion of the present invention is also characterized in that the element X in the metal acid compound dispersion is lithium, and the molar ratio Li / m of lithium (Li) to the total amount (m) of the metal species M is 0.001 or more and 50 or less. When the element X in the metal acid compound dispersion of the present invention is lithium, and the molar ratio Li / m of lithium (Li) to the total amount (m) of the metal species M is 0.01 or more and 50 or less, it is preferable from the viewpoint of improving dispersibility and solubility in water, and it is more preferable to be 0.01 or more and 40 or less, still more preferable to be 0.01 or more and 35 or less, and particularly preferable to be 0.5 or more and 35 or less. When the element X in the metal acid compound dispersion of the present invention is lithium, the molar ratio Li / m of lithium (Li) to the total amount (m) of the metal species M may be 0.01 or more and 40 or less, or may be 0.5 or more and 40 or less.

[0087] The metal acid compound dispersion of the present invention is also characterized in that the molar ratio m / A of the total amount (m) of the metal species M to the total amount (A) of the organic acid in the metal acid compound dispersion is 0.001 or more and 10 or less.

[0088] The molar ratio (m / A) of the total amount (m) of the metal species M to the total amount (A) of the organic acids in the metal acid compound dispersion of the present invention is preferably 0.001 or more and 10 or less, since this provides excellent stability over time in the solution state. Furthermore, the molar ratio (m / A) is more preferably 0.001 or more and 4.9 or less, even more preferably 0.01 or more and 3 or less, particularly preferably 0.01 or more and 2 or less, even more particularly preferably 0.01 or more and 1.5 or less, and even more preferably 0.01 or more and 1 or less. Typically, the molar ratio (m / A) may be 0.001 or more, 0.01 or more, or 0.1 or more. On the other hand, the molar ratio (m / A) may be 4 or less, 3 or less, 2 or less, 1.5 or less, or 1 or less.

[0089] Here, in the molar ratio (m / A), "A" represents the content (mol) of the organic acid in the metal acid compound dispersion of the present invention. On the other hand, in the molar ratio (m / A), "m" represents the content (mol) of the metal species M in the metal acid compound dispersion of the present invention, on a per-atom basis.

[0090] Here, the total amount (m) of the metal species M is as described above, and therefore a detailed description thereof will be omitted.

[0091] For example, when the metal species M is tantalum (Ta), the molar ratio (Ta / A) is preferably 0.001 or more and 10 or less, more preferably 0.001 or more and 4.9 or less, even more preferably 0.01 or more and 3 or less, particularly preferably 0.01 or more and 2 or less, more particularly preferably 0.01 or more and 1.5 or less, and even more preferably 0.01 or more and 1 or less. Typically, the molar ratio (Ta / A) may be 0.001 or more, 0.01 or more, or 0.1 or more. On the other hand, the molar ratio (Ta / A) may be 4 or less, 3 or less, 2 or less, 1.5 or less, or 1 or less.

[0092] The metal acid compound dispersion of the present invention is characterized in that the molar ratio (x + m) / A of the sum of the total amount (x) of the element X and the total amount (m) of the metal species M to the total amount (A) of the organic acid in the metal acid compound dispersion is 0.001 or more and 10 or less. It is preferable that the molar ratio (x + m) / A of the sum of the total amount (x) of the element X and the total amount (m) of the metal species M to the total amount (A) of the organic acid in the metal acid compound dispersion of the present invention is 0.001 or more and 10 or less, since this provides excellent stability over time in the solution state. The molar ratio (x + m) / A is more preferably 0.001 or more and 4.9 or less, even more preferably 0.01 or more and 3 or less, particularly preferably 0.01 or more and 2 or less, even more particularly preferably 0.01 or more and 1.5 or less, and even more preferably 0.01 or more and 1 or less. Typically, the molar ratio (x + m) / A may be 0.001 or greater, 0.01 or greater, or 0.1 or greater. On the other hand, the molar ratio (x + m) / A may be 4 or less, 3 or less, 2 or less, 1.5 or less, or 1 or less.

[0093] Here, "A" in the molar ratio (x+m) / A represents the organic acid content (mol) in the metal acid compound dispersion of the present invention, while "x+m" represents the sum of the content (mol) of element X in terms of element X atoms and the content (mol) of metal species M in terms of metal species M atoms in the metal acid compound dispersion of the present invention.

[0094] Here, the total amount (m) of the metal species M is as described above, and therefore a detailed description thereof will be omitted.

[0095] The metal acid compound dispersion of the present invention is characterized in that the element X in the metal acid compound dispersion is lithium, and the molar ratio (Li + m) / A of the sum of the total amount (m) of the lithium (Li) and the metal species M to the total amount (A) of the organic acid is 0.001 or more and 10 or less. It is preferable that the element X in the metal acid compound dispersion of the present invention is lithium, and the molar ratio (Li + m) / A of the sum of the total amount (m) of the lithium (Li) and the metal species M to the total amount (A) of the organic acid is 0.001 or more and 10 or less, in terms of excellent transmittance stability over time in the solution state. The molar ratio (Li + m) / A is more preferably 0.001 or more and 4.9 or less, even more preferably 0.01 or more and 3 or less, particularly preferably 0.01 or more and 2 or less, even more particularly preferably 0.01 or more and 1.5 or less, and even more preferably 0.01 or more and 1 or less. Typically, the molar ratio (Li+m) / A may be 0.001 or more, 0.01 or more, or 0.1 or more, while the molar ratio (Li+m) / A may be 4 or less, 3 or less, 2 or less, 1.5 or less, or 1 or less.

[0096] Here, "A" in the molar ratio (Li+m) / A represents the organic acid content (mol) in the metal acid compound dispersion of the present invention, while "Li+m" represents the sum of the lithium content (mol) in terms of Li atoms and the metal species M content (mol) in terms of metal species M atoms in the metal acid compound dispersion of the present invention.

[0097] Here, the total amount (m) of the metal species M is as described above, and therefore a detailed description thereof will be omitted.

[0098] Furthermore, the metal acid compound dispersion of the present invention is characterized in that the molar ratio x / P of the total amount of element X (x) to the total amount of phosphorus compound (P) in the metal acid compound dispersion is 0.001 or more and 10 or less. A molar ratio x / P of the total amount of element X (x) to the total amount of phosphorus compound (P) in the metal acid compound dispersion of the present invention is preferable in that it is 0.001 or more and 10 or less in terms of excellent long-term stability of the solution state. Furthermore, the molar ratio x / P is more preferably 0.001 or more and 4.9 or less, even more preferably 0.01 or more and 3 or less, particularly preferably 0.01 or more and 2 or less, even more preferably 0.01 or more and 1 or less. Typically, the molar ratio x / P may be 0.001 or more, 0.01 or more, or 0.1 or more. On the other hand, the molar ratio x / P may be 4 or less, 3 or less, 2 or less, 1.5 or less, or 1 or less.

[0099] Here, "P" in the molar ratio x / P represents the phosphorus content (mol) in the metal acid compound dispersion of the present invention, while "x" represents the content (mol) of element X in the metal acid compound dispersion of the present invention in terms of X atoms.

[0100] Furthermore, the metal acid compound dispersion of the present invention is characterized in that the element X in the metal acid compound dispersion is lithium, and the molar ratio Li / P of lithium (Li) to the total amount (P) of the phosphorus compound is 0.001 or more and 10 or less. In the metal acid compound dispersion of the present invention, the element X in the metal acid compound dispersion is lithium, and the molar ratio Li / (P+A) of lithium (Li) to the total amount (P) of the phosphorus compound is 0.001 or more and 10 or less is preferable in that it provides excellent long-term stability of the solution state. Furthermore, the molar ratio Li / P is more preferably 0.001 or more and 4.9 or less, even more preferably 0.01 or more and 3 or less, particularly preferably 0.01 or more and 2 or less, even more preferably 0.01 or more and 1 or less. Typically, the molar ratio Li / P may be 0.001 or more, 0.01 or more, or 0.1 or more. On the other hand, the molar ratio Li / P may be 4 or less, 3 or less, 2 or less, 1.5 or less, or 1 or less.

[0101] Here, "P" in the molar ratio Li / P indicates the phosphorus content (mol) in the metal acid compound dispersion of the present invention, while "Li" indicates the lithium content (mol) in terms of Li atoms in the metal acid compound dispersion of the present invention.

[0102] The metal acid compound dispersion of the present invention is characterized in that the molar ratio m / P of the total amount (m) of the metal species M to the total amount (P) of the phosphorus compounds in the metal acid compound dispersion is 0.001 or more and 10 or less. A molar ratio m / P of the total amount (m) of the metal species M to the total amount (P) of the phosphorus compounds in the metal acid compound dispersion of the present invention of 0.001 or more and 10 or less is preferable in terms of excellent stability over time in the solution state. Furthermore, the molar ratio m / P is more preferably 0.001 or more and 4.9 or less, even more preferably 0.01 or more and 3 or less, particularly preferably 0.01 or more and 2 or less, even more particularly preferably 0.01 or more and 1.5 or less, and even more particularly preferably 0.01 or more and 1 or less. Typically, the molar ratio m / P may be 0.001 or more, 0.01 or more, or 0.1 or more. On the other hand, the molar ratio m / P may be 4 or less, 3 or less, 2 or less, 1.5 or less, or 1 or less.

[0103] Here, "P" in the molar ratio m / P represents the phosphorus content (mol) in the metal acid compound dispersion of the present invention, while "Ta" represents the content (mol) of the metal species M in the metal acid compound dispersion of the present invention, calculated as metal species M atoms.

[0104] Here, the total amount (m) of the metal species M is as described above, and therefore a detailed description thereof will be omitted.

[0105] The metal acid compound dispersion of the present invention is characterized in that the molar ratio x / (P+A) of the total amount of element X (x) to the sum of the total amount of phosphorus compounds (P) and the total amount of organic acids (A) in the metal acid compound dispersion is 0.001 or more and 10 or less. It is preferable that the molar ratio x / (P+A) of the total amount of element X (x) to the sum of the total amount of phosphorus compounds (P) and the total amount of organic acids (A) in the metal acid compound dispersion of the present invention is 0.001 or more and 10 or less, because the solution state has excellent stability over time. The molar ratio x / (P+A) is more preferably 0.001 or more and 4.9 or less, even more preferably 0.01 or more and 3 or less, particularly preferably 0.01 or more and 2 or less, even more particularly preferably 0.01 or more and 1.5 or less, and even more particularly preferably 0.01 or more and 1 or less. Typically, the molar ratio x / (P+A) may be 0.001 or more, 0.01 or more, or 0.1 or more. On the other hand, the molar ratio x / (P+A) may be 4 or less, 3 or less, 2 or less, 1.5 or less, or 1 or less.

[0106] Here, "P+A" in the molar ratio x / (P+A) represents the sum of the phosphorus content (mol) and the organic acid content (mol) in the metal acid compound dispersion of the present invention, while "x" represents the content (mol) of element X in the metal acid compound dispersion of the present invention in terms of X atoms.

[0107] The metal acid compound dispersion of the present invention is characterized in that the element X in the metal acid compound dispersion is lithium, and the molar ratio Li / (P+A) of the lithium (Li) to the sum of the total amount of the phosphorus compounds (P) and the total amount of the organic acids (A) is 0.001 or more and 10 or less. It is preferable that the element X in the metal acid compound dispersion of the present invention is lithium, and the molar ratio Li / (P+A) of the lithium (Li) to the sum of the total amount of the phosphorus compounds (P) and the total amount of the organic acids (A) is 0.001 or more and 10 or less, in terms of excellent stability over time in the solution state. The molar ratio Li / (P+A) is more preferably 0.001 or more and 4.9 or less, even more preferably 0.01 or more and 3 or less, particularly preferably 0.01 or more and 2 or less, even more particularly preferably 0.01 or more and 1.5 or less, and even more particularly preferably 0.01 or more and 1 or less. Typically, the molar ratio Li / (P+A) may be 0.001 or greater, 0.01 or greater, or 0.1 or greater. On the other hand, the molar ratio Li / (P+A) may be 4 or less, 3 or less, 2 or less, 1.5 or less, or 1 or less.

[0108] Here, in the molar ratio Li / (P+A), "P+A" represents the sum of the phosphorus content (mol) and organic acid content (mol) in the metal acid compound dispersion of the present invention. On the other hand, "Li" represents the lithium content (mol) in terms of Li atoms in the metal acid compound dispersion of the present invention.

[0109] The metal acid compound dispersion of the present invention is characterized in that the molar ratio m / (P+A) of the total amount (m) of the metal species M to the sum of the total amount (P) of the phosphorus compounds and the total amount (A) of the organic acids in the metal acid compound dispersion is 0.001 or more and 10 or less. It is preferable that the molar ratio m / (P+A) of the total amount (m) of the metal species M to the sum of the total amount (P) of the phosphorus compounds and the total amount (A) of the organic acids in the metal acid compound dispersion of the present invention is 0.001 or more and 10 or less, since this provides excellent stability over time in the solution state. The molar ratio m / (P+A) is more preferably 0.001 or more and 4.9 or less, even more preferably 0.01 or more and 3 or less, particularly preferably 0.01 or more and 2 or less, even more particularly preferably 0.01 or more and 1.5 or less, and even more particularly preferably 0.01 or more and 1 or less. Typically, the molar ratio m / (P+A) may be 0.001 or greater, 0.01 or greater, or 0.1 or greater. On the other hand, the molar ratio m / (P+A) may be 4 or less, 3 or less, 2 or less, 1.5 or less, or 1 or less.

[0110] Here, in the molar ratio m / (P+A), "P+A" represents the sum of the phosphorus content (mol) and organic acid content (mol) in the metal acid compound dispersion of the present invention. On the other hand, "m" represents the content (mol) of metal species M in the metal acid compound dispersion of the present invention, on a per-atom basis.

[0111] Here, the total amount (m) of the metal species M is as described above, and therefore a detailed description thereof will be omitted.

[0112] Furthermore, the metal acid compound dispersion of the present invention is characterized in that the molar ratio (x + m) / (P + A) of the total amount of element X (x) and the total amount of metal species M (m) in the metal acid compound dispersion to the total amount of phosphorus compound (P) and the total amount of organic acid (A) is 0.001 or more and 10 or less. A molar ratio (x + m) / (P + A) of the total amount of element X (x) and the total amount of metal species M (m) in the metal acid compound dispersion of the present invention to the total amount of phosphorus compound (P) and the total amount of organic acid (A) is 0.001 or more and 10 or less is preferable in that it provides excellent long-term stability of the solution state. Furthermore, the molar ratio (x+m) / (P+A) is more preferably 0.001 or more and 4.9 or less, even more preferably 0.01 or more and 3 or less, particularly preferably 0.01 or more and 2 or less, even more preferably 0.01 or more and 1 or less. Typically, the molar ratio (x+m) / (P+A) may be 0.001 or more, 0.01 or more, or 0.1 or more. On the other hand, the molar ratio (x+m) / (P+A) may be 4 or less, 3 or less, 2 or less, 1.5 or less, or 1 or less.

[0113] Here, in the molar ratio (x+m) / (P+A), "P+A" represents the sum of the phosphorus content (mol) and organic acid content (mol) in the metal acid compound dispersion of the present invention. On the other hand, "x+m" represents the sum of the content of element X in terms of X atoms (mol) and the content of metal species M in terms of metal species M atoms (mol).

[0114] Here, the total amount (m) of the metal species M is as described above, and therefore a detailed description thereof will be omitted.

[0115] Furthermore, the metal acid compound dispersion of the present invention is characterized in that the element X in the metal acid compound dispersion is lithium, and the molar ratio (Li + m) / (P + A) of the total amount of lithium (Li) and the total amount of the metal species M (m) to the total amount of the phosphorus compound (P) and the total amount of the organic acid (A) is 0.001 or more and 10 or less. When the element X in the metal acid compound dispersion of the present invention is lithium, and the molar ratio (Li + m) / (P + A) of the total amount of lithium (Li) and the total amount of the metal species M (m) to the total amount of the phosphorus compound (P) and the total amount of the organic acid (A) is 0.001 or more and 10 or less, it is preferable in that the stability of the solution state over time is excellent. Furthermore, the molar ratio (Li+m) / (P+A) is more preferably 0.001 or more and 4.9 or less, even more preferably 0.01 or more and 3 or less, particularly preferably 0.01 or more and 2 or less, even more preferably 0.01 or more and 1 or less. Typically, the molar ratio ((Li+m) / (P+A) may be 0.001 or more, 0.01 or more, or 0.1 or more. On the other hand, the molar ratio (Li+m) / (P+A) may be 4 or less, 3 or less, 2 or less, 1.5 or less, or 1 or less.

[0116] Here, in the molar ratio (Li + m) / (P + A), "P + A" represents the sum of the phosphorus content (mol) and organic acid content (mol) in the metal acid compound dispersion of the present invention. On the other hand, "Li + m" represents the sum of the lithium content (mol) in terms of Li atoms and the content (mol) of metal species M in terms of metal species M atoms in the metal acid compound dispersion of the present invention.

[0117] Here, the total amount (m) of the metal species M is as described above, and therefore a detailed description thereof will be omitted.

[0118] The metal acid compound dispersion of the present invention is also characterized by being an aqueous dispersion. Because the metal acid compound in the metal acid compound dispersion of the present invention has high dispersibility in water and good solubility in water, pure water can be used as the solvent. Organic solvents may also be used. Examples of organic solvents include alcohol solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents, and aliphatic hydrocarbon solvents, and mixtures of these organic solvents with pure water may also be used. Examples of alcohol solvents include alcohols having 5 or fewer carbon atoms (methanol, ethanol, n-propanol, isopropyl alcohol, butanol, ethylene glycol, and propylene glycol), high-boiling point solvents, and acetone. The above-mentioned solvents are preferably compatible with water. The metal acid compound dispersion of the present invention may contain one or more solvents in any proportion, as long as stability is not impaired.

[0119] Examples of high-boiling point solvents include polyhydric alcohol solvents and glycol solvents, such as glycerin (boiling point: 290°C), 1,6-hexanediol (boiling point: 250°C), and 1,7-heptanediol (boiling point: 259°C). Examples of glycol-based solvents include ethylene glycol (boiling point: 197.3°C), propylene glycol (boiling point: 188.2°C), diethylene glycol (boiling point: 244.3°C), triethylene glycol (boiling point: 287.4°C), oligoethylene glycol (boiling point: 287°C to 460°C), polyethylene glycol (PEG) (boiling point: 460°C or higher), polyethylene glycol (PEG)-polypropylene glycol (PPG) copolymer (boiling point: 460°C or higher), diethylene glycol monohexyl ether (boiling point: 260°C), polyoxyalkylene monoalkyl ether (boiling point: 260°C or higher), polyoxyethylene sorbitan monolaurate (boiling point: 321°C or higher), other anionic fluorine-based surfactants (boiling point: 180°C or higher), amphoteric fluorine-based surfactants (boiling point: 180°C or higher), nonionic fluorine-based surfactants (boiling point: 180°C or higher), and amine oxides (boiling point: 180°C or higher). The boiling points mentioned above are those at 1 atmosphere.

[0120] The metal acid compound dispersion of the present invention is characterized in that the pH of the metal acid compound dispersion is from 2 to 11. A pH of from 2 to 11 is preferred for the metal acid compound dispersion of the present invention, as it stabilizes the polyacid ions contained in the dispersion. Depending on the application, an acidic metal acid compound dispersion, a neutral metal acid compound dispersion, or a basic metal acid compound dispersion may be preferred. Unless otherwise specified, in this specification, "pH" refers to both the "initial pH," which is the pH of the metal acid compound dispersion of the present invention adjusted to a liquid temperature of 25°C immediately after production, and the "aged pH," which is the pH of the metal acid compound dispersion of the present invention after being left to stand for one month from the day of production in an incubator set at room temperature of 25°C.

[0121] When an acidic metal acid compound dispersion is preferred, the pH of the metal acid compound dispersion of the present invention is preferably less than 7, and preferably from 2 to less than 7. The pH is more preferably 6 or less, even more preferably 5 or less, and particularly preferably 4 or less. On the other hand, the pH is preferably 3 or more. Furthermore, the pH may be 3 or less, or may be 2 or more. When a neutral metal acid compound dispersion is preferred, the pH of the metal acid compound dispersion of the present invention is preferably from 6 to 8, and more preferably 7. Furthermore, when a basic metal acid compound dispersion is preferred, the pH of the metal acid compound dispersion of the present invention is preferably 7 or more, more preferably 8 or more, even more preferably 9 or more, and particularly preferably 10 or more. On the other hand, the pH is preferably 11 or less. Furthermore, the pH may be 11 or more, or may be 12 or more.

[0122] Here, the pH of the metal acid compound dispersion of the present invention is measured by immersing an electrode (manufactured by HORIBA: Standard ToupH electrode 9615S-10D) of a pH meter (manufactured by HORIBA: Glass electrode type hydrogen ion concentration indicator D-51) in the metal acid compound dispersion of the present invention, and after confirming that the liquid temperature has stabilized at 25°C.

[0123] The metal acid compound dispersion of the present invention may also contain, as an additive, an element or compound thereof that does not constitute the metal acid compound contained in the metal acid compound dispersion of the present invention. Examples of such additives include elements or compounds such as Al, Si, V, Mn, Fe, Co, Ni, Cu, Zn, Ge, and Sn. Examples of compounds include oxides, alkali metal salts of metal acids, alkaline earth metal salts of metal acids, chlorides, alkoxides of metal acids, and polyoxometalates. Furthermore, with regard to the content of additives in the metal acid compound dispersion of the present invention, when the total number of moles of each additive element is designated as Z, the molar ratio Z / m of the total number of moles of each additive element (Z) to the total amount of metal species M (m) may be 0.001 to 75, 0.002 to 50, 0.01 to 40, 0.2 to 30, 0.5 to 25, 0.8 to 1.5, 0.8 to 1.3, 0.9 to 1.2, or 0.9 to 1.1. The content of each element corresponding to the additive is calculated by measuring the mass % of each element in terms of atomic amounts of each element, similar to the content of metal species M described above. Furthermore, since the metal acid compound dispersion of the present invention is a uniform dispersion, improved uniformity and improved reactivity (reaction rate) are expected even when these compounds are in a suspended state. Furthermore, if these compounds are dissolved in the metal oxide compound dispersion of the present invention to form a uniform dispersion, the composite element can be made to have the most favorable reactivity.

[0124] Furthermore, the metal acid compound dispersion of the present invention may contain components other than the components derived from metals or metal acids, ammonia, organic nitrogen compounds, and the components derived from element X (hereinafter referred to as "other components"), provided that the effects of the metal acid compound dispersion are not impaired. Examples of other components include Al, Si, V, Mn, Fe, Co, Ni, Cu, Zn, Ge, and Sn, but are not limited thereto. When the metal acid compound dispersion of the present invention is taken as 100% by mass, the content of other components is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less. The content of each element corresponding to the other components is calculated by measuring the mass% of each element in atomic terms, similar to the content of the metal species M described above. It is anticipated that the metal acid compound dispersion of the present invention may contain unavoidable impurities, although this is not intended. The content of unavoidable impurities is preferably 0.01% by mass or less.

[0125] The metal acid compound powder of the present invention is characterized by containing the metal acid compound in the metal acid compound dispersion of the present invention described above. The metal acid compound powder of the present invention includes a dried powder obtained by drying the metal acid compound dispersion of the present invention, for example, by vacuum drying, and a fired powder obtained by firing the resulting dried powder. The metal acid compound powder of the present invention also includes metal acid compound powders with different physical properties, such as crystalline structure, that are produced by vacuum drying or firing the metal acid compound dispersion of the present invention, and may have an amorphous structure, a single crystal structure, or a polycrystalline structure. A method for producing the metal acid compound powder of the present invention will be described later.

[0126] The metal acid compound film of the present invention is characterized by containing the metal acid compound in the metal acid compound dispersion of the present invention described above. The metal acid compound film of the present invention encompasses both a dried film obtained by applying the metal acid compound dispersion of the present invention to the surface of a substrate and then drying, for example, by vacuum drying, and a fired film obtained by firing the resulting dried film. The metal acid compound film of the present invention also encompasses metal acid compound films with different physical properties, such as crystalline structure, produced by vacuum drying or firing the metal acid compound dispersion of the present invention. These films may have an amorphous structure, a single crystal structure, or a polycrystalline structure. Because the metal compounds used as raw materials for the metal acid compound film of the present invention have high chemical resistance, coating the surface of a substrate with the metal acid compound film of the present invention can improve the high-temperature properties (e.g., protection from thermal degradation of the substrate) and chemical resistance of the substrate. A method for producing the metal acid compound film of the present invention will be described later.

[0127] The metal acid compound dispersion of the present invention is characterized in that it is used for coating a positive electrode or a positive electrode material for a lithium ion secondary battery. The metal acid compound dispersion of the present invention can also be used for coating a positive electrode or a positive electrode material for a lithium ion secondary battery.

[0128] The positive electrode active material for a lithium ion secondary battery of the present invention is characterized in that the surface thereof is coated with a metal acid compound derived from the above-mentioned metal acid compound dispersion of the present invention. ２ O ４ (Merck: spinel type, particle size <0.5 μm), LiCoO ２ , LiNiO ２ , LiFeO ２ , Li ２ MnO ３ , LiFePO ４ , LiCoPO ４ , LiNiPO ４ , LiMnPO ４ , LiNi ０．５ Mn １．５ O ４ , LiMn １／３ Co １／３ Ni １／３ O２ LiCo ０．２ Ni ０．４ Mn ０．４ O ２ , LiMnO ４ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMnO ２ etc. can be used.

[0129] Furthermore, the lithium-ion secondary battery of the present invention is characterized by having a positive electrode whose surface is coated with the positive electrode active material for lithium-ion secondary batteries of the present invention described above.

[0130] The method for producing the above-mentioned metal acid compound dispersion of the present invention will be described below.

[0131] When the metal species M is zirconium, niobium, tantalum, molybdenum, tungsten, or titanium, the method is characterized by the steps of: mixing and stirring a halide of zirconium, niobium, tantalum, molybdenum, tungsten, or titanium with hydrogen peroxide to obtain a mixture; reacting the mixture with an alkaline compound, separating the resulting precipitate by solid-liquid separation and recovering it; washing the recovered precipitate with an alkaline compound; adding pure water and an organic acid to the washed precipitate to dissolve it; and mixing the precipitate dissolved by the addition of the organic acid with one or more elements X selected from the group consisting of alkali metals and / or alkaline earth metals.

[0132] First, a mixture is obtained by mixing and stirring a halide of zirconium, niobium, tantalum, molybdenum, tungsten, or titanium with hydrogen peroxide. Specifically, the mixture is obtained by adding hydrogen peroxide to the halide of the metal species M placed in a stirring container and stirring for 1 minute to 5 hours, preferably 5 minutes to 1 hour, and more preferably 5 minutes to 30 minutes. There is no need to heat the mixture, and it can be carried out at room temperature (25°C).

[0133] The mixture obtained in this way undergoes a complexing reaction with hydrogen peroxide, which is presumed to be the process by which zirconium, niobium, tantalum, molybdenum, tungsten, and titanium exist as hydroxides of zirconium, niobium, tantalum, molybdenum, tungsten, and titanium. For example, if the metal species M is tantalum, it exists in the mixture as tantalum hydroxide.

[0134] The halide is preferably a fluoride and / or chloride of zirconium, niobium, tantalum, molybdenum, tungsten, or titanium. In particular, niobium and tantalum are more preferably fluorides of niobium and tantalum.

[0135] For example, tantalum fluoride is obtained by adding water (e.g., pure water) to convert tantalum into Ta. ２ O ５ It is preferable to adjust the tantalum content to 1 to 100 g / L in terms of Ta. ２ O ５ When the tantalum content is 1 g / L or more in terms of Ta, the resulting tantalic acid compound hydrate is easily soluble in water, and when productivity is taken into consideration, the tantalum content is more preferably 10 g / L or more, and even more preferably 20 g / L or more. ２ O ５ A concentration of 100 g / L or less is preferable because it results in a tantalic acid compound hydrate that is easily soluble in water. To more reliably synthesize a tantalic acid compound hydrate that is easily soluble in water, a concentration of 90 g / L or less is preferable, an even preferable concentration of 80 g / L or less is preferable, and a concentration of 70 g / L or less is particularly preferable.

[0136] The hydrogen peroxide content in the mixture is preferably more than 0% by mass and 10% by mass or less, more preferably 0.001% by mass or more and 5% by mass or less, even more preferably 0.01% by mass or more and 1% by mass or less, and particularly preferably 0.1% by mass or more and 0.8% by mass or less. Typically, the hydrogen peroxide content may be 0.01% by mass or more, 0.05% by mass or more, 0.1% by mass or more, or 0.5% by mass or more. On the other hand, the hydrogen peroxide content may be 8% by mass or less, 6% by mass or less, 4% by mass or less, or 2% by mass or less.

[0137] The hydrogen peroxide (H ２ O ２ ) content is the molar ratio (H ２ O ２ / h) can be expressed by the molar ratio (H ２ O ２ / h) is preferably more than 0.01 and not more than 1.5, more preferably 0.01 or more and 1.3 or less, and even more preferably 0.01 or more and 1.2 or less. Typically, the molar ratio (H ２ O ２ / h) may be 0.5 or more, 0.7 or more, 0.75 or more, or 0.8 or more. ２ O ２ / h) may be 1.3 or less, 1.2 or less, or 1.1 or less.

[0138] Here, the molar ratio (H ２ O ２ / h) in "H ２ O ２ " indicates the hydrogen peroxide content (mol) in the mixture. Meanwhile, the molar ratio (H ２ O ２ / h), "h" indicates the content (mol) of zirconium, niobium, tantalum, molybdenum, tungsten, and titanium in the mixture in terms of each atom.

[0139] Specifically, when the halide is tantalum fluoride, the molar ratio of hydrogen peroxide to tantalum (H ２ O ２ / Ta) is preferably more than 0.5 and not more than 1.5, more preferably 0.7 or more and 1.3 or less, and even more preferably 0.8 or more and 1.2 or less. Typically, the molar ratio (H ２ O ２ / Ta) may be 0.65 or more, 0.7 or more, or 0.75 or more. ２ O ２ / Ta) may be 1.3 or less, 1.2 or less, or 1.1 or less.

[0140] Next, the resulting mixture is reacted with an alkaline compound, and the resulting precipitate is subjected to solid-liquid separation and recovered. Specifically, the alkaline compound is added to the resulting mixture at a rate of, for example, 1000 mL / min to obtain a white precipitate. The white precipitate is then placed in a centrifuge tube and centrifuged at 4500 rpm for 20 minutes, after which the supernatant is discarded and only the white precipitate is recovered.

[0141] The precipitate thus recovered is a precipitate of complexed zirconium, niobium, tantalum, molybdenum, tungsten, or titanium, which is formed by reaction of the complexed zirconium, niobium, tantalum, molybdenum, tungsten, or titanium with the alkaline compound. For example, in the case of tantalum, the precipitate is a precipitate of complexed tantalum hydroxide.

[0142] The alkaline compound used to react with the complexed zirconium, niobium, tantalum, molybdenum, tungsten, or titanium is preferably one or more compounds selected from ammonia and organic nitrogen compounds. Examples of organic nitrogen compounds include amine compounds, quaternary ammonium compounds, guanidine compounds, and azole compounds. An amine compound or a quaternary ammonium compound is preferred, and methylamine, dimethylamine, tetramethylammonium hydroxide (TMAH), or tetraethylammonium hydroxide (TEAH) is more preferred. The alkaline compound may also be an alkaline solution in which the alkaline compound is dissolved. The alkaline solution is preferably an alkaline aqueous solution, particularly aqueous ammonia.

[0143] The content of the alkaline compound used to react with the complexed zirconium, niobium, tantalum, molybdenum, tungsten, or titanium is preferably more than 0% by mass and less than 50% by mass, and more preferably 0.01% by mass or more and 15% by mass or less. From the viewpoint of reactivity and dispersibility, a higher content of the alkaline compound is desirable. Typically, the content of the alkaline compound may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more. On the other hand, the content of the alkaline compound may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 10% by mass or less.

[0144] When the alkaline compound used to react with the complexed zirconium, niobium, tantalum, molybdenum, tungsten, or titanium is ammonia water, the ammonia content is preferably more than 0% by mass and less than 50% by mass, and more preferably 0.01% by mass or more and 15% by mass or less. From the viewpoint of reactivity and dispersibility, a higher ammonia content is desirable. Typically, the ammonia content may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more. On the other hand, the ammonia content may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 10% by mass or less.

[0145] Next, the recovered precipitate is washed with an alkaline compound. Specifically, the alkaline compound is added to the precipitate, mixed, and then placed back into a centrifuge tube. After centrifugation at 4500 rpm for 20 minutes, the supernatant is discarded, and only the precipitate is recovered.

[0146] By repeating this series of operations multiple times (for example, three times), excess alkaline compounds and hydrogen peroxide contained in the precipitate can be removed. Excess fluorine and halogen elements such as chlorine can also be removed.

[0147] Removing excess alkaline compounds from the precipitate makes it easier to use in terms of safety and workability. Also, removing excess hydrogen peroxide from the precipitate can suppress changes in the precipitate due to the evaporation of hydrogen peroxide, making it easier to use in terms of safety and compliance with regulations.

[0148] The alkaline compound used to wash the recovered precipitate is preferably one or more compounds selected from ammonia and organic nitrogen compounds. Examples of organic nitrogen compounds include amine compounds, quaternary ammonium compounds, guanidine compounds, and azole compounds. An amine compound or a quaternary ammonium compound is preferred, and methylamine, dimethylamine, ethylamine, diethylamine, tetramethylammonium hydroxide (TMAH), or tetraethylammonium hydroxide (TEAH) is more preferred. The alkaline compound may also be an alkaline solution in which the alkaline compound is dissolved. The alkaline solution is preferably an alkaline aqueous solution, particularly ammonia water.

[0149] The alkaline compound content used to wash the recovered precipitate is preferably more than 0% by mass and less than 50% by mass, and more preferably 0.01% by mass or more and 4% by mass or less. From the viewpoints of reactivity and dispersibility, a higher alkaline compound content is desirable. Typically, the alkaline compound content may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more. On the other hand, the alkaline compound content may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 10% by mass or less.

[0150] When the alkaline compound used to wash the recovered precipitate is aqueous ammonia, the ammonia content is preferably greater than 0% by mass and less than 50% by mass, and more preferably between 0.01% by mass and 4% by mass. From the viewpoint of reactivity and dispersibility, a higher ammonia content is desirable. Typically, the ammonia content may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more. On the other hand, the ammonia content may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 10% by mass or less.

[0151] The washed precipitate is dissolved by adding pure water and an organic acid. Specifically, the washed precipitate is dissolved by adding pure water and an organic acid, and then the precipitate is dissolved by, for example, ultrasonic treatment or a shaker.

[0152] Organic acids added to the washed precipitate include carboxylic acids. Examples of carboxylic acids include saturated fatty acids, unsaturated fatty acids, hydroxy acids, aromatic carboxylic acids, dicarboxylic acids, tricarboxylic acids, oxocarboxylic acids, and carboxylic acid derivatives. Examples of saturated fatty acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, and stearic acid. Examples of unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and sorbic acid. Examples of hydroxy acids include lactic acid, malic acid, citric acid, tartaric acid, glycolic acid, hydroxybutyric acid, and glyceric acid. Examples of aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, melitic acid, and cinnamic acid. Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, and maleic acid. Examples of tricarboxylic acids include aconic acid. Examples of oxocarboxylic acids include pyruvate and oxaloacetate. Examples of carboxylic acid derivatives include amino acids and nitrocarboxylic acids. Examples of amino acids include alanine, arginine, and aspartic acid. Other examples of carboxylic acids include ethylenediaminetetraacetic acid. Alkali metal salts or alkaline earth metal salts of the organic acid may also be used. For example, sodium ethylenediaminetetraacetate and disodium ethylenediaminetetraacetate may be used. In particular, organic acids that do not contain nitrogen atoms are preferred, for example carboxylic acids, saturated fatty acids, and hydroxy acids are preferred, and it is more preferable to contain one or more selected from citric acid, tartaric acid, lactic acid, malic acid, acetic acid, and their salts.

[0153] The content of the organic acid added to the washed precipitate is preferably more than 0% by mass and less than 100% by mass, more preferably 1% by mass or more and 40% by mass or less, and preferably 5% by mass or more and 30% by mass or less. Typically, the content of the organic acid may be 0.1% by mass or more, 0.5% by mass or more, 2% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more. On the other hand, the content of the organic acid may be 45% by mass or less, 35% by mass or less, 25% by mass or less, 20% by mass or less, or 10% by mass or less. Here, when the organic acid added is a mixture of two or more organic acids, the content of the organic acid is the total content of the two or more organic acids added.

[0154] The content of the organic acid added to the washed precipitate can be expressed by a molar ratio (m / A). It is preferable to add the organic acid so that the molar ratio (m / A) is greater than 0 and less than or equal to 50. From the viewpoint of the stability and cost reduction of the metal acid compound dispersion liquid of the present invention, the molar ratio is more preferably 0.001 to 10, even more preferably 0.01 to 9, and particularly preferably 0.01 to 6. Typically, the molar ratio (m / A) may be 0.005 or greater, 0.5 or greater, 1 or greater, 2 or greater, 3 or greater, or 5 or greater. On the other hand, the molar ratio (m / A) may be 20 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.8 or less, or 0.5 or less.

[0155] Here, "A" in the molar ratio (m / A) represents the content of the organic acid in the metal acid compound dispersion of the present invention. When two or more organic acids are contained, the content (mol) of the organic acid is the total content (mol) of these two or more organic acids. Meanwhile, "m" in the molar ratio (m / A) represents the content (mol) of the metal species M in the metal acid compound dispersion of the present invention, calculated as metal species M atoms.

[0156] For example, when the metal species M to be mixed is tantalum hydroxide, the organic acid is preferably added so that the molar ratio of the organic acid to tantalum (Ta / A) is greater than 0 and less than 50. From the viewpoint of the stability of the metal acid compound dispersion liquid of the present invention and cost reduction, the molar ratio is more preferably 0.001 to 10, even more preferably 0.01 to 9, and particularly preferably 0.01 to 6. Typically, the molar ratio (m / A) may be 0.005 or greater, 0.5 or greater, 1 or greater, 2 or greater, 3 or greater, or 5 or greater. On the other hand, the molar ratio (m / A) may be 20 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.8 or less, or 0.5 or less.

[0157] The precipitate dissolved by adding the organic acid is then mixed with one or more elements X selected from the group consisting of alkali metals and / or alkaline earth metals, thereby obtaining the metal acid compound dispersion of the present invention.

[0158] The type of compound of element X, i.e., alkali metal or alkaline earth metal, is not limited, but hydroxides, oxides, carbonates, hydrochlorides, sulfates, nitrates, and phosphates are preferred in terms of maintaining high dispersibility, and hydroxides are more preferred, such as sodium hydroxide, potassium hydroxide, lithium hydroxide, and calcium hydroxide.

[0159] When the element X is lithium, a lithium compound dispersion obtained by dissolving a commercially available lithium compound in pure water may be mixed with the precipitate dissolved in the organic acid. Examples of the lithium compound include lithium hydroxide, lithium carbonate, lithium acetate, trilithium citrate, and lithium lactate.

[0160] In addition to the above-mentioned pure water and organic acids, the following organic solvents can be used as the solvent to be added to the washed precipitate. Examples of organic solvents include alcohol solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents, and aliphatic hydrocarbon solvents, and the solvent may be a mixture of these organic solvents and pure water. Examples of alcohol solvents include alcohols having 5 or less carbon atoms (methanol, ethanol, n-propanol, isopropyl alcohol, butanol, ethylene glycol, and propylene glycol), acetone, and high-boiling point solvents. It is preferable that the above-mentioned solvents and water are compatible with each other.

[0161] Examples of high-boiling-point solvents include polyhydric alcohol-based solvents and glycol-based solvents. Examples of polyhydric alcohol-based solvents include glycerin (boiling point: 290°C), 1,6-hexanediol (boiling point: 250°C), and 1,7-heptanediol (boiling point: 259°C). Examples of glycol-based solvents include ethylene glycol (boiling point: 197.3°C), propylene glycol (boiling point: 188.2°C), diethylene glycol (boiling point: 244.3°C), triethylene glycol (boiling point: 287.4°C), oligoethylene glycol (boiling point: 287°C to 460°C), polyethylene glycol (PEG) (boiling point: 460°C or higher), polyethylene glycol (PEG)-polypropylene glycol (PPG) copolymer (boiling point: 460°C or higher), diethylene glycol monohexyl ether (boiling point: 260°C), polyoxyalkylene monoalkyl ether (boiling point: 260°C or higher), polyoxyethylene sorbitan monolaurate (boiling point: 321°C or higher), other anionic fluorine-based surfactants (boiling point: 180°C or higher), amphoteric fluorine-based surfactants (boiling point: 180°C or higher), nonionic fluorine-based surfactants (boiling point: 180°C or higher), and amine oxides (boiling point: 180°C or higher). The boiling points mentioned above are those at 1 atmosphere.

[0162] In addition to the solvent added to the washed precipitate, a resin may also be added. The resin may be a polyolefin compound or a polyvinyl compound. Furthermore, the resin added to the solvent may be an anionic water-soluble resin, and / or a nonionic water-soluble resin.

[0163] Here, the cationic water-soluble resin is a resin that has a positive charge in the polymer in water at pH = 7, and has any functional group such as an amino group, an imino group, a tertiary amine group, a quaternary ammonium group, a hydrazino group, an azole group, an alkylated azole group, an imidazole group, or an imidazolium group. The anionic water-soluble resin is a resin that has a negative charge in the polymer in water at pH = 7, and has any functional group such as a carboxyl group, a sulfonic acid group, a sulfate ester group, or a phosphate ester group. The nonionic water-soluble resin is a resin that does not fall under the category of the above-mentioned cationic water-soluble resin or anionic water-soluble resin, and has any functional group such as a hydroxyl group, an ether group, or an amide group in the polymer.

[0164] Furthermore, these resins may contain one or more water-soluble homopolymers selected from the group consisting of acrylic polymers, urethane polymers, styrene polymers, olefin polymers, amide polymers, siloxane polymers, epoxy polymers, vinyl chloride polymers, and vinyl acetate polymers, and / or water-soluble copolymers consisting of two or more of these polymers. In particular, it is preferable for the resins to contain one or more water-soluble homopolymers of acrylic polymers, styrene polymers, and olefin polymers, and / or water-soluble copolymers consisting of two or more of these polymers.

[0165] When the metal species M is lanthanum, a commercially available lanthanum compound is dissolved in pure water to obtain an aqueous lanthanum solution, and the resulting solution is mixed with one or more elements X selected from the group consisting of alkali metals and / or alkaline earth metals to obtain the metal acid compound dispersion of the present invention. Examples of the lanthanum compound include lanthanum acetate (n-hydrate) and lanthanum ethylenediaminetetraacetate complex.

[0166] When the metal species M is yttrium, a commercially available yttrium compound is dissolved in pure water to obtain an aqueous yttrium solution, and the resulting solution is mixed with one or more elements X selected from the group consisting of alkali metals and / or alkaline earth metals to obtain the metal oxide compound dispersion of the present invention. Examples of the yttrium compound include yttrium acetate (n-hydrate) and ethylenediaminetetraacetic acid yttrium complex.

[0167] When the metal species M is cerium, a commercially available cerium compound is dissolved in pure water to obtain an aqueous cerium solution, and the resulting solution is mixed with one or more elements X selected from the group consisting of alkali metals and / or alkaline earth metals to obtain the metal acid compound dispersion of the present invention. Examples of the cerium compound include cerium acetate (n-hydrate) and ethylenediaminetetraacetic acid cerium complex.

[0168] When the metal species M is neodymium, a commercially available neodymium compound is dissolved in pure water to obtain a neodymium aqueous solution, and the resulting solution is mixed with one or more elements X selected from the group consisting of alkali metals and / or alkaline earth metals to obtain the metal acid compound dispersion of the present invention. Examples of the neodymium compound include neodymium acetate (n-hydrate) and neodymium ethylenediaminetetraacetate complex.

[0169] When the metal species M is zirconium, in addition to the above-mentioned production method, a commercially available zirconium compound can be dissolved in pure water to obtain an aqueous zirconium solution, and then the resulting solution can be mixed with one or more elements X selected from the group consisting of alkali metals and / or alkaline earth metals to obtain the metal acid compound dispersion of the present invention. Examples of the zirconium compound include zirconium acetate (n-hydrate) and ammonium zirconium carbonate.

[0170] When the metal species M is ammonium, the metal acid compound dispersion of the present invention is obtained by dissolving a commercially available ammonium compound in pure water, and then mixing the resulting aluminum aqueous solution with one or more elements X selected from the group consisting of alkali metals and / or alkaline earth metals. Examples of the aluminum compound include aluminum acetate, aluminum lactate, ethylenediaminetetraacetate aluminum complex, and aluminum hydroxide complex.

[0171] The method for producing the metal acid compound powder containing the metal acid compound in the metal acid compound dispersion of the present invention will be described below.

[0172] Among the metal acid compound powders, the method for producing the dried metal acid compound powder involves placing the metal acid compound dispersion obtained by the method for producing the metal acid compound dispersion of the present invention described above into a standing furnace and drying it at a heating temperature of approximately 60°C to 200°C for 1 to 72 hours, for example by vacuum drying, thereby evaporating the water from the metal acid compound dispersion of the present invention and obtaining a dried metal acid compound powder containing crystalline particles of the metal acid compound contained in the metal acid compound dispersion of the present invention.

[0173] On the other hand, the method for producing the calcined powder of the metal acid compound is as described above: the dispersion of the metal acid compound of the present invention is vacuum dried, the resulting dried powder of the metal acid compound is placed in a standing furnace, and calcined under air at a calcination temperature of 300°C to 1,200°C for a calcination time of 1 hour to 72 hours, thereby obtaining the calcined powder of the metal acid compound.

[0174] The metal acid compound powder may be prepared by pulverizing the dry powder and calcined powder of the metal acid compound described above. Regardless of whether or not the powder is pulverized, the dry powder and calcined powder of the metal acid compound described above may be classified using a sieve or the like to obtain the undersized particles (fine particles) and used as the metal acid compound powder. The oversized particles (coarse particles) may be re-pulverized and classified before use. It is also possible to combine pulverization and classification using a vibrating sieve containing nylon- or fluororesin-coated iron balls as a grinding medium. By combining classification and pulverization in this way, even if excessively large metal acid compound powder particles are present, they can be removed. Specifically, when using a sieve for classification, it is preferable to use one with a mesh size of 150 μm to 1,000 μm. A mesh size of 150 μm to 1,000 μm prevents the proportion of oversized particles from becoming too high, eliminating the need for repeated pulverization, and also prevents the undersized particles from being classified, which require pulverization.

[0175] The metal acid compound powder thus obtained can be mixed with water or an organic solvent as a dispersion medium and wet-pulverized using media such as beads to obtain a metal acid compound powder dispersion. Examples of organic solvents used as dispersion media include alcohols, esters, ketones, aromatic hydrocarbons, aliphatic hydrocarbons, ethers, and mixtures thereof. Furthermore, a binder such as a resin component may be added to improve the film-forming properties of a metal acid compound film using the metal acid compound powder dispersion. Examples of resin components used as binders include acrylic resins, polyurethanes, epoxy resins, polystyrene, polycarbonates, glycol-based resins, cellulose-based resins, and mixtures and copolymer resins thereof.

[0176] Furthermore, a method for producing a metal acid compound film containing the metal acid compound in the metal acid compound dispersion of the present invention will be described below.

[0177] Among the metal acid compound films, the method for producing a metal acid compound dry film includes a coating step of coating a metal acid compound dispersion onto the surface of a substrate, and a film drying step of drying the metal acid compound dispersion coated on the surface of the substrate to obtain a dry film.

[0178] Specifically, the metal acid compound dispersion obtained by the method for producing a metal acid compound dispersion of the present invention described above is dropped onto the surface of a substrate using a syringe while, if necessary, filtering it through a filter with a pore size of 1 μm, for example, and then applied by spin coating (700 rpm, 10 seconds, followed by 1500 rpm, 30 seconds).Then, the resulting mixture is dried at 110° C. for 30 minutes to form a dry metal acid compound film on the surface of the substrate.

[0179] Among the metal acid compound films, the method for producing a calcined metal acid compound film includes a coating step of coating a metal acid compound dispersion onto the surface of a substrate, a film drying step of drying the metal acid compound dispersion coated on the surface of the substrate in the atmosphere or under vacuum to obtain a dried film, and a film calcination step of calcining the dried film in the atmosphere at a temperature of 300°C or higher and 1,200°C or lower for a calcination time of 1 hour or higher and 12 hours or lower to obtain a calcined film.

[0180] Specifically, as described above, a metal acid compound dispersion is applied to the surface of a substrate, and the substrate is dried to form a metal acid compound dry film. The substrate is then placed in a static furnace and baked in the atmosphere at a baking temperature of 300°C or higher and 1,200°C or lower for a baking time of 1 hour or higher and 12 hours or lower, thereby forming a metal acid compound baked film on the surface of the substrate.

[0181] Furthermore, a method for producing a positive electrode active material for a lithium ion secondary battery coated with a metal acid compound derived from the metal acid compound dispersion of the present invention will be described below.

[0182] The method includes a step of mixing the metal acid compound dispersion of the present invention, a positive electrode active material, and, if necessary, an aqueous lithium hydroxide solution to produce a positive electrode active material slurry for a battery containing the metal acid compound, and a step of drying the positive electrode active material slurry for a battery containing the metal acid compound.

[0183] First, the metal acid compound dispersion of the present invention is diluted with pure water, and a positive electrode active material for batteries, such as LiMn, is added to the metal acid compound dispersion. ２ O ４(Merck: spinel type, particle size <0.5 μm) is added to obtain a slurry containing a metal acid compound. Then, while stirring the slurry containing the metal acid compound, an aqueous lithium hydroxide solution is added dropwise, and the mixture is maintained at 90° C. for 10 minutes, thereby producing a slurry of a positive electrode active material for a battery containing the metal acid compound.

[0184] Next, the battery positive electrode active material slurry containing the metal acid compound is dried in an atmospheric drying furnace for 15 hours while maintaining the furnace temperature at 110°C, thereby producing a positive electrode active material for a lithium ion secondary battery coated with the metal acid compound.

[0185] In this specification, when "X to Y" (X and Y are any numbers) is expressed, unless otherwise specified, it means "X or more and Y or less", and also means "preferably larger than X" or "preferably smaller than Y". Furthermore, when "X or more" (X is any number) or "Y or less" (Y is any number), it also means "preferably larger than X" or "preferably smaller than Y".

[0186] The metal acid compound dispersion of the present invention exhibits excellent storage stability.

[0187] 1 is a table listing the compositions of metal acid compound dispersions according to Examples 1 to 10 of the present invention and Comparative Example 1. FIG. 2 is a table listing the composition ratios of metal acid compound dispersions according to Examples 1 to 10 of the present invention and Comparative Example 1. FIG. 3 is a table listing the measurement results of metal acid compound dispersions according to Examples 1 to 10 of the present invention and Comparative Example 1. FIG. 4 is a table listing the compositions of metal acid compound dispersions according to Examples 11 to 21 of the present invention and Comparative Example 2. FIG. 5 is a table listing the composition ratios of metal acid compound dispersions according to Examples 11 to 21 of the present invention and Comparative Example 2. FIG. 6 is a table listing the measurement results of metal acid compound dispersions according to Examples 11 to 21 of the present invention and Comparative Example 2. FIG. 7 is a table listing the compositions of metal acid compound dispersions according to Examples 22 to 26 of the present invention and Comparative Example 1. FIG. 8 is a table listing the composition ratios of metal acid compound dispersions according to Examples 22 to 26 of the present invention and Comparative Example 1. FIG. 9 is a table listing the measurement results of metal acid compound dispersions according to Examples 22 to 26 of the present invention and Comparative Example 1.

[0188] The metal acid compound dispersion according to embodiments of the present invention will be further described below with reference to the following examples. However, the following examples are not intended to limit the present invention.

[0189] (Example 1) Lanthanum acetate "La(CH ３ COO) ３ ” Aqueous solution (La ２ O ３ 63.8 g / L, 5.91 mass%, manufactured by Nippon Yttrium Co., Ltd.) 10 g, and zirconium acetate "ZrO(CH ３ COO) ２ ”Aqueous solution (ZrO ２ 1.41 g of zircozol ZA-20 (20.08% by mass, manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.), 16.02 g of 5% by mass lithium DL-lactate aqueous solution, 0.14 g of tantalum lactate aqueous solution, and 22.44 g of pure water were added and mixed to obtain 50 g of the metal acid compound dispersion according to Example 1.

[0190] Here, a 5% by mass aqueous solution of DL-lithium lactate was obtained by mixing 25 g of DL-lithium lactate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) with 475 g of pure water.

[0191] The tantalum lactate aqueous solution was obtained as follows.

[0192] In a 5L beaker, add Ta ２ O ５ TaF equivalent to 80.0 g / L (0.24 mol in terms of Ta atoms) ５ After adding 658 mL of aqueous solution, 20.8 g (0.21 mol) of 35% by mass hydrogen peroxide solution was added, and the mixture was stirred at room temperature for 10 minutes using a stirrer tip to obtain the mixture.

[0193] To the resulting mixture, approximately 490 g (7.2 mol) of 25% by mass aqueous ammonia was added to obtain a white precipitate. The obtained white precipitate was placed in a centrifuge tube and centrifuged at 4500 rpm for 20 minutes. The supernatant was discarded, and only the white precipitate was collected.

[0194] Approximately 250 g of 5% by mass aqueous ammonia was added to the recovered white precipitate, mixed, and then centrifuged again at 4,500 rpm for 20 minutes. The supernatant was discarded, and only the white precipitate was recovered. This series of operations was repeated three times.

[0195] Then, pure water was added to the white precipitate washed with 5% ammonia water, and the total weight of the white precipitate and pure water was adjusted to 167 g. 69.5 g (0.77 mol) of lactic acid was then added and dissolved using ultrasound. The mixture was then vacuum dried at 80°C for 12 hours to remove excess ammonia and lactic acid. The resulting dried powder was then added with 20% Ta. ２ O ５ Pure water was added to form a dispersion, and 250 g of tantalum lactate aqueous solution (Ta ２ O ５ : 19.587% by mass, lactic acid: 28.9% by mass.

[0196] Example 2 10 g of a lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 0.74 g of a zirconium acetate aqueous solution (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.: Zircosol ZA-20), 13.93 g of a 5 mass % lithium DL-lactate aqueous solution, 1.36 g of a tantalum lactate aqueous solution, and 23.97 g of pure water were placed in a polypropylene container and mixed, thereby obtaining 50 g of a metal acid compound dispersion liquid according to Example 2.

[0197] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 2 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0198] Example 3 10 g of a lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 0.00 g of a zirconium acetate aqueous solution (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.: Zircosol ZA-20), 11.61 g of a 5 mass % lithium DL-lactate aqueous solution, 2.73 g of a tantalum lactate aqueous solution, and 25.67 g of pure water were placed in a polypropylene container and mixed, thereby obtaining 50 g of a metal acid compound dispersion liquid according to Example 3.

[0199] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 3 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0200] (Example 4) 10 g of lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 0.74 g of zirconium acetate aqueous solution (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.: Zircozol ZA-20), 23.21 g of 5% by mass DL-lithium lactate aqueous solution, 1.36 g of tantalum lactate aqueous solution, and 14.68 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of the metal acid compound dispersion according to Example 4.

[0201] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 4 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0202] (Example 5) 0.50 g of lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 1.11 g of zirconium acetate aqueous solution (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.: Zircozol ZA-20), 20.89 g of 5% by mass DL-lithium lactate aqueous solution, 2.05 g of tantalum lactate aqueous solution, and 25.45 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of the metal acid compound dispersion according to Example 5.

[0203] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 5 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0204] (Example 6) 30.00 g of lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 0.67 g of zirconium acetate aqueous solution (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.: Zircozol ZA-20), 12.53 g of 5% by mass DL-lithium lactate aqueous solution, 1.23 g of tantalum lactate aqueous solution, and 5.57 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of the metal acid compound dispersion according to Example 6.

[0205] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 6 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0206] (Example 7) 18.00 g of lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 0.13 g of zirconium acetate aqueous solution (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.: Zircozol ZA-20), 25.07 g of 5% by mass DL-lithium lactate aqueous solution, 2.45 g of tantalum lactate aqueous solution, and 4.34 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of the metal acid compound dispersion according to Example 7.

[0207] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 7 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0208] (Example 8) 10.00 g of lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 7.42 g of zirconium acetate aqueous solution (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.: Zircozol ZA-20), 13.93 g of 5% by mass DL-lithium lactate aqueous solution, 1.36 g of tantalum lactate aqueous solution, and 17.29 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of the metal acid compound dispersion according to Example 8.

[0209] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 8 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0210] (Example 9) 10.00 g of lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 0.74 g of zirconium acetate aqueous solution (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.: Zircozol ZA-20), 13.93 g of 5% by mass DL-lithium lactate aqueous solution, 13.64 g of tantalum lactate aqueous solution, and 11.70 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of the metal acid compound dispersion according to Example 9.

[0211] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 9 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0212] (Example 10) 5.00 g of lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 0.37 g of zirconium acetate aqueous solution (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.: Zircozol ZA-20), 6.96 g of 5% by mass lithium DL-lactate aqueous solution, 0.68 g of tantalum lactate aqueous solution, 486.37 g of pure water, and 0.62 g of 88% by mass DL-lactic acid were placed in a polypropylene container and mixed to obtain 500 g of the metal acid compound dispersion according to Example 10.

[0213] Furthermore, the 88% by mass DL-lactic acid used in Example 10 was 85-92% by mass DL-lactic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). Note that the lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5% by mass lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 10 are the same as those in Example 1, so a detailed explanation is omitted.

[0214] (Example 11) 0.41 g of an 85% phosphoric acid aqueous solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 12.29 g of a 5% by mass lithium DL-lactate aqueous solution, 1.20 g of a tantalum lactate aqueous solution, and 21.10 g of pure water were placed in a polypropylene container and mixed to obtain 35 g of a metal acid compound dispersion according to Example 11.

[0215] The 5 mass % aqueous solution of lithium DL-lactate and the aqueous solution of tantalum lactate used in Example 11 were the same as those used in Example 1, and therefore detailed description thereof will be omitted.

[0216] (Example 12) 0.3 g of an 85% aqueous solution of phosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 24.98 g of a 5% by mass aqueous solution of DL-lithium lactate, 0.88 g of an aqueous solution of tantalum lactate, and 8.84 g of pure water were placed in a polypropylene container and mixed to obtain 35 g of a metal acid compound dispersion according to Example 12.

[0217] The 5 mass % aqueous solution of lithium DL-lactate and the aqueous solution of tantalum lactate used in Example 12 were the same as those used in Example 1, and therefore detailed explanations thereof will be omitted.

[0218] Example 13 0.2 g of an 85% aqueous solution of phosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 33.31 g of a 5 mass % aqueous solution of lithium DL-lactate, 0.59 g of an aqueous solution of tantalum lactate, and 0.90 g of pure water were placed in a polypropylene container and mixed, thereby obtaining 35 g of a metal acid compound dispersion liquid according to Example 13.

[0219] The 5 mass % aqueous solution of lithium DL-lactate and the aqueous solution of tantalum lactate used in Example 13 were the same as those used in Example 1, and therefore detailed explanations thereof will be omitted.

[0220] Example 14 0.41 g of an 85% aqueous solution of phosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 6.02 g of a 10% by mass aqueous solution of trilithium citrate tetrahydrate, 1.20 g of an aqueous solution of tantalum lactate, and 27.37 g of pure water were placed in a polypropylene container and mixed, thereby obtaining 35 g of a metal acid compound dispersion liquid according to Example 14.

[0221] The 10% by mass aqueous solution of trilithium citrate tetrahydrate used in Example 14 was obtained by mixing 50 g of trilithium citrate tetrahydrate and 450 g of pure water for 1 hour. The aqueous solution of tantalum lactate used in Example 14 was the same as that used in Example 1, and therefore a detailed description thereof will be omitted.

[0222] Example 15 0.6 g of a 5 mass % aqueous solution of lithium DL-lactate, 3.52 g of an aqueous solution of tantalum lactate, and 45.88 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of a metal acid compound dispersion liquid according to Example 15.

[0223] The 5 mass % aqueous solution of lithium DL-lactate and the aqueous solution of tantalum lactate used in Example 15 were the same as those used in Example 1, and therefore detailed explanations thereof will be omitted.

[0224] Example 16 6.0 g of a 5 mass % aqueous solution of lithium DL-lactate, 3.52 g of an aqueous solution of tantalum lactate, and 40.48 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of a metal acid compound dispersion liquid according to Example 16.

[0225] The 5 mass % aqueous solution of lithium DL-lactate and the aqueous solution of tantalum lactate used in Example 16 were the same as those used in Example 1, and therefore detailed explanations thereof will be omitted.

[0226] Example 17 45.0 g of a 5 mass % aqueous solution of lithium DL-lactate, 2.64 g of an aqueous solution of tantalum lactate, and 2.36 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of a metal acid compound dispersion liquid according to Example 17.

[0227] The 5 mass % aqueous solution of lithium DL-lactate and the aqueous solution of tantalum lactate used in Example 17 were the same as those used in Example 1, and therefore detailed explanations thereof will be omitted.

[0228] Example 18 0.3 g of a 5 mass % aqueous solution of lithium DL-lactate, 0.18 g of an aqueous solution of tantalum lactate, and 49.52 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of a metal acid compound dispersion according to Example 18.

[0229] The 5 mass % aqueous solution of lithium DL-lactate and the aqueous solution of tantalum lactate used in Example 18 were the same as those used in Example 1, and therefore detailed explanations thereof will be omitted.

[0230] Example 19 30.0 g of a 5 mass % aqueous solution of lithium DL-lactate, 17.62 g of an aqueous solution of tantalum lactate, and 2.38 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of a metal acid compound dispersion according to Example 19.

[0231] The 5 mass % aqueous solution of lithium DL-lactate and the aqueous solution of tantalum lactate used in Example 19 were the same as those used in Example 1, and therefore detailed description thereof will be omitted.

[0232] (Example 20) 3.00 g of a 10% by mass aqueous solution of trilithium citrate tetrahydrate, 3.60 g of aqueous solution of tantalum lactate, and 43.40 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of a metal acid compound dispersion according to Example 20.

[0233] The tantalum lactate aqueous solution used in Example 20 is the same as that used in Example 1, so a detailed explanation is omitted. The 10% by mass trilithium citrate tetrahydrate aqueous solution used in Example 20 is the same as that used in Example 14, so a detailed explanation is omitted.

[0234] (Example 21) 5% by mass of LiOH·H was added to a polypropylene container. ２ By adding 2.60 g of aqueous solution O, 3.49 g of aqueous solution tantalum lactate, and 43.91 g of pure water and mixing them together, 50 g of the metal acid compound dispersion according to Example 21 was obtained.

[0235] Here, 5 mass% LiOH·H ２ The O solution is LiOH·H ２ This was obtained by mixing 25 g of O with 475 g of pure water for 1 hour.

[0236] The tantalum lactate aqueous solution used in Example 21 was the same as that used in Example 1, and therefore a detailed description thereof will be omitted.

[0237] (Example 22) 7.00 g of lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 1.56 g of zirconium acetate aqueous solution (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.: Zircozol ZA-20), 4.87 g of 5% by mass lithium DL-lactate aqueous solution, 0.29 g of tantalum lactate aqueous solution, 0.90 g of 5% by mass ammonium molybdate tetrahydrate aqueous solution, and 35.39 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of the metal acid compound dispersion according to Example 22.

[0238] Here, the 5 mass % aqueous solution of ammonium molybdate tetrahydrate is (NH ４ ) ６ Mo7O ２４ ・4H ２ It was obtained by mixing 5 g of ethanol with 95 g of pure water.

[0239] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 22 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0240] (Example 23) In a polypropylene container, 7.00 g of a lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 1.56 g of a zirconium acetate aqueous solution (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.: Zircosol ZA-20), 4.87 g of a 5 mass% DL-lithium lactate aqueous solution, 0.29 g of a tantalum lactate aqueous solution, 0.22 g of a titanium lactate aqueous solution (manufactured by Matsumoto Fine Chemical Co., Ltd.: Orgatix TC-355), and 36.06 g of pure water were added and mixed, thereby obtaining 50 g of a metal acid compound dispersion according to Example 23.

[0241] Here, the titanium lactate aqueous solution contained 5.5% by mass of titanium and 20.7% by mass of lactic acid.

[0242] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 23 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0243] (Example 24) 7.00 g of a lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 1.56 g of a zirconium acetate aqueous solution (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.: Zircosol ZA-20), 4.87 g of a 5 mass% DL-lithium lactate aqueous solution, 0.29 g of a tantalum lactate aqueous solution, 0.48 g of a niobium lactate aqueous solution, and 35.81 g of pure water were placed in a polypropylene container and mixed, thereby obtaining 50 g of a metal acid compound dispersion according to Example 24.

[0244] The aqueous niobium lactate solution was obtained as follows.

[0245] In a 5 L beaker, ２ O ５ converted to 100.0 g / L (0.35 mol in terms of Nb atoms) of NbF ５ After 465.6 mL of the aqueous solution was added, 17.0 g (0.167 mol) of 35% by mass hydrogen peroxide solution was added, and the mixture was stirred at room temperature for 10 minutes using a stirrer tip to obtain a mixture.

[0246] To the resulting mixture, approximately 716 g (10.5 mol) of 25% by mass aqueous ammonia was added to obtain a white precipitate. The resulting white precipitate was placed in a centrifuge tube and centrifuged at 4,500 rpm for 20 minutes. The supernatant was discarded, and only the white precipitate was collected.

[0247] Approximately 250 g of 25% by mass aqueous ammonia was added to the recovered white precipitate, mixed, and then centrifuged again at 4,500 rpm for 20 minutes. The supernatant was discarded, and only the white precipitate was recovered. This series of operations was repeated three times.

[0248] Subsequently, pure water was added to the white precipitate, which had been washed with 25% by mass ammonia water, to a total weight of 620 g of the white precipitate and pure water. 198.3 g (1.94 mol) of lactic acid was added to 600 g of the mixture of the white precipitate and pure water, and dissolved while heating at 80°C for 5 hours. The solution was adjusted by replenishing the evaporated pure water as needed, resulting in 600 g of niobium lactate aqueous solution (Nb ２ O ５ The result was 4.96% by mass of lactic acid and 28.2% by mass of lactic acid.

[0249] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 24 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0250] (Example 25) 7.00 g of lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 1.56 g of zirconium acetate aqueous solution (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.: Zircozol ZA-20), 4.87 g of 5% by mass of DL-lithium lactate aqueous solution, 0.29 g of tantalum lactate aqueous solution, 0.93 g of yttrium acetate aqueous solution, and 35.35 g of pure water were placed in a polypropylene container and mixed to obtain 50 g of a metal acid compound dispersion according to Example 25.

[0251] Here, the yttrium acetate aqueous solution consisted of yttrium: 2.42% by mass and acetic acid: 4.90% by mass.

[0252] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 25 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0253] Example 26 7.00 g of a lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 1.56 g of a zirconium acetate aqueous solution (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.: Zircosol ZA-20), 4.87 g of a 5 mass% DL-lithium lactate aqueous solution, 0.29 g of a tantalum lactate aqueous solution, 0.62 g of a cerium acetate aqueous solution, and 35.67 g of pure water were placed in a polypropylene container and mixed, thereby obtaining 50 g of a metal acid compound dispersion according to Example 26.

[0254] Here, the cerium acetate aqueous solution contained 5.78% by mass of cerium and 7.43% by mass of acetic acid.

[0255] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, 5 mass % lithium DL-lactate aqueous solution, and tantalum lactate aqueous solution used in Example 26 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0256] Comparative Example 1 10.00 g of a lanthanum acetate aqueous solution (manufactured by Nippon Yttrium), 0.74 g of a zirconium acetate aqueous solution (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.: Zircosol ZA-20), 13.93 g of a 5 mass % lithium DL-lactate aqueous solution, 0.27 g of tantalum oxide powder (manufactured by Mitsui Mining & Smelting Co., Ltd., purity 99.9%), and 25.06 g of pure water were placed in a polypropylene container and mixed, thereby obtaining 50 g of a metal acid compound dispersion according to Comparative Example 1.

[0257] The lanthanum acetate aqueous solution, zirconium acetate aqueous solution, and 5 mass % lithium DL-lactate aqueous solution used in Comparative Example 1 were the same as those in Example 1, and therefore detailed description thereof will be omitted.

[0258] Comparative Example 2 6.00 g of a 5 mass % aqueous solution of lithium DL-lactate, 0.69 g of tantalum oxide powder (manufactured by Mitsui Mining & Smelting Co., Ltd., purity 99.9%), and 43.31 g of pure water were placed in a polypropylene container and mixed, thereby obtaining 50 g of a metal acid compound dispersion liquid according to Comparative Example 2.

[0259] The 5 mass % aqueous solution of lithium DL-lactate used in Comparative Example 2 was the same as that used in Example 1, and therefore a detailed description thereof will be omitted.

[0260] The following physical properties were measured for the metal acid compound dispersions of Examples 1 to 26 and Comparative Examples 1 and 2. The measured physical properties and the methods for measuring those properties are shown below. The compositions of the metal acid compound dispersions of Examples 1 to 10 and Comparative Example 1 are shown in FIG. 1, the composition ratios of the metal acid compound dispersions of Examples 1 to 10 and Comparative Example 1 are shown in FIG. 2, and the measurement results of the metal acid compound dispersions of Examples 1 to 10 and Comparative Example 1 are shown in FIG. 3. The compositions of the metal acid compound dispersions of Examples 11 to 21 and Comparative Example 2 are shown in FIG. 4, the composition ratios of the metal acid compound dispersions of Examples 11 to 21 and Comparative Example 2 are shown in FIG. 5, and the measurement results of the metal acid compound dispersions of Examples 11 to 21 and Comparative Example 2 are shown in FIG. 6. Furthermore, the compositions of the metal acid compound dispersions of Examples 22 to 26 and Comparative Example 1 are shown in Figure 7, the composition ratios of the metal acid compound dispersions of Examples 22 to 26 and Comparative Example 1 are shown in Figure 8, and the measurement results of the metal acid compound dispersions of Examples 22 to 26 and Comparative Example 1 are shown in Figure 9.

[0261] <Elemental Analysis> If necessary, the sample was appropriately diluted with dilute hydrochloric acid, and using ICP optical emission spectrometry (AG-5110 manufactured by Agilent Technologies) in accordance with JIS K0116:2014, La mass % in terms of La atoms, Zr mass % in terms of Zr atoms, Ta mass % in terms of Ta atoms, and Li mass % in terms of Li atoms were measured for the metal acid compound dispersions according to Examples 1 to 10 and Comparative Example 1. Ta mass % in terms of Ta atoms and Li mass % in terms of Li atoms were measured for the metal acid compound dispersions according to Examples 11 to 21 and Comparative Example 2. For the metal acid compound dispersions of Examples 22 to 26, La mass% in terms of La atoms, Zr mass% in terms of Zr atoms, Ta mass% in terms of Ta atoms, Mo mass% in terms of Mo atoms, Ti mass% in terms of Ti atoms, Nb mass% in terms of Nb atoms, Y mass% in terms of Y atoms, Ce mass% in terms of Ce atoms, and Li mass% in terms of Li atoms were measured.

[0262] <pH Measurement> The pH of the metal acid compound dispersions of Examples 1 to 26 and Comparative Examples 1 and 2 was measured using an electrode (HORIBA Standard ToupH electrode 9615S-10D) of a pH meter (HORIBA Glass Electrode Hydrogen Ion Concentration Indicator D-51) after confirming that the liquid temperature had stabilized at 25°C. The "initial pH" in Figures 3, 6, and 9 refers to the pH of the metal acid compound dispersions whose liquid temperature was adjusted to 25°C immediately after production. The "pH over time" in Figures 3, 6, and 9 refers to the pH of the metal acid compound dispersions of Examples 1 to 26 and Comparative Examples 1 and 2 after they were allowed to stand for one month from the day of production in an incubator set at room temperature of 25°C.

[0263] <Dynamic Light Scattering Method> Particle size distribution was evaluated by dynamic light scattering in accordance with JIS Z 8828:2019 using a zeta potential, particle size, and molecular weight measurement system (ELSZ-2000, manufactured by Otsuka Electronics Co., Ltd.). Just before measurement, the metal acid compound dispersions of Examples 1 to 26 were filtered through a 1-μm pore size filter to remove dust and other particles. Furthermore, D50 indicates the particle size at which the volume fraction reaches 50%. In Figures 3, 6, and 9, "initial particle diameter D50 (nm)" refers to the D50 of the metal acid compound dispersion immediately after production. In Figures 3, 6, and 9, "aged particle diameter D50 (nm)" refers to the D50 of the metal acid compound dispersions of Examples 1 to 26 and Comparative Examples 1 and 2 after they were left standing for one month from the day of production in an incubator set at room temperature of 25°C. Furthermore, for the metal acid compound dispersions of Comparative Examples 1 and 2, because precipitates were visible in the dispersions immediately after production, measurement of the particle diameter over time D50 (nm) was not performed. The above-mentioned filtering was performed when measuring the "initial particle diameter D50 (nm)," but not when measuring the "particle diameter over time D50 (nm)." Only ultrasonic treatment was performed. Furthermore, it is not possible to clearly observe whether the metal acid compounds in the metal acid compound dispersions of Examples 1 to 26 are dissolved in the solvent or present as particles in the solvent. Therefore, the numerical values ​​shown as "initial particle diameter D50 (nm)" and "particle diameter over time D50 (nm)" in Figures 3, 6, and 9 refer to "values ​​measured as particle diameters."

[0264] <Transmittance Measurement> 3 ml of the metal acid compound dispersions according to Examples 1 to 26 and Comparative Examples 1 and 2 were placed in a synthetic quartz cell with an optical path length of 5 mm, and the transmittance of the metals according to Examples 1 to 26 and Comparative Examples 1 and 2 in the wavelength region of 400 nm to 760 nm (specifically, the transmittance at wavelengths of 400 nm, 600 nm, and 750 nm) was measured using a spectrophotometer under the transmittance measurement conditions described above. The "initial transmittance" in Figures 3, 6, and 9 refers to the transmittance of the metal acid compound dispersions adjusted to a liquid temperature of 25°C immediately after production. The "aged transmittance" in Figures 3, 6, and 9 refers to the transmittance of the metal acid compound dispersions according to Examples 1 to 26 after being left to stand for one month from the day of production in an incubator set at room temperature of 25°C. Since the metal acid compound dispersions according to Comparative Examples 1 and 2 had initial transmittances of less than 70%T, the aged transmittance was not measured.

[0265] < １ H-NMR> Measurement samples were prepared by mixing 70 μL of the metal acid compound dispersions according to Examples 1 to 26 and Comparative Examples 1 and 2, 70 μL of a DSS-d6 deuterium oxide solution prepared by dissolving sodium 3-(trimethylsilyl)-1-propane-1,1,2,2,3,3-d6-sulfonate (hereinafter referred to as DSS-d6) in deuterium oxide at a concentration of 10 g / L, and 560 μL of deuterium oxide. The prepared measurement samples were analyzed by the above-mentioned method. １ According to the H-NMR spectrum measurement conditions, １ The H-NMR spectrum was measured. １ The organic acid contents in the metal acid compound dispersions of Examples 1 to 26 and Comparative Examples 1 and 2 were determined from the H-NMR spectra.

[0266] <Film Formability Test> The appearance of the coating film formed on the surface of a glass substrate, which served as a substitute for a current collector plate, was evaluated by observation with an optical microscope. First, the metal acid compound dispersions of Examples 1 to 26 and Comparative Examples 1 and 2 were allowed to stand for one month from the day of production in an incubator set at room temperature (25°C). Next, the metal acid compound dispersions of Examples 1 to 26 and Comparative Examples 1 and 2 after standing for one month were dropped onto a 50 mm x 50 mm glass substrate that had been degreased and washed with acetone using a syringe while being filtered through a 0.22 μm pore size filter, and then dried. The coating was applied by spin coating (700 rpm, 10 seconds, followed by 1500 rpm, 15 seconds). The coated area was then allowed to dry naturally, forming a coating film on the glass substrate. The glass substrate was observed with an optical microscope (magnification: 40x) in a central 15 mm x 15 mm area of ​​the formed coating film. If no particles were present and a film was formed, the substrate was evaluated as having excellent film-forming properties and was rated as "○ (GOOD)," and if particles were observed, the substrate was evaluated as having poor film-forming properties and was rated as "× (BAD)."

[0267] As shown in FIGS. 1 to 9 , the metal acid compound dispersions according to Examples 1 to 26 were metal acid compound dispersions containing one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum, and containing one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and an organic acid. When the D50 (volume integrated basis) measured by dynamic light scattering for the metal acid compound dispersion was 100 nm or less, the dispersions had excellent storage stability.

[0268] The metal acid compound dispersions according to Examples 1 to 26 were metal acid compound dispersions containing one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum, and also contained one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and an organic acid. When the maximum value of the transmittance in the wavelength region of 400 nm to 760 nm was 70%T or more, the dispersions had excellent storage stability.

[0269] The metal acid compound dispersions of Examples 1 to 26 had excellent stability over time when the content of the metal species M in the metal acid compound dispersions of Examples 1 to 26 was 0.01 mass% or more and 30 mass% or less in terms of metal species M atoms.

[0270] The metal acid compound dispersions of Examples 1 to 26 had excellent stability over time when the organic acid content in the metal acid compound dispersions of Examples 1 to 26 was 0.01% by mass or more and 30% by mass or less.

[0271] 3, 6, and 9, the metal acid compound dispersions of Examples 1 to 26 showed excellent stability over time, with the particle diameter over time (D50) not significantly different from the initial particle diameter (D50) even after one month had passed. However, precipitates were observed in the metal acid compound dispersions of Comparative Examples 1 and 2.

[0272] 2, 5, and 8, the metal acid compound dispersions according to Examples 1 to 26 exhibited improved stability during long-term storage when the molar ratio x / m of the total amount (x) of one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements to the total amount (m) of one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum was 0.001 or more and 50 or less. Furthermore, when the element X was lithium, the metal acid compound dispersions according to Examples 1 to 26 exhibited improved stability during long-term storage when the molar ratio Li / m of lithium (Li) to the total amount (m) of the metal species M was 0.001 or more and 50 or less.

[0273] The metal acid compound dispersions according to Examples 1 to 26 were excellent in stability over time in the solution state when the molar ratio m / A of the total amount (m) of one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum to the total amount (A) of organic acids was 0.001 or more and 10 or less.

[0274] The metal acid compound dispersions according to Examples 1 to 26 exhibited excellent stability over time in the solution state when the molar ratio (x+m) / A of the total amount (m) of one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements and the total amount (x) of one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum to the total amount (A) of organic acids was 0.001 or more and 10 or less. Furthermore, the metal acid compound dispersions according to Examples 1 to 21 exhibited excellent stability over time in the solution state when the element X was lithium and the molar ratio (Li+m) / A of the total amount (m) of lithium (Li) and the metal species M to the total amount (A) of organic acids was 0.001 or more and 10 or less.

[0275] As shown in FIGS. 3, 6 and 9, the metal acid compound dispersions according to Examples 1 to 26 had excellent stability over time when the pH of the dispersions was 2 or more and 11 or less.

[0276] The metal acid compound films formed from the metal acid compound dispersions of Examples 1 to 26 were observed with an optical microscope to show that the coating films formed from each metal acid compound dispersion contained no coarse particles and had excellent film-forming properties.

[0277] The inventions disclosed in this specification include, in addition to the configurations of each invention and embodiment, those specified by changing these partial configurations to other configurations disclosed in this specification, to the extent applicable, or those specified by adding other configurations disclosed in this specification to these configurations, or those specified as higher-level concepts specified by deleting these partial configurations to the extent that partial effects can be obtained.

[0278] The metal acid compound dispersion according to the present invention has excellent storage stability. Furthermore, because the metal acid compound dispersion according to the present invention has excellent storage stability and can suppress the rate of defective products caused by sedimentation due to changes over time, it is possible to reduce waste and the energy costs associated with waste disposal. These advantages contribute to the sustainable management and efficient use of natural resources, as well as the achievement of decarbonization (carbon neutrality).

Claims

1. A metal acid compound dispersion containing one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum, the metal acid compound dispersion containing one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and an organic acid, wherein the metal acid compound dispersion has a D50 (volume-integrated basis) of 100 nm or less as measured by dynamic light scattering.

2. A metal acid compound dispersion containing one or more metal species M selected from the group consisting of lanthanum, yttrium, cerium, neodymium, zirconium, niobium, tantalum, molybdenum, tungsten, titanium, and aluminum, comprising one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and an organic acid, wherein the metal acid compound dispersion has a maximum transmittance of 70%T or more in a wavelength region of 400 nm to 760 nm.

3. The metal acid compound dispersion liquid according to claim 1 or 2, wherein the metal species M contains lanthanum, zirconium, or tantalum.

4. The metal acid compound dispersion liquid according to claim 1 or 2, characterized in that the metal species M contains lanthanum and zirconium.

5. The metal oxide compound dispersion liquid according to claim 1 or 2, wherein the element X contains lithium.

6. The metal acid compound dispersion liquid according to claim 1 or 2, characterized in that the organic acid contains one or more selected from the group consisting of carboxylic acids, saturated fatty acids, hydroxy acids, citric acid, tartaric acid, lactic acid, acetic acid, and salts thereof.

7. The metal acid compound dispersion liquid according to claim 1 or 2, further comprising hydrogen peroxide.

8. The metal acid compound dispersion according to claim 1 or 2, further comprising ammonia and / or an organic nitrogen compound.

9. The metal acid compound dispersion according to claim 1 or 2, further comprising a phosphorus compound and / or a chlorine compound.

10. A metal acid compound dispersion liquid according to claim 1 or 2, characterized in that the content of metal species M in the metal acid compound dispersion liquid is 0.01 mass % or more and 30 mass % or less in terms of metal species M atoms.

11. The metal acid compound dispersion liquid according to claim 1 or 2, characterized in that the organic acid content in the metal acid compound dispersion liquid is 0.01% by mass or more and 30% by mass or less.

12. The metal acid compound dispersion liquid according to claim 1 or 2, wherein the molar ratio x / m of the total amount (x) of the element X to the total amount (m) of the metal species M in the metal acid compound dispersion liquid is 0.001 or more and 50 or less.

13. The metal acid compound dispersion liquid according to claim 1 or 2, wherein the element X in the metal acid compound dispersion liquid is lithium, and the molar ratio Li / m of lithium (Li) to the total amount (m) of the metal species M is 0.001 or more and 50 or less.

14. A metal acid compound dispersion liquid according to claim 1 or 2, characterized in that the molar ratio m / A of the total amount (m) of the metal species M to the total amount (A) of the organic acid in the metal acid compound dispersion liquid is 0.001 or more and 10 or less.

15. The metal acid compound dispersion liquid according to claim 1 or 2, wherein the molar ratio (x+m) / A of the sum of the total amount (x) of the element X and the total amount (m) of the metal species M in the metal acid compound dispersion liquid to the total amount (A) of the organic acid is 0.001 or more and 10 or less.

16. The metal acid compound dispersion liquid according to claim 1 or 2, wherein the element X in the metal acid compound dispersion liquid is lithium, and the molar ratio (Li+m) / A of the sum of the total amount (m) of the lithium (Li) and the metal species M to the total amount (A) of the organic acid is 0.001 or more and 10 or less.

17. A metal acid compound powder comprising the metal acid compound in the metal acid compound dispersion liquid according to claim 1 or 2.

18. A metal acid compound film comprising the metal acid compound in the metal acid compound dispersion liquid according to claim 1 or 2.

19. The metal acid compound dispersion liquid according to claim 1 or 2, which is used for coating a positive electrode or a positive electrode material for a lithium ion secondary battery.

20. A positive electrode active material for a lithium ion secondary battery, characterized in that the surface is coated with a metal acid compound derived from the metal acid compound dispersion liquid described in claim 1 or 2.

21. A lithium ion secondary battery characterized by having a positive electrode the surface of which is coated with the positive electrode active material for lithium ion secondary batteries as defined in claim 20.

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