Classifications

• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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  • C01G33/00—Compounds of niobium
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  • C01G33/003—Preparation involving a liquid-liquid extraction, an adsorption or an ion-exchange
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
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  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
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  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/362—Composites
  • H01M4/366—Composites as layered products
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
  • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
  • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/51—Particles with a specific particle size distribution
• • C—CHEMISTRY; METALLURGY
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  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/40—Electric properties
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  • C01P2006/80—Compositional purity
• • H—ELECTRICITY
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  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/028—Positive electrodes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to a lithium niobate solution and a method for producing the same.
• Patent Document 1 discloses a technique for reducing the interfacial resistance that occurs in .
• the lithium niobate precursor aqueous solution disclosed in Patent Literature 1 is added with a hydrogen peroxide solution in order to improve storage stability.
• Patent Document 1 discloses the following points to be noted regarding the lithium niobate precursor aqueous solution to which the hydrogen peroxide solution is added. If the concentration of the hydrogen peroxide solution is less than 0.1 mol per 1 mol of niobium, the resulting niobium polyacid reacts with hydroxide ions and decomposes. If the amount of free hydrogen peroxide is less than 0.01% by mass, it is difficult to maintain the stability of the aqueous precursor solution. It is disclosed that some of the solubilized niobic acid may form unstable peroxo complexes.
• the present invention provides a lithium niobate solution that has high dispersibility in water, good solubility in water, and excellent storage stability, and a method for producing the same.
• the lithium niobate solution of the present invention which has been made to solve the above problems, is a niobate containing lithium niobate and ammonium ions, wherein the molar ratio Li/Nb of lithium and niobium is 0.8 or more and 2.0 or less.
• the lithium solution is characterized by having a lithium niobate particle size (D50) of 100 nm or less as determined by a dynamic light scattering method.
• the lithium niobate (LiNbO 3 ) in the lithium niobate solution has a molar ratio Li/Nb of lithium to niobium of 0.8 or more and 2.0 or less, The stability of the solution is improved, such as by suppressing the precipitation of precipitates. Further, the molar ratio Li/Nb of lithium and niobium in the lithium niobate solution is more preferably 0.9 or more and 1.5 or less, and even more preferably 0.9 or more and 1.2 or less.
• the lithium niobate in the lithium niobate solution of the present invention is presumed to exist in the solution as ions in which niobate and lithium are ionically bonded.
• the lithium niobate solution of the present invention while hydroxide ions are present as anions, halide ions such as fluoride ions and chloride ions are almost absent, and lithium is believed to be present as cations.
• niobium is considered to exist as an anion such as NbO 3 - or as a polyoxometalate (polyacid) ion in which a plurality of niobium atoms and oxygen atoms are bonded.
• the lithium niobate solution of the present invention contains ammonium ions in addition to lithium niobate.
• the method for producing the lithium niobate solution of the present invention will be described later in detail. Since the lithium niobate solution of the present invention is produced after the ammonium cake is produced, it is believed that the ammonium ions substituted for the lithium ions are present in the solution as cations.
• the method of measuring the concentration of ammonium ions present in the solution includes adding sodium hydroxide to the solution, separating the ammonia by distillation, and quantifying the concentration of ammonium ions using an ion meter.
• a method of quantifying with a thermal conductivity meter, the Kjeldahl method, gas chromatography (GC), ion chromatography, GC-MS (mass spectrometry) and the like can be mentioned.
• the ammonium ion concentration of the ammonium ions contained in the lithium niobate solution of the present invention is preferably 0.001% by mass or more and 25% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less. It is more preferable in it being more than mass % and 8 mass % or less.
• the lithium niobate particle size (D50) in the lithium niobate solution measured by the dynamic light scattering method is 100 nm or less in view of high dispersibility.
• the lithium niobate particle size (D50) in the lithium niobate solution is smaller, it is stable due to less change over time, and good coating film formation without uncoated areas during film formation can be achieved. , is preferable from the viewpoint of ensuring a sufficient coating weight.
• the lithium niobate particle size (D50) in the lithium niobate solution is more preferably 80 nm or less, further preferably 50 nm or less, particularly preferably 30 nm or less, and even more preferably 20 nm or less, It is more particularly preferably 10 nm or less, particularly preferably 5 nm or less, and even more particularly preferably 3 nm or less.
• the lithium niobate particle size (D50) is 100 nm or less.
• the liquid be the "lithium niobate solution" of the present invention.
• the dynamic light scattering method measures the light scattering intensity from a group of particles moving in Brownian motion by irradiating a solution such as a suspension solution with light such as a laser beam.
• This is a method for determining the particle size and distribution.
• the particle size distribution evaluation method uses a zeta potential/particle size/molecular weight measurement system (manufactured by Otsuka Electronics Co., Ltd.: ELSZ-2000), JIS Z 8828: 2019 "Particle size analysis-dynamic light scattering to comply with the law.
• the particle diameter (D50) refers to the median diameter (D50), which is the particle diameter showing the 50% integrated value of the cumulative distribution curve.
• the "solution" in the present invention is not limited to one in which a solute is dispersed or mixed in a solvent in a monomolecular state, but an assembly in which a plurality of molecules are attracted by intermolecular interactions, such as (1 ) polymeric molecules, (2) solvated molecules, (3) molecular clusters, (4) colloidal particles, etc., dispersed in a solvent.
• the lithium niobate solution of the present invention preferably does not contain hydrogen peroxide.
• hydrogen peroxide is added to improve stability in order to suppress decomposition by reaction with hydroxide ions.
• the lithium niobate solution of the present invention can ensure long-term stability even in the absence of hydrogen peroxide due to the presence of ammonium ions in the solution.
• the method for detecting hydrogen peroxide in a solution is to use, for example, the standard addition method to measure the relative intensity of the absorbance with a standard solution of hydrogen peroxide, so that the solution does not contain hydrogen peroxide. can be confirmed. Specifically, from the ultraviolet-visible absorption spectra of a standard solution containing a known concentration of hydrogen peroxide, for example, 1% by mass, and a standard solution to which no hydrogen peroxide is added, changes in absorbance due to peroxo complex formation are observed.
• the sample with unknown hydrogen peroxide concentration in that wavelength region is less than 1%, the sample with unknown hydrogen peroxide concentration It can be confirmed that substantially no hydrogen peroxide is contained in the If the solution contains hydrogen peroxide, the hydrogen peroxide reacts with the niobium polyacid to form a peroxo complex. By confirming the difference, it can be confirmed that the solution does not contain hydrogen peroxide.
• a method of adding a reagent that reacts with hydrogen peroxide to color the solution and measuring the color development may be performed by adding a reagent that reacts with hydrogen oxide and fluorescence, and measuring the emitted light.
• the lithium niobate solution of the present invention is preferably an aqueous solution. Since lithium niobate in the lithium niobate solution of the present invention has high dispersibility in water and good solubility in water, pure water can be used as a solvent.
• the lithium niobate solution of the present invention is characterized in that the lithium niobate concentration in the lithium niobate solution is 0.1 to 30% by mass. Further, the lithium niobate solution of the present invention is characterized in that the lithium niobate concentration in the lithium niobate solution is 5 to 20% by mass. It is preferable that the lithium niobate concentration in the lithium niobate solution is 0.1 to 30% by mass in terms of both practicality and stability of the lithium niobate solution, and more preferably 1 to 25% by mass. , more preferably 3 to 21% by mass, and particularly preferably 5 to 20% by mass.
• the lithium niobate concentration in the lithium niobate solution is determined by appropriately diluting the solution with dilute hydrochloric acid as necessary, and using ICP emission spectrometry (manufactured by Agilent Technologies: AG-5110), JIS K0116: 2014, the Nb weight fraction in terms of niobium oxide (Nb 2 O 5 ) and the Li weight fraction are measured and calculated.
• Niobic acid in the lithium niobate solution of the present invention does not necessarily exist in the form of Nb 2 O 5 . The reason why the content of niobic acid is shown in terms of Nb 2 O 5 is based on the convention when showing the niobium concentration.
• the lithium niobate solution of the present invention can be used for coating a positive electrode for a lithium ion secondary battery or a positive electrode material, or for coating a positive electrode for an all-solid lithium ion battery or a positive electrode material.
• the lithium niobate solution of the present invention was subjected to a temporal stability test in which the state of the solution was visually observed after standing for one month in a thermostat set at room temperature (25 ° C.), and a dynamic light scattering method.
• the lithium niobate solution of the present invention is a lithium ion secondary battery. It is suitable as a positive electrode for use or a material for covering a positive electrode material.
• 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 lithium niobate contained in the lithium niobate solution.
• the surface of the positive electrode active material is coated with lithium niobate. can be verified.
• the coating amount of lithium niobate covering the surface of the positive electrode active material for lithium ion secondary batteries of the present invention is obtained by dissolving the positive electrode active material for lithium ion secondary batteries in an appropriate amount of hydrofluoric acid, and obtaining ICP light emission.
• the niobium weight fraction concentration is preferably 1 or more, more preferably more than 1, still more preferably 1.1 or more, and particularly preferably 1.2 or more.
• the lithium niobate solution of the present invention may contain components other than the components derived from lithium niobate and the components derived from ammonia (referred to as "other components") within a range that does not impair the effects thereof. good.
• other components include Na, Mg, Si, K, Ca, Ti, Mn, Ni, Zn, Sr, Zr, Ta, Mo, Ba and W.
• the content of other components in the lithium niobate solution of the present invention is preferably less than 5% by mass, more preferably less than 4% by mass, and even more preferably less than 3% by mass.
• the lithium niobate solution of the present invention is unintentionally assumed to contain unavoidable impurities.
• the content of unavoidable impurities is preferably less than 0.01% by mass.
• the lithium ion secondary battery of the present invention is characterized by having a positive electrode coated with the positive electrode active material.
• the positive electrode active material coated with the lithium niobate solution of the present invention is suitable for coating the surface of the positive electrode for a lithium ion secondary battery as described above, and therefore the lithium niobate solution of the present invention can be used.
• the performance of the lithium ion secondary battery can be improved.
• the method for producing a lithium niobate solution of the present invention comprises the steps of: producing an acidic niobium solution containing niobium; and obtaining a precipitation slurry containing niobium by a reverse neutralization method in which the acidic niobium solution is added to aqueous ammonia. and a step of obtaining a lithium niobate solution by maintaining the mixture obtained by mixing the obtained precipitation slurry containing niobium, lithium hydroxide and pure water at 20° C. to 100° C. while stirring.
• the acidic niobium solution contains fluoride ions obtained by solvent extraction of a solution of niobium dissolved in an acidic solution containing hydrofluoric acid.
• fluoride ions obtained by solvent extraction of a solution of niobium dissolved in an acidic solution containing hydrofluoric acid.
• the niobium referred to in this specification includes niobate compounds unless otherwise specified.
• the acidic niobium solution containing fluoride ions eg, an aqueous niobium fluoride solution
• the acidic niobium solution containing fluoride ions is preferably adjusted to contain 1 to 100 g/L of niobium in terms of Nb 2 O 5 by adding water (eg, pure water).
• water eg, pure water
• the niobium concentration is 1 g/L or more in terms of Nb 2 O 5
• the niobium concentration is 100 g/L or less in terms of Nb 2 O 5 , it is preferable because the niobate compound hydrate is easily soluble in water, and the niobate compound hydrate that is more reliably soluble in water is synthesized. To achieve this, it is more preferably 90 g/L or less, even more preferably 80 g/L or less, and particularly preferably 70 g/L or less.
• 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.
• the acidic niobium solution containing fluoride ions is added to a predetermined It is preferable to obtain a niobium-containing precipitation slurry by addition into concentrated aqueous ammonia, ie, by a reverse neutralization method.
• the ammonia concentration of the ammonia water used for reverse neutralization is preferably 10% by mass to 30% by mass.
• the ammonia concentration is 10% by mass, niobium is less likely to remain undissolved, and niobium or niobium acid can be completely dissolved in water.
• the ammonia concentration is 30% by mass or less, it is close to a saturated aqueous solution of ammonia, which is preferable.
• the ammonia concentration 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.
• the ammonia concentration is preferably 30% by mass or less, more preferably 29% by mass or less, and even more preferably 28% by mass or less.
• the amount of the niobium fluoride aqueous solution added to the aqueous ammonia is preferably such that the molar ratio of NH 3 /Nb 2 O 5 is 95 or more and 500 or less, more preferably 100 or more and 450 or less. More preferably, it is 110 or more and 400 or less.
• the amount of the niobium fluoride aqueous solution added to the ammonia water is preferably such that the NH 3 /HF molar ratio is 3.0 or more from the viewpoint of generating amines and niobic acid compounds that dissolve in dilute ammonia water. It is more preferably 4.0 or more, and even more preferably 5.0 or more.
• the NH 3 /HF molar ratio is preferably 100 or less, more preferably 50 or more, and even more preferably 40 or more.
• the time required for adding the aqueous niobium fluoride solution to the aqueous ammonia is preferably within 1 minute, more preferably within 30 seconds, and even more preferably within 10 seconds. That is, instead of gradually adding the niobium fluoride aqueous solution over time, it is preferable to add the aqueous solution of niobium fluoride at once, for example, to the ammonia water in the shortest possible time for neutralization reaction.
• the neutralization reaction can be carried out while maintaining a high pH.
• the niobium fluoride aqueous solution and ammonia water can be used at room temperature.
• the method for producing a lithium niobate solution of the present invention includes a step of removing fluoride ions from the niobium-containing precipitation slurry obtained by the reverse neutralization method to obtain a niobium-containing precipitate from which fluoride ions have been removed.
• Fluorine compounds such as ammonium fluoride are present as impurities in the precipitation slurry containing niobium obtained by the inverse neutralization method, and therefore these are preferably removed.
• the method for removing the fluorine compound is arbitrary, but for example, a method by filtration using a membrane such as reverse osmosis filtration using ammonia water or pure water, ultrafiltration, or microfiltration, centrifugation, or other known methods. can be adopted.
• a membrane such as reverse osmosis filtration using ammonia water or pure water, ultrafiltration, or microfiltration, centrifugation, or other known methods.
• temperature control is not particularly required, and the removal may be performed at room temperature.
• the precipitation slurry containing niobium obtained by the reverse neutralization method is decanted using a centrifuge, and washing is repeated until the amount of free fluoride ions is 100 mg / L or less. , a niobium-containing precipitate from which fluoride ions are removed is obtained.
• the cleaning liquid used for removing fluoride ions is aqueous ammonia.
• ammonia water of 5.0 mass% or less is preferable, ammonia water of 4.0 mass% or less is more preferable, ammonia water of 3.0 mass% or less is further preferable, and ammonia of 2.5 mass% Water is particularly preferred. If the ammonia water content is 5.0% by mass or less, ammonia and ammonium ions are suitable for fluorine, and an unnecessary increase in cost can be avoided.
• niobium-containing precipitate slurry By diluting the obtained niobium-containing precipitate from which fluoride ions have been removed, with pure water or the like, a niobium-containing precipitate slurry from which fluoride ions have been removed is obtained.
• the niobium concentration of the niobium-containing precipitation slurry was determined by taking part of the slurry, drying it at 110°C for 24 hours, and then calcining it at 1,000°C for 4 hours to generate Nb 2 O 5 . .
• the weight of Nb 2 O 5 thus produced can be measured and the niobium concentration of the slurry can be calculated from the weight.
• the mixture obtained by mixing the niobium-containing precipitation slurry and the lithium hydroxide--monohydrate from which fluoride ions have been removed is maintained at 20° C. to 100° C. while stirring, thereby obtaining the present invention.
• a lithium niobate solution is obtained.
• the lithium niobate concentration of the final mixture is 0.1 to 30% by mass in terms of Nb 2 O 5 , and the molar ratio Li/Nb of lithium and niobium is 0.8 or more and 2.0 or less.
• pure water or an alkaline aqueous solution such as aqueous ammonia may be added to and mixed with the mixture obtained by mixing the niobium-containing precipitation slurry and lithium hydroxide monohydrate.
• the ammonia concentration of the ammonia water added to the mixture may be any concentration. For example, it may be 0.1% by mass or more and 30% by mass or less, or 10% by mass or more and 25% by mass or less.
• lithium niobate solution is allowed to cool to room temperature.
• Lithium niobate powder can be obtained by drying the lithium niobate solution of the present invention.
• the lithium niobate solution of the present invention obtained by the above-described production method has a pH of 9 or more, because the lithium niobate solution is stable. Furthermore, the pH of the lithium niobate solution of the present invention is more preferably 10 or higher, more preferably 10.5 or higher, and particularly preferably 11 or higher.
• a method for producing a positive electrode active material for a lithium ion secondary battery coated with a lithium niobate solution includes mixing a lithium niobate solution, a positive electrode active material, and an aqueous solution of lithium hydroxide to prepare a lithium niobate-containing positive electrode active material for a battery containing lithium niobate.
• the method is characterized by comprising a step of producing a positive electrode active material slurry and a step of drying the battery positive electrode active material slurry containing lithium niobate.
• a battery positive electrode active material such as LiMn 2 O 4 (manufactured by Merck: spinel type, particle size ⁇ 0.5 ⁇ m) is added to an aqueous solution of lithium niobate obtained by diluting the lithium niobate solution of the present invention with pure water. By doing so, a slurry containing lithium niobate is obtained. Then, while stirring the slurry containing lithium niobate, an aqueous solution of lithium hydroxide is added dropwise, and the slurry is maintained at 90° C. for 10 minutes to produce a positive electrode active material slurry for batteries containing lithium niobate.
• LiMn 2 O 4 manufactured by Merck: spinel type, particle size ⁇ 0.5 ⁇ m
• the positive electrode active material slurry for a battery containing lithium niobate is dried in an air drying furnace for 15 hours while maintaining the temperature in the furnace at 110° C., thereby obtaining lithium coated with lithium niobate.
• a positive electrode active material for an ion secondary battery can be produced.
• the positive electrode active material for batteries is added in the method for producing the positive electrode active material for lithium ion secondary batteries described above, it may be changed as appropriate according to the application.
• dispersants, pH adjusters, colorants, thickeners, wetting agents, binder resins and the like may be added.
• the lithium niobate solution of the present invention has high dispersibility in water, good solubility in water, and excellent storage stability.
• lithium niobate solution of the embodiment according to the present invention will be further described with reference to the following examples. However, the following examples do not limit the present invention.
• reaction liquid was a slurry of niobate compound hydrate, in other words, a slurry of niobium-containing precipitates.
• this reaction liquid was decanted using a centrifuge and washed until the amount of liberated fluoride ions became 100 mg/L or less to obtain a niobium-containing precipitate from which the fluoride ions were removed. At this time, ammonia water was used as a cleaning liquid.
• the niobium-containing precipitate from which the fluoride ions were 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 Nb 2 O 5 , and the concentration of Nb 2 O 5 contained in the slurry was calculated from its weight.
• the slurry of the niobium-containing precipitate diluted with pure water was diluted with lithium hydroxide so that the final mixture had a niobium concentration of 1% by mass in terms of Nb 2 O 5 and a Li/Nb molar ratio of 1.
• a translucent slurry mixture was obtained by mixing the hydrate and pure water. While this mixture was stirred, it was maintained at a liquid temperature of 50° C. to 100° C., for example, 70° C. for 1 hour.
• the pH of the obtained lithium niobate aqueous solution according to Example 1 was 11.
• Example 2 In Example 2, the same production method as in Example 1 was carried out, except that the concentration of niobium in the semi-transparent slurry mixture was 5% by mass in terms of Nb 2 O 5 . An aqueous lithium oxide solution was obtained. The pH of the obtained lithium niobate aqueous solution according to Example 2 was 11.
• Example 3 In Example 3, the same production method as in Example 1 was carried out, except that the concentration of niobium in the semi-transparent slurry mixture was 10% by mass in terms of Nb 2 O 5 . An aqueous lithium oxide solution was obtained. The pH of the obtained lithium niobate aqueous solution according to Example 3 was 11.
• Example 4 In Example 4, the same production method as in Example 1 was carried out, except that the concentration of niobium in the translucent slurry mixture was 20% by mass in terms of Nb 2 O 5 , and colorless and transparent niobium according to Example 4 was prepared. An aqueous lithium oxide solution was obtained. The pH of the obtained lithium niobate aqueous solution according to Example 4 was 11.
• Example 5 In Example 5, the same production method as in Example 1 was carried out, except that the concentration of niobium in the translucent slurry mixture was 10% by mass in terms of Nb 2 O 5 and the molar ratio of Li/Nb was 2. Then, a colorless and transparent lithium niobate aqueous solution according to Example 5 was obtained. The pH of the obtained lithium niobate aqueous solution according to Example 5 was 11.
• Example 6 In Example 6, the production method was the same as in Example 1, except that the concentration of niobium in the translucent slurry mixture was 10% by mass in terms of Nb 2 O 5 and the molar ratio of Li/Nb was 0.9. was carried out to obtain a colorless and transparent lithium niobate aqueous solution according to Example 6. The pH of the obtained lithium niobate aqueous solution according to Example 6 was 11.
• Example 7 the translucent slurry mixture obtained in Example 1 was heated to 70° C. in a water bath, held with stirring for 2 hours, and then cooled to room temperature. In order to replenish the water evaporated by this heating, pure water is added, and the concentration is adjusted so that the niobium concentration of the colorless and transparent slurry mixture is 5% by mass in terms of Nb 2 O 5 . A colorless and transparent lithium niobate aqueous solution was obtained. The pH of the obtained lithium niobate aqueous solution according to Example 7 was 11.
• Example 8 In Example 8, the translucent slurry mixture obtained in Example 1 was heated to 70° C. in a water bath, held with stirring for 6 hours, and then cooled to room temperature. In order to replenish the moisture evaporated by this heating, pure water is added, and the concentration is adjusted so that the niobium concentration of the colorless and transparent slurry mixture is 5% by mass in terms of Nb 2 O 5 . A colorless and transparent lithium niobate aqueous solution was obtained. The pH of the obtained lithium niobate aqueous solution according to Example 8 was 11.
• Example 9 In Example 9, the translucent slurry mixture obtained in Example 1 was heated to 70° C. in a water bath, held with stirring for 25 hours, and then cooled to room temperature. In order to replenish the moisture evaporated by this heating, pure water is added, and the concentration is adjusted so that the niobium concentration of the colorless and transparent slurry mixture is 5% by mass in terms of Nb 2 O 5 . A colorless and transparent lithium niobate aqueous solution was obtained. The pH of the obtained lithium niobate aqueous solution according to Example 9 was 11.
• Example 10 the slurry of the niobium-containing precipitate according to Example 1 was prepared such that the translucent slurry mixture had a niobium concentration of 5 wt% as Nb2O5 and a NH3 concentration of 5.5 wt%. and, when mixing lithium hydroxide monohydrate and pure water, the same production method as in Example 1 except that part of the pure water was replaced with ammonia water ( NH concentration of 25% by mass) A colorless and transparent lithium niobate aqueous solution according to Example 10 was obtained. The pH of the obtained lithium niobate aqueous solution according to Example 10 was 11.
• Example 11 In Example 11, the slurry of the niobium - containing precipitate according to Example 1 and When lithium hydroxide monohydrate and pure water were mixed, the same production method as in Example 1 was carried out, except that part of the pure water was replaced with ammonia water ( NH3 concentration: 25% by mass). , a colorless and transparent lithium niobate aqueous solution according to Example 11 was obtained. The pH of the obtained lithium niobate aqueous solution according to Example 11 was 11.
• Example 12 In Example 12, the translucent slurry mixture obtained in Example 1 was heated to 70° C. in a water bath, held with stirring for 6 hours, and then cooled to room temperature. In order to replenish the moisture evaporated by this heating, pure water is added, and the concentration is adjusted so that the niobium concentration of the colorless and transparent slurry mixture is 10% by mass in terms of Nb 2 O 5 . A colorless and transparent lithium niobate aqueous solution was obtained. The pH of the obtained lithium niobate aqueous solution according to Example 12 was 11.
• Example 13 the slurry of the niobium-containing precipitate according to Example 1 was prepared such that the translucent slurry mixture had a niobium concentration of 10 % by weight as Nb2O5 and a NH3 concentration of 8.2% by weight. and, when mixing lithium hydroxide monohydrate and pure water, the same production method as in Example 1 except that part of the pure water was replaced with ammonia water ( NH concentration of 25% by mass) A colorless and transparent lithium niobate aqueous solution according to Example 13 was obtained. The pH of the obtained lithium niobate aqueous solution according to Example 13 was 11.
• Comparative example 1 In Comparative Example 1, 35% hydrogen peroxide solution was added to the colorless and transparent lithium niobate aqueous solution according to Example 1 so that the H 2 O 2 /Nb molar ratio was 0.3. An aqueous lithium niobate solution was obtained. The obtained lithium niobate aqueous solution according to Comparative Example 1 had a pH of 11.
• Comparative example 2 In Comparative Example 2, 35% hydrogen peroxide solution was added to the colorless and transparent lithium niobate aqueous solution of Example 1 so that the molar ratio of H 2 O 2 /Nb was 1, and the niobic acid of Comparative Example 2 was prepared. An aqueous lithium solution was obtained. The obtained lithium niobate aqueous solution according to Comparative Example 2 had a pH of 8.
• Comparative Example 3 (Comparative Example 3)
• the above-described niobium fluoride aqueous solution was slowly added to 500 mL of a 1% lithium hydroxide aqueous solution, and the Nb 2 O 5 content was 5% by mass and the Li/Nb molar ratio was 1.
• a fine particle dispersion was obtained.
• this fine particle dispersion was filtered and washed until the amount of liberated fluoride ions reached 100 mg/L, and a lithium niobate sol according to Comparative Example 3 was obtained.
• the obtained lithium niobate sol according to Comparative Example 3 had a pH of 8.6.
• Comparative Example 4 In Comparative Example 4, the translucent slurry mixture obtained in Example 1 was heated to 70° C. in a water bath, maintained with stirring for 73 hours, and then cooled to room temperature. It was confirmed that a precipitate was formed by heating for 73 hours. In order to replenish the moisture evaporated by this heating, pure water was added to adjust the niobium concentration of the slurry mixture to 5% by mass in terms of Nb 2 O 5 , and lithium niobate according to Comparative Example 4. An aqueous solution was obtained. The obtained lithium niobate aqueous solution according to Comparative Example 4 had a pH of 11.
• the sample is appropriately diluted with dilute hydrochloric acid, and using ICP emission spectrometry (manufactured by Agilent Technologies: AG-5110), in accordance with JIS K0116: 2014, Nb weight fraction in terms of Nb 2 O 5 and , and the Li weight fraction were measured.
• ICP emission spectrometry manufactured by Agilent Technologies: AG-5110
• Measurement conditions for the ultraviolet-visible absorption spectrum may be as follows.
• ⁇ Apparatus UH4150 type spectrophotometer (manufactured by Hitachi High-Tech Science Co., Ltd.)
• ⁇ Measurement mode wavelength scan
• ⁇ Data mode %T (transmission)
• ⁇ Measurement wavelength range 200 to 2,600 nm
• ⁇ Scan speed 600 nm/min
• ⁇ Sampling interval 2 nm
• ⁇ Dynamic light scattering method> The particle size distribution is evaluated using a zeta potential/particle size/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 method”. Carried out.
• the solution was filtered with a filter with a pore size of 2 ⁇ m, and an ultrasonic cleaner (manufactured by AS ONE: VS-100III) was used at 28 kHz for 3 minutes. Sonication was performed.
• the particle diameter (D50) refers to the median diameter (D50), which is the particle diameter showing the 50% integrated value of the integrated distribution curve.
• “Initial particle size D50 (nm)” in Table 1 refers to the lithium niobate particle size (D50) in the lithium niobate aqueous solution immediately after being produced.
• particle size over time D50 (nm) refers to the particle size (D50) of lithium niobate in an aqueous solution of lithium niobate after standing for one month in a constant temperature chamber set at room temperature of 25°C. .
• ⁇ Temporal stability test> The lithium niobate aqueous solutions of Examples 1 to 13 and Comparative Examples 1, 2, and 4, and the lithium niobate sol of Comparative Example 3 were allowed to stand in a thermostat set at room temperature of 25° C. for one month, after which a white precipitate was formed. The presence or absence of gelation was visually observed. Those in which no white precipitation or gelation was observed were evaluated as having stability over time as " ⁇ ", and those in which even one white precipitation or gelation was observed were evaluated as having no stability over time and " ⁇ " ” was evaluated.
• gelation was determined by placing each tantalate compound dispersion in a plastic container, and judging that the dispersion that did not drop quickly when the container was turned upside down was gelling.
• the particle size (D50) of lithium niobate over time in the lithium niobate aqueous solutions of Examples 1 to 13 and Comparative Examples 1, 2, and 4 after standing for one month, and in the lithium niobate sol of Comparative Example 3. was measured using the dynamic light scattering method described above.
• the positive electrode active materials coated with the lithium niobate aqueous solutions of Examples 1 to 13 and Comparative Examples 1, 2, and 4, and the lithium niobate sol of Comparative Example 3 were observed for coating and the amount of coating was measured.
• the positive electrode active material for which coating observation and coating amount measurement were performed was produced by the following production procedure.
• the lithium niobate aqueous solution after standing at room temperature of 25° C. for one month was diluted with pure water so that the niobium concentration was 2.3 mass % in terms of Nb 2 O 5 . Further, when the niobium concentration in the lithium niobate aqueous solution after standing for one month was less than 2.3% by mass in terms of Nb 2 O 5 , no dilution was performed.
• a positive electrode active material slurry containing lithium niobate is obtained by adding a positive electrode active material (lithium manganate) to a diluted lithium niobate aqueous solution so that the weight ratio of niobium/lithium manganate is 2/100. rice field.
• the coated state of the particle surface of the positive electrode active material coated with lithium niobate was evaluated by observing with a scanning electron microscope (SEM). Using a scanning electron microscope (SEM), five SEM images (20 ⁇ m ⁇ 20 ⁇ m) at a magnification of 50,000 were observed under the condition of an acceleration voltage of 1 kV to observe the coating state of the particle surface of the positive electrode active material. Under the observation conditions described above, the particles were evaluated as "good” when no uncovered 1 ⁇ m square area on the surface of the particles was observed, and as “poor” when even one area was observed.
• SEM scanning electron microscope
• the aqueous solutions of lithium niobate according to Examples 1 to 13 had a molar ratio Li/Nb of lithium to niobium of 0.8 or more and 2.0 or less.
• the lithium niobate particle size (D50) is 100 nm or less, good results were obtained in all the results of the aging stability test, the film formation test, and the safety test.
• the particle size (D50) of the lithium niobate over time remained the same as that of the initial particles even after one month had passed. No large difference was observed compared to the diameter (D50), and the stability over time was excellent.
• the initial particle size (D50) and particle size over time (D50) of lithium niobate in the lithium niobate aqueous solution according to Comparative Example 2 could not be measured due to gelation.
• the lithium niobate aqueous solution according to Comparative Example 4 had precipitates, and the initial particle size (D50) and the particle size over time (D50) of lithium niobate were not measured.
• the lithium niobate aqueous solutions according to Examples 1 to 13 had improved stability during long-term storage when the lithium niobate concentration in the aqueous solution was 0.1 to 30% by mass.
• the lithium niobate aqueous solution according to the present invention has high dispersibility in water, good solubility in water, and excellent storage stability. It is suitable as

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