Metal acid compound dispersion and method for producing same

Abstract

A metal acid compound dispersion containing at least two metals M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium, said metal acid compound dispersion containing: at least one element X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements; and a phosphorus compound and / or a chlorine compound. The particle diameter (D50) of the particles in the metal acid compound dispersion is at most 1000 nm as obtained by a dynamic light scattering method.

Description

Metallic acid compound dispersion and method for producing the same

[0001] The present invention relates to a metal acid compound dispersion and a method for producing the same.

[0002] Lithium metal oxides, which are metal oxide compounds obtained by combining metal elements such as niobium, tantalum, molybdenum, and tungsten with lithium, an alkali metal element, are used in nonlinear optical materials, piezoelectric elements, 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 metal oxides are cited as lithium ion conductive oxides that coat at least a portion of the surface of the composite active material particles. Furthermore, 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. The piezoelectric sensor disclosed in Patent Document 1 forms the piezoelectric film layer by spray-coating a mixture of lithium niobate powder and a sol-gel solution, followed by sintering. Furthermore, the tantalum oxide sol, specifically lithium tantalate, disclosed in Patent Document 2 has excellent optical, nonlinear, and electro-optical properties and is used in piezoelectric elements and the like.

[0003] JP 2023-63187 A JP 8-143315 A

[0004] However, in the piezoelectric sensor disclosed in Patent Document 1, when spray-coating a mixture of lithium niobate powder and a sol-gel solution, if the lithium niobate powder has low dispersibility or solubility in the solvent, it becomes difficult to form a uniform piezoelectric film layer. Furthermore, if the mixture of lithium niobate powder and a solvent has poor storage stability, the spray-coating process becomes cumbersome. Furthermore, the tantalum oxide sol disclosed in Patent Document 2 contains an organic component, such as oxalic acid, which is difficult to volatilize. This organic component can hinder the formation of a uniform film and, when used as a catalyst additive, can inhibit catalytic activity. Furthermore, compared to lithium niobate, lithium tantalate has poor dispersibility and solubility in water, is prone to precipitate over time, and does not have excellent storage stability.

[0005] In view of the above problems, the present invention provides a metal acid compound dispersion liquid that has high dispersibility in polar solvents, particularly water, good solubility in water, and excellent storage stability, and a method for producing the same.

[0006] The metal acid compound dispersion of the present invention, which has been made to solve the above problems, is a metal acid compound dispersion containing two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium, one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and a phosphorus compound and / or a chlorine compound, and is characterized in that the particle diameter (D50) of particles in the metal acid compound dispersion measured by dynamic light scattering is 1000 nm or less. The metal acid compound dispersion of the present invention contains two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium, one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and a phosphorus compound and / or a chlorine compound, and is characterized in that the particle diameter (D50) of particles in the tantalum acid compound dispersion measured by dynamic light scattering is 1000 nm or less, which is preferable in terms of improved dispersibility and solubility in polar solvents, particularly water.

[0007] The metal acid compound dispersion of the present invention contains two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium. The metal species M is considered to exist as an oxide in the metal acid compound dispersion of the present invention. Specifically, niobium is represented by NbO ３ － Tantalum is thought to exist as an anion such as TaO or as a polyoxometalate (polyacid) ion in which multiple niobium atoms are bonded to oxygen atoms. ３ － It is believed that molybdenum exists as an anion such as MoO or as a polyoxometalate (polyacid) ion in which multiple tantalum atoms are bonded to oxygen atoms. ４ ２－It is believed that tungsten exists as an anion such as (W ２ O ７ ) ２－ Ya, (W １２ O １０ ) ８－ It is believed that titanium exists as an anion such as (Ti ３ O ７ ) ２－ These titanium atoms are thought to exist as anions such as those shown below, or as polyoxometalate (polyacid) ions in which multiple titanium atoms are bonded to oxygen atoms.

[0008] Furthermore, it is preferable that the metal species M contains tantalum. Specifically, the metal species M may be two metal species: tantalum and one metal species selected from niobium, molybdenum, tungsten, or titanium; three metal species: tantalum and two metal species selected from niobium, molybdenum, tungsten, or titanium; four metal species: tantalum and three metal species selected from niobium, molybdenum, tungsten, or titanium; or may include all five metal species: tantalum, niobium, molybdenum, tungsten, and titanium. Note that the metal species M may be two metal species selected from niobium, molybdenum, tungsten, or titanium excluding tantalum; three metal species selected from niobium, molybdenum, tungsten, or titanium; or four metal species selected from niobium, molybdenum, tungsten, and titanium.

[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 Li. Furthermore, the element X is not limited to only one alkali metal element, Li, but is preferably two alkali metal elements, Li and Na or K, or three alkali metal elements, Li, Na, and K. Furthermore, the element X may be one alkali metal element, Na or K, or two alkali metal elements, Na and K.

[0011] The metal acid compound dispersion of the present invention contains a phosphorus compound. In addition, in the metal acid compound dispersion of the present invention, the phosphorus compound preferably contains one or more compounds selected from inorganic phosphorus compounds, organic phosphorus compounds, and salts thereof.

[0012] 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).

[0013] 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).

[0014] 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).

[0015] 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.

[0016] An example of the organic phosphinic acids is triphenylphosphine (CAS number: 603-35-0).

[0017] 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.

[0018] 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. When the phosphorus compound is phosphoric acid or a salt of phosphoric acid, this is more preferable when adjusting a solution to a pH closer to neutral. On the other hand, when the phosphorus compound is condensed phosphoric acid, or when the condensed phosphoric acid is pyrophosphoric acid, polyphosphoric acid, or a salt of condensed phosphoric acid, this is more preferable when adjusting a solution to a high pH.

[0019] 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.

[0020] The metal acid compound dispersion of the present invention further contains a chlorine compound, such as 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), or perchloric acid (CAS No. 7601-90-3).

[0021] The chlorine compound may also 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, with ammonium salts and lithium salts being preferred. 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).

[0022] 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.

[0023] Furthermore, when the particle diameter (D50) of the particles in the metal acid compound dispersion liquid measured by dynamic light scattering is 1000 nm or less, it is preferable from the viewpoints of high dispersibility, little change over time, stability, reactivity during reaction or compounding with other substances, and film uniformity during film formation. Furthermore, the particle diameter (D50) is preferably smaller, more preferably 800 nm or less, even more preferably 600 nm or less, particularly preferably 500 nm or less, more particularly preferably 300 nm or less, even more particularly preferably 200 nm or less, even particularly preferably 100 nm or less, even more preferably 50 nm or less, even more preferably 30 nm or less, even more particularly preferably 20 nm or less, even more particularly preferably 10 nm or less, especially more preferably 8 nm or less, even more particularly preferably 6 nm or less, even more particularly preferably 4 nm or less, even more particularly more particularly preferably 2 nm or less, even more particularly more particularly preferably 1 nm or less, especially preferably 0.6 nm or less, and most preferably greater than 0. In this way, a liquid in which the particle diameter (D50) of the particles in the metal acid compound dispersion of the present invention is 1000 nm or less as a result of measurement using dynamic light scattering is defined as the "metal acid compound dispersion" of the present invention.

[0024] 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 fluctuation of that intensity. Specifically, the 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. The particle size (D50) refers to the median diameter (D50), which is the particle size that represents the 50% integrated value of the integrated distribution curve. Furthermore, in this specification, unless otherwise specified, the term "particle diameter (D50)" includes both the "initial particle diameter D50" which indicates the particle diameter (D50) of particles in the metal acid compound dispersion liquid of the present invention adjusted to a liquid temperature of 25°C immediately after production, and the "aged particle diameter D50" which indicates the particle diameter (D50) of particles in the metal acid compound dispersion liquid of the present invention after it has been left to stand for one month from the day the metal acid compound dispersion liquid of the present invention was produced in an incubator set at room temperature of 25°C.

[0025] The metal acid compound dispersion of the present invention is a metal acid compound dispersion containing two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium, 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 a phosphorus compound and / or a chlorine compound, and has a maximum transmittance of 70% T or more in a wavelength region of 400 nm to 760 nm. Here, the two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium, the one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and the phosphorus compound and / or a chlorine compound in the metal acid compound dispersion of the present invention are as described above, and therefore detailed description thereof will be omitted.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] =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

[0032] 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.

[0033] The metal acid compound dispersion of the present invention may further contain hydrogen peroxide. Since the metal acid compound dispersion of the present invention can produce an aqueous tantalum compound solution by adding hydrogen peroxide water to an aqueous tantalum fluoride solution and mixing them in the method for producing a tantalum acid compound dispersion, which will be described later, the metal acid compound dispersion of the present invention may contain hydrogen peroxide.

[0034] 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.

[0035] 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.

[0036] As will be explained in detail in the method for producing a metal acid compound dispersion of the present invention, which will be described later, in a method for producing a tantalic acid compound dispersion, for example, a reverse neutralization method is used to add an acidic tantalum complex aqueous solution to an alkaline aqueous solution, for example, aqueous ammonia, to produce a tantalic acid-containing precipitate, which is a tantalum-containing precipitate slurry, such as an aqueous ammonium tantalate cake, and then the tantalic acid compound dispersion is produced. Therefore, it is believed that ammonia contains ammonium ions and exists in the dispersion as cations. Furthermore, in a method for producing a tantalic acid compound dispersion, a neutralized aqueous tantalum compound solution is produced by mixing the tantalic acid-containing precipitate obtained through the reverse neutralization method of adding the tantalum complex aqueous solution to aqueous ammonia with an organic nitrogen compound, and therefore the organic nitrogen compound is believed to exist in the dispersion as cations.

[0037] 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.

[0038] Examples of organic nitrogen compounds include aliphatic amines, aromatic amines, amino alcohols, amino acids, polyamines, quaternary ammonium compounds, guanidine compounds, and azole compounds.

[0039] 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.

[0040] 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.

[0041] 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:

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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).

[0047] 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).

[0048] 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.

[0049] The content of the metal species M can be determined as follows.

[0050] When the metal species M contained in the metal acid compound dispersion of the present invention is two types, tantalum and niobium, the sum of the tantalum content in terms of Ta atoms and the niobium content in terms of Nb 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.

[0051] Furthermore, when the metal species M contained in the metal acid compound dispersion of the present invention are three types, namely tantalum, niobium, and molybdenum, the total of the tantalum content in terms of Ta atoms, the niobium content in terms of Nb atoms, and the molybdenum content in terms of Mo 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.

[0052] Furthermore, when the metal species M contained in the metal acid compound dispersion liquid of the present invention is one of the four types, namely tantalum, molybdenum, tungsten, and titanium, the total of the tantalum content in terms of Ta atoms, the molybdenum content in terms of Mo atoms, the tungsten content in terms of W atoms, and the titanium content in terms of Ti atoms in the metal acid compound dispersion liquid of the present invention is the content of the metal species M in the metal acid compound dispersion liquid of the present invention.

[0053] Furthermore, when the metal species M contained in the metal acid compound dispersion liquid of the present invention is one of the five metal species, namely tantalum, niobium, molybdenum, tungsten, and titanium, the total of the tantalum content in terms of Ta atoms, the niobium content in terms of Nb atoms, the molybdenum content in terms of Mo atoms, the tungsten content in terms of W atoms, and the titanium content in terms of Ti atoms in the metal acid compound dispersion liquid of the present invention is the content of the metal species M in the metal acid compound dispersion liquid of the present invention.

[0054] 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 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, and Ti mass% in terms of Ti 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, similarly to the metal species M content. By specifying the metal species M content and lithium content in the metal acid compound dispersion of the present invention, the molar ratio Li / m of lithium (Li) to the metal species M(m) in the lithium metal acid contained in the metal acid compound dispersion of the present invention can be specified. 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, similarly to the content of the metal species M.

[0055] The metal acid compound dispersion of the present invention is characterized in that the phosphorus content in the metal acid compound dispersion is 0.01% by mass to 10% by mass in terms of P atoms. A phosphorus content of 0.01% by mass to 10% by mass in terms of P atoms in the metal acid compound dispersion of the present invention is preferred in terms of improving dispersibility and solubility in polar solvents, particularly water. Furthermore, a phosphorus content of 0.01% by mass to 5% by mass in terms of P atoms is more preferred, a content of 0.05% by mass to 2% by mass in terms of P atoms is even more preferred, and a content of 0.05% by mass to 1% by mass in terms of P atoms is particularly preferred.

[0056] The phosphorus content in the metal acid compound dispersion of the present invention is calculated by appropriately diluting the dispersion with dilute hydrochloric acid as needed, and measuring the P mass % in terms of P atoms using ICP emission spectrometry (AG-5110 manufactured by Agilent Technologies) in accordance with JIS K0116:2014.

[0057] The phosphorus content in the metal oxide compound dispersion of the present invention is preferably analyzed by the above-mentioned ICP emission spectrometry. ３１ It can also be determined by measuring P-NMR spectrum. Specifically, the phosphorus 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 the metal acid compound dispersion of the present invention with 650 μL of a phosphonoacetic acid heavy water solution prepared by dissolving 10 g / L of phosphonoacetic acid in heavy water. The prepared measurement sample is subjected to the following measurement. ３１ According to the P-NMR spectrum measurement conditions, ３１ The P-NMR spectrum is measured.

[0058] = ３１P-NMR spectrum measurement conditions = Magnetic field: 14.1 T (1H 600 MHz) 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 phosphorus amount: Phosphonoacetic acid Chemical shift value reference: The apex of the central peak of the triplet peak of phosphonoacetic acid is set to 14.96 ppm. Spectral center (O1 value - SR value (chemical shift value)): 0.00 ppm Radio frequency pulse intensity: The intensity is set so that 14 μs results in a 90-degree pulse with respect to the peak at the irradiation center. Radio frequency pulse width: 14 μs Measurement interval: 80 μs (DW = 40 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

[0059] As mentioned above ３１ By performing a Fourier transform on the FID data measured under the P-NMR spectrum measurement conditions without using a window function, ３１ P-NMR spectrum was obtained. ３１ The peak areas of the P-NMR spectrum can be calculated using the Integrate function of the measurement and data processing software described above, and the contents of phosphonoacetic acid and each phosphate ion can be calculated from the peak areas. For example, in the case of the diphosphate raw material, the peak area is 6.5 ppm (PO ４ -1.7 ppm (presumed to be derived from the chemical shift value of P ２ O ７ (presumed origin) and ３１ In the phosphoric acid raw material, a peak of 6.2 ppm (PO ４ (presumed origin) ３１ The P peak is observed. The chemical shifts vary depending on the pH of the sample, so calculations should be made taking this into consideration.

[0060] Furthermore, the metal acid compound dispersion of the present invention preferably has a chlorine content of 0.0% by mass or more and 2.0% by mass or less in terms of Cl atoms. A chlorine content of 0.0% by mass or more and 2.0% by mass or less in terms of Cl atoms is preferred from the viewpoint of corrosion of the substrate. Furthermore, a chlorine content of 0.001% by mass or more and 2.0% by mass or less in terms of Cl atoms is more preferred, a chlorine content of 0.001% by mass or more and 0.5% by mass or less in terms of Cl atoms is even more preferred, a chlorine content of 0.001% by mass or more and 0.2% by mass or less in terms of Cl atoms is particularly preferred, and a chlorine content of 0.001% by mass or more and 0.1% by mass or less in terms of Cl atoms is even more preferred.

[0061] The chlorine content in the metal acid compound dispersion of the present invention is calculated by diluting the dispersion appropriately with dilute hydrochloric acid as needed, and measuring the mass % of Cl in terms of Cl atoms using ICP optical emission spectrometry (AG-5110 manufactured by Agilent Technologies) in accordance with JIS K0116: 2014. In this case, the chlorine content in the metal acid compound dispersion of the present invention can be determined by subtracting the chlorine content derived from the dilute hydrochloric acid used for dilution.

[0062] Furthermore, the metal acid compound dispersion of the present invention preferably has a total content of the phosphorus content calculated as P atoms and the chlorine content calculated as Cl atoms of 0.01% by mass or more and 10% by mass or less. A total content of 0.01% by mass or more and 10% by mass or less in the metal acid compound dispersion of the present invention is preferable in terms of improving dispersibility and solubility in polar solvents, particularly water. Furthermore, the total content is more preferably 0.01% by mass or more and 5% by mass or less, even more preferably 0.05% by mass or more and 2% by mass or less, and particularly preferably 0.05% by mass or more and 1% by mass or less.

[0063] The metal acid compound dispersion of the present invention is characterized in that the molar ratio x / m of the total amount (x) of the elements X to the total amount (m) of the metal species M in the metal acid compound dispersion is 0.01 or more and 10 or less. When the molar ratio x / m of the total amount (x) of the elements X to the total amount (m) of the metal species M in the metal acid compound dispersion of the present invention is 0.01 or more and 10 or less, the dispersibility and solubility in water are improved, and it is more preferably 0.05 or more and 9 or less, even more preferably 0.1 or more and 8 or less, and particularly preferably 1 or more and 7 or less. The molar ratio x / m of the total amount (x) of the elements X to the total amount (m) of the metal species M in the metal acid compound dispersion of the present invention may be 0.1 or more and 9 or less, or may be 0.1 or more and 7 or less.

[0064] The total amount (m) of the metal species M can be determined as follows.

[0065] When the metal species M contained in the metal acid compound dispersion of the present invention are two types, tantalum and niobium, the sum of the number of moles of tantalum and the number of moles of niobium 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.

[0066] Furthermore, when the metal species M contained in the metal acid compound dispersion of the present invention are three types, namely tantalum, niobium, and molybdenum, the sum of the number of moles of tantalum, the number of moles of niobium, and the number of moles of molybdenum 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.

[0067] Furthermore, when the metal species M contained in the metal acid compound dispersion of the present invention are four types, namely tantalum, molybdenum, tungsten, and titanium, the total amount (m) of the metal species M in the metal acid compound dispersion of the present invention is the sum of the number of moles of tantalum, the number of moles of molybdenum, the number of moles of tungsten, and the number of moles of titanium per liter of the metal acid compound dispersion of the present invention.

[0068] Furthermore, when the metal species M contained in the metal acid compound dispersion of the present invention are five types, namely tantalum, niobium, molybdenum, tungsten, and titanium, the total amount (m) of the metal species M in the metal acid compound dispersion of the present invention is the sum of the number of moles of tantalum, the number of moles of niobium, the number of moles of molybdenum, the number of moles of tungsten, and the number of moles of titanium per liter of the metal acid compound dispersion of the present invention.

[0069] The metal acid compound dispersion of the present invention is characterized in that the element X in the metal acid compound dispersion is Li, 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 10 or less. When the element X in the metal acid compound dispersion of the present invention is Li, 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 10 or less, it is preferable in terms of improving dispersibility and solubility in water, and it is more preferable to be 0.05 or more and 9 or less, even more preferable to be 0.1 or more and 8 or less, and particularly preferable to be 1 or more and 7 or less. When the element X in the metal acid compound dispersion of the present invention is Li, the molar ratio Li / m of lithium (Li) to the total amount (m) of the metal species M may be 0.1 or more and 9 or less, or may be 0.1 or more and 7 or less.

[0070] The metal acid compound dispersion of the present invention is characterized in that the molar ratio x / (P+Cl) of the total amount (x) of element X to the total amount (P+Cl) of the phosphorus compounds and / or chlorine compounds in the metal acid compound dispersion is 0.01 or more and 5 or less. It is preferable that the molar ratio x / (P+Cl) of the total amount (x) of element X to the total amount (P+Cl) of the phosphorus compounds and / or chlorine compounds in the metal acid compound dispersion of the present invention is 0.01 or more and 5 or less, in terms of improving dispersibility and solubility in water, and is more preferably 0.01 or more and 2 or less, even more preferably 0.05 or more and 2 or less, and particularly preferably 0.1 or more and 1.95 or less. In this specification, unless otherwise specified, the total amount (P+Cl) of phosphorus compounds and / or chlorine compounds is the sum of the value (P) calculated in terms of P atoms and the value (Cl) calculated in terms of Cl atoms. Furthermore, when the metal acid compound dispersion of the present invention is used for a positive electrode for a lithium ion secondary battery described later or for coating a positive electrode material, it is preferable that the total amount of phosphorus compounds and / or chlorine compounds (P+Cl) is Cl=0.

[0071] Furthermore, in the metal acid compound dispersion of the present invention, the molar ratio x / P of the total amount (x) of the element X to the total amount (P) of the phosphorus compounds in the metal acid compound dispersion is more preferably 0.01 or more and 5 or less. If the molar ratio x / P of the total amount (x) of the element X to the total amount (P) of the phosphorus compounds in the metal acid compound dispersion of the present invention is 0.01 or more and 5 or less, it is preferable from the viewpoint of improving dispersibility and solubility in water, more preferably 0.01 or more and 2 or less, even more preferably 0.05 or more and 2 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0072] The metal acid compound dispersion of the present invention is characterized in that the molar ratio x / (P+Cl) of the total amount (x) of the element X to the total amount (P+Cl) of the phosphorus compounds and / or chlorine compounds in the metal acid compound dispersion is from 0.01 to 5. If the molar ratio x / (P+Cl) of the total amount (x) of the element X to the total amount (P+Cl) of the phosphorus compounds and / or chlorine compounds in the metal acid compound dispersion of the present invention is from 0.01 to 5, this is preferred in terms of improving dispersibility and solubility in water, and is more preferably from 0.01 to 2, even more preferably from 0.05 to 2, and particularly preferably from 0.1 to 1.95.

[0073] Furthermore, in the metal acid compound dispersion of the present invention, the molar ratio x / P of the total amount (x) of the element X to the total amount (P) of the phosphorus compounds in the metal acid compound dispersion is more preferably from 0.01 to 5. If the molar ratio x / P of the total amount (x) of the element X to the total amount (P) of the phosphorus compounds in the metal acid compound dispersion of the present invention is from 0.01 to 5, this is preferred in terms of improving dispersibility and solubility in water, more preferably from 0.01 to 2, even more preferably from 0.05 to 2, and particularly preferably from 0.1 to 1.95.

[0074] The metal acid compound dispersion of the present invention is characterized in that the element X in the metal acid compound dispersion is Li, and the molar ratio Li / (P+Cl) of lithium (Li) to the total amount (P+Cl) of the phosphorus compound and / or chlorine compound is 0.01 or more and 5 or less. When the element X in the metal acid compound dispersion of the present invention is Li, and the molar ratio Li / (P+Cl) of lithium (Li) to the total amount (P+Cl) of the phosphorus compound and / or chlorine compound is 0.01 or more and 5 or less, it is preferable in terms of improving dispersibility and solubility in water, and is more preferably 0.01 or more and 2 or less, even more preferably 0.05 or more and 2 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0075] Furthermore, in the metal acid compound dispersion of the present invention, it is more preferable that the element X in the metal acid compound dispersion is Li, and the molar ratio Li / P of lithium (Li) to the total amount (P) of the phosphorus compounds is 0.01 or more and 5 or less. If the element X in the metal acid compound dispersion of the present invention is Li, and the molar ratio Li / P of lithium (Li) to the total amount (P) of the phosphorus compounds is 0.01 or more and 5 or less, it is preferable in terms of improving dispersibility and solubility in water, and it is more preferable that it is 0.01 or more and 2 or less, even more preferable that it is 0.05 or more and 2 or less, and particularly preferable that it is 0.1 or more and 1.95 or less.

[0076] The metal acid compound dispersion of the present invention is characterized in that the molar ratio m / (P+Cl) of the total amount (m) of the metal species M to the total amount (P+Cl) of the phosphorus compounds and / or chlorine compounds is 0.01 or more and 10 or less. When the molar ratio m / (P+Cl) of the total amount (m) of the metal species M to the total amount (P+Cl) of the phosphorus compounds and / or chlorine compounds in the metal acid compound dispersion of the present invention is 0.01 or more and 10 or less, it is preferable from the viewpoint of improving dispersibility and solubility in water, and is more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0077] Furthermore, in the metal acid compound dispersion of the present invention, the molar ratio m / P of the total amount (m) of the metal species M to the total amount (P) of the phosphorus compounds is more preferably 0.01 or more and 10 or less. When 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 of the present invention is 0.01 or more and 10 or less, it is preferable from the viewpoint of improving dispersibility and solubility in water, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0078] Furthermore, in the metal acid compound dispersion of the present invention, when the metal species M in the metal acid compound dispersion is Nb, the molar ratio Nb / (P+Cl) of niobium (Nb) to the total amount (P+Cl) of the phosphorus compound and / or the chlorine compound is preferably 0.01 or more and 10 or less, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0079] Furthermore, in the metal acid compound dispersion of the present invention, when the metal species M in the metal acid compound dispersion is Nb, the molar ratio Nb / P of niobium (Nb) to the total amount (P) of the phosphorus compounds is preferably 0.01 or more and 10 or less, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0080] In the metal acid compound dispersion of the present invention, when the metal species M in the metal acid compound dispersion is Ta, the molar ratio Ta / (P+Cl) of tantalum (Ta) to the total amount (P+Cl) of the phosphorus compound and / or the chlorine compound is preferably 0.01 or more and 10 or less, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0081] In the metal acid compound dispersion of the present invention, when the metal species M in the metal acid compound dispersion is Ta, the molar ratio Ta / P of tantalum (Ta) to the total amount (P) of the phosphorus compounds is preferably 0.01 or more and 10 or less, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0082] In the metal acid compound dispersion of the present invention, when the metal species M in the metal acid compound dispersion is Mo, the molar ratio Mo / (P+Cl) of molybdenum (Mo) to the total amount (P+Cl) of the phosphorus compound and / or the chlorine compound is preferably 0.01 or more and 10 or less, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0083] Furthermore, in the metal acid compound dispersion of the present invention, when the metal species M in the metal acid compound dispersion is Mo, the molar ratio Mo / P of molybdenum (Mo) to the total amount (P) of the phosphorus compounds is preferably 0.01 or more and 10 or less, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0084] In the metal acid compound dispersion of the present invention, when the metal species M in the metal acid compound dispersion is W, the molar ratio W / (P+Cl) of tungsten (W) to the total amount (P+Cl) of the phosphorus compound and / or the chlorine compound is preferably 0.01 or more and 10 or less, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0085] Furthermore, in the metal acid compound dispersion of the present invention, when the metal species M in the metal acid compound dispersion is W, the molar ratio W / P of tungsten (W) to the total amount (P) of the phosphorus compounds is preferably 0.01 or more and 10 or less, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0086] In the metal acid compound dispersion of the present invention, when the metal species M in the metal acid compound dispersion is Ti, the molar ratio Ti / (P+Cl) of titanium (Ti) to the total amount (P+Cl) of the phosphorus compound and / or the chlorine compound is preferably 0.01 or more and 10 or less, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0087] In the metal acid compound dispersion of the present invention, when the metal species M in the metal acid compound dispersion is Ti, the molar ratio Ti / P of titanium (Ti) to the total amount (P) of the phosphorus compounds is preferably 0.01 or more and 10 or less, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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. 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. 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. Note that, if an organic acid is contained in the metal acid compound dispersion of the present invention, it will fluctuate the pH and may cause interactions between the components in the metal acid compound dispersion of the present invention and the organic acid, so it is preferable that the metal acid compound dispersion of the present invention does not contain an organic acid.

[0092] 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.

[0093] 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, Zr, Sn, and La. Here, examples of the compound include oxides, alkali metal salts of metal acids, alkaline earth metal salts of metal acids, chlorides, metal alkoxides, 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.

[0094] 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, Zr, Sn, and La, 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.

[0095] 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.

[0096] 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.

[0097] The coating agent of the present invention is characterized by containing the above-mentioned metal acid compound dispersion of the present invention. The coating agent of the present invention contains the metal acid compound dispersion of the present invention, which has high dispersibility in water, good solubility in water, and excellent storage stability.

[0098] The coating agent of the present invention is characterized by containing the above-mentioned metal acid compound powder of the present invention. The coating agent of the present invention contains the metal acid compound powder of the present invention, which has high dispersibility in water, good solubility in water, and excellent storage stability.

[0099] 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.

[0100] 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 the metal acid compound contained in the 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 O ２ , LiCo ０．２ Ni ０．４ Mn ０．４ O ２ , lithium molybdate, LiMnO ４ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMnO ２ etc. can be used

[0101] The lithium ion secondary battery of the present invention is characterized by having a positive electrode the surface of which is coated with the above-mentioned positive electrode active material for lithium ion secondary batteries of the present invention.

[0102] The method for producing the above-mentioned metal acid compound dispersion of the present invention will be described below.

[0103] The method for producing a metal acid compound dispersion of the present invention may include a mixing step of mixing a neutralized aqueous metal compound solution containing two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium with a phosphorus compound or a phosphorus compound solution and / or a chlorine compound or a chlorine compound solution.

[0104] Specifically, a phosphorus compound or a phosphorus compound solution and / or a chlorine compound or a chlorine compound solution is added to a neutralized aqueous solution of a metal compound containing two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium, which will be described later, and the mixture is mixed at room temperature for 0.1 to 2 hours, thereby obtaining the metal acid compound dispersion of the present invention.

[0105] Here, the phosphorus compound preferably contains at least one selected from inorganic phosphorus compounds, organic phosphorus compounds, and salts thereof.

[0106] Furthermore, it is preferable that the phosphorus compound contains one or more compounds 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.

[0107] Alternatively, the metal oxide compound dispersion of the present invention may be a phosphorus compound solution obtained by adding pure water to the above-mentioned phosphorus compound and adjusting the concentration so that the phosphorus content in terms of P atoms in the metal oxide compound dispersion of the present invention is 0.01 mass % or more and 10 mass % or less.

[0108] Examples of chlorine compounds include hydrochloric acid (CAS number: 7647-01-0), hypochlorous acid (CAS number: 7790-92-3), chlorous acid (CAS number: 13898-47-0), chloric acid (CAS number: 7790-93-4), and perchloric acid (CAS number: 7601-90-3).

[0109] The chlorine compound may also 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, with ammonium salts and lithium salts being preferred. 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).

[0110] Alternatively, the metal oxide compound dispersion of the present invention may be a chlorine compound solution obtained by adding pure water to the above-mentioned chlorine compound and adjusting the concentration so that the chlorine content in terms of Cl atoms in the metal oxide compound dispersion of the present invention is 0.0 mass % or more and 2.0 mass % or less.

[0111] The methods for producing neutralized aqueous solutions of metal compounds containing two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium, which are used in the above-mentioned method for producing a metal acid compound dispersion of the present invention, will be described below separately for a neutralized aqueous solution of a niobium compound, a neutralized aqueous solution of a tantalum compound, a neutralized aqueous solution of a molybdenum compound, a neutralized aqueous solution of a tungsten compound, and a neutralized aqueous solution of a titanium compound.

[0112] The method for producing a neutralized aqueous solution of a niobium compound includes a reaction step of producing a niobium fluoride aqueous solution, and a neutralization reaction step of adding the niobium fluoride aqueous solution to an alkaline aqueous solution containing one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements to produce a neutralized aqueous solution of a niobium compound.

[0113] First, the niobium fluoride aqueous solution is prepared by reacting niobium, niobium oxide, or niobium hydroxide with hydrofluoric acid (HF), such as an aqueous solution of hydrofluoric acid, to obtain niobium fluoride (H ２ NbF ７ ) and dissolving it in water to prepare the product.

[0114] Here, the niobium fluoride aqueous solution is prepared by adding water (e.g., pure water) to convert niobium into Nb ２ O ５It is preferable to adjust the niobium content to 1 to 100 g / L in terms of Nb ２ O ５ When the niobium content is 1 g / L or more in terms of Nb, a niobium compound hydrate that is easily soluble in water is obtained, and when productivity is taken into consideration, the niobium 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 in terms of conversion is preferable because it results in a niobic acid compound hydrate that is easily soluble in water, and in order to more reliably synthesize a niobic acid compound hydrate that is easily soluble in water, a concentration of 90 g / L or less is more preferable, a concentration of 80 g / L or less is even more preferable, and a concentration of 70 g / L or less is particularly preferable. Note that the pH of the niobium fluoride aqueous solution is preferably 2 or less, more preferably 1 or less, from the viewpoint of completely dissolving niobium or niobium oxide.

[0115] The neutralization reaction step of adding the obtained niobium fluoride aqueous solution to an alkaline aqueous solution containing one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements to produce a neutralized niobium compound aqueous solution is as follows.

[0116] In the neutralization reaction step, the obtained niobium fluoride aqueous solution is first added to ammonia water, i.e., a reverse neutralization method is used to obtain a niobium-containing precipitate slurry. Then, fluoride ions are removed from the obtained niobium-containing precipitate slurry to obtain a niobium-containing precipitate from which fluoride ions have been removed.

[0117] The ammonia content of the ammonia water used for reverse neutralization is preferably 10% by mass to 30% by mass. When the ammonia content is 10% by mass, niobium is less likely to remain undissolved, and niobium or niobic acid can be completely dissolved in water. On the other hand, when the ammonia content is 30% by mass or less, it is preferably close to a saturated aqueous solution of ammonia.

[0118] From this viewpoint, the ammonia content of the ammonia water is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass, while the ammonia content is preferably 30% by mass or less, more preferably 29% by mass or less, and even more preferably 28% by mass or less.

[0119] The amount of niobium fluoride aqueous solution added to the ammonia water is NH ３ / Nb ２ O ５ The molar ratio of NH to NH is preferably 95 or more and 500 or less, more preferably 100 or more and 450 or less, and even more preferably 110 or more and 400 or less. In addition, the amount of niobium fluoride aqueous solution added to ammonia water is adjusted to NH ３ The molar ratio of NH to HF is preferably 3.0 or more, more preferably 4.0 or more, and even more preferably 5.0 or more. ３ The molar ratio of HF to HCl is preferably 100 or less, more preferably 50 or more, and even more preferably 40 or more.

[0120] The time for adding the niobium fluoride aqueous solution to the ammonia water is preferably within 1 minute, more preferably within 30 seconds, and even more preferably within 10 seconds. That is, rather than gradually adding the niobium fluoride aqueous solution over time, it is preferable to add it to the ammonia water in as short a time as possible, for example, by adding it all at once, and carry out the neutralization reaction. In addition, in the reverse neutralization step, the acidic niobium fluoride aqueous solution is added to the alkaline ammonia water, so the neutralization reaction can be carried out while maintaining a high pH. The niobium fluoride aqueous solution and the ammonia water can be used at room temperature.

[0121] Then, fluoride ions are removed from the niobium-containing precipitate slurry obtained by the reverse neutralization method, thereby obtaining a niobium-containing precipitate from which fluoride ions have been removed. Since fluorine compounds such as ammonium fluoride are present as impurities in the niobium-containing precipitate slurry obtained by the reverse neutralization method, it is preferable to remove these.

[0122] Any method for removing fluorine compounds can be used, and examples of such methods include reverse osmosis filtration using aqueous ammonia or pure water, filtration using a membrane such as ultrafiltration or microfiltration, centrifugation, and other known methods. When removing fluoride ions from a niobium-containing precipitate slurry, temperature control is not particularly required, and the removal may be carried out at room temperature.

[0123] Specifically, the niobium-containing precipitate slurry obtained by the reverse neutralization method is decanted using a centrifuge, and washing is repeated until the amount of liberated fluoride ions becomes 100 mg / L or less, thereby obtaining a niobium-containing precipitate from which fluoride ions have been removed.

[0124] The cleaning solution used to remove fluoride ions is preferably ammonia water. Specifically, ammonia water of 5.0 mass % or less is preferred, ammonia water of 4.0 mass % or less is more preferred, ammonia water of 3.0 mass % or less is even more preferred, and ammonia water of 2.5 mass % is particularly preferred. When the ammonia water is 5.0 mass % or less, ammonia containing ammonium ions is suitable for fluoride ions, and unnecessary cost increases can be avoided.

[0125] The niobium-containing precipitate thus obtained, from which fluoride ions have been removed, is diluted with pure water or the like to obtain a precipitate slurry containing niobium from which fluoride ions have been removed. The niobium content of the niobium-containing precipitate slurry can be determined by collecting a portion of the slurry, drying it at 110°C for 24 hours, and then calcining it at 1,000°C for 4 hours to obtain a Nb ２ O ５ The Nb produced in this way ２ O ５The weight of the slurry is measured, and the niobium content of the slurry can be calculated from the weight.

[0126] Next, in the neutralization reaction step, the produced fluoride ions are removed to obtain a niobium-containing precipitate slurry.The niobium-containing precipitate slurry from which the fluoride ions have been removed, a hydroxide of element X (e.g., lithium hydroxide monohydrate), and pure water are mixed together and stirred at 20°C to 100°C for 0.1 to 72 hours to obtain a neutralized aqueous solution of a niobium compound.

[0127] Another example of the method for producing a neutralized aqueous solution of a niobium compound may include a reaction step of producing a niobium fluoride aqueous solution, and a neutralization reaction step of adding the niobium fluoride aqueous solution to an alkaline aqueous solution containing an organic nitrogen compound to produce a neutralized aqueous solution of a niobium compound.

[0128] Here, in this other example of the method for producing a neutralized aqueous solution of a niobium compound, the steps up to obtaining a niobium-containing precipitate slurry from which fluoride ions have been removed are the same as those in the above-mentioned method for producing a neutralized aqueous solution of a niobium compound, and therefore detailed description thereof will be omitted.

[0129] In the same manner as in the above-described method for producing a neutralized aqueous solution of a niobium compound, the resulting niobium-containing precipitate slurry from which fluoride ions have been removed, an organic nitrogen compound, and pure water are mixed together, and the resulting mixture is maintained at 5°C to 90°C for 0.1 to 48 hours with stirring, thereby obtaining a neutralized aqueous solution of a niobium compound.

[0130] The organic nitrogen compound to be mixed with the niobium-containing precipitation slurry is preferably an aliphatic amine, an aromatic amine, an amino alcohol, an amino acid, a polyamine, a quaternary ammonium, a guanidine compound, or an azole compound, as described above, and more preferably an aliphatic amine and / or a quaternary ammonium compound.

[0131] From the viewpoint of solubility, the aliphatic amine is preferably mixed so that the aliphatic amine content in the niobium-containing precipitation slurry is 40% by mass or less, more preferably 20% by mass or less. From the same viewpoint, the aliphatic amine is preferably mixed so that the aliphatic amine content in the niobium-containing precipitation slurry is 0.1% by mass or more, more preferably 1% by mass or more, and may be 5% by mass or more, or may be 10% by mass or more. The aliphatic amine is more preferably methylamine or dimethylamine.

[0132] From the viewpoint of solubility, the quaternary ammonium compound is preferably mixed so that the content of the quaternary ammonium compound in the niobium-containing precipitation slurry is 40% by mass or less, more preferably 20% by mass or less. From the same viewpoint, the quaternary ammonium compound is preferably mixed so that the content of the quaternary ammonium compound in the niobium-containing precipitation slurry is 0.1% by mass or more, more preferably 1% by mass or more, and may be 5% by mass or more, or may be 10% by mass or more. The quaternary ammonium compound is more preferably tetramethylammonium hydroxide (TMAH) or tetraethylammonium hydroxide (TEAH).

[0133] The method for producing a neutralized aqueous solution of a tantalum compound includes a reaction step of adding hydrogen peroxide to an aqueous solution of tantalum fluoride to produce an aqueous solution of a tantalum compound, and a neutralization reaction step of adding the aqueous solution of a tantalum compound to an alkaline aqueous solution containing one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements to produce a neutralized aqueous solution of a tantalum compound.

[0134] First, the tantalum fluoride aqueous solution is prepared by reacting tantalum, tantalum oxide, or tantalum hydroxide with hydrofluoric acid (HF), such as a hydrofluoric acid aqueous solution, to produce tantalum fluoride (H ２ TaF ７ ) and dissolving it in water to prepare the product.

[0135] Here, an acidic tantalum solution containing fluoride ions, for example, a tantalum fluoride aqueous solution, is prepared by adding water (for example, pure water) to convert tantalum into Ta. ２O 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 in terms of conversion is preferred because it results in a tantalic acid compound hydrate that is easily soluble in water, and in order to more reliably synthesize a tantalic acid compound hydrate that is easily soluble in water, a concentration of 90 g / L or less is more preferred, a concentration of 80 g / L or less is even more preferred, and a concentration of 70 g / L or less is particularly preferred. Note that the pH of the tantalum fluoride aqueous solution is preferably 2 or less, more preferably 1 or less, from the viewpoint of completely dissolving tantalum or tantalum oxide.

[0136] Next, in the reaction step of adding hydrogen peroxide to the tantalum fluoride aqueous solution to produce a tantalum compound aqueous solution, the hydrogen peroxide solution is added to the tantalum fluoride aqueous solution and mixed to obtain a tantalum compound aqueous solution. It is presumed that at least a portion of the obtained tantalum compound aqueous solution forms a peroxo complex.

[0137] Here, the hydrogen peroxide content of the hydrogen peroxide solution added to the tantalum fluoride aqueous solution is preferably 0.5% by mass to 35% by mass. ２ O ２ It is preferable to add hydrogen peroxide so that / Ta is 0.6 or more and 1.5 or less, and since there is a possibility that hydrogen peroxide may decompose during mixing, it is more preferable that it is 0.7 or more and 1.2 or less.

[0138] The neutralization reaction step in which the obtained aqueous tantalum compound solution is added to an alkaline aqueous solution containing one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements to produce a neutralized aqueous tantalum compound solution is as follows.

[0139] In the neutralization reaction step, the obtained aqueous tantalum compound solution is first added to aqueous ammonia, i.e., a reverse neutralization method is used to obtain a precipitate slurry containing tantalum. Fluoride ions are then removed from the obtained precipitate slurry containing tantalum, thereby obtaining a tantalum-containing precipitate from which fluoride ions have been removed.

[0140] The ammonia content of the ammonia water used for reverse neutralization is preferably 10% by mass to 30% by mass. When the ammonia content is 10% by mass, tantalum is less likely to remain undissolved, and tantalum or tantalic acid can be completely dissolved in water. On the other hand, when the ammonia content is 30% by mass or less, the ammonia content is close to a saturated aqueous solution of ammonia, which is preferable.

[0141] From this viewpoint, the ammonia content of the ammonia water is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass or more, while the ammonia content is preferably 30% by mass or less, more preferably 29% by mass or less, and even more preferably 28% by mass or less.

[0142] The amount of tantalum fluoride aqueous solution added to the ammonia water is NH ３ The molar ratio of NH 3 to Ta is preferably 95 or more and 500 or less, more preferably 100 or more and 450 or less, and even more preferably 110 or more and 400 or less. In addition, the amount of tantalum fluoride aqueous solution added to the ammonia water is set to NH 3 from the viewpoint of generating tantalic acid compounds that are soluble in amines or diluted ammonia water. ３ The molar ratio of NH to HF is preferably 3.0 or more, more preferably 4.0 or more, and even more preferably 5.0 or more. ３ The molar ratio of HF to HCl is preferably 100 or less, more preferably 50 or less, and even more preferably 40 or less.

[0143] The time for adding the tantalum fluoride aqueous solution to the ammonia water is preferably within 10 minutes, more preferably within 8 minutes, and even more preferably within 5 minutes. That is, rather than gradually adding the tantalum fluoride aqueous solution over time, it is preferable to add it to the ammonia water in as short a time as possible, for example, by adding it all at once, and carry out the neutralization reaction. In addition, since the acidic tantalum fluoride aqueous solution is added to the alkaline ammonia water, the neutralization reaction can be carried out while maintaining a high pH. Note that the tantalum fluoride aqueous solution and the ammonia water can be used at room temperature.

[0144] Then, by removing fluoride ions from the tantalum-containing precipitate slurry obtained by the reverse neutralization method, a tantalum-containing precipitate from which fluoride ions have been removed can be obtained. Since fluorine compounds such as ammonium fluoride are present as impurities in the tantalum-containing precipitate slurry obtained by the reverse neutralization method, it is preferable to remove these.

[0145] Any method for removing fluorine compounds can be used, and examples of methods that can be used include reverse osmosis filtration using aqueous ammonia or pure water, filtration using a membrane such as ultrafiltration or microfiltration, centrifugation, and other known methods. When removing fluoride ions from a tantalum-containing precipitate slurry, temperature control is not particularly required, and the removal can be carried out at room temperature.

[0146] Specifically, the tantalum-containing precipitate slurry obtained by the reverse neutralization method is decanted using a centrifuge and repeatedly washed until the amount of liberated fluoride ions becomes 100 mg / L or less, thereby obtaining a tantalum-containing precipitate from which fluoride ions have been removed. Note that by repeating this washing, the hydrogen peroxide added in the reaction step is also removed.

[0147] The cleaning solution used to remove fluoride ions is preferably ammonia water. Specifically, ammonia water having a concentration of 1 mass % to 35 mass % is preferred. With such ammonia water, ammonia is suitable for fluoride ions, and unnecessary cost increases can be avoided.

[0148] Next, in the neutralization reaction step, the tantalum-containing precipitate from which the produced fluoride ions have been removed is diluted with pure water or the like to obtain a tantalum-containing precipitate slurry from which the fluoride ions have been removed.The tantalum-containing precipitate slurry from which the fluoride ions have been removed, a hydroxide of element X, for example, lithium hydroxide monohydrate, and pure water are mixed together and maintained at 5°C to 100°C for 0.1 to 72 hours with stirring to obtain a neutralized aqueous tantalum compound solution.

[0149] Another example of the method for producing a neutralized aqueous tantalum compound solution may include a reaction step of adding hydrogen peroxide to an aqueous tantalum fluoride solution to produce an aqueous tantalum compound solution, and a neutralization reaction step of adding the aqueous tantalum compound solution to an alkaline aqueous solution containing an organic nitrogen compound to produce a neutralized aqueous tantalum compound solution.

[0150] In this other example of the method for producing a neutralized aqueous solution of a tantalum compound, the steps up to obtaining a tantalum-containing precipitate slurry from which fluoride ions have been removed are the same as those in the above-mentioned method for producing a neutralized aqueous solution of a tantalum compound, and therefore detailed description thereof will be omitted.

[0151] In the same manner as in the above-described method for producing a neutralized aqueous solution of a tantalum compound of the present invention, the resulting tantalum-containing precipitate slurry from which fluoride ions have been removed, an organic nitrogen compound, and pure water are mixed together, and the resulting mixture is maintained at 5°C to 90°C for 0.1 to 48 hours with stirring, thereby obtaining a neutralized aqueous solution of a tantalum compound.

[0152] As described above, the organic nitrogen compound to be mixed with the tantalum-containing precipitation slurry is preferably an aliphatic amine, an aromatic amine, an amino alcohol, an amino acid, a polyamine, a quaternary ammonium, a guanidine compound, or an azole compound, and is particularly preferably an aliphatic amine and / or a quaternary ammonium compound.

[0153] From the viewpoint of solubility, the aliphatic amine is preferably mixed so that the aliphatic amine content in the tantalum-containing precipitation slurry is 40 mass% or less, more preferably 20 mass% or less. From the same viewpoint, the aliphatic amine is preferably mixed so that the aliphatic amine content in the tantalum-containing precipitation slurry is 0.1 mass% or more, more preferably 1 mass% or more, and may be 5 mass% or more, or even 10 mass% or more. The aliphatic amine is more preferably methylamine or dimethylamine.

[0154] Furthermore, from the viewpoint of solubility, the quaternary ammonium compound is preferably mixed so that the content of the quaternary ammonium compound in the tantalum-containing precipitation slurry is 40% by mass or less, more preferably 20% by mass or less. From the same viewpoint, the quaternary ammonium compound is preferably mixed so that the content of the quaternary ammonium compound in the tantalum-containing precipitation slurry is 0.1% by mass or more, more preferably 1% by mass or more, and may be 5% by mass or more, or even 10% by mass or more. The quaternary ammonium compound is more preferably tetramethylammonium hydroxide (TMAH) or tetraethylammonium hydroxide (TEAH).

[0155] The neutralized aqueous solution of a molybdenum compound may be prepared by dissolving commercially available lithium molybdate in pure water.

[0156] Specifically, lithium molybdate is mixed with pure water so that the final mixture has a molybdenum content of 0.001% by mass or more and 22% by mass or less in terms of Mo atoms and a lithium-to-molybdenum molar ratio (Li / Mo) of 0.001 to 5, and the mixture is stirred while maintaining the liquid temperature at 25°C for 1 hour to obtain a neutralized aqueous solution of a molybdenum compound. Lithium hydroxide may be added when mixing lithium molybdate with pure water. Furthermore, the following concentration adjustment step may be performed to remove ammonia components from the resulting neutralized aqueous solution of a molybdenum compound. In the concentration adjustment step, the mixture is heated and stirred at, for example, 60°C to 90°C for 1 hour to 100 hours, and then cooled to room temperature. Subsequently, a solvent (e.g., pure water) is added to replenish the evaporated solvent (e.g., pure water). The amount of solvent added is adjusted so that the molybdenum content of the neutralized aqueous solution of a molybdenum compound after the removal of the ammonia components is equal to the molybdenum content of the neutralized aqueous solution of a molybdenum compound before the removal of the ammonia components.

[0157] The method for producing a neutralized aqueous solution of a tungsten compound includes a step of mixing an alkaline aqueous solution containing ammonium paratungstate and one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements with pure water, and maintaining the mixture at 20°C to 100°C while stirring to obtain a neutralized aqueous solution of a tungsten compound.

[0158] A neutralized aqueous solution of a tungsten compound is obtained by mixing a mixture of ammonium paratungstate, lithium hydroxide monohydrate (an alkaline aqueous solution containing ammonium paratungstate, one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements), and pure water, and maintaining the mixture at 15°C to 100°C for 5 minutes to 1 hour while stirring. The following concentration adjustment step may be performed to remove the ammonia component from the resulting neutralized aqueous solution of a tungsten compound. In the concentration adjustment step, the mixture is heated and stirred at 60°C to 90°C for 1 hour to 100 hours, and then cooled to room temperature. Subsequently, a solvent (e.g., pure water) is added to replenish the evaporated solvent (e.g., pure water). The amount of solvent added is adjusted so that the tungsten content of the neutralized aqueous solution of a tungsten compound after the removal of the ammonia component is the same as the tungsten content of the neutralized aqueous solution of a tungsten compound before the removal of the ammonia component.

[0159] As another example of the method for producing a neutralized aqueous solution of a tungsten compound, tungsten is treated with WO ３ An example of a production method includes the steps of adding an acidic tungsten aqueous solution containing 1 to 100 g / L of tungsten in terms of tungsten ion concentration to a 10 to 30 mass % ammonia aqueous solution to produce a tungsten-containing precipitate; adding an organic nitrogen compound to the tungsten-containing precipitate slurry obtained by slurrying the tungsten-containing precipitate to produce a tungsten acid dispersion; and adding lithium hydroxide and pure water to the tungsten acid dispersion to produce a neutralized tungsten compound aqueous solution.

[0160] Specifically, tungsten is WO ３ In the step of adding an acidic tungsten aqueous solution containing 1 to 100 g / L of tungsten in terms of tungsten sulfate equivalent to tungsten sulfate, to a 10 to 30 mass % aqueous ammonia solution, to produce a tungsten-containing precipitate, the acidic tungsten aqueous solution refers to a tungsten sulfate aqueous solution obtained by solvent extraction of a solution in which tungsten is dissolved in an acidic aqueous solution containing sulfuric acid.

[0161] Here, the tungsten sulfate aqueous solution is prepared by adding water (e.g., pure water) to convert tungsten into WO ３It is preferable to adjust the tungsten content to 1 to 100 g / L in terms of WO ３ When the tungsten content is 1 g / L or more in terms of WO, a tungsten acid compound hydrate that is easily soluble in water is obtained, which is preferable, and when productivity is taken into consideration, a tungsten content of 10 g / L or more is more preferable, and a tungsten content of 20 g / L or more is even more preferable. ３ A converted concentration of 100 g / L or less is preferable because it results in a tungstic acid compound hydrate that is easily soluble in water, and in order to more reliably synthesize a tungstic acid compound hydrate that is easily soluble in water, a concentration of 90 g / L or less is more preferable, a concentration of 80 g / L or less is even more preferable, and a concentration of 70 g / L or less is particularly preferable. Note that, from the viewpoint of completely dissolving tungsten or tungsten oxide, the pH of the tungsten sulfate aqueous solution is preferably 2 or less, and more preferably 1 or less.

[0162] When the aqueous tungsten sulfate solution is added to the aqueous ammonia solution, in a so-called reverse neutralization method, it is preferable to add the aqueous tungsten sulfate solution to a 10 mass % to 30 mass % aqueous ammonia solution, i.e., to obtain a slurry of a tungsten acid compound hydrate, that is, a slurry of a tungsten-containing precipitate, by the reverse neutralization method.

[0163] The ammonia content of the aqueous ammonia solution used for reverse neutralization is preferably 10% by mass to 30% by mass. When the ammonia content is 10% by mass, tungsten is less likely to remain undissolved, and tungsten or tungsten oxide can be completely dissolved in water. On the other hand, when the ammonia content is 30% by mass or less, the solution is close to a saturated aqueous ammonia solution, which is preferable.

[0164] From this viewpoint, the ammonia content of the aqueous ammonia solution is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass, while the ammonia content is preferably 30% by mass or less, more preferably 29% by mass or less, and even more preferably 28% by mass or less.

[0165] In the reverse neutralization, the amount of tungsten sulfate aqueous solution added to the ammonia water is NH３ / WO ３ The molar ratio of NH to NH is preferably 0.1 or more and 300 or less, more preferably 5 or more and 200 or less. In addition, the tungsten sulfate aqueous solution added to the ammonia water contains NH from the viewpoint of generating a tungsten acid compound that is soluble in amines or diluted ammonia water. ３ / SO ４ ２－ On the other hand, from the viewpoint of cost reduction, the molar ratio of NH ３ / SO ４ ２－ The molar ratio is preferably 200 or less, more preferably 150 or less, and even more preferably 100 or less.

[0166] In the reverse neutralization, the time required for adding the tungsten sulfate aqueous solution to the ammonia water is preferably within 1 minute, more preferably within 30 seconds, and even more preferably within 10 seconds. That is, rather than gradually adding the tungsten sulfate aqueous solution over time, it is preferable to add it to the ammonia water in as short a time as possible, for example, by adding it all at once, and carry out the neutralization reaction. In addition, in the reverse neutralization, since the acidic tungsten sulfate aqueous solution is added to the alkaline ammonia water, the neutralization reaction can be carried out while maintaining a high pH. The tungsten sulfate aqueous solution and the ammonia water can be used at room temperature.

[0167] The sulfur content is then removed from the slurry of the tungsten-containing precipitate obtained by the reverse neutralization method to produce a sulfur-free tungsten-containing precipitate. The slurry of the tungsten-containing precipitate obtained by the reverse neutralization method contains, as impurities, sulfate ions that remain without reacting with tungsten or tungsten oxide, and sulfur content in the form of hydrogen sulfate ions, and it is therefore preferable to remove these.

[0168] Any method for removing sulfur may be used, and examples of methods that can be used include reverse osmosis filtration using aqueous ammonia or pure water, filtration using a membrane such as ultrafiltration or microfiltration, centrifugation, and other known methods. Note that temperature control is not particularly required when removing sulfur from the tungsten-containing precipitate slurry, and the removal may be carried out at room temperature.

[0169] Specifically, the tungsten-containing precipitate slurry obtained by the reverse neutralization method is decanted using a centrifuge, and washing is repeated until the conductivity of the tungsten-containing precipitate slurry reaches 500 μS / cm or less, thereby obtaining a tungsten-containing precipitate from which the sulfur content has been removed. The conductivity was measured by adjusting the liquid temperature of the tungsten-containing precipitate slurry to 25°C, immersing the measuring part of a conductivity meter (ASCON2 manufactured by AS ONE Corporation) in the supernatant liquid of the precipitate slurry, and reading the conductivity value after it stabilized.

[0170] The cleaning solution used to remove sulfur is preferably ammonia water. Specifically, ammonia water of 5.0 mass % or less is preferred, ammonia water of 4.0 mass % or less is more preferred, ammonia water of 3.0 mass % or less is even more preferred, and ammonia water of 2.5 mass % is particularly preferred. When the ammonia water is 5.0 mass % or less, ammonia containing ammonium ions is suitable for the sulfur content, and unnecessary increases in costs can be avoided.

[0171] Next, in the step of adding an organic nitrogen compound to the tungsten-containing precipitate slurry obtained by slurriing the tungsten-containing precipitate, the tungsten-containing precipitate slurry is obtained by diluting the tungsten-containing precipitate from which the sulfur content has been removed with pure water or the like to obtain a slurry. The tungsten content of the tungsten-containing precipitate slurry from which the sulfur content has been removed can be determined by taking a portion of the slurry, drying it at 110°C for 24 hours, and then calcining it at 1,000°C for 4 hours to obtain a tungsten content of WO ３ The WO ３ The weight of the slurry is measured, and the tungsten content of the slurry can be calculated from the weight.

[0172] Then, an organic nitrogen compound is mixed with the tungsten-containing precipitate slurry from which the sulfur content has been removed, thereby obtaining a tungstic acid dispersion.

[0173] Specifically, the tungsten content of the final mixture is WO ３ The obtained tungsten-containing precipitate slurry is added to an organic nitrogen compound so that the tungsten-containing precipitate slurry has a tungsten content of 0.1 mass % or more and 40 mass % or less, calculated as tungsten content, and the resulting mixture is mixed with pure water. The mixture is stirred while maintaining the liquid temperature at room temperature (25°C) for 1 hour, thereby obtaining a colorless and transparent tungstic acid dispersion.

[0174] Preferably, the organic nitrogen compound mixed with the tungsten-containing precipitation slurry is an aliphatic amine and / or a quaternary ammonium.

[0175] From the viewpoint of solubility, the aliphatic amine is preferably mixed so that the aliphatic amine content in the tungsten-containing precipitate slurry is 40 mass % or less, more preferably 0.1 mass % to 30 mass %, even more preferably 0.5 mass % to 20 mass %, and particularly preferably 1 mass % to 10 mass %. The aliphatic amine is more preferably methylamine, dimethylamine, ethylamine, trimethylamine, or a mixture thereof.

[0176] On the other hand, from the viewpoint of solubility, the quaternary ammonium is preferably mixed so that the content of the quaternary ammonium in the tungsten-containing precipitate slurry is 40% by mass or less, more preferably 0.1% by mass or more and 30% by mass or less, even more preferably 0.5% by mass or more and 20% by mass or less, and particularly preferably 1% by mass or more and 10% by mass or less. The quaternary ammonium is more preferably tetramethylammonium hydroxide (TMAH) or tetraethylammonium hydroxide (TEAH).

[0177] Furthermore, the organic nitrogen compound to be mixed with the tungsten-containing precipitation slurry may be a mixture of two or more of aliphatic amines or quaternary ammonium compounds, rather than a single compound. For example, a mixture of two or more organic nitrogen compounds, such as methylamine and tetramethylammonium hydroxide (TMAH), dimethylamine and tetramethylammonium hydroxide (TMAH), or methylamine and dimethylamine, or a mixture of three or more organic nitrogen compounds, such as methylamine, dimethylamine, and tetramethylammonium hydroxide (TMAH), may be used. The mixture may be appropriately selected depending on the application.

[0178] The tungstic acid dispersion thus produced, lithium hydroxide monohydrate, and pure water are weighed out so that the molar ratio Li / W of lithium to tungsten in the final mixture is 0.2 or more and 20 or less, and the resulting mixture is stirred and held at 10°C to 100°C for 1 minute to 3 days, thereby obtaining a neutralized aqueous solution of a tungsten compound.

[0179] Specifically, a tungsten compound neutralized aqueous solution is obtained by mixing and stirring a tungsten acid dispersion, lithium hydroxide monohydrate, and pure water so that the tungsten content of the final mixture is 0.001% by mass or more and 23% by mass or less in terms of W atoms and the lithium to tungsten molar ratio Li / W is 0.001% by mass or more and 5% by mass or less. Furthermore, the following concentration adjustment step may be performed to remove ammonia components contained in the resulting tungsten compound neutralized aqueous solution. In the concentration adjustment step, the mixture is heated and stirred at, for example, 60°C to 90°C for 1 hour to 100 hours, and then cooled to room temperature. Subsequently, a solvent (e.g., pure water) is added to replenish the evaporated solvent (e.g., pure water). The amount of solvent added is adjusted so that the tungsten content of the tungsten compound neutralized aqueous solution after the ammonia component removal is the same as the tungsten content of the tungsten compound neutralized aqueous solution before the ammonia component removal.

[0180] The method for producing a neutralized aqueous solution of a titanium compound includes the steps of mixing a titanium salt solution with aqueous ammonia to produce a neutralized reaction solution, washing a titanium-containing precipitate produced in the neutralized reaction solution, and mixing the washed titanium-containing precipitate with a quaternary ammonium salt and water to obtain a neutralized aqueous solution of a titanium compound.

[0181] The titanium salt solution may be any solution in which titanium is dissolved, and examples thereof include an aqueous titanyl sulfate solution, an aqueous titanyl chloride solution, and an aqueous titanium fluoride solution.

[0182] The titanyl sulfate aqueous solution is obtained by dissolving titanyl sulfate in hot water. ２ It is preferable to adjust the content so that it is 8 to 15 mass % in terms of converted value.

[0183] A neutralized reaction solution can be produced by mixing and reacting the above-mentioned titanium salt solution, for example, an aqueous titanyl sulfate solution with aqueous ammonia. Here, it is preferable to carry out so-called reverse neutralization, in which the aqueous titanyl sulfate solution is added to aqueous ammonia and reacted.

[0184] The ammonia content of the aqueous ammonia solution used for reverse neutralization is preferably 10% by mass to 40% by mass. If the ammonia content is 25% by mass, titanium is less likely to remain undissolved, and titanium or titanium oxide can be completely dissolved in water. On the other hand, if the ammonia content is 30% by mass or less, the solution is close to a saturated aqueous ammonia solution, which is preferable.

[0185] From this viewpoint, the ammonia content of the aqueous ammonia solution is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass, while the ammonia content is preferably 30% by mass or less, more preferably 35% by mass or less, and even more preferably 40% by mass or less.

[0186] In the reverse neutralization, the amount of titanyl sulfate aqueous solution added to the ammonia water is NH ３ / TiO ２The molar ratio of NH to NH is preferably 1 or more and 200 or less, more preferably 10 or more and 100 or less. In addition, the titanyl sulfate aqueous solution to be added to the ammonia water contains NH from the viewpoint of producing a titanic acid compound that dissolves in diluted ammonia water. ３ / SO ４ ２－ The molar ratio of NH is preferably 1 or more, more preferably 5 or more, and even more preferably 10 or more. ３ / SO ４ ２－ The molar ratio is preferably 50 or less, more preferably 40 or less, and even more preferably 30 or less.

[0187] In the reverse neutralization, the time required for adding the titanyl sulfate aqueous solution to the ammonia water is preferably within 1 minute, more preferably within 30 seconds, and even more preferably within 10 seconds. That is, rather than gradually adding the titanyl sulfate aqueous solution over a period of time, it is preferable to add it to the ammonia water in as short a time as possible, for example, all at once, to carry out the neutralization reaction. Furthermore, in the reverse neutralization, since the acidic titanyl sulfate aqueous solution is added to the alkaline ammonia water, the neutralization reaction can be carried out while maintaining a high pH.

[0188] The slurry of titanium-containing precipitate in the neutralization reaction solution obtained by reverse neutralization is washed to remove impurities and obtain a titanium-containing precipitate. The slurry of titanium-containing precipitate obtained by reverse neutralization contains unnecessary components other than titanium or titanium oxide hydrates or ions and ammonia, such as sulfate compounds such as ammonium sulfate, as impurities, and it is therefore preferable to remove these.

[0189] Any washing method, for example, a method for removing sulfate compounds, can be used. For example, a method using a membrane such as reverse osmosis filtration, ultrafiltration, or microfiltration using aqueous ammonia or pure water, as well as centrifugation and other known methods can be used. Note that these steps may be carried out at room temperature, and there is no particular need to adjust the temperature of each step.

[0190] Then, to the titanium-containing precipitate obtained after removing the impurities, a dispersion medium such as water and a quaternary ammonium salt are added, and the mixture is stirred as necessary to promote the reaction, thereby producing a neutralized aqueous solution of the titanium compound.

[0191] Examples of the quaternary ammonium salt include tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, methyltripropylammonium hydroxide, methyltributylammonium hydroxide, tetrapentylammonium hydroxide, tetrahexylammonium hydroxide, ethyltrimethylammonium hydroxide, dimethyldiethylammonium hydroxide, benzyltrimethylammonium hydroxide, hexadecyltrimethylammonium hydroxide, and (2-hydroxyethyl)trimethylammonium hydroxide.

[0192] As described above, the amount of quaternary ammonium salt added is such that the greater the amount of quaternary ammonium, the greater the solubility of titanium or titanic acid in water, and therefore, in the above step, a quaternary ammonium salt containing 0.44 mol or more of quaternary ammonium per mol of titanium contained in the titanium-containing precipitate after washing is preferably mixed. On the other hand, from the viewpoint that an excessive amount of quaternary ammonium may cause problems such as impeding film-forming properties or inhibiting catalytic action, it is preferable to mix a quaternary ammonium salt having 1.0 mol or less of quaternary ammonium per mol of titanium contained in the titanium-containing precipitate after washing.

[0193] Each step in the above-described method for producing a neutralized aqueous titanium compound solution may be carried out at room temperature, and there is no particular need to adjust the temperature of each step.

[0194] Furthermore, titanium alkoxides may be used as the neutralized aqueous solution of titanium compounds. Examples of titanium alkoxides include titanium tetraisopropoxide, titanium i-propoxide, titanium n-butoxide, titanium 2-ethylhexoxide, titanium tert-butoxide, titanium stearyl alkoxide, and tetraisopropoxy titanium.

[0195] Another example of the method for producing a metal acid compound dispersion of the present invention may include a step of mixing one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements with a phosphorus compound, or a phosphorus compound solution and / or a chlorine compound, or a chlorine compound solution to produce a phosphorus compound mixed solution and / or a chlorine compound mixed solution, and a mixing step of mixing the phosphorus compound mixed solution and / or the chlorine compound mixed solution with a neutralized aqueous solution of metal compounds containing two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium.

[0196] First, one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements are mixed with a phosphorus compound, or a phosphorus compound solution and / or a chlorine compound, or a chlorine compound solution to produce a phosphorus compound mixed solution and / or a chlorine compound mixed solution.

[0197] Here, the one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements include, for example, lithium hydroxide monohydrate.

[0198] The phosphorus compound may contain at least one selected from inorganic phosphorus compounds, organic phosphorus compounds, and salts thereof.

[0199] Furthermore, it is preferable that the phosphorus compound contains one or more compounds 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.

[0200] Alternatively, the metal oxide compound dispersion of the present invention may be a phosphorus compound solution obtained by adding pure water to the above-mentioned phosphorus compound and adjusting the concentration so that the phosphorus content in terms of P atoms in the metal oxide compound dispersion of the present invention is 0.01 mass % or more and 10 mass % or less.

[0201] Examples of chlorine compounds include hydrochloric acid (CAS number: 7647-01-0), hypochlorous acid (CAS number: 7790-92-3), chlorous acid (CAS number: 13898-47-0), chloric acid (CAS number: 7790-93-4), and perchloric acid (CAS number: 7601-90-3).

[0202] The chlorine compound may also 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, with ammonium salts and lithium salts being preferred. 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).

[0203] Alternatively, the metal oxide compound dispersion of the present invention may be a chlorine compound solution obtained by adding pure water to the above-mentioned chlorine compound and adjusting the concentration so that the chlorine content in terms of Cl atoms in the metal oxide compound dispersion of the present invention is 0.0 mass % or more and 2.0 mass % or less.

[0204] Then, by mixing the phosphorus compound mixed solution and / or the chlorine compound mixed solution with a neutralized aqueous solution of a metal compound containing two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium, the metal acid compound dispersion of the present invention is obtained.

[0205] The aqueous solution of neutralized metal compounds containing two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium can be an aqueous solution of neutralized metal compounds obtained by the above-mentioned method for producing an aqueous solution of neutralized metal compounds.

[0206] In order to remove the ammonia component contained in the metal acid compound dispersion of the present invention obtained by the above-mentioned production method, the following concentration adjustment step may be carried out. In the concentration adjustment step, the dispersion is heated and stirred, for example, at 60°C to 90°C for 1 hour to 100 hours, and then cooled to room temperature. Thereafter, a solvent (e.g., pure water) is added to replenish the evaporated solvent (e.g., pure water). The amount of solvent added is adjusted so that the content of the metal species M in the metal acid compound dispersion of the present invention after the ammonia component has been removed matches the content of the metal species M in the metal acid compound dispersion of the present invention before the ammonia component has been removed.

[0207] Specifically, the metal acid compound dispersion of the present invention is obtained by mixing and stirring the obtained metal compound neutralized aqueous solution with a phosphorus compound or a phosphorus compound solution and / or a chlorine compound or a chlorine compound solution so that the content of the metal species M in the final mixture is 0.1 mass % to 30 mass % in terms of atoms of the metal species M. The composition ratio of each component in the metal acid compound dispersion of the present invention obtained in this manner is preferably as follows:

[0208] When the element X contained in the metal acid compound dispersion of the present invention is lithium, the molar ratio Li / (P+Cl) of lithium (Li) to the total amount of phosphorus compounds and / or chlorine compounds (P+Cl) is preferably from 0.01 to 5 in terms of improving dispersibility and solubility in water, more preferably from 0.01 to 2, even more preferably from 0.05 to 2, and particularly preferably from 0.1 to 1.95. When the element X contained in the metal acid compound dispersion of the present invention is an element X selected from alkali metal elements and / or alkaline earth metal elements other than lithium, the molar ratio x / (P+Cl) of the total amount of element X (x) to the total amount of phosphorus compounds and / or chlorine compounds (P+Cl) is also preferably from 0.01 to 5 in terms of improving dispersibility and solubility in water, more preferably from 0.01 to 2, even more preferably from 0.05 to 2, and particularly preferably from 0.1 to 1.95. The element X may be a combination of lithium and other alkali metal elements and / or alkaline earth metal elements, or may be a combination of alkali metal elements other than lithium and / or alkaline earth metal elements.

[0209] When the element X contained in the metal acid compound dispersion of the present invention is lithium, the molar ratio Li / P of lithium (Li) to the total amount of phosphorus compounds (P) is preferably 0.01 to 5 in terms of improving dispersibility and solubility in water, more preferably 0.01 to 2, even more preferably 0.05 to 2, and particularly preferably 0.1 to 1.95. When the element X contained in the metal acid compound dispersion of the present invention is an element X selected from alkali metal elements and / or alkaline earth metal elements other than lithium, the molar ratio x / P of the total amount of element X (x) to the total amount of phosphorus compounds (P) is also preferably 0.01 to 5 in terms of improving dispersibility and solubility in water, more preferably 0.01 to 2, even more preferably 0.05 to 2, and particularly preferably 0.1 to 1.95.

[0210] Furthermore, the molar ratio m / (P+Cl) of the total amount (m) of metal species M contained in the metal acid compound dispersion of the present invention to the total amount (P+Cl) of phosphorus compounds and / or chlorine compounds is preferably 0.01 or more and 10 or less, from the viewpoint of improving dispersibility and solubility in water, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0211] Furthermore, the molar ratio m / P of the total amount (m) of metal species M contained in the metal acid compound dispersion of the present invention to the total amount (P) of phosphorus compounds is preferably 0.01 or more and 10 or less, in terms of improving dispersibility and solubility in water, more preferably 0.05 or more and 5 or less, even more preferably 0.1 or more and 3 or less, and particularly preferably 0.1 or more and 1.95 or less.

[0212] Furthermore, when the element X contained in the metal acid compound dispersion liquid of the present invention is lithium, the molar ratio Li / m of lithium (Li) to the total amount (m) of metal species M is preferably 0.01 or more and 10 or less, from the viewpoint of improving dispersibility and solubility in water, more preferably 0.05 or more and 9 or less, even more preferably 0.1 or more and 8 or less, and particularly preferably 1 or more and 7 or less. When the element X contained in the metal acid compound dispersion liquid of the present invention is an element X selected from alkali metal elements and / or alkaline earth metal elements other than lithium, the molar ratio m / x of the total amount (x) of element X to the total amount (m) of metal species M is also preferably 0.01 or more and 10 or less, from the viewpoint of improving dispersibility and solubility in water, more preferably 0.05 or more and 9 or less, even more preferably 0.1 or more and 8 or less, and particularly preferably 1 or more and 7 or less. Note that this also includes cases where the element X is a combination of multiple elements, such as lithium and other alkali metal elements and / or alkaline earth metal elements, and cases where the element X is a combination of multiple elements selected from alkali metal elements and / or alkaline earth metals other than lithium.

[0213] The order of adding the metal compound neutralized aqueous solution, the phosphorus compound or phosphorus compound solution and / or the chlorine compound or chlorine compound solution, one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, pure water, etc., which are mixed in the mixing step of the method for producing a metal acid compound dispersion of the present invention, is not limited to the order described above and can be changed as appropriate.

[0214] 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.

[0215] Among the metal acid compound powders, a method for producing a dry powder of a metal acid compound involves placing the metal acid compound dispersion obtained by the method for producing the metal acid compound dispersion of the present invention described above in a static furnace and drying, for example vacuum drying, for 1 hour to 72 hours at a heating temperature of about 60°C to 200°C, thereby evaporating the water content of the metal acid compound dispersion of the present invention and producing a dry powder of the metal acid compound containing crystal particles of the metal acid compound contained in the metal acid compound dispersion of the present invention.

[0216] On the other hand, a method for producing a calcined powder of a metal acid compound includes vacuum-drying the metal acid compound dispersion of the present invention as described above, placing the obtained dry powder of the metal acid compound in a static furnace, and calcining it in the atmosphere at a calcination temperature of 300°C or higher and 1,200°C or lower for a calcination time of 1 hour or higher and 72 hours or lower, thereby obtaining a calcined powder of the metal acid compound.

[0217] 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.

[0218] 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.

[0219] 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.

[0220] 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.

[0221] 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.

[0222] 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.

[0223] 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.

[0224] Furthermore, a method for producing a positive electrode active material for a lithium ion secondary battery coated with a metal acid compound contained in the metal acid compound dispersion of the present invention will be described below.

[0225] 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.

[0226] First, the metal oxide compound dispersion of the present invention is diluted with pure water, and a positive electrode active material for a battery, for example, LiMn 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.

[0227] 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.

[0228] 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".

[0229] The metal acid compound dispersion of the present invention has high dispersibility in polar solvents, particularly water, good solubility in water, and excellent storage stability. Furthermore, the method for producing a metal acid compound dispersion of the present invention can produce a metal acid compound dispersion that has high dispersibility in polar solvents, particularly water, good solubility in water, and excellent storage stability.

[0230] 1 is a table listing the compositions of metal acid compound dispersions according to Examples 1 to 19 of the present invention and Comparative Examples 1 to 4. 2 is a table listing the composition ratios of metal acid compound dispersions according to Examples 1 to 19 of the present invention and Comparative Examples 1 to 4. 3 is a table listing the measurement results of metal acid compound dispersions according to Examples 1 to 19 of the present invention and Comparative Examples 1 to 4.

[0231] The metal oxide compound dispersion liquid according to the embodiment of the present invention will be further described below with reference to the following examples, although the present invention is not limited to these examples.

[0232] Example 1 0.3 g of pyrophosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name: diphosphoric acid (containing phosphoric acid), CAS number: 2466-09-3) and 26.48 g of pure water were placed in a polypropylene container, and 4.23 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the resulting aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0233] Here, the 5 mass % lithium hydroxide monohydrate aqueous solution is LiOH·H ２ It was obtained by mixing 15 g of 0 with 285 g of pure water.

[0234] Then, 1.63 g of a niobium compound neutralized aqueous solution and 2.25 g of a tantalum compound neutralized aqueous solution, which will be described later, were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes, thereby obtaining a metal acid compound dispersion liquid according to Example 1.

[0235] The neutralized aqueous solution of a niobium compound according to Example 1 was obtained as follows.

[0236] 100 g of niobium pentoxide was dissolved in 200 g of 55% aqueous hydrofluoric acid solution, and 830 mL of pure water was added to obtain a niobium fluoride aqueous solution containing 100 g / L of niobium calculated as NbO (NbO = 8.85 wt%). 200 mL of this niobium fluoride aqueous solution was added to 1 L of aqueous ammonia (NH concentration 25 wt%) over a period of less than 1 minute (NH / NbO molar ratio = 176.9, NH / HF molar ratio = 12.1) to obtain a reaction solution (pH 11). This reaction solution was a slurry of niobium acid compound hydrate, in other words, a slurry of niobium-containing precipitate.

[0237] The reaction solution was then decanted using a centrifuge and washed until the amount of liberated fluoride ions was 100 mg / L or less, thereby obtaining a niobium-containing precipitate from which the fluoride ions had been removed. At this time, aqueous ammonia was used as the washing liquid.

[0238] Furthermore, the niobium-containing precipitate from which the fluoride ions had been removed was diluted with pure water to obtain a slurry. A portion of this slurry was dried at 110°C for 24 hours and then calcined at 1,000°C for 4 hours to produce NbO, and the weight of the NbO contained in the slurry was calculated. ２ O ５ The content was calculated.

[0239] The niobium-containing precipitate slurry diluted with pure water, 5 mass % lithium hydroxide, and pure water were mixed to obtain a translucent slurry mixture. This mixture was stirred and maintained at a liquid temperature of 50°C to 100°C, for example, 70°C, for 1 hour to obtain a neutralized aqueous solution of a niobium compound according to Example 1. The niobium content in the neutralized aqueous solution of a niobium compound according to Example 1 was 2.86 mass %, and the lithium content was 0.23 mass %.

[0240] The neutralized aqueous solution of a tantalum compound according to Example 1 was obtained as follows.

[0241] First, 137.9 g of tantalum hydroxide (Ta ２ O ５ A tantalum fluoride aqueous solution (Ta 66 mass%) was dissolved in 120 g of a 55 mass% hydrofluoric acid aqueous solution, and 849 mL of pure water was added to the solution. ２ O ５ A content of 8.2% by mass was obtained.

[0242] 1,000 g of this tantalum fluoride aqueous solution was mixed with 36.1 g of hydrogen peroxide (H ２ O ２ Content 35 mass%) was added (H ２ O ２ The mixture was stirred for 5 minutes (molar ratio of tantalum to tantalum = 1.0), to obtain an aqueous solution of a tantalum compound.

[0243] 1,036.1 g of this tantalum compound aqueous solution was added to 6.82 L of ammonia water (NH3 concentration 25 mass %) over a period of less than 1 minute (NH ３ / Ta molar ratio = 245, NH ３ A reaction solution (pH 11) was obtained (mole ratio of HCl / HF=30.6). This reaction solution was a slurry of a tantalic acid compound hydrate, in other words, a slurry of a tantalum-containing precipitate.

[0244] The reaction solution was then decanted using a centrifuge and washed until the amount of liberated fluoride ions was 100 mg / L or less, yielding a tantalum-containing precipitate from which the fluoride ions had been removed, using aqueous ammonia as the washing liquid.

[0245] The tantalum-containing precipitate from which the fluoride ions had been removed was diluted with pure water to obtain a tantalum-containing precipitate slurry. A portion of this tantalum-containing precipitate slurry was dried at 110°C for 24 hours and then fired at 1,000°C for 4 hours to obtain Ta. ２ O ５ and from the weight thereof, the Ta contained in the tantalum-containing precipitation slurry is calculated. ２ O ５ The content was calculated.

[0246] Then, pure water adjusted to a temperature of 70°C to 80°C, the tantalum-containing precipitate slurry diluted with pure water, and a 5 mass% aqueous solution of lithium hydroxide monohydrate were mixed to obtain the neutralized aqueous solution of a tantalum compound according to Example 1. The tantalum content in the neutralized aqueous solution of a tantalum compound according to Example 1 was 4.06 mass%, and the lithium content was 0.14 mass%.

[0247] Example 2 In Example 2, 0.3 g of pyrophosphoric acid and 27.25 g of pure water were placed in a polypropylene container, and 4.02 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the resulting aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0248] Then, 2.74 g of the niobium compound neutralized aqueous solution used in Example 1 and 0.58 g of the molybdenum compound neutralized aqueous solution described below were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes, thereby obtaining a metal acid compound dispersion liquid according to Example 2.

[0249] The neutralized aqueous solution of a molybdenum compound according to Example 2 was obtained by the above-described method for producing a neutralized aqueous solution of a molybdenum compound. The molybdenum content in the neutralized aqueous solution of a molybdenum compound according to Example 2 was 2.80 mass %, and the lithium content was 0.37 mass %.

[0250] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 2 were the same as those used in Example 1.

[0251] Example 3 In Example 3, 0.31 g of pyrophosphoric acid and 26.94 g of pure water were placed in a polypropylene container, and 4.20 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the resulting aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0252] Then, 2.74 g of the niobium compound neutralized aqueous solution used in Example 1 and 0.88 g of a tungsten compound neutralized aqueous solution described below were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes, thereby obtaining a metal acid compound dispersion liquid according to Example 3.

[0253] The neutralized aqueous solution of a tungsten compound according to Example 3 was obtained by the above-described method for producing a neutralized aqueous solution of a tungsten compound. The tungsten content in the neutralized aqueous solution of a tungsten compound according to Example 3 was 3.46 mass %, and the lithium content was 0.27 mass %.

[0254] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 3 were the same as those used in Example 1.

[0255] Example 4 In Example 4, 0.31 g of pyrophosphoric acid and 25.95 g of pure water were placed in a polypropylene container, and 4.34 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the resulting aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0256] Then, 2.74 g of the niobium compound neutralized aqueous solution used in Example 1 and 1.61 g of the titanium compound neutralized aqueous solution described below were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes, thereby obtaining a metal oxide compound dispersion liquid according to Example 4.

[0257] The neutralized aqueous solution of titanium compound according to Example 4 was obtained by the above-mentioned method for producing a neutralized aqueous solution of titanium compound. The titanium content in the neutralized aqueous solution of titanium compound according to Example 4 was 0.48 mass%.

[0258] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 4 were the same as those used in Example 1.

[0259] Example 5 In Example 5, 0.29 g of pyrophosphoric acid and 25.90 g of pure water were placed in a polypropylene container, and 4.01 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the resulting aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0260] Then, 1.63 g of the neutralized aqueous solution of niobium compounds used in Example 1, 0.57 g of the neutralized aqueous solution of molybdenum compounds used in Example 2, 0.88 g of the neutralized aqueous solution of tungsten compounds used in Example 3, and 1.59 g of the neutralized aqueous solution of titanium compounds used in Example 4 were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes to obtain a metal acid compound dispersion liquid according to Example 5.

[0261] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 5 were the same as those used in Example 1.

[0262] Example 6 In Example 6, 0.32 g of pyrophosphoric acid and 26.4 g of pure water were placed in a polypropylene container, and 4.17 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the resulting aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0263] Then, 3.72 g of the neutralized aqueous solution of tantalum compounds used in Example 1 and 0.58 g of the neutralized aqueous solution of molybdenum compounds used in Example 2 were added to the phosphorus compound mixed solution, and the mixture was stirred for 30 minutes to obtain a metal acid compound dispersion liquid according to Example 6.

[0264] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 6 were the same as those used in Example 1.

[0265] Example 7 In Example 7, 0.29 g of pyrophosphoric acid and 25.99 g of pure water were placed in a polypropylene container, and 4.15 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the resulting aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0266] Then, 3.75 g of the tantalum compound neutralized aqueous solution used in Example 1 and 0.86 g of the tungsten compound neutralized aqueous solution used in Example 3 were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes to obtain a metal acid compound dispersion liquid according to Example 7.

[0267] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 7 were the same as those used in Example 1.

[0268] Example 8 In Example 8, 0.3 g of pyrophosphoric acid and 24.7 g of pure water were placed in a polypropylene container, and 4.45 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the resulting aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0269] Then, 3.74 g of the tantalum compound neutralized aqueous solution used in Example 1 and 1.63 g of the titanium compound neutralized aqueous solution used in Example 4 were added to the phosphorus compound mixed solution, and the mixture was stirred for 30 minutes to obtain a metal oxide compound dispersion liquid according to Example 8.

[0270] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 8 were the same as those used in Example 1.

[0271] Example 9 In Example 9, 0.29 g of pyrophosphoric acid and 25.00 g of pure water were placed in a polypropylene container, and 4.17 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the obtained aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0272] Then, 2.24 g of the neutralized aqueous solution of tantalum compounds used in Example 1, 0.58 g of the neutralized aqueous solution of molybdenum compounds used in Example 2, 0.88 g of the neutralized aqueous solution of tungsten compounds used in Example 3, and 1.64 g of the neutralized aqueous solution of titanium compounds used in Example 4 were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes to obtain a metal acid compound dispersion liquid of Example 9.

[0273] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 9 were the same as those used in Example 1.

[0274] Example 10 In Example 10, 0.31 g of pyrophosphoric acid and 24.24 g of pure water were placed in a polypropylene container, and 3.83 g of a 5 mass% aqueous solution of lithium hydroxide monohydrate was added to the resulting aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0275] Then, 1.09 g of the neutralized aqueous solution of niobium compounds used in Example 1, 2.23 g of the neutralized aqueous solution of tantalum compounds used in Example 1, 0.58 g of the neutralized aqueous solution of molybdenum compounds used in Example 2, 0.89 g of the neutralized aqueous solution of tungsten compounds used in Example 3, and 1.63 g of the neutralized aqueous solution of titanium compounds used in Example 4 were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes to obtain a metal acid compound dispersion liquid of Example 10.

[0276] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 10 were the same as those used in Example 1.

[0277] Example 11 In Example 11, 0.31 g of pyrophosphoric acid and 25.98 g of pure water were placed in a polypropylene container, and 5.47 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the obtained aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0278] Then, 2.71 g of the niobium compound neutralized aqueous solution used in Example 1 and 0.58 g of the molybdenum compound neutralized aqueous solution used in Example 2 were added to the phosphorus compound mixed solution, and the mixture was stirred for 30 minutes to obtain a metal acid compound dispersion liquid according to Example 11.

[0279] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 11 were the same as those used in Example 1.

[0280] Example 12 In Example 12, 0.3 g of pyrophosphoric acid and 29.59 g of pure water were placed in a polypropylene container, and 0.79 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the obtained aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0281] Then, 3.75 g of the tantalum compound neutralized aqueous solution used in Example 1 and 0.6 g of the molybdenum compound neutralized aqueous solution used in Example 2 were added to the phosphorus compound mixed solution, and the mixture was stirred for 30 minutes to obtain a metal acid compound dispersion liquid according to Example 12.

[0282] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 12 were the same as those used in Example 1.

[0283] Example 13 In Example 13, 0.3 g of pyrophosphoric acid and 27.89 g of pure water were placed in a polypropylene container, and 2.48 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the obtained aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0284] Then, 3.75 g of the neutralized aqueous solution of tantalum compounds used in Example 1 and 0.6 g of the neutralized aqueous solution of molybdenum compounds used in Example 2 were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes, thereby obtaining a metal acid compound dispersion liquid according to Example 13.

[0285] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 13 were the same as those used in Example 1.

[0286] Example 14 In Example 14, 0.38 g of 85 mass% phosphoric acid and 25.93 g of pure water were placed in a polypropylene container, and 4.13 g of 5 mass% lithium hydroxide monohydrate aqueous solution was added to the obtained phosphorus compound aqueous solution to obtain a phosphorus compound mixed solution.

[0287] Then, 3.9 g of the neutralized aqueous solution of a tantalum compound and 0.58 g of the neutralized aqueous solution of a molybdenum compound used in Example 2 were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes to obtain a metal acid compound dispersion liquid of Example 14.

[0288] The neutralized aqueous solution of a tantalum compound of Example 14 was obtained in the same manner as the neutralized aqueous solution of a tantalum compound of Example 1, except that the aqueous solution was prepared so that the tantalum content was 3.89% by mass and the lithium content was 0.15% by mass.

[0289] The 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 14 was the same as that used in Example 1.

[0290] Example 15 In Example 15, 3.38 g of 1 mol / L hydrochloric acid and 23.01 g of pure water were placed in a polypropylene container, and 4.1 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the obtained aqueous solution of chlorine compounds to obtain a mixed solution of chlorine compounds.

[0291] Then, 3.9 g of the tantalum compound neutralized aqueous solution used in Example 14 and 0.58 g of the molybdenum compound neutralized aqueous solution used in Example 2 were added to the chlorine compound mixed solution, and the mixture was stirred and mixed for 30 minutes, thereby obtaining a metal acid compound dispersion liquid according to Example 15.

[0292] The 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 15 was the same as that used in Example 1.

[0293] Example 16 In Example 16, 0.28 g of phosphonic acid and 25.97 g of pure water were placed in a polypropylene container, and 4.14 g of a 5 mass% aqueous solution of lithium hydroxide monohydrate was added to the obtained aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0294] Then, 3.95 g of the neutralized aqueous solution of tantalum compounds used in Example 14 and 0.58 g of the neutralized aqueous solution of molybdenum compounds used in Example 2 were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes, thereby obtaining a metal acid compound dispersion liquid of Example 16.

[0295] The 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 16 was the same as that used in Example 1.

[0296] Example 17 In Example 17, 0.73 g of 30 mass% phosphinic acid and 25.63 g of pure water were placed in a polypropylene container, and 4.14 g of 5 mass% lithium hydroxide monohydrate aqueous solution was added to the obtained phosphorus compound aqueous solution to obtain a phosphorus compound mixed solution.

[0297] Then, 3.91 g of the neutralized aqueous solution of tantalum compounds used in Example 14 and 0.58 g of the neutralized aqueous solution of molybdenum compounds used in Example 2 were added to the phosphorus compound mixed solution, and the mixture was stirred for 30 minutes to obtain a metal acid compound dispersion liquid of Example 17.

[0298] The 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 17 was the same as that used in Example 1.

[0299] (Example 18) In Example 18, a polypropylene container was filled with 80% by mass of P ２ O ５ 0.33 g of polyphosphoric acid and 26.02 g of pure water were added, and to the resulting aqueous solution of phosphorus compounds, 4.12 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to obtain a mixed solution of phosphorus compounds.

[0300] Then, 3.9 g of the neutralized aqueous solution of tantalum compounds used in Example 14 and 0.58 g of the neutralized aqueous solution of molybdenum compounds used in Example 2 were added to the phosphorus compound mixed solution, and the mixture was stirred for 30 minutes to obtain a metal acid compound dispersion liquid of Example 18.

[0301] The 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 18 was the same as that used in Example 1.

[0302] Example 19 In Example 19, 0.6 g of triethyl phosphate and 25.8 g of pure water were placed in a polypropylene container, and 4.13 g of a 5 mass% aqueous solution of lithium hydroxide monohydrate was added to the obtained aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0303] Then, 3.9 g of the neutralized aqueous solution of tantalum compounds used in Example 14 and 0.58 g of the neutralized aqueous solution of molybdenum compounds used in Example 2 were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes, thereby obtaining a metal acid compound dispersion liquid of Example 19.

[0304] The 5 mass % aqueous solution of lithium hydroxide monohydrate used in Example 19 was the same as that used in Example 1.

[0305] Comparative Example 1 In Comparative Example 1, 0.29 g of pyrophosphoric acid and 29.68 g of pure water were placed in a polypropylene container, and 4.25 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the resulting aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0306] Then, 0.12 g of lithium niobate powder (manufactured by Kojundo Chemical Laboratory Co., Ltd.) and 0.58 g of the molybdenum compound neutralized aqueous solution used in Example 2 were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes to obtain a metal oxide compound dispersion liquid according to Comparative Example 2.

[0307] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Comparative Example 1 were the same as those used in Example 1.

[0308] Comparative Example 2 In Comparative Example 2, 0.3 g of pyrophosphoric acid and 29.67 g of pure water were placed in a polypropylene container, and 4.24 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the resulting aqueous solution of phosphorus compounds to obtain a mixed solution of phosphorus compounds.

[0309] Then, 0.2 g of lithium tantalate powder (manufactured by Kojundo Chemical Laboratory Co., Ltd.) and 0.59 g of the molybdenum compound neutralized aqueous solution used in Example 2 were added to the phosphorus compound mixed solution, and the mixture was stirred and mixed for 30 minutes to obtain a metal oxide compound dispersion liquid according to Comparative Example 2.

[0310] The pyrophosphoric acid and the 5 mass % aqueous solution of lithium hydroxide monohydrate used in Comparative Example 2 were the same as those used in Example 1.

[0311] Comparative Example 3 In Comparative Example 3, 3.29 g of 10 mass % sulfuric acid and 23.07 g of pure water were placed in a polypropylene container, and 4.11 g of 5 mass % aqueous solution of lithium hydroxide monohydrate was added to the obtained aqueous sulfur compound solution to obtain a sulfur compound mixed solution.

[0312] Then, 3.9 g of the tantalum compound neutralized aqueous solution used in Example 14 and 0.58 g of the molybdenum compound neutralized aqueous solution used in Example 2 were added to the sulfur compound mixed solution, and the mixture was stirred and mixed for 30 minutes to obtain a metal acid compound dispersion liquid according to Comparative Example 3.

[0313] The 5 mass % aqueous solution of lithium hydroxide monohydrate used in Comparative Example 3 was the same as that used in Example 1.

[0314] Comparative Example 4 In Comparative Example 4, 4.39 g of a 5 mass % aqueous solution of lithium hydroxide monohydrate, 6.52 g of the neutralized aqueous solution of tantalum compound used in Example 14, and 0.95 g of the neutralized aqueous solution of molybdenum compound used in Example 2 were added to 23.15 g of pure water placed in a polypropylene container, and the mixture was stirred and mixed for 30 minutes to obtain a metal acid compound dispersion liquid according to Comparative Example 4.

[0315] The 5 mass % aqueous solution of lithium hydroxide monohydrate used in Comparative Example 4 was the same as that used in Example 1.

[0316] The following physical properties were measured for the metal acid compound dispersions of Examples 1 to 19 and Comparative Examples 1 to 4. The measured physical properties and the methods for measuring the physical properties are shown below. The compositions of the metal acid compound dispersions of Examples 1 to 19 and Comparative Examples 1 to 4 are shown in Figure 1, the composition ratios of the metal acid compound dispersions of Examples 1 to 19 and Comparative Examples 1 to 4 are shown in Figure 2, and the measurement results of the metal acid compound dispersions of Examples 1 to 19 and Comparative Examples 1 to 4 are shown in Figure 3.

[0317] <Elemental Analysis> If necessary, the sample was appropriately diluted with dilute hydrochloric acid, and for the metal acid compound dispersions according to Examples 1 to 19 and Comparative Examples 1 to 4, 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, P mass % in terms of P atoms, Li mass % in terms of Li atoms, Cl mass % in terms of Cl atoms, and S mass % in terms of S atoms were measured using ICP optical emission spectrometry (AG-5110 manufactured by Agilent Technologies) in accordance with JIS K0116:2014.

[0318] <pH Measurement> The pH of each of the metal acid compound dispersions according to Examples 1 to 19 and Comparative Examples 1 to 4 was measured using an electrode (HORIBA: Standard ToupH electrode 9615S-10D) of a pH meter (HORIBA: Glass electrode type hydrogen ion concentration indicator D-51) after confirming that the liquid temperature had stabilized at 25°C. The "initial pH" in Fig. 3 refers to the pH of the metal acid compound dispersion whose liquid temperature was adjusted to 25°C immediately after production. The "pH over time" in Fig. 3 refers to the pH of the metal acid compound dispersions according to Examples 1 to 19 and Comparative Examples 1 to 4 after they were allowed to stand for one month from the day of production in an incubator set at room temperature of 25°C.

[0319] <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 19 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 FIG. 3 , "initial particle size D50 (nm)" refers to the particle size (D50) of particles in the metal acid compound dispersion immediately after production. In FIG. 3 , "aged particle size D50 (nm)" refers to the particle size (D50) of particles in the metal acid compound dispersions of Examples 1 to 19 and Comparative Examples 1 to 4 after they were left standing in an incubator set at room temperature of 25°C for one month from the day of production. Furthermore, for the metal acid compound dispersions according to Comparative Examples 1 to 3, measurements of the initial particle diameter D50 (nm) and the aged particle diameter D50 (nm) were not performed because precipitates were visible in the dispersions immediately after production. Note that the above-mentioned filtering was performed when measuring the "initial particle diameter D50 (nm)," but was not performed when measuring the "aged particle diameter D50 (nm)," and only ultrasonic treatment was performed.

[0320] <Transmittance Measurement> 3 ml of the metal acid compound dispersions according to Examples 1 to 19 and Comparative Examples 1 to 4 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 19 and Comparative Examples 1 to 4 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 FIG. 3 refers to the transmittance of the metal acid compound dispersions adjusted to a liquid temperature of 25°C immediately after production. Furthermore, the "temporary transmittance" in FIG. 3 refers to the transmittance of the metal acid compound dispersions according to Examples 1 to 19 and Comparative Examples 1 to 4 after they were left to stand for one month from the day of production in an incubator set at room temperature of 25°C.

[0321] <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 19 and Comparative Examples 1 to 4 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 19 and Comparative Examples 1 to 4 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)."

[0322] As shown in FIGS. 1 to 3 , the metal acid compound dispersions according to Examples 1 to 19 contained two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium, and had one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and a phosphorus compound and / or a chlorine compound. When the particle diameter (D50) of the particles in the metal acid compound dispersions measured by dynamic light scattering in the dispersions was 1000 nm or less, the dispersions had high dispersibility in the dispersion medium and excellent solubility.

[0323] The metal acid compound dispersions according to Examples 1 to 19 contained two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium, and had one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and a phosphorus compound and / or a chlorine compound. When the maximum transmittance in the wavelength region of 400 nm to 760 nm was 70% T or more, the dispersions had high dispersibility in the dispersion medium and excellent solubility.

[0324] The metal acid compound dispersions of Examples 1 to 19 had excellent stability over time when the content of the metal species M in the metal acid compound dispersions of Examples 1 to 19 was 0.01 mass% or more and 30 mass% or less in terms of metal species M atoms.

[0325] The metal acid compound dispersions of Examples 1 to 19 had excellent stability over time when the phosphorus content in the metal acid compound dispersions of Examples 1 to 19 was 0.01 mass % or more and 10 mass % or less in terms of P atoms.

[0326] The metal acid compound dispersions of Examples 1 to 19 showed excellent stability over time, with the particle diameter (D50) not significantly different from the initial particle diameter (D50) even after one month. However, precipitates were observed in the metal acid compound dispersions of Comparative Examples 1 and 2.

[0327] The metal acid compound dispersions according to Examples 1 to 19 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 two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium was 0.01 or more and 10 or less. Furthermore, when the element X is Li, the metal acid compound dispersions according to Examples 1 to 19 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 0.01 or more and 10 or less.

[0328] The metal acid compound dispersions according to Examples 1 to 19 exhibited improved stability during long-term storage when the molar ratio x / (P+Cl) 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 (P+Cl) of phosphorus compounds and / or chlorine compounds was 0.01 or more and 5 or less. Furthermore, when the element X is Li, the metal acid compound dispersions according to Examples 1 to 19 exhibited improved stability during long-term storage when the molar ratio Li / (P+Cl) of lithium (Li) to the total amount (P+Cl) of phosphorus compounds and / or chlorine compounds was 0.01 or more and 5 or less.

[0329] In the metal acid compound dispersions of Examples 1 to 19, when the molar ratio m / (P+Cl) of the total amount (m) of two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten, and titanium to the total amount (P+Cl) of phosphorus compounds and / or chlorine compounds was 0.01 or more and 10 or less, the stability during long-term storage was improved.

[0330] The metal acid compound dispersions according to Examples 1 to 19 were excellent in stability over time when the pH of the dispersions was 2 or more and 11 or less.

[0331] The metal acid compound films formed from the metal acid compound dispersions of Examples 1 to 19 were observed under an optical microscope, and were found to have excellent film-forming properties, with no coarse particles present in the coating films.

[0332] 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.

[0333] The metal acid compound dispersion according to the present invention has high dispersibility in polar solvents, particularly water, good solubility in water, and excellent storage stability. Furthermore, because the metal acid compound dispersion according to the present invention has excellent storage stability, it is possible to reduce the rate of defective products caused by sediment formation over time, thereby reducing 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 liquid containing two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten and titanium, one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and a phosphorus compound and / or a chlorine compound, wherein the particle diameter (D50) of particles in the metal acid compound dispersion liquid as measured by dynamic light scattering method is 1000 nm or less.

2. A metal acid compound dispersion liquid containing two or more metal species M selected from the group consisting of niobium, tantalum, molybdenum, tungsten and titanium, one or more elements X selected from the group consisting of alkali metal elements and / or alkaline earth metal elements, and a phosphorus compound and / or a chlorine compound, wherein the maximum transmittance in the wavelength region of 400 nm to 760 nm is 70% T or more.

3. The metal acid compound dispersion according to claim 1 or 2, characterized in that the metal species M contains tantalum.

4. The metal acid compound dispersion liquid according to claim 1 or 2, characterized in that the element X contains Li.

5. The metal acid compound dispersion according to claim 1 or 2, characterized in that the phosphorus compound contains at least one type selected from the group consisting of inorganic phosphorus compounds, organic phosphorus compounds, and salts thereof.

6. The metal acid compound dispersion liquid according to claim 5, characterized in that the phosphorus compound contains one or more compounds selected from the group consisting of phosphoric acid, condensed phosphoric acid, pyrophosphoric acid, polyphosphoric acid, phosphorous acid, hypophosphorous acid, ammonium phosphate, primary ammonium phosphate, secondary ammonium phosphate, ammonium pyrophosphate, and ammonium polyphosphate.

7. The metal acid compound dispersion 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 liquid according to claim 1 or 2, characterized in that the content of the 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.

10. The metal acid compound dispersion liquid according to claim 1 or 2, characterized in that the phosphorus content in the metal acid compound dispersion liquid is 0.01% by mass or more and 10% by mass or less in terms of P atoms.

11. 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 0.01 or more and 10 or less.

12. The metal acid compound dispersion liquid according to claim 1 or 2, wherein the element X in the metal acid compound dispersion liquid is Li, 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 10 or less.

13. The metal acid compound dispersion liquid according to claim 1 or 2, wherein the molar ratio x / (P+Cl) of the total amount (x) of the element X to the total amount (P+Cl) of the phosphorus compounds and / or chlorine compounds in the metal acid compound dispersion liquid is 0.01 or more and 5 or less.

14. The metal acid compound dispersion liquid according to claim 1 or 2, wherein the element X in the metal acid compound dispersion liquid is Li, and the molar ratio Li / (P+Cl) of lithium (Li) to the total amount (P+Cl) of the phosphorus compound and / or the chlorine compound is 0.01 or more and 5 or less.

15. A metal acid compound dispersion liquid as described in claim 1 or 2, characterized in that the molar ratio m / (P+Cl) of the total amount (m) of the metal species M in the metal acid compound dispersion liquid to the total amount (P+Cl) of the phosphorus compounds and / or the chlorine compounds is 0.01 or more and 10 or less.

16. The metal acid compound dispersion according to claim 1 or 2, characterized in that the metal acid compound dispersion is an aqueous dispersion.

17. A metal acid compound dispersion according to claim 1 or 2, characterized in that the particle diameter (D50) of particles in the metal acid compound dispersion as measured by dynamic light scattering is 100 nm or less.

18. The metal acid compound dispersion according to claim 1 or 2, characterized in that the metal acid compound dispersion has a pH of 2 or more and 11 or less.

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

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

21. A coating agent comprising the metal acid compound dispersion liquid according to claim 1 or 2.

22. A coating agent comprising the metal acid compound powder according to claim 19.

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

24. A positive electrode active material for a lithium ion secondary battery, the surface of which is coated with a metal acid compound contained in the metal acid compound dispersion liquid according to claim 1 or 2.

25. A lithium ion secondary battery 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 24.