JP5166850B2 - Method for producing sintered composite metal oxide - Google Patents

Description

  The present invention relates to a method for producing a composite metal oxide fired body containing a transition metal or the like and an alkali metal, and more particularly, a method for producing a composite metal oxide fired body that can be suitably used as a positive electrode active material for a lithium battery. Etc.

Nonaqueous electrolyte secondary batteries are characterized by a higher operating voltage and higher energy density than conventional nickel cadmium secondary batteries, and are widely used as power sources for electronic devices. As the positive electrode active material of this non-aqueous electrolyte secondary battery, lithium transition metal composite oxides typified by LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _{4 and the} like are used.

Among them, LiMn ₂ O ₄ and those in which a part of Mn is substituted with other metals (hereinafter, collectively referred to as lithium manganate) have a large amount of constituent element manganese as a resource, so the raw material is inexpensive. It is easy to obtain and has an advantage that the load on the environment is small. In order to take advantage of this advantage, nonaqueous electrolyte secondary batteries using lithium manganate have been used for mobile electronic devices such as mobile phones, notebook computers, digital cameras and the like.

  In recent years, mobile electronic devices have become more demanding due to high functionality such as various functions added and use at high and low temperatures. In addition, application to power sources such as batteries for electric vehicles is expected, and a battery capable of high-output and high-speed discharge that can follow sudden acceleration and rapid acceleration of an automobile is desired.

  Therefore, the development of lithium manganate that can smoothly insert and desorb Li is desired, and one particle design that embodies it is thought to be a method of refining the primary particles of lithium manganate. .

  As a technique for refining primary particles of lithium manganate, for example, as described in Patent Document 1, there is a technique of pulverizing lithium manganate or the like using a dry bead mill or the like.

  Patent Document 2 proposes spherical hollow particles composed of secondary particles in which primary particles are aggregated on a spherical surface by a technique such as spray pyrolysis. At that time, as a spray pyrolysis method, a solution of lithium nitrate and manganese nitrate (not slurry) is sprayed into a vertical pyrolysis furnace in a mist form to thermally decompose to obtain a composite oxide powder. A method of annealing at temperature is disclosed.

  Further, as disclosed in Patent Document 3, a spherical manganese compound is mixed with a lithium compound while maintaining its shape, and the mixture is heat-treated. The manufacturing method which obtains is proposed.

  Patent Document 4 discloses a method for producing an active material for a non-aqueous electrolyte secondary battery mainly composed of lithium and a transition metal, in which a lithium compound and a transition metal compound are pulverized in a liquid medium, The average particle size is 2 μm or less, and then the obtained solid-liquid mixture is spray-dried by using a rotary dryer or a spray dryer equipped with a nozzle atomizer. A method for producing an active material for a non-aqueous electrolyte secondary battery that is fired in the presence is disclosed. Here, a lithium compound that is soluble in water as a liquid medium is described as a preferred example, and a method of baking a powdered solid obtained by spray drying as it is as a baking step is described.

JP 2003-48719 A Japanese Patent Laid-Open No. 10-83816 JP 2002-151079 A Japanese Patent Laid-Open No. 10-106562

  However, none of the lithium manganate obtained by the prior art described above has been sufficiently enhanced.

  That is, in the method of pulverizing lithium manganate as in Patent Document 1, depending on the pulverization mode, the crystallinity may be lowered, and the particles become very fine. For example, a non-aqueous electrolyte secondary When forming a positive electrode for a battery (hereinafter also simply referred to as a battery), the formability tends to deteriorate.

  On the other hand, as disclosed in Patent Document 2, hollow particles composed of secondary particles in which primary particles are aggregated have been proposed, but secondary particles are hollow and sufficient density cannot be obtained. turn into.

  In addition, as in Patent Document 3 for improving this, in a high-density active material in which the active material is clogged up to the inside of the spherical particles, because the density is high, the speed at which Li diffuses into the active material is reduced, resulting in a result. It became clear that the high-speed discharge characteristics were low.

  Furthermore, in the manufacturing method described in Patent Document 4, fine pores of an appropriate size are not formed in the fired body obtained after firing, and high-speed discharge characteristics as a positive electrode active material may be insufficient. It became clear.

  Accordingly, the present invention provides a positive electrode active material that can smoothly move Li by making the spray granule porous in the firing process, has excellent formability when forming a positive electrode, and has excellent high-speed discharge characteristics. An object of the present invention is to provide a method for producing a fired composite metal oxide.

  The present inventors spray-granulates a slurry in which a metal compound such as a transition metal oxide and an alkali metal salt is dispersed in a solvent, and then heats the granulated body at a specific temperature and then fires it to make it porous. As a result, it was found that a positive electrode active material capable of smoothly moving Li was obtained, and the present invention was completed.

That is, the method for producing a fired composite metal oxide according to the present invention includes at least one metal oxide selected from the group consisting of transition metal oxides and oxides of metals belonging to 3B, 4B, and 5B of the periodic table. Spray granulation to obtain a granulated body by spray granulation of slurry containing (a) and one or more metal compounds (b) selected from the group consisting of alkali metal compounds and alkaline earth metal compounds, and a solvent A step of heating the granulated body at a decomposition temperature ± 200 ° C. of the metal compound (b), and firing the granulated body after the heat retaining step to obtain a fired body of a porous composite metal oxide A method for producing a particulate composite metal oxide fired body including a step, which satisfies the following (I) and (II).
(I) The metal oxide (a) and the metal compound (b) are hardly soluble in the solvent.
(II) The metal compound (b) contains at least a nonmetallic element component that is desorbed in the heat retaining step.

  According to the method for producing a fired composite metal oxide of the present invention, it is considered that a smooth movement of Li is possible by heating a spray granulated body at a specific temperature and then baking it to make it porous. When forming the composite metal oxide fired body, which is a positive electrode active material having excellent formability and high-speed discharge characteristics.

  The method for producing a fired composite metal oxide according to the present invention comprises spray granulating a slurry containing the metal oxide (a) satisfying the above (I) and (II) and the metal compound (b), and the granulated body. Spray granulation step for obtaining the above, a heat retention step for heating the granulation body at a decomposition temperature of ± 200 ° C. of the metal compound (b), and firing the granulation body after the heat retention step to form a porous composite metal oxide And a firing step for obtaining a fired body. In the present invention, since a fired body is obtained from the spray granulated body, a particulate composite metal oxide fired body is obtained (hereinafter sometimes referred to as “granular fired body”). This composite metal oxide fired body is an aggregated particle obtained by aggregating a plurality of primary particles produced by the reaction of the metal oxide (a) and the metal compound (b) under the firing.

  The average primary particle diameter of the fired composite metal oxide obtained by the production method of the present invention tends to be determined by the average particle diameter of the metal oxide (a) as a raw material. Therefore, the primary particle size of the granular fired body obtained in the present invention can be controlled by adjusting the particle size of the raw metal oxide (a) to a desired particle size by pulverization or the like.

  In the present invention, primary particles are the smallest units that can be confirmed as particles when observed with an electron microscope. “Average primary particle diameter” refers to the number average particle diameter of primary particles observed with an electron microscope. In addition, the various physical-property values in this invention are values specifically measured by the method as described in an Example.

  Aggregated particles are aggregates of particles formed by the primary particles being strongly gathered, and the metal oxide (a), metal compound (b), or composite metal oxide fired body according to the present invention is made of water or the like. Particles that cannot be unraveled by irradiating with ultrasonic waves in a solvent or applying external force such as shearing force with a homogenizer. The average value of the particle size of the particles is referred to as an average aggregate particle size, and a specific method for measuring the average aggregate particle size will be described later.

  The average aggregate particle diameter of the composite metal oxide fired body obtained by the production method of the present invention can be controlled by the spraying conditions of the spray granulation method. Spray granulation is a method for producing particles having a spherical shape and a relatively sharp particle size distribution by spraying a raw material slurry from a spray nozzle and drying it with hot air or the like. By controlling the size of droplets generated by spraying, the average aggregate particle size of the granular fired body of the present invention can be controlled.

  As the metal oxide (a) and the metal compound (b) contained in the slurry, substances that are hardly soluble in the solvent of the slurry are used. By doing so, a solid granular fired body in which a solid is filled up to the inside by spray granulation can be obtained. That is, when a soluble substance is used in the solvent, the solvent evaporates while moving from the central part of the granulated particle to the outer surface layer part in the process of drying the droplets generated by spray granulation. . At that time, the substance dissolved in the solvent moves to the particle surface and concentrates along with the movement of the solvent, and as a result, the center part becomes a hollow particle. On the other hand, if a substance hardly soluble in the solvent is used, it is considered that the particle surface layer of the component raw material does not concentrate and solid particles can be obtained.

The granular fired body obtained by the present invention has a porous structure with fine pores. It is considered that the micropores are formed in the process in which the nonmetallic element component of the metal compound (b) is desorbed at least in the heat-retaining step, and the remainder of the metal compound (b) reacts with the metal oxide (a). It is done. That is, it is considered that after spray granulation, the metal compound (b) disappears in the heat retaining step, so that voids are formed in the place occupied by the metal compound (b) (hereinafter referred to as porous in the present invention). Is a state having holes formed in this manner). Therefore, since the pores obtained tend to be determined by the average particle size of the metal compound (b), the pore size can be controlled by controlling the average particle size. That is, in the present invention, it is necessary to satisfy the following condition (II).
(II) The metal compound (b) contains at least a nonmetallic element component that is desorbed in the heat retaining step.

  Here, “at least the nonmetallic element component desorbed in the heat retaining step” is a nonmetallic element component contained in the metal compound (b), and is decomposed from the metal compound (b) at least in the heat retaining step described later, It refers to those desorbed with sublimation. Examples of such non-metallic element components include carbon, nitrogen, hydrogen, oxygen, and sulfur contained in carbonates, nitrates, hydroxides, sulfides, chlorides, acetates, oxalates, and the like that are metal compounds. And elemental components such as chlorine. That is, a metal compound such as carbonate or oxalate that causes elimination of carbon dioxide or the like, or a hydroxide that causes elimination of water or the like is used as the metal compound (b).

  In the present invention, from the viewpoint of ensuring a larger total pore volume of the granular fired body, it is a substance other than the metal oxide (a) and the metal compound (b), hardly soluble in the slurry solvent, and thermally decomposed during spray granulation. Instead, it is preferable to add to the slurry at least a substance (c) that undergoes thermal decomposition (for example, oxidative decomposition) by firing after spray granulation. It is considered that the substance (c) can suppress the shrinkage of the granulated body and can ensure a large total pore volume of the granular fired body until it is fired after spray granulation using the slurry. From the viewpoint of obtaining a solid granular fired body, the average aggregated particle diameter of the substance (c) is preferably 50% or less, more preferably 40% or less of the average aggregated particle diameter of the target granular fired body. From the same viewpoint, the content of the substance (c) in the slurry is preferably 30% by weight or less, more preferably 25% by weight or less, based on the total amount of the metal oxide (a) and the metal compound (b). More preferably, it is 20% by weight or less. In addition to ensuring the larger total pore volume of the granular fired body obtained in the present invention, from the viewpoint of preventing the impurities from remaining in the granular fired body obtained in the present invention, the substance (c) is sprayed. Any material can be used as long as it is not thermally decomposed until it is granulated, and at least when thermally decomposed during firing.

  Examples of the substance (c) include carbons, polystyrenes (polystyrene, poly α-methylstyrene, etc.), polyolefins (polyethylene, polypropylene, etc.), fluorine-containing resins (polyvinylidene fluoride, polytetrafluoroethylene, etc.), Examples include organic polymers (preferably thermoplastic resins) such as poly (meth) acrylic acid esters, poly (meth) acrylonitriles, poly (meth) acrylamides, and copolymers thereof. Furthermore, thermosetting resins such as urethane resin, phenol resin and epoxy resin, thermoplastic resins and elastomers such as polyethylene and polypropylene, or vinylidene fluoride, ethylene fluoride, acrylonitrile, ethylene oxide, propylene oxide, methyl methacrylate, polyvinyl alcohol A homopolymer or a copolymer such as polyvinyl butyral can be used. Furthermore, organic short fibers or organic polymer particles such as polyamide, acrylic, acetate, polyester, and polymethyl methacrylate (PMMA) can also be used. In the present specification, (meth) acrylic acid refers to acrylic acid or methacrylic acid. The same applies to (meth) acrylonitrile and (meth) acrylamide.

As described above, in the present invention, since a technique called spray granulation is used to make a granular fired body, a step of dispersing a raw material in a solvent and forming a slurry is required. And since the particle diameter of the metal oxide (a) and metal compound (b) used as a raw material is important as a factor which determines the average primary particle diameter and pore diameter of the obtained granular fired body, these average grains From the viewpoint of suppressing the change in diameter, both of them need to be hardly soluble in the solvent. Furthermore, in order to form a solid granular fired body, it is necessary that the raw material is hardly soluble in the solvent. In addition, a raw material is hardly soluble in a solvent means that the solubility of the raw material at 20 ° C. in 100 g of the solvent is 5 g or less, preferably 3 g or less, more preferably 2 g or less. Hereinafter, the solubility at 20 ° C. is also simply referred to as solubility. That is, in the present invention, it is necessary to satisfy the condition (I).
(I) The metal oxide (a) and the metal compound (b) are hardly soluble in the solvent.

  The shape of the composite metal oxide fired body obtained in the present invention may be any particle form that can be obtained by spray granulation, but from the viewpoint of formability when forming a positive electrode for a battery, spray granulation Usually obtained spherical shape is preferable. Here, the term “spherical” does not necessarily mean only a spherical shape, but the surface of the particle is somewhat uneven, the entire sphere is slightly distorted, partially dented, missing, It is a concept that includes several aggregates.

  Further, from the viewpoint of increasing the energy density of the electrode, the obtained porous fired body is preferably solid. Here, the “solid” refers to a structure in which a hollow portion other than the voids formed by the disappearance of the metal compound (b) or the metal compound (b) and the substance (c) does not substantially exist.

  The metal oxide (a) in the present invention is one or more metal oxides selected from the group consisting of transition metal oxides and oxides of metals belonging to 3B, 4B, and 5B of the periodic table, and the periodic table. Transition metal oxides belonging to 3A, 4A, 5A, 6A, 7A, 8, 1B, 2B and / or oxides of at least one metal belonging to 3B, 4B, 5B, or two or more thereof These composite oxides are mentioned. Of these, those which are hardly soluble in water or ethanol are particularly preferred.

  In particular, when the composite metal oxide fired body is used as a material for a battery, preferably a lithium battery, the metal oxide (a) is an oxide of one or more metals selected from the group consisting of Mn, Fe, Co, and Ni. It is preferable that

  The metal compound (b) in the present invention is one or more metal compounds selected from the group consisting of alkali metal compounds and alkaline earth metal compounds. Specific examples of the metal compound (b) include carbonates, nitrates, hydroxides, sulfides, chlorides, acetates, and oxalates of organic low molecular weight carboxylates of the elements belonging to 1A and 2A of the periodic table. One kind or two or more kinds of metal compounds such as acid salts may be mentioned. Of these, those that are insoluble or hardly soluble in water or ethanol are preferred, and those that do not leave any components other than metal oxides after heat treatment at 600 ° C. or lower are preferred. Specifically, carbonates, nitrates and hydroxides are preferable, and those insoluble in water and ethanol are more preferable.

The production method of the present invention is suitable for production of a functional material obtained by firing. For example, BaTiO _{3 as} a dielectric material, ferrite (MgFe ₂ O ₄ ) as a magnetic material, Nb _{3 as} a piezoelectric element, NaCoO ₄ as a heat transfer conversion element, SrZrO _{5 as} a solid electrolyte, and LiNbO _{3 as a} laser element. , LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiFeO _2, etc., which are non-aqueous electrolyte secondary battery materials (lithium battery materials). Among these, it is more suitably used for production of lithium manganate such as LiM ₂ O ₄ which is a lithium battery material. Therefore, in the present invention, the metal oxide (a) is an oxide of one or more metals selected from the group consisting of Mn, Fe, Co, and Ni, and the metal compound (b) is a lithium salt. preferable.

Lithium manganate obtained in the present invention (strictly refers to “lithium / manganese-containing metal composite oxide”) has a general formula LiMn _2−x M _x O ₄ (where M represents an element other than Mn, 0 ≦ x ≦ 0.3) is typical, and may include a substitution element other than Mn.

  The amount of the substitution element M is preferably x = 0 from the viewpoint of improving the initial charge / discharge characteristics, and preferably 0 <x ≦ 0.3 from the viewpoint of improving the repeated charge / discharge characteristics (cycle characteristics).

  The substitution element M is preferably an element that replaces Mn of lithium manganate and works as an effective element for suppressing elution of Mn into the electrolytic solution, and has an effect of improving battery performance and rate characteristics. Are Li, K, Ca, Mg, Ba, Fe, Ni, Zn, Co, Cr, Al, B, V, Si, Sn, P, Sb, Nb, Ta, Mo, and W, F, Ti, Cu At least one element selected from the group consisting of Zr, Pb, Ga, Sc, Sr, Y, In, La, Ce, Nd, S, and Bi is preferable. Of these, Mg, Al, Co, Fe, Cr, Ni, Zn, B and the like are more preferably used.

  The crystal phase of the obtained lithium manganate is preferably a spinel type, and specifically, JCPDS (Joint committee on powder diffusion standards): No. As shown in 35-782, with respect to the main peak obtained by X-ray diffraction measurement, the relative diffraction intensity corresponding to other d is 100 when the diffraction intensity corresponding to d = 4.764 ± 0.030 is 100. The relative diffraction intensity corresponding to d = 2.487 ± 0.030 is preferably 20 to 50, and the relative diffraction intensity corresponding to d = 2.62 ± 0.030 is preferably 20 to 50. .

  The average aggregate particle diameter of the metal oxide (a) in the slurry is preferably 0.03 to 2.5 μm from the viewpoint of generating an average primary particle diameter suitable for the obtained granular fired body, 0.05 More preferably, it is -2 micrometers, and it is still more preferable that it is 0.1-1.8 micrometers.

  The average aggregate particle diameter of the metal compound (b) in the slurry is preferably 0.1 to 10 μm, and preferably 0.2 to 5 μm, from the viewpoint of imparting suitable porosity to the obtained granular fired body. Is more preferable, and it is still more preferable that it is 0.2-3 micrometers.

  Therefore, from the above viewpoint, it is preferable that the average aggregated particle diameter of the metal oxide (a) and the average aggregated particle diameter of the metal compound (b) in the slurry are both in the above-described preferable range.

  In the present invention, a metal oxide (a) and a metal compound (b) (for example, when lithium manganate is produced as a fired composite metal oxide, Mn oxide (Mn source) as a metal oxide (a), and metal It is possible to prepare a slurry by a slurrying step in which a Li salt (Li source)) is pulverized as a compound (b) to a desired particle size, mixed with a solvent that does not dissolve the pulverized product, and slurried. it can. The pulverization may be performed by mixing the metal oxide (a) and the metal compound (b), but it is preferable to pulverize separately from the viewpoint of appropriately controlling the particle size after pulverization. The spray granulation step of spray granulating the slurry to obtain a granulated body, the heat retaining step of heating the granulated body within the range of the decomposition temperature of the metal compound (b) ± 200 ° C., and the granulation after the heat retaining step. A particulate composite oxide (for example, lithium manganate) fired body is manufactured through a firing step of firing the granule to obtain a porous composite metal oxide fired body.

  In the case of producing particulate lithium manganate according to the present invention, the element M added to improve the cycle characteristics of the battery is added when the Li source or the Mn source is pulverized, or a slurry of the Li source and the Mn source. Is preferably added when mixing. As an addition form of the M element, a salt containing the M element may be added after being dissolved in a solvent. When the salt of the M element is insoluble, it may be added at the time of wet pulverization, or may be added in a solution or 0. When the Li source is added, it may be added together in the form of fine particles of 5 μm or less.

  The average primary particle size of the obtained lithium manganate tends to be determined by the average aggregated particle size of the Mn source. That is, it is considered that the primary particle aggregates (aggregated particles) of the Mn source are sintered while taking in the Li source during the firing process, and change into primary particles of lithium manganate. Therefore, the primary particles of lithium manganate to be generated can be controlled by controlling the average aggregated particle size of the Mn source by wet grinding or the like.

As the Mn source, one or more of MnO, Mn ₃ O ₄ , Mn ₂ O ₃ and MnO ₂ are preferably used, and among these, MnO ₂ and Mn ₂ O ₃ are more preferably used.

  As the Li source, lithium compounds such as lithium carbonate, lithium hydroxide, lithium oxide, lithium nitrate, lithium acetate, and lithium sulfate are preferable, and among these, ease of primary particle control of lithium manganate and preferable solvent, water From the viewpoint of low solubility of lithium carbonate, lithium carbonate is preferably used.

  In the present invention, the average primary particle size of the metal oxide (a) before pulverization is not particularly limited, but is preferably 0.01 to 0.5 μm from the viewpoint of ease of pulverization to a desired particle size, 0.01-0.1 micrometer is more preferable and 0.01-0.05 micrometer is still more preferable. In addition, the average aggregate particle diameter before pulverization is preferably 0.03 to 100 μm, and more preferably 0.03 to 50 μm, from the viewpoint of ease of wet pulverization.

  In the present invention, the average primary particle size of the metal compound (b) before pulverization is not particularly limited, but is preferably 0.01 to 10 μm from the viewpoint of reactivity with the metal oxide (a). Moreover, 0.03-100 micrometers is preferable from a reactive viewpoint with a metal oxide (a), and, as for the average aggregate particle diameter before a grinding | pulverization, 0.03-50 micrometers is more preferable.

  In the present invention, the average agglomerated particle size can be controlled by a method such as classification and pulverization. However, considering slurrying in a later step, wet classification and wet pulverization are preferable. Grinding is preferred. For the wet pulverization, a ball medium type mill such as a wet bead mill, a ball mill, an attritor or a vibration mill is preferably used. Moreover, when using the metal compound (b) which is not melt | dissolved in a solvent, you may grind | pulverize a metal compound (b) separately with a metal oxide (a) separately. However, it is preferable that the metal oxide (a) and the metal compound (b) are separately wet pulverized from the viewpoint of easy control of the aggregate particle diameter.

  As a method of controlling the average aggregate particle size during pulverization by wet pulverization, etc., a method of adjusting the pulverization time, a method of changing the particle size of a pulverization medium such as beads, a method of adjusting the pulverization energy, or a method of combining these methods Etc. can be adopted.

  The solvent to be used has a boiling point of preferably 250 ° C. or less, more preferably 200 ° C. or less, and further preferably 120 ° C. or less from the viewpoint of easy drying when removed by spray drying. Even more preferred is 70 ° C to 120 ° C. Specific examples of such solvents include N-methyl-2-pyrrolidone (NMP, boiling point 202 ° C.), dimethylformamide (DMF, boiling point 153 ° C.), dimethylacetamide (boiling point 165 ° C.), toluene (boiling point 110.8). ° C), water (boiling point 100 ° C), methyl ethyl ketone (boiling point 79.5 ° C), ethanol (boiling point 78.3 ° C), ethyl acetate (boiling point 76.8 ° C), acetone (boiling point 56.3 ° C), tetrahydrofuran (boiling point) 66 ° C.). Among these, from the viewpoint of ease of handling, preferred solvents are water and ethanol, and water is more preferred.

The average aggregate particle diameter of the metal oxide (a) in the slurry used in the spray granulation step after pulverization is a viewpoint of generating an average primary particle diameter suitable for the composite metal oxide fired body according to the present invention. From the viewpoint of securing a peak pore diameter of 0.05 to 0.5 μm in the fired composite metal oxide obtained in the present invention, 0.03 μm to 2.5 μm is preferable, 0.05 to 2 μm is more preferable, 0.1 More preferably, ˜1.8 μm. Moreover, from the same viewpoint, the average primary particle diameter of the metal oxide (a) used in the spray granulation step is preferably 0.01 to 2.5 μm, more preferably 0.03 to 2 μm, 0.05 More preferably, it is -1.7 micrometers.

  As the concentration at the time of wet pulverization, the total solid content of the metal oxide (a) and the metal compound (b) is preferably 1% by weight or more of the total amount of slurry, and more preferably 2% by weight or more from the viewpoint of productivity. 5% by weight or more is more preferable. Further, from the viewpoint of the grinding efficiency of the slurry, it is preferably 70% by weight or less, more preferably 50% by weight or less, and particularly preferably 30% by weight or less. When these viewpoints are put together, 1 to 70% by weight is preferable, 2 to 50% by weight is more preferable, and 5 to 30% by weight is still more preferable.

  Moreover, it is preferable to add a dispersing agent from a viewpoint of improving the grinding efficiency at the time of wet grinding. When a dispersant is used, an anionic, nonionic or cationic surfactant, or a polymer dispersant can be used as the dispersant, but a polymer dispersant is preferably used from the viewpoint of dispersion performance. Further, from the viewpoint of keeping the purity of the granular fired product of the present invention high, a polymer dispersant that is completely decomposed after firing and does not leave a residue is more preferable.

  Although various compounds can be used as the polymer dispersant, a polycarboxylic acid polymer dispersant having a plurality of carboxyl groups in the molecule and a polyamine polymer dispersant having a plurality of amino groups in the molecule A polymer dispersant having a plurality of amide groups in the molecule and a polymer dispersant containing a plurality of polycyclic aromatic compounds in the molecule are preferred.

  Examples of the polycarboxylic acid polymer dispersant include poly (meth) acrylic acid and derivatives thereof. Specific examples of the derivative include a copolymer of (meth) acrylic acid and (meth) acrylic acid ester, a copolymer of (meth) acrylic acid and maleic anhydride, and an amidated or esterified product thereof. Examples thereof include a copolymer of (meth) acrylic acid and maleic acid, and a comb polymer having a (meth) acrylic acid unit.

  Examples of the polyamine-based polymer dispersant include polyalkyleneamine and derivatives thereof, polyallylamine and derivatives thereof, polydiallylamine and derivatives thereof, poly N, N-dimethylaminoethyl methacrylate and derivatives thereof, and polyesters to be grafted onto the above polyamines. Type polymer and the like.

  Examples of the polymer dispersant having a plurality of amide groups in the molecule include polyamides obtained by condensation reaction and derivatives thereof, polyvinylpyrrolidone and derivatives thereof, poly N, N-dimethylacrylamide and derivatives thereof, and polyesters and derivatives thereof. Examples thereof include a comb-type polymer grafted with polyalkylene glycol.

  Examples of the polymeric dispersant containing a polycyclic aromatic compound include copolymers of vinyl monomers having a pyrene or quinacridone skeleton and various monomers.

  These dispersing agents can be used alone or in admixture of two or more kinds of dispersing agents. When the dispersant is used, a preferable addition amount is 0.05 to 20% by weight with respect to the slurry. Moreover, from a viewpoint of preventing the residue of the residue after baking, it is 0.05 to 10 weight% more preferably.

  In the present invention, the particle sizes of the metal oxide (a) and the metal compound (b) are factors that determine the average primary particle size and pore size of the granular fired body, and therefore it is preferable to adjust the particle size separately. In that case, the slurry adjusted to the desired particle size is mixed and spray granulation is performed, but the mixer used at that time is not particularly limited, and a paddle type stirrer and a disperser capable of uniformly mixing the slurry are not limited. It is preferable to mix using a dispersing machine such as a homomixer.

  The production method of the present invention includes a spray granulation step of obtaining a granulated body by spray granulation of the slurry as described above. In the spray granulation step, the mixed raw material slurry is sprayed from a spray nozzle to form atomized droplets, and then dried to form a spherical powder.

  The atomized droplets are usually distinguished from spray when the diameter exceeds 10 μm and mist when the diameter is 10 μm or less, but the latter is preferably used. That is, in the spray granulation step in the present invention, the slurry is preferably sprayed so that the droplet diameter is 10 μm or less, and the slurry is sprayed so that the droplet diameter is 0.1 to 10 μm. More preferred.

  Slurry droplet formation can be performed using a rotating disk (change in the number of rotations), a pressure nozzle (liquid pressure), a two-fluid nozzle (gas pressure), a four-fluid nozzle (gas pressure), or the like.

  Among these, a two-fluid nozzle or a four-fluid nozzle, which is one type of nozzle using compressed air, is preferable because it can spray droplets as mist.

  The drying method can be performed by a technique such as freeze drying, spray drying, or spray pyrolysis, but spray drying is preferable from the viewpoint of reducing manufacturing costs. The drying temperature is preferably in the range from the boiling point of the solvent to 800 ° C, more preferably in the range of 50 ° C to 350 ° C from the boiling point of the solvent, from the viewpoint of controlling the pore diameter.

  In the present invention, the fine pores of the particulate composite metal oxide fired body are considered to be generated by the disappearance of the metal compound (b) in the heat retention step following spray granulation. Since the decomposition temperature of the metal compound (b) is usually lower than the crystallization temperature of the metal oxide (a), the generated vacancies may disappear in the method of rapidly raising the temperature to the firing temperature. .

  Therefore, in the present invention, from the viewpoint of forming desired micropores, it is necessary to stop the temperature increase in the heat retaining step near the decomposition temperature of the metal compound (b) and to heat within the range of the decomposition temperature ± 200 ° C. . That is, in the firing step of the present invention, prior to the heat treatment at the firing temperature, it is necessary to perform a heat treatment (a heat retaining step) for holding the heating temperature in a lower temperature range. From the same viewpoint, the upper limit temperature of the heating temperature is preferably within the range of decomposition temperature + 150 ° C., more preferably decomposition temperature + 100 ° C., and further preferably decomposition temperature + 80 ° C. Further, the lower limit temperature of the heating temperature is preferably within the range of the decomposition temperature of −150 ° C., more preferably the decomposition temperature of −100 ° C., and further preferably the decomposition temperature of −80 ° C. from the same viewpoint. Here, for example, holding within the range of the decomposition temperature of the metal compound (b) ± 200 ° C. means holding the temperature constant or substantially constant, and holding the temperature within a certain temperature range (temperature increase) Including the case where the speed is low). Furthermore, from the same viewpoint, the holding time is preferably 0.5 to 5 hours, more preferably 0.8 to 4 hours, and further preferably 1 to 3 hours.

  The preferable average temperature rising rate until the heat retaining step is preferably 100 to 400 ° C./hour, more preferably 150 to 300 ° C./hour.

  The production method of the present invention comprises a firing step in which a granulated body (granule, powder, etc.) obtained in the spray granulation step as described above is kept warm and then fired to obtain a porous composite metal oxide fired body. Including. By firing, a metal oxide (a) (for example, Mn source) and a metal compound (b) (for example, Li source) are reacted to form a porous composite metal oxide fired body (for example, lithium manganate) crystal. It is considered that pores can be formed by decomposing the metal compound (b).

In the present invention, “sintering” refers to heat treatment (annealing) until the spray granulated body that has been subjected to the heat retaining process is sintered, thereby improving the crystallinity of the composite metal oxide, For example, when used for a positive electrode for a battery, high-speed discharge characteristics are improved. By such firing, a positive electrode active material cured in a porous state can be obtained. Here, the sintering means that when the aggregate of the mixed mineral powder is heated and the powder particles are bonded by a bonding reaction involving a pure solid phase or a part of the liquid phase between the solids, Refers to the reaction (from the Chemical Dictionary 4 (Kyoritsu Shuppan, published October 15, 1981)). In this invention, it is preferable that it is in any one of the following states by a baking process.
(1) The half width of the X-ray diffraction peak of the (111) plane attributed to lithium manganate in the granular fired body is 2.5 or less.
(2) The weight loss when the granular fired body is heated in air at 600 ° C. for 1 hour is less than 1%.

  In the case where the inside of the furnace containing the spray granulated body that has undergone the heat retaining step is fired at T ° C. for H hours after reaching T ° C. at an average heating rate t ° C./hour, suitable firing conditions include high-speed discharge characteristics. From the viewpoint and the viewpoint of improving crystallinity, t, T, and H satisfy the following.

That is, preferably
t = 200 to 800, T = 650 to 1200, H = [4000/10 ^{(1 + T / 273)} ] to [204000/10 ^{(1 + T / 273)} ], more preferably
t = 300 to 700, T = 650 to 1000, H = [4000/10 ^{(1 + T / 273)} ] to [180000/10 ^{(1 + T / 273)} ], more preferably
t = 300 to 600, T = 700 to 900, H = [8500/10 ^{(1 + T / 273)} ] to [128000/10 ^{(1 + T / 273)} ], and more preferably,
t = 300 to 500, T = 700 to 850, H = [17000/10 ^{(1 + T / 273)} ] to [85000/10 ^{(1 + T / 273)} ].

  Further, from the viewpoint of ensuring productivity, H preferably does not exceed 20, more preferably does not exceed 10, and further preferably does not exceed 6.

It is known from experience that the sinterability of the active material is preferably large when T is low, and can be sufficiently ensured even when H is small when T is high. The inventors of the present invention favorably provide such a relationship between T and H by the product [10 ^{(1 + T / 273)} ] × H, and satisfy the preferable range of the product, so H can be obtained.

  For example, when t = 200 to 800 and T = 650 to 1200, a satisfactory sintered state can be obtained by selecting H that satisfies the product = 4000 to 204000.

  In the firing step, it is possible to remove the gas generated in the firing step, such as air, oxygen, and nitrogen, and perform firing while supplying the gas into the firing atmosphere.

  The fired body obtained as described above has almost no sticking between particles, maintains the particle size at the time of spray granulation, and can be used as a positive electrode active material, in order to improve the fluidity of the powder. In addition, classification using a sieve may be performed.

  Moreover, the fired body (composite metal oxide fired body) obtained in the firing step is porous, and has a pore distribution measured by a mercury porosimeter of at least 0.05 to 0.5 μm (preferably 0.2 to 0). .4 μm) and 0.5 μm to 10 μm or less, respectively, and preferably have a peak pore diameter. Fine pores having a size of 0.05 to 0.5 μm (preferably 0.2 to 0.4 μm) are formed as the metal compound (b) or the metal compound (b) and the substance (c) disappear. Are pores inside the fired body. When the fired body is lithium manganate and it is used for a positive electrode for a battery, it is considered that Li ions can smoothly be inserted and desorbed when Li ions enter the pores. Moreover, it is thought that the hole exceeding 0.5 micrometer is a hole produced by the clearance gap between the sintered bodies which are aggregated particles. This hole corresponds to a hole clogged with a conductive auxiliary agent such as carbon black when the fired body is made of lithium manganate and is used as a positive electrode for a battery, smoothing the flow of electrons and reducing the resistance of the electrode. It is thought that it corresponds to what plays a role. It is thought that the above-mentioned fine pores can express characteristics excellent in high-speed discharge characteristics.

Hereinafter, a specific method for producing lithium manganate (LiMn ₂ O ₄ ), which is the most preferable application example of the granular fired body of the present invention, will be described.

  The average aggregate particle diameter of the Li source used after the pulverization, that is, in the spray granulation step is preferably 0.1 to 10 μm from the viewpoint of imparting suitable porosity to the obtained lithium manganate. 5 μm is more preferable. Moreover, 0.01-10 micrometers is preferable from the same viewpoint, and, as for the average primary particle diameter of Li source used at a spray granulation process, 0.01-5 micrometers is more preferable.

  The mixing ratio (Li / Mn molar ratio) is preferably in the range of 0.5 to 1.1, more preferably 0.55 to 1.02. When the substitution element M is contained, the molar ratio of Li / (Mn + M) is preferably in the above range.

  The particle size of the granulated product to be spray granulated can be controlled by the droplet size at the time of spraying and the particle size of the raw material particles, but the particle size of the granulated product can be controlled by manganic acid obtained after firing. It is determined in accordance with the average aggregate particle diameter of lithium, that is, the fired body obtained in the firing step.

  The average agglomerated particle diameter of the obtained lithium manganate is preferably 15 μm or less from the viewpoint of maintaining the smoothness of the coating film when forming the positive electrode of the battery and improving the insertion / desorption ability of Li, 10 μm or less is more preferable, and further preferably 8 μm or less. Moreover, when producing the said coating film, from a viewpoint of reducing the quantity of a binder, 0.7 micrometer or more is preferable and 1 micrometer or more is more preferable. Taking the above viewpoints together, the average aggregate particle diameter of lithium manganate is preferably 0.7 to 15 μm, more preferably 1 to 10 μm, and even more preferably 1 to 8 μm.

  The average primary particle size of lithium manganate is preferably 0.03 to 3 μm, preferably 0.05 to 2 μm, from the viewpoint of suppressing elution of Mn into the electrolyte and ensuring high-speed discharge characteristics (rate characteristics) stably. Is more preferable.

The BET specific surface area of the lithium manganate, that is, the BET specific surface area of the granular fired body obtained in the firing step is preferably 1 m ² / g or more, more preferably 1.5 m ² / g or more from the viewpoint of the permeability of the electrolytic solution. preferably, preferably ^{40 m} 2 / g or less from the viewpoint of binder amount reduced in making the positive electrode, more preferably not more than ^{20m 2 / g, 10m 2 /} g or less is more preferable. Taken together the above viewpoints, the BET specific surface area of the lithium manganate is preferably 1~40m ² / g, more preferably 1.5~20m ² / g, more preferably 1.5~10m ² / g.

  Lithium manganate, that is, the fired body obtained in the firing step, has a pore distribution measured by a mercury porosimeter of at least 0.05 to 0.5 μm (preferably 0.2 to 0.4 μm) and 0.5 μm. Preferably, each has a peak pore diameter in the range of 10 μm or less.

  Further, the lithium manganate preferably has a total pore volume measured by a mercury porosimeter of 0.6 to 2 ml / g, preferably 0.6 to 1 from the viewpoint of the balance between porosity and energy density required for Li migration. 4 ml / g is more preferable, and 0.6 to 1 ml / g is still more preferable.

  Moreover, as for the strongest peak intensity | strength of the X-ray-diffraction spectrum (XRD) of lithium manganate, the value obtained by the method of an Example description from the viewpoint of a high-speed discharge characteristic has preferable 10000-50000.

  Since the lithium manganate obtained by the present invention is solid porous particles, the compression density measured by the measurement method described in the examples is preferably 1.92 or more from the viewpoint of increasing the energy density. More preferably, it is 1.95 or more, More preferably, it is 2.0 or more. Moreover, from a viewpoint of ensuring the porosity for promoting the movement of Li ion, Preferably it is 2.4 or less, More preferably, it is 2.3 or less, More preferably, it is 2.2 or less.

  The lithium manganate obtained by the present invention can be suitably used as a positive electrode active material for a lithium battery. When using lithium manganate as a positive electrode active material, for example, a positive electrode active material, a slurry mixed with a conductive material such as carbon black, a binder, and a solvent are coated and dried on a metal foil serving as a current collector. A lithium battery is manufactured by stacking together with a negative electrode and a separator and injecting an electrolyte solution.

  A lithium battery produced using the lithium manganate obtained by the present invention has excellent high-speed discharge characteristics. The high-speed discharge characteristics are preferably 55% or more, more preferably 60% or more, as defined by battery characteristic evaluation described later.

  In the production method of the present invention, when manganese oxide having a specific average agglomerated particle size is used, lithium manganate having an appropriate average primary particle size is easily obtained after firing, and Li insertion / extraction is smoothly performed. Conceivable. Moreover, when fine primary particles are aggregated by spray granulation and the average aggregate particle diameter is 0.7 to 15 μm, the coating film forming property for forming the positive electrode is improved, and a high surface smoothness is obtained. It is done. Furthermore, by using a raw material that is hardly soluble in the solvent, solid particles are obtained, and pores are formed at the disappearance location of the Li source during firing, so that the penetration of the electrolyte into the active material is smooth, and Li It is considered that a product that easily exhibits the insertion / desorption function of can be obtained. As a result, it is considered that lithium manganate excellent in high-speed discharge characteristics particularly in a lithium battery can be provided as compared with conventional lithium manganate.

  As described above, the lithium manganate obtained by the production method of the present invention is superior in high-speed discharge characteristics particularly in a lithium battery as compared with conventional lithium manganate.

  The use of batteries using lithium manganate is not particularly limited. For example, it can be used for electronic devices such as notebook computers, ebook players, DVD players, portable audio players, video movies, portable TVs, and cell phones, and cordless cleaning. It can be used for consumer equipment such as machines, cordless power tools, batteries for electric vehicles, hybrid cars, etc., and auxiliary power sources for fuel cell vehicles. Among these, it is suitably used as a battery for automobiles that require particularly high output.

  Examples and the like specifically showing the present invention will be described below. In addition, the evaluation item in an Example etc. measured as follows.

(1) Decomposition temperature Particles obtained through a spray granulation step in which a slurry containing a metal oxide (a), a metal compound (b), and a solvent is spray-granulated to obtain a granulated product are subjected to differential thermal balance. Using Thermo Plus 2 (manufactured by Rigaku), when thermogravimetric analysis was performed from 30 ° C. to 1000 ° C. at a heating rate of 10 ° C./min under an air flow, the TG The peak top temperature of the endothermic or exothermic peak accompanying weight loss was defined as the decomposition temperature.

(2) Average agglomerated particle diameter A laser diffraction / scattering particle size distribution measuring device LA920 (manufactured by Horiba Seisakusho) is used, and in the case of slurry, the dispersion medium is the same as that of the slurry. The particle size distribution after 1 minute of ultrasonic irradiation was measured at a relative refractive index of 1.5.

(3) Average primary particle diameter Among aggregated particles obtained by aggregating primary particles using a field emission scanning electron microscope S-4000 (manufactured by Hitachi, Ltd.), average aggregate particle diameter ± (average aggregated particle diameter × 0.2) The agglomerated particles were selected, and the agglomerated particles were observed with the microscope, and SEM images were taken at a magnification at which 50 to 100 two-dimensional SEM images of primary particles (hereinafter referred to as primary particle images) were included in the microscope field of view. Then, 50 primary particle images were extracted from the photographed primary particle images, their ferret diameters were measured, and the average value of the ferret diameters for the 50 particles was taken as the average primary particle diameter. Note that the ferret diameter of one of the 50 extracted primary particle images is a straight line group parallel to an arbitrary straight line L that passes through (including touches) the one primary particle image. The distance between two parallel lines that are the farthest away. However, the distance between the two parallel lines refers to the length of a line segment that is cut by the two parallel lines from a straight line perpendicular to the two parallel lines. In addition, when the sample was a slurry, what removed the solvent was observed.

(4) BET specific surface area The BET specific surface area was measured using a specific surface area measuring apparatus Flowsorb III2305 (manufactured by Shimadzu Corporation). In addition, when the sample was a slurry, the measurement was performed using the sample from which the solvent was removed.

(5) Peak pore diameter and total pore volume Using a mercury intrusion pore distribution measuring device Pore Sizer 9320 (manufactured by Shimadzu Corporation), the pore volume in the range of 0.008 μm to 200 μm was measured, and the obtained value was The total pore volume was used. Further, among the peaks of the pore distribution obtained by measurement, the maximum peak pore diameter that appears in the pore diameter range of 0.05 to 0.5 μm was defined as the fine peak pore diameter. Further, the maximum pore diameter in a range exceeding 0.5 μm was defined as the interparticle peak pore diameter.

(6) Compression density About 1.5 g of powder was added to a cylindrical mold having a diameter of 16 mm and pressed at a pressure of 1 t. And the value which divided the said powder mass by the volume of the obtained molded object was made into the compression density.

(7) XRD strongest peak intensity of lithium manganate d = when the sample was measured with an X-ray diffractometer RINT2500VPC (manufactured by Rigaku) at an output of 120 kV, 40 mA, a scanning speed of 10 ° / min, and a sampling of 0.01 °. The intensity of the diffraction peak near 4.7 was taken as the XRD strongest peak intensity.

(8) Preparation of battery For 40 parts by weight of lithium manganate, 5 parts by weight of carbon black, 5 parts by weight of polyvinylidene fluoride (PVDF) powder, and 75 parts by weight of N-methyl-2-pyrrolidone were uniformly mixed and coated. A paste was prepared. The paste was uniformly coated on an aluminum foil (thickness 20 μm) used as a current collector with a coater (YBA type baker applicator), and dried at 140 ° C. for 10 minutes or more. After drying, the film was formed into a uniform film thickness with a press machine, and then cut into a predetermined size (20 × 15 mm ² ) to obtain a test positive electrode. At this time, the thickness of the electrode active material layer was set to 25 μm. A test cell was prepared using the test positive electrode. A metal lithium foil was cut into a predetermined size for the negative electrode, and Celgard # 2400 (manufactured by Celgard) was used as the separator. As the electrolyte, 1 mol / L LiPF ₆ / ethylene carbonate: diethyl carbonate (1: 1 vol%) was used. The test cell was assembled in a glove box under an argon atmosphere. After the test cell was assembled, it was allowed to stand at 25 ° C. for 24 hours, and then high-speed discharge characteristics were evaluated.

(9) Fast discharge characteristics evaluation After performing constant current charge / discharge on the test cell at 0.2 CA under the conditions of an upper limit voltage of 4.2 V and a lower limit voltage of 2.0 V, (1) constant current charge at 0.5 CA. Then, the ratio of the capacity (A) discharged at a constant current at 1 CA to the capacity (B) discharged at a constant current of 60 CA after further charging (2) at a constant current of 0.5 CA was defined as high-speed discharge characteristics.
High-speed discharge characteristics (%) = B / A × 100

Example 1
420 g of MnO ₂ having an average primary particle size of 0.03 μm and an average agglomerated particle size of 34 μm is mixed with 2580 g of water, 7 g of a dispersant poise 532A (manufactured by Kao) is added, and DYNOMILL MULTI LAB type (manufactured by Shinmaru Enterprises: capacity 0) 6L, filled with 1836 g of 0.2 mm zirconia beads) and wet pulverized under the following conditions to obtain a slurry of MnO ₂ having an average primary particle size of 0.03 μm and an average aggregated particle size of 0.2 μm. Next, 420 g of lithium carbonate having an average primary particle size of 25 μm and an average aggregated particle size of 84 μm is mixed with 2380 g of water, 20 g of a dispersant poise 532A (manufactured by Kao) is added, and DYNOMILL MULTI LAB type (manufactured by Shinmaru Enterprises: capacity 0) 6L, filled with 1836 g of 0.2 mm zirconia beads) and wet pulverized under the following conditions to obtain a lithium carbonate slurry having an average primary particle size of 0.06 μm and an average aggregated particle size of 0.4 μm. After mixing 100 parts by weight of the obtained MnO ₂ slurry and 21.8 parts by weight of lithium carbonate slurry with a disper, using a spray dryer SD-1000 (manufactured by Tokyo Rika Kikai Co., Ltd.), a hot air supply temperature of about 135 ° C. and a dryer Spray-drying was performed under the condition of an outlet temperature of about 80 ° C.
<MnO ₂ grinding conditions>
Disk peripheral speed: 14 m / s, flow rate: 160 g / min, time: 150 minutes <lithium carbonate grinding conditions>
Disk peripheral speed: 14m / s, flow rate: 160g / min, time: 60 minutes

The obtained powder was heated to 450 ° C. at a heating rate of 200 ° C./Hr and held at 450 ° C. for 2 hours. Then, it heated up to 800 degreeC at 200 degreeC / Hr, and baked at 800 degreeC for 5 hours. Table 1 shows the physical properties of the obtained powder. In addition, as a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782. The X-ray diffraction result at this time is shown in FIG. When evaluating by powder X-ray diffraction, the numerical value of 2θ (deg) was read from the chart of FIG. However, in the following formula, λ is the X-ray wavelength used, and in this example, CuKα ray was used, so it was set to 1.5405 mm.
d = λ / 2sin ((θ / 360) × 2π)

Example 2
In the same manner as in Example 1, a slurry of MnO ₂ having an average primary particle size of 0.03 μm and an average aggregate particle size of 0.2 μm was obtained. A slurry of lithium carbonate having an average primary particle size of 0.8 μm and an average aggregated particle size of 2.7 μm was obtained in the same manner as in Example 1 except that the pulverization time was 15 minutes. After mixing 100 parts by weight of the obtained MnO ₂ slurry and 21.8 parts by weight of the lithium carbonate slurry with a disper, spray drying and firing were performed under the same conditions as in Example 1 to obtain a powder. Table 1 shows the physical properties of the obtained powder. In addition, as a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Example 3
A slurry of MnO ₂ having an average aggregate particle size of 1.1 μm was obtained in the same manner except that the pulverization time was adjusted in Example 1. Further, a slurry of lithium carbonate having an average aggregated particle size of 1.4 μm was obtained in the same manner except that the pulverization time was adjusted in Example 1. After mixing 100 parts by weight of the obtained MnO ₂ slurry and 21.8 parts by weight of the lithium carbonate slurry with a disper, spray drying and firing were performed under the same conditions as in Example 1 to obtain a powder. Table 1 shows the physical properties of the obtained powder. In addition, as a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Example 4
A slurry of MnO ₂ having an average aggregate particle diameter of 1.7 μm was obtained in the same manner except that the pulverization time was adjusted in Example 1. Further, a slurry of lithium carbonate having an average aggregated particle size of 1.4 μm was obtained in the same manner except that the pulverization time was adjusted in Example 1. After mixing 100 parts by weight of the obtained MnO ₂ slurry and 21.8 parts by weight of the lithium carbonate slurry with a disper, spray drying and firing were performed under the same conditions as in Example 1 to obtain a powder. Table 1 shows the physical properties of the obtained powder. In addition, as a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Example 5
The spray-dried powder obtained in the same manner as in Example 1 was heated to 300 ° C. at a heating rate of 200 ° C./Hr and held at 300 ° C. for 2 hours. Then, it heated up to 800 degreeC at 200 degreeC / Hr, and baked at 800 degreeC for 5 hours. Table 1 shows the physical properties of the obtained powder. In addition, as a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Example 6
The spray-dried powder obtained in the same manner as in Example 1 was heated to 600 ° C. at a temperature rising rate of 200 ° C./Hr and held at 600 ° C. for 2 hours. Then, it heated up to 800 degreeC at 200 degreeC / Hr, and baked at 800 degreeC for 5 hours. Table 1 shows the physical properties of the obtained powder. In addition, as a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Example 7
100 parts by weight of MnO ₂ slurry obtained in the same manner as in Example 1, 21.8 parts by weight of lithium carbonate slurry, 1.38 parts by weight of acrylic particles having 2 μm diameter (substance (c): pore forming agent), After mixing with a disper, a spray-dried powder was obtained under the same conditions as in Example 1. Next, the powder was heated to 450 ° C. at a temperature rising rate of 200 ° C./Hr and held at 450 ° C. for 2 hours. Then, it heated up to 800 degreeC at 200 degreeC / Hr, and baked at 800 degreeC for 5 hours. Table 1 shows the physical properties of the obtained powder. In addition, as a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Example 8
A slurry of MnO ₂ having an average aggregate particle size of 2.7 μm was obtained in the same manner except that the pulverization time was adjusted in Example 1. Further, a slurry of lithium carbonate having an average aggregate particle size of 1.8 μm was obtained in the same manner except that the pulverization time was adjusted in Example 1. After mixing 100 parts by weight of the obtained MnO ₂ slurry and 21.8 parts by weight of the lithium carbonate slurry with a disper, spray drying and firing were performed under the same conditions as in Example 1 to obtain a powder. Table 1 shows the physical properties of the obtained powder. In addition, as a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Comparative Example 1
100 parts by weight of the MnO ₂ slurry obtained in Example 1 and 21.8 parts by weight of the lithium carbonate slurry were mixed with a disper and then evaporated to dryness with a rotary evaporator. After the obtained powder was pulverized in a mortar, the temperature was increased to 450 ° C. at a temperature increase rate of 200 ° C./Hr and held at 450 ° C. for 2 hours. Then, it heated up to 800 degreeC at 200 degreeC / Hr, and baked at 800 degreeC for 5 hours. The obtained powder was dry-pulverized with a rotor speed mill (P-14 Flitchchu) to obtain a powder having an average primary particle size of 0.8 μm and an average aggregated particle size of 1.2 μm. Table 1 shows the physical properties of the obtained powder. In addition, as a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Comparative Example 2
In 100 parts by weight of water, 4.06 parts by weight of LiNO ₃ was dissolved. Next, 30.72 parts by weight of Mn (NO ₃ ) ₂ .6H ₂ O was added and stirred to obtain an aqueous solution in which a Li source and a Mn source were mixed. This aqueous solution was spray-dried using a spray dryer SD-1000 (manufactured by Tokyo Rika Kikai Co., Ltd.) at a hot air supply temperature of about 135 ° C. and a dryer outlet temperature of about 80 ° C. The obtained powder was heated to 450 ° C. at a heating rate of 200 ° C./Hr and held at 450 ° C. for 2 hours. Then, it heated up to 800 degreeC at 200 degreeC / Hr, and baked at 800 degreeC for 5 hours. Table 1 shows the physical properties of the obtained powder.

Comparative Example 3
100 parts by weight of spherical MnO _{2 having a} particle diameter of 10 μm and 18.95 parts by weight of Li ₂ CO ₃ having a particle diameter of 8 μm were mixed with 300 parts by weight of water, and the resulting slurry was evaporated to dryness using a rotary evaporator. The obtained powder was manually pulverized for 3 minutes using an agate mortar with a diameter of 13 cm, heated to 450 ° C. at a heating rate of 200 ° C./Hr, held at 450 ° C. for 2 hours, and then 800 ° C. at 200 ° C./Hr. And heated at 800 ° C. for 5 hours. Table 1 shows the physical properties of the obtained powder. In addition, as a result of powder X-ray diffraction measurement, JCPDS No. It corresponded to LiMn ₂ O ₄ having a spinel structure described in 35-782.

Comparative Example 4
The powder obtained by spray drying in Example 1 was heated from room temperature to 800 ° C. at a temperature rising rate of 200 ° C./Hr without firing, and calcined at 800 ° C. for 5 hours. Table 1 shows the physical properties of the obtained powder.

  As the result of Table 1 shows, the particles of Examples 1 to 8 exhibited excellent high-speed discharge characteristics as compared with the particles of Comparative Examples 1 to 4. In particular, since the fine pores were formed in the range of 0.05 to 0.5 μm in the particles of Examples 1 to 7, the movement of Li ions was smooth during battery discharge, and excellent high-speed discharge characteristics were obtained. It is thought that it was done. Further, in the particles of Examples 1 to 7, since the average aggregated particle diameter of the metal oxide (a) was 0.03 to 2.5 μm, fine pores were formed as compared with Example 8, so that It is considered that a high-speed discharge characteristic superior to that of Example 8 was obtained. The particles of Examples 1 to 7 also had a peak pore diameter (inter-particle peak pore diameter) in the range of more than 0.5 μm and 10 μm or less.

  In Comparative Example 1, since spray granulation was not performed, it was considered that high-speed discharge characteristics could not be obtained because fine pores were not generated. In Comparative Example 2, it is considered that high high-speed discharge characteristics could not be obtained because fine pores were not vacant. Further, since the particles are hollow, the low density is considered to be one of the causes of the low fast discharge characteristics. Although the comparative example 3 is a high density particle | grain, since it does not have a micropore, it is thought that the result of a high-speed discharge characteristic was lower than the thing of this invention. In Comparative Example 4, as a result of not maintaining the temperature within the range of the decomposition temperature of the Li source ± 200 ° C., it was considered that micropores were not obtained and the high-speed discharge characteristics were lower than those of the present invention. It is done.

3 is a chart showing the X-ray diffraction results of Example 1.

Claims (8)

A transition metal oxide, and one or more metal oxides (a) selected from the group consisting of oxides of metals belonging to 3B, 4B, and 5B of the periodic table, and an alkali metal compound and an alkaline earth metal compound One or more metal compounds (b) selected from the group, and a spray granulation step of obtaining a granulated product by spray granulating a slurry containing a solvent; and the decomposition temperature of the granulated product with the metal compound (b) A method for producing a particulate composite metal oxide fired body comprising a heat retaining step of heating at ± 200 ° C. and a firing step of firing the granulated body after the heat retaining step to obtain a fired body of a porous composite metal oxide A method for producing a particulate composite metal oxide fired body satisfying the following (I) and (II):
(I) The metal oxide (a) and the metal compound (b) are hardly soluble in the solvent.
(II) The metal compound (b) contains at least a nonmetallic element component that is desorbed in the heat retaining step.   The composite according to claim 1, wherein the metal oxide (a) is an oxide of one or more metals selected from the group consisting of Mn, Fe, Co, and Ni, and the metal compound (b) is a lithium salt. A method for producing a metal oxide fired body.   The average aggregate particle diameter of the metal oxide (a) in the slurry is 0.03 to 2.5 μm, and the average aggregate particle diameter of the metal compound (b) is 0.1 to 10 μm. A method for producing a fired composite metal oxide.   The method for producing a composite metal oxide fired body according to any one of claims 1 to 3, wherein an average aggregate particle diameter of the fired body obtained in the firing step is 0.7 to 15 µm.   The fired body obtained in the firing step has a peak pore diameter in a pore distribution measured with a mercury porosimeter, at least in a range of 0.05 to 0.5 μm and in a range of more than 0.5 μm and 10 μm or less, respectively. Item 5. A method for producing a fired composite metal oxide according to any one of Items 1 to 4. The method for producing a composite metal oxide fired body according to claim 1, wherein the fired body obtained in the firing step has a BET specific surface area of 1 to 40 m ² / g.   The method for producing a fired composite metal oxide according to any one of claims 1 to 6, wherein the obtained fired composite metal oxide is used for a positive electrode active material for a nonaqueous electrolyte secondary battery. The slurry further contains a substance (c) different from the metal oxide (a) and the metal compound (b),
The composite metal oxidation according to any one of claims 1 to 7, wherein the substance (c) is a substance that is hardly soluble in the solvent and that is not thermally decomposed at the time of spray granulation and is thermally decomposed at least by the subsequent firing. A method for producing a fired product.

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