WO2014077274A1 - Positive electrode active material, production method for same, positive electrode for non-aqueous electrolyte secondary cell, and non-aqueous electrolyte secondary cell - Google Patents

Positive electrode active material, production method for same, positive electrode for non-aqueous electrolyte secondary cell, and non-aqueous electrolyte secondary cell Download PDF

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WO2014077274A1
WO2014077274A1 PCT/JP2013/080667 JP2013080667W WO2014077274A1 WO 2014077274 A1 WO2014077274 A1 WO 2014077274A1 JP 2013080667 W JP2013080667 W JP 2013080667W WO 2014077274 A1 WO2014077274 A1 WO 2014077274A1
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particle
positive electrode
active material
particles
lithium
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PCT/JP2013/080667
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French (fr)
Japanese (ja)
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吉則 風間
陽介 平山
耕二 幡谷
智洋 権田
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古河電気工業株式会社
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Priority to CN201380059410.7A priority Critical patent/CN104781966B/en
Priority to JP2014547001A priority patent/JP5847329B2/en
Priority to KR1020157005638A priority patent/KR101649082B1/en
Publication of WO2014077274A1 publication Critical patent/WO2014077274A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/0018—Mixed oxides or hydroxides
    • C01G49/0072—Mixed oxides or hydroxides containing manganese
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0421—Methods of deposition of the material involving vapour deposition
    • H01M4/0428—Chemical vapour deposition
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/58—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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
    • 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
    • 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
    • C01P2006/42—Magnetic properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • 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 transition metal phosphate based positive electrode active material and the like used in a non-aqueous electrolyte secondary battery.
  • lithium cobalt oxide uses cobalt, which is a rare metal, it has large resource limitations, is expensive, and has problems with price stability.
  • lithium cobaltate releases a large amount of oxygen when the temperature reaches 180 ° C. or higher, and therefore, an explosion may occur at the time of abnormal heat generation or a short circuit of the battery.
  • lithium phosphate transition metal having an olivine structure such as lithium iron phosphate (LiFePO 4 ) or manganese lithium phosphate (LiMnPO 4 ), which is more excellent in thermal stability than lithium cobaltate, is resource aspect and cost.
  • LiFePO 4 lithium iron phosphate
  • LiMnPO 4 manganese lithium phosphate
  • solid phase method As a method of synthesizing lithium iron phosphate, a method called solid phase method is known.
  • the outline of the solid phase method is a method in which powders of a lithium source, an iron source and a phosphorus source are mixed and subjected to a baking treatment under an inert atmosphere. This method has a problem that the composition of the product does not become as intended if the calcination conditions are not properly selected, and control of the particle size is difficult.
  • a hydrothermal synthesis method using hydrothermal synthesis in a liquid phase is also known.
  • the hydrothermal synthesis is carried out in the presence of high temperature and pressure hot water. A much purer product is obtained at a much lower temperature than solid phase methods.
  • the control of the particle size is performed depending on the preparation conditions such as the reaction temperature and time, the reproducibility of the control of the particle size is poor and the control of the particle size is difficult (see Patent Document 1).
  • a fine mist is generated from a mixed solution of a carbon-containing compound, a lithium-containing compound, an iron-containing compound and a phosphorus-containing compound, and thermal decomposition is performed by heating while flowing the generated fine mist.
  • a fine powder comprising a lithium iron phosphate precursor containing the above is formed, and the fine powder thus produced is heated and fired in an inert gas-hydrogen mixed gas atmosphere to produce a lithium iron phosphate powder containing carbon. It is a method of generating a body (see Patent Document 2).
  • lithium iron phosphate remains at 3.4 V while the potential of lithium cobaltate is 3.9 V
  • LiCoPO 4 and LiNiPO 4 (wherein Ni and Co are substituted by one or more of Ni, Co, Mn, Fe, Mg, Cu, Cr, V, Li, Nb, Ti and Zr other than the elements)
  • Li 1-x FePO 4 (however, part of Fe is Co, Ni, Mn, Fe, Mg, Cu, Cr, V, Li, etc.) around the first positive electrode active material which may be
  • a positive electrode for a secondary battery comprising a second positive electrode active material, which may be substituted with one or more of Nb, Ti and Zr, and x represents a number of 0 or more and less than 1).
  • a core-shell type positive electrode active material particle is disclosed in which the core particle and the shell layer contain an olivine type phosphoric acid compound containing Fe and / or Mn and Li (see Patent Document 6).
  • lithium manganese phosphate has a smaller electron conductivity and a smaller diffusion coefficient of lithium ions than lithium iron phosphate, and furthermore, it is difficult to sufficiently cover the surface with carbon, so lithium manganese phosphate is used.
  • the used positive electrode active material has a problem that a sufficient discharge capacity can not be obtained.
  • the surface of large lithium manganese phosphate particles is coated with lithium iron phosphate.
  • the diffusion coefficient of lithium ion of lithium manganese phosphate is smaller than that of lithium iron phosphate, there is a problem that the lithium ion is not deintercalated to the center of large lithium manganese phosphate particles during charge and discharge.
  • lithium iron phosphate (LiFe x Mn 1 -x PO 4 ) in which iron atoms in lithium iron phosphate crystals are replaced with manganese atoms in a solid phase method or a hydrothermal synthesis method is manufactured or
  • a lithium transition metal phosphate having an olivine structure using iron and manganese has been obtained by simply mixing lithium iron phosphate and lithium manganese phosphate.
  • these lithium transition metal phosphates are different from the structure in which lithium manganese phosphate particles are attached to the surface of lithium iron phosphate particles as in the present invention.
  • the positive electrode active material described in Patent Document 5 is not intended to utilize lithium manganese phosphate, and the second positive electrode active material particles in the periphery of the first positive electrode active material are lithium iron phosphate. is there. Moreover, the positive electrode active material described in Patent Document 5 can also have a configuration that does not contain manganese.
  • the positive electrode active material described in Patent Document 6, above containing metal phosphate that Me m P n O p as essential, the core particle and the shell layer in each embodiment is using the same material.
  • the present invention has been made in view of the above-mentioned problems, and its object is to provide a positive electrode active material containing lithium manganese phosphate and having a large discharge capacity and energy density.
  • the inventors of the present invention have an energy density by arranging lithium manganese phosphate having a small particle diameter and a low diffusion coefficient but high potential on the surface of lithium iron phosphate excellent in electron conductivity and diffusion coefficient of lithium ions. It has been found that an excellent positive electrode active material can be obtained. It has also been found that such a positive electrode active material can be obtained by mixing a precursor of lithium iron phosphate and a precursor of lithium manganese phosphate and then calcining the mixture.
  • a second particle mainly containing lithium manganese phosphate smaller in particle diameter than the first particle is attached to at least a part of the surface of the first particle mainly containing lithium iron phosphate
  • a positive electrode for a non-aqueous electrolyte secondary battery comprising a current collector and an active material layer containing the positive electrode active material described in (3) on at least one surface of the current collector.
  • a lithium ion according to (4) including the positive electrode for a non-aqueous electrolyte secondary battery, a negative electrode capable of absorbing and desorbing lithium ions, and a separator disposed between the positive electrode and the negative electrode, A non-aqueous electrolyte secondary battery comprising the positive electrode, the negative electrode, and the separator in a conductive electrolyte.
  • the third particle is manufactured by a method of supplying a solution containing lithium, iron and phosphorus into a flame together with a combustion supporting gas and a flammable gas as droplets in the form of mist
  • the particles of the present invention are characterized in that they are produced by a method of supplying a solution containing lithium, manganese and phosphorus in the form of atomized droplets into a flame together with a combustion supporting gas and a flammable gas (6)
  • the manufacturing method of the positive electrode active material as described.
  • BRIEF DESCRIPTION OF THE DRAWINGS The schematic sectional drawing which shows the particle
  • BRIEF DESCRIPTION OF THE DRAWINGS The schematic of the microparticles
  • BRIEF DESCRIPTION OF THE DRAWINGS The schematic sectional drawing of the non-aqueous electrolyte secondary battery using the positive electrode active material which concerns on this Embodiment. (A) to (c) SEM photographs of particles before firing according to an example.
  • FIG. 1 is a view showing a particle 1 according to the present embodiment.
  • the particle 1 is a particle formed by attaching the second particle 5 to the surface of the first particle 3. Note that the entire surface of the first particle 3 may be covered by the plurality of second particles 5, or only a part of the surface of the first particle 3 is covered by the second particle 5. Also good.
  • grains 1 gathered can be used as a positive electrode active material of a non-aqueous electrolyte secondary battery.
  • the first particles 3 are particles mainly containing lithium iron phosphate (LiFePO 4 ).
  • the first particles 3 preferably have a particle size of 100 nm to 10 ⁇ m. If the first particles 3 are smaller than 100 nm, the packing density of the powder when used as an electrode does not increase, and the energy density of the electrode is inferior. If the first particles 3 are larger than 10 ⁇ m, the power density as an electrode is inferior. Also, in order for the second particle to have a structure covering the surface of the first particle as in the present invention, the particle diameter of the second particle covering the surface of the first particle is the particle size of the first particle It needs to be smaller than the diameter.
  • the average particle diameter of the first particles 3 is preferably 100 nm to 10 ⁇ m, and more preferably 200 nm to 2 ⁇ m.
  • the second particles 5 are particles mainly containing lithium manganese phosphate (LiMnPO 4 ).
  • the second particles 5 preferably have a particle size of 200 nm or less. If the size of the second particle 5 is too large, the lithium can not be deintercalated to the center of the particle, so the power density as an electrode is inferior.
  • the particle diameter of the second particles is not a problem to be small for obtaining the effect of the present invention, and the lower limit of the particle diameter is not particularly defined. However, it is preferably 5 nm or more because it is often about 5 nm at the minimum in consideration of the limit from the process of precursor production and the convenience of the operation of mixing with the first particles.
  • the average particle diameter of the second particles 5 is preferably 5 nm to 200 nm, and more preferably 10 nm to 100 nm.
  • containing mainly means that the ratio of lithium iron phosphate contained in the first particles 3 is 80% by mass or more with respect to the first particles 3. Furthermore, the proportion of lithium iron phosphate is preferably 90% by mass or more. The same applies to the proportion of lithium manganese phosphate contained in the second particles 5.
  • the ratio of lithium iron phosphate to lithium phosphate transition metal contained in the first particles 3 is preferably 80% by mass or more, and more preferably 90% by mass or more.
  • the surface of particle 1 may be coated with carbon. That is, at least a part of the surface of either or both of the first particle 3 and the second particle 5 constituting the particle 1 may be coated with carbon.
  • the electric conductivity of the particle 1 becomes high, a conductive path to lithium iron phosphate fine particles or lithium manganese phosphate fine particles is obtained, and when using the particle 1 as a positive electrode active material, high speed
  • the electrode characteristics can be improved, for example, by
  • the particles containing lithium manganese phosphate (LiMnPO 4 ) of the second particles 5 attached to the particles containing LiFePO 4 ) may not be attached to the entire surface of the first particles 3.
  • fine particles containing lithium manganese phosphate which is hard to be carbon-coated on the surface are also easily carbon-coated.
  • the particles including the first particles 3 come into direct contact with the electrolytic solution during charge and discharge, and the particles 1 become a positive electrode active material. The electrode characteristics when used are improved.
  • a part of PO 4 can be replaced by another anion.
  • the powder in which the particles 1 or a plurality of particles 1 are collected can be used as a positive electrode active material used for a positive electrode for a non-aqueous electrolyte secondary battery.
  • the positive electrode active material according to the present embodiment adheres lithium manganese phosphate excellent in potential and energy density to the surface of lithium iron phosphate particles excellent in electron conductivity and lithium ion diffusion, phosphoric acid Manganese lithium can be sufficiently utilized for charge and discharge reactions.
  • a conductive auxiliary such as carbon black is further added to the positive electrode active material, and polytetrafluoroethylene, polyvinylidene fluoride, Aluminum containing at least 95% by weight of aluminum containing a binder such as polyimide, a dispersant such as butadiene rubber, and a thickener such as carboxymethylcellulose and cellulose derivatives, and adding it to an aqueous solvent or an organic solvent to form a slurry
  • the solution is applied on one side or both sides on a current collector such as an alloy foil and fired to evaporate the solvent to dryness.
  • the adhesion between the current collector and the active material layer, and the current collecting property it was granulated and fired by a spray dry method using a positive electrode active material and a carbon source.
  • the following particles can be used by being contained in the slurry.
  • the agglomerated secondary particle mass becomes a large mass of about 0.5 to 20 ⁇ m, which improves the slurry coatability and further improves the characteristics and life of the battery electrode.
  • the slurry used in the spray drying method may be either an aqueous solvent or a non-aqueous solvent.
  • the surface roughness of the current collector surface of the active material layer is determined according to Japanese Industrial Standard (JIS B 0601-1994). It is desirable that the defined ten-point average roughness Rz be 0.5 ⁇ m or more.
  • JIS B 0601-1994 Japanese Industrial Standard
  • Rz the defined ten-point average roughness
  • Non-aqueous electrolyte secondary battery In order to obtain a high-capacity secondary battery using the positive electrode of the present embodiment, various materials such as a negative electrode using a conventionally known negative electrode active material, an electrolytic solution, a separator, and a battery case are used without particular limitations. Can.
  • the non-aqueous electrolyte secondary battery 31 shown in FIG. 3 can be exemplified.
  • the positive electrode 33 and the negative electrode 35 are stacked and arranged in the order of separator-negative electrode-separator-positive electrode via the separator 37, and wound so that the positive electrode 33 is inside.
  • the electrode plate group is constructed and inserted into the battery can 41.
  • the positive electrode 33 is connected to the positive electrode terminal 47 via the positive electrode lead 43
  • the negative electrode 35 is connected to the battery can 41 via the negative electrode lead 45, and chemical energy generated inside the non-aqueous electrolyte secondary battery 31 is used as electrical energy. To be able to take out.
  • the battery can 41 is filled with the electrolyte 39 so as to cover the electrode plate group, and the upper end (opening) of the battery can 41 is composed of a circular cover plate and a positive electrode terminal 47 on the top thereof. It can manufacture by attaching the sealing body 49 which incorporated the through the annular insulation gasket.
  • the secondary battery using the positive electrode according to the present embodiment has a high capacity and good electrode characteristics can be obtained, the non-aqueous solvent containing fluorine in the electrolytic solution using the non-aqueous solvent constituting the secondary battery When or is added, the capacity is unlikely to decrease even after repeated charging and discharging, and the life is extended.
  • the electrolytic solution may contain fluorine or fluorine in order to suppress large expansion and contraction due to doping and de-doping of Li ions. It is desirable to use an electrolytic solution containing a non-aqueous solvent having as a substituent.
  • the fluorine-containing solvent relaxes the volume expansion of the silicon-based film due to the alloying with Li ions at the time of charge, particularly at the first charge treatment, so that the capacity decrease due to charge and discharge can be suppressed.
  • fluorine-containing nonaqueous solvent fluorinated ethylene carbonate, fluorinated linear carbonate, etc. can be used.
  • Mono-tetrafluoro-ethylene carbonate (4-fluoro-1,3-dioxolan-2-one, FEC) for fluorinated ethylene carbonate, methyl 2,2,2-trifluoroethyl carbonate for fluorinated linear carbonate And ethyl 2,2,2-trifluoroethyl carbonate, etc., which may be used singly or in combination of two or more in combination with the electrolytic solution. Since the fluorine group easily bonds to silicon and is strong, it is believed that the film can be stabilized and contributed to the suppression of expansion even in the case of expansion due to charge alloying with Li ions.
  • the particles according to the present embodiment can be obtained by mixing a third particle, which is a precursor of lithium iron phosphate, and a fourth particle, which is a precursor of lithium manganese phosphate, and then firing the mixture. .
  • the third particle and the fourth particle are a precursor particle of lithium iron phosphate and a precursor particle of lithium manganese phosphate, which are synthesized by a spray combustion method such as a flame hydrolysis method or a thermal oxidation method. .
  • FIG. 2 An example of a production apparatus for producing precursor particles by the spray combustion method is shown in FIG.
  • the particle synthesis nozzle 13 is disposed in the container, and the flammable gas, the combustion supporting gas, and the raw material solution are supplied into the flame generated from the nozzle 13.
  • an exhaust pipe 19 for exhausting the generated particulates and reaction products is provided, and the precursor particles 17 in the exhaust gas are recovered by the particulate collection filter 15.
  • the constituent material is supplied into the flame together with the combustion supporting gas and the flammable gas by a method of supplying a raw material gas such as chloride or a method of supplying a raw material liquid or a raw material solution through a vaporizer.
  • a method of supplying a raw material gas such as chloride or a method of supplying a raw material liquid or a raw material solution through a vaporizer.
  • VAD Vapor-phase Axial Deposition
  • the temperature of these flames varies depending on the mixing ratio of the flammable gas and the combustion supporting gas, and the addition ratio of the constituent materials, but is usually between 1000 and 3000 ° C., especially around 1500 to 2500 ° C.
  • the temperature be about 1500 to 2000.degree. If the flame temperature is low, fine particles may come out of the flame before the reaction in the flame is completed. In addition, when the flame temperature is high, the crystallinity of the particles to be generated becomes too high, and a phase which is a stable phase but is not preferable as a positive electrode active material is easily generated in the subsequent firing step.
  • the flame hydrolysis method is a method in which a constituent material is hydrolyzed in a flame.
  • an oxyhydrogen flame is generally used as a flame.
  • the target material is obtained by simultaneously supplying the constituent materials of the positive electrode active material and the flame raw materials (oxygen gas and hydrogen gas) to the base of the flame where hydrogen gas as combustible gas and oxygen gas as combustion supporting gas are supplied simultaneously. Synthesize.
  • the flame hydrolysis method it is possible to obtain nanoscale ultrafine particles of an objective substance consisting mainly of an amorphous substance in an inert gas filled atmosphere.
  • the thermal oxidation method is a method in which a constituent material is thermally oxidized in a flame.
  • a hydrocarbon flame is generally used as the flame.
  • the target material is synthesized while supplying the constituent raw material and the flame raw material (for example, propane gas and oxygen gas) simultaneously from the nozzle to the source of the flame to which hydrocarbon-based gas is supplied as combustible gas and air is supplied as combustion-supporting gas.
  • hydrocarbon gas paraffin hydrocarbon gas such as methane, ethane, propane and butane, or olefin hydrocarbon gas such as ethylene, propylene and butylene can be used.
  • the constituent materials for obtaining the precursor particles of the present embodiment are a lithium source, a transition metal source, and a phosphorus source.
  • the raw material is solid, it is supplied as a powder, dispersed in a liquid, or dissolved in a solvent to form a solution, and is supplied to the flame through a vaporizer.
  • the vapor pressure can be increased and vaporized and supplied by heating or depressurization and bubbling in front of the supply nozzle.
  • lithium inorganic acid salts such as lithium chloride, lithium hydroxide, lithium carbonate, lithium acetate, lithium nitrate, lithium nitrate, lithium bromide, lithium phosphate, lithium sulfate, lithium oxalate, lithium acetate, lithium naphthenate and the like
  • Lithium organic acid salts lithium alkoxides such as lithium ethoxide, organic lithium compounds such as ⁇ -diketonato compounds of lithium, lithium oxide, lithium peroxide and the like can be used.
  • Naphthenic acid is a mixture of different carboxylic acids in which a plurality of acidic substances in petroleum are mainly mixed, and the main component is a carboxylic acid compound of cyclopentane and cyclohexane.
  • ferric chloride iron oxalate, iron acetate, ferrous sulfate, iron nitrate, iron hydroxide, 2-ethylhexanoate Diiron, iron naphthenate and the like
  • organic metal salts of iron such as stearic acid, dimethyldithiocarbamic acid, acetylacetonate, oleic acid, linoleic acid, linolenic acid, iron oxide, etc. are also used depending on the conditions.
  • a transition metal source manganese chloride, manganese oxalate, manganese acetate, manganese sulfate, manganese nitrate, manganese oxyhydroxide, manganese 2-hydroxy-2-oxide, Manganese naphthenate, manganese hexoate and the like can be used. Furthermore, stearic acid, dimethyldithiocarbamic acid, acetylacetonate, organometallic salts of manganese such as oleic acid, linoleic acid and linolenic acid, manganese oxide and the like are also used depending on the conditions.
  • phosphoric acid As a phosphorus source of the precursor, phosphoric acid, phosphoric acid such as orthophosphoric acid or metaphosphoric acid, pyrophosphoric acid, ammonium hydrogen phosphate such as ammonium hydrogen phosphate such as ammonium hydrogen phosphate or ammonium hydrogen phosphate, ammonium phosphate
  • phosphoric acid such as orthophosphoric acid or metaphosphoric acid
  • pyrophosphoric acid As a phosphorus source of the precursor, phosphoric acid, phosphoric acid such as orthophosphoric acid or metaphosphoric acid, pyrophosphoric acid, ammonium hydrogen phosphate such as ammonium hydrogen phosphate such as ammonium hydrogen phosphate or ammonium hydrogen phosphate, ammonium phosphate
  • ammonium hydrogen phosphate such as ammonium hydrogen phosphate such as ammonium hydrogen phosphate or ammonium hydrogen phosphate
  • Various phosphates such as sodium or pyrophosphates, and phosphates of introduced transition metals such as ferr
  • a raw material of an oxide of transition metal and boric acid is added as an anion source.
  • borates such as diboron, sodium metaborate, sodium tetraborate and borax can be used depending on the desired anion source and synthesis conditions.
  • the generated precursor particles can be recovered from the exhaust with a filter. Also, it can be generated around the core rod as follows.
  • a silica or silicon core rod (also called a seed rod) is installed in the reactor, and a lithium source, transition metal source, and phosphorus source are supplied together with the flame raw material in the oxyhydrogen flame and propane flame sprayed thereto.
  • a lithium source, transition metal source, and phosphorus source are supplied together with the flame raw material in the oxyhydrogen flame and propane flame sprayed thereto.
  • fine particles of mainly nano order form and adhere to the surface of the core rod.
  • These generated fine particles are recovered and optionally filtered or sieved to remove impurities and coarse aggregates.
  • the precursor particles thus obtained are composed of fine particles that are mainly amorphous and have an extremely small particle size of nanoscale.
  • precursor particles that can be produced are amorphous, and the particle size is also small. Furthermore, in the spray combustion method, a large amount of synthesis can be performed in a short time as compared with the conventional hydrothermal synthesis method or the solid phase method, and homogeneous precursor particles can be obtained at low cost.
  • the positive electrode active material can be obtained by mixing the third particles and the fourth particles as precursors, mixing with a reducing agent, and calcining.
  • the precursor in this embodiment is a material capable of obtaining crystals of transition metal phosphate by firing.
  • the precursor in the present embodiment has trivalent iron and manganese and is amorphous, but the valence of iron and manganese changes from trivalent to bivalent by mixing with a reducing agent and firing. Do.
  • the composition of the particles containing lithium iron phosphate and lithium manganese phosphate constituting the precursor particles satisfy the stoichiometric composition, but if the composition is very small, the ideal stoichiometry due to the inclusion of impurities etc. Deviations from the theoretical composition are acceptable. It is preferable that the spatial distribution of the elements in the microparticles constituting the precursor particles is uniform. In particular, it is preferable that the spatial distribution of the transition metal and phosphorus in the fine particles be uniform.
  • the precursor particles have a substantially spherical shape, and the average aspect ratio (long diameter / short diameter) of the particles is 1.5 or less, preferably 1.2 or less, and more preferably 1.1 or less.
  • the particles are approximately spherical does not mean that the particle shape is geometrically strictly spherical or elliptical, and even if there are slight protrusions, the surface of the particle is a roughly smooth curved surface It should just be comprised.
  • carbon is burned in the flame, and thus the obtained precursor particles do not contain carbon. Even if the carbon component is mixed, it is a very small amount, which is not a sufficient amount as a conductive aid at the time of using the positive electrode.
  • the mixing ratio of the third particles to the fourth particles is preferably 60:40 to 90:10 by weight, and more preferably 70:30.
  • the mixture of the amorphous compound and the oxide form contained in the precursor particles is converted to a compound of the crystal form of a lithium transition metal phosphate based on the olivine structure mainly by firing.
  • a mixed crystal phase represented by LiFe 1-x Mn x PO 4 (0 ⁇ x ⁇ 1) may be included in the vicinity of the interface of the particles.
  • the lattice strain at the bonding interface is relaxed compared to the case where the bonding interface of the third particle and the fourth particle directly constitutes the heterogeneous interface.
  • the bonding strength at the bonding interface can be stabilized.
  • the particle size of the third particles is preferably 100 nm to 10 ⁇ m, and the particle size of the fourth particles is preferably 200 nm or less. Also, the fourth particles have a smaller particle size than the third particles.
  • the particle diameter of the fourth particle is not a problem to be small for obtaining the effect of the present invention, and the lower limit of the particle diameter is not particularly defined. However, due to the limit from the process of precursor production, the convenience of the operation of mixing with the first particle, etc., it is often at least about 5 nm at the minimum. In the precursor particles and the positive electrode active material, the particle diameter does not substantially change before and after the firing, and by firing the precursor, the particle diameter can be maintained without causing fusion or particle growth. is there.
  • the average particle diameter of the third particles is preferably 100 nm to 10 ⁇ m, and more preferably 200 nm to 2 ⁇ m. Furthermore, in the powder in which a large number of fourth particles are collected, the average particle diameter of the fourth particles 5 is preferably 5 nm to 200 nm, and more preferably 10 nm to 100 nm.
  • the carbon source in the atmosphere filled with an inert gas, can be prevented from burning at the time of firing and the positive electrode active material can be prevented from being oxidized.
  • an inert gas nitrogen gas, argon gas, neon gas, helium gas, carbon dioxide gas, etc. can be used.
  • Organic compounds that are conductive carbon sources such as polyalcohols such as polyvinyl alcohol, polymers such as polyvinyl pyrrolidone, carboxymethyl cellulose, acetyl cellulose, saccharides such as sucrose, saccharides such as carbon black, in order to increase the conductivity of the product after heat treatment
  • the compound is added to the powder in which the third and fourth particles are mixed before heat treatment, and the mixture is calcined.
  • polyvinyl alcohol is particularly preferable because it can reduce iron and manganese during firing.
  • Coating with carbon or supporting treatment is carried out in the same firing step together with crystallization of precursor particles.
  • the heat treatment conditions can be a combination of a temperature of 300 to 900 ° C. and a treatment time of 0.5 to 10 hours to obtain a fired product of desired crystallinity and particle size as appropriate. Excessive heat load due to heat treatment at high temperature or long time should be avoided as it can generate coarse single crystals, and should be under heating conditions such that the desired crystalline or microcrystalline lithium transition metal lithium compound can be obtained. And heat treatment conditions that can suppress the size of the crystallite as small as possible.
  • the temperature of the heat treatment is preferably about 400 to 700.degree.
  • the fourth particle does not have to be attached to the entire surface of the third particle, and the exposed portion is present on the surface of the third particle containing lithium iron phosphate which is easily carbon-coated.
  • the particles of 4 are also well coated with carbon.
  • the obtained positive electrode active material is often aggregated in the firing step, it can be made into fine particles again by being subjected to a grinding means such as a mortar or a ball mill.
  • the positive electrode active material can be synthesized continuously and on a large scale.
  • the positive electrode active material according to the present embodiment adheres lithium manganese phosphate excellent in electric potential and energy density to the surface of lithium iron phosphate particles excellent in electron conductivity and lithium ion diffusivity, Lithium manganese phosphate can be sufficiently utilized for charge and discharge reaction.
  • the lithium metal transition metal phosphate based positive electrode active material according to the present embodiment can ensure the migration path of lithium ions, and efficiently use the active material constituting the particles. Can.
  • the flame temperature was about 2000 ° C.
  • the method for producing precursor particles by the spray combustion method is as follows. First, a predetermined amount of N 2 gas was supplied to make the inside of the reaction vessel an inert gas atmosphere. Under such conditions, a solution in which the lithium source, the iron source and the phosphoric acid source were respectively mixed was made into droplets of 20 ⁇ m through an atomizer and supplied to a flame together with propane gas and air. Precursor particles which are a mixture of lithium oxide, iron oxide, fine particles of phosphorus oxide and the like, fine particles of lithium iron phosphate compound and the like generated in a flame were collected by a fine particle collection filter. The obtained precursor particles are precursor particles a. The average particle size of the primary particles of the precursor particles a confirmed by the electron microscope was about 500 nm.
  • Synthesis example 2 (spray combustion method) (Preparation of lithium manganese phosphate precursor particles by spray combustion method) Further, as in Synthesis Example 1, the precursor particles b are synthesized by supplying propane gas, air, and a raw material solution having a predetermined concentration described below into a flame of propane gas by a spray combustion method, and thermally oxidizing the raw material solution. Collected. The average particle diameter of the primary particles of the precursor particles b confirmed by the electron microscope was about 100 nm.
  • the positive electrode active material B is a powder in which a large number of lithium iron phosphate particles are collected.
  • the positive electrode active material C is a powder in which a large number of particles of lithium manganese phosphate are collected.
  • a precursor particle d of lithium cobalt phosphate is obtained by the same spray combustion method as in Synthesis Example 1 except that cobalt (II) 2-ethylhexanoate is used instead of iron (II) 2-ethylhexanoate as the raw material solution.
  • the average particle size of the primary particles of the precursor particles d confirmed by the electron microscope was about 500 nm.
  • lithium iron phosphate precursor particles a ′ were obtained by the same spray fuel method as in Synthesis Example 2 except that manganese sulfate is used as the raw material solution and iron sulfate is used.
  • the average particle size of the primary particles of the precursor particles a ′ confirmed by the electron microscope was about 100 nm.
  • the polyvinyl alcohol After mixing precursor particle d of lithium cobalt phosphate and precursor particle a 'of lithium iron phosphate smaller in particle diameter at a weight ratio of 70:30, the polyvinyl alcohol will be 10 wt% of the powder The mixture was added to and mixed, and then fired and pulverized in the same manner as in the example to obtain a positive electrode active material D.
  • the positive electrode active material D is a powder in which a large number of particles in which small lithium iron phosphate particles are attached to the periphery of lithium cobalt phosphate particles are collected.
  • a precursor particle e of lithium nickel phosphate is obtained by the same spray combustion method as in Synthesis Example 1 except that nickel (II) 2-ethylhexanoate is used instead of iron (II) 2-ethylhexanoate as the raw material solution.
  • the average particle size of the primary particles of the precursor particles e confirmed by the electron microscope was about 500 nm.
  • After mixing precursor particle e of lithium nickel phosphate and precursor particle a 'of lithium iron phosphate smaller in particle diameter at a weight ratio of 70:30, make the polyvinyl alcohol 10 wt% of the powder The mixture was added to and mixed, and then fired and pulverized in the same manner as in the example to obtain a positive electrode active material E.
  • the positive electrode active material E is a powder in which a large number of particles in which small particles of lithium iron phosphate adhere to the periphery of lithium lithium phosphate particles.
  • a precursor particle f of lithium manganese phosphate is obtained by the same spray combustion method as in Synthesis Example 1 except that manganese (II) 2-ethylhexanoate is used instead of iron (II) 2-ethylhexanoate as the raw material solution.
  • the average particle size of the primary particles of the precursor particles f confirmed by the electron microscope was about 500 nm.
  • the positive electrode active material F is a powder in which a large number of particles in which small lithium iron phosphate particles are attached around the lithium manganese phosphate particles.
  • the particles constituting the powder before firing were particles of about 50 to 200 nm, and some coarse particles of 500 nm or more existed.
  • FIG.5 (a) is a HAADF-STEM image of the particle
  • FIG.5 (b) is an EDS map of the manganese atom in the same observation location
  • FIG.5 (c) is the same.
  • 5 (c) is an EDS map of oxygen atom at the same observation point
  • FIG. 5 (d) is an EDS map of phosphorus atom at the same observation point. is there.
  • FIG. 5A it can be seen that minute particles exist around the approximately spherical particles having a particle diameter of about 500 nm. Furthermore, in FIG. 5 (b) to (e), although the large particles having a substantially spherical shape contain iron, oxygen and phosphorus, manganese is hardly detected from the large particles, and manganese is present from the fine particle part at the bottom of the observation field of view. was detected.
  • FIGS. 6A to 6D are STEM images and EDS maps in fields of view different from those in FIG. Assemblage of small particles with a particle size of about 100 nm was observed, iron was not detected in this field of view, and manganese, phosphorus and oxygen were detected. In each particle, the elements are uniformly distributed.
  • FIG.7 (a) is a HAADF-STEM image of the positive electrode active material of an Example
  • FIG.7 (b) is an EDS map of the manganese atom in the same observation location
  • FIG.7 (c) is the same.
  • FIG. 7 (d) is an EDS map of iron atom at the observation site
  • FIG. 7 (d) is an EDS map of oxygen atom at the same observation site
  • FIG. 7 (e) is an EDS map of phosphorus atom at the same observation site .
  • the positive electrode active material A of the example has a structure in which lithium manganese phosphate particles having a particle diameter of about 50 to 200 nm adhere to lithium iron phosphate particles having a particle diameter of about 1 ⁇ m.
  • lithium manganese phosphate particles do not cover the entire surface of lithium iron phosphate particles, and a part of the surface of lithium iron phosphate particles is exposed.
  • the positive electrode slurry was applied at a coating amount of 50 g / m 2 to a 15 ⁇ m thick aluminum foil current collector, and dried at 120 ° C. for 30 minutes. Thereafter, the resultant was rolled to a density of 2.0 g / cm 3 by a roll press, and punched into a disc shape of 2 cm 2 to obtain a positive electrode.
  • a lithium secondary battery is prepared by dissolving LiPF 6 at a concentration of 1 M in a mixed solvent in which the positive electrode and the negative electrode are mixed with metal lithium in the negative electrode and ethylene carbonate and diethyl carbonate in the electrolyte at a volume ratio of 1: 1. Made. Note that the dew point was set to ⁇ 50 ° C. or less for the preparation atmosphere. Each electrode was crimped to a battery can with a current collector. A coin-type lithium secondary battery having a diameter of 25 mm and a thickness of 1.6 mm was formed using the positive electrode, the negative electrode, the electrolyte, and the separator.
  • test evaluation of the electrode characteristics of the positive electrode active material was performed as follows using the coin-type lithium secondary battery described above. At a test temperature of 25 ° C. or 60 ° C., at a current rate of 0.1 C, charging is performed to a predetermined potential (vs. Li / Li + ) at which the charge curve becomes a plateau by CC-CV method. After dropping to 01C, charging was stopped. Thereafter, the battery was discharged to 2.5 V (same as above) by the CC method at a 0.1 C rate, and the initial charge and discharge capacity was measured. Moreover, charge and discharge were repeated, the discharge capacity after that was measured, and the capacity retention rate was measured.
  • the initial charge / discharge curve of a lithium ion secondary battery using the positive electrode active material according to the example is shown in FIG. 8 (a).
  • the charge went to 4.5V.
  • (a-1) shows a charge curve
  • (a-2) shows a discharge curve.
  • the value of the horizontal axis at the right end of the discharge curve is the discharge capacity.
  • the lithium ion secondary battery according to the example has an initial discharge capacity of about 120 mAh / g at 25 ° C. and an energy density of 438 Wh / kg.
  • transition of the discharge capacity at the time of repeating charging / discharging in FIG.8 (b) is shown.
  • the charge went to 4.5V.
  • the lithium ion secondary battery using the positive electrode active material according to the example has a discharge capacity of 110 mAh / g, and the 100 cycle capacity retention rate is about 92%.
  • the first time charge / discharge curve at 60 ° C. of a lithium ion secondary battery using the positive electrode active material A according to the example is shown in FIG.
  • the charge went to 4.5V.
  • (a-1) shows a charge curve
  • (a-2) shows a discharge curve.
  • the value of the horizontal axis at the right end of the discharge curve is the discharge capacity.
  • the lithium ion secondary battery according to the example has an initial discharge capacity of about 140 mAh / g at 60 ° C. and an energy density of 520 Wh / kg.
  • the initial charge / discharge curve at 25 ° C. of a lithium ion secondary battery using the positive electrode active material B according to Comparative Example 1 is shown in FIG. Also in this case, charging was performed up to 4.5V.
  • FIG. 10 (a-1) shows a charge curve, and (a-2) shows a discharge curve.
  • the initial discharge capacity of a lithium ion secondary battery using a positive electrode active material containing only lithium iron phosphate according to Comparative Example 1 is about 120 mAh / g at 25 ° C., which is substantially the same value as the Example, but the energy density is about It was 395 Wh / kg, which was a lower value than in the example.
  • the first time charge / discharge curve at 25 ° C. of a lithium ion secondary battery using the positive electrode active material C according to Comparative Example 2 is shown in FIG. Also in this case, charging was performed up to 4.5V.
  • FIG. 11 (a-1) shows a charge curve, and (a-2) shows a discharge curve.
  • the initial discharge capacity of a lithium ion secondary battery using a positive electrode active material containing only lithium manganese phosphate according to Comparative Example 2 is about 30 mAh / g at 25 ° C., and the energy density is about 97 Wh / kg. Was significantly lower.
  • the initial discharge capacity of the lithium ion secondary battery using the positive electrode active material D according to Comparative Example 3 was about 59 mAh / g at 25 ° C., and the energy density was about 217 Wh / kg, which were significantly lower than those of Examples. .
  • charge was performed to 4.8V which the charge curve of lithium cobalt phosphate becomes a plateau.
  • the initial discharge capacity of the lithium ion secondary battery using the positive electrode active material E according to Comparative Example 4 was about 48 mAh / g at 25 ° C., and the energy density was about 168 Wh / kg, which were significantly lower than those of Examples. .
  • charging was performed up to 5.0 V at which the charge curve of lithium nickel phosphate became a plateau.
  • the initial discharge capacity of the lithium ion secondary battery using the positive electrode active material F according to Comparative Example 5 was about 66 mAh / g at 25 ° C., and the energy density was about 235 Wh / kg, which were significantly lower than those of Examples. . Also in Comparative Example 4, charging was performed to 4.5 V.
  • the positive electrode for a non-aqueous electrolyte secondary battery in which the positive electrode active material of the present invention is coated on a predetermined current collector is a charge and discharge including a lithium ion secondary battery using a non-aqueous electrolyte
  • the spray combustion method which is a method for producing the precursor particles of the present invention, is excellent in mass productivity and can provide a product at low cost.

Abstract

The purpose of the present invention is to provide a positive electrode active material containing lithium manganese phosphate and exhibiting a high discharge capacity and energy density. In the present invention, a particulate (1) used as the positive electrode active material is characterized in that parts of the surface of a first particle (3), which contains lithium iron phosphate, have a second particle (5), which contains lithium manganese phosphate and has a smaller particle diameter than the first particle (3), adhered thereto. It is preferable for the particle diameter of the first particle (3) to be 100nm-10µm, and for the particle diameter of the second particle (5) be equal to or less than 200nm. In addition, it is preferable for at least one part of the surface of the particulate (1) to be covered by carbon.

Description

正極活物質及びその製造方法、並びに非水電解質二次電池用正極、非水電解質二次電池Positive electrode active material, method for producing the same, and positive electrode for non-aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery
　本発明は、非水電解質二次電池に用いられるリン酸遷移金属リチウム系正極活物質などに関する。 The present invention relates to a lithium transition metal phosphate based positive electrode active material and the like used in a non-aqueous electrolyte secondary battery.
　近年、電子機器のモバイル化と高機能化に伴い、駆動電源である二次電池は最重要部品のひとつになっている。特に、リチウムイオン二次電池は、用いられる正極活物質と負極活物質の高い電圧から得られるエネルギー密度の高さから、従来のＮｉＣｄ電池やＮｉ水素電池に替わり、二次電池の主流の位置を占めるに至っている。しかしながら、現在のＬｉイオン電池に用いられ、標準となっているコバルト酸リチウム（ＬｉＣｏＯ２）系正極活物質と黒鉛主体のカーボン系負極活物質の組み合わせによるＬｉイオン二次電池は、昨今の高機能高負荷電子部品の消費電力量を充分に供給することができず、携帯電源としては要求性能を満たすことができなくなっている。 2. Description of the Related Art In recent years, with the increasing mobility and functionality of electronic devices, secondary batteries, which are driving power supplies, have become one of the most important components. In particular, the lithium ion secondary battery is replaced with the conventional NiCd battery or Ni hydrogen battery due to the high energy density obtained from the high voltage of the positive electrode active material and the negative electrode active material used. It has taken over. However, a Li-ion secondary battery using a combination of a lithium cobaltate (LiCoO 2 ) -based positive electrode active material and a carbon-based negative electrode active material mainly composed of graphite, which are used in current Li-ion batteries and is a standard, has high functionality today. The power consumption of high-load electronic components can not be sufficiently supplied, and the portable power supply can not meet the required performance.
　さらに、コバルト酸リチウムは、レアメタルであるコバルトを用いているため、資源的制約が大きく、高価であり、価格安定性に課題がある。また、コバルト酸リチウムは、１８０℃以上の高温になると、多量の酸素を放出するため、異常発熱時や電池の短絡時には爆発が起きる可能性がある。 Furthermore, since lithium cobalt oxide uses cobalt, which is a rare metal, it has large resource limitations, is expensive, and has problems with price stability. In addition, lithium cobaltate releases a large amount of oxygen when the temperature reaches 180 ° C. or higher, and therefore, an explosion may occur at the time of abnormal heat generation or a short circuit of the battery.
　そのため、コバルト酸リチウムよりも熱的安定性に優れる、リン酸鉄リチウム（ＬｉＦｅＰＯ４）やリン酸マンガンリチウム（ＬｉＭｎＰＯ４）を始めとするオリビン構造を有するリン酸遷移金属リチウムが、資源面、コスト面、安全面を満たす材料として、注目を集めている。 Therefore, lithium phosphate transition metal having an olivine structure, such as lithium iron phosphate (LiFePO 4 ) or manganese lithium phosphate (LiMnPO 4 ), which is more excellent in thermal stability than lithium cobaltate, is resource aspect and cost. Has attracted attention as a material that meets the aspects of safety and safety.
　リン酸鉄リチウムを合成する方法として、固相法と呼ばれる方法が知られている。固相法の概略は、リチウム源、鉄源、リン源の各粉末を混合し、不活性雰囲気下で焼成処理するという方法である。この方法は、焼成条件をうまく選ばないと生成物の組成が目的どおりにならず、かつ粒径の制御が難しいという問題点を有する。 As a method of synthesizing lithium iron phosphate, a method called solid phase method is known. The outline of the solid phase method is a method in which powders of a lithium source, an iron source and a phosphorus source are mixed and subjected to a baking treatment under an inert atmosphere. This method has a problem that the composition of the product does not become as intended if the calcination conditions are not properly selected, and control of the particle size is difficult.
　また、リン酸鉄リチウムを合成する方法として、液相での水熱合成を利用した水熱合成法も知られている。水熱合成法は、高温高圧の熱水の存在下で行われる。固相法に比べてはるかに低温で、純度の高い生成物が得られる。しかし、粒径の制御を反応温度や時間などの調製条件により行うが、粒径の制御の再現性に乏しく、粒径の制御が困難であった（特許文献１を参照）。 Further, as a method of synthesizing lithium iron phosphate, a hydrothermal synthesis method using hydrothermal synthesis in a liquid phase is also known. The hydrothermal synthesis is carried out in the presence of high temperature and pressure hot water. A much purer product is obtained at a much lower temperature than solid phase methods. However, although the control of the particle size is performed depending on the preparation conditions such as the reaction temperature and time, the reproducibility of the control of the particle size is poor and the control of the particle size is difficult (see Patent Document 1).
　また、リン酸鉄リチウムを合成する方法として、噴霧熱分解法がある。噴霧熱分解法は、炭素含有化合物、リチウム含有化合物、鉄含有化合物及びリン含有化合物の混合溶液から微小なミストを生成し、生成された微小ミストを流通させながら加熱することで熱分解させ、炭素を含有するリン酸鉄リチウム前駆体からなる微粉体を生成し、生成された前記微粉体を不活性ガス－水素混合ガス雰囲気中で加熱して焼成することで炭素を含有するリン酸鉄リチウム粉体を生成する方法である（特許文献２を参照）。 Further, as a method of synthesizing lithium iron phosphate, there is a spray pyrolysis method. In the spray pyrolysis method, a fine mist is generated from a mixed solution of a carbon-containing compound, a lithium-containing compound, an iron-containing compound and a phosphorus-containing compound, and thermal decomposition is performed by heating while flowing the generated fine mist. A fine powder comprising a lithium iron phosphate precursor containing the above is formed, and the fine powder thus produced is heated and fired in an inert gas-hydrogen mixed gas atmosphere to produce a lithium iron phosphate powder containing carbon. It is a method of generating a body (see Patent Document 2).
　また、出願人らは、固相法や水熱合成法、噴霧熱分解法に代えて、小粒径で元素の空間分布が均一であるリン酸遷移金属リチウムを、連続的かつ大規模に合成可能な噴霧燃焼法を開発した（特許文献３を参照）。 In addition, applicants continuously and extensively synthesized lithium transition metal lithium having a small particle size and uniform spatial distribution of elements, instead of the solid phase method, the hydrothermal synthesis method, or the spray pyrolysis method. A possible spray combustion method has been developed (see Patent Document 3).
　さらに、コバルト酸リチウムの電位が３．９Ｖであるのに対し、リン酸鉄リチウムの電位が３．４Ｖにとどまることから、４．１Ｖの高い電位を持つリン酸マンガンリチウムに注目が集まっている。 Furthermore, since the potential of lithium iron phosphate remains at 3.4 V while the potential of lithium cobaltate is 3.9 V, attention is focused on lithium manganese phosphate having a high potential of 4.1 V. .
　しかしながら、リン酸マンガンリチウムの表面は、有機物の炭化反応による炭素被覆がされにくいという課題があった。そこで、リン酸マンガンリチウムからなる粒子の表面を、リン酸鉄リチウムを含む被覆層により被覆した電極活物質が報告されている（特許文献４を参照）。 However, there has been a problem that the surface of lithium manganese phosphate is less likely to be covered with carbon by the carbonization reaction of an organic substance. Then, the electrode active material which coat | covered the surface of the particle | grains which consist of lithium manganese phosphate with the coating layer containing lithium iron phosphate is reported (refer patent document 4).
　また、ＬｉＣｏＰＯ４及びＬｉＮｉＰＯ４（ただし、Ｎｉ及びＣｏはその元素以外の、Ｎｉ、Ｃｏ、Ｍｎ、Ｆｅ、Ｍｇ、Ｃｕ、Ｃｒ、Ｖ、Ｌｉ、Ｎｂ、Ｔｉ及びＺｒのうちの１種以上で置換されていてもよい）などである第１の正極活物質の周囲に、Ｌｉ１－ｘＦｅＰＯ４（ただし、Ｆｅの一部はＣｏ、Ｎｉ、Ｍｎ、Ｆｅ、Ｍｇ、Ｃｕ、Ｃｒ、Ｖ、Ｌｉ、Ｎｂ、Ｔｉ及びＺｒのうちの１種以上で置換されていてもよく、ｘは０以上１未満の数を示す）からなる第２の正極活物質を備える二次電池用正極が開示されている（特許文献５を参照）。 Also, LiCoPO 4 and LiNiPO 4 (wherein Ni and Co are substituted by one or more of Ni, Co, Mn, Fe, Mg, Cu, Cr, V, Li, Nb, Ti and Zr other than the elements) Li 1-x FePO 4 (however, part of Fe is Co, Ni, Mn, Fe, Mg, Cu, Cr, V, Li, etc.) around the first positive electrode active material which may be And a positive electrode for a secondary battery comprising a second positive electrode active material, which may be substituted with one or more of Nb, Ti and Zr, and x represents a number of 0 or more and less than 1). (See Patent Document 5).
　また、コア粒子とシェル層が、Ｆｅおよび／またはＭｎとＬｉとを含むオリビン型リン酸化合物を含むことを特徴とするコアシェル型正極活物質粒子が開示されている（特許文献６を参照）。 Further, a core-shell type positive electrode active material particle is disclosed in which the core particle and the shell layer contain an olivine type phosphoric acid compound containing Fe and / or Mn and Li (see Patent Document 6).
国際公開２００９／１３１０９５号公報International Publication 2009/131095 特開２００９－０７０６６６号公報JP, 2009-070666, A 国際公開２０１２／１０５６３７号公報International Publication 2012/105637 特開２０１１－１８１３７５号公報JP, 2011-181375, A 特開２０１１－２１０６９３号公報JP 2011-210693 A 国際公開２０１２／０４２７２７号公報International Publication 2012/042727
　しかしながら、リン酸マンガンリチウムは、リン酸鉄リチウムに比べて、電子伝導性とリチウムイオンの拡散係数が小さく、さらに、表面の炭素被覆を十分に行うことが困難であるため、リン酸マンガンリチウムを使用した正極活物質は十分な放電容量が得られないという問題点があった。 However, lithium manganese phosphate has a smaller electron conductivity and a smaller diffusion coefficient of lithium ions than lithium iron phosphate, and furthermore, it is difficult to sufficiently cover the surface with carbon, so lithium manganese phosphate is used. The used positive electrode active material has a problem that a sufficient discharge capacity can not be obtained.
　また、特許文献４に記載された電極活物質では、炭素被覆の問題を解決するために大きなリン酸マンガンリチウム粒子の表面をリン酸鉄リチウムで被覆している。しかし、リン酸マンガンリチウムのリチウムイオンの拡散係数は、リン酸鉄リチウムのそれより小さいため、充放電時に大きなリン酸マンガンリチウム粒子の中心部までリチウムイオンの脱挿入が起こらないという問題点があった。 Moreover, in the electrode active material described in Patent Document 4, in order to solve the problem of carbon coating, the surface of large lithium manganese phosphate particles is coated with lithium iron phosphate. However, since the diffusion coefficient of lithium ion of lithium manganese phosphate is smaller than that of lithium iron phosphate, there is a problem that the lithium ion is not deintercalated to the center of large lithium manganese phosphate particles during charge and discharge. The
　また、従来、固相法や水熱合成法において、リン酸鉄リチウムの結晶中の鉄原子をマンガン原子で置き換えたリン酸鉄マンガンリチウム（ＬｉＦｅｘＭｎ１－ｘＰＯ４）を製造することや、単純に得られたリン酸鉄リチウムとリン酸マンガンリチウムを混合することにより、鉄とマンガンを使用したオリビン構造を有するリン酸遷移金属リチウムが得られていた。しかし、これらのリン酸遷移金属リチウムは、本発明のような、リン酸鉄リチウム粒子の表面にリン酸マンガンリチウム粒子を付着させる構造とは異なる。 In addition, conventionally, lithium iron phosphate (LiFe x Mn 1 -x PO 4 ) in which iron atoms in lithium iron phosphate crystals are replaced with manganese atoms in a solid phase method or a hydrothermal synthesis method is manufactured or A lithium transition metal phosphate having an olivine structure using iron and manganese has been obtained by simply mixing lithium iron phosphate and lithium manganese phosphate. However, these lithium transition metal phosphates are different from the structure in which lithium manganese phosphate particles are attached to the surface of lithium iron phosphate particles as in the present invention.
　また、特許文献５に記載の正極活物質は、リン酸マンガンリチウムを活用することを目的としておらず、第１の正極活物質の周囲にある第２の正極活物質粒子はリン酸鉄リチウムである。また、特許文献５に記載の正極活物質は、マンガンを含まない構成も採ることができる。 Further, the positive electrode active material described in Patent Document 5 is not intended to utilize lithium manganese phosphate, and the second positive electrode active material particles in the periphery of the first positive electrode active material are lithium iron phosphate. is there. Moreover, the positive electrode active material described in Patent Document 5 can also have a configuration that does not contain manganese.
　さらに、特許文献６に記載の正極活物質は、ＭｅｍＰｎＯｐという金属リン酸塩を必須として含む上に、各実施例ではコア粒子とシェル層が同じ材料を使用している。 Further, the positive electrode active material described in Patent Document 6, above containing metal phosphate that Me m P n O p as essential, the core particle and the shell layer in each embodiment is using the same material.
　本発明は、前述した問題点に鑑みてなされたもので、その目的とすることは、リン酸マンガンリチウムを含み、放電容量およびエネルギー密度が大きい正極活物質を提供することである。 The present invention has been made in view of the above-mentioned problems, and its object is to provide a positive electrode active material containing lithium manganese phosphate and having a large discharge capacity and energy density.
　本発明者らは、電子伝導性とリチウムイオンの拡散係数に優れるリン酸鉄リチウムの表面に、小粒径で拡散係数に劣るが電位の高いリン酸マンガンリチウムを配置することで、エネルギー密度の優れる正極活物質を得ることができることを見出した。また、そのような正極活物質をリン酸鉄リチウムの前駆体とリン酸マンガンリチウムの前駆体を混合した後に焼成することで得られることも見出した。 The inventors of the present invention have an energy density by arranging lithium manganese phosphate having a small particle diameter and a low diffusion coefficient but high potential on the surface of lithium iron phosphate excellent in electron conductivity and diffusion coefficient of lithium ions. It has been found that an excellent positive electrode active material can be obtained. It has also been found that such a positive electrode active material can be obtained by mixing a precursor of lithium iron phosphate and a precursor of lithium manganese phosphate and then calcining the mixture.
　すなわち、本発明は、以下の特徴を備える。
（１）リン酸鉄リチウムを主として含む第１の粒子の表面の少なくとも一部に、前記第１の粒子より粒径の小さい、リン酸マンガンリチウムを主として含む第２の粒子が付着していることを特徴とする正極活物質。
（２）前記第１の粒子の粒径が１００ｎｍ～１０μｍであり、前記第２の粒子の粒径が２００ｎｍ以下であることを特徴とする（１）に記載の正極活物質。
（３）前記第１の粒子および／または前記第２の粒子の表面の少なくとも一部が、炭素によって被覆されていることを特徴とする（１）に記載の正極活物質。
（４）集電体と、前記集電体の少なくとも片面に、（３）に記載の正極活物質を含む活物質層と、を有することを特徴とする非水電解質二次電池用正極。
（５）（４）に記載の非水電解質二次電池用正極と、リチウムイオンを吸蔵および放出可能な負極と、前記正極と前記負極との間に配置されたセパレータとを有し、リチウムイオン伝導性を有する電解質中に、前記正極と前記負極と前記セパレータとを設けたことを特徴とする非水電解質二次電池。
（６）リン酸鉄リチウムの前駆体である第３の粒子と、前記第３の粒子より粒径の小さいリン酸マンガンリチウムの前駆体である第４の粒子を混合する工程と、さらに炭素源を混合する工程と、混合して得られた粒子を焼成する工程と、を含むことを特徴とする正極活物質の製造方法。
（７）前記第３の粒子と前記第４の粒子の混合比が、重量比で６０：４０～９０：１０であることを特徴とする（６）に記載の正極活物質の製造方法。
（８）前記第３の粒子の粒径が１００ｎｍ～１０μｍであり、前記第４の粒子の粒径が２００ｎｍ以下であることを特徴とする（６）に記載の正極活物質の製造方法。
（９）前記第３の粒子は、リチウム、鉄およびリンを含む溶液を、霧状の液滴にて、支燃性ガスと可燃性ガスとともに火炎中に供給する方法により製造され、前記第４の粒子は、リチウム、マンガンおよびリンを含む溶液を、霧状の液滴にて、支燃性ガスと可燃性ガスとともに火炎中に供給する方法により製造されることを特徴とする（６）に記載の正極活物質の製造方法。
（１０）前記炭素源が、ポリビニルアルコール、ポリビニルピロリドン、カルボキシメチルセルロース、アセチルセルロース、ショ糖、カーボンブラックのいずれか一つ以上であることを特徴とする（６）に記載の正極活物質の製造方法。 That is, the present invention comprises the following features.
(1) A second particle mainly containing lithium manganese phosphate smaller in particle diameter than the first particle is attached to at least a part of the surface of the first particle mainly containing lithium iron phosphate A positive electrode active material characterized by
(2) The positive electrode active material according to (1), wherein the particle size of the first particle is 100 nm to 10 μm, and the particle size of the second particle is 200 nm or less.
(3) The positive electrode active material according to (1), wherein at least a part of the surface of the first particle and / or the second particle is coated with carbon.
(4) A positive electrode for a non-aqueous electrolyte secondary battery comprising a current collector and an active material layer containing the positive electrode active material described in (3) on at least one surface of the current collector.
(5) A lithium ion according to (4), including the positive electrode for a non-aqueous electrolyte secondary battery, a negative electrode capable of absorbing and desorbing lithium ions, and a separator disposed between the positive electrode and the negative electrode, A non-aqueous electrolyte secondary battery comprising the positive electrode, the negative electrode, and the separator in a conductive electrolyte.
(6) mixing a third particle, which is a precursor of lithium iron phosphate, and a fourth particle, which is a precursor of lithium manganese phosphate having a smaller particle size than the third particle, and a carbon source And a step of calcining the particles obtained by the mixing, and a method of manufacturing a positive electrode active material.
(7) The method for producing a positive electrode active material according to (6), wherein the mixing ratio of the third particles to the fourth particles is 60:40 to 90:10 by weight.
(8) The method for producing a positive electrode active material according to (6), wherein the particle diameter of the third particle is 100 nm to 10 μm, and the particle diameter of the fourth particle is 200 nm or less.
(9) The third particle is manufactured by a method of supplying a solution containing lithium, iron and phosphorus into a flame together with a combustion supporting gas and a flammable gas as droplets in the form of mist, The particles of the present invention are characterized in that they are produced by a method of supplying a solution containing lithium, manganese and phosphorus in the form of atomized droplets into a flame together with a combustion supporting gas and a flammable gas (6) The manufacturing method of the positive electrode active material as described.
(10) The method for producing a positive electrode active material according to (6), wherein the carbon source is any one or more of polyvinyl alcohol, polyvinyl pyrrolidone, carboxymethyl cellulose, acetyl cellulose, sucrose and carbon black .
　本発明により、リン酸マンガンリチウムを含み、放電容量およびエネルギー密度が大きい正極活物質を提供することができる。 According to the present invention, it is possible to provide a positive electrode active material containing lithium manganese phosphate and having a large discharge capacity and energy density.
本実施の形態に係る粒子１を示す概略断面図。BRIEF DESCRIPTION OF THE DRAWINGS The schematic sectional drawing which shows the particle | grains 1 which concern on this Embodiment. 本実施の形態に係る噴霧燃焼法により前駆体粒子を製造する微粒子製造装置の概略図。BRIEF DESCRIPTION OF THE DRAWINGS The schematic of the microparticles | fine-particles manufacturing apparatus which manufactures precursor particle | grains by the spray combustion method which concerns on this Embodiment. 本実施の形態に係る正極活物質を用いた非水電解質二次電池の概略断面図。BRIEF DESCRIPTION OF THE DRAWINGS The schematic sectional drawing of the non-aqueous electrolyte secondary battery using the positive electrode active material which concerns on this Embodiment. （ａ）～（ｃ）実施例に係る焼成前の粒子のＳＥＭ写真。(A) to (c) SEM photographs of particles before firing according to an example. （ａ）実施例の焼成前の粒子のＨＡＡＤＦ－ＳＴＥＭ像、（ｂ）～（ｅ）同一の観察箇所におけるマンガン、鉄、酸素、リンのＥＤＳマップ。(A) HAADF-STEM image of particles before firing in Example, (b) to (e) EDS maps of manganese, iron, oxygen and phosphorus at the same observation site. （ａ）実施例の焼成前の粒子の図５とは別の視野でのＨＡＡＤＦ－ＳＴＥＭ像、（ｂ）～（ｄ）同一の観察箇所におけるマンガン、酸素、リンのＥＤＳマップ。(A) HAADF-STEM image in a different field of view from that of FIG. 5 of the particles before firing, (b) to (d) EDS maps of manganese, oxygen, and phosphorus at the same observation point. （ａ）実施例の焼成後の正極活物質のＨＡＡＤＦ－ＳＴＥＭ像、（ｂ）～（ｅ）同一の観察箇所におけるマンガン、鉄、酸素、リンのＥＤＳマップ。(A) HAADF-STEM images of the positive electrode active material after firing in Example, (b) to (e) EDS maps of manganese, iron, oxygen, and phosphorus at the same observation point. （ａ）実施例に係る正極活物質を用いたリチウムイオン二次電池の２５℃での初回充放電曲線、（ｂ）２５℃で充放電を繰り返した際の放電容量の推移。(A) Initial charge / discharge curve at 25 ° C. of a lithium ion secondary battery using the positive electrode active material according to the example, (b) Transition of discharge capacity when charge / discharge is repeated at 25 ° C. 実施例に係る正極活物質を用いたリチウムイオン二次電池の６０℃での初回充放電曲線。The first time charging / discharging curve at 60 ° C of the lithium ion secondary battery using the quality of cathode active material concerning an example. 比較例１に係る正極活物質を用いたリチウムイオン二次電池の２５℃での初回充放電曲線。The initial charge / discharge curve at 25 degrees C of the lithium ion secondary battery using the positive electrode active material which concerns on the comparative example 1. FIG. 比較例２に係る正極活物質を用いたリチウムイオン二次電池の２５℃での初回充放電曲線。The initial charge / discharge curve at 25 degrees C of the lithium ion secondary battery using the positive electrode active material which concerns on the comparative example 2. FIG.
　（粒子）
　以下図面に基づいて、本発明の実施の形態を詳細に説明する。
　図１は、本実施の形態に係る粒子１を示す図である。粒子１は、第１の粒子３の表面に、第２の粒子５が付着してなる粒子である。なお、第１の粒子３の表面の全部が複数の第２の粒子５により覆われていても良いし、第１の粒子３の表面の一部のみが第２の粒子５により覆われていても良い。粒子１、または、複数の粒子１が集まった粉体は、非水電解質二次電池の正極活物質として用いることができる。 (particle)
Hereinafter, embodiments of the present invention will be described in detail based on the drawings.
FIG. 1 is a view showing a particle 1 according to the present embodiment. The particle 1 is a particle formed by attaching the second particle 5 to the surface of the first particle 3. Note that the entire surface of the first particle 3 may be covered by the plurality of second particles 5, or only a part of the surface of the first particle 3 is covered by the second particle 5. Also good. The powder which the particle | grains 1 or several particle | grains 1 gathered can be used as a positive electrode active material of a non-aqueous electrolyte secondary battery.
　第１の粒子３は、リン酸鉄リチウム（ＬｉＦｅＰＯ４）を主として含む粒子である。第１の粒子３は、粒径が１００ｎｍ～１０μｍであることが好ましい。第１の粒子３が１００ｎｍより小すぎると、電極にした際の粉体の充填密度が上がらず、電極のエネルギー密度に劣る。第１の粒子３が１０μｍより大きいと、電極としての出力密度に劣る。また、本発明のような第２の粒子が第１の粒子の表面を覆う構造を取るためには、第１の粒子の表面を覆う第２の粒子の粒径は、第１の粒子の粒径より小さいことが必要である。第２の粒子の粒径が第１の粒子の粒径より小さくないと、第１の粒子の表面を、第２の粒子の表面を覆う構造を取ることが難しくなるからである。また、粒子１が多数集まった粉体において、第１の粒子３の平均粒径は１００ｎｍ～１０μｍであることが好ましく、２００ｎｍ～２μｍであることがより好ましい。 The first particles 3 are particles mainly containing lithium iron phosphate (LiFePO 4 ). The first particles 3 preferably have a particle size of 100 nm to 10 μm. If the first particles 3 are smaller than 100 nm, the packing density of the powder when used as an electrode does not increase, and the energy density of the electrode is inferior. If the first particles 3 are larger than 10 μm, the power density as an electrode is inferior. Also, in order for the second particle to have a structure covering the surface of the first particle as in the present invention, the particle diameter of the second particle covering the surface of the first particle is the particle size of the first particle It needs to be smaller than the diameter. If the particle diameter of the second particle is not smaller than the particle diameter of the first particle, it is difficult to form a structure covering the surface of the first particle with the surface of the second particle. In the powder in which a large number of particles 1 are collected, the average particle diameter of the first particles 3 is preferably 100 nm to 10 μm, and more preferably 200 nm to 2 μm.
　第２の粒子５は、リン酸マンガンリチウム（ＬｉＭｎＰＯ４）を主として含む粒子である。第２の粒子５は、粒径が２００ｎｍ以下であることが好ましい。第２の粒子５が大きすぎると、粒子の中心部までリチウムの脱挿入が起こらないため、電極としての出力密度に劣る。第２の粒子の粒径は、本発明の効果を得るためには小さい分には問題なく、粒径の下限は特に規定されない。しかし、前駆体製造の工程から来る限界や、第1の粒子との混合の操作の都合などから、最小で５ｎｍ程度になる場合が多いことから、５ｎｍ以上であることが望ましい。また、粒子１が多数集まった粉体において、第２の粒子５の平均粒径は５ｎｍ～２００ｎｍであることが好ましく、１０ｎｍ～１００ｎｍであることがより好ましい。 The second particles 5 are particles mainly containing lithium manganese phosphate (LiMnPO 4 ). The second particles 5 preferably have a particle size of 200 nm or less. If the size of the second particle 5 is too large, the lithium can not be deintercalated to the center of the particle, so the power density as an electrode is inferior. The particle diameter of the second particles is not a problem to be small for obtaining the effect of the present invention, and the lower limit of the particle diameter is not particularly defined. However, it is preferably 5 nm or more because it is often about 5 nm at the minimum in consideration of the limit from the process of precursor production and the convenience of the operation of mixing with the first particles. In the powder in which a large number of particles 1 are collected, the average particle diameter of the second particles 5 is preferably 5 nm to 200 nm, and more preferably 10 nm to 100 nm.
　また、主として含むとは、第１の粒子３に含まれるリン酸鉄リチウムの割合が第１の粒子３に対して８０質量％以上であることを意味する。さらに、リン酸鉄リチウムの割合は９０質量％以上であることが好ましい。第２の粒子５に含まれるリン酸マンガンリチウムの割合についても、同様である。
　また、第１の粒子３に含まれるリン酸遷移金属リチウムに対するリン酸鉄リチウムの割合は、８０質量％以上であることが好ましく、９０質量％以上であることがより好ましい。 Moreover, containing mainly means that the ratio of lithium iron phosphate contained in the first particles 3 is 80% by mass or more with respect to the first particles 3. Furthermore, the proportion of lithium iron phosphate is preferably 90% by mass or more. The same applies to the proportion of lithium manganese phosphate contained in the second particles 5.
The ratio of lithium iron phosphate to lithium phosphate transition metal contained in the first particles 3 is preferably 80% by mass or more, and more preferably 90% by mass or more.
　粒子１の表面は、炭素によって被覆されていてもよい。すなわち、粒子１を構成する第１の粒子３と第２の粒子５の、いずれか一方または両方の粒子の表面の少なくとも一部が、炭素によって被覆されていてもよい。炭素によって被覆することで、粒子１の電気伝導性が高くなり、リン酸鉄リチウム微粒子またはリン酸マンガンリチウム微粒子への導電パスが得られ、粒子１を正極活物質に用いた際に、高速での充放電が可能になるなど電極特性が向上する。 The surface of particle 1 may be coated with carbon. That is, at least a part of the surface of either or both of the first particle 3 and the second particle 5 constituting the particle 1 may be coated with carbon. By coating with carbon, the electric conductivity of the particle 1 becomes high, a conductive path to lithium iron phosphate fine particles or lithium manganese phosphate fine particles is obtained, and when using the particle 1 as a positive electrode active material, high speed The electrode characteristics can be improved, for example, by
　また、粒子１中のリン酸鉄リチウムとリン酸マンガンリチウムの重量比は、ＬｉＦｅＰＯ４：ＬｉＭｎＰＯ４＝６０：４０～９０：１０であることが好ましい。さらに、粒径の大きい第１の粒子３の粒径が１００ｎｍ～１０μｍであり、粒径の小さい第２の粒子の粒径が２００ｎｍ以下であるため、第１の粒子３のリン酸鉄リチウム（ＬｉＦｅＰＯ４）を含む粒子に付着する第２の粒子５のリン酸マンガンリチウム（ＬｉＭｎＰＯ４）を含む粒子は、第１の粒子３の表面全体に付着していなくても良い。第１の粒子３の表面が剥き出しの部分が存在することで、表面が炭素被覆されにくいリン酸マンガンリチウムを含む微粒子も炭素被覆されやすくなる。また、第１の粒子３の表面が剥き出しの部分が存在することで、充放電を行う際に第１の粒子３を含む粒子が直接電解液と接触することとなり、粒子１を正極活物質に用いた際の電極特性が向上する。 The weight ratio of lithium iron phosphate to lithium manganese phosphate in the particles 1 is preferably LiFePO 4 : LiMnPO 4 = 60: 40 to 90:10. Furthermore, since the particle diameter of the first particle 3 having a large particle diameter is 100 nm to 10 μm and the particle diameter of the second particle having a small particle diameter is 200 nm or less, the lithium iron phosphate of the first particle 3 The particles containing lithium manganese phosphate (LiMnPO 4 ) of the second particles 5 attached to the particles containing LiFePO 4 ) may not be attached to the entire surface of the first particles 3. By the presence of the exposed portion of the surface of the first particle 3, fine particles containing lithium manganese phosphate which is hard to be carbon-coated on the surface are also easily carbon-coated. In addition, when the surface of the first particles 3 is exposed, the particles including the first particles 3 come into direct contact with the electrolytic solution during charge and discharge, and the particles 1 become a positive electrode active material. The electrode characteristics when used are improved.
　また、ＰＯ４の一部を他のアニオンにより置換させることもできる。例えば、前記の遷移金属の酸である、チタン酸（ＴｉＯ４）やクロム酸（ＣｒＯ４）、バナジン酸（ＶＯ４、Ｖ２Ｏ７）、ジルコン酸（ＺｒＯ４）、モリブデン酸（ＭｏＯ４、Ｍｏ７Ｏ２４）、タングステン酸（ＷＯ４）、等々であり、あるいはホウ酸（ＢＯ３）による置換である。リン酸イオンの一部をこれらのアニオン種により置換することにより、Ｌｉイオンの脱離と挿入の繰り返しによる結晶構造変化の抑制と安定化に寄与し、サイクル寿命を向上させる。また、これらのアニオン種は、高温においても酸素を放出し難いので、発火につながることもなく安全に用いることができる。 Also, a part of PO 4 can be replaced by another anion. For example, titanic acid (TiO 4 ) or chromic acid (CrO 4 ), vanadic acid (VO 4 , V 2 O 7 ), zirconic acid (ZrO 4 ), molybdic acid (MoO 4 ), which are the above-mentioned transition metal acids. Mo 7 O 24 ), tungstic acid (WO 4 ), etc., or substitution with boric acid (BO 3 ). By substituting a part of phosphate ion with these anion species, it contributes to suppression and stabilization of crystal structure change by repetition of elimination and insertion of Li ion, and improves cycle life. Moreover, since these anion species do not easily release oxygen even at high temperatures, they can be used safely without leading to ignition.
（正極活物質）
　粒子１、または、複数の粒子１が集まった粉体は、非水電解質二次電池用正極に使用される正極活物質として使用可能である。 (Positive electrode active material)
The powder in which the particles 1 or a plurality of particles 1 are collected can be used as a positive electrode active material used for a positive electrode for a non-aqueous electrolyte secondary battery.
　本実施の形態に係る正極活物質は、電子伝導性とリチウムイオン拡散性に優れるリン酸鉄リチウムの粒子の表面に、電位とエネルギー密度に優れるリン酸マンガンリチウムを付着させているため、リン酸マンガンリチウムを十分に充放電反応に活用できる。 Since the positive electrode active material according to the present embodiment adheres lithium manganese phosphate excellent in potential and energy density to the surface of lithium iron phosphate particles excellent in electron conductivity and lithium ion diffusion, phosphoric acid Manganese lithium can be sufficiently utilized for charge and discharge reactions.
　（非水電解質二次電池用正極）
　正極活物質を用いて非水電解質二次電池用正極を形成するには、正極活物質に、必要に応じてさらにカーボンブラックなどの導電助剤を加えると共に、ポリテトラフルオロエチレンやポリフッ化ビニリデン、ポリイミドなどの結着剤、ブタジエンゴムなどの分散剤、カルボキシメチルセルロースほかセルロース誘導体などの増粘剤を加え、水系溶媒か有機溶媒中に加えてスラリーとしたものを、アルミニウムを９５重量％以上含むアルミニウム合金箔などの集電体上に、片面ないしは両面に塗布し、焼成して溶媒を揮発乾固する。これにより、集電体上に正極活物質を含む活物質層を有する、非水電解質二次電池用正極が得られる。 (Positive electrode for non-aqueous electrolyte secondary battery)
In order to form a positive electrode for a non-aqueous electrolyte secondary battery using a positive electrode active material, if necessary, a conductive auxiliary such as carbon black is further added to the positive electrode active material, and polytetrafluoroethylene, polyvinylidene fluoride, Aluminum containing at least 95% by weight of aluminum containing a binder such as polyimide, a dispersant such as butadiene rubber, and a thickener such as carboxymethylcellulose and cellulose derivatives, and adding it to an aqueous solvent or an organic solvent to form a slurry The solution is applied on one side or both sides on a current collector such as an alloy foil and fired to evaporate the solvent to dryness. Thereby, the positive electrode for nonaqueous electrolyte secondary batteries which has an active material layer containing a positive electrode active material on a collector is obtained.
　この際に、スラリーの塗布性や集電体と活物質層との密着性、集電性を上げるために、正極活物質と炭素源等を用いてスプレードライ法により造粒して焼成した二次粒子を、スラリー中に含有させて用いることができる。造粒した二次粒子の塊は概略０．５～２０μｍ程度の大きな塊になるが、これによりスラリー塗布性が向上して、電池電極の特性と寿命もさらに良好となる。スプレードライ法に用いるスラリーは水系溶媒または非水系溶媒のいずれも用いることができる。 At this time, in order to improve the coating property of the slurry, the adhesion between the current collector and the active material layer, and the current collecting property, it was granulated and fired by a spray dry method using a positive electrode active material and a carbon source. The following particles can be used by being contained in the slurry. The agglomerated secondary particle mass becomes a large mass of about 0.5 to 20 μm, which improves the slurry coatability and further improves the characteristics and life of the battery electrode. The slurry used in the spray drying method may be either an aqueous solvent or a non-aqueous solvent.
　さらに、正極活物質を含むスラリーをアルミニウム合金箔等の集電体上に塗工形成した正極において、活物質層形成面の集電体表面粗さとして日本工業規格（ＪＩＳ　Ｂ　０６０１－１９９４）に規定される十点平均粗さＲｚが０．５μｍ以上であることが望ましい。形成した活物質層と集電体との密着性に優れ、Ｌｉイオンの挿入脱離に伴う電子伝導性および集電体までの集電性が増し、充放電のサイクル寿命が向上する。 Furthermore, in the case of a positive electrode formed by coating a slurry containing a positive electrode active material on a current collector such as an aluminum alloy foil, the surface roughness of the current collector surface of the active material layer is determined according to Japanese Industrial Standard (JIS B 0601-1994). It is desirable that the defined ten-point average roughness Rz be 0.5 μm or more. The adhesion between the formed active material layer and the current collector is excellent, the electron conductivity accompanying the insertion and desorption of Li ions and the current collection to the current collector are increased, and the cycle life of charge and discharge is improved.
　（非水電解質二次電池）
　本実施の形態の正極を用いた高容量な二次電池を得るには、従来公知の負極活物質を用いた負極や電解液、セパレータ、電池ケース等の各種材料を、特に制限なく使用することができる。 (Non-aqueous electrolyte secondary battery)
In order to obtain a high-capacity secondary battery using the positive electrode of the present embodiment, various materials such as a negative electrode using a conventionally known negative electrode active material, an electrolytic solution, a separator, and a battery case are used without particular limitations. Can.
　具体的には、図３に示す非水電解質二次電池３１を例にあげられる。本実施の形態の非水電解質二次電池３１は、正極３３、負極３５を、セパレータ３７を介して、セパレータ－負極－セパレータ－正極の順に積層配置し、正極３３が内側になるように巻回して極板群を構成し、これを電池缶４１内に挿入する。そして正極３３は正極リード４３を介して正極端子４７に、負極３５は負極リード４５を介して電池缶４１にそれぞれ接続し、非水電解質二次電池３１内部で生じた化学エネルギーを電気エネルギーとして外部に取り出し得るようにする。次いで、電池缶４１内に電解質３９を極板群を覆うように充填した後、電池缶４１の上端（開口部）に、円形蓋板とその上部の正極端子４７からなり、その内部に安全弁機構を内蔵した封口体４９を、環状の絶縁ガスケットを介して取り付けることで製造することができる。 Specifically, the non-aqueous electrolyte secondary battery 31 shown in FIG. 3 can be exemplified. In the non-aqueous electrolyte secondary battery 31 of the present embodiment, the positive electrode 33 and the negative electrode 35 are stacked and arranged in the order of separator-negative electrode-separator-positive electrode via the separator 37, and wound so that the positive electrode 33 is inside. The electrode plate group is constructed and inserted into the battery can 41. The positive electrode 33 is connected to the positive electrode terminal 47 via the positive electrode lead 43, and the negative electrode 35 is connected to the battery can 41 via the negative electrode lead 45, and chemical energy generated inside the non-aqueous electrolyte secondary battery 31 is used as electrical energy. To be able to take out. Next, the battery can 41 is filled with the electrolyte 39 so as to cover the electrode plate group, and the upper end (opening) of the battery can 41 is composed of a circular cover plate and a positive electrode terminal 47 on the top thereof. It can manufacture by attaching the sealing body 49 which incorporated the through the annular insulation gasket.
　本実施の形態に係る正極を用いた二次電池は、容量が高く、良好な電極特性が得られるが、二次電池を構成する非水溶媒を用いる電解液に、フッ素を含有する非水溶媒を用いるか、または添加すると、充放電による繰り返しを経ても容量が低下し難く長寿命となる。例えば、特にはシリコン系の高容量な負極活物質を含む負極を用いる場合には、Ｌｉイオンのドープ・脱ドープによる大きな膨張収縮を抑制するために、電解液にフッ素を含有するか、フッ素を置換基として有する非水溶媒を含む電解液を用いることが望ましい。フッ素含有溶媒は充電時、特に初めての充電処理の際のＬｉイオンとの合金化によるシリコン系皮膜の体積膨張を緩和するので、充放電による容量低下を抑制することができる。フッ素含有非水溶媒にはフッ素化エチレンカーボネートやフッ素化鎖状カーボネートなどを用いることができる。フッ素化エチレンカーボネートにはモノ－テトラ－フルオロエチレンカーボネート（４－フルオロ－１，３－ジオキソラン－２－オン、ＦＥＣ）が、フッ素化鎖状カーボネートにはメチル２，２，２－トリフルオロエチルカーボネート、エチル２，２，２－トリフルオロエチルカーボネートなどがあり、これらを単一または複数併用して電解液に添加して用いることができる。フッ素基はシリコンと結合し易く強固でもあるので、Ｌｉイオンとの充電合金化による膨張の際にも皮膜を安定化させ膨張の抑制に寄与することができるとみられる。 Although the secondary battery using the positive electrode according to the present embodiment has a high capacity and good electrode characteristics can be obtained, the non-aqueous solvent containing fluorine in the electrolytic solution using the non-aqueous solvent constituting the secondary battery When or is added, the capacity is unlikely to decrease even after repeated charging and discharging, and the life is extended. For example, in the case of using a negative electrode containing a silicon-based high-capacity negative electrode active material, for example, the electrolytic solution may contain fluorine or fluorine in order to suppress large expansion and contraction due to doping and de-doping of Li ions. It is desirable to use an electrolytic solution containing a non-aqueous solvent having as a substituent. The fluorine-containing solvent relaxes the volume expansion of the silicon-based film due to the alloying with Li ions at the time of charge, particularly at the first charge treatment, so that the capacity decrease due to charge and discharge can be suppressed. As the fluorine-containing nonaqueous solvent, fluorinated ethylene carbonate, fluorinated linear carbonate, etc. can be used. Mono-tetrafluoro-ethylene carbonate (4-fluoro-1,3-dioxolan-2-one, FEC) for fluorinated ethylene carbonate, methyl 2,2,2-trifluoroethyl carbonate for fluorinated linear carbonate And ethyl 2,2,2-trifluoroethyl carbonate, etc., which may be used singly or in combination of two or more in combination with the electrolytic solution. Since the fluorine group easily bonds to silicon and is strong, it is believed that the film can be stabilized and contributed to the suppression of expansion even in the case of expansion due to charge alloying with Li ions.
　（本実施の形態に係る粒子の製造方法）
　本実施の形態に係る粒子は、リン酸鉄リチウムの前駆体である第３の粒子と、リン酸マンガンリチウムの前駆体である第４の粒子とを、混合した上で焼成することにより得られる。 (Method of producing particles according to the present embodiment)
The particles according to the present embodiment can be obtained by mixing a third particle, which is a precursor of lithium iron phosphate, and a fourth particle, which is a precursor of lithium manganese phosphate, and then firing the mixture. .
　さらに、正極活物質として用いる場合には粒子の表面を炭素で被覆することが好ましいため、第３の粒子と第４の粒子と炭素源を混合した後に焼成することで、本実施の形態に係る正極活物質が得られる。 Furthermore, since it is preferable to coat the surface of the particles with carbon when it is used as a positive electrode active material, it is preferable to mix the third particles, the fourth particles, and the carbon source and then bake the mixture according to the present embodiment. A positive electrode active material is obtained.
　第３の粒子と第４の粒子は、火炎加水分解法や熱酸化法などの噴霧燃焼法により合成された、それぞれリン酸鉄リチウムの前駆体粒子と、リン酸マンガンリチウムの前駆体粒子である。 The third particle and the fourth particle are a precursor particle of lithium iron phosphate and a precursor particle of lithium manganese phosphate, which are synthesized by a spray combustion method such as a flame hydrolysis method or a thermal oxidation method. .
　（噴霧燃焼法による前駆体粒子の製造方法）
　（前駆体粒子の作製）
　噴霧燃焼法により前駆体粒子を製造する製造装置の例を図２に示す。図２に示す微粒子製造装置１１の反応容器は、容器内に微粒子合成ノズル１３が配置され、可燃性ガス、支燃性ガス、及び原料溶液がノズル１３から生じる火炎中に供給される。他方に、生成微粒子や反応生成物を排気する排気管１９を有し、排気中の前駆体粒子１７を微粒子回収フィルタ１５により回収する。
　噴霧燃焼法は、塩化物などの原料気体を供給する方法や、気化器を通して原料液体または原料溶液を供給する方法により、支燃性ガスと可燃性ガスとともに構成原料を火炎中へ供給し、構成原料を反応させ、目的物質を得る方法である。噴霧燃焼法として、ＶＡＤ（Ｖａｐｏｒ－ｐｈａｓｅ　Ａｘｉａｌ　Ｄｅｐｏｓｉｔｉｏｎ）法などが好適な例として挙げられる。これらの火炎の温度は、可燃性ガスと支燃性ガスの混合比や、さらに構成原料の添加割合によって変化するが、通常１０００～３０００℃の間にあり、特に１５００～２５００℃程度であることが好ましく、さらに１５００～２０００℃程度であることがより好ましい。火炎温度が低温であると、火炎中での反応が完了する前に、微粒子が火炎の外へ出てしまう可能性がある。また、火炎温度が高温であると、生成する微粒子の結晶性が高くなりすぎ、その後の焼成工程において、安定相であるが、正極活物質としては好ましくない相が生成しやすくなってしまう。 (Method of producing precursor particles by spray combustion method)
(Preparation of precursor particles)
An example of a production apparatus for producing precursor particles by the spray combustion method is shown in FIG. In the reaction container of the particle manufacturing apparatus 11 shown in FIG. 2, the particle synthesis nozzle 13 is disposed in the container, and the flammable gas, the combustion supporting gas, and the raw material solution are supplied into the flame generated from the nozzle 13. On the other hand, an exhaust pipe 19 for exhausting the generated particulates and reaction products is provided, and the precursor particles 17 in the exhaust gas are recovered by the particulate collection filter 15.
In the spray combustion method, the constituent material is supplied into the flame together with the combustion supporting gas and the flammable gas by a method of supplying a raw material gas such as chloride or a method of supplying a raw material liquid or a raw material solution through a vaporizer. This is a method of reacting the raw materials to obtain the target substance. As a spray combustion method, VAD (Vapor-phase Axial Deposition) method is mentioned as a suitable example. The temperature of these flames varies depending on the mixing ratio of the flammable gas and the combustion supporting gas, and the addition ratio of the constituent materials, but is usually between 1000 and 3000 ° C., especially around 1500 to 2500 ° C. Is more preferable, and it is more preferable that the temperature be about 1500 to 2000.degree. If the flame temperature is low, fine particles may come out of the flame before the reaction in the flame is completed. In addition, when the flame temperature is high, the crystallinity of the particles to be generated becomes too high, and a phase which is a stable phase but is not preferable as a positive electrode active material is easily generated in the subsequent firing step.
　また、火炎加水分解法は、火炎中で構成原料が加水分解される方法である。火炎加水分解法では、火炎として酸水素火炎が一般に用いられる。可燃性ガスとして水素ガスが、支燃性ガスとして酸素ガスが供給された火炎の元に正極活物質の構成原料と、火炎原料（酸素ガスと水素ガス）を同時にノズルから供給して目的物質を合成する。火炎加水分解法では、不活性ガス充填雰囲気中、ナノスケールの極微小な、主として非晶質からなる目的物質の微粒子を得ることができる。 Moreover, the flame hydrolysis method is a method in which a constituent material is hydrolyzed in a flame. In the flame hydrolysis method, an oxyhydrogen flame is generally used as a flame. The target material is obtained by simultaneously supplying the constituent materials of the positive electrode active material and the flame raw materials (oxygen gas and hydrogen gas) to the base of the flame where hydrogen gas as combustible gas and oxygen gas as combustion supporting gas are supplied simultaneously. Synthesize. In the flame hydrolysis method, it is possible to obtain nanoscale ultrafine particles of an objective substance consisting mainly of an amorphous substance in an inert gas filled atmosphere.
　また、熱酸化法とは、火炎中で構成原料が熱酸化される方法である。熱酸化法では、火炎として炭化水素火炎が一般に用いられる。可燃性ガスとして炭化水素系ガスが、支燃性ガスとして空気が供給された火炎の元に、構成原料と火炎原料（例えば、プロパンガスと酸素ガス）を同時にノズルから供給しながら目的物質を合成する。炭化水素系ガスとしては、メタン、エタン、プロパン、ブタンなどのパラフィン系炭化水素ガスや、エチレン、プロピレン、ブチレンなどのオレフィン系炭化水素ガスを使用できる。 The thermal oxidation method is a method in which a constituent material is thermally oxidized in a flame. In the thermal oxidation method, a hydrocarbon flame is generally used as the flame. The target material is synthesized while supplying the constituent raw material and the flame raw material (for example, propane gas and oxygen gas) simultaneously from the nozzle to the source of the flame to which hydrocarbon-based gas is supplied as combustible gas and air is supplied as combustion-supporting gas. Do. As the hydrocarbon gas, paraffin hydrocarbon gas such as methane, ethane, propane and butane, or olefin hydrocarbon gas such as ethylene, propylene and butylene can be used.
　（前駆体粒子を得るための構成原料）
　本実施の形態の前駆体粒子を得るための構成原料は、リチウム源、遷移金属源、リン源である。原料が固体の場合は、粉末のまま供給するか、液体に分散して、または溶媒に溶かして溶液とし、気化器を通じて、火炎に供給する。原料が液体の場合には、気化器を通じるほかに、供給ノズル前に加熱または減圧およびバブリングによって蒸気圧を高めて気化供給することもできる。特に、リチウム源、遷移金属源、リン源の混合溶液を、直径２０μｍ以下の霧状の液滴にて供給することが好ましい。 (Constituent raw material for obtaining precursor particles)
The constituent materials for obtaining the precursor particles of the present embodiment are a lithium source, a transition metal source, and a phosphorus source. When the raw material is solid, it is supplied as a powder, dispersed in a liquid, or dissolved in a solvent to form a solution, and is supplied to the flame through a vaporizer. When the raw material is liquid, in addition to passing through the vaporizer, the vapor pressure can be increased and vaporized and supplied by heating or depressurization and bubbling in front of the supply nozzle. In particular, it is preferable to supply a mixed solution of a lithium source, a transition metal source, and a phosphorus source in the form of mist droplets of 20 μm or less in diameter.
　リチウム源としては、塩化リチウム、水酸化リチウム、炭酸リチウム、酢酸リチウム、硝酸リチウム、臭化リチウム、リン酸リチウム、硫酸リチウムなどのリチウム無機酸塩、シュウ酸リチウム、酢酸リチウム、ナフテン酸リチウムなどのリチウム有機酸塩、リチウムエトキシドなどのリチウムアルコキシド、リチウムのβ―ジケトナト化合物などの有機リチウム化合物、酸化リチウム、過酸化リチウム、などを用いることができる。なお、ナフテン酸とは、主に石油中の複数の酸性物質が混合した異なるカルボン酸の混合物で、主成分はシクロペンタンとシクロヘキサンのカルボン酸化合物である。 As a lithium source, lithium inorganic acid salts such as lithium chloride, lithium hydroxide, lithium carbonate, lithium acetate, lithium nitrate, lithium nitrate, lithium bromide, lithium phosphate, lithium sulfate, lithium oxalate, lithium acetate, lithium naphthenate and the like Lithium organic acid salts, lithium alkoxides such as lithium ethoxide, organic lithium compounds such as β-diketonato compounds of lithium, lithium oxide, lithium peroxide and the like can be used. Naphthenic acid is a mixture of different carboxylic acids in which a plurality of acidic substances in petroleum are mainly mixed, and the main component is a carboxylic acid compound of cyclopentane and cyclohexane.
　前駆体としての第３の粒子を得る場合には、遷移金属源としては、塩化第二鉄、シュウ酸鉄、酢酸鉄、硫酸第一鉄、硝酸鉄、水酸化鉄、２－エチルヘキサン酸第二鉄、ナフテン酸鉄等を用いることができる。さらに、ステアリン酸、ジメチルジチオカルバミン酸、アセチルアセトネート、オレイン酸、リノール酸、リノレン酸などの鉄の有機金属塩や、酸化鉄なども条件により使用される。
　前駆体としての第４の粒子を得る場合には、遷移金属源としては、塩化マンガン、シュウ酸マンガン、酢酸マンガン、硫酸マンガン、硝酸マンガン、オキシ水酸化マンガン、２－エチルヘキサン酸第二マンガン、ナフテン酸マンガン、ヘキソエートマンガン等を用いることができる。さらに、ステアリン酸、ジメチルジチオカルバミン酸、アセチルアセトネート、オレイン酸、リノール酸、リノレン酸などのマンガンの有機金属塩、酸化マンガンなども条件により使用される。 When a third particle as a precursor is obtained, as a transition metal source, ferric chloride, iron oxalate, iron acetate, ferrous sulfate, iron nitrate, iron hydroxide, 2-ethylhexanoate Diiron, iron naphthenate and the like can be used. Furthermore, organic metal salts of iron such as stearic acid, dimethyldithiocarbamic acid, acetylacetonate, oleic acid, linoleic acid, linolenic acid, iron oxide, etc. are also used depending on the conditions.
When a fourth particle as a precursor is to be obtained, as a transition metal source, manganese chloride, manganese oxalate, manganese acetate, manganese sulfate, manganese nitrate, manganese oxyhydroxide, manganese 2-hydroxy-2-oxide, Manganese naphthenate, manganese hexoate and the like can be used. Furthermore, stearic acid, dimethyldithiocarbamic acid, acetylacetonate, organometallic salts of manganese such as oleic acid, linoleic acid and linolenic acid, manganese oxide and the like are also used depending on the conditions.
　前駆体のリン源としては、亜リン酸、オルトリン酸やメタリン酸などのリン酸、ピロリン酸、リン酸水素２アンモニウムやリン酸２水素アンモニウムなどのリン酸水素アンモニウム塩、リン酸アンモニウム、リン酸ナトリウムなどの各種リン酸塩またはピロリン酸塩、およびリン酸第一鉄など導入遷移金属のリン酸塩、などを用いることができる。 As a phosphorus source of the precursor, phosphoric acid, phosphoric acid such as orthophosphoric acid or metaphosphoric acid, pyrophosphoric acid, ammonium hydrogen phosphate such as ammonium hydrogen phosphate such as ammonium hydrogen phosphate or ammonium hydrogen phosphate, ammonium phosphate Various phosphates such as sodium or pyrophosphates, and phosphates of introduced transition metals such as ferrous phosphate can be used.
　また、リン酸遷移金属リチウム化合物のリン酸の一部を他のアニオンにより置換する場合は、アニオン源として、遷移金属の酸化物、ホウ酸の原料を加える。
　例えば、酸化チタン、亜チタン酸鉄や亜チタン酸マンガンなどの亜チタン酸金属塩、チタン酸亜鉛やチタン酸マグネシウム、チタン酸バリウムなどのチタン酸塩、酸化バナジウム、メタバナジン酸アンモニウム、酸化クロム、クロム酸塩や二クロム酸塩、酸化マンガン、過マンガン酸塩やマンガン酸塩、コバルト酸塩、酸化ジルコニウム、ジルコン酸塩、酸化モリブデン、モリブデン酸塩、酸化タングステン、タングステン酸塩、ホウ酸や三酸化二ホウ素、メタホウ酸ナトリウムや四ホウ酸ナトリウム、ホウ砂などの各種ホウ酸塩を、それぞれ所望のアニオン源と合成条件に応じて用いることができる。 In addition, when a part of the phosphoric acid of the lithium transition metal phosphate compound is substituted with another anion, a raw material of an oxide of transition metal and boric acid is added as an anion source.
For example, titanium oxide, a metal salt of titanate such as iron titanate or manganese titanate, a titanate such as zinc titanate or magnesium titanate or barium titanate, vanadium oxide, ammonium metavanadate, chromium oxide, chromium And dichromate, manganese oxide, permanganate and manganate, cobaltate, zirconium oxide, zirconate, molybdenum oxide, molybdate, tungsten oxide, tungstate, boric acid and trioxide Various borates such as diboron, sodium metaborate, sodium tetraborate and borax can be used depending on the desired anion source and synthesis conditions.
　これらの原料を同一反応系に火炎原料と共に供給して前駆体粒子を合成する。生成した前駆体粒子は、排気中からフィルタで回収することができる。また、以下のように芯棒の周囲に生成させることもできる。反応器の中にシリカやシリコン系の芯棒（種棒とも呼ばれる）を設置し、これに吹き付けている酸水素火炎中やプロパン火炎中に火炎原料と共にリチウム源、遷移金属源、リン源を供給し、加水分解または酸化反応させると、芯棒表面に主にナノオーダーの微粒子が生成付着する。これらの生成微粒子を回収し、場合によってはフィルタやふるいに掛けて、不純物や凝集粗大分を除く。このようにして得られた前駆体粒子は、ナノスケールの極微小な粒径を持ち、主として非晶質である微粒子からなる。 These raw materials are supplied to the same reaction system together with the flame raw material to synthesize precursor particles. The generated precursor particles can be recovered from the exhaust with a filter. Also, it can be generated around the core rod as follows. A silica or silicon core rod (also called a seed rod) is installed in the reactor, and a lithium source, transition metal source, and phosphorus source are supplied together with the flame raw material in the oxyhydrogen flame and propane flame sprayed thereto. When it is hydrolyzed or oxidized, fine particles of mainly nano order form and adhere to the surface of the core rod. These generated fine particles are recovered and optionally filtered or sieved to remove impurities and coarse aggregates. The precursor particles thus obtained are composed of fine particles that are mainly amorphous and have an extremely small particle size of nanoscale.
　本実施の形態に係る前駆体粒子の製造方法である噴霧燃焼法は、製造できる前駆体粒子が、非晶質であり、粒子の大きさも小さい。さらに、噴霧燃焼法では、従来の水熱合成法や固相法に比べて、短時間で大量の合成が可能であり、低コストで均質な前駆体粒子を得ることができる。 In the spray combustion method which is a method for producing precursor particles according to the present embodiment, precursor particles that can be produced are amorphous, and the particle size is also small. Furthermore, in the spray combustion method, a large amount of synthesis can be performed in a short time as compared with the conventional hydrothermal synthesis method or the solid phase method, and homogeneous precursor particles can be obtained at low cost.
　（噴霧燃焼法により得られる前駆体粒子の特徴）
　本発明においては、前駆体としての第３の粒子と第４の粒子を混合して、還元剤と混ぜて焼成することで、正極活物質を得ることができる。本実施の形態における前駆体とは、焼成することで、リン酸遷移金属の結晶を得ることができる材料である。特に、本実施の形態における前駆体は、鉄やマンガンの価数が３価でありアモルファスであるが、還元剤と混ぜて焼成することで鉄やマンガンの価数が３価から２価に変化する。前駆体粒子を構成するリン酸鉄リチウムやリン酸マンガンリチウムを含む粒子の組成は、化学量論的組成を満足することが望ましいが、極く僅かであれば不純物の含有などによる理想の化学量論的組成からのずれは許容される。
　前駆体粒子を構成する微粒子内の元素の空間分布が均一であることが好ましい。特に、微粒子内で遷移金属とリンの空間分布に偏りがないことが好ましい。また、前駆体粒子の形状が略球形であり、粒子の平均アスペクト比（長径／短径）が、１．５以下、好ましくは１．２以下、より好ましくは１．１以下である。
　なお、粒子が略球形であるとは、粒子形状が幾何学的に厳密な球形や楕円球形であることまでは意味せず、わずかな突起部があっても粒子の表面がおおむね滑らかな曲面で構成されていればよい。 (Characteristics of precursor particles obtained by the spray combustion method)
In the present invention, the positive electrode active material can be obtained by mixing the third particles and the fourth particles as precursors, mixing with a reducing agent, and calcining. The precursor in this embodiment is a material capable of obtaining crystals of transition metal phosphate by firing. In particular, the precursor in the present embodiment has trivalent iron and manganese and is amorphous, but the valence of iron and manganese changes from trivalent to bivalent by mixing with a reducing agent and firing. Do. It is desirable that the composition of the particles containing lithium iron phosphate and lithium manganese phosphate constituting the precursor particles satisfy the stoichiometric composition, but if the composition is very small, the ideal stoichiometry due to the inclusion of impurities etc. Deviations from the theoretical composition are acceptable.
It is preferable that the spatial distribution of the elements in the microparticles constituting the precursor particles is uniform. In particular, it is preferable that the spatial distribution of the transition metal and phosphorus in the fine particles be uniform. The precursor particles have a substantially spherical shape, and the average aspect ratio (long diameter / short diameter) of the particles is 1.5 or less, preferably 1.2 or less, and more preferably 1.1 or less.
Incidentally, that the particles are approximately spherical does not mean that the particle shape is geometrically strictly spherical or elliptical, and even if there are slight protrusions, the surface of the particle is a roughly smooth curved surface It should just be comprised.
　これら前駆体粒子を２θ＝１０～６０°の範囲の粉末法Ｘ線回折を測定すると、ほとんど回折ピークを有しないか、有したとしても回折ピークが小さく幅の広い回折角を示す。すなわち、前駆体粒子は、結晶子の小さい微粒子または小さな単結晶の集まった多結晶微粒子で構成されるか、これら微粒子の周囲に非晶質成分が存在する微結晶形態である。 When these precursor particles are measured by powder method X-ray diffraction in the range of 2θ = 10 to 60 °, they have little or no diffraction peak and exhibit small diffraction peaks and wide diffraction angles. That is, the precursor particles are composed of fine particles of small crystallites or polycrystalline fine particles in which small single crystals are collected, or are microcrystalline forms in which an amorphous component exists around these fine particles.
　本実施の形態の噴霧燃焼法では、火炎中で炭素は燃焼するので、得られた前駆体粒子には、炭素が含まれない。仮に炭素成分が混入したとしても、ごく微量であり、正極に使用する際の導電助剤となるほどの量ではない。 In the spray combustion method of the present embodiment, carbon is burned in the flame, and thus the obtained precursor particles do not contain carbon. Even if the carbon component is mixed, it is a very small amount, which is not a sufficient amount as a conductive aid at the time of using the positive electrode.
　（正極活物質の製造）
　噴霧燃焼法による得られた、リン酸鉄リチウムの前駆体である第３の粒子と、リン酸マンガンリチウムの前駆体である第４の粒子とを、混合し、さらに炭素源と混合した後に、不活性ガス充填雰囲気下で焼成することにより、正極活物質が得られる。この際、第３の粒子と第４の粒子の混合比が、重量比で６０：４０～９０：１０であることが好ましく、７０：３０であることがより好ましい。前駆体粒子に含まれる非晶質な化合物や酸化物形態の混合物が、焼成により主にオリビン構造のリン酸遷移金属リチウム系の結晶形態の化合物に変化する。この際、焼成時に粒子同士の融着が起こり、粒子の界面近傍において、ＬｉＦｅ１－ｘＭｎｘＰＯ４（０＜ｘ＜１）で表される混晶相を含んでいても良い。このように、粒子の接合界面に混晶相を形成することで、第３の粒子と第４の粒子の接合界面が直接異質界面を構成する場合に比べて、接合界面における格子歪みを緩和して接合界面における接合強度を安定化させることができる。 (Production of positive electrode active material)
After mixing the third particles obtained by the spray combustion method, which is a precursor of lithium iron phosphate, and the fourth particles which are a precursor of lithium manganese phosphate, and further mixing with a carbon source, By firing in an inert gas filled atmosphere, a positive electrode active material can be obtained. At this time, the mixing ratio of the third particles to the fourth particles is preferably 60:40 to 90:10 by weight, and more preferably 70:30. The mixture of the amorphous compound and the oxide form contained in the precursor particles is converted to a compound of the crystal form of a lithium transition metal phosphate based on the olivine structure mainly by firing. At this time, fusion between particles occurs during firing, and a mixed crystal phase represented by LiFe 1-x Mn x PO 4 (0 <x <1) may be included in the vicinity of the interface of the particles. Thus, by forming the mixed crystal phase at the bonding interface of the particles, the lattice strain at the bonding interface is relaxed compared to the case where the bonding interface of the third particle and the fourth particle directly constitutes the heterogeneous interface. Thus, the bonding strength at the bonding interface can be stabilized.
　第３の粒子の粒径が１００ｎｍ～１０μｍであり、第４の粒子の粒径が２００ｎｍ以下であることが好ましい。また、第４の粒子は、第３の粒子よりも粒径が小さい。第４の粒子の粒径は、本発明の効果を得るためには小さい分には問題なく、粒径の下限は特に規定されない。しかし、前駆体製造の工程から来る限界や、第１の粒子との混合の操作の都合などから、最小で５ｎｍ程度になる場合が多い。前駆体粒子と正極活物質では、焼成の前後で実質的な粒径が変化せず、前駆体を焼成することで融着や粒子成長が起きずに、粒径を維持することができるからである。また、第３の粒子が多数集まった粉体において、第３の粒子の平均粒径は１００ｎｍ～１０μｍであることが好ましく、２００ｎｍ～２μｍであることがより好ましい。さらに、第４の粒子が多数集まった粉体において、第４の粒子５の平均粒径は５ｎｍ～２００ｎｍであることが好ましく、１０ｎｍ～１００ｎｍであることがより好ましい。 The particle size of the third particles is preferably 100 nm to 10 μm, and the particle size of the fourth particles is preferably 200 nm or less. Also, the fourth particles have a smaller particle size than the third particles. The particle diameter of the fourth particle is not a problem to be small for obtaining the effect of the present invention, and the lower limit of the particle diameter is not particularly defined. However, due to the limit from the process of precursor production, the convenience of the operation of mixing with the first particle, etc., it is often at least about 5 nm at the minimum. In the precursor particles and the positive electrode active material, the particle diameter does not substantially change before and after the firing, and by firing the precursor, the particle diameter can be maintained without causing fusion or particle growth. is there. In the powder in which a large number of third particles are collected, the average particle diameter of the third particles is preferably 100 nm to 10 μm, and more preferably 200 nm to 2 μm. Furthermore, in the powder in which a large number of fourth particles are collected, the average particle diameter of the fourth particles 5 is preferably 5 nm to 200 nm, and more preferably 10 nm to 100 nm.
　また、不活性ガス充填雰囲気下では、焼成時に炭素源が燃焼してしまうこと、正極活物質が酸化してしまうことを防ぐことができる。不活性ガスとしては、窒素ガス、アルゴンガス、ネオンガス、ヘリウムガス、二酸化炭素ガスなどを使用することができる。熱処理後の生成物の導電性を高めるために、ポリビニルアルコールなどの多価アルコール、ポリビニルピロリドン、カルボキシメチルセルロース、アセチルセルロースなどのポリマー、ショ糖などの糖類、カーボンブラックなどの導電性炭素源である有機化合物を、熱処理前に第３の粒子と第４の粒子を混合した粉体に加えて焼成する。ポリビニルアルコールは、焼成前の前駆体粒子のバインダとしての役割を果たすうえ、焼成中に鉄やマンガンを還元できるので、特に好ましい。 In addition, in the atmosphere filled with an inert gas, the carbon source can be prevented from burning at the time of firing and the positive electrode active material can be prevented from being oxidized. As an inert gas, nitrogen gas, argon gas, neon gas, helium gas, carbon dioxide gas, etc. can be used. Organic compounds that are conductive carbon sources such as polyalcohols such as polyvinyl alcohol, polymers such as polyvinyl pyrrolidone, carboxymethyl cellulose, acetyl cellulose, saccharides such as sucrose, saccharides such as carbon black, in order to increase the conductivity of the product after heat treatment The compound is added to the powder in which the third and fourth particles are mixed before heat treatment, and the mixture is calcined. In addition to serving as a binder for precursor particles before firing, polyvinyl alcohol is particularly preferable because it can reduce iron and manganese during firing.
　前駆体粒子の結晶化と共に炭素によるコーティングまたは担持処理を同一焼成工程で行う。熱処理条件は温度３００～９００℃と処理時間０．５～１０時間の組み合わせで適宜所望の結晶性と粒径の焼成物を得ることができる。高温や長時間の熱処理による過大な熱負荷は粗大な単結晶を生成させ得るので回避すべきであり、所望の結晶性または微結晶性のリン酸遷移金属リチウム化合物が得られる程度の加熱条件で、結晶子の大きさを極力小さく抑制できる熱処理条件が望ましい。熱処理の温度は４００～７００℃程度であることが好ましい。この際、第３の粒子の表面全体に第４の粒子が付着していなくてもよく、炭素被覆されやすいリン酸鉄リチウムを含む第３の粒子表面に剥き出しの部分が存在することで、第４の粒子も炭素によって良くコーティングされる。 Coating with carbon or supporting treatment is carried out in the same firing step together with crystallization of precursor particles. The heat treatment conditions can be a combination of a temperature of 300 to 900 ° C. and a treatment time of 0.5 to 10 hours to obtain a fired product of desired crystallinity and particle size as appropriate. Excessive heat load due to heat treatment at high temperature or long time should be avoided as it can generate coarse single crystals, and should be under heating conditions such that the desired crystalline or microcrystalline lithium transition metal lithium compound can be obtained. And heat treatment conditions that can suppress the size of the crystallite as small as possible. The temperature of the heat treatment is preferably about 400 to 700.degree. At this time, the fourth particle does not have to be attached to the entire surface of the third particle, and the exposed portion is present on the surface of the third particle containing lithium iron phosphate which is easily carbon-coated. The particles of 4 are also well coated with carbon.
　なお、得られた正極活物質は、焼成工程において凝集していることが多いため、乳鉢やボールミルほか粉砕手段に掛けることにより、再び微粒子とすることができる。 In addition, since the obtained positive electrode active material is often aggregated in the firing step, it can be made into fine particles again by being subjected to a grinding means such as a mortar or a ball mill.
　（本実施の形態の効果）
　本実施の形態によれば、噴霧燃焼法を用いるため、正極活物質を、連続的かつ大規模に合成可能である。 (Effect of this embodiment)
According to the present embodiment, since the spray combustion method is used, the positive electrode active material can be synthesized continuously and on a large scale.
　また、本実施の形態に係る正極活物質は、電子伝導性とリチウムイオン拡散性に優れるリン酸鉄リチウムの粒子の表面に、電位とエネルギー密度に優れるリン酸マンガンリチウムを付着させているため、リン酸マンガンリチウムを十分に充放電反応に活用できる。 Moreover, since the positive electrode active material according to the present embodiment adheres lithium manganese phosphate excellent in electric potential and energy density to the surface of lithium iron phosphate particles excellent in electron conductivity and lithium ion diffusivity, Lithium manganese phosphate can be sufficiently utilized for charge and discharge reaction.
　さらに、本実施の形態に係るリン酸遷移金属リチウム系正極活物質は、元素の空間分布が均一であるため、リチウムイオンの移動経路を確保でき、粒子を構成する活物質を効率よく使用することができる。 Furthermore, since the spatial distribution of elements is uniform, the lithium metal transition metal phosphate based positive electrode active material according to the present embodiment can ensure the migration path of lithium ions, and efficiently use the active material constituting the particles. Can.
　以下に、本発明を実施例により説明するが、本実施例に本発明が何ら限定されることはない。 Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the examples.
　（１－１）合成例１
　（リン酸鉄リチウムの前駆体粒子の噴霧燃焼法による作製）
　噴霧燃焼法により前駆体粒子を製造する製造装置を図２に示す。図２に示す装置の反応容器において、可燃性ガスとしてはプロパンガス（Ｃ３Ｈ８）を使用し、支燃性ガスとしては空気（Ａｉｒ）を使用し、原料溶液がノズル１３から、火炎中に供給される。他方に、生成微粒子や反応生成物を排気する排気管を有し、排気中の前駆体粒子１７を微粒子回収フィルタ１５により回収する。ノズルに供給する原料の種類と供給条件は以下とした。また、原料溶液は、液滴の大きさが２０μｍとなるよう、二流体ノズルを用いて火炎中に供給した。火炎の温度は約２０００℃であった。
　プロパン（Ｃ３Ｈ８）：１ｄｍ３／ｍｉｎ、
　空気：５ｄｍ３／ｍｉｎ、
　ナフテン酸リチウム（４Ｍ溶液）：０．０２５ｄｍ３／ｍｉｎ
　Ｃ１６Ｈ３０ＦｅＯ４（２－エチルヘキサン酸鉄（II））（１Ｍ溶液）：０．１ｄｍ３／ｍｉｎ
　ホスホノ酢酸トリエチル（１Ｍ溶液）：０．１ｄｍ３／ｍｉｎ (1-1) Synthesis Example 1
(Preparation of precursor particles of lithium iron phosphate by spray combustion method)
An apparatus for producing precursor particles by the spray combustion method is shown in FIG. In the reaction container of the apparatus shown in FIG. 2, propane gas (C 3 H 8 ) is used as the flammable gas, air is used as the combustion supporting gas, and the raw material solution is in flame from the nozzle 13 Supplied to On the other hand, an exhaust pipe for exhausting the generated particulates and reaction products is provided, and the precursor particles 17 in the exhaust gas are recovered by the particulate collection filter 15. The types of raw materials to be supplied to the nozzles and the supply conditions were as follows. Also, the raw material solution was supplied into the flame using a two-fluid nozzle so that the droplet size was 20 μm. The flame temperature was about 2000 ° C.
Propane (C 3 H 8 ): 1 dm 3 / min,
Air: 5 dm 3 / min,
Lithium naphthenate (4 M solution): 0.025 dm 3 / min
C 16 H 30 FeO 4 (2-ethylhexanoate iron (II)) (1 M solution): 0.1 dm 3 / min
Triethyl phosphonoacetate (1 M solution): 0.1 dm 3 / min
　噴霧燃焼法による前駆体粒子の製造方法は以下のとおりである。まず、Ｎ２ガスを所定量供給し、反応容器中を不活性ガス雰囲気とした。このような条件下で、リチウム源、鉄源、リン酸源をそれぞれ混合した溶液を、霧化器を通じて２０μｍの液滴にし、プロパンガス及び空気とともに火炎に供給した。火炎中で生成した酸化リチウム、酸化鉄、リン酸化物等の微粒子、リン酸鉄リチウム化合物の微粒子などの混合物である前駆体粒子を微粒子回収フィルタにて回収した。得られた前駆体粒子が前駆体粒子ａである。電子顕微鏡で確認した前駆体粒子ａの一次粒子の平均粒径は約５００ｎｍであった。 The method for producing precursor particles by the spray combustion method is as follows. First, a predetermined amount of N 2 gas was supplied to make the inside of the reaction vessel an inert gas atmosphere. Under such conditions, a solution in which the lithium source, the iron source and the phosphoric acid source were respectively mixed was made into droplets of 20 μm through an atomizer and supplied to a flame together with propane gas and air. Precursor particles which are a mixture of lithium oxide, iron oxide, fine particles of phosphorus oxide and the like, fine particles of lithium iron phosphate compound and the like generated in a flame were collected by a fine particle collection filter. The obtained precursor particles are precursor particles a. The average particle size of the primary particles of the precursor particles a confirmed by the electron microscope was about 500 nm.
　（１－２）合成例２（噴霧燃焼法）
　（リン酸マンガンリチウムの前駆体粒子の噴霧燃焼法による作製）
　また、合成例１と同様に、噴霧燃焼法にて、プロパンガスによる火炎中へ、プロパンガス、空気、及び下記の所定濃度の原料溶液を供給し、熱酸化させることにより前駆体粒子ｂを合成して収集した。電子顕微鏡で確認した前駆体粒子ｂの一次粒子の平均粒径は約１００ｎｍであった。
　プロパン（Ｃ３Ｈ８）：１ｄｍ３／ｍｉｎ、
　空気：５ｄｍ３／ｍｉｎ、
　ＬｉＣｌ（４Ｍ水溶液）：０．０２５ｄｍ３／ｍｉｎ、
　ＭｎＳＯ４・５Ｈ２Ｏ（１Ｍ水溶液）：０．１ｄｍ３／ｍｉｎ、
　ホスホノ酢酸トリエチル（１Ｍ溶液）：０．１ｄｍ３／ｍｉｎ、 (1-2) Synthesis example 2 (spray combustion method)
(Preparation of lithium manganese phosphate precursor particles by spray combustion method)
Further, as in Synthesis Example 1, the precursor particles b are synthesized by supplying propane gas, air, and a raw material solution having a predetermined concentration described below into a flame of propane gas by a spray combustion method, and thermally oxidizing the raw material solution. Collected. The average particle diameter of the primary particles of the precursor particles b confirmed by the electron microscope was about 100 nm.
Propane (C 3 H 8 ): 1 dm 3 / min,
Air: 5 dm 3 / min,
LiCl (4 M aqueous solution): 0.025 dm 3 / min,
MnSO 4 · 5H 2 O (1M aq): 0.1dm 3 / min,
Triethyl phosphonoacetate (1 M solution): 0.1 dm 3 / min,
　（２－１）実施例
　リン酸鉄リチウムの前駆体粒子ａとリン酸マンガンリチウムの前駆体粒子ｂとを、重量比７０：３０で混合した後、ポリビニルアルコールを粉体の１０ｗｔ％になるように加えて混合した後、Ｎ２ガス雰囲気下で、２５０℃で４時間の仮焼成を行い、さらに６５０℃で８時間の本焼成を行った。仮焼成中にポリビニルアルコールの溶融と粉体中への含浸が起こり、本焼成中にポリビニルアルコールの炭化と遷移金属の還元が起き、リン酸遷移金属リチウムの生成と結晶化が起きる。得られた凝集体に粉砕処理を行い、正極活物質Ａを得た。正極活物質Ａは、大きなリン酸鉄リチウムの粒子の周囲に小さなリン酸マンガンリチウムの粒子が付着した粒子が、多数集まった粉体である。 (2-1) Example After the precursor particle a of lithium iron phosphate and the precursor particle b of lithium manganese phosphate are mixed at a weight ratio of 70:30, the polyvinyl alcohol becomes 10 wt% of the powder. after mixing in addition to, under N 2 gas atmosphere, subjected to calcination for 4 hours at 250 ° C., was the sintering of 8 hours at 650 ° C.. During the pre-baking, melting of the polyvinyl alcohol and impregnation into the powder occur, and during the main-baking, carbonization of the polyvinyl alcohol and reduction of the transition metal occur, and generation and crystallization of lithium transition metal phosphate occur. The obtained aggregate was pulverized to obtain a positive electrode active material A. The positive electrode active material A is a powder in which a large number of particles in which small particles of lithium manganese phosphate are attached around large particles of lithium iron phosphate are collected.
　（２－２）比較例１
　リン酸鉄リチウムの前駆体粒子ａのみを使用し、ポリビニルアルコールを前駆体粒子ａに対して１０ｗｔ％加えて混合した後、実施例と同様に焼成・粉砕を行い、正極活物質Ｂを得た。正極活物質Ｂは、リン酸鉄リチウムの粒子が多数集まった粉体である。 (2-2) Comparative Example 1
After using only precursor particle a of lithium iron phosphate and adding 10 wt% of polyvinyl alcohol with respect to precursor particle a and mixing, firing and crushing were performed in the same manner as in Example to obtain a positive electrode active material B . The positive electrode active material B is a powder in which a large number of lithium iron phosphate particles are collected.
　（２－３）比較例２
　リン酸マンガンリチウムの前駆体粒子ｂのみを使用し、ポリビニルアルコールを前駆体粒子ｂに対して１０ｗｔ％加えて混合した後、実施例と同様に焼成・粉砕を行い、正極活物質Ｃを得た。正極活物質Ｃは、リン酸マンガンリチウムの粒子が多数集まった粉体である。 (2-3) Comparative Example 2
After using only precursor particle b of lithium manganese phosphate and adding and mixing 10 wt% of polyvinyl alcohol with respect to precursor particle b, baking and crushing were performed in the same manner as in Example to obtain a positive electrode active material C . The positive electrode active material C is a powder in which a large number of particles of lithium manganese phosphate are collected.
（２－４）比較例３
　原料溶液に２－エチルヘキサン酸鉄（II）に変えて２－エチルヘキサン酸コバルト（II）を用いる以外は合成例１と同様の噴霧燃焼法で、リン酸コバルトリチウムの前駆体粒子ｄを得た。電子顕微鏡で確認した前駆体粒子ｄの一次粒子の平均粒径は約５００ｎｍであった。
　また、原料溶液に硫酸マンガンに変えて硫酸鉄を用いる以外は合成例２と同様の噴霧燃料法で、リン酸鉄リチウムの前駆体粒子ａ’を得た。電子顕微鏡で確認した前駆体粒子ａ’の一次粒子の平均粒径は約１００ｎｍであった。
　リン酸コバルトリチウムの前駆体粒子ｄと、それより粒径の小さいリン酸鉄リチウムの前駆体粒子ａ’を、重量比７０：３０で混合した後、ポリビニルアルコールを粉体の１０ｗｔ％になるように加えて混合した後、実施例と同様に焼成・粉砕を行い、正極活物質Ｄを得た。正極活物質Ｄは、リン酸コバルトリチウムの粒子の周囲に小さなリン酸鉄リチウムの粒子が付着した粒子が、多数集まった粉体である。 (2-4) Comparative Example 3
A precursor particle d of lithium cobalt phosphate is obtained by the same spray combustion method as in Synthesis Example 1 except that cobalt (II) 2-ethylhexanoate is used instead of iron (II) 2-ethylhexanoate as the raw material solution. The The average particle size of the primary particles of the precursor particles d confirmed by the electron microscope was about 500 nm.
Further, lithium iron phosphate precursor particles a ′ were obtained by the same spray fuel method as in Synthesis Example 2 except that manganese sulfate is used as the raw material solution and iron sulfate is used. The average particle size of the primary particles of the precursor particles a ′ confirmed by the electron microscope was about 100 nm.
After mixing precursor particle d of lithium cobalt phosphate and precursor particle a 'of lithium iron phosphate smaller in particle diameter at a weight ratio of 70:30, the polyvinyl alcohol will be 10 wt% of the powder The mixture was added to and mixed, and then fired and pulverized in the same manner as in the example to obtain a positive electrode active material D. The positive electrode active material D is a powder in which a large number of particles in which small lithium iron phosphate particles are attached to the periphery of lithium cobalt phosphate particles are collected.
（２－５）比較例４
　原料溶液に２－エチルヘキサン酸鉄（II）に変えて２－エチルヘキサン酸ニッケル（II）を用いる以外は合成例１と同様の噴霧燃焼法で、リン酸ニッケルリチウムの前駆体粒子ｅを得た。電子顕微鏡で確認した前駆体粒子ｅの一次粒子の平均粒径は約５００ｎｍであった。
　リン酸ニッケルリチウムの前駆体粒子ｅと、それより粒径の小さいリン酸鉄リチウムの前駆体粒子ａ’を、重量比７０：３０で混合した後、ポリビニルアルコールを粉体の１０ｗｔ％になるように加えて混合した後、実施例と同様に焼成・粉砕を行い、正極活物質Ｅを得た。正極活物質Ｅは、リン酸ニッケルリチウムの粒子の周囲に小さなリン酸鉄リチウムの粒子が付着した粒子が、多数集まった粉体である。 (2-5) Comparative Example 4
A precursor particle e of lithium nickel phosphate is obtained by the same spray combustion method as in Synthesis Example 1 except that nickel (II) 2-ethylhexanoate is used instead of iron (II) 2-ethylhexanoate as the raw material solution. The The average particle size of the primary particles of the precursor particles e confirmed by the electron microscope was about 500 nm.
After mixing precursor particle e of lithium nickel phosphate and precursor particle a 'of lithium iron phosphate smaller in particle diameter at a weight ratio of 70:30, make the polyvinyl alcohol 10 wt% of the powder The mixture was added to and mixed, and then fired and pulverized in the same manner as in the example to obtain a positive electrode active material E. The positive electrode active material E is a powder in which a large number of particles in which small particles of lithium iron phosphate adhere to the periphery of lithium lithium phosphate particles.
（２－６）比較例５
　原料溶液に２－エチルヘキサン酸鉄（II）に変えて２－エチルヘキサン酸マンガン（II）を用いる以外は合成例１と同様の噴霧燃焼法で、リン酸マンガンリチウムの前駆体粒子ｆを得た。電子顕微鏡で確認した前駆体粒子ｆの一次粒子の平均粒径は約５００ｎｍであった。
　リン酸マンガンリチウムの前駆体粒子ｆと、それより粒径の小さいリン酸鉄リチウムの前駆体粒子ａ’を、重量比７０：３０の割合で混合した後、ポリビニルアルコールを粉体の１０ｗｔ％になるように加えて混合した後、実施例と同様に焼成・粉砕を行い、正極活物質Ｆを得た。正極活物質Ｆは、リン酸マンガンリチウムの粒子の周囲に小さなリン酸鉄リチウムの粒子が付着した粒子が、多数集まった粉体である。 (2-6) Comparative Example 5
A precursor particle f of lithium manganese phosphate is obtained by the same spray combustion method as in Synthesis Example 1 except that manganese (II) 2-ethylhexanoate is used instead of iron (II) 2-ethylhexanoate as the raw material solution. The The average particle size of the primary particles of the precursor particles f confirmed by the electron microscope was about 500 nm.
After mixing the precursor particle f of lithium manganese phosphate and the precursor particle a 'of lithium iron phosphate smaller in particle diameter at a weight ratio of 70:30, the polyvinyl alcohol is made 10 wt% of the powder After adding and mixing so that it might become, it baked and grind | pulverized it similarly to the Example, and obtained the positive electrode active material F. The positive electrode active material F is a powder in which a large number of particles in which small lithium iron phosphate particles are attached around the lithium manganese phosphate particles.
　（３）試料の評価
　（３－１）走査型電子顕微鏡（ＳＥＭ）観察
　前駆体粒子ａと前駆体粒子ｂとを混合した実施例の粉体について、ＳＥＭにより観察を行った。ＳＥＭ像観察結果を図４に示す。 (3) Evaluation of sample (3-1) Observation by scanning electron microscope (SEM) The powder of the example in which the precursor particles a and the precursor particles b were mixed was observed by SEM. The SEM image observation result is shown in FIG.
　図４（ａ）～（ｃ）に示すとおり、焼成前の粉体を構成する粒子は、５０～２００ｎｍ程度の粒子であり、一部５００ｎｍ以上の粗大粒子が存在した。 As shown in FIGS. 4 (a) to 4 (c), the particles constituting the powder before firing were particles of about 50 to 200 nm, and some coarse particles of 500 nm or more existed.
　（３－２）焼成前の粒子のＥＤＳによる組成分析
　前駆体粒子ａと前駆体粒子ｂとを混合した粉体に含まれる実施例の粒子の形状観察と組成分析を、走査透過型電子顕微鏡を用いて、ＨＡＡＤＦ－ＳＴＥＭ（Ｈｉｇｈ－Ａｎｇｌｅ－Ａｎｎｕｌａｒ－Ｄａｒｋ－Ｆｉｅｌｄ－Ｓｃａｎｎｉｎｇ－Ｔｒａｎｓｍｉｓｓｉｏｎ－Ｅｌｅｃｔｒｏｎ－Ｍｉｃｒｏｓｃｏｐｙ：高角度散乱暗視野－走査透過型電子顕微鏡法）による粒子形状の観察と、ＥＤＳ分析（Ｅｎｅｒｇｙ　Ｄｉｓｐｅｒｓｉｖｅ　Ｓｐｅｃｔｒｏｓｃｏｐｙ：エネルギー分散型Ｘ線分析）により行った。図５（ａ）は、実施例の焼成前の粒子のＨＡＡＤＦ－ＳＴＥＭ像であり、図５（ｂ）は、同一の観察箇所におけるマンガン原子のＥＤＳマップであり、図５（ｃ）は、同一の観察箇所における鉄原子のＥＤＳマップであり、図５（ｃ）は、同一の観察箇所における酸素原子のＥＤＳマップであり、図５（ｄ）は、同一の観察箇所におけるリン原子のＥＤＳマップである。 (3-2) Compositional Analysis of Particles Before Firing by EDS The shape observation and compositional analysis of the particles of the example contained in the powder in which the precursor particles a and the precursor particles b are mixed, a scanning transmission electron microscope Observation of particle shape by HAADF-STEM (High-Angle-Annular-Dark-Field-Scanning-Transmission-Electron-Microscopy) and EDS analysis (Energy Dispersive) Spectroscopy: energy dispersive X-ray analysis). Fig.5 (a) is a HAADF-STEM image of the particle | grains before baking of an Example, FIG.5 (b) is an EDS map of the manganese atom in the same observation location, FIG.5 (c) is the same. 5 (c) is an EDS map of oxygen atom at the same observation point, and FIG. 5 (d) is an EDS map of phosphorus atom at the same observation point. is there.
　図５（ａ）において、略球形の粒径約５００ｎｍの粒子の周囲に微小な粒子が存在することがわかる。さらに、図５（ｂ）～（ｅ）において、略球形の大きな粒子は鉄と酸素とリンとを含むが、マンガンは大きな粒子からはほとんど検出されず、観測視野の下部の微粒子部分からマンガンが検出された。 In FIG. 5A, it can be seen that minute particles exist around the approximately spherical particles having a particle diameter of about 500 nm. Furthermore, in FIG. 5 (b) to (e), although the large particles having a substantially spherical shape contain iron, oxygen and phosphorus, manganese is hardly detected from the large particles, and manganese is present from the fine particle part at the bottom of the observation field of view. was detected.
　図６（ａ）～（ｄ）は、図５とは別の視野でのＳＴＥＭ像やＥＤＳマップである。粒径約１００ｎｍの小さな粒子の集まりが観察され、この視野では鉄が検出されず、マンガンとリンと酸素が検出された。各粒子において、元素は均一に分布している。 FIGS. 6A to 6D are STEM images and EDS maps in fields of view different from those in FIG. Assemblage of small particles with a particle size of about 100 nm was observed, iron was not detected in this field of view, and manganese, phosphorus and oxygen were detected. In each particle, the elements are uniformly distributed.
　（３－３）焼成後の実施例の正極活物質のＥＤＳによる組成分析
　焼成後の実施例の正極活物質Ａについて、同様に粒子形状の観察と組成分析を行った。図７（ａ）は、実施例の正極活物質のＨＡＡＤＦ－ＳＴＥＭ像であり、図７（ｂ）は、同一の観察箇所におけるマンガン原子のＥＤＳマップであり、図７（ｃ）は、同一の観察箇所における鉄原子のＥＤＳマップであり、図７（ｄ）は、同一の観察箇所における酸素原子のＥＤＳマップであり、図７（ｅ）は、同一の観察箇所におけるリン原子のＥＤＳマップである。 (3-3) Compositional analysis of positive electrode active material of the example after firing based on EDS With respect to the positive electrode active material A of the example after firing, observation of particle shape and composition analysis were similarly performed. Fig.7 (a) is a HAADF-STEM image of the positive electrode active material of an Example, FIG.7 (b) is an EDS map of the manganese atom in the same observation location, FIG.7 (c) is the same. FIG. 7 (d) is an EDS map of iron atom at the observation site, FIG. 7 (d) is an EDS map of oxygen atom at the same observation site, and FIG. 7 (e) is an EDS map of phosphorus atom at the same observation site .
　図７（ａ）～（ｅ）より、実施例の正極活物質Ａが、粒径約１μｍのリン酸鉄リチウム粒子に、粒径５０～２００ｎｍ程度のリン酸マンガンリチウム粒子が付着する構造をとっていることがわかる。また、リン酸マンガンリチウム粒子がリン酸鉄リチウム粒子の表面全体を覆わず、リン酸鉄リチウム粒子の一部表面が露出していることがわかる。 As shown in FIGS. 7 (a) to 7 (e), the positive electrode active material A of the example has a structure in which lithium manganese phosphate particles having a particle diameter of about 50 to 200 nm adhere to lithium iron phosphate particles having a particle diameter of about 1 μm. Know that Further, it can be seen that lithium manganese phosphate particles do not cover the entire surface of lithium iron phosphate particles, and a part of the surface of lithium iron phosphate particles is exposed.
　（４）正極活物質を用いた試験評価用正極電極と二次電池の作製
　実施例及び比較例で得た正極活物質Ａ～Ｆに対して、導電助剤（カーボンブラック）を１０重量％となるように混合し、内部を窒素で置換したボールミルを用いて更に５時間混合した。混合粉末と結着剤であるポリフッ化ビニリデン（ＰＶｄＦ）を、重量比９５：５の割合で混合し、Ｎ－メチル－２－ピロリドン（ＮＭＰ）を加えて十分混練し、正極スラリーを得た。 (4) Preparation of a positive electrode for test evaluation using a positive electrode active material and a secondary battery With respect to the positive electrode active materials A to F obtained in Examples and Comparative Examples, 10% by weight of a conductive support agent (carbon black) The resulting mixture was mixed and mixed for 5 hours using a ball mill whose inside was replaced with nitrogen. The mixed powder and polyvinylidene fluoride (PVdF) as a binder were mixed at a weight ratio of 95: 5, N-methyl-2-pyrrolidone (NMP) was added, and the mixture was sufficiently kneaded to obtain a positive electrode slurry.
　厚さ１５μｍのアルミニウム箔集電体に、正極スラリーを５０ｇ／ｍ２の塗工量で塗布し、１２０℃で３０分間乾燥した。その後、ロールプレスで２．０ｇ／ｃｍ３の密度になるように圧延加工し、２ｃｍ２の円盤状に打抜いて正極とした。 The positive electrode slurry was applied at a coating amount of 50 g / m 2 to a 15 μm thick aluminum foil current collector, and dried at 120 ° C. for 30 minutes. Thereafter, the resultant was rolled to a density of 2.0 g / cm 3 by a roll press, and punched into a disc shape of 2 cm 2 to obtain a positive electrode.
　これらの正極と、負極に金属リチウム、電解液にエチレンカーボネート及びジエチルカーボネートを体積比１：１の割合で混合した混合溶媒にＬｉＰＦ６を１Ｍの濃度で溶解したものを用い、リチウム二次電池を作製した。なお、作製雰囲気は露点が－５０℃以下とした。各極は集電体の付いた電槽缶に圧着して用いた。上記正極、負極、電解質及びセパレータを用いて直径２５ｍｍ、厚さ１．６ｍｍのコイン型リチウム二次電池とした。 A lithium secondary battery is prepared by dissolving LiPF 6 at a concentration of 1 M in a mixed solvent in which the positive electrode and the negative electrode are mixed with metal lithium in the negative electrode and ethylene carbonate and diethyl carbonate in the electrolyte at a volume ratio of 1: 1. Made. Note that the dew point was set to −50 ° C. or less for the preparation atmosphere. Each electrode was crimped to a battery can with a current collector. A coin-type lithium secondary battery having a diameter of 25 mm and a thickness of 1.6 mm was formed using the positive electrode, the negative electrode, the electrolyte, and the separator.
（５）正極活物質の電極特性の評価
　次に、前記のコイン型リチウム二次電池により、正極活物質の電極特性の試験評価を、次のように実施した。
　試験温度２５℃または６０℃、０．１Ｃの電流レートにて、ＣＣ－ＣＶ法により、充電カーブがプラトーとなる所定の電位（対Ｌｉ／Ｌｉ＋）まで充電を行い、その後電流レートが０．０１Ｃまで低下した後に充電を停止した。その後、０．１Ｃレートにて、ＣＣ法により２．５Ｖ（前記に同じ）まで放電を行って、初期の充放電容量を測定した。また、充放電を繰り返して後の放電容量を測定し、容量維持率を測定した。 (5) Evaluation of Electrode Characteristics of Positive Electrode Active Material Next, test evaluation of the electrode characteristics of the positive electrode active material was performed as follows using the coin-type lithium secondary battery described above.
At a test temperature of 25 ° C. or 60 ° C., at a current rate of 0.1 C, charging is performed to a predetermined potential (vs. Li / Li + ) at which the charge curve becomes a plateau by CC-CV method. After dropping to 01C, charging was stopped. Thereafter, the battery was discharged to 2.5 V (same as above) by the CC method at a 0.1 C rate, and the initial charge and discharge capacity was measured. Moreover, charge and discharge were repeated, the discharge capacity after that was measured, and the capacity retention rate was measured.
　図８（ａ）に、実施例に係る正極活物質を用いたリチウムイオン二次電池の初回充放電曲線を示す。充電は４．５Ｖまで行った。図８（ａ）において、（ａ－１）は充電曲線を示し、（ａ－２）は放電曲線を示す。放電曲線の右側の末端の横軸の値が放電容量となる。図８（ａ）によれば、実施例に係るリチウムイオン二次電池は２５℃では１２０ｍＡｈ／ｇ程度の初回放電容量を有し、４３８Ｗｈ／ｋｇのエネルギー密度を有する。なお、図８（ａ）の充電曲線（ａ－１）における３．５Ｖ付近の反応と、放電曲線（ａ－２）における３．５Ｖ付近の反応は、リン酸鉄リチウムの充放電反応である。また、図８（ａ）の充電曲線（ａ－１）における４．１Ｖ付近の反応と、放電曲線（ａ－２）における３．９Ｖ付近の反応は、リン酸マンガンリチウムの充放電反応である。すなわち、実施例に係る正極活物質の充放電反応は、２段階で起きていることがわかる。 The initial charge / discharge curve of a lithium ion secondary battery using the positive electrode active material according to the example is shown in FIG. 8 (a). The charge went to 4.5V. In FIG. 8 (a), (a-1) shows a charge curve, and (a-2) shows a discharge curve. The value of the horizontal axis at the right end of the discharge curve is the discharge capacity. According to FIG. 8A, the lithium ion secondary battery according to the example has an initial discharge capacity of about 120 mAh / g at 25 ° C. and an energy density of 438 Wh / kg. The reaction in the vicinity of 3.5 V in the charge curve (a-1) of FIG. 8A and the reaction in the vicinity of 3.5 V in the discharge curve (a-2) are charge and discharge reactions of lithium iron phosphate . Further, the reaction in the vicinity of 4.1 V in the charge curve (a-1) of FIG. 8A and the reaction in the vicinity of 3.9 V in the discharge curve (a-2) are charge and discharge reactions of lithium manganese phosphate. . That is, it can be seen that the charge / discharge reaction of the positive electrode active material according to the example occurs in two steps.
　また、図８（ｂ）に、充放電を繰り返した際の放電容量の推移を示す。充電は４．５Ｖまで行った。１００サイクルの充放電を行った後でも、実施例に係る正極活物質を用いたリチウムイオン二次電池は、１１０ｍＡｈ／ｇの放電容量を有し、１００サイクル容量維持率は約９２％である。 Moreover, transition of the discharge capacity at the time of repeating charging / discharging in FIG.8 (b) is shown. The charge went to 4.5V. Even after 100 cycles of charge and discharge, the lithium ion secondary battery using the positive electrode active material according to the example has a discharge capacity of 110 mAh / g, and the 100 cycle capacity retention rate is about 92%.
　図９に、実施例に係る正極活物質Ａを用いたリチウムイオン二次電池の６０℃での初回充放電曲線を示す。充電は４．５Ｖまで行った。図９において、（ａ－１）は充電曲線を示し、（ａ－２）は放電曲線を示す。放電曲線の右側の末端の横軸の値が放電容量となる。図９によれば、実施例に係るリチウムイオン二次電池は６０℃では１４０ｍＡｈ／ｇ程度の初回放電容量を有し、５２０Ｗｈ／ｋｇのエネルギー密度を有する。 The first time charge / discharge curve at 60 ° C. of a lithium ion secondary battery using the positive electrode active material A according to the example is shown in FIG. The charge went to 4.5V. In FIG. 9, (a-1) shows a charge curve, and (a-2) shows a discharge curve. The value of the horizontal axis at the right end of the discharge curve is the discharge capacity. According to FIG. 9, the lithium ion secondary battery according to the example has an initial discharge capacity of about 140 mAh / g at 60 ° C. and an energy density of 520 Wh / kg.
　図１０に、比較例１に係る正極活物質Ｂを用いたリチウムイオン二次電池の２５℃での初回充放電曲線を示す。この場合も充電は４．５Ｖまで行った。図１０において、（ａ－１）は充電曲線を示し、（ａ－２）は放電曲線を示す。比較例１に係る、リン酸鉄リチウムのみの正極活物質を用いたリチウムイオン二次電池の初回放電容量は２５℃で約１２０ｍＡｈ／ｇで実施例とほぼ同じ値であるものの、エネルギー密度は約３９５Ｗｈ／ｋｇであり、実施例に比べて低い値となった。 The initial charge / discharge curve at 25 ° C. of a lithium ion secondary battery using the positive electrode active material B according to Comparative Example 1 is shown in FIG. Also in this case, charging was performed up to 4.5V. In FIG. 10, (a-1) shows a charge curve, and (a-2) shows a discharge curve. The initial discharge capacity of a lithium ion secondary battery using a positive electrode active material containing only lithium iron phosphate according to Comparative Example 1 is about 120 mAh / g at 25 ° C., which is substantially the same value as the Example, but the energy density is about It was 395 Wh / kg, which was a lower value than in the example.
　図１１に、比較例２に係る正極活物質Ｃを用いたリチウムイオン二次電池の２５℃での初回充放電曲線を示す。この場合も充電は４．５Ｖまで行った。図１１において、（ａ－１）は充電曲線を示し、（ａ－２）は放電曲線を示す。比較例２に係る、リン酸マンガンリチウムのみの正極活物質を用いたリチウムイオン二次電池の初回放電容量は２５℃で約３０ｍＡｈ／ｇ、エネルギー密度は約９７Ｗｈ／ｋｇであり、実施例に比べて大幅に低かった。 The first time charge / discharge curve at 25 ° C. of a lithium ion secondary battery using the positive electrode active material C according to Comparative Example 2 is shown in FIG. Also in this case, charging was performed up to 4.5V. In FIG. 11, (a-1) shows a charge curve, and (a-2) shows a discharge curve. The initial discharge capacity of a lithium ion secondary battery using a positive electrode active material containing only lithium manganese phosphate according to Comparative Example 2 is about 30 mAh / g at 25 ° C., and the energy density is about 97 Wh / kg. Was significantly lower.
　比較例３に係る、正極活物質Ｄを用いたリチウムイオン二次電池の初回放電容量は２５℃で約５９ｍＡｈ／ｇ、エネルギー密度は約２１７Ｗｈ／ｋｇであり、実施例に比べて大幅に低かった。なお、比較例３においては、充電はリン酸コバルトリチウムの充電カーブがプラトーとなる４．８Ｖまで行った。 The initial discharge capacity of the lithium ion secondary battery using the positive electrode active material D according to Comparative Example 3 was about 59 mAh / g at 25 ° C., and the energy density was about 217 Wh / kg, which were significantly lower than those of Examples. . In addition, in the comparative example 3, charge was performed to 4.8V which the charge curve of lithium cobalt phosphate becomes a plateau.
　比較例４に係る、正極活物質Ｅを用いたリチウムイオン二次電池の初回放電容量は２５℃で約４８ｍＡｈ／ｇ、エネルギー密度は約１６８Ｗｈ／ｋｇであり、実施例に比べて大幅に低かった。なお、比較例４においては、充電はリン酸ニッケルリチウムの充電カーブがプラトーとなる５．０Ｖまで行った。 The initial discharge capacity of the lithium ion secondary battery using the positive electrode active material E according to Comparative Example 4 was about 48 mAh / g at 25 ° C., and the energy density was about 168 Wh / kg, which were significantly lower than those of Examples. . In Comparative Example 4, charging was performed up to 5.0 V at which the charge curve of lithium nickel phosphate became a plateau.
　比較例５に係る、正極活物質Ｆを用いたリチウムイオン二次電池の初回放電容量は２５℃で約６６ｍＡｈ／ｇ、エネルギー密度は約２３５Ｗｈ／ｋｇであり、実施例に比べて大幅に低かった。比較例４においても、充電は４．５Ｖまで行った。 The initial discharge capacity of the lithium ion secondary battery using the positive electrode active material F according to Comparative Example 5 was about 66 mAh / g at 25 ° C., and the energy density was about 235 Wh / kg, which were significantly lower than those of Examples. . Also in Comparative Example 4, charging was performed to 4.5 V.
　以上に説明したように、本発明の正極活物質を、所定の集電体に塗工した非水電解質二次電池用正極は、非水電解質を用いるリチウムイオン二次電池をはじめとする充放電可能な二次電池において、優れた充放電特性を示す正極として用いることができる。しかも、本発明の前駆体粒子の製造法である噴霧燃焼法は量産性に優れ、低コストで製品を提供できることが可能になる。 As described above, the positive electrode for a non-aqueous electrolyte secondary battery in which the positive electrode active material of the present invention is coated on a predetermined current collector is a charge and discharge including a lithium ion secondary battery using a non-aqueous electrolyte In a possible secondary battery, it can be used as a positive electrode showing excellent charge and discharge characteristics. In addition, the spray combustion method, which is a method for producing the precursor particles of the present invention, is excellent in mass productivity and can provide a product at low cost.
　以上、添付図面を参照しながら、本発明の好適な実施の形態について説明したが、本発明は係る例に限定されない。当業者であれば、本願で開示した技術的思想の範疇内において、各種の変更例または修正例に想到しえることは明らかであり、それらについても当然に本発明の技術的範囲に属するものと了解される。 The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is apparent that those skilled in the art can conceive of various modifications or alterations within the scope of the technical idea disclosed in the present application, and of course these also fall within the technical scope of the present invention. It is understood.
　１………粒子
　３………第１の粒子
　５………第２の粒子
　１１………微粒子製造装置
　１３………微粒子合成ノズル
　１５………微粒子回収フィルタ
　１７………前駆体粒子
　２１………原料溶液
　２３………可燃性ガス
　２５………支燃性ガス
　２７………排気
　３１………非水電解質二次電池
　３３………正極
　３５………負極
　３７………セパレータ
　３９………電解質
　４１………電池缶
　４３………正極リード
　４５………負極リード
　４７………正極端子
　４９………封口体 DESCRIPTION OF SYMBOLS 1 ............ Particle 3 ......... 1st particle 5 ............ 2nd particle 11 ............ microparticles | fine-particles manufacturing apparatus 13 ............ microparticles | fine-particles synthetic | combination nozzle 15 ............ microparticles | fine-particles collection | recovery filter 17 ............ Precursor particle 21 ......... Raw material solution 23 ... ... Combustible gas 25 ... ... Combustion gas 27 ... ... Exhaust gas 31 ......... Non-aqueous electrolyte secondary battery 33 ......... Positive electrode 35 ......... Negative electrode 37 ... Separator 39: Electrolyte 41: Battery can 43: Positive electrode lead 45: Negative electrode lead 47: Positive electrode terminal 49: Sealant

Claims (10)

  1. 　リン酸鉄リチウムを主として含む第１の粒子の表面の少なくとも一部に、
    　前記第１の粒子より粒径の小さい、リン酸マンガンリチウムを主として含む第２の粒子が付着していることを特徴とする正極活物質。     At least a portion of the surface of the first particle mainly comprising lithium iron phosphate,
    A positive electrode active material to which a second particle mainly comprising lithium manganese phosphate, having a particle diameter smaller than that of the first particle, is attached.
  2. 　前記第１の粒子の粒径が１００ｎｍ～１０μｍであり、
    　前記第２の粒子の粒径が２００ｎｍ以下であることを特徴とする請求項１に記載の正極活物質。     The particle size of the first particle is 100 nm to 10 μm,
    The particle diameter of said 2nd particle | grains is 200 nm or less, The positive electrode active material of Claim 1 characterized by the above-mentioned.
  3. 　前記第１の粒子および／または前記第２の粒子の表面の少なくとも一部が、炭素によって被覆されていることを特徴とする請求項１に記載の正極活物質。 The positive electrode active material according to claim 1, wherein at least a part of the surface of the first particle and / or the second particle is coated with carbon.
  4. 　集電体と、
    　前記集電体の少なくとも片面に、請求項３に記載の正極活物質を含む活物質層と、
    　を有することを特徴とする非水電解質二次電池用正極。     Current collector,
    An active material layer comprising the positive electrode active material according to claim 3 on at least one side of the current collector,
    And a positive electrode for a non-aqueous electrolyte secondary battery.
  5. 　請求項４に記載の非水電解質二次電池用正極と、
    　リチウムイオンを吸蔵および放出可能な負極と、
    　前記正極と前記負極との間に配置されたセパレータとを有し、
    　リチウムイオン伝導性を有する電解質中に、前記正極と前記負極と前記セパレータとを設けたことを特徴とする非水電解質二次電池。     A positive electrode for a non-aqueous electrolyte secondary battery according to claim 4;
    An anode capable of absorbing and desorbing lithium ions;
    A separator disposed between the positive electrode and the negative electrode;
    A non-aqueous electrolyte secondary battery comprising the positive electrode, the negative electrode and the separator in an electrolyte having lithium ion conductivity.
  6. 　リン酸鉄リチウムの前駆体である第３の粒子と、前記第３の粒子より粒径の小さいリン酸マンガンリチウムの前駆体である第４の粒子を混合する工程と、
    　さらに炭素源を混合する工程と、
    　混合して得られた粒子を焼成する工程と、
    　を含むことを特徴とする正極活物質の製造方法。     Mixing a third particle, which is a precursor of lithium iron phosphate, and a fourth particle, which is a precursor of lithium manganese phosphate having a particle diameter smaller than that of the third particle;
    Mixing the carbon source further;
    Firing the particles obtained by mixing;
    A method of producing a positive electrode active material, comprising:
  7. 　前記第３の粒子と前記第４の粒子の混合比が、重量比で６０：４０～９０：１０であることを特徴とする請求項６に記載の正極活物質の製造方法。 The method for producing a positive electrode active material according to claim 6, wherein a mixing ratio of the third particles to the fourth particles is 60:40 to 90:10 by weight.
  8. 　前記第３の粒子の粒径が１００ｎｍ～１０μｍであり、
    　前記第４の粒子の粒径が２００ｎｍ以下であることを特徴とする請求項６に記載の正極活物質の製造方法。     The particle size of the third particle is 100 nm to 10 μm,
    The particle diameter of said 4th particle | grain is 200 nm or less, The manufacturing method of the positive electrode active material of Claim 6 characterized by the above-mentioned.
  9. 　前記第３の粒子は、リチウム、鉄およびリンを含む溶液を、霧状の液滴にて、支燃性ガスと可燃性ガスとともに火炎中に供給する方法により製造され、
    　前記第４の粒子は、リチウム、マンガンおよびリンを含む溶液を、霧状の液滴にて、支燃性ガスと可燃性ガスとともに火炎中に供給する方法により製造されることを特徴とする請求項６に記載の正極活物質の製造方法。     The third particle is manufactured by a method of supplying a solution containing lithium, iron and phosphorus in the form of droplets in the form of mist into a flame together with a combustion supporting gas and a flammable gas.
    The fourth particles are produced by a method of supplying a solution containing lithium, manganese and phosphorus in the form of droplets in the form of mist into a flame together with a combustion supporting gas and a flammable gas. Item 7. A method of producing a positive electrode active material according to Item 6.
  10. 　前記炭素源が、ポリビニルアルコール、ポリビニルピロリドン、カルボキシメチルセルロース、アセチルセルロース、ショ糖、カーボンブラックのいずれか一つ以上であることを特徴とする請求項６に記載の正極活物質の製造方法。
          The method for producing a positive electrode active material according to claim 6, wherein the carbon source is any one or more of polyvinyl alcohol, polyvinyl pyrrolidone, carboxymethyl cellulose, acetyl cellulose, sucrose and carbon black.
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JP2016149297A (en) * 2015-02-13 2016-08-18 三井造船株式会社 Manufacturing method of positive electrode active material of lithium secondary battery
CN106158412A (en) * 2015-03-25 2016-11-23 江苏集盛星泰新能源科技有限公司 A kind of lithium-ion capacitor and preparation method thereof
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